Radiation-sensitive composition, pattern formation method, and compound

Abstract

Provided are a radiation-sensitive composition that can exhibit, at sufficient levels when forming a pattern, sensitivity, CDU, LWR, MEEF, EL, development defect suppression properties, pattern circularity, pattern rectangularity, and DOF; a pattern formation method; and a compound. This radiation-sensitive composition comprises a compound represented by formula (1), a polymer including a structural unit (I) having an acid-dissociable group, and a solvent. (In the formula, W represents a substituted or unsubstituted ring structure including an acetal structure. L represents a substituted or unsubstituted divalent hydrocarbon group having 1-5 carbon atoms, or a group including a divalent heteroatom-containing group between carbon-carbon in said hydrocarbon group. R1 represents a hydrogen atom, -CN, -NO2, -F, -CF2Ra, -SO2Rb, -CORc, or a monovalent organic group (a). Z+ and Zg + each represent a monovalent organic cation. Lg represents a single bond, a divalent heteroatom-containing group, or a divalent organic group having 1-20 carbon atoms. A- represents -COO- or -SO3 -.)

Description

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

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

[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 photoacid generators, which are the main components of resist compositions, various technologies have been proposed to improve sensitivity, resolution, and other aspects (see International Publication No. 2024 / 143131).

[0005] International Publication No. 2024 / 143131

[0006] With the advancement of next-generation technologies, there is a growing demand for resist performance that is equivalent to or better than conventional standards in terms of sensitivity, CDU (Critical Dimension Uniformity), LWR (Line Width Roughness), MEEF (Mask Error Enhancement Factor), EL (Exposure Latitude), development defect suppression, pattern circularity, pattern rectangularity, DOF (Depth of Focus), etc.

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

[0008] As a result of intensive studies to solve this problem, the present inventors have found that the above object can be achieved by adopting the following configuration, and have completed the present invention.

[0009] That is, in one embodiment, the present invention relates to a radiation-sensitive composition containing a compound represented by the following formula (1) (hereinafter also referred to as "compound (1)"), a polymer containing a structural unit (I) having an acid dissociable group, and a solvent. (In formula (1), W is a substituted or unsubstituted cyclic structure containing an acetal structure. L is a substituted or unsubstituted divalent hydrocarbon group having 1 to 5 carbon atoms, or a group containing a divalent heteroatom-containing group between carbon-carbon atoms of the hydrocarbon group. R １ is a hydrogen atom, -CN, -NO ２ , -F, -CF ２ R ａ , -SO ２ R ｂ , -COR ｃ , or a monovalent organic group (a) having 1 to 20 carbon atoms other than -CN, -CF ２ R ａ , -SO ２ R ｂ , -COR ｃ or -CF ３ outside. R ａ is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. R ｂ and R ｃ are each independently a monovalent organic group having 1 to 20 carbon atoms. Z ＋ is a monovalent organic cation. L ｇ is a single bond, a divalent heteroatom-containing group, or a divalent organic group having 1 to 20 carbon atoms. A - is -COO - or -SO ３ - is. Z ｇ＋ (where g is a monovalent organic cation; g is 0 or 1.)

[0010] The radiation-sensitive composition contains compound (1) as a radiation-sensitive acid generator, and therefore exhibits excellent sensitivity, CDU, LWR, MEEF, EL, development defect suppression, pattern circularity, pattern rectangularity, and DOF during pattern formation. The reason for this is presumed to be as follows, although it is not bound by any theory.

[0011] In compound (1), an electron-withdrawing and polar cyano group is bonded to the carbon atom adjacent to the sulfur atom of the sulfonate anion. This allows compound (1) to generate a sufficiently strong acid, enabling it to exhibit the given resist properties and improve dissolution contrast. Furthermore, since the carbon atom adjacent to the sulfur atom of the sulfonate anion forms a chain structure, the generated acid can easily approach the acid-dissociable group, promoting acid dissociation and suppressing development defects. In addition, the acetal structure introduced into compound (1) is deprotected by the generated acid to form a diol. This allows for control of solubility, and acid diffusion is suppressed by the interaction between the diol and other components. Moreover, compound (1) has a relatively rigid structure with a short chain length between the cyclic structure and the sulfonate anion, which also allows for appropriate control of acid diffusion, and it is particularly excellent in controlling acid diffusion in the overexposed region at the top of the pattern. Furthermore, by reducing the fluorine atom content, dispersibility in the resist film can be improved and the environmental impact can be limited. It is presumed that the above-mentioned resist properties are achieved through the combined action of these factors.

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

[0013] In this pattern formation method, since the above-mentioned radiation-sensitive composition, which is excellent in sensitivity, CDU, LWR, MEEF, EL, development defect suppression, pattern circularity, pattern rectangularity, and DOF, is used during pattern formation, high-quality resist patterns can be efficiently formed.

[0014] In yet another embodiment, the present invention relates to a compound represented by the following formula (1). (In formula (1), W is a substituted or unsubstituted cyclic structure containing an acetal structure. L is a substituted or unsubstituted divalent hydrocarbon group having 1 to 5 carbon atoms, or a group containing a divalent heteroatom between the carbon atoms of the hydrocarbon group. １ These are hydrogen atoms, -CN, and -NO ２ -F, -CF ２ R ａ , -SO ２ R ｂ ,-COR ｃ , or -CN, -CF ２ R ａ , -SO ２ R ｂ ,-COR ｃ Or -CF ３ (a) is a monovalent organic group with 1 to 20 carbon atoms other than R. ａ R is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. ｂ and R ｃ Each of these is independently a monovalent organic group having 1 to 20 carbon atoms. １ If multiple R １ They are the same or different. １ Z is an integer between 1 and 4. ＋ L is a monovalent organic cation. ｇ This refers to a single bond, a divalent heteroatom-containing group, or a divalent organic group having 1 to 20 carbon atoms. - -COO - or -SO ３ - That is. Z ｇ ＋ (where g is a monovalent organic cation; g is 0 or 1.)

[0015] Because the compound has the specific structure described above, it is suitable for radiation-sensitive compositions where excellent sensitivity, CDU, LWR, MEEF, EL, development defect suppression, pattern circularity, pattern rectangularity, and DOF are required during pattern formation.

[0016] In this specification, "condensed ring" refers to a polycyclic structure formed by two adjacent rings sharing one edge (two adjacent atoms). "Spiro ring" refers to a polycyclic structure formed by two adjacent rings sharing one carbon atom. "Ring assembly" refers to a structure in which two rings are joined by a single bond. "Bridged alicyclic hydrocarbon structure" refers to a polycyclic alicyclic hydrocarbon structure in which two non-adjacent carbon atoms constituting the alicyclic are bonded together by a linking group containing one or more carbon atoms. "Organic group" refers to a group containing at least one carbon atom.

[0017] 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.

[0018] <Radiation-sensitive composition> The radiation-sensitive composition according to this embodiment (hereinafter also simply referred to as "composition") contains compound (1), a polymer containing a structural unit (I) having an acid-dissociable group, and a solvent. It further contains an acid diffusion control agent as needed. The above composition may contain other optional components as long as they do not impair the effects of the present invention.

[0019] (Compound) Compound (1) is a compound represented by the above formula (1), and has the function of generating an acid that dissociates the above acid-dissociable group by exposure.

[0020] The cyclic structure containing the acetal structure represented by W is not particularly limited as long as the acetal structure is incorporated into the cyclic structure as the main framework. Therefore, the acetal structure also exhibits a cyclic structure (cyclic acetal structure).

[0021] The acetal structure in W is preferably the structure represented by the following formula (α) (i.e., a cyclic acetal structure). In the following formula (α), the bonds with other structures in compound (1) are omitted. (In equation (α), n is an integer between 1 and 3.)

[0022] n is preferably 1 or 2, and more preferably 1.

[0023] Examples of cyclic structures in W include combinations of the above-mentioned cyclic acetal structure and at least one cyclic structure selected from the group consisting of alicyclic structures, aromatic ring structures, aliphatic heterocyclic structures, and aromatic heterocyclic structures. Examples of these combinations of cyclic structures include fused ring structures, spiro ring structures, ring aggregate structures, or combinations thereof.

[0024] Examples of the above-mentioned alicyclic structures include monocyclic or polycyclic saturated hydrocarbon structures, or monocyclic or polycyclic unsaturated hydrocarbon structures. Examples of monocyclic saturated hydrocarbon structures include monocyclic cycloalkane structures with 3 to 20 carbon atoms, such as cyclopropane, cyclobutane, cyclopentane, cyclohexane, cycloheptane, and cyclooctane. Preferred polycyclic saturated hydrocarbon structures (polycyclic cycloalkane structures) include bridged alicyclic hydrocarbon structures with 6 to 20 carbon atoms, such as norbornane, adamantane, tricyclodecane, and tetracyclododecane. Examples of monocyclic unsaturated hydrocarbon structures include monocyclic cycloalkene structures with 3 to 20 carbon atoms, such as cyclopropene, cyclobutene, cyclopentene, and cyclohexene. Examples of polycyclic unsaturated hydrocarbon structures include polycyclic cycloalkenes with 6 to 20 carbon atoms, such as norbornene, tricyclodecene, and tetracyclododen.

[0025] Examples of the above aromatic ring structures include aromatic ring structures having 3 to 40 carbon atoms, such as aromatic hydrocarbon structures having 6 to 40 carbon atoms, such as benzene, naphthalene, anthracene, phenalene, phenanthrene, pyrene, fluorene, perylene, coronene, and biphenyl; aromatic heterocyclic structures having 3 to 40 carbon atoms, such as triazole, imidazole, furan, pyrrole, thiophene, phosphole, pyrazole, oxazole, isoxazole, thiazole, pyridine, pyrazine, pyrimidine, pyridazine, and triazine; or combinations thereof.

[0026] Examples of the above-mentioned aromatic heterocyclic structures include oxygen-containing aromatic heterocyclic structures such as furan, pyran, benzofuran, and benzopyran; nitrogen-containing aromatic heterocyclic structures such as pyrrole, imidazole, pyridine, pyrimidine, pyrazine, indole, quinoline, isoquinoline, acridine, phenazine, and carbazole; sulfur-containing aromatic heterocyclic structures such as thiophene; and aromatic heterocyclic structures containing multiple heteroatoms such as thiazole, benzothiazole, thiazine, and oxazine.

[0027] Examples of the above-mentioned aliphatic heterocyclic structures include oxygen-containing aliphatic heterocyclic structures such as oxirane, tetrahydrofuran, tetrahydropyran, dioxolane (cyclic acetal), and dioxane; nitrogen-containing aliphatic heterocyclic structures such as aziridine, pyrrolidine, piperidine, and piperazine; sulfur-containing aliphatic heterocyclic structures such as thiethane, thiolane, and thian; and aliphatic heterocyclic structures containing multiple heteroatoms such as morpholine, 1,2-oxathiolane, and 1,3-oxathiolane.

[0028] Examples of the above aliphatic heterocyclic structures include structures containing lactone structures, cyclic carbonate structures, or sultone structures.

[0029] W is preferably a cyclic acetal structure, or a combination of the cyclic acetal structure and a cycloalkane structure that forms a spiro ring structure or a fused ring structure, and more preferably a combination of the cyclic acetal structure and a polycyclic cycloalkane structure that forms a spiro ring structure or a fused ring structure.

[0030] The cyclic structure represented by W in formula (1) above preferably includes either the acetal-containing substructure represented by formula (W-1) or formula (W-2) below. (In equations (W-1) and (W-2), * represents a combination with L in equation (1) above. W ２２ This represents a ring structure with 3 to 20 carbon atoms. ** represents the bonding with atoms other than the acetal-containing substructure in the cyclic structure represented by W. p1 and p2 are independently integers between 0 and 2.

[0031] In the above formula (W-2), W ２２ As the ring structure having 3 to 20 carbon atoms represented by the above formula (1), at least one ring structure selected from the group consisting of alicyclic structures, aromatic ring structures, aliphatic heterocyclic structures, and aromatic heterocyclic structures shown in W can be suitably adopted. ２２ It forms a fused ring with the five-membered ring cyclic acetal structure of formula (W-2) above.

[0032] When the cyclic structure in W has substituents, examples of substituents include halogen atoms such as fluorine, chlorine, bromine, and iodine atoms; hydroxyl groups; carboxyl groups; cyano groups; nitro groups; monovalent organic groups having 1 to 20 carbon atoms; and oxo groups (=O).

[0033] Examples of monovalent organic groups having 1 to 20 carbon atoms in substituents of the cyclic structure of W 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 terminus 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.

[0034] Examples of monovalent hydrocarbon groups having 1 to 20 carbon atoms include monovalent linear 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.

[0035] Examples of monovalent chain hydrocarbon groups having 1 to 20 carbon atoms include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, s-butyl, and t-butyl groups; alkenyl groups such as ethenyl, propenyl, and butenyl groups; and alkynyl groups such as ethynyl, propynyl, and butynyl groups.

[0036] As a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, a group obtained by removing one hydrogen atom from the alicyclic structure in W corresponding to the structure with 3 to 20 carbon atoms can be suitably adopted.

[0037] Examples of monovalent aromatic hydrocarbon groups having 6 to 20 carbon atoms include aryl groups such as phenyl, tolyl, xyl, naphthyl, and anthryl groups, and aralkyl groups such as benzyl, phenethyl, naphthylmethyl, and anthrylmethyl groups.

[0038] Examples of heteroatoms that constitute a divalent or monovalent heteroatom-containing group include oxygen atoms, nitrogen atoms, sulfur atoms, phosphorus atoms, silicon atoms, halogen atoms, and the like.

[0039] Examples of divalent heteroatom-containing groups include -CO-, -CS-, -O-, -S-, and -SO ２ Examples include -, -NR'-, or groups combining two or more of these. R' is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms.

[0040] Examples of monovalent heteroatom-containing groups include hydroxyl groups, carboxyl groups, sulfanyl groups, cyano groups, nitro groups, and halogen atoms.

[0041] Examples of divalent hydrocarbon groups having 1 to 5 carbon atoms in L include divalent chain hydrocarbon groups having 1 to 5 carbon atoms and divalent alicyclic hydrocarbon groups having 3 to 5 carbon atoms.

[0042] Examples of the monovalent chain hydrocarbon groups having 1 to 5 carbon atoms include linear or branched saturated hydrocarbon groups having 1 to 5 carbon atoms, or linear or branched unsaturated hydrocarbon groups having 1 to 5 carbon atoms.

[0043] Examples of the above-mentioned C3-C5 divalent alicyclic hydrocarbon groups include C3-C5 cycloalkanediyl groups such as cyclopropanediyl, cyclobutanediyl, and cyclopentanediyl groups, and C3-C5 cycloalkenediyl groups such as cyclopropene, cyclobutene, and cyclopentene.

[0044] The divalent heteroatom-containing groups in L are as described above.

[0045] L is preferably a divalent chain saturated hydrocarbon group having 1 to 5 carbon atoms or a divalent group containing an ester bond between carbon atoms of the chain saturated hydrocarbon group, more preferably an alkanediyl group having 1 to 4 carbon atoms or a divalent group containing an ester bond between carbon atoms of the alkanediyl group, and even more preferably a methanediyl group or an ethanediyl group.

[0046] R １ In R ａ , R ｂ and R ｃ As the monovalent organic group having 1 to 20 carbon atoms represented by , the monovalent organic group having 1 to 20 carbon atoms shown as a substituent on the cyclic structure of W can be suitably adopted.

[0047] Among them, R ａ , R ｂ and R ｃ The organic group is preferably a monovalent hydrocarbon group having 1 to 10 carbon atoms, a group having an ether bond on the bonding side of the hydrocarbon group, more preferably an alkyl group or alkoxy group, and even more preferably a methyl group, ethyl group, methoxy group, or ethoxy group.

[0048] R １ It is preferable that it is -CN.

[0049] L ｇ The divalent heteroatom-containing group represented by is as described above.

[0050] L ｇ As the divalent organic group having 1 to 20 carbon atoms represented by , a group obtained by removing one hydrogen atom from the monovalent organic group having 1 to 20 carbon atoms shown in W can be suitably adopted. ｇ It is preferable that the hydrocarbon group is a divalent hydrocarbon group having 1 to 10 carbon atoms, or a divalent group containing an ester bond between carbon atoms or at the terminal of the hydrocarbon group.

[0051] g is preferably 0.

[0052] Specific examples of the anionic portion of compound (1) include, but are not limited to, the structures shown in the following formulas (1-1-1) to (1-1-92). In the following formulas, "Me" represents a methyl group.

[0053]

[0054]

[0055]

[0056]

[0057]

[0058]

[0059]

[0060]

[0061] Z ＋ and Z ｇ ＋ The monovalent organic cation represented by is not particularly limited, and examples include onium cations containing elements such as S, I, O, N, P, Cl, Br, F, As, Se, Sn, Sb, Te, and Bi. Examples of onium cations include sulfonium cations, tetrahydrothiophenium cations, iodonium cations, phosphonium cations, diazonium cations, pyridinium cations, and ammonium cations.

[0062] Z ＋ and Z ｇ ＋ It is preferable that the onium cation is 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.

[0063] The above organic cation preferably has at least one selected from the group consisting of an iodine group and a fluoro group. The above organic cation preferably contains the above iodine group-containing aromatic ring structure as the form of the iodine group. In the organic cation, the fluoro group is preferably in the form of a fluoro group-containing aromatic ring structure. The fluoro group-containing aromatic ring structure is a structure in which some or all of the hydrogen atoms of the aromatic ring are replaced by fluoro groups. As the aromatic ring in the fluoro group-containing aromatic ring structure, the aromatic ring in the iodine group-containing aromatic ring structure can be suitably adopted. By introducing an iodine group or a fluoro group, the radiation absorption efficiency can be increased, thereby improving sensitivity.

[0064] The sulfonium cation or iodonium cation is preferably represented by the following formulas (X-1) to (X-6).

[0065]

[0066] In the above equation (X-1), R ａ１ , 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, hydroxyl group, 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 Ｔis, independently of one another, 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 an integer of 0 to 5. R ａ１ ~R ａ３ as well as R Ｐ , R Ｑ and R Ｔ when there are a plurality of each of R ａ１ ~R ａ３ as well as R Ｐ , R Ｑ and R Ｔ may be the same or different from each other.

[0067] In the above formula (X-2), R ｂ１ is a substituted or unsubstituted linear or branched alkyl group 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, a halogen atom or a hydroxy group. n ｋ is 0 or 1. n ｋ when n is 0, k4 is an integer of 0 to 4, and when n ｋ is 1, k4 is an integer of 0 to 7. R ｂ１ when there are a plurality of R ｂ１ may be the same or different from each other, and a plurality of R ｂ１ may represent a ring structure formed by combining with each other. R ｂ２ 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. L Ｃ is a single bond or a divalent linking group. k5 is an integer of 0 to 4. R ｂ２ when there are a plurality of R ｂ２ may be the same or different from each other, and a plurality of R ｂ２ may represent a ring structure formed by combining with each other. q is an integer of 0 to 3. In the formula, the ring structure containing S ＋ may contain heteroatoms such as O and S between the carbon-carbon bonds forming the skeleton.

[0068] 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.

[0069] 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, halogen atom, or hydroxyl group having 6 to 8 carbon atoms. 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 ｇ３ Each 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.

[0070] In the above equation (X-5), R ｄ１ and R ｄ２Each 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.

[0071] 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.

[0072] Specific examples of organic cations used as the above-mentioned radiation-sensitive onium cation include, but are not limited to, the structures shown in the following formulas (1-2-1) to (1-2-63).

[0073]

[0074]

[0075]

[0076] Compound (1) can be obtained by appropriately combining the above-mentioned anionic moiety and the above-mentioned radiation-sensitive onium cation. Specific examples, though not limited to specific examples, include structures of formulas (1-1) to (1-65) below.

[0077]

[0078]

[0079]

[0080]

[0081]

[0082]

[0083]

[0084]

[0085] The lower limit of the content of compound (1) (total if multiple types of compound (1) are included) is preferably 0.1 parts by mass, more preferably 1 part by mass, and still more preferably 3 parts by mass, per 100 parts by mass of the polymer described later. The upper limit of the above content is preferably 70 parts by mass, more preferably 60 parts by mass, and still more preferably 55 parts by mass. The content of compound (1) is appropriately selected depending on the type of polymer used, exposure conditions, and the required sensitivity. As a result, the composition can exhibit excellent sensitivity, CDU, LWR, MEEF, EL, development defect suppression, pattern circularity, pattern rectangularity, and DOF when forming resist patterns.

[0086] (Method for synthesizing compound (1)) As a method for synthesizing compound (1), in the above formula (1), L is a methanediyl group, and R １ Let's take the case where is a cyano group as an example. A typical scheme is shown below.

[0087] (In the scheme, X is a halogen atom, independently of others. (S) is a sulfonating agent. (O) is an oxidizing agent. Cy is a cyclic structure formed with the carbon atoms of the carbonyl group in the scheme. Z ＋ This is equivalent to equation (1) above.

[0088] Dicyanonium salt can be obtained by reacting allyl halide with malononitrile to form a dicyanate, treating this dicyanate with a sulfonating agent to introduce a sulfonic acid group, and then reacting it with an onium cation halide salt corresponding to the onium cation moiety to carry out salt exchange. The target compound (1) can be synthesized by treating the allyl group moiety with an oxidizing agent and reacting the resulting diol with a cyclic ketone to form a cyclic acetal. Alternatively, it is possible to react the allyl group moiety with a diene before oxidation to form an unsaturated cyclized product, and then oxidize the unsaturated bond portion to form a diol for acetal formation. Compounds (1) with other structures can also be synthesized in a similar manner by appropriately selecting starting materials and precursors corresponding to the anionic and onium cation moieties.

[0089] (Polymer) A polymer is an aggregate of polymer chains having structural unit (I) containing an acid-dissociable group (hereinafter, this polymer is also called the "base polymer"). 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).

[0090] The base polymer preferably has structural unit (II) in addition to structural unit (I), which includes at least one selected from the group consisting of lactone structures, cyclic carbonate structures, and sultone structures, as described later. It may also have other structural units besides structural units (I) and (II). Each structural unit will be described below.

[0091] [Structural Unit (I)] 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, a structural unit having an acetal bond, etc. 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.

[0092]

[0093] 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 ２０ Each 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.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] L １１ａThe substituents that the 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.

[0098] The above R １８ As the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the above formula (1), the monovalent hydrocarbon group having 1 to 20 carbon atoms shown in the substituents that the cyclic structure of W in the above formula (1) can have can be preferably adopted.

[0099] The above R １８ Preferably, the hydrocarbon group is a straight-chain or branched-chain saturated hydrocarbon group having 1 to 10 carbon atoms, or an alicyclic hydrocarbon group having 3 to 20 carbon atoms.

[0100] 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 each other and bonded together with the carbon atoms, can preferably be a group obtained by removing one hydrogen atom from the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, as shown in the substituents that the cyclic structure of W in formula (1) may have.

[0101] Among these, R １８ R is an alkyl group, alkenyl group, or phenyl group having 1 to 4 carbon atoms. １９ and R ２０ It is preferable that the alicyclic structure formed by combining these elements with the carbon atoms to which they are bonded is a polycyclic or monocyclic cycloalkane structure.

[0102] 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.

[0103] 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)").

[0104]

[0105]

[0106] 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. 3a are each independently integers from 0 to 3. If 3a is 2 or more, multiple R Ｌ１１ They are either identical or different from each other. a4 is an integer between 1 and 3.

[0107] 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).

[0108] Furthermore, the polymer may contain structural units (I) represented by the following formulas (1f) to (2f).

[0109]

[0110] 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.

[0111] The above R βｆ Preferably, it is a hydrogen atom, a methyl group, or an ethyl group. １ 1 or 2 is preferred.

[0112] The lower limit of the content of structural unit (I) in the total structural units constituting the polymer (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. 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.

[0113] [Structural Unit (II)] Structural Unit (II) is a structural unit comprising at least one selected from the group consisting of lactone structures, cyclic carbonate structures, and sultone structures. By further comprising Structural Unit (II), the solubility of the base polymer in the developer can be adjusted, and as a result, the radiation-sensitive composition can improve lithography performance such as resolution. Furthermore, the adhesion between the resist pattern formed from the base polymer and the substrate can be improved.

[0114] Examples of structural units (II) include structural units represented by the following formulas (T-1) to (T-11).

[0115]

[0116] In the above formula, R Ｌ１ R is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Ｌ２ ~R Ｌ５ These 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.

[0117] The above R Ｌ４ and R Ｌ５When 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.

[0118] 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-.

[0119] 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.

[0120] When the base polymer has structural unit (II), the lower limit of the content of structural unit (II) (total content if multiple types are included) is preferably 2 mol%, more preferably 5 mol%, and even more preferably 8 mol%, relative to the total structural units constituting the base polymer. 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 unit (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.

[0121] [Structural Unit (III)] The base polymer optionally contains structural unit (III) which includes a polar group (excluding those corresponding to structural units (I) and (II)). By further containing structural unit (III), the solubility 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 hydroxyl group, carboxyl group, cyano group, nitro group, sulfonamide group, etc. Among these, hydroxyl group and carboxyl group are preferred, and hydroxyl group is more preferred.

[0122] Examples of structural units (III) include structural units represented by the following formula.

[0123]

[0124]

[0125] In the above formula, R Ｋ This is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0126] When the base polymer has structural unit (III) having the polar group described above, the lower limit of the content of structural unit (III) (total content if multiple types are included) is preferably 1 mol%, more preferably 2 mol%, and even more preferably 3 mol%, relative to the total structural units constituting the base polymer. The upper limit of the content is preferably 30 mol%, more preferably 20 mol%, and even more preferably 15 mol%. By setting the content of structural unit (III) within the above range, the lithographic performance, such as resolution, of the radiation-sensitive composition can be further improved.

[0127] [Structural Unit (IV)] The base polymer optionally contains structural units having phenolic hydroxyl groups (hereinafter also referred to as "structural unit (IV)"). Structural unit (IV) contributes to improved etching resistance and improved difference in developer solubility between exposed and unexposed areas (dissolution contrast). It can be suitably applied to pattern formation using exposure with radiation of wavelength 50 nm or less, such as KrF excimer lasers, electron beams, and EUV.

[0128] The structural unit having a phenolic hydroxyl group is preferably represented by the following formula (4).

[0129] (In the above formula (4), R β L is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ＣＡ This is a single bond, -COO- ＊ Or -O-. * indicates a bond on the aromatic ring side. R １０２ R is a halogen atom, cyano group, nitro group, alkyl group, alkoxycarbonyl group, acyl group, or acyloxy group. １０２ If multiple R １０２ They are either identical or different from each other. ３ m is an integer between 0 and 2. ３ m is an integer from 1 to 8. ４ Each of these is an independent integer between 0 and 8, where 1 ≤ m. ３ +m ４ ≤ 2n ３ (Saves +5.)

[0130] The above R β 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.

[0131] L ＣＡ For example, a single bond or -COO- ＊ It is preferable.

[0132] R １０２ In this case, an iodine atom is preferred as the halogen atom.

[0133] The above n ３ 0 or 1 is more preferable, and 0 is even more preferable.

[0134] The above m ３ Preferably, the integer is between 1 and 3, and more preferably 1 or 2.

[0135] The above m ４ Preferably, the integer is between 0 and 3, and more preferably between 0 and 2.

[0136] 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). Polymerization of the monomer may also be carried out without protecting the phenolic hydroxyl group.

[0137] 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 units (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. The upper limit of the above content is preferably 70 mol%, and more preferably 60 mol%.

[0138] [Other structural units] The base polymer may also contain structural units other than those listed above, such as 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.)

[0139] In the above formula (6), R ２α As the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the above formula (1), the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms shown in the substituents that the cyclic structure of W in the above formula (1) can have can be preferably adopted.

[0140] When the base polymer 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. The upper limit of the above content is preferably 30 mol%, more preferably 20 mol%, and even more preferably 15 mol%.

[0141] (Method for synthesizing base polymers) Base polymers 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.

[0142] 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.

[0143] Solvents used in the above polymerization include, for example, 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; and 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.

[0144] 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.

[0145] The molecular weight of the base polymer 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 30,000, more preferably 20,000, and even more preferably 12,000. 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.

[0146] The ratio of Mw to the polystyrene-equivalent number-average molecular weight (Mn) of the base polymer (Mw / Mn) determined by GPC is usually between 1 and 5, preferably between 1 and 3, and more preferably between 1 and 2.

[0147] In this specification, the Mw and Mn values ​​of polymers are measured using gel permeation chromatography (GPC) under the following conditions.

[0148] 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

[0149] The base polymer content 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.

[0150] (Other Polymers) The radiation-sensitive composition of this embodiment may also contain, as other polymers, a polymer that is more hydrophobic than the base polymer (hereinafter also referred to as a "highly hydrophobic polymer"). The highly hydrophobic polymer is a polymer that has a higher mass content of fluorine atoms or a higher introduction rate of hydrocarbon groups compared to the base polymer. When the radiation-sensitive composition contains a highly hydrophobic polymer, it can be made to be unevenly distributed on the surface of the resist film relative to the base polymer, and as a result, the water repellency of the surface of the resist film during immersion exposure can be improved, and the surface modification of the resist film and the distribution of the composition within the film can be controlled during EUV exposure.

[0151] As a highly hydrophobic polymer, it may have, for example, a structural unit represented by the following formula (5) (hereinafter also referred to as "structural unit (V)").

[0152]

[0153] 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 ２ ONH-, -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.

[0154] 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.

[0155] 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.

[0156] 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.

[0157] 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.

[0158] 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.

[0159] When the highly hydrophobic 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 highly hydrophobic polymer. 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 units (V) within the above range, the mass content of fluorine atoms in the highly hydrophobic 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.

[0160] The highly hydrophobic polymer 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). By having structural unit (f-2), the highly hydrophobic polymer can improve its solubility in alkaline developers and suppress the occurrence of development defects.

[0161]

[0162] 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 both (x) and (y), in the above formula (f-2), R ＣR 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 end of the side are an oxygen atom, a sulfur atom, and -NR ｄｄ -A structure to which a carbonyl group, -COO-, -OCO-, or -CONH- is bonded, 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.

[0163] If structural unit (VI) has (x) an alkali-soluble group, R Ｆ A is a hydrogen atom, １ is an oxygen atom, -COO-* or -SO ２ It is 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-methanediyl group.

[0164] 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 It is O-*. 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 -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. １ If 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 is -COO-*, R Ｆ Or W １ Alternatively, it is particularly preferable that both of these contain fluorine atoms.

[0165] 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.

[0166] When the highly hydrophobic 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 highly hydrophobic 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 to suppress the occurrence of development defects.

[0167] [Other structural units] The highly hydrophobic polymer may, if necessary, include structural units other than those listed above, such as structural unit (I), structural unit (III), and structural unit (VII) in the base polymer.

[0168] When the highly hydrophobic polymer contains structural unit (I), the lower limit of the content of structural unit (I) is preferably 10 mol%, and more preferably 15 mol%, relative to the total structural units constituting the highly hydrophobic polymer. The upper limit of the above content is preferably 60 mol%, and more preferably 50 mol%.

[0169] When the highly hydrophobic 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 highly hydrophobic polymer. The upper limit of the above content is preferably 40 mol%, and more preferably 30 mol%.

[0170] When the highly hydrophobic polymer contains structural unit (VII), the lower limit of the content of structural unit (VII) is preferably 20 mol%, and more preferably 30 mol%, relative to the total structural units constituting the highly hydrophobic polymer. The upper limit of the above content is preferably 60 mol%, and more preferably 50 mol%.

[0171] The highly hydrophobic polymer may have a structural unit having a primary, secondary, or tertiary hydrocarbyl ester structure (however, different from structural unit (I) in the base polymer; hereinafter also referred to as "structural unit (VIII)") instead of the above structural units (V) and (VI). In this case, the highly hydrophobic polymer preferably does not contain fluorine atoms. Structural unit (VIII) preferably has a secondary hydrocarbyl ester structure. Structural unit (VIII) is preferably a structural unit represented by the following formula (VIII-1). (In formula (VIII-1), R γ R is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. ３１ and R ３２ Each of these is independently a monovalent linear hydrocarbon group having 3 to 10 carbon atoms, or a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, or a group in which some or all of the hydrogen atoms of the alicyclic hydrocarbon group are substituted with alkyl groups, or R ３１ and R ３２ This represents a monovalent alicyclic group having 3 to 20 carbon atoms, which can be combined with the carbon atoms to which they are bonded, or a group in which some or all of the hydrogen atoms of the alicyclic group are replaced with alkyl groups.

[0172] R γ As the C1-C10 alkyl group represented by the above formula (1), groups corresponding to C1-C10 from the alkyl groups shown in the substituent of the cyclic structure of W can be suitably adopted.

[0173] R ３１ and R ３２ As the monovalent chain hydrocarbon group having 3 to 10 carbon atoms represented by the above formula (1), groups corresponding to 3 to 10 carbon atoms from the monovalent chain hydrocarbon groups having 1 to 20 carbon atoms shown in the substituent of the cyclic structure of W can be suitably adopted. In particular, R ３１ and R ３２ The monovalent chain hydrocarbon group having 3 to 10 carbon atoms represented by isopropyl, isobutyl, t-butyl, and n-hexyl groups are preferred.

[0174] R ３１ and R ３２As the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the above formula (1), the above monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms shown in the substituent of the cyclic structure of W can be suitably adopted. As the alkyl group that substitutes some or all of the hydrogen atoms of the alicyclic hydrocarbon group, R γ A C1 to C10 alkyl group represented by [the formula shown] can be preferably used.

[0175] R ３１ and R ３２ As a monovalent alicyclic group having 3 to 20 carbon atoms formed by combining these, the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms shown in the substituent of the cyclic structure of W in formula (1) above can be suitably adopted. Among them, R ３１ and R ３２ As a monovalent alicyclic group having 3 to 20 carbon atoms formed by combining these groups, monocyclic or polycyclic cycloalkyl groups are preferred, and cyclopentyl, cyclohexyl, and norbornyl groups are more preferred. As an alkyl group that substitutes some or all of the hydrogen atoms of the above monovalent alicyclic group, R γ C1 to C10 alkyl groups represented by can be suitably used. In particular, the alkyl group used as a substituent is preferably a methyl group, an ethyl group, an isopropyl group, or a t-butyl group.

[0176] When the highly hydrophobic polymer has structural unit (VIII), the content of structural unit (VIII) (total content if multiple types are included) is preferably 30 mol%, more preferably 40 mol%, and even more preferably 50 mol% relative to the total structural units constituting the highly hydrophobic polymer. Furthermore, the upper limit of the above content is preferably 90 mol%, more preferably 80 mol%, and even more preferably 70 mol%. By setting the content of structural unit (VIII) 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 to suppress the occurrence of development defects.

[0177] If the highly hydrophobic polymer has structural unit (VIII), it may optionally include structural unit (I) in the base polymer as a structural unit other than structural unit (VIII).

[0178] When the highly hydrophobic polymer contains structural unit (I), the content of structural unit (I) is preferably 15 mol%, and more preferably 30 mol%, relative to the total structural units constituting the highly hydrophobic polymer. Furthermore, the upper limit of the above content is preferably 60 mol%, and more preferably 50 mol%.

[0179] The lower limit of Mw for the highly hydrophobic polymer is preferably 3,000, and more preferably 4,000. The upper limit of Mw is preferably 20,000, and more preferably 14,000.

[0180] The lower limit of Mw / Mn for a highly hydrophobic polymer is usually 1, with 1.1 being more preferred. The upper limit of Mw / Mn is usually 5, with 3 being preferred, and 2 being more preferred.

[0181] If the radiation-sensitive composition contains a highly hydrophobic polymer, the lower limit of the content of the highly hydrophobic polymer is preferably 0.1 parts by mass, more preferably 0.2 parts by mass, and even more preferably 0.3 parts by mass, per 100 parts by mass of the base polymer. The upper limit of the content is preferably 15 parts by mass, more preferably 10 parts by mass, and even more preferably 6 parts by mass.

[0182] By setting the content of the highly hydrophobic polymer within the above range, the highly hydrophobic polymer can be more effectively localized to the surface layer of the resist film. As a result, it is possible to enhance 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 highly hydrophobic polymers.

[0183] (Method for synthesizing highly hydrophobic polymers) Highly hydrophobic polymers can be synthesized by the same method as the base polymer synthesis method described above.

[0184] (Acid Diffusion Control Agent) The radiation-sensitive composition may optionally contain an acid diffusion control agent. The acid diffusion control agent controls the diffusion phenomenon of the acid generated from compound (1) by exposure in the resist film, and has the effect of suppressing undesirable chemical reactions in 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 setting time from exposure to development can be suppressed, resulting in a radiation-sensitive composition with excellent process stability.

[0185] Examples of acid diffusion control agents 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, and onium salts having quaternary ammonium cations.

[0186]

[0187] 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.

[0188] 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.

[0189] Examples of nitrogen-containing compounds (II) include ethylenediamine and N,N,N',N'-tetramethylethylenediamine.

[0190] Examples of nitrogen-containing compounds (III) include polyamine compounds such as polyethyleneimine and polyallylamine; and polymers such as dimethylaminoethylacrylamide.

[0191] 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.

[0192] Examples of urea compounds include urea, methyl urea, 1,1-dimethylurea, 1,3-dimethylurea, 1,1,3,3-tetramethylurea, 1,3-diphenylurea, and tributylthiourea.

[0193] 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.

[0194] Furthermore, compounds having an acid-dissociable group can also be used as the nitrogen-containing organic compound. Examples of 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.

[0195] Examples of onium salts having a quaternary ammonium cation include tetrabutylammonium salicylate, tetrabutylammonium benzoate, and ammonium camphorsulfonate.

[0196] Furthermore, a radiation-sensitive weak acid generator that generates a weak acid upon exposure can be suitably used as an acid diffusion control agent. The acid generated from the above-mentioned radiation-sensitive weak acid generator 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.

[0197] Examples of radiation-sensitive weak acid generators 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).

[0198]

[0199] 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 This is a single bond or a monovalent organic group having 1 to 30 carbon atoms. Preferably, this organic group can be one that extends the monovalent organic group having 1 to 20 carbon atoms, as shown in the substituents that W in formula (1) can have, up to 30 carbon atoms. α -SO ３ -In the case of the anion represented by the above, it is preferable that neither a fluorine atom nor a fluorinated hydrocarbon group is bonded to either the α-position or the β-position carbon atom of the sulfonate anion.

[0200] Examples of the above-mentioned radiation-sensitive weak acid generating agent include compounds represented by the following formula.

[0201]

[0202]

[0203] The lower limit of the acid diffusion control agent content is preferably 0.5 parts by mass, and more preferably 1 part by mass, per 100 parts by mass of the polymer. The upper limit of the above content is preferably 60 parts by mass, and more preferably 50 parts by mass. By setting the acid diffusion control agent content 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.

[0204] (Solvent) The radiation-sensitive composition according to this embodiment contains a solvent. The solvent is not particularly limited as long as it is capable of dissolving or dispersing at least compound (1) and the base polymer, as well as any optional components that may be contained therein.

[0205] Examples of solvents include alcohol-based solvents, ether-based solvents, ketone-based solvents, amide-based solvents, ester-based solvents, and hydrocarbon-based solvents.

[0206] 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. 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.

[0207] 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.

[0208] 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.

[0209] 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.

[0210] 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.

[0211] Examples of hydrocarbon solvents include aliphatic hydrocarbon solvents such as n-hexane, cyclohexane, and methylcyclohexane; and aromatic hydrocarbon solvents such as benzene, toluene, di-isopropylbenzene, and n-amylnaphthalene.

[0212] 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, 2-hydroxyisobutyrate methyl, diacetone alcohol, propylene glycol monomethyl ether acetate, γ-butyrolactone, and cyclohexanone are even more preferred. The radiation-sensitive composition may contain one or more solvents.

[0213] (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 promoters, surfactants, alicyclic skeleton-containing compounds, sensitizers, etc. These other optional components may be used individually or in combination of two or more types.

[0214] <Method for preparing a radiation-sensitive composition> The above radiation-sensitive composition can be prepared, for example, by mixing compound (1), a polymer, and optionally a highly hydrophobic polymer, and a solvent in predetermined proportions. 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.

[0215] <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").

[0216] According to the pattern formation method described above, since the radiation-sensitive composition that exhibits excellent sensitivity, CDU, LWR, MEEF, EL, development defect suppression, pattern circularity, pattern rectangularity, and DOF is used during pattern formation, high-quality resist patterns can be efficiently formed. Each step will be described below.

[0217] [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.

[0218] 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.

[0219] When performing immersion exposure, regardless of whether or not the above-mentioned hydrophobic polymer additive is present in the radiation-sensitive composition, a protective immersion film insoluble in the immersion liquid may be provided on the formed resist film to avoid direct contact between the immersion liquid and the resist film. As the protective immersion 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, Japanese Patent Application Publication Nos. WO2005-069076 and WO2006-035790) may be used. However, from the viewpoint of throughput, it is preferable to use a developer-peelable protective immersion film.

[0220] [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.

[0221] 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.

[0222] 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.

[0223] [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.

[0224] Examples of developers used in the above development process 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.

[0225] Furthermore, in the case of organic solvent development, examples of organic solvents include hydrocarbon solvents, ether solvents, ester solvents, ketone solvents, alcohol solvents, etc., 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.

[0226] 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.

[0227] 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 leaving it 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).

[0228] <Compound> Another embodiment of the present invention is an onium salt compound represented by the following formula (1). (In formula (1), W is a substituted or unsubstituted cyclic structure containing an acetal structure. L is a substituted or unsubstituted divalent hydrocarbon group having 1 to 5 carbon atoms, or a group containing a divalent heteroatom between the carbon atoms of the hydrocarbon group. １ These are hydrogen atoms, -CN, and -NO ２ -F, -CF ２ R ａ , -SO ２ R ｂ ,-COR ｃ , or -CN, -CF ２ R ａ , -SO ２ R ｂ ,-COR ｃ Or -CF ３ (a) is a monovalent organic group with 1 to 20 carbon atoms other than R. ａ R is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. ｂ and R ｃ These are, independently, monovalent organic groups having 1 to 20 carbon atoms. ＋ L is a monovalent organic cation. ｇ This refers to a single bond, a divalent heteroatom-containing group, or a divalent organic group having 1 to 20 carbon atoms. - -COO - or -SO ３- That is. Z ｇ ＋ (where g is a monovalent organic cation; g is 0 or 1.)

[0229] In this embodiment, compound (1) contained in the above-mentioned radiation-sensitive composition can be suitably used as the compound represented by formula (1).

[0230] 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.

[0231] [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.

[0232] [ １３ [C-NMR analysis] Polymer １３ C-NMR analysis was performed using a nuclear magnetic resonance spectrometer (JEOL Ltd.'s "JNM-Delta400").

[0233] <Synthesis of Polymers> The monomers used in the synthesis of each polymer in each example and comparative example are shown below. In the following synthesis examples, unless otherwise specified, parts by mass refers to the value when the total mass of the monomers used is 100 parts by mass, and mol% refers to the value when the total number of moles of the monomers used is 100 mol%.

[0234]

[0235] [Synthesis Example 1] (Synthesis of Polymer (A-1)) Monomers (M-1), (M-2), (M-5), (M-10), and (M-14) were dissolved in 200 parts by mass of 2-butanone in a molar ratio of 40 / 10 / 20 / 25 / 5 (mol%). AIBN (azobisisobutyronitrile) (5 mol% relative to the total 100 mol% of the monomers used) was added as an initiator to prepare a monomer solution. 100 parts by mass of 2-butanone 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 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 polymerization reaction was completed, 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 24 hours to obtain a white powdery polymer (A-1) (yield: 80%). The Mw of polymer (A-1) was 5,900, and the Mw / Mn ratio was 1.61. Furthermore, １３ ¹³C-NMR analysis revealed that the content percentages of each structural unit derived from (M-1), (M-2), (M-5), (M-10), and (M-14) were 39.3 mol%, 9.4 mol%, 20.5 mol%, 24.8 mol%, and 6.0 mol%, respectively.

[0236] [Synthesis Examples 2-11] (Synthesis of Polymers (A-2) to (A-11)) Polymers (A-2) to (A-11) were synthesized in the same manner as in Synthesis Example 1, except that monomers of the types and proportions shown in Table 1 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 1 below. Note that "-" in Table 1 below indicates that the corresponding monomer was not used (the same applies to subsequent tables).

[0237]

[0238] [Synthesis Example 12] (Synthesis of Polymer (A-12)) Monomers (M-4), (M-5), and (M-18) were dissolved in 1-methoxy-2-propanol (200 parts by mass) in a molar ratio of 55 / 15 / 30 (mol%), and MAIB (dimethyl 2,2'-azobisisobutyrate) (7 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, and the resulting solid was dissolved in acetone (100 parts by mass) and added dropwise to water (500 parts by mass) to solidify the polymer. The resulting solid was filtered and dried at 50°C for 13 hours to obtain a white powdery polymer (A-12) (yield: 85%). The Mw of polymer (A-12) was 5,600, and the Mw / Mn ratio was 1.57. １３ 13C-NMR analysis revealed that the content of each structural unit derived from (M-4), (M-5), and (M-18) was 55.6 mol%, 14.9 mol%, and 29.5 mol%, respectively.

[0239] [Synthesis Examples 13-15] (Synthesis of Polymers (A-13) to (A-15)) Polymers (A-13) to (A-15) were synthesized in the same manner as in Synthesis Example 12, except that monomers of the types and proportions shown in Table 2 below were used. Note that the monomers that give structural unit (IV) in the polymer were, １３13C-NMR measurements confirmed the disappearance of the carbonyl group peak of the acetyl group, indicating that virtually all alkali-dissociable groups had been hydrolyzed to phenolic hydroxyl groups. The content percentage (mol%) and physical properties (Mw and Mw / Mn) of each structural unit of the obtained polymer are shown in Table 2 below.

[0240]

[0241] [Synthesis Example 16] (Synthesis of highly hydrophobic polymer (F-1)) Monomer (M-4), monomer (M-17), and monomer (M-21) were dissolved in 2-butanone (200 parts by mass) in a molar ratio of 25 / 5 / 70 (mol%), and AIBN (5 mol%) was added as an initiator to prepare monomer solutions. 2-butanone (100 parts by mass) 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 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 substituting the solvent with propylene glycol monomethyl ether acetate, a solution of the highly hydrophobic polymer (F-1) was obtained (yield: 75%). The Mw of the highly hydrophobic polymer (F-1) was 6,600, and the Mw / Mn ratio was 1.67. １３ ¹³C-NMR analysis revealed that the content of each structural unit derived from (M-4), (M-17), and (M-21) was 24.6 mol%, 5.2 mol%, and 70.2 mol%, respectively.

[0242] [Synthesis Examples 17-21] (Synthesis of highly hydrophobic polymers (F-2) to (F-6)) Highly hydrophobic polymers (F-2) to (F-6) were synthesized in the same manner as in Synthesis Example 16, 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 highly hydrophobic polymers are also shown in Table 3 below.

[0243]

[0244] <Synthesis of Radiation-Sensitive Acid Generator (B)> [Example B1] (Synthesis of Compound (B-1)) Compound (B-1) as a radiation-sensitive acid generator (B) was synthesized according to the following synthesis scheme.

[0245]

[0246] 20.0 mmol of allyl bromide, 20.0 mmol of malononitrile, 30.0 mmol of potassium carbonate, and 50 g of acetone were added to a reaction vessel and stirred at 50°C for 12 hours. Then, saturated aqueous ammonium chloride 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 with saturated aqueous sodium chloride solution and then with water. After drying over sodium sulfate, the solvent was removed by distillation, and the dicyano compound was obtained in good yield by column chromatography.

[0247] 30.0 mmol of chlorosulfonic acid, 3.0 mmol of potassium carbonate, and 50 g of dichloromethane were added to the above dicyano compound and the mixture was stirred at room temperature for 12 hours. Then, 30.0 mmol of triphenylsulfonium bromide and 50 g of water were added to the reaction solution and the mixture was stirred at room temperature for 1 hour. Dichloromethane was then added for extraction, and the organic layer was separated. The obtained organic layer was dried over sodium sulfate, the solvent was removed by distillation, and the compound (B-1-a) was purified by column chromatography in good yield.

[0248] To the above compound (B-1-a), 40.0 mmol of potassium permanganate and 50 g of acetonitrile were added and the mixture was stirred at 50°C for 10 hours. Then, saturated sodium thiosulfate aqueous solution was added to stop the reaction, and dichloromethane was added for extraction, separating the organic layer. The obtained organic layer was dried over sodium sulfate, and the solvent was removed by distillation to obtain the diol compound in good yield.

[0249] 20.0 mmol of 5-hydroxy-2-adamantanone, 2.00 mmol of sulfuric acid, and 50 g of dichloromethane were added to the above diol and the mixture was stirred at room temperature for 24 hours. After dilution with water, the mixture was extracted with dichloromethane, and the organic layer was separated. The obtained organic layer was washed with saturated sodium chloride aqueous solution, and then with water. After drying with sodium sulfate, the solvent was removed by distillation, and the compound (B-1) represented by the above formula (B-1) was purified by column chromatography to obtain compound (B-1) in good yield.

[0250] [Examples B2 to B4] (Synthesis of compounds (B-2) to (B-4)) Compounds as radiation-sensitive acid generators represented by the following formulas (B-2) to (B-4) were synthesized in the same manner as in Example B1, except that the raw materials and precursors were appropriately changed.

[0251]

[0252] [Example B5] (Synthesis of compound (B-5)) Compound (B-5) as a radiation-sensitive acid generator (B) was synthesized according to the following synthesis scheme.

[0253]

[0254] 20.0 mmol of the above compound (B-1-a), 40.0 mmol of cyclopentadiene, and 50 g of methylene chloride were added to a reaction vessel and stirred at room temperature for 24 hours. After dilution with water, methylene chloride was added for extraction, and the organic layer was separated. The obtained organic layer was washed with saturated sodium chloride aqueous solution, and then with water. After drying over sodium sulfate, the solvent was removed by distillation, and the norbornene compound was obtained in good yield by column chromatography.

[0255] The norbornene mixture was mixed with 40.0 mmol of potassium permanganate and 50 g of acetonitrile, and stirred at 50°C for 10 hours. The reaction was then stopped by adding saturated sodium thiosulfate aqueous solution, followed by extraction with dichloromethane to separate the organic layer. The resulting organic layer was dried over sodium sulfate, and the solvent was removed by distillation to obtain compound (B-5-a) in good yield.

[0256] 20.0 mmol of 2-adamantanone, 2.00 mmol of sulfuric acid, and 50 g of toluene were added to the above compound (B-5-a), and the mixture was stirred at 100 °C for 24 hours. Then, water was added for dilution, followed by addition of dichloromethane for extraction, and the organic layer was separated. The obtained organic layer was washed with a saturated aqueous sodium chloride solution and then with water. After drying over sodium sulfate, the solvent was distilled off, and the compound (B-5) represented by the above formula (B-5) was obtained in a good yield by purification by column chromatography.

[0257] [Examples B6 to B8] (Synthesis of Compounds (B-6) to (B-8)) Compounds as radiation-sensitive acid generators represented by the following formulas (B-6) to (B-8) were synthesized in the same manner as in Example B5, except that the raw materials and precursors were appropriately changed.

[0258]

[0259] [Example B9] (Synthesis of Compound (B-9)) The compound (B-9) as a radiation-sensitive acid generator (B) was synthesized according to the following synthesis scheme.

[0260]

[0261] 20.0 mmol of 1,2-isopropylidene glycol, 20.0 mmol of bromoacetyl bromide, 30.0 mmol of pyridine, and 50 g of methylene chloride were added to a reaction vessel, and the mixture was stirred at room temperature for 24 hours. Then, water was added for dilution, followed by addition of methylene chloride for extraction, and the organic layer was separated. The obtained organic layer was washed with a saturated aqueous sodium chloride solution and then with water. After drying over sodium sulfate, the solvent was distilled off to obtain the bromo compound in a good yield.

[0262] 20.0 mmol of malononitrile, 30.0 mmol of potassium carbonate, and 50 g of acetone were added to the above bromo compound, and the mixture was stirred at 五十℃ for 12 hours. Then, a saturated aqueous ammonium chloride solution was added to the reaction solution to terminate the reaction, followed by addition of ethyl acetate for extraction, and the organic layer was separated. The obtained organic layer was washed with a saturated aqueous sodium chloride solution and then with water. After drying over sodium sulfate, the solvent was distilled off, and the dicyano compound was obtained in a good yield by purification by column chromatography. It should be noted that the "五十℃" in the original text seems to be incorrect. I translated it as "五十℃" as it is, but it might be a typo. It should probably be "50 °C".

[0263] 30.0 mmol of N-bromosuccinimide (NBS) and 50 g of dichloromethane were added to the above dicyano compound, and the mixture was stirred at room temperature for 12 hours. Then, saturated sodium thiosulfate aqueous solution was added to the reaction solution to terminate the reaction, and dichloromethane was added for extraction, separating the organic layer. The obtained organic layer was washed with saturated sodium chloride aqueous solution, and then with water. After drying over sodium sulfate, the solvent was removed by distillation, and the bromo compound was obtained in good yield by column chromatography.

[0264] The above bromo compound was mixed with acetonitrile and water (1:1 by mass) to make a 1 M solution, then 40.0 mmol of sodium dithionite and 60.0 mmol of sodium bicarbonate were added and the mixture was reacted at 70°C for 4 hours. After extraction with acetonitrile and removal of the solvent, a mixture of acetonitrile and water (3:1 by mass) was added to make a 0.5 M solution. 60.0 mmol of hydrogen peroxide and 2.00 mmol of sodium tungstate were added and the mixture was heated and stirred at 50°C for 12 hours. The sodium sulfonate salt compound was obtained by extraction with acetonitrile and removal of the solvent. 20.0 mmol of benzyltrimethylammonium chloride was added to the above sodium sulfonate salt compound, and a mixture of water and dichloromethane (1:3 by mass) was added to make a 0.5 M solution. After vigorous stirring at room temperature for 3 hours, dichloromethane was added for extraction, and the organic layer was separated. The resulting organic layer was dried over sodium sulfate, and the solvent was removed by distillation to obtain compound (B-9-a) in good yield.

[0265] To the above compound (B-9-a), 20.0 mmol of 4-tert-butylcyclohexanone, 2.00 mmol of sulfuric acid, and 50 g of toluene were added and the mixture was stirred at 100°C for 24 hours. Then, to the reaction solution, 30.0 mmol of diphenyl(p-tolyl)sulfonium bromide, 50 g of dichloromethane, and 50 g of water were added and the mixture was stirred at room temperature for 5 hours. After that, dichloromethane was added for extraction, and the organic layer was separated. The obtained organic layer was dried over sodium sulfate, the solvent was removed by distillation, and the compound (B-9) represented by the above formula (B-9) was purified by column chromatography to obtain the compound (B-9) represented by the above formula in good yield.

[0266] [Examples B10-B11] (Synthesis of compounds (B-10)-(B-11)) Compounds as radiation-sensitive acid generators represented by the following formulas (B-10)-(B-11) were synthesized in the same manner as in Example B9, except that the raw materials and precursors were appropriately changed.

[0267]

[0268] [Example B11] (Synthesis of compound (B-11)) Compound (B-11) as a radiation-sensitive acid generator (B) was synthesized according to the following synthesis scheme.

[0269]

[0270] 20.0 mmol of the above compound (B-9-a), 40.0 mmol of sodium borohydride, and 50 g of tetrahydrofuran were added to a reaction vessel and stirred at room temperature for 12 hours. Then, saturated aqueous ammonium chloride solution was added to the reaction solution to terminate the reaction, and then 30.0 mmol of (4-(tert-butyl)phenyl)diphenylsulfonium bromide, 50 g of dichloromethane, and 50 g of water were added and stirred at room temperature for 10 hours. After that, dichloromethane was added for extraction and the organic layer was separated. The obtained organic layer was dried over sodium sulfate, the solvent was removed by distillation, and the alcohol was purified by column chromatography to obtain the alcohol in good yield.

[0271] 20.0 mmol of 5-norbornene-2-carboxylic acid, 30.0 mmol of dicyclohexylcarbodiimide, and 50 g of acetonitrile were added to the above alcohol mixture and stirred at 60°C for 4 hours. After dilution with water, the mixture was extracted with dichloromethane, and the organic layer was separated. The obtained organic layer was washed with saturated sodium chloride aqueous solution, and then with water. After drying over sodium sulfate, the solvent was removed by distillation, and the ester was obtained in good yield by column chromatography.

[0272] The above ester was mixed with 40.0 mmol of potassium permanganate and 50 g of acetonitrile, and stirred at 50°C for 10 hours. Then, saturated sodium thiosulfate aqueous solution was added to stop the reaction, and dichloromethane was added for extraction, separating the organic layer. The resulting organic layer was dried over sodium sulfate, and the solvent was removed by distillation to obtain the diol compound in good yield.

[0273] The above diol was mixed with 20.0 mmol of dicyclohexyl ketone, 2.00 mmol of sulfuric acid, and 50 g of toluene, and stirred at 100°C for 24 hours. After dilution with water, the mixture was extracted with dichloromethane, and the organic layer was separated. The obtained organic layer was washed with saturated sodium chloride aqueous solution, and then with water. After drying with sodium sulfate, the solvent was removed by distillation, and the compound (B-12) represented by the above formula (B-12) was purified by column chromatography to obtain compound (B-12) in good yield.

[0274] [Examples B13 to B16] (Synthesis of compounds (B-13) to (B-16)) Compounds as radiation-sensitive acid generators represented by the following formulas (B-13) to (B-16) were synthesized in the same manner as in Example B12, except that the raw materials and precursors were appropriately changed.

[0275]

[0276] [Example B17] (Synthesis of compound (B-17)) Compound (B-17) as a radiation-sensitive acid generator (B) was synthesized according to the following synthesis scheme.

[0277]

[0278] 20.0 mmol of ethyl 2-cyanopropionate, 30.0 mmol of chlorosulfonic acid, and 50 g of dichloromethane were added to a reaction vessel and stirred at room temperature for 12 hours. Then, 30.0 mmol of tri-p-tolylsulfonium bromide and 20 g of water were added to the reaction solution and stirred at room temperature for 1 hour. After that, dichloromethane was added for extraction, and the organic layer was separated. The obtained organic layer was dried over sodium sulfate, and the solvent was removed by distillation to obtain the onium salt in good yield.

[0279] 50 g of 1 M aqueous sodium hydroxide solution and 50 g of ethanol were added to the above onium salt and the mixture was stirred at 0°C for 2 hours. Then, dichloromethane was added to the reaction solution for extraction, and the organic layer was separated. The solvent of the resulting organic layer was removed by distillation to obtain the carboxylic acid compound in good yield.

[0280] The above carboxylic acid mixture was mixed with 20.0 mmol of oxalyl chloride and 50 g of acetonitrile and stirred at room temperature for 2 hours. Then, 20.0 mmol of 5-hydroxy-2-adamantanone, 30.0 mmol of triethylamine, and 3.0 mmol of 4-dimethylaminopyridine were added to the reaction solution and stirred at 80°C for 24 hours. After that, the reaction was stopped by adding saturated ammonium chloride aqueous solution, and then the organic layer was separated by extraction with dichloromethane. The obtained organic layer was washed with saturated sodium chloride aqueous solution and then with water. After drying with sodium sulfate, the solvent was removed by distillation and the ketone body was purified by column chromatography in good yield.

[0281] The above ketone body was mixed with 20.0 mmol of D-erythronolactone, 2.00 mmol of sulfuric acid, and 50 g of toluene, and stirred at 100°C for 24 hours. After dilution with water, the mixture was extracted with dichloromethane, and the organic layer was separated. The obtained organic layer was washed with saturated sodium chloride aqueous solution, and then with water. After drying with sodium sulfate, the solvent was removed by distillation, and the compound (B-17) represented by the above formula (B-17) was obtained in good yield by purification by column chromatography.

[0282] [Examples B18-B20] (Synthesis of compounds (B-18)-(B-20)) Compounds as radiation-sensitive acid generators represented by the following formulas (B-18)-(B-20) and (B-22)-(B-26) were synthesized in the same manner as in Example B17, except that the raw materials and precursors were appropriately changed.

[0283]

[0284] [Example B21] (Synthesis of compound (B-21)) Compound (B-21) as a radiation-sensitive acid generator (B) was synthesized according to the following synthesis scheme.

[0285]

[0286] 20.0 mmol of the above compound (B-5-a), 20.0 mmol of 5-formylsalicylic acid, 2.00 mmol of sulfuric acid and 50 g of toluene were added to a reaction vessel, and the mixture was stirred at 100 ° C for 24 hours. Then, water was added for dilution, followed by addition of dichloromethane for extraction, and the organic layer was separated. The obtained organic layer was washed with a saturated aqueous sodium chloride solution and then with water. After drying over sodium sulfate, the solvent was distilled off, and the compound (B-21-a) was obtained in a good yield by purification by column chromatography.

[0287] 30.0 mmol of sodium hydrogen carbonate and 20.0 mmol of triphenylsulfonium bromide were added to the above compound (B-21-a), and a mixed solution of water:dichloromethane (1:1 (mass ratio)) was added to make a 0.5 M solution. After vigorously stirring at room temperature for 3 hours, dichloromethane was added for extraction, and the organic layer was separated. The obtained organic layer was dried over sodium sulfate, and the solvent was distilled off to obtain the compound (B-21) represented by the above formula (B-21) in a good yield.

[0288] The following compounds were used as components other than the above synthesized components.

[0289] [Radiation-sensitive acid generators other than (B-1) to (B-26)] b-1 to b-10: Compounds represented by the following formulas (b-1) to (b-10) (hereinafter, the compounds represented by the formulas (b-1) to (b-10) may be respectively described as "compound (b-1)" to "compound (b-10)").

[0290]

[0291] [Acid diffusion control agents (C)] C-1 to C-10: Compounds represented by the following formulas (C-1) to (C-10) (hereinafter, the compounds represented by the formulas (C-1) to (C-10) may be respectively described as "compound (C-1)" to "compound (C-10)").

[0292]

[0293] [Solvent (E)] E-1: Propylene glycol monomethyl ether acetate E-2: Propylene glycol monomethyl ether E-3: γ-Butyrolactone E-4: Cyclohexanone E-5: Methyl 2-hydroxyisobutyrate E-6: Diacetone alcohol

[0294] [Other additive components (W)] W-1: MEGAFACE EFS-321 (manufactured by DIC Corporation) (non-fluorine type) W-2: BYK-399 (manufactured by Big Chemie Japan Co., Ltd.) (non-silicone type)

[0295] [Preparation of positive-type radiation-sensitive composition for ArF immersion exposure] [Example 1] 100 parts by mass of (A-1) as polymer (A), 12.0 parts by mass of (B-1) as radiation-sensitive acid generator (B), 8.0 parts by mass of (C-1) as acid diffusion control agent (C), 2.0 parts by mass (solids) of (F-1) as highly hydrophobic polymer (F), 0.1 parts by mass of (W-1) as other additive component (W), and 3,400 parts by mass (mass ratio 2240 / 960 / 200) of a mixed solvent of (E-1) / (E-2) / (E-3) as solvent (E) were mixed and filtered through a membrane filter with a pore size of 0.2 μm to prepare a radiation-sensitive composition (J-1).

[0296] [Examples 2-47, 47a-47j and Comparative Examples 1-7] Radiation-sensitive compositions (J-2)-(J-47), (J-47a)-(J-47j) and (CJ-1)-(CJ-7) were prepared in the same manner as in Example 1, except that the components of the types and amounts shown in Tables 4-1 and 4-2 below were used.

[0297]

[0298]

[0299] <Formation of a resist pattern using a positive-type radiation-sensitive composition for ArF immersion 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. The positive-type radiation-sensitive composition for ArF immersion lithography prepared above was 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 85 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 Dipole (σ = 0.9 / 0.7) through a mask pattern with 45 nm holes and a 90 nm pitch. 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 then dried to form a positive-type resist pattern (45 nm holes, 90 nm pitch).

[0300] <Evaluation> The resist patterns formed using the above ArF immersion exposure positive-type radiation-sensitive composition were evaluated for sensitivity, CDU, MEEF, EL, number of development defects, pattern circularity, and pattern rectangularity according to the following methods. The results are shown in Tables 5-1 and 5-2 below. A scanning electron microscope (Hitachi High-Technologies Corporation's "CG-5000") was used to measure the length of the resist patterns.

[0301] [Sensitivity] In forming a resist pattern using the above ArF immersion lithography positive-type radiation-sensitive composition, the exposure amount used to form a pattern with 45 nm holes and a 90 nm pitch 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 conditions are considered "good": 30 mJ / cm² ２ If it exceeded this value, it was rated as "poor."

[0302] [CDU] A resist pattern with 45 nm holes and a 90 nm pitch was measured at 1,800 arbitrary points from the top of the pattern using the scanning electron microscope described above. The dimensional variation (3σ) was determined and defined as CDU (nm). A smaller CDU value indicates less variation in hole diameter over long periods and therefore better performance. CDU performance was evaluated as "good" if it was 3.5 nm or less, and "poor" if it exceeded 3.5 nm.

[0303] [MEEF] For resist patterns resolved by irradiating with the optimal exposure amount described above, the slope of the straight line was calculated when the diameter of the resist pattern formed using mask patterns with hole diameters of 47 nm, 49 nm, 51 nm, 53 nm, and 55 nm was plotted on the vertical axis and the diameter 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."

[0304] [EL (Exposure Margin)] Within the range of exposure amounts including the above optimal exposure amount, the exposure amount is 1 mJ / cm². ２ Each resist pattern was formed by varying the exposure dose, and the diameter of each hole pattern was measured using the scanning electron microscope described above. From the relationship between the obtained diameter and exposure dose, the exposure dose E(49.5) that resulted in a diameter of 49.5 nm and the exposure dose E(40.5) that resulted in a diameter of 40.5 nm were determined, and the exposure margin (EL) was calculated using the formula {(E(40.5) - E(49.5)) / (optimal exposure dose)} × 100. The larger the exposure margin value, the smaller the variation in the size of the pattern obtained when the exposure dose is varied, and the higher the yield during device fabrication. An EL of 7% or more was evaluated as "good," and an EL of less than 7% was evaluated as "poor."

[0305] [Development Defect Count] A resist film was exposed at the optimal exposure level to form a resist pattern with 45 nm holes and a 90 nm pitch, 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 5 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 150 or less, and as "poor" if it exceeded 150.

[0306] [Pattern Circularity] The 45 nm holes and 90 nm pitch contact holes formed by irradiating with the optimal exposure amount determined in the sensitivity evaluation above were observed in plan view using the scanning electron microscope described above, and the vertical and horizontal sizes were measured. If the ratio of vertical size to horizontal size was 0.90 or more and 1.10 or less, it was evaluated as "A" (good), and if it was less than 0.90 or greater than 1.10, it was evaluated as "C" (poor).

[0307] [Pattern Rectangularity] The 45 nm holes and 90 nm pitch contact holes formed by irradiating with the optimal exposure amount determined in the sensitivity evaluation above were observed using the scanning electron microscope described above, and the cross-sectional shape of the contact hole pattern was evaluated. The rectangularity of the resist pattern was evaluated as follows: if the ratio of the length of the lower side to the length of the upper side in the cross-sectional shape of the hole portion was 1 or more and 1.05 or less, it was evaluated as "A" (very good); if it was greater than 1.05 and 1.10 or less, it was evaluated as "B" (good); and if it was greater than 1.10, it was evaluated as "C" (poor).

[0308]

[0309]

[0310] As is clear from the results in Tables 5-1 and 5-2, when the radiation-sensitive composition of the example was used in ArF immersion lithography, it exhibited good sensitivity, CDU, MEEF, EL, development defect performance, and pattern shape, whereas the comparative example exhibited inferior characteristics compared to the example. Therefore, when the radiation-sensitive composition of the example is used in ArF immersion lithography, it is possible to form a resist pattern with high sensitivity and good roughness performance, yield, development defect performance, and pattern shape.

[0311] [Preparation of a negative-type radiation-sensitive composition for ArF immersion 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-8) as a polymer (A), 6.0 parts by mass of (B-5) and 2.0 parts by mass of (b-8) as radiation-sensitive acid generators (B), 3.0 parts by mass of (C-2) as an acid diffusion control agent (C), 5.0 parts by mass of (F-4) as a highly hydrophobic polymer (F) (solid content), and 3,230 parts by mass of a mixed solvent (E) of (E-1) / (E-2) / (E-3) (mass ratio 2,240 / 960 / 30) and filtering the mixture through a membrane filter with a pore size of 0.2 μm.

[0312] 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 100 nm. On this base layer anti-reflective coating, the ArF immersion lithography negative-type radiation-sensitive composition (J-48) prepared above was applied 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 150 nm was formed by cooling at 23°C for 30 seconds. Next, this 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) through a mask pattern with 80 nm holes and a 150 nm pitch. After exposure, post-exposure baking (PEB) was performed at 100°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 (a contact hole pattern with 80 nm holes and a 150 nm pitch).

[0313] The sensitivity, CDU, MEEF, and pattern circularity of the resist pattern using the above-mentioned ArF immersion exposure negative-type radiation-sensitive composition were evaluated in the same manner as the evaluation of the resist pattern using the above-mentioned ArF immersion exposure positive-type radiation-sensitive composition. As a result, the radiation-sensitive composition of Example 48 showed good sensitivity, MEEF, CDU, and pattern circularity even when a negative-type resist pattern was formed by ArF immersion exposure.

[0314] [Preparation of positive-type radiation-sensitive composition for ArF-Dry exposure] [Example 49] 100 parts by mass of (A-6) as polymer (A), 6.0 parts by mass of (B-2) as radiation-sensitive acid generator (B), 2.0 parts by mass of (C-8) as acid diffusion control agent (C), 0.5 parts by mass of (W-1) as other additive component (W), and 2,530 parts by mass of a mixed solvent (E) of (E-1) / (E-4) / (E-3) (mass ratio 1500 / 1000 / 30) were mixed and filtered through a membrane filter with a pore size of 0.2 μm to prepare a radiation-sensitive composition (J-49).

[0315] [Preparation of positive-type radiation-sensitive composition for ArF-Dry exposure, formation and evaluation of resist patterns using this composition] An anti-reflective underlayer film formation composition (ARC29 from Brewer Sciences) was applied to an 8-inch silicon wafer using a spin coater (CLEAN TRACK ACT8 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 77 nm. The positive-type radiation-sensitive composition for ArF-Dry exposure (J-49) prepared above was applied to this anti-reflective underlayer film using the spin coater, and pre-bake (PB) was performed at 100°C for 60 seconds. Subsequently, a resist film with an average thickness of 250 nm was formed by cooling at 23°C for 30 seconds. Next, a 100 nm line-and-space resist pattern was formed on this resist film using an ArF excimer laser exposure system (Nikon's "S306C") under optical conditions of NA = 0.75 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, washed with water after development, and then dried to form a positive-type resist pattern (100 nm line-and-space resist pattern).

[0316] <Evaluation> For resist patterns formed using the above-mentioned positive-type radiation-sensitive composition for ArF-Dry exposure, sensitivity, pattern rectangularity, and number of development defects were evaluated in the same manner as for resist patterns using the above-mentioned positive-type radiation-sensitive composition for ArF immersion exposure. In addition, LWR and DOF were evaluated according to the following method.

[0317] [LWR] A 100 nm line-and-space resist pattern was formed by irradiating with the optimal exposure amount determined in the sensitivity evaluation above. 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. This 3-sigma value was defined as LWR (nm). A smaller LWR value indicates less line roughness and better quality. An LWR of 3.0 nm or less was evaluated as "good," and an LWR greater than 3.0 nm was evaluated as "poor."

[0318] [DOF (Depth of Focus)] In the resist pattern resolved at the optimal exposure amount determined in the sensitivity evaluation above, the dimensions were observed when the focus was changed in the depth direction. The margin in the depth direction where the pattern dimensions fall within 90% to 110% of the standard without bridging or residue was measured, and this measured value was defined as the depth of focus (nm). A larger depth of focus indicates better performance. A depth of focus of 100 nm or more was evaluated as "good," and a depth of focus of less than 100 nm was evaluated as "poor."

[0319] As a result, the radiation-sensitive composition of Example 49 exhibited good sensitivity, LWR, DOF, pattern rectangularity, and development defect performance even when a positive-type resist pattern was formed by ArF-Dry exposure.

[0320] [Preparation of positive-type radiation-sensitive composition for extreme ultraviolet (EUV) exposure] [Example 50] 100 parts by mass of (A-12) as polymer (A), 50.0 parts by mass of (B-7) as radiation-sensitive acid generator (B), 40.0 parts by mass of (C-5) as acid diffusion control agent (C), 3.0 parts by mass (solids) of (F-5) as highly hydrophobic polymer (F), 0.1 parts by mass of (W-1) as other additive component (W), and 6,200 parts by mass (mass ratio 2,000 / 4,200) of a mixed solvent of (E-1) / (E-2) as solvent (E) were mixed and filtered through a membrane filter with a pore size of 0.2 μm to prepare a radiation-sensitive composition (J-50).

[0321] [Examples 51-67 and Comparative Examples 8-12] Radiation-sensitive compositions (J-51) to (J-67) and (CJ-8) to (CJ-12) were prepared in the same manner as in Example 50, except that the types and amounts of each component shown in Table 6 below were used.

[0322]

[0323] <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 prepared positive-type radiation-sensitive composition for EUV exposure was applied to this anti-reflective underlayer film using the spin coater, and PB (plate blot) was performed at 130°C for 60 seconds. Subsequently, a resist film with an average thickness of 50 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, washed with water after development, and then dried to form a positive-type resist pattern (25 nm contact hole pattern).

[0324] <Evaluation> The resist patterns formed using the above-mentioned positive-type radiation-sensitive composition for EUV exposure were evaluated for sensitivity, CDU, number of development defects, and pattern circularity 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.

[0325] [Sensitivity] In forming a resist pattern using the above-mentioned positive-type radiation-sensitive composition for EUV exposure, the exposure amount used to form a 25 nm contact hole pattern was defined as the optimal exposure amount, and this optimal exposure amount was defined as the sensitivity (mJ / cm²). The sensitivity was 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."

[0326] [CDU] The mask size was adjusted to form a 25 nm contact hole 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 hole diameter was measured at 16 points in the range of 500 nm and the average value was calculated. This average value was then measured at a total of 500 points at arbitrary points, and the 3-sigma value was calculated from the distribution of the measured values, which was defined as CDU (nm). A smaller CDU value indicates less variation in hole diameter over long periods and is therefore better. A CDU of 3.0 nm or less was evaluated as "good," and a value greater than 3.0 nm was evaluated as "poor."

[0327] [Development Defect Count] A 25 nm contact hole pattern was formed by exposing a resist film with the optimal exposure dose, and this was used as a wafer for defect inspection. The number of defects on this wafer for defect inspection was measured using a defect inspection device (KLA-Tencor's "KLA2810"). Defects with a diameter of 5 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 100 or less, and as "poor" if it exceeded 100.

[0328] [Pattern Circularity] The 25 nm contact holes formed by irradiating with the optimal exposure amount determined in the sensitivity evaluation above were observed in plan view using the scanning electron microscope described above, and their vertical and horizontal sizes were measured. If the ratio of vertical size to horizontal size was 0.90 or more and 1.10 or less, it was evaluated as "A" (good), and if it was less than 0.90 or greater than 1.10, it was evaluated as "C" (poor).

[0329]

[0330] As is clear from the results in Table 7, the radiation-sensitive compositions of the examples showed good sensitivity, CDU, development defect performance, and pattern circularity when used in EUV exposure, whereas the comparative examples exhibited inferior characteristics compared to the examples.

[0331] [Preparation of a negative-type radiation-sensitive composition for EUV exposure, formation and evaluation of a resist pattern using this composition] [Example 68] A radiation-sensitive composition (J-68) was prepared by mixing 100 parts by mass of (A-15) as polymer (A), 40.0 parts by mass of (B-4) as radiation-sensitive acid generator (B), 20.0 parts by mass of (C-1) as acid diffusion control agent (C), 2.0 parts by mass of (F-1) as highly hydrophobic polymer (F) (solids content), and 6,110 parts by mass of a mixed solvent of (E-1) / (E-2) (mass ratio 4,280 / 1,830) as solvent (E), and filtering the mixture through a membrane filter with a pore size of 0.2 μm.

[0332] 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 105 nm. On this base layer anti-reflective coating, the prepared negative-type radiation-sensitive composition for EUV exposure (J-68) was applied 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 55 nm was formed by cooling at 23°C for 30 seconds. Next, this resist film was exposed using an EUV exposure apparatus ("NXE3300" from ASML) with NA = 0.33, illumination conditions: Conventional s = 0.89, and mask: imecDEFECT32FFR15. After exposure, PEB was performed at 120°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 (a contact hole pattern with 20 nm holes and a 40 nm pitch).

[0333] The resist patterns using the above-mentioned negative-type radiation-sensitive composition for EUV exposure were evaluated in the same manner as the evaluation of the resist patterns using the above-mentioned positive and negative-type radiation-sensitive compositions for ArF immersion exposure. As a result, the radiation-sensitive composition of Example 68 showed good sensitivity, CDU, and pattern circularity even when a negative-type resist pattern was formed by EUV exposure.

[0334] The radiation-sensitive composition, pattern-forming method, and compound described above exhibit good sensitivity to exposure light during pattern formation, and can demonstrate excellent CDU, LWR, MEEF, EL, development defect suppression, pattern circularity, pattern rectangularity, and DOF. Therefore, these can be suitably used in semiconductor device processing processes and the like, where further miniaturization is expected in the future.

Claims

The compound represented by the following formula (1), A polymer containing a structural unit (I) having an acid-dissociable group, Solvent and A radiation-sensitive composition containing [a specific substance]. (In formula (1), W is a substituted or unsubstituted cyclic structure containing an acetal structure. L is a substituted or unsubstituted divalent hydrocarbon group having 1 to 5 carbon atoms, or a group containing a divalent heteroatom between the carbon atoms of the hydrocarbon group. R １ is a hydrogen atom, -CN, -NO ２ , -F, -CF ２ R ａ , -SO ２ R ｂ , -COR ｃ , or a monovalent organic group (a) having 1 to 20 carbon atoms other than -CN, -CF ２ R ａ , -SO ２ R ｂ , -COR ｃ or -CF ３ is a monovalent organic group (a) having 1 to 20 carbon atoms other than. R ａ is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. R ｂ and R ｃ are each independently a monovalent organic group having 1 to 20 carbon atoms. Z ＋ It is a monovalent organic cation. L ｇ This refers to a single bond, a divalent heteroatom-containing group, or a divalent organic group having 1 to 20 carbon atoms. A - -COO - or -SO ３ - That is the case. Z ｇ ＋ It is a monovalent organic cation. g is either 0 or 1. R １ The radiation-sensitive composition according to claim 1, wherein is -CN. 　 The radiation-sensitive composition according to claim 1, wherein L is a divalent chain-like saturated hydrocarbon group having 1 to 5 carbon atoms or a divalent group containing an ester bond between carbon atoms of the chain-like saturated hydrocarbon group. 　 The radiation-sensitive composition according to claim 1, wherein L is a methanediyl group or an ethanediyl group. 　 The radiation-sensitive composition according to any one of claims 1 to 4, wherein W is a cyclic acetal structure, or a combination of the cyclic acetal structure and a cycloalkane structure that forms a spiro ring structure or a fused ring structure. Z ＋ The radiation-sensitive composition according to any one of claims 1 to 4, wherein is a monovalent radiation-sensitive onium cation. Z ＋ The radiation-sensitive composition according to claim 6, wherein is a monovalent sulfonium cation or iodonium cation. 　 The radiation-sensitive composition according to any one of claims 1 to 4, wherein the content of the above compound is 0.1 parts by mass or more and 70 parts by mass or less per 100 parts by mass of the above polymer. 　 The above-mentioned structural unit (I) having an acid-dissociable group is represented by the following formula (3), the radiation-sensitive composition according to any one of claims 1 to 4. (In formula (3), R １７ These are a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R １８ This is a monovalent substituted or unsubstituted hydrocarbon group having 1 to 20 carbon atoms. R １９ and R ２０ Each of these is independently either a monovalent substituted or unsubstituted linear hydrocarbon group having 1 to 10 carbon atoms, or a monovalent substituted or unsubstituted alicyclic hydrocarbon group having 3 to 20 carbon atoms, or R １９ and R ２０ These elements combine with each other to form a divalent alicyclic group with 3 to 20 carbon atoms, which is composed of carbon atoms to which they are bonded. L 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. 　 The radiation-sensitive composition according to claim 9, wherein the content of the structural unit (I) in the total structural units constituting the polymer is 1 mol% or more and 70 mol% or less. 　 A radiation-sensitive composition according to any one of claims 1 to 4, further comprising an acid diffusion control agent. 　 A step of forming a resist film by directly or indirectly applying a radiation-sensitive composition according to any one of claims 1 to 4 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 formation method according to claim 12, wherein the exposure is performed using an ArF excimer laser or extreme ultraviolet light. 　 A compound represented by the following formula (1). (In formula (1), W is a substituted or unsubstituted cyclic structure containing an acetal structure. L is a substituted or unsubstituted divalent hydrocarbon group having 1 to 5 carbon atoms, or a group containing a divalent heteroatom between the carbon atoms of the hydrocarbon group. R １ These are hydrogen atoms, -CN, and -NO ２ -F, -CF ２ R ａ , -SO ２ R ｂ ,-COR ｃ , or -CN, -CF ２ R ａ , -SO ２ R ｂ ,-COR ｃ Or -CF ３ (a) is a monovalent organic group with 1 to 20 carbon atoms other than R. ａ R is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. ｂ and R ｃ Each of these is independently a monovalent organic group having 1 to 20 carbon atoms. Z ＋ It is a monovalent organic cation. L ｇ This refers to a single bond, a divalent heteroatom-containing group, or a divalent organic group having 1 to 20 carbon atoms. A - -COO - or -SO ３ - That is the case. Z ｇ ＋ It is a monovalent organic cation. g is either 0 or 1.

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