Protective film forming agent and method for manufacturing semiconductor chip

Abstract

Provided are: a protective film forming agent which is used for forming a protective film on the surface of a semiconductor wafer during dicing of the semiconductor wafer, and which is capable of forming a protective film having excellent laser processability and suppressed generation of cracks; and a method for manufacturing a semiconductor chip using the protective film forming agent. The present invention is a protective film-forming agent comprising (A) a water-soluble resin, (B) a light-absorbing agent, (C) at least one plasticizer selected from monosaccharides and disaccharides, and (S) a solvent. The water-soluble resin (A) preferably contains a water-soluble resin (A1) having an aromatic ring and a water-soluble group.

Description

Technical Field

[0001] The present invention relates to a protective film forming agent and a method for producing a semiconductor chip using the protective film forming agent. Background Art

[0002] The wafer formed in the semiconductor device manufacturing process is obtained by dividing a stack of insulating films and functional films stacked on the surface of a semiconductor substrate such as silicon according to predetermined grid-like dividing lines called streets, and each area divided by the streets becomes a semiconductor chip such as IC and LSI.

[0003] By cutting the wafer along the track, multiple semiconductor chips can be obtained. In addition, in the optical device wafer, a stacked body stacked with gallium nitride compound semiconductors and the like is divided into multiple regions by the track. By cutting along the track, the optical device wafer is divided into optical devices such as light emitting diodes and laser diodes. These optical devices are widely used in electrical equipment.

[0004] In the past, such wafers were cut along the streets using a cutting device called a dicer. However, in this method, since the wafers having a laminated structure are made of highly brittle materials, there are problems such as damage and cracks when the wafers are cut into semiconductor chips using a cutting blade (cutting edge), or the insulating film required for the circuit elements formed on the chip surface is peeled off.

[0005] In order to eliminate such undesirable situations, the following method has been proposed: a mask containing a layer of a water-soluble material is formed on the surface of a semiconductor substrate, and then a laser is irradiated on the mask to decompose and remove a portion of the mask, thereby exposing the surface of the semiconductor substrate in a portion of the mask, and then the semiconductor substrate exposed from the portion of the mask is cut by plasma etching to divide the semiconductor substrate into semiconductor chips (ICs) (see Patent Document 1).

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application No. 2014-523112 Summary of the invention

[0009] Problems to be solved by the invention

[0010] As described above, by irradiating the mask with laser light, a portion of the mask is decomposed and removed, and the surface of the semiconductor substrate is exposed in a portion of the mask, thereby forming a processed groove having a pattern corresponding to the shape of the semiconductor chip.

[0011] However, when using a conventional water-soluble material such as the water-soluble material described in Patent Document 1 to form a protective film as a mask, there is the following problem: sometimes the straightness of the processing groove formed by laser irradiation (the straightness of the side wall of the protective film constituting the processing groove) and the rectangularity of the cross-section of the processing groove (the rectangularity of the cross-section of the protective film constituting the processing groove) are poor, that is, the laser processability is poor.

[0012] If the straightness of the processed groove is poor, the straightness of the cross section of the semiconductor chip obtained by cutting the semiconductor substrate by plasma etching, etc. will be poor. In addition, if the rectangularity of the cross section of the processed groove is poor, the position cut by plasma etching, etc. is difficult to be the desired position.

[0013] In addition, there is a problem that cracks may occur when forming a protective film using a conventional water-soluble material such as the water-soluble material described in Patent Document 1. In the case of a thick protective film, cracks are particularly likely to occur.

[0014] The present invention is made in view of the above-mentioned problems, and its purpose is to provide a protective film forming agent for forming a protective film on the surface of a semiconductor chip during the cutting of the semiconductor chip, which can form a protective film with excellent laser processability and inhibits the generation of cracks, and a method for manufacturing a semiconductor chip using the protective film forming agent.

[0015] Means for solving problems

[0016] The inventors of the present application have found that the above-mentioned problems can be solved by using a protective film forming agent comprising a water-soluble resin (A), a light absorber (B), at least one plasticizer (C) selected from monosaccharides and disaccharides, and a solvent (S), thereby completing the present invention. More specifically, the present invention provides the following aspects.

[0017] [1] A protective film forming agent for forming a protective film on the surface of a semiconductor wafer during dicing of the semiconductor wafer,

[0018] The protective film forming agent comprises a water-soluble resin (A), a light absorber (B), at least one plasticizer (C) selected from monosaccharides and disaccharides, and a solvent (S).

[0019] [2] The protective film-forming agent according to the above [1], wherein the water-soluble resin (A) comprises a water-soluble resin (A1) having an aromatic ring and a water-soluble group.

[0020] [3] The protective film forming agent according to [2] above, wherein the content of the plasticizer (C) is 20 parts by mass or more and 100 parts by mass or less based on 100 parts by mass of the water-soluble resin (A1).

[0021] [4] The protective film forming agent according to the above [2] or [3], wherein the water-soluble resin (A1) contains a resin having a phenolic hydroxyl group.

[0022] [5] The protective film-forming agent according to any one of [1] to [4] above, wherein the water-soluble resin (A) comprises a polyvinyl alcohol-based resin.

[0023] [6] The protective film forming agent according to any one of [1] to [5] above, wherein the solvent (S) contains water.

[0024] [7] A method for manufacturing a semiconductor chip, which is a method for manufacturing a semiconductor chip by processing a semiconductor wafer, the method comprising the following steps:

[0025] A step of applying the protective film forming agent described in any one of [1] to [6] above on the semiconductor wafer to form a protective film; and

[0026] A step of irradiating a predetermined position of one or more layers including the protective film on the semiconductor wafer with laser light to form a processing groove having a pattern corresponding to the shape of the semiconductor chip and exposing the surface of the semiconductor wafer.

[0027] [8] The method for manufacturing a semiconductor chip as described in [7] above, comprising the step of cutting the position of the processed groove in the semiconductor wafer.

[0028] Effects of the Invention

[0029] According to the present invention, there can be provided a protective film forming agent for forming a protective film on the surface of a semiconductor wafer in a semiconductor chip manufacturing method for manufacturing a semiconductor chip from a semiconductor wafer, and capable of forming a protective film having excellent laser processability and suppressing the generation of cracks, and a method for manufacturing a semiconductor chip using the protective film forming agent. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] [ Figure 1 ] shows a stereoscopic view of a semiconductor wafer processed by a wafer processing method using the protective film forming agent of the present invention.

[0031] [ Figure 2 ] Figure 1 An enlarged cross-sectional view of a semiconductor wafer is shown.

[0032] [ Figure 3 ] An enlarged cross-sectional view of the main part of a semiconductor chip on which a protective film is formed.

[0033] [ Figure 4 ] is a three-dimensional view showing a state in which a semiconductor chip formed with a protective film is supported on a ring-shaped frame via a protective tape.

[0034] [ Figure 5 ] A three-dimensional view of the main parts of a laser processing device that implements a laser beam irradiation process.

[0035] [ Figure 6 ] An enlarged cross-sectional view of a semiconductor chip having a protective film and a processed groove formed by laser irradiation.

[0036] [ Figure 7 ] shows the Figure 6 An explanatory diagram of plasma irradiation of a semiconductor wafer is shown.

[0037] [ Figure 8 ] shows an enlarged cross-sectional view of a state in which a semiconductor wafer is divided into semiconductor chips by plasma irradiation.

[0038] [ Fig. 9 ] shows an enlarged cross-sectional view of the state where the protective film on the semiconductor chip has been removed.

[0039] [ Fig.10 ] A cross-sectional view illustrating a method for evaluating cross-sectional rectangularity. DETAILED DESCRIPTION

[0040] 《Protective film forming agent》

[0041] The protective film forming agent is used to form a protective film on the surface of a semiconductor wafer during dicing of the semiconductor wafer. The protective film forming agent comprises a water-soluble resin (A), a light absorber (B), at least one plasticizer (C) selected from monosaccharides and disaccharides, and a solvent (S).

[0042] Specifically, the protective film forming agent can be suitably used for forming a protective film in a method for manufacturing a semiconductor chip, the method comprising the following steps:

[0043] a step of irradiating a protective film formed on a semiconductor wafer with laser light to form a processing groove having a pattern corresponding to the shape of the semiconductor chip and exposing the surface of the semiconductor wafer; and

[0044] A step of processing the position of a processing groove in a semiconductor wafer.

[0045] It should be noted that after the processing groove is formed, the position of the processing groove in the semiconductor wafer can be cut off to manufacture semiconductor chips.

[0046] From the perspective of easily removing the protective film by water washing after processing the semiconductor wafer and of ensuring sufficient durability of the protective film against plasma irradiation when plasma irradiation is performed in the semiconductor chip manufacturing method described later, the thickness of the protective film is typically preferably from 0.1 μm to 100 μm, and more preferably from 1 μm to 100 μm.

[0047] When laser irradiation is performed, the thickness of the protective film is preferably 0.1 μm to 30 μm.

[0048] Hereinafter, essential components or optional components contained in the protective film forming agent will be described.

[0049] <Water-soluble resin (A)>

[0050] The water-soluble resin (A) is a base material of a protective film formed using a protective film forming agent. The water-soluble resin (A) is a resin that can be dissolved in a solvent such as water and can be applied and dried to form a film.

[0051] In addition, a resin that becomes soluble in water by a hydrolysis reaction or a treatment using an alkali in an aqueous medium is also equivalent to the water-soluble resin (A). As such a resin, a resin having a carboxylic acid anhydride group and a resin having a phenolic hydroxyl group are equivalent to this. The carboxylic acid anhydride group becomes soluble in water by generating a carboxyl group or a carboxylate group through hydrolysis or a treatment using an alkali in an aqueous medium. Regarding the resin having a phenolic hydroxyl group, there are cases where it is water-soluble and cases where it is insoluble in water, depending on its structure. In the case where the resin having a phenolic hydroxyl group is insoluble in water, the phenolic hydroxyl group is converted into a salt (phenolate) by treating the resin in an alkaline aqueous medium, so that the resin becomes soluble in water.

[0052] The term "water-soluble" means that 0.5 g or more of a solute (water-soluble resin) is dissolved in 100 g of water or alkaline aqueous solution at 25°C.

[0053] The water-soluble resin (A) preferably includes a water-soluble resin (A1) which is a water-soluble resin having an aromatic ring and a water-soluble group. By including the water-soluble resin (A1) having an aromatic ring and a water-soluble group, the formed protective film has better laser processability and, in addition, has excellent durability against plasma irradiation when plasma irradiation is performed.

[0054] The aromatic ring contained in the water-soluble resin (A1) may be an aromatic hydrocarbon ring or an aromatic heterocyclic ring.

[0055] The aromatic ring may be a monocyclic structure or a polycyclic structure. The polycyclic structure may be a polycyclic structure in which two or more monocyclic rings are fused together, or a polycyclic structure in which two or more rings are bonded to each other via a single bond or a linking group.

[0056] Examples of the aromatic ring having a monocyclic structure include a benzene ring.

[0057] Examples of the polycyclic aromatic ring include a naphthalene ring, a biphenyl ring, an anthracene ring, and a phenanthrene ring.

[0058] The water-soluble group contained in the water-soluble resin (A1) is not particularly limited as long as it is a group that can impart water solubility to the resin. Examples of the water-soluble group include -SO3 - X + (X + is an alkali metal cation, a proton, or N + R4.), -COO - X + (X + As described above. ), carboxylic anhydride group (-CO-O-CO-), hydroxyl group, or ether bond (-O-). The carboxylic anhydride group (-CO-O-CO-) is provided by hydrolysis or treatment with an alkali in water. - X + In the case where the hydroxyl group is a phenolic hydroxyl group, the hydroxyl group may form a salt such as an alkali metal salt. It should be noted that R is a hydrogen atom, an alkyl group, or a hydroxyalkyl group. Examples of the alkali metal include sodium, potassium, and strontium.

[0059] Examples of the water-soluble resin (A1) include resins having a phenolic hydroxyl group. The phenolic hydroxyl group refers to a hydroxyl group (OH) directly bonded to a carbon atom in an aromatic ring.

[0060] Examples of the resin having a phenolic hydroxyl group include phenolic resins (resins obtained using phenols and formaldehydes as raw materials).

[0061] As the phenol resin as the water-soluble resin (A1), there can be mentioned resins having a structural unit represented by the following formula (1).

[0062] [Chemical formula 1]

[0063]

[0064] (In formula (1), R 31 is a water-soluble group. n31 is an integer of 0 to 3.)

[0065] As the water-soluble group, -SO3 - X + (X + is an alkali metal cation, a proton, or N + R4.), -COO - X + (X +As described above. ), a hydroxyl group, or an ether bond (-O-). When the hydroxyl group is a phenolic hydroxyl group, the hydroxyl group may form a salt such as an alkali metal salt.

[0066] n31 is preferably 1. R on the benzene ring 31 The substitution position may be any of the ortho, meta, and para positions relative to the OH group on the benzene ring.

[0067] Specific examples of the phenolic resin as the water-soluble resin (A1) include a phenolic resin having a structural unit represented by the following formula (1-1), a phenolic resin having a structural unit represented by the following formula (1-2), and a phenolic resin having a structural unit represented by the following formula (1-1) and a structural unit represented by the following formula (1-2). Regarding the phenolic resin having a structural unit represented by the following formula (1-1) and a structural unit represented by the following formula (1-2), the ratio of the number of moles of the structural unit represented by the following formula (1-1) to the total number of moles of the structural unit represented by the following formula (1-1) and the structural unit represented by the following formula (1-2) is preferably 0.1 to 0.9, and more preferably 0.7 to 0.9.

[0068] [Chemical formula 2]

[0069]

[0070] (Where X + is an alkali metal cation, or N + R4, R is a hydrogen atom, an alkyl group, or a hydroxyalkyl group.)

[0071] Examples of the water-soluble resin (A1) include resins containing styrene units, such as resins having a structural unit represented by the following formula (2). The styrene unit is a structural unit derived from styrene or a styrene derivative having a substituent at the α position or on the benzene ring.

[0072] [Chemical formula 3]

[0073]

[0074] (In formula (2), R 32 is a water-soluble group. n32 is an integer of 0 to 3.)

[0075] As the water-soluble group, -SO3 - X + (X + is an alkali metal cation, a proton, or N + R4.), -COO - X + (X +As described above. ), a hydroxyl group, or an ether bond (-O-). When the hydroxyl group is a phenolic hydroxyl group, the hydroxyl group may form a salt such as an alkali metal salt.

[0076] n32 is preferably 1. R on the benzene ring 32 The substitution position may be any of the ortho, meta, and para positions.

[0077] As the water-soluble resin (A1), a solution of a resin having a structural unit represented by the formula (2) can be neutralized with ammonia and used.

[0078] Specific examples of the resin having a structural unit represented by the formula (2) as the water-soluble resin (A1) include a resin having a structural unit represented by the following formula (2-1), and a resin having a structural unit represented by the following formula (2-1) and a structural unit represented by the following formula (2-2).

[0079] [Chemical formula 4]

[0080]

[0081] (Where X + is an alkali metal cation, a proton, or N + R4, R is a hydrogen atom, an alkyl group, or a hydroxyalkyl group,

[0082] M + is an alkali metal cation, a proton, or N + R 01 4. R 01 is a hydrogen atom, an alkyl group, or a hydroxyalkyl group.

[0083] Examples of alkali metals include sodium, potassium, and strontium.)

[0084] As the water-soluble resin (A1), a copolymer of styrene and maleic anhydride can also be mentioned. Styrene maleic anhydride copolymer is a resin having a structural unit represented by the following formula (3-1) and a structural unit represented by the following formula (3-2). Styrene maleic anhydride copolymer is a resin containing a styrene-based unit.

[0085] [Chemical formula 5]

[0086]

[0087] The mass average molecular weight of the water-soluble resin (A1) is preferably 100 to 300,000, more preferably 500 to 200,000, and even more preferably 1,000 to 200,000. In the present specification, the mass average molecular weight is a molecular weight measured by GPC in terms of polystyrene.

[0088] From the viewpoint of film-forming properties, the content of the water-soluble resin (A1) in the total solid content of the protective film forming agent is preferably 1% by mass or more and 99% by mass or less, more preferably 30% by mass or more and 70% by mass or less, and further preferably 40% by mass or more and 60% by mass or less. In this specification, the so-called solid content refers to the components other than the solvent (S). It should be noted that when the protective film forming agent contains a component other than the solvent (S) that is liquid at the temperature at which the protective film forming agent is used, for convenience, the liquid component is included in the solid content.

[0089] The water-soluble resin (A) may contain a water-soluble resin other than the water-soluble resin (A1). When the water-soluble resin (A) contains the water-soluble resin (A1) and a water-soluble resin other than the water-soluble resin (A1), the ratio of the mass of the water-soluble resin (A1) to the mass of the water-soluble resin (A) is, for example, 30% by mass or more and less than 100% by mass, preferably 40% by mass or more and 85% by mass or less, and more preferably 50% by mass or more and 80% by mass or less.

[0090] Examples of water-soluble resins other than the water-soluble resin (A1) (hereinafter also referred to as "other water-soluble resins") include vinyl resins, cellulose resins, polyethylene oxide, polyglycerol, and water-soluble nylon.

[0091] The vinyl resin is not particularly limited as long as it is a homopolymer or copolymer of a monomer having a vinyl group and is water-soluble.

[0092] Examples of the vinyl resin include polyvinyl alcohol resins, such as polyvinyl alcohol, polyvinyl acetal (including vinyl acetate copolymers), butene glycol-vinyl alcohol copolymers, polyvinyl alcohol-polyacrylic acid block copolymers, and polyvinyl alcohol-polyacrylate block copolymers.

[0093] Examples of the vinyl resin include polyvinyl pyrrolidone, polyacrylamide, poly(N-alkylacrylamide), polyallylamine, poly(N-alkylallylamine), partially amidated polyallylamine, poly(diallylamine), allylamine·diallylamine copolymers, and polyacrylic acid.

[0094] The cellulose resin is not particularly limited as long as it is a water-soluble cellulose derivative. Examples of the cellulose resin include methyl cellulose, ethyl cellulose, and hydroxypropyl cellulose.

[0095] These may be used alone or in combination of two or more.

[0096] It should be noted that, when the water-soluble resin (A) contains a water-soluble resin (A1) and a cellulose-based resin, the ratio of the mass of the water-soluble resin (A1) to the mass of the water-soluble resin (A) is preferably from 60 mass % to 85 mass %, and more preferably from 65 mass % to 80 mass %.

[0097] Specific examples of other water-soluble resins include vinyl resins and cellulose resins, and more preferably polyvinyl pyrrolidone and hydroxypropyl cellulose, from the viewpoint of less proneness to deterioration of the shape of the processed grooves due to heat depression of the protective film.

[0098] In addition, from the viewpoint of film-forming properties, cellulose-based resins are preferred.

[0099] For the protective film formed on the surface of the semiconductor wafer, it is usually removed from the surface of the semiconductor wafer or the semiconductor chip at an appropriate time point after the processing groove is formed, corresponding to the method of processing the semiconductor wafer having the protective film and the processing groove into the semiconductor chip. Therefore, from the aspect of the water washability of the protective film, other water-soluble resins are preferably water-soluble resins with low affinity to the surface of the semiconductor wafer. As water-soluble resins with low affinity to the surface of the semiconductor wafer, resins having only ether bonds, hydroxyl groups, and amide bonds as polar groups, such as polyvinyl alcohol, polyethylene glycol, polyvinyl pyrrolidone, and hydroxypropyl cellulose are preferred.

[0100] The mass average molecular weight of other water-soluble resins is preferably from 5,000 to 300,000, and more preferably from 10,000 to 200,000.

[0101] The ratio of the mass of the water-soluble resin (A) in the protective film forming agent to the total mass of the water-soluble resin (A) and the mass of the light absorber (B) is preferably 60 mass % to 99 mass %, more preferably 80 mass % to 95 mass %, from the viewpoint of preventing the occurrence of opening defects when forming the machined groove by irradiating the protective film with a laser, deterioration of the shape of the machined groove due to heat depression of the protective film, and the like.

[0102] <Light Absorber (B)>

[0103] As the light absorber (B), light absorbers generally used for protective film forming agents can be used.

[0104] As the light absorber (B), water-soluble light absorbers such as water-soluble dyes, water-soluble pigments, and water-soluble ultraviolet absorbers are preferably used. Water-soluble light absorbers are advantageous in that they can be uniformly present in the protective film. Examples of water-soluble light absorbers include organic acids having carboxyl groups and sulfonic groups; sodium salts, potassium salts, ammonium salts, and quaternary ammonium salts of organic acids; and compounds having hydroxyl groups.

[0105] When a water-soluble light absorber is used, the storage stability of the protective film forming agent is high, and the occurrence of undesirable phenomena such as phase separation of the protective film forming agent and sedimentation of the light absorber during storage of the protective film forming agent is suppressed. Therefore, it is also advantageous from the perspective of easily maintaining good coating properties of the protective film forming agent for a long period of time.

[0106] It should be noted that water-insoluble light absorbers such as pigments may also be used. When a water-insoluble light absorber is used, although it may not necessarily cause a fatal obstacle to the use of a protective film forming agent, there are cases where the laser absorption ability of the protective film is biased, or it is difficult to obtain a protective film forming agent with excellent storage stability and coating properties, or it is difficult to form a protective film of uniform thickness.

[0107] Examples of the light absorber (B) include benzophenone compounds, cinnamic acid compounds, anthraquinone compounds, naphthalene compounds, and biphenyl compounds.

[0108] Examples of the benzophenone-based compound include compounds represented by the following formula (B1): The compound represented by the following formula (B1) is preferred because it enables the protective film to efficiently absorb the energy of the laser beam and promotes thermal decomposition of the protective film.

[0109] [Chemical formula 6]

[0110]

[0111] (In formula (B1), R 1 and R 3 are each independently hydroxyl or carboxyl, R 2 and R 4 Each is independently hydroxyl, carboxyl, or -NR 5 R 6 The group represented by R 5 and R 6 Each is independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and m and n are each independently an integer of 0 to 2.)

[0112] The compound represented by the above formula (B1) has a high extinction coefficient and shows a high extinction coefficient even when added to the protective film forming agent together with a base. Therefore, when a protective film is formed using a protective film forming agent containing the compound represented by the above formula (B1) as a light absorber (B), the protective film can be partially decomposed by laser when forming a mask for cutting.

[0113] In the above formula (B1), R 2 and R 4 Sometimes -NR 5 R 6Represents a group. 5 and R 6 Each independently represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. 5 and R 6 The alkyl group may be straight chain or branched. 5 and R 6 Specific examples of the alkyl group are methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl and tert-butyl.

[0114] AS-NR 5 R 6 The group represented by is preferably an amino group, a methylamino group, an ethylamino group, a dimethylamino group, and a diethylamino group, and more preferably an amino group, a dimethylamino group, and a diethylamino group.

[0115] The compound represented by the formula (B1) is preferably a compound represented by the following formula (B1-1) in view of the height of the extinction coefficient in the presence of a base.

[0116] [Chemical formula 7]

[0117]

[0118] (In formula (B1-1), R 1 ~R 4 , m, and n are the same as those in formula (B1).

[0119] In view of the high extinction coefficient in the presence of a base, in the above formula (B1) and formula (B1-1), R 1 and R 3 At least one of them is a hydroxyl group.

[0120] The compound represented by formula (B1-1) is preferably a compound represented by any one of the following formulas (B1-1a) to (B1-1e).

[0121] [Chemical formula 8]

[0122]

[0123] (In formula (B1-1a) to formula (B1-1e), R 1 ~R 4 They are the same as those in formula (B1).

[0124] Among the compounds represented by formula (B1-1a) to formula (B1-1e), the compound represented by formula (B1-1a) is preferred.

[0125] Among the compounds represented by formula (B1-1a) to formula (B1-1e), R 2 For-NR5 R 6 The aforementioned group represented by R 5 and R 6 Each independently represents an alkyl group having 1 to 4 carbon atoms.

[0126] Preferred specific examples of the compound represented by formula (B1) include the following compounds.

[0127] These compounds are preferred from the viewpoint of easy availability and showing a high absorption coefficient even in the presence of a base.

[0128] [Chemical formula 9]

[0129]

[0130] When the light absorber (B) contains a compound represented by formula (B1), the ratio of the mass of the compound represented by formula (B1) to the mass of the light absorber (B) is not particularly limited within the range not hindering the purpose of the present invention. The ratio of the mass of the compound represented by formula (B1) to the mass of the light absorber (B) is preferably 70% by mass or more, more preferably 80% by mass or more, further preferably 95% by mass or more, and particularly preferably 100% by mass.

[0131] Examples of benzophenone compounds include 4,4′-dicarboxybenzophenone, benzophenone-4-carboxylic acid, and tetrahydroxybenzophenone, all of which are water-soluble ultraviolet absorbers.

[0132] Examples of the cinnamic acid-based compound include compounds represented by the following formula (B2): The compound represented by the following formula (B2) is preferred because it enables the protective film to efficiently absorb the energy of the laser beam and promotes thermal decomposition of the protective film.

[0133] [Chemical formula 10]

[0134]

[0135] (In formula (B2), R 11 is hydroxyl, alkoxy, or -NR 12 R 13 The group represented by R 12 and R 13 are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, p is an integer of 0 to 3, and when p is 2 or more, a plurality of R 11 Can be the same or different.)

[0136] In the above formula (B2), R 11 The alkoxy group of R may be straight chain or branched. 11The alkoxy group of R is preferably an alkoxy group having 1 to 4 carbon atoms. 11 Specific examples of the alkoxy group are methoxy, ethoxy, n-propoxy, isopropoxy, and n-butoxy.

[0137] In the above formula (B2), R 11 Sometimes -NR 12 R 13 Represents a group. 12 and R 13 Each independently represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. 12 and R 13 The alkyl group may be straight chain or branched. 12 and R 13 Specific examples of the alkyl group are methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl and tert-butyl.

[0138] The compound represented by formula (B2) is preferably a compound represented by the following formula (B2-1).

[0139] [Chemical formula 11]

[0140]

[0141] (In formula (B2-1), R 11 With R in formula (B2) 11 same.)

[0142] Specific examples of the cinnamic acid-based compound include 4-aminocinnamic acid, 3-aminocinnamic acid, 2-aminocinnamic acid, sinapinic acid (3,5-dimethoxy-4-hydroxycinnamic acid), ferulic acid, and caffeic acid.

[0143] Among them, 4-aminocinnamic acid, 3-aminocinnamic acid, 2-aminocinnamic acid, and ferulic acid are preferred, 4-aminocinnamic acid and ferulic acid are more preferred, and 4-aminocinnamic acid is particularly preferred.

[0144] Specific examples of the anthraquinone-based compound include 2-carboxyanthraquinone, 2,6-anthraquinone disulfonic acid, and 2,7-anthraquinone disulfonic acid.

[0145] Specific examples of the naphthalene-based compound include 1,2-naphthalene dicarboxylic acid, 1,8-naphthalene dicarboxylic acid, 2,3-naphthalene dicarboxylic acid, 2,6-naphthalene dicarboxylic acid, and 2,7-naphthalene dicarboxylic acid.

[0146] Specific examples of the biphenyl-based compound include biphenyl-4-sulfonic acid and the like.

[0147] Examples of the light absorber (B) also include water-soluble amines such as curcumin and EAB-F (4,4'-bis(diethylamino)benzophenone).

[0148] Specific examples of the water-soluble dye can be selected from azo dyes (monoazo and polyazo dyes, metal complex azo dyes, pyrazolone azo dyes, stilbene azo dyes, thiazole azo dyes), anthraquinone dyes (anthraquinone derivatives, anthrone derivatives), indigo dyes (indigo derivatives, thioindigo derivatives), phthalocyanine dyes, carbonium dyes (diphenylmethane dyes, triphenylmethane dyes, xanthene dyes, acridine dyes), quinoneimine dyes (azine dyes, oxazine dyes, thiazine dyes), methine dyes (cyanine dyes, methineimine dyes), quinoline dyes, nitroso dyes, benzoquinone and naphthoquinone dyes, naphthalenedicarboximide dyes, perinone dyes, and other dyes, etc.

[0149] As the water-soluble pigment, from the aspect of low environmental load, etc., food additive pigments such as Food Red No. 2, Food Red No. 40, Food Red No. 102, Food Red No. 104, Food Red No. 105, Food Red No. 106, Food Yellow NY, Food Yellow No. 4 Tartrazine, Food Yellow No. 5, Food Yellow No. 5 Sunset Yellow FCF, Food Orange AM, Food Red No. 1, Food Red No. 4, Food Red No. 101, Food Blue No. 1, Food Blue No. 2, Food Green No. 3, Food Melon Color B, and Food Egg Color No. 3 are preferred.

[0150] The content of the light absorber (B) in the protective film-forming agent is not particularly limited as long as it does not hinder the object of the present invention. With respect to the total solid component amount of the protective film-forming agent, the content of the light absorber (B) in the protective film-forming agent is preferably 0.1% by mass or more and 20% by mass or less, more preferably 5% by mass or more and 15% by mass or less.

[0151] From the aspect of less likely to cause opening defects when irradiating the protective film with a laser to form a processing groove, deterioration of the shape of the processing groove due to thermal depression of the protective film, etc., the ratio of the mass of the light absorber (B) in the protective film-forming agent to the total mass of the water-soluble resin (A) and the mass of the light absorber (B) is preferably 0.1% by mass or more and 50% by mass or less, more preferably 1% by mass or more and 40% by mass or less, and further preferably 2.5% by mass or more and 20% by mass or less.

[0152] The content of the light absorbent (B) can be set so that the absorbance of the protective film formed by applying the protective film forming agent becomes a desired value. The absorbance of the protective film formed by applying the protective film forming agent is not particularly limited. For example, the absorbance of the protective film formed by applying the protective film forming agent per 1 μm film thickness at a wavelength of 355 nm is preferably 0.3 or more, more preferably 0.8 or more, and even more preferably 1.0 or more.

[0153] <Plasticizer (C)>

[0154] The plasticizer (C) is at least one selected from monosaccharides and disaccharides.

[0155] In this specification, the plasticizer is a substance that can impart flexibility or elasticity to a protective film formed using a protective film forming agent.

[0156] Examples of the monosaccharides include aldose (monosaccharide having a formyl group), ketose (monosaccharide having a carbonyl group), and derivatives thereof.

[0157] Examples of the derivatives include aldonic acid (a carboxylic acid obtained by converting the formyl group at the 1-position of an aldose into a carboxyl group), uronic acid (a carboxylic acid obtained by converting the hydroxymethyl group at the terminal of the main chain of a monosaccharide into a carboxyl group), and aldaric acid (a dicarboxylic acid obtained by converting both the formyl group at the 1-position of an aldose and the hydroxymethyl group at the terminal of the main chain into carboxyl groups).

[0158] Specific examples of aldose include D-glyceraldehyde, D-erythrose, D-threose, D-ribose, D-arabinose, D-xylose, D-lyxose, D-glucose, D-galactose, D-allose, D-altrose, D-mannose, D-gulose, D-idose, and D-talose.

[0159] Specific examples of ketose include dihydroxyacetone, D-erythrulose, D-xylulose, D-ribulose, D-fructose, D-psicose, D-sorbose, D-tagatose, and D-sedoheptulose.

[0160] Specific examples of the derivatives include gluconic acid, glucuronic acid, saccharic acid, and inositol.

[0161] Examples of the disaccharides include disaccharides formed from the above monosaccharides described as monosaccharides. Specific examples of the disaccharides include maltose, sucrose, lactose, lactulose, trehalose, and cellobiose.

[0162] Among them, D-ribose, D-xylose, D-glucose, D-galactose, D-fructose, inositol, and maltose are preferred, and D-ribose, D-glucose, D-galactose, D-fructose, inositol, and maltose are more preferred.

[0163] Since the protective film forming agent contains a water-soluble resin (A), a light absorber (B), a solvent (S), and at least one plasticizer (C) selected from monosaccharides and disaccharides, a protective film having excellent laser processability and suppressed crack generation can be formed as shown in the examples described below. It should be noted that in this specification, the so-called laser processability refers to the straightness of the processed groove formed by laser irradiation (the straightness of the side wall of the protective film constituting the processed groove) and the rectangularity of the cross section of the processed groove (the rectangularity of the cross section of the protective film constituting the processed groove).

[0164] The reason why the protective film forming agent comprising the water-soluble resin (A), the light absorber (B), the solvent (S), and at least one plasticizer (C) selected from monosaccharides and disaccharides as described above can form a protective film having excellent laser processability and suppressing the generation of cracks is unknown. The reason can be speculated as follows.

[0165] First, as described above, monosaccharides and disaccharides are used as plasticizers (C). It is believed that the excellent plasticizing effect of monosaccharides and disaccharides on the water-soluble resin (A) such as the water-soluble resin (A1) plasticizes the protective film well, thereby suppressing the occurrence of cracks.

[0166] In addition, it is believed that the monosaccharide and disaccharide as the plasticizer (C) can plasticize the protective film without excessively reducing the heat resistance of the protective film. Therefore, it is believed that during laser processing, the laser irradiated portion of the protective film will not be excessively softened or fluidized, and as a result, a processing groove having a smooth side (side wall) and a rectangular cross section is formed by laser processing.

[0167] On the other hand, when sugars other than monosaccharides or disaccharides (e.g., celluloses) are used instead of monosaccharides or disaccharides, or when non-sugar plasticizers (e.g., trimethylolpropane, neopentyl glycol, polyethylene glycol) are used instead of monosaccharides or disaccharides, cracks may occur in the formed protective film, or the linearity and cross-sectional rectangularity of the processed groove may deteriorate.

[0168] This is presumably because when a large molecular weight sugar or a compound having a small number of hydroxyl groups per molecule is used as a plasticizer, the plasticizing effect is weak or it is difficult to form a dense network based on hydrogen bonds between the plasticizer (C) and the water-soluble resin (A).

[0169] In addition, since the protective film forming agent contains a water-soluble resin (A), a light absorber (B) and a solvent (S), and at least one plasticizer (C) selected from monosaccharides and disaccharides, the stickiness (tackiness) of the formed protective film can be suppressed, and a non-sticky protective film or a protective film with a low degree of stickiness can be obtained.

[0170] The content of at least one plasticizer (C) selected from monosaccharides and disaccharides is preferably 5 to 100 parts by mass, more preferably 10 to 80 parts by mass, based on 100 parts by mass of the water-soluble resin (A).

[0171] The content of at least one plasticizer (C) selected from monosaccharides and disaccharides is preferably 20 to 100 parts by mass, more preferably 20 to 70 parts by mass, based on 100 parts by mass of the water-soluble resin (A1).

[0172] <Other additives>

[0173] The protective film forming agent may contain other additives in addition to the water-soluble resin (A), the light absorber (B), and the plasticizer (C) as long as they do not hinder the purpose of the present invention. For example, other additives may be used, such as alkaline compounds, preservatives, and surfactants.

[0174] (Basic Compounds)

[0175] When the protective film forming agent contains the compound represented by the formula (B1), the protective film forming agent may contain a basic compound for the purpose of easily dissolving the compound represented by the formula (B1).

[0176] As the basic compound, both inorganic compounds and organic compounds can be used. As the basic compound, an organic compound is preferred.

[0177] Specific examples of the alkaline compound include alkaline inorganic compounds such as sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium silicate, sodium metasilicate, and ammonia; and alkaline organic compounds such as ethylamine, n-propylamine, monoethanolamine, diethylamine, di-n-propylamine, diethanolamine, triethylamine, methyldiethylamine, dimethylethanolamine, triethanolamine, tetramethylammonium hydroxide, tetraethylammonium hydroxide, pyrrole, piperidine, 1,8-diazabicyclo[5,4,0]-7-undecene, and 1,5-diazabicyclo[4,3,0]-5-nonane.

[0178] The amount of the basic compound used is not particularly limited within the scope of not hindering the purpose of the present invention. Relative to 1 mole of the compound represented by formula (B1), the amount of the basic compound used is preferably more than 1 mole, more preferably more than 1 mole and less than 20 moles. Relative to 1 mole of the compound represented by formula (B1), the lower limit of the amount of the basic compound used can be more than 1.5 moles, can be more than 2 moles, can be more than 3 moles. Relative to 1 mole of the compound represented by formula (B1), the upper limit of the amount of the basic compound used can be less than 15 moles, can be less than 10 moles, can be less than 5 moles.

[0179] (preservative)

[0180] As the preservative, benzoic acid, butyl paraben, ethyl paraben, methyl paraben, propyl paraben, sodium benzoate, sodium propionate, benzalkonium chloride, benzethonium chloride, benzyl alcohol, cetylpyridinium chloride, chlorobutanol, phenol, phenylethanol, 2-phenoxyethanol, phenylmercuric nitrate, thimerosal, m-cresol, lauryl dimethylamine oxide, or a combination thereof can be used.

[0181] Not only from the perspective of the anti-corrosion of the protective film forming agent, but also from the perspective of reducing the load of the treatment of the waste liquid after washing the semiconductor wafer, it is preferred to use a preservative. A large amount of washing water is usually used to wash the semiconductor wafer. However, in the process using the aforementioned protective film forming agent, there is concern about the growth of miscellaneous bacteria in the waste liquid caused by the water-soluble resin (A) contained in the protective film forming agent. Therefore, it is desirable to treat the waste liquid from the process using the aforementioned protective film forming agent separately from the waste liquid from the process without the protective film forming agent. However, when the protective film forming agent contains a preservative, the growth of miscellaneous bacteria caused by the water-soluble resin (A) is suppressed. Therefore, the waste liquid from the process using the protective film forming agent can be treated in the same manner as the waste liquid from the process without the protective film forming agent. Therefore, the load of the wastewater treatment process can be reduced.

[0182] (Surfactant)

[0183] The surfactant can be used, for example, to improve defoaming properties during the production of the protective film forming agent, the stability of the protective film forming agent, and the coating properties of the protective film forming agent. In particular, it is preferred to use a surfactant from the perspective of defoaming properties during the production of the protective film forming agent.

[0184] Generally, the protective film is formed by spin coating a protective film forming agent. However, there are cases where unevenness is generated due to bubbles when the protective film is formed. In order to suppress the generation of such unevenness, a defoaming agent such as a surfactant is preferably used.

[0185] As the surfactant, a water-soluble surfactant can be preferably used. As the surfactant, any surfactant among nonionic surfactants, cationic surfactants, anionic surfactants, and amphoteric surfactants can be used. The surfactant can also be silicone-based. From the aspect of washing properties, nonionic surfactants are preferred.

[0186] <Solvent (S)>

[0187] In order to dissolve the water-soluble resin (A), the light absorber (B), and at least one plasticizer (C) selected from monosaccharides and disaccharides, the protective film forming agent contains a solvent (S). As the solvent (S), any solvent selected from water, an organic solvent, and an aqueous solution of an organic solvent can be used. From the perspective of less danger such as flammability during use and cost, the solvent (S) preferably contains water. Specifically, the solvent (S) is preferably water and an aqueous solution of an organic solvent, and more preferably water.

[0188] From the viewpoint of flammability, the content of the organic solvent in the solvent (S) is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less.

[0189] The solvent (S) is preferably selected so that the protective film forming agent does not have a flash point at 1 atmosphere. Specifically, by adjusting the water content in the protective film forming agent, the flash point of the protective film and the presence or absence of the flash point can be adjusted.

[0190] The protective film forming agent without a flash point is safe, for example, it can be placed in a non-explosion-proof environment. Specifically, the storage, transportation, use, etc. of the protective film forming agent can be carried out in a non-explosion-proof environment. For example, not only can the protective film forming agent be introduced into a semiconductor factory in a non-explosion-proof environment, but also the protective film can be formed in a non-explosion-proof environment. Therefore, the protective film forming agent without a flash point is very advantageous in the industry from the perspective of not requiring an explosion-proof environment such as usually expensive explosion-proof equipment.

[0191] The flash point can be obtained by measuring with a Tag closed type at 1 atmosphere when the liquid temperature is 80°C or lower, and by measuring with a Cleveland open type when the liquid temperature exceeds 80°C.

[0192] In the specification and claims of the present application, the case where the flash point cannot be measured even by the Cleveland open test is regarded as having no flash point.

[0193] Examples of the organic solvent that may be contained in the protective film forming agent include methanol, ethanol, alkylene glycol, alkylene glycol monoalkyl ether, and alkylene glycol monoalkyl ether acetate.

[0194] Examples of the alkylene glycol include ethylene glycol and propylene glycol. Examples of the alkylene glycol monoalkyl ether include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, and propylene glycol monoethyl ether. Examples of the alkylene glycol monoalkyl ether acetate include ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, and propylene glycol monoethyl ether acetate.

[0195] The protective film forming agent may contain two or more organic solvents in combination.

[0196] The solid content concentration of the protective film forming agent is not particularly limited within a range not hindering the purpose of the present invention. The solid content concentration is, for example, preferably 5 mass % to 60 mass %, more preferably 10 mass % to 50 mass %.

[0197] Semiconductor chip manufacturing method

[0198] The method for manufacturing a semiconductor chip is a method including a step of processing a semiconductor wafer to manufacture a semiconductor chip.

[0199] More specifically, the method for manufacturing a semiconductor chip is a method comprising the following steps:

[0200] A step of applying the protective film forming agent on the semiconductor wafer to form a protective film; and

[0201] A step of irradiating a predetermined position of one or more layers including a protective film on a semiconductor wafer with laser light to form a processing groove having a pattern corresponding to the shape of the semiconductor chip while exposing the surface of the semiconductor wafer.

[0202] Typically, the above-mentioned method for manufacturing a semiconductor chip includes a step of cutting the position of the processed groove in the semiconductor wafer (the position corresponding to the position of the street).

[0203] Hereinafter, forming a protective film is also described as a “protective film forming step”, forming a processing groove is also described as a “processing groove forming step”, and cutting off the position of the processing groove in the semiconductor chip is also described as a “cutting step”.

[0204] <Protective Film Formation Step>

[0205] In the protective film forming step, the protective film forming agent described above is applied on the semiconductor wafer to form a protective film.

[0206] The shape of the processed surface of the semiconductor wafer is not particularly limited as long as the desired processing can be performed on the semiconductor wafer. Typically, the processed surface of the semiconductor wafer has many concave and convex portions. Furthermore, a concave portion is formed in the area corresponding to the track.

[0207] The processing surface of a semiconductor wafer is divided into a plurality of regions corresponding to semiconductor chips by streets.

[0208] The thickness of the protective film is typically preferably 0.1 μm to 100 μm, more preferably 1 μm to 100 μm, from the perspective of easy removal of the protective film by water washing after processing and sufficient durability of the protective film against plasma irradiation when plasma irradiation is performed in the cutting step described later.

[0209] When laser irradiation is performed in the machining groove forming step, the thickness of the protective film is preferably 0.1 μm or more and 30 μm or less.

[0210] Hereinafter, a method for manufacturing semiconductor chips by dicing a semiconductor wafer having a plurality of semiconductor chips partitioned by grid-like streets using the protective film forming agent will be described with reference to the drawings as one preferred embodiment of the method for manufacturing semiconductor chips.

[0211] Figure 1 A perspective view showing a semiconductor wafer to be processed. Figure 2 Show Figure 1 An enlarged cross-sectional view of a main portion of a semiconductor wafer is shown. Figure 1 and Figure 2 In the semiconductor wafer 2 shown, a stacked body 21 formed by stacking insulating films and functional films forming circuits is provided on a surface 20a of a semiconductor substrate 20 such as silicon. In the stacked body 21, a plurality of semiconductor chips 22 such as ICs and LSIs are formed in a matrix.

[0212] Here, the shape and size of the semiconductor chip 22 are not particularly limited and can be appropriately set according to the design of the semiconductor chip 22 .

[0213] Each semiconductor chip 22 is divided by a grid-shaped track 23. It should be noted that in the illustrated embodiment, the insulating film used as the stack 21 includes a low dielectric constant insulator film (Low-k film) formed by a SiO2 film, an inorganic film such as SiOF, BSG (SiOB), or an organic film such as a polymer film such as a polyimide film or a parylene film.

[0214] The surface of the laminate 21 described above corresponds to the surface 2a as a processed surface. On the surface 2a described above, a protective film is formed using the protective film forming agent described above.

[0215] In the protective film forming step, for example, a protective film is formed by applying a protective film forming agent to the surface 2a of the semiconductor wafer 2 using a spin coater. The method for applying the protective film forming agent is not particularly limited as long as a protective film having a desired film thickness can be formed.

[0216] Then, the liquid protective film forming agent covering the surface 2a is dried as needed. Figure 3 As shown, a protective film 24 is formed on the surface 2 a of the semiconductor wafer 2 .

[0217] Since the protective film 24 is formed by using the protective film forming agent containing a water-soluble resin (A), a light absorber (B), a solvent (S), and at least one plasticizer (C) selected from monosaccharides and disaccharides, the generation of cracks can be suppressed, and a protective film 24 with no cracks or few cracks can be formed. In addition, a protective film 24 with suppressed stickiness can be formed.

[0218] After the protective film 24 is formed on the surface 2a of the semiconductor wafer 2 as described above, the protective film 24 is formed on the back side of the semiconductor wafer 2. Figure 4 As shown, a protective tape 6 is attached to the ring-shaped frame 5 .

[0219] <Processing Groove Forming Step>

[0220] In the machining groove forming step, laser light is irradiated onto predetermined positions of one or more layers including the protective film 24 on the semiconductor wafer 2 to form machining grooves having a pattern corresponding to the shape of the semiconductor chip 22 while exposing the surface 20 a of the semiconductor substrate 20 .

[0221] Specifically, laser light is irradiated onto the surface 2a (track 23) on the semiconductor wafer 2 through the protective film 24. The irradiation of laser light is performed as follows. Figure 5 This is carried out using a laser beam irradiation mechanism 72 as shown.

[0222] From the aspect of intensity, the laser is preferably an ultraviolet laser having a wavelength of 100 nm to 400 nm, and preferably a YVO4 laser or a YAG laser having a wavelength of 266 nm, 355 nm, etc.

[0223] The laser irradiation in the machining groove forming step is performed, for example, under the following machining conditions: It should be noted that the focused spot diameter can be appropriately selected in consideration of the width of the machining groove 25 .

[0224] Laser light source: YVO4 laser or YAG laser

[0225] Wavelength: 355nm

[0226] Repetition frequency: 50kHz or more and 100kHz or less

[0227] Output power: 0.3W or more and 4.0W or less

[0228] Processing conveying speed: above 1mm / sec and below 800mm / sec

[0229] By implementing the above-mentioned processing groove forming process, Figure 6As shown, in the laminate 21 having the track 23 in the semiconductor wafer 2, the processed groove 25 is formed along the track 23. Since the protective film 24 is formed by using the above-mentioned protective film forming agent containing a water-soluble resin (A), a light absorber (B) and a solvent (S), and at least one plasticizer (C) selected from monosaccharides and disaccharides, by irradiating the protective film 24 with laser as described above, a groove (processed groove 25) with excellent straight running property and cross-sectional rectangularity can be formed in the protective film 24.

[0230] When laser irradiation is performed along the predetermined track 23 as described above, the semiconductor wafer 2 held on the chuck table 71 is indexed and moved in the direction indicated by the arrow Y at intervals corresponding to the track, and laser irradiation is performed again.

[0231] After the laser irradiation and indexing movement are performed for all the tracks 23 extending in the specified direction as described above, the semiconductor wafer 2 held on the chuck table 71 is rotated 90 degrees, and the laser irradiation and indexing movement are performed in the same manner as described above along each track 23 extending at right angles to the specified direction. As described above, the processing grooves 25 can be formed along all the tracks 23 formed in the stacked body 21 on the semiconductor wafer 2.

[0232] <Cutting process>

[0233] In the cutting step, the semiconductor wafer 2 having the processed grooves 25 at positions corresponding to the positions of the streets 23 is cut.

[0234] As a cutting method, the following methods can be cited: a method of cutting a semiconductor wafer 2 having a protective film 24 or a semiconductor wafer 2 from which the protective film 24 has been peeled off using a blade; a method of cutting a semiconductor wafer 2 having a protective film 24 and a processed groove 25 by irradiating a laser or plasma to the semiconductor wafer 2.

[0235] When cutting with a blade, for example, the semiconductor wafer 2 is cut along the position of the processing groove 25 with the blade while supplying pure water to the cutting portion.

[0236] When irradiating with laser light, the processed groove 25 is irradiated with laser light in order to cut the semiconductor wafer 2. The laser light irradiated in the cutting step may be the same as or different from the laser light irradiated in the processed groove forming step.

[0237] When irradiating with plasma, plasma is irradiated onto a part or the entire surface of the semiconductor wafer 2 having the protective film so that the plasma is exposed to the surface of the processed groove 25 .

[0238] Hereinafter, a cutting method by plasma irradiation will be described.

[0239] like Figure 7 As shown in FIG. 2 , plasma is irradiated to the semiconductor wafer 2 having the protective film 24 and the processed groove 25. By doing so, Figure 8 As shown, the position of the processing groove 25 in the semiconductor wafer 2 is cut.

[0240] Specifically, in the semiconductor chip 2 covered with the protective film 24, after the processing groove 25 is formed as described above, the protective film 24 and the surface 20a of the semiconductor substrate 20 exposed from the processing groove 25 are plasma irradiated, thereby cutting the semiconductor chip 2 into the shape of the semiconductor chip 22, and the semiconductor chip 2 is divided into the semiconductor chips 22.

[0241] The plasma irradiation conditions are not particularly limited as long as the semiconductor wafer 2 can be cut well at the position of the processed groove 25. The plasma irradiation conditions can be appropriately set within the range of general conditions for plasma etching of the semiconductor substrate 20 in consideration of the material of the semiconductor wafer 2, the type of plasma, etc.

[0242] The gas used to generate plasma during plasma irradiation can be appropriately selected according to the material of the semiconductor wafer 2. Typically, SF6 gas can be used to generate plasma.

[0243] Alternatively, the semiconductor wafer 2 may be cut by alternately performing sidewall protection by supplying C4F6 or C4F8 gas or the like and etching the semiconductor wafer 2 by plasma irradiation according to a so-called BOSCH process. The BOSCH process enables etching with a high aspect ratio, and the semiconductor wafer 2 can be easily cut even when the semiconductor wafer 2 is thick.

[0244] Since the protective film 24 is formed by using the protective film forming agent containing a water-soluble resin (A), a light absorber (B), a solvent (S), and at least one plasticizer (C) selected from monosaccharides and disaccharides, the processed groove 25 has excellent straightness and cross-sectional rectangularity. Therefore, it is possible to cut at a desired position by plasma irradiation or the like, and a semiconductor chip with excellent straightness can be obtained.

[0245] In addition, since the protective film 24 is formed by using the above-mentioned protective film forming agent containing a water-soluble resin (A), a light absorber (B) and a solvent (S), and at least one plasticizer (C) selected from monosaccharides and disaccharides, there is no crack or few cracks. Therefore, the positions other than the position to be cut can be fully protected, and the undesired positions (positions other than the processing groove) can be prevented from being cut due to plasma irradiation or the like. In addition, it is possible to suppress the contamination of the semiconductor substrate caused by gases such as fluorine-based gases used in plasma irradiation.

[0246] Next, if Fig. 9 As shown, the protective film 24 covering the surface of the semiconductor chip 22 is removed. As described above, the protective film 24 is formed using a protective film forming agent containing a water-soluble resin (A), and therefore the protective film 24 can be washed away with water (or warm water).

[0247] The above is a description of a method for manufacturing a semiconductor chip by processing a semiconductor wafer based on an embodiment. The protective film forming agent and the method for manufacturing a semiconductor chip according to the present invention can be applied to various methods for manufacturing semiconductor chips as long as the method includes the steps of forming a protective film on the surface of a semiconductor wafer and forming a processing groove on the surface of the semiconductor wafer having the protective film at a position corresponding to the track.

[0248] Example

[0249] The present invention will be described in detail below by way of examples and comparative examples, but the present invention is not limited to the following examples.

[0250] [Examples 1 to 24 and Comparative Examples 1 to 16]

[0251] In Examples and Comparative Examples, as the water-soluble resin (A), the following A1 to A4 as water-soluble resins (A1) having an aromatic ring and a water-soluble group, A5 as a cellulose-based resin, and A6 as a polyvinyl alcohol-based resin were used.

[0252] The numbers on the lower right side of the brackets in each structural unit in the following structural formula represent the molar ratio of the structural unit in each resin.

[0253] A1 is WSR-SP82 manufactured by Konishi Chemical Industries, Ltd. and has a mass average molecular weight of 22,000.

[0254] [Chemical formula 12]

[0255]

[0256] A2 is an ammonia-neutralized product (pH 7) of PS-1H manufactured by TOSOH FineChem Co., Ltd., and has a mass average molecular weight of 22,000.

[0257] [Chemical formula 13]

[0258]

[0259] A3 was used in the form of a solution of XIRAN 3000P manufactured by POLYSCOPE (resin solid content concentration: 14% by mass, solvent: propylene glycol monomethyl ether and water, ammonia concentration: 5% by mass).

[0260] The mass average molecular weight of A3 is 10,000.

[0261] [Chemical formula 14]

[0262]

[0263] A4 is DHDPS resin manufactured by Konishi Chemical Industry Co., Ltd. (a product of a reaction product of DHDPS (dihydroxydiphenyl sulfone) and formaldehyde in which the water solubility is increased by phenolate ions) and has a mass average molecular weight of 1,000.

[0264] [Chemical formula 15]

[0265]

[0266] A5 is HPC-SSL (hydroxypropyl cellulose) manufactured by Nippon Soda Co., Ltd., and has a mass average molecular weight of 25,000.

[0267] A6 is NICHIGO G Polymer manufactured by Mitsubishi Chemical Corporation TM AZF8035W (butene glycol vinyl alcohol copolymer), estimated degree of polymerization is 300.

[0268] In the examples and comparative examples, a compound B1 represented by the following formula was used as the light absorber (B).

[0269] [Chemical formula 16]

[0270]

[0271] In Examples and Comparative Examples, compounds C1 to C10 represented by the following formulae were used as plasticizers (C). The structures of C1 to C10 are described below.

[0272] C1: D(+)-glucose

[0273] C2: D(+)-Galactose

[0274] C3: D(+)-Xylose

[0275] C4: D(-)-fructose

[0276] C5: D(-)-ribose

[0277] C6: myo-inositol

[0278] C7: D(+)-maltose

[0279] C8: Trimethylolpropane

[0280] C9: Neopentyl glycol

[0281] C10: Polyethylene glycol

[0282] [Chemical formula 17]

[0283]

[0284] [Chemical formula 18]

[0285]

[0286] In the examples and comparative examples, monoethanolamine was used as the basic compound.

[0287] The water-soluble resin (A), light absorber (B), plasticizer (C), monoethanolamine as a basic compound, and solvent (S) of the types listed in Tables 1 to 6 were placed in a container so that the mass ratio of the solvent in the obtained protective film forming agent was 85 mass % of water and 15 mass % of propylene glycol monomethyl ether, and the solid content concentration was set as listed in Tables 1 to 6, and stirred for 3 hours to obtain the protective film forming agent of each example and comparative example. It should be noted that the mass parts of the water-soluble resin (A), light absorber (B), plasticizer (C), and monoethanolamine in the obtained protective film forming agent are as listed in Tables 1 to 6.

[0288] [Evaluation of stickiness (tackiness) of protective film]

[0289] The obtained protective film forming agent was applied on a silicon substrate by a spin coating method so as to have a film thickness of 5 μm to form a coating film.

[0290] Next, the coating film was naturally dried at room temperature for about 15 minutes, and the surface of the dried coating film was touched with a finger to evaluate whether the coating film surface was sticky. The results are shown in Tables 1 to 6.

[0291] [Evaluation of cracks in protective film (film forming properties)]

[0292] A coating film was formed in the same manner as in the above-mentioned [Evaluation of tackiness (stickiness) of protective film].

[0293] Next, the coating film was dried under reduced pressure to a SEM (scanning electron microscope) measurement environment (6.0 Pa), and the coating film after reduced pressure drying was observed using a 10-fold optical microscope, and the case where cracks were generated was marked as ×, and the case where no cracks were generated and a good coating film was formed was marked as ○, and the cracks (film forming properties) were evaluated. The results are shown in Tables 1 to 6.

[0294] [Evaluation of laser processability (straightness and cross-sectional rectangularity) of machined grooves]

[0295] The obtained protective film forming agent was applied on a silicon substrate by a spin coating method so as to have a film thickness of 5 μm to form a coating film.

[0296] After the coating film was naturally dried at room temperature for about 15 minutes, the surface of the protective film side of the silicon substrate having the protective film (dried coating film) was laser irradiated in a straight line under the following conditions, and the surface and cross-sectional shape of the laser-irradiated portion of the protective film were observed using SEM (scanning electron microscope), and the linearity and cross-sectional rectangularity of the processed groove were evaluated according to the evaluation criteria described below. The magnification of the SEM was 100 times for linearity and 500 times for rectangularity. The results are shown in Tables 1 to 6. It should be noted that in the case of cracks, the laser processability was not evaluated.

[0297] <Laser irradiation conditions>

[0298] Wavelength: 355nm

[0299] Frequency: 100kHz

[0300] Output power: 0.1W

[0301] Defocus: -0.1mm

[0302] Conveying speed: 100mm / s

[0303] Pass: 2

[0304] <Straight Linearity>

[0305] Evaluation was performed based on the following criteria.

[0306] ⊚: The cross section of the protective film (side wall of the processed groove) is flat, and straight grooves (grooves) without gaps are formed.

[0307] ○: The cross section of the protective film is relatively flat, and relatively straight grooves (grooves) are formed with slight gaps.

[0308] △: The cross section of the protective film is not flat, and grooves (trench) with large gaps are formed.

[0309] ×: Processing failure (the pattern softened due to the heat of the laser and could not maintain its shape, so a processed groove could not be formed.)

[0310] <Cross-sectional rectangularity>

[0311] In the cross section, Fig.10 As shown, the angle θ formed between the surface 81 of the silicon substrate 80 and the side wall 91 of the protective film 90 was obtained and evaluated according to the following criteria.

[0312] ◎: θ is 45° or more and 90° or less.

[0313] ○: θ is greater than 30° and less than 45°.

[0314] △: θ is 30° or less.

[0315] ×: Processing failure (the pattern softened due to the heat of the laser and could not maintain its shape, so a processed groove could not be formed.)

[0316] [Table 1]

[0317]

[0318] [Table 2]

[0319]

[0320] [Table 3]

[0321]

[0322] [Table 4]

[0323]

[0324] [Table 5]

[0325]

[0326] [Table 6]

[0327]

[0328] As shown in Tables 1 to 6, it can be seen that the protective film 24 uses the protective film forming agents of Examples 1 to 24 containing a water-soluble resin (A), a light absorber (B), at least one plasticizer (C) selected from monosaccharides and disaccharides, and a solvent (S), so that a protective film with excellent laser processability and suppressed crack generation can be formed. In addition, it can be seen that the protective film formed using the protective film forming agents of Examples 1 to 24 can also suppress stickiness.

[0329] Description of Reference Numerals

[0330] 2: Semiconductor wafer

[0331] 20: Substrate

[0332] 21: Laminated body

[0333] 22: Semiconductor chips

[0334] 23: Trail

[0335] 24: Protective film

[0336] 25: Laser processing groove

[0337] 5: Ring frame

[0338] 6: Protective tape

[0339] 7: Laser processing equipment

[0340] 71: Chuck table for laser processing equipment

[0341] 72: Laser beam irradiation mechanism

Claims

1. A protective film forming agent for forming a protective film on the surface of a semiconductor wafer during dicing of the semiconductor wafer, The protective film forming agent comprises a water-soluble resin (A), a light absorber (B), at least one plasticizer (C) selected from monosaccharides and disaccharides, and a solvent (S).

2. The protective film forming agent according to claim 1, wherein The water-soluble resin (A) includes a water-soluble resin (A1) having an aromatic ring and a water-soluble group.

3. The protective film forming agent according to claim 2, wherein The content of the plasticizer (C) is 20 parts by mass or more and 100 parts by mass or less relative to 100 parts by mass of the water-soluble resin (A1).

4. The protective film forming agent according to claim 2, wherein The water-soluble resin (A1) includes a resin having a phenolic hydroxyl group.

5. The protective film forming agent according to claim 2, wherein The water-soluble resin (A) includes a polyvinyl alcohol-based resin.

6. The protective film forming agent according to claim 1, wherein The solvent (S) comprises water.

7. A method for manufacturing a semiconductor chip, which is a method for manufacturing a semiconductor chip by processing a semiconductor wafer, the method comprising the following steps: A step of applying the protective film forming agent according to any one of claims 1 to 6 on the semiconductor wafer to form a protective film; and A step of irradiating a predetermined position of one or more layers including the protective film on the semiconductor wafer with laser light to form a processing groove having a pattern corresponding to the shape of the semiconductor chip and exposing the surface of the semiconductor wafer.

8. The method for manufacturing a semiconductor chip according to claim 7, comprising a step of cutting the position of the processed groove in the semiconductor wafer.

Images