Protective sheet for semiconductor processing and method for manufacturing semiconductor device

Abstract

[Problem] To provide: a protective sheet for semiconductor processing, the protective sheet being suppressed in breakage of a wafer when the protective sheet for semiconductor processing is removed therefrom even in cases where the wafer after back grinding is thin, while being sufficiently suppressed in the occurrence of electrification during the processing of the wafer; and a method for producing a semiconductor device, the method using this protective sheet for semiconductor processing. [Solution] A protective sheet for semiconductor processing, the protective sheet comprising a base material, an antistatic layer and an energy ray-curable adhesive layer, wherein the peel strength at the time when the adhesive layer after energy ray curing is peeled off from a silicon wafer at a peeling rate of 600 mm / minute in such a manner that the angle between the adhesive layer and the silicon wafer is 90° is not less than 0.035 N / 25 mm but less than 0.15 N / 25 mm.

Description

[Technical Field]

[0001] The present invention relates to a protective sheet for semiconductor processing and a method for manufacturing a semiconductor device. In particular, it relates to a protective sheet for semiconductor processing that is suitably used in a method for grinding the back surface of a wafer to obtain a thin wafer, and to a method for manufacturing a semiconductor device using the protective sheet for semiconductor processing. [Background technology]

[0002] Various electronic devices incorporate numerous semiconductor devices on which semiconductor chips, obtained by separating semiconductor wafers with circuits formed on them, are mounted. Electronic devices are rapidly becoming smaller and more multifunctional, and semiconductor chips are also required to be smaller, lower profile, and higher density. To miniaturize and lower the profile of chips, it is common practice to form circuits on the surface of a semiconductor wafer and then grind the back surface of the semiconductor wafer to adjust the thickness of the chip.

[0003] During back-grinding of semiconductor wafers, a protective sheet called backgrind tape is applied to the wafer surface to protect the circuits on the wafer surface and to hold the semiconductor wafer in place.

[0004] Backgrind tape is required to adhere strongly to the wafer surface during back-side grinding to adequately protect circuits and other components, and to be easily peeled off the wafer after back-side grinding. Therefore, the adhesive layer of the backgrind tape attached to the wafer is usually composed of an energy-ray curable adhesive. By curing the adhesive layer with energy rays during peeling and reducing its adhesive strength, a balance is achieved between adhesion during back-side grinding and peelability after back-side grinding.

[0005] Furthermore, it is known that static electricity can occur during wafer processing (for example, during dicing, back grinding, cleaning, and peeling off back grind tape). When static electricity occurs, problems arise such as increased susceptibility to discharge damage of circuits on the wafer or individual chips, and increased adhesion of cut dust generated during grinding and minute foreign matter present in the environment to the wafer or individual chips.

[0006] Patent Document 1 discloses an antistatic adhesive tape for semiconductor processing, comprising a base film, an antistatic layer, and an adhesive layer, wherein the surface resistivity of the adhesive layer after UV curing is within a predetermined range, and the 90-degree peel-off adhesive strength of the adhesive layer after UV curing is within a predetermined range. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2011-210944 [Overview of the project] [Problems that the invention aims to solve]

[0008] In recent years, in order to achieve high-density mounting in electronic devices, semiconductor chips have become even smaller, lower in profile, and higher in density. Therefore, in order to make the chips even smaller and lower in profile, it has become necessary to make the wafer thickness even thinner after back-grinding.

[0009] However, if the thickness of the wafer after back grinding is reduced, wafer damage may occur when peeling off the back grinding tape from the wafer after back grinding. For example, in Patent Document 1, when the thickness of the wafer after back grinding is 100 μm, no wafer damage occurs due to peeling off the antistatic semiconductor processing adhesive tape. However, when the thickness of the wafer after back grinding is further reduced, there is a problem in that wafer damage occurs due to peeling off the antistatic semiconductor processing adhesive tape.

[0010] The present invention has been made in view of such circumstances, and an object of the present invention is to provide a protective sheet for semiconductor processing that can suppress damage to a wafer when the protective sheet for semiconductor processing is peeled off even when the wafer after back surface grinding is thin, and sufficiently suppress charging that occurs during processing of the wafer, and to provide a method for manufacturing a semiconductor device using the protective sheet for semiconductor processing. Means for Solving the Problem

[0011] Aspects of the present invention are as follows. [1] A protective sheet for semiconductor processing comprising a base material, an antistatic layer, and an energy ray-curable pressure-sensitive adhesive layer, wherein the adhesive strength of the pressure-sensitive adhesive layer after energy ray curing is 0.035 N / 25 mm or more and less than 0.15 N / 25 mm, when the pressure-sensitive adhesive layer after energy ray curing is peeled from a silicon wafer at a peeling speed of 600 mm / min such that the angle formed between the pressure-sensitive adhesive layer and the silicon wafer is 90°.

[0012] [2] The protective sheet for semiconductor processing according to [1], wherein the ratio of the adhesive strength when the pressure-sensitive adhesive layer after energy ray curing is peeled from a silicon wafer at a peeling speed of 600 mm / min such that the angle formed between the pressure-sensitive adhesive layer and the silicon wafer is 90° to the adhesive strength when the pressure-sensitive adhesive layer before energy ray curing is peeled from a silicon wafer under the same peeling conditions is 4% or less.

[0013] [3] The surface resistivity of the pressure-sensitive adhesive layer after energy ray curing is 5.1×10 12 Ω / cm 2 or more and 1.0×10 15 Ω / cm 2 or less, which is the protective sheet for semiconductor processing according to [1] or [2].

[0014] [4] The protective sheet for semiconductor processing according to any one of [1] to [3], wherein the protective sheet for semiconductor processing further comprises a buffer layer.

[0015] A step of attaching the protective sheet for semiconductor processing according to any one of [5] [1] to [4] onto a surface of a wafer; A step of grinding a wafer, having the protective sheet for semiconductor processing attached to a surface thereof, from a back side thereof; A step of peeling off the protective sheet for semiconductor processing from the wafer after back surface grinding, which is a method for manufacturing a semiconductor device. Effects of the Invention

[0016] According to the present invention, even when the wafer after back surface grinding is thin, it is possible to provide a protective sheet for semiconductor processing in which breakage of the wafer is suppressed during peeling of the protective sheet for semiconductor processing, and static electricity generated during processing of the wafer is sufficiently suppressed, and to provide a method for manufacturing a semiconductor device using said protective sheet for semiconductor processing. Brief Description of Drawings

[0017] [Figure 1A] FIG. 1A is a schematic cross-sectional view showing an example of the protective sheet for semiconductor processing according to the present embodiment. [Figure 1B] FIG. 1B is a schematic cross-sectional view showing another example of the protective sheet for semiconductor processing according to the present embodiment. [Figure 2] FIG. 2 is a schematic cross-sectional view showing a state where the protective sheet for semiconductor processing according to the present embodiment is attached to a circuit surface of a wafer. Mode for Carrying Out the Invention

[0018] Hereinafter, the present invention will be described in detail based on specific embodiments with reference to the drawings. First, main terms used in the present specification will be explained.

[0019] Singulation of a wafer refers to dividing the wafer into individual circuits to obtain chips.

[0020] The "front surface" of a wafer refers to the surface on which circuits, electrodes and the like are formed, and the "back surface" of a wafer refers to the surface on which circuits and the like are not formed.

[0021] DBG (Dicing Before Grinding) is a method of forming grooves of a predetermined depth on the surface side of a wafer, and then grinding the wafer from the back side to separate it into individual pieces. The grooves formed on the surface side of the wafer are created by methods such as blade dicing, laser dicing, or plasma dicing.

[0022] Furthermore, LDBG (Laser Dicing Before Grinding) is a variation of DBG, and refers to a method in which a modified region is created inside the wafer using a laser, and the wafer is fragmented into individual pieces by the stress during backside grinding.

[0023] The term "chip group" refers to a plurality of chips held on the semiconductor processing protective sheet according to this embodiment after the wafer has been separated into individual pieces. These chips, as a whole, form a shape similar to that of the wafer.

[0024] The term "(meth)acrylate" is used to refer to both "acrylate" and "methacrylate," and the same applies to other similar terms.

[0025] "Energy rays" refer to ultraviolet rays, electron beams, etc., and are preferably ultraviolet rays.

[0026] Unless otherwise specified, "weight-average molecular weight" is a polystyrene-converted value measured by gel permeation chromatography (GPC). Measurements using this method are performed, for example, with a high-speed GPC instrument "HLC-8120GPC" manufactured by Tosoh Corporation and a high-speed column "TSK guard column H XL -H", "TSK Gel GMH" XL "TSK Gel G2000 H XL The following components (all manufactured by Tosoh Corporation) are connected in this order, and the test is performed with a column temperature of 40°C and a liquid delivery rate of 1.0 mL / min, using a differential refractometer as the detector.

[0027] (1. Protective sheet for semiconductor processing) As shown in Figure 1A, the semiconductor processing protective sheet 1 according to this embodiment has a configuration in which an antistatic layer 20 and an adhesive layer 30 are provided in that order on one main surface 10a of the substrate 10. From the viewpoint of antistatic function, it is preferable that the antistatic layer be close to the peel interface of the semiconductor processing protective sheet, that is, the surface 30a of the adhesive layer. Therefore, as shown in Figure 1A, it is preferable that the antistatic layer 20 be provided on one main surface 10a of the substrate 10 rather than on the other main surface 10b of the substrate 10. When the semiconductor processing protective sheet 1 is used, the surface 30a of the adhesive layer 30 is temporarily attached to the adherend and then peeled off from the adherend.

[0028] Furthermore, the semiconductor processing protective sheet may have other layers, as long as the effects of the present invention are obtained. That is, if the semiconductor processing protective sheet has a base material, an antistatic layer, and an adhesive layer, for example, other layers may be formed between the base material and the adhesive layer, or other layers may be formed between the base material and the antistatic layer.

[0029] Another example of a protective sheet for semiconductor processing is a protective sheet for semiconductor processing, as shown in Figure 1B, in which an antistatic layer 20 and an adhesive layer 30 are provided in that order on one main surface 10a of the substrate 10, and a buffer layer 40 is provided on the other main surface 10b of the substrate 10.

[0030] The semiconductor processing protective sheet shown in Figure 1B is suitable as a semiconductor processing protective sheet used during backside grinding of a wafer in a process known as the pre-dicing method (DBG).

[0031] The pre-dicing method involves forming grooves of a predetermined depth from the surface side of the wafer using a dicing blade, then grinding from the back side of the wafer, bringing the grinding surface to the grooves or near the grooves to fragment the wafer and obtain chips. It may also be used in LDBG (Laser Dicing Before Grinding), a variation of DBG, in which a modified region is created inside the wafer using a laser, and the wafer is fragmented by the stress during back-side grinding.

[0032] The following section describes the protective sheet for semiconductor processing shown in Figure 1A.

[0033] As shown in Figure 2, the surface 30a of the adhesive layer is attached to the circuit surface of the wafer 100, i.e., the surface 100a of the wafer 100, thereby protecting the surface 100a of the wafer 100 when grinding the back surface 100b of the wafer 100 according to this embodiment.

[0034] Since the adhesive layer 30 of the semiconductor processing protective sheet 1 is energy ray curable, when backside grinding, it is attached to the surface 100a of the wafer 100 in an uncured state, and its high adhesive strength can adequately protect the surface 100a of the wafer 100.

[0035] After backside grinding is complete, the semiconductor processing protective sheet 1 is peeled off from the surface 100a of the wafer 100. At this time, the adhesive layer 30 of the semiconductor processing protective sheet 1 is irradiated with energy rays to harden the adhesive layer 30 and reduce its adhesive strength. This makes it easier to peel off the semiconductor processing protective sheet 1.

[0036] However, when the protective sheet for semiconductor processing is peeled off, stress is applied to the wafer after backside grinding. If the wafer is thin after backside grinding, it may not be able to withstand the stress and may break. The stress generated during peeling increases with the adhesive strength of the adhesive layer after energy ray curing. Therefore, the protective sheet for semiconductor processing according to this embodiment reduces wafer damage when the protective sheet for semiconductor processing is peeled off by setting the adhesive strength of the adhesive layer after energy ray curing within a predetermined range.

[0037] In this case, a higher amount of energy-ray polymerizable carbon-carbon double bonds in the adhesive layer before curing is preferable because it tends to accelerate the curing of the adhesive layer and decrease the adhesive strength of the adhesive layer after curing. However, a higher amount of energy-ray polymerizable carbon-carbon double bonds in the adhesive layer before curing increases the number of crosslinking points in the adhesive layer after curing, making it more difficult for charges to move and thus more prone to becoming charged.

[0038] Consequently, during wafer processing, including the back grinding described above, in addition to the static charge generated on the wafer, static charge originating from the adhesive layer also occurs, making it difficult to alleviate the static charge. As a result, more foreign matter and other substances adhere to the wafer due to the static charge, which may lead to wafer damage during back grinding. Therefore, in this embodiment, in addition to the adhesive strength of the adhesive layer after curing, the semiconductor processing protective sheet includes an antistatic layer to alleviate static electricity and reduce the static voltage of the wafer.

[0039] The components of the protective sheet for semiconductor processing will be described in detail below.

[0040] (2. Base material) The substrate is not limited as long as it is made of a material that can support the wafer before back grinding and hold the wafer after back grinding. For example, various resin films used as substrates for back grinding tapes are examples of substrates. The substrate may consist of a single-layer film made of one resin film, or it may consist of a multi-layer film made by laminating multiple resin films.

[0041] (2.1 Physical properties of the substrate) In this embodiment, it is preferable that the substrate has high rigidity. High rigidity of the substrate suppresses vibrations during backside grinding, which in turn improves wafer support and holding performance, reducing wafer damage and cracks. It also contributes to reducing stress when peeling the semiconductor processing protective sheet from the wafer, reducing wafer damage and cracks that occur during peeling. Furthermore, it improves the workability when attaching the semiconductor processing protective sheet to the wafer. Specifically, the Young's modulus of the substrate at 23°C is preferably 1000 MPa or higher, and more preferably 1800 MPa or higher. There is no particular upper limit to the Young's modulus, but it is approximately 30000 MPa. The Young's modulus of the substrate can be controlled by selecting the resin composition, adding plasticizers, and stretching conditions during resin film manufacturing.

[0042] In this embodiment, the thickness of the substrate is preferably 15 μm or more and 110 μm or less, and more preferably 20 μm or more and 105 μm or less.

[0043] (2.2 Material of the base material) As for the material of the base material, it is preferable to select a material such that the Young's modulus of the base material falls within the above range. In this embodiment, examples of materials include polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polyesters such as fully aromatic polyesters, polyimides, polyamides, polycarbonates, polyacetals, modified polyphenylene oxide, polyphenylene sulfide, polysulfones, polyether ketones, and biaxially oriented polypropylene. Among these, it is preferable that one or more are selected from polyester, polyamides, polyimides, and biaxially oriented polypropylene, more preferably polyester, and even more preferably polyethylene terephthalate.

[0044] Furthermore, the substrate may contain plasticizers, lubricants, infrared absorbers, ultraviolet absorbers, fillers, colorants, antistatic agents, antioxidants, catalysts, etc., to the extent that it does not impair the effects of the present invention. The substrate may also be transparent or opaque, and may be colored or vapor-deposited as desired.

[0045] Furthermore, at least one main surface of the substrate may be subjected to an adhesive treatment such as corona treatment to improve adhesion with other layers. The substrate may also have a primer layer on at least one of its main surfaces.

[0046] The primer layer forming composition is not particularly limited, but examples include compositions containing polyester resins, urethane resins, polyester-urethane resins, acrylic resins, etc. The primer layer forming composition may optionally contain crosslinking agents, photopolymerization initiators, antioxidants, plasticizers, fillers, rust inhibitors, pigments, dyes, etc.

[0047] The thickness of the primer layer is preferably 0.01 to 10 μm, more preferably 0.03 to 5 μm. Because the material of the primer layer is soft, it has little effect on the Young's modulus, and the Young's modulus of the substrate is substantially the same as that of the resin film, even when the primer layer is present.

[0048] (3. Adhesive layer) The adhesive layer is attached to the circuit surface of a semiconductor wafer and protects the circuit surface and supports the semiconductor wafer until it is peeled off from the circuit surface. In this embodiment, the adhesive layer is energy ray curable. The adhesive layer may consist of one layer (single layer) or two or more layers. If the adhesive layer has multiple layers, these multiple layers may be the same or different from each other, and there are no particular restrictions on the combination of layers that make up these multiple layers.

[0049] The thickness of the adhesive layer is not particularly limited, but is preferably 3 μm to 200 μm, and more preferably 5 μm to 100 μm. By keeping the thickness of the adhesive layer within the above range, cracking of the wafer can be suppressed.

[0050] Note that the thickness of the adhesive layer refers to the total thickness of the adhesive layer. For example, the thickness of an adhesive layer composed of multiple layers refers to the sum of the thicknesses of all the layers that make up the adhesive layer.

[0051] In this embodiment, the adhesive layer has the following physical properties.

[0052] (3.1 90° peel-off adhesive strength of the adhesive layer after energy ray curing) In this embodiment, the adhesive force when the adhesive layer after energy ray curing is peeled from the silicon wafer at an angle of 90° between the adhesive layer and the silicon wafer (hereinafter also referred to as the 90° peel adhesive force of the energy ray cured adhesive layer) is 0.035 N / 25 mm or more and less than 0.15 N / 25 mm. Because the 90° peel adhesive force of the energy ray cured adhesive layer is within the above range, it is possible to suppress the occurrence of process errors caused by the tape peeling off at an unexpected timing before the predetermined tape peeling process, while the adhesive force is sufficiently reduced, making it easy to peel off the adhesive layer even if the wafer is thin after back grinding. Therefore, wafer damage is effectively suppressed, and adhesive residue on the wafer can be reduced.

[0053] The 90° peel-off adhesive strength of the adhesive layer after energy ray curing is preferably 0.14 N / 25 mm or less, and more preferably 0.13 N / 25 mm or less.

[0054] In this embodiment, the 90° peel-off adhesive strength of the adhesive layer after energy ray curing is measured in accordance with JIS Z 0237. This is achieved by attaching the adhesive layer to a silicon wafer, curing the adhesive layer with energy rays, and then peeling the cured adhesive layer from the silicon wafer at a 90° angle at a peeling speed of 600 mm / min. The specific measurement conditions will be described later in the examples.

[0055] (3.2 Ratio of 90° peel adhesion of the adhesive layer before and after energy ray curing) In this embodiment, it is preferable that the ratio of the 90° peel adhesion strength of the adhesive layer before and after energy ray curing is 4% or less. That is, it is preferable that the ratio of the 90° peel adhesion strength of the adhesive layer after energy ray curing (hereinafter also referred to as the adhesion ratio) to the adhesion strength when the adhesive layer before energy ray curing is peeled from the silicon wafer so that the angle between the adhesive layer and the silicon wafer is 90° (hereinafter also referred to as the 90° peel adhesion strength of the adhesive layer before energy ray curing) is 4% or less.

[0056] Because the adhesion ratio is within the above range, during backside grinding, the adhesive layer adheres sufficiently to the wafer surface to protect the circuit, and after backside grinding, even if the wafer is thin, the adhesive layer can be easily peeled off, thereby suppressing wafer damage.

[0057] The adhesion ratio is more preferably 3% or less, and even more preferably 2% or less. On the other hand, there is no particular lower limit to the adhesion ratio, but it is usually around 0.3%.

[0058] The 90° peel adhesion strength of the adhesive layer before energy ray curing can be measured using the same method as for measuring the 90° peel adhesion strength of the adhesive layer after energy ray curing, except that the adhesive strength of the adhesive layer before energy ray curing is measured. Specific measurement conditions will be described later in the examples.

[0059] (3.3 Surface resistivity) In this embodiment, the surface resistivity of the adhesive layer after energy ray curing is 5.1 × 10⁻⁶. 12 Ω / cm2 Above 1.0×10 15 Ω / cm 2 It is preferably not more than the aforementioned value. Note that this surface resistivity is the surface resistivity of the surface of the pressure-sensitive adhesive layer that is to be attached to an adherend (the surface 30a of the pressure-sensitive adhesive layer in FIG. 1A).

[0060] The present inventors have found that the amount of carbon-carbon double bonds in the pressure-sensitive adhesive layer before curing affects not only the adhesive force of the pressure-sensitive adhesive layer after curing, but also the charging property of the pressure-sensitive adhesive layer. That is, even if the protective sheet for semiconductor processing according to the present embodiment has an antistatic layer, charging of the wafer may cause adhesion of foreign substances or the like to the wafer. Therefore, in such a case, for example, by controlling the amount of energy-ray-polymerizable carbon-carbon double bonds in the pressure-sensitive adhesive layer before curing, it is preferable to control the surface resistivity of the pressure-sensitive adhesive layer to fall within the above range.

[0061] When the surface resistivity is within the above range, static electricity easily escapes from the protective sheet for semiconductor processing, and charging of the wafer during processing of the wafer to which the protective sheet for semiconductor processing is attached can be suppressed. As a result, adhesion of foreign substances or the like to the wafer can be suppressed in processes such as the step of attaching the protective sheet for semiconductor processing to the surface of the wafer, the step of grinding the back surface of the wafer, the step of peeling the protective sheet for semiconductor processing, and the step of conveying the wafer after peeling the protective sheet for semiconductor processing. Therefore, damage and cracking of the wafer caused by adhesion of foreign substances or the like are suppressed.

[0062] Note that when the surface resistivity is lower than the above range, this indicates, for example, insufficient curing of the pressure-sensitive adhesive layer. As a result, when the thickness of the wafer after grinding is small, damage to the wafer may occur during peeling of the protective sheet for semiconductor processing. In addition, a part of the pressure-sensitive adhesive layer may remain adhered to the wafer (adhesive residue).

[0063] It is more preferable that the surface resistivity is 9.5×10 14 Ω / cm 2 or less, and even more preferably 9.0×10 14 Ω / cm 2It is even more preferable that the following conditions are met. On the other hand, the surface resistivity is 5.2 × 10⁻⁶. 12 Ω / cm 2 More preferably, 5.5 × 10 12 Ω / cm 2 It is even more preferable that the above conditions are met.

[0064] In this embodiment, the surface resistivity is measured in accordance with JIS K 7194. That is, it is measured in the same way as the measurement method specified in JIS K 7194, although the measurement conditions may differ. The specific measurement conditions will be described later in the examples.

[0065] (3.4 Composition of the adhesive layer) The composition of the adhesive layer is not particularly limited as long as the adhesive layer before curing has sufficient tackiness to protect the circuit surface of the wafer, and the tackiness of the adhesive layer after curing is within the above range. In this embodiment, the adhesive layer is preferably composed of a composition (adhesive layer composition) that includes, for example, an acrylic adhesive, a urethane adhesive, a rubber adhesive, a silicone adhesive, etc., as an adhesive component (adhesive resin) capable of exhibiting tackiness.

[0066] Furthermore, from the viewpoint of easily achieving the above-mentioned adhesive strength and adhesive strength ratio after energy ray curing, the adhesive layer composition includes an energy ray curable adhesive.

[0067] (3.5 Composition for adhesive layer) As mentioned above, the adhesive layer is energy-ray curable, and is therefore formed from an energy-ray curable composition (adhesive layer composition). The adhesive layer composition will be described below.

[0068] The adhesive layer composition may have energy-ray curability by incorporating an energy-ray curable compound separately from the adhesive resin, but it is preferable that the adhesive resin itself has energy-ray curability. When the adhesive resin itself has energy-ray curability, an energy-ray polymerizable group is introduced into the adhesive resin, and it is preferable that the energy-ray polymerizable group is introduced into the main chain or side chain of the adhesive resin.

[0069] Furthermore, when an energy-ray curable compound is added separately from the adhesive resin, the energy-ray curable compound used is a monomer or oligomer having an energy-ray polymerizable group. The oligomer is an oligomer with a weight-average molecular weight (Mw) of less than 10,000, and an example of this is urethane (meth)acrylate.

[0070] In this embodiment, from the viewpoint of controlling the amount of energy-ray polymerizable carbon-carbon double bonds, the amount is preferably 0.1 to 300 parts by mass, more preferably 0.5 to 200 parts by mass, and even more preferably 1 to 150 parts by mass, per 100 parts by mass of the non-energy-ray curable adhesive resin.

[0071] The following will provide a more detailed explanation of the case where the energy-curable adhesive resin contained in the adhesive layer composition is an energy-curable acrylic polymer (hereinafter also referred to as "acrylic polymer (A)").

[0072] (3.5.1 Acrylic polymer (A)) Acrylic polymer (A) is an acrylic polymer into which energy-ray polymerizable groups are introduced and which has constituent units derived from (meth)acrylate. It is preferable that the energy-ray polymerizable groups are introduced into the side chains of the acrylic polymer.

[0073] The acrylic polymer (A) is preferably a reaction product obtained by reacting an acrylic copolymer (A0) having structural units derived from alkyl (meth)acrylate (a1) and structural units derived from functional group-containing monomer (a2) with a polymerizable compound (Xa) having an energy-ray polymerizable group.

[0074] Alkyl (meth)acrylate (a1) used is an alkyl (meth)acrylate in which the alkyl group has 1 to 18 carbon atoms. Specifically, examples include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, n-tridecyl (meth)acrylate, myristyl (meth)acrylate, palmityl (meth)acrylate, stearyl (meth)acrylate, etc.

[0075] Among these, alkyl(meth)acrylate (a1) is preferably an alkyl(meth)acrylate in which the alkyl group has 4 to 8 carbon atoms. Specifically, 2-ethylhexyl(meth)acrylate and n-butyl(meth)acrylate are preferred, and n-butyl(meth)acrylate is more preferred. These may be used individually or in combination of two or more.

[0076] In the acrylic copolymer (A0), the content of constituent units derived from alkyl (meth)acrylate (a1) is preferably 40 to 98% by mass, more preferably 45 to 95% by mass, and even more preferably 50 to 90% by mass, relative to the total constituent units (100% by mass) of the acrylic copolymer (A0), from the viewpoint of improving the adhesive strength of the formed adhesive layer.

[0077] For example, alkyl (meth)acrylate (a1) may contain ethyl (meth)acrylate, methyl (meth)acrylate, etc., in addition to the 2-ethylhexyl (meth)acrylate and n-butyl (meth)acrylate mentioned above. Including these monomers makes it easier to adjust the adhesive performance of the adhesive layer to the desired level.

[0078] The functional group-containing monomer (a2) is a monomer having a functional group such as a hydroxyl group, carboxyl group, epoxy group, amino group, cyano group, nitrogen atom-containing ring group, or alkoxysilyl group. Among the above, one or more of the hydroxyl group-containing monomer, carboxyl group-containing monomer, and epoxy group-containing monomer are preferred as the functional group-containing monomer (a2).

[0079] Examples of monomers containing a hydroxyl group 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.

[0080] Examples of monomers containing a carboxyl group include (meth)acrylic acid, maleic acid, fumaric acid, and itaconic acid.

[0081] Examples of epoxy-containing monomers include epoxy-group-containing (meth)acrylic acid esters and non-acrylic epoxy-group-containing monomers. Examples of epoxy-group-containing (meth)acrylic acid esters include glycidyl (meth)acrylate, β-methylglycidyl (meth)acrylate, (3,4-epoxycyclohexyl)methyl (meth)acrylate, and 3-epoxycyclo-2-hydroxypropyl (meth)acrylate. Examples of non-acrylic epoxy-group-containing monomers include glycidyl crotonate and allyl glycidyl ether.

[0082] The functional group-containing monomer (a2) may be used alone or in combination of two or more types.

[0083] Among the above, hydroxyl group-containing monomers are more preferred as functional group-containing monomers (a2), and among them, hydroxyalkyl (meth)acrylate is more preferred, and 2-hydroxyethyl (meth)acrylate is even more preferred.

[0084] (a2) By using hydroxyalkyl (meth)acrylate as component, it becomes possible to react the polymerizable compound (Xa) with the acrylic copolymer (A0) relatively easily.

[0085] In the acrylic copolymer (A0), the content of constituent units derived from the functional group-containing monomer (a2) is preferably 1 to 35% by mass, more preferably 3 to 32% by mass, and even more preferably 6 to 30% by mass, relative to the total constituent units (100% by mass) of the acrylic copolymer (A0).

[0086] If the content is 1% by mass or more, a certain amount of functional groups that serve as reaction sites with polymerizable compound (Xa) can be secured. Therefore, the adhesive layer can be properly cured by energy ray irradiation, making it possible to reduce the adhesive strength after energy ray irradiation. Furthermore, if the content is 30% by mass or less, a sufficient pot life can be ensured when applying a solution of the adhesive layer composition to form the adhesive layer.

[0087] The acrylic copolymer (A0) may be a copolymer of alkyl (meth)acrylate (a1) and a functional group-containing monomer (a2), or it may be a copolymer of component (a1), component (a2), and other monomers (a3) ​​other than components (a1) and (a2).

[0088] Other monomers (a3) ​​include, for example, cyclic (meth)acrylates such as cyclohexyl (meth)acrylate, benzyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, and dicyclopentenyloxyethyl (meth)acrylate, as well as vinyl acetate and styrene. Other monomers (a3) ​​may be used individually or in combination of two or more.

[0089] The content of constituent units derived from other monomers (a3) ​​in the acrylic copolymer (A0) is preferably 0 to 30% by mass, more preferably 0 to 10% by mass, and even more preferably 0 to 5% by mass, relative to the total constituent units (100% by mass) of the acrylic copolymer (A0).

[0090] Polymerizable compound (Xa) is a compound having an energy-ray polymerizable group and a substituent (hereinafter also simply referred to as "reactive substituent") that can react with a functional group in the constituent unit derived from component (a2) of the acrylic copolymer (A0).

[0091] The energy-ray polymerizable group can be any group containing an energy-ray polymerizable carbon-carbon double bond. Examples include (meth)acryloyl groups and vinyl groups, with (meth)acryloyl groups being preferred. Furthermore, the polymerizable compound (Xa) is preferably a compound having 1 to 5 energy-ray polymerizable groups per molecule.

[0092] The reactive substituent in the polymerizable compound (Xa) can be appropriately changed depending on the functional group of the functional group-containing monomer (a2), but examples include isocyanate groups, carboxyl groups, epoxy groups, etc., and an isocyanate group is preferred from the viewpoint of reactivity, etc. If the polymerizable compound (Xa) has an isocyanate group, it can react easily with the acrylic copolymer (A0), for example, when the functional group of the functional group-containing monomer (a2) is a hydroxyl group.

[0093] Specific polymerizable compounds (Xa) include, for example, (meth)acryloyloxyethyl isocyanate, meta-isopropenyl-α,α-dimethylbenzyl isocyanate, (meth)acryloyl isocyanate, allyl isocyanate, glycidyl (meth)acrylate, and (meth)acrylic acid. These polymerizable compounds (Xa) may be used individually or in combination of two or more.

[0094] Among these, (meth)acryloyloxyethyl isocyanate is preferred from the viewpoint of having an isocyanate group suitable as the reactive substituent and having an appropriate distance between the main chain and the energy-ray polymerizable group.

[0095] From the viewpoint of controlling the amount of carbon-carbon double bonds that can be polymerized by energy rays, of the total amount of functional groups (100 equivalents) derived from the functional group-containing monomer (a2) in the acrylic copolymer (A0), preferably 50 to 98 equivalents, more preferably 55 to 93 equivalents, are reacted with functional groups.

[0096] The weight-average molecular weight (Mw) of the acrylic polymer (A) is preferably 300,000 to 1,600,000, more preferably 400,000 to 1,400,000. Having such an Mw makes it possible to impart appropriate tackiness to the adhesive layer.

[0097] Even if the adhesive resin is energy-ray curable, it is preferable that the adhesive layer composition contains an energy-ray curable compound other than the adhesive resin. Such energy-ray curable compounds are preferably monomers or oligomers that have an unsaturated group in their molecule and can be polymerized and cured by energy irradiation.

[0098] Specifically, examples include polyvalent (meth)acrylate monomers such as trimethylolpropane tri(meth)acrylate, pentaerythritol (meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,4-butylene glycol di(meth)acrylate, and 1,6-hexanediol (meth)acrylate, as well as oligomers such as urethane (meth)acrylate, polyester (meth)acrylate, polyether (meth)acrylate, and epoxy (meth)acrylate.

[0099] Among these, urethane (meth)acrylate oligomers are preferred because they have a relatively high molecular weight and allow the surface resistivity of the adhesive layer to be within the range described above.

[0100] From the viewpoint of controlling the amount of energy-ray polymerizable carbon-carbon double bonds, the content of the energy-ray curable compound is preferably 0.1 to 300 parts by mass, more preferably 0.5 to 200 parts by mass, and even more preferably 1 to 150 parts by mass, per 100 parts by mass of the acrylic polymer (A).

[0101] (3.5.2 Crosslinking agents) The adhesive layer composition preferably further contains a crosslinking agent. The adhesive layer composition is crosslinked by the crosslinking agent, for example, by heating after application. When the acrylic polymer (A) in the adhesive layer is crosslinked by the crosslinking agent, a coating film is properly formed, and the adhesive layer is more likely to function as an adhesive layer.

[0102] Examples of crosslinking agents include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, aziridine-based crosslinking agents, and chelating crosslinking agents, with isocyanate-based crosslinking agents being preferred among these. The crosslinking agents may be used individually or in combination of two or more types.

[0103] Examples of isocyanate-based crosslinking agents include polyisocyanate compounds. Specific examples of polyisocyanate compounds include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate; and alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate. In addition, biuret and isocyanurate compounds of these compounds, as well as adduct compounds resulting from reactions with low-molecular-weight active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil, can also be used.

[0104] Among the above, polyhydric alcohol (e.g., trimethylolpropane) adducts of aromatic polyisocyanates such as tolylene diisocyanate are preferred.

[0105] The crosslinking agent content is preferably 0.01 to 10 parts by mass, more preferably 0.03 to 7 parts by mass, per 100 parts by mass of acrylic polymer (A).

[0106] (3.5.3 Photopolymerization initiators) The adhesive layer composition preferably further contains a photopolymerization initiator. The inclusion of a photopolymerization initiator in the adhesive layer composition facilitates the curing of the adhesive layer composition by energy rays such as ultraviolet light.

[0107] Examples of photopolymerization initiators include acetophenone, 2,2-diethoxybenzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, Michler ketone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzyl diphenysulfide, tetramethylthiuram monosulfide, benzyl dimethyl ketal, dibenzyl, diacetyl, 1-chloranthraquinone, 2-chloranthraquinone, 2-ethylanthraquinone, 2,2-dimethoxy-1,2-diphenylethane-1-one, 1 Examples include low molecular weight polymerization initiators such as -hydroxycyclohexylphenyl ketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropanone-1,2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1,2-hydroxy-2-methyl-1-phenyl-propan-1-one, diethylthioxanthone, isopropylthioxanthone, and 2,4,6-trimethylbenzoyldiphenyl-phosphine oxide, as well as oligomerized polymerization initiators such as oligo{2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone}.

[0108] The photopolymerization initiator may be used alone or in combination of two or more. Among those mentioned above, 2,2-dimethoxy-1,2-diphenylethane-1-one and 1-hydroxycyclohexylphenyl ketone are preferred.

[0109] The content of the photopolymerization initiator is preferably 0.01 to 10 parts by mass, more preferably 0.03 to 7 parts by mass, and even more preferably 0.05 to 5 parts by mass, per 100 parts by mass of the acrylic polymer (A).

[0110] The adhesive layer composition may contain other additives as long as they do not impair the effects of the present invention. Examples of other additives include tackifiers, antioxidants, plasticizers, fillers, rust inhibitors, pigments, dyes, and the like. When these additives are included, the content of each additive is preferably 0.01 to 6 parts by mass, more preferably 0.02 to 2 parts by mass, per 100 parts by mass of the acrylic polymer (A).

[0111] The tackiness of the adhesive layer can be adjusted, for example, by the type and amount of monomers constituting the acrylic polymer (A), and the amount of energy-ray polymerizable groups introduced into the acrylic polymer (A). The surface resistivity of the adhesive layer can also be adjusted to some extent by these factors. The above describes a preferred range for the amount of energy-ray polymerizable groups introduced into the acrylic polymer (A). For example, increasing the amount of energy-ray polymerizable groups tends to decrease the tackiness after curing and increase the surface resistivity. However, the tackiness and surface resistivity of the adhesive layer can also be adjusted by factors other than those mentioned above. For example, they can be appropriately adjusted by the amount of crosslinking agent and photopolymerization initiator incorporated into the adhesive layer.

[0112] (4. Antistatic layer) The antistatic layer is placed between the substrate and the adhesive layer. The antistatic component in the antistatic layer can suppress the increase in static voltage caused by the leakage of static charge resulting from processing of the wafer to which the semiconductor processing protective sheet is attached. The composition of the antistatic layer only needs to have enough antistatic properties to keep the peeling static voltage when peeling the adhesive layer from the wafer below a predetermined value. In this embodiment, it is preferable to keep the peeling static voltage below 500V.

[0113] The thickness of the antistatic layer is preferably 10 nm or more, more preferably 15 nm or more, even more preferably 20 nm or more, and particularly preferably 60 nm or more. Furthermore, the thickness is preferably 300 nm or less, more preferably 250 nm or less, and even more preferably 200 nm or less.

[0114] (4.1 Composition for antistatic layer) In this embodiment, the antistatic layer is preferably composed of a composition containing a polymer compound (composition for the antistatic layer). Examples of such compositions include a composition containing a conductive polymer compound as an antistatic component, and a composition containing an antistatic component and a polymer compound. The composition for the antistatic layer is preferably a composition containing a conductive polymer compound.

[0115] Examples of conductive polymer compounds include polythiophene-based polymers, polypyrrole-based polymers, and polyaniline-based polymers. In this embodiment, polythiophene-based polymers are preferred.

[0116] Examples of polythiophene polymers include polythiophene, poly(3-alkylthiophene), poly(3-thiophene-β-ethanesulfonic acid), and mixtures of polyalkylenedioxythiophene and polystyrene sulfonate (PSS) (including doped mixtures). Among these, a mixture of polyalkylenedioxythiophene and polystyrene sulfonate is preferred. Examples of the above polyalkylenedioxythiophene include poly(3,4-ethylenedioxythiophene) (PEDOT), polypropylenedioxythiophene, and poly(ethylene / propylene)dioxythiophene, with poly(3,4-ethylenedioxythiophene) being preferred. In other words, among the above, a mixture of poly(3,4-ethylenedioxythiophene) and polystyrene sulfonate (PSS-doped PEDOT) is particularly preferred.

[0117] Examples of polypyrrole polymers include polypyrrole, poly-3-methylpyrrole, and poly-3-octylpyrrole.

[0118] Examples of polyaniline-based polymers include polyaniline, polymethylaniline, and polymethoxyaniline.

[0119] A composition containing an antistatic component and a polymer compound is an example of a composition containing an antistatic component and a binder resin. Examples of antistatic components include the conductive polymer compounds, surfactants, ionic liquids, conductive inorganic compounds, and the like.

[0120] The surfactant can be at least one selected from cationic surfactants, anionic surfactants, amphoteric surfactants, and nonionic surfactants. For example, cationic surfactants containing quaternary ammonium salts are exemplified. Examples of conductive inorganic compounds include various metals and conductive oxides.

[0121] Furthermore, the binder resin is not particularly limited. Examples include polyester resin, acrylic resin, polyvinyl resin, urethane resin, melamine resin, epoxy resin, etc. Crosslinking agents may also be used in combination. Examples of crosslinking agents include methylolated or alkylolated melamine compounds, urea compounds, glyoxal compounds, acrylamide compounds, epoxy compounds, isocyanate compounds, etc.

[0122] The amount of antistatic agent in the antistatic layer composition can be appropriately determined according to the desired antistatic performance. Specifically, the amount of antistatic agent in the antistatic layer composition is preferably 0.1 to 20% by mass.

[0123] (5.Buffer layer) As described above, in the semiconductor processing protective sheet shown in Figure 1B, the buffer layer is formed on the main surface of the substrate opposite to the main surface on which the adhesive layer is formed. The buffer layer will be described below.

[0124] The buffer layer is a softer layer compared to the substrate, and it relieves stress during back-side grinding of the wafer, preventing cracks and chips from occurring in the wafer. Furthermore, when a wafer with a semiconductor processing protective sheet attached is placed on a vacuum table via the semiconductor processing protective sheet during back-side grinding, having a buffer layer as a constituent layer of the semiconductor processing protective sheet makes it easier to properly hold the wafer on the vacuum table.

[0125] Such buffer layers are useful when processing wafers with DBG, especially LDBG.

[0126] The thickness of the buffer layer is preferably 5 to 100 μm, more preferably 1 to 100 μm, and even more preferably 5 to 80 μm. By setting the thickness of the buffer layer within the above range, the buffer layer can appropriately relieve stress during backside grinding.

[0127] The buffer layer may be a layer formed from a buffer layer composition containing an energy ray polymerizable compound, or it may be a film such as a polypropylene film, an ethylene-vinyl acetate copolymer film, an ionomer resin film, an ethylene-(meth)acrylic acid copolymer film, an ethylene-(meth)acrylic acid ester copolymer film, an LDPE film, or an LLDPE film.

[0128] (5.1 Composition for buffer layer) A buffer layer composition containing an energy-ray polymerizable compound can be cured by irradiation with energy rays.

[0129] Furthermore, the buffer layer composition containing the energy ray polymerizable compound more specifically preferably contains a urethane (meth)acrylate (b1) and a polymerizable compound (b2) having an alicyclic or heterocyclic group with 6 to 20 ring-forming atoms. In addition, the buffer layer composition may contain a polymerizable compound (b3) having a functional group in addition to the above components (b1) and (b2). In addition, the buffer layer composition may contain a photopolymerization initiator in addition to the above components. Furthermore, the buffer layer composition may contain other additives and resin components to the extent that they do not impair the effects of the present invention.

[0130] The following describes in detail each component contained in the buffer layer composition containing energy ray polymerizable compounds.

[0131] (5.1.1 Urethane (meth)acrylate (b1)) Urethane (meth)acrylate (b1) is a compound having at least a (meth)acryloyl group and a urethane bond, and possessing the property of polymerization curing by energy ray irradiation. Urethane (meth)acrylate (b1) is an oligomer or polymer.

[0132] The weight-average molecular weight (Mw) of component (b1) is preferably 1,000 to 100,000, more preferably 2,000 to 60,000, and even more preferably 3,000 to 20,000. The number of (meth)acryloyl groups in component (b1) (hereinafter also referred to as "number of functional groups") may be monofunctional, difunctional, or trifunctional or more, but monofunctional or difunctional is preferred.

[0133] Component (b1) can be obtained, for example, by reacting a terminal isocyanate urethane prepolymer, which is obtained by reacting a polyol compound with a polyvalent isocyanate compound, with a (meth)acrylate having a hydroxyl group. Component (b1) may be used alone or in combination of two or more components.

[0134] The polyol compound used as a raw material for component (b1) is not particularly limited as long as it is a compound having two or more hydroxyl groups. It may be a bifunctional diol, a trifunctional triol, or a polyol with four or more functions, but a bifunctional diol is preferred, and a polyester-type diol or a polycarbonate-type diol is more preferred.

[0135] Examples of polyvalent isocyanate compounds include aliphatic polyisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, and trimethylhexamethylene diisocyanate; alicyclic diisocyanates such as isophorone diisocyanate, norbornane diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, dicyclohexylmethane-2,4'-diisocyanate, and ω,ω'-diisocyanate dimethylcyclohexane; and aromatic diisocyanates such as 4,4'-diphenylmethane diisocyanate, tolylene diisocyanate, xylylene diisocyanate, tolidine diisocyanate, tetramethylene xylylene diisocyanate, and naphthalene-1,5-diisocyanate.

[0136] Among these, isophorone diisocyanate, hexamethylene diisocyanate, and xylylene diisocyanate are preferred.

[0137] A urethane (meth)acrylate (b1) can be obtained by reacting the above-mentioned polyol compound with a polyvalent isocyanate compound to obtain a terminal isocyanate urethane prepolymer, and then reacting the prepolymer with a (meth)acrylate having a hydroxyl group. The (meth)acrylate having a hydroxyl group is not particularly limited as long as it is a compound having at least one molecule containing both a hydroxyl group and a (meth)acryloyl group.

[0138] Specific examples of (meth)acrylates having a hydroxyl group include, for example, hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 4-hydroxycyclohexyl (meth)acrylate, 5-hydroxycyclooctyl (meth)acrylate, 2-hydroxy-3-phenyloxypropyl (meth)acrylate, pentaerythritol tri(meth)acrylate, polyethylene glycol mono(meth)acrylate, and polypropylene glycol mono(meth)acrylate; hydroxyl group-containing (meth)acrylamides such as N-methylol (meth)acrylamide; and reaction products obtained by reacting vinyl alcohol, vinyl phenol, and diglycidyl esters of bisphenol A with (meth)acrylic acid.

[0139] Among these, hydroxyalkyl (meth)acrylate is preferred, and 2-hydroxyethyl (meth)acrylate is more preferred.

[0140] The content of component (b1) in the buffer layer composition is preferably 10 to 70% by mass, more preferably 20 to 60% by mass, and even more preferably 25 to 55% by mass, based on the total amount (100% by mass) of the buffer layer composition.

[0141] (5.1.2 Polymerizable compounds having alicyclic or heterocyclic groups with 6 to 20 ring-forming atoms (b2)) Component (b2) is a polymerizable compound having an alicyclic or heterocyclic group with 6 to 20 ring-forming atoms, and more preferably a compound having at least one (meth)acryloyl group, and more preferably a compound having one (meth)acryloyl group. By using component (b2), the film-forming properties of the resulting buffer layer composition can be improved.

[0142] Specific examples of component (b2) include alicyclic group-containing (meth)acrylates such as isobornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyloxy (meth)acrylate, cyclohexyl (meth)acrylate, and adamantane (meth)acrylate; heterocyclic group-containing (meth)acrylates such as tetrahydrofurfuryl (meth)acrylate and morpholin (meth)acrylate; and so on. Component (b2) may be used alone or in combination of two or more. Among alicyclic group-containing (meth)acrylates, isobornyl (meth)acrylate is preferred, and among heterocyclic group-containing (meth)acrylates, tetrahydrofurfuryl (meth)acrylate is preferred.

[0143] The content of component (b2) in the buffer layer composition is preferably 10 to 70% by mass, more preferably 20 to 60% by mass, and even more preferably 25 to 55% by mass, based on the total amount (100% by mass) of the buffer layer composition.

[0144] (5.1.3 Polymerizable compounds having functional groups (b3)) Component (b3) is a polymerizable compound containing functional groups such as hydroxyl groups, epoxy groups, amide groups, and amino groups, and is more preferably a compound having at least one (meth)acryloyl group, and more preferably a compound having one (meth)acryloyl group.

[0145] Component (b3) has good compatibility with component (b1), making it easier to adjust the viscosity of the buffer layer composition to an appropriate range. In addition, good buffering performance is achieved even when the buffer layer is relatively thin.

[0146] Examples of component (b3) include hydroxyl group-containing (meth)acrylate, epoxy group-containing compound, amide group-containing compound, and amino group-containing (meth)acrylate. Among these, hydroxyl group-containing (meth)acrylate is preferred.

[0147] Examples of hydroxyl group-containing (meth)acrylates include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, phenylhydroxypropyl (meth)acrylate, and 2-hydroxy-3-phenoxypropyl acrylate. Among these, hydroxyl group-containing (meth)acrylates having an aromatic ring, such as phenylhydroxypropyl (meth)acrylate, are more preferred.

[0148] Furthermore, component (b3) may be used alone or in combination of two or more types. The content of component (b3) in the buffer layer composition is preferably 5 to 40% by mass, more preferably 7 to 35% by mass, and even more preferably 10 to 30% by mass, based on the total amount (100% by mass) of the buffer layer composition, in order to improve the film-forming properties of the buffer layer composition.

[0149] (5.1.4 Polymerizable compounds other than components (b1) to (b3) (b4)) The buffer layer forming composition may also contain other polymerizable compounds (b4) other than the above components (b1) to (b3), as long as the effects of the present invention are not impaired.

[0150] Examples of component (b4) include alkyl (meth)acrylates having an alkyl group with 1 to 20 carbon atoms; vinyl compounds such as styrene, hydroxyethyl vinyl ether, hydroxybutyl vinyl ether, N-vinylformamide, N-vinylpyrrolidone, and N-vinylcaprolactam. Component (b4) may be used alone or in combination of two or more.

[0151] The content of component (b4) in the buffer layer forming composition is preferably 0 to 20% by mass, more preferably 0 to 10% by mass, even more preferably 0 to 5% by mass, and particularly preferably 0 to 2% by mass.

[0152] (5.1.5 Photopolymerization initiators) The buffer layer composition preferably contains a photopolymerization initiator, from the viewpoint of shortening the polymerization time by energy ray irradiation and reducing the amount of energy ray irradiation when forming the buffer layer.

[0153] Examples of photopolymerization initiators include benzoin compounds, acetophenone compounds, acyl phosphinoxide compounds, titanocene compounds, thioxanthone compounds, peroxide compounds, and photosensitizers such as amines and quinones. More specifically, examples include 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzyl phenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyrolnitrile, dibenzyl, diacetyl, 8-chloranthraquinone, and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

[0154] These photopolymerization initiators can be used individually or in combination of two or more.

[0155] The amount of photopolymerization initiator in the buffer layer composition is preferably 0.05 to 15 parts by mass, more preferably 0.1 to 10 parts by mass, and even more preferably 0.3 to 5 parts by mass, based on 100 parts by mass of the total amount of energy ray polymerizable compounds.

[0156] (5.1.6 Other additives) The buffer layer composition may contain other additives as long as they do not impair the effects of the present invention. Examples of other additives include antistatic agents, antioxidants, plasticizers, fillers, rust inhibitors, pigments, dyes, and the like. When these additives are included, the amount of each additive in the buffer layer composition is preferably 0.01 to 6 parts by mass, more preferably 0.1 to 3 parts by mass, based on 100 parts by mass of the total amount of energy ray polymerizable compounds.

[0157] A buffer layer formed from a buffer layer composition containing an energy-ray polymerizable compound is obtained by polymerizing and curing the buffer layer composition of the above composition by energy-ray irradiation. In other words, the buffer layer is a cured product of the buffer layer composition.

[0158] Therefore, it is preferable that the buffer layer contains polymerization units derived from component (b1) and polymerization units derived from component (b2). The buffer layer may also contain polymerization units derived from component (b3) or component (b4). The proportion of each polymerization unit in the buffer layer usually corresponds to the ratio (compounding ratio) of each component constituting the buffer layer composition.

[0159] (6. Release sheet) A release sheet may be attached to the surface of the semiconductor processing protective sheet. Specifically, the release sheet is attached to the surface of the adhesive layer of the semiconductor processing protective sheet. By being attached to the surface of the adhesive layer, the release sheet protects the adhesive layer during transportation and storage. The release sheet is attached to the semiconductor processing protective sheet in a removable manner and is peeled off and removed from the semiconductor processing protective sheet before use (i.e., before wafer attachment).

[0160] The release sheet used is one in which at least one side has been treated to release the material. Specifically, this includes a release sheet in which a release agent is applied to the surface of a release sheet substrate.

[0161] A resin film is preferred as the substrate for the release sheet, and examples of resins constituting the resin film include polyester resin films such as polyethylene terephthalate resin, polybutylene terephthalate resin, and polyethylene naphthalate resin, and polyolefin resins such as polypropylene resin and polyethylene resin. Examples of release agents include rubber elastomers such as silicone resins, olefin resins, isoprene resins, and butadiene resins, long-chain alkyl resins, alkyd resins, and fluorine resins.

[0162] The thickness of the release sheet is not particularly limited, but is preferably 10 to 200 μm, and more preferably 20 to 150 μm.

[0163] (7. Method for manufacturing protective sheets for semiconductor processing) The method for manufacturing the semiconductor processing protective sheet according to this embodiment is not particularly limited as long as it can form an antistatic layer and an adhesive layer on the main surface of the substrate, and any known method may be used. Below, a method for manufacturing the semiconductor processing protective sheet shown in Figure 1A will be described.

[0164] First, as a composition for forming an antistatic layer, for example, an antistatic layer composition containing the above-mentioned components, or a composition obtained by diluting the antistatic layer composition with a solvent, etc., is prepared. Similarly, as a composition for forming an adhesive layer, for example, an adhesive layer composition containing the above-mentioned components, or a composition obtained by diluting the adhesive layer composition with a solvent, etc., is prepared. Similarly, as a composition for forming a buffer layer, for example, a buffer layer composition containing the above-mentioned components, or a composition obtained by diluting the buffer layer composition with a solvent, etc., is prepared.

[0165] Examples of solvents include organic solvents such as methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran, dioxane, cyclohexane, n-hexane, toluene, xylene, n-propanol, and isopropanol.

[0166] First, an antistatic layer composition is applied to the release surface of the first release sheet by known methods such as spin coating, spray coating, bar coating, knife coating, roll coating, blade coating, die coating, or gravure coating, and then heated and dried to form an antistatic layer on the first release sheet. After that, the antistatic layer on the first release sheet is bonded to one side of the substrate, and the first release sheet is removed.

[0167] Next, the adhesive layer composition is applied to the release surface of the second release sheet by a known method and heated and dried to form an adhesive layer on the second release sheet. Then, the adhesive layer on the second release sheet and the antistatic layer on the substrate are bonded together to obtain a semiconductor processing protective sheet in which the antistatic layer and the adhesive layer are formed in that order on one main surface of the substrate. The second release sheet can be removed when using the semiconductor processing protective sheet.

[0168] Furthermore, when manufacturing the semiconductor processing protective sheet shown in Figure 1B, the following procedure should be followed.

[0169] A buffer layer composition is applied to the release surface of the third release sheet by a known method to form a coating film, and this coating film is partially cured to form a buffer layer film on the release sheet. The buffer layer film formed on the release sheet is bonded to the other surface of the substrate, and the buffer layer film is completely cured to form a buffer layer on the substrate.

[0170] In this embodiment, curing of the coating film is preferably performed by irradiation with energy rays. Furthermore, curing of the coating film may be performed in a single curing treatment or in multiple stages.

[0171] Furthermore, it is preferable to form a buffer layer on the substrate before forming the antistatic layer and the adhesive layer.

[0172] (8. Method of manufacturing semiconductor devices) The semiconductor processing protective sheet according to the present invention is preferably used to protect the surface of a wafer by being attached to it when the back surface of the wafer is being ground.

[0173] As a non-exclusive example of the use of protective sheets for semiconductor processing, a method for manufacturing semiconductor devices will be described in more detail below.

[0174] The method for manufacturing a semiconductor device specifically comprises at least the following steps 1 to 3. Step 1: The process of attaching the above-mentioned semiconductor processing protective sheet to the surface of the wafer. Step 2: A wafer with a semiconductor processing protective sheet attached to its surface is ground from the back side. Step 3: The semiconductor processing protective sheet is peeled off the wafer after back grinding.

[0175] The following describes in detail each step of the manufacturing method for the semiconductor device described above.

[0176] (Process 1) In step 1, as shown in Figure 2, the main surface 30a of the adhesive layer 30 of the semiconductor processing protective sheet 1 according to this embodiment is attached to the surface 100a of the semiconductor wafer 100. By attaching the semiconductor processing protective sheet to the surface of the semiconductor wafer, the surface of the semiconductor wafer is sufficiently protected.

[0177] The semiconductor wafer used in this manufacturing method may be a silicon wafer, or it may be a wafer made of gallium arsenide, silicon carbide, lithium tantalate, lithium niobate, gallium nitride, indium phosphide, or glass wafer. In this embodiment, the semiconductor wafer is preferably a silicon wafer.

[0178] The thickness of a semiconductor wafer before grinding is not particularly limited, but it is usually around 500 to 1000 μm. Furthermore, semiconductor wafers typically have circuits formed on their surface. Circuit formation on the wafer surface can be carried out by various methods, including conventionally used methods such as etching and lift-off methods.

[0179] A semiconductor wafer, with a protective sheet for semiconductor processing attached, is placed on a chuck table and held in place by suction to the chuck table. During this process, the semiconductor wafer is positioned with its surface facing the table.

[0180] (Process 2) After step 1, the back surface of the semiconductor wafer on the chuck table is ground to obtain a wafer after back-ground grinding. In this embodiment, the thickness of the wafer after back-ground grinding is not particularly limited, but is, for example, 100 μm or less. When the thickness of the wafer after back-ground grinding is within the above range, miniaturization and low-profile semiconductor chips can be easily achieved.

[0181] (Step 3) Next, the semiconductor processing protective sheet is peeled off the semiconductor wafer. This step is carried out, for example, by the following method.

[0182] In this embodiment, the adhesive layer of the semiconductor processing protective sheet is formed from an energy-ray curable adhesive, so the adhesive layer is cured and shrunk by irradiation with energy rays, reducing its adhesive strength to the adherend. Next, a pickup tape is attached to the back side of the semiconductor wafer after backside grinding, and its position and orientation are adjusted so that it can be picked up. At this time, the ring frame placed on the outer circumference of the wafer is also attached to the pickup tape, and the outer edge of the pickup tape is fixed to the ring frame. The wafer and ring frame may be attached to the pickup tape at the same time, or at different times. Next, the semiconductor processing protective sheet is peeled off from the semiconductor wafer held on the pickup tape.

[0183] Since the semiconductor processing protective sheet according to this embodiment has the above-described characteristics, even when the thickness of the semiconductor wafer after backside grinding is thin, and even when the semiconductor processing protective sheet is peeled off the semiconductor wafer after backside grinding, damage to the semiconductor wafer and static charge can be suppressed.

[0184] Subsequently, multiple semiconductor chips are picked up from the pickup tape and fixed onto a substrate or other surface to manufacture a semiconductor device.

[0185] The pickup tape is not particularly limited, but for example, it is composed of a base material and an adhesive sheet having an adhesive layer provided on one side of the base material.

[0186] Furthermore, the semiconductor processing protective sheet according to the present invention is also suitably used in a semiconductor device manufacturing method utilizing a pre-dicing method. In this case, it is preferable to use the semiconductor processing protective sheet shown in Figure 1B.

[0187] In a semiconductor device manufacturing method utilizing the pre-dicing method, in addition to steps 1 to 3 described above, the method includes a step (step 4) of forming grooves from the surface side of the semiconductor wafer, or forming a modified region inside the semiconductor wafer from the surface or back surface of the semiconductor wafer.

[0188] When forming a modified region on a semiconductor wafer, it is preferable to perform step 1 before step 4. On the other hand, when forming grooves on the surface of a semiconductor wafer by dicing or the like, step 1 is performed after step 4. That is, in step 1, a semiconductor processing protective sheet is attached to the surface of the wafer having grooves formed in step 4, which will be described later.

[0189] In step 4, grooves are formed from the surface side of the semiconductor wafer. Alternatively, a modified region is formed inside the semiconductor wafer from either the surface or back surface.

[0190] The grooves formed in this process are shallower than the thickness of the semiconductor wafer. The grooves can be formed by dicing using conventionally known wafer dicing equipment. In addition, in step 3 described above, the semiconductor wafer is divided into multiple semiconductor chips along the grooves by back grinding.

[0191] Furthermore, the modified region is a brittle part of the semiconductor wafer, and it is the starting point for fragmentation into semiconductor chips when the semiconductor wafer is thinned by grinding during the grinding process or when force is applied due to grinding, causing the modified region of the semiconductor wafer to break down. In other words, in step 4, the groove and the modified region are formed along the dividing line that occurs when the semiconductor wafer is divided and fragmented into semiconductor chips in step 3 described above.

[0192] The modified region is formed by irradiating the semiconductor wafer with a laser focused on the interior of the wafer, and the modified region is formed inside the semiconductor wafer. The laser irradiation may be performed from either the front or back side of the semiconductor wafer. In the embodiment in which the modified region is formed, if step 4 is performed after step 1 and the laser irradiation is performed from the wafer surface, the laser will be irradiated onto the semiconductor wafer through a semiconductor processing protective sheet.

[0193] In the pre-dicing method, the back grinding in step 2 is performed to thin the semiconductor wafer at least to the bottom of the groove, if grooves are formed on the semiconductor wafer. This back grinding turns the grooves into cuts that penetrate the wafer, and the semiconductor wafer is divided by these cuts into individual semiconductor chips.

[0194] On the other hand, if a modified region is formed, the grinding surface (back surface of the wafer) may reach the modified region through grinding, but it does not need to reach the modified region precisely. In other words, grinding should be done up to a position close to the modified region so that the semiconductor wafer is broken down into individual semiconductor chips, starting from the modified region. For example, the actual fragmentation of semiconductor chips may be performed by attaching a pickup tape, as described later, and then stretching the pickup tape.

[0195] Additionally, after the backside grinding is complete and prior to picking up the chip, dry polishing may be performed.

[0196] The shape of the individual semiconductor chips may be rectangular or elongated, such as a rectangle. The thickness of the individual semiconductor chips is not particularly limited, but is preferably around 5 to 100 μm, and more preferably 10 to 45 μm. With LDBG, which involves creating a modified region inside the wafer with a laser and fragmenting the wafer using stress during back-side grinding, it becomes easy to achieve a thickness of 50 μm or less, more preferably 10 to 45 μm. The size of the individual semiconductor chips is not particularly limited, but a chip size of 600 mm is preferred. 2Less than, more preferably 400 mm 2 Less than 120 mm, more preferably 120 mm 2 It is less than.

[0197] Step 3 can be carried out as described above, but the protective sheet for semiconductor processing will be peeled off from the individualized semiconductor wafer. Even in this case, damage to the individualized semiconductor wafer can be suppressed, and static charge can be suppressed.

[0198] Although embodiments of the present invention have been described above, the present invention is not limited in any way to the embodiments described above, and may be modified in various ways within the scope of the present invention. [Examples]

[0199] The invention will be described in more detail below using examples, but the present invention is not limited to these examples.

[0200] The measurement and evaluation methods in this embodiment are as follows.

[0201] (Adhesion strength of the adhesive layer when peeled at a 90° angle before and after energy ray curing) The semiconductor processing protective sheets prepared in the examples and comparative examples were cut to a width of 25 mm to prepare test specimens. The adhesive layer of the test specimens was attached to a silicon mirror wafer without a circuit surface using a roller with a mass of 2 kg. After standing for 1 hour, the test specimens were peeled off at a peeling speed of 600 mm / min at a 90° angle to the silicon mirror wafer in accordance with JIS Z 0237, and the adhesive strength (adhesion strength of the adhesive layer peeled at 90° before energy ray curing) was measured.

[0202] Furthermore, the adhesive layer of another test specimen was attached to a silicon mirror wafer using a roller with a mass of 2 kg. Ultraviolet light at an irradiance of 220 mW / cm² was then applied to the adhesive layer of this test specimen from the substrate side of a semiconductor processing protective sheet. 2 , light intensity 380mJ / cm 2After curing the adhesive layer by irradiation under the specified conditions, the test piece was peeled off at a peeling speed of 600 mm / min so that it was at a 90° angle to the silicon mirror wafer, in accordance with JIS Z 0237, and the adhesive strength (adhesion strength of the adhesive layer after energy ray curing when peeled at 90°) was measured.

[0203] (Surface resistivity of the adhesive layer after energy ray curing) The semiconductor processing protective sheets prepared in the examples and comparative examples were cut to a size of 10 cm x 10 cm, and the adhesive layer of the semiconductor processing protective sheets was cured by irradiating it with ultraviolet light. The surface resistivity of the cured adhesive layer was measured using an Advantest surface resistivity meter R8252 under conditions of 23°C, 50% RH, and an applied voltage of 100 V, in accordance with JIS K 7194.

[0204] (Peel band voltage of protective sheets for semiconductor processing) The semiconductor processing protective sheets prepared in the examples and comparative examples were attached to the surface of a silicon wafer. Using a wafer mounter (product name "RAD-2700F / 12", manufactured by Lintec Corporation), the semiconductor processing protective sheets were peeled off the silicon wafer at a peeling speed of 600 mm / min and a temperature of 40°C. While peeling, the voltage was measured at a point 10 mm away from the peeled side of the wafer surface and adhesive layer using a Prostat PFM-711A peeling voltage meter, and the voltage value on the wafer side was defined as the peeling band voltage value. In this example, samples with a peeling band voltage of 500V or less were judged to be good.

[0205] (Crack occurrence rate) A silicon wafer with a diameter of 12 inches and a thickness of 775 μm was coated with the semiconductor processing protective sheets prepared in the examples and comparative examples using a backgrind tape laminator (Lintec Corporation, model name "RAD-3510F / 12"). A laser saw (Disco Corporation, model name "DFL7361") was used to form a grid-like modified region on the wafer. The grid size was 10 mm x 10 mm.

[0206] Next, using a backside grinding machine (Disco Corporation, machine name "DGP8761"), the wafer was ground (including dry polishing) until it reached a thickness of 30 μm, and the wafer was separated into multiple chips.

[0207] After the grinding process, the chips were irradiated with energy rays (ultraviolet light), and dicing tape (Lintec Corporation, Adwill D-175) was applied to the opposite side of the semiconductor processing protective sheet. The semiconductor processing protective sheet was then peeled off. The individual chips were then observed using a digital microscope (product name "VHX-1000", KEYENCE Corporation), and the number of chips with cracks was counted. The chips were then classified according to the following criteria based on the size of the cracks. The crack size (μm) was determined by comparing the length of the crack along the longitudinal direction of the chip (μm) with the length of the crack along the transverse direction of the chip (μm), and the larger value was used. (standard) Large cracks: Cracks with a size exceeding 50 μm Medium cracks: Cracks with a size of 20 μm or more and 50 μm or less. Small cracks: Cracks with a size of less than 20 μm

[0208] Furthermore, the crack occurrence rate (%) was calculated based on the following formula. A crack occurrence rate of 2.0% or less, with 0 large cracks, 10 or fewer medium cracks, and 20 or fewer small cracks was evaluated as "good," while all other cases were evaluated as "poor." Crack occurrence rate (%) = (Number of chips with cracks / Total number of chips) × 100

[0209] (Example 1) (1) Adhesive layer (Preparation of composition for adhesive layer) An acrylic polymer was 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 (2HEA). 2-methacryloyloxyethyl isocyanate (MOI) was reacted with this polymer to add 2-methacryloyloxyethyl isocyanate (MOI) to 80 mol% of the total hydroxyl groups of the acrylic polymer, thereby obtaining an energy-ray curable acrylic resin (Mw: 500,000). To 100 parts by mass of this energy-ray curable acrylic resin, 6 parts by mass of a polyfunctional urethane acrylate (trade name: Shiko UT-4332, manufactured by Mitsubishi Chemical Corporation), 0.375 parts by mass (based on solid content) of an isocyanate-based crosslinking agent (manufactured by Tosoh Corporation, trade name: Coronate L), and 1 part by mass of a photopolymerization initiator consisting of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide were added, and the mixture was diluted with a solvent to prepare a coating solution for an adhesive layer composition.

[0210] (Formation of the adhesive layer) A release sheet with an adhesive layer was prepared by applying a solution of the above adhesive composition to the release-treated surface of a release sheet (Lintec Corporation, product name "SP-PET381031", polyethylene terephthalate (PET) film treated with silicone release agent, thickness: 38 μm) and drying it, thereby producing a release sheet with an adhesive layer having a thickness of 20 μm.

[0211] (2) Preparation of substrate with antistatic layer As a substrate, a 50 μm thick primer-coated PET film (manufactured by Toyobo Co., Ltd., product name "PET50A-4100") was prepared, with a primer layer (first primer layer) on one side. The Young's modulus of this PET film was 2500 MPa.

[0212] A polythiophene-based conductive polymer (Denatron P-400MP, manufactured by Nagase Chemtec Corporation) was applied to the surface of the PET film opposite to the surface where the first primer layer was provided, and dried to form an antistatic layer with a thickness of 120 nm on the PET film.

[0213] (3)Buffer layer (Synthesis of urethane acrylate oligomer (UA-1)) A terminal isocyanate urethane prepolymer obtained by reacting a polyester diol with isophorone diisocyanate was reacted with 2-hydroxyethyl acrylate to obtain a bifunctional urethane acrylate oligomer (UA-1) with a weight-average molecular weight (Mw) of 5000.

[0214] (Preparation of buffer layer forming composition) A buffer layer-forming composition was prepared by blending 40 parts by mass of the urethane acrylate oligomer (UA-1) synthesized above, 40 parts by mass of isobornyl acrylate (IBXA), and 20 parts by mass of phenylhydroxypropyl acrylate (HPPA) as energy ray polymerizable compounds, and further blending 2.0 parts by mass of 1-hydroxycyclohexyl phenyl ketone (manufactured by IGM Resins, product name "OMNIRAD184") as a photopolymerization initiator, and 0.2 parts by mass of a phthalocyanine pigment.

[0215] (Formation of a buffer layer) The above-mentioned buffer layer-forming composition was applied to the peeled surface of a release sheet (Lintec Corporation, product name "SP-PET381031", polyethylene terephthalate (PET) film with silicone release treatment, thickness: 38 μm) to form a coating film. Then, the coating film was irradiated with ultraviolet light to partially cure it, forming a buffer layer-forming film with a thickness of 50 μm.

[0216] The above ultraviolet irradiation was performed using a belt conveyor type ultraviolet irradiation device (product name "ECS-401GX", manufactured by iGraphix Co., Ltd.) and a high-pressure mercury lamp (H04-L41, manufactured by iGraphix Co., Ltd.: H04-L41), with a lamp height of 150 mm, lamp output of 3 kW (equivalent output of 120 mW / cm), and an illuminance of 120 mW / cm at a light wavelength of 365 nm. 2 , irradiation amount 100mJ / cm 2 The procedure was performed under the following irradiation conditions.

[0217] The surface of the formed buffer layer-forming film was bonded to the first primer layer of the substrate with the antistatic layer, and ultraviolet light was irradiated again from the release sheet side on the buffer layer-forming film to completely cure the buffer layer-forming film, forming a buffer layer with a thickness of 50 μm.

[0218] The above ultraviolet irradiation was performed using the aforementioned ultraviolet irradiation device and high-pressure mercury lamp, with a lamp height of 150 mm, lamp output of 3 kW (equivalent output of 120 mW / cm), and an illuminance of 160 mW / cm at a light wavelength of 365 nm. 2 , irradiation amount 500mJ / cm 2 The procedure was performed under the following irradiation conditions.

[0219] (4) Fabrication of protective sheets for semiconductor processing A protective sheet for semiconductor processing was fabricated in which the antistatic layer and the adhesive layer of a release sheet with an adhesive layer are formed in that order on one main surface of the substrate, and a buffer layer is formed on the other main surface of the substrate, by laminating the adhesive layer of an adhesive sheet onto an antistatic layer.

[0220] (Example 2) A protective sheet for semiconductor processing was obtained using the same method as in Example 1, except that the thickness of the antistatic layer was 150 nm and the thickness of the adhesive layer was 5 μm.

[0221] (Example 3) A protective sheet for semiconductor processing was obtained using the same method as in Example 1, except that the antistatic layer thickness was 80 nm and the adhesive layer thickness was 200 μm.

[0222] (Example 4) A protective sheet for semiconductor processing was obtained by the same method as in Example 1, except that the adhesive layer was formed using the following adhesive layer composition.

[0223] (Preparation of composition for adhesive layer) An acrylic polymer (Mw: 800,000) was obtained by copolymerizing 89 parts by mass of n-butyl acrylate (BA), 8 parts by mass of methyl methacrylate (MMA), and 3 parts by mass of 2-hydroxyethyl acrylate (2HEA).

[0224] To 100 parts by mass of the above-mentioned acrylic polymer, 1 part by mass (solids) of a tolylene diisocyanate-based crosslinking agent (manufactured by Tosoh Corporation, product name "Coronate L"), 2 parts by mass (solids) of an epoxy-based crosslinking agent (1,3-bis(N,N-diglycidylaminomethyl)cyclohexane), 45 parts by mass (solids) of an energy-ray-curable compound (manufactured by Mitsubishi Chemical Corporation, product name "Shiko UV-3210EA"), and 1 part by mass (solids) of a photopolymerization initiator (manufactured by IGM Resins, product name "OMNIRAD184") were mixed and diluted with a solvent to obtain a coating liquid for an adhesive layer composition.

[0225] (Example 5) A protective sheet for semiconductor processing was obtained by the same method as in Example 1, except that an adhesive layer was formed using the following adhesive layer composition, and the thickness of the antistatic layer was 25 nm and the thickness of the adhesive layer was 5 μm.

[0226] (Preparation of composition for adhesive layer) An acrylic polymer was obtained by copolymerizing 75 parts by mass of butyl acrylate (BA), 20 parts by mass of methyl methacrylate (MMA), and 5 parts by mass of 2-hydroxyethyl acrylate (2HEA). 2-methacryloyloxyethyl isocyanate (MOI) was then reacted with this polymer to obtain an energy-ray curable acrylic resin (Mw: 500,000) by adding 2-methacryloyloxyethyl isocyanate (MOI) to 90 mol% of the total hydroxyl groups of the acrylic polymer.

[0227] To 100 parts by mass of this energy-ray curable acrylic resin, 0.375 parts by mass of an isocyanate-based crosslinking agent (manufactured by Tosoh Corporation, trade name: Coronate L) and 1 part by weight of a photopolymerization initiator consisting of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide were added, and the mixture was diluted with a solvent to prepare a coating solution for the adhesive layer composition.

[0228] (Example 6) Low-density polyethylene (LDPE; Sumitomo Chemical Co., Ltd., Sumikasen L705) was extruded using a small T-die extruder to obtain an LDPE film with a thickness of 100 μm. One side of the LDPE film was subjected to corona treatment, and a polythiophene-based conductive polymer (Nagase Chemtec Co., Ltd., Denatron P-400MP) was applied to the corona-treated side and dried to form an antistatic layer with a thickness of 120 nm on the LDPE film, thereby obtaining a substrate with an antistatic layer.

[0229] A protective sheet for semiconductor processing was obtained by the same method as in Example 1, except that the adhesive layer of a release sheet with an adhesive layer was bonded onto the antistatic layer of this substrate.

[0230] (Comparative Example 1) A protective sheet for semiconductor processing was obtained using the same method as in Example 1, except that an antistatic layer was not provided.

[0231] (Comparative Example 2) A protective sheet for semiconductor processing was obtained by the same method as in Example 1, except that an adhesive layer was formed using the following adhesive layer composition and the thickness of the antistatic layer was set to 50 nm.

[0232] (Preparation of composition for adhesive layer) An acrylic polymer was 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 (2HEA). 2-methacryloyloxyethyl isocyanate (MOI) was then reacted with this polymer to add 2-methacryloyloxyethyl isocyanate to 90 mol% of the total hydroxyl groups of the acrylic polymer, thereby obtaining an energy-ray curable acrylic resin (Mw: 500,000).

[0233] To 100 parts by mass of this energy-ray curable acrylic resin, 20 parts by weight of a polyfunctional urethane acrylate (product name: Shiko UT-4332, manufactured by Mitsubishi Chemical Corporation), which is an energy-ray curable compound, 0.375 parts by mass (based on solid content) of an isocyanate-based crosslinking agent (manufactured by Tosoh Corporation, product name: Coronate L), and 1 part by weight of a photopolymerization initiator consisting of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide were added, and the mixture was diluted with a solvent to prepare a coating solution for the adhesive layer composition.

[0234] (Comparative Example 3) A protective sheet for semiconductor processing was obtained by the same method as in Example 1, except that the adhesive layer was formed using the following adhesive layer composition.

[0235] (Preparation of composition for adhesive layer) An acrylic polymer was obtained by copolymerizing 75 parts by mass of butyl acrylate (BA), 20 parts by mass of methyl methacrylate (MMA), and 5 parts by mass of 2-hydroxyethyl acrylate (2HEA). 2-methacryloyloxyethyl isocyanate (MOI) was then reacted with this polymer to add 2-methacryloyloxyethyl isocyanate to 50 mol% of the total hydroxyl groups of the acrylic polymer, thereby obtaining an energy-ray curable acrylic resin (Mw: 500,000).

[0236] To 100 parts by mass of this energy-ray curable acrylic resin, 0.375 parts by mass of an isocyanate-based crosslinking agent (manufactured by Tosoh Corporation, trade name: Coronate L) and 1 part by weight of a photopolymerization initiator consisting of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide were added, and the mixture was diluted with a solvent to prepare a coating solution for the adhesive layer composition.

[0237] [Table 1]

[0238] The above measurements and evaluations were performed on the obtained samples (Examples 1-6 and Comparative Examples 1-3). The adhesion ratio was calculated from the 90° peel adhesion of the adhesive layer before and after energy ray curing. The results are shown in Table 1.

[0239] Table 1 shows that when the 90° peel adhesive strength of the adhesive layer of the semiconductor processing protective sheet is within the range described above, and when the semiconductor processing protective sheet includes an antistatic layer, the voltage generated when the semiconductor processing protective sheet is peeled off is low, and the rate of crack occurrence due to chip shift is also low. [Explanation of Symbols]

[0240] 1…Protective sheet for semiconductor processing 10...Base material 20…Antistatic layer 30…Adhesive layer 40...Buffer layer

Claims

1. It comprises a base material, an antistatic layer, and an energy ray curable adhesive layer, A protective sheet for semiconductor processing, wherein the adhesive strength when the adhesive layer, after energy ray curing, is peeled off from a silicon wafer at a peeling speed of 600 mm / min so that the angle between the adhesive layer and the silicon wafer is 90° is 0.035 N / 25 mm or more and less than 0.15 N / 25 mm.

2. A protective sheet for semiconductor processing according to claim 1, wherein the ratio of the adhesive force when the adhesive layer before energy ray curing is peeled off the silicon wafer at a peeling speed of 600 mm / min so that the angle between the adhesive layer and the silicon wafer is 90° to the adhesive force when the adhesive layer after energy ray curing is peeled off the silicon wafer at a peeling speed of 600 mm / min so that the angle between the adhesive layer and the silicon wafer is 90° is 4% or less.

3. The surface resistivity of the adhesive layer after energy ray curing is 5.1 × 10⁻⁶. 12 Ω / sq. More than 1.0×10 15 A protective sheet for semiconductor processing according to claim 1 or 2, wherein the Ω / sq. is less than or equal to the specified value.

4. The semiconductor processing protective sheet according to any one of claims 1 to 3, further comprising a buffer layer.

5. A step of attaching a semiconductor processing protective sheet according to any one of claims 1 to 4 to the surface of a wafer, A step of grinding a wafer, on which the semiconductor processing protective sheet is attached to the surface, from the back side, A method for manufacturing a semiconductor device, comprising the step of peeling off the semiconductor processing protective sheet from a wafer after backside grinding.

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