JP6935669B2 - Resist pattern formation method - Google Patents

Description

The present invention relates to a resist pattern forming method, and more particularly to a resist pattern forming method using a positive resist composition containing a polymer that can be suitably used as a positive resist.

Conventionally, in fields such as semiconductor manufacturing, ionizing radiation such as electron beams and short-wavelength light such as ultraviolet rays (hereinafter, ionizing radiation and short-wavelength light may be collectively referred to as "ionizing radiation and the like"). A polymer in which the main chain is cleaved by irradiation and the solubility in a developing solution is increased is used as a main chain cleaving type positive resist.

For example, Patent Document 1 describes α-methylstyrene / α-chloroacrylic acid containing α-methylstyrene (AMS) units and methyl α-chloroacrylate (ACAM) units as a main chain-cleaving positive resist. A positive resist made of a methyl copolymer is disclosed. According to Patent Document 1, the positive resist has high sensitivity and can form a good resist pattern even when the irradiation amount of ionizing radiation or the like is small.

Special Fair 8-3636 Gazette

Here, in the process of forming a resist pattern using a resist, usually, a developing film obtained through an exposure treatment by irradiation with ionizing radiation or the like and a development treatment with a developing solution is subjected to a rinsing treatment using a rinsing solution. By doing so, the developing solution remaining on the surface of the developing film is removed and the development is stopped. As the rinse liquid, in order to suppress the loss of the pattern top and obtain a resist pattern having a good shape, the polymer constituting the resist is difficult to dissolve, the developer can be easily replaced, and the rinse liquid is highly volatile. A solvent is used.

However, when the developing film made of the polymer described in Patent Document 1 is rinsed, the polymer whose molecular weight is reduced by irradiation with ionizing radiation or the like and dissolved in the developing solution is rinsed as a poor solvent. Depending on the use of the liquid, it may precipitate as a residue. Such a residue may adhere to the surface of the resist pattern and cause defects when manufacturing a circuit or the like using the resist pattern.

Therefore, an object of the present invention is to provide a method for efficiently forming a resist pattern by suppressing the amount of irradiation such as ionizing radiation while suppressing the formation of residues on the surface of the resist pattern.

The present inventor has made diligent studies to achieve the above object. Then, the present inventor uses a predetermined polymer formed by using a predetermined monomer containing three or more fluorine atoms as a main chain cutting type positive resist, and develops the residue remaining on the developer film surface. We have found that by removing the liquid by drying, it is possible to efficiently form a resist pattern by reducing the irradiation amount of ionizing radiation, etc., while suppressing the formation of residues on the surface of the resist pattern, and completed the present invention. ..

（式（Ｉ）中、Ｒ^１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、Ｒ^２は、フッ素原子の数が３以上１１以下の有機基であり、Ｒ^３およびＲ^４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、Ｒ^５、Ｒ^６、Ｒ^８およびＲ^９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、Ｒ^７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）とを有する重合体と、溶剤とを含む、ポジ型レジスト組成物を用いてレジスト膜を形成する工程と、前記レジスト膜を露光する工程と、露光された前記レジスト膜を現像液と接触させて現像し、現像膜を得る工程と、前記現像膜を乾燥させて、前記現像膜表面に残存する前記現像液を除去する工程と、を含むことを特徴とする。上述した単量体単位（Ａ）および単量体単位（Ｂ）を含有する重合体は、十分に高い感度を有する。そして、この重合体を含んでなるポジ型レジスト組成物を用いて現像膜を形成し、当該現像膜を乾燥させれば、リンス液を用いたリンス処理を行わずとも、現像膜表面に残存する現像液を除去することができる。従って、上述したレジストパターン形成方法を用いれば、レジストパターン表面における残渣の生成を抑制しつつ、電離放射線等の照射量を低減して効率よくレジストパターンを形成することができる。
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Ｒ^６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Ｒ^７は互いに同一でも異なっていてもよい。 That is, the present invention aims to advantageously solve the above problems, and the resist pattern forming method of the present invention is described in the following general formula (I):

In formula (I), R ¹ is an alkyl group substituted with a chlorine atom, a fluorine atom or a fluorine atom, R ² is an organic group having 3 or more and 11 or less fluorine atoms, and R ³ and R ⁴ is a monomer unit (A) represented by a hydrogen atom, a fluorine atom, an unsubstituted alkyl group or an alkyl group substituted with a fluorine atom, which may be the same as or different from each other.
The following general formula (II):

In formula (II), R ⁵ , R ⁶ , R ⁸ and R ⁹ are hydrogen atoms, fluorine atoms, unsubstituted alkyl groups or alkyl groups substituted with fluorine atoms, which may be the same or different from each other. Often, R ⁷ is an alkyl group substituted with a hydrogen atom, an unsubstituted alkyl group or a fluorine atom, and p and q are integers of 0 or more and 5 or less, and p + q = 5). A step of forming a resist film using a positive-type resist composition containing a polymer having a monomer unit (B) and a solvent, a step of exposing the resist film, and the exposed resist. It is characterized by including a step of bringing the film into contact with a developing solution to develop it to obtain a developing film, and a step of drying the developing film to remove the developing solution remaining on the surface of the developing film. The polymer containing the above-mentioned monomer unit (A) and monomer unit (B) has sufficiently high sensitivity. Then, if a developing film is formed using a positive resist composition containing this polymer and the developing film is dried, it remains on the surface of the developing film even if it is not rinsed with a rinsing solution. The developer can be removed. Therefore, by using the resist pattern forming method described above, it is possible to efficiently form a resist pattern by reducing the irradiation amount of ionizing radiation or the like while suppressing the formation of residues on the surface of the resist pattern.
In the present invention, when p in the formula (II) is 2 or more, the plurality of R ^6s may be the same or different from each other, and when q in the formula (II) is 2 or more. The plurality of R ^7s may be the same or different from each other.

Here, in the resist pattern forming method of the present invention, it is preferable that the developing film is dried by spraying a gas. If the developing film is dried by spraying a gas, the developing solution remaining on the surface of the developing film can be physically blown off as well as vaporized, and the developing film can be efficiently dried.

Further, in the resist pattern forming method of the present invention, ^{it is preferable that R 1} is a chlorine atom. ^{When R 1} of the monomer unit (A) is a chlorine atom, the breakability of the main chain when irradiated with ionizing radiation or the like can be improved. Therefore, the irradiation amount of ionizing radiation or the like can be further reduced, and the resist pattern can be formed more efficiently. Further, it is easy to prepare a polymer in which ^{R 1 of} the monomer unit (A) is a chlorine atom.

Further, in the resist pattern forming method of the present invention, it is preferable that R ³ and R ⁴ are hydrogen atoms or unsubstituted alkyl groups. ^{If R 3} and R ⁴ of the monomer unit (A) are hydrogen atoms or unsubstituted alkyl groups, the breakability of the main chain when irradiated with ionizing radiation or the like can be improved. Therefore, the irradiation amount of ionizing radiation or the like can be further reduced, and the resist pattern can be formed more efficiently.

Then, in the resist pattern forming method of the present invention, it is preferable that R ^{5 to} R ⁹ are hydrogen atoms or unsubstituted alkyl groups. ^{A polymer in which R 5 to} R ⁹ of the monomer unit (B) is a hydrogen atom or an unsubstituted alkyl group can improve the breakability of the main chain when irradiated with ionizing radiation or the like. Therefore, the irradiation amount of ionizing radiation or the like can be further reduced, and the resist pattern can be formed more efficiently. ^{Further, a polymer in which R 5 to} R ⁹ of the monomer unit (B) is a hydrogen atom or an unsubstituted alkyl group is easy to prepare.

Here, in the resist pattern forming method of the present invention, the surface tension of the developer is preferably 17 mN / m or less. A developer having a surface tension of 17 mN / m or less easily enters fine gaps. Therefore, if development is performed using a developing solution having a surface tension of 17 mN / m or less, the clarity of the obtained resist pattern can be improved.
In the present invention, the surface tension of the developing solution can be measured, for example, at 25 ° C. by using the ring method.

According to the resist pattern forming method of the present invention, it is possible to efficiently form a resist pattern by suppressing the amount of irradiation such as ionizing radiation while suppressing the formation of residues on the surface of the resist pattern.

Hereinafter, embodiments of the present invention will be described in detail.
Here, the resist pattern forming method of the present invention is a step of forming a resist film using a positive resist composition containing a predetermined polymer formed by using a predetermined monomer containing three or more fluorine atoms. (Resist film forming step), exposing the resist film (exposure step), developing the resist film after exposure by contacting it with a developing solution to obtain a developing film (developing step), and drying the developing film. At least a step (drying step) of removing the developing solution remaining on the surface of the developing film is included. Then, the resist pattern forming method of the present invention can be used, for example, when forming a resist pattern in a manufacturing process of a printed circuit board such as a build-up board.

(Resist film forming process)
In the resist film forming step, a positive resist composition is applied onto a work piece such as a substrate to be processed using a resist pattern, and the applied positive resist composition is dried to form a resist film. .. Here, the substrate is not particularly limited, and a substrate having an insulating layer and a copper foil provided on the insulating layer, which is used for manufacturing a printed circuit board or the like, can be used. Further, the method for applying and drying the positive resist composition is not particularly limited, and a method generally used for forming a resist film can be used. Then, in the pattern forming method of the present invention, the following positive resist composition is used.

<Positive resist composition>
The positive resist composition contains a predetermined polymer containing a fluorine atom, which will be described in detail below, and a solvent, and optionally further contains a known additive that can be incorporated into the resist composition.

（式（Ｉ）中、Ｒ^１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、Ｒ^２は、フッ素原子の数が３以上１１以下の有機基であり、Ｒ^３およびＲ^４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、Ｒ^３およびＲ^４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、Ｒ^５、Ｒ^６、Ｒ^８およびＲ^９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、Ｒ^５、Ｒ^６、Ｒ^８およびＲ^９は互いに同一でも異なっていてもよく、Ｒ^７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。 << Polymer >>
The polymer used in the resist pattern forming method of the present invention is a main chain cutting type positive resist in which the main chain is cut by irradiation with ionizing radiation such as an electron beam or short wavelength light such as ultraviolet rays to reduce the molecular weight. It is a polymer that can be used satisfactorily as. Then, the polymer has the following general formula (I):

In formula (I), R ¹ is an alkyl group substituted with a chlorine atom, a fluorine atom or a fluorine atom, R ² is an organic group having 3 or more and 11 or less fluorine atoms, and R ³ and R ⁴ is 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). Unit (A) and
The following general formula (II):

In formula (II), R ⁵ , R ⁶ , R ⁸ and R ⁹ are alkyl groups substituted with a hydrogen atom, a fluorine atom, an unsubstituted alkyl group or a fluorine atom, and are R ⁵ , R ⁶ , R. ⁸ and R ⁹ may be the same or different from each other, R ⁷ is an alkyl group substituted with a hydrogen atom, an unsubstituted alkyl group or a fluorine atom, and p and q are integers of 0 or more and 5 or less. It has a monomer unit (B) represented by p + q = 5).

The above-mentioned polymer may contain any monomer unit other than the monomer unit (A) and the monomer unit (B), but among all the monomer units constituting the polymer. The ratio of the monomer unit (A) and the monomer unit (B) is preferably 90 mol% or more in total, more preferably 100 mol%, and 100 mol% (that is,). , The polymer contains only the monomer unit (A) and the monomer unit (B)).

Further, as long as the above-mentioned polymer has a monomer unit (A) and a monomer unit (B), for example, a random polymer, a block polymer, an alternating polymer (ABAB ...), And the like. Any of these may be used, but a polymer containing 90% by mass or more of the alternating polymer (upper limit is 100% by mass) is preferable. Here, it is preferable that the alternating polymers do not form a crosslinked product. ^{Since the fluorine atom is contained in R 2} of the monomer unit (A), a crosslinked product is not formed.

Here, since the above-mentioned polymer contains a predetermined monomer unit (A) and a monomer unit (B), ionizing radiation or the like (for example, electron beam, KrF laser, ArF laser, EUV laser, etc.) ) Is irradiated, the main chain is cleaved and the molecular weight is reduced.

In addition, since the above-mentioned polymer has at least a fluorine atom in the monomer unit (A), it also has a property of being able to suppress the occurrence of the resist pattern collapse when used as a resist. The reason why the occurrence of the resist pattern collapse can be suppressed by containing the monomer unit having a fluorine atom is not clear, but since the fluorine atom improves the liquid repellency of the polymer, the resist It is presumed that this is because it is possible to suppress the occurrence of tension between the patterns when the developer is removed by drying in the pattern forming process.

（式（ＩＩＩ）中、Ｒ^１〜Ｒ^４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) is represented by the following general formula (III):

(In the formula (III), R ^{1 to} R ⁴ are the same as those in the formula (I)), which is a structural unit derived from the monomer (a) represented by the formula (I).

The ratio of the monomer unit (A) to all the monomer units constituting the polymer is not particularly limited, and can be, for example, 30 mol% or more and 70 mol% or less.

^{Here, the alkyl group substituted with a fluorine atom that can constitute R 1} , R ³ , and R ⁴ in the formula (I) and the formula (III) is not particularly limited, and hydrogen in the alkyl group is not particularly limited. Examples thereof include a group having a structure in which a part or all of an atom is replaced with a fluorine atom.
^{Further, the unsubstituted alkyl group that can form R 3} and R ⁴ in the formulas (I) and (III) is not particularly limited, and an unsubstituted alkyl group having 1 or more and 10 or less carbon atoms is used. Can be mentioned. Of these, ^{as the unsubstituted alkyl group capable of forming R 3} and R ⁴ , a methyl group or an ethyl group is preferable.

Then, from the viewpoint of improving the breakability of the main chain of the polymer when irradiated with ionizing radiation or the like, R ¹ in the formulas (I) and (III) is replaced with a chlorine atom, a fluorine atom or a fluorine atom. It is preferably an alkyl group having 1 or more and 5 or less carbon atoms, more preferably a chlorine atom, a fluorine atom or a perfluoromethyl group, further preferably a chlorine atom or a fluorine atom, and a chlorine atom. Is particularly preferred. ^{The monomer (a) in which R 1} in the formula (III) is a chlorine atom has excellent polymerizable properties, and the monomer unit (A) in which ^{R 1 in the formula (I) is a chlorine atom.} The polymer having the above is also excellent in that it is easy to prepare.

Further, from the viewpoint of improving the cleavage property of the main chain of the polymer when irradiated with ionizing radiation or the like, R ³ and R ⁴ in the formulas (I) and (III) are hydrogen atoms or unsubstituted, respectively. It is preferably an alkyl group of, more preferably a hydrogen atom or an unsubstituted alkyl group having 1 or more and 5 or less carbon atoms, and further preferably a hydrogen atom.

Further, from the viewpoint of improving the breakability 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 organic group having 3 or more fluorine atoms. It is necessary to have an organic group having 5 or more fluorine atoms. On the other hand, from the viewpoint of ensuring the clarity of the resist pattern obtained when used as a positive resist, R ² in the formulas (I) and (III) is an organic group having 11 or less fluorine atoms. It is necessary to have an organic group having 7 or less fluorine atoms, and more preferably an organic group having 6 or less fluorine atoms. ^{It is particularly preferable that R 2} in the formulas (I) and (III) is an organic group having 5 fluorine atoms.
The carbon number of R ² is preferably 2 or more and 10 or less, more preferably 3 or more and 4 or less, and further preferably 3. If the number of carbon atoms is too small, the solubility in a developing solution may not be improved, and if the number of carbon atoms is too large, the glass transition point may be lowered and the clarity of the pattern may not be guaranteed.

^{Specifically, R 2} in the formulas (I) and (III) is preferably a fluoroalkyl group, a fluoroalkoxyalkyl group, or a fluoroalkoxyalkenyl group, and more preferably a fluoroalkyl group.
Here, as the fluoroalkyl group, a 2,2,2-trifluoroethyl group (the number of fluorine atoms is 3, the number of carbon atoms is 2) and a 2,2,3,3,3-pentafluoropropyl group (fluorine). 5 atoms, 3 carbon atoms), 3,3,4,5,4-pentafluorobutyl group (5 fluorine atoms, 4 carbon atoms), 2- (perfluorobutyl) ethyl group ( 9 fluorine atoms, 6 carbon atoms), 1H, 1H, 3H-tetrafluoropropyl group (4 fluorine atoms, 3 carbon atoms), 1H, 1H, 5H-octafluoropentyl group (fluorine atom) 8 and 5 carbon atoms), 1H-1- (trifluoromethyl) trifluoroethyl group (6 fluorine atoms, 3 carbon atoms), 1H, 1H, 3H-hexafluorobutyl group (fluorine) 6 atoms, 4 carbon atoms), 2,2,3,3,4,5,4-heptafluorobutyl group (7 fluorine atoms, 4 carbon atoms), or 1,2,2, 2,2-Tetrafluoro-1- (trifluoromethyl) ethyl group (7 fluorine atoms, 3 carbon atoms) is preferable, and 2,2,3,3,3-pentafluoropropyl group, 1H-1- (trifluoromethyl) trifluoroethyl group, 1H, 1H, 3H-hexafluorobutyl group, 2,2,3,3,4,5,4-heptafluorobutyl group, or 1,2,2, It is more preferably a 2,2-tetrafluoro-1- (trifluoromethyl) ethyl group, and even more preferably a 2,2,3,3,3-pentafluoropropyl group.
The fluoroalkoxyalkyl group may be, for example, a pentafluoroethoxymethyl group (5 fluorine atoms, 3 carbon atoms) or a pentafluoroethoxyethyl group (5 fluorine atoms, 4 carbon atoms). It is preferable to have.
The fluoroalkoxyalkenyl group is preferably, for example, a pentafluoroethoxyvinyl group (having 5 fluorine atoms and 4 carbon atoms).

The monomer (a) represented by the above-mentioned formula (III), which can form the monomer unit (A) represented by the above-mentioned formula (I), is not particularly limited. For example, α-chloroacrylic acid 2,2,2-trifluoroethyl, α-chloroacrylic acid 2,2,3,3,3-pentafluoropropyl, α-chloroacrylic acid 3,3,4,4,4 -Pentafluorobutyl, 2- (perfluorobutyl) ethyl α-chloroacrylic acid, α-chloroacrylic acid 1H, 1H, 3H-tetrafluoropropyl, α-chloroacrylic acid 1H, 1H, 5H-octafluoropentyl, α -Chloroacrylic acid 1H-1- (trifluoromethyl) trifluoroethyl, α-chloroacrylic acid 1H, 1H, 3H-hexafluorobutyl, α-chloroacrylic acid 2,2,3,3,4,4,4 Α-Chloroacrylic acid fluoroalkyl esters such as −heptafluorobutyl, α-chloroacrylic acid 1,2,2,2-tetrafluoro-1- (trifluoromethyl) ethyl; α-fluoroacrylic acid 2,2 2-Trifluoroethyl, α-fluoroacrylic acid 2,2,3,3,3-pentafluoropropyl, α-fluoroacrylic acid 3,3,4,5,4-pentafluorobutyl, α-fluoroacrylic acid 2 -(Perfluorobutyl) ethyl, α-fluoroacrylic acid 1H, 1H, 3H-tetrafluoropropyl, α-fluoroacrylic acid 1H, 1H, 5H-octafluoropentyl, α-fluoroacrylic acid 1H-1- (trifluoro) Methyl) trifluoroethyl, α-fluoroacrylic acid 1H, 1H, 3H-hexafluorobutyl, α-fluoroacrylic acid 2,2,3,3,4,5,4-heptafluorobutyl, α-fluoroacrylic acid Α-fluoroacrylic acid fluoroalkyl ester such as 1,2,2,2-tetrafluoro-1- (trifluoromethyl) ethyl; α-chloroacrylic acid pentafluoroethoxymethyl ester, α-chloroacrylic acid pentafluoroethoxyethyl Α-chloroacrylic acid fluoroalkoxyalkyl ester such as ester; α-fluoroacrylic acid fluoroalkoxyalkyl ester such as α-fluoroacrylic acid pentafluoroethoxymethyl ester, α-fluoroacrylic acid pentafluoroethoxyethyl ester; α-chloroacrylic acid Α-Chloroacrylic acid fluoro such as acid pentafluoroethoxyvinyl ester Alkoxyalkoxyesters; α-fluoroacrylic acid fluoroalkoxyalkenyl esters such as α-fluoroacrylic acid pentafluoroethoxyvinyl ester; and the like.

From the viewpoint of further improving the breakability of the main chain of the polymer when irradiated with ionizing radiation or the like, the monomer unit (A) is a structural unit derived from α-chloroacrylic acid fluoroalkyl ester. Is preferable. ^{That is, in R 1} , R ² , and R ⁴ in the formula (I) and the formula (III), it is preferable that R ¹ is a chlorine atom and R ³ and R ^{4 are hydrogen atoms.}

（式（ＩＶ）中、Ｒ^５〜Ｒ^９、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)]
Further, the monomer unit (B) is represented by the following general formula (IV):

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

The ratio of the monomer unit (B) to all the monomer units constituting the polymer is not particularly limited, and can be, for example, 30 mol% or more and 70 mol% or less.

^{Here, the alkyl group substituted with a fluorine atom that can constitute R 5 to} R ⁹ in the formulas (II) and (IV) is not particularly limited, and is one of the hydrogen atoms in the alkyl group. Examples thereof include groups having a structure in which some or all of them are replaced with hydrogen atoms.
^{Further, the unsubstituted alkyl group which can constitute R 5 to} R ⁹ in the formula (II) and the formula (IV) is not particularly limited, and an unsubstituted alkyl group having 1 or more and 5 or less carbon atoms is used. Can be mentioned. Of these, ^{as the unsubstituted alkyl group that can constitute R 5 to} R ⁹ , a methyl group or an ethyl group is preferable.

The ease of preparation of the polymer and the ionizing radiation or the like from the viewpoint of improving the cutting of the main chain when irradiated is, R ⁵ in formula (II) and formula (IV) is a hydrogen atom or an unsubstituted It is preferably an alkyl group of, more preferably an unsubstituted alkyl group having 1 or more and 5 or less carbon atoms, and further preferably a methyl group.

Further, from the viewpoint of improving the ease of preparation of the polymer, a plurality of R ⁶ and / or R ⁷ present in the formulas (II) and (IV) are all hydrogen atoms or unsubstituted alkyl groups. It is preferably a hydrogen atom or an unsubstituted alkyl group having 1 or more and 5 or less carbon atoms, and further preferably a hydrogen atom.
From the viewpoint of improving the ease of preparation of the polymer, a p in formula (II) and formula (IV) is 5, q is 0, all 5 There R ⁶ is or a hydrogen atom preferably an unsubstituted alkyl group, there are five more preferably all are hydrogen atom or an unsubstituted alkyl group having 1 to 5 carbon atoms of R ^6, there are five all R ⁶ is hydrogen It is more preferably an atom.
Further, from the viewpoint of solubility in a developing solution, it is preferable that one ^{of a plurality of R 6} and R ⁷ existing in the formula (II) and the formula (IV) contains one fluorine atom.

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

Further, from the viewpoint of improving the ease of preparation of the polymer and the breakability of the main chain when irradiated with ionizing radiation or the like, R ⁸ and R ⁹ in the formulas (II) and (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 or more and 5 or less carbon atoms, and further preferably a hydrogen atom.

The monomer (b) represented by the above-mentioned formula (IV), which can form the monomer unit (B) represented by the above-mentioned formula (II), is not particularly limited. For example, α-methylstyrene (AMS) and its derivatives such as the following (b-1) to (b-11) can be mentioned.

From the viewpoint of improving the ease of preparation of the polymer, the monomer unit (B) preferably does not contain a fluorine atom, and more preferably a structural unit derived from α-methylstyrene. That, ^R 5 to R ⁹ in the formula (II) and Formula (IV), and, p and q are p = 5, q = 0, ^{R 5} is a methyl group, There are five ^{R 6} It is particularly preferable that all of them are hydrogen atoms, and R ⁸ and R ^{9 are hydrogen atoms.} Further, from the viewpoint of solubility in a developing solution, the monomer unit (B) preferably contains one fluorine atom. ^{For example, R 5 to} R ⁹ in formulas (II) and (IV), and p and q are p = 5, q = 0, R ⁵ is a methyl group, and there are five R ⁶ 's. It is particularly preferable that any one is a fluorine atom and the other four are hydrogen atoms, and R ⁸ and R ^{9 are hydrogen atoms.}

[Weight average molecular weight]
Here, the weight average molecular weight (Mw) of the polymer is preferably 10,000 or more, and more preferably 20,000 or more. When the weight average molecular weight (Mw) of the polymer is 10,000 or more, it is possible to suppress the excessive increase in the solubility of the resist film in the developing solution at a low irradiation amount, and the clarity is excessively reduced. Can be suppressed.

[Number average molecular weight]
The number average molecular weight (Mn) of the polymer is preferably 5000 or more, and more preferably 10000 or more. When the number average molecular weight (Mn) of the polymer is 5000 or more, it is possible to suppress the excessive increase in solubility of the resist film in the developing solution at a low irradiation amount, and it is possible to suppress the excessive decrease in clarity. can do.

[Molecular weight distribution]
The molecular weight distribution (Mw / Mn) of the polymer is preferably 1.15 or more, more preferably 1.20 or more, preferably 1.70 or less, and 1.65 or less. More preferably. When the molecular weight distribution (Mw / Mn) of the polymer is 1.15 or more, the ease of producing the polymer can be improved. On the other hand, when the molecular weight distribution (Mw / Mn) of the polymer is 1.70 or less, the clarity of the obtained resist pattern can be enhanced when used as a positive resist.

[Surface free energy]
Here, it produced using the polymer film (membrane) is preferably surface free energy is 15 mJ / ^{m 2} or more, more preferably 20 mJ / ^{m 2} or more, at 30 mJ / ^{m 2} or less It is preferably 25 mJ / m ² or less, and more preferably 25 mJ / m 2. When the surface free energy is 15 mJ / m ² or more, a developer with guaranteed wettability can be selected. When the surface free energy is 30 mJ / m ² or less, the irradiation region can be selectively dissolved.
The surface free energy is determined by using a contact angle meter to set the contact angle of two types of solvents (water and diiodomethane) whose surface tension, polarity term (p) and dispersion force term (d) are known as follows. The surface free energy of the polymer can be calculated by evaluating the surface free energy by the method of Owns-Wendt (extended Fowkes formula).

[Method for preparing polymer]
Then, the polymer having the above-mentioned monomer unit (A) and monomer unit (B) polymerizes, for example, a monomer composition containing the monomer (a) and the monomer (b). After that, it can be prepared by purifying the obtained polymer 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 the polymerization. Further, the weight average molecular weight and the number average molecular weight can be reduced by increasing the polymerization temperature. Further, the weight average molecular weight and the number average molecular weight can be reduced by shortening the polymerization time.

-Polymerization of monomeric composition-
Here, the monomer composition used for preparing the polymer includes a monomer component containing the monomer (a) and the monomer (b), an optionally usable solvent, and a polymerization initiator. , A mixture with an optionally added additive can be used. Then, the polymerization of the monomer composition can be carried out by using a known method. Above all, when a solvent is used, it is preferable to use cyclopentanone or the like as the solvent. Further, as the polymerization initiator, it is preferable to use a radical polymerization initiator such as azobisisobutyronitrile. The weight average molecular weight and the number average molecular weight of the polymer can also be adjusted by changing the blending amount of the polymerization initiator. Specifically, the weight average molecular weight and the number average molecular weight can be increased by reducing the blending amount of the polymerization initiator, and conversely, can be reduced by increasing the blending amount of the polymerization initiator. ..

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

-Purification of polymer-
The purification method used when purifying the obtained polymer is not particularly limited, and examples thereof include known purification methods such as a reprecipitation method and a column chromatography method. Above all, it is preferable to use the reprecipitation method as the purification method.
The purification of the polymer may be repeated a plurality of times.

Then, in the purification of the polymer by the reprecipitation method, for example, the obtained polymer is dissolved in a good solvent such as tetrahydrofuran, and then the obtained solution is mixed 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. In this way, if the polymer solution is dropped into the mixed solvent of the good solvent and the poor solvent to purify the polymer, the weight obtained by changing the types and mixing ratios 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 coalescence can be easily adjusted. Specifically, for example, the higher the proportion of the good solvent in the mixed solvent, the larger the molecular weight of the polymer precipitated in the mixed solvent.

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

<< Solvent >>
As the solvent, a known solvent can be used as long as it is a solvent capable of dissolving the above-mentioned polymer. Among them, from the viewpoint of obtaining a positive resist composition having an appropriate viscosity and improving the coatability of the positive resist composition, the solvent used is propylene glycol methyl ether acetate (PGMEA); n-pentyl acetate or the like. Examples include n-pentyl esters of organic acids; n-hexyl esters of organic acids, such as n-hexyl acetate. One of these may be used alone, or a plurality of types may be mixed and used.

(Exposure process)
In the exposure step, the resist film formed in the resist film forming step is irradiated with ionizing radiation or light to draw a desired pattern. A known drawing device such as an electron beam drawing device or a laser drawing device can be used for ionizing radiation or light irradiation.

(Development process)
In the developing step, the resist film exposed in the exposure step and the developing solution are brought into contact with each other to develop the resist film, and a developing film is formed on the workpiece.
Here, the method of bringing the resist film into contact with the developing solution is not particularly limited, and known methods such as immersing the resist film in the developing solution and applying the developing solution to the resist film can be used. ..

<Developer>
The surface tension of the developing solution is preferably 17 mN / m or less, more preferably 16.5 mN / m or less, and even more preferably 15 mN / m or less. The resist film formed by using the positive resist composition containing the above-mentioned predetermined polymer has a low surface energy, but if the surface tension of the developer is 17 mN / m or less, the resist pattern to be developed is fine. Even in such a case, the developing solution easily enters the fine gaps. Therefore, if development is performed using a developing solution having a surface tension of 17 mN / m or less, the clarity of the obtained resist pattern can be improved. Further, as the developing solution, it is preferable to use a solvent having a boiling point of 63 ° C. or lower, more preferably a solvent having a boiling point of 60 ° C. or lower, and further preferably using a solvent having a boiling point of 58 ° C. or lower. If a solvent having a boiling point of 63 ° C. or lower is used as the developing solution, the developing film can be easily dried in the subsequent drying step.
A fluorine-based solvent can be used as the developing solution having a surface tension of 17 mN / m or less. Examples of the fluorocarbon solvent include CF ₃ CFHCHFCF ₂ CF ₃ (surface tension: 14.1 mN / m), CF ₃ CF ₂ CHCl ₂ (surface tension 16.2 mN / m), and CClF ₂ CF ₂ CHClF (surface tension). 16.2 mN / m), CF ₃ CF ₂ CF ₂ CF ₂ OCH ₃ (surface tension 13.6 mN / m), C ₈ F ₁₈ (surface tension 13.6 mN / m), C ₄ F ₉ OC ₂ H ₅ (surface tension 13.6 mN / m) Fluorocarbons such as surface tension 13.6 mN / m), C ₂ F ₅ CF (OCH ₃ ) C ₃ F ₇ (surface tension 15.1 mN / m), and mixtures thereof can be used, among which CF ₃ CFHCHFCF. ₂ It is preferable to use CF _3. In selecting a fluorinated solvent that can be used as a developing solution, it is preferable to select a fluorinated solvent that does not dissolve the resist film before the exposure step is performed. Further, as long as the surface tension of the developing solution is 17 mN / m or less, a solvent having a surface tension of 17 or more may be mixed with a solvent of 17 or less. Examples of the solvent that can be mixed include methanol, ethanol, 1-propanol; alcohols such as 2-propanol (isopropyl alcohol); acetic acid esters having an alkyl group such as amyl acetate and hexyl acetate; and the like. As long as the surface tension of the developer as a whole is 17 mN / m or less, by mixing these solvents having different solubilitys in the resist film formed by using the above-mentioned polymer, fine gaps in the resist pattern are mixed. It is possible to achieve both the ease of penetration into the resist film and the solubility of the resist film. On the other hand, the use of a single type of solvent is advantageous in that it can be easily recovered or reused. The SP value of the developing solution is preferably 6.2 to 7.3. When the SP value of the developer is 6.2 to 7.3, the polymer can be rapidly dissolved and a clear pattern can be formed. When a mixture of a plurality of solvents containing a fluorine-based solvent is used as a developer, the ratio of the fluorine-based solvent to the entire developer is preferably more than 50% by volume, and more than 75% by volume. It is more preferably 90% by volume or more, and particularly preferably 95% by volume or more.

<Development conditions>
The development conditions can be appropriately set so as to obtain a resist pattern of desired quality. The temperature of the developer described above can be, for example, 21 ° C. or higher and 25 ° C. or lower. Further, the developing time is preferably 10 seconds or more, more preferably 30 seconds or more, and preferably 30 minutes or less when a developing solution having a surface tension of 17 mN / m or less, such _{as CF 3} CFHCHFCF ₂ CF _{3, is used as the developing solution.} , 20 minutes or less is more preferable, 10 minutes or less is further preferable, and 5 minutes or less is particularly preferable.

(Drying process)
In the drying step, the developing film obtained in the above-mentioned developing step is dried to remove the developing solution remaining on the surface of the developing film. By performing such a drying step, the developing solution can be removed without performing the rinsing treatment, and as a result, the adhesion of the residue to the surface of the resist pattern due to the rinsing treatment can be suppressed.

Here, the drying method is not particularly limited as long as the developing solution can be removed and the developing film can be dried, but it is preferable to blow the developing film with a gas such as air or nitrogen to dry it. If the developing film is dried by spraying a gas, the developing solution remaining on the surface of the developing film can be physically blown off as well as vaporized, and the developing film can be efficiently dried.
The temperature of the gas to be blown is not particularly limited, but can be 5 ° C. or higher and 50 ° C. or lower. The time for blowing the gas is not particularly limited, but can be 0.1 seconds or more and 10 minutes or less.

As described above, in the resist pattern forming method of the present invention, the development can be stopped without performing the rinsing treatment using the rinsing liquid. On the other hand, in order to physically wash away dust and the like existing on the surface of the developing film after drying while removing a small amount of developing solution that may remain after the drying step, the resist pattern forming method of the present invention is used after the drying step. The developing film of No. 1 may include a step of performing a rinsing treatment using a rinsing solution (rinsing step). However, from the viewpoint of reducing the number of steps, it is preferable that the resist pattern forming method of the present invention does not include a rinsing step.
Here, as the rinsing solution, it is preferable to select a rinsing solution that is more difficult to dissolve the resist in the unexposed portion than the developing solution used and is easily mixed with the developing solution. For example, when the rinsing step is carried out when _{CF 3} CFHC HFCF ₂ CF ₃ is used as the developing solution _{, fluorocarbon (for example, CF 2} CF ₂ CF ₂ CF ₂ OCH ₃ , C ₄ F ₉ OC ₂ H) is used as the rinsing solution. _5. Hydrofluoroethers such as C ₂ F ₅ CF (OCH ₃ ) C ₃ F ₇ and perfluorocarbons such as C ₈ F ₁₈ ) can be used.

Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. In the following description, "%" and "part" representing quantities are based on mass unless otherwise specified.
Here, in Examples and Comparative Examples, the weight average molecular weight, the number average molecular weight and the molecular weight distribution of the polymer, and the surface free energy of the film produced by using the polymer were measured by the following methods.
<Weight average molecular weight, number average molecular weight and molecular weight distribution>
The weight average molecular weight (Mw) and the number average molecular weight (Mn) of the obtained polymer were measured by gel permeation chromatography, and the molecular weight distribution (Mw / Mn) was calculated. Specifically, a gel permeation chromatograph (manufactured by Tosoh Corporation, HLC-8220) is used, and tetrahydrofuran is used as a developing solvent, and the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the polymer are converted into standard polystyrene equivalent values. Asked as. Then, the molecular weight distribution (Mw / Mn) was calculated.
<Surface free energy>
For a film (membrane) prepared by the following method using the obtained polymer, a contact angle meter (Drop Master700 manufactured by Kyowa Interface Science Co., Ltd.) was used to obtain a surface tension, a polar term (p) and a dispersive force term (p). The contact angles of two kinds of solvents (water and diiodomethane) whose d) are known are measured under the following conditions, the surface free energy is evaluated by the Owns-Wendt (extended Fowkes formula) method, and the surface free energy of the polymer is evaluated. Was calculated.
<< How to make a film >>
Using a spin coater (MS-A150 manufactured by Mikasa), the positive resist composition was applied onto a silicon wafer having a diameter of 4 inches to a thickness of 500 nm. Then, the applied positive resist composition was heated on a hot plate at a temperature of 180 ° C. for 3 minutes to form a film on a silicon wafer.
<< Measurement conditions for contact angle measurement >>
Needle: Metal needle 22G (water), Teflon (registered trademark) coating 22G (diiodomethane)
Wait time: 1000ms
Liquid volume: 1.8 μL
Liquid landing recognition: 50 dat of water, 100 dat of diiodomethane
Temperature: 23 ° C

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。
＜Ｅｔｈ（感度）＞
「γ値（明瞭性）」の評価方法と同様にしてシリコンウェハ上にレジスト膜を形成した。得られたレジスト膜の初期厚みＴ_０を光学式膜厚計（大日本スクリーン製、ラムダエース）で測定した。また、γ値の算出の際に得られた直線（感度曲線の傾きの近似線）の残膜率が０となる際の、電子線の総照射量Ｅｔｈ（μＣ／ｃｍ^２）を求めた。なお、Ｅｔｈの値が小さいほど、レジスト膜の感度が高く、レジストパターンの形成効率が高いことを意味する。 (Example 1)
<Preparation of polymer>
3.0 g of α-chloroacrylic acid 2,2,2-trifluoroethyl (ACATFE) as the monomer (a) and 4.40 g of α-methylstyrene as the monomer (b) as a polymerization initiator. A monomer composition containing 0.006975 g of azobisisobutyronitrile and 1.85 g of cyclopentanone as a solvent was placed in a glass container, and the glass container was sealed and replaced with nitrogen at 78 ° C. under a nitrogen atmosphere. The mixture was stirred in a constant temperature bath for 6 hours. Then, the temperature was returned to room temperature, the inside of the glass container was released to the atmosphere, and then 10 g of tetrahydrofuran (THF) was added to the obtained solution. Then, the solution to which THF was added was added dropwise to 300 g of methanol to precipitate a polymer. Then, the solution containing the precipitated polymer was filtered through a Kiriyama funnel to obtain a white coagulated product (polymer). This polymer was used as it was as a polymer. The weight average molecular weight (Mw), number average molecular weight (Mn), and molecular weight distribution (Mw / Mn) of the obtained polymer were measured. In addition, the surface free energy of a film produced using the obtained polymer was measured. The results are shown in Table 1. The obtained polymer contained 50 mol% of α-chloroacrylic acid 2,2,2-trifluoroethyl unit and 50 mol% of α-methylstyrene unit.
<Preparation of positive resist composition>
The obtained polymer was dissolved in PGMEA (manufactured by Tokyo Chemical Industry Co., Ltd.) as a solvent to prepare a resist solution (positive resist composition) having a polymer concentration of 11% by mass. Then, the presence or absence of residue on the surface of the resist pattern, the γ value (clarity), and Eth (sensitivity) were evaluated according to the following. The results are shown in Table 1.
<Presence or absence of residue on the surface of the resist pattern>
A positive resist composition was applied onto a silicon wafer having a diameter of 4 inches using a spin coater (MS-A150 manufactured by Mikasa). 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 50 nm on a silicon wafer (resist film forming step). Then, the resist film was exposed to the optimum exposure amount (Eop) using an electron beam drawing apparatus (ELS-S50 manufactured by Elionix Inc.), and a pattern was drawn (exposure step). Then, a fluorosolve having a surface tension of 14.1 mN / m (Bertrel XF (registered trademark) manufactured by Mitsui-Dupont Fluorochemical Co., Ltd., CF _{3 CFHCHFCF 2} CF ₃ ) was used as a developing solution for resist at a temperature of 23 ° C. The development process was carried out for 1 minute (development step). Then, the developed film was dried by blowing air at a temperature of 23 ° C. on the developed film after the developing process for 5 seconds to form a resist pattern (drying step). The formed resist pattern was cross-sectioned and photographed from diagonally above using a scanning electron microscope (SEM) to confirm the presence or absence of resist residue on the bottom surface between the patterns. The optimum exposure amount (Eop) was appropriately set with a value of about twice that of Eth as a guide. The resist pattern line (unexposed area) and space (exposed area) were set to 25 nm, respectively.
<Γ value (clarity)>
Using a spin coater (MS-A150 manufactured by Mikasa), the positive resist composition was applied onto a silicon wafer having a diameter of 4 inches to a thickness of 500 nm. Then, 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 a silicon wafer (resist film forming step). Then, using an electron beam drawing apparatus (ELS-S50 manufactured by Elionix Inc.), a plurality of patterns (dimensions 500 μm × 500 μm) having different electron beam irradiation amounts are drawn on the resist film (exposure step), and development for resist is performed. As a liquid, a fluorinated solvent having a surface tension of 14.1 mN / m (Mitsui-Dupont Fluorochemical Co., Ltd., Bartlel _{XF (registered trademark), CF 3 CFHCHFCF 2} CF ₃ ) was used at a temperature of 23 ° C. for 1 minute. (Development process). Then, the developed film was dried by blowing air at a temperature of 23 ° C. for 5 seconds on the developed film after the developing process (drying step). 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 part was measured with an optical film thickness meter (Lambda Ace, manufactured by Dainippon Screen), and the common logarithm of the total irradiation amount of the electron beam and the residual film ratio of the resist film after development were measured. A sensitivity curve showing the relationship with (= (thickness of the resist film after development / thickness of the resist film formed on the silicon wafer) was created. Then, the obtained sensitivity curve (horizontal axis: total of electron beams) was created. For the common logarithm of the irradiation amount, vertical axis: residual film ratio of the resist film (0 ≤ residual film ratio ≤ 1.00)), the γ value was calculated using the following formula. In the following formula, E _0. Fits the sensitivity curve to a quadratic function in the range of 0.20 to 0.80 residual film ratio, and remains for the obtained quadratic function (function of residual film ratio and common logarithm of total irradiation dose). It is the logarithmic equation of the total irradiation amount obtained when the film ratio 0 is substituted. Further, E ₁ connects the point of the residual film ratio 0 and the point of the residual film ratio 0.50 on the obtained quadratic function. The total obtained when a straight line (approximate line of the slope of the sensitivity curve) is created and the residual film ratio 1.00 is substituted for the obtained straight line (function of the residual film ratio and the common logarithm of the total irradiation dose). It is a logarithmic equation of the irradiation amount, and the following formula represents the inclination of the above straight line between the residual film ratio of 0 and 1.00.

The larger the γ value, the larger the slope of the sensitivity curve, indicating that a pattern with high clarity can be formed satisfactorily.
<Eth (sensitivity)>
A resist film was formed on the silicon wafer in the same manner as in the evaluation method of "γ value (clarity)". The resulting resist initial thickness T ₀ of the optical film thickness meter of film (Dainippon Screen Co., Ltd., Lambda Ace) were determined by. ^{In addition, the total irradiation amount Eth (μC / cm 2} ) of the electron beam when the residual film ratio of the straight line (approximate line of the slope of the sensitivity curve) obtained in the calculation of the γ value becomes 0 was obtained. The smaller the Eth value, the higher the sensitivity of the resist film and the higher the efficiency of forming the resist pattern.

(Example 2)
The polymer obtained in the same manner as in Example 1 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 to precipitate a white coagulated product (polymer). .. Then, the solution containing the precipitated polymer was filtered through a Kiriyama funnel to obtain a white polymer. Various measurements were carried out on the obtained polymer. Further, a positive resist composition was prepared in the same manner as in Example 1 except that the obtained polymer was used, and a resist pattern was formed to perform various evaluations. The results are shown in Table 1.

(Example 3)
The amount of azobisisobutyronitrile as the polymerization initiator was changed to 0.005231 g, and a polymer was obtained in the same manner as in Example 1 except that 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. The obtained polymer contained 50 mol% of α-chloroacrylic acid 2,2,2-trifluoroethyl unit and 50 mol% of α-methylstyrene unit.
The obtained polymer was dissolved in 100 g of THF, and the obtained solution was added dropwise to a mixed solvent of 200 g of THF and 800 g of methanol to precipitate a white coagulated product (polymer). Then, the solution containing the precipitated polymer was filtered through a Kiriyama funnel to obtain a white polymer. Various measurements were carried out on the obtained polymer. Further, a positive resist composition was prepared in the same manner as in Example 1 except that the obtained polymer was used, and a resist pattern was formed to perform various evaluations. The results are shown in Table 1.

(Example 4)
The polymer was produced in the same manner as in Example 1 except that the amount of the polymerization initiator azobisisobutyronitrile was changed to 0.069751 g and the amount of the solvent cyclopentanone was changed to 1.87 g. Got The obtained polymer contained 50 mol% of α-chloroacrylic acid 2,2,2-trifluoroethyl unit and 50 mol% of α-methylstyrene unit. This polymer was used as it was as a polymer. Various measurements were carried out on the obtained polymer. Further, a positive resist composition was prepared in the same manner as in Example 1 except that the obtained polymer was used, and a resist pattern was formed to perform various evaluations. The results are shown in Table 1.

(Example 5)
The polymer obtained in the same manner as in Example 4 was dissolved in 100 g of THF, and the obtained solution was added dropwise to a mixed solvent of 100 g of THF and 900 g of methanol to precipitate a white coagulated product (polymer). .. Then, the solution containing the precipitated polymer was filtered through a Kiriyama funnel to obtain a white polymer. Then, various measurements were carried out on the obtained polymer. Further, a positive resist composition was prepared in the same manner as in Example 1 except that the obtained polymer was used, and a resist pattern was formed to perform various evaluations. The results are shown in Table 1.

(Example 6)
<Preparation of polymer>
3. 3.0 g of α-chloroacrylic acid 2,2,3,3,3-pentafluoropropyl (ACAPFP) as the monomer (a) and α-methylstyrene (AMS) as the monomer (b). A monomer composition containing 4764 g, 0.0055 g of azobisisobutyronitrile as a polymerization initiator, and 1.6205 g of cyclopentanone as a solvent was placed in a glass container, and the glass container was sealed and replaced with nitrogen. In a nitrogen atmosphere, the mixture was stirred in a constant temperature bath at 78 ° C. for 6 hours. Then, the temperature was returned to room temperature, the inside of the glass container was released to the atmosphere, and then 10 g of tetrahydrofuran (THF) was added to the obtained solution. Then, the solution to which THF was added was added dropwise to 300 g of methanol to precipitate a polymer. Then, the solution containing the precipitated polymer was filtered through a Kiriyama funnel to obtain a white coagulated product (polymer). This polymer was used as it was as a polymer. Various measurements were carried out on the obtained polymer. The obtained polymer contained 50 mol% of α-chloroacrylic acid 2,2,3,3,3-pentafluoropropyl unit and 50 mol% of α-methylstyrene unit.
<Preparation of positive resist composition>
A resist solution in which the obtained polymer is dissolved in n-hexyl acetate as a solvent (ZED-N60 manufactured by Nippon Zeon Corporation, including impurities inevitably mixed in the production), and the concentration of the polymer is 4% by mass. (Positive resist composition) was prepared. Then, a resist pattern was formed in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 1.

(Example 7)
The polymer obtained in the same manner as in Example 6 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 to precipitate a white coagulated product (polymer). Then, the solution containing the precipitated polymer was filtered through a Kiriyama funnel to obtain a white polymer. Then, various measurements were carried out on the obtained polymer. Further, a positive resist composition was prepared in the same manner as in Example 6 except that the obtained polymer was used, and a resist pattern was formed to perform various evaluations. The results are shown in Table 1.

(Comparative Example 1)
<Preparation of polymer>
3.0 g of methyl α-chloroacrylate (ACAM) and 6.88 g of α-methylstyrene (AMS) as monomers, 2.47 g of cyclopentanone as a solvent, and azobisisobuty as a polymerization initiator. A monomer composition containing 0.01091 g of bnitrile was placed in a glass container, the glass container was sealed and replaced with nitrogen, and the mixture was stirred in a constant temperature bath at 78 ° C. for 6.5 hours under a nitrogen atmosphere. Then, the temperature was returned to room temperature, the inside of the glass container was released to the atmosphere, and then 30 g of tetrahydrofuran (THF) was added to the obtained solution. Then, a solution to which THF was added was added dropwise to 300 g of methanol to precipitate a polymer. Then, the solution containing the precipitated polymer was filtered through a Kiriyama funnel to obtain a white coagulated product (polymer). This polymer was used as it was as a polymer. Various measurements were carried out on the obtained polymer. The obtained polymer contained 50 mol% each of α-methylstyrene unit and α-methylchloroacrylate unit.
<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, a resist pattern was formed in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 1.

(Comparative Example 2)
A positive resist composition was prepared in the same manner as in Comparative Example 1. Then, after using amyl acetate as the developing solution for resist and rinsing the developing film obtained after the developing step with isopropyl alcohol (IPA) as the rinsing solution for 10 seconds, the rinsing solution remaining on the surface of the developing film is used. A resist pattern was formed in the same manner as in Example 1 except that it was removed by blowing air, and various evaluations were performed. The results are shown in Table 1.

From Table 1, in Examples 1 to 7 in which a predetermined polymer containing a fluorine atom was used as the positive resist and a drying step was carried out after the developing step to form a resist pattern, the clarity was excellent at a low irradiation amount. It can be seen that the resist pattern can be formed well and the formation of residues on the surface of the resist pattern can be suppressed.
On the other hand, in Comparative Example 1 in which the α-methylstyrene / α-methylchloroacrylate copolymer was used as the positive resist, it was found that Eth was high and a good resist pattern could not be formed with a low irradiation amount.
Further, in Comparative Example 2 in which an α-methylstyrene / α-methylchloroacrylate copolymer was used as the positive resist and the developer was removed in the rinsing step instead of the drying step, the residue on the surface of the resist pattern was used. It can be seen that the generation cannot be suppressed.

According to the resist pattern forming method of the present invention, it is possible to efficiently form a resist pattern by suppressing the amount of irradiation such as ionizing radiation while suppressing the formation of residues on the surface of the resist pattern.

Claims (5)

The following general formula (I):

(In the formula (I), R ¹ is an alkyl group substituted with a chlorine atom, a fluorine atom or a fluorine atom, R ² is a fluoroalkyl group having 3 or more and 6 or less fluorine atoms, and R 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 as or different from each other) with the monomer unit (A). ,
The following general formula (II):

In formula (II), R ⁵ , R ⁶ , R ⁸ and R ⁹ are hydrogen atoms, fluorine atoms, unsubstituted alkyl groups or alkyl groups substituted with fluorine atoms, which may be the same or different from each other. Often, R ⁷ is an alkyl group substituted with a hydrogen atom, an unsubstituted alkyl group or a fluorine atom, and p and q are integers of 0 or more and 5 or less, and p + q = 5). A step of forming a resist film using a positive-type resist composition containing a polymer having a monomer unit (B) and a solvent.
The step of exposing the resist film and
A step of developing the exposed resist film by contacting it with a developing solution having a surface tension of 17 mN / m or less and a fluorosolve to obtain a developing film.
A step of removing the developer remaining on the surface of the developing film by drying, and
A method for forming a resist pattern, including. The resist pattern forming method according to claim 1, wherein the drying is performed by spraying a gas. The resist pattern forming method according to claim 1 or 2, wherein R ^{1 is a chlorine atom.} The resist pattern forming method according to any one of claims 1 to 3, wherein R ³ and R ^{4 are hydrogen atoms or unsubstituted alkyl groups.} The resist pattern forming method according to any one of claims 1 to 4, wherein R ^{5 to} R ^{9 are hydrogen atoms or unsubstituted alkyl groups.}