Radiation-sensitive composition, pattern formation method, and radiation-sensitive acid generation agent

Abstract

The purpose of the present invention is to provide a radiation-sensitive composition whereby it is possible to form a resist film capable of exhibiting sensitivity, LWR, MEEF, CDU, development defect performance, pattern rectangularity, and pattern circularity at adequate levels, and a pattern formation method. Another purpose of the present invention is to provide a radiation-sensitive acid generation agent that can be applied to the radiation-sensitive composition. This radiation-sensitive composition contains: a polymer (A) including a structural unit (I) with an acid-dissociable group; a radiation-sensitive acid generation agent (B) represented by formula (1); and a solvent (E).　Chemical Formula 1 (In formula (1), R1 is a hydrogen atom, a nitro group, a hydroxyl group, a cyano group, a carboxy group, a methyl group, or an ethyl group. When there are a plurality of R1, the plurality of R1 are each the same or different from each other. R2 and R3 are each independently a hydrogen atom, a nitro group, a hydroxyl group, a cyano group, a carboxy group, a thiol group, a halogen atom, a monovalent organic group, or a divalent alicyclic group that has 3 to 20 carbon atoms and is formed together with carbon atoms bonding together R2 and R3 when combined. When there are a plurality of R2 and R3, the plurality of R2 and R3 are the same or different from each other. L is a divalent linking group. R4 is a monovalent linear organic group having 3 or more carbon atoms or a monovalent branched organic group having 5 or more carbon atoms. m is an integer of 1 to 5. n is an integer of 0 to 4. M+ is a monovalent onium cation.)

Description

Radiation-sensitive composition, pattern forming method, and radiation-sensitive acid generator

[0001] The present invention relates to a radiation-sensitive composition, a pattern forming method, and a radiation-sensitive acid generator.

[0002] Photolithography techniques using resist compositions are used to form fine circuits in semiconductor elements. A typical procedure involves, for example, exposing a coating of the resist composition to radiation through a mask pattern to generate an acid, which is then catalyzed by a reaction that causes a difference in the solubility of the polymer in alkaline or organic developers between exposed and unexposed areas, thereby forming a resist pattern on a substrate.

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

[0004] As for the photoacid generator, which is a main component of a resist composition, perfluoroalkylsulfonic acids capable of imparting strong acidity are often used in order to improve sensitivity, resolution, etc. Meanwhile, due to the recent increase in environmental awareness, photoacid generators with reduced fluorine atom content have been investigated (see JP 2014-126767 A).

[0005] Japanese Patent Application Laid-Open No. 2014-126767

[0006] Even with a photoacid generator having a reduced content of fluorine atoms, resist performance equivalent to or better than conventional ones is required in terms of LWR (Line Width Roughness), which indicates variations in sensitivity, line width, and line width of a resist pattern, MEEF (Mask Error Enhancement Factor), which is an index indicating mask error tolerance and is the amount of change in line width or hole diameter relative to the amount of change in mask size, CDU (Critical Dimension Uniformity), which is an index of uniformity of line width and hole diameter, development defect performance, pattern rectangularity, pattern circularity, and the like.

[0007] An object of the present invention is to provide a radiation-sensitive composition and a pattern forming method capable of forming a resist film that exhibits sufficient levels of sensitivity, LWR, MEEF, CDU, development defect performance, pattern rectangularity, and pattern circularity. Another object of the present invention is to provide a radiation-sensitive acid generator that can be used in the radiation-sensitive composition.

[0008] As a result of extensive research into solving the above problem, the present inventors have found that the above object can be achieved by employing the following configuration, and have thus completed the present invention.

[0009] That is, in one embodiment, the present invention relates to a radiation-sensitive composition comprising: a polymer (A) including a structural unit (I) having an acid-dissociable group; a radiation-sensitive acid generator (B) represented by the following formula (1); and a solvent (E): (In the above formula (1), R １ is a hydrogen atom, a nitro group, a hydroxyl group, a cyano group, a carboxy group, a methyl group, or an ethyl group. １ If there are multiple R １ are the same or different. ２ and R ３ are each independently a hydrogen atom, a nitro group, a hydroxyl group, a cyano group, a carboxy group, a thiol group, a halogen atom, or a monovalent organic group, or R ２ and R ３ is a divalent alicyclic group having 3 to 20 carbon atoms formed by combining together with the carbon atom to which they are bonded. ２and R ３ If there are multiple R ２ and R ３ are the same or different. L is a divalent linking group. R ４ is a monovalent linear organic group having 3 or more carbon atoms, or a monovalent branched organic group having 5 or more carbon atoms. m is an integer of 1 to 5. n is an integer of 0 to 4. M ＋ is a monovalent onium cation.

[0010] The radiation-sensitive composition contains the radiation-sensitive acid generator (B) represented by the above formula (1), and thereby can form a resist film that exhibits excellent sensitivity, LWR, MEEF, CDU, development defect performance, pattern rectangularity, and pattern circularity at sufficient levels. Without being bound by any theory, the reason for this is presumed to be as follows.

[0011] In a radiation-sensitive acid generator, if only one fluoro group is bonded to the carbon atom adjacent to the sulfonate anion, the acidity of the generated sulfonic acid may be weakened, resulting in insufficient dissociation of the acid-dissociable group in the polymer. In particular, in resists with a resist film thickness of 200 nm or more, the insufficient dissociation of the acid-dissociable group has a significant effect, leading to a deterioration in LWR and frequent occurrence of development defects. However, although the radiation-sensitive acid generator (B) has only one fluoro group bonded to the carbon atom adjacent to the sulfonate anion, the presence of a monovalent linear organic group having 3 or more carbon atoms or a monovalent branched organic group having 5 or more carbon atoms in its structure improves dispersibility and diffusibility, and as a result, various performances such as LWR and development defect performance can be improved regardless of the thickness of the resist film. Furthermore, since the radiation-sensitive acid generator (B) contains few fluorine atoms and has a chain structure, it is believed to be able to suppress aggregation of the acid generated by exposure. This improves the solubility in a developer, and as a result, it is presumed that the radiation-sensitive composition can improve the pattern rectangularity, pattern circularity, etc. Furthermore, when the chain length of the chain organic group in the radiation-sensitive acid generator is short or when two fluoro groups are bonded to the carbon atom adjacent to the sulfonate anion, the generated acid tends to diffuse over a long distance, resulting in poor MEEF. The radiation-sensitive acid generator (B) has a structure that includes a monovalent linear organic group having 3 or more carbon atoms or a monovalent branched organic group having 5 or more carbon atoms, and has one fluoro group bonded to the carbon atom adjacent to the sulfonate anion, and therefore it is presumed that the diffusion of the generated acid can be appropriately suppressed, thereby improving the MEEF. Furthermore, when the carbon atom adjacent to the sulfonate anion has a substituent having 3 or more carbon atoms other than a fluoro group or a highly flexible substituent, the vicinity of the generated sulfonic acid becomes sterically crowded, which may result in a loss of the ability of the polymer to efficiently dissociate the acid-dissociable group, resulting in poor LWR and development defect performance.The radiation-sensitive acid generator (B) has only a relatively small substituent or an electron-withdrawing group, other than a fluoro group, on the carbon atom adjacent to the sulfonate anion, and therefore is thought to be less likely to inhibit the reaction of dissociating the acid-dissociable group of the polymer, thereby improving LWR and development defect performance. Furthermore, the reduction in the fluorine atom content can also limit the environmental impact.

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

[0013] The pattern formation method uses the radiation-sensitive composition capable of forming a resist film that is excellent in sensitivity, LWR, MEEF, CDU, development defect performance, pattern rectangularity, and pattern circularity, and therefore can efficiently form a high-quality resist pattern.

[0014] In another embodiment, the present invention relates to a radiation-sensitive acid generator represented by the following formula (1): (In the above formula (1), R １ R is a hydrogen atom, a nitro group, a hydroxyl group, a cyano group, a carboxy group, a methyl group, or an ethyl group. １ If there are multiple R １ are the same or different. ２ and R ３ are each independently a hydrogen atom, a nitro group, a hydroxyl group, a cyano group, a carboxy group, a thiol group, a halogen atom, or a monovalent organic group, or R ２ and R ３ is a divalent alicyclic group having 3 to 20 carbon atoms formed by combining together with the carbon atom to which they are bonded. ２ and R ３ If there are multiple R ２ and R ３ are the same or different. L is a divalent linking group. R ４is a monovalent linear organic group having 3 or more carbon atoms, or a monovalent branched organic group having 5 or more carbon atoms. m is an integer of 1 to 5. n is an integer of 0 to 4. M ＋ is a monovalent onium cation.

[0015] By preparing a radiation-sensitive composition containing the radiation-sensitive acid generator, it is possible to form a resist film that is excellent in sensitivity, LWR, MEEF, CDU, development defect performance, pattern rectangularity, and pattern circularity.

[0016] Hereinafter, the embodiments of the present invention will be described in detail, but the present invention is not limited to these embodiments. Combinations of preferred embodiments are also preferred.

[0017] <Radiation-Sensitive Composition> The radiation-sensitive composition according to this embodiment (hereinafter also simply referred to as "composition") includes a polymer (A) containing a structural unit (I) having an acid-dissociable group, a radiation-sensitive acid generator (B) represented by the above formula (1), and a solvent (E). The composition may include other optional components as long as the effects of the present invention are not impaired.

[0018] <Polymer (A)> The polymer (A) is an aggregate of polymer chains containing a structural unit having an acid-dissociable group (hereinafter also referred to as "structural unit (I)") (hereinafter this polymer will also be referred to as "base polymer (A)"). The "acid-dissociable group" refers to a group that substitutes a hydrogen atom in a carboxy group, a phenolic hydroxyl group, an alcoholic hydroxyl group, a sulfo group, or the like, and that dissociates under the action of an acid. The radiation-sensitive composition has excellent pattern formability because the polymer (A) contains the structural unit (I).

[0019] In addition to the structural unit (I), the base polymer (A) preferably contains a structural unit (II) containing at least one selected from the group consisting of a lactone structure, a cyclic carbonate structure, and a sultone structure, which will be described later, and may contain structural units other than the structural units (I) and (II). Each structural unit will be described below.

[0020] [Structural Unit (I)] The structural unit (I) is a structural unit having an acid-dissociable group. The "acid-dissociable group" refers to a group that substitutes a hydrogen atom of a carboxy group, a phenolic hydroxyl group, an alcoholic hydroxyl group, a sulfo group, or the like, and dissociates under the action of an acid. The acid generated from the radiation-sensitive acid generator (B), which will be described later, upon exposure dissociates the acid-dissociable group in the structural unit (I) to generate a carboxy group or the like. This results in a difference in solubility in a developer between the exposed and unexposed areas of the resist film, making it possible to form a pattern.

[0021] The structural unit (I) is not particularly limited as long as it contains an acid-dissociable group, and examples thereof include a structural unit having a tertiary alkyl ester moiety, a structural unit having a structure in which the hydrogen atom of a phenolic hydroxyl group is substituted with a tertiary alkyl group, and a structural unit having an acetal bond. From the viewpoint of improving the pattern formability of the radiation-sensitive composition, a structural unit represented by the following formula (2) (hereinafter, also referred to as "structural unit (I-1)") is preferred. (In the above formula (2), R α is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Ａ１ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms. Ａ２ and R Ａ３ are each independently a monovalent chain hydrocarbon group having 1 to 20 carbon atoms or a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, or R Ａ２ and R Ａ３ are combined together with the carbon atoms to which they are bonded to form a divalent alicyclic group having 3 to 20 carbon atoms. m11 and m12 are each independently 0 or 1. However, when m11 is 1, m12 is 1. When m11 is 0, L Ａ１ represents a single bond or a divalent linking group; when m11 is 1, L Ａ１ is a divalent linking group.

[0022] L Ａ１ Examples of the divalent linking group represented by the formula (I) include an alkanediyl group, a cycloalkanediyl group, an alkenediyl group, an arenediyl group, and groups having —CO—, —CS—, —O—, —S—, —SO— between the carbon-carbon bonds of these groups.２ Examples include -, -NR'-, or a group containing a combination of two or more of these, or a group combining these. R' is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. Some or all of the hydrogen atoms in these groups may be substituted with, for example, a halogen atom such as a fluorine atom, a chlorine atom, a bromine atom or an iodine atom; a hydroxy group; a carboxy group; a cyano group; a nitro group; an alkyl group; an alkoxy group; an alkoxycarbonyl group; an alkoxycarbonyloxy group; an acyl group; an acyloxy group, or a group in which the hydrogen atoms of these groups have been substituted with halogen atoms.

[0023] The alkanediyl group is preferably an alkanediyl group having 1 to 8 carbon atoms, such as a methanediyl group, an ethanediyl group, a 1,3-propanediyl group, or a 2,2-propanediyl group.

[0024] Examples of the cycloalkanediyl group include monocyclic cycloalkanediyl groups such as cyclopentanediyl and cyclohexanediyl groups, and polycyclic cycloalkanediyl groups such as norbornanediyl and adamantanediyl groups. The cycloalkanediyl group is preferably a cycloalkanediyl group having 5 to 12 carbon atoms.

[0025] Examples of the alkenediyl group include an ethenediyl group, a propenediyl group, a butenediyl group, etc. The alkenediyl group is preferably an alkenediyl group having 2 to 6 carbon atoms.

[0026] Examples of the arenediyl group include a benzenediyl group, a toluenediyl group, a naphthalenediyl group, etc. The arenediyl group is preferably an arenediyl group having 6 to 15 carbon atoms.

[0027] The above R Ａ１ Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) include a 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] R Ａ１ ~R Ａ３Examples of the monovalent linear hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) include a monovalent linear or branched saturated hydrocarbon group having 1 to 20 carbon atoms, or a monovalent linear or branched unsaturated hydrocarbon group having 2 to 20 carbon atoms. Examples of the monovalent linear or branched saturated hydrocarbon group having 1 to 20 carbon atoms include alkyl groups such as a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, a 2-methylpropyl group, a 1-methylpropyl group, a t-butyl group, an n-pentyl group, an isopentyl group, and a neopentyl group. Examples of the monovalent linear or branched unsaturated hydrocarbon group having 2 to 20 carbon atoms include 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] The above R Ａ１ ~R Ａ３ Examples of the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the formula (I) include monocyclic or polycyclic saturated hydrocarbon groups, and monocyclic or polycyclic unsaturated hydrocarbon groups. Examples of monocyclic saturated hydrocarbon groups include cycloalkyl groups such as cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl. Examples of polycyclic saturated hydrocarbon groups include bridged alicyclic hydrocarbon groups such as norbornyl, adamantyl, tricyclodecyl, and tetracyclododecyl. Examples of monocyclic unsaturated hydrocarbon groups include monocyclic cycloalkenyl groups such as cyclopropenyl, cyclobutenyl, cyclopentenyl, and cyclohexenyl. Examples of polycyclic unsaturated hydrocarbon groups include polycyclic cycloalkenyl groups such as norbornenyl, tricyclodecenyl, and tetracyclododecenyl. The bridged alicyclic hydrocarbon group refers to a polycyclic alicyclic hydrocarbon group in which two carbon atoms that are not adjacent to each other among the carbon atoms that constitute the alicyclic ring are linked by a linking group containing one or more carbon atoms.

[0030] The above R Ａ１ Examples of the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms represented by the formula (I) include aryl groups such as a phenyl group, a tolyl group, a xylyl group, a naphthyl group, and an anthryl group; and aralkyl groups such as a benzyl group, a phenethyl group, and a naphthylmethyl group.

[0031] The above R Ａ１ As the alkyl group, a linear or branched saturated hydrocarbon group having 1 to 20 carbon atoms, or a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms is preferred.

[0032] R Ａ２ and R Ａ３ As the divalent alicyclic group having 3 to 20 carbon atoms constituted by combining these together with the carbon atoms to which they are bonded, a group in which one hydrogen atom has been removed from the above-mentioned monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms can be suitably used.

[0033] R Ａ２ and R Ａ３ is a monovalent chain hydrocarbon group having 1 to 10 carbon atoms, or R Ａ２ and R Ａ３ are combined together together with the carbon atoms to which they are bonded, and a divalent alicyclic group having 3 to 20 carbon atoms is preferred, a monovalent linear hydrocarbon group having 1 to 10 carbon atoms or a divalent alicyclic group having 5 to 10 carbon atoms is more preferred, and as the monovalent linear hydrocarbon group having 1 to 10 carbon atoms or the divalent alicyclic group having 5 to 10 carbon atoms, a methyl group, an ethyl group, an isopropyl group, a tert-butyl group, a cyclopentanediyl group, a cyclohexanediyl group, or an adamantanediyl group is even more preferred.

[0034] When m11 is 0, L Ａ１ is preferably a single bond or an arenediyl group. Ａ１ is preferably an alkanediyl group.

[0035] Examples of the structural unit (I) include structural units represented by the following formulas (1-1) to (1-14) (hereinafter also referred to as "structural units (I-1) to (I-14)").

[0036]

[0037]

[0038] In the above formulas (1-1) to (1-14), R α , R Ａ１ ~R Ａ３has the same meaning as in formula (2) above. X is a hydroxy group, a halogen atom, a carboxy group, a cyano group, a nitro group, an alkyl group, a fluorinated alkyl group, an alkoxycarbonyloxy group, an acyl group, an acyloxy group, or an alkoxy group. i and j are each independently an integer of 1 to 4. k and l are 0 or 1. a1 is an integer of 0 to 3. When a1 is 2 or more, multiple Xs are the same or different. a4 is an integer of 1 to 3.

[0039] i and j are preferably 1 or 2. k and l are preferably 1. R Ａ１ R is preferably a methyl group, an ethyl group, an isopropyl group, a t-butyl group, a phenyl group, or an iodophenyl group. Ａ２ and R Ａ３ As X, a methyl group, an ethyl group, or an isopropyl group is preferable. As X, a hydroxy group, an iodine atom, or an alkyl group is preferable.

[0040] Furthermore, the polymer (A) may contain, as the structural unit (I), structural units represented by the following formulae (1f) to (2f).

[0041]

[0042] In the above formulas (1f) to (2f), R αｆ R are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. βｆ are each independently a hydrogen atom or a chain alkyl group having 1 to 5 carbon atoms. h1 is an integer of 1 to 4.

[0043] The above R βｆ is preferably a hydrogen atom, a methyl group or an ethyl group. h1 is preferably 1 or 2.

[0044] Specific examples of the structural unit (I) include, but are not limited to, those shown below.

[0045] (In the formula, R α is the same as the above formula (2).

[0046] (In the formula, R α is the same as the above formula (2).

[0047] The base polymer (A) may contain one type of structural unit (I) or a combination of two or more types.

[0048] The lower limit of the content of the structural unit (I) (the total content when multiple types are contained) relative to all structural units constituting the base polymer (A) is preferably 5 mol%, more preferably 7 mol%, and even more preferably 10 mol%. The upper limit of the content is preferably 80 mol%, more preferably 70 mol%, and even more preferably 60 mol%. By setting the content of the structural unit (I) within the above range, the pattern formability of the radiation-sensitive composition can be further improved.

[0049] [Structural Unit (II)] The structural unit (II) is a structural unit containing at least one selected from the group consisting of a lactone structure, a cyclic carbonate structure, a sultone structure, and a cyclic sulfone structure. By further containing the structural unit (II), the base polymer (A) can adjust its solubility in a developer, and as a result, the radiation-sensitive composition can improve its lithography performance, such as resolution. In addition, the adhesion between a resist pattern formed from the base polymer (A) and a substrate can be improved.

[0050] Examples of the structural unit (II) include structural units represented by the following formulae (T-1) to (T-11).

[0051]

[0052] In the above formula, R Ｌ１ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Ｌ２ ~R Ｌ５ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a cyano group, a trifluoromethyl group, a methoxy group, a methoxycarbonyl group, a hydroxy group, a hydroxymethyl group, a dimethylamino group, or —COOR Ｌ６ It is. Ｌ６ is a monovalent hydrocarbon group having 1 to 20 carbon atoms. Ｌ４ and R Ｌ５may be combined with each other to form a divalent alicyclic hydrocarbon group having 3 to 8 carbon atoms together with the carbon atoms to which they are attached. ２ is a single bond or a divalent linking group. X is an oxygen atom or a methylene group. k is an integer of 0 to 3. m is an integer of 1 to 3.

[0053] The above R Ｌ４ and R Ｌ５ Examples of the divalent alicyclic hydrocarbon group having 3 to 8 carbon atoms formed by combining these groups together with the carbon atoms to which they are bonded include R Ａ２ and R Ａ３ Among divalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms which are formed by combining together with the carbon atoms to which they are bonded, groups having 3 to 8 carbon atoms are exemplified. One or more hydrogen atoms on this alicyclic hydrocarbon group may be substituted with a hydroxy group.

[0054] The above R Ｌ６ The monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the formula (2) is R Ａ１ A monovalent hydrocarbon group having 1 to 20 carbon atoms and represented by the following formula can be suitably used.

[0055] The above L ２ Examples of the divalent linking group represented by the formula (I) include a divalent linear or branched hydrocarbon group having 1 to 10 carbon atoms, a divalent alicyclic hydrocarbon group having 4 to 12 carbon atoms, or a group composed of one or more of these hydrocarbon groups and at least one group selected from -CO-, -O-, -NH-, and -S-.

[0056] The above L ２ As the divalent linear or branched hydrocarbon group having 1 to 10 carbon atoms in the formula (2), R Ａ１ A group in which one hydrogen atom has been removed from a chain hydrocarbon group having 1 to 20 carbon atoms, represented by the following formula, can be suitably used.

[0057] The above L ２ As the divalent alicyclic hydrocarbon group having 4 to 12 carbon atoms, R Ａ１ A group in which one hydrogen atom has been removed from a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, represented by the following formula, can be suitably used.

[0058] Of these, the structural unit (II) is preferably a structural unit containing a lactone structure, more preferably a structural unit containing a norbornane lactone structure, and even more preferably a structural unit derived from norbornane lactone-yl (meth)acrylate.

[0059] The base polymer (A) may contain one type of structural unit (II) or a combination of two or more types.

[0060] When the base polymer (A) contains the structural unit (II), the lower limit of the content of the structural unit (II) (the total content when multiple types are contained) is preferably 5 mol%, more preferably 10 mol%, and even more preferably 15 mol%, based on all structural units constituting the base polymer (A). The upper limit of the content is preferably 80 mol%, more preferably 70 mol%, and even more preferably 60 mol%. By setting the content of the structural unit (II) within the above range, the radiation-sensitive composition can further improve lithography performance such as resolution and adhesion of the formed resist pattern to the substrate.

[0061] [Structural Unit (III)] The base polymer (A) optionally contains other structural units in addition to the structural units (I) and (II). Examples of the other structural units include a structural unit (III) containing a polar group (excluding those corresponding to the structural unit (II)). By further containing the structural unit (III), the base polymer (A) can adjust its solubility in a developer, thereby improving the lithography performance, such as the resolution, of the radiation-sensitive composition. Examples of the polar group include a hydroxy group, a carboxy group, a cyano group, a nitro group, and a sulfonamide group. Among these, a hydroxy group and a carboxy group are preferred, and a hydroxy group is more preferred.

[0062] Examples of the structural unit (III) include structural units represented by the following formula:

[0063]

[0064]

[0065] In the above formula, R Ｋ is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.

[0066] When the base polymer (A) contains the structural unit (III), the lower limit of the content of the structural unit (III) is preferably 1 mol%, more preferably 3 mol%, and even more preferably 5 mol%, based on the total structural units constituting the base polymer. The upper limit of the content is preferably 80 mol%, more preferably 70 mol%, and even more preferably 65 mol%. By setting the content of the structural unit (III) within the above range, the lithography performance, such as resolution, of the radiation-sensitive composition can be further improved.

[0067] [Structural Unit (IV)] In addition to the structural unit (III) having the polar group, the base polymer (A) optionally has, as other structural units, a structural unit derived from hydroxystyrene or a structural unit having a phenolic hydroxyl group (hereinafter, both of these are also referred to as "structural unit (IV)"). The structural unit (IV) contributes to improving etching resistance and improving the difference in developer solubility (dissolution contrast) between exposed and unexposed areas. In particular, it is suitable for pattern formation using exposure to radiation with a wavelength of 50 nm or less, such as electron beams or EUV. In this case, it is preferable that the polymer has the structural unit (I) in addition to the structural unit (IV).

[0068] The structural units derived from hydroxystyrene are represented, for example, by the following formulas (4-1) to (4-3), and the structural units having a phenolic hydroxyl group are represented, for example, by the following formulas (4-4) to (4-6).

[0069]

[0070] In the above formulas (4-1) to (4-6), R ４１are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Y is a halogen atom, a trifluoromethyl group, a cyano group, an alkyl group or an alkoxy group having 1 to 6 carbon atoms, or an acyl group, acyloxy group, or alkoxycarbonyl group having 2 to 7 carbon atoms. When there are multiple Ys, the multiple Ys are the same or different. t is an integer of 0 to 4.

[0071] In order to obtain the structural unit (IV), it is preferable to carry out polymerization in a state in which the phenolic hydroxyl group is protected with a protecting group such as an alkali-dissociable group (e.g., an acyl group) during polymerization, and then to obtain the structural unit (IV) by deprotecting the phenolic hydroxyl group by hydrolysis. Alternatively, a monomer that gives the structural unit (IV) may be polymerized without protecting the phenolic hydroxyl group.

[0072] In the case of a polymer intended for exposure to radiation having a wavelength of 50 nm or less, the lower limit of the content of the structural unit (IV) is preferably 10 mol %, more preferably 20 mol %, based on the total structural units constituting the base polymer (A), and the upper limit of this content is preferably 80 mol %, more preferably 70 mol %.

[0073] [Other Structural Units] The base polymer (A) may contain, as a structural unit other than the structural units listed above, a structural unit having an alicyclic structure represented by the following formula (6) (hereinafter also referred to as "structural unit (VII)"). (In the above formula (6), R １α is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ２α is a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms.

[0074] In the above formula (6), R ２α The monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the formula (2) is R Ａ１ A monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms and represented by the following formula can be suitably used.

[0075] When the base polymer (A) contains the structural unit (VII), the lower limit of the content of the structural unit (VII) is preferably 2 mol%, more preferably 5 mol%, and even more preferably 8 mol%, based on the total structural units constituting the base polymer, and the upper limit of the content is preferably 30 mol%, more preferably 20 mol%, and even more preferably 15 mol%.

[0076] (Method of Synthesizing Base Polymer) The base polymer can be synthesized, for example, by polymerizing monomers that provide each structural unit in an appropriate solvent using a radical polymerization initiator or the like.

[0077] Examples of the radical polymerization initiator include azo radical initiators such as azobisisobutyronitrile (AIBN), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2-cyclopropylpropionitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), and dimethyl 2,2'-azobisisobutyrate; and peroxide radical initiators such as benzoyl peroxide, t-butyl hydroperoxide, and cumene hydroperoxide. Of these, AIBN and dimethyl 2,2'-azobisisobutyrate are preferred, and AIBN is more preferred. These radical initiators can be used alone or in combination of two or more.

[0078] Examples of the solvent used in the polymerization include alkanes such as n-pentane, n-hexane, n-heptane, n-octane, n-nonane, and n-decane; cycloalkanes such as cyclohexane, cycloheptane, cyclooctane, decalin, and norbornane; aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, and cumene; halogenated hydrocarbons such as chlorobutanes, bromohexanes, dichloroethanes, hexamethylene dibromide, and chlorobenzene; saturated carboxylic acid esters such as ethyl acetate, n-butyl acetate, i-butyl acetate, and methyl propionate; lactones such as γ-butyrolactone and δ-valerolactone; ketones such as acetone, 2-butanone, 4-methyl-2-pentanone, 2-heptanone, and cyclohexanone; ethers such as cyclic ethers such as propylene glycol monomethyl ether, dimethoxyethanes, diethoxyethanes, tetrahydrofuran, and 1,4-dioxane; Examples of the solvent include alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-methoxy-2-propanol, and 4-methyl-2-pentanol; polyhydric alcohol partial ether acetate solvents such as diethylene glycol mono-n-butyl ether acetate, propylene glycol monomethyl ether acetate (PGMEA), and dipropylene glycol monomethyl ether acetate; etc. These solvents used in the polymerization may be used alone or in combination of two or more.

[0079] The reaction temperature in the polymerization is usually 40° C. to 150° C., preferably 50° C. to 120° C. The reaction time is usually 1 hour to 48 hours, preferably 1 hour to 24 hours.

[0080] The molecular weight of the base polymer is not particularly limited, but the lower limit of the weight average molecular weight (Mw) in terms of polystyrene measured by gel permeation chromatography (GPC) is preferably 2,000, more preferably 3,000, even more preferably 4,000, and particularly preferably 4,500. The upper limit of Mw is preferably 30,000, more preferably 20,000, even more preferably 12,000, and particularly preferably 10,000. By setting the Mw of the base polymer within the above range, it is possible to impart good developability to the resulting resist film.

[0081] The ratio (Mw / Mn) of Mw to the polystyrene-equivalent number average molecular weight (Mn) of the base polymer as determined by GPC is usually 1 or more and 5 or less, preferably 1 or more and 3 or less, and more preferably 1 or more and 2 or less.

[0082] The Mw and Mn of the polymer in this specification are values ​​measured using gel permeation chromatography (GPC) under the following conditions.

[0083] GPC columns: two G2000HXL, one G3000HXL, one G4000HXL (all manufactured by Tosoh Corporation) Column temperature: 40°C Elution solvent: tetrahydrofuran Flow rate: 1.0 mL / min Sample concentration: 1.0 mass% Sample injection volume: 100 μL Detector: differential refractometer Standard material: monodisperse polystyrene

[0084] The content of the base polymer (A) is preferably 60% by mass or more, more preferably 65% ​​by mass or more, and even more preferably 70% by mass or more, based on the total solid content of the radiation-sensitive composition.

[0085] <Radiation-Sensitive Acid Generator (B)> The radiation-sensitive acid generator (B) is represented by the following formula (1). (In the above formula (1), R １ is a hydrogen atom, a nitro group, a hydroxyl group, a cyano group, a carboxy group, a methyl group, or an ethyl group. １ If there are multiple R １ are the same or different. ２ and R ３are each independently a hydrogen atom, a nitro group, a hydroxyl group, a cyano group, a carboxy group, a thiol group, a halogen atom, or a monovalent organic group, or R ２ and R ３ is a divalent alicyclic group having 3 to 20 carbon atoms formed by combining together with the carbon atom to which they are bonded. ２ and R ３ If there are multiple R ２ and R ３ are the same or different. L is a divalent linking group. R ４ is a monovalent linear organic group having 3 or more carbon atoms, or a monovalent branched organic group having 5 or more carbon atoms. m is an integer of 1 to 5. n is an integer of 0 to 4. M ＋ is a monovalent onium cation.

[0086] The radiation-sensitive acid generator (B) has a function of generating an acid by exposure to dissociate an acid-dissociable group contained in the polymer, thereby generating a carboxyl group or the like.

[0087] The above R １ is a hydrogen atom, a nitro group, a hydroxyl group, a cyano group, a carboxy group, a methyl group, or an ethyl group, and among these, a hydrogen atom, a cyano group, or a methyl group is preferred, and a hydrogen atom or a cyano group is particularly preferred.

[0088] The above R ２ and R ３ Examples of the monovalent organic group represented by the formula (I) include a monovalent hydrocarbon group having 1 to 20 carbon atoms, a group having a divalent heteroatom-containing group between carbon atoms of the hydrocarbon group or at the carbon chain terminal, a group in which some or all of the hydrogen atoms of the hydrocarbon group have been substituted with a monovalent heteroatom-containing group, or a combination thereof.

[0089] The monovalent hydrocarbon group having 1 to 20 carbon atoms in the organic group is R Ａ１ A monovalent hydrocarbon group having 1 to 20 carbon atoms and represented by the following formula can be suitably used.

[0090] Examples of heteroatoms constituting the monovalent heteroatom-containing group and divalent heteroatom-containing group include oxygen atoms, nitrogen atoms, sulfur atoms, phosphorus atoms, silicon atoms, and halogen atoms. Examples of halogen atoms include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms.

[0091] Examples of the monovalent heteroatom-containing group include a hydroxy group, a carboxy group, a sulfanyl group, a cyano group, a nitro group, and a halogen atom.

[0092] Examples of the divalent heteroatom-containing group include -CO-, -C(=O)O-, -CS-, -NH-, -O-, -S-, -SO-, and -SO ２ -, or a combination thereof.

[0093] The above R ２ and R ３ Examples of the divalent alicyclic group having 3 to 20 carbon atoms formed by combining these groups together with the carbon atoms to which they are bonded include R Ａ２ and R Ａ３ A divalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, which is formed by combining these together with the carbon atom to which they are bonded, can be suitably used.

[0094] The above R ２ and R ３ is a hydrogen atom, a monovalent non-fluorine-containing organic group, or R ２ and R ３ are combined with each other together with the carbon atoms to which they are bonded, forming a divalent alicyclic group having 3 to 20 carbon atoms. Here, the "fluorine-free organic group" is a monovalent organic group described above that does not contain a fluorine atom.

[0095] The divalent linking group represented by L includes an ester bond (-C(=O)O-), an amide bond (-C(=O)NR Ｌ -), ether bond (-O-), sulfonyl bond (-SO ２It is preferable that the R in the amide bond is a linking group containing at least one bond selected from the group consisting of a carbonyl group (-C(=O)-), a carbonyl group (-C(=O)-), and a carbonate bond (-OC(=O)O-). Ｌ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. Among these, a linking group containing at least one bond selected from the group consisting of an ester bond, an ether bond, an amide bond, and a carbonate bond is preferred, and a linking group containing an ester bond or a carbonate bond is more preferred.

[0096] The divalent linear or branched hydrocarbon group having 1 to 10 carbon atoms includes R Ａ１ A group in which one hydrogen atom has been removed from a chain hydrocarbon group having 1 to 20 carbon atoms, represented by the following formula, can be suitably used.

[0097] The above R ４ The monovalent linear organic group having 3 or more carbon atoms and represented by the formula (I) refers to a group having 3 or more carbon atoms, a chain structure not containing a cyclic structure, and not containing a branched structure. ２ and R ３ Among the monovalent organic groups represented by the formula (I), those having 3 or more carbon atoms, a chain structure not containing a cyclic structure, and not containing a branched structure can be preferably used. In the present disclosure, the term "organic group" refers to a group containing at least one carbon atom and not containing an ionic structure.

[0098] The above R ４ The monovalent branched organic group having 5 or more carbon atoms and represented by the formula (I) refers to a group having 5 or more carbon atoms, a chain structure not containing a cyclic structure, and further containing a branched structure. ２ and R ３ Among the monovalent organic groups represented by the following formula, those having 5 or more carbon atoms, a chain structure not containing a cyclic structure, and further containing a branched structure can be suitably used.

[0099] Among these, the above R ４From the viewpoint of MEEF, the alkyl group is preferably a monovalent chain organic group (straight-chain organic group, branched-chain organic group) having 5 to 20 carbon atoms, and more preferably a monovalent chain organic group (straight-chain organic group, branched-chain organic group) having 5 to 15 carbon atoms.

[0100] In addition, the above R ４ is a difluoromethylene group (-CF ２ -) is preferably not included.

[0101] m is an integer of 1 to 5, preferably an integer of 1 to 3, and more preferably 1 or 2.

[0102] n is an integer of 0 to 4, preferably an integer of 0 to 3, and more preferably 0 or 1.

[0103] Specific examples of the anion of the radiation-sensitive acid generator (B) include, but are not limited to, structures of the following formulas:

[0104]

[0105]

[0106]

[0107] In the above formula (1), the above M ＋ The onium cation represented by the formula (X) is preferably a radiation-sensitive onium cation, and examples thereof include radiation-decomposable onium cations containing elements such as S, I, O, N, P, Cl, Br, F, As, Se, Sn, Sb, Te, and Bi. Examples of the radiation-decomposable onium cation include sulfonium cation, tetrahydrothiophenium cation, iodonium cation, phosphonium cation, diazonium cation, and pyridinium cation. Of these, sulfonium cation or iodonium cation is preferred. The sulfonium cation or iodonium cation is preferably represented by the following formulas (X-1) to (X-6).

[0108]

[0109] In the above formula (X-1), R ａ１ , R ａ２and R ａ３ are each independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, an alkoxy group or an alkoxycarbonyloxy group, a substituted or unsubstituted monocyclic or polycyclic cycloalkyl group having 3 to 12 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, a hydroxy group, a halogen atom, or —OSO ２ -R Ｐ , -SO ２ -R Ｑ , -S-R Ｔ , —O—, —CO—, or a combination thereof, or a ring structure formed by combining two or more of these groups. The ring structure may contain a heteroatom such as O or S between the carbon-carbon bonds that form the skeleton. Ｐ , R Ｑ and R Ｔ are each independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted alicyclic hydrocarbon group having 5 to 25 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms. k1, k2, and k3 are each independently an integer of 0 to 5. R ａ１ ~R ａ３ and R Ｐ , R Ｑ and R Ｔ If there are multiple R ａ１ ~R ａ３ and R Ｐ , R Ｑ and R Ｔ may be the same or different.

[0110] In the above formula (X-2), R ｂ１ is a substituted or unsubstituted linear or branched alkyl group or alkoxy group having 1 to 20 carbon atoms, an alkoxyalkyloxy group, a substituted or unsubstituted acyl group having 2 to 8 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 8 carbon atoms, or a hydroxy group. ｋ is 0 or 1. ｋ When is 0, k4 is an integer from 0 to 4, and n ｋ When is 1, k4 is an integer from 0 to 7. ｂ１If there are multiple R ｂ１ may be the same or different, and multiple R ｂ１ may represent a ring structure formed by combining with each other. ｂ２ is a substituted or unsubstituted linear or branched alkyl group having 1 to 7 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 or 7 carbon atoms. Ｃ is a single bond or a divalent linking group. k5 is an integer of 0 to 4. R ｂ２ If there are multiple R ｂ２ may be the same or different, and multiple R ｂ２ may represent a ring structure formed by combining with each other, and q is an integer of 0 to 3. ＋ The ring structure containing the following may contain a heteroatom such as O or S between the carbon-carbon bonds that form the skeleton.

[0111] In the above formula (X-3), R ｃ１ , R ｃ２ and R ｃ３ are each independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms.

[0112] In the above formula (X-4), R ｇ１ is a substituted or unsubstituted linear or branched alkyl or alkoxy group having 1 to 20 carbon atoms, a substituted or unsubstituted acyl group having 2 to 8 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 8 carbon atoms, or a hydroxy group. ｋ２ is 0 or 1. ｋ２ When is 0, k10 is an integer from 0 to 4, and n ｋ２ When is 1, k10 is an integer from 0 to 7. ｇ１ If there are multiple R ｇ１ may be the same or different, and multiple R ｇ１ may represent a ring structure formed by combining with each other. ｇ２ and R ｇ３are each independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, an alkoxy group or an alkoxycarbonyloxy group, a substituted or unsubstituted monocyclic or polycyclic cycloalkyl group having 3 to 12 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, a hydroxy group, a halogen atom, or a ring structure formed by combining these groups together. k11 and k12 are each independently an integer of 0 to 4. R ｇ２ and R ｇ３ If there are multiple R ｇ２ and R ｇ３ may be the same or different.

[0113] In the above formula (X-5), R ｄ１ and R ｄ２ are each independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, an alkoxy group or an alkoxycarbonyl group, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, a halogen atom, a halogenated alkyl group having 1 to 4 carbon atoms, a nitro group, or a ring structure formed by combining two or more of these groups. k6 and k7 are each independently an integer of 0 to 5. R ｄ１ and R ｄ２ If there are multiple R ｄ１ and R ｄ２ may be the same or different.

[0114] In the above formula (X-6), R ｅ１ and R ｅ２ are each independently a halogen atom, a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms. k8 and k9 are each independently an integer of 0 to 4.

[0115] Specific examples of the radiation-sensitive onium cation include, but are not limited to, structures of the following formulae (1-2-1) to (1-2-64).

[0116] (In the formula, tBu represents a t-butyl group, and Me represents a methyl group.)

[0117]

[0118]

[0119]

[0120] The radiation-sensitive acid generator (B) can be obtained by appropriately combining the above-mentioned anions with the above-mentioned radiation-sensitive onium cations. Specific examples include, but are not limited to, structures of the following formulae (1-3-1) to (1-3-32).

[0121]

[0122]

[0123]

[0124]

[0125]

[0126]

[0127]

[0128]

[0129] The lower limit of the content of the radiation-sensitive acid generator (B) (the total amount of the radiation-sensitive acid generators (B) when multiple types of the radiation-sensitive acid generators (B) are included) is preferably 1 part by mass, more preferably 3 parts by mass, and even more preferably 5 parts by mass, per 100 parts by mass of the polymer (A). The upper limit of the content is preferably 30 parts by mass, more preferably 25 parts by mass. The content of the radiation-sensitive acid generator (B) is appropriately selected depending on the type of polymer used, exposure conditions, desired sensitivity, and the like. This allows excellent sensitivity, LWR, and pattern rectangularity to be exhibited during resist pattern formation.

[0130] The radiation-sensitive composition may contain other radiation-sensitive acid generators (for example, the following radiation-sensitive acid generator (P1)) in addition to the radiation-sensitive acid generator (B).

[0131] <Radiation-sensitive acid generator (P1)> Examples of the radiation-sensitive acid generator (P1) include onium salt compounds (P1) represented by the following formula (P1) (excluding those corresponding to the radiation-sensitive acid generator (B)): (In formula (P1), R ４０ R is a monovalent organic group having 1 to 40 carbon atoms. ｆ２１ and R ｆ２２ are each independently a hydrogen atom, a cyano group, a fluorine atom, or a monovalent fluorinated hydrocarbon group, provided that R bonded to the carbon atom adjacent to the sulfonate anion ｆ２１ and R ｆ２２ At least one of R is a fluorine atom, a cyano group, or a monovalent fluorinated hydrocarbon group. ｆ２１ and R ｆ２２ If there are multiple R ｆ２１ and R ｆ２２ are the same or different, and n is an integer of 1 to 4. Z ２ ＋ is a radiation-sensitive onium cation.

[0132] R ４０ The monovalent organic group having 1 to 40 carbon atoms represented by the formula (1) is R ２ and R ３ A monovalent organic group represented by the following formula can be suitably used.

[0133] R ｆ２１ and R ｆ２２ The monovalent fluorinated hydrocarbon group represented by the formula (2) is R Ａ１ and groups in which some or all of the hydrogen atoms of a monovalent hydrocarbon group having 1 to 20 carbon atoms, represented by the following formula, have been substituted with fluorine atoms.

[0134] Specific examples of the anion of the onium salt compound (P1) include, but are not limited to, structures of the following formulae:

[0135]

[0136]

[0137]

[0138]

[0139]

[0140] Specific examples of the radiation-sensitive onium cation of the onium salt compound (P1) are not limited, but the structures given as specific examples of the radiation-sensitive onium cation of the above formula (1) can be suitably used.

[0141] The onium salt compound (P1) may have a structure in which the above anion and the above radiation-sensitive onium cation are combined in any order.

[0142] Examples of the onium salt compound (P1) include compounds represented by the following formula:

[0143]

[0144]

[0145]

[0146] In addition, as a radiation-sensitive acid generator other than the onium salt compound (P1), an inner salt compound (P2) containing a cation and an anion in the same molecule, represented by the following formula (Y-1), can also be used.

[0147] In the above formula (Y-1), R ａ１ , R ａ２ , R ａ３ , k1, k2, and k3 have the same meanings as in formula (X-1) above. ａ１ is a single bond or a divalent linking group. ａ , X ｂ are each independently a hydrogen atom, a fluorine atom, or a trifluoromethyl group, and k11 is an integer of 1 to 4.

[0148] Examples of the divalent linking group include the L ２ and the above-mentioned divalent heteroatom-containing groups can be suitably employed.

[0149] Specific examples of the radiation-sensitive onium cation represented by formula (Y-1) above include, but are not limited to, structures of the following formulae (1-4-1) to (1-4-9).

[0150]

[0151] When the radiation-sensitive composition contains a radiation-sensitive acid generator (P1), the lower limit of the content of the radiation-sensitive acid generator (P1) (when multiple types of onium salt compounds (P1) and / or inner salt compounds (P2) are contained, the total amount thereof) is preferably 0.5 parts by mass, more preferably 1 part by mass, and even more preferably 1.5 parts by mass, relative to 100 parts by mass of the polymer (A). The upper limit of the content is preferably 50 parts by mass, more preferably 40 parts by mass, even more preferably 30 parts by mass, and particularly preferably 25 parts by mass. The content of the radiation-sensitive acid generator other than the radiation-sensitive acid generator (B) is appropriately selected depending on the type of polymer used, the exposure conditions, the desired sensitivity, and the like.

[0152] <Acid Diffusion Controller (D)> The radiation-sensitive composition may contain an acid diffusion controller (D) as needed. The acid diffusion controller (D) controls the diffusion phenomenon in the resist film of the acid generated from the radiation-sensitive acid generator upon exposure, thereby suppressing undesirable chemical reactions in unexposed regions. The storage stability of the resulting radiation-sensitive composition is also improved. Furthermore, the resolution of the resist pattern is further improved, and changes in the line width of the resist pattern due to variations in the incubation time from exposure to development can be suppressed, resulting in a radiation-sensitive composition with excellent process stability.

[0153] Examples of the acid diffusion controller (D) include a compound represented by the following formula (7) (hereinafter also referred to as "nitrogen-containing compound (I)"), a compound having two nitrogen atoms in the same molecule (hereinafter also referred to as "nitrogen-containing compound (II)"), a compound having three nitrogen atoms (hereinafter also referred to as "nitrogen-containing compound (III)"), an amide group-containing compound, a urea compound, and a nitrogen-containing heterocyclic compound.

[0154]

[0155] In the above formula (7), R ２２ , R２３ and R ２４ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted aralkyl group.

[0156] Examples of the nitrogen-containing compound (I) include monoalkylamines such as n-hexylamine; dialkylamines such as di-n-butylamine; trialkylamines such as triethylamine and triamylamine; and aromatic amines such as aniline and 2,6-di-i-propylaniline.

[0157] Examples of the nitrogen-containing compound (II) include ethylenediamine and N,N,N',N'-tetramethylethylenediamine.

[0158] Examples of the nitrogen-containing compound (III) include polyamine compounds such as polyethyleneimine and polyallylamine; and polymers such as dimethylaminoethylacrylamide.

[0159] Examples of the amide group-containing compound include formamide, N-methylformamide, N,N-dimethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, propionamide, benzamide, pyrrolidone, and N-methylpyrrolidone.

[0160] Examples of the urea compound include urea, methylurea, 1,1-dimethylurea, 1,3-dimethylurea, 1,1,3,3-tetramethylurea, 1,3-diphenylurea, and tributylthiourea.

[0161] Examples of the nitrogen-containing heterocyclic compound include pyridines such as pyridine and 2-methylpyridine; morpholines such as N-propylmorpholine and N-(undecylcarbonyloxyethyl)morpholine; pyrazine, pyrazole, and the like.

[0162] Furthermore, a compound having an acid-dissociable group can also be used as the nitrogen-containing organic compound. Examples of such nitrogen-containing organic compounds having an acid-dissociable group include N-t-butoxycarbonylpiperidine, N-t-butoxycarbonylimidazole, N-t-butoxycarbonylbenzimidazole, N-t-butoxycarbonyl-2-phenylbenzimidazole, N-(t-butoxycarbonyl)di-n-octylamine, N-(t-butoxycarbonyl)diethanolamine, N-(t-butoxycarbonyl)dicyclohexylamine, N-(t-butoxycarbonyl)diphenylamine, N-t-butoxycarbonyl-4-hydroxypiperidine, N-t-butoxycarbonyl-4-acetoxypiperidine, and N-t-amyloxycarbonyl-4-hydroxypiperidine.

[0163] Furthermore, as the acid diffusion controller (D), an onium salt compound (d) that generates an acid with a higher pKa than the acid generated from the radiation-sensitive acid generator upon irradiation with radiation can also be suitably used. The acid generated from the onium salt compound (d) is a weak acid that does not induce dissociation of the acid-dissociable group in the polymer under conditions that dissociate the acid-dissociable group. In this specification, "dissociation" of the acid-dissociable group refers to dissociation upon post-exposure baking at 110°C for 60 seconds.

[0164] The onium salt compound (d) is preferably represented by the following formulas (8-1) to (8-4).

[0165] In the above formula (8-1) and formula (8-2), J ＋ is a sulfonium cation, and U ＋ is an iodonium cation. E in the above formula (8-1) and formula (8-2) － and Q － are each independently R ８ SO ３ － , R ８ COO － , and (R ８ SO ２ ) N － Preferably, R is at least one selected from the group consisting of８ COO － Further, examples of the compound include a compound represented by the above formula (8-3) containing a sulfonium cation and an anion in the same molecule, and a compound represented by the above formula (8-4) containing an iodonium cation and an anion in the same molecule. In the above formulas (8-3) and (8-4), J' ＋ is a monovalent group having a sulfonium cation structure, and U' ＋ is a monovalent group having an iodonium cation structure. － and Q' － are each independently -R ８１ SO ３ － , -R ８１ COO － , and -R ８１ SO ２ N － SO ２ R ８ Preferably, the group is at least one selected from the group consisting of -R ８１ COO － It is more preferable that the above R ８ is a monovalent organic group, and the R ８１ is a single bond or a divalent organic group.

[0166] The monovalent organic group is R ２ and R ３ A monovalent organic group represented by the following formula can be suitably used.

[0167] The divalent organic group is R ２ and R ３ A group in which one hydrogen atom has been removed from a monovalent organic group represented by the following formula can be suitably used.

[0168] Examples of the onium salt compound (d) include compounds represented by the following formula:

[0169]

[0170]

[0171] The onium salt compound (d) can be synthesized by a known method, particularly a salt exchange reaction. Known acid diffusion controllers other than those mentioned above can also be used as long as they do not impair the effects of the present invention.

[0172] These acid diffusion controllers (D) may be used alone or in combination of two or more. The lower limit of the content of the acid diffusion controller (D) (total amount when multiple types are used) is preferably 0.1 parts by mass, more preferably 0.5 parts by mass, and even more preferably 1 part by mass, per 100 parts by mass of the polymer (A). The upper limit of the content is preferably 50 parts by mass, more preferably 40 parts by mass, and even more preferably 30 parts by mass. This allows excellent sensitivity and CDU to be exhibited during resist pattern formation.

[0173] <Other Polymers> The radiation-sensitive composition of the present embodiment may contain, as another polymer, a polymer having a higher mass content of fluorine atoms than the base polymer (hereinafter also referred to as a "high-fluorine content polymer"). When the radiation-sensitive composition contains a high-fluorine content polymer, the high-fluorine content polymer can be unevenly distributed in the surface layer of the resist film relative to the base polymer. As a result, it is possible to increase the water repellency of the surface of the resist film during immersion exposure, and to modify the surface of the resist film during EUV exposure and control the distribution of composition within the film.

[0174] The high-fluorine content polymer preferably has, for example, a structural unit represented by the following formula (5) (hereinafter also referred to as "structural unit (V)"), and may have the structural unit (I) or the structural unit (III) of the base polymer, as necessary.

[0175]

[0176] In the above formula (5), R ７３ is a hydrogen atom, a methyl group, or a trifluoromethyl group. Ｌ represents a single bond, an alkanediyl group having 1 to 5 carbon atoms, an oxygen atom, a sulfur atom, —COO—, —OCO—, or —SO ２ ONH-, -CONH-, -OCONH- or a combination thereof. ７４is a monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms or a monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms.

[0177] The above R ７３ As the alkyl group, from the viewpoint of copolymerizability of the monomer that gives the structural unit (V), a hydrogen atom or a methyl group is preferred, and a methyl group is more preferred.

[0178] Above G Ｌ As the alkyl group, from the viewpoint of copolymerizability of the monomer that provides the structural unit (V), a combination of at least one of a single bond, —COO—, —COO—, and —OCO— with an alkanediyl group having 1 to 5 carbon atoms is preferred, and —COO— is more preferred.

[0179] The above R ７４ Examples of the monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) include a linear or branched alkyl group having 1 to 20 carbon atoms in which some or all of the hydrogen atoms have been substituted with fluorine atoms.

[0180] The above R ７４ Examples of the monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the formula (I) include monocyclic or polycyclic hydrocarbon groups having 3 to 20 carbon atoms in which some or all of the hydrogen atoms have been substituted with fluorine atoms.

[0181] The above R ７４ As the alkyl group, a fluorinated chain hydrocarbon group is preferred, and a fluorinated alkyl group is more preferred.

[0182] When the high-fluorine content polymer has the structural unit (V), the lower limit of the content of the structural unit (V) is preferably 40 mol%, more preferably 50 mol%, and even more preferably 55 mol%, based on all structural units constituting the high-fluorine content polymer. The upper limit of the content is preferably 90 mol%, more preferably 85 mol%, and even more preferably 80 mol%. By setting the content of the structural unit (V) within the above range, the mass content of fluorine atoms in the high-fluorine content polymer can be more appropriately adjusted, further promoting uneven distribution of fluorine atoms in the surface layer of the resist film, and as a result, the water repellency of the resist film during immersion exposure can be further improved.

[0183] The high-fluorine content polymer may have a fluorine atom-containing structural unit represented by the following formula (f-2) (hereinafter also referred to as structural unit (VI)) in addition to or instead of the structural unit (V). By having the structural unit (f-2), the high-fluorine content polymer has improved solubility in an alkaline developer, and can suppress the occurrence of development defects.

[0184]

[0185] The structural unit (VI) is roughly classified into two types: (x) a case having an alkali-soluble group, and (y) a case having a group that dissociates under the action of an alkali to increase the solubility in an alkali developer (hereinafter simply referred to as an "alkali-dissociable group"). In both (x) and (y), R Ｃ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Ｄ is a single bond, a hydrocarbon group having 1 to 20 carbon atoms and a valence of (s+1), and R Ｅ At the end of the side, there is an oxygen atom, a sulfur atom, and -NR ｄｄ R has a structure in which -, a carbonyl group, -COO-, -OCO-, or -CONH- is bonded, or a structure in which some of the hydrogen atoms in this hydrocarbon group are substituted with an organic group having a hetero atom. ｄｄ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. s is an integer of 1 to 3.

[0186] When the structural unit (VI) has an alkali-soluble group (x), R Ｆ is a hydrogen atom, and A １ is an oxygen atom, -COO-* or -SO ２ O-*. * is R Ｆ The binding site of W is shown. １ represents a single bond, a hydrocarbon group having 1 to 20 carbon atoms, or a divalent fluorinated hydrocarbon group. １ is an oxygen atom, W １ is A １ is a fluorinated hydrocarbon group having a fluorine atom or a fluoroalkyl group on the carbon atom to which R is bonded. Ｅ is a single bond or a divalent organic group having 1 to 20 carbon atoms. When s is 2 or 3, multiple R Ｅ , W１ , A １ and R Ｆ may be the same or different. When the structural unit (VI) has an alkali-soluble group (x), it is possible to increase affinity for an alkaline developer and suppress development defects. As the structural unit (VI) having an alkali-soluble group (x), A １ is an oxygen atom and W １ It is particularly preferred that is a 1,1,1,3,3,3-hexafluoro-2,2-methanediyl group.

[0187] When the structural unit (VI) has an alkali-dissociable group (y), R Ｆ is a monovalent organic group having 1 to 30 carbon atoms, and A １ is an oxygen atom, -NR ａａ -, -COO-*, -OCO-* or -SO ２ O-*. ａａ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. * is R Ｆ The binding site of W is shown. １ is a single bond or a divalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. Ｅ is a single bond or a divalent organic group having 1 to 20 carbon atoms. １ is -COO-*, -OCO-* or -SO ２ If O-*, then W １ or R Ｆ is A １ A has a fluorine atom on the carbon atom bonded to or adjacent to the carbon atom. １ is an oxygen atom, W １ , R Ｅ is a single bond, and R Ｄ is a hydrocarbon group having 1 to 20 carbon atoms. Ｅ A carbonyl group is bonded to the end of the R Ｆ is an organic group having a fluorine atom. When s is 2 or 3, a plurality of R Ｅ , W １ , A １ and R Ｆmay be the same or different. When the structural unit (VI) has an alkali-dissociable group (y), the surface of the resist film changes from hydrophobic to hydrophilic in the alkali development step. As a result, affinity to the developer is significantly increased, and development defects can be more efficiently suppressed. Examples of the structural unit (VI) having an alkali-dissociable group (y) include A １ is -COO-*, and R Ｆ Or W １ It is particularly preferred that both of them have a fluorine atom.

[0188] R Ｃ As the alkyl group, from the viewpoint of copolymerizability of the monomer that gives the structural unit (VI), a hydrogen atom or a methyl group is preferred, and a methyl group is more preferred.

[0189] R Ｅ When is a divalent organic group, it is preferably a group having a lactone structure, more preferably a group having a polycyclic lactone structure, and more preferably a group having a norbornane lactone structure.

[0190] When the high-fluorine content polymer has the structural unit (VI), the lower limit of the content of the structural unit (VI) is preferably 40 mol%, more preferably 50 mol%, and even more preferably 55 mol%, based on all structural units constituting the high-fluorine content polymer. The upper limit of the content is preferably 95 mol%, more preferably 90 mol%, and even more preferably 85 mol%. By setting the content of the structural unit (VI) within the above range, the water repellency of the resist film during immersion exposure can be further improved, and development defects can be suppressed.

[0191] [Other Structural Units] The high fluorine content polymer may contain, as a structural unit other than the structural units listed above, the structural unit (VII) represented by the above formula (6), in addition to the structural unit (I) and the structural unit (III) in the base polymer.

[0192] When the high fluorine content polymer contains the structural unit (I) or the structural unit (III), the content ratio of each structural unit in the high fluorine content polymer can suitably be the content ratio described for the base polymer.

[0193] When the high-fluorine content polymer contains the structural unit (VII), the lower limit of the content of the structural unit (VII) is preferably 10 mol %, more preferably 20 mol %, and even more preferably 30 mol %, based on all structural units constituting the high-fluorine content polymer, and the upper limit of the content is preferably 60 mol %, more preferably 50 mol %, and even more preferably 45 mol %.

[0194] The lower limit of Mw of the high fluorine content polymer is preferably 2,000, more preferably 3,000, even more preferably 4,000, and particularly preferably 5,000. The upper limit of Mw is preferably 30,000, more preferably 20,000, even more preferably 10,000, and particularly preferably 8,000.

[0195] The lower limit of Mw / Mn of the high fluorine content polymer is usually 1, more preferably 1.1. The upper limit of Mw / Mn is usually 5, preferably 3, more preferably 2.

[0196] When the radiation-sensitive composition contains a high-fluorine-containing polymer, the content of the high-fluorine-containing polymer is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, even more preferably 1.5 parts by mass or more, and particularly preferably 2 parts by mass or more, relative to 100 parts by mass of the base polymer, and is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, even more preferably 8 parts by mass or less, and particularly preferably 6 parts by mass or less.

[0197] By setting the content of the high-fluorine-containing polymer within the above range, the high-fluorine-containing polymer can be more effectively localized in the surface layer of the resist film, which results in improving the water repellency of the surface of the resist film during immersion lithography, and enabling control of the surface modification of the resist film and the distribution of the composition within the film during EUV exposure. The radiation-sensitive composition may contain one or more high-fluorine-containing polymers.

[0198] (Method for synthesizing high fluorine content polymer) The high fluorine content polymer can be synthesized by the same method as the above-mentioned method for synthesizing the base polymer.

[0199] <Solvent (E)> The radiation-sensitive composition according to this embodiment contains a solvent (E). The solvent (E) is not particularly limited as long as it is a solvent that can dissolve or disperse at least the polymer (A), the radiation-sensitive acid generator (B), and optionally the acid diffusion controller (D).

[0200] Examples of the solvent include alcohol-based solvents, ether-based solvents, ketone-based solvents, amide-based solvents, ester-based solvents, and hydrocarbon-based solvents.

[0201] Examples of alcohol-based solvents include monoalcohol-based solvents having 1 to 18 carbon atoms, such as iso-propanol, 4-methyl-2-pentanol, 3-methoxybutanol, n-hexanol, 2-ethylhexanol, furfuryl alcohol, cyclohexanol, 3,3,5-trimethylcyclohexanol, and diacetone alcohol; polyhydric alcohol-based solvents having 2 to 18 carbon atoms, such as ethylene glycol, 1,2-propylene glycol, 2-methyl-2,4-pentanediol, 2,5-hexanediol, diethylene glycol, dipropylene glycol, triethylene glycol, and tripropylene glycol; and polyhydric alcohol partial ether-based solvents in which some of the hydroxy groups in the above-mentioned polyhydric alcohol-based solvents have been etherified. In the present embodiment, alcoholic acid ester solvents such as methyl lactate, ethyl lactate, propyl lactate, butyl lactate, methyl 2-hydroxyisobutyrate, i-propyl 2-hydroxyisobutyrate, i-butyl 2-hydroxyisobutyrate, and n-butyl 2-hydroxyisobutyrate are also included in the alcoholic solvents.

[0202] Examples of ether-based solvents include dialkyl ether-based solvents such as diethyl ether, dipropyl ether, and dibutyl ether; cyclic ether-based solvents such as tetrahydrofuran and tetrahydropyran; aromatic ring-containing ether-based solvents such as diphenyl ether and anisole (methyl phenyl ether); and polyhydric alcohol ether-based solvents obtained by etherifying the hydroxy groups of the above-mentioned polyhydric alcohol-based solvents.

[0203] Examples of ketone solvents include chain ketone solvents such as acetone, butanone, and methyl-iso-butyl ketone; cyclic ketone solvents such as cyclopentanone, cyclohexanone, and methylcyclohexanone; and 2,4-pentanedione, acetonylacetone, and acetophenone.

[0204] Examples of the amide solvent include cyclic amide solvents such as N,N'-dimethylimidazolidinone and N-methylpyrrolidone; and chain amide solvents such as N-methylformamide, N,N-dimethylformamide, N,N-diethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, and N-methylpropionamide.

[0205] Examples of ester-based solvents include monocarboxylic acid ester-based solvents such as n-butyl acetate; polyhydric alcohol partial ether acetate-based solvents such as diethylene glycol mono-n-butyl ether acetate, propylene glycol monomethyl ether acetate, and dipropylene glycol monomethyl ether acetate; lactone-based solvents such as γ-butyrolactone and valerolactone; carbonate-based solvents such as diethyl carbonate, ethylene carbonate, and propylene carbonate; and polyvalent carboxylic acid diester-based solvents such as propylene glycol diacetate, methoxytriglycol acetate, diethyl oxalate, ethyl acetoacetate, and diethyl phthalate.

[0206] Examples of hydrocarbon solvents include aliphatic hydrocarbon solvents such as n-hexane, cyclohexane, and methylcyclohexane; and aromatic hydrocarbon solvents such as benzene, toluene, di-isopropylbenzene, and n-amylnaphthalene.

[0207] Among these, ester-based solvents, ether-based solvents, and alcohol-based solvents are preferred, polyhydric alcohol partial ether acetate-based solvents, lactone-based solvents, monocarboxylic acid ester-based solvents, ketone-based solvents, and alcohol acid ester-based solvents are more preferred, and propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether acetate, γ-butyrolactone, ethyl lactate, cyclohexanone, propylene glycol monomethyl ether, and methyl 2-hydroxyisobutyrate are even more preferred. The radiation-sensitive composition may contain one or more solvents.

[0208] (Other Optional Components) The radiation-sensitive composition may contain other optional components in addition to the components described above. Examples of the other optional components include a crosslinking agent, a localization promoter, a surfactant, an alicyclic skeleton-containing compound, and a sensitizer. These other optional components may be used alone or in combination of two or more.

[0209] The surfactant is not particularly limited, but a non-fluorine-based surfactant or a non-silicone-based surfactant can be suitably used.

[0210] When the radiation-sensitive composition contains a surfactant, the content of the surfactant is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and preferably 5 parts by mass or less, more preferably 3 parts by mass or less, and even more preferably 1 part by mass or less, per 100 parts by mass of the base polymer (A).

[0211] <Method for Preparing Radiation-Sensitive Composition> The radiation-sensitive composition can be prepared, for example, by mixing the polymer (A), the radiation-sensitive acid generator (B), the solvent (E), and, if necessary, other radiation-sensitive acid generators, the acid diffusion controller (D), a high-fluorine-content polymer, and the like, in predetermined proportions. After mixing, the radiation-sensitive composition is preferably filtered, for example, through a filter having a pore size of approximately 0.05 μm to 0.40 μm. The solids concentration of the radiation-sensitive composition is usually 0.1% to 50% by mass, preferably 0.5% to 30% by mass, and more preferably 1% to 20% by mass.

[0212] <Pattern Forming Method> A pattern forming method according to one embodiment of the present invention includes: a step (1) of applying the radiation-sensitive composition directly or indirectly to a substrate to form a resist film (hereinafter also referred to as a "resist film forming step"); a step (2) of exposing the resist film (hereinafter also referred to as an "exposure step"); and a step (3) of developing the exposed resist film (hereinafter also referred to as a "development step").

[0213] According to the above-described resist pattern forming method, a high-quality resist pattern can be formed because the above-described radiation-sensitive composition is used, which is capable of forming a resist film that is excellent in sensitivity, LWR, MEEF, CDU, development defect performance, pattern rectangularity, and pattern circularity in the exposure step.

[0214] [Resist Film Forming Step] In this step (step (1) above), a resist film is formed from the radiation-sensitive composition. Examples of substrates on which the resist film is formed include conventionally known substrates such as silicon wafers, silicon dioxide wafers, and aluminum-coated wafers. Alternatively, an organic or inorganic anti-reflective coating, such as those disclosed in JP-B-6-12452 and JP-A-59-93448, may be formed on the substrate. Examples of coating methods include spin coating, casting coating, and roll coating. After coating, if necessary, pre-baking (PB) may be performed to volatilize the solvent in the coating film. The PB temperature is typically 60°C to 150°C, and preferably 80°C to 140°C. The PB time is typically 5 to 600 seconds, and preferably 10 to 300 seconds.

[0215] The lower limit of the thickness of the resist film to be formed is preferably 10 nm, more preferably 15 nm, and even more preferably 20 nm. The upper limit of the thickness is preferably 500 nm, more preferably 400 nm, and even more preferably 300 nm. In particular, when a thick resist film is exposed to ArF excimer laser light in the exposure step described below, the lower limit of the thickness may be 100 nm, 150 nm, or 200 nm.

[0216] When performing immersion exposure, regardless of whether the radiation-sensitive composition contains a water-repellent polymer additive such as a high-fluorine-content polymer, a protective film for immersion exposure that is insoluble in the immersion liquid may be provided on the formed resist film in order to prevent direct contact between the immersion liquid and the resist film. The protective film for immersion exposure may be either a solvent-removable protective film that is removed with a solvent before the development step (see, for example, JP-A 2006-227632), or a developer-removable protective film that is removed simultaneously with development in the development step (see, for example, WO 2005 / 069076 and WO 2006 / 035790). However, from the viewpoint of throughput, it is preferable to use a developer-removable protective film for immersion exposure.

[0217] When the next exposure step is carried out using radiation having a wavelength of 50 nm or less, it is preferable to use a polymer having the structural units (I) and (IV) as the base polymer in the composition.

[0218] [Exposure Step] In this step (step (2) above), the resist film formed in the resist film formation step (1) above is exposed to radiation through a photomask (or, in some cases, through an immersion liquid such as water). Examples of radiation used for exposure include electromagnetic waves such as visible light, ultraviolet light, far ultraviolet light, EUV (extreme ultraviolet), X-rays, and gamma rays; and charged particle beams such as electron beams and alpha rays, depending on the line width of the desired pattern. Among these, far ultraviolet light, electron beams, and EUV are preferred, with ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), electron beams, and EUV being more preferred, and electron beams and EUV with wavelengths of 50 nm or less, which are positioned as next-generation exposure technologies, being even more preferred.

[0219] When exposure is performed by immersion exposure, examples of the immersion liquid used include water and fluorine-based inert liquids. The immersion liquid is preferably a liquid that is transparent to the exposure wavelength and has as small a temperature coefficient of refractive index as possible so as to minimize distortion of the optical image projected onto the film. However, particularly when the exposure light source is an ArF excimer laser beam (wavelength 193 nm), water is preferred from the above-mentioned viewpoints, as well as from the viewpoints of ease of availability and ease of handling. When water is used, a small proportion of an additive that reduces the surface tension of water and increases its surfactant power may be added. It is preferable that this additive does not dissolve the resist film on the wafer and has negligible effect on the optical coating on the underside of the lens. Distilled water is preferred as the water used.

[0220] After the exposure, post-exposure baking (PEB) is preferably performed to promote dissociation of acid-dissociable groups in the polymer or the like in the exposed portions of the resist film by the acid generated from the radiation-sensitive acid generator upon exposure. This PEB results in a difference in solubility in a developer between the exposed and unexposed portions. The PEB temperature is typically 50°C to 180°C, preferably 80°C to 130°C. The PEB time is typically 5 seconds to 600 seconds, preferably 10 seconds to 300 seconds.

[0221] [Development Step] In this step (step (3) above), the resist film exposed in the exposure step (step (2) above) is developed. This allows a predetermined 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.

[0222] In the case of alkaline development, examples of the developer used in the 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 aqueous TMAH solution is more preferred.

[0223] In the case of organic solvent development, examples of the organic solvent include hydrocarbon solvents, ether solvents, ester solvents, ketone solvents, and alcohol solvents, as well as solvents containing an organic solvent. Examples of the organic solvent include one or more of the solvents listed above as solvents for the radiation-sensitive composition. Among these, ether solvents, ester solvents, and ketone solvents are preferred. As ether solvents, glycol ether solvents are preferred, with ethylene glycol monomethyl ether and propylene glycol monomethyl ether being more preferred. As ester solvents, acetate ester solvents are preferred, with n-butyl acetate and amyl acetate being more preferred. As ketone solvents, chain ketones are preferred, with 2-heptanone being more preferred. The content of the organic solvent in the developer is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 99% by mass or more. Examples of components other than the organic solvent in the developer include water and silicone oil.

[0224] As mentioned above, the developer may be either an alkaline developer or an organic solvent developer, and can be appropriately selected depending on whether the desired pattern is a positive or negative pattern.

[0225] 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 piling up a developer on the surface of the substrate by surface tension and leaving it to stand for a certain period of time to develop (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).

[0226] <Radiation-Sensitive Acid Generator> The radiation-sensitive acid generator according to this embodiment is represented by the following formula (1). (In the above formula (1), R １ R is a hydrogen atom, a nitro group, a hydroxyl group, a cyano group, a carboxy group, a methyl group, or an ethyl group. １ If there are multiple R １ are the same or different. ２ and R ３ are each independently a hydrogen atom, a nitro group, a hydroxyl group, a cyano group, a carboxy group, a thiol group, a halogen atom, or a monovalent organic group, or R ２ and R ３ is a divalent alicyclic group having 3 to 20 carbon atoms formed by combining together with the carbon atom to which they are bonded. ２ and R ３ If there are multiple R ２ and R ３ are the same or different. L is a divalent linking group. R ４ is a monovalent linear organic group having 3 or more carbon atoms, or a monovalent branched organic group having 5 or more carbon atoms. m is an integer of 1 to 5. n is an integer of 0 to 4. M ＋ is a monovalent onium cation.

[0227] As the radiation-sensitive acid generator represented by the formula (1), the radiation-sensitive acid generator (B) in the radiation-sensitive composition can be suitably used.

[0228] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Measurement methods for various physical properties are shown below.

[0229] [Weight-average molecular weight (Mw) and number-average molecular weight (Mn)] The Mw and Mn of the polymer were measured under the conditions described above. The dispersity (Mw / Mn) was calculated from the measurement results of Mw and Mn.

[0230] [ １３ C-NMR analysis of polymer １３ C-NMR analysis was carried out using a nuclear magnetic resonance spectrometer (JNM-Delta400 manufactured by JEOL Ltd.).

[0231] <Synthesis of Polymer> The monomers used in the synthesis of each polymer in each Example and Comparative Example are shown below. In the following synthesis examples, unless otherwise specified, parts by mass refer to a value when the total mass of the monomers used is taken as 100 parts by mass, and mol % refers to a value when the total number of moles of the monomers used is taken as 100 mol %.

[0232]

[0233] Synthesis Example 1 Synthesis of Polymer (A-1) Monomer (M-1), monomer (M-2), monomer (M-5), monomer (M-10), and monomer (M-14) were dissolved in 2-butanone (200 parts by mass) to give a molar ratio of 40 / 10 / 20 / 25 / 5 (mol %), and AIBN (azobisisobutyronitrile) (3 mol % relative to 100 mol % of the total monomers used) was added as an initiator to prepare a monomer solution. 2-Butanone (100 parts by mass) was placed in a reaction vessel, and after purging with nitrogen for 30 minutes, the reaction vessel was heated to 80°C, and the monomer solution was added dropwise over 3 hours with stirring. The start of the dropwise addition marked the start of the polymerization reaction, and the polymerization reaction was carried out for 6 hours. After completion of the polymerization reaction, the polymerized solution was cooled with water to below 30°C. The cooled polymerization solution was poured into methanol (2,000 parts by mass), and the precipitated white powder was filtered off. The filtered white powder was washed twice with methanol, filtered off, and dried at 50°C for 24 hours to obtain a white powdery polymer (A-1) (yield: 80%). The Mw of the polymer (A-1) was 9,200, and the Mw / Mn was 1.61. １３As a result of C-NMR analysis, the contents of the structural units derived from (M-1), (M-2), (M-5), (M-10) and (M-14) were 40.1 mol%, 8.9 mol%, 20.3 mol%, 26.0 mol% and 4.7 mol%, respectively.

[0234] Synthesis Examples 2 to 11 Synthesis of Polymers (A-2) to (A-11) Polymers (A-2) to (A-11) were synthesized in the same manner as in Synthesis Example 1, except that the types and blending ratios of monomers shown in Table 1 below were used. The content (mol %) of each structural unit and physical properties (Mw and Mw / Mn) of the resulting polymers are also shown in Table 1 below. In Table 1 below, "-" indicates that the corresponding monomer was not used (the same applies to the following tables).

[0235]

[0236] Synthesis Example 12 Synthesis of Polymer (A-12) Monomer (M-1) and monomer (M-18) were dissolved in 1-methoxy-2-propanol (200 parts by mass) to a molar ratio of 50 / 50 (mol %), and MAIB (dimethyl 2,2'-azobisisobutyrate) (4 mol %) was added as an initiator to prepare a monomer solution. 1-Methoxy-2-propanol (100 parts by mass) was placed in a reaction vessel, and after purging with nitrogen for 30 minutes, the reaction vessel was heated to 80°C, and the monomer solution was added dropwise over 3 hours with stirring. The start of the dropwise addition marked the start of the polymerization reaction, and the polymerization reaction was carried out for 6 hours. After completion of the polymerization reaction, the polymerization solution was cooled with water to below 30°C. The cooled polymerization solution was poured into hexane (2,000 parts by mass), and the precipitated white powder was separated by filtration. The white powder collected by filtration was washed twice with hexane, filtered, and then dissolved in 1-methoxy-2-propanol (300 parts by mass). Methanol (500 parts by mass), triethylamine (50 parts by mass), and ultrapure water (10 parts by mass) were then added, and a hydrolysis reaction was carried out at 70°C for 6 hours with stirring. After completion of the reaction, the residual solvent was distilled off, and the resulting solid was dissolved in acetone (100 parts by mass) and added dropwise to water (500 parts by mass) to coagulate the polymer. The resulting solid was collected by filtration and dried at 50°C for 13 hours to obtain a white powdery polymer (A-12) (yield: 85%). The Mw of the polymer (A-12) was 7,700, and the Mw / Mn was 1.62. １３ As a result of C-NMR analysis, the content ratios of the structural units derived from (M-1) and (M-18) were 50.2 mol % and 49.8 mol %, respectively.

[0237] [Synthesis Examples 13 to 15] (Synthesis of Polymers (A-13) to (A-15)) Polymers (A-13) to (A-15) were synthesized in the same manner as in Synthesis Example 12, except that the types and blending ratios of monomers shown in Table 2 below were used. Note that the monomer that gives the structural unit (IV) is １３ C-NMR analysis confirmed that the peaks of the carbonyl groups of the acetyl groups had disappeared, and that substantially all of the alkali-dissociable groups had been hydrolyzed to phenolic hydroxyl groups. The content (mol %) of each structural unit and physical properties (Mw and Mw / Mn) of the obtained polymer are also shown in Table 2 below.

[0238]

[0239] Synthesis Example 16 Synthesis of High Fluorine Content Polymer (F-1) Monomer (M-1), monomer (M-15), and monomer (M-20) were dissolved in 2-butanone (200 parts by mass) to give a molar ratio of 20 / 10 / 70 (mol %), and AIBN (5 mol %) was added as an initiator to prepare a monomer solution. 2-Butanone (100 parts by mass) was placed in a reaction vessel, and after purging with nitrogen for 30 minutes, the reaction vessel was heated to 80°C and the monomer solution was added dropwise over 3 hours with stirring. The start of the dropwise addition marked the start time of the polymerization reaction, and the polymerization reaction was carried out for 6 hours. After completion of the polymerization reaction, the polymerized solution was cooled to below 30°C with water. The solvent was replaced with acetonitrile (400 parts by mass), and then hexane (100 parts by mass) was added, stirred, and the acetonitrile layer was recovered. This process was repeated three times. The solvent was replaced with propylene glycol monomethyl ether acetate to obtain a solution of high fluorine content polymer (F-1) (yield: 75%). The high fluorine content polymer (F-1) had an Mw of 7,000 and an Mw / Mn ratio of 1.67. １３ As a result of C-NMR analysis, the contents of the structural units derived from (M-1), (M-15) and (M-20) were 19.7 mol %, 10.1 mol % and 70.2 mol %, respectively.

[0240] Synthesis Examples 17 to 20 (Synthesis of high fluorine content polymer (F-2) to high fluorine content polymer (F-5)) High fluorine content polymer (F-2) to high fluorine content polymer (F-5) were synthesized in the same manner as in Synthesis Example 16, except for using monomers of the types and blending ratios shown in Table 3 below. The content (mol %) of each structural unit and physical properties (Mw and Mw / Mn) of the obtained high fluorine content polymers are also shown in Table 3 below.

[0241]

[0242] <Synthesis of Radiation-Sensitive Acid Generator (B)> [Example B1] (Synthesis of Onium Salt Compound (B-1)) An onium salt compound (B-1) serving as the radiation-sensitive acid generator (B) was synthesized according to the following synthesis scheme.

[0243]

[0244] A 1 M solution was prepared by adding 20.0 mmol of ethyl bromofluoroacetate to a reaction vessel and a mixture of acetonitrile and water (1:1 (mass ratio)), followed by the addition of 40.0 mmol of sodium dithionite and 60.0 mmol of sodium bicarbonate, and the mixture was allowed to react at 70°C for 4 hours. After extraction with acetonitrile and the solvent was distilled off, a 0.5 M solution was prepared by adding a mixture of acetonitrile and water (3:1 (mass ratio)). 60.0 mmol of aqueous hydrogen peroxide and 2.00 mmol of sodium tungstate were added, and the mixture was heated and stirred at 50°C for 12 hours. Extraction with acetonitrile and the solvent was distilled off yielded a sodium sulfonate salt compound. 20.0 mmol of triphenylsulfonium bromide was added to the sodium sulfonate salt compound, and a 0.5 M solution was prepared by adding a mixture of water and dichloromethane (1:3 (mass ratio)). After vigorously stirring for 3 hours at room temperature, dichloromethane was added for extraction, and the organic layer was separated. The resulting organic layer was dried over sodium sulfate, the solvent was distilled off, and the residue was purified by column chromatography to obtain the onium salt (B-1-a) in good yield.

[0245] 50 g of a 2 M aqueous sodium hydroxide solution and 50 g of methanol were added to the onium salt (B-1-a) and stirred at room temperature for 3 hours. Then, a 2 M aqueous hydrochloric acid solution was added to terminate the reaction, followed by extraction with methylene chloride and separation of the organic layer. The resulting organic layer was dried over sodium sulfate, and the solvent was removed by distillation to obtain the carboxylic acid (B-1-b) in good yield.

[0246] To the carboxylic acid compound (B-1-b), 20.0 mmol of n-hexanol, 30.0 mmol of dicyclohexylcarbodiimide, and 50 g of methylene chloride were added, and the mixture was stirred at room temperature for 3 hours. After that, the mixture was diluted with water, and then extracted with methylene chloride, and the organic layer was separated. The resulting organic layer was washed with a saturated aqueous sodium chloride solution and then with water. After drying with sodium sulfate, the solvent was distilled off, and the mixture was purified by column chromatography, yielding compound (B-1) represented by formula (B-1) in good yield.

[0247] Examples B2 to B7 Synthesis of Onium Salt Compounds (B-2) to (B-7) Onium salt compounds represented by the following formulas (B-2) to (B-7) were synthesized as radiation-sensitive acid generators in the same manner as in Example B1, except that the raw materials and precursors were appropriately changed.

[0248]

[0249] Example B8 (Synthesis of Onium Salt Compound (B-8)) Onium salt compound (B-8) as the radiation-sensitive acid generator (B) was synthesized according to the following synthesis scheme.

[0250]

[0251] 20.0 mmol of the onium salt (B-1-a), 60.0 mmol of lithium aluminum hydride, and 50 g of tetrahydrofuran were added to a reaction vessel and stirred at room temperature for 3 hours. Subsequently, a saturated aqueous solution of potassium sodium tartrate was added to terminate the reaction, and methylene chloride was added for extraction, and the organic layer was separated. The resulting organic layer was dried over sodium sulfate, and the solvent was then distilled off, yielding the alcohol (B-1-c) in good yield.

[0252] To the alcohol (B-1-c), 20.0 mmol of decanoic acid, 30.0 mmol of dicyclohexylcarbodiimide, and 50 g of methylene chloride were added, and the mixture was stirred at room temperature for 3 hours. After that, the mixture was diluted with water, and then extracted with methylene chloride, and the organic layer was separated. The resulting organic layer was washed with a saturated aqueous sodium chloride solution and then with water. After drying with sodium sulfate, the solvent was distilled off, and the mixture was purified by column chromatography, yielding compound (B-8) represented by formula (B-8) in good yield.

[0253] [Examples B9 to B13] (Synthesis of onium salt compounds (B-9) to (B-13)) Onium salt compounds represented by the following formulas (B-9) to (B-13) were synthesized as radiation-sensitive acid generators in the same manner as in Example B8, except that the raw materials and precursors were appropriately changed.

[0254]

[0255] Example B14 Synthesis of Onium Salt Compound (B-14) An onium salt compound (B-14) as a radiation-sensitive acid generator (B) was synthesized according to the following synthesis scheme.

[0256]

[0257] 20.0 mmol of the onium salt (B-1-a), 60.0 mmol of methylmagnesium bromide, and 50 g of tetrahydrofuran were added to a reaction vessel and stirred at 60°C for 12 hours. Thereafter, a saturated aqueous ammonium chloride solution was added to terminate the reaction, and methylene chloride was added for extraction, and the organic layer was separated. The resulting organic layer was dried over sodium sulfate, and the solvent was then distilled off to obtain an alcohol in good yield.

[0258] To the alcohol product, 20.0 mmol of 3-ethylheptanoyl chloride, 30.0 mmol of triethylamine, and 50 g of methylene chloride were added, followed by stirring at 60°C for 10 hours. After dilution with water, the mixture was extracted with methylene chloride and the organic layer was separated. The resulting organic layer was washed with a saturated aqueous sodium chloride solution and then with water. After drying with sodium sulfate, the solvent was distilled off, and the residue was purified by column chromatography to obtain compound (B-14) represented by formula (B-14) in good yield.

[0259] Example B15 (Synthesis of Onium Salt Compound (B-15)) An onium salt compound as a radiation-sensitive acid generator represented by the following formula (B-15) was synthesized in the same manner as in Example B14, except that the raw materials and precursors were appropriately changed.

[0260]

[0261] Example B16 (Synthesis of Onium Salt Compound (B-16)) Onium salt compound (B-16) as the radiation-sensitive acid generator (B) was synthesized according to the following synthesis scheme.

[0262]

[0263] 20.0 mmol of the alcohol (B-1-c), 30.0 mmol of sodium hydride, 30.0 mmol of tert-butyl bromoacetate, and 50 g of tetrahydrofuran were added to a reaction vessel and stirred at 60°C for 12 hours. Thereafter, a saturated aqueous solution of ammonium chloride was added to terminate the reaction, and methylene chloride was added for extraction and separation of the organic layer. The resulting organic layer was washed with a saturated aqueous solution of sodium chloride and then with water. After drying over sodium sulfate, the solvent was distilled off, and the mixture was purified by column chromatography to obtain compound (B-16) represented by the above formula (B-16) in good yield.

[0264] The following compounds were used as components other than the components synthesized above.

[0265] [Radiation-sensitive acid generators other than radiation-sensitive acid generators (B-1) to (B-16)] b-1 to b-8: Compounds represented by the following formulas (b-1) to (b-8) (hereinafter, the compounds represented by formulas (b-1) to (b-8) may be referred to as "compound (b-1)" to "compound (b-8)," respectively). The radiation-sensitive acid generator (b-1) has the same structure as the onium salt (B-1-a).

[0266]

[0267]

[0268] [Acid Diffusion Controller (D)] D-1 to D-7: Compounds represented by the following formulas (D-1) to (D-7).

[0269] [Solvent (E)] E-1: Propylene glycol monomethyl ether acetate E-2: Propylene glycol monomethyl ether E-3: γ-butyrolactone E-4: Cyclohexanone E-5: Methyl 2-hydroxyisobutyrate

[0270] [Other additive components (W)] W-1: MEGAFACE EFS-321 (manufactured by DIC Corporation) (non-fluorine-based) W-2: BYK-399 (manufactured by BYK Japan Co., Ltd.) (non-silicone-based)

[0271] [Preparation of Positive Radiation-Sensitive Composition for ArF Immersion Exposure] [Example 1] 100 parts by mass of (A-1) as the polymer (A), 10.0 parts by mass of (B-1) as the radiation-sensitive acid generator (B), 4.0 parts by mass of (D-1) as the acid diffusion controller (D), 5.0 parts by mass (solids content) of (F-1) as the high fluorine content polymer (F), 0.5 parts by mass of (W-1) as the other additive component (W), and 3,400 parts by mass of a mixed solvent of (E-1) / (E-2) / (E-3) as the solvent (E) were mixed and the mixture was filtered through a membrane filter having a pore size of 0.2 μm to prepare a radiation-sensitive composition (J-1).

[0272] [Examples 2 to 43, 101 to 106 and Comparative Examples 1 to 6] Radiation-sensitive compositions (J-2) to (J-43), (J-101) to (J-106), and (CJ-1) to (CJ-6) were prepared in the same manner as in Example 1, except that the types and amounts of each component shown in Tables 4-1 and 4-2 below were used.

[0273]

[0274] <Formation of Resist Pattern Using Positive Radiation-Sensitive Composition for ArF Immersion Exposure> A composition for forming a bottom antireflective coating (Brewer Science's ARC66) was applied to a 12-inch silicon wafer using a spin coater (Tokyo Electron Limited's CLEAN TRACK ACT12), and then heated at 205°C for 60 seconds to form a bottom antireflective coating with an average thickness of 100 nm. The positive radiation-sensitive composition for ArF exposure prepared above was applied to this bottom antireflective coating using the spin coater, and prebaked at 100°C for 60 seconds. The wafer was then cooled at 23°C for 30 seconds to form a resist film with an average thickness of 220 nm. Next, this resist film was exposed to light through a 60 nm line-and-space mask pattern using an ArF excimer laser immersion exposure system (ASML's "TWINSCAN XT-1900i") under optical conditions of NA = 1.35 and dipole (σ = 0.9 / 0.7). After exposure, a PEB (post-exposure bake) was performed at 100°C for 60 seconds. Thereafter, the resist film was subjected to alkaline development using a 2.38 mass% aqueous TMAH solution as an alkaline developer, and after development, it was washed with water and further dried to form a positive resist pattern (120 nm line-and-space pattern).

[0275] <Evaluation> The resist patterns formed using the above-described positive-working radiation-sensitive composition for ArF immersion exposure were evaluated for sensitivity, LWR, MEEF, number of development defects, and pattern rectangularity according to the methods described below. The results are shown in Tables 5-1 and 5-2 below. The resist patterns were measured using a scanning electron microscope (CG-5000 manufactured by Hitachi High-Technologies Corporation).

[0276] [Sensitivity] In forming a resist pattern using the positive radiation-sensitive composition for ArF immersion exposure, the exposure dose required to form a 120 nm line and space pattern was defined as the optimum exposure dose, and this optimum exposure dose was defined as the sensitivity (mJ / cm ２ The sensitivity was 40 mJ / cm ２ "Good" if below 40 mJ / cm ２ If it exceeded this, it was rated as "poor".

[0277] [LWR] A 120 nm line-and-space resist pattern was formed by irradiating the resist with the optimal exposure dose determined in the sensitivity evaluation. The formed resist pattern was observed from above the pattern using the scanning electron microscope described above. The line width variation was measured at a total of 500 points, and a 3 sigma value was calculated from the distribution of the measured values, and this 3 sigma value was taken as the LWR (nm). The smaller the LWR value, the smaller the line roughness and the better the result. LWR was evaluated as "good" when it was 4.0 nm or less, and as "poor" when it exceeded 4.0 nm.

[0278] [MEEF] In resist patterns resolved by irradiation with the above-mentioned optimum exposure dose, the line widths of resist patterns formed using mask patterns with line widths of 124 nm, 128 nm, 132 nm, 136 nm, and 140 nm were plotted on the vertical axis against the size of the mask pattern on the horizontal axis, and the slope of the line was calculated and defined as MEEF. MEEF values ​​closer to 1 indicate better mask reproducibility. MEEF values ​​of 2 or less were evaluated as "good," and values ​​above 2 were evaluated as "poor."

[0279] [Number of Development Defects] A resist film was exposed to an optimum exposure dose to form a 120 nm line and space pattern, which was used as a wafer for defect inspection. The number of defects on this wafer for defect inspection was measured using a defect inspection device (KLA-Tencor's "KLA2810"). Defects with a diameter of 50 μm or less were determined to be derived from the resist film, and the number of defects was calculated. After development, the number of defects determined to be derived from the resist film was evaluated as "good" when the number of defects was 100 or less, and as "poor" when the number of defects was more than 100.

[0280] [Pattern rectangularity] A 120 nm line-and-space resist pattern formed by irradiating with the optimum exposure dose obtained in the sensitivity evaluation was observed using the scanning electron microscope, and the cross-sectional shape of the line-and-space pattern was evaluated. The rectangularity of the resist pattern was evaluated as "A" (very good) if the ratio of the length of the bottom side to the length of the top side in the cross-sectional shape was 1 or more and 1.05 or less, "B" (good) if it was more than 1.05 and 1.10 or less, and "C" (poor) if it was more than 1.10.

[0281]

[0282] As is clear from the results in Tables 5-1 and 5-2, when the radiation-sensitive compositions of the Examples were used in ArF immersion exposure, they exhibited good sensitivity, LWR, MEEF, development defect performance, and pattern rectangularity, whereas the Comparative Examples were inferior in each of the properties to the Examples. Therefore, when the radiation-sensitive compositions of the Examples are used in ArF immersion exposure, resist patterns with high sensitivity and good LWR, MEEF, development defect performance, and pattern rectangularity can be formed.

[0283] [Preparation of positive-tone radiation-sensitive composition for ArF-dry exposure] [Example 44] 100 parts by mass of (A-1) as the polymer (A), 7.0 parts by mass of (B-1) as the radiation-sensitive acid generator (B), 2.0 parts by mass of (D-5) as the acid diffusion controller (D), 0.5 parts by mass of (W-1) as the other additive component (W), and 3,230 parts by mass of a mixed solvent of (E-1) / (E-4) / (E-3) as the solvent (E) were mixed and filtered through a membrane filter having a pore size of 0.2 μm, to prepare a radiation-sensitive composition (J-44).

[0284] Examples 45 to 57 and Comparative Examples 7 to 11 Radiation-sensitive compositions (J-45) to (J-57) and (CJ-7) to (CJ-11) were prepared in the same manner as in Example 44, except that the types and amounts of each component shown in Table 6 below were used.

[0285]

[0286] <Formation of Resist Pattern Using Positive Radiation-Sensitive Composition for ArF-Dry Exposure> A composition for forming a bottom antireflective coating ("ARC29" from Brewer Science) was applied to an 8-inch silicon wafer using a spin coater ("CLEAN TRACK ACT8" from Tokyo Electron Limited), and then heated at 205°C for 60 seconds to form a bottom antireflective coating with an average thickness of 77 nm. The positive radiation-sensitive composition for ArF-Dry exposure prepared above was applied to this bottom antireflective coating using the spin coater, and prebaked at 100°C for 60 seconds. The wafer was then cooled at 23°C for 30 seconds to form a resist film with an average thickness of 270 nm. Next, a resist pattern with a line width of 90 nm, line-and-space, was formed on this resist film using an ArF excimer laser exposure device (Nikon Corporation's "S306C") under optical conditions of NA = 0.75 and annular (σ = 0.8 / 0.6). After exposure, PEB (post-exposure bake) was performed at 100 ° C. for 60 seconds. Thereafter, the resist film was subjected to alkaline development using a 2.38 mass % TMAH aqueous solution as an alkaline developer, and after development, it was washed with water and further dried to form a positive resist pattern (150 nm line-and-space resist pattern).

[0287] <Evaluation> The resist patterns formed using the positive radiation-sensitive composition for ArF-Dry exposure were evaluated for sensitivity, LWR, MEEF, and the number of development defects according to the methods described below. The results are shown in Table 7. A scanning electron microscope ("S-9380" manufactured by Hitachi High-Technologies Corporation) was used to measure the length of the resist patterns.

[0288] [Sensitivity] In forming a resist pattern using the positive-working radiation-sensitive composition for ArF-Dry exposure, the exposure amount required to form a 150 nm line and space pattern was defined as the optimum exposure amount, and this optimum exposure amount was defined as the sensitivity (mJ / cm ２ The sensitivity was 40 mJ / cm ２ The following cases are considered "good" and 40 mJ / cm ２ If it exceeded this, it was rated as "poor".

[0289] [LWR] A 150 nm line-and-space resist pattern was formed by irradiating the resist with the optimal exposure dose determined in the sensitivity evaluation. The formed resist pattern was observed from above the pattern using the scanning electron microscope described above. The line width variation was measured at a total of 500 points, and a 3 sigma value was calculated from the distribution of the measured values, and this 3 sigma value was taken as the LWR (nm). The smaller the LWR value, the smaller the line roughness and the better the result. LWR was evaluated as "good" when it was 3.0 nm or less, and as "poor" when it exceeded 3.0 nm.

[0290] [MEEF] In resist patterns resolved by irradiation with the above-mentioned optimum exposure dose, the line widths of resist patterns formed using mask patterns with line widths of 154 nm, 158 nm, 162 nm, 166 nm, and 170 nm were plotted on the vertical axis against the size of the mask pattern on the horizontal axis, and the slope of the line was calculated and defined as MEEF. MEEF values ​​closer to 1 indicate better mask reproducibility. MEEF values ​​of 2 or less were evaluated as "good," and values ​​above 2 were evaluated as "poor."

[0291] [Number of Development Defects] A resist film was exposed to an optimum exposure dose to form a 150 nm line and space pattern, which was used as a wafer for defect inspection. The number of defects on this wafer for defect inspection was measured using a defect inspection device (KLA-Tencor's "KLA2810"). Defects with a diameter of 50 μm or less were determined to be derived from the resist film, and the number of defects was calculated. After development, the number of defects determined to be derived from the resist film was evaluated as "good" when the number of defects was 100 or less, and as "poor" when the number of defects was more than 100.

[0292]

[0293] As is clear from the results in Table 7, when the radiation-sensitive compositions of the Examples were used for ArF-dry exposure, the sensitivity, LWR, MEEF, and development defect performance were good, whereas the Comparative Examples were inferior in each property to the Examples. Therefore, when the radiation-sensitive compositions of the Examples are used for ArF-dry exposure, resist patterns can be formed with high sensitivity and good LWR, MEEF, and development defect performance.

[0294] [Preparation of Positive-Working Radiation-Sensitive Composition for Extreme Ultraviolet (EUV) Exposure] [Example 58] 100 parts by mass of (A-12) as the polymer (A), 30.0 parts by mass of (B-1) as the radiation-sensitive acid generator (B), 25.0 parts by mass of (D-2) as the acid diffusion controller (D), 5.0 parts by mass (solids content) of (F-5) as the high fluorine-content polymer (F), and 5,500 parts by mass of a mixed solvent of (E-1) / (E-2) as the solvent (E) were mixed and the mixture was filtered through a membrane filter having a pore size of 0.2 μm, thereby preparing a radiation-sensitive composition (J-58).

[0295] Examples 59 to 71 and Comparative Examples 12 to 16 Radiation-sensitive compositions (J-59) to (J-71) and (CJ-12) to (CJ-16) were prepared in the same manner as in Example 58, except that the types and amounts of each component shown in Table 8 below were used.

[0296]

[0297] <Formation of Resist Pattern Using Positive Radiation-Sensitive Composition for EUV Exposure> A composition for forming a bottom antireflective coating ("ARC66" from Brewer Science) was applied to a 12-inch silicon wafer using a spin coater ("CLEAN TRACK ACT12" from Tokyo Electron Limited), and then heated at 205°C for 60 seconds to form a bottom antireflective coating with an average thickness of 105 nm. The positive radiation-sensitive composition for EUV exposure prepared above was applied to this bottom antireflective coating using the spin coater, and then subjected to PB at 130°C for 60 seconds. Subsequently, the wafer was cooled at 23°C for 30 seconds to form a resist film with an average thickness of 65 nm. Next, this resist film was exposed using an EUV exposure apparatus (ASML's "NXE3300") with NA = 0.33, illumination conditions: Conventional s = 0.89, and mask: imecDEFECT32FFR02. After exposure, PEB was performed at 120°C for 60 seconds. Thereafter, the resist film was subjected to alkaline development using a 2.38 mass% aqueous TMAH solution as an alkaline developer, and after development, the resist film was washed with water and further dried to form a positive resist pattern (23 nm line and space pattern).

[0298] <Evaluation> The resist patterns formed using the above-described positive-working radiation-sensitive composition for EUV exposure were evaluated for sensitivity, LWR, MEEF, and number of development defects according to the methods described below. The results are shown in Table 9. The resist patterns were measured using a scanning electron microscope (CG-5000 manufactured by Hitachi High-Technologies Corporation).

[0299] [Sensitivity] In forming a resist pattern using the positive-working radiation-sensitive composition for EUV exposure, the exposure dose required to form a 23 nm line and space pattern was defined as the optimum exposure dose, and this optimum exposure dose was used as the sensitivity (mJ / cm ２ The sensitivity was 50 mJ / cm ２ The following cases are considered "good" and 50mJ / cm ２ If it exceeded this, it was rated as "poor".

[0300] [LWR] A resist pattern was formed by irradiating the resist with the optimal exposure dose determined in the sensitivity evaluation above, and adjusting the mask size to form a 23 nm line-and-space pattern. The formed resist pattern was observed from above the pattern using the scanning electron microscope described above. The line width variation was measured at a total of 500 points, and a 3 sigma value was calculated from the distribution of the measured values, and this 3 sigma value was taken as the LWR (nm). The smaller the LWR value, the smaller the line chatter and the better the result. LWR was evaluated as "good" when it was 4.0 nm or less, and as "poor" when it exceeded 4.0 nm.

[0301] [MEEF] In resist patterns resolved by irradiation with the above-mentioned optimum exposure dose, the line widths of resist patterns formed using mask patterns with line widths of 25 nm, 27 nm, 29 nm, 31 nm, and 33 nm were plotted on the vertical axis against the size of the mask pattern on the horizontal axis, and the slope of the line was calculated and defined as MEEF. MEEF values ​​closer to 1 indicate better mask reproducibility. MEEF values ​​of 2 or less were evaluated as "good," and values ​​above 2 were evaluated as "poor."

[0302] [Number of Development Defects] A resist film was exposed to an optimum exposure dose to form a 23 nm line and space pattern, which was used as a wafer for defect inspection. The number of defects on this wafer for defect inspection was measured using a defect inspection device (KLA-Tencor's "KLA2810"). Defects with a diameter of 50 μm or less were determined to be derived from the resist film, and the number of defects was calculated. After development, the number of defects determined to be derived from the resist film was evaluated as "good" when the number of defects was 100 or less, and as "poor" when the number of defects was more than 100.

[0303]

[0304] As is clear from the results in Table 9, when the radiation-sensitive compositions of the Examples were used for EUV exposure, the sensitivity, LWR, MEEF, and development defect performance were good, whereas the Comparative Examples were inferior to the Examples in each property.

[0305] [Preparation of Negative Radiation-Sensitive Composition for ArF Immersion Exposure, and Formation and Evaluation of Resist Pattern Using This Composition] [Example 72] 100 parts by mass of (A-8) as the polymer (A), 11.0 parts by mass of (B-2) as the radiation-sensitive acid generator (B), 1.0 part by mass of the radiation-sensitive acid generator (b-11), 4.0 parts by mass of (D-6) as the acid diffusion controller (D), 3.0 parts by mass (solids content) of (F-2) as the high fluorine-containing polymer (F), and 3,230 parts by mass of a mixed solvent of (E-1) / (E-2) / (E-3) (mass ratio 2,240 / 960 / 30) as the solvent (E) were mixed, and the mixture was filtered through a membrane filter having a pore size of 0.2 μm, to prepare a radiation-sensitive composition (J-72).

[0306] A composition for forming a bottom antireflective coating ("ARC66" from Brewer Science) was applied to a 12-inch silicon wafer using a spin coater ("CLEAN TRACK ACT12" from Tokyo Electron Limited), and then heated at 205°C for 60 seconds to form a bottom antireflective coating with an average thickness of 100 nm. The negative radiation-sensitive composition for ArF exposure (J-72) prepared above was applied to this bottom antireflective coating using the spin coater, and prebaked at 100°C for 60 seconds. The wafer was then cooled at 23°C for 30 seconds to form a resist film with an average thickness of 230 nm. Next, this resist film was exposed to light using an ArF excimer laser immersion exposure system (ASML's "TWINSCAN XT-1900i") under optical conditions of NA = 1.35 and annular (σ = 0.8 / 0.6) through a mask pattern with 50 nm holes and a 100 nm pitch. After exposure, a post-exposure bake (PEB) was performed at 100°C for 60 seconds. The resist film was then developed using n-butyl acetate as an organic solvent developer and dried to form a negative resist pattern (a contact hole pattern with 80 nm holes and a 150 nm pitch).

[0307] The resist patterns prepared using the negative-working radiation-sensitive composition for ArF immersion exposure were evaluated for sensitivity and MEEF in the same manner as in the evaluation of the resist patterns prepared using the positive-working radiation-sensitive composition for ArF immersion exposure. Furthermore, the CDU and pattern circularity were evaluated according to the following methods.

[0308] [CDU] Contact holes with 80 nm holes and a 150 nm pitch were formed by irradiating the resist with the optimal exposure dose determined in the sensitivity evaluation. The formed resist pattern was observed from above the pattern using the scanning electron microscope described above. The variation in the diameter of the contact holes was measured at a total of 500 points, and a 3 sigma value was calculated from the distribution of the measured values, and this 3 sigma value was taken as CDU (nm). The smaller the CDU value, the smaller the hole roughness and the better the result. CDU was evaluated as "good" when it was less than 3.5 nm, and as "poor" when it was 3.5 nm or more.

[0309] [Pattern circularity] The 50 nm holes and 100 nm pitch contact holes formed by irradiating with the optimum exposure dose obtained in the sensitivity evaluation were observed in plan view using the scanning electron microscope, and their vertical and horizontal sizes were measured. A ratio of vertical size to horizontal size of 0.95 or more and less than 1.05 was evaluated as "A" (very good), a ratio of 0.90 or more and less than 0.95 or 1.05 or more and less than 1.10 was evaluated as "B" (good), and a ratio of less than 0.90 or 1.10 or more was evaluated as "C" (poor).

[0310] As a result, the radiation-sensitive composition of Example 72 exhibited excellent sensitivity, MEEF, CDU, and pattern circularity even when a negative resist pattern was formed by ArF immersion exposure.

[0311] [Preparation of Negative Radiation-Sensitive Composition for EUV Exposure, and Formation and Evaluation of Resist Pattern Using This Composition] [Example 73] 100 parts by mass of (A-15) as the polymer (A), 20.0 parts by mass of (B-19) as the radiation-sensitive acid generator (B), 5.0 parts by mass of the radiation-sensitive acid generator (b-12), 18.0 parts by mass of (D-4) as the acid diffusion controller (D), 2.0 parts by mass (solids content) of (F-2) as the high fluorine-content polymer (F), and 6,110 parts by mass of a mixed solvent of (E-1) / (E-2) (mass ratio 4,280 / 1,830) as the solvent (E) were mixed, and the mixture was filtered through a membrane filter having a pore size of 0.2 μm, to prepare a radiation-sensitive composition (J-73).

[0312] A composition for forming a bottom antireflective coating ("ARC66" from Brewer Science) was applied to a 12-inch silicon wafer using a spin coater ("CLEAN TRACK ACT12" from Tokyo Electron Limited), and then heated at 205°C for 60 seconds to form a bottom antireflective coating with an average thickness of 105 nm. The negative radiation-sensitive composition for EUV exposure (J-73) prepared above was applied to this bottom antireflective coating using the spin coater, and baked at 130°C for 60 seconds. This was then cooled at 23°C for 30 seconds to form a resist film with an average thickness of 55 nm. Next, this resist film was exposed to light using an EUV exposure system ("NXE3300" from ASML) with NA=0.33, illumination conditions: Conventional s=0.89, and a mask: imecDEFECT32FFR15. After the exposure, PEB was performed for 60 seconds at 120° C. Thereafter, the resist film was developed with n-butyl acetate as an organic solvent developer and dried to form a negative resist pattern (a contact hole pattern with 25 nm holes and a 50 nm pitch).

[0313] The resist pattern formed using the negative-tone radiation-sensitive composition for EUV exposure was evaluated in the same manner as the evaluation of the resist pattern formed using the negative-tone radiation-sensitive composition for ArF immersion exposure. As a result, the radiation-sensitive composition of Example 73 exhibited good sensitivity, MEEF, CDU, and pattern circularity, even when a negative-tone resist pattern was formed by EUV exposure.

[0314] The radiation-sensitive composition, pattern forming method, and radiation-sensitive acid generator described above can form a resist pattern that has good sensitivity to exposure light and is excellent in LWR, MEEF, development defect performance, pattern rectangularity, CDU, and pattern circularity. Therefore, these compositions can be suitably used in processing processes for semiconductor devices, which are expected to become increasingly miniaturized in the future.

Claims

1. A radiation-sensitive composition comprising: a polymer (A) containing a structural unit (I) having an acid-dissociable group; a radiation-sensitive acid generator (B) represented by the following formula (1); and a solvent (E): (In the above formula (1), R １ R is a hydrogen atom, a nitro group, a hydroxyl group, a cyano group, a carboxy group, a methyl group, or an ethyl group. １ When there are multiple R １ are the same or different. ２ and R ３ are each independently a hydrogen atom, a nitro group, a hydroxyl group, a cyano group, a carboxy group, a thiol group, a halogen atom, or a monovalent organic group, or R ２ and R ３ R is a divalent alicyclic group having 3 to 20 carbon atoms formed by combining with each other and bonding to the carbon atom. ２ and R ３ When there are multiple R ２ and R ３ are the same or different. L is a divalent linking group. ４ is a monovalent linear organic group having 3 or more carbon atoms, or a monovalent branched organic group having 5 or more carbon atoms. m is an integer from 1 to 5. n is an integer from 0 to 4. M ＋ is a monovalent onium cation.

2. The radiation-sensitive composition according to claim 1, wherein the divalent linking group contains at least one bond selected from the group consisting of an ester bond, an amide bond, an ether bond, a sulfonyl bond, a carbonyl group, and a carbonate bond.

3. The radiation-sensitive composition according to claim 1, wherein the content of the radiation-sensitive acid generator (B) is from 1 part by mass to 30 parts by mass per 100 parts by mass of the polymer (A).

4. R above ２ and R ３ are each independently a hydrogen atom or a monovalent non-fluorine-containing organic group, or R ２ and R ３ 2. The radiation-sensitive composition according to claim 1, wherein: are combined with each other to form a divalent alicyclic group having 3 to 20 carbon atoms together with the carbon atom to which they are bonded.

5. R above ４ The radiation-sensitive composition according to claim 1 , wherein is a monovalent chain organic group having 5 to 20 carbon atoms.

6. The radiation-sensitive composition according to claim 1, wherein the structural unit (I) having an acid-dissociable group is represented by the following formula (2): (In the above formula (2), R α R is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Ａ１ R is a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms. Ａ２ and R Ａ３ each independently represents a monovalent linear hydrocarbon group having 1 to 20 carbon atoms or a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, or R Ａ２ and R Ａ３ are combined together with the carbon atom to which they are bonded to form a divalent alicyclic group having 3 to 20 carbon atoms. m11 and m12 are each independently 0 or 1. However, when m11 is 1, m12 is 1. When m11 is 0, L Ａ１ represents a single bond or a divalent linking group; when m11 is 1, L Ａ１ is a divalent linking group.

7. The radiation-sensitive composition according to claim 1, wherein the polymer (A) further contains a structural unit having a phenolic hydroxyl group.

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

9. The radiation-sensitive composition according to claim 1, further comprising an acid diffusion controller (D).

10. A pattern forming method comprising the steps of: applying the radiation-sensitive composition according to any one of claims 1 to 9 directly or indirectly to a substrate to form a resist film; exposing the resist film to light; and developing the exposed resist film.

11. The pattern forming method according to claim 10, wherein the exposure is carried out with a KrF excimer laser, an ArF excimer laser or extreme ultraviolet light.

12. A radiation-sensitive acid generator represented by the following formula (1): (In the above formula (1), R １ R is a hydrogen atom, a nitro group, a hydroxyl group, a cyano group, a carboxy group, a methyl group, or an ethyl group. １ When there are multiple R １ are the same or different. ２ and R ３ are each independently a hydrogen atom, a nitro group, a hydroxyl group, a cyano group, a carboxy group, a thiol group, a halogen atom, or a monovalent organic group, or R ２ and R ３ R is a divalent alicyclic group having 3 to 20 carbon atoms formed by combining with each other and bonding to the carbon atom. ２ and R ３ When there are multiple R ２ and R ３ are the same or different. L is a divalent linking group. ４ is a monovalent linear organic group having 3 or more carbon atoms, or a monovalent branched organic group having 5 or more carbon atoms. m is an integer from 1 to 5. n is an integer from 0 to 4. M ＋ is a monovalent onium cation.

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