Positive resist composition and method for formating resist pattern

Abstract

The objective of the present invention is to provide a positive resist composition having a wide exposure margin and exhibiting high sensitivity. A positive resist composition according to the present invention contains a polymer A, a polymer B different from the polymer A, and a solvent. The difference between the surface free energy of the polymer A and the surface free energy of the polymer B is equal to or higher than 3 mJ / m2. The polymer A contains a monomer unit (I) derived from a monomer represented by formula (I) and a monomer unit (II) derived from a monomer represented by formula (II). In the formula, R1 to R9 are predetermined groups, m is an integer of 1 to 5, and m + n = 5.

Description

Positive resist composition and method for forming a resist pattern

[0001] The present invention relates to a positive resist composition and a method of forming a resist pattern.

[0002] BACKGROUND ART In the field of semiconductor manufacturing and the like, polymers whose main chains are scissed and whose solubility in a developer is increased by irradiation with ionizing radiation such as electron beams or short-wavelength light such as ultraviolet light (including extreme ultraviolet light (EUV)) (hereinafter, ionizing radiation and short-wavelength light may be collectively referred to as "ionizing radiation, etc.") have conventionally been used as main-chain scission-type positive resists.

[0003] Such polymers are used, for example, in the formation of resist patterns as positive resist compositions containing the polymer and a solvent. Specifically, a positive resist film (hereinafter sometimes simply referred to as "resist film") is formed by removing the solvent from the positive resist composition supplied to a substrate, and the resist film is then irradiated (exposed) with ionizing radiation or the like to form a desired pattern. The exposed resist film is then brought into contact with a developer (developed) to dissolve the exposed portions of the resist film, thereby forming a resist pattern consisting of unexposed portions on the substrate. Conventionally, improvements have been made to positive resist compositions that can be used to form main chain scission-type positive resists in order to improve the properties of the resist pattern.

[0004] For example, Patent Document 1 discloses an actinic ray-sensitive or radiation-sensitive resin composition containing a resin containing a predetermined repeating unit and a compound that generates an acid upon irradiation with actinic rays or radiation. According to Patent Document 1, the use of this composition makes it possible to form a pattern that is excellent in roughness performance and has good rectangularity.

[0005] International Publication No. 2023 / 047992

[0006] Here, a main chain scission type positive resist is required to have a wide tolerance for the amount of exposure in the exposure step (i.e., a wide exposure margin). Furthermore, a main chain scission type positive resist composition is also required to enhance the sensitivity of the resist film to ionizing radiation and the like (i.e., to improve the sensitivity in resist pattern formation). However, the above-mentioned conventional positive resist compositions have room for improvement in terms of improving the sensitivity in resist pattern formation while ensuring a wide exposure margin.

[0007] Therefore, an object of the present invention is to provide a positive resist composition that exhibits a wide exposure margin and high sensitivity, and a method of forming a resist pattern that is capable of forming a resist pattern with high sensitivity while ensuring a wide exposure margin.

[0008] The present inventors have conducted extensive research to achieve the above object, and have found that a polymer containing two predetermined types of monomer units and a polymer having a surface free energy difference of 3 mJ / m ２ The present inventors have newly discovered that by using a positive resist composition containing the above-mentioned other polymer, it is possible to form a resist pattern with high sensitivity while ensuring a wide exposure margin, and have completed the present invention.

[0009] That is, an object of the present invention is to advantageously solve the above-mentioned problems, and according to the present invention, there are provided positive resist compositions as set forth in [1] to [9] below, and methods of forming a resist pattern as set forth in

[10] to

[11] below.

[0010] [1] A positive resist composition comprising a polymer A, a polymer B different from the polymer A, and a solvent, wherein the difference in surface free energy between the polymer A and the polymer B is 3 mJ / m ２ The polymer A is represented by the following formula (I): [In formula (I), R １ is a halogen atom or an alkyl group substituted with a halogen atom, and R ２ is an organic group, and R ３ and R ４are each independently a hydrogen atom, a fluorine atom, an unsubstituted alkyl group, or an alkyl group substituted with a fluorine atom, and may be the same or different from each other.] and a monomer unit (I) derived from a monomer represented by the following formula (II): [In formula (II), R ５ , R ８ and R ９ are each independently a hydrogen atom, a halogen atom, an unsubstituted alkyl group, or an alkyl group substituted with a halogen atom, and may be the same or different from each other; R ６ is a hydrogen atom or an organic group, m is an integer of 1 or more and 5 or less, m+n=5, and R ７ are represented by the following formulas (III) to (V): (In formulas (III) to (V), R １０ , R １２ ~R １４ and R １６ are each independently an optionally substituted alkyl group, an optionally substituted cycloalkyl group, or an optionally substituted alkenyl group, and R １５ is a hydrogen atom, an optionally substituted alkyl group, an optionally substituted cycloalkyl group, or an optionally substituted alkenyl group, and R １１ is an alkylene group which may have a substituent, a cycloalkylene group which may have a substituent, or an alkenylene group which may have a substituent, and R １２ ~R １４ Two of R may be bonded to each other to form a ring structure; １５ ~R １６ may be bonded to each other to form a ring structure. ) is a substituent selected from the following. A positive resist composition comprising at least a monomer unit (II) derived from a monomer represented by the following formula: and a monomer unit (II) derived from a monomer represented by the following formula: In the present invention, "may have a substituent" means "unsubstituted or substituted." In addition, in the present invention, "monomer unit derived from a monomer" means "a repeating unit derived from that monomer that is contained in a polymer obtained using that monomer."

[0011] [2] The polymer A is represented by the following formula (VI): [In formula (VI), R １７ , R １９ and R ２０ are each independently a hydrogen atom, a halogen atom, an unsubstituted alkyl group, or an alkyl group substituted with a halogen atom, and may be the same or different from each other; R １８ represents an organic group or a halogen atom, and p represents an integer of 0 or more and 5 or less.] and further comprises a monomer unit (VI) derived from a monomer different from the monomer represented by formula (II).

[0012] [3] The positive resist composition according to [2] above, wherein the total proportion of the monomer units (II) and (VI) in all the monomer units constituting the polymer A is 40 mol % or more. In this specification, the proportion of each monomer unit in all the monomer units constituting the polymer A is defined as: 1 It can be measured using a nuclear magnetic resonance (NMR) method such as H-NMR, and more specifically, it can be measured according to the method described in the Examples of this specification.

[0013] [4] The R ２ is a group represented by L-Ar, wherein L is a single bond or a divalent linking group having a halogen atom, and Ar is an aromatic ring group which may have a substituent.

[0014] [5] The positive resist composition according to any one of [1] to [4] above, wherein the proportion of the monomer unit (II) in all the monomer units constituting the polymer A is 40 mol % or less.

[0015] [6] The R １ [6] The positive resist composition according to any one of the above [1] to [5], wherein is a chlorine atom.

[0016] [7] The polymer B is represented by the following formula (VII): [In formula (VII), R ２１ is a halogen atom or an alkyl group substituted with a halogen atom, and R ２２ is an organic group having a fluorine atom, and R ２３and R ２４ are each independently a hydrogen atom, a fluorine atom, an unsubstituted alkyl group, or an alkyl group substituted with a fluorine atom, and may be the same or different from each other.]

[0017] [8] The R ２２ The positive resist composition according to the above item [7], wherein represents an organic group having 4 or more fluorine atoms.

[0018] [9] The polymer B is represented by the following formula (VIII): [In formula (VIII), R ２５ , R ２７ and R ２８ are each independently a hydrogen atom, a halogen atom, an unsubstituted alkyl group, or an alkyl group substituted with a halogen atom, and may be the same or different from each other; R ２６ represents an organic group or a halogen atom, and q is an integer of 0 or more and 5 or less.] and further comprises a monomer unit (VIII) derived from a monomer different from the monomer represented by formula (II).

[0019]

[10] A method for forming a resist pattern, comprising: a step of forming a positive resist film using the positive resist composition according to any one of [1] to [9] above; a step of exposing the positive resist film; and a step of developing the exposed positive resist film by contacting it with a developer to obtain a developed film.

[0020]

[11] The method for forming a resist pattern according to

[10] above, wherein the developer contains an alcohol having from 1 to 5 carbon atoms.

[0021] According to the present invention, it is possible to provide a positive resist composition that exhibits a wide exposure margin and high sensitivity, and also to provide a method of forming a resist pattern that is capable of forming a resist pattern with high sensitivity while ensuring a wide exposure margin.

[0022] FIG. 10 is a diagram showing an example of evaluation criteria for the resist pattern shape.

[0023] Embodiments of the present invention are described in detail below. The positive resist composition of the present invention is used to form a resist film when forming a resist pattern using ionizing radiation such as an electron beam or EUV. The method of forming a resist pattern of the present invention forms a resist pattern using the positive resist composition of the present invention. The method of forming a resist pattern of the present invention is not particularly limited, and can be used, for example, when forming a resist pattern in the manufacturing processes of semiconductors, photomasks, molds, etc.

[0024] (Positive Resist Composition) The positive resist composition of the present invention contains at least polymer A, polymer B, and a solvent, and may optionally further contain components other than polymer A, polymer B, and the solvent (other components). Here, the positive resist composition of the present invention is a composition in which the difference in surface free energy between polymer A and polymer B is 3 mJ / m ２ The polymer A is characterized in that it contains the predetermined monomer units (I) and (II).

[0025] The positive resist composition of the present invention comprises a polymer A containing predetermined monomer units (I) and (II) in a solvent, and a polymer B having a surface free energy difference of 3 mJ / m ２ Because the positive resist composition of the present invention contains the above-described polymer B, it is possible to form a resist pattern with high sensitivity while ensuring a wide exposure margin. The reason why the above effects are achieved by using the positive resist composition of the present invention is not clear, but it is presumed to be as follows.

[0026] First, the positive resist composition of the present invention contains a polymer A containing predetermined monomer units (I) and (II). Since the polymer A contains the monomer units (I) and (II), when the polymer A is irradiated with ionizing radiation or the like, the main chain of the polymer A is efficiently cleaved only in the irradiated portion, resulting in a low molecular weight. The low molecular weight component is then efficiently dissolved in a developer. Furthermore, the monomer unit (II) contained in the polymer A is preferably a protecting group (R ７) is a repeating unit derived from a monomer having such a protecting group. The inventors' investigations have revealed that by using a monomer having such a protecting group in the preparation of polymer A, it is possible to ensure a wide exposure margin and to form a resist pattern with high sensitivity without adding a photoacid generator. In addition, the positive resist composition of the present invention has a surface free energy difference from polymer A of 3 mJ / m ２ The positive resist composition of the present invention contains a polymer B having the above structure. Therefore, when a resist film is formed on a substrate using the positive resist composition of the present invention, the polymer with the lower surface free energy may be localized at the air interface (upper layer), and the polymer with the higher surface free energy may be localized at the surface that contacts the substrate (lower layer). A resist film having such a two-layer structure is thought to widen the exposure margin and contribute to improving the sensitivity in resist pattern formation. For the above reasons, it is thought that by using the positive resist composition of the present invention, a resist pattern can be formed with high sensitivity while ensuring a wide exposure margin.

[0027] <Difference in surface free energy> The difference (absolute value) between the surface free energy of polymer A and the surface free energy of polymer B is 3 mJ / m ２ The difference (absolute value) between the surface free energy of polymer A and the surface free energy of polymer B must be 3 mJ / m or more. ２ If the surface free energy of polymer A is less than 3 mJ / m, it will be impossible to satisfactorily form a resist film having the above-mentioned two-layer structure, the exposure margin will be narrowed, and the sensitivity in resist pattern formation will decrease. Furthermore, in order to further widen the exposure margin and further increase the sensitivity in resist pattern formation, it is preferable that the surface free energy of polymer A is greater than the surface free energy of polymer B. That is, in the positive resist composition of the present invention, the value obtained by subtracting the surface free energy of polymer B from the surface free energy of polymer A ("surface free energy of polymer A" - "surface free energy of polymer B") is 3 mJ / m ２ The difference (absolute value) between the surface free energy of polymer A and the surface free energy of polymer B is preferably 4 mJ / m or more. ２ It is preferable that the concentration is 5 mJ / m or more. ２More preferably, it is 5.5 mJ / m or more. ２ More preferably, it is 6.1 mJ / m or more. ２ More preferably, it is 6.3 mJ / m or more. ２ It is particularly preferable that the concentration is 12 mJ / m or more. ２ Preferably, it is 11 mJ / m or less. ２ More preferably, it is 10 mJ / m or less. ２ More preferably, it is 8.8 mJ / m or less. ２ It is even more preferable that the value is 7.3 mJ / m or less. ２ It is particularly preferable that the difference (absolute value) between the surface free energy of polymer A and the surface free energy of polymer B is 4 mJ / m or less. ２ If the difference (absolute value) between the surface free energy of polymer B and the surface free energy of polymer B is 12 mJ / m or more, a resist film having the above-described two-layer structure can be formed more satisfactorily. Therefore, the exposure margin can be further widened and the sensitivity in resist pattern formation can be further improved. ２ If the surface free energy is less than 100 wt %, the polymer A and the polymer B can be uniformly mixed, and the exposure margin can be further increased. In the present invention, the "surface free energy" can be measured using the method described in the examples of this specification.

[0028] <Polymer A> Polymer A contains at least the monomer units (I) and (II) and may optionally further contain the monomer unit (VI). Polymer A may contain a monomer unit (other monomer unit) other than the monomer units (I), (II), and (VI).

[0029] The polymer A may be, for example, any of a random copolymer, a block copolymer, an alternating copolymer, etc., so long as it contains the monomer unit (I) and the monomer unit (II).

[0030] <<Monomer Unit (I)>> The monomer unit (I) is a monomer unit represented by the following formula (I): [In formula (I), R １ is a halogen atom or an alkyl group substituted with a halogen atom, and R ２ is an organic group, and R３ and R ４ are each independently a hydrogen atom, a fluorine atom, an unsubstituted alkyl group, or an alkyl group substituted with a fluorine atom, and may be the same or different from each other.]

[0031] The monomer unit (I) is represented by the following formula (I'): [In formula (I'), R １ ~R ４ has the same meaning as formula (I).

[0032] Here, R in formula (I) １ From the viewpoint of the efficiency of absorbing ionizing radiation, etc., it is necessary for the group to be a halogen atom or an alkyl group substituted with a halogen atom.

[0033] R in formula (I) １ Examples of halogen atoms that can constitute the group include fluorine atom (F), chlorine atom (Cl), bromine atom (Br), iodine atom (I), and astatine atom (At).

[0034] R in formula (I) １ Examples of alkyl groups substituted with halogen atoms that can constitute the above formula include groups having a structure in which some or all of the hydrogen atoms in an alkyl group having 1 to 5 carbon atoms are substituted with halogen atoms.

[0035] Among the above, from the viewpoint of further widening the exposure margin and further increasing the sensitivity in resist pattern formation, R １ is preferably a chlorine atom, a fluorine atom, or an alkyl group having 1 to 5 carbon atoms substituted with a fluorine atom, more preferably a chlorine atom, a fluorine atom, or a perfluoromethyl group, further preferably a chlorine atom or a fluorine atom, and particularly preferably a chlorine atom. １ The monomer in which R is a chlorine atom has excellent polymerizability. １ The polymer A having the monomer unit (I) derived from a monomer in which is a chlorine atom is also advantageous in that it can be easily prepared.

[0036] R in formula (I) ３ ~R ４ The unsubstituted alkyl group that can constitute the above group is not particularly limited, and examples thereof include unsubstituted alkyl groups having 1 to 5 carbon atoms.

[0037] R in formula (I) ３ ~R ４ The alkyl group substituted with a fluorine atom that can constitute the above group is not particularly limited, and examples thereof include groups having a structure in which some or all of the hydrogen atoms in an alkyl group having 1 to 5 carbon atoms are substituted with fluorine atoms.

[0038] Among the above, from the viewpoint of improving the ease of preparation of polymer A, R ３ ~R ４ are each preferably a hydrogen atom or an unsubstituted alkyl group, more preferably a hydrogen atom or an unsubstituted alkyl group having 1 to 5 carbon atoms, and even more preferably a hydrogen atom.

[0039] R in formula (I) ２ The organic group that can constitute the above formula (1) is not particularly limited, and examples thereof include an aliphatic group that may have a substituent, such as an alkyl group having from 1 to 15 carbon atoms, which may have a substituent, an alkenyl group having from 2 to 15 carbon atoms, which may have a substituent, an alkynyl group having from 2 to 15 carbon atoms, which may have a substituent, or a cycloalkyl group having from 2 to 15 carbon atoms, which may have a substituent; an aromatic hydrocarbon group having from 6 to 12 carbon atoms, which may have a substituent; and an aromatic heterocyclic group having from 1 to 12 carbon atoms, which may have a substituent.

[0040] The substituent is not particularly limited, and examples thereof include a halogen atom, a hydroxyl group, a carboxyl group, an amino group, a cyano group, an alkoxy group, a vinyl group, a halogenated alkyl group, etc. Among these, from the viewpoint of ensuring favorable severability of the main chain of the polymer A when irradiated with ionizing radiation or the like, a halogen atom is preferred, and a fluorine atom is more preferred.

[0041] Here, R in formula (I) ２is preferably a group represented by L-Ar (wherein L is a single bond or a divalent linking group having a halogen atom, and Ar is an aromatic ring group which may have a substituent). ２ is a group represented by L-Ar, the exposure margin can be further widened and the sensitivity in resist pattern formation can be further increased.

[0042] L is preferably a divalent linking group having a halogen atom. The halogen atom that L may have is preferably a fluorine atom, and the divalent linking group of L is preferably an alkylene group having 1 to 5 carbon atoms, more preferably a methylene group. L is preferably a divalent linking group having a fluorine atom, such as a trifluoromethylmethylene group, a pentafluoroethylmethylene group, a bis(trifluoromethyl)methylene group, or a heptafluoroisopropylmethylene group, more preferably an alkylene group having a fluorine atom and having 1 to 5 carbon atoms, a bis(trifluoromethyl)methylene group, a pentafluoroethylmethylene group, or a heptafluoroisopropylmethylene group is even more preferred, and a bis(trifluoromethyl)methylene group is particularly preferred.

[0043] The number of halogen atoms in L is preferably 3 or more, more preferably 4 or more, and even more preferably 5 or more, and is preferably 13 or less, and more preferably 10 or less. When the number of halogen atoms in L is equal to or greater than the above-mentioned lower limit, the exposure margin can be further widened and the sensitivity in resist pattern formation can be further increased. On the other hand, when the number of halogen atoms in L is equal to or less than the above-mentioned upper limit, the production efficiency of polymer A can be improved.

[0044] Furthermore, examples of the aromatic ring group which may have a substituent and which may constitute Ar in the group represented by L-Ar include an aromatic hydrocarbon ring group which may have a substituent and an aromatic heterocyclic group which may have a substituent.

[0045] The aromatic hydrocarbon ring group is not particularly limited, and examples thereof include a benzene ring group, a biphenyl ring group, a naphthalene ring group, an azulene ring group, an anthracene ring group, a phenanthrene ring group, a pyrene ring group, a chrysene ring group, a naphthacene ring group, a triphenylene ring group, an o-terphenyl ring group, an m-terphenyl ring group, a p-terphenyl ring group, an acenaphthene ring group, a coronene ring group, a fluorene ring group, a fluoranthrene ring group, a pentacene ring group, a perylene ring group, a pentaphene ring group, a picene ring group, and a pyranthrene ring group.

[0046] Furthermore, the aromatic heterocyclic group is not particularly limited, and examples thereof include a furan ring group, a thiophene ring group, a pyridine ring group, a pyridazine ring group, a pyrimidine ring group, a pyrazine ring group, a triazine ring group, an oxadiazole ring group, a triazole ring group, an imidazole ring group, a pyrazole ring group, a thiazole ring group, an indole ring group, a benzimidazole ring group, a benzothiazole group, a benzoxazole ring group, a quinoxaline ring group, a quinazoline ring group, a phthalazine ring group, a benzofuran ring group, a dibenzofuran ring group, a benzothiophene ring group, a dibenzothiophene ring group, and a carbazole ring group.

[0047] Furthermore, the substituent that Ar may have is not particularly limited, and examples thereof include an alkyl group, a fluorine atom, a fluoroalkyl group, etc. Examples of the alkyl group that Ar may have as a substituent include a chain alkyl group having 1 to 6 carbon atoms, such as a methyl group, an ethyl group, a propyl group, an n-butyl group, an isobutyl group, etc. Examples of the fluoroalkyl group that Ar may have as a substituent include a fluoroalkyl group having 1 to 5 carbon atoms, such as a trifluoromethyl group, a trifluoroethyl group, a pentafluoropropyl group, etc.

[0048] Among these, Ar is preferably an aromatic hydrocarbon ring group which may have a substituent, more preferably an unsubstituted aromatic hydrocarbon ring group, and even more preferably a benzene ring group (phenyl group).

[0049] L-Ar may be, for example, a benzyl group (C ６ H ５ -CH ２ -) -CH２ A structure in which at least one, preferably both, of the two hydrogen atoms of - are substituted with a fluorine atom or a fluoroalkyl group having 1 to 5 carbon atoms is exemplified. ２ A structure in which - is substituted with a perfluoroalkyl group having 1 to 5 carbon atoms is preferred, and -CH of a benzyl group is preferred. ２ A structure in which - is substituted with a trifluoromethyl group, a pentafluoroethyl group, or a heptafluoroisopropyl group is more preferred, and -CH of a benzyl group is ２ A structure in which - is substituted with a trifluoromethyl group is more preferred.

[0050] From the viewpoint of further widening the exposure margin and further increasing the sensitivity in resist pattern formation, it is preferable that R ２ is preferably a group represented by L-Ar, and in formula (I), R １ is a chlorine atom, and R ３ and R ４ is a hydrogen atom, and R ２ is more preferably a group represented by L-Ar.

[0051] Preferred examples of the monomer (a) represented by the above formula (I) include α-chloroacrylate-1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl (ACAFPh; a monomer represented by the following formula (a-1)), α-chloroacrylate-1-phenyl-2,2,3,3,3-pentafluoropropyl (a monomer represented by the following formula (a-2)), α-chloroacrylate-1-phenyl-2-trifluoromethyl-2,3,3,3-tetrafluoropropyl (a monomer represented by the following formula (a-3)), and α-chloroacrylate-1-phenyl-2,2,2-trifluoroethyl (a monomer represented by the following formula (a-4)). Among these, it is preferable to use α-chloroacrylate-1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl (ACAFPh).

[0052] The proportion of the monomer units (I) in polymer A is preferably 20 mol% or more, more preferably 30 mol% or more, and even more preferably 40 mol% or more, and preferably 80 mol% or less, more preferably 70 mol% or less, and even more preferably 60 mol% or less, when the total amount of all monomer units in polymer A is taken as 100 mol%. When the proportion of the monomer units (I) in polymer A is within the above range, the exposure margin can be further widened and the sensitivity in resist pattern formation can be further increased.

[0053] <<Monomer Unit (II)>> The monomer unit (II) is a monomer unit represented by the following formula (II): [In formula (II), R ５ , R ８ and R ９ are each independently a hydrogen atom, a halogen atom, an unsubstituted alkyl group, or an alkyl group substituted with a halogen atom, and may be the same or different from each other; R ６ is a hydrogen atom or an organic group, m is an integer of 1 or more and 5 or less, m+n=5, and R ７ is represented by formulas (III) to (V): (In formulas (III) to (V), R １０ , R １２ ~R １４ and R １６ are each independently an optionally substituted alkyl group, an optionally substituted cycloalkyl group, or an optionally substituted alkenyl group, and R １５ is a hydrogen atom, an optionally substituted alkyl group, an optionally substituted cycloalkyl group, or an optionally substituted alkenyl group, and R １１ is an alkylene group which may have a substituent, a cycloalkylene group which may have a substituent, or an alkenylene group which may have a substituent, and R １２ ~R １４ Two of R may be bonded to each other to form a ring structure; １５ ~R １６may be bonded to each other to form a ring structure.) It is a repeating unit derived from a monomer represented by the following formula (hereinafter referred to as "monomer (b)"). ６ The organic group that can constitute the ７ isn't it.

[0054] The monomer unit (II) is represented by the following formula (II'): [In formula (II'), R ５ ~R ９ , m and n have the same meanings as in formula (II). ７ is the repeating unit of hydrogen atoms.

[0055] R in formula (II) ５ and R ８ ~R ９ Examples of halogen atoms that can constitute the group include R １ The halogen atoms may be the same as those that can constitute the above halogen atoms.

[0056] R in formula (II) ５ and R ８ ~R ９ Examples of unsubstituted alkyl groups that can constitute the formula (I) include R ３ ~R ４ Examples include unsubstituted alkyl groups which can be formed as above and similar groups.

[0057] R in formula (II) ５ and R ８ ~R ９ Examples of the alkyl group substituted with a halogen atom that can constitute the group include R １ Examples include the same groups as alkyl groups substituted with halogen atoms that can constitute the above.

[0058] Among the above, from the viewpoint of improving the ease of preparation of polymer A, R ５is preferably a hydrogen atom or an unsubstituted alkyl group, more preferably a hydrogen atom or an unsubstituted alkyl group having 1 to 5 carbon atoms, further preferably a hydrogen atom or a methyl group, and particularly preferably a methyl group. ８ ~R ９ are each preferably a hydrogen atom or an unsubstituted alkyl group, more preferably a hydrogen atom or an unsubstituted alkyl group having 1 to 5 carbon atoms, further preferably a hydrogen atom or a methyl group, and particularly preferably a hydrogen atom.

[0059] R in formula (II) ６ Examples of the organic group that can constitute the formula include O-R ７ However, there is no particular limitation as long as it does not fall under the above condition. For example, ２ The organic groups include the same groups as those that can constitute the above.

[0060] Among the above, from the viewpoint of improving the ease of preparation of polymer A, R ６ is preferably a hydrogen atom or an unsubstituted alkyl group, more preferably a hydrogen atom or an unsubstituted alkyl group having 1 to 5 carbon atoms, further preferably a hydrogen atom or a methyl group, and particularly preferably a hydrogen atom.

[0061] In addition, R ６ When there are a plurality of R (i.e., when n is an integer of 2 or more and 4 or less), ６ may be the same or different. ７ When there are a plurality of R (i.e., when m is an integer of 2 or more and 5 or less), ７ may be the same or different from each other.

[0062] In formula (II), m must be an integer of 1 or more and 5 or less. From the viewpoint of improving the ease of preparation of polymer A, m in formula (II) is preferably 1 or 2, and more preferably 1.

[0063] Here, R in formula (II) ７is required to be a substituent selected from the above-mentioned formulas (III) to (V). R included in the substituent represented by formulas (III) to (V) １０ , R １２ ~R １４ and R １６ is an alkyl group which may have a substituent, a cycloalkyl group which may have a substituent, or an alkenyl group which may have a substituent, and R １５ is required to be a hydrogen atom, an alkyl group which may have a substituent, a cycloalkyl group which may have a substituent, or an alkenyl group which may have a substituent. １５ is an optionally substituted alkyl group, an optionally substituted cycloalkyl group, or an optionally substituted alkenyl group, and R １５ ~R １６ may be bonded to each other to form a ring structure.

[0064] R in formulas (III) to (V) １０ and R １２ ~R １６ The alkyl group which may have a substituent and which can constitute the above group is not particularly limited, and examples thereof include alkyl groups having 1 to 5 carbon atoms which may have a substituent.

[0065] R in formulas (III) to (V) １０ and R １２ ~R １６ Examples of the cycloalkyl group which may have a substituent include a cycloalkyl group having 3 to 20 carbon atoms which may have a substituent.

[0066] R in formulas (III) to (V) １０ and R １２ ~R １６ Examples of the optionally substituted alkenyl group that can constitute the above formula include an optionally substituted alkenyl group having from 2 to 20 carbon atoms.

[0067] R in formula (IV) １１The alkylene group which may have a substituent and which can form the formula (I) is not particularly limited, and examples thereof include alkylene groups having 1 to 5 carbon atoms which may have a substituent.

[0068] R in formula (IV) １１ The cycloalkylene group which may have a substituent and which can form the formula (I) is not particularly limited, and examples thereof include cycloalkylene groups which may have a substituent and have 3 to 20 carbon atoms.

[0069] R in formula (IV) １１ The alkenylene group which may have a substituent and which can form the formula (I) is not particularly limited, and examples thereof include alkenylene groups having from 2 to 20 carbon atoms which may have a substituent.

[0070] R １０ ~R １６ The substituent that may be possessed by is not particularly limited, and examples thereof include a halogen atom, a hydroxyl group, a carboxyl group, an amino group, a cyano group, a vinyl group, an alkoxy group, and a halogenated alkyl group.

[0071] R １２ ~R １４ a ring structure that can be formed by combining two of R １５ ~R １６ The ring structure that can be formed by bonding together is not particularly limited and may be either monocyclic or polycyclic. Examples of monocyclic ring structures include monocyclic aliphatic hydrocarbon rings and monocyclic aliphatic heterocycles. Examples of polycyclic ring structures include polycyclic aliphatic hydrocarbon rings and polycyclic aliphatic heterocycles. These ring structures may have the above-mentioned substituents.

[0072] Here, R in formula (III) １０ is preferably an unsubstituted alkyl group, more preferably an unsubstituted alkyl group having 1 to 5 carbon atoms, even more preferably an unsubstituted branched alkyl group having 1 to 5 carbon atoms, and particularly preferably a tert-butyl group. １２ ~R １４are each preferably an unsubstituted alkyl group, more preferably an unsubstituted alkyl group having 1 to 10 carbon atoms, further preferably a methyl group or an ethyl group, and particularly preferably a methyl group. １５ is preferably a hydrogen atom or an unsubstituted alkyl group, more preferably a hydrogen atom or an unsubstituted alkyl group having 1 to 10 carbon atoms, further preferably a hydrogen atom, a methyl group or an ethyl group, and particularly preferably a hydrogen atom or a methyl group. １６ is preferably an unsubstituted alkyl group, more preferably an unsubstituted alkyl group having 1 to 5 carbon atoms, further preferably a methyl group or an ethyl group, and particularly preferably an ethyl group. １１ is preferably an unsubstituted alkylene group, more preferably an unsubstituted alkylene group having 1 to 5 carbon atoms, further preferably a methylene group or an ethylene group, and particularly preferably a methylene group.

[0073] Examples of the substituent represented by formula (III) include —C(═O)—O—C(CH ３ ) ３ In addition, examples of the substituent represented by formula (IV) include -CH ２ -C(=O)-OC(CH ３ ) ３ , -CH ２ -C(=O)-O-CH ３ (C ５ H ８ ) [following formula (4a)], —CH ２ -C(=O)-O-C ２ H ５ (C ５ H ８ ) [following formula (4b)], —CH ２ -C(=O)-O-CH ３ (C ６ H １０ ) [following formula (4c)], —CH ２ -C(=O)-O-C ２ H ５ (C ６H １０ ) [formula (4d)], —CH ２ -C(=O)-O-CH ３ (C １０ H １４ ) [following formula (4e)], —CH ２ -C(=O)-O-C ２ H ５ (C １０ H １４ ) [following formula (4f)], —CH ２ -C(=O)-O-CCH(CH ３ ) ２ -(C １０ H １４ ) [the following formula (4g)] is preferred. Examples of the substituent represented by formula (V) include -CH(CH ３ )-O-C ２ H ５ , -CH(CH ３ )-O-C ６ H １１ [the following formula (5a)], —CH ２ -O-(C １０ H １４ ) [formula (5b)], —CH(CH ３ )—O—(C １０ H １４ ) [the following formula (5c)] is preferably mentioned.

[0074] From the viewpoint of further widening the exposure margin and further increasing the sensitivity in forming a resist pattern, the monomer (b) represented by formula (II) capable of forming the monomer unit (II) is selected from the group consisting of 4-t-butoxycarbonyloxy-α-methylstyrene (monomer of formula (b-1) below), 1,1-dimethylethenyl-2-[4-(1-methylethenyl)phenoxy]acetate (monomer of formula (b-2) below), 1-(1-ethoxyethoxy)-4-(1-methylethenyl)benzene (monomer of formula (b-3) below), 1-ethylcyclopentyl-2-[4-(1-methylethenyl)phenoxy]acetate (monomer of formula (b-4) below), Preferred are 1-methylcyclopentyl-2-[4-(1-methylethenyl)phenoxy]acetate (monomer of formula (b-5) below), 2-methyladamantyl-2-[4-(1-methylethenyl)phenoxy]acetate (monomer of formula (b-6) below), 1-[1-(cyclohexyloxy)ethoxy]-4-(1-methylethenyl)benzene (monomer of formula (b-7) below), 1-[1-(adamantyloxy)methoxy]-4-(1-methylethenyl)benzene (monomer of formula (b-8) below), and 1-[1-(adamantyloxy)ethoxy]-4-(1-methylethenyl)benzene (monomer of formula (b-9) below).

[0075] Furthermore, the proportion of the monomer unit (II) in polymer A is preferably 40 mol% or less, more preferably 30 mol% or less, and even more preferably 20 mol% or less, when the total monomer units constituting polymer A is 100 mol%. If the proportion of the monomer unit (II) is equal to or less than the above upper limit, the exposure margin can be further widened and the sensitivity in resist pattern formation can be further increased. Furthermore, a resist pattern having a good shape can be formed. The lower limit of the proportion of the monomer unit (II) in polymer A is not particularly limited, and can be, for example, 1 mol% or more, or 3 mol% or more.

[0076] <<Monomer Unit (VI)>> The monomer unit (VI) is represented by the following formula (VI): [In formula (VI), R １７ , R １９and R ２０ are each independently a hydrogen atom, a halogen atom, an unsubstituted alkyl group, or an alkyl group substituted with a halogen atom, and may be the same or different from each other; R １８ is an organic group or a halogen atom, and p is an integer of 0 to 5.] and is a repeating unit derived from a monomer (hereinafter referred to as "monomer (c)") different from the monomer (b) represented by the above formula (II) (i.e., R １８ The organic group that can constitute the ７ isn't it.).

[0077] The monomer unit (VI) has the following formula (VI'): In formula (VI'), R １７ ~R ２０ and p has the same meaning as in formula (VI). When polymer A contains monomer unit (VI), it is possible to further widen the exposure margin and further increase the sensitivity in resist pattern formation. It is also possible to form a resist pattern with a good shape.

[0078] R in formula (VI) １７ , R １９ and R ２０ Specific examples and preferred examples of ５ , R ８ and R ９ is the same as

[0079] R in formula (VI) １８ Examples of the organic group that can constitute the formula include O-R ７ However, there is no particular limitation as long as it does not fall under the above condition. For example, ２ The organic groups include the same groups as those that can constitute the above.

[0080] R in formula (VI) １８ The halogen atoms that can constitute the formula (I) include R １ The halogen atoms may be the same as those that can constitute the above halogen atoms.

[0081] In formula (VI), p must be an integer of 0 or more and 5 or less, and is preferably 0 or 1, and is further preferably 0. １８ When there are a plurality of R (i.e., when p is an integer of 2 or more and 5 or less), １８ may be the same or different from each other.

[0082] The monomer (c) represented by formula (VI) capable of forming the monomer unit (VI) is not particularly limited, and examples thereof include α-methylstyrene (AMS) and its derivatives, such as the following monomers (c-1) to (c-19):

[0083] From the viewpoint of improving the ease of preparation of polymer A, the monomer unit (VI) preferably does not contain a fluorine atom, and is more preferably a monomer unit derived from α-methylstyrene. １９ and R ２０ is a hydrogen atom, and R １７ It is preferred that is a methyl group and p=0.

[0084] When polymer A contains monomer units (VI), the proportion of monomer units (VI) in polymer A is preferably 10 mol% or more, more preferably 20 mol% or more, even more preferably 30 mol% or more, particularly preferably 40 mol% or more, and preferably 60 mol% or less, and more preferably 50 mol% or less, based on 100 mol% of all monomer units constituting polymer A. When the proportion of monomer units (VI) in polymer A is within the above range, the exposure margin can be further widened and the sensitivity in resist pattern formation can be further increased.

[0085] Furthermore, the total proportion of the monomer units (II) and (VI) in polymer A is preferably 40 mol % or more, more preferably 45 mol % or more, and preferably 60 mol % or less, and more preferably 55 mol % or less, when the total monomer units constituting polymer A is taken as 100 mol %. When the total proportion of the monomer units (II) and (VI) in polymer A is within the above range, the exposure margin can be further widened and the sensitivity in resist pattern formation can be further increased.

[0086] <<Other Monomer Units>> The other monomer units are not particularly limited, and examples thereof include monomer units derived from known monomers copolymerizable with the above-mentioned monomers (a) and (b). Polymer A may contain one type of other monomer unit, or two or more types thereof.

[0087] The proportion of other monomer units in polymer A is preferably 30 mol % or less, more preferably 10 mol % or less, even more preferably 1 mol % or less, and particularly preferably 0 mol % (i.e., polymer A does not contain other monomer units), based on 100 mol % of all monomer units constituting polymer A.

[0088] <<Properties>> [Surface free energy] Here, the surface free energy of polymer A is 25 mJ / m ２ It is preferable that the concentration is 27 mJ / m or more. ２ More preferably, it is 29 mJ / m or more. ２ More preferably, it is 30.5 mJ / m or more. ２ It is particularly preferable that the concentration is 40 mJ / m or more. ２ Preferably, it is 35 mJ / m or less. ２ More preferably, it is 33 mJ / m or less. ２ More preferably, it is 31.5 mJ / m or less. ２ It is particularly preferred that:

[0089] [Weight-Average Molecular Weight] The weight-average molecular weight of polymer A is preferably 5,000 or more, more preferably 10,000 or more, even more preferably 30,000 or more, even more preferably 60,000 or more, particularly preferably 150,000 or more, and preferably 500,000 or less, more preferably 400,000 or less, even more preferably 300,000 or less, even more preferably 250,000 or less, particularly preferably 181,000 or less. If the weight-average molecular weight of polymer A is at least the above-mentioned lower limit, it is possible to prevent the solubility of the resist film in the developer from excessively increasing even at a low irradiation dose, and it is possible to form a resist pattern with a good shape. On the other hand, if the weight-average molecular weight of polymer A is at most the above-mentioned upper limit, a positive resist composition can be easily prepared.

[0090] [Molecular Weight Distribution] The molecular weight distribution of polymer A (the value obtained by dividing the weight average molecular weight of polymer A by the number average molecular weight of polymer A) is preferably 1.05 or more, more preferably 1.30 or more, and even more preferably 1.60 or more, and is preferably 2.80 or less, more preferably 2.50 or less, and even more preferably 2.00 or less. When the molecular weight distribution of polymer A is equal to or greater than the above lower limit, the ease of production of polymer A can be improved. When the molecular weight distribution of polymer A is equal to or less than the above upper limit, the exposure margin can be further widened and the sensitivity in resist pattern formation can be further increased.

[0091] The weight-average molecular weight and number-average molecular weight of polymer A can be measured by the method described in the Examples of this specification. The weight-average molecular weight and number-average molecular weight of polymer A can be adjusted, for example, by changing the type and amount of monomers in the monomer composition used in polymerization, polymerization conditions, etc.

[0092] <<Method for Preparing Polymer A>> Polymer A having the above-described monomer unit (I) and monomer unit (II) can be prepared, for example, by polymerizing a monomer composition containing the above-described monomer (a) and monomer (b), and then optionally purifying the obtained polymer.

[0093] [Polymerization of Monomer Composition] Here, the monomer composition used to prepare polymer A can be a mixture of monomer components containing monomer (a) and monomer (b), and optionally containing monomer (c), an optionally usable solvent, a polymerization initiator, and optionally added additives. The polymerization of the monomer composition can be carried out using a known method. Among these, when a solvent is used, it is preferable to use cyclopentanone or the like as the solvent. Furthermore, it is preferable to use a radical polymerization initiator such as azobisisobutyronitrile as the polymerization initiator.

[0094] The polymer obtained by polymerizing the monomer composition may be used as Polymer A as it is, but is not particularly limited thereto. For example, a good solvent such as tetrahydrofuran may be added to a solution containing the polymer, and then the solution to which the good solvent has been added is dropped into a poor solvent such as methanol to coagulate the polymer, thereby recovering it, and then purifying it as follows:

[0095] [Purification of Polymer] The purification method used to purify the obtained polymer to obtain the polymer A having the above-mentioned properties is not particularly limited, and known purification methods such as reprecipitation and column chromatography can be used. Among them, the reprecipitation method is preferably used as the purification method. The purification of the polymer may be repeated multiple times.

[0096] The purification of the polymer by the reprecipitation method is preferably carried out, for example, by dissolving the obtained polymer in a good solvent such as tetrahydrofuran, and then dropping the obtained solution into a mixed solvent of a good solvent such as tetrahydrofuran and a poor solvent such as methanol to precipitate a portion of the polymer. In this way, by dropping a solution of the polymer into a mixed solvent of a good solvent and a poor solvent to purify the polymer, the molecular weight distribution and weight-average molecular weight of the obtained polymer A can be easily adjusted by changing the type and mixing ratio of the good solvent and the poor solvent. Specifically, for example, the molecular weight of the polymer A precipitated in the mixed solvent can be increased by increasing the proportion of the good solvent in the mixed solvent. When purifying the polymer by the reprecipitation method, the polymer precipitated in the mixed solvent of a good solvent and a poor solvent may be used as polymer A, as long as it satisfies the desired properties, or the polymer not precipitated in the mixed solvent (i.e., the polymer dissolved in the mixed solvent) may be used. The polymer not precipitated in the mixed solvent can be recovered from the mixed solvent using known techniques such as concentration to dryness.

[0097] <Polymer B> The polymer B contained in the positive resist composition of the present invention has a surface free energy difference of 3 mJ / m from the above-mentioned polymer A. ２ As long as the above is satisfied, there is no particular limitation.

[0098] Polymer B may be, for example, any of a random copolymer, a block copolymer, and an alternating copolymer.

[0099] From the viewpoints of further widening the exposure margin and further increasing the sensitivity in resist pattern formation, polymer B preferably contains at least monomer unit (VII), and more preferably contains both monomer unit (VII) and monomer unit (VIII). Polymer B may contain monomer units other than monomer units (VII) and (VIII) (other monomer units).

[0100] <<Monomer Unit (VII)>> The monomer unit (VII) is a monomer unit represented by the following formula (VII): [In formula (VII), R ２１ is a halogen atom or an alkyl group substituted with a halogen atom, and R２２ is an organic group having a fluorine atom, and R ２３ and R ２４ are each independently a hydrogen atom, a fluorine atom, an unsubstituted alkyl group, or an alkyl group substituted with a fluorine atom, and may be the same or different from each other.]

[0101] The monomer unit (VII) has the following formula (VII'): In formula (VII'), R ２１ ~R ２４ has the same meaning as formula (VII).

[0102] R in formula (VII) ２１ , R ２３ and R ２４ Specific and preferred examples of R in formula (I) １ , R ３ and R ４ The specific examples and preferred examples are the same as those of the above.

[0103] R ２２ The number of fluorine atoms contained in R is preferably 4 or more, more preferably 5 or more, and is preferably 15 or less, more preferably 10 or less. ２２ When the number of fluorine atoms in R is equal to or greater than the lower limit, the exposure margin can be further widened and the sensitivity in resist pattern formation can be further increased. ２２ When the number of fluorine atoms contained in is equal to or less than the upper limit, the production efficiency of the polymer B can be improved.

[0104] And R ２２Examples of the alkyl group include an aliphatic alkyl group having a fluorine atom and an aromatic alkyl group having a fluorine atom. Examples of the aliphatic alkyl group having a fluorine atom include aliphatic alkyl groups having 2 to 5 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom, such as a 2,2,3,3,3-pentafluoropropyl group (5 fluorine atoms, 3 carbon atoms), a 3,3,4,4,4-pentafluorobutyl group (5 fluorine atoms, 4 carbon atoms), a 1H-1-(trifluoromethyl)trifluoroethyl group (6 fluorine atoms, 3 carbon atoms), a 1H,1H,3H-hexafluorobutyl group (6 fluorine atoms, 4 carbon atoms), a 1,2,2,2-tetrafluoro-1-(trifluoromethyl)ethyl group (7 fluorine atoms, 3 carbon atoms), a 2,2,3,3,4,4,4-heptafluorobutyl group (7 fluorine atoms, 4 carbon atoms), and a 2,2,3,3,4,4,5,5,5-nonafluoropentyl group (9 fluorine atoms, 5 carbon atoms). Examples of aromatic alkyl groups having a fluorine atom include aromatic alkyl groups having 7 to 12 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom, such as a 1,1,1,3,3,3-hexafluoro-2-phenylpropyl group, a 1,1,1,2,2-pentafluoro-3-phenylpropyl group, a 1,1,1-trifluoro-2-fluoro-2-trifluoromethyl-3-phenylpropyl group, and a 1,1,1-trifluoro-2-phenylethyl group. ２２ As the alkyl group, a 2,2,3,3,3-pentafluoropropyl group, a 2,2,3,3,4,4,5,5,5-nonafluoropentyl group, and a 1,1,1,3,3,3-hexafluoro-2-phenylpropyl group are preferred.

[0105] Examples of the monomer (d) represented by the above formula (VII) include 1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl α-chloroacrylate (ACAFPh), 1-phenyl-2,2,3,3,3-pentafluoropropyl α-chloroacrylate, 1-phenyl-2-trifluoromethyl-2,3,3,3-tetrafluoropropyl α-chloroacrylate, 1-phenyl-2,2,2-trifluoroethyl α-chloroacrylate, 2,2,3,3,3-pentafluoropropyl α-chloroacrylate (ACAPFP), and 2,2,3,3,4,4,5,5,5-nonafluoropentyl α-chloroacrylate (ACANFP). Among these, 1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl α-chloroacrylate (ACAFPh), 2,2,3,3,3-pentafluoropropyl α-chloroacrylate (ACAPFP), and 2,2,3,3,4,4,5,5,5-nonafluoropentyl α-chloroacrylate (ACANFP) are preferred.

[0106] The proportion of the monomer unit (VII) in polymer B is preferably 30 mol% or more, more preferably 40 mol% or more, and even more preferably 45 mol% or more, and preferably 70 mol% or less, more preferably 60 mol% or less, and even more preferably 55 mol% or less, relative to 100 mol% of all monomer units constituting polymer B. When the proportion of the monomer unit (VII) in polymer B is within the above range, the exposure margin can be further widened and the sensitivity in resist pattern formation can be further increased.

[0107] <<Monomer Unit (VIII)>> The monomer unit (VIII) is represented by the following formula (VIII): [In formula (VIII), R ２５ , R ２７ and R ２８ are each independently a hydrogen atom, a halogen atom, an unsubstituted alkyl group, or an alkyl group substituted with a halogen atom, and may be the same or different from each other; R ２６is an organic group or a halogen atom, and q is an integer of 0 to 5.] and is a repeating unit derived from a monomer (hereinafter referred to as "monomer (e)") different from the monomer (b) represented by the above formula (II) (i.e., R ２６ The organic group that can constitute the ７ isn't it).

[0108] The monomer unit (VIII) is represented by the following formula (VIII'): [In formula (VIII'), R ２５ ~R ２８ and q has the same meaning as in formula (VIII).

[0109] And, R in formula (VIII) ２５ ~R ２８ Specific examples and preferred examples of １７ ~R ２０ The specific and preferred examples are the same as those of the formula (VIII). The preferred range of q in formula (VIII) is the same as the preferred range of p in formula (VI).

[0110] The monomer (e) represented by formula (VIII) capable of forming the monomer unit (VIII) is not particularly limited, and examples thereof include α-methylstyrene (AMS) and its derivatives, such as the above-mentioned monomers (c-1) to (c-9). From the viewpoint of improving the ease of preparation of the polymer B, the monomer unit (VIII) preferably does not contain a fluorine atom, and is more preferably a monomer unit derived from α-methylstyrene. That is, in formula (VIII), R ２７ and R ２８ is a hydrogen atom, and R ２５ It is preferred that is a methyl group and q=0.

[0111] When polymer B contains monomer units (VIII), the proportion of monomer units (VIII) in polymer B is preferably 30 mol% or more, more preferably 40 mol% or more, and even more preferably 45 mol% or more, and preferably 70 mol% or less, more preferably 60 mol% or less, and even more preferably 55 mol% or less, relative to 100 mol% of all monomer units constituting polymer B. When the proportion of monomer units (VIII) in polymer B is within the above range, the exposure margin can be further widened and the sensitivity in resist pattern formation can be further increased.

[0112] <<Other Monomer Units>> The other monomer units are not particularly limited, and examples thereof include monomer units derived from known monomers copolymerizable with the above-mentioned monomers (d) and (e). Polymer B may contain one type of other monomer unit, or two or more types thereof.

[0113] The proportion of other monomer units in polymer B is preferably 30 mol % or less, more preferably 10 mol % or less, even more preferably 1 mol % or less, and particularly preferably 0 mol % (i.e., polymer B does not contain other monomer units), based on 100 mol % of all monomer units constituting polymer B.

[0114] <<Properties>> [Surface free energy] Here, the surface free energy of polymer B is 15 mJ / m ２ It is preferable that the concentration is 18 mJ / m or more. ２ More preferably, it is 20 mJ / m or more. ２ More preferably, it is 21.7 mJ / m or more. ２ It is particularly preferable that the concentration is 30 mJ / m or more. ２ Preferably, it is 28 mJ / m or less. ２ More preferably, it is 25 mJ / m or less. ２ More preferably, it is 24.2 mJ / m or less. ２ It is particularly preferred that:

[0115] [Weight-average molecular weight] The weight-average molecular weight of polymer B is preferably 5,000 or more, more preferably 10,000 or more, even more preferably 15,000 or more, even more preferably 20,000 or more, particularly preferably 27,000 or more, and preferably 200,000 or less, more preferably 150,000 or less, even more preferably 100,000 or less, even more preferably 80,000 or less, particularly preferably 45,000 or less. If the weight-average molecular weight of polymer B is at least the above-mentioned lower limit, it is possible to prevent the solubility of the resist film in the developer from excessively increasing even at a low irradiation dose, and it is possible to form a resist pattern with a good shape. On the other hand, if the weight-average molecular weight of polymer B is at most the above-mentioned upper limit, a positive resist composition can be easily prepared.

[0116] [Molecular Weight Distribution] The molecular weight distribution of polymer B (the value obtained by dividing the weight average molecular weight of polymer B by the number average molecular weight of polymer B) is preferably 1.05 or more, more preferably 1.30 or more, and preferably 2.80 or less, preferably 2.50 or less, and even more preferably 2.00 or less. If the molecular weight distribution of polymer B is equal to or greater than the above lower limit, the ease of production of polymer B can be improved. If the molecular weight distribution of polymer B is equal to or less than the above upper limit, the exposure margin can be further widened and the sensitivity in resist pattern formation can be further improved. The weight average molecular weight and number average molecular weight of polymer B can be measured by the method described in the Examples of this specification. The weight average molecular weight and number average molecular weight of polymer B can be adjusted, for example, by changing the type and amount of monomers in the monomer composition used in polymerization, polymerization conditions, etc.

[0117] <<Method for Preparing Polymer B>> Polymer B can be prepared, for example, by polymerizing a monomer composition containing the above-mentioned monomer (d) and monomer (e), and then optionally purifying the resulting polymer. The polymerization of the monomer composition and the purification of the polymer can be performed in the same manner as in the case of Polymer A.

[0118] <Solvent> The solvent is not particularly limited as long as it is capable of dissolving the above-mentioned polymer A and polymer B, and known solvents such as those described in Japanese Patent No. 5938536 can be used. Among them, from the perspective of obtaining a positive resist composition with an appropriate viscosity and improving the coatability of the positive resist composition, anisole, propylene glycol monomethyl ether acetate (PGMEA), cyclopentanone, cyclohexanone, and isoamyl acetate are preferred as the solvent, and isoamyl acetate is more preferred. Note that one type of solvent may be used alone, or multiple types may be used in combination.

[0119] <Other Components> In addition to the components described above, the positive resist composition of the present invention may optionally further contain known additives that can be incorporated into resist compositions. There are no particular restrictions on the amount of additives that can be incorporated, and an appropriate amount can be added depending on the application.

[0120] The positive resist composition of the present invention typically does not substantially contain low-molecular-weight compounds (components with a molecular weight of 3,000 or less) that generate acid when irradiated with actinic rays or radiation (for example, the bright line spectrum of a mercury lamp, far ultraviolet rays represented by excimer lasers, extreme ultraviolet rays (EUV), X-rays, or electron beams). By using the positive resist composition of the present invention, it is possible to form resist patterns with high sensitivity without adding low-molecular-weight compounds that generate acid when irradiated with actinic rays or radiation. In the present invention, the phrase "substantially free of low-molecular-weight compounds" refers to the content of low-molecular-weight compounds being at least 0 parts by mass and not more than 0.5 parts by mass per 100 parts by mass of the combined total of polymer A and polymer B. The content of the low-molecular-weight compounds in the positive resist composition of the present invention is preferably less than 0.1 parts by mass, and more preferably 0 parts by mass, per 100 parts by mass of the combined total of polymer A and polymer B (i.e., the positive resist composition of the present invention does not contain low-molecular-weight compounds).

[0121] Furthermore, the ratio of polymer A to polymer B in the positive resist composition of the present invention is not particularly limited, but the ratio of polymer B is preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more, and preferably 70% by mass or less, more preferably 50% by mass or less, and even more preferably 30% by mass or less, per 100% by mass of the total of polymer A and polymer B. When the ratio of polymer B is equal to or greater than the above-mentioned lower limit, it is possible to prevent the solubility of the resist film in the developer from excessively increasing even at a low exposure dose, and it is possible to form a resist pattern with further improved contrast. When the ratio of polymer B is equal to or less than the above-mentioned upper limit, it is possible to further widen the exposure margin and form a resist pattern with a good shape.

[0122] <Method of Preparing Positive Resist Composition> The positive resist composition can be prepared by mixing the above-mentioned polymer A, polymer B, and solvent, as well as any other components that are used optionally. There are no particular limitations on the mixing method, and mixing can be carried out using a known method. Alternatively, the positive resist composition can be prepared by mixing the components and then filtering the mixture.

[0123] (Method of Forming Resist Pattern) The method of forming a resist pattern of the present invention comprises the steps of forming a positive resist film using the positive resist composition of the present invention described above (resist film forming step), exposing the resulting positive resist film (exposure step), and developing the exposed positive resist film by contacting it with a developer to obtain a developed film (developing step). Furthermore, the method of forming a resist pattern of the present invention may also comprise the steps of heating the exposed positive resist film after the exposure step (post-exposure bake step) and / or removing the developer after the development step (developer removal step). Furthermore, since the method of forming a resist pattern of the present invention uses the positive resist composition of the present invention, the method of forming a resist pattern of the present invention can form a resist pattern with high sensitivity while ensuring a wide exposure margin. Each step will be described below.

[0124] <Resist Film Formation Process> In the resist film formation process, a positive resist composition is applied to a workpiece, such as a substrate, to be processed using a resist pattern, and the applied positive resist composition is dried to form a resist film. The substrate is not particularly limited, and examples include silicon substrates used in semiconductor devices such as LSI (Large Scale Integration), and mask blanks formed with a light-shielding layer on a substrate. The application and drying methods for the positive resist composition are also not particularly limited, and methods commonly used for forming resist films can be used. For example, a resist film can be formed by applying a resist solution to a substrate by spin coating, followed by soft baking on a hot plate. The soft baking temperature is not particularly limited, but can be 100°C or higher and 200°C or lower. The soft baking time can be, for example, 30 seconds to 60 minutes. The resist pattern formation method of the present invention uses the positive resist composition of the present invention described above.

[0125] <Exposure Step> In the exposure step, the resist film formed in the resist film formation step is irradiated with ionizing radiation or the like to write a desired pattern. In the exposed region irradiated with ionizing radiation or the like, the main chains of polymer A and polymer B forming the resist film are cleaved, and polymer A and polymer B are reduced in molecular weight. The resist film formed using the positive resist composition of the present invention contains the above-mentioned specified monomer unit (II), and this monomer unit (II) is usually represented by R ７ The polymer A of the present invention contains a protecting group represented by the formula:

[0033] Although the reason is not clear, the protecting group is also deprotected when the main chain is cleaved, and therefore, a resist pattern can be formed with high sensitivity without adding a photoacid generator as in the case of a chemically amplified resist. For the irradiation of ionizing radiation or the like, known lithography devices such as an electron beam lithography device and a laser lithography device can be used.

[0126] <Developing Step> In the developing step, the resist film exposed in the exposure step is brought into contact with a developer to develop the resist film, thereby forming a resist pattern on the workpiece. The method for bringing the resist film into contact with the developer is not particularly limited, and known techniques such as immersing the resist film in the developer or applying the developer to the resist film can be used. The temperature of the developer is not particularly limited, but can be, for example, −20° C. or higher and 25° C. or lower. The development time can be, for example, 30 seconds or higher and 10 minutes or lower.

[0127] <<Developer>> The developer can be appropriately selected depending on the properties of polymer A and polymer B. Specifically, when selecting a developer, it is preferable to select a developer that does not dissolve the resist film before the exposure step, but can dissolve the exposed portion of the resist film after the exposure step. Among these, from the viewpoint of being able to form a resist pattern with a good shape, it is preferable to use an alcohol having from 1 to 5 carbon atoms. Note that one type of developer may be used alone, or multiple types may be used in combination.

[0128] Examples of alcohols having 1 to 5 carbon atoms that are suitable for use as a developer include alcohols having 1 carbon atom such as methanol, alcohols having 2 carbon atoms such as ethanol, alcohols having 3 carbon atoms such as 1-propanol and isopropyl alcohol (also known as 2-propanol), alcohols having 4 carbon atoms such as 1-butanol, 2-methyl-1-propanol, 2-butanol, and 2-methyl-2-propanol, and alcohols having 5 carbon atoms such as 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol, 3-methyl-1-butanol, 2-methyl-2-butanol, 3-methyl-2-butanol, and 2,2-dimethyl-1-propanol. Among these, from the viewpoint of being able to form a resist pattern having a good shape, alcohols having 2 to 4 carbon atoms are preferred, alcohols having 3 carbon atoms are more preferred, and isopropyl alcohol is even more preferred.

[0129] The proportion of the alcohol having 1 to 5 carbon atoms in the developer is preferably 50% by volume or more, more preferably 70% by volume or more, even more preferably 90% by volume or more, and particularly preferably 100% by volume (i.e., the developer contains only alcohol-based solvents having 1 to 5 carbon atoms), assuming the total amount of the developer to be 100% by volume. When the proportion of the alcohol-based solvent having 1 to 5 carbon atoms in the developer is equal to or more than the above-mentioned lower limit, a resist pattern having a good shape can be formed.

[0130] <Developer Removal Step> In the developer removal step optionally included in the resist pattern formation method of the present invention, the developer is removed from the developed resist film to form a resist pattern on the workpiece. The developer can be removed by air blowing using a gas such as nitrogen, or by rinsing using a rinse solution. Here, the method for contacting the developed resist film with the rinse solution in the rinsing step is not particularly limited, and known techniques such as immersing the resist film in the rinse solution or applying the rinse solution to the resist film can be used. Specific examples of rinse solutions include the same developers as those exemplified in the "Development Step" section, as well as hydrocarbon solvents such as octane and heptane, and water. Here, the rinse solution may contain a surfactant. When selecting a rinse solution, it is preferable to select a rinse solution that is less likely to dissolve the resist film prior to the exposure step than the developer used in the development step and that is easily mixed with the developer.

[0131] <Post-exposure bake step> In the post-exposure bake step, which is optionally included in the method of forming a resist pattern of the present invention, the exposed resist film is heated. By performing the post-exposure bake step, the surface roughness of the resist pattern can be reduced.

[0132] Here, the heating temperature when heating the resist film in the post-exposure bake step is preferably 70° C. or higher, more preferably 80° C. or higher, and even more preferably 90° C. or higher, and is preferably 200° C. or lower, more preferably 170° C. or lower, and even more preferably 150° C. or lower. When the heating temperature is within the above range, the clarity of the resist pattern can be improved while the surface roughness of the resist pattern can be effectively reduced.

[0133] The time for heating the resist film in the post-exposure bake step (heating time) is preferably 10 seconds or longer, more preferably 20 seconds or longer, and even more preferably 30 seconds or longer. A heating time of 10 seconds or longer can sufficiently reduce the surface roughness of the resist pattern while improving the clarity of the resist pattern. On the other hand, from the viewpoint of production efficiency, the heating time is, for example, preferably 10 minutes or shorter, more preferably 5 minutes or shorter, and even more preferably 3 minutes or shorter.

[0134] The method for heating the resist film in the post-exposure bake step is not particularly limited, and examples thereof include a method of heating the resist film on a hot plate, a method of heating the resist film in an oven, and a method of blowing hot air onto the resist film.

[0135] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples. In the following description, "%" and "parts" representing amounts are based on mass unless otherwise specified. Furthermore, in a copolymer produced by copolymerizing multiple types of monomers, the proportion of a monomer unit formed by polymerizing a certain monomer in the copolymer usually coincides with the ratio (feed ratio) of that certain monomer to all monomers used in the polymerization of the copolymer, unless otherwise specified. In the examples and comparative examples, various measurements and evaluations were performed using the following methods.

[0136] <Surface Free Energy> Films were produced by the following method using the positive resist composition (A) and the positive resist composition (B) prepared in each of the Examples and Comparative Examples. Next, for the resulting film, the contact angle of two solvents (water and diiodomethane) with known surface tensions, polarity terms (p), and dispersion terms (d) was measured using a contact angle meter (Drop Master 700, manufactured by Kyowa Interface Science Co., Ltd.) under the following conditions. The surface free energy was evaluated using the Owens-Wendt (extended Fowkes equation) method, and the surface free energy of the film was calculated. The surface free energy of the film produced using the positive resist composition (A) was designated the "surface free energy of polymer A," and the surface free energy of the film produced using the positive resist composition (B) was designated the "surface free energy of polymer B," and the difference between the surface free energy of polymer A and the surface free energy of polymer B (= "surface free energy of polymer A" - "surface free energy of polymer B") was calculated. <Weight Average Molecular Weight, Number Average Molecular Weight, and Molecular Weight Distribution> The weight average molecular weight (Mw) and number average molecular weight (Mn) of the polymers obtained in the Examples and Comparative Examples were determined as standard polystyrene equivalent values ​​using a gel permeation chromatograph (Tosoh Corporation, HLC-8420) connected to columns of TSKgel (registered trademark) G4000HXL, TSKgel G2000HXL, and TSKgel G1000HXL (all manufactured by Tosoh Corporation), and using tetrahydrofuran as a developing solvent, which is a good solvent capable of dissolving the polymers obtained in the Examples and Comparative Examples. The molecular weight distribution (Mw / Mn) was then calculated from the determined weight average molecular weight (Mw) and number average molecular weight (Mn). <Proportion of Monomer Units in Polymer> For the polymers obtained in the Examples and Comparative Examples, １３The proportion of the monomer units in the polymer was calculated using C-NMR. Specifically, the polymer was dissolved in chloroform-d, 99.8% (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) to a concentration of 10%, and this solution was measured using a nuclear magnetic resonance spectrometer (manufactured by JEOL, 400 MHz). From the measurement results, the proportion of each monomer unit in the polymer was calculated. <Sensitivity> Resist patterns were formed using the positive resist compositions (A / B mixed systems) obtained in the Examples and Comparative Examples, and the sensitivity was evaluated. Specifically, first, using a spin coater (manufactured by Mikasa Co., Ltd., MS-A150), the positive resist composition was applied to a silicon wafer with a diameter of 4 inches to a thickness of 50 nm. Next, the applied positive resist composition was heated on a hot plate at 140°C for 1 minute to form a resist film on the silicon wafer (resist film formation process). The resist film had a thickness of 50 nm. Then, the resist film was coated with an electron beam lithography system (ELS-S50, manufactured by Elionix) at a dose of 100 μC / cm ２ to 400 μC / cm ２ Within the range of 10 μC / cm ２ The resist film was exposed to light at different exposure times, forming a pattern (exposure step). The lines (unexposed areas) and spaces (exposed areas) of the resist pattern were each 30 nm. After the exposure step, the resist film was subjected to a development process using isopropyl alcohol (IPA) as a developer at a temperature of 23°C for 1 minute (development step). Thereafter, the developer was removed by nitrogen blowing to form a resist pattern (developer removal step). The line and space pattern with a half pitch of 30 nm thus formed was subjected to a certain electron beam irradiation dose (irradiated 100 to 400 μC / cm) without regard to the quality of the pattern. ２ When the minimum exposure dose of the electron beam capable of forming a pattern was 140 μC / cm or less, it was confirmed using a scanning electron microscope whether or not a pattern could be formed overall. The sensitivity was then evaluated according to the following criteria. The lower the minimum exposure dose of the electron beam capable of forming a pattern, the higher the sensitivity of the resist film to ionizing radiation and the like, and the higher the efficiency of forming a resist pattern. A: The minimum exposure dose capable of forming a pattern was 140 μC / cm or less. ２ B: The minimum irradiation dose capable of forming a pattern is 140 μC / cm ２More than 160μC / cm ２ C: The minimum irradiation dose capable of forming a pattern is 160 μC / cm ２ <Exposure Margin> Resist patterns were formed using the positive resist compositions (A / B mixed systems) obtained in the examples and comparative examples, and the exposure margin was evaluated. Specifically, first, a spin coater (MS-A150, manufactured by Mikasa) was used to apply the positive resist composition to a thickness of 40 nm on a silicon wafer with a diameter of 4 inches. Next, the applied positive resist composition was heated on a hot plate at a temperature of 140°C for 1 minute to form a resist film on the silicon wafer (resist film formation step). The resist film had a thickness of 50 nm. Then, an electron beam lithography system (ELS-S50, manufactured by Elionix) was used to coat the resist film at 100 μC / cm ２ to 400 μC / cm ２ Within the range of 10 μC / cm ２ The resist film was exposed to light at different exposure times, forming a pattern (exposure step). The lines (unexposed areas) and spaces (exposed areas) of the resist pattern were each 30 nm. After the exposure step, the resist film was subjected to a development process using isopropyl alcohol (IPA) as a developer at a temperature of 23°C for 1 minute (development step). Thereafter, the developer was removed by nitrogen blowing to form a resist pattern (developer removal step). The line and space pattern with a half pitch of 30 nm thus formed was subjected to a certain electron beam irradiation dose (irradiated 100 to 400 μC / cm) without regard to the quality of the pattern. ２ In the case where the exposure dose was within the range of 200 μC / cm or less, it was confirmed by a scanning electron microscope whether or not a pattern was formed overall. Then, the width of the range of exposure dose at which a pattern could be formed (the difference between the minimum exposure dose at which a pattern could be formed and the maximum exposure dose at which a pattern could be formed) was determined, and the exposure margin was evaluated according to the following criteria: A: The width of the range of exposure dose at which a pattern could be formed was 200 μC / cm or less. ２ Ultra B: The width of the range of exposure dose in which a pattern could be formed was 50 μC / cm ２ More than 200μC / cm ２ C: The width of the range of exposure dose that allowed a pattern to be formed was 50 μC / cm ２<Resist Pattern Shape> Resist patterns were formed using the positive resist compositions (A / B mixed systems) obtained in the examples and comparative examples, and the resist pattern shapes were evaluated. Specifically, in the above-mentioned evaluation of the exposure margin, exposure was performed at an electron beam irradiation dose at the median value within the range of exposure doses at which a pattern could be formed, and the shape of the resulting pattern was observed using a scanning electron microscope. The shape of the resist pattern was then evaluated according to the following criteria. An example of an A rating and a B rating is shown in Figure 1. A: The sidewalls of the resist pattern are straight. B: The sidewalls of the resist pattern are not straight.

[0137] <Preparation of Polymer A> <<Preparation Example 1: Preparation of Polymer A1>> A monomer composition A1 containing 13.38 g of 1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl α-chloroacrylate (ACAFPh) as the monomer (a), 3.77 g of 4-t-butoxycarbonyloxy-α-methylstyrene (BocAMS) as the monomer (b), 2.85 g of α-methylstyrene (AMS) as the monomer (c), 0.0037 g of V-601 (dimethyl 2,2′-azobis(2-methylpropionate)) as a polymerization initiator, and 13.33 g of cyclopentanone as a solvent was placed in a glass container, the glass container was sealed and purged with nitrogen, and the mixture was stirred in a 78° C. constant temperature bath under a nitrogen atmosphere for 6 hours. Thereafter, the temperature was returned to room temperature, and the glass container was opened to the atmosphere. Then, 33.55 g of tetrahydrofuran (THF) was added to the obtained solution. Then, the solution to which THF had been added was dropped into 807.11 g of methanol as a solvent to precipitate a polymer. Thereafter, the solution containing the precipitated polymer was filtered using a Kiriyama funnel to obtain a white coagulated product (polymer A1). The proportion of the monomer units in the obtained polymer A1 was １Calculations using H-NMR revealed that polymer A1 was a copolymer containing 54 mol% of α-chloroacrylate-1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl units as monomer units (I), 18 mol% of 4-t-butoxycarbonyloxy-α-methylstyrene units as monomer units (II), and 28 mol% of α-methylstyrene units as monomer units (VI). Thereafter, the number average molecular weight, weight average molecular weight, and molecular weight distribution of the obtained polymer A1 were measured. The results are shown in Table 1.

[0138] <<Preparation Example 2: Preparation of Polymer A2>> Various operations, measurements, and evaluations were carried out in the same manner as in Preparation Example 1, except that polymer A2 was prepared using monomer composition A2 containing 14.39 g of 1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl α-chloroacrylate (ACAFPh) as monomer (a), 1.01 g of 4-t-butoxycarbonyloxy-α-methylstyrene (BocAMS) as monomer (b), 4.60 g of α-methylstyrene (AMS) as monomer (c), 0.0024 g of V-601 (dimethyl 2,2′-azobis(2-methylpropionate)) as a polymerization initiator, and 13.33 g of cyclopentanone as a solvent, instead of monomer composition A1. The results are shown in Table 1.

[0139] <<Preparation Example 3: Preparation of Polymer A3>> Various operations, measurements, and evaluations were carried out in the same manner as in Preparation Example 1, except that polymer A3 was prepared using monomer composition A3 containing 2.93 g of 1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl α-chloroacrylate (ACAFPh) as monomer (a), 2.07 g of 4-t-butoxycarbonyloxy-α-methylstyrene (BocAMS) as monomer (b), 0.039 g of V-601 (dimethyl 2,2′-azobis(2-methylpropionate)) as a polymerization initiator, and 3.29 g of cyclopentanone as a solvent, instead of monomer composition A1. The results are shown in Table 1.

[0140] <<Preparation Example 4: Preparation of Polymer A4>> 9.80 g of α-chloroacrylate-1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl (ACAFPh) as monomer (a), 2.77 g of 4-t-butoxycarbonyloxy-α-methylstyrene (BocAMS) as monomer (b), 2.09 g of α-methylstyrene (AMS) as monomer (c), and 0.11 g of azobisisobutyronitrile as a polymerization initiator were placed in a glass container. Furthermore, 47.74 g of a 7.5% solids aqueous solution of sodium laurate was added, the glass container was sealed and purged with nitrogen, and the mixture was stirred for 3 hours in a constant temperature bath at 75 °C under a nitrogen atmosphere. The mixture was then returned to room temperature, and the glass container was opened to the atmosphere. The resulting solution was then added dropwise to 488.34 g of methanol to precipitate a polymer. The precipitated polymer was then recovered by filtration. The polymer recovered by filtration was dissolved in 35.18 g of THF, and a mixed solution of 123.12 g of THF and 316.58 g of methanol was added dropwise to the resulting solution to precipitate a white coagulum (polymer). Then, the polymer recovered by decantation was dissolved in 35.18 g of THF, and the resulting solution was added dropwise to 351.76 g of methanol to precipitate a polymer. Then, the solution containing the precipitated polymer was filtered using a Kiriyama funnel to obtain a coagulum (polymer A4). For this polymer A4, the number average molecular weight, weight average molecular weight, and molecular weight distribution were measured. The results are shown in Table 1.

[0141] <<Preparation Example 5: Preparation of Polymer A5>> Various operations, measurements, and evaluations were carried out in the same manner as in Preparation Example 4, except that polymer A5 was prepared using monomer composition A5 containing 10.57 g of 1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl α-chloroacrylate (ACAFPh) as monomer (a), 0.76 g of 4-t-butoxycarbonyloxy-α-methylstyrene (BocAMS) as monomer (b), 3.37 g of α-methylstyrene (AMS) as monomer (c), and 0.092 g of azobisisobutyronitrile as a polymerization initiator, instead of monomer composition A4. The results are shown in Table 1.

[0142] <<Preparation Example 6: Preparation of Polymer A6>> Various operations, measurements, and evaluations were carried out in the same manner as in Preparation Example 1, except that polymer A6 was prepared using monomer composition A6 containing 3.22 g of 1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl α-chloroacrylate (ACAFPh) as monomer (a), 1.20 g of 1,1-dimethylethenyl-2-[4-(1-methylethenyl)phenoxy]acetate (tBuOAMS) as monomer (b), 0.57 g of α-methylstyrene (AMS) as monomer (c), 0.0036 g of V-601 (dimethyl 2,2′-azobis(2-methylpropionate)) as a polymerization initiator, and 3.16 g of cyclopentanone as a solvent, instead of monomer composition A1. The results are shown in Table 1.

[0143] <<Preparation Example 7: Preparation of Polymer A7>> Various operations, measurements, and evaluations were carried out in the same manner as in Preparation Example 4, except that polymer A7 was prepared using monomer composition A7 containing 10.50 g of 1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl α-chloroacrylate (ACAFPh) as monomer (a), 0.78 g of 1,1-dimethylethenyl-2-[4-(1-methylethenyl)phenoxy]acetate (tBuOAMS) as monomer (b), 3.36 g of α-methylstyrene (AMS) as monomer (c), and 0.085 g of azobisisobutyronitrile as a polymerization initiator, instead of monomer composition A4. The results are shown in Table 1.

[0144] <<Preparation Example 8: Preparation of Polymer A8>> Various operations, measurements, and evaluations were carried out in the same manner as in Preparation Example 4, except that polymer A8 was prepared using monomer composition A8 containing 10.51 g of 1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl α-chloroacrylate (ACAFPh) as monomer (a), 0.65 g of 1-(1-ethoxyethoxy)-4-(1-methylethenyl)benzene (4EEAMS) as monomer (b), 3.37 g of α-methylstyrene (AMS) as monomer (c), and 0.085 g of azobisisobutyronitrile as a polymerization initiator, instead of monomer composition A4. The results are shown in Table 1.

[0145] <<Preparation Example 9: Preparation of Polymer A9>> Various operations, measurements, and evaluations were carried out in the same manner as in Preparation Example 1, except that polymer A9 was prepared using, instead of monomer composition A1, a monomer composition A9 containing 11.07 g of 1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl α-chloroacrylate (ACAFPh) as monomer (a), 3.93 g of α-methylstyrene (AMS) as monomer (c), 0.012 g of V-601 (dimethyl 2,2′-azobis(2-methylpropionate)) as a polymerization initiator, and 9.99 g of cyclopentanone as a solvent. The results are shown in Table 1.

[0146] <<Preparation Example 10: Preparation of Polymer A10>> Various operations, measurements, and evaluations were carried out in the same manner as in Preparation Example 4, except that Polymer A10 was prepared using a monomer composition A10 containing 10.50 g of 1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl α-chloroacrylate (ACAFPh) as the monomer (a), 3.73 g of α-methylstyrene (AMS) as the monomer (c), and 0.083 g of azobisisobutyronitrile as a polymerization initiator, instead of the monomer composition A4. The results are shown in Table 1.

[0147] <Preparation of Polymer B> <<Preparation Example 11: Preparation of Polymer B1>> A monomer composition B1 containing 2.04 g of 2,2,3,3,3-pentafluoropropyl α-chloroacrylate (ACAPFP) as the monomer (d), 2.96 g of α-methylstyrene (AMS) as the monomer (e), 0.019 g of azobisisobutyronitrile as a polymerization initiator, and 1.25 g of cyclopentanone as a solvent was placed in a glass container, the glass container was sealed and purged with nitrogen, and the mixture was stirred for 6 hours in a constant temperature bath at 78°C under a nitrogen atmosphere. The mixture was then returned to room temperature, and the glass container was opened to the atmosphere. 43.68 g of tetrahydrofuran (THF) was then added to the resulting solution. The solution to which THF had been added was then added dropwise to 499.69 g of methanol as a solvent, causing a polymer to precipitate. The solution containing the precipitated polymer was then filtered using a Kiriyama funnel to obtain a white coagulum (Polymer B1). The ratio of the monomer units in the obtained polymer B1 was １３Calculation using C-NMR revealed that polymer B1 was a copolymer containing 48 mol % of 2,2,3,3,3-pentafluoropropyl α-chloroacrylate units as monomer units (VII) and 52 mol % of α-methylstyrene units as monomer units (VIII). Thereafter, the number average molecular weight, weight average molecular weight, and molecular weight distribution of the obtained polymer B1 were measured. The results are shown in Table 1.

[0148] <<Preparation Example 12: Preparation of Polymer B2>> Various operations, measurements, and evaluations were carried out in the same manner as in Preparation Example 11, except that polymer B2 was prepared using monomer composition B2 containing 0.54 g of 1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl α-chloroacrylate (ACAFPh) as monomer (d), 2.21 g of 2,2,3,3,4,4,5,5,5-nonafluoropentyl α-chloroacrylate (ACANFP) as monomer (d), 2.25 g of α-methylstyrene (AMS) as monomer (e), 0.0050 g of V-601 (dimethyl 2,2′-azobis(2-methylpropionate)) as a polymerization initiator, and 1.24 g of cyclopentanone as a solvent, instead of monomer composition B1. The results are shown in Table 1.

[0149] Example 1 Preparation of Positive Resist Compositions A positive resist composition containing only polymer A was prepared by dissolving the polymer A1 prepared as described above in isoamyl acetate as a solvent to prepare a positive resist composition (A) with a concentration of 2%. Furthermore, a positive resist composition containing only polymer B was prepared by dissolving the polymer B1 prepared as described above in isoamyl acetate as a solvent to prepare a positive resist composition (B) with a concentration of 2%. Furthermore, a positive resist composition containing polymer A and polymer B was prepared by dissolving the polymer A1 prepared as described above and the polymer B1 prepared as described above in isoamyl acetate as a solvent so that the mass ratio of polymer A1 to polymer B1 was 80:20, to prepare a positive resist composition (A / B mixed system) with a concentration of 2%. A resist pattern was formed using the resulting positive resist composition (A / B mixed system), and the sensitivity, exposure margin, and resist pattern shape were evaluated. Furthermore, the surface free energy of each of the resulting positive resist compositions (A) and (B) was measured, and the results are shown in Tables 1 and 2.

[0150] Examples 2 to 11, Comparative Examples 1 to 3 Positive resist compositions were prepared in the same manner as in Example 1, except that the types of polymer A and polymer B, and the mass ratio of polymer A to polymer B, were changed as shown in Table 2. Using the resulting positive resist compositions, various measurements and evaluations were carried out in the same manner as in Example 1. The results are shown in Tables 1 and 2.

[0151] In Tables 1 and 2 shown below, "ACAFPh" represents 1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl α-chloroacrylate, "BocAMS" represents 4-t-butoxycarbonyloxy-α-methylstyrene, "tBuOAMS" represents 1,1-dimethylethenyl-2-[4-(1-methylethenyl)phenoxy]acetate, "4EEAMS" represents 1-(1-ethoxyethoxy)-4-(1-methylethenyl)benzene, "AMS" represents α-methylstyrene, "ACAPFP" represents 2,2,3,3,3-pentafluoropropyl α-chloroacrylate, "ACANFP" represents 2,2,3,3,4,4,5,5,5-nonafluoropentyl α-chloroacrylate, "Mw" represents weight average molecular weight, "Mw / Mn" indicates molecular weight distribution, "IPA" indicates isopropyl alcohol, and "difference in surface free energy" indicates the difference (absolute value) between the surface free energy of polymer A and the surface free energy of polymer B.

[0152]

[0153]

[0154] According to the present invention, it is possible to provide a positive resist composition that exhibits a wide exposure margin and high sensitivity, and also to provide a method of forming a resist pattern that is capable of forming a resist pattern with high sensitivity while ensuring a wide exposure margin.

Claims

1. A positive resist composition comprising a polymer A, a polymer B different from the polymer A, and a solvent, wherein the difference in surface free energy between the polymer A and the polymer B is 3 mJ / m ２ The polymer A is represented by the following formula (I): [In formula (I), R １ is a halogen atom or an alkyl group substituted with a halogen atom, and R ２ is an organic group, and R ３ and R ４ are each independently a hydrogen atom, a fluorine atom, an unsubstituted alkyl group, or an alkyl group substituted with a fluorine atom, and may be the same or different from each other.] and a monomer unit (I) derived from a monomer represented by the following formula (II): [In formula (II), R ５ , R ８ and R ９ are each independently a hydrogen atom, a halogen atom, an unsubstituted alkyl group, or an alkyl group substituted with a halogen atom, and may be the same or different from each other; R ６ is a hydrogen atom or an organic group, m is an integer of 1 or more and 5 or less, m+n=5, and R ７ are represented by the following formulas (III) to (V): (In formulas (III) to (V), R １０ , R １２ ~R １４ and R １６ are each independently an optionally substituted alkyl group, an optionally substituted cycloalkyl group, or an optionally substituted alkenyl group, and R １５ is a hydrogen atom, an optionally substituted alkyl group, an optionally substituted cycloalkyl group, or an optionally substituted alkenyl group, and R １１ is an alkylene group which may have a substituent, a cycloalkylene group which may have a substituent, or an alkenylene group which may have a substituent, and R １２ ~R １４ Two of R may be bonded to each other to form a ring structure; １５ ~R １６ may be bonded to each other to form a ring structure.) A positive resist composition comprising at least a monomer unit (II) derived from a monomer represented by the following formula:

2. The polymer A is represented by the following formula (VI): [In formula (VI), R １７ , R １９ and R ２０ are each independently a hydrogen atom, a halogen atom, an unsubstituted alkyl group, or an alkyl group substituted with a halogen atom, and may be the same or different from each other; R １８ is an organic group or a halogen atom, and p is an integer of 0 or more and 5 or less.] and further comprises a monomer unit (VI) derived from a monomer different from the monomer represented by formula (II).

3. A positive resist composition according to claim 2, wherein the total proportion of said monomer units (II) and said monomer units (VI) in all monomer units constituting said polymer A is 40 mol % or more.

4. The above R ２ is a group represented by L-Ar, wherein L is a single bond or a divalent linking group having a halogen atom, and Ar is an aromatic ring group which may have a substituent.

5. A positive resist composition according to claim 1, wherein the proportion of said monomer unit (II) in all monomer units constituting said polymer A is 40 mol % or less.

6. The above R １ 2. The positive resist composition according to claim 1, wherein is a chlorine atom.

7. The polymer B is represented by the following formula (VII): [In formula (VII), R ２１ is a halogen atom or an alkyl group substituted with a halogen atom, and R ２２ is an organic group having a fluorine atom, and R ２３ and R ２４ and each independently represent a hydrogen atom, a fluorine atom, an unsubstituted alkyl group, or a fluorine atom-substituted alkyl group, and may be the same or different from each other.

8. The above R ２２ 8. The positive resist composition according to claim 7, wherein is an organic group having four or more fluorine atoms.

9. The polymer B is represented by the following formula (VIII): [In formula (VIII), R ２５ , R ２７ and R ２８ are each independently a hydrogen atom, a halogen atom, an unsubstituted alkyl group, or an alkyl group substituted with a halogen atom, and may be the same or different from each other; R ２６ is an organic group or a halogen atom, and q is an integer of 0 or more and 5 or less.] and further comprises a monomer unit (VIII) derived from a monomer different from the monomer represented by formula (II).

10. A method for forming a resist pattern, comprising the steps of: forming a positive resist film using the positive resist composition according to any one of claims 1 to 9; exposing the positive resist film; and developing the exposed positive resist film by bringing it into contact with a developer to obtain a developed film.

11. The method for forming a resist pattern according to claim 10, wherein the developer contains an alcohol having 1 to 5 carbon atoms.

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