JP2010107790A - Composition for forming resist lower layer film, and pattern forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composition for forming a resist lower layer film for forming a lower layer film superior in pattern transferability (particularly, resist bend resistance in RIE). <P>SOLUTION: The composition for forming the resist lower layer film contains: novolac resin (A) including at least two phenolic hydroxyl groups and an aromatic ring having an alkyl thienyl group as a repeating structure unit; and organic solvent (B). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a resist underlayer film forming composition and a pattern forming method. More specifically, the present invention relates to a resist underlayer film forming composition and a pattern forming method capable of forming an underlayer film excellent in pattern transferability (particularly resist bending resistance in reactive ion etching (RIE)).

  2. Description of the Related Art A semiconductor device manufacturing process includes a number of steps of laminating a plurality of work films on a silicon wafer and patterning the work films into a desired pattern. In the patterning of the film to be processed, first, a photosensitive material generally called a resist is deposited on the film to be processed to form a resist film, and a predetermined region of the resist film is exposed. Next, the exposed or unexposed portion of the resist film is developed and removed to obtain a resist pattern on which a predetermined pattern is formed. Thereafter, using the resist pattern as an etching mask, the film to be processed is patterned by dry etching.

  In such a process, an ultraviolet light such as an ArF excimer laser is used as an exposure light source for exposing a resist film. Recently, there is an increasing demand for miniaturization of a large scale integrated circuit (LSI). The required resolution has become below the wavelength of exposure light (ultraviolet light). Thus, when the required resolution is less than or equal to the wavelength of the exposure light, the exposure process tolerance such as the exposure tolerance and the focus tolerance is insufficient. In order to compensate for this lack of exposure process tolerance, it is effective to reduce the resist film thickness to improve resolution, but reducing the film thickness is necessary for etching the film to be processed. It becomes difficult to ensure a sufficient resist film thickness.

  For this reason, a resist underlayer film (hereinafter sometimes simply referred to as “underlayer film”) is formed between the film to be processed and the resist film, and the resist pattern is temporarily transferred to the underlayer film to form the underlayer film pattern. After forming the film, a process for transferring the pattern to the film to be processed using the lower layer film pattern as an etching mask has been studied.

  In such a process, the lower layer film is preferably made of a material having etching resistance, and the material includes, for example, a benzene ring that absorbs energy during etching and is known to have etching resistance. A composition containing a resin, in particular, a thermosetting phenol novolak, a composition containing a polymer having an acenaphthylene skeleton, and the like have been proposed (see, for example, Patent Documents 1 and 2). A composition containing a copolymer of a styrene derivative or an allylbenzene derivative and a nortricyclene derivative has also been proposed (see, for example, Patent Document 3).

JP 2001-40293 A JP 2000-143937 A JP 2008-65303 A

  However, with further miniaturization of the etching pattern, overetching of the resist underlayer film has become a big problem, and even underlayer films formed by the compositions described in Patent Documents 1 to 3 are sufficiently etched. There is a demand for the development of a composition that can form a lower layer film that does not have resistance and that has further improved etching resistance.

  Further, as the etching pattern is further miniaturized, the aspect ratio of the lower layer film pattern (the ratio of the pattern width (line width) to the film thickness of the lower layer film pattern) increases, and the lower layer film pattern is bent when the substrate to be processed is etched. There was also a problem. For example, since the composition described in Patent Document 3 has low bending resistance when used as an underlayer film pattern, the underlayer film pattern is bent during etching of the substrate to be processed, and the resist pattern is faithfully applied to the substrate to be processed. It was difficult to transfer.

  The present invention has been made to solve the above-described problems of the prior art, and for forming a resist underlayer film capable of forming an underlayer film excellent in pattern transferability (particularly resist bending resistance in RIE). It is an object to provide a composition and a pattern forming method.

  The present invention provides the following resist underlayer film forming composition and pattern forming method.

[1] Composition for forming a resist underlayer film containing a novolak resin (A) containing an aromatic ring having two or more phenolic hydroxyl groups and an alkyl thienyl group as a repeating structural unit, and an organic solvent (B) object.

[2] The novolac resin was obtained by reacting a compound having two or more phenolic hydroxyl groups in the molecule and a condensation reaction product obtained by the reaction of a condensing agent with an alcohol or aldehyde having a thienyl group. The composition for forming a resist underlayer film according to [1] above.

[3] The composition for forming a resist underlayer film according to [2], wherein the compound is at least one compound selected from the group consisting of a dihydroxybenzene derivative, a dihydroxynaphthalene derivative, and a dihydroxyanthracene derivative.

[4] The resist underlayer film forming composition according to [2] or [3], wherein the condensing agent is an aldehyde.

[5] (1) Step of applying the composition for forming a resist underlayer film according to any one of [1] to [4] on a substrate to be processed to form a resist underlayer film, and the formed resist (2) a step of forming a resist film by applying a resist composition on the lower layer film; and (3) a step of selectively irradiating the formed resist film with radiation to expose the resist film. The exposed resist film is developed to form a resist pattern (4), and the resist underlayer film and the substrate to be processed are dry-etched using the resist pattern as a mask to form the resist substrate. And (5) forming a predetermined pattern.

  The composition for forming a resist underlayer film of the present invention has an effect that an underlayer film excellent in pattern transferability (particularly, resistance to resist bending by RIE) can be formed.

  The pattern forming method of the present invention has an effect that a pattern having excellent pattern transferability (particularly resistance to resist bending by RIE) can be formed.

  Hereinafter, the best mode for carrying out the present invention will be described, but the present invention is not limited to the following embodiment. That is, it is understood that modifications and improvements as appropriate to the following embodiments are also within the scope of the present invention based on ordinary knowledge of those skilled in the art without departing from the spirit of the present invention. Should be.

[1] Composition for forming a resist underlayer film:
The composition for forming a resist underlayer film of the present invention includes a novolak resin (A) containing an aromatic ring having two or more phenolic hydroxyl groups and an alkyl thienyl group as a repeating structural unit, an organic solvent (B), It contains. Such a composition for forming a resist underlayer film can form an underlayer film excellent in pattern transferability (particularly resist bending resistance in reactive ion etching (RIE)). That is, it is excellent in etching resistance, and in particular, in a dry etching process, it is possible to form a lower layer film that has less over-etching and the lower layer film pattern is difficult to bend (has bending resistance), and the resist pattern is processed with high reproducibility. It can be transferred to a substrate. Therefore, according to the composition for forming a resist underlayer film of the present invention, an improvement in yield can be expected in microfabrication in a lithography process using various types of radiation, particularly in the manufacture of highly integrated circuit elements.

[1-1] Novolak resin (A):
The novolac resin (A) has two or more phenolic hydroxyl groups, and preferably 2 to 4 phenolic hydroxyl groups. When the number of phenolic hydroxyl groups is 1, bending resistance cannot be sufficiently obtained.

  Since the composition for forming a resist underlayer film of the present invention contains a novolac resin (A) containing two or more phenolic hydroxyl groups and an aromatic ring having an alkylthienyl group as a repeating structural unit, these phenols The neutral hydroxyl group and the thienyl group combine to produce the effects of the present invention. Here, in this specification, an alkyl thienyl group is a group represented by the following general formula (1).

（但し、上記一般式（１）中、Ｒは、置換されていてもよいアルキレンである。）

(However, in said general formula (1), R is alkylene which may be substituted.)

  R in the general formula (1) is preferably an optionally substituted alkylene having 1 to 20 carbon atoms, and more preferably an optionally substituted alkylene having 1 to 10 carbon atoms.

  The novolak resin (A) is a compound having two or more phenolic hydroxyl groups in the molecule (hereinafter sometimes referred to as “compound (α)”), and a condensation reaction product obtained by a reaction of a condensing agent, It is preferably obtained by a reaction with an alcohol or aldehyde having an alkyl thienyl group. When such a novolak resin (A) is contained, the refractive index of the resulting lower layer film is improved. Therefore, when the lower layer film is combined with a resist film having a high refractive index, there is an advantage that the antireflection performance is improved.

  Examples of the compound (α) include a dihydroxybenzene derivative, a dihydroxynaphthalene derivative, a dihydroxyanthracene derivative, a dihydroxyfluorene derivative, and a dihydroxyacenaphthylene derivative. Among these, from the viewpoint of good film curability and antireflection performance, at least one compound selected from the group consisting of a dihydroxybenzene derivative, a dihydroxynaphthalene derivative, and a dihydroxyanthracene derivative is preferable.

  Examples of the dihydroxybenzene derivative include pyrogallol, 4,4′-dihydroxydiphenylmethane, 4,4′-dihydroxydiphenyl ether, tris (4-hydroxyphenyl) methane, 1,1-bis (4-hydroxyphenyl) -1-phenyl. Ethane, tris (4-hydroxyphenyl) ethane, 1,3-bis (1- (4-hydroxyphenyl) -1-methylethyl) benzene, 1,4-bis (1- (4-hydroxyphenyl) -1- Methylethyl) benzene, 4,6-bis (1- (4-hydroxyphenyl) -1-methylethyl) -1,3-dihydroxybenzene, 1,1-bis (4-hydroxyphenyl) -1- (4- (1- (4-hydroxyphenyl) -1-methylethyl) phenyl) ethane, 1,1,2,2-tetra 4-hydroxyphenyl) ethane, compounds such as bisphenol A; catechol, resorcinol, and 1,4-hydroquinone.

  Examples of the dihydroxynaphthalene derivative include 1,2-dihydroxynaphthalene, 1,3-dihydroxynaphthalene, 1,4-dihydroxynaphthalene, 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 1,7-dihydroxynaphthalene, Examples include 1,8-dihydroxynaphthalene, 2,3-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, 2,7-dihydroxynaphthalene. Among these, 2,6-dihydroxynaphthalene and 2,7-dihydroxynaphthalene are preferable because they have the advantage of good bending resistance and excellent antireflection performance.

  Examples of the dihydroxyanthracene derivative include 1,2-dihydroxyanthracene, 1,3-dihydroxyanthracene, 1,4-dihydroxyanthracene, 1,5-dihydroxyanthracene, 1,6-dihydroxyanthracene, 1,7-dihydroxyanthracene, 1,8-dihydroxyanthracene, 1,9-dihydroxyanthracene, 1,10-dihydroxyanthracene, 2,3-dihydroxyanthracene, 2,4-dihydroxyanthracene, 2,5-dihydroxyanthracene, 2,6-dihydroxyanthracene, 2 , 7-dihydroxyanthracene, 2,8-dihydroxyanthracene, 2,9-dihydroxyanthracene, 2,10-dihydroxyanthracene, 9,10-dihydroxyanthracene, etc. It can be mentioned.

  The condensing agent is not particularly limited as long as it can undergo a condensation reaction with the compound (α), and examples thereof include aldehydes, ketones, and alcohols. Among these, an aldehyde is preferable because there is an advantage that the condensation reaction proceeds rapidly.

  Examples of the aldehyde include, for example, saturated aliphatic aldehydes such as formaldehyde, paraformaldehyde, acetaldehyde, and propylaldehyde; unsaturated aliphatic aldehydes such as acrolein and methacrolein; heterocyclic aldehydes such as furfural; benzaldehyde, naphthylaldehyde, Aromatic aldehydes such as anthraldehyde can be exemplified. Among these, formaldehyde, paraformaldehyde, and furfural are preferable. In addition, an aldehyde may be used individually by 1 type, and 2 or more types may be mixed and used for it.

  The amount of the condensing agent to be used is preferably 20 to 2000 parts by mass, more preferably 50 to 1000 parts by mass, and 100 to 500 parts by mass with respect to 100 parts by mass of the compound (α). Particularly preferred. If the amount used is less than 20 parts by mass, the condensation reaction does not proceed, and therefore there is a possibility that a polymer cannot be obtained. On the other hand, if it exceeds 1000 parts by mass, the condensation reaction proceeds rapidly, and therefore the condensation reaction may not be controlled.

  In order to obtain a condensation reaction product, the reaction may be performed using other compound (i) in addition to the compound (α) and the condensing agent.

  Examples of other compounds (i) include styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, o-acetoxystyrene, m-acetoxystyrene, p-acetoxystyrene, p- Styrene derivatives such as t-butoxystyrene; vinyl carboxylates such as vinyl acetate, vinyl propionate and vinyl caproate; vinyl cyanide compounds such as (meth) acrylonitrile and α-chloroacrylonitrile; methyl (meth) acrylate, ethyl ( Unsaturated carboxylic ester compounds such as (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, n-hexyl (meth) acrylate, glycidyl (meth) acrylate;

  Unsaturated group-containing unsaturated carboxylic acid ester compounds such as ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, vinyl (meth) acrylate, dimethylvinylmethacryloyloxymethylsilane; 2-chloroethyl vinyl ether, chloroacetic acid Halogen-containing vinyl compounds such as vinyl and allyl chloroacetate; hydroxyl-containing vinyl compounds such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate and (meth) allyl alcohol;

  Amide group-containing vinyl compounds such as (meth) acrylamide and crotonic acid amide; Carboxyl group-containing vinyl compounds such as 2-methacryloyloxyethylsuccinic acid and 2-methacryloyloxyethylmaleic acid; benzene, naphthalene, anthracene, phenanthrene, acenaphthene Unsubstituted aromatic hydrocarbon compounds such as

  Alkyl-substituted aromatic hydrocarbon compounds such as toluene, m-xylene, p-xylene and 1-methylnaphthalene; carboxyl group-substituted aromatic hydrocarbon compounds such as benzoic acid, 1-naphthalenecarboxylic acid and 9-anthracenecarboxylic acid; aniline Amino group-substituted aromatic hydrocarbon compounds such as chlorobenzene, bromobenzene, and other halogenated aromatic hydrocarbon compounds;

  Butadiene, vinylbenzene, divinylbenzene, dicyclopentadiene, tetrahydroindene, 4-vinylcyclohexene, 5-vinylnorborna-2-ene, α-pinene, β-pinene, limonene, 5-vinylnorbornadiene, 1-vinylnaphthalene, 2- Examples thereof include vinyl compounds such as vinyl naphthalene, 9-vinyl anthracene and 9-vinyl carbazole. Among these, divinylbenzene, dicyclopentadiene, 5-vinylnorborna-2-ene, 1-vinylnaphthalene, and 2-vinylnaphthalene are preferable. In addition, other compounds (i) may be used individually by 1 type, and 2 or more types may be mixed and used for them.

  The amount of the other compound (i) used is preferably 0.5 to 300 parts by mass, more preferably 1 to 50 parts by mass, with respect to 100 parts by mass of the compound (α). The part by mass is particularly preferred. When the use amount is 0.5 to 300 parts by mass, the etching resistance is improved, so that the pattern transfer property is improved.

  Conventionally known conditions can be adopted as the reaction conditions for obtaining the condensation reaction product. Specifically, the compound (α) and the condensing agent can be reacted at the following reaction temperature and reaction time in the presence of an acid catalyst. The reaction temperature is preferably 40 to 200 ° C, more preferably 60 to 150 ° C, and particularly preferably 70 to 100 ° C. The reaction time varies depending on the reaction temperature, but is preferably 30 minutes to 72 hours, more preferably 1 to 24 hours, and particularly preferably 2 to 10 hours.

  Examples of the acid catalyst include mineral acids such as sulfuric acid, phosphoric acid and perchloric acid; organic sulfonic acids such as p-toluenesulfonic acid; carboxylic acids such as formic acid and oxalic acid. Although the usage-amount of an acid catalyst changes with kinds of acid catalyst to be used, it is preferable that it is 0.001-30 mass parts with respect to 100 mass parts of total amounts of a compound ((alpha)) and a condensing agent, 0.01 It is more preferable that it is -10 mass parts, and it is especially preferable that it is 0.1-5 mass parts.

  The alcohol having a thienyl group is preferably an alcohol having 1 to 20 carbon atoms having a thienyl group, and more preferably an alcohol having 1 to 10 carbon atoms having a thienyl group. Specific examples include thiophene methanol and thiophene ethanol.

  The amount of the alcohol having a thienyl group is preferably 10 to 1000 parts by mass, more preferably 30 to 500 parts by mass, and 50 to 200 parts by mass with respect to 100 parts by mass of the condensation reaction product. It is particularly preferred. There exists a possibility that antireflection ability may fall that the said usage-amount is less than 10 mass parts. On the other hand, if it exceeds 1000 parts by mass, the pattern transferability may decrease. When the amount used is 10 to 1000 parts by mass, a lower layer film excellent in antireflection function and pattern transferability can be formed.

  The aldehyde having a thienyl group is preferably an aldehyde having 1 to 20 carbon atoms having a thienyl group, and more preferably an aldehyde having 1 to 10 carbon atoms having a thienyl group. Specific examples include 2-thiophenaldehyde, 3-thiophenaldehyde, 5-chlorothiophene-2-carboxaldehyde, 5-bromothiophene-2-carboxaldehyde, and the like.

  The amount of the aldehyde having a thienyl group is preferably 10 to 1000 parts by weight, more preferably 30 to 500 parts by weight, and 50 to 200 parts by weight with respect to 100 parts by weight of the condensation reaction product. It is particularly preferred. When the amount used is less than 10 parts by mass, when the lower layer film is formed, the refractive index of the lower layer film is lowered, so that the antireflection ability may be lowered. On the other hand, if it exceeds 1000 parts by mass, the pattern transferability of the formed lower layer film may be lowered.

  When the condensation reaction product is reacted with an alcohol or aldehyde having a thienyl group, another compound (ii) can be further added. Examples of the other compound (ii) include p-toluenesulfonic acid, phosphorus halide, succinic acid, sulfuric acid, methyl isobutyl ketone, toluene, xylene and the like.

  The reaction between the condensation reaction product and the alcohol or aldehyde having a thienyl group is obtained, for example, by mixing the condensation reaction product, the alcohol or aldehyde having a thienyl group and another compound (ii) to obtain a mixture. The resulting mixture can be reacted at 20 to 180 ° C. (preferably 60 to 120 ° C.) for 1 to 72 hours (preferably 2 to 24 hours).

  The novolak resin (A) preferably has a weight average molecular weight in terms of polystyrene (hereinafter sometimes referred to as “Mw”) measured by gel permeation column chromatography of 1,000 to 5,000. 1,500 to 4,000 is more preferable, and 1,500 to 3,000 is particularly preferable. If the weight average molecular weight is less than 1,000, the etching selectivity of the resist underlayer film to be formed may not be sufficiently obtained. On the other hand, if it exceeds 5,000, the viscosity increases and the embedding property in vias decreases, so that it may be difficult to form a resist underlayer film on a fine substrate with a large aspect ratio.

[1-2] Organic solvent (B):
The organic solvent (B) is not particularly limited as long as it can dissolve the novolac resin (A). For example, ethylene glycol monoalkyl ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-n-propyl ether, ethylene glycol mono-n-butyl ether; ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate Ethylene glycol monoalkyl ether acetates such as ethylene glycol mono-n-propyl ether acetate and ethylene glycol mono-n-butyl ether acetate; diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol di-n-propyl ether, diethylene glycol di-n-butyl ether Diethylene glycol etc. Alkyl ethers; triethylene glycol dimethyl ether, triethylene glycol dialkyl ethers such as triethylene glycol diethyl ether;

  Propylene glycol monoalkyl ethers such as propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-n-propyl ether, propylene glycol mono-n-butyl ether; propylene glycol dimethyl ether, propylene glycol diethyl ether, propylene glycol di-n -Propylene glycol dialkyl ethers such as propyl ether and propylene glycol di-n-butyl ether; propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol mono-n-propyl ether acetate, propylene glycol mono-n-butyl ether acetate Propylene glycol such as Roh alkyl ether acetates;

  Lactic acid esters such as methyl lactate, ethyl lactate, n-propyl lactate, i-propyl lactate, n-butyl lactate, i-butyl lactate; methyl formate, ethyl formate, n-propyl formate, i-propyl formate, n-formate Butyl, i-butyl formate, n-amyl formate, i-amyl formate, methyl acetate, ethyl acetate, n-propyl acetate, i-propyl acetate, n-butyl acetate, i-butyl acetate, n-amyl acetate, i-acetate -Amyl, n-hexyl acetate, methyl propionate, ethyl propionate, n-propyl propionate, i-propyl propionate, n-butyl propionate, i-butyl propionate, methyl butyrate, ethyl butyrate, n-propyl butyrate Aliphatic carboxylic acid esters such as i-propyl butyrate, n-butyl butyrate and i-butyl butyrate;

  Ethyl hydroxyacetate, ethyl 2-hydroxy-2-methylpropionate, methyl 3-methoxy-2-methylpropionate, methyl 2-hydroxy-3-methylbutyrate, ethyl methoxyacetate, ethyl ethoxyacetate, methyl 3-methoxypropionate , Ethyl 3-ethoxypropionate, ethyl 3-methoxypropionate, 3-methoxypropyl acetate, 3-methoxybutyl acetate, 3-methyl-3-methoxybutyl acetate, 3-methyl-3-methoxybutylpropionate, 3 -Other esters such as methyl-3-methoxybutyl butyrate, methyl acetoacetate, methyl pyruvate, ethyl pyruvate;

  Aromatic hydrocarbons such as toluene and xylene; ketones such as methyl ethyl ketone, methyl-n-propyl ketone, methyl-n-butyl ketone, 2-heptanone, 3-heptanone, 4-heptanone and cyclohexanone; N-methylformamide, N , N-dimethylformamide, N-methylacetamide, N, N-dimethylacetamide, N-methylpyrrolidone and other amides; γ-butyrolactone and other lactones.

  Among these, propylene glycol monomethyl ether, ethylene glycol monoethyl ether acetate, ethyl lactate, n-butyl acetate, ethyl 3-ethoxypropionate, methyl 3-methoxypropionate, 2-heptanone, cyclohexanone, and γ-butyrolactone are preferable. In addition, an organic solvent (B) may be used individually by 1 type, and 2 or more types may be mixed and used for it.

  The content of the organic solvent (B) is preferably such that the solid content concentration of the resist underlayer film forming composition is 5 to 80% by mass, and more preferably 5 to 40% by mass. The amount is preferably 10 to 30% by mass, particularly preferably. If the solid content concentration of the composition for forming a resist underlayer film is less than 5% by mass, the amount of resin is small, and it may be difficult to form an underlayer film having a sufficient thickness. On the other hand, if it is more than 80% by mass, a solid content is precipitated, and thus there is a possibility that defects may occur during film formation.

[1-3] Other components:
The resist underlayer film forming composition of the present invention is within the range not impairing the desired effect, and other components such as an acid generator (C), a crosslinking agent (D), and an additive (E) as necessary. Can be contained.

  The acid generator (C) is a component that generates an acid upon exposure or heating. In the present specification, an acid generator that generates an acid upon exposure is referred to as a “photoacid generator”, and an acid generator that generates an acid upon heating is referred to as a “thermal acid generator”. Moreover, a photo-acid generator and a thermal acid generator can also be used together as an acid generator (C).

  Specific examples of photoacid generators include diphenyliodonium trifluoromethanesulfonate, diphenyliodonium nonafluoro-n-butanesulfonate, diphenyliodonium pyrenesulfonate, diphenyliodonium n-dodecylbenzenesulfonate, diphenyliodonium 10-camphorsulfonate, diphenyliodonium naphthalene. Sulfonate, diphenyliodonium hexafluoroantimonate, bis (4-t-butylphenyl) iodonium trifluoromethanesulfonate, bis (4-t-butylphenyl) iodonium nonafluoro-n-butanesulfonate, bis (4-t-butylphenyl) Iodonium n-dodecylbenzenesulfonate, bis (4-t-butylphenyl) iodonium 1 - camphorsulfonate, bis (4-t- butylphenyl) iodonium naphthalene sulfonate, bis (4-t- butylphenyl) iodonium hexafluoroantimonate,

  Triphenylsulfonium trifluoromethanesulfonate, triphenylsulfonium nonafluoro-n-butanesulfonate, triphenylsulfonium n-dodecylbenzenesulfonate, triphenylsulfonium naphthalenesulfonate, triphenylsulfonium 10-camphorsulfonate, triphenylsulfonium hexafluoroantimonate, 4 -Hydroxyphenyl phenyl methylsulfonium p-toluenesulfonate, 4-hydroxyphenyl benzyl methylsulfonium p-toluenesulfonate,

  Cyclohexyl methyl 2-oxocyclohexylsulfonium trifluoromethanesulfonate, 2-oxocyclohexyldicyclohexylsulfonium trifluoromethanesulfonate, 2-oxocyclohexyldimethylsulfonium trifluoromethanesulfonate, 1-naphthyldimethylsulfonium trifluoromethanesulfonate, 1-naphthyldiethylsulfonium trifluoromethanesulfonate 4-cyano-1-naphthyldimethylsulfonium trifluoromethanesulfonate, 4-cyano-1-naphthyldiethylsulfonium trifluoromethanesulfonate, 4-nitro-1-naphthyldimethylsulfonium trifluoromethanesulfonate, 4-nitro-1-naphthyldiethylsulfonium trifluoro Lome Sulfonate, 4-methyl-1-naphthyldimethylsulfonium trifluoromethanesulfonate, 4-methyl-1-naphthyldiethylsulfonium trifluoromethanesulfonate, 4-hydroxy-1-naphthyldimethylsulfonium trifluoromethanesulfonate, 4-hydroxy-1-naphthyldiethyl Sulfonium trifluoromethanesulfonate,

  1- (4-hydroxynaphthalen-1-yl) tetrahydrothiophenium trifluoromethanesulfonate, 1- (4-methoxynaphthalen-1-yl) tetrahydrothiophenium trifluoromethanesulfonate, 1- (4-ethoxynaphthalene-1- Yl) tetrahydrothiophenium trifluoromethanesulfonate, 1- (4-methoxymethoxynaphthalen-1-yl) tetrahydrothiophenium trifluoromethanesulfonate, 1- (4-ethoxymethoxynaphthalen-1-yl) tetrahydrothiophenium trifluoromethane Sulfonate, 1- (4- (1-methoxyethoxy) naphthalen-1-yl) tetrahydrothiophenium trifluoromethanesulfonate, 1- (4- (2-methoxyethoxy) naphthalene 1-yl) tetrahydrothiophenium trifluoromethanesulfonate, 1- (4-methoxycarbonyloxynaphthalen-1-yl) tetrahydrothiophenium trifluoromethanesulfonate, 1- (4-ethoxycarbonyloxynaphthalen-1-yl) tetrahydrothio Phenium trifluoromethanesulfonate, 1- (4-n-propoxycarbonyloxynaphthalen-1-yl) tetrahydrothiophenium trifluoromethanesulfonate,

  1- (4-i-propoxycarbonyloxynaphthalen-1-yl) tetrahydrothiophenium trifluoromethanesulfonate, 1- (4-n-butoxycarbonyloxynaphthalen-1-yl) tetrahydrothiophenium trifluoromethanesulfonate, (4-t-butoxycarbonyloxynaphthalen-1-yl) tetrahydrothiophenium trifluoromethanesulfonate, 1- (4- (2-tetrahydrofuranyloxy) naphthalen-1-yl) tetrahydrothiophenium trifluoromethanesulfonate, 1- (4- (2-Tetrahydropyranyloxy) naphthalen-1-yl) tetrahydrothiophenium trifluoromethanesulfonate, 1- (4-benzyloxy) tetrahydrothiophenium trifluoro Methanesulfonate, 1- (naphthyl acetamide methyl) onium salt photoacid generators such as tetrahydrothiophenium trifluoromethanesulfonate;

  Halogen-containing compound-based photoacid generators such as phenylbis (trichloromethyl) -s-triazine, 4-methoxyphenylbis (trichloromethyl) -s-triazine, 1-naphthylbis (trichloromethyl) -s-triazine; 2-naphthoquinonediazide-4-sulfonyl chloride, 1,2-naphthoquinonediazide-5-sulfonyl chloride, 1,3,4-naphthoquinonediazide-4-sulfonic acid ester of 2,3,4,4′-tetrahydroxybenzophenone or 1, Diazoketone compound photoacid generators such as 2-naphthoquinonediazide-5-sulfonic acid ester; sulfone compound photoacid generators such as 4-trisphenacylsulfone, mesitylphenacylsulfone, and bis (phenylsulfonyl) methane Benzoin tosylate, pyrogallol Lith (trifluoromethanesulfonate), nitrobenzyl-9,10-diethoxyanthracene-2-sulfonate, trifluoromethanesulfonylbicyclo [2,2,1] hept-5-ene-2,3-dicarbodiimide, N-hydroxysuccinimide Examples include sulfonic acid compound photoacid generators such as trifluoromethanesulfonate and 1,8-naphthalenedicarboxylic acid imide trifluoromethanesulfonate.

  Among these, diphenyliodonium trifluoromethanesulfonate, diphenyliodonium nonafluoro-n-butanesulfonate, diphenyliodonium pyrenesulfonate, diphenyliodonium n-dodecylbenzenesulfonate, diphenyliodonium 10-camphorsulfonate, diphenyliodonium naphthalenesulfonate, bis (4-t -Butylphenyl) iodonium trifluoromethanesulfonate, bis (4-t-butylphenyl) iodonium nonafluoro-n-butanesulfonate, bis (4-t-butylphenyl) iodonium n-dodecylbenzenesulfonate, bis (4-t-butyl) Phenyl) iodonium 10-camphorsulfonate, bis (4-tert-butylphenyl) iodoni Arm naphthalene sulfonate, and the like are preferable. In addition, a photo-acid generator may be used individually by 1 type, and 2 or more types may be mixed and used for it.

  Specific examples of the thermal acid generator include 2,4,4,6-tetrabromocyclohexadienone, benzoin tosylate, 2-nitrobenzyl tosylate, and alkyl sulfonates. In addition, a thermal acid generator may be used individually by 1 type, and 2 or more types may be mixed and used for it.

  The content of the acid generator (C) is preferably 30 parts by mass or less, more preferably 1 to 20 parts by mass with respect to 100 parts by mass of the novolak resin (A), and 3 to 10 parts by mass. It is particularly preferred that When the resist underlayer film forming composition contains the acid generator (C), a crosslinking reaction can be effectively caused between the molecular chains of the novolak resin (A) at a relatively low temperature including normal temperature.

  The crosslinking agent (D) prevents intermixing between the lower layer film obtained by curing the composition for forming the resist lower layer film and the resist film formed on the lower layer film. It is a component having the action of preventing the occurrence of cracks. As such a crosslinking agent (D), polynuclear phenols and various commercially available curing agents can be used. Moreover, these can also be used together.

  Specific examples of polynuclear phenols include binuclear phenols such as 4,4′-biphenyldiol, 4,4′-methylenebisphenol, 4,4′-ethylidenebisphenol, and bisphenol A; 4,4 ′, 4 "Trimethylphenols such as" -methylidenetrisphenol, 4,4 '-(1- (4- (1- (4-hydroxyphenyl) -1-methylethyl) phenyl) ethylidene) bisphenol "; polyphenols such as novolak Among these, 4,4 ′-(1- (4- (1- (4-hydroxyphenyl) -1-methylethyl) phenyl) ethylidene) bisphenol, novolac, etc. are preferable. Polynuclear phenols may be used individually by 1 type, and 2 or more types may be mixed and used for them.

  As commercially available curing agents, specifically, 2,3-tolylene diisocyanate, 2,4-tolylene diisocyanate, 3,4-tolylene diisocyanate, 3,5-tolylene diisocyanate, 4,4 Diisocyanates such as' -diphenylmethane diisocyanate, hexamethylene diisocyanate, 1,4-cyclohexane diisocyanate; hereinafter referred to as “Epicoat 812”, 815, 826, 828, 834, 836, 871, 1001, 1004, 1007, 1009, 1031 (Oilized Shell Epoxy, Inc.), “Araldite 6600”, 6700, 6800, 502, 6071, 6084 6097, 6099 (above, manufactured by Ciba Geigy), "DER331", 332, 333, 661, the 644, the 667 (manufactured by Dow Chemical Co.) epoxy compounds such as;

  "Cymel 300", 301, 303, 350, 370, 771, 325, 327, 703, 712, 701, 272, 202, "My Coat 506", 508 ( As described above, melamine type curing agents such as Mitsui Cyanamid Co., Ltd .; “Cymel 1123”, 1123-10, 1128, “My Coat 102”, 105, 106, 130 (above, Mitsui Cyanamid Co., Ltd.) Benzoguanamine-based curing agents, such as “Cymel 1170”, 1172 (above, manufactured by Mitsui Cyanamid), glycoluril-based curing agents such as “Nikalac N-2702” (manufactured by Sanwa Chemical), and the like. Among these, melamine type curing agents, glycoluril type curing agents and the like are preferable. In addition, a hardening | curing agent may be used individually by 1 type, and 2 or more types may be mixed and used for it.

  The content of the crosslinking agent (D) is preferably 30 parts by mass or less and more preferably 10 parts by mass or less with respect to 100 parts by mass of the novolak resin (A).

  The additive (E) is one that excludes the acid generator (C) and the cross-linking agent (D) from among the components contained in the resist underlayer film forming composition, and is an interface between the underlayer film and the resist film. It is a component having effects such as preventing mixing and improving applicability of the resist underlayer film forming composition. Examples of the additive (E) include a binder resin, a radiation absorber, a surfactant, a storage stabilizer, an antifoaming agent, and an adhesion aid.

  As the binder resin, various thermoplastic resins and thermosetting resins can be used. Specific examples of the thermoplastic resin include polyethylene, polypropylene, poly-1-butene, poly-1-pentene, poly-1-hexene, poly-1-heptene, poly-1-octene, poly-1-decene, Α-olefin polymers such as poly-1-dodecene, poly-1-tetradecene, poly-1-hexadecene, poly-1-octadecene, and polyvinylcycloalkane; poly-1,4-pentadiene, poly-1,4 Non-conjugated diene polymers such as hexadiene and poly-1,5-hexadiene; α, β-unsaturated aldehyde polymers; poly (methyl vinyl ketone), poly (aromatic vinyl ketone), poly (cyclic vinyl ketone) ), Etc .; (meth) acrylic acid, α-chloroacrylic acid, (meth) acrylate, (meth) acrylic acid Polymers of α, β-unsaturated carboxylic acids or derivatives thereof such as tellurium and (meth) acrylic acid halides; α, β-unsaturated polymers of poly (meth) acrylic anhydride and maleic anhydride Polymers of saturated carboxylic acid anhydrides; Polymers of unsaturated polybasic carboxylic acid esters such as methylenemalonic acid diester and itaconic acid diester;

  Polymers of diolefin carboxylic acid esters such as sorbic acid ester and muconic acid ester; Polymers of α, β-unsaturated carboxylic acid thioesters such as (meth) acrylic acid thioester and α-chloroacrylic acid thioester; ) Polymers of (meth) acrylonitrile such as acrylonitrile and α-chloroacrylonitrile or derivatives thereof; Polymers of (meth) acrylamide or derivatives thereof such as (meth) acrylamide, N, N-dimethyl (meth) acrylamide; Polymers of metal compounds; Polymers of vinyloxy metal compounds; Polyimines; Polyethers such as polyphenylene oxide, poly-1,3-dioxolane, polyoxirane, polytetrahydrofuran, polytetrahydropyran; Polysulfides; Polysulfonamides Polypeptides; Polyamides such as nylon 66 and nylon 1 to nylon 12; Polyesters such as aliphatic polyester, aromatic polyester, alicyclic polyester, and polycarbonate; Polyureas; Polysulfones; Polyazines; Polyamines Polyaromatic ketones, polyimides, polybenzimidazoles, polybenzoxazoles, polybenzothiazoles, polyaminotriazoles, polyoxadiazoles, polypyrazoles, polytetrazoles, polyquinoxalines, polytriazines Polybenzoxazinones; polyquinolines; polyanthrazolins and the like.

  The thermosetting resin is a component that is cured by heating and becomes insoluble in a solvent, and has an action of preventing intermixing between the lower layer film and the resist film formed thereon. Specific examples of thermosetting resins include thermosetting acrylic resins, phenol resins, urea resins, melamine resins, amino resins, aromatic hydrocarbon resins, epoxy resins, alkyd resins. Etc. Among these, urea resins, melamine resins, aromatic hydrocarbon resins and the like are preferable.

  In addition, binder resin may be used individually by 1 type, and 2 or more types may be mixed and used for it. The content of the binder resin is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less with respect to 100 parts by mass of the novolak resin (A).

  Examples of the radiation absorber include oil-soluble dyes, disperse dyes, basic dyes, methine dyes, pyrazole dyes, imidazole dyes, hydroxyazo dyes, and the like; bixin derivatives, norbixine, stilbene, 4,4 Fluorescent brighteners such as' -diaminostilbene derivatives, coumarin derivatives, pyrazoline derivatives; UV absorbers such as hydroxyazo dyes, trade names “Tinuvin 234” and 1130 (above, manufactured by Ciba Geigy); anthracene derivatives, There are aromatic compounds such as anthraquinone derivatives. In addition, a radiation absorber may be used individually by 1 type, and may mix and use 2 or more types. The content of the radiation absorber is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less with respect to 100 parts by mass of the novolak resin (A).

  The surfactant is a component having an action of improving coating properties, striation, wettability, developability and the like. Examples of such surfactants include polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene-n-octylphenyl ether, polyoxyethylene-n-nonylphenyl ether, and polyethylene. Nonionic surfactants such as glycol dilaurate and polyethylene glycol distearate, and “KP341” (manufactured by Shin-Etsu Chemical Co., Ltd.), “Polyflow No. 75”, and No. 95 (above, manufactured by Kyoeisha Yushi Chemical Co., Ltd.),

  "F Top EF101", EF204, EF303, EF352 (above, manufactured by Tochem Products), "Megafac F171", F172, F173 (above, manufactured by Dainippon Ink and Chemicals), "Florade FC430 FC431, FC135, FC93 (above, manufactured by Sumitomo 3M Ltd.), Asahi Guard AG710, Surflon S382, SC101, SC102, SC103, SC104, SC104, SC106 (above, Asahi Glass Co., Ltd.). In addition, surfactant may be used individually by 1 type and may be used in mixture of 2 or more types. The content of the surfactant is preferably 5 parts by mass or less, more preferably 1 part by mass or less with respect to 100 parts by mass of the novolak resin (A).

[2] Pattern formation method:
The pattern forming method of the present invention comprises a step (1) of applying a resist underlayer film forming composition of the present invention on a substrate to be processed to form a resist underlayer film, and a resist composition on the formed resist underlayer film. (2) step of applying an object to form a resist film, and exposing the resist film by selectively irradiating the formed resist film with radiation through a photomask on which a predetermined mask pattern is formed ( 3) Step, developing the exposed resist film to form a resist pattern (4) Step: Using the resist pattern as a mask, the resist underlayer film and the substrate to be processed are dry-etched to form a predetermined pattern on the substrate to be processed. (5) The process of forming this pattern is provided.

By such a process, it is possible to form a pattern excellent in pattern transferability (particularly resist bending resistance in RIE). That is, in the dry etching process, the resist pattern can be faithfully transferred to the substrate to be processed with good reproducibility. Therefore, the pattern formation method of the present invention is a pattern formation method using a multilayer resist process in an area finer than 90 nm (ArF, ArF, F ₂ , EUV, nanoimprint in immersion exposure) among multilayer resist processes. It can be particularly preferably used.

[2-1] (1) Step:
Step (1) is a step of forming a resist underlayer film by applying the resist underlayer film forming composition of the present invention on a substrate to be processed. By this step, a substrate with a resist underlayer film in which a resist underlayer film is formed on a substrate to be processed can be obtained.

  As the substrate to be processed, for example, an insulating film such as silicon oxide, silicon nitride, silicon oxynitride, polysiloxane, etc., all of which are “Black Diamond” (manufactured by AMAT), “Silk” (manufactured by Dow Chemical Company). ), An interlayer insulating film such as a wafer coated with a low dielectric insulating film such as “LKD5109” (manufactured by JSR) can be used. As the substrate to be processed, a patterned substrate such as a wiring groove (trench) or a plug groove (via) can be used.

  There is no restriction | limiting in particular about the method of apply | coating the composition for resist underlayer film formation on a to-be-processed substrate, For example, a spin coat method etc. can be mentioned.

  In addition, a resist underlayer film can be formed by hardening the coating film formed by apply | coating the composition for resist underlayer film formation by exposure and / or heating. As the radiation used for exposure, for example, when the resist underlayer film forming composition further contains an acid generator (C), visible light, ultraviolet rays are used depending on the type of the acid generator (C). , Deep ultraviolet rays, X-rays, electron beams, γ-rays, molecular beams, ion beams, and the like. When the resist underlayer film forming composition contains a photoacid generator, the coating film can be sufficiently cured even at room temperature.

  Moreover, it is preferable that the temperature at the time of heating the said coating film is 90-550 degreeC, It is still more preferable that it is 90-450 degreeC, It is especially preferable that it is 90-300 degreeC. When the composition for forming a resist underlayer film contains a thermal acid generator, for example, the coating film can be sufficiently cured even at about 90 to 150 ° C.

  When the coating film is exposed and / or heated, it is preferably performed in an inert gas atmosphere. Here, for example, nitrogen gas, argon gas, helium gas, xenon gas, or krypton gas can be used as the inert gas. Thus, by forming the resist underlayer film in an inert gas atmosphere, an increase in the oxygen content in the resist underlayer film can be prevented. If it does in this way, the etching tolerance of a resist underlayer film can further be improved.

  The thickness of the resist underlayer film is not particularly limited, but is preferably 100 to 20000 nm.

  In the pattern forming method of the present invention, after this step, a step of further forming an intermediate layer on the resist underlayer film (hereinafter sometimes referred to as “(1-1) step”) is further performed as necessary. May be. This intermediate layer supplements the functions of the lower layer film and / or resist film in resist pattern formation, and is also required to provide functions that the lower layer film and / or resist film do not have. It has a predetermined function. For example, when an antireflection film is formed as the intermediate layer, the antireflection function of the lower layer film can be supplemented.

  This intermediate layer can be formed using an organic compound or an inorganic oxide. Examples of the organic compound include commercially available materials such as “DUV-42”, “DUV-44”, “ARC-28”, and “ARC-29” manufactured by Brewer Science. Alternatively, materials commercially available under trade names such as “AR-3” and “AR-19” manufactured by Rohm and Haas can be used. Examples of the inorganic oxide include materials commercially available under trade names such as “NFC SOG01” and “NFC SOG04” manufactured by JSR, polysiloxane formed by CVD, titanium oxide, alumina oxide, and oxide. Tungsten or the like can be used.

  Examples of the method for forming the intermediate layer include a coating method and a CVD method. Among these, a coating method is preferable. When the coating method is used, there is an advantage that the intermediate layer can be continuously formed after the lower layer film is formed.

  The film thickness of the intermediate layer can be appropriately selected according to the function required for the intermediate layer. For example, in a general lithography process, it is preferably 10 to 3000 nm, and preferably 20 to 300 nm. More preferably. If the film thickness of the intermediate layer is less than 10 nm, the intermediate layer may be scraped and lost during the etching process of the lower layer film. On the other hand, when it exceeds 3000 nm, there is a possibility that the processing conversion difference becomes large when the resist pattern is transferred to the intermediate layer.

[2-2] (2) Step:
(2) The step is a step of forming a resist film by applying a resist composition on the formed resist underlayer film. When the intermediate layer is formed by performing the above-described step (1-1), a resist film is formed on the intermediate layer.

  Examples of the resist composition include a positive or negative chemically amplified resist composition containing a photoacid generator, a positive resist composition comprising an alkali-soluble resin and a quinonediazide-based photosensitizer, and an alkali-soluble resin and a crosslink And negative resist compositions comprising an agent.

  The solid content concentration of the resist composition is preferably, for example, 5 to 50% by mass. Moreover, as a resist composition, it is preferable to use what was filtered with the filter of the hole diameter of about 0.2 micrometer. In addition, the pattern formation method of this invention can also use a commercially available resist composition as a resist composition as it is.

  Examples of the method for applying the resist composition include conventional methods such as a spin coating method. The application amount of the resist composition is adjusted so that a resist film having a predetermined film thickness is obtained.

  The resist film can be formed by volatilizing the solvent in the coating film (that is, the solvent contained in the resist composition) by pre-baking the coating film of the resist composition. Although the temperature at the time of prebaking can be suitably set according to the kind etc. of resist composition to be used, it is preferable that it is 30-200 degreeC, and it is still more preferable that it is 50-150 degreeC.

[2-3] (3) Step:
(3) The process is a process of exposing the resist film by selectively irradiating the formed resist film with radiation. Examples of the method of selectively irradiating with radiation include a method of irradiating the resist film with radiation through a photomask having a predetermined mask pattern formed thereon.

Irradiation can be appropriately selected according to the type of acid generator used in the resist composition. For example, visible light, ultraviolet light, far ultraviolet light, X-rays, electron beams, gamma rays, molecules A line, an ion beam, etc. can be mentioned. Among these, far ultraviolet rays are preferable, and in particular, KrF excimer laser (248 nm), ArF excimer laser (193 nm), F ₂ excimer laser (wavelength 157 nm), Kr ₂ excimer laser (wavelength 147 nm), ArKr excimer laser (wavelength 134 nm). Extreme ultraviolet rays (wavelength 13 nm, etc.) are more preferable.

[2-4] (4) Step:
(4) The process is a process of developing the exposed resist film to form a resist pattern.

  The developer used for development can be appropriately selected according to the type of resist composition used. For example, when using a positive chemically amplified resist composition or a positive resist composition containing an alkali-soluble resin, sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, ammonia, ethylamine , N-propylamine, diethylamine, di-n-propylamine, triethylamine, methyldiethylamine, dimethylethanolamine, triethanolamine, tetramethylammonium hydroxide, tetraethylammonium hydroxide, pyrrole, piperidine, choline, 1,8-diazabicyclo Alkaline aqueous solutions such as [5.4.0] -7-undecene and 1,5-diazabicyclo [4.3.0] -5-nonene can be used. These alkaline aqueous solutions may be those obtained by adding an appropriate amount of a water-soluble organic solvent, for example, an alcohol such as methanol or ethanol, or a surfactant.

  Further, when using a negative chemically amplified resist composition or a negative resist composition containing an alkali-soluble resin, sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, aqueous ammonia, etc. Inorganic alkalis, primary amines such as ethylamine and n-propylamine, secondary amines such as diethylamine and di-n-butylamine, tertiary amines such as triethylamine and methyldiethylamine, dimethylethanolamine and triethanolamine Alcohol amines such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, choline and other quaternary ammonium salts, and alkaline aqueous solutions such as pyrrole and piperidine cyclic amines can be used.

  In this step, after developing with the developer, it can be washed and dried. In order to improve resolution, pattern profile, developability, etc., it is preferable to perform post-baking before developing the resist film (that is, between the steps (3) and (4)). The post-baking temperature is appropriately adjusted according to the type of resist composition to be used, but is preferably 50 to 200 ° C, and more preferably 80 to 150 ° C.

[2-5] (5) Step:
The step (5) is a step of forming a predetermined pattern on the substrate to be processed by dry etching the resist underlayer film and the substrate to be processed using the resist pattern as a mask. When the intermediate layer is formed on the resist underlayer film, the intermediate layer is also dry etched together with the resist underlayer film and the substrate to be processed.

A conventionally known dry etching apparatus can be used for the dry etching. The source gas at the time of dry etching is appropriately selected according to the elemental composition of the film to be etched, but includes an oxygen atom gas such as O ₂ , CO, CO ₂ , an inert gas such as He, N ₂ , Ar, A chlorine-based gas such as Cl ₂ or BCl ₄ , a gas of H ₂ or NH ₄ , or the like can be used. In addition, these gases can also be mixed and used.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example and a comparative example, this invention is not limited to these Examples and a comparative example. In the description of Examples, “parts” and “%” are based on mass unless otherwise specified.

  The weight average molecular weights (Mw) of the polymers (a1), (a2), (A1), and (A2) obtained in the following synthesis examples are “GPC columns” manufactured by Tosoh Corporation (G2000HXL: 2, G3000HXL: 1), a flow rate of 1.0 ml / min, tetrahydrofuran as an eluting solvent, and a gel permeation chromatograph (detector “differential refractometer”) using monodisperse polystyrene as the standard under the analysis conditions at a column temperature of 40 ° C. ).

In addition, the polymers (a1), (a2), (A1), and (A2) are model numbers “JNM-ECA-500” manufactured by JEOL Ltd., and DMSO-d ₆ is used as a measurement solvent. ¹ H-NMR analysis was performed.

(Synthesis Example 1)
A reactor equipped with a condenser, a thermometer, and a stirrer was charged with 100 parts of 2,7-dihydroxynaphthalene, 100 parts of propylene glycol monomethyl ether acetate, and 50 parts of paraformaldehyde, and 2 parts of oxalic acid was added, while dehydrating, 120 The polymer (condensation product) (a1) was obtained by raising the temperature to 0 ° C. and reacting for 5 hours. The polymer (a1) was confirmed to have a structure represented by the following formula (2) by ¹ H-NMR analysis. Moreover, the weight average molecular weight (Mw) of the polymer (a1) was 1500.

(Synthesis Example 2)
In a reactor equipped with a condenser, a thermometer and a stirrer, 125 parts of the polymer (a1) obtained in Synthesis Example 1, 25 parts of thiophene methanol, 20 parts of p-toluenesulfonic acid, and 150 parts of methyl isobutyl ketone were added. The polymer (condensation product) (A1) was obtained by charging and raising the temperature to 100 ° C. and reacting for 4 hours. The polymer (A1) was confirmed to have a structure represented by the following formula (3) by ¹ H-NMR analysis. Moreover, the weight average molecular weight (Mw) of the polymer (A1) was 2800.

(Synthesis Example 3)
A polymer (condensation reaction product) (a2) was obtained in the same manner as in Synthesis Example 1 except that 2,6-dihydroxynaphthalene was used. The polymer (a2) was confirmed to have a structure represented by the following formula (4) by ¹ H-NMR analysis. Moreover, the weight average molecular weight (Mw) of the polymer (a2) was 1500.

(Synthesis Example 4)
A polymer (condensation reaction product) (A2) was obtained in the same manner as in Synthesis Example 2 except that the polymer (a2) obtained in Synthesis Example 3 was used. The polymer (A2) was confirmed to have a structure represented by the following formula (5) by ¹ H-NMR analysis. Moreover, the weight average molecular weight (Mw) of the polymer (A2) was 2800.

Example 1
100 parts of the polymer (A1) and 0.005 part of the surfactant were dissolved in 450 parts of cyclohexanone (organic solvent (B)). Thereafter, this solution was filtered through a membrane filter having a pore diameter of 0.1 μm to prepare a resist underlayer film forming composition. The following evaluation was performed about the prepared composition for resist underlayer film formation.

(1) Formation of lower layer film:
A resist underlayer film forming composition was applied on a silicon wafer having a diameter of 8 inches by spin coating. Thereafter, heating was performed at 180 ° C. for 60 seconds in a hot plate having an oxygen concentration of 20% by volume. Then, it heated at 350 degreeC for 120 second, and formed the 0.3-micrometer-thick lower layer film.

(2) Elemental composition:
(1) About the lower layer film formed by formation of the lower layer film, the mass conversion value of each element was computed using carbon, hydrogen, and nitrogen simultaneous determination apparatus "JM10" (made by Jay Science Laboratories). Thereafter, the number of atoms of each element (carbon, hydrogen, nitrogen) contained in the film was calculated by the formula: mass-converted value (mass%) of each element / mass (g) of each element. Subsequently, the element (carbon / hydrogen / nitrogen) composition (atom%) in the lower layer film was calculated by the formula: number of atoms in the film / total number of atoms in the film. In Table 1, “element composition (atom%)” is shown.

(3) Pattern shape after substrate processing (pattern transfer performance):
(1) On the lower layer film formed by the formation of the lower layer film, a three-layer resist process intermediate layer forming composition solution (trade name “NFC SOG508” manufactured by JSR) is spin-coated, and then on a hot plate at 200 ° C. Heated for 60 seconds. Then, it heated for 60 second on the 300 degreeC hotplate, and formed the intermediate | middle layer film with a film thickness of 0.05 micrometer. Thereafter, a resist composition solution for ArF (trade name “NFC AIM5056” manufactured by JSR) was spin-coated on the intermediate layer film, and pre-baked on a hot plate at 130 ° C. for 90 seconds to obtain a film thickness of 0.2 μm. A resist film was formed.

  Then, using an ArF excimer laser exposure apparatus (manufactured by NIKON, lens numerical aperture: 0.78, exposure wavelength: 193 nm), the resist film is exposed for an optimal exposure time through a photomask on which a predetermined mask pattern is formed. did. Then, it post-baked for 90 seconds on a 130 degreeC hotplate. Next, it developed for 1 minute at 25 degreeC using the tetramethylammonium hydroxide aqueous solution of 2.38% density | concentration. Thereafter, it was washed with water and dried to obtain a pattern-formed resist film in which a positive resist pattern for ArF was formed. Using this pattern forming resist film as a mask, the resist pattern was transferred to the intermediate film. Next, the resist pattern was transferred to the lower layer film using the intermediate film to which the resist pattern was transferred as a mask. Next, the resist pattern was transferred to a substrate (a silicon wafer having a diameter of 8 inches) using the lower layer film to which the resist pattern was transferred as a mask.

At this time, the lower layer film on which the resist pattern was formed was observed with a scanning electron microscope (SEM) and evaluated according to the following criteria. In Table 1, “pattern transfer performance” is shown.
○: Lower layer pattern is standing ×: Lower layer pattern is falling or bent

(4) Etching resistance:
(1) The lower layer film formed by the formation of the lower layer film is subjected to CF ₄ / Ar / O ₂ (CF ₄ : 40 mL / min, Ar: 20 mL / min) using an etching apparatus (“EXAM” manufactured by Shinko Seiki Co., Ltd.). Etching was performed under the conditions of: minutes, O ₂ : 5 mL / min; pressure: 20 Pa; RF power: 200 W; treatment time: 40 seconds; The film thickness before and after the etching treatment at this time was measured, the etching rate was calculated, and the etching resistance was evaluated. The evaluation criteria are as follows. In Table 1, “etching rate” is shown.
○: When the etching rate is 150 nm / min or less Δ: When the etching rate exceeds 150 nm / min and less than 200 nm / min x: When the etching rate is 200 nm / min or more

(5) Refractive coefficient:
A composition for forming a resist underlayer film was applied onto a silicon substrate by spin coating, and baked at 200 ° C. for 60 seconds to obtain an underlayer film having a thickness of 300 nm. Thereafter, an optical constant (refractive coefficient) at a wavelength of 193 nm was calculated using a spectroscopic ellipsometer “VUV-VASE” (manufactured by JA Woollam) (shown as “refractive coefficient” in Table 1). If the refractive index is in the range of 1.40 to 1.60, it can be determined that the ArF exposure resist process has a sufficient function as an antireflection film.

(6) extinction coefficient:
A composition for forming a resist underlayer film was applied onto a silicon substrate by spin coating, and baked at 200 ° C. for 60 seconds to obtain an underlayer film having a thickness of 300 nm. Thereafter, an optical constant (extinction coefficient) at a wavelength of 193 nm was calculated using a spectroscopic ellipsometer “VUV-VASE” (manufactured by JA Woollam) (shown as “extinction coefficient” in Table 1). When the extinction coefficient is in the range of 0.25 to 0.40, it can be determined that the ArF exposure resist process has a sufficient function as an antireflection film.

  The composition for forming a resist underlayer film of this example is 54 atom% for carbon, 24 atom% for hydrogen, and 21 atom% for oxygen, the pattern transfer performance is evaluated as “◯”, and the etching resistance is evaluated as “◯”. The refractive index was 1.45 and the extinction coefficient was 0.42. The evaluation results are shown in Table 1.

(Example 2)
A resist underlayer film forming composition was prepared in the same manner as in Example 1 except that the polymer (A2) was used. The prepared resist underlayer film forming composition was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

(Comparative Example 1)
100 parts of the polymer (a1) obtained in Synthesis Example 1 and 0.005 part of a surfactant were dissolved in 450 parts of cyclohexanone (organic solvent (B)) to obtain a solution. Thereafter, this solution was filtered through a membrane filter having a pore size of 0.1 μm to prepare a resist underlayer film forming composition. The prepared resist underlayer film forming composition was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

  As is clear from Examples 1 and 2 and Comparative Example 1, the resist underlayer film forming compositions of Examples 1 and 2 were more resistant to pattern transfer (particularly, compared to the resist underlayer film forming composition of Comparative Example 1). It was confirmed that a lower layer film excellent in resist bending resistance by RIE) can be formed.

  The composition for forming a resist underlayer film according to the present invention is suitable as a material for forming an underlayer film used in a multi-layer resist process suitable for microfabrication in a lithography process, particularly for manufacturing a highly integrated circuit element.

  The pattern formation method of the present invention is suitable as a pattern formation method in a multilayer resist process suitable for microfabrication in a lithography process, particularly for manufacturing a highly integrated circuit element.

Claims (5)

A novolac resin (A) containing an aromatic ring having two or more phenolic hydroxyl groups and an alkylthienyl group as a repeating structural unit;
A composition for forming a resist underlayer film comprising an organic solvent (B).   The novolak resin is obtained by reacting a compound having two or more phenolic hydroxyl groups in the molecule and a condensation reaction product obtained by the reaction of a condensing agent with an alcohol or aldehyde having a thienyl group. The composition for forming a resist underlayer film according to claim 1.   The resist underlayer film forming composition according to claim 2, wherein the compound is at least one compound selected from the group consisting of a dihydroxybenzene derivative, a dihydroxynaphthalene derivative, and a dihydroxyanthracene derivative.   The composition for forming a resist underlayer film according to claim 2 or 3, wherein the condensing agent is an aldehyde. (1) step of applying the composition for forming a resist underlayer film according to any one of claims 1 to 4 on a substrate to be processed to form a resist underlayer film;
(2) Step of applying a resist composition on the formed resist underlayer film to form a resist film;
(3) the step of exposing the resist film by selectively irradiating the formed resist film with radiation;
(4) a step of developing the exposed resist film to form a resist pattern;
(5) A step of forming a predetermined pattern on the substrate to be processed by dry etching the resist underlayer film and the substrate to be processed using the resist pattern as a mask.