Wafer processing tape and wafer processing method

Abstract

To provide a wafer processing tape which can be used across semiconductor processing steps by having heat resistance, and to provide a wafer processing method which can integrate a plurality of semiconductor processing steps by using the tape.SOLUTION: A wafer-processing tape comprising: a following-up layer; and a heat-resistant layer laminated on a back surface of the following-up layer, wherein the heat-resistant layer is a B-stage sheet.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] When semiconductor wafers are processed, adhesive sheets are applied to protect them from damage. For example, in the backgrinding process of semiconductor wafer processing, adhesive sheets are applied to protect the patterned surface of the semiconductor wafer. In addition, various tapes are used in each process in semiconductor processing, such as backgrinding tape, heat-resistant tape, conductive tape, dicing tape, and pick-up tape.

[0003] As an example, a substrate used in an adhesive sheet for processing semiconductor wafers is known, which has a thermal shrinkage rate of 0% or more in both MD and TD after heating at 130°C for 10 minutes, with the aim of increasing the adhesion of the substrate to the stage during the semiconductor wafer processing process (Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] WO2023 / 068088 Summary of the Invention [Problem to be solved by the invention]

[0005] In semiconductor processing, different tape is used for each process because different characteristics are required for the wafer processing tape. However, the wafer processing tape needs to be replaced after each process, which increases the number of steps required for semiconductor processing.

[0006] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a wafer processing tape that is heat resistant and can be used across semiconductor processing steps, and a wafer processing method that uses this tape to enable the integration of multiple semiconductor processing steps. [Means for solving the problem]

[0007] The present inventors have conducted extensive research to solve the above problems, and as a result have found that the above problems can be solved by using a B-stage sheet as a heat-resistant layer, which has led to the completion of the present invention.

[0008] That is, the present invention is as follows. [1] A follow-up layer and a heat-resistant layer laminated on the back surface of the follow-up layer, The heat-resistant layer is a B-stage sheet. Tape for wafer processing. [2] The heat-resistant layer contains an acrylic resin and an epoxy resin. The wafer processing tape according to [1]. [3] The hardening rate of the B-stage sheet is 30-95%. The wafer processing tape according to [1] or [2]. [4] the ratio (Eh200 / Eh140) of the storage modulus Eh140 at 140°C to the storage modulus Eh200 at 200°C of the heat-resistant layer is 10 to 100; The tape for wafer processing according to any one of [1] to [3]. [5] The ratio (Eh25 / Eh140) of the storage modulus Eh140 at 140°C to the storage modulus Eh25 at 25°C of the heat-resistant layer is 25 to 250. The tape for wafer processing according to any one of [1] to [4]. [6] a lamination step of laminating the wafer processing tape according to any one of [1] to [5] to the element-forming surface of the wafer; a back grinding step of grinding a non-element forming surface of the wafer bonded to the wafer processing tape, Wafer processing method. [7] a metal layer forming step of forming a metal layer on the surface of the wafer opposite to the surface to which the wafer processing tape is attached, The wafer processing method according to [6]. [8] The method further includes a dicing step of dicing the wafer. The wafer processing method according to [6]. [9] a peeling step of heating and peeling off the wafer processing tape after the back-grinding step; The wafer processing method according to [6]. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a wafer processing tape that has heat resistance and can be used across semiconductor processing steps, and a wafer processing method that uses this tape to integrate multiple semiconductor processing steps. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic cross-sectional view showing a tape for wafer processing according to an embodiment of the present invention. [Figure 2] 3 is a flowchart showing a wafer processing method according to the present embodiment. [Figure 3] FIG. 1 is a top view of a test piece with thickness measurement locations indicated. DETAILED DESCRIPTION OF THE INVENTION

[0011] Below, we will explain in detail the embodiment of the present invention (hereinafter referred to as the ``present embodiment''), but the present invention is not limited to this and various modifications are possible within the scope of the gist of the present invention.

[0012] 1. Wafer processing tape The wafer processing tape of this embodiment has a follower layer and a heat-resistant layer laminated on the back surface of the follower layer, and the heat-resistant layer is a B-stage sheet.

[0013] FIG. 1 shows a schematic cross-sectional view of the wafer processing tape of this embodiment. As shown in FIG. 1, the wafer processing tape 10 of this embodiment has a follower layer 12 and a heat-resistant layer 13 laminated on the follower layer 12. The wafer processing tape of this embodiment may also have a release layer 11 on the surface 12a of the follower layer 12 opposite the surface 12b on which the heat-resistant layer 13 is laminated. The surface 12a (exposed surface) of the follower layer 12 adheres to the semiconductor element forming surface 20a of the wafer 20, thereby protecting the semiconductor element forming surface 20a of the wafer 20. Furthermore, as shown in FIG. 1, if the release layer 11 is present, the surface 11a (exposed surface) of the release layer 11 adheres to the semiconductor element forming surface 20a of the wafer 20, thereby protecting the semiconductor element forming surface 20a of the wafer 20. In this embodiment, the surface of the wafer processing tape and each layer thereof that contacts the wafer is referred to as the front surface, and the opposite surface is referred to as the back surface.

[0014] Generally, the conformal layer 12 is configured to easily conform to the irregularities of the semiconductor element forming surface 20a, and therefore may soften further at high temperatures, making it difficult to maintain its shape. When it becomes difficult to maintain its shape, the in-plane film thickness distribution of the wafer processing tape becomes uneven. Continuing the semiconductor processing process using a wafer processing tape with an uneven film thickness distribution is undesirable because it reduces the subsequent processing accuracy.

[0015] For example, the backgrinding tape used in the backgrinding process is generally designed to easily conform to the irregularities of the semiconductor element forming surface 20a. However, in the BSM (Back Side Metallization) process, which forms a metal layer on the backside of the wafer after backgrinding, the backgrinding tape is exposed to high temperatures, so it is necessary to replace the backgrinding tape with a different tape for wafer processing.

[0016] In this regard, the wafer processing tape of this embodiment includes a B-stage sheet as the heat-resistant layer 13. This allows the heat-resistant layer 13 to be a layer with excellent conformability before heating, such as in a backgrinding process, and hardens during heating, such as in a BSM process. The heat-resistant layer 13 hardens during heating to become a support layer, thereby maintaining the shape of the conforming layer 12 that softened at high temperatures and making it possible to maintain the film thickness distribution.

[0017] 1.1.Heat-resistant layer The heat-resistant layer 13 is a B-stage sheet, and is a layer laminated on the back surface 12b of the follower layer 12. Before heating, the heat-resistant layer 13 is in a B-stage state, and when heated, hardening progresses to a C-stage state.

[0018] In this embodiment, "B stage" refers to an intermediate stage in the reaction of certain thermosetting resins, in accordance with JIS K6900:1994, where the material swells when in contact with certain liquids and softens when heated, but does not completely dissolve or melt. In contrast to the B stage, the A stage refers to the initial stage in the preparation of certain thermosetting resins, where the material is still soluble in certain liquids and fusible. Furthermore, the C stage refers to the final stage in the reaction of certain thermosetting resins, where the material is virtually insoluble and infusible. The resin in a fully cured thermosetting molded product is in the C stage.

[0019] Whether the wafer processing tape is in the B-stage state can also be evaluated by the cure rate of the wafer processing tape. In this embodiment, the B-stage state means that the cure rate of the wafer processing tape is preferably 30 to 95%, 35 to 90%, or 40 to 85%. The cure rate is a value representing the amount of heat generated until the tape reaches a semi-cured (B-stage) state, with the total heat generated when the tape is converted from an uncured state to a fully cured state being 100%. The cure rate can be determined using a thermal analyzer such as a differential scanning calorimeter.

[0020] The ratio (Eh200 / Eh140) of the storage modulus Eh140 of the heat-resistant layer at 140°C to the storage modulus Eh200 at 200°C is preferably 10 to 100, 20 to 90, 30 to 80, or 40 to 70. When the ratio (Eh200 / Eh140) is within the above range, the heat-resistant layer has improved heat resistance at temperatures of 140°C or higher, and the uniformity of the film thickness distribution of the follow-up layer during heating tends to be improved.

[0021] Eh200 is preferably 2.5 x 10 5 ~2.5×10 7 Pa, 5.0 x 10 5 ~1.0×10 7 Pa, 7.5 x 10 5 ~7.5×10 6 Pa, 1.0 x 10 6 ~5.0×10 6 Pa. When Eh200 is within the above range, the heat resistance of the heat-resistant layer is improved, and the uniformity of the film thickness distribution of the follow-up layer during heating tends to be improved.

[0022] Eh140 is preferably 1.0 x 10 3 ~1.0×10 6 Pa, 5.0 x 10 3 ~5.0×10 5 Pa, 1.0 x 10 4 ~1.0×10 5 Pa, 2.5 x 10 4 ~5.0×10 4 Pa. When Eh140 is within the above range, the heat-resistant layer softens once as the temperature rises, and therefore conformability tends to be further improved.

[0023] Furthermore, the ratio (Eh25 / Eh140) of the storage modulus Eh140 at 140°C to the storage modulus Eh25 at 25°C of the heat-resistant layer is preferably 25 to 250, 50 to 200, 75 to 175, or 100 to 150. When the ratio (Eh25 / Eh140) is within the above range, the heat-resistant layer softens at temperatures up to 140°C, which tends to contribute to improved conformability.

[0024] Eh25 is preferably 1.0 x 10 5 ~1.0×10 9 Pa, 5.0 x 10 5 ~5.0×10 8 Pa, 1.0 x 10 6 ~1.0×10 7 Pa. When Eh25 is within the above range, the performance of protecting the irregularities on the semiconductor element forming surface 20a at room temperature tends to be further improved.

[0025] The storage modulus Eh of the heat-resistant layer and the storage modulus Ec of the follow-up layer can be adjusted by the type of resin constituting each layer, the type of filler if any, and the content ratio of the resin and filler.

[0026] The thickness of the heat-resistant layer is preferably 25 to 300 μm, 50 to 250 μm, or 75 to 200 μm. When the thickness of the heat-resistant layer is within the above range, the uniformity of the film thickness distribution of the follow-up layer during heating tends to be further improved.

[0027] Resin The heat-resistant layer is not particularly limited as long as it is a B-stage sheet, but preferably contains, for example, a thermosetting resin. The thermosetting resin is not particularly limited, but is preferably, for example, an epoxy resin or an acrylic resin having a functional group reactive with the epoxy resin. This allows the curing reaction to proceed quickly when heated, and tends to further improve the in-plane thickness uniformity when heated.

[0028] Epoxy resins include, but are not limited to, bisphenol A epoxy resins, bisphenol AP epoxy resins, bisphenol AF epoxy resins, bisphenol B epoxy resins, bisphenol BP epoxy resins, bisphenol C epoxy resins, bisphenol E epoxy resins, bisphenol F epoxy resins, bisphenol G epoxy resins, bisphenol M epoxy resins, bisphenol S epoxy resins, bisphenol P epoxy resins, bisphenol PH epoxy resins, bisphenol TMC epoxy resins, bisphenol Z epoxy resins, polypropylene glycol epoxy resins, polytetramethylene glycol epoxy resins, naphthalene epoxy resins such as 1,6-naphthalenediol epoxy resins, anthracene epoxy resins such as 9,10-anthracenediol epoxy resins, phenylmethane epoxy resins, tetrakisphenolmethane epoxy resins, biphenyl epoxy resins, epoxy resins with a triazine skeleton, and bisphenol A alkylene oxide adduct epoxy resins. Epoxy resins having two or more epoxy groups per molecule are preferred.

[0029] The epoxy resin may also contain a prepolymer of the above-mentioned epoxy resin and a polyol. The polyol is not particularly limited, but examples thereof include aliphatic diols such as ethylene glycol, propanediol, butanediol, hexanediol, and decanediol; alicyclic diols such as cyclohexanediol; bisphenols such as bisphenol F, bisphenol A, bisphenol B, bisphenol AD, bisphenol S, and halogenated bisphenol A; and novolac resins having hydroxyl groups, such as phenol novolac resins and bisphenol novolac resins.

[0030] The content of the epoxy resin is preferably 10 to 50 parts by mass, 15 to 45 parts by mass, 20 to 40 parts by mass, or 25 to 35 parts by mass relative to 100 parts by mass of the resin component of the heat-resistant layer. When the content of the epoxy resin is within the above range, non-uniformity of the thickness at high temperatures is suppressed, and the glass transition temperature of the obtained cured product tends to be further improved.

[0031] Examples of acrylic resins having a functional group reactive with epoxy resins include acrylic resins having a carboxyl group, a hydroxyl group, an epoxy group, etc. By using such an acrylic resin, flexibility and stress relaxation properties can be imparted to the heat-resistant layer, and uneven thickness at high temperatures tends to be suppressed.

[0032] Furthermore, the monomer having a reactive functional group that constitutes such an acrylic resin is not particularly limited, but examples thereof include carboxyl group-containing (meth)acrylic acids such as acrylic acid and methacrylic acid; hydroxyl group-containing (meth)acrylic acid esters such as hydroxyalkyl acrylate and hydroxyalkyl methacrylate; and epoxy group-containing (meth)acrylic acid esters such as glycidyl acrylate and glycidyl methacrylate.

[0033] Furthermore, the monomer without a reactive functional group that constitutes such an acrylic resin is not particularly limited, but 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, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, dimethylacrylamide, diethylacrylamide, acryloylmorpholine, and isobornyl acrylate.

[0034] The content of the acrylic resin is preferably 30 to 65 parts by mass, 35 to 60 parts by mass, 40 to 55 parts by mass, or 45 to 50 parts by mass, relative to 100 parts by mass of the resin component of the heat-resistant layer. When the content of the acrylic resin is within the above range, flexibility and stress relaxation properties can be imparted to the heat-resistant layer, and uneven thickness at high temperatures tends to be suppressed.

[0035] The total resin content is preferably 60 to 95 parts by mass, 65 to 90 parts by mass, 70 to 85 parts by mass, or 75 to 80 parts by mass, relative to 100 parts by mass of the resin components of the heat-resistant layer. When the total resin content is within the above range, flexibility and stress relaxation properties can be imparted to the heat-resistant layer, thickness non-uniformity at high temperatures is suppressed, and the glass transition temperature of the obtained cured product tends to be further improved.

[0036] In this embodiment, the term "resin component" refers to the amount of components excluding the filler and the solvent.

[0037] 1.1.2.Other ingredients The heat-resistant layer is not particularly limited, but may further contain, for example, a curing agent, a curing accelerator, and a filler as other components.

[0038] The curing agent is not particularly limited, but examples thereof include phenol-based curing agents, amine-based curing agents, acid anhydride-based curing agents, and thiol-based curing agents. Among these, phenol-based curing agents are preferred. By using such a curing agent, thickness non-uniformity at high temperatures is suppressed, and the glass transition temperature of the resulting cured product tends to be further improved.

[0039] The phenolic curing agent is not particularly limited, but examples thereof include cresol novolac type phenol, phenol novolac, xylylene novolac, alkylphenol novolac, bisphenol A type novolac, dicyclopentadiene type phenol, xyloc type phenol, terpene-modified phenol, polyvinylphenols, naphthol aralkyl type phenol, biphenyl aralkyl type phenol, naphthalene type phenol, aminotriazine novolac type phenol, etc. The phenolic curing agent is preferably one having two or more phenolic hydroxyl groups in one molecule.

[0040] The amine-based curing agent is not particularly limited, but examples thereof include aromatic amine-based curing agents, aliphatic amine-based curing agents, and dicyandiamide.

[0041] The acid anhydride curing agent is not particularly limited, but examples thereof include aliphatic acid anhydrides such as phthalic anhydride derivatives, and aromatic acid anhydrides such as maleic anhydride.

[0042] The thiol-based curing agent is not particularly limited, but examples thereof include aliphatic polythioethers, aliphatic polythioesters, and aromatic-containing polythioethers.

[0043] The content of the curing agent is preferably 5 to 40 parts by mass, 10 to 35 parts by mass, 15 to 30 parts by mass, or 20 to 25 parts by mass relative to 100 parts by mass of the resin component of the heat-resistant layer. When the content of the curing agent is 5 parts by mass or more, the glass transition temperature and strength of the B-stage sheet tend to be further improved. Furthermore, when the amount of the curing agent used is 40 parts by mass or less, embrittlement due to excessive hardness of the B-stage sheet tends to be further suppressed.

[0044] The heat-resistant layer may contain a curing accelerator. While a curing agent forms the main skeleton of the cured product, a curing accelerator does not form the main skeleton of the cured product but contributes to the curing speed and curing temperature.

[0045] Such a curing accelerator is not particularly limited, but examples thereof include imidazole-based curing accelerators and phosphorus-based curing accelerators.

[0046] The imidazole curing accelerator is not particularly limited, but examples thereof include 2-methylimidazole, 2-ethylimidazole, 2-undecylimidazole, 2,4-dimethylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 1,2-diethylimidazole, 2-phenyl-4-methylimidazole, 2,4,5-triphenylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 1-benzyl-2-phenylimidazole, 1-(2-cyanoethyl)-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, and 1-cyanoethyl-2-undecylimidazole. 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-S-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-S-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-S-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-S-triazine isocyanuric acid adduct, and 2-phenyl-4-methyl-5-hydroxymethylimidazole.

[0047] The phosphorus-based curing accelerator is not particularly limited, but examples thereof include tetraphenylphosphonium tetra-p-tolylborate, tetraphenylphosphonium tetraphenylborate, triphenylphosphine, tri-p-tolylphosphine, tris(4-chlorophenyl)phosphine, tris(2,6-dimethoxyphenyl)phosphine, triphenylphosphine triphenylborane, tetraphenylphosphonium dicyanamide, and tetraphenylphosphonium tetra(4-methylphenyl)borate.

[0048] The total content of the curing accelerator is preferably 0.03 to 4.5 parts by mass, 0.05 to 3.5 parts by mass, 0.10 to 2.5 parts by mass, or 0.15 to 1.5 parts by mass, relative to 100 parts by mass of the resin component of the wafer processing tape. When the total content of the curing accelerator is 0.01 part by mass or more, the glass transition temperature and strength of the B-stage sheet tend to be further improved. Furthermore, when the total content of the curing accelerator is 4.5 parts by mass or less, embrittlement due to excessive hardness of the B-stage sheet tends to be further suppressed.

[0049] The heat-resistant layer may contain a filler, which makes it possible to adjust the storage modulus before and after curing.

[0050] The filler is not particularly limited, but examples thereof include silica, boron nitride, aluminum nitride, aluminum oxide, silicon nitride, silicon oxide, magnesium oxide, metallic aluminum, and zinc oxide.

[0051] The content of the filler is preferably 50 to 500 parts by mass, 100 to 400 parts by mass, or 150 to 300 parts by mass per 100 parts by mass of the resin component. When the content of the curing agent is 50 parts by mass or more, the strength of the B-stage sheet tends to be further improved. Furthermore, when the amount of the curing agent used is 500 parts by mass or less, embrittlement due to the B-stage sheet becoming too hard tends to be further suppressed.

[0052] The composition before preparing the wafer processing tape may contain a solvent. The solvent is not particularly limited, but examples thereof include alcohol-based solvents, glycol ether-based solvents, aromatic solvents, and ketone-based solvents. Examples of alcohol-based solvents include isopropyl alcohol and diacetone alcohol. Examples of glycol ether-based solvents include ethyl cellosolve and butyl cellosolve. Examples of aromatic solvents include toluene and xylene. Examples of ketone-based solvents include methyl ethyl ketone and methyl isobutyl ketone.

[0053] 1.2. Follower layer The conforming layer 12 conforms to the unevenness of the wafer 20, protecting the unevenness from being damaged during the wafer processing process, and also contributes to improving adhesion by exhibiting high conforming properties and preventing gaps from forming between the release layer and the semiconductor element forming surface 20a.

[0054] The following layer 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 copolymer, and ethylene-acrylic acid copolymer. These resins may be used alone or in combination of two or more. More specifically, the following resins may be a mixture, copolymer, or laminate of one resin with another.

[0055] 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.

[0056] 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.

[0057] The polyolefin ionomer is not particularly limited, but examples thereof include ethylene-methacrylate copolymer, ethylene-acrylate copolymer, and ethylene-methacrylate-acrylate copolymer.

[0058] 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, and a methacrylic acid ester-methacrylate copolymer.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] The resin may contain an elastomer. Examples of the elastomer include, but are not limited to, natural rubber, butyl rubber, isoprene rubber, chloroprene rubber, silicone rubber, ethylene-vinyl acetate copolymer, ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acrylic acid ester copolymer, polybutadiene resin, polycarbonate resin, thermoplastic polyimide resin, polyamide resin such as 6-nylon and 6,6-nylon, (meth)acrylic resin, polyester resin such as polyethylene terephthalate and polybutylene terephthalate, polyamideimide resin, fluororesin, and phenoxy resin. These elastomers may be used alone or in combination.

[0063] The content of the resin is preferably 80 to 100 mass %, 85 to 100 mass %, or 90 to 100 mass % relative to the total amount of the follow-up layer.

[0064] The following layer may contain additives other than the resin 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.

[0065] The thickness of the conformal layer is preferably 50 to 500 μm, 75 to 400 μm, or 100 to 300 μm. When the thickness of the conformal layer is within the above range, conformability to the irregularities of the wafer is further improved, and voids are less likely to be formed between the wafer processing tape and the semiconductor element forming surface, tending to improve adhesion.

[0066] 1.3.Release layer The release layer 11 is a layer laminated on the surface 12a of the follower layer 12. During the semiconductor processing, the release layer 11 adheres to the wafer 20 to protect the semiconductor element forming surface 20a, and also prevents the follower layer, whose adhesive strength becomes too high at high temperatures, from coming into direct contact with the semiconductor element forming surface 20a. In addition, after the processing, the release layer 11 can be peeled off without leaving any adhesive residue.

[0067] The thickness of the release layer is preferably 0.2 to 15 μm, 0.5 to 10 μm, 0.7 to 7.0 μm, or 1.0 to 5.0 μm. When the thickness is within the above range, the followability is less likely to be hindered and adhesive residue tends to be suppressed.

[0068] The base polymer constituting the main component of the release layer is not particularly limited, and examples thereof include (meth)acrylic acid ester copolymers. The shape of the (meth)acrylic acid ester copolymer is not particularly limited, and examples thereof include linear, branched, or crosslinked shapes. Among these, a crosslinked shape is preferred. By using such a base polymer, the physical properties of the release layer can be adjusted. The base polymer having a crosslinked or branched shape may be a base polymer in which epoxy groups or the like of a linear or branched shape are bonded via a curing agent, which will be described later.

[0069] The monomer constituting the (meth)acrylic acid ester copolymer is not particularly limited, but examples thereof include (meth)acrylic acid alkyl esters having an alkyl group with 1 to 3 carbon atoms, (meth)acrylic acid esters having a glycidyl group, (meth)acrylic acid esters having a hydroxyl group, and monomers having an aromatic group. The (meth)acrylic acid ester copolymer may also contain a copolymerizable vinyl monomer other than the acrylic monomer.

[0070] The (meth)acrylic acid alkyl ester having an alkyl group having 1 to 3 carbon atoms is not particularly limited, but examples thereof include methyl (meth)acrylate, ethyl (meth)acrylate, and propyl (meth)acrylate.

[0071] The (meth)acrylic acid ester having a glycidyl group is not particularly limited, but examples thereof include glycidyl (meth)acrylate and allyl glycidyl ether. A structural unit derived from a (meth)acrylic acid ester having a glycidyl group may be used for the purpose of introducing an epoxy group into a base polymer. When the epoxy group introduced into the base polymer reacts with a curing agent described below, the base polymers bond to each other and are crosslinked three-dimensionally.

[0072] The (meth)acrylic acid ester having a hydroxyl group is not particularly limited, but examples thereof include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, pentaerythritol triacrylate, glycidol di(meth)acrylate, and dipentaerythritol pentaacrylate. A structural unit derived from a (meth)acrylic acid ester having a hydroxyl group may be used for the purpose of introducing an epoxy group into a base polymer. The hydroxyl group introduced into the base polymer reacts with a curing agent described below, causing the base polymers to bond together and crosslink three-dimensionally.

[0073] The monomer having an aromatic group is not particularly limited, but examples thereof include styrene, phenoxyethyl (meth)acrylate, and benzyl (meth)acrylate.

[0074] When the structural units of the base polymer have the above composition, the dynamic viscoelasticity of the release layer tends to be adjusted to fall within the above range.

[0075] The glass transition temperature of the base polymer is preferably −25 to 15° C., −20 to 10° C., −15 to 5° C., or −10 to 0° C. When the glass transition temperature of the base polymer is −25° C. or higher, releasability is improved and contamination due to residue from the tape tends to be more effectively suppressed. When the glass transition temperature of the base polymer is 15° C. or lower, adhesion is improved and contamination due to wet areas tends to be more effectively suppressed.

[0076] The content of the base polymer relative to the total amount of the release layer is preferably 85 to 98 mass %, 90 to 97 mass %, or 92 to 96 mass %.

[0077] 2. Manufacturing method of wafer processing tape The manufacturing method of the wafer processing tape of this embodiment is not particularly limited, but is not particularly limited as long as it includes, for example, a step of forming a heat-resistant layer 13 on the back surface 12b of the follower layer 12, and may also include a step of forming a release layer 11 on the front surface 12a of the follower layer 12, if necessary.

[0078] The method for forming the release layer 11 and the heat-resistant layer 13 is not particularly limited, but for example, films may be dry-laminated together, or a composition may be applied to the surface of the follower layer 12 and then dried or photo-cured to form the release layer 11 and the heat-resistant layer 13. Alternatively, the release layer 11 and the heat-resistant layer 13 may be attached to the follower layer 12 via an adhesive layer.

[0079] 3. Wafer processing method The wafer processing method of this embodiment includes a laminating step of laminating the wafer processing tape to the device-formed side of the wafer, a back-grinding step of polishing the non-device-formed side of the wafer that has been laminated to the wafer processing tape, and, if necessary, may include a metal layer forming step of forming a metal layer on the side of the wafer opposite to the side to which the wafer processing tape is laminated, a dicing step of dicing the wafer, and a peeling step of heating and peeling off the wafer processing tape. Figure 2 shows a flowchart illustrating the wafer processing method of this embodiment using schematic cross-sectional views.

[0080] 3.1.Lamination process The laminating step S1 is a step of laminating the wafer processing tape 10 to the semiconductor element forming surface 20a of the wafer 20. The surface of the wafer 20 to which the wafer processing tape 10 is laminated may be the non-element forming surface 20b.

[0081] In the laminating step, the wafer processing tape 10 may be preheated before being laminated to the wafer main surface 20a, or the wafer processing tape 10 may be laminated to the wafer main surface 20a and then heated. By laminating the surface 11a of the release layer 11 to the semiconductor element forming surface 20a of the wafer in a heated state, the surface 11a of the release layer 11 can be laminated to the semiconductor element forming surface 20a of the wafer in a state where it conforms to the semiconductor element forming surface 20a of the wafer (see S2 in FIG. 2). In this way, by immersing the convex portions in the wafer processing tape 10, the semiconductor element forming surface 20a of the wafer having the convex portions can be protected.

[0082] The heating temperature is preferably 60 to 150° C., more preferably 70 to 140° C., and even more preferably 80 to 130° C. The heating time of the wafer processing tape 10 is preferably 3 to 120 seconds, and more preferably 5 to 90 seconds. By keeping the heating conditions within the above range, the conformability of the wafer processing tape 10 tends to be further improved.

[0083] 3.2. Processing process The processing step for processing the wafer 20 in a state in which the wafer processing tape 10 and the wafer 20 are bonded together is not particularly limited, and any wafer processing process can be appropriately applied. Examples of processing steps include a backgrinding process in which the back surface 20b of the wafer, which is not bonded to the wafer processing tape 10, is ground to obtain a thinned wafer, a metal layer forming process in which a metal layer 21 is formed on the back surface 20b of the wafer opposite to the semiconductor element forming surface 20a to which the wafer processing tape 10 is bonded, and a dicing process in which the wafer 20 is diced to obtain semiconductor chips.

[0084] 2, an example of a combined processing process is a method in which, after the back-grinding steps S2 and S3, a metal layer forming step S4 of forming a metal layer 21 and a dicing step S5 of dicing the thinned wafer by blade dicing or the like are performed. In the following, a process in which the metal layer forming step S4 and the dicing step S5 are performed after the back-grinding steps S2 and S3 is described, but the present embodiment is not limited to this.

[0085] 3.2.1.Back grinding process The backgrinding steps S2 and S3 are steps for polishing the non-element forming surface 20b of the wafer 20 bonded to the wafer processing tape 10. Specifically, from the viewpoint of protecting the semiconductor element forming surface 20a, the wafer processing tape 10 is bonded to the semiconductor element forming surface 20a as a backgrinding tape, and the non-element forming surface 20b of the wafer 20 is ground (backgrinded) to a desired thickness.

[0086] The specific method of back-grinding is not particularly limited, and known methods can be used. For example, a method of grinding while supplying a slurry containing abrasive grains to the back surface 20b of the wafer 20 can be used. The thickness of the thinned wafer obtained by this method is not particularly limited as long as it is a thickness suitable for the processing purpose, but as an example, it is preferably 300 μm or less, 150 μm or less, or 50 μm or less.

[0087] In backgrinding, a load is applied in the thickness direction of the wafer 20, which can easily damage protrusions and reduce yield. In contrast, by using the wafer processing tape 10 of this embodiment, processing can be performed with at least a portion of the protrusions embedded in the wafer processing tape 10, making it possible to avoid damage to the protrusions.

[0088] In the wafer processing method of this embodiment, when a wafer has modified portions and grooves formed in advance on its surface for singulation, and a back-grinding process is performed to thin the wafer 20 from the back surface 20b of the wafer 20, the wafer 20 may be thinned to approximately the same depth as the modified portions and grooves. This allows thinning by back-grinding and singulation to be performed simultaneously.

[0089] 3.2.2. Metal layer formation process The metal layer forming step S4 is a step of forming a metal layer 21 on the surface 20b of the wafer 20 opposite to the surface 20a to which the wafer processing tape 10 is attached. The method for forming the metal layer is not particularly limited, but examples thereof include ALD (atomic layer deposition) and CVD (chemical vapor deposition). The conditions for forming the metal layer using these methods are not particularly limited, but examples thereof include treatment at 200 to 300°C for 3 to 10 minutes.

[0090] 3.2.3.Dicing process The dicing step S5 is a step of dicing the wafer 20. The dicing method is not particularly limited, but examples thereof include blade dicing, in which the wafer is cut into semiconductor chips 30 by a dicing blade.

[0091] 3.3. Peeling process The peeling step S6 is a step of peeling the wafer processing tape 10 from the wafer 20 or the semiconductor chip 30. The peeling step of picking up the semiconductor chip 30 from the wafer processing tape is also called a pick-up step.

[0092] In the peeling step S6, the wafer processing tape 10 may be peeled off at room temperature, or may be peeled off under heating. Furthermore, in the peeling step S6, if the release layer 11 contains a monomer and a photopolymerization initiator, the release layer 11 may be cured by irradiating it with ultraviolet light before peeling, thereby reducing its adhesive strength to the wafer 20. This tends to further improve the releasability and further suppress contamination due to residues derived from the tape.

[0093] Furthermore, when picking up the semiconductor chip 30 from the wafer processing tape, although not particularly limited, for example, the semiconductor chip 30 may be pushed up by a push-up needle and then picked up by suction using a suction collet.

[0094] Furthermore, during pick-up, an expanding device may be used to stretch the wafer processing tape 10 in the planar direction, and the semiconductor chips 30 may be picked up by a pick-up device in a state where they are separated from each other. [Example]

[0095] The present invention will be described in more detail below using examples and comparative examples, but the present invention is not limited to the following examples.

[0096] (Comparative Example 1) In Comparative Example 1, a 250 μm thick ionomer sheet (Fanclea, HMD250, manufactured by Gunze Co., Ltd.) was prepared as a wafer processing tape and cut into a 100 mm square to prepare a test piece as shown in Figure 3. This test piece was heated at 200°C for 5 minutes, returned to room temperature, and then the thickness was measured with a dial gauge at nine points shown in Figure 3. From the thickness values ​​at the nine points, the maximum value, minimum value, average value, variance, and standard deviation were calculated and obtained as data indicating the thickness distribution.

[0097] Similarly, the thickness distribution was measured when the test piece was heated at 250°C for 5 minutes, and when it was heated at 275°C for 5 minutes. Furthermore, for reference, the thickness distribution was also measured at room temperature (23°C) before heating. The results are shown in Table 1.

[0098] As shown in Table 1, the HMD250 single-layer follower sheet melts when heated, and compared to the thickness distribution at room temperature (23°C) before heating, the higher the heating temperature, the greater the difference between the maximum and minimum thickness values, resulting in a loss of uniformity. When HMD250 is used as a protective sheet, for example, when processing is performed at high temperatures in the BSM process to form a metal layer on the backside of a wafer after back-grinding, the thickness of the protective sheet will vary, which can reduce the accuracy of subsequent processes and result in a loss of yield.

[0099] (Comparative Example 2) As Comparative Example 2, a sheet was prepared as a wafer processing tape, in which a 25 μm thick polyethylene terephthalate sheet (PET25, manufactured by Toray Industries, Inc., Lumirror S10) was laminated as a heat-resistant layer with a 150 μm thick ionomer sheet (manufactured by Gunze Ltd., Fanclair, HMD150) as a follow-up layer. This sheet was then cut into a 100 mm square to prepare a test piece, as shown in Figure 3.

[0100] This test piece was heated at 260°C for 5 minutes, and after returning to room temperature, the thickness was measured using a dial gauge at nine points shown in Figure 3. From the thickness values ​​at those nine points, the maximum, minimum, average, variance, and standard deviation were calculated and used as data showing the thickness distribution. For reference, the thickness distribution at room temperature (23°C) before heating was also measured. The results are shown in Table 1.

[0101] As shown in Table 1, even in wafer processing tapes laminated with PET25 and HMD150, the HMD150, which acts as a follower layer, melts when heated. Compared to the thickness distribution at room temperature (23°C) before heating, the higher the heating temperature, the greater the difference between the maximum and minimum thickness values, resulting in a loss of uniformity. This is thought to be because polyethylene terephthalate has a low glass transition temperature of approximately 80°C and a low melting point of approximately 260°C, so PET25 does not function as a heat-resistant layer at the high temperatures expected in the BSM process. Therefore, at high temperatures, PET25 is unable to suppress the melting of HMD150 and the resulting unevenness in thickness distribution, resulting in a loss of uniformity in thickness distribution.

[0102] Example 1 A composition for the heat-resistant layer was prepared by mixing 75 parts by mass of an epoxy resin (manufactured by DIC Corporation, product name EXP-830CRP), 60.75 parts by mass of a phenolic curing agent (manufactured by DIC Corporation, product name TD2090-60M), 125 parts by mass of an acrylic resin having an epoxy group (manufactured by Nagase ChemteX Corporation, product name SG-P3), and 0.25 parts by mass of a curing accelerator (manufactured by Shikoku Chemicals Corporation, product name 2PZ-CN).

[0103] Furthermore, 62 parts by mass of ethyl acrylate, 30 parts by mass of methyl methacrylate, 5 parts by mass of 2-hydroxyethyl methacrylate, 3 parts by mass of glycidyl methacrylate, 0.2 parts by mass of styrene, and azobisisobutyronitrile as a polymerization initiator were added to a polymerization vessel, and polymerization was carried out for 4 hours at 60° C. As a result, acrylic polymer 1 having a glass transition temperature of −5° C. and a weight average molecular weight of 600,000 was obtained.

[0104] Furthermore, 100 parts by mass of acrylic polymer 1, 4 parts by mass of acrylic monomer 1 (manufactured by Kyoeisha Chemical Co., Ltd., product name "Light Acrylate DPE-6A", dipentaerythritol hexaacrylate), and 10 parts by mass of photopolymerization initiator (manufactured by IGM, product name "Omnirad-184", α-hydroxyalkylphenone) were mixed to prepare a composition for the release layer.

[0105] The heat-resistant layer composition prepared as described above was applied to one surface of a 250 μm thick ionomer sheet (Gunze Fanclea, HMD250) serving as a follow-up layer, and semi-cured by treatment at 160° C. for 1 hour to form a 160 μm thick B-stage layer as a heat-resistant layer. The cure rate was measured by differential scanning calorimetry (DSC) as the ratio of the heat amount when semi-cured by treatment at 160° C. for 1 hour to the heat amount when completely cured, and was found to be 89%.

[0106] In addition, the release layer composition prepared as described above was applied to the other surface of the ionomer sheet, which was the follow-up layer, and the release layer composition was irradiated with ultraviolet light using a UV irradiation device (UVC-4800-4, manufactured by Ushio Inc.) at a high-pressure mercury illumination intensity of 160 W and a cumulative irradiation dose of 1280 mJ, thereby causing a curing reaction to proceed and forming a release layer (HC) with a thickness of 2 μm.

[0107] In this way, a wafer processing tape having a heat-resistant layer, a conforming layer, and a release layer, which is a B-stage sheet, was produced, and a test piece was prepared by cutting it into a 100 mm square as shown in FIG.

[0108] The storage modulus Eh140 of the B-stage sheet at 140°C is 4.2 x 10 4 Pa, and the storage modulus Eh200 at 200°C is 2.5 × 10 6 Pa, and the storage modulus Eh25 at 25°C is 5.3 × 10 6 Pa. The ratio (Eh200 / Eh140) was 58.7, and the ratio (Eh25 / Eh140) was 125.

[0109] This test piece was heated at 260°C for 5 minutes, and after returning to room temperature, the thickness was measured using a dial gauge at nine points shown in Figure 3. From the thickness values ​​at those nine points, the maximum, minimum, average, variance, and standard deviation were calculated and used as data showing the thickness distribution. For reference, the thickness distribution at room temperature (23°C) before heating was also measured. The results are shown in Table 1.

[0110] As shown in Table 1, in the wafer processing tape using a B-stage sheet as the heat-resistant layer, the decrease in thickness distribution uniformity is suppressed, even though the same follower layer as in Comparative Example 1 is used. This is thought to be because the curing reaction progresses as the B-stage sheet approaches 260°C, preventing the flow of the follower layer that has softened at high temperatures. In other words, the B-stage sheet functions to suppress the melting of HMD250 and the resulting non-uniformity in thickness distribution.

[0111] Furthermore, by using a B-stage sheet that is not hardened at room temperature instead of a C-stage sheet that is hardened at room temperature, the sheet can better conform to the irregularities on the semiconductor element forming surface of the wafer in processes such as the back grinding process that is carried out at room temperature or close to room temperature before the BSM process.

[0112] Example 2 A wafer processing tape of Example 2 was produced in the same manner as in Example 1, except that no release layer (HC) was provided, and the same evaluations were carried out as above. As a result, similar results were obtained for the sheet without the release layer, as shown in Table 1. This also confirmed the effect of using a B-stage sheet as a heat-resistant layer in suppressing thickness non-uniformity at high temperatures.

[0113] As shown in Table 1, it was found that the B-stage sheet had excellent thickness uniformity even at high temperatures.

[0114] [Table 1] [Industrial Applicability]

[0115] The present invention has industrial applicability as a wafer processing tape that can be used across semiconductor processing steps by combining heat resistance with conformability. [Explanation of symbols]

[0116] 10...wafer processing tape, 11...release layer, 11a...surface, 12...following layer, 12a...surface, 12b...back surface, 13...heat-resistant layer, 20...wafer, 20a...semiconductor element forming surface, 20b...non-element forming surface, 21...metal layer, 30...semiconductor chip, S1...bonding step, S2...back grinding step, S3...back grinding step, S4...metal layer forming step, S5...dicing step, S6...peeling step

Claims

1. A follow-up layer and a heat-resistant layer laminated on the back surface of the follow-up layer, The heat-resistant layer is a B-stage sheet. Tape for wafer processing.

2. The heat-resistant layer contains an acrylic resin and an epoxy resin. The wafer processing tape according to claim 1 .

3. The cure rate of the B-stage sheet is 30 to 95%. The wafer processing tape according to claim 1 .

4. the ratio (Eh200 / Eh140) of the storage modulus Eh140 at 140°C to the storage modulus Eh200 at 200°C of the heat-resistant layer is 10 to 100; The wafer processing tape according to claim 1 .

5. the ratio (Eh25 / Eh140) of the storage modulus Eh140 at 140°C to the storage modulus Eh25 at 25°C of the heat-resistant layer is 25 to 250; The wafer processing tape according to claim 1 .

6. a lamination step of laminating the wafer processing tape according to any one of claims 1 to 5 to the element-forming surface of the wafer; a back grinding step of grinding a non-element forming surface of the wafer bonded to the wafer processing tape, Wafer processing method.

7. a metal layer forming step of forming a metal layer on the surface of the wafer opposite to the surface to which the wafer processing tape is attached, The wafer processing method according to claim 6.

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

9. a peeling step of heating and peeling off the wafer processing tape after the back-grinding step; The wafer processing method according to claim 6.

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