Protective film forming agent and method for manufacturing semiconductor chips

Abstract

To provide a protective film formation agent which is used to form a protective film on a surface of a semiconductor wafer in dicing of a semiconductor wafer, exhibits an excellent processing property, and can form a protective film which causes less cracks, and a method for manufacturing a semiconductor chip by using the protective film formation agent.SOLUTION: After a protective film 24 is formed on a surface of a semiconductor wafer 2, and a processed trench 25 is formed along a street in a laminate body 21 having a street 23 of the semiconductor wafer. A protective film formation agent used to form a protective film includes a water-soluble resin, a light absorbing agent, a plasticizer made of at least one type selected from monosaccharide and disaccharide, and a solvent. The water-soluble resin desirably includes a water-soluble resin having an aromatic ring and a water-soluble group.SELECTED DRAWING: Figure 6

Description

Technical Field

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

[0002] A wafer formed in a semiconductor device manufacturing process is obtained by partitioning a laminate, in which an insulating film and a functional film are laminated on a surface of a semiconductor substrate made of silicon or the like, with grid-like scheduled division lines called streets, and each region partitioned by the streets forms a semiconductor chip such as an IC or an LSI.

[0003] A plurality of semiconductor chips can be obtained by cutting the wafer along these streets. Further, in an optical device wafer, a laminate obtained by laminating gallium nitride-based compound semiconductors or the like is partitioned into a plurality of regions by streets. Cutting along the streets divides the optical device wafer into optical devices such as light-emitting diodes and laser diodes. These optical devices are widely used in electrical equipment.

[0004] In the past, cutting such a wafer along the streets was performed by a cutting device called a dicer. However, in this method, since a wafer having a laminated structure is made of a highly brittle material, when the wafer is cut and divided into semiconductor chips or the like by a cutting blade, problems such as generation of scratches and chipping, and peeling of the insulating film required as a circuit element formed on the chip surface may occur.

[0005] In order to solve such problems, a method has been proposed in which a mask including a layer of a water-soluble material is formed on the surface of a semiconductor substrate, then the mask is irradiated with laser to decompose and remove a part of the mask, thereby exposing the surface of the semiconductor substrate at a part of the mask, and then the semiconductor substrate exposed from the part of the mask is cut by plasma etching to divide the semiconductor substrate into semiconductor chips (ICs) (see Patent Document 1). Prior Art Documents [Patent Documents]

[0006] [Patent Document 1] Special Publication No. 2014-523112 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] In this way, a laser is irradiated onto the mask, partially disassembling and removing the mask, and exposing the surface of the semiconductor substrate in that part of the mask, thereby forming a pattern of grooves corresponding to the shape of the semiconductor chip. However, when forming a protective film as a mask using conventional water-soluble materials such as the water-soluble material described in Patent Document 1, there is a problem that the straightness of the processing grooves formed by laser irradiation (straightness of the side walls of the protective film constituting the processing grooves) and the rectangularity of the cross-section of the processing grooves (rectangularity of the cross-section of the protective film constituting the processing grooves) may be poor, in other words, the laser processability may be poor. If the straightness of the processing groove is poor, the straightness of the cut surface of the semiconductor chip obtained by plasma etching of the semiconductor substrate will also be poor. Furthermore, if the rectangularity of the cross-section of the processing groove is poor, it will be difficult for the cutting position to be the desired position by plasma etching or the like.

[0008] Furthermore, when forming a protective film using conventional water-soluble materials such as the water-soluble material described in Patent Document 1, there is a problem that cracks may occur. Cracks are particularly likely to occur when the protective film is thick.

[0009] The present invention has been made in view of the above problems, and aims to provide a protective film forming agent that can be used to form a protective film on the surface of a semiconductor wafer in the dicing of a semiconductor wafer, and which can form a protective film that has excellent laser processability and suppresses the occurrence of cracks, and a method for manufacturing a semiconductor chip using the protective film forming agent. [Means for solving the problem]

[0010] The inventors have discovered that the above problems can be solved by a protective film-forming agent comprising a water-soluble resin (A), a light-absorbing agent (B), at least one plasticizer (C) selected from monosaccharides and disaccharides, and a solvent (S), and have completed the present invention. More specifically, the present invention provides the following.

[0011] [1] A protective film forming agent used in the dicing of semiconductor wafers to form a protective film on the surface of a semiconductor wafer, A protective film-forming agent comprising a water-soluble resin (A), a light-absorbing agent (B), at least one plasticizer (C) selected from monosaccharides and disaccharides, and a solvent (S).

[0012] [2] The protective film-forming agent according to [1] above, wherein the water-soluble resin (A) comprises a water-soluble resin (A1) having an aromatic ring and a water-soluble group.

[0013] [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 per 100 parts by mass of the water-soluble resin (A1).

[0014] [4] The protective film-forming agent according to [2] or [3] above, wherein the water-soluble resin (A1) includes a resin having phenolic hydroxyl groups.

[0015] [5] The protective film-forming agent according to any one of [1] to [4] above, wherein the water-soluble resin (A) contains a polyvinyl alcohol-based resin.

[0016] [6] A protective film-forming agent according to any one of [1] to [5] above, wherein the solvent (S) contains water.

[0017] [7] A method for manufacturing a semiconductor chip, which involves processing a semiconductor wafer, A protective film is formed on the semiconductor wafer by applying one of the protective film-forming agents described in any one of [1] to [6] above, Laser light is irradiated onto predetermined positions of one or more layers, including the protective film, on the semiconductor wafer, exposing the surface of the semiconductor wafer and forming processing grooves in a pattern corresponding to the shape of the semiconductor chip. A method for manufacturing semiconductor chips, including

[0018] [8] A method for manufacturing a semiconductor chip according to [7], comprising cutting the position of the processing groove in the semiconductor wafer. [Effects of the Invention]

[0019] According to the present invention, in a method for manufacturing semiconductor chips from semiconductor wafers, it is possible to provide a protective film forming agent used to form a protective film on the surface of a semiconductor wafer, which has excellent laser processability and can form a protective film that suppresses the occurrence of cracks, and a method for manufacturing semiconductor chips using the protective film forming agent. [Brief explanation of the drawing]

[0020] [Figure 1] A perspective view showing a semiconductor wafer processed by a wafer processing method using the protective film-forming agent of the present invention. [Figure 2] A magnified cross-sectional view of the semiconductor wafer shown in Figure 1. [Figure 3] Enlarged cross-sectional view of a key part of a semiconductor wafer with a protective film formed on it. [Figure 4] A perspective view showing a semiconductor wafer with a protective film formed on it, supported by protective tape on a ring-shaped frame. [Figure 5] A perspective view of the main components of a laser processing apparatus that performs the laser beam irradiation process. [Figure 6] A magnified cross-sectional view of a semiconductor wafer equipped with a protective film and processed grooves formed by laser irradiation. [Figure 7] Figure 6 is an explanatory diagram illustrating plasma irradiation of a semiconductor wafer. [Figure 8] A magnified cross-sectional view showing a semiconductor wafer separated into semiconductor chips by plasma irradiation. [Figure 9] A magnified cross-sectional view showing the semiconductor chip with the protective film removed. [Figure 10] A cross-sectional diagram illustrating a method for evaluating the rectangularity of the cross-section. [Modes for carrying out the invention]

[0021] ≪Protective film-forming agent≫ A protective film-forming agent is used in semiconductor wafer dicing to form a protective film on the surface of a 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).

[0022] Specifically, the protective film forming agent involves irradiating the protective film formed on the semiconductor wafer with laser light to expose the surface of the semiconductor wafer and to form processing grooves in a pattern corresponding to the shape of the semiconductor chip. Processing the position of the processing groove on the semiconductor wafer, This material is suitably used for forming a protective film in a semiconductor chip manufacturing method that includes [the specified material]. After forming the processing groove, the semiconductor chip can be manufactured by cutting the semiconductor wafer at the location of the processing groove.

[0023] In order to facilitate the removal of the protective film by washing with water after processing the semiconductor wafer, and to ensure 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 0.1 μm to 100 μm, and more preferably 1 μm to 100 μm. When irradiating with a laser, the thickness of the protective film is preferably 0.1 μm or more and 30 μm or less.

[0024] The following describes the essential and optional components of the protective film-forming agent.

[0025] <Water-soluble resin (A)> Water-soluble resin (A) is a substrate for a protective film formed using a protective film-forming agent. Water-soluble resin (A) is a resin that can form a film by dissolving it in a solvent such as water, applying it, and drying it. Furthermore, resins that become solubilized in water through hydrolysis or treatment with a base in an aqueous medium also fall under the category of water-soluble resins (A). Examples of such resins include resins having carboxylic acid anhydride groups and resins having phenolic hydroxyl groups. Carboxylic acid anhydride groups become solubilized in water by generating carboxyl groups or carboxylic acid bases through hydrolysis or treatment with a base in an aqueous medium. Resins having phenolic hydroxyl groups may be water-soluble or sparingly soluble in water, depending on their structure. If a resin having phenolic hydroxyl groups is sparingly soluble in water, it can be made water-soluble by treating it in a basic aqueous medium and converting the phenolic hydroxyl groups into salts (phenolates). Water solubility means that 0.5 g or more of the solute (water-soluble resin) dissolves in 100 g of water or alkaline aqueous solution at 25°C.

[0026] The water-soluble resin (A) preferably contains a water-soluble resin (A1) which has 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 protective film formed has better laser processability and also better resistance to plasma irradiation when plasma irradiation is performed. The aromatic ring contained in the water-soluble resin (A1) may be either an aromatic hydrocarbon ring or an aromatic heterocycle. Furthermore, the aromatic ring may be monocyclic or polycyclic. The polycyclic structure may be a polycyclic structure formed by the condensation of two or more monocyclic rings, or a polycyclic structure in which two or more rings are linked to each other via single bonds or linking groups. An example of a monocyclic aromatic ring is the benzene ring. Examples of polycyclic aromatic rings include naphthalene rings, biphenyl rings, anthracene rings, and phenanthrene rings.

[0027] The water-soluble group contained in the water-soluble resin (A1) is not particularly limited as long as it is a group capable of imparting water solubility to the resin. Examples of the water-soluble group include -SO3 - X + (X + represents an alkali metal cation, a proton, or N + R4. ), -COO - X + (X + is as defined above. ), a carboxylic acid anhydride group (-CO-O-CO-), a hydroxyl group, or an ether bond (-O-). The carboxylic acid anhydride group (-CO-O-CO-) is a group that gives -COO - X + by hydrolysis or treatment with a base in water. When the hydroxyl group is a phenolic hydroxyl group, the hydroxyl group may form a salt such as an alkali metal salt. Here, R represents a hydrogen atom, an alkyl group, or a hydroxyalkyl group. Examples of the alkali metal include sodium, potassium, strontium and the like.

[0028] Examples of the water-soluble resin (A1) include resins having a phenolic hydroxyl group. The phenolic hydroxyl group means a hydroxyl group (OH) directly bonded to a carbon atom in an aromatic ring. Examples of the resin having a phenolic hydroxyl group include phenol resins (resins using phenols and formaldehydes as raw materials). Examples of the phenol resin as the water-soluble resin (A1) include resins having a structural unit represented by the following formula (1).

Chemical Formula

[0029] Specific examples of phenolic resins as water-soluble resins (A1) include phenolic resins having constituent units represented by the following formula (1-1), phenolic resins having constituent units represented by the following formula (1-2), and phenolic resins having constituent units represented by the following formula (1-1) and constituent units represented by the following formula (1-2). For phenolic resins having constituent units represented by the following formula (1-1) and constituent units represented by the following formula (1-2), the ratio of moles of the constituent unit represented by the following formula (1-1) to the total number of moles of the constituent units represented by the following formula (1-2) is preferably 0.1 to 0.9, and more preferably 0.7 to 0.9. [ka] (In the formula, X + is an alkali metal cation, or N + R4 is a hydrogen atom, an alkyl group, or a hydroxyalkyl group.

[0030] Examples of water-soluble resins (A1) include styrene-based unit-containing resins such as resins having structural units represented by the following formula (2). Styrene-based units are structural units derived from styrene or styrene derivatives having substituents on the α-position or benzene ring. [ka] (In formula (2), R 32 (This is a water-soluble group. n32 is an integer between 0 and 3, inclusive.) As mentioned above, the water-soluble group is -SO3 - X + (X +These are alkali metal cations, protons, or N + It is R4. ) -COO - X + (X + As mentioned above, examples include a hydroxyl group or an ether bond (-O-). If the hydroxyl group is a phenolic hydroxyl group, it may form a salt such as an alkali metal salt. n32 is preferably 1. R in the benzene ring 32 The substitution position can be the ortho, meta, or para position. As the water-soluble resin (A1), a solution of a resin having the constituent units represented by formula (2) may be used after neutralizing it with ammonia.

[0031] Specific examples of resins having the constituent units represented by formula (2) as water-soluble resins (A1) include resins having the constituent units represented by the following formula (2-1), and resins having the constituent units represented by the following formula (2-1) and the constituent units represented by the following formula (2-2). [ka] (In the formula, X + These are alkali metal cations, protons, or N + R4 is a hydrogen atom, an alkyl group, or a hydroxyalkyl group. M + These are alkali metal cations, protons, or N + R 01 4, R 01 is a hydrogen atom, an alkyl group, or a hydroxyalkyl group. Examples of alkali metals include sodium, potassium, and strontium.

[0032] Examples of water-soluble resins (A1) include copolymers of styrene and maleic anhydride. Styrene-maleic anhydride copolymer is a resin having constituent units represented by the following formula (3-1) and constituent units represented by the following formula (3-2). Styrene-maleic anhydride copolymer is a styrene-based unit-containing resin. [ka]

[0033] 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 this specification, the mass-average molecular weight is the molecular weight on a polystyrene basis, measured by GPC.

[0034] 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% to 99% by mass, more preferably 30% to 70% by mass, and even more preferably 40% to 60% by mass. In this specification, solid content refers to components other than the solvent (S). If the protective film-forming agent contains components other than the solvent (S) that are liquid at the temperature in which the protective film-forming agent is used, for convenience, such liquid components are included in the solid content.

[0035] The water-soluble resin (A) may contain water-soluble resins other than water-soluble resin (A1). When water-soluble resin (A) contains water-soluble resin (A1) and water-soluble resins other than water-soluble resin (A1), the ratio of the mass of water-soluble resin (A1) to the mass of 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. Examples of water-soluble resins other than water-soluble resin (A1) (hereinafter also referred to as "other water-soluble resins") include vinyl resins, cellulose resins, polyethylene oxide, polyglycerin, and water-soluble nylon. The vinyl resin is not particularly limited as long as it is a homopolymer or copolymer of monomers having vinyl groups and is water-soluble. Examples of vinyl resins include polyvinyl alcohol resins. These include polyvinyl alcohol, polyvinyl acetal (including vinyl acetate copolymer), butenediol-vinyl alcohol copolymer, polyvinyl alcohol-polyacrylic acid block copolymer, and polyvinyl alcohol-polyacrylic acid ester block copolymer. Other vinyl resins include polyvinylpyrrolidone, polyacrylamide, poly(N-alkylacrylamide), polyallylamine, poly(N-alkylallylamine), partially amidated polyallylamine, poly(diallylamine), allylamine-diallylamine copolymer, and polyacrylic acid. The cellulose-based resin is not particularly limited as long as it is a water-soluble cellulose derivative. Examples of cellulose-based resins include methylcellulose, ethylcellulose, and hydroxypropylcellulose. These can be used individually or in combination of two or more types. Furthermore, when the water-soluble resin (A) contains both water-soluble resin (A1) and a cellulose-based resin, the ratio of the mass of water-soluble resin (A1) to the mass of water-soluble resin (A) is preferably 60% by mass or more and 85% by mass or less, and more preferably 65% ​​by mass or more and 80% by mass or less.

[0036] Among other water-soluble resins, vinyl resins and cellulose resins are preferred because they are less prone to deterioration of the shape of the processed grooves due to thermal sagging of the protective film, and polyvinylpyrrolidone and hydroxypropylcellulose are more preferred. Furthermore, from the viewpoint of film-forming properties, cellulose-based resins are preferred.

[0037] The protective film formed on the surface of a semiconductor wafer is usually removed from the surface of the semiconductor wafer or semiconductor chip at an appropriate point after the formation of the processing grooves, depending on the method of processing the semiconductor wafer, which has the protective film and processing grooves, into a semiconductor chip. For this reason, from the viewpoint of the washability of the protective film, it is preferable that the other water-soluble resin is a water-soluble resin with low affinity to the semiconductor wafer surface. Preferred water-soluble resins with low affinity to the semiconductor wafer surface include resins having only ether bonds, hydroxyl groups, and amide bonds as polar groups, such as polyvinyl alcohol, polyethylene glycol, polyvinylpyrrolidone, and hydroxypropyl cellulose.

[0038] The mass-average molecular weight of the other water-soluble resins is preferably 5,000 to 300,000, and more preferably 10,000 to 200,000.

[0039] To prevent problems such as opening defects when forming processing grooves by irradiating the protective film with laser light, and deterioration of the processing groove shape due to thermal deformation of the protective film, the ratio of the mass of the water-soluble resin (A) to the total amount of the absorbent (B) in the protective film forming agent is preferably 60% by mass or more and 99% by mass or less, and more preferably 80% by mass or more and 95% by mass or less.

[0040] <Light absorber (B)> As the light absorber (B), a light absorber commonly used as a protective film-forming agent can be used. As the light absorber (B), it is preferable to use a water-soluble light absorber such as a water-soluble dye, water-soluble pigment, or water-soluble ultraviolet absorber. Water-soluble light absorbers are advantageous in ensuring uniform distribution within the protective film. Examples of water-soluble light absorbers include organic acids having carboxyl or sulfo groups; sodium salts, potassium salts, ammonium salts, and quaternary ammonium salts of organic acids; and compounds having hydroxyl groups. When using a water-soluble light-absorbing agent, the storage stability of the protective film-forming agent is high, and problems such as phase separation of the protective film-forming agent and sedimentation of the light-absorbing agent during storage are suppressed. This is advantageous because it makes it easier to maintain good applicability of the protective film-forming agent for a long period of time.

[0041] Furthermore, water-insoluble light-absorbing agents such as pigments can also be used. While using water-insoluble light-absorbing agents does not necessarily cause fatal problems with the use of protective film-forming agents, it may result in variations in the laser absorption capacity of the protective film, difficulty in obtaining protective film-forming agents with excellent storage stability and coatability, and difficulty in forming protective films of uniform thickness.

[0042] Examples of light-absorbing agents (B) include benzophenone compounds, cinnamic acid compounds, anthraquinone compounds, naphthalene compounds, and biphenyl compounds. Examples of benzophenone compounds include those represented by the following formula (B1). Compounds represented by the following formula (B1) are preferred because they can efficiently absorb the energy of laser light into the protective film and promote the thermal decomposition of the protective film. [ka] (In formula (B1), R 1 and R 3 Each of these is independently a hydroxyl group or a carboxyl group, and R 2 and R 4 These are, independently, a hydroxyl group, a carboxyl group, or -NR. 5 R 6 It is a group represented by R 5 and R 6 Each of these is independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and m and n are independently integers between 0 and 2.

[0043] The compound represented by formula (B1) above has a high absorption coefficient and exhibits a high absorption coefficient even when added to a protective film-forming agent together with an alkali. Therefore, when a protective film is formed using a protective film-forming agent containing the compound represented by formula (B1) above as the absorbent (B), partial laser decomposition of the protective film can be performed effectively during the formation of a mask for dicing.

[0044] In the above formula (B1), R 2 and R 4 -NR 5 R 6 It may be a group represented by R. 5 and R 6 Each of these is independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. 5 and R 6 The alkyl group may be linear or branched. 5 and R 6 Specific examples of alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, and tert-butyl groups.

[0045] -NR 5 R 6 The groups represented by are preferably amino groups, methylamino groups, ethylamino groups, dimethylamino groups, and diethylamino groups, and more preferably amino groups, dimethylamino groups, and diethylamino groups.

[0046] Of the compounds represented by formula (B1), the compound represented by the following formula (B1-1) is preferred due to its high extinction coefficient in the presence of a base. [ka] (Formula (in B1-1), R 1 ~R 4 , m, and n are the same as those in equation (B1).

[0047] Due to the high extinction coefficient in the presence of a base, in the above equations (B1) and (B1-1), R 1and R 3 It is preferable that at least one of them is a hydroxyl group.

[0048] The compound represented by formula (B1-1) is preferably a compound represented by any of the following formulas (B1-1a) to (B1-1e). [ka] (In formulas (B1-1a) to (B1-1e), R 1 ~R 4 These are similar to those in equation (B1).

[0049] Among the compounds represented by formulas (B1-1a) to (B1-1e), the compound represented by formula (B1-1a) is preferred. In the compounds represented by formulas (B1-1a) to (B1-1e), R 2 However, -NR 5 R 6 The aforementioned base represented by R 5 and R 6 However, it is preferable that each is an alkyl group having 1 to 4 carbon atoms independently.

[0050] The following compounds are suitable examples of compounds represented by formula (B1). These compounds are preferred due to their availability and their high extinction coefficient even in the presence of a base. [ka]

[0051] 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 as long as it does not hinder the objective 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, even more preferably 95% by mass or more, and particularly preferably 100% by mass.

[0052] Benzophenone compounds also include 4,4'-dicarboxybenzophenone, benzophenone-4-carboxylic acid, and tetrahydroxybenzophenone. All of these are water-soluble ultraviolet absorbers.

[0053] Examples of cinnamic acid compounds include those represented by the following formula (B2). Compounds represented by the following formula (B2) are preferred because they can efficiently absorb the energy of laser light into the protective film and promote the thermal decomposition of the protective film. [ka] (In formula (B2), R 11 is a hydroxyl group, an alkoxy group, or -NR 12 R 13 It is a group represented by R 12 and R 13 Each is independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, p is an integer between 0 and 3, and if p is 2 or more, multiple R 11 They may be the same or different.

[0054] In the above formula (B2), R 11 The alkoxy group may be linear or branched. 11 The alkoxy group is preferably an alkoxy group having 1 to 4 carbon atoms. 11 Specific examples of alkoxy groups include the methoxy group, ethoxy group, n-propoxy group, isopropoxy group, and n-butoxy group.

[0055] In the above formula (B2), R 11 -NR 12 R 13 It may be a group represented by R. 12 and R 13 Each of these is independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. 12 and R 13 The alkyl group may be linear or branched. 12 and R13 Specific examples of alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, and tert-butyl groups.

[0056] The compound represented by formula (B2) is preferably the compound represented by the following formula (B2-1). [ka] (In formula (B2-1), R 11 This is R in equation (B2). 11 It is similar to this.

[0057] Specific examples of cinnamic acid compounds include 4-aminocinnamic acid, 3-aminocinnamic acid, 2-aminocinnamic acid, sinapic acid (3,5-dimethoxy-4-hydroxycinnamic acid), ferulic acid, and caffeic acid. Among these, 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.

[0058] Specific examples of anthraquinone compounds include 2-carboxyanthraquinone, 2,6-anthraquinone disulfonic acid, and 2,7-anthraquinone disulfonic acid.

[0059] Specific examples of naphthalene compounds include 1,2-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 2,7-naphthalenedicarboxylic acid.

[0060] Specific examples of biphenyl compounds include biphenyl-4-sulfonic acid.

[0061] Examples of light-absorbing agents (B) include curcumin and water-soluble amines such as EAB-F (4,4'-bis(diethylamino)benzophenone).

[0062] Specific examples of water-soluble dyes include water-soluble dyes selected from among 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), indigoid dyes (indigoid derivatives, thioindigoid 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, azomethine dyes), quinoline dyes, nitroso dyes, benzoquinone and naphthoquinone dyes, naphthalimide dyes, perinone dyes, and other dyes.

[0063] Food additives such as Red No. 2, Red No. 40, Red No. 102, Red No. 104, Red No. 105, Red No. 106, Yellow NY, Yellow No. 4 Tartrazine, Yellow No. 5, Yellow No. 5 Sunset Yellow FCF, Orange AM, Vermilion No. 1, Vermilion No. 4, Vermilion No. 101, Blue No. 1, Blue No. 2, Green No. 3, Melon B, and Egg Yellow No. 3 are suitable as water-soluble pigments due to their low environmental impact.

[0064] 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 objective of the present invention. 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, and more preferably 5% by mass or more and 15% by mass or less, based on the total solid content of the protective film-forming agent. To prevent problems such as opening defects when forming processing grooves by irradiating the protective film with laser light, and deterioration of the shape of the processing grooves due to thermal deformation of the protective film, the ratio of the mass of the light absorber (B) to the total amount of the water-soluble resin (A) and the mass of the light absorber (B) in the protective film forming agent 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 even more preferably 2.5% by mass or more and 20% by mass or less. The content of the light absorber (B) can be set so that the absorbance of the protective film formed by applying the protective film-forming agent is a desired value. The absorbance of the protective film formed by applying the protective film-forming agent is not particularly limited, but for example, the absorbance per 1 μm of film thickness at a wavelength of 355 nm of the protective film formed by applying the protective film-forming agent is preferably 0.3 or higher, more preferably 0.8 or higher, and even more preferably 1.0 or higher.

[0065] <Plasticizer (C)> The plasticizer (C) is at least one selected from monosaccharides and disaccharides. In this specification, a plasticizer is a substance that can impart flexibility or elasticity to a protective film formed using a protective film-forming agent.

[0066] Examples of monosaccharides include aldoses (monosaccharides containing a formyl group), ketoses (monosaccharides containing a carbonyl group), and their derivatives. Examples of derivatives include aldonic acid (a carboxylic acid in which the formyl group at position 1 of the aldose is converted to a carboxyl group), uronic acid (a carboxylic acid in which the hydroxymethyl group at the end of the main chain of the monosaccharide is converted to a carboxyl group), and aldalic acid (a dicarboxylic acid in which both the formyl group at position 1 of the aldose and the hydroxymethyl group at the end of the main chain are replaced with carboxyl groups).

[0067] Specific examples of aldoses 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-glucose, D-idosose, and D-talose. Specific examples of ketoses include dihydroxyacetone, D-erythrulose, D-xylulose, D-ribulose, D-fructose, D-psicose, D-sorbose, D-tagatose, and D-sedoheptulose. Specific examples of derivatives include gluconic acid, glucuronic acid, glucaric acid, and inositol.

[0068] Disaccharides include those composed of the monosaccharides described above. Specific examples of disaccharides include maltose, sucrose, lactose, lactulose, trehalose, and cellobiose.

[0069] Among these, 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.

[0070] The protective film-forming agent contains a water-soluble resin (A), a photoabsorbent (B), a solvent (S), and at least one plasticizer (C) selected from monosaccharides and disaccharides, thereby forming a protective film with excellent laser processability and suppressed crack formation, as shown in the examples described later. In this specification, laser processability refers to the straightness of the processed groove formed by laser irradiation (straightness of the side walls of the protective film constituting the processed groove) and the rectangularity of the cross-section of the processed groove (rectangularity of the cross-section of the protective film constituting the processed groove).

[0071] Thus, the reason why a protective film-forming agent containing a water-soluble resin (A), a photoabsorbent (B), a solvent (S), and at least one plasticizer (C) selected from monosaccharides and disaccharides can form a protective film with excellent laser processability and suppressed crack formation is unknown. The reason for this is speculated to be as follows. First, as mentioned above, monosaccharides and disaccharides are used as plasticizers (C). It is believed that the excellent plasticizing effect of monosaccharides and disaccharides on water-soluble resins (A), such as water-soluble resin (A1), leads to good plasticization of the protective film, thereby suppressing the occurrence of cracks. Furthermore, monosaccharides and disaccharides used as plasticizers (C) are thought to be able to plasticize the protective film without excessively reducing its heat resistance. Therefore, during laser processing, the laser-irradiated areas of the protective film do not become excessively softened or fluidized, and as a result, it is thought that the laser processing creates a processed groove with smooth sides (sidewalls) and a rectangular cross-section.

[0072] On the other hand, if non-monosaccharides or disaccharides (e.g., celluloses) are used instead of monosaccharides or disaccharides, or if non-sugar plasticizers (e.g., trimethylolpropane, neopentyl glycol, or polyethylene glycol) are used instead of monosaccharides or disaccharides, cracks may occur in the protective film that is formed, or the straightness and rectangular cross-section of the processed grooves may deteriorate. It is presumed that when using sugars with large molecular weights or compounds with a small number of hydroxyl groups per molecule as plasticizers, the plasticizing effect is weak, or it is difficult to form a dense network of hydrogen bonds between the plasticizer (C) and the water-soluble resin (A).

[0073] Furthermore, by including at least one plasticizer (C) selected from monosaccharides and disaccharides, along with a soluble resin (A), a light absorber (B), and a solvent (S), the protective film-forming agent can suppress the stickiness (tack) of the formed protective film, making it possible to obtain a protective film that is non-sticky or has minimal stickiness.

[0074] The content of at least one plasticizer (C) selected from monosaccharides and disaccharides is preferably 5 parts by mass or more and 100 parts by mass or less, and more preferably 10 parts by mass or more and 80 parts by mass or less, per 100 parts by mass of water-soluble resin (A). Furthermore, the content of at least one plasticizer (C) selected from monosaccharides and disaccharides is preferably 20 parts by mass or more and 100 parts by mass or less, and more preferably 20 parts by mass or more and 70 parts by mass or less, per 100 parts by mass of the water-soluble resin (A1).

[0075] <Other additives> The protective film-forming agent may contain other additives in addition to the water-soluble resin (A), light-absorbing agent (B), and plasticizer (C), as long as they do not hinder the objectives of the present invention. Examples of other additives include basic compounds, preservatives, and surfactants.

[0076] (Basic compounds) If the protective film-forming agent contains a compound represented by formula (B1), the protective film-forming agent may also contain a basic compound for the purpose of facilitating the dissolution of the compound represented by formula (B1). Both inorganic and organic compounds can be used as the basic compound. Organic compounds are preferred as the basic compound. Specific examples of basic compounds include basic inorganic compounds such as sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium silicate, sodium metasilicate, and ammonia, as well as basic 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.

[0077] The amount of basic compound used is not particularly limited as long as it does not hinder the objective of the present invention. Preferably, the amount of basic compound used is 1 mole or more, and more preferably 1 mole to 20 moles, per mole of the compound represented by formula (B1). The lower limit of the amount of basic compound used may be 1.5 moles or more, 2 moles or more, or 3 moles or more, per mole of the compound represented by formula (B1). The upper limit of the amount of basic compound used may be 15 moles or less, 10 moles or less, or 5 moles or less, per mole of the compound represented by formula (B1).

[0078] (Preservative) As preservatives, benzoic acid, butylparaben, ethylparaben, methylparaben, propylparaben, sodium benzoate, sodium propionate, benzalkonium chloride, benzethonium chloride, benzyl alcohol, cetylpyridinium chloride, chlorobutanol, phenol, phenylethyl alcohol, 2-phenoxyethanol, phenylmercuric nitrate, thimerosal, metacresol, lauryldimethylamine oxide, or combinations thereof may be used.

[0079] It is preferable to use a preservative not only for the preservation of the protective film-forming agent, but also for reducing the burden of treating wastewater after semiconductor wafer cleaning. Large amounts of cleaning water are generally used for cleaning semiconductor wafers. However, in processes using the aforementioned protective film-forming agent, there is concern about the proliferation of bacteria in the wastewater due to the water-soluble resin (A) contained in the protective film-forming agent. Therefore, it is desirable that the wastewater from processes using the aforementioned protective film-forming agent be treated separately from the wastewater from processes that do not use the protective film-forming agent. However, if a preservative is included in the protective film-forming agent, the proliferation of bacteria caused by the water-soluble resin (A) is suppressed, allowing the wastewater from processes using the protective film-forming agent and those not using the protective film-forming agent to be treated similarly. This reduces the burden on the wastewater treatment process.

[0080] (Surfactants) Surfactants are used, for example, to improve the defoaming properties, stability, and applicability of protective film-forming agents during their manufacture. Using surfactants is particularly preferable in terms of defoaming properties during the manufacture of protective film-forming agents.

[0081] Generally, protective films are formed by spin-coating a protective film-forming agent. However, irregularities caused by air bubbles may occur during the formation of the protective film. To suppress the occurrence of such irregularities, it is preferable to use an antifoaming agent such as a surfactant.

[0082] As the surfactant, a water-soluble surfactant is preferably used. Any of the following surfactants can be used: nonionic surfactants, cationic surfactants, anionic surfactants, and amphoteric surfactants. The surfactant may also be silicone-based. Nonionic surfactants are preferred from the viewpoint of cleaning properties.

[0083] <Solvent (S)> The protective film-forming agent contains a solvent (S) to dissolve a water-soluble resin (A), a light absorber (B), and at least one plasticizer (C) selected from monosaccharides and disaccharides. The solvent (S) can be water, an organic solvent, or an aqueous solution of an organic solvent. Water is preferred as the solvent (S) due to its low risk of ignition during use and its cost-effectiveness. Specifically, the solvent (S) is preferably water or an aqueous solution of an organic solvent, with water being more preferred.

[0084] From the viewpoint of flammability, the content of 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.

[0085] The solvent (S) is preferably selected such that the protective film-forming agent does not have a flash point at 1 atmosphere. Specifically, the flash point of the protective film, or whether or not it has a flash point, can be adjusted by adjusting the water content in the protective film-forming agent. Protective film-forming agents that have no flash point are safe and can be stored in non-explosion-proof environments. Specifically, the storage, transportation, and use of protective film-forming agents can be carried out in non-explosion-proof environments. For example, not only can protective film-forming agents be introduced into semiconductor factories, but the formation of protective films can also be carried out in non-explosion-proof environments. Therefore, protective film-forming agents with no flash point are industrially very advantageous because they eliminate the need for explosion-proof environments, such as explosion-proof equipment, which are usually expensive.

[0086] The flash point is determined by measuring it using a TAG sealed filter at 1 atmosphere when the liquid temperature is 80°C or below, and by measuring it using a Cleveland open filter when the liquid temperature is above 80°C. In the specification and claims of this application, if the flash point cannot be measured using the Cleveland open-type flash detector, it is considered to have no flash point.

[0087] Examples of organic solvents that may be included in protective film-forming agents include methyl alcohol, ethyl alcohol, alkylene glycol, alkylene glycol monoalkyl ether, and alkylene glycol monoalkyl ether acetate. Examples of alkylene glycols include ethylene glycol and propylene glycol. Examples of alkylene glycol monoalkyl ethers include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, and propylene glycol monoethyl ether. Examples of alkylene glycol monoalkyl ether acetates include ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, and propylene glycol monoethyl ether acetate. The protective film-forming agent may contain a combination of two or more organic solvents.

[0088] The solid content concentration of the protective film-forming agent is not particularly limited as long as it does not hinder the objectives of the present invention. The solid content concentration is preferably, for example, 5% by mass or more and 60% by mass or less, and more preferably 10% by mass or more and 50% by mass or less.

[0089] ≪Method of manufacturing semiconductor chips≫ A method for manufacturing a semiconductor chip includes a method for manufacturing a semiconductor chip by processing a semiconductor wafer. More specifically, the method for manufacturing semiconductor chips is: Forming a protective film on a semiconductor wafer by applying the aforementioned protective film-forming agent, A laser beam is irradiated onto a predetermined location in one or more layers, including a protective film, on a semiconductor wafer, exposing the surface of the semiconductor wafer and forming processing grooves in a pattern corresponding to the shape of the semiconductor chip. This method includes [something]. Typically, the above-described method for manufacturing a semiconductor chip includes cutting the semiconductor wafer at the locations of the processing grooves (locations corresponding to the street locations). Hereafter, the process of forming a protective film will also be referred to as the "protective film formation process," the process of forming a processing groove will also be referred to as the "processing groove formation process," and the process of cutting the semiconductor wafer at the location of the processing groove will also be referred to as the "cutting process."

[0090] <Protective film formation process> In the protective film formation process, the aforementioned protective film forming agent is applied to the semiconductor wafer to form a protective film.

[0091] The shape of the processed surface of a semiconductor wafer is not particularly limited, as long as it allows for the desired processing of the semiconductor wafer. Typically, the processed surface of a semiconductor wafer has numerous irregularities, with recesses formed in areas corresponding to streets. On the processed surface of a semiconductor wafer, multiple areas corresponding to semiconductor chips are demarcated by streets. In terms of ease of removal of the protective film by washing with water after processing, and sufficient durability of the protective film against plasma irradiation when plasma irradiation is performed in the cutting process described later, the thickness of the protective film is typically preferably 0.1 μm to 100 μm, and more preferably 1 μm to 100 μm. When a laser is irradiated during the groove formation process, the thickness of the protective film is preferably 0.1 μm or more and 30 μm or less.

[0092] The following describes, with reference to the drawings, a preferred embodiment of a semiconductor chip manufacturing method in which a semiconductor wafer comprising multiple semiconductor chips partitioned by grid-like streets is diced using the aforementioned protective film agent.

[0093] Figure 1 shows a perspective view of the semiconductor wafer to be processed. Figure 2 shows an enlarged cross-sectional view of the main part of the semiconductor wafer shown in Figure 1. In the semiconductor wafer 2 shown in Figures 1 and 2, a laminate 21 is provided on the surface 20a of a semiconductor substrate 20 such as silicon, in which an insulating film and a functional film forming a circuit are stacked. Multiple semiconductor chips 22 such as ICs and LSIs are formed in a matrix in the laminate 21. 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.

[0094] Each semiconductor chip 22 is demarcated by a grid-like street 23. In the illustrated embodiment, the insulating film used as the laminate 21 consists of a low-dielectric constant insulating film (Low-k film) made of an SiO2 film, an inorganic film such as SiOF or BSG (SiOB), or an organic film such as a polymer film such as a polyimide or parylene.

[0095] The surface of the laminate 21 described above corresponds to the processed surface 2a. A protective film is formed on the surface 2a using the protective film forming agent described above.

[0096] In the protective film formation process, 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 of applying the protective film-forming agent is not particularly limited as long as it can form a protective film of the desired thickness.

[0097] Next, the liquid protective film-forming agent covering the surface 2a is dried as needed. This forms a protective film 24 on the surface 2a of the semiconductor wafer 2, as shown in Figure 3. Since the protective film 24 is formed by the above-described protective film-forming agent, which includes a soluble resin (A), a light absorber (B), a solvent (S), and at least one plasticizer (C) selected from monosaccharides and disaccharides, crack formation is suppressed, and a protective film 24 with no cracks or very few cracks can be formed. Furthermore, a protective film 24 with suppressed stickiness can also be formed.

[0098] After the protective film 24 is formed on the surface 2a of the semiconductor wafer 2 in this manner, a protective tape 6 mounted on an annular frame 5 is attached to the back surface of the semiconductor wafer 2, as shown in Figure 4.

[0099] <Processing groove forming process> In the groove formation process, laser light is irradiated onto predetermined locations in one or more layers, including the protective film 24, on the semiconductor wafer 2, exposing the surface 20a of the semiconductor substrate 20 and forming grooves in a pattern corresponding to the shape of the semiconductor chip 22.

[0100] Specifically, laser light is irradiated onto the surface 2a (street 23) on the semiconductor wafer 2 through the protective film 24. This laser light irradiation is performed using a laser beam irradiation means 72, as shown in Figure 5. From the standpoint of intensity, ultraviolet lasers with wavelengths between 100 nm and 400 nm are preferred. Additionally, YVO4 lasers with wavelengths of 266 nm, 355 nm, etc., and YAG lasers are also preferred.

[0101] The laser beam irradiation in the groove formation process is performed under the following processing conditions, for example. The diameter of the focused spot is appropriately selected considering the width of the groove 25. Laser light source: YVO4 laser or YAG laser Wavelength: 355nm Repetition frequency: 50kHz to 100kHz Output: 0.3W to 4.0W Machining feed rate: 1 mm / sec to 800 mm / sec

[0102] By performing the groove formation process described above, grooves 25 are formed along the streets 23 in the laminate 21 having streets 23 on the semiconductor wafer 2, as shown in Figure 6. The protective film 24 is formed from the protective film forming agent described above, which includes a water-soluble resin (A), a light absorber (B), a solvent (S), and at least one plasticizer (C) selected from monosaccharides and disaccharides. Therefore, by irradiating the protective film 24 with laser light as described above, grooves (grooves 25) with excellent straightness and rectangular cross-section can be formed in the protective film 24.

[0103] As described above, once the laser beam is irradiated along the predetermined street 23, the semiconductor wafer 2 held on the chuck table 71 is moved by the distance of the street in the direction indicated by arrow Y, and the laser beam is irradiated again.

[0104] After performing laser irradiation and indexing movement along all streets 23 extending in a predetermined direction in this manner, the semiconductor wafer 2 held on the chuck table 71 is rotated 90 degrees, and laser irradiation and indexing movement are performed along each street 23 extending perpendicular to the predetermined direction in the same manner as above. In this way, processing grooves 25 can be formed along all streets 23 formed in the laminate 21 on the semiconductor wafer 2.

[0105] <Cutting process> In the cutting process, the semiconductor wafer 2, which has processing grooves 25 at positions corresponding to the positions of street 23, is cut. Methods of cutting include cutting a semiconductor wafer 2 equipped with a protective film 24, or a semiconductor wafer 2 from which the protective film 24 has been removed, with a blade, or cutting a semiconductor wafer 2 equipped with a protective film 24 and a processing groove 25 by irradiating the semiconductor wafer 2 with a laser or plasma. When cutting is performed with a blade, for example, while pure water is supplied to the cutting area, the semiconductor wafer 2 is cut by the blade along the position of the processing groove 25. When a laser is irradiated, the laser is directed at the processing groove 25 in order to cut the semiconductor wafer 2. The laser irradiated in the cutting process may be the same as or different from the laser light irradiated in the processing groove formation process. When irradiating with plasma, the plasma is irradiated onto a part or the entire surface of the semiconductor wafer 2 that has a protective film, so that the plasma is exposed to the surface of the processed groove 25. The following describes the cutting method using plasma irradiation.

[0106] As shown in Figure 7, plasma is irradiated onto a semiconductor wafer 2 having a protective film 24 and a processing groove 25. As a result, the processing groove 25 on the semiconductor wafer 2 is cut, as shown in Figure 8. Specifically, in a semiconductor wafer 2 covered with a protective film 24, after forming a processing groove 25 as described above, plasma irradiation is performed on the protective film 24 and the surface 20a of the semiconductor substrate 20 exposed from the processing groove 25, thereby cutting the semiconductor wafer 2 according to the shape of the semiconductor chip 22, and dividing the semiconductor wafer 2 into semiconductor chips 22.

[0107] The plasma irradiation conditions are not particularly limited as long as they allow for good cutting of the semiconductor wafer 2 at the location of the processing groove 25. The plasma irradiation conditions are set appropriately within the range of general conditions for plasma etching of the semiconductor substrate 20, taking into consideration the material of the semiconductor wafer 2, the type of plasma, etc. The gas used to generate plasma during plasma irradiation is appropriately selected depending on the material of the semiconductor wafer 2. Typically, SF6 gas is used to generate plasma. Alternatively, the semiconductor wafer 2 may be cut by alternately performing sidewall protection by supplying C4F6 or C4F8 gas, etc., and etching the semiconductor wafer 2 by plasma irradiation, in accordance with the so-called BOSCH process. According to the BOSCH process, etching at a high aspect ratio is possible, and the semiconductor wafer 2 can be easily cut even when the semiconductor wafer 2 is thick.

[0108] Since the protective film 24 is formed by the above-mentioned protective film forming agent, which includes 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 rectangular cross-section. As a result, a semiconductor chip can be obtained that can be cut at a desired position by plasma irradiation or the like, and has excellent straightness. Furthermore, since the protective film 24 is formed by the aforementioned protective film-forming agent, which includes a water-soluble resin (A), a light absorber (B), a solvent (S), and at least one plasticizer (C) selected from monosaccharides and disaccharides, it is crack-free or has few cracks. Therefore, areas other than the cutting position can be adequately protected, and cutting due to plasma irradiation, etc., at undesirable locations (locations other than the processing groove) can be prevented. In addition, contamination of the semiconductor substrate by gases such as fluorine-based gases used in plasma irradiation can be suppressed.

[0109] Next, as shown in Figure 9, 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), so the protective film 24 can be washed away with water (or hot water).

[0110] The above describes a method for manufacturing a semiconductor chip by processing a semiconductor wafer, based on embodiments. The protective film forming agent and semiconductor chip manufacturing method according to the present invention can be applied to various semiconductor chip manufacturing methods, as long as the method includes forming a protective film on the surface of the semiconductor wafer and forming processing grooves at positions corresponding to streets on the surface of the semiconductor wafer with the protective film. [Examples]

[0111] The present invention will be specifically described below with reference to examples and comparative examples. The present invention is not limited in any way to the following examples.

[0112] [Examples 1-24 and Comparative Examples 1-16] In the examples and comparative examples, the water-soluble resin (A) used included A1 to A4 below 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. In the structural formula below, the number in the lower right corner of the parentheses within each constituent unit represents the molar ratio of that constituent unit in the resin.

[0113] A1 is WSR-SP82 manufactured by Konishi Chemical Industry Co., Ltd., and its mass-average molecular weight is 22,000. [ka]

[0114] A2 is the ammonia neutralized product (pH 7) of PS-1H manufactured by Tosoh Finechem Co., Ltd., and has a mass-average molecular weight of 22,000. [ka]

[0115] A3 was used as a solution of XIRAN 3000P manufactured by POLYSCOPE (resin solids concentration: 14% by mass, solvent: propylene glycol monomethyl ether and water, ammonia concentration: 5% by mass). A3 has a mass-average molecular weight of 10,000. [ka]

[0116] A4 is DHDPS resin manufactured by Konishi Chemical Industry Co., Ltd. (a reaction product of DHDPS (dihydroxydiphenylsulfone) and formaldehyde, with increased water solubility using phenolate ions), and has a mass-average molecular weight of 1000. [ka]

[0117] A5 is HPC-SSL (hydroxypropyl cellulose) manufactured by Nippon Soda Co., Ltd., and its mass-average molecular weight is 25,000.

[0118] A6 is manufactured by Nichigo G Polymer, a company of Mitsubishi Chemical Corporation. TM It is AZF8035W (butenediol vinyl alcohol copolymer) and has an estimated degree of polymerization of 300.

[0119] In the examples and comparative examples, compound B1, represented by the following formula, was used as the light absorber (B). [ka]

[0120] In the examples and comparative examples, compounds C1 to C10, represented by the following formulas, were used as plasticizers (C). The structures of C1 to C10 are shown below. C1:D(+)-glucose C2:D(+)-Galactose C3:D(+)-Xylose C4:D(-)-fructose C5:D(-)-Ribose C6: myo-inositol C7:D(+)-Maltose C8: Trimethylolpropane C9: Neopentyl glycol C10: Polyethylene glycol [ka] [ka]

[0121] In the examples and comparative examples, monoethanolamine was used as the basic compound.

[0122] The water-soluble resin (A), light-absorbing agent (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 and stirred for 3 hours to obtain the protective film-forming agents for each example and comparative example. The mass ratio of the solvent in the obtained protective film-forming agent was 85% by mass of water and 15% by mass of propylene glycol monomethyl ether, and the solid content concentration was as listed in Tables 1 to 6. The mixture was then stirred for 3 hours. The parts by mass of the water-soluble resin (A), light-absorbing agent (B), plasticizer (C), and monoethanolamine in the obtained protective film-forming agent are as listed in Tables 1 to 6.

[0123] [Evaluation of the stickiness (tackiness) of the protective film] The obtained protective film-forming agent was applied to a silicon substrate by spin coating to a thickness of 5 μm to form a coated film. Next, the coated film was allowed to air dry at room temperature for approximately 15 minutes. After drying, the surface of the coated film was touched with a finger to evaluate whether or not it was sticky. The results are shown in Tables 1-6.

[0124] [Evaluation of crack formation (film-forming ability) of protective films] The coating film was formed in the same manner as described above for [evaluation of the tackiness of the protective film]. Next, the coated film was dried under reduced pressure to a scanning electron microscope (SEM) measurement environment (6.0 Pa). The coated film after reduced-pressure drying was observed with a 10x optical microscope, and crack formation (film formation ability) was evaluated by marking × if cracks were present and ○ if no cracks occurred and a good coated film was formed. The results are shown in Tables 1 to 6.

[0125] [Evaluation of laser machinability of machined grooves (straightness and rectangular cross-section)] The obtained protective film-forming agent was applied to a silicon substrate by spin coating to a thickness of 5 μm to form a coated film. After the coating film was air-dried at room temperature for approximately 15 minutes, a laser was linearly irradiated onto the protective film side of a silicon substrate equipped with a protective film (the dried coating film) under the following conditions. The surface and cross-sectional shape of the laser-irradiated area of ​​the protective film were observed using a scanning electron microscope (SEM), and the linearity and rectangularity of the processed groove were evaluated according to the evaluation criteria described later. The SEM magnification was 100x for linearity and 500x for rectangularity. The results are shown in Tables 1 to 6. Note that if cracks occurred, the laser processability was not evaluated.

[0126] <Laser irradiation conditions> Wavelength: 355nm Frequency: 100kHz Output: 0.1W Defocus: -0.1mm Feed speed: 100 mm / s Pass:2

[0127] <Straight-line movement> The following criteria were used for evaluation. ◎: The cross-section of the protective film (sidewall of the processed groove) is flat, and a straight groove (trench) without any wobbling is formed. ○: The cross-section of the protective film was relatively flat, and although there was some looseness, relatively straight grooves (trenches) were formed. △: The cross-section of the protective film is not flat, and large, uneven grooves (trenches) are formed. ×: Processing defect (The pattern softened due to the heat of the laser, making it impossible to maintain its shape and form the processing groove.)

[0128] <Cross-sectional rectangularity> In the cross-section, as shown in Figure 10, the angle θ between the surface 81 of the silicon substrate 80 and the side wall 91 of the protective film 90 was determined and evaluated according to the following criteria. ◎: θ is between 45° and 90°. ○: θ is greater than 30° and less than 45°. △: θ is 30° or less. ×: Processing defect (The pattern softened due to the heat of the laser, making it impossible to maintain its shape and form the processing groove.)

[0129] [Table 1]

[0130] [Table 2]

[0131] [Table 3]

[0132] [Table 4]

[0133] [Table 5]

[0134] [Table 6]

[0135] As shown in Tables 1-6, by using the protective film-forming agents of Examples 1-21, which comprise a water-soluble resin (A), a photoabsorbent (B), at least one plasticizer (C) selected from monosaccharides and disaccharides, and a solvent (S), it is possible to form a protective film with excellent laser processability and suppressed crack formation. Furthermore, it can be seen that the protective films formed using the protective film-forming agents of Examples 1-21 also exhibit suppressed stickiness. [Explanation of Symbols]

[0136] 2: Semiconductor wafers 20: Circuit board 21: Laminate 22: Semiconductor chips 23: Street 24:Protective film 25: Laser-cut grooves 5: Circular frame 6: Protective tape 7: Laser processing equipment 71: Chuck table for laser processing equipment 72: Laser beam irradiation means

Claims

1. A protective film forming agent used in the dicing of semiconductor wafers to form a protective film on the surface of a semiconductor wafer, The material comprises a water-soluble resin (A), a light-absorbing agent (B), at least one plasticizer (C) selected from monosaccharides and disaccharides, and a solvent (S). The monosaccharide is at least one selected from the group consisting of aldoses and ketoses. A protective film-forming agent wherein the disaccharide is at least one selected from the disaccharides comprising the monosaccharides.

2. The protective film-forming agent according to claim 1, wherein the water-soluble resin (A) comprises 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 per 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) comprises a resin having phenolic hydroxyl groups.

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

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

7. A method for manufacturing semiconductor chips, which involves processing semiconductor wafers, A protective film is formed on the semiconductor wafer by applying the protective film forming agent according to any one of claims 1 to 6, Laser light is irradiated onto predetermined positions of one or more layers, including the protective film, on the semiconductor wafer, exposing the surface of the semiconductor wafer and forming processing grooves in a pattern corresponding to the shape of the semiconductor chip. A method for manufacturing semiconductor chips, including

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

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