JP6511931B2 - Polysiloxane composition for forming resist lower layer film and pattern forming method - Google Patents

Description

  The present invention relates to a polysiloxane composition for forming a resist underlayer film and a pattern forming method using the polysiloxane composition for forming a resist underlayer film.

  In recent years, with the miniaturization of semiconductor elements and the like, it is required to form a finer resist pattern. In response to this request, various multilayer resist processes using a resist underlayer film have been developed. Examples of such a multilayer resist process include the following. First, a resist underlayer film is formed on a substrate to be processed using a composition for forming a resist underlayer film containing silicon atoms. Next, a resist film is formed on the resist underlayer film using a photoresist composition. The resist film is an organic film having an etching selectivity different from that of the resist underlayer film. Thereafter, the resist film is exposed and developed with a developer to obtain a resist pattern. Subsequently, the resist pattern is transferred onto the resist underlayer film and the substrate to be processed by dry etching to obtain a substrate having a desired pattern.

  In the composition for forming a resist underlayer film described above, an acid generator is added to improve the resist pattern formed on the resist underlayer film (Japanese Patent Laid-Open No. 2007-164148 and See JP 2010-122297 A). However, these compositions for forming a resist underlayer film have the disadvantage that defects are generated in the resist underlayer film due to the acid generator, which makes it difficult to form a fine resist pattern.

JP 2007-164148 A Unexamined-Japanese-Patent No. 2010-122297

  The present invention has been made based on the above circumstances, and an object thereof is a polysiloxane composition for forming a resist underlayer film capable of suppressing the occurrence of a defect in a resist underlayer film in a multilayer resist process, and the resist underlayer film It is an object of the present invention to provide a method for forming a pattern using a forming polysiloxane composition.

  The present invention made to solve the above problems is a polysiloxane composition for forming a resist underlayer film containing a polysiloxane and an acid generator, wherein the acid generator contains an onium cation and an acid anion, and the onium The cation is characterized in that it includes an alicyclic structure, an aliphatic heterocyclic structure, an aromatic ring structure having a chain substituent, or a combination thereof.

  Further, another present invention made to solve the above problems is a step of forming a resist underlayer film on one side of a substrate, and forming a resist pattern on the side opposite to the substrate of the resist underlayer film. And a step of dry etching the resist underlayer film and the substrate sequentially using the resist pattern as a mask, and the resist underlayer film is formed of the polysiloxane composition for forming the resist underlayer film.

  Here, the "acid anion" refers to an anion that becomes an acid by addition of a proton.

  According to the polysiloxane composition for resist underlayer film formation and pattern formation method of this invention, generation | occurrence | production of the defect in a resist underlayer film can be suppressed in a multilayer resist process. Therefore, these can be suitably used for pattern formation in semiconductor device manufacturing etc. which are expected to be further miniaturized in the future.

<Polysiloxane composition for forming resist lower layer film>
The said polysiloxane composition for resist underlayer film formation contains polysiloxane and an acid generator. The acid generator includes an onium cation and an acid anion, and the onium cation includes an alicyclic structure, an aliphatic heterocyclic structure, an aromatic ring structure having a chain substituent, or a combination thereof. Thereby, in the resist underlayer film formed from the said polysiloxane composition for resist underlayer film formation, the defect resulting from an acid generator is reduced. Although the reason which produces the said effect by the said polysiloxane composition for resist lower layer film | membrane formation having said structure is not clear, it can presume as follows, for example. That is, when the onium cation has a bulky structure, the cohesiveness of the acid generator itself is reduced, and the dispersibility of the acid generator in the resist underlayer film is improved. As a result, it is possible to reduce the occurrence of defects such as a local change in etching rate due to the aggregation of the acid generator, and the occurrence of local gelation etc. due to denaturation of the polysiloxane by the aggregated acid generator. It is considered that the generation of defects in the resist underlayer film can be suppressed. In addition, as a result of these, the shape of the resist pattern formed on the resist underlayer film becomes good.

  The polysiloxane composition for forming a resist lower layer film may contain other components such as a solvent and a nitrogen-containing compound as long as the above effects are not impaired. Each component will be described below.

[Polysiloxane]
The polysiloxane is not particularly limited as long as it is a polymer having a siloxane bond, but a hydrolytic condensate of a silane compound represented by the following formula (i) is preferable. The silane compounds used in the synthesis of the polysiloxane may be used alone or in combination of two or more.

  Here, "hydrolysis condensation product" means a hydrolysis condensation product in which some silanol groups of the hydrolyzed silane compound are condensed.

In said formula (i), R ^<A> is a hydrogen atom or a C1-C20 monovalent organic group. X is a halogen atom or -OR ^B. R ^B is a C 1-20 monovalent organic group. a is an integer of 0 to 3; When R ^A is plural, plural R ^A may be the same or different. When there are a plurality of X's, the plurality of X's may be the same or different.

  Here, "organic group" refers to a group containing at least one carbon atom.

The monovalent organic group having 1 to 20 carbon atoms represented by R ^A or R ^B is, for example, a monovalent hydrocarbon group, a group containing a hetero atom-containing group between carbon and carbon of the hydrocarbon group, The group etc. which substituted some or all of the hydrogen atoms of these groups by the substituent are mentioned.

  As said monovalent hydrocarbon group, a chain | strand-shaped hydrocarbon group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group is mentioned, for example.

Examples of the above-mentioned chain hydrocarbon group include alkyl groups such as methyl group, ethyl group, propyl group and butyl group;
Alkenyl groups such as ethenyl, propenyl and butenyl;
And alkynyl groups such as ethynyl group, propynyl group and butynyl group.

Examples of the alicyclic hydrocarbon group include cycloalkyl groups such as cyclopropyl group, cyclopentyl group, cyclohexyl group, norbornyl group, adamantyl group and the like;
And cycloalkenyl groups such as cyclopropenyl group, cyclopentenyl group, cyclohexenyl group and norbornenyl group.

Examples of the aromatic hydrocarbon group include aryl groups such as phenyl group, tolyl group, xylyl group, naphthyl group, anthryl group and the like;
And aralkyl groups such as benzyl group, phenethyl group and naphthylmethyl group.

  The said hetero atom containing group means group which has a bivalent or more hetero atom in a structure. The hetero atom-containing group may have one hetero atom, or may have two or more hetero atoms.

  The divalent or higher valence of the hetero atom-containing group is not particularly limited as long as it is a hetero atom having a divalent or higher valence, and examples thereof include an oxygen atom, a nitrogen atom, a sulfur atom, a silicon atom, and a phosphorus atom And boron atoms.

Examples of the hetero atom-containing group include groups consisting only of hetero atoms such as -SO-, -SO _2- , -SO ₂ O- and -SO _3- ;
-CO-, -COO-, -COS-, -CONH-, -OCOO-, -OCOS-, -OCONH-, -SCONH-, -SCSNH-, -SCSS-, etc. combining a carbon atom and a hetero atom Groups and the like.

  As said substituent, a halogen atom, a hydroxyl group, a carboxy group, a nitro group, a cyano group etc. are mentioned, for example.

  As said a, the integer of 0-2 is preferable and 1 and 2 are more preferable.

Examples of the silane compound represented by the above formula (i) include alkyltrialkoxysilanes such as methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane and methyltris (dimethylsiloxy) silane;
Alkenyltrialkoxysilanes such as vinyltrimethoxysilane, vinyltriethoxysilane, allyltrimethoxysilane and allyltriethoxysilane;
Aryltrialkoxysilanes such as phenyltrimethoxysilane;
Aryltrialkoxysilanes wherein one or more of hydrogen atoms on an aromatic ring such as 4-methylphenyltrimethoxysilane is substituted by an alkyl group, a hydroxy group, an alkoxy group, an amino group or an alkylcarbonyloxy group;
Aralkyl trialkoxysilanes;
Tetraalkoxysilanes such as tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetra-iso-propoxysilane, tetra-n-butoxysilane, tetra-sec-butoxysilane, tetra-t-butoxysilane;
Tetraarylsilanes such as tetraphenoxysilane;
Epoxy group-containing silanes such as oxetanyl trimethoxysilane, oxiranyltrimethoxysilane, oxiranylmethyltrimethoxysilane, 3-glycidyloxypropyltrimethoxysilane, etc .;
Acids such as 3- (trimethoxysilyl) propyl succinic anhydride, 2- (trimethoxysilyl) ethyl succinic anhydride, 3- (trimethoxysilyl) propyl maleic anhydride, 2- (trimethoxysilyl) ethyl glutaric anhydride Anhydride group-containing silanes;
Tetrahalosilanes, such as tetrachlorosilane, etc. are mentioned.

  Among these, tetramethoxysilane and tetraethoxysilane are preferable from the viewpoint of excellent dry etching resistance of the resulting resist underlayer film.

  Also, from the viewpoint of the reactivity of the silane compound and the ease of handling of the substance, phenyltrimethoxysilane, 4-methylphenyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, Allyltrimethoxysilane and allyltriethoxysilane are preferred.

  Furthermore, from the viewpoint of suppressing the pattern collapse of the resist pattern, oxetanyltrimethoxysilane, 3-glycidyloxypropyltrimethoxysilane, 3- (trimethoxysilyl) propyl succinic anhydride, and 4-hydroxyphenyltrimethoxysilane are preferable.

For the synthesis of the above-mentioned polysiloxane, silane compounds other than the silane compound represented by the above-mentioned formula (i) can also be used. As such a silane compound, for example, hexamethoxydisilane, hexaethoxydisilane, hexaphenoxydisilane, 1,1,1,2,2-pentamethoxy-2-methyldisilane, 1,1,1,2,2-penta Ethoxy-2-methyldisilane, 1,1,2,2-tetramethoxy-1,2-dimethyldisilane, 1,1,2,2-tetraethoxy-1,2-dimethyldisilane, 1,1,2,2 -Tetraphenoxy-1,2-dimethyldisilane,
1,1,2-trimethoxy-1,2,2-trimethyldisilane, 1,1,2-triethoxy-1,2,2-trimethyldisilane, 1,1,2-triphenoxy-1,2,2-trimethyl Disilane, 1,2-dimethoxy-1,1,2,2-tetramethyldisilane, 1,2-diethoxy-1,1,2,2-tetramethyldisilane, 1,2-diphenoxy-1,1,2,2, 2-Tetramethyldisilane,
Bis (trimethoxysilyl) methane, bis (triethoxysilyl) methane, 1,2-bis (trimethoxysilyl) ethane, 1,2-bis (triethoxysilyl) ethane, 1- (dimethoxymethylsilyl) -1- (Trimethoxysilyl) methane, 1- (diethoxymethylsilyl) -1- (triethoxysilyl) methane,
Bis (dimethoxymethylsilyl) methane, bis (diethoxymethylsilyl) methane, 1,2-bis (dimethoxymethylsilyl) ethane, 1,2-bis (diethoxymethylsilyl) ethane,
1- (Dimethoxymethylsilyl) -1- (trimethylsilyl) methane, 1- (diethoxymethylsilyl) -1- (trimethylsilyl) methane,
Disilanes such as bis (trimethoxysilyl) benzene and bis (triethoxysilyl) benzene;
And polycarbosilanes such as polydimethoxymethylcarbosilane and polydiethoxymethylcarbosilane.

  The lower limit of the content of the polysiloxane in the polysiloxane composition for forming a resist underlayer film is preferably 80% by mass, and more preferably 90% by mass, with respect to the total solid content in the polysiloxane composition for forming a resist underlayer film. 95% by mass is more preferable. The polysiloxane composition for forming a resist underlayer film may contain only one type of polysiloxane, or may contain two or more types. Here, "solid content" means, for example, the ratio of the residue obtained by firing the solution at 250 ° C. for 30 minutes to the solution before firing.

  The lower limit of the polystyrene equivalent weight average molecular weight (Mw) by gel permeation chromatography (GPC) of polysiloxane is preferably 500, more preferably 800, still more preferably 1,000, and particularly preferably 1,200. On the other hand, the upper limit of the Mw is preferably 20,000, more preferably 15,000, still more preferably 10,000, and particularly preferably 5,000.

  In addition, Mw in this specification uses GPC column (two G2000HXL, one G3000HXL, one G4000HXL) of Tosoh Corporation under the analysis conditions of flow rate 1.0 mL / min, elution solvent tetrahydrofuran, column temperature 40 ° C. This is a value measured by gel permeation chromatography (GPC) using monodispersed polystyrene as a standard.

  As a method of hydrolyzing and condensing the silane compound represented by the above-mentioned formula (i) and the other silane compound optionally used, a known method of hydrolytic condensation can be used.

[Acid generator]
The acid generator contains onium cation and acid anion. The onium cation includes at least one of an alicyclic structure, an aliphatic heterocyclic structure, and an aromatic ring structure having a chain substituent. The acid generator generates an acid upon exposure or heating. The acid causes a crosslinking reaction between molecular chains such as polysiloxane. Thereby, the shape of the resist pattern formed on the resist underlayer film is improved. In addition, since the onium cation of the acid generator has the above-described specific structure, it is suitably dispersed in the resist underlayer film as described above, and as a result, the resist underlayer due to the acid generator It is believed that the occurrence of defects in the film is suppressed.

  Examples of the alicyclic structure include monocyclic cycloalkane structures such as cyclopropane structure, cyclobutane structure, cyclopentane structure and cyclohexane structure; and polycyclic cycloalkane structures such as norbornane structure and adamantane structure.

Examples of the aliphatic heterocyclic structure include single ring structures such as an oxirane structure, an oxetane structure, an oxolane structure, a thiolane structure, and a thiane structure;
Examples thereof include an oxa norbornane structure, an aza norbornane structure, a thia norbornane structure, a norbornane lactone structure, an oxa norbornane lactone structure, and a polycyclic structure such as a norbornane sultone structure.

  As the aromatic ring structure having a chain substituent, for example, one in which a part or all of hydrogen atoms of the aromatic ring structure is substituted with a chain hydrocarbon group is mentioned.

  Examples of the aromatic ring structure include a benzene structure, a naphthalene structure, an anthracene structure, and a phenalene structure.

As said chain | strand-shaped hydrocarbon group, alkyl groups, such as a methyl group, an ethyl group, a propyl group, a butyl group, for example;
Alkenyl groups such as ethenyl, propenyl and butenyl;
And alkynyl groups such as ethynyl group, propynyl group and butynyl group.

  As the onium cation, cations represented by the following formulas (1-1) and (1-2) are preferable.

R ^<1a> , R ^<1b> and R ^<1c> are respectively independently C1-C20 monovalent organic groups in said Formula (1-1). However, at least one of R ^1a , R ^1b and R ^1c has an alicyclic structure. m1, m2 and m3 are each independently an integer of 0 to 3. However, all of m1, m2 and m3 will never be zero. n1, n2 and n3 are each independently an integer of 0-2. When m1 is 2 or more, a plurality of R ^1a may be the same or different. When m2 is 2 or more, a plurality of R ^1b may be the same or different. When m3 is 2 or more, a plurality of R ^1c may be the same or different.
In the above formula (1-2), ^{R 2} is a monovalent organic group having 1 to 20 carbon atoms. p, q and r are each independently an integer of 0 to 2; When p is 2 or more, plural R ^{2 s} may be the same or different.

As a C1-C20 monovalent organic group represented by said R ^<1a> , R ^<1b> and R ^<1c >, the group similar to what was illustrated as said R ^<A> or R < ^B >, etc. are mentioned, for example. Among these, as R ^1a , R ^1b and R ^1c , an alicyclic hydrocarbon group is preferable, a cycloalkyl group is more preferable, and a cyclohexyl group is more preferable.

  As the above m1, m2 and m3, 0 and 1 are preferable. It is more preferable that only one of m1, m2 and m3 be 1 and the remaining 2 be 0. As said n1, n2 and n3, 0 and 1 are preferable and 0 is more preferable.

As a C1-C20 monovalent organic group represented by said R < ² >, the group similar to what was illustrated as said R ^<A> or R < ^B >, etc. are mentioned, for example. Among them, as R ² , a chain hydrocarbon group having a hetero atom is preferable, an alkyl group having an oxygen atom is more preferable, and a butyl group having an oxygen atom is more preferable.

  As said p, q and r, 0 and 1 are preferable and 1 is more preferable.

  Examples of the acid anion include oxo acid anion and sulfonylimidate anion. Examples of the oxo acid anion include sulfonate anion, carboxylate anion, phosphonate anion and the like. Among these, sulfonate anions are preferred from the viewpoint of the strength of the generated acid.

As the above-mentioned sulfonate anion, an anion represented by the following formula (2-a) is preferable.

In the formula (2-a), ^{R 3} is a monovalent organic group having 1 to 20 carbon atoms.

Examples of the monovalent organic group having 1 to 20 carbon atoms represented by R ^3, for example, the R ^A or same groups as those exemplified as R ^B, and the like. Among them, R ³ is preferably a hydrocarbon group having a halogen atom, more preferably a hydrocarbon group having a fluorine atom, still more preferably a hydrocarbon group having 1 to 6 carbon atoms having a fluorine atom, a fluorine atom The hydrocarbon group having 4 to 6 carbon atoms is particularly preferable.

  Moreover, as said sulfonyl imide acid anion, the anion represented by a following formula (2-b) is preferable.

  In said Formula (2-b), L is a C2-C6 alkylene group (Hereinafter, it is also mentioned "fluorinated alkylene group.") By which at least 1 hydrogen atom was substituted by the fluorine atom.

  As a carbon number of the said fluorinated alkylene group, 3, 4 and 5 are preferable, and 3 are more preferable. The elution to the water of the said polysiloxane composition for resist lower layer film formation can be reduced because the said carbon number is the said numerical value.

  Moreover, as a lower limit of the fluorination rate which is a ratio of what is substituted by the fluorine atom among the hydrogen atoms which the said fluorinated alkylene group has, 70% is preferable and 90% is more preferable. On the other hand, as an upper limit of the said fluorination rate, 100% is preferable. When the fluorination rate is in the above range, the strength of the acid generated from the acid generator is appropriately adjusted.

  As said fluorinated alkylene group, the perfluoro alkylene group by which all the hydrogen atoms which an alkylene group has was substituted by the fluorine atom is preferable.

  As the fluorinated alkylene group, for example, tetrafluoroethylene group, 1,2-hexafluoropropylene group, 1,3-hexafluoropropylene group, 1,2-octafluorobutylene group, 1,3-octafluorobutylene group, 1,4-octafluorobutylene group, 2-trifluoromethyl-1,3-pentafluoropropylene group, 1,5-perfluoropentylene group, 1,6-perfluorohexylene group, 1,7-perfluoro Examples include heptylene group and 1,8-perfluorooctylene group.

  Moreover, as an anion represented by said Formula (2-b), what is represented by following formula (2-b-1)-(2-b-3) is preferable.

  The lower limit of the sum of the atomic weights of the atoms constituting the acid anion is preferably 150, more preferably 180, and still more preferably 190. On the other hand, the upper limit of the sum of the atomic weights is preferably 350, more preferably 320, and still more preferably 300. If the sum of the atomic weights is less than the above lower limit, the diffusion length of the acid generated from the acid generator may be excessively long, and the shape of the resist pattern may be defective. Conversely, when the sum of the atomic weights exceeds the upper limit, the dispersibility of the acid generator in the film formed from the polysiloxane composition for forming a resist underlayer film may be reduced.

  Examples of the acid generator include compounds (3-1) to (3-8) represented by the following formulas (3-1) to (3-8). Among these, compound (3-1), compound (3-2), compound (3-7) and compound (3-8) are preferable.

  As a minimum of content of an acid generator to 100 mass parts of polysiloxane, 3 mass parts is preferred, and 5 mass parts is more preferred. On the other hand, as an upper limit of the above-mentioned content, 20 mass parts is preferred, and 10 mass parts is more preferred. Moreover, an acid generator can be used 1 type or 2 types or more.

[Other ingredients]
Examples of other components that can be contained in the polysiloxane composition for forming a resist underlayer film include solvents, nitrogen-containing compounds, β-diketones, colloidal silica, colloidal alumina, organic polymers, surfactants, base generators, etc. It can be mentioned.

(solvent)
The solvent is not particularly limited as long as it can dissolve or disperse the above-mentioned polysiloxane and other optional components. Examples of the solvent include organic solvents such as alcohol solvents, ether solvents, ketone solvents, amide solvents, ester solvents, hydrocarbon solvents and the like.

Examples of the alcohol solvents include aliphatic monoalcohol solvents having 1 to 18 carbon atoms such as 4-methyl-2-pentanol and n-hexanol;
Alicyclic monoalcohol solvents having 3 to 18 carbon atoms such as cyclohexanol;
Polyhydric alcohol solvents having 3 to 18 carbon atoms such as 1,2-propylene glycol;
Examples thereof include C3-C19 polyhydric alcohol partial ether solvents such as propylene glycol monoethyl ether.

Examples of the ether solvents include difatty ether solvents such as diethyl ether, dipropyl ether and dibutyl ether;
Aromatic ring ether solvents such as anisole and diphenyl ether;
Examples thereof include cyclic ether solvents such as tetrahydrofuran and dioxane.

Examples of the ketone solvents include acetone, methyl ethyl ketone, methyl-n-propyl ketone, methyl-n-butyl ketone, diethyl ketone, methyl-iso-butyl ketone, methyl-n-amyl ketone, ethyl-n-butyl ketone, methyl-n- Chain ketone solvents such as hexyl ketone, di-iso-butyl ketone, trimethylnonanone, acetophenone;
Cyclic ketone solvents such as cyclopentanone, cyclohexanone, cycloheptanone, cyclooctanone, methylcyclohexanone;
Diketone solvents such as 2,4-pentanedione and acetonylacetone are listed.

Examples of the above-mentioned amide solvents include N-methylformamide, N, N-dimethylformamide, N, N-diethylformamide, acetamide, N-methylacetamide, N, N-dimethylacetamide, N-methylpropionamide, etc. Amide solvents;
Examples thereof include cyclic amide solvents such as N-methylpyrrolidone and N, N'-dimethylimidazolidinone.

Examples of the ester solvents include monocarboxylic acid ester solvents such as n-butyl acetate and ethyl lactate;
lactone solvents such as γ-butyrolactone and valerolactone;
Polyhydric alcohol partial ether carboxylate solvents such as propylene glycol monomethyl ether acetate;
Polyvalent carboxylic acid diester solvents such as diethyl oxalate;
Carbonate solvents such as dimethyl carbonate and diethyl carbonate may, for example, be mentioned.

Examples of the hydrocarbon solvents include n-pentane, iso-pentane, n-hexane, iso-hexane, n-heptane, iso-heptane, 2,2,4-trimethylpentane, n-octane and iso-octane, for example. Aliphatic hydrocarbon solvents such as cyclohexane and methylcyclohexane;
Aromatics such as benzene, toluene, xylene, mesitylene, ethylbenzene, trimethylbenzene, methylethylbenzene, n-propylbenzene, iso-propylbenzene, diethylbenzene, iso-butylbenzene, triethylbenzene, di-iso-propylbenzene, n-amylnaphthalene Group hydrocarbon solvents;
Halogen-containing solvents such as dichloromethane, chloroform, fluorocarbon, chlorobenzene, dichlorobenzene and the like can be mentioned.

  Among these, preferred solvents are alcohol solvents and ester solvents, polyhydric alcohol partial ether solvents, and polyhydric alcohol monoalkyl ether acetate solvents are more preferable, propylene glycol monoethyl ether, and propylene More preferred is glycol monomethyl ether acetate. The solvents may be used alone or in combination of two or more.

(water)
The polysiloxane composition for forming a resist underlayer film may contain water. Since the polysiloxane is hydrated when it contains water, storage stability is improved. In addition, when water is contained, hardening at the time of film formation of the resist underlayer film is promoted, and a dense film can be obtained.

  When the said polysiloxane composition for resist lower layer film formation contains water, as a minimum of the content rate of water, 0.1 mass% is preferable and 0.2 mass% is more preferable. On the other hand, as an upper limit of the above-mentioned content rate, 30 mass% is preferred, 20 mass% is more preferred, and 15 mass% is still more preferred. When the content of water exceeds the above upper limit, the storage stability of the polysiloxane composition for forming a resist lower layer film may be reduced, and the uniformity of the coated film may be reduced.

(Nitrogen-containing compounds)
The nitrogen-containing compound is a compound having a basic amino group or a compound having a group that becomes a basic amino group by the action of an acid. The nitrogen-containing compound has an effect of improving properties such as ashing resistance of the resist underlayer film obtained from the polysiloxane composition for forming the resist underlayer film. This effect is considered to be due to the fact that the crosslinking reaction in the resist underlayer film is promoted by the presence of the nitrogen-containing compound in the resist underlayer film.

  As a nitrogen containing compound, an amine compound, an amido group containing compound, a urea compound, a nitrogen-containing heterocyclic compound etc. are mentioned, for example.

  Examples of the amine compound include mono (cyclo) alkylamines; di (cyclo) alkylamines; tri (cyclo) alkylamines; substituted alkylanilines or derivatives thereof; ethylenediamine, N, N, N ', N'- Tetramethylethylenediamine, tetramethylenediamine, hexamethylenediamine, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylether, 4,4′-diaminobenzophenone, 4,4′-diaminodiphenylamine, 2,2-bis 4-aminophenyl) propane, 2- (3-aminophenyl) -2- (4-aminophenyl) propane, 2- (4-aminophenyl) -2- (3-hydroxyphenyl) propane, 2- (4-aminophenyl) propane Aminophenyl) -2- (4-hydroxyphenyl) propane, , 4-Bis (1- (4-aminophenyl) -1-methylethyl) benzene, 1,3-bis (1- (4-aminophenyl) -1-methylethyl) benzene, bis (2-dimethylaminoethyl) benzene ) Ether, bis (2-diethylaminoethyl) ether, 1- (2-hydroxyethyl) -2-imidazolidinone, 2-quinoxalinol, N, N, N ′, N′-tetrakis (2-hydroxypropyl) Ethylenediamine, N, N, N ', N''N' '-pentamethyldiethylene triamine etc. are mentioned.

  Examples of the amide group-containing compounds include N-t-butoxycarbonyl group-containing amino compounds, N-t-amyloxycarbonyl group-containing amino compounds, formamide, N-methylformamide, N, N-dimethylformamide, acetamide, N- Examples include methylacetamide, N, N-dimethylacetamide, propionamide, benzamide, pyrrolidone, N-methylpyrrolidone, N-acetyl-1-adamantylamine, tris (2-hydroxyethyl) isocyanurate and the like.

  Examples of the above-mentioned urea compounds include urea, methylurea, 1,1-dimethylurea, 1,3-dimethylurea, 1,1,3,3-tetramethylurea, 1,3-diphenylurea and tri-n-butylthiourea. Etc.

  The nitrogen-containing heterocyclic compounds include, for example, imidazoles; pyridines; piperazines; pyrazine, pyrazole, pyridazine, quinozalin, purine, pyrrolidine, piperidine, piperidine ethanol, 3-piperidino-1,2-propanediol, morpholine, 4 -Methylmorpholine, 1- (4-morpholinyl) ethanol, 4-acetylmorpholine, 3- (N-morpholino) -1,2-propanediol, 1,4-dimethylpiperazine, 1,4-diazabicyclo [2.2. 2) octane and the like.

  Among these, as the nitrogen-containing compound, an amide group-containing compound is preferable, and an N-t-butoxycarbonyl group-containing amino compound and an N-t-amyloxy carbonyl-containing amino compound are more preferable.

  The upper limit of the content of the nitrogen-containing compound is preferably 30 parts by mass, more preferably 10 parts by mass, with respect to 100 parts by mass of the polysiloxane composition for forming a resist underlayer film, from the viewpoint of improving the pattern shape. 1 part by mass is more preferred. The nitrogen-containing compound can be used alone or in combination of two or more.

<Method of preparing polysiloxane composition for forming resist lower layer film>
The polysiloxane composition for forming a resist underlayer film is obtained, for example, by mixing a polysiloxane, an acid generator and optionally other components and dissolving or dispersing in a solvent. As a minimum of solid content concentration of the polysiloxane composition for resist lower layer films concerned concerned, 0.5 mass% is preferred and 1 mass% is more preferred. On the other hand, as a maximum of the above-mentioned solid content concentration, 20 mass% is preferred, and 10 mass% is more preferred.

<Pattern formation method>
In the pattern forming method of the present invention, the step of forming a resist underlayer film on one side of the substrate (hereinafter, also referred to as “resist underlayer film forming step”), the side of the resist underlayer film opposite to the substrate A step of forming a resist pattern (hereinafter also referred to as a “resist pattern forming step”) and a step of sequentially dry etching the resist underlayer film and the substrate using the resist pattern as a mask (hereinafter also referred to as a “dry etching step”) Say). Each step will be described below.

[Resist lower layer forming process]
In the resist underlayer film forming step, the polysiloxane composition for forming a resist underlayer film is applied to one surface side of a substrate to be processed and then heated to crosslink the polysiloxane, thereby forming a resist underlayer film.

  As the substrate to be processed, for example, a conventionally known substrate such as a silicon wafer or a wafer coated with aluminum can be used.

  Examples of the method of applying the polysiloxane composition for forming a resist lower layer film include spin coating, cast coating, roll coating, and the like. The lower limit of the average thickness of the resist underlayer film to be formed is preferably 0.01 μm. On the other hand, as an upper limit of the above-mentioned average thickness, 1 micrometer is preferred and 0.5 micrometer is more preferred.

  After the application of the polysiloxane composition for forming a resist underlayer film, the solvent in the coating film may be volatilized by prebaking (PB), if necessary. The temperature of PB is appropriately selected depending on the composition of the polysiloxane composition for forming a resist underlayer film, but is preferably 30 ° C. or more and 200 ° C. or less. Moreover, as time of PB, 5 to 600 second is preferable.

  The heating temperature after application of the polysiloxane composition for forming a resist lower layer film is not particularly limited, but the lower limit thereof is preferably 100 ° C., more preferably 120 ° C., still more preferably 150 ° C., and particularly preferably 200 ° C. On the other hand, as a maximum of the above-mentioned heating temperature, 450 ° C is preferred, 400 ° C is more preferred, 300 ° C is still more preferred, and 240 ° C is especially preferred.

  The lower limit of the heating time is preferably 10 seconds, more preferably 15 seconds, still more preferably 20 seconds, and particularly preferably 40 seconds. On the other hand, the upper limit of the heating time is preferably 1 hour, more preferably 10 minutes, still more preferably 150 seconds, and particularly preferably 80 seconds.

  By setting the heating temperature and time for forming the resist underlayer film in the above range, the resist underlayer film can be formed simply and reliably. Further, the atmosphere at the time of heating is not particularly limited, and may be an air atmosphere or an inert gas atmosphere such as nitrogen gas.

  In addition, an organic underlayer film may be formed on the substrate to be processed before the resist underlayer film forming step, and a resist underlayer film may be formed on the organic underlayer film in the resist underlayer film forming step. By providing the organic underlayer film between the substrate to be processed and the resist underlayer film in the multilayer resist process, the effects of the present invention can be exhibited more. The organic underlayer film can be formed by applying and drying a composition for forming an organic underlayer film.

  Furthermore, an organic antireflective film can be formed on a substrate to be processed, and a resist underlayer film or the like can be formed thereon. As the organic antireflective film, those described in, for example, Japanese Patent Publication No. 6-12452 and Japanese Patent Laid-Open Publication No. 59-93448 can be adopted.

[Resist pattern formation process]
The resist pattern forming step is, for example, a step of forming a resist film on the surface side of the resist underlayer film opposite to the substrate using a radiation sensitive resin composition (hereinafter also referred to as “resist film forming step”). A step of exposing the resist film (hereinafter, also referred to as “exposure step”), and a step of developing the exposed resist film using an organic solvent (hereinafter, also referred to as “development step”) are provided.

(Resist film formation process)
In this step, a radiation sensitive resin composition is applied to the surface of the resist underlayer film opposite to the above substrate to form a resist film.

Radiation-sensitive resin composition
The radiation sensitive resin composition contains, for example, a base polymer having an acid dissociable group, an acid generator and a solvent. The radiation sensitive resin composition may also contain other components such as a fluorine-containing polymer and an acid diffusion control agent.

  The base polymer has an acid dissociable group. The acid dissociable group is a group which is dissociated by an acid generated from an acid generator or the like. The dissociation of the acid dissociable group generates a polar group such as a carboxy group in the base polymer, resulting in a difference in solubility of the exposed area and the unexposed area in the developer.

  As a base polymer which has the said acid dissociative group, the polymer which a radiation sensitive resin composition contains can usually be used, and it has a structure derived from 1-alkyl 1- cycloalkyl (meth) acrylate Polymer, polymer having a structure derived from 2-cycloalkylpropan-2-yl (meth) acrylate, polymer having a structure derived from 2-alkyl-2-adamantyl (meth) acrylate, 2- (adamantane- Polymers having a structure derived from 1-yl) propan-2-yl (meth) acrylate are preferred.

  Further, the base polymer may have a structure such as a lactone structure, a cyclic carbonate structure or a sultone structure. By having these structures, the solubility of the resist film in a developer can be further improved.

  The lower limit of the content of the base polymer is preferably 70% by mass, more preferably 75% by mass, and still more preferably 80% by mass, based on the total solid content of the radiation sensitive resin composition.

  Examples of the form of containing the acid generator include a form of a low molecular weight compound, a form in which the low molecular weight compound is incorporated into a part of a polymer, and a form of both of them. As said low molecular weight compound, the compound similar to the acid generator illustrated, for example in the said polysiloxane composition for resist lower layer film formation is mentioned. Among these, onium salt compounds are preferable, and sulfonium salts and tetrahydrothiophenium salts are more preferable.

  When the above-mentioned acid generator is the above-mentioned low molecular weight compound, 0.5 mass part is more preferred as a minimum of content of an acid generator to 100 mass parts of base polymers, 1 mass part is still more preferred, and 3 mass parts Particularly preferred. On the other hand, as an upper limit of the above-mentioned content, 30 mass parts is preferred, 20 mass parts is more preferred, and 15 mass parts is still more preferred. By making content of an acid generator into the said range, the sensitivity and the developability of the said radiation sensitive resin composition improve. The acid generator can be used alone or in combination of two or more.

  As said solvent, the thing similar to the solvent illustrated, for example in the said polysiloxane composition for resist underlayer film formation is mentioned. Among these, ester solvents and ketone solvents are preferable, and propylene glycol monomethyl ether acetate and cyclohexanone are more preferable. The said solvent can be used 1 type or 2 types or more.

  Examples of the acid diffusion control agent include the same ones as the above-mentioned nitrogen-containing compound exemplified in the polysiloxane composition for forming a resist lower layer film, and a photodisintegrable base.

  The photodisintegrable base is a compound that generates a weak acid upon exposure, and in the unexposed area, an acid capturing function by an anion is exhibited to function as a quencher, capturing an acid diffused from the exposed area. On the other hand, in the exposed area, an acid is generated and the anion disappears, so that the acid trapping function is lost. That is, since it functions as a quencher only in the unexposed area, the contrast of the dissociation reaction of the acid dissociable group is improved. As said photodisintegrable base, the onium salt compound etc. which are decomposed | disassembled by exposure and loses acid diffusion controllability are mentioned, for example. Examples of this onium salt compound include sulfonium salt compounds and iodonium salt compounds.

  As an acid diffusion control agent, a photodisintegrable base is preferable, and triphenyl sulfonium salicylate and triphenyl sulfonium camphor sulfonate are more preferable.

  When the radiation sensitive resin composition contains an acid diffusion controller and the acid diffusion controller is an acid diffusion controller, the lower limit of the content of the acid diffusion controller per 100 parts by mass of the base polymer is as follows: 0.1 mass part is preferable and 0.3 mass part is more preferable. On the other hand, as an upper limit of the above-mentioned content, 10 mass parts is preferred, 7 mass parts is more preferred, and 5 mass parts is still more preferred. When content of an acid diffusion control agent exceeds the said upper limit, the sensitivity of the radiation sensitive resin composition obtained may fall. The acid diffusion inhibitors may be used alone or in combination of two or more.

  As a coating method of the said radiation sensitive resin composition, the thing similar to the thing in a resist underlayer film formation process can be used, for example. The lower limit of the average thickness of the resist film to be formed is preferably 0.01 μm. On the other hand, as an upper limit of the above-mentioned average thickness, 1 micrometer is preferred and 0.5 micrometer is more preferred.

  Moreover, after apply | coating the said radiation sensitive resin composition, you may volatilize the solvent in a coating film by prebaking (PB) as needed. The temperature and time of PB can be the same as PB in the resist underlayer film.

  Furthermore, in order to prevent the influence of basic impurities and the like contained in the environmental atmosphere, a protective film can be provided on the above-formed resist film. Examples of this protective film include those described in JP-A-5-188598. In addition, in order to prevent the acid generator and the like from flowing out of the resist film, a liquid immersion protective film described in, for example, JP 2005-352384 A can be provided on the resist film. These techniques can be used together.

(Exposure process)
At this process, the resist film formed at the said resist film formation process is exposed. As this exposure, for example, an iso-trench pattern can be formed by performing reduction projection exposure in a desired area via an iso-line pattern mask. The exposure may be performed twice or more depending on the desired pattern and the mask pattern. When the exposure is performed twice or more, the exposure is preferably performed continuously. When multiple exposures are performed, for example, a first reduction projection exposure is performed on a desired area through a line and space pattern mask, and a line intersects the exposure portion subjected to the first exposure subsequently. Perform a reduced projection exposure of The first exposure unit and the second exposure unit are preferably orthogonal to each other. By being orthogonal, it becomes easy to form a perfect circular contact hole pattern in the unexposed area surrounded by the exposed area.

  When immersion exposure is performed as the exposure, examples of the immersion liquid used in the exposure include water and a fluorine-based inert liquid. The immersion liquid is preferably a liquid that is transparent to the exposure wavelength and has a temperature coefficient of refractive index as small as possible to minimize distortion of the optical image projected onto the film, but the exposure light source is particularly preferably ArF. In the case of excimer laser light (wavelength 193 nm), it is preferable to use water from the viewpoints of easy availability and easy handling in addition to the above-mentioned viewpoints. When water is used, additives that increase the surface activity and reduce the surface tension of water may be added in small proportions. The additive is preferably one which does not dissolve the resist layer on the wafer and has negligible effect on the optical coat on the lower surface of the lens. Distilled water is preferred as water to be used.

  The radiation used for exposure is appropriately selected according to the type of the acid generator contained in the above radiation sensitive resin composition, and for example, ultraviolet light, far ultraviolet light, visible light, EUV, X-rays, γ-rays, etc. Of electromagnetic waves; electron beams; charged particle beams such as .alpha. Among these, far ultraviolet rays, EUV and electron beams are preferable, and ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), EUV (extreme ultraviolet) and electron beams are more preferable. Exposure conditions, such as an exposure amount, are suitably selected according to the compounding composition of the said radiation sensitive resin composition, the kind of additive, etc. The pattern formation method may have a plurality of exposure steps, and in this case, the plurality of exposures may use the same light source or different light sources.

  Also, post exposure bake (PEB) is preferably performed after exposure. By performing PEB, the dissociative reaction of the acid dissociatable group in the said radiation sensitive resin composition can be advanced smoothly. As a minimum of PEB temperature, 30 ° C is preferred, 50 ° C is more preferred, and 70 ° C is still more preferred. On the other hand, as an upper limit of the above-mentioned PEB temperature, 200 ° C is preferred, 170 ° C is more preferred, and 120 ° C is still more preferred. As a minimum of PEB time, 5 seconds are preferred and 10 seconds are more preferred. On the other hand, as a maximum of PEB time, 600 seconds are preferred and 300 seconds are more preferred.

(Development process)
In this step, the resist film exposed in the exposure step is developed using a developer, and a drying process and the like are performed. Thereby, a predetermined resist pattern can be formed.

  In the case of organic solvent development, examples of the developer used for the development include organic solvents such as hydrocarbon solvents, ether solvents, ester solvents, ketone solvents, alcohol solvents and the like. Examples of the organic solvent include one or more of the solvents listed as the solvent for the composition for forming a resist lower layer film described above, and the like. Among these, ester solvents and ketone solvents are preferable. As an ester solvent, an acetic acid ester solvent is preferable, and n-butyl acetate is more preferable. As a ketone solvent, a chain ketone is preferable, and 2-heptanone is more preferable. The lower limit of the content of the organic solvent in the developer is preferably 80% by mass, more preferably 90% by mass, still more preferably 95% by mass, and particularly preferably 99% by mass.

  An appropriate amount of surfactant can be added to the developer as needed. As the surfactant, for example, an ionic or non-ionic fluorine-based and / or silicon-based surfactant can be used.

  In addition, alkaline development may be performed using an alkaline solution. In this case, examples of the developer used for the development include sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, aqueous ammonia, ethylamine, n-propylamine, diethylamine, di-n-propyl Amine, triethylamine, methyl diethylamine, ethyldimethylamine, triethanolamine, tetramethylammonium hydroxide (TMAH), pyrrole, piperidine, choline, 1,8-diazabicyclo- [5.4.0] -7-undecene, 1, The aqueous alkali solution etc. which dissolved at least 1 sort (s) of alkaline compounds, such as 5-diazabicyclo- [4.3.0] -5- nonene, etc. are mentioned. Among these, TMAH aqueous solution is preferable and 2.38 mass% TMAH aqueous solution is more preferable.

  As a developing method, for example, a method of immersing a substrate in a bath filled with a developer for a certain time (dip method), a method of raising a developer on the substrate surface by surface tension and developing by standing for a certain time (paddle method A method of spraying a developer onto the substrate surface (spray method), a method of continuously coating a developer onto a substrate rotating at a constant speed while scanning a developer coating nozzle at a constant speed (dynamic dispense method) Etc.

  After the development, the formed resist pattern is preferably washed using a rinse solution. As the rinse solution, in the case of organic solvent development, alcohol solvents and ester solvents are preferable, and monovalent alcohol solvents having 6 to 8 carbon atoms are more preferable, and 1-hexanol, 2-hexanol, 2-heptanol And 4-methyl-2-pentanol are more preferred. In the case of alkali development, water is preferred, and pure water is more preferred.

  As a method of cleaning treatment, for example, a method of continuously applying a rinse liquid on a substrate rotating at a constant speed (rotation coating method), a method of immersing a substrate in a bath filled with a rinse liquid for a predetermined time (dip method) And a method (spray method) of spraying a rinse liquid on the substrate surface.

[Dry etching process]
In the dry etching step, the resist underlayer film is dry etched using the resist pattern as a mask to form an underlayer pattern. Thereafter, using the lower layer pattern as a mask, the substrate to be processed is dry etched to form a pattern on the substrate to be processed.

This dry etching can be performed using a known dry etching apparatus. The etching gas used for dry etching can be appropriately selected depending on the elemental composition of the resist underlayer film to be etched, and the like. For example, CHF ₃ , CF ₄ , C ₂ F ₆ , C ₃ F ₈ , SF ₆ etc. Fluorine-based gases, chlorine-based gases such as Cl ₂ and BCl ₃ , oxygen-based gases such as O ₂ , O ₃ , and H ₂ O, gases such as H ₂ , NH ₃ , CO, and CO ₂ , He, N ₂ , Inert gases such as Ar may be mentioned. These gases may be used alone or in combination of two or more.

  As an etching gas used for etching the resist underlayer film, a fluorine-based gas is preferable, and a mixture of a fluorine-based gas and an oxygen-based gas and an inert gas is preferable. As an etching gas used for etching the substrate to be processed, an oxygen-based gas is preferable, and a mixture of an oxygen-based gas and an inert gas is more preferable.

  When the organic lower layer film is formed, in the dry etching step, the organic lower layer film is etched using the lower layer pattern as a mask, and then the substrate to be processed is etched. As an etching gas used for etching the organic lower layer film, an oxygen-based gas is preferable, and a mixture of an oxygen-based gas and an inert gas is more preferable.

  Hereinafter, the present invention will be described in detail based on examples, but the present invention is not construed as being limited to these examples. The measuring method of various physical-property values is shown below.

[Determination of solid content ratio]
The weight of the solid content relative to 0.5 g of the resin solution was measured by baking 0.5 g of the siloxane resin solution for 30 minutes at 250 ° C., and the content ratio of the solid content of the siloxane resin solution was determined.

[Mw and Mn measurement]
The Mw and Mn of the polymer were measured by gel permeation chromatography (GPC) under the following conditions.
Column: Two Tosoh "G2000 H XL", one "G 3000 H XL" and one "G 4000 H XL" Elution solvent: tetrahydrofuran Column temperature: 40 ° C
Flow rate: 1.0 mL / min Detector: Differential refractometer Standard substance: Monodispersed polystyrene

<Synthesis of Polysiloxane>
10.9 g of oxalic acid was heated and dissolved in 163.8 g of water to prepare an aqueous oxalic acid solution. Next, 252.6 g (75 mol%) of tetraethoxysilane, 33.0 g (15 mol%) of methyltrimethoxysilane, 32.1 g (10 mol%) of phenyltrimethoxysilane, and propylene having a cooling pipe and an addition device In a 5 L flask containing 507.7 g of glycol monoethyl ether (PGEE), a cooling pipe and a dropping funnel containing the oxalic acid aqueous solution prepared above were set. Next, after heating to 60 ° C. with an oil bath, an oxalic acid aqueous solution was slowly dropped, and allowed to react at 60 ° C. for 4 hours. After completion of the reaction, the flask containing the reaction solution was allowed to cool and then set in an evaporator, and the alcohol produced by the reaction was distilled off. After adding 692.0 g of propylene glycol monoethyl ether (PGEE) to the obtained solution, PGEE and the like are distilled off with an evaporator to carry out solvent substitution to obtain a mixed solution containing polysiloxane (hereinafter referred to as “polysiloxane It obtained 846.0g of mixed solution (it is also called "). As a result of measuring solid content concentration of the obtained polysiloxane liquid mixture by a calcination method, it was 6.9 mass%. Moreover, as a result of GPC measurement, Mw of polysiloxane was 3,000.

<Preparation of polysiloxane composition for forming resist lower layer film>
Each component used for preparation of the polysiloxane composition for resist underlayer film formation is shown below.

[Acid generator]
B-1: Compound represented by the following formula (B-1) B-2: Compound represented by the following formula (B-2) B-3: Compound represented by the following formula (B-3) B-4: Formula (B) -4) Compound B-5: Compound represented by the following formula (B-5) B-6: Compound represented by the following formula (B-6) B-7: Compound represented by the following formula (B-7)

[solvent]
C-1: Propylene glycol monomethyl ether acetate (PGMEA)
C-2: Propylene glycol monoethyl ether (PGEE)

Example 1
In preparation of the polysiloxane composition for resist lower layer film formation, the circulation filtration apparatus provided with a solution tank, filter A, filter B, a diaphragm pump, and a Teflon (trademark) tube (inner diameter 4 mm, length 200 mm) was used. As the filter A, a polyamide-based synthetic fiber membrane (Nippon Pall Co., Ltd. "filter capsule Photocree DDF Ultipleated P-nylon", pore diameter 20 nm, filter cloth area 0.53 m ² ) (Japan Paul's "filter capsule photo clean DDF PE- clean", a pore size of 10nm, filter cloth area 0.51m ²⁾ was used. At this time, the filter A was on the upstream side and the filter B was on the downstream side, and the two filters were connected by a Teflon (registered trademark) tube (inner diameter 4 mm, length 100 mm).

  Next, 591 g of the above-prepared polysiloxane mixed solution was charged into a solution tank. 2.5 parts by mass of the acid generator (B-1), 5037 parts by mass of the solvent (C-1) and 2157 parts by mass of (C-2) with respect to 100 parts by mass of the polysiloxane in the polysiloxane mixture After the addition and dissolution, this solution is subjected to circulation filtration under normal pressure and at a flow rate of 450 g / min until the number of circulations reaches 20 times, whereby the polysiloxane composition for forming a resist underlayer film of Example 1 is obtained. Obtained.

Examples 2 to 4 and Comparative Examples 1 to 3
The polysiloxane compositions for forming a resist underlayer film of Examples 2 to 4 and Comparative Examples 1 to 3 were obtained in the same manner as Example 1 except that each compound of the type and amount used shown in Table 1 below was used.

<Evaluation>
The polysiloxane composition for forming a resist underlayer film of the above Example and Comparative Example is applied inline on a 12 inch silicon wafer using a spin coater (“ACT12” from Tokyo Electron Ltd.) and baked at 215 ° C. for 60 seconds Then, a substrate for defect inspection on which a resist underlayer film having an average thickness of 33 nm was formed was obtained. With respect to the obtained substrate for defect inspection, the number of defects was measured under the conditions of a pixel size of 0.23 μm and a threshold of 10 using a defect inspection apparatus (“KLA 2810” by KLA Tencor Corporation). The defect controllability was evaluated as “A” when the number of defects per defect inspection substrate was 25 or less, and was evaluated as “B” when it exceeded 25. Of these evaluations, A was accepted. The number of defects and the evaluation are shown in Table 2.

  As shown in Table 2, the polysiloxane composition for forming a resist underlayer film of the example had few defects in the resist underlayer film. On the other hand, all of the polysiloxane compositions for forming a resist underlayer film of the comparative example had many defects in the resist underlayer film.

<Pattern shape>
The shape of the pattern formed on the resist underlayer film was evaluated by the following procedure.

[Preparation of radiation sensitive resin composition]
The compounds used for the synthesis of the base polymer (a-1) and the fluorine-containing polymer (a-2) are shown below.

(Synthesis of Base Polymer (a-1))
12.9 g (50 mol%) of the following compound (M-1) and 17.1 g (50 mol%) of the compound (M-2) are dissolved in 60 g of methyl ethyl ketone, and further 2,2'-azobisisobutyronitrile 1.77 g of (AIBN) was added and dissolved to prepare a monomer solution. Next, a 200 mL three-necked flask charged with 30 g of methyl ethyl ketone is purged with nitrogen for 30 minutes, and then the reaction kettle is heated to 80 ° C. while stirring, and the above monomer solution is dropped using a dropping funnel over 3 hours did. The polymerization reaction was carried out for 6 hours, with the dripping start as the polymerization start time. After completion of the polymerization, the polymerization reaction solution was water-cooled and cooled to 30 ° C. or less, and poured into 600 g of methanol, and the precipitated white powder was separated by filtration. The filtered white powder was slurried twice with 150 g of methanol, washed again, filtered again, and dried at 50 ° C. for 17 hours to obtain a white powder base polymer (a-1). Obtained (yield 80%). As a result of ¹³ C-NMR, the content ratio of the structural units derived from the compound (M-1) / (M-2) in the base polymer (a-1) was 49/51 (mol%). Moreover, Mw of the base polymer (a-1) was 6,900, and Mw / Mn was 1.35.

(Synthesis of Fluorine-Containing Polymer (a-2))
10.4 g (30 mol%) of the following compound (M-3) and 19.6 g (70 mol%) of the compound (M-4) are dissolved in 60 g of methyl ethyl ketone, and 2,2'-azobis (isobutyronitrile) 0.91 g (5 mol%) was charged to prepare a monomer solution. Next, a 200 mL three-necked flask charged with 30 g of methyl ethyl ketone is purged with nitrogen for 30 minutes, and then the reaction kettle is heated to 80 ° C. while stirring, and the above prepared monomer solution is added using a dropping funnel for 3 hours It dripped over. The polymerization reaction was carried out for 6 hours, with the dripping start as the polymerization start time. After completion of the polymerization, the solution was water-cooled, cooled to 30 ° C. or less, and poured into 600 g of methanol, and the precipitated white powder was separated by filtration. The filtered white powder was slurried twice with 150 g of methanol, washed again, filtered off again, and dried at 50 ° C. for 12 hours to obtain a fluorine-containing polymer (a-2) of a white powder (Yield 68%). As a result of ¹³ C-NMR, the content ratio of structural units derived from (M-3) / (M-4) in the fluorine-containing polymer (a-2) was 31/69 (mol%). Moreover, Mw of the fluorine-containing polymer (a-2) was 5,900, and Mw / Mn was 1.58.

  The components other than the base polymer (a-1) and the fluorine-containing polymer (a-2) used for the preparation of the radiation sensitive resin composition are shown below.

(Acid generator)
b-1: Triphenylsulfonium 1,1,2,2-tetrafluoro-6- (1-adamantanecarbonyloxy) -hexane-1-sulfonate (compound represented by the following formula (b-1))

(Acid diffusion control agent)
c-1: triphenylsulfonium salicylate (compound represented by the following formula (c-1))

(solvent)
d-1: Propylene glycol monomethyl ether acetate d-2: Cyclohexanone d-3: γ-butyrolactone

(Preparation of radiation sensitive resin composition (J-1))
100 parts by mass of base polymer (a-1), 3 parts by mass of fluorine-containing polymer (a-2), 10.8 parts by mass of acid generator (b-1), acid diffusion control agent (c-1) 4. 3 parts by mass, 2,185 parts by mass of solvent (d-1), 935 parts by mass of solvent (d-2) and 30 parts by mass of solvent (d-3) are mixed to obtain a radiation sensitive resin composition (J-1) Was prepared.

[Formation of line and space pattern]
An antireflective film-forming material ("HM8006" manufactured by JSR Corporation) was spin-coated on a 12-inch silicon wafer. For the spin coating, a coating / developing apparatus (“CLEAN TRACK ACT 12” from Tokyo Electron Ltd.) was used (hereinafter, the same apparatus was used for those not described in particular). Thereafter, PB (250 ° C., 60 seconds) was performed to form an antireflective film having an average thickness of 100 nm. The polysiloxane composition (S-1) for forming a resist underlayer film of Example 1 is spin-coated on this antireflection film, and after PB (220 ° C., 60 seconds), it is cooled (23 ° C., 60 seconds) Thus, a resist underlayer film having an average thickness of 30 nm was formed. The average thickness of the resist underlayer film was measured by a film thickness measurement apparatus ("M-2000D" manufactured by JA Woollam Co., Ltd.). Next, the resist underlayer film on which the radiation sensitive resin composition (J-1) was formed was spin coated, and after PB (90 ° C., 60 seconds), cooling (23 ° C., 30 seconds) gave an average thickness of 100 nm. Resist film was formed.

  Next, using an ArF immersion exposure apparatus ("S610C" manufactured by NIKON), exposure was performed through a mask of mask size for forming a 40 nm line / 80 nm pitch under the optical conditions of NA: 1.30 and Dipole. Perform PEB (100 ° C., 60 seconds) on the above “CLEAN TRACK Lithius Pro-i” hot plate, cool (23 ° C., 30 seconds), and then paddle develop (30 seconds) using butyl acetate as a developer. Rinse with MIBC. By spin-drying at 2,000 rpm for 15 seconds by shaking off, a substrate for evaluation on which a resist pattern of 40 nm line / 80 nm pitch was formed was obtained.

  The pattern shape was evaluated using the obtained evaluation substrate. A scanning electron microscope ("CG-4000" manufactured by Hitachi High-Technologies Corporation) was used to measure and observe the resist pattern on the evaluation substrate. The resist pattern did not fall down and no bottoming on the bottom, and the pattern shape was good.

As described above, according to the polysiloxane composition for forming a resist underlayer film and the pattern forming method of the present invention, the occurrence of defects in the resist underlayer film can be suppressed in the multilayer resist process. Therefore, these can be suitably used for pattern formation in semiconductor device manufacturing etc. which are expected to be further miniaturized in the future.

Claims (6)

A polysiloxane composition for forming a resist underlayer film comprising a polysiloxane and an acid generator, which is a polysiloxane composition comprising:
The acid generator contains an onium cation and an acid anion,
The polysiloxane composition for forming a resist underlayer film, wherein the onium cation comprises a cation represented by the following formula (1-1), a cation represented by the following formula (1-2), or a combination thereof .

(In formula (1-1), R ^1a , R ^1b and R ^1c are each independently a monovalent organic group having 1 to 20 carbon atoms, provided that among R ^1a , R ^1b and R ^1c At least one has an alicyclic structure, and m1, m2 and m3 are each independently an integer of 0 to 3. However, all of m1, m2 and m3 are never 0. n1 and n2 And n3 are each independently an integer of 0 to 2. When m1 is 2 or more, plural R ^1a may be the same or different, and when m2 is 2 or more, plural R ^1b is the same When m3 is 2 or more, plural R ^{1c 's} may be the same or different.
In formula (1-2), R ² is a monovalent organic group having 1 to 20 carbon atoms. p, q and r are each independently an integer of 0 to 2; When p is 2 or more, plural R ^{2 s} may be the same or different. ) Resist underlayer film forming polysiloxane composition according to claim 1 the sum of the atomic weights of atoms constituting the acid anion is 350 or less. The polysiloxane composition for resist lower layer film formation of Claim 1 or Claim 2 in which the said acid anion is represented by a following formula (2-a).

(In formula (2-a), R ³ is a monovalent organic group having 1 to 20 carbon atoms.) The polysiloxane composition for forming a resist underlayer film according to claim 1 , wherein the polysiloxane is a hydrolytic condensate of a compound containing a silane compound represented by the following formula (i).

(In formula (i), R ^A is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. X is a halogen atom or —OR ^B. R ^B is a ^C 1 to 20 carbon atom. ^A is an integer of 0 to 3. When R ^A is plural, plural R ^{A s} may be the same or different, and when X is plural, plural Xs may be the same But it may be different.) Forming a resist underlayer film on one side of the substrate;
Forming a resist pattern on the side opposite to the substrate of the resist underlayer film, and dry etching the resist underlayer film and the substrate sequentially using the resist pattern as a mask,
The pattern formation method which forms the said resist underlayer film with the polysiloxane composition for resist underlayer film formation of any one of Claims 1-4 . The step of forming the resist pattern is
Forming a resist film on the surface of the resist underlayer film opposite to the substrate using a radiation sensitive resin composition;
The pattern formation method according to claim 5 , comprising the steps of: exposing the resist film; and developing the exposed resist film using an organic solvent.