TW201938729A - Adhesive tape for back grinding capable of being peeled off without any residue of the paste - Google Patents

Abstract

An object of the present invention is to provide an adhesive tape for back surface polishing, which is suitable for conforming to bumps or electrode projections when it is attached to a semiconductor wafer having bumps or electrode projections, and the like. The occurrence rate of wafer damage or wafer damage is extremely small. Furthermore, when the adhesive tape is peeled off, the incidence of damage to the bumps or electrode protrusions is extremely small. There will be no paste residue on the surface, which can be easily peeled off and can be fully suppressed. The thickness of the wafer after back grinding is uneven.
As a solution of the present invention, an adhesive tape for back grinding is provided. The adhesive tape for back grinding of a semiconductor wafer having a substrate and an intermediate resin layer and an adhesive layer formed on the substrate in this order is characterized in that The intermediate resin layer has a storage elastic modulus (G ') of 0.15 × 10 ⁶ to 1.51 × 10 ⁶ Pa at a temperature of 55 to 80 ° C. The adhesive layer is composed of a non-hardening adhesive. This non-hardening adhesive contains an acrylic adhesive polymer having an acid value of 2.0 mgKOH / g or less and a hydroxyl value of 1.0 to 15.0 mgKOH / g as a main component.

Description

Adhesive tape for back grinding

The present invention relates to an adhesive tape for back grinding, which is attached for the purpose of protecting the surface of a semiconductor wafer when grinding the back of a semiconductor wafer.

A semiconductor wafer manufactured in a large-diameter state is formed into a specified circuit pattern on the surface of the semiconductor wafer by photoresist, etching, ion implantation, polishing, or the like, or an electrode is formed by sputtering to a specified thickness. The back surface grinding process (hereinafter, also referred to as "back surface grinding") is carried out in accordance with the method, and if necessary, back surface processing (etching, polishing, etc.), cutting processing, and the like are performed.

Structures such as electrical circuits and electrodes are formed on the surface of the semiconductor wafer. In order to prevent the structure from being damaged by trauma or contamination due to contact with grinding chips or grinding water during the above-mentioned back surface polishing, an adhesive tape called an adhesive tape for back surface polishing is attached to the surface of the semiconductor wafer in advance. A method of peeling the adhesive tape from a semiconductor wafer after back grinding.

The adhesive tape for back surface polishing is used for back surface polishing, so that the surface of the semiconductor wafer is not immersed in grinding chips or grinding water, and the surface of the semiconductor wafer needs to be very close when attached. On the other hand, in order not to damage or contaminate the structure on the surface of the semiconductor wafer, the adhesive is not easily left (sticky) when the adhesive tape for back surface polishing is peeled off, and it is necessary to detach it.

In recent years, with the miniaturization and high density of electronic devices, flip chip mounting has become the mainstream as a method for mounting semiconductor devices with the smallest area. In this mounting method, a bump composed of solder or gold has been formed on the electrode of the semiconductor element, and the bump and the wiring on the circuit board have been electrically connected. For example, in the case of a wafer-level package, the height of the bump is the semiconductor wafer with bumps that is 250-350 μm, which is the higher one.

However, since semiconductor wafers with bumps have large uneven shapes on the surface, it is difficult to process thin films. When using ordinary adhesive tape for backside grinding, the so-called (1) immersion in grinding chips or grinding water, ( 2) The semiconductor wafer is cracked, (3) the thickness accuracy of the semiconductor wafer after the back grinding is deteriorated, and (4) the depression (dent) is generated on the grinding surface. Therefore, it is used for the grinding of semiconductor wafers with bumps. A surface protection tape specially designed to conform to the height of the above bumps so as to absorb the unevenness of the surface, is used for the back grinding process. Furthermore, since there is still a strong demand to change the finished thickness of the wafer after grinding on the back side, various types of adhesive wafers or sheets for surface protection of semiconductor wafers with various configurations having higher performance are being developed.

Patent Document 1 discloses that when a back surface of an adherend having a large unevenness on the surface is processed, it is adhered to the surface and is preferably used to protect the surface. In particular, it is possible to grind the adherend to an extremely thin thickness. Uniform thickness grinding for the purpose of preventing the occurrence of dent-like adhesive sheets. It consists of a substrate, an intermediate layer formed thereon, and an adhesive layer formed on the intermediate layer. The sheet is an adhesive sheet for surface protection of a semiconductor wafer whose elastic modulus at 40 ° C. of the intermediate layer is less than 1.0 × 10 ⁶ Pa.

Patent Document 2 discloses that it is possible to provide protection of bumps and recesses on the wafer surface and grinding chips or grinding on the surface of the wafer to provide a method for grinding the back surface of the wafer to a level difference between bumps and recesses formed on the wafer surface. The purpose of preventing the intrusion of water and the prevention of damage to the wafer after grinding is to use an adhesive sheet for semiconductor wafer protection, which is a semiconductor formed by laminating a substrate and at least one intermediate layer and an adhesive layer in this order. Adhesive sheet for wafer protection, the bonding temperature between the adhesive sheet and the semiconductor wafer is 50 ° C to 100 ° C, and the loss tangent (tanδ) of the bonding temperature of the intermediate layer on the side in contact with the adhesive layer is 0.5 or more, The adhesive sheet for semiconductor wafer protection having a loss of elasticity at the bonding temperature of the intermediate layer on the side in contact with the adhesive layer is 0.005 MPa to 0.5 MPa.

Patent Document 3 discloses a method for providing a semiconductor wafer surface protection that does not cause damage or seepage of the semiconductor wafer even if it is ground, and can be easily peeled off from the semiconductor wafer, and the residue of the paste can be suppressed. Adhesive tape is used for the purpose. It is an adhesive tape for semiconductor wafer surface protection with an adhesive layer on the substrate film. The adhesive force for stainless steel at 23 ℃ is 0.3 ～ 10N / 25mm, and the adhesive force when heated to 50 ℃. It is less than 40% of the adhesive force at 23 ° C, and the contact angle of pure water immediately after dropping on the surface of the adhesive layer is 100 ° or more, and the contact angle of pure water after dropping to 10 minutes is 65 ° or more A semiconductor wafer surface protection adhesive tape containing a (meth) acrylic polymer having an acid value of 20 to 50 (mgKOH / g) in the adhesive layer.

Patent Document 4 discloses a method for protecting the surface of a semiconductor wafer that can be firmly adhered to the semiconductor wafer during processing, and that there is no damage or residue of the semiconductor wafer during peeling. For the purpose of the adhesive tape, it is an adhesive tape for a semiconductor wafer which is heated and bonded at a temperature of 60 ° C. or higher with respect to a wafer having an unevenness of 20 μm or more on the surface of the wafer. The intermediate resin layer and the adhesive layer on the surface are composed of three layers. The base film has a melting point of more than 90 ° C and a flexural modulus of 1 GPa to 10 GPa. The intermediate resin layer is composed of ethylene-methyl acrylate copolymer resin, ethylene- Ethyl acrylate copolymer resin or ethylene-butyl acrylate copolymer resin is composed of two resin layers and a polyethylene resin layer. The base film side is a polyethylene resin layer, and the layer ratio is a polyethylene resin layer: Copolymer resin layer = 1: 9 to 5: 5, the thickness of the intermediate resin layer is greater than the height of the bumps, the melting point is in the range of 50 ° C to 90 ° C, and the flexural elasticity is in the range of 1 MPa to 100 MPa. Adhesive tape for semiconductor wafers.
[Prior technical literature]
[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2000-212530
[Patent Document 2] Japanese Patent Laid-Open No. 2010-258426
[Patent Document 3] Japanese Patent No. 5855299
[Patent Document 4] Japanese Patent Laid-Open No. 2016-164953

[Questions to be Solved by the Invention]

When the adhesive sheet of Patent Document 1 is used, the occurrence of depressions or unevenness in wafer thickness is suppressed after the back surface grinding. However, the intermediate layer is composed of an acrylic adhesive composition containing an acrylic adhesive and a diisocyanate curing agent, or a resin containing a photopolymerizable urethane acrylate oligomer and a photopolymerizable monomer. The composition is formed, so the elastic modulus is relatively small at 40 ° C, and tanδ is relatively large in the range of 0 ° C to 60 ° C. That is, because the intermediate layer is highly sticky (soft), after the adhesive sheet is attached to the wafer, there is a possibility that the adhesive cutting chips may cause contamination of the wafer along the outer periphery of the wafer when cutting the adhesive tape. Or when the back grinding makes the wafer with the bump height higher and the wafer with bumps is thinner, the pressure on the adhesive sheet is used to squeeze out the intermediate layer, which can not sufficiently suppress the damage to the wafer or the thickness of the wafer after grinding. Risk of unevenness.

When the adhesive sheet of Patent Document 2 is used, solder bumps can be bonded to the surface of the semiconductor wafer without voids. Even if the back surface of the semiconductor wafer is ground, the damage rate of the semiconductor wafer or the incidence of water intrusion into the ground can be 0. %. However, when the loss tangent (tan δ) of the bonding temperature (50 ° C to 100 ° C) of the intermediate layer is as large as 0.5 or more, the loss elastic modulus is as small as 0.005 MPa to 0.5 MPa. That is, because the intermediate layer is highly viscous (soft), the adhesive and the intermediate layer bite into the unevenness of the semiconductor wafer surface such as bumps without voids, and the anchoring effect is enhanced. For example, an ultraviolet curing adhesive is used as the adhesive. Sometimes, it may become difficult to peel off. In this case, although there is no damage to the wafer, the influence of the increase in the elastic modulus of the adhesive after UV curing may cause damage to the bumps.

When the adhesive tape of Patent Document 3 is used, it is suitable for conforming to semiconductor wafers with a surface step difference of 50 μm or less, without damage or leakage of the semiconductor wafer, and can be easily peeled from the semiconductor wafer. However, since the adhesive tape needs to be heated to 50 ° C., there is room for improvement in workability and temperature management. In addition, since the (meth) acrylic polymer having an acid value of 20 to 50 (mgKOH / g) is contained in the adhesive layer, the adhesiveness with the wafer at the initial stage is high, and the height of the back grinding bump is higher. It is unknown whether the wafers can be easily peeled without residue.

When the adhesive tape of Patent Document 4 is used, even in the case of attaching high bumps or narrowing the pitch between bumps, the adhesive tape is bonded by heating during semiconductor wafer processing to melt the intermediate resin layer. The bumps are fully compliant, firmly adhered to the semiconductor wafer, and when peeled off, the semiconductor wafer can be peeled off without damage to the semiconductor wafer or residue of paste. However, the adhesive completely conforms to the unevenness of the surface of the semiconductor wafer such as a bump together with the intermediate layer, and the anchoring effect is enhanced. For example, when an adhesive containing a radiation hardening polymer is used as the adhesive, it may become difficult to peel off. Although there is no damage to the wafer, the influence of the increase in the elastic modulus of the adhesive after UV curing may cause damage to the bumps.

As described above, even in the conventional surface protection adhesive tape or sheet used for semiconductor wafers that are specially designed to have uneven shapes such as bumps or electrode protrusions, the wafer after the back grinding or the bump portion is damaged Not all of the occurrence rate, the paste residue around the bumps or the wafer surface, and the thickness accuracy of the wafer after grinding are fully satisfied, and there is still room for improvement.

The present invention is to solve the above-mentioned conventional problems, and an object thereof is to provide an adhesive tape for back grinding, which is adapted to appropriately conform to bumps or electrode protrusions when attached to a semiconductor wafer having bumps or electrode protrusions, etc. In addition, when the back grinding is performed, the occurrence of dents or wafer damage is extremely small. Furthermore, when the adhesive tape is peeled off, the occurrence of damage to the bumps or electrode protrusions is extremely small, which does not occur on the surface to be landed. The residue of the paste can be easily peeled off, which can sufficiently suppress the unevenness of the thickness of the wafer after the back grinding.

[Means to solve the problem]

In view of the above-mentioned problems, as a result of intensive studies, the present inventors have found that at least a substrate film, an intermediate resin layer, and a non-radiation-curable adhesive layer are adhered to the surface of a semiconductor wafer having an uneven shape by heating. The semiconductor wafer composed of three layers is constructed with adhesive tape, and the storage elastic modulus (G ') in the temperature range of the intermediate resin layer and the acid value and hydroxyl value of the adhesive layer are set in specific ranges. The above conventional problems can be solved, and the present invention is finally completed.

That is, the present invention provides an adhesive tape for back surface polishing, which is a adhesive tape for back surface polishing of a semiconductor wafer having a substrate and an intermediate resin layer and an adhesive layer formed on the substrate in this order, which is characterized in that: The intermediate resin layer has a storage elastic modulus (G ') of 0.15 × 10 ⁶ to 1.51 × 10 ⁶ Pa at any temperature of 55 to 80 ° C. The adhesive layer is composed of a non-hardening adhesive. The hardenable (addition is not performed after external energy is added) the adhesive contains an acrylic adhesive polymer having an acid value of 2.0 mgKOH / g or less and a hydroxyl value of 1.0 to 15.0 mgKOH / g as a main component.
Here, the storage elasticity (G ') having an intermediate resin layer of 0.15 × 10 ⁶ to 1.51 × 10 ⁶ Pa at any temperature of 55 to 80 ° C. means a temperature range of 55 to 80 ° C. The storage elastic modulus (G ') of the intermediate resin layer at a specific temperature is 0.15 × 10 ⁶ to 1.51 × 10 ⁶ Pa.

The intermediate resin layer preferably has a thickness of 1.2 times or more the height difference of the uneven shape existing on the surface of the semiconductor wafer.

Furthermore, it is preferable that the intermediate resin layer includes an ethylene-vinyl acetate copolymer (EVA).

The ethylene-vinyl acetate copolymer (EVA) preferably contains 25 to 40% by mass of vinyl acetate.

Further, the substrate preferably has a thickness of 50 to 200 μm.

Moreover, it is preferable that the said adhesive layer has a thickness of 10-50 micrometers.

Furthermore, it is preferable that the diameter of the bump measured by the adhesive tape when the adhesive tape is attached to the surface of the semiconductor wafer with bumps as viewed from directly above the microscope is set to r _b . When the diameter of the non-adhesive portion of the circular shape formed by the adhesive tape on the surface of the semiconductor wafer that cannot be adhered to the surface of the semiconductor wafer is defined as r _a , the value of r _a / r _b is 1.15 to 1.50.

Furthermore, it is preferable that the height difference of the uneven shape existing on the surface of the semiconductor wafer is 50 to 300 μm.

Moreover, in a certain aspect, the attaching temperature at the time of attaching the said back-grinding adhesive tape to the said semiconductor wafer is any one of 55-80 degreeC.

[Inventive effect]

The adhesive tape for back surface polishing of the present invention is adapted to conform to bumps or electrode protrusions appropriately when it is attached to a semiconductor wafer having bumps or electrode protrusions, etc., and when the back grinding is performed, depressions or crystals are formed. The incidence of circle damage is extremely small. Furthermore, when the adhesive tape is peeled off, the incidence of damage to the bumps or electrode protrusions is extremely small. There will be no paste residue on the surface to be adhered, and it can be easily peeled off, which can sufficiently suppress the back surface grinding. The thickness of the wafer is uneven.

FIG. 1 is a cross-sectional view showing a layer structure of an adhesive tape for back grinding according to an embodiment of the present invention. The adhesive tape for back-grinding shown in FIG. 1 has a substrate 1 and an intermediate resin layer 2 and an adhesive layer 3 formed on the substrate in this order. As shown in FIG. 2, the adhesive tape for back surface polishing of the present invention is used on the surface of a semiconductor wafer with solder bumps.

The constituent members and the layer structure of the adhesive tape for back surface polishing of the present invention are not limited to the embodiment shown in FIG. 1. The adhesive tape for back grinding of the present invention may have layers other than the substrate 1, the intermediate resin layer 2, and the adhesive layer 3.

The back surface polishing adhesive tape may be provided with a release liner (not shown) to protect the adhesive surface of the adhesive layer 3 until use. Such a release liner is not particularly limited, and can be appropriately selected and used from known release liners.

The substrate 1 may be a material having a strength capable of withstanding the use environment, and includes paper, a polymer material, a cloth, a metal foil, and the like. Preferred are vinyl chloride, polystyrene, polyimide, polyimide, poly (tetrafluoroethylene), (polyethylene terephthalate, polyethylene naphthalate, etc.) polyester, etc. Polymer materials. Among them, it is preferable that after the back surface grinding of the semiconductor wafer is performed, the semiconductor wafer that becomes thin and brittle is not damaged, and a high-rigidity polyester film is used as the substrate 1 for transportation. In addition, when a polyester film is used as the substrate 1, since the rigidity and non-adhesion are high, the adhesion of the substrate 1 and the chuck table can be suppressed after the back surface grinding of the semiconductor wafer is finished. The shape of these substrates is a thin film, and the thickness is generally 50 to 200 μm, and preferably 75 to 100 μm.

When the thickness of the substrate is thinner than 50 μm, the rigidity is insufficient, and there is a possibility that the semiconductor wafer cannot be suppressed from being bent after the back grinding or the surface of the semiconductor wafer after the back grinding may be depressed. When the thickness of the substrate is thicker than 200 μm, the release liner may peel when the adhesive tape is in the form of a roll, or the semiconductor wafer may be damaged when the adhesive tape is peeled off after grinding on the back surface.

If necessary, it is known in this technical field to apply a primer composition to a substrate, or apply a corona treatment or flame treatment to the substrate, and modify the substrate before applying the resin composition of the intermediate resin layer. The surface of the material can improve the adhesion between the resin composition of the intermediate resin layer and the substrate. The use of a primer is particularly suitable when using a substrate of polyethylene terephthalate or polyethylene naphthalate.

The intermediate resin layer 2 is a layer that absorbs the height difference caused by the uneven shape when the adhesive layer is attached to the surface of the semiconductor wafer, and maintains the upper layer, that is, the surface of the base film in a flat state. In addition, it also has the function of a moderate buffer layer that does not damage the semiconductor wafer with pressure or impact during back grinding. Here, the difference in height caused by the uneven shape is the distance from the surface where the bump or the protruding electrode is never formed to the highest position of the bump or the protruding electrode.

The intermediate resin layer 2 has a storage elastic modulus (G ') at an attachment temperature to the surface of the semiconductor wafer to which the adhesive tape is attached, which is 0.15 × 10 ⁶ to 1.51 × 10 ⁶ Pa. When the storage elastic modulus of the intermediate resin layer 2 at the attachment temperature is less than 0.15 × 10 ⁶ Pa, it is too soft, and it engages the unevenness of the surface without gaps. When the adhesive tape is peeled off, the bumps may be damaged. Or it is easy to be battered. On the other hand, when the storage elastic modulus at the application temperature of the intermediate resin layer 2 exceeds 1.51 × 10 ⁶ Pa, it is too hard, which reduces the compliance with the unevenness of the surface to be adhered, and it is easy to be immersed in grinding chips or grinding water during back grinding. . The storage elastic modulus at the application temperature of the intermediate resin layer 2 is preferably 0.30 × 10 ⁶ Pa to 1.00 × 10 ⁶ Pa.

The intermediate resin layer 2 preferably has a storage elastic modulus (G ′) at 23 ° C. of 5.00 × 10 ⁶ to 7.00 × 10 ⁶ Pa. Although the adhesive tape attached during the grinding of the back surface of the semiconductor wafer has changed from normal temperature to about 40 ° C, when the storage elastic modulus (G ') at 23 ° C is within this range, the adhesive tape is attached to the surface of the semiconductor wafer Later, when semiconductor wafers are grinded on the backside, the pressure applied to the adhesive tape prevents the intermediate resin layer from flowing or protruding. Since the adhesive tape can properly hold the semiconductor wafer, it can moderately reduce the impact during the backside grinding. When the back surface of the wafer is ground, the damage to the semiconductor wafer is suppressed. After the back surface is ground, the occurrence of depressions on the surface of the semiconductor wafer is suppressed, and the thickness unevenness of the semiconductor wafer can be reduced.

The intermediate resin layer 2 preferably contains a thermoplastic resin from the viewpoint of adjusting the storage elasticity at the attachment temperature. One type of thermoplastic resin may be used, or two or more types may be used in combination.

Typical examples of thermoplastic resins include polyethylene (PE); polybutene; ethylene-propylene copolymer (EPM), ethylene-propylene-diene copolymer (EPDM), and ethylene-ethyl acrylate copolymer (EEA) , Ethylene-ethyl acrylate-maleic anhydride copolymer (EEAMAH), ethylene-glycidyl methacrylate copolymer (EGMA), ethylene-methacrylic acid copolymer (EMAA), ethylene-vinyl acetate copolymer (EVA ) And other ethylene copolymers; polyolefin-based copolymers; thermoplastic elastomers such as butadiene-based elastomers, ethylene-isoprene-based elastomers, and ester-based elastomers; thermoplastic polyesters; polyamide 12 copolymers Resins such as polyamines; polyurethanes; polystyrene resins; cellophane; acrylic resins such as polyacrylates and polymethyl methacrylates; vinyl chloride-vinyl acetate copolymers; Polyvinyl chloride-based resin.

The range of the weight average molecular weight of the thermoplastic resin is preferably 20,000 to 300,000, and more preferably 30,000 to 250,000.

The intermediate resin layer 2 is preferably made of an ethylene-vinyl acetate copolymer (EVA). When the intermediate resin layer contains an ethylene-vinyl acetate copolymer, even if the height difference due to the uneven shape on the surface of the semiconductor wafer is 50 to 300 μm, it is easy to have a moderate compliance with the uneven shape. In one aspect, the intermediate resin layer is substantially composed of an ethylene-vinyl acetate copolymer.

The ethylene-vinyl acetate copolymer contains 25 to 40% by mass of vinyl acetate. When the content of vinyl acetate in EVA is less than 25% by mass, the flexibility of the intermediate resin layer is insufficient, and the compliance with the unevenness of the surface to be contacted is reduced. When it exceeds 40% by mass, the intermediate resin layer becomes too soft. Agglomeration is easy to occur, and stable film formation becomes difficult, which reduces productivity.

The ethylene-vinyl acetate copolymer contains 25 to 40% by mass of vinyl acetate. In particular, the melt mass flow rate (MFR) is preferably 2 to 700 g / 10 minutes, and more preferably 5 to 400 g / 10 minutes. When the melt mass flow rate is within this range, it may have moderate compliance with the uneven shape on the surface of the semiconductor wafer, and at the same time, stable melt extrusion filming of the substrate 1 as an intermediate resin layer becomes possible.

The intermediate resin layer 2 may contain other components as long as the characteristics are not impaired. Examples of such components include adhesion-imparting agents, plasticizers, softeners, fillers, antioxidants, and anticaking agents. Although the intermediate resin layer 2 may be composed of one layer, it may have a multilayer structure composed of a plurality of layers of the same or different kinds. When the intermediate resin layer has a multilayer structure, the thickness of the intermediate resin layer refers to the total thickness of a plurality of layers.

The thickness of the intermediate resin layer 2 is determined in accordance with the height difference caused by the uneven shape of the surface to be faced or the unevenness in the height difference when the uneven portion is formed. The thickness of the intermediate resin layer is, for example, 1.2 times or more the height difference caused by the uneven shape of the surface to be landed. When the thickness of the intermediate resin layer is less than 1.2 times the height difference caused by the uneven shape of the surface to be adhered, the unevenness of the height of the uneven surface to be absorbed cannot be fully absorbed, the surface cannot be adhered closely, and the surface is immersed in grinding during back grinding Dust or grinding water. In addition, when the adhesive tape is affixed, the convex and concave convex portions of the surface to be protruded protrude from the base material, so that the surface of the semiconductor wafer after the back grinding may be recessed or the thickness of the semiconductor wafer may be uneven. The thickness of the intermediate resin layer is preferably 1.4 to 1.6 times the height difference due to the uneven shape.

Although the method of laminating the intermediate resin layer 2 on the substrate 1 is not particularly limited, for example, an extruder may be used to extrude the intermediate resin layer 2 into a film shape, and the substrate is prepared in advance. 1 a method of laminating, a method of co-extruding the base material 1 and the intermediate resin layer 2, a method of applying a dry resin solution to the base material 1, and the like. Examples of the extrusion method include a T-die extrusion method and an expansion method.

The adhesive layer 3 is sealed on the surface of the semiconductor wafer by being tightly closed to prevent immersion of grinding chips or grinding water in the back surface polishing, and in the back surface polishing, the adhesive is provided with the adhesive force required to maintain the minimum required for the semiconductor wafer.剂 FORMING. It is necessary for the adhesive layer 3 to be easily peeled off after the back surface grinding is finished. As long as the adhesive force can satisfy the above characteristics, it is preferably as weak as possible.

The adhesive force of the adhesive layer 3 to the stainless steel at 25 ° C is 0.10N / 25mm or more and 0.50N / 25mm or less. When the above-mentioned adhesive force of the adhesive layer is less than 0.10N / 25mm, the sealing of the surface to be adhered becomes insufficient, and there may be a risk of immersion in the grinding surface or grinding water on the surface to be ground during back grinding. In addition, after bonding the adhesive tape to the surface of the semiconductor wafer having the uneven shape, there is a possibility that the adhesive tape from the surface of the wafer floats. When the above-mentioned adhesive force of the adhesive layer exceeds 0.50N / 25mm, when peeling after the back grinding is completed, there may be a residue of paste on the surface to be adhered, or a structure on the surface to be adhered, such as damage to the circuit pattern or the electrode or The risk of bumps.

For the "adhesion" of the stainless steel of the adhesive layer 3, it means that the adhesive tape is affixed to the stainless steel polished with water-resistant abrasive paper No. 280 specified in JIS R 6253 by reciprocating the roller once at 23 ° C and 2kg. The 180-degree peeling adhesive force when the adhered adhesive layer was peeled at an angle of 180 degrees at a peeling speed of 300 mm / min at 23 ° C.

After the adhesive layer 3 is peeled from the surface to be adhered, it is formed of an adhesive that does not remain on the surface to be adhered. Examples of the adhesive constituting the adhesive layer 3 include an acrylic adhesive. For example, when air is mixed on the adhesive surface of the adhesive layer, specifically, even if air is mixed in the peripheral portion of the bump of the semiconductor wafer with the bump, when peeling it, it is necessary to prevent the radiation due to radiation. The curing type acrylic adhesive is observed in the form of an oxygen barrier that causes poor curing and the remaining paste is left. The acrylic adhesive polymer is used as the main component of the adhesive, and it is finally manufactured into an adhesive tape. The state is better for non-hardening.

The wording "main component" means a component contained in a sufficient amount in order to determine the physical properties and characteristics of a material. In the adhesive, the main component is generally contained in an amount of 50% by mass or more, 70% by mass or more, or 85% by mass or more. Examples of the components of the adhesive other than the main component include additives such as a crosslinking agent, a plasticizer, a softener, a filler, and an antioxidant. The wording "non-hardening" means that the adhesive does not have a hardening property when the adhesive layer is peeled from the surface of the semiconductor wafer. That is, when the adhesive layer is peeled from the surface of the semiconductor wafer, it is added by external energy such as radiation or heat, and the adhesive is not hardened. Specifically, it refers to an adhesive that does not remain in the polymerization reaction site or the crosslinking reaction site such as a light-sensing group or a heat-sensing group in a state of being finally manufactured into an adhesive tape.

The adhesive containing an acrylic adhesive polymer preferably has an acid value of 2.0 mgKOH / g or less and a hydroxyl value of 1.0 to 15.0 mgKOH / g. Here, the acid value refers to the amount (mg) of potassium hydroxide necessary to neutralize the acid component contained in 1 g of the object. The term “hydroxyl value” refers to the amount (mg) of potassium hydroxide necessary for the OH group contained in 1 g of the ethylation target. By setting the acid value and the hydroxyl value of the adhesive containing the acrylic adhesive polymer to the above-mentioned range, the combination of the above-mentioned base material 1 and the intermediate resin layer 2 can set the adhesive force to the above-mentioned appropriate range. As a result, in the back surface grinding, it is prevented that the grinding surface or the grinding water is immersed in the ground surface, and after the back surface grinding, there is no residue on the ground surface, and the adhesive tape can be easily peeled off.

When the acid value of the adhesive containing an acrylic adhesive polymer exceeds 2.0 mgKOH / g, the peeling force of the adhesive layer increases, and paste residue tends to occur on the surface to be adhered. The acid value of the adhesive containing an acrylic adhesive polymer is preferably 1.0 mgKOH / g or less. Although the acid value of the adhesive containing an acrylic adhesive polymer is preferably 0, when an acrylate is used, it is substantially difficult to completely eliminate the acid value.

When the hydroxyl value of the adhesive containing an acrylic adhesive polymer is less than 1.0 mgKOH / g, especially when a compound containing an isocyanate group that reacts with a hydroxyl group is used as a crosslinking agent, the crosslinking density in the adhesive layer is reduced, Decrease cohesive force, easy to produce paste residue. When the hydroxyl value of the adhesive containing an acrylic adhesive polymer exceeds 15.0 mgKOH / g, the peeling force of the adhesive layer increases, and paste residue tends to occur on the surface. The hydroxyl value of the adhesive containing an acrylic adhesive polymer is preferably 2.0 to 5.0 mgKOH / g.

Specific examples of the acrylic adhesive polymer include a (meth) acrylic polymer (A) having at least an alkyl group-containing (meth) acrylic monomer (a1) as a monomer component.

Specific examples of the (meth) acrylic monomer (a1) containing an alkyl group include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, and (methyl) (Isopropyl) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, s-butyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate Ester, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (methyl Nonyl acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate Tridecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, cetyl (meth) acrylate, heptadecyl (meth) acrylate , Octadecyl (meth) acrylate, cyclohexyl (meth) acrylate, and the like. These can be used individually or in plural. Among these, it is preferably selected from the group consisting of methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, and At least one member of the group consisting of 2-ethylhexyl (meth) acrylate. When a (meth) acrylic monomer (a1) containing a plurality of alkyl groups is used, one kind may be used as a main monomer, and the other may be used as a comonomer. The number of alkyl groups in the (meth) acrylic monomer (a1) containing an alkyl group is not particularly limited, but in consideration of production cost, it is preferably 10 or less, and more preferably 8 or less. The (meth) acrylic monomer (a1) containing an alkyl group is preferably a polymer having a glass transition temperature of 0 ° C or lower.

The total content of the (meth) acrylic monomer (a1) containing an alkyl group in the (meth) acrylic polymer (A) is preferably 50 to 100% by mass based on the total amount of the monomer components.

If the (meth) acrylic polymer (A) has one of the (meth) acrylic monomers (a1) containing the alkyl group as a main monomer, it may be one having a functional group as a comonomer. Copolymer of (meth) acrylic monomer. By using a (meth) acrylic monomer containing a functional group, other characteristics such as cohesion can be improved.

Specific examples of the (meth) acrylic monomer containing a functional group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and 4- (meth) acrylate 4- Hydroxyl-containing (meth) acrylic monomers such as hydroxybutyl ester and 6-hydroxyhexyl (meth) acrylate; epoxy-containing (meth) acrylic monomers such as glycidyl (meth) acrylate (Meth) acrylic monomers containing carboxyl groups such as (meth) acrylic acid; (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N-butyl (methyl Acrylamide, N-methylol (meth) acrylamide, N-methylolpropane (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N- Butylamine-containing (meth) acrylic monomers such as butoxymethyl (meth) acrylamide; aminoethyl (meth) acrylate, N, N-dimethyl (meth) acrylate (Meth) acrylic monomers containing amine groups such as aminoethyl esters, t-butylaminoethyl (meth) acrylate, and (meth) acrylic acids containing cyano groups such as (meth) acrylonitrile Monomers; methoxyethyl (meth) acrylate, ethyl (meth) acrylate Ethyl group, etc. The alkoxy group-containing (meth) acrylic monomer and the like. These may be used alone or in plural. Such a (meth) acrylic monomer containing a functional group is preferably a polymer having a higher glass transition temperature than 0 ° C.

The total content of the functional group-containing (meth) acrylic monomer in the (meth) acrylic polymer (A) is preferably 0 to 30% by mass relative to the total amount of the monomer component. The acid value of the adhesive containing the acrylic adhesive polymer may be appropriately adjusted so that the acid value becomes 2.0 mgKOH / g or less and the hydroxyl group falls within the range of 1.0 to 15.0 mgKOH / g.

Further, the (meth) acrylic polymer (A) is intended to improve other properties such as cohesion, and may further contain other monomers as a comonomer. Examples of such other monomers include monomers containing anhydride groups such as maleic anhydride and itaconic anhydride; vinyl ester monomers such as vinyl acetate and vinyl propionate; methyl vinyl ether and ethyl vinyl Vinyl ether-based monomers such as methyl ether; N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N- Vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-vinylmorpholine, N-vinylcaprolactam, N- ( A monomer having a nitrogen atom-containing ring such as meth) acrylfluorenylmorpholine. These may be used alone or in plural. The total content of these other monomers is preferably 0 to 10% by mass relative to the total amount of the monomer components. However, if the acid value of the adhesive containing the acrylic adhesive polymer is finally reduced to 2.0 mgKOH / g or less As long as the hydroxyl group is in the range of 1.0 to 15.0 mgKOH / g, it may be appropriately adjusted.

Examples of the polymerization method for synthesizing the (meth) acrylic polymer (A) include a conventionally known solution polymerization method, emulsion polymerization method, block polymerization method, and suspension polymerization method. Among these methods, preferred is A solution polymerization method in which polymerization is performed uniformly. Specific examples of the organic solvent used in the solution polymerization include ketone-based, ester-based, alcohol-based, and aromatic-based organic solvents. These organic solvents may be used alone or in combination. Among these, general (meth) acrylic polymerization with respect to toluene, ethyl acetate, isopropyl alcohol, benzyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, etc. is preferred. The substance (A) is an organic solvent that is a good solvent and has a boiling point of 60 to 120 ° C. Examples of the polymerization initiator include free radical generators such as azobis based on α, α'-azobisisobutyronitrile, and organic peroxides based on benzophenone peroxide.

The weight average molecular weight MwA of the (meth) acrylic polymer (A) obtained as described above is preferably 100,000 to 1 million, and more preferably 300,000 to 700,000. When the weight-average molecular weight MwA is less than 100,000, the adhesive component may be lost at a high temperature, and the retention may be reduced, or a paste residue may be left on the adherend. On the other hand, when the weight average molecular weight MwA is larger than 1 million, the adhesive component may gel during synthesis and coating, or the compliance with the unevenness of the surface to be coated may be reduced. In this specification, the weight average molecular weight, number average molecular weight, and molecular weight distribution are measured values (solvent: tetrahydrofuran) in terms of polystyrene conversion by GPC (gel permeation chromatography).

When the (meth) acrylic polymer (A) has a (meth) acrylic monomer containing a functional group as the comonomer, the adhesive layer 3 may contain the functional group containing (meth) acrylic Monomer, and a cross-linking agent that cross-links with a functional group introduced into the molecule. By using such a cross-linking agent, a three-dimensional cross-linked structure can be formed, and cohesion can be improved.

Specific examples of the crosslinking agent include polyisocyanate-based crosslinking agents, epoxy-based crosslinking agents, aziridine-based crosslinking agents, melamine resin-based crosslinking agents, urea resin-based crosslinking agents, and acid anhydride compounds. Based crosslinking agents, polyamine based crosslinking agents, polymer based crosslinking agents containing carboxyl groups, and the like. These crosslinking agents may be used alone or in combination. Among these, a polyisocyanate-based crosslinking agent having an isocyanate group having excellent reactivity is preferred.

Although the content of the cross-linking agent varies depending on the content of the (meth) acrylic monomer containing a functional group, it is preferably 0.1 to 10 masses relative to 100 mass parts of the (meth) acrylic polymer (A). Serving. The crosslinking temperature is preferably 20 to 70 ° C, and the crosslinking time is preferably 1 to 7 days.

Although the thickness of the adhesive layer 3 can be appropriately selected within a range that does not damage the unevenness of the pattern surface of the circuit pattern or the retention and protection properties of the semiconductor wafer, it is preferably 5 to 50 μm. More preferably, it is 10 to 30 μm. When the thickness of the adhesive layer is less than 5 μm, the adhesive force may be reduced, and the grinding chips or grinding water may be immersed during the back surface grinding. When the thickness of the adhesive layer exceeds 50 μm, the adhesive force increases, and when the adhesive tape is peeled off, the adhered surface may cause paste residue or damage to structures such as bumps or protruding electrodes.

The method for forming the adhesive layer 3 is not particularly limited, but is formed by, for example, a coating method. That is, the adhesive is diluted with an organic solvent such as toluene or ethyl acetate to obtain an adhesive layer coating solution. Next, the obtained adhesive layer coating liquid is applied on the surface of the intermediate resin layer 2 laminated on the substrate 1 in advance, dried and hardened to form the adhesive layer 3. If necessary, a release liner may be attached on the adhesive layer 3. Alternatively, the adhesive layer coating solution may be applied to the surface of the release liner at one time and dried, and then, the surface of the intermediate resin layer 2 laminated on the substrate 1 may be pasted together with the release liner in advance to perform Hardened to form an adhesive layer 3. From the viewpoint of workability, it is preferably formed by the latter coating transfer method.

The adhesive tape for back surface polishing of the present invention is preferably applied to the surface of a semiconductor wafer having an uneven shape. Examples of the uneven shape include external shapes of structures such as protruding bump electrodes and circuits. Although the height difference of the uneven shape to which the adhesive tape for back surface polishing of the present invention is applicable is not particularly specified, the height difference of the uneven shape existing on the surface to be faced is suitably 50 to 300 μm.

When applying the adhesive tape for back grinding of the present invention to back grinding, the adhesive tape for back grinding is deformed along the uneven shape of the adhered layer in order to deform the adhesive layer and the intermediate resin layer, and is heated to a temperature with sufficient flexibility to paste the adhesive layer. Attached to the surface of the semiconductor wafer. The temperature for attaching the adhesive tape for back grinding is usually 55 to 80 ° C, preferably 60 to 75 ° C.

As shown in FIG. 3, the back side abrasive adhesive tape of the present invention is preferably a semiconductor wafer attached to the surface of a bump with a bump, and when viewed from directly above by a microscope, the diameter of the bump measured by the adhesive tape is determined. Is r _b , and when the diameter of the non-adherent portion of the circular shape formed by the adhesive tape on the surface of the semiconductor wafer which cannot be adhered to the surface of the bump is defined as r _a , the value of r _a / r _b is 1.15 to 1.50. The closer the value of r _a / r _b is to 1.0, it means that the air around the bumps cannot be mixed into the air, and the adhesive tape completely conforms to the bumps. However, when fully compliant, the possibility of damaging the bump portion of the semiconductor wafer is increased when the adhesive tape is peeled off. By setting the value of r _a / r _b to the above range, the back-grinding adhesive tape of the present invention makes a suitable conforming state that does not fully conform to the bumps. When combined with the above-mentioned adhesive layer 3, the semiconductor is suppressed during back-grinding. When the wafer is damaged, when the adhesive tape is peeled off, the bump portion of the semiconductor wafer is suppressed from being damaged, and the method can be performed in a manner that no residue of paste is generated on the surface to be bonded. As described above, when a radiation-curable acrylic adhesive is applied to the adhesive, it cannot fully comply with the bumps. Although the hardening caused by the oxygen barrier contained in the air may cause poor adhesion to the adhered paste, However, since the adhesive layer of the back-grinding adhesive tape of the present invention is a non-hardening adhesive layer with suitable adhesive force, as shown in FIG. 2, it is assumed that even if air is mixed in, the adhesive tape may not be generated on the adhered surface when it is peeled off. The way the paste remains. When the value of r _a / r _b exceeds 1.50, the possibility of the surface being immersed in grinding chips or grinding water during back grinding is increased.

After the back surface polishing is completed, the back surface polishing adhesive tape of the present invention is detached from the surface to be peeled off by the adhesive layer. Detachment of the adhesive layer is performed by removing the adhesive tape for back grinding from the surface of the semiconductor wafer. The adhesive contained in the adhesive layer is non-hardening and does not require radiation or heating during peeling.

Hereinafter, although the present invention will be described in further detail through examples, the present invention is not limited to these examples. In the following, the term "part" means "mass part".

[Example]

(Example 1)
＜ Production of laminated body of base material and intermediate resin layer ＞
As a base material, it is prepared on one side of a polyethylene terephthalate (PET) film (thickness: 75 μm), and is easily adhered by an anchor coating (thickness: 1 μm) of a polyolefin resin. As the thermoplastic resin of the intermediate resin layer, an ethylene-vinyl acetate copolymer resin (EVA) (vinyl acetate (VA) content: 32% by mass, melt mass flow rate: 30g / 10 minutes) was used by a melt extrusion method Forming an intermediate resin layer on the anchor coating layer of the substrate to a thickness of 350 μm, continuously, and performing a corona treatment on the surface of the intermediate resin layer, and then bonding a protective film on the corona treated surface for winding, A laminate of a substrate with a protective film and an intermediate resin layer was produced.

＜ Production of Adhesive Solution A ＞
100 parts by mass of an acrylic adhesive (acid value: 0.3 mgKOH / g, hydroxyl value: 3.2 mgKOH / g, molecular weight Mw: 400,000, solvent: toluene) composed of an acrylate copolymer having a solid content concentration of 44% by mass Parts, 2.07 parts by mass of methylenediphenyl diisocyanate-based cross-linking agent (solid content concentration: 75% by mass), and 28.07 parts by mass of ethyl acetate, to produce an adhesive solution A having a solid content concentration of 35% by mass.

＜ Formation of adhesive layer and production of adhesive tape for back grinding ＞
The above-mentioned adhesive solution A was coated and dried on the silicone-treated side of the release-treated PET film (thickness: 38 μm) that was treated with silicone on one side so that the thickness after drying became 20 μm. The surface of the dried adhesive layer was substantially adhered to the surface on the intermediate resin layer side of the laminate of the base material of the release protective film and the intermediate resin layer, and rolled up. Next, the obtained roll was passed through a coating machine again, and after the release PET film was peeled off, a polyethylene-based protective film (thickness: 100 μm) was bonded to the surface of the adhesive layer again and corrected. This roll was aged at 40 ° C for 72 hours to prepare an adhesive tape for back grinding.

＜ Measurement of adhesive force (= peeling force) ＞
About the said adhesive tape for back surface grinding | polishing, the adhesive force was measured with the following method. By heating the above-mentioned adhesive tape for back surface polishing to the same temperature as that of the adhesive tape for back surface polishing of semiconductor wafers with bumps described later, the temperature was increased to 75 ° C., and the 2 kg roller was reciprocated at a time, and the above-mentioned adhesive layer for back surface polishing was heated. Attach to stainless steel polished with water-resistant abrasive paper No. 280 stipulated in JIS R 6253, and measure the 180-degree peeling when the adhered adhesive layer is peeled at a temperature of 300 mm / minute at 23 ° C at a 180-degree angle. Adhesion.
The adhesive force of the above-mentioned back surface polishing adhesive tape was 0.40 N / 25 mm (attachment temperature: 75 ° C).

<Measurement of storage elasticity (G ') and loss tangent (tanδ)>
The storage elastic modulus (G ') and loss tangent (tanδ) of the intermediate resin layer used for the above-mentioned back-side polishing adhesive tape were measured by the following methods. A resin sample (thickness 500 μm) used for the intermediate resin layer was prepared, and a viscoelasticity measuring device DMA6100 (product name) manufactured by Hitachi High-Technologies Co., Ltd. was used to measure dynamic viscoelasticity to obtain a storage elastic modulus. The measurement conditions were given a shear strain at a frequency of 1 Hz, and the heating rate was set to 5 ° C / min, the temperature was changed from 0 ° C to 85 ° C, and the loss elasticity (G) and storage elasticity ( G '). The loss tangent (tan δ) is calculated using the following formula.
Tangent of loss (tanδ) = loss of elasticity (G ”) / storage elasticity (G ')
The storage elastic modulus (G ') of the intermediate resin layer used in the above-mentioned adhesive tape for back grinding at 75 ° C was 0.37 × 10 ⁶ Pa, and the loss tangent (tan δ) was 0.30. The storage elastic modulus (G ') at 23 ° C was 5.62 × 10 ⁶ Pa, and the loss tangent (tan δ) was 0.08.

＜ Attach the adhesive tape for polishing the back surface of the semiconductor wafer with bumps ＞
As a semiconductor wafer with bumps, it is used on the surface of an 8-inch wafer (thickness: 800 μm), and solder bumps are provided with the following heights and intervals.
Solder bump height: 250μm
Solder bump diameter: 350μm
Solder bump pitch: 900 μm
As the adhesive tape placement machine, RAD3510 (product name) manufactured by Lindec was used. The attachment temperature was set at 75 ° C. While applying a certain pressure of 0.45 MPa, the back surface was adhered at a speed of 2.0 mm / sec. Adhesive tape is attached to the semiconductor wafer with bumps to make samples for grinding. In this case, the thickness of the intermediate resin layer is 1.4 times the height of the bump.

(Example 2)
Except having changed the adhesive solution A to the following adhesive solution B, it carried out similarly to Example 1, and produced the adhesive tape for back surface grinding, and the sample for grinding. The adhesive force of the adhesive tape for back surface polishing is 0.50 N / 25 mm.

＜ Production of Adhesive Solution B ＞
100 parts by mass of an acrylic adhesive (acid value: 1.9 mgKOH / g, hydroxyl value: 3.2 mgKOH / g, molecular weight Mw: 500,000, solvent: toluene) composed of an acrylate copolymer having a solid content concentration of 30% by mass. Parts, methylenephenyl diisocyanate-based crosslinking agent (solid content concentration: 75% by mass), 0.24 parts by mass, and ethyl acetate 0.36 parts by mass, to produce an adhesive solution B having a solid content concentration of 30% by mass.

(Example 3)
Except having changed the adhesive solution A into the following adhesive solution C, it carried out similarly to Example 1, and produced the adhesive tape for back surface grinding, and the sample for grinding. The adhesive force of the above-mentioned back surface adhesive tape is 0.33N / 25mm.

＜ Production of Adhesive Solution C ＞
100 parts by mass of an acrylic adhesive (acid value: 0.1 mgKOH / g, hydroxyl value: 15.0 mgKOH / g, molecular weight Mw: 450,000, solvent: toluene) composed of an acrylate copolymer having a solid content concentration of 60% by mass Parts, methylenephenyl diisocyanate-based cross-linking agent (solid content concentration: 75% by mass), 0.6 parts by mass, and 72.1 parts by mass of ethyl acetate to prepare an adhesive solution C having a solid content concentration of 35% by mass.

(Example 4)
The same procedure as in Example 1 was performed except that the temperature for attaching the backside polishing adhesive tape to the semiconductor wafer with bumps was changed from 75 ° C to 80 ° C, and a backside polishing adhesive tape and a grinding sample were produced. The storage elastic modulus (G ') at 80 ° C of the intermediate resin layer used for the above-mentioned adhesive tape for back-grinding was 0.19 × 10 ⁶ Pa, and the loss tangent (tan δ) was 0.45. Moreover, the adhesive force of the said adhesive tape for back surface grinding was 0.43N / 25mm (attachment temperature 80 degreeC).

(Example 5)
The same procedure as in Example 1 was performed except that the bonding temperature of the backside polishing adhesive tape for the semiconductor wafer with bumps was changed from 75 ° C to 55 ° C, and a backside polishing adhesive tape and a grinding sample were produced. The storage elastic modulus (G ') at 55 ° C of the intermediate resin layer used for the above-mentioned back-grinding adhesive tape was 1.51 × 10 ⁶ Pa, and the loss tangent (tan δ) was 0.13. Moreover, the adhesive force of the said adhesive tape for back surface grinding was 0.22N / 25mm (sticking temperature 55 degreeC).

(Example 6)
Except for the thermoplastic resin used as the intermediate resin layer, the ethylene-vinyl acetate copolymer resin (EVA) (the content of vinyl acetate (VA): 28% by mass, the melt mass flow rate: 150g / 10 minutes), Example 1 was carried out in the same manner, and an adhesive tape for back grinding and a sample for grinding were prepared. The adhesive force of the above-mentioned back-side polishing adhesive tape was 0.33 N / 25 mm (attachment temperature: 75 ° C). In addition, the storage elastic modulus (G ') of the intermediate resin layer used for the above-mentioned adhesive tape for back-grinding at 75 ° C was 0.15 × 10 ⁶ Pa, the loss tangent (tanδ) was 0.40, and the storage elastic modulus (G at 23 ° C) ') Was 6.84 × 10 ⁶ Pa, and the loss tangent (tan δ) was 0.08.

(Example 7)
In addition to the thermoplastic resin used as the intermediate resin layer, two types of ethylene-vinyl acetate copolymer resin (EVA) (vinyl acetate (VA) content: 32% by mass and melt flow rate: 30g) having different vinyl acetate contents were used instead. EVA and vinyl acetate (VA) content: 42% by mass, melt mass flow rate: 70g / 10 minutes) EVA (vinyl acetate (VA) content: 37% by mass, Except for the melt mass flow rate: 50 g / 10 minutes), other procedures were carried out in the same manner as in Example 1 to produce adhesive tapes for back grinding and samples for grinding. The adhesive force of the above-mentioned back-side polishing adhesive tape was 0.45 N / 25 mm (attachment temperature: 75 ° C). In addition, the storage elastic modulus (G ') of the intermediate resin layer used in the above-mentioned adhesive tape for back grinding at 75 ° C was 0.18 × 10 ⁶ Pa, the loss tangent (tanδ) was 0.49, and the storage elastic modulus (G at 23 ° C) ') Is 4.73 × 10 ⁶ Pa, and the loss tangent (tan δ) is 0.08.

(Example 8)
Except having changed the thickness of the intermediate resin layer to 300 micrometers, it carried out similarly to Example 1, and produced the adhesive tape for back surface grinding, and the sample for grinding. In this case, the thickness of the intermediate resin layer is 1.2 times the bump height. The adhesive force of the above-mentioned back-side polishing adhesive tape was 0.38 N / 25 mm (attachment temperature: 75 ° C).

(Example 9)
Except having changed the thickness of the intermediate resin layer to 400 micrometers, it carried out similarly to Example 1, and produced the adhesive tape for back surface grinding, and the sample for grinding. In this case, the thickness of the intermediate resin layer is 1.6 times the height of the bump. The adhesive force of the above-mentioned back-side polishing adhesive tape was 0.40 N / 25 mm (attachment temperature: 75 ° C).

(Example 10)
Except having changed the thickness of a base material to 50 micrometers, it carried out similarly to Example 1, and produced the adhesive tape for back surface grinding, and the sample for grinding. The adhesive force of the above-mentioned back-side polishing adhesive tape was 0.45 N / 25 mm (attachment temperature: 75 ° C).

(Example 11)
The same procedure as in Example 1 was performed except that the thickness of the substrate was changed to 200 μm, and an adhesive tape for back surface polishing and a sample for grinding were prepared. The adhesive force of the above-mentioned back-side polishing adhesive tape was 0.23 N / 25 mm (attachment temperature: 75 ° C).

(Example 12)
Except having changed the thickness of the adhesive layer to 10 micrometers, it carried out similarly to Example 1, and produced the adhesive tape for back surface grinding, and the sample for grinding. The adhesive force of the adhesive tape for back surface polishing is 0.18 N / 25 mm (attachment temperature: 75 ° C).

(Example 13)
Except having changed the thickness of the adhesive layer to 40 micrometers, it carried out similarly to Example 1, and produced the adhesive tape for back surface grinding, and the sample for grinding. The adhesive force of the above-mentioned back-side polishing adhesive tape was 0.48 N / 25 mm (attachment temperature: 75 ° C).

(Comparative example 1)
Except having changed the adhesive solution A to the following adhesive solution D, it carried out similarly to Example 1, and produced the adhesive tape for back surface grinding, and the sample for grinding. The adhesive force of the above-mentioned back-side polishing adhesive tape was 0.82 N / 25 mm (attachment temperature: 75 ° C).

＜ Production of Adhesive Solution D ＞
Acrylic adhesive (acid value: 12.4 mgKOH / g, hydroxyl value: 1.5 mgKOH / g, molecular weight Mw: 1 million, solvent: toluene) composed of acrylate copolymer having a solid content concentration of 40% by mass, 1.2 parts by mass of a phenylene diisocyanate-based crosslinking agent (solid content concentration: 75% by mass) and 15.66 parts by mass of ethyl acetate were used to prepare an adhesive solution D having a solid content concentration of 35% by mass.

(Comparative example 2)
Except having changed the adhesive solution A into the following adhesive solution E, it carried out similarly to Example 1, and produced the adhesive tape for back surface grinding, and the sample for grinding. The adhesive force of the above-mentioned back-side polishing adhesive tape was 0.12 N / 25 mm (attachment temperature: 75 ° C).

＜ Production of Adhesive Solution E ＞
100 parts by mass of an acrylic adhesive (acid value: 0.5 mgKOH / g, hydroxyl value: 0.9 mgKOH / g, molecular weight Mw: 330,000, solvent: toluene) composed of an acrylate copolymer having a solid content concentration of 35% by mass. Parts, 0.1 parts by mass of hexamethylene diisocyanate-based cross-linking agent (solid content concentration: 100% by mass), and 0.19 parts by mass of ethyl acetate, to produce an adhesive solution E having a solid content concentration of 35% by mass.

(Comparative example 3)
Except having changed the adhesive solution A into the following adhesive solution F, it carried out similarly to Example 1, and produced the adhesive tape for back surface grinding, and the sample for grinding. The adhesive force of the adhesive tape for back surface polishing is 0.52N / 25mm (attachment temperature: 75 ° C).

＜ Production of Adhesive Solution F ＞
Acrylic adhesive (acid value: <1 mgKOH / g, hydroxyl value: 43 mgKOH / g, molecular weight Mw: 100,000, solvent: ethyl acetate, toluene) ) 20 parts by mass, hexamethylene diisocyanate-based cross-linking agent (solid content concentration: 100% by mass), 2.33 parts by mass, and ethyl acetate 0.32 parts by mass, and an adhesive solution F having a solid content concentration of 35% by mass was prepared.

(Comparative Example 4)
The same procedure as in Example 1 was performed except that the temperature for attaching the backside polishing adhesive tape to the semiconductor wafer with bumps was changed from 75 ° C to 85 ° C, and a backside polishing adhesive tape and a grinding sample were produced. The storage elastic modulus (G ') of the intermediate resin layer used in the above-mentioned adhesive tape for back surface polishing at 85 ° C was 0.12 × 10 ⁶ Pa, and the loss tangent (tan δ) was 0.60. Moreover, the adhesive force of the said adhesive tape for back surface grinding was 0.45N / 25mm (attachment temperature 85 degreeC).

(Comparative example 5)
The same procedure as in Example 1 was performed except that the bonding temperature of the adhesive tape for back grinding of the semiconductor wafer with bumps was changed from 75 ° C. to 50 ° C., and an adhesive tape for back grinding and a sample for grinding were produced. The storage elastic modulus (G ') at 50 ° C of the intermediate resin layer used for the above-mentioned adhesive tape for back grinding was 1.88 × 10 ⁶ Pa, and the loss tangent (tan δ) was 0.13. Moreover, the adhesive force of the said adhesive tape for back surface grinding | polishing was 0.11N / 25mm (attachment temperature 50 degreeC).

(Comparative Example 6)
Except having changed the adhesive solution A into the adhesive solution G which consists of the following ultraviolet curable adhesive, it carried out similarly to Example 1, and produced the adhesive tape for back surface grinding, and the sample for grinding. In addition, the adhesive force after irradiating ultraviolet rays (integrated light amount: 300 mJ / cm ² ) from the substrate side of the back surface polishing adhesive tape was 0.02 N / 25 mm (attachment temperature: 75 ° C.).

＜ Production of Adhesive Solution G ＞
Acrylic adhesive (acid value: 6.5 mgKOH / g, hydroxyl value: 40.0 mgKOH / g, molecular weight Mw: 600,000, solvent: ethyl acetate) composed of an acrylate copolymer having a solid content concentration of 33% by mass. 100 parts by mass, 0.5 parts by mass of methylenephenyl diisocyanate-based cross-linking agent (solid content concentration: 45% by mass), 0.7 parts by weight of α-hydroxyketone photopolymerization initiator, and 10.3 parts by mass of ethyl acetate to prepare a solid Adhesive solution G with a component concentration of 30% by mass.

The following tests were performed on the adhesive tapes for back surface polishing and grinding samples prepared in Examples 1 to 13 and Comparative Examples 1 to 6 to evaluate their performance. The evaluation results are described in Tables 1 to 3 below.

＜ Bump compliance ＞
When a back-grinding adhesive tape was attached to a surface of a semiconductor wafer with bumps for grinding, when viewed from directly above, using a microscope "VHX-1000" (product name) manufactured by Keyence, it was observed through the adhesive tape. The diameter of an arbitrary bump to be measured is defined as r _b . When the diameter of a non-adhered portion of a circular shape formed by the adhesive tape that cannot be adhered to the surface of the semiconductor wafer at the peripheral portion of the bump is determined as r _a , The value of r _a / r _b evaluates the bump compliance. Yet, measured for each respective diameter directions for 4:00, and the average value as r _b, r value of _a.

＜ Incidence rate of intrusion of grinding water (grinding chips) (%) ＞
Five samples for grinding were attached to the surface of the semiconductor wafer with bumps with adhesive tape for back grinding. From the back of the wafer, a silicon wafer grinding machine "DFG8540" manufactured by Disco Corporation (products) Name) Grinding is performed until the thickness of the wafer becomes 250 μm. Regarding five semiconductor wafers with bumps after back grinding, the state of the immersion of grinding water on the wafer surface was observed with a microscope, and the incidence of grinding water immersion was calculated by the following formula.
Incidence of grinding water immersion (%) = (number of wafers immersed in grinding water / number of wafers after grinding) × 100

＜ Destruction rate of semiconductor wafer with bump after back grinding (%) ＞
Regarding the five semiconductor wafers with bumps after the back grinding, the damage and crack occurrence of the wafers were observed visually or with a microscope, and the damage rate of the semiconductor wafers was calculated by the following formula.
Damage rate of semiconductor wafers (%) = (number of damaged wafers / number of polished wafers) × 100

<Damage rate of bump portion of semiconductor wafer with bump after back grinding (%)>
Regarding any one of the five semiconductor wafers with bumps after back grinding, the damage state of the bump portion of the wafer was observed with a microscope, and the damage of the bump portion of the semiconductor wafer was calculated by the following formula. rate.
Damage rate of bump portion of semiconductor wafer (%) = (number of damaged bumps / number of wafer bumps) × 100

<Presence or absence of depression of semiconductor wafer with bump after back grinding>
For 5 semiconductor wafers with bumps after back grinding, the presence or absence of depressions on the wafer grinding surface was observed visually. In addition, for those who visually observed the depression, a surface roughness measuring instrument "Surtoronic 4" (product name) manufactured by Tylor Hobson was used to measure the maximum depth Rz of the depression, and judged using the following criteria.
◎: No depression was observed by visual inspection ○: Although depression was observed by visual inspection, but the maximum depth was less than 2.5 μm ×: Although depression was observed by visual inspection, the maximum depth was 2.5 μm or more

<Uneven thickness of semiconductor wafer with bumps after back grinding>
The thickness accuracy TTV (maximum thickness-minimum thickness) of the wafer surface with bumps was measured for five semiconductor wafers after back grinding. The thickness accuracy measurement TTV (maximum thickness-minimum thickness) was measured using a thickness system measuring device "SemDex" (product name) manufactured by ISIS. When the measurement interval is X direction: 0.1 mm, Y direction: 10 mm, the entire wafer is measured (in a range of 200 mm × 200 mm), and the following criteria are used for determination.
○: TTV is less than 3 μm ×: TTV is 3 μm or more

<Are there any residues on the surface of the semiconductor wafer with bumps after peeling the adhesive tape for back grinding?>
Regarding 5 semiconductor wafers with bumps after grinding on the back surface, the presence or absence of paste on the surface of the semiconductor wafers with bumps after peeling off the adhesive tape for back grinding was observed with a microscope.

As shown in Tables 1 to 3, it is understood that when the back surface polishing adhesive tapes of Examples 1 to 13 were attached to the semiconductor wafer with solder bumps, the solder bumps were appropriately adapted, and when the back grinding was performed, the recessed Occurrence or damage to the wafer is extremely small. Furthermore, when the adhesive tape is peeled off, there is very little damage to the bumps. No paste residue will be generated on the wafer surface, which can be easily peeled off, which can sufficiently suppress the wafer after back grinding. The thickness is uneven.

On the other hand, in Comparative Example 1, the back surface polishing adhesive tape-based adhesive has a high acid value, and causes the semiconductor wafer with solder bumps to be firmly adhered, and when the adhesive tape is peeled off, paste residues are generated on the solder bumps.

The adhesive tape for back surface polishing of Comparative Example 2 had a low hydroxyl value of the adhesive and insufficient cross-linking by the adhesive of the cross-linking agent, and the cohesive force of the adhesive was insufficient. When the adhesive tape was peeled off, a paste residue was generated on the solder bumps .

The adhesive tape type adhesive for back surface polishing of Comparative Example 3 had a high hydroxyl value, and caused strong adhesion to a semiconductor wafer with solder bumps, and when the adhesive tape was peeled off, a paste residue was generated.

The adhesive tape for back surface polishing of Comparative Example 4 is because the adhesive tape is attached at a higher temperature than the specified temperature, which reduces the storage elasticity of the resin in the intermediate layer, causing the bumps of the semiconductor wafer with solder bumps to intersect without clearance, and the adhesive tape is peeled As a result, solder bumps are damaged.

Since the adhesive tape for back surface polishing of Comparative Example 5 has a lower adhesive temperature than the specified temperature, the storage elasticity of the intermediate layer resin is high, and the unevenness of the semiconductor wafer with solder bumps does not conform, so it is polished on the back surface. When immersed in grinding water.

The adhesive tape for back surface polishing of Comparative Example 6 was mixed with air around the solder bumps of the semiconductor wafer with solder bumps, and the hardening caused by ultraviolet irradiation was poor. As a result, the adhesive tapes were peeled off when the adhesive tapes were peeled off. Paste residue.

[Industrial availability]

According to the present invention, it is possible to provide an adhesive tape for back surface polishing, which is suitable for conforming to bumps or electrode protrusions when it is attached to a semiconductor wafer having uneven shapes such as bumps or electrode protrusions, and is recessed during back grinding. The occurrence rate of wafer damage or wafer damage is extremely small. Furthermore, when the adhesive tape is peeled off, the incidence of damage to the bumps or electrode protrusions is extremely small. There will be no paste residue on the surface, which can be easily peeled off and can be fully suppressed The thickness of the wafer after back grinding is uneven.

1‧‧‧ substrate

2‧‧‧ intermediate resin layer

3‧‧‧ Adhesive layer

4‧‧‧ semiconductor wafer

5‧‧‧solder bump

[FIG. 1] A sectional view showing a layer structure of an adhesive tape for back surface polishing according to an embodiment of the present invention.

[FIG. 2] A cross-sectional view when a back surface polishing adhesive tape according to an embodiment of the present invention is attached to the surface of a semiconductor wafer with solder bumps.

[Fig. 3] A top view of an adhesive tape for back grinding according to an embodiment of the present invention, which is observed through the adhesive tape when it is attached to the surface of a semiconductor wafer with solder bumps.

Claims (9)

An adhesive tape for back grinding is provided. The adhesive tape for back grinding of a semiconductor wafer having a substrate and an intermediate resin layer and an adhesive layer sequentially formed on the substrate is characterized in that the intermediate resin layer is at 55 At any temperature of ~ 80 ° C, it has a storage elastic modulus (G ') of 0.15 × 10 ⁶ to 1.51 × 10 ⁶ Pa. The adhesive layer is composed of a non-hardening adhesive. The non-hardening adhesive will have The acrylic adhesive polymer having an acid value of 2.0 mgKOH / g or less and a hydroxyl value of 1.0 to 15.0 mgKOH / g is contained as a main component. For example, the adhesive tape for back surface polishing of claim 1, wherein the intermediate resin layer has a thickness of 1.2 times or more the height difference of the uneven shape existing on the surface of the semiconductor wafer. The adhesive tape for back surface polishing according to claim 1 or 2, wherein the intermediate resin layer is made of ethylene-vinyl acetate copolymer (EVA). The adhesive tape for back surface grinding according to any one of claims 1 to 3, wherein the ethylene-vinyl acetate copolymer contains 25 to 40% by mass of vinyl acetate. The adhesive tape for back surface polishing according to claim 1 or 2, wherein the base material has a thickness of 50 to 200 μm. The adhesive tape for back grinding according to any one of claims 1 to 5, wherein the adhesive layer has a thickness of 5 to 50 µm. The adhesive tape for back grinding according to any one of claims 1 to 6, which is attached to the surface of the semiconductor wafer and observed from directly above the microscope, the diameter of the bump measured by the adhesive tape is determined. Is r _b , and when the diameter of the non-adherent portion of the circular shape formed by the adhesive tape on the surface of the semiconductor wafer which cannot be adhered to the surface of the bump is defined as r _a , the value of r _a / r _b is 1.15 to 1.50. The adhesive tape for back surface polishing according to any one of claims 1 to 7, wherein the height difference of the uneven shape existing on the surface of the semiconductor wafer is 50 to 300 μm. According to the adhesive tape for back surface polishing according to any one of claims 1 to 8, the temperature at which the adhesive tape is attached to the semiconductor wafer is any one of 55 to 80 ° C.