WO2021131280A1 - Radiation-sensitive resin composition and method of forming resist pattern - Google Patents

Abstract

Provided are: a radiation-sensitive resin composition from which a resist pattern can be formed having good sensitivity to exposure light, excellent LWR performance, and resolution; and a method of forming a resist pattern. A radiation-sensitive resin composition comprising: a polymer having a first structural unit including a phenolic hydroxyl group and a second structural unit including an acid-dissociable group; and a radiation-sensitive acid generator, wherein the radiation-sensitive acid generator has a monovalent radiation-sensitive onium cation represented by formula (1).

Description

Radiation-sensitive resin composition and resist pattern forming method

The present invention relates to a radiation-sensitive resin composition and a resist pattern forming method.

Radiation-sensitive resin compositions used for micromachining by lithography include far-ultraviolet rays such as ArF excimer laser light (wavelength 193 nm) and KrF excimer laser light (wavelength 248 nm), and extreme ultraviolet rays (EUV) (wavelength 13.5 nm). An acid is generated in the exposed part by irradiation with radiation such as an electromagnetic wave or a charged particle beam such as an electron beam, and a chemical reaction using this acid as a catalyst causes a difference in the dissolution rate of the exposed part and the non-exposed part in the developing solution. This forms a resist pattern on the substrate.

The radiation-sensitive resin composition has good sensitivity to exposure light such as extreme ultraviolet rays and electron beams, and also has excellent LWR (Line With Roughness) performance and resolvability, which indicate uniformity of line width. Required.

In response to these requirements, the types of polymers, acid generators and other components used in radiation-sensitive resin compositions, molecular structures, etc. have been studied, and their combinations have also been studied in detail (specially). Open 2010-134279, Japanese Patent Application Laid-Open No. 2014-224984, and Japanese Patent Application Laid-Open No. 2016-047815).

Japanese Unexamined Patent Publication No. 2010-134279 Japanese Unexamined Patent Publication No. 2014-224988 Japanese Unexamined Patent Publication No. 2016-047815

Now that the refining of the resist pattern has progressed to the level of line width 40 nm or less, the required level of the above performance is further increased, and the above-mentioned conventional radiation-sensitive resin composition satisfies the above-mentioned requirement. Not done.

The present invention has been made based on the above circumstances, and an object of the present invention is radiation-sensitive property capable of forming a resist pattern having good sensitivity to exposure light and excellent LWR performance and resolution. It is an object of the present invention to provide a resin composition and a method for forming a resist pattern.

The invention made to solve the above problems is a polymer having a first structural unit containing a phenolic hydroxyl group and a second structural unit containing an acid dissociable group (hereinafter, also referred to as "[A] polymer"). , The radiosensitizing acid generator (hereinafter, also referred to as “[B] acid generator”), and the radiosensitizing acid generator is monovalent radiosensitivity represented by the following formula (1). It is a radiation-sensitive resin composition having an onium cation.

(In the formula (1), Ar ¹ is a group obtained by removing (m + 1) hydrogen atoms on an aromatic ring from an array having 6 to 20 ring members. M is an integer of 0 to 11. for 1, R ¹ is a monovalent organic group having 1 to 20 carbon atoms, hydroxy groups, if .m is 2 or more nitro groups or halogen atoms, more of R ¹ is equal to or different from each other, the number of carbon atoms An alicyclic structure having 1 to 20 monovalent organic groups, a hydroxy group, a nitro group or a halogen atom, or an alicyclic structure having 4 to 20 ring members composed of carbon chains in which these groups are combined with each other and bonded to each other. It is a part of the aliphatic heterocyclic structure. Ar ² is a group obtained by removing hydrogen atoms on n aromatic rings from an array having 6 to 20 ring members which is fused with the thiophene ring. N is 0 to 0 to. It is an integer of 10. When n is 1, R ² is a monovalent organic group, hydroxy group, nitro group or halogen atom having 1 to 20 carbon atoms. When n is 2 or more, a plurality of R ^{2 are used.} Are the same or different from each other and are monovalent organic groups, hydroxy groups, nitro groups or halogen atoms having 1 to 20 carbon atoms, or the number of rings formed by combining these groups with each other and forming a carbon chain to which they are bonded. It is a part of the alicyclic structure or the aliphatic heterocyclic structure of 4 to 20. R ³ and R ⁴ are independently monovalent organic groups having 1 to 20 carbon atoms, hydroxy groups, nitro groups, and halogens. Atom or hydrogen atom.)

Another invention made to solve the above problems is a step of directly or indirectly applying the above-mentioned radiation-sensitive resin composition to a substrate, and a step of exposing a resist film formed by the above-mentioned coating step. This is a resist pattern forming method including the above-mentioned step of developing the exposed resist film.

According to the radiation-sensitive resin composition and the resist pattern forming method of the present invention, it is possible to form a resist pattern having good sensitivity to exposure light and excellent LWR performance and resolution. Therefore, these can be suitably used for processing processes of semiconductor devices, which are expected to be further miniaturized in the future.

Hereinafter, the radiation-sensitive resin composition and the resist pattern forming method of the present invention will be described in detail.

<Radiation-sensitive resin composition>
The radiation-sensitive resin composition contains a [A] polymer and a [B] acid generator. The radiation-sensitive resin composition usually contains an organic solvent (hereinafter, also referred to as “[D] organic solvent”). The radiation-sensitive resin composition may contain an acid diffusion control body (hereinafter, also referred to as “[C] acid diffusion control body”) as a suitable component. The radiation-sensitive resin composition may contain other optional components as long as the effects of the present invention are not impaired.

By containing the [A] polymer and the [B] acid generator, the radiation-sensitive resin composition forms a resist pattern having good sensitivity to exposure light and excellent LWR performance and resolution. be able to. The reason why the radiation-sensitive resin composition exerts the above-mentioned effect by having the above-mentioned constitution is not always clear, but it can be inferred as follows, for example. That is, since the [B] acid generator contained in the radiation-sensitive resin composition has a cation having a specific structure, it becomes easy to absorb the exposure light and the acid generation efficiency by the exposure is improved, and as a result, It is considered that the radiation-sensitive resin composition has good sensitivity to exposure light and can form a resist pattern excellent in LWR performance and resolution. Further, the radiation-sensitive resin composition is excellent in defect suppression property by containing the [A] polymer and the [B] acid generator.

Hereinafter, each component contained in the radiation-sensitive resin composition will be described.

<[A] Polymer>
[A] The polymer has a structural unit containing a phenolic hydroxyl group (hereinafter, also referred to as “structural unit (I)”) and a structural unit containing an acid dissociative group (hereinafter, also referred to as “structural unit (II)”). Have. [A] The polymer may have other structural units (hereinafter, also simply referred to as “other structural units”) other than the structural unit (I) and the structural unit (II). [A] The polymer may have one or more structural units. The radiation-sensitive resin composition may contain one or more [A] polymers.

Hereinafter, each structural unit of the [A] polymer will be described.

[Structural unit (I)]
The structural unit (I) is a structural unit containing a phenolic hydroxyl group. The "phenolic hydroxyl group" refers not only to the hydroxy group directly connected to the benzene ring but to all the hydroxy groups directly connected to the aromatic ring.

[A] When the polymer has the structural unit (I), the hydrophilicity of the resist film can be enhanced, the solubility in the developing solution can be appropriately adjusted, and in addition, the resist pattern can be applied to the substrate. Adhesion can be improved. Further, when extreme ultraviolet rays or electron beams are used as the radiation to be irradiated in the exposure step in the resist pattern forming method described later, the sensitivity to the exposure light can be further improved. Therefore, the radiation-sensitive resin composition can be suitably used as a radiation-sensitive resin composition for extreme ultraviolet exposure or electron beam exposure.

Examples of the structural unit (I) include a structural unit represented by the following formula (3).

In the above formula (3), R ¹⁷ is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. L is a single bond, -O-, -COO- or -CONH-. Ar ³ is a group obtained by removing (a + b + 1) hydrogen atoms on an aromatic ring from an array having 6 to 20 ring members. a is an integer from 0 to 10. When a is 1, R ¹⁸ is a monovalent organic group or halogen atom having 1 to 20 carbon atoms. When a is 2 or more, the plurality of R ^18s are the same or different, and are organic groups or halogen atoms having 1 to 20 carbon atoms, or carbons ^{in which two or more of the plurality of R 18s} are combined with each other and these are bonded to each other. It is a part of an alicyclic structure or an aliphatic heterocyclic structure having 4 to 20 ring members, which is composed together with a chain. b is an integer from 1 to 11. However, a + b is 11 or less.

As R ¹⁷ , a hydrogen atom or a methyl group is preferable, and a hydrogen atom is more preferable, from the viewpoint of copolymerizability of the monomer giving the structural unit (I).

When L is -COO-, the oxyoxygen atom is ^{preferably bonded to Ar 3,} and when L is -CONH-, the nitrogen atom is preferably bonded to ^{Ar 3.} That is, if * ^{indicates a binding site with Ar 3} , -COO- is preferably -COO- *, and -CONH- is preferably -CONH- *. As L, a single bond or -COO- is preferable, and a single bond is more preferable.

The "number of ring members" refers to the number of atoms constituting the rings of the alicyclic structure, the aromatic carbocyclic structure, the aliphatic heterocyclic structure and the aromatic heterocyclic structure, and in the case of a polycycle, it constitutes this polycycle. The number of atoms.

Examples of the arene having 6 to 20 ring members that give Ar ³ include benzene, naphthalene, anthracene, phenanthrene, tetracene, and pyrene. As ^{the arene having 6 to 20 ring members that gives Ar 3} , benzene or naphthalene is preferable, and benzene is more preferable.

"Organic group" means a group containing at least one carbon atom. "Carbon number" means the number of carbon atoms constituting a group. The monovalent organic group having 1 to 20 carbon atoms represented by R ^18, for example, monovalent hydrocarbon group having 1 to 20 carbon atoms, the hydrocarbon group having a carbon - divalent heteroatom-containing between carbon A group containing a group (α), a group (β) in which a part or all of the hydrogen atom of the above hydrocarbon group or the above group (α) is replaced with a monovalent heteroatom-containing group, the above hydrocarbon group, the above group. Examples thereof include (α) or a group (γ) in which the above group (β) and a divalent heteroatom-containing group are combined.

The "hydrocarbon group" includes a chain hydrocarbon group, an alicyclic hydrocarbon group and an aromatic hydrocarbon group. This "hydrocarbon group" may be a saturated hydrocarbon group or an unsaturated hydrocarbon group. The "chain hydrocarbon group" refers to a hydrocarbon group that does not contain a cyclic structure and is composed only of a chain structure, and includes both a linear hydrocarbon group and a branched hydrocarbon group. The "alicyclic hydrocarbon group" refers to a hydrocarbon group containing only an alicyclic structure as a ring structure and not containing an aromatic ring structure, and refers to a monocyclic alicyclic hydrocarbon group and a polycyclic alicyclic group. Contains both hydrocarbon groups. However, it does not have to be composed only of an alicyclic structure, and a chain structure may be included as a part thereof. The "aromatic hydrocarbon group" refers to a hydrocarbon group containing an aromatic ring structure as a ring structure. However, it does not have to be composed only of an aromatic ring structure, and a chain structure or an alicyclic structure may be included as a part thereof.

Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms include a monovalent chain hydrocarbon group having 1 to 20 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, and 6 carbon atoms. Examples thereof include to 20 monovalent aromatic hydrocarbon groups.

Examples of the monovalent chain hydrocarbon group having 1 to 20 carbon atoms include an alkyl group such as a methyl group, an ethyl group, an n-propyl group and an i-propyl group, and an alkenyl group such as an ethenyl group, a propenyl group and a butenyl group. , Ethynyl group, propynyl group, alkynyl group such as butynyl group and the like.

Examples of the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms include an alicyclic saturated hydrocarbon group such as a cyclopentyl group, a cyclohexyl group, a norbornyl group, an adamantyl group, a tricyclodecyl group and a tetracyclododecyl group. Examples thereof include an alicyclic unsaturated hydrocarbon group such as a cyclopentenyl group, a cyclohexenyl group, a norbornenyl group, a tricyclodecenyl group and a tetracyclododecenyl group.

Examples of the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms include an aryl group such as a phenyl group, a tolyl group, a xsilyl group, a naphthyl group and an anthryl group, a benzyl group, a phenethyl group, a naphthylmethyl group and an anthrylmethyl group. Examples include an aralkyl group such as a group.

Examples of the hetero atom constituting the monovalent or divalent hetero atom-containing group include an oxygen atom, a nitrogen atom, a sulfur atom, a phosphorus atom, a silicon atom, a halogen atom and the like. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.

Examples of the divalent heteroatom-containing group include -O-, -CO-, -S-, -CS-, -NR'-, a group in which two or more of these are combined, and the like. R'is a hydrogen atom or a monovalent hydrocarbon group.

As R ¹⁸ , a monovalent hydrocarbon group is preferable, and an alkyl group is more preferable.

Examples of the alicyclic structure having 4 to 20 ring members, in which two or more of a plurality of R ^18s are combined with each other and together with a carbon chain to which they are bonded, include a cyclopentane structure, a cyclohexane structure, a cyclopentene structure, and a cyclohexene structure. Can be mentioned.

The aliphatic heterocyclic structure consisting ring members 4-20 with carbon chain more than two are combined they are bound to each other of the plurality of R ^18, for example, azacyclopentane structure, azacyclohexane structure, Chiashikuro Examples thereof include a pentane structure, a thiacyclohexane structure, an oxacyclopentane structure, and an oxacyclohexane structure.

As a, 0 to 2 is preferable, 0 or 1 is more preferable, and 0 is further preferable.

As b, 1 to 3 is preferable, 1 or 2 is more preferable, and 1 is further preferable.

The structural unit (I) is, for example, a structural unit represented by the following formulas (I-1) to (I-14) (hereinafter, also referred to as “structural unit (I-1) to (I-14)”) and the like. Can be mentioned.

In the above formulas (I-1) to (I-14), R ¹⁷ has the same meaning as the above formula (3).

As the structural unit (I), the structural unit (I-1) or the structural unit (I-8) is preferable, and the structural unit (I-1) is more preferable.

The lower limit of the content ratio of the structural unit (I) in the [A] polymer is preferably 20 mol%, more preferably 25 mol%, and 30 mol% with respect to all the structural units constituting the [A] polymer. Is even more preferable. The upper limit of the content ratio is preferably 70 mol%, more preferably 60 mol%, still more preferably 55 mol%. By setting the content ratio of the structural unit (I) within the above range, the sensitivity, LWR performance, and resolution of the radiation-sensitive resin composition to exposure light can be further enhanced.

[Structural unit (II)]
The structural unit (II) is a structural unit containing an acid dissociative group. The "acid dissociable group" means a group that replaces a hydrogen atom in a carboxy group, a hydroxy group, or the like, and dissociates by the action of an acid to give a carboxy group, a hydroxy group, or the like. The acid dissociative group is dissociated by the action of the acid generated from the [B] acid generator or the like by the exposure, and the solubility of the [A] polymer in the developing solution in the exposed portion is changed to form a resist pattern. be able to.

The structural unit (II) includes, for example, a structural unit represented by the following formulas (4-1) to (4-3) (hereinafter, also referred to as “structural unit (II-1) to (II-3)”). Can be mentioned. Incidentally, for example, in the following formulas (4-1), ^-C binding oxy oxygen atom derived from a carboxy group ^{(R X) (R Y)} (R Z) corresponds to the acid-dissociable group.

In the above formula (4-1), formula (4-2) and formula (4-3), ^RT is independently a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.

In the above formula (4-1), ^RX is a monovalent hydrocarbon group having 1 to 20 carbon atoms. ^RY and R ^Z are independently monovalent hydrocarbon groups having 1 to 20 carbon atoms, or have 3 to 3 ring members composed of carbon atoms in which these groups are combined with each other and bonded to each other. It is part of the alicyclic structure of 20.

In the above formula (4-2), ^RA is a hydrogen atom. R ^B and R ^C are each independently a monovalent hydrocarbon group having a hydrogen atom or a C 1-20. R ^{D is} a divalent hydrocarbon group of R A, ^{R B} and ^{R C} is C 1 -C 20 constituting the unsaturated alicyclic structure ring members 4-20 with the carbon atom bonded respectively.

In the above formula (4-3), ^{R U} and ^{R V} are each independently a monovalent hydrocarbon group having a hydrogen atom or a carbon number of 1-20, ^{R W} is 1 1 to 20 carbon atoms whether the valence of the hydrocarbon group, it is part of an alicyclic structure composed ring members 3-20 together with the carbon atom to which R ^U and R ^V are combined they are bound together, or R ^U and R ^W There is a part of the aliphatic heterocyclic structure consisting ring members 4-20 together with oxygen atom bonding the carbon atoms and R ^W that keyed R ^U, bonded to each other.

^{R X, R Y, R Z} , R B, R C, R U, the monovalent hydrocarbon group ^{R V} or 1 to 20 carbon atoms represented by ^{R W,} for example, the above formula (3) R Examples thereof include a group similar to the group exemplified as the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by ^18.

^{Examples of the alicyclic structure having 3 to 20 ring members, in which RY} and R ^Z are combined with each other and composed of carbon atoms to which they are bonded, include a single ring such as a cyclopropane structure, a cyclobutene structure, a cyclopentene structure, and a cyclohexane structure. Polycyclic saturated alicyclic structure such as saturated alicyclic structure, norbornene structure, adamantan structure, monocyclic unsaturated alicyclic structure such as cyclopropene structure, cyclobutene structure, cyclopentene structure, cyclohexene structure, polycyclic structure such as norbornene structure An unsaturated alicyclic structure and the like can be mentioned.

As the divalent hydrocarbon group having 1 to 20 carbon atoms represented by ^RD , for example, the group exemplified as the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by ^{R 18 of the above formula (3).} Examples thereof include a group obtained by removing one hydrogen atom from the group.

Examples of the unsaturated alicyclic structure having 4 to 20 ring members in which R ^D is ^{composed of carbon atoms to which RA} , R ^B and ^RC are bonded are monocyclic unsaturated structures such as cyclobutene structure, cyclopentene structure and cyclohexene structure. Examples thereof include a polycyclic unsaturated alicyclic structure such as an alicyclic structure and a norbornene structure.

The alicyclic structure R ^U and R ^V are combined with each other configured with the carbon atoms to which they are attached ring members 3-20, for example, R ^Y and R ^Z are combined with each other is constructed together with the carbon atom to which they are attached Examples thereof include a structure similar to the structure exemplified as the alicyclic structure having 3 to 20 ring members.

The aliphatic heterocyclic structure R ^U and R ^W are carbon atoms and R ^W that keyed R ^U, bonded to each other is formed with an oxygen atom bonded ring members 4-20, for example oxacyclobutane structure, oxacyclopentane Examples thereof include a saturated oxygen-containing heterocyclic structure such as a structure and an oxacyclohexane structure, an unsaturated oxygen-containing heterocyclic structure such as an oxacyclobutane structure, an oxacyclopentene structure, and an oxacyclohexene structure.

As the ^RT , a hydrogen atom or a methyl group is preferable from the viewpoint of copolymerizability of the monomer giving the structural unit (II).

The R ^X, preferably a chain hydrocarbon group or an aromatic hydrocarbon group, more preferably an alkyl group or an aryl group, more preferably an ethyl group or a phenyl group.

It is preferable that ^RY and R ^Z are a part of an alicyclic structure having 3 to 20 ring members, in which they are combined with each other and composed of carbon atoms to which they are bonded. As the alicyclic structure, a saturated alicyclic structure is preferable, a monocyclic saturated alicyclic structure is more preferable, and a cyclopentane structure or a cyclohexane structure is further preferable.

As the structural unit (II), the structural unit (II-1) is preferable.

The lower limit of the content ratio of the structural unit (II) in the [A] polymer is preferably 30 mol%, more preferably 40 mol%, and 45 mol% with respect to all the structural units constituting the [A] polymer. Is even more preferable. The upper limit of the content ratio is preferably 70 mol%, more preferably 60 mol%, still more preferably 55 mol%. By setting the content ratio of the structural unit (II) within the above range, the sensitivity, LWR performance, and resolution of the radiation-sensitive resin composition to exposure light can be further enhanced.

[Other structural units]
Examples of other structural units include a structural unit containing an alcoholic hydroxyl group (hereinafter, also referred to as “structural unit (III)”), a lactone structure, a cyclic carbonate structure, a sultone structure, or a structural unit containing a combination thereof (hereinafter, “Structural unit”). Structural unit (IV) ”) and the like. [A] The polymer can further appropriately adjust the solubility in a developing solution by further having a structural unit (III), a structural unit (IV), or a combination thereof, and as a result, the radiation-sensitive radiation. The sensitivity, LWR performance and resolution of the sex resin composition to exposure light can be further improved. Further, the adhesion between the resist pattern and the substrate can be further improved.

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

In the above formula, ^RL2 is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.

When the [A] polymer has a structural unit (III), the lower limit of the content ratio of the structural unit (III) is preferably 1 mol% and 5 mol% with respect to all the structural units in the [A] polymer. Is more preferable. The upper limit of the content ratio is preferably 20 mol%, more preferably 15 mol%.

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

In the above formula, ^RL1 is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.

As the structural unit (IV), a structural unit containing a lactone structure is preferable.

When the polymer [A] has a structural unit (IV), the lower limit of the content ratio of the structural unit (IV) is preferably 1 mol% and 5 mol% with respect to all the structural units in the [A] polymer. Is more preferable. The upper limit of the content ratio is preferably 20 mol%, more preferably 15 mol%.

[A] The lower limit of the polystyrene-equivalent weight average molecular weight (Mw) of the polymer by gel permeation chromatography (GPC) is preferably 2,000, more preferably 3,000, and even more preferably 4,000. The upper limit of Mw is preferably 10,000, more preferably 9,000, and even more preferably 8,500. By setting the Mw of the polymer in the above range, the solubility in a developing solution can be appropriately adjusted.

[A] The upper limit of the ratio of Mw (Mw / Mn, hereinafter also referred to as "dispersity") to the polystyrene-equivalent number average molecular weight (Mn) of the polymer by GPC is preferably 2.50, more preferably 2.00. 1.75 is even more preferred. The lower limit of the ratio is usually 1.00, preferably 1.10, and more preferably 1.20. By setting the Mw / Mn of the polymer in the above range, the coatability of the radiation-sensitive resin composition can be further improved.

The Mw and Mn of the polymer in the present specification are values measured by gel permeation chromatography (GPC) under the following conditions.
GPC column: 2 "G2000HXL", 1 "G3000HXL" and 1 "G4000HXL" from Toso Co., Ltd. Elution solvent: Tetrahydrofuran Flow rate: 1.0 mL / min Sample concentration: 1.0% by mass
Sample injection volume: 100 μL
Column temperature: 40 ° C
Detector: Differential refractometer Standard material: Monodisperse polystyrene

The lower limit of the content ratio of the [A] polymer in the radiation-sensitive resin composition is preferably 50% by mass, more preferably 60% by mass, and 70% by mass with respect to all the components other than the [D] organic solvent. Is more preferable, and 80% by mass is particularly preferable.

The [A] polymer can be synthesized, for example, by polymerizing a monomer giving each structural unit by a known method.

<[B] Acid generator>
[B] The acid generator has a monovalent radiation-sensitive onium cation represented by the following formula (1) described later (hereinafter, also simply referred to as “radiation-sensitive onium cation”). [B] The acid generator is a substance that generates an acid upon exposure. Examples of the exposure light include those similar to those exemplified as the exposure light in the exposure step of the resist pattern forming method described later. The acid generated by the exposure dissociates the acid dissociative group of the polymer or the like [A] to generate a carboxy group or the like, and there is a difference in the solubility of the resist film in the developing solution between the exposed part and the non-exposed part. By generating, a resist pattern can be formed.

The form of the [B] acid generator in the radiation-sensitive resin composition is not particularly limited as long as it contains the above-mentioned radiation-sensitive onium cation. It may be in the form of a radiation-sensitive acid-generating polymer (hereinafter, also referred to as “[B] acid-generating polymer”), which will be described later, or in both forms. In the present specification, the “radiation-sensitive acid-generating polymer” means a polymer having a structural unit that generates an acid upon exposure. In other words, the [B] radiation-sensitive acid-generating polymer can be said to be a form in which the [B] acid-generating polymer is incorporated as a part of the polymer. The radiation-sensitive resin composition may contain one or more [B] acid generators.

[Radiation-sensitive onium cation]
The radiation-sensitive onium cation is represented by the following formula (1).

In the above formula (1), Ar ¹ is a group obtained by removing (m + 1) hydrogen atoms on an aromatic ring from an array having 6 to 20 ring members. m is an integer from 0 to 11. When m is 1, R ¹ is a monovalent organic group, a hydroxy group, a nitro group or a halogen atom having 1 to 20 carbon atoms. when m is 2 or more, plural R ¹ are equal to or different from each other, a monovalent organic group having 1 to 20 carbon atoms, hydroxy group, or a nitro group or a halogen atom, or these groups are combined with each other these It is a part of an alicyclic structure or an aliphatic heterocyclic structure having 4 to 20 ring members, which is composed of a carbon chain to which is bonded. Ar ² is a group obtained by removing hydrogen atoms on n aromatic rings from an array having 6 to 20 ring members which is fused with the thiophene ring. n is an integer from 0 to 10. When n is 1, R ² is a monovalent organic group, a hydroxy group, a nitro group or a halogen atom having 1 to 20 carbon atoms. when n is 2 or more, plural R ² are equal to or different from each other, a monovalent organic group having 1 to 20 carbon atoms, hydroxy group, or a nitro group or a halogen atom, or these groups are combined with each other these It is a part of an alicyclic structure or an aliphatic heterocyclic structure having 4 to 20 ring members, which is composed of a carbon chain to which is bonded. R ³ and R ⁴ are independently monovalent organic groups having 1 to 20 carbon atoms, hydroxy groups, nitro groups, halogen atoms or hydrogen atoms.

Examples of the arene having 6 to 20 ring members that give Ar ¹ or Ar ² include benzene, naphthalene, anthracene, phenanthrene, tetracene, and pyrene. As ^{the arene having 6 to 20 ring members that gives Ar 1} or Ar ² , benzene or naphthalene is preferable, and benzene is more preferable from the viewpoint of further improving the sensitivity of the radiation-sensitive resin composition to exposure light.

As a monovalent organic group having 1 to 20 carbon atoms represented by ^{R 1} , R ² , R ³ or R ⁴ , for example, a monovalent organic group having 1 to 20 carbon atoms represented by ^{R 18 in the above formula (3).} Examples of the organic group of the above include groups similar to those exemplified above.

The alicyclic structure of a plurality of ring members 4-20 that constitute together with the carbon chain R ¹ or a plurality of R ² are combined they are bound to each other, two of the plurality of R ¹⁸ in the example above formula (3) Examples thereof include a structure similar to that exemplified as an alicyclic structure having 4 to 20 ring members, which is formed by combining the above with each other and forming a carbon chain to which these are bonded.

The aliphatic heterocyclic structure ring members 4-20 that constitute together with the carbon chain in which a plurality of R ¹ or R ² is combined they are bound together, for example, of a plurality of R ¹⁸ in the formula (3) Examples thereof include a structure similar to that exemplified as an aliphatic heterocyclic structure having 4 to 20 ring members, in which two or more are combined with each other and formed together with a carbon chain to which they are bonded.

As R ¹ , from the viewpoint of further improving the sensitivity of the radiation-sensitive resin composition to exposure light, a monovalent organic group having 1 to 20 carbon atoms, a hydroxy group or a halogen atom is preferable, and R 1 has 1 to 6 carbon atoms. Alkyl fluorinated groups or fluorine atoms are more preferred.

As m, 0 to 5, more preferably 0 to 4, and even more preferably 0 to 3.

The R ^2, from the viewpoint of further improving the sensitivity to exposure light of the radiation-sensitive resin composition, a monovalent organic group having 1 to 20 carbon atoms, a nitro group or a halogen atom is preferable, the number of 1 to 6 carbon atoms Alkyl fluorinated groups or fluorine atoms are more preferred.

As n, 0 to 5 is preferable, and 0 to 3 is more preferable. 0 or 1 is more preferred.

As R ³ or R ⁴ , a monovalent organic group or a hydrogen atom having 1 to 20 carbon atoms is preferable, and a methyl group, an acetyl group or a hydrogen atom is more preferable.

As the radiation-sensitive onium cation, the radiation-sensitive onium cation represented by the following formulas (1-1) to (1-15) is preferable (hereinafter, "radiation-sensitive onium cation (1-1) to (1-)". 15) ”).

In the radiation-sensitive resin composition, when the content form of the [B] acid generator is the form of a low molecular weight compound ([B] acid generator), the [B] acid generator is represented by the following formula (2). Examples thereof include the represented compounds.

In the above formula (2), ^{R 5} is a monovalent organic group having 1 to 30 carbon atoms. R ⁶ is a divalent linking group. R ⁷ and R ⁸ are independently hydrogen atoms or monovalent hydrocarbon groups having 1 to 20 carbon atoms. R ⁹ and R ¹⁰ are independently fluorine atoms or monovalent fluorinated hydrocarbon groups having 1 to 20 carbon atoms. p is an integer from 0 to 10. q is an integer from 0 to 10. r is an integer from 0 to 10. However, p + q + r is 1 or more and 30 or less. when p is 2 or more, plural R ⁶ may be the same or different from each other. when q is 2 or more, plural R ⁷ are equal to or different from each other, a plurality of R ⁸ may be the same or different from each other. when r is 2 or more, plural R ⁹ are equal to or different from each other, a plurality of R ¹⁰ may be the same or different from each other. T ⁺ is a monovalent radiation-sensitive onium cation represented by the above formula (1).

The monovalent organic group having 1 to 30 carbon atoms represented by ^{R 5} is the same as that exemplified as the monovalent organic group having 1 to 20 carbon atoms represented by ^{R 18 in the above formula (3), for example.} The basis of.

The R ^5, 1 monovalent radical containing ring members 5 or more ring structures is preferred. Examples of the monovalent group containing a ring structure having 5 or more ring members include a monovalent group containing an alicyclic structure having 5 or more ring members, a monovalent group containing an aliphatic heterocyclic structure having 5 or more ring members, and a ring. Examples thereof include a monovalent group containing an aromatic carbocyclic structure having 5 or more members, a monovalent group containing an aromatic heterocyclic structure having 5 or more members, and the like.

Examples of the alicyclic structure having 5 or more ring members include a monocyclic saturated alicyclic structure such as a cyclopentane structure, a cyclohexane structure, a cycloheptane structure, a cyclooctane structure, a cyclononane structure, a cyclodecane structure, and a cyclododecane structure, a cyclopentene structure, and a cyclohexene. Structure, cycloheptene structure, cyclooctene structure, monocyclic unsaturated alicyclic structure such as cyclodecene structure, norbornene structure, adamantan structure, tricyclodecane structure, polycyclic saturated alicyclic structure such as tetracyclododecane structure, norbornene structure, Examples thereof include a polycyclic unsaturated alicyclic structure such as a tricyclodecane structure.

Examples of the aliphatic heterocyclic structure having 5 or more ring members include a lactone structure such as a hexanolactone structure and a norbornane lactone structure, a sulton structure such as a hexanosulton structure and a norbornane sulton structure, an oxacycloheptane structure, and an oxanorbornane structure. Examples thereof include a nitrogen atom-containing heterocyclic structure such as an oxygen atom-containing heterocyclic structure, an azacyclohexane structure and a diazabicyclooctane structure, and a sulfur atom-containing heterocyclic structure such as a thiacyclohexane structure and a thianorbornane structure.

Examples of the aromatic carbocyclic ring structure having 5 or more ring members include a benzene structure, a naphthalene structure, a phenanthrene structure, and an anthracene structure.

Examples of the aromatic heterocyclic structure having 5 or more ring members include an oxygen atom-containing heterocyclic structure such as a furan structure, a pyran structure, a benzofuran structure, and a benzopyran structure, and a nitrogen atom-containing heterocyclic structure such as a pyridine structure, a pyrimidine structure, and an indole structure. And so on.

As ^{the lower limit of the number of ring members of the ring structure of R 5} , 6 is preferable, 8 is more preferable, 9 is further preferable, and 10 is particularly preferable. As the upper limit of the number of ring members, 15 is preferable, 14 is more preferable, 13 is further preferable, and 12 is particularly preferable.

Examples of the divalent linking group represented by R ⁶ include a carbonyl group, an ether group, a carbonyloxy group, an oxycarbonyl group, an oxycarbonyloxy group, a sulfide group, a thiocarbonyl group, a sulfonyl group and a divalent hydrocarbon group. , Or a group combining these. Among these, a carbonyloxy group, a sulfonyl group, an alkanediyl group or a divalent alicyclic saturated hydrocarbon group is preferable, and a carbonyloxy group or a sulfonyl group is more preferable. When p is 2 or more, the divalent linking group excluding the divalent hydrocarbon group is usually adjacent only to the divalent hydrocarbon group.

Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by R ⁷ or R ^{8 include an alkyl group having 1 to 20 carbon atoms.}

As R ⁷ or R ⁸ , a hydrogen atom or an alkyl group having 1 to 20 carbon atoms is preferable, and a hydrogen atom is more preferable.

As the ^{monovalent fluorinated hydrocarbon group having 1 to 20 carbon atoms represented by R 9} or R ¹⁰ , for example, at least one hydrogen atom possessed by the monovalent hydrocarbon group having 1 to 20 carbon atoms is a fluorine atom. Examples thereof include groups substituted with.

As R ⁹ or R ¹⁰ , a fluorine atom or a fluorinated alkyl group having 1 to 20 carbon atoms is preferable, and a fluorine atom is more preferable.

As p, 0 to 5, more preferably 0 to 2, and even more preferably 0 or 1.

As q, 0 to 5 is preferable, 0 to 2 is more preferable, and 0 or 1 is further preferable.

As the lower limit of r, 1 is preferable, and 2 is more preferable. By setting r to 1 or more, the strength of the acid generated from the compound represented by the above formula (2) can be increased, and as a result, the exposure light of the resist pattern formed by the radiation-sensitive resin composition can be increased. The sensitivity to the light and the LWR performance can be further improved. As the upper limit of r, 4 is preferable, 3 is more preferable, and 2 is further preferable.

As the lower limit of p + q + r, 2 is preferable, and 4 is more preferable. As the upper limit of p + q + r, 20 is preferable, and 10 is more preferable.

[B] As the acid generator, for example, compounds represented by the following formulas (2-1) to (2-20) (hereinafter, also referred to as "acid generators (2-1) to (2-20)"). And so on.

In the above formulas (2-1) to (2-20), T ⁺ is synonymous with the above formula (2).

When the content form of the [B] acid generator in the radiation-sensitive resin composition is a radiation-sensitive acid-generating polymer ([B] acid-generating polymer "), the [B] acid-generating polymer is, for example, A polymer having a structural unit represented by the following formula (2') (hereinafter, also referred to as "structural unit (V)") is preferable. The structural unit (V) may be included as a structural unit constituting the [A] polymer, or may be included as a structural unit constituting a polymer other than the [A] polymer. When the [A] polymer has a structural unit (V), the [A] polymer also functions as a [B] acid generator.

In the above formula (2'), R ¹¹ is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. R ¹² is a divalent linking group. R ¹³ and R ¹⁴ are independently hydrogen atoms or monovalent hydrocarbon groups having 1 to 20 carbon atoms. R ¹⁵ and R ¹⁶ are independently fluorine atoms or monovalent fluorinated hydrocarbon groups having 1 to 20 carbon atoms. R ¹¹ is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. s is an integer from 0 to 10. t is an integer from 0 to 10. u is an integer from 0 to 10. However, s + t + u is 1 or more and 30 or less. When s is 2 or more, the plurality of R ^12s are the same or different from each other. When t is 2 or more, the plurality of R ^13s are the same or different from each other, and the plurality of R ^14s are the same or different from each other. When u is 2 or more, the plurality of R ^15s are the same or different from each other, and the plurality of R ^16s are the same or different from each other. T ⁺ is a monovalent radiation-sensitive onium cation represented by the above formula (1).

Examples of the divalent linking group represented by R ¹² include groups similar to the group exemplified as the divalent linking group represented by ^{R 6 in the above formula (2).} As R ¹² , a carbonyloxy group or ^{a group represented by —Ar 4-} O— is preferable, and a carbonyloxy group is more preferable. Ar ⁴ is a group obtained by removing two hydrogen atoms from an arene having 6 to 20 ring members. Examples of the arene having 6 to 20 ring members giving Ar ⁴ include those similar to those exemplified as the arene having 6 to 20 ring members giving ^{Ar 1} or Ar ^{2 in the above formula (1).}

Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by R ¹³ or R ¹⁴ include the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by ^{R 7} or R ^{8 of the above formula (2).} Examples thereof include groups similar to the groups exemplified as the hydrogen group.

As R ¹³ or R ¹⁴ , a hydrogen atom or an alkyl group having 1 to 20 carbon atoms is preferable, and a hydrogen atom is more preferable.

The monovalent fluorinated hydrocarbon group having 1 to 20 carbon atoms represented by ^{R 15} or R ¹⁶ is, for example, the monovalent group having 1 to 20 carbon atoms represented by ^{R 9} or R ^{10 in the above formula (2).} Examples of the group similar to the group exemplified as the fluorinated hydrocarbon group of the above can be mentioned.

As R ¹⁵ or R ¹⁶ , a fluorine atom or a fluorinated alkyl group having 1 to 20 carbon atoms is preferable, and a fluorine atom is more preferable.

As s, 0 to 5 is preferable, 0 to 2 is more preferable, and 1 is even more preferable.

As t, 0 to 5, more preferably 0 to 2, and even more preferably 1.

As the lower limit of u, 1 is preferable, and 2 is more preferable. By setting r to 1 or more, the strength of the acid generated from the structural unit represented by the above formula (2') can be increased, and as a result, the resist pattern formed by the radiation-sensitive resin composition can be increased. The sensitivity to exposure light and the LWR performance can be further improved. As the upper limit of r, 4 is preferable, 3 is more preferable, and 2 is further preferable.

As the lower limit of s + t + u, 2 is preferable, and 4 is more preferable. As the upper limit of s + t + u, 20 is preferable, and 10 is more preferable.

As the structural unit (V), a structural unit represented by the following formula (2-21) (hereinafter, also referred to as “structural unit (V-1)”) is preferable.

In the above formula (2-21), R ¹¹ and T ⁺ are synonymous with the above formula (2').

When the [B] acid generator is a [B] acid generator, the lower limit of the content of the [B] acid generator is preferably 5 parts by mass with respect to 100 parts by mass of the [A] polymer. Parts by mass are more preferred, and parts by mass 15 are even more preferred. The upper limit of the content is preferably 60 parts by mass, more preferably 55 parts by mass, and even more preferably 50 parts by mass. [B] By setting the content of the acid generator in the above range, the sensitivity, LWR performance and resolution of the radiation-sensitive resin composition to exposure light can be further improved. Further, when the content of the [B] acid generator is more than 20 parts by mass, the sensitivity, LWR performance and resolution of the radiation-sensitive resin composition to exposure light can be further improved. Further, the defect suppressing property can be further improved.

When the [A] polymer has a structural unit (V), the lower limit of the content ratio of the structural unit (V) is preferably 5 mol% with respect to all the structural units constituting the [A] polymer. More preferably mol%. On the other hand, the upper limit of the content ratio of the structural unit is preferably 30 mol%, more preferably 20 mol%, based on all the structural units constituting the polymer [A]. By setting the content ratio of the structural unit in the above range, the sensitivity, LWR performance and resolution of the radiation-sensitive resin composition to exposure light can be further improved.

<[C] Acid diffusion control agent>
The [C] acid diffusion control agent has the effect of controlling the diffusion phenomenon of the acid generated from the [B] acid generator or the like in the resist film by exposure and controlling an unfavorable chemical reaction in the non-exposed region. By containing the [C] acid diffusion control agent in the radiation-sensitive resin composition, the sensitivity, LWR performance and resolution of the radiation-sensitive resin composition to exposure light can be further improved. The radiation-sensitive resin composition may contain one or more [C] acid diffusion control agents.

Examples of the [C] acid diffusion control agent include nitrogen atom-containing compounds, photodisintegrating bases that are exposed to exposure and generate weak acids, and the like.

Examples of the nitrogen atom-containing compound include amine compounds such as trypentylamine and trioctylamine, amide group-containing compounds such as formamide and N, N-dimethylacetamide, urea compounds such as urea and 1,1-dimethylurea, and pyridine. Examples thereof include nitrogen-containing heterocyclic compounds such as N- (undecylcarbonyloxyethyl) morpholine and Nt-pentyloxycarbonyl-4-hydroxypiperidin.

Examples of the photodisintegrating base include compounds containing an onium cation and a weak acid anion that are decomposed by exposure. In the photodisintegrating base, a weak acid is generated from a proton generated by decomposition of an onium cation and an anion of a weak acid in an exposed portion, so that the acid diffusion controllability is lowered.

Examples of the onium cation decomposed by the above exposure include a triphenylsulfonium cation, a radiation-sensitive onium cation represented by the above formula (1), and the like.

Examples of the weak acid anion include salicylate anion.

When the radiation-sensitive resin composition is a compound containing a radiation-sensitive onium cation represented by the above formula (1) and a weak acid anion as the [C] acid diffusion control agent, this compound is the compound. It can also function as the above-mentioned [B] acid generator in the radiation-sensitive resin composition.

When the radiation-sensitive resin composition contains the [C] acid diffusion control agent, the lower limit of the content ratio of the [C] acid diffusion control agent is 10 mol with respect to 100 mol% of the [B] acid generator. % Is preferred, 20 mol% is more preferred, and 30 mol% is even more preferred. The upper limit of the content is preferably 200 mol%, more preferably 100 mol%, still more preferably 60 mol%.

<[D] Organic solvent>
The radiation-sensitive resin composition usually contains [D] an organic solvent. The [D] organic solvent is not particularly limited as long as it is a solvent capable of dissolving or dispersing at least the [A] polymer and the [B] acid generator, and other optional components contained as necessary.

[D] Examples of the organic solvent include alcohol solvents, ether solvents, ketone solvents, amide solvents, ester solvents, hydrocarbon solvents and the like. The radiation-sensitive resin composition may contain one or more [D] organic solvents.

Examples of the alcohol solvent include an aliphatic monoalcohol solvent having 1 to 18 carbon atoms such as 4-methyl-2-pentanol and n-hexanol, and an alicyclic monoalcohol solvent having 3 to 18 carbon atoms such as cyclohexanol. Examples thereof include a solvent, a polyhydric alcohol solvent having 2 to 18 carbon atoms such as 1,2-propylene glycol, and a polyhydric alcohol partial ether solvent having 3 to 19 carbon atoms such as propylene glycol 1-monomethyl ether.

Examples of the ether-based solvent include dialkyl ether-based solvents such as diethyl ether, dipropyl ether, dibutyl ether, dipentyl ether, diisoamyl ether, dihexyl ether and diheptyl ether, cyclic ether-based solvents such as tetrahydrofuran and tetrahydropyran, and diphenyl ethers. Examples thereof include an aromatic ring-containing ether-based solvent such as anisole.

Examples of the ketone solvent include acetone, methyl ethyl ketone, methyl-n-propyl ketone, methyl-n-butyl ketone, diethyl ketone, methyl-iso-butyl ketone, 2-heptanone, ethyl-n-butyl ketone, methyl-n-hexyl ketone, and the like. Chain ketone solvents such as di-iso-butyl ketone and trimethylnonanone, cyclic ketone solvents such as cyclopentanone, cyclohexanone, cycloheptanone, cyclooctanone and methylcyclohexanone, 2,4-pentandione and acetonylacetone. , Acetphenone and the like.

Examples of the amide solvent include cyclic amide solvents such as N, N'-dimethylimidazolidinone and N-methylpyrrolidone, N-methylformamide, N, N-dimethylformamide, N, N-diethylformamide, acetamide, and N. Examples thereof include chain amide solvents such as -methylacetamide, N, N-dimethylacetamide and N-methylpropionamide.

Examples of the ester solvent include a monocarboxylic acid ester solvent such as n-butyl acetate and ethyl lactate, a lactone solvent such as γ-butyrolactone and valerolactone, a polyhydric alcohol carboxylate solvent such as propylene glycol acetate, and propylene acetate. Examples thereof include a polyhydric alcohol partial ether carboxylate solvent such as glycol monomethyl ether, a polyvalent carboxylic acid diester solvent such as diethyl oxalate, and a carbonate solvent such as dimethyl carbonate and diethyl carbonate.

Examples of the hydrocarbon solvent include an aliphatic hydrocarbon solvent having 5 to 12 carbon atoms such as n-pentane and n-hexane, and an aromatic hydrocarbon solvent having 6 to 16 carbon atoms such as toluene and xylene. Be done.

[D] As the organic solvent, an alcohol solvent and / or an ester solvent is preferable, a polyhydric alcohol partial ether solvent having 3 to 19 carbon atoms and / or a polyhydric alcohol partial ether carboxylate solvent is more preferable, and propylene. Glycol 1-monomethyl ether and / or propylene glycol monomethyl ether acetate are more preferred.

When the radiation-sensitive resin composition contains the [D] organic solvent, the lower limit of the content ratio of the [D] organic solvent is 50% by mass with respect to all the components contained in the radiation-sensitive resin composition. % Is preferable, 60% by mass is more preferable, 70% by mass is further preferable, and 80% by mass is particularly preferable. The upper limit of the content ratio is preferably 99.9% by mass, preferably 99.5% by mass, and even more preferably 99.0% by mass.

<Other optional ingredients>
Examples of other optional components include other acid generators other than the [B] acid generator (hereinafter, also simply referred to as “other acid generators”), surfactants, and the like. The radiation-sensitive resin composition may contain one or more other optional components, respectively.

Examples of other acid generators include triphenylsulfonium salts, diphenyliodonium salts, and compounds described in paragraphs [0080] to [0113] of JP2009-134088A.

<Preparation method of radiation-sensitive resin composition>
The radiation-sensitive resin composition comprises, for example, a [A] polymer and a [B] acid generator, and, if necessary, a [C] acid diffusion control agent, [D] an organic solvent, and other optional components. The mixture is preferably prepared by filtering the obtained mixture with a membrane filter having a pore size of 0.2 μm or less.

<Resist pattern formation method>
The resist pattern forming method involves directly or indirectly coating a substrate with a radiation-sensitive resin composition (hereinafter, also referred to as a “coating step”) and exposing the resist film formed by the coating step. It includes a step (hereinafter, also referred to as “exposure step”) and a step of developing the exposed resist film (hereinafter, also referred to as “development step”).

According to the resist pattern forming method, by using the above-mentioned radiation-sensitive resin composition as the radiation-sensitive resin composition in the coating process, the sensitivity to exposure light is good, and the LWR performance and resolution are good. It is possible to form an excellent resist pattern.

Hereinafter, each process included in the resist pattern forming method will be described.

[Coating process]
In this step, the radiation-sensitive resin composition is applied directly or indirectly to the substrate. As a result, a resist film is formed directly or indirectly on the substrate.

In this step, the above-mentioned radiation-sensitive resin composition is used as the radiation-sensitive resin composition.

Examples of the substrate include conventionally known ones such as silicon wafers, silicon dioxide, and wafers coated with aluminum. In addition, examples of the case where the radiation-sensitive resin composition is indirectly applied to the substrate include, for example, the case where the radiation-sensitive resin composition is applied onto the antireflection film formed on the substrate. Examples of such an antireflection film include organic or inorganic antireflection films disclosed in Japanese Patent Application Laid-Open No. 6-12452 and JP-A-59-93448.

Examples of the coating method include rotary coating (spin coating), cast coating, roll coating, and the like. After coating, if necessary, prebaking (hereinafter, also referred to as “PB”) may be performed in order to volatilize the solvent in the coating film. As the lower limit of the temperature of PB, 60 ° C. is preferable, and 80 ° C. is more preferable. The upper limit of the temperature is preferably 150 ° C., more preferably 140 ° C. As the lower limit of the PB time, 5 seconds is preferable, and 10 seconds is more preferable. As the lower limit of the time, 600 seconds is preferable, and 300 seconds is more preferable. The lower limit of the average thickness of the resist film formed is preferably 10 nm, more preferably 20 nm. The upper limit of the average thickness is preferably 1,000 nm, more preferably 500 nm.

[Exposure process]
In this step, the resist film formed by the above coating step is exposed. This exposure is performed by irradiating the exposure light through a photomask (in some cases, through an immersion medium such as water). The exposure light includes electromagnetic waves such as visible light, ultraviolet rays, far ultraviolet rays, extreme ultraviolet rays (EUV), X-rays, and γ-rays; charged particles such as electron beams and α-rays, depending on the line width of the target pattern. Examples include lines. Among these, far ultraviolet rays, EUV or electron beams are preferable, ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), EUV (wavelength 13.5 nm) or electron beams are more preferable, and ArF excimer laser light. , EUV or electron beam is more preferable, and EUV or electron beam is particularly preferable.

After the above exposure, post-exposure baking (hereinafter, also referred to as “PEB”) is performed, and in the exposed portion of the resist film, the [A] polymer or the like due to the acid generated from the [B] acid generator or the like by the exposure is formed. It is preferable to promote the dissociation of the acid dissociative group having. With this PEB, it is possible to increase the difference in solubility in the developing solution between the exposed portion and the non-exposed portion. As the lower limit of the temperature of PEB, 50 ° C. is preferable, 80 ° C. is more preferable, and 100 ° C. is further preferable. The upper limit of the temperature is preferably 180 ° C., more preferably 130 ° C. As the lower limit of the PEB time, 5 seconds is preferable, 10 seconds is more preferable, and 30 seconds is further preferable. The upper limit of the time is preferably 600 seconds, more preferably 300 seconds, and even more preferably 100 seconds.

[Development process]
In this step, the exposed resist film is developed. As a result, a predetermined resist pattern can be formed. After development, it is generally washed with a rinse solution such as water or alcohol and dried. The developing method in the developing step may be alkaline development or organic solvent development.

In the case of alkaline development, the developing solution used for development includes, for example, sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, aqueous ammonia, ethylamine, n-propylamine, diethylamine, di-n-. Propylamine, triethylamine, methyldiethylamine, ethyldimethylamine, triethanolamine, tetramethylammonium hydroxide (hereinafter, also referred to as "TMAH"), pyrrole, piperidine, choline, 1,8-diazabicyclo- [5.4.0] Examples thereof include an alkaline aqueous solution in which at least one alkaline compound such as -7-undecene and 1,5-diazabicyclo- [4.3.0] -5-nonen are dissolved. Among these, the TMAH aqueous solution is preferable, and the 2.38 mass% TMAH aqueous solution is more preferable.

In the case of organic solvent development, examples of the developing solution include organic solvents such as hydrocarbon solvents, ether solvents, ester solvents, ketone solvents and alcohol solvents, and solutions containing the above organic solvents. Examples of the organic solvent include one or more of the solvents exemplified as the [D] organic solvent of the above-mentioned radiation-sensitive resin composition. Among these, an ester solvent or a ketone solvent is preferable. As the ester solvent, an acetate ester solvent is preferable, and n-butyl acetate is more preferable. As the ketone solvent, a chain ketone is preferable, and 2-heptanone is more preferable. The lower limit of the content of the organic solvent in the developing solution is preferably 80% by mass, more preferably 90% by mass, further preferably 95% by mass, and particularly preferably 99% by mass. Examples of the components other than the organic solvent in the developing solution include water, silicone oil and the like.

Examples of the developing method include a method of immersing the substrate in a tank filled with a developing solution for a certain period of time (dip method), and a method of developing by raising the developing solution on the surface of the substrate by surface tension and allowing it to stand still for a certain period of time (paddle method). ), A method of spraying the developer on the surface of the substrate (spray method), a method of continuing to apply the developer on the substrate rotating at a constant speed while scanning the developer dispensing nozzle at a constant speed (dynamic discharge method). And so on.

Examples of the pattern formed by the resist pattern forming method include a line-and-space pattern and a hole pattern.

Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. The measurement method of various physical property values is shown below.

[Weight average molecular weight (Mw), number average molecular weight (Mn) and dispersity (Mw / Mn)]
The Mw and Mn of the polymer were obtained by gel permeation chromatography (GPC) using a GPC column (2 "G2000HXL", 1 "G3000HXL", and 1 "G4000HXL") of Toso Co., Ltd. It was measured according to the conditions of. The dispersity (Mw / Mn) was calculated from the measurement results of Mw and Mn.
Elution solvent: Tetrahydrofuran Flow rate: 1.0 mL / min Sample concentration: 1.0% by mass
Sample injection volume: 100 μL
Column temperature: 40 ° C
Detector: Differential refractometer Standard material: Monodisperse polystyrene

<[B] Synthesis of acid generator>
[Synthesis Example 1] Synthesis of acid generator (B-1) In a reaction vessel, a salt (1.2 mmol) represented by the following formula (Zp), benzothiophene (1 mmol) and copper acetate (II) (0. 1 mmol) was mixed and stirred at 135 ° C. for 1 hour. After allowing to cool to room temperature, methylene chloride and ion-exchanged water were added for extraction, and the organic layer was separated. The obtained organic layer is dried over sodium sulfate, the solvent is distilled off, and the residue is purified by column chromatography. The compound represented by the following formula (Z-c1) (hereinafter, "Compound (Z-c1)"". (Also referred to as) was obtained in a good yield. The synthetic scheme of compound (Z-c1) is shown below.

Add compound (Z-c1) (0.5 mmol), compound represented by the following formula (Z-a1) (0.5 mmol), methylene chloride (5 mL) and ion-exchanged water (5 mL) to the reaction vessel for 1 hour. After stirring, the organic layer is separated and the solvent is distilled off to obtain a compound represented by the following formula (B-1) (hereinafter, also referred to as “acid generator (B-1)”) in a good yield. Obtained. The synthetic scheme of the acid generator (B-1) is shown below.

[Synthesis Examples 2 to 21] Synthesis of Acid Generators (B-2) to (B-21) The following formulas (B-2) to (B) are the same as in Synthesis Example 1 except that precursors are appropriately selected. A compound represented by -21) (hereinafter, also referred to as "acid generators (B-2) to (B-21)") was synthesized.

<[A] Synthesis of polymer>
The monomers used in the synthesis of each polymer in each Example and Comparative Example are shown below. In the following Synthesis Examples 22 to 26, unless otherwise specified, parts by mass mean a value when the total mass of the used monomers is 100 parts by mass, and mol% means the value of the used monomer. It means a value when the total number of moles is 100 mol%.

[Synthesis Example 22] Synthesis of Polymer (A-1) Propylene glycol 1-monomethyl ether (M-1) and monomer (M-2) are mixed so that the molar ratio is 50/50. 200 parts by mass). A monomer solution was prepared by adding 2,2'-azobis (methyl isobutyrate) (12 mol%) as an initiator. On the other hand, propylene glycol 1-monomethyl ether (100 parts by mass with respect to the total amount of monomers) was added to an empty reaction vessel, and the mixture was heated to 85 ° C. with stirring. Next, the monomer solution prepared above was added dropwise over 3 hours, and then heated at 85 ° C. for another 3 hours, and the polymerization reaction was carried out for a total of 6 hours. After completion of the polymerization reaction, the polymerization solution was cooled to room temperature. The polymerization solution was added dropwise to n-hexane (1000 parts by mass) to coagulate and purify the polymer. Propylene glycol 1-monomethyl ether (150 parts by mass) was added to the polymer again. Further, methanol (150 parts by mass), triethylamine (1.5 molar equivalents with respect to the amount of compound (M-1) used) and water (1.5 molar equivalents with respect to the amount of monomer (M-1) used). Was added, and the hydrolysis reaction was carried out for 8 hours while refluxing. After completion of the reaction, the solvent and triethylamine were distilled off under reduced pressure, and the obtained polymer was dissolved in acetone (150 parts by mass). This was added dropwise to water (2000 parts by mass) to solidify, and the produced white powder was filtered off. The polymer (A-1) in the form of a white powder was obtained in good yield by drying at 50 ° C. for 17 hours. The Mw of the polymer (A-1) was 6,400, and the Mw / Mn was 1.50.

[Synthesis Examples 23 to 24] Synthesis of Polymers (A-2) to (A-3) The weight is the same as that of Synthesis Example 22 except that the monomers of the types and proportions shown in Table 1 below are used. Combined (A-2) to (A-3) were synthesized.

[Synthesis Example 25] Synthesis of Polymer (A-4) The molar ratio of the monomer (M-2), the monomer (M-7) and the acid generator (B-21) is 50/35/15. It was dissolved in 2-butanone (200 parts by mass) so as to become. AIBN (azobisisobutyronitrile, 5 mol%) was added thereto as an initiator to prepare a monomer solution. 2-Butanone (100 parts by mass) was placed in a reaction vessel, and nitrogen was purged for 30 minutes. The temperature inside the reaction vessel was set to 80 ° C., and the monomer solution was added dropwise over 3 hours with stirring. The start of dropping was set as the start time of the polymerization reaction, and the polymerization reaction was carried out for 6 hours. After completion of the polymerization reaction, the polymerization solution was cooled to 30 ° C. or lower. The cooled polymerization solution was put into methanol (2000 parts by mass), and the precipitated white powder was filtered off. The filtered white powder was washed twice with methanol, filtered, and dried at 50 ° C. for 17 hours to obtain a white powdery polymer (A-4) in a good yield. The Mw of the polymer (A-4) was 8,100, and the Mw / Mn was 1.58. Since the polymer (A-4) has a structural unit derived from the acid generator (B-21), it is a radiation-sensitive acid-generating polymer that also functions as a [B] acid generator.

[Synthesis Example 26] Synthesis of Polymer (a-1) Polymer (a-1) is synthesized in the same manner as in Synthesis Example 25, except that the types and proportions of the monomers shown in Table 1 below are used. did.

Table 1 below shows the usage ratios of the monomers giving each structural unit of the obtained polymer, Mw and Mw / Mn. In Table 1, "-" indicates that the corresponding monomer was not used.

<[C] Synthesis of acid diffusion control agent>
[Synthesis Example 27] Synthesis of Compound (C-1) A compound represented by the following formula (C-1) (hereinafter referred to as “Compound (C—”) is the same as in Synthesis Example 1 except that a precursor is appropriately selected. 1) ”) was synthesized.

<Preparation of radiation-sensitive resin composition>
[B] Acid generators other than the [B] acid generator used in the preparation of the radiation-sensitive resin composition (hereinafter, also simply referred to as “other acid generators”), [C] other than the compound (C-1). The acid diffusion control agent and the [D] organic solvent are shown below. In the following Examples and Comparative Examples, unless otherwise specified, parts by mass mean a value when the mass of the [A] polymer used is 100 parts by mass, and mol% is used [B]. It means a value when the number of moles of the acid generator is 100 mol%.

[Other acid generators]
(B-1) to (b-2): Compounds represented by the following formulas (b-1) to (b-2) (hereinafter, also referred to as "acid generators (b-1) to (b-2)"). Say)

[[C] Acid diffusion control agent]
(C-2) to (C-3): Compounds represented by the following formulas (C-2) to (C-3) (hereinafter, also referred to as "compounds (C-2) to (C-3)").

[[D] Organic solvent]
(D-1): Propylene glycol monomethyl ether acetate (D-2): Propylene glycol 1-monomethyl ether

[Example 1] Preparation of radiation-sensitive resin composition (R-1) [A] 100 parts by mass of (A-1) as a polymer, [B] 20 parts by mass of (B-1) as an acid generator , [C] (C-2) as an acid diffusion inhibitor in an amount of 50 mol% based on (B-1), and [D] 7,700 parts by mass of (D-1) as an organic solvent and (D-). 2) A radiation-sensitive resin composition (R-1) was prepared by mixing 3,300 parts by mass.

[Examples 2 to 29 and Comparative Examples 1 to 3] Preparation of Radiation Sensitive Resin Compositions (R-2) to (R-29) and (CR-1) to (CR-3) Types shown in Table 2 below The radiation-sensitive resin compositions (R-2) to (R-29) and (CR-1) to (CR-3) were prepared in the same manner as in Example 1 except that each component of the content was used. Prepared. In Table 2 below, "-" indicates that the corresponding component is not used.

<Formation of resist pattern>
The above preparation was made using a spin coater ("CLEAN TRACK ACT12" of Tokyo Electron Limited) on the surface of a 12-inch silicon wafer on which an underlayer film ("AL412" of Brewer Science) having an average thickness of 20 nm was formed. The radiation-sensitive resin composition was applied, soft-baked (SB) was performed at 100 ° C. for 60 seconds, and then cooled at 23 ° C. for 30 seconds to form a resist film having an average thickness of 30 nm. Next, via a mask pattern that forms a line and space (1L / 1S) on this resist film, an EUV exposure machine (ASML's "NXE3300", NA = 0.33, lighting conditions: Continental s = 0. 89, the mask imageDEFECT32FFR02) was used to irradiate EUV light. The resist film was post-exposure baked (PEB) at 100 ° C. for 60 seconds. Then, using 2.38 mass% of TMAH aqueous solution, it was developed at 23 ° C. for 30 seconds to form a positive line-and-space pattern.

<Evaluation>
For each of the formed resist patterns, the sensitivity, LWR performance and resolution of each radiation-sensitive resin composition were evaluated according to the following method. A scanning electron microscope (“CG-4100” of Hitachi High-Technologies Corporation) was used to measure the length of the resist pattern. Further, among the formed resist patterns, those using the radiation-sensitive resin compositions of Examples 1, 2, 21, 24-26, 29 and Comparative Examples 1 to 3 were subjected to defect suppression according to the following method. evaluated. The evaluation results of sensitivity, LWR performance and resolution are shown in Table 3 below, and the evaluation results of defect suppression are shown in Table 4 below.

[sensitivity]
In the formation of the resist pattern, the exposure amount for forming the 26 nm half-pitch line and space pattern was defined as the optimum exposure amount, and this optimum exposure amount was defined as Eop (mJ / cm ² ). The smaller the value of Eop, the better the sensitivity. The sensitivity was evaluated as "good" when Eop was 60 mJ / cm ² or less, and as "poor" when it exceeded ^{60 mJ / cm 2.}

[LWR performance]
Using the scanning electron microscope, the 26 nm half-pitch line and space pattern formed above was observed from above. A total of 50 points of line width were measured at arbitrary points, and a 3-sigma value was obtained from the distribution of the measured values, which was defined as LWR (unit: nm). The LWR performance indicates that the smaller the LWR value, the smaller the rattling of the line and the better. The LWR performance was evaluated as "good" when the LWR was 4.0 nm or less and "poor" when the LWR exceeded 4.0 nm.

[Resolution]
At the above optimum exposure amount, the dimension of the minimum resist pattern that is resolved when the size of the mask pattern forming the line and space (1L / 1S) is changed is measured, and this measured value is used as the resolution (unit: nm). And said. The resolution shows that the smaller the resolution value, the finer the pattern can be formed, which is better. The resolution was evaluated as "good" when the resolution was 20 nm or less, and as "poor" when the resolution exceeded 20 nm.

As is clear from the results in Table 3, all of the radiation-sensitive resin compositions of Examples had better sensitivity, LWR performance, and resolution as compared with the radiation-sensitive resin compositions of Comparative Examples.

[Defect suppression]
In the resist pattern resolved at the optimum exposure amount, the number of defects (unit: pieces / cm ² ) was measured using a defect inspection device (“KLA2925” manufactured by KLA-Tencor). Defect suppression shows that the smaller the number of defects, the better. Defect suppression property, if the number of defects is 1 / cm ² or less as "good", if more than one / cm ² was evaluated as "poor".

As is clear from the results in Table 4, all of the radiation-sensitive resin compositions of Examples had good defect suppression properties as compared with the radiation-sensitive resin compositions of Comparative Examples.

According to the radiation-sensitive resin composition and the resist pattern forming method of the present invention, a resist pattern having good sensitivity to exposure light and excellent LWR performance and resolution can be formed. Therefore, it can be suitably used for forming a fine resist pattern in the lithography process of various electronic devices such as semiconductor devices and liquid crystal devices.

Claims (8)

1. A polymer having a first structural unit containing a phenolic hydroxyl group and a second structural unit containing an acid dissociative group,
   Contains a radiation-sensitive acid generator,
   A radiation-sensitive resin composition in which the radiation-sensitive acid generator has a monovalent radiation-sensitive onium cation represented by the following formula (1).
   

   

   (In the formula (1), Ar ¹ is a group obtained by removing (m + 1) hydrogen atoms on an aromatic ring from an array having 6 to 20 ring members. M is an integer of 0 to 11. for 1, R ¹ is a monovalent organic group having 1 to 20 carbon atoms, hydroxy groups, if .m is 2 or more nitro groups or halogen atoms, more of R ¹ is equal to or different from each other, the number of carbon atoms An alicyclic structure having 1 to 20 monovalent organic groups, a hydroxy group, a nitro group or a halogen atom, or an alicyclic structure having 4 to 20 ring members composed of carbon chains in which these groups are combined with each other and bonded to each other. It is a part of the aliphatic heterocyclic structure. Ar ² is a group obtained by removing hydrogen atoms on n aromatic rings from an array having 6 to 20 ring members which is fused with the thiophene ring. N is 0 to 0 to. It is an integer of 10. When n is 1, R ² is a monovalent organic group, hydroxy group, nitro group or halogen atom having 1 to 20 carbon atoms. When n is 2 or more, a plurality of R ^{2 are used.} Are the same or different from each other and are monovalent organic groups, hydroxy groups, nitro groups or halogen atoms having 1 to 20 carbon atoms, or the number of rings formed by combining these groups with each other and forming a carbon chain to which they are bonded. It is a part of the alicyclic structure or the aliphatic heterocyclic structure of 4 to 20. R ³ and R ⁴ are independently monovalent organic groups having 1 to 20 carbon atoms, hydroxy groups, nitro groups, and halogens. Atom or hydrogen atom.)
2. ^{The radiation-sensitive resin composition according to claim 1, wherein R 1} in the above formula (1) is a fluorinated alkyl group or a fluorine atom having 1 to 6 carbon atoms.
3. ^{The radiation-sensitive resin composition according to claim 1 or 2} , wherein R 2 in the above formula (1) is a fluorinated alkyl group or a fluorine atom having 1 to 6 carbon atoms.
4. The radiation-sensitive resin composition according to claim 1, claim 2 or claim 3, wherein the radiation-sensitive acid generator is a compound represented by the following formula (2).
   

   

   (In the formula (2), R ⁵ is a monovalent organic group having 1 to 30 carbon atoms. R ⁶ is a divalent linking group. R ⁷ and R ⁸ are independent hydrogens. It is an atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms. R ⁹ and R ¹⁰ are independently fluorine atoms or a monovalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. Is an integer of 0 to 10. q is an integer of 0 to 10. r is an integer of 0 to 10. However, p + q + r is 1 or more and 30 or less. When p is 2 or more. when a plurality of R ⁶ may be the same or different from each other .q is 2 or more, plural R ⁷ are equal to or different from each other, when a plurality of R ⁸ may be the same or different from each other .r is 2 or more, plural R ⁹ is The same or different from each other, and a plurality of R ^10s are the same or different from each other. T ⁺ is a monovalent radiosensitive onium cation represented by the above formula (1).)
5. The radiation-sensitive substance according to claim 1, claim 2 or 3, wherein the radiation-sensitive acid generator is a radiation-sensitive acid-generating polymer having a structural unit represented by the following formula (2'). Resin composition.
   

   

   (In the formula (2'), R ¹² is a divalent linking group. R ¹³ and R ¹⁴ are independently hydrogen atoms or monovalent hydrocarbon groups having 1 to 20 carbon atoms. R ¹⁵ and R ¹⁶ are independently fluorine atoms or monovalent fluorinated hydrocarbon groups having 1 to 20 carbon atoms. R ¹¹ is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. S is an integer of 0 to 10. t is an integer of 0 to 10. u is an integer of 0 to 10. However, s + t + u is 1 or more and 30 or less. S is 2 In the above case, the plurality of R ^12s are the same or different from each other. When t is 2 or more, the plurality of R ^13s are the same or different from each other, and the plurality of R ^14s are the same or different from each other. R ¹⁵ are the same or different from each other, and a plurality of R ¹⁶ are the same or different from each other. T ⁺ is a monovalent radiosensitive onium cation represented by the above formula (1).
6. The radiation-sensitive resin composition according to any one of claims 1 to 5, wherein the first structural unit is represented by the following formula (3).
   

   

   (In formula (3), R ¹⁷ is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. L is a single bond, -O-, -COO- or -CONH-. Ar ³ is. , A group having 6 to 20 ring members minus (a + b + 1) hydrogen atoms on the aromatic ring. A is an integer of 0 to 10. When a is 1, R ¹⁸ is the number of carbon atoms. It is a monovalent organic group or halogen atom of 1 to 20. When a is 2 or more, a plurality of R ^18s are the same or different, and are a monovalent organic group or a halogen atom having 1 to 20 carbon atoms, or two or more are combined with each other is part of the alicyclic structure or aliphatic heterocyclic structure consisting ring members 4-20 with the carbon chain to which they are attached .b of the plurality of R ¹⁸ is 1 to 11 However, a + b is 11 or less.)
7. The radiation-sensitive resin composition according to any one of claims 1 to 6, which is for extreme ultraviolet exposure or electron beam exposure.
8. The process of directly or indirectly applying the radiation-sensitive resin composition to the substrate,
   A step of exposing the resist film formed by the above coating step and a step of exposing the resist film.
   The process of developing the exposed resist film is provided.
   The radiation-sensitive resin composition is
   A polymer having a first structural unit containing a phenolic hydroxyl group and a second structural unit containing an acid dissociative group,
   Contains a radiation-sensitive acid generator,
   A method for forming a resist pattern in which the radiation-sensitive acid generator has a monovalent radiation-sensitive onium cation represented by the following formula (1).
   

   

   (In the formula (1), Ar ¹ is a group obtained by removing (m + 1) hydrogen atoms on an aromatic ring from an array having 6 to 20 ring members. M is an integer of 0 to 11. for 1, R ¹ is a monovalent organic group having 1 to 20 carbon atoms, hydroxy groups, if .m is 2 or more nitro groups or halogen atoms, more of R ¹ is equal to or different from each other, the number of carbon atoms An alicyclic structure having 1 to 20 monovalent organic groups, a hydroxy group, a nitro group or a halogen atom, or an alicyclic structure having 4 to 20 ring members composed of carbon chains in which these groups are combined with each other and bonded to each other. It is a part of the aliphatic heterocyclic structure. Ar ² is a group obtained by removing hydrogen atoms on n aromatic rings from an array having 6 to 20 ring members which is fused with the thiophene ring. N is 0 to 0 to. It is an integer of 10. When n is 1, R ² is a monovalent organic group, hydroxy group, nitro group or halogen atom having 1 to 20 carbon atoms. When n is 2 or more, a plurality of R ^{2 are used.} Are the same or different from each other and are monovalent organic groups, hydroxy groups, nitro groups or halogen atoms having 1 to 20 carbon atoms, or the number of rings formed by combining these groups with each other and forming a carbon chain to which they are bonded. It is a part of the alicyclic structure or the aliphatic heterocyclic structure of 4 to 20. R ³ and R ⁴ are independently monovalent organic groups having 1 to 20 carbon atoms, hydroxy groups, nitro groups, and halogens. Atom or hydrogen atom.)