阅读说明：本技术 耐受过氧化氢水溶液的保护膜形成用组合物 (Composition for forming protective film resistant to aqueous hydrogen peroxide solution ) 是由 德永光 桥本雄人 桥本圭祐 坂本力丸 于 2018-04-10 设计创作，主要内容包括：本发明的课题是提供耐受过氧化氢水溶液的保护膜形成用组合物。解决手段是一种耐受过氧化氢水溶液的保护膜形成用组合物,其包含：树脂；下述式(1a)、式(1b)或式(1c)所示的化合物；交联剂；交联催化剂；以及溶剂,其中,相对于上述树脂,以80质量％为上限含有上述式(1a)、式(1b)或式(1c)所示的化合物,并含有5质量％～40质量％的上述交联剂。(式中,X表示羰基或亚甲基,l和m各自独立地表示满足3≤l+m≤10的关系式的0～5的整数,n表示2～5的整数,u和v各自独立地表示满足3≤u+v≤8的关系式的0～4的整数,R<Sup>1</Sup>、R<Sup>2</Sup>、R<Sup>3</Sup>和R<Sup>4</Sup>各自独立地表示氢原子、羟基、可以具有至少1个羟基作为取代基且可以在主链具有至少1个双键的碳原子数1～10的烃基、或可以具有至少1个羟基作为取代基的碳原子数6～20的芳基,在R<Sup>1</Sup>、R<Sup>2</Sup>、R<Sup>3</Sup>和R<Sup>4</Sup>表示该碳原子数1～10的烃基的情况下,R<Sup>1</Sup>和R<Sup>2</Sup>、R<Sup>3</Sup>和R<Sup>4</Sup>可以与它们所结合的环碳原子一起形成苯环,该苯环可以具有至少1个羟基作为取代基,j和k各自独立地表示0或1。)<Image he="536" wi="700" file="DDA0002253128340000011.GIF" imgContent="drawing" imgFormat="GIF" orientation="portrait" inline="no"></Image>(The invention provides a composition for forming a protective film which is resistant to an aqueous hydrogen peroxide solution. The solution is a composition for forming a protective film resistant to an aqueous hydrogen peroxide solution, comprising: a resin; represented by the following formula (1a), formula (1b) or formula (1c)A compound; a crosslinking agent; a crosslinking catalyst; and a solvent, wherein the compound represented by the formula (1a), the formula (1b) or the formula (1c) is contained in an amount of 80 mass% as an upper limit relative to the resin, and the crosslinking agent is contained in an amount of 5 to 40 mass%. (wherein X represents a carbonyl group or a methylene group, l and m each independently represent an integer of 0 to 5 satisfying the relational expression of 3. ltoreq. l + m. ltoreq.10, n represents an integer of 2 to 5, u and v each independently represent an integer of 0 to 4 satisfying the relational expression of 3. ltoreq. u + v. ltoreq.8, and R 1 、R 2 、R 3 And R 4 Each independently represents a hydrogen atom, a hydroxyl group, a hydrocarbon group having 1 to 10 carbon atoms which may have at least 1 hydroxyl group as a substituent and may have at least 1 double bond in the main chain, or an aryl group having 6 to 20 carbon atoms which may have at least 1 hydroxyl group as a substituent, wherein R is 1 、R 2 、R 3 And R 4 When the hydrocarbon group having 1 to 10 carbon atoms is represented, R 1 And R 2 、R 3 And R 4 May form a benzene ring, which may have at least 1 hydroxyl group as a substituent, together with the ring carbon atoms to which they are bonded, and j and k each independently represent 0 or 1. ))

1. A composition for forming a protective film resistant to an aqueous hydrogen peroxide solution, comprising: a resin; a compound represented by the following formula (1a), formula (1b) or formula (1 c); a crosslinking agent; a crosslinking catalyst; and a solvent, wherein the compound represented by the formula (1a), the formula (1b) or the formula (1c) is contained in an amount of 80 mass% as an upper limit relative to the resin, and the crosslinking agent is contained in an amount of 5 to 40 mass%,

Wherein X represents a carbonyl group or a methylene group, l and m each independently represent an integer of 0 to 5 satisfying the relational expression of 3. ltoreq. l + m.ltoreq.10, n represents an integer of 2 to 5, u and v each independently represent an integer of 0 to 4 satisfying the relational expression of 3. ltoreq. u + v.ltoreq.8, and R¹、R²、R³And R⁴Each independently represents a hydrogen atom, a hydroxyl group, a hydrocarbon group having 1 to 10 carbon atoms which may have at least 1 hydroxyl group as a substituent and may have at least 1 double bond in the main chain, or an aryl group having 6 to 20 carbon atoms which may have at least 1 hydroxyl group as a substituent, wherein R is¹、R²、R³And R⁴When the hydrocarbon group having 1 to 10 carbon atoms is represented, R¹And R²May form together with the ring carbon atoms to which they are bound a benzene ring, R³And R⁴May form a benzene ring, which may have at least 1 hydroxyl group as a substituent, together with the ring carbon atoms to which they are bonded, and j and k each independently represent 0 or 1.

2. The composition for forming a protective film that is resistant to an aqueous hydrogen peroxide solution according to claim 1, wherein the resin is a polymer having a weight-average molecular weight of 1000 or more.

3. The composition for forming a protective film that is resistant to an aqueous hydrogen peroxide solution according to claim 1, wherein the resin is a monomer having a molecular weight of 600 or less.

4. The composition for forming a protective film that is resistant to an aqueous hydrogen peroxide solution according to claim 3, wherein the monomer is a compound represented by the following formula (2),

Ar-Q-Ar

(2)

Wherein 2 Ar's each represent an aryl group having at least 1 hydroxyl group as a substituent, and Q represents a divalent linking group having at least 1 benzene ring or naphthalene ring, or a methylene group.

5. The composition for forming a protective film that is resistant to an aqueous hydrogen peroxide solution according to any one of claims 1 to 4, wherein the compound represented by formula (1a) is a compound represented by any one of formulae (1a-1) to (1a-5), the compound represented by formula (1b) is a compound represented by formula (1b-1) or formula (1b-2), and the compound represented by formula (1c) is a compound represented by formula (1c-1),

6. The composition for forming a protective film that is resistant to an aqueous hydrogen peroxide solution according to any one of claims 1 to 5, which is a composition for forming a resist underlayer film.

7. A pattern forming method comprising forming a protective film on a semiconductor substrate having a surface on which an inorganic film can be formed by using the composition for forming a protective film resistant to an aqueous hydrogen peroxide solution according to any one of claims 1 to 6, forming a resist pattern on the protective film, dry-etching the protective film using the resist pattern as a mask to expose the surface of the inorganic film or the semiconductor substrate, and wet-etching and cleaning the inorganic film or the semiconductor substrate using an aqueous hydrogen peroxide solution using the protective film after the dry-etching as a mask.

Technical Field

The present invention relates to a composition for forming a protective film excellent in resistance to an aqueous hydrogen peroxide solution in a photolithography process. Further relates to a method for forming a pattern by using the above protective film.

Background

A photolithography process is known in which a resist underlayer film is provided between a substrate and a resist film formed thereon to form a resist pattern having a desired shape. However, conventional resist underlayer films, for example, resist underlayer films formed from a composition containing an aminoplast-based crosslinking agent as described in patent document 1 below, have poor resistance to aqueous hydrogen peroxide. Therefore, such a resist underlayer film cannot be used as a mask in a wet etching process using an aqueous hydrogen peroxide solution.

Patent document 2 below describes a composition for forming a lower layer film for lithography, which contains a compound having a protected carboxyl group, a compound having a group capable of reacting with a carboxyl group, and a solvent, or a composition for forming a lower layer film for lithography, which contains a compound having a group capable of reacting with a carboxyl group and a protected carboxyl group, and a solvent, and which does not contain an aminoplast-based crosslinking agent as an essential component. However, patent document 2 does not describe or suggest any resistance of a resist underlayer film formed from the composition against an aqueous hydrogen peroxide solution.

Patent document 3 below describes a pattern forming method using a resist underlayer film having resistance to an alkaline aqueous hydrogen peroxide solution. The composition for forming the resist underlayer film contains a polymer having an epoxy group and a solvent, wherein the polymer has a weight average molecular weight of 1000 to 100,000.

Disclosure of Invention

Problems to be solved by the invention

In recent years, there has been a growing demand for protective films having improved resistance to aqueous hydrogen peroxide compared to conventional protective films. The purpose of the present invention is to provide a novel composition for forming a protective film having resistance to aqueous hydrogen peroxide, and a pattern forming method using the protective film.

Means for solving the problems

The present inventors have solved the above problems by applying a composition containing a benzophenone derivative, a diphenylmethane derivative or a benzoic acid derivative having a plurality of phenolic hydroxyl groups and a crosslinking agent in a specific amount relative to the content of a resin component. Here, the phenolic hydroxyl group means a hydroxyl group bonded to a benzene ring.

A first aspect of the present invention is a composition for forming a protective film resistant to an aqueous hydrogen peroxide solution, comprising: a resin; a compound represented by the following formula (1a), formula (1b) or formula (1 c); a crosslinking agent; a crosslinking catalyst; and a solvent, wherein the compound represented by the formula (1a), the formula (1b) or the formula (1c) is contained in an amount of 80 mass% as an upper limit relative to the resin, and the crosslinking agent is contained in an amount of 5 to 40 mass%.

(wherein X represents a carbonyl group or a methylene group, l and m each independently represent an integer of 0 to 5 satisfying the relational expression of 3. ltoreq. l + m. ltoreq.10, n represents an integer of 2 to 5, u and v each independently represent an integer of 0 to 4 satisfying the relational expression of 3. ltoreq. u + v. ltoreq.8, and R¹、R²、R³And R⁴Each independently represents a hydrogen atom, a hydroxyl group, a hydrocarbon group having 1 to 10 carbon atoms which may have at least 1 hydroxyl group as a substituent and may have at least 1 double bond in the main chain, or an aryl group having 6 to 20 carbon atoms which may have at least 1 hydroxyl group as a substituent, wherein R is¹、R²、R³And R⁴When the hydrocarbon group having 1 to 10 carbon atoms is represented, R¹And R²May form together with the ring carbon atoms to which they are bound a benzene ring, R³And R⁴May form a benzene ring, which may have at least 1 hydroxyl group as a substituent, together with the ring carbon atoms to which they are bonded, and j and k each independently represent 0 or 1. )

the resin is, for example, a polymer having a weight average molecular weight of 1000 or more, or a monomer having a molecular weight of 600 or less. The monomer is, for example, a compound represented by the following formula (2).

(in the formula, 2 Ar's each represent an aryl group having at least 1 hydroxyl group as a substituent, and Q represents a divalent linking group having at least 1 benzene ring or naphthalene ring or a methylene group.)

The compound represented by the formula (1a) is, for example, a compound represented by the following formula (1a-1) to formula (1a-5), the compound represented by the formula (1b) is, for example, a compound represented by the following formula (1b-1) or formula (1b-2), and the compound represented by the formula (1c) is, for example, a compound represented by the following formula (1 c-1).

The above-mentioned composition for forming a protective film is also a composition for forming a resist underlayer film.

A second aspect of the present invention is a pattern forming method for forming a protective film on a semiconductor substrate having a surface on which an inorganic film can be formed, by using the composition for forming a protective film that is resistant to an aqueous hydrogen peroxide solution according to the first aspect of the present invention, forming a resist pattern on the protective film, dry-etching the protective film using the resist pattern as a mask to expose the surface of the inorganic film or the semiconductor substrate, and wet-etching the inorganic film or the semiconductor substrate using the aqueous hydrogen peroxide solution and cleaning the inorganic film or the semiconductor substrate using the protective film after the dry-etching as a mask.

Examples of the aqueous hydrogen peroxide solution include an alkaline aqueous hydrogen peroxide solution containing ammonia, sodium hydroxide, potassium hydroxide, sodium cyanide, potassium cyanide, triethanolamine, or urea, and an acidic aqueous hydrogen peroxide solution containing hydrochloric acid or sulfuric acid. In the case where the aqueous hydrogen peroxide solution is an aqueous alkaline hydrogen peroxide solution containing ammonia, the aqueous alkaline hydrogen peroxide solution is, for example, a mixture of 25 to 30 mass% of an aqueous ammonia solution (a), 30 to 36 mass% of an aqueous hydrogen peroxide solution (B), and water (C), and the volume ratio of the aqueous hydrogen peroxide solution (B) to the aqueous ammonia solution (a): (B) for example, 0.1 to 20.0, and the volume ratio of the water (C) to the aqueous ammonia solution (A): (C) the value of/(A) is, for example, 1.0 to 50.0.

ADVANTAGEOUS EFFECTS OF INVENTION

The protective film formed from the protective film-forming composition of the present invention has resistance to an aqueous hydrogen peroxide solution. Therefore, the protective film formed from the protective film-forming composition of the present invention can be used as a mask in an etching process and a cleaning process using an aqueous hydrogen peroxide solution.

Detailed Description

The components contained in the protective film-forming composition of the present invention will be described in detail below.

[ resin ]

The protective film-forming composition of the present invention contains a resin as an essential component. As the resin, a polymer having a weight average molecular weight of 1000 or more can be used. The polymer is not particularly limited, and examples thereof include polyester, polyether ether ketone, novolac resin, maleimide resin, acrylic resin, and methacrylic resin. The upper limit of the weight average molecular weight of the above polymer is, for example, 100,000 or 50,000.

As the resin, instead of the polymer having a weight average molecular weight of 1000 or more, a monomer having a molecular weight of 600 or less may be used. The monomer is, for example, a compound represented by the above formula (2), and has a molecular weight of, for example, 150 to 600. In formula (2), examples of the aryl group represented by Ar include phenyl, biphenyl, naphthyl, anthryl, and phenanthryl. In addition, in the case where Q represents a divalent linking group having at least 1 benzene ring or naphthalene ring, examples of the divalent linking group include a divalent group in which at least 1 of 2 hydrogen atoms of a methylene group is substituted with a phenyl group, a biphenyl group or a naphthyl group, a divalent aromatic group selected from a phenylene group, a biphenylene group and a naphthylene group, and a divalent group having the divalent aromatic group and a methylene group, an ether group (-O-group) or a thioether group (-S-group). Examples of the monomer include compounds represented by the following formulae (2-1) to (2-3).

[ Compound represented by formula (1a), formula (1b) or formula (1c) ]

The composition for forming a protective film of the present invention contains a compound represented by the above formula (1a), formula (1b) or formula (1c) as an essential component. Examples of the compound represented by the formula (1a) include compounds represented by the following formulae.

Among the compounds represented by the above formula (1a), for example, 2,3,3 ', 4, 4', 5 '-hexahydroxybenzophenone, 2', 4,4 '-tetrahydroxybenzophenone, 2,3, 4-trihydroxydiphenylmethane, and 2,3,4, 4' -tetrahydroxydiphenylmethane are preferable in that they can be easily obtained. Among the compounds represented by the above formula (1a), benzophenone derivatives having a plurality of phenolic hydroxyl groups are more preferable in terms of improvement in resistance to aqueous hydrogen peroxide.

Examples of the compound represented by the formula (1b) include compounds represented by the following formulae (1b-A) to (1 b-P).

Examples of the compound represented by the formula (1C) include compounds represented by the following formulae (1C-A), (1C-B) and (1C-C). In the formula (1c), in R¹、R²、R³And R⁴When a hydrocarbon group having 1 to 10 carbon atoms is used, examples of the hydrocarbon group having 1 to 10 carbon atoms include alkyl groups such as methyl group, ethyl group, and isopropyl group, alkenyl groups such as vinyl group and allyl group, alkylene groups such as ethylene group and isopropylidene group, and allylene group. In addition, in R¹、R²、R³And R⁴When the aryl group having 6 to 20 carbon atoms is represented, examples of the aryl group having 6 to 20 carbon atoms include phenyl, biphenyl, naphthyl, anthryl, and phenanthryl.

The composition for forming a protective film of the present invention contains, for example, 0.01 to 80% by mass, preferably 0.1 to 75% by mass of the compound represented by the formula (1a), the formula (1b) or the formula (1c) based on the content of the resin. When the content of the compound represented by the formula (1a), the formula (1b) or the formula (1c) is less than 0.01% by mass, the effect of the present invention may not be obtained. On the other hand, when the content of the compound represented by the formula (1a), the formula (1b) or the formula (1c) exceeds 80% by mass, it may be difficult to uniformly coat the protective film forming composition on the substrate.

[ crosslinking agent ]

The protective film-forming composition of the present invention contains a crosslinking agent as an essential component. As the crosslinking agent, a crosslinkable compound having at least 2 crosslinking-forming substituents, for example, a melamine-based compound, a substituted urea-based compound or a phenol-based compound having a crosslinking-forming substituent such as a methylol group or a methoxymethyl group, is preferably used. Examples of the melamine-based compound and the substituted urea-based compound include tetramethoxymethyl glycoluril, tetrabutoxymethyl glycoluril, hexamethoxymethyl melamine, hexabutoxymethyl melamine, tetramethoxymethyl benzoguanamine, tetrabutoxymethyl benzoguanamine, tetramethoxymethyl urea, tetrabutoxymethyl urea, and tetramethoxymethyl thiourea. Examples of the phenol compound include compounds represented by the following formulae (3-1) to (3-28). In the following formula, "Me" represents a methyl group.

Among the above phenolic compounds, for example, compounds represented by the formula (3-23) can be given as trade names: TMOM-BP (manufactured by chemical industries, Ltd., Japan), and compounds represented by the formulae (3-20) are available under the trade name: TM-BIP-A (manufactured by Asahi organic materials industries, Ltd.).

These crosslinking agents may be contained alone in 1 kind, or may be contained in a combination of 2 or more kinds. Among the above crosslinking catalysts, compounds represented by the formula (3-23), compounds represented by the formula (3-24), compounds represented by the formula (3-25) and compounds represented by the formula (3-20), and derivatives obtained by reacting a crosslinking-forming substituent of the compounds with an alcohol such as propylene glycol monomethyl ether are particularly preferable in view of improving the resistance to aqueous hydrogen peroxide.

In the protective film-forming composition of the present invention, the crosslinking agent is contained in an amount of 5 to 40 mass%, preferably 10 to 30 mass%, based on the content of the resin. When the content of the crosslinking agent is too small or too large, the resistance of the formed film against a resist solvent may not be easily obtained.

[ crosslinking catalyst ]

The protective film forming composition of the present invention contains a crosslinking catalyst (acid catalyst) for promoting a crosslinking reaction as an essential component. Examples of the crosslinking catalyst include pyridineP-toluenesulfonate salt and pyridineP-hydroxybenzene sulfonate and pyridineThermal acid generators such as trifluoromethanesulfonate, p-toluenesulfonic acid, p-hydroxybenzenesulfonic acid, trifluoromethanesulfonic acid, salicylic acid, camphorsulfonic acid, 5-sulfosalicylic acid, chlorobenzenesulfonic acid, 4-phenolsulfonic acid methyl ester, sulfonic acid and carboxylic acid compounds such as benzenesulfonic acid, naphthalenesulfonic acid, citric acid and benzoic acid, and K-PURE [ registered trademark ] TAG2689, K-PURETAG2690, K-PURE TAG2678 and K-PURE CXC-1614 (see above, manufactured by キ ン グ イ ン ダ ス ト リ ー ズ Co., Ltd.), 2,4,4, 6-tetrabromocyclohexadienone, benzoin tosylate, 2-nitrobenzyl tosylate and other alkyl organosulfonates. These acid catalysts may be contained alone in 1 kind, or may be contained in a combination of 2 or more kinds. Further, in the above crosslinking catalyst, the crosslinking catalyst is soluble in hydrogen peroxide waterPyridine which generates trifluoromethanesulfonic acid is particularly preferable in terms of improvement of liquid resistanceTrifluoromethanesulfonate and TAG 2689.

The composition for forming a protective film of the present invention contains the crosslinking catalyst in an amount of, for example, 1 to 30% by mass, preferably 5 to 15% by mass, based on the content of the crosslinking agent.

[ solvent ]

The composition for forming a protective film of the present invention can be prepared by dissolving the above components in a solvent, and can be used in a uniform solution state. Examples of the solvent include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, methyl cellosolve acetate, ethyl cellosolve acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol monoethyl ether, propylene glycol monomethyl ether acetate, propylene glycol propyl ether acetate, toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, cycloheptanone, 4-methyl-2-pentanol, methyl 2-hydroxyisobutyrate, ethyl ethoxyacetate, 2-hydroxyethyl acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, methyl pyruvate, ethyl acetate, methyl acetate, ethyl acetate, and mixtures thereof, Butyl acetate, ethyl lactate, butyl lactate, 2-heptanone, methoxycyclopentane, anisole, gamma-butyrolactone, N-methylpyrrolidone, N-dimethylformamide, and N, N-dimethylacetamide. These solvents may be used alone in 1 kind or in combination of 2 or more kinds.

[ other ingredients ]

The protective film-forming composition of the present invention may contain a surfactant as an optional component in order to improve coatability to a semiconductor substrate. Examples of the surfactant include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene cetyl ether and polyoxyethylene oleyl ether, polyoxyethylene alkylaryl ethers such as polyoxyethylene octylphenyl ether and polyoxyethylene nonylphenyl ether, polyoxyethylene/polyoxypropylene block copolymers, sorbitan fatty acid esters such as sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan monooleate, sorbitan trioleate and sorbitan tristearate, nonionic sorbitan fatty acid esters such as polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan trioleate and polyoxyethylene sorbitan tristearate Surfactant system, fluorine-based surfactant such as エ フ ト ッ プ (registered trademark) EF301, エ フ ト ッ プ EF303, エ フ ト ッ プ EF352 (see above, Mitsubishi マ テ リ ア ル electronic chemical corporation), メ ガ フ ァ ッ ク (registered trademark) F171, メ ガ フ ァ ッ ク F173, メ ガ フ ァ ッ ク R-30, メ ガ フ ァ ッ ク R-30N, メ ガ フ ァ ッ ク R-40, メ ガ フ ァ ッ ク R-40-LM (see above, DIC (trade name), フ ロ ラ ー ド FC430, フ ロ ラ ー ド FC431 (see above, Sumitomo ス リ ー エ ム (trade name)), ア サ ヒ ガ ー ド (registered trademark) AG710, サ ー フ ロ ン (registered trademark) S-382, サ ー フ ロ ン SC101, サ ー フ ロ ン SC102, サ ー フ ロ ン SC103, サ ー フ ロ ン SC104, サ ー フ ロ ン SC105, サ ー フ ロ ン SC106 (see above, Asahi glass corporation), etc, Organosiloxane polymer KP341 (product of shin-Etsu chemical Co., Ltd.). These surfactants may be used alone in 1 kind or in combination of 2 or more kinds. When the protective film-forming composition of the present invention contains a surfactant, the content thereof is, for example, 0.005 to 10% by mass, preferably 0.01 to 5% by mass, relative to the resin.

The prepared composition for forming a protective film is preferably used after filtration using a filter having a pore size of, for example, 0.2 μm or 0.1 μm and/or a filter having a pore size of 0.01 μm.

A method for forming a pattern using the composition for forming a protective film of the present invention will be described below.

Examples of the semiconductor substrate to which the composition for forming a protective film of the present invention is applied include silicon substrates, germanium substrates, and compound semiconductor wafers such as gallium arsenide, indium phosphide, gallium nitride, indium nitride, and aluminum nitride. In the case of using a semiconductor substrate having an inorganic film formed on the surface thereof, the inorganic film is formed by, for example, an ALD (atomic layer deposition) method, a CVD (chemical vapor deposition) method, a reactive sputtering method, an ion plating method, a vacuum evaporation method, or a spin-on-glass (SOG) method. Examples of the inorganic film include a polysilicon film, a silicon oxide film, a silicon nitride film, a BPSG (Boro-phosphate Glass) film, a titanium nitride oxide film, a tungsten film, a gallium nitride film, and a gallium arsenide film.

The protective film-forming composition of the present invention is applied to such a semiconductor substrate by an appropriate application method such as a spin coater or a coater. Then, the protective film is formed by baking using a heating device such as a hot plate. The baking conditions are appropriately selected from the baking temperature of 100 ℃ to 400 ℃ and the baking time of 0.3 minute to 60 minutes. Preferably, the baking temperature is 120-350 ℃, the baking time is 0.5-30 minutes, more preferably, the baking temperature is 150-300 ℃, and the baking time is 0.8-10 minutes. The thickness of the protective film to be formed is, for example, 0.001 to 10 μm, preferably 0.002 to 1 μm, and more preferably 0.005 to 0.5. mu.m. When the temperature during baking is lower than the above range, crosslinking may be insufficient, and resistance of the formed protective film to a resist solvent or an aqueous hydrogen peroxide solution may not be easily obtained. On the other hand, when the temperature during baking is higher than the above range, the protective film may be decomposed by heat.

Next, a resist pattern is formed on the protective film. The formation of the resist pattern can be performed by a general method, that is, by applying a photoresist solution on the protective film, performing prebaking, exposure, post-exposure baking (if necessary) called PEB for short, development, and rinsing. The photoresist solution used for forming the resist pattern is not particularly limited as long as it is a photoresist solution that is sensitive to light used for exposure, and a positive type photoresist can be used. Examples thereof include a chemically amplified photoresist composed of a binder having a group whose alkali dissolution rate is increased by decomposition with an acid and a photoacid generator, a chemically amplified photoresist composed of a low-molecular compound whose alkali dissolution rate is increased by decomposition with an acid, an alkali-soluble binder and a photoacid generator, a chemically amplified photoresist composed of a binder having a group whose alkali dissolution rate is increased by decomposition with an acid, a low-molecular compound whose alkali dissolution rate is increased by decomposition with an acid and a photoacid generator, and a non-chemically amplified photoresist of the DNQ-novolak type using a difference in alkali dissolution rates between an exposed portion and an unexposed portion. Examples thereof include trade names manufactured by sumitomo chemical corporation: PAR710, trade name manufactured by Tokyo industries Ltd.: trade names of TDUR-P3435LP, THMR-iP1800, and shin-Etsu chemical industries (Ltd.): SEPR 430. Instead of a positive photoresist, a negative photoresist may be used.

The exposure is performed through a mask (reticle) for forming a predetermined pattern, and for example, i-ray, KrF excimer laser, ArF excimer laser, EUV (extreme ultraviolet) or EB (electron beam) is used. The developing is carried out using an alkaline developer, and the developing temperature is suitably selected from 5 to 50 ℃ and the developing time is suitably selected from 10 to 300 seconds. Examples of the alkaline developing solution include alkaline aqueous solutions such as aqueous solutions of alkali metal hydroxides such as potassium hydroxide and sodium hydroxide, aqueous solutions of quaternary ammonium hydroxides such as tetramethylammonium hydroxide, tetraethylammonium hydroxide and choline, and aqueous solutions of amines such as ethanolamine, propylamine and ethylenediamine. Further, a surfactant or the like may be added to these developer solutions. It is also possible to use: and a method of developing a portion of the photoresist where the alkali dissolution rate is not increased by developing the photoresist with an organic solvent such as butyl acetate instead of the alkali developer.

Then, the protective film is dry-etched using the formed resist pattern as a mask. In this case, the surface of the inorganic film is exposed when the inorganic film is formed on the surface of the semiconductor substrate to be used, and the surface of the semiconductor substrate is exposed when the inorganic film is not formed on the surface of the semiconductor substrate to be used.

Further, a desired pattern is formed by wet etching using an aqueous hydrogen peroxide solution with the protective film after dry etching (the resist pattern is also used when the resist pattern remains on the protective film) as a mask. Examples of the chemical solution for wet etching include a substance exhibiting alkalinity, and examples thereof include an alkaline aqueous hydrogen peroxide solution in which an organic amine such as ammonia, sodium hydroxide, potassium hydroxide, sodium cyanide, potassium cyanide, or triethanolamine is mixed with an aqueous hydrogen peroxide solution to make the pH alkaline, and an acidic aqueous hydrogen peroxide solution in which an inorganic acid such as hydrochloric acid or sulfuric acid is mixed with an aqueous hydrogen peroxide solution. Further, a substance having an alkaline pH, for example, a substance obtained by mixing urea with hydrogen peroxide water and heating the mixture to cause thermal decomposition of urea, thereby generating ammonia, may be used as a chemical solution for wet etching. The use temperature of the aqueous alkaline hydrogen peroxide solution and the aqueous acidic hydrogen peroxide solution is desirably 25 to 90 ℃, and more desirably 40 to 80 ℃. The wet etching time is preferably 0.5 to 30 minutes, and more preferably 1 to 20 minutes.