Protective film forming agent and method for manufacturing semiconductor chips

Abstract

Provided are: a protective film formation agent that, in dicing of a semiconductor wafer, is used in order to form a protective film on the surface of the semiconductor wafer, the protective film formation agent being capable of forming a protective film that has exceptional laser workability, and having exceptional solubility of a light-absorbing agent; and a method for manufacturing a semiconductor chip using the protective film formation agent.　The protective film formation agent contains a water-soluble resin (A), a light-absorbing agent (B), a basic compound (C), and a solvent (S). The basic compound (C) is preferably an alkylamine, an alkanolamine, an imidazole compound, ammonia, or an alkali metal hydroxide. The light-absorbing agent (B) content of the protective film formation agent is preferably 0.1-10 mass% (inclusive).

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 technology]

[0002] Wafers formed in the semiconductor device manufacturing process are made by dividing a laminate of insulating and functional films on the surface of a semiconductor substrate such as silicon by grid-like intended division lines called streets, and each area divided by the streets becomes a semiconductor chip such as an IC or LSI.

[0003] By cutting the wafer along these streets, multiple semiconductor chips are obtained. In the case of an optical device wafer, a laminate in which gallium nitride compound semiconductors and the like are stacked is divided into multiple regions by the streets. By cutting along these streets, 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, cutting along the streets of such wafers was done with a cutting device called a dicer. However, because the wafers, which have a laminated structure, are made of a highly brittle material, this method had problems such as scratches and chips being generated when the wafer was cut and divided into semiconductor chips with a cutting blade, and the insulating film formed on the surface of the chips, which is necessary for the circuit elements, peeling off.

[0005] In order to eliminate such problems, a method has been proposed in which a mask containing a layer of a water-soluble material is formed on the surface of a semiconductor substrate, then a laser is irradiated onto the mask to decompose and remove part of the mask to expose the surface of the semiconductor substrate at that 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 Summary of the Invention [Problem to be solved by the invention]

[0007] When forming a protective film as a mask in the method described in Patent Document 1, a light absorbing agent such as a water-soluble ultraviolet absorber is often used together with a water-soluble resin. The protective film as a mask is required to be decomposable and removable by a laser, that is, to be laser processable. The use of a light absorbing agent can improve the laser processability. Furthermore, in recent years, the thickness of protective films has tended to become thicker than before, and therefore, in order to improve laser processability, it has become necessary in many cases to increase the amount of light absorbing agent added to the protective film forming agent. When a large amount of light absorbing agent is added to the protective film forming agent, there is a problem that the absorbent becomes difficult to dissolve in the solvent.

[0008] The present invention has been made in consideration of the above problems, and aims to provide a protective film forming agent that is used to form a protective film on the surface of a semiconductor wafer during dicing of the semiconductor wafer, which is capable of forming a protective film that has excellent laser processability and excellent solubility of a light absorbent, and a method for manufacturing semiconductor chips that uses the protective film forming agent. [Means for solving the problem]

[0009] The present inventors have found that the above problems can be solved by adding a basic compound (C) to a protective film forming agent containing a water-soluble resin (A), a light-absorbing agent (B), and a solvent (S), and have completed the present invention. More specifically, the present invention provides the following.

[0010] A first aspect of the present invention is a protective film forming agent used for forming a protective film on a surface of a semiconductor wafer in dicing the semiconductor wafer, comprising: The protective film-forming agent contains a water-soluble resin (A), a light-absorbing agent (B), a basic compound (C), and a solvent (S).

[0011] A second aspect of the present invention is a method for manufacturing a semiconductor chip, comprising processing a semiconductor wafer, the method comprising: Applying the protective film forming agent according to the first embodiment onto a semiconductor wafer to form a protective film; Irradiating a laser beam to a predetermined position of one or more layers including a protective film on a semiconductor wafer, thereby exposing a surface of the semiconductor wafer and forming a processed groove having a pattern corresponding to the shape of a semiconductor chip; The present invention relates to a method for manufacturing a semiconductor chip, comprising the steps of: Effect of the Invention

[0012] According to the present invention, in a semiconductor chip manufacturing method for manufacturing semiconductor chips from a semiconductor wafer, it is possible to provide a protective film forming agent that is used to form a protective film on the surface of a semiconductor wafer, which can form a protective film that is excellent in laser processability and has excellent solubility of a light absorbent, and a semiconductor chip manufacturing method that uses the protective film forming agent. [Brief description of the drawings]

[0013] [Figure 1] 1 is a perspective view showing a semiconductor wafer processed by a wafer processing method using a protective film forming agent of the present invention. [Diagram 2] 2 is an enlarged cross-sectional view of the semiconductor wafer shown in FIG. 1; [Diagram 3] FIG. 2 is an enlarged cross-sectional view of a main portion of a semiconductor wafer on which a protective film is formed. [Figure 4] 1 is a perspective view showing a state in which a semiconductor wafer having a protective film formed thereon is supported by an annular frame via a protective tape; [Diagram 5] FIG. 2 is a perspective view of a main part of a laser processing device that performs a laser beam irradiation step. [Figure 6]1 is an enlarged cross-sectional view of a semiconductor wafer having a protective film and a processed groove formed by laser light irradiation. [Figure 7] FIG. 7 is an explanatory diagram showing plasma irradiation to the semiconductor wafer shown in FIG. 6. [Figure 8] FIG. 2 is an enlarged cross-sectional view showing a state in which a semiconductor wafer is divided into semiconductor chips by plasma irradiation. [Figure 9] FIG. 4 is an enlarged cross-sectional view showing a state in which a protective film on a semiconductor chip has been removed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] <Protective film forming agent> 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 includes a water-soluble resin (A), a light absorbing agent (B), a basic compound (C), and a solvent (S). Hereinafter, the protective film forming agent is also referred to as a "protective film forming agent."

[0015] Specifically, the protective film forming agent includes irradiating a laser beam onto a protective film formed on a semiconductor wafer, thereby exposing the surface of the semiconductor wafer and forming a processing groove having a pattern corresponding to the shape of a semiconductor chip; Irradiating a laser or plasma onto a semiconductor wafer having the protective film and the groove, to process the position of the groove in the semiconductor wafer; The present invention is preferably used for forming a protective film in a method for manufacturing a semiconductor chip including the steps of:

[0016] From the viewpoints of ease of removal of the protective film by washing with water after processing of the semiconductor wafer and sufficient durability of the protective film against plasma irradiation when plasma irradiation is performed in the manufacturing method of semiconductor chips described later, the thickness of the protective film is typically preferably 1 μm or more and 100 μm or less, more preferably 10 μm or more and 100 μm or less, and even more preferably 30 μm or more and 100 μm or less. When irradiating with a laser, the thickness of the protective film is preferably 0.1 μm or more and 10 μm or less.

[0017] The essential and optional components contained in the protective film-forming agent will be described below.

[0018] <Water-soluble resin (A)> The water-soluble resin (A) is a base material for a protective film formed using a protective film forming agent. The type of water-soluble resin is not particularly limited as long as it can be dissolved in a solvent such as water, coated, and dried to form a film. Water solubility means that 0.5 g or more of the solute (water-soluble resin) dissolves in 100 g of water at 25°C.

[0019] The water-soluble resin (A) is preferably a resin that exhibits a weight loss rate of 80% by weight or more when heated to 500° C. in thermogravimetry. The weight loss rate when heated to 500° C. is more preferably 90% by weight or more, and even more preferably 95% by weight or more. When using a protective film forming agent containing a water-soluble resin (A) whose weight loss rate when heated to 500°C is within the above range, the decomposition of the water-soluble resin (A) by the energy of the laser light proceeds well in the protective film, making it easy to form a well-open processed groove in the protective film by irradiation with laser light.

[0020] The weight loss rate of the water-soluble resin (A) when heated to 350° C. in thermogravimetry is preferably 10% by weight or more, and more preferably 15% by weight or more. When such a water-soluble resin (A) is used, the water-soluble resin (A) is easily decomposed with a minimum amount of energy provided by the laser light, and a well-open processed groove is easily formed in the protective film even when a low-power laser is irradiated.

[0021] The thermogravimetric measurement for determining the weight loss rate can be carried out according to a general thermogravimetric measurement method.

[0022] There is no particular limitation on the method for adjusting the weight loss rate of the water-soluble resin (A). In general, for the same type of resin, the smaller the average molecular weight, the higher the weight loss rate of the water-soluble resin (A).

[0023] From the viewpoint of achieving both decomposability upon irradiation with laser light and film-formability, the weight average molecular weight of the water-soluble resin (A) is preferably 15,000 or more and 300,000 or less, and more preferably 20,000 or more and 200,000 or less.

[0024] Specific examples of the water-soluble resin (A) 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 a monomer having a vinyl group and is a water-soluble resin. Examples of the vinyl resin include polyvinyl alcohol, polyvinyl acetal (including vinyl acetate copolymer), polyvinylpyrrolidone, polyacrylamide, poly(N-alkylacrylamide), polyallylamine, poly(N-alkylallylamine), partially amidated polyallylamine, poly(diallylamine), allylamine-diallylamine copolymer, polyacrylic acid, polyvinyl alcohol-polyacrylic acid block copolymer, and polyvinyl alcohol-polyacrylic acid ester block copolymer. The cellulose-based resin is not particularly limited as long as it is a water-soluble cellulose derivative, and examples of the cellulose-based resin include methyl cellulose, ethyl cellulose, and hydroxypropyl cellulose. It is preferable that the water-soluble resin (A) does not have an acidic group. These may be used alone or in combination of two or more.

[0025] Among the specific examples of the water-soluble resin (A) listed above, vinyl-based resins and cellulose-based resins are preferred, since they are less likely to cause deterioration of the shape of the processed groove due to heat sagging of the protective film, and polyvinylpyrrolidone and hydroxypropyl cellulose are more preferred.

[0026] The protective film formed on the surface of the semiconductor wafer is usually removed from the surface of the semiconductor wafer or the semiconductor chip at an appropriate time after the formation of the groove, depending on the method of processing the semiconductor wafer having the protective film and the groove into a semiconductor chip. Therefore, from the viewpoint of the water washability of the protective film, a water-soluble resin having low affinity with the semiconductor wafer surface is preferred. As the water-soluble resin having low affinity with the semiconductor wafer surface, a resin having only an ether bond, a hydroxyl group, or an amide bond as a polar group, such as polyvinyl alcohol, polyethylene glycol, polyvinylpyrrolidone, and hydroxypropyl cellulose, is preferred.

[0027] In order to prevent poor opening when irradiating the protective film with laser light to form a groove, and deterioration of the shape of the groove due to thermal sagging of the protective film, the ratio of the mass of the water-soluble resin (A) to the total mass of the water-soluble resin (A) and the light-absorbing agent (B) in the protective film forming agent is preferably 60 mass% or more and 99 mass% or less, and more preferably 80 mass% or more and 95 mass% or less.

[0028] <Light absorbing agent (B)> As the light absorbing agent (B), light absorbing agents generally used in protective film forming agents can be used. As the light absorbent (B), it is preferable to use a water-soluble light absorbent such as a water-soluble dye, a water-soluble pigment, or a water-soluble ultraviolet absorbent. The water-soluble light absorbent is advantageous in that it is uniformly present in the protective film. Examples of the water-soluble light absorbent include organic acids having a carboxyl group or a sulfo group; sodium salts, potassium salts, ammonium salts, and quaternary ammonium salts of organic acids; and compounds having a hydroxyl group. When a water-soluble light-absorbing agent is used, the protective film-forming agent has high storage stability, and problems such as phase separation of the protective film-forming agent and sedimentation of the light-absorbing agent during storage of the protective film-forming agent are suppressed, which is advantageous in that the protective film-forming agent can easily maintain good coatability for a long period of time.

[0029] A water-insoluble light absorbing agent such as a pigment may also be used. When a water-insoluble light absorbing agent is used, the use of the protective film forming agent is not fatally hindered, but the laser absorption ability of the protective film may vary, it may be difficult to obtain a protective film forming agent having excellent storage stability and coatability, or it may be difficult to form a protective film of uniform thickness.

[0030] Examples of the light absorbing agent (B) include benzophenone-based compounds, cinnamic acid-based compounds, anthraquinone-based compounds, naphthalene-based compounds, and biphenyl-based compounds. Benzophenone compounds include compounds represented by the following formula (B1): The compound represented by the following formula (B1) is preferred because it allows the protective film to efficiently absorb the energy of the laser light and promotes the thermal decomposition of the protective film. [ka] (In formula (B1), R 1 and R 3 are each independently a hydroxyl group or a carboxyl group, R 2 and R 4 each independently represents a hydroxyl group, a carboxyl group, or -NR 5 R 6 R 5 and R 6 are each 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.

[0031] The compound represented by the above formula (B1) has a high absorption coefficient, and even when added to a protective film forming agent together with an alkali, it shows a high absorption coefficient. Therefore, when a protective film is formed using a protective film forming agent containing the compound represented by the above formula (B1) as an absorbent (B), partial decomposition of the protective film by a laser can be performed well when forming a dicing mask.

[0032] In the above formula (B1), R 2 and R 4 -NR 5 R6 R may be a group represented by the formula: 5 and R 6 are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. 5 and R 6 The alkyl group as R may be linear or branched. 5 and R 6 Specific examples of the alkyl group as include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group.

[0033] -NR 5 R 6 The group represented by the formula (I) is preferably an amino group, a methylamino group, an ethylamino group, a dimethylamino group, or a diethylamino group, and more preferably an amino group, a dimethylamino group, or a diethylamino group.

[0034] Of the compounds represented by formula (B1), the compounds represented by the following formula (B1-1) are preferred because of their 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 formula (B1).

[0035] Due to the high extinction coefficient in the presence of a base, R 1 and R 3 At least one of these is preferably a hydroxyl group.

[0036] The compound represented by formula (B1-1) is preferably a compound represented by any one of the following formulae (B1-1a) to (B1-1e). [ka] (In formulas (B1-1a) to (B1-1e), R 1 ~R 4are the same as those in formula (B1).

[0037] Among the compounds represented by formulae (B1-1a) to (B1-1e), the compound represented by formula (B1-1a) is preferred. In the compounds represented by formulae (B1-1a) to (B1-1e), R 2 But -NR 5 R 6 The aforementioned group represented by R 5 and R 6 are each preferably an alkyl group having 1 to 4 carbon atoms.

[0038] Preferable specific examples of the compound represented by formula (B1) include the following compounds. These compounds are preferred because they are easily available and exhibit a high extinction coefficient even in the presence of a base. [ka]

[0039] When the light absorbent (B) contains a compound represented by formula (B1), the mass ratio of the compound represented by formula (B1) to the mass of the light absorbent (B) is not particularly limited within the range that does not impair the object of the present invention. The mass ratio of the compound represented by formula (B1) to the mass of the light absorbent (B) is preferably 70 mass% or more, more preferably 80 mass% or more, even more preferably 95 mass% or more, and particularly preferably 100 mass%.

[0040] Benzophenone compounds also include 4,4'-dicarboxybenzophenone, benzophenone-4-carboxylic acid, and tetrahydroxybenzophenone, all of which are water-soluble UV absorbers.

[0041] Examples of cinnamic acid compounds include compounds represented by the following formula (B2): The compound represented by the following formula (B2) is preferable because it can efficiently absorb the energy of the 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 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 may be the same or different.)

[0042] In the above formula (B2), R 11 The alkoxy group as R may be linear or branched. 11 The alkoxy group represented by R is preferably an alkoxy group having 1 to 4 carbon atoms. 11 Specific examples of the alkoxy group as the aryl group include a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, and an n-butoxy group.

[0043] In the above formula (B2), R 11 -NR 12 R 13 R may be a group represented by the formula: 12 and R 13 are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. 12 and R 13 The alkyl group as R may be linear or branched. 12 and R 13 Specific examples of the alkyl group as include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group.

[0044] The compound represented by formula (B2) is preferably a compound represented by the following formula (B2-1). [ka] (In formula (B2-1), R11 is R in formula (B2). 11 is equivalent to.)

[0045] 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.

[0046] Specific examples of the anthraquinone compound include 2-carboxyanthraquinone, 2,6-anthraquinone disulfonic acid, and 2,7-anthraquinone disulfonic acid.

[0047] 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.

[0048] A specific example of the biphenyl compound is biphenyl-4-sulfonic acid.

[0049] Examples of the light absorbing agent (B) include water-soluble amines such as curcumin and EAB-F (4,4'-bis(diethylamino)benzophenone).

[0050] Specific examples of water-soluble dyes include 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.

[0051] As water-soluble dyes, for example, food additive dyes 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 Vermilion No. 1, Food Vermilion No. 4, Food Vermilion 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 suitable because of their low environmental impact.

[0052] The content of the light absorbing agent (B) in the protective film forming agent is not particularly limited as long as it does not impair the object of the present invention. The content of the light absorbing agent (B) in the protective film forming agent is preferably 0.1 mass% or more and 10 mass% or less. The protective film forming agent has excellent solubility of the light absorbing agent (B), so the content of the light absorbing agent (B) can be increased. In order to prevent poor opening when irradiating the protective film with laser light to form a processed groove, and deterioration of the shape of the processed groove due to heat sagging of the protective film, the ratio of the mass of the light absorbent (B) to the total mass of the water-soluble resin (A) and the mass of the light absorbent (B) in the protective film forming agent is preferably 1 mass% or more and 50 mass% or less, more preferably 5 mass% or more and 40 mass% or less, and even more preferably 10 mass% or more and 40 mass% or less. The content of the light absorbing agent (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 more, more preferably 0.8 or more, and even more preferably 1.0 or more.

[0053] <Basic Compound (C)> The protective film forming agent contains a basic compound (C) as an essential component. By containing the basic compound (C), a protective film having excellent laser processability can be formed, and the protective film forming agent can have excellent solubility for the light absorbent (B). Since the protective film forming agent has excellent solubility for the light absorbent (B), the content of the light absorbent (B) in the protective film forming agent can be increased. In addition, since the formed protective film has excellent laser processability, desired grooves can be easily formed in the protective film.

[0054] As the basic compound (C), both inorganic and organic compounds can be used, and examples thereof include alkylamines, alkanolamines, imidazole compounds, ammonia and hydroxides of alkali metals. Specific examples of the basic compound (C) include sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium silicate, sodium metasilicate, ammonia; ethylamine, n-propylamine, monoethanolamine, diethylamine, di-n-propylamine, diethanolamine, triethylamine, methyldiethylamine, dimethylethanolamine, triethanolamine, tetramethylammonium hydroxide, tetraethylammonium hydroxide, imidazole, 2-methylimidazole, 1,2-methylimidazole, N-methylimidazole, 4-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, pyrrole, piperidine, 1,8-diazabicyclo[5,4,0]-7-undecene, and 1,5-diazabicyclo[4,3,0]-5-nonane. In this specification, the basic compound (C) is defined as a component that does not fall under the category of the solvent (S).

[0055] The amount of the basic compound (C) used is not particularly limited as long as it does not impair the object of the present invention. The amount of the basic compound (C) used is preferably 1 mole or more, more preferably 1 mole or more and 20 moles or less, per mole of the light absorbent (B). The lower limit of the amount of the basic compound (C) used may be 1.5 moles or more, 2 moles or more, or 3 moles or more, per mole of the light absorbent (B). The upper limit of the amount of the basic compound (C) used may be 15 moles or less, 10 moles or less, or 5 moles or less, per mole of the light absorbent (B).

[0056] <Other additives> The protective film forming agent may contain other additives in addition to the water-soluble resin (A), the light-absorbing agent (B) and the basic compound (C) as long as the object of the present invention is not hindered. Examples of the other additives that can be used include preservatives and surfactants.

[0057] Preservatives that can be used include benzoic acid, butylparaben, ethylparaben, methylparaben, propylparaben, benzalkonium chloride, benzethonium chloride, benzyl alcohol, cetylpyridinium chloride, chlorobutanol, phenol, phenylethyl alcohol, 2-phenoxyethanol, phenylmercuric nitrate, thimerosal, metacresol, lauryldimethylamine oxide, or combinations thereof.

[0058] It is preferable to use a preservative not only from the viewpoint of preserving the protective film forming agent but also from the viewpoint of reducing the load of treating the waste liquid after washing the semiconductor wafer. A large amount of washing water is generally used for washing the semiconductor wafer. However, in the process using the above-mentioned protective film forming agent, there is a concern about the proliferation of various bacteria in the waste liquid caused by the water-soluble resin (A) contained in the protective film forming agent. Therefore, it is desirable that the waste liquid derived from the process using the above-mentioned protective film forming agent is treated separately from the waste liquid derived from the process not using the protective film forming agent. However, when the protective film forming agent contains a preservative, the proliferation of various bacteria caused by the water-soluble resin (A) is suppressed, so that the waste liquid derived from the process using the protective film forming agent and the waste liquid derived from the process not using the protective film forming agent can be treated in the same way. Therefore, the load of the waste water treatment process can be reduced.

[0059] The surfactant is used, for example, to improve the defoaming property during production of the protective film forming agent, the stability of the protective film forming agent, the coatability of the protective film forming agent, etc. In particular, it is preferable to use a surfactant in terms of the defoaming property during production of the protective film forming agent.

[0060] Generally, a protective film is formed by spin-coating a protective film forming agent. However, when forming the protective film, unevenness may occur due to air bubbles. In order to suppress the occurrence of such unevenness, it is preferable to use an antifoaming agent such as a surfactant.

[0061] As the surfactant, a water-soluble surfactant can be preferably used. As the surfactant, any of a nonionic surfactant, a cationic surfactant, an anionic surfactant, and an amphoteric surfactant can be used. The surfactant may be a silicone surfactant. From the viewpoint of cleaning properties, a nonionic surfactant is preferred.

[0062] <Solvent (S)> The protective film forming agent contains a solvent (S) for dissolving the water-soluble resin (A), the light absorbing agent (B) and the basic compound (C). As the solvent (S), any of water, an organic solvent and an aqueous solution of an organic solvent can be used. As the solvent (S), water and an aqueous solution of an organic solvent are preferred, and water is more preferred, in terms of low risk of ignition during use and cost.

[0063] From the viewpoint of flammability, the content of the organic solvent in the solvent (S) is preferably 20 mass % or less, more preferably 15 mass % or less, even more preferably 10 mass % or less, even more preferably 5 mass % or less, and particularly preferably 3 mass % or less.

[0064] The solvent (S) is preferably selected so that the protective film-forming agent does not have a flash point at 1 atmosphere. Specifically, the flash point of the protective film or the presence or absence of a flash point is adjusted by adjusting the water content in the protective film-forming agent. A protective film forming agent having no flash point is safe and can be placed in, for example, a non-explosion-proof environment. Specifically, the protective film forming agent can be stored, transported, used, and otherwise handled in a non-explosion-proof environment. For example, not only can the protective film forming agent be introduced into a semiconductor factory, but also the formation of a protective film can be performed in a non-explosion-proof environment. Therefore, a protective film forming agent having no flash point is extremely advantageous industrially in that an explosion-proof environment such as a normally expensive explosion-proof facility is not required.

[0065] The flash point is measured at 1 atmospheric pressure using a tag closed-type flash point measurement system when the liquid temperature is 80°C or lower, and using a Cleveland open-type flash point measurement system when the liquid temperature is over 80°C. In this specification, when the flash point cannot be measured even when measured by the Cleveland open cup test, it is considered that there is no flash point.

[0066] Examples of organic solvents that may be contained in the protective film forming agent include methyl alcohol, ethyl alcohol, alkylene glycol, alkylene glycol monoalkyl ether, and alkylene glycol monoalkyl ether acetate. 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. The protective film forming agent may contain two or more organic solvents in combination.

[0067] The solid content concentration of the protective film forming agent is not particularly limited as long as it does not impair the object of the present invention. The solid content concentration is, for example, preferably 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.

[0068] <Method of manufacturing semiconductor chips> A method for manufacturing semiconductor chips is a method that includes processing a semiconductor wafer to manufacture semiconductor chips. More specifically, the method for manufacturing a semiconductor chip includes: Applying the protective film forming agent onto a semiconductor wafer to form a protective film; Irradiating a laser beam to a predetermined position of one or more layers including a protective film on a semiconductor wafer, thereby exposing a surface of the semiconductor wafer and forming a processed groove having a pattern corresponding to the shape of a semiconductor chip; The method includes: Typically, the above-mentioned method for manufacturing semiconductor chips includes a cutting step for cutting the semiconductor wafer at the locations of the streets. Hereinafter, forming the protective film will also be referred to as a "protective film forming process", forming the processed groove will also be referred to as a "processed groove forming process", and cutting the semiconductor wafer at the street positions will also be referred to as a "cutting process".

[0069] <Protective film formation process> In the protective film forming step, the protective film is formed on the semiconductor wafer by applying the above-mentioned protective film forming agent.

[0070] The shape of the processing surface of the semiconductor wafer is not particularly limited as long as the desired processing can be performed on the semiconductor wafer. Typically, the processing surface of the semiconductor wafer has many projections and recesses. In addition, recesses are formed in the areas corresponding to the streets. On the processing surface of a semiconductor wafer, a plurality of regions corresponding to semiconductor chips are partitioned by streets. From the viewpoints 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 step described below, the thickness of the protective film is typically preferably 1 μm or more and 100 μm or less, more preferably 10 μm or more and 100 μm or less, and even more preferably 30 μm or more and 100 μm or less. When a laser is irradiated in the groove forming step and / or the cutting step, the thickness of the protective film is preferably 0.1 μm or more and 10 μm or less. In the cutting step, when cutting with a blade, the thickness of the protective film is not particularly limited. When cutting with a blade, the thickness of the protective film is preferably, for example, 0.1 μm or more and 100 μm or less, since the protective film can be easily removed by washing with water after processing.

[0071] Below, with reference to the drawings, a method for manufacturing semiconductor chips in which a dicing process is performed using the above-mentioned protective film agent on a semiconductor wafer having a plurality of semiconductor chips partitioned by grid-like streets will be described as a preferred embodiment of the method for manufacturing semiconductor chips.

[0072] Fig. 1 shows a perspective view of a semiconductor wafer to be processed. Fig. 2 shows an enlarged cross-sectional view of a main part of the semiconductor wafer shown in Fig. 1. In the semiconductor wafer 2 shown in Fig. 1 and Fig. 2, a laminate 21 in which functional films forming insulating films and circuits are laminated is provided on a surface 20a of a semiconductor substrate 20 such as silicon. In the laminate 21, a plurality of semiconductor chips 22 such as ICs and LSIs are formed in a matrix. Here, the shape and size of the semiconductor chip 22 are not particularly limited, and can be set appropriately depending on the design of the semiconductor chip 22 .

[0073] Each semiconductor chip 22 is partitioned by streets 23 formed in a lattice pattern. In the illustrated embodiment, the insulating film used as the laminate 21 is made of a low dielectric constant insulator coating (Low-k film) made of an inorganic film such as a SiO2 film, SiOF, BSG (SiOB), or an organic film such as a polyimide-based or parylene-based polymer film.

[0074] The surface of the laminate 21 corresponds to the surface 2a, which is the processed surface. A protective film is formed on the surface 2a using the protective film forming agent described above.

[0075] 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 of applying the protective film forming agent is not particularly limited as long as a protective film having a desired thickness can be formed.

[0076] Next, the liquid protective film-forming agent covering the surface 2a is dried, thereby forming a protective film 24 on the surface 2a of the semiconductor wafer 2 as shown in FIG.

[0077] After the protective film 24 is thus formed on the front surface 2a of the semiconductor wafer 2, a protective tape 6 attached to an annular frame 5 is attached to the back surface of the semiconductor wafer 2, as shown in FIG.

[0078] <Processing groove forming process> In the groove formation process, laser light is irradiated to predetermined positions of one or more layers, including the protective film 24, on the semiconductor wafer 2 to expose the surface 20a of the semiconductor substrate 20 and form grooves in a pattern corresponding to the shape of the semiconductor chip 22.

[0079] Specifically, using a laser processing device 7, a laser beam is irradiated onto the surface 2a (streets 23) of the semiconductor wafer 2 through the protective film 24. This irradiation of the laser beam is performed using a laser beam application means 72 as shown in FIG. From the viewpoint of intensity, the laser is preferably an ultraviolet laser having a wavelength of 100 nm or more and 400 nm or less, and more preferably a YVO4 laser or a YAG laser having a wavelength of 266 nm, 355 nm, etc.

[0080] The laser light irradiation in the groove forming step is performed under the following processing conditions, for example: The diameter of the focused spot is appropriately selected in consideration of 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 Processing feed speed: 1mm / sec to 800mm / sec

[0081] 6, a groove 25 is formed along the street 23 in the stack 21 having the street 23 in the semiconductor wafer 2. When the protective film 24 is formed from the protective film forming agent described above, it has excellent laser processability, that is, excellent decomposition and removal by laser. Therefore, by irradiating the protective film 24 with a laser beam as described above, a groove of a desired shape can be easily formed in the protective film 24.

[0082] After irradiating the laser beam along a predetermined street 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 by the distance of the street, and irradiation of the laser beam is performed again.

[0083] After the irradiation of the laser light and the indexing movement have been performed in this manner for all the streets 23 extending in the predetermined direction, the semiconductor wafer 2 held on the chuck table 71 is rotated 90 degrees, and the irradiation of the laser light and the indexing movement are performed in the same manner as described above along each street 23 extending perpendicular to the predetermined direction. In this manner, the machined grooves 25 can be formed along all the streets 23 formed in the stack 21 on the semiconductor wafer 2.

[0084] <Cutting process> In the cutting step, the semiconductor wafer 2 having the grooves 25 at positions corresponding to the positions of the streets 23 is cut. Preferred methods include a method of cutting the semiconductor wafer 2 by irradiating the semiconductor wafer 2 having the protective film 24 and the grooves 25 with a laser or plasma, and a method of cutting the semiconductor wafer 2 having the protective film 24 or the semiconductor wafer 2 from which the protective film 24 has been peeled off with a blade. When irradiating with a laser, the grooves 25 are irradiated with a laser to cut the semiconductor wafer 2. When irradiating with plasma, the plasma is irradiated to a part or the entire surface of the protective film of the semiconductor wafer 2 so that the surface of the grooves 25 is exposed to the plasma. When cutting with a blade, the semiconductor wafer 2 is cut with the blade along the position of the grooves 25 while pure water is supplied to the cutting portion. A cutting method using plasma irradiation, which is a preferred cutting method, will be described below.

[0085] 7, the semiconductor wafer 2 having the protective film 24 and the groove 25 is irradiated with plasma. By doing so, the semiconductor wafer 2 is cut at the position of the groove 25 as shown in FIG. Specifically, after forming the processing groove 25 in the semiconductor wafer 2 covered with the protective film 24 as described above, the protective film 24 and the surface 20a of the semiconductor substrate 20 exposed from the processing groove 25 are irradiated with plasma, whereby the semiconductor wafer 2 is cut according to the shape of the semiconductor chip 22, and the semiconductor wafer 2 is divided into the semiconductor chips 22.

[0086] The plasma irradiation conditions are not particularly limited as long as they can satisfactorily cut the semiconductor wafer 2 at the position of the processing groove 25. The plasma irradiation conditions are appropriately set within the range of general conditions for plasma etching of a semiconductor substrate, taking into consideration the material of the semiconductor wafer 2, the type of plasma, and the like. The gas used to generate plasma in the 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 supplying C4F6 or C4F8 gas or the like to protect the sidewall and irradiating plasma to etch the semiconductor wafer 2. The BOSCH process allows etching with a high aspect ratio, and makes it easy to cut the semiconductor wafer 2 even if the semiconductor wafer 2 is thick.

[0087] 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 the water-soluble resin (A), and therefore the protective film 24 can be washed away with water (or warm water).

[0088] The method for manufacturing semiconductor chips by processing a semiconductor wafer has been described above based on the embodiments. The protective film forming agent and the method for manufacturing semiconductor chips 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 a semiconductor wafer and forming processing grooves at positions corresponding to streets on the surface of the semiconductor wafer that is provided with the protective film. EXAMPLES

[0089] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples in any way.

[0090] [Examples 1 to 15 and Comparative Examples 1 to 12] In Examples 1 to 15 and Comparative Examples 1 to 12, hydroxypropyl cellulose (A1) and polyvinylpyrrolidone (A2) were used as the water-soluble resin (A). As the light absorbing agent (B), B1 to B4 represented by the following formulae were used. [ka] As the basic compound (C), monoethanolamine (C1), diethanolamine (C2), triethanolamine (C3), imidazole (C4), ammonia (C5), and NaOH (C6) were used. As the solvent (S), water (S1) and propylene glycol monomethyl ether (PGME) (S2) were used.

[0091] (Production of protective film forming agent) The water-soluble resin (A), the light absorbent (B), the basic compound (C), and the solvent (S) were added to a container and stirred for 8 hours to obtain protective film-forming agents for each Example and Comparative Example. The units of the numerical values ​​(amounts) of the compositions in Tables 1 to 3 are % by mass.

[0092] (Evaluation of solubility of light absorbent) The protective film-forming agent thus obtained was visually observed and evaluated according to the evaluation criteria described below. The results are shown in Tables 1 to 3. <Evaluation criteria for solubility of light absorbent> ◯: No residual light absorbing agent was found. ×: some of the light absorbing agent remained undissolved.

[0093] (Measurement of absorbance of protective film (coating film)) The obtained protective film forming agent was used to form a protective film on a glass substrate by spin coating (spin coating conditions: 2000 rpm, 120 seconds). The transmittance of the formed protective film was measured using a spectrophotometer (MCPD-3000 (Otsuka Electronics)), and the absorbance per 1 μm of film thickness at a wavelength of 355 nm was measured from the transmittance measurement results. The measurement results are shown in Tables 1 to 3. Note that the absorbance was not measured for protective film forming agents in which residual absorbent was observed.

[0094] (Evaluation of laser processability) The obtained protective film forming agent was applied onto a silicon substrate by spin coating to a thickness of 2 μm to form a protective film. A laser was irradiated linearly under the following conditions onto the surface of the protective film side of a silicon substrate having a protective film. The protective film was then removed, and the laser irradiated area (processed area) and its vicinity were observed under an optical microscope and evaluated according to the evaluation criteria described below. If the laser processability is poor, it is difficult to decompose and remove the protective film, and the protective film is not decomposed and removed, but peels off from the substrate in film form, and debris from the substrate adheres to the peeled off area. Therefore, the laser processability can be evaluated by observing the processed area and its vicinity after removing the protective film.

[0095] <Laser irradiation conditions> Wavelength: 355nm Frequency: 100kHz Output power: 0.8W Defocus: -0.0mm Feed speed: 100mm / s Pass:1

[0096] <Cross-section shape evaluation criteria> ◯: No debris was observed adhering to the outside of the processed area. ×: Debris adhesion was observed on the outside of the processed portion.

[0097] [Table 1]

[0098] [Table 2]

[0099] [Table 3]

[0100] It can be seen from Tables 1 to 3 that the protective film forming agents of Examples 1 to 14, which contain a water-soluble resin (A), a light absorbing agent (B), a basic compound (C), and a solvent (S), are excellent in solubility of the light absorbing agent. It can also be seen that the protective films formed using the protective film forming agents of Examples 1 to 14 have high absorbance and excellent laser processability. On the other hand, it is clear from Tables 1 to 3 that the protective film forming agents of Comparative Examples 1 to 12, which do not contain a basic compound (C), have poor solubility of the light absorbing agent and poor laser processability of the protective film. [Explanation of symbols]

[0101] 2: Semiconductor wafers 20: Substrate 21: Laminate 22: Semiconductor chips 23: Street 24:Protective film 25: Laser processed groove 26: Cutting groove 3: Spin coater 5: Circular frame 6: Protective tape 7: Laser processing equipment 71: Chuck table of laser processing equipment 72: Laser beam irradiation means

Claims

1. A protective film forming agent used for forming a protective film on a surface of a semiconductor wafer in dicing of the semiconductor wafer, comprising: A water-soluble resin (A), a light-absorbing agent (B), a basic compound (C), and a solvent (S), A protective film forming agent, wherein the water-soluble resin (A) comprises hydroxypropyl cellulose or polyvinylpyrrolidone.

2. The protective film forming agent described in claim 1, wherein the water-soluble resin (A) is hydroxypropyl cellulose or polyvinylpyrrolidone.

3. 3. The protective film-forming agent according to claim 1, wherein the basic compound (C) comprises at least one selected from the group consisting of alkylamines, alkanolamines, imidazole compounds, ammonia, and hydroxides of alkali metals.

4. The protective film forming agent according to claim 1 or 2, wherein the light absorbent (B) comprises at least one selected from the group consisting of benzophenone-based compounds, cinnamic acid-based compounds, anthraquinone-based compounds, naphthalene-based compounds and biphenyl-based compounds.

5. The protective film forming agent according to any one of claims 1 to 4, wherein the content of the light absorbing agent (B) is 0.1 mass % or more and 10 mass % or less.

6. The protective film-forming agent according to any one of claims 1 to 5, wherein the solvent (S) comprises water.

7. The protective film-forming agent according to any one of claims 1 to 6, wherein the content of the organic solvent in the solvent (S) is 20 mass % or less.

8. A method for manufacturing semiconductor chips by processing a semiconductor wafer, comprising the steps of: forming a protective film on the semiconductor wafer by applying the protective film forming agent according to any one of claims 1 to 7; Irradiating a laser beam to a predetermined position of one or more layers including the protective film on the semiconductor wafer, thereby exposing a surface of the semiconductor wafer and forming a processed groove having a pattern corresponding to a shape of a semiconductor chip; A method for manufacturing a semiconductor chip, comprising:

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