Radiation-sensitive composition, pattern forming method, compound, and polymer

Abstract

The purpose of the present invention is to provide: a radiation-sensitive composition which is capable of exhibiting sensitivity, LWR, MEEF, development defect suppressing properties, and CDU at sufficient levels when a pattern is formed; a pattern forming method; a compound; and a polymer. This radiation-sensitive composition contains: a polymer (A) which comprises a structural unit (M) derived from a compound represented by formula (1); and a solvent (D). (In formula (1), R1 is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. L1 is a divalent linking group having 1-5 carbon atoms. R2 is a hydrogen atom or a monovalent organic group having 1-20 carbon atoms. R3 is a monovalent organic group containing an ester bond between carbons and having 3-20 carbon atoms.)

Description

Radiation-sensitive compositions, pattern-forming methods, compounds, and polymers

[0001] The present invention relates to radiation-sensitive compositions, pattern-forming methods, compounds, and polymers.

[0002] Photolithography, which uses resist compositions, is employed to form fine circuits in semiconductor devices. A typical procedure involves, for example, generating acid by irradiating a resist composition film with radiation through a mask pattern. This acid then acts as a catalyst, creating a difference in the solubility of the polymer in alkaline or organic developers between the exposed and unexposed areas, thereby forming a resist pattern on the substrate.

[0003] The above-mentioned photolithography techniques utilize short-wavelength radiation such as ArF excimer lasers, and further advance pattern miniaturization by employing liquid immersion lithography, a method in which exposure is performed with the space between the lens of the exposure apparatus and the resist film filled with a liquid medium. As next-generation technologies, lithography using even shorter-wavelength radiation such as electron beams, X-rays, and EUV (extreme ultraviolet) is also being considered.

[0004] Regarding the resin, which is the main component of the resist composition, various technologies have been proposed to improve sensitivity, resolution, and other aspects (Patent No. 5621431).

[0005] Patent No. 5621431

[0006] With the advancement of next-generation technologies, there is a growing demand for resist performance that is equivalent to or better than conventional levels in terms of sensitivity, LWR (Line Width Roughness), MEEF (Mask Error Enhancement Factor), development defect suppression, and CDU (Critical Dimension Uniformity).

[0007] The present invention aims to provide a radiation-sensitive composition, a pattern-forming method, a compound, and a polymer that can exhibit sufficient levels of sensitivity, LWR, MEEF, development defect suppression, and CDU during pattern formation.

[0008] The inventors of this invention conducted extensive research to solve this problem and, as a result, found that the above objective can be achieved by adopting the following configuration, thus completing the present invention.

[0009] In other words, the present invention relates in one embodiment to a radiation-sensitive composition containing a polymer (A) comprising a structural unit (M) derived from a compound represented by the following formula (1), and a solvent (D). (In formula (1), R １ L is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. １ R is a divalent linking group having 1 to 5 carbon atoms. ２ R is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. ３ (It is a monovalent organic group with 3 to 20 carbon atoms that contains an ester bond between carbon atoms.)

[0010] Because the radiation-sensitive composition contains polymer (A) and structural unit (M), it can exhibit excellent sensitivity, LWR, MEEF, development defect suppression, and CDU during pattern formation. The reason for this is presumed to be as follows, although it is not bound by any theory.

[0011] Because the structural unit (M) has an amide structure, the acid diffusion length is suppressed by the interaction between the amide structure and the acid generated from the radiation-sensitive acid generator. Also, the amide structure is L １ Because it exists via a divalent linking group (with 1 to 5 carbon atoms), the amide structure is located at an appropriate distance from the main chain of polymer (A). As a result, the interaction with the generated acid is increased, and the acid diffusion length can be suppressed to an appropriate length. In addition, the presence of the amide structure makes polymer (A) highly polar. As a result, the pattern formation properties of LWR, MEEF, CDU, etc. are improved. Furthermore, because the structural unit (M) has an ester bond, the solubility in the developer is improved, and development defects can be suppressed. It is presumed that the above-mentioned resist properties are exhibited through the combined action of these factors.

[0012] In another embodiment, the present invention relates to a patterning method including the steps of: applying the radiation-sensitive composition directly or indirectly onto a substrate to form a resist film; exposing the resist film; and developing the exposed resist film with a developer.

[0013] In this patterning method, since the radiation-sensitive composition excellent in sensitivity, LWR, MEEF, development defect suppression property, and CDU is used during pattern formation, a high-quality resist pattern can be efficiently formed.

[0014] In yet another embodiment, the present invention relates to a compound represented by the following formula (1-1). (In formula (1-1), １ R is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. L １ is a divalent linking group having 1 to 5 carbon atoms. R ２ is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. R ３１ is a monovalent organic group having 3 to 18 carbon atoms containing a lactone structure. However, the ester bond in the monovalent organic group exists between carbon-carbon atoms.)

[0015] Since the compound has the above specific structure, it is suitable for forming a polymer of a radiation-sensitive composition that requires excellent sensitivity, LWR, MEEF, development defect suppression property, and CDU during pattern formation.

[0016] In yet another embodiment, the present invention relates to a polymer containing a structural unit derived from the above compound.

[0017] Since the polymer has the above specific structure, it is suitable for forming a radiation-sensitive composition that requires excellent sensitivity, LWR, MEEF, development defect suppression property, and CDU during pattern formation.

[0018] As used herein, the term "organic group" refers to a group having at least one carbon atom (however, groups that alone constitute a functional group or characteristic group such as -CN, -COOH, -CO-, -COO-, -O-CO-O- are excluded).

[0019] The embodiments of the present invention will be described in detail below, but the present invention is not limited to these embodiments. A preferred combination of embodiments is also preferable.

[0020] <<Radiation-sensitive composition>> The radiation-sensitive composition according to this embodiment (hereinafter also simply referred to as "composition") contains a polymer (A) containing a structural unit (M) derived from the compound represented by formula (1) above, and a solvent (D). It may further contain a radiation-sensitive acid generator (B) or an acid diffusion control agent (C) as needed. The above composition may contain other optional components as long as they do not impair the effects of the present invention.

[0021] <Polymer (A)> Polymer (A) is an aggregate of polymer chains having structural units (M) derived from the compound represented by formula (1) above (hereinafter, this polymer will also be called "base polymer (A)"). Base polymer (A) may have structural units other than structural unit (M). Each structural unit will be described below.

[0022] [Structural Unit (M)] Structural unit (M) is a structural unit derived from the compound represented by the following formula (1). The presence of structural unit (M) in the base polymer (A) allows for sufficient levels of sensitivity, LWR, MEEF, development defect suppression, and CDU. (In formula (1), R １ L is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. １ R is a divalent linking group having 1 to 5 carbon atoms. ２ R is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. ３ (It is a monovalent organic group with 3 to 20 carbon atoms that contains an ester bond between carbon atoms.)

[0023] R ２Examples of monovalent organic groups having 1 to 20 carbon atoms represented by include monovalent hydrocarbon groups having 1 to 20 carbon atoms, groups (α) having a divalent heteroatom-containing group between carbon atoms (between two adjacent or non-adjacent carbon atoms) or at the terminal end of the hydrocarbon group, groups in which some or all of the hydrogen atoms of the hydrocarbon group or group (α) are replaced with monovalent heteroatom-containing groups, or combinations thereof.

[0024] Examples of the above-mentioned monovalent hydrocarbon groups having 1 to 20 carbon atoms include 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.

[0025] Examples of the above-mentioned monovalent linear hydrocarbon groups having 1 to 20 carbon atoms include monovalent linear or branched saturated hydrocarbon groups having 1 to 20 carbon atoms, or monovalent linear or branched unsaturated hydrocarbon groups having 2 to 20 carbon atoms. Examples of the above-mentioned monovalent linear or branched saturated hydrocarbon groups having 1 to 20 carbon atoms include alkyl groups such as methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, 2-methylpropyl group, 1-methylpropyl group, t-butyl group, n-pentyl group, isopentyl group, and neopentyl group. Examples of the above-mentioned monovalent linear or branched unsaturated hydrocarbon groups having 2 to 20 carbon atoms include alkenyl groups such as ethenyl group, propenyl group, and butenyl group; and alkynyl groups such as ethynyl group, propynyl group, and butynyl group.

[0026] Examples of monovalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms include monocyclic or polycyclic saturated hydrocarbon groups, or monocyclic or polycyclic unsaturated hydrocarbon groups. Examples of monocyclic saturated hydrocarbon groups include cycloalkyl groups such as cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl groups. Examples of polycyclic saturated hydrocarbon groups include bridged alicyclic hydrocarbon groups such as norbornyl, adamantyl, tricyclodecyl, and tetracyclododecyl groups. Examples of monocyclic unsaturated hydrocarbon groups include monocyclic cycloalkenyl groups such as cyclopropenyl, cyclobutenyl, cyclopentenyl, and cyclohexenyl groups. Examples of polycyclic unsaturated hydrocarbon groups include polycyclic cycloalkenyl groups such as norborneyl, tricyclodecenyl, and tetracyclododecenyl groups. A bridged alicyclic hydrocarbon group is a polycyclic alicyclic hydrocarbon group in which two non-adjacent carbon atoms constituting the alicyclic ring are bonded together by a linking group containing one or more carbon atoms.

[0027] Examples of the monovalent aromatic hydrocarbon groups having 6 to 20 carbon atoms include aryl groups such as phenyl, tolyl, xyl, naphthyl, and anthyl groups; and aralkyl groups such as benzyl, phenethyl, and naphthylmethyl groups.

[0028] Examples of heteroatoms that constitute the monovalent heteroatom-containing groups and divalent heteroatom-containing groups mentioned above include oxygen atoms, nitrogen atoms, sulfur atoms, phosphorus atoms, silicon atoms, and halogen atoms. Examples of halogen atoms include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms.

[0029] Examples of the monovalent heteroatom-containing groups mentioned above include hydroxyl groups, carboxyl groups, sulfanyl groups, cyano groups, nitro groups, halogen atoms, and the like.

[0030] Examples of the above-mentioned divalent heteroatom-containing groups include -CO-, -C(=O)O-, -CS-, -NR'-, -O-, -S-, -SO-, and -SO ２ - or combinations thereof are examples. R' is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms.

[0031] R ２ From the viewpoint of pattern formation, hydrogen atoms or monovalent chain hydrocarbon groups having 1 to 5 carbon atoms are preferred, and hydrogen atoms are more preferred.

[0032] The above L １ Examples of divalent linking groups having 1 to 5 carbon atoms represented by include divalent linear or branched hydrocarbon groups having 1 to 5 carbon atoms, divalent alicyclic hydrocarbon groups having 3 to 5 carbon atoms, or groups composed of one or more of these hydrocarbon groups and at least one of the groups -CO-, -O-, -NH-, and -S-.

[0033] The above-mentioned divalent linear or branched hydrocarbon group having 1 to 5 carbon atoms is R ２ In this material, monovalent chain hydrocarbon groups having 1 to 20 carbon atoms can be suitably selected from groups with a corresponding number of carbon atoms, with one hydrogen atom removed.

[0034] The above-mentioned divalent alicyclic hydrocarbon group having 3 to 5 carbon atoms is R ２ In this context, monovalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms can be suitably adopted, specifically those obtained by removing one hydrogen atom from the group corresponding to the number of carbon atoms.

[0035] Among these, L １ From the viewpoint of pattern formation, the linking group is preferably a chain-like linking group, more preferably a divalent chain-like hydrocarbon group having 1 to 3 carbon atoms, and even more preferably a methanediyl group.

[0036] R ３ As for the monovalent organic group having 3 to 20 carbon atoms in the above R, ２ Among the monovalent organic groups having 1 to 20 carbon atoms, those with the corresponding number of carbon atoms can be suitably adopted. ３ In this case, an ester bond (-C(=O)-O-, -O-C(=O)-) is present between carbon atoms. The ester bond may be present between carbon atoms of a chain hydrocarbon group, or it may be present between carbon atoms constituting a cyclic hydrocarbon group to form a lactone structure.

[0037] R ３As such, an organic group containing a lactone structure is preferred. Examples of lactone structures include those represented by the following formulas (i) to (iv). (In formulas (i) to (iv), p is an integer from 1 to 5. X is an oxygen atom or a methylene group. Y is a halogen atom, a hydroxyl group, a carboxyl group, a cyano group, a nitro group, an alkyl group, a fluorinated alkyl group, an alkoxycarbonyloxy group, an acyl group, an acyloxy group, or an alkoxy group. q is an integer from 0 to 5, except when p is 1, when q is 0. q1 is an integer from 0 to 5.)

[0038] As the alkyl group, alkoxycarbonyloxy group, acyl group, acyloxy group, and alkoxy group represented by Y above, the examples listed in substituent (T) described later can be suitably adopted.

[0039] The fluorinated alkyl group represented by Y above is R, as described later in formula (5). １４ A fluorinated alkyl group can be suitably used in this.

[0040] The above value of p is preferably an integer between 2 and 4, and more preferably 3 or 4.

[0041] q and q1 are each preferably 0 or 1 independently.

[0042] Examples of compounds (monomers) that give the above structural unit (M) include those represented by the following formula. In the following formula, R １ This is equivalent to equation (1) above.

[0043]

[0044]

[0045]

[0046] The base polymer (A) may contain one or more structural units (M) in combination.

[0047] The lower limit of the content of the structural unit (M) in the total structural units constituting the polymer (A) (or the total content if multiple types are included) is preferably 1 mol%, more preferably 3 mol%, and even more preferably 5 mol% relative to the total structural units constituting the base polymer (A). The upper limit of the above content is preferably 40 mol%, more preferably 30 mol%, and even more preferably 25 mol%. By setting the content of structural unit (M) within the above range, the pattern-forming properties of the radiation-sensitive composition can be further improved.

[0048] [Structural Unit (I)] Polymer (A) preferably has structural unit (I) having an acid-dissociable group, together with the above structural unit (M). An "acid-dissociable group" is a hydrogen atom-substituting group such as a carboxyl group, phenolic hydroxyl group, alcoholic hydroxyl group, or sulfo group, which dissociates upon the action of an acid. The radiation-sensitive composition exhibits excellent pattern-forming properties because the polymer has structural unit (I).

[0049] Structural unit (I) is a structural unit having an acid-dissociable group. Structural unit (I) is not particularly limited as long as it contains an acid-dissociable group, and examples 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 replaced by a tertiary alkyl group, and a structural unit having an acetal bond. However, from the viewpoint of improving the pattern-forming properties of the radiation-sensitive composition, a structural unit represented by the following formula (3) (hereinafter also referred to as "structural unit (I-1)") is preferred.

[0050]

[0051] In the above formula (3), R １７ R is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. １８ R is a monovalent substituted or unsubstituted hydrocarbon group having 1 to 20 carbon atoms. １９ and R ２０Each of these independently represents either a monovalent substituted or unsubstituted linear hydrocarbon group having 1 to 10 carbon atoms, a monovalent substituted or unsubstituted 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 with the carbon atoms to which they are bonded. １１ teeth, ＊ -COO- ＊ -L １１ａ COO- or ＊ - COOL １１ａ Represents COO-. １１ａ * is a substituted or unsubstituted alkanediyl group or arenediyl group. １７ This is the bonding site with the carbon atom to which it is bonded.

[0052] The above R １７ From the viewpoint of copolymerization of the monomer that gives the structural unit (I-1), hydrogen atoms and methyl groups are preferred, and methyl groups are more preferred.

[0053] L １１ａ Examples of alkanediyl groups represented by include methylene groups, ethanediyl groups, 1,3-propanediyl groups, and 2,2-propanediyl groups, which have 1 to 10 carbon atoms. １１ａ Methylene groups and ethanediyl groups are preferred as the base group.

[0054] L １１ａ Examples of the arenediyl group represented by include divalent aromatic hydrocarbon groups having 6 to 20 carbon atoms, such as benzenediyl groups and naphthalenediyl groups. １１ａ A benzenediyl group is preferred as the group.

[0055] L １１ａ Substituents that the alkanediyl group or arenediyl group represented by can have include halogen atoms, hydroxyl groups, carboxyl groups, cyano groups, nitro groups, alkyl groups, fluorinated alkyl groups, alkoxycarbonyloxy groups, acyl groups, acyloxy groups, and alkoxy groups.

[0056] The above R １８ As a monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the above formula (1), R ２Monovalent hydrocarbon groups having 1 to 20 carbon atoms can be suitably used in this material.

[0057] The above R １８ Preferably, the group is a straight-chain or branched-chain saturated hydrocarbon group or an alicyclic hydrocarbon group having 1 to 10 carbon atoms.

[0058] The above R １９ and R ２０ As a monovalent chain hydrocarbon group having 1 to 10 carbon atoms represented by the above formula (1), R ２ Among the monovalent chain hydrocarbon groups having 1 to 20 carbon atoms, those with the corresponding number of carbon atoms can be suitably adopted. Also, the above R １９ and R ２０ As a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the above formula (1), R ２ A monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms can be suitably used in this material.

[0059] The above R １９ and R ２０ The divalent alicyclic group having 3 to 20 carbon atoms, which is formed when these are combined with the carbon atoms to which they are bonded, is R in formula (1) above. ２ A group obtained by removing one hydrogen atom from a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms can be suitably adopted.

[0060] The above R １９ and R ２０ Preferably, the alicyclic structure, which consists of an alkyl group having 1 to 4 carbon atoms, or these alkyl groups combined with the carbon atoms to which they are bonded, is a polycyclic or monocyclic cycloalkane structure.

[0061] The above R １８ ~R ２０ The substituents that can be present are L １１ａ The substituents that the arenediyl group represented by can have can be suitably adopted.

[0062] Examples of structural units (I-1) include those represented by the following formulas (3-1) to (3-15) (hereinafter also referred to as "structural units (I-1-1) to (I-1-15)").

[0063]

[0064]

[0065] In the above equations (3-1) to (3-15), R １７ ~R ２０ This is equivalent to equation (3) above. R Ｌ１１ R is a halogen atom, hydroxyl group, carboxyl group, cyano group, nitro group, alkyl group, fluorinated alkyl group, alkoxycarbonyloxy group, acyl group, acyloxy group, or alkoxy group. i and j are each independently integers from 1 to 4. k and l are 0 or 1. a3 are each independently integers from 0 to 3. If a3 is 2 or more, multiple R Ｌ１１ They are either identical or different from each other. a4 is an integer between 1 and 3.

[0066] i and j are preferably 1 or 2. １８ Preferred groups include methyl, ethyl, isopropyl, t-butyl, cyclopentyl, ethenyl, phenyl, and iodophenyl groups. １９ and R ２０ Preferably, the group is a methyl group, an ethyl group, or an isopropyl group. Ｌ１１ By employing an iodine atom, an iodine group can be suitably introduced into the structural unit (I).

[0067] Furthermore, the polymer may contain structural units (I) represented by the following formulas (1f) to (2f).

[0068]

[0069] In the above equations (1f) to (2f), R αｆ Each of these is independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. βｆ Each of these is independently a hydrogen atom or a chain alkyl group having 1 to 5 carbon atoms. １ is an integer between 1 and 4.

[0070] The above R βｆ Preferably, it is a hydrogen atom, a methyl group, or an ethyl group. １ 1 or 2 is preferred.

[0071] While there are no particular limitations on specific examples of structural units (I), one example is the structure represented by the following formula. In the formula, R １７ This is equivalent to equation (3) above.

[0072]

[0073]

[0074]

[0075]

[0076] The lower limit of the content of structural unit (I) in the total structural units constituting the polymer (A) (or the total content if multiple types are included) is preferably 1 mol%, more preferably 15 mol%, and even more preferably 25 mol% relative to the total structural units constituting the base polymer (A). The upper limit of the above content is preferably 80 mol%, more preferably 70 mol%, and even more preferably 65 mol%. By setting the content of structural unit (I) within the above range, the pattern-forming properties of the radiation-sensitive composition can be further improved.

[0077] [Structural Unit (II)] Structural unit (II) is a structural unit that includes at least one selected from the group consisting of lactone structures, cyclic carbonate structures, and sultone structures (excluding those corresponding to structural unit (M)). The base polymer can have its solubility in the developer adjusted by further including structural unit (II), and as a result, the radiation-sensitive composition can improve lithography performance such as resolution. It can also improve the adhesion between the resist pattern formed from the base polymer and the substrate.

[0078] Examples of structural units (II) include structural units represented by the following formulas (T-1) to (T-11).

[0079]

[0080] In the above formula, R Ｌ１ R is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Ｌ２ ~R Ｌ５These are, independently, a hydrogen atom, a C1-C4 alkyl group, a cyano group, a trifluoromethyl group, a methoxy group, a methoxycarbonyl group, a hydroxyl group, a hydroxymethyl group, and a dimethylamino group. Ｌ４ and R Ｌ５ These may be divalent alicyclic groups having 3 to 8 carbon atoms, which can be combined with each other and bonded together with the carbon atoms. ２ is a single bond or a divalent linking group. X is an oxygen atom or a methylene group. k is an integer from 0 to 3. m is an integer from 1 to 3.

[0081] The above R Ｌ４ and R Ｌ５ When these are combined with each other, the divalent alicyclic group having 3 to 8 carbon atoms, formed together with the carbon atoms to which they are bonded, is R in formula (3) above. １９ and R ２０ Examples include divalent alicyclic groups with 3 to 20 carbon atoms, where these groups are combined with each other and formed together with the carbon atoms to which they are bonded, specifically groups with 3 to 8 carbon atoms. One or more hydrogen atoms on these alicyclic groups may be substituted with hydroxyl groups.

[0082] The above L ２ Examples of divalent linking groups represented by include divalent linear or branched hydrocarbon groups having 1 to 10 carbon atoms, divalent alicyclic hydrocarbon groups having 4 to 12 carbon atoms, or groups composed of one or more of these hydrocarbon groups and at least one of the groups -CO-, -O-, -NH-, and -S-.

[0083] Among these, structural units (II) are preferably those containing a lactone structure, more preferably those containing a γ-butyrolactone structure or a nonorbornane lactone structure, and even more preferably those derived from γ-butyrolactone-yl-(meth)acrylate or norbornane lactone-yl(meth)acrylate.

[0084] When the base polymer (A) has structural units (II), the lower limit of the content of structural units (II) (total content if multiple types are included) is preferably 3 mol%, more preferably 5 mol%, and even more preferably 10 mol%, relative to the total structural units constituting the base polymer (A). The upper limit of the above content is preferably 80 mol%, more preferably 70 mol%, and even more preferably 60 mol%. By setting the content of structural units (II) within the above range, the radiation-sensitive composition can further improve lithography performance such as resolution and the adhesion of the formed resist pattern to the substrate.

[0085] [Structural Unit (III)] The base polymer (A) optionally contains structural unit (III) which includes a polar group (excluding those corresponding to structural units (M), (I), and (II)). By further containing structural unit (III), the solubility of the base polymer (A) in the developer can be adjusted, and as a result, the lithographic performance such as resolution of the radiation-sensitive composition can be improved. Examples of the above polar group include a hydroxyl group, a carboxyl group, a cyano group, a nitro group, a sulfonamide group, etc. Among these, a hydroxyl group and a carboxyl group are preferred, and a hydroxyl group is more preferred.

[0086] Examples of structural units (III) include structural units represented by the following formula.

[0087]

[0088]

[0089] In the above formula, R Ｋ This is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0090] When the base polymer (A) has the structural unit (III) having the polar group, the lower limit of the content ratio of the structural unit (III) (the total content ratio in the case of including a plurality of types) is preferably 1 mol%, more preferably 2 mol%, and still more preferably 3 mol% with respect to all the structural units constituting the base polymer. Further, the upper limit of the content ratio is preferably 30 mol%, more preferably 20 mol%, and still more preferably 15 mol%. By setting the content ratio of the structural unit (III) within the above range, the lithography performance such as the resolution of the radiation-sensitive composition can be further improved.

[0091] [Structural unit (IV)] The base polymer may optionally have a structural unit having a phenolic hydroxyl group (hereinafter also referred to as "structural unit (IV)"). The structural unit (IV) contributes to the improvement of etching resistance and the improvement of the difference in developer solubility (dissolution contrast) between the exposed portion and the unexposed portion. It can be suitably applied to pattern formation using exposure with radiation having a wavelength of 50 nm or less, such as KrF excimer laser, electron beam, or EUV.

[0092] The structural unit having a phenolic hydroxyl group is preferably represented by the following formula (4).

[0093] (In the above formula (4), β R is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ＣＡ L is a single bond, -COO- ＊ or -O-. * is a bond on the aromatic ring side. １０２ R is a halogen atom, a cyano group, a nitro group, an alkyl group, an alkoxycarbonyl group, an acyl group, or an acyloxy group. When there are a plurality of １０２ Rs, the plurality of １０２ Rs may be the same as or different from each other. ３ n is an integer of 0 to 2, ３ m is an integer of 1 to 8, ４ m is, independently of each other, an integer of 0 to 8. However, 1 ≤ m ３ + m ４ ≤ 2n ３ + 5 is satisfied.)

[0094] The aboveβ From the viewpoint of copolymerization of the monomer that gives the structural unit (IV), it is preferable that it be a hydrogen atom or a methyl group.

[0095] L ＣＡ For example, a single bond or -COO- ＊ It is preferable.

[0096] R １０２ In this case, an iodine atom is preferred as the halogen atom.

[0097] The above n ３ 0 or 1 is more preferable, and 0 is even more preferable.

[0098] The above m ３ Preferably, the integer is between 1 and 3, and more preferably 1 or 2.

[0099] The above m ４ Preferably, the integer is between 0 and 3, and more preferably between 0 and 2.

[0100] When obtaining structural units (IV), it is preferable to polymerize the monomer while protecting the phenolic hydroxyl group of the corresponding monomer with a protecting group such as an alkali-dissociable group (e.g., an acyl group), and then deprotect it by hydrolysis to obtain structural units (IV). However, polymerization of the monomer may be carried out without protecting the phenolic hydroxyl group.

[0101] For polymers used for exposure with KrF excimer lasers or radiation with wavelengths of 50 nm or less, the lower limit of the content of structural unit (IV) (total content if multiple types are included) is preferably 15 mol%, and more preferably 25 mol%, relative to the total structural units constituting the base polymer (A). The upper limit of the above content is preferably 70 mol%, and more preferably 60 mol%.

[0102] [Other structural units] In addition to the structural units listed above, the base polymer (A) may also contain structural units having an alicyclic structure represented by the following formula (6) (hereinafter also referred to as "structural unit (VII)"). (In the above formula (6), R １α R is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ２α(It is a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms.)

[0103] In the above formula (6), R ２α As a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the above formula (1), R ２ A monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms can be suitably used in this material.

[0104] When the base polymer (A) contains structural unit (VII), the lower limit of the content of structural unit (VII) is preferably 2 mol%, more preferably 5 mol%, and even more preferably 8 mol%, relative to the total structural units constituting the base polymer (A). The upper limit of the above content is preferably 50 mol%, more preferably 40 mol%, and even more preferably 35 mol%.

[0105] (Method for synthesizing base polymer (A)) Base polymer (A) can be synthesized, for example, by polymerizing monomers that give each structural unit in a suitable solvent using a radical polymerization initiator or the like.

[0106] Examples of the radical polymerization initiators mentioned above include azo-based radical initiators such as azobisisobutyronitrile (AIBN), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2-cyclopropylpropionitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), and dimethyl 2,2'-azobisisobutyrate; and peroxide-based radical initiators such as benzoyl peroxide, t-butyl hydroperoxide, and cumene hydroperoxide. Among these, AIBN and dimethyl 2,2'-azobisisobutyrate are preferred. These radical initiators can be used individually or in combination of two or more.

[0107] Examples of solvents used in the above polymerization include: alkanes such as n-pentane, n-hexane, n-heptane, n-octane, n-nonane, and n-decane; cycloalkanes such as cyclohexane, cycloheptane, cyclooctane, decalin, and norbornane; aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, and cumene; halogenated hydrocarbons such as chlorobutanes, bromohexanes, dichloroethanes, hexamethylene dibromide, and chlorobenzene; saturated carboxylic acid esters such as ethyl acetate, n-butyl acetate, isobutyl acetate, methyl propionate, and propylene glycol monomethyl ether acetate; ketones such as acetone, methyl ethyl ketone, 2-butanone, 4-methyl-2-pentanone, 2-heptanone, and cyclohexanone; Examples include linear ethers such as dimethoxyethanes and diethoxyethanes; cyclic ethers such as tetrahydrofurans and 1,4-dioxanes; polyhydric alcohol partial ethers such as 1-methoxy-2-propanol (propylene glycol monomethyl ether); alcohols such as methanol, ethanol, 1-propanol, 2-propanol, and 4-methyl-2-pentanol; and lactones such as γ-butyrolactone. The solvents used in these polymerizations may be used alone or in combination of two or more.

[0108] The reaction temperature in the polymerization described above is usually 40°C to 150°C, with 50°C to 120°C being preferred. The reaction time is usually 1 hour to 48 hours, with 1 hour to 24 hours being preferred.

[0109] The molecular weight of the base polymer (A) is not particularly limited, but the lower limit of the polystyrene-equivalent weight-average molecular weight (Mw) determined by gel permeation chromatography (GPC) is preferably 3,000, more preferably 4,000, and even more preferably 5,000. The upper limit of Mw is preferably 40,000, more preferably 30,000, and even more preferably 20,000. By keeping the Mw of the base polymer within the above range, good heat resistance and developability can be obtained in the resulting resist film.

[0110] The ratio of Mw to the polystyrene-equivalent number-average molecular weight (Mn) (Mw / Mn) of the base polymer (A) 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.

[0111] In this specification, the Mw and Mn values ​​of polymers are measured using gel permeation chromatography (GPC) under the following conditions.

[0112] GPC columns: 2 x G2000HXL, 1 x G3000HXL, 1 x G4000HXL (all manufactured by Tosoh) Column temperature: 40°C Elution solvent: Tetrahydrofuran Flow rate: 1.0 mL / min Sample concentration: 1.0% by mass Sample injection volume: 100 μL Detector: Differential refractometer Standard material: Monodisperse polystyrene

[0113] The content of the base polymer (A) is preferably 40% by mass or more, and more preferably 50% by mass or more, relative to the total solid content of the radiation-sensitive composition.

[0114] (Other polymers (E)) The radiation-sensitive composition of this embodiment may also contain, as other polymers, a polymer (E) having a higher mass content of fluorine atoms than the base polymer (A) (hereinafter also referred to as "high fluorine-content polymer (E)"). When the radiation-sensitive composition contains the high fluorine-content polymer (E), it can be unevenly distributed on the surface of the resist film relative to the base polymer (A), and as a result, the water repellency of the surface of the resist film during immersion exposure can be enhanced, and the surface modification of the resist film and the distribution of the composition within the film can be controlled during EUV exposure.

[0115] The high-fluorine-content polymer (E) may, for example, have a structural unit represented by the following formula (5) (hereinafter also referred to as "structural unit (V)").

[0116]

[0117] In the above formula (5), R １３ This is a hydrogen atom, a methyl group, or a trifluoromethyl group. Ｌ It consists of a single bond, an alkanediyl group with 1 to 5 carbon atoms, an oxygen atom, a sulfur atom, -COO-, and -SO ２ONH-, -CONH-, -OCONH-, or a combination thereof. １４ This is a monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms or a monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms.

[0118] The above R １３ From the viewpoint of copolymerizability of the monomer that gives the structural unit (V), hydrogen atoms and methyl groups are preferred, and methyl groups are more preferred.

[0119] The above G Ｌ From the viewpoint of copolymerization of monomers that provide structural units (V), single bonds and -COO- are preferred, and -COO- is more preferred.

[0120] The above R １４ Examples of monovalent fluorinated linear hydrocarbon groups having 1 to 20 carbon atoms, represented by , include those in which some or all of the hydrogen atoms in a linear or branched alkyl group having 1 to 20 carbon atoms are substituted with fluorine atoms.

[0121] The above R １４ Examples of monovalent fluorinated alicyclic hydrocarbon groups having 3 to 20 carbon atoms, represented by , include those in which some or all of the hydrogen atoms in a monocyclic or polycyclic hydrocarbon group having 3 to 20 carbon atoms are substituted with fluorine atoms.

[0122] The above R １４ Preferably, the group is a fluorinated chain hydrocarbon group, more preferably a fluorinated alkyl group, and even more preferably a 2,2,2-trifluoroethyl group, a 2,2,3,3,3-pentafluoropropyl group, a 1,1,1,3,3,3-hexafluoropropyl-2-yl group, and a 5,5,5-trifluoro-1,1-diethylpentyl group.

[0123] When a high-fluorine-content polymer has structural units (V), the lower limit of the content of structural units (V) is preferably 40 mol%, more preferably 50 mol%, and even more preferably 55 mol%, relative to the total structural units constituting the high-fluorine-content polymer. The upper limit of the above content is preferably 90 mol%, more preferably 80 mol%, and even more preferably 75 mol%. By setting the content of structural units (V) within the above range, the mass content of fluorine atoms in the high-fluorine-content polymer can be more appropriately adjusted, further promoting the uneven distribution on the surface of the resist film, and as a result, the water repellency of the resist film during immersion exposure can be further improved.

[0124] High-fluorine polymers may have a fluorine atom-containing structural unit (hereinafter also referred to as structural unit (VI)) represented by the following formula (f-2), either together with or in place of structural unit (V). The presence of structural unit (f-2) in high-fluorine polymers improves solubility in alkaline developers and suppresses the occurrence of development defects.

[0125]

[0126] Structural units (VI) can be broadly classified into two types: (x) those having an alkali-soluble group, and (y) those having a group that dissociates under the action of alkali, increasing its solubility in an alkaline developer (hereinafter also simply referred to as an "alkali-dissociable group"). In common to both (x) and (y), in the above formula (f-2), R Ｃ R is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Ｄ R is a single bond, a (s+1) valent hydrocarbon group with 1 to 20 carbon atoms, and this hydrocarbon group Ｅ At the terminal end of the side are an oxygen atom, a sulfur atom, and -NR ｄｄ -, a carbonyl group, -COO-, -OCO-, or -CONH- bonded to the hydrocarbon group, or a structure in which some of the hydrogen atoms of this hydrocarbon group are substituted by an organic group having a heteroatom. ｄｄ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. s is an integer from 1 to 3.

[0127] If structural unit (VI) has (x) an alkali-soluble group, R ＦA is a hydrogen atom, １ is an oxygen atom, -COO-* or -SO ２ O-*. * is R Ｆ This indicates the binding site. １ This is a single bond, a hydrocarbon group having 1 to 20 carbon atoms, or a divalent fluorinated hydrocarbon group. １ If is an oxygen atom, W １ is A １ It is a fluorinated hydrocarbon group having a fluorine atom or a fluoroalkyl group at the carbon atom to which it is bonded. Ｅ is a single bond or a divalent organic group having 1 to 20 carbon atoms. When s is 2 or 3, multiple R Ｅ , W １ A １ and R Ｆ These may be the same or different. Having an alkali-soluble group in structural unit (VI) increases its affinity for alkaline developers and suppresses development defects. A structural unit (VI) having an alkali-soluble group is A １ is an oxygen atom and W １ It is particularly preferable that the group is a 1,1,1,3,3,3-hexafluoro-2,2-propanediyl group.

[0128] If the structural unit (VI) has an alkali-dissociable group (y), R Ｆ A is a monovalent organic group having 1 to 30 carbon atoms. １ is an oxygen atom, -NR ａａ -, -COO-*, -OCO-*, or -SO ２ O-*. R ａａ * is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. Ｆ This indicates the binding site. １ R is a single bond or a divalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. Ｅ A is a single bond or a divalent organic group having 1 to 20 carbon atoms. １ ga -COO-*, -OCO-*, or -SO ２ If it is O-*, then W １ or R Ｆ is A １ It has a fluorine atom on the carbon atom bonded to it or on an adjacent carbon atom. １If is an oxygen atom, W １ , R Ｅ It is a single bond, R Ｄ R is a hydrocarbon group having 1 to 20 carbon atoms. Ｅ It is a structure in which a carbonyl group is bonded to the terminal end, R Ｆ is an organic group having a fluorine atom. When s is 2 or 3, multiple R Ｅ , W １ A １ and R Ｆ These may be the same or different. The presence of a (y) alkali-dissociable group in structural unit (VI) causes the resist film surface to change from hydrophobic to hydrophilic during the alkali development process. As a result, the affinity for the developer is significantly increased, and development defects can be suppressed more efficiently. Examples of structural units (VI) having a (y) alkali-dissociable group include A １ ga -COO-*, R Ｆ Or W １ Alternatively, it is particularly preferable that both of these contain fluorine atoms.

[0129] R Ｃ From the viewpoint of copolymerizability of monomers that provide structural unit (VI), hydrogen atoms and methyl groups are preferred, and methyl groups are more preferred.

[0130] When a high-fluorine-content polymer has structural units (VI), the lower limit of the content of structural units (VI) is preferably 30 mol%, more preferably 40 mol%, and even more preferably 50 mol%, relative to the total structural units constituting the high-fluorine-content polymer. The upper limit of the above content is preferably 95 mol%, more preferably 90 mol%, and even more preferably 85 mol%. By setting the content of structural units (VI) within the above range, it is possible to improve the water repellency of the resist film during immersion exposure and improve solubility in alkaline developers, thereby suppressing the occurrence of development defects.

[0131] [Other structural units] High-fluorine polymers may, if necessary, include structural units other than those listed above, such as structural unit (I), structural unit (III), structural unit (VII), and structural unit (M) in the base polymer (A).

[0132] When a high-fluorine-content polymer contains structural unit (I), the lower limit of the content of structural unit (I) is preferably 5 mol%, and more preferably 10 mol%, relative to the total structural units constituting the high-fluorine-content polymer. The upper limit of the above content is preferably 60 mol%, and more preferably 50 mol%.

[0133] When a high-fluorine-content polymer contains structural unit (III), the lower limit of the content of structural unit (III) is preferably 2 mol%, and more preferably 4 mol%, relative to the total structural units constituting the high-fluorine-content polymer. The upper limit of the above content is preferably 40 mol%, and more preferably 30 mol%.

[0134] When a high-fluorine-content polymer contains structural unit (VII), the lower limit of the content of structural unit (VII) is preferably 10 mol%, and more preferably 20 mol%, relative to the total structural units constituting the high-fluorine-content polymer. The upper limit of the above content is preferably 60 mol%, and more preferably 50 mol%.

[0135] When a high-fluorine-content polymer contains structural units (M), the lower limit of the structural unit (M) content is preferably 1 mol%, and more preferably 5 mol%, relative to the total structural units constituting the high-fluorine-content polymer. The upper limit of the above content is preferably 30 mol%, and more preferably 20 mol%.

[0136] The lower limit of Mw for the high-fluorine-content polymer is preferably 3,000, and more preferably 4,000. The upper limit of Mw is preferably 20,000, and more preferably 16,000.

[0137] The lower limit of Mw / Mn for high-fluorine-content polymers is usually 1, and 1.1 is more preferred. The upper limit of Mw / Mn is usually 5, 3 is preferred, and 2 is more preferred.

[0138] If the radiation-sensitive composition contains a high-fluorine content polymer, the lower limit of the high-fluorine content polymer is preferably 0.5 parts by mass, more preferably 1 part by mass, and even more preferably 1.5 parts by mass, per 100 parts by mass of the base polymer (A). The upper limit of the above content is preferably 15 parts by mass, more preferably 10 parts by mass, and even more preferably 6 parts by mass.

[0139] By setting the content of the high-fluorine polymer within the above range, the high-fluorine polymer can be more effectively distributed to the surface layer of the resist film. As a result, it is possible to improve the water repellency of the surface of the resist film during immersion exposure, and to control the surface modification of the resist film and the distribution of the internal composition during EUV exposure. The radiation-sensitive composition may contain one or more high-fluorine polymers.

[0140] (Method for synthesizing high-fluorine-content polymer (E)) High-fluorine-content polymer (E) can be synthesized by the same method as the synthesis method for base polymer (A) described above.

[0141] (Radiation-sensitive acid generator (B)) The above radiation-sensitive composition may contain a radiation-sensitive acid generator (B). The radiation-sensitive acid generator (B) is a compound having an organic acid anion and an onium cation, which generates an acid that dissociates the above acid-dissociable group upon exposure.

[0142] Examples of organic acid anions include sulfonic acid anions, sulfonimide anions, and sulfonmethide anions.

[0143] Examples of such acids include: (1) compounds in which one or more fluorine atoms, fluorinated hydrocarbon groups, or cyano groups are substituted on the α or β carbon atoms of a sulfo group, or in which an ester bond is interposed between carbon atoms; (2) compounds having a sulfonimide structure containing a fluorine atom; and (3) compounds having a sulfonemethide structure containing a fluorine atom.

[0144] The radiation-sensitive acid generator (B) is preferably a compound represented by the following formula (z-a). (In formula (za), R ４ｚ It is a monovalent organic group having 2 to 40 carbon atoms. However, -SO ３ － A fluorine atom or a monovalent fluorinated hydrocarbon group is bonded to the carbon atom at the α or β position. ＋ (This is a monovalent organic cation.)

[0145] R ４ｚAs a monovalent organic group having 2 to 40 carbon atoms represented by the above formula (1), R ２ A monovalent organic group having 1 to 20 carbon atoms, as shown above, can be suitably adopted as a group having 2 to 40 carbon atoms.

[0146] R ４ｚ It is preferable that the group is a monovalent organic group having 4 to 40 carbon atoms and containing at least one structure selected from the group consisting of a cyclic structure, a carbonyl group, and an ether bond. The cyclic structure may be monocyclic, polycyclic, or a combination thereof. The cyclic structure may also be an alicyclic structure, an aromatic ring structure, a heterocyclic structure, or a combination thereof. In the case of a combination, the ring structures may be linked in a chain structure, and two or more ring structures may form a fused ring structure, a bridged ring structure, or a spiro-ring structure. A divalent heteroatom-containing group may be present between the carbon atoms forming the skeleton of the cyclic or chain structure, and some or all of the hydrogen atoms on the carbon atoms of the cyclic or chain structure may be substituted with other substituents.

[0147] The above alicyclic structure is R in formula (1) above. ２ A structure corresponding to a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms can be suitably adopted.

[0148] The above aromatic ring structure is R in formula (1) above. ２ A structure corresponding to a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms can be suitably adopted.

[0149] Examples of the above heterocyclic structures include: oxygen atom-containing aliphatic heterocyclic structures such as oxirane, tetrahydrofuran, tetrahydropyran, dioxolane, and dioxane; nitrogen atom-containing aliphatic heterocyclic structures such as aziridine, pyrrolidine, piperidine, and piperazine; sulfur atom-containing aliphatic heterocyclic structures such as thiethane, thiolane, and thian; aliphatic heterocyclic structures containing multiple types of heteroatoms such as morpholine, 1,2-oxathiolane, and 1,3-oxathiolane; oxygen atom-containing aromatic heterocyclic structures such as furan, benzofuran, and dibenzofuran; nitrogen atom-containing aromatic heterocyclic structures such as pyrrole, pyrazole, triazine, pyridine, pyrazine, pyrimidine, and pyridazine; sulfur atom-containing aromatic heterocyclic structures such as thiophene; and aromatic heterocyclic structures containing multiple types of heteroatoms such as oxazole, isothiazole, and thiazine.

[0150] Heterocyclic structures include lactone structures, cyclic carbonate structures, sultone structures, cyclic acetals, or combinations thereof.

[0151] The above chain-like structure is R in formula (1) above. ２ In this material, monovalent chain hydrocarbon groups having 1 to 20 carbon atoms, or divalent chain hydrocarbon groups obtained by removing one hydrogen atom from the monovalent chain hydrocarbon group, can be suitably used.

[0152] As a divalent heteroatom-containing group, R in formula (1) above is ２ The divalent heteroatom-containing group shown can be suitably adopted.

[0153] Examples of substituents (T) that substitute for some or all of the hydrogen atoms on the carbon atoms of the above-mentioned cyclic or chain-like structure include halogen atoms such as fluorine, chlorine, bromine, and iodine; hydroxyl groups; carboxyl groups; cyano groups; nitro groups; alkyl groups; alkoxy groups; alkoxycarbonyl groups; alkoxycarbonyloxy groups; acyl groups; acyloxy groups; or groups in which the hydrogen atoms of these groups are substituted with halogen atoms.

[0154] Examples of alkyl groups as substituents (T) include linear or branched alkyl groups having 1 to 8 carbon atoms, such as methyl, ethyl, propyl, and t-butyl groups. Examples of alkoxy groups include linear or branched alkoxy groups having 1 to 8 carbon atoms, such as methoxy, ethoxy, and propoxy groups. Examples of alkoxycarbonyl groups include alkoxycarbonyl groups having 1 to 6 carbon atoms, such as methoxycarbonyl and ethoxycarbonyl groups. Examples of alkoxycarbonyloxy groups include linear or alicyclic alkoxycarbonyloxy groups having 2 to 16 carbon atoms, such as methoxycarbonyloxy, butoxycarbonyloxy, and adamantylmethyloxycarbonyloxy. Examples of acyl groups include aliphatic or aromatic acyl groups having 2 to 12 carbon atoms, such as acetyl, propionyl, benzoyl, and acryloyl groups. Examples of acyloxy groups include aliphatic or aromatic acyloxy groups having 2 to 12 carbon atoms, such as acetyloxy groups, propionyloxy groups, benzoyloxy groups, and acryloyloxy groups.

[0155] The monovalent fluorinated hydrocarbon group mentioned above is R in formula (1) above. ２ Examples include groups in which some or all of the hydrogen atoms of a monovalent hydrocarbon group having 1 to 20 carbon atoms are replaced by fluorine atoms.

[0156] Za ＋ The monovalent organic cation represented by is not particularly limited, but it is preferably a monovalent radiation-sensitive onium cation. Examples of radiation-sensitive onium cations include sulfonium cations, tetrahydrothiophenium cations, and iodonium cations. Among these, sulfonium cations or iodonium cations are preferred, and sulfonium cations are more preferred.

[0157] The sulfonium cation or iodonium cation is preferably represented by the following formulas (X-1) to (X-6).

[0158]

[0159] In the above equation (X-1), Rａ１ , R ａ２ and R ａ３ Each of these independently comprises a substituted or unsubstituted linear or branched alkyl group, alkoxy group or alkoxycarbonyloxy group having 1 to 12 carbon atoms, a substituted or unsubstituted monocyclic or polycyclic cycloalkyl group having 3 to 12 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, a hydroxyl group, a halogen atom, or -OSO ２ -R Ｐ , -SO ２ -R Ｑ , -S-R Ｔ R represents a ring structure consisting of -O-, -CO-, or a combination thereof, or two or more of these groups combined with each other. This ring structure may contain heteroatoms such as O or S between the carbon-carbon bonds forming the skeleton. Ｐ , R Ｑ and R Ｔ Each of these is independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted alicyclic hydrocarbon group having 5 to 25 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms. k1, k2, and k3 are each independently integers from 0 to 5. R ａ１ ~R ａ３ And R Ｐ , R Ｑ and R Ｔ If each of them is multiple, then multiple R ａ１ ~R ａ３ And R Ｐ , R Ｑ and R Ｔ These may be the same or different.

[0160] In the above equation (X-2), R ｂ１ This is a substituted or unsubstituted linear or branched alkyl or alkoxy group having 1 to 20 carbon atoms, an alkoxyalkyloxy group, a substituted or unsubstituted acyl group having 2 to 8 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 8 carbon atoms, or a hydroxyl group. ｋ n is either 0 or 1. ｋ When is 0, k4 is an integer from 0 to 4, and n ｋWhen k4 is 1, k4 is an integer from 0 to 7. ｂ１ If there are multiple R ｂ１ They may be the same or different, and there may be multiple R's. ｂ１ R may represent a ring structure formed by combining with other elements. ｂ２ This is a substituted or unsubstituted linear or branched alkyl group having 1 to 7 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 or 7 carbon atoms. Ｃ k5 is a single bond or a divalent linking group. k5 is an integer from 0 to 4. ｂ２ If there are multiple R ｂ２ They may be the same or different, and there may be multiple R's. ｂ２ may represent a ring structure formed by combining with each other. q is an integer from 0 to 3. In the formula, S ＋ The ring structure containing may include heteroatoms such as O or S between the carbon-carbon bonds that form the skeleton.

[0161] In the above equation (X-3), R ｃ１ , R ｃ２ and R ｃ３ Each of these is independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms.

[0162] In the above equation (X-4), R ｇ１ This is a substituted or unsubstituted linear or branched alkyl or alkoxy group having 1 to 20 carbon atoms, a substituted or unsubstituted acyl group having 2 to 8 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 8 carbon atoms, or a hydroxyl group. ｋ２ n is either 0 or 1. ｋ２ When is 0, k10 is an integer from 0 to 4, and n ｋ２ When is 1, k10 is an integer from 0 to 7. ｇ１ If there are multiple R ｇ１ They may be the same or different, and there may be multiple R's. ｇ１ R may represent a ring structure formed by combining with other elements. ｇ２ and R ｇ３Each of these independently represents a substituted or unsubstituted linear or branched alkyl group, alkoxy group or alkoxycarbonyloxy group having 1 to 12 carbon atoms, a substituted or unsubstituted monocyclic or polycyclic cycloalkyl group having 3 to 12 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group, hydroxyl group, halogen atom having 6 to 12 carbon atoms, or a ring structure formed by combining these groups. k11 and k12 are each independently integers from 0 to 4. R ｇ２ and R ｇ３ If each of them is multiple, then multiple R ｇ２ and R ｇ３ These may be the same or different.

[0163] In the above equation (X-5), R ｄ１ and R ｄ２ Each of these independently represents a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, an alkoxy group or alkoxycarbonyl group, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, a halogen atom, a halogenated alkyl group having 1 to 4 carbon atoms, a nitro group, or a ring structure formed by two or more of these groups combined. k6 and k7 are each independently integers from 0 to 5. R ｄ１ and R ｄ２ If each of them is multiple, then multiple R ｄ１ and R ｄ２ These may be the same or different.

[0164] In the above formula (X-6), R ｅ１ and R ｅ２ k8 and k9 are each independently a halogen atom, 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.

[0165] Specific examples of organic cations used as radiation-sensitive onium cations include, but are not limited to, the structure shown in the following formula.

[0166]

[0167]

[0168]

[0169] Specific examples of the radiation-sensitive acid generator (B) include, but are not limited to, structures represented by the following formula.

[0170]

[0171]

[0172]

[0173] In addition to the above, a compound in which an organic acid anion and an onium cation are covalently bonded can also be used as the radiation-sensitive acid generator (B).

[0174] When the radiation-sensitive composition contains a radiation-sensitive acid generator (B), the lower limit of the content of the radiation-sensitive acid generator (B) (total if multiple types are included) is preferably 1 part by mass, and more preferably 3 parts by mass, per 100 parts by mass of the base polymer (A). The upper limit of the above content is preferably 50 parts by mass, and more preferably 40 parts by mass. As a result, the composition can exhibit excellent sensitivity, CDU, LWR, MEEF, and development defect suppression when forming resist patterns.

[0175] (Acid diffusion control agent (C)) The radiation-sensitive composition may optionally contain an acid diffusion control agent (C). The acid diffusion control agent (C) controls the diffusion phenomenon of the acid generated from the radiation-sensitive acid generator (B) by exposure in the resist film, and has the effect of suppressing undesirable chemical reactions in the unexposed areas. In addition, the storage stability of the resulting radiation-sensitive composition is improved. Furthermore, the resolution of the resist pattern is further improved, and changes in the line width of the resist pattern due to variations in the holding time from exposure to development can be suppressed, resulting in a radiation-sensitive composition with excellent process stability.

[0176] Examples of acid diffusion control agents (C) include compounds represented by the following formula (7) (hereinafter also referred to as "nitrogen-containing compounds (I)"), compounds having two nitrogen atoms in the same molecule (hereinafter also referred to as "nitrogen-containing compounds (II)"), compounds having three nitrogen atoms (hereinafter also referred to as "nitrogen-containing compounds (III)"), amide group-containing compounds, urea compounds, nitrogen-containing heterocyclic compounds, onium salts having quaternary ammonium cations, and the like.

[0177]

[0178] In the above formula (7), R ２２ , R ２３ and R ２４ Each of these is independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted aralkyl group.

[0179] Examples of nitrogen-containing compounds (I) include monoalkylamines such as n-hexylamine; dialkylamines such as di-n-butylamine; trialkylamines such as triethylamine; and aromatic amines such as aniline and 2,6-di-i-propylaniline.

[0180] Examples of nitrogen-containing compounds (II) include ethylenediamine and N,N,N',N'-tetramethylethylenediamine.

[0181] Examples of nitrogen-containing compounds (III) include polyamine compounds such as polyethyleneimine and polyallylamine; and polymers such as dimethylaminoethylacrylamide.

[0182] Examples of amide group-containing compounds include formamide, N-methylformamide, N,N-dimethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, propionamide, benzamide, pyrrolidone, and N-methylpyrrolidone.

[0183] Examples of urea compounds include urea, methyl urea, 1,1-dimethylurea, 1,3-dimethylurea, 1,1,3,3-tetramethylurea, 1,3-diphenylurea, and tributylthiourea.

[0184] Examples of nitrogen-containing heterocyclic compounds include pyridines such as pyridine and 2-methylpyridine; morpholines such as N-propylmorpholine and N-(undecylcarbonyloxyethyl)morpholine; and pyrazines and pyrazoles.

[0185] Furthermore, compounds having an acid-dissociable group can also be used as the nitrogen-containing organic compound. Examples of such nitrogen-containing organic compounds having an acid-dissociable group include N-t-butoxycarbonylpiperidine, N-t-butoxycarbonylimidazole, N-t-butoxycarbonylbenzimidazole, N-t-butoxycarbonyl-2-phenylbenzimidazole, N-(t-butoxycarbonyl)di-n-octylamine, N-(t-butoxycarbonyl)diethanolamine, N-(t-butoxycarbonyl)dicyclohexylamine, N-(t-butoxycarbonyl)diphenylamine, N-t-butoxycarbonyl-4-hydroxypiperidine, N-t-butoxycarbonyl-4-acetoxypiperidine, and N-t-amyloxycarbonyl-4-hydroxypiperidine.

[0186] Examples of onium salts having a quaternary ammonium cation include tetrabutylammonium salicylate, tetrabutylammonium benzoate, and ammonium camphorsulfonate.

[0187] Furthermore, a radiation-sensitive weak acid generator that generates a weak acid upon exposure can be suitably used as the acid diffusion control agent (C). The acid generated from the above-mentioned radiation-sensitive weak acid generator (B) is a weak acid that does not cause the acid-dissociable groups in the polymer to dissociate under conditions that would normally cause such groups to dissociate.

[0188] Examples of radiation-sensitive weak acid generators (C) include onium salt compounds that decompose upon exposure and lose their ability to control acid diffusion. Examples of onium salt compounds include sulfonium salt compounds represented by the following formula (8-1) and iodonium salt compounds represented by the following formula (8-2). Also, examples include compounds containing a sulfonium cation and anion in the same molecule, represented by the following formula (8-3), and compounds containing an iodonium cation and anion in the same molecule, represented by the following formula (8-4).

[0189]

[0190] In the above formulas (8-1) to (8-4), J ＋ It is a sulfonium cation, U ＋ This is an iodonium cation. ＋ Examples of sulfonium cations represented by the above formulas (X-1) to (X-4) include U ＋ Examples of iodonium cations represented by the above formulas (X-5) to (X-6) include iodonium cations represented by E. － and Q － Each of them is independent of OH － , R α - COO － , R α -SO ３ － This is an anion represented by R. α R is a single bond or a monovalent organic group having 1 to 30 carbon atoms. The organic group is R in formula (1) above. ２ In this material, monovalent organic groups with 1 to 20 carbon atoms can be suitably adopted, with the number of carbon atoms extended up to 30.

[0191] Examples of the above-mentioned radiation-sensitive weak acid generator (C) include compounds represented by the following formula.

[0192]

[0193]

[0194]

[0195] The lower limit of the content of the acid diffusion control agent (C) is preferably 0.5 parts by mass, and more preferably 1 part by mass, per 100 parts by mass of the polymer (A). The upper limit of the content is preferably 60 parts by mass, and more preferably 50 parts by mass. By setting the content of the acid diffusion control agent within the above range, the lithography performance of the radiation-sensitive composition can be further improved. The radiation-sensitive composition may contain one or more types of acid diffusion control agents.

[0196] (Solvent (D)) The radiation-sensitive composition according to this embodiment contains solvent (D). Solvent (D) is not particularly limited as long as it is a solvent capable of dissolving or dispersing at least polymer (A) and any optional components that may be contained therein.

[0197] Examples of solvents include alcohol-based solvents, ether-based solvents, ketone-based solvents, amide-based solvents, ester-based solvents, and hydrocarbon-based solvents.

[0198] Examples of alcohol-based solvents include monoalcohol solvents having 1 to 18 carbon atoms, such as isopropanol, 4-methyl-2-pentanol, 3-methoxybutanol, n-hexanol, 2-ethylhexanol, furfuryl alcohol, cyclohexanol, 3,3,5-trimethylcyclohexanol, and diacetone alcohol; polyhydric alcohol 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 solvents, such as propylene glycol monomethyl ether, which are obtained by etherifying some of the hydroxyl groups in the above-mentioned polyhydric alcohol solvents.

[0199] In this embodiment, alcohol acid ester solvents such as methyl lactate, ethyl lactate, propyl lactate, butyl lactate, methyl 2-hydroxyisobutyrate, isopropyl 2-hydroxyisobutyrate, isobutyl 2-hydroxyisobutyrate, and n-butyl 2-hydroxyisobutyrate are also included in the alcohol-based solvents.

[0200] Examples of ether-based solvents include dialkyl ether solvents such as diethyl ether, dipropyl ether, and dibutyl ether; cyclic ether solvents such as tetrahydrofuran and tetrahydropyran; aromatic ring-containing ether solvents such as diphenyl ether and anisole (methylphenyl ether); and polyhydric alcohol ether solvents obtained by etherifying the hydroxyl groups of the above-mentioned polyhydric alcohol solvents.

[0201] Examples of ketone solvents include linear ketone solvents such as acetone, butanone, and methyl-isobutyl ketone; cyclic ketone solvents such as cyclopentanone, cyclohexanone, and methylcyclohexanone; and 2,4-pentanedione, acetonylacetone, and acetophenone.

[0202] Examples of amide solvents include cyclic amide solvents such as N,N'-dimethylimidazolidinone and N-methylpyrrolidone; and chain-like amide solvents such as N-methylformamide, N,N-dimethylformamide, N,N-diethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, and N-methylpropionamide.

[0203] Examples of ester solvents include monocarboxylic acid ester solvents such as n-butyl acetate; polyhydric alcohol partial ether acetate solvents such as diethylene glycol mono-n-butyl ether acetate, propylene glycol monomethyl ether acetate, and dipropylene glycol monomethyl ether acetate; lactone solvents such as γ-butyrolactone and valerolactone; carbonate solvents such as diethyl carbonate, ethylene carbonate, and propylene carbonate; and polyhydric carboxylic acid diester solvents such as propylene glycol diacetate, methoxytriglycol acetate, diethyl oxalate, ethyl acetoethyl acetate, and diethyl phthalate.

[0204] Examples of hydrocarbon solvents include aliphatic hydrocarbon solvents such as n-hexane, cyclohexane, and methylcyclohexane; and aromatic hydrocarbon solvents such as benzene, toluene, diisopropylbenzene, and n-amylnaphthalene.

[0205] Among these, alcohol-based solvents, ester-based solvents, and ketone-based solvents are preferred, polyhydric alcohol partial ether-based solvents, alcoholic acid ester-based solvents, C1-C18 monoalcohol-based solvents, polyhydric alcohol partial ether acetate-based solvents, lactone-based solvents, and cyclic ketone-based solvents are more preferred, and propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, γ-butyrolactone, and ethyl lactate are even more preferred. The radiation-sensitive composition may contain one or more solvents.

[0206] (Other optional components) The above-mentioned radiation-sensitive composition may contain other optional components in addition to the components listed above. Examples of these other optional components include crosslinking agents, localization accelerators, surfactants, alicyclic skeleton-containing compounds, sensitizers, and the like. These other optional components may be used individually or in combination of two or more types.

[0207] <Method for preparing a radiation-sensitive composition> The above radiation-sensitive composition can be prepared by mixing a polymer (A), a high-fluorine-content polymer (E) if necessary, and a solvent (D) in a predetermined ratio. After mixing, the above radiation-sensitive composition is preferably filtered using a filter with a pore size of approximately 0.05 μm to 0.40 μm. The solid content concentration of the above radiation-sensitive composition is usually 0.1% to 50% by mass, preferably 0.5% to 30% by mass, and more preferably 1% to 20% by mass.

[0208] <Pattern Forming Method> The pattern forming method according to this embodiment includes the steps of: applying the above-mentioned radiation-sensitive composition directly or indirectly to a substrate to form a resist film (hereinafter also referred to as the "resist film forming step"), exposing the resist film to light (hereinafter also referred to as the "exposure step"), and developing the exposed resist film (hereinafter also referred to as the "development step").

[0209] According to the pattern formation method described above, since the radiation-sensitive composition that exhibits excellent sensitivity, LWR, MEEF, development defect suppression, and CDU is used during pattern formation, high-quality resist patterns can be efficiently formed. The following describes each step.

[0210] [Resist Film Formation Process] In this process, a resist film is formed using the above-mentioned radiation-sensitive composition. Examples of substrates for forming this resist film include conventionally known materials such as silicon wafers, silicon dioxide wafers, and aluminum-coated wafers. Alternatively, an organic or inorganic anti-reflective film, such as those disclosed in Japanese Patent Publication No. 6-12452 or Japanese Patent Publication No. 59-93448, may be formed on the substrate. Examples of coating methods include spin coating, casting, and roll coating. After coating, pre-baking (PB) may be performed as needed to volatilize the solvent in the coating film. The PB temperature is usually 80°C to 180°C, with 100°C to 150°C being preferred. The PB time is usually 5 seconds to 600 seconds, with 10 seconds to 300 seconds being preferred.

[0211] The lower limit of the thickness of the formed resist film is preferably 10 nm, more preferably 20 nm, and even more preferably 30 nm. The upper limit of the thickness is preferably 500 nm, more preferably 400 nm, and even more preferably 300 nm. In particular, when a thick resist film is exposed to ArF excimer laser light in the exposure process described later, the lower limit of the thickness may be 100 nm, 150 nm, or 200 nm.

[0212] When performing immersion exposure, regardless of the presence or absence of water-repellent polymer additives such as the high-fluorine-content polymer in the radiation-sensitive composition, an immersion-insoluble protective film may be provided on the formed resist film to avoid direct contact between the immersion liquid and the resist film. As the immersion-protective film, either a solvent-peelable protective film that is peeled off with a solvent before the development process (see, for example, Japanese Patent Application Publication No. 2006-227632) or a developer-peelable protective film that is peeled off simultaneously with development in the development process (see, for example, International Publication No. 2005 / 069076 and International Publication No. 2006 / 035790) may be used. However, from the viewpoint of throughput, it is preferable to use a developer-peelable immersion-protective film.

[0213] [Exposure Process] In this process, the resist film formed in the resist film formation process described above is exposed by irradiating it with radiation through a photomask (and, in some cases, through an immersion liquid such as water). The radiation used for exposure can be electromagnetic waves such as visible light, ultraviolet light, far ultraviolet light, EUV (extreme ultraviolet light), X-rays, and gamma rays, depending on the line width of the desired pattern; electron beams, alpha rays, and other charged particle beams. Among these, far ultraviolet light, electron beams, and EUV are preferred, ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), electron beams, and EUV are more preferred, and electron beams and EUV with wavelengths of 50 nm or less, which are positioned as next-generation exposure technologies, are even more preferred.

[0214] When exposure is performed by immersion lithography, the immersion liquid used can be, for example, water or a fluorine-based inert liquid. The immersion liquid is preferably transparent to the exposure wavelength and has the smallest possible temperature coefficient of refractive index to minimize distortion of the optical image projected onto the film. In particular, when the exposure light source is ArF excimer laser light (wavelength 193 nm), in addition to the above considerations, water is preferred due to its availability and ease of handling. When water is used, a small amount of an additive that reduces the surface tension of the water and increases its surfactant properties may be added. This additive is preferably one that does not dissolve the resist film on the wafer and has negligible effect on the optical coating on the underside of the lens. Distilled water is preferred as the water used.

[0215] After the exposure described above, it is preferable to perform a post-exposure bake (PEB) to promote the dissociation of acid-dissociable groups of polymers, etc., in the exposed portion of the resist film by the acid generated from the radiation-sensitive acid generator during exposure. This PEB creates a difference in solubility in the developer between the exposed and unexposed portions. The PEB temperature is usually 60°C to 160°C, with 80°C to 140°C being preferred. The PEB time is usually 5 seconds to 600 seconds, with 10 seconds to 300 seconds being preferred.

[0216] [Development Process] In this process, the resist film exposed in the exposure process described above is developed. This allows for the formation of a predetermined resist pattern. After development, it is common to wash the film with a rinsing solution such as water or alcohol and then dry it.

[0217] Examples of developers used in the above-mentioned development include, in the case of alkaline development, an alkaline aqueous solution containing at least one alkaline compound 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.

[0218] Furthermore, in the case of organic solvent development, examples of organic solvents include hydrocarbon solvents, ether solvents, ester solvents, ketone solvents, alcohol solvents, or solvents containing organic solvents. Examples of the above organic solvents include one or more of the solvents listed above as solvents for the radiation-sensitive composition. Among these, ether solvents, ester solvents, and ketone solvents are preferred. As for ether solvents, glycol ether solvents are preferred, and ethylene glycol monomethyl ether and propylene glycol monomethyl ether are more preferred. As for ester solvents, acetate ester solvents are preferred, and n-butyl acetate and amyl acetate are more preferred. As for ketone solvents, chain ketones are preferred, and 2-heptanone is more preferred. The content of organic solvents 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 organic solvents in the developer include water and silicone oil.

[0219] As mentioned above, either an alkaline developer or an organic solvent developer may be used as the developer. The appropriate choice can be made depending on whether a positive or negative pattern is desired.

[0220] Examples of development methods include immersing the substrate in a tank filled with developer solution for a certain period of time (dip method), developing by puddling the developer solution onto the substrate surface using surface tension and letting it remain still for a certain period of time (paddle method), spraying the developer solution onto the substrate surface (spray method), and continuously dispensing the developer solution while scanning a developer solution dispensing nozzle at a constant speed onto a substrate rotating at a constant speed (dynamic dispensing method).

[0221] <<Compounds>> Another compound according to the present invention is represented by the following formula (1-1). (In formula (1-1), R １ L is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. １ R is a divalent linking group having 1 to 5 carbon atoms. ２R is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. ３１ This refers to a monovalent organic group having 3 to 18 carbon atoms that contains a lactone structure. (However, the ester bond in a monovalent organic group is located between carbon atoms.)

[0222] The above R １ , L １ , R ２ This is equivalent to equation (1) above.

[0223] R ３１ In this, the monovalent organic group having 3 to 18 carbon atoms is R in formula (1) above. ２ Among the monovalent organic groups having 1 to 20 carbon atoms shown, those with the corresponding number of carbon atoms can be suitably adopted.

[0224] R ３１ The lactone structure in this is R in formula (1) above. ３ The lactone structure shown can be suitably adopted.

[0225] As for the compound, among the compounds represented by the above formula (1) shown in the above structural unit (M), R in formula (1) ３ However, preferred examples include monovalent organic groups having 3 to 18 carbon atoms that contain a lactone structure.

[0226] ≪Polymers≫ A polymer according to another embodiment of the present invention includes structural units derived from the compound represented by formula (1-1) above. The polymer is, among polymers (A) above, R in formula (1) above. ３ However, polymers containing a structural unit which is a monovalent organic group having 3 to 18 carbon atoms and a lactone structure can be preferred.

[0227] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples. The methods for measuring various physical properties are shown below.

[0228] [Weight-average molecular weight (Mw) and number-average molecular weight (Mn)] The Mw and Mn of the polymer were measured under the conditions described above. The degree of dispersion (Mw / Mn) was calculated from the measured results of Mw and Mn.

[0229] [ １３[C-NMR analysis] Polymer １３ C-NMR analysis was performed using a nuclear magnetic resonance spectrometer (JEOL Ltd.'s "JNM-Delta400").

[0230] <Synthesis of Compounds (Monomers)> [Synthesis Example 1] (Synthesis of Monomer (M-1)) Compound (M-1) was synthesized according to the following synthesis scheme.

[0231] 20.0 mmol of α-amino-γ-butyrolactone, 2.0 mmol of triethylamine, 22.0 mmol of chloroacetyl chloride, and 50 g of dichloromethane were added to a reaction vessel and stirred at room temperature for 10 hours. After that, water was added to the reaction solution to terminate the reaction, and then dichloromethane was added for extraction, and the organic layer was separated. The obtained organic layer was washed with saturated sodium chloride aqueous solution. After drying with sodium sulfate, the solvent was removed by distillation to obtain the compound represented by the above formula (M-1-a) (hereinafter also referred to as "compound (M-1-a)") in good yield.

[0232] To the above (M-1-a), 30.0 mmol of methacrylic acid, 40.0 mmol of potassium carbonate, 4.0 mmol of potassium iodide, and 50 g of DMF were added and the mixture was stirred at 60°C for 5 hours. Then, saturated ammonium chloride aqueous solution was added to the reaction solution to terminate the reaction, and ethyl acetate was added for extraction, separating the organic layer. The obtained organic layer was washed twice with saturated sodium chloride aqueous solution. After drying with sodium sulfate, the solvent was removed by distillation, and the compound represented by the above formula (M-1) (hereinafter also referred to as "monomer (M-1)") was obtained in good yield by purification by column chromatography.

[0233] [Synthesis Examples 2-15] (Synthesis of monomer (M-2) to monomer (M-15)) Compounds represented by the following formulas (M-2) to (M-15) were synthesized in the same manner as in Synthesis Example 1, except that the raw materials and precursors were changed as appropriate. Hereinafter, the compounds represented by formulas (M-2) to (M-15) may be referred to as "compound (M-2)" to "compound (M-15)" or "monomer (M-2)" to "monomer (M-15)," respectively.

[0234]

[0235] The monomers used in the synthesis of each polymer, excluding monomers (M-1) to (M-15), are shown below. Hereafter, the compounds represented by formulas (m-1) to (m-24) may be referred to as "compound (m-1)" to "compound (m-24)" or "monomer (m-1)" to "monomer (m-24)," respectively.

[0236]

[0237]

[0238] <Synthesis of Polymers> In the following synthesis examples, unless otherwise specified, "parts by mass" refers to the value when the total mass of the monomers used in the synthesis of each polymer is set to 100 parts by mass, and "mol%" refers to the value when the total number of moles of the monomers used in the synthesis of each polymer is set to 100 mol%.

[0239] [Synthesis Example 16] (Synthesis of Polymer (A-1)) Monomer (M-1), monomer (m-1), and monomer (m-5) were dissolved in 2-butanone (200 parts by mass) in a molar ratio of 10 / 50 / 40 (mol%), and AIBN (azobisisobutyronitrile) (5 mol% relative to the total 100 mol% of monomers used) was added as an initiator to prepare a monomer solution. 2-butanone (100 parts by mass) was placed in an empty reaction vessel, and after purging with nitrogen for 30 minutes, the reaction vessel was heated to 80°C, and the monomer solution was added dropwise over 3 hours while stirring. The start of the dropwise addition was defined as the start time of the polymerization reaction, and the polymerization reaction was carried out for 6 hours. After the completion of the polymerization reaction, the polymerization solution was cooled to below 30°C by water cooling. The cooled polymerization solution was added to methanol (2,000 parts by mass), and the precipitated white powder was filtered off. The filtered white powder was washed twice with methanol, filtered again, and dried at 50°C for 10 hours to obtain a white powdery polymer (A-1) (yield: 85%). The Mw of polymer (A-1) was 6,600, and the Mw / Mn ratio was 1.61. １３ 13C-NMR analysis revealed that the content percentages of each structural unit derived from monomer (M-1), monomer (m-1), and monomer (m-5) were 10.5 mol%, 49.3 mol%, and 40.2 mol%, respectively.

[0240] [Synthesis Examples 17-38] (Synthesis of Polymers (A-2) to (A-23)) Polymers (A-2) to (A-23) were synthesized in the same manner as in Synthesis Example 16, except that monomers of the types and proportions shown in Tables 1 and 2 below were used. The content percentage (mol%) and physical properties (Mw, Mw / Mn) of each structural unit of the obtained polymers are shown in Tables 1 and 2 below. Note that "-" in Tables 1 to 4 below indicates that the corresponding monomer was not used.

[0241]

[0242]

[0243] [Synthesis Example 39] (Synthesis of Polymer (A-24)) Monomer (M-1), monomer (m-1), and monomer (m-18) were dissolved in 1-methoxy-2-propanol (200 parts by mass) in a molar ratio of 20 / 50 / 30 (mol%), and AIBN (5 mol%) was added as an initiator to prepare monomer solutions. 100 parts by mass of 1-methoxy-2-propanol was placed in a reaction vessel, and after purging with nitrogen for 30 minutes, the reaction vessel was heated to 80°C, and the monomer solutions were added dropwise over 3 hours while stirring. The start of the dropwise addition was defined as the start time of the polymerization reaction, and the polymerization reaction was carried out for 6 hours. After the polymerization reaction was completed, the polymerization solution was cooled to below 30°C by water cooling. The cooled polymerization solution was added to hexane (2,000 parts by mass), and the precipitated white powder was filtered off. The filtered white powder was washed twice with hexane, filtered again, and dissolved in 1-methoxy-2-propanol (300 parts by mass). Then, methanol (500 parts by mass), triethylamine (50 parts by mass), and ultrapure water (10 parts by mass) were added, and the hydrolysis reaction was carried out at 70°C for 6 hours with stirring. After the reaction was complete, the residual solvent was removed by distillation. The obtained solid was dissolved in acetone (100 parts by mass) and added dropwise to water (500 parts by mass) to solidify the resin. The obtained solid was filtered and dried at 50°C for 13 hours to obtain a white powdery polymer (A-24) (yield: 65%). The Mw of polymer (A-24) was 7,000, and the Mw / Mn ratio was 1.61. １３13C-NMR analysis revealed that the content percentages of each structural unit derived from monomer (M-1), monomer (m-1), and monomer (m-18) were 20.3 mol%, 50.2 mol%, and 29.5 mol%, respectively.

[0244] [Synthesis Examples 40-45] (Synthesis of Polymers (A-25) to (A-30)) Polymers (A-25) to (A-30) were synthesized in the same manner as in Synthesis Example 39, except that monomers of the types and proportions shown in Table 3 below were used. The content percentage (mol%) and physical properties (Mw and Mw / Mn) of each structural unit of the obtained polymers are also shown in Table 3 below.

[0245]

[0246] [Synthesis Example 46] (Synthesis of Polymer (E-1)) Monomer (m-2) and monomer (m-14) were dissolved in 2-butanone (200 parts by mass) to a molar ratio of 30 / 70 (mol%), and AIBN (2 mol%) was added as an initiator to prepare a monomer solution. 2-butanone (100 parts by mass) was placed in a reaction vessel, and after purging with nitrogen for 30 minutes, the temperature inside the reaction vessel was set to 80°C, and the monomer solution was added dropwise over 3 hours while stirring. The start of the dropwise addition was defined as the start time of the polymerization reaction, and the polymerization reaction was carried out for 6 hours. After the completion of the polymerization reaction, the polymerization solution was cooled to below 30°C by water cooling. The solvent was replaced with acetonitrile (400 parts by mass), and hexane (100 parts by mass) was added and stirred, and the acetonitrile layer was recovered. This process was repeated three times. By replacing the solvent with propylene glycol monomethyl ether acetate, a solution of polymer (E-1) was obtained (yield: 87%). The Mw of polymer (E-1) was 14,800, and the Mw / Mn ratio was 1.70. Also, １３ ¹³C-NMR analysis revealed that the content of each structural unit derived from monomer (m-2) and monomer (m-14) was 29.7 mol% and 70.3 mol%, respectively.

[0247] [Synthesis Examples 47-51] (Synthesis of Polymers (E-2) to (E-6)) Polymers (E-2) to (E-6) were synthesized in the same manner as in Synthesis Example 46, except that monomers of the types and proportions shown in Table 4 below were used. The content percentage (mol%) and physical properties (Mw and Mw / Mn) of each structural unit of the obtained polymers are also shown in Table 4 below.

[0248]

[0249] <Preparation of Radiation-Sensitive Compositions> The components other than polymers (A) and (E) used in the preparation of each radiation-sensitive composition are shown below.

[0250] • Radiation-sensitive acid generator (B) B-1 to B-8: Compounds represented by the following formulas (B-1) to (B-8)

[0251]

[0252] • Acid diffusion control agent (C) C-1 to C-6: Compounds represented by the following formulas (C-1) to (C-6)

[0253]

[0254] • Solvent (D) D-1: Propylene glycol monomethyl ether acetate D-2: Propylene glycol monomethyl ether D-3: γ-butyrolactone D-4: Ethyl lactate

[0255] <Preparation of positive-type radiation-sensitive composition for ArF exposure> [Example 1] A radiation-sensitive composition (J-1) was prepared by mixing 100 parts by mass of (A-1) as polymer (A), 10.0 parts by mass of (B-1) as radiation-sensitive acid generator (B), 6.0 parts by mass of (C-1) as acid diffusion control agent (C), 3.0 parts by mass (solids) of (E-1) as polymer (E), and 3,400 parts by mass of a mixed solvent (D) with (D-1) / (D-2) / (D-3) = 1500 / 1700 / 200 (parts by mass), and filtering the mixture through a membrane filter with a pore size of 0.2 μm.

[0256] [Examples 2-37 and Comparative Examples 1-5] Radiation-sensitive compositions (J-2) to (J-37) and (CJ-1) to (CJ-5) were prepared in the same manner as in Example 1, except that the components of the types and amounts shown in Tables 5 and 6 below were used.

[0257]

[0258]

[0259] <Formation of a resist pattern using a positive-type radiation-sensitive composition for ArF lithography> An anti-reflective underlayer film formation composition ("ARC66" from Brewer Science) was applied to a 12-inch silicon wafer using a spin coater ("CLEAN TRACK ACT12" from Tokyo Electron Limited), and then heated at 205°C for 60 seconds to form an anti-reflective underlayer film with an average thickness of 100 nm. An anti-reflective underlayer film was then applied to this anti-reflective underlayer film using the same spin coater, and pre-bake (PB) was performed at 100°C for 60 seconds. Subsequently, a resist film with an average thickness of 120 nm was formed by cooling at 23°C for 30 seconds. Next, the resist film was exposed to a 50 nm line-and-space mask pattern using an ArF excimer laser immersion lithography system (ASML's "TWINSCAN XT-1900i") under optical conditions of NA = 1.35 and Annular (σ = 0.8 / 0.6). After exposure, post-exposure baking (PEB) was performed at 100°C for 60 seconds. Subsequently, the resist film was alkaline developed using a 2.38 mass% TMAH aqueous solution as the alkaline developer. After development, it was washed with water and further dried to form a positive-type resist pattern (50 nm line-and-space pattern).

[0260] <Evaluation> The sensitivity, LWR, number of development defects, and MEEF of resist patterns formed using a positive-type radiation-sensitive composition for ArF exposure were evaluated according to the following method. The results are shown in Table 7 below. A scanning electron microscope (Hitachi High-Technologies Corporation's "CG-5000") was used to measure the length of the resist patterns.

[0261] [Sensitivity] In forming a resist pattern using a positive-type radiation-sensitive composition for ArF exposure, the exposure amount used to form a 50 nm line-and-space pattern is defined as the optimal exposure amount, and this optimal exposure amount is defined as the sensitivity (mJ / cm²). ２ The sensitivity was set to 30 mJ / cm². ２ The following cases are evaluated as "good" and 30 mJ / cm². ２ If it exceeded this value, it was rated as "poor."

[0262] [LWR] The mask size was adjusted to form a 50 nm line-and-space pattern by irradiating with the optimal exposure amount determined in the sensitivity evaluation above, and a resist pattern was formed. The formed resist pattern was observed from the top of the pattern using a scanning electron microscope. The variation in line width was measured at a total of 500 points, and the 3-sigma value was determined from the distribution of these measurements, and this 3-sigma value was defined as LWR (nm). A smaller LWR value indicates less line roughness and better quality. An LWR of 3.5 nm or less was evaluated as "good," and an LWR greater than 3.5 nm was evaluated as "poor."

[0263] [Development Defect Count] A resist film was exposed at the optimal exposure level to form a 50 nm line-and-space pattern, and this was used as a wafer for defect inspection. The number of defects on this wafer was measured using a defect inspection device (KLA-Tencor's "KLA2810"). Defects with a diameter of 50 μm or less were judged to be originating from the resist film, and their number was calculated. After development, the defect count was evaluated as "good" if the number of defects judged to be originating from the resist film was 50 or less, and as "poor" if it exceeded 50.

[0264] [MEEF] For resist patterns resolved by irradiating with the optimal exposure amount described above, the slope of the straight line was calculated when the line width of the resist pattern formed using mask patterns with line widths of 52 nm, 54 nm, 56 nm, 58 nm, and 60 nm was plotted on the vertical axis and the size of the mask pattern on the horizontal axis, and this was defined as MEEF. A MEEF value closer to 1 indicates better mask reproducibility. MEEF values ​​of 2 or less were evaluated as "good," and values ​​greater than 2 were evaluated as "poor."

[0265]

[0266] As is clear from the results in Table 7, the radiation-sensitive composition of the example showed good sensitivity, LWR, development defect count, and MEEF when used in positive-type ArF exposure. In contrast, the comparative example showed inferior characteristics compared to the example. Therefore, it can be said that when the radiation-sensitive composition of the example is used in ArF exposure, it is possible to form a resist pattern with high sensitivity and good LWR, development defect count, and MEEF.

[0267] <Preparation of positive-type radiation-sensitive composition for extreme ultraviolet (EUV) exposure> [Example 38] 100 parts by mass of (A-24) as polymer (A), 30.0 parts by mass of (B-1) as radiation-sensitive acid generator (B), 20.0 parts by mass of (C-1) as acid diffusion control agent (C), 3.0 parts by mass of (E-6) as polymer (E), and 6,100 parts by mass of a mixed solvent (D) of (D-1) / (D-2) / (D-4) = 1500 / 4500 / 100 (parts by mass) were mixed and filtered through a membrane filter with a pore size of 0.2 μm to prepare a radiation-sensitive composition (J-38).

[0268] [Examples 39-46 and Comparative Examples 6-9] Radiation-sensitive compositions (J-39) to (J-46) and (CJ-6) to (CJ-9) were prepared in the same manner as in Example 38, except that the components of the types and amounts shown in Table 8 below were used.

[0269]

[0270] <Formation of a resist pattern using a positive-type radiation-sensitive composition for EUV exposure> An anti-reflective underlayer film (ARC66 from Brewer Science) was applied to a 12-inch silicon wafer using a spin coater (CLEAN TRACK ACT12 from Tokyo Electron Limited), and then heated at 205°C for 60 seconds to form an anti-reflective underlayer film with an average thickness of 105 nm. The positive-type radiation-sensitive composition for EUV exposure was applied to this anti-reflective underlayer film using the same spin coater, and PB (plate blot) was performed at 130°C for 60 seconds. Subsequently, a resist film with an average thickness of 65 nm was formed by cooling at 23°C for 30 seconds. Next, the resist film was exposed using an EUV lithography system (ASML's "NXE3300") with NA = 0.33, illumination conditions: Conventional s = 0.89, and mask: imecDEFECT32FFR02. After exposure, PEB was performed at 120°C for 60 seconds. Subsequently, the resist film was alkaline developed using a 2.38 mass% TMAH aqueous solution as the alkaline developer. After development, it was washed with water and then dried to form a positive-type resist pattern (20 nm line and space pattern).

[0271] <Evaluation> The sensitivity, LWR, number of development defects, and MEEF of resist patterns formed using a positive-type radiation-sensitive composition for EUV exposure were evaluated according to the method described below. The results are shown in Table 9 below. A scanning electron microscope (Hitachi High-Technologies Corporation's "CG-5000") was used to measure the length of the resist patterns.

[0272] [Sensitivity] In forming a resist pattern using a positive-type radiation-sensitive composition for EUV exposure, the exposure amount used to form a 20 nm line-and-space pattern is defined as the optimal exposure amount, and this optimal exposure amount is defined as the sensitivity (mJ / cm²). ２ The sensitivity was set to 40 mJ / cm². ２ In the following cases, it is considered "good" and 40 mJ / cm². ２ If it exceeded this value, it was rated as "poor."

[0273] [LWR] The mask size was adjusted to form a 20 nm line-and-space pattern by irradiating with the optimal exposure amount determined in the sensitivity evaluation above, and a resist pattern was formed. The formed resist pattern was observed from the top of the pattern using the scanning electron microscope described above. The variation in line width was measured at a total of 500 points, and the 3-sigma value was determined from the distribution of these measurements, and this 3-sigma value was defined as LWR (nm). A smaller LWR value indicates less line jaggedness and better quality. An LWR of 4.0 nm or less was evaluated as "good," and an LWR greater than 4.0 nm was evaluated as "poor."

[0274] [Development Defect Count] A resist film was exposed at the optimal exposure level to form a 20 nm line and space, and this was used as a wafer for defect inspection. The number of defects on this wafer was measured using a defect inspection device (KLA-Tencor's "KLA2810"). Defects with a diameter of 50 μm or less were judged to be originating from the resist film, and their number was calculated. After development, the defect count was evaluated as "good" if the number of defects judged to be originating from the resist film was 50 or less, and as "poor" if it exceeded 50.

[0275] [MEEF] For resist patterns resolved by irradiating with the optimal exposure amount described above, the slope of the straight line was calculated when the line width of the resist pattern formed using mask patterns with line widths of 22 nm, 24 nm, 26 nm, 28 nm, and 30 nm was plotted on the vertical axis and the size of the mask pattern on the horizontal axis, and this was defined as MEEF. A MEEF value closer to 1 indicates better mask reproducibility. MEEF values ​​of 2 or less were evaluated as "good," and values ​​greater than 2 were evaluated as "poor."

[0276]

[0277] As is clear from the results in Table 9, the radiation-sensitive compositions of the examples showed good sensitivity, LWR, development defect count, and MEEF when used in EUV exposure. In contrast, the comparative examples exhibited inferior characteristics compared to the examples.

[0278] <Preparation of a negative-type radiation-sensitive composition for ArF exposure, and formation and evaluation of a resist pattern using this composition> [Example 47] A radiation-sensitive composition (J-47) was prepared by mixing 100 parts by mass of (A-1) as polymer (A), 7.0 parts by mass of (B-3) as radiation-sensitive acid generator (B), 4.0 parts by mass of (C-4) as acid diffusion control agent (C), 4.0 parts by mass of (E-3) as polymer (E) (solid content), and 3,230 parts by mass of a mixed solvent (D) with a mass ratio of (D-1) / (D-2) / (D-3) = 2240 / 960 / 30. The mixture was then filtered through a membrane filter with a pore size of 0.2 μm.

[0279] On a 12-inch silicon wafer, a base layer anti-reflective coating composition ("ARC66" from Brewer Science) was applied using a spin coater ("CLEAN TRACK ACT12" from Tokyo Electron Limited), and then heated at 205°C for 60 seconds to form a base layer anti-reflective coating with an average thickness of 85 nm. On this base layer anti-reflective coating, an ArF exposure negative type radiation-sensitive composition (J-47) was applied using the same spin coater, and pre-bake (PB) was performed at 90°C for 60 seconds. Subsequently, a resist film with an average thickness of 90 nm was formed by cooling at 23°C for 30 seconds. Next, the resist film was exposed using an ArF excimer laser immersion lithography system (ASML's "TWINSCAN XT-1900i") under optical conditions of NA = 1.35 and Annular (σ = 0.8 / 0.6) via a mask pattern with 40 nm spacing and 105 nm pitch. After exposure, post-exposure baking (PEB) was performed at 90°C for 60 seconds. Subsequently, the resist film was developed using n-butyl acetate as the organic solvent developer and dried to form a negative-type resist pattern (mask pattern with 60 nm holes and 120 nm pitch).

[0280] For resist patterns using the above-mentioned ArF exposure negative-type radiation-sensitive composition, sensitivity, number of development defects, and MEEF were evaluated in the same manner as for resist patterns using the above-mentioned ArF exposure positive-type radiation-sensitive composition. Furthermore, CDU was evaluated according to the method described below.

[0281] [CDU] The optimal exposure dose determined in the sensitivity evaluation above was used to form 60 nm holes and 120 nm pitch contact holes. The formed resist pattern was observed from the top using the scanning electron microscope described above. The variation of the contact holes was measured at a total of 500 points, and the 3-sigma value was determined from the distribution of these measurements. This 3-sigma value was defined as the CDU (nm). A smaller CDU value indicates less roughness of the holes and a better quality. A CDU of less than 3.5 nm was evaluated as "good," and a CDU of 3.5 nm or more was evaluated as "poor."

[0282] As a result, the radiation-sensitive composition of Example 47 showed good sensitivity, CDU, development defect count, and MEEF even when a negative-type resist pattern was formed by ArF exposure.

[0283] <Preparation of a negative-type radiation-sensitive composition for EUV exposure, formation and evaluation of a resist pattern using this composition> [Example 48] A radiation-sensitive composition (J-48) was prepared by mixing 100 parts by mass of (A-26) as polymer (A), 20.0 parts by mass of (B-2) as a radiation-sensitive acid generator (B), 15.0 parts by mass of (C-5) as an acid diffusion control agent (C), 5.0 parts by mass of (E-6) as polymer (E), and 6,000 parts by mass of a mixed solvent (D) with a ratio of (D-1) / (D-2) = 1000 / 5000 (by mass ratio), and filtering the mixture through a membrane filter with a pore size of 0.2 μm.

[0284] Onto a 12-inch silicon wafer, using a spin coater ("CLEAN TRACK ACT12" from Tokyo Electron Limited), a composition for forming an anti-reflection film for the lower layer ("ARC66" from Brewer Science, Inc.) was applied, and then heated at 205 °C for 60 seconds to form an anti-reflection film for the lower layer with an average thickness of 105 nm. Onto this anti-reflection film for the lower layer, a negative-type radiation-sensitive composition for EUV lithography ("J-48") was applied using the above spin coater, and PB was performed at 130 °C for 60 seconds. Thereafter, by cooling at 23 °C for 30 seconds, a resist film with an average thickness of 55 nm was formed. Next, with respect to this resist film, using an EUV exposure apparatus ("NXE3300" from ASML), exposure was performed with NA = 0.33, illumination condition: Conventional s = 0.89, mask: imecDEFECT32FFR15. After exposure, PEB was performed at 120 °C for 60 seconds. Thereafter, the resist film was developed with an organic solvent developer, n-butyl acetate, and dried to form a negative-type resist pattern (contact hole pattern with 25-nm holes and 40-nm pitch).

[0285] With respect to the resist pattern using the above negative-type radiation-sensitive composition for EUV lithography, evaluation was performed in the same manner as the evaluation of the resist pattern using the above negative-type radiation-sensitive composition for ArF lithography. As a result, even when the radiation-sensitive composition of Example 48 formed a negative-type resist pattern by EUV exposure, the sensitivity, CDU, number of development defects, and MEEF were good.

[0286] According to the radiation-sensitive composition, pattern formation method, compound, and polymer described above, a resist pattern with good sensitivity to exposure light and excellent LWR, CDU, number of development defects, and MEEF can be formed. Therefore, these can be suitably used for semiconductor device processing processes and the like, which are expected to further miniaturize in the future.

Claims

A polymer (A) containing a structural unit (M) derived from a compound represented by the following formula (1), Solvent (D) and A radiation-sensitive composition containing the following: (In formula (1), R １ This is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. L １ This is a divalent linking group having 1 to 5 carbon atoms. R ２ This is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. R ３ (It is a monovalent organic group with 3 to 20 carbon atoms that contains an ester bond between carbon atoms.) 　 In the above formula (1), L 1 The radiation-sensitive composition according to claim 1, wherein the linking group is a chain-like linking group. 　 In the above formula (1), L 1 The radiation-sensitive composition according to claim 1, wherein is a divalent hydrocarbon group having 1 to 3 carbon atoms. 　 In the above formula (1), L 1 The radiation-sensitive composition according to claim 1, wherein is a methanediyl group. 　 In the above formula (1), R ２ The radiation-sensitive composition according to claim 1, wherein is a hydrogen atom. 　 In the above formula (1), R ３ The radiation-sensitive composition according to claim 1, wherein is an organic group containing a lactone structure. 　 The radiation-sensitive composition according to any one of claims 1 to 6, wherein the content of the structural unit (M) in the total structural units constituting the polymer (A) is 1 mol% or more and 40 mol% or less. 　 The radiation-sensitive composition according to any one of claims 1 to 6, wherein the polymer (A) further comprises a structural unit (I) having an acid-dissociable group. A radiation-sensitive composition according to any one of claims 1 to 6, further comprising a radiation-sensitive acid generator. 　 A radiation-sensitive composition according to any one of claims 1 to 6, further comprising an acid diffusion control agent. 　 A step of forming a resist film by directly or indirectly applying the radiation-sensitive composition according to any one of claims 1 to 6 to a substrate, The process of exposing the above-mentioned resist film, The process involves developing the exposed resist film with a developer solution. A pattern formation method, including the following. 　 The pattern forming method according to claim 11, wherein the exposure is performed using extreme ultraviolet light or an electron beam. 　 A compound represented by the following formula (1-1). (In formula (1-1), R １ These are a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. L １ This is a divalent linking group having 1 to 5 carbon atoms. R ２ This is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. R ３１ This refers to a monovalent organic group having 3 to 18 carbon atoms that contains a lactone structure. (However, the ester bond in a monovalent organic group is located between carbon atoms.) 　 A polymer comprising a structural unit derived from the compound described in claim 13.

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