Wafer processing film and wafer processing method

Abstract

To provide a wafer processing film which is less likely to cause contamination of a wafer when the film is peeled off from the wafer, and provide a wafer processing method using the wafer processing film.SOLUTION: The present invention provides a wafer processing film to be used by being bonded to an element forming surface of a wafer in a back grinding step. A wetting tension T75 at 75°C on a main surface of the wafer processing film in contact with the element forming surface is 32 mN / m or more and 40 mN / m or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a wafer processing film and a wafer processing method. [Background technology]

[0002] In the backgrinding process of a semiconductor wafer (hereinafter also referred to as "wafer"), the surface of the wafer on which elements and the like are formed is attached to a backgrinding tape (hereinafter also referred to as "wafer processing film"), the back surface of the wafer is backgrinded, and then the backgrinding tape is peeled off from the wafer.

[0003] As such a backgrind tape, for example, Patent Document 1 discloses an adhesive film including a base layer, an irregularity-absorbing resin layer, and an adhesive resin layer in this order. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-065168 Summary of the Invention [Problem to be solved by the invention]

[0005] Patent document 1 explains that by providing an adhesive film with an irregularity-absorbing resin layer, the irregularities caused by the bumps can be absorbed even if the size of the bumps formed on the surface of the wafer becomes large, and that by making the irregularity-absorbing resin layer have a specific composition, the cutting ability of the adhesive film can be improved.

[0006] However, if the adhesive strength of the backgrind tape is high, adhesive components of the backgrind tape may remain on the wafer when the backgrind tape is peeled off from the wafer, contaminating the wafer.

[0007] The present invention has been made in consideration of the above problems, and aims to provide a wafer processing film that is less likely to contaminate a wafer when peeled off from the wafer, and a wafer processing method using the wafer processing film. [Means for solving the problem]

[0008] The present inventors have conducted extensive research to solve the above problems. As a result, it has been found that the wetting tension T 75 The present inventors have found that the above problems can be solved by setting the strain to 32 mN / m or more and 40 mN / m or less, and have completed the present invention.

[0009] That is, the present invention is as follows. [1] A wafer processing film used by being attached to the element formation surface of a wafer in a back grinding process, The wetting tension T at 75°C on the main surface of the wafer processing film that is in contact with the element formation surface 75 is 32mN / m or more and 40mN / m or less, Film for wafer processing. [2] It has a structure in which a substrate layer and a coating layer are laminated in this order, The main surface is the surface of the coating layer. [1] The wafer processing film according to the present invention. [3] Further, an adhesive layer is laminated on the coating layer, the adhesive layer has an opening with a diameter smaller than the diameter of the wafer; The main surface is a surface of the coating layer at the opening. [2] The wafer processing film according to [2]. [4] the substrate layer contains a (meth)acrylic ionomer, the coating layer contains a base polymer containing a (meth)acrylic acid ester copolymer, a monomer, and a photopolymerization initiator; The content of the monomer is 1 to 20 parts by mass relative to 100 parts by mass of the base polymer. [2] or [3], the wafer processing film. [5] Wetting tension T on the main surface at 25°C 25 is 32mN / m or more, The film for wafer processing according to any one of [1] to [4]. [6] a bonding step of bonding the main surface of the wafer processing film according to any one of [1] to [5] to the element formation surface of the wafer; a back grinding step of grinding a non-element forming surface of the wafer bonded to the wafer processing film, Wafer processing method. [7] The method further includes a dicing step of dicing the wafer. [6] The wafer processing method according to [6]. [8] In the dicing step, a modified portion is generated inside the wafer by stealth dicing. [7] The wafer processing method according to [7]. [9] After the back-grinding step, a peeling step of heating and peeling off the wafer processing film is included. The wafer processing method according to any one of [6] to [8]. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a wafer processing film that is less likely to contaminate a wafer when peeled off from the wafer, and a wafer processing method using the wafer processing film. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1(a) shows an example of a perspective view of the wafer processing film of this embodiment, and FIG. 1(b) shows an example of a cross-sectional view taken along line AA' in FIG. 1(a). [Figure 2]An example of a wafer 2 to be attached to a wafer processing film 1 is shown. [Figure 3] FIG. 3(a) shows an example of a perspective view of the back grinding process, and FIG. 3(b) shows an example of a cross-sectional view taken along line AA' in FIG. 3(a). [Figure 4] FIG. 4(a) shows an example of a perspective view of the dicing step, and FIG. 4(b) shows an example of a cross-sectional view taken along line AA' in FIG. 4(a). DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described in detail with reference to the drawings as necessary, but the present invention is not limited to this, and various modifications are possible without departing from the spirit of the present invention. In the drawings, the same elements are given the same reference numerals, and redundant explanations will be omitted. Furthermore, positional relationships such as up, down, left, and right will be based on the positional relationships shown in the drawings unless otherwise specified. Furthermore, the dimensional ratios of the drawings are not limited to those shown in the drawings.

[0013] 1.Wafer processing film The wafer processing film of this embodiment is a wafer processing film that is used by being attached to the element forming surface of a wafer in a back grinding process, and has a wet tension T at 75°C on the main surface of the wafer processing film that contacts the element forming surface. 75 is between 32mN / m and 40mN / m.

[0014] FIG. 1(a) shows an example of a perspective view of the wafer processing film of this embodiment, and FIG. 1(b) shows an example of a cross-sectional view taken along line A-A' in FIG. 1(a). The wafer processing film 1 of this embodiment may have a structure in which a base layer 10 and a coating layer 11 are laminated in this order. The coating layer 11 may be laminated on the first surface 101 of the base layer 10, or an intermediate layer may be provided as necessary from the viewpoint of interlayer adhesion and bonding. In this case, the main surface 1a in contact with the device-forming surface of the wafer 2 becomes the first surface 111 of the coating layer 11.

[0015] The wafer processing film 1 may also have an adhesive layer laminated on the coating layer 11. The adhesive layer may have an opening (opening area) with a diameter smaller than the diameter of the wafer 2. In this case, the main surface 1a becomes the first surface 111 of the coating layer 11 in the opening.

[0016] In addition, an intermediate layer may be provided between the layers as needed from the viewpoint of adhesion and bonding between the layers.

[0017] 2 shows an example of a wafer 2 attached to the wafer processing film 1. The wafer 2 has an element-forming surface 21 on which elements 23 such as circuits are formed, and a non-element-forming surface 22 opposite the element-forming surface 21 on which no elements 23 are formed. The element-forming surface 21 has a central region 211 where the elements 23 are present and an outer edge region 212 where no elements 23 are present.

[0018] The wafer 2 is not particularly limited, but may be a conventional general-purpose semiconductor wafer such as a silicon wafer, a gallium nitride wafer, a silicon carbide wafer, or a sapphire wafer.

[0019] The wafer processing film 1 is bonded to the element-forming surface 21 of the wafer 2 before back-grinding the non-element-forming surface 22 of the wafer 2. After back-grinding, the wafer processing film 1 is peeled off from the wafer 2. There are no particular restrictions on the conditions for peeling, but the film may be peeled off while heated in order to soften the main surface so as not to damage the element-forming surface 21. Here, it is necessary to prevent contamination from the wafer processing film 1 from occurring on the wafer 2 after the wafer processing film 1 has been peeled off. In addition, the wafer processing film 1 and the wafer 2 must be in sufficient contact with each other during back-grinding.

[0020] From this viewpoint, in the wafer processing film 1 of this embodiment, the wetting tension T 75The wetting tension T is specified to be 32 to 40 mN / m. 75 By making the wetting tension T 75 When the adhesive strength is 32 mN / m or more, the wafer processing film 1 has an appropriate adhesion to the wafer 2. Because the wafer processing film 1 is prevented from adhering excessively to the wafer 2, the releasability when peeling the wafer processing film 1 from the wafer 2 is improved, and as a result, contamination of the wafer 2 after the wafer processing film 1 is peeled away is prevented. In other words, the contamination of the wafer processing film 1 is reduced. Furthermore, because the wafer processing film 1 has an appropriate adhesive strength to the wafer 2, the wafer processing film 1 tends to be able to fix the wafer 2 to a sufficient degree. In other words, the fixation of the wafer processing film 1 tends to be improved.

[0021] Wetting tension T on main surface 1a at 75°C 75 is preferably 33 to 39 mN / m, and more preferably 34 to 38 mN / m.

[0022] In this embodiment, 75°C is used as a reference value for the temperature when peeling the wafer processing film 1 from the wafer 2. In this regard, it is assumed that the wafer processing film 1 may be peeled from the wafer 2 at a temperature higher or lower than 75°C in some cases. However, even if the actual temperature when peeling the wafer processing film 1 from the wafer 2 is not 75°C but is higher or lower than this, the wetting tension T measured with 75°C as the reference is 75 When the thickness satisfies the predetermined range, the contamination of the wafer processing film 1 is reduced and the adhesive strength is improved.

[0023] Furthermore, it is preferable that the wafer processing film 1 can sufficiently fix the wafer 2 when the non-element forming surface 22 of the wafer 2 is back-ground at room temperature.

[0024] From this viewpoint, the wetting tension T 25is preferably 32 mN / m or more, 32 to 40 mN / m, 33 to 39 mN / m, or 34 to 38 mN / m. 25 When the thickness is within the above range, the adhesion between the wafer processing film 1 and the wafer 2 is improved, and as a result, the wafer processing film 1 tends to be able to sufficiently fix the wafer 2. In other words, the fixation of the wafer processing film 1 tends to be improved.

[0025] In this embodiment, 25°C is used as a reference value for the temperature when back-grinding the non-element-formed surface 22 of the wafer 2. In this regard, it is conceivable that the non-element-formed surface 22 of the wafer 2 may be back-ground at a temperature higher or lower than 25°C in some cases. However, even if the actual temperature when back-grinding the non-element-formed surface 22 of the wafer 2 is not 25°C but is higher or lower than this, the wet tension T measured with 25°C as the reference is 25 If the value satisfies the predetermined range, the fixation of the wafer processing film 1 can be improved when the non-element forming surface 22 of the wafer 2 is back-ground.

[0026] Wetting tension T on the main surface 1a at 25°C 25 Wetting tension T at 75°C 75 The ratio (T 75 / T 25 ) is preferably 0.2 to 2.0, 0.5 to 1.5, or 0.7 to 1.3. 75 / T 25 When the thickness is within the above range, the contamination of the wafer processing film 1 tends to be reduced and the fixation tends to be improved.

[0027] Wetting tension T on the main surface 1a at 25°C 25 and wetting tension T at 75°C 75 can be adjusted by the type and composition of the material that forms the main surface 1a, and by the corona treatment.

[0028] Each component of the wafer processing film of this embodiment will be described in detail below.

[0029] 1.1. Base material layer The wafer processing film 1 of this embodiment may have a base layer 10.

[0030] The thickness of the base layer 10 is preferably 10 to 500 μm, 25 to 250 μm, 50 to 200 μm, 100 to 175 μm, or 120 to 160 μm. When the thickness of the base layer 10 is within the above range, the base layer 10 absorbs the irregularities on the element forming surface 21 of the wafer 2, making it easier for the wafer processing film 1 to adhere to the wafer 2. As a result, the fixation of the wafer processing film 1 tends to be improved.

[0031] The base layer 10 preferably contains a resin. The resin is not particularly limited, but examples thereof include ionomer resin, polyvinyl chloride, polyethylene terephthalate, ethylene-vinyl acetate copolymer, ethylene-acrylic acid-acrylic acid ester film, ethylene-ethyl acrylate copolymer, polyethylene, polypropylene, propylene-based copolymer, and ethylene-acrylic acid copolymer. Among these, ionomer resin is preferred. These resins may be used alone or in combination of two or more. More specifically, a mixture, copolymer, or laminate of one of these resins with another may be used.

[0032] Ionomer resins have a cross-linked structure formed by metal ions, and therefore can maintain shape stability even when exposed to temporary or localized high temperatures, such as those encountered during semiconductor processing.

[0033] The ionomer resin is not particularly limited as long as it is a resin in which a predetermined polymer is intermolecularly bonded by a metal ion, and examples thereof include polyolefin-based ionomers, (meth)acrylic ionomers, polystyrene-based ionomers, and polyester-based ionomers. These ionomer resins may be used alone or in combination of two or more. Among these, polyolefin-based ionomers and (meth)acrylic ionomers are preferred, and (meth)acrylic ionomers are more preferred.

[0034] The polyolefin ionomer is not particularly limited, but examples thereof include ethylene-methacrylate copolymer, ethylene-acrylate copolymer, and ethylene-methacrylate-acrylate copolymer.

[0035] The (meth)acrylic ionomer is not particularly limited, but examples thereof include an acrylic acid ester-acrylate copolymer, an acrylic acid ester-methacrylate copolymer, a methacrylic acid ester-acrylate copolymer, a methacrylic acid ester-methacrylate copolymer, and an ethylene-methacrylic acid-acrylate copolymer. Note that the ethylene-methacrylic acid-acrylate copolymer as a (meth)acrylic ionomer is also referred to as an ethylene-methacrylic acid-acrylate ionomer.

[0036] The polystyrene ionomer is not particularly limited, but examples thereof include a styrene-styrene sulfonate copolymer, a styrene-acrylate copolymer, a styrene-methacrylate copolymer, a styrene-styrene carboxylate copolymer, and a styrene-N-methyl 4-vinylpyridinium salt copolymer.

[0037] The polyester ionomer is not particularly limited, but examples thereof include sulfoterephthalic acid salt copolymerized polyethylene terephthalate, sulfoisophthalic acid salt copolymerized polyethylene terephthalate, sulfoterephthalic acid copolymerized polybutylene terephthalate, and sulfoisophthalic acid copolymerized polybutylene terephthalate.

[0038] The metal ions constituting the salt of the ionomer resin are not particularly limited, but examples thereof include monovalent metal ions such as sodium ions and lithium ions; divalent metal ions such as zinc ions, calcium ions, and magnesium ions; and trivalent metal ions such as aluminum ions, with zinc ions being preferred. The polymer and metal ions in the ionomer resin can be used in any combination based on the ionic functional group in the polymer and the valence of the metal ions.

[0039] The content of the resin in the base layer 10 is preferably 80 to 100 mass %, 85 to 98 mass %, or 90 to 95 mass %, based on the entire base layer 10.

[0040] The substrate layer 10 may contain additives other than resins as needed. Examples of additives include, but are not limited to, plasticizers, heat stabilizers, colorants, organic lubricants, inorganic lubricants, surfactants, processing aids, and antistatic agents. The additives may be used alone or in combination.

[0041] The content of the additives relative to the entire base layer 10 is preferably 0.1 to 10.0 mass %, 0.5 to 5.0 mass %, or 1.0 to 2.5 mass %.

[0042] The substrate layer 10 may be a single layer or multi-layer structure comprising the materials described above.

[0043] The first surface 101 side of the base layer 10 may be hydrophilized. The hydrophilization treatment is not particularly limited, but examples thereof include corona treatment and plasma treatment. When the first surface 101 side is hydrophilized, the first surface 101 of the base layer 10 becomes hydrophilic, and as a result, the fixation of the wafer processing film 1 tends to be improved.

[0044] 1.2.Coating Layer The wafer processing film 1 of this embodiment may have a coating layer 11. The main surface 1a is preferably a first surface 111 of the coating layer 11. The coating layer 11 contributes to the peelability between the wafer processing film 1 and the wafer 2. The coating layer 11 may be provided on the entire first surface 101 of the base layer 10, or may be provided on a partial region of the first surface 101.

[0045] When the main surface 1a of the wafer processing film 1 is the first surface 111 of the coating layer 11, the wet tension T 75 The wetting tension T at 75°C is 32 to 40 mN / m, preferably 33 to 39 mN / m, and more preferably 34 to 38 mN / m. 75 When the thickness is within the above range, the contamination of the wafer processing film 1 tends to be reduced and the fixation tends to be improved.

[0046] When the main surface 1a of the wafer processing film 1 is the first surface 111 of the coating layer 11, the wetting tension T 25 is preferably 32 mN / m or more, 32 to 40 mN / m, 33 to 39 mN / m, or 34 to 38 mN / m. 25 When the thickness is within the above range, the fixation of the wafer processing film 1 tends to be improved.

[0047] When the main surface 1a of the wafer processing film 1 is the first surface 111 of the coating layer 11, the wetting tension T 25 Wetting tension T at 75°C 75 The ratio (T 75 / T 25 ) is preferably 0.2 to 2.0, 0.5 to 1.5, or 0.7 to 1.3. 75 / T 25 When the thickness is within the above range, the contamination of the wafer processing film 1 tends to be reduced and the fixation tends to be improved.

[0048] Wetting tension T on the first surface 111 at 25°C 25and wetting tension T at 75°C 75 can be adjusted by the type and composition of the material constituting the coating layer 11 and the UV irradiation. Specifically, the wetting tension increases when the proportion of hydrophilic groups in the coating layer is increased.

[0049] The wet tension is measured in accordance with the wet tension test method described in JIS K6768:1999, except that the temperature condition is 25°C or 75°C.

[0050] The thickness of the coating layer 11 is preferably 1 to 10 μm, 1 to 5 μm, or 1 to 4 μm.

[0051] The coating layer 11 may contain a base polymer, a monomer, a photopolymerization initiator, and a curing agent. By containing the monomer and the photopolymerization initiator, a coating layer composition serving as a precursor of the coating layer 11 is applied to the base layer, and then a polymerization reaction proceeds by irradiating the composition with light, thereby forming the coating layer 11.

[0052] When the base polymer contained in the coating layer composition has hydroxyl groups or epoxy groups, the hydroxyl groups or epoxy groups tend to crosslink, resulting in a reaction in which the base polymers crosslink with each other. The glass transition temperature Tg of the coating layer composition after the crosslinking reaction is preferably 20 to 80°C, 25 to 70°C, or 30 to 65°C. When the glass transition temperature Tg of the coating layer composition after the crosslinking reaction is 20°C or higher, the contamination of the wafer processing film 1 tends to be reduced. Furthermore, when the glass transition point of the coating layer composition after the crosslinking reaction is 80°C or lower, the fixation property of the wafer processing film 1 tends to be improved.

[0053] 1.2.1. Base polymer By including a base polymer in the coating layer 11, the elastic modulus is reduced and flexibility is improved, making it easier for the wafer processing film 1 to adhere appropriately to the wafer 2, which tends to improve the fixation of the wafer processing film 1. The base polymer is a component that constitutes the main component of the coating layer 11.

[0054] The base polymer is not particularly limited, but examples thereof include (meth)acrylic acid ester copolymers having polymerizable double bonds. The shape of the (meth)acrylic acid ester copolymer is not particularly limited, but examples thereof include linear, branched, and crosslinked shapes. Among these, crosslinked shapes are preferred. By using such a base polymer, the adhesion between the wafer processing film 1 and the wafer 2 becomes appropriate, which results in improved fixation of the wafer processing film 1 and tends to reduce contamination of the wafer processing film 1. The crosslinked or branched base polymer may be one in which epoxy groups or the like of a linear or branched base polymer are bonded via a curing agent, which will be described later.

[0055] The (meth)acrylic acid ester monomer constituting the (meth)acrylic acid ester copolymer is not particularly limited, and examples thereof include alkyl (meth)acrylates having a linear or branched alkyl group such as methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl, isobutyl, amyl, isoamyl, hexyl, heptyl, cyclohexyl, 2-ethylhexyl, octyl, isooctyl, nonyl, isononyl, decyl, isodecyl, undecyl, lauryl, tridecyl, tetradecyl, stearyl, octadecyl, and dodecyl. These alkyl (meth)acrylates may be used alone or in combination of two or more.

[0056] Furthermore, the monomer component other than the alkyl (meth)acrylate is not particularly limited, but examples thereof include carboxyl group-containing monomers such as acrylic acid, methacrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid; acid anhydride monomers such as maleic anhydride and itaconic anhydride; 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 1-hydroxypropyl (meth)acrylate, 2 ... Examples of suitable monomers include hydroxyl group-containing monomers such as hydroxydecyl, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)methyl (meth)acrylate; sulfonic acid group-containing monomers such as styrenesulfonic acid, allylsulfonic acid, 2-(meth)acrylamido-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, sulfopropyl (meth)acrylate, and (meth)acryloyloxynaphthalenesulfonic acid; phosphoric acid group-containing monomers such as 2-hydroxyethylacryloylphosphate; and epoxy group-containing monomers such as glycidyl (meth)acrylate. These other monomers may be used alone or in combination of two or more.

[0057] Among these, (meth)acrylic acid ester copolymers containing an alkyl (meth)acrylate and a carboxyl group-containing monomer, (meth)acrylic acid ester copolymers containing an alkyl (meth)acrylate and a hydroxyl group-containing monomer, and (meth)acrylic acid ester copolymers containing an alkyl (meth)acrylate, a hydroxyl group-containing monomer, and an epoxy group-containing monomer are preferred.

[0058] The base polymer preferably has a hydroxyl group or an epoxy group, which may be derived from a hydroxyl group-containing monomer or an epoxy group-containing monomer, a hydroxyl group or an epoxy group derived from a modifying agent, or a hydroxyl group or an epoxy group generated by a reaction between a monomer unit such as a carboxyl group-containing monomer and a modifying agent.

[0059] When the base polymer has hydroxyl groups or epoxy groups, the multiple polymers can be further crosslinked via the hydroxyl groups or epoxy groups, which tends to further improve the cohesive strength of the coating layer 11 and reduce the contamination of the wafer processing film 1. This crosslinking reaction between the polymers may be accelerated by using a curing agent, which will be described later.

[0060] Among the monomer units contained in the base polymer, the total amount of monomer units having a hydroxyl group or an epoxy group is preferably 1.0 to 30.0 mol%, 1.5 to 25.0 mol%, or 2.0 to 20.0 mol%, relative to 100 mol% of all monomer units. When the total amount of monomer units having a hydroxyl group or an epoxy group is within the above range, the cohesive strength of the coating layer 11 is further improved, and the contamination of the wafer processing film 1 tends to be reduced.

[0061] The weight average molecular weight of the base polymer is preferably 1.0×10 5 ~2.0×10 6 is 2.0 × 10 5 ~1.0×10 6 is 2.5 × 10 5 ~8.0×10 5 The weight average molecular weight of the base polymer is 1.0 × 10 5 By satisfying the above condition, the amount of high molecular weight components increases, and the higher the molecular weight, the more opportunities there are for one base polymer to polymerize with another base polymer via a polymerizable double bond, which tends to reduce the contamination of the wafer processing film 1. 6By satisfying the condition below, the base polymers are more mobile and there are more opportunities for one base polymer to polymerize with another base polymer, which tends to reduce contamination of the wafer processing film 1.

[0062] The "weight average molecular weight" described in this specification is the molecular weight measured using a gel permeation chromatograph of a sample prepared by dissolving a base polymer in tetrahydrofuran. The content of component A1 can be determined by calculating the percentage of the area of ​​the chromatogram at the retention time at which the weight average molecular weight is 20,000 or less, based on a standard polystyrene-equivalent molecular weight calibration curve, assuming the area of ​​the chromatogram of the base polymer to be 100%.

[0063] The glass transition temperature Tg of the base polymer before the crosslinking reaction is preferably −80 to 40° C., −60 to 30° C., or −40 to 25° C. If the glass transition temperature Tg of the base polymer before the crosslinking reaction is −80° C. or higher, the contamination of the wafer processing film 1 tends to be reduced. If the glass transition point of the base polymer before the crosslinking reaction is 40° C. or lower, the fixation of the wafer processing film 1 tends to be improved.

[0064] The glass transition temperature Tg of the base polymer after the crosslinking reaction is preferably 20 to 80° C., 25 to 70° C., or 30 to 65° C. When the glass transition temperature Tg of the base polymer after the crosslinking reaction is 20° C. or higher, the contamination of the wafer processing film 1 tends to be reduced. Furthermore, when the glass transition point of the base polymer after the crosslinking reaction is 80° C. or lower, the fixation property of the wafer processing film 1 tends to be improved.

[0065] The content of the base polymer is preferably 80.0 to 100 mass%, 85.0 to 99.5 mass%, or 87.5 to 99.5 mass% relative to the total amount of the coating layer 11. When the content of the base polymer is within the above range, the contamination of the wafer processing film 1 tends to be reduced.

[0066] Monomers The coating layer 11 may contain a polymerizable compound (monomer). The monomer undergoes a polymerization reaction with a photopolymerization initiator as described above. This causes the monomer to form a copolymer separately from the base polymer, and the copolymer and the base polymer form a structure in which they are intertwined with each other. This improves the curability of the coating layer 11, prevents the wafer processing film 1 from excessively adhering to the wafer 2, and tends to reduce contamination of the wafer processing film 1. Here, the monomer can function as a crosslinking agent.

[0067] As the monomer, polyfunctional (meth)acrylates such as difunctional (meth)acrylates, trifunctional (meth)acrylates, tetrafunctional (meth)acrylates, pentafunctional (meth)acrylates and hexafunctional (meth)acrylates are preferred.

[0068] The bifunctional (meth)acrylate is not particularly limited, but examples thereof include diethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, 2-(2-vinyloxyethoxy)ethyl acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, and 1,4-butanediol di(meth)acrylate. Examples of the di(meth)acrylates include 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, dimethylol-tricyclodecane di(meth)acrylate, EO (ethylene oxide) adduct di(meth)acrylate of bisphenol A, PO (propylene oxide) adduct di(meth)acrylate of bisphenol A, hydroxypivalic acid neopentyl glycol di(meth)acrylate, and polytetramethylene glycol di(meth)acrylate.

[0069] The trifunctional (meth)acrylate is not particularly limited, but examples thereof include trimethylolpropane tri(meth)acrylate, glycerin tri(meth)acrylate, and pentaerythritol tri(meth)acrylate.

[0070] The tetrafunctional (meth)acrylate is not particularly limited, but examples thereof include pentaerythritol tetra(meth)acrylate and trimethylolpropane tetra(meth)acrylate.

[0071] The pentafunctional (meth)acrylate is not particularly limited, but examples thereof include dipentaerythritol penta(meth)acrylate and trimethylolpropane penta(meth)acrylate.

[0072] The hexafunctional (meth)acrylate is not particularly limited, but examples thereof include dipentaerythritol hexa(meth)acrylate and trimethylolpropane hexa(meth)acrylate.

[0073] The content of the monomer is preferably 5.0 to 30.0 mass%, 6.0 to 27.5 mass%, or 7.0 to 25.0 mass% relative to the total amount of the coating layer 11. When the content of the monomer is within the above range, the contamination of the wafer processing film 1 tends to be reduced.

[0074] In the coating layer 11, the content of the monomer is preferably 1 to 20 parts by mass, 2 to 18 parts by mass, or 5 to 15 parts by mass relative to 100 parts by mass of the base polymer. When the content of the monomer is within the above range, the contamination of the wafer processing film 1 tends to be reduced.

[0075] 1.2.3. Photopolymerization initiator The photopolymerization initiator is not particularly limited, but examples thereof include alkylphenone-based photopolymerization initiators, acylphosphine oxide-based photopolymerization initiators, thioxanthone-based photopolymerization initiators, aromatic ketones, aromatic onium salt compounds, organic peroxides, thio compounds (e.g., thiophenyl group-containing compounds), α-aminoalkylphenone compounds, hexaarylbiimidazole compounds, ketoxime ester compounds, borate compounds, azinium compounds, metallocene compounds, active ester compounds, compounds having a carbon-halogen bond, and alkylamine compounds. Among these, alkylphenone-based photopolymerization initiators are preferred. These photopolymerization initiators may be used alone or in combination of two or more. Specific examples of the photopolymerization initiator include 2,2-dimethoxy-2-phenylacetophenone.

[0076] The content of the photopolymerization initiator is preferably 0.1 to 5.0 mass%, 0.2 to 4.0 mass%, or 0.3 to 3.0 mass% relative to the total amount of the coating layer 11. When the content of the photopolymerization initiator is within the above range, contamination of the wafer processing film 1 tends to be reduced.

[0077] In the coating layer 11, the content of the photopolymerization initiator is preferably 0.1 to 5.0 parts by mass, more preferably 0.2 to 1.0 part by mass, relative to 100 parts by mass of the base polymer. When the content of the photopolymerization initiator is within the above range, contamination of the wafer processing film 1 tends to be reduced.

[0078] 1.2.4. Hardener When the coating layer 11 contains a base polymer and a curing agent, the base polymers are cross-linked by heating or the like, thereby curing the coating layer 11. This prevents the wafer processing film 1 from being too closely attached to the wafer 2, and tends to reduce the contamination of the wafer processing film 1.

[0079] The curing agent is not particularly limited, but examples thereof include isocyanate compounds, epoxy compounds, and amine compounds. Among these, isocyanate compounds are preferred. These curing agents may be used alone or in combination of two or more.

[0080] The isocyanate compound is not particularly limited, but examples thereof include aromatic diisocyanates such as tolylene diisocyanate, 4,4-diphenylmethane diisocyanate, and xylylene diisocyanate; alicyclic diisocyanates such as isophorone diisocyanate and methylene bis(4-cyclohexyl isocyanate); and aliphatic diisocyanates such as hexamethylene diisocyanate and trimethylhexamethylene diisocyanate. These isocyanate compounds may be used alone or in combination of two or more. Among these, a polyfunctional isocyanate compound having two or more functionalities is preferred as the curing agent.

[0081] In the coating layer 11, the content of the curing agent is preferably 0.1 to 5.0 parts by mass, and more preferably 0.2 to 1.0 part by mass, per 100 parts by mass of the base polymer. When the content of the curing agent is 0.1 part by mass or more, the crosslink density of the coating layer 11 is improved, and the contamination of the wafer processing film 1 tends to be reduced. When the content of the curing agent is 5.0 parts by mass or less, the crosslink density is reduced and the elastic modulus is lowered, and the fixation of the wafer processing film 1 tends to be improved.

[0082] The content of the curing agent is preferably 0.1 to 2.0 mass %, 0.2 to 1.5 mass %, or 0.3 to 1.0 mass % relative to the total amount of the coating layer 11. When the content of the curing agent is within the above range, contamination of the wafer processing film 1 tends to be reduced and fixation tends to be improved.

[0083] Additives The additives are not particularly limited, but examples thereof include tackifiers, crosslinking retarders, antioxidants, and the like.

[0084] The tackifier is not particularly limited, but examples thereof include petroleum-based resins, terpene resins, terpene-phenolic resins, aromatic-modified terpene resins, coumarone-indene resins, natural resin rosin, modified rosin, glycerin ester rosin, pentaerythritol ester rosin, phenolic resins, xylene resins, alicyclic petroleum resins, styrene-based resins, and dicyclopentadiene resins. These tackifiers may be used alone or in combination. The content of the tackifier is preferably 0.1 to 2.0 mass%, 0.2 to 1.5 mass%, or 0.3 to 1.0 mass% relative to the total amount of the coating layer 11.

[0085] The crosslinking retarder is not particularly limited, but for example, in a pressure-sensitive adhesive composition containing an isocyanate-based curing agent, it is a compound that can suppress excessive viscosity increase of the pressure-sensitive adhesive composition by blocking the isocyanate groups of the curing agent. Examples of such crosslinking retarders include, but are not limited to, β-diketones such as acetylacetone, hexane-2,4-dione, heptane-2,4-dione, and octane-2,4-dione; β-ketoesters such as methyl acetoacetate, ethyl acetoacetate, propyl acetoacetate, butyl acetoacetate, octyl acetoacetate, oleyl acetoacetate, lauryl acetoacetate, and stearyl acetoacetate; and benzoylacetone. These crosslinking retarders may be used alone or in combination. The content of the crosslinking retarder is preferably 0.1 to 2.0 mass%, 0.2 to 1.5 mass%, or 0.3 to 1.0 mass% relative to the total amount of the coating layer 11.

[0086] The antioxidant is not particularly limited, but examples thereof include methylhydroquinone, hydroquinone, 2,2-methylene-bis(4-methyl-6-tert-butylphenol), catechol, hydroquinone monomethyl ether, monotert-butylhydroquinone, 2,5-ditert-butylhydroquinone, p-benzoquinone, 2,5-diphenyl-p-benzoquinone, 2,5-ditert-butyl-p-benzoquinone, picric acid, citric acid, phenothiazine, tert-butylcatechol, 2-butyl-4-hydroxyanisole, 2,6-ditert-butyl-p-cresol, and 4-[[4,6-bis(octylthio)-1,3,5-triazin-2-yl]amino]-2,6-ditert-butylphenol. These antioxidants may be used alone or in combination. The content of the antioxidant relative to the total amount of the coating layer 11 is preferably 0.1 to 2.0 mass %, 0.2 to 1.5 mass %, or 0.3 to 1.0 mass %.

[0087] 1.3. Adhesive layer The wafer processing film 1 of this embodiment may have an adhesive layer. The adhesive layer contributes to adhesion between the wafer 2 and the wafer processing film 1. The adhesive layer may have an opening with a diameter smaller than the diameter of the wafer 2. When the adhesive layer has such an opening, an area of ​​the element-forming surface 21 of the wafer 2 where no elements are present is attached to the adhesive layer so that the area of ​​the element-forming surface 21 where elements are present is positioned within the opening. In this case, the area of ​​the element-forming surface 21 where elements are present does not come into contact with the adhesive layer, which tends to prevent adhesive residue in that area. The ratio of the diameter of the opening to the diameter of the wafer 2 is preferably 0.950 to 0.995, and more preferably 0.960 to 0.990.

[0088] The thickness of the adhesive layer is preferably 1 to 100 μm, 5 to 75 μm, 10 to 70 μm, 15 to 60 μm, or 20 to 50 μm.

[0089] The adhesive layer may contain a (meth)acrylate polymer, and preferably contains a (meth)acrylate polymer and a crosslinking agent.

[0090] 1.3.1. (Meth)acrylate polymers The (meth)acrylate monomer contained in the (meth)acrylate polymer is not particularly limited, and examples thereof 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, cyclohexane (meth)acrylate, and the like. Examples of (meth)acrylic monomers such as hexyl (meth)acrylate, benzyl (meth)acrylate, dimethylacrylamide, diethylacrylamide, acryloylmorpholine, and isobornyl acrylate, and functional group-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 2-hydroxybutyl (meth)acrylate, which have a hydroxyl group; (meth)acrylic acid, crotonic acid, maleic acid, itaconic acid, fumaric acid, acrylamido-N-glycolic acid, and cinnamic acid, which have a carboxyl group; and allyl glycidyl ether and (meth)acrylic acid glycidyl ether, which have an epoxy group.

[0091] The content of the (meth)acrylate polymer is preferably 80 to 100 mass %, 85 to 99.5 mass %, or 90 to 99.0 mass %, relative to the total amount of the adhesive layer.

[0092] The glass transition temperature (Tg) of the (meth)acrylate polymer is preferably from -30 to 5°C, and more preferably from -25 to -5°C.

[0093] 1.3.2. Crosslinking Agents Examples of crosslinking agents include polyfunctional isocyanate crosslinking agents, polyfunctional epoxy crosslinking agents, etc. When the crosslinking agent reacts with the functional group, a crosslinked structure is formed with the functional group as the base point, which increases the cohesive strength of the adhesive and tends to reduce the contamination of the wafer processing film 1.

[0094] The content of the crosslinking agent is preferably 0.1 to 10.0 mass %, 0.5 to 8.0 mass %, or 1.0 to 6.0 mass %, relative to the total amount of the adhesive layer.

[0095] In the adhesive layer, the mass ratio of the crosslinking agent to the (meth)acrylate polymer (mass of crosslinking agent / mass of (meth)acrylate polymer) is preferably 0.1 to 10.0 mass%, 0.5 to 8.0 mass%, or 1.0 to 6.0 mass%.

[0096] 2. Manufacturing method of wafer processing film The method for producing the wafer processing film 1 of this embodiment is not particularly limited, but examples thereof include the following methods.

[0097] The means for forming the substrate layer 10 is not particularly limited, but the above-mentioned various materials are mixed using a conventional melt kneader or various mixing devices (single-screw or twin-screw extruder, roll, Banbury mixer, various kneaders, etc.) so that the components are uniformly dispersed, and the mixture is formed into the substrate by the T-die method, calendar method, or inflation method. Preferably, the T-die method using an extruder with good thickness accuracy is used.

[0098] The means for forming the coating layer 11 is not particularly limited, but may be such that the various materials described above are dissolved in a solvent such as an organic solvent to form a varnish, which is then applied to the substrate layer 10 by knife coating, roll coating, spray coating, gravure coating, bar coating, curtain coating, or the like, and cured by light irradiation or heat to form the coating layer 11. The various materials described above in the form of a varnish may be applied to a forming film, the solvent may be removed to form the coating layer 11, and the resulting film may be attached to the substrate layer 10 to form the coating layer 11 on the substrate layer 10.

[0099] The means for forming the adhesive layer is not particularly limited, but may be such that the various materials described above are dissolved in a solvent such as an organic solvent to form a varnish, which is then applied to the coating layer 11 by knife coating, roll coating, spray coating, gravure coating, bar coating, curtain coating, or the like, and the solvent is removed to form an adhesive layer. Alternatively, the various materials described above in varnish form may be applied to a molding film, the solvent is removed to form an adhesive layer, and the adhesive layer may be attached to the coating layer 11 to form an adhesive layer on the coating layer 11.

[0100] 3.Wafer processing method The wafer processing method using the wafer processing film 1 of this embodiment includes a bonding process s101 in which the main surface 1a of the wafer processing film 1 is bonded to the element forming surface 21 of the wafer 2, and a back grinding process s102 in which the non-element forming surface 22 of the wafer 2 bonded to the wafer processing film 1 is polished.

[0101] Each step of the wafer processing method of this embodiment will be described in detail below.

[0102] 3.1. Bonding process In the wafer processing method of this embodiment, first, the main surface 1 a of the wafer processing film 1 is bonded to the element formation surface 21 of the wafer 2 .

[0103] 3.2.Back grinding process Fig. 3(a) shows an example of a perspective view of the back-grinding step s102, and Fig. 3(b) shows an example of a cross-sectional view taken along line A-A' in Fig. 3(a). As shown in Figs. 3(a) and 3(b), in the back-grinding step s102, the non-element forming surface 22 of the wafer 2 is polished to thin the wafer 2.

[0104] 3.3.Dicing process The wafer processing method of this embodiment may further include a dicing step s103 of dicing the wafer 2. FIG. 4(a) shows an example of a perspective view of the dicing step s103, and FIG. 4(b) shows an example of a cross-sectional view taken along line A-A' in FIG. 4(a). Note that FIG. 4 shows an example of a case where stealth dicing, a type of laser dicing, is used as the dicing method. The dashed lines in FIG. 4 indicate the trajectory of the laser irradiated portion, and in a subsequent step of forming die chips, the wafer 2 is divided along the dashed line portions.

[0105] 4(a) and 4(b), when stealth dicing is employed in the dicing step s103, a laser is irradiated onto the wafer 2 to generate a modified region 24 inside the wafer 2. More specifically, in the dicing step s103, it is preferable to focus a pulsed laser on the inside of the wafer 2 to form the modified region 24 inside the wafer 2. At this time, it is preferable that the modified region 24 does not appear on the surface of the wafer 2.

[0106] The laser source is not particularly limited, but examples thereof include ultraviolet lasers, visible light lasers, near-infrared lasers, and far-infrared lasers. More specifically, for example, an Nd:YAG laser can be used.

[0107] The surface of the wafer 2 that is irradiated with the laser may be the element formation surface 21 or the non-element formation surface 22.

[0108] The dicing method in the dicing process is not limited to stealth dicing, but also includes laser ablation dicing, in which a laser is irradiated onto the wafer 2 to evaporate and sublimate part of the wafer 2; blade dicing, which uses a blade; and plasma dicing, which uses plasma.

[0109] 4 illustrates the dicing step s103 being performed with the wafer 2 attached to the wafer processing film 1, but the dicing step s103 may also be performed with the wafer 2 attached to a known adhesive tape other than the wafer processing film 1. From the viewpoint of performing the back-grinding step s102 and the dicing step s103 continuously and efficiently, it is preferable to perform the dicing step s103 with the wafer 2 attached to the wafer processing film 1.

[0110] 3.4. Peeling process The wafer processing method of this embodiment may include a peeling step s104 of heating and peeling off the wafer processing film 1 after the back-grinding step s102. In the peeling step s104, the wafer processing film 1 is peeled off from the wafer 2 while being heated. The peeling step s104 is performed after the back-grinding step s102.

[0111] In the peeling step s104, in order to improve peelability, the wafer processing film 1 is heated when peeling the wafer processing film 1 from the wafer 2. When the heating is performed, it is preferable to heat the wafer processing film 1 so that its temperature is 75°C or higher, and it is more preferable to heat the wafer processing film 1 so that its temperature is 75°C or higher and 150°C or lower.

[0112] Although the wafer processing method has been exemplified above, the wafer processing film 1 of this embodiment may be used to process an adherend such as a semiconductor package instead of a wafer.

[0113] The order in which the above steps are performed is not particularly limited. Below, examples of the wafer processing method of this embodiment in which the order in which the steps are performed is changed will be given. [Table 1] [Example]

[0114] The present invention will be described in more detail below using examples and comparative examples. The present invention is not limited to the following examples. Unless otherwise specified, the experiments were carried out at 25°C and 1 atmosphere.

[0115] [Example 1] An ionomer resin (manufactured by Mitsui-Dow Polychemicals, product name "Himilan 1855") was molded into a sheet with a thickness of 150 μm to obtain a substrate layer.

[0116] Next, 62 parts by mass of ethyl acrylate, 30 parts by mass of methyl methacrylate, 5 parts by mass of 2-hydroxyethyl methacrylate, and 3 parts by mass of glycidyl methacrylate were copolymerized to obtain base polymer A. This base polymer A had a weight average molecular weight Mw of 600,000 and a glass transition temperature Tg of -5°C.

[0117] A coating layer composition was prepared by mixing 100 parts by mass of the base polymer A obtained as described above, 10 parts by mass of dipentaerythritol hexaacrylate (manufactured by Kyoei Chemical Co., Ltd., product name DPE-6A) as a crosslinking agent, and 0.4 parts by mass of 2,2-dimethoxy-2-phenylacetophenone (manufactured by BASF, product name Irgacure 651) as a photopolymerization initiator. The Tg of this coating layer composition was 35°C. Here, the epoxy groups and hydroxy groups of the base polymer A reacted, causing a crosslinking reaction between the base polymers A.

[0118] The coating layer composition was then applied onto the substrate layer and cured by UV irradiation to form a coating layer with a thickness of 2 μm, thereby obtaining the wafer processing film of Example 1. By irradiating with UV, a polymerization reaction between dipentaerythritol hexaacrylate molecules proceeded, and a copolymer was formed separately from the base polymer A.

[0119] [Example 2] Base polymer B was obtained by copolymerizing 56 parts by mass of ethyl acrylate, 36 parts by mass of methyl methacrylate, 5 parts by mass of 2-hydroxyethyl methacrylate, and 3 parts by mass of glycidyl methacrylate. This base polymer B had a weight average molecular weight Mw of 580,000 and a glass transition temperature Tg of 0°C.

[0120] A coating layer composition was prepared by mixing 100 parts by weight of the base polymer B obtained as described above, 10 parts by weight of dipentaerythritol hexaacrylate (DPE-6A (product name) manufactured by Kyoei Chemical Co., Ltd.) as a crosslinking agent, 0.4 parts by weight of 2,2-dimethoxy-2-phenylacetophenone (Irgacure 651 (product name) manufactured by BASF) as a photopolymerization initiator, and 0.4 parts by weight of polyisocyanate (Duranate TPA-100 (product name) manufactured by Asahi Kasei Corporation, an isocyanate-based compound) as a curing agent. The Tg of this coating layer composition was 39°C.

[0121] A film for wafer processing of Example 2 was obtained in the same manner as in Example 1, except that the coating layer composition obtained as described above was used.

[0122] [Example 3] Base polymer C was obtained by copolymerizing 52 parts by mass of ethyl acrylate, 40 parts by mass of methyl methacrylate, 5 parts by mass of 2-hydroxyethyl methacrylate, and 3 parts by mass of glycidyl methacrylate. This base polymer C had a weight average molecular weight Mw of 580,000 and a glass transition temperature Tg of 4°C.

[0123] Then, 100 parts by mass of the base polymer C obtained as described above, 10 parts by mass of dipentaerythritol hexaacrylate (manufactured by Kyoei Chemical Co., Ltd., product name DPE-6A) as a crosslinking agent, and 0.4 parts by mass of 2,2-dimethoxy-2-phenylacetophenone (manufactured by BASF, product name Irgacure 651) as a photopolymerization initiator were mixed to prepare a coating layer composition. The Tg of this coating layer composition was 42°C.

[0124] A film for wafer processing of Example 3 was obtained in the same manner as in Example 1, except that the coating layer composition obtained as described above was used.

[0125] [Example 4] Base polymer D was obtained by copolymerizing 40 parts by mass of ethyl acrylate, 52 parts by mass of methyl methacrylate, 5 parts by mass of 2-hydroxyethyl methacrylate, and 3 parts by mass of glycidyl methacrylate. This base polymer D had a weight average molecular weight Mw of 620,000 and a glass transition temperature Tg of 13°C.

[0126] Then, 100 parts by mass of the base polymer D obtained as described above, 10 parts by mass of dipentaerythritol hexaacrylate (manufactured by Kyoei Chemical Co., Ltd., product name DPE-6A) as a crosslinking agent, and 0.4 parts by mass of 2,2-dimethoxy-2-phenylacetophenone (manufactured by BASF, product name Irgacure 651) as a photopolymerization initiator were mixed to prepare a coating layer composition. The Tg of this coating layer composition was 49°C.

[0127] A film for wafer processing of Example 4 was obtained in the same manner as in Example 1, except that the coating layer composition obtained as described above was used.

[0128] [Example 5] Base polymer E was obtained by copolymerizing 30 parts by mass of ethyl acrylate, 62 parts by mass of methyl methacrylate, 5 parts by mass of 2-hydroxyethyl methacrylate, and 3 parts by mass of glycidyl methacrylate. This base polymer E had a weight average molecular weight Mw of 600,000 and a glass transition temperature Tg of 24°C.

[0129] Then, 100 parts by mass of the base polymer E obtained as described above, 10 parts by mass of dipentaerythritol hexaacrylate (manufactured by Kyoei Chemical Co., Ltd., product name DPE-6A) as a crosslinking agent, and 0.4 parts by mass of 2,2-dimethoxy-2-phenylacetophenone (manufactured by BASF, product name Irgacure 651) as a photopolymerization initiator were mixed to prepare a coating layer composition. The Tg of this coating layer composition was 60°C.

[0130] A film for wafer processing of Example 5 was obtained in the same manner as in Example 1, except that the coating layer composition obtained as described above was used.

[0131] [Comparative Example 1] A polyolefin resin (manufactured by Diaplus Film Co., Ltd., product name "Artply a grade") was molded into a sheet with a thickness of 150 μm to obtain a wafer processing film of Comparative Example 1.

[0132] Comparative Example 2 An ionomer resin (manufactured by Mitsui-Dow Polychemicals, product name "Himilan 1855") was molded into a sheet with a thickness of 250 μm to obtain a substrate layer.

[0133] Next, 10 parts by mass of ethyl acrylate, 90 parts by mass of methyl methacrylate, 5 parts by mass of 2-hydroxyethyl methacrylate, and 3 parts by mass of glycidyl methacrylate were copolymerized to obtain base polymer F. This base polymer F had a weight average molecular weight Mw of 560,000 and a glass transition temperature Tg of 49°C.

[0134] Then, 100 parts by mass of the base polymer F obtained as described above, 10 parts by mass of dipentaerythritol hexaacrylate (manufactured by Kyoei Chemical Co., Ltd., product name DPE-6A) as a crosslinking agent, and 0.4 parts by mass of 2,2-dimethoxy-2-phenylacetophenone (manufactured by BASF, product name Irgacure 651) as a photopolymerization initiator were mixed to prepare a coating layer composition. The Tg of this coating layer composition was 83°C.

[0135] Then, the coating layer composition was applied onto the base layer and cured by UV irradiation to form a coating layer with a thickness of 2 μm, thereby obtaining a film for wafer processing of Comparative Example 2.

[0136] Comparative Example 3 An ionomer resin (manufactured by Mitsui-Dow Polychemicals, product name "Himilan 1855") was molded into a sheet with a thickness of 250 μm to obtain a substrate layer.

[0137] [Wetting tension measurement] For the main surface of each example of the wafer processing film, the wetting tension was measured according to the method described in JIS K6768, except that the temperature during measurement was 25° C. or 75° C. A mixed solution for wetting tension testing (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used as the droplet.

[0138] [Removability (adhesive residue)] A wafer was prepared with bumps of 130 μm diameter and 85 μm height spaced 65 μm apart on its surface. The exposed surface of the coating layer side of each wafer processing film, i.e., the main surface, was pressed against the device-forming surface of the wafer with the bumps at 75°C for 30 seconds to adhere it. The temperature was then lowered to room temperature (25°C). When peeling the wafer processing film from the wafer, it was visually inspected to see if it could be peeled off without leaving any adhesive or wafer processing film residue, and the evaluation was based on the following criteria. [Evaluation criteria] ◯: No adhesive residue or wafer processing film residue was observed. ×: Adhesive residue or wafer processing film residue is observed.

[0139] [Adhesive strength] A 750 μm thick wafer was prepared, with bumps of 130 μm diameter and 85 μm height spaced 65 μm apart on its surface. The exposed surface of the coating layer side of each wafer processing film, i.e., the main surface, was pressed against the device-formed surface of the wafer with the bumps at 75°C for 30 seconds to adhere it. The temperature was then lowered to room temperature (25°C). The non-device-formed surface of the wafer was then ground until the wafer thickness was reduced to 200 μm. Grinding was performed using a polishing machine (Disco Corporation, Backgrinder DFG-841). After grinding, the wafer processing film was visually inspected for peeling from the wafer, and evaluated based on the following criteria. (Evaluation criteria) ◯: The wafer processing film did not peel off from the wafer after grinding. ×: The wafer processing film peeled off from the wafer after grinding.

[0140] The evaluation results for each of the examples and comparative examples are shown in Table 2.

[0141] [Table 2] [Explanation of symbols]

[0142] 1...wafer processing film, 1a...main surface, 10...base material layer, 101...first surface, 11...coating layer, 111...first surface, 2...wafer, 21...element-forming surface, 211...central region, 212...peripheral region, 22...non-element-forming surface, 23...element, 24...modified portion

Claims

1. A wafer processing film used by being attached to the element formation surface of a wafer in a back grinding process, The wetting tension T at 75°C on the main surface of the wafer processing film in contact with the element formation surface 75 is 32 mN / m or more and 40 mN / m or less, Film for wafer processing.

2. It has a structure in which a substrate layer and a coating layer are laminated in this order, The main surface is the surface of the coating layer. The wafer processing film according to claim 1 .

3. Further, an adhesive layer is laminated on the coating layer, the adhesive layer has an opening with a diameter smaller than the diameter of the wafer; The main surface is a surface of the coating layer at the opening. The wafer processing film according to claim 2 .

4. the substrate layer contains a (meth)acrylic ionomer, the coating layer contains a base polymer containing a (meth)acrylic acid ester copolymer, a monomer, and a photopolymerization initiator; The content of the monomer is 1 to 20 parts by mass relative to 100 parts by mass of the base polymer. The wafer processing film according to claim 2 .

5. Wet tension T on the main surface at 25°C 25 is 32 mN / m or more, The wafer processing film according to claim 1 .

6. a bonding step of bonding a main surface of the wafer processing film according to any one of claims 1 to 5 to an element-forming surface of a wafer; a back grinding step of grinding a non-element forming surface of the wafer bonded to the wafer processing film, Wafer processing method.

7. The method further includes a dicing step of dicing the wafer. The wafer processing method according to claim 6.

8. In the dicing step, a modified portion is generated inside the wafer by stealth dicing. The wafer processing method according to claim 7.

9. After the back-grinding step, a peeling step of heating and peeling off the wafer processing film is included. The wafer processing method according to claim 6.

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