Film for wafer processing and wafer processing method

Abstract

The purpose of the present invention is to provide a film for wafer processing that is unlikely to contaminate a wafer when peeled from the wafer, and a wafer processing method using said film for wafer processing. The present disclosure relates to a film for wafer processing that, when used, is bonded to an element formation surface of a wafer in a back grinding step, wherein the wet tension T75 at 75°C on the main surface of the wafer processing film that is in contact with the element formation surface is 32–40 mN / m.

Description

Wafer processing film and wafer processing method

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

[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.

[0004] Japanese Patent Application Laid-Open No. 2019-065168

[0005] Patent Document 1 explains that by providing an adhesive film with an irregularity-absorbing resin layer, even if the size of the bumps formed on the surface of the wafer becomes large, the irregularities caused by the bumps can be absorbed, 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.

[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 rate 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 stuck to an element-forming surface of a wafer in a back-grinding process, wherein the wet tension T at 75° C. of the main surface of the wafer processing film in contact with the element-forming surface is ７５ A wafer processing film having a wet tension T of 32 mN / m or more and 40 mN / m or less. [2] The wafer processing film according to [1], having a structure in which a base layer and a coating layer are laminated in this order, and the main surface is the surface of the coating layer. [3] The wafer processing film according to [2], further having an adhesive layer laminated on the coating layer, the adhesive layer having an opening with a diameter smaller than the diameter of the wafer, and the main surface being the surface of the coating layer at the opening. [4] The wafer processing film according to [2] or [3], wherein the base layer contains a (meth)acrylic ionomer, and the coating layer contains a base polymer containing a (meth)acrylic acid ester copolymer, a monomer, and a photopolymerization initiator, and the content of the monomer is 1 to 20 parts by mass per 100 parts by mass of the base polymer. [5] The wafer processing film according to [2] or [3], having a wet tension T of 32 mN / m or more and 40 mN / m or less at 25°C on the main surface. ２５

[0013] The wafer processing film according to any one of [1] to [4], having a compressive strength of 32 mN / m or more. [6] A wafer processing method comprising: a laminating step of laminating a main surface of the wafer processing film according to any one of [1] to [5] to an element-forming surface of a wafer; and a back-grinding step of polishing a non-element-forming surface of the wafer laminated to the wafer processing film. [7] The wafer processing method according to [6], further comprising a dicing step of dicing the wafer. [8] The wafer processing method according to [7], in which a modified region is generated inside the wafer by stealth dicing in the dicing step. [9] The wafer processing method according to any one of [6] to [8], further comprising a peeling step of heating and peeling off the wafer processing film after the back-grinding step.

[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.

[0011] 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). An example of a wafer 2 attached to the wafer processing film 1 is shown. 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 A-A' in Fig. 3(a). Fig. 4(a) shows an example of a perspective view of the dicing process, and Fig. 4(b) shows an example of a cross-sectional view taken along line A-A' in Fig. 4(a).

[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. However, the present invention is not limited to this embodiment, 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 are 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 attached to the device-forming surface of a wafer in a backgrinding process, and has a wet tension T at 75°C on the main surface of the wafer processing film that contacts the device-forming surface. ７５ is 32 mN / m or more and 40 mN / m or less.

[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 standpoint of interlayer adhesion and bonding. In this case, the main surface 1a in contact with the device-forming surface of the wafer 2 is 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 on the opposite side of 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 being 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. Furthermore, 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 ７５ The wetting tension T is regulated 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 degree of adhesion to the wafer 2. Since 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, since 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 property of the wafer processing film 1 tends to be improved.

[0021] Wet tension T on main surface 1a at 75 ° C. ７５ is preferably 33 to 39 mN / m, 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. 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 be able to sufficiently fix the wafer 2 when the non-device forming surface 22 of the wafer 2 is back-ground at room temperature.

[0024] From this viewpoint, 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 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-forming surface 22 of the wafer 2. In this regard, it is conceivable that the non-element-forming surface 22 of the wafer 2 may be back-grinded at a temperature higher or lower than 25° C. However, even if the actual temperature when back-grinding the non-element-forming surface 22 of the wafer 2 is not 25° C. but is higher or lower than this, the wetting tension T measured with 25° C. as the reference is ２５ By satisfying the predetermined range, it can be said that the fixation of the wafer processing film 1 is improved when the non-element forming surface 22 of the wafer 2 is back-ground.

[0026] Wet 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] Wet 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 material 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 copolymers, ethylene-acrylate copolymers, and ethylene-methacrylate-acrylate copolymers.

[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 material layer 10 is preferably 80 to 100 mass %, 85 to 98 mass %, or 90 to 95 mass %, based on the entire base material 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 of two or more.

[0041] The content of the additive is preferably 0.1 to 10.0 mass %, 0.5 to 5.0 mass %, or 1.0 to 2.5 mass %, based on the entire substrate layer 10 .

[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. Examples of hydrophilization treatments include, but are not limited to, corona treatment and plasma treatment. When the first surface 101 side is hydrophilized, the first surface 101 of the base layer 10 becomes hydrophilic, which tends to improve the fixation of the wafer processing film 1.

[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 wetting tension T ７５ 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] Wet tension T on the first surface 111 at 25°C ２５ and wetting tension T at 75 ° C. ７５can 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 can be applied to the base layer, and then irradiated with light to cause a polymerization reaction to proceed, 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 When the coating layer 11 contains a base polymer, the elastic modulus decreases and flexibility improves, 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-based 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 ... 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; 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] By having hydroxyl groups or epoxy groups in the base polymer, it is possible to further crosslink multiple polymers 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. Furthermore, this crosslinking reaction between polymers may be accelerated by using a curing agent, which will be described later.

[0060] Of 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 x 10 ６ is 2.0 × 10 ５ ~1.0 x 10 ６ is 2.5 × 10 ５ ~8.0 x 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 this condition, 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 calibration curve of the molecular weight converted into standard polystyrene, assuming that the area of ​​the chromatogram of the base polymer is 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. When 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. When the glass transition point of the base polymer before the crosslinking reaction is 40° C. or lower, the fixation property 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] 1.2.2. Monomer The coating layer 11 may contain a polymerizable compound (monomer). As described above, the monomer undergoes a polymerization reaction in the presence of a photopolymerization initiator. This causes the monomer to form a copolymer separately from the base polymer, resulting in a structure in which the copolymer and the base polymer are intertwined. This improves the curing properties of the coating layer 11, prevents excessive adhesion of the wafer processing film 1 to the wafer 2, and tends to reduce contamination of the wafer processing film 1. Here, the monomer can function as a cross-linking agent.

[0067] The monomer is preferably a polyfunctional (meth)acrylate such as a difunctional (meth)acrylate, a trifunctional (meth)acrylate, a tetrafunctional (meth)acrylate, a pentafunctional (meth)acrylate, or a hexafunctional (meth)acrylate.

[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. bisphenol A di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, dimethylol-tricyclodecane di(meth)acrylate, ethylene oxide (EO) adduct di(meth)acrylate of bisphenol A, propylene oxide (PO) adduct di(meth)acrylate of bisphenol A, neopentyl glycol hydroxypivalate 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] The content of the photopolymerization initiator in the coating layer 11 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 photopolymerization initiator is within the above range, the contamination of the wafer processing film 1 tends to be reduced.

[0078] 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 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 methylenebis(4-cyclohexylisocyanate); 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 further 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 further 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, the contamination of the wafer processing film 1 tends to be reduced and the fixation tends to be improved.

[0083] 1.2.5. Additives The additives are not particularly limited, but examples thereof include tackifiers, crosslinking retarders, and antioxidants.

[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 of two or more. 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 of two or more. 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 Polymer 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 ...cyclohexane (meth)acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, tridecyl (meth)acrylate, myristyl (meth)acrylate, cetyl (meth)acrylate, cyclohexane (meth)acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, tridecyl (meth)acrylate, myristyl (meth) Examples of (meth)acrylic monomers and functional group-containing monomers include hexyl (meth)acrylate, benzyl (meth)acrylate, dimethylacrylamide, diethylacrylamide, acryloylmorpholine, and isobornyl acrylate; hydroxyl group-containing 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 2-hydroxybutyl (meth)acrylate; carboxyl group-containing (meth)acrylic acid, crotonic acid, maleic acid, itaconic acid, fumaric acid, acrylamido-N-glycolic acid, and cinnamic acid; and epoxy group-containing allyl glycidyl ether and (meth)acrylic acid glycidyl ether.

[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, more preferably from -25 to -5°C.

[0093] 1.3.2 Crosslinking Agent 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 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% by mass, 0.5 to 8.0% by mass, or 1.0 to 6.0% by 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. Method for Producing the 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 kneading method 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 a T-die method, a calendar method, or an 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 include dissolving the various materials in a solvent such as an organic solvent to form a varnish, applying this to the coating layer 11 by knife coating, roll coating, spray coating, gravure coating, bar coating, curtain coating, or the like, and then removing the solvent to form an adhesive layer.The various materials in the varnish form may be applied to a molding film, and the solvent may be removed to form an adhesive layer, which may then 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 step s101 of bonding the main surface 1a of the wafer processing film 1 to the element forming surface 21 of the wafer 2, and a back-grinding step s102 of polishing the non-element forming surface 22 of the wafer 2 bonded to the wafer processing film 1.

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

[0102] 3.1 Bonding Step 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(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 process s103 for dicing the wafer 2. FIG. 4(a) shows an example of a perspective view of the dicing process 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 process 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 inside 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-formed surface 21 or the non-element-formed 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] 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, from the viewpoint of improving peelability, the wafer processing film 1 is heated when peeling the wafer processing film 1 from the wafer 2. When the above heating is performed, it is preferable to heat the wafer processing film 1 so that its temperature is 75° C. or higher, and more preferably 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.

[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 to crosslink the base polymers A together.

[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 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 were copolymerized to obtain a base polymer B. 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 mass of the base polymer B obtained as described above, 10 parts by mass of dipentaerythritol hexaacrylate (DPE-6A (product name) manufactured by Kyoei Chemical Co., Ltd.) as a crosslinking agent, 0.4 parts by mass of 2,2-dimethoxy-2-phenylacetophenone (Irgacure 651 (product name) manufactured by BASF) as a photopolymerization initiator, and 0.4 parts by mass of polyisocyanate (Duranate TPA-100 (product name), an isocyanate-based compound manufactured by Asahi Kasei Corporation) 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 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 were copolymerized to obtain a base polymer C. This base polymer C had a weight average molecular weight Mw of 580,000 and a glass transition temperature Tg of 4°C.

[0123] A coating layer composition was prepared by mixing 100 parts by mass of the base polymer C obtained as described above, 10 parts by mass of dipentaerythritol hexaacrylate (DPE-6A (product name) manufactured by Kyoei Chemical Co., Ltd.) as a crosslinking agent, and 0.4 parts by mass of 2,2-dimethoxy-2-phenylacetophenone (Irgacure 651 (product name) manufactured by BASF) as a photopolymerization initiator. 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 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 were copolymerized to obtain base polymer D. This base polymer D had a weight average molecular weight Mw of 620,000 and a glass transition temperature Tg of 13°C.

[0126] A coating layer composition was prepared by mixing 100 parts by mass of the base polymer D obtained as described above, 10 parts by mass of dipentaerythritol hexaacrylate (DPE-6A (product name) manufactured by Kyoei Chemical Co., Ltd.) as a crosslinking agent, and 0.4 parts by mass of 2,2-dimethoxy-2-phenylacetophenone (Irgacure 651 (product name) manufactured by BASF) as a photopolymerization initiator. 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 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 were copolymerized to obtain base polymer E. This base polymer E had a weight average molecular weight Mw of 600,000 and a glass transition temperature Tg of 24°C.

[0129] A coating layer composition was prepared by mixing 100 parts by mass of the base polymer E obtained as described above, 10 parts by mass of dipentaerythritol hexaacrylate (DPE-6A (product name) manufactured by Kyoei Chemical Co., Ltd.) as a crosslinking agent, and 0.4 parts by mass of 2,2-dimethoxy-2-phenylacetophenone (Irgacure 651 (product name) manufactured by BASF) as a photopolymerization initiator. 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 having 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 having 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] A coating layer composition was prepared by mixing 100 parts by mass of the base polymer F obtained as described above, 10 parts by mass of dipentaerythritol hexaacrylate (DPE-6A (product name) manufactured by Kyoei Chemical Co., Ltd.) as a crosslinking agent, and 0.4 parts by mass of 2,2-dimethoxy-2-phenylacetophenone (Irgacure 651 (product name) manufactured by BASF) as a photopolymerization initiator. 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 having a thickness of 2 μm, thereby obtaining a wafer processing film 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 having a thickness of 250 μm to obtain a substrate layer.

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

[0138] [Removability (Adhesive Residue)] A wafer was prepared having 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 element-forming surface of the wafer on which the bumps were formed 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 confirmed whether it could be peeled without leaving any adhesive residue or wafer processing film residue, and evaluated based on the following evaluation criteria. [Evaluation Criteria] ◯: No adhesive residue or wafer processing film residue was observed. ×: Adhesive residue or wafer processing film residue was observed.

[0139] [Adhesion 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 bond the film. 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 reached 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 from the wafer after grinding. ×: The wafer processing film peeled from the wafer after grinding.

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

[0141]

[0142] DESCRIPTION OF SYMBOLS 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, wherein the wet tension T at 75°C on the main surface of the wafer processing film that contacts the element formation surface ７５ A wafer processing film having a surface tension of 32 mN / m or more and 40 mN / m or less.

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

3. The wafer processing film according to claim 2, further comprising an adhesive layer laminated on the coating layer, the adhesive layer having an opening with a diameter smaller than the diameter of the wafer, and the main surface being the surface of the coating layer at the opening.

4. The wafer processing film according to claim 2, wherein 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, and the content of the monomer is 1 to 20 parts by mass per 100 parts by mass of the base polymer.

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

6. A wafer processing method comprising: a lamination step of laminating 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; and a back-grinding step of polishing a non-element-forming surface of the wafer that has been laminated to the wafer processing film.

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

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

9. The wafer processing method according to claim 6, further comprising a peeling step of heating and peeling off the wafer processing film after the back-grinding step.

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