Radiation-sensitive composition and pattern forming method

Abstract

To provide a radiation-sensitive composition and a pattern forming method, capable of exhibiting LWR performance and over-exposure margins equivalent to or better than those of conventional products.SOLUTION: A radiation-sensitive composition includes: a first polymer comprising a structural unit (I) having an acid-dissociable group; a second polymer comprising a structural unit (i) represented by formula (f1); and a solvent, wherein the acid-dissociable group has an iodo group.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a radiation-sensitive composition and a patterning method.

Background Art

[0002] Photolithography technology using a resist composition is utilized for forming fine circuits in semiconductor elements. As a typical procedure, for example, acid is generated by exposure of a resist composition film through a mask pattern to radiation having a short wavelength such as an ArF excimer laser, and a difference in solubility of a polymer in an alkaline or organic solvent-based developer between an exposed portion and an unexposed portion is caused by a reaction using the acid as a catalyst, thereby forming a resist pattern on a substrate.

[0003] In the above photolithography technology, pattern miniaturization is promoted by using radiation having a short wavelength such as an ArF excimer laser, or by combining this radiation with a liquid immersion exposure method (liquid immersion lithography). As a next-generation technology, use of radiation having an even shorter wavelength such as an electron beam, X-ray, and EUV (extreme ultraviolet ray) is contemplated.

[0004] As pattern miniaturization progresses, a technique of adding a fluorine-containing polymer to a resist composition has been proposed for the purpose of controlling the film quality of a resist film (Japanese Patent No. 5712247).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In developing the above-described next-generation technology, resist performance equivalent to or better than that of the prior art is required in terms of sensitivity, line width roughness (LWR) performance indicating variations in the line width of the resist pattern, over-exposure margin (Max CD) indicating the tolerance of the space dimension during over-exposure, and the like.

[0007] An object of the present invention is to provide a radiation-sensitive composition and a pattern forming method that are excellent in sensitivity during pattern formation and can exhibit LWR performance and over-exposure margin at levels equivalent to or better than those of the prior art.

Means for Solving the Problems

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

[0009] In one embodiment, the present invention relates to a first polymer containing a structural unit (I) having an acid dissociable group, a second polymer containing a structural unit (i) represented by the following formula (f1), a solvent, and is contained, and relates to a radiation-sensitive composition in which the acid dissociable group has an iodine group.

Chemical Formula

[0010] According to the radiation - sensitive composition, when forming a resist pattern, it can exhibit excellent sensitivity, LWR performance equal to or better than the conventional one, and over - exposure margin. Although the reason is not clear, it is speculated as follows

[0011] The absorption by the iodine group (iodine atom) of radiation such as EUV with a wavelength of 13.5 nm is large. As a result, the secondary electron generation efficiency increases, and the resulting resist film becomes highly sensitive. Also, thereby the acid generation efficiency is improved, and a good dissolution contrast is obtained between the exposed part and the unexposed part. On the other hand, the component containing an iodine atom has low solubility, and pattern collapse may occur during development. According to the radiation - sensitive composition, during alkali development, a dissociation reaction occurs in the structural unit (i) in the second polymer present near the surface of the resist film, and the solubility of the resist film surface layer in the developer can be improved. Thereby, even if over - exposure occurs, the resist film can exhibit good solubility in the developer, and pattern collapse and the like can be suppressed. It is speculated that the above - mentioned resist performance can be exhibited by these combined actions

[0012] In another embodiment, the present invention a step of forming a resist film by applying the radiation-sensitive composition directly or indirectly onto a substrate; a step of exposing the resist film; a step of developing the exposed resist film with a developer and relates to a patterning method comprising the same.

[0013] In this patterning method, since the radiation-sensitive composition capable of exhibiting sensitivity equivalent to or higher than that of the conventional one and LWR performance and overexposure margin equivalent to or higher than those of the conventional one during resist pattern formation is used, a high-quality resist pattern can be efficiently formed.

BEST MODE FOR CARRYING OUT THE INVENTION

[0014] Hereinafter, 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.

[0015] <<Radiation-Sensitive Composition>> The radiation-sensitive composition according to the present embodiment (hereinafter, also simply referred to as "composition") contains a first polymer (hereinafter, also referred to as "base polymer"), a second polymer, and a solvent. The composition may contain other optional components as long as the effects of the present invention are not impaired.

[0016] <<First Polymer>> The first polymer (i.e., the base polymer) is an aggregate of polymer chains containing a structural unit (I) having an acid dissociable group. The acid dissociable group has an iodine group (hereinafter, the acid dissociable group having an iodine group is also referred to as "iodine group-containing acid dissociable group"). By incorporating an iodine group in the base polymer, the radiation absorption efficiency can be increased, and the sensitivity can be improved by increasing the secondary electron generation efficiency. In addition to the structural unit (I), the base polymer may contain a structural unit having an acid dissociable group not having an iodine group (hereinafter, also referred to as "structural unit (II)"), a structural unit having a phenolic hydroxyl group (hereinafter, also referred to as "structural unit (III)"), and the like.

[0017] (Structural unit (I)) The structural unit (I) is a structural unit having an iodine group-containing acid dissociable group (however, among the structures corresponding to the structural unit (III), the structure having an iodine group-containing acid dissociable group is treated as the structural unit (I)). The "acid dissociable group" is a group that substitutes a hydrogen atom possessed by a carboxy group, a phenolic hydroxyl group, an alcoholic hydroxyl group, a sulfo group, etc., and is a group that dissociates by the action of an acid. The acid generated from the radiation-sensitive acid generator by exposure or the structural unit (IV) described later dissociates the acid dissociable group in the structural unit (I) to generate a carboxy group or the like. As a result, a difference in solubility in the developing solution between the exposed portion and the unexposed portion of the resist film occurs, enabling pattern formation.

[0018] The above acid dissociable group preferably contains an iodine group in the form of an iodine group-containing aromatic ring structure. The iodine group-containing aromatic ring structure is a structure in which some or all of the hydrogen atoms of the aromatic ring are substituted with iodine groups. Other structural units constituting the base polymer may contain an iodine group-containing aromatic ring structure.

[0019] The aromatic ring in the iodine group-containing aromatic ring structure is not particularly limited as long as it is a ring structure having aromaticity. Examples of the aromatic ring include aromatic hydrocarbon rings such as benzene ring, naphthalene ring, anthracene ring, phenalene ring, phenanthrene ring, pyrene ring, fluorene ring, perylene ring, coronene ring, and aromatic heterocycles such as furan ring, pyrrole ring, thiophene ring, phosphole ring, pyrazole ring, oxazole ring, isoxazole ring, thiazole ring, pyridine ring, pyrazine ring, pyrimidine ring, pyridazine ring, triazine ring, carbazole ring, dibenzofuran ring, or combinations thereof. Among them, the benzene ring is preferable as the aromatic ring.

[0020] Although the number of iodine atoms in the above iodine group-containing aromatic ring structure is not particularly limited, it is preferably 1 to 4, more preferably 1, 2, or 3, and even more preferably 1 or 2.

[0021] The structural unit (I) is not particularly limited as long as it contains an iodine group-containing acid dissociable group. For example, 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, a structural unit having an acetal bond, a structural unit having a primary or secondary alkyl ester moiety substituted with an aromatic ring (including an aromatic heterocyclic ring), etc. may be mentioned.

[0022] The above structural unit (I) is preferably a structural unit represented by the following formula (1) (hereinafter, also referred to as "structural unit (I-1)"). [Chemical formula] (In formula (1), R α is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. L 1 is a divalent linking group. R 1A and R 1B are each independently a hydrogen atom, a monovalent linear hydrocarbon group having 1 to 10 carbon atoms or a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, or these groups 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 attached. However, there is no case where both R 1A and R 1B are hydrogen atoms. R 101 is a nitro group, a cyano group, a hydroxy group, an alkoxy group or an amino group. When there are a plurality of R 101 , the plurality of R 101 may be the same or different from each other. m1 and m2 are each independently 0 or 1. However, when m1 is 1, m2 is 1. p is an integer of 1 to 3. q is an integer of 0 to 3. However, p + q is 5 or less.)

[0023] L 1Examples of the divalent linking group represented by include an alkanediyl group, a cycloalkanediyl group, an alkenediyl group, an arenediyl group, and a group containing -CO-, -CS-, -O-, -S-, -SO 2 -,-NR'- or a group containing a combination of two or more of these, or a group formed by combining these, etc. R' is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. Some or all of the hydrogen atoms of 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 atom of these groups is substituted with a halogen atom, etc.

[0024] As the above alkanediyl group, 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 is preferable.

[0025] Examples of the above cycloalkanediyl group include monocyclic cycloalkanediyl groups such as a cyclopentanediyl group and a cyclohexanediyl group; polycyclic cycloalkanediyl groups such as a norbornanediyl group and an adamantanediyl group, etc. As the above cycloalkanediyl group, a cycloalkanediyl group having 5 to 12 carbon atoms is preferable.

[0026] Examples of the above alkenediyl group include an ethenediyl group, a propenediyl group, a butenediyl group, etc. As the above alkenediyl group, an alkenediyl group having 2 to 6 carbon atoms is preferable.

[0027] Examples of the above arenediyl group include a phenylene group, a tolylene group, a naphthylene group, etc. As the above arenediyl group, an arenediyl group having 6 to 15 carbon atoms is preferable.

[0028] L 1Examples of the divalent linking group represented by include an alkanediyl group and an arenediyl group, with an alkanediyl group having 1 to 4 carbon atoms and an arenediyl group having 6 to 10 carbon atoms being more preferred, and a methanediyl group and a benzenediyl group being even more preferred.

[0029] R 1A and R 1B Examples of the monovalent chain hydrocarbon group having 1 to 10 carbon atoms represented by include a monovalent straight-chain or branched-chain saturated hydrocarbon group having 1 to 10 carbon atoms, or a monovalent straight-chain or branched-chain unsaturated hydrocarbon group having 1 to 10 carbon atoms. Examples of the monovalent straight-chain or branched-chain saturated hydrocarbon group having 1 to 10 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 straight-chain or branched-chain unsaturated hydrocarbon group having 2 to 10 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.

[0030] R 1A and R 1B Examples of the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by include a monocyclic or polycyclic saturated hydrocarbon group, or a monocyclic or polycyclic unsaturated hydrocarbon group. Preferred examples of the monocyclic saturated hydrocarbon group include a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group. Preferred examples of the polycyclic cycloalkyl group include bridged alicyclic hydrocarbon groups such as a norbornyl group, an adamantyl group, a tricyclodecyl group, and a tetracyclododecyl group. Examples of the monocyclic unsaturated hydrocarbon group include monocyclic cycloalkenyl groups such as a cyclopropenyl group, a cyclobutenyl group, a cyclopentenyl group, and a cyclohexenyl group. Examples of the polycyclic unsaturated hydrocarbon group include polycyclic cycloalkenyl groups such as a norbornenyl group, a tricyclodecenyl group, and a tetracyclododecenyl group. Note that a bridged alicyclic hydrocarbon group refers to a polycyclic alicyclic hydrocarbon group in which two non-adjacent carbon atoms among the carbon atoms constituting the alicyclic ring are bonded by a linking group containing one or more carbon atoms.

[0031] R 1A and R 1B As the divalent alicyclic group having 3 to 20 carbon atoms formed together with the carbon atoms to which these are bonded and to which they are attached to each other, a group obtained by removing one hydrogen atom from the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms can be preferably employed.

[0032] R 1A and R 1B include a monovalent chain hydrocarbon group having 1 to 10 carbon atoms, or R 1A and R 1B are preferably a divalent alicyclic group having 3 to 20 carbon atoms formed together with the carbon atoms to which these are bonded and to which they are attached to each other, more preferably a monovalent straight-chain hydrocarbon group having 1 to 10 carbon atoms or a divalent alicyclic group having 5 to 10 carbon atoms, and even more preferably a methyl group, an ethyl group, a cyclopentanediyl group, a cyclohexanediyl group.

[0033] R 101 Examples of the alkoxy group represented by include alkoxy groups having 1 to 5 carbon atoms such as a methoxy group, an ethoxy group, and a propoxy group.

[0034] p is preferably 1 or 2.

[0035] Although not particularly limited as specific examples of the structural unit (I), for example, structures represented by the following formulas (1-1) to (1-29) can be mentioned. The structural units represented by the following formulas (1-1) to (1-18) also fall under the above structural unit (I-1).

[0036]

Chemical formula

[0037]

Chemical formula

[0038] In the above formulas, R α has the same meaning as in the above formula (1).

[0039] The lower limit of the content ratio of structural unit (I) (when multiple types are included, the total content ratio) is preferably 20 mol%, more preferably 30 mol%, still more preferably 35 mol% with respect to all the structural units constituting the base polymer. Further, the upper limit of the above content ratio is preferably 85 mol%, more preferably 80 mol%, still more preferably 75 mol%, and particularly preferably 70 mol%. By setting the content ratio of structural unit (I) within the above range, the sensitivity of the radiation-sensitive composition can be further improved.

[0040] (Structural unit (II)) Structural unit (II) is a structural unit having an acid dissociable group that does not have an iodine group (hereinafter, also referred to as an "iodine group-free acid dissociable group"). As structural unit (II), a structure obtained by removing the iodine group from structural unit (I) can be preferably employed. However, a structural unit having both an iodine group-free acid dissociable group and a phenolic hydroxyl group is treated as structural unit (III) described later. The base polymer may contain structural unit (II) alone or in combination of two or more.

[0041] Examples of structural unit (II) include structural units represented by the following formulas (3-1) to (3-4) (hereinafter, also referred to as "structural units (II-1) to (II-4)") and the like.

[0042] [Chemical formula]

[0043] In the above formulas (3-1) to (3-4), R 7 is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. R 8 is a monovalent hydrocarbon group having 1 to 20 carbon atoms. R 9 and R 10Each independently represents a monovalent linear hydrocarbon group having 1 to 10 carbon atoms or a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, or a divalent alicyclic group having 3 to 20 carbon atoms formed by combining these groups together with the carbon atoms to which they are attached. i and j are each independently an integer from 1 to 4.

[0044] The above R 8 Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by include a linear hydrocarbon group having 1 to 10 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms, and the like.

[0045] The above R 8 ~R 10 As the linear hydrocarbon group having 1 to 10 carbon atoms represented by, the monovalent linear hydrocarbon group having 1 to 10 carbon atoms represented by R and R in the above formula (1) can be preferably employed. 1A and R 1B The above R

[0046] ~R 8 ~R 10 As the alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by, the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by R and R in the above formula (1) can be preferably employed. 1A and R 1B The above R

[0047] ~R 8 Examples of the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms represented by include, for example, aryl groups such as phenyl group, tolyl group, xylyl group, naphthyl group, anthryl group; aralkyl groups such as benzyl group, phenethyl group, naphthylmethyl group, and the like.

[0048] The above R 9 and R 10 As the divalent alicyclic group having 3 to 20 carbon atoms formed by combining these groups together with the carbon atoms to which they are attached, a group obtained by removing one hydrogen atom from the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms can be preferably employed.

[0049] R 8 ~R 10 is preferably a methyl group, an ethyl group, an isopropyl group, an ethenyl group or a phenyl group.

[0050] i and j are preferably 1, 2 or 4.

[0051] Furthermore, the base polymer may contain a structural unit represented by the following formulas (1f) to (2f) as the structural unit (II) other than the above.

[0052]

Chemical formula

[0053] In the above formulas (1f) to (2f), R αf is each independently a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. R βf is each independently a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms. h 1 is an integer of 1 to 4.

[0054] As the above R βf is preferably a hydrogen atom, a methyl group or an ethyl group. h 1 is preferably 1 or 2.

[0055] When the base polymer contains the structural unit (II), the lower limit of the content ratio of the structural unit (II) (the total content ratio when multiple types are included) is preferably 10 mol%, more preferably 15 mol%, and even more preferably 20 mol% with respect to all the structural units constituting the base polymer. The upper limit of the above content ratio is preferably 50 mol%, more preferably 40 mol%, and even more preferably 35 mol%. By setting the content ratio of the structural unit (II) within the above range, the pattern forming property of the radiation-sensitive composition can be further improved.

[0056] (Structural unit (III)) The base polymer preferably contains a structural unit (III) having a phenolic hydroxyl group. By including the structural unit (III) in the polymer, the solubility in the developer can be more appropriately adjusted, and as a result, the sensitivity and the like of the above radiation-sensitive composition can be further improved. Further, when KrF excimer laser light, EUV, electron beam, etc. are used as the radiation irradiated in the exposure step in the resist pattern forming method, the structural unit (III) contributes to the improvement of the etching resistance and the improvement of the difference in the solubility in the developer (dissolution contrast) between the exposed portion and the unexposed portion. In particular, it can be suitably applied to pattern formation using exposure with radiation having a wavelength of 50 nm or less such as an electron beam or EUV. The structural unit (III) is preferably represented by the following formula (2).

[0057] [Chemical formula] (In the above formula (2), R β is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. L CA is a single bond, -COO- * or -O-. * is a bond on the aromatic ring side. R 101 is an acid dissociable group. R 102 is a halogen atom, a cyano group, a nitro group, an alkyl group, an alkoxycarbonyl group, an acyl group or an acyloxy group. When there are a plurality of R 102 , the plurality of R 102 are the same as or different from each other. n 3 is an integer from 0 to 2, m 3 is an integer from 1 to 8, m 4 and m 5 are each independently an integer from 0 to 8. However, 1 ≤ m 3 + m 4 + m 5 ≤ 2n 3 + 5 is satisfied.)

[0058] The above R βFrom the viewpoint of the copolymerizability of the monomer that gives the structural unit (III), it is preferably a hydrogen atom or a methyl group.

[0059] L CA is preferably a single bond or -COO- * is preferred.

[0060] The acid dissociable group represented by the above R 101 is not particularly limited. For example, a structure that forms a tertiary alkyl ester moiety together with -COO- to which R 101 is bonded, a structure that forms a secondary unsaturated alkyl ester moiety having a double bond between the β-carbon and the γ-carbon of the terminal oxygen atom of -COO- together with -COO- to which R 101 is bonded, a structure that forms an acetal bond together with -COO- to which R 101 is bonded, and the like can be mentioned.

[0061] R 102 The halogen atom in is preferably an iodine atom.

[0062] The above n 3 is more preferably 0 or 1, and even more preferably 0.

[0063] The above m 3 is preferably an integer of 1 to 3, and more preferably 1 or 2.

[0064] The above m 4 is preferably an integer of 0 to 3, and more preferably an integer of 0 to 2.

[0065] The above m 5 is preferably an integer of 0 to 3, and more preferably an integer of 0 to 2.

[0066] As the above structural unit (III), structural units represented by the following formulas (2-1) to (2-26) (hereinafter, also referred to as "structural units (III-1) to structural units (III-26)") and the like are preferable.

[0067] [Chemistry]

[0068] [Chemistry]

[0069] [Chemistry]

[0070] In the above formulas (2-1) to (2-26), R β is the same as in the above formula (2).

[0071] As the lower limit of the content ratio of the structural unit (III) (when there are a plurality of types of the structural unit (III), the total), 10 mol% is preferable, 20 mol% is more preferable, and 30 mol% is even more preferable with respect to all the structural units constituting the polymer. As the upper limit of the above content ratio, 80 mol% is preferable, 70 mol% is more preferable, and 65 mol% is even more preferable. By setting the content ratio of the structural unit (III) within the above range, the above radiation-sensitive composition can further improve the sensitivity and development contrast.

[0072] (Structural unit (IV)) The base polymer may contain a structural unit (IV) having a first organic acid anion and a first onium cation and including a first acid-generating structure that generates an acid for dissociating the acid-dissociable group by exposure. The onium salt structure formed by the first organic acid anion and the first onium cation (that is, the first acid-generating structure) functions as a radiation-sensitive acid-generating structure, so to speak.

[0073] In the present specification, the "dissociation" of the acid-dissociable group means dissociation when post-exposure baking is performed at 110 °C for 60 seconds.

[0074] When the base polymer contains the above radiation-sensitive acid-generating structure, the polarity of the base polymer in the exposed area increases, becoming soluble in the developer in the case of alkali aqueous solution development, while becoming hardly soluble in the developer in the case of organic solvent development.

[0075] The forms of inclusion of the first organic acid anion and the first onium cation in the structural unit (IV) of the base polymer are not particularly limited, and the base polymer may have the above first organic acid anion as a side chain portion, or may have the first onium cation as a side chain portion. Having as a side chain portion means that the corresponding first organic acid anion or first onium cation is bonded (covalently bonded) to the main chain as a side chain structure of the base polymer. When the first organic acid anion is bonded to the main chain as a side chain structure of the base polymer, the first onium cation is ionically bonded to the first organic acid anion as a counter ion of the first organic acid anion. On the other hand, when the first onium cation is bonded to the main chain as a side chain structure of the base polymer, the first organic acid anion is ionically bonded to the first onium cation as a counter ion of the first onium cation. From the viewpoint of controlling the acid diffusion length, it is preferable that the base polymer has the above first organic acid anion as a side chain portion.

[0076] The above first organic acid anion preferably has at least one selected from the group consisting of sulfonate anion, carboxylate anion and sulfonimide anion as an acid anion portion. Examples of the acid generated by exposure include sulfonic acid, carboxylic acid, and sulfonimide corresponding to the above acid anion portion.

[0077] The above first organic acid anion preferably contains -O-, -CO-, a cyclic structure or a combination thereof as a structure other than the above acid anion portion. The combination also includes a structure (heterocyclic structure) in which -O- or -CO- is incorporated as a portion forming a ring in the cyclic structure.

[0078] The cyclic structure may be any of a monocyclic, polycyclic, or a combination thereof. Further, the cyclic structure may be any of an alicyclic structure, an aromatic ring structure, a heterocyclic structure, or a combination thereof. In the case of a combination, the ring structure may be a structure in which ring structures are bonded by a chain structure, or two or more ring structures may form a fused ring structure, a bridged ring structure, or a spiro ring structure. A divalent heteroatom-containing group may be present between carbon-carbon atoms forming the skeleton of the cyclic structure or the chain structure, and some or all of the hydrogen atoms on the carbon atoms of the cyclic structure or the chain structure may be substituted with other substituents.

[0079] Examples of the divalent heteroatom-containing group include, for example, -CO-, -CS-, -NR’-, -O-, -S-, -SO 2 - or a divalent group obtained by combining these, etc. R’ is a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms.

[0080] As the substituent that substitutes some or all of the hydrogen atoms on the carbon atoms of the cyclic structure or the chain structure, the substituent that the divalent linking group represented by the above formula (1) may have can be preferably employed. 1

[0081] In the above first acid generation structure, it is preferable that the first organic acid anion has a sulfonate anion as an acid anion part, and an electron-withdrawing group is bonded to the carbon atom adjacent to the sulfur atom in the sulfonate anion. Thereby, the first acid generation structure can efficiently exhibit the above function. Examples of the electron-withdrawing group include a fluorine atom, a fluorinated hydrocarbon group, a nitro group, a cyano group, etc. As the fluorinated hydrocarbon group, a perfluoroalkyl group having 1 to 5 carbon atoms is preferable.

[0082] The first organic acid anion preferably has an iodine group. As the content mode of the iodine group, the first organic acid anion preferably contains the iodine group-containing aromatic ring structure.

[0083] Examples of the first onium cation include radiation-decomposable onium cations. Examples of the radiation-decomposable onium cations include sulfonium cations, tetrahydrothiophenium cations, iodonium cations, and the like. Among them, sulfonium cations or iodonium cations are preferable, and sulfonium cations are more preferable.

[0084] The first onium cation preferably has an iodine group. As the form of the iodine group contained in the first onium cation, it preferably contains the iodine group-containing aromatic ring structure.

[0085] The first onium cation in the structural unit (IV) is preferably a fluorine group-containing onium cation having a fluorine group. The fluorine group-containing onium cation preferably has a fluorine group-containing aromatic ring structure. The fluorine group-containing aromatic ring structure is a structure in which some or all of the hydrogen atoms of the aromatic ring are substituted with fluorine groups. As the aromatic ring in the fluorine group-containing aromatic ring structure, the aromatic ring in the iodine group-containing aromatic ring structure can be preferably adopted. Thereby, the sensitivity can be improved by increasing the radiation absorption efficiency.

[0086] By having the structural unit (IV) in combination with the above structures, the above-mentioned functions can be efficiently exhibited.

[0087] The structural unit (IV) is preferably a structural unit represented by the following formula (a1) (hereinafter, also referred to as "structural unit (IV-1)") or a structural unit represented by the following formula (a2) (hereinafter, also referred to as "structural unit (IV-2)").

[0088]

Chemical formula

[0089] In the formula, R V is a hydrogen atom or a methyl group. V 1 is a single bond or an ester group. V 2is a linear, branched or cyclic alkylene group having 1 to 12 carbon atoms, a cycloalkylene group having 3 to 12 carbon atoms, or an arylene group having 6 to 10 carbon atoms or a combination thereof, or an amide bond, and a part of the methylene groups constituting the alkylene group, the cycloalkylene group or the arylene group may be substituted with an ether group, an ester group or a lactone ring-containing group. V 3 is a single bond, an ether group, an ester group, or a linear or branched alkylene group having 1 to 12 carbon atoms, a cyclic cycloalkylene group having 3 to 12 carbon atoms, and a part of the methylene groups constituting the alkylene group may be substituted with an ether group or an ester group. V 2 and V 3 Some or all of the hydrogen atoms possessed by may be substituted with a heteroatom or a monovalent hydrocarbon group having 1 to 20 carbon atoms which may contain a heteroatom. R f1 ~R f4 are each independently a hydrogen atom, a fluorine atom or a trifluoromethyl group, but at least one is a fluorine atom or a fluorinated hydrocarbon group. R 43 ~R 47 are each independently a monovalent hydrocarbon group having 1 to 20 carbon atoms which may contain a heteroatom, R 43 and R 44 may combine with each other to form a ring together with the sulfur atom to which they are attached. R 43 ~R 45 At least one of, and R 46 ~R 47 At least one of is preferably a iodo group-containing aromatic ring structure or a fluoro group-containing aromatic ring structure respectively.

[0090] V 2 and V 3 , R 43 ~R 47Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms include an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or an aryl group having 6 to 20 carbon atoms. Some or all of the hydrogen atoms of these groups may be substituted with a heteroatom-containing group such as a hydroxy group, a carboxy group, a halogen atom, an oxo group, a cyano group, an amide group, a nitro group, a sultone group, a sulfone group or a sulfonium salt-containing group, an alkoxy group, an alkoxycarbonyl group, etc. Some of the methylene groups constituting these groups may be substituted with an ether group, an ester group, a carbonyl group, a carbonate group or a sulfonic acid ester group.

[0091] The structural units (IV-1) to (IV-2) are preferably represented by the following formulas (a1-1) and (a2-1), respectively.

[0092]

Chemical formula

[0093] In the formula, R V , R 43 to R 47 , R f1 to R f4 and V 1 are synonymous with the above formula (a1) or (a2). R 48 is a linear, branched or cyclic alkyl group having 1 to 4 carbon atoms, a halogen atom other than iodine, a hydroxy group, a linear, branched or cyclic alkoxy group having 1 to 4 carbon atoms, or a linear, branched or cyclic alkoxycarbonyl group having 2 to 5 carbon atoms. m is an integer of 0 to 4. n is an integer of 0 to 3.

[0094] Examples of the first organic acid anion of the monomer that provides the structural unit (IV) (including the structural unit (IV-1) and the structural unit (IV-2)) include, but are not limited to, those shown below. Among those shown below, the first organic acid anions containing an aromatic ring structure all have an iodine group-containing aromatic ring structure, but the structural unit (IV) does not necessarily require an iodine group-containing aromatic ring structure. As the first organic acid anion having no iodine group-containing aromatic ring structure, a structure in which the iodine atom in the following formula is substituted with a hydrogen atom, another substituent, etc. can be preferably adopted. In the following formula, R V has the same meaning as described above.

[0095]

Chemical formula

[0096]

Chemical formula

[0097]

Chemical formula

[0098]

Chemical formula

[0099]

Chemical formula

[0100] In the above formula, R V has the same meaning as the above formula (a1).

[0101] The first onium cation of the structural unit (IV-1) is preferably represented by the following formula (Q-1).

[0102]

Chemical formula

[0103] In the above formula (Q-1), Ra1 and Ra2 each independently represent a substituent. n1 represents an integer from 0 to 5. When n1 is 2 or more, the plurality of Ra1s may be the same or different. n2 represents an integer from 0 to 5. When n2 is 2 or more, the plurality of Ra2s may be the same or different. n3 represents an integer from 0 to 5. When n3 is 2 or more, the plurality of Ra3s may be the same or different. Ra3 represents a substituent. Ra1 and Ra2 may be linked to each other to form a ring. When n1 is 2 or more, the plurality of Ra1s may be linked to each other to form a ring. When n2 is 2 or more, the plurality of Ra2s may be linked to each other to form a ring.

[0104] Preferred substituents represented by Ra1, Ra2 and Ra3 include an alkyl group, a cycloalkyl group, an alkoxy group, a cycloalkyloxy group, an alkoxycarbonyl group, an alkylsulfonyl group, a hydroxyl group, a halogen atom, and a halogenated hydrocarbon group.

[0105] The alkyl groups of Ra1 and Ra2 may be a linear alkyl group or a branched alkyl group. The alkyl group preferably has 1 to 10 carbon atoms. Examples include 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, a neopentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, a 2-ethylhexyl group, an n-nonyl group, and an n-decyl group. Among these, a methyl group, an ethyl group, an n-butyl group, and a t-butyl group are particularly preferred.

[0106] Examples of the cycloalkyl groups for Ra1 and Ra2 include monocyclic or polycyclic cycloalkyl groups (preferably cycloalkyl groups having 3 to 20 carbon atoms), such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclododecanyl, cyclopentenyl, cyclohexenyl, and cyclooctadienyl groups. Among these, cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl groups are particularly preferred.

[0107] Examples of the alkyl group portion of the alkoxy groups for Ra1 and Ra2 include those exemplified above as the alkyl groups for Ra1 and Ra2. Particularly preferred as this alkoxy group are methoxy, ethoxy, n-propoxy, and n-butoxy groups.

[0108] Examples of the cycloalkyl group portion of the cycloalkyloxy groups for Ra1 and Ra2 include those exemplified above as the cycloalkyl groups for Ra1 and Ra2. Particularly preferred as this cycloalkyloxy group are cyclopentyloxy and cyclohexyloxy groups.

[0109] Examples of the alkoxy group portion of the alkoxycarbonyl groups for Ra1 and Ra2 include those exemplified above as the alkoxy groups for Ra1 and Ra2. Particularly preferred as this alkoxycarbonyl group are methoxycarbonyl, ethoxycarbonyl, and n-butoxycarbonyl groups.

[0110] Examples of the alkyl group moiety of the alkylsulfonyl groups Ra1 and Ra2 include those previously listed as the alkyl groups of Ra1 and Ra2. Examples of the cycloalkyl group moiety of the cycloalkylsulfonyl groups Ra1 and Ra2 include those previously listed as the cycloalkyl groups of Ra1 and Ra2. Particularly preferred as these alkylsulfonyl groups or cycloalkylsulfonyl groups are methanesulfonyl group, ethanesulfonyl group, n-propanesulfonyl group, n-butanessulfonyl group, cyclopentanesulfonyl group and cyclohexanesulfonyl group.

[0111] Each of the groups Ra1 and Ra2 may further have a substituent. Examples of this substituent include halogen atoms such as a fluorine atom (preferably a fluorine atom), hydroxy group, carboxy group, cyano group, nitro group, alkoxy group, cycloalkyloxy group, alkoxyalkyl group, cycloalkyloxyalkyl group, alkoxycarbonyl group, cycloalkyloxycarbonyl group, alkoxycarbonyloxy group, and cycloalkyloxycarbonyloxy group.

[0112] Examples of the halogen atoms of Ra1 and Ra2 include fluorine atom, chlorine atom, bromine atom, and iodine atom, with fluorine atom and iodine atom being preferred.

[0113] As the halogenated hydrocarbon group of Ra1 and Ra2, a halogenated alkyl group is preferred. Examples of the alkyl group and halogen atom constituting the halogenated alkyl group are the same as those described above. Among them, a fluorinated alkyl group is preferred, and CF 3 is more preferred.

[0114] As described above, Ra1 and Ra2 may be linked to each other to form a ring (i.e., a heterocyclic ring containing a sulfur atom). In this case, it is preferable that Ra1 and Ra2 are bonded to each other to form a single bond or a divalent linking group. Examples of the divalent linking group include, for example, -COO-, -OCO-, -CO-, -O-, -S-, -SO-, -SO 2- An alkylene group, a cycloalkylene group, an alkenylene group, or a combination of two or more thereof is exemplified, and those having 20 or less carbon atoms in total are preferred. When Ra1 and Ra2 are linked to each other to form a ring, Ra1 and Ra2 are preferably bonded to each other to form -COO-, -OCO-, -CO-, -O-, -S-, -SO-, -SO 2 - or a single bond. Among them, it is more preferable to form -O-, -S- or a single bond, and it is particularly preferable to form a single bond. When n1 is 2 or more, a plurality of Ra1 may be linked to each other to form a ring, and when n2 is 2 or more, a plurality of Ra2 may be linked to each other to form a ring. Examples of such cases include, for example, a mode in which two Ra1 are linked to each other and form a naphthalene ring together with the benzene ring to which they are bonded.

[0115] Ra3 is preferably a fluorine atom, an iodine atom, or a group having one or more fluorine atoms. Examples of the group having a fluorine atom include groups in which the alkyl group, cycloalkyl group, alkoxy group, cycloalkyloxy group, alkoxycarbonyl group, and alkylsulfonyl group as Ra1 and Ra2 are substituted with a fluorine atom. Among them, a fluorinated alkyl group can be preferably cited, such as CF 3 , C 2 F 5 , C 3 F 7 , C 4 F 9 , C 5 F 11 , C 6 F 13 , C 7 F 15 , C 8 F 17 , CH 2 CF 3 , CH 2 CH 2 CF 3 , CH 2 C 2 F 5 , CH 2 CH 2 C 2 F 5 , CH 2 C 3F 7 、 CH 2 CH 2 C 3 F 7 、 CH 2 C 4 F 9 and CH 2 CH 2 C 4 F 9 can be more preferably cited, and CF 3 can be particularly preferably cited.

[0116] Ra3 is preferably a fluorine atom, an iodine atom or CF 3 and more preferably a fluorine atom or an iodine atom.

[0117] n1 and n2 are each independently preferably an integer from 0 to 3, and more preferably an integer from 0 to 2.

[0118] n3 is preferably an integer from 1 to 3, and more preferably 1 or 2.

[0119] (n1 + n2 + n3) is preferably an integer from 1 to 15, more preferably an integer from 1 to 9, still more preferably an integer from 2 to 6, and particularly preferably an integer from 3 to 6. When (n1 + n2 + n3) is 1, n3 = 1 and Ra3 is preferably a fluorine atom, an iodine atom or CF 3 When (n1 + n2 + n3) is 2, the combinations where n1 = n3 = 1 and Ra1 and Ra3 are each independently a fluorine atom, an iodine atom or CF 3 and the combination where n3 = 2 and Ra3 is a fluorine atom, an iodine atom or CF 3 are preferred. When (n1 + n2 + n3) is 3, the combination where n1 = n2 = n3 = 1 and Ra1 - Ra3 are each independently a fluorine atom, an iodine atom or CF 3 is preferred. When (n1 + n2 + n3) is 4, the combination where n1 = n3 = 2 and Ra1 and Ra3 are each independently a fluorine atom, an iodine atom or CF 3The combination where (n1 + n2 + n3) is 5, n1 = n2 = 1 and n3 = 3, and Ra1 to Ra3 are each independently a fluorine atom, an iodine atom or CF 3 The combination where n1 = n2 = 2 and n3 = 1, and Ra1 to Ra3 are each independently a fluorine atom, an iodine atom or CF 3 The combination where n3 = 5 and Ra3 are each independently a fluorine atom, an iodine atom or CF 3 The combination where (n1 + n2 + n3) is 6, n1 = n2 = n3 = 2, and Ra1 to Ra3 are each independently a fluorine atom, an iodine atom or CF 3 The combination is preferred.

[0120] Specific examples of the onium cation represented by the above formula (Q-1) include the following. The fluorine atoms and iodine atoms in the following onium cations may be substituted with hydrogen atoms or other substituents.

[0121]

Chemical formula

[0122]

Chemical formula

[0123]

Chemical formula

[0124]

Chemical formula

[0125] The onium cation of structural unit (IV-2) is preferably a diaryliodonium cation having one or more fluorine atoms or iodine atoms. At least one of the aryl groups of the onium cation of structural unit (IV-2) preferably has a fluoro group-containing aromatic ring structure or an iodo group-containing aromatic ring structure.

[0126] As the side chain structure of the base polymer, an embodiment can also be adopted in which the first onium cation is bonded to the main chain, and the first organic acid anion is ionically bonded to the first onium cation as a counter ion of the first onium cation. In this case, the first onium cation is bonded to the main chain via a divalent linking group or a single bond, and V in the above formula (a1) or (a2) 2 from SO 3 - to the structure up to is preferably ionically bonded to the first onium cation as a counter ion. As the divalent linking group, the divalent linking group represented by L in the above formula (1) 1 can be preferably adopted.

[0127] When the base polymer contains structural unit (IV), the lower limit of the content ratio of structural unit (IV) (the total content ratio in the case of containing multiple types) is preferably 2 mol%, more preferably 3 mol%, and still more preferably 5 mol% with respect to all the structural units constituting the base polymer. Further, the upper limit of the above content ratio is preferably 30 mol%, more preferably 25 mol%, and still more preferably 20 mol%. By setting the content ratio of structural unit (IV) within the above range, the function as an acid generation structure can be sufficiently exhibited, and the above resist properties can be exhibited.

[0128] The monomers that give structural unit (IV-1) to structural unit (IV-2) can be synthesized, for example, in the same manner as the sulfonium salts having polymerizable anions described in Japanese Patent No. 5201363.

[0129] (Structural unit (V)) The base polymer may contain a structural unit (V) having a second organic acid anion and a second onium cation and including a second acid generating structure that generates an acid that does not dissociate the acid dissociable group upon exposure. The onium salt structure formed by the second organic acid anion and the second onium cation (i.e., the second acid generating structure) functions as an acid diffusion control structure. Specifically, the second acid generating structure has a function of substantially not dissociating the acid dissociable group of the structural unit (I) under the pattern forming conditions using the above radiation-sensitive composition and suppressing the diffusion of the acid generated from the first acid generating structure in the unexposed portion by salt exchange. It can be said that the acid generated from the second acid generating structure is a relatively weak acid (an acid with a high pKa) compared to the acid generated from the first acid generating structure. Whether the onium salt structure functions as a radiation-sensitive acid generating structure or an acid diffusion control structure is determined by the energy required to dissociate the acid dissociable group of the base polymer and the acidity of the onium salt structure or the generated acid.

[0130] The form of inclusion of the second organic acid anion and the second onium cation in the structural unit (V) of the base polymer is not particularly limited, and the base polymer may have the second organic acid anion as a side chain portion, or may have the second onium cation as a side chain portion. Having as a side chain portion means that the corresponding second organic acid anion or second onium cation is bonded (covalently bonded) to the main chain as a side chain structure of the base polymer. When the second organic acid anion is bonded to the main chain as a side chain structure of the base polymer, the second onium cation is ionically bonded to the second organic acid anion as a counter ion of the second organic acid anion. On the other hand, when the second onium cation is bonded to the main chain as a side chain structure of the base polymer, the second organic acid anion is ionically bonded to the second onium cation as a counter ion of the second onium cation. From the viewpoint of development contrast, it is preferable that the base polymer has the second organic acid anion as a side chain portion.

[0131] The above-mentioned second organic acid anion preferably has a sulfonic acid anion or a carboxylic acid anion as the acid anion part, and more preferably has a carboxylic acid anion. However, when the above-mentioned second organic acid anion has the above-mentioned sulfonic acid anion, an electron-withdrawing group is not bonded to the carbon atom adjacent to the sulfur atom in the above-mentioned sulfonic acid anion. Examples of the electron-withdrawing group include the electron-withdrawing groups that the above-mentioned first organic acid anion may have in the above-mentioned first acid generation structure. The acid generated by exposure becomes a carboxylic acid or a sulfonic acid corresponding to the above-mentioned acid anion part.

[0132] As a structure other than the above-mentioned acid anion part, the above-mentioned second organic acid anion preferably contains -O-, -CO-, a cyclic structure, or a combination thereof. As such a structure, the structure represented by the above-mentioned first organic acid anion can be preferably adopted.

[0133] The above-mentioned second organic acid anion preferably has an iodine group or a hydroxy group. As a content mode of the iodine group, the above-mentioned second organic acid anion preferably contains the above-mentioned iodine group-containing aromatic ring structure.

[0134] Examples of the above-mentioned second onium cation include radiation-decomposable or non-radiation-decomposable onium cations. Examples of the radiation-decomposable or non-radiation-decomposable onium cation include a sulfonium cation, a tetrahydrothiophenium cation, an iodonium cation, an ammonium cation, and the like. Among them, a sulfonium cation or an iodonium cation is preferable, and a sulfonium cation is more preferable.

[0135] The above-mentioned second onium cation preferably has an iodine group. As a content mode of the iodine group, the above-mentioned second onium cation preferably contains the above-mentioned iodine group-containing aromatic ring structure.

[0136] The second onium cation in the structural unit (V) preferably has the above fluorine group-containing aromatic ring structure. Thereby, the sensitivity can be improved by increasing the radiation absorption efficiency.

[0137] By having the structural unit (V) combine the above structures, the above-mentioned functions can be efficiently exerted.

[0138] The structural unit (V) is preferably a structural unit represented by the following formula (p1) (hereinafter, also referred to as "structural unit (V-1)").

[0139]

Chemical formula

[0140] In formula (p1), R A is a hydrogen atom or a methyl group.

[0141] In formula (p1), X 1 is a single bond, an ester bond, an ether bond, a phenylene group or a naphthylene group.

[0142] In formula (p1), X 2 is a single bond, a saturated hydrocarbylene group having 1 to 12 carbon atoms or a phenylene group, and the saturated hydrocarbylene group may contain an ether bond, an ester bond, an amide bond, a lactone ring or a sultone ring. X 2The hydrocarbylene group represented by can be linear, branched or cyclic. Specific examples thereof include alkanediyl groups having 1 to 12 carbon atoms such as methylene group, ethane-1,1-diyl group, ethane-1,2-diyl group, propane-1,2-diyl group, propane-1,3-diyl group, propane-2,2-diyl group, butane-1,2-diyl group, butane-1,3-diyl group, butane-1,4-diyl group, butane-2,2-diyl group, butane-2,3-diyl group, 2-methylpropane-1,3-diyl group, pentane-1,5-diyl group, hexane-1,6-diyl group, heptane-1,7-diyl group, octane-1,8-diyl group, nonane-1,9-diyl group, decane-1,10-diyl group; cyclic saturated hydrocarbylene groups having 3 to 12 carbon atoms such as cyclopentanediyl group, cyclohexanediyl group, norbornanediyl group, adamantanediyl group; groups obtained by combining these, and the like.

[0143] In formula (p1), X 3 is a single bond, an ester bond or an ether bond.

[0144] In formula (p1), R X is a linear, branched or cyclic alkyl group having 1 to 5 carbon atoms, a halogen atom, a hydroxy group, a linear, branched or cyclic alkoxy group having 1 to 4 carbon atoms, or a linear, branched or cyclic alkoxycarbonyl group having 2 to 5 carbon atoms.

[0145] In formula (p1), R 43 ~R 45 has the same meaning as in the above formula (a1).

[0146] In formula (p1), x1 is an integer of 0 to 3. When x1 is 2 or more, a plurality of R X are the same or different.

[0147] Instead of the sulfonium cation in the above formula (p1), an iodonium cation can also be used. As the iodonium cation, a diaryliodonium cation shown as the onium cation of structural unit (II-2) can be preferably employed.

[0148] Examples of the second organic acid anion of the monomer that provides the structural unit (V) include, but are not limited to, those shown below. Note that all of the second organic acid anions shown below have an iodine group or a hydroxy group, but the structural unit (V) does not necessarily require an iodine group or a hydroxy group. As the second organic acid anion that does not have an iodine group or a hydroxy group, a structure in which the iodine group or the hydroxy group in the following formula is substituted with a hydrogen atom, another substituent, etc. can be preferably employed. In the following formula, R A is the same as described above. Note that the second organic acid anion preferably has a carboxylic acid anion and a hydroxy group. In this case, it is preferable that the carboxylic acid anion and the hydroxy group are bonded to the same aromatic ring in the second organic acid anion, and in the same aromatic ring, the carbon atom to which the carboxylic acid anion is bonded and the carbon atom to which the hydroxy group is bonded are more preferably directly bonded to each other.

[0149]

Chemical formula

[0150]

Chemical formula

[0151]

Chemical formula

[0152]

Chemical formula

[0153]

Chemical formula

[0154]

Chemical formula

[0155] [Chem.]

[0156] [Chem.]

[0157] [Chem.]

[0158] As the second onium cation of the structural unit (V), the sulfonium cation represented by the above formula (Q-1) can be preferably adopted.

[0159] As the side chain structure of the base polymer, a mode can also be adopted in which the second onium cation is bonded to the main chain and the second organic acid anion is ionically bonded to the second onium cation as the counter ion of the second onium cation. In this case, the second onium cation is bonded to the main chain via a divalent linking group or a single bond, and X in the above formula (p1) 1 from COO - to is preferably ionically bonded to the second onium cation as the counter ion. As the divalent linking group, the divalent linking group represented by L in the above formula (1) 1 can be preferably adopted.

[0160] When the base polymer contains the structural unit (V), the lower limit of the content ratio of the structural unit (V) (the total content ratio in the case of containing a plurality of types) is preferably 1 mol%, more preferably 2 mol%, and even more preferably 3 mol% with respect to all the structural units constituting the base polymer. Further, the upper limit of the content ratio is preferably 15 mol%, more preferably 10 mol%, and even more preferably 8 mol%. By setting the content ratio of the structural unit (V) within the above range, the function as an acid diffusion control structure can be sufficiently exhibited.

[0161] (Method for synthesizing base polymer) The base polymer can be synthesized, for example, by polymerizing monomers that provide each structural unit in a suitable solvent using a radical polymerization initiator or the like.

[0162] Examples of the radical polymerization initiator include azo-based radical initiators such as azobisisobutyronitrile (AIBN), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2-cyclopropylpropionitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), and dimethyl 2,2'-azobisisobutyrate; peroxide-based radical initiators such as benzoyl peroxide, t-butyl hydroperoxide, and cumene hydroperoxide. Among 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.

[0163] As the solvent used in the above polymerization, the solvents described below can be preferably employed. These solvents used in the polymerization may be used alone or in combination of two or more.

[0164] The reaction temperature in the above 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.

[0165] The molecular weight of the base polymer is not particularly limited, but the lower limit of the polystyrene-equivalent weight average molecular weight (Mw) by gel permeation chromatography (GPC) is preferably 2,000, more preferably 3,000, and even more preferably 4,000. The upper limit of Mw is preferably 20,000, more preferably 16,000, and even more preferably 14,000. By setting the Mw of the base polymer within the above range, the resulting resist film can exhibit good heat resistance and developability.

[0166] The ratio (Mw / Mn) of the weight-average molecular weight (Mw) to the polystyrene-reduced number-average molecular weight (Mn) of the base polymer 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.

[0167] The measurement methods of Mw and Mn of the polymer in this specification are according to the description in the examples.

[0168] As the lower limit of the content ratio of the base polymer, 30% by mass is preferable, 40% by mass is more preferable, and 50% by mass is even more preferable with respect to the total solid content of the radiation-sensitive composition. As the upper limit of the above content ratio, 80% by mass is preferable, and 70% by mass is more preferable.

[0169] <Second polymer> The radiation-sensitive composition of this embodiment contains a second polymer. Since the second polymer contains a structural unit (i) represented by the following formula (f1), it can be said that it is a polymer having a higher mass content ratio of fluorine atoms than the above base polymer. By containing the second polymer in the radiation-sensitive composition, it can be unevenly distributed on the surface layer of the resist film with respect to the above base polymer. As a result, surface modification of the resist film during EUV exposure or control of the distribution of the composition in the film can be achieved.

[0170] [Chemical formula] (In the above formula (f1), R K1 is a hydrogen atom, a fluorine atom, an alkyl group having 1 to 6 carbon atoms, a halogenated alkyl group having 1 to 6 carbon atoms, or -R K2 -X-R K3 represented group (wherein R K2 is a single bond, an alkanediyl group having 1 to 6 carbon atoms, or a halogenated alkanediyl group having 1 to 6 carbon atoms, X is a divalent linking group having a hetero atom, and R K3 is an alkyl group having 1 to 6 carbon atoms or a halogenated alkyl group having 1 to 6 carbon atoms). L Y1 is a divalent hydrocarbon group having 1 to 10 carbon atoms. L Y2is -COO- * or -OCO- * . * is the bond on the R f1 side. R f1 is a monovalent hydrocarbon group having 1 to 10 carbon atoms or a monovalent fluorinated hydrocarbon group having 1 to 10 carbon atoms. R f2 and R f3 are each independently a fluorine atom or a monovalent fluorinated hydrocarbon group having 1 to 10 carbon atoms. R f2 and R f3 When there are a plurality of R f2 and R f3 they may be the same or different from each other. s is an integer from 0 to 3. However, when R f1 is a monovalent hydrocarbon group having 1 to 10 carbon atoms, s is an integer from 1 to 3.)

[0171] R K1 and R K3 As the alkyl group having 1 to 6 carbon atoms represented by, the group corresponding to 1 to 6 carbon atoms among the monovalent linear or branched saturated hydrocarbon groups having 1 to 10 carbon atoms in R 1A and R 1B in the above formula (1) can be preferably adopted.

[0172] R K1 and R K3 As the halogenated alkyl group having 1 to 6 carbon atoms represented by, a group in which some or all of the hydrogen atoms of the above alkyl group having 1 to 6 carbon atoms are substituted with halogen atoms can be mentioned. As the halogen atom, a fluorine atom is preferable. Examples of the halogenated alkyl group having 1 to 6 carbon atoms include a trifluoromethyl group, a 2,2,2-trifluoroethyl group, a pentafluoroethyl group, a 2,2,3,3,3-pentafluoropropyl group, a 1,1,1,3,3,3-hexafluoropropyl group, a heptafluoro n-propyl group, a heptafluoro isopropyl group, a nonafluoro n-butyl group, a nonafluoro isobutyl group, a nonafluoro t-butyl group, a 2,2,3,3,4,4,5,5-octafluoro n-pentyl group, a tridecafluoro n-hexyl group, and the like.

[0173] R K2 Examples of the C1-C6 alkanediyl group represented by the above are the groups obtained by removing one hydrogen atom from the alkyl groups having 1 to 6 carbon atoms represented by the above R K1 and R K3 Examples of the group obtained by removing one hydrogen atom from the halogenated alkyl groups having 1 to 6 carbon atoms represented by the above are the groups obtained by removing one hydrogen atom from the halogenated alkyl groups having 1 to 6 carbon atoms represented by the above R

[0174] R K2 Examples of the C1-C6 halogenated alkanediyl group represented by the above are the groups obtained by removing one hydrogen atom from the halogenated alkyl groups having 1 to 6 carbon atoms represented by the above R K1 and R K3 Examples of the group obtained by removing one hydrogen atom from the halogenated alkyl groups having 1 to 6 carbon atoms represented by the above are the groups obtained by removing one hydrogen atom from the halogenated alkyl groups having 1 to 6 carbon atoms represented by the above R

[0175] L Y1 Examples of the divalent hydrocarbon group having 1 to 10 carbon atoms represented by the above are the groups obtained by removing one hydrogen atom from the groups corresponding to those having 1 to 10 carbon atoms among the monovalent hydrocarbon groups having 1 to 20 carbon atoms represented by R in the above formula (3-1). Among them, as the divalent hydrocarbon group having 1 to 10 carbon atoms represented by L 8 the methylene group, ethanediyl group, and propanediyl group are preferable. Y1 Examples of the divalent hydrocarbon group having 1 to 10 carbon atoms represented by the above are the methylene group, ethanediyl group, and propanediyl group.

[0176] L Y2 is preferably -COO- *

[0177] R f1 Examples of the monovalent hydrocarbon group having 1 to 10 carbon atoms represented by the above are the groups corresponding to those having 1 to 10 carbon atoms among the monovalent hydrocarbon groups having 1 to 20 carbon atoms represented by R in the above formula (3-1). Among them, as the monovalent hydrocarbon group having 1 to 10 carbon atoms represented by R 8 the methyl group, ethyl group, and propyl group are preferable. f1 Examples of the monovalent hydrocarbon group having 1 to 10 carbon atoms represented by the above are the methyl group, ethyl group, and propyl group.

[0178] R f1 R f2 and R f3 ​Examples of the monovalent fluorinated hydrocarbon group having 1 to 10 carbon atoms represented by [the formula] include, for example, a monovalent fluorinated linear hydrocarbon group having 1 to 10 carbon atoms, a monovalent fluorinated alicyclic hydrocarbon group having 3 to 10 carbon atoms, and the like.

[0179] Examples of the monovalent fluorinated linear hydrocarbon group having 1 to 10 carbon atoms include the above R K1 and R K3 a fluorinated alkyl group obtained by expanding a halogenated alkyl group having 1 to 6 carbon atoms represented by [the formula] to 10 carbon atoms and replacing the halogen atom with a fluorine atom; a fluorinated alkenyl group such as a trifluoroethenyl group or a pentafluoropropenyl group; a fluorinated alkynyl group such as a fluoroethynyl group or a trifluoropropynyl group.

[0180] Examples of the monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms include a fluorinated cycloalkyl group such as a fluorocyclopentyl group, a difluorocyclopentyl group, a nonafluorocyclopentyl group, a fluorocyclohexyl group, a difluorocyclohexyl group, an undecafluorocyclohexylmethyl group, a fluoronorbornil group, a fluoroadamantyl group, a fluorobornyl group, a fluoroisobornyl group, a fluorotricyclodecyl group, or a fluorotetracyclodecyl group; a fluorinated cycloalkenyl group such as a fluorocyclopentenyl group or a nonafluorocyclohexenyl group.

[0181] R f1 , R f2 and R f3 As the monovalent fluorinated hydrocarbon group having 1 to 10 carbon atoms represented by [the formula], a monovalent fluorinated linear hydrocarbon group having 1 to 10 carbon atoms is preferable, a monovalent fluorinated linear hydrocarbon group having 1 to 6 carbon atoms is more preferable, and a monovalent fluorinated linear saturated hydrocarbon group having 1 to 4 carbon atoms is even more preferable.

[0182] s is preferably an integer of 0 to 2, and more preferably 0 or 1.

[0183] In the above formula (f1), R f1 is a monovalent fluorinated hydrocarbon group having 1 to 10 carbon atoms, and s is preferably 0.

[0184] The monomers that give the structural unit (i) are preferably represented by the following formulas (f1-1) and (f1-12), respectively.

[0185]

Chemical formula

[0186] The lower limit of the content ratio of the structural unit (i) (when a plurality of types are included, the total content ratio) is preferably 30 mol%, more preferably 40 mol%, and even more preferably 45 mol% with respect to all the structural units constituting the second polymer. Also, the upper limit of the above content ratio is preferably 100 mol%, more preferably 90 mol%, and even more preferably 80 mol%. By setting the content ratio of the structural unit (V) within the above range, the solubility of the resist film surface layer by the second polymer can be improved.

[0187] (Other structural units) The second polymer may contain the structural unit (II) in the above base polymer as a structural unit other than the above structural unit (i). Further, it may contain the following structural units (ii), (iii), and a structural unit derived from (meth) acrylic acid.

[0188] (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, and a sultone structure. The second polymer can adjust the solubility in the developer by further having the structural unit (ii).

[0189] When the second polymer contains the structural unit (ii), the lower limit of the content ratio of the structural unit (ii) is preferably 5 mol%, more preferably 10 mol%, and still more preferably 15 mol% with respect to all the structural units constituting the second polymer. The upper limit of the above content ratio is preferably 40 mol%, more preferably 30 mol%, and still more preferably 25 mol%. By setting the content ratio of the structural unit (ii) within the above range, the solubility of the second polymer in the developer can be efficiently adjusted.

[0190] (Structural unit (iii)) Examples of the structural unit (iii) include structural units containing a polar group (however, those corresponding to the structural units (III) to (V) and the structural unit (ii) are excluded). By further having the structural unit (iii), the solubility of the second polymer in the developer can be adjusted. Examples of the above polar group include a hydroxy group, a carboxy group, a cyano group, a nitro group, a sulfonamide group, etc. Among these, a hydroxy group and a carboxy group are preferable, and a hydroxy group is more preferable.

[0191] Examples of the structural unit (iii) include structural units represented by the following formulae.

[0192] [Chemical formula]

[0193] In the above formula, R K is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.

[0194] When the second polymer has the structural unit (iii) having the above polar group, the lower limit of the content ratio of the structural unit (iii) is preferably 5 mol%, more preferably 10 mol%, and still more preferably 15 mol% with respect to all the structural units constituting the second polymer. The upper limit of the above content ratio is preferably 40 mol%, more preferably 30 mol%, and still more preferably 25 mol%. By setting the content ratio of the structural unit (iii) within the above range, the solubility of the second polymer in the developer can be efficiently adjusted.

[0195] When the second polymer has a structural unit derived from the above (meth)acrylic acid, the lower limit of the content ratio of the structural unit is preferably 5 mol%, more preferably 10 mol%, and even more preferably 15 mol% with respect to all the structural units constituting the second polymer. As the upper limit of the above content ratio, 50 mol% is preferable, 40 mol% is more preferable, and 30 mol% is even more preferable.

[0196] The lower limit of Mw of the second polymer is preferably 8,000, more preferably 12,000, and even more preferably 16,000. Further, the upper limit of the Mw is preferably 35,000, more preferably 30,000, and even more preferably 25,000.

[0197] The lower limit of Mw / Mn of the second polymer is usually 1, and more preferably 1.1. Further, the upper limit of the Mw / Mn is usually 5, preferably 3, and more preferably 2.

[0198] The lower limit of the content of the second polymer is preferably 0.1 part by mass, more preferably 1 part by mass, even more preferably 2 parts by mass, and particularly preferably 3 parts by mass with respect to 100 parts by mass of the base polymer. Further, the upper limit of the content is preferably 20 parts by mass, more preferably 15 parts by mass, even more preferably 10 parts by mass, and particularly preferably 6 parts by mass.

[0199] By setting the content of the second polymer within the above range, the second polymer can be more effectively unevenly distributed on the surface layer of the resist film. As a result, the solubility of the surface layer of the resist film during development can be improved, and surface modification of the resist film and control of the distribution of the composition within the film during EUV exposure can be achieved. The radiation-sensitive composition may contain one or more second polymers.

[0200] (Synthesis method of the second polymer) The second polymer can be synthesized by the same method as the synthesis method of the above base polymer.

[0201] (Radiation-sensitive acid generator) The radiation-sensitive composition may contain a radiation-sensitive acid generator. The radiation-sensitive acid generator contains a third organic acid anion and a third onium cation, and forms an onium salt structure. The radiation-sensitive acid generator is a component that generates an acid upon exposure. The acid generated upon exposure has a function of dissociating an acid-dissociable group possessed by the base polymer and generating a carboxy group or the like. The radiation-sensitive acid generator has a form in which the onium salt structure exists alone as a low-molecular compound (released from the polymer), and is different from a radiation-sensitive acid generation structure in which a first organic acid anion or a first onium cation is bonded (covalently bonded) to the main chain as a side chain structure of the base polymer, such as the structural unit (IV) in the above base polymer.

[0202] At least one selected from the group consisting of the above third organic acid anion and third onium cation preferably has an iodine group, and more preferably has the above iodine group-containing aromatic ring structure.

[0203] The structure of the third organic acid anion of the radiation-sensitive acid generator is V in the above formula (a1) or (a2) of the base polymer 2 from SO 3 - In addition to the structure up to, a conventionally known structure can be preferably adopted.

[0204] Examples of the third organic acid anion of the radiation-sensitive acid generator include, but are not limited to, those shown below. Instead of the first organic acid anion having an iodine group-containing aromatic ring structure, as the third organic acid anion having no iodine group-containing aromatic ring structure, a structure in which the iodine group in the following formula is substituted with a hydrogen atom, another substituent, or the like can be preferably adopted.

[0205]

Chemical formula

[0206]

Chemical formula

[0207]

Chem.

[0208] The structure of the third onium cation of the radiation-sensitive acid generator can preferably adopt the structure of the first onium cation of the structural unit (IV) in the above base polymer.

[0209] The above radiation-sensitive acid generator can also be synthesized by a known method, particularly by a salt exchange reaction. As long as the effects of the present invention are not impaired, a known radiation-sensitive acid generator can also be used.

[0210] These radiation-sensitive acid generators may be used alone or in combination of two or more. When the radiation-sensitive composition contains a radiation-sensitive acid generator, the lower limit of the content of the radiation-sensitive acid generator (total in the case of multiple types) is preferably 5 parts by mass, more preferably 10 parts by mass, and even more preferably 15 parts by mass with respect to 100 parts by mass of the base polymer. Further, the upper limit of the above content is preferably 100 parts by mass, more preferably 90 parts by mass, and even more preferably 80 parts by mass. Thereby, excellent sensitivity can be exhibited during resist pattern formation.

[0211] <Acid diffusion control agent> The radiation-sensitive composition may contain an acid diffusion control agent. The acid diffusion control agent contains a fourth organic acid anion and a fourth onium cation, and generates an acid having a higher pKa than the acid generated from the above radiation-sensitive acid generator by irradiation with radiation. The acid diffusion control agent has a function of substantially not dissociating the acid dissociable group of the base polymer under the pattern formation conditions using the radiation-sensitive composition and suppressing the diffusion of the acid generated from the above radiation-sensitive acid generator in the unexposed portion by salt exchange.

[0212] By containing the above acid diffusion control agent in the radiation-sensitive composition, the diffusion of the acid in the unexposed portion can be suppressed, and a resist pattern having better LWR performance and development contrast can be formed.

[0213] At least one selected from the group consisting of the above fourth organic acid anion and fourth onium cation preferably has an iodine group, and more preferably has the above iodine group-containing aromatic ring structure.

[0214] Although the structure of the above fourth organic acid anion is not specified, it preferably contains -O-, -CO-, a cyclic structure, or a combination thereof. As the cyclic structure, the cyclic structure in the above first organic acid anion of the structural unit (IV) of the base polymer can be preferably adopted.

[0215] In the acid diffusion controller, it is preferable that the above fourth organic acid anion has a sulfonic acid anion or a carboxylic acid anion as the acid anion part (however, when the above fourth organic acid anion has the above sulfonic acid anion, neither a fluorine atom nor a fluorinated hydrocarbon group is bonded to the carbon atom adjacent to the sulfur atom of the above sulfonic acid anion). Thereby, the acid diffusion controller can efficiently exhibit the above function.

[0216] Examples of the acid diffusion controller include sulfonium salt compounds represented by the following formula (8-1), iodonium salt compounds represented by the following formula (8-2), etc. Further, compounds containing a sulfonium cation and an anion in the same molecule represented by the following formula (8-3), and compounds containing an iodonium cation and an anion in the same molecule represented by the following formula (8-4) are included.

[0217]

Chemical formula

[0218] In the above formulas (8-1) to (8-4), J + is a sulfonium cation, and U + is an iodonium cation. E - and Q - are each independently OH - 、R α -COO -, R α -SO 3 - is the fourth organic acid anion represented by the formula. In the above formulas (8-1) to (8-2), R α is a monovalent organic group having 1 to 30 carbon atoms. In the above formulas (8-3) to (8-4), R α is a single bond or a divalent organic group having 1 to 30 carbon atoms. Examples of this organic group include a monovalent hydrocarbon group having 1 to 20 carbon atoms, a group having a divalent heteroatom-containing group at the carbon-carbon bond or the end of the carbon chain of this hydrocarbon group, a group in which some or all of the hydrogen atoms of the above hydrocarbon group are substituted with a monovalent heteroatom-containing group, or a combination thereof, and the like.

[0219] As the monovalent hydrocarbon group having 1 to 20 carbon atoms in the above organic group, the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by R 8 in the above formula (3-1) can be preferably employed. As the divalent heteroatom-containing group, the divalent heteroatom-containing group in the above first organic acid anion of the structural unit (IV) of the base polymer can be preferably employed. Examples of the monovalent heteroatom-containing group include a hydroxy group, a carboxy group, a sulfanyl group, a cyano group, a nitro group, a halogen atom, and the like.

[0220] Examples of the fourth organic acid anion of the above acid diffusion controller include, but are not limited to, the following. Compounds containing an iodonium cation and an anion in the same molecule and compounds containing a sulfonium cation and an anion in the same molecule are also exemplified. As the organic acid anion having no iodo group-containing aromatic ring structure, a structure in which the iodo group in the following formula is substituted with an atom or group other than the iodo group such as a hydrogen atom or another substituent can be preferably employed.

[0221]

Chemical formula

[0222]

Chemical formula

[0223] As the fourth onium cation in the acid diffusion controller, the structure of the first onium cation of the structural unit (IV) in the base polymer can be preferably adopted.

[0224] When the fourth onium cation is an iodonium cation, it is preferably a diaryliodonium cation. The diaryliodonium cation more preferably has one or more fluoro groups or iodo groups.

[0225] The acid diffusion controller can also be synthesized by a known method, particularly by a salt exchange reaction.

[0226] These acid diffusion controllers may be used alone or in combination of two or more. When the radiation-sensitive composition contains an acid diffusion controller, the lower limit of the content of the acid diffusion controller (the total in the case of multiple types) is preferably 10 mol%, more preferably 15 mol%, and still more preferably 20 mol% with respect to the total of the content ratio of the structural unit (IV) of the base polymer and the content of the radiation-sensitive acid generator. The upper limit of the above content is preferably 40 mol%, more preferably 35 mol%, and still more preferably 30 mol%.

[0227] <Solvent> The radiation-sensitive composition according to this embodiment contains a solvent. The solvent is not particularly limited as long as it can dissolve or disperse the base polymer and additives contained as desired.

[0228] Examples of the solvent include alcohol solvents, ether solvents, ketone solvents, amide solvents, ester solvents, hydrocarbon solvents, and the like.

[0229] Examples of the alcohol solvent include Monoalcohol solvents with 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, diacetone alcohol; Polyhydric alcohol solvents with 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, tripropylene glycol; Examples include polyhydric alcohol partial ether solvents in which some of the hydroxy groups of the above polyhydric alcohol solvents are etherified. In this embodiment, alcohol acid ester solvents such as methyl lactate, ethyl lactate, propyl lactate, butyl lactate, methyl 2-hydroxyisobutyrate, i-propyl 2-hydroxyisobutyrate, i-butyl 2-hydroxyisobutyrate, n-butyl 2-hydroxyisobutyrate are also included in the alcohol solvents.

[0230] As ether solvents, for example, Dialkyl ether solvents such as diethyl ether, dipropyl ether, dibutyl ether; Cyclic ether solvents such as tetrahydrofuran, tetrahydropyran; Aromatic ring-containing ether solvents such as diphenyl ether, anisole (methyl phenyl ether); Examples include polyhydric alcohol ether solvents in which the hydroxy groups of the above polyhydric alcohol solvents are etherified.

[0231] As ketone solvents, for example, chain ketone solvents such as acetone, butanone, methyl-iso-butyl ketone: Cyclic ketone solvents such as cyclopentanone, cyclohexanone, methylcyclohexanone: Examples include 2,4-pentanedione, acetonylacetone, acetophenone.

[0232] Examples of amide solvents include cyclic amide solvents such as N,N'-dimethylimidazolidinone and N-methylpyrrolidone; Chain amide solvents such as N-methylformamide, N,N-dimethylformamide, N,N-diethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, N-methylpropionamide, etc. can be mentioned.

[0233] Examples of ester solvents include, for example, Monocarboxylic acid ester solvents such as n-butyl acetate; Polyhydric alcohol partial ether acetate solvents such as diethylene glycol mono-n-butyl ether acetate, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether acetate, etc.; Lactone solvents such as γ-butyrolactone and valerolactone; Carbonate solvents such as diethyl carbonate, ethylene carbonate, and propylene carbonate; Polycarboxylic acid diester solvents such as dipropylene glycol diacetate, methoxytriglycol acetate, diethyl oxalate, ethyl acetoacetate, and diethyl phthalate can be mentioned.

[0234] Examples of hydrocarbon solvents include, for example, Aliphatic hydrocarbon solvents such as n-hexane, cyclohexane, and methylcyclohexane; Aromatic hydrocarbon solvents such as benzene, toluene, di-iso-propylbenzene, and n-amylnaphthalene, etc. can be mentioned.

[0235] Among these, ester solvents, ether solvents, and alcohol solvents are preferred, polyhydric alcohol partial ether acetate solvents, polyhydric alcohol partial ether solvents, lactone solvents, monoalcohol solvents, and alcohol acid ester solvents are more preferred, and propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, γ-butyrolactone, diacetone alcohol, ethyl lactate, and methyl 2-hydroxyisobutyrate are even more preferred. The radiation-sensitive composition may contain one or more solvents.

[0236] <Other optional components> In addition to the above components, the radiation-sensitive composition may also contain other optional components. Examples of the other optional components include crosslinking agents, uneven distribution promoters, surfactants, alicyclic skeleton-containing compounds, sensitizers, and the like. These other optional components may be used in combination of one or more of each.

[0237] <Method for preparing the radiation-sensitive composition> The radiation-sensitive composition can be prepared, for example, by mixing a base polymer and a solvent, and optionally other optional components, in a predetermined ratio. After mixing, the radiation-sensitive composition is preferably filtered, for example, with a filter having a pore size of about 0.05 μm to 0.4 μm. The solid content concentration of the radiation-sensitive composition is usually 0.1% by mass to 50% by mass, preferably 0.5% by mass to 30% by mass, and more preferably 1% by mass to 20% by mass.

[0238] <Pattern formation method> The pattern formation method in this embodiment is a step (1) of directly or indirectly applying the radiation-sensitive composition onto a substrate to form a resist film (hereinafter, also referred to as "resist film formation step"), a step (2) of exposing the resist film (hereinafter, also referred to as "exposure step"), and a step (3) of developing the exposed resist film with a developer (hereinafter, also referred to as "development step").

[0239] According to the above-described pattern formation method, since the radiation-sensitive composition capable of exhibiting LWR performance and over-exposure margin equal to or better than those of the conventional ones with excellent sensitivity during pattern formation is used, a high-quality resist pattern can be formed. Hereinafter, each step will be described.

[0240] [Resist film formation step] In this step (the above step (1)), a resist film is formed using the above radiation-sensitive composition. Examples of the substrate on which this resist film is formed include conventionally known ones such as silicon wafers, silicon dioxide, and wafers coated with aluminum. Further, for example, an organic or inorganic antireflection film disclosed in Japanese Patent Publication No. 6-12452 or Japanese Unexamined Patent Application Publication No. 59-93448 may be formed on the substrate. Examples of the coating method include spin coating, casting coating, roll coating, etc. After coating, pre-baking (PB) may be performed as necessary to volatilize the solvent in the coating film. The PB temperature is usually 60°C to 160°C, preferably 80°C to 140°C. The PB time is usually 5 seconds to 600 seconds, preferably 10 seconds to 300 seconds. The film thickness of the formed resist film is preferably 10 nm to 1,000 nm, more preferably 10 nm to 500 nm.

[0241] [Exposure step] In this step (the above step (2)), the resist film formed in the resist film formation step which is the above step (1) is irradiated with radiation through a photomask for exposure. Examples of the radiation used for exposure include electromagnetic waves such as visible light, ultraviolet light, far ultraviolet light, EUV (extreme ultraviolet light), X-rays, γ-rays, etc.; charged particle beams such as electron beams, α-rays, etc., according to the line width of the target pattern. Among these, far ultraviolet light, electron beams, and EUV are preferred, ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), electron beams, and EUV are more preferred, and electron beams and EUV with a wavelength of 50 nm or less positioned as the next-generation exposure technology are even more preferred.

[0242] After the above exposure, post-exposure baking (PEB) is preferably performed to promote dissociation of acid-labile groups of polymers or the like due to acids generated from a radiation-sensitive acid generator or structural unit (IV) in the exposed portion of the resist film. By this PEB, a difference in solubility in the developer occurs between the exposed portion and the unexposed portion. The PEB temperature is usually 50°C to 180°C, preferably 80°C to 150°C. The PEB time is usually 5 seconds to 600 seconds, preferably 10 seconds to 300 seconds.

[0243] [Development step] In this step (the above step (3)), the resist film exposed in the above exposure step (the above step (2)) is developed with a developer. Thereby, a predetermined resist pattern can be formed. After development, it is common to wash with a rinse solution such as water or alcohol and then dry.

[0244] Examples of the developer used for the above development include, in the case of alkali development, an aqueous alkali solution in which at least one alkaline compound such as sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, aqueous ammonia, ethylamine, n-propylamine, diethylamine, di-n-propylamine, triethylamine, methyldiethylamine, ethyldimethylamine, triethanolamine, tetramethylammonium hydroxide (TMAH), pyrrole, piperidine, choline, 1,8-diazabicyclo-[5.4.0]-7-undecene, 1,5-diazabicyclo-[4.3.0]-5-nonene is dissolved. Among these, an aqueous TMAH solution is preferred, and a 2.38 mass% aqueous TMAH solution is more preferred.

[0245] In the case of organic solvent development, examples of the organic solvent include hydrocarbon solvents, ether solvents, ester solvents, ketone solvents, alcohol solvents, and other organic solvents, or solvents containing an organic solvent. Examples of the above organic solvents include one or more of the solvents listed as the solvents of the above radiation-sensitive composition. Among these, ester solvents and ketone solvents are preferred. As the ester solvent, an acetic acid ester solvent is preferred, and n-butyl acetate and amyl acetate are more preferred. As the ketone solvent, a chain ketone is preferred, and 2-heptanone is 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, still more preferably 95% by mass or more, and particularly preferably 99% by mass or more. Examples of the components other than the organic solvent in the developer include water, silicone oil, and the like.

[0246] Examples of the development method include a method of immersing a substrate in a tank filled with a developer for a certain period of time (dip method), a method of developing by raising the developer on the substrate surface by surface tension and allowing it to stand for a certain period of time (paddle method), a method of spraying the developer on the substrate surface (spray method), a method of continuously discharging the developer while scanning a developer discharge nozzle at a constant speed on a substrate rotating at a constant speed (dynamic dispense method), and the like.

Examples

[0247] Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. The physical property values in the examples were measured as follows.

[0248] [Synthesis Example] Synthesis of Base Polymer The monomers shown in the following formula were combined in the composition shown in Table 1 below and copolymerized in a tetrahydrofuran (THF) solvent. The copolymer was crystallized in methanol, and after repeated washing with hexane, it was isolated and dried to obtain A-1 to A-40 as base polymers having the following compositions. In Table 1, "-" indicates that the corresponding component was not used. The same applies to the following tables.

[0249] The Mw and dispersity (Mw / Mn) of the polymer were measured under the following conditions using GPC columns (two "G2000HXL", one "G3000HXL", and one "G4000HXL") manufactured by Tosoh Corporation by gel permeation chromatography (GPC). (Measurement conditions) Eluent: Tetrahydrofuran (manufactured by Wako Pure Chemical Industries, Ltd.) Flow rate: 1.0 mL / min Sample concentration: 1.0 mass% Sample injection volume: 100 μL Column temperature: 40 °C Detector: Differential refractometer Standard substance: Monodisperse polystyrene

[0250]

Chemical formula

[0251]

Chemical formula

[0252]

Table 1

[0253] [Synthesis example] Synthesis of the second polymer The monomers shown in the following formula were combined in the composition shown in Table 2 below and copolymerized under a tetrahydrofuran (THF) solvent. After polymerization, the solvent was replaced with acetonitrile and washed with hexane. Then, the solvent was replaced with propylene glycol monomethyl ether acetate to obtain FP-1 to FP-21 as the second polymer.

[0254]

Chemical formula

[0255]

Table 2

[0256] In addition to the above-synthesized polymer, the components used in the preparation of the radiation-sensitive composition are shown below.

[0257] <[Radiation-sensitive acid generator]>

[0258] [Chemical formula]

[0259] [Chemical formula]

[0260] <[Acid diffusion controller]>

[0261] [Chemical formula]

[0262] <[Solvent]> D-1: Propylene glycol monomethyl ether acetate D-2: Propylene glycol 1-monomethyl ether

[0263] [Example 1] [A] 100 parts by mass of the first polymer (A-6), [B] 20 parts by mass of (B-1) as a radiation-sensitive acid generator, [C] 25 mol% of (Z-1) as an acid diffusion controller with respect to (B-1), [F] 5 parts by mass of the second polymer (FP-1), 2,000 parts by mass of [D] (D-1) as a solvent, and 4,800 parts by mass of (D-2) were blended to prepare a radiation-sensitive composition (R-1).

[0264] [Examples 2 to 64 and Comparative Examples 1 to 62] The radiation-sensitive compositions (R-2) to (R-64) and (cR-1) to (cR-62) were prepared in the same manner as in Example 1, except that the components of the types and blending amounts shown in Tables 3-1 and 3-2 and Tables 4-1 and 4-2 below were used.

[0265]

Table 3-1

[0266]

Table 3-2

[0267]

Table 4-1

[0268]

Table 4-2

[0269] <Formation of Resist Pattern> (EUV Exposure, Alkaline Development) On the surface of a 12-inch silicon wafer on which a lower layer film (AL412, manufactured by Brewer Science) with a film thickness of 50 nm was formed, the above-prepared radiation-sensitive composition was applied using a spin coater (CLEAN TRACK ACT12, manufactured by Tokyo Electron), and after performing PB at 130 °C for 60 seconds, it was cooled at 23 °C for 30 seconds to form a resist film with a film thickness of 50 nm. Next, this resist film was irradiated with EUV light using an EUV exposure machine (model "NXE3300", manufactured by ASML, NA = 0.33, illumination condition: Conventional s = 0.89, mask imecDEFECT32FFR02). PEB was performed on the above resist film at 110 °C for 60 seconds. Then, using a 2.38 wt% aqueous TMAH solution, development was carried out at 23 °C for 30 seconds to form a positive 32 nm line and space pattern.

[0270] <Evaluation> For each of the formed resist patterns, the sensitivity, LWR performance, and overexposure margin of each radiation-sensitive composition were evaluated by measuring according to the following method. A scanning electron microscope ("CG-4100" manufactured by Hitachi High-Technologies Corporation) was used for measuring the length of the resist pattern. The evaluation results are shown in Tables 5-1 and 5-2 and Tables 6-1 and 6-2 below.

[0271] [Sensitivity] In the formation of the above EUV resist pattern, the exposure dose for forming a 32 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 ). Sensitivity was classified as A (excellent) when it was less than 30 mJ / cm 2 , B (good) when it was 30 mJ / cm 2 or more and less than 33 mJ / cm 2 , and C (unacceptable) when it was 33 mJ / cm 2 or more.

[0272] [LWR Performance] Using the above scanning electron microscope, the resist pattern formed by the above EUV was observed from above. The line width was measured at 50 arbitrary points, and the 3-sigma value was obtained from the distribution of the measured values and defined as LWR (unit: nm). LWR was classified as A (excellent) when it was less than 2.8 nm, B (good) when it was 2.8 nm or more and less than 3.2 nm, and C (unacceptable) when it was 3.2 nm or more.

[0273] [Overexposure Margin (Max CD)] In the above 32 nm line-and-space pattern, the maximum value of the width of the space pattern that could be resolved without pattern collapse / line break was defined as Max CD (nm). Max CD was classified as A (excellent) when it was 19 nm or more, B (good) when it was 16 nm or more and less than 19 nm, and C (unacceptable) when it was less than 16 nm.

[0274]

Table 5-1

[0275]

Table 5-2

[0276]

Table 6-1

[0277]

Table 6-2

[0278] As is clear from the results of Table 5-1, Table 5-2, Table 6, and Table 6-2 above, in all of the radiation-sensitive compositions of the examples, the sensitivity, LWR, and Max CD were better than those of the radiation-sensitive compositions of the comparative examples.

Industrial Applicability

[0279] According to the radiation-sensitive composition and the pattern forming method of the present invention, the sensitivity, LWR, and overexposure margin can be improved as compared with the prior art. Therefore, these can be suitably used for forming fine resist patterns in the lithography process of various electronic devices such as semiconductor devices and liquid crystal devices.

Claims

1. a first polymer including a structural unit (I) having an acid dissociable group; A second polymer including a structural unit (i) represented by the following formula (f1): Solvent and Contains The radiation-sensitive composition, wherein the acid-dissociable group has an iodine group. 【Chemistry 1】 (In the above formula (f1), R Ｋ１ is a hydrogen atom, a fluorine atom, an alkyl group having 1 to 6 carbon atoms, a halogenated alkyl group having 1 to 6 carbon atoms, or -R Ｋ２ -X-R Ｋ３ (wherein R Ｋ２ is a single bond, an alkanediyl group having 1 to 6 carbon atoms, or a halogenated alkanediyl group having 1 to 6 carbon atoms; X is a divalent linking group having a heteroatom; R Ｋ３ is an alkyl group having 1 to 6 carbon atoms or a halogenated alkyl group having 1 to 6 carbon atoms). L Ｙ１ is a divalent hydrocarbon group having 1 to 10 carbon atoms. L Ｙ２ Is -COO- ＊ Or -OCO- ＊ It is. ＊ is R ｆ１ It is the connecting part on the side. R ｆ１ is a monovalent hydrocarbon group having 1 to 10 carbon atoms or a monovalent fluorinated hydrocarbon group having 1 to 10 carbon atoms. R ｆ２ and R ｆ３ are each independently a fluorine atom or a monovalent fluorinated hydrocarbon group having 1 to 10 carbon atoms. ｆ２ and R ｆ３ When there are multiple R ｆ２ and R ｆ３ are the same or different. s is an integer from 0 to 3. ｆ１ is a monovalent hydrocarbon group having 1 to 10 carbon atoms, then s is an integer of 1 to 3.

2. The radiation-sensitive composition according to claim 1 , wherein the acid-dissociable group comprises an aromatic ring structure containing an iodine group.

3. 3. The radiation-sensitive composition according to claim 2, wherein the aromatic ring in the iodo group-containing aromatic ring structure is a benzene ring.

4. 2. The radiation-sensitive composition according to claim 1, wherein the acid-dissociable group contains one, two or three iodine groups.

5. The radiation-sensitive composition according to any one of claims 1 to 4, wherein the structural unit (I) is represented by the following formula (1): 【Chemistry 2】 (In formula (1), R α is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. L １ is a divalent linking group. R １Ａ and R １Ｂ each independently represents a hydrogen atom, a monovalent linear hydrocarbon group having 1 to 10 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, or a divalent alicyclic group having 3 to 20 carbon atoms constituted by combining these groups together with the carbon atom to which they are bonded. １Ａ and R １Ｂ There is no case where both are hydrogen atoms. R １０１ R is a nitro group, a cyano group, a hydroxy group, an alkoxy group, or an amino group. １０１ When there are multiple R １０１ are the same or different from each other. m1 and m2 each independently represent 0 or 1, provided that when m1 is 1, m2 is 1. p is an integer from 1 to 3. q is an integer from 0 to 3. However, p+q is 5 or less.

6. 5. The radiation-sensitive composition according to claim 1, wherein a content ratio of the structural unit (I) in all structural units constituting the first polymer is 20 mol % or more and 70 mol % or less.

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

8. In the above formula (f1), L Ｙ２ Is -COO- ＊ The radiation-sensitive composition according to any one of claims 1 to 4, wherein

9. In the above formula (f1), R ｆ１ 5. The radiation-sensitive composition according to claim 1, wherein: is a monovalent fluorinated hydrocarbon group having 1 to 10 carbon atoms; and s is 0.

10. 5. The radiation-sensitive composition according to claim 1, wherein the content of the structural unit (i) in all structural units constituting the second polymer is 30 mol % or more and 100 mol % or less.

11. 5. The radiation-sensitive composition according to claim 1, wherein the content of the second polymer is 0.1 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the first polymer.

12. The radiation-sensitive composition according to any one of claims 1 to 4, further comprising a radiation-sensitive acid generator.

13. The radiation-sensitive composition according to claim 12 , wherein the radiation-sensitive acid generator has an iodine group.

14. The radiation-sensitive composition according to any one of claims 1 to 4, further comprising an acid diffusion controller.

15. The radiation-sensitive composition according to claim 14 , wherein the acid diffusion controller has an iodine group.

16. A step of directly or indirectly applying the radiation-sensitive composition according to any one of claims 1 to 4 to a substrate to form a resist film; exposing the resist film to light; developing the exposed resist film with a developer; A pattern forming method comprising the steps of:

17. The pattern forming method according to claim 16, wherein the exposure is carried out using extreme ultraviolet rays or electron beams.

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