Method for manufacturing protective wafers and semiconductor devices for semiconductor processing

Abstract

[Problem] A method for manufacturing a semiconductor processing protective sheet and a semiconductor device using the aforementioned semiconductor processing protective sheet is provided, which suppresses wafer breakage when peeling off the aforementioned semiconductor processing protective sheet even when the wafer becomes thinner after back-side grinding, and sufficiently suppresses static electricity generated on the wafer during processing. [Solution] A protective sheet for semiconductor processing includes: a substrate, an antistatic layer, and an adhesive layer that is heat-curable. When the heat-cured adhesive layer is peeled from a silicon wafer at a peeling speed of 600 mm / min with the forming angle between the adhesive layer and the silicon wafer being 90°, the adhesion is 0.035 N / 25 mm or more but less than 0.15 N / 25 mm.

Description

[Technical Field]

[0001] This invention relates to a protective sheet for semiconductor processing and a method for manufacturing a semiconductor device. In particular, it relates to a protective sheet for semiconductor processing suitable for use in a method of obtaining a thin wafer by performing back-side grinding of a wafer, and a method for manufacturing a semiconductor device using the protective sheet for semiconductor processing. [Previous Technology]

[0002] Most electronic devices are equipped with semiconductor devices that have semiconductor chips mounted on semiconductor wafers formed by individual semiconductor wafers with circuits. With the rapid advancement of miniaturization and multifunctionality in electronic devices, semiconductor chips also need to be miniaturized, reduced in height, and increased in density. In order to achieve miniaturization and reduced height of the chips, after forming circuits on the surface of the semiconductor wafer, the thickness of the chip is adjusted by grinding the back side of the semiconductor wafer.

[0003] During the back grinding of a semiconductor wafer, in order to protect the circuitry on the wafer surface and maintain the semiconductor wafer, a protective sheet called back grinding tape is generally attached to the wafer surface.

[0004] During back-side grinding of a wafer, the back-side grinding tape adheres strongly to the wafer surface and adequately protects the circuitry. After back-side grinding, when peeling the back-side grinding tape off the wafer, it needs to be easy to peel off. Therefore, the adhesive layer of the back-side grinding tape attached to the wafer is usually composed of an energy-line hardening adhesive. During peeling, the adhesive layer is hardened by irradiating energy lines, thereby reducing the adhesive strength and achieving both adhesion during back-side grinding and peelability after back-side grinding.

[0005] Furthermore, it is known that static electricity is generated during wafer processing (e.g., during dicing, back-side grinding, cleaning, and peeling off back-side grinding tape). The generation of static electricity can easily lead to problems such as discharge damage to circuits on the wafer or the monomerized wafer, cut dust generated during grinding, and minute foreign matter present in the environment easily adhering to the wafer or the monomerized wafer.

[0006] Patent Document 1 discloses an antistatic adhesive tape for semiconductor processing, comprising: a substrate film, an antistatic layer, and an adhesive layer. The surface resistivity of the adhesive layer after UV curing is within a predetermined range, and the 90-degree peel adhesion of the adhesive layer after UV curing is within a predetermined range. [Prior Art Document] [Patent Document]

[0007] Patent Document 1: Japanese Patent Application Publication No. 2011-210944. [Summary of the Invention]

[0008] [The problem the invention aims to solve]

[0009] In recent years, in order to achieve high-density mounting of various electronic devices, the miniaturization, height reduction, and high density of semiconductor chips have been further developed. Therefore, in order to make the chips smaller and lower in height, it is necessary to reduce the thickness of the wafer after back-side grinding.

[0010] However, if the thickness of the wafer after back-grinding is reduced, wafer breakage sometimes occurs when the back-grinding tape is peeled off from the wafer. For example, in Patent Document 1, when the thickness of the wafer after back-grinding is 100 μm, wafer breakage does not occur due to the peeling off of the antistatic semiconductor processing adhesive tape. However, if the thickness of the wafer after back-grinding is further reduced, there is a problem that wafer breakage occurs due to the peeling off of the antistatic semiconductor processing adhesive tape.

[0011] In view of the actual situation, the present invention aims to provide a protective sheet for semiconductor processing and a method for manufacturing a semiconductor device using the protective sheet. The protective sheet suppresses wafer breakage during the removal of the protective sheet even when the wafer becomes thinner after back-side grinding, and sufficiently suppresses static electricity generation on the wafer during processing. [Means for solving the problem]

[0012] The present invention is as follows. [1] A protective sheet for semiconductor processing has: a substrate, an antistatic layer, and an adhesive layer that is heat-curable by energy lines. When the heat-cured adhesive layer is peeled from a silicon wafer at a peeling speed of 600 mm / min with the forming angle between the adhesive layer and the silicon wafer being 90°, the adhesion force is 0.035 N / 25 mm or more and less than 0.15 N / 25 mm.

[0013] [2] As described in [1], the adhesive force when the adhesive layer after energy line hardening is peeled from the silicon wafer at a peeling speed of 600 mm / min in a manner with the forming angle between the adhesive layer and the silicon wafer being 90° is less than 4% compared to the adhesive force when the adhesive layer before energy line hardening is peeled from the silicon wafer at a peeling speed of 600 mm / min in a manner with the forming angle between the adhesive layer and the silicon wafer being 90°.

[0014] [3] The protective sheet for semiconductor processing as described in [1] or [2], wherein the surface resistivity of the adhesive layer after the energy line is hardened is 5.1×10¹²Ω / cm² or more and 1.0×10¹⁵Ω / cm² or less.

[0015] [4] A protective sheet for semiconductor processing as described in any one of [1] to [3], wherein the protective sheet for semiconductor processing further has a buffer layer.

[0016] [5] A method for manufacturing a semiconductor device includes the following steps: attaching a semiconductor processing protective sheet as described in any one of [1] to [4] to the surface of a wafer; grinding the wafer with the semiconductor processing protective sheet attached to the surface from the back side; and peeling off the semiconductor processing protective sheet from the back side of the wafer after grinding. [Effects of the Invention]

[0017] According to the present invention, a protective sheet for semiconductor processing and a method for manufacturing a semiconductor device using the protective sheet for semiconductor processing can be provided. The protective sheet for semiconductor processing suppresses wafer breakage when the protective sheet for semiconductor processing is peeled off, even when the wafer becomes thinner after back-side grinding, and sufficiently suppresses static electricity generated during wafer processing.

Implementation Method

[0019] [Form for implementing the invention]

[0020] Hereinafter, the present invention will be described in detail using drawings based on specific embodiments. First, the main terms used in this specification will be explained.

[0021] Wafer unitization refers to dividing a wafer into individual circuits to obtain a chip.

[0022] The “surface” of a wafer refers to the side on which circuits, electrodes, etc. are formed, while the “back side” of a wafer refers to the side on which circuits, etc. are not formed.

[0023] DBG (Dicing Before Grinding) refers to a method of wafer monomerization by grinding after a trench of predetermined depth is formed on the surface side of the wafer. The trench formed on the surface side of the wafer can be formed by methods such as blade dicing, laser dicing, and plasma dicing.

[0024] In addition, LDBG (Laser Dicing Before Grinding) is a variation of DBG, which means a method of setting a modified region inside the wafer by laser and using the stress during wafer back grinding to monolithize the wafer.

[0025] "Chip cluster" refers to a plurality of chips that remain on the semiconductor processing protective film of this embodiment after the wafer is monolithically assembled. These chips, as a whole, form a shape that is the same as the shape of the wafer.

[0026] "(meth)acrylate" is used to indicate both "acrylate" and "methacrylate", and other similar terms are the same.

[0027] "Energy line" refers to ultraviolet rays, electron rays, etc., with ultraviolet rays being preferred.

[0028] Unless otherwise specified, the "weight average molecular weight" is a converted value of polystyrene determined by gel permeation chromatography (GPC). This determination is performed, for example, by connecting a Tosoh-manufactured high-speed GPC apparatus, the "HLC-8120GPC," to high-speed columns "TSK guard column HXL-H," "TSK Gel GMHXL," and "TSK Gel G2000 HXL" (all manufactured by Tosoh), at a column temperature of 40°C and a feed rate of 1.0 mL / min, using a differential refractive index detector.

[0029] (1. Protective sheet for semiconductor processing) The protective sheet 1 for semiconductor processing in this embodiment, as shown in FIG1A, has the following configuration: an antistatic layer 20 and an adhesive layer 30 are sequentially disposed on a main surface 10a of a substrate 10. From the viewpoint of antistatic function, it is preferable that the antistatic layer is close to the peeling interface of the protective sheet for semiconductor processing, that is, close to the surface 30a of the adhesive layer. Therefore, as shown in FIG1A, it is preferable that the antistatic layer 20 is disposed on a main surface 10a of the substrate 10 rather than on the other main surface 10b of the substrate 10. When using the protective sheet 1 for semiconductor processing, the surface 30a of the adhesive layer 30 is temporarily attached to the adherend and then peeled off from the adherend.

[0030] Furthermore, as long as the effects of the present invention can be obtained, the protective sheet for semiconductor processing can have other layers. That is, if the protective sheet for semiconductor processing has a substrate, an antistatic layer and an adhesive layer, for example, other layers can be formed between the substrate and the adhesive layer, or between the substrate and the antistatic layer.

[0031] As another example of a protective sheet for semiconductor processing, as shown in FIG1B, a protective sheet for semiconductor processing having the following configuration can be illustrated: an antistatic layer 20 and an adhesive layer 30 are sequentially disposed on one main surface 10a of the substrate 10, and a buffer layer 40 is disposed on the other main surface 10b of the substrate 10.

[0032] As shown in Figure 1B, the semiconductor processing protective sheet is suitable for use in the back-side grinding of wafers in the so-called Dicing Before Grinding (DBG) process.

[0033] The pre-cutting method involves forming a groove of predetermined depth from the surface of the wafer using a dicing tool, followed by grinding from the back side of the wafer until the grinding surface reaches or is near the groove, thereby isolating the wafer and obtaining a chip. Furthermore, as a variation of DBG, it can also be used in LDBG (Laser Dicing Before Grinding), a method that uses lasers to create modified regions inside the wafer and then grinds the back side of the wafer to isolate the wafer.

[0034] Hereinafter, the protective sheet for semiconductor processing shown in FIG1A will be described.

[0035] As shown in FIG2, by means of the circuit surface of the wafer 100, which is the adhered body, that is, the surface 30a on the surface 100a of the wafer 100 to which the adhesive layer is attached, the semiconductor processing protective sheet 1 of this embodiment protects the surface 100a of the wafer 100 when the back side 100b of the wafer 100 is ground.

[0036] The adhesive layer 30 of the semiconductor processing protective sheet 1 is energy line hardening. Therefore, during back-side grinding, it is attached to the surface 100a of the wafer 100 in the state before energy line hardening, and the surface 100a of the wafer 100 can be fully protected by the high adhesion.

[0037] After back-side grinding is completed, the semiconductor processing protective sheet 1 is peeled off from the surface 100a of the wafer 100. At this time, energy lines are irradiated onto the adhesive layer 30 of the semiconductor processing protective sheet 1 to harden the adhesive layer 30 and reduce its adhesion. In this way, the semiconductor processing protective sheet 1 can be easily peeled off.

[0038] However, during the peeling of the protective sheet for semiconductor processing, pressure is applied to the wafer after back-side grinding. Therefore, if the thickness of the wafer after back-side grinding is reduced, it may be unable to withstand the stress and break. The higher the adhesion of the adhesive layer after the energy lines are hardened, the higher the stress occurs during peeling. Therefore, the protective sheet for semiconductor processing in this embodiment reduces wafer breakage during peeling by setting the adhesion of the adhesive layer after the energy lines are hardened to a predetermined range.

[0039] Here, if the amount of energy-line polymerizable carbon-carbon double bonds in the adhesive layer before curing increases, the curing of the adhesive layer is easier to proceed, and the adhesive force of the cured adhesive layer tends to decrease, which is therefore preferable. However, if the amount of energy-line polymerizable carbon-carbon double bonds in the adhesive layer before curing increases, the crosslinking points in the cured adhesive layer increase, thus making it difficult for charges to move and making it easier to generate static electricity.

[0040] As a result, during the processing of a wafer including the aforementioned back-side grinding, in addition to the static electricity generated by the wafer, there is also static electricity generated from the adhesive layer, making it difficult to mitigate static electricity. Consequently, more foreign matter and other contaminants adhere to the wafer due to static electricity, increasing the risk of wafer breakage during back-side grinding. Therefore, in this embodiment, in addition to the adhesive strength of the hardened adhesive layer, the semiconductor processing protective sheet includes an antistatic layer to mitigate static electricity and reduce the static voltage of the wafer.

[0041] Hereinafter, the constituent elements of the protective sheet for semiconductor processing will be described in detail.

[0042] (2. Substrate) The substrate is not limited as long as it is made of a material that can support the wafer before back-side grinding and can hold the wafer after back-side grinding. For example, various resin films used as substrates for back-side grinding tapes can be cited as examples of substrates. The substrate can be a single layer film formed from a single resin film or a multiple layer film formed by multiple layers of resin films.

[0043] (2.1 Substrate Properties) In this embodiment, a substrate with high rigidity is preferred. High rigidity of the substrate can suppress vibrations during back-side grinding, thereby improving wafer support and retention performance and reducing wafer breakage and cracks. Furthermore, it helps reduce stress during the removal of the semiconductor processing protective film from the wafer, reducing wafer breakage and cracks during removal. Further, the workability of the semiconductor processing protective film when attached to the wafer is also improved. Specifically, a Young's modulus of 1000 MPa or higher at 23°C is preferred, and 1800 MPa or higher is even better. There is no particular upper limit to the Young's modulus, but it is approximately 30,000 MPa. The Young's modulus of the substrate can be controlled by the selection of the resin composition, the addition of plasticizers, and the stretching conditions during resin film manufacturing.

[0044] 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.

[0045] (2.2 Material of Substrate) It is preferable to select a material whose Young's modulus falls within the aforementioned range as the material of the substrate. In this embodiment, examples include polyesters such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, and fully aromatic polyesters, as well as polyimide, polyamide, polycarbonate, polyacetal, modified polyphenylene oxide, polyphenylene sulfide, polyetherketone, and biaxially oriented polypropylene. Among these, it is preferable to select one or more of polyester, polyamide, polyimide, and biaxially oriented polypropylene, with polyester being more preferred, and polyethylene terephthalate being even more preferred.

[0046] Furthermore, without impairing the effects of the present invention, the substrate may also contain plasticizers, lubricants, infrared absorbers, ultraviolet absorbers, fillers, colorants, antistatic agents, antioxidants, catalysts, etc. In addition, the substrate may be transparent or opaque, and may be colored or vapor-deposited as needed.

[0047] Furthermore, in order to improve adhesion to other layers, a bonding treatment such as corona treatment can be applied to at least one of the main surfaces of the substrate. Additionally, the substrate may have a primer layer on at least one of its main surfaces.

[0048] The composition for forming a primer layer is not particularly limited, and examples include, for instance, compositions comprising polyester resins, ethyl carbamate resins, polyester ethyl carbamate resins, acrylic resins, etc. The composition for forming a primer layer may also contain, as needed, crosslinking agents, photopolymerization initiators, antioxidants, softeners (plasticizers), fillers, rust inhibitors, pigments, dyes, etc.

[0049] The thickness of the primer layer is preferably 0.01~10μm, and more preferably 0.03~5μm. Since the primer layer is soft, it has little effect on Young's modulus. Even when a primer layer is present, the Young's modulus of the substrate is substantially the same as that of the resin film.

[0050] (3. Adhesive Layer) The adhesive layer is attached to the circuit surface of the semiconductor wafer until it is peeled off, protecting the circuit surface and supporting the semiconductor wafer. In this embodiment, the adhesive layer is energy line hardening. The adhesive layer can consist of one layer (single layer) or multiple layers (two or more). When the adhesive layer has multiple layers, these multiple layers can be the same or different from each other, and there is no particular limitation on the combination of the layers constituting these multiple layers.

[0051] The thickness of the adhesive layer is not particularly limited, but it is preferably 3 μm or more and 200 μm or less, and even more preferably 5 μm or more and 100 μm or less. By keeping the thickness of the adhesive layer within the above range, wafer cracking and the like can be suppressed.

[0052] In addition, the thickness of the adhesive layer refers to the overall thickness of the adhesive layer. For example, the thickness of an adhesive layer consisting of multiple layers refers to the total thickness of all the layers that make up the adhesive layer.

[0053] In this embodiment, the adhesive layer has the following physical properties.

[0054] (3.1 90° Peel Adhesion of the Adhesive Layer After Power Line Hardening) In this embodiment, the adhesive layer after power line hardening is peeled from the silicon wafer at a 90° angle to the silicon wafer (hereinafter referred to as the 90° peel adhesion of the adhesive layer after power line hardening) to a value of 0.035 N / 25 mm or more but less than 0.15 N / 25 mm. By ensuring that the 90° peel adhesion of the adhesive layer after power line hardening is within the above range, the possibility of process errors caused by tape peeling off at an unexpected time before the predetermined peeling step is suppressed, while the adhesion is sufficiently reduced. Therefore, even if the wafer becomes thinner after backside grinding, the adhesive layer is easily peeled off. Thus, wafer breakage can be effectively suppressed, and paste residue on the wafer can be further reduced.

[0055] The 90% peel adhesion of the adhesive layer after the energy line is hardened is preferably below 0.14N / 25mm, and even better is below 0.13N / 25mm.

[0056] In this embodiment, the 90° peel adhesion of the adhesive layer after energy line hardening is measured according to JIS 0237. The adhesive layer is attached to a silicon wafer, and after the adhesive layer is hardened by energy line hardening, the adhesion when the hardened adhesive layer is peeled off from the silicon wafer at a 90° angle is measured at a peeling speed of 600 nm / min. The specific measurement conditions will be described in the examples below.

[0057] (3.2 90° Peel-off Adhesion Ratio of Adhesive Layer Before and After Energy Line Curing) In this embodiment, the 90° peel-off adhesion ratio of the adhesive layer before and after energy line curing is preferably 4% or less. In other words, the 90° peel-off adhesion ratio of the adhesive layer after energy line curing is preferably 4% or less, relative to the adhesion when the adhesive layer before energy line curing is peeled from the silicon wafer at a formation angle of 90° to the silicon wafer (hereinafter referred to as the 90° peel-off adhesion ratio of the adhesive layer before energy line curing).

[0058] By ensuring that the adhesion ratio is within the above range, the adhesive layer can be fully adsorbed onto the surface of the wafer during back-side grinding to protect the circuit. After back-side grinding, even if the wafer becomes thinner, the adhesive layer becomes easier to peel off and wafer breakage can be suppressed.

[0059] An adhesion ratio of 3% or less is preferred, and 2% or less is even more preferred. On the other hand, there is no particular limitation on the lower limit of the adhesion ratio, which is usually around 0.3%.

[0060] The 90° peel adhesion of the adhesive layer before energy line curing can be determined using the same method as the method for determining the 90° peel adhesion of the adhesive layer after energy line curing, except that the adhesion of the adhesive layer before energy line curing is measured. Specific measurement conditions will be described in the examples below.

[0061] (3.3 Surface Resistivity) In this embodiment, the surface resistivity of the adhesive layer after energy line curing is preferably 5.1 × 10¹² Ω / cm² or more and 1.0 × 10¹⁵ Ω / cm² or less. Furthermore, this surface resistivity refers to the surface resistivity of the adhesive layer on the surface adhered to the object being bonded (surface 30a of the adhesive layer in FIG. 1A).

[0062] The inventors have discovered that the amount of carbon-carbon double bonds in the adhesive layer before curing affects not only the adhesion of the cured adhesive layer but also its electrostatic properties. That is, even though the semiconductor processing protective sheet of this embodiment has an antistatic layer, foreign matter or the like can still adhere to the wafer due to the electrostatic charge on the wafer. Therefore, in such cases, it is preferable to control the surface resistivity of the adhesive layer by controlling the amount of energy-line polymerizable carbon-carbon double bonds in the adhesive layer before curing, and preferably within the range described above.

[0063] By setting the surface resistivity within the aforementioned range, static electricity becomes easier to escape from the semiconductor processing protective sheet, and the wafer with the semiconductor processing protective sheet attached can suppress wafer static electricity during processing. As a result, in steps such as attaching the semiconductor processing protective sheet to the surface of the wafer, grinding the back side of the wafer, peeling off the semiconductor processing protective sheet, and wafer transporting after peeling off the semiconductor processing protective sheet, the adhesion of foreign matter to the wafer can be suppressed. Therefore, wafer damage and cracks caused by the adhesion of foreign matter can be suppressed.

[0064] Furthermore, if the surface resistivity is smaller than the above-mentioned range, for example, it indicates that the adhesive layer is not sufficiently hardened. As a result, if the thickness of the wafer after grinding is thin, wafer breakage may occur when the protective film for semiconductor processing is peeled off. In addition, a portion of the adhesive layer may still adhere to the wafer (paste residue), leading to wafer cracks.

[0065] A surface resistivity of 9.5 × 10¹⁴ Ω / cm² or less is preferred, and 9.0 × 10¹⁴ Ω / cm² or less is even more preferred. On the other hand, a surface resistivity of 5.2 × 10¹² Ω / cm² or more is preferred, and 5.5 × 10¹² Ω / cm² or more is even more preferred.

[0066] In this embodiment, the surface resistivity is measured according to JIS K 7194. That is, it is measured using the same method as specified in JIS K 7194, but the measurement conditions may be different. Specific measurement conditions will be described in the examples below.

[0067] (3.4 Composition of the adhesive layer) The composition of the adhesive layer is not particularly limited if the adhesive layer before curing has adhesiveness sufficient to protect the circuit surface of the wafer, and the adhesiveness of the cured adhesive layer is within the above-mentioned range. In this embodiment, the adhesive layer, as the adhesive component (adhesive resin) exhibiting adhesiveness, is preferably composed of, for example, a composition (adhesive layer composition) including acrylic adhesives, ethyl carbamate adhesives, rubber adhesives, silicone adhesives, etc.

[0068] Furthermore, from the viewpoint that it is easy to achieve the above-mentioned adhesion and adhesion ratio after energy line hardening, the adhesive layer composition contains an energy line hardening adhesive.

[0069] (3.5 Adhesive Layer Composition) As described above, since the adhesive layer is energy-curable, it is formed from a composition having energy-curable properties (adhesive layer composition). Hereinafter, the adhesive layer composition will be described.

[0070] A heat-curing composition different from the adhesive resin can be formulated to give the adhesive layer composition heat-curing properties, but it is preferable that the adhesive resin itself has heat-curing properties. When the adhesive resin itself has heat-curing properties, a heat-polymerizable group is introduced into the adhesive resin, but it is preferable that the heat-polymerizable group is introduced into the main chain or side chain of the adhesive resin.

[0071] Furthermore, when formulating an energy-line curing compound that is different from the adhesive resin, a monomer or oligomer having an energy-line polymerizable group is used as the energy-line curing compound. The oligomer is an oligomer with a weight average molecular weight (Mw) of less than 10,000, for example, ethyl carbamate (meth)acrylate.

[0072] In this embodiment, from the viewpoint of controlling the amount of carbon-carbon double bonds that exhibit energy line polymerization, the amount is preferably 0.1 to 300 parts by mass relative to 100 parts by mass of an adhesive resin that does not exhibit energy line hardening, more preferably 0.5 to 200 parts by mass, and even more preferably 1 to 150 parts by mass.

[0073] Hereinafter, a more detailed description will be given regarding the case where the adhesive layer composition contains an energy-curing adhesive resin that is an energy-curing acrylic compound (hereinafter also referred to as "acrylic polymer (A)").

[0074] (3.5.1 Acrylic polymer (A)) The acrylic polymer (A) is an acrylate polymer that incorporates a polymerizable energy line group and has constituent units derived from (meth)acrylates. Preferably, the polymerizable energy line group is incorporated into the side chain of the acrylic polymer.

[0075] An acrylic polymer (A) is preferably a reactant in which an acrylic copolymer (A0) having a constituent unit derived from an alkyl methacrylate (a1) and a constituent unit derived from a functional monomer (a2) reacts with a polymeric compound (Xa) having a polymeric group with an energy line polymerizability group.

[0076] As an alkyl methacrylate (a1), an alkyl methacrylate having 1 to 18 carbon atoms in the alkyl group is used. Specifically, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, n-pentyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, isooctyl methacrylate, n-decyl methacrylate, dodecyl methacrylate, tridecyl methacrylate, myristyl methacrylate, palmitate methacrylate, stearyl methacrylate, etc.

[0077] Among these, alkyl methacrylates (a1) with alkyl groups having 4 to 8 carbon atoms are preferred. Specifically, 2-ethylhexyl methacrylate and n-butyl methacrylate are preferred, with n-butyl methacrylate being more preferred. In addition, one of these can be used alone, or two or more can be used in combination.

[0078] In the acrylic copolymer (A0), from the viewpoint of improving the adhesive layer formed, the content of the constituent units derived from (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).

[0079] For example, in addition to 2-ethylhexyl methacrylate and n-butyl methacrylate mentioned above, alkyl methacrylate (a1) may also contain ethyl methacrylate, methyl methacrylate, etc. By containing these monomers, the adhesive properties of the adhesive layer become easier to adjust to the desired level.

[0080] The functionalized monomer (a2) is a monomer having a functional group such as a hydroxyl group, a carboxyl group, an epoxy group, an amino group, a cyano group, a nitrogen-containing cyclic group, or an alkoxysilyl group. As the functionalized monomer (a2), it is preferable to select one or more of the above-mentioned monomers, such as hydroxyl-containing monomers, carboxyl-containing monomers, and epoxy-containing monomers.

[0081] As hydroxyl-containing monomers, examples include, for instance, hydroxyalkyl esters of (meth)acrylate such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 2-hydroxybutyl acrylate, 3-hydroxybutyl acrylate, and 4-hydroxybutyl acrylate; and unsaturated alcohols such as vinyl alcohol and allyl alcohol.

[0082] As a carboxyl-containing monomer, examples include (meth)acrylic acid, maleic acid, fumaric acid, itaconic acid, etc.

[0083] Examples of epoxy-containing monomers include epoxy-containing (meth)acrylates and non-acrylic epoxy-containing monomers. Examples of epoxy-containing (meth)acrylates include, for example, 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-containing monomers include, for example, glycidyl crotonate and allyl glycidyl ether.

[0084] The functional group-containing monomer (a2) can be used alone or in combination of two or more.

[0085] As a functional group-containing monomer (a2), among the above, a hydroxyl-containing monomer is more preferred, and alkyl hydroxy(meth)acrylate is more preferred, and 2-hydroxyethyl(meth)acrylate is even more preferred.

[0086] As component (a2), by using alkyl hydroxy(meth)acrylate, it is easier to react the acrylic copolymer (A0) with the polymeric compound (Xa).

[0087] In the acrylic copolymer (A0), the content of constituent units derived from functional 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).

[0088] If the content is 1% by mass or more, a certain amount of functional groups that can become reaction sites with the polymerizable compound (Xa) can be ensured. Therefore, by irradiating the adhesive layer with energy beams, the adhesive force after irradiation with energy beams can be reduced. In addition, if the content is 30% by mass or less, a sufficient pot life can be ensured when the solution of the adhesive layer composition is applied to form the adhesive layer.

[0089] The acrylic copolymer (A0) can be a copolymer of (meth)acrylate alkyl ester (a1) and functional monomer (a2), or a copolymer of component (a1), component (a2), and other monomers (a3) ​​other than components (a1) and (a2).

[0090] Other monomers (a3) ​​include, for example, cyclic esters of (meth)acrylate, vinyl acetate, styrene, etc., having a cyclic structure, such as cyclohexyl (meth)acrylate, benzyl (meth)acrylate, isocamphenyl (meth)acrylate, dicyclopentyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenoxyethyl (meth)acrylate, etc. Other monomers (a3) ​​may be used alone or in combination of two or more.

[0091] In the acrylic copolymer (A0), the content of constituent units derived from other monomers (a3) ​​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).

[0092] The polymerizable compound (Xa) is a compound having a polymerizable energy line group and a substituent (hereinafter also referred to as "reactive substituent") that can react with the functional group in the constituent unit of the acrylic copolymer (A0) derived from the component (a2).

[0093] The energy-line polymerizable group can be a group containing a carbon-carbon double bond that is energy-line polymerizable. Examples include (meth)acrylyl, vinyl, etc., with (meth)acrylyl being preferred. Furthermore, the polymerizable compound (Xa) is preferably a compound having 1 to 5 energy-line polymerizable groups per molecule.

[0094] The reactive substituent in the polymerizable compound (Xa) can be appropriately changed according to the functional group of the functionalized monomer (a2). For example, isocyanate group, carboxyl group, epoxy group, etc. can be listed. From the viewpoint of reactivity, isocyanate group is preferred. If the polymerizable compound (Xa) has an isocyanate group, for example, if the functional group of the functionalized monomer (a2) is hydroxyl, it can easily react with acrylic copolymer (A0).

[0095] Specific polymerizable compounds (Xa) include, for example, (meth)acryloxyethyl isocyanate, meth-isopropenyl-α,α-dimethylbenzyl isocyanate, (meth)acrylyl isocyanate, allyl isocyanate, (meth)acrylate glycidyl ester, (meth)acrylic acid, etc. These polymerizable compounds (Xa) can be used alone or in combination of two or more.

[0096] Among these, from the viewpoint of a compound having a suitable isocyanate group and an appropriate distance between the main chain and the energy line polymerizing group, (meth)acrylic oxyethyl isocyanate is preferred as the above-mentioned reactive substituent.

[0097] From the viewpoint of controlling the amount of carbon-carbon double bonds that polymerize at energy lines, the polymerizable compound (Xa) reacts with the functional groups in the acrylic copolymer (A0) from the total amount (100 equivalents) of the functional groups derived from the functional group-containing monomer (a2). It is preferable that the amount of the polymerizable compound (Xa) is 50 to 98 equivalents, and more preferably 55 to 93 equivalents.

[0098] 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. By having such a Mw, suitable adhesive properties can be imparted to the adhesive layer.

[0099] Even if the adhesive resin has energy-curing properties, the adhesive layer composition preferably includes an energy-curing compound other than the adhesive resin. As such an energy-curing compound, a monomer or oligomer having unsaturated groups in its molecule that can be polymerized and cured by energy-line irradiation is preferred.

[0100] Specifically, examples include polyvalent (meth)acrylate monomers such as trimethylolpropane tri(meth)acrylate, neopentyl tert-methacrylate, neopentyl tert-methacrylate, dinepentyl tert-hexa(meth)acrylate, 1,4-butanediol di(meth)acrylate, and 1,6-hexanediol (meth)acrylate, as well as oligomers such as ethyl carbamate (meth)acrylate, polyester (meth)acrylate, polyether (meth)acrylate, and epoxy (meth)acrylate.

[0101] Among these, from the viewpoint that the molecular weight is relatively high and the surface resistivity of the adhesive layer is set within the above range, ethyl carbamate (meth)acrylate oligomer is preferred.

[0102] From the viewpoint of controlling the amount of carbon-carbon double bonds in energy line polymerizability, the content of energy line hardening compound is preferably 0.1 to 300 parts by mass relative to 100 parts by mass of acrylic polymer (A), more preferably 0.5 to 200 parts by mass, and even more preferably 1 to 150 parts by mass.

[0103] (3.5.2 Crosslinking agent) The adhesive layer composition preferably further contains a crosslinking agent. The adhesive layer composition is crosslinked by a crosslinking agent, for example, by heating after coating. The adhesive layer, by crosslinking an acrylic polymer (A) with a crosslinking agent, appropriately forms a coating film and readily performs its function as an adhesive layer.

[0104] As a crosslinking agent, examples include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, aziridine-based crosslinking agents, and chelate-based crosslinking agents. Among these, isocyanate-based crosslinking agents are preferred. Crosslinking agents can be used alone or in combination of two or more.

[0105] Examples of isocyanate-based crosslinking agents include polyisocyanate compounds. Examples of polyisocyanate compounds include aromatic polyisocyanates such as toluene diisocyanate, diphenylmethane diisocyanate, and xylene diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate; and alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate. Furthermore, examples include biuret bodies, isocyanurate bodies, and adducts of these compounds that react with low-molecular-weight active hydrogen compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil.

[0106] Of the above, polyol adducts of aromatic polyisocyanates such as toluene diisocyanate (e.g., trimethylolpropane) are preferred.

[0107] The content of crosslinking agent is preferably 0.01 to 10 parts by weight, and more preferably 0.03 to 7 parts by weight, relative to 100 parts by weight of acrylic polymer (A).

[0108] (3.5.3 Photopolymerization initiator) The adhesive layer composition preferably further contains a photopolymerization initiator. By containing a photopolymerization initiator, the adhesive layer composition is easily cured by energy lines such as ultraviolet light.

[0109] As polymerization initiators, examples include, for instance, acetophenone, 2,2-diethoxydiphenyl ketone, 4-methyldiphenyl ketone, 2,4,6-trimethyldiphenyl ketone, Michler's ketone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzyl diphenyl sulfide, tetramethylthiuram monosulfide, benzyl dimethyl ketal, dibenzyl, diacetyl, 1-chloroanthraquinone, 2-chloroanthraquinone, 2-ethylanthraquinone, 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxycyclohexylphenyl ketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropanol-1,2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1,2-hydroxy-2-methyl-1 Low molecular weight polymerization initiators such as phenyl-propane-1-one, diethylthioxanone, isopropylthioxanone, and 2,4,6-trimethylbenzyldiphenylphosphine oxide, and oligomerized polymerization initiators such as oligomeric {2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone}.

[0110] In addition, two or more photopolymerization initiators can be used alone or in combination. Among the above, 2,2-dimethoxy-1,2-diphenylethane-1-one and 1-hydroxycyclohexylphenyl ketone are preferred.

[0111] The content of photopolymerization initiator is preferably 0.01 to 10 parts by weight, more preferably 0.03 to 7 parts by weight, and even more preferably 0.05 to 5 parts by weight, relative to 100 parts by weight of acrylic polymer (A).

[0112] Without impairing the effects of the present invention, the adhesive layer composition may also contain other additives. Examples of other additives include, for instance, tackifiers, antioxidants, softeners (plasticizers), fillers, rust inhibitors, pigments, dyes, etc. When these additives are present, the content of each additive relative to 100 parts by weight of the acrylic polymer (A) is preferably 0.01 to 6 parts by weight, more preferably 0.02 to 2 parts by weight.

[0113] Furthermore, the adhesive strength 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-line polymerizable groups introduced into the acrylic polymer (A). In addition, the surface resistivity of the adhesive layer can also be adjusted to some extent based on these factors. The preferred ranges for the amount of energy-line polymerizable groups introduced into the acrylic polymer (A) are described above. For example, increasing the amount of energy-line polymerizable groups tends to decrease the adhesive strength after curing and increase the surface resistivity. However, the adhesive strength and surface resistivity of the adhesive layer can also be adjusted based on factors other than those mentioned above. For example, they can be appropriately adjusted based on the amount of crosslinking agent and photopolymerization initiator formulated in the adhesive layer.

[0114] (4. Antistatic Layer) An antistatic layer is disposed between the substrate and the adhesive layer. In the antistatic layer, the antistatic components can suppress the increase of static voltage caused by static electricity during processing of the wafer to which the semiconductor processing protective sheet is attached due to leakage. The composition of the antistatic layer can be antistatic, which is to a degree that the peel static voltage when the adhesive layer is peeled from the wafer, etc., is set to below a predetermined value. In this embodiment, the peel static voltage is preferably set to 500V or less.

[0115] 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 especially preferably 60 nm or more. In addition, the thickness is preferably 300 nm or less, more preferably 250 nm or less, and even more preferably 200 nm or less.

[0116] (4.1 Composition for Antistatic Layer) In this embodiment, the antistatic layer is preferably composed of a composition containing a polymeric compound (composition for antistatic layer). Examples of such compositions include compositions containing a conductive polymeric compound as an antistatic component, and compositions containing both an antistatic component and a polymeric compound. The composition for antistatic layer is preferably a composition containing a conductive polymeric compound.

[0117] Examples of conductive polymer compounds include polythiophene polymers, polypyrrole polymers, and polyaniline polymers. In this embodiment, polythiophene polymers are preferred.

[0118] Examples of polythiophene polymers include polythiophene, poly(3-alkylthiophene), poly(3-thiophene-β-ethanesulfonic acid), and mixtures (including dopants) of polyalkyldioxythiophene and polystyrene sulfonate (PSS). Among these, mixtures of polyalkyldioxythiophene and polystyrene sulfonate are preferred. Examples of the aforementioned polyalkyldioxythiophene include poly(3,4-ethylenedioxythiophene) (PEDOT), polypropylenedioxythiophene, and poly(ethylene / propylene)dioxythiophene, among which poly(3,4-ethylenedioxythiophene) is preferred. That is, among the above, mixtures of poly(3,4-ethylenedioxythiophene) and polystyrene sulfonate (PEDOT doped with PSS) are particularly preferred.

[0119] As a polypyrrole polymer, examples include polypyrrole, poly-3-methylpyrrole, poly-3-octylpyrrole, etc.

[0120] As a polyaniline polymer, examples include polyaniline, polymethylaniline, polymethoxyaniline, etc.

[0121] Examples of compositions comprising an antistatic component and a polymeric compound include compositions comprising an antistatic component and an adhesive resin. Examples of antistatic components include the aforementioned conductive polymeric compound, surfactant, ionic liquid, and conductive inorganic compound.

[0122] As a surfactant, at least one type can be selected from cationic surfactants, anionic surfactants, amphoteric surfactants, and nonionic surfactants. For example, cationic surfactants containing quaternary ammonium salts can be cited. As conductive inorganic compounds, various metals, conductive oxides, etc., can be cited.

[0123] Furthermore, there are no particular limitations on the adhesive resin. Examples include polyester resin, acrylic resin, polyethylene resin, polyurethane resin, melamine resin, epoxy resin, etc. Examples of crosslinking agents include, for example, hydroxymethylated or hydroxyalkylated melamine compounds, urea compounds, glyoxal compounds, acrylamide compounds, epoxy compounds, and isocyanate compounds.

[0124] The content of the antistatic agent in the composition for the antistatic layer can be appropriately determined according to the desired antistatic properties. Specifically, the content of the antistatic agent in the composition for the antistatic layer is preferably 0.1 to 20% by mass.

[0125] (5. Buffer layer) As described above, in the protective sheet for semiconductor processing shown in FIG1B, a buffer layer is formed on the main surface opposite to the main surface of the substrate on which the adhesive layer is formed. Hereinafter, the buffer layer will be described.

[0126] Compared to the substrate, the buffer layer is a soft layer that alleviates the stress during back-side grinding of the wafer and prevents the wafer from cracking and breaking. In addition, when a wafer with a semiconductor processing protective sheet attached is placed on a vacuum stage via the semiconductor processing protective sheet during back-side grinding, it is easy to maintain it properly on the vacuum stage because the buffer layer is a constituent layer of the semiconductor processing protective sheet.

[0127] Such a buffer layer is useful when processing wafers using DBG, especially LDBG.

[0128] 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 alleviate the stress during backside grinding.

[0129] The buffer layer may be a layer formed by a buffer layer composition containing an energy line polymerizable compound, or it may be a polypropylene film, an ethylene-vinyl acetate copolymer film, an ionomer resin film, an ethylene-(meth)acrylate copolymer film, an ethylene-(meth)acrylate copolymer film, an LDPE film, an LLDPE film, etc.

[0130] (5.1 Buffer layer composition) A buffer layer composition comprising an energy line polymerizable compound that can be hardened by irradiation with an energy line.

[0131] Furthermore, the buffer layer composition comprising an energy-line polymerizable compound is more specifically preferably a polymerizable compound comprising ethyl carbamate (meth)acrylate (b1) and an alicyclic or heterocyclic group having 6 to 20 ring atoms (b2). In addition to the components (b1) and (b2) described above, the buffer composition may also contain a polymerizable compound (b3) having a functional group. Furthermore, in addition to the components described above, the buffer composition may also contain a photopolymerization initiator. Further, without impairing the effects of the present invention, the buffer layer composition may contain other additives, resin components, etc.

[0132] Hereinafter, each component contained in the composition for a buffer layer containing an energy line polymerizable compound will be described in detail.

[0133] (5.1.1 Ethyl carbamate (meth)acrylate (b1)) Ethyl carbamate (meth)acrylate (b1) means a compound having at least a (meth)acrylic acid group and an ethyl carbamate bond, which has the property of being polymerized and hardened by energy beam irradiation. Ethyl carbamate (meth)acrylate (b1) is an oligomer or a polymer.

[0134] 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. In addition, the (meth)acrylic acid group (hereinafter also referred to as "functional group") in component (b1) can be monofunctional, difunctional, or trifunctional or more, but monofunctional or difunctional is preferred.

[0135] Component (b1), for example, is obtained by reacting a hydroxyl-containing (meth)acrylate with a terminal isocyanate ethyl carbamate prepolymer obtained by reacting a polyol compound with a polyvalent isocyanate compound. Additionally, component (b1) may be used alone or in combination with two or more other components.

[0136] The polyol compound that becomes the raw material of component (b1) is not particularly limited as long as it has two or more hydroxyl groups. It can be any of the following: difunctional diol, trifunctional triol, or polyol with four or more functions, but difunctional diol is preferred, and polyester diol or polycarbonate diol is even more preferred.

[0137] As a polyvalent isocyanate, examples include aliphatic polyisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, and trimethylhexamethylene diisocyanate; alicyclic diisocyanates such as isophorone diisocyanate, norcamphene diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, dicyclohexylmethane-2,4'-diisocyanate, and ω,ω'-diisocyanate dimethylcyclohexane; and aromatic diisocyanates such as 4,4'-diphenylmethane diisocyanate, toluene diisocyanate, xylyl diisocyanate, toluidine diisocyanate, tetramethylene xylyl diisocyanate, and naphthalene-1,5-diisocyanate.

[0138] Among these, isophorone diisocyanate, hexamethylene diisocyanate, and xylene diisocyanate are preferred.

[0139] Ethyl carbamate (meth)acrylate (b1) can be obtained by reacting a hydroxyl-containing (meth)acrylate with the above-mentioned polyol compound and a polyvalent isocyanate compound to obtain a terminal isocyanate ethyl carbamate prepolymer. As for the hydroxyl-containing (meth)acrylate, there is no particular limitation as long as it is a compound having a hydroxyl group and a (meth)acrylic group in at least one molecule.

[0140] Specific examples of (meth)acrylates having hydroxyl groups include, for example, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 4-hydroxycyclohexyl (meth)acrylate, 5-hydroxycyclooctyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, neopentyl terephthalol tri(meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, etc., and hydroxyalkyl (meth)acrylates; hydroxyl-containing (meth)acrylamides such as N-hydroxymethyl (meth)acrylamide; reactants obtained by reacting (meth)acrylate with diglycidyl esters of vinyl alcohol, vinylphenol, and bisphenol A; etc.

[0141] Of these, hydroxyalkyl methacrylate is preferred, and 2-hydroxyethyl methacrylate is even more preferred.

[0142] 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, relative to the total amount (100% by mass) of the buffer layer composition.

[0143] (5.1.2 Polymerizable compound having an alicyclic or heterocyclic group having 6 to 20 ring atoms (b2)) Component (b2) is a polymerizable compound having an alicyclic or heterocyclic group having 6 to 20 ring atoms. More preferably, it is a compound having at least one (meth)acrylic group, and even more preferably, it is a compound having one (meth)acrylic group. By using component (b2), the film-forming properties of the obtained buffer layer composition can be improved.

[0144] Specific components (b2) may include, for example, alicyclic (meth)acrylates such as isocamphene methacrylate, dicyclopentenyl (meth)acrylate, dicyclopentyl (meth)acrylate, dicyclopentenoxy (meth)acrylate, cyclohexyl (meth)acrylate, and adamantane (meth)acrylate; heterocyclic (meth)acrylates such as tetrahydrofurfuryl (meth)acrylate and morpholine (meth)acrylate; etc. Furthermore, component (b2) may be used alone or in combination of two or more. Among alicyclic (meth)acrylates, isocamphene methacrylate is preferred, and among heterocyclic (meth)acrylates, tetrahydrofurfuryl (meth)acrylate is preferred.

[0145] 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, relative to the total amount (100% by mass) of the buffer layer composition.

[0146] (5.1.3 Polymerizable compound with functional group (b3)) Component (b3) is a polymerizable compound containing functional groups such as hydroxyl, epoxy, amide, and amino groups. More preferably, it is a compound having at least one (meth)acrylic acid group, and even more preferably, it is a compound having one (meth)acrylic acid group.

[0147] Component (b3) and component (b1) have good compatibility, making it easy to adjust the viscosity of the composition for the buffer layer to a suitable range. Furthermore, even when the buffer layer is set to be relatively thin, the buffering performance remains good.

[0148] As a component (b3), examples include hydroxyl-containing (meth)acrylates, epoxy-containing compounds, amide-containing compounds, and amine-containing (meth)acrylates. Among these, hydroxyl-containing (meth)acrylates are preferred.

[0149] Examples of hydroxyl-containing (meth)acrylates include, for example, 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 (meth)acrylate. Among these, hydroxyl-containing (meth)acrylates having an aromatic ring, such as phenylhydroxypropyl (meth)acrylate, are more preferred.

[0150] In addition, component (b3) can be used alone or in combination of two or more. In order to improve the film-forming properties of the buffer layer composition, the content of component (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, relative to the total amount (100% by mass) of the buffer layer composition.

[0151] (5.1.4 Polymer compounds (b4) other than components (b1) to (b3)) To the extent that the effects of the present invention are not impaired, the composition for forming the buffer layer may contain polymer compounds (b4) other than the above-mentioned components (b1) to (b3).

[0152] As a component (b4), examples include, for example, alkyl (meth)acrylates having an alkyl group having 1 to 20 carbon atoms; vinyl compounds such as styrene, hydroxyethyl vinyl ether, hydroxybutyl vinyl ether, N-vinylmethylamine, N-vinylpyrrolidone, and N-vinylcaprolactam; etc. Furthermore, component (b4) may be used alone or in combination of two or more.

[0153] The content of component (b4) in the composition for the buffer layer is preferably 0 to 20% by mass, more preferably 0 to 10% by mass, further preferably 0 to 5% by mass, and especially preferably 0 to 2% by mass.

[0154] (5.1.5 Photopolymerization initiator) In the composition for the buffer layer, from the viewpoint of shortening the polymerization time by energy line irradiation or reducing the amount of energy line irradiation, it is preferable to further contain a photopolymerization initiator when forming the buffer layer.

[0155] Examples of photopolymerization initiators include, for example, benzoin compounds, acetophenone compounds, phosphine oxide compounds, dicene compounds, thioxanone compounds, peroxide compounds, and further, photosensitizers such as amines and quinones. More specifically, examples include, for example, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propane-1-one, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzyl phenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, dibenzyl, diacetylated, 8-chloroanthraquinone, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, etc.

[0156] These photopolymerization initiators can be used alone or in combination of two or more.

[0157] The content of photopolymerization initiator in the composition for buffer layer 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, relative to 100 parts by mass of the energy line polymerizable compound.

[0158] (5.1.6 Other Additives) Other additives may be included in the buffer layer composition without impairing the effects of the present invention. Examples of other additives include, for instance, antistatic agents, antioxidants, softeners (plasticizers), fillers, rust inhibitors, pigments, dyes, etc. When these additives are formulated, the content of each additive in the buffer layer composition is preferably 0.01 to 6 parts by weight, more preferably 0.1 to 3 parts by weight, relative to 100 parts by weight of the total mass of the energy-line polymerizable compound.

[0159] The buffer layer formed from the buffer layer composition containing an energy-line polymerizable compound can be obtained by polymerizing and curing the buffer layer composition by energy-line irradiation. That is, the buffer layer is a cured product of the buffer layer composition.

[0160] Therefore, the buffer layer preferably contains polymer units derived from component (b1) and polymer units derived from component (b2). Furthermore, the buffer layer may contain polymer units derived from component (b3) or polymer units derived from component (b4). The proportion of each polymer unit in the buffer layer is generally consistent with the ratio (feed ratio) of each component in the composition constituting the buffer layer.

[0161] (6. Release Sheet) A release sheet may be attached to the surface of a protective sheet for semiconductor processing. Specifically, the release sheet is attached to the surface of the adhesive layer of the protective sheet for semiconductor processing. By attaching the release sheet to the surface of the adhesive layer, the adhesive layer is protected during transport and storage. The release sheet is attached to a peelable protective sheet for semiconductor processing and is removed by peeling it off before using the protective sheet for semiconductor processing (i.e., before attaching the wafer).

[0162] Release sheets may be exemplified by those that have been treated with a release agent and are used on at least one side, and more specifically, those that have a release agent coated on the surface of the substrate for the release sheet.

[0163] As the substrate for the release sheet, a resin film is preferred. Examples of resins constituting the resin film include, for example, polyester resins such as polyethylene terephthalate resin, polybutylene terephthalate resin, and polyethylene naphthalate resin, polyolefin resins such as polypropylene resin, and polyethylene resin films. Examples of release agents include, for example, rubber-based elastomers such as silicone resins, olefin resins, isoprene resins, and butadiene resins, long-chain alkyl resins, alkyd resins, and fluorinated resins.

[0164] The thickness of the release sheet is not particularly limited, but it is preferably 10~200μm, more preferably 20~150μm.

[0165] (7. Method for manufacturing a protective sheet for semiconductor processing) The method for manufacturing the protective sheet for semiconductor processing according to this embodiment is not particularly limited as long as the method for forming an antistatic layer and an adhesive layer on the main surface of the substrate can be known. Hereinafter, the method for manufacturing the protective sheet for semiconductor processing shown in FIG1A will be described.

[0166] First, as a composition for forming an antistatic layer, for example, a composition for an antistatic layer containing the above-mentioned components is prepared, or a composition for an antistatic layer diluted with a solvent or the like is prepared. Similarly, as a composition for an adhesive layer for forming an adhesive layer, for example, a composition for an adhesive layer containing the above-mentioned components is prepared, or a composition for an adhesive layer diluted with a solvent or the like is prepared. Similarly, as a composition for a buffer layer for forming a buffer layer, for example, a composition for a buffer layer containing the above-mentioned components is prepared, or a composition for a buffer layer diluted with a solvent or the like is prepared.

[0167] 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.

[0168] First, the antistatic layer composition is applied to the peel-treated surface of the first release sheet using a known method such as spin coating, spray coating, bar coating, knife coating, roller coating, blade coating, mold coating, gravure coating, etc., and then heated and dried to form an antistatic layer on the first release sheet. Afterwards, the antistatic layer on the first release sheet is bonded to one side of the substrate, and the first release sheet is removed.

[0169] Next, an adhesive layer composition is applied to the peeling surface of the second release sheet using a known method, and then heated and dried to form an adhesive layer on the second release sheet. Afterward, by bonding the adhesive layer on the second release sheet to the antistatic layer on the substrate, a semiconductor processing protective sheet with an antistatic layer and an adhesive layer sequentially formed on one main surface of the substrate can be obtained. Furthermore, the second release sheet can be removed when using the semiconductor processing protective sheet.

[0170] Furthermore, in the case of manufacturing a protective sheet for semiconductor processing as shown in FIG1B, the following steps can be performed.

[0171] A buffer layer composition for the release treatment surface of the third release sheet is coated to form a coating film by a known method, and the coating film is semi-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 side of the substrate, and the buffer layer film is fully cured to form a buffer layer on the substrate.

[0172] In this embodiment, the coating film is preferably cured by irradiation with an energy beam. Furthermore, the curing of the coating film can be performed in a single curing process or in multiple processes.

[0173] In addition, after forming a buffer layer on the substrate, it is preferable to form an antistatic layer and an adhesive layer.

[0174] (8. Method for manufacturing a semiconductor device) The semiconductor processing protective sheet of the present invention is preferably used during the back-side grinding of a wafer to protect the surface of the wafer.

[0175] As a non-limiting example of the use of a protective sheet for semiconductor processing, the manufacturing method of a semiconductor device will be specifically described below.

[0176] A method for manufacturing a semiconductor device, specifically, includes at least the following steps 1 to 3. Step 1: A step of attaching the aforementioned semiconductor processing protective sheet to a wafer. Step 2: A step of grinding the wafer with the semiconductor processing protective sheet attached to its surface from the back side. Step 3: A step of peeling the semiconductor processing protective sheet off the wafer.

[0177] Hereinafter, each step of the above-described method for manufacturing the semiconductor device will be described in detail.

[0178] (Step 1) In step 1, as shown in FIG2, the main surface 30a of the adhesive layer 30 of the semiconductor processing protective sheet 1 of 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 can be adequately protected.

[0179] The semiconductor wafer used in this manufacturing method can be a silicon wafer, or a wafer of gallium arsenide, silicon carbide, lithium tantalate, lithium niobate, gallium nitride, indium phosphide, etc., or a glass wafer. In this embodiment, a silicon wafer is preferred.

[0180] The thickness of a semiconductor wafer before polishing is not particularly limited, but it is usually around 500 to 1000 μm. In addition, semiconductor wafers typically have circuits formed on their surface. The formation of circuits on the wafer surface can be carried out by various conventionally used methods, including etching and lift-off methods.

[0181] A semiconductor wafer with a protective sheet for semiconductor processing attached is placed on a chuck and held in place by adsorption onto the chuck. At this time, the surface side of the semiconductor wafer is disposed on the chuck side and adsorbed.

[0182] (Step 2) After step 1, a back-side-ground wafer can be obtained by grinding the back side of the semiconductor wafer on the grinding chuck. In this embodiment, the thickness of the back-side-ground wafer is not particularly limited, for example, it is 100 μm or less. When the thickness of the back-side-ground wafer is within the above range, miniaturization and height reduction of the semiconductor wafer can be easily achieved.

[0183] (Step 3) Next, the semiconductor processing protective film is peeled off from the semiconductor wafer. This step is performed, for example, by the following method.

[0184] In this embodiment, the adhesive layer of the semiconductor processing protective sheet is formed of an energy line hardening adhesive. Therefore, the adhesive layer can be hardened and shrunk by irradiation with an energy line, reducing the adhesion to the substrate. Next, a pick-up tape is attached to the back side of the back-side of the back-polished semiconductor wafer, and its position and orientation are adjusted in a pick-up manner. At this time, the ring frame disposed on the outer periphery of the wafer is also attached to the pick-up tape, fixing the outer periphery of the pick-up tape to the ring frame. The pick-up tape can be attached to both the wafer and the ring frame simultaneously, or it can be attached at different times. Next, the semiconductor processing protective sheet is peeled off from the semiconductor wafer held on the pick-up tape.

[0185] Since the semiconductor processing protective sheet of this embodiment has the above-mentioned characteristics, even if the thickness of the semiconductor wafer after back-grinding becomes thinner, the semiconductor processing protective sheet can be peeled off from the semiconductor wafer after back-grinding to suppress damage to the semiconductor wafer and suppress static electricity.

[0186] Then, a plurality of semiconductor wafers are picked up from the pick-up tape and fixed onto a substrate or the like to manufacture a semiconductor device.

[0187] In addition, there is no particular limitation on the pickup tape, but for example, it is composed of an adhesive sheet having an adhesive layer provided on one side of the substrate and the substrate.

[0188] Furthermore, the semiconductor processing protective sheet of the present invention is also suitable for use in the manufacturing method of a semiconductor device using a pre-cutting method. In this case, it is preferable to use the semiconductor processing protective sheet shown in FIG. 1B as the semiconductor processing protective sheet.

[0189] In the method for manufacturing a semiconductor device using the pre-cutting method, in addition to steps 1 to 3 above, there may also be a step of forming a trench from the surface side of the semiconductor wafer, or forming a modified region inside the semiconductor wafer from the surface or back side of the semiconductor wafer (step 4).

[0190] When a modified region is formed on a semiconductor wafer, it is preferable to perform step 1 before step 4. On the other hand, when a groove is formed on the surface of a semiconductor wafer by cutting 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 the groove formed in step 4, which will be described later.

[0191] In step 4, a trench is formed from the surface side of the semiconductor wafer. Alternatively, a modified region is formed from the surface or back side of the semiconductor wafer inside the semiconductor wafer.

[0192] The trench formed in this step is a trench with a depth shallower than the thickness of the semiconductor wafer. The trench can be formed by cutting using conventional wafer dicing equipment. Furthermore, in step 3 above, the semiconductor wafer is diced into a plurality of semiconductor wafers along the trench by back-side grinding.

[0193] Furthermore, the modified region is a brittle portion within the semiconductor wafer. Due to the polishing process, the semiconductor wafer becomes thinner, and the force applied during polishing destroys the modified region of the semiconductor wafer, becoming the starting point for monomerization into a semiconductor wafer. That is, the trench and modified region in step 4 are formed along the dividing line where the semiconductor wafer is diced in step 3 to monomerize into a semiconductor wafer.

[0194] The modified region is formed by laser irradiation with the interior of the semiconductor wafer as the focal point, and the modified region is formed inside the semiconductor wafer. The laser irradiation can be performed from the surface side of the semiconductor wafer or from the back side. In addition, in the case where step 4 is performed after step 1 and laser irradiation is performed from the wafer surface, the semiconductor wafer is irradiated with laser via a semiconductor processing protective sheet.

[0195] In the pre-cutting method, the back-side grinding in step 2 is performed in such a way that the semiconductor wafer is thinned to at least the bottom of the trench. Through this back-side grinding, the trench becomes a notch that runs through the wafer, and the semiconductor wafer is divided by the notch, becoming individual semiconductor wafers.

[0196] On the other hand, when a modified region is formed, the polishing surface (back side of the wafer) can be brought to the modified region by polishing, but it is not necessary to reach the modified region precisely. That is, the semiconductor wafer can be destroyed and monomerized into a semiconductor wafer by starting with the modified region, and polishing can be performed until the position is close to the modified region. For example, the actual monomerization of the semiconductor wafer can be carried out by attaching the pick-up tape described later and extending the pick-up tape.

[0197] In addition, after the back side is ground, dry polishing can also be performed before the wafer is picked up.

[0198] The shape of the monomerized semiconductor wafer can be square or rectangular, or other elongated shapes. Furthermore, the thickness of the monomerized semiconductor wafer is not particularly limited, but is preferably around 5 to 100 μm, more preferably 10 to 45 μm. Based on LDBG, which uses lasers to create modified regions inside the wafer and performs monomerization using stress during back-side grinding, the thickness of the monomerized semiconductor wafer is easily less than 50 μm, more preferably 10 to 45 μm. Furthermore, the size of the monomerized semiconductor wafer is not particularly limited, but the wafer size is preferably less than 600 mm², more preferably less than 400 mm², and even more preferably less than 120 mm².

[0199] Step 3 can be performed as described above, but the protective sheet for semiconductor processing is peeled off from the monomerized semiconductor wafer. Even in this case, damage to the monomerized semiconductor wafer can be suppressed, and static electricity can be suppressed.

[0200] The embodiments of the present invention have been described above, but the present invention is not limited to any of the above embodiments, and can be modified in various ways within the scope of the present invention. [Example]

[0201] Hereinafter, the invention will be described in more detail using examples, but the invention is not limited to these examples.

[0202] The measurement and evaluation methods in this embodiment are as follows.

[0203] (90° peel adhesion of adhesive layer before and after energy line curing) Semiconductor processing protective sheets prepared according to the examples and comparative examples were cut into 25mm wide pieces as test sheets. The adhesive layer of the test sheet was attached to a mirror silicon wafer without circuit surfaces using a 2kg roller. After 1 hour, the test sheet was peeled off at a peeling speed of 600mm / min according to JIS Z 0237, with the mirror silicon wafer at a 90° angle, and the adhesion (90° peel adhesion of adhesive layer before energy line curing) was measured.

[0204] In addition, the adhesive layer of another test piece was attached to the mirror silicon wafer using a 2 kg roller. The adhesive layer of this test piece was irradiated with ultraviolet light from the substrate side of the semiconductor processing protective film under conditions of 20 mW / cm² illuminance and 380 mJ / cm² light intensity to harden the adhesive layer. Then, according to JIS Z 0237, the test piece was peeled off at a peeling speed of 600 mm / min with the mirror silicon wafer at a 90° angle, and the adhesion (90° peel adhesion of the adhesive layer after energy line hardening) was measured.

[0205] (Surface resistivity of the adhesive layer after energy line curing) Semiconductor processing protective sheets prepared according to the examples and comparative examples were cut into 10cm × 10cm pieces. The adhesive layer of the semiconductor processing protective sheet was irradiated with ultraviolet light to cure it. The surface resistivity of the cured adhesive layer was measured using an Advantest surface resistivity meter R8252, according to JIS K 7194, at 23°C, 50%RH, and an applied voltage of 100V.

[0206] (Peeling Static Voltage of Protective Sheet for Semiconductor Processing) Protective sheets for semiconductor processing, prepared according to 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), the protective sheets were peeled from the silicon wafer at a peeling speed of 600 mm / min and a temperature of 40°C. Simultaneously, a Prostat PFM-711A peeling electrostatic meter was used to measure the voltage at a distance of 10 mm from the peeling surface of the wafer and the adhesive layer. The voltage value on the wafer side was taken as the peeling static voltage value. In this example, samples with a peeling static voltage of 500V or less were considered good.

[0207] (Crack Occurrence Rate) The semiconductor processing protective sheet manufactured according to the examples and comparative examples was attached to a 12-inch diameter, 775μm thick silicon wafer using a back-side polishing tape laminator (Lintec Corporation, device name "RAD-3510F / 12"). A lattice-shaped modified region was formed on the wafer using a laser saw (DISCO Corporation, device name "DFL7361"). The lattice size was 10mm × 10mm.

[0208] Next, a back-side polishing apparatus (manufactured by DISCO, apparatus name "DGP8761") is used to polish (including dry polishing) until the thickness becomes 30μm, thus converting the wafer into multiple chips.

[0209] After the polishing step, the wafer is irradiated with an energy beam (ultraviolet light). A cutting tape (Lintec, Adwill D-175) is then applied to the opposite side of the substrate of the semiconductor processing protective film. The protective film is then peeled off. Afterwards, the monomerized wafer is observed using a digital microscope (product name "VHX-1000", KEYENCE). Wafers with cracks are counted, and the size of each crack is classified according to the following criteria. The crack size (μm) is the larger of the length (μm) of the crack along the longitudinal direction of the wafer and the length (μm) of the crack along the transverse direction of the wafer. (Criteria) Large crack: Crack size exceeds 50 μm. Medium crack: Crack size is 20 μm or more but less than 50 μm. Small crack: Crack size is less than 20 μm.

[0210] Furthermore, the crack incidence rate (%) is calculated based on the following formula. A crack incidence rate of 2.0% or less, 0 large cracks, 10 or less medium cracks, and 20 or less small cracks are rated as "Good," while other conditions are rated as "Poor." Crack incidence rate (%) = (Number of wafers with cracks / Total number of wafers) × 100

[0211] (Example 1) (1) Adhesive layer (Preparation of composition for adhesive layer) An acrylic polymer 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) was reacted with 2-methacryloxyethyl isocyanate (MOI) to obtain an energy-line curable acrylic resin (Mw: 500,000). To 100 parts by weight of this energy-line curable acrylic resin, 6 parts by weight of polyfunctional aminocarbamate acrylate (trade name: Ziguang UT-4332, manufactured by Mitsubishi Chemical Corporation), 0.375 parts by weight of isocyanate crosslinking agent (manufactured by TOSOH Corporation, trade name: CORONATE L) on a solids basis, and 1 part by weight of photopolymerization initiator composed of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide are added. The coating liquid of the adhesive layer composition is prepared by diluting with a solvent.

[0212] (Formation of adhesive layer) On the release-treated surface of the release sheet (manufactured by Lintec Corporation, trade name "SP-PET381031", a polyethylene terephthalate (PET) film with silicone release treatment, thickness: 38μm), a solution of the above adhesive composition is applied and dried to produce a release sheet with an adhesive layer having an adhesive layer thickness of 20μm.

[0213] (2) Preparation of an antistatic layer As a substrate, a PET film with a primer layer (first primer layer) of 50 μm thickness is prepared on one side (manufactured by Toyobo Co., Ltd., trade name "PET50A-4100"). The Young's modulus of this PET film is 2500 MPa.

[0214] On the side opposite to the PET film where the first primer layer is provided, a polythiophene-based conductive polymer (manufactured by Nagase Chemtech Inc., Denatron P-400MP) is coated and dried to form an antistatic layer with a thickness of 120 nm on the PET film.

[0215] (3) Buffer layer (synthesis of ethyl carbamate acrylate oligomer (UA-1)) The terminal isocyanate ethyl carbamate prepolymer obtained by reacting polyester diol with isophorone diisocyanate is reacted with 2-hydroxyethyl acrylate to obtain a 2-functional ethyl carbamate acrylate oligomer (UA-1) with a weight average molecular weight (Mw) of 5000.

[0216] (Preparation of composition for buffer layer formation) As an energy-line polymerizable compound, 40 parts by weight of the synthesized ethyl carbamate acrylate oligomer (UA-1), 40 parts by weight of isoborneol acrylate (IBXA), and 20 parts by weight of phenyl hydroxypropyl acrylate (HPPA) were further prepared, along with 2.0 parts by weight of 1-hydroxycyclohexylphenyl ketone (manufactured by IGM Resins, product name "OMNIRAD184") as a photopolymerization initiator and 0.2 parts by weight of phthalocyanine pigment, to prepare a composition for buffer layer formation.

[0217] (Formation of the buffer layer) The above-mentioned buffer layer forming composition is coated on the release-treated surface of the release sheet (manufactured by Lintec Corporation, trade name "SP-PET381031", a silicone-released polyethylene terephthalate (PET) film, thickness: 38 μm) to form a coated film. Then, the coated film is irradiated with ultraviolet light to semi-harden the coated film, forming a buffer layer forming film with a thickness of 50 μm.

[0218] In addition, the above-mentioned ultraviolet irradiation was carried out using a belt conveyor type ultraviolet irradiation device (product name "ECS-401GX", manufactured by EYE GRAPHICS) and a high-pressure mercury lamp (H04-L41, manufactured by EYE GRAPHICS: H04-L41), under the following conditions: lamp height 150mm, lamp output 3kW (equivalent to output 120mW / cm), illuminance of 120mW / cm2 with light wavelength of 365nm, and irradiation dose of 100mJ / cm2.

[0219] The surface of the formed buffer layer forming film is bonded to the first primer layer of the substrate with the antistatic layer, and ultraviolet light is irradiated again from the release sheet side of the buffer layer forming film to completely harden the buffer layer forming film, forming a buffer layer with a thickness of 50 μm.

[0220] In addition, the above-mentioned ultraviolet irradiation was carried out using the above-mentioned ultraviolet irradiation device and high-pressure mercury lamp, under the following conditions: lamp height 150mm, lamp output 3kW (equivalent to output 120mW / cm), illuminance of 160mW / cm2 with light wavelength of 365nm, and irradiation dose of 500mJ / cm2.

[0221] (4) The semiconductor processing protective sheet is manufactured by bonding an antistatic layer to the adhesive layer of a release sheet with an adhesive layer attached, thereby forming an antistatic layer and an adhesive layer on one side of the substrate and a buffer layer on the other side of the substrate.

[0222] (Example 2) Except that the thickness of the antistatic layer is set to 150 nm and the thickness of the adhesive layer is set to 5 μm, a protective sheet for semiconductor processing is obtained by the same method as in Example 1.

[0223] (Example 3) Except that the thickness of the antistatic layer is set to 80 nm and the thickness of the adhesive layer is set to 200 μm, a protective sheet for semiconductor processing is obtained by the same method as in Example 1.

[0224] (Example 4) Except for using the following adhesive layer composition to form the adhesive layer, a protective sheet for semiconductor processing was obtained by the same method as in Example 1.

[0225] (Preparation of composition for adhesive layer) 89 parts by weight of n-butyl acrylate (BA), 8 parts by weight of methyl methacrylate (MMA) and 3 parts by weight of 2-hydroxyethyl acrylate (2HEA) were copolymerized to obtain an acrylic polymer (Mw: 800,000).

[0226] Relative to 100 parts by weight of the above-mentioned acrylic polymer, 1 part by weight (solids) of toluene diisocyanate crosslinking agent (TOSOH, product name "CORONATE L"), 2 parts by weight (solids) of epoxy crosslinking agent (1,3-bis(N,N-diglycidylaminomethyl)cyclohexane), 45 parts by weight (solids) of energy line curing compound (manufactured by Mitsubishi Chemical Corporation, product name "UV-3210EA") and 1 part by weight (solids) of photopolymerization initiator (manufactured by IGM Resins, product name "OMNIRAD184") were mixed and diluted with a solvent to obtain a coating liquid of the adhesive layer composition.

[0227] (Example 5) Except that the following adhesive layer composition is used to form the adhesive layer, the thickness of the antistatic layer is set to 25 nm, and the thickness of the adhesive layer is set to 5 μm, a protective sheet for semiconductor processing is obtained by the same method as in Example 1.

[0228] (Preparation of the composition for adhesive layer) An acrylic polymer obtained by copolymerizing 75 parts by weight of butyl acrylate (BA), 20 parts by weight of methyl methacrylate (MMA), and 5 parts by weight of 2-hydroxyethyl acrylate (2HEA) by adding 90 moles of hydroxyl groups to the full hydroxyl groups of the acrylic polymer is reacted with 2-methacryloyloxyethyl isocyanate (MOI) to obtain an energy-line curable acrylic resin (Mw: 500,000).

[0229] 100 parts by weight of the energy-curable acrylic resin are mixed with 0.375 parts by weight of an isocyanate crosslinking agent (TOSOH, trade name "CORONATE L") based on solids, and 1 part by weight of a photopolymerization initiator formed from bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide. The mixture is then diluted with a solvent to prepare a coating liquid for the adhesive layer composition.

[0230] (Example 6) Low-density polyethylene (LDPE: manufactured by Sumitomo Chemical Co., Ltd., SUMIKATHENE L705) was extruded using a small T-die extruder to obtain an LDPE film with a thickness of 100 μm. Corona treatment was performed on one side of the LDPE film, and a polythiophene-based conductive polymer (manufactured by Nagase Chemtech Co., Ltd., Denatron P-400MP) was coated on the corona-treated side and dried to form an antistatic layer with a thickness of 120 nm on the LDPE film, thus obtaining a substrate with an antistatic layer.

[0231] Except for attaching a release sheet with an adhesive layer to the antistatic layer of this substrate, a protective sheet for semiconductor processing is obtained by the same method as in Example 1.

[0232] (Comparative Example 1) Except that no antistatic layer was provided, a protective sheet for semiconductor processing was obtained by the same method as in Example 1.

[0233] (Comparative Example 2) Except that the following adhesive layer composition is used to form the adhesive layer and the thickness of the antistatic layer is set to 50 nm, a protective sheet for semiconductor processing is obtained by the same method as in Example 1.

[0234] (Preparation of the composition for adhesive layer) An acrylic polymer obtained by copolymerizing 65 parts by weight of butyl acrylate (BA), 20 parts by weight of methyl methacrylate (MMA), and 15 parts by weight of 2-hydroxyethyl acrylate (2HEA) by adding 90 moles of hydroxyl groups to the full hydroxyl groups of the acrylic polymer is reacted with 2-methacryloyloxyethyl isocyanate (MOI) to obtain an energy-line curable acrylic resin (Mw: 500,000).

[0235] In this energy-line curable acrylic resin, 100 parts by weight of polyfunctional amino ethyl acrylate (trade name: Ziguang UT-4332, manufactured by Mitsubishi Chemical Corporation), 20 parts by weight of energy-line curable compound, 0.375 parts by weight of isocyanate crosslinking agent (TOSOH, trade name "CORONATE L") based on solids, and 1 part by weight of photopolymerization initiator formed by bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide are added, and the mixture is diluted with a solvent to prepare a coating liquid for the adhesive layer composition.

[0236] (Comparative Example 3) Except for using the following adhesive layer composition to form the adhesive layer, a protective sheet for semiconductor processing was obtained by the same method as in Example 1.

[0237] (Preparation of the composition for adhesive layer) An acrylic polymer obtained by copolymerizing 75 parts by weight of butyl acrylate (BA), 20 parts by weight of methyl methacrylate (MMA), and 5 parts by weight of 2-hydroxyethyl acrylate (2HEA) by adding 50 moles of hydroxyl groups to the full hydroxyl groups of the acrylic polymer is reacted with 2-methacryloyloxyethyl isocyanate (MOI) to obtain an energy-line curable acrylic resin (Mw: 500,000).

[0238] 100 parts by weight of the energy-curable acrylic resin are mixed with 0.375 parts by weight of an isocyanate crosslinking agent (TOSOH, trade name "CORONATE L") based on solids, and 1 part by weight of a photopolymerization initiator formed from bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide. The mixture is then diluted with a solvent to prepare a coating liquid for the adhesive layer composition.

[0239] [Table 1] Protective film for semiconductor processing evaluate Adhesive layer Antistatic layer Stripping static voltage (Wafer side) (V) Crack incidence determination 90° adhesion UV front (N / 25mm) 90° adhesion UV after (N / 25mm) Adhesion ratio After UV exposure / UV front (%) Surface resistance (Ω / cm 2 ) thickness (μm) thickness (nm) Example 1 10.8 0.06 0.6 2.1×10 13 20 120 100 good ○ Example 2 5.3 0.05 0.9 6.0×10 12 5 150 50 good ○ Example 3 18.5 0.14 0.8 8.9×10 14 200 80 200 good ○ Example 4 3.3 0.13 3.9 5.6×10 12 20 120 50 good ○ Example 5 6.2 0.22 3.5 9.3×10 14 5 25 450 good ○ Example 6 9.6 0.04 0.4 9.1×10 12 20 120 30 good ○ Comparative Example 1 10.8 0.06 0.6 1.3×10 15 20 0 4300 good × Comparative Example 2 11.2 0.03 0.3 1.1×10 15 20 50 3300 good × Comparative Example 3 13.0 1.83 14.1 7.5×10 11 20 120 40 bad ×

[0240] The obtained samples (Examples 1-6 and Comparative Examples 1-3) were subjected to the above measurements and evaluations. The adhesive force ratio was calculated from the 90% peel adhesion of the adhesive layer before and after energy line curing. The results are shown in Table 1.

[0241] According to Table 1, when the 90% peel adhesion of the adhesive layer of the protective sheet for semiconductor processing is within the above range, and the protective sheet for semiconductor processing includes an antistatic layer, it is confirmed that the static voltage accompanying the peeling of the protective sheet for semiconductor processing is low, and further, the incidence of cracks caused by wafer misalignment is low. [Simplified Explanation of the Diagram]

[0018] FIG1A is a cross-sectional schematic diagram showing an example of the semiconductor processing protective sheet of this embodiment. FIG1B is a cross-sectional schematic diagram showing another example of the semiconductor processing protective sheet of this embodiment. FIG2 is a cross-sectional schematic diagram showing the appearance of the semiconductor processing protective sheet of this embodiment attached to the circuit surface of a wafer.

Claims

1. A protective sheet for semiconductor processing, comprising: a substrate, an antistatic layer, and an adhesive layer that is heat-curable, wherein the adhesive force when the heat-cured adhesive layer is peeled from a silicon wafer at a peeling speed of 600 mm / min with the forming angle between the adhesive layer and the silicon wafer being 90° is 0.035 N / 25 mm or more and less than 0.15 N / 25 mm, wherein the adhesive force when the heat-cured adhesive layer is peeled from the silicon wafer at a peeling speed of 600 mm / min with the forming angle between the adhesive layer and the silicon wafer being 90° is 4% or less compared to the adhesive force when the adhesive layer before heat curing is peeled from the silicon wafer at a peeling speed of 600 mm / min with the forming angle between the adhesive layer and the silicon wafer being 90°.

2. The protective sheet for semiconductor processing as described in claim 1, wherein the surface resistivity of the adhesive layer after energy line curing is 5.1×10¹² Ω / □ or more and 1.0×10¹⁵ Ω / □ or less.

3. The semiconductor processing protective sheet as described in claim 1 or 2, wherein the aforementioned semiconductor processing protective sheet further has a buffer layer.

4. A method for manufacturing a semiconductor device, comprising the following steps: attaching a semiconductor processing protective sheet as described in any one of claims 1 to 3 to the surface of a wafer; grinding the wafer with the semiconductor processing protective sheet attached to the surface from the back side; and peeling off the semiconductor processing protective sheet from the wafer after grinding from the back side.

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