JP2011236272A - Protective film composition and cleaning method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a protective film composition which provides a wafer protective film, the wafer protective film having resistance to an alkaline processing treatment agent when a wafer is subjected to processing such as polishing and chamfering using the processing treatment agent upon wafer processing, the wafer protective film further having such excellent detergency that the wafer protective film which has been made needless after the processing is easily cleaned away with an alkali aqueous solution without giving damage to the wafer in a state in which an environmental load is reduced, and to provide a cleaning method which cleans away the wafer protective film which has been made needless.SOLUTION: The protective film composition contains at least a film-forming material (X) with a homopolymer (a) expressed by general formula (1) (wherein, n is an integer) as the main component, is insoluble in an alkali aqueous solution with a hydrogen exponent (pH) of ≤11, and is also soluble in an alkali aqueous solution with a hydrogen exponent (pH) of ≥13.

Description

  The present invention relates to a wafer protective film composition (hereinafter simply referred to as “protective film composition”) for forming a wafer protective film for temporarily protecting a wafer surface other than the processed surface when processing the wafer. ”). More specifically, when the wafer is polished or chamfered using an alkaline processing agent, the resistance to the processing agent and the protective film that has become unnecessary after processing are damaged to the wafer. The present invention relates to a composition for a protective film and a cleaning method that can provide a wafer protective film having excellent detergency that can be easily washed and removed with an alkaline aqueous solution without reducing the environmental burden.

  Conventionally, when polishing or chamfering a thin plate substrate such as a liquid crystal substrate or a semiconductor substrate (hereinafter sometimes simply referred to as a wafer), the wafer surface other than the processed surface is etched with an alkaline processing agent. Alternatively, a wafer protective film is coated to prevent contamination and scratching.

  In the above polishing process, for example, the wafer holding surface, which is the surface opposite to the polishing surface, is held on the wafer holder by suction or the like so that the wafer does not move, and the polishing surface is pressed onto the rotating platen of the polishing machine. The polishing surface is polished while dripping an alkaline abrasive. In the chamfering process, for example, to improve quality, the cut surface of the wafer is smoothed by polishing with a cloth impregnated with an alkaline solution or the like, and scraps adhering to the cut surface are cleaned and removed.

  The protective film for wafers used in the above-mentioned wafer processing is completed when the polishing process or chamfering process is completed and the role of the protective film is completed. It has been removed by immersing it in an oxidizing cleaning agent such as liquid or a cleaning agent such as warm water.

  However, organic solvent-based cleaning agents have problems such as environmental impact and making the wafer surface hydrophobic. Oxidizing cleaning agents can easily erode the wafer and cause damage to the wafer. There were problems such as short. Further, a water cleaning agent such as warm water is preferable without causing environmental load, but the wafer protective film cleaned and removed by these water cleaning agents is inferior in resistance to an abrasive made of an alkaline aqueous solution.

  As a composition for forming the wafer protective film, certain wafer protective film compositions (Patent Documents 1 and 2) are disclosed. The resin composition for a silicon wafer protective film disclosed in Patent Document 1 is prepared by dissolving polyvinyl alcohol having a saponification degree of 90 mol% or more as a film forming material in a solvent, and further improves alkali resistance. In addition, a compound having a double bond such as an acrylic ester, a methacrylic ester, or an epoxy compound is blended.

  In general, since polyvinyl alcohol is a polymer compound obtained by saponifying polyvinyl acetate, it includes those having an acetate group remaining, and those having a saponification degree of less than 90 mol% are inferior in alkali resistance. Therefore, even if the above-mentioned polyvinyl alcohol having a saponification degree of 90 mol% or more is used, it is difficult to completely eliminate contamination with a saponification degree of less than 90 mol%, and complete alkali resistance against an alkaline abrasive is obtained. Absent. Further, when the degree of saponification is increased, it dissolves in hot water of 75 ° C. or higher but becomes insoluble in water, and the setting of conditions such as temperature setting for cleaning and removing the unnecessary wafer protective film after wafer processing becomes complicated.

  In addition, the coating composition for protective film disclosed in Patent Document 2 is a water-soluble resin such as polyvinyl alcohol, polyvinyl pyrrolidone, and a water-soluble cellulose derivative. Does not have sufficient resistance.

  From the above, when processing a wafer such as polishing or chamfering using an alkaline processing agent, the resistance to the processing agent and damage to the wafer after the processing becomes unnecessary. There is a need for a protective film composition that can provide a wafer protective film that can be easily washed and removed without reducing the environmental burden.

JP-A-10-120965 JP-A-9-106981

  Accordingly, the object of the present invention is to provide resistance to a processing agent when the wafer is ground or chamfered using an alkaline processing agent in wafer processing, and the above-mentioned processing becomes unnecessary after processing. Protective film composition that can provide a wafer protective film with excellent cleaning properties that can be easily washed and removed with an alkaline aqueous solution without damaging the protective film to the wafer while reducing the environmental load, and unnecessary wafer protection A cleaning method for cleaning and removing a film is provided.

  As a result of intensive studies to solve the above problems, the inventor of the present invention temporarily protects the wafer surface by a protective film composition containing a film-forming material mainly composed of the following homopolymer (a). When a wafer protective film is formed and the wafer surface other than the one coated with the protective film is subjected to processing such as polishing or chamfering using an alkaline processing agent, the wafer protective film is processed. It has been found that the protective film is excellent in resistance to the agent, and can be easily washed and removed with an alkaline aqueous solution without damaging the wafer after processing without damaging the wafer.

（上記式中のｎは、整数である） The above object is achieved by the present invention described below. That is, the present invention contains a film-forming material (X) containing at least a homopolymer (a) represented by the following general formula (1) as a main component, and is insoluble in an alkaline aqueous solution having a hydrogen index (pH) of 11 or less. And a composition for a protective film, which is soluble in an alkaline aqueous solution having a hydrogen index (pH) of 13 or more.

(N in the above formula is an integer)

  In a preferred embodiment of the present invention, the homopolymer (a) has a weight average molecular weight of 1,500 to 12,000, and the film forming material (X) has a melting point of 100 ° C. to 200 ° C. Furthermore, it contains a silane coupling agent, and the blending ratio of the homopolymer (a) and the silane coupling agent (b) is b / a = 1/100 to 10/100 (mass ratio). Yes, and the solid content concentration of the film-forming material (X) is preferably 10 to 40% by mass.

  In addition, the present invention provides a cleaning method characterized by cleaning and removing a wafer protective film formed by applying the protective film composition to a wafer substrate with an alkaline aqueous solution having a hydrogen index (pH) of 13 or more. I will provide a.

  According to the present invention, the composition for a protective film of the present invention has excellent resistance to an alkaline processing agent such as an abrasive used when processing a wafer, without damaging the wafer after processing, This is effective for obtaining a wafer protective film that can be easily washed and removed with an alkaline aqueous solution in a state where the environmental load is also reduced.

  Next, the present invention will be described in more detail with reference to preferred embodiments for carrying out the present invention. The composition for a protective film of the present invention contains the following homopolymer (a) as a main component as a film forming material, thereby providing excellent resistance to an alkaline processing agent and a protective film that is no longer necessary after processing. A protective film for a wafer that can be easily washed away with an alkaline aqueous solution is obtained.

（上記式中のｎは、整数である） The homopolymer (a) that mainly characterizes the present invention is a homopolymer represented by the following general formula (1). The homopolymer (a), as a constituent of the film forming material (X), has resistance and resistance to an alkaline abrasive used for the wafer protective film obtained when the wafer is polished or chamfered. Abrasion resistance such as frictional properties is improved, and a detergency that can be easily removed by washing with an alkaline aqueous solution having a pH of 13 or higher after processing is provided.

(N in the above formula is an integer)

  The homopolymer (a) has a weight average molecular weight of 1,400 to 25,000, preferably 1,500 to 12,000. Those within the above molecular weight range are effective for imparting the above performance to the obtained wafer protective film. The said homopolymer (a) can be used individually or in mixture of 2 or more types.

  Among the homopolymers (a), those having a weight average molecular weight of 1,600 to 2,400 (a1), those having a weight average molecular weight of 4,000 to 6,000 (a2), and having a weight average molecular weight of 9 , 1,000 to 11,000 (a3) is preferable, and (a2) or (a3) or a mixture of (a2) and (a3) is preferable. In addition, the weight average molecular weight in this invention is a value of polystyrene conversion by a gel permeation chromatography (GPC) method.

  The homopolymer (a) is obtained by polymerizing a vinylphenol monomer by a known method, and (a1), (a2), and (a3) having the weight average molecular weight are mainly used.

  The film-forming material (X) is the above-mentioned homopolymer (a) as a component constituting the obtained wafer protective film, or the homopolymer (a) is used as a film-forming material (to the extent that the object of the present invention is not hindered). X) An amount of 80% by mass or more in the total amount is contained as a main component, and other resins can be used in combination. The homopolymer (a) alone is preferable.

  Examples of the other resins include shellac, vinyl acetate resin, rosin, phenol resin, novolac resin, methacrylic resin, acrylic copolymer, epoxy resin, rosin ester resin, poly p-vinylphenol derivative, and preferably acid. Resins such as rosin ester resins, acrylic copolymers, epoxy resins and the like having a value of less than 20 mg KOH / g can be mentioned. If the amount of the resin is too large, the resistance of the resulting wafer protective film to the polishing agent and the detergency of washing and removing the protective film that has become unnecessary after processing with an alkaline aqueous solution having a pH of 13 or more are reduced. Moreover, when the value of the acid value is too high, the resistance to the alkaline abrasive is lowered. In addition, said acid value is the value measured according to JISK5902.

  The melting point of the film forming material (X) is preferably 100 ° C to 200 ° C. The above melting point range is effective as heat resistance when polishing a wafer. If the melting point is too low, heat resistance when polishing a wafer is poor.

  The film-forming material (X) preferably further contains a silane coupling agent in order to improve the adhesion between the wafer and the resulting wafer protective film.

  Examples of the silane coupling agent include ureido silane coupling agents such as γ-ureidopropyltriethoxysilane, γ-ureidopropyltrimethoxysilane, and γ-ureidopropyldimethoxysilane; γ-glycidoxytrimethylsilane, γ -Epoxy silane coupling agents such as glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; γ-aminopropyltriethoxysilane, γ- (methacryloyloxypropyl) trimethoxysilane, vinyltris ( β-methoxyethoxy) silane, γ-chloropropyltrimethoxysilane and the like. The silane coupling agent can be used alone or in combination of two or more.

  The blending ratio of the homopolymer (a) and the silane coupling agent (b) is preferably b / a = 1/100 to 10/100. Even if the blending ratio of the silane coupling agent exceeds the above upper limit, no further adhesion effect to the wafer of the obtained wafer protective film can be obtained, and conversely, adhesion inhibition occurs. On the other hand, if the blending ratio is less than the above lower limit, the effect of improving adhesion cannot be obtained.

  The solid content concentration of the film-forming material (X) is preferably 10 to 40% by mass in the protective film composition. When the solid content concentration exceeds the upper limit, applicability to the wafer decreases. On the other hand, when the solid content concentration is less than the lower limit, the polishing resistance of the obtained wafer protective film to the alkaline abrasive is lowered.

  The composition for a protective film of the present invention suitably comprises the film-forming material (X), a silane coupling agent, and other additives such as a spreading agent that imparts flexibility to the resulting wafer protective film. It is prepared by dissolving and dispersing in an organic solvent by a known method.

  Examples of the spreading agent include tricresyl phosphate, dibutyl phthalate, dimethyl phthalate, diethyl phthalate, dibutyl maleate, and the like, and mixtures thereof.

  Examples of the organic solvent include ethanol, isopropanol, butanol, octanol, benzyl alcohol, diacetone alcohol, allyl alcohol, tetrahydrofurfuryl alcohol, ethylene glycol, propylene glycol, methyl cellosolve, ethyl cellosolve, methyl cellosolve acetate, acetone. , Methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methyl acetate, ethyl acetate, n-butyl acetate, isoamyl acetate, and the like, and mixtures thereof.

  As an example of using the protective film composition of the present invention, for example, the protective film composition of the present invention is formed with a film thickness of about 2 μm to 3 μm (dried) on one side of a silicon wafer substrate of a semiconductor substrate by a spin coat coater. Thickness) and dried at 80 ° C. to 120 ° C. to form a wafer protective film on the wafer surface. The wafer surface on which the wafer protective film is formed is set on, for example, a wafer holder of a commercially available polishing machine (manufactured by Okamoto Machine Tool Co., Ltd., polishing machine PNX-332B), and the opposite processing wafer surface is set to pH 10. While dripping with an alkaline abrasive made of colloidal silica adjusted to 5, polishing is performed under conditions of a polishing load of 15 kPa, a normal rotation speed of 30 rpm, a polishing time of 4 min, and an abrasive supply speed of 500 ml / min. Further, if necessary, finish polishing is further performed using a polishing agent for finish polishing. After the polishing process is completed, the wafer on which the wafer protective film is formed is taken out from the wafer holder, and the wafer protective film that is no longer needed is cleaned and removed by the following cleaning method.

  Examples of the alkaline abrasive include those prepared by appropriately dissolving and dispersing an alkali compound, a water-soluble polymer compound, and colloidal silica in water. Examples of the alkali compound include basic organic compounds such as ammonia, tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrabutylammonium hydroxide, and basic inorganic compounds such as sodium hydroxide and potassium hydroxide. It is done. Examples of the water-soluble polymer compound include celluloses, polyvinyl alcohol, and polyvinyl pyrrolidone.

  As the cleaning method, after the processing is completed, the wafer protective film formed by applying the protective film composition to the wafer substrate is washed and removed with an alkaline aqueous solution having a hydrogen index (pH) of 13 or more. In the cleaning and removal, the wafer protective film that is no longer needed is immersed in the alkaline aqueous solution, or the alkaline aqueous solution is sprayed on the surface of the wafer protective film and washed away from the wafer surface.

  Examples of the alkaline aqueous solution used for the washing and removal include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide and lithium hydroxide, alkali metal phosphates such as potassium pyrophosphate, sodium pyrophosphate and potassium tripolyphosphate. Salt, alkali metal silicates such as sodium silicate and potassium silicate, inorganic alkali compounds such as alkali metal carbonates such as sodium carbonate and potassium carbonate, alkanolamines, amino alcohols, water-soluble amines, tetramethylammonium hydroxide, etc. And an aqueous alkali solution adjusted to pH 13 or higher, such as ammonia / hydrogen peroxide solution, and the like. The alkaline aqueous solution can contain a surfactant as required.

  Examples of the wafer substrate include a wafer substrate such as silicon, gallium arsenide, gallium phosphide, ceramic, sapphire, and quartz glass, and preferably a silicon wafer substrate.

  Next, the present invention will be described more specifically with reference to examples and comparative examples. In the text, “part” or “%” is based on mass unless otherwise specified. In addition, this invention is not limited to the following Example.

[Examples 1 to 5] (Compositions R1 to R5 for protective film)
The film forming material (X), the silane coupling agent, the spreading agent, and the organic solvent were blended as shown in Table 1 and mixed uniformly to prepare the protective film compositions R1 to R5 of the present invention. The film forming material (X), the silane coupling agent, and the spreading agent are as follows.

・ Film forming material (X)
Homopolymer of the general formula (1) (a)
Homopolymer (a1): Poly p-vinylphenol having a weight average molecular weight of 1,600 to 2,400 Homopolymer (a2): Poly p-vinylphenol having a weight average molecular weight of 4,000 to 6,000 Homopolymer (a3): Poly p-vinylphenol rosin ester resin having a weight average molecular weight of 9,000 to 11,000: rosin ester resin having an acid value of 10 mgKOH / g (manufactured by Arakawa Chemical Industries, super ester A-115)
・ Silane coupling agent γ- (methacryloyloxypropyl) trimethoxysilane ・ Spreading agent Dibutyl maleate

[Comparative Examples 1 and 2] (Compositions for protective film S1 and S2)
The film-forming material (X) in the examples was replaced with polyvinyl alcohol and blended with water as shown in Table 1 to prepare protective film compositions S1 to S2. The polyvinyl alcohol is as follows.
Polyvinyl alcohol a1: Polyvinyl alcohol with a saponification degree of 86% a2: Polyvinyl alcohol with a saponification degree of 99%

表中の数値は配合部数を表す。

The numerical values in the table represent the number of blending parts.

  Each of the protective film compositions obtained above was applied to a 6-inch silicon wafer surface to a thickness of 3 μm (dry thickness) using a spin coater and heated on a hot plate heated to 100 ° C. A wafer protective film was formed by drying for 30 seconds. The above-mentioned wafer protective film was measured and evaluated by the following methods for polishing resistance and alkali cleaning properties. The evaluation results are shown in Table 2.

[Abrasive resistance]
The sample on which the wafer protective film was formed was immersed in an aqueous NaOH solution (water temperature 40 ° C.) adjusted to a hydrogen index (pH) 11 for 30 minutes, and the state of the wafer protective film surface was evaluated according to the following criteria.
○: No swelling or erosion of the wafer protective film is observed.
Δ: Swelling or erosion of the wafer protective film is slightly observed.
X: Swelling or erosion of the wafer protective film is considerably observed.
Said evaluation shows the tolerance with respect to an alkaline wafer abrasive | polishing agent.

[Alkali detergency]
(Cleanability)
The sample on which the wafer protective film was formed was immersed in an aqueous NaOH solution (cleaning agent) adjusted to a hydrogen index (pH) of 13 or more, and the cleaning removal property of the wafer protective film with respect to the cleaning agent was evaluated according to the following criteria.
○: The wafer protective film is completely removed by washing.
Δ: Residue is observed in the wafer protective film and is not completely removed by washing.
X: The wafer protective film is not removed by washing.

(Wafer erosion resistance)
The condition of erosion by the cleaning agent on the wafer surface on which the wafer protective film of the sample used for the cleaning removal property was not formed was evaluated according to the following criteria.
○: The wafer surface is not eroded by the cleaning agent.
Δ: The wafer surface is slightly eroded by the cleaning agent.
X: The wafer surface is eroded by the cleaning agent.

  From the above evaluation results, the composition for a protective film of the present invention is such that the obtained wafer protective film has excellent abrasive resistance in polishing processing and damages the protective film that is no longer necessary after processing to the wafer. It was demonstrated that it can be easily washed away with an alkaline aqueous solution without any problems.

  The composition for a protective film of the present invention provides a wafer protective film having excellent polishing agent resistance and alkali cleaning properties, so that a wafer such as silicon used for a semiconductor substrate, a liquid crystal substrate or the like is polished or chamfered. At this time, it can be effectively used to obtain a wafer protective film that temporarily protects the wafer surface other than the processed surface. In addition, a high-quality processed wafer can be obtained because a cleaning method is provided that can easily clean and remove the protective film that has become unnecessary after processing without damaging the wafer.

Claims (7)

It contains a film-forming material (X) containing at least a homopolymer (a) represented by the following general formula (1) as a main component, is insoluble in an alkaline aqueous solution having a hydrogen index (pH) of 11 or less, and hydrogen A composition for a protective film, which is soluble in an aqueous alkali solution having an index (pH) of 13 or more.

(N in the above formula is an integer)   The composition for a protective film according to claim 1, wherein the homopolymer (a) has a weight average molecular weight of 1,500 to 12,000.   The composition for a protective film according to claim 1 or 2, wherein the film forming material (X) has a melting point of 100C to 200C.   Furthermore, the composition for protective films of any one of Claims 1-3 containing a silane coupling agent.   The blending ratio of the homopolymer (a) and the silane coupling agent (b) is b / a = 1/100 to 10/100 (mass ratio). 5. Composition for protective film.   The composition for protective films according to claim 1, wherein the solid content concentration of the film-forming material (X) is 10 to 40% by mass.   A wafer protective film formed by applying the protective film composition according to any one of claims 1 to 6 to a wafer substrate is washed and removed with an alkaline aqueous solution having a hydrogen index (pH) of 13 or more. A characteristic cleaning method.