JP2017132965A - Polymer and positive resist composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polymer that can sufficiently suppress occurrence of collapse of a resist pattern, has specific solubility with a developer and gives a resist pattern having high clarity when the polymer is used as a positive resist composition using ionization radiation or the like.SOLUTION: The polymer has a monomer unit (A) and a monomer unit (B), in which at least one of the monomer unit (A) and the monomer unit (B) has at least one fluorine atom; and the polymer has a weight average molecular weight of 22000 or more. The monomer unit (A) is a α-halo acrylic acid ester, in which an alcohol residue is composed of an F-substituted or unsubstituted alkyl group; and the monomer unit (B) is styrene comprising a H- or F-substituted or unsubstituted alkyl group.SELECTED DRAWING: None

Description

  The present invention relates to a polymer and a positive resist composition, and particularly relates to a polymer that can be suitably used as a positive resist and a positive resist composition containing the polymer.

  Conventionally, in the field of semiconductor manufacturing and the like, ionizing radiation such as an electron beam and short wavelength light such as ultraviolet rays (hereinafter, ionizing radiation and short wavelength light may be collectively referred to as “ionizing radiation or the like”). A polymer whose main chain is cleaved by irradiation and has increased solubility in a developing solution is used as a main chain-cutting positive resist.

  For example, Patent Document 1 discloses that α-methylstyrene / methyl α-chloroacrylate containing an α-methylstyrene unit and an α-methylchloroacrylate unit as a high-sensitivity main-chain-breaking positive resist. A positive resist made of a copolymer is disclosed.

Japanese Patent Publication No. 8-3636

  Here, in the resist pattern formation process using a resist, the resist pattern collapses when the resist pattern is formed through irradiation with ionizing radiation or the like, development processing using a developer, and rinsing processing using a rinsing liquid. May occur. Therefore, in forming a resist pattern using a resist, it is required to suppress the collapse of the resist pattern.

  In the main chain cutting type positive resist, the obtained resist pattern is clear, that is, the boundary between the portion where the resist film remains (the remaining film) and the dissolved portion is clear. It is required to be. Specifically, from the viewpoint of enabling a clearer resist pattern to be formed, the resist does not dissolve in the developer unless the irradiation amount reaches a specific amount, and promptly when the specific amount is reached. Expresses the magnitude of the slope of the sensitivity curve indicating the relationship between the common logarithm of the irradiation amount of ionizing radiation and the like and the residual film thickness of the resist after development that the main chain is cleaved and dissolved in the developer. There is a demand for increasing the γ value.

  However, the positive resist made of the α-methylstyrene / α-chloroacrylate methyl copolymer described in Patent Document 1 cannot sufficiently suppress the collapse of the resist pattern. Further, with such a positive resist, the clarity of the pattern obtained cannot be sufficiently improved.

Therefore, the present invention provides a polymer that can sufficiently suppress the occurrence of resist pattern collapse when used as a main-chain-breaking positive resist and has high clarity of the resulting resist pattern. With the goal.
Another object of the present invention is to provide a positive resist composition that can sufficiently suppress the occurrence of resist pattern collapse during formation of a resist pattern, and that has a high γ value and can provide a clear pattern. And

  The inventor has intensively studied to achieve the above object. Then, the present inventor found that when a copolymer containing one or more fluorine atoms and having a weight average molecular weight of 22,000 or more is used as a main chain cutting type positive resist composition, the resist pattern collapses. The inventors have found that the occurrence of the occurrence can be sufficiently suppressed, the γ value is high, and the clarity of the resulting pattern is high, and the present invention has been completed.

（式（Ｉ）中、Ｒ¹は、塩素原子、フッ素原子またはフッ素原子で置換されたアルキル基であり、Ｒ²は、非置換のアルキル基またはフッ素原子で置換されたアルキル基であり、Ｒ³およびＲ⁴は、水素原子、フッ素原子、非置換のアルキル基またはフッ素原子で置換されたアルキル基であり、互いに同一でも異なっていてもよい。）で表される単量体単位（Ａ）と、下記一般式（ＩＩ）：

（式（ＩＩ）中、Ｒ⁵、Ｒ⁶、Ｒ⁸およびＲ⁹は、水素原子、フッ素原子、非置換のアルキル基またはフッ素原子で置換されたアルキル基であり、互いに同一でも異なっていてもよく、Ｒ⁷は、水素原子、非置換のアルキル基またはフッ素原子で置換されたアルキル基であり、ｐおよびｑは、０以上５以下の整数であり、ｐ＋ｑ＝５である。）で表される単量体単位（Ｂ）とを有し、前記単量体単位（Ａ）および前記単量体単位（Ｂ）の少なくとも一方がフッ素原子を一つ以上有し、且つ、重量平均分子量が２２０００以上であることを特徴とする。少なくとも一方がフッ素原子を一つ以上有する所定の単量体単位（Ａ）および単量体単位（Ｂ）を含有し、且つ重量平均分子量が２２０００以上である重合体は、ポジ型レジストとして使用した際にレジストパターンの倒れの発生を十分に抑制可能であるとともに、γ値が高く、得られるパターンの明瞭性を高めることができるため、主鎖切断型のポジ型レジストとして良好に使用することができる。
なお、本発明において、式（ＩＩ）中のｐが２以上の場合には、複数あるＲ⁶は互いに同一でも異なっていてもよく、また、式（ＩＩ）中のｑが２以上の場合には、複数あるＲ⁷は互いに同一でも異なっていてもよい。また、本発明において「重量平均分子量（Ｍｗ）」は、ゲル浸透クロマトグラフィーを用いて測定することができる。 That is, this invention aims at solving the said subject advantageously, The polymer of this invention is the following general formula (I):

(In the formula (I), R ¹ is a chlorine atom, a fluorine atom or an alkyl group substituted with a fluorine atom, R ² is an unsubstituted alkyl group or an alkyl group substituted with a fluorine atom, ³ and R ⁴ are 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 the following general formula (II):

(In the formula (II), R ⁵ , R ⁶ , R ⁸ and R ⁹ are 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. R ⁷ is often a hydrogen atom, an unsubstituted alkyl group or an alkyl group substituted with a fluorine atom, and p and q are integers of 0 or more and 5 or less, and p + q = 5. Monomer unit (B), at least one of the monomer unit (A) and the monomer unit (B) has one or more fluorine atoms, and the weight average molecular weight is 22,000. It is the above. A polymer containing a predetermined monomer unit (A) and monomer unit (B) each having at least one fluorine atom and having a weight average molecular weight of 22,000 or more was used as a positive resist. In addition, the occurrence of resist pattern collapse can be sufficiently suppressed, and the γ value is high, and the clarity of the resulting pattern can be improved. it can.
In the present invention, when p in the formula (II) is 2 or more, a plurality of R ⁶ may be the same or different from each other, and when q in the formula (II) is 2 or more. The plurality of R ⁷ may be the same as or different from each other. In the present invention, the “weight average molecular weight (Mw)” can be measured using gel permeation chromatography.

  Here, the polymer of the present invention preferably has a weight average molecular weight of 110,000 or less. When the weight average molecular weight of the polymer is 110,000 or less, the sensitivity can be improved moderately when used as a main-chain-breaking positive resist composition.

Furthermore, the polymer of the present invention preferably has a molecular weight distribution (Mw / Mn) of less than 1.60. If the molecular weight distribution of the polymer is less than 1.60, the γ value can be further improved and the clarity of the resulting pattern can be further improved when used as a main-chain-breaking positive resist composition. .
In the present invention, “molecular weight distribution (Mw / Mn)” refers to the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn). In the present invention, the “number average molecular weight (Mn)” can be measured using gel permeation chromatography in the same manner as the “weight average molecular weight (Mw)” described above.

Furthermore, in the polymer of the present invention, the R ¹ is preferably a chlorine atom. When R ¹ of the monomer unit (A) is a chlorine atom, the main chain can be cut when irradiated with ionizing radiation or the like. Therefore, when used as a main chain-cutting positive resist, the clarity of the resist pattern can be further improved and the sensitivity can be improved moderately. A polymer in which R ^{1 of} the monomer unit (A) is a chlorine atom is easy to prepare.

In the polymer of the present invention, R ² is preferably an alkyl group substituted with a fluorine atom, and R ³ and R ⁴ are preferably a hydrogen atom or an unsubstituted alkyl group. When R ² of the monomer unit (A) is an alkyl group substituted with a fluorine atom, and R ³ and R ⁴ are a hydrogen atom or an unsubstituted alkyl group, the main chain upon irradiation with ionizing radiation or the like The cutting property can be improved. Therefore, it can be used particularly well as a main chain cutting type positive resist.

Furthermore, in the polymer of the present invention, R ^{5 to} R ⁹ are preferably a hydrogen atom or an unsubstituted alkyl group, and the monomer unit (A) preferably has one or more fluorine atoms. A polymer in which R ^{5 to} R ⁹ of the monomer unit (B) is a hydrogen atom or an unsubstituted alkyl group and the monomer unit (A) has one or more fluorine atoms is easy to produce. In addition, the main chain is excellent in cleavability when irradiated with ionizing radiation or the like.

  Moreover, this invention aims at solving the said subject advantageously, and the positive resist composition of this invention contains either of the polymer mentioned above, and a solvent, It is characterized by the above-mentioned. When the polymer described above is contained as a positive resist, it is possible to sufficiently suppress the occurrence of the resist pattern collapse when used for forming a resist pattern and to form a clear resist pattern.

According to the polymer of the present invention, it is possible to provide a positive resist that can sufficiently suppress the occurrence of a collapse of a resist pattern when used as a resist and has high clarity of the resulting pattern.
In addition, according to the positive resist composition of the present invention, a clear value pattern can be satisfactorily formed with a high γ value.

Hereinafter, embodiments of the present invention will be described in detail.
Here, the polymer of the present invention can be used favorably as a main chain-cutting positive resist in which the main chain is cut by irradiation with ionizing radiation such as an electron beam or light having a short wavelength such as ultraviolet light to reduce the molecular weight. can do. The positive resist composition of the present invention contains the polymer of the present invention as a positive resist, and can be used, for example, when forming a resist pattern in a manufacturing process of a printed board such as a build-up board. it can.

（式（Ｉ）中、Ｒ¹は、塩素原子、フッ素原子またはフッ素原子で置換されたアルキル基であり、Ｒ²は、非置換のアルキル基またはフッ素原子で置換されたアルキル基であり、Ｒ³およびＲ⁴は、水素原子、フッ素原子、非置換のアルキル基またはフッ素原子で置換されたアルキル基であり、Ｒ³およびＲ⁴は互いに同一でも異なっていてもよい。）で表される単量体単位（Ａ）と、
下記の一般式（ＩＩ）：

（式（ＩＩ）中、Ｒ⁵、Ｒ⁶、Ｒ⁸およびＲ⁹は、水素原子、フッ素原子、非置換のアルキル基またはフッ素原子で置換されたアルキル基であり、Ｒ⁵、Ｒ⁶、Ｒ⁸およびＲ⁹は互いに同一でも異なっていてもよく、Ｒ⁷は、水素原子、非置換のアルキル基またはフッ素原子で置換されたアルキル基であり、ｐおよびｑは、０以上５以下の整数であり、ｐ＋ｑ＝５である。）で表される単量体単位（Ｂ）とを有する。また、本発明の重合体は、単量体単位（Ａ）および単量体単位（Ｂ）の少なくとも一方がフッ素原子を一つ以上有する。即ち、本発明の重合体は、単量体単位（Ａ）がフッ素原子を一つ以上有し、単量体単位（Ｂ）がフッ素原子を有していなくてもよいし、単量体単位（Ｂ）がフッ素原子を一つ以上有し、単量体単位（Ａ）がフッ素原子を有していなくてもよいし、単量体単位（Ａ）および単量体単位（Ｂ）のそれぞれがフッ素原子を一つ以上有していてもよい。さらに、本発明の重合体は、重量平均分子量が２２０００以上である。
なお、本発明の重合体は、単量体単位（Ａ）および単量体単位（Ｂ）以外の任意の単量体単位を含んでいてもよいが、重合体を構成する全単量体単位中で単量体単位（Ａ）および単量体単位（Ｂ）が占める割合は、合計で９０ｍｏｌ％以上であることが好ましく、１００ｍｏｌ％（即ち、重合体は単量体単位（Ａ）および単量体単位（Ｂ）のみを含む）ことが好ましい。 (Polymer)
The polymer of the present invention has the following general formula (I):

(In the formula (I), R ¹ is a chlorine atom, a fluorine atom or an alkyl group substituted with a fluorine atom, R ² is an unsubstituted alkyl group or an alkyl group substituted with a fluorine atom, ³ and R ⁴ are a hydrogen atom, a fluorine atom, an unsubstituted alkyl group or an alkyl group substituted with a fluorine atom, and R ³ and R ⁴ may be the same or different from each other. A monomer unit (A);
The following general formula (II):

(In the formula (II), R ⁵ , R ⁶ , R ⁸ and R ⁹ are a hydrogen atom, a fluorine atom, an unsubstituted alkyl group or an alkyl group substituted with a fluorine atom, and R ⁵ , R ⁶ , R ⁸ and R ⁹ may be the same or different from each other, R ⁷ is a hydrogen atom, an unsubstituted alkyl group or an alkyl group substituted with a fluorine atom, and p and q are integers of 0 or more and 5 or less. And p + q = 5.) The monomer unit (B) represented by In the polymer of the present invention, at least one of the monomer unit (A) and the monomer unit (B) has one or more fluorine atoms. That is, in the polymer of the present invention, the monomer unit (A) may have one or more fluorine atoms, the monomer unit (B) may not have a fluorine atom, (B) has one or more fluorine atoms, the monomer unit (A) may not have a fluorine atom, and each of the monomer unit (A) and the monomer unit (B) May have one or more fluorine atoms. Furthermore, the polymer of the present invention has a weight average molecular weight of 22,000 or more.
The polymer of the present invention may contain any monomer unit other than the monomer unit (A) and the monomer unit (B), but all monomer units constituting the polymer. The proportion of the monomer unit (A) and the monomer unit (B) is preferably 90 mol% or more in total, and 100 mol% (that is, the polymer is composed of the monomer unit (A) and the single unit. It is preferable that only a monomer unit (B) is included.

And since the polymer of this invention contains the predetermined monomer unit (A) and monomer unit (B), ionizing radiation etc. (for example, electron beam, KrF laser, ArF laser, EUV laser, etc.) ) Is irradiated, the main chain is cleaved to lower the molecular weight. In the polymer of the present invention, since at least one of the monomer unit (A) and the monomer unit (B) has one or more fluorine atoms, the resist pattern collapses when used as a resist. Can be sufficiently suppressed.
The reason why the occurrence of resist pattern collapse can be suppressed by containing a fluorine atom in at least one of the monomer unit (A) and the monomer unit (B) is not clear. This is presumably because the liquid repellency is improved, and it is possible to suppress the occurrence of tension between the patterns when the developing solution or the rinsing solution is removed in the process of forming the resist pattern.
Further, since the polymer of the present invention has a weight average molecular weight of 22000 or more, when used as a positive resist, it does not excessively reduce the film thickness when the amount of radiation such as ionizing radiation is low. Since it can be improved and the resist pattern obtained is excellent in clarity, it can be used favorably as a main chain cutting type positive resist. Moreover, if the weight average molecular weight of the polymer is 22000 or more, the elasticity of a positive resist formed using such a polymer can be improved, so that the occurrence of a resist pattern collapse can be further suppressed. is there.

（式（ＩＩＩ）中、Ｒ¹〜Ｒ⁴は、式（Ｉ）と同様である。）で表される単量体（ａ）に由来する構造単位である。 <Monomer unit (A)>
Here, the monomer unit (A) has the following general formula (III):

(In formula (III), R < ¹ > -R < ⁴ > is the same as that of formula (I).) Is a structural unit derived from the monomer (a) represented.

  And the ratio of the monomer unit (A) in all the monomer units which comprise a polymer is not specifically limited, For example, it can be 30 mol% or more and 70 mol% or less.

Here, the alkyl group substituted with a fluorine atom that can constitute R ^{1 to} R ⁴ in the formula (I) and the formula (III) is not particularly limited, and one of hydrogen atoms in the alkyl group is not limited. And groups having a structure in which part or all are substituted with fluorine atoms.
In addition, the unsubstituted alkyl group that can constitute R ^{2 to} R ⁴ in formula (I) and formula (III) is not particularly limited, and an unsubstituted alkyl group having 1 to 10 carbon atoms can be used. Can be mentioned. Especially, as an unsubstituted alkyl group which can comprise R < ² > -R < ⁴ >, a methyl group or an ethyl group is preferable.

And from the viewpoint of improving the scissibility of the main chain of the polymer when irradiated with ionizing radiation, R ¹ in formula (I) and formula (III) is substituted with a chlorine atom, a fluorine atom or a fluorine atom. It is preferably an alkyl group having 1 to 5 carbon atoms, more preferably a chlorine atom, a fluorine atom or a perfluoromethyl group, still more preferably a chlorine atom or a fluorine atom, and a chlorine atom. It is particularly preferred. In particular, a polymer in which R ¹ is a chlorine atom has a higher main chain cleavability than a polymer in which R ¹ is a fluorine atom when used as a main-chain-breaking positive resist. In addition, the sensitivity can be improved moderately. The monomer (a) in which R ¹ in the formula (III) is a chlorine atom is excellent in polymerizability, and the monomer unit (A) in which R ¹ in the formula (I) is a chlorine atom. The polymer having the is also excellent in that it is easy to prepare.

Further, from the viewpoint of improving the cleavability of the main chain of the polymer when irradiated with ionizing radiation or the like, R ² in the formulas (I) and (III) is an alkyl group substituted with a fluorine atom. More preferably, it is an alkyl group having 1 to 10 carbon atoms substituted with a fluorine atom, 2,2,2-trifluoroethyl group, 2,2,3,3,3-pentafluoropropyl. Group, 2- (perfluorobutyl) ethyl group, 2- (perfluorohexyl) ethyl group, 1H, 1H, 3H-tetrafluoropropyl group, 1H, 1H, 5H-octafluoropentyl group, 1H, 1H, 7H- Dodecafluoroheptyl group, 1H-1- (trifluoromethyl) trifluoroethyl group, 1H, 1H, 3H-hexafluorobutyl group or 1,2,2,2-tetrafluoro- - further preferably (trifluoromethyl) ethyl group, and particularly preferably a 2,2,2-trifluoroethyl group.

Furthermore, R ³ and R ⁴ in formula (I) and formula (III) are each a hydrogen atom or an unsubstituted group from the viewpoint of improving the cleavability of the main chain of the polymer when irradiated with ionizing radiation or the like. The alkyl group is preferably a hydrogen atom or an unsubstituted alkyl group having 1 to 5 carbon atoms, and more preferably a hydrogen atom.

  The monomer (a) represented by the above formula (I) that can form the monomer unit (A) represented by the above formula (I) is not particularly limited. For example, α-chloroacrylate 2,2,2-trifluoroethyl, α-chloroacrylate 2,2,3,3,3-pentafluoropropyl, α-chloroacrylate 2- (perfluorobutyl) ethyl, α-chloroacrylic acid 2- (perfluorohexyl) ethyl, α-chloroacrylic acid 1H, 1H, 3H-tetrafluoropropyl, α-chloroacrylic acid 1H, 1H, 5H-octafluoropentyl, α-chloroacrylic acid 1H , 1H, 7H-dodecafluoroheptyl, α-chloroacrylic acid 1H-1- (trifluoromethyl) trifluoroethyl, α-chloroacrylic acid 1H, 1H, 3H-hexa Α-chloroacrylic acid fluoroalkyl ester such as bromobutyl, α-chloroacrylic acid 1,2,2,2-tetrafluoro-1- (trifluoromethyl) ethyl; methyl α-fluoroacrylate, ethyl α-fluoroacrylate Α-fluoroacrylic acid alkyl ester such as α-trifluoromethyl acrylate methyl, α-trifluoromethyl ethyl acrylate and the like α-fluoroalkyl acrylic acid alkyl ester; α-fluoroacrylic acid 2,2,2-trimethyl Fluoroethyl, α-fluoroacrylic acid 2,2,3,3,3-pentafluoropropyl, α-fluoroacrylic acid 2- (perfluorobutyl) ethyl, α-fluoroacrylic acid 2- (perfluorohexyl) ethyl, α-Fluoroacrylic acid 1H, 1H, 3H-tetrafluoro Propyl, α-fluoroacrylic acid 1H, 1H, 5H-octafluoropentyl, α-fluoroacrylic acid 1H, 1H, 7H-dodecafluoroheptyl, α-fluoroacrylic acid 1H-1- (trifluoromethyl) trifluoroethyl, α-fluoroacrylic acid fluoroalkyl esters such as α-fluoroacrylic acid 1H, 1H, 3H-hexafluorobutyl, α-fluoroacrylic acid 1,2,2,2-tetrafluoro-1- (trifluoromethyl) ethyl; Is mentioned.

The monomer unit (A) is a structural unit derived from α-chloroacrylic acid fluoroalkyl ester from the viewpoint of further improving the cleavability of the main chain of the polymer when irradiated with ionizing radiation or the like. It is preferable. That is, R ^{1 to} R ⁴ in formula (I) and formula (III) are R ¹ is a chlorine atom, R ² is an alkyl group substituted with a fluorine atom, and R ³ and R ⁴ are hydrogen atoms. It is particularly preferred that

（式（ＩＶ）中、Ｒ⁵〜Ｒ⁹、並びに、ｐおよびｑは、式（ＩＩ）と同様である。）で表される単量体（ｂ）に由来する構造単位である。 <Monomer unit (B)>
The monomer unit (B) has the following general formula (IV):

(In formula (IV), R ^{5 to} R ⁹ , and p and q are the same as in formula (II).) Are structural units derived from the monomer (b).

  And the ratio of the monomer unit (B) in all the monomer units which comprise a polymer is not specifically limited, For example, it can be 30 mol% or more and 70 mol% or less.

Here, the alkyl group substituted with a fluorine atom, which can constitute R ^{5 to} R ⁹ in the formulas (II) and (IV), is not particularly limited, and one of hydrogen atoms in the alkyl group is not limited. And groups having a structure in which part or all are substituted with fluorine atoms.
The unsubstituted alkyl group that can constitute R ^{5 to} R ⁹ in formula (II) and formula (IV) is not particularly limited, and an unsubstituted alkyl group having 1 to 5 carbon atoms can be used. Can be mentioned. Especially, as an unsubstituted alkyl group which can comprise R < ⁵ > -R < ⁹ >, a methyl group or an ethyl group is preferable.

From the viewpoint of improving the ease of polymer preparation and the main chain scissibility upon irradiation with ionizing radiation, R ⁵ in formula (II) and formula (IV) is a hydrogen atom or unsubstituted. The alkyl group is preferably an unsubstituted alkyl group having 1 to 5 carbon atoms, and more preferably a methyl group.

Moreover, from the viewpoint of improving the ease of polymer preparation and the main chain scissibility upon irradiation with ionizing radiation or the like, a plurality of R ⁶ and / or R present in formula (II) and formula (IV). All of ⁷ are preferably hydrogen atoms or unsubstituted alkyl groups, more preferably hydrogen atoms or unsubstituted alkyl groups having 1 to 5 carbon atoms, and even more preferably hydrogen atoms.
From the viewpoint of improving the ease of preparation of the polymer and the ability to cut the main chain when irradiated with ionizing radiation or the like, p in formula (II) and formula (IV) is 5, and q is 0. It is preferable that all five R ⁶ are a hydrogen atom or an unsubstituted alkyl group, and all five R ⁶ are a hydrogen atom or an unsubstituted alkyl group having 1 to 5 carbon atoms. More preferably, all of the five R ⁶ are hydrogen atoms.

On the other hand, from the viewpoint of further suppressing the occurrence of the collapse of the resist pattern when the polymer is used for forming the resist pattern, a plurality of R ⁶ and / or R ⁷ present in the formulas (II) and (IV) are: , A fluorine atom or an alkyl group substituted with a fluorine atom is preferable, and a fluorine atom or an alkyl group having 1 to 5 carbon atoms substituted with a fluorine atom is more preferable.

Furthermore, from the viewpoint of improving the ease of preparation of the polymer and the main chain cleavability when irradiated with ionizing radiation and the like, R ⁸ and R ⁹ in formula (II) and formula (IV) are respectively: It 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, and even more preferably a hydrogen atom.

And as a monomer (b) represented by the above-mentioned formula (IV) which can form the monomer unit (B) represented by the above-mentioned formula (II), it is not limited in particular, Examples thereof include α-methylstyrene and derivatives thereof such as the following (b-1) to (b-11).

The monomer unit (B) does not contain a fluorine atom from the viewpoint of improving the ease of preparation of the polymer and the main chain cleavability upon irradiation with ionizing radiation (ie, monomer). Preferably, only the unit (A) contains a fluorine atom), more preferably a structural unit derived from α-methylstyrene. That is, R ^{5 to} R ⁹ in formula (II) and formula (IV), and p and q are p = 5, q = 0, R ⁵ is a methyl group, and five R ⁶ are It is particularly preferred that all are hydrogen atoms and R ⁸ and R ⁹ are hydrogen atoms.

(Properties of polymer)
<Weight average molecular weight>
Here, the weight average molecular weight (Mw) of the polymer of the present invention needs to be 22000 or more, preferably 25000 or more, more preferably 55000 or more, and preferably 110,000 or less, More preferably, it is 100,000 or less, and further preferably 90000 or less. If the polymer has a weight average molecular weight (Mw) of 22,000 or more, the remaining film in a region not irradiated with ionizing radiation or the like used for patterning (hereinafter also referred to as a non-irradiated region) when used as a positive resist. By increasing the rate, the γ value can be increased and the clarity of the resulting resist pattern can be further enhanced. Moreover, if the weight average molecular weight of the polymer is 22000 or more, the elasticity of a positive resist formed using such a polymer can be improved, so that the occurrence of a resist pattern collapse can be further suppressed. is there. Moreover, if the weight average molecular weight (Mw) of a polymer is 110000 or less, the sensitivity at the time of using as a positive resist can be improved moderately, and the ease of manufacture of a polymer can be improved.

[Number average molecular weight]
The number average molecular weight (Mn) of the polymer of the present invention is preferably 15000 or more, more preferably 20000 or more, and further preferably 35000 or more. When the number average molecular weight (Mn) of the polymer is 15000 or more, the γ value when a resist formed using a positive resist composition containing such a polymer is used as a positive resist can be further increased. .

<Molecular weight distribution>
The molecular weight distribution (Mw / Mn) of the polymer of the present invention is preferably less than 1.60, more preferably less than 1.45, more preferably less than 1.40, and 1.20. It is preferably above, more preferably 1.26 or more, and further preferably 1.30 or more. If the molecular weight distribution (Mw / Mn) of the polymer is less than 1.60, the γ value when used as a positive resist can be further increased, and the clarity of the resulting resist pattern can be further enhanced. Moreover, if the molecular weight distribution (Mw / Mn) of the polymer is 1.20 or more, the ease of production of the polymer can be enhanced. Furthermore, when the molecular weight distribution of a polymer having a weight average molecular weight of 22,000 or more (Mw / Mn) is 1.20 or more, the elasticity of a positive resist formed using such a polymer can be further improved. Therefore, it is possible to further suppress the occurrence of the collapse of the resist pattern.

<Ratio of components having a molecular weight of less than 6000>
In the polymer of the present invention, the proportion of components having a molecular weight of less than 6000 is preferably 6% or less, more preferably 2% or less, further preferably 1% or less, and 0.2% or less. Particularly preferred is 0%, and even more preferred is 0%. When the proportion of the component having a molecular weight of less than 6000 is 6% or less, excessive reduction in film thickness is suppressed when the dose of radiation, etc. is small when used as a positive resist, and the γ value is further increased. And the clarity of the resulting resist pattern can be further enhanced.

<Ratio of components having a molecular weight of less than 10,000>
In the polymer of the present invention, the proportion of the component having a molecular weight of less than 10,000 is preferably 15% or less, more preferably 2.7% or less, further preferably 2% or less, and more preferably 1% or less. It is particularly preferred that When the proportion of the component having a molecular weight of less than 10,000 is 15% or less, the γ value when used as a positive resist can be further increased, and the clarity of the resulting resist pattern can be further enhanced.

<Ratio of components having a molecular weight exceeding 20000>
In the polymer of the present invention, the proportion of components having a molecular weight of more than 20000 is preferably 60% or more, and more preferably 90% or more. When the proportion of the component having a molecular weight of more than 20000 is 60% or more, when used as a positive resist, by increasing the residual film ratio in the non-irradiated region, the γ value is increased and the resulting resist pattern is clear. Can be further enhanced.

<Ratio of components having a molecular weight exceeding 100,000>
In the polymer of the present invention, the proportion of components having a molecular weight exceeding 100,000 is preferably 40% or less. If the proportion of the component having a molecular weight of over 100,000 is 40% or less, it is easy to produce a polymer, and a resist formed using a positive resist composition containing such a polymer is used as a positive resist. The sensitivity can be increased moderately.

(Polymer preparation method)
And the polymer which has the monomer unit (A) and monomer unit (B) mentioned above superposes | polymerizes the monomer composition containing a monomer (a) and a monomer (b), for example Then, it can be prepared by purifying the polymer obtained arbitrarily.
The composition, molecular weight distribution, weight average molecular weight and number average molecular weight of the polymer can be adjusted by changing the polymerization conditions and the purification conditions. Specifically, for example, the composition of the polymer can be adjusted by changing the content ratio of each monomer in the monomer composition used for polymerization. Further, the weight average molecular weight and the number average molecular weight can be decreased by increasing the polymerization temperature. Furthermore, the weight average molecular weight and the number average molecular weight can be reduced by shortening the polymerization time.

<Polymerization of monomer composition>
Here, the monomer composition used for the preparation of the polymer of the present invention includes a monomer component including the monomer (a) and the monomer (b), an optionally usable solvent, and polymerization. Mixtures of initiators and optionally added additives can be used. The polymerization of the monomer composition can be performed using a known method. Among these, when a solvent is used, it is preferable to use cyclopentanone or the like as the solvent. Moreover, it is preferable to use radical polymerization initiators, such as azobisisobutyronitrile, as a polymerization initiator. In addition, the weight average molecular weight and number average molecular weight of a polymer can also be adjusted by changing the compounding quantity of a polymerization initiator. Specifically, the weight average molecular weight and the number average molecular weight can be increased by decreasing the blending amount of the polymerization initiator, and conversely, can be decreased by increasing the blending amount of the polymerization initiator. . In addition, when increasing the weight average molecular weight and number average molecular weight of the polymer, the amount of the solvent in the monomer composition may be decreased, or the monomer composition solvent may not be added.

  The polymer obtained by polymerizing the monomer composition may be used as a polymer as it is, but is not particularly limited, and a good solvent such as tetrahydrofuran is added to the solution containing the polymer. Thereafter, the solution to which the good solvent is added is dropped into a poor solvent such as methanol to solidify the polymer, and the solution can be purified as follows.

<Purification of polymer>
The purification method used for purifying the obtained polymer is not particularly limited, and known purification methods such as a reprecipitation method and a column chromatography method can be mentioned. Among them, it is preferable to use a reprecipitation method as a purification method.
The purification of the polymer may be repeated a plurality of times.

  The purification of the polymer by the reprecipitation method is performed, for example, by dissolving the obtained polymer in a good solvent such as tetrahydrofuran, and then mixing the obtained solution with a good solvent such as tetrahydrofuran and a poor solvent such as methanol. It is preferable to carry out by dropping into a solvent and precipitating a part of the polymer. Thus, if the polymer solution is purified by dropping a polymer solution into a mixed solvent of a good solvent and a poor solvent, the weight obtained by changing the type and mixing ratio of the good solvent and the poor solvent can be obtained. The molecular weight distribution, weight average molecular weight and number average molecular weight of the coalesced can be easily adjusted. Specifically, for example, the molecular weight of the polymer precipitated in the mixed solvent can be increased as the proportion of the good solvent in the mixed solvent is increased.

  When the polymer is purified by the reprecipitation method, the polymer of the present invention may be a polymer precipitated in a mixed solvent of a good solvent and a poor solvent, or may not be precipitated in the mixed solvent. Alternatively, a polymer (that is, a polymer dissolved in a mixed solvent) may be used. Here, the polymer which did not precipitate in the mixed solvent can be recovered from the mixed solvent by using a known method such as concentration to dryness.

(Positive resist composition)
The positive resist composition of the present invention contains the above-described polymer and a solvent, and optionally further contains known additives that can be blended into the resist composition. And since the positive resist composition of this invention contains the polymer mentioned above as a positive resist, when it is used for formation of a resist pattern, generation | occurrence | production of the fall of a resist pattern can fully be suppressed. .

<Solvent>
In addition, as a solvent, if it is a solvent which can dissolve the polymer mentioned above, a known solvent can be used. Among these, from the viewpoint of obtaining a positive resist composition having an appropriate viscosity and improving the coating property of the positive resist composition, it is preferable to use anisole as the solvent.

<Formation of resist pattern>
Moreover, the formation of the resist pattern using the positive resist composition of the present invention is not particularly limited, and can be performed using a known resist pattern forming method. Specifically, the resist pattern is formed using the positive resist composition of the present invention by, for example, (1) the above-described positive resist on a workpiece such as a substrate processed using the resist pattern. After applying the composition and drying the applied positive resist composition to form a resist film, (2) drawing a desired pattern by irradiating the resist film with ionizing radiation or light, and (3) Furthermore, the resist film on which the pattern is drawn is brought into contact with a developing solution to develop the resist film, and (4) the last developed resist film is rinsed with a rinsing solution.

In particular, as the developing solution and the rinsing liquid, for example, fluorine such as CF ₃ CFHCFHCF ₂ CF ₃ , CF ₃ CF ₂ CHCl ₂ , CClF ₂ CF ₂ CHClF, CF ₃ CF ₂ CF ₂ CF ₂ OCH ₃ , C ₈ F _18, etc. Solvents: Alcohols such as methanol, ethanol, 1-propanol and 2-propanol (isopropyl alcohol); Acetic acid esters having alkyl groups such as amyl acetate and hexyl acetate; Mixtures of fluorinated solvents and alcohols; Fluorinated solvents and alkyls A mixture of an acetate ester having a group; a mixture of an alcohol ester with an alkyl ester; a mixture of a fluorine-based solvent, an alcohol ester with an alkyl group; and the like can be used. The combination of the developing solution and the rinsing solution can be determined in consideration of, for example, the solubility of the resist containing the polymer of the present invention. Specifically, a solvent having higher resist solubility can be used as a developing solution, and a solvent having lower resist solubility can be used as a rinsing solution. In selecting the developer, it is preferable to select a developer that does not dissolve the resist film before the step (2) is performed. Furthermore, in selecting the rinse solution, it is preferable to select a rinse solution that is easily mixed with the developer so that the replacement with the developer is facilitated.

EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples. In the following description, “%” and “part” representing amounts are based on mass unless otherwise specified.
In Examples and Comparative Examples, the weight average molecular weight, number average molecular weight and molecular weight distribution of the polymer, the proportion of each molecular weight component in the polymer, and the pattern collapse resistance of the positive resist made of the polymer, γ Values and remaining film ratios were measured and evaluated by the following methods.

<Weight average molecular weight, number average molecular weight and molecular weight distribution>
The obtained polymer was measured for weight average molecular weight (Mw) and number average molecular weight (Mn) using gel permeation chromatography, and molecular weight distribution (Mw / Mn) was calculated. Specifically, gel permeation chromatograph (manufactured by Tosoh Corporation, HLC-8220) is used, tetrahydrofuran is used as a developing solvent, and the weight average molecular weight (Mw) and number average molecular weight (Mn) of the polymer are converted into standard polystyrene values. As sought. And molecular weight distribution (Mw / Mn) was computed.

<Ratio of each molecular weight component in the polymer>
A gel permeation chromatograph (manufactured by Tosoh Corporation, HLC-8220) was used, and tetrahydrofuran was used as a developing solvent to obtain a polymer chromatograph. Then, from the obtained chromatogram, the total area (A) of the peaks and the total area (X) of the peak areas of the components having a molecular weight within a predetermined range were obtained. Specifically, the ratio was calculated for a component having a molecular weight within a predetermined range determined by the following plurality of threshold values.
Ratio of component having molecular weight less than 6000 (%) = (X ₆ / A) × 100
Ratio of component having molecular weight less than 10,000 (%) = (X ₁₀ / A) × 100
Ratio of component having molecular weight of more than 20000 (%) = (X ₂₀ / A) × 100
Ratio of component having molecular weight of over 100,000 (%) = (X ₁₀₀ / A) × 100

<Pattern collapse resistance of resist film>
Using a spin coater (manufactured by Mikasa, MS-A150), the positive resist composition was applied onto a silicon wafer having a diameter of 4 inches. Next, the applied positive resist composition was heated on a hot plate at a temperature of 180 ° C. for 3 minutes to form a resist film having a thickness of 40 nm on the silicon wafer. And the resist film was exposed by the optimal exposure amount (Eop) using the electron beam drawing apparatus (The Elionix company make, ELS-S50), and the pattern was drawn. Then, isopropyl alcohol and a fluorine-based solvent (Mitsui DuPont Fluoro Chemical Co., Ltd., Bartrel XF (registered trademark), CF ₃ CFHCCFHCF ₂ CF ₃ ) are mixed as a resist developer so that the volume ratio is 1: 1. After developing for 1 minute at a temperature of 23 ° C. using the developer thus obtained, a fluorine-based solvent (Mitsui / Dupont Fluoro Chemical Co., Ltd., Vertrel XF (registered trademark), CF ₃ CFHCHFCF ₂ as a rinse solution) A resist pattern was formed by rinsing with CF ₃ ) for 10 seconds. And the presence or absence of the pattern collapse of the formed resist pattern was observed. Note that the optimum exposure amount (Eop) was appropriately set with a value approximately twice as large as Eth as a guide. The resist pattern line (unexposed area) and space (exposed area) were each 20 nm.
And the pattern collapse resistance was evaluated according to the following criteria.
A: No pattern collapse B: Pattern collapse

γ値の値が大きいほど、感度曲線の傾きが大きく、明瞭性の高いパターンを良好に形成し得ることを示す。 <Γ value of resist film>
Using a spin coater (manufactured by Mikasa, MS-A150), the positive resist composition was applied on a silicon wafer having a diameter of 4 inches to a thickness of 500 nm. The applied positive resist composition was heated on a hot plate at a temperature of 180 ° C. for 3 minutes to form a resist film on the silicon wafer. Then, using an electron beam drawing apparatus (ELS-S50, manufactured by Elionix Co., Ltd.), a plurality of patterns (dimensions 500 μm × 500 μm) having different electron beam doses are drawn on the resist film, and isopropyl is used as a resist developer. Using a developer obtained by mixing alcohol and a fluorine-based solvent (Mitsui / DuPont Fluoro Chemical Co., Ltd., Bertrell XF (registered trademark), CF ₃ CFHCCFHCF ₂ CF ₃ ) in a volume ratio of 1: 1. Then, after developing for 1 minute at a temperature of 23 ° C., rinsing was performed for 10 seconds with a fluorine-based solvent (Mitsui DuPont Fluoro Chemical Co., Ltd., Bartrel XF (registered trademark), CF ₃ CFHCCFHCF ₂ CF ₃ ). The irradiation amount of the electron beam was varied in the range of 4μC / cm ² of 200μC / cm ² by 4μC / cm ^2. Next, the thickness of the resist film in the drawn portion is measured with an optical film thickness meter (Dainippon Screen, Lambda Ace), the common logarithm of the total irradiation amount of the electron beam, and the remaining film ratio of the resist film after development (= (Film thickness of developed resist film / film thickness of resist film formed on a silicon wafer)) was created, and a sensitivity curve (horizontal axis: total electron beam) was obtained. common logarithm of dose, ordinate:. residual film ratio of the resist film for (0 ≦ residual film ratio ≦ 1.00)), was determined γ values using the following formula in the formulas below, E ₀ Fits the sensitivity curve to a quadratic function in the range of the residual film ratio of 0.20 to 0.80, and the residual function is obtained with respect to the obtained quadratic function (function of the residual film ratio and the common logarithm of the total irradiation amount). a total dose of log obtained when substituting film ratio 0. Moreover, E ₁ is the residual film rate on the resulting quadratic function 0 Create a straight line (approximate line of the slope of the sensitivity curve) connecting the point and the point with the remaining film ratio of 0.50, and the remaining straight line (a function of the remaining film ratio and the common logarithm of the total irradiation amount) This is the logarithm of the total irradiation amount obtained when the film ratio 1.00 is substituted, and the following equation represents the slope of the straight line between the remaining film ratios 0 and 1.00.

The larger the γ value, the larger the slope of the sensitivity curve, indicating that a clear pattern can be formed better.

<Residual film ratio of resist film>
A resist film was formed on a silicon wafer in the same manner as in the evaluation method for “γ value of resist film”. The initial thickness T ₀ of the obtained resist film was measured with an optical film thickness meter (manufactured by Dainippon Screen, Lambda Ace). In addition, the total electron beam dose Eth (μC / cm ² ) when the remaining film ratio of the straight line (approximate line of the sensitivity curve slope) obtained in the calculation of the γ value was 0 was obtained. Then, it was used to create the sensitivity curve, the dose of the electron beam having different portions 4μC / cm ² in a range of 4μC / cm ² of 200μC / cm ² (i.e., 4, 8, 12, 16 ... 196, 200 μC / cm ² ) was divided by the Eth determined as described above. If there is an electron beam irradiation amount at which the obtained value (electron beam irradiation amount / Eth) is 0.85, the remaining film rate at the electron beam irradiation amount is expressed as the remaining film rate (0.85 Eth). did. When there is no electron beam irradiation amount at which the obtained value (electron beam irradiation amount / Eth) is 0.85, among these values, two values closest to 0.85 are specified, and this value The electron beam doses at the two points were P (μC / cm ² ) and P + 4 (μC / cm ² ), respectively. And the remaining film rate (0.85 Eth) was determined by the following formula. The results are shown in Table 1.
Residual film ratio (0.85 Eth) = S − {(ST) / (V−U)} × (0.85−U)
In this formula,
S represents the remaining film rate at the electron beam irradiation dose P;
T represents the remaining film rate at the electron beam irradiation dose P + 4,
U represents P / Eth and
V represents (P + 4) / Eth.
Similarly, the residual film ratio (0.80 Eth) at the electron beam irradiation amount at which the obtained value (electron beam irradiation amount / Eth) was 0.80 was determined.
As the remaining film ratios at 0.85 Eth and 0.80 Eth as calculated here are higher, the total irradiation amount of the electron beam (that is, Eth (μC / cm ² )) that can make the remaining film ratio approximately zero. However, at a low dose, the resist film is difficult to dissolve in the developer. In other words, the resist film has low solubility in the developer in the peripheral area (non-irradiation area) of the pattern formation area on the resist film, which is an area with a relatively small amount of irradiation. Therefore, the fact that the remaining film ratio calculated as described above is high means that the boundary between the area that should be dissolved on the resist film to form the pattern and the area that should remain without being dissolved is clear. Means high clarity.

Example 1
<Preparation of polymer>
Α-chloroacrylic acid 2,2,2-trifluoroethyl 3.0 g as monomer (a), α-methylstyrene 4.40 g as monomer (b), and azobis as a polymerization initiator A monomer composition containing 0.006975 g of isobutyronitrile and 1.85 g of cyclopentanone as a solvent is placed in a glass container, the glass container is sealed and replaced with nitrogen, and a constant temperature bath at 78 ° C. in a nitrogen atmosphere. For 6 hours. Then, after returning to room temperature and releasing the inside of the glass container to the atmosphere, 10 g of tetrahydrofuran (THF) was added to the resulting solution. And the solution which added THF was dripped in 300 g of methanol, and the polymer was deposited. Thereafter, the solution containing the precipitated polymer was filtered through a Kiriyama funnel to obtain a white coagulated product (polymer). The weight average molecular weight (Mw) of the obtained polymer was 50883, the number average molecular weight (Mn) was 31303, and the molecular weight distribution (Mw / Mn) was 1.63. Moreover, the obtained polymer contained 50 mol% of α-chloroacrylic acid 2,2,2-trifluoroethyl units and 50 mol% of α-methylstyrene units.
[Purification of polymer]
Subsequently, the obtained polymer was dissolved in 100 g of THF, and the obtained solution was added dropwise to a mixed solvent of 150 g of THF and 850 g of methanol (MeOH), and a white coagulum (α-methylstyrene unit and α-chloroacrylic acid) was added. A polymer containing acid 2,2,2-trifluoroethyl units). Thereafter, the solution containing the precipitated polymer was filtered through a Kiriyama funnel to obtain a white polymer. And about the obtained polymer, the weight average molecular weight, the number average molecular weight, molecular weight distribution, and the ratio of the component of each molecular weight in a polymer were measured. The results are shown in Table 1.
<Preparation of positive resist composition>
The obtained polymer was dissolved in anisole as a solvent to prepare a resist solution (positive resist composition) having a polymer concentration of 11% by mass. Then, the pattern collapse resistance, γ value, and remaining film rate of the positive resist film made of the polymer were evaluated according to the above. The results are shown in Table 1.

(Example 2)
A polymer was obtained in the same manner as in Example 1 except that the amount of azobisisobutyronitrile as a polymerization initiator was changed to 0.005231 g and no solvent was added. The weight average molecular weight (Mw) of the obtained polymer was 49744, the number average molecular weight (Mn) was 30184, and the molecular weight distribution (Mw / Mn) was 1.65. Moreover, the obtained polymer contained 50 mol% of α-chloroacrylic acid 2,2,2-trifluoroethyl units and 50 mol% of α-methylstyrene units.
In purifying the polymer, a polymer was obtained in the same manner as in Example 1 except that the obtained solution was dropped into a mixed solvent of 200 g of THF and 800 g of methanol (MeOH). And about the obtained polymer, it carried out similarly to Example 1, and measured the ratio of the component of each molecular weight in a weight average molecular weight, a number average molecular weight and molecular weight distribution, and a polymer. The results are shown in Table 1. Further, a positive resist composition was prepared in the same manner as in Example 1, and measurement and evaluation were performed. The results are shown in Table 1.

(Example 3)
A polymer was obtained in the same manner as in Example 1 except that the amount of azobisisobutyronitrile as a polymerization initiator was changed to 0.0699751 g and the amount of cyclopentanone as a solvent was changed to 1.87 g. Got. The weight average molecular weight (Mw) of the obtained polymer was 21807, the number average molecular weight (Mn) was 14715, and the molecular weight distribution (Mw / Mn) was 1.48. Moreover, the obtained polymer contained 50 mol% of α-chloroacrylic acid 2,2,2-trifluoroethyl units and 50 mol% of α-methylstyrene units.
In purifying the polymer, a polymer was obtained in the same manner as in Example 1 except that the obtained solution was dropped into a mixed solvent of 100 g of THF and 900 g of methanol (MeOH). And about the obtained polymer, it carried out similarly to Example 1, and measured the ratio of the component of each molecular weight in a weight average molecular weight, a number average molecular weight and molecular weight distribution, and a polymer. The results are shown in Table 1. Further, a positive resist composition was prepared in the same manner as in Example 1, and measurement and evaluation were performed. The results are shown in Table 1.

Example 4
The positive resist composition was used for preparation as it was without purifying the polymer prepared in Example 1. Table 1 shows the results obtained by measuring and evaluating in the same manner as in Example 1 using the prepared resist composition.

(Example 5)
The positive resist composition was used for preparation as it was without purifying the polymer prepared in Example 2. Table 1 shows the results obtained by measuring and evaluating in the same manner as in Example 1 using the prepared resist composition.

(Comparative Example 1)
The positive resist composition was used for preparation as it was without purifying the polymer prepared in Example 3. Table 1 shows the results obtained by measuring and evaluating in the same manner as in Example 1 using the prepared resist composition.

  From the above Table 1, it can be seen that when a positive resist composition containing a polymer containing a fluorine atom and having a weight average molecular weight of 22000 or more is used, the pattern collapse resistance is excellent. Furthermore, according to the positive resist compositions according to these examples, while maintaining a high γ value, the remaining film rate at an irradiation dose in the vicinity of Eth can be kept relatively high, and a resist pattern with high clarity can be obtained. It turns out that it can form favorable.

According to the polymer of the present invention, a main-chain-breaking positive resist that can sufficiently suppress the occurrence of a resist pattern collapse when used as a resist and can improve the clarity of the resist pattern. Can be provided.
Moreover, according to the positive resist composition of the present invention, a highly clear resist pattern can be formed satisfactorily.

Claims (7)

The following general formula (I):

(In the formula (I), R ¹ is a chlorine atom, a fluorine atom or an alkyl group substituted with a fluorine atom, R ² is an unsubstituted alkyl group or an alkyl group substituted with a fluorine atom, ³ and R ⁴ are 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 the following general formula (II):

(In the formula (II), R ⁵ , R ⁶ , R ⁸ and R ⁹ are 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. R ⁷ is often a hydrogen atom, an unsubstituted alkyl group or an alkyl group substituted with a fluorine atom, and p and q are integers of 0 or more and 5 or less, and p + q = 5. Monomer unit (B), at least one of the monomer unit (A) and the monomer unit (B) has one or more fluorine atoms, and
A polymer having a weight average molecular weight of 22,000 or more.   The polymer according to claim 1, having a weight average molecular weight of 110,000 or less.   The polymer of Claim 1 or 2 whose molecular weight distribution (Mw / Mn) is less than 1.60. The polymer according to any one of claims 1 to 3, wherein R ¹ is a chlorine atom. R ² is an alkyl group substituted with a fluorine atom,
The polymer according to claim 4, wherein R ³ and R ⁴ are a hydrogen atom or an unsubstituted alkyl group. R ^{5 to} R ⁹ are a hydrogen atom or an unsubstituted alkyl group,
The polymer according to any one of claims 1 to 5, wherein the monomer unit (A) has one or more fluorine atoms.   A positive resist composition comprising the polymer according to claim 1 and a solvent.