TWI905152B - Manufacturing method of protective sheet for semiconductor processing and semiconductor device - Google Patents

Abstract

This invention provides a semiconductor processing protective sheet that can fully follow the unevenness of a semiconductor wafer even when thinning it using methods such as DBG, and can suppress the formation of cracks in the wafer after grinding. The semiconductor processing protective sheet has a substrate, and an intermediate layer and an adhesive layer are sequentially provided on one main surface of the substrate; and satisfies the following (a) and (b): (a) the loss tangent of the intermediate layer at 50°C measured at 1Hz is 0.40 to 0.65; (b) the ratio [A/I] of the storage modulus A of the adhesive layer to the storage modulus I of the intermediate layer measured at 50°C at 1Hz is 0.80 to 3.50.

Description

Manufacturing method of protective sheet for semiconductor processing and semiconductor device

This invention relates to a protective sheet for semiconductor processing and a method for manufacturing a semiconductor device. In particular, it relates to a protective sheet for semiconductor processing suitable for grinding the back side of a semiconductor wafer with uneven surfaces and singulating the semiconductor wafer using grinding stress, etc., and a method for manufacturing a semiconductor device using the protective sheet for semiconductor processing.

In the process of miniaturization and multifunctionality of various electronic devices, the semiconductor chips carried in these devices also require miniaturization and thinning. To achieve chip thinning, the back side of the semiconductor wafer is usually ground to adjust its thickness. In addition, to obtain thinner chips, a process called Dicing Before Grinding (DBG) is sometimes used. In DBG, grooves of a specified depth are formed from the surface of the wafer using a dicing tool, and then the back side of the wafer is ground. The grinding process monolithizes the wafer, resulting in a chip. DBG can perform back-side grinding and wafer monolithization simultaneously, thus enabling the efficient production of thin chips.

In the past, when performing back-side grinding of semiconductor wafers or when manufacturing chips using DBG, adhesive tape called back-grinding tape was usually attached to the surface of the wafer to protect the circuitry on the wafer surface or to hold the semiconductor wafer and semiconductor chip together.

As a backing abrasive used in DBG, an adhesive tape is used that has a substrate and an adhesive layer disposed on one side of the substrate. As an example of such an adhesive tape, Patent 1 and Patent 2 disclose an adhesive tape having a substrate with a high Young's modulus, and having a cushioning layer disposed on one side of the substrate and an adhesive layer disposed on the other side.

In recent years, as a variation of the pre-dicing method, a method has been proposed that uses lasers to create modified regions inside the wafer and utilizes the stress generated during the grinding of the wafer's back side to achieve wafer monolithization. This method is sometimes referred to as LDBG (Laser Dicing Before Grinding). In LDBG, the wafer is cut along the grain direction starting from the modified region, thus reducing chipping compared to pre-dicing methods that use a dicing blade. This results in wafers with excellent flexural strength and facilitates further wafer thinning. Furthermore, compared to DBG, which uses a dicing blade to form grooves of a predetermined depth on the wafer surface, LDBG offers superior wafer yield because there is no area where the wafer is removed by the dicing blade, resulting in a very small kerf width.

On the other hand, when mounting multi-pin LSI packages for MPUs or gate arrays on printed circuit boards, flip-chip mounting has always been used. In this mounting method, a semiconductor chip with raised electrodes (bumps) formed on its pads, composed of eutectic solder, high-temperature solder, gold, etc., is used. These bumps are then brought face-down to corresponding terminals on the chip mounting substrate for fusion and diffusion bonding. [Prior Art Documents] [Patent Documents]

Patent Document 1: International Publication No. 2015/156389 Patent Document 2: Japanese Patent Application Publication No. 2015-183008

[The technical problem this invention aims to solve]

The semiconductor wafer used in this mounting method is obtained by monolithically processing a semiconductor wafer with uneven surfaces, such as a semiconductor wafer with convex electrodes. When this uneven semiconductor wafer is polished by DBG, as described above, back-polishing tape is attached to the electrical surface of the semiconductor wafer to protect the electrical surface during polishing and to prevent wafer movement after monolithic processing.

However, when the back-grinding tapes described in Patent 1 and Patent 2 are attached to the electrical surface of a semiconductor wafer with uneven surfaces and polished by DBG, the back-grinding tapes described in Patent 1 and Patent 2 cannot fully follow the unevenness of the semiconductor wafer, resulting in problems such as water seeping into the electrical surface during polishing and wafer movement (wafer displacement) after wafer monolithization.

This invention was made in view of the above circumstances, and its purpose is to provide a protective sheet for semiconductor processing that can fully follow the unevenness of the wafer even when performing thinning processes such as DBG on semiconductor wafers with irregularities, and can suppress the formation of cracks in the wafer after grinding. [Technical Means for Solving the Technical Problem]

The invention is as follows: [1] A protective sheet for semiconductor processing, comprising a substrate, wherein an intermediate layer and an adhesive layer are sequentially formed on a main surface of the substrate, and satisfying the following (a) and (b): (a) The loss tangent of the intermediate layer at 50°C measured at 1 Hz is 0.40 to 0.65; (b) The ratio of the storage modulus A of the adhesive layer to the storage modulus I of the intermediate layer at 50°C measured at 1 Hz [A/I] is 0.80 to 3.50.

[2] The semiconductor processing protective sheet according to [1], wherein a buffer layer is provided on another main surface of the substrate.

[3] A protective sheet for semiconductor processing according to [1] or [2], wherein the Young's modulus of the substrate is 1000 MPa or more.

[4] A protective sheet for semiconductor processing according to any one of [1] to [3], wherein the thickness of the intermediate layer is more than 60 μm and less than 250 μm.

[5] A protective sheet for semiconductor processing according to any one of [1] to [4], wherein the adhesive layer is energy-cured.

[6] A protective sheet for semiconductor processing according to any one of [1] to [5], wherein the intermediate layer is energy-cured.

[7] The semiconductor processing protective sheet according to any one of [1] to [6] is used in the step of grinding the back side of a semiconductor wafer on which grooves are formed and assembling the semiconductor wafer into a semiconductor chip by the grinding.

[8] A method for manufacturing a semiconductor device, comprising: a step of attaching a semiconductor processing protective sheet as described in any one of [1] to [7] to the surface of a semiconductor wafer having uneven surfaces; a step of forming grooves from the surface side of the semiconductor wafer, or a step of forming a modified region inside the semiconductor wafer from the surface or back side of the semiconductor wafer; a step of grinding the semiconductor wafer on which the semiconductor processing protective sheet is attached and on which grooves or modified regions are formed, from the back side, and converting it into multiple wafers starting from the grooves or modified regions; and a step of peeling the semiconductor processing protective sheet from the converted semiconductor wafers. [Effects of the Invention]

According to the present invention, a protective sheet for semiconductor processing can be provided that can fully follow the unevenness of the wafer even when the semiconductor wafer is thinned by DBG or the like and can suppress the generation of cracks in the wafer after grinding.

The invention will now be described in detail using diagrams based on specific embodiments. First, the main terms used in this specification will be explained.

Semiconductor wafer monolithization refers to dividing a semiconductor wafer into individual circuits to obtain a semiconductor chip.

The "surface" of a semiconductor wafer refers to the side where circuits, electrodes, etc. are formed, while the "back side" refers to the side where circuits, etc. are not formed.

DBG (Deep-Groove) refers to a method of single-chipping a wafer by grinding it from the back side after forming grooves of a specified depth on the surface side. The grooves formed on the surface side of the wafer can be created by methods such as blade cutting, laser cutting, or plasma cutting.

In addition, LDBG is a variation of DBG, which refers to a method of using lasers to create modified regions inside the wafer and using stress during the grinding of the back side of the wafer to monolithize the wafer.

"Chipset" refers to multiple semiconductor chips that are held on the semiconductor processing protection chip of the present invention after the semiconductor wafer is monolithically processed. These semiconductor chips form a whole with the same shape as the semiconductor wafer.

In this manual, for example, "(meth)acrylate" is used as a term to refer to both "acrylate" and "methacrylate", and other similar terms are used in the same way.

"Energy rays" refer to ultraviolet rays, electron beams, etc., with ultraviolet rays being preferred.

(1. Protective Sheet for Semiconductor Processing) As shown in Figure 1A, the protective sheet 1 for semiconductor processing in this embodiment has a structure in which an intermediate layer 20 and an adhesive layer 30 are sequentially laminated on a substrate 10.

The semiconductor processing protective sheet of this embodiment is attached to a semiconductor wafer with uneven surfaces. For example, a semiconductor wafer with uneven surfaces can be illustrated by forming convex electrodes.

For example, as shown in FIG2, the semiconductor processing protective sheet 1 of this embodiment is used such that its main surface 30a of the adhesive layer is attached to the bump forming surface 101a of a bumped semiconductor wafer, wherein the bumped semiconductor wafer 101 has bumps 102 formed on the semiconductor wafer 101 as convex electrodes. The bumps are formed in a manner that allows them to be electrically connected to the circuits formed on the semiconductor wafer, therefore the bump forming surface 101a is an electrical surface.

In this embodiment, a bumped semiconductor wafer is singled into multiple semiconductor chips using DBG or LDBG. That is, before or after attaching the semiconductor processing protective sheet, grooves are formed on the surface (electrical surface) or a modified region is formed inside the semiconductor wafer. Then, the side of the semiconductor wafer to which the semiconductor processing protective sheet is attached, i.e., the back side, is ground.

When bumps and depressions such as convex electrodes are formed on a semiconductor wafer, if the thickness of the semiconductor wafer is reduced through grinding, the size of the bumps and depressions increases relatively to the thickness of the semiconductor wafer. Therefore, when the bumps and depressions are not properly embedded in the semiconductor processing protective film, the following problems become more pronounced due to DBG or LDBG. That is, water seeps into the electrical surface of the semiconductor wafer during back-side grinding, adhesive residue remains on the cut when peeling off the semiconductor processing protective film after grinding, and the movement of the individual wafers after grinding causes them to collide with each other, resulting in cracks on the wafers.

The semiconductor processing protective sheet of this embodiment, having the intermediate layer and adhesive layer described later, can effectively suppress the occurrence of the above-mentioned problems.

The protective sheet for semiconductor processing is not limited to the structure shown in FIG1A. Other layers may be formed as long as the effects of the present invention can be achieved. That is, as long as the substrate, intermediate layer and adhesive layer are stacked in sequence, other layers may be formed, for example, between the substrate and the intermediate layer, or between the intermediate layer and the adhesive layer.

In particular, in this embodiment, as shown in FIG1B, a buffer layer 40 is preferably provided on the main surface of the substrate 10 opposite to the main surface on which the adhesive layer 30 is formed. By having a buffer layer 40, the occurrence of the above-mentioned problems can be further suppressed.

The structural elements of the semiconductor processing protective sheet 1 shown in Figure 1B will be described in detail below.

(2. Substrate) The substrate is not limited as long as it is made of a material capable of supporting the semiconductor wafer. For example, various resin films used as substrates for backing adhesive tapes can be exemplified. The substrate can be composed of a single layer of resin film or a multilayer film consisting of multiple layers of resin film.

(2.1 Physical Properties of the Substrate) In this embodiment, a high-rigidity substrate is preferred. Due to the high rigidity of the substrate, even if the thickness of the semiconductor wafer is reduced due to grinding, the wafer can be maintained without wafer breakage. Specifically, the Young's modulus of the preferred substrate is 1000 MPa or higher, more preferably 1500 MPa or higher, and even more preferably 2000 MPa or higher.

In this embodiment, the thickness of the substrate is preferably 15μm to 200μm, and more preferably 40μm to 150μm.

(2.2 Substrate Material) As the substrate material, materials with a Young's modulus within the aforementioned range are preferred. In this embodiment, examples include polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, fully aromatic polyesters, polyamides, polycarbonate, polyacetal, modified polyphenylene ether, polyphenylene sulfide, polyurethane, polyetherketone, and biaxially stretched polypropylene. Among these, polyesters are preferred, and polyethylene terephthalate is even more preferred.

(3. Intermediate Layer) The intermediate layer is a layer disposed between the substrate and the adhesive layer. In this embodiment, the intermediate layer, together with the adhesive layer, can fully follow the irregularities formed on the surface of the semiconductor wafer, embedding the irregularities into the adhesive layer and the intermediate layer. As a result, even when the semiconductor wafer is ground very thin and force is applied to convex electrodes, the adhesive layer and the intermediate layer can adequately protect the convex electrodes, etc. Furthermore, when convex electrodes, etc., penetrate the adhesive layer, the intermediate layer embeds and protects them. The intermediate layer can consist of a single layer (monolayer) or multiple layers (two or more).

The thickness of the intermediate layer 20 can be set taking into account the size of the semiconductor wafer's unevenness, such as the height of the convex electrode. In this embodiment, the thickness of the intermediate layer 20 is preferably 60 μm to 250 μm, and more preferably 100 μm to 200 μm. Furthermore, the thickness of the intermediate layer refers to the total thickness of the entire intermediate layer. For example, the thickness of an intermediate layer composed of multiple layers refers to the total thickness of all layers constituting the intermediate layer.

In this embodiment, the intermediate layer has the following physical properties.

(3.1 Loss Tangent at 50°C) In this embodiment, the loss tangent (tanδ) of the intermediate layer at 50°C is in the range of 0.40° to 0.65°. The loss tangent is defined as "loss modulus/storage modulus," which is a value measured using a dynamic viscoelasticity measuring device by observing the response to stress applied to an object.

By setting the loss tangent of the intermediate layer at 50°C to 0.40° or higher, the unevenness formed on the wafer surface is fully embedded in the semiconductor processing protective film, thus suppressing water immersion during polishing. Furthermore, by setting the loss tangent of the intermediate layer at 50°C to 0.65° or lower, wafer displacement after wafer monolithization can be suppressed.

In addition, in this embodiment, when the intermediate layer has energy-curable properties, the tangent of the loss angle of the intermediate layer at 50°C is the tangent of the loss angle before energy-curable.

The loss tangent of the intermediate layer at 50°C is preferably 0.42 or higher. Furthermore, the loss tangent of the intermediate layer at 50°C is preferably 0.64 or lower.

The loss tangent of the intermediate layer at 50°C can be determined by known methods. In this embodiment, the intermediate layer is made into a sample of a specified size, and the sample is deformed at a frequency of 1Hz within a specified temperature range using a dynamic viscoelasticity measuring device. The elastic modulus is measured, and the loss tangent can be calculated from the measured elastic modulus.

(3.2 Ratio of the storage modulus I of the intermediate layer to the storage modulus A of the adhesive layer) In this embodiment, when the storage modulus (G’) of the intermediate layer at 50°C is set as the storage modulus I, and the storage modulus (G’) of the adhesive layer (described later) is set as the storage modulus A, the ratio of storage modulus I to storage modulus A, "A/I", is 0.80 or more and 3.50 or less.

By setting the A/I ratio at 50°C to 0.80 or higher, the semiconductor processing protective film fully tracks the unevenness of the semiconductor wafer, resulting in proper embedding of the semiconductor wafer within the protective film. Consequently, water immersion during polishing can be suppressed. Furthermore, by setting the A/I ratio at 50°C to 3.50 or lower, adhesive adhesion to the cut surface during the removal of the semiconductor processing protective film can be suppressed.

In addition, in this embodiment, when the intermediate layer has energy-radiation curing properties, the storage modulus I is the storage modulus before energy-radiation curing.

The storage module I is not specifically limited as long as it meets the range of "A/I" mentioned above. In this embodiment, the storage module I is preferably between 0.03MPa and 0.08MPa.

The storage modulus (storage modulus I) of the intermediate layer at 50°C can be determined by known methods. For example, the intermediate layer can be made into a sample of a specified size, and the sample can be deformed at a frequency of 1Hz within a specified temperature range using a dynamic viscoelasticity measuring device. The elastic modulus can be measured, and the storage modulus I can be calculated from the measured elastic modulus.

(3.3 Intermediate Layer Composition) As long as the intermediate layer possesses the aforementioned physical properties, its composition is not particularly limited. However, in this embodiment, the intermediate layer is preferably composed of a resin-containing composition (intermediate layer composition). Specifically, the preferred intermediate layer composition contains an acrylic polymer (A) with a weight average molecular weight of 300,000 to 1,500,000 and an energy-curable acrylic polymer (B) with a weight average molecular weight of 50,000 to 250,000. The acrylic polymer (A) can be either non-energy-curable or energy-curable, but in this embodiment, non-energy-curable is preferred.

In addition, unless otherwise specified in this instruction manual, the "weight average molecular weight" is the converted value of polystyrene determined by gel osmosis chromatography (GPC). As a determination performed by this method, for example, a high-speed GPC apparatus "HLC-8120GPC" manufactured by TOSOH, in which high-speed chromatography columns "TSK gurd column H _XL -H", "TSK Gel GMH _XL ", and "TSK Gel G2000H _XL " (all manufactured by TOSOH) are connected in sequence, and the measurement is performed using a differential refractive index meter under the conditions of a chromatography column temperature of 40°C and a liquid feed rate of 1.0 mL/min.

(3.3.1 Acrylic Polymer (A)) As described above, the acrylic polymer (A) can be energy-curable or non-energy-curable. In this embodiment, the case where the acrylic polymer (A) is non-energy-curable will be explained. The acrylic polymer (A) is preferably a non-energy-curable polymer having structural units derived from (meth)acrylates. Specifically, the acrylic polymer (A) is more preferably composed of an acrylic copolymer having structural units derived from alkyl (meth)acrylates (a1) and structural units derived from functionalized monomers (a2).

Alkyl methacrylates with 1 to 18 carbon atoms in the alkyl group can be used as alkyl methacrylates (a1). Specifically, examples include methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, n-pentyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, isooctyl methacrylate, n-decyl methacrylate, n-dodecyl methacrylate, n-tridecyl methacrylate, myristyl methacrylate, palmityl(meth)acrylate, and stearate methacrylate.

The alkyl methacrylate (a1) is preferably an alkyl methacrylate with 4 to 8 carbon atoms in the alkyl group. Specifically, n-butyl methacrylate is preferred. In addition, one alkyl methacrylate (a1) may be used alone or in combination with two or more.

The content of structural units derived from alkyl methacrylate (a1) in acrylic polymer (A) is preferably 50 to 99.5% by mass, more preferably 60 to 99% by mass, and even more preferably 80 to 95% by mass, relative to all structural units (100% by mass) of acrylic polymer (A).

If the content is 50% by mass or more, the retention performance of the adhesive sheet can be improved, and the tracking of the substrate with large unevenness can be improved. In addition, if it is 99.5% by mass or less, the structural units from component (a2) can be ensured to be in a certain amount.

The functional group-containing monomer (a2) is a monomer having functional groups such as hydroxyl, carboxyl, epoxy, amino, cyano, nitrogen-containing cyclo, alkoxysilyl, etc. Preferably, the functional group-containing monomer (a2) is selected from one or more of hydroxyl-containing monomers, carboxyl-containing monomers, and epoxy-containing monomers.

Examples of hydroxyl-containing monomers include hydroxyalkyl esters of methacrylates such as 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 3-hydroxybutyl methacrylate, and 4-hydroxybutyl methacrylate, as well as unsaturated alcohols such as vinyl alcohol and acryl alcohol.

Examples of carboxyl-containing monomers include (meth)acrylic acid, maleic acid, fumaric acid, and itaconic acid.

Examples of epoxy-containing monomers include epoxy-containing (meth)acrylates and non-acrylic epoxy-containing monomers. Examples of epoxy-containing (meth)acrylates include glycidyl (meth)acrylate, β-methyl glycidyl (meth)acrylate, (3,4-epoxycyclohexyl)meth(meth)acrylate, and 3-epoxycyclo-2-hydroxypropyl (meth)acrylate. Examples of non-acrylic epoxy-containing monomers include glycidyl crotonate and allyl glycidyl ether.

A functional group monomer (a2) can be used alone or in combination of two or more.

Among functionalized monomers (a2), carboxyl-containing monomers are preferred, with (meth)acrylic acid being the most preferred and acrylic acid being the most preferred. When a carboxyl-containing monomer is used as the functionalized monomer (a2), the cohesive force of the intermediate layer increases, making it easier to improve the retention properties of the intermediate layer.

The content of structural units derived from functional group monomers (a2) in acrylic polymer (A) is preferably 0.5 to 40% by mass, more preferably 3 to 20% by mass, and even more preferably 5 to 15% by mass, relative to all structural units (100% by mass) of acrylic polymer (A).

If the content of structural units from component (a2) is 0.5% by mass or more, the cohesion of the intermediate layer increases, and it is also easier to make it compatible with component (B). On the other hand, if the content is 40% by mass or less, it can be ensured that the structural units from component (a1) are in a certain quantity.

The acrylic polymer (A) can be a copolymer of (meth)acrylate (a1) and a functionalized monomer (a2), but it can also be a copolymer of (a1), (a2) and other monomers (a3) besides these (a1) and (a2) components.

Other monomers (a3) include, for example, cyclohexyl methacrylate, benzyl methacrylate, isobornyl methacrylate, dicyclopentyl methacrylate, dicyclopentenyl methacrylate, dicyclopentenoxyethyl methacrylate, and other cyclic methacrylates, vinyl acetate, styrene, etc. Other monomers (a3) can be used alone or in combination of two or more.

The content of structural units derived from other monomers (a3) in acrylic polymer (A) is preferably 0 to 20% by mass, more preferably 0 to 10% by mass, and even more preferably 0 to 5% by mass, relative to all structural units (100% by mass) of acrylic polymer (A).

The weight-average molecular weight (Mw) of the acrylic polymer (A) is preferably 300,000 to 1,500,000, more preferably 400,000 to 1,100,000, and even more preferably 450,000 to 900,000. By setting Mw below the above upper limit, the compatibility between the acrylic polymer (A) and the acrylic polymer (B) becomes good. Furthermore, by setting Mw within the above range, the retention performance of the adhesive sheet can be easily improved.

The content of acrylic polymer (A) in the intermediate layer composition is preferably 40 to 95% by mass, more preferably 45 to 90% by mass, relative to the total amount (100% by mass) of the intermediate layer composition.

Furthermore, when the intermediate layer composition is diluted with a diluent such as an organic solvent as described later, the total amount of the intermediate layer composition represents the total amount of solid components excluding the diluent. The same applies to the adhesive layer composition described later.

(3.3.2 Acrylic Polymer (B)) Acrylic polymer (B) is an acrylic polymer that acquires radiopolymerizability through the introduction of radiopolymerizable groups. The weight-average molecular weight (Mw) of acrylic polymer (B) is 50,000 to 250,000. In this embodiment, by using component (B) in the intermediate layer, the convex electrodes can be fully embedded during the backside grinding of the semiconductor wafer before radiopolymerization. Furthermore, radiopolymerization after grinding prevents cohesive failure of the intermediate layer and facilitates easy peeling from the semiconductor wafer.

The weight average molecular weight (Mw) of the acrylic polymer (B) is preferably 60,000 to 220,000, more preferably 70,000 to 200,000, and even more preferably 85,000 to 150,000.

Acrylic polymer (B) is an acrylic polymer incorporating radiopolymerizable groups and having structural units derived from (meth)acrylates. The radiopolymerizable groups in acrylic polymer (B) are preferably incorporated into the side chains of the acrylic polymer. The radiopolymerizable groups can be groups containing radiopolymerizable carbon-carbon double bonds, such as (meth)acrylyl, vinyl, etc., with (meth)acrylyl being preferred.

The acrylic polymer (B) is preferably a reaction product obtained by reacting a polymeric compound (Xb) having energy-emitting radiopolymerizable groups with an acrylic copolymer (B0), said acrylic copolymer (B0) having structural units derived from alkyl (meth)acrylate (b1) and structural units derived from functionalized monomers (b2).

Alkyl methacrylates with 1 to 18 carbon atoms in the alkyl group can be used as (meth)acrylate (b1). Specific examples include compounds listed as component (a1). Preferably, the (meth)acrylate (b1) is an alkyl methacrylate with 4 to 8 carbon atoms in the alkyl group. Specifically, n-butyl methacrylate is preferred. Furthermore, these alkyl methacrylates can be used alone or in combination of two or more.

The content of structural units derived from alkyl methacrylate (b1) in the acrylic copolymer (B0) is preferably 50-95% by mass, more preferably 60-85% by mass, and even more preferably 65-80% by mass, relative to all structural units (100% by mass) of all structural units in the acrylic copolymer (B0). If this content is 50% by mass or more, the shape of the formed intermediate layer can be adequately maintained. Furthermore, if it is 95% by mass or less, it can be ensured that the structural units derived from component (b2), which serve as the reaction site with the polymerizable compound (Xb), are present in a certain amount.

As a functionalized monomer (b2), examples of monomers having the functional groups exemplified in the above-described functionalized monomers (a2) can be listed, preferably selected from one or more of hydroxyl-containing monomers, carboxyl-containing monomers, and epoxy-containing monomers. As specific compounds of these functionalized monomers, compounds identical to those exemplified by components (a2) can be shown.

Furthermore, as a functionalized monomer (b2), hydroxyl-containing monomers are preferred, among which, various hydroxyalkyl esters of (meth)acrylate, such as 2-hydroxyethyl (meth)acrylate, are even more preferred. By using hydroxyalkyl esters of (meth)acrylate, it is easier to react the polymerizable compound (Xb) with the acrylic copolymer (B0).

Furthermore, the functional groups in the functionalized monomer (a2) used in the acrylic polymer (A) and the functionalized monomer (b2) used in the acrylic polymer (B) may be the same or different, but they are preferably different. That is, for example, if the functionalized monomer (a2) is a carboxyl-containing monomer, then the functionalized monomer (b2) is preferably a hydroxyl-containing monomer. In this way, when the functional groups are different, the acrylic polymer (B) can be crosslinked preferentially, for example, by a crosslinking agent described later, which makes it easier to improve the retention performance of the adhesive sheet.

The content of structural units derived from functionalized monomers (b2) in the acrylic copolymer (B0) is preferably 10-45% by mass, more preferably 15-40% by mass, and even more preferably 20-35% by mass, relative to all structural units (100% by mass) of the acrylic copolymer (B0). If it is 10% by mass or more, it ensures a greater number of reaction sites with the polymerizable compound (Xb), facilitating the introduction of energy-emitting polymerizable groups into the side chains. Furthermore, if it is 45% by mass or less, it ensures sufficient maintenance of the shape of the formed intermediate layer.

Acrylic copolymers (B0) can be copolymers of alkyl methacrylates (b1) and functionalized monomers (b2), but can also be copolymers of components (b1), (b2), and other monomers (b3) besides these components (b1) and (b2).

As other units (b3), the units exemplified above as unit (a3) can be listed.

The content of structural units derived from other monomers (b3) in the acrylic copolymer (B0) is preferably 0 to 30% by mass, more preferably 0 to 10% by mass, and even more preferably 0 to 5% by mass, relative to all structural units (100% by mass) of the acrylic copolymer (B0).

Polymerizable compounds (Xb) are compounds having energy-emitting polymerizable groups and substituents (hereinafter sometimes referred to as "reactive substituents") that can react with functional groups in structural units of acrylic copolymers (B0) derived from component (b2).

As mentioned above, examples of energy-emitting polymerizable groups include (meth)acrylyl and vinyl groups, with (meth)acrylyl being the preferred choice. Furthermore, the polymerizable compound (Xb) is preferably a compound having 1 to 5 energy-emitting polymerizable groups per molecule.

As a reactive substituent in the polymerizable compound (Xb), it can be appropriately modified according to the functional groups possessed by the functional group-containing monomer (b2). For example, isocyanate groups, carboxyl groups, epoxy groups, etc. can be listed. From the perspective of reactivity, isocyanate groups are preferred. When the polymerizable compound (Xb) has isocyanate groups, for example, when the functional group of the functional group-containing monomer (b2) is a hydroxyl group, it can readily react with acrylic copolymers (B0).

Specific polymerizable compounds (Xb) include, for example, (meth)acryloxyethyl isocyanate, m-isopropenyl-α,α-dimethylbenzyl isocyanate, (meth)acrylyl isocyanate, allyl isocyanate, (meth)acrylate glycidyl ester, (meth)acrylic acid, etc. These polymerizable compounds (Xb) can be used alone or in combination of two or more.

Among these, from the perspective of compounds having isocyanate groups suitable for use as the above-mentioned reactive substituents and having an appropriate distance between the main chain and the energy-emitting polymerizable groups, (meth)acrylic oxyethyl isocyanate is preferred.

The polymeric compound (Xb) is preferably reacted with 40 to 98 functional groups of the acrylic polymer (B) derived from the functional group monomer (b2) in a total amount (100 equivalents), more preferably with 60 to 90 functional groups, and even more preferably with 70 to 85 functional groups.

In the intermediate layer composition, the content of acrylic polymer (B) is preferably 5 to 60 parts by mass relative to 100 parts by mass of acrylic polymer (A), and more preferably 10 to 50 parts by mass. By setting the content of component (B) to a smaller amount, the intermediate layer can easily follow the unevenness of the semiconductor wafer.

(3.3.3 Crosslinking Agent) The intermediate layer composition preferably further contains a crosslinking agent. Examples of crosslinking agents include isocyanate crosslinking agents, epoxy crosslinking agents, aziridine crosslinking agents, and metal chelate crosslinking agents, with isocyanate crosslinking agents being preferred. If an isocyanate crosslinking agent is used, then, for example, when component (B) has a hydroxyl group, the crosslinking agent preferentially crosslinks with the acrylic polymer (B).

Intermediate layers are cross-linked using crosslinking agents, for example, by heating after coating. Because the crosslinking agents include acrylic polymers, especially low molecular weight acrylic polymers (B), the intermediate layers can properly form a coating film and easily perform their function as intermediate layers.

The crosslinking agent content is preferably 0.1 to 10 parts by weight relative to 100 parts by weight of acrylic polymer (A), more preferably 0.5 to 7 parts by weight, and even more preferably 1 to 5 parts by weight.

As isocyanate crosslinking agents, polyisocyanate compounds can be listed. Specific examples of polyisocyanate compounds include aromatic polyisocyanates such as toluene diisocyanate, diphenylmethane diisocyanate, and xylene diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate; and alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate. Furthermore, their biuret forms, isocyanurate esters, and adducts as reaction products with low-molecular-weight, reactive hydrogen compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil can also be listed.

These isocyanate crosslinkers can be used alone or in combination of two or more. In addition, polyol adducts (such as trimethylolpropane) of aromatic polyisocyanates such as toluene diisocyanate are preferred.

In addition, examples of epoxy crosslinking agents include 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-m-phenylenediamine, ethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trihydroxypropane diglycidyl ether, diglycidylaniline, and diglycidylamine. These epoxy crosslinking agents can be used alone or in combination of two or more.

Metal chelate crosslinking agents include, for example, compounds formed by coordination of acetoacetone, ethyl acetoacetate, tris(2,4-pentanedione) with polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium. These metal chelate crosslinking agents can be used alone or in combination of two or more.

Examples of aziridinium crosslinking agents include diphenylmethane-4,4'-bis(1-aziridinium methylamine), trihydroxymethylpropane tri-β-aziridinium propionate, tetrahydroxymethylmethane tri-β-aziridinium propionate, toluene-2,4-bis(1-aziridinium methylamine), triethylene melamine, bis(2-methylaziridinium)-1-(2-methylaziridinium), tri-1-(2-methylaziridinium)phosphine, trihydroxymethylpropane tri-β-(2-methylaziridinium) propionate, and hexa[1-(2-methyl)-aziridinyl]triphosphatriazine.

(3.3.4 Photopolymerization Initiator) The intermediate layer composition preferably further contains a photopolymerization initiator. By including a photopolymerization initiator in the intermediate layer composition, the intermediate layer composition can be easily cured by energy radiation such as ultraviolet light.

Examples of photopolymerization initiators include acetophenone, 2,2-diethoxybenzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, milchnerone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzyl diphenyl sulfide, tetramethylthiuram monosulfide, benzyl dimethyl ketone, dibenzyl, diacetyl, 1-chloroanthraquinone, 2-chloroanthraquinone, 2-ethylanthraquinone, 2,2-dimethoxy-1,2-diphenylethane-1-one, and 1-hydroxyl. Low molecular weight polymerization initiators such as cyclohexylphenyl ketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinylacetone-1,2-benzyl-2-dimethylamino-1-(4-morpholinylphenyl)-butanone-1,2-hydroxy-2-methyl-1-phenyl-propane-1-one, diethylthiotonone, isopropylthiotonone, and 2,4,6-trimethylbenzyldiphenylphosphine oxide, as well as oligomerized polymerization initiators such as oligomerized {2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]acetone}, are available. These photopolymerization initiators can be used alone or in combination of two or more. Among them, 1-hydroxycyclohexylphenyl ketone is preferred.

In order to ensure sufficient curing even when the content of acrylic polymer (B) is low, the content of photopolymerization initiator is preferably 1 to 10 parts by weight, and more preferably 2 to 8 parts by weight, relative to 100 parts by weight of acrylic polymer (A).

Without impairing the effectiveness of the invention, the intermediate layer composition may also contain other additives. Examples of other additives include, for instance, antioxidants, softeners (plasticizers), fillers, rust inhibitors, pigments, dyes, and tackifiers. When these additives are present, the content of each additive is preferably 0.01 to 6 parts by weight, more preferably 0.01 to 2 parts by weight, relative to 100 parts by weight of the acrylic polymer (A).

Furthermore, the storage modulus and loss tangent of the intermediate layer can be adjusted, for example, when using acrylic polymers (B), by adjusting the type and amount of monomers constituting acrylic polymer (B), and the amount of energy-intensive polymerizable groups introduced into the acrylic polymer (B). For example, the storage modulus tends to increase when the amount of energy-intensive polymerizable groups is increased. Moreover, it can also be appropriately adjusted by adjusting the amount of crosslinking agents and photopolymerization initiators incorporated into the intermediate layer.

(4. Adhesive Layer) An adhesive layer is attached to the electrical surface of the semiconductor wafer, protecting and supporting the semiconductor wafer until it is peeled off. In this embodiment, the adhesive layer, together with the intermediate layer, fully follows the irregularities formed on the surface of the semiconductor wafer, embedding the irregularities into the semiconductor processing protective sheet. As a result, even when the semiconductor wafer is ground to a very thin thickness and force is applied to the convex electrodes, the semiconductor processing protective sheet can adequately protect the convex electrodes, etc. Furthermore, even when the semiconductor wafer is monolithically processed, contact between semiconductor chips can be suppressed. In addition, the adhesive layer can consist of a single layer (monolayer) or multiple layers (two or more).

There is no particular limitation on the thickness of the adhesive layer, as long as it is sufficient to adequately support the semiconductor wafer. In this embodiment, the thickness of the adhesive layer is preferably 5 μm to 500 μm, and more preferably 8 μm to 100 μm. Furthermore, the thickness of the adhesive layer refers to the overall thickness of the adhesive layer. For example, the thickness of an adhesive layer composed of multiple layers refers to the total thickness of all layers constituting the adhesive layer.

In this embodiment, the adhesive layer has the following physical properties.

(4.1 Storage Modulus A of Adhesive Layer) As described above, the storage modulus (G’) of the adhesive layer at 50°C is denoted by storage modulus A. Storage modulus A is not limited as long as it meets the range of "A/I" described above. In this embodiment, storage modulus A is preferably 0.03 MPa or more and 0.15 MPa or less. Furthermore, storage modulus A is more preferably 0.04 MPa or more, and even more preferably 0.12 MPa or more. Furthermore, storage modulus A is more preferably 0.05 MPa or less, and even more preferably 0.10 MPa or less. Additionally, in this embodiment, when the adhesive layer has energy-curable properties, storage modulus A is the storage modulus before energy-curing.

The storage modulus (storage modulus A) of the adhesive layer at 50°C can be determined by known methods. For example, the adhesive layer can be made into a sample of a specified size, and the sample can be deformed at a frequency of 1Hz within a specified temperature range using a dynamic viscoelasticity measuring device. The elastic modulus can be measured, and the storage modulus A can be calculated from the measured elastic modulus.

(4.2 Adhesive Layer Composition) The composition of the adhesive layer is not particularly limited as long as it possesses the aforementioned physical properties. In this embodiment, the adhesive layer is preferably composed of a resin-containing composition (adhesive layer composition). Specifically, the adhesive layer composition is preferably energy-curable. By making the adhesive layer composition energy-curable, it possesses high adhesion to the semiconductor wafer before energy irradiation, and after energy irradiation, the adhesive layer undergoes a decrease in adhesion due to curing. Even when the semiconductor wafer, as the adhered object, is monolithically detached, it is easily peeled from the monolithically detached semiconductor wafer.

The adhesive layer composition for forming the adhesive layer contains, for example, acrylic polymers, polyurethanes, rubber polymers, polyolefins, and silicone, as adhesive components (adhesive resins) that enable the adhesive layer to exhibit adhesiveness. Among these, acrylic polymers are preferred.

For adhesive layer compositions forming adhesive layers, energy-curable properties can be acquired by incorporating energy-curable compounds different from those of the adhesive resin, but preferably the adhesive resin itself has energy-curable properties. When the adhesive resin itself has energy-curable properties, energy-polymerizable groups are introduced into the adhesive resin, preferably in the main chain or side chain of the adhesive resin.

Furthermore, when a radioactive compound different from the adhesive resin is incorporated, a monomer or oligomer having radioactive polymerizable groups can be used as the radioactive compound. The oligomer is a weight-average molecular weight (Mw) less than 10,000, such as urethane(meth)acrylate. Moreover, even when the adhesive resin itself is radioactively curable, a radioactive compound can be incorporated into the adhesive layer composition in addition to the adhesive resin.

The following is a more detailed explanation of the case where the adhesive layer is made of an acrylic polymer (hereinafter also referred to as "acrylic polymer (C)").

(4.2.1 Acrylic Polymers (C)) Acrylic polymers (C) are acrylic polymers with energy-emitting polymerizable groups and structural units derived from (meth)acrylates. The energy-emitting polymerizable groups are preferably introduced into the side chains of the acrylic polymer.

The acrylic polymer (C) is preferably a reaction product obtained by reacting a polymeric compound (Xc) having energy-emitting radiopolymerizable groups with an acrylic copolymer (C0), said acrylic copolymer (C0) having structural units derived from alkyl (meth)acrylate (C1) and structural units derived from functionalized monomers (C2).

As the alkyl methacrylate (c1), alkyl methacrylates with 1 to 18 carbon atoms in the alkyl group can be used. Specific examples include alkyl methacrylates with 1 to 18 carbon atoms in the alkyl group listed as component (a1). Preferably, the alkyl methacrylate (c1) is an alkyl methacrylate with 4 to 8 carbon atoms in the alkyl group. Specifically, 2-ethylhexyl methacrylate and n-butyl methacrylate are preferred, with n-butyl methacrylate being more preferred. Furthermore, these alkyl methacrylates can be used alone or in combination of two or more.

From the perspective of improving the adhesive force of the formed adhesive layer, the content of the structural unit derived from (meth)acrylate (c1) in the acrylic copolymer (C0) is preferably 50-99% by mass, more preferably 60-97% by mass, and even more preferably 70-96% by mass, relative to all structural units (100% by mass) of the acrylic copolymer (C0).

For example, in addition to 2-ethylhexyl (meth)acrylate and n-butyl (meth)acrylate mentioned above, alkyl (meth)acrylate (C1) may also contain ethyl (meth)acrylate and methyl (meth)acrylate. By including these monomers, the adhesive properties of the adhesive layer can be easily adjusted to the desired adhesive properties.

As a functional group-containing monomer (c2), examples of monomers having the functional groups exemplified by the functional group-containing monomer (a2) described above can be listed. Specifically, one or more of hydroxyl-containing monomers, carboxyl-containing monomers, and epoxy-containing monomers are preferred. As specific compounds of these functional group-containing monomers, compounds identical to those exemplified by component (a2) can be shown.

As a functional group-containing monomer (c2), among the above monomers, hydroxyl-containing monomers are more preferred, among which hydroxyalkyl esters of (meth)acrylate are more preferred, 2-hydroxyethyl esters of (meth)acrylate and 4-hydroxybutyl esters of (meth)acrylate are further preferred, and 4-hydroxybutyl esters of (meth)acrylate are particularly preferred.

By using hydroxyalkyl methacrylate as the (C2) component, the reaction between the polymerizable compound (XC) and the acrylic copolymer (C0) is made easier. In addition, when 4-hydroxybutyl methacrylate is used, the tensile strength of the intermediate layer is increased, which helps to prevent the formation of residues.

The content of structural units derived from functional monomers (c2) in acrylic copolymers (C0) is preferably 1 to 40% by mass, more preferably 2 to 35% by mass, and even more preferably 3 to 30% by mass, relative to all structural units (100% by mass) of the acrylic copolymer (C0).

If the content is 1% by mass or more, a certain amount of functional groups that act as reaction sites with the polymerizable compound (Xc) can be ensured. Therefore, the adhesive layer can be properly cured by irradiation with energy rays, thus reducing the adhesive force after irradiation. Furthermore, it is easy to improve the interlaminar strength between the adhesive layer and the intermediate layer after irradiation with energy rays. In addition, if the content is 40% by mass or less, a sufficient pot life can be ensured when the adhesive layer is formed by applying a solution of the composition.

Acrylic copolymers (C0) can be copolymers of alkyl (meth)acrylate (C1) and functionalized monomers (C2), but can also be copolymers of (C1) component, (C2) component, and other monomers (C3) besides these (C1) and (C2) components.

As other units (c3), the units exemplified above as unit (a3) can be listed.

The content of structural units derived from other monomers (c3) in the acrylic copolymer (C0) is preferably 0 to 30% by mass, more preferably 0 to 10% by mass, and even more preferably 0 to 5% by mass, relative to all structural units (100% by mass) of the acrylic copolymer (C0).

Similar to the polymerizable compound (Xb) described above, the polymerizable compound (Xc) is a compound having energy-emitting polymerizable groups and substituents (reactive substituents) that can react with functional groups in the structural units of the acrylic copolymer (C0) derived from the (C2) component, preferably a compound having 1 to 5 energy-emitting polymerizable groups per molecule.

Specific examples of reactive substituents and energy-polymerizable groups are the same as those of polymerizable compound (Xb), therefore, isocyanate groups are preferred for reactive substituents, and (meth)acrylic groups are preferred for energy-polymerizable groups.

Furthermore, as a specific polymerizable compound (Xc), examples of compounds identical to those exemplified by the polymerizable compound (Xb) described above can be listed, with (meth)acrylic oxyethyl isocyanate being a preferred choice. Additionally, two or more polymerizable compounds (Xc) can be used alone or in combination.

The polymeric compound (Xc) is preferably reacted with 30 to 98 equivalents of the total amount (100 equivalents) of functional groups from the functional group-containing monomer (C2) in the acrylic polymer (C0), and more preferably with 40 to 95 equivalents of functional groups.

The weight average molecular weight (Mw) of the acrylic polymer (C) is preferably 100,000 to 1,500,000, more preferably 250,000 to 1,000,000, and even more preferably 350,000 to 800,000. With such a Mw, the adhesive layer can be endowed with appropriate adhesion.

Even when the adhesive resin has energy-curing properties, it is preferable that the adhesive layer composition contains an energy-curing compound other than the adhesive resin. As such an energy-curing compound, monomers or oligomers that have unsaturated groups in their molecules and can be polymerized and cured by irradiation with energy rays are preferred.

Specifically, examples include trimethylolpropane tri(meth)acrylate, pentaerythritol (meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol (meth)acrylate and other poly(meth)acrylate monomers, urethane (meth)acrylate, polyester (meth)acrylate, polyether (meth)acrylate, epoxy (meth)acrylate and other oligomers.

Among them, from the perspective of higher molecular weight and less reduction of the elastic modulus of the adhesive layer, urethane (meth)acrylate oligomers are preferred.

(4.2.2 Crosslinking Agent) The adhesive layer composition preferably further contains a crosslinking agent. The adhesive layer composition is crosslinked, for example, by heating after coating, using the crosslinking agent. In the adhesive layer, the acrylic polymer (C) is crosslinked by the crosslinking agent, thereby enabling suitable film formation and facilitating its function as an adhesive layer.

Crosslinking agents include isocyanate crosslinking agents, epoxy crosslinking agents, aziridine crosslinking agents, and chelate crosslinking agents, with isocyanate crosslinking agents being preferred. Crosslinking agents can be used alone or in combination of two or more. Furthermore, specific examples of isocyanate crosslinking agents include those exemplified as crosslinking agents that can be used in intermediate layer compositions, and the preferred isocyanate crosslinking agents are also the same.

The crosslinking agent content is preferably 0.01 to 10 parts by weight, more preferably 0.1 to 7 parts by weight, and even more preferably 0.3 to 4 parts by weight, relative to 100 parts by weight of acrylic polymer (C).

(4.2.3 Photopolymerization Initiator) The adhesive layer composition preferably further contains a photopolymerization initiator. Examples of photopolymerization initiators exemplified above as photopolymerization initiators used in the intermediate layer composition can be listed as such. Furthermore, the photopolymerization initiator can be used alone or in combination of two or more. Among the aforementioned photopolymerization initiators, 2,2-dimethoxy-1,2-diphenylethane-1-one and 1-hydroxycyclohexylphenylone are preferred.

The preferred content of the photopolymerization initiator is 0.5 to 15 parts by weight, more preferably 1 to 12 parts by weight, and even more preferably 4.5 to 10 parts by weight, relative to 100 parts by weight of acrylic polymer (C).

Without impairing the effectiveness of the invention, the adhesive layer composition may also contain other additives. Examples of other additives include, for instance, tackifiers, antioxidants, softeners (plasticizers), fillers, rust inhibitors, pigments, and dyes. When these additives are present, the content of each additive is preferably 0.01 to 6 parts by weight, more preferably 0.02 to 2 parts by weight, relative to 100 parts by weight of the acrylic polymer (C).

Furthermore, the storage modulus and loss tangent of the adhesive layer, for example, when using acrylic polymers (C), can be adjusted by the type and amount of monomers constituting the acrylic polymer (C), and the amount of energy-intensive polymerizable groups introduced into the acrylic polymer (C). For example, the elastic modulus tends to increase when the amount of energy-intensive polymerizable groups is increased. Moreover, it can also be appropriately adjusted by the amount of crosslinking agents and photopolymerization initiators incorporated into the adhesive layer.

(5. Buffer Layer) As shown in Figure 1B, a buffer layer is formed on the main surface of the substrate opposite to the main surface where the adhesive layer is formed. The buffer layer 40 is softer than the substrate, relieving stress during grinding of the back side of the semiconductor wafer and preventing cracks and defects. Furthermore, during back side grinding, the semiconductor wafer with the semiconductor processing protective sheet attached is positioned on the vacuum table through the protective sheet. However, due to the buffer layer serving as the structural layer for the semiconductor processing protective sheet, it is easily and properly held on the vacuum table.

The thickness of the buffer layer is preferably 1~100μm, more preferably 5~80μm, and even more preferably 10~60μm. By setting the thickness of the buffer layer within the above range, the buffer layer can properly relieve the stress during grinding of the back side.

The buffer layer can be a layer formed by a combination of buffer layers containing energy-emitting polymerizable compounds, or it can be a polypropylene film, an ethylene-vinyl acetate copolymer film, an ionomer resin film, an ethylene-(meth)acrylic acid copolymer film, an ethylene-(meth)acrylic acid copolymer film, an LDPE film, an LLDPE film, etc.

In addition, a substrate with a cushioning layer can be obtained by laminating a cushioning layer on one or both sides of the substrate.

(5.1 Components for Cushioning Layers) Components for cushioning layers containing energy-emitting polymerizable compounds can be cured by irradiation with energy rays.

Furthermore, more specifically, the buffer composition containing an energy-emitting polymerizable compound preferably contains urethane (meth)acrylate (d1) and a polymerizable compound (d3) having an alicyclic or heterocyclic group having 6 to 20 ring atoms. In addition to the components (d1) and (d3) mentioned above, the buffer composition may also contain a multifunctional polymerizable compound (d2) and/or a polymerizable compound having functional groups (d4). Furthermore, in addition to the components mentioned above, the buffer composition may also contain a photopolymerization initiator. Moreover, the buffer composition may also contain other additives or resin components, to the extent that it does not impair the effects of the invention.

The following is a detailed description of the components contained in the buffer layer composition containing the energy-emitting polymerizable compound.

(5.1.1 Carbamate (Meth)acrylate (d1)) Carbamate (meth)acrylate (d1) is a compound having at least a (meth)acrylic group and a carbamate bond, possessing the property of polymerizing and curing upon exposure to energetic radiation. Carbamate (meth)acrylate (d1) is either an oligomer or a polymer.

The weight-average molecular weight (Mw) of component (d1) is preferably 1,000 to 100,000, more preferably 2,000 to 60,000, and even more preferably 3,000 to 20,000. In addition, the number of (meth)acrylic acid groups in component (d1) (hereinafter also referred to as "functional group number") can be monofunctional, difunctional, or trifunctional or above, but monofunctional or difunctional is preferred.

Component (d1) can be obtained by reacting a hydroxyl-containing (meth)acrylate with a terminal isocyanate urethane prepolymer, which is obtained by reacting a polyol compound with a polyisocyanate compound. Alternatively, component (d1) can be used alone or in combination with two or more other components.

The polyol compound used as a raw material for component (d1) is not particularly limited as long as it has two or more hydroxyl groups. It can be any of the following: difunctional diol, trifunctional triol, or polyol with more than four functions, but difunctional diols are preferred, and polyester-type diols or polycarbonate-type diols are even more preferred.

Examples of polyisocyanate compounds include aliphatic polyisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, and trimethylhexamethylene diisocyanate; alicyclic diisocyanates such as isophorone diisocyanate, norbornene diisocyanate, dicyclohexylmethane-4,4’-diisocyanate, dicyclohexylmethane-2,4’-diisocyanate, and ω,ω’-diisocyanate dimethylcyclohexane; and aromatic diisocyanates such as 4,4’-diphenylmethane diisocyanate, toluene diisocyanate, xylene diisocyanate, dimethylbiphenyl diisocyanate, tetramethylene xylene diisocyanate, and naphthalene-1,5-diisocyanate.

Among them, isophorone diisocyanate, hexamethylene diisocyanate, and xylene diisocyanate are preferred.

Urea (meth)acrylate (d1) can be obtained by reacting a hydroxyl-containing (meth)acrylate with a terminal isocyanate urethane prepolymer, wherein the terminal isocyanate urethane prepolymer is obtained by reacting the aforementioned polyol compound with a polyisocyanate compound. There is no particular limitation on the hydroxyl-containing (meth)acrylate, as long as it is a compound having both a hydroxyl group and a (meth)acrylic group in at least one molecule.

Specific examples of hydroxyl-containing (meth)acrylates include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 4-hydroxycyclohexyl (meth)acrylate, 5-hydroxycyclooctyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, pentaerythritol tri(meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, and other hydroxyalkyl (meth)acrylates; N-hydroxymethyl (meth)acrylamide and other hydroxyl-containing (meth)acrylamides; and reaction products obtained by reacting (meth)acrylate with vinyl alcohol, vinyl phenol, or diglycidyl esters of bisphenol A.

Among them, hydroxyalkyl methacrylate is preferred, and 2-hydroxyethyl methacrylate is even more preferred.

As for the conditions for reacting the terminal isocyanate urethane prepolymer and the hydroxyl-containing (meth)acrylate, it is preferred to react at 60~100°C for 1~4 hours in the presence of solvent and catalyst added as needed.

The content of component (d1) in the buffer layer composition is preferably 10 to 70% by mass, more preferably 20 to 60% by mass, and even more preferably 25 to 55% by mass, relative to the total amount (100% by mass) of the buffer layer composition.

(5.1.2 Multifunctional Polymerizable Compounds (d2)) Multifunctional polymerizable compounds are compounds having two or more photopolymerizable unsaturated groups. These photopolymerizable unsaturated groups are functional groups containing carbon-carbon double bonds, such as (meth)acrylonitrile, vinyl, allyl, and vinylbenzyl. Two or more photopolymerizable unsaturated groups can also be used in combination. A three-dimensional network structure (crosslinked structure) is formed by reacting the photopolymerizable unsaturated groups in the multifunctional polymerizable compound with the (meth)acrylonitrile group in component (d1), or by reacting the photopolymerizable unsaturated groups in component (d2) with each other. When using multifunctional polymeric compounds, compared to using compounds containing only one photopolymerizable unsaturated group, the increased cross-linking structures formed by irradiation with energy rays result in a buffer layer exhibiting unique viscoelasticity, effectively mitigating stress during back-side grinding.

Furthermore, there is overlap between the definition of component (d2) and the definitions of component (d3) or component (d4) described later, but the overlapping portion is included in component (d2). For example, a compound having an alicyclic or heterocyclic group with 6 to 20 cyclic atoms and having two or more (meth)acrylic acid groups is included in both definitions of component (d2) and component (d3), but in this invention, such a compound is considered to be included in component (d2). Similarly, a compound containing functional groups such as hydroxyl, epoxy, amide, or amino groups and having two or more (meth)acrylic acid groups is included in both definitions of component (d2) and component (d4), but in this invention, such a compound is considered to be included in component (d2).

From the above perspective, the number of photopolymerizable unsaturated groups (functional groups) in multifunctional polymerizable compounds is preferably 2 to 10, and more preferably 3 to 6.

In addition, the weight average molecular weight of component (d2) is preferably 30 to 40,000, more preferably 100 to 10,000, and even more preferably 200 to 1,000.

Specific components (d2) may include, for example, diethylene glycol di(meth)acrylate, ethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, trihydroxymethylpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, divinylbenzene, vinyl(meth)acrylate, divinyl adipate, N,N'-methylenebis(meth)acrylamide, etc. Dipentaerythritol hexa(meth)acrylate is preferred. Furthermore, components (d2) can be used alone or in combination of two or more.

The content of component (d2) in the buffer layer composition is preferably 0 to 40% by mass, more preferably 3 to 20% by mass, and even more preferably 5 to 15% by mass, relative to the total amount (100% by mass) of the buffer layer composition.

(5.1.3 Polymerizable compound (d3) having an alicyclic or heterocyclic group having 6 to 20 ring atoms) Component (d3) is a polymerizable compound having an alicyclic or heterocyclic group having 6 to 20 ring atoms, and preferably a compound having at least one (meth)acrylonitrile group, more preferably a compound having one (meth)acrylonitrile group. By using component (d3), the film-forming properties of the resulting buffer layer composition can be improved.

Furthermore, there is overlap between the definition of component (d3) and the definition of component (d4) described later, but the overlapping part is included in component (d4). For example, a compound having at least one (meth)acrylic acid group, an alicyclic or heterocyclic group having 6 to 20 cyclic atoms, and functional groups such as hydroxyl, epoxy, amide, and amino groups is included in both definitions of component (d3) and component (d4), but in this invention, such a compound is considered to be included in component (d4).

Specific examples of ingredient (d3) include isobornyl methacrylate, dicyclopentenyl methacrylate, dicyclopentyl methacrylate, dicyclopentenoxy methacrylate, cyclohexyl methacrylate, and azurane methacrylate, which are methacrylates containing alicyclic groups; and tetrahydrofurfuryl methacrylate and morpholine(meth)acrylate, which are methacrylates containing heterocyclic groups. Furthermore, ingredient (d3) can be used alone or in combination with two or more other ingredients.

Among (meth)acrylates containing alicyclic groups, isobornyl (meth)acrylate is preferred, and among (meth)acrylates containing heterocyclic groups, tetrahydrofurfuryl (meth)acrylate is preferred.

The content of component (d3) in the buffer layer composition is preferably 10 to 80% by mass, more preferably 20 to 70% by mass, and even more preferably 25 to 60% by mass, relative to the total amount (100% by mass) of the buffer layer composition.

(5.1.4 Polymerizable Compounds with Functional Groups (d4)) Component (d4) is a polymerizable compound containing functional groups such as hydroxyl, epoxy, amide, and amino groups, and preferably a compound having at least one (meth)acrylic group, more preferably a compound having one (meth)acrylic group.

Component (d4) and component (d1) are well compatible, making it easy to adjust the viscosity of the buffer layer composition to an appropriate range. Furthermore, even when the buffer layer is made thin, the cushioning performance remains good.

As a component (d4), examples include (meth)acrylates containing hydroxyl groups, compounds containing epoxy groups, compounds containing amide groups, and (meth)acrylates containing amino groups. Among these, (meth)acrylates containing hydroxyl groups are preferred.

Examples of hydroxyl-containing (meth)acrylates include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, phenylhydroxypropyl (meth)acrylate, and 2-hydroxy-3-phenoxypropyl acrylate. Among these, hydroxyl-containing (meth)acrylates with aromatic rings, such as phenylhydroxypropyl (meth)acrylate, are more preferred. Furthermore, component (d4) can be used alone or in combination of two or more.

In order to improve the film-forming properties of the buffer layer composition, the content of component (d4) in the buffer layer composition is preferably 0 to 40% by mass, more preferably 7 to 35% by mass, and even more preferably 10 to 30% by mass, relative to the total amount (100% by mass) of the buffer layer composition.

(5.1.5 Polymer compounds (d5) other than components (d1) to (d4)) Without impairing the effectiveness of the invention, the buffer layer composition may also contain polymer compounds (d5) other than the aforementioned components (d1) to (d4).

Examples of components (d5) include alkyl (meth)acrylates having alkyl groups having 1 to 20 carbon atoms, styrene, hydroxyethyl vinyl ether, hydroxybutyl vinyl ether, N-vinylmethylamine, N-vinylpyrrolidone, N-vinylcaprolactam, and other vinyl compounds. Furthermore, components (d5) can be used alone or in combination of two or more.

The content of component (d5) in the buffer layer composition is preferably 0-20% by mass, more preferably 0-10% by mass, further preferably 0-5% by mass, and especially preferably 0-2% by mass.

(5.1.6 Photopolymerization Initiator) From the perspective of shortening the photopolymerization time and reducing the amount of light irradiation during buffer layer formation, the buffer layer composition preferably further contains a photopolymerization initiator.

Examples of photopolymerization initiators include benzoin compounds, acetophenone compounds, phosphine oxide compounds, titanium cyclohexane compounds, thiatonone compounds, peroxides, and photosensitizers such as amines or quinones. More specifically, examples include 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propane-1-one, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzylphenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, bibenzyl, diacetyl, 8-chloroanthraquinone, and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide. These photopolymerization initiators can be used alone or in combination of two or more.

The content of photopolymerization initiator in the buffer layer composition is preferably 0.05 to 15 parts by mass relative to 100 parts by mass of the total energy-emitting polymerizable compound, more preferably 0.1 to 10 parts by mass, and even more preferably 0.3 to 5 parts by mass.

(5.1.7 Other Additives) Without impairing the effectiveness of the invention, the buffer layer composition may also contain other additives. Examples of other additives include, for instance, antistatic agents, antioxidants, softeners (plasticizers), fillers, rust inhibitors, pigments, dyes, etc. When these additives are incorporated, the content of each additive in the buffer layer composition is preferably 0.01 to 6 parts by weight, more preferably 0.1 to 3 parts by weight, relative to 100 parts by weight of the total energy-emitting polymerizable compound.

A buffer layer is obtained by polymerizing and curing a buffer layer composition containing an energy-emitting polymerizable compound by irradiating it with energy rays. That is, the buffer layer is a product formed by curing a buffer layer composition.

Therefore, the buffer layer preferably contains polymer units from component (d1) and polymer units from component (d3). Furthermore, the buffer layer may also contain polymer units from component (d2) and/or polymer units from component (d4), and may also contain polymer units from component (d5). The proportion of each polymer unit in the buffer layer is generally consistent with the proportion (addition ratio) of each component in the composition constituting the buffer layer.

(6. Peel-off Sheet) A peel-off sheet can be attached to the surface of the semiconductor processing protective sheet. Specifically, the peel-off sheet is attached to the surface of the adhesive layer of the semiconductor processing protective sheet. The peel-off sheet protects the adhesive layer during transportation and storage by being attached to its surface. The peel-off sheet is attached to the semiconductor processing protective sheet in a peelable manner and is removed by peeling it off before using the semiconductor processing protective sheet (i.e., before attaching the wafer).

A peeling sheet is a peeling sheet in which at least one side has been treated with a peeling agent. Specifically, peeling sheets made by coating a peeling agent on the surface of a peeling sheet substrate can be listed.

As the substrate for the peeling sheet, a resin film is preferred. Examples of resins constituting the resin film include polyester resin films such as polyethylene terephthalate (PET), polybutylene terephthalate (PET), and polyethylene naphthalate (PET), as well as polyolefin resins such as polypropylene and polyethylene. Examples of peeling agents include rubber elastomers such as organosilicon resins, olefin resins, isoprene resins, and butadiene resins, long-chain alkyl resins, alkyd resins, and fluorinated resins.

There is no particular limitation on the thickness of the peel, but 10~200μm is preferred, and 20~150μm is even more preferred.

(7. Method for Manufacturing a Protective Sheet for Semiconductor Processing) The method for manufacturing the protective sheet for semiconductor processing according to this embodiment is not particularly limited, as long as it enables the formation of an intermediate layer and an adhesive layer on one main surface of the substrate and a buffer layer on the other main surface of the substrate; any known method may be used.

First, for example, an intermediate layer composition containing the above-mentioned components, or a composition obtained by diluting the intermediate layer composition with a solvent, is prepared as a composition for forming an intermediate layer. Similarly, for example, an adhesive layer composition containing the above-mentioned components, or a composition obtained by diluting the adhesive layer composition with a solvent, is prepared as an adhesive layer composition for forming an adhesive layer. Likewise, for example, a buffer layer composition containing the above-mentioned components, or a composition obtained by diluting the buffer layer composition with a solvent, is prepared as a buffer layer composition for forming a buffer layer.

Examples of solvents include methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran, dioxane, cyclohexane, n-hexane, toluene, xylene, n-propanol, and isopropanol.

Next, using known methods such as spin coating, spray coating, rod coating, knife coating, roller coating, blade coating, mold coating, and gravure coating, the buffer layer is coated onto the release surface of the first release sheet using a composite material, thereby forming a coating film. This coating film is then semi-cured, thus forming a buffer layer film on the release sheet. The buffer layer film formed on the release sheet is then bonded to a substrate, allowing the buffer layer film to fully cure, thereby forming the buffer layer.

In this embodiment, curing of the coating is preferably performed by irradiation with energy rays. Furthermore, the curing of the coating can be carried out in a single curing process or in multiple stages.

Next, the intermediate layer is coated with the composition onto the peeling surface of the second peel sheet using a known method and then heated and dried to form an intermediate layer on the second peel sheet. Then, the intermediate layer on the second peel sheet is bonded to the surface of the substrate where the buffer layer has not been formed, and the second peel sheet is removed.

Next, using a known method, an adhesive layer is coated onto the peeling surface of the third peel sheet using a compound and then heated and dried to form an adhesive layer on the third peel sheet. Then, by bonding the adhesive layer on the third peel sheet to an intermediate layer, a semiconductor processing protective sheet is obtained, in which an intermediate layer and an adhesive layer are sequentially formed on one main surface of the substrate, and a buffer layer is formed on another main surface of the substrate. The third peel sheet can be removed when using the semiconductor processing protective sheet.

(8. Method for Manufacturing a Semiconductor Device) The semiconductor processing guard sheet of the present invention is preferably used when it is attached to the surface of a semiconductor wafer in a die-gluing plate (DBG) for back-side grinding. In particular, the semiconductor processing guard sheet of this embodiment is preferably used in an LDBG that can obtain a wafer array with a small kerf width when isolating semiconductor wafers.

As a non-limiting example of the use of protective sheets for semiconductor processing, the manufacturing method of semiconductor devices will be further explained below.

Specifically, the manufacturing method of a semiconductor device includes at least the following steps 1 through 4. Step 1: Attaching the semiconductor processing protective sheet to the surface of a semiconductor wafer with uneven surfaces; Step 2: Forming grooves from the surface of the semiconductor wafer, or forming modified regions from the surface or back of the semiconductor wafer inside the semiconductor wafer; Step 3: Grinding the semiconductor wafer with the semiconductor processing protective sheet attached and the grooves or modified regions formed therein, starting from the back side, to convert it into multiple wafers, using the grooves or modified regions as starting points; Step 4: Peeling the semiconductor processing protective sheet off the converted semiconductor wafers (i.e., multiple semiconductor wafers).

The following is a detailed explanation of each step in the manufacturing method of the aforementioned semiconductor device.

(Step 1) In Step 1, the semiconductor processing protective sheet of the present invention is attached to the surface of a semiconductor wafer with unevenness via an adhesive layer. This step can be performed before or after Step 2, which will be described later. For example, when a modified region is formed in the semiconductor wafer, Step 1 is preferably performed before Step 2. On the other hand, when trenches are formed on the surface of the semiconductor wafer by dicing or the like, Step 1 is performed after Step 2. That is, the semiconductor processing protective sheet is attached to the grooved wafer surface formed in Step 2, which will be described later, via Step 1.

The semiconductor wafer used in this manufacturing method can be a silicon wafer, or it can be a wafer made of gallium arsenide, silicon carbide, lithium tantalum, lithium niobate, gallium nitride, indium phosphide, or a glass wafer. The thickness of the semiconductor wafer before grinding is not particularly limited, but is typically around 500-1000 μm. Furthermore, circuits are typically formed on the surface of the semiconductor wafer. These circuits can be formed on the wafer surface using various conventional methods, including etching and peeling. In particular, in this embodiment, convex electrodes (bumps) are formed on the electrical surface of the semiconductor wafer. As a result, compared to a semiconductor wafer without convex electrodes, there are uneven surfaces on the electrical surface of the semiconductor wafer. Additionally, the height of the convex electrodes is not particularly limited, but is typically 5-200 μm.

(Step 2) In Step 2, trenches are formed from the surface side of the semiconductor wafer, or modified regions are formed from the surface or back side of the semiconductor wafer inside the semiconductor wafer.

The trenches formed in this step are shallower than the thickness of the semiconductor wafer. The trenches can be formed by cutting using conventionally known wafer dicing equipment. Furthermore, in step 3 described later, the semiconductor wafer is diced into multiple semiconductor wafers along the trenches.

Furthermore, the modified region is the embrittled portion of the semiconductor wafer, serving as the starting point for the wafer to be monolithically processed into semiconductor wafers. In this monolithization process, the semiconductor wafer is thinned through grinding in the polishing step, and the force generated by the polishing is applied, thereby breaking the semiconductor wafer and thus monolithically processing it into semiconductor wafers. Specifically, the trenches and modified regions in step 2 are formed along the dividing lines used in the subsequent step 3 when the semiconductor wafer is diced and monolithically processed into semiconductor wafers.

The modified region is formed by focusing laser irradiation on the interior of the semiconductor wafer. The laser irradiation can be performed from either the surface or the back side of the semiconductor wafer. Furthermore, in the method of forming the modified region, when step 2 is performed after step 1 and laser irradiation is performed from the wafer surface, the semiconductor wafer is irradiated through a semiconductor processing protective sheet.

A semiconductor wafer, with a protective sheet for semiconductor processing attached and grooves or modified regions formed therein, is placed on a chuck table and held in place by the chuck table. At this time, the surface side of the semiconductor wafer is positioned and held against the side of the table.

(Step 3) Following Steps 1 and 2, the back side of the semiconductor wafer on the chuck stage is ground to separate the semiconductor wafer into multiple semiconductor chips.

Here, when trenches are formed on the semiconductor wafer, back-side grinding is performed to thin the semiconductor wafer to at least the bottom of the trench. Through this back-side grinding, the trenches are formed into cuts that penetrate the wafer, and the semiconductor wafer is divided through the cuts into individual semiconductor chips.

On the other hand, when a modified region is formed, the polishing surface (back side of the wafer) can reach the modified region through polishing, but it may also reach the modified region imprecisely. That is, polishing can be done to a position close to the modified region so that the semiconductor wafer can be broken down from the modified region and thus monolithically formed into a semiconductor chip. For example, the actual monolithization of the semiconductor chip can be performed by extending the pick-up tape after applying the pick-up tape described later.

In addition, dry polishing can be performed after the back-side grinding is completed and before the wafer is picked up.

The shape of the monolithic semiconductor wafer can be square or rectangular and other elongated shapes. Furthermore, the thickness of the monolithic semiconductor wafer is not particularly limited, but is preferably around 5 to 100 μm, and more preferably 10 to 45 μm. Based on LDBG (Laser-Based Deposition Technology), which uses lasers to create modified regions inside the wafer and utilizes the stress generated during wafer back-side grinding for wafer monolithic wafer formation, it is easy to manufacture the thickness of the monolithic semiconductor wafer to be less than 50 μm, and more preferably 10 to 45 μm. Furthermore, the size of the monolithic semiconductor wafer is not particularly limited, but the wafer size is preferably less than 600 ^mm² , more preferably less than 400 ^mm² , and even more preferably less than 120 ^mm² .

If the semiconductor processing protective sheet of the present invention is used, even for such a thin and/or small semiconductor wafer, cracks can be prevented from forming on the semiconductor wafer during back-side grinding (step 3) and during the removal of the semiconductor processing protective sheet (step 4).

(Step 4) Next, the semiconductor processing protective film is peeled off from the monolithized semiconductor wafer (i.e., multiple semiconductor chips). This step is performed, for example, by the following method.

First, when the adhesive layer of the semiconductor processing protective sheet is formed by an energy-curable adhesive, the adhesive layer is cured by irradiation with energy rays. Next, a pick-up tape is attached to the back side of the monolithized semiconductor wafer, and aligned in a pick-up manner. At this time, a ring frame disposed on the outer periphery of the wafer is also attached to the pick-up tape, fixing the outer periphery of the pick-up tape to the ring frame. The wafer and the ring frame can be attached to the pick-up tape simultaneously, or they can be attached at different times. Next, the semiconductor processing protective sheet is peeled off from the multiple semiconductor wafers held on the pick-up tape.

Then, multiple semiconductor chips located on the pick-up tape are picked up and fixed onto a substrate or the like, thereby manufacturing a semiconductor device.

In addition, there are no special limitations on the pickup tape, for example, it consists of an adhesive sheet having a substrate and an adhesive layer disposed on one side of the substrate.

The above describes examples of the application of the semiconductor processing protective sheet of the present invention in methods for monolithizing semiconductor wafers using DBG or LDBG. However, the semiconductor processing protective sheet of the present invention is preferably applied in LDBG, which can obtain a wafer array with a small kerf width and thinner wafers when monolithizing semiconductor wafers.

The embodiments of the present invention have been described above, but the present invention is not limited to any of the above embodiments and can be modified in various ways within the scope of the present invention. [Examples]

The invention will now be described in more detail with reference to embodiments, but the invention is not limited to these embodiments.

The testing and evaluation methods in this embodiment are as follows.

(Loss tangent and storage modulus of the intermediate layer) The intermediate layer described below is formed using a knife coater into a 50μm thick intermediate layer with polyethylene terephthalate (PET) film laminated on both sides (product name "SP-PET381031", thickness 38μm, manufactured by LINTEC Corporation).

Prepare multiple intermediate layers formed in the above manner, peel off the PET-type release film, align the peel surfaces with each other and stack them sequentially, thereby creating a laminate of intermediate layers (1,000 μm thick).

Next, the resulting intermediate layer laminate was punched into a circle with a diameter of 10 mm to obtain a sample for testing viscoelasticity.

Using a viscoelasticity measuring device (product name "ARES", manufactured by TA Instruments), the above sample was subjected to deformation at a frequency of 1 Hz, and the storage modulus (G') from -30 to 120 °C was measured at a heating rate of 10 °C/min. The loss tangent (tanδ) at 50 °C and the storage modulus (G') at 50 °C were calculated from the measured values. The calculated storage modulus value is set as storage modulus I.

(Damage tangent and storage modulus of the adhesive layer) Using the adhesive layer composition described later, a 50μm thick adhesive layer is formed by applying a polyethylene terephthalate (PET) film-like release liner (product name "SP-PET381031", thickness 38μm, manufactured by LINTEC Corporation) to both sides using a blade coating machine.

Prepare multiple adhesive layers formed in the above manner, peel off the PET-type release film, align the peel surfaces with each other and stack them sequentially, thereby creating a laminate of adhesive layers (1,000 μm thick).

Next, the resulting adhesive layer laminate was punched into a circle with a diameter of 10 mm to obtain a sample for testing viscoelasticity.

Using a viscoelasticity measuring device (product name "ARES", manufactured by TA Instruments), the above sample was subjected to a deformation at a frequency of 1 Hz, and the storage modulus from -30 to 120°C was measured at a heating rate of 10°C/min. The storage modulus (G') at 50°C was calculated from the measured value. This value was set as the storage modulus A.

(DBG Wafer Crack Evaluation) After trenches are formed on the surface of a 12-inch diameter silicon wafer, a semiconductor processing protective sheet manufactured in the embodiments and comparative examples is attached to the wafer surface. The wafer is then monolithized by grinding the back side, thereby monolithizing it into wafers with a thickness of 50μm and a wafer size of 5mm square using a pre-dicing method. Then, without removing the semiconductor processing protective sheet, the corners of the monolithized wafers are observed from the ground surface using a digital microscope (product name "VHX-1000", manufactured by KEYENCE CORPORATION). The presence of cracks in each wafer is observed, and the crack initiation rate among 700 wafers is measured and evaluated using the following evaluation criteria. A: Less than 1.0%, B: 1.0~2.0%, C: Greater than 2.0%

(LDBG Wafer Crack Evaluation) Using a back-grinding tape laminator (manufactured by LINTEC Corporation, device name "RAD-3510F/12"), semiconductor processing protective sheets manufactured in the embodiments and comparative examples were attached to a 12-inch diameter, 775μm thick silicon wafer. A laser saw (manufactured by DISCO Corporation, device name "DFL7361") was used to form a grid-like modified region on the wafer. The grid size was 5mm × 5mm.

Next, a back-side polishing device (manufactured by DISCO Corporation, device name "DGP8761") is used to polish (including dry polishing) until the thickness is 50μm, thus breaking the wafer down into multiple chips.

After the grinding process, the wafers are irradiated with energy rays (ultraviolet light). Cutting tape (manufactured by LINTEC Corporation, Adwill D-176) is applied to the opposite side of the semiconductor processing protective film, and then the protective film is peeled off. The individual wafers are then observed using a digital microscope (product name "VHX-1000", manufactured by KEYENCE CORPORATION). Wafers with cracks are counted, and the crack infestation rate among 700 wafers is determined and evaluated using the following criteria: A: Less than 1.0%, B: 1.0~2.0%, C: Greater than 2.0%

(Evaluation of Cut-in Adhesion) The release liner from the semiconductor processing protective sheet manufactured in the embodiments and comparative examples was peeled off. The semiconductor processing protective sheet was then placed in a tape laminator (manufactured by LINTEC Corporation, product name "RAD-3510") and adhered to a 12-inch silicon wafer (760μm thick) with grooves formed on its surface by a pre-dicing method, under the following conditions: Roll height: 0mm, Roll temperature: 23℃ (room temperature), Table temperature: 23℃ (room temperature)

The silicon wafer with the semiconductor processing protective sheet is monolithically sized into 50μm thick and 5mm square wafers by back-side grinding (pre-dicing method). The monolithically sized semiconductor processing protective sheet with the wafer is then mounted on a dicing tape applicator (LINTEC Corporation, product name "RAD-2700"), and irradiated with ultraviolet light from the tape side (conditions: 230mW/cm, 380mJ/cm) to cure the adhesive. Then, within the same RAD-2700 apparatus, a pick-up tape (LINTEC Corporation, product name "D-510T") is attached from the wafer side. At this time, a fixture called a ring frame, used in the pick-up step, is also aligned and attached to the pick-up tape. Next, within the RAD-2700 apparatus, the cured semiconductor processing protective film was peeled off. Using a digital microscope (product name "VHX-1000", manufactured by KEYENCE CORPORATION), the 700 wafers after the semiconductor processing protective film was peeled off were observed to check for any residual adhesive near the cut. Those without adhesive residue were marked as ○, and those with adhesive residue were marked as ×.

(Bump Absorbency Evaluation) Using a laminator (product name "RAD-3510F/12", manufactured by LINTEC Corporation), semiconductor processing protective sheets manufactured in the following embodiments and comparative examples were attached to a wafer (8-inch wafer, manufactured by WALTZ Corporation) with spherical bumps. The spherical bumps had a bump height of 80 μm, a spacing of 200 μm, and a diameter of 100 μm, and were made of Sn-3Ag-0.5Cu alloy. Furthermore, during attachment, the temperature of the lamination stage and lamination rollers was set to 50°C.

After lamination, a digital optical microscope (product name "VHX-1000", manufactured by KEYENCE CORPORATION) was used to measure the diameter of the circular gaps around the protrusions from the substrate side.

The smaller the diameter of the void, the higher the absorption capacity of the bump in the semiconductor processing protection sheet. The following criteria are used to determine the quality of bump absorption: ○: Void diameter less than 150 μm. ×: Void diameter 150 μm or more.

(Example 1) (1) Substrate A PET film (COSMOSHINE A4300 manufactured by TOYOBO CO., LTD., thickness: 50 μm, Young's modulus at 23°C: 2550 MPa) with easy-to-adhere layers on both sides was prepared as the substrate.

(2) Buffer Layer (Synthesis of Carbamate Acrylate Oligomers) 2-Hydroethyl acrylate is reacted with a terminal isocyanate carbamate prepolymer to obtain a carbamate acrylate oligomer (UA-2) with a weight average molecular weight (Mw) of approximately 9000. The terminal isocyanate carbamate prepolymer is obtained by reacting a polyester diol with isophorone diisocyanate.

(Preparation of the buffer layer composition) A buffer layer composition was prepared by mixing 40 parts by weight of the above-synthesized urethane acrylate oligomer (UA-2), 20 parts by weight of isobornyl acrylate (IBXA), 20 parts by weight of tetrahydrofurfuryl acrylate (THFA), and 20 parts by weight of acrylamide (ACMO), and further mixing in 2.0 parts by weight of 2-hydroxy-2-methyl-1-phenyl-propane-1-one (manufactured by BASF Japan Ltd, product name "IRGACURE 1173"), which serves as a photopolymerization initiator.

(Manufacturing of the substrate with a cushioning layer) A cushioning layer composition is coated onto the peel-treated surface of another peel sheet (manufactured by LINTEC Corporation, product name "SP-PET381031") to form a coating film. Next, the coating film is irradiated with ultraviolet light to semi-cur it, forming a cushioning layer film with a thickness of 53 μm.

In addition, the above-mentioned ultraviolet irradiation was carried out using a conveyor belt ultraviolet irradiation device (manufactured by EYE GRAPHICS Co., Ltd., device name "US2-0801") and a high-pressure mercury lamp (manufactured by EYE GRAPHICS Co., Ltd., device name "H08-L41") under irradiation conditions of lamp height of 230mm, output power of 80mW/cm, illuminance of light with wavelength of 365nm of 90mW/ ^cm2 , and irradiation dose of 50mJ/ ^cm2 .

Next, the surface of the formed buffer layer film is bonded to the substrate, and ultraviolet light is irradiated again from the peeling sheet side of the buffer layer film to completely cure the buffer layer film, forming a buffer layer with a thickness of 53 μm. Furthermore, using the aforementioned ultraviolet irradiation device and high-pressure mercury lamp, the above-mentioned ultraviolet irradiation is performed under irradiation conditions of a lamp height of 220 mm, a converted output power of 120 mW/cm, an illuminance of 160 mW/ ^cm² at a wavelength of 365 nm, and an irradiation dose of 650 mJ/ ^cm² .

(3) Substrate A with an intermediate layer 91 parts by weight of n-butyl acrylate (BA) and 9 parts by weight of acrylic acid (AA) were copolymerized to obtain a non-energy-curable acrylic copolymer (a) (Mw: 600,000).

Unlike the acrylic copolymer (a), 62 parts by mass of n-butyl acrylate (BA), 10 parts by mass of methyl methacrylate (MMA), and 28 parts by mass of 2-hydroxyethyl acrylate (2HEA) were copolymerized to obtain an acrylic polymer. Then, 2-methacryloyloxyethyl isocyanate (MOI) was reacted with the acrylic polymer by adding 80 equivalents of the total hydroxyl groups (100 equivalents) of the acrylic polymer to obtain an energy-curable acrylic copolymer (b) (Mw: 100,000).

To 100 parts by weight of the non-energy-curable acrylic copolymer (a), 13 parts by weight of the energy-curable acrylic copolymer (b) were added, along with 2.79 parts by weight of an isocyanate crosslinker (manufactured by TOSOH, product name "CORONATE L") as a crosslinking agent, and 3.71 parts by weight of 1-hydroxycyclohexylphenyl ketone (manufactured by BASF, Irgacure 184) as a photopolymerization initiator. The solid content was adjusted to 37% using toluene, and the mixture was stirred for 30 minutes to prepare an intermediate layer composition.

Next, the prepared intermediate layer composition solution is coated onto a PET release film (manufactured by LINTEC Corporation, SP-PET381031, 38μm thick) and dried to form an intermediate layer with a thickness of 60μm. This intermediate layer is then bonded to the side of the substrate with the aforementioned buffer layer opposite to the side where the buffer layer is formed. The adhesive layer composition solution is then repeatedly coated onto the PET release film (manufactured by LINTEC Corporation, SP-PET381031, 38μm thick), and this operation is repeated twice to form a substrate A with an intermediate layer and a thickness of 180μm.

(4) Adhesive Layer (Preparation of the Adhesive Layer Composite) 52 parts by mass of n-butyl acrylate (BA), 20 parts by mass of methyl methacrylate (MMA), and 28 parts by mass of 2-hydroxyethyl acrylate (2HEA) were copolymerized to obtain an acrylic polymer. 2-Methacryloxyethyl isocyanate (MOI) was reacted with the acrylic polymer by adding 90 equivalents of the total hydroxyl groups (100 equivalents) of the acrylic polymer to obtain an energy-curable acrylic copolymer (c) (Mw: 500,000).

To 100 parts by weight of the energy-curable acrylic copolymer (c), 12 parts by weight of a multifunctional urethane acrylate (manufactured by Mitsubishi Chemical Corporation, SHIKOH UT-4332), 1.1 parts by weight of an isocyanate crosslinker (manufactured by TOSOH CORPORATION, product name "CORONATE L"), and 1 part by weight of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (manufactured by BASF, IrgacureTPO) as a photopolymerization initiator were added, and the mixture was diluted with methyl ethyl ketone to prepare a coating solution of an adhesive layer composition with a solid content concentration of 34% by weight.

(Manufacturing of Protective Sheets for Semiconductor Processing) A coating solution of the adhesive layer composition obtained above is applied to the peeling surface of a release sheet (manufactured by LINTEC Corporation, product name "SP-PET381031"), and then heated and dried to form an adhesive layer with a thickness of 10 μm on the release sheet.

Then, an adhesive layer is bonded to the surface of the substrate A with the intermediate layer to manufacture a protective sheet for semiconductor processing. The type of substrate, composition and thickness of the intermediate layer and adhesive layer are shown in Table 1.

(Example 2) Except for the intermediate layer thickness being 120 μm, a protective sheet for semiconductor processing was obtained using the same method as in Example 1. The type of substrate, the composition and thickness of the intermediate layer and adhesive layer are shown in Table 1.

(Example 3) Except for changing the amount of the acrylic copolymer (b) in the intermediate layer composition to 34 parts by weight, a protective sheet for semiconductor processing was obtained using the same method as in Example 1. The types of substrates, the composition and thickness of the intermediate layer and adhesive layer are shown in Table 1.

(Example 4) Except for changing the amount of the acrylic copolymer (b) in the intermediate layer composition to 67 parts by weight, a protective sheet for semiconductor processing was obtained using the same method as in Example 1. The types of substrates, the composition and thickness of the intermediate layer and adhesive layer are shown in Table 1.

(Example 5) Except for changing the amount of the acrylic copolymer (b) in the intermediate layer composition to 100 parts by weight, a protective sheet for semiconductor processing was obtained using the same method as in Example 1. The types of substrates, the composition and thickness of the intermediate layer and adhesive layer are shown in Table 1.

(Example 6) Except for the following two changes, a protective sheet for semiconductor processing is obtained using the same method as in Example 1. The type of substrate, the composition and thickness of the intermediate layer and adhesive layer are shown in Table 1. (1) The thickness of the intermediate layer is 120 μm. (2) As an adhesive layer composition, 60 parts by weight of 2-ethyl hydroxyl acrylate (2EHA), 15 parts by weight of ethyl acrylate (EA), 5 parts by weight of methyl methacrylate (MMA), and 20 parts by weight of 2-hydroxyethyl acrylate (2HEA) are copolymerized to obtain an acrylic polymer. 2-Methacryloxyethyl isocyanate (MOI) is then reacted with the acrylic polymer by adding 60 equivalents of the total hydroxyl groups (100 equivalents) of the acrylic polymer to obtain an energy-curable acrylic copolymer (d) (Mw: 500,000).

To 100 parts by weight of the energy-curable acrylic copolymer (d), 1.2 parts by weight of an isocyanate crosslinker (manufactured by TOSOH CORPORATION, product name "CORONATE L") and 7.29 parts by weight of 2,2-dimethoxy-2-phenylacetophenone (manufactured by BASF, Irgacure 651) as a photopolymerization initiator were added, and the mixture was diluted with toluene to prepare a coating solution of the adhesive layer composition with a solid content concentration of 25% by weight.

(Example 7) Except for the following changes, a protective sheet for semiconductor processing is obtained using the same method as in Example 1. The type of substrate, the composition and thickness of the intermediate layer and adhesive layer are shown in Table 1.

As an adhesive layer composition, 75 parts by weight of n-butyl acrylate (BA), 10 parts by weight of isobutyl acrylate (iBA), 5 parts by weight of methyl methacrylate (MMA), and 10 parts by weight of 4-hydroxybutyl acrylate (4HBA) are copolymerized to obtain an acrylic polymer. 2-Methacryloxyethyl isocyanate (MOI) is reacted with the acrylic polymer by adding 90 equivalents of the total hydroxyl groups (100 equivalents) of the acrylic polymer to obtain an energy-curable acrylic copolymer (e) (Mw: 500,000).

To 100 parts by weight of the energy-curable acrylic copolymer (e), 1.8 parts by weight of an isocyanate crosslinker (manufactured by TOSOH CORPORATION, product name "CORONATE L") and 7.29 parts by weight of 2,2-dimethoxy-2-phenylacetophenone (manufactured by BASF, Irgacure 651), used as a photopolymerization initiator, were added, and the mixture was diluted with toluene to prepare a coating solution of the adhesive layer composition with a solid content concentration of 25% by weight.

(Example 8) Except for changing the substrate with the cushioning layer to a PET substrate, a protective sheet for semiconductor processing is obtained using the same method as in Example 2. The type of substrate, the composition and thickness of the intermediate layer and adhesive layer are shown in Table 1.

(Comparative Example 1) Except for changing the amount of the acrylic copolymer (b) in the intermediate layer to 134 parts by weight, a protective sheet for semiconductor processing was obtained using the same method as in Example 1. The types of substrates, the composition and thickness of the intermediate layer and adhesive layer are shown in Table 1.

(Comparative Example 2) Except for using the adhesive layer composition of Example 6 as the adhesive layer composition, a protective sheet for semiconductor processing was obtained using the same method as in Example 1. The types of substrates, the composition of the intermediate layer, and the thickness of the adhesive layer are shown in Table 1.

(Comparative Example 3) Except for using a substrate D with an intermediate layer manufactured as described below, and using the adhesive layer composition of Example 6 as the adhesive layer composition, a protective sheet for semiconductor processing was obtained using the same method as in Example 1. The types of substrates, the composition of the intermediate layer, and the thickness of the adhesive layer are shown in Table 1.

Substrate D with an intermediate layer Combined with 40 parts by weight (solid content ratio) of monofunctional urethane acrylate, 45 parts by weight (solid content ratio) of isobornyl acrylate (IBXA), 15 parts by weight (solid content ratio) of hydroxypropyl acrylate (HPA), and pentaerythritol tetrakis(3-phenylbutyrate) ester (product name "KARENZ MT PE1", SHOWA DENKO) The UV-curable resin composition was prepared by spraying a foam die onto a polyethylene terephthalate (PET) film-like release film (manufactured by LINTEC Corporation, SP-PET381031, thickness 38μm) to form a film with a solid content of 3.5 parts by mass (solid content ratio) of K.K., tetrafunctional secondary thiol compound, solid content concentration of 100 parts by mass), 1.8 parts by mass of UV reactive thermal crosslinking agent, and 1.0 parts by mass of 2-hydroxy-2-methyl-1-phenyl-propane-1-one (product name "Darocur1173", manufactured by BASF, solid content concentration of 100 parts by mass) as a photopolymerization initiator. Furthermore, ultraviolet light is irradiated onto the self-coating side, thereby forming a semi-cured layer.

In addition, a conveyor belt-type ultraviolet irradiation device (product name "ECS-401GX", manufactured by EYE GRAPHICS Co., Ltd.) was used as the ultraviolet irradiation device, and a high-pressure mercury lamp (H04-L41, manufactured by EYE GRAPHICS Co., Ltd.) was used as the ultraviolet light source. The irradiation conditions were as follows: the illuminance of light with a wavelength of 365nm was 112mW/ ^cm2 , and the light intensity was 177mJ/ ^cm2 (measured by "UVPF-A1" manufactured by EYE GRAPHICS Co., Ltd.).

A polyethylene terephthalate (PET) film (Lumirror 75U403, 75 μm thick, manufactured by TORAY INDUSTRIES, INC.) is laminated on the formed semi-cured layer, and ultraviolet light is further irradiated from the PET film side (using the aforementioned ultraviolet irradiation device and ultraviolet source, and as the irradiated repair part, the illuminance is 271 mW/cm ² and the light intensity is 1200 mJ/cm ² ), so that it is completely cured, forming an intermediate layer with a thickness of 400 μm on the PET film of the substrate.

[Table 1] middle layer Adhesive layer substrate acrylic copolymer Cross-linking agent Thickness (μm) acrylic copolymer Carbamate acrylate Cross-linking agent Thickness (μm) (a) (b) (c) (d) (e) Implementation Example 1 100 13 2.79 180 100 12 1.1 10 PET substrate with buffer layer Implementation Example 2 100 13 2.79 120 100 12 1.1 10 Implementation Example 3 100 34 2.79 120 100 12 1.1 10 Implementation Example 4 100 67 2.79 120 100 12 1.1 10 Implementation Example 5 100 100 2.79 120 100 12 1.1 10 Implementation Example 6 100 13 2.34 120 100 1.2 10 Implementation Example 7 100 67 2.79 120 100 1.8 10 Implementation Example 8 100 13 2.79 120 100 12 1.1 10 PET substrate Comparative example 1 100 134 2.79 120 100 12 1.1 10 PET substrate with buffer layer Comparative example 2 100 13 2.79 120 100 1.2 10 Comparative example 3 Carbamate acrylates 400 100 1.2 10 PET

The obtained samples (Examples 1-8 and Comparative Examples 1-3) were subjected to the above tests and evaluations. The results are shown in Table 2.

[Table 2] characteristic Evaluation 50℃ DBG evaluation results LDBG Evaluation Results Incision Adhesion bump Middle layer I (MPa) Adhesive layer A (MPa) A/I ratio Intermediate layer Tanδ (-) Crystal displacement (cracks) Evaluation Crystal displacement (cracks) Evaluation Residual glue Embedded Implementation Example 1 0.078 0.067 0.86 0.44 without A without A ○ ○ Implementation Example 2 0.078 0.067 0.86 0.44 without A without A ○ ○ Implementation Example 3 0.066 0.067 1.02 0.47 without A without A ○ ○ Implementation Example 4 0.043 0.067 1.56 0.57 without A without A ○ ○ Implementation Example 5 0.035 0.067 1.91 0.63 Small B Small B ○ ○ Implementation Example 6 0.062 0.055 0.89 0.44 without A without A ○ ○ Implementation Example 7 0.031 0.103 3.32 0.62 without A without A ○ ○ Implementation Example 8 0.078 0.067 0.86 0.44 Small B Small B ○ ○ Comparative example 1 0.017 0.067 3.94 0.72 big C big C × ○ Comparative example 2 0.078 0.055 0.71 0.44 without A without A ○ × Comparative example 3 0.657 0.055 0.08 1.72 big C big C ○ ○

As can be seen from Table 2, when the loss angle tangent of the AI and the intermediate layer is within the above range, even when the wafer with unevenness is monolithized by DBG and LDBG, the unevenness can be fully embedded, the crack generation rate caused by wafer displacement is low, and no nick residue is observed.

1: Protective sheet for semiconductor processing 10: Substrate 20: Intermediate layer 30: Adhesive layer 30a: Main surface 40: Cushion layer 101: Semiconductor wafer 101a: Surface 102: Bump

Figure 1A is a schematic cross-sectional view showing an example of the semiconductor processing protective sheet according to this embodiment. Figure 1B is a schematic cross-sectional view showing another example of the semiconductor processing protective sheet according to this embodiment. Figure 2 is a schematic cross-sectional view showing the semiconductor processing protective sheet of this embodiment attached to the electrical surface of a semiconductor wafer.

1: Protective sheet for semiconductor processing 10: Substrate 20: Intermediate layer 30: Adhesive layer 30a: Main surface

Claims (8)

A protective sheet for semiconductor processing has a substrate and an intermediate layer and an adhesive layer sequentially formed on a main surface of the substrate, and satisfies the following (a) and (b), wherein the intermediate layer is composed of an intermediate layer composition, wherein the intermediate layer composition contains an acrylic polymer (A) with a weight average molecular weight of 300,000 to 1,500,000 and an energy-curable acrylic polymer (B) with a weight average molecular weight of 50,000 to 250,000: (a) the loss tangent of the intermediate layer at 50°C measured at a frequency of 1 Hz is 0.40 to 0.65; (b) the ratio of the storage modulus A of the adhesive layer to the storage modulus I of the intermediate layer [A/I] at 50°C measured at a frequency of 1 Hz is 0.80 to 3.50. The protective sheet for semiconductor processing according to claim 1, wherein a buffer layer is provided on another main surface of the substrate. The protective sheet for semiconductor processing according to claim 1 or 2, wherein the Young's modulus of the substrate is 1000 MPa or more. The protective sheet for semiconductor processing according to claim 1 or 2, wherein the thickness of the intermediate layer is more than 60 μm and less than 250 μm. The protective sheet for semiconductor processing according to claim 1 or 2, wherein the adhesive layer is energy-curable. The protective sheet for semiconductor processing according to claim 1 or 2, wherein the intermediate layer is energy-cured. According to claim 1 or 2, the semiconductor processing protective sheet is used in the step of grinding the back side of a semiconductor wafer with grooves formed on its surface and isolating the semiconductor wafer into a semiconductor chip by the grinding process. A method for manufacturing a semiconductor device includes: a step of attaching a semiconductor processing protective sheet as described in any one of claims 1 to 7 to the surface of a semiconductor wafer having uneven surfaces; a step of forming a groove from the surface side of the semiconductor wafer, or forming a modified region inside the semiconductor wafer from the surface or back side of the semiconductor wafer; a step of grinding the semiconductor wafer on which the semiconductor processing protective sheet is attached and on which the groove or the modified region is formed, from the back side, and converting it into a plurality of wafers starting from the groove or the modified region; and a step of peeling the semiconductor processing protective sheet from the converted semiconductor wafers.