JP5075516B2 - Method for producing polymer solution for resist protective film - Google Patents

Description

The present invention relates to a method for producing a polymer used in a resin composition used as a protective film on an upper layer of a resist during semiconductor processing. More specifically, the present invention relates to a method for producing a polymer used for an immersion protective film when exposure is performed using an immersion exposure system.

  In recent years, along with the high integration of LSI, semiconductor patterns have been miniaturized rapidly. Until now, light source light using g-line (436 nm) or i-line (365 nm) as a light source has been widely used as exposure light used in forming a resist pattern, and KrF excimer laser (248 nm) is now mainstream, Photolithography using an ArF excimer laser (193 nm) is starting up. However, even an ArF excimer laser can be used up to the 65 nm node, but since a sufficient resolution cannot be obtained at the 45 nm node, further technological development is underway.

  One of the candidates for the new technology is to shorten the wavelength of the exposure light, and F2 (157 nm) lithography has been studied. However, many problems have been raised in terms of both equipment and materials. Excimer lasers are expected to become the mainstay at the 45 nm node and are being actively studied.

  Various compounds having a refractive index smaller than that of air have been studied as a liquid to be immersed in the immersion exposure system, but water has been studied from the viewpoints of price, ease of handling, and the like. Here, various problems due to the presence of water on the resist were pointed out. This includes shape change caused by dissolution of the generated acid and an amine compound added to the resist as a quencher in water, and pattern collapse due to swelling. Therefore, it has been proposed that it is effective to provide a protective film between the resist and water.

  For this purpose, Patent Document 1 proposes a method of using a water-insoluble and alkali-soluble material as a resist protective film. In this patent, a polymer obtained by copolymerizing a repeating unit having fluorine and a repeating unit having a sulfo group or a carboxyl group as a hydrophilic group dissolved in an alkali is used.

  When a protective film made of such a polymer is formed on a resist, a spin coating method is generally used from the viewpoints of cost and process ease. However, if the solution to be spin-coated has affinity with the resist, the solvent dissolves the resist that has been formed first, so the smoothness of the resist film is lost, or the low molecular components in the resist film are protected by the protective film. It will be difficult to obtain a fine shape. For this reason, alcohol-based or fluorine-based solvents are generally used for the protective film composition.

  On the other hand, when synthesizing a polymer for a protective film, generally, a ketone-based, ester-based, or ether-based solvent having high affinity with a resist is used. In addition, when a polymer is synthesized, a reaction at a high temperature is often performed. Therefore, a solvent having a high boiling point is often selected from the viewpoint of safety.

  Polymerization is performed using a solvent having a high boiling point as described above, and after purification, the product solvent is replaced with an alcohol solvent or a fluorine solvent. If the boiling point of the protective film forming solvent is lower than that of the polymerization solvent, heating is performed. Alternatively, since the solvent cannot be replaced efficiently under reduced pressure, a polymerization solvent having a high affinity with the resist remains in the final product. The polymerization solvent, which is an impurity remaining in the product, dissolves the resist film during spin coating, making it difficult to form a fine profile.

  In the case of resist polymers, many methods have been proposed so far to remove residual monomers, initiators, chain transfer agents, and impurities generated during polymerization by purification. A method of reprecipitation of solid content by mixing a polymerization solution with a poor solvent is known. However, impurities such as unreacted monomers cannot be sufficiently removed by performing reprecipitation only once. In addition, it is possible to perform reprecipitation twice or more. In this case, it is necessary to repeat the operations of precipitation, filtration, and re-dissolution.

  In order to solve such a problem, Patent Document 2 discloses a method of performing reprecipitation, filtration, and repulping using a special device. However, this method has not only a special device but also a repulping method. Therefore, since a large amount of solvent is required, productivity is lowered, which is not preferable.

Patent Document 3 discloses a method of performing repulping or rinsing using a poor solvent after precipitation and purification of a copolymer using a monomer having a specific structure. There is no mention of the relationship between the boiling point, the relationship between the boiling point of the rinsing solvent and the protective film forming solvent, and the influence of the number of rinsings on the removal of the polymerization solvent.
JP 2006-91798 A JP 2005-132974 A JP 2003-231721 A

  Therefore, an object of the present invention is to provide a protective film that has a low content of a solvent having an affinity for a resist, does not cause an interaction with the resist at the time of coating, and can obtain a good pattern profile of the resist. It is providing the manufacturing method of the polymer for protective film formation which can be formed.

The present invention
(1) A step in which a monomer and an initiator dissolved in a polymerization solvent are dropped into a preheated polymerization solvent, and after completion of the dropwise addition, the mixture is aged under heating to polymerize,
(2) contacting the polymerization solution with a poor solvent for the polymer to precipitate the polymer;
(3) the precipitated polymer, centrifugal filtration step of solid-liquid separation at least one method selected from the group consisting of vacuum filtration and pressure filtration,
(4) a step of rinsing the obtained solid polymer,
(5) A step of concentrating the obtained solid polymer after dissolving it in a film-forming solvent,
In the method for producing a polymer solution for a resist protective film including the above steps, the solvent for rinsing the solid polymer is a poor solvent for the polymer, and has a boiling point lower than that of the coating film forming solvent. A method for producing a polymer solution for a resist protective film is provided.

  The present invention also provides the method for producing a polymer solution for a resist protective film as described above, wherein the rinsing is performed twice or more in the method for producing a polymer solution for a resist protective film.

  The present invention further provides the method for producing a polymer solution for a resist protective film as described above, wherein the coating film forming solvent is a fluorine-based solvent, an alcohol-based solvent, or a mixed solvent containing them.

In the obtained resist protective film polymer solution, the content of the polymerization solvent used in the polymerization step is 1% by weight or less based on the solid content contained in the resist protective film polymer solution. A method for producing a polymer solution for a resist protective film as described above is provided.

The present invention further provides a repeating unit in which the polymer has either a repeating unit having fluorine, a sulfo group as a hydrophilic group that dissolves in an alkali, a carboxyl group, or an alcoholic hydroxyl group having a fluoroalkyl group at least at the α-position carbon atom. The method for producing a polymer solution for a resist protective film as described above, wherein the polymer solution is obtained by copolymerizing a unit.
In this specification, in addition to the above invention,
(1) A step of superposing and polymerizing a solution in which a monomer, an initiator and a polymerization solvent are mixed,
(2) contacting the polymerization solution with a poor solvent for the polymer to precipitate the polymer;
(3) a step of solid-liquid separation of the precipitated polymer by a method such as centrifugal filtration, reduced pressure filtration, or pressure filtration;
(4) a step of rinsing the obtained solid polymer,
(5) A step of concentrating the obtained solid polymer after dissolving it in a film-forming solvent,
In the method for producing a polymer solution for a resist protective film including the above steps, the solvent for rinsing the solid polymer is a poor solvent for the polymer, and has a boiling point lower than that of the coating film forming solvent. The manufacturing method of the polymer solution for resist protective films is also demonstrated.

  According to the present invention, a solution having a low content of a solvent having a high affinity with a resist contained in the composition for forming a protective film can be produced by a simple method, which has an influence on the resist film. Therefore, a protective film can be formed on the resist film without any problem, and therefore a good pattern profile can be obtained.

  The polymer for forming a protective film to be purified in the present invention is a polymer used for forming a film that is formed in the upper layer of a resist and used for protecting the resist. Examples of such a protective film include a protective film for suppressing the resist shape caused by environmental amines from being T-top, an upper antireflection film, an immersion protective film, and the like. As the polymer, any material can be used as long as it does not interact with the resist film and has a function of protecting the resist from external influences. For example, water-soluble resins such as polyvinyl ether and polyvinyl pyrrolidone, perfluoroalkyl compounds, fluorine resins, monomers having functional groups substituted with fluorine, carboxyl groups, sulfonyl groups, and fluoroalkyls at least at the α-position carbon atom Examples thereof include a copolymer of a monomer having a functional group such as a repeating unit having an alcoholic hydroxyl group having a group.

  When used as an immersion protection film, from the standpoint of resistance to immersion liquid and ease of processing after exposure processing, it gives solubility in alkaline developers and repeating units having fluorine atoms that can provide water repellency to immersion liquid A copolymer of a repeating unit having a functional group such as a carboxyl group, a sulfonyl group, or an alcoholic hydroxyl group having a fluoroalkyl group at least at the α-position carbon atom can be particularly preferably used.

  Examples of the repeating unit having a fluorine atom include units represented by the following formulas (1) and (2).

（式中、Ｒ^１、Ｒ^２、Ｒ^３、Ｒ^４は、同一又は異なって、水素原子、フッ素原子、ヒドロキシル基を有していてもよい炭素数１〜１０のアルキル基、ヒドロキシル基を有していてもよい炭素数３〜１５のシクロアルキル基、ヒドロキシル基を有していてもよい炭素数１〜１０のフルオロアルキル基、ヒドロキシル基を有していてもよい炭素数３〜１５のフルオロシクロアルキル基、ヒドロキシル基を有していてもよい炭素数１〜１０のハロアルキルオキシ基、ヒドロキシル基を有していてもよい炭素数３〜１０のハロシクロアルキルオキシ基を示し、Ｒ^３とＲ^４は互いに結合して隣接する２個の炭素原子とともに環を形成していてもよい。但し、Ｒ^１〜Ｒ^４のうち少なくとも１つはフッ素原子を含有する基である。）

(In the formula, R ¹ , R ² , R ³ and R ⁴ are the same or different and each has a hydrogen atom, a fluorine atom or a hydroxyl group which may have a C 1-10 alkyl group or hydroxyl group. A cycloalkyl group having 3 to 15 carbon atoms which may have, a fluoroalkyl group having 1 to 10 carbon atoms which may have a hydroxyl group, a fluoro having 3 to 15 carbon atoms which may have a hydroxyl group A cycloalkyl group, a haloalkyloxy group having 1 to 10 carbon atoms which may have a hydroxyl group, and a halocycloalkyloxy group having 3 to 10 carbon atoms which may have a hydroxyl group, R ³ and R ⁴ may be bonded to each other to form a ring with two adjacent carbon atoms, provided that at least one of R ^{1 to} R ⁴ is a group containing a fluorine atom.

（式中、Ｒ^５は、水素原子、フッ素原子、メチル基、トリフルオロメチル基、又はカルボキシメチル基を示す。Ｒ^６は、置換基を有していてもよく、またエステル基、エーテル基、ヒドロキシル基又はアミド基を有していてもよい、炭素数１〜２０の脂肪族炭化水素基もしくは炭素数５〜２０の脂環式炭化水素基、又はこれらが２以上結合した基を示す）
前記アルキル基としては、メチル、エチル、プロピル、イソプロピル、ブチル、イソブチル、ｓ−ブチル、ｔ−ブチル、ペンチル、ヘキシル、オクチル、デシル基等が挙げられる。シクロアルキル基としては、シクロペンチル、シクロへキシル基等が挙げられる。フルオロアルキル基としては、トリフルオロメチル基、トリフルオロエチル基、ペンタフルオロエチル基などが挙げられる。ヒドロキシル基を有するフルオロアルキル基としては、−Ｃ（ＣＦ_３）_２−ＯＨ、−ＣＨ_２−Ｃ（ＣＦ_３）_２−ＯＨなどが挙げられる。フルオロシクロアルキル基としては、ヘキサフルオロシクロアルキル基などが挙げられる。ハロアルキルオキシ基としては、−ＯＣＦ_３、−ＯＣ_３Ｆ_７、−ＯＣ_４Ｆ_９、−ＯＣ_８Ｆ_１７、−ＯＣＨ_２ＣＦ_３、−ＯＣＨ_２Ｃ_３Ｆ_７、−ＯＣＨ_２ＣＦ_２ＣＦ_２ＣＦ_２ＣＦ_２Ｈなどが挙げられる。Ｒ^３とＲ^４は互いに結合して隣接する２個の炭素原子とともに形成する環としては、フッ素原子又はフッ素原子含有基を有していてもよいシクロブタン環、フッ素原子又はフッ素原子含有基を有していてもよいシクロヘプタン環、フッ素原子又はフッ素原子含有基を有していてもよいシクロヘキサン環、フッ素原子又はフッ素原子含有基を有していてもよい１，３‐ジオキソラン環などが挙げられる。

(In the formula, R ⁵ represents a hydrogen atom, a fluorine atom, a methyl group, a trifluoromethyl group, or a carboxymethyl group. R ⁶ may have a substituent, and an ester group, an ether group, An aliphatic hydrocarbon group having 1 to 20 carbon atoms or an alicyclic hydrocarbon group having 5 to 20 carbon atoms, or a group in which two or more thereof are bonded, which may have a hydroxyl group or an amide group)
Examples of the alkyl group include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, s-butyl, t-butyl, pentyl, hexyl, octyl, and decyl groups. Examples of the cycloalkyl group include cyclopentyl and cyclohexyl groups. Examples of the fluoroalkyl group include a trifluoromethyl group, a trifluoroethyl group, and a pentafluoroethyl group. Examples of the fluoroalkyl group having a hydroxyl group include —C (CF ₃ ) ₂ —OH, —CH ₂ —C (CF ₃ ) ₂ —OH, and the like. Examples of the fluorocycloalkyl group include a hexafluorocycloalkyl group. Halo alkyl _{group, -OCF 3, -OC 3 F 7} , -OC 4 F 9, -OC 8 F 17, -OCH 2 CF 3, -OCH 2 C 3 F 7, -OCH 2 CF 2 CF 2 CF ₂ CF ₂ H and the like. R ³ and R ⁴ are bonded to each other to form a ring together with two adjacent carbon atoms. The ring formed by R ² and R ⁴ has a cyclobutane ring, fluorine atom or fluorine atom-containing group which may have a fluorine atom or fluorine atom-containing group. And a cycloheptane ring which may have a fluorine atom or a fluorine atom-containing group, a 1,3-dioxolane ring which may have a fluorine atom or a fluorine atom-containing group, etc. .

Examples of the aliphatic hydrocarbon group having 1 to 20 carbon atoms in R ⁶ include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, s-butyl, t-butyl, pentyl, hexyl, octyl and decyl groups; And alkynyl groups such as propynyl groups. Examples of the alicyclic hydrocarbon group having 5 to 20 carbon atoms in R ⁶ include cycloalkyl groups such as cyclopentyl and cyclohexyl groups; cycloalkenyl groups such as cyclopentenyl and cyclohexenyl groups; and bridges such as norbornyl and adamantyl groups And cyclic groups. The substituent that the aliphatic hydrocarbon group or alicyclic hydrocarbon group may have is not particularly limited, and preferred examples of the substituent include a fluorine atom and a hydroxyl group.

The following are mentioned as a typical example of the repeating unit represented by Formula (1).
^{· R 1 = H, R 2} = F, R 3 = H, R 4 = H a is repeating unit ^{· R 1 = H, R 2} = F, R 3 = H, repeating units · ^R is 4 = F R ¹ = H, R ² = F, R ³ = F, R ⁴ = F repeating unit R ¹ = F, R ² = F, R ³ = F, R ⁴ = F repeating unit R ¹ = Repeating units H, R ² = F, R ³ = H, R ⁴ = CF ₃ · R ¹ = F, R ² = F, R ³ = H, R ⁴ = Repeating unit R ₃ = CF ₃ · R ¹ = F, R ² = F, R ³ = F, R ⁴ = CF ₃ repeating unit · R ¹ = H, R ² = H, R ³ = H, R ⁴ = OCF ₃ repeating unit · R ¹ = ^{H, R 2 = H, R} 3 = H, R 4 = OC 3 F 7 in which the repeating units ^{· R 1 = H, R 2} = H, R 3 = H, repeated a R 4 = _OC 4 _{F 9} Unit ^· R ¹ = ^{H and, R 2 = H, R 3} = H, R 4 = OC 8 F 17 a is repeating unit ^{· R 1 = H, R 2} = H, R 3 = H, R 4 = OCH 2 Repeating unit that is CF _3. Repeating unit that is R ¹ = H, R ² = H, R ³ = H, R ⁴ = OCH ₂ C ₃ F ₇ • R ¹ = F, R ² = F, R ³ = F , R ⁴ = OC ₃ F ₇ and the repeating unit R ¹ = F, R ² = F, R ³ and R ⁴ are combined to form a tetrafluorobutane ring with two adjacent carbon atoms Repeating unit R ¹ = F, R ² = F, R ³ and R ⁴ are combined to form a hexafluoropentane ring with two adjacent carbon atoms. R ¹ = F, R ² = F, together with the two carbon atoms to ^{which R 3} and ^{R 4} are adjacent bonded, 2,2-bis (triphenylmethyl Oromechiru) -1,3-dioxolane repeating units ^· R 1 ^{= H,} which forms a ring by which, together with R 2 = H, 2 carbon atoms of the adjacent bonded ^{R 3} and ^{R 4,} 2- (2, 2,2-trifluoro-1-trifluoromethyl-1-hydroxyethyl) repeating unit forming a norbornane ring. R ¹ = H, R ² = H, R ³ and R ⁴ are bonded and adjacent 2 A repeating unit forming a 2- (3,3,3-trifluoro-2-trifluoromethyl-1-hydroxypropyl) norbornane ring together with carbon atoms.

The following are mentioned as a typical example of the repeating unit represented by Formula (2).
• Repeating units where R ⁵ = H, CH ₃ , F or CF ₃ , R ⁶ = CH ₂ CF ₃ • Repeating where R ⁵ = H, CH ₃ , F or CF ₃ , R ⁶ = CH ₂ CF ₂ H The unit R ⁵ = H, CH ₃ , F or CF ₃ , R ⁶ = CH ₂ CF ₂ CF ₃ repeating unitR ⁵ = H, CH ₃ , F or CF ₃ , R ⁶ = CH ₂ CF ₂ CF Repeating units that are ₂ H • Repeating units that are R ⁵ = H, CH ₃ , F or CF ₃ , R ⁶ = CH ₂ CF (CF ₃ ) • R ⁵ = H, CH ₃ , F or CF ₃ , R ⁶ = CH ₂ CF ₂ CFHCF ₃ repeating unit · R ⁵ = H, CH ₃ , F or CF ₃ , R ⁶ = CH ₂ CF ₂ CF ₂ CF ₂ CF ₃ repeating unit · R ⁵ = H, CH ₃ , F, or _{^{CF 3, R 6 = CH 2}} CF 2 F ₂ CF ₂ CF ₂ H in which the repeating units _{^{· R 5 = H, CH 3}} , F or _{^{CF 3, R 6 = CH 2}} CH 2 CF 2 CF 2 CF 2 CF 3 a is repeating unit ^· R 5 = H, CH ₃ , F or CF ₃ , R ⁶ = CH ₂ CF ₂ CF ₂ CF ₂ CF ₂ CF ₂ CF ₂ CF ₂ CF ₃ repeating unit R ⁵ = H, CH ₃ , F or CF ₃ , R ⁶ = Repeating unit that is CH ₂ CH ₂ CF ₂ CF ₂ CF ₂ CF ₂ CF ₂ CF ₂ CF ₃ • R ⁵ = H, CH ₃ , F or CF ₃ , R ⁶ = 4- (2,2,2-trifluoro -1-trifluoromethyl-2-hydroxyethyl) cyclohexyl group repeating unit R ⁵ = H, CH ₃ , F or CF ₃ , R ⁶ = 2- (2,2,2-trifluoro-1 -Trifluoromethyl-2 Hydroxyethyl) repeating units ^· R 5 = H is a cyclohexyl group, _CH 3, F or ^{_{CF 3, R 6 = 4- (}} 1,1,3,3,3- pentafluoro-12-hydroxy-propyl) cyclo Repeating unit which is a hexyl group. R ⁵ = H, CH ₃ , F or CF ₃ , R ⁶ = 4- (1,1,3,3,3-pentafluoro-12-hydroxypropyl) -4-hydroxycyclo Repeating unit that is a hexyl group. R ⁵ = H, CH ₃ , F or CF ₃ , R ⁶ = 4- (1,1,3,3,3-pentafluoro-12-hydroxypropyl) cyclohexyl-methyl Repeating unit as a group R ⁵ = H, CH ₃ , F or CF ₃ , R ⁶ = 4- (1,1,3,3,3-pentafluoro-12-hydroxypropyl) -4-hydroxycyclohexyl −Me Repeating units ^· R 5 is a le radical = H, _CH 3, F or ^{_{CF 3, R 6 = 4- (}} 1,1,2,2,3,3,4,4- octa fluoride butyl) cyclohexyl group R ⁵ = H, CH ₃ , F or CF ₃ , R ⁶ = 5- (2,2,2-trifluoro-1-trifluoromethyl-1-hydroxyethyl) norbornan-2-yl group R ⁵ = H, CH ₃ , F or CF ₃ , R ⁶ = 5- (3,3,3-trifluoro-2-trifluoromethyl-1-hydroxypropyl) norbornan-2-yl group A repeating unit of R ⁵ = H, CH ₃ , F or CF ₃ , R ⁶ = 5-trifluoromethyl-5-hydroxynorbornan-2-yl group.R ⁵ = H, CH ₃ , F or _CF ^{3, R} 6 = 6 Is a 6-difluoro-5-trifluoromethyl-5-hydroxy-norbornane-2-yl group repeating units _{^{· R 5 = H, CH 3}} , F or ^{_{CF 3, R 6 = 6- (}} 2,2,3,3 , 4,4,5,5-octafluoropentyloxycarbonyl) norbornan-2-yl group. R ⁵ = H, CH ₃ , F or CF ₃ , R ⁶ = 6- (2,2,3 , 3,4,4,5,5,5-nonafluoropentyloxycarbonyl) norbornan-2-yl group and the like.

  As the repeating unit having a sulfo group, a carboxyl group or an alcoholic hydroxyl group having a fluoroalkyl group at least at the α-position carbon atom capable of imparting solubility in an alkali developer, a sulfo group or a carboxyl group, at least at the α-position is used. If it has the alcoholic hydroxyl group which has a fluoroalkyl group in a carbon atom, it will not specifically limit.

  Representative examples of the unsaturated compound (polymerizable monomer) corresponding to the repeating unit having a sulfo group include, for example, vinyl sulfonic acid (ethylene sulfonic acid), 2-propene sulfonic acid, 3-butene sulfonic acid, 4-pentene. Sulfonic acid, (meth) acrylic sulfomethyl, (meth) acrylic acid 2-sulfoethyl, (meth) acrylic acid 3-sulfopropyl, (meth) acrylic acid 2-methyl-3-sulfopropyl, (meth) acrylic acid 4- Sulfobutyl, N- (2-sulfoethyl) (meth) acrylic acid 4-sulfobutyl, N- (2-sulfoethyl) (meth) acrylic acid amide, N- (1-methyl-2-sulfoethyl) (meth) acrylic acid amide, N- (2-methyl-3-sulfopropyl) (meth) acrylic acid amide, N- (4-sulfobutyl) (meth) acrylic acid amide, etc. It is, but is not limited to this.

  Representative examples of unsaturated compounds (polymerizable monomers) corresponding to a repeating unit having a carboxyl group include, for example, (meth) acrylic acid, 3-butenoic acid, 4-pentenoic acid, 2-fluoroacrylic acid, 2- Trifluoromethyl acrylic acid, 3-vinyloxypropionic acid, 4-vinyloxybutyric acid, 3-carboxy-3-butenoic acid, carboxycyclohexyl (meth) acrylate, carboxynorbornyl (meth) acrylate, (meth) acrylic acid Examples thereof include carboxyadamantyl, carboxymethyl (meth) acrylate, 2-carboxyethyl (meth) acrylate, and 3-carboxypropyl (meth) acrylate.

  A typical example of the repeating unit corresponding to a repeating unit having an alcoholic hydroxyl group having a fluoroalkyl group at least at the α-position is a repeating unit represented by the formula (3).

式（３） においてＲ⁷ は水素原子または炭素数１ 〜 ４ のアルキル基を、Ｒ⁸ は２ 価の有機基を、それぞれ表す。

In the formula (3), R ⁷ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R ⁸ represents a divalent organic group.

  Examples of the alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, a 2-methylpropyl group, a 1-methylpropyl group, and a t-butyl group. And the like.

  The divalent organic group is preferably a divalent hydrocarbon group, and among the divalent hydrocarbon groups, a chain or cyclic hydrocarbon group is preferable.

Preferable R ⁸ is a methylene group, an ethylene group, a propylene group such as a 1,3-propylene group or a 1,2-propylene group, a tetramethylene group, a pentamethylene group, a hexamethylene group, a heptamethylene group, an octamethylene group, Nonamethylene group, Decamemethylene group, Undecamethylene group, Dodecamethylene group, Tridecamethylene group, Tetradecamethylene group, Pentadecamethylene group, Hexadecamethylene group, Heptadecamethylene group, Octadecamethylene group, Nonadecamethylene group, Insalene group, 1-methyl-1,3-propylene group, 2-methyl-1,3-propylene group, 2-methyl-1,2-propylene group, 1-methyl-1,4-butylene group, 2-methyl -1,4-butylene group, methylidene group, ethylidene group, propylidene group Or a saturated chain hydrocarbon group such as a 2-propylidene group, a cyclobutylene group such as a 1,3-cyclobutylene group, a cyclopentylene group such as a 1,3-cyclopentylene group, 1,4- A cyclohexylene group such as a cyclohexylene group, a monocyclic hydrocarbon ring group such as a cycloalkylene group having 3 to 10 carbon atoms such as a cyclooctylene group such as a 1,5-cyclooctylene group and the like, 1,4-norbornylene Group or a norbornylene group such as a 2,5-norbornylene group, a hydrocarbon ring having 2 to 4 cyclic carbon atoms and 4 to 30 carbon atoms such as a 1,5-adamantylene group, an adamantylene group such as 2,6-adamantylene group, etc. And a crosslinked cyclic hydrocarbon ring group such as a group.

In particular, when R ⁸ contains a divalent aliphatic cyclic hydrocarbon group, an alkylene group having 1 to 4 carbon atoms is used as a spacer between the bistrifluoromethyl-hydroxy-methyl group and the aliphatic cyclic hydrocarbon group. It is preferable to insert.
R ⁸ is preferably a hydrocarbon group containing a 2,5-norbornylene group, a 1,2-ethylene group, or a propylene group.

  In the polymer constituting the resin composition for forming a resist protective film of the present invention, the ratio of the repeating unit that imparts solubility to an alkaline developer is, for example, 1 to 1 with respect to all repeating units (all monomer units). It is 99 mol%, preferably 10 to 80 mol%, more preferably about 15 to 70 mol%. If the ratio of the repeating units is too small, the alkali solubility is lowered, and defects such as scum at the time of alkali development tend to occur. On the other hand, if the ratio of repeating units is too large, the water repellency may be lowered.

  When the polymer has a repeating unit having a fluorine atom, the proportion thereof is, for example, 1 to 99 mol%, preferably 5 to 95 mol%, more preferably, based on all repeating units (total monomer units). It is about 10-90 mol%. When the proportion of repeating units having fluorine atoms is small, water repellency is lowered and defects such as watermarks are likely to occur, and when the proportion of repeating units having fluorine atoms is too large, alkali solubility is likely to be lowered. .

  In the protective film-forming polymer of the present invention, it is possible to copolymerize a repeating unit other than a repeating unit that imparts solubility to an alkaline developer and a repeating unit having a fluorine atom within a range that does not interfere with the above-mentioned purpose. . There is no particular limitation as long as it is copolymerizable with a repeating unit that imparts solubility to an alkali developer and a repeating unit having a fluorine atom. Among them, preferred repeating units are linear, branched or cyclic alkyl groups having 1 to 20 carbon atoms, and may have (meth) derivatives, vinyl ether derivatives, norbornene which may have ethers, esters, lactones, and the like. Derivatives, norbornadiene derivatives and the like can be mentioned. Among them, preferred monomers include a monomer containing a lactone skeleton, a monomer containing a group that is eliminated by an acid and becomes alkali-soluble, and a monomer containing an alicyclic skeleton having a hydroxyl group.

  The weight average molecular weight (Mw; value in terms of polystyrene by gel permeation chromatography (GPC)) of the polymer for forming a resist protective film of the present invention is, for example, about 1000 to 500000, preferably 2000 to 30000, more preferably 2000 to 2000. About 15000. If the weight average molecular weight is too small, mixing with the resist material occurs, or it becomes easy to dissolve in water. On the other hand, if the weight average molecular weight is too large, there may be a problem in film formability during spin coating, or the alkali solubility may be reduced.

  In obtaining the resist protective film-forming polymer of the present invention, the polymerization of the monomer mixture is a conventional method used for producing acrylic polymers such as solution polymerization, bulk polymerization, suspension polymerization, emulsion polymerization, etc. In particular, solution polymerization is preferable. Furthermore, drop polymerization is preferable among solution polymerization. Specifically, for example, (i) a monomer solution previously dissolved in an organic solvent and a polymerization initiator solution dissolved in an organic solvent are prepared in an organic solvent maintained at a constant temperature. A method in which the monomer solution and the polymerization initiator solution are respectively dropped, and (ii) a method in which a mixed solution in which the monomer and the polymerization initiator are dissolved in an organic solvent is dropped in an organic solvent maintained at a constant temperature. , (Iii) A monomer solution previously dissolved in an organic solvent and a polymerization initiator solution dissolved in the organic solvent are respectively prepared, and the polymerization initiator solution is dropped into the monomer solution maintained at a constant temperature. (Iv) preparing a monomer solution previously dissolved in a separate organic solvent and a polymerization initiator solution dissolved in an organic solvent, and each of the monomer solutions in an organic solvent maintained at a constant temperature. For methods such as dropping each of the polymerization initiator solutions More done.

  As the polymerization solvent, a known solvent can be used. For example, ether (chain ether such as diethyl ether, propylene glycol monomethyl ether, etc., cyclic ether such as tetrahydrofuran, dioxane, etc.), ester (methyl acetate, ethyl acetate, Glycol ether esters such as butyl acetate, ethyl lactate, propylene glycol monomethyl ether acetate), ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc.), amides (N, N-dimethylacetamide, N, N-dimethylformamide, etc.) ), Sulfoxide (dimethylsulfoxide, etc.), alcohol (methanol, ethanol, propanol, etc.), hydrocarbon (benzene, toluene, xylene, etc.) Aromatic hydrocarbons, aliphatic hydrocarbons such as hexane, and alicyclic hydrocarbons such as cyclohexane), and mixtures of these solvents. From the viewpoint of the solubility of the monomer used as a raw material and the polymer produced by polymerization, ether-based, ester-based, and ketone-based solvents can be preferably used as the solvent. Further, from the viewpoint of ensuring safety in carrying out the polymerization reaction, the boiling point of the solvent is preferably 80 ° C. or higher, more preferably 100 ° C. or higher, more preferably 120 ° C. or higher. Moreover, a well-known polymerization initiator can be used as a polymerization initiator. The polymerization temperature can be appropriately selected within a range of, for example, about 30 to 150 ° C. Preferably, it is 50-120 degreeC, More preferably, it is the range of 55-110 degreeC.

  The resulting polymer can be purified by precipitation or reprecipitation. The precipitation or reprecipitation solvent may be either an organic solvent or water, or a mixed solvent. Examples of the organic solvent used as the precipitation or reprecipitation solvent include hydrocarbons (aliphatic hydrocarbons such as pentane, hexane, heptane, and octane; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; Aromatic hydrocarbons), halogenated hydrocarbons (halogenated aliphatic hydrocarbons such as methylene chloride, chloroform and carbon tetrachloride; halogenated aromatic hydrocarbons such as chlorobenzene and dichlorobenzene), nitro compounds (nitromethane, nitroethane, etc.) , Nitrile (acetonitrile, benzonitrile, etc.), ether (chain ether such as diethyl ether, diisopropyl ether, dimethoxyethane; cyclic ether such as tetrahydrofuran, dioxane), ketone (acetone, methyl ether) Ruketone, diisobutyl ketone, etc.), ester (ethyl acetate, butyl acetate, etc.), carbonate (dimethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, etc.), alcohol (methanol, ethanol, propanol, isopropyl alcohol, butanol, etc.), carboxylic acid (Acetic acid etc.), mixed solvents containing these solvents, and the like.

Among these, as the organic solvent used as the precipitation or reprecipitation solvent, a solvent containing at least a hydrocarbon (particularly an aliphatic hydrocarbon such as hexane) is preferable. In such a solvent containing at least hydrocarbon, the ratio of hydrocarbon (for example, aliphatic hydrocarbon such as hexane) and other solvent is, for example, the former / the latter (weight ratio) = 10/90 to 100/0, The former / the latter (weight ratio) = 30/70 to 100/0, more preferably the former / the latter (weight ratio) = about 50/50 to 100/0.
The polymer purified by the precipitation or reprecipitation is separated by filtration. Examples of the filtration method include natural filtration, pressure filtration, vacuum filtration, and centrifugal filtration. Considering the uniformity of the residual solvent in the polymer containing the solvent recovered by filtration (wet polymer), the amount of the residual solvent, etc., it is preferable to select centrifugal filtration from the viewpoint of the separation efficiency. The amount of the solvent contained in the wet polymer at the time of separation is not specified, but the amount of the polymer recovered is considered in consideration of the amount of monomer, initiator, polymerization solvent and product impurities remaining in the product. It is preferably 5 times by weight or less. More preferably, it is 3 times or less, more preferably 2 times or less. The wet polymer separated by filtration is subjected to the next rinsing step as it is without being immediately recovered.
The solvent used in the rinsing step is not particularly limited, but it is preferable that the boiling point is lower than that of the product solvent because of easy removal in the concentration step. The boiling point of the rinsing solvent is not particularly limited, but is preferably 5 ° C. or lower than the boiling point of the product solvent. More preferably, it is 10 ° C. or higher, more preferably 20 ° C. or lower. If the boiling point of the rinsing solvent is not different from the boiling point of the product solvent (also referred to as a protective film-forming solvent) or higher than the boiling point of the product solvent, it cannot be easily removed in the subsequent concentration step. There is a possibility of causing problems such as an increase in number and remaining as impurities in the product.
As the rinsing solvent, it is necessary to use a poor solvent having low affinity with the polymer. If a solvent having a high affinity with the polymer is used as the rinsing solvent, the polymer dispersed in a powdery state will be dissolved, and it will become sticky and impurities will not be sufficiently removed, If the dissolution process makes it difficult to dissolve and the dissolution time becomes longer, or if the affinity is higher, the polymer dissolves and the yield decreases. Whether or not the rinsing solvent is a poor polymer solvent can be easily determined by mixing the wet polymer powder with the rinsing solvent and allowing it to stand for about 1 hour, and then whether or not the wet polymer remains powdery. Can do.
The temperature at the time of rinsing is not particularly limited, but it is preferable that the temperature is higher because the remaining monomer other than the solvent is easily removed. The temperature of the rinse solvent is preferably room temperature or higher. When the temperature of the rinsing solvent increases, the affinity with the polymer may change. Therefore, when changing the temperature during rinsing, it is necessary to confirm the dispersion stability of the wet polymer at the actual temperature.

  The rinse solvent may be either an organic solvent or water as long as the above characteristics are satisfied, or may be a mixed solvent. Moreover, it is preferable to use the solvent used by precipitation or reprecipitation from a viewpoint of not increasing the kind of impurity.

  Examples of organic solvents used as the rinsing solvent include hydrocarbons (aliphatic hydrocarbons such as pentane, hexane, heptane, and octane; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; aromatic hydrocarbons such as benzene, toluene, and xylene. ), Halogenated hydrocarbons (halogenated aliphatic hydrocarbons such as methylene chloride, chloroform and carbon tetrachloride; halogenated aromatic hydrocarbons such as chlorobenzene and dichlorobenzene), nitro compounds (nitromethane, nitroethane, etc.), nitriles ( Acetonitrile, benzonitrile, etc.), ethers (chain ethers such as diethyl ether, diisopropyl ether, dimethoxyethane; cyclic ethers such as tetrahydrofuran, dioxane), ketones (acetone, methyl ethyl keto) , Diisobutyl ketone, etc.), ester (ethyl acetate, butyl acetate, etc.), carbonate (dimethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, etc.), alcohol (methanol, ethanol, propanol, isopropyl alcohol, butanol, etc.), carboxylic acid ( Acetic acid and the like), and mixed solvents containing these solvents.

Among these, as the organic solvent used as the rinse solvent, a solvent containing at least a hydrocarbon (particularly an aliphatic hydrocarbon such as hexane) is preferable. In such a solvent containing at least hydrocarbon, the ratio of hydrocarbon (for example, aliphatic hydrocarbon such as hexane) and other solvent is, for example, the former / the latter (weight ratio) = 10/90 to 100/0, The former / the latter (weight ratio) = 30/70 to 100/0, more preferably the former / the latter (weight ratio) = about 50/50 to 100/0.
The amount of the rinse solvent used can be selected in the range of 1 to 100 times the polymer weight. Preferably it is 2-50 times, More preferably, it is 5-20 times. If it is less than 1 time, the effect of rinsing is lowered, and if it exceeds 100 times, the usage rate is lowered. The rinsing solvent may be added directly to the wet polymer filtered in a filtration device such as a centrifugal filter, or the wet polymer may be recovered once in another device and added in another device. It is preferable to process as it is in the separation apparatus. After adding the rinse solvent to the wet polymer, the solvent can be separated and removed by pressurization, decompression, or centrifugation.
The amount of solvent contained in the wet polymer at the time of separation after rinsing is not specified, but it is recovered considering the amount of monomer, initiator, polymerization solvent and product impurities remaining in the product The amount is preferably 5 times by weight or less of the polymer. More preferably, it is 3 times or less, more preferably 2 times or less.
The rinsing step is preferably performed twice or more. The number of times is not particularly limited as long as it is twice or more. In the absence of the rinsing step, the polymerization solvent is not sufficiently removed, resulting in an increase in the load of the subsequent concentration step and an increase in the amount of the polymerization solvent contained in the product.

  The rinsed resin (wet polymer) contains low-boiling impurities such as the solvent used in the precipitation operation. If such a low boiling point impurity is present in the protective film, the performance deteriorates, and it is necessary to remove it. Examples of the method for removing low-boiling impurities include a method of drying the wet polymer, a method of re-dissolving the wet polymer in a protective film-forming solvent, and distilling off the low-boiling impurities by distillation. However, in the method of drying the wet polymer to remove low-boiling impurities, once the resin is dried, the adhesion between the particles becomes stronger due to drying, or it is very soluble when dissolved in the protective film forming solvent. It becomes difficult. In addition, there is a problem that some of the functional groups in the resin react with heat applied during drying. Therefore, in order to obtain a resin having good solubility, the wet polymer is redissolved in a solvent containing at least one type of protective film-forming solvent, and the obtained redissolved solution is concentrated to be contained in the wet polymer. It is preferred to distill off the low boiling impurities contained. According to this method, denaturation of the resin can also be suppressed.

  The polymer solution for forming a resist protective film of the present invention is usually prepared by dissolving the polymer in a solvent. The solvent used is preferably a solvent that does not dissolve the resist. In this case, the solvent used is not particularly limited, but a solvent that dissolves the resist is not preferable. For example, cyclohexanone used as a resist solvent, ketones such as methyl-2-n-amyl ketone, propylene glycol monomethyl ether, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, propylene glycol dimethyl ether, diethylene glycol dimethyl ether, etc. Ethers, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, ethyl lactate, ethyl pyruvate, butyl acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate, tert-propionate Butyl, propylene glycol mono-tert-butyl ether acetate And esters such as 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, and 1-ethoxy-2-propanol are not preferred.

  Examples of the solvent that does not dissolve the resist layer include higher alcohols having 4 or more carbon atoms, hydrocarbons, chain ethers, and fluorine-containing solvents. You may use a solvent individually or in mixture of 2 or more types. In addition, a solvent having a low polarity and a solvent having a high polarity can be used in combination.

  Examples of the alcohol having 4 or more carbon atoms include 1-butyl alcohol, 2-butyl alcohol, isobutyl alcohol, tert-butyl alcohol, 1-pentanol, 2-pentanol, 3-pentanol, and tert-amyl. Alcohol, neopentyl alcohol, 2-methyl-1-butanol, 3-methyl-1-butanol, 3-methyl-3-pentanol, cyclopentanol, 1-hexanol, 2-hexanol, 3-hexanol, 2, 3 -Dimethyl-2-butanol, 3,3-dimethyl-1-butanol, 3,3-dimethyl-2-butanol, 2-diethyl-1-butanol, 2-methyl-1-pentanol, 2-methyl-2- Pentanol, 2-methyl-3-pen Nord, 3-methyl-1-pentanol, 3-methyl-2-pentanol, 3-methyl-3-pentanol, 4-methyl-1-pentanol, 4-methyl-2-pentanol, 4-methyl -3-Pentanol, cyclohexanol and the like can be mentioned. Examples of the hydrocarbon include aliphatic hydrocarbons such as hexane, heptane, and octane; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; and aromatic hydrocarbons such as toluene, xylene, ethylbenzene, and isopropylbenzene. Examples of the chain ether include anisole and dibutyl ether. Examples of the fluorine-containing solvent include 2-fluoroanisole, 3-fluoroanisole, 4-fluoroanisole, 2,3-difluoroanisole, 2,4-difluoroanisole, 2,5-difluoroanisole, 5,8-difluoro. -1,4-benzodioxane, 2,3-difluorobenzyl alcohol, 1,3-difluoro-2-propanol, 2 ', 4'-difluoropropiophenone, 2,4-difluorotoluene, trifluoroacetaldehyde ethyl hemiacetal , Trifluoroacetamide, trifluoroethanol, 2,2,2-trifluoroethyl butyrate, ethyl heptafluorobutyrate, ethyl heptafluorobutyl acetate, ethyl hexafluoroglutaryl , Ethyl-3-hydroxy-4,4,4-trifluorobutyrate, ethyl-2-methyl-4,4,4-trifluoroacetoacetate, ethyl pentafluorobenzoate, ethyl pentafluoropropionate, ethyl penta Fluoropropynyl acetate, ethyl perfluorooctanoate, ethyl-4,4,4-trifluoroacetoacetate, ethyl-4,4,4-trifluorobutyrate, ethyl-4,4,4-trifluorocrotonate, Ethyl trifluorosulfonate, ethyl-3- (trifluoromethyl) butyrate, ethyl trifluoropyruvate, S-ethyl trifluoroacetate, fluorocyclohexane, 2, 2, 3, 3, 4, 4, 4, 4-heptafluoro-1 Butanol, 1,1,1,1,2,2,3,3-heptafluoro-7,7-dimethyl-4,6-octanedione, 1,1,1,3,5,5,5-heptafluoropentane -2,4-dione, 3,3,4,4,5,5,5-heptafluoro-2-pentanol, 3,3,4,4,5,5,5-heptafluoro-2-pentanone, Isopropyl 4,4,4-trifluoroacetoacetate, methyl perfluorodenanoate, methyl perfluoro (2-methyl-3-oxahexanoate), methyl perfluorononanoate, methyl perfluorooctanoate, methyl- 2,3,3,3-tetrafluoropropionate, methyl trifluoroacetoacetate, 1,1 1,2,2,2,6,6,6-octafluoro-2,4-hexanedione, 2,2,3,3,4,4,5,5-octafluoro-1-pentanol, 1H, 1H , 2 H, 2 H-perfluoro-1-decanol, perfluoro (2,5-dimethyl-3,6-dioxane anionic) acid methyl ester, 2 H-perfluoro-5-methyl-3,6-dioxanonane 1 H, 1 H, 2 H, 3 H, 3 H-perfluorononane-1,2-diol, 1 H, 1 H, 9 H-perfluoro-1-nonanol, 1 H, 1 H-perfluoro Octanol, 1 H, 1 H, 2 H, 2 H-perfluorooctanol, 2 H-perfluoro-5, 8, 11, 14-tetramethyl Ru-3,6,9,12,15-pentaoxaoctadecane, perfluorotributylamine, perfluorotrihexylamine, perfluoro-2,5,8-trimethyl-3,6,9-trioxadodecanoic acid Methyl ester, perfluorotripentylamine, perfluorotripropylamine, 1H, 1H, 2H, 3H, 3H-perfluoroundecane-1, 2-diol, trifluorobutanol 1,1,1-tri Fluoro-5-methyl-2,4-hexanedione, 1,1,1-trifluoro-2-propanol, 3,3,3-trifluoro-1-propanol, 1,1,1-trifluoro-2- Propyl acetate, perfluorobutyltetrahydrofuran, perfluoro (Butyltetrahydrofuran), perfluorodecalin, perfluoro (1,2-dimethylcyclohexane), perfluoro (1,3-dimethylcyclohexane), propylene glycol trifluoromethyl ether acetate, propylene glycol methyl ether trifluoromethyl acetate, trifluoro Methyl butyl acetate, methyl 3-trifluoromethoxypropionate, perfluorocyclohexanone, propylene glycol trifluoromethyl ether, butyl trifluoroacetate, 1,1,1-trifluoro-5,5-dimethyl-2,4-hexanedione 1,1,1,1,3,3,3-hexafluoro-2-propanol, 1,1,1,3,3,3-hexafluoro-2-methyl- -Propanol, 2,2,3,4,4,4-hexafluoro-1-butanol, 2-trifluoromethyl-2-propanol, 2,2,3,3-tetrafluoro-1-propanol, 3,3 , 3-trifluoro-1-propanol, 4,4,4-trifluoro-1-butanol and the like.

  A particularly preferable solvent as a solvent in the polymer solution for forming a resist protective film of the present invention is an alcohol having 4 or more carbon atoms (in particular, an aliphatic alcohol or alicyclic alcohol having 4 to 6 carbon atoms), or 2 or more carbon atoms. Fluorinated alcohols (particularly fluorinated alcohols having 4 to 10 carbon atoms) in which some or all of the hydrogen atoms bonded to the carbon atoms of the aliphatic or alicyclic alcohol are substituted with fluorine atoms are included.

The solvent used for redissolving the wet polymer may contain at least one protective film forming solvent. That is, for example, when a mixed solvent of two kinds of solvents is used as the protective film forming solvent, the wet polymer may be redissolved using one kind of solvent, and the wet polymer may be obtained using a mixed solvent of two kinds of solvents. May be redissolved. Alternatively, the wet polymer may be redissolved using a protective film-forming solvent and another solvent (a solvent having a boiling point lower than that of the protective film-forming solvent). When a solvent other than the protective film-forming solvent is used as the redissolving solvent, the amount of the solvent other than the protective film-forming solvent can be appropriately selected according to the solubility of the resin, etc. It is preferably 20% by weight or less, more preferably 10% by weight or less, and particularly preferably 5% by weight or less, based on the total amount of the solvent. In addition, when using 2 or more types of mixed solvents as a protective film formation solvent, the solvent which was not used for re-dissolution of the said wet polymer can be added during concentration or after concentration.
When the wet polymer is dissolved in the protective film-forming solvent, it is preferable to dissolve the wet polymer so that the solid content concentration is lower than the solid content concentration of the final product. It is possible to remove low-boiling impurities contained in the wet polymer by concentrating the solution with a lower solid content than the final product and concentrating it to a higher solid content than the final product. It is. The concentration at which the wet polymer is dissolved in the protective film-forming solvent is preferably 2% or more lower than the solid content concentration of the final product. More preferably, the lower one is 5% or more.

Distillation of the redissolved solution thus obtained is preferably carried out by circulating a heating medium or steam at 140 ° C. or lower through a heating jacket and / or a tube (such as a coiled tube) of the distillation can. As the distillation column, a conventional distillation column such as a single distillation column, a plate column, or a packed column can be used. By setting the temperature of the heat medium or steam (preferably both temperatures when both the heat medium and steam are used) to 140 ° C. or lower, modification of the polymer by heat can be remarkably suppressed. The temperature of the heat medium or steam is preferably 1 30 ° C. or lower, more preferably 1 20 ° C. or lower, and particularly preferably 1 10 ° C. or lower. The lower limit of the temperature is, for example, about 40 ° C., preferably about 50 ° C. When a heating medium or steam having a temperature exceeding 140 ° C. is passed through the heating jacket or tube, the polymer is decomposed on the wall surface of the heating jacket or tube even if the liquid temperature in the distillation can is lowered. If the temperature of the heating medium or steam used for heating is lower than 40 ° C, it is necessary to reduce the degree of vacuum considerably, and the temperature of the cooling water for cooling and condensing the distilled solvent becomes too low, which is disadvantageous in terms of cost. It is easy to become.
During distillation, it is preferable to distill while stirring the inside of the distillation can with a stirrer. Distilling while stirring is particularly effective when the viscosity of the solution increases, that is, when the concentration of the dissolved resin increases. The reason is considered to be that the solution is renewed smoothly on the surface of the jacket or coil by stirring, and the overheating of the solution can be prevented. The strength of stirring is not particularly limited as long as the internal solution can be stirred and mixed.

  The pressure at the time of distillation varies depending on the kind of the redissolving solvent and the like, but generally 500 to 1 torr (66.5 to 0.133 kPa), preferably 400 to 2 torr (53.2 to 0). .266 kP a). If the pressure is high, the distillation temperature becomes high and there is a concern about the thermal decomposition of the resin. If the pressure is too low, the temperature of the refrigerant required for condensing the evaporated solvent needs to be lowered, which is not economical. The liquid temperature in the distillation can (can liquid temperature) is preferably 100 ° C. or lower, more preferably 80 ° C. or lower.

  In distillation, in order to completely remove low boiling point impurities, a part of the protective film forming solvent is used together with the low boiling point impurities (if a solvent other than the protective film forming solvent is also used, the solvent and a part of the protective film forming solvent are used. ) Is distilled off. The distillation rate [(distillation amount / charge amount) × 1 0 0 (% by weight)] in distillation is appropriately determined depending on the content of low-boiling impurities in the wet polymer, the type and composition of the solvent for re-dissolution, and the like. In general, it is about 30 to 90% by weight, preferably about 50 to 87% by weight.

  The polymer concentration of the polymer solution finally concentrated in the distillation is, for example, about 10 to 70% by weight, preferably about 20 to 60% by weight, particularly preferably about 30 to 50% by weight.

After removing low-boiling impurities by distillation, a protective film-forming solvent is added to the residual liquid as necessary to prepare a polymer solution having a desired concentration. The polymer concentration in the final polymer solution is, for example, 5 to 50% by weight, preferably 10 to 30% by weight.
The ratio of the polymerization solvent contained in the obtained resist protective film-forming polymer solution is preferably 1% by weight or less based on the solid content. More preferably, it is 0.5 weight% or less. If it exceeds 1% by weight, the resist film will be affected during spin coating.

  The polymer solution for forming a resist protective film of the present invention may contain appropriate additives as necessary.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. The solid content concentration of the polymer solution was obtained from 1 g of the polymer solution collected in an evaporating dish, dried at 160 ° C., and the weight residue. The solid content concentration of the polymer solution may be simply referred to as the polymer concentration to indicate the polymer (solid content) content.

The weight average molecular weight (M w) and molecular weight distribution (M w / M n) of the polymer were measured using GPC using a refractometer (RI) as a detector and tetrahydrofuran (THHF) as an eluent. By measurement, it was calculated in terms of standard polystyrene. GPC measurement was performed using three columns of “Shodex KF-8006 L” (trade name) manufactured by Showa Denko KK in series, with a sample concentration of 0. 5%, sample injection volume 35 μl, column temperature 40 ° C., R I temperature 40 ° C., eluent flow rate 0. The test was performed under the conditions of 8 ml / min and an analysis time of 60 minutes. “GPCLC-10A” manufactured by Shimadzu Corporation was used as a GPC measurement device.
The residual solvent was determined by GC measurement using FID as a detector and helium as a carrier gas. The measurement was performed using a solution having a sample concentration of 10 wt% to which an internal standard substance was added, under conditions of a sample injection amount of 1 μL, an injection temperature of 250 ° C., and a detector temperature of 250 ° C. A calibration curve was prepared based on the ratio between the solvent weight and the peak area, and the amount of residual solvent contained in the sample was quantified. A GC-17A manufactured by Shimadzu Corporation was used as the GC measuring device.

Example 1
Into a glass separable flask equipped with a glass stirrer, thermometer, reflux condenser, dropping funnel and nitrogen introducing tube, 365.5 g of propylene glycol monomethyl ether acetate (PGMEA, boiling point 146 ° C.) was introduced. The temperature was raised to 80 ° C. Meanwhile, 30 g (0.348 mol) of methacrylic acid (MAA, MW = 86.09), 120 g (0.400 mol) of 1H, 1H, 5H-octafluoropentyl methacrylate (OFPMA, MW = 300.15), dimethyl- 12 g of 2,2′-azobis (2-methylpropionate) (initiator; manufactured by Wako Pure Chemical Industries, trade name “V-601”) was dissolved in 484.5 g of propylene glycol monomethyl ether acetate (PGMEA). A meter solution was prepared. The monomer solution was dropped into the flask over 5 hours. Meanwhile, the temperature in the flask was controlled at 80 ° C. After completion of dropping, the mixture was aged at the same temperature for 2 hours. The obtained reaction solution (polymer solution) was cooled and then added dropwise to 8000 g of hexane as a reprecipitation solvent with stirring. After completion of the addition, the mixture was further stirred for 30 minutes. The deposited precipitate was centrifuged with a centrifuge. Without taking out the obtained wet polymer, 1000 g of hexane (boiling point: 69 ° C.) as a rinse solvent was added from above the wet polymer, and the operation of performing centrifugation was repeated twice. The amount of solvent contained in the wet polymer was 1.45 times that of the polymer. The taken out wet polymer was dissolved in 900 g of 1-pentanol (1-PEN, boiling point 138 ° C.) as a protective film forming solvent by stirring. The obtained solution was charged into an evaporator having a hot water bath and a reflux pipe through which a 0 ° C. refrigerant flows, and concentrated under reduced pressure while being heated in a 60 ° C. hot water bath while rotating the evaporator. Concentration was stopped when the liquid volume reached approximately 400 ml. The concentration of the concentrated polymer was measured and found to be 40% by weight. 1-Pentanol was added to prepare a 1-pentanol solution having a polymer concentration of 20% by weight.
Moreover, when the solution after preparation was sampled and analyzed by GPC, the weight average molecular weight (Mw) was 10240 and molecular weight distribution (Mw / Mn) was 2.05. Moreover, content with respect to solid content of PGMEA which is a polymerization solvent was 0.40 weight%. Hexane was not detected.

Example 2
A cyclohexanone solution was prepared in the same manner as in Example 1 except that the polymerization solvent in Example 1 was changed from PGMEA to cyclohexanone (CHO, boiling point 156 ° C.). The amount of the solvent contained in the wet polymer before being dissolved in the protective film-forming solvent was 1.51 times the weight of the polymer. Moreover, when the solution after preparation was sampled and analyzed by GPC, the weight average molecular weight (Mw) was 9950, and molecular weight distribution (Mw / Mn) was 1.98. Moreover, content with respect to solid content of CHO which is a polymerization solvent was 0.47 weight%. Hexane was not detected.

Example 3
A 1-butanol solution was prepared in the same manner as in Example 1 except that the protective film-forming solvent was changed from 1-pentanol to 1-butanol (boiling point 117 ° C.) in Example 1. The amount of the solvent contained in the wet polymer before being dissolved in the protective film-forming solvent was 1.38 times that of the polymer. Moreover, when the solution after preparation was sampled and analyzed by GPC, the weight average molecular weight (Mw) was 10430 and molecular weight distribution (Mw / Mn) was 2.00. Moreover, content with respect to solid content of PGMEA which is a polymerization solvent was 0.49 weight%. Hexane was not detected.

Example 4
A 1-pentanol solution was prepared in the same manner as in Example 1 except that the reprecipitation and rinse solvent in Example 1 was changed from hexane to heptane (boiling point 98 ° C.). The amount of the solvent contained in the wet polymer before being dissolved in the protective film-forming solvent was 1.39 times by weight of the polymer. Moreover, when the solution after preparation was sampled and analyzed by GPC, the weight average molecular weight (Mw) was 10250 and molecular weight distribution (Mw / Mn) was 2.05. Moreover, content with respect to solid content of PGMEA which is a polymerization solvent was 0.39 weight%. Heptane was not detected.

Comparative Example 1
The wet polymer obtained by centrifugation in Example 1 was taken out without adding 1000 g of hexane, 1-pentanol was added, and the mixture was stirred and dissolved. A ethanol solution was prepared. The amount of the solvent contained in the wet polymer before being dissolved in the protective film-forming solvent was 1.42 times the weight of the polymer. Further, the prepared solution was sampled and analyzed by GPC. As a result, the polymerization average molecular weight (Mw) was 10270, and the molecular weight distribution (Mw / Mn) was 2.02. Moreover, content with respect to solid content of PGMEA which is a polymerization solvent was 6.80 weight%. Hexane was not detected.

Comparative Example 2
The wet polymer obtained by centrifugation in Example 2 was taken out without adding 1000 g of hexane, 1-pentanol was added, and the mixture was stirred and dissolved. A ethanol solution was prepared. The amount of the solvent contained in the wet polymer before being dissolved in the protective film-forming solvent was 1.31 times by weight of the polymer. Further, when the prepared solution was sampled and subjected to GPC analysis, the polymerization average molecular weight (Mw) was 9930, and the molecular weight distribution (Mw / Mn) was 2.01. Moreover, content with respect to solid content of the polymerization solvent cyclohexanenone (CHO) was 9.38 weight%. Hexane was not detected.

Comparative Example 3
A 1-butanol solution was obtained in the same manner as in Example 1 except that 1000 g of hexane was taken out from the wet polymer obtained by centrifugation in Example 3 and 1-butanol was added and dissolved by stirring. Was prepared. The amount of the solvent contained in the wet polymer before being dissolved in the protective film-forming solvent was 1.46 times by weight of the polymer. Further, the prepared solution was sampled and subjected to GPC analysis. As a result, the polymerization average molecular weight (Mw) was 10410, and the molecular weight distribution (Mw / Mn) was 2.00. Moreover, content with respect to solid content of PGMEA which is a polymerization solvent was 12.70 weight%. Hexane was not detected.

Comparative Example 4
The wet polymer obtained by centrifugation in Example 4 was taken out without adding 1000 g of heptane, 1-pentanol was added, and the mixture was stirred and dissolved. A ethanol solution was prepared. The amount of the solvent contained in the wet polymer before being dissolved in the protective film-forming solvent was 1.40 times by weight of the polymer. Further, the prepared solution was sampled and analyzed by GPC. As a result, the polymerization average molecular weight (Mw) was 10210, and the molecular weight distribution (Mw / Mn) was 2.06. Moreover, content with respect to solid content of PGMEA which is a polymerization solvent was 6.67 weight%. Heptane was not detected.

  The results of Examples and Comparative Examples are shown in Tables 1 and 2.

Claims (5)

(1) A step in which a monomer and an initiator dissolved in a polymerization solvent are dropped into a preheated polymerization solvent, and after completion of the dropwise addition, the mixture is aged under heating to polymerize,
(2) contacting the polymerization solution with a poor solvent for the polymer to precipitate the polymer;
(3) the precipitated polymer, centrifugal filtration step of solid-liquid separation at least one method selected from the group consisting of vacuum filtration and pressure filtration,
(4) a step of rinsing the obtained solid polymer,
(5) A step of concentrating the obtained solid polymer after dissolving it in a film-forming solvent,
In the method for producing a polymer solution for a resist protective film including the above steps, the solvent for rinsing the solid polymer is a poor solvent for the polymer, and has a boiling point lower than that of the coating film forming solvent. A method for producing a polymer solution for a resist protective film. The method for producing a polymer solution for a resist protective film according to claim 1, wherein the rinsing is performed twice or more in the method for producing the polymer solution for a resist protective film. 2. The method for producing a polymer solution for a resist protective film according to claim 1, wherein the coating film forming solvent is a fluorine-based solvent, an alcohol-based solvent, or a mixed solvent containing them. In the obtained resist protective film polymer solution, the content of the polymerization solvent used in the polymerization step is 1% by weight or less based on the solid content contained in the resist protective film polymer solution. The manufacturing method of the polymer solution for resist protective films of Claim 1 . Copolymerized with recurring units polymer has fluorine, sulfo group as a hydrophilic group to dissolve in alkali, carboxyl group and a repeating unit having one alcoholic hydroxyl group having a fluoroalkyl group on the carbon atom of at least α-position 2. The method for producing a polymer solution for a resist protective film according to claim 1, wherein the polymer solution is a cured polymer.