WO2018173446A1

WO2018173446A1 - Pattern forming method

Info

Publication number: WO2018173446A1
Application number: PCT/JP2018/001668
Authority: WO
Inventors: 信也峯岸; 恭志中川; 智昭瀬古; 大貴中津
Original assignee: Jsr株式会社
Priority date: 2017-03-22
Filing date: 2018-01-19
Publication date: 2018-09-27

Abstract

This pattern forming method comprises: a step for coating a substrate with an underlayer film-forming composition; a step for directly or indirectly coating a underlayer film formed in the underlayer film-forming composition coating step with a resist film-forming radiation sensitive composition; a step for exposing the resist film formed in the resist film-forming radiation sensitive composition coating step; and a step for developing the exposed resist film, wherein the underlayer film-forming composition contains a radiation sensitive base generator for generating a base through the effect of radiation or a radiation sensitive acid generator for generating an acid through the effect of radiation, and the resist film-forming radiation sensitive composition contains 50% or more by mass, in terms of the solid content, of a metal-containing compound. Preferably, the underlayer film forming composition further contains an organic polymer, and an organic underlayer film is formed in the underlayer film-forming composition coating step. The carbon content in the organic underlayer film is preferably 50% by mass or more.

Description

Pattern formation method

The present invention relates to a pattern forming method.

In a general pattern forming method used for microfabrication by lithography, a resist film formed from a radiation-sensitive composition for forming a resist film is treated with deep ultraviolet light (for example, ArF excimer laser light, KrF excimer laser light, etc.), extreme ultraviolet light ( The exposed portion is exposed to an electromagnetic wave such as EUV) or a charged particle beam such as an electron beam to generate an acid at the exposed portion. Then, a chemical reaction using this acid as a catalyst causes a difference in the dissolution rate with respect to the developer in the exposed area and the unexposed area, thereby forming a pattern on the substrate. The formed pattern can be used as a mask or the like in substrate processing.

Such a pattern forming method is required to improve resist performance such as sensitivity as the processing technique becomes finer. In response to this requirement, the types of organic polymers, acid generators and other components used in the radiation-sensitive composition for resist film formation, the molecular structure, and the like have been studied, and further their combinations have been studied in detail ( (See JP-A-11-125907, JP-A-8-146610, and JP-A-2000-298347). In addition, in the pattern formation method, a radiation sensitive composition for forming a resist film containing a metal-containing compound is used instead of an organic polymer in order to improve sensitivity, or a finer pattern is formed on the resist film. Therefore, the use of a lower layer film has been studied.

JP-A-11-125907 JP-A-8-146610 JP 2000-298347 A

As a result, pattern miniaturization has progressed to the level of 40 nm or less at present, but higher resist performance is required in the pattern forming method, and further improvement in sensitivity is particularly required. In addition, when using the conventional composition for forming a lower layer film, the pattern collapse in the resist film formed on the lower layer film, so-called pattern collapse tends to occur, so suppression of this pattern collapse is also required. Yes.

The present invention has been made based on the above circumstances, and an object thereof is to provide a pattern forming method capable of suppressing pattern collapse while exhibiting excellent sensitivity.

The invention made in order to solve the above-mentioned problems includes a step of applying a composition for forming an underlayer film on a substrate, and a resist directly or indirectly on an underlayer film formed by the above-described composition application process for forming an underlayer film. A step of applying the radiation-sensitive composition for film formation, a step of exposing the resist film formed by the radiation-sensitive composition application step for forming the resist film, and a step of developing the exposed resist film The underlayer film forming composition contains a radiation sensitive base generator that generates a base by the action of radiation or a radiation sensitive acid generator that generates an acid by the action of radiation, and the resist film The forming radiation-sensitive composition is a pattern forming method containing a metal-containing compound in an amount of 50% by mass or more in terms of solid content.

Here, "radiation" is a concept that includes not only electromagnetic waves such as far ultraviolet rays and extreme ultraviolet rays but also charged particle beams such as electron beams.

According to the pattern forming method of the present invention, pattern collapse can be suppressed while exhibiting excellent sensitivity. Therefore, this pattern forming method can be suitably used for a semiconductor device processing process and the like that are expected to be further miniaturized in the future.

<Pattern formation method>
The pattern forming method includes a step of applying a composition for forming an underlayer film on a substrate (a composition applying step for forming an underlayer film) and an underlayer film formed by the above-described composition applying step for forming an underlayer film The resist film-forming radiation-sensitive composition is applied directly or indirectly (resist-film-forming radiation-sensitive composition coating process) and the resist film-forming radiation-sensitive composition coating process. A step of exposing the resist film (exposure step) and a step of developing the exposed resist film (development step). The composition for forming an underlayer film is a radiation-sensitive base generator that generates a base by the action of radiation (hereinafter also referred to as “[A1] photobase generator”), or a radiation-sensitive that generates an acid by the action of radiation. Acid acid generator (hereinafter also referred to as “[A2] photoacid generator”). The radiation-sensitive composition for forming a resist film contains a metal-containing compound (hereinafter also referred to as “[P] metal-containing compound”) in an amount of 50% by mass or more in terms of solid content.

The pattern forming method includes the above-described steps, and the underlayer film forming composition used in the underlayer film forming composition coating step contains [A1] a photobase generator or [A2] a photoacid generator, The radiation sensitive composition for resist film formation used in the resist film forming radiation sensitive composition coating step contains [P] metal-containing compound in an amount of 50% by mass or more in terms of solid content, thereby exhibiting excellent sensitivity. While pattern collapse can be suppressed. The reason why the pattern forming method has the above-described configuration provides the above-mentioned effect is not necessarily clear, but can be estimated as follows, for example. That is, in the pattern forming method, in the exposed portion of the resist film, the [P] metal-containing compound or the like absorbs exposure light and emits secondary electrons, and the secondary electrons crosslink the [P] metal-containing compound or the like. It is considered that the pattern can be formed because the solubility in the developing solution is reduced due to the occurrence of. Here, in the pattern formation method, since the lower layer film contains [A1] photobase generator or [A2] photoacid generator, the region below the exposed portion of the resist film in the lower layer film is caused by the action of exposure light. It is considered that a base or acid is generated, and this base or acid promotes cross-linking of the [P] metal-containing compound at the bottom of the exposed portion of the resist film. As described above, in the pattern formation method, the [P1] metal-containing compound at the bottom of the exposed portion of the resist film is cross-linked by the [A1] photobase generator or the [A2] photoacid generator contained in the lower layer film. Therefore, it is considered that pattern collapse can be suppressed while exhibiting excellent sensitivity.

Hereinafter, for the pattern formation method, the underlayer film forming composition used in the underlayer film forming composition coating process and the resist film forming radiation sensitive composition used in the resist film forming radiation sensitive composition coating process Then, the details of each step will be described.

[Composition for forming lower layer film]
The underlayer film forming composition contains [A1] a photobase generator or [A2] a photoacid generator. The composition for forming the lower layer film has an organic polymer (hereinafter also referred to as “[B1] organic polymer”), an inorganic polymer (hereinafter also referred to as “[B2] inorganic polymer”), and / or a molecular weight of 600. It is preferable to further contain 3,000 or less aromatic ring-containing compounds (hereinafter also referred to as “[B3] aromatic ring-containing compound”), and more preferably [B1] an organic polymer. Moreover, it is preferable that the composition for lower layer film formation contains a solvent (henceforth "[C] solvent") further. Here, the “organic polymer” refers to a polymer containing a carbon atom in the main chain, and the “inorganic polymer” refers to a polymer not containing a carbon atom in the main chain. Hereinafter, each component will be described.

([A1] Photobase generator)
[A1] The photobase generator is a component that generates a base by the action of radiation. [A1] Examples of the base generated from the photobase generator include amines such as primary amine, secondary amine, and tertiary amine. [A1] The photobase generator can be used alone or in combination of two or more.

[A1] Examples of the photobase generator include transition metal complexes such as cobalt, orthonitrobenzyl carbamates, α, α-dimethyl-3,5-dimethoxybenzyl carbamates, acyloxyiminos, acetophenone compounds, and the like. Can do.

Examples of the cobalt transition metal complex include compounds described in paragraph [0198] of JP-A-2017-009673.

Examples of orthonitrobenzyl carbamates include [[(2-nitrobenzyl) oxy] carbonyl] methylamine, [[(2-nitrobenzyl) oxy] carbonyl] propylamine, and [[(2-nitrobenzyl) oxy] carbonyl. ] Hexylamine, [[(2-nitrobenzyl) oxy] carbonyl] cyclohexylamine, [[(2-nitrobenzyl) oxy] carbonyl] aniline, [[(2-nitrobenzyl) oxy] carbonyl] piperidine, bis [[ (2-Nitrobenzyl) oxy] carbonyl] hexamethylenediamine, bis [[(2-nitrobenzyl) oxy] carbonyl] phenylenediamine, bis [[(2-nitrobenzyl) oxy] carbonyl] toluenediamine, bis [[( 2-Nitrobenzyl) oxy Carbonyl] diaminodiphenylmethane, bis [[(2-nitrobenzyl) oxy] carbonyl] piperazine, [[(2,6-dinitrobenzyl) oxy] carbonyl] methylamine, [[(2,6-dinitrobenzyl) oxy] carbonyl ] Propylamine, [[(2,6-dinitrobenzyl) oxy] carbonyl] hexylamine, [[(2,6-dinitrobenzyl) oxy] carbonyl] cyclohexylamine, [[(2,6-dinitrobenzyl) oxy] Carbonyl] aniline, [[(2,6-dinitrobenzyl) oxy] carbonyl] piperidine, bis [[(2,6-dinitrobenzyl) oxy] carbonyl] hexamethylenediamine, bis [[(2,6-dinitrobenzyl) Oxy] carbonyl] phenylenediamine, bis [ (2,6-dinitrobenzyl) oxy] carbonyl] toluenediamine, bis [[(2,6-dinitrobenzyl) oxy] carbonyl] diaminodiphenylmethane, bis [[(2,6-dinitrobenzyl) oxy] carbonyl] piperazine, etc. Is mentioned.

Examples of α, α-dimethyl-3,5-dimethoxybenzyl carbamates include [[(α, α-dimethyl-3,5-dimethoxybenzyl) oxy] carbonyl] methylamine, [[(α, α-dimethyl- 3,5-dimethoxybenzyl) oxy] carbonyl] propylamine, [[(α, α-dimethyl-3,5-dimethoxybenzyl) oxy] carbonyl] hexylamine, [[(α, α-dimethyl-3,5- Dimethoxybenzyl) oxy] carbonyl] cyclohexylamine, [[(α, α-dimethyl-3,5-dimethoxybenzyl) oxy] carbonyl] aniline, [[(α, α-dimethyl-3,5-dimethoxybenzyl) oxy] Carbonyl] piperidine, bis [[(α, α-dimethyl-3,5-dimethoxybenzyl) oxy] carbonyl] he Samethylenediamine, bis [[(α, α-dimethyl-3,5-dimethoxybenzyl) oxy] carbonyl] phenylenediamine, bis [[(α, α-dimethyl-3,5-dimethoxybenzyl) oxy] carbonyl] toluene Diamine, bis [[(α, α-dimethyl-3,5-dimethoxybenzyl) oxy] carbonyl] diaminodiphenylmethane, bis [[(α, α-dimethyl-3,5-dimethoxybenzyl) oxy] carbonyl] piperazine, etc. Can be mentioned.

Examples of acyloxyiminos include propionyl acetophenone oxime, propionyl benzophenone oxime, propionyl acetone oxime, butyryl acetophenone oxime, butyryl benzophenone oxime, butyryl acetone oxime, adipoyl acetophenone oxime, adipoyl benzophenone oxime, adipoyl acetone Examples thereof include oxime, acryloyl acetophenone oxime, acryloyl benzophenone oxime, and acryloyl acetone oxime.

Examples of acetophenone compounds include 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) butan-1-one, 2-dimethylamino-2- (4-methylbenzyl) -1- (4-morpho Acetophenone compounds having an α-aminoketone structure, such as phosphorus-4-yl-phenyl) -butan-1-one, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one, etc. Is mentioned.

[A1] Photobase generators include, for example, 2-nitrobenzylcyclohexyl carbamate, O-carbamoylhydroxyamide, O-carbamoylhydroxyamide and the like in addition to the compound examples described above.

[A1] As the photobase generator, an acetophenone compound and 2-nitrobenzylcyclohexyl carbamate are preferable, an acetophenone compound having an α-aminoketone structure and 2-nitrobenzylcyclohexyl carbamate are more preferable, and 2-methyl-1- [ 4- (Methylthio) phenyl] -2-morpholinopropan-1-one and 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) butan-1-one are more preferred.

([A2] Photoacid generator)
[A2] The photoacid generator is a component that generates an acid by the action of radiation. [A2] The photoacid generator can be used alone or in combination of two or more.

[A2] The acid generated from the photoacid generator is preferably a sulfonic acid, more preferably a fluorinated alkylsulfonic acid having 1 to 10 carbon atoms and a sulfonic acid having an alicyclic structure, and perfluoroalkylsulfonic acid and 10- Camphorsulfonic acid is more preferable, and trifluoromethanesulfonic acid, nonafluorobutanesulfonic acid and 10-camphorsulfonic acid are particularly preferable.

[A2] Examples of the photoacid generator include onium salt compounds, N-sulfonyloxyimide compounds, halogen-containing compounds, diazoketone compounds, and the like.

Examples of the onium salt compounds include sulfonium salts, tetrahydrothiophenium salts, iodonium salts, phosphonium salts, diazonium salts, pyridinium salts, and the like.

Examples of the anion of the onium compound include an anion represented by the following formula.

Examples of the cation of the onium compound include a cation represented by the following formula.

As the onium salt compound, an appropriate combination of the above anions and the above cations can be used.

Examples of the N-sulfonyloxyimide compound include compounds represented by the following formulas.

[A2] As the photoacid generator, an onium salt compound is preferable, a sulfonium salt is more preferable, and triphenylsulfonium trifluoromethanesulfonate, triphenylsulfonium nonafluorobutanesulfonate, and triphenylsulfonium camphorsulfonate are more preferable.

The lower limit of the content in terms of solid content of [A1] photobase generator or [A2] photoacid generator in the composition for forming an underlayer film is preferably 0.1% by mass, more preferably 1% by mass, 5 mass% is more preferable. On the other hand, the upper limit of the content is preferably 50% by mass, more preferably 30% by mass, and still more preferably 20% by mass. By making the said content into the said range, the sensitivity of the said pattern formation method can be improved more, and pattern collapse can be suppressed more reliably. Here, solid content in the composition for lower layer film formation means components other than the [C] solvent mentioned later.

([B1] organic polymer)
[B1] The organic polymer, [B2] inorganic polymer, and [B3] aromatic ring-containing compound described later serve as a base resin for the lower layer film formed in the pattern forming method. When the composition for forming a lower layer film contains the [B1] organic polymer, the etching selectivity of the lower layer film and the resist film can be improved. [B1] The organic polymer can be used alone or in combination of two or more.

[B1] The upper limit of the weight average molecular weight (Mw) of the organic polymer is preferably 100,000, more preferably 30,000. Here, Mw in this specification and the number average molecular weight (Mn) described later are values measured by gel permeation chromatography (GPC) under the following conditions.
GPC column: For example, two “G2000HXL”, one “G3000HXL” and one “G4000HXL” manufactured by Tosoh Corporation Column temperature: 40 ° C.
Elution solvent: Tetrahydrofuran Flow rate: 1.0 mL / min Sample concentration: 1.0% by mass
Sample injection volume: 100 μL
Detector: Differential refractometer Standard material: Monodisperse polystyrene

[B1] As the organic polymer, from the viewpoint of improving heat resistance and etching resistance, an organic polymer having an aromatic ring is preferable, an organic polymer having an aromatic ring in the main chain is more preferable, and obtained by polycondensation, More preferred are organic polymers having an aromatic ring in the main chain.

As the aromatic ring, for example, an aromatic carbon ring such as a benzene ring, naphthalene ring, anthracene ring, indene ring, pyrene ring, fluorenylidene biphenyl ring, fluorenylidene binaphthalene ring, furan ring, pyrrole ring, thiophene ring, Examples include phosphole ring, pyrazole ring, oxazole ring, isoxazole ring, thiazole ring, pyridine ring, pyrazine ring, pyrimidine ring, pyridazine ring and triazine ring.

[B1] As the organic polymer, for example, those described in paragraphs [0040] to [0116] of JP-A-2016-206676 can be used, but from the viewpoint of further improving the etching resistance of the lower layer film, Novolac resins, resol resins, aromatic ring-containing vinyl resins, acenaphthylene resins, indene resins, polyarylene resins, triazine resins, calixarene resins, fullerene resins and pyrene resins are preferred, novolak resins And acenaphthylene resins are more preferred.

As the lower limit of Mw of novolak resin, resol resin, aromatic ring-containing vinyl resin, acenaphthylene resin, indene resin, polyarylene resin, triazine resin, fullerene resin or pyrene resin, 500 is preferable, 1,000 is more preferred, and 2,000 is even more preferred. On the other hand, the upper limit of Mw is preferably 10,000. The lower limit of the ratio of Mw to Mn (Mw / Mn) of these resins is preferably 1.1. On the other hand, the upper limit of the Mw / Mn is preferably 5, more preferably 3, and even more preferably 2. By setting the Mw and Mw / Mn within the above ranges, the flatness and surface coatability of the lower layer film can be improved.

The lower limit of the molecular weight of the calixarene resin is preferably 500, more preferably 700, and even more preferably 1,000 from the viewpoint of improving the flatness of the resist underlayer film. The upper limit of the molecular weight is preferably 5,000, more preferably 3,000, and further preferably 1,500. When the calixarene resin has a molecular weight distribution, the molecular weight of the calixarene resin means Mw in terms of polystyrene by GPC.

([B2] inorganic polymer)
[B2] Examples of the inorganic polymer include [B2-1] polysiloxane, a plurality of metal atoms, an oxygen atom that bridges between the metal atoms (hereinafter also referred to as “bridged oxygen atom”), and the metal atom. And a [B2-2] complex (binuclear complex) containing a multidentate ligand coordinated to the. [B2] The inorganic polymer can be used alone or in combination of two or more.

[[B2-1] polysiloxane]
Examples of the [B2-1] polysiloxane include those having the structural unit (I) represented by the following formula (I) and / or the structural unit (II) represented by the following formula (II). . [B2-1] Each structural unit in the polysiloxane can be used alone or in combination of two or more.

In the above formula (I), R ^X1 is a monovalent organic group having 1 to 20 carbon atoms.

Here, “organic group” refers to a group having at least one carbon atom.

Examples of the monovalent organic group represented by R ^X1 include a monovalent hydrocarbon group, a monovalent fluorinated hydrocarbon group, and a divalent heteroatom-containing group between carbon and carbon of the monovalent hydrocarbon group. And a monovalent chain hydrocarbon group, a monovalent aromatic hydrocarbon group, a monovalent fluorinated aromatic hydrocarbon group, and a group containing a heterocyclic ring are more preferred. , An alkyl group, an aryl group, a fluoroaryl group and a group containing a nitrogen-containing heterocyclic ring are more preferred. Examples of the nitrogen-containing heterocycle include an azocycloalkane ring and an isocyanuric ring.

Examples of the structural unit (I) include a structural unit represented by the following formula.

[B2-1] The lower limit of the content ratio of the structural unit (I) in the polysiloxane is preferably 1 mol%, and more preferably 5 mol%. On the other hand, as an upper limit of the content rate of structural unit (I), 60 mol% is preferable and 40 mol% is more preferable.

[B2-1] The lower limit of the content ratio of the structural unit (II) in the polysiloxane is preferably 40 mol%, more preferably 60 mol%. On the other hand, as an upper limit of the content rate of structural unit (II), 99 mol% is preferable and 95 mol% is more preferable.

[B2-1] The lower limit of Mw of the polysiloxane is preferably 500, more preferably 800, and further preferably 1,200. On the other hand, the upper limit of the Mw is preferably 100,000, more preferably 30,000, still more preferably 10,000, and particularly preferably 5,000.

[[B2-2] complex]
The metal atom in the [B2-2] complex is preferably titanium, tantalum, zirconium and tungsten (hereinafter also referred to as “specific metal atom”), more preferably titanium and zirconium. By using these metal atoms, the pattern formability in the pattern forming method and the etching selectivity of the resist film and the lower layer film can be improved. These metal atoms can be used singly or in combination of two or more. However, in order to ensure in-plane uniformity of the etching rate of the lower layer film in the nanometer order during etching, one kind alone. It is preferable to use it.

The [B2-2] complex can be a stable binuclear complex by containing a bridging oxygen atom, and as a result, the pattern forming property and etching selectivity in the pattern forming method are improved. A plurality of bridging oxygen atoms are preferably bonded to one metal atom, but some of the metal atoms may be bonded to one metal atom. [B2-2] The complex preferably mainly contains a structure in which two bridging oxygen atoms are bonded to one metal atom. Since the [B2-2] complex mainly includes such a structure, a straight chain represented by -M ¹ -OM ¹ -O- (M ¹ is a metal atom such as a specific metal atom) It becomes possible to take a structure close to the shape, and the solubility is improved. As a result, the removability when removing the lower layer film using the cleaning solvent (hereinafter, also referred to as “removability of the lower layer film”) is improved. Here, “mainly comprising” the above structure means that 50 mol% or more, preferably 70 mol% or more, more preferably 90 mol% or more, particularly preferably 90% by mol or more of all metal atoms constituting the [B2-2] complex. It means that two bridging oxygen atoms are bonded to each other with respect to 95 mol% or more of metal atoms.

[B2-2] The complex may have other bridging ligand such as peroxide ligand (—O—O—) in addition to the bridging oxygen atom.

The multidentate ligand in the [B2-2] complex improves the solubility of the [B2-2] complex, thereby improving the removability of the lower layer film. The polydentate ligand is derived from hydroxy acid ester, β-diketone, β-keto ester, malonic acid diester optionally substituted at the α-position carbon atom and hydrocarbon having π bond, or these compounds. A ligand is preferred. By using a multidentate ligand as the above ligand, the removability of the lower layer film can be further improved. These compounds usually form a polydentate ligand as an anion obtained by obtaining one electron, form a polydentate ligand as an anion from which a proton is eliminated, or have a structure as it is. Forms a bidentate ligand.

The lower limit of the molar ratio of the polydentate ligand to the metal atom (polydentate ligand / metal atom) in the [B2-2] complex is preferably 1, more preferably 1.5, and even more preferably 1.8. . On the other hand, the upper limit of the ratio is preferably 3, more preferably 2.5, and even more preferably 2.2.

The [B2-2] complex may contain other ligands in addition to the above-mentioned bridging ligand and multidentate ligand.

The lower limit of the absolute molecular weight of the [B2-2] complex measured by the static light scattering method is preferably 400, more preferably 1,200, and even more preferably 2,000. The upper limit of the absolute molecular weight is preferably 50,000, more preferably 20,000, still more preferably 10,000, and particularly preferably 5,000. By setting the absolute molecular weight within the above range, the removability of the lower layer film can be further improved, and volatilization of the [B2-2] complex during the formation of the lower layer film can be suppressed.

The absolute molecular weight of the [B2-2] complex by the static light scattering method is a value measured under the following conditions.
Apparatus: Light scattering measurement apparatus (for example, “ALV-5000” of ALV Germany)
Measurement concentration: 2.5 mass%, 5.0 mass%, 7.5 mass%, 10.0 mass%, 4 points Standard liquid: Toluene Measurement temperature: 23 ° C
The refractive index of the solution and the density of the solution necessary for calculating the absolute molecular weight are values measured by the following apparatus.
Measuring device for refractive index of solution: refractometer (for example, “RA-500” of Kyoto Electronics Co., Ltd.)
Solution density measuring device: Density / specific gravity meter (for example, “DA-100” manufactured by Kyoto Electronics Industry Co., Ltd.)
In addition, in the measurement of absolute molecular weight using the above-mentioned manufacturer and model number apparatus, a method of setting a sample solution in a quartz cell is used, but in addition, a multi-angle laser light scattering detector for injecting a sample solution into a flow cell A method using (MALLS) may be used.

([B3] aromatic ring-containing compound)
[B3] The aromatic ring-containing compound is a compound having an aromatic ring and having a molecular weight of 600 or more and 3,000 or less. [B3] When the aromatic ring-containing compound has a molecular weight distribution, the molecular weight of [B3] aromatic ring-containing compound means, for example, a weight average molecular weight (Mw) in terms of polystyrene by GPC. When the composition for forming the lower layer film contains the [B3] aromatic ring-containing compound, the heat resistance and the etching resistance of the lower layer film can be improved as in the case of containing the [B1] organic polymer having an aromatic ring. [B3] Specific examples of the aromatic ring-containing compound include compounds described in paragraphs [0117] to [0179] of JP-A-2016-206676.

The lower limit of the total content of the [B1] organic polymer, [B2] inorganic polymer and [B3] aromatic ring-containing compound in the composition for forming the lower layer film is preferably 50% by mass, and 70% by mass. % Is more preferable, and 80% by mass is even more preferable. On the other hand, the upper limit of the total content is preferably 99% by mass, and more preferably 95% by mass.

([C] solvent)
[C] Solvents include [A1] photobase generator or [A2] photoacid generator, and [B1] organic polymer, [B2] inorganic polymer, and [B3] aromatic ring contained as necessary. Although it will not specifically limit if arbitrary components, such as a containing compound, can be melt | dissolved or disperse | distributed, For example, an alcohol solvent, a ketone solvent, an amide solvent, an ether solvent, an ester solvent, etc. are mentioned. [C] A solvent can be used individually by 1 type or in combination of 2 or more types.

Examples of the alcohol solvent include methanol, ethanol, n-propanol, iso-propanol, n-butanol, iso-butanol, sec-butanol, t-butanol, n-pentanol, iso-pentanol, sec-pentanol. And monoalcohol solvents such as t-pentanol, 2-methylpentanol and 4-methyl-2-pentanol.

Examples of the ether solvent include polyhydric alcohol partial ether solvents such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol dimethyl ether, propylene glycol monoethyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate. And polyhydric alcohol partial ether acetate solvents such as propylene glycol monomethyl ether acetate (PGMEA) and propylene glycol monoethyl ether acetate.

[C] Solvents described in paragraphs [0185] to [0189] of JP-A-2016-206676 can be used as the solvent other than the solvents described above.

[C] As the solvent, ether solvents, ketone solvents and ester solvents are preferable, and ether solvents are more preferable. The ether solvent is preferably a polyhydric alcohol partial ether solvent and a polyhydric alcohol partial ether acetate solvent, more preferably a polyhydric alcohol partial ether solvent and propylene glycol monoalkyl ether acetate, propylene glycol monoethyl ether and PGMEA. Is more preferable.

[C] The solvent contains a polyhydric alcohol partial ether acetate solvent, particularly propylene glycol monoalkyl ether acetate, particularly PGMEA, from the viewpoint of improving the coating property of the composition for forming a lower layer film to a substrate such as a silicon wafer. It is preferable to do. Since each component such as the [B1] organic polymer contained in the composition for forming the lower layer film tends to dissolve in the polyhydric alcohol partial ether acetate solvent, the [C] solvent is a polyhydric alcohol partial ether acetate type. By containing a solvent, the applicability | paintability of the composition for lower layer film formation can be improved, As a result, the embedding property of a lower layer film can be improved. [C] The lower limit of the content ratio of the polyhydric alcohol partial ether acetate solvent in the solvent is preferably 20% by mass, more preferably 60% by mass, and still more preferably 90% by mass. Moreover, as said content rate, 100 mass% is the most preferable.

(Other ingredients)
The composition for forming an underlayer film may further contain other components such as a crosslinking agent, a surfactant, and an adhesion assistant. The other components can be used alone or in combination of two or more.

The cross-linking agent is a component that forms a cross-linking bond such as [B1] organic polymers by the action of heat or acid. When the composition for forming a lower layer film contains a crosslinking agent, the hardness of the lower layer film can be improved.

Examples of the crosslinking agent include polyfunctional (meth) acrylate compounds, epoxy compounds, hydroxymethyl group-substituted phenol compounds, alkoxyalkyl group-containing phenol compounds, and compounds having an alkoxyalkylated amino group. Specific examples of these compounds include compounds described in paragraphs [0203] to [0207] of JP-A-2016-206676. In addition to the compounds described above, for example, compounds described in paragraphs [0209] to [0210] of JP-A No. 2016-206676 can be used as the crosslinking agent.

The surfactant improves the uniformity of the coating surface of the lower layer film to be formed and suppresses the occurrence of coating spots. As specific examples of the surfactant, for example, those described in paragraph [0216] of JP-A-2016-206676 can be used.

The adhesion assistant improves the adhesion between the lower layer film and the underlying substrate. As the adhesion assistant, for example, a known adhesion assistant can be used.

(Method for preparing composition for forming underlayer film)
The composition for forming an underlayer film comprises [A1] a photobase generator or [A2] photoacid generator, and [B1] organic polymer, [B2] inorganic polymer, and [B3] aromatic ring that are used as necessary. The contained compound, the [C] solvent, other components, and the like are mixed at a predetermined ratio, and the mixture obtained is preferably prepared by filtering with a membrane filter of about 0.45 μm. As a minimum of solid content concentration in a constituent for lower layer film formation, 0.1 mass% is preferred, 1 mass% is more preferred, and 2 mass% is still more preferred. On the other hand, the upper limit of the solid content concentration is preferably 50% by mass, more preferably 30% by mass, and even more preferably 15% by mass.

[Radiosensitive composition for resist film formation]
The radiation-sensitive composition for forming a resist film contains 50% by mass or more of [P] metal-containing compound in terms of solid content. The radiation-sensitive composition for forming a resist film preferably further contains a [Q] solvent, and may further contain other components. Since the radiation sensitive composition for forming a resist film contains 50% by mass or more of [P] metal-containing compound in terms of solid content, a resist film having excellent etching resistance can be formed.

([P] metal-containing compound)
[P] The metal-containing compound is a compound containing a metal atom. [P] A metal containing compound can be used individually by 1 type or in combination of 2 or more types. Moreover, the metal atom which comprises a [P] metal containing compound can be used individually by 1 type or in combination of 2 or more types. Here, the “metal atom” is a concept including a semimetal, that is, boron, silicon, germanium, arsenic, antimony and tellurium.

[P] The metal atom constituting the metal-containing compound is not particularly limited, and examples thereof include group 3 to group 16 metal atoms. Specific examples of the metal atom include a group 4 metal atom such as titanium, zirconium and hafnium, a group 5 metal atom such as tantalum, a group 6 metal atom such as chromium and tungsten, iron, ruthenium and the like. Group 8 metal atoms such as cobalt, Group 9 metal atoms such as cobalt, Group 10 metal atoms such as nickel, Group 11 metal atoms such as copper, Group 12 metals such as zinc, cadmium and mercury Group 13 metal atoms such as atoms, boron, aluminum, gallium, indium and thallium, Group 14 metal atoms such as germanium, tin and lead, Group 15 metal atoms such as antimony and bismuth, Group such as tellurium Examples include group 16 metal atoms.

[P] The metal atom constituting the metal-containing compound includes the first metal atom belonging to Group 4, Group 12, or Group 14 in the periodic table and belonging to the fourth period, the fifth period, or the sixth period. Good. That is, the metal atom may include at least one of titanium, zirconium, hafnium, zinc, cadmium, mercury, germanium, tin, and lead. As described above, since the [P] metal-containing compound contains the first metal atom, the secondary electrons are emitted from the exposed portion of the resist film, and the [P] metal-containing compound is dissolved in the developer by the secondary electrons. Sex change is promoted more. As a result, the sensitivity of the pattern forming method can be further improved, and pattern collapse can be more reliably suppressed. As the first metal atom, tin is preferable.

[P] It is preferable that the metal-containing compound further has an atom other than the metal atom. As said other atom, a carbon atom, a hydrogen atom, an oxygen atom, a nitrogen atom, a phosphorus atom, a sulfur atom, a halogen atom etc. are mentioned, for example, Among these, a carbon atom, a hydrogen atom, and an oxygen atom are preferable. [P] Other atoms in the metal-containing compound can be used alone or in combination of two or more.

The lower limit of the content of the [P] metal-containing compound in terms of solid content in the radiation-sensitive composition for resist film formation is preferably 70% by mass, more preferably 90% by mass, and still more preferably 95% by mass. Further, the content may be 100% by mass. Here, solid content in the radiation sensitive composition for resist film formation means components other than the [Q] solvent mentioned later.

(Method for synthesizing [P] metal-containing compound)
[P] The metal-containing compound includes, for example, a hydrolytic condensate reaction, a metal compound having a metal atom and a hydrolyzable group, a hydrolyzate of the metal compound, a hydrolyzed condensate of the metal compound, or a combination thereof. It can be obtained by a method of performing a ligand exchange reaction or the like. The said metal compound can be used individually by 1 type or in combination of 2 or more types.

[P] The metal-containing compound is preferably derived from a metal compound having a metal atom and a hydrolyzable group represented by the following formula (1) (hereinafter also referred to as “metal compound (1)”). By using such a metal compound (1), a stable [P] metal-containing compound can be obtained.

In the above formula (1), M is a metal atom. L is a ligand or a monovalent organic group having 1 to 20 carbon atoms. a is an integer of 0-6. When a is 2 or more, the plurality of L may be the same or different. Y is a monovalent hydrolyzable group. b is an integer of 2 to 6. A plurality of Y may be the same or different. L is a ligand or organic group not corresponding to Y.

As the metal atom represented by M, the first metal atom is preferable, and tin is more preferable.

The hydrolyzable group represented by Y can be appropriately changed according to the metal atom represented by M. For example, a substituted or unsubstituted ethynyl group, a halogen atom, an alkoxy group, an acyloxy group, a substituted or non-substituted group. Examples include substituted amino groups.

As the substituent in the substituted or unsubstituted ethynyl group represented by Y and the substituted or unsubstituted amino group, a monovalent hydrocarbon group having 1 to 20 carbon atoms is preferable, and a chain hydrocarbon group is more preferable. An alkyl group is more preferable.

Examples of the halogen atom represented by Y include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Of these, a chlorine atom is preferred.

Examples of the alkoxy group represented by Y include a methoxy group, an ethoxy group, an n-propoxy group, an i-propoxy group, and an n-butoxy group. Of these, an ethoxy group, i-propoxy group, and n-butoxy group are preferable.

As the acyloxy group represented by Y, for example, formyl group, acetoxy group, ethylyloxy group, propionyloxy group, n-butyryloxy group, t-butyryloxy group, t-amylyloxy group, n-hexanecarbonyloxy group, n-octane Examples thereof include a carbonyloxy group. Of these, an acetoxy group is preferred.

Examples of the substituted or unsubstituted amino group represented by Y include an amino group, a methylamino group, a dimethylamino group, a diethylamino group, and a dipropylamino group. Among these, a dimethylamino group and a diethylamino group are preferable.

Hereinafter, preferred combinations of the metal atom represented by M and the hydrolyzable group represented by Y will be described. When the metal atom represented by M is tin, the hydrolyzable group represented by Y includes a substituted or unsubstituted ethynyl group, a halogen atom, an alkoxy group, an acyloxy group, and a substituted or unsubstituted amino group. Preferably, a halogen atom is more preferable. When the metal atom represented by M is germanium, the hydrolyzable group represented by Y is preferably a halogen atom, an alkoxy group, an acyloxy group, or a substituted or unsubstituted amino group. When the metal atom represented by M is hafnium, zirconium and titanium, the hydrolyzable group represented by Y is preferably a halogen atom, an alkoxy group or an acyloxy group.

Examples of the ligand represented by L include a monodentate ligand and a polydentate ligand.

Examples of the monodentate ligand include a hydroxo ligand, a nitro ligand, and ammonia.

Examples of the polydentate ligand include the polydentate ligand exemplified in the [B2-2] complex, diphosphine and the like.

Examples of the diphosphine include 1,1-bis (diphenylphosphino) methane, 1,2-bis (diphenylphosphino) ethane, 1,3-bis (diphenylphosphino) propane, and 2,2′-bis (diphenyl). Phosphino) -1,1′-binaphthyl, 1,1′-bis (diphenylphosphino) ferrocene and the like.

Examples of the monovalent organic group represented by L include the same groups as those exemplified as the monovalent organic group represented by R ^X1 in the above formula (I). The lower limit of the carbon number of the monovalent organic group represented by L is preferably 2, and more preferably 3. On the other hand, the upper limit of the carbon number is preferably 10, and more preferably 5. The monovalent organic group represented by L is preferably a substituted or unsubstituted hydrocarbon group, more preferably a substituted or unsubstituted chain hydrocarbon group, still more preferably a substituted or unsubstituted alkyl group, t A butyl group is particularly preferred.

A is preferably 1 or 2, and more preferably 1.

B is preferably an integer of 2 to 4. By making b into the said numerical value, the content rate of the metal atom in a [P] metal containing compound can be raised, and generation | occurrence | production of the secondary electron by a [P] metal containing compound can be accelerated | stimulated more effectively. As a result, the sensitivity of the pattern forming method can be further improved, and pattern collapse can be more reliably suppressed.

As the metal compound (1), a metal halide compound is preferable, and a compound represented by the following formula is more preferable.

As a method for performing a hydrolysis-condensation reaction on the metal compound (1), for example, in the presence of a base such as tetramethylammonium hydroxide used as necessary, the metal compound (1) in water or a solvent containing water. And the like. In this case, you may add the other compound which has a hydrolysable group as needed. The lower limit of the amount of water used for this hydrolysis-condensation reaction is preferably 0.2 times mole, more preferably 1 time mole, and even more preferably 3 times mole relative to the hydrolyzable group of the metal compound (1) and the like. preferable. By making the amount of water in the hydrolysis condensation reaction within the above range, the [P] metal-containing compound can be obtained easily and reliably.

[P] In the synthesis reaction of the metal-containing compound, in addition to the metal compound (1), it becomes a compound or a bridging ligand that can be a multidentate ligand represented by L in the compound of the above formula (1). You may add the compound etc. which are obtained. Examples of the compound that can be a bridging ligand include compounds having two or more coordinateable groups such as a hydroxy group, an isocyanate group, an amino group, an ester group, and an amide group.

[P] The lower limit of the temperature of the synthesis reaction of the metal-containing compound is preferably 0 ° C, and more preferably 10 ° C. As an upper limit of the said temperature, 150 degreeC is preferable, 100 degreeC is more preferable, and 50 degreeC is further more preferable.

[P] The lower limit of the synthesis reaction of the metal-containing compound is preferably 1 minute, more preferably 10 minutes, and even more preferably 1 hour. The upper limit of the time is preferably 100 hours, more preferably 50 hours, further preferably 24 hours, and particularly preferably 4 hours.

([Q] solvent)
[Q] The solvent is preferably an organic solvent. Specific examples of the organic solvent include those similar to those exemplified as the [C] solvent in the composition for forming a lower layer film.

[Q] The solvent is preferably an alcohol solvent, more preferably a monoalcohol solvent, and even more preferably 4-methyl-2-pentanol.

[Other optional ingredients]
In addition to the [P] metal-containing compound and the [Q] solvent, the radiation-sensitive composition for forming a resist film may contain other optional components such as a compound that can be a ligand and a surfactant.

[Compound that can be a ligand]
Examples of the compound that can be a ligand include compounds that can be a multidentate ligand or a bridging ligand. Specifically, the polydentate ligand exemplified in the method for synthesizing a [P] metal-containing compound. Or the thing similar to the compound which can become a bridge | crosslinking ligand etc. are mentioned.

[Surfactant]
A surfactant is a component that exhibits an effect of improving coatability, striation and the like. Examples of the surfactant include polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene n-octylphenyl ether, polyoxyethylene n-nonylphenyl ether, polyethylene glycol dilaurate, polyethylene glycol diacrylate. In addition to nonionic surfactants such as stearate, the following trade names are KP341 (Shin-Etsu Chemical Co., Ltd.), Polyflow No. 75, no. 95 (above, Kyoeisha Chemical Co., Ltd.), F-Top EF301, EF303, EF352 (above, Tochem Products), MegaFuck F171, F173 (above, Dainippon Ink and Chemicals), Florard FC430, FC431 ( Sumitomo 3M), Asahi Guard AG710, Surflon S-382, SC-101, SC-102, SC-103, SC-104, SC-105, SC-105, SC-106 (above, Asahi Glass Co., Ltd.) ) And the like.

(Method for preparing radiation-sensitive composition for resist film formation)
The radiation-sensitive composition for forming a resist film is obtained by, for example, mixing [P] a metal-containing compound and other optional components such as a [Q] solvent as necessary, and preferably the obtained mixture. Can be prepared by filtering through a membrane filter having a pore size of about 0.2 μm. When the radiation-sensitive composition for forming a resist film contains a [Q] solvent, the lower limit of the solid content concentration of the radiation-sensitive composition for forming a resist film is preferably 0.1% by mass, and 0.5% by mass. Is more preferable, 1% by mass is more preferable, and 2% by mass is particularly preferable. On the other hand, the upper limit of the solid content concentration is preferably 50% by mass, more preferably 30% by mass, further preferably 15% by mass, and particularly preferably 4% by mass.

Hereinafter, each step of the pattern forming method using the above-described composition for forming a lower layer film and the radiation-sensitive composition for forming a resist film will be described.

[Underlayer forming composition coating process]
In this step, the above-described composition for forming a lower layer film is applied to a substrate. Specifically, the composition for forming the lower layer film is applied to one surface side of the substrate so that the obtained lower layer film has a desired thickness, and then the composition for forming the lower layer film by pre-baking (PB) as necessary. The lower layer film is formed by volatilizing the [C] solvent of the product. The method for applying the composition for forming the lower layer film to the substrate is not particularly limited, and appropriate application means such as spin coating, cast coating, roll coating, etc. can be employed. Examples of the substrate include a silicon wafer and a wafer coated with aluminum.

The lower limit of the average thickness of the lower layer film formed in this step is preferably 1 nm, more preferably 10 nm, and further preferably 20 nm. On the other hand, the upper limit of the average thickness is preferably 20,000 nm, more preferably 1,000 nm, and even more preferably 100 nm.

The lower limit of the PB temperature in this step is preferably 150 ° C, more preferably 200 ° C, and even more preferably 250 ° C. On the other hand, the upper limit of the PB temperature is preferably 400 ° C., more preferably 350 ° C., and further preferably 300 ° C. or less. Further, the lower limit of the PB time is preferably 15 seconds, more preferably 30 seconds, and even more preferably 45 seconds. On the other hand, the upper limit of the PB time is preferably 1,200 seconds, more preferably 600 seconds, and even more preferably 300 seconds. By setting the PB temperature and the PB temperature in the above ranges, it is possible to reliably exhibit the characteristics necessary for the lower layer film.

In this step, it is preferable to form an organic underlayer film using a composition for forming an underlayer film containing [B1] an organic polymer. Thereby, the etching selectivity of the lower layer film and the resist film can be improved. In this case, as a minimum of the carbon content rate in an organic underlayer film, 50 mass% is preferred, 60 mass% is more preferred, and 80 mass% is still more preferred. On the other hand, the upper limit of the carbon atom content is preferably 99% by mass, and more preferably 95% by mass. The etching selectivity of a lower layer film and a resist film can be improved more by making the said carbon atom content rate into the said range. Here, the carbon atom content is a value measured by elemental analysis by a combustion method.

[Resistance film forming radiation sensitive composition coating process]
In this step, the above-mentioned radiation sensitive composition for forming a resist film is applied directly or indirectly on the lower layer film formed by the lower layer film forming composition coating step. Specifically, the resist film-forming radiation-sensitive composition is applied on the surface of the lower layer film opposite to the substrate so that the resulting resist film has a desired thickness, and then pre-baked (PB) as necessary. The resist film is formed by volatilizing the [Q] solvent or the like of the radiation-sensitive composition for forming a resist film. Although it does not specifically limit as a method to apply the radiation sensitive composition for resist film formation, For example, the method similar to the coating method illustrated in the composition application | coating process for lower layer film | membrane etc. is mentioned.

The lower limit of the average thickness of the resist film formed in this step is preferably 1 nm, more preferably 5 nm, still more preferably 10 nm, and particularly preferably 20 nm. On the other hand, the upper limit of the average thickness is preferably 1,000 nm, more preferably 200 nm, still more preferably 100 nm, and particularly preferably 70 nm.

As the lower limit of the PB temperature in this step, 50 ° C is preferable, and 70 ° C is more preferable. On the other hand, the upper limit of the PB temperature is preferably 140 ° C, and more preferably 100 ° C. The lower limit of the PB time is preferably 5 seconds, and more preferably 10 seconds. On the other hand, the upper limit of the PB time is preferably 600 seconds, and more preferably 300 seconds.

In this step, for example, a protective film can be provided on the formed resist film in order to prevent the influence of basic impurities and the like contained in the environmental atmosphere. Further, as described later, when immersion exposure is performed in the exposure step, an immersion protective film may be provided on the formed resist film in order to avoid direct contact between the immersion medium and the resist film.

[Exposure process]
In this step, the resist film formed in the radiation sensitive composition coating step for forming a resist film is exposed. Specifically, for example, the resist film is irradiated with radiation through a mask having a predetermined pattern. In this step, radiation irradiation through an immersion medium such as water, that is, immersion exposure may be employed as necessary. Examples of radiation to be exposed include visible rays, ultraviolet rays, far ultraviolet rays, EUV (wavelength 13.5 nm), electromagnetic waves such as X-rays and γ rays, and charged particle beams such as electron rays and α rays. Among these, EUV and an electron beam are preferable from the viewpoint of improving sensitivity.

[Development process]
In this step, the resist film exposed in the exposure step is developed. As a result, a predetermined negative pattern is formed. Examples of the developer include an alkaline aqueous solution and an organic solvent-containing solution. From the viewpoint of developability and the like, an organic solvent-containing solution is preferable.

Examples of the alkaline aqueous solution include sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, ammonia, ethylamine, n-propylamine, diethylamine, di-n-propylamine, triethylamine, methyldiethylamine, ethyl Dimethylamine, triethanolamine, tetramethylammonium hydroxide (TMAH), pyrrole, piperidine, choline, 1,8-diazabicyclo- [5.4.0] -7-undecene, 1,5-diazabicyclo- [4.3 0.0] -5-nonene, and an alkaline aqueous solution in which at least one kind is dissolved.

The lower limit of the content of the alkaline compound in the alkaline aqueous solution is preferably 0.1% by mass, more preferably 0.5% by mass, and even more preferably 1% by mass. As an upper limit of the said content, 20 mass% is preferable, 10 mass% is more preferable, and 5 mass% is further more preferable.

As the alkaline aqueous solution, a TMAH aqueous solution is preferable, and a 2.38% by mass TMAH aqueous solution is more preferable.

Examples of the organic solvent in the organic solvent-containing liquid include the same organic solvents exemplified as the [Q] solvent in the radiation-sensitive composition for forming a resist film. Of these, ether solvents are preferred, polyhydric alcohol partial ether acetate solvents are more preferred, and propylene glycol monomethyl ether acetate is even more preferred.

The lower limit of the content of the organic solvent in the organic solvent-containing liquid is preferably 80% by mass, more preferably 90% by mass, further preferably 95% by mass, and particularly preferably 99% by mass. By making content of the said organic solvent into the said range, the contrast of the dissolution rate with respect to the developing solution in an exposure part and an unexposed part can be improved more. In addition, as components other than the organic solvent of the said organic solvent containing liquid, water, silicone oil, etc. are mentioned, for example.

An appropriate amount of a surfactant may be added to the developer as necessary. As the surfactant, for example, an ionic or nonionic fluorine-based surfactant, a silicone-based surfactant, or the like can be used.

As a developing method, for example, a method in which a substrate is immersed in a tank filled with a developer for a certain period of time (dip method), a method in which the developer is raised on the surface of the substrate by surface tension and is left stationary for a certain time (paddle method) ), A method of spraying the developer on the substrate surface (spray method), a method of continuously discharging the developer while scanning the developer discharge nozzle at a constant speed on the substrate rotating at a constant speed (dynamic dispensing method), etc. Is mentioned.

The substrate after the development is preferably rinsed with a rinse liquid such as water or alcohol and then dried. As the rinsing method, for example, a method of continuously discharging a rinsing liquid onto a substrate rotating at a constant speed (rotary coating method), a method of immersing the substrate in a tank filled with the rinsing liquid for a predetermined time (dip method) ), A method (spray method) of spraying a rinse liquid on the substrate surface, and the like.

Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples.

<Metal-containing compounds>
(Synthesis Example 1)
10.0 mmol of tert-butyltrichlorotin (compound represented by the following formula (p-1)) was added to 100 g of 0.3M tetramethylammonium hydroxide aqueous solution, and stirred vigorously at room temperature for 90 minutes. The deposited precipitate was filtered and washed twice with 50 g of water to obtain a metal-containing compound (P-1) represented by the following formula (P-1).

<Preparation of radiation-sensitive composition for resist film formation>
(Synthesis Example 2)
3.0 parts by mass of the metal-containing compound (P-1) and 97.0 parts by mass of 4-methyl-2-pentanol as a [Q] solvent were mixed, and the resulting mixture was mixed with a membrane having a pore size of 0.2 μm. By filtering with a filter, a radiation-sensitive composition (J-1) for forming a resist film was prepared.

<Preparation of composition for forming lower layer film>
[A1] Photobase generator, [A2] Photoacid generator, [B1] organic polymer, [B2] inorganic polymer, and [C] solvent used for the preparation of the underlayer film forming composition are shown below. .

([A1] Photobase generator)
A-1: 2-nitrobenzylcyclohexyl carbamate (compound represented by the following formula (a-1))
A-2: 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one (compound represented by the following formula (a-2))
A-3: 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) butan-1-one (compound represented by the following formula (a-3))

([A2] Photoacid generator)
A-4: Triphenylsulfonium nonafluoro-n-butanesulfonate (compound represented by the following formula (a-4))
A-5: Triphenylsulfonium trifluoromethanesulfonate (compound represented by the following formula (a-5))
A-6: Triphenylsulfonium-10-camphorsulfonate (compound represented by the following formula (a-6))

([B1] organic polymer)
B-1: Resin represented by the following formula (b-1) (Mw: 2,000)
B-2: Resin represented by the following formula (b-2) (Mw: 1,100)
B-3: Resin represented by the following formula (b-3) (Mw: 2,000)
B-4: Resin represented by the following formula (b-4) (Mw: 1,800)
B-5: Resin represented by the following formula (b-5) (Mw: 2,800)
B-6: Resin represented by the following formula (b-6) (Mw: 2,000)

([B2] inorganic polymer)
B-7: Resin represented by the following formula (b-7) (Mw: 1,500)
B-8: Resin represented by the following formula (b-8) (Mw: 2,000)
B-9: Resin represented by the following formula (b-9) (Mw: 2,000)
B-10: Resin represented by the following formula (b-10) (Mw: 3,000)
B-11: Resin represented by the following formula (b-11) (Mw: 2,500)
B-12: Resin represented by the following formula (b-12) (Mw: 3,000)

The organic polymers (B-1) to (B-6) and the inorganic polymers (B-7) to (B-12) were synthesized by a conventionally known method.

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

[Preparation of composition for forming lower layer film]
(Synthesis Example 3)
0.3 parts by mass of the photobase generator (A-1) and 2.7 parts by mass of the organic polymer (B-1) were dissolved in 97.0 parts by mass of the solvent (C-1). This solution was filtered through a membrane filter having a pore diameter of 0.45 μm to prepare a composition for forming an underlayer film (U-1).

(Synthesis Examples 4 to 26)
Except that the types and contents of the respective components are as shown in Table 1 below, the same operations as in Synthesis Example 3 were performed, and the underlayer film forming compositions (U-2) to (U-21) and (U-1) to (u-3) were prepared. “-” In Table 1 indicates that the corresponding component was not used.

<Evaluation>
A pattern was formed by the following method using the radiation-sensitive composition for forming a resist film and the compositions for forming a lower layer film of Examples and Comparative Examples, and the sensitivity and pattern collapse resistance in each pattern forming method were evaluated. The evaluation results are shown in Table 2.

[Formation of lower layer film]
In “Clean Track ACT-8” of Tokyo Electron Co., Ltd., after spin-coating a composition for forming an underlayer film on a silicon substrate, PB was performed at 270 ° C. for 180 seconds to form an underlayer film having an average thickness of 50 nm. Formed.

[Formation of resist film]
In the “Clean Track ACT-8” of Tokyo Electron Co., Ltd., after spin-coating the radiation-sensitive composition (J-1) for forming a resist film on the silicon substrate on which the lower layer film was formed, it was heated at 80 ° C. for 60 seconds. PB was performed under the conditions to form a resist film having an average thickness of 50 nm.

[Pattern formation]
The resist film was irradiated with an electron beam using a simple electron beam drawing apparatus (“HL800D” manufactured by Hitachi, Ltd., output: 50 KeV, current density: 5.0 amperes / cm ² ). After the electron beam irradiation, the resist film is developed with propylene glycol monomethyl ether acetate at 23 ° C. for 1 minute in the “Clean Track ACT-8” by the paddle method and then dried to form a pattern. Formed.

[sensitivity]
The pattern is formed while varying the exposure amount, and a line-and-space pattern (1L1S) consisting of a line portion having a line width of 150 nm and a space portion having a width of 150 nm formed between adjacent line portions is 1: 1. The exposure amount (optimal exposure amount) that can be formed with a line width of was determined. This optimum exposure amount was defined as sensitivity (μC / cm ² ). It can be evaluated that the lower the numerical value, the better the sensitivity.

[Pattern fall resistance]
In the formation of the above line and space pattern, the line width of the pattern obtained by varying the exposure dose is gradually narrowed to obtain the minimum line pattern line width in which the resist pattern is not confirmed to be collapsed. The previous dimension (nm) was used. It can be evaluated that the pattern collapse resistance is better as the numerical value of the minimum collapse dimension (nm) is lower.

As is clear from Table 2, the sensitivity and the pattern collapse resistance of the pattern formation method of the example were better than those of the pattern formation method of the comparative example.

Claims

Applying a composition for forming an underlayer film to a substrate;
Coating the radiation-sensitive composition for forming a resist film directly or indirectly on the lower layer film formed by the above-mentioned composition for forming a lower layer film; and
Exposing the resist film formed by the radiation sensitive composition coating process for forming the resist film;
A step of developing the exposed resist film,
The composition for forming an underlayer film contains a radiation-sensitive base generator that generates a base by the action of radiation, or a radiation-sensitive acid generator that generates an acid by the action of radiation,
The pattern formation method in which the said radiation sensitive composition for resist film formation contains a metal containing compound 50 mass% or more in conversion of solid content.
The underlayer film forming composition further contains an organic polymer,
The pattern forming method according to claim 1, wherein an organic underlayer film is formed in the underlayer film forming composition coating step.
The pattern formation method according to claim 2, wherein the organic underlayer film has a carbon content of 50% by mass or more.
The pattern forming method according to claim 2 or 3, wherein the organic polymer has a weight average molecular weight of 30,000 or less.
The pattern forming method according to claim 2, wherein the organic polymer has an aromatic ring.
The pattern formation method according to any one of claims 1 to 5, wherein the metal-containing compound is derived from a compound represented by the following formula (1).

(In the formula (1), M is a metal atom. L is a ligand or a monovalent organic group having 1 to 20 carbon atoms. A is an integer of 0 to 6. a is 2) In the above case, a plurality of L may be the same or different, Y is a monovalent hydrolyzable group, b is an integer of 2 to 6. A plurality of Y may be the same or different. (Note that L is a ligand or organic group not corresponding to Y.)
The metal atom constituting the metal-containing compound includes a first metal atom belonging to Group 4, Group 12, or Group 14 in the periodic table and belonging to the fourth period, the fifth period, or the sixth period. The pattern formation method of any one of Claims 1-6.