Adhesive sheet for back grinding, semiconductor wafer manufacturing method, and base sheet

Abstract

Provided is an adhesive sheet for rear surface grinding with which an adhesive layer is prevented from peeling off and a wafer can be easily peeled off from the adhesive sheet.　According to the present invention, this adhesive sheet for rear surface grinding of a semiconductor wafer having a protrusion comprises a base material layer, and an adhesive layer provided on the base material layer, wherein: the adhesive layer has an opening that is smaller in diameter than the semiconductor wafer and is affixed to the outer periphery of the semiconductor wafer such that the protrusion of the semiconductor wafer is disposed inside the opening; the protrusion is protected by the base material layer in a state in which the semiconductor wafer is affixed to the adhesive layer; the base material layer includes a cushion layer and a surface treatment layer provided thereon; the adhesive layer is provided on the surface treatment layer; the surface treatment layer is formed from an acrylic resin composition containing an acrylic resin; the acrylic resin is crosslinked by photoirradiation or heating; and the adhesive layer is formed from the acrylic resin composition containing an acrylic resin.

Description

[Technical Field]

[0001] The present invention relates to an adhesive sheet for backgrinding, a method for manufacturing a semiconductor wafer using the same, and a base sheet. [Background technology]

[0002] When semiconductor wafers are processed, adhesive sheets are applied to protect them from damage. For example, in the back grinding process when processing semiconductor wafers, adhesive sheets are applied to protect the patterned surface of the semiconductor wafer. The adhesive sheet is required to have adhesion to patterned surfaces with irregularities such as protruding electrodes (bumps), and to be able to follow the irregularities of the patterned surface (step-following ability) from the standpoint of reliable protection of the patterned surface.

[0003] In order to give adhesive sheets conformability, it is common on the market to increase the thickness of the adhesive or to provide a cushioning, flexible resin layer between the base film and the adhesive, but if the pattern surface is very uneven, there is a higher risk of insufficient conformability or adhesive residue.

[0004] In Patent Document 1, an adhesive sheet is configured with an adhesive layer having an opening with a diameter smaller than the outer diameter of a semiconductor wafer on one side of a base layer, and the adhesive layer is attached to the outer periphery of a semiconductor wafer by vacuum mounting so that the convex portions of the semiconductor wafer are positioned within the openings of the adhesive layer, and the convex portions are embedded in the base layer, thereby preventing adhesive residue and a decrease in protective function. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-140387 Summary of the Invention [Problem to be solved by the invention]

[0006] The present inventors conducted extensive research into the pressure-sensitive adhesive sheet disclosed in Patent Document 1 and discovered that the pressure-sensitive adhesive layer may peel off from the base layer. Furthermore, they conducted extensive research to solve this problem and discovered that by subjecting the base layer to a corona discharge treatment, the adhesion between the pressure-sensitive adhesive layer and the base layer is improved, thereby solving the problem of the pressure-sensitive adhesive layer peeling off.

[0007] Although it is possible to apply corona discharge treatment only to the region of the base layer where the adhesive layer is to be formed by using a mask or the like, this significantly reduces productivity. For this reason, corona discharge treatment was performed on the entire surface of the base layer. Then, when a wafer was attached to the adhesive sheet produced in this manner, it was found that a new problem occurred in that the wafer was strongly adhered to the base layer as well, making it difficult to peel the wafer from the adhesive sheet.

[0008] The present invention has been made in consideration of these circumstances, and provides an adhesive sheet for back grinding that suppresses peeling of the adhesive layer and allows the wafer to be easily peeled off from the adhesive sheet. [Means for solving the problem]

[0009] According to the present invention, the following inventions are provided. (1) An adhesive sheet for backgrinding a semiconductor wafer having a convex portion, comprising: a base layer; and an adhesive layer provided on the base layer, wherein the adhesive layer has an opening with a diameter smaller than the diameter of the semiconductor wafer, and is attached to the outer periphery of the semiconductor wafer so that the convex portion of the semiconductor wafer is positioned within the opening, and wherein the convex portion is protected by the base layer when the semiconductor wafer is attached to the adhesive layer, the base layer comprises a cushion layer and a surface treatment layer provided thereon, the adhesive layer is provided on the surface treatment layer, the surface treatment layer is formed of an acrylic resin composition containing an acrylic resin, the acrylic resin is crosslinked by light irradiation or heat, and the adhesive layer is formed of an acrylic resin composition containing an acrylic resin. (2) The pressure-sensitive adhesive sheet according to (1), wherein the surface treatment layer has a storage modulus of 1.0 × 10 at 180 ° C. 4 Pa~1.0×10 8 Pa is an adhesive sheet. (3) The pressure-sensitive adhesive sheet according to (1) or (2), wherein the convex portions are protected by being embedded in the base layer. (4) The pressure-sensitive adhesive sheet according to any one of (1) to (3), wherein the semiconductor wafer is attached to the pressure-sensitive adhesive layer under reduced pressure. (5) An adhesive sheet according to any one of (1) to (4), wherein the semiconductor wafer to which the base layer of a test piece cut out from the adhesive sheet is bonded is heated in an atmosphere of 100°C for 1 minute, and after cooling to room temperature, the adhesive strength between the base layer and the semiconductor wafer at 23°C measured in accordance with JIS Z0237 is less than 6 N / 200 mm. (6) A method for manufacturing a semiconductor wafer using the adhesive sheet according to any one of (1) to (5), comprising a frame attaching step, a wafer attaching step, a heating step, a cutting step, a resin curing step, and a grinding step, wherein in the frame attaching step, the adhesive sheet is attached to a ring frame, in the wafer attaching step, the adhesive sheet is attached to the outer periphery of the semiconductor wafer under reduced pressure on the surface of the semiconductor wafer on which the convex portion is provided, in the heating step, the base layer is heated, in the cutting step, the adhesive sheet is cut along the outer periphery of the semiconductor wafer, in the resin curing step, the base layer is brought into contact with a curable resin after the wafer attaching step and the curable resin is cured in that state, and in the grinding step, the back surface of the semiconductor wafer is ground. (7) A substrate sheet comprising a cushion layer and a surface treatment layer provided thereon, the surface treatment layer being formed of an acrylic resin composition containing an acrylic resin, and the acrylic resin being crosslinked by light irradiation or heat. (8) The substrate sheet according to (7), wherein the storage modulus of the surface treatment layer at 180°C is 1.0 × 10 4 Pa~1.0×10 8Pa, the base sheet.

[0010] As a result of extensive research, the inventors have found that the above-mentioned problems can be solved by employing a surface treatment layer and a pressure-sensitive adhesive layer having specific configurations, and have thus completed the present invention. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view showing a state before a ring frame 3 is attached to an adhesive sheet 10 of one embodiment of the present invention. [Figure 2] 2 is a cross-sectional view showing the state after a ring frame 3 has been attached to an adhesive sheet 10 in the state shown in FIG. 1. FIG. [Figure 3] 2. FIG. 3 is a cross-sectional view showing the state after semiconductor wafer 4 has been attached to adhesive sheet 10 and placed in decompression chamber 16. [Figure 4] 4 is a cross-sectional view showing the state after semiconductor wafer 4 with adhesive sheet 10 attached thereto has been removed from decompression chamber 16, following the state shown in FIG. 3. FIG. [Figure 5] 5 is a cross-sectional view showing a state after the ring frame 3 has been removed from the state shown in FIG. 4 and the semiconductor wafer 4 has been sucked by the decompression unit 6. FIG. [Figure 6] 6 is a cross-sectional view showing a state in which adhesive sheet 10 is pressed against hardening resin 8 from the state of FIG. 5, and hardening resin 8 is being hardened. FIG. [Figure 7] 7 is a cross-sectional view showing a state after the hardening of hardening resin 8 has been completed following the state shown in FIG. 6. FIG. [Figure 8] 8 is a cross-sectional view showing a state after the back surface 4b of the semiconductor wafer 4 has been ground from the state shown in FIG. 7. FIG. [Figure 9] 9 is a cross-sectional view showing the state after the semiconductor wafer 4 has been peeled off from the adhesive sheet 10 in the state shown in FIG. [Figure 10] FIG. 1 is a cross-sectional view showing a base sheet 11 according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] The following describes embodiments of the present invention. The various features shown in the following embodiments can be combined with each other. Furthermore, each feature can be an invention independently.

[0013] 1. Adhesive sheet An adhesive sheet 10 according to one embodiment of the present invention will be described with reference to Figures 1 to 9. The adhesive sheet 10 of this embodiment comprises a base layer 1 and an adhesive layer 2 provided on the base layer 1. This adhesive sheet 10 is used when grinding the back surface 4b of a semiconductor wafer 4 having protrusions 5. Each component will be described below.

[0014] 1-1. Base material layer 1 As shown in Fig. 1, the base layer 1 includes a cushion layer 1a, a surface treatment layer 1b, and a barrier layer 1c. The surface treatment layer 1b is provided on the cushion layer 1a. The barrier layer 1c is preferably provided on the opposite side of the cushion layer 1a from the surface treatment layer 1b (or the pressure-sensitive adhesive layer 2). The barrier layer 1c is preferably attached to the cushion layer 1a via an adhesive layer (not shown). The barrier layer 1c is optional.

[0015] The total thickness of the base layer 1 is preferably 50 to 400 μm, more preferably 100 to 350 μm, and even more preferably 200 to 300 μm. Specific examples of this thickness include 50, 100, 150, 200, 250, 300, 350, and 400 μm, and may be within a range between any two of the numerical values ​​exemplified here.

[0016] <Cushion layer 1a> The cushion layer 1a is a layer for protecting the protrusions 5 of the semiconductor wafer 4 shown in FIG. 2. The cushion layer 1a is preferably made of a thermoplastic resin. The composition of the thermoplastic resin is not particularly limited, but examples include ionomer resins in which the carboxyl groups of simple and / or complex materials such as ethylene-methacrylic acid-acrylic acid ester terpolymers, ethylene-methacrylic acid copolymers, and ethylene-acrylic acid copolymers are crosslinked with metal ions such as sodium ions, lithium ions, and magnesium ions; flexible polypropylene resins in which polypropylene resins are blended with styrene-butadiene copolymer rubber, styrene-butadiene-styrene block copolymer rubber, styrene-isoprene-styrene block copolymer rubber, ethylene-propylene rubber, and the like; low-density polyethylene; ethylene-propylene block copolymers; ethylene-propylene random copolymers; ethylene-vinyl acetate copolymers; ethylene-methacrylic acid copolymers; ethylene-1-octene copolymers; and polybutene. Among these, ionomer resins are preferred.

[0017] The proportion Ra (mass%) of (meth)acrylic monomer units in the resin constituting the cushion layer 1a is preferably lower than the proportion Rb (mass%) of (meth)acrylic monomer units in the acrylic resin constituting the surface-treated layer 1b. In this case, the adhesion between the pressure-sensitive adhesive layer 2 composed of the acrylic resin composition and the surface-treated layer 1b is higher than the adhesion between the pressure-sensitive adhesive layer 2 and the cushion layer 1a, making the provision of the surface-treated layer 1b technically significant. The value of (Rb-Ra) is, for example, 10 to 100 mass%, preferably 30 to 100 mass%. Specific examples of this value include 10, 20, 30, 40, 50, 60, 70, 80, 90, and 100 mass%, and may be within a range between any two of the values ​​exemplified here.

[0018] The storage modulus E'a of the cushion layer 1a at 180°C is preferably lower than the storage modulus E'b of the surface treatment layer 1b at 180°C. If the storage modulus E'a of the cushion layer 1a under high-temperature conditions is low, the cushion layer 1a may be excessively softened during heating, resulting in strong adhesion to the wafer and difficulty in peeling. The provision of the surface treatment layer 1b prevents such problems. Therefore, the provision of the surface treatment layer 1b is technically significant when the storage modulus E'a is lower than the storage modulus E'b. If the storage modulus E'a cannot be measured due to melting of the cushion layer 1a, the storage modulus E'a is set to 0 for convenience.

[0019] The weight average molecular weight (Mw) of the thermoplastic resin is preferably from 10,000 to 1,000,000, and more preferably from 50,000 to 500,000. The weight average molecular weight (Mw) is a value measured by gel permeation chromatography (GPC) in terms of polystyrene.

[0020] The softening temperature (JIS K7206) of the thermoplastic resin is preferably 45 to 200° C., more preferably 55 to 150° C. Specific examples of the softening temperature include 45, 50, 55, 60, 65, 70, 75, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, and 200° C., and may be within a range between any two of the values ​​exemplified here.

[0021] The melting point (JIS K7121) of the thermoplastic resin is preferably 60 to 200° C., more preferably 80 to 150° C. Specific examples of the melting point include 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, and 200° C., and may be within a range between any two of the values ​​exemplified here.

[0022] The melt flow rate (MFR) (JIS K7210, 125°C / 10.0 kg load) of the thermoplastic resin is preferably 0.2 to 30 g / 10 min, more preferably 0.3 to 20 g / 10 min.

[0023] When the thermoplastic resin has the above physical properties, the cushion layer 1a is softened appropriately as the base layer 1 is heated, so that the protrusions 5 can be easily embedded in the base layer 1.

[0024] The thickness of the cushion layer 1a is preferably 50 to 400 μm, more preferably 100 to 350 μm, and even more preferably 200 to 300 μm. Specific examples of the thickness include 50, 100, 150, 200, 250, 300, 350, and 400 μm, and may be within a range between any two of the values ​​exemplified here.

[0025] <Surface treatment layer 1b> The surface treatment layer 1b is formed of an acrylic resin composition containing an acrylic resin, and is crosslinked by light irradiation or heating. If the pressure-sensitive adhesive layer 2 is formed directly on the cushion layer 1a, peeling of the pressure-sensitive adhesive layer 2 may occur if the adhesion between the cushion layer 1a and the pressure-sensitive adhesive layer 2 is poor. However, by forming the surface treatment layer 1b on the cushion layer 1a and then forming the pressure-sensitive adhesive layer 2 from an acrylic resin composition, peeling of the pressure-sensitive adhesive layer 2 can be suppressed.

[0026] Furthermore, if the cushion layer 1a is subjected to a corona discharge treatment to enhance the adhesion between the cushion layer 1a and the adhesive layer 2 and then attached to a semiconductor wafer, the adhesive strength between the cushion layer 1a and the semiconductor wafer may become too high, making it difficult to peel the semiconductor wafer from the cushion layer 1a. Therefore, in this embodiment, a surface treatment layer 1b is formed on the cushion layer 1a, and the surface treatment layer 1b is attached to the semiconductor wafer. As described above, the surface treatment layer 1b has excellent adhesion to the adhesive layer 2 even without corona discharge treatment, so there is no need to perform corona discharge treatment on the surface treatment layer 1b. Therefore, by providing the surface treatment layer 1b, it is possible to reduce the adhesive strength between the base layer 1 and the semiconductor wafer.

[0027] Specifically, by providing the surface treatment layer 1b, a semiconductor wafer to which a base layer 1 of a test piece cut out from the pressure-sensitive adhesive sheet 10 has been bonded is heated in a 100°C atmosphere for 1 minute, and then cooled to room temperature. The adhesive strength between the base layer 1 and the semiconductor wafer at 23°C, as measured in accordance with JIS Z0237, can be reduced to less than 6 N / 200 mm. This is preferable because the adhesive strength between the base layer 1 and the semiconductor wafer is smaller than the adhesive strength between the pressure-sensitive adhesive layer 2 and the semiconductor wafer. This adhesive strength is, for example, 0 to 5.9 N / 200 mm, more preferably 0.1 to 3 N / 200 mm, and even more preferably 0.5 to 2 N / 200 mm. This adhesive strength is, for example, 0, 0.1, specifically, for example, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, or 5.9 N / 200 mm, and may be within a range between any two of the numerical values ​​exemplified here. Furthermore, the adhesive strength under the above measurement conditions before heating is preferably 5 N / 200 mm or less. This adhesive strength is, for example, 0 to 5 N / 200 mm, specifically, for example, 0, 0.1, 0.5, 1, 2, 3, 4, or 5 N / 200 mm, and may be within a range between any two of the numerical values ​​exemplified here.

[0028] The acrylic resin refers to a resin containing 50% by mass or more of (meth)acrylic monomer units. The (meth)acrylic monomer refers to a compound having a (meth)acryloyl group. The (meth)acrylic monomer is preferably monofunctional.

[0029] Examples of (meth)acrylic monomers include (meth)acrylic acid and / or (meth)acrylic acid esters. Examples of (meth)acrylic acid esters include alkyl (meth)acrylates, hydroxyalkyl (meth)acrylates, and (meth)acrylates having a cyclic ether skeleton. These may be used alone or in combination.

[0030] The alkyl(meth)acrylate is preferably a (meth)acrylate represented by the following general formula (A).

[0031] (A)ZOR (In the formula, Z represents a (meth)acryloyl group, and R represents an alkyl group having 1 to 10 carbon atoms.)

[0032] Examples of such alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, lauryl (meth)acrylate, and dodecyl (meth)acrylate.

[0033] Hydroxyalkyl (meth)acrylates include 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, and glycerol mono(meth)acrylate.

[0034] Examples of (meth)acrylates having a cyclic ether skeleton include glycidyl (meth)acrylate, furfuryl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, 3-ethyl-3-oxetanylmethyl (meth)acrylate, (2-methyl-ethyl-1,3-dioxolan-4-yl)methyl (meth)acrylate, cyclic trimethylolpropane formal (meth)acrylate, γ-butyrolactone (meth)acrylate, dioxolane (meth)acrylate, dioxane glycol di(meth)acrylate, and oxetane (meth)acrylate. One or more of these can be used. Among the cyclic ether skeletons, 5- to 6-membered rings are preferred. The cyclic ether skeleton preferably has 1 oxygen atom. The cyclic ether skeleton preferably has 2 to 5 carbon atoms. Among the (meth)acrylates having a cyclic ether skeleton, glycidyl (meth)acrylate is preferred.

[0035] The acrylic resin may contain only (meth)acrylic monomer units, or may contain other monomer units in addition to (meth)acrylic monomer units, such as olefins (ethylene, propylene, etc.), aliphatic vinyls (vinyl acetate, etc.), and aromatic vinyls (styrene, etc.).

[0036] The proportion of (meth)acrylic monomer units in the acrylic resin constituting the surface treatment layer 1b is, for example, 50 to 100 mass%, specifically, for example, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100 mass%, and may be within a range between any two of the numerical values ​​exemplified here.

[0037] The acrylic resin can be obtained by polymerizing a monomer mixture containing the above-mentioned monomers.

[0038] The acrylic resin composition preferably contains a crosslinking agent. The acrylic resin is crosslinked by the reaction between the acrylic resin and the crosslinking agent. Examples of the crosslinking agent include acrylate crosslinking agents, isocyanate crosslinking agents, epoxy crosslinking agents, and amine crosslinking agents. These may be used alone or in combination of two or more.

[0039] Examples of acrylate crosslinking agents include compounds having multiple (e.g., two) (meth)acryloyl groups, and specific examples include 1,9-nonanediol diacrylate, 1,6-hexanediol diacrylate, triethylene glycol diacrylate, polytetramethylene glycol diacrylate, neopentyl glycol diacrylate, and 3-methyl-1,5 pentanediol diacrylate.

[0040] Examples of isocyanate crosslinking agents include polyvalent isocyanate compounds such as 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, diphenylmethane-4,4'-diisocyanate, diphenylmethane-2,4'-diisocyanate, 3-methyldiphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, dicyclohexylmethane-2,4'-diisocyanate, and lysine isocyanate, as well as derivatives thereof (adducts, biuret compounds, isocyanurates), etc. These may be used alone or in combination of two or more.

[0041] The amount of crosslinking agent blended relative to 100 parts by mass of the acrylic resin is, for example, 0.5 to 30 parts by mass, preferably 4 to 25 parts by mass, and more preferably 7 to 20 parts by mass. Specific examples of this blending amount include 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, and 30 parts by mass, and may be within a range between any two of the numerical values ​​exemplified here.

[0042] The acrylic resin is crosslinked by irradiation with light or heat.

[0043] In the case of crosslinking by light irradiation, the acrylic resin composition preferably contains a photopolymerization initiator. Specific examples of the photopolymerization initiator include, but are not limited to, benzoin ether-based photopolymerization initiators, acetophenone-based photopolymerization initiators, α-ketol-based photopolymerization initiators, aromatic sulfonyl chloride-based photopolymerization initiators, photoactive oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzyl-based photopolymerization initiators, benzophenone-based photopolymerization initiators, ketal-based photopolymerization initiators, thioxanthone-based photopolymerization initiators, and acylphosphine oxide-based photopolymerization initiators, with acetophenone-based photopolymerization initiators being preferred.

[0044] Specific examples of acetophenone-based photopolymerization initiators include 1-hydroxycyclohexyl phenyl ketone, 4-phenoxydichloroacetophenone, 4-t-butyl-dichloroacetophenone, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, and methoxyacetophenone.

[0045] The Mw of the acrylic resin before crosslinking is preferably 300,000 to 2,000,000, and more preferably 450,000 to 800,000. If the Mw is too low, heat resistance may be insufficient, while if the Mw is too high, the viscosity may be too high, making coating difficult and reducing productivity. Specific examples of Mw include 300,000, 350,000, 400,000, 450,000, 500,000, 550,000, 600,000, 650,000, 700,000, 750,000, 800,000, 900,000, 1,000,000, 1,100,000, 1,200,000, 1,300,000, 1,400,000, 1,500,000, 1,600,000, 1,700,000, 1,800,000, 1,900,000, and 2,000,000, and may fall within a range between any two of the values ​​exemplified here.

[0046] The acrylic resin preferably has a glass transition temperature (Tg) before crosslinking of -15 to 40°C, more preferably -10 to 30°C. Specific examples of the Tg include -15, -10, -5, 0, 5, 10, 15, 20, 25, 30, 35, and 40°C, and may be within a range between any two of the values ​​exemplified here. The acrylic resin preferably has a Tg after crosslinking of 10 to 80°C, more preferably 20 to 70°C. Specific examples of the Tg include 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, and 80°C, and may be within a range between any two of the values ​​exemplified here.

[0047] In this specification, Tg is measured as follows: Differential scanning calorimetry (DSC) is performed according to JIS K 7121: 1987. Tg is defined as the intersection of the tangent to the baseline of the DSC curve and the tangent to the steep drop in the endothermic region due to glass transition.

[0048] The surface treatment layer 1b has a storage modulus of 1.0 × 10 at 180 °C. 4 Pa~1.0×10 8 It is preferable that the storage modulus is 0.05 Pa. If this storage modulus is too low, when the adhesive sheet 10 is heated during attachment of the wafer to the adhesive sheet 10, the surface treatment layer 1b becomes too soft, and as a result, the surface treatment layer 1b breaks as the cushion layer 1a melts, and residues of the surface treatment layer 1b may remain on the wafer or the peelability may be impaired. If this storage modulus is too high, the surface treatment layer 1b may be too hard, and the ability to follow the convex portions 5 of the base layer 1 may be impaired.

[0049] Specifically, the storage modulus is, for example, 1.0×10 4 Pa, 1.0 × 10 5 Pa, 1.0 × 10 6 Pa, 1.0 × 10 7 Pa, 1.0 × 10 8 Pa and may be in the range between any two of the values ​​exemplified here.

[0050] The thickness of the surface treatment layer 1b is, for example, 0.1 to 10 μm, preferably 0.5 to 5 μm, and more preferably 1 to 4 μm. When the surface treatment layer 1b has such a thickness, the effect of providing the surface treatment layer 1b is likely to be properly exhibited. Specific examples of this thickness include 0.1, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, and 10.0 μm, and may be within a range between any two of the values ​​exemplified here.

[0051] <Barrier layer 1c> The barrier layer 1c is a layer for reducing the oxygen permeability of the base layer 1. If the base layer 1 is easily permeable to air, outside air may enter the sealed space 2b through the base layer 1, making it difficult to reduce the pressure inside the sealed space 2b. As a result, a problem may arise in which the base layer 1 is less likely to conform to the protrusions 5.

[0052] The barrier layer 1c is a layer with low oxygen permeability. When the oxygen permeability is low, the air permeability is usually also low, so by providing the barrier layer 1c, the intrusion of outside air into the sealed space 2b through the base layer 1 is suppressed, and this has the effect of making the base layer 1 more likely to conform to the protrusions 5.

[0053] The barrier layer 1c has an oxygen permeability of 1000 ml / (m2) measured based on JIS K 7162-2 (constant pressure method) at 25°C and 0% RH of the base layer 1. 2 In order to set the oxygen permeability of the substrate layer 1 in this range, it is preferable that the oxygen permeability of the barrier layer 1c alone under the same conditions is 1000 ml / (m2·24h·atm) or less. In this case, the above-mentioned effect is easily exhibited. The oxygen permeability of the substrate layer 1 or the barrier layer 1c is, for example, 0 to 1000 ml / (m 2 ·24h·atm) and 0~500ml / (m 2 24h atm), and specifically, for example, 0, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000 ml / (m 2 ·24h·atm) and may be within a range between any two of the values ​​given here as examples.

[0054] Under the above conditions, the oxygen permeability of the barrier layer 1c is preferably lower than that of the cushion layer 1a. The value of (oxygen permeability of the cushion layer 1a - oxygen permeability of the barrier layer 1c) is 100 ml / (m 2 This value is preferably 100 to 3000 ml / (m 2 ·24h·atm), and specifically, for example, 100, 500, 1000, 1500, 2000, 2500, 3000 ml / (m 2 ·24h·atm) and may be within a range between any two of the values ​​given here as examples.

[0055] The barrier layer 1c can be formed of any material that can achieve the above oxygen permeability, and polyester (for example, polyethylene terephthalate), polyimide, and polyamide are preferred from the viewpoint of ease of reducing oxygen permeability.

[0056] The thickness of the barrier layer 1c is, for example, 5 to 50 μm, and preferably 10 to 30 μm. If the barrier layer 1c is too thin, the oxygen permeability of the base layer 1 may not be sufficiently low. If the barrier layer 1c is too thick, the ability of the base layer 1 to conform to the protrusions 5 may be poor. Specific examples of this thickness are 5, 10, 15, 20, 25, 30, 35, 40, 45, and 50 μm, and may be within a range between any two of the values ​​exemplified here.

[0057] 2. Adhesive layer 2 The adhesive layer 2 is a layer for adhering the adhesive sheet 10 to the semiconductor wafer 4, and is formed from an adhesive. The adhesive layer 2 has an opening 2a with a diameter smaller than the diameter of the semiconductor wafer 4. In other words, the adhesive layer 2 is annular. The opening 2a is a portion where no adhesive is provided, and has a diameter smaller than the diameter of the semiconductor wafer 4. The ratio of the diameter of the opening 2a to the diameter of the semiconductor wafer 4 is preferably 0.950 to 0.995, and more preferably 0.960 to 0.990.

[0058] The outer peripheral portion 4a of the semiconductor wafer 4 is attached to the adhesive layer 2 so that the protruding portions 5 of the semiconductor wafer 4 are positioned within the openings 2a. Therefore, the protruding portions 5 do not come into contact with the adhesive, and adhesive residue on the protruding portions 5 is prevented.

[0059] The width of the pressure-sensitive adhesive layer 2 is preferably 10 to 100 mm, more preferably 30 to 70 mm. The thickness of the pressure-sensitive adhesive layer 2 is preferably 1 to 100 μm, more preferably 5 to 50 μm. Specific examples of this thickness include 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, and 100 μm, and may be within a range between any two of the values ​​exemplified here.

[0060] The pressure-sensitive adhesive layer 2 is formed of an acrylic resin composition containing an acrylic resin. The acrylic resin of the pressure-sensitive adhesive layer 2 may have the same composition as or different from the acrylic resin of the surface treatment layer 1b.

[0061] The proportion of (meth)acrylic monomer units contained in the acrylic resin constituting the pressure-sensitive adhesive layer 2 is, for example, 50 to 100 mass%, specifically, for example, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100 mass%, and may be within a range between any two of the numerical values ​​exemplified here.

[0062] Examples of (meth)acrylic monomers include butyl (meth)acrylate, 2-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, tridecyl (meth)acrylate, myristyl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, and butyl (meth)acrylate. Examples of (meth)acrylic monomers and functional group-containing monomers include benzyl (meth)acrylate, dimethylacrylamide, diethylacrylamide, acryloylmorpholine, isobornyl acrylate, etc., 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, etc., which have a hydroxyl group; (meth)acrylic acid, crotonic acid, maleic acid, itaconic acid, fumaric acid, acrylamido-N-glycolic acid, cinnamic acid, etc., which have a carboxyl group; allyl glycidyl ether and (meth)acrylic acid glycidyl ether, etc., which have an epoxy group.

[0063] It is preferable to blend a crosslinking agent into the acrylic resin composition that constitutes the pressure-sensitive adhesive layer 2. Examples of crosslinking agents include polyfunctional isocyanate crosslinking agents and polyfunctional epoxy crosslinking agents. When the crosslinking agent reacts with the functional group, a crosslinked structure is formed using the functional group as the base point, thereby increasing the cohesive strength of the pressure-sensitive adhesive and reducing adhesive residue. Furthermore, (meth)acrylates in which one or more (meth)acryloyl groups are added to the end or side chain of an oligomer / polymer, such as 1,2-polybutadiene-terminated urethane (meth)acrylate, its hydrogenated derivatives, 1,4-polybutadiene-terminated urethane (meth)acrylate, polyisoprene-terminated (meth)acrylate, polyester-based urethane (meth)acrylate, polyether-based urethane (meth)acrylate, polyester (meth)acrylate, or bis-A type epoxy (meth)acrylate, may also be used.

[0064] The amount of crosslinking agent blended per 100 parts by mass of the acrylic resin is, for example, 0.1 to 10 parts by mass, preferably 0.5 to 8 parts by mass, and more preferably 1 to 6 parts by mass. Specific examples of this blending amount include 0.1, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, and 10.0 parts by mass, and may be within a range between any two of the numerical values ​​exemplified here.

[0065] The glass transition temperature (Tg) of the acrylic resin after crosslinking is preferably −30 to 5° C., more preferably −25 to −5° C. Specific examples of Tg include −30, −25, −20, −15, −10, −5, 0, and 5° C., and may be within a range between any two of the values ​​exemplified here.

[0066] The adhesive layer 2 can be formed by coating the adhesive onto the base layer 1 using a coating method such as a common comma coating, gravure coating, roll coating, or screen coating, or by coating the adhesive onto a release film and transferring it to the base layer 1.

[0067] The adhesive strength between the adhesive layer 2 and the semiconductor wafer, measured in accordance with JIS Z0237 at 23°C after heating the semiconductor wafer to which the adhesive layer 2 is attached for 1 minute in an atmosphere at 100°C and cooling to room temperature, is preferably 6 to 50 N / 200 mm, and more preferably 10 to 30 N / 200 mm. The adhesive strength under the above measurement conditions before heating is preferably 6 N / 200 mm or more, for example, 6 to 50 N / 200 mm. Specific examples of such adhesive strengths include 6, 10, 15, 20, 25, 30, 35, 40, 45, and 50 N / 200 mm, and may be within a range between any two of the values ​​exemplified here.

[0068] <Semiconductor wafer 4> The semiconductor wafer 4 has a protrusion 5. The protrusion 5 is any structure that protrudes out of the plane of the semiconductor wafer 4. Examples of the protrusion 5 include a protruding electrode and a protrusion of a circuit having irregularities.

[0069] Examples of the semiconductor wafer 4 include not only silicon wafers but also germanium wafers, gallium-arsenide wafers, gallium-phosphorus wafers, and gallium-arsenide-aluminum wafers. The diameter of the semiconductor wafer 4 is preferably 1 to 16 inches, and more preferably 4 to 12 inches. The thickness of the semiconductor wafer 4 is not particularly limited, but is preferably 500 to 800 μm, and more preferably 520 to 775 μm.

[0070] The height of the protrusions 5 is preferably 10 to 500 μm, and more preferably 100 to 300 μm. Specific examples of the height include 10, 50, 100, 150, 200, 250, 300, 350, 400, 450, and 500 μm, and may be within a range between any two of the values ​​exemplified here.

[0071] The semiconductor wafer 4 preferably has an outer periphery 4a that is not provided with the protrusions 5. The width of the outer periphery 4a is preferably 1.0 to 3.0 mm, and more preferably 1.5 to 2.5 mm.

[0072] Final products using the semiconductor wafer 4 having the protrusions 5 include electronic components for logic, memory, sensors, power supplies, and the like.

[0073] <Curable resin 8> The curable resin 8 is a resin that is cured by stimulation with energy rays (for example, ultraviolet rays), heat, etc. The curable resin 8 is disposed between the base layer 1 and the support film 7.

[0074] The viscosity of the curable resin 8 before curing is preferably 100 to 3000 mPa·s, and more preferably 200 to 1000 mPa·s. When the viscosity is 100 mPa·s or higher, the curable resin 8 forms point contact rather than surface contact, which prevents air bubbles from being mixed in during the pressing process and provides excellent grindability. When the viscosity is 3000 mPa·s or lower, the curable resin 8 is less likely to entrap air bubbles when flowing between adjacent protrusions 5, providing excellent grindability. The viscosity is measured using an E-type viscometer at 23°C and 50 rpm.

[0075] The curable resin 8 preferably has a Shore D hardness after curing of 5 to 70, more preferably 10 to 60. When the Shore D hardness is 5 or more, the retention of the convex portions 5 is high, resulting in excellent grinding properties. When the Shore D hardness is 70 or less, the adhesive sheet 10 is easily curved when peeled off from the semiconductor wafer 4. The Shore D hardness is measured under conditions in accordance with JIS K 6253.

[0076] The curable resin 8 is preferably a photocurable resin, more preferably an ultraviolet curable resin.

[0077] The curable resin 8 is preferably based on an acrylic resin, and although its composition is not particularly limited, a curable resin containing 1,2-hydrogenated polybutadiene-terminated urethane (meth)acrylate, isobornyl acrylate, or diethylacrylamide is preferred because it can improve the adhesion between the base layer 1 and the support film 7.

[0078] The cure shrinkage rate of the curable resin 8 is preferably 7% or less.

[0079] If the height of the protrusions 5 is Td (μm), the thickness of the curable resin 8 is preferably (Td+20) to (Td+200) μm, and more preferably (Td+50) to (Td+150) μm.

[0080] <Support film 7> The support film 7 is any film capable of supporting the curable resin 8, and can be formed from polyolefins such as ethylene vinyl acetate, polyethylene, polypropylene, polybutene, polybutadiene, as well as polyvinyl chloride, polyethylene terephthalate, polyethylene naphthalate, polystyrene, polycarbonate, polyimide, etc.

[0081] The thickness of the support film 7 is preferably 10 to 300 μm, and more preferably 30 to 250 μm.

[0082] 2. Semiconductor wafer manufacturing method 1 to 9, a method for manufacturing a semiconductor wafer using an adhesive sheet 10 will be described. This manufacturing method comprises a frame attaching step, a heating step, a cutting step, a resin curing step, a grinding step, and a peeling step. The order in which these steps are performed is not limited to this order, and the order can be changed as appropriate. Each step will be described below.

[0083] <Frame attachment process> As shown in Figures 1 and 2, in the frame attachment step, an adhesive sheet 10 is attached to a ring frame 3. The ring frame 3 has an opening 3a with a larger diameter than the opening 2a in the adhesive layer 2, and the ring frame 3 can be attached to the adhesive layer 2. This allows the adhesive sheet 10 to be stably held by the ring frame 3, making the adhesive sheet 10 easy to handle.

[0084] <Wafer bonding process / heating process> 2 and 3, in the wafer attachment step, an adhesive sheet 10 is attached under reduced pressure to the outer periphery 4a of the semiconductor wafer 4 on the surface of the semiconductor wafer 4 on which the protrusions 5 are provided. The width of the attachment surface where the semiconductor wafer 4 is attached to the adhesive layer 2 is preferably 1.0 to 3.0 mm, and more preferably 1.5 to 2.5 mm.

[0085] This step can be performed by attaching the semiconductor wafer 4 to the adhesive sheet 10 in a decompression chamber 16. The pressure in the decompression chamber 16 should be lower than atmospheric pressure, and is preferably 1000 Pa or less, more preferably 500 Pa or less, and even more preferably 100 Pa or less. The lower limit of the pressure in the decompression chamber 16 is not particularly specified, but is, for example, 10 Pa.

[0086] By attaching the semiconductor wafer 4 to the adhesive sheet 10 under reduced pressure in this manner, the inside of the sealed space 2b surrounded by the semiconductor wafer 4 and the adhesive sheet 10 becomes a reduced pressure state.

[0087] When the pressure-sensitive adhesive sheet 10 with the semiconductor wafer 4 attached thereto is removed from the decompression chamber 16 and exposed to atmospheric pressure, the base layer 1 is pushed by the atmospheric pressure and attempts to enter the sealed space 2b. The base layer 1 has high rigidity when not heated, and therefore does not enter the sealed space 2b at all. On the other hand, when the base layer 1 is heated to 60 to 150°C in the heating step, the base layer 1 is softened and enters the sealed space 2b as shown in FIG. 4. Therefore, the protrusions 5 are embedded in the base layer 1 and are protected by the base layer 1. The ratio of the height of the embedded portion of the protrusions 5 to the total height of the protrusions 5 is preferably 0.2 to 1, more preferably 0.5 to 1, and even more preferably 0.8 to 1. The heating temperature of the base layer 1 is preferably 80 to 120°C. The heating time of the base layer 1 is preferably 3 to 120 seconds, more preferably 5 to 60 seconds.

[0088] The base layer 1 may be heated before or after the semiconductor wafer 4 is attached to the adhesive sheet 10. Furthermore, this heating may be performed inside or outside the decompression chamber 16.

[0089] <Cutting process> 4 and 5, in the cutting step, the adhesive sheet 10 is cut along the outer periphery of the semiconductor wafer 4. As a result, the adhesive sheet 10 to which the semiconductor wafer 4 is attached is separated from the ring frame 3. The cutting step may be performed after the resin curing step.

[0090] <Resin curing process> In the resin curing step, after the wafer bonding step, the base layer 1 is brought into contact with the curable resin 8, and in this state, the curable resin 8 is cured. This step can be performed, for example, by the following method.

[0091] First, as shown in FIGS. 5 and 6, adhesive sheet 10 is placed opposite curable resin 8 supplied on support film 7, and adhesive sheet 10 is moved to spread curable resin 8.

[0092] In one example, the semiconductor wafer 4 is adsorbed to a decompression unit 6 having decompression holes 6a, and in this state, the adhesive sheet 10 is pressed against the curable resin 8. In this state, the adhesive sheet 10 is moved along the surface of the support film 7, thereby spreading the curable resin 8.

[0093] Next, as shown in FIGS. 6 and 7, the base layer 1 is brought into contact with the hardening resin 8, and the hardening resin 8 is hardened.

[0094] In one example, the curable resin 8 can be cured into a cured resin 18 by irradiating it with energy rays 9 such as ultraviolet rays through the support film 7. This allows the adhesive sheet 10 to be stably held on the support film 7.

[0095] <Grinding process> As shown in FIGS. 7 and 8, in the grinding step, the back surface 4b of the semiconductor wafer 4 is ground.

[0096] The back surface 4b of the semiconductor wafer 4 is the surface opposite to the surface on which the protrusions 5 are provided. There are no particular limitations on the method for grinding the back surface of the wafer, and any known grinding method can be used. Grinding is preferably performed while cooling the wafer and grinding stone (diamond, etc.) by spraying water on them. The thickness of the thinned wafer is preferably 300 μm or less, and more preferably 50 μm or less.

[0097] During back grinding, a load is applied to the protrusions 5 in the in-plane direction of the semiconductor wafer 4, which makes the protrusions 5 prone to breakage. However, in this embodiment, at least a portion of the protrusions 5 is embedded in the base layer 1 and the cured curable resin 8, and therefore the protrusions 5 are stably supported by the base layer 1 and the cured curable resin 8, making the protrusions 5 less likely to break.

[0098] <Peeling process> 8 and 9, in the peeling step, the adhesive sheet 10 is peeled off from the semiconductor wafer 4. The adhesive sheet 10 can be peeled off by bending the adhesive sheet 10 in a direction in which the adhesive sheet 10 moves away from the semiconductor wafer 4.

[0099] This completes the backside grinding process for the semiconductor wafer 4. When backside grinding is performed using an adhesive sheet in which the protrusions 5 are in contact with the adhesive, the adhesive may adhere to the protrusions 5. However, in this embodiment, the protrusions 5 do not contact the adhesive layer 2, and therefore adhesion of the adhesive to the protrusions 5 is suppressed.

[0100] Note that a dicing step may be performed before the peeling step. In the dicing step, the semiconductor wafer 4 is diced to divide the semiconductor wafer 4 into a plurality of semiconductor chips. The dicing method is not particularly limited, and may be any method such as blade dicing, laser dicing, stealth dicing, or plasma dicing.

[0101] After the dicing step, a plurality of semiconductor chips are attached to the adhesive sheet 10. Therefore, the peeling step is a step of peeling each of the plurality of semiconductor chips from the adhesive sheet 10.

[0102] 3. Base sheet As shown in Fig. 10, a base sheet 11 according to one embodiment of the present invention can have a configuration similar to that of the above-described base layer 1. That is, the base sheet 11 includes a cushion layer 1a and a surface treatment layer 1b provided thereon, the surface treatment layer 1b being formed of an acrylic resin composition containing an acrylic resin, and the acrylic resin being crosslinked by light irradiation or heating. The base sheet 11 may also include a barrier layer 1c. The descriptions of the base layer 1, cushion layer 1a, surface treatment layer 1b, and barrier layer 1c are the same as those in "1-1. Base layer 1."

[0103] The base sheet 11 can be used as the base layer 1 of the adhesive sheet 10 for backgrinding a semiconductor wafer 4 having protrusions 5. Alternatively, the base sheet 11 may be used as a sheet for backgrinding a semiconductor wafer 4 having protrusions 5 without providing the adhesive layer 2 on the base sheet 11. In this case, for example, after the enclosed space 2b formed by pressing the base sheet 11 against the semiconductor wafer 4 in the decompression chamber 16 described above in the <Wafer Attachment Step / Heating Step> of "2. Semiconductor Wafer Manufacturing Method" is decompressed, the base sheet 11 and the semiconductor wafer 4 are removed from the decompression chamber 16, whereby the base sheet 11 can be tightly attached to the semiconductor wafer 4 by the action of atmospheric pressure. To form the enclosed space 2b, for example, a ring-shaped packing having a shape similar to the adhesive layer 2 may be placed between the base sheet 11 and the semiconductor wafer 4. [Example]

[0104] 1. Manufacturing of adhesive sheet 10 Example 1 In Example 1, a pressure-sensitive adhesive sheet 10 was produced by forming a surface-treated layer 1b on a cushion layer 1a, and then forming a circular pressure-sensitive adhesive layer 2 having an opening 2a on the surface-treated layer 1b.

[0105] A more detailed explanation follows.

[0106] Preparation of cushion layer 1a First, a cushion layer 1a was prepared, which was composed of a 150 μm-thick metal ion crosslinked ethylene-methacrylic acid copolymer (Fanclea HMD, manufactured by Gunze Ltd.). The ethylene-methacrylic acid copolymer had a methacrylic acid unit ratio of 15 mass%, an MFR (JIS K7210, 125°C / 10.0 kg load) of 5 g / 10 min, and a melting point (JIS K7121) of 72°C.

[0107] Formation of surface treatment layer 1b An acrylic copolymer was polymerized using 80 parts by weight of ethyl acrylate, 12 parts by weight of methyl methacrylate, 5 parts by weight of 2-hydroxyethyl methacrylate, and 3 parts by weight of glycidyl methacrylate as constituent monomers, and 12 parts by weight of a crosslinking agent (Kyoeisha Chemical, Light Acrylate 1.9ND-A) and 1 part by weight of a photopolymerization initiator (BASF Omnilat 184) were added to 100 parts by weight of this acrylic copolymer to prepare a surface treatment agent. The acrylic copolymer had a Mw of 600,000 before crosslinking, a Tg of -7°C, and a Tg of 32°C after crosslinking.

[0108] Next, a surface treatment agent was coated on the cushion layer 1a, and the surface treatment layer 1b was formed to a thickness of 2 μm by UV irradiation.

[0109] Formation of adhesive layer 2 A liquid composition was prepared by mixing 54.4 parts by weight of hydrogenated polybutadiene diacrylate (Osaka Organic Chemical Co., Ltd., product name BAC-45), 13.6 parts by weight of isodecyl acrylate (Osaka Organic Chemical Co., Ltd., product name IDAA), 32 parts by weight of isobornyl acrylate (Osaka Organic Chemical Co., Ltd., product name IBXA), 7 parts by weight of α-aminoalkylphenone (BASF, product name Omnilat 379EG) as a photopolymerization initiator, 3 parts by weight of vinyl ether polymer (Kyoeisha Chemical Co., Ltd., FLOWLEN AC-903) as an antifoaming agent, and 3 parts by weight of isocyanate (Asahi Kasei Corporation, product name "TPA-100") as a crosslinking agent. This composition was screen-printed into a specific shape onto the surface treatment layer 1b, irradiated with UV light, and aged at 40°C for 4 days to form a 10 μm-thick circular pressure-sensitive adhesive layer 2.

[0110] <Example 2> An adhesive sheet 10 was produced in the same manner as in Example 1, except that the surface treatment layer 1b was formed after the cushion layer 1a was subjected to a corona discharge treatment.

[0111] Example 3 An adhesive sheet 10 was produced in the same manner as in Example 1, except that the surface treatment layer 1b was formed by the method described below.

[0112] Formation of surface treatment layer 1b An acrylic copolymer was polymerized using 50 parts by weight of ethyl acrylate, 42 parts by weight of methyl methacrylate, 5 parts by weight of 2-hydroxyethyl methacrylate, and 3 parts by weight of glycidyl methacrylate as constituent monomers, and 2 parts by weight of an isocyanate crosslinking agent (Coronate L-45E, manufactured by Nippon Polyurethane Co., Ltd.) was added to 100 parts by weight of this acrylic copolymer to prepare a surface treatment agent. The acrylic copolymer had an Mw of 600,000 and a Tg of 24°C before crosslinking, and a Tg of 61°C after crosslinking.

[0113] Next, a surface treatment agent was coated on the cushion layer 1a, and the surface treatment layer 1b was formed to a thickness of 2 μm by heating at 40° C. for 7 days.

[0114] Example 4 An adhesive sheet 10 was produced in the same manner as in Example 3, except that the surface treatment layer 1b was formed after the cushion layer 1a was subjected to a corona discharge treatment.

[0115] <Comparative Example 1> An adhesive sheet 10 was produced in the same manner as in Example 1, except that the surface treatment layer 1b was not formed and the adhesive layer 2 was formed on the cushion layer 1a.

[0116] <Comparative Example 2> An adhesive sheet 10 was produced in the same manner as in Example 2, except that the surface treatment layer 1b was not formed and the adhesive layer 2 was formed on the cushion layer 1a.

[0117] <Comparative Example 3> The adhesive sheet 10 was produced in the same manner as in Example 2, except that the surface treatment layer 1b was formed by the method described below.

[0118] Formation of surface treatment layer 1b An acrylic copolymer having constituent monomers of 50 parts by mass of ethyl acrylate, 42 parts by mass of methyl methacrylate, 5 parts by mass of 2-hydroxyethyl methacrylate, and 3 parts by mass of glycidyl methacrylate was polymerized and coated on cushion layer 1a as a surface treatment agent to form surface treatment layer 1b.

[0119] <Comparative Example 4> An adhesive sheet 10 was produced in the same manner as in Example 2, except that the adhesive layer 2 was formed in the following manner.

[0120] Formation of adhesive layer 2 A rubber-based pressure-sensitive adhesive composition solution was prepared by dissolving 100 parts by weight of natural rubber (Mooney viscosity 75), 30 parts by weight of SIS (Zeon Corporation, product name "Quintac 3460C," radial structure SIS, styrene content 25% by weight), and 40 parts by weight of maleic anhydride-modified C5,C9 resin (Zeon Corporation, product name "Quinton D-200") in toluene, followed by the addition of 3 parts by weight of aromatic isocyanate (Nippon Polyurethane Co., Ltd., product name "Coronate L") as a crosslinking agent. This composition was coated onto a separator and heat-cured to obtain a 10 μm-thick pressure-sensitive adhesive film. The resulting pressure-sensitive adhesive film was punched into a shape with an opening and laminated onto the surface-treated layer to form a 10 μm-thick circular pressure-sensitive adhesive layer 2.

[0121] 2. Backside grinding of semiconductor wafers Using the adhesive sheet 10 produced above, the backside of the semiconductor wafer 4 was ground by the following method.

[0122] <Frame attachment process> First, the adhesive sheet 10 was attached to the ring frame 3.

[0123] <Wafer bonding process / heating process> Next, the adhesive sheet 10 was attached to the outer peripheral portion 4a of the semiconductor wafer 4 on the surface on which the protrusions 5 of the semiconductor wafer 4 were formed in a decompression chamber 16. The semiconductor wafer 4 used had a diameter of 8 inches, a thickness of 725 μm, and had bumps (protruding electrodes) with a height of 230 μm formed in an area other than 3.0 mm from the outer periphery. The width of the attachment surface where the semiconductor wafer 4 was attached to the adhesive layer 2 was 2.0 mm. The pressure inside the decompression chamber 16 was 100 Pa. Inside the decompression chamber 16, the base layer 1 was heated to 100°C.

[0124] Next, the adhesive sheet 10 with the semiconductor wafer 4 attached thereto was removed from the decompression chamber 16 .

[0125] <Cutting process> Next, the adhesive sheet 10 was cut along the outer periphery of the semiconductor wafer 4 to separate the ring frame 3 from the adhesive sheet 10.

[0126] <Resin curing process> Next, with the adhesive sheet 10 facing the curable resin 8 supplied on the support film 7, the adhesive sheet 10 was moved in the in-plane direction of the support film 7 to spread the curable resin 8. The curable resin 8 used was composed of 1,2-hydrogenated polybutadiene-terminated urethane (meth)acrylate, isobornyl acrylate, and diethylacrylamide. The viscosity of the curable resin 8 before curing (measured using an E-type viscometer at 23°C and 50 rpm) was 470 mPa s.

[0127] Next, the base layer 1 was brought into contact with the curable resin 8, and the curable resin 8 was cured to form a cured resin 18. The curable resin 8 was irradiated from the support film 7 side with an integrated light intensity of 2000 mJ / cm 2 at a wavelength of 365 nm. 2 The cured resin 18 had a Shore D hardness (JIS K 6253) of 15.

[0128] <Grinding process> Next, the back surface of the semiconductor wafer 4 was ground until the thickness of the semiconductor wafer 4 reached 200 μm. The back surface was ground using a grinding machine (Back Grinder DFG-841 manufactured by Disco Corporation).

[0129] <Peeling process> Next, the adhesive sheet 10 was peeled off from the semiconductor wafer 4.

[0130] 3. Evaluation The produced pressure-sensitive adhesive sheet 10 was subjected to various evaluations. The results are shown in Table 1.

[0131] As shown in Table 1, all Examples obtained good results in all evaluation items. In Comparative Example 1, in which the cushion layer 1a was not subjected to corona discharge treatment and no surface treatment layer 1b was formed, the adhesion between the base layer 1 and the pressure-sensitive adhesive layer 2 was insufficient. In Comparative Example 2, in which the cushion layer 1a was subjected to corona discharge treatment and no surface treatment layer 1b was formed, the peelability between the base layer 1 and the wafer 4 was insufficient. In Comparative Example 3, in which a non-crosslinked surface treatment layer 1b was provided, not only was the adhesion between the cushion layer 1a and the surface treatment layer 1b insufficient, but adhesive residue also occurred on the wafer. In Comparative Example 4, in which the pressure-sensitive adhesive layer 2 was formed using a natural rubber-based pressure-sensitive adhesive, the adhesion between the base layer 1 and the pressure-sensitive adhesive layer 2 was insufficient.

[0132] [Table 1]

[0133] The details of the evaluation method are as follows. <Bump-following ability> The bump-following ability was evaluated by the following method.

[0134] After the cutting process of "2. Grinding the backside of the semiconductor wafer" was performed, the adhesive sheet 10 to which the semiconductor wafer 4 was attached was measured for the distance that the base layer 1 followed between the bumps, and the following rate (= distance that the base layer 1 followed between the bumps / height of the bump) was calculated.

[0135] The bump-following property was evaluated based on the following criteria from the follow-up rate. Excellent: Tracking rate of 70% or more × (Not acceptable): Tracking rate less than 70%

[0136] <Adhesion between cushion layer and surface treatment layer> The surface treatment layer 1b formed on the cushion layer 1a is provided with a grid cross-cut (1 mm 2 After applying a grid pattern (100 squares of this type), a cellophane adhesive tape conforming to JIS Z 1522 (manufactured by Nichiban Co., Ltd.) was attached to the surface treatment layer 1b, pressed firmly with a finger, and then peeled off in a 90° direction, and the surface treatment layer 1b was evaluated for peeling. 〇(Excellent): No peeling × (Not acceptable): Peeling

[0137] <Adhesion between the base layer and the adhesive layer> After the peeling step of "2. Grinding the backside of the semiconductor wafer" was carried out, the adhesive layer 2 of the adhesive sheet 10 was visually inspected for peeling. 〇(Excellent): No peeling × (Unacceptable): More than half or the whole has peeled off

[0138] <Adhesion and peelability between substrate layer and wafer> The adhesive strength between the substrate layer and the wafer was measured using the following method. A 10 mm wide and 100 mm long test piece was cut from a portion of the adhesive sheet 10 near the center where the adhesive layer 2 was not formed (i.e., the portion where the substrate layer was exposed). This test piece was used to measure adhesive strength in accordance with JIS Z0237 (2009) (Method 1: Test method in which the tape and sheet are peeled at 180° from a stainless steel test plate). Specifically, the test piece was pressure-bonded to a surface-cleaned adherend (a Si wafer) using a pressure-bonding device (roller weight 2 kg), and then heated on a hot plate at 100°C for 1 minute. The adhesive strength when the test piece was peeled at 180° from the adherend was measured using a universal tensile tester (ORIENTEC Corporation, Tensilon, model number: RTG-1210) under the following conditions at a temperature of 23°C and a humidity of 50%, and the measurement results were converted to a value for a 200 mm width. Measurement mode: Tensile Pulling speed: 300 mm / min Chuck distance: 50mm Measurement sample width: 10 mm

[0139] From the obtained adhesive strength measurement results, the peelability between the base layer and the wafer was evaluated according to the following criteria. 〇(Excellent): 0.5~50N / 200mm ×(Not allowed): More than 50N / 200mm

[0140] <Adhesive residue on wafer> Furthermore, in the above test, the presence or absence of adhesive residue on the silicon wafer after peeling was visually confirmed and evaluated according to the following criteria. ○ (Excellent): No adhesive residue × (Not acceptable): Glue remains

[0141] <Storage modulus E' of surface treatment layer at 180°C> The surface treatment agent used in each example and comparative example was applied to the release-treated surface of a release-treated polyethylene terephthalate film and dried at 100°C for 1 minute to obtain a 25 μm surface treatment layer. After the curing reaction, the surface treatment layer was cut into a 3 mm wide and 7 mm long sample. Measurements were performed in tension mode using a viscoelasticity measuring device (TA Instruments RSA-3) under the following conditions to obtain the storage modulus E' at 180°C. Frequency f=1Hz Temperature 30~180℃ Heating rate: 5℃ / min Chuck distance 10mm [Explanation of symbols]

[0142] 1: base layer, 1a: cushion layer, 1b: surface treatment layer, 1c: barrier layer, 2: adhesive layer, 2a: opening, 2b: sealed space, 3: ring frame, 3a: opening, 4: semiconductor wafer, 4a: outer periphery, 4b: back surface, 5: convex portion, 6: decompression unit, 6a: decompression hole, 7: support film, 8: curable resin, 9: energy beam, 10: adhesive sheet, 11: base sheet, 16: decompression chamber, 18: curable resin

Claims

1. An adhesive sheet for backgrinding a semiconductor wafer having a convex portion, A substrate layer and a pressure-sensitive adhesive layer provided on the substrate layer, the pressure-sensitive adhesive layer has an opening with a diameter smaller than the diameter of the semiconductor wafer, and is attached to the outer periphery of the semiconductor wafer so that a convex portion of the semiconductor wafer is positioned within the opening, The semiconductor wafer is configured so that the convex portions are protected by the base layer when the semiconductor wafer is attached to the adhesive layer, the base material layer includes a cushion layer and a surface treatment layer provided thereon; the pressure-sensitive adhesive layer is provided on the surface treatment layer, the surface treatment layer is formed of an acrylic resin composition containing an acrylic resin, and the acrylic resin is crosslinked by light irradiation or heating; The pressure-sensitive adhesive sheet, wherein the pressure-sensitive adhesive layer is formed from an acrylic resin composition containing an acrylic resin.

2. The pressure-sensitive adhesive sheet according to claim 1, A base sheet, wherein the storage modulus of the cushion layer at 180°C is lower than the storage modulus of the surface treatment layer at 180°C.

3. The pressure-sensitive adhesive sheet according to claim 1 or claim 2, The storage modulus of the surface treatment layer at 180°C is 1.0 × 10 ４ Pa ~ 1.0 x 10 ８ Pa, adhesive sheet.

4. The pressure-sensitive adhesive sheet according to claim 1 or claim 2, The pressure-sensitive adhesive sheet, wherein the convex portions are protected by being embedded in the base layer.

5. The pressure-sensitive adhesive sheet according to claim 1 or claim 2, The semiconductor wafer is attached to the adhesive layer under reduced pressure.

6. The pressure-sensitive adhesive sheet according to claim 1 or claim 2, A pressure-sensitive adhesive sheet in which the semiconductor wafer to which the base layer of a test piece cut out from the pressure-sensitive adhesive sheet has been bonded is heated in an atmosphere of 100°C for 1 minute, and after cooling to room temperature, the adhesive strength between the base layer and the semiconductor wafer at 23°C measured in accordance with JIS Z0237 is less than 6 N / 200 mm.

7. A method for manufacturing a semiconductor wafer using the pressure-sensitive adhesive sheet according to claim 1 or 2, The method includes a frame attaching step, a wafer attaching step, a heating step, a cutting step, a resin curing step, and a grinding step, In the frame attaching step, the adhesive sheet is attached to a ring frame, In the wafer bonding step, the pressure-sensitive adhesive sheet is bonded to the outer periphery of the semiconductor wafer on the surface of the semiconductor wafer on which the convex portion is provided under reduced pressure; In the heating step, the base material layer is heated, In the cutting step, the adhesive sheet is cut along the outer periphery of the semiconductor wafer, In the resin curing step, after the wafer bonding step, the base layer is brought into contact with a curable resin, and the curable resin is cured in this state; In the grinding step, a back surface of the semiconductor wafer is ground.

8. A substrate sheet for back grinding, comprising: The cushioning layer has a surface treatment layer formed thereon, the surface treatment layer is formed of an acrylic resin composition containing an acrylic resin, and the acrylic resin is crosslinked by light irradiation or heating; A base sheet, wherein the storage modulus of the cushion layer at 180°C is lower than the storage modulus of the surface treatment layer at 180°C.

9. The substrate sheet according to claim 8, The storage modulus of the surface treatment layer at 180°C is 1.0 × 10 ４ Pa ~ 1.0 x 10 ８ Pa.

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