TWI892961B - Adhesive tape and method for manufacturing semiconductor device - Google Patents

Abstract

The present invention is to provide an adhesive tape capable of stably holding a wafer, etc., even during dry polishing after pre-dicing. The present invention addresses this problem by providing an adhesive tape for use in a dry polishing step after grinding the backside of a semiconductor wafer having grooves formed on its surface, singulating the semiconductor wafer into semiconductor chips by grinding. The adhesive tape comprises a substrate and an adhesive layer disposed on one side of the substrate. The substrate has a tensile storage modulus of 250 MPa or greater at temperatures below 60°C.

Description

Adhesive tape and method for manufacturing semiconductor device

The present invention relates to an adhesive tape, and more specifically, to an adhesive tape suitable for temporarily fixing semiconductor wafers, chips, etc. when semiconductor devices are manufactured by dry polishing after the semiconductor wafers are diced using a so-called predicing method, and a method for manufacturing semiconductor devices using the adhesive tape.

As various electronic devices become increasingly miniaturized and multifunctional, the semiconductor chips they carry are also required to be miniaturized and thinned. To achieve this, the back of the semiconductor wafer is usually ground to adjust its thickness. Another technique used is the pre-cutting method, which involves forming a groove of a predetermined depth on the surface of the wafer and then grinding it from the back. The bottom of the groove is removed by grinding, and the wafer is then sliced to obtain chips. Because the pre-cutting method allows for simultaneous back grinding and wafer slicing, thin chips can be manufactured efficiently.

Previously, when grinding the backside of a semiconductor wafer and manufacturing chips using a pre-cutting method, an adhesive tape called a back grinding sheet was typically attached to the wafer surface to protect the circuits on the wafer surface and to pre-secure the semiconductor wafer and semiconductor chip.

As a back grinding sheet used in the pre-cutting method, an adhesive tape having a substrate and an adhesive layer provided on one side of the substrate can be exemplified. As an example of such an adhesive tape, Japanese Patent Publication No. 2015-185691 (Patent Document 1) proposes an adhesive tape for semiconductor wafer processing in which a radiation-curable adhesive layer is provided on a substrate film. Patent Document 1 discloses, as a preferred specific example, a substrate film formed by laminating two different materials selected from at least polyethylene terephthalate, polypropylene, and ethylene-vinyl acetate copolymer. A substrate film composed of three layers of polyethylene/polyethylene terephthalate/polyethylene is disclosed.

When wafers are singulated using the pre-dicing method described above, backside grinding is performed while water is supplied to the grinding surface to remove heat and grinding debris generated during grinding. However, this conventional backside grinding method leaves grinding marks on the backside of the wafer, which is known to be a major factor in reducing the wafer's flexural strength. In particular, as wafers become thinner and smaller, increased wafer damage and reduced flexural strength are considered a problem. [Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Application Laid-Open No. 2015-185691

[Problem to be solved by the invention]

To remove grinding marks (hereinafter referred to as "damage") such as those described above, studies have been conducted on the method of performing dry polishing after back grinding using water to remove the damage and improve the wafer's flexural strength. Dry polishing refers to the process of polishing with a polishing buff without the use of water or abrasive slurry.

However, unlike back grinding, dry polishing does not use water, so the heat generated during polishing cannot be removed by water, causing the wafer to retain heat. The heat from the wafer is transferred to the adhesive tape attached to the wafer. As a result, the temperature of the adhesive tape during dry polishing can reach over 60°C.

Because the adhesive tape's base material is made of a resin component, it's easily deformed by heat. During dry polishing, if this deformation occurs, the tape's end portions may not be securely fixed, effectively preventing the wafer from being held securely on the tape. This can cause the wafer to peel off and scatter. This wafer scattering not only reduces productivity but can also damage other wafers by contacting them, or damage the grinding equipment, leading to poor transport to the next step.

The present invention was developed in light of this practical situation, with the goal of providing an adhesive tape capable of stably holding a wafer, etc., even during dry polishing after a so-called pre-cutting process. [Means for Solving the Problem]

The present invention is as follows: [1] An adhesive tape, which is used by grinding the back side of a semiconductor wafer having grooves formed on the surface of the semiconductor wafer, and then individualizing the semiconductor wafer into semiconductor chips by grinding, and then attaching the adhesive tape to the surface of the semiconductor wafer during a dry polishing step, comprising a substrate and an adhesive layer provided on one side thereof, and wherein the tensile storage modulus of the substrate at 60°C is 250 MPa or more.

[2] A method for manufacturing a semiconductor device comprises the following steps: forming a groove from the surface side of a semiconductor wafer; attaching an adhesive tape comprising a substrate and an adhesive layer provided on one side thereof, the adhesive tape having a tensile storage modulus of 250 MPa or more at 60°C, to the surface of the semiconductor wafer; grinding the semiconductor wafer having the adhesive tape attached thereto and the grooves formed thereon from the back side to remove the bottom of the grooves and thereby singulate the semiconductor wafer into a plurality of chips; dry polishing the semiconductor wafer after singulating the semiconductor wafer into semiconductor chips; and peeling the chips from the adhesive tape. [Effects of the invention]

The adhesive tape of the present invention can stably hold the semiconductor chip even when the temperature of the adhesive tape rises due to the heat generated during dry polishing. Therefore, even when a pre-cutting method including a dry polishing step is performed, semiconductor chips can be manufactured with a high yield.

Form used to implement the invention

The adhesive tape of the present invention will be described in detail below. First, the main terms used in this specification will be described.

In this specification, for example, the term "(meth)acrylate" is used to refer to both "acrylate" and "methacrylate," and the same applies to other similar terms.

Adhesive tape refers to a laminate comprising a substrate and an adhesive layer disposed on one side thereof. It may also include other constituent layers. For example, a primer layer may be formed on the substrate surface adjacent to the adhesive layer to improve adhesion between the substrate surface and the adhesive layer or to prevent migration of low-molecular-weight components. Furthermore, peeling sheets may be deposited on the adhesive layer surface to protect the adhesive layer until use. Furthermore, the substrate may be a single layer or a multilayer structure with functional layers such as a buffer layer. The same applies to the adhesive layer.

The "front" of a semiconductor wafer refers to the side with circuits formed on it, while the "back" refers to the side without circuits. Singulation of a semiconductor wafer refers to dividing the semiconductor wafer into individual circuits to create semiconductor chips.

Dry polishing refers to the process of polishing with a polishing wheel without using a slurry containing water, abrasive particles, etc. This specification also refers to the process as a "dry polishing step."

Various general-purpose grinding wheels can be used as abrasive polishing wheels for dry polishing. Commercially available products include, but are not limited to, DISCO's "Gettering DP" and "DP08 Series" grinding wheels. Dry polishing removes damaged areas on the wafer, i.e., grinding marks.

The so-called pre-dicing method refers to a method in which grooves of a predetermined depth are formed on the front side of the wafer, and then the back side of the wafer is ground to separate the wafer into pieces.

Back grinding tape refers to the adhesive tape used to protect the wafer's electrical path surface during back grinding of semiconductor wafers. In this specification, it specifically refers to adhesive tape suitable for use in the pre-cutting process.

(1. Adhesive Tape) The adhesive tape of the present invention can be used as the aforementioned back grinding tape during the dry polishing step. The adhesive tape of the present invention comprises a substrate and an adhesive layer disposed on one surface thereof. The components of the adhesive tape are described in detail below.

(1.1. Base Material) The adhesive tape of this embodiment can be made from various resin films used as base materials for back grinding tapes.

An example of a substrate used in the present invention is described in detail below. However, this is only described to facilitate the acquisition of the substrate and should not be interpreted in any limiting manner.

(1.2. Physical Properties of the Substrate) In this embodiment, the tensile storage modulus ( _E'60 ) of the substrate at 60°C is preferably 250 MPa or greater. The tensile storage modulus (E') is one of the indicators of the substrate's ease of deformation (hardness). By keeping the tensile storage modulus ( _E'60 ) of the substrate at 60°C within the above range, the chip can be prevented from being peeled off from the adhesive tape due to thermal deformation of the substrate, and deformation of the substrate due to stress during processing steps, especially dry polishing, can be prevented. In addition, the buffering performance of the corresponding force during back grinding and dry polishing can be appropriately maintained.

Furthermore, during backside grinding and dry polishing, the semiconductor wafer with the adhesive tape attached is positioned on the suction machine via the adhesive tape. By maintaining the substrate's tensile storage modulus ( _E'60 ) within the aforementioned range, the adhesive tape's adhesion to the suction machine is improved, and vibration during backside grinding and dry polishing can be suppressed. Furthermore, after backside grinding and dry polishing, the adhesive tape can be easily removed from the suction machine.

_E'60 is preferably 270 MPa or more, more preferably 300 MPa or more. On the other hand, _E'60 is preferably 4000 MPa or less, more preferably 1100 MPa or less.

Therefore, in this embodiment, by controlling the tensile storage modulus of the substrate at 60°C within the above range, chip scattering can be effectively suppressed during dry polishing even when the adhesive layer is heated.

The tensile storage modulus of the substrate can be measured using conventional methods, similar to the loss tangent and shear storage modulus of the adhesive layer. For example, a sample of a predetermined size made of the same material as the sheet or film constituting the substrate can be prepared. Using a dynamic viscoelasticity measuring device, strain can be applied to the sample at a predetermined frequency within a predetermined temperature range to measure the modulus. The tensile storage modulus can then be calculated from the measured modulus.

The tensile storage modulus (E') of a substrate can be controlled by appropriately selecting the film that constitutes the substrate, taking into account its material, physical properties, and thickness. For example, by selecting a film with a relatively high Tg as the constituent film and performing an annealing treatment during film formation, the tensile storage modulus can be controlled within a predetermined range.

(1.3. Specific Examples of Substrates) Specific examples of substrates are described below. However, these examples are provided for ease of obtaining substrates and should not be construed in any limiting sense.

The substrate of the present invention may be, for example, a relatively hard resin film. Furthermore, the substrate of the present invention may be a laminate in which a buffer layer composed of a relatively soft resin film is laminated on one or both sides of a relatively hard resin film.

The thickness of the substrate is not particularly limited, but is preferably 500 μm or less, more preferably 15 to 350 μm, and even more preferably 20 to 160 μm. By setting the substrate thickness to 500 μm or less, the peeling force of the adhesive tape can be easily controlled. Furthermore, by setting the substrate thickness to 15 μm or greater, the substrate can more easily function as a support for the adhesive tape.

Various resin films can be used as the substrate material. Examples of substrates having a tensile storage modulus of 250 MPa or greater include resin films made of polyesters such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, and wholly aromatic polyesters, polyamides, polycarbonates, polyacetals, modified polyphenylene ethers, polyphenylene sulfides, polysulfones, polyetherketones, and biaxially oriented polypropylene.

Among the resin films, films comprising at least one selected from polyester films, polyamide films, and biaxially oriented polypropylene films are preferred, polyester films are more preferred, and polyethylene terephthalate films are even more preferred.

Furthermore, the substrate may contain a plasticizer, a lubricant, an infrared absorber, an ultraviolet absorber, a filler, a colorant, an antistatic agent, an antioxidant, a catalyst, etc., within a range that does not impair the effects of the present invention. Furthermore, the substrate is transmissive to the energy beam irradiated when the adhesive layer is cured.

Furthermore, in order to improve adhesion with at least one of the buffer layer and the adhesive layer, at least one surface of the substrate may be subjected to a bonding treatment such as a corona treatment. Furthermore, the substrate may also have the aforementioned resin film and an easily bonded layer (primer layer) coated on at least one surface of the resin film.

The composition for forming the easily adhesive layer is not particularly limited, and examples thereof include compositions containing polyester resins, urethane resins, polyesterurethane resins, acrylic resins, and the like. The composition for forming the easily adhesive layer may also contain a crosslinking agent, a photopolymerization initiator, an antioxidant, a softener (plasticizer), a filler, a rustproofing agent, a pigment, a dye, and the like, as needed.

The thickness of the adhesive layer is preferably 0.01-10 μm, more preferably 0.03-5 μm. Furthermore, the thickness of the adhesive layer is relatively small compared to the thickness of the substrate, and the adhesive layer is made of a relatively flexible material, so its effect on the tensile storage modulus is minimal. Even with the adhesive layer, the tensile storage modulus of the substrate is essentially the same as that of the resin film.

(1.4. Buffer Layer) A buffer layer may be provided on one or both sides of the substrate. The buffer layer, composed of a relatively soft resin film, can dampen vibrations caused by grinding the semiconductor wafer and prevent cracks and defects in the semiconductor wafer. Furthermore, when the semiconductor wafer attached to the adhesive tape is placed on a suction machine during backside grinding, the presence of the buffer layer facilitates proper retention of the adhesive tape on the machine.

The thickness of the buffer layer is preferably 8-80 μm, more preferably 10-60 μm.

The buffer layer is preferably made of polypropylene film, ethylene-vinyl acetate copolymer film, ionic polymer resin film, ethylene-(meth)acrylic acid copolymer film, ethylene-(meth)acrylate copolymer film, LDPE film, or LLDPE film. Alternatively, the buffer layer may be formed from a buffer layer-forming composition containing an energy-beam-polymerizable compound. A substrate having a buffer layer can be laminated to the above-mentioned film to obtain a substrate.

(1.5. Adhesive Layer) The following describes an example of an adhesive layer used in the present invention in order of physical properties and composition. However, this description is provided solely to facilitate the manufacture or acquisition of the adhesive layer and should not be construed in any limiting sense.

(1.6. Adhesive Layer Properties) The adhesive layer is not particularly limited as long as it is configured to achieve the desired properties of the adhesive tape. In this embodiment, as described above, the temperature of the adhesive tape during dry polishing may reach 60°C or higher.

Therefore, in this embodiment, the loss tangent (tan δ ₆₀ ) of the adhesive layer at 60°C is preferably 0.40 or less, and the shear storage modulus (G' ₆₀ ) of the adhesive layer at 60°C is preferably 3.0×10 ⁴ Pa or more.

Loss tangent (tanδ) is defined as the ratio of loss modulus to storage modulus. It is measured using a dynamic viscoelasticity tester based on the object's response to stresses such as tensile stress and torsional stress. When the adhesive layer's loss tangent (tanδ ₆₀ ) at 60°C is within the above range, deformation of the adhesive layer is suppressed even when stress is applied during processing, particularly dry polishing. Chip alignment is maintained, thus tending to suppress chip scattering.

Furthermore, tan δ ₆₀ is more preferably 0.05 or more, and even more preferably 0.10 or more. On the other hand, tan δ ₆₀ is more preferably 0.37 or less.

Furthermore, the shear storage modulus (G') is an indicator of the adhesive layer's deformation ease (hardness). When the shear storage modulus ( _G'60 ) of the adhesive layer at 60°C is within the above range, the wafer-to-wafer adhesion is good even when stress is applied to the adhesive layer during processing steps, particularly dry polishing. The adhesive layer's holding force on the wafer is maintained, thus tending to suppress wafer scattering.

Furthermore, G' ₆₀ is more preferably 3.5×10 ⁴ Pa or more, and even more preferably 3.7×10 ⁴ Pa or more. On the other hand, G' ₆₀ is more preferably 5.0×10 ⁵ Pa or less, and even more preferably 1.0×10 ⁵ Pa or less.

Therefore, in this embodiment, by controlling both the loss tangent and the shear storage modulus of the adhesive layer at 60°C within the above range, the effect of effectively suppressing chip flying can be further improved even when the adhesive layer is heated during dry polishing.

The loss tangent and shear storage modulus of an adhesive layer can be measured using known methods. For example, the adhesive layer can be formed into a sample of a predetermined size. Using a dynamic viscoelasticity measuring device, strain can be applied to the sample at a predetermined frequency within a predetermined temperature range to measure the modulus. The loss tangent and shear storage modulus can then be calculated from the measured modulus.

The loss tangent and shear storage modulus described above refer to the physical properties of the uncured adhesive layer at 60°C before attachment to a semiconductor wafer or chip. If the adhesive layer is formed using an energy-beam-curable adhesive, these refer to the physical properties of the adhesive layer at 60°C before energy-beam curing.

Furthermore, the aforementioned loss tangent and shear storage modulus can be varied by, for example, adjusting the composition of the adhesive composition constituting the adhesive layer.

The thickness of the adhesive layer is preferably less than 200 μm, more preferably 5 to 80 μm, and even more preferably 10 to 70 μm. By thinning the adhesive layer in this manner, the proportion of the adhesive tape with low rigidity can be reduced, thereby further preventing semiconductor chip defects caused by backside grinding.

(1.7. Adhesive Layer Composition) The composition of the adhesive layer is not particularly limited. To achieve the aforementioned physical properties, in this embodiment, the adhesive layer is composed of, for example, an acrylic adhesive, a urethane adhesive, a rubber adhesive, or a silicone adhesive, with an acrylic adhesive being preferred.

Furthermore, the adhesive layer is preferably formed of an energy-beam-curable adhesive. By forming the adhesive layer from an energy-beam-curable adhesive, the loss tangent and shear storage modulus are set within the above-mentioned ranges before curing by energy-beam irradiation, and the peeling force after curing can be easily reduced to 1000 mN/50 mm or less.

Specific examples of the adhesive are described in detail below, but these are non-limiting examples, and the adhesive layer of the present invention should not be construed as being limited to these.

As energy-ray-curing adhesives, for example, energy-ray-curing adhesive compositions containing a non-energy-ray-curing adhesive resin (also referred to as "adhesive resin I") and an energy-ray-curing compound other than the adhesive resin (hereinafter also referred to as "X-type adhesive composition") can be used. Furthermore, as energy-ray-curing adhesives, adhesive compositions containing as a main component an energy-ray-curing adhesive resin (hereinafter also referred to as "adhesive resin II") in which unsaturated groups are introduced into the side chains of a non-energy-ray-curing adhesive resin and containing no energy-ray-curing compound other than the adhesive resin (hereinafter also referred to as "Y-type adhesive composition") can also be used.

Furthermore, as the energy ray-curable adhesive, a combination of X-type and Y-type adhesives may be used, that is, an energy ray-curable adhesive composition containing, in addition to the energy ray-curable adhesive resin II, an energy ray-curable compound other than the adhesive resin (hereinafter also referred to as an "XY-type adhesive composition").

Among these, the XY type adhesive composition is preferred. The XY type provides sufficient adhesion before curing and also significantly reduces the peeling force on the semiconductor wafer after curing.

However, the adhesive may also be formed from a non-energy ray-curable adhesive composition that does not cure even when irradiated with energy rays. The non-energy ray-curable adhesive composition is an adhesive composition that contains at least a non-energy ray-curable adhesive resin I and does not contain the aforementioned energy ray-curable adhesive resin II and energy ray-curable compound.

In the following description, the term "adhesive resin" is used to refer to one or both of the above-mentioned adhesive resins I and II. Specific examples of adhesive resins include acrylic resins, urethane resins, rubber resins, and silicone resins, with acrylic resins being preferred.

(1.7.1. Acrylic Resins) The following describes in more detail acrylic adhesives using acrylic resins as adhesive resins.

The acrylic resin can use an acrylic polymer (a). The acrylic polymer (a) is obtained by polymerizing a monomer containing at least an alkyl (meth)acrylate, and contains structural units derived from the alkyl (meth)acrylate. Examples of the alkyl (meth)acrylate include those having an alkyl group with 1 to 20 carbon atoms, and the alkyl group may be a linear or branched group. Specific examples of the alkyl (meth)acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, and dodecyl (meth)acrylate. The alkyl (meth)acrylate can be used alone or in combination of two or more.

Furthermore, from the perspective of improving the adhesive strength of the adhesive layer, the acrylic polymer (a) preferably contains structural units derived from an alkyl (meth)acrylate having an alkyl group with 4 or more carbon atoms. The alkyl (meth)acrylate preferably has 4 to 12 carbon atoms, and more preferably 4 to 6 carbon atoms. Furthermore, the alkyl (meth)acrylate having an alkyl group with 4 or more carbon atoms is preferably an alkyl acrylate.

In the acrylic polymer (a), the content ratio of the (meth)acrylate having an alkyl group having 4 or more carbon atoms relative to the total amount of monomers constituting the acrylic polymer (a) (hereinafter also referred to as "total monomer amount") is preferably 40 to 98% by mass, more preferably 45 to 95% by mass, and even more preferably 50 to 90% by mass.

In addition to structural units derived from an alkyl (meth)acrylate having an alkyl group with 4 or more carbon atoms, the acrylic polymer (a) preferably comprises a copolymer containing structural units derived from an alkyl (meth)acrylate having an alkyl group with 1 to 3 carbon atoms in order to adjust the modulus and adhesive properties of the adhesive layer. Furthermore, the alkyl (meth)acrylate is preferably an alkyl (meth)acrylate having 1 or 2 carbon atoms, more preferably methyl (meth)acrylate, and most preferably methyl methacrylate. In the acrylic polymer (a), the alkyl (meth)acrylate having an alkyl group with 1 to 3 carbon atoms accounts for preferably 1 to 30% by mass, more preferably 3 to 26% by mass, and even more preferably 6 to 22% by mass, relative to the total monomer weight.

The acrylic polymer (a) preferably has structural units derived from a functional group-containing monomer in addition to the structural units derived from the aforementioned alkyl (meth)acrylate. Examples of the functional group of the functional group-containing monomer include hydroxyl groups, carboxyl groups, amino groups, and epoxy groups. The functional group-containing monomer can react with a crosslinking agent described below to serve as a crosslinking starting point, or react with an unsaturated group-containing compound to introduce an unsaturated group into the side chains of the acrylic polymer (a).

Examples of functional group-containing monomers include hydroxyl-containing monomers, carboxyl-containing monomers, amino-containing monomers, and epoxy-containing monomers. These monomers may be used alone or in combination of two or more. Among these, hydroxyl-containing monomers and carboxyl-containing monomers are preferred, and hydroxyl-containing monomers are more preferred.

Examples of the hydroxyl group-containing monomer include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; and unsaturated alcohols such as vinyl alcohol and allyl alcohol.

Examples of carboxyl group-containing monomers include ethylenically unsaturated monocarboxylic acids such as (meth)acrylic acid and crotonic acid; ethylenically unsaturated dicarboxylic acids such as fumaric acid, itaconic acid, maleic acid, and citric acid; and their anhydrides; and 2-carboxyethyl methacrylate.

The content ratio of the functional group monomer is preferably 1 to 35 mass %, more preferably 3 to 32 mass %, and even more preferably 6 to 30 mass % relative to the total amount of monomers constituting the acrylic polymer (a).

Furthermore, the acrylic polymer (a) may contain structural units derived from monomers copolymerizable with the acrylic monomers, such as styrene, α-methylstyrene, vinyltoluene, vinyl formate, vinyl acetate, acrylonitrile, and acrylamide, in addition to the above-mentioned monomers.

The acrylic polymer (a) can be used as a non-energy ray-curable adhesive resin I (acrylic resin). Energy ray-curable acrylic resins include those obtained by reacting a compound having a photopolymerizable unsaturated group (also referred to as an unsaturated group-containing compound) with the functional groups of the acrylic polymer (a).

The unsaturated group-containing compound is a compound having both a substituent capable of bonding to a functional group of the acrylic polymer (a) and a photopolymerizable unsaturated group. Examples of the photopolymerizable unsaturated group include (meth)acryloyl, vinyl, allyl, and vinylbenzyl groups, with (meth)acryloyl being preferred.

Furthermore, examples of substituents capable of bonding to functional groups possessed by unsaturated group-containing compounds include isocyanate groups, glycidyl groups, and the like. Thus, examples of unsaturated group-containing compounds include (meth)acryloyloxyethyl isocyanate, (meth)acryloyl isocyanate, and glycidyl (meth)acrylate.

Furthermore, the unsaturated group-containing compound preferably reacts with a portion of the functional groups of the acrylic polymer (a). Specifically, the unsaturated group-containing compound preferably reacts with 50 to 98 mol% of the functional groups of the acrylic polymer (a), and more preferably reacts with 55 to 93 mol%. In this manner, a portion of the functional groups in the energy ray-curable acrylic resin remain without reacting with the unsaturated group-containing compound, making crosslinking with the crosslinking agent more readily possible.

The weight average molecular weight (Mw) of the acrylic resin is preferably 300,000 to 1.6 million, more preferably 400,000 to 1.4 million, and even more preferably 500,000 to 1.2 million.

(1.7.2. Energy-Beam-Curing Compounds) The energy-beam-curing compound contained in the X-type or XY-type adhesive composition is preferably a monomer or oligomer having an unsaturated group in the molecule and capable of polymerization and curing upon exposure to energy beams.

Examples of such energy ray-curable compounds include poly(meth)acrylate monomers such as trihydroxymethylpropane tri(meth)acrylate, pentaerythritol (meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,4-butanediol di(meth)acrylate, and 1,6-hexanediol (meth)acrylate; and oligomers such as urethane (meth)acrylate, polyester (meth)acrylate, polyether (meth)acrylate, and epoxy (meth)acrylate.

Among these, urethane (meth)acrylate oligomers are preferred due to their higher molecular weight and less tendency to reduce the modulus of the adhesive layer. The molecular weight of the energy ray-curable compound (weight average molecular weight for oligomers) is preferably 100-12,000, more preferably 200-10,000, even more preferably 400-8,000, and particularly preferably 600-6,000.

The content of the energy ray-curable compound in the X-type adhesive composition is preferably 40 to 200 parts by mass, more preferably 50 to 150 parts by mass, and even more preferably 60 to 90 parts by mass, relative to 100 parts by mass of the adhesive resin.

On the other hand, the content of the energy-beam-curable compound in the XY-type adhesive composition is preferably 1-30 parts by mass, more preferably 2-20 parts by mass, and even more preferably 3-15 parts by mass, relative to 100 parts by mass of the adhesive resin. In XY-type adhesive compositions, because the adhesive resin is energy-beam-curable, even with a relatively low content of the energy-beam-curable compound, the peeling force can be sufficiently reduced after energy-beam irradiation.

(1.7.3. Crosslinking Agent) The adhesive composition preferably further contains a crosslinking agent. A crosslinking agent is, for example, a substance that reacts with functional groups derived from functional group monomers contained in the adhesive resin to crosslink the adhesive resins. Examples of crosslinking agents include isocyanate-based crosslinking agents such as toluene diisocyanate, hexamethylene diisocyanate, and adducts thereof; epoxy-based crosslinking agents such as ethylene glycol glycidyl ether; aziridine-based crosslinking agents such as hexa[1-(2-methyl)-aziridinyl]triphosphatriazine; and chelate-based crosslinking agents such as aluminum chelates. These crosslinking agents may be used alone or in combination of two or more.

Among these, isocyanate-based crosslinking agents are preferred from the viewpoints of enhancing cohesive strength and thus improving adhesiveness, and from the viewpoints of easy availability.

From the perspective of promoting the crosslinking reaction, the amount of the crosslinking agent is preferably 0.01-10 parts by mass, more preferably 0.03-7 parts by mass, and even more preferably 0.05-4 parts by mass, relative to 100 parts by mass of the adhesive resin.

(1.7.4. Photopolymerization Initiator) If the adhesive composition is energy-beam-curable, it is preferable to further contain a photopolymerization initiator. The inclusion of a photopolymerization initiator allows the adhesive composition to fully cure even with relatively low-energy energy such as ultraviolet light.

As the photopolymerization initiator, there can be mentioned, for example, benzoin compounds, acetophenone compounds, acylphosphine oxide compounds, titanocene compounds, 9-oxosulfur compounds, Photosensitizers such as thioxanthone compounds, peroxide compounds, and amines and quinones can be specifically mentioned. For example, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propane-1-one, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzyl phenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, dibenzyl, diacetyl, 8-chloroanthraquinone, and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide can be mentioned.

These photopolymerization initiators may be used alone or in combination. The amount of the photopolymerization initiator to be added is preferably 0.01 to 10 parts by mass, more preferably 0.03 to 5 parts by mass, and even more preferably 0.05 to 5 parts by mass, per 100 parts by mass of the adhesive resin.

(1.7.5. Other Additives) The adhesive composition may contain other additives, as long as they do not impair the effectiveness of the present invention. Examples of such additives include antistatic agents, antioxidants, softeners (plasticizers), fillers, rustproofing agents, pigments, and dyes. When mixing these additives, the amount of the additive is preferably 0.01 to 6 parts by weight per 100 parts by weight of the adhesive resin.

Furthermore, from the perspective of improving coating properties on substrates, buffer layers, release sheets, etc., the adhesive composition may be further diluted with an organic solvent to obtain a solution of the adhesive composition.

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

The organic solvents used in the synthesis of the adhesive resin may be used directly, or one or more organic solvents other than the organic solvents used in the synthesis may be added so that the adhesive composition solution can be evenly applied.

(1.8. Peel Sheet) A peel sheet may also be attached to the surface of the adhesive tape. Specifically, the peel sheet is attached to the adhesive layer of the adhesive tape. While the peel sheet is attached to the adhesive layer during transportation, it protects the adhesive layer during storage. The peel sheet is attached to the adhesive tape in a removable manner and is removed from the tape before use (i.e., before back grinding the wafer).

The release sheet is a release sheet having at least one surface subjected to a release treatment. Specifically, a release sheet obtained by coating a release agent on the surface of a release sheet substrate can be cited.

The release sheet substrate is preferably a resin film. Examples of the resin constituting the resin film include polyester resin films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, and polyolefin resins such as polypropylene and polyethylene. Examples of the release agent include rubber elastomers such as silicone resins, olefin resins, isoprene resins, and butadiene resins, long-chain alkyl resins, alkyd resins, and fluororesins.

The thickness of the peeling sheet is not particularly limited, but is preferably 10-200 μm, more preferably 20-150 μm.

(2. Adhesive Tape Manufacturing Method) The adhesive tape of the present invention can be manufactured using any known method without particular limitation.

For example, by laminating an adhesive layer provided on a release sheet to one side of a substrate, an adhesive tape with a release sheet attached to the surface of the adhesive layer can be produced. Alternatively, by laminating a buffer layer provided on a release sheet to the substrate and then removing the release sheet, a laminate of the buffer layer and substrate can be obtained. Furthermore, by laminating an adhesive layer provided on a release sheet to the substrate side of the laminate, an adhesive tape with a release sheet attached to the surface of the adhesive layer can be produced. Furthermore, when the buffer layer is provided on both sides of the substrate, the adhesive layer can be formed on the buffer layer. The peeling sheet attached to the surface of the adhesive layer can be removed by appropriately peeling it off before using the adhesive tape.

The adhesive layer can be formed on the release sheet by directly applying the adhesive composition to the release sheet using a known coating method, and then heating and drying the coated film to evaporate the solvent. Examples of coating methods include spin coating, spray coating, rod coating, doctor blade coating, roll coating, blade coating, die coating, and gravure coating. Similarly, the adhesive composition can be directly coated on one side of the substrate or on the buffer layer to form an adhesive layer.

(3. Semiconductor Device Manufacturing Method) The adhesive tape of the present invention is particularly suitable for use when attached to the surface of a semiconductor wafer during pre-cutting, followed by backside grinding and subsequent dry polishing. As a non-limiting example of the use of the adhesive tape, a semiconductor device manufacturing method is described in more detail below.

Specifically, the method for manufacturing a semiconductor device comprises at least the following steps 1 to 4. Step 1: Forming trenches on the front surface of a semiconductor wafer; Step 2: Attaching the adhesive tape to the surface of the semiconductor wafer; Step 3: Grinding the semiconductor wafer with the adhesive tape attached and the trenches formed thereon from the back side to remove the bottoms of the trenches and singulate the wafers into a plurality of chips, and dry-polishing the singulated chips; and Step 4: Peeling the adhesive tape off the singulated semiconductor wafer (i.e., the plurality of semiconductor chips).

The following describes in detail each step of the method for manufacturing the semiconductor device.

(3.1. Step 1) In Step 1, trenches are formed from the surface of the semiconductor wafer. The trenches formed in this step are shallower than the thickness of the semiconductor wafer. The trenches can be formed by dicing using a conventional wafer dicing device. Furthermore, in Step 3, described later, the bottoms of the trenches are removed, thereby separating the semiconductor wafer into a plurality of semiconductor chips along the trenches.

The semiconductor wafer used in this manufacturing method can be a silicon wafer, but can also be a wafer made of gallium-arsenic, glass wafer, or sapphire wafer. The thickness of the semiconductor wafer before grinding is not particularly limited, but is typically around 500-1000μm. Furthermore, semiconductor wafers typically have circuits formed on their surfaces. Circuits can be formed on the wafer surface using a variety of methods, including etching, lift-off, and blade methods, which have been widely used.

(3.2. Step 2) In step 2, the adhesive tape of the present invention is attached to the surface of the semiconductor wafer having the trenches formed therein through the adhesive layer.

A semiconductor wafer with grooves formed on it and adhesive tape attached is placed on a suction machine and held by suction. The semiconductor wafer is held by suction with its top surface facing the machine.

(3.3. Step 3) After Steps 1 and 2, the backside of the semiconductor wafer on the suction machine is ground and sliced into multiple semiconductor chips.

Here, because the semiconductor wafer has trenches shallower than its thickness, back grinding is performed to thin the semiconductor wafer to at least the bottom of the trenches. This back grinding creates cuts through the wafer, and the semiconductor wafer is divided by these cuts into individual semiconductor chips.

The shape of the individualized semiconductor chips can be square or an elongated shape such as a rectangle. The thickness of the individualized semiconductor chips is not particularly limited, but is preferably approximately 5 to 100 μm, more preferably 10 to 45 μm. The size of the individualized semiconductor chips is not particularly limited, but is preferably less than 50 ^mm² , more preferably less than 30 ^mm² , and even more preferably less than 10 ^mm² .

After back grinding, dry polishing is performed.

Back grinding leaves residual grinding marks on the back of the wafer, which is a major factor in damaging the wafer's flexural strength. As wafers become thinner and smaller, wafer damage and reduced flexural strength are becoming a problem. To remove these grinding marks (damage), it is best to perform dry polishing after back grinding, removing the damage and improving the wafer's flexural strength.

However, unlike back grinding, dry polishing does not use water, so the heat generated during grinding cannot be removed by water, resulting in the wafer retaining heat. The heat of the wafer is transferred to the adhesive tape to which the wafer is attached. As a result, during dry polishing, the temperature of the adhesive tape reaches 60°C or higher, and the adhesive tape's holding force on the wafer becomes insufficient, causing the wafer to peel off and scatter. However, by using the adhesive tape of the present invention, deformation of the adhesive tape can be suppressed, and wafer scattering can be reduced. Therefore, the adhesive tape of the present invention is particularly suitable for use in pre-cutting methods that include a dry polishing step to hold semiconductor wafers, chips, etc.

That is, by using the adhesive tape of the present invention, even such a thin and/or small semiconductor chip can be prevented from being damaged during back grinding and dry polishing (step 3) and when the adhesive tape is peeled off (step 4).

(3.4. Step 4) Next, the adhesive tape is peeled off from the singulated semiconductor wafer (i.e., multiple semiconductor chips). For example, this step is performed using the following method.

First, when the adhesive layer of the adhesive tape is formed from an energy-beam-hardening adhesive, the energy beam is irradiated to harden the adhesive layer. Next, the pick-up tape is attached to the back side of the individualized semiconductor wafer and aligned in position and direction so that it can be picked up. At this time, the annular frame arranged on the outer peripheral side of the wafer is also attached to the pick-up tape, and the outer peripheral portion of the pick-up tape is fixed to the annular frame. The wafer and the annular frame can be attached to the pick-up tape at the same time, or they can be attached at different time points. Next, the adhesive tape is peeled off from the multiple semiconductor chips fixed on the pick-up tape.

Subsequently, multiple semiconductor chips on the pickup tape are picked up and fixed on a substrate, etc. to manufacture semiconductor devices.

The pickup tape is not particularly limited, and may be, for example, an adhesive sheet including a base material and an adhesive layer provided on one side of the base material.

Furthermore, adhesive tape can be used instead of pickup tape. Adhesive tape can be a laminate of a film adhesive and a peeling sheet, a laminate of a dicing tape and a film adhesive, or a dicing/die bonding tape composed of an adhesive layer and a peeling sheet that functions as both dicing tape and die bonding tape. Furthermore, before attaching the pickup tape, a film adhesive can be applied to the backside of the singulated semiconductor wafer. When using a film adhesive, the film adhesive can also be the same shape as the wafer.

When using adhesive tape or applying a film of adhesive to the backside of a singulated semiconductor wafer before attaching a pickup tape, multiple semiconductor chips are picked up along with the adhesive layer, which has been separated into identical shapes. The semiconductor chips are then secured to a substrate or other surface through the adhesive layer, thereby manufacturing semiconductor devices. The separation of the adhesive layer can be performed using lasers, expansion, or other methods.

The adhesive tape of the present invention has been described above mainly by using an example to illustrate a method of singulating a semiconductor wafer by a pre-dicing method and performing dry polishing.

The above describes the embodiments of the present invention. However, the present invention is not limited to the above embodiments and can be modified and adopted in various forms within the scope of the present invention. [Examples]

Hereinafter, the present invention will be described in more detail based on embodiments, but the present invention is not limited to these embodiments.

The measurement method and evaluation method in this embodiment are as follows.

(Tensile Storage Modulus) Prepare a 15 mm wide x 2310 mm long film made of the same material as the substrate film or sheet. Using a dynamic viscoelasticity device (ORIENTEC, trade name "Rheovibron DDV-II-EP1"), measure the tensile modulus of ten specimens of the film at an 11 Hz frequency and a temperature range of -20°C to 150°C. The average tensile modulus of the ten specimens at 60°C is designated as _E'60 .

(Wafer Scattering Evaluation) The adhesive tapes with release sheets obtained in the Examples and Comparative Examples were mounted on a tape laminator ("RAD-3510," manufactured by LINTEC Co., Ltd.) while peeling the release sheets. The tapes were then attached to a 12-inch silicon wafer (760 μm thick) with pre-cut grooves formed on the wafer surface under the following conditions. Roller Height: 0 mm Roller Temperature: 23°C (Room Temperature) Machine Temperature: 23°C (Room Temperature)

The obtained silicon wafer with adhesive tape attached was sliced into squares with a thickness of 30 μm and a chip size of 1 mm using back grinding (pre-dicing method).

After back grinding, the ground surface was dry-polished using a DISCO DPG8760 grinding wheel. A DISCO Gettering DP grinding wheel was used. This dry polishing removed any damage (grinding marks) from the wafer.

After dry polishing, the wafers held at the ends of the adhesive tape are visually inspected for any chip scattering. A chip without chip scattering is judged "good," while a chip with chip scattering is judged "poor." Furthermore, since chips located in the outermost region of the silicon wafer have a different shape (usually triangular) than the required shape (usually square), the aforementioned evaluation does not consider chip scattering. In other words, the aforementioned evaluation only assesses the presence of chip scattering in square-shaped chips.

In addition, all the mass parts in the following Examples and Comparative Examples are solid content values.

(Compound Substrate) Polyethylene terephthalate films (tensile storage modulus: 2500 MPa) with a thickness of 25.0 μm and 75.0 μm were used as the substrates. A compound substrate was prepared with a 27.5 μm thick buffer layer (LDPE, low-density polyethylene) provided on both sides of these substrates. The compound substrate composition is as follows: Compound Substrate 1: LDPE (27.5 μm)/PET (25.0 μm)/LDPE (27.5 μm) Compound Substrate 2: LDPE (27.5 μm)/PET (75.0 μm)/LDPE (27.5 μm)

(Preparation of Adhesive Composition A) An acrylic polymer (a) obtained by copolymerizing 65 parts by mass of butyl acrylate (BA), 20 parts by mass of methyl methacrylate (MMA), and 15 parts by mass of 2-hydroxyethyl acrylate (HEA) was reacted with 2-methacryloyloxyethyl isocyanate (MOI) to add 80 mol% of hydroxyl groups to the total hydroxyl groups in the acrylic polymer (a), thereby obtaining an energy-ray-curable acrylic resin (Mw: 500,000).

With respect to 100 parts by mass of the obtained energy ray-curable acrylic polymer, 6 parts by mass of a urethane acrylate oligomer (UT-4220, manufactured by Nippon Gosei Kagaku Kogyo Co., Ltd.) as an energy ray-curable compound, 0.375 parts by mass of a toluene diisocyanate-based crosslinker (CORONATE L, manufactured by TOSOH Corporation) (solid content), and 1.00 parts by mass of a photopolymerization initiator (IRGACURE 184, manufactured by Ciba Specialty Chemicals Co., Ltd.) (solid ratio) were mixed to obtain an energy ray-curable adhesive composition A.

(Preparation of Adhesive Composition B) An acrylic polymer (a) obtained by copolymerizing 52 parts by mass of butyl acrylate (BA), 20 parts by mass of methyl methacrylate (MMA), and 28 parts by mass of 2-hydroxyethyl acrylate (HEA) was reacted with 2-methacryloyloxyethyl isocyanate (MOI) to obtain an energy-beam-curable acrylic resin (Mw: 600,000) by adding hydroxyl groups to the total hydroxyl groups of the acrylic polymer (a).

With respect to 100 parts by mass of the obtained energy ray-curable acrylic polymer, 0.50 parts by mass (solid content) of a toluene diisocyanate-based crosslinking agent (manufactured by TOSOH Corporation, product name "CORONATE L") and 3.70 parts by mass (solid ratio) of a photopolymerization initiator (manufactured by Ciba Specialty Chemicals Co., Ltd., product name "IRGACURE 184") were mixed to obtain an energy ray-curable adhesive composition B.

(Example 1) The energy-beam-curable adhesive composition A obtained above was applied to the release-treated surface of a release sheet (manufactured by LINTEC Co., Ltd., trade name: SP-PET381031). The coating was then heat-dried at 100°C for 1 minute to form a 20 μm thick adhesive layer on the release sheet.

The formed adhesive layer was bonded to one side of a composite substrate 1 to produce an adhesive tape. The resulting adhesive tape was tested for its tensile storage modulus (E'60 ₎ at 60°C and evaluated for chip scattering. The results are shown in Table 1.

Example 2: An adhesive tape was produced in the same manner as Example 1, except that composite substrate 2 was used as the substrate. The resulting adhesive tape was tested for its tensile storage modulus (E'60 ₎ at 60°C and evaluated for chip scattering. The results are shown in Table 1.

(Comparative Example 1) An adhesive tape was produced in the same manner as in Example 1, except that an 80 μm thick polyvinyl chloride substrate was used and Adhesive Composition B was used as the adhesive layer. The resulting adhesive tape was tested for its tensile storage modulus ( _E'60) at 60°C and wafer scattering. The results are shown in Table 1.

(Comparative Example 2) An adhesive tape was produced in the same manner as in Example 1, except that an 80 μm thick polyolefin substrate was used and Adhesive Composition B was used as the adhesive layer. The resulting adhesive tape was tested for its tensile storage modulus ( _E'60) at 60°C and wafer scattering. The results are shown in Table 1.

[Table 1] In the table, "aE+b" means a×10 ^b

From Table 1, it can be confirmed that when the tensile storage modulus _E'60 of the substrate at 60°C is within the above range, chip scattering can be suppressed.

without.

without.

Claims (1)

A method for manufacturing a semiconductor device comprises the following steps: forming a groove from the surface side of a semiconductor wafer; attaching an adhesive tape to the surface of the semiconductor wafer, wherein the adhesive tape comprises a substrate and an adhesive layer provided on one side thereof, wherein the substrate has a buffer layer on both sides thereof, and the buffer layer is an LDPE film, wherein the tensile storage modulus of the substrate at 60°C is greater than 250 MPa and 110 0 MPa or less, the adhesive layer being composed of an energy-ray-curing acrylic adhesive; grinding the semiconductor wafer having the adhesive tape attached to its surface and the trenches formed thereon from the back side to remove the bottoms of the trenches and thereby singulate the semiconductor wafer into a plurality of chips; dry polishing the semiconductor wafer after singulating the semiconductor chips; and peeling the chips from the adhesive tape.