Radiation-sensitive composition, and method for forming resist pattern

Abstract

This radiation-sensitive composition contains: a polymer containing at least one structural unit selected from the group consisting of structural units represented by formula (1-1) to formula (1-3); and a compound represented by formula (2). In the formulae, A1 represents an (n1+n2+1)-valent aromatic ring group. R2 is an acid-dissociable group. A2 is a substituted or unsubstituted aromatic ring group. R5 and R6 are alkyl groups having 1 to 10 carbon atoms, or are combined with each other to represent an aliphatic ring structure constituted together with carbon atoms to which R5 and R6 are bonded. However, R8 and R9 are combined with each other to form an aliphatic ring structure, and either the aliphatic ring structure has an ethylenically unsaturated bond or R10 has an ethylenically unsaturated bond. R11, R12 and R13 are monovalent aliphatic hydrocarbon groups having 1 to 20 carbon atoms.

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. 2024-46331, filed on March 22, 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] As the structures of various electronic devices become finer, there is a demand for even finer resist patterns in lithography processes. Furthermore, in response to the demand for even finer 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 resin containing a specific structural unit having a phenolic hydroxyl group or a protective structure that generates a phenolic hydroxyl group upon the action of an acid, and an acid-dissociable group; a radiation-sensitive acid generator consisting of a sulfonate anion and an onium cation; and a solvent.

[0004] Japanese Patent Application Laid-Open No. 2022-007909

[0005] In recent years, attempts have been made to form fine patterns with line widths of, for example, 40 nm or less. Radiation-sensitive compositions for forming resist films are required to exhibit high sensitivity while also further improving CDU (Critical Dimension Uniformity), which is an index of pattern quality.

[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 is excellent in sensitivity and CDU performance and that is capable of forming a resist pattern with little variation in film thickness, as well as a method of forming a resist pattern using the radiation-sensitive composition.

[0008] According to one aspect of the present disclosure, there is provided a radiation-sensitive composition containing a polymer including at least one structural unit selected from the group consisting of a structural unit represented by the following formula (1-1), a structural unit represented by the following formula (1-2), and a structural unit represented by the following formula (1-3), and a compound represented by the following formula (2): (In formula (1-1), R １ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. １ is an (n1+n2+1)-valent aromatic ring group. ２ is an acid-dissociable group. ３ Is -COOR ２ n1 is an integer of 1 or more. n2 is an integer of 0 or more. When n1 is 2 or more, a plurality of R ２ When n2 is 2 or more, a plurality of R ３ are the same or different. In formula (1-2), R ４ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ２ is a substituted or unsubstituted aromatic ring group. ５ and R ６ are each independently an alkyl group having 1 to 10 carbon atoms, or are combined together to form R ５ and R ６ represents an aliphatic ring structure formed together with the carbon atom to which R is attached. ７ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ８ and R ９are each independently an alkyl group having 1 to 10 carbon atoms, or are combined together to form R ８ and R ９ represents an aliphatic ring structure formed together with the carbon atom to which R is attached. １０ is a hydrogen atom or a monovalent chain hydrocarbon group. ８ , R ９ and R １０ Among them, R ８ and R ９ and R １０ has an ethylenically unsaturated bond.) (In formula (2), 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 is capable of forming a resist pattern that has excellent sensitivity and CDU performance and that has little variation in film thickness. 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 form a resist pattern with good shape and quality.

[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 formed 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 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 polymer (hereinafter also referred to as "polymer (P)") including at least one selected from the group consisting of a structural unit represented by the following formula (1-1), a structural unit represented by the following formula (1-2), and a structural unit represented by the following formula (1-3), and a compound represented by the following formula (2) (hereinafter also referred to as "compound (E)").

[0016] (In formula (1-1), R １ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. １ is an (n1+n2+1)-valent aromatic ring group. ２ is an acid-dissociable group. ３ Is -COOR ２ n1 is an integer of 1 or more. n2 is an integer of 0 or more. When n1 is 2 or more, a plurality of R ２ When n2 is 2 or more, a plurality of R ３ are the same or different. In formula (1-2), R ４ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ２ is a substituted or unsubstituted aromatic ring group. ５ and R ６ are each independently an alkyl group having 1 to 10 carbon atoms, or are combined together to form R ５ and R ６represents an aliphatic ring structure formed together with the carbon atom to which R is attached. ７ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ８ and R ９ are each independently an alkyl group having 1 to 10 carbon atoms, or are combined together to form R ８ and R ９ represents an aliphatic ring structure formed together with the carbon atom to which R is attached. １０ is a hydrogen atom or a monovalent chain hydrocarbon group. ８ , R ９ and R １０ Among them, R ８ and R ９ and R １０ has an ethylenically unsaturated bond.)

[0017] (In formula (2), R １１ , R １２ and R １３ are each independently a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms.

[0018] The present composition containing polymer (P) and compound (E) can form a coating film that exhibits excellent sensitivity and CDU performance, minimizes film thickness variation, and exhibits excellent film thickness uniformity. While the reasons for this effect are unclear, the following may be considered: The structural units represented by the above formulas (1-1) to (1-3) are highly sensitive to radiation, which is thought to contribute to improving the sensitivity of the radiation-sensitive composition. Furthermore, if the components in the radiation-sensitive composition are likely to interact through π-π interactions, the dispersibility of the components in the radiation-sensitive composition is improved, which is thought to improve the CDU performance of the resist film. On the other hand, π-π interactions in the radiation-sensitive composition are thought to cause a decrease in film fluidity during film formation, which tends to reduce the surface smoothness of the resulting coating film. In this regard, compound (E) has a relatively high boiling point and exhibits high solubility in polymer (P) and the radiation-sensitive acid generator. It is therefore thought that the present composition can provide a resist film that exhibits high sensitivity while achieving a good balance between improved CDU performance and film thickness uniformity. However, the above reasons are merely speculation and do not limit the present invention in any way.

[0019] The components contained in the present composition and the components that may be optionally blended are specifically described below. Note that, unless otherwise specified, each component contained in the present composition may be used alone or in combination of two or more.

[0020] <Polymer (P)> The polymer (P) comprises at least one structural unit (hereinafter also referred to as a "first structural unit") selected from the group consisting of the structural unit represented by the above formula (1-1), the structural unit represented by the above formula (1-2), and the structural unit represented by the above formula (1-3). The first structural unit has a partial structure in which a hydrogen atom in a carboxy group is replaced with an acid-dissociable group, and the first structural unit has an aromatic ring in the acid-dissociable group or in a portion other than the acid-dissociable group, or the acid-dissociable group has an ethylenically unsaturated bond. By incorporating a polymer (P) comprising such a first structural unit into the present composition, the acid-dissociable group is eliminated by the action of acid to generate a carboxy group, thereby changing the solubility of the polymer (P) in a developer. Furthermore, the polymer (P) comprising the first structural unit has high sensitivity to radiation, and the acid-dissociable group can be eliminated with a small amount of exposure.

[0021] (First structural unit) In the above formula (1-1), A １ The (n1+n2+1)-valent aromatic ring group represented by the formula (I) is a group obtained by removing (n1+n2+1) hydrogen atoms from an 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. Of these, a benzene ring or a naphthalene ring is preferred, and a benzene ring is more preferred.

[0022] R ２ The acid-dissociable group represented by "-COOR" is not particularly limited as long as it is a group that dissociates under the action of an acid to generate a carboxy group. ２ Specific examples of the group represented by " include R ２but having a tertiary carbon atom, a benzylic carbon atom, or an allylic carbon atom and bonding to the oxygen atom in the oxycarbonyl group (-COO-) via such a carbon atom; a group having an acetal ester structure of a carboxylic acid; a group having a ketal ester structure of a carboxylic acid; etc. Examples of the group having an acetal ester structure of a carboxylic acid include a 1-methoxyethoxycarbonyl group, a 1-cyclohexyloxyethoxycarbonyl group, and a 2-tetrahydropyranyloxycarbonyl group. Examples of the group having a ketal ester structure of a carboxylic acid include a 1-methyl-1-methoxyethoxycarbonyl group, a 1-methyl-1-cyclohexyloxyethoxycarbonyl group, and a 2-(2-methyltetrahydropyranyl)oxycarbonyl group.

[0023] R ２ The acid-dissociable group represented by the formula (I) preferably has a tertiary carbon atom, a benzylic carbon atom or an allylic carbon atom, and is bonded to the oxygen atom in the oxycarbonyl group via one of these carbon atoms.

[0024] Acid dissociable group (R ２ ) is preferably a group represented by the following formula (r2-1): (In formula (r2-1), R ２１ is a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms. ２２ and R ２３ are each independently a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, a monovalent aromatic heterocyclic group, or R ２２ and R ２３ are aligned with each other and R ２２ and R ２３ represents an alicyclic hydrocarbon structure having 3 to 20 carbon atoms, which is formed together with the carbon atom to which R is bonded. ２１ When is a hydrogen atom, R ２２ and R ２３ 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 ２２and R ２３ are aligned with each other and R ２２ and R ２３ 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. "*" represents a bond to an oxygen atom.)

[0025] R ２１ ~R ２３ Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) 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.

[0026] The monovalent chain hydrocarbon group having 1 to 20 carbon atoms may be saturated or unsaturated, and may be linear or branched. Examples of the monovalent chain hydrocarbon group having 1 to 20 carbon atoms include alkyl groups such as methyl, ethyl, n-propyl, i-propyl, n-butyl, and t-butyl; alkenyl groups such as ethenyl, propenyl, and butenyl; and alkynyl groups such as ethynyl, propynyl, and butynyl. Among these, R ２１ ~R ２３ The monovalent chain hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) is preferably an alkyl group or an alkenyl group, more preferably an alkyl group having 1 to 4 carbon atoms or an alkenyl group having 2 to 4 carbon atoms.

[0027] Examples of the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms 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.

[0028] Examples of the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms include aryl groups such as phenyl, tolyl, xylyl, mesityl, naphthyl, methylnaphthyl, anthryl, methylanthryl, and indenyl; and aralkyl groups such as benzyl, phenethyl, naphthylmethyl, and anthrylmethyl. Examples of the monovalent aromatic heterocyclic group include furyl and thienyl.

[0029] R ２２ and R ２３ are aligned with each other and R ２２ and R ２３ 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 aliphatic hydrocarbon structures such as a cyclopropane structure, cyclobutane structure, cyclopentane structure, cyclohexane structure, cycloheptane structure, and cyclooctane structure; monocyclic unsaturated aliphatic hydrocarbon structures such as cyclopentene and cyclohexene; and polycyclic aliphatic hydrocarbon structures such as a norbornane structure, adamantane structure, tricyclodecane structure, and tetracyclododecane structure.

[0030] R ２１ ~R ２３ When the group represented by the formula (r2-1) has a substituent, examples of the substituent include a halogen atom (a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc.), a hydroxyl group, an alkoxy group having 1 to 3 carbon atoms, etc. ２１ , R ２２ and R ２３ is preferably a tertiary carbon atom, a benzylic carbon atom, or an allylic carbon atom, and any of these carbon atoms is preferably bonded to the oxygen atom in the above formula (1-1).

[0031] R in the above formula (1-1) ３ The substituent represented by "-COOR ２ " may be any group different from the group represented by R ３Specific examples of the alkyl group include halogen atoms (fluorine atom, chlorine atom, bromine atom, iodine atom, etc.), hydroxyl group, alkyl group having 1 to 12 carbon atoms, halogenated alkyl group having 1 to 12 carbon atoms, hydroxyalkyl group having 1 to 12 carbon atoms, alkoxy group having 1 to 12 carbon atoms, halogenated alkoxy group having 1 to 12 carbon atoms, hydroxyalkoxy group having 1 to 12 carbon atoms, cyano group, nitro group, carboxy group, ester group, cycloalkyl group having 3 to 12 carbon atoms, halogenated cycloalkyl group having 3 to 12 carbon atoms, hydroxycycloalkyl group having 3 to 12 carbon atoms, alkylsulfonyl group, cycloalkylsulfonyl group, etc.

[0032] In the above formula (1-1), one or more R ３ When R in the above formula (1-1) contains a hydroxyl group or a group having a hydroxyl group (such as a hydroxyalkyl group), the CDU performance of the present composition can be made even better. ３ The number of hydroxyl groups or groups having a hydroxyl group is preferably 1 to 3, and more preferably 1 or 2.

[0033] In the above formula (1-2), A ２ The substituted or unsubstituted aromatic ring group represented by the following formula (I) is a group in which one hydrogen atom has been removed from the ring portion of a substituted or unsubstituted aromatic ring. Specific and preferred examples of the aromatic ring include: １ Specific examples and preferred examples of the aromatic ring forming A include the same rings as those mentioned above. ２ When R has a substituent, specific examples of the substituent include R ３ Among these, the specific examples of A ２ is preferably a phenyl group, a naphthyl group or an iodophenyl group. In the present specification, when an "iodophenyl group" is referred to, it is sufficient that the number of iodine atoms bonded to the benzene ring is one or more.

[0034] In the above formula (1-2), R ５ or R ６ or an alkyl group having 1 to 10 carbon atoms represented by the formula (1-3) ８ or R ９Examples of the alkyl group having 1 to 10 carbon atoms represented by the formula (I) include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, and a t-butyl group.

[0035] In the above formula (1-2), R ５ and R ６ are combined together to form R ５ and R ６ an aliphatic ring structure formed together with the carbon atom to which R is bonded, or ８ and R ９ are combined together to form R ８ and R ９ The aliphatic ring structure formed together with the carbon atom to which R is bonded is preferably an aliphatic hydrocarbon structure. ２２ and R ２３ The aliphatic ring structures may have a substituent on the ring portion. Examples of the substituent include R ３ Specific examples of the above include the same groups as those mentioned above.

[0036] R in the above formula (1-2) ５ and R ６ However, when combined with each other, R ５ and R ６ is an aliphatic ring structure formed together with the carbon atom to which it is bonded, this is preferable in that the sensitivity of the present composition can be further increased.

[0037] R in the above formula (1-3) ８ and R ９ However, when combined with each other, R ８ and R ９ When R is an unsaturated aliphatic ring structure formed together with the carbon atom to which it is bonded, it is preferable in that the CDU performance of the present composition can be further improved. １０ is preferably a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. １０ is a hydrogen atom, or R １０ is a monovalent chain hydrocarbon group, and the chain hydrocarbon group does not have an ethylenically unsaturated bond, R ８ and R ９ are combined together to form R８ and R ９ represents an aliphatic ring structure formed together with the carbon atom to which it is bonded, and the aliphatic ring structure has an ethylenically unsaturated bond.

[0038] In the above formula (1-3), R １０ Specific and preferred examples of the monovalent chain hydrocarbon group represented by R ２１ ~R ２３ Specific examples and preferred examples of the monovalent chain hydrocarbon group having 1 to 20 carbon atoms in the description of R １０ is a monovalent unsaturated chain hydrocarbon group, which is preferable in that the sensitivity of the present composition can be further increased.

[0039] R ８ and R ９ is an alkyl group having 1 to 10 carbon atoms, or R ８ and R ９ However, when combined with each other, R ８ and R ９ represents an aliphatic ring structure formed together with the carbon atom to which it is bonded, and the aliphatic ring structure does not have an ethylenically unsaturated bond, R １０ has an ethylenically unsaturated bond. １０ is a group having an ethylenically unsaturated bond, R ８ and R ９ are each independently an alkyl group having 1 to 10 carbon atoms, or are combined together to form R ８ and R ９ is preferably a saturated aliphatic ring structure formed together with the carbon atom to which it is bonded.

[0040] The group "-CR ８ R ９ R １０ From the viewpoint of improving the releasability of ", ８ , R ９ and R １０ is preferably a carbon atom at the allylic position or a carbon atom adjacent to the carbon at the allylic position, and is preferably bonded to the oxygen atom in the above formula (1-3) through either of these carbon atoms.

[0041] In the above formulas (1-1) to (1-3), R １ , R ４ or R ７ is preferably a hydrogen atom or a methyl group from the viewpoint of copolymerizability with other monomers.

[0042] It is preferable that at least a part of the first structural units contained in the polymer (P) have an iodine group, since this allows for a well-balanced improvement in the sensitivity, CDU performance, and film thickness uniformity of the composition. From the viewpoint of sufficiently enhancing the effect of improving the sensitivity of the composition, it is preferable that the iodine group in the first structural unit is bonded to an aromatic ring. Furthermore, from the viewpoint of further enhancing the effect of improving CDU performance, it is more preferable that the acid-dissociable group in the first structural unit has an aromatic ring, and that the iodine group is bonded to the aromatic ring. Specifically, R in the above formula (1-1) ２ is a group represented by the above formula (r2-1), and R ２１ is an iodophenyl group, or A in the above formula (1-2) ２ is preferably an iodophenyl group.

[0043] Specific examples of the first structural unit include the structural unit represented by the above formula (1-1), such as the structural unit represented by the following formula: (In the formula, R １ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0044] Specific examples of the structural unit represented by the above formula (1-2) include structural units represented by the following formulas: (In the formula, R ４ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0045] Specific examples of the structural unit represented by the above formula (1-3) include structural units represented by the following formulas. (In the formula, R ７ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0046] The content of the first structural unit in the polymer (P) is preferably 10 mol% or more, more preferably 20 mol% or more, and even more preferably 30 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 keeping the content of the first structural unit within the above range, it is possible to ensure the uniformity of the film thickness of a coating film formed using the composition while maintaining good CDU performance of the composition.

[0047] The polymer (P) preferably constitutes the base resin of the composition. Here, in this specification, "base resin" refers to a polymer component that accounts for 50% by mass or more of the total amount of solids contained in the composition. When the polymer (P) is composed of two or more polymers, the total content of these two or more polymers is preferably 50% by mass or more of the total amount of solids contained in the composition. "Solids" refers to components other than the solvent contained in the composition.

[0048] (Other structural units) The polymer (P) may further contain structural units different from the first structural unit (hereinafter also referred to as "other structural units"). Examples of other structural units include a structural unit having an aromatic ring and a hydroxyl group bonded to the aromatic ring (excluding those corresponding to the first structural unit; hereinafter also referred to as "second structural units"); a structural unit having an acid-dissociable group (excluding those corresponding to the first structural unit; hereinafter also referred to as "third structural units"); a structural unit having an onium salt structure formed from a radiation-sensitive onium cation and an organic anion (hereinafter also referred to as "fourth structural units"); a structural unit having a lactone structure, a cyclic carbonate structure, a sultone structure, or a ring structure combining two or more of these (hereinafter also referred to as "fifth structural units"); and a structural unit having an alcoholic hydroxyl group (hereinafter also referred to as "sixth structural units").

[0049] Second structural unit The second structural unit is a structural unit having an aromatic ring and a hydroxy group bonded to the aromatic ring. The inclusion of the second structural unit in the polymer (P) is advantageous in that it can further improve the development resolution of the composition, and is highly effective in suppressing dissolution of unexposed areas into a developer, thereby sufficiently reducing development defects. In particular, polymers having a hydroxy 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. The second structural unit is different from the structural unit represented by the above formula (1-1) and the structural unit represented by the above formula (1-2).

[0050] Examples of aromatic rings to which hydroxy groups are bonded include a benzene ring, a naphthalene ring, an anthracene ring, and a phenanthrene ring. Of these, a benzene ring or a naphthalene ring is preferred, and a benzene ring is more preferred. The number of hydroxy groups bonded to the aromatic ring is not particularly limited. The number of hydroxy groups bonded to the aromatic ring is preferably 1 to 3, and more preferably 1 or 2. The position of the hydroxy group bonded to the aromatic ring is also not particularly limited. For example, when the second structural unit has a hydroxy group bonded to a benzene ring, the bonding position of the hydroxy group on the benzene ring in the second structural unit may be any of the ortho, meta, and para positions relative to other groups.

[0051] The aromatic ring to which the hydroxy group is bonded may further have a substituent different from the hydroxy group bonded thereto. Examples of such a substituent include an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, and a halogen atom (a fluorine atom, a chlorine atom, a bromine atom, an iodine atom). When an iodine group is bonded to the aromatic ring to which the hydroxy group is bonded, this is preferred in that the sensitivity can be further increased while maintaining good CDU performance of the present composition.

[0052] A specific example of the second structural unit is a structural unit represented by the following formula (3). (In formula (3), R ７１ is a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group. ５ represents a single bond, -O-, -CO-, *６ -COO- or * ６ -CONH-. ６ " represents a bond to the main chain. ６ is a monovalent group having an aromatic ring and a hydroxyl group bonded to the aromatic ring. ６ The aromatic ring in the middle contains -COOR ２ (R ２ is an acid-labile group) is not bonded.

[0053] In the above formula (3), R ７１ is preferably a hydrogen atom or a methyl group from the viewpoint of copolymerizability of the monomer that provides the second structural unit. ５ is a single bond or * ６ —COO— is preferred, and a single bond is more preferred in that it can further increase the sensitivity of the present composition. ６ is preferably a group in which one hydrogen atom has been removed from the ring portion of the aromatic ring to which the hydroxy group is bonded (i.e., a monovalent aromatic ring group substituted with a hydroxy group). ６ The aromatic ring in ２ The substituent may further have a substituent different from the above. Examples of the substituent include a halogen atom and an alkyl group having 1 to 3 carbon atoms.

[0054] Further specific examples of the second structural unit include structural units represented by the following formulas: However, the specific examples of the second structural unit are not limited to these. (In the formula, R ７１ is a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group.

[0055] In this specification, a structural unit having an acid-dissociable group and a hydroxyl group bonded to an aromatic ring and not corresponding to the first structural unit is classified as the third structural unit, and a structural unit having an onium salt structure formed from a radiation-sensitive onium cation and an organic anion and a hydroxyl group bonded to an aromatic ring is classified as the fourth structural unit.

[0056] In the polymer (P), the content of the second structural unit is preferably 10 mol% or more, more preferably 20 mol% or more, and even more preferably 30 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 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 second structural unit within the above range, the resolution of the composition can be further improved.

[0057] Third Structural Unit In the present composition, the sensitivity of the polymer (P) and the solubility in a developer may be adjusted by introducing a third structural unit into the polymer (P) together with the first structural unit. The acid-dissociable group in the third structural unit is a group that substitutes a hydrogen atom in an acid group such as a carboxy group or a hydroxy group, and may be a group that is eliminated by the action of an acid. However, the second structural unit is not limited to a -COOR bonded to an aromatic ring. ２ (R ２ is an acid-dissociable group), —COO—CA ２ R ５ R ６ (However, A ２ , R ５ and R ６ has the same meaning as in formula (1-2) above) and —COO—CR ８ R ９ R １０ (However, R ８ , R ９ and R １０ is synonymous with the above formula (1-3).

[0058] 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. ７２ is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.

[0059] The content of the third structural unit in the polymer (P) is preferably 20 mol % or less, more preferably 10 mol % or less, and even more preferably 5 mol % or less, based on the total amount of structural units 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 the exposed and unexposed areas can be appropriately increased while sufficiently improving the CDU performance of the composition, and a resist film having a good pattern shape can be obtained.

[0060] Fourth Structural Unit The fourth structural unit has an onium salt structure formed by a radiation-sensitive onium cation and an organic anion. It is believed that the radiation-sensitive onium cation in the fourth structural unit decomposes under the action of radiation to liberate an organic anion, 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. In this specification, the term "radiation" includes electron beams (visible light, ultraviolet light, far ultraviolet light, extreme ultraviolet light (EUV), etc.) and electromagnetic waves (X-rays, gamma rays, etc.).

[0061] When the organic anion in the fourth structural unit is a sulfonate anion, the fourth structural unit is considered 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 fourth structural unit is a carboxylate anion, the fourth structural unit is considered 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.

[0062] The fourth 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 CDU performance of the present composition, it is preferable that the fourth 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.

[0063] The radiation-sensitive cation in the fourth 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.

[0064] It is preferable that at least a portion of the fourth 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 CDU performance of the present composition. When the fourth structural unit has an iodo group, the iodo group is preferably bonded to an aromatic ring. Furthermore, when the fourth 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.

[0065] 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 ２０ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ＋is a radiation-sensitive onium cation. － is a sulfonate anion.)

[0066] (In the formula, R ３０ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ＋ is a radiation-sensitive onium cation. － is a carboxylate anion.)

[0067] When the polymer (P) contains a fourth structural unit, the content of the fourth 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). Furthermore, the content of the fourth 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 fourth structural unit within the above range, the CDU performance of the composition can be sufficiently improved.

[0068] Fifth Structural Unit The fifth structural unit is a structural unit (excluding the first to fourth structural units) having a lactone structure, a cyclic carbonate structure, a sultone structure, or a ring structure formed by combining two or more of these.

[0069] Specific examples of the fifth structural unit include structural units represented by the following formulas: However, the specific examples of the fifth 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.

[0070] When the polymer (P) contains the fifth structural unit, the content of the fifth structural unit is preferably 1 mol% or more, more preferably 2 mol% or more, based on the total amount of structural units contained in the polymer (P). The content of the sixth structural unit in the polymer (P) is preferably 30 mol% or less, more preferably 20 mol% or less, and even more preferably 15 mol% or less, based on the total amount of structural units contained in the polymer (P).

[0071] Sixth Structural Unit The sixth structural unit is a structural unit having an alcoholic hydroxyl group (excluding the first to fifth structural units). By introducing the sixth 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 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.

[0072] The sixth 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 sixth structural unit is not particularly limited. Specific examples of the sixth structural unit include structural units represented by the following formulas. However, specific examples of the sixth 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.

[0073] When the polymer (P) contains the sixth structural unit, from the viewpoint of enhancing the effect of suppressing development defects in the resist pattern, the content of the sixth 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 sixth 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).

[0074] In addition to the above, examples of structural units possessed by 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, etc.); 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, etc.), a structural unit derived from vinylnaphthalene, a structural unit derived from n-pentyl(meth)acrylate, etc.); 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 disclosure are not impaired.

[0075] 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 structural unit and the other structural unit 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.

[0076] The weight average molecular weight (Mw) of the polymer (P) measured by gel permeation chromatography (GPC) in terms of polystyrene 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.

[0077] 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.

[0078] 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 present composition.

[0079] The polymer (P) can be synthesized, for example, by polymerizing monomers that provide each structural unit in an appropriate solvent using a known radical polymerization initiator. Examples of the radical polymerization initiator include azo radical initiators (e.g., azobisisobutyronitrile (AIBN), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile)), peroxide radical initiators (e.g., benzoyl peroxide), and the like. Examples of the solvent used in the polymerization include linear alkanes, cycloalkanes, aromatic hydrocarbons, halogenated hydrocarbons, saturated carboxylic acid esters, ketones, ethers, and alcohols. The reaction temperature in the polymerization is preferably 40 to 150°C, more preferably 50 to 120°C. The reaction time is preferably 1 to 48 hours, more preferably 2 to 24 hours.

[0080] <Compound (E)> Compound (E) is represented by the following formula (2): Compound (E) is preferably blended in the present composition as a solvent. (In formula (2), R １１ , R １２ and R １３ are each independently a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms.

[0081] In the above formula (2), R １１ , R １２ or R １３ Examples of the monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms represented by the formula (r2-1) 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 ２１ ~R ２３ Specific examples of the monovalent chain hydrocarbon group having 1 to 20 carbon atoms and represented by the following formula (I) and the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms include the same groups as those exemplified above.

[0082] From the viewpoint of the solubility of the polymer (P) and the availability of the compound (E), R １１ , R １２ or R １３is 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.

[0083] Specific examples of compound (E) 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.

[0084] The content of compound (E) in the composition is preferably 10% by mass or more relative to the total amount of solvent contained in the composition. When the content of compound (E) is within the above range, a coating film with sufficiently small film thickness variation can be formed while ensuring the sensitivity and CDU performance of the composition. The content of compound (E) is more preferably 15% by mass or more, even more preferably 20% by mass or more, even more preferably 25% by mass or more, and particularly preferably 30% by mass or more relative to the total amount of solvent contained in the composition.

[0085] <Other Components> The present composition may further contain, in addition to the polymer (P) and the compound (E), a component different from the polymer (P) and the compound (E) (hereinafter also referred to as "other components"). Examples of the other components include a solvent different from the compound (E) (hereinafter also referred to as "other solvents"), a radiation-sensitive acid generator, a high-fluorine-containing polymer, etc.

[0086] (Other Solvents) The present composition may contain other solvents together with compound (E). The other solvent is preferably a solvent capable of dissolving or dispersing the components blended in the present composition, and an organic solvent can be preferably used. Specific examples of other solvents include alcohols, ethers, ketones, amides, esters, hydrocarbons, etc. 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.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] 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 forming a coating film with excellent film thickness uniformity while ensuring the sensitivity and CDU performance 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.

[0094] 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 solvent, the coating film (and thus the resist pattern) obtained from the present composition can have better film thickness uniformity. Of 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.

[0095] When the composition contains other solvents, the content of the hydroxyl group-containing compound in the composition is preferably 30% by mass or more, more preferably 40% by mass or more, and even more preferably 50% by mass or more, based on the total amount of solvents contained in the composition, in order to ensure excellent thickness uniformity of the coating film. Also, the content of the hydroxyl group-containing compound is preferably 90% by mass or less, more preferably 85% by mass or less, even more preferably 80% by mass or less, even 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.

[0096] Furthermore, when the present composition contains other solvents, the content of the hydroxyl group-containing compound in the present composition is preferably 25% by mass or more, more preferably 35% by mass or more, and even more preferably 50% by mass or more, based on the total amount of the other solvents.

[0097] (Radiation-sensitive acid generator) A radiation-sensitive acid generator is a substance that generates an acid upon irradiation with radiation. The radiation-sensitive acid generator may be an ionic radiation-sensitive acid generator or a non-ionic radiation-sensitive acid generator. The radiation-sensitive acid generator is preferably an ionic radiation-sensitive acid generator, and an onium salt having 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.

[0098] The radiation-sensitive acid generator may be a so-called radiation-sensitive acid generator or an acid diffusion controller. The present composition may contain both an acid generator and an acid diffusion controller as the radiation-sensitive acid generator. The acid generator is a substance that, upon exposure, generates a strong acid in the present composition that can dissociate an acid-dissociable group from an acid-dissociable group contained in a component of the radiation-sensitive composition. The acid diffusion controller is a substance that can inhibit the diffusion of an acid derived from the acid generator generated upon exposure in the resist film, thereby inhibiting a chemical reaction caused by the acid in unexposed regions. The radiation-sensitive acid generator is classified as an acid generator or an acid diffusion controller depending on the strength of its acid relative to the components in the present composition (specifically, the polymer (P) when it contains a fourth structural unit, or other radiation-sensitive acid generators when it contains two or more radiation-sensitive acid generators). The acidity can be evaluated by the acid dissociation constant (pKa). For example, the acid dissociation constant of the acid generated by the acid diffusion controller is usually −3 or more, preferably −1≦pKa≦7, and more preferably 0≦pKa≦5.

[0099] The radiation-sensitive acid generator is a component different from the polymer (P). That is, the radiation-sensitive acid generator is a compound that does not have any of the structural units represented by the above formula (1-1), the above formula (1-2), and the above formula (1-3). The radiation-sensitive acid generator may be a so-called low-molecular-weight compound (also referred to as a non-polymer) that does not have a molecular weight distribution, or may be a polymer. A low-molecular-weight compound (non-polymer) is preferably used as the radiation-sensitive acid generator because it allows for easy adjustment of the sensitivity of the present composition and provides a high degree of freedom in selecting the radiation-sensitive acid generator to be incorporated into the present 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.

[0100] Acid Generator The type of acid generator to be incorporated into the composition is not particularly limited, and any known radiation-sensitive acid generator used in resist pattern formation can be used as appropriate. The acid generator is preferably a compound that generates, under the above-mentioned normal conditions, an acid in the composition that is more acidic (preferably a strong acid such as a sulfonic acid, imidic acid, or methide acid) than the acid generated by the acid diffusion controller (more specifically, the photodegradable base), thereby inducing dissociation of the acid-dissociable group.

[0101] When an onium salt is used as the acid generator, from the viewpoint of increasing the sensitivity of the present composition and forming a resist film with superior lithography performance, the 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 cations represented by the following formulas:

[0102] The organic anion contained in the acid generator is not particularly limited, but is preferably a sulfonate anion, an imide anion, or a methide anion, in that it can increase the sensitivity of the present composition. For example, specific examples of sulfonate anions include anions represented by the following formula:

[0103] When an acid generator is incorporated into the composition, the content of the acid generator is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and even more preferably 2 parts by mass or more, relative to 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 30 parts by mass or less, more preferably 25 parts by mass or less, and even more preferably 20 parts by mass or less, relative to 100 parts by mass of polymer (P).

[0104] When an acid generator is incorporated into the present composition, an onium salt having an iodine atom is preferably used as the acid generator, since this can further enhance the CDU performance of the present composition. In the acid generator having an iodine atom, the number of iodine atoms in one molecule is preferably two or more, from the viewpoint of sufficiently improving the CDU performance of the radiation-sensitive composition. In the 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 present 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 present composition. Note that 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.

[0105] Acid Diffusion Controller: From the viewpoint of improving the lithography properties of the present composition, the present composition preferably contains, as an acid diffusion controller, an onium salt having a radiation-sensitive onium cation and an organic anion that is a 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 is preferably used as the photodegradable base.

[0106] Specific examples of the radiation-sensitive onium cation contained in the photodecomposable base include the same onium cations as those exemplified as the radiation-sensitive onium cation that may be contained in the acid generator.

[0107] Examples of the organic anion contained in the photodegradable base include anions represented by the following formula:

[0108] When an acid diffusion controller is blended in the composition, the content of the acid diffusion controller 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 obtaining the effects of improving 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 ratio 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).

[0109] When an acid diffusion controller is blended in the composition, the content of the acid diffusion controller in the composition 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 fourth 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 structural unit (I). By setting the content of the acid diffusion controller within the above range, the CDU performance of the composition can be further improved.

[0110] 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 one or more, more preferably two or more, from the viewpoint of sufficiently improving the CDU performance of the radiation-sensitive composition. When the organic anion in the acid diffusion controller has one or more iodine atoms, this is preferred, since it can improve the sensitivity, CDU performance, and film thickness uniformity of the present composition in a well-balanced manner. Furthermore, when the organic anion has an aromatic ring and two or more hydroxyl groups bonded to the aromatic ring, this is preferred, since it can provide excellent sensitivity, CDU performance, and film thickness uniformity of the present composition.

[0111] (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 contained in the composition of the present invention, 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.

[0112] 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.

[0113] When the composition contains polymer (F), the content of polymer (F) in the composition is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and even more preferably 0.5 parts by mass or more, per 100 parts by mass of polymer (P). The content of polymer (F) is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, per 100 parts by mass of polymer (P).

[0114] (Other Optional Components) The present composition may further contain components other than the polymer (P), compound (E), radiation-sensitive acid generator, other solvents, and polymer (F) (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 each compound, as long as the effects of the present invention are not impaired.

[0115] <Method for producing radiation-sensitive composition> The present composition can be produced, for example, by mixing the polymer (P) and compound (E), as well as other components blended as necessary, in desired proportions, and filtering the resulting mixture, preferably using a filter (for example, a filter with a pore size of about 0.2 μm). The solids concentration of the present 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 concentration of the present 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 concentration of the present composition within the above range, good coatability can be achieved, and a good resist pattern shape can be obtained, which is advantageous.

[0116] 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.

[0117] <<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.

[0118] [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.

[0119] [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.

[0120] 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.

[0121] [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.

[0122] 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.

[0123] 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).

[0124] 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.

[0125] 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

[0126] <Synthesis of [P] Polymers> [Synthesis Examples 1 to 36] Synthesis of polymers (P-1) to (P-34), (Pc-1), and (Pc-2) 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, polymers (P-1) to (P-34), (Pc-1), and (Pc-2) were obtained, each having the composition shown in Table 1. The resulting polymers had the following composition: 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.

[0127]

[0128]

[0129] <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 59 and Comparative Examples 1 to 6 are shown below.

[0130] [A] Radiation-sensitive Acid Generator Compounds represented by the following formulae (A-1) to (A-12) were used as radiation-sensitive acid generators.

[0131] [D] Acid Diffusion Controller Compounds represented by the following formulae (D-1) to (D-8) were used as acid diffusion controllers.

[0132] [E] Solvents 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)

[0133] Example 1 100 parts by mass of (P-1) as a polymer [P], 45 parts by mass of (A-7) as a radiation-sensitive acid generator [A], 35 mol % of (D-1) as an acid diffusion controller [D] based on the total anion of (A-7), and 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 a solvent [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).

[0134] [Examples 2 to 59 and Comparative Examples 1 to 6] Radiation-sensitive compositions (R-2) to (R-59) and (CR-1) to (CR-6) were prepared in the same manner as in Example 1, except that the types and amounts of each component shown in Tables 2 and 3 were used. In Tables 2 and 3, "-" indicates that the corresponding component was not used. The content of the acid diffusion controller [D] represents the proportion (mol %) to the total amount of the acid generator [A] and the monomer that provides the fourth structural unit in the polymer [P].

[0135]

[0136]

[0137] <Formation of Resist Pattern> Each radiation-sensitive composition was applied to the surface of a 12-inch silicon wafer on which a 20-nm-thick underlayer film (AL412 (Brewer Science)) had been formed, using a spin coater (CLEAN TRACK ACT12, Tokyo Electron Ltd.). After soft baking (SB) at 100°C for 60 seconds, the wafer was cooled at 23°C for 30 seconds to form a 45-nm-thick resist film. Next, this resist film was irradiated with EUV light using an EUV exposure machine (model "NXE3400," ASML, NA = 0.33, illumination conditions: Conventional s = 0.89). The exposed resist film was then subjected to PEB (post-exposure bake) at 110°C for 60 seconds. Next, development was carried out using a 2.38 wt % aqueous solution of TMAH at 23° C. for 30 seconds to form a positive-type 48 nm pitch, 24 nm contact hole pattern.

[0138] <Evaluation> The sensitivity, CDU, and film thickness uniformity of each radiation-sensitive composition were evaluated by measuring each of the resist patterns formed above according to the methods described below. A scanning electron microscope (Hitachi High-Technologies Corporation's "CG-5000") was used to measure the resist patterns. The evaluation results are shown in Tables 4 and 5.

[0139] [Sensitivity] In forming the resist pattern, the exposure dose for forming a 24 nm contact hole pattern was defined as the optimum exposure dose, and this optimum exposure dose was used as the sensitivity (mJ / cm ２ The smaller the sensitivity, the better. The sensitivity was 35 mJ / cm ２ "A" (very good) if less than 35 mJ / cm ２ 39mJ / cm or more ２ "B" (good) in the following cases: 39 mJ / cm ２ When the test result exceeded this, it was judged as "C" (poor).

[0140] [CDU] Using the scanning electron microscope, the 24 nm contact hole pattern was observed from above, and a total of 800 lengths were measured at random points. The dimensional variation (3σ) was calculated and used as the CDU (nm). The smaller the CDU value, the smaller the long-period hole diameter variation (i.e., the diameter variation between different holes) and the better the result. CDU was evaluated as "A" (very good) when it was less than 3.4 nm, "B" (good) when it was 3.4 nm or more but less than 3.6 nm, and "C" (poor) when it was 3.6 nm or more.

[0141] [Film Thickness Uniformity] Each radiation-sensitive composition 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, using an optical interference film thickness measuring device VM-3210 (manufactured by SCREEN), film thickness was measured at a total of 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 measured values ​​(3σ) was determined to evaluate film thickness uniformity. Film thickness uniformity was evaluated as "A" (very good) when the variation in the measured 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.

[0142]

[0143]

[0144] As shown in Tables 4 and 5, the sensitivity, CDU performance, and film thickness uniformity of all of the radiation-sensitive compositions of Examples 1 to 59 were evaluated as extremely good, good, or fairly good. In contrast, Comparative Examples 1 and 2, which used radiation-sensitive compositions containing compound (E) but not polymer (P), were evaluated as poor in CDU performance or sensitivity. Furthermore, Comparative Examples 3 and 4, which used radiation-sensitive compositions containing neither polymer (P) nor compound (E), were evaluated as poor in multiple evaluation items. Furthermore, Comparative Examples 5 and 6, which used radiation-sensitive compositions containing polymer (P) but not compound (E), were evaluated as poor in film thickness uniformity. From these results, it can be said that the radiation-sensitive compositions of Examples 1 to 59 can achieve well-balanced improvements in sensitivity, CDU performance, and film thickness uniformity.

[0145] Furthermore, when Examples 53 to 59, which had the same components except for the solvent, were compared, among Examples 53, 54, and 56 to 59, which contained other solvents, the more hydroxyl group-containing compounds they contained and the higher the proportion of these compounds, the better the film thickness uniformity tended to be.

[0146] The above results demonstrate that the radiation-sensitive composition and method for forming a resist pattern according to the present disclosure can improve sensitivity, CDU performance, and film thickness uniformity in a well-balanced manner, and 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 polymer containing at least one structural unit selected from the group consisting of a structural unit represented by the following formula (1-1), a structural unit represented by the following formula (1-2), and a structural unit represented by the following formula (1-3); and a compound represented by the following formula (2). (In formula (1-1), R １ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. １ is an (n1+n2+1)-valent aromatic ring group. ２ is an acid-dissociable group. ３ Is -COOR ２ n1 is an integer of 1 or more. n2 is an integer of 0 or more. When n1 is 2 or more, a plurality of R ２ When n2 is 2 or more, a plurality of R ３ are the same or different. In formula (1-2), R ４ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ２ is a substituted or unsubstituted aromatic ring group. ５ and R ６ are each independently an alkyl group having 1 to 10 carbon atoms, or are combined together to form R ５ and R ６ represents an aliphatic ring structure formed together with the carbon atom to which R is attached. ７ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ８ and R ９ are each independently an alkyl group having 1 to 10 carbon atoms, or are combined together to form R ８ and R ９ represents an aliphatic ring structure formed together with the carbon atom to which R is attached. １０ is a hydrogen atom or a monovalent chain hydrocarbon group. ８ , R ９ and R １０ Among them, R ８ and R ９ and R １０ has an ethylenically unsaturated bond.) (In formula (2), 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, wherein the polymer further contains a structural unit having an aromatic ring and a hydroxyl group bonded to the aromatic ring, and which is different from the structural unit represented by formula (1-1) and the structural unit represented by formula (1-2).

3. The radiation-sensitive composition according to claim 1, further comprising a radiation-sensitive acid generator comprising a radiation-sensitive cation and an organic anion.

4. The radiation-sensitive composition according to claim 1, which contains the compound represented by formula (2) as a solvent, and the content of the compound represented by formula (2) is 10 mass % or more based on the total amount of the solvent.

5. The radiation-sensitive composition according to claim 1, which contains, as solvents, the compound represented by formula (2) and another solvent different from the compound represented by formula (2).

6. The radiation-sensitive composition according to claim 5, wherein the other solvent is at least one selected from the group consisting of alcohols, ethers, ketones and esters.

7. A method for forming a resist pattern, comprising: forming a resist film on a substrate using the radiation-sensitive composition according to any one of claims 1 to 6; exposing the resist film; and developing the exposed resist film.

Images