JP2008152203A - Underlying resist composition, novel compound useful for the composition and pattern forming method using the composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composition capable of forming an underlying resist layer which excels in etching resistance and antireflection function and reduces scum on an upper layer for image formation, a novel compound added to the composition, and a pattern forming method using the composition. <P>SOLUTION: The underlying resist composition comprises (A) a resin having at least one of an aromatic cyclic hydrocarbon structure and an alicyclic hydrocarbon structure, (B) a methylol phenol compound or a methylol melamine compound which has at least one or more of adamantane structure, is activated by an acid and reacts with the component (A) to form a crosslinked structure, and (C) a compound which is thermally decomposed to generate an acid. The novel compound is a methylol novel phenol compound which is useful for the composition, has at least one or more of adamantane structure, is activated by an acid and reacts with the component (A) to form a crosslinked structure. The pattern forming method uses the composition. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a curable composition whose properties change by reaction with heat or light, a compound used in the curable composition, and a pattern forming method using the photosensitive composition. More specifically, semiconductor manufacturing processes such as ICs, circuit boards such as liquid crystals and thermal heads, and other photofabrication processes, lithographic printing plates, photosensitive compositions used in acid curable compositions, and the curability The present invention relates to a compound used in a composition and a pattern forming method using the curable composition.

Conventionally, it is known that a multilayer resist process such as a two-layer resist process or a three-layer resist process is excellent for forming a high aspect ratio pattern on a stepped substrate.
As the resist underlayer film used in the two-layer resist process, for example, a hydrocarbon compound that can be etched with oxygen gas is suitable, and furthermore, it serves as a mask when etching the underlying substrate, and therefore has high etching resistance. desirable. When the etching of the resist lower layer film using the resist upper layer film as a mask is performed by oxygen gas etching, it is desirable that the resist lower layer film is composed only of hydrocarbons not containing silicon atoms. In addition, in order to improve the line width controllability of the resist upper layer film containing silicon atoms and to reduce the pattern sidewall irregularities and pattern collapse due to standing waves, the resist underlayer film also functions as an antireflection film. Specifically, it is desirable that the reflectance from the lower layer film into the resist upper layer film can be suppressed to 1% or less.

Reflectivity is controlled by setting the material with the optimal refractive index (real part of refractive index) n value and extinction coefficient (imaginary part of refractive index) k value of the resist underlayer film to an appropriate film thickness. (Patent Document 1).
In the two-layer resist process, a resist underlayer film having a low k value and being transparent and having high etching resistance is required. In the three-layer resist process, by having higher etching resistance during substrate etching and having an appropriate k value, the substrate reflectivity can be kept low even when the resist intermediate layer film is thin. There is a need for a resist underlayer film that can be used.
In addition, as disclosed in Patent Documents 2 to 5, various resist compositions capable of forming a lower resist layer that does not require image forming ability have been proposed, and as a lower resist, dry etching resistance, antireflection performance, scum There has been a demand for compatibility of performance such as reduction.

JP 2006-293207 A Japanese Patent Laid-Open No. 2003-300923 JP 2004-177952 A JP 2002-539473 A JP-A-10-62993

  The present invention has been made in view of such problems, and is a composition capable of forming a lower resist layer having excellent etching resistance and antireflection function and having reduced scum in the upper layer for image formation, and the composition A novel compound to be added to a product and a pattern forming method using the composition are provided.

The above problems have been achieved by the following configuration.
(1) (A) a resin having at least one of an aromatic cyclic hydrocarbon structure and an alicyclic hydrocarbon structure;
(B) a methylolated phenolic compound or methylolated melamine compound having at least one adamantane structure, activated by an acid, and reacting with the component (A) to form a crosslinked structure; and
(C) A lower layer resist composition containing a compound that decomposes by heat and generates an acid.

(2) The lower resist composition according to (1), wherein the component (B) is a compound represented by the general formula (I), (IIa) or (IIb).

R ₁ , R ₃ and R ₅ each independently represents a hydrogen atom, an alkyl group, a cycloalkyl group, or —CH ₂ OW. However, either R ₁ or R ₃ represents —CH ₂ OW.
R ₂ , R ₄ , R _{6 to} R ₁₀ each independently represents a hydrogen atom, an alkyl group, or a cycloalkyl group.
X represents an n-valent linking group (preferably an n-valent group corresponding to an alkylene group, a cycloalkylene group, or a combination thereof).
n represents 2-4.
W represents a hydrogen atom or a methyl group.
However, in formula (I), any of R _{1 to} R ₄ , W, in formula (IIa), any of R _{5 to} R ₇ , W, X, or in formula (IIb), R _{8 to} R Any one of ₁₀ , W, and X has an adamantane structure.

(3) A novel compound represented by any one of the above general formulas (I), (IIa) and (IIb).
However, any _one of R _{1 to} R ₄ in formula (I), any of R _{5 to} R ₇ and X in formula (IIa), and any of R _{8 to} R ₁₀ and X in formula (IIb) is Contains an adamantane structure.

(4) A novel compound represented by the following general formula (III), (IV) or (V).

R _{11 to} R ₁₃ each represent a hydrogen atom or an alkyl group, X _{1 to} X ₂ independently represent a single bond, an alkylene or a cycloalkylene linking group, and W represents a hydrogen atom or a methyl group.
(5) A pattern forming method including a step of applying the lower layer resist composition according to (1) or (2).

The lower layer resist composition of the present invention sufficiently satisfies the dry etching resistance and antireflection function, and solves the problem of scum generation.
In addition to being used as a lower layer of a two-layer resist, the present lower layer resist can be used as a single-layer antireflection film or can be used as a multilayer resist.

Hereinafter, the present invention will be described in detail.
In addition, in the description of the group (atomic group) in this specification, the description which does not describe substitution and non-substitution includes what does not have a substituent and what has a substituent. . For example, the “alkyl group” includes not only an alkyl group having no substituent (unsubstituted alkyl group) but also an alkyl group having a substituent (substituted alkyl group).

  The lower layer resist composition of the present invention has (A) a resin having at least one of an aromatic cyclic hydrocarbon structure and an alicyclic hydrocarbon structure, and (B) at least one adamantane structure, and is activated by an acid. And a methylolated phenolic compound or methylolated melamine compound that reacts with the component (A) to form a crosslinked structure, and (C) a compound that decomposes by heat to generate an acid.

[1] (A) Resin having at least one of aromatic ring hydrocarbon structure and alicyclic hydrocarbon structure Resin (A) having at least one of aromatic ring hydrocarbon structure and alicyclic hydrocarbon structure is Furthermore, it has a reactive group for reacting with the thermal crosslinking agent (B). Examples of the reactive group include an alcoholic hydroxyl group, a phenolic hydroxyl group, an epoxy group, a phenol skeleton, and a melamine skeleton.
Content of the repeating unit which has a reactive group in resin (A) is 10-100 mol% normally with respect to all the repeating units which comprise resin (A), Preferably it is 30-100 mol%.

  The aromatic cyclic hydrocarbon structure of the resin (A) preferably has 5 to 20 carbon atoms, and examples thereof include benzene, naphthalene, anthracene, indene, and fluorene.

The alicyclic hydrocarbon structure may be monocyclic or polycyclic. Specific examples include groups having a monocyclo, bicyclo, tricyclo, tetracyclo structure or the like having 5 or more carbon atoms. The carbon number is preferably 6-30, and particularly preferably 7-25. These cycloalkyl groups may have a substituent.
For example, adamantyl group, diamantyl group, noradamantyl group, decalin residue, tricyclodecanyl group, tetracyclododecanyl group, norbornyl group, cedrol group, cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group, cyclodecanyl group And cyclododecanyl group, and cyclohexyl, norbornane, tricyclodecane, tetracyclododecane, adamantane and diamantane are preferable.

More specifically, examples of the resin (A) include novolak resin, melamine resin, polystyrene resin, poly (meth) acrylate resin, polyacetal resin, polyolefin resin, and acenaphthene resin (for example, described in JP-A No. 2000-143937). ) And the like, and may be a homopolymer, a copolymer, or a mixture of two or more.
From the viewpoint of the antireflection function in the thin film, the content of the aromatic cyclic hydrocarbon structure is preferably 50% by mass or less.
In the resin (A), the repeating unit having at least one of an aromatic hydrocarbon structure and an alicyclic hydrocarbon structure is preferably 30 to 100 mol% with respect to all the repeating units constituting the resin (A). 50 to 100 mol% is more preferable.
The resin (A) is preferably not decomposed by the action of an acid (specifically, it does not have an acetal structure or a tertiary ester structure).
The resin (A) preferably has less impurities such as metal.
The weight average molecular weight of the resin (A) is usually 500 to 200,000, preferably 1000 to 20,000.

  As a preferred form of the resin (A), a resin having the following repeating unit is exemplified.

X represents a hydrogen atom or a methyl group.
R ₂₁ and R ₂₂ each independently represents an organic group containing at least one of an aromatic cyclic hydrocarbon structure and an alicyclic hydrocarbon structure.
R _{23 to} R ₅₃ each independently represents a hydrogen atom, an alkyl group, a hydroxyl group, an alkoxy group, or an organic group containing at least one of an aromatic hydrocarbon structure and an alicyclic hydrocarbon structure.

  The content of the resin (A) in the composition is generally 50 to 95% by mass, preferably 60 to 90% by mass, based on the total solid content.

[2] Thermal crosslinking agent that can be activated by acid (B) and react with the component (A) to form a crosslinked structure The thermal crosslinking agent used in the present invention has at least one adamantane structure And a phenol compound or a melamine compound which is activated by an acid and reacts with the component (A) to form a crosslinked structure.
The number of adamantane structures possessed by the thermal crosslinking agent is preferably 1 to 5, and more preferably 1 to 3.
2-20 are preferable and, as for the number of the methylol groups which a thermal crosslinking agent has, 2-8 are more preferable.
The molecular weight of these thermal crosslinking agents is generally 280 to 3000, preferably 280 to 1000.

(B1) As the phenol compound, a compound represented by any one of the general formulas (I), (IIa) and (IIb) is preferable.

R ₁ , R ₃ and R ₅ each independently represents a hydrogen atom, an alkyl group, a cycloalkyl group, or —CH ₂ OW. However, either R ₁ or R ₃ represents —CH ₂ OW.
R ₂ , R ₄ , R _{6 to} R ₁₀ each independently represents a hydrogen atom, an alkyl group, or a cycloalkyl group.
X represents an n-valent linking group (preferably an alkylene group, a cycloalkylene group, or an n-valent group obtained by removing n-2 arbitrary hydrogen atoms for a divalent group obtained by combining these groups). .
n represents 2-4.
W represents a hydrogen atom or a methyl group.
However, in formula (I), any one of R _{1 to} R ₄ , W, in formula (IIa), any of R _{5 to} R ₇ , W, X, or in formula (IIb), R _{8 to} R ₁₀ , W, or X has an adamantane structure.

In particular, a methylolated phenol compound represented by any one of the above general formulas (I), (IIa) and (IIb) (provided that any _one of R _{1 to} R ₄ in formula (I), formula (IIa) Is any one of R _{5 to} R ₇ and X, and in formula (IIb), any one of R _{8 to} R ₁₀ and X contains an adamantane structure.

  A compound represented by the following general formula (III), (IV) or (V).

R _{11 to} R ₁₃ each represent a hydrogen atom or an alkyl group, X _{1 to} X ₂ independently represent a single bond, an alkylene group or a cycloalkylene group, and W represents a hydrogen atom or a methyl group.

  As the compound represented by the formula (I), a compound represented by the formula (III) is preferable.

  Preferred specific examples of the compound represented by the formula (III) are listed below. W represents a hydrogen atom or a methyl group.

  Preferred specific examples of the compound represented by formula (I) (other than the compound represented by formula (III)) are shown below.

As the compound represented by the formula (IIa), a compound represented by the formula (IV) or (V) is preferable.
Preferred specific examples of the compound represented by the formula (IV) are shown below.

  Preferred specific examples of the compound represented by the formula (V) are shown below.

  Preferred specific examples of the compound represented by the formula (IIb) are shown below.

(B2) Examples of methylolated melamine compounds include compounds represented by the following general formula.

Q _{1 to} Q ₆ each independently represent a hydrogen atom, a cyclohexyl group, a group containing an adamantane structure, or —CH ₂ OW. W represents a hydrogen atom or a methyl group. At least one of Q _{1 to} Q ₆ is a group containing an adamantane structure, and at least one of Q _{1 to} Q ₆ is —CH ₂ OH.

  Preferred specific examples of methylolated melamine compounds are listed below. W represents a hydrogen atom or a methyl group.

The thermal crosslinking agent (B1) can be synthesized, for example, as follows.
There are a method of using phenol containing adamantane as a raw material and a method of introducing adamantane into a phenol compound. In general, a phenol containing adamantane is used as a raw material, and methylolation is performed according to the description in JP-A No. 2003-300923. There is also a method in which phenol containing adamantane is once converted into a derivative such as dimethylaminomethylol and then led to the target product.
The thermal crosslinking agent (B2) is generally a method of reacting an adamantane-containing amine with a melamine compound to form a methylol.
The addition amount of the thermal crosslinking agent is generally 1 to 100% by mass, preferably 10 to 50% by mass, based on the total solid content of the composition.

[3] (C) Compound that decomposes by heat to generate acid (thermal acid generator)
(C) A component is a compound which decomposes | disassembles by heating and generates the acid which accelerates | stimulates the thermal crosslinking reaction of (A) resin and (B) thermal crosslinking agent.
Examples of such a compound that decomposes by heat to generate an acid include iodonium salts such as sulfonic acid ester compounds, disulfone compounds, sulfonium salts, and diaryl iodonium salts, preferably sulfonic acid ester compounds and diaryl iodonium. Salt.

For use in an antireflective film material composition for resist or a lower layer forming composition of a multilayer resist, a compound having a temperature of 150 to 200 ° C. at which it decomposes to generate an acid is suitable. It has been found that a thermal acid generator compound having a decomposition temperature lower than 150 ° C. causes a problem in storage stability, that is, a crosslinking reaction occurs during storage and the molecular weight increases, thereby impairing the coating property. On the other hand, a compound having a thermal decomposition temperature exceeding 200 ° C. is inefficient because a high temperature is required for crosslinking, and the degree of crosslinking tends to vary in the coating film.
(C) The temperature which begins to generate | occur | produce an acid with the heat | fever of the thermal acid generator used as a component is 150-200 degreeC, Preferably it is 170-190 degreeC.

Examples of the diaryl iodonium salt compound include salts of a diaryl iodonium cation and an organic sulfonic acid anion, SbF ₆ anion, PF 6 anion or AsF ₆ anion. Here, the anion of an organic sulfonic acid is preferable as the anion. Specific examples of the diaryliodonium salt compound include the following compounds.

  Among these, a salt of diaryliodonium and organic sulfonic acid is preferable from the viewpoints of stability and solvent solubility. Among them, a salt of a diaryl iodonium cation and an organic sulfonate anion having a linear or branched alkyl group having 1 to 12 carbon atoms or an alkoxy group having 1 to 12 carbon atoms as a substituent on an aryl group is from the viewpoint of safety. Is also preferable. Here, as a linear or branched alkyl group having 1 to 12 carbon atoms or an alkoxy group having 1 to 12 carbon atoms, methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, sec -Butyl group, i-butyl group, t-butyl group, n-amyl group, i-amyl group, t-amyl group, n-hexyl group, n-heptyl group, n-octyl group, 2-ethylhexyl group, n Examples include -decyl group, n-dodecyl group, cyclopropyl group, cyclopentyl group, cyclohexyl group, methoxy group, ethoxy group, propoxy group, and butoxy group. In addition, examples of the aryl group include a phenyl group, a naphthyl group, an anthryl group, and a phenanthryl group. Examples of the organic sulfonate anion include trifluoromethanesulfonate, methanesulfonate, a linear or branched alkyl group having 1 to 12 carbon atoms on an aryl group, and an alkoxy group having 1 to 12 carbon atoms (these alkyl groups, alkoxy groups). Examples of the group are the same as those described above.) Alternatively, an aryl sulfonate that may have a halogen atom as a substituent is preferred from the viewpoint of solvent solubility. Examples of the aryl group are the same as those described above. These thermal acid generators can be used singly or in combination of two or more.

  As the sulfonate compound, a compound represented by the following general formula (ZIV), (ZV) or (ZVI) is preferable.

In general formulas (ZIV) to (ZVI),
Ar ₃ and Ar ₄ each independently represents an aryl group.
R ₂₀₆ represents an alkyl group or an aryl group.
_R207 and _R208 each independently represents an alkyl group, an aryl group, or an electron-withdrawing group. R ₂₀₇ is preferably an aryl group.
R ₂₀₈ is preferably an electron-withdrawing group, more preferably a cyano group or a fluoroalkyl group.
A represents an alkylene group, an alkenylene group or an arylene group.

  Specific examples of preferred sulfonic acid ester compounds are listed below, but are not limited thereto.

  The amount of the thermal acid generator added is generally 0.1 to 5% by mass, preferably 0.5 to 3% by mass, based on the total solid content of the composition.

[4] (D) Solvent and (E) Other Additives The resist composition of the present invention can be further added with a light absorber, an adhesion assistant, and a surfactant as necessary.

  Examples of the light absorber include anthracene and derivatives thereof, β-carbonylnaphthalene and derivatives thereof, benzophenone and derivatives thereof, phenanthrene and derivatives thereof, quinoline and derivatives thereof, acridine and derivatives thereof, and thioxanthone and derivatives thereof. Specifically, anthracene, 9-hydroxymethylanthracene, 9-carboxyanthracene, 2-naphthoic acid, 1-hydroxy-2-naphthoic acid, 3-hydroxy-2-naphthoic acid, 7-methoxy-3-hydroxy-2- Naphthoic acid, benzophenone, 2,4-dihydroxybenzophenone, 4,4′-dihydroxybenzophenone, 2,3,4-trihydroxybenzophenone, phenanthrene, hydroxyphenanthrene, quinoline, N-phenylacridine, thioxanthone, diethylthioxanthone, etc. Can be mentioned. The light absorber is usually blended at a ratio of 30 parts by mass or less, preferably 20 parts by mass or less, with respect to 100 parts by mass of the composition.

  The adhesion assistant is added mainly for the purpose of improving the adhesion to the substrate or another resist layer and preventing the resist from peeling off in the etching process. Specific examples include chlorosilanes such as trimethylchlorosilane, dimethylvinylchlorosilane, methyldiphenylchlorosilane, chloromethyldimethylchlorosilane, trimethylmethoxysilane, dimethyldiethoxysilane, methyldimethoxysilane, dimethylvinylethoxysilane, diphenyldimethoxysilane, Alkoxysilanes such as enyltriethoxysilane, hexamethyldisilazane, N, N′-bis (trimethylsiline) urea, silazanes such as dimethyltrimethylsilylamine, trimethylsilylimidazole, vinyltrichlorosilane, γ-chloropropyltrimethoxysilane, γ -Silanes such as aminopropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane, benzotriazole, benzimidazole , Indazole, imidazole, 2-mercaptobenzimidazole, 2-mercaptobenzthiazole, 2-mercaptobenzoxazole, urazolethiouracil, mercaptoimidazole, mercaptopyrimidine, etc., 1,1-dimethylurea, 1,3-dimethylurea, etc. And urea or thiourea compounds.

  These adhesion assistants are usually blended at a ratio of 0 to 10% by mass, preferably 0 to 5% by mass with respect to 100% by mass of the composition.

  In the composition of the present invention, a surfactant can be blended in order to further improve coating properties such as striation. Examples of the surfactant include polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene cetyl ether, polyoxyethylene alkyl ethers such as polyoxyethylene oleyl ether, polyoxyethylene octylphenol ether, polyoxyethylene nonyl Polyoxyethylene alkyl allyl ethers such as phenol ether, polyoxyethylene / polyoxypropylene block copolymers, sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan monooleate, sorbitan trioleate, sorbitan tristearate Sorbitan fatty acid esters such as rate, polyoxyethylene sorbitan monolaurate, polyoxyethylene sol Nonionic surfactants such as tan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan trioleate, polyoxyethylene sorbitan tristearate, and other polyoxyethylene sorbitan fatty acid esters, megafacs F171, F173 (large Nippon Ink Co., Ltd.), Florard FC430, FC431 (Sumitomo 3M Co., Ltd.), Asahi Guard AG710, Surflon S-382, SC101, SC102, SC103, SC104, SC105, SC106 (Asahi Glass Co., Ltd.) Fluorine-based surfactant, organosiloxane polymer KP341 (manufactured by Shin-Etsu Chemical Co., Ltd.), acrylic acid-based or methacrylic acid-based (co) polymerized polyflow No. 75, no. 95 (manufactured by Kyoeisha Yushi Chemical Co., Ltd.). Of these surfactants, fluorine-based surfactants and silicon-based surfactants are particularly preferable. The compounding quantity of these surfactant is 0-2 mass% normally per 100 mass% of solid content in the composition of this invention, Preferably it is 0-1 mass%.

  These surfactants may be added alone or in some combination.

As the solvent (D) for dissolving the composition of the present invention, an appropriate solvent for dissolving the resin (A) is usually used. For example, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, methyl cellosolve acetate, ethyl cellosolve acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol methyl ether acetate, propylene glycol propyl ether acetate, toluene, xylene, methyl ethyl ketone, cyclopenta Non, cyclohexanone, ethyl 2-hydroxypropionate, ethyl 2-hydroxy-2-methylpropionate, ethyl ethoxyacetate, ethyl hydroxyacetate, methyl 2-hydroxy-3-methylbutanoate, methyl 3-methoxypropionate, 3-methoxy Ethyl propionate, ethyl 3-ethoxypropionate, 3-ethoxypro Methyl propionic acid, methyl pyruvate, ethyl pyruvate, ethyl acetate, can be used butyl acetate. These organic solvents are used alone or in combination of two or more.
Preferred solvents include propylene glycol methyl ether, cyclohexanone, 2-heptanone, ethyl lactate, and propylene glycol monoethyl ether acetate.
Further, a high boiling point solvent such as N-methylformamide, N, N-dimethylformamide, N-methylacetamide, N, N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, benzyl ethyl ether can be mixed and used. it can.

[5] Usage Method A preferable solid content concentration in the preparation of the resist is 5 to 20% by mass.
The prepared solution is applied by a spin coating method, a spray method, or the like, and a resist layer is formed on the substrate. The film thickness is preferably from 0.1 to 1.2 μm, more preferably from 0.2 to 0.5 μm.
The first resist layer is heat treated. As temperature of heat processing, 150-250 degreeC is preferable, Furthermore, 170-240 degreeC is preferable, and 180-230 degreeC is especially preferable. This heat treatment can be performed using an apparatus such as a hot plate or a heat oven. Moreover, although the heat processing time changes with the said heat processing temperature, in the case of 180-230 degreeC heat processing, it is preferable to set to the range of 10 second-1000 second, and also 20-600 second is preferable.

  The second resist layer is formed on the first resist layer, and can be performed in the same manner as the formation of the first resist layer. Usually, a silicon-containing composition is used for the second resist layer. The film thickness of the second resist layer is preferably 0.03 to 0.5 μm, more preferably 0.04 to 0.3 μm, and particularly preferably 0.05 to 0.15 μm.

The obtained two-layer resist is then subjected to a pattern formation step. As a first step, the second layer resist composition is first subjected to pattern formation processing. Mask alignment is performed as necessary, and high energy rays are irradiated through the mask to make the irradiated resist composition soluble in an alkaline aqueous solution and developed with the alkaline aqueous solution to form a pattern.
Next, dry etching is performed as a second stage, and this operation is performed by oxygen plasma etching using the resist composition film pattern as a mask to form a fine pattern having a high aspect ratio. The etching of the organic polymer film by the oxygen plasma etching is exactly the same technique as the plasma etching used when the resist film is peeled off after completion of the etching process of the substrate by the conventional photoetching operation. This operation can be performed, for example, by a cylindrical plasma etching apparatus using oxygen as a reactive gas, that is, an etching gas. A gas such as sulfurous acid gas may be mixed with oxygen gas.

(Synthesis of thermal crosslinking agent)
<Synthesis of Compound (B-1)>

100 mL of a 20% aqueous solution of potassium hydroxide was prepared in a 500 mL eggplant flask, and 26.4 g of adamantylphenol and 50 mL of methanol were added and well stirred. Then, while cooling with ice water, 112.3 mL of 37% formalin aqueous solution was added dropwise over 30 minutes and stirred at room temperature for 30 hours. After completion of the reaction, the reaction mixture was neutralized with 1 mol / L dilute hydrochloric acid and extracted twice with ethyl acetate. The oil layer was washed with pure water, dried over sodium sulfate, concentrated, and then separated on a silica gel column (hexane: ethyl acetate = 2: 1) to obtain 10 g of the desired compound (B-1).
¹ H-NMR (400 MHz, DMSO) δ 1.65-1.90 (m, 13H), 2.00-2.10 (bs, 3H), 4.54 (d, 4H), 5.19 (t, 2H), 7.13 (s, 2H), 8.34 (s, 1H)

<Synthesis of Compound (B-2)>

  Compound (B-2) was synthesized in the same manner as for compound (B-1).

<Synthesis of Compound (B-3)>

When 1.5 L of an aqueous sodium hydroxide solution is prepared, 10 g of 2-chloro-4,6-diamino-1,3,5-triazine and 17 g of adamantylamine are added. The reaction is heated to reflux with good stirring for 48 hours. After completion of the reaction, the reaction mixture was cooled to room temperature, the crystals were filtered, and then separated on a silica gel column (chloroform: methanol = 20: 1) to obtain 10 g of compound (B-3-1).
Add the compound (B-3-1) to 10 mL of 37% formalin solution and dissolve well. The mixture is stirred at 75 ° C. for 1 hour under heating conditions. After completion of the reaction, the reaction mixture was cooled to room temperature, the crystals were filtered, and then separated on a silica gel column (chloroform: methanol = 10: 1) to obtain 8 g of compound (B-3).

<Synthesis of Compound (B-4)>

  Compound (B-4) was synthesized in the same manner as Compound (B-1) except that the reaction temperature was changed to 50 ° C.

<Synthesis of Compound (B-5)>

20.0 g of the raw material (B-5-1) was well dissolved in 200 mL of ethyl acetate and 40 mL of ethanol. Thereafter, while cooling with ice water, 72 mL of 50% dimethylamine aqueous solution and then 26 mL of 37% formalin aqueous solution were added dropwise over 30 minutes, and the mixture was stirred at 50 ° C. for 30 hours. After completion of the reaction, the precipitated white solid was filtered to obtain 20 g of compound (B-5-2). This was dissolved in acetic anhydride mL and stirred at 130 ° C. for an hour. After completion of the reaction, the mixture was extracted twice with ethyl acetate, and the oil layer was washed with sodium bicarbonate and pure water, dried over sodium sulfate and concentrated to obtain 16 g of compound (B-5-3). This was dissolved in 100 mL of tetrahydrofuran, and a 20% aqueous potassium hydroxide solution was added dropwise over 10 minutes, followed by stirring for 1 hour. After completion of the reaction, the reaction mixture was neutralized with 1 mol / L dilute hydrochloric acid and extracted twice with ethyl acetate. The oil layer was washed with pure water, dried over sodium sulfate, concentrated, and then separated on a silica gel column (hexane: ethyl acetate = 2: 1) to obtain 10 g of the desired compound (B-5).
¹ H-NMR (400 MHz, CDCl ₃ ) δ 1.80-1.55 (m, 36H), 4.65 (d, 4H), 6.82 (d, 2H), 7.02 (s, 2H), 7.20 (d, 2H), 7.44 (bs, 2H)

<Synthesis of Comparative Compound (Ba)>

  Synthesized according to the examples of JP-A-2003-300923.

<Synthesis of Comparative Compound (Bb)>

  Compound (Bb) was synthesized in the same manner as for compound (B-1).

<Preparation of lower layer resist>
The components shown in the following table were dissolved in a solvent to prepare a positive resist solution by filtration through a 0.1 μm polyethylene filter. The prepared positive resist composition was evaluated by the following method, and the results are shown in the following table. All numerical units are g.

The weight average molecular weights and dispersities (Mw / Mn) of the resins (A-1) to (A-5) are as follows.
Resin (A-1): Weight average molecular weight; 15000, dispersity: 1.7
Resin (A-2): Weight average molecular weight; 12000, dispersity: 4.6
Resin (A-3): Weight average molecular weight; 12000, dispersity: 2.0
Resin (A-4): Weight average molecular weight; 8000, dispersity: 2.2
Resin (A-5): Weight average molecular weight; 4000, degree of dispersion; 2.0

PGMEA: Propylene glycol methyl ether acetate MAK: 2-heptanone EL: Ethyl lactate W-1: Troisol S366 (manufactured by Troy Chemical Co., silicon)
W-2: MegaFuck F176 (Dainippon Ink Chemical Co., Ltd., fluorine-based)

<Antireflection evaluation>
Resists 1 to 12 and comparative resists A and B were spin-coated on a silicon wafer and baked at 200 ° C. for 60 seconds to form a 300 nm antireflection film. The optical parameter k value at 196 nm of the obtained film was measured with an ellipsometer (manufactured by JA Woollam Japan). A smaller value indicates better antireflection performance.

<Scum evaluation>
Resists 1 to 12 and comparative resists A and B were spin-coated on a silicon wafer and baked at 200 ° C. for 60 seconds to form a 500 nm antireflection film. On this first resist layer, an upper layer resist composition TIS-2000 (manufactured by Fuji Film Co., Ltd.) having a solid content concentration of 6% is similarly applied, heated at 130 ° C. for 90 seconds, and an upper layer resist layer having a thickness of 150 nm. Got. The wafer thus obtained was exposed to an ArF excimer stepper manufactured by ASML with a resolution mask and the exposure amount varied. Then, after heating at 100 ° C. for 90 seconds in a clean room, the film was developed with 2.38 mass% tetramethylammonium hydroxide developer for 60 seconds, rinsed with distilled water and dried to obtain a pattern (upper layer pattern). The formed resist pattern was observed with a scanning electron microscope. Evaluation was made based on the remaining amount of development residue (scum) in a resist pattern having a line width of 90 nm. Evaluation was made with ◯ indicating that the residue was not observed, × indicating that the residue was observed, and Δ indicating the middle.

<Dry etching resistance evaluation>
The upper layer pattern obtained above was further etched (dry development) using a parallel plate type reactive ion etching apparatus DES-245R manufactured by Plasma System, and a pattern was formed on the lower layer. The etching gas was oxygen, the pressure was 20 mTorr, and the applied power was 100 mW / cm ² .
The etching resistance is shown as a relative ratio of etching rate to polyhydroxystyrene having a molecular weight of 8000.
The results are shown in Table 2.

  From the results in Table 2, it can be seen that the composition of the present invention is good in terms of overall performance.

Claims (5)

(A) a resin having at least one of an aromatic cyclic hydrocarbon structure and an alicyclic hydrocarbon structure;
(B) a methylolated phenolic compound or methylolated melamine compound having at least one adamantane structure, activated by an acid, and reacting with the component (A) to form a crosslinked structure; and
(C) A lower layer resist composition containing a compound that decomposes by heat to generate an acid. The underlayer resist composition according to claim 1, wherein the component (B) is a compound represented by the following general formula (I), (IIa) or (IIb).

R ₁ , R ₃ and R ₅ each independently represents a hydrogen atom, an alkyl group, a cycloalkyl group, or —CH ₂ OW. However, either R ₁ or R ₃ represents —CH ₂ OW.
R ₂ , R ₄ , R _{6 to} R ₁₀ each independently represents a hydrogen atom, an alkyl group, or a cycloalkyl group.
X represents an n-valent linking group.
n represents 2-4.
W represents a hydrogen atom or a methyl group.
However, in formula (I), any one of R _{1 to} R ₄ , W, in formula (IIa), any of R _{5 to} R ₇ , W, X, or in formula (IIb), R _{8 to} R ₁₀ , W, or X has an adamantane structure. A compound represented by the following general formula (I), (IIa) or (IIb).

R ₁ , R ₃ and R ₅ each independently represents a hydrogen atom, an alkyl group, a cycloalkyl group, or —CH ₂ OW. However, either R ₁ or R ₃ represents —CH ₂ OW.
R ₂ , R ₄ , R _{6 to} R ₁₀ each independently represents a hydrogen atom, an alkyl group, or a cycloalkyl group.
X represents an n-valent linking group, and n represents 2 to 4.
W represents a hydrogen atom or a methyl group.
However, any _one of R _{1 to} R ₄ in formula (I), any of R _{5 to} R ₇ and X in formula (IIa), and any of R _{8 to} R ₁₀ and X in formula (IIb) is Has an adamantane structure. A compound represented by the following general formula (III), (IV) or (V).

R _{11 to} R ₁₃ each represent a hydrogen atom or an alkyl group, X _{1 to} X ₂ independently represent a single bond, an alkylene group or a cycloalkylene group, and W represents a hydrogen atom or a methyl group.   The pattern formation method including the process of apply | coating the lower layer resist composition of Claim 1 or 2.