Radioactive-ray-sensitive resin composition and pattern formation method

Abstract

Provided are: a radioactive-ray-sensitive resin composition which makes it possible to form a resist film having satisfactory storage stability and also having excellent sensitivity and LWR performance when a next-generation technology is applied; and a pattern formation method.　This radioactive-ray-sensitive resin composition contains: a radioactive-ray-sensitive onium salt including a fluorine atom at a cation portion; a compound represented by formula (H); and a resin including a structural unit having an acid-dissociable group. (In formula (H), R1-R3 each independently represent a substituted or unsubstituted aliphatic hydrocarbon group having 1-20 carbon atoms.)

Description

Radiation-sensitive resin composition and pattern forming method

[0001] The present invention relates to a radiation-sensitive resin composition and a pattern forming method.

[0002] Photolithography techniques using resist compositions are used to form fine circuits in semiconductor elements. A typical procedure involves, for example, exposing a coating of the resist composition to radiation through a mask pattern to generate an acid, which is then catalyzed by a reaction that causes a difference in the solubility of the resin in an alkaline or organic solvent-based developer between the exposed and unexposed areas, thereby forming a resist pattern on a substrate.

[0003] The photolithography technology described above promotes pattern miniaturization by using short-wavelength radiation such as an ArF excimer laser or by combining this radiation with liquid immersion lithography. As a next-generation technology, the use of even shorter-wavelength radiation such as electron beams, X-rays, and EUV (extreme ultraviolet) is being considered, and resist materials containing acid generators with fluorine-substituted benzene rings that have improved radiation absorption efficiency are also being investigated (Patent Document 1).

[0004] Japanese Patent Application Laid-Open No. 2014-2359

[0005] However, it has been found that when the above-mentioned technology for improving radiation absorption efficiency is applied, the storage stability of the resist composition decreases.

[0006] An object of the present invention is to provide a radiation-sensitive resin composition and a pattern forming method that have good storage stability and are capable of forming a resist film that has excellent sensitivity and LWR (Line Width Roughness) performance when next-generation technology is applied.

[0007] As a result of extensive research into solving the above problem, the present inventors have found that the above object can be achieved by employing the following configuration, and have thus completed the present invention.

[0008] In one embodiment, the present invention relates to a radiation-sensitive resin composition comprising: a radiation-sensitive onium salt containing a fluorine atom in its cation moiety; a compound represented by the following formula (H); and a resin containing a structural unit having an acid-dissociable group: (In the above formula (H), R １ ~R ３ are each independently a substituted or unsubstituted aliphatic hydrocarbon group having 1 to 20 carbon atoms.

[0009] The radiation-sensitive resin composition has good storage stability and can form a resist film that satisfies the sensitivity and LWR performance. Although the reason for this is unclear, it is presumed as follows: The fluorine-containing onium cation moiety of the onium salt significantly increases the absorption of radiation such as EUV having a wavelength of 13.5 nm by fluorine atoms, thereby increasing the secondary electron generation efficiency and improving the sensitivity of the radiation-sensitive resin composition.

[0010] On the other hand, in systems in which, for example, the conventionally widely used salicylate anion is simply used as the organic acid anion moiety, the introduction of the fluorine-containing onium cation moiety may result in a decrease in storage stability. The present inventors investigated the cause of this and concluded that, because the fluorine-containing onium cation is highly electrophilic, its combined use with a highly basic organic acid anion may result in a decrease in storage stability. In contrast, it is believed that the presence of the compound represented by formula (H) above can suppress decomposition of the fluorine-containing onium cation moiety and thereby exhibit good storage stability.

[0011] In another embodiment, the present invention relates to a pattern forming method, comprising: a step of applying the radiation-sensitive resin composition directly or indirectly onto a substrate to form a resist film; a step of exposing the resist film; and a step of developing the exposed resist film with a developer.

[0012] The pattern formation method uses the radiation-sensitive resin composition, which has good storage stability and is capable of forming a resist film that is excellent in sensitivity and LWR performance, and therefore can efficiently form a high-quality resist pattern.

[0013] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to these embodiments.

[0014] <Radiation-Sensitive Resin Composition> The radiation-sensitive resin composition (hereinafter also simply referred to as "composition") according to this embodiment contains a compound represented by the following formula (H) and a resin. The composition may contain other optional components as long as the effects of the present invention are not impaired. By containing a specific onium salt, the radiation-sensitive resin composition can exhibit good storage stability and can impart high levels of sensitivity and LWR performance to the resulting resist film.

[0015] <Onium Salt> The onium salt is a component that contains an organic acid anion moiety and an onium cation moiety and generates an acid upon exposure. When at least a part of the onium cation moieties in the onium salt are fluorine-containing onium cation moieties containing a fluorine atom, high sensitivity can be achieved by improving the radiation absorption efficiency (and secondary electron generation efficiency) and subsequently the acid generation efficiency.

[0016] Although the form of the onium salt contained in the radiation-sensitive resin composition is not particularly limited, the onium salt is preferably at least one selected from the group consisting of a radiation-sensitive acid generator containing the organic acid anion moiety and an acid diffusion controller that contains the organic acid anion moiety and the onium cation moiety and generates an acid having a higher pKa than the acid generated from the radiation-sensitive acid generator upon irradiation with radiation. The different functions of these are described below.

[0017] The acid generated by exposure of an onium salt is thought to have two functions in the radiation-sensitive resin composition, depending on the strength of the acid. The first function is to dissociate the acid-dissociable group of a structural unit of the resin containing the acid-dissociable group, thereby generating a carboxyl group or the like. An onium salt having this first function is called a radiation-sensitive acid generator. The second function is to inhibit the diffusion of the acid generated from the radiation-sensitive acid generator in unexposed areas by salt exchange without substantially dissociating the acid-dissociable group of the resin under pattern formation conditions using the radiation-sensitive resin composition. An onium salt having this second function is called an acid diffusion controller. The acid generated from the radiation-sensitive acid generator can be said to be a relatively stronger acid (having a lower pKa) than the acid generated from the acid diffusion controller. Whether an onium salt functions as a radiation-sensitive acid generator or an acid diffusion controller is determined by the energy required to dissociate the acid-dissociable group of the resin and the acidity of the onium salt. The radiation-sensitive acid generator is preferably contained in the radiation-sensitive resin composition in a form in which the onium salt structure exists alone as a (low molecular weight) compound.

[0018] When the radiation-sensitive resin composition contains the radiation-sensitive acid generator, the polarity of the resin in the exposed area increases, and the resin in the exposed area becomes soluble in the developer in the case of development with an aqueous alkaline solution, while becoming poorly soluble in the developer in the case of development with an organic solvent.

[0019] Furthermore, by including the acid diffusion controller in the radiation-sensitive resin composition, it is possible to suppress the diffusion of acid in unexposed areas, and to form a resist pattern that is superior in pattern developability and LWR performance.

[0020] In this embodiment, the onium cation moiety in the radiation-sensitive acid generator is a fluorine-containing onium cation moiety. Preferably, both the onium cation moiety in the acid diffusion controller and the onium cation moiety in the radiation-sensitive acid generator are fluorine-containing onium cation moieties.

[0021] Although the form of fluorine atom inclusion in the fluorine-containing onium cation moiety is not particularly limited, the fluorine-containing onium cation moiety preferably contains an aromatic ring structure having a fluorine atom (hereinafter also referred to as a "fluorine-substituted aromatic ring structure"). By combining an electron-withdrawing fluorine atom with an aromatic ring structure, further improvement in radiation absorption efficiency can be expected. Note that the "aromatic ring structure having a fluorine atom" includes not only a structure in which a fluorine atom is directly bonded to an aromatic ring structure, but also a structure in which a fluorine atom is bonded to an aromatic ring structure via another atom (for example, a structure in which a fluorine atom is bonded to a substituent bonded to an aromatic ring structure).

[0022] <Radiation-Sensitive Acid Generator> The radiation-sensitive resin composition contains a radiation-sensitive acid generator that generates an acid having a lower pKa than the acid generated from the acid diffusion controller upon irradiation (exposure) with radiation. When the radiation-sensitive resin composition contains the radiation-sensitive acid generator, the acid generated upon exposure dissociates an acid-dissociable group in the resin, generating a carboxy group or the like. As a result, the polarity of the resin in the exposed areas increases, and the resin in the exposed areas becomes soluble in a developer in the case of aqueous alkaline development, but becomes sparingly soluble in a developer in the case of organic solvent development.

[0023] The radiation-sensitive acid generator is preferably a radiation-sensitive onium salt containing an organic acid anion moiety and an onium cation moiety. The organic acid anion moiety preferably contains at least one anion selected from the group consisting of sulfonate anions and sulfonimide anions. Examples of the acid generated by exposure include sulfonic acid and sulfonimide, corresponding to the organic acid anion moiety. The organic acid anion moiety preferably contains an iodine-substituted aromatic ring structure.

[0024] The onium cation moiety in the radiation-sensitive acid generator can be a fluorine-containing onium cation moiety.

[0025] Furthermore, as a radiation-sensitive acid generator that generates sulfonic acid upon exposure, a compound having one or more fluorine atoms or fluorinated hydrocarbon groups bonded to a carbon atom adjacent to a sulfonate anion can be suitably used.

[0026] The radiation-sensitive onium salt serving as the radiation-sensitive acid generator is preferably represented by the following formula (1).

[0027]

[0028] In formula (1), R ｃ１ ~R ｃ３ are each independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, ｃ１ ~R ｃ３ At least one of contains a fluorine atom or a trifluoromethyl group.

[0029] R ｃ１ ~R ｃ３ The linear or branched alkyl group having 1 to 12 carbon atoms represented by the formula (I) is preferably an alkyl group having 1 to 12 carbon atoms or a cycloalkyl group having 3 to 12 carbon atoms, and some or all of the hydrogen atoms in these groups may be substituted with a hydroxy group, a carboxy group, a halogen atom, an oxo group, a cyano group, an amide group, a nitro group, a sultone group, a sulfone group or a sulfonium salt-containing group, and some of the methylene groups constituting these groups may be substituted with an ether group, an ester group, a carbonyl group, a carbonate group or a sulfonate ester group.

[0030] R ｃ１ ~R ｃ３ The substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms represented by the formula (I) is preferably an aryl group having 6 to 12 carbon atoms, and some or all of the hydrogen atoms in these groups may be substituted with a hydroxy group, a carboxy group, a halogen atom, an oxo group, a cyano group, an amide group, a nitro group, a sultone group, a sulfone group or a sulfonium salt-containing group, and some of the methylene groups constituting these groups may be substituted with an ether group, an ester group, a carbonyl group, a carbonate group or a sulfonate ester group. ｃ１ ~R ｃ３It is preferable that at least one of the above is a phenyl group containing a fluorine atom or a trifluoromethyl group at the para position, a phenyl group containing a fluorine atom or a trifluoromethyl group at the meta position, or a phenyl group containing an iodine atom at the para position.

[0031] In formula (1), Y ｃ ― is a monovalent anion.

[0032] Y ｃ ― The monovalent anion represented by the formula (I) is not particularly limited, but may be, for example, R ｃα -SO ３ － Examples of anions include those represented by the following formula:

[0033] In formula (1), R ｃα is a monovalent organic group.

[0034] R ｃα Examples of monovalent organic groups represented by the formula (I) include groups obtained by removing one hydrogen atom from a monovalent organic group having 1 to 40 carbon atoms. The monovalent organic group having 1 to 40 carbon atoms may be a group having a chain structure, a cyclic structure, or a combination thereof. Examples of the chain structure include a chain hydrocarbon group, whether saturated or unsaturated, straight or branched. Examples of the cyclic structure include a cyclic hydrocarbon group, whether alicyclic, aromatic, or heterocyclic. Among these, preferred monovalent organic groups are monovalent chain hydrocarbon groups having 1 to 20 carbon atoms, monovalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms, monovalent aromatic hydrocarbon groups having 6 to 20 carbon atoms, or combinations thereof. In particular, preferred monovalent organic groups are groups containing a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms.

[0035] The radiation-sensitive onium salt preferably contains an iodine atom. ｃαThe monovalent organic group represented by the formula (I) is preferably a monovalent organic group having 1 to 40 carbon atoms and containing 1 to 6 iodine atoms, and more preferably a monovalent organic group having 6 to 40 carbon atoms and containing a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms and substituted with 1 to 3 iodine atoms. The radiation-sensitive onium salt also preferably contains a partial structure having an acid-dissociable group. Examples of the partial structure having an acid-dissociable group include a group in which a hydrogen atom of a carboxy group is substituted with a group that dissociates under the action of an acid. Examples of the group that dissociates under the action of an acid include the same acid-dissociable groups as those contained in the base resin described below.

[0036] Examples of the onium cation moiety of the radiation-sensitive acid generator represented by formula (1) include, but are not limited to, those shown below.

[0037]

[0038]

[0039]

[0040]

[0041]

[0042] Examples of the organic acid anion moiety of the radiation-sensitive acid generator represented by formula (1) include, but are not limited to, those shown below. Note that, as the organic acid anion moiety not having an iodine-substituted aromatic ring structure, a structure in which the iodine atom in the following formula is substituted with an atom or group other than an iodine atom, such as a hydrogen atom or another substituent, can be suitably used.

[0043]

[0044]

[0045]

[0046]

[0047]

[0048] Examples of the radiation-sensitive onium salt represented by formula (1) include, but are not limited to, compounds represented by the following (B-1) to (B-11).

[0049]

[0050] These radiation-sensitive acid generators may be used alone or in combination of two or more. The lower limit of the content of the radiation-sensitive acid generator is preferably 1 part by mass, more preferably 3 parts by mass, even more preferably 5 parts by mass, and particularly preferably 8 parts by mass, per 100 parts by mass of the resin. The upper limit of the content is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, even more preferably 30 parts by mass or less, and particularly preferably 25 parts by mass or less, per 100 parts by mass of the resin. This allows for excellent sensitivity and CDU performance to be exhibited during resist pattern formation.

[0051] <Acid Diffusion Controller> The acid diffusion controller contains an organic acid anion moiety and an onium cation moiety, and generates an acid having a higher pKa than the acid generated from the radiation-sensitive acid generator upon irradiation with radiation. Examples of such an organic acid anion moiety include carboxylic acids. The organic acid anion moiety preferably contains an iodine-substituted aromatic ring structure. The acid diffusion controller is preferably represented by the following formula (S-1) or (S-2):

[0052]

[0053] In formulas (S-1) and (S-2), R １ represents a hydrogen atom, a hydroxy group, a fluorine atom, a chlorine atom, a bromine atom, an amino group, a nitro group, a carboxy group, a cyano group, or an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an acyloxy group having 2 to 6 carbon atoms, or an alkylsulfonyloxy group having 1 to 4 carbon atoms, which may be substituted with a halogen atom, or -NR １Ａ -C(=O)-R １Ｂ Or -NR １Ａ -C(=O)-OR １Ｂ It is. １Ａ is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R １Ｂis an alkyl group having 1 to 6 carbon atoms or an alkenyl group having 2 to 8 carbon atoms.

[0054] The alkyl group having 1 to 6 carbon atoms may be linear, branched, or cyclic, and specific examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, a cyclopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a cyclobutyl group, an n-pentyl group, a cyclopentyl group, an n-hexyl group, and a cyclohexyl group. Examples of the alkyl moiety of the alkoxy group having 1 to 6 carbon atoms, the acyloxy group having 2 to 7 carbon atoms, and the alkoxycarbonyl group having 2 to 7 carbon atoms include the same as the specific examples of the alkyl group described above, and examples of the alkyl moiety of the alkylsulfonyloxy group having 1 to 4 carbon atoms include the specific examples of the alkyl group having 1 to 4 carbon atoms described above. The alkenyl group having 2 to 8 carbon atoms may be linear, branched, or cyclic, and specific examples thereof include a vinyl group, a 1-propenyl group, and a 2-propenyl group. Of these, R １ Examples of the alkyl group include a fluorine atom, a chlorine atom, a hydroxy group, an amino group, an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, an acyloxy group having 2 to 4 carbon atoms, and —NR １Ａ -C(=O)-R １Ｂ , -NR １Ａ -C(=O)-OR １Ｂ etc. are preferred.

[0055] R ３ , R ４ , R ５ , R ６ and R ７ are each independently a monovalent hydrocarbon group having 1 to 20 carbon atoms which may contain a heteroatom. When the onium cation moiety of the acid diffusion controller has a fluorine atom, R ３ , R ４ and R ５ At least one of R contains one or more fluorine atoms, ６ and R ７ At least one of R contains one or more fluorine atoms. ３ , R ４ and R ５Any two of the above may be bonded to each other to form a ring together with the sulfur atom to which they are bonded. The monovalent hydrocarbon group may be linear, branched, or cyclic, and specific examples thereof include alkyl groups having 1 to 12 carbon atoms, alkenyl groups having 2 to 12 carbon atoms, alkynyl groups having 2 to 12 carbon atoms, aryl groups having 6 to 20 carbon atoms, and aralkyl groups having 7 to 12 carbon atoms. In addition, some or all of the hydrogen atoms of these groups may be substituted with hydroxy groups, carboxy groups, halogen atoms, cyano groups, amide groups, nitro groups, mercapto groups, sultone groups, sulfone groups, or sulfonium salt-containing groups, and some of the carbon atoms of these groups may be substituted with ether bonds, ester bonds, carbonyl groups, carbonate groups, or sulfonate ester bonds. Among these, R ３ , R ４ and R ５ At least one of R is preferably a phenyl group containing a fluorine atom or a trifluoromethyl group at the para position, a phenyl group containing a fluorine atom or a trifluoromethyl group at the meta position, or a phenyl group containing an iodine atom at the para position. ６ and R ７ It is preferable that at least one of the above is a phenyl group containing a fluorine atom or a trifluoromethyl group at the para position, a phenyl group containing a fluorine atom or a trifluoromethyl group at the meta position, or a phenyl group containing an iodine atom at the para position.

[0056] L １ represents a single bond or a divalent linking group having 1 to 20 carbon atoms, which may contain an ether bond, a carbonyl group, an ester bond, an amide bond, a sultone ring, a lactam ring, a carbonate bond, a halogen atom, a hydroxy group, or a carboxy group.

[0057] m and n are integers satisfying 0≦m≦5, 0≦n≦3, and 0≦m+n≦5, but preferably integers satisfying 1≦m≦3 and 0≦n≦3, or 0≦m≦3 and 1≦n≦3. When n is 1, R １ is preferably a hydroxy group. When n is 2 or more, at least one R １is preferably a hydroxy group, a fluorine atom, or a fluorinated hydrocarbon group. １ are both hydroxy groups, or one R １ is a hydroxy group and the remaining R １ is preferably a fluorine atom or a fluorinated hydrocarbon group.

[0058] Examples of the organic acid anion moiety of the acid diffusion controller represented by formula (S-1) or (S-2) above include, but are not limited to, the following: All of the following are organic acid anion moieties having an iodine-substituted aromatic ring structure, but as organic acid anion moieties not having an iodine-substituted aromatic ring structure, structures in which the iodine atom in the following formula is substituted with an atom or group other than an iodine atom, such as a hydrogen atom or other substituent, can be suitably used.

[0059]

[0060]

[0061]

[0062] The onium cation moiety in the acid diffusion controller represented by the formulas (S-1) and (S-2) is preferably an onium cation containing an aromatic ring structure having a fluorine atom, and is preferably a fluorine atom or CF ３ Onium cations containing an aromatic ring structure having a group are more preferred. Specific examples include the onium cations in the radiation-sensitive onium salts represented by the above formula (1).

[0063] The acid diffusion controllers represented by the formulas (S-1) and (S-2) can be synthesized by known methods, particularly by salt exchange reactions. Known acid diffusion controllers can also be used as long as they do not impair the effects of the present invention.

[0064] These acid diffusion controllers may be used alone or in combination of two or more. The content of the acid diffusion controller relative to the content of the radiation-sensitive acid generator is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more. Furthermore, the content is preferably 100% by mass or less, more preferably 80% by mass or less, and even more preferably 60% by mass or less. This allows excellent sensitivity and LWR performance to be exhibited during resist pattern formation.

[0065] The content of the acid diffusion controller relative to the radiation-sensitive acid generator (when a plurality of acid generators are contained, the total content of the acid diffusion controllers) is preferably 5 mol % or more, more preferably 10 mol % or more, and even more preferably 15 mol % or more. The content is preferably 50 mol % or less, more preferably 40 mol % or less, and even more preferably 30 mol % or less. This allows the storage stability to be exhibited.

[0066] <Compound Represented by Formula (H)> The compound represented by formula (H) (hereinafter also referred to as "compound (H)")) is represented by the following formula.

[0067] (In the above formula (H), R １ ~R ３ are each independently a substituted or unsubstituted aliphatic hydrocarbon group having 1 to 20 carbon atoms.

[0068] R １ ~R ３ The aliphatic hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) may be any of linear, branched, and cyclic. Specific examples thereof include an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, and an alkynyl group having 2 to 20 carbon atoms. The linear structure may be a linear hydrocarbon group, whether saturated or unsaturated, linear or branched. The cyclic structure may be an alicyclic cyclic hydrocarbon group. In addition, R ２ and R ３may be bonded to each other to form a ring together with the sulfur atom to which they are bonded. In addition, some or all of the hydrogen atoms of these groups may be substituted with hydroxy groups, carboxy groups, halogen atoms, cyano groups, amide groups, nitro groups, mercapto groups, sultone groups, sulfone groups, or sulfonium salt-containing groups, and some of the carbon atoms of these groups may be substituted with ether bonds, ester bonds, carbonyl groups, carbonate groups, or sulfonate ester bonds.

[0069] The alkyl group having 1 to 20 carbon atoms may be linear, branched, or cyclic, and specific examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, a cyclopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a cyclobutyl group, an n-pentyl group, a cyclopentyl group, an n-hexyl group, and a cyclohexyl group. The alkenyl group having 2 to 20 carbon atoms may be linear, branched, or cyclic, and specific examples thereof include a vinyl group, a 1-propenyl group, and a 2-propenyl group. The alkynyl group having 2 to 20 carbon atoms may be linear, branched, or cyclic, and specific examples thereof include an ethynyl group, a propargyl group, and the like.

[0070] As the compound (H), known or novel compounds can be used as appropriate.

[0071] Examples of the compound (H) include methyl 2-hydroxyisobutyrate, ethyl 2-hydroxyisobutyrate, isopropyl 2-hydroxyisobutyrate, methyl 2-hydroxy-2-methylbutyrate, etc. These may be used alone or in combination of two or more.

[0072] The compound (H) may be used alone or in combination of two or more. The content of the compound (H) (when a plurality of compounds (H) are contained, the total content thereof) is preferably 30% by mass or more, more preferably 40% by mass or more, even more preferably 50% by mass or more, particularly preferably 55% by mass or more, and even more preferably 60% by mass or more, based on the radiation-sensitive resin composition. The content is preferably 90% by mass or less, more preferably 85% by mass or less, even more preferably 80% by mass or less, and particularly preferably 75% by mass or less. This allows the storage stability to be exhibited.

[0073] When the radiation-sensitive resin composition of this embodiment contains a solvent described below, the content of the compound (H) is preferably 5% by mass or more, more preferably 15% by mass or more, even more preferably 45% by mass or more, particularly preferably 55% by mass or more, and even more preferably 65% ​​by mass or more, based on the total of the compound (H) and the solvent. This allows the composition to exhibit storage stability. The content may be 100% by mass (i.e., the composition may not contain the solvent described below), or may be 95% by mass or less.

[0074] <Resin> The resin is an assembly of polymers containing a structural unit having an acid-dissociable group (hereinafter also referred to as "structural unit (I)") (hereinafter this resin will also be referred to as "base resin"). In addition to the structural unit (I), the base resin may also contain a structural unit (II) having a phenolic hydroxyl group, a structural unit (III) containing a heteroatom-containing substituent, a structural unit (IV) containing a lactone structure, etc. Each structural unit will be described below.

[0075] (Structural Unit (I)) The structural unit (I) is a structural unit having an acid-dissociable group. In this specification, the term "acid-dissociable group" refers to a group that substitutes a hydrogen atom of an alkali-soluble group such as a carboxy group, a phenolic hydroxyl group, a sulfo group, or a sulfonamide group, and that dissociates under the action of an acid. Therefore, the acid-dissociable group is bonded to the oxygen atom that was previously bonded to the hydrogen atom in these functional groups.

[0076] The structural unit (I) is not particularly limited as long as it has an acid-dissociable group, and examples thereof include a structural unit having a tertiary alkyl ester moiety, a structural unit having a structure in which the hydrogen atom of a phenolic hydroxyl group is substituted with a tertiary alkyl group, a structural unit having an acetal bond, etc. Among these, from the viewpoint of improving the pattern formability of the radiation-sensitive resin composition, a structural unit represented by the following formula (3) (hereinafter also referred to as "structural unit (1-1)") is preferred.

[0077]

[0078] In the above formula (3), R ７ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ８ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms. ９ and R １０ are each independently a monovalent chain hydrocarbon group having 1 to 10 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, or a divalent alicyclic group having 3 to 20 carbon atoms formed by combining these groups together with the carbon atoms to which they are bonded. Ar is a single bond or a substituted or unsubstituted phenylene group. L １ represents a single bond or a divalent linking group.

[0079] The above R ７ As the alkyl group, from the viewpoint of copolymerizability of the monomer that gives the structural unit (1-1), a hydrogen atom or a methyl group is preferred, and a methyl group is more preferred.

[0080] The above R ８ Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) include a chain hydrocarbon group having 1 to 10 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, and a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms.

[0081] The above R ８ ~R １０ Examples of the chain hydrocarbon group having 1 to 10 carbon atoms represented by the formula (I) include a linear or branched saturated hydrocarbon group having 1 to 10 carbon atoms, and a linear or branched unsaturated hydrocarbon group having 1 to 10 carbon atoms.

[0082] The above R ８ ~R１０ Examples of the alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the formula (I) include monocyclic or polycyclic saturated hydrocarbon groups, and monocyclic or polycyclic unsaturated hydrocarbon groups. Preferred monocyclic saturated hydrocarbon groups are cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl groups. Preferred polycyclic cycloalkyl groups are bridged alicyclic hydrocarbon groups such as norbornyl, adamantyl, tricyclodecyl, and tetracyclododecyl groups. Note that a bridged alicyclic hydrocarbon group refers to a polycyclic alicyclic hydrocarbon group in which two non-adjacent carbon atoms constituting the alicyclic ring are linked by a linking group containing one or more carbon atoms.

[0083] The above R ８ Examples of the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms represented by the formula (I) include aryl groups such as a phenyl group, a tolyl group, a xylyl group, a naphthyl group, and an anthryl group; and aralkyl groups such as a benzyl group, a phenethyl group, and a naphthylmethyl group.

[0084] The above R ８ As the alkyl group, a linear or branched saturated hydrocarbon group having 1 to 10 carbon atoms, an alicyclic hydrocarbon group having 3 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 10 carbon atoms is preferred.

[0085] The above R ９ and R １０ The divalent alicyclic group having 3 to 20 carbon atoms formed by combining these together with the carbon atoms to which they are bonded is not particularly limited as long as it is a group formed by removing two hydrogen atoms from the same carbon atom constituting a carbon ring of a monocyclic or polycyclic alicyclic hydrocarbon having the above carbon number. Either a monocyclic hydrocarbon group or a polycyclic hydrocarbon group may be used, and the polycyclic hydrocarbon group may be either a bridged alicyclic hydrocarbon group or a fused alicyclic hydrocarbon group, and may be either a saturated hydrocarbon group or an unsaturated hydrocarbon group. Note that a fused alicyclic hydrocarbon group refers to a polycyclic alicyclic hydrocarbon group formed in such a way that multiple alicyclic rings share a side (a bond between two adjacent carbon atoms).

[0086] Among the monocyclic alicyclic hydrocarbon groups, preferred saturated hydrocarbon groups include cyclopentanediyl, cyclohexanediyl, cycloheptanediyl, and cyclooctanediyl groups, and preferred unsaturated hydrocarbon groups include cyclopentenediyl, cyclohexenediyl, cycloheptenediyl, cyclooctenediyl, and cyclodecenediyl groups. Preferred polycyclic alicyclic hydrocarbon groups are bridged alicyclic saturated hydrocarbon groups, such as bicyclo[2.2.1]heptane-2,2-diyl (norbornane-2,2-diyl), bicyclo[2.2.2]octane-2,2-diyl, and tricyclo[3.3.1.1]heptane-2,2-diyl. ３，７ ] Decane-2,2-diyl group (adamantane-2,2-diyl group) and the like are preferred.

[0087] The phenylene group represented by Ar may be any of a 1,4-phenylene group, a 1,3-phenylene group, and a 1,2-phenylene group.

[0088] The above L １ Examples of the divalent linking group represented by the formula (I) include an alkanediyl group, a cycloalkanediyl group, an alkenediyl group, * -R ＬＡ O-, * -R ＬＢ COO- (* indicates a bond to an oxygen atom). * -R ＬＢ In the case of a group other than COO—, the carbon atom bonded to the oxygen atom of —COO— in the above formula (3) is a tertiary carbon and does not have a hydrogen atom.

[0089] R ８ ~R １０ and L １ Some or all of the hydrogen atoms on the carbon atoms in the alkyl group may be substituted with a halogen atom such as a fluorine atom, a chlorine atom, or an iodine atom, a halogenated alkyl group such as a trifluoromethyl group, an alkoxy group such as a methoxy group, a cyano group, or the like.

[0090] Examples of the alkanediyl group include methanediyl group, 1,1-ethanediyl group, 1,2-ethanediyl group, 1,1-propanediyl group, 1,2-propanediyl group, 1,3-propanediyl group, 1,4-butanediyl group, 1,5-pentanediyl group, 1,6-hexanediyl group, 1,7-heptanediyl group, 1,8-octanediyl group, 1,9-nonanediyl group, 1,10-decanediyl group, etc. The alkanediyl group is preferably an alkanediyl group having 1 to 8 carbon atoms.

[0091] Examples of the cycloalkanediyl group include monocyclic cycloalkanediyl groups such as cyclopentanediyl and cyclohexanediyl groups, and polycyclic cycloalkanediyl groups such as norbornanediyl and adamantanediyl groups. The cycloalkanediyl group is preferably a cycloalkanediyl group having 5 to 12 carbon atoms.

[0092] Examples of the alkenediyl group include an ethenediyl group, a propenediyl group, a butenediyl group, etc. The alkenediyl group is preferably an alkenediyl group having 2 to 6 carbon atoms.

[0093] the above * -R ＬＡ O-R ＬＡ Examples of the alkyl group include the above-mentioned alkanediyl group, the above-mentioned cycloalkanediyl group, and the above-mentioned alkenediyl group. * -R ＬＢ COO-R ＬＢ Examples of the arenediyl group include the above-mentioned alkanediyl group, cycloalkanediyl group, alkenediyl group, and arenediyl group. Examples of the arenediyl group include a phenylene group, a tolylene group, and a naphthylene group. The arenediyl group is preferably an arenediyl group having 6 to 15 carbon atoms.

[0094] Among these, R ８ is an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 10 carbon atoms, and R ９ and R １０ The alicyclic structure formed by combining these together with the carbon atoms to which they are bonded is preferably a polycyclic or monocyclic cycloalkane structure.１ is a single bond or * -R ＬＡ It is preferably O-. ＬＡ is preferably an alkanediyl group.

[0095] Examples of the structural unit (1-1) include structural units represented by the following formulas (3-1) to (3-8) (hereinafter also referred to as "structural units (1-1-1) to (1-1-8)").

[0096]

[0097] In the above formulas (3-1) to (3-8), R ７ ~R １０ , R ＬＡ and Ar have the same meaning as in formula (3). ＬＭ and R ＬＮ are each independently a monovalent hydrocarbon group having 1 to 10 carbon atoms. i and j are each independently an integer of 1 to 4. n Ａ , n Ｂ , n Ｃ are each independently 0 or 1.

[0098] R ＬＭ and R ＬＮ As the R in the above formula (3), ８ Examples include groups having 1 to 10 carbon atoms among monovalent hydrocarbon groups having 1 to 20 carbon atoms represented by the following formula: ＬＭ and R ＬＮ is preferably a methyl group, an ethyl group or an isopropyl group.

[0099] i and j are preferably 1, 2 or 4. ８ ~R １０ is preferably a methyl group, an ethyl group, an isopropyl group, a phenyl group or an iodophenyl group.

[0100] The base resin may contain one or more types of structural unit (I) in combination.

[0101] Furthermore, the resin may contain, as the structural unit (I), structural units represented by the following formulae (1f) to (2f) in addition to or instead of the structural unit (1-1).

[0102]

[0103] In the above formulas (1f) to (2f), R αｆ R are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. βｆ are each independently a hydrogen atom or a chain alkyl group having 1 to 5 carbon atoms. Ar has the same meaning as in formula (3) above. １ are each independently an integer of 1 to 4.

[0104] The above R βｆ is preferably a hydrogen atom, a methyl group, or an ethyl group. １ As the number, 1 or 2 is preferred.

[0105] The lower limit of the content of the structural unit (I) relative to all structural units constituting the base resin is preferably 20 mol%, more preferably 30 mol%, even more preferably 40 mol%, and particularly preferably 50 mol%. The upper limit of the content 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 pattern formability of the radiation-sensitive resin composition can be further improved.

[0106] (Structural Unit (II)) The structural unit (II) is a structural unit having a phenolic hydroxyl group (excluding the structural unit (I)). In the present invention, the phenolic hydroxyl group of the structural unit (II) also includes a phenolic hydroxyl group produced by deprotection due to the action of an acid generated by exposure. When the resin contains the structural unit (II), the solubility in a developer can be more appropriately adjusted, thereby further improving the sensitivity of the radiation-sensitive resin composition. Furthermore, when KrF excimer laser light, EUV, electron beam, or the like is used as the radiation irradiated in the exposure step of the resist pattern formation method, the structural unit (II) contributes to improving the etching resistance and the difference in developer solubility (dissolution contrast) between exposed and unexposed areas. In particular, the structural unit (II) is suitable for pattern formation using exposure to radiation having a wavelength of 50 nm or less, such as electron beam or EUV. The structural unit (II) is preferably represented by the following formula (2):

[0107] (In the above formula (2), R α is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ＣＡ represents a single bond, -COO- ＊ or -O-. * is a bond on the aromatic ring side. R １０１ is a hydrogen atom or a protecting group that is deprotected by the action of an acid. １０１ If there are multiple R １０１ are the same or different. １０２ R is a cyano group, a nitro group, an alkyl group, a fluorinated alkyl group, an alkoxycarbonyloxy group, an acyl group, or an acyloxy group. １０２ If there are multiple R １０２ are the same or different. ３ is an integer from 0 to 2, and m ３ is an integer from 1 to 8, and m ４ is an integer from 0 to 8, provided that 1≦m ３ +m ４ ≦2n ３ Meets +5.)

[0108] The above R α From the viewpoint of copolymerizability of the monomer that gives the structural unit (II), the substituent is preferably a hydrogen atom or a methyl group.

[0109] L ＣＡ is a single bond or —COO— ＊ is preferred.

[0110] The above R １０１ Examples of the protecting group that can be deprotected by the action of an acid represented by the formula (AL-1) include groups represented by the following formulas (AL-1) to (AL-3).

[0111] In the above formulas (AL-1) and (AL-2), R Ｍ１ and R Ｍ２is a monovalent hydrocarbon group, which may contain a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom, or a fluorine atom. The monovalent hydrocarbon group may be linear, branched, or cyclic, and is preferably an alkyl group having 1 to 40 carbon atoms, more preferably an alkyl group having 1 to 20 carbon atoms. In formula (AL-1), a is an integer of 0 to 10, and preferably an integer of 1 to 5. In the above formulas (AL-1) to (AL-3), * represents a bond to another moiety.

[0112] In the above formula (AL-2), R Ｍ３ and R Ｍ４ are each independently a hydrogen atom or a monovalent hydrocarbon group, which may contain a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom, or a fluorine atom. The monovalent hydrocarbon group may be linear, branched, or cyclic, and is preferably an alkyl group having 1 to 20 carbon atoms. Ｍ２ , R Ｍ３ and R Ｍ４ Any two of the above may be bonded to each other to form a ring having 3 to 20 carbon atoms together with the carbon atom or the carbon atom and oxygen atom to which they are bonded. As the ring, a ring having 4 to 16 carbon atoms is preferred, and an alicyclic ring is particularly preferred.

[0113] In the above formula (AL-3), R Ｍ５ , R Ｍ６ and R Ｍ７ are each independently a monovalent hydrocarbon group, which may contain a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom, or a fluorine atom. The monovalent hydrocarbon group may be linear, branched, or cyclic, and is preferably an alkyl group having 1 to 20 carbon atoms. Ｍ５ , R Ｍ６ and R Ｍ７ Any two of the above may be bonded to each other together with the carbon atoms to which they are bonded to form a ring having 3 to 20 carbon atoms. As the ring, a ring having 4 to 16 carbon atoms is preferred, and an alicyclic ring is particularly preferred.

[0114] Among these, the group represented by the above formula (AL-3) is preferred as a protecting group that can be deprotected by the action of an acid.

[0115] R １０２Examples of the alkyl group in the formula (I) include linear or branched alkyl groups having 1 to 8 carbon atoms, such as methyl, ethyl, and propyl. Examples of the fluorinated alkyl group include linear or branched fluorinated alkyl groups having 1 to 8 carbon atoms, such as trifluoromethyl and pentafluoroethyl. Examples of the alkoxycarbonyloxy group include linear or alicyclic alkoxycarbonyloxy groups having 2 to 16 carbon atoms, such as methoxycarbonyloxy, butoxycarbonyloxy, and adamantylmethyloxycarbonyloxy. Examples of the acyl group include aliphatic or aromatic acyl groups having 2 to 12 carbon atoms, such as acetyl, propionyl, benzoyl, and acryloyl. Examples of the acyloxy group include aliphatic or aromatic acyloxy groups having 2 to 12 carbon atoms, such as acetyloxy, propionyloxy, benzoyloxy, and acryloyloxy.

[0116] The above n ３ is more preferably 0 or 1, and even more preferably 0.

[0117] The above m ３ is preferably an integer of 1 to 3, more preferably 1 or 2.

[0118] The above m ４ is preferably an integer of 0 to 3, and more preferably an integer of 0 to 2.

[0119] The structural unit (II) is preferably a structural unit represented by the following formulas (2-1) to (2-11) (hereinafter also referred to as "structural unit (2-1) to structural unit (2-11)"), or the like.

[0120]

[0121] In the above formulas (2-1) to (2-11), R α is the same as the above formula (2).

[0122] Among these, the above structural units (2-1) to (2-4), (2-6), (2-8), (2-9) and (2-11) are preferred.

[0123] The lower limit of the content of the structural unit (II) (total content when multiple types of structural unit (II) are present) relative to all structural units constituting the base resin is preferably 10 mol%, more preferably 15 mol%, even more preferably 20 mol%, and particularly preferably 25 mol%. The upper limit of the content is preferably 60 mol%, more preferably 55 mol%, even more preferably 50 mol%, and particularly preferably 45 mol%. By setting the content of the structural unit (II) within the above range, the radiation-sensitive resin composition can achieve further improvements in sensitivity, LWR performance, and resolution.

[0124] When a monomer having a phenolic hydroxyl group such as hydroxystyrene is polymerized, it is preferred that the polymerization be carried out in a state in which the phenolic hydroxyl group is protected with a protecting group such as an alkali-dissociable group, and then the structural unit (II) is obtained by deprotecting the phenolic hydroxyl group by hydrolysis.

[0125] (Structural Unit (III)) The structural unit (III) is a structural unit (excluding structures corresponding to the structural units (I) to (II)) having a heteroatom-containing substituent such as a fluorine atom, an alcoholic hydroxyl group, a carboxy group, a cyano group, a nitro group, or a sulfonamide group. Among these, a structural unit having a fluorine atom, a structural unit having an alcoholic hydroxyl group, and a structural unit having a carboxy group are preferred, and a structural unit having a fluorine atom and a structural unit having an alcoholic hydroxyl group are more preferred.

[0126] Examples of the structural unit (III) include structural units represented by the following formula:

[0127]

[0128] In the above formula, R Ａ is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.

[0129] When the resin contains the structural unit (III), the lower limit of the content of the structural unit (III) is preferably 3 mol%, more preferably 5 mol%, and even more preferably 8 mol% relative to the total structural units constituting the base resin.The upper limit of the content is preferably 20 mol%, more preferably 15 mol%, and even more preferably 12 mol%.By making the content of the structural unit (III) within the above range, the solubility of the resin in the developer can be more appropriate.

[0130] (Structural Unit (IV)) The structural unit (IV) is a structural unit containing at least one selected from the group consisting of a lactone structure, a cyclic carbonate structure, and a sultone structure. By further including the structural unit (IV), the base resin can adjust its solubility in a developer, and as a result, the radiation-sensitive resin composition can improve lithography performance such as resolution. In addition, the adhesion between a resist pattern formed from the base resin and a substrate can be improved.

[0131] (Method of Synthesizing Resin) The base resin can be synthesized, for example, by polymerizing monomers that provide each structural unit in an appropriate solvent using a known radical polymerization initiator or the like.

[0132] The molecular weight of the base resin is not particularly limited, but the lower limit of the weight average molecular weight (Mw) in terms of polystyrene measured by gel permeation chromatography (GPC) is preferably 1,000, more preferably 2,000, even more preferably 3,000, and particularly preferably 4,000. The upper limit of the Mw is preferably 30,000, more preferably 20,000, even more preferably 10,000, and particularly preferably 8,000. When the Mw of the resin is within the above range, the heat resistance and developability of the resulting resist film are good.

[0133] The ratio (Mw / Mn) of Mw to the polystyrene-equivalent number average molecular weight (Mn) of the base resin as determined by GPC is usually 1 or more and 5 or less, preferably 1 or more and 3 or less, and more preferably 1 or more and 2 or less.

[0134] The method for measuring Mw and Mn of the resin in this specification is as described in the Examples.

[0135] The content of the resin is preferably 70% by mass or more, more preferably 75% by mass or more, and even more preferably 80% by mass or more, based on the total solid content of the radiation-sensitive resin composition.

[0136] (Structural Unit (V)) The resin may further contain a structural unit having an organic acid anion moiety and an onium cation moiety as the structural unit (V). When the resin contains the structural unit (V), the resin can function as an acid generator. In this case, the composition may or may not contain a radiation-sensitive acid generator. The structural unit (V) is preferably represented by the following formula (a1) or (a2):

[0137]

[0138] In the formula, R Ａ is a hydrogen atom or a methyl group. １ is a single bond or an ester group. ２ is a linear, branched or cyclic alkylene group having 1 to 12 carbon atoms or an arylene group having 6 to 10 carbon atoms, and a part of the methylene groups constituting the alkylene group may be substituted with an ether group, an ester group or a lactone ring-containing group; and X ２ At least one hydrogen atom contained in X may be substituted with an iodine atom. ３ Rf is a single bond, an ether group, an ester group, or a linear, branched, or cyclic alkylene group having 1 to 12 carbon atoms, and some of the methylene groups constituting the alkylene group may be substituted with an ether group or an ester group. １ ~Rf ４ are each independently a hydrogen atom, a fluorine atom, or a trifluoromethyl group, provided that at least one is a fluorine atom or a fluorinated hydrocarbon group. ４３ ~R ４７ are each independently a monovalent hydrocarbon group having 1 to 20 carbon atoms which may contain a heteroatom, and R ４３ and R ４４ may be bonded to each other to form a ring together with the sulfur atom to which they are attached.

[0139] R ４３ ~R４７ In the formula (I), the monovalent hydrocarbon group having 1 to 20 carbon atoms which may contain a hetero atom is preferably an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or an aryl group having 6 to 20 carbon atoms, and some or all of the hydrogen atoms in these groups may be substituted with hydroxy groups, carboxy groups, halogen atoms, oxo groups, cyano groups, amide groups, nitro groups, sultone groups, sulfone groups, or sulfonium salt-containing groups, and some of the methylene groups constituting these groups may be substituted with ether groups, ester groups, carbonyl groups, carbonate groups, or sulfonate ester groups.

[0140] The above formulas (a1) and (a2) are preferably represented by the following formulas (a1-1) and (a2-1), respectively.

[0141]

[0142] In the formula, R Ａ , R ４３ ~R ４７ , Rf １ ~Rf ４ and X １ has the same meaning as in formula (a1) or (a2). ４８ is a linear, branched, or cyclic alkyl group having 1 to 4 carbon atoms, a halogen atom other than iodine, a hydroxy group, a linear, branched, or cyclic alkoxy group having 1 to 4 carbon atoms, or a linear, branched, or cyclic alkoxycarbonyl group having 2 to 5 carbon atoms. m is an integer of 0 to 4. n is an integer of 0 to 3.

[0143] Examples of the organic acid anion moiety of the monomer that provides the structural unit (V) include, but are not limited to, those shown below. Note that all of the organic acid anion moieties shown below have an iodine-substituted aromatic ring structure, but as an organic acid anion moiety that does not have an iodine-substituted aromatic ring structure, a structure in which the iodine atom in the following formula is substituted with an atom or group other than an iodine atom, such as a hydrogen atom or another substituent, can be suitably used.

[0144]

[0145]

[0146]

[0147]

[0148]

[0149]

[0150]

[0151] The onium cation moiety in the structural unit (V) can be suitably the onium cation moiety of the radiation-sensitive acid generator and acid diffusion controller described above.

[0152] When the resin contains the structural unit (V), the lower limit of the content of the structural unit (V) (the total content when multiple types are contained) is preferably 5 mol%, more preferably 10 mol%, and even more preferably 12 mol% of all structural units constituting the base resin. The upper limit of the content is preferably 30 mol%, more preferably 25 mol%, and even more preferably 20 mol%. By keeping the content of the structural unit (V) within the above range, the resin can fully exhibit its function as an acid generator.

[0153] The monomer that provides the structural unit (V) can be synthesized, for example, by a method similar to that for the sulfonium salt having a polymerizable anion described in Japanese Patent No. 5201363.

[0154] <Other Resins> The radiation-sensitive resin composition of the present embodiment may contain, as another resin, a resin having a higher mass content of fluorine atoms than the base resin (hereinafter also referred to as a "high-fluorine-content resin"). When the radiation-sensitive resin composition contains a high-fluorine-content resin, the high-fluorine-content resin can be unevenly distributed in the surface layer of the resist film relative to the base resin, and as a result, the state of the surface of the resist film and the component distribution in the resist film can be controlled to a desired state.

[0155] (Method of synthesizing high-fluorine-content resin) The high-fluorine-content resin can be synthesized by the same method as the above-mentioned method of synthesizing the base resin.

[0156] <Solvent> The radiation-sensitive resin composition according to this embodiment may further contain a solvent, as desired. The solvent is not particularly limited as long as it can dissolve or disperse at least the onium salt, the base resin, and the compound represented by formula (H), as well as any additives that may be added as needed.

[0157] The solvents do not include those corresponding to the above-mentioned "compounds represented by the above formula (H)."

[0158] Examples of the solvent include alcohol-based solvents, ether-based solvents, ketone-based solvents, amide-based solvents, ester-based solvents, and hydrocarbon-based solvents.

[0159] Examples of alcohol-based solvents include monoalcohol-based solvents having 1 to 18 carbon atoms, such as iso-propanol, 4-methyl-2-pentanol, 3-methoxybutanol, n-hexanol, 2-ethylhexanol, furfuryl alcohol, cyclohexanol, 3,3,5-trimethylcyclohexanol, and diacetone alcohol; polyhydric alcohol-based solvents having 2 to 18 carbon atoms, such as ethylene glycol, 1,2-propylene glycol, 2-methyl-2,4-pentanediol, 2,5-hexanediol, diethylene glycol, dipropylene glycol, triethylene glycol, and tripropylene glycol; and polyhydric alcohol partial ether-based solvents in which some of the hydroxy groups in the above-mentioned polyhydric alcohol-based solvents have been etherified.

[0160] Examples of ether-based solvents include dialkyl ether-based solvents such as diethyl ether, dipropyl ether, and dibutyl ether; cyclic ether-based solvents such as tetrahydrofuran and tetrahydropyran; aromatic ring-containing ether-based solvents such as diphenyl ether and anisole (methyl phenyl ether); and polyhydric alcohol ether-based solvents obtained by etherifying the hydroxy groups of the above-mentioned polyhydric alcohol-based solvents.

[0161] Examples of the ketone solvent include chain ketone solvents such as acetone, butanone, and methyl-iso-butyl ketone; cyclic ketone solvents such as cyclopentanone, cyclohexanone, and methylcyclohexanone; and 2,4-pentanedione, acetonylacetone, and acetophenone.

[0162] Examples of the amide solvent include cyclic amide solvents such as N,N'-dimethylimidazolidinone and N-methylpyrrolidone; and chain amide solvents such as N-methylformamide, N,N-dimethylformamide, N,N-diethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, and N-methylpropionamide.

[0163] Examples of ester-based solvents include monocarboxylic acid ester-based solvents such as n-butyl acetate and ethyl lactate; polyhydric alcohol partial ether acetate-based solvents such as diethylene glycol mono-n-butyl ether acetate, propylene glycol monomethyl ether acetate and dipropylene glycol monomethyl ether acetate; lactone-based solvents such as γ-butyrolactone and valerolactone; carbonate-based solvents such as diethyl carbonate, ethylene carbonate and propylene carbonate; and polyvalent carboxylic acid diester-based solvents such as propylene glycol diacetate, methoxytriglycol acetate, diethyl oxalate, ethyl acetoacetate, ethyl lactate and diethyl phthalate.

[0164] Examples of hydrocarbon solvents include aliphatic hydrocarbon solvents such as n-hexane, cyclohexane, and methylcyclohexane; and aromatic hydrocarbon solvents such as benzene, toluene, di-isopropylbenzene, and n-amylnaphthalene.

[0165] Among these, ether-based solvents and ester-based solvents are preferred, polyhydric alcohol partial ether-based solvents and polyhydric alcohol partial ether acetate-based solvents are more preferred, and propylene glycol monomethyl ether and propylene glycol monomethyl ether acetate are even more preferred. The radiation-sensitive resin composition may contain one or more solvents.

[0166] <Other Optional Components> The radiation-sensitive resin composition may contain other optional components in addition to the components described above. Examples of the other optional components include a crosslinking agent, a localization promoter, a surfactant, an alicyclic skeleton-containing compound, and a sensitizer. These other optional components may be used alone or in combination of two or more.

[0167] <Method for Preparing Radiation-Sensitive Resin Composition> The radiation-sensitive resin composition can be prepared, for example, by mixing an onium salt, a base resin, and a compound represented by formula (H) above, and, if necessary, other optional components, in a predetermined ratio. After mixing, the radiation-sensitive resin composition is preferably filtered, for example, through a filter having a pore size of about 0.05 μm to 0.4 μm. The solids concentration of the radiation-sensitive resin composition is usually 0.1% to 50% by mass, preferably 0.5% to 30% by mass, and more preferably 1% to 20% by mass.

[0168] <<Pattern Forming Method>> The pattern forming method of the present embodiment includes: a step (1) of applying the radiation-sensitive resin composition directly or indirectly to a substrate to form a resist film (hereinafter also referred to as a "resist film forming step"); a step (2) of exposing the resist film to light (hereinafter also referred to as an "exposure step"); and a step (3) of developing the exposed resist film (hereinafter also referred to as a "development step").

[0169] According to the pattern forming method, a high-quality resist pattern can be formed because the radiation-sensitive resin composition has excellent sensitivity and LWR performance in the exposure step. Each step will be described below.

[0170] [Resist Film Forming Step] In this step (step (1) above), a resist film is formed from the radiation-sensitive resin composition. Examples of substrates on which the resist film is formed include conventionally known substrates such as silicon wafers, silicon dioxide wafers, and aluminum-coated wafers. Alternatively, an organic or inorganic anti-reflective coating, such as those disclosed in JP-B-6-12452 and JP-A-59-93448, may be formed on the substrate. Examples of coating methods include spin coating, casting coating, and roll coating. After coating, pre-baking (PB) may be performed, if necessary, to volatilize the solvent in the coating film. The PB temperature is typically 60°C to 150°C, and preferably 80°C to 140°C. The PB time is typically 5 seconds to 600 seconds, and preferably 10 seconds to 300 seconds. The thickness of the resist film formed is preferably 10 nm to 1,000 nm, and more preferably 10 nm to 500 nm.

[0171] When the subsequent exposure step is carried out using radiation with a wavelength of 50 nm or less, it is preferable to use a resin having the structural unit (I) and the structural unit (II), and optionally the structural unit (III), as the base resin in the composition.

[0172] [Exposure Step] In this step (step (2) above), the resist film formed in the resist film formation step (1) above is exposed to radiation through a photomask (or, in some cases, through an immersion medium such as water). Examples of radiation used for exposure include electromagnetic waves such as visible light, ultraviolet light, far ultraviolet light, EUV (extreme ultraviolet), X-rays, and gamma rays; and charged particle beams such as electron beams and alpha rays, depending on the line width of the desired pattern. Among these, far ultraviolet light, electron beams, and EUV are preferred, with ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), electron beams, and EUV being more preferred, and electron beams and EUV with wavelengths of 50 nm or less, which are positioned as next-generation exposure technologies, being even more preferred.

[0173] After the exposure, post-exposure baking (PEB) is preferably performed to promote dissociation of acid-dissociable groups in the resin or the like in the exposed portions of the resist film by the acid generated from the radiation-sensitive acid generator upon exposure. This PEB results in a difference in solubility in a developer between the exposed and unexposed portions. The PEB temperature is typically 50°C to 180°C, preferably 80°C to 130°C. The PEB time is typically 5 seconds to 600 seconds, preferably 10 seconds to 300 seconds.

[0174] [Development Step] In this step (step (3) above), the resist film exposed in the exposure step (step (2) above) is developed. This allows a predetermined resist pattern to be formed. After development, the resist film is generally washed with a rinse liquid such as water or alcohol, and then dried.

[0175] In the case of alkaline development, examples of the developer used in the development include an alkaline aqueous solution containing at least one alkaline compound dissolved therein, such as 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 (TMAH), pyrrole, piperidine, choline, 1,8-diazabicyclo-[5.4.0]-7-undecene, and 1,5-diazabicyclo-[4.3.0]-5-nonene. Among these, an aqueous TMAH solution is preferred, and a 2.38% by mass aqueous TMAH solution is more preferred.

[0176] In the case of organic solvent development, examples of the organic solvent include hydrocarbon solvents, ether solvents, ester solvents, ketone solvents, and alcohol solvents, as well as solvents containing an organic solvent. Examples of the organic solvent include one or more of the solvents listed above as solvents for the radiation-sensitive resin composition. Among these, ester solvents and ketone solvents are preferred. As the ester solvent, acetate ester solvents are preferred, with n-butyl acetate and amyl acetate being more preferred. As the ketone solvent, a chain ketone is preferred, with 2-heptanone being more preferred. The content of the organic solvent in the developer is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 99% by mass or more. Examples of components other than the organic solvent in the developer include water and silicone oil.

[0177] Examples of the developing method include a method of immersing a substrate in a tank filled with a developer for a certain period of time (dip method), a method of piling up a developer on the surface of the substrate by surface tension and leaving it to stand for a certain period of time to develop (puddle method), a method of spraying the developer onto the surface of the substrate (spray method), and a method of continuously discharging the developer while scanning a developer discharging nozzle at a constant speed onto a substrate that is rotating at a constant speed (dynamic dispense method).

[0178] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Physical properties in the examples were measured as follows.

[0179] [Weight-average molecular weight (Mw) and number-average molecular weight (Mn)] Measurements were performed by gel permeation chromatography (GPC) using Tosoh GPC columns (2 G2000HXL, 1 G3000HXL, 1 G4000HXL) under the following analytical conditions: flow rate: 1.0 mL / min, elution solvent: tetrahydrofuran, sample concentration: 1.0 mass%, sample injection volume: 100 μL, column temperature: 40 ° C., detector: differential refractometer, using monodisperse polystyrene as the standard. The dispersity (Mw / Mn) was calculated from the measurement results of Mw and Mn.

[0180] <[A] Synthesis of Polymer> The monomers used in the synthesis of each polymer in each example and comparative example are shown below.

[0181]

[0182] [Synthesis Example] Synthesis of Polymer (A-1) Compound (M-1) and compound (M-4) were dissolved in 1-methoxy-2-propanol (200 parts by mass relative to the total amount of monomers) so that the molar ratio was 40 / 60. Next, azobisisobutyronitrile was added as an initiator in an amount of 6 mol % relative to the total amount of monomers to prepare a monomer solution. Meanwhile, 1-methoxy-2-propanol (100 parts by mass relative to the total amount of monomers) was added to an empty reaction vessel and 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 an additional 3 hours. After completion of the polymerization reaction, the polymerization solution was cooled to room temperature.

[0183] The cooled polymerization solution was poured into hexane (500 parts by mass relative to the polymerization solution), and the precipitated white powder was filtered off. The filtered white powder was washed twice with hexane (100 parts by mass relative to the polymerization solution) and then dissolved in 1-methoxy-2-propanol (300 parts by mass). Next, 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.

[0184] After the reaction was completed, the remaining solvent was distilled off, and the resulting solid was dissolved in acetone (100 parts by mass). This solution was added dropwise to 500 parts by mass of water to coagulate the resin, and the resulting solid was filtered off. The resulting mixture was dried at 50°C for 12 hours to obtain a white powdery polymer (A-1).

[0185] Synthesis Examples 2 to 12 and 14 Polymers (A-2) to (A-12) and (A-14) were synthesized in the same manner as in Synthesis Example 1 above, except that the monomer types and ratios were changed as shown in Table 1.

[0186] Synthesis Example 13 4-Hydroxystyrene, (M-4), and compound (M-3) were dissolved in 1-methoxy-2-propanol (200 parts by mass relative to the total amount of monomers) so that the molar ratio was 30 / 60 / 10. Next, azobisisobutyronitrile was added as an initiator in an amount of 6 mol % relative to the total amount of monomers to prepare a monomer solution. Meanwhile, 1-methoxy-2-propanol (100 parts by mass relative to the total amount of monomers) was added to an empty reaction vessel and heated to 85°C with stirring. Next, the monomer solution prepared above was added dropwise over 3 hours, and then the mixture was heated at 85°C for an additional 3 hours. After completion of the polymerization reaction, the polymerization solution was cooled to room temperature.

[0187] The cooled polymerization solution was poured into hexane (500 parts by mass relative to the polymerization solution), and the precipitated white powder was filtered off. The filtered white powder was washed twice with hexane (100 parts by mass relative to the polymerization solution), and then dried at 50°C for 12 hours to obtain a white powdery polymer (A-11).

[0188] Synthesis Examples 15 and 16 Polymers (A-15) and (A-16) were also synthesized in the same manner as in Synthesis Example 13 above, except that the monomer types and ratios were changed as shown in Table 1.

[0189]

[0190] <[B] Radiation-Sensitive Acid Generator> The compounds represented by the following (B-1) to (B-11) were used as the radiation-sensitive acid generator.

[0191]

[0192] <[C] Acid Diffusion Controller> Compounds represented by the following (C-1) to (C-7) were used as acid diffusion controllers.

[0193]

[0194] Example 1 100 parts by mass of [A] polymer (A-1), 20 parts by mass of [B] radiation-sensitive acid generator (B-1), [C] acid diffusion controller (C-1) in an amount of 20 mol% relative to (B-1), 2,000 parts by mass of [E] organic solvent (E-1), and 4,800 parts by mass of [D] organic solvent (D-1) were blended and mixed, and then filtered through a filter having a pore size of 0.20 μm to prepare a radiation-sensitive resin composition (R-1).

[0195] [Examples 2 to 34 and Comparative Examples 1 to 6] Radiation-sensitive resin compositions (R-2) to (R-34) and (CR-1) to (CR-6) were prepared in the same manner as in Example 1, except that the types and amounts of each component shown in Table 2 below were used. Then, the sensitivity, LWR performance, and storage stability were evaluated in the same manner as in Example 1. The results are shown in Table 3.

[0196]

[0197] <[D] Organic Solvent and [E] Organic Solvent> D-1: Methyl 2-hydroxyisobutyrate D-2: Ethyl 2-hydroxyisobutyrate D-3: Isopropyl 2-hydroxyisobutyrate D-4: Methyl 2-hydroxy 2-methylbutyrate E-1: Propylene glycol monomethyl ether acetate E-2: Propylene glycol 1-monomethyl ether E-3: Ethyl lactate E-4: Ethyl 3-ethoxypropionate

[0198]

[0199] <Formation of Resist Pattern (EUV Exposure, Alkali Development)> The radiation-sensitive resin composition prepared above was applied to the surface of a 12-inch silicon wafer on which a 50-nm-thick underlayer film (AL412 (Brewer Science)) had been formed, using a spin coater (CLEAN TRACK ACT12, Tokyo Electron). After SB at 130°C for 60 seconds, the wafer was cooled at 23°C for 30 seconds to form a 50-nm-thick resist film. Next, this resist film was irradiated with EUV light using an EUV exposure machine (model "NXE3300," ASML, NA = 0.33, illumination conditions: Conventional s = 0.89, mask imecDEFECT32FFR02). The resist film was subjected to PEB at 110°C for 60 seconds. Then, the resist was developed using a 2.38 wt % aqueous solution of TMAH at 23° C. for 30 seconds to form a positive 32 nm line and space pattern.

[0200] <Formation of Resist Pattern (KrF Exposure, Alkali Development)> The radiation-sensitive resin composition prepared above was applied to the surface of a 12-inch silicon wafer on which a 20-nm-thick underlayer film (DUV42 (Nissan Chemicals)) had been formed using a spin coater (CLEAN TRACK ACT12, Tokyo Electron). After SB at 130°C for 60 seconds, the wafer was cooled at 23°C for 30 seconds to form a 70-nm-thick resist film. Next, the resist film was irradiated with KrF light using a KrF exposure machine (model "S210D," Nikon, NA = 0.55, illumination conditions: Annular s = 0.8, mask 150 nm LS). The resist film was subjected to PEB at 110°C for 60 seconds. The wafer was then developed at 23°C for 30 seconds using a 2.38 wt% TMAH aqueous solution to form a positive 150-nm line-and-space pattern.

[0201] [Sensitivity] In the formation of an EUV resist pattern by EUV exposure, the exposure amount for forming a 32 nm line and space pattern is defined as the optimum exposure amount, and this optimum exposure amount is used as the sensitivity (mJ / cm ２ The sensitivity was 30 mJ / cm ２ Below "A" (good), 30 mJ / cm ２ Super 32mJ / cm ２The following cases are "B" (fairly good), 32 mJ / cm ２ If it exceeded this, it was judged as "C" (inferior).

[0202] [LWR Performance] A resist pattern formed by the above-described resist pattern formation method using EUV exposure was observed from above using a scanning electron microscope. Line widths were measured at 50 random locations, and the 3-sigma value was calculated from the distribution of the measured values, which was designated as the LWR (unit: nm). The smaller the LWR value, the smaller the line chatter and the better the LWR performance. LWR performance was evaluated as "A" (good) when the LWR was 4.0 nm or less, "B" (fairly good) when it was greater than 4.0 nm and less than 4.2 nm, and "C" (poor) when it was greater than 4.2 nm.

[0203] [Storage Stability] After preparing the radiation-sensitive resin composition, it was stored at -15°C for 2 weeks or at 35°C for 2 weeks. Thereafter, the sensitivity was determined according to the sensitivity evaluation method described above. Based on the sensitivity of the radiation-sensitive resin composition stored at 15°C for 2 weeks as the standard, if the sensitivity of the radiation-sensitive resin composition stored at 35°C for 2 weeks was increased by 1% or decreased by 1% or more, it was judged to be "poor". In all other cases, it was judged to be "good". The composition was stored at -15°C for 2 weeks or at 35°C for 2 weeks. Thereafter, the optimal exposure dose for forming a 150 nm line and space pattern was determined in the resist pattern formation by KrF exposure described above. Based on the optimal exposure dose of the radiation-sensitive resin composition stored at 15°C for two weeks, if the optimal exposure dose of the radiation-sensitive resin composition stored at 35°C for two weeks increased the sensitivity by 1.0% or more or decreased the sensitivity by 1.0% or more, it was evaluated as "C." If the optimal exposure dose increased the sensitivity by 0.7% or more but less than 1.0% or decreased the sensitivity by 0.7% or more but less than 1.0%, it was evaluated as "B." Otherwise, it was evaluated as "A."

[0204]

[0205] As is clear from the results in Table 3, the radiation-sensitive resin compositions of the Examples all had good sensitivity and LWR while ensuring storage stability compared to the radiation-sensitive resin compositions of the Comparative Examples.

[0206] The radiation-sensitive resin composition and method for forming a resist pattern of the present invention can improve sensitivity and LWR while ensuring storage stability, and therefore can be suitably used for forming fine resist patterns in lithography processes for various electronic devices such as semiconductor devices and liquid crystal devices.

Claims

1. a radiation-sensitive onium salt containing a fluorine atom in the cation moiety; A compound represented by the following formula (H): a resin including a structural unit having an acid-dissociable group; A radiation-sensitive resin composition comprising: 【Chemistry 1】 (In the above formula (H), R １ ~R ３ are each independently a substituted or unsubstituted aliphatic hydrocarbon group having 1 to 20 carbon atoms.

2. 2. The radiation-sensitive resin composition according to claim 1, wherein the radiation-sensitive onium salt is represented by the following formula (1): 【Chemistry 2】 (In the above formula (1), R ｃ１ ~R ｃ３ are each independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, ｃ１ ~R ｃ３ At least one of contains a fluorine atom or a trifluoromethyl group. Y ｃ － is a monovalent anion.)

3. R ｃ１ ~R ｃ３ and each independently represent a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms.

4. The radiation-sensitive resin composition according to claim 1 , wherein the radiation-sensitive onium salt contains an iodine atom.

5. (delete)

6. (delete)

7. In the compound represented by the above formula (H), R １ ~R ３ and each independently represent a substituted or unsubstituted aliphatic hydrocarbon group having 1 to 5 carbon atoms.

8. 2. The radiation-sensitive resin composition according to claim 1, wherein the resin comprises a structural unit having a phenolic hydroxyl group.

9. The radiation-sensitive resin composition according to claim 1 , further comprising an acid diffusion controller.

10. The radiation-sensitive resin composition according to claim 9 , wherein the acid diffusion controller is a carboxylic acid-containing acid diffusion controller.

11. a step of directly or indirectly applying the radiation-sensitive resin composition according to any one of claims 1 to 4 and 7 to 10 onto a substrate to form a resist film; exposing the resist film to light; developing the exposed resist film with a developer; A pattern forming method comprising:

12. The pattern forming method according to claim 11, wherein the exposure is carried out with extreme ultraviolet light or an electron beam.

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