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

Abstract

The invention provides a radiation-sensitive composition, a pattern forming method and an onium salt compound. The radiation-sensitive composition can exert sensitivity or LWR performance and CDU performance at a sufficient level when a resist pattern is formed and has good storage stability. A radiation-sensitive composition containing an onium salt compound represented by formula (1), a polymer containing a structural unit (I) having an acid-dissociable group, and a solvent (in formula (1), W represents a cyclic structure having 3-40 ring members and formed together with two carbon atoms; the following formula between carbon and carbon represents a single bond or a double bond; a represents a group represented by formula (A-1), a group represented by formula (A-2), a group represented by formula (A-3), a group represented by formula (A-4), a group represented by formula (A-5), a group represented by formula (A-6), or a group represented by formula (A-7); (In formula (A-3) and formula (A-4), RA1 and RA2 are each independently a monovalent hydrocarbon group having 1 to 20 carbon atoms; * represents a carbon atom-bonded bond) R1 represents a monovalent organic group having 1-20 carbon atoms, a cyano group, a nitro group, a carboxyl group, a hydroxyl group, an amino group, a halogen atom, or a thiol group; when a plurality of R1 are present, the plurality of R1 are the same as or different from each other; m1 is an integer of 0-4; and Z + represents a monovalent radiation-sensitive onium cation. > # imgabs0 #

Description

Technical Field

[0001] The present invention relates to a radiation-sensitive composition, a pattern forming method and an onium salt compound. Background Art

[0002] Photolithography using a resist composition is utilized to form fine circuits in semiconductor devices. A typical process involves exposing a film of the resist composition to radiation through a mask pattern to generate an acid. This acid acts as a catalyst for a reaction that creates a difference in the solubility of the polymer in an alkaline or organic developer between the exposed and unexposed areas, thereby forming a resist pattern on a substrate.

[0003] In this lithography technology, pattern miniaturization is being promoted by utilizing short-wavelength radiation such as ArF excimer lasers, or by using liquid immersion lithography, in which exposure is performed while the space between the lens and the resist film of the exposure device is filled with a liquid medium. Research is also underway as a next-generation technology using lithography with even shorter wavelengths, such as electron beams, X-rays, and extreme ultraviolet (EUV).

[0004] Regarding photoacid generators, which are the main components of resist compositions, perfluoroalkylsulfonic acids, which can impart strong acids, are often used to improve sensitivity and resolution. Meanwhile, due to increasing environmental awareness in recent years, research has been conducted on photoacid generators with reduced fluorine atom content (see Japanese Patent No. 7015295).

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent No. 7015295 Summary of the Invention

[0008] Problems to be solved by the invention

[0009] Even photoacid generators with reduced fluorine atom content are required to have equivalent or better resist performance than before in terms of sensitivity, line width roughness (LWR) performance indicating line width or line width deviation of resist patterns, and critical dimension uniformity (CDU) performance.

[0010] Meanwhile, the present inventors have studied photoacid generators having a reduced fluorine atom content and have found that the storage stability of the resist composition may be reduced.

[0011] An object of the present invention is to provide a radiation-sensitive composition, a pattern forming method, and an onium salt compound that can exhibit sufficient sensitivity, LWR performance, and CDU performance during resist pattern formation and have good storage stability.

[0012] Technical means to solve the problem

[0013] The present inventors have diligently studied to solve the problem and, as a result, have found that the object can be achieved by adopting the following structure, thereby completing the present invention.

[0014] That is, the present invention, in one embodiment, relates to a radiation-sensitive composition comprising:

[0015] An onium salt compound represented by the following formula (1) (hereinafter also referred to as "onium salt compound (1)"),

[0016] A polymer containing a structural unit (I) having an acid-dissociable group, and

[0017] solvent.

[0018] [Chemistry 1]

[0019]

[0020] (In formula (1),

[0021] W is a cyclic structure with 3 to 40 ring members formed together with two carbon atoms;

[0022] The following formulas between carbon-carbons represent single bonds or double bonds;

[0023] [Chemistry 2]

[0024]

[0025] A is a group represented by the following formula (A-1), a group represented by the following formula (A-2), a group represented by the following formula (A-3), a group represented by the following formula (A-4), a group represented by the following formula (A-5), a group represented by the following formula (A-6), or a group represented by the following formula (A-7) (hereinafter, these groups are collectively referred to as "specific polar groups");

[0026] [Chemistry 3]

[0027]

[0028] (In formula (A-3) and formula (A-4), RA1 and R A2 are each independently a monovalent hydrocarbon group having 1 to 20 carbon atoms; * is a bond to a carbon atom)

[0029] R 1 is a monovalent organic group with 1 to 20 carbon atoms, a cyano group, a nitro group, a carboxyl group, a hydroxyl group, an amino group, a halogen atom or a thiol group; in R 1 When there are multiple R 1 the same as or different from each other;

[0030] m1 is an integer from 0 to 4;

[0031] Z + (a monovalent radiosensitive linear onium cation)

[0032] Since the radiation-sensitive composition contains the onium salt compound (1) as a radiation-sensitive acid generator, it can exhibit excellent sensitivity, LWR performance, and CDU performance during pattern formation and also has good storage stability. The reasons for this are, without being bound by any theory, presumably as follows.

[0033] It is speculated that in the onium salt compound (1), a specific polar group containing a hydrogen atom is bonded to a carbon atom adjacent to the carbon atom bonded to the sulfonate anion. By generating a hydrogen bond between the sulfonate anion and the hydrogen atom of the specific polar group due to the above-mentioned stereo configuration, the anion can be stabilized, and as a result, the strength of the generated acid is increased, and the various properties of the above-mentioned resist can be exerted. On the other hand, in the previous photoacid generators in which electron-withdrawing groups (including ester bonds) are arranged around the sulfonate anion, there are cases where the sensitivity becomes extremely low or the ester bond is decomposed and the storage stability is reduced depending on the positional relationship of these or the degree of freedom of the sulfonate anion. In the onium salt compound (1), the strong acidification is adopted, which is caused by the anion stabilization caused by the hydrogen bond between the sulfonate anion and the specific polar group bonded to the β-position carbon in the ring structure (or the ortho position if the ring structure is an aromatic ring), rather than the strong acidification caused by the arrangement of the electron-withdrawing group. This can reduce the influence of the electron-withdrawing group or the degree of freedom of the sulfonate anion, and can control the sensitivity to an appropriate range. Furthermore, the instability (decomposition, etc.) of the compound itself caused by the electron-withdrawing group can be suppressed, thereby achieving good storage stability. In addition, the so-called organic group refers to a group containing at least one carbon atom.

[0034] In another embodiment, the present invention relates to a method for forming a pattern, comprising:

[0035] a step of directly or indirectly coating the radiation-sensitive composition on a substrate to form a resist film;

[0036] a step of exposing the resist film to light; and

[0037] A step of developing the exposed resist film using a developer.

[0038] In the pattern forming method, since the radiation-sensitive composition having excellent sensitivity, LWR performance, and CDU performance and good storage stability is used during pattern formation, a high-quality resist pattern can be formed with good yield.

[0039] In another embodiment, the present invention relates to an onium salt compound represented by the following formula (1).

[0040] [Chemistry 4]

[0041]

[0042] (In formula (1),

[0043] W is a cyclic structure with 3 to 40 ring members formed together with two carbon atoms;

[0044] The following formulas between carbon-carbons represent single bonds or double bonds;

[0045] [Chemistry 5]

[0046]

[0047] A is a group represented by the following formula (A-1), a group represented by the following formula (A-2), a group represented by the following formula (A-3), a group represented by the following formula (A-4), a group represented by the following formula (A-5), a group represented by the following formula (A-6), or a group represented by the following formula (A-7);

[0048] [Chemistry 6]

[0049]

[0050] (In formula (A-3) and formula (A-4), R A1 and R A2 are each independently a monovalent hydrocarbon group having 1 to 20 carbon atoms; * is a bond to a carbon atom)

[0051] R 1 is a monovalent organic group with 1 to 20 carbon atoms, a cyano group, a nitro group, a carboxyl group, a hydroxyl group, an amino group, a halogen atom or a thiol group; in R 1 When there are multiple R 1 the same as or different from each other;

[0052] m1 is an integer from 0 to 4;

[0053] Z + (a monovalent radiosensitive linear onium cation)

[0054] Since the onium salt compound has the specific structure, when used in a radiation-sensitive composition, the onium salt compound has good storage stability and can exhibit excellent sensitivity, LWR performance, and CDU performance during pattern formation. DETAILED DESCRIPTION

[0055] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to these embodiments. In addition, combinations of preferred embodiments are also preferred.

[0056] <Radiation-sensitive composition>

[0057] The radiation-sensitive composition of this embodiment (hereinafter also referred to as "composition") comprises an onium salt compound (1), a polymer, and a solvent. It may further comprise an acid diffusion controller as needed. The composition may also comprise other optional components as long as the effects of the present invention are not impaired.

[0058] (Onium salt compound (1))

[0059] The onium salt compound (1) is represented by the above formula (1) and functions as a radiation-sensitive acid generator that generates an acid upon irradiation with radiation.

[0060] As the cyclic structure of the ring member number 3~40 constituted together with two carbon atoms represented by W, though not particularly limited, it is preferably the alicyclic hydrocarbon structure of carbon number 3~20, the aromatic hydrocarbon structure of carbon number 6~20, the aliphatic heterocyclic structure of carbon number 3~20 or the aromatic heterocyclic structure of carbon number 5~20.Or, these ring structures can be combined.As the form of combination, it is possible to enumerate: the condensed ring that two adjacent rings have a limit (bond between two adjacent atoms), the ring aggregate that two adjacent rings utilize single bond bonding, the spirocycle that two adjacent rings have a carbon atom etc.As the form of combination, it is preferably condensed ring.

[0061] As the alicyclic hydrocarbon structure having 3 to 20 carbon atoms, a structure corresponding to a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms can be preferably used. Examples of the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms include monocyclic or polycyclic saturated hydrocarbon groups, or monocyclic or polycyclic unsaturated hydrocarbon groups. Monocyclic saturated hydrocarbon groups are preferably cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl. Polycyclic cycloalkyl groups are preferably bridged alicyclic hydrocarbon groups such as norbornyl, adamantyl, tricyclodecyl, and tetracyclododecyl. Monocyclic unsaturated hydrocarbon groups include monocyclic cycloalkenyl groups such as cyclopropenyl, cyclobutenyl, cyclopentenyl, and cyclohexenyl. Polycyclic unsaturated hydrocarbon groups include polycyclic cycloalkenyl groups such as norbornyl, tricyclodecenyl, and tetracyclododecenyl. The bridged alicyclic hydrocarbon group refers to a polycyclic alicyclic hydrocarbon group in which two carbon atoms that are not adjacent to each other among the carbon atoms constituting the alicyclic ring are bonded via a linking group containing one or more carbon atoms.

[0062] As the aromatic hydrocarbon structure having 6 to 20 carbon atoms, a structure corresponding to a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms can be preferably used. Examples of the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms include aryl groups such as phenyl, tolyl, xylyl, naphthyl, and anthracenyl; and aralkyl groups such as benzyl, phenethyl, and naphthylmethyl.

[0063] Examples of the aliphatic heterocyclic structure having 3 to 20 carbon atoms include:

[0064] Aliphatic heterocyclic structures containing oxygen atoms such as oxadiazine, tetrahydrofuran, tetrahydropyran, dioxolane, and dioxane;

[0065] Aliphatic heterocyclic structures containing nitrogen atoms such as aziridine, pyrrolidine, piperidine, and piperazine;

[0066] Aliphatic heterocyclic structures containing sulfur atoms such as thietane, thiolane, and thiazane;

[0067] Aliphatic heterocyclic structures containing multiple heteroatoms such as morpholine, 1,2-oxathiolane, and 1,3-oxathiolane.

[0068] Examples of the aliphatic heterocyclic structure include lactone structures, cyclic carbonate structures, sultone structures, and structures containing cyclic acetals and cyclic ketones. Examples of such structures include the structures represented by the following formulas (H-1) to (H-12). Furthermore, although all carbon-carbon bonds in the structural formulas shown below are saturated bonds, unsaturated bonds may be introduced as long as the atomic valence permits.

[0069] [Chemistry 7]

[0070]

[0071] In the above formula, γ is an integer of 1 to 3.

[0072] Examples of the aromatic heterocyclic structure having 5 to 20 carbon atoms include:

[0073] Aromatic heterocyclic structures containing oxygen atoms such as furan, pyran, benzofuran, and benzopyran;

[0074] Aromatic heterocyclic structures containing nitrogen atoms such as pyrrole, imidazole, pyridine, pyrimidine, pyrazine, indole, quinoline, isoquinoline, acridine, phenazine, and carbazole;

[0075] Aromatic heterocyclic structures containing sulfur atoms such as thiophene;

[0076] Aromatic heterocyclic structures containing multiple heteroatoms such as thiazole, benzothiazole, thiazine, and oxazine.

[0077] When the following formula between carbon and carbon in W in the above formula (1) represents a double bond, the double bond also includes a conjugated bond when the cyclic structure exhibits aromaticity.

[0078] [Chemistry 8]

[0079]

[0080] Among them, the cyclic structure with 3 to 40 ring members as W is more preferably a polycyclic alicyclic hydrocarbon structure with 6 to 14 carbon atoms, an aromatic hydrocarbon structure with 6 to 12 carbon atoms, a monocyclic aliphatic unsaturated heterocyclic structure with 5 to 8 carbon atoms, or an aromatic heterocyclic structure with 5 to 8 carbon atoms.

[0081] As R in the formula (A-3) and formula (A-4) A1 and R A2 Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms include a monovalent chain hydrocarbon group having 1 to 20 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms, and combinations thereof.

[0082] Examples of the monovalent chain hydrocarbon group having 1 to 20 carbon atoms include a linear or branched saturated hydrocarbon group having 1 to 20 carbon atoms, and a linear or branched unsaturated hydrocarbon group having 1 to 20 carbon atoms.

[0083] As the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms shown in W can be preferably used.

[0084] As the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms, the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms shown in W can be preferably used.

[0085] As R in the formula (A-3) and formula (A-4) A1 and R A2 The monovalent hydrocarbon group having 1 to 20 carbon atoms is preferably a monovalent chain hydrocarbon group having 1 to 20 carbon atoms, more preferably a monovalent chain saturated hydrocarbon group having 1 to 10 carbon atoms, and further preferably a monovalent branched chain saturated hydrocarbon group having 1 to 5 carbon atoms.

[0086] As R in the formula (1) 1Examples of the monovalent organic group having 1 to 20 carbon atoms represented by the group include a monovalent hydrocarbon group having 1 to 20 carbon atoms, a group in which a portion or all of the hydrogen atoms contained in the hydrocarbon group are substituted with a substituent (hereinafter also referred to as "group (α)"), a group containing -CO-, -CS-, -O-, -S-, -SO2-, -NR'-, or a combination of two or more of these between carbon atoms in the hydrocarbon group or group (α) (hereinafter also referred to as "group (β)"), or a combination thereof. R' is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms.

[0087] As the monovalent hydrocarbon group having 1 to 20 carbon atoms, R in the formula (A-3) and (A-4) can be preferably used. A1 and R A2 The represented monovalent hydrocarbon group has 1 to 20 carbon atoms.

[0088] Examples of the substituent that replaces a part or all of the hydrogen atoms possessed by the organic group include: a halogen atom such as a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom; a hydroxyl group; a carboxyl group; a cyano group; a nitro group; an alkyl group, an alkoxy group, an alkoxycarbonyl group, an alkoxycarbonyloxy group, an acyl group, an acyloxy group, or a group in which the hydrogen atoms of these groups are substituted with a halogen atom; a pendant oxy group (=O), and the like.

[0089] As R in the formula (1) 1 Examples of the halogen atom represented by include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc. The halogen atom is preferably a chlorine atom, a bromine atom, or an iodine atom, and more preferably an iodine atom.

[0090] m1 is preferably an integer of 0-3, more preferably an integer of 0-2.

[0091] Specific examples of the anion of the onium salt compound (1) are not limited, but include structures of the following formulae (1-1-1) to (1-1-22).

[0092] [Chemistry 9]

[0093]

[0094] [Chemistry 10]

[0095]

[0096] In the formula (1), Z +The monovalent radiation-sensitive onium cation represented by Z includes, for example, radiation-decomposable onium cations containing elements such as S, I, O, N, P, Cl, Br, F, As, Se, Sn, Sb, Te, and Bi. Examples of the radiation-decomposable onium cation include sulfonium cations, tetrahydrothiophenium cations, iodonium cations, phosphonium cations, diazonium cations, and pyridinium cations. Among them, sulfonium cations and iodonium cations are preferred. + It is preferably a monovalent sulfonium cation containing at least one aromatic ring, more preferably a monovalent iodonium cation containing at least one aromatic ring. The sulfonium cation or iodonium cation is preferably represented by the following formula (X-1) to formula (X-6).

[0097] [Chemistry 11]

[0098]

[0099] In the formula (X-1), R a1 、R a2 and R a3 are independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, an alkoxy group or an alkoxycarbonyloxy group, a substituted or unsubstituted monocyclic or polycyclic cycloalkyl group having 3 to 12 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, a hydroxyl group, a halogen atom, -OSO2-R P 、-SO2-R Q or -SR T , or represents a ring structure formed by combining two or more of these groups. The ring structure may contain heteroatoms such as O or S between the carbon-carbon bonds forming the skeleton. P 、R Q and R T Each of k1, k2 and k3 is independently an integer from 0 to 5. In R a1 ~R a3 and R P 、R Q and R T In the case of multiple R a1 ~R a3 and R P 、R Q and R T They may be the same or different.

[0100] In the formula (X-2), R b1It is a substituted or unsubstituted linear or branched alkyl group having 1 to 20 carbon atoms, or an alkoxy group, a substituted or unsubstituted acyl group having 2 to 8 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 8 carbon atoms, or a hydroxyl group. k is 0 or 1. k When n is 0, k4 is an integer from 0 to 4. k When is 1, k4 is an integer from 0 to 7. b1 In the case of multiple R b1 Can be the same or different. In addition, multiple R b1 It can also be expressed as a ring structure formed by mutual combination. b2 L is a substituted or unsubstituted linear or branched alkyl group having 1 to 7 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 or 7 carbon atoms. C is a single bond or a divalent linking group. k5 is an integer from 0 to 4. b2 In the case of multiple R b2 Can be the same or different. In addition, multiple R b2 It can also be expressed as a ring structure formed by mutual bonding. q is an integer from 0 to 3. + The ring structure may contain heteroatoms such as O or S between the carbon-carbon bonds forming the skeleton.

[0101] In the formula (X-3), R c1 、R c2 and R c3 Each is independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 12 carbon atoms. c1 、R c2 and R c3 At least one of the group is a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms.

[0102] In the formula (X-4), R g1 It is a substituted or unsubstituted linear or branched alkyl group or alkoxy group having 1 to 20 carbon atoms, a substituted or unsubstituted acyl group having 2 to 8 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 8 carbon atoms, or a hydroxyl group. k2 is 0 or 1. k2 When n is 0, k10 is an integer from 0 to 4. k2 When it is 1, k10 is an integer from 0 to 7. g1 In the case of multiple R g1 Can be the same or different. In addition, multiple R g1 It can also be expressed as a ring structure formed by mutual combination. g2 and Rg3 Each of k11 and k12 is independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, an alkoxy group or an alkoxycarbonyloxy group, a substituted or unsubstituted monocyclic or polycyclic cycloalkyl group having 3 to 12 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, a hydroxyl group, a halogen atom, or a ring structure formed by combining these groups. k11 and k12 are each independently an integer from 0 to 4. In R g2 and R g3 In the case of multiple R g2 and R g3 They may be the same or different.

[0103] In the formula (X-5), R d1 and R d2 Each of k6 and k7 is independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, an alkoxy group or an 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 combining two or more of these groups. k6 and k7 are independently an integer from 0 to 5. In R d1 and R d2 In the case of multiple R d1 and R d2 They may be the same or different.

[0104] In the formula (X-6), R e1 and R e2 Each of k8 and k9 is 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. k8 and k9 are each independently an integer of 0 to 4.

[0105] Specific examples of the radiation-sensitive onium cation include, but are not limited to, structures represented by the following formulae (1-2-1) to (1-2-50).

[0106] [Chemistry 12]

[0107]

[0108] [Chemistry 13]

[0109]

[0110] [Chemistry 14]

[0111]

[0112] The onium salt compound (1) can be obtained by appropriately combining the above anion and the above radiation-sensitive onium cation. Specific examples thereof are not particularly limited, but include the structures of the following formulae (1-1) to (1-22).

[0113] [Chemistry 15]

[0114]

[0115] [Chemistry 16]

[0116]

[0117] [Chemistry 17]

[0118]

[0119] [Chemistry 18]

[0120]

[0121] The lower limit of the content of the onium salt compound (1) (the total of these when multiple onium salt compounds (1) are included) relative to 100 parts by mass of the polymer described later is preferably 1 part by mass, more preferably 3 parts by mass, further preferably 5 parts by mass, and particularly preferably 8 parts by mass. The upper limit of the content is preferably 40 parts by mass, more preferably 30 parts by mass, further preferably 20 parts by mass, and further more preferably 15 parts by mass. The content of the onium salt compound (1) can be appropriately selected according to the type of polymer used, exposure conditions or required sensitivity, etc. Thus, the storage stability of the composition can be maintained, and excellent sensitivity or LWR performance and CDU performance can be exerted when the resist pattern is formed.

[0122] (Synthesis Method of Onium Salt Compound (1))

[0123] The method for synthesizing an onium salt compound (1) will be described for the case where A in the formula (1) is a hydroxyl group. The target onium salt compound (1) can be synthesized by reacting a hydroxysulfonate salt (e.g., potassium salt, etc.) corresponding to the target anion structure with an onium cation halide salt (e.g., bromide salt, etc.) corresponding to the onium cation structure, followed by salt exchange. Onium salt compounds (1) having other structures can also be synthesized similarly by appropriately selecting starting materials or precursors corresponding to the anion and onium cation structure.

[0124] (polymer)

[0125] A polymer is an aggregate of polymer chains (hereinafter also referred to as a "base polymer") containing a structural unit having an acid-dissociable group (hereinafter also referred to as "structural unit (I)"). The term "acid-dissociable group" refers to a group that replaces a hydrogen atom possessed by a carboxyl group, a phenolic hydroxyl group, an alcoholic hydroxyl group, a sulfonic group, or the like, and that dissociates upon the action of an acid. The radiation-sensitive composition, due to the presence of structural unit (I) in the polymer, exhibits excellent pattern-forming properties.

[0126] The base polymer preferably includes, in addition to the structural unit (I), a structural unit (II) comprising at least one selected from the group consisting of a lactone structure, a cyclic carbonate structure, and a sultone structure, as described below. It may also include structural units other than the structural units (I) and (II). Each structural unit is described below.

[0127] [Structural unit (I)]

[0128] Structural unit (I) is a structural unit containing an acid-dissociable group. Structural unit (I) is not particularly limited as long as it contains an acid-dissociable group. Examples thereof include structural units having a tertiary alkyl ester moiety, structural units having a structure in which the hydrogen atom of a phenolic hydroxyl group is substituted with a tertiary alkyl group, and structural units having an acetal bond. From the perspective 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.

[0129] [Chemistry 19]

[0130]

[0131] In the formula (3), R 17 is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. 18 is a monovalent hydrocarbon group having 1 to 20 carbon atoms. 19 and R 20 are independently a monovalent chain hydrocarbon group having 1 to 10 carbon atoms or a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, or R 19 and R 20 These carbon atoms are bonded to each other and together with these bonded carbon atoms form a divalent alicyclic group having 3 to 20 carbon atoms.

[0132] As the R 17 From the viewpoint of improving the copolymerizability of the monomer of the structural unit (I-1), a hydrogen atom or a methyl group is preferred, and a methyl group is more preferred.

[0133] As the R 18 The monovalent hydrocarbon group having 1 to 20 carbon atoms represented by is preferably R in the formula (A-3) and (A-4).A1 and R A2 The represented monovalent hydrocarbon group has 1 to 20 carbon atoms.

[0134] As the R 18 , preferably a linear or branched saturated hydrocarbon group having 1 to 10 carbon atoms, an alicyclic hydrocarbon group having 3 to 20 carbon atoms, or an aromatic hydrocarbon group having 6 to 10 carbon atoms.

[0135] The R 19 and R 20 The divalent alicyclic group having 3 to 20 carbon atoms, which is formed by combining these carbon atoms, is not particularly limited as long as it is a group formed by removing two hydrogen atoms from the same carbon atom of a carbon ring of a monocyclic or polycyclic alicyclic hydrocarbon having the above carbon number. It can be either a monocyclic hydrocarbon group or a polycyclic hydrocarbon group. As a polycyclic hydrocarbon group, it can be either a bridged alicyclic hydrocarbon group or a condensed alicyclic hydrocarbon group, and it can be either a saturated hydrocarbon group or an unsaturated hydrocarbon group. In addition, the so-called condensed alicyclic hydrocarbon group refers to a polycyclic alicyclic hydrocarbon group composed of multiple alicyclic rings sharing a common edge (a bond between two adjacent carbon atoms).

[0136] As the saturated hydrocarbon group in the monocyclic alicyclic hydrocarbon group, cyclopentanediyl, cyclohexanediyl, cycloheptanediyl, cyclooctanediyl and the like are preferred, and as the unsaturated hydrocarbon group, cyclopentendiyl, cyclohexendiyl, cycloheptenediyl, cyclooctendiyl, cyclodecenediyl and the like are preferred. As the polycyclic alicyclic hydrocarbon group, a bridged alicyclic saturated hydrocarbon group is preferred, for example, bicyclo[2.2.1]heptane-2,2-diyl (norbornane-2,2-diyl), bicyclo[2.2.2]octane-2,2-diyl, tricyclo[3.3.1.1 3,7 ]Decan-2,2-diyl (adamantane-2,2-diyl), etc.

[0137] Among these, R 18 is an alkyl group with 1 to 4 carbon atoms or a phenyl group, R 19 and R 20 The alicyclic structure formed by combining these carbon atoms with each other is a polycyclic or monocyclic cycloalkane structure.

[0138] Examples of the structural unit (I-1) include structural units represented by the following formulae (3-1) to (3-8) (hereinafter also referred to as “structural units (I-1-1) to (I-1-8)”).

[0139] [Chemistry 20]

[0140]

[0141] In the above formulas (3-1) to (3-8), R 17 ~R 20It has the same meaning as in the above formula (3). h is an integer of 1 to 4. i and j are each independently an integer of 1 to 4. k and l are 0 or 1.

[0142] i and j are preferably 1. 18 , preferably methyl, ethyl, isopropyl, tert-butyl, cyclopentyl or phenyl. 19 and R 20 , preferably methyl or ethyl.

[0143] As the structural unit (I-1), the structural unit (I-1-1) represented by the above formula (3-1) is preferred. In this case, R 18 Preferred are isopropyl, tert-butyl or phenyl.

[0144] The base polymer may contain one type of structural unit (I) or a combination of two or more types.

[0145] The lower limit of the content ratio of the structural unit (I) relative to all the structural units constituting the base polymer (the total content ratio when multiple structural units are included) is preferably 10 mol%, more preferably 20 mol%, further preferably 30 mol%, and particularly preferably 40 mol%. Furthermore, the upper limit of the content ratio is preferably 80 mol%, more preferably 70 mol%, further preferably 60 mol%, and particularly preferably 55 mol%. By setting the content ratio of the structural unit (I) within the above range, the pattern forming properties of the radiation-sensitive composition can be further improved.

[0146] [Structural unit (II)]

[0147] Structural unit (II) is a structural unit comprising at least one selected from the group consisting of a lactone structure, a cyclic carbonate structure, and a sultone structure. By further comprising structural unit (II), the base polymer can adjust its solubility in a developer, resulting in improved lithographic performance, such as resolution, of the radiation-sensitive composition. Furthermore, the adhesion between a resist pattern formed from the base polymer and a substrate can be improved.

[0148] Examples of the structural unit (II) include structural units represented by the following formulae (T-1) to (T-11).

[0149] [Chemistry 21]

[0150]

[0151] In the formula, R L1 is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. L2 ~R L5R is independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a cyano group, a trifluoromethyl group, a methoxy group, a methoxycarbonyl group, a hydroxyl group, a hydroxymethyl group, or a dimethylamino group. L4 and R L5 It may also be a divalent alicyclic group having 3 to 8 carbon atoms formed by combining with each other and with these bonded 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.

[0152] As the R L4 and R L5 The divalent alicyclic group having 3 to 8 carbon atoms formed by combining with each other and with these carbon atoms to which they are bonded includes R in the above formula (3): 19 and R 20 A group having 3 to 8 carbon atoms in a divalent alicyclic group having 3 to 20 carbon atoms formed by combining these carbon atoms with each other. One or more hydrogen atoms in the alicyclic group may be substituted with a hydroxyl group.

[0153] As the L 2 Examples of the divalent linking group include a divalent linear or branched hydrocarbon group having 1 to 10 carbon atoms, a divalent alicyclic hydrocarbon group having 4 to 12 carbon atoms, or a group composed of one or more of these hydrocarbon groups and at least one of -CO-, -O-, -NH-, and -S-.

[0154] Among these, the structural unit (II) is preferably a structural unit containing a lactone structure, more preferably a structural unit containing a norbornane lactone structure, and still more preferably a structural unit derived from norbornane lactone-based (meth)acrylate.

[0155] The lower limit of the content ratio of the structural unit (II) relative to all structural units constituting the base polymer (the total content ratio when multiple structural units are included) is preferably 10 mol%, more preferably 20 mol%, and even more preferably 30 mol%. Furthermore, the upper limit of the content ratio is preferably 80 mol%, more preferably 70 mol%, and even more preferably 60 mol%. By setting the content ratio of the structural unit (II) within the above range, the radiation-sensitive composition can further improve lithographic performance such as resolution and adhesion between the formed resist pattern and the substrate.

[0156] [Structural unit (III)]

[0157] In addition to the structural units (I) and (II), the base polymer may optionally have other structural units. Examples of the other structural units include structural units (III) containing polar groups (excluding those corresponding to structural units (II)). By further including structural units (III), the base polymer can adjust its solubility in the developer, thereby improving the lithographic performance of the radiation-sensitive composition, such as the resolution. Examples of the polar groups include hydroxyl groups, carboxyl groups, cyano groups, nitro groups, and sulfonamide groups. Among these, hydroxyl groups and carboxyl groups are preferred, and hydroxyl groups are more preferred.

[0158] Examples of the structural unit (III) include structural units represented by the following formula.

[0159] [Chemistry 22]

[0160]

[0161] In the formula, R A is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.

[0162] When the base polymer contains the structural unit (III) having the polar group, the lower limit of the content ratio of the structural unit (III) relative to all structural units constituting the base polymer (the total content ratio when the base polymer contains multiple types) is preferably 3 mol%, more preferably 5 mol%, and even more preferably 8 mol%. Furthermore, the upper limit of the content ratio is preferably 40 mol%, more preferably 30 mol%, and even more preferably 25 mol%. By setting the content ratio of the structural unit (III) within the above range, the lithographic performance such as resolution of the radiation-sensitive composition can be further improved.

[0163] [Structural unit (IV)]

[0164] In addition to the structural unit (III) having the polar group, the base polymer may optionally contain a structural unit having a phenolic hydroxyl group (hereinafter also referred to as "structural unit (IV)") as another structural unit. Structural unit (IV) contributes to improving etching resistance and improving the difference in developer solubility between the exposed and unexposed areas (solution contrast). In particular, it is preferably applicable to pattern formation using exposure based on radiation with a wavelength of 50 nm or less, such as electron beams or EUV. In such a case, the polymer preferably contains structural unit (IV) as well as structural unit (I).

[0165] The structural unit having a phenolic hydroxyl group is represented by, for example, the following formula (4-1) to formula (4-6).

[0166] [Chemistry 23]

[0167]

[0168] In the above formulas (4-1) to (4-6), R 41 Each of the Y groups is independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Y is a halogen atom, a trifluoromethyl group, a cyano group, an alkyl group or an alkoxy group having 1 to 6 carbon atoms, or an acyl group, an acyloxy group, or an alkoxycarbonyl group having 2 to 7 carbon atoms. When there are multiple Y groups, the multiple Y groups may be the same or different. t is an integer from 0 to 4.

[0169] When obtaining structural unit (IV), it is preferred to carry out polymerization while the phenolic hydroxyl group is protected by a protecting group such as an alkali-dissociable group (e.g., an acyl group), followed by hydrolysis and deprotection to obtain structural unit (IV). Alternatively, the monomer providing structural unit (IV) may be polymerized without protecting the phenolic hydroxyl group.

[0170] In the case of a polymer for exposure to radiation with a wavelength of 50 nm or less, the lower limit of the content ratio of the structural unit (IV) relative to all the structural units constituting the polymer is preferably 10 mol%, more preferably 20 mol%. In addition, the upper limit of the content ratio is preferably 70 mol%, more preferably 60 mol%.

[0171] [Other structural units]

[0172] The base polymer may contain a structural unit having an alicyclic structure represented by the following formula (6) (hereinafter also referred to as "structural unit (VII)") as a structural unit other than the structural units listed above.

[0173] [Chemistry 24]

[0174]

[0175] (In the formula (6), R 1α is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group; R 2α is a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms)

[0176] In the formula (6), R 2α The monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by can be preferably the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms listed as W in the above formula (1).

[0177] When the base polymer contains the structural unit (VII), the lower limit of the content ratio of the structural unit (VII) relative to all the structural units constituting the base polymer is preferably 2 mol%, more preferably 5 mol%, and even more preferably 8 mol%. The upper limit of the content ratio is preferably 40 mol%, more preferably 30 mol%, and even more preferably 20 mol%.

[0178] (Method for synthesizing base polymer)

[0179] The base polymer can be synthesized by, for example, polymerizing monomers providing each structural unit in an appropriate solvent using a radical polymerization initiator or the like.

[0180] Examples of the radical polymerization initiator include 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, tert-butyl hydroperoxide, and cumene hydroperoxide. Among these, AIBN and dimethyl 2,2'-azobisisobutyrate are preferred, with AIBN being more preferred. These radical initiators may be used alone or in combination of two or more.

[0181] Examples of the solvent used in the polymerization include:

[0182] Alkanes such as n-pentane, n-hexane, n-heptane, n-octane, n-nonane, and n-decane;

[0183] Cycloalkanes such as cyclohexane, cycloheptane, cyclooctane, decahydronaphthalene, and norbornane;

[0184] Aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, and cumene;

[0185] Halogenated hydrocarbons such as chlorobutanes, brominated hexanes, dichloroethanes, hexamethylene dibromide, and chlorobenzene;

[0186] Saturated carboxylic acid esters such as ethyl acetate, n-butyl acetate, isobutyl acetate, and methyl propionate;

[0187] γ-butyrolactone and other cyclic esters;

[0188] Ketones such as acetone, 2-butanone, 4-methyl-2-pentanone, and 2-heptanone;

[0189] Ethers such as tetrahydrofuran, dimethoxyethanes, diethoxyethanes, and some polyol ethers;

[0190] Alcohols such as methanol, ethanol, 1-propanol, 2-propanol, and 4-methyl-2-pentanol, etc. These solvents used in the polymerization may be used alone or in combination of two or more.

[0191] The reaction temperature in the polymerization is usually 40° C. to 150° C., preferably 50° C. to 120° C. The reaction time is usually 1 hour to 48 hours, preferably 1 hour to 24 hours.

[0192] The molecular weight of the base polymer is not particularly limited. However, the lower limit of the polystyrene-equivalent weight average molecular weight (Mw) obtained by gel permeation chromatography (GPC) is preferably 3,000, more preferably 4,000, further preferably 5,000, and particularly preferably 6,000. The upper limit of Mw is preferably 20,000, more preferably 15,000, further preferably 10,000, and particularly preferably 8,000. By setting the Mw of the base polymer within this range, the resulting resist film can exhibit excellent heat resistance and developability.

[0193] The ratio (Mw / Mn) of the base polymer Mw to the polystyrene-equivalent number average molecular weight (Mn) obtained by GPC is usually 1 to 5, preferably 1 to 3, and more preferably 1 to 2.

[0194] The Mw and Mn of the polymer in this specification are values ​​measured using gel permeation chromatography (GPC) under the following conditions.

[0195] GPC columns: 2 G2000HXL, 1 G3000HXL, 1 G4000HXL (all manufactured by Tosoh)

[0196] Column temperature: 40°C

[0197] Solvent: Tetrahydrofuran

[0198] Flow rate: 1.0 mL / min

[0199] Sample concentration: 1.0 mass%

[0200] Sample injection volume: 100 μL

[0201] Detector: Differential refractometer

[0202] Standard material: monodisperse polystyrene

[0203] The content of the base polymer is preferably 60% by mass or more, more preferably 65% ​​by mass or more, and even more preferably 70% by mass or more, based on the total solid content of the radiation-sensitive composition.

[0204] (Other polymers)

[0205] The radiation-sensitive composition of this embodiment may also contain, as an additional polymer, a polymer having a higher fluorine atom mass content than the base polymer (hereinafter also referred to as a "high-fluorine-content polymer"). When the radiation-sensitive composition contains a high-fluorine-content polymer, the polymer can be preferentially present in the surface layer of the resist film relative to the base polymer. This can improve the surface water repellency of the resist film during immersion exposure, improve the surface properties of the resist film during EUV exposure, and control the distribution of the composition within the film.

[0206] The high fluorine content polymer preferably has, for example, a structural unit represented by the following formula (5) (hereinafter also referred to as "structural unit (V)"), and may optionally have structural unit (I) or structural unit (III) in the base polymer.

[0207] [Chemistry 25]

[0208]

[0209] In the formula (5), R 13 is a hydrogen atom, a methyl group or a trifluoromethyl group. L R is a single bond, an alkanediyl group having 1 to 5 carbon atoms, an oxygen atom, a sulfur atom, -COO-, -SO2ONH-, -CONH-, -OCONH-, or a combination thereof. 14 It 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.

[0210] As the R 13 From the viewpoint of improving the copolymerizability of the monomer of the structural unit (V), a hydrogen atom and a methyl group are preferred, and a methyl group is more preferred.

[0211] As the G L From the viewpoint of improving the copolymerizability of the monomer of the structural unit (V), a single bond and -COO- are preferred, and -COO- is more preferred.

[0212] As the R 14 Examples of the monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms include a group in which a part or all of the hydrogen atoms in a linear or branched alkyl group having 1 to 20 carbon atoms are substituted with fluorine atoms.

[0213] As the R 14 Examples of the monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms include a group in which a part or all of the hydrogen atoms in a monocyclic or polycyclic hydrocarbon group having 3 to 20 carbon atoms are substituted with fluorine atoms.

[0214] As the R 14, preferably a fluorinated chain hydrocarbon group, more preferably a fluorinated alkyl group, and still more preferably a 2,2,2-trifluoroethyl group, a 2,2,3,3,3-pentafluoropropyl group, a 1,1,1,3,3,3-hexafluoropropyl group and a 5,5,5-trifluoro-1,1-diethylpentyl group.

[0215] When the high fluorine content polymer has a structural unit (V), the lower limit of the content ratio of the structural unit (V) relative to all the structural units constituting the high fluorine content polymer is preferably 50 mol%, more preferably 60 mol%, and further preferably 70 mol%. In addition, the upper limit of the content ratio is preferably 95 mol%, more preferably 90 mol%, and further preferably 85 mol%. By setting the content ratio of the structural unit (V) within the above range, the mass content of fluorine atoms in the high fluorine content polymer can be more appropriately adjusted, further promoting the partial presence of fluorine atoms in the surface layer of the resist film. As a result, the water repellency of the resist film during immersion exposure or the film quality adjustment of the resist film during EUV exposure can be further improved.

[0216] The high fluorine content polymer may also have a fluorine atom-containing structural unit represented by the following formula (f-2) (hereinafter also referred to as structural unit (VI)) in addition to structural unit (V) or in place of structural unit (V). When the high fluorine content polymer has structural unit (f-2), its solubility in alkaline developer can be improved, thereby suppressing the occurrence of development defects.

[0217] [Chemistry 26]

[0218]

[0219] Structural unit (VI) can be broadly divided into two types: one having (x) an alkali-soluble group and one having (y) a group that dissociates by the action of an alkali and increases solubility in an alkaline developer (hereinafter also referred to as an "alkali-dissociable group"). Both (x) and (y) are common. In the above formula (f-2), R C is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. D is a single bond, a hydrocarbon group having 1 to 20 carbon atoms and a valence of (s+1), and R in the hydrocarbon group E The end of the side is bonded with oxygen atoms, sulfur atoms, -NR dd -, carbonyl, -COO-, -OCO- or -CONH-, or a structure in which a part of the hydrogen atoms possessed by the above hydrocarbon group is 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 of 1 to 3.

[0220] When the structural unit (VI) has (x) an alkali-soluble group, R F A is a hydrogen atom, 1It is an oxygen atom, -COO-* or -SO2O-*. * indicates that it is bonded to R F W 1 is a single bond, a hydrocarbon group having 1 to 20 carbon atoms, or a divalent fluorinated hydrocarbon group. 1 When W is an oxygen atom, 1 For A 1 A fluorinated hydrocarbon group having a fluorine atom or a fluoroalkyl group on the carbon atom to which it is bonded. E is a single bond or a divalent organic group having 1 to 20 carbon atoms. E 、W 1 、A 1 and R F The structural unit (VI) having an alkali-soluble group (x) can improve the affinity for alkaline developer and suppress development defects. As the structural unit (VI) having an alkali-soluble group (x), A is particularly preferred. 1 is an oxygen atom and W 1 This is the case of 1,1,1,3,3,3-hexafluoro-2,2-methanediyl.

[0221] When the structural unit (VI) has (y) an alkali-dissociable group, R F A is a monovalent organic group with 1 to 30 carbon atoms, 1 is an oxygen atom, -NR aa -, -COO-*, -OCO-* or -SO2O-*. R aa It is a hydrogen atom or a monovalent hydrocarbon group with 1 to 10 carbon atoms. * indicates a bond to R F W 1 R is a single bond or a divalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. E It is a single bond or a divalent organic group with 1 to 20 carbon atoms. 1 In the case of -COO-*, -OCO-* or -SO2O-*, W 1 or R F In with A 1 There is a fluorine atom on the carbon atom to which the bond is made or on the carbon atom adjacent to it. 1 When W is an oxygen atom, 1 、R E is a single bond, R D R is a hydrocarbon group having 1 to 20 carbon atoms E The structure formed by the carbonyl group bonded to the end of the side, 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 FThey may be the same or different. When the structural unit (VI) has the (y) alkali dissociating group, the surface of the resist film changes from hydrophobic to hydrophilic during the alkali development process. As a result, the affinity for the developer can be greatly improved, and development defects can be suppressed more efficiently. As the structural unit (VI) having the (y) alkali dissociating group, A is particularly preferred. 1 is -COO-* and R F or W 1 or both of them have fluorine atoms.

[0222] As R C From the viewpoint of improving the copolymerizability of the monomer of the structural unit (VI), a hydrogen atom and a methyl group are preferred, and a methyl group is more preferred.

[0223] In R E In the case of a divalent organic group, a group having a lactone structure is preferred, a group having a polycyclic lactone structure is more preferred, and a group having a norbornane lactone structure is further preferred.

[0224] When the high fluorine content polymer has structural unit (VI), the lower limit of the content ratio of structural unit (VI) relative to all structural units constituting the high fluorine content polymer is preferably 40 mol%, more preferably 50 mol%, and further preferably 55 mol%. In addition, the upper limit of the content ratio is preferably 95 mol%, more preferably 90 mol%, and further preferably 85 mol%. By setting the content ratio of structural unit (VI) within the above range, the water repellency of the resist film during immersion exposure can be improved, or the solubility in an alkaline developer can be improved to suppress the occurrence of development defects.

[0225] [Other structural units]

[0226] The high fluorine content polymer may contain, in addition to the structural unit (I) or the structural unit (III) in the base polymer, a structural unit (VII) as a structural unit other than the above-mentioned structural units.

[0227] When the high fluorine content polymer contains the structural unit (I) or the structural unit (III) or the structural unit (VII), the content ratio of each structural unit in the high fluorine content polymer can preferably adopt the content ratio described for the base polymer.

[0228] The lower limit of the Mw of the high fluorine content polymer is preferably 2,000, more preferably 3,000, further preferably 4,000, and particularly preferably 5,000. The upper limit of the Mw is preferably 20,000, more preferably 15,000, further preferably 10,000, and particularly preferably 8,000.

[0229] The lower limit of Mw / Mn of the high fluorine content polymer is usually 1, more preferably 1.1. The upper limit of Mw / Mn is usually 5, preferably 3, more preferably 2.

[0230] When the radiation-sensitive composition contains a high-fluorine content polymer, the content of the high-fluorine content polymer is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, further preferably 1.5 parts by mass or more, and particularly preferably 2 parts by mass or more, relative to 100 parts by mass of the base polymer. Furthermore, it is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, further preferably 8 parts by mass or less, and particularly preferably 6 parts by mass or less.

[0231] By setting the content of the high-fluorine-content polymer within the above range, the high-fluorine-content polymer can be more effectively localized in the surface layer of the resist film. As a result, the water repellency of the resist film surface during immersion exposure can be improved, and the surface of the resist film can be modified or the distribution of the composition within the film can be controlled during EUV exposure. The radiation-sensitive composition may contain one or more high-fluorine-content polymers.

[0232] (Synthesis Method of High Fluorine Content Polymer)

[0233] The high fluorine content polymer can be synthesized using the same method as the synthesis method of the base polymer.

[0234] (Acid Diffusion Controller)

[0235] The radiation-sensitive composition may optionally contain an acid diffusion controller. The acid diffusion controller controls the diffusion of the acid generated from the onium salt compound (1) during exposure into the resist film and suppresses undesirable chemical reactions in unexposed areas. Furthermore, the storage stability of the resulting radiation-sensitive composition is improved. Furthermore, the resolution of the resist pattern is further improved, and variations in the line width of the resist pattern caused by variations in the standing time from exposure to development can be suppressed, thereby achieving a radiation-sensitive composition with excellent process stability.

[0236] Examples of acid diffusion controllers 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-containing compounds, urea compounds, nitrogen-containing heterocyclic compounds, and the like.

[0237] [Chemistry 27]

[0238]

[0239] In the formula (7), R 22 、R 23 and R 24 are each 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.

[0240] Examples of the nitrogen-containing compound (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-isopropylaniline.

[0241] Examples of the nitrogen-containing compound (II) include ethylenediamine and N,N,N',N'-tetramethylethylenediamine.

[0242] Examples of the nitrogen-containing compound (III) include polyamine compounds such as polyethyleneimine and polyallylamine; and polymers such as dimethylaminoethylacrylamide.

[0243] Examples of the amide group-containing compound include formamide, N-methylformamide, N,N-dimethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, propionamide, benzamide, pyrrolidone, and N-methylpyrrolidone.

[0244] Examples of the urea compound include urea, methylurea, 1,1-dimethylurea, 1,3-dimethylurea, 1,1,3,3-tetramethylurea, 1,3-diphenylurea, and tributylthiourea.

[0245] Examples of the nitrogen-containing heterocyclic compound include pyridines such as pyridine and 2-methylpyridine; morpholines such as N-propylmorpholine and N-(undecylcarbonyloxyethyl)morpholine; pyrazines and pyrazoles.

[0246] In addition, as the nitrogen-containing organic compound, a compound having an acid-dissociable group can also be used. Examples of such nitrogen-containing organic compounds having an acid-dissociable group include: N-tert-butoxycarbonylpiperidine, N-tert-butoxycarbonylimidazole, N-tert-butoxycarbonylbenzimidazole, N-tert-butoxycarbonyl-2-phenylbenzimidazole, N-(tert-butoxycarbonyl)di-n-octylamine, N-(tert-butoxycarbonyl)diethanolamine, N-(tert-butoxycarbonyl)dicyclohexylamine, N-(tert-butoxycarbonyl)diphenylamine, N-tert-butoxycarbonyl-4-hydroxypiperidine, N-tert-butoxycarbonyl-4-acetoxypiperidine, and N-tert-amyloxycarbonyl-4-hydroxypiperidine.

[0247] Alternatively, a radiation-sensitive weak acid generator that generates a weak acid upon exposure can be preferably used as an acid diffusion controller. The acid generated by the radiation-sensitive weak acid generator is a weak acid that does not induce dissociation of the acid-dissociable groups in the polymer under conditions that dissociate the acid-dissociable groups. Furthermore, in this specification, "dissociation" of the acid-dissociable groups refers to dissociation during a 60-second post-exposure bake at 110°C.

[0248] Examples of radiation-sensitive weak acid generators include onium salt compounds that decompose upon exposure and lose their acid diffusion control properties. 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). Examples include compounds containing a sulfonium cation and an anion in the same molecule, such as those represented by the following formula (8-3), and compounds containing an iodonium cation and anion in the same molecule, such as those represented by the following formula (8-4).

[0249] [Chemistry 28]

[0250]

[0251] In the above formulas (8-1) to (8-4), J + is a sulfonium cation, U + As J + The sulfonium cation represented by U can be exemplified by the sulfonium cations represented by the formula (X-1) to the formula (X-4). + Examples of the iodonium cations represented by E include the iodonium cations represented by the above formulas (X-5) to (X-6). - and Q - are independently OH - 、R α -COO - 、R α -SO3 - The anion represented by R α is a single bond or a monovalent organic group having 1 to 30 carbon atoms. Examples of the organic group include a monovalent hydrocarbon group having 1 to 20 carbon atoms, a group having a divalent heteroatom-containing group between carbon atoms of the hydrocarbon group or at a carbon chain terminal, a group in which a part or all of the hydrogen atoms of the hydrocarbon group are substituted with a monovalent heteroatom-containing group, or a combination thereof.

[0252] As the monovalent hydrocarbon group having 1 to 20 carbon atoms, R in the formula (A-3) and (A-4) can be preferably used. A1 and R A2 The represented monovalent hydrocarbon group has 1 to 20 carbon atoms.

[0253] Examples of the heteroatom constituting the divalent or monovalent heteroatom-containing group include oxygen, nitrogen, sulfur, phosphorus, silicon, and halogen atoms. Examples of the halogen atom include fluorine, chlorine, bromine, and iodine atoms.

[0254] Examples of the divalent heteroatom-containing group include -CO-, -CS-, -NH-, -O-, -S-, -SO-, -SO2-, and combinations thereof.

[0255] Examples of the monovalent heteroatom-containing group include a hydroxyl group, a thiol group, a cyano group, a nitro group, and a halogen atom.

[0256] Examples of the radiation-sensitive weak acid generator include compounds represented by the following formula.

[0257] [Chemistry 29]

[0258]

[0259] [Chemistry 30]

[0260]

[0261] As the radiation-sensitive weak acid generator, among these, sulfonium salts are preferred, triarylsulfonium salts are more preferred, and triphenylsulfonium salicylate and triphenylsulfonium 10-camphorsulfonate are further preferred.

[0262] The lower limit of the amount of the acid diffusion controller relative to 100 parts by mass of the polymer is preferably 0.5 parts by mass, more preferably 1 part by mass, and further preferably 2 parts by mass. Furthermore, the upper limit of the amount is preferably 30 parts by mass, more preferably 20 parts by mass, and further preferably 15 parts by mass.

[0263] By setting the content of the acid diffusion controller within the above range, the lithographic performance of the radiation-sensitive composition can be further improved. The radiation-sensitive composition may contain one or more acid diffusion controllers.

[0264] (Solvent)

[0265] The radiation-sensitive composition of the present embodiment contains a solvent. The solvent is not particularly limited as long as it can dissolve or disperse at least the onium salt compound (1) and the polymer, and optionally, the acid diffusion controller and the like.

[0266] Examples of the solvent include alcohol solvents, ether solvents, ketone solvents, amide solvents, ester solvents, and hydrocarbon solvents.

[0267] Examples of the alcoholic solvent include:

[0268] Monohydric alcohol solvents with 1 to 18 carbon atoms, such as isopropyl alcohol, 4-methyl-2-pentanol, 3-methoxybutanol, n-hexanol, 2-ethylhexanol, furfuryl alcohol, cyclohexanol, 3,3,5-trimethylcyclohexanol, and diacetone alcohol;

[0269] Polyol 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;

[0270] Polyol partial ether solvents obtained by etherifying part of the hydroxyl groups of the polyol solvents, and the like.

[0271] In the present embodiment, alcohol solvents include alcoholic 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.

[0272] Examples of the ether solvent include:

[0273] Dialkyl ether solvents such as diethyl ether, dipropyl ether, and dibutyl ether;

[0274] Cyclic ether solvents such as tetrahydrofuran and tetrahydropyran;

[0275] Ether solvents containing aromatic rings such as diphenyl ether and anisole (methyl phenyl ether);

[0276] Polyol ether solvents obtained by etherifying the hydroxyl groups of the polyol solvents mentioned above.

[0277] Examples of the ketone solvent include chain ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone;

[0278] Cyclic ketone solvents such as cyclopentanone, cyclohexanone, and methylcyclohexanone;

[0279] 2,4-pentanedione, acetonylacetone, acetophenone, etc.

[0280] Examples of the amide solvent include cyclic amide solvents such as N,N′-dimethylimidazolidinone and N-methylpyrrolidone;

[0281] Chain amide solvents such as N-methylformamide, N,N-dimethylformamide, N,N-diethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, and N-methylpropionamide.

[0282] Examples of the ester solvent include:

[0283] Monocarboxylic acid ester solvents such as n-butyl acetate;

[0284] Polyol partial ether acetate solvents such as diethylene glycol mono-n-butyl ether acetate, propylene glycol monomethyl ether acetate, and dipropylene glycol monomethyl ether acetate;

[0285] Lactone solvents such as γ-butyrolactone and valerolactone;

[0286] Carbonate solvents such as diethyl carbonate, ethylene carbonate, and propylene carbonate;

[0287] Polycarboxylic acid diester solvents such as propylene glycol diacetate, methoxytriglycol acetate, diethyl oxalate, ethyl acetoacetate, and diethyl phthalate.

[0288] Examples of hydrocarbon solvents include:

[0289] Aliphatic hydrocarbon solvents such as n-hexane, cyclohexane, and methylcyclohexane;

[0290] Aromatic hydrocarbon solvents such as benzene, toluene, diisopropylbenzene, and n-pentylnaphthalene.

[0291] Among these, alcohol solvents, ester solvents, and ether solvents are preferred, with alcohol ester solvents, polyol partial ether acetate solvents, lactone solvents, monocarboxylic acid ester solvents, and ketone solvents being more preferred, and propylene glycol monomethyl ether acetate, γ-butyrolactone, ethyl lactate, and cyclohexanone being even more preferred. The radiation-sensitive composition may contain one or more solvents.

[0292] (Other optional ingredients)

[0293] The radiation-sensitive composition may contain other optional components in addition to the above components. Examples of such other optional components include crosslinking agents, polarization accelerators, surfactants, compounds containing an alicyclic skeleton, and sensitizers. These other optional components may be used alone or in combination of two or more.

[0294] <Method for preparing radiation-sensitive composition>

[0295] The radiation-sensitive composition can be prepared, for example, by mixing an onium salt compound (1), a polymer, and, if necessary, an acid diffusion controller, and a solvent in a predetermined ratio. The radiation-sensitive composition is preferably filtered, for example, using a filter having a pore size of about 0.05 μm to 0.40 μm after mixing. The solid content concentration of the radiation-sensitive composition is generally 0.1% to 50% by mass, preferably 0.5% to 30% by mass, and more preferably 1% to 20% by mass.

[0296] <Pattern Formation Method>

[0297] A pattern forming method according to one embodiment of the present invention includes:

[0298] a step of directly or indirectly applying the radiation-sensitive composition on a substrate to form a resist film (hereinafter also referred to as a "resist film forming step");

[0299] a step of exposing the resist film to light (hereinafter also referred to as an "exposure step"); and

[0300] A step of developing the exposed resist film (hereinafter also referred to as a "development step") is performed.

[0301] According to the pattern forming method, a high-quality resist pattern can be efficiently formed by using the radiation-sensitive composition having good storage stability and exhibiting excellent sensitivity, LWR performance, and CDU performance during pattern formation.

[0302] [Resist Film Formation Step]

[0303] In this process, a resist film is formed using the radiation-sensitive composition. Examples of substrates for forming the resist film include silicon wafers, silicon dioxide, and aluminum-coated wafers. Alternatively, an organic or inorganic antireflection film such as that disclosed in Japanese Patent Publication No. 6-12452 or Japanese Patent Application Laid-Open No. 59-93448 may be formed on the substrate. Examples of coating methods include spin coating, cast coating, and roller coating. After coating, a prebake (PB) may be performed as needed to volatilize the solvent in the coating film. The PB temperature is typically 70°C to 150°C, preferably 90°C to 140°C. The PB time is typically 5 seconds to 600 seconds, preferably 10 seconds to 300 seconds.

[0304] The lower limit of the thickness of the resist film to be formed is preferably 10 nm, more preferably 15 nm, and further preferably 20 nm. The upper limit of the thickness is preferably 500 nm, more preferably 400 nm, and further preferably 300 nm. However, in the case where a thick resist film is exposed to ArF excimer laser light in the exposure step described later, the lower limit of the thickness may be 100 nm, 150 nm, or even 200 nm.

[0305] In the case of immersion exposure, regardless of the presence or absence of a hydrophobic polymer additive such as the high fluorine content polymer in the radiation-sensitive composition, a liquid immersion protective film that is insoluble in the immersion liquid may be provided on the formed resist film for the purpose of avoiding direct contact between the immersion liquid and the resist film. As the liquid immersion protective film, a solvent-peelable protective film that is peeled off using a solvent before the development process (for example, see Japanese Patent Laid-Open No. 2006-227632) or a developer-peelable protective film that is peeled off simultaneously with the development of the development process (for example, see WO2005-069076 and WO2006-035790) may be used. Among them, from the perspective of production output, it is preferred to use a developer-peelable liquid immersion protective film.

[0306] When the subsequent exposure step is performed using radiation having a wavelength of 50 nm or less, it is preferred to use a polymer having the structural unit (I) and the structural unit (IV) as the base polymer in the composition.

[0307] [Exposure process]

[0308] In this process, the resist film formed in the resist film forming process is exposed by irradiating radiation through a photomask (optionally through an immersion liquid such as water). As the radiation used for exposure, depending on the line width of the target pattern, for example, electromagnetic waves such as visible light, ultraviolet light, far ultraviolet light, extreme ultraviolet light (EUV), X-rays, and gamma rays; charged particle beams such as electron beams and alpha rays, etc. are listed. Of these, far ultraviolet light, electron beams, and EUV are preferred, and ArF excimer laser light (wavelength 193nm), KrF excimer laser light (wavelength 248nm), electron beams, and EUV are more preferred. Electron beams and EUV with wavelengths of 50nm or less, which are positioned as next-generation exposure technologies, are further preferred.

[0309] In the case of exposure by immersion exposure, as the immersion liquid used, for example, water, fluorine-based inactive liquids, etc. can be cited. The immersion liquid is preferably a liquid that is transparent to the exposure wavelength and has a temperature coefficient of refractive index that is as small as possible to minimize the deformation of the optical image projected onto the film, particularly when the exposure light source is ArF excimer laser light (wavelength 193nm). On the basis of the above viewpoint, in terms of ease of acquisition, ease of operation, etc., it is preferred to use water. In the case of using water, an additive that reduces the surface tension of water and increases interfacial activity can also be added in a slight proportion. The additive preferably does not dissolve the resist film on the wafer, and the influence on the optical coating on the lower surface of the lens can be ignored. As the water used, distilled water is preferred.

[0310] After the exposure, a post-exposure bake (PEB) is preferably performed. In the exposed portions of the resist film, the acid generated by the radiation-sensitive acid generator during exposure promotes the dissociation of acid-dissociable groups in the polymer, etc. This PEB creates a difference in solubility in the developer between the exposed and unexposed areas. The PEB temperature is typically 50°C to 160°C, preferably 80°C to 130°C. The PEB time is typically 5 seconds to 600 seconds, preferably 10 seconds to 300 seconds.

[0311] [Development Process]

[0312] In this step, the resist film exposed in the exposure step is developed. This forms a desired resist pattern. Generally, after development, the film is rinsed with a rinse solution such as water or alcohol and then dried.

[0313] In the case of alkali development, examples of the developer used for the development include alkaline aqueous solutions containing at least one alkaline compound dissolved therein, such as sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, aqueous ammonia, ethylamine, n-propylamine, diethylamine, di-n-propylamine, triethylamine, methyldiethylamine, ethyldimethylamine, triethanolamine, tetramethylammonium hydroxide (TMAH), pyrrole, piperidine, choline, 1,8-diazabicyclo-[5.4.0]-7-undecene, and 1,5-diazabicyclo-[4.3.0]-5-nonene. Among these, a TMAH aqueous solution is preferred, and a 2.38% by mass TMAH aqueous solution is more preferred.

[0314] In the case of organic solvent development, examples include organic solvents such as hydrocarbon solvents, ether solvents, ester solvents, ketone solvents, and alcohol solvents, or solvents containing organic solvents. Examples of the organic solvent include one or more of the solvents listed as solvents for the radiation-sensitive composition. Of these, ether solvents, ester solvents, and ketone solvents are preferred. Ether solvents are preferably glycol ether solvents, more preferably ethylene glycol monomethyl ether and propylene glycol monomethyl ether. Ester solvents are preferably acetate solvents, more preferably n-butyl acetate and amyl acetate. Ketone solvents are preferably chain ketones, more preferably 2-heptanone. The content of the organic solvent in the developer is preferably 80% by mass or greater, more preferably 90% by mass or greater, further preferably 95% by mass or greater, and particularly preferably 99% by mass or greater. Examples of components other than the organic solvent in the developer include water and silicone oil.

[0315] As described above, the developer may be an alkaline developer or an organic solvent developer, and may be appropriately selected depending on whether the target pattern is a positive-tone pattern or a negative-tone pattern.

[0316] Examples of the developing method include: a method of immersing a substrate in a tank filled with a developer for a fixed period of time (immersion method); a method of performing development by utilizing surface tension to deposit the developer on the surface of the substrate and allowing the developer to remain stationary for a fixed period of time (puddle method); a method of spraying the developer onto the surface of the substrate (spray method); a method of continuously spraying the developer onto the substrate rotating at a fixed speed while scanning a developer spray nozzle at a fixed speed (dynamic distribution method), etc.

[0317] <Onium salt compounds>

[0318] The onium salt compound according to another embodiment is a compound represented by the following formula (1).

[0319] [Chemistry 31]

[0320]

[0321] (In formula (1),

[0322] W is a cyclic structure with 3 to 40 ring members formed together with two carbon atoms;

[0323] The following formulas between carbon-carbons represent single bonds or double bonds;

[0324] [Chemistry 32]

[0325]

[0326] A is a group represented by the following formula (A-1), a group represented by the following formula (A-2), a group represented by the following formula (A-3), a group represented by the following formula (A-4), a group represented by the following formula (A-5), a group represented by the following formula (A-6), or a group represented by the following formula (A-7);

[0327] [Chemistry 33]

[0328]

[0329] (In formula (A-3) and formula (A-4), R A1 and R A2 are each independently a monovalent hydrocarbon group having 1 to 20 carbon atoms; * is a bond to a carbon atom)

[0330] R 1 is a monovalent organic group with 1 to 20 carbon atoms, a cyano group, a nitro group, a carboxyl group, a hydroxyl group, an amino group, a halogen atom or a thiol group; in R 1 When there are multiple R1 the same as or different from each other;

[0331] m1 is an integer from 0 to 4;

[0332] Z + (a monovalent radiosensitive linear onium cation)

[0333] As the onium salt compound represented by the formula (1) in this embodiment, the onium salt compound (1) contained in the radiation-sensitive composition can be preferably used.

[0334] Example

[0335] Hereinafter, the present invention will be described in detail based on examples, but the present invention is not limited to these examples. The following describes the measurement methods of various physical properties.

[0336] [Weight average molecular weight (Mw) and number average molecular weight (Mn)]

[0337] The Mw and Mn of the polymer were measured under the above-mentioned conditions. The dispersion degree (Mw / Mn) was calculated based on the measurement results of Mw and Mn.

[0338] [ 13 C-NMR ( 13 C-Nuclear Magnetic Resonance, 13 C-NMR) analysis]

[0339] Various polymers 13 C-NMR analysis was performed using a nuclear magnetic resonance apparatus ("JNM-Delta400" manufactured by JEOL Ltd.).

[0340] [A] Polymer Synthesis

[0341] The monomers used in the synthesis of each polymer in each Example and each 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 taken as 100 parts by mass, and mol % refers to the value when the total number of moles of the monomers used is taken as 100 mol %.

[0342] [Chemistry 34]

[0343]

[0344] [Synthesis example 1]

[0345] (Synthesis of Polymer (A-1))

[0346] Monomers (M-1), (M-2), (M-5), (M-10), and (M-14) were dissolved in 2-butanone (200 parts by mass) at a molar ratio of 40 / 10 / 20 / 20 / 10 (mol%). A monomer solution was prepared by adding azobisisobutyronitrile (AIBN) as an initiator (5 mol% relative to the total 100 mol% of the monomers used). 2-Butanone (100 parts by mass) was placed in a reaction vessel and purged with nitrogen for 30 minutes. The reaction vessel was then set to 80°C and the monomer solution was added dropwise over 3 hours while stirring. The polymerization reaction was initiated by the start of the addition, and the reaction was allowed to proceed for 6 hours. After the polymerization reaction was completed, the polymerization solution was cooled to below 30°C with water. The cooled polymerization solution was added to methanol (2,000 parts by mass), and the precipitated white powder was separated by filtration. The white powder separated by filtration was washed twice with methanol, separated by filtration, and dried at 50°C for 24 hours to obtain a white powder polymer (A-1) (yield: 85%). The Mw of polymer (A-1) was 7,100, and the Mw / Mn was 1.61. 13 As a result of C-NMR analysis, the contents of the structural units derived from (M-1), (M-2), (M-5), (M-10), and (M-14) were 40.3 mol%, 9.2 mol%, 20.5 mol%, 19.8 mol%, and 10.2 mol%, respectively.

[0347] [Synthesis Example 2 to Synthesis Example 11]

[0348] (Synthesis of Polymers (A-2) to (A-11))

[0349] Polymers (A-2) to (A-11) were synthesized in the same manner as in Synthesis Example 1, except that the monomers of the types and blending ratios shown in Table 1 were used. The content ratios (mol %) of the structural units and the physical properties (Mw and Mw / Mn) of the resulting polymers are shown in Table 1. "-" in Table 1 indicates that the corresponding monomer was not used (the same applies to the following tables).

[0350] [Table 1]

[0351]

[0352] (Synthesis of Polymer (A-12))

[0353] The monomer (M-1) and monomer (M-18) were dissolved in 1-methoxy-2-propanol (200 parts by mass) at a molar ratio of 50 / 50 (mol%), and AIBN (5 mol%) was added as an initiator to prepare a monomer solution. 1-methoxy-2-propanol (100 parts by mass) was placed in a reaction vessel and purged with nitrogen for 30 minutes. The reaction vessel was then set to 80°C and the monomer solution was added dropwise over 3 hours while stirring. The start of the addition marked the start of the polymerization reaction, and the polymerization reaction was carried out for 6 hours. After the polymerization reaction was completed, the polymerization solution was water-cooled to below 30°C. The cooled polymerization solution was added to hexane (2,000 parts by mass), and the precipitated white powder was separated by filtration. The separated white powder was washed twice with hexane, separated by filtration, 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 a hydrolysis reaction was carried out at 70°C for 6 hours while stirring. After the reaction was completed, the residual solvent was distilled off, and the obtained solid was dissolved in acetone (100 parts by mass) and added dropwise to water (500 parts by mass) to solidify the polymer. The obtained solid was separated by filtration and dried at 50°C for 13 hours to obtain a white powdery polymer (A-12) (yield: 81%). The Mw of the polymer (A-12) was 5,500, and the Mw / Mn was 1.62. In addition, 13 As a result of C-NMR analysis, the content ratios of the structural units derived from (M-1) and (M-18) were 50.2 mol% and 49.8 mol%, respectively.

[0354] [Synthesis Example 13 to Synthesis Example 15]

[0355] (Synthesis of Polymers (A-13) to (A-15))

[0356] Polymers (A-13) to (A-15) were synthesized in the same manner as in Synthesis Example 12 except that the monomers of the types and blending ratios shown in Table 2 below were used. 13 C-NMR measurement confirmed that the peak of the carbonyl group of the acetyl group disappeared, and substantially all of the alkali-dissociable groups were hydrolyzed to form phenolic hydroxyl groups. The content ratio (mol %) of each structural unit of the obtained polymer and the physical property values ​​(Mw and Mw / Mn) are shown in Table 2 below.

[0357] [Table 2]

[0358]

[0359] [Synthesis Example 16]

[0360] (Synthesis of High Fluorine Content Polymer (F-1))

[0361] The monomer (M-1) and monomer (M-20) were dissolved in 2-butanone (200 parts by mass) at a molar ratio of 20 / 80 (mol%), and AIBN (4 mol%) was added as an initiator to prepare a monomer solution. 2-Butanone (100 parts by mass) was placed in a reaction vessel, and after nitrogen flushing for 30 minutes, the temperature in the reaction vessel was set to 80°C, and the monomer solution was added dropwise over 3 hours while stirring. The start of the addition was set 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 water-cooled and cooled to below 30°C. After the solvent was replaced with acetonitrile (400 parts by mass), hexane (100 parts by mass) was added, stirred, and the acetonitrile layer was recovered, and the operation was repeated three times. By replacing the solvent with propylene glycol monomethyl ether acetate, a solution of a high fluorine content polymer (F-1) was obtained (yield: 75%). The high fluorine content polymer (F-1) had an Mw of 6,200 and an Mw / Mn of 1.77. 13 As a result of C-NMR analysis, the content ratios of the structural units derived from (M-1) and (M-20) were 19.5 mol% and 80.5 mol%, respectively.

[0362] [Synthesis Example 17 to Synthesis Example 20]

[0363] (Synthesis of High Fluorine Content Polymers (F-2) to (F-5))

[0364] High fluorine content polymers (F-2) to (F-5) were synthesized in the same manner as in Synthesis Example 16, except that the monomers of the types and blending ratios shown in Table 3 were used. The content ratios (mol %) of the structural units and the physical properties (Mw and Mw / Mn) of the obtained high fluorine content polymers are shown in Table 3.

[0365] [Table 3]

[0366]

[0367] <[B] Synthesis of Onium Salt Compound (1)>

[0368] Compounds (B-1) to (B-10) as onium salt compounds (1) serving as radiation-sensitive acid generators were synthesized as follows.

[0369] [Chemistry 35]

[0370]

[0371] [Example B1]

[0372] (Synthesis of Compound (B-1))

[0373] Compound (B-1) was synthesized according to the following synthesis scheme.

[0374] [Chemistry 36]

[0375]

[0376] A reaction vessel was charged with 20.0 mmol of potassium hydroquinonesulfonate and 20.0 mmol of triphenylsulfonium bromide, followed by a mixture of water and dichloromethane (1:3 (mass ratio)) to prepare 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, the solvent was distilled off, and the product was purified by column chromatography to obtain compound (B-1) represented by formula (B-1) in good yield.

[0377] [Example B2 to Example B3]

[0378] (Synthesis of Compounds (B-2) to (B-3))

[0379] Onium salt compounds (1) represented by the following formulae (B-2) to (B-3) were synthesized in the same manner as in Example B1 except that the raw materials and precursors were appropriately changed.

[0380] [Chemistry 37]

[0381]

[0382] [Example B4]

[0383] (Synthesis of Compound (B-4))

[0384] Compound (B-4) was synthesized according to the following synthesis scheme.

[0385] [Chemistry 38]

[0386]

[0387] A 0.5 M solution of 5,5-dimethyl-1,3-cyclohexanedione (Dimedone) (20.0 mmol), chlorosulfonic acid (30.0 mmol), and 1,4-dioxane was added to a reaction vessel. After reacting at 70°C for 6 hours, the reaction was terminated by adding aqueous sodium hydroxide. Extraction was performed with dichloromethane, and the organic layer was separated. The resulting organic layer was dried over sodium sulfate, and the solvent was distilled off to obtain the sodium sulfonate salt in good yield.

[0388] 20.0 mmol of sulfonium bromide was added to the sodium sulfonate salt, followed by a mixture of water and dichloromethane (1:3 (mass ratio)) to prepare 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 obtained organic layer was dried over sodium sulfate, the solvent was distilled off, and the product was purified by column chromatography to obtain the compound (B-4) represented by the formula (B-4) in a good yield.

[0389] [Example B5]

[0390] (Synthesis of Compound (B-5))

[0391] Compound (B-5) was synthesized according to the following synthesis scheme.

[0392] [Chemistry 39]

[0393]

[0394] A 0.5 M solution was prepared by adding 20.0 mmol of tetracyclododecene and 30.0 mmol of N-bromosuccinimide to a reaction vessel, followed by a mixture of water and acetone (1:5 (mass ratio)). After reacting at 0°C for 1 hour, the reaction was terminated by adding aqueous sodium bicarbonate. The acetone was distilled off, followed by extraction with dichloromethane, and the organic layer was separated. The resulting organic layer was dried over sodium sulfate, the solvent was distilled off, and the product was purified by column chromatography to obtain the bromide in good yield.

[0395] A mixture of acetonitrile and water (1:1 (mass ratio)) was added to the bromide to prepare a 1M solution. Then, 40.0 mmol of sodium disulfite and 60.0 mmol of sodium bicarbonate were added and reacted at 70°C for 6 hours. Extraction was performed with acetonitrile, and the solvent was distilled off. Then, a mixture of acetonitrile and water (3:1 (mass ratio)) was added to prepare a 0.5M solution. 60.0 mmol of aqueous hydrogen peroxide and 2.00 mmol of sodium tungstate were added, and the mixture was heated and stirred at 50°C for 12 hours. Extraction was performed with acetonitrile, and the solvent was distilled off to obtain the sodium sulfonate salt.

[0396] 20.0 mmol of sulfonium bromide was added to the sodium sulfonate salt, and a mixture of water and dichloromethane (1:3 (mass ratio)) was added to prepare 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 obtained organic layer was dried over sodium sulfate, the solvent was distilled off, and the product was purified by column chromatography to obtain the compound (B-5) represented by the formula (B-5) in a good yield.

[0397] [Example B6]

[0398] (Synthesis of Compound (B-6))

[0399] Compound (B-6) was synthesized according to the following synthesis scheme.

[0400] [Chemistry 40]

[0401]

[0402] 20.0 mmol of 3-bromothiophene-2-carboxylic acid, 24.0 mmol of sodium bisulfite, and 2.0 mmol of copper chloride were added to a reaction vessel, and an aqueous sodium hydroxide solution was added to adjust the pH to 7.5-7.7. After reacting at 100°C for 3 hours, insoluble matter was removed by filtration. The recovered filtrate was cooled to 0°C and allowed to stand for 12 hours, after which the precipitated crystals were separated by filtration. The separated crystals were washed with acetone to obtain the sodium sulfonate salt in a good yield.

[0403] 20.0 mmol of sulfonium bromide was added to the sodium sulfonate salt, and a mixture of water and dichloromethane (1:3 (mass ratio)) was added to prepare 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 obtained organic layer was dried over sodium sulfate, the solvent was distilled off, and the product was purified by column chromatography to obtain the compound (B-6) represented by the formula (B-6) in a good yield.

[0404] [Example B7]

[0405] (Synthesis of Compound (B-7))

[0406] Compound (B-7) was synthesized according to the following synthesis scheme.

[0407] [Chemistry 41]

[0408]

[0409] 20.0 mmol of tetraiodo-2-sulfobenzoic anhydride and aqueous sodium hydroxide solution were added to a reaction vessel to prepare a 0.5 M solution. After reacting at 70°C for 6 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 distilled off to obtain the sodium sulfonate salt in good yield.

[0410] 20.0 mmol of sulfonium bromide was added to the sodium sulfonate salt, and a mixture of water and dichloromethane (1:3 (mass ratio)) was added to prepare 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 obtained organic layer was dried over sodium sulfate, the solvent was distilled off, and the product was purified by column chromatography to obtain the compound (B-7) represented by the formula (B-7) in a good yield.

[0411] [Example B8]

[0412] (Synthesis of Compound (B-8))

[0413] Compound (B-8) was synthesized according to the following synthesis scheme.

[0414] [Chemistry 42]

[0415]

[0416] 20.0 mmol of 2-sulfobenzoic anhydride, 30.0 mmol of isopropylamine, and tetrahydrofuran were added to a reaction vessel to prepare a 0.5 M solution. After reacting at 70°C for 6 hours, the reaction was terminated by adding aqueous sodium hydroxide. Extraction was performed with dichloromethane, and the organic layer was separated. The resulting organic layer was dried over sodium sulfate, and the solvent was distilled off to obtain the sodium sulfonate salt in good yield.

[0417] 20.0 mmol of sulfonium bromide was added to the sodium sulfonate salt, followed by a mixture of water and dichloromethane (1:3 (mass ratio)) to prepare 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 obtained organic layer was dried over sodium sulfate, the solvent was distilled off, and the product was purified by column chromatography to obtain the compound (B-8) represented by the formula (B-8) in a good yield.

[0418] [Example B9]

[0419] (Synthesis of Compound (B-9))

[0420] Compound (B-9) was synthesized according to the following synthetic scheme.

[0421] [Chemistry 43]

[0422]

[0423] 20.0 mmol of 2-amino-5-methoxybenzenesulfonic acid, 30.0 mmol of isobutyl chloride, and tetrahydrofuran were added to a reaction vessel to prepare a 0.5 M solution. After reacting at 70°C for 6 hours, the reaction was terminated by adding aqueous sodium hydroxide. Extraction was performed with dichloromethane, and the organic layer was separated. The resulting organic layer was dried over sodium sulfate, and the solvent was distilled off to obtain the sodium sulfonate salt in good yield.

[0424] 20.0 mmol of sulfonium bromide was added to the sodium sulfonate salt, and a mixture of water and dichloromethane (1:3 (mass ratio)) was added to prepare 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 obtained organic layer was dried over sodium sulfate, the solvent was distilled off, and the product was purified by column chromatography to obtain the compound (B-9) represented by the formula (B-9) in a good yield.

[0425] [Example B10]

[0426] (Synthesis of Compound (B-10))

[0427] Compound (B-10) was synthesized according to the following synthetic scheme.

[0428] [Chemistry 44]

[0429]

[0430] 20.0 mmol of tert-butyl 5-norbornene-2-carboxylate, 30.0 mmol of bromine, and dichloromethane were added to a reaction vessel to prepare a 0.5 M solution. After reacting at room temperature for 6 hours, water was added to stop the reaction. Dichloromethane was added for extraction, and the organic layer was separated. After drying the obtained organic layer with sodium sulfate, the solvent was distilled off to obtain the bromoform in a good yield.

[0431] A mixture of acetonitrile and water (1:1 (mass ratio)) was added to the bromide to prepare a 1M solution. Then, 60.0 mmol of sodium disulfite and 80.0 mmol of sodium bicarbonate were added and reacted at 70°C for 6 hours. Extraction was performed with acetonitrile, and the solvent was distilled off. Then, a mixture of acetonitrile and water (3:1 (mass ratio)) was added to prepare a 0.5M solution. 60.0 mmol of aqueous hydrogen peroxide and 2.00 mmol of sodium tungstate were added, and the mixture was heated and stirred at 50°C for 12 hours. Extraction was performed with acetonitrile, and the solvent was distilled off to obtain the sodium sulfonate salt.

[0432] 20.0 mmol of sulfonium bromide was added to the sodium sulfonate salt, followed by a mixture of water and dichloromethane (1:3 (mass ratio)) to prepare 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 obtained organic layer was dried over sodium sulfate, the solvent was distilled off, and the product was purified by column chromatography to obtain the compound (B-10) represented by the formula (B-10) in a good yield.

[0433] As components other than the above-synthesized components, the following compounds were used.

[0434] [Radiosensitive Acid Generators Other Than Compounds (B-1) to (B-10) as Onium Salt Compounds (1)]

[0435] b-1 to b-11: Compounds represented by the following formulas (b-1) to (b-11) (hereinafter, the compounds represented by formulas (b-1) to (b-11) may be referred to as "compound (b-1)" to "compound (b-11)", respectively)

[0436] [Chemistry 45]

[0437]

[0438] [[D] Acid diffusion controller]

[0439] D-1 to D-7: compounds represented by the following formulas (D-1) to (D-7).

[0440] [Chemistry 46]

[0441]

[0442] [[E]Solvent]

[0443] E-1: Propylene glycol monomethyl ether

[0444] E-2: Cyclohexanone

[0445] E-3: γ-butyrolactone

[0446] E-4: Ethyl lactate

[0447] [Preparation of positive radiation-sensitive composition for ArF immersion exposure]

[0448] [Example 1]

[0449] 100 parts by mass of (A-1) as the polymer [A], 10.0 parts by mass of (B-1) as the onium salt compound (1) [B], 4.0 parts by mass of (D-1) as the acid diffusion controller [D], 5.0 parts by mass of (F-1) as the high fluorine content polymer [F] (solid content), and 3,400 parts by mass of a mixed solvent of (E-1) / (E-2) / (E-3) as the solvent [E] were mixed and filtered through a membrane filter having a pore size of 0.2 μm to prepare a radiation-sensitive composition (J-1).

[0450] [Examples 2 to 38 and Comparative Examples 1 to 3]

[0451] Radiation-sensitive compositions (J-2) to (J-38) and radiation-sensitive compositions (CJ-1) to (CJ-3) were prepared in the same manner as in Example 1 except that the types and contents of the components shown in Table 4 below were used.

[0452] [Table 4]

[0453]

[0454] <Formation of a Resist Pattern Using a Positive-Tone Radiation-Sensitive Composition for ArF Immersion Exposure>

[0455] A lower antireflective film-forming composition (Brewer Science's "ARC66") was applied to a 12-inch silicon wafer using a spin coater (Tokyo Electron's "CLEAN TRACK ACT12") and then heated at 205°C for 60 seconds to form an lower antireflective film with an average thickness of 100 nm. The prepared positive-type radiation-sensitive composition for ArF exposure was then applied to the lower antireflective film using the spin coater and prebaked (PB) at 100°C for 60 seconds. The film was then cooled at 23°C for 30 seconds to form a resist film with an average thickness of 90 nm. Next, the resist film was exposed using an ArF excimer laser immersion exposure system (ASML's "TWINSCAN XT-1900i") under optical conditions of NA = 1.35 and dipole (σ = 0.9 / 0.7) through a mask pattern of 60 nm lines and spaces. After exposure, a post-exposure bake (PEB) was performed at 100°C for 60 seconds. Thereafter, the resist film was alkaline developed using a 2.38% by mass aqueous TMAH solution as an alkaline developer. After development, the film was rinsed with water and dried to form a positive resist pattern (60 nm line and space pattern).

[0456] <Evaluation>

[0457] The sensitivity, LWR performance, and storage stability of the resist pattern formed using the positive-type radiation-sensitive composition for ArF immersion exposure were evaluated according to the following methods. The results are shown in Table 5. The resist pattern length was measured using a scanning electron microscope ("CG-5000" manufactured by Hitachi High-Technologies Corporation).

[0458] [sensitivity]

[0459] In forming a resist pattern using the positive radiation-sensitive composition for ArF immersion exposure, the exposure dose for forming a 60 nm line and space pattern was defined as the optimum exposure dose, and the optimum exposure dose was defined as the sensitivity (mJ / cm 2 ). Regarding sensitivity, 30mJ / cm 2 The following cases are evaluated as "good" and will exceed 30mJ / cm 2 The situation was rated as “poor”.

[0460] [LWR performance]

[0461] The optimal exposure amount obtained in the evaluation of the sensitivity is irradiated to form a resist pattern of 60nm lines and spaces. Using the scanning electron microscope, the formed resist pattern is observed from the top of the pattern. The deviation of the line width at a total of 500 points is measured, and the 3 sigma value is calculated based on the distribution of the measured values, and the 3 sigma value is set to LWR (nm). The smaller the value of LWR, the smaller the roughness of the line and the better. Regarding the LWR performance, the case below 3.0nm is evaluated as "good", and the case exceeding 3.0nm is evaluated as "poor".

[0462] [Storage stability]

[0463] After the positive-type radiation-sensitive composition for ArF immersion exposure was stored at 35°C for 30 days, the optimum exposure dose for forming a 60 nm line and space pattern, i.e., the sensitivity, was measured again. If the sensitivity after 30 days of storage (S 30 ) is evaluated as "A" (extremely good) if the rate of change of the sensitivity (S0) relative to the sensitivity before storage is greater than 0% and less than 1.0%, and is evaluated as "B" (good) if it exceeds 1.0% and is less than 2.0%, and is evaluated as "C" (poor) if it exceeds 2.0%.

[0464] Sensitivity change rate (%) = | (S 30 -S0) / S0|×100

[0465] [Table 5]

[0466]

[0467] The results in Table 5 clearly show that the radiation-sensitive compositions of the Examples exhibited excellent sensitivity, LWR performance, and storage stability when used for ArF immersion lithography. In contrast, the comparative examples exhibited inferior properties compared to the Examples. Therefore, when the radiation-sensitive compositions of the Examples were used for ArF immersion lithography, they exhibited excellent storage stability and could form resist patterns with optimal sensitivity and excellent LWR performance.

[0468] [Preparation of positive-type radiation-sensitive composition for ArF-dry exposure]

[0469] [Example 39]

[0470] 100 parts by mass of (A-1) as the polymer [A], 6.0 parts by mass of (B-1) as the onium salt compound (1) [B], 3.0 parts by mass of (D-6) as the acid diffusion controller [D], and 3,230 parts by mass of a mixed solvent of (E-1) / (E-2) / (E-3) as the solvent [E] were mixed and filtered through a membrane filter having a pore size of 0.2 μm to prepare a radiation-sensitive composition (J-39).

[0471] [Examples 40 to 52 and Comparative Examples 4 to 6]

[0472] Radiation-sensitive compositions (J-40) to (J-52) and radiation-sensitive compositions (CJ-4) to (CJ-6) were prepared in the same manner as in Example 39 except that the types and contents of the components shown in Table 6 below were used.

[0473] [Table 6]

[0474]

[0475] <Formation of a Resist Pattern Using a Positive-Tone Radiation-Sensitive Composition for ArF-Dry Exposure>

[0476] A lower antireflection film-forming composition (Brewer Science's "ARC29") was applied to an 8-inch silicon wafer using a spin coater (Tokyo Electron's "CLEAN TRACK ACT8") and then heated at 205°C for 60 seconds to form an lower antireflection film with an average thickness of 77 nm. The prepared positive-type radiation-sensitive composition for ArF dry exposure was applied to the lower antireflection film using the spin coater and prebaked (PB) at 100°C for 60 seconds. The composition was then cooled at 23°C for 30 seconds to form a resist film with an average thickness of 250 nm. Next, a line-and-space resist pattern with a line width of 90 nm was formed on the 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, a post-exposure bake (PEB) was performed at 100° C. for 60 seconds. The resist film was then developed using a 2.38% by mass aqueous TMAH solution as an alkaline developer, rinsed with water, and dried to form a positive resist pattern (90 nm line and space resist pattern).

[0477] <Evaluation>

[0478] The sensitivity, LWR performance, and storage stability of the resist pattern formed using the positive-working radiation-sensitive composition for ArF dry exposure were evaluated according to the following methods. The results are shown in Table 7. The resist pattern length was measured using a scanning electron microscope (S-9380, manufactured by Hitachi High-Technologies Corporation).

[0479] [sensitivity]

[0480] In forming a resist pattern using the positive radiation-sensitive composition for ArF-dry exposure, the exposure amount for forming a 90 nm line and space pattern was defined as the optimum exposure amount, and the optimum exposure amount was defined as the sensitivity (mJ / cm 2 ). Regarding sensitivity, 30mJ / cm 2 The following cases are evaluated as "good" and will exceed 30mJ / cm 2 The situation was rated as “poor”.

[0481] [LWR performance]

[0482] The optimal exposure amount obtained in the evaluation of the sensitivity is irradiated to form a resist pattern of 90nm lines and spaces. Using the scanning electron microscope, the formed resist pattern is observed from the top of the pattern. The deviation of the line width at a total of 500 points is measured, and the 3 sigma value is calculated based on the distribution of the measured values, and the 3 sigma value is set to LWR (nm). The smaller the value of LWR, the smaller the roughness of the line and the better. Regarding the LWR performance, the case below 4.0nm is evaluated as "good", and the case exceeding 4.0nm is evaluated as "poor".

[0483] [Storage stability]

[0484] After the ArF-dry exposure positive radiation-sensitive composition was stored at 35°C for 30 days, the optimum exposure dose for forming a 90 nm line and space pattern, i.e., the sensitivity, was measured again. If the sensitivity (S) after storage for 30 days is expressed by the following formula: 30 ) is evaluated as "A" (extremely good) if the rate of change of the sensitivity (S0) relative to the sensitivity before storage is greater than 0% and less than 1.0%, and is evaluated as "B" (good) if it exceeds 1.0% and is less than 2.0%, and is evaluated as "C" (poor) if it exceeds 2.0%.

[0485] Sensitivity change rate (%) = | (S 30 -S0) / S0|×100

[0486] [Table 7]

[0487]

[0488] The results in Table 7 clearly show that the radiation-sensitive compositions of the Examples exhibited excellent sensitivity, LWR performance, and storage stability when used for ArF dry exposure. In contrast, the comparative examples exhibited inferior properties compared to the Examples. Therefore, when the radiation-sensitive compositions of the Examples were used for ArF dry exposure, they exhibited excellent storage stability and could form resist patterns with optimal sensitivity and excellent LWR performance.

[0489] [Preparation of positive-type radiation-sensitive composition for extreme ultraviolet (EUV) exposure]

[0490] [Example 53]

[0491] 100 parts by mass of (A-12) as the polymer [A], 20.0 parts by mass of (B-1) as the onium salt compound (1) [B], 10.0 parts by mass of (D-4) as the acid diffusion controller [D], 3.0 parts by mass of (F-5) as the high fluorine content polymer [F] (solid content), and 6,110 parts by mass of a mixed solvent of (E-1) / (E-4) as the solvent [E] were mixed and filtered through a membrane filter having a pore size of 0.2 μm to prepare a radiation-sensitive composition (J-53).

[0492] [Examples 54 to 63 and Comparative Examples 7 to 9]

[0493] Radiation-sensitive compositions (J-54) to (J-63) and radiation-sensitive compositions (CJ-7) to (CJ-9) were prepared in the same manner as in Example 53 except that the types and contents of the components shown in Table 8 below were used.

[0494] [Table 8]

[0495]

[0496] <Formation of a Resist Pattern Using a Positive-Tone Radiation-Sensitive Composition for EUV Exposure>

[0497] A lower antireflective film-forming composition (Brewer Science's "ARC66") was applied to a 12-inch silicon wafer using a spin coater (Tokyo Electron's "CLEAN TRACK ACT12") and then heated at 205°C for 60 seconds to form an lower antireflective film with an average thickness of 105 nm. The prepared positive-tone radiation-sensitive composition for EUV exposure was applied to the lower antireflective film using the spin coater and subjected to photolithography (PB) at 130°C for 60 seconds. This was followed by cooling at 23°C for 30 seconds to form a resist film with an average thickness of 55 nm. Next, the resist film was exposed using an EUV exposure system (ASML's "NXE3300") with an NA of 0.33, illumination conditions: conventional s = 0.89, and a mask: imecDEFECT32FFR02. After exposure, photolithography (PEB) was performed at 120°C for 60 seconds. Thereafter, the resist film was subjected to alkali development using a 2.38 mass % TMAH aqueous solution as an alkaline developer, and after development, it was washed with water and dried to form a positive resist pattern (25 nm line and space pattern).

[0498] <Evaluation>

[0499] The sensitivity, LWR performance, and storage stability of the resist pattern formed using the positive-tone radiation-sensitive composition for EUV exposure were evaluated according to the following methods. The results are shown in Table 9. The length of the resist pattern was measured using a scanning electron microscope ("CG-5000" manufactured by Hitachi High-Technologies Corporation).

[0500] [sensitivity]

[0501] In forming a resist pattern using the positive radiation-sensitive composition for EUV exposure, the exposure dose for forming a 25 nm line and space pattern was defined as the optimal exposure dose, and the optimal exposure dose was defined as the sensitivity (mJ / cm 2 ). Regarding sensitivity, 40mJ / cm 2 The following cases are evaluated as "good" and will exceed 40mJ / cm 2 The situation was rated as “poor”.

[0502] [LWR performance]

[0503] The optimal exposure amount obtained in the evaluation of the sensitivity is irradiated, and the mask size is adjusted in a manner to form a 25nm line and space pattern to form a resist pattern. Using the scanning electron microscope, the formed resist pattern is observed from the top of the pattern. The deviation of the line width at a total of 500 points is measured, and the 3 sigma value is calculated based on the distribution of the measured values, and the 3 sigma value is set to LWR (nm). The smaller the value of LWR, the smaller the line shake and the better. Regarding the LWR performance, the case below 4.0nm is evaluated as "good", and the case exceeding 4.0nm is evaluated as "poor".

[0504] [Storage stability]

[0505] After the positive-type radiation-sensitive composition for EUV exposure was stored at 35°C for 30 days, the optimum exposure dose for forming a 90 nm line and space pattern, i.e., the sensitivity, was measured again. If the sensitivity after storage for 30 days (S 30 ) is evaluated as "A" (extremely good) if the rate of change of the sensitivity (S0) relative to the sensitivity before storage is greater than 0% and less than 1.0%, and is evaluated as "B" (good) if it exceeds 1.0% and is less than 2.0%, and is evaluated as "C" (poor) if it exceeds 2.0%.

[0506] Sensitivity change rate (%) = | (S 30 -S0) / S0|×100

[0507] [Table 9]

[0508]

[0509] The results in Table 9 clearly show that the radiation-sensitive compositions of Examples have good sensitivity, LWR performance, and storage stability when used for EUV exposure, whereas the Comparative Examples are inferior in various properties compared to the Examples.

[0510] [Preparation of Negative-Tone Radiation-Sensitive Composition for ArF Exposure, Formation and Evaluation of Resist Pattern Using the Composition]

[0511] [Example 64]

[0512] 100 parts by mass of (A-1) as the polymer [A], 12.0 parts by mass of (B-1) as the onium salt compound (1) [B], 10.0 parts by mass of (D-7) as the acid diffusion controller [D], 2.0 parts by mass of (F-3) as the high fluorine content polymer [F] (solid content), and 3,230 parts by mass of a mixed solvent of (E-1) / (E-2) / (E-3) as the solvent [E] (compounded amounts: 2240 parts by mass / 960 parts by mass / 30 parts by mass) were mixed and filtered through a membrane filter having a pore size of 0.2 μm to prepare a radiation-sensitive composition (J-64).

[0513] A lower antireflective film-forming composition (Brewer Science's "ARC66") was applied to a 12-inch silicon wafer using a spin coater (Tokyo Electron's "CLEAN TRACK ACT12") and then heated at 205°C for 60 seconds to form an lower antireflective film with an average thickness of 100 nm. The prepared negative-type radiation-sensitive composition for ArF exposure (J-64) was applied to the lower antireflective film using the spin coater and prebaked (PB) at 100°C for 60 seconds. The film was then cooled at 23°C for 30 seconds to form a resist film with an average thickness of 90 nm. Next, the resist film was exposed using an ArF excimer laser immersion lithography system (ASML's "TWINSCAN XT-1900i") under optical conditions of NA = 1.35 and annular (σ = 0.8 / 0.6) through a mask pattern with 50 nm holes and 100 nm pitch. After exposure, a post-exposure bake (PEB) was performed at 100°C for 60 seconds. The resist film was then organically developed using n-butyl acetate as an organic solvent developer and dried to form a negative-tone resist pattern (contact hole pattern with 50 nm holes and 100 nm pitch).

[0514] The sensitivity of the resist pattern using the negative-type radiation-sensitive composition for ArF exposure was evaluated in the same manner as the evaluation of the resist pattern using the positive-type radiation-sensitive composition for ArF exposure. In addition, the CDU performance and storage stability were evaluated according to the following methods.

[0515] [CDU performance]

[0516] The optimal exposure dose determined in the sensitivity evaluation was used to form contact holes with a 50 nm hole and a 100 nm pitch. The resulting resist pattern was observed from the top of the pattern using the scanning electron microscope. The deviation in contact hole diameter was measured at a total of 500 locations, and a 3 sigma value was calculated based on the distribution of the measured values. This 3 sigma value was designated as CDU (nm). A smaller CDU value indicates a smaller and better hole roughness. Regarding CDU performance, a value less than 3.5 nm was evaluated as "good," and a value greater than 3.5 nm was evaluated as "poor."

[0517] [Storage stability]

[0518] After the ArF exposure negative radiation-sensitive composition was stored at 35°C for 30 days, the optimum exposure dose for forming 50 nm holes and 100 nm pitch contact holes, i.e., the sensitivity, was measured again. If the sensitivity after 30 days of storage (S 30 ) is evaluated as "A" (extremely good) if the rate of change of the sensitivity (S0) relative to the sensitivity before storage is greater than 0% and less than 1.0%, and is evaluated as "B" (good) if it exceeds 1.0% and is less than 2.0%, and is evaluated as "C" (poor) if it exceeds 2.0%.

[0519] Sensitivity change rate (%) = | (S 30 -S0) / S0|×100

[0520] As a result, the radiation-sensitive composition of Example 64 exhibited excellent sensitivity, CDU performance, and storage stability even when a negative-type resist pattern was formed by ArF exposure.

[0521] [Preparation of Negative-Tone Radiation-Sensitive Composition for EUV Exposure, Formation and Evaluation of Resist Pattern Using the Composition]

[0522] [Example 65]

[0523] 100 parts by mass of (A-15) as the polymer [A], 30.0 parts by mass of (B-7) as the onium salt compound (1) [B], 10.0 parts by mass of (D-4) as the acid diffusion controller [D], 5.0 parts by mass of (F-5) as the high fluorine content polymer [F] (solid content), and 6,110 parts by mass of a mixed solvent of (E-1) / (E-4) as the solvent [E] (compounded amounts: 4280 parts by mass / 1830 parts by mass) were mixed and filtered through a membrane filter having a pore size of 0.2 μm to prepare a radiation-sensitive composition (J-65).

[0524] A lower antireflective film-forming composition (Brewer Science's "ARC66") was applied to a 12-inch silicon wafer using a spin coater (Tokyo Electron's "CLEAN TRACK ACT12") and then heated at 205°C for 60 seconds to form an lower antireflective film with an average thickness of 105 nm. The prepared negative-type radiation-sensitive composition for EUV exposure (J-65) was applied to the lower antireflective film using the spin coater and subjected to PB at 130°C for 60 seconds. The film was then cooled at 23°C for 30 seconds to form a resist film with an average thickness of 55 nm. The resist film was then exposed using an EUV exposure system (ASML's "NXE3300") with an NA of 0.33, conventional illumination conditions of s = 0.89, and an imecDEFECT32FFR15 mask. After exposure, PEB was performed for 60 seconds at 120° C. Then, the resist film was developed with n-butyl acetate as an organic solvent developer and dried to form a negative resist pattern (contact hole pattern with 20 nm holes and 40 nm pitch).

[0525] Resist patterns formed using the negative-working radiation-sensitive composition for EUV exposure were evaluated in the same manner as the resist patterns formed using the negative-working radiation-sensitive composition for ArF exposure. The results showed that the radiation-sensitive composition of Example 65 exhibited excellent sensitivity, CDU performance, and storage stability even when forming a negative-working resist pattern using EUV exposure.

[0526] Industrial applicability

[0527] The radiation-sensitive composition and resist pattern forming method described above exhibit excellent storage stability, good sensitivity to exposure light, and can form a resist pattern with excellent LWR and CDU performance. Therefore, these compositions are preferably used in processes for semiconductor devices, which are expected to undergo further miniaturization.

Claims

1. A radiation-sensitive composition comprising: An onium salt compound represented by the following formula (1): A polymer containing a structural unit (I) having an acid-dissociable group, and solvents; [Chemistry 1] (In formula (1), W is a cyclic structure with 3 to 40 ring members formed together with two carbon atoms; The following formulas between carbon-carbons represent single bonds or double bonds; [Chemistry 2] A is a group represented by the following formula (A-1), a group represented by the following formula (A-2), a group represented by the following formula (A-3), a group represented by the following formula (A-4), a group represented by the following formula (A-5), a group represented by the following formula (A-6), or a group represented by the following formula (A-7); [Chemistry 3] (In formula (A-3) and formula (A-4), R A1 and R A2 are each independently a monovalent hydrocarbon group having 1 to 20 carbon atoms; * is a bond to a carbon atom) R 1 is a monovalent organic group with 1 to 20 carbon atoms, a cyano group, a nitro group, a carboxyl group, a hydroxyl group, an amino group, a halogen atom or a thiol group; in R 1 When there are multiple R 1 the same as or different from each other; m1 is an integer from 0 to 4; Z + is a monovalent radiosensitive linear onium cation).

2. The radiation-sensitive composition according to claim 1, wherein W is an alicyclic hydrocarbon structure having 3 to 20 carbon atoms, an aromatic hydrocarbon structure having 6 to 20 carbon atoms, an aliphatic heterocyclic structure having 3 to 20 carbon atoms, or an aromatic heterocyclic structure having 5 to 20 carbon atoms.

3. The radiation-sensitive composition according to claim 1, wherein The content of the onium salt compound is 1 part by mass or more and 30 parts by mass or less relative to 100 parts by mass of the polymer.

4. The radiation-sensitive composition according to any one of claims 1 to 3, wherein The structural unit (I) is represented by the following formula (3); [Chemistry 4] (In formula (3), R 17 is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group; R 18 A monovalent hydrocarbon group having 1 to 20 carbon atoms; R 19 and R 20 are independently a monovalent chain hydrocarbon group having 1 to 10 carbon atoms or a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, or R 19 and R 20 (a divalent alicyclic group having 3 to 20 carbon atoms that is bonded to each other and formed together with these bonded carbon atoms).

5. The radiation-sensitive composition according to any one of claims 1 to 3, wherein The structural unit (I) is represented by the following formula (3-1); [Chemistry 5] (In formula (3-1), R 17 is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group; R 18 is isopropyl, tert-butyl or phenyl; i is an integer from 1 to 4).

6. The radiation-sensitive composition according to any one of claims 1 to 3, wherein The content ratio of the structural unit (I) in all the structural units constituting the polymer is 40 mol% or more and 80 mol% or less.

7. The radiation-sensitive composition according to any one of claims 1 to 3, wherein The polymer further includes a structural unit (II) containing at least one selected from the group consisting of a lactone structure, a cyclic carbonate structure, and a sultone structure.

8. The radiation-sensitive composition according to claim 7, wherein The content ratio of the structural unit (II) in all the structural units constituting the polymer is 20 mol% or more and 60 mol% or less. 9 . The radiation-sensitive composition according to claim 1 , further comprising an acid diffusion controller.

10. A pattern forming method comprising: A step of directly or indirectly applying the radiation-sensitive composition according to any one of claims 1 to 3 on a substrate to form a resist film; a step of exposing the resist film to light; and A step of developing the exposed resist film using a developer.

11. The pattern forming method according to claim 10, wherein: The exposure is performed by ArF excimer laser or extreme ultraviolet rays.

12. An onium salt compound represented by the following formula (1); [Chemistry 6] (In formula (1), W is a cyclic structure with 3 to 40 ring members formed together with two carbon atoms; The following formulas between carbon-carbons represent single bonds or double bonds; [Chemistry 7] A is a group represented by the following formula (A-1), a group represented by the following formula (A-2), a group represented by the following formula (A-3), a group represented by the following formula (A-4), a group represented by the following formula (A-5), a group represented by the following formula (A-6), or a group represented by the following formula (A-7); [Chemistry 8] (In formula (A-3) and formula (A-4), R A1 and R A2 are each independently a monovalent hydrocarbon group having 1 to 20 carbon atoms; * is a bond to a carbon atom) R 1 is a monovalent organic group with 1 to 20 carbon atoms, a cyano group, a nitro group, a carboxyl group, a hydroxyl group, an amino group, a halogen atom or a thiol group; in R 1 When there are multiple R 1 the same as or different from each other; m1 is an integer from 0 to 4; Z + is a monovalent radiosensitive linear onium cation).

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