JP7396360B2 - Radiation-sensitive resin composition, resist pattern forming method, and radiation-sensitive acid generator - Google Patents

Description

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

The radiation-sensitive resin composition used for microfabrication by lithography is capable of radiating far ultraviolet rays such as ArF excimer laser light (wavelength 193 nm) and KrF excimer laser light (wavelength 248 nm), extreme ultraviolet rays (EUV) (wavelength 13.5 nm), etc. Acid is generated in the exposed area by irradiation with radiation such as electromagnetic waves or charged particle beams such as electron beams, and a chemical reaction catalyzed by this acid causes a difference in the rate of dissolution in the developer between the exposed area and the non-exposed area. This forms a resist pattern on the substrate.

In addition to having good sensitivity to exposure light such as extreme ultraviolet rays and electron beams, the radiation-sensitive resin composition also has excellent LWR (Line Width Roughness) performance, which indicates uniformity of line width, and resolution. Excellence is required.

In order to meet these demands, the types and molecular structures of polymers, acid generators, and other components used in radiation-sensitive resin compositions have been studied, and their combinations have also been studied in detail (particularly (See JP-A No. 2010-134279, JP-A No. 2014-224984, and JP-A No. 2016-047815).

Japanese Patent Application Publication No. 2010-134279 JP2014-224984A Japanese Patent Application Publication No. 2016-047815

Nowadays, the miniaturization of resist patterns has progressed to the level of line widths of 40 nm or less, and the above-mentioned performance requirements have further increased, and the above-mentioned conventional radiation-sensitive resin compositions cannot satisfy the above-mentioned demands. has not been completed.

The present invention has been made based on the above-mentioned circumstances, and its purpose is to provide a radiation-sensitive resist pattern that has good sensitivity to exposure light and can form a resist pattern with excellent LWR performance and resolution. An object of the present invention is to provide a resin composition, a resist pattern forming method, and a radiation-sensitive acid generator.

The invention made to solve the above problems is directed to a polymer (hereinafter referred to as "[A] polymer") having a first structural unit containing a first acid-dissociable group that dissociates under the action of an acid to give an alkali-soluble group. ) and a radiation-sensitive acid generator (hereinafter also referred to as "[B] acid generator"), the radiation-sensitive acid generator having a sulfonate anion and a radiation-sensitive onium cation. A radiation-sensitive resin composition in which the sulfonate anion has a (thio)acetal structure, a carbonyloxy group, and a second acid-dissociable group that is dissociated by the action of an acid to give a carboxyl group.

Another invention made to solve the above problems includes a step of directly or indirectly coating the radiation-sensitive resin composition on a substrate, a step of exposing a resist film formed by the above coating step, A resist pattern forming method includes a step of developing the exposed resist film.

Yet another invention made to solve the above problems is a radiation-sensitive acid generator containing a compound having a sulfonate anion and a radiation-sensitive onium cation, wherein the sulfonate anion has a (thio)acetal structure, It is a radiation-sensitive acid generator ([B] acid generator) having a carbonyloxy group and an acid-dissociable group that dissociates to give a carboxy group by the action of an acid.

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

<Radiation-sensitive resin composition>
The radiation-sensitive resin composition contains [A] a polymer and [B] an 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 controller (hereinafter also referred to as "[C] acid diffusion controller") as a suitable component. The radiation-sensitive resin composition may contain other optional components within a range that does not impair the effects of the present invention.

By containing the [A] polymer and the [B] acid generator, the radiation-sensitive resin composition has good sensitivity to exposure light and forms a resist pattern with excellent LWR performance and resolution. be able to. Although the reason why the radiation-sensitive resin composition achieves the above effects by having the above structure is not necessarily clear, it can be inferred as follows, for example. That is, since the acid generator [B] contained in the radiation-sensitive resin composition contains a sulfonate anion having a specific structure, the rate of dissolution of the exposed area into the developer is improved. As a result, it is thought that the radiation-sensitive resin composition has good sensitivity to exposure light and can form a resist pattern with excellent LWR performance and resolution.

Each component contained in the radiation-sensitive resin composition will be explained below.

<[A] Polymer>
[A] The polymer is a structural unit (hereinafter referred to as "structural unit") containing a first acid-dissociable group (hereinafter also referred to as "acid-dissociable group (a)") which dissociates under the action of an acid to give an alkali-soluble group. (I)”).

[A] The polymer preferably has a structural unit containing a phenolic hydroxyl group (hereinafter also referred to as "structural unit (II)") in addition to the structural unit (I). [A] The polymer may further have structural units other than the structural unit (I) and the structural unit (II). The radiation-sensitive resin composition can contain one or more kinds of [A] polymers.

Hereinafter, each structural unit contained in the [A] polymer will be explained.

[Structural unit (I)]
Structural unit (I) is a structural unit containing an acid-dissociable group (a) that dissociates under the action of an acid to give an alkali-soluble group. As used herein, "alkali-soluble group" refers to a carboxy group or hydroxy group, and "acid-dissociable group (a)" is a group that substitutes a hydrogen atom in an alkali-soluble group, and is A group that dissociates to give an alkali-soluble group. Upon exposure to light, the acid-dissociable group (a) dissociates due to the action of the acid generated from the acid generator [B] to generate an alkali-soluble group, and the solubility of the [A] polymer in the developing solution in the exposed area changes. By this, a resist pattern can be formed.

As the structural unit (I), for example, a structural unit represented by the following formula (I-1A) (hereinafter also referred to as "structural unit (I-1A)"), a structure represented by the following formula (I-1B) unit (hereinafter also referred to as "structural unit (I-1B)"), structural unit represented by the following formula (I-1C) (hereinafter also referred to as "structural unit (I-1C)"), the following formula (I -2A) (hereinafter also referred to as "structural unit (I-2A)"), the structural unit represented by the following formula (I-2B) (hereinafter referred to as "structural unit (I-2B)") ), etc. Note that ^the acid-dissociable group (a) is, for ^example , -C( ^R

In the above formula (I-1A), formula (I-1B), formula (I-1C), formula (I-2A) and formula (I-2B), R ^T is a hydrogen atom, a fluorine atom, a methyl group or It is a trifluoromethyl group.

In the above formulas (I-1A) and (I-1B), R ^X is a monovalent hydrocarbon group having 1 to 20 carbon atoms. R ^Y and R ^Z are each independently a monovalent hydrocarbon group having 1 to 20 carbon atoms, or a group having 3 to 20 ring members formed by combining these groups together with the carbon atom to which they are bonded. It is part of 20 saturated alicyclic structures.

In the above formula (I-1C), R ^B , R ^C and R ^E each independently represent a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms. R ^A and R ^D are each independently a monovalent hydrocarbon group having 1 to 20 carbon atoms, or the number of ring members formed by combining these groups together with the unsaturated carbon chain to which they are bonded. It is part of 4 to 20 unsaturated alicyclic structures.

In the above formulas (I-2A) and (I-2B), R ^U and R ^V each independently represent a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms, and R ^W is Is it a monovalent hydrocarbon group having 1 to 20 carbon atoms, or is it part of an alicyclic structure having 3 to 20 ring members formed by combining R ^U and R ^V together with the carbon atoms to which they are bonded? , or is part of an aliphatic heterocyclic structure having 5 to 20 ring members formed by combining R ^U and R ^W together with the carbon atom to which R ^U is bonded and the oxygen atom to which R ^W is bonded.

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 term "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 linear hydrocarbon groups and branched hydrocarbon groups. "Alicyclic hydrocarbon group" refers to a hydrocarbon group that contains only an alicyclic structure as a ring structure and does not contain an aromatic ring structure, and includes a monocyclic alicyclic hydrocarbon group and a polycyclic alicyclic hydrocarbon group. Contains both hydrocarbon groups. However, it is not necessary to be composed only of an alicyclic structure, and a part thereof may include a chain structure. "Aromatic hydrocarbon group" refers to a hydrocarbon group containing an aromatic ring structure as a ring structure. However, it is not necessary to consist only of an aromatic ring structure, and a part thereof may include a chain structure or an alicyclic structure.

The monovalent hydrocarbon groups having 1 to 20 carbon atoms represented by R ^X , R ^Y , R ^Z , R ^A , R ^B , R ^C , R ^D , R ^E , R ^U , R ^V and R ^W are , for example, a monovalent chain hydrocarbon group having 1 to 20 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms, etc. It will be done.

Examples of monovalent chain hydrocarbon groups having 1 to 20 carbon atoms include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, sec-butyl group, iso-butyl group, tert - an alkyl group such as a butyl group;
Alkenyl groups such as ethenyl group, propenyl group, butenyl group;
Examples include alkynyl groups such as ethynyl group, propynyl group, and butynyl group.

Examples of monovalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms include alicyclic saturated hydrocarbon groups such as cyclopentyl group, cyclohexyl group, norbornyl group, adamantyl group, tricyclodecyl group, and tetracyclododecyl group;
Examples include alicyclic unsaturated hydrocarbon groups 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 aryl groups such as phenyl group, tolyl group, xylyl group, naphthyl group, and anthryl group;
Examples include aralkyl groups such as benzyl group, phenethyl group, naphthylmethyl group, and anthrylmethyl group.

A saturated alicyclic structure having 3 to 20 ring members formed by combining R ^Y and R ^Z together with the carbon atom to which they are bonded is, for example, a monocyclic structure such as a cyclopropane structure, a cyclobutane structure, a cyclopentane structure, a cyclohexane structure, etc. saturated alicyclic structure;
Examples include polycyclic saturated alicyclic structures such as norbornane structure and adamantane structure.

Examples of alicyclic structures having 3 to 20 ring members formed by combining R ^U and R ^V together with the carbon atoms to which they are bonded include monocyclic structures such as cyclopropane structures, cyclobutane structures, cyclopentane structures, and cyclohexane structures. Saturated alicyclic structure;
Polycyclic saturated alicyclic structures such as norbornane structure and adamantane structure;
Monocyclic unsaturated alicyclic structures such as cyclopropene structure, cyclobutene structure, cyclopentene structure, cyclohexene structure;
Examples include polycyclic unsaturated alicyclic structures such as norbornene structures.

Examples of unsaturated alicyclic structures having 4 to 20 ring members formed by combining R ^A and R ^D with unsaturated carbon chains to which they are bonded include monocyclic unsaturated structures such as cyclobutene structures, cyclopentene structures, and cyclohexene structures. Saturated alicyclic structure;
Examples include polycyclic unsaturated alicyclic structures such as norbornene structures.

Examples of aliphatic heterocyclic structures having 5 to 20 ring members formed by combining R ^U and R ^W together with the oxygen atom to which R ^U is bonded and the carbon atom to which R ^W is bonded include, for example, oxacyclobutane structure, oxacyclopentane structure. structure, saturated oxygen-containing heterocyclic structure such as oxacyclohexane structure;
Examples include unsaturated oxygen-containing heterocyclic structures such as an oxacyclobutene structure, an oxacyclopentene structure, and an oxacyclohexene structure.

From the viewpoint of copolymerizability of the monomer providing the structural unit (I), R ^T is preferably a hydrogen atom or a methyl group.

R ^X is preferably a chain hydrocarbon group or an aromatic hydrocarbon group, more preferably an alkyl group or an aryl group, and even more preferably a methyl group, ethyl group, i-propyl group, tert-butyl group, or phenyl group.

R ^Y and R ^Z are preferably part of a saturated alicyclic structure having 3 to 20 ring members formed by combining them together with the carbon atoms to which they are bonded. The alicyclic structure is preferably a monocyclic saturated alicyclic structure, and more preferably a cyclopentane structure.

As R ^B and R ^C , a hydrogen atom is preferable.

R ^E is preferably a hydrogen atom or a chain hydrocarbon group, more preferably a hydrogen atom or an alkyl group, and more preferably a hydrogen atom or a methyl group.

It is preferable that R ^A and R ^D be part of an unsaturated alicyclic structure formed by combining them together with the carbon atoms to which they are bonded. The unsaturated alicyclic structure is preferably a monocyclic unsaturated alicyclic structure, and more preferably a cyclopentene structure or a cyclohexene structure.

Structural unit (I) is preferably structural unit (I-1A) or structural unit (I-1C).

Structural units (I-1A) include structural units represented by the following formulas (I-1A-1) to (I-1A-5) (hereinafter referred to as "structural units (I-1A-1) to (I-1A-5)"). 1A-5)” is preferred.

In the above formulas (I-1A-1) to (I-1A-5), R ^T has the same meaning as in the above formula (I-1A).

Structural units (I-1C) are structural units represented by the following formulas (I-1C-1) to (I-1C-2) (hereinafter referred to as "structural units (I-1C-1) to (I-1C-2)"). 1C-2)” is preferred.

In the above formulas (I-1C-1) and (I-1C-2), R ^T has the same meaning as in the above formula (I-1C).

The lower limit of the content of the structural unit (I) is preferably 5 mol%, more preferably 10 mol%, even more preferably 15 mol%, and even more preferably 20 mol%, based on the total structural units constituting the polymer [A]. % is particularly preferred. The upper limit of the content ratio is preferably 90 mol%, more preferably 80 mol%, even more preferably 70 mol%, and particularly preferably 65 mol%. By setting the content of the structural unit (I) within the above range, the sensitivity to exposure light, LWR performance, and resolution of the radiation-sensitive resin composition can be further improved.

[Structural unit (II)]
Structural unit (II) is a structural unit containing a phenolic hydroxyl group. The term "phenolic hydroxyl group" refers not only to hydroxy groups directly connected to benzene rings, but also to all hydroxy groups directly connected to aromatic rings. In the case of KrF exposure, EUV exposure or electron beam exposure, the [A] polymer having the structural unit (II) can further increase the sensitivity of the radiation-sensitive resin composition to exposure light.

Examples of the structural unit (II) include structural units represented by the following formulas (II-1) to (II-15) (hereinafter also referred to as "structural units (II-1) to (II-15)"), etc. can be mentioned.

In the above formulas (II-1) to (II-15), R ^P is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.

From the viewpoint of copolymerizability of the monomer providing the structural unit (II), R ^P is preferably a hydrogen atom or a methyl group, and more preferably a hydrogen atom.

Structural unit (II) is preferably structural unit (II-1) or structural unit (II-2).

When the [A] polymer has a structural unit (II), the lower limit of the content of the structural unit (II) is preferably 10 mol%, and 20% by mole based on the total structural units constituting the [A] polymer. More preferably mol %, and even more preferably 25 mol %. The upper limit of the content ratio is preferably 80 mol%, more preferably 60 mol%, and even more preferably 50 mol%. By setting the content ratio of structural unit (II) within the above range, the sensitivity to exposure light, LWR performance, and resolution of the radiation-sensitive resin composition can be further improved.

[Other structural units]
Other structural units include, for example, a structural unit containing an alcoholic hydroxyl group (hereinafter also referred to as "structural unit (III)" or "third structural unit"), a lactone structure, a cyclic carbonate structure, a sultone structure, or a combination thereof. Examples include structural units containing

(Structural unit (III))
Examples of the structural unit (III) include structural units represented by the following formula. [A] By further having the structural unit (III), the polymer can further improve LWR performance and resolution.

In the above formula, R ^L2 is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.

[A] When the polymer has other structural units, the upper limit of the content of the other structural units is preferably 30 mol%, and 15 mol% based on the total structural units constituting the [A] polymer. is more preferable.

The lower limit of the content of the [A] polymer in the radiation-sensitive resin composition is preferably 50% by mass, and 60% by mass based on all components other than the organic solvent [D] in the radiation-sensitive resin composition. % is more preferable, and 70% by mass is even more preferable. The upper limit of the content ratio is preferably 99% by mass, more preferably 95% by mass.

[A] The lower limit of the polystyrene equivalent weight average molecular weight (Mw) of the polymer measured by gel permeation chromatography (GPC) is preferably 1,000, more preferably 3,000, even more preferably 4,000, 5, 000 is particularly preferred. The upper limit of Mw is preferably 50,000, more preferably 30,000, even more preferably 20,000, and particularly preferably 10,000. [A] By setting the Mw of the polymer within the above range, the coating properties of the radiation-sensitive resin composition can be improved.

[A] The upper limit of the ratio of Mw to polystyrene equivalent number average molecular weight (Mn) determined by GPC of the polymer (hereinafter also referred to as "dispersity" or "Mw/Mn") is preferably 5, more preferably 3, 2 is more preferred, and 1.8 is particularly preferred. The lower limit of the above ratio is usually 1, preferably 1.1.

The Mw and Mn of the polymer in this specification are values measured using gel permeation chromatography (GPC) under the following conditions.
GPC columns: 2 “G2000HXL”, 1 “G3000HXL” and 1 “G4000HXL” from Tosoh Co., Ltd. Column temperature: 40°C
Elution solvent: Tetrahydrofuran (Fuji Film Wako Pure Chemical Industries, Ltd.)
Flow rate: 1.0mL/min Sample concentration: 1.0% by mass
Sample injection volume: 100μL
Detector: Differential refractometer Standard material: Monodisperse polystyrene

<[B] Acid generator>
[B] The acid generator has a sulfonate anion and a radiation-sensitive onium cation, and the sulfonate anion is dissociated by the action of a (thio)acetal structure, a carbonyloxy group, and an acid to give a carboxy group. (hereinafter also referred to as "compound (B)"). Compound (B) is a substance that generates acid upon irradiation with radiation. Examples of the radiation include electromagnetic waves such as visible light, ultraviolet rays, far ultraviolet rays, extreme ultraviolet rays (EUV), X-rays, and gamma rays, and charged particle beams such as electron beams and alpha rays. The acid generated from the compound (B) upon irradiation with radiation dissociates the acid-dissociable group (a), etc. contained in the structural unit (I) of the [A] polymer, producing an alkali-soluble group, and the [A] in the exposed area. A] A resist pattern can be formed by changing the solubility of the polymer in a developer. The radiation-sensitive resin composition may contain one or more [B] acid generators.

In compound (B), the acid dissociable group (b) of compound (B) is dissociated by the acid etc. generated from compound (B) by radiation irradiation (exposure), and a carboxy group is generated, so that the exposed part The difference in solubility of the resist film in the developing solution (dissolution contrast) between the resist film and the non-exposed area increases. Therefore, it is considered that the radiation-sensitive resin composition can form a resist pattern with excellent LWR performance and resolution.

Hereinafter, each structure possessed by compound (B) will be explained.

[Sulfonate anion]
The sulfonate anion has a (thio)acetal structure, a carbonyloxy group, and an acid-dissociable group (b) that is dissociated by the action of an acid to give a carboxyl group. It is preferable that the sulfonate anion further has an alicyclic structure (hereinafter also referred to as "alicyclic structure (c)") other than the acid-dissociable group (b). It is preferable that the sulfonate anion further has a partial structure (hereinafter also referred to as "partial structure (d)") represented by the following formula (3) described below. Further, the sulfonate anion may have a structure other than the above structure as necessary.

Hereinafter, each structure possessed by the sulfonate anion will be explained.

((thio)acetal structure)
As used herein, the term "(thio)acetal structure" is a concept that includes both "acetal structure" and "thioacetal structure." Further, the "(thio)acetal structure" includes both "chain (thio)acetal structure" and "cyclic (thio)acetal structure". Furthermore, "thioacetal structure" includes both "monothioacetal structure" and "dithioacetal structure".

As the (thio)acetal structure, a cyclic (thio)acetal structure is preferable when focusing on the structure, and an acetal structure or a monothioacetal structure is preferable when paying attention to the constituent atoms. When the (thio)acetal structure has the above structure, the LWR performance and resolution of the radiation-sensitive resin composition can be further improved. That is, the (thio)acetal structure is preferably a cyclic (thio)acetal structure, more preferably a cyclic acetal structure or a cyclic monothioacetal structure, and even more preferably a cyclic acetal structure.

Examples of the cyclic (thio)acetal structure include a structure represented by the following formula (1).

In the above formula (1), X ¹ and X ² are each independently -O- or -S-. R ¹ is an (n+2)-valent hydrocarbon group having 1 to 10 carbon atoms. n is an integer from 0 to 2. * indicates a bonding site with a portion other than the structure represented by the above formula (1) in the above sulfonate anion.

Regarding the classification of the above-mentioned cyclic (thio)acetal structure, in the above formula (1), when both X ¹ and X ² are -O-, it is a "cyclic acetal structure", and at least of X ¹ and X ² When one of the structures is -S-, it is a "cyclic thioacetal structure". Furthermore, when one of X ¹ and X ² is -O- and the other is -S-, it is a "cyclic monothioacetal structure", and when both X ¹ and X ² are -S-, it is a "cyclic monothioacetal structure". cyclic dithioacetal structure.

As for X ¹ and X ² , it is preferable that at least one of X ¹ and X ² is -O-. In this case, the sensitivity to exposure light, LWR performance, and resolution of the radiation-sensitive resin composition can be further improved.

Examples of the (n+2)-valent hydrocarbon group having 1 to 10 carbon atoms represented by R ¹ include groups obtained by removing (n+2) hydrogen atoms from alkanes such as methane, ethane, n-propane, and n-butane. can be mentioned. As R ¹ , a hydrocarbon group having a carbon number such that the cyclic (thio)acetal structure represented by the above formula (1) has 5 or 7 ring members is preferable. That is, R ¹ is preferably a group obtained by removing (n+2) hydrogen atoms from ethane or n-butane. In addition, "the number of ring members of a cyclic (thio) acetal structure" means the number of atoms that constitute the ring structure of a cyclic (thio) acetal structure.

(Carbonyloxy group and acid dissociable group (b))
In the sulfonate anion, the acid-dissociable group (b) is an ethereal oxygen atom (carbon atom) of a carbonyloxy group (hereinafter sometimes referred to as "-C(=O)O-" or simply "-COO-"). and an oxygen atom that is bonded with a single bond). When the acid-dissociable group (b) dissociates from the carbonyloxy group by the action of an acid, a carboxyl group is generated.

The acid-dissociable group (b) is a group that dissociates under the action of an acid to give a carboxy group. More specifically, the "acid-dissociable group (b)" is a group that substitutes a hydrogen atom in a carboxy group, and is a group that dissociates under the action of an acid to give a carboxy group.

Examples of the acid-dissociable group (b) include a group represented by the following formula (2-1) and a group represented by the following formula (2-2).

In the above formulas (2-1) and (2-2), ** represents the bonding site of the carbonyloxy group with the etheric oxygen atom in the sulfonate anion.

In the above formula (2-1), R ² is a monovalent hydrocarbon group having 1 to 20 carbon atoms or a group containing the above (thio)acetal structure. R ³ and R ⁴ are each independently a monovalent hydrocarbon group having 1 to 20 carbon atoms, or a group having 3 to 20 ring members formed by combining these groups together with the carbon atom to which they are bonded. It is part of 20 saturated alicyclic structures.

In the above formula (2-2), R ⁶ , R ⁷ and R ⁹ are each independently a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms. R ⁵ and R ⁸ are each independently a monovalent hydrocarbon group having 1 to 20 carbon atoms, or the number of ring members formed by combining these groups together with the unsaturated carbon chain to which they are bonded. It is part of 4 to 20 unsaturated alicyclic structures.

Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by R ² , R ³ and R ⁴ include the carbon numbers represented by R ^X , R ^Y and R ^Z in the above formula (I-1A). Examples of the 1-20 monovalent hydrocarbon group include the same groups as those exemplified.

A saturated alicyclic structure having 3 to 20 ring members formed by combining R ³ and R ⁴ together with the carbon atom to which they are bonded is, for example, a saturated alicyclic structure formed by R ^Y and R ^Z in the above formula (I-1A). Examples of the alicyclic structure include structures similar to those exemplified.

Examples of monovalent hydrocarbon groups having 1 to 20 carbon atoms represented by R ⁵ , R ⁶ , R ⁷ , R ⁸ and R ⁹ include R ^A , R ^B , R ^C of the above formula (I-1C); , R ^D and R ^E , the same groups as those exemplified as monovalent hydrocarbon groups having 1 to 20 carbon atoms, and the like.

When R ² is a monovalent hydrocarbon group having 1 to 20 carbon atoms, R ² is preferably a chain hydrocarbon group, more preferably an alkyl group, and even more preferably a methyl group or an ethyl group.

When R ² is a group containing the above (thio)acetal structure, R ² is preferably a group containing a cyclic (thio)acetal structure, and a group containing the structure represented by the above formula (1). More preferably, it is a group containing the structure represented by the above formula (1) and an alicyclic structure (c) described below.

R ² is preferably a monovalent hydrocarbon group having 1 to 20 carbon atoms. When R ² is a monovalent hydrocarbon group having 1 to 20 carbon atoms, sensitivity to exposure light, LWR performance, and resolution can be further improved.

When R ³ and R ⁴ are monovalent hydrocarbon groups having 1 to 20 carbon atoms, R ³ and R ⁴ are preferably chain hydrocarbon groups, more preferably alkyl groups, and methyl or ethyl groups. More preferred.

When R ³ and R ⁴ are part of an alicyclic structure having 3 to 20 ring members that is formed together with the carbon atoms to which they are combined, the alicyclic structure is a saturated alicyclic structure. Preferably, a monocyclic saturated alicyclic structure is more preferable, and a cyclopentane structure is even more preferable.

A hydrogen atom is preferred as R ⁶ and R ⁷ .

R ⁹ is preferably a chain hydrocarbon group, more preferably an alkyl group, and even more preferably a methyl group.

R ⁵ and R ⁸ are preferably part of an unsaturated alicyclic structure having 4 to 20 ring members that is formed together with the unsaturated carbon chain to which they are combined. As the unsaturated alicyclic structure, a monocyclic unsaturated alicyclic structure is preferable, and a cyclohexene structure is more preferable.

(Alicyclic structure (c))
It is preferable that the sulfonate anion further has an alicyclic structure (alicyclic structure (c)) other than the acid-dissociable group (b). When the sulfonate anion further has an alicyclic structure (c), the diffusion of the acid generated from the compound (B) can be appropriately suppressed, and as a result, the resolution and LWR performance can be further improved.

Examples of the alicyclic structure (c) include structures similar to those exemplified as the alicyclic structure constituted by R ^U and R ^V in formula (I-2A) above.

As the alicyclic structure (c), a saturated alicyclic structure is preferable, and a cyclohexane structure, a norbornane structure, or an adamantane structure is more preferable.

Moreover, it is preferable that the alicyclic structure (c) shares a part of the carbon atom or carbon chain with the above-mentioned (thio)acetal structure. For example, when the alicyclic structure (c) is a norbornane structure, some carbon chains constituting the norbornane structure and some carbon chains constituting the (thio)acetal structure may be in common. Can be mentioned. For example, when the alicyclic structure (c) is a cyclohexane structure or an adamantane structure, one carbon atom constituting the cyclohexane structure or adamantane structure and one carbon atom constituting the (thio)acetal structure are common. Examples include aspects in which

(Substructure (d))
It is preferable that the sulfonate anion further has a partial structure (partial structure (d)) represented by the following formula (3). When the sulfonate anion further has the partial structure (d), the acid generated from the compound (B) becomes a stronger acid, and the acid dissociable group (a) contained in the structural unit (I) of the polymer [A] It can further promote dissociation.

In the above formula (3), R ¹⁰ and R ¹¹ are each independently a hydrogen atom, a fluorine atom, a monovalent hydrocarbon group having 1 to 20 carbon atoms, or a monovalent fluorinated carbon group having 1 to 20 carbon atoms. It is a hydrogen group. However, at least one of R ¹⁰ and R ¹¹ is a fluorine atom or a monovalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. m is an integer from 1 to 10. When m is 2 or more, a plurality of R ^10s are the same or different from each other, and a plurality of R ^11s are the same or different from each other. *** indicates a bonding site with a portion other than the structure represented by formula (3) in the sulfonate anion.

Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by R ¹⁰ and R ¹¹ include those having 1 to 20 carbon atoms represented by R ^X , R ^Y and R ^Z of the above formula (I-1A). Examples of the monovalent hydrocarbon group include the same groups as those exemplified.

As the monovalent fluorinated hydrocarbon group having 1 to 20 carbon atoms ^represented by R ¹⁰ and R ¹¹ , ^the monovalent fluorinated hydrocarbon group having 1 to ²⁰ carbon atoms represented by R Examples include a group in which at least one hydrogen atom of the group exemplified as the monovalent hydrocarbon group in No. 20 is replaced with a fluorine atom.

The sulfonate anion only needs to have each of the above structures, and the positions and orientations of the (thio)acetal structure, carbonyloxy group, and acid-dissociable group (b) in the chemical structure of the sulfonate anion are not particularly limited. The sulfonate anion preferably has an acid-dissociable group (b) at the end. By having the acid dissociable group (b) at the end of the sulfonate anion, sensitivity to exposure light, LWR performance, and resolution can be further improved. Furthermore, when the above (thio)acetal structure is a cyclic (thio)acetal structure represented by the above formula (1), it is preferable that R ¹ be oriented toward the SO ^{3 -} side. Since R ¹ in the above formula (1) is oriented toward the SO ^{3 −} side, sensitivity to exposure light, LWR performance, and resolution can be further improved.

Examples of the sulfonate anion include a structure represented by the following formula (4-1) or a structure represented by the following formula (4-2).

In the above formulas (4-1) and (4-2), X is a group containing a (thio)acetal structure. Y is an acid-dissociable group (b). L ¹ and L ² are each independently a single bond or a divalent linking group.

Examples of the divalent linking group represented by L ¹ and L ² include a divalent hetero atom-containing group, a divalent hydrocarbon group, and the divalent hetero atom-containing group between carbon and carbon of the hydrocarbon group. group (hereinafter also referred to as "group (α)"), a group in which some or all of the hydrogen atoms of the above hydrocarbon group are substituted with a monovalent heteroatom-containing group (hereinafter referred to as "group (β)") ), a group in which part or all of the hydrogen atoms of the above group (α) are substituted with a monovalent heteroatom-containing group (hereinafter also referred to as “group (γ)”), and the like.

Examples of the divalent heteroatom-containing group include -CO-, -CS-, -NH-, -O-, -S-, and a combination thereof.

Examples of the monovalent heteroatom-containing group include a hydroxy group, a sulfanyl group, a cyano group, a nitro group, and a halogen atom.

As the divalent hydrocarbon group, for example, one of the groups exemplified as monovalent hydrocarbon groups having 1 to 20 carbon atoms represented by R ^X , R ^Y and R ^Z of the above formula (I-1A). Examples include groups excluding hydrogen atoms.

When the sulfonate anion further has an alicyclic structure (c), the alicyclic structure (c) is included in the divalent linking group represented by L ¹ or L ² , or is a combination of the (thio)acetal structure and the alicyclic structure. Structure (c) shares a carbon atom or part of a carbon chain with structure (c).

L ² preferably includes the structure of -(CR ¹⁰ R ¹¹ ) _m - in the above formula (3).

As the sulfonate anion, a structure represented by the above formula (4-1) is preferable. When the sulfonate anion has the above formula (4-1), sensitivity to exposure light, LWR performance, and resolution can be further improved.

Examples of the structure represented by the above formula (4-1) include a structure represented by the following formula (4-1-1) or a structure represented by the formula (4-1-2).

In the above formulas (4-1-1) and (4-1-2), Y, L ¹ and L ² have the same meanings as in the above formula (4-1). R ¹ , X ¹ and X ² have the same meanings as in formula (1) above.

In the above formula (4-1-1), L ¹¹ is a divalent linking group, L ¹² is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms, or L ¹¹ and L ¹² are It is a part of a ring structure having 3 to 20 ring members that is formed together with the carbon atoms to which they are combined.

In the above formula (4-1-2), L ²¹ is a divalent linking group, L ²² is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms, or L ²¹ and L ²² are It is a part of a ring structure having 3 to 20 ring members that is formed together with the carbon atoms to which they are combined.

"Organic group" means a group containing at least one carbon atom.

Examples of the divalent linking groups represented by L ¹¹ and L ²¹ include the same groups as those exemplified as the divalent linking groups represented by L ¹ and L ² in formula (4-1) above. Can be mentioned.

Examples of the monovalent organic group having 1 to 20 carbon atoms represented by L ¹² and L ²² include a monovalent hydrocarbon group having 1 to 20 carbon atoms, and a divalent organic group having 1 to 20 carbon atoms, and a divalent organic group having 1 to 20 carbon atoms. A group containing a heteroatom-containing group (hereinafter also referred to as "group (α')"), a group in which some or all of the hydrogen atoms of the above hydrocarbon group are substituted with a monovalent heteroatom-containing group (hereinafter, " (also referred to as "group (β')"), a group in which part or all of the hydrogen atoms of the above group (α') are substituted with a monovalent heteroatom-containing group (hereinafter also referred to as "group (γ')") Examples include.

Examples of ring structures having 3 to 20 ring members in which L ¹¹ and L ¹² or L ²¹ and L ²² are combined together with the carbon atoms to which they are bonded include R ^Y and R ^Z of the above formula (I-1A). Examples of the alicyclic structure constituted by include structures similar to those exemplified.

The structure represented by the above formula (4-1) is preferably the structure represented by the above formula (4-1-1). When the sulfonate anion has the above formula (4-1-1), sensitivity to exposure light, LWR performance, and resolution can be further improved.

[Radiation-sensitive onium cation]
Examples of radiation-sensitive onium cations include monovalent cations represented by the following formula (ra) (hereinafter also referred to as "cations (ra)"), and monovalent cations represented by the following formula (r-b). Monovalent cations (hereinafter also referred to as "cations (r-b)"), monovalent cations represented by the following formula (rc) (hereinafter also referred to as "cations (r-c)"), etc. Can be mentioned.

In the above formula (ra), b1 is an integer of 0 to 4. When b1 is 1, R ^B1 is a monovalent organic group having 1 to 20 carbon atoms, a hydroxy group, a nitro group, or a halogen atom. When b1 is 2 or more, the plurality of R ^B1s are the same or different and are a monovalent organic group having 1 to 20 carbon atoms, a hydroxy group, a nitro group, or a halogen atom, or these groups are combined with each other. These are part of a ring structure with 4 to 20 ring members that is formed together with the carbon chains to which they are bonded. b2 is an integer from 0 to 4. When b2 is 1, R ^B2 is a monovalent organic group having 1 to 20 carbon atoms, a hydroxy group, a nitro group, or a halogen atom. When b2 is 2 or more, the plurality of R ^B2s are the same or different and are a monovalent organic group having 1 to 20 carbon atoms, a hydroxy group, a nitro group, or a halogen atom, or these groups are combined with each other. These are part of a ring structure with 4 to 20 ring members that is formed together with the carbon chains to which they are bonded. R ^B3 and R ^B4 are each independently a hydrogen atom, a monovalent organic group having 1 to 20 carbon atoms, a hydroxy group, a nitro group, or a halogen atom, or R ^B3 and R ^B4 are combined with each other. Represents a single bond. b3 is an integer from 0 to 11. When b3 is 1, R ^B5 is a monovalent organic group having 1 to 20 carbon atoms, a hydroxy group, a nitro group, or a halogen atom. When b3 is 2 or more, the plurality of R ^B5s are the same or different and are a monovalent organic group having 1 to 20 carbon atoms, a hydroxy group, a nitro group, or a halogen atom, or these groups are combined with each other. These are part of a ring structure with 4 to 20 ring members that is formed together with the carbon chains to which they are bonded. n _b1 is an integer from 0 to 3.

In the above formula (rb), b4 is an integer from 0 to 9. When b4 is 1, R ^B6 is a monovalent organic group having 1 to 20 carbon atoms, a hydroxy group, a nitro group, or a halogen atom. When b4 is 2 or more, the plurality of R ^B6s are the same or different and are a monovalent organic group having 1 to 20 carbon atoms, a hydroxy group, a nitro group, or a halogen atom, or these groups are combined with each other. These are part of a ring structure with 4 to 20 ring members that is formed together with the carbon chains to which they are bonded. b5 is an integer from 0 to 10. When b5 is 1, R ^B7 is a monovalent organic group having 1 to 20 carbon atoms, a hydroxy group, a nitro group, or a halogen atom. When b5 is 2 or more, the plurality of R ^B7s are the same or different and are a monovalent organic group having 1 to 20 carbon atoms, a hydroxy group, a nitro group, or a halogen atom, or these groups are combined with each other. These are part of a ring structure having 3 to 20 ring members that is formed together with the carbon atoms or carbon chains to which they are bonded. n _b3 is an integer from 0 to 3. R ^B8 is a single bond or a divalent organic group having 1 to 20 carbon atoms. n _b2 is an integer from 0 to 2.

In the above formula (rc), b6 is an integer from 0 to 5. When b6 is 1, R ^B9 is a monovalent organic group having 1 to 20 carbon atoms, a hydroxy group, a nitro group, or a halogen atom. When b6 is 2 or more, the plurality of R ^B9s are the same or different and are a monovalent organic group having 1 to 20 carbon atoms, a hydroxy group, a nitro group, or a halogen atom, or these groups are combined with each other. These are part of a ring structure with 4 to 20 ring members that is formed together with the carbon chains to which they are bonded. b7 is an integer from 0 to 5. When b7 is 1, R ^B10 is a monovalent organic group having 1 to 20 carbon atoms, a hydroxy group, a nitro group, or a halogen atom. When b7 is 2 or more, the plurality of R ^B10s are the same or different and are a monovalent organic group having 1 to 20 carbon atoms, a hydroxy group, a nitro group, or a halogen atom, or these groups are combined with each other. These are part of a ring structure with 4 to 20 ring members that is formed together with the carbon chains to which they are bonded.

Examples of monovalent organic groups having 1 to 20 carbon atoms represented by R ^B1 , R ^B2 , R ^B3 , R ^B4 , R ^B5 , R ^B6 , R ^B7 , R ^B9 and R ^B10 include the above formula (4- Examples include groups similar to those exemplified as the monovalent organic group having 1 to 20 carbon atoms represented by L ¹² in 1-1).

The divalent organic group represented by R ^B8 is, for example, one of the groups exemplified as the monovalent organic group having 1 to 20 carbon atoms represented by L ¹² in the above formula (4-1-1). Examples include groups excluding hydrogen atoms.

R ^B1 , R ^B2 and R ^B5 are preferably a halogen atom, a hydroxy group or a monovalent hydrocarbon group having 1 to 20 carbon atoms, more preferably a halogen atom, a hydroxy group or an alicyclic hydrocarbon group; , a hydroxy group or a saturated alicyclic hydrocarbon group are more preferred, and a fluorine atom, a hydroxy group or a cyclohexyl group are particularly preferred.

R ^B3 and R ^B4 are preferably a hydrogen atom or a single bond in which R ^B4 and R ^B5 are combined with each other.

b1 and b2 are preferably 0 to 2, more preferably 0 or 1, and even more preferably 0. b3 is preferably 0 to 4, more preferably 0 to 2, and even more preferably 0 or 1. As n _b1 , 0 or 1 is preferable.

As the radiation-sensitive onium cation, the cation (ra) is preferred.

As the cation (ra), for example, cations represented by the following formulas (ra-1) to (ra-8) (hereinafter referred to as "cations (ra-1) to (ra-a- 8).

Compound (B) can be an appropriate combination of the above-mentioned sulfonate anion and the above-mentioned radiation-sensitive onium cation.

As the compound (B), compounds represented by the following formulas (B1) to (B13) (hereinafter also referred to as "compounds (B1) to (B13)") are preferable. Incidentally, examples of the acid-dissociable group (b) containing a (thio)acetal structure include compounds (B11) to (B13).

In the above formulas (B1) to (B13), T ⁺ is the above radiation-sensitive onium cation.

The lower limit of the content of the acid generator [B] in the radiation-sensitive resin composition is preferably 5 parts by mass, more preferably 10 parts by mass, and 15 parts by mass based on 100 parts by mass of the polymer [A]. is even more preferable. The upper limit of the content is preferably 65 parts by mass, more preferably 60 parts by mass, and even more preferably 55 parts by mass. [B] By setting the content of the acid generator within the above range, sensitivity to exposure light, LWR performance, and resolution can be further improved.

<[C] Acid diffusion controller>
[C] The acid diffusion controller has the function of controlling the diffusion phenomenon of acid generated from the [B] acid generator and the like in the resist film upon exposure, and suppressing undesirable chemical reactions in non-exposed areas. Moreover, the storage stability of the radiation-sensitive resin composition is improved, and the resolution can be further improved. Furthermore, it is possible to suppress changes in the line width of the resist pattern due to fluctuations in the standing time from exposure to development, and a radiation-sensitive resin composition with excellent process stability can be obtained. The content form of the [C] acid diffusion control agent in the radiation-sensitive resin composition includes the form of a low molecular compound (hereinafter also referred to as "[C] acid diffusion control agent"), the form of a [A] polymer, etc. Both forms are incorporated as part of the polymer. The radiation-sensitive resin composition can contain one or more [C] acid diffusion controllers.

[C] Examples of the acid diffusion control agent include a nitrogen atom-containing compound, a photodegradable base that generates a weak acid upon exposure to light, and the like.

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

Examples of the photodegradable base include compounds containing an onium cation and a weak acid anion that decompose upon exposure to light. The photodegradable base generates acid in the exposed area, increases the solubility or insolubility of the [A] polymer in the developer, and as a result suppresses roughness on the surface of the exposed area after development. On the other hand, in the non-exposed area, the anion exhibits a high acid-trapping function and functions as a quencher, trapping the acid diffused from the exposed area. That is, since it functions as a quencher only in the non-exposed area, the contrast of the deprotection reaction is improved, and as a result, resolution can be further improved.

Examples of the onium cation that decomposes upon exposure include those similar to the radiation-sensitive onium cations exemplified in the section <[B] Acid generator> above.

Examples of the anion of the weak acid include anions represented by the following formulas (C1) to (C4).

As the photodegradable base, a compound obtained by appropriately combining the onium cation that decomposes upon exposure to light and the anion of the weak acid described above can be used.

When the radiation-sensitive resin composition contains [C] acid diffusion control agent, the lower limit of the content ratio of [C] acid diffusion control agent is 1 mol per 100 mol% of [B] acid generator. % is preferable, 5 mol% is more preferable, and 10 mol% is even more preferable. The upper limit of the content is preferably 100 mol%, more preferably 50 mol%, and even more preferably 30 mol%. [C] By setting the content ratio of the acid diffusion control agent within the above range, the sensitivity to exposure light, LWR performance, and resolution of the resist pattern formed by the radiation-sensitive resin composition can be further improved. .

<[D] Organic solvent>
The radiation-sensitive resin composition usually contains [D] an organic solvent. [D] The organic solvent may be any solvent that can dissolve or disperse at least the [A] polymer, [B] the acid generator, and optionally the [C] acid diffusion controller and other optional components. There are no particular limitations.

[D] Examples of the organic solvent include alcohol solvents, ether solvents, ketone solvents, amide solvents, ester solvents, and hydrocarbon solvents. [D] The organic solvent may contain one type or two or more types.

Examples of alcoholic solvents include aliphatic monoalcohols having 1 to 18 carbon atoms such as 4-methyl-2-pentanol and n-hexanol, and alicyclic monoalcohols having 3 to 18 carbon atoms such as cyclohexanol. Examples include solvents, polyhydric alcohol solvents having 2 to 18 carbon atoms such as 1,2-propylene glycol, and partial ether solvents of polyhydric alcohols having 3 to 19 carbon atoms such as propylene glycol-1-monomethyl ether.

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

Examples of ketone solvents 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, Chain ketone solvents such as di-iso-butyl ketone and trimethylnonanone, cyclic ketone solvents such as cyclopentanone, cyclohexanone, cycloheptanone, cyclooctanone, and methylcyclohexanone, 2,4-pentanedione, and acetonyl acetone. , acetophenone, etc.

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

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

Examples of hydrocarbon solvents include aliphatic hydrocarbon solvents having 5 to 12 carbon atoms such as n-pentane and n-hexane, and aromatic hydrocarbon solvents having 6 to 16 carbon atoms such as toluene and xylene. It will be done.

[D] The organic solvent is preferably an alcohol solvent or an ester solvent, more preferably a polyhydric alcohol partial ether solvent having 3 to 19 carbon atoms or a polyhydric alcohol partial ether carboxylate solvent, propylene glycol-1- More preferred are monomethyl ether or propylene glycol acetate monomethyl ether.

When the radiation-sensitive resin composition contains [D] an organic solvent, the lower limit of the content ratio of the [D] organic solvent is 50% by mass with respect to all components contained in the radiation-sensitive resin composition. %, more preferably 60% by weight, even more preferably 70% by weight, particularly preferably 80% by weight. 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>
Other optional components include, for example, surfactants. The radiation-sensitive resin composition may contain one or more other optional components.

<Method for preparing radiation-sensitive resin composition>
The radiation-sensitive resin composition includes, for example, [A] a polymer, [B] an acid generator, and optionally a [C] acid diffusion controller, [D] an organic solvent, and other optional components. It can be prepared by mixing in a predetermined ratio and preferably filtering the resulting mixture through a membrane filter with a pore size of 0.2 μm or less.

The radiation-sensitive resin composition can be used both for forming a positive resist pattern using an alkaline developer and for forming a negative resist pattern using a developer containing an organic solvent.

The radiation-sensitive resin composition is for exposure with radiation (exposure light) irradiated in an exposure step in a resist pattern forming method described below. Among exposure lights, extreme ultraviolet rays (EUV) or electron beams have relatively high energy, but according to the radiation-sensitive resin composition, even when extreme ultraviolet rays or electron beams are used as exposure light, exposure A resist pattern having good sensitivity to light and excellent LWR performance and resolution can be formed. Therefore, the radiation-sensitive resin composition can be particularly suitably used for extreme ultraviolet exposure or electron beam exposure.

<Resist pattern formation method>
The resist pattern forming method includes a step of directly or indirectly coating the radiation-sensitive resin composition on the substrate (hereinafter also referred to as "coating step"), and exposing the resist film formed by the above coating step to light. (hereinafter also referred to as "exposure step"); and a step of developing the exposed resist film (hereinafter also referred to as "developing step").

According to the resist pattern forming method, by using the radiation-sensitive resin composition described above in the coating step, a resist pattern having good sensitivity to exposure light and excellent LWR performance and resolution is formed. be able to.

Each step included in the resist pattern forming method will be described below.

[Coating process]
In this step, the radiation-sensitive resin composition is applied directly or indirectly to the substrate. A resist film is thereby formed. Examples of the substrate include conventionally known substrates such as silicon wafers, silicon dioxide, and aluminum-coated wafers. In addition, examples of cases in which the radiation-sensitive resin composition is indirectly applied to the substrate include, for example, cases in which the radiation-sensitive resin composition is applied onto an antireflection film formed on the substrate. Examples of such an antireflection film include organic or inorganic antireflection films disclosed in Japanese Patent Publication No. 6-12452, Japanese Patent Application Laid-Open No. 59-93448, and the like.

Examples of the coating method include rotation coating (spin coating), casting coating, roll coating, and the like. After coating, if necessary, pre-baking (hereinafter also referred to as "PB") may be performed in order to volatilize the solvent in the coating film. The lower limit of the temperature of PB is preferably 60°C, more preferably 80°C. The upper limit of the above temperature is preferably 150°C, more preferably 140°C. The lower limit of the PB time is preferably 5 seconds, more preferably 10 seconds. The upper limit of the above time is preferably 600 seconds, more preferably 300 seconds. The lower limit of the average thickness of the resist film to be 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 in the above coating step is exposed. This exposure is performed by irradiating exposure light through a photomask (in some cases, through an immersion medium such as water). The exposure light can be 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, etc. Examples include lines. Among these, far ultraviolet rays, EUV or electron beams are preferred, ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), EUV (wavelength 13.5 nm) or electron beams are more preferred, and ArF excimer laser light , EUV or electron beams are more preferred, and EUV or electron beams are particularly preferred.

After the above-mentioned exposure, a post-exposure bake (hereinafter also referred to as "PEB") is performed, and in the exposed portion of the resist film, [A] polymers etc. are formed by the acid generated from [B] acid generator etc. due to exposure. It is preferable to promote the dissociation of the acid dissociable group. This PEB can increase the difference in solubility in the developer between the exposed area and the non-exposed area. The lower limit of the temperature of PEB is preferably 50°C, more preferably 80°C, and even more preferably 100°C. The upper limit of the above temperature is preferably 180°C, more preferably 130°C. The lower limit of the PEB time is preferably 5 seconds, more preferably 10 seconds, and even more preferably 30 seconds. The upper limit of the above 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. Thereby, a predetermined resist pattern can be formed. After development, it is common to wash with a rinsing liquid such as water or alcohol and dry. The developing method in the developing step may be alkaline development or organic solvent development.

In the case of alkaline development, the developer 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 include aqueous alkaline solutions in which at least one alkaline compound such as -7-undecene and 1,5-diazabicyclo-[4.3.0]-5-nonene is dissolved. Among these, a TMAH aqueous solution is preferred, and a 2.38% by mass TMAH aqueous solution is more preferred.

In the case of organic solvent development, examples of the developer 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 organic solvent [D] in the radiation-sensitive resin composition described above. Among these, ester solvents or ketone solvents are preferred. As the ester solvent, an acetate ester solvent is preferred, and n-butyl acetate is more preferred. As the ketone solvent, chain ketones are preferred, and 2-heptanone is more preferred. The lower limit of the content of the organic solvent in the developer is preferably 80% by mass, more preferably 90% by mass, even more preferably 95% by mass, and particularly preferably 99% by mass. Examples of components other than the organic solvent in the developer include water, silicone oil, and the like.

Development methods include, for example, a method in which the 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 the substrate is left stationary for a certain period of time (paddle method). ), a method in which the developer is sprayed onto the surface of the substrate (spray method), and a method in which the developer is continuously applied while scanning the developer application nozzle at a constant speed onto a rotating substrate (dynamic dispensing method). etc.

Examples of patterns formed by the resist pattern forming method include line and space patterns, hole patterns, and the like.

<Radiation-sensitive acid generator>
The radiation-sensitive acid generator has a sulfonate anion and a radiation-sensitive onium cation, and the sulfonate anion has a (thio)acetal structure, a carbonyloxy group, and an acid-dissociable property that dissociates to give a carboxyl group by the action of an acid. Contains compounds with groups. By using the radiation-sensitive acid generator as a component of the radiation-sensitive resin composition described above, it is possible to form a resist pattern that has good sensitivity to exposure light and has excellent LWR performance and resolution. . The radiation-sensitive acid generator is described as the above-mentioned [B] acid generator.

Hereinafter, the present invention will be specifically explained based on Examples, but the present invention is not limited to these Examples. The methods for measuring various physical property values are shown below.

[Weight average molecular weight (Mw), number average molecular weight (Mn) and dispersity (Mw/Mn)]
The weight average molecular weight (Mw) and number average molecular weight (Mn) of the polymer were measured under the conditions described in the section <[A] Polymer> above. Further, the degree of dispersion (Mw/Mn) was calculated from the measurement results of Mw and Mn.

[Content ratio of each structural unit of polymer]
The content ratio of each structural unit of the polymer was measured by ¹³ C-NMR analysis using a nuclear magnetic resonance apparatus (JNM-Delta400, manufactured by JEOL Ltd.).

<[A] Synthesis of polymer>
The monomers used in the synthesis of each polymer in each Example and Comparative Example are shown below. In addition, in the following synthesis examples, unless otherwise specified, parts by mass mean the values when the total mass of the monomers used is 100 parts by mass, and mol% means the total number of moles of the monomers used. It means the value when it is taken as 100 mol%.

[Synthesis Example 1] Synthesis of Polymer (A-1) Monomer (M-1) and monomer (M-3) were mixed with propylene glycol-1-monomethyl ether (200% parts by mass). A monomer solution was prepared by adding 6 mol % of azobisisobutyronitrile (AIBN) as an initiator. Meanwhile, propylene glycol-1-monomethyl ether (100 parts by mass) was added to an empty reaction vessel, and the mixture was heated to 85° C. with stirring. The above monomer solution was added dropwise over 3 hours, and then heated at 85°C for an additional 3 hours to carry out the polymerization reaction for a total of 6 hours. After the polymerization reaction was completed, the polymerization solution was cooled to room temperature.

The cooled polymerization solution was poured into hexane (500 parts by mass based on the polymerization solution), and the precipitated white powder was filtered out. The filtered white powder was washed twice with 100 parts by mass of hexane based on the polymerization solution, filtered, and dissolved in propylene glycol-1-monomethyl ether (300 parts by mass). Methanol (500 parts by mass), triethylamine (50 parts by mass) and ultrapure water (10 parts by mass) were added, and a hydrolysis reaction was carried out at 70° C. for 6 hours with stirring. After the hydrolysis reaction was completed, the remaining solvent was distilled off, and the obtained solid was dissolved in acetone (100 parts by mass). The resin was solidified by dropping it into 500 parts by mass of water, and the resulting solid was filtered out. It was dried at 50° C. for 12 hours to obtain a white powdery polymer (A-1).

The Mw of the polymer (A-1) was 5,700, and the Mw/Mn was 1.61. Furthermore, as a result of ¹³ C-NMR analysis, the content ratio of each structural unit derived from monomer (M-1) and monomer (M-3) in polymer (A-1) was 41.2 mol each. % and 58.8 mol%.

[Synthesis Examples 2 to 9] Synthesis of Polymers (A-2) to (A-9) Polymers were produced in the same manner as Synthesis Example 1, except that the types and blending ratios of monomers shown in Table 1 below were used. Combined compounds (A-2) to (A-9) were synthesized.

<[B] Synthesis of acid generator>
[Synthesis Example 10] Synthesis of acid generator (B-1) In a reaction vessel, 10 mmol of the compound represented by the following formula (S-1), 10 mmol of 4-hydroxybenzaldehyde, and 1 mmol of p-toluenesulfonic acid were dissolved in toluene and 1M And so. A Dean-Stark tube was installed in the reaction vessel, and the solution was stirred under reflux conditions for 5 hours. After the reaction was completed, a saturated aqueous sodium bicarbonate solution was added, and dichloromethane was added for extraction, and the organic layer was separated. After drying the organic layer with sodium sulfate, the solvent was removed and column purification was performed to obtain a compound represented by the following formula (Z-1) (hereinafter also referred to as "compound (Z-1)") with a yield of 55%. I got it.

10 mmol of compound (Z-1), 15 mmol of a compound represented by the following formula (P-1), 15 mmol of potassium carbonate, and 100 g of acetone were added to a reaction vessel. After the solution was kept under reflux for 5 hours, the acetone was distilled off. After adding dichloromethane, the mixture was washed three times with ultrapure water. After drying with sodium sulfate, the solvent was distilled off and purified by column chromatography to obtain a compound represented by the following formula (B-1) (hereinafter also referred to as "acid generator (B-1)"). Ta.

The synthesis scheme of the acid generator (B-1) is shown below.

In the above synthetic scheme, pTsOH is p-toluenesulfonic acid. TPS ⁺ is a triphenylsulfonium cation.

[Synthesis Examples 11 to 22] Synthesis of acid generators (B-2) to (B-13) The following formulas (B-2) to (B -13) (hereinafter also referred to as "acid generators (B-2) to (B-13)") were synthesized.

<Preparation of radiation-sensitive resin composition>
Acid generators other than the [B] acid generator used in the preparation of the radiation-sensitive resin compositions of comparative examples, and [C] acid diffusion control used in the preparation of the radiation-sensitive resin compositions of the examples and comparative examples The agent and [D] organic solvent are shown below. In addition, in the following examples and comparative examples, unless otherwise specified, "parts by mass" means the value when the mass of the polymer used is 100 parts by mass, and "mol%" means the number of moles of the acid generator used. It means the value when it is taken as 100 mol%.

[[B] Acid generator other than acid generator]
b-1 to b-3: Compounds represented by the following formulas (b-1) to (b-3)

[[C] Acid diffusion control agent]
C-1 to C-4: Compounds represented by the following formulas (C-1) to (C-4)

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

[Example 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-1) as an acid diffusion control agent (B) -1) Radiation sensitive resin composition by mixing 20 mol% to 100 mol% and 4,800 parts by mass of (D-1) and 2,000 parts by mass of (D-2) as [D] solvent Product (R-1) was prepared.

[Examples 2 to 27 and Comparative Examples 1 to 3]
Radiation-sensitive resin compositions (R-2) to (R-27) and (CR-1) to (CR-3) was prepared.

<Formation of resist pattern>
The above prepared film was applied to the surface of a 12-inch silicon wafer on which a lower layer film ("AL412" manufactured by Brewer Science) with an average thickness of 20 nm was formed using a spin coater ("CLEAN TRACK ACT12" manufactured by Tokyo Electron Ltd.). Each radiation-sensitive resin composition was applied, soft-baked (SB) at 130°C for 60 seconds, and cooled at 23°C for 30 seconds to form a resist film with an average thickness of 50 nm. Next, this resist film was irradiated with EUV light using an EUV exposure machine (“NXE3300” manufactured by ASML, NA=0.33, illumination conditions: Conventional s=0.89, mask imecDEFECT32FFR02). After irradiation, PEB was performed on the resist film at 130° C. for 60 seconds. Next, development was performed at 23° C. for 30 seconds using a 2.38% by mass TMAH aqueous solution to form a positive resist pattern (32 nm line and space pattern).

<Evaluation>
Regarding each resist pattern formed above, the sensitivity, LWR performance, and resolution of each radiation-sensitive resin composition were evaluated according to the following method. Note that a scanning electron microscope (“CG-4100” manufactured by Hitachi High-Technologies Corporation) was used to measure the length of the resist pattern. The evaluation results are shown in Table 3 below.

[sensitivity]
In forming the resist pattern, the exposure amount for forming a 32 nm line-and-space pattern was defined as the optimum exposure amount, and this optimum exposure amount was defined as Eop (unit: mJ/cm ² ). The sensitivity can be evaluated as "good" when Eop is 30 mJ/cm ² or less, and "poor" when it exceeds 30 mJ/cm ² .

[LWR performance]
The resist pattern formed in the formation of the resist pattern was observed from above using the scanning electron microscope. The line width was measured at a total of 50 points at arbitrary locations, a 3 sigma value was determined from the distribution of the measured values, and this was defined as LWR (unit: nm). The smaller the value of LWR, the less wobbling the line is, indicating that it is better. The LWR performance can be evaluated as "good" when the LWR is 4.0 nm or less, and "poor" when it exceeds 4.0 nm.

[Resolution]
At the optimum exposure amount above, measure the dimension of the minimum resist pattern that is resolved when changing the size of the mask pattern forming line and space (1L/1S), and calculate this measurement value as the resolution (unit: nm). And so. The smaller the resolution value, the better the ability to form a finer pattern. Regarding resolution, if the resolution is 25 nm or less, it can be evaluated as "good", and if it exceeds 25 nm, it can be evaluated as "poor".

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 than the radiation-sensitive resin compositions of Comparative Examples.

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

Claims (9)

A polymer having a first structural unit containing a first acid-dissociable group that dissociates under the action of an acid to give an alkali-soluble group , and a second structural unit containing a phenolic hydroxyl group ;
Contains a radiation-sensitive acid generator and
The radiation-sensitive acid generator includes a compound having a sulfonate anion and a radiation-sensitive onium cation,
A radiation-sensitive resin in which the sulfonate anion has a (thio)acetal structure, a carbonyloxy group , a second acid-dissociable group that dissociates to give a carboxyl group by the action of an acid, and a partial structure represented by the following formula (3). Composition.

(In formula (3), R ¹⁰ and R ¹¹ are each independently a hydrogen atom, a fluorine atom, a monovalent hydrocarbon group having 1 to 20 carbon atoms, or a monovalent fluorinated carbon group having 1 to 20 carbon atoms. A hydrogen group. However, at least one of R ¹⁰ and R ¹¹ is a fluorine atom or a monovalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. m is an integer of 2 to 10. R ^10s are the same or different from each other, and a plurality of R ^11s are the same or different from each other. *** indicates a bonding site with a moiety other than the structure represented by formula (3) in the sulfonate anion.) The radiation-sensitive resin composition according to claim 1, wherein the (thio)acetal structure is a cyclic (thio)acetal structure. The radiation-sensitive resin composition according to claim 2, wherein the cyclic (thio)acetal structure is represented by the following formula (1).

(In formula (1), X ¹ and X ² are each independently -O- or -S-. R ¹ is an (n+2)-valent hydrocarbon group having 1 to 10 carbon atoms. n is an integer of 0 to 2. * indicates a bonding site with a moiety other than the structure represented by formula (1) in the sulfonate anion.) The radiation-sensitive resin composition according to claim 1, claim 2, or claim 3, wherein the second acid-dissociable group is represented by the following formula (2-1) or (2-2).

(In formulas (2-1) and (2-2), ** represents the bonding site of the carbonyloxy group with the etheric oxygen atom in the sulfonate anion.
In formula (2-1), R ² is a monovalent hydrocarbon group having 1 to 20 carbon atoms or a group containing the above-mentioned (thio)acetal structure. R ³ and R ⁴ are each independently a monovalent hydrocarbon group having 1 to 20 carbon atoms, or a group having 3 to 20 ring members formed by combining these groups together with the carbon atom to which they are bonded. It is part of the alicyclic structure of 20.
In formula (2-2), R ⁶ , R ⁷ and R ⁹ are each independently a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms. R ⁵ and R ⁸ are each independently a monovalent hydrocarbon group having 1 to 20 carbon atoms, or the number of ring members formed by combining these groups together with the unsaturated carbon chain to which they are bonded. It is part of 4 to 20 unsaturated alicyclic structures. ) The radiation-sensitive resin composition according to any one of claims 1 to 4, wherein the sulfonate anion further has an alicyclic structure. Coating the radiation-sensitive resin composition according to any one of claims 1 to 5 directly or indirectly onto a substrate;
a step of exposing the resist film formed by the above coating step;
A resist pattern forming method comprising : developing the exposed resist film. A radiation-sensitive acid generator containing a compound having a sulfonate anion and a radiation-sensitive onium cation,
A radiation-sensitive acid generator in which the sulfonate anion has a (thio)acetal structure, a carbonyloxy group , an acid-dissociable group that dissociates to give a carboxyl group by the action of an acid, and a partial structure represented by the following formula (3). agent.

(In formula (3), R ¹⁰ and R ¹¹ are each independently a hydrogen atom, a fluorine atom, a monovalent hydrocarbon group having 1 to 20 carbon atoms, or a monovalent fluorinated carbon group having 1 to 20 carbon atoms. A hydrogen group. However, at least one of R ¹⁰ and R ¹¹ is a fluorine atom or a monovalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. m is an integer of 2 to 10. R ^10s are the same or different from each other, and a plurality of R ^11s are the same or different from each other. *** indicates a bonding site with a moiety other than the structure represented by formula (3) in the sulfonate anion.) 8. The sulfonate anion has a cyclic (thio)acetal structure represented by the following formula (1) and an acid-dissociable group represented by the following formula (2-1) or (2-2). Radiation sensitive acid generator.

(In formula (1), X ¹ and X ² are each independently -O- or -S-. R ¹ is an (n+2)-valent hydrocarbon group having 1 to 10 carbon atoms. n is an integer of 0 to 2. * indicates a bonding site with a moiety other than the structure represented by formula (1) in the sulfonate anion.)

(In formulas (2-1) and (2-2), ** represents the bonding site of the carbonyloxy group with the etheric oxygen atom in the sulfonate anion.
In formula (2-1), R ² is a monovalent hydrocarbon group having 1 to 20 carbon atoms or a group containing the above-mentioned (thio)acetal structure. R ³ and R ⁴ are each independently a monovalent hydrocarbon group having 1 to 20 carbon atoms, or a group having 3 to 20 ring members formed by combining these groups together with the carbon atom to which they are bonded. It is part of the alicyclic structure of 20.
In formula (2-2), R ⁶ , R ⁷ and R ⁹ are each independently a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms. R ⁵ and R ⁸ are each independently a monovalent hydrocarbon group having 1 to 20 carbon atoms, or a group having 4 to 20 ring members formed by combining these groups together with the carbon atom to which they are bonded. It is part of 20 unsaturated alicyclic structures. ) The radiation-sensitive acid generator according to claim 7 or 8, wherein the sulfonate anion further has an alicyclic structure.