Method for manufacturing protective sheets for semiconductor processing and semiconductor devices

Abstract

Issue: This invention provides a protective sheet for semiconductor processing and a method for manufacturing a semiconductor device using this protective sheet, which effectively suppresses static electricity generated during wafer processing, even when wafers are thinned using methods such as DBG, and suppresses the occurrence of wafer cracks during peeling. Solution: A protective sheet for semiconductor processing comprises: a substrate, an antistatic layer, an adhesive layer with energy line hardening properties, and a buffer layer, wherein the surface resistivity of the adhesive layer after energy line hardening is 5.1 × 10¹² Ω / cm² or more and 1.0 × 10¹⁵ Ω / cm² or less.

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 and a method for manufacturing a semiconductor device using this protective sheet, which is suitable for methods of grinding the back side of a wafer and individually wafer-forming using stress or the like. [Previous Technology]

[0002] With the miniaturization and multifunctionality of various electronic devices, the semiconductor chips mounted on these devices also require miniaturization and thinning. To achieve chip thinning, the thickness is typically adjusted by grinding the back side of the semiconductor wafer. Furthermore, to obtain thinner chips, a process called Dicing Before Grinding (DBG) is sometimes used. This process involves forming trenches of a predetermined depth from the surface of the wafer using a dicing blade, followed by grinding from the back side of the wafer. This grinds the wafer to the trench or its vicinity, allowing for wafer chipping. In DBG, since back-side grinding and wafer chipping can be performed simultaneously, thin chips can be manufactured efficiently.

[0003] Previously, when grinding the back of a semiconductor wafer or manufacturing a chip using DBG, an adhesive tape called a back grinding sheet was usually attached to the wafer surface in order to protect the circuitry on the wafer surface or to hold the semiconductor wafer and semiconductor chip.

[0004] As examples of back-side grinding sheets, Patent Document 1 and Patent Document 2 disclose an adhesive tape, which is an adhesive tape in which a buffer layer is provided on one surface of a substrate with a high Young's modulus and an adhesive layer is provided on the other surface.

[0005] In recent years, as a variation of DBG (Drill-by-Grinding), a method has been proposed that uses a laser to create a modified region inside the wafer and then uses the stress during back-side grinding to individually wafer-size the wafer. Hereinafter, this method will sometimes be referred to as Laser Dicing Before Grinding (LDBG). In LDBG, since the modified region is used as a starting point to cut the wafer in the crystal direction, the occurrence of cracks can be reduced compared to DBG, which uses a dicing blade. As a result, it can help to further reduce the wafer's thickness. Furthermore, compared to DBG, which forms grooves of a predetermined depth on the wafer surface using a dicing blade, since there is no area of ​​the wafer removed by the dicing blade, i.e., the kerf width is extremely small, resulting in excellent wafer yield. [Prior Art Documents] [Patent Documents]

[0006] [Patent Document 1] International Publication No. 2015 / 156389 [Patent Document 2] Japanese Patent Application Publication No. 2015-183008 [Summary of the Invention]

[0007] [Problem to be Solved by the Invention] It is known that static electricity is generated during wafer processing (e.g., during dicing, back-side grinding, cleaning, and stripping of the back-side grinding tape). When static electricity is generated, cutting chips generated during grinding, tiny foreign objects present in the environment, etc., can easily adhere to the wafer or the wafer after being individually assembled.

[0008] For example, during back-side grinding, when chips, foreign matter, etc., adhere to the wafer, the pressure during back-side grinding is concentrated on the adhered foreign matter, and the wafer may be damaged starting from the foreign matter. In particular, when DBG is performed with the goal of wafer thinning, the slight concentration of pressure can easily cause wafer damage. Therefore, it is necessary to suppress the static electricity generated during wafer processing.

[0009] Furthermore, the back-side polishing tape adheres strongly to the wafer surface during back-side polishing to adequately protect circuitry, etc. After back-side polishing, it is required that the back-side polishing tape be easily peeled off from the wafer. Therefore, the adhesive layer of the back-side polishing tape attached to the wafer is usually composed of an energy line hardening adhesive. During peeling, the adhesive layer is irradiated with energy lines to harden it and reduce its adhesion, thereby achieving a balance between adhesion during back-side polishing and peelability after back-side polishing.

[0010] However, when the energy line irradiation does not sufficiently harden the adhesive layer, the adhesive may remain on the wafer during peeling, or the individual wafers may come into contact with each other due to poor peeling, which may cause wafer breakage or damage (hereinafter sometimes referred to as wafer cracks). In particular, in LDBG, due to the small wafer kerf width, even slight peeling defects may cause wafer cracks.

[0011] When the back-side polishing tape described in Patent Document 1 and Patent Document 2 is used in DBG, especially in LDBG, there are problems that the static electricity generated during wafer processing is not sufficiently suppressed, and the occurrence of wafer cracks is not sufficiently suppressed when the back-side polishing tape is peeled off.

[0012] In view of this practical situation, the object of the present invention is to provide a protective sheet for semiconductor processing, and a method for manufacturing a semiconductor device using this protective sheet, wherein even when wafers are thinned by methods such as DBG, static electricity generated during wafer processing is sufficiently suppressed, and the occurrence of wafer cracks during peeling is suppressed. [Means for solving the problem]

[0013] The present invention is as follows. [1] A protective sheet for semiconductor processing, comprising a substrate, an antistatic layer, an adhesive layer with energy line hardening properties, and a buffer layer, wherein the surface resistivity of the adhesive layer after energy line hardening is 5.1×10¹²Ω / cm² or more and 1.0×10¹⁵Ω / cm² or less.

[0014] [2] As described in [1], the adhesive force when peeling the hardened adhesive layer from the silicon wafer at a peeling speed of 600 mm / min and with the angle between the adhesive layer and the silicon wafer being 90° is less than 0.15 N / 25 mm.

[0015] [3] The protective sheet for semiconductor processing as described in [1] or [2], wherein 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 and with the angle between the adhesive layer and the silicon wafer being 90° is 4% or less, relative 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 and with the angle between the adhesive layer and the silicon wafer being 90°.

[0016] [4] The protective sheet for semiconductor processing as described in any one of [1] to [3], wherein the Young's modulus of the substrate is 1000 MPa or more.

[0017] [5] The protective sheet for semiconductor processing as described in any one of [1] to [4] has a configuration in which an adhesive layer is provided on one main surface of a substrate, an antistatic layer is provided between the substrate and the adhesive layer, and a buffer layer is provided on the other main surface of the substrate; or, it has a configuration in which an adhesive layer is provided on one main surface of a substrate, and an antistatic layer and a buffer layer are provided between the substrate and the adhesive layer.

[0018] [6] The protective sheet for semiconductor processing as described in any one of [1] to [5] is used to attach to the surface of the wafer in the step of forming a groove on the surface of the wafer or forming a modified region in the interior, and then grinding the back side of the wafer to form a wafer.

[0019] [7] 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 [6] to the surface of a wafer; forming trenches from the surface side of the wafer, or forming modified regions from the surface or back side of the wafer into the wafer interior; grinding the wafer with the semiconductor processing protective sheet attached to its surface and with trenches or modified regions formed therein from the back side, and wafering it into a plurality of wafers starting from the trenches or modified regions; and peeling the semiconductor processing protective sheet from the wafers that have been wafered. [Effects of the Invention]

[0020] 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, wherein even when the wafer is thinned by DBG or the like, the static electricity generated during wafer processing is sufficiently suppressed, and the occurrence of wafer cracks during peeling is suppressed.

Implementation Method

[0022] Hereinafter, a detailed description will be given using drawings based on the specific features of the present invention. First, the main terms used in this specification will be explained.

[0023] Wafer individualization refers to dividing a wafer into individual circuits to obtain wafers.

[0024] The “surface” of a wafer refers to the surface on which circuits, electrodes, etc. are formed, while the “back side” of a wafer refers to the surface on which circuits, etc. are not formed.

[0025] DBG (Dicing Before Grinding) refers to a method of wafer individualization by grinding after forming trenches of a predetermined depth on the surface side of the wafer. The trenches formed on the surface side of the wafer are formed by methods such as blade cutting, laser cutting, and plasma cutting.

[0026] In addition, LDBG (Laser Dicing Before Grinding) is a variation of DBG, which refers to a method of wafer individualization by setting a modified region inside the wafer with a laser and using stress during wafer back grinding, etc.

[0027] "Chip cluster" refers to a plurality of chips that remain on the semiconductor processing protective sheet in this embodiment after the wafer is individually chipped. These chips are arranged as a whole and have the same shape as the wafer.

[0028] "(meth)acrylate" is a term used to refer to both "acrylate" and "methacrylate", and the same applies to other similar terms.

[0029] "Energy line" refers to ultraviolet light, electron beam, etc., with ultraviolet light being preferred.

[0030] Unless otherwise specified, "weight average molecular weight" refers to the converted value of polystyrene measured by gel permeation chromatography (GPC). Measurements performed using this method, for example, in a high-speed GPC apparatus "HLC-8120GPC" manufactured by TOSOH, were performed using a TSK guard column "HXL-H", "TSK Gel GMHXL", and "TSK Gel G2000 HXL" (all manufactured by TOSOH) connected in sequence, with the column temperature at 40°C and the liquid feed rate at 1.0 mL / min, using a differential refractometer as the detector.

[0031] (1. Protective Sheet for Semiconductor Processing) As shown in FIG1A, the protective sheet 1 for semiconductor processing of this embodiment has an antistatic layer 20 and an adhesive layer 30 sequentially disposed on one main surface 10a of a substrate 10, and a buffer layer 40 disposed on the other main surface 10b of the substrate 10. From the viewpoint of antistatic function, the antistatic layer is preferably located near the peeling interface of the protective sheet for semiconductor processing, that is, preferably near the surface 30a of the adhesive layer. Therefore, as shown in FIG1A, the antistatic layer 20 is preferably disposed on one 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.

[0032] The protective sheet for semiconductor processing is not limited to the configuration shown in FIG1A. For example, as shown in FIG1B, the protective sheet 1 for semiconductor processing may have an antistatic layer 20, an adhesive layer 30, and a buffer layer 40 disposed on a main surface 10a of a substrate 10. The antistatic layer 20 and the buffer layer 40 are disposed between the substrate 10 and the adhesive layer 30. From the viewpoint of ease of manufacturing of the protective sheet for semiconductor processing, as shown in FIG1B, it is preferable to sequentially arrange the antistatic layer 20, the buffer layer 40, and the adhesive layer 30 on the substrate 10. On the other hand, as described above, from the viewpoint of antistatic function, it is preferable to sequentially arrange the buffer layer 40, the antistatic layer 20, and the adhesive layer 30 on the substrate 10.

[0033] Furthermore, as long as the effects of the present invention can be obtained, the protective sheet for semiconductor processing may also have other layers. That is, if the protective sheet for semiconductor processing has a substrate, an antistatic layer, a buffer layer and an adhesive layer, for example, other layers may be formed between the substrate and the buffer layer, or between the substrate and the antistatic layer.

[0034] Hereinafter, we will describe the situation where the protective sheet for semiconductor processing has the structure shown in FIG1A.

[0035] As shown in FIG2, the circuit surface of the wafer 100 is used as the adhered body, that is, the surface 30a of the surface 100a of the wafer 100 is attached with an adhesive layer, thereby protecting the surface 100a of the wafer 100 when the back side 100b of the wafer 100 is ground.

[0036] As described above, during the processing of wafers including back-side grinding, static electricity is generated on the wafers or wafer arrays. If this static electricity cannot be mitigated, foreign matter caused by static electricity will adhere to the wafers, raising concerns about damage to the wafers. Therefore, the semiconductor processing protective sheet of this embodiment includes an antistatic layer, and the surface resistivity of the adhesive layer is within a predetermined range, thereby reducing static voltage and mitigating static electricity.

[0037] Furthermore, the inventors have discovered that the surface resistivity of the adhesive layer reflects the degree of hardening of the adhesive layer after energy line irradiation. When the amount of energy line polymerizable carbon-carbon double bonds in the adhesive layer before hardening is greater, the hardening of the adhesive layer is easier. After hardening, the number of cross-linking points in the adhesive layer increases, making charge movement difficult and causing the surface resistivity to tend to increase. On the other hand, when the amount of energy line polymerizable carbon-carbon double bonds in the adhesive layer before hardening is less, although the surface resistivity tends to decrease, the hardening of the adhesive layer is prone to incomplete due to the reduced starting point of the polymerization reaction. As a result, when the protective sheet for semiconductor processing is peeled off from the wafer, etc., poor peeling of the adhesive layer tends to occur, leading to wafer breakage, cracks, etc. Therefore, in this embodiment, for example, by controlling the amount of carbon-carbon double bonds in the adhesive layer before curing, the composition of the adhesive layer is made such that it is fully cured by energy line irradiation, while the surface resistivity of the adhesive layer is controlled within a predetermined range to alleviate static electricity and suppress damage and cracks to the wafer caused by poor peeling of the adhesive layer.

[0038] The following details the constituent elements of protective sheets for semiconductor processing.

[0039] (2. Substrate) The material of the substrate is not limited as long as it is made of a material that can support the wafer before back-side grinding and hold the wafer after back-side grinding. For example, various resin films used as substrates for back-side grinding belts can be cited as examples of substrates. The substrate can be composed of a single layer film formed by one resin film or a multilayer film formed by stacking multiple resin films.

[0040] (2.1 Substrate Properties) In this embodiment, it is preferable that the substrate has high rigidity. High rigidity of the substrate can suppress vibrations during back-side grinding, thereby improving the support and holding performance of the wafer, reducing wafer breakage and cracking. Furthermore, it can reduce stress when peeling the semiconductor processing protective sheet from the wafer, reducing wafer breakage and cracking during peeling. Moreover, it provides good workability when attaching the semiconductor processing protective sheet to the wafer. Specifically, in a substrate at 23°C, the Young's modulus is preferably 1000 MPa or higher, more preferably 1800 MPa or higher. There is no particular upper limit to the Young's modulus, but it is approximately 30,000 MPa.

[0041] 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.

[0042] (2.2 Material of Substrate) The material of the substrate can be selected from materials that allow the Young's modulus of the substrate to be within the range described above. In this embodiment, examples include: polyethylene terephthalate, polyethylene naphthalate, polyethylene terephthalate, fully aromatic polyesters, polyesters, polyimide, polyamide, polycarbonate, polyacetal, modified polyphenylene ether, polyphenylene sulfide, polyetherketone, biaxially extended polypropylene, etc. Among these, it is preferable to select one or more from polyester, polyamide, polyimide, and biaxially extended polypropylene, more preferably polyester, and even more preferably polyethylene terephthalate.

[0043] Furthermore, without impairing the effects of the present invention, the substrate may contain plasticizers, lubricants, infrared absorbers, ultraviolet absorbers, fillers, colorants, antistatic agents, antioxidants, catalysts, etc. Additionally, the substrate may be transparent or opaque, and may be colored or vapor-deposited as needed.

[0044] Furthermore, in order to improve adhesion to other layers, a bonding treatment such as corona treatment can be performed on at least one main surface of the substrate. Additionally, the substrate may have a primer layer on at least one main surface.

[0045] The composition for forming the primer layer is not particularly limited, but examples include compositions containing polyester resins, ethyl carbamate resins, polyester ethyl carbamate resins, acrylic resins, etc. The composition for forming the primer layer may, as needed, contain crosslinking agents, photopolymerization initiators, antioxidants, softeners (plasticizers), fillers, corrosion inhibitors, pigments, dyes, etc.

[0046] The thickness of the primer layer is preferably 0.01~10 μm, more preferably 0.03~5 μm. Since the primer layer is relatively soft, it has little effect on Young's modulus. In the presence of the primer layer, the Young's modulus of the substrate is substantially the same as that of the resin film.

[0047] For example, the Young's modulus of the substrate can be controlled by the selection of resin composition, the addition of plasticizer, and the stretching conditions during the manufacturing of resin film.

[0048] (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.

[0049] There is no particular limitation on the thickness of the adhesive layer, but it is preferably 3 μm or more and 200 μm or less, and more preferably 5 μm or more and 100 μm or less. By keeping the thickness of the adhesive layer within the above range, wafer cracks and wafer movement can be suppressed.

[0050] It should be noted that the thickness of the adhesive layer refers to the overall thickness of the adhesive layer. For example, the thickness of an adhesive layer composed of multiple layers refers to the total thickness of all the layers that make up the adhesive layer.

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

[0052] (3.1 Surface Resistivity) In this embodiment, the surface resistivity of the adhesive layer after energy line curing is 5.1 × 10¹² Ω / cm² or more and 1.0 × 10¹⁵ Ω / cm² or less. It should be noted that this surface resistivity is the surface resistivity of the adhesive layer on the surface of the adherend (in FIG. 1A, it is the surface 30a of the adhesive layer).

[0053] By maintaining the surface resistivity within the aforementioned range, static electricity can easily escape from the semiconductor processing protective sheet. During processing, the wafer to which the semiconductor processing protective sheet is attached can be kept free from static electricity. Therefore, 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 transporting the wafer or wafer group after peeling off the semiconductor processing protective sheet, the adhesion of foreign matter to the wafer can be suppressed. As a result, damage and cracks to the wafer caused by the adhesion of foreign matter are suppressed.

[0054] Furthermore, by keeping the surface resistivity within the aforementioned range, even when the protective sheet for semiconductor processing is peeled off, the movement of the wafers after individual wafer assembly can be suppressed. Since the contact between wafers is reduced, wafer cracking can be suppressed. As described above, the surface resistivity can be controlled to some extent by the amount of carbon-carbon double bonds in the adhesive layer before curing, which exhibits energy line polymerization. When the adhesive layer is cured, the surface resistivity tends to increase. Therefore, when the surface resistivity is less than the aforementioned range, the adhesive layer is not sufficiently cured. As a result, when peeling off the protective sheet for semiconductor processing, it cannot be properly peeled off from the wafer or chip, and a portion of the adhesive layer remains attached to the wafer or chip (residual adhesive), which may lead to wafer cracking.

[0055] The surface resistivity is preferably 9.5 × 10¹⁴ Ω / cm² or less, more preferably 9.0 × 10¹⁴ Ω / cm² or less. On the other hand, the surface resistivity is preferably 5.2 × 10¹² Ω / cm² or more, more preferably 5.5 × 10¹² Ω / cm² or more.

[0056] In this embodiment, the surface resistivity is measured according to JIS K 7194. That is, the same measurement method as defined in JIS K 7194 is used, but the measurement conditions may be different. Specific measurement conditions will be described in the embodiments described later.

[0057] (3.2 90° Peel Adhesion of the Adhesive Layer After Power Line Curing) In this embodiment, the adhesive layer after power line curing is peeled from the silicon wafer at a 90° angle (hereinafter also referred to as the 90° peel adhesion of the adhesive layer after power line curing) preferably less than 0.15 N / 25 mm. By keeping the 90° peel adhesion of the adhesive layer after power line curing within the above range, the adhesion is sufficiently reduced, making it easier to peel the adhesive layer from the back-side-polished wafer assembly. Therefore, residual adhesive on the wafer, wafer cracks, etc., can be reduced.

[0058] The 90° peel adhesion of the adhesive layer after the energy line has been cured is preferably 0.14 N / 25 mm or less, and more preferably 0.13 N / 25 mm or less. On the other hand, if the 90° peel adhesion of the adhesive layer after the energy line has been cured is too low, the adhesive tape may peel off unexpectedly before the predetermined adhesive tape peeling step, resulting in a process error. Therefore, the 90° peel adhesion of the adhesive layer after the energy line has been cured is preferably 0.035 N / 25 mm or more.

[0059] In this embodiment, the 90° peel adhesion of the adhesive layer after energy line hardening is measured based on JIS Z 0237. The adhesive layer is attached to the silicon wafer, and after hardening the adhesive layer using energy lines, the adhesion is measured when the hardened adhesive layer is peeled off from the silicon wafer at a 90° angle at a peeling speed of 600 mm / min. Specific measurement conditions will be described in the embodiments described later.

[0060] It should be noted that a peel speed of 600 mm / min tends to be faster than the peel speed used in typical adhesion measurements. This condition assumes the peel speed when peeling the adhesive layer from wafers polished by DBG, LDBG, etc. Generally, as the peel speed increases, the adhesion tends to increase.

[0061] (3.3 Ratio of 90° peel adhesion of adhesive layer before and after energy line curing) In this embodiment, the ratio of 90° peel adhesion of adhesive layer before and after energy line curing is preferably 4% or less. That is, the ratio of the 90° peel adhesion of adhesive layer after energy line curing to the adhesion when the adhesive layer before energy line curing is peeled from the silicon wafer (hereinafter referred to as the 90° peel adhesion of adhesive layer before energy line curing) when the angle between the adhesive layer and the silicon wafer is 90° (hereinafter referred to as the adhesion ratio) is preferably 4% or less.

[0062] By keeping the adhesion ratio within the above range, during back-side grinding, while the adhesive layer is fully adhered to the surface of the wafer to protect the circuit, the adhesive layer can be easily peeled off from the wafer after back-side grinding, which can suppress wafer cracks.

[0063] The adhesion ratio is preferably 3% or less, and even more preferably 2% or less. On the other hand, there is no particular limitation on the lower limit of the adhesion ratio, but it is usually around 0.3%.

[0064] In addition to measuring the adhesion of the adhesive layer before energy line curing, the 90° peel adhesion of the adhesive layer before energy line curing can be measured using the same method as the 90° peel adhesion of the adhesive layer after energy line curing. Specific measurement conditions will be described in the embodiments described later.

[0065] (3.4 Composition of the adhesive layer) The composition of the adhesive layer is not particularly limited as long as the adhesive layer has adhesiveness sufficient to protect the circuit surface of the wafer and has the aforementioned surface resistivity. In this embodiment, as an adhesive component (adhesive resin) that can exhibit adhesiveness, the adhesive layer is preferably composed of, for example, a composition (adhesive layer composition) including acrylic adhesives, urethane adhesives, rubber adhesives, silicone adhesives, etc.

[0066] Furthermore, from the viewpoint of easily achieving the above-mentioned adhesion and adhesion ratio after energy line hardening, the composition of the adhesive layer includes an energy line hardening adhesive.

[0067] (3.5 Adhesive layer composition) As described above, since the adhesive layer is energy-curable, it is formed from a composition (adhesive layer composition) that is energy-curable. Hereinafter, the adhesive layer composition will be explained.

[0068] The composition of the adhesive layer can be formulated with an energy-line curing compound of a different kind than that of the adhesive resin to have energy-line curing properties, but the adhesive resin itself preferably has energy-line curing properties. When the adhesive resin itself has energy-line curing properties, an energy-line polymerizable group is introduced into the adhesive resin, preferably by introducing the energy-line polymerizable group into the main chain or side chain of the adhesive resin.

[0069] 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, such as ethyl carbamate (meth)acrylate.

[0070] In this embodiment, from the viewpoint of controlling the amount of energy line polymerizable carbon-carbon double bonds, the amount is preferably 0.1 to 300 parts by mass relative to 100 parts by mass of adhesive resin that does not have energy line hardening properties, more preferably 0.5 to 200 parts by mass, and even more preferably 1 to 150 parts by mass.

[0071] Hereinafter, we will explain in more detail the case where the adhesive layer composition contains an energy-curing adhesive resin that is an energy-curing acrylic polymer (hereinafter referred to as "acrylic polymer (A)").

[0072] (3.5.1 Acrylic polymer (A)) Acrylic polymer (A) is an acrylic polymer that incorporates a line-polymerizable group and has structural units derived from (meth)acrylates. The line-polymerizable group is preferably a side chain of the acrylic polymer.

[0073] The acrylic polymer (A) is preferably a product obtained by reacting an acrylic copolymer (A0) with a polymeric compound (Xa) having a polymeric group with energy line polymerizability, wherein the acrylic copolymer (A0) has structural units derived from alkyl (meth)acrylate (a1) and structural units derived from monomers containing functional groups (a2).

[0074] As an alkyl (meth)acrylate (a1), an alkyl (meth)acrylate with 1 to 18 carbon atoms is used. Specifically, examples include: meth (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, n-tridecyl (meth)acrylate, tetradecyl (meth)acrylate, palmitic (meth)acrylate, stearic acid (meth)acrylate, etc.

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

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

[0077] For example, in alkyl (meth)acrylates (a1), in addition to the above-mentioned 2-ethylhexyl (meth)acrylate and n-butyl (meth)acrylate, ethyl (meth)acrylate, meth (meth)acrylate, etc. may also be contained. By containing these monomers, the adhesive properties of the adhesive layer can be easily adjusted to the desired level.

[0078] The monomer containing a functional group (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 cyclo group, or an alkoxysilyl group. As the monomer containing a functional group (a2), it is preferably selected from one or more monomers containing a hydroxyl group, a carboxyl group, and an epoxy group.

[0079] Examples of monomers containing hydroxyl groups include: hydroxyalkyl methacrylates such as 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 3-hydroxybutyl methacrylate, 4-hydroxybutyl methacrylate, etc.; and unsaturated alcohols such as vinyl alcohol and allyl alcohol.

[0080] As monomers containing carboxyl groups, examples include: (meth)acrylic acid, maleic acid, fumaric acid, itaconic acid, etc.

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

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

[0083] As a monomer containing a functional group (a2), among the above, it is more preferably a monomer containing a hydroxyl group, wherein it is more preferably a hydroxyalkyl (meth) acrylate, and even more preferably a 2-hydroxyethyl (meth) acrylate.

[0084] As component (a2), by using hydroxyalkyl (meth)acrylate, the acrylic copolymer (A0) can be reacted with the polymeric compound (Xa) relatively easily.

[0085] In the acrylic copolymer (A0), the content of structural units derived from the monomer (a2) containing functional groups 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 all structural units (100% by mass) of the acrylic copolymer (A0).

[0086] As long as the content is 1% by mass or more, a certain amount of functional groups can be ensured as reaction sites for the polymerizable compound (Xa). Therefore, since the adhesive layer can be properly hardened by irradiation with energy beams, the adhesion after irradiation with energy beams can be reduced. In addition, as long as the content is 30% by mass or less, a sufficient service life can be ensured when the adhesive layer is formed by coating the adhesive layer with a solution of the composition.

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

[0088] Other monomers (a3) ​​may include, for example, cyclohexyl methacrylate, benzyl methacrylate, isocamphenyl methacrylate, dicyclopentyl methacrylate, dicyclopentenyl methacrylate, dicyclopentenyl oxyethyl methacrylate, etc., which have cyclic structures, as well as vinyl acetate, styrene, etc. Other monomers (a3) ​​may be used alone or in combination of two or more.

[0089] In the acrylic copolymer (A0), the content of structural 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 all structural units (100% by mass) of the acrylic copolymer (A0).

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

[0091] In the energy-line polymerizable group, any group containing a carbon-carbon double bond that is energy-line polymerizable is acceptable. 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.

[0092] The reactive substituent in the polymerizable compound (Xa) can be appropriately changed according to the functional group possessed by the monomer (a2) containing the functional group, but examples such as isocyanate group, carboxyl group, epoxy group, etc. are preferred. From the viewpoint of reactivity, isocyanate is preferred. When the polymerizable compound (Xa) has an isocyanate group, for example, when the functional group of the monomer (a2) containing the functional group is hydroxyl, it can readily react with the acrylic copolymer (A0).

[0093] Specific polymerizable compounds (Xa) include, for example: (meth)acryloxyethyl isocyanate, meth-isopropenyl-α, α-dimethylbenzyl isocyanate, (meth)acryloxyisocyanate, allyl isocyanate, glycidyl (meth)acrylate, (meth)acrylic acid, etc. These polymerizable compounds (Xa) can be used alone or in combination of two or more.

[0094] Among these, from the viewpoint of a compound having a suitable isocyanate group as the above-mentioned reactive substituent and having an appropriate distance between the main chain and the energy line polymerizable group, (meth)acrylic oxyethyl isocyanate is preferred.

[0095] From the viewpoint of controlling the amount of carbon-carbon double bonds in the polymerizability of the energy line, the polymerizability of the compound (Xa) is preferably 50 to 98 equivalents, and more preferably 55 to 93 equivalents, of the total amount of functional groups (100 equivalents) of the monomer (a2) containing functional groups derived from the acrylic copolymer (A0) reacting with the functional groups.

[0096] The weight average molecular weight (Mw) of the acrylic polymer (A) is preferably 300,000 to 1,600,000, more preferably 400,000 to 1,400,000. By having such a Mw, the adhesive layer can be given appropriate adhesion.

[0097] Even when the adhesive resin has energy-curing properties, the composition of the adhesive layer is preferably an energy-curing compound other than the adhesive resin. As such an energy-curing compound, it is preferably a monomer or oligomer having unsaturated groups in the molecule that can be polymerized and cured by energy-line irradiation.

[0098] Specifically, examples include: trimethylolpropane tri(meth)acrylate, neopentyl tert-methacrylate, neopentyl tert-methacrylate, dinepentyl tert-hexa(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol (meth)acrylate and other polyvalent (meth)acrylate monomers, ethyl carbamate (meth)acrylate, polyester (meth)acrylate, polyether (meth)acrylate, epoxy (meth)acrylate and other oligomers.

[0099] Among these, from the viewpoint that the molecular weight is relatively high and the surface resistivity of the adhesive layer is within the above range, ethyl carbamate (meth)acrylate oligomer is preferred.

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

[0101] (3.5.2 Crosslinking agent) The adhesive layer composition preferably further contains a crosslinking agent. For example, by heating after coating the adhesive layer composition, it is crosslinked by the crosslinking agent. By crosslinking the acrylic polymer (A) by the crosslinking agent, the adhesive layer is properly formed into a coating film, which can easily perform its function as an adhesive layer.

[0102] 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.

[0103] As isocyanate-based crosslinking agents, polyisocyanate compounds can be listed. Specific examples of polyisocyanate compounds include: aromatic polyisocyanates such as toluene diisocyanate, diphenylmethane diisocyanate, and xylene diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate; and alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate. Furthermore, biuret forms and isocyanurate forms of these compounds can also be listed, and adducts of reaction products with low-molecular-weight, reactive hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil can be further listed.

[0104] Among the above, it is preferred to be a polyol adduct of an aromatic polyisocyanate such as toluene diisocyanate (e.g., trimethylolpropane).

[0105] 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).

[0106] (3.5.3 Photopolymerization Initiator) The adhesive layer composition preferably further contains a photopolymerization initiator. By containing a photopolymerization initiator in the adhesive layer composition, the adhesive layer composition is more easily subjected to energy line curing by ultraviolet light, etc.

[0107] Examples of photopolymerization initiators include: acetophenone, 2,2-diethoxybenzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, milchnerone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzyl diphenyl sulfide, tetramethylthiuram monosulfide, benzyl dimethyl ketal, bibenzyl, diacetyl, 1-chloroanthraquinone, 2-chloroanthraquinone, 2-ethanthraquinone, 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxycyclohexyl Low molecular weight polymerization initiators for phenyl ketones, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropanone, 1,2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone, 1,2-hydroxy-2-methyl-1-phenyl-propane-1-one, diethylthioxanone, isopropylthioxanone, 2,4,6-trimethylbenzyldiphenylphosphine oxide, etc., and oligomerization polymerization initiators for oligosaccharides such as {2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone}, etc.

[0108] It should be noted that the photopolymerization initiator can be used alone or in combination of two or more. Furthermore, among the above, 2,2-dimethoxy-1,2-diphenylethane-1-one and 1-hydroxycyclohexylphenyl ketone are preferred.

[0109] 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).

[0110] Without impairing the effects of the present invention, the composition for the adhesive layer may contain other additives. Examples of other additives include: tackifiers, antioxidants, softeners (plasticizers), fillers, corrosion inhibitors, pigments, dyes, etc. When these additives are contained, the content of each additive is preferably 0.01 to 6 parts by weight, more preferably 0.02 to 2 parts by weight, relative to 100 parts by weight of the acrylic polymer (A).

[0111] It should be noted that the surface resistivity and adhesion of the adhesive layer can be adjusted by adjusting, for example, the type and amount of monomers constituting the acrylic polymer (A), and the number of energy-line polymerizable groups introduced into the acrylic polymer (A). Among the above, preferred ranges for the number of energy-line polymerizable groups introduced into the acrylic polymer (A) are described. For example, when the number of energy-line polymerizable groups is increased, the adhesion after curing decreases, and the surface resistivity tends to increase. However, the surface resistivity and adhesion of the adhesive layer can also be adjusted by factors other than those mentioned above. For example, they can be appropriately adjusted by adjusting the crosslinking dosage and photopolymerization initiation dosage incorporated into the adhesive layer.

[0112] (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 generated during the processing of the wafer to which the protective sheet for leaking semiconductor processing is attached. The composition of the antistatic layer is sufficient to have antistatic properties that reduce the peeling static voltage to below a predetermined value when the adhesive layer is peeled off from the wafer, etc. In this embodiment, the peeling static voltage is preferably 500 V or less.

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

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

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

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

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

[0118] Examples of polyaniline polymers include: polyaniline, polymethylaniline, polymethoxyaniline, etc.

[0119] Examples of compositions containing antistatic components and polymeric compounds include compositions containing antistatic components and adhesive resins. Examples of antistatic components include the aforementioned conductive polymeric compounds, surfactants, ionic liquids, and conductive inorganic compounds.

[0120] As a surfactant, it is acceptable to select at least one of cationic surfactants, anionic surfactants, amphoteric surfactants, and nonionic surfactants. For example, cationic surfactants containing fourth-order ammonium salts can be cited. As conductive inorganic compounds, examples include various metals and conductive oxides.

[0121] Furthermore, there are no particular limitations on the adhesive resin. Examples include: polyester resin, acrylic resin, polyethylene resin, ethyl carbamate resin, melamine resin, epoxy resin, etc. It can also be used in combination with a crosslinking agent. Examples of crosslinking agents include: hydroxymethylated or alkylated melamine compounds, urea compounds, glyoxal compounds, acrylamide compounds, epoxy compounds, isocyanate compounds, etc.

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

[0123] (5. Buffer Layer) As shown in FIG1A, a buffer layer is formed on the main surface opposite to the main surface of the substrate on which the adhesive layer is formed. The buffer layer 40 is a softer layer than the substrate, which alleviates the stress during back-side grinding of the wafer and prevents the wafer from cracking and breaking. In addition, when the wafer with the semiconductor processing protective sheet attached is back-side ground, it is placed on the vacuum stage through the semiconductor processing protective sheet, and by having the buffer layer as a constituent layer, the semiconductor processing protective sheet can be easily and properly held on the vacuum stage.

[0124] This buffer layer is useful when the wafer is processed by DBG, especially by LDBG.

[0125] 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 keeping the thickness of the buffer layer within the above range, the buffer layer can appropriately alleviate the stress during back-side grinding.

[0126] 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 membrane, an ethylene-vinyl acetate copolymer membrane, an ionomer resin membrane, an ethylene-(meth)acrylate copolymer membrane, an ethylene-(meth)acrylate copolymer membrane, an LDPE membrane, an LLDPE membrane, etc.

[0127] (5.1 Buffer layer composition) A buffer layer composition containing an energy line polymerizable compound that can be hardened by irradiation with an energy line.

[0128] 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 atoms forming a ring (b2). In addition to the components (b1) and (b2) described above, the buffer layer composition may also contain a polymerizable compound having functional groups (b3). Furthermore, in addition to the components described above, the buffer layer 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.

[0129] Hereinafter, we will explain in detail the individual components contained in the composition of the buffer layer containing the energy line polymeric compound.

[0130] (5.1.1 Ethyl carbamate (meth)acrylate (b1)) Ethyl carbamate (meth)acrylate (b1) refers to a compound having at least a (meth)acrylic acid group and an ethyl carbamate bond, and possessing the property of being polymerized and hardened by energy beam irradiation. Ethyl carbamate (meth)acrylate (b1) is an oligomer or polymer.

[0131] 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 referred to as "functional group") in component (b1) can be monofunctional, difunctional, or trifunctional or more, but is preferably monofunctional or difunctional.

[0132] For example, a polyol compound can be reacted with a polyvalent isocyanate compound to obtain a prepolymer with an isocyanate aminocarbamate terminus, and this prepolymer can be reacted with a (meth)acrylate having hydroxyl groups to obtain component (b1). It should be noted that component (b1) can be used alone or in combination of two or more.

[0133] The polyol compound used as a raw material for component (b1) is not particularly limited as long as it has two or more hydroxyl groups. It can be any of a difunctional diol, a trifunctional triol, or a polyol with four or more functions, but is preferably a difunctional diol, and more preferably a polyester diol or a polycarbonate diol.

[0134] Examples of polyisocyanate compounds include: aliphatic polyisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, and trimethylhexamethylene diisocyanate; alicyclic diisocyanates such as isophorone diisocyanate, norborneol diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, dicyclohexylmethane-2,4'-diisocyanate, and ω,ω'-diisocyanate dimethylcyclohexane; and aromatic diisocyanates such as 4,4'-diphenylmethane diisocyanate, toluene diisocyanate, xylene diisocyanate, triazine diisocyanate, tetramethylene xylene diisocyanate, and naphthalene-1,5-diisocyanate.

[0135] Among these, isophorone diisocyanate, hexamethylene diisocyanate, and xylene diisocyanate are preferred.

[0136] An isocyanate-terminated ethyl carbamate prepolymer can be obtained by reacting the above-mentioned polyol compound with a polyvalent isocyanate compound, and this prepolymer can be reacted with a hydroxyl-containing (meth)acrylate to obtain ethyl carbamate (meth)acrylate (b1). As for the hydroxyl-containing (meth)acrylate, it is not particularly limited as long as at least one molecule of the compound has a hydroxyl group and a (meth)acrylic acid group.

[0137] Specific examples of (meth)acrylates having hydroxyl groups include: 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, cyclohexyl 4-hydroxy (meth)acrylate, cyclooctyl 5-hydroxy (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, neopentyl tetramethylol trimethacrylate, polyethylene glycol monomethacrylate, polypropylene glycol monomethacrylate, etc., and hydroxyalkyl (meth)acrylates; N-hydroxymethyl (meth)acrylates containing hydroxyl groups, such as N-hydroxymethyl (meth)acrylate; and reaction products obtained by reacting diglycidyl esters of vinyl alcohol, vinylphenol, or bisphenol A with (meth)acrylate.

[0138] Among these, hydroxyalkyl (meth)acrylate is preferred, and 2-hydroxyethyl (meth)acrylate is more preferred.

[0139] 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.

[0140] (5.1.2 Polymerizable compound having 6 to 20 alicyclic or heterocyclic atoms forming a ring (b2)) Component (b2) is a polymerizable compound having 6 to 20 alicyclic or heterocyclic atoms forming a ring, more preferably a compound having at least one (meth)acrylonitrile group, and even more preferably a compound having one (meth)acrylonitrile group. By using component (b2), the film-forming properties of the obtained buffer layer composition can be improved.

[0141] Specific examples of component (b2) include: isocamphenyl methacrylate, dicyclopentenyl methacrylate, dicyclopentyl methacrylate, dicyclopentenyl methacrylate, cyclohexyl methacrylate, adamantane methacrylate, etc., which contain alicyclic groups; tetrahydrofurfuryl methacrylate, morpholine methacrylate, etc., which contain heterocyclic groups, etc. It should be noted that component (b2) can be used alone or in combination of two or more. Among the alicyclic methacrylates, isocamphenyl methacrylate is preferred, and among the heterocyclic methacrylates, tetrahydrofurfuryl methacrylate is preferred.

[0142] 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.

[0143] (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.

[0144] Component (b3) and component (b1) have good compatibility, making it easy to adjust the viscosity of the buffer layer composition to a suitable range. In addition, good buffering performance is obtained even when the buffer layer is relatively thin.

[0145] Examples of components (b3) include: (meth)acrylates containing hydroxyl groups, compounds containing epoxy groups, compounds containing amide groups, and (meth)acrylates containing amino groups. Among these, (meth)acrylates containing hydroxyl groups are preferred.

[0146] Examples of hydroxyl-containing (meth)acrylates include: 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, phenyl hydroxypropyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, etc. Among these, hydroxyl-containing (meth)acrylates having an aromatic ring, such as phenyl hydroxypropyl (meth)acrylate, are preferred.

[0147] It should be noted that 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.

[0148] (5.1.4 Polymer compounds (b4) other than components (b1) to (b3)) Without impairing the effects of the present invention, the composition for forming the buffer layer may contain polymer compounds (b4) other than the components (b1) to (b3) mentioned above.

[0149] Examples of ingredients (b4) include: 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. It should be noted that ingredients (b4) may be used alone or in combination of two or more.

[0150] The content of component (b4) in the composition for forming 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 particularly preferably 0 to 2% by mass.

[0151] (5.1.5 Photopolymerization initiator) From the viewpoint of shortening the polymerization time by irradiating with energy lines when forming the buffer layer, or from the viewpoint of reducing the amount of energy line irradiation, the composition of the buffer layer is preferably further containing a photopolymerization initiator.

[0152] Examples of photopolymerization initiators include: benzoin compounds, acetophenone compounds, phosphine oxide compounds, dicene compounds, thioxanone compounds, peroxide compounds, and further examples include photosensitizers such as amines and quinones. More specifically, examples include: 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propane-1-one, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzyl phenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, bibenzyl, diacetyl, 8-chloroanthraquinone, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, etc.

[0153] These photopolymerization initiators can be used alone or in combination of two or more.

[0154] Relative to the total amount of the energy line polymerizable compound (100 parts by mass), the content of the photopolymerization initiator in the buffer layer composition is preferably 0.05 to 15 parts by mass, more preferably 0.1 to 10 parts by mass, and even more preferably 0.3 to 5 parts by mass.

[0155] (5.1.6 Other Additives) Without impairing the effects of the present invention, the composition for the buffer layer may contain other additives. Examples of other additives include: antistatic agents, antioxidants, softeners (plasticizers), fillers, corrosion inhibitors, pigments, dyes, etc. When these additives are formulated, the content of each additive in the composition for the buffer layer is preferably 0.01 to 6 parts by mass, more preferably 0.1 to 3 parts by mass, relative to 100 parts by mass of the total amount of the energy-line polymerizable compound.

[0156] The buffer layer formed from a buffer layer composition containing an energy-line polymerizable compound is obtained by polymerizing and hardening the buffer layer composition by irradiating it with energy lines. That is, this buffer layer is a hardened form of the buffer layer composition.

[0157] Therefore, this buffer layer preferably contains polymeric units derived from component (b1) and polymeric units derived from component (b2). Furthermore, this buffer layer may contain polymeric units derived from component (b3) or polymeric units derived from component (b4). The content ratio of each polymeric unit in the buffer layer is generally consistent with the ratio (proportion) of each component constituting the buffer layer composition.

[0158] (6. Release Sheet) A release sheet may be attached to the surface of the 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. When the release sheet is attached to the surface of the adhesive layer and transported and stored, the release sheet protects the adhesive layer. The release sheet is attached to the protective sheet for semiconductor processing in a peelable manner, and is peeled off and removed from the protective sheet for semiconductor processing before use (i.e., before being attached to the wafer).

[0159] The release sheet is a release sheet with at least one side treated for release. Specifically, examples include coating the surface of the substrate for the release sheet with a release agent.

[0160] The substrate for the release sheet is preferably a resin film. Examples of resins constituting this resin film include polyester resin films such as polyethylene terephthalate resin, polybutylene terephthalate resin, and polyethylene naphthalate resin, as well as polyolefin resins such as polypropylene resin and polyethylene resin. Examples of release agents include rubber-based elastomers such as silicone resins, olefin resins, isoprene resins, and butadiene resins, long-chain alkyl resins, alkyd resins, and fluorinated resins.

[0161] The thickness of the release sheet is not particularly limited, but it is preferably 10~200 μm, more preferably 20~150 μm.

[0162] (7. Method for manufacturing a protective sheet for semiconductor processing) The method for manufacturing a protective sheet for semiconductor processing in this embodiment is not particularly limited as long as the method for forming an antistatic layer, a buffer layer, and an adhesive layer on the main surface of the substrate is known, and any known method can be used. The following describes the method for manufacturing the protective sheet for semiconductor processing shown in FIG1A.

[0163] First, as a component for forming an antistatic layer, for example, an antistatic layer component containing the above-mentioned components is used, or the component is prepared by diluting the antistatic layer component with a solvent or the like. Similarly, as a component for forming an adhesive layer, an adhesive layer component containing the above-mentioned components is used, or the component is prepared by diluting the adhesive layer component with a solvent or the like. Similarly, as a component for forming a buffer layer, a buffer layer component containing the above-mentioned components is used, or the component is prepared by diluting the buffer layer component with a solvent or the like.

[0164] 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.

[0165] Then, on the peeling surface of the first release sheet, a buffer layer is formed by applying the composition using a known method such as spin coating, spraying, bar coating, knife coating, roller coating, scraping coating, mold coating, gravure coating, etc., and this coating is semi-cured to form a buffer layer film on the release sheet. The buffer layer film formed on the release sheet is then adhered to one side of the substrate, and the buffer layer film is fully cured to form a buffer layer on the substrate.

[0166] In this embodiment, the coating is preferably cured by irradiation with an energy beam. Furthermore, the curing of the coating can be performed in a single curing process or in multiple stages.

[0167] Subsequently, on the peeling surface of the second release sheet, an antistatic layer composition is applied by a known method, and an antistatic layer is formed on the second release sheet by heating and drying. Afterward, the antistatic layer on the second release sheet is adhered to the side of the substrate where the buffer layer is not formed, and the second release sheet is removed.

[0168] Subsequently, on the peeling surface of the third release sheet, an adhesive layer composition is applied by a known method and dried by heating to form an adhesive layer on the third release sheet. Then, the adhesive layer on the third release sheet is adhered to an antistatic layer on a substrate, thereby obtaining a protective sheet for semiconductor processing, wherein an antistatic layer and an adhesive layer are sequentially formed on one main surface of the substrate, and a buffer layer is formed on the other main surface of the substrate. It should be noted that the third release sheet can be removed when using the protective sheet for semiconductor processing.

[0169] (8. Method for manufacturing a semiconductor device) The protective sheet for semiconductor processing of the present invention is preferably used in a die-gluing process (DBG) to be attached to the surface of a semiconductor wafer during back-side grinding. In particular, the protective sheet for semiconductor processing of the present invention is preferably used in a die-gluing process (LDBG) to obtain a wafer group with a small kerf width when individual semiconductor wafers are wafer-sized.

[0170] As a non-limiting example of the use of protective sheet for semiconductor processing, the method of manufacturing a semiconductor device will be further described in detail below.

[0171] A method for manufacturing a semiconductor device specifically includes at least the following steps 1 to 4. Step 1: attaching the aforementioned semiconductor processing protective sheet to the surface of a semiconductor wafer; Step 2: forming trenches on the surface side of the semiconductor wafer, or forming modified regions from the surface or back side of the semiconductor wafer into the interior of the semiconductor wafer; Step 3: grinding the semiconductor wafer with the semiconductor processing protective sheet attached to its surface and the aforementioned trenches or modified regions formed thereon from the back side, and wafering it into a plurality of wafers starting from the trenches or modified regions; Step 4: peeling the semiconductor processing protective sheet from the wafered semiconductor wafers (i.e., the wafer group).

[0172] Hereinafter, each step of the above-described method for manufacturing the semiconductor device will be described in detail.

[0173] (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 is adequately protected.

[0174] This step can be performed before or after step 2, which will be described later. For example, when a modified region is formed on a semiconductor wafer, it is preferable to perform step 1 before step 2. On the other hand, when trenches are formed on the surface of a semiconductor wafer by cutting or the like, step 1 is performed after step 2. That is, the semiconductor processing protective sheet from step 1 is attached to the surface of the wafer having the trenches formed in step 2, which will be described later.

[0175] 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, or a glass wafer. In this embodiment, the semiconductor wafer is preferably a silicon wafer.

[0176] The thickness of a semiconductor wafer before polishing is not particularly limited, but it is typically around 500 to 1000 μm. Furthermore, circuits are usually formed on the surface of a semiconductor wafer. Forming circuits on the wafer surface includes various methods that can be performed using previously common methods such as etching and stripping.

[0177] (Step 2) In step 2, 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 toward the interior of the semiconductor wafer.

[0178] The trenches formed in this step are shallower than the thickness of the semiconductor wafer. The trenches can be formed by cutting using a previously known wafer dicing apparatus or the like. Furthermore, in step 3 described later, the semiconductor wafer is divided into a plurality of semiconductor wafers along the trenches.

[0179] Furthermore, in a semiconductor wafer, the modified region is a brittle portion. During the polishing step, when the semiconductor wafer is thinned by polishing, the force applied by polishing destroys the modified region of the semiconductor wafer, serving as the starting point for wafer fabrication into semiconductor wafers. That is, in step 3 described later, when the semiconductor wafer is diced and wafers are fabricated into semiconductor wafers, the trenches and modified regions in step 2 are formed along the dicing lines.

[0180] The modified region is formed by irradiation with a laser focused inside the semiconductor wafer. The modified region is formed inside the semiconductor wafer. The laser irradiation can be performed from the surface side or the back side of the semiconductor wafer. It should be noted that in the case of forming the modified region, when step 2 is performed after step 1 and laser irradiation is performed from the wafer surface, the semiconductor wafer is irradiated with laser through a semiconductor processing protective sheet.

[0181] A semiconductor wafer with a protective sheet for semiconductor processing attached and having trenches or modified regions formed is placed on a chuck and held by the chuck. At this time, the surface side of the semiconductor wafer is disposed on the chuck side and is held by the chuck.

[0182] (Step 3) After Step 1 and Step 2, the semiconductor wafer is chipped into a plurality of semiconductor wafers by grinding the back side of the semiconductor wafer on the chuck, thereby obtaining a wafer group.

[0183] In this case, when a trench is formed on a semiconductor wafer, back-side grinding is performed in a manner that thins the semiconductor wafer to at least reach 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 and individually chipped into individual semiconductor wafers.

[0184] On the other hand, when a modified region is formed, the polishing surface (back side of the wafer) can reach the modified region by polishing, but it is not necessary to reach the modified region precisely. That is, as long as the semiconductor wafer is broken and individually assembled into a semiconductor wafer by starting from the modified region, polishing can be done until the position is close to the modified region. For example, the individual assembly of semiconductor wafers can actually be carried out by attaching a pick-up tape as described later and extending the pick-up tape.

[0185] In addition, after the back-side grinding is completed, dry polishing is performed before the wafer is picked up.

[0186] The shape of the individual semiconductor wafer can be square or rectangular, or other elongated shapes. Furthermore, the thickness of the individual 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 employs stress during wafer back-side grinding, the thickness of the individual semiconductor wafer can easily be less than 50 μm, preferably 10 to 45 μm. Furthermore, the size of the individual 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.

[0187] When using the semiconductor processing protective sheet of this embodiment, even for thin and / or small semiconductor wafers, static electricity is prevented during back-side grinding (step 3) and during the peeling of the semiconductor processing protective sheet (step 4), and cracks are prevented in the semiconductor wafer.

[0188] (Step 4) Next, the semiconductor processing protective sheet is peeled off from the individual semiconductor wafers (i.e., multiple semiconductor wafers). For example, this step is performed by the following method.

[0189] In this embodiment, the adhesive layer of the semiconductor processing protective sheet is formed of an energy line hardening adhesive. By irradiating an energy line, the adhesive layer hardens and shrinks, reducing its adhesion to the substrate (the individually wafered semiconductor wafer). Next, a pick-up tape is attached to the back side of the individually wafered semiconductor wafer, positioned and oriented for easy pickup. At this time, a ring frame disposed on the outer periphery of the wafer is also attached to the pick-up tape, fixing the outer periphery of the pick-up tape to the ring frame. The pick-up tape can be attached to the ring frame simultaneously with the wafer, or at different times. Next, the semiconductor processing protective sheet is peeled off from the plurality of semiconductor wafers held on the pick-up tape.

[0190] Because the semiconductor processing protective sheet of this embodiment has the above-mentioned characteristics, even if the peeling speed is faster when peeling the semiconductor processing protective sheet from the semiconductor wafer, static electricity can be suppressed, and no residue will be generated on the semiconductor wafer, etc., and peeling can be performed in a state that suppresses contact between wafers.

[0191] Subsequently, a plurality of semiconductor wafers on the pick-up belt are picked up and fixed on a substrate or the like to manufacture a semiconductor device.

[0192] It should be noted that the pickup tape is not particularly limited, for example, it is constructed by an adhesive sheet having a substrate and an adhesive layer provided on one side of the substrate.

[0193] The above describes the use of the method of individualizing semiconductor wafers by means of DBG or LDBG in relation to the protective sheet for semiconductor processing of the present invention. However, the protective sheet for semiconductor processing of the present invention is preferably used to obtain a chip group with a smaller cut width and thinner wafer group when individualizing semiconductor wafers.

[0194] The embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments and can be modified in various ways within the scope of the present invention. [Example]

[0195] Hereinafter, the present invention will be described in more detail using examples, but the present invention is not limited to these examples.

[0196] The measurement and evaluation methods in this embodiment are as follows.

[0197] (Surface resistivity of the adhesive layer after curing with energy lines) The semiconductor processing protective sheet prepared in the examples and comparative examples was cut into 10 cm × 10 cm pieces, and 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 a surface resistivity meter R8252 made of an ADVANTEST multimeter at 23°C, 50%RH, and an applied voltage of 100 V, according to JIS K 7194.

[0198] (90° peel adhesion of adhesive layer before and after energy line curing) The semiconductor processing protective sheet prepared in the examples and comparative examples was cut into test pieces with a width of 25 mm. The adhesive layer of the test piece was attached to a silicon mirror wafer without a circuit surface in a 2 kg drum. After 1 hour, the test piece was peeled off at a peeling speed of 600 mm / min and at a 90° angle to the silicon mirror wafer according to JIS Z 0237, and the adhesion (90° peel adhesion of adhesive layer before energy line curing) was measured.

[0199] In addition, the adhesive layer of another test piece was attached to a silicon mirror wafer in a 2 kg roller. After the adhesive layer of this test piece was cured by irradiating it with ultraviolet light from the substrate side of the semiconductor processing protective sheet under the conditions of 220 mW / cm2 illuminance and 380 mJ / cm2 light intensity, the test piece was peeled off at a peeling speed of 600 mm / min and at a 90° angle to the silicon mirror wafer according to JIS Z 0237, and the adhesion (90° peel adhesion of the adhesive layer after energy line hardening) was measured.

[0200] (Peeling Static Voltage of Protective Sheet for Semiconductor Processing) The protective sheet for semiconductor processing prepared in the Examples and Comparative Examples was attached to the surface of a silicon wafer. Using a wafer attachment apparatus (product name "RAD-2700F / 12", manufactured by Lintec Corporation), the protective sheet for semiconductor processing was peeled from the silicon wafer at a peeling speed of 600 mm / min and a temperature of 40°C. Simultaneously, a peeling electrostatic tester PFM-711A manufactured by Prostat was used to measure the voltage at a distance of 10 mm from the peeling side of the wafer surface and the adhesive layer. The voltage value on the wafer side was taken as the peeling static voltage. In this example, samples with a peeling static voltage of 500 V or less were judged to be good.

[0201] (Crack Incidence Rate) Using a back-side grinding and bonding machine (Lintec Corporation, device name "RAD-3510F / 12"), the semiconductor processing protective sheet prepared in the examples and comparative examples was attached to a 12-inch diameter, 775 μm thick silicon wafer. A laser saw (DISCO Corporation, device name "DFL7361") was used to form a lattice-shaped modified region on the wafer. It should be noted that the lattice size was 10 mm × 10 mm.

[0202] Next, the wafer is polished using a back-side polishing apparatus (DISCO, device name "DGP8761") until the thickness is 30 μm (including dry polishing), thus splitting the wafer into multiple chips.

[0203] After the polishing step, the wafers are irradiated with an energy beam (ultraviolet light). A dicing tape (Adwill D-175, manufactured by Lintec Corporation) is attached to the opposite side of the attachment surface of the semiconductor processing protective sheet, and then the semiconductor processing protective sheet is peeled off. Afterwards, the individualized wafers are observed using a digital microscope (product name "VHX-1000", manufactured by KEYENCE Corporation), and the number of wafers with cracks is counted. The size of the cracks is classified according to the following criteria. It should be noted that 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

[0204] Furthermore, the crack incidence rate (%) is calculated based on the following formula. A crack incidence rate of 2.0% or less, with 0 large cracks, 10 or less medium cracks, and 20 or less small cracks is rated as "Good," while other situations are rated as "Poor." Crack incidence rate (%) = (Number of wafers with cracks / Total number of wafers) × 100

[0205] (Example 1) (1) Adhesive layer (Preparation of adhesive layer composition) 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) were copolymerized to obtain an acrylic polymer. The polymer was reacted with 2-methacryloyloxyethyl isocyanate (MOI) by adding 80 moles of hydroxyl groups to the total hydroxyl groups of the acrylic polymer to obtain an energy line curable acrylic resin (Mw: 500,000). To 100 parts by weight of this energy-line curable acrylic resin, the following components are added: 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) (based on solid content), and 1 part by weight of photopolymerization initiator formed from bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide; the coating liquid of the adhesive layer composition is prepared by solvent dilution.

[0206] (Formation of adhesive layer) A solution of the above-mentioned adhesive composition is applied to the peeled surface of the release sheet (manufactured by Lintec Corporation, trade name "SP-PET381031", silicone-peeled polyethylene terephthalate (PET) film, thickness: 38 μm) and dried to produce a release sheet with an adhesive layer having a thickness of 20 μm.

[0207] (2)Preparation of a substrate with 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.

[0208] On the side of the PET film opposite to the side where the first primer layer is provided, a polythiophene-based conductive polymer (manufactured by Nagase ChemteX Co., Ltd., Denatron P-400MP) is coated and dried to form an antistatic layer with a thickness of 120 nm on the PET film.

[0209] (3) Buffer layer (synthesis of ethyl carbamate acrylate oligomer (UA-1)) Polyester diol was reacted with isophorone diisocyanate to obtain an isocyanate-terminated ethyl carbamate prepolymer, and this prepolymer was 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.

[0210] (Preparation of composition for buffer layer formation) As an energy-line polymerizable compound, 40 parts by mass of ethyl carbamate acrylate oligomer (UA-1) synthesized in Manufacturing Example 1, 40 parts by mass of isobornyl acrylate (IBXA) and 20 parts by mass of phenyl hydroxypropyl acrylate (HPPA) were formulated, and 2.0 parts by mass of 1-hydroxycyclohexylphenyl ketone (manufactured by IGM Resins, product name "OMNIRAD184") as a photopolymerization initiator and 0.2 parts by mass of phthalocyanine pigment were further formulated to prepare a composition for buffer layer formation.

[0211] (Formation of the buffer layer) The above-described buffer layer forming composition is coated onto the peeled surface of a release sheet (manufactured by Lintec Corporation, trade name "SP-PET381031", a silicone-peeled polyethylene terephthalate (PET) film, thickness: 38 μm) to form a coating film. Then, the coating film is irradiated with ultraviolet light to semi-cur the coating film, forming a buffer layer forming film with a thickness of 50 μm.

[0212] It should be noted that the above-mentioned ultraviolet irradiation was carried out using a conveyor belt type ultraviolet irradiation device (product name "ECS-401GX", manufactured by EYEGRAPHICS) and a high-pressure mercury lamp (H04-L41, manufactured by EYEGRAPHICS: H04-L41), under the following conditions: lamp height of 150 mm, lamp output of 3 kW (equivalent to 120 mW / cm), light wavelength of 365 nm, illuminance of 120 mW / cm2, and irradiation dose of 100 mJ / cm2.

[0213] The surface on which the buffer layer forming film is formed 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.

[0214] It should be noted that the above-mentioned ultraviolet irradiation is carried out using the above-mentioned ultraviolet irradiation device and high-pressure mercury lamp, under the following conditions: lamp height is 150 mm, lamp output is 3 kW (equivalent to 120 mW / cm), light wavelength is 365 nm, illuminance is 160 mW / cm2, and irradiation dose is 500 mJ / cm2.

[0215] (4)The semiconductor processing protective sheet is fabricated by bonding the adhesive layer of the release sheet with the adhesive layer to the antistatic layer, forming the antistatic layer and the adhesive layer sequentially on one main surface of the substrate, and forming a buffer layer on the other main surface of the substrate to fabricate the semiconductor processing protective sheet.

[0216] (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.

[0217] (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.

[0218] (Example 4) Except for using the following adhesive layer composition to form the adhesive layer, a protective sheet for semiconductor processing is obtained by the same method as in Example 1.

[0219] (Preparation of composition for adhesive layer) An acrylic polymer (Mw: 800,000) is obtained by copolymerizing 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).

[0220] Relative to 100 parts by weight of the acrylic polymer mentioned above, 1 part by weight (solid component) of toluene diisocyanate crosslinking agent (manufactured by TOSOH Corporation, product name "CORONATE L"), 2 parts by weight (solid component) of epoxy crosslinking agent (1,3-bis(N,N-diglycidylaminomethyl)cyclohexane), 45 parts by weight (solid component) of energy line curing compound (manufactured by Mitsubishi Chemical Corporation, product name "UV-3210EA") and 1 part by weight (solid component) of photopolymerization initiator (manufactured by IGM Resins Corporation, product name "OMNIRAD184") are mixed and diluted with a solvent to obtain a coating liquid for the adhesive layer composition.

[0221] (Example 5) Except that the adhesive layer is formed using the following adhesive layer composition, and 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.

[0222] (Preparation of Adhesive Layer Composition) 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) are copolymerized to obtain an acrylic polymer. The polymer is then reacted with 2-methacryloyloxyethyl isocyanate (MOI) in such a way that 90 moles of the total hydroxyl groups of the acrylic polymer are added to obtain an energy-line curable acrylic resin (Mw: 500,000).

[0223] To 100 parts by weight of this energy-curable acrylic resin, the following components are added: 0.375 parts by weight of isocyanate crosslinking agent (manufactured by TOSOH Corporation, trade name: CORONATE L) (based on solid content), and 1 part by weight of photopolymerization initiator formed from bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide; the coating liquid of the adhesive layer composition is prepared by dilution with solvent.

[0224] (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.

[0225] (Comparative Example 2) Except for using the following adhesive layer composition to form the adhesive layer and setting the thickness of the antistatic layer to 50 nm, a protective sheet for semiconductor processing was obtained by the same method as in Example 1.

[0226] (Preparation of composition for adhesive layer) 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) are copolymerized to obtain an acrylic polymer. The polymer is then reacted with 2-methacryloyloxyethyl isocyanate (MOI) in such a way that 90 moles of the total hydroxyl groups of the acrylic polymer are added to obtain an energy-line curable acrylic resin (Mw: 500,000).

[0227] To 100 parts by weight of this energy-line curable acrylic resin, the following components are added: 20 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) (based on solid content), and 1 part by weight of photopolymerization initiator formed by bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide; the coating solution of the adhesive layer composition is prepared by solvent dilution.

[0228] (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.

[0229] (Preparation of Adhesive Layer Composition) 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) are copolymerized to obtain an acrylic polymer. The polymer is then reacted with 2-methacryloyloxyethyl isocyanate (MOI) by adding 50 moles of hydroxyl groups to the total hydroxyl groups of the acrylic polymer to obtain an energy-line curable acrylic resin (Mw: 500,000).

[0230] To 100 parts by weight of this energy-curable acrylic resin, the following components are added: 0.375 parts by weight of isocyanate crosslinking agent (manufactured by TOSOH Corporation, trade name: CORONATE L) (based on solid content), and 1 part by weight of photopolymerization initiator formed from bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide; the coating liquid of the adhesive layer composition is prepared by dilution with solvent.

[0231] Table 1 Protective Sheets for Semiconductor Processing evaluate Adhesive layer Antistatic layer Stripping static voltage (Wafer side) (V) crack Incidence determination Surface resistivity (Ω / cm) 2 ) 90° Adhesion UV front (N / 25mm) 90° Adhesion UV after (N / 25mm) Adhesion ratio After UV / Before UV (%) thickness (μm) thickness (nm) Example 1 2.1 × 10 13 10.8 0.06 0.6 20 120 100 good ○ Example 2 6.0 × 10 12 5.3 0.05 0.9 5 150 50 good ○ Example 3 8.9 × 10 14 18.5 0.14 0.8 200 80 200 good ○ Example 4 5.6 × 10 12 3.3 0.13 3.9 20 120 50 good ○ Example 5 9.3 × 10 14 6.2 0.22 3.5 5 25 450 good ○ Comparative Example 1 1.3 × 10 15 10.8 0.06 0.6 20 0 4300 good ╳ Comparative Example 2 1.1 × 10 15 11.2 0.03 0.3 20 50 3300 good ╳ Comparative Example 3 7.5 × 10 11 13.0 1.83 14.1 20 120 40 bad ╳

[0232] The obtained samples (Examples 1-5 and Comparative Examples 1-3) were subjected to the above measurements and evaluations. The adhesion 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.

[0233] As can be seen from Table 1, when the surface resistivity of the adhesive layer of the semiconductor processing protective sheet is within the above range, and the semiconductor processing protective sheet contains an antistatic layer, it has been confirmed that the static voltage accompanying the peeling from the semiconductor processing protective sheet can be reduced, and the cracking rate caused by wafer displacement can be further reduced. [Simplified Explanation of the Diagram]

[0021] FIG1A is a cross-sectional schematic diagram showing an example of the protective sheet for semiconductor processing according to this embodiment. FIG1B is a cross-sectional schematic diagram showing another example of the protective sheet for semiconductor processing according to this embodiment. FIG2 is a cross-sectional schematic diagram showing the appearance of the protective sheet for semiconductor processing according to this embodiment attached to the circuit surface of a wafer.

Claims

1. A protective sheet for semiconductor processing, comprising a substrate, an antistatic layer, an adhesive layer with energy line hardening properties, and a buffer layer, wherein the surface resistivity of the adhesive layer after energy line hardening is 5.1 × 10¹² Ω / □ or higher and 1.0 × 10¹⁵ Ω / □ or lower.

2. The protective sheet for semiconductor processing as claimed in claim 1, wherein the adhesive force when peeling the energy line hardened adhesive layer from the silicon wafer at a peeling speed of 600 mm / min and with the angle between the adhesive layer and the silicon wafer being 90° is less than 0.15 N / 25 mm.

3. The protective sheet for semiconductor processing as claimed in claim 1 or 2, wherein 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 and with the angle between the adhesive layer and the silicon wafer being 90° is 4% or less, compared with 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 and with the angle between the adhesive layer and the silicon wafer being 90°.

4. The protective sheet for semiconductor processing as claimed in claim 1 or 2, wherein the Young's modulus of the substrate is 1000 MPa or more.

5. The protective sheet for semiconductor processing as claimed in claim 1 or 2, wherein the protective sheet for semiconductor processing has the adhesive layer on one main surface of the substrate, the antistatic layer is disposed between the substrate and the adhesive layer, and the buffer layer is disposed on another main surface of the substrate; or, the protective sheet for semiconductor processing has the adhesive layer on one main surface of the substrate, and the antistatic layer and the buffer layer are disposed between the substrate and the adhesive layer.

6. The protective sheet for semiconductor processing as described in claim 1 or 2, used to be attached to the surface of a wafer in the step of forming a wafer into a chip by grinding the back side of the wafer after forming trenches on the surface of the wafer or forming a modified region inside the wafer.

7. A method for manufacturing a semiconductor device, comprising the steps of: attaching a semiconductor processing protective sheet as described in any one of claims 1 to 6 to the surface of a wafer; forming trenches from the surface side of the wafer, or forming modified regions from the surface or back side of the wafer toward the interior of the wafer; grinding the wafer with the semiconductor processing protective sheet attached to its surface and with the trenches or modified regions formed therein from the back side, and wafering it into a plurality of wafers starting from the trenches or modified regions; and peeling the semiconductor processing protective sheet from the wafers that have been wafered.

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