Radiation-sensitive composition and method for forming resist pattern

Abstract

This radiation-sensitive composition comprises: a compound represented by formula (1) and a radiation-sensitive acid-generating body formed from a radiation-sensitive cation and an organic anion having a steroid skeleton or a 9,10-ethanoanthracene skeleton. In formula (1), R11, R12, and R13 are each independently, a C1-20 monovalent aliphatic hydrocarbon group.

Description

Radiation-sensitive composition and method for forming resist pattern

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims priority to Japanese Patent Application No. 2024-75904, filed May 8, 2024, the entire contents of which are incorporated herein by reference. The present disclosure relates to a radiation-sensitive composition and a method for forming a resist pattern.

[0002] In lithography techniques used in the manufacturing processes of various electronic devices such as semiconductor devices and liquid crystal devices, a radiation-sensitive composition is irradiated with far ultraviolet rays (such as an ArF excimer laser), extreme ultraviolet rays (EUV), electron beams, or the like to generate an acid in the exposed area, and a chemical reaction involving this acid causes a difference in the dissolution rate in a developer between the exposed area and the unexposed area, thereby forming a resist pattern on a substrate.

[0003] With the miniaturization of various electronic device structures, there is a demand for further miniaturization of resist patterns in lithography processes. Furthermore, in response to the demand for further miniaturization of resist patterns, various efforts have been made to improve the resolution and resist pattern shape of radiation-sensitive compositions used in lithographic microfabrication (see, for example, Patent Document 1). Patent Document 1 discloses a radiation-sensitive resin composition containing: a first polymer having a structural unit containing a phenolic hydroxy group and a structural unit containing an acid-dissociable group; a second polymer having at least one of a fluorine atom and a silicon atom and a structural unit containing an alkali-dissociable group; a specific first compound that generates an acid that dissociates the acid-dissociable group in the first polymer upon irradiation with radiation; and a specific second compound that generates an acid that does not substantially dissociate the acid-dissociable group in the first polymer upon irradiation with radiation.

[0004] International Publication No. 2018 / 230334

[0005] In recent years, attempts have been made to form fine patterns, for example, with line widths of 40 nm or less. Furthermore, as resist patterns become finer, further improvements in various performances are desired. As one such improvement, suppressing the occurrence of defects during resist pattern formation has become increasingly important as resist patterns become finer.

[0006] Furthermore, from the viewpoint of achieving even higher quality in semiconductor devices and the like, resist patterns are required to have little variation in film thickness and a high degree of flatness (film thickness uniformity).

[0007] The present disclosure has been made in consideration of the above-mentioned problems, and a primary object of the present disclosure is to provide a radiation-sensitive composition that can suppress the occurrence of defects during resist pattern formation and can form a resist pattern with excellent film thickness uniformity, and a method of forming a resist pattern that uses the radiation-sensitive composition.

[0008] According to one aspect of the present disclosure, there is provided a radiation-sensitive composition comprising: a radiation-sensitive acid generator including an organic anion having a steroid skeleton or a 9,10-ethanoanthracene skeleton and a radiation-sensitive cation; and a compound represented by the following formula (1): (In formula (1), R １１ , R １２ and R １３ are each independently a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms.

[0009] According to another aspect of the present disclosure, there is provided a method for forming a resist pattern, the method including the steps of forming a resist film on a substrate using the radiation-sensitive composition described above, exposing the resist film to light, and developing the exposed resist film.

[0010] According to the present disclosure, it is possible to obtain a radiation-sensitive composition that can suppress the occurrence of defects during resist pattern formation and can form a resist pattern with excellent film thickness uniformity. Furthermore, according to the method of forming a resist pattern of the present disclosure, by using the radiation-sensitive composition of the present disclosure, it is possible to suppress the occurrence of defects and form a resist pattern with excellent film thickness uniformity.

[0011] Matters relating to the embodiments will be described in detail below. In this specification, a numerical range described using "to" means that the numerical values ​​before and after "to" are included as the lower and upper limits.

[0012] In this specification, the term "hydrocarbon group" includes chain hydrocarbon groups, alicyclic hydrocarbon groups, and aromatic hydrocarbon groups. The term "chain hydrocarbon group" refers to a linear hydrocarbon group or a branched hydrocarbon group that does not contain a cyclic structure and is composed solely of a chain structure. However, the chain hydrocarbon group may be saturated or unsaturated. The term "alicyclic hydrocarbon group" refers to a hydrocarbon group that contains only an alicyclic hydrocarbon structure as a ring structure and does not contain an aromatic ring structure. However, the alicyclic hydrocarbon group does not necessarily have to be composed solely of an alicyclic hydrocarbon structure and may also contain a chain structure as part of it. The term "aromatic hydrocarbon group" refers to a hydrocarbon group that contains an aromatic ring structure as a ring structure. However, the aromatic hydrocarbon group does not necessarily have to be composed solely of an aromatic ring structure and may contain a chain structure or an alicyclic hydrocarbon structure as part of it. The term "organic group" refers to an atomic group obtained by removing any hydrogen atom from a carbon-containing compound (i.e., an organic compound). The term "aromatic ring" refers to an aromatic hydrocarbon ring and an aromatic heterocycle.

[0013] The "main chain" of a polymer refers to the "backbone" portion of the polymer, which is the longest chain of atoms. It is acceptable for this "backbone" portion to contain a ring structure. For example, "having a specific structure in the main chain" means that the specific structure constitutes part of the main chain of the polymer. A "side chain" refers to a portion branched from the "backbone" of the polymer. A "structural unit" refers to a unit that primarily constitutes the main chain structure, and at least two or more of which are contained in the main chain structure. A structural unit is typically a monomer unit. However, a "structural unit" also includes a unit obtained by reacting a monomer unit having a reactive group with a compound having a functional group capable of reacting with the reactive group, and a unit obtained by polymerizing a monomer protected with a protecting group such as an alkali-labile group and then deprotecting the monomer by hydrolysis. "(Meth)acrylate" is a term that encompasses both "acrylate" and "methacrylate."

[0014] The expression "substituted or unsubstituted p-valent hydrocarbon group (where p is an integer of 1 or more)" encompasses p-valent hydrocarbon groups (i.e., unsubstituted p-valent hydrocarbon groups) and groups in which p hydrogen atoms have been removed from the hydrocarbon structural portion of a substituted hydrocarbon group. Examples of substituted or unsubstituted p-valent hydrocarbon groups include alkyl groups and fluoroalkyl groups where p=1, and alkanediyl groups and fluoroalkanediyl groups where p=2. Of these, fluoroalkyl groups are "substituted monovalent hydrocarbon groups," and fluoroalkanediyl groups are "substituted divalent hydrocarbon groups." The same applies to other groups to which "substituted or unsubstituted" is attached.

[0015] <Radiation-Sensitive Composition> The radiation-sensitive composition of the present disclosure (hereinafter also referred to as "the composition") contains a radiation-sensitive acid generator (hereinafter also referred to as "specific acid generator") consisting of an organic anion having a steroid skeleton or a 9,10-ethanoanthracene skeleton and a radiation-sensitive cation, and a compound represented by the following formula (1) (hereinafter also referred to as "compound (Ex)"): (In formula (1), R １１ , R １２ and R １３ are each independently a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms.

[0016] The present composition containing a specific acid generator and compound (Ex) can suppress the occurrence of defects during resist pattern formation and can provide a radiation-sensitive composition that exhibits excellent film thickness uniformity and minimal film thickness variation in the resist film. While the reason for this effect is unclear, the following is thought to be an example. When the organic anion constituting the radiation-sensitive acid generator has a cyclic structure (an alicyclic structure or an aromatic ring structure), acid is less likely to diffuse into the resist film after exposure, which is thought to result in excellent lithography performance. On the other hand, when the organic anion constituting the radiation-sensitive acid generator has a cyclic structure, for example, the radiation-sensitive acid generator is more likely to aggregate due to the high planarity of the cyclic structure, which can easily result in film thickness variation in the resist film formed using the radiation-sensitive acid generator. In contrast, when a radiation-sensitive acid generator contains an organic cation having a steroid skeleton or a 9,10-ethanoanthracene skeleton, its high three-dimensionality is thought to suppress aggregation of the radiation-sensitive acid generator. Furthermore, compound (Ex) has a relatively high boiling point and exhibits high solubility in the specific acid generator. It is believed that these factors combined together make it possible for the composition containing the specified acid generator and compound (Ex) to suppress the occurrence of defects during resist pattern formation and to form a resist pattern with excellent film thickness uniformity. However, the reasons stated above are merely speculation and do not limit the present invention in any way.

[0017] The specific acid generator is a substance that generates an acid upon irradiation with radiation. The specific acid generator may be a so-called radiation-sensitive acid generator or an acid diffusion controller. Furthermore, the present composition may contain both an acid generator and an acid diffusion controller as the specific acid generator. Here, the acid generator is a substance that, upon exposure, generates in the present composition a strong acid capable of cleaving an acid-dissociable group possessed by a component in the radiation-sensitive composition from the component. The acid diffusion controller is a substance that can suppress the diffusion of an acid derived from the acid generator generated upon exposure within the resist film, thereby suppressing a chemical reaction caused by the acid in unexposed regions. In this specification, the term "radiation" encompasses electron beams (visible light, ultraviolet light, far ultraviolet light, extreme ultraviolet light (EUV), etc.) and electromagnetic waves (X-rays, gamma rays, etc.).

[0018] Radiation-sensitive acid generators are classified as acid generators or acid diffusion controllers depending on the strength of their acidity relative to the components in the present composition (specifically, the structural units derived from the radiation-sensitive onium salt in the polymer contained in the present composition, or the other radiation-sensitive acid generators when two or more types of radiation-sensitive acid generators are contained). The level of acidity can be evaluated by the acid dissociation constant (pKa). For example, the acid dissociation constant of the acid generated by an acid diffusion controller is usually −3 or more, preferably −1≦pKa≦7, and more preferably 0≦pKa≦5.

[0019] The present composition preferably contains a polymer as a base resin, together with the specified acid generator and compound (Ex). Specific embodiments of the present composition include, for example, the following embodiments [1] to [3]. Embodiment [1]: Contains a base resin, a specified acid generator, and compound (Ex), an acid generator as the specified acid generator, and an acid diffusion controller as a radiation-sensitive acid generator different from the specified acid generator (hereinafter also referred to as "other acid generator"). Embodiment [2]: Contains a base resin, a specified acid generator, and compound (Ex), an acid diffusion controller as the specified acid generator, and an acid generator as the other acid generator. Embodiment [3]: Contains a base resin, a specified acid generator, and compound (Ex), and an acid generator and an acid diffusion controller as the specified acid generator.

[0020] The radiation-sensitive compositions of the above-mentioned embodiments [1] to [3] may further contain other solid components (for example, other acid generators (acid generators, acid diffusion controllers), high-fluorine-containing polymers, solvents different from compound (Ex)), etc.) in addition to the components contained in each embodiment. For example, embodiment [1] may further contain an acid generator as the other acid generator, may further contain a solvent different from compound (Ex), or may further contain a high-fluorine-containing polymer. In this specification, the term "base resin" refers to the main component of the polymer components contained in the radiation-sensitive composition. In this composition, it is preferable that the base resin is a polymer containing a structural unit having an aromatic ring and a hydroxyl group bonded to the aromatic ring (polymer (P) shown below).

[0021] Next, the components contained in the present composition and the components that may be optionally blended will be described in detail. Note that, unless otherwise specified, each component contained in the present composition may be used alone or in combination of two or more.

[0022] <Specific Acid Generator> The specific acid generator is a non-polymer composed of an organic anion having a steroid skeleton or a 9,10-ethanoanthracene skeleton and a radiation-sensitive cation. The organic anion is the conjugate base of the acid, and is usually an anion formed by removing a proton from the acid group of an organic acid. As the specific acid generator, a low-molecular-weight compound (non-polymer) is preferably used because it allows for easy adjustment of the sensitivity of the composition and provides a high degree of freedom in selecting the radiation-sensitive acid generator to be incorporated into the composition. The molecular weight of the radiation-sensitive acid generator is preferably 1,000 or less, more preferably 850 or less, and even more preferably 750 or less.

[0023] (Organic Anion) The organic anion constituting the specific acid generator (hereinafter also referred to as "specific anion") is not particularly limited as long as it has a steroid skeleton or a 9,10-ethanoanthracene skeleton. Here, "steroid skeleton" refers to a cyclopentanoperhydrophenanthrene skeleton (a skeleton represented by the following formula (a)) or a skeleton having a structure closely related to the cyclopentanoperhydrophenanthrene skeleton. Examples of skeletons having a structure closely related to the cyclopentanoperhydrophenanthrene skeleton include skeletons containing a double bond within the ring and skeletons in which one or two rings are aromatic rings. The 9,10-ethanoanthracene skeleton is represented by the following formula (b). The steroid skeleton and the 9,10-ethanoanthracene skeleton may each have a substituent on the ring moiety. Furthermore, one side of the steroid skeleton and the 9,10-ethanoanthracene skeleton may each form a fused ring with a ring other than the ring constituting the steroid skeleton or the 9,10-ethanoanthracene skeleton.

[0024] Examples of the specific anion include a sulfonate anion, an imidate anion, a methide anion, and a carboxylate anion. Of these, the specific anion is preferably a sulfonate anion or a carboxylate anion. Specifically, examples of the specific anion include an anion represented by the following formula (2-1) and an anion represented by the following formula (2-2). (In formula (2-1), W １ is a monovalent group having a steroid skeleton or a 9,10-ethanoanthracene skeleton. １ is a single bond or a divalent linking group. １ , R ２ and R ３ are each independently a hydrogen atom, a fluorine atom or a fluoroalkyl group. ｆ is a fluorine atom or a fluoroalkyl group. a is an integer of 0 to 8. In formula (2-2), W ２ is a monovalent group having a steroid skeleton or a 9,10-ethanoanthracene skeleton. ２ is a single bond or a divalent linking group.

[0025] In the above formula (2-1) or (2-2), W １ Or W ２ When W is a monovalent group having a steroid skeleton, preferred examples of the monovalent group include groups represented by the following formula (w-1). １ Or W ２ When is a monovalent group having a 9,10-ethanoanthracene skeleton, preferred examples of the monovalent group include groups represented by the following formula (w-2): (In formula (w-1), R ２０ is a substituent. r1 is an integer of 1 to 20. When r1 is 2 or more, multiple R ２０ are the same or different, provided that (r1) R ２０ In formula (w-2), one of R ２１ , R ２２ , R ２３ , R ２４ , R ２５ and R ２６ are each independently a hydrogen atom or a substituent, or R２１ , R ２２ , R ２３ , R ２４ , R ２５ and R ２６ represents a ring structure formed by two of the R ２７ and R ２８ are each independently a substituent. r2 and r3 are each independently 0 to 4. When r2 is 2 or more, a plurality of R １７ are the same or different. When r3 is 2 or more, multiple R ２８ are the same or different, provided that R ２１ , R ２２ , R ２３ , R ２４ , R ２５ and R ２６ , (r2) R ２７ and (r3) R ２８ One of them is a bond.)

[0026] In the above formula (w-1), R ２０ and a substituent represented by R in the above formula (w-2). ２１ , R ２２ , R ２３ , R ２４ , R ２５ , R ２６ , R ２７ or R ２８ (Hereinafter referred to as “R ２１ ~R ２８ Examples of the substituent represented by W include a monovalent hydrocarbon group having 1 to 20 carbon atoms, a monovalent group having 3 to 20 carbon atoms and a heterocyclic structure, a halogen atom (such as a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom), a hydroxyl group, a carboxy group, an acyl group, a nitro group, a cyano group, and an oxo group. １ and W ２ From the viewpoint of sensitivity, it is preferable that the compound does not contain a fluorine atom.

[0027] 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, and a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms.

[0028] Specific examples of the monovalent chain hydrocarbon group include alkyl groups such as a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, and a t-butyl group; alkenyl groups such as an ethenyl group, a propenyl group, and a butenyl group; and alkynyl groups such as an ethynyl group, a propynyl group, and a butynyl group.

[0029] Specific examples of the monovalent alicyclic hydrocarbon group include monovalent monocyclic alicyclic saturated hydrocarbon groups such as a cyclopentyl group, a cyclohexyl group, a methylcyclopentyl group, an ethylcyclopentyl group, a methylcyclohexyl group, and an ethylcyclohexyl group; monovalent monocyclic unsaturated hydrocarbon groups such as a cyclopentenyl group, a cyclohexenyl group, a methylcyclopentenyl group, and a methylcyclohexenyl group; monovalent polycyclic saturated alicyclic hydrocarbon groups such as a norbornyl group, an adamantyl group, and a tricyclodecyl group; and monovalent polycyclic unsaturated alicyclic hydrocarbon groups such as a norbornenyl group, a tricyclodecenyl group, and an indanyl group.

[0030] Specific examples of the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms include aryl groups such as a phenyl group, a tolyl group, a xylyl group, a mesityl group, a naphthyl group, a methylnaphthyl group, an anthryl group, a methylanthryl group, and an indenyl group; and aralkyl groups such as a benzyl group, a phenethyl group, a naphthylmethyl group, and an anthrylmethyl group.

[0031] In the monovalent group having a heterocyclic structure and having 3 to 20 carbon atoms, examples of the heterocyclic structure include an aliphatic heterocyclic structure having 3 to 20 carbon atoms and an aromatic heterocyclic structure having 4 to 20 carbon atoms. Specific examples of these include a cyclic ether structure, a lactone structure, a cyclic carbonate structure, a sultone structure, and a thioxane structure as the aliphatic heterocyclic structure having 3 to 20 carbon atoms. The aliphatic heterocyclic structure may be either a monocyclic structure or a polycyclic structure, and may also be any of a bridged structure, a fused ring structure, and a spiro ring structure. Examples of the aromatic heterocyclic structure having 4 to 20 carbon atoms include a furan ring structure, a benzofuran ring structure, a thiophene structure, a benzothiophene ring structure, a pyridine ring structure, a quinoline ring structure, and an isoquinoline ring structure. The heterocyclic structure may be directly bonded to the steroid skeleton or the 9,10-ethanoanthracene skeleton, or may be bonded via a divalent linking group. Examples of the divalent linking group include -O-, -CO-, -COO-, -OCO-, -O-CO-O-, -S-, and -SO ２ -, -CONH-, -NHCO-, a divalent hydrocarbon group having 1 to 12 carbon atoms, a methylene group of the hydrocarbon group being -O-, -CO-, -COO-, -OCO-, -O-CO-O-, -S-, -SO ２ Examples include divalent groups having 1 to 12 carbon atoms substituted with -, -CONH-, or -NHCO-.

[0032] R ２１ , R ２２ , R ２３ , R ２４ , R ２５ and R ２６ Examples of the ring structure formed by bonding two of the above rings together include aliphatic rings such as a cyclopentane ring, a cyclohexane ring, a cyclopentene ring, and a cyclohexene ring; and aromatic rings such as a benzene ring and a naphthalene ring.

[0033] It is preferable that the specific acid generator has a 9,10-ethanoanthracene skeleton, since it can improve the film thickness uniformity. １ It is preferable that W in the above formula (w-2) does not have an aromatic ring. ２Preferably, R in the above formula (w-1) does not have an aromatic ring in a portion other than the 9,10-ethanoanthracene skeleton. ２０ Preferably, two or more of these are hydroxyl groups.

[0034] L １ or L ２ Examples of the divalent linking group represented by the formula: ２ -, -CONH-, -NHCO-, a divalent hydrocarbon group having 1 to 20 carbon atoms, a methylene group of the hydrocarbon group being -O-, -CO-, -COO-, -OCO-, -O-CO-O-, -S-, -SO ２ Examples of the divalent hydrocarbon group include a divalent group having 1 to 20 carbon atoms substituted with -, -CONH-, or -NHCO-, and a divalent group in which one or more hydrogen atoms of the divalent group or a divalent hydrocarbon group having 1 to 20 carbon atoms have been substituted with a substituent. Examples of the divalent hydrocarbon group having 1 to 20 carbon atoms include a group in which one hydrogen atom has been further removed from a monovalent hydrocarbon group having 1 to 20 carbon atoms. Examples of the substituent include a halogen atom, a hydroxyl group, and a carboxy group.

[0035] L １ or L ２ From the viewpoint of ease of synthesis of the specific acid generator, the divalent linking group represented by the formula (I) is preferably a divalent group having a chain structure among the above, and the methylene group in the alkanediyl group is preferably -O-, -CO-, -COO-, -OCO-, -O-CO-O-, -S-, or -SO ２ A divalent group having 1 to 20 carbon atoms substituted with --, --CONH-- or --NHCO-- is preferred.

[0036] R １ , R ２ , R ３ and R ｆExamples of the fluoroalkyl group represented by the formula (I) include a trifluoromethyl group, a 2,2,2-trifluoroethyl group, a pentafluoroethyl group, a 2,2,3,3,3-pentafluoropropyl group, a 1,1,1,3,3,3-hexafluoropropyl group, a heptafluoro n-propyl group, a heptafluoro i-propyl group, a nonafluoro n-butyl group, a nonafluoro i-butyl group, a nonafluoro t-butyl group, a 2,2,3,3,4,4,5,5-octafluoro n-pentyl group, a tridecafluoro n-hexyl group, and a 5,5,5-trifluoro-1,1-diethylpentyl group. １ , R ２ , R ３ and R ｆ The fluoroalkyl group represented by the formula (I) is preferably a fluoroalkyl group having 1 to 3 carbon atoms, more preferably a trifluoromethyl group.

[0037] Among the above, R １ , R ２ , R ３ and R ｆ is preferably a fluorine atom or a trifluoromethyl group in that it can improve sensitivity. a is preferably 0 to 5, and more preferably 0 to 2.

[0038] Specific examples of the anion represented by the above formula (2-1) or (2-2) include anions represented by the following formulas, however, the specific anion is not limited to the following specific examples.

[0039] Among the above-mentioned specific anions, onium salts formed from a sulfonate anion and a radiation-sensitive cation are preferably used as acid generators (hereinafter also referred to as "specific acid generators").Furthermore, among the above-mentioned specific anions, onium salts formed from a carboxylate anion and a radiation-sensitive cation are preferably used as acid diffusion controllers (hereinafter also referred to as "specific acid diffusion controllers").

[0040] (Radiation-Sensitive Cation) Examples of the radiation-sensitive cation constituting the specific acid generator include radiation-decomposable onium cations containing elements such as S, I, O, N, P, Cl, Br, F, As, Se, Sn, Sb, Te, and Bi. Specific examples of the radiation-decomposable onium cation include sulfonium cation, tetrahydrothiophenium cation, iodonium cation, phosphonium cation, diazonium cation, and pyridinium cation. Of these, the counter ion of the specific anion is preferably a sulfonium cation or an iodonium cation, and specific examples include the cations represented by the following formulas (4) to (6). (In formula (4), R １ａ and R ２ａ are each independently a monovalent substituent, or R １ａ and R ２ａ are combined together to represent a single bond or a divalent group connecting the rings to which they are attached. ３ａ is a monovalent substituent. a1 and a2 are each independently an integer of 0 to 5. a3 is an integer of 0 to (2×r+5). r is 0 or 1. In formula (5), R ４ａ and R ５ａ are each independently a monovalent substituent. a4 and a5 are each independently an integer of 0 to 5. In formula (6), a6 is an integer of 0 to 7. When a6 is 1, R ６ａ is a monovalent organic group having 1 to 20 carbon atoms, a hydroxy group, a nitro group, or a halogen group. ６ａ are the same or different and are a monovalent organic group having 1 to 20 carbon atoms, a hydroxy group, a nitro group, or a halogen group, or a plurality of R ６ａ When two of the groups are combined together, they represent a ring structure having 4 to 20 ring members, which is formed together with the carbon atoms to which they are attached. a7 is an integer of 0 to 6. When a7 is 1, R ７ａ is a monovalent organic group having 1 to 20 carbon atoms, a hydroxy group, a nitro group, or a halogen group. ７ａ are the same or different and are a monovalent organic group having 1 to 20 carbon atoms, a hydroxy group, a nitro group or a halogen group, or a plurality of R ７ａTwo of these are combined together to form a ring structure having 3 to 20 ring members together with the carbon atoms to which they are attached. t1 is an integer of 0 to 3. R ８ａ is a single bond or a divalent organic group having 1 to 20 carbon atoms. t2 is 0 or 1.

[0041] In the above formulas (4) and (5), R １ａ , R ２ａ , R ３ａ , R ４ａ and R ５ａ (Hereinafter referred to as “R １ａ ~R ５ａ ") include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted cycloalkyloxy group, an ester group, an alkylsulfonyl group, a cycloalkylsulfonyl group, a hydroxy group, a carboxy group, a cyano group, and a nitro group.

[0042] R １ａ ~R ５ａ The alkyl group represented by the formula (I) may be linear or branched. The alkyl group preferably has 1 to 10 carbon atoms. １ａ ~R ５ａ The alkyl group represented by the formula (I) preferably has 1 to 5 carbon atoms, and more preferably is a methyl group, an ethyl group, an n-butyl group, or a t-butyl group. １ａ ~R ５ａ Specific examples of when is an alkoxy group include groups having the alkyl group exemplified above in the alkyl group moiety that constitutes the alkoxy group. The alkoxy group is preferably a methoxy group, an ethoxy group, an n-propoxy group, or an n-butoxy group.

[0043] R １ａ ~R ５ａThe cycloalkyl group represented by the formula (I) may be either monocyclic or polycyclic. Among these, examples of monocyclic cycloalkyl groups include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, and a cyclooctyl group. Examples of polycyclic cycloalkyl groups include a norbornyl group, an adamantyl group, a tricyclodecyl group, and a tetracyclododecyl group. R １ａ ~R ５ａ Specific examples of when R is a cycloalkyloxy group include groups having the above-mentioned cycloalkyl groups in the cycloalkyl group moiety constituting the cycloalkyloxy group. １ａ ~R ５ａ The cycloalkyloxy group represented by the following formula is preferably a cyclopentyloxy group or a cyclohexyloxy group.

[0044] R １ａ ~R ５ａ When has a substituent, examples of the substituent include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a hydroxy group, a carboxy group, a cyano group, a nitro group, and an alkoxy group having 1 to 5 carbon atoms.

[0045] R １ａ ~R ５ａ When R is an ester group (—COOR), examples of the hydrocarbon portion (R) of the ester group include the above-mentioned substituted or unsubstituted alkyl groups and substituted or unsubstituted cycloalkyl groups. １ａ ~R ５ａ is an ester group, R １ａ ~R ５ａ is preferably a methoxycarbonyl group, an ethoxycarbonyl group, or an n-butoxycarbonyl group. １ａ ~R ５ａ When R is an alkylsulfonyl group, the alkyl group moiety constituting the alkylsulfonium group may be the substituted or unsubstituted alkyl groups exemplified above. １ａ ~R ５ａ When is a cycloalkylsulfonyl group, examples of the alkyl group constituting the cycloalkylsulfonium group include the substituted or unsubstituted cycloalkyl groups exemplified above.

[0046] R １ａ and R ２ａ When these are combined together to represent a divalent group connecting the rings to which they are bonded, examples of the divalent group include -COO-, -OCO-, -CO-, -O-, -SO-, and -SO ２ -, -S-, an alkanediyl group having 1 to 3 carbon atoms, an alkenediyl group having 2 or 3 carbon atoms, -O-, -S-, -COO-, -OCO-, -CO-, -SO-, or -SO between the carbon-carbon bonds of the ethylene group ２ Among these, groups having R １ａ and R ２ａ is preferably a single bond connecting the rings, or forms —O— or —S—.

[0047] Each of a1, a2, and a3 is preferably an integer of 0 to 2. １ａ , R ２ａ and R ３ａ At least one of a4 and a5 is preferably a fluorine atom, an iodine atom, or a trifluoromethyl group. Each of a4 and a5 is preferably an integer of 0 to 2. ４ａ and R ５ａ At least one of the groups is preferably a fluorine atom, an iodine atom, or a trifluoromethyl group.

[0048] In the above formula (6), R ６ａ and R ７ａ The monovalent organic group having 1 to 20 carbon atoms represented by the formula (I) includes a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, -OR ｋ , -COOR ｋ , —O—CO—R ｋ , -O-R ｋｋ -COOR ｋ , -R ｋｋ -CO-R ｋ , -OSO ２ -R ｋ or -SO ２ -R ｋ etc. ｋ is a monovalent hydrocarbon group having 1 to 10 carbon atoms. ｋｋis a single bond or a divalent hydrocarbon group having 1 to 10 carbon atoms. Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms include the same groups as those exemplified in the above formula (w-1) and formula (w-2). ６ａ and R ７ａ In the above, examples of the substituents that substitute hydrogen atoms of the hydrocarbon group include the above R １ａ ~R ５ａ Examples of the substituents that the group represented by the formula (R) has include the same groups as those exemplified above. ８ａ Examples of the divalent organic group represented by the formula: ６ａ and R ７ａ Examples of such groups include groups in which one hydrogen atom has been removed from the monovalent organic groups having 1 to 20 carbon atoms exemplified above.

[0049] R ６ａ and R ７ａ is a linear or branched monovalent alkyl group, a monovalent fluoroalkyl group, a monovalent aromatic hydrocarbon group, or —OSO ２ -R ｋ or -SO ２ -R ｋ a6 is preferably an integer of 0 to 2, more preferably 0 or 1. a7 is preferably an integer of 0 to 2, more preferably 0 or 1. t2 is preferably 0. t1 is preferably 2 or 3.

[0050] Specific examples of the radiation-sensitive onium cation include cations represented by the following formulas: However, the radiation-sensitive onium cation is not limited to the following specific examples.

[0051] A preferred example of the specific acid generator is an onium salt composed of an anion represented by the above formula (2-1) or formula (2-2) and a sulfonium cation or an iodonium cation. Specifically, an onium salt represented by the following formula (3-1) or formula (3-2) can be mentioned. (In formula (3-1), W １ , L １ , R １ , R ２ , R３ , R ｆ and a are the same as in the formula (2-1). ２ and L ２ are the same as those in the formula (2-2) above. ＋ is a sulfonium cation or an iodonium cation.

[0052] Specific examples of the organic anion in the above formulas (3-1) and (3-2) include the anions shown as specific examples of the specific anion. Specific examples of the sulfonium cation and iodonium cation include the cations shown in the above formulas (4) to (6).

[0053] An onium salt having an iodine atom is preferably used as the specific acid generator, since it can enhance the sensitivity and CDU performance of the composition while sufficiently suppressing the occurrence of coating defects in a resist pattern formed using the composition. In the specific acid generator having an iodine atom, the number of iodine atoms per molecule is preferably two or more, from the viewpoint of sufficiently improving the sensitivity and CDU performance of the radiation-sensitive composition. In the specific acid generator, it is preferable that the organic anion has one or more iodine atoms, since this can improve the sensitivity and CDU performance of the composition in a well-balanced manner. Furthermore, it is preferable that the radiation-sensitive onium cation has one or more iodine atoms, since this can further enhance the CDU performance of the composition. When the radiation-sensitive onium cation has one or more iodine atoms, the radiation-sensitive onium cation may be an iodonium cation or a sulfonium cation having an iodo group. The iodo group in the specific acid generator is preferably bonded to an aromatic ring.

[0054]

[0033] Furthermore, from the viewpoint of further improving the CDU performance of the present composition while sufficiently suppressing the occurrence of coating defects, an onium salt having a fluorine atom can be preferably used as the specified acid generator. In the specified acid generator having a fluorine atom, the number of fluorine atoms in one molecule is preferably 2 or more, from the viewpoint of sufficiently improving the CDU performance of the radiation-sensitive composition. The fluorine atom in the specified acid generator is preferably bonded to an aromatic ring.

[0055] <Compound (Ex)> The compound (Ex) is represented by the following formula (1): The compound (Ex) is preferably blended in the present composition as a solvent. (In formula (1), R １１ , R １２ and R １３ are each independently a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms.

[0056] In the above formula (1), R １１ , R １２ or R １３ Examples of the monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms represented by the formula (w-1) include a monovalent chain hydrocarbon group having 1 to 20 carbon atoms and a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms. Specific examples of these include R ２０ , R ２１ ~R ２８ Examples of the substituent include the same groups as those shown in the description of the substituent represented by the formula:

[0057] From the viewpoint of the reactivity of the polymer component contained in the present composition with alkali and the availability of the compound (Ex), １１ , R １２ or R １３ is preferably a monovalent chain hydrocarbon group having 1 to 20 carbon atoms, more preferably an alkyl group having 1 to 10 carbon atoms, and even more preferably an alkyl group having 1 to 6 carbon atoms. １１ and R １２ is preferably an alkyl group having 1 to 3 carbon atoms, more preferably a methyl group or an ethyl group. １３ is preferably an alkyl group having 1 to 4 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms.

[0058] Specific examples of compound (Ex) include methyl 2-hydroxyisobutyrate, ethyl 2-hydroxyisobutyrate, isopropyl 2-hydroxyisobutyrate, tert-butyl 2-hydroxyisobutyrate, methyl 2-hydroxy-2-methylbutyrate, ethyl 2-hydroxy-2-methylbutyrate, and isopropyl 2-hydroxy-2-methylbutyrate.

[0059] The content of compound (Ex) in the composition is preferably 10% by mass or more relative to the total amount of solvent contained in the composition. By setting the content of compound (Ex) within the above range, the film thickness uniformity of the composition can be made more excellent. In order to further enhance the effect of improving the film thickness uniformity of the composition, the content of compound (Ex) is more preferably 15% by mass or more relative to the total amount of solvent contained in the composition, even more preferably 20% by mass or more, even more preferably 25% by mass or more, and particularly preferably 30% by mass or more.

[0060] <Other Components> The present composition may further contain, in addition to the specific acid generator and compound (Ex), a component other than the specific acid generator and compound (Ex) (hereinafter also referred to as "other component"). Examples of other components include a polymer (polymer (P)) containing a structural unit having an aromatic ring and a hydroxyl group bonded to the aromatic ring, a radiation-sensitive acid generator other than the specific acid generator (hereinafter also referred to as "other acid generator"), a solvent other than compound (Ex) (hereinafter also referred to as "other solvent"), a high-fluorine-containing polymer, etc.

[0061] <Polymer (P)> The polymer (P) includes a structural unit having an aromatic ring and a hydroxyl group bonded to the aromatic ring (this will be referred to as a "first structural unit"). One preferred embodiment of the present composition contains the polymer (P), a specific acid generator, and a compound (Ex).

[0062] The polymer (P) may contain, together with the first structural unit, one or more of the following: a structural unit having an acid-dissociable group (this will be referred to as the "second structural unit"); a structural unit having an onium salt structure formed from a radiation-sensitive onium cation and an organic anion (this will be referred to as the "third structural unit"); a structural unit having a lactone structure, a cyclic carbonate structure, a sultone structure, or a ring structure combining two or more of these (this will be referred to as the "fourth structural unit"); and a structural unit having an alcoholic hydroxyl group (this will be referred to as the "fifth structural unit"). Each structural unit will be described in detail below.

[0063] (First structural unit) The polymer (P) having a hydroxyl group bonded to an aromatic ring is preferable in that it can further improve the LWR (line width roughness) performance and CDU (critical dimension uniformity) performance of the present composition, and it is effective in suppressing the dissolution of unexposed areas into a developer, thereby further reducing development defects. In addition, the polymer (P) having a hydroxyl group bonded to an aromatic ring can be preferably used in pattern formation using exposure to radiation with a wavelength of 50 nm or less, such as electron beams or EUV.

[0064] The first structural unit differs from the second structural unit in that it does not have an acid-dissociable group, and differs from the third structural unit in that it does not have an onium salt structure. That is, in this specification, a structural unit having an acid-dissociable group together with a hydroxyl group bonded to an aromatic ring is classified as the second structural unit, and a structural unit having an onium salt structure together with a hydroxyl group bonded to an aromatic ring is classified as the third structural unit.

[0065] A specific example of the first structural unit is a structural unit represented by the following formula (7). In formula (7), R ５０ is a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group. ３ represents a single bond, —COO—, or —CONH—. ２ is a group obtained by removing (n1+n2+1) hydrogen atoms from an aromatic ring. ４is a substituent different from a hydroxyl group. n1 is an integer of 1 or more. n2 is an integer of 0 or more. When n2 is 2 or more, a plurality of R ４ are the same or different.)

[0066] In the above formula (7), R ５０ is preferably a hydrogen atom or a methyl group from the viewpoint of copolymerizability of the monomer that provides the first structural unit.

[0067] A ２ is a group obtained by removing (n1+n2+1) hydrogen atoms from the ring portion of a substituted or unsubstituted aromatic ring. The aromatic ring is preferably an aromatic hydrocarbon ring, such as a benzene ring, a naphthalene ring, an anthracene ring, or a phenanthrene ring. From the viewpoint of ease of synthesis of a monomer that provides the first structural unit and sensitivity, A ２ The aromatic ring contained in the first structural unit is preferably a benzene ring or a naphthalene ring, more preferably a benzene ring. The position of the hydroxyl group bonded to the aromatic ring is not particularly limited. For example, when the first structural unit has a hydroxyl group bonded to a benzene ring, the bonding position of the hydroxyl group on the benzene ring in the first structural unit may be any of the ortho-position, meta-position, and para-position relative to other groups.

[0068] R ４ R may be any group other than a hydroxyl group. ４ Specific examples of n1 include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted cycloalkyloxy group, an ester group (—COOR), an alkylsulfonyl group, a cycloalkylsulfonyl group, a carboxy group, a cyano group, and a nitro group. n1 is preferably 1 to 3, and more preferably 1 or 2. n2 is preferably 0 to 5, more preferably 0 to 2, and even more preferably 0 or 1.

[0069] Specific examples of the first structural unit include structural units represented by the following formulae: However, the first structural unit is not limited to these specific examples. (In the formula, R ５０ is a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group.

[0070] In the polymer (P), the content of the first structural unit is preferably 10 mol% or more, more preferably 20 mol% or more, and even more preferably 25 mol% or more, based on the total amount of structural units contained in the polymer (P). Furthermore, the content of the first structural unit is preferably 70 mol% or less, more preferably 65 mol% or less, and even more preferably 60 mol% or less, based on the total amount of structural units contained in the polymer (P). By setting the content of the first structural unit within the above range, the CDU performance of the present composition can be made even better.

[0071] (Second structural unit) The second structural unit is a structural unit having an acid-dissociable group. The second structural unit is introduced into the polymer (P), for example, to increase the difference in solubility of the polymer (P) between the exposed and unexposed areas. Here, in this specification, the term "acid-dissociable group" refers to a group that substitutes a hydrogen atom of an acid group such as a carboxy group or a hydroxyl group, and is released by the action of an acid. In this specification, a structural unit having an acid-dissociable group and a hydroxyl group bonded to an aromatic ring is classified as a second structural unit.

[0072] The second structural unit is not particularly limited as long as it has an acid-dissociable group. Examples of the second structural unit include a structural unit represented by the following formula (8-1) (hereinafter also referred to as "structural unit (iia)"), a structural unit represented by the following formula (8-2) (hereinafter also referred to as "structural unit (iib)"), and a structural unit represented by the following formula (8-3) (hereinafter also referred to as "structural unit (iic)"). (In formula (8-1), R ３０ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ４ R is a divalent chain organic group or an alicyclic hydrocarbon group. ３１ is a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms. ３２ and R ３３ are each independently a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, a monovalent aromatic heterocyclic group, or R ３２ and R ３３ are aligned with each other and R ３２ and R３３ represents an alicyclic hydrocarbon structure having 3 to 20 carbon atoms, which is formed together with the carbon atom to which R is bonded. ３１ When is a hydrogen atom, R ３２ and R ３３ or both of which are, independently of each other, a substituted or unsubstituted monovalent alicyclic unsaturated hydrocarbon group, a substituted or unsubstituted monovalent aromatic hydrocarbon group, or a monovalent aromatic heterocyclic group, or R ３２ and R ３３ are aligned with each other and R ３２ and R ３３ represents an alicyclic unsaturated hydrocarbon structure having 3 to 20 carbon atoms, which is formed together with the carbon atom to which it is bonded. g1 is 0 or 1. In formula (8-2), R ３０ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ５ represents a single bond, -O-, -CO-, * ２ -COO- or * ２ -CONH-. ２ " represents a bond to the main chain. ３４ , R ３５ and R ３６ are each independently a hydrogen atom, a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, or a substituted or unsubstituted monovalent oxyhydrocarbon group having 1 to 20 carbon atoms. ２８ is -O-C(R ３４ ) (R ３５ ) (R ３６ g2 is an integer of 0 to 4. In formula (8-3), R ３０ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ６ represents a single bond, -O-, -CO-, * ３ -COO- or * ３ -CONH-. ３ " represents a bond to the main chain. ３７ R is a hydrogen atom, a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, or a substituted or unsubstituted monovalent oxyhydrocarbon group having 1 to 20 carbon atoms. ３８ and R ３９are each independently a hydrogen atom, a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, or a substituted or unsubstituted monovalent oxyhydrocarbon group having 1 to 20 carbon atoms, or R ３８ and R ３９ are aligned with each other and R ３８ and R ３９ represents an alicyclic hydrocarbon structure having 3 to 20 carbon atoms formed together with the carbon atom to which R is bonded. ２９ is -COO-C(R ３７ ) (R ３８ ) (R ３９ g3 is an integer of 0 to 4.

[0073] In the above formula (8-1), R ３０ In view of the copolymerizability of the monomer that gives the structural unit (iia), R is preferably a hydrogen atom or a methyl group, and more preferably a methyl group. ３０ is preferably a hydrogen atom from the viewpoint of copolymerizability of the monomer that gives the structural unit (iib). ３０ is preferably a hydrogen atom or a methyl group. ５ and L in formula (8-3) ６ are each preferably a single bond, —COO— or —CONH—.

[0074] L in the above formula (8-1) ４ The divalent chain organic group represented by the formula (I) includes a linear or branched saturated hydrocarbon group having 1 to 20 carbon atoms, a methylene group contained in the chain or branched saturated hydrocarbon group being a heteroatom-containing group (for example, -O-, -S-, -CO-, -COO-, -NH-, -NHCO-, -SO ２ -), and a divalent group having 2 to 20 carbon atoms. ４ Specific and preferred examples of the divalent alicyclic hydrocarbon group represented by the formula (w-1) and the formula (w-2) include R ２０ , R ２１ ~R ２８ Examples of the monovalent alicyclic hydrocarbon group include groups in which one hydrogen atom has been removed from the groups exemplified as the monovalent alicyclic hydrocarbon group in the description of the substituent represented by the formula: ４ is preferably a chain organic group.

[0075] R in the above formulas (8-1) to (8-3) ３１ ~R ３３ , R ３４ ~R ３６ or R ３７ ~R ３９ Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the formula (w-1) include a monovalent chain hydrocarbon group having 1 to 20 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, and a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms. Specific examples of these groups include R ２０ , R ２１ ~R ２８ Examples of the monovalent hydrocarbon groups include the same groups as those exemplified in the description of the substituent represented by the formula:

[0076] R ３２ and R ３３ are aligned with each other and R ３２ and R ３３ an alicyclic hydrocarbon structure having 3 to 20 carbon atoms formed together with the carbon atom to which R is bonded, and ３５ and R ３６ are aligned with each other and R ３５ and R ３６ Examples of the alicyclic hydrocarbon structure having 3 to 20 carbon atoms constituted together with the carbon atom to which it is bonded include monocyclic saturated alicyclic hydrocarbon structures such as a cyclopropane structure, cyclobutane structure, cyclopentane structure, cyclohexane structure, cycloheptane structure, and cyclooctane structure; monocyclic unsaturated alicyclic hydrocarbon structures such as cyclopentene and cyclohexene; and polycyclic alicyclic hydrocarbon structures such as a norbornane structure, adamantane structure, tricyclodecane structure, and tetracyclododecane structure.

[0077] R ３４ ~R ３６ or R ３７ ~R ３９ Examples of the monovalent oxyhydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) include the above-mentioned R ３１ ~R ３３ , R ３４ ~R ３６ and R ３６ ~R ３６and a group containing an oxygen atom at the bond-side terminal of a monovalent hydrocarbon group having 1 to 20 carbon atoms. ３１ ~R ３３ or R ３６ ~R ３９ Of these, the monovalent oxyhydrocarbon group represented by the formula (I) is preferably an alkoxy group, a cycloalkoxy group, or a cycloalkylalkoxy group.

[0078] R ３１ ~R ３３ , R ３４ ~R ３６ or R ３７ ~R ３９ When the group represented by R has a substituent, examples of the substituent include a halogen atom, a hydroxyl group, and an alkoxy group having 1 to 3 carbon atoms. ３２ and R ３３ are aligned with each other and R ３２ and R ３３ forms an alicyclic hydrocarbon structure having 3 to 20 carbon atoms together with the carbon atom to which it is bonded, or ３８ and R ３９ are aligned with each other and R ３８ and R ３９ When the ring structure is an alicyclic hydrocarbon structure having 3 to 20 carbon atoms together with the carbon atom to which it is bonded, the above-exemplified substituents and alkyl groups may be bonded to the ring.

[0079] R ２８ or R ２９ Examples of the monovalent substituent represented by the formula (I) include an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a hydroxyl group, a halogen atom (for example, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom), etc. g2 and g3 are each preferably 0 to 2.

[0080] Specific examples of the structural unit (iia) among the second structural units include structural units represented by the following formula: In addition, the structural unit (ii) is not limited to the specific examples shown below. ３０ is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.

[0081] Specific examples of the structural unit (iib) include structural units represented by the following formulas:

[0082] Specific examples of the structural unit (iic) include structural units represented by the following formulas:

[0083] In the polymer (P), the content of the second structural unit is preferably 5 mol% or more, more preferably 10 mol% or more, and even more preferably 20 mol% or more, based on the total amount of structural units contained in the polymer (P). Furthermore, the content of the second structural unit is preferably 65 mol% or less, more preferably 60 mol% or less, and even more preferably 55 mol% or less, based on the total amount of structural units contained in the polymer (P). By setting the content of the second structural unit within the above range, the difference in dissolution rate in a developer between an exposed portion and an unexposed portion can be appropriately increased while maintaining good sensitivity of the composition, thereby improving the LWR performance and CDU performance of the composition.

[0084] (Third Structural Unit) The polymer (P) may further contain a third structural unit. The third structural unit is thought to liberate an organic anion by the decomposition of a radiation-sensitive onium cation by the action of radiation, and the liberated organic anion bonds with hydrogen abstracted from components contained in the composition (e.g., a radiation-sensitive acid generator, an acid diffusion controller, a solvent, etc.), thereby generating an acid derived from the organic anion. Examples of the organic anion include a sulfonate anion and a carboxylate anion.

[0085] When the organic anion in the third structural unit is a sulfonate anion, the third structural unit is thought to function primarily as a radiation-sensitive acid generator by generating a strong acid that induces dissociation of the acid-dissociable group under normal conditions. On the other hand, when the organic anion in the third structural unit is a carboxylate anion, the third structural unit is thought to function primarily as an acid diffusion controller by generating a weak acid that does not induce dissociation of the acid-dissociable group under normal conditions. Here, "normal conditions" refers to conditions in which post-exposure baking (PEB) is performed at 110°C for 60 seconds.

[0086] The third structural unit is typically a structural unit derived from a monomer having a radiation-sensitive onium cation, an organic anion, and a group participating in polymerization. ３ － Ya-COO － ) may be bonded to the main chain of the polymer via a linking group, and the radiation-sensitive onium cation may form a counter ion. Alternatively, the radiation-sensitive onium cation may be bonded to the main chain of the polymer via a linking group, and the organic anion may form a counter ion. In order to further improve the LWR performance and CDU performance of the present composition, it is preferable that the third structural unit be bonded to the main chain of the polymer via a linking group, and that the organic anion be a sulfonate anion (—SO ３ － ) is more preferably bonded to the main chain of the polymer via a linking group.

[0087] The radiation-sensitive cation in the third structural unit is preferably a sulfonium cation or an iodonium cation, more preferably a triarylsulfonium cation or a diaryliodonium cation, from the viewpoint of enhancing the sensitivity of the present composition. From the viewpoint of further enhancing the sensitivity of the present composition, the aromatic ring (i.e., S) possessed by the triarylsulfonium cation or diaryliodonium cation is preferably a ＋ or I ＋ Preferably, at least one of an iodo group, a fluoro group, and a fluoroalkyl group is bonded to the aromatic ring bonded to the aromatic ring. The fluoroalkyl group is preferably a trifluoromethyl group.

[0088] It is preferable that at least a portion of the third structural units contained in the polymer (P) have an iodo group in the structural unit, since this can further increase the sensitivity while maintaining good LWR performance and CDU performance of the present composition. When the third structural unit has an iodo group, the iodo group is preferably bonded to an aromatic ring. Furthermore, when the third structural unit has an iodo group, the radiation-sensitive onium cation may have an iodo group, the organic anion may have an iodo group, or both the radiation-sensitive onium cation and the organic anion may have an iodo group.

[0089] Specific examples of the third structural unit include structural units represented by the following formulas: However, the specific examples of the third structural unit are not limited to these. (In the formula, R ４０ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ＋ is a radiation-sensitive onium cation. － is a sulfonate anion or a carboxylate anion.

[0090] When the polymer (P) contains a third structural unit, the content of the third structural unit in the polymer (P) is preferably 1 mol % or more, more preferably 2 mol % or more, and even more preferably 5 mol % or more, based on the total amount of structural units contained in the polymer (P). The content of the third structural unit in the polymer (P) is preferably 25 mol % or less, more preferably 20 mol % or less, based on the total amount of structural units contained in the polymer (P). By setting the content of the third structural unit within the above range, the LWR performance and CDU performance of the composition can be sufficiently improved.

[0091] (Fourth structural unit) The fourth structural unit is a structural unit having a lactone structure, a cyclic carbonate structure, a sultone structure, or a ring structure formed by combining two or more of these (excluding those corresponding to the first to third structural units).

[0092] Specific examples of the fourth structural unit include structural units represented by the following formulas: However, the specific examples of the fourth structural unit are not limited to these. (In the formula, R Ｌ１ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0093] When the polymer (P) contains the fourth structural unit, the content of the fourth structural unit is preferably 2 mol% or more, more preferably 5 mol% or more, based on the total amount of the structural units contained in the polymer (P), and the content of the fourth structural unit in the polymer (P) is preferably 35 mol% or less, more preferably 25 mol% or less, based on the total amount of the structural units contained in the polymer (P).

[0094] (Fifth structural unit) The fifth structural unit is a structural unit having an alcoholic hydroxyl group (excluding those corresponding to the first to fourth structural units). By introducing the fifth structural unit into the polymer (P), it is possible to enhance the effect of suppressing development defects when a resist pattern is formed using the present composition. Here, in this specification, an "alcoholic hydroxyl group" refers to a group having a structure in which a hydroxy group is directly bonded to an aliphatic hydrocarbon group. The aliphatic hydrocarbon group may be a chain hydrocarbon group or an alicyclic hydrocarbon group.

[0095] The fifth structural unit is preferably a structural unit derived from an unsaturated monomer having an alcoholic hydroxyl group. The structure of the unsaturated monomer that provides the fifth structural unit is not particularly limited. Specific examples of the fifth structural unit include structural units represented by the following formulas. However, specific examples of the fifth structural unit are not limited to these. (In the formula, R Ａ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0096] When the polymer (P) contains the fifth structural unit, from the viewpoint of enhancing the effect of suppressing development defects in the resist pattern, the content of the fifth structural unit is preferably 1 mol% or more, more preferably 3 mol% or more, based on the total amount of structural units contained in the polymer (P), and the content of the fifth structural unit is preferably 30 mol% or less, more preferably 20 mol% or less, based on the total amount of structural units contained in the polymer (P).

[0097] In addition to the above, examples of structural units contained in the polymer (P) include structural units containing a cyano group, a nitro group, or a sulfonamide group (specifically, a structural unit derived from 2-cyanomethyladamantan-2-yl(meth)acrylate); structural units containing a non-acid-dissociable hydrocarbon group (specifically, a structural unit derived from styrene or a halogenated styrene (e.g., a styrene unit, a bromostyrene unit), a structural unit derived from vinylnaphthalene, a structural unit derived from n-pentyl(meth)acrylate); and structural units derived from (meth)acrylic acid. The content ratio of these structural units can be appropriately set depending on each structural unit, as long as the effects of the present invention are not impaired.

[0098] From the viewpoint of obtaining a radiation-sensitive composition having excellent sensitivity, the polymer (P) preferably has an iodine group. When the polymer (P) has an iodine group, only one of the first to fifth structural units described above may have an iodine group, or two or more of them may have an iodine group. Furthermore, for example, when the first structural unit has an iodine group, some of the first structural units may have an iodine group, or all of the first structural units may have an iodine group.

[0099] The weight average molecular weight (Mw) of the polymer (P) in terms of polystyrene as determined by GPC is preferably 1,000 or more, more preferably 2,000 or more, even more preferably 3,000 or more, and even more preferably 4,000 or more. The Mw of the polymer (P) is preferably 50,000 or less, more preferably 30,000 or less, even more preferably 20,000 or less, and even more preferably 15,000 or less. By setting the Mw of the polymer (P) within the above range, the coatability of the composition can be improved and development defects can be sufficiently suppressed, which is advantageous.

[0100] The ratio of Mw to the polystyrene-equivalent number average molecular weight (Mn) of the polymer (P) determined by GPC (Mw / Mn, hereinafter also referred to as "dispersity") is preferably 5.0 or less, more preferably 3.0 or less, and even more preferably 2.0 or less. Mw / Mn is usually 1.0 or more.

[0101] In the present composition, the content of the polymer (P) is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 85% by mass or more, based on the total amount of solids contained in the composition. The polymer (P) can be synthesized by polymerizing monomers that provide each structural unit in an appropriate solvent using a known radical polymerization initiator or the like. In this specification, the term "solids" refers to components other than the solvent contained in the present composition.

[0102] (Other Acid Generators) The other acid generator may be an ionic radiation-sensitive acid generator or a non-ionic radiation-sensitive acid generator. The other acid generator is preferably an ionic radiation-sensitive acid generator, and an onium salt containing a radiation-sensitive onium cation and an organic anion that is a conjugate base of an acid is preferably used. The organic anion is usually an anion obtained by removing a proton from an acid group of an organic acid.

[0103] As the radiation-sensitive acid generator, a low-molecular-weight compound (non-polymer) can be preferably used because it is easy to adjust the sensitivity of the composition and there is a high degree of freedom in selecting the radiation-sensitive acid generator to be incorporated into the composition. The molecular weight of the radiation-sensitive acid generator is preferably 1,000 or less, more preferably 800 or less, and even more preferably 600 or less. The other acid generator may be a so-called radiation-sensitive acid generator or an acid diffusion controller. Furthermore, the composition may contain both an acid generator and an acid diffusion controller as the other acid generator.

[0104]

[0043] When an acid generator (hereinafter also referred to as "other acid generator") is contained in the present composition as another acid generator, the type of acid generator to be incorporated into the present composition is not particularly limited, and any known radiation-sensitive acid generator used in resist pattern formation can be used as appropriate. As the other acid generator, a compound that generates in the composition under the above-mentioned normal conditions an acid (preferably a strong acid such as a sulfonic acid, imidic acid, or methide acid) that is more acidic than the acid generated by the acid diffusion controller (more specifically, the photodegradable base), thereby inducing dissociation of the acid-dissociable group, is preferably used.

[0105] When an onium salt is used as the other acid generator, from the viewpoint of increasing the sensitivity of the composition and forming a resist film with superior lithography performance, the other acid generator preferably has a sulfonium cation or an iodonium cation, and more preferably has an arylsulfonium cation or an aryliodonium cation. Specific examples of the radiation-sensitive onium cation include the cations represented by the above formulas (4) to (6) exemplified as the radiation-sensitive cations constituting the specific acid generator, and specific examples thereof.

[0106] The organic anion contained in the other acid generator is not particularly limited as long as it does not have a steroid skeleton or a 9,10-ethanoanthracene skeleton. In terms of increasing the sensitivity of the present composition, the organic anion constituting the other acid generator is preferably a sulfonate anion, an imide anion, or a methide anion. Specific examples of sulfonate anions include anions represented by the following formula:

[0107]

[0108]

[0109] In the present composition, the content of the acid generator (total amount of the specific acid generator and other acid generators) is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of polymer (P), from the viewpoint of fully obtaining the effect of improving sensitivity due to the incorporation of the acid generator. Furthermore, from the viewpoint of suppressing the occurrence of development defects due to the acid generator, the content of the acid generator is preferably 60 parts by mass or less, more preferably 55 parts by mass or less, and even more preferably 50 parts by mass or less, per 100 parts by mass of polymer (P).

[0110] When a polymer containing a third structural unit is blended in the composition as polymer (P), the total amount of the specific acid generator, the other acid generator, and the monomer that provides the third structural unit is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, per 100 parts by mass of polymer (P).The total amount of the specific acid generator, the other acid generator, and the monomer that provides the third structural unit is preferably 60 parts by mass or less, more preferably 55 parts by mass or less, per 100 parts by mass of polymer (P).

[0111] Acid Diffusion Controller: From the viewpoint of improving the lithography properties of the present composition, the present composition preferably contains, as the acid diffusion controller (at least one of the specific acid diffusion controller and the other acid diffusion controller), an onium salt having a radiation-sensitive onium cation and an organic anion that is the conjugate base of the acid (hereinafter also referred to as a "photodegradable base"). The photodegradable base is preferably an onium salt that generates a carboxylic acid, a sulfonic acid, or a sulfonamide upon exposure. Furthermore, in terms of being able to form a resist film with higher lithography performance, an onium salt having a sulfonium cation or an iodonium cation can be preferably used as the photodegradable base.

[0112] Specific examples of the radiation-sensitive onium cation contained in the photodecomposable base serving as another acid diffusion controller include the same onium cations as those exemplified as the radiation-sensitive onium cation that may be contained in the specific acid generator.

[0113] The organic anion contained in the photodegradable base serving as another acid diffusion controller is not particularly limited as long as it has a steroid skeleton and a 9,10-ethanoanthracene skeleton. Specific examples of the organic anion include anions represented by the following formula:

[0114] In the present composition, the content of the acid diffusion controller (total amount of the specific acid diffusion controller and other acid diffusion controllers) is preferably 1 part by mass or more, more preferably 2 parts by mass or more, per 100 parts by mass of polymer (P), from the viewpoint of sufficiently improving the sensitivity, CDU performance, and film thickness uniformity. Furthermore, from the viewpoint of suppressing the occurrence of development defects due to the acid diffusion controller, the content of the acid diffusion controller is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, per 100 parts by mass of polymer (P).

[0115] The content of the acid diffusion controller in the composition (total amount of the specific acid diffusion controller and other acid diffusion controllers) is preferably 2 mol% or more, more preferably 5 mol% or more, and even more preferably 10 mol% or more, based on the total amount of the acid generator contained in the composition and the monomer that provides the third structural unit in the polymer (P). The content of the acid diffusion controller is preferably 90 mol% or less, more preferably 80 mol% or less, and even more preferably 70 mol% or less, based on the total amount of the acid generator contained in the composition and the monomer that provides the third structural unit. By setting the content of the acid diffusion controller within the above range, the CDU performance of the composition can be further improved.

[0116] When an acid diffusion controller is incorporated into the present composition, an onium salt having an iodine atom is preferably used as the acid diffusion controller, since this can further enhance the CDU performance of the present composition. The number of iodine atoms in one molecule of the acid diffusion controller is preferably 1 or more, more preferably 2 or more, from the viewpoint of sufficiently improving the CDU performance of the radiation-sensitive composition. In the acid diffusion controller, it is preferable that the organic anion has one or more iodine atoms, since this can improve the sensitivity, CDU performance, and film thickness uniformity of the present composition in a balanced manner.

[0117] (Other Solvents) The present composition may contain other solvents together with the compound (Ex). The other solvents are preferably solvents capable of dissolving or dispersing the components blended in the present composition. Specific examples of other solvents include various organic solvents, such as alcohols, ethers, ketones, amides, esters, and hydrocarbons. From the viewpoint of ensuring good film thickness uniformity, at least one selected from the group consisting of alcohols, ethers, ketones, and esters is preferred.

[0118] Examples of alcohols include aliphatic monoalcohols having 1 to 18 carbon atoms, such as 4-methyl-2-pentanol and n-hexanol; alicyclic monoalcohols having 3 to 18 carbon atoms, such as cyclohexanol; polyhydric alcohols having 2 to 18 carbon atoms, such as 1,2-propylene glycol; and partial ethers of polyhydric alcohols having 3 to 19 carbon atoms, such as propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-n-propyl ether, and propylene glycol mono-n-butyl ether.

[0119] Examples of ethers include dialkyl ethers such as diethyl ether, dipropyl ether, dibutyl ether, dipentyl ether, diisoamyl ether, dihexyl ether, and diheptyl ether; cyclic ethers such as tetrahydrofuran and tetrahydropyran; and aromatic ring-containing ethers such as diphenyl ether and anisole.

[0120] Examples of ketones include chain ketones such as acetone, methyl ethyl ketone, methyl n-propyl ketone, methyl n-butyl ketone, diethyl ketone, methyl isobutyl ketone, 2-heptanone, ethyl n-butyl ketone, methyl n-hexyl ketone, di-isobutyl ketone, and trimethylnonanone; cyclic ketones such as cyclopentanone, cyclohexanone, cycloheptanone, cyclooctanone, and methylcyclohexanone; and 2,4-pentanedione, acetonylacetone, acetophenone, and diacetone alcohol.

[0121] Examples of the amides include cyclic amides such as N,N'-dimethylimidazolidinone and N-methylpyrrolidone; and chain amides such as N-methylformamide, N,N-dimethylformamide, N,N-diethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, and N-methylpropionamide.

[0122] Examples of esters include monocarboxylic acid esters such as n-butyl acetate and ethyl lactate; polyhydric alcohol carboxylates such as propylene glycol diacetate; polyhydric alcohol partial ether carboxylates such as propylene glycol monomethyl ether acetate; polycarboxylic acid diesters such as diethyl oxalate; carbonates such as dimethyl carbonate and diethyl carbonate; and cyclic esters such as γ-butyrolactone.

[0123] Examples of hydrocarbons include aliphatic hydrocarbons having 5 to 12 carbon atoms, such as n-pentane and n-hexane; and aromatic hydrocarbons having 6 to 16 carbon atoms, such as toluene and xylene.

[0124] When the composition contains other solvents, the content of the other solvents is preferably 90% by mass or less, based on the total amount of solvents contained in the composition, from the viewpoint of improving the storage stability of the composition, more preferably 85% by mass or less, even more preferably 80% by mass or less, still more preferably 75% by mass or less, and particularly preferably 70% by mass or less, based on the total amount of solvents contained in the composition.

[0125] As the other solvent, a compound having a hydroxyl group (hereinafter also referred to as a "hydroxyl group-containing compound") can be preferably used. When the present composition contains other solvents, by using a hydroxyl group-containing compound as at least a part of the other solvents, the film thickness uniformity of the coating film (and thus the resist pattern) obtained from the present composition can be improved. Among the above, the hydroxyl group-containing compound is preferably at least one selected from the group consisting of alcohols and ketones, and more preferably at least one selected from the group consisting of polyhydric alcohol partial ethers having 3 to 19 carbon atoms and diacetone alcohol. When the present composition contains other solvents, the content of the hydroxyl group-containing compound in the present composition is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more, based on the total amount of solvents contained in the present composition.

[0126] (High-Fluorine Content Polymer) The high-fluorine content polymer (hereinafter also referred to as "polymer (F)") is a polymer having a higher mass content of fluorine atoms than polymer (P). Polymer (F) is blended into the present composition, for example, as a water-repellent additive, a surface modifier that adjusts the hydrophilicity / hydrophobicity of the surface of a resist film, or a modifier that further improves lithography performance.

[0127] The fluorine atom content of the polymer (F) is not particularly limited as long as it is larger than that of the polymer (P). The fluorine atom content of the polymer (F) is preferably 1% by mass or more, more preferably 4% by mass or more, and even more preferably 7% by mass or more. The fluorine atom content of the polymer (F) is preferably 60% by mass or less, more preferably 40% by mass or less. The fluorine atom content (% by mass) of the polymer is １３ The polymer structure can be determined by C-NMR spectrum measurement or the like, and the amount can be calculated from the structure.

[0128] When the present composition contains the polymer (F), the content of the polymer (F) in the present composition is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, per 100 parts by mass of the polymer (P).

[0129] (Other Optional Components) The composition may further contain components other than the above-described specific acid generator, compound (Ex), polymer (P), other acid generators, other solvents, and high-fluorine content polymer (hereinafter also referred to as "other optional components"). Examples of other optional components include surfactants, alicyclic skeleton-containing compounds (e.g., 1-adamantanecarboxylic acid, 2-adamantanone, t-butyl deoxycholate, etc.), sensitizers, and uneven distribution promoters. The content of the other optional components can be appropriately set depending on the respective compounds, as long as the effects of the present invention are not impaired.

[0130] <Method for producing radiation-sensitive composition> The composition can be produced, for example, by mixing the specific acid generator, the compound (Ex), and other optional components in desired proportions, and filtering the resulting mixture, preferably using a filter (e.g., a filter with a pore size of about 0.2 μm). The solids content of the composition is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more. The solids content of the composition is preferably 50% by mass or less, more preferably 20% by mass or less, and even more preferably 5% by mass or less. By setting the solids content of the composition within the above range, good coatability can be achieved, and a good resist pattern shape can be obtained, which is advantageous.

[0131] The composition thus obtained can be used as a positive pattern-forming composition for forming a pattern using an alkaline developer, or as a negative pattern-forming composition for forming a pattern using a developer containing an organic solvent.

[0132] <<Method of Forming Resist Pattern>> The method of forming a resist pattern according to the present disclosure includes a step of applying the present composition to one surface of a substrate (hereinafter also referred to as a "coating step"), a step of exposing the resist film obtained by the coating step (hereinafter also referred to as an "exposure step"), and a step of developing the resist film exposed by the exposure step (hereinafter also referred to as a "developing step"). Examples of patterns formed by the method of forming a resist pattern according to the present disclosure include a line-and-space pattern and a hole pattern. Because the method of forming a resist pattern according to the present disclosure uses the present composition to form a resist film, it is possible to form a resist pattern that has good sensitivity and CDU performance and few development defects. Each step will be described below.

[0133] [Coating Step] In the coating step, the composition is applied to one side of a substrate to form a resist film on the substrate. Conventional substrates can be used as the substrate on which the resist film is formed, including, for example, silicon wafers, silicon dioxide wafers, and aluminum-coated wafers. Alternatively, an organic or inorganic anti-reflective coating, such as that disclosed in JP-A-59-93448, may be formed on the substrate. Examples of methods for applying the composition include spin coating, casting coating, and roll coating. After coating, a soft bake (hereinafter also referred to as "SB") may be performed to volatilize the solvent in the coating. The SB temperature is preferably 60°C or higher, more preferably 80°C or higher. The SB temperature is preferably 140°C or lower, more preferably 120°C or lower. The SB time is preferably 5 seconds or longer, more preferably 10 seconds or longer. The SB time is preferably 600 seconds or shorter, more preferably 300 seconds or shorter. The average thickness of the resist film formed is preferably 10 to 1,000 nm, and more preferably 20 to 500 nm. Soft baking is also called pre-baking.

[0134] [Exposure Step] In the exposure step, the resist film obtained in the coating step is exposed. This exposure is carried out by irradiating the resist film with radiation through a photomask, and optionally through an immersion medium such as water. Examples of radiation include 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, depending on the line width of the desired pattern. Among these, the radiation irradiated onto the resist film formed using the present composition is preferably far ultraviolet light, EUV, or electron beams, more preferably ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), EUV, or electron beams, even more preferably ArF excimer laser light, EUV, or electron beams, even more preferably EUV or electron beams, and particularly preferably EUV.

[0135] After the exposure, post-exposure baking (PEB) is preferably performed to promote dissociation of acid-dissociable groups in the exposed portions of the resist film by acid generated from a compound that generates acid upon exposure (such as a radiation-sensitive acid generator). This PEB can increase the difference in solubility in a developer between the exposed and unexposed portions. The PEB temperature is preferably 50°C or higher, more preferably 80°C or higher. The PEB temperature is preferably 180°C or lower, more preferably 130°C or lower. The PEB time is preferably 5 seconds or longer, more preferably 10 seconds or longer. The PEB time is preferably 600 seconds or shorter, more preferably 300 seconds or shorter.

[0136] [Development Step] In the development step, the exposed resist film is developed. This allows a desired resist pattern to be formed. After development, the resist film is generally washed with a rinse liquid such as water or alcohol, and then dried. The development method in the development step may be alkali development or organic solvent development.

[0137] In the case of alkaline development, examples of the developer used for development include an alkaline aqueous solution containing at least one alkaline compound dissolved therein, such as sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, aqueous ammonia, ethylamine, n-propylamine, diethylamine, di-n-propylamine, triethylamine, methyldiethylamine, ethyldimethylamine, triethanolamine, tetramethylammonium hydroxide (TMAH), pyrrole, piperidine, choline, 1,8-diazabicyclo-[5.4.0]-7-undecene, and 1,5-diazabicyclo-[4.3.0]-5-nonene. Among these, an aqueous TMAH solution is preferred, and a 2.38% by mass TMAH solution is more preferred. In the case of organic solvent development, examples of the developer include one or more organic solvents such as hydrocarbons, ethers, esters, ketones, and alcohols, and solvents containing the above organic solvents.

[0138] Examples of the developing method include a method of immersing a substrate in a tank filled with a developer for a certain period of time (dip method), a method of developing by piling up the developer on the surface of the substrate by surface tension and leaving it to stand for a certain period of time (puddle method), a method of spraying the developer onto the surface of the substrate (spray method), and a method of continuously discharging the developer while scanning a developer discharging nozzle at a constant speed onto a substrate that is rotating at a constant speed (dynamic dispense method).

[0139] The present invention will be specifically described below with reference to synthesis examples, examples, and comparative examples, but the present invention is not limited to the following examples. In the following examples, "parts" and "%" are by mass unless otherwise specified.

[0140] The methods for measuring the physical properties of the polymer are shown below. [Weight-average molecular weight (Mw) and number-average molecular weight (Mn)] The Mw and Mn of the polymer were measured by gel permeation chromatography (GPC) using GPC columns manufactured by Tosoh Corporation (two "G2000HXL", one "G3000HXL", and one "G4000HXL") under the following conditions: Eluent: tetrahydrofuran (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) Flow rate: 1.0 mL / min Sample concentration: 1.0 mass% Sample injection amount: 100 μL Column temperature: 40° C. Detector: differential refractometer Standard material: monodisperse polystyrene

[0141] <[P] Polymer Synthesis> [Synthesis Examples 1 to 36] Synthesis of Base Polymers (P-1) to (P-36) Each monomer was combined and copolymerized in tetrahydrofuran (THF) solvent. The resulting mixture was crystallized in methanol and repeatedly washed with hexane. After isolation and drying, base polymers (P-1) to (P-36) with the compositions shown in Table 1 were obtained. The resulting base polymers had the following compositions: １ The Mw and dispersity (Mw / Mn) were confirmed under the above-mentioned GPC conditions. The types and proportions of each monomer are shown in Table 1.

[0142]

[0143]

[0144] <Preparation of Radiation-Sensitive Composition> [A] Radiation-sensitive acid generator, [D] acid diffusion controller, and [E] solvent used in preparing the radiation-sensitive compositions of Examples 1 to 53 and Comparative Examples 1 to 3 are shown below.

[0145] [A] Radiation-sensitive Acid Generator Compounds represented by the following formulae (A-1) to (A-9) were used as radiation-sensitive acid generators.

[0146] [D] Acid Diffusion Controller Compounds represented by the following formulae (D-1) to (D-5) were used as acid diffusion controllers.

[0147] [E] Solvent The following solvents (E-1) to (E-6) were used as solvents: (E-1): PGMEA (propylene glycol monomethyl ether acetate) (E-2): HBM (methyl 2-hydroxyisobutyrate) (E-3): PGME (propylene glycol monomethyl ether) (E-4): DAA (diacetone alcohol) (E-5): HBE (ethyl 2-hydroxyisobutyrate) (E-6): HBP (isopropyl 2-hydroxyisobutyrate)

[0148] [Example 1] 100 parts by mass of (P-1) as a polymer [P] 45 parts by mass of (A-1) as a radiation-sensitive acid generator [A] 35 mol% of (D-1) as an acid diffusion controller [D] relative to the anion of (A-1) 2,000 parts by mass of (E-1), 4,000 parts by mass of (E-2), and 4,000 parts by mass of (E-3) as solvents [E] were blended together. The mixture was filtered through a membrane filter with a pore size of 0.2 μm to prepare a radiation-sensitive composition (R-1).

[0149] Examples 2 to 55 and Comparative Examples 1 to 3 Radiation-sensitive compositions (R-2) to (R-55) and (CR-1) to (CR-3) were prepared in the same manner as in Example 1, except that the types and amounts of each component were changed as shown in Tables 2 and 3. In Tables 2 and 3, the content of the acid diffusion controller [D] represents the proportion (mol %) to the total amount of the radiation-sensitive acid generator [A] and the monomer that provides the third structural unit in the polymer [P].

[0150]

[0151]

[0152] <Evaluation> The radiation-sensitive compositions of Examples 1 to 55 and Comparative Examples 1 to 3 were evaluated for coating defects and film thickness uniformity by the methods described below. The evaluation results are shown in Table 4.

[0153] [Evaluation of Coating Defects] Each of the radiation-sensitive compositions prepared above was applied to the surface of a 12-inch silicon wafer using a spin coater (CLEAN TRACK ACT12, manufactured by Tokyo Electron Limited). After soft baking (SB) at 100°C for 60 seconds, the wafer was cooled at 23°C for 30 seconds to form a resist film with a thickness of 45 nm. Next, the silicon wafer with the resist film was subjected to defect inspection using a dark-field defect inspection device SP5 manufactured by KLA-Tencor Corporation, and the number of defects with a size of 45 nm or more (number of defects) was measured. The number of defects was judged as "A" (very good) when the number of defects was less than 20, "B" (good) when the number of defects was 20 or more but less than 35, "C" (fair) when the number of defects was 35 or more but less than 50, and "D" (poor) when the number of defects was 50 or more.

[0154] [Evaluation of Film Thickness Uniformity] Each of the radiation-sensitive compositions prepared above was applied to the surface of a 12-inch silicon wafer using a spin coater (CLEAN TRACK ACT12, manufactured by Tokyo Electron Limited). After soft baking (SB) at 100°C for 60 seconds, the wafer was cooled at 23°C for 30 seconds to form a resist film with a film thickness of 45 nm. Next, using an optical interference film thickness measuring device VM-3210 (manufactured by SCREEN), film thickness was measured at 21 points at 1-centimeter intervals from the center of the wafer to a radius of 10 centimeters in the radial direction, and the variation in the measurement values ​​(3σ) was determined to evaluate film thickness uniformity. Film thickness uniformity was evaluated as "A" (very good) when the variation in the measurement values ​​(3σ) was less than 0.5 nm, "B" (good) when it was 0.5 nm or more but less than 1.0 nm, "C" (fairly good) when it was 1.0 nm or more but less than 1.5 nm, and "D" (poor) when it was 1.5 nm or more.

[0155]

[0156] As shown in Table 4, the radiation-sensitive compositions of Examples 1 to 55 were all rated A or B for coating defects and A, B, or C for film thickness uniformity. In contrast, the radiation-sensitive composition of Comparative Example 1, which contained a specific acid generator but no compound (Ex), was rated C for coating defects and D for film thickness uniformity. The radiation-sensitive composition of Comparative Example 2, which contained compound (Ex) but no specific acid generator, was rated C for both coating defects and film thickness uniformity. The radiation-sensitive composition of Comparative Example 3, which contained neither a specific acid generator nor compound (Ex), was rated D for both coating defects and film thickness uniformity. From these results, it can be said that the radiation-sensitive compositions of Examples 1 to 55 were able to improve coating defects and film thickness uniformity in a well-balanced manner.

[0157] As described above, the radiation-sensitive composition and method for forming a resist pattern according to the present disclosure can improve coating defects and film thickness uniformity in a well-balanced manner. Therefore, the radiation-sensitive composition and method for forming a resist pattern according to the present disclosure can be suitably used in processes for fabricating semiconductor devices, which are expected to become even more miniaturized in the future.

Claims

1. A radiation-sensitive composition comprising: a radiation-sensitive acid generator comprising an organic anion having a steroid skeleton or a 9,10-ethanoanthracene skeleton and a radiation-sensitive cation; and a compound represented by the following formula (1): (In formula (1), R １１ , R １２ and R １３ are each independently a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms.

2. The radiation-sensitive composition according to claim 1, further comprising a polymer containing a structural unit having an aromatic ring and a hydroxyl group bonded to the aromatic ring.

3. The radiation-sensitive composition according to claim 2, wherein the polymer further comprises a structural unit having an acid-dissociable group.

4. The radiation-sensitive composition according to claim 1, wherein the radiation-sensitive cation is a sulfonium cation or an iodonium cation.

5. The radiation-sensitive composition according to claim 1, wherein one or both of the organic anion and the radiation-sensitive cation has an iodine atom.

6. The radiation-sensitive composition according to claim 1, wherein one or both of the organic anion and the radiation-sensitive cation has a fluorine atom.

7. The radiation-sensitive composition according to claim 1, which contains the compound represented by formula (1) as a solvent component, and the content of the compound represented by formula (1) is 10 mass % or more based on the total amount of the solvent component.

8. The radiation-sensitive composition according to claim 1, which contains, as solvent components, a compound represented by the above formula (1) and another solvent different from the compound represented by the above formula (1).

9. The radiation-sensitive composition according to claim 8, wherein the other solvent is at least one selected from the group consisting of esters, ethers, and cyclic lactones.

10. A method for forming a resist pattern, comprising the steps of: forming a resist film on a substrate using the radiation-sensitive composition according to any one of claims 1 to 9; exposing the resist film; and developing the exposed resist film.

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