Liquid surface protection material for semiconductor wafer processing

Abstract

Provided is a liquid surface protection material for processing a semiconductor wafer, which has excellent filling properties on the surface of the semiconductor wafer and is capable of suppressing paste residue (adhesion of a residue of the surface protection material) on the surface of the semiconductor wafer after peeling. A liquid surface protection material for processing a semiconductor wafer according to an embodiment of the present invention contains an acrylic emulsion resin. In addition, a protective film according to an embodiment of the present invention is formed from the liquid surface protective material for semiconductor wafer processing. A method for processing a semiconductor wafer according to an embodiment of the present invention comprises: forming a protective film by applying a liquid surface protective material for processing a semiconductor wafer to a surface of a semiconductor wafer on which a circuit pattern is formed; grinding the surface of the semiconductor wafer on which the protective film is not formed; and stripping and removing the protective film.

Description

Technical Field

[0001] The present invention relates to a liquid surface protection material for semiconductor wafer processing, a protective film formed from the liquid surface protection material for semiconductor wafer processing, and a method for processing a semiconductor wafer. Background Art

[0002] A semiconductor wafer is supplied to a processing step such as a back grinding step in a state where a surface on which a circuit is formed is protected by a protection material. As a representative protection material for a semiconductor wafer, an adhesive tape (for example, Patent Document 1) is known. In recent years, the circuit surface of a semiconductor wafer has become complicated, and sometimes the adhesive tape cannot be sufficiently filled into the unevenness of the circuit surface. In the case of insufficient filling, water may penetrate between the adhesive layer of the adhesive tape and the semiconductor wafer surface, and wafer scattering and cracking may occur. In addition, foreign matter may adhere to the insufficiently filled portion.

[0003] As a method for protecting the circuit surface of a semiconductor wafer other than the adhesive tape, a method of coating a liquid composition and forming a protective film has been proposed (for example, Patent Documents 2 to 6). However, after the protective film formed by these methods is removed, residues may adhere to the circuit surface, resulting in contamination of the circuit surface caused by the protective film. In addition, in the removal step, a removal step using a solvent may sometimes be required, which may increase the burden on the environment.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2015-185641

[0007] Patent Document 2: Japanese Patent Application Laid-Open No. 10-120965

[0008] Patent Document 3: Japanese Patent Application Laid-Open No. 2000-315668

[0009] Patent Document 4: Japanese Patent Application Laid-Open No. 2014-212179

[0010] Patent Document 5: Japanese Patent Application Laid-Open No. 2011-23272

[0011] Patent Document 6: Japanese Patent Application Laid-Open No. 2014-19889 Summary of the Invention

[0012] Problems to be Solved by the Invention

[0013] The present invention is completed to solve the above-mentioned existing problems, and its object is to provide a liquid surface protection material for semiconductor wafer processing that has excellent fillability on the surface of a semiconductor wafer and can suppress the paste residue (attachment of residues of the surface protection material) on the surface of the semiconductor wafer after peeling.

[0014] Solution to the problem

[0015] 1. The liquid surface protection material for semiconductor wafer processing according to an embodiment of the present invention contains an acrylic emulsion resin.

[0016] 2. Optionally, in the liquid surface protection material for semiconductor wafer processing described in 1 above, the acid value of the acrylic emulsion resin is 10 mg / KOH or less.

[0017] 3. Optionally, in the liquid surface protection material for semiconductor wafer processing described in 1 above, the SP value of the acrylic emulsion resin is 9 (cal / cm 3 ) 1 / 2 ~11 (cal / cm 3 ) 1 / 2 .

[0018] 4. Optionally, in the liquid surface protection material for semiconductor wafer processing described in any one of 1 to 3 above, the BH viscosity is 0.1 Pa·s to 10 Pa·s.

[0019] 5. Another aspect of an embodiment of the present invention provides a protective film. This protective film is formed by using the liquid surface protection material for semiconductor wafer processing described in any one of 1 to 4 above.

[0020] 6. Optionally, in the protective film described in 5 above, the tensile modulus at 23°C is 0.1 GPa to 1.1 GPa.

[0021] 7. Optionally, in the protective film described in 5 or 6 above, the adhesion to a silicon wafer is 1.0 N / 25 mm or less.

[0022] 8. Another aspect of an embodiment of the present invention provides a method for processing a semiconductor wafer. This method for processing a semiconductor wafer includes: coating the liquid surface protection material for semiconductor wafer processing described in any one of 1 to 4 above on the surface of the semiconductor wafer on which a circuit pattern is formed to form a protective film; grinding the surface of the semiconductor wafer on which the protective film is not formed; and peeling off and removing the protective film.

[0023] Advantageous effects of the invention

[0024] According to an embodiment of the present invention, there is provided a liquid surface protection material for semiconductor wafer processing, which has excellent filling properties on the surface of a semiconductor wafer (more specifically, the circuit surface), and can suppress paste residue (attachment of residues of the surface protection material) on the surface of the semiconductor wafer after peeling off the protective film. Further, the protective film formed by using the liquid surface protection material for semiconductor wafer processing according to the embodiment of the present invention can be peeled off and removed without performing a removal process using a solvent. Therefore, the environmental burden caused by the use of a solvent can be reduced. Further, paste residue (attachment of residues of the surface protection material) on the surface of the semiconductor wafer after peeling can also be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 FIG. is a schematic cross-sectional view of a semiconductor wafer and a protective film in a processing step of a semiconductor wafer according to an embodiment of the present invention.

[0026] Figure 2 FIG. is a schematic cross-sectional view of a semiconductor wafer and a protective film in a processing step of a semiconductor wafer according to another embodiment of the present invention.

[0027] Figure 3 FIG. is a schematic cross-sectional view of a semiconductor wafer and a protective film in a processing step of a semiconductor wafer according to still another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0028] A. Liquid surface protection material for semiconductor wafer processing

[0029] The liquid surface protection material for semiconductor wafer processing according to an embodiment of the present invention (hereinafter, also referred to as the liquid surface protection material) contains an acrylic emulsion resin. The liquid surface protection material according to the embodiment of the present invention is, for example, used by coating it on the circuit surface of a semiconductor wafer. The shape of the circuit surface of the semiconductor wafer becomes complex, and in order to appropriately protect the circuit surface in the processing step of the semiconductor wafer, a surface protection material with more excellent filling properties is sought. Since the surface protection material according to the embodiment of the present invention is in a liquid state, even if the circuit surface of the semiconductor wafer has a complex shape, the filling properties of the surface of the semiconductor wafer (more specifically, the circuit surface) are excellent. In addition, the protective film formed by the liquid surface protection material according to the embodiment of the present invention can be easily removed by peeling. Therefore, there is no need for a dissolution and removal process using a solvent, and the environmental burden caused by the solvent can be reduced. Further, paste residue (attachment of residues of the surface protection material) on the surface of the semiconductor wafer can also be suppressed.

[0030] The BH viscosity of the liquid surface protection material according to the embodiment of the present invention is preferably from 0.1 Pa·s to 10 Pa·s, more preferably from 0.2 Pa·s to 5 Pa·s, still more preferably from 0.3 Pa·s to 3 Pa·s, and particularly preferably from 0.5 Pa·s to 2 Pa·s. If the BH viscosity is within the above range, the liquid surface protection material can be well coated on the surface of the semiconductor wafer. The BH viscosity can be adjusted to any appropriate value according to the coating method. In this specification, the BH viscosity refers to the viscosity measured by a BH viscometer under the conditions of 30 °C and 2 rpm. The rotor used for measurement can be any appropriate rotor according to the viscosity, for example, the No. 2 rotor can be used.

[0031] A-1. Acrylic emulsion resin

[0032] As the acrylic emulsion resin, a resin obtained by emulsion polymerization of any appropriate monomer components can be used. As described above, the liquid surface protection material according to the embodiment of the present invention contains an acrylic emulsion resin. The liquid surface protection material containing the acrylic emulsion resin forms a protective film on the surface of the semiconductor wafer after coating and drying. This protective film can appropriately protect the surface of the semiconductor wafer during the processing process of the semiconductor wafer and can be peeled off without using a solvent after use. Furthermore, it can also suppress the paste residue (attachment of residues of the surface protection material) on the surface of the semiconductor wafer after peeling. The types of monomers of the acrylic emulsion resin are abundant, and by selecting the types of copolymerized monomers, a liquid surface protection material capable of forming a protective film with appropriate physical properties can be obtained.

[0033] The acid value of the acrylic emulsion resin is preferably 10 mg / KOH or less, more preferably from 0 mg / KOH to 8 mg / KOH, still more preferably from 0 mg / KOH to 5 mg / KOH, and particularly preferably from 0 mg / KOH to 3 mg / KOH. If the acid value of the acrylic emulsion resin is within the above range, the peelability of the protective film formed by the liquid surface protection material (for example, suppressing the tearing and defect generation of the protective film during peeling) is improved, and it can be easily peeled off from the surface of the semiconductor wafer. In this specification, the acid value of the acrylic emulsion resin refers to the value measured by the potentiometric titration method specified in JIS K0070:1992.

[0034] The SP value of the acrylic emulsion resin is preferably from 9 (cal / cm 3 ) 1 / 2 to 11 (cal / cm 3 ) 1 / 2 , more preferably from 9 (cal / cm 3 ) 1 / 2 to 10.8 (cal / cm 3 )1 / 2 , more preferably 9 (cal / cm 3 ) 1 / 2 ~10.5 (cal / cm 3 ) 1 / 2 . If the SP value is within the above range, it is possible to suppress the occurrence of peeling defects caused by excessive adhesion of the protective film formed by the liquid surface protection material to the surface of the semiconductor wafer, and the adhesion of the residue of the surface protection material to the surface of the semiconductor wafer. In this specification, the SP value refers to the value of the solubility parameter calculated according to the basic structure of the compound by the method proposed by Fedors.

[0035] The glass transition temperature (Tg) of the acrylic emulsion resin can be set to any appropriate value. The glass transition temperature of the acrylic emulsion resin is preferably -30°C to 30°C, more preferably -25°C to 25°C, and further preferably -20°C to 20°C. If the Tg of the acrylic emulsion resin is within the above range, the adhesion of the protective film formed by the liquid surface protection material to the semiconductor wafer is improved, and a liquid surface protection material with more excellent filling properties can be provided. In this specification, the glass transition temperature of the acrylic emulsion resin refers to the theoretical value calculated using the Fox formula based on the monomer units and their ratios constituting each resin (polymer). The theoretical glass transition temperature obtained using the Fox formula can be consistent with the measured glass transition temperature obtained by methods such as differential scanning calorimetry (DSC) or dynamic viscoelasticity measurement. It should be noted that in the case where the theoretical value cannot be calculated, the measured glass transition temperature can be used.

[0036] The Fox formula is as follows, and it refers to the relationship between the Tg of the acrylic polymer and the glass transition temperature Tgi of the homopolymer obtained by homopolymerizing each monomer constituting the acrylic polymer.

[0037] 1 / Tg = Σ(Wi / Tgi)

[0038] (In the formula, Tg represents the glass transition temperature of the acrylic polymer (unit: K), Wi represents the weight fraction of monomer i in the acrylic polymer (the copolymerization ratio based on weight), and Tgi represents the glass transition temperature of the homopolymer of monomer i (unit: K)).

[0039] As the glass transition temperature of the homopolymer used for Tg calculation, the value recorded in any appropriate data can be used. For example, for the monomers listed below, the following values are used as the glass transition temperature of the homopolymer of the monomer.

[0040] n-Butyl acrylate -55°C.

[0041] Acrylonitrile: 97 °C

[0042] Methyl methacrylate: 105 °C

[0043] Acrylic acid: 106 °C

[0044] Vinyl acetate: 32 °C

[0045] For the glass transition temperature of the homopolymer of monomers other than those exemplified above, for example, the values described in "Polymer Handbook" (Third Edition, John Wiley & Sons, Inc., 1989) can be used. It should be noted that in the case where multiple values are described, the highest value is adopted.

[0046] For monomers for which the glass transition temperature of the homopolymer is not described in the above Polymer Handbook, the values obtained by using the measurement method described in Japanese Patent Application Laid-Open No. 2007-51271 (measured glass transition temperature) can be used. Specifically, into a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux condenser, 100 parts by weight of the monomer, 0.2 parts by weight of azobisisobutyronitrile, and 200 parts by weight of ethyl acetate as a polymerization solvent are charged, and while introducing nitrogen, it is stirred for 1 hour. After removing the oxygen in the polymerization system in this way, the temperature is raised to 63 °C and reacted for 10 hours. Then, it is cooled to room temperature to obtain a homopolymer solution with a solid content concentration of 33% by weight. Next, this homopolymer solution is cast and coated on a release liner and dried to produce a test sample (sheet-like homopolymer) with a thickness of about 2 mm. This test sample is punched into a disc shape with a diameter of 7.9 mm, clamped by parallel plates, and using a viscoelasticity tester (ARES, manufactured by Rheometrics), while applying a shear strain of 1 Hz, the viscoelasticity is measured in a temperature range of -70 °C to 150 °C at a heating rate of 5 °C / minute in a shear mode, and the peak temperature of tanδ is set as the Tg of the homopolymer.

[0047] A-1-1. Monomer composition

[0048] As described above, the acrylic emulsion resin can be obtained by emulsion polymerization of an arbitrary suitable monomer composition. The monomer composition includes (meth)acrylic monomers and / or any suitable monomers that can copolymerize with (meth)acrylic monomers. The monomer components can include only one monomer or two or more monomers can be used in combination. In this specification, (meth)acrylic acid means acrylic acid and / or methacrylic acid.

[0049] Typically, the monomer composition preferably contains a (meth)acryloyl group-containing monomer. The (meth)acryloyl group-containing monomer can be used alone or in combination of two or more. The content ratio of the (meth)acryloyl group-containing monomer is preferably 40 parts by weight or more, more preferably 60 parts by weight or more, further preferably 65 parts by weight or more, and particularly preferably 70 parts by weight or more based on 100 parts by weight in total of all monomer components. The (meth)acryloyl group-containing monomer is, for example, 95 parts by weight or less based on 100 parts by weight in total of all monomer components. If the content ratio of the (meth)acryloyl group-containing monomer is within the above range, the protective film formed from the liquid surface protective material can be peeled off, and further, paste residue (adhesion of residues of the surface protective material) on the semiconductor wafer surface can be suppressed.

[0050] As the (meth)acryloyl group-containing monomer, any suitable (meth)acryloyl group-containing monomer can be used. It is preferred to use an alkyl (meth)acrylate as the (meth)acryloyl group-containing monomer. By adjusting the type and / or content ratio of the alkyl (meth)acrylate used, the storage elastic modulus of the liquid surface protective material, the SP value of the acrylic emulsion resin, and the tensile properties of the formed protective film can be adjusted to any suitable values. The alkyl (meth)acrylate can be used alone or in combination of two or more.

[0051] As the alkyl (meth)acrylate, any suitable alkyl (meth)acrylate can be used. Specifically, examples include alkyl (meth)acrylates having 1 to 20 carbon atoms such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate (hereinafter also referred to as (meth)acrylic acid C1-C20 alkyl esters).

[0052] The monomer composition preferably contains an alkyl (meth)acrylate having an alkyl group with 4 to 20 carbon atoms ((meth)acrylate C4-C20 alkyl ester), more preferably contains an alkyl (meth)acrylate having an alkyl group with 4 to 14 carbon atoms, and still more preferably contains an alkyl (meth)acrylate having an alkyl group with 4 to 9 carbon atoms. When these (meth)acrylate C4-C20 alkyl esters are used, the peeling of the protective film formed using the liquid surface protective material can be easily performed. Furthermore, the paste residue (attachment of the residue of the surface protective material) on the semiconductor wafer surface after peeling can also be suppressed. Specifically, the monomer composition preferably contains n-butyl acrylate (BA) and / or 2-ethylhexyl acrylate (2EHA), and more preferably contains BA. The (meth)acrylate C4-C20 alkyl ester can be used alone or in combination of two or more.

[0053] In the monomer composition, the (meth)acrylate C4-C20 alkyl ester can be used in any appropriate content ratio. The content ratio of the (meth)acrylate C4-C20 alkyl ester is preferably 40 parts by weight or more, more preferably 60 parts by weight or more, and still more preferably 65 parts by weight or more in 100 parts by weight in total of all monomer components. When the content ratio of the (meth)acrylate C4-C20 alkyl ester is within the above range, the peeling of the protective film formed using the liquid surface protective material can be easily performed. In addition, the adhesion to the semiconductor wafer surface can be adjusted to an appropriate value, and the damage to the semiconductor wafer surface during peeling can be suppressed.

[0054] The monomer composition preferably further contains a nitrogen atom-containing monomer. As the nitrogen atom-containing monomer, any suitable nitrogen atom-containing monomer can be used. Specifically, examples include: cyano group-containing monomers such as acrylonitrile, methacrylonitrile, 2-cyanoethyl (meth)acrylate; amide group-containing monomers such as (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N-butyl(meth)acrylamide, N-hydroxymethyl(meth)acrylamide, N-hydroxyethyl(meth)acrylamide, N-methoxymethyl(meth)acrylamide, N-butoxymethyl(meth)acrylamide, diacetone(meth)acrylamide; amino group-containing monomers such as aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, tert-butylaminoethyl (meth)acrylate; monomers having a nitrogen atom-containing ring such as N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-vinylmorpholine, N-vinylcaprolactam, N-(meth)acryloylmorpholine; etc. The nitrogen atom-containing monomer is preferably a cyano group-containing monomer, more preferably acrylonitrile. By using an acrylic emulsion resin obtained from a monomer composition containing these nitrogen atom-containing monomers, the peeling of the protective film formed using a liquid surface protective material can be easily performed, and damage to the semiconductor wafer surface can be suppressed. In addition, the Tg and SP values of the obtained acrylic emulsion resin can be adjusted well to arbitrary values. The nitrogen atom-containing monomer can be used alone or in combination of two or more.

[0055] In the monomer composition, the nitrogen atom-containing monomer can be used in any suitable content ratio. In 100 parts by weight in total of all monomer components, the nitrogen atom-containing monomer is preferably 10 parts by weight or more, more preferably 15 parts by weight or more, further preferably 20 parts by weight or more, and particularly preferably 25 parts by weight or more. If the content ratio of the nitrogen atom-containing monomer is within the above range, the peeling of the protective film formed using a liquid surface protective material can be easily performed. Furthermore, the paste residue (adhesion of residues of the surface protective material) on the semiconductor wafer surface after peeling can also be reduced. The content ratio of the nitrogen atom-containing monomer is preferably 50 parts by weight or less in 100 parts by weight in total of all monomer components.

[0056] The monomer composition preferably further contains an alkyl (meth)acrylate having an alkyl group with 1 to 3 carbon atoms ((meth)acrylate C1-C3 alkyl ester). If a monomer composition further containing these (meth)acrylate alkyl esters is used, the peeling of the protective film formed using the liquid surface protection material can be easily performed, and damage to the surface of the semiconductor wafer can be suppressed. As the (meth)acrylate C1-C3 alkyl ester, methyl methacrylate (MMA) and ethyl methacrylate are preferably used. The (meth)acrylate C1-C3 alkyl ester may be used alone or in combination of two or more.

[0057] In the monomer composition, the (meth)acrylate C1-C3 alkyl ester can be used in any appropriate content ratio. The content ratio of the (meth)acrylate C1-C3 alkyl ester is preferably 6 parts by weight or more, more preferably 8 parts by weight or more, still more preferably 10 parts by weight or more, and particularly preferably 15 parts by weight or more in 100 parts by weight in total of all monomer components. If the content ratio of the (meth)acrylate C1-C3 alkyl ester is within the above range, the peeling of the protective film formed using the liquid surface protection material can be easily performed, and damage to the surface of the semiconductor wafer during peeling can be suppressed. The content ratio of the (meth)acrylate C1-C3 alkyl ester is, for example, 50 parts by weight or less in 100 parts by weight in total of all monomer components.

[0058] The monomer composition may further contain any suitable other monomer components. As other monomer compositions, specifically, the following can be cited: carboxyl group-containing monomers such as acrylic acid (AA), methacrylic acid (MAA), carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid; (meth)acrylic acid hydroxyalkyl esters such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate, and hydroxyl group (OH group)-containing monomers such as polypropylene glycol mono(meth)acrylate; acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride; epoxy group-containing monomers such as glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, and allyl glycidyl ether; ketone group-containing monomers such as diacetone (meth)acrylate, vinyl methyl ketone, vinyl ethyl ketone, allyl acetoacetate, and vinyl acetoacetate; alkoxysilyl group-containing monomers such as 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, and 3-(meth)acryloxypropylmethyldiethoxysilane; and other functional group-containing monomers. When further containing functional group-containing monomers, the cohesion of the acrylic emulsion resin can be improved. Furthermore, the tensile properties of the formed protective film and the SP value of the acrylic emulsion resin can be adjusted to any suitable values.

[0059] For purposes such as improving cohesion, the monomer composition may further contain other copolymerizable components in addition to the above-mentioned monomers. Examples of other copolymerizable components include: vinyl ester monomers such as vinyl acetate (VAc), vinyl propionate, and vinyl laurate; aromatic vinyl compounds such as styrene, substituted styrene (such as α-methylstyrene), and vinyltoluene; cycloalkyl (meth)acrylates such as cyclohexyl (meth)acrylate, cyclopentyl (meth)acrylate, and isobornyl (meth)acrylate; (meth)acrylates containing an aromatic ring such as (meth)acrylic acid aryl ester (such as phenyl (meth)acrylate), (meth)acrylic acid aryloxyalkyl ester (such as phenoxyethyl (meth)acrylate), and (meth)acrylic acid arylalkyl ester (such as benzyl (meth)acrylate); olefin monomers such as ethylene, propylene, isoprene, butadiene, and isobutene; monomers containing a chlorine atom such as vinyl chloride and vinylidene chloride; alkoxy-containing monomers such as methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, and ethyl carbitol (meth)acrylate; vinyl ether monomers such as methyl vinyl ether and ethyl vinyl ether; polyfunctional monomers having two or more (such as three or more) polymerizable functional groups (such as (meth)acryloyl) in one molecule, such as 1,6-hexanediol di(meth)acrylate and trimethylolpropane tri(meth)acrylate; and the like.

[0060] The above-mentioned other monomer components and other copolymerizable components can be used in any suitable content ratio. For example, in the monomer composition, the total of the above-mentioned C4-C20 alkyl (meth)acrylates, nitrogen atom-containing monomers, and C1-C3 alkyl (meth)acrylates is used in an amount of 100 parts by weight.

[0061] A-1-2. Synthesis of acrylic emulsion resin

[0062] The acrylic emulsion resin can be obtained by emulsion polymerization of the above-mentioned monomer composition. The monomer supply method in emulsion polymerization can be a one-time input method in which all monomer raw materials are supplied at once, a continuous supply (dropwise addition) method, or a batch supply (dropwise addition) method. In addition, a part or all of the monomer components can be premixed with water and an emulsifier for emulsification, and the emulsion can be supplied to the polymerization vessel.

[0063] The polymerization temperature can be set to any suitable value according to the types of monomers and solvents used, the type of polymerization initiator, etc. The polymerization temperature is, for example, 20 °C or higher, preferably 40 °C or higher, more preferably 50 °C or higher. In addition, the polymerization temperature is preferably 95 °C or lower, more preferably 85 °C or lower.

[0064] As the polymerization initiator, any suitable initiator can be used. For example, the following can be cited: azo polymerization initiators, peroxide initiators, redox initiators based on the combination of peroxide and reducing agent, substituted ethane initiators, etc. Specifically, the following can be cited: azo initiators such as 2,2'-azobisisobutyronitrile, 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] hydrate, 2,2'-azobis(2-methylpropionamidine) disulfate, 2,2'-azobis(2-methylpropionamidine) dihydrochloride, 2,2'-azobis(2-methylpropionamidine) dihydrochloride, 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis(N,N'-dimethylisobutylamidine) dihydrochloride; persulfates such as potassium persulfate and ammonium persulfate; peroxide initiators such as benzoyl peroxide, tert-butyl hydroperoxide, di-tert-butyl peroxide, diisopropylbenzene peroxide, dilauroyl peroxide, dioctanoyl peroxide, di(4-methylbenzoyl) peroxide, tert-butyl peroxybenzoate, tert-butyl peroxyisobutyrate, tert-hexyl peroxypivalate, tert-butyl peroxypivalate, bis(2-ethylhexyl) peroxydicarbonate, bis(4-tert-butylcyclohexyl) peroxydicarbonate, di-sec-butyl peroxydicarbonate, tert-butyl peroxyneodecanoate, 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-butylperoxy) cyclododecane, 1,1-bis(tert-hexylperoxy) cyclohexane, hydrogen peroxide; redox initiators such as the combination of peroxide and ascorbic acid (for example, the combination of hydrogen peroxide and ascorbic acid), the combination of peroxide and ferrous salt (the combination of hydrogen peroxide and ferrous salt), the combination of persulfate and sodium bisulfite.

[0065] The polymerization initiator can be used in any suitable content. For example, relative to 100 parts by weight of the total monomer components, it is preferably 0.001 to 5 parts by weight, more preferably 0.01 to 3 parts by weight, and still more preferably 0.01 to 2 parts by weight.

[0066] Emulsion polymerization is usually carried out in the presence of an emulsifier. As the emulsifier, any suitable emulsifier can be used. As the emulsifier, an anionic emulsifier, a nonionic emulsifier, etc. can be used. The emulsifier can be used alone or in combination of two or more.

[0067] Examples of anionic emulsifiers include sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzenesulfonate, polyoxyethylene sodium lauryl sulfate, polyoxyethylene alkyl ether sodium sulfate, polyoxyethylene alkylphenyl ether ammonium sulfate, polyoxyethylene alkylphenyl ether sodium sulfate, polyoxyethylene alkyl sulfosuccinate, and the like. Examples of nonionic emulsifiers include polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene fatty acid ester, polyoxyethylene-polyoxypropylene block polymer, and the like. In addition, as the emulsifier, an emulsifier having a reactive functional group (reactive emulsifier) can be used. Examples of the reactive emulsifier include a radical polymerizable emulsifier having a structure in which a radical polymerizable functional group such as an allyl group or an allyl ether group is introduced into the above-mentioned anionic emulsifier or nonionic emulsifier.

[0068] The emulsifier can be used in any suitable amount. With respect to 100 parts by weight in total of the monomer components, the emulsifier is preferably 0.2 part by weight or more, more preferably 0.5 part by weight or more, still more preferably 1.0 part by weight or more, and particularly preferably 1.5 part by weight or more. From the viewpoints of suppressing emulsion polymerization and foaming of the resulting composition containing the emulsion, the amount of the emulsifier used is usually preferably 10 parts by weight or less, more preferably 5 parts by weight or less, still more preferably 3 parts by weight or less with respect to 100 parts by weight in total of the monomer components.

[0069] Emulsion polymerization can be carried out in the presence of a protective colloid. Examples of the protective colloid include polyvinyl alcohol-based polymers such as partially saponified polyvinyl alcohol, completely saponified polyvinyl alcohol, and modified polyvinyl alcohol; cellulose derivatives such as hydroxyethyl cellulose, hydroxypropyl cellulose, and carboxymethyl cellulose salts; natural polysaccharides such as guar gum; and the like. The protective colloid can be used alone or in combination of two or more.

[0070] The saponification degree of the partially saponified polyvinyl alcohol is, for example, less than 95 mol%, preferably less than 92 mol%, more preferably less than 90 mol%. From the viewpoints of the stability of the emulsion and the like, the saponification degree of the partially saponified polyvinyl alcohol is preferably 65 mol% or more, more preferably 70 mol% or more, still more preferably 80 mol% or more, and particularly preferably 85 mol% or more. It should be noted that, as described above, completely saponified polyvinyl alcohol can also be used.

[0071] As the modified polyvinyl alcohol, for example, anionic modified polyvinyl alcohol having an anionic group such as a carboxyl group and / or a sulfonic acid group introduced therein; cationic modified polyvinyl alcohol having a cationic group such as a quaternary ammonium salt introduced therein, etc. can be cited. The saponification degree of the modified polyvinyl alcohol is, for example, less than 98 mol%, preferably less than 95 mol%, more preferably less than 92 mol%, and further preferably less than 90 mol%. In addition, the saponification degree of the modified polyvinyl alcohol is, for example, 55 mol% or more, and from the viewpoint of emulsion stability and the like, it is preferably 65 mol% or more, more preferably 70 mol% or more, further preferably 80 mol% or more, and particularly preferably 85 mol% or more.

[0072] The protective colloid can be used in any appropriate amount. The content of the protective colloid is preferably 0.1 part by weight or more, more preferably 0.5 part by weight or more, and further preferably 0.7 part by weight or more, based on 100 parts by weight in total of the monomer components. In addition, the content of the protective colloid is preferably 10 parts by weight or less, more preferably 5 parts by weight or less, further preferably 3 parts by weight or less, and particularly preferably 2 parts by weight or less, based on 100 parts by weight in total of the monomer components. The protective colloid can be used in combination with the above emulsifier, or the emulsifier may not be used and only the protective colloid may be used. It is preferable to use the above emulsifier in combination with the protective colloid. For example, emulsion polymerization can be carried out as follows: water and a protective colloid are added to a polymerization vessel, and a part or all of the monomer composition is previously mixed with water and an emulsifier to be emulsified into an emulsion, and the emulsion is supplied to the above polymerization vessel. It should be noted that in the case of using an anionic protective colloid (for example, anionic modified polyvinyl alcohol) in combination with an emulsifier, from the viewpoint of polymerization stability and the like, as the emulsifier, it is preferable to use at least one emulsifier selected from the group consisting of anionic emulsifiers and nonionic emulsifiers.

[0073] In addition, at the time of polymerization, any appropriate chain transfer agent can be used. As the chain transfer agent, for example, thiols such as n-dodecyl mercaptan, tert-dodecyl mercaptan, and mercaptoacetic acid can be cited. In addition, a chain transfer agent containing no sulfur atom (non-sulfur-based chain transfer agent) can also be used. Specific examples of the non-sulfur-based chain transfer agent include anilines such as N, N-dimethylaniline and N, N-diethylaniline; terpenoids such as α-pinene and terpinolene; styrenes such as α-methylstyrene and α-methylstyrene dimer; compounds having a benzylidene group such as dibenzylideneacetone, cinnamyl alcohol, and cinnamaldehyde; hydroquinones such as hydroquinone and dihydroxynaphthalene; quinones such as benzoquinone and naphthoquinone; olefins such as 2, 3-dimethyl-2-butene and 1, 5-cyclooctadiene; alcohols such as phenol, benzyl alcohol, and allyl alcohol; benzyl hydrogens such as diphenylbenzene and triphenylbenzene; etc. The chain transfer agent can be used alone or in combination of two or more. When using a chain transfer agent, its content is, for example, 0.01 part by weight to 1 part by weight based on 100 parts by weight in total of the monomer components.

[0074] A-2. Additive

[0075] The liquid surface protection material for semiconductor wafer processing may further contain any suitable additive as needed. Examples of the additive include: catalysts (e.g., platinum catalysts), thickeners, plasticizers, pigments, dyes, fillers, anti-aging agents, conductive agents, ultraviolet absorbers, light stabilizers, stripping regulators, softeners, flame retardants, solvents, leveling agents, film-forming aids, tackifiers, thixotropic agents, defoamers, etc. The additive can be used in any suitable amount according to the purpose.

[0076] A-3. Manufacturing Method of Liquid Surface Protection Material for Semiconductor Wafer Processing

[0077] The liquid surface protection material for semiconductor wafer processing can be manufactured by any suitable method. For example, an acrylic emulsion resin and any additive can be added to any suitable solvent and mixed, or any additive can be added to and mixed with the solution after the emulsion polymerization of the acrylic emulsion resin. In addition, the acrylic emulsion resin can be directly used. Further, for example, ammonia water can be added to the acrylic emulsion resin to adjust the pH to about 6 to 8, any suitable solvent can be added, the resin concentration can be adjusted, and the obtained material can be used as the liquid surface protection material.

[0078] As the solvent, any suitable solvent can be used. An aqueous solvent is preferably used. In this specification, an aqueous solvent means water or a mixed solvent having water as the main component (including components exceeding 50% by weight). As the solvent other than water constituting the mixed solvent, an organic solvent capable of being uniformly mixed with water can be used. Specifically, lower alcohols, etc. can be cited. The organic solvent capable of being uniformly mixed with water can be used alone or in combination of two or more. The water content ratio of the aqueous solvent is, for example, 90% by weight or more, preferably 95% to 100% by weight.

[0079] B. Protective Film

[0080] The protective film according to the embodiment of the present invention can be formed using the liquid surface protection material for semiconductor wafer processing described in Item A above. The protective film can be formed, for example, by coating the liquid surface protection material on the surface of the semiconductor wafer by any suitable method and then drying.

[0081] The thickness of the protective film can be set to any appropriate value. For example, the thickness can be set to match the height of the convex portions on the surface of the semiconductor wafer on which the protective film is formed. The thickness of the protective film is, for example, 50 μm to 500 μm, preferably 100 μm to 300 μm, and more preferably 100 μm to 200 μm. If the thickness of the protective film is within the above range, the surface of the semiconductor wafer (e.g., the circuit surface) can be appropriately protected during the semiconductor wafer processing step. In addition, after the processing of the semiconductor wafer, the protective film can be easily peeled off without breaking.

[0082] The tensile modulus of the protective film at 23°C is preferably 0.1 GPa to 1.1 GPa, more preferably 0.12 GPa to 1.0 GPa, and further preferably 0.13 GPa to 0.95 GPa. If the tensile modulus of the protective film at 23°C is within the above range, the protective film can be peeled off using a tape peeling device used for peeling the adhesive tape. In this specification, the elastic modulus of the protective film at 23°C refers to the value measured by the following method. A protective film (film) with a thickness of 100 μm is cut into a size of 100 mm in length and 25 mm in width, and using a precision universal testing machine (manufactured by Shimadzu Corporation, device name "Autograph AG-IS"), it is stretched at a chuck distance of 50 mm and a stretching speed of 300 mm / minute, and the stress change until the film undergoes plastic deformation is recorded to obtain a stress-strain curve. The tensile modulus is obtained by linear regression of the curve between the strains ε1 = 1 and ε2 = 2 at two specified points. The above measurement is performed using three test pieces cut from different parts, and their average value is set as the tensile modulus. It should be noted that the above measurement is carried out in accordance with JIS K 7161 at 23°C and 50% RH (relative humidity).

[0083] The adhesive force of the protective film to the silicon wafer is preferably 1.0 N / 25 mm or less, more preferably 0.8 N / 25 mm or less, still more preferably 0.3 N / 25 mm or less, and particularly preferably 0.1 N / 25 mm or less. The adhesive force to the silicon wafer is, for example, 0.08 N / 25 mm or more. If the adhesive force to the silicon wafer is within the above range, the surface of the semiconductor wafer can be appropriately protected in the processing step of the semiconductor wafer, and it can be easily peeled off and removed after the processing step without damaging the surface of the semiconductor wafer. In this specification, the adhesive force to the silicon wafer refers to the adhesive force measured by the following method. A liquid surface protective material is coated on a mirror wafer (manufactured by Shin-Etsu Chemical Co., Ltd.) such that the wet coating thickness becomes 200 μm and the length becomes 100 mm or more, and after drying at 80 °C for 5 minutes, a protective film with a thickness of about 100 μm is formed. Then, it is allowed to stand at 23 °C for 30 minutes. Next, a 180° peel test is carried out at 23 °C and 50% RH atmosphere under the condition of a tensile speed of 300 mm / minute to measure the adhesive force.

[0084] The adhesive force of the protective film to the silicon wafer after water immersion is preferably 0.7 N / 25 mm or less, more preferably 0.3 N / 25 mm or less, still more preferably 0.2 N / 25 mm or less, and particularly preferably 0.15 N / 25 mm or less. The adhesive force to the silicon wafer after water immersion is, for example, 0.05 N / 25 mm or more. If the adhesive force to the silicon wafer after water immersion is within the above range, it can be suitably used for the processing step of the semiconductor wafer. In this specification, the adhesive force to the silicon wafer after water immersion refers to the adhesive force measured by the following method. A liquid surface protective material is coated on a mirror wafer (manufactured by Shin-Etsu Chemical Co., Ltd.) such that the wet coating thickness becomes 200 μm and the length becomes 100 mm or more, and after drying at 80 °C for 5 minutes, a protective film with a thickness of about 100 μm is formed. At 23 °C, the silicon wafer with the protective film formed thereon is immersed in water and left for 30 minutes. Next, a 180° peel test is carried out at 23 °C and 50% RH atmosphere under the condition of a tensile speed of 300 mm / minute to measure the adhesive force.

[0085] C. Method for processing semiconductor wafer

[0086] The processing method of a semiconductor wafer according to an embodiment of the present invention includes: coating a liquid surface protection material for processing a semiconductor wafer on the surface of the semiconductor wafer where a circuit pattern is formed to form a protective film; grinding the surface of the semiconductor wafer where the protective film is not formed; and peeling off and removing the protective film. As described above, the liquid surface protection material has excellent filling properties on the surface of the semiconductor wafer. Therefore, it is not easy to form a gap between the semiconductor wafer and the protective film, and the generation of defects such as damage to the semiconductor wafer caused by water seeping into the gap and the attachment of foreign substances can be suppressed. In addition, as described above, the protective film formed using the liquid surface protection material does not need to be removed by dissolving with a solvent, and can be peeled off and removed using a peeling device or the like used for peeling the adhesive tape. Therefore, the environmental burden caused by using a solvent can be reduced. In addition, the paste residue (attachment of residues of the surface protection material) on the surface of the semiconductor wafer after peeling can be suppressed.

[0087] Figures 1 to 3 FIG. is a schematic cross-sectional view of a semiconductor wafer and a protective film in a semiconductor wafer processing process according to an embodiment of the present invention. In Figures 1 to 3 FIG., (a) shows the protective film 100 and the semiconductor wafer 200 after the protective film forming process, (b) shows the protective film 100 and the semiconductor wafer 200 after the back grinding process, and (c) shows the protective film 100 and the semiconductor wafer 200 after peeling off and removing. In the processing method of a semiconductor wafer according to an embodiment of the present invention, the protective film 100 is formed in contact with the semiconductor wafer 200. As described above, the protective film 100 formed using the liquid surface protection material has excellent filling properties on the surface of the semiconductor wafer. Therefore, for example, even on the surface of a semiconductor wafer with a relatively high height of the convex portion of the bump and a semiconductor wafer densely formed with bumps, good filling can be achieved.

[0088] C-1. Formation of the protective film

[0089] The protective film can be formed by any suitable method. For example, the liquid surface protection material described in item A above can be coated on the surface of the semiconductor wafer where the circuit pattern is formed by any suitable method and dried to form the protective film.

[0090] Regarding the protective film 100, as shown in (a) of Figure 1 FIG., the liquid surface protection material can be coated to fill the convex portion of the bump of the semiconductor wafer 200 to form the protective film 100, or as shown in (a) of Figure 2 FIG. and Figure 3 FIG., the liquid surface protection material can be coated on the semiconductor wafer 200 to form the protective film 100, and then the adhesive sheet 300 can be further bonded in contact with the protective film 100 using the adhesive layer 320.

[0091] As coating methods, for example, spin coating, spray coating, belt coating, curtain coating, roll coating, brush coating, bar coater coating, air knife coating, gravure coating, reverse gravure coating, reverse roll coating, die lip coating, die coating, dip coating, offset printing, flexographic printing, screen printing, etc. can be cited. Spin coating, curtain coating, and spray coating are preferably used. By using these methods, the filling performance of the unevenness on the surface of the semiconductor wafer can be further improved.

[0092] As a drying method, any appropriate method can be used. For example, natural drying, air drying, vacuum drying, heat drying, etc. can be cited. Heat drying is preferably used. In the case of heat drying, the heating temperature is, for example, 30°C to 100°C. In addition, the drying time is, for example, 1 minute to 60 minutes.

[0093] In an embodiment of further bonding the adhesive sheet 300 ( Figure 2 and Figure 3 in the embodiment), the protective film 100 can be formed to have a thickness greater than or equal to the thickness of the convex portion of the bump ( Figure 2 in (a) of), or can be formed to have a thickness less than the height of the convex portion of the bump ( Figure 3 in (a) of). As shown in Figure 2 in (a) of and Figure 3 in (a) of, when the liquid surface protection material and the adhesive sheet are used in combination, the thickness of the surface protection material can be thinned, and the operation time (for example, the drying time of the protective film) can be shortened. In addition, in the back grinding process described below, the TTV (Total Thickness Variation) of the semiconductor wafer can be improved. In addition, in Figure 2 in (a) of and Figure 3 in (a) of the embodiment, in the above coating process, the portion of the semiconductor wafer surface where the protective film is not formed can be thinly coated with the liquid surface protection material (not shown due to its thinness). In this embodiment, the portion where the adhesive layer 320 of the adhesive sheet 300 is in direct contact with the semiconductor wafer 200 is reduced, and the paste residue of the adhesive layer 320 on the surface of the semiconductor wafer 200 can be suppressed. It should be noted that the liquid surface protection material thinly coating the semiconductor wafer surface can be peeled off from the semiconductor wafer surface together with the protective film 100 and / or the adhesive sheet 300 in the peeling process described below.

[0094] The adhesive sheet 300 typically includes a base material 310 and an adhesive layer 320. As the adhesive sheet, for example, any suitable back grinding tape can be used. Specifically, a back grinding tape that can fill the height of the convex portions not filled by the protective film 100 can be used. As the adhesive sheet, it is preferably that the adhesive force obtained by the 180° peel test with respect to the protective film 100 is 2 N / 25 mm or more. If the adhesive force to the protective film 100 is within the above range, the semiconductor wafer can be appropriately held in the back grinding process, and in the peeling and removing process, it can be peeled off without leaving the paste of the liquid surface protection material.

[0095] C-2. Back Grinding

[0096] Back grinding (back lapping) of the semiconductor wafer can be performed by any suitable method ([ Figure 1 of (b), Figure 2 of (b), Figure 3 of (b)). Back grinding is performed on the surface of the semiconductor wafer where no circuit is formed (the surface of the semiconductor wafer where no protective film is formed). Back grinding is usually performed while cooling with water. As described above, the filling property of the protective film formed using the liquid surface protection material is excellent. Therefore, during back grinding, it is possible to suppress water from penetrating between the semiconductor wafer and the protective film, and it is possible to suppress the generation of the bulge of the protective film and the generation of the breakage of the semiconductor wafer.

[0097] C-3. Peeling and Removing

[0098] After back grinding, the protective film can be peeled off and removed from the semiconductor wafer at any suitable stage ([ Figure 1 of (c), Figure 2 of (c), Figure 3 of (c)). As described above, the protective film formed using the liquid surface protection material can be peeled off and removed without dissolving the protective film with a solvent such as an organic solvent for removal. Therefore, the environmental burden caused by using the solvent can be reduced. In addition, the above protective film can be peeled off and removed by the peeling device used for peeling off the adhesive tape. Therefore, it can be directly used in the production line of semiconductor wafers using adhesive tapes such as back grinding tapes.

[0099] Examples

[0100] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited by these examples. In addition, in the examples, unless otherwise specified, "parts" and "%" are both based on weight.

[0101] [Synthesis Example 1] Synthesis of Acrylic Emulsion Resin

[0102] To a reaction vessel equipped with a cooling tube, a nitrogen inlet tube, a thermometer, and a stirring device, 50 parts by weight of ion-exchanged water and 1 part by weight of an anion-modified polyvinyl alcohol (manufactured by Mitsubishi Chemical Corporation, trade name "GOHSENX L-3266") were added, and while introducing nitrogen, dissolution was carried out at room temperature, and the temperature was raised to 60 °C. Next, 0.1 part by weight of a polymerization initiator (2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] hydrate; manufactured by Wako Pure Chemical Industries, Ltd., trade name "VA-057") was added to the reaction vessel. In addition, using a homogenizer, a monomer composition containing 65 parts by weight of n-butyl acrylate (BA), 25 parts by weight of acrylonitrile (AN), and 10 parts by weight of methyl methacrylate (MMA); 0.05 part by weight of a chain transfer agent (n-dodecyl mercaptan); and 2 parts by weight of an emulsifier (sodium lauryl polyoxyethylene sulfate; manufactured by Kao Corporation, trade name "LATEMUL E118B") were added to 40 parts by weight of ion-exchanged water, and while performing nitrogen replacement, mixing was carried out to obtain a monomer emulsion. The obtained monomer emulsion was introduced into the reaction vessel over 3 hours, and an emulsion polymerization reaction was carried out. Further, the obtained reaction mixture was kept at a temperature for 3 hours to be cured. Then, after cooling to room temperature, 10% ammonia water was added to adjust the pH to 7.5, and an acrylic emulsion resin was obtained.

[0103] [Synthesis Examples 2 to 5] Synthesis of Acrylic Emulsion Resin

[0104] The monomer composition was changed as shown in Table 1, and otherwise, the same operations as in Synthesis Example 1 were carried out to obtain an acrylic emulsion resin.

[0105] [Examples 1 to 5]

[0106] The acrylic emulsion resins obtained in Synthesis Examples 1 to 5 were directly used as a liquid surface protection material, and the following evaluations were carried out.

[0107] (Comparative Example)

[0108] A water-soluble resin (manufactured by JAPAN VAM&POVAL Co., Ltd., trade name "JC-25") was dissolved in water so that the resin concentration became 20% by weight to obtain a liquid surface protection material.

[0109] <Evaluation>

[0110] Using the liquid surface protection materials obtained in the examples and the comparative example, the following evaluations were carried out. The results are shown in Table 1.

[0111] 1. Tensile Modulus

[0112] A liquid surface protection material was coated on the release-treated surface of a release-treated support to form a film with a thickness of 100 μm. The obtained film was cut into a size of 100 mm in length and 25 mm in width to prepare test pieces. Using a precision universal testing machine (manufactured by Shimadzu Corporation, device name "Autograph AG-IS"), the test pieces were stretched at a distance between chucks of 50 mm and a stretching speed of 300 mm / minute, and the stress change until the test pieces underwent plastic deformation was recorded to obtain a stress-strain curve. The tensile modulus was obtained by linear regression of the curve between the strains ε1 = 1 and ε2 = 2 at specified two points. Using three test pieces cut from different parts, the above measurements were carried out, and their average value was set as the tensile modulus of the test pieces. It should be noted that the above measurements were carried out in accordance with JIS K 7161 at 23°C and 50% RH.

[0113] 2. Adhesion

[0114] A liquid surface protection material was coated on the surface of a dummy wafer (manufactured by Shin-Etsu Chemical Co., Ltd.) to a width of 25 mm and a thickness of 200 μm, and dried to form a protective film. Then, it was left standing at 23°C for 30 minutes. Next, a 180° peel test was carried out at a stretching speed of 300 mm / minute in an atmosphere of 23°C and 50% RH to measure the adhesion.

[0115] Similarly, a liquid surface protection material was coated on the surface of a dummy wafer (manufactured by Shin-Etsu Chemical Co., Ltd.) to a width of 25 mm and a thickness of 200 μm, and dried to form a protective film. The dummy wafer with the protective film formed thereon was immersed in water at 23°C and left standing for 30 minutes. Next, a 180° peel test was carried out at a stretching speed of 300 mm / minute in an atmosphere of 23°C and 50% RH to measure the adhesion.

[0116] 3. Fillability

[0117] A liquid surface protection material was coated on the surface of a silicon mirror wafer (8 inches, bump height 75 μm, diameter 90 μm, pitch 200 μm) to form a protective film with a thickness of 200 μm. The bonding state between the protective film and the wafer was observed from the side of the wafer with the protective film formed through a laser microscope (magnification: 100 times). In addition, a photograph was taken from the side with the protective film formed to a dummy wafer with the protective film formed, and using image analysis software (ImageJ (free software)), binarization of the image was performed (8-bit grayscale, brightness: 0 - 255, threshold: 114). Five bumps were randomly selected, and the number of points used for the display of one bump was measured. When the average number of points for the five bumps was 600 or less, it was evaluated as ○ (good), and when the average number of points exceeded 600, it was evaluated as × (bad). It should be noted that the image of only the bumps without the protective film formed had 220 points. When the protective film was formed, the number of points was greater than 220. If the average number of points was 600 or less, it indicated excellent filling property of the unevenness on the wafer surface.

[0118] 4. Paste residue (residue of the surface protection material) and solder removal

[0119] After the peeling of the protective film, the silicon wafer used for the evaluation of the above adhesive force was observed through a laser microscope. If there was no paste residue (residue of the protective film) on the bumps at all, it was set as ○ (good), and if there was paste residue (residue of the protective film) on the bumps, it was set as × (bad). In addition, when no solder residue was confirmed on the surface of the semiconductor wafer, it was set as ○ (good), and when solder residue was visually confirmed, it was set as × (bad).

[0120] 5. Peelability

[0121] A surface protection material was coated on the silicon wafer so that the thickness after drying became 100 μm to form a protective film. The formed protective film was peeled off by hand. When the protective film could be peeled off without breaking, it was set as ○ (good), and when breakage occurred halfway, it was set as × (bad).

[0122] [Table 1]

[0123]

[0124] BA: Butyl acrylate

[0125] AN: Acrylonitrile

[0126] Vac: Vinyl acetate

[0127] MMA: Methyl methacrylate

[0128] AA: Acrylic acid

[0129] The filling property of the liquid surface protection material for semiconductor wafer processing according to the embodiments of the present invention is excellent. In addition, the protective film formed by coating the liquid surface protection material can be peeled off and removed, and the adhesion of the residue of the protective film is also suppressed.

[0130] Industrial applicability

[0131] The liquid surface protection material for semiconductor wafer processing according to the embodiment of the present invention is suitable for use in the processing step of semiconductor wafers.

[0132] Description of reference numerals

[0133] 100: Protective film; 200: Semiconductor wafer; 300: Adhesive sheet; 310: Substrate; 320: Adhesive layer.

Claims

1. A liquid surface protection material for semiconductor wafer processing, wherein, it contains an acrylic emulsion resin.

2. The liquid surface protection material for semiconductor wafer processing according to claim 1, wherein, the acid value of the acrylic emulsion resin is 10 mg / KOH or less.

3. The liquid surface protection material for semiconductor wafer processing according to claim 1, wherein, The SP value of the acrylic emulsion resin is 9 (cal / cm 3 ) 1 / 2 ~11 (cal / cm 3 ) 1 / 2 。 4. The liquid surface protection material for semiconductor wafer processing according to claim 1, wherein, the BH viscosity is 0.1 Pa·s to 10 Pa·s.

5. A protective film, which is formed by using the liquid surface protection material for semiconductor wafer processing according to any one of claims 1 to 4.

6. The protective film according to claim 5, wherein, the tensile modulus at 23°C is 0.1 GPa to 1.1 GPa.

7. The protective film according to claim 5, wherein, the adhesion to a silicon wafer is 1.0 N / 25 mm or less.

8. A method for processing a semiconductor wafer, which includes: coating the liquid surface protection material for semiconductor wafer processing according to any one of claims 1 to 4 on the surface of the semiconductor wafer on which a circuit pattern is formed to form a protective film; grinding the surface of the semiconductor wafer on which the protective film is not formed; and peeling off and removing the protective film.

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