JP2006002096A - Conversion of polymer terminal group - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for the conversion of a polymer terminal structure expressed by general formula (1) (R<SB>1</SB>is a substituted or unsubstituted alkyl group, alkenyl group, aryl group, a saturated or unsaturated carbocyclic or heterocyclic group, an alkoxy group or a heterocyclic group bonding through nitrogen atom) and provide a method for producing a resist resin having narrow dispersion and excellent transmittance. <P>SOLUTION: The terminal structure of a narrow dispersion polymer having a polymer terminal structure of general formula (1) is converted by reacting the polymer with a chain transfer agent and a free radical source. A polymer having enhanced ultraviolet transmittance than that before conversion can be produced by the method. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to conversion of polymer end groups, and more particularly to a method for producing a resin component of a resist suitable for a fine processing technique.

Along with the miniaturization of semiconductors, lithography processes using excimer lasers such as KrF and ArF are frequently used. Under such circumstances, development and improvement of a resin that realizes higher sensitivity and resolution as a resist resin are energetically advanced.

For example, as a chemically amplified resist resin used in this lithography process, in the case of KrF excimer laser lithography, polyhydroxystyrene having a high transparency mainly at 248 nm and its hydroxyl group protected with an acid dissociable, dissolution inhibiting group are used. In the case of ArF excimer laser lithography, acrylic resin or cycloolefin resin having high transparency mainly at 193 nm is used. Thus, a resist resin having a low absorbance in the light source wavelength region used for exposure is selected and used.

  Moreover, those resist resins are usually polymer copolymers composed of a plurality of types of monomer units, and in order to achieve high sensitivity and high resolution, the composition ratio, the degree of polymerization, of course, Research is underway to analyze and control molecular weight distribution, stereoregularity, polymerization chain structure and its distribution. And it is expected to control line edge roughness by controlling them.

Conventionally, in radical polymerization that is industrially advantageous, it has been very difficult to precisely control the factors that determine the properties of these polymers, but Reversible is one of the living radical polymerizations that have been actively studied in recent years. It was reported that the molecular weight distribution of the polymer can be controlled by the addition-fragmentation chain transfer (hereinafter referred to as RAFT) method. This is a living polymerization method that exhibits an effect even in an acrylic resin in which narrowing of the dispersion is particularly difficult (Patent Documents 1 and 2).

However, since the polymer obtained by the living radical polymerization method as described above is a living polymer, the polymerization terminal (in the text, the polymerization terminal is the polymerization terminal only on the growth terminal side unless otherwise specified). ), The RAFT reagent residue as a dormant species remains. The remaining ratio of the terminal groups varies depending on the polymerization conditions and is not particularly limited, but is about 50% to 100%.

On the other hand, since the RAFT reagent residue having an unsaturated bond in the structure has a strong absorption band in the ultraviolet region, it is considered that the polymer using the same inhibits ultraviolet light transmission in a specific wavelength region. . In other words, the RAFT reagent is often not sufficient for improving the performance of a resist resin even if it is effective for controlling polymerization.

In order to solve this problem, the terminal group derived from the RAFT transfer agent is brought into contact with a radical source such as 2,2′-azobisisobutyronitrile (hereinafter referred to as AIBN) to thereby terminate the 1-cyano-1-methylethyl terminal. A method for converting to a non-patent document has been found (Patent Document 3), and a similar academic conference has been made (Non-Patent Document 1). However, end group conversion using only AIBN is not necessarily efficient because the transmittance is not sufficiently improved for the number of converted end groups.
WO98 / 01478 WO03 / 020773 Japanese Patent Application No. 2004-38902 Polymer Science Society Proceedings Vol. 53 No. 1 (2004) p313

The object of the present invention is to provide a polymer having a narrow molecular weight distribution and excellent light transmission in the wavelength region during exposure, and particularly derived from a terminal group structure that should be said to be a problem due to the RAFT polymerization method. It is to provide a polymer with improved transmittance reduction.

The present invention adds a free radical source and a chain transfer agent and activates the polymer growth terminal in a dormant state to promote recombination, disproportionation, and chain transfer, and the terminal structure has a specific wavelength transmittance. It is based on the conversion to a structure that does not damage the structure.

  That is, the present invention is a method for converting the terminal structure of a polymer by adding at least one chain transfer agent and at least one free radical source and reacting them.

（式中Ｒ_１は置換もしくは非置換のアルキル基、アルケニル基、アリール基、飽和または不飽和の炭素環または複素環、アルコキシ基、窒素原子を介して結合する複素環を示す。） Another aspect of the present invention is that the terminal structure is obtained by adding at least one chain transfer agent and at least one free radical source to a polymer having a terminal structure represented by the following general formula (1). Is a way to convert

(Wherein R ₁ represents a substituted or unsubstituted alkyl group, alkenyl group, aryl group, saturated or unsaturated carbocyclic or heterocyclic ring, alkoxy group, or a heterocyclic ring bonded via a nitrogen atom.)

（式中Ｒ_２、Ｒ_３はそれぞれ同一でも異なっても良く、置換もしくは非置換のアルキル基、アルケニル基、アリール基、飽和の炭素環、不飽和の炭素環、芳香族、複素環、アルコキシ基、窒素原子を介して結合する複素環を示す。）

（Ｒ_２は式（２）と同じ、Ｒ_４は置換もしくは非置換のアルキル基、アリール基または飽和炭素環または不飽和の炭素環もしくはアルコキシ基を示す。） Still another embodiment of the present invention provides at least one selected from at least one ethylenically unsaturated monomer, at least one free radical source, and a RAFT reagent represented by the following general formula (2) or (3). Into the radical polymerization system containing at least one kind of free radical source (which may be the same as or different from the one used earlier) and at least one kind of chain transfer agent after the polymerization reaction starts. It is a method of converting the terminal structure by adding and reacting.

(Wherein R ₂ and R ₃ may be the same or different and each represents a substituted or unsubstituted alkyl group, alkenyl group, aryl group, saturated carbocyclic ring, unsaturated carbocyclic ring, aromatic group, heterocyclic ring, alkoxy group) Represents a heterocyclic ring bonded through a nitrogen atom.)

(R ₂ is the same as in formula (2), and R ₄ represents a substituted or unsubstituted alkyl group, aryl group, saturated carbocyclic ring, unsaturated carbocyclic ring or alkoxy group.)

Still another embodiment of the present invention is a polymer in which the terminal structure is converted by the above method, in particular, a molecular weight distribution of 1.4 or less, and a weight at which the absorbance of ultraviolet rays having a wavelength of 193 nm per 1 μm film thickness is 0.3 or less. It is a coalescence.

According to the present invention, a terminal group derived from a so-called RAFT reagent used for living radical polymerization can be converted, and a polymer having a higher ultraviolet transmittance at a specific wavelength than before conversion can be provided. When the present invention is applied to a resist resin for an lithography process using an ArF excimer laser, it is possible to improve a decrease in polymer transmittance due to terminal groups.

Hereinafter, the present invention will be described in detail. First, the polymer that is the subject of the treatment according to the present invention can be obtained by conducting a polymerization reaction in the presence of a polymerization initiator by a known method. The polymer may be a homopolymer or a copolymer of two or more, and in the case of a copolymer, the arrangement state may be random or block.

The monomer used as the raw material is not particularly limited as long as it can be polymerized, but an ethylenically unsaturated monomer, in particular, when using a polymer as an ArF resist resin, use of an alicyclic structure ester compound of (meth) acrylic acid. This is preferable in terms of extracting resist performance such as transparency, dry etching resistance and adhesion. Examples thereof include (meth) acrylic acid esters of adamantane, norbornane lactone, γ-butyrolactone, and derivatives having substituents such as an alkyl group, a hydroxyl group, and a carboxyl group on these alicyclic rings. Specifically, 2-methyl-2-adamantyl (meth) acrylate, 2-ethyl-2-adamantyl (meth) acrylate, α-hydroxy-γ-butyrolactone (meth) acrylate, norbornane carbolactyl (meta ) Acrylate, 3-hydroxy-1-adamantyl (meth) acrylate, and the like.

Although the weight average molecular weight of the polymer which concerns on this invention is not specifically limited, 2000-300000 are preferable at the point which exhibits the effect as a resist material, More preferably, it is 3000-30000. The molecular weight distribution represented by Mw / Mn is not particularly limited, but is preferably 1.6 or less, more preferably 1.4 or less, and particularly preferably 1.3 or less in terms of improving line edge roughness.

The kind of the radical polymerization initiator that can be used to obtain the polymer that is the object of the treatment according to the present invention is not particularly limited, but an initiator that generates a radical by heat is preferable. For example, 2,2′-azobis 2,2'-azobisbutyronitriles such as isobutyronitrile (AIBN) and 2,2'-azobis (2-methylbutyronitrile), 2,2'-azobis (4-methoxy-2,4 -Dimethylvaleronitrile), 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobisvaleronitriles, 2,2'-azobis (2-hydroxymethylpropionitrile), etc. 1,2′-azobispropionitriles, 1,1′-azobis-1-alkanenitriles such as 1,1′-azobis (cyclohexane-1-carbonitrile), 2,2 Azo compounds such as azobis (isobutyric acid) dimethyl, di-t-butyl peroxide, dicumyl peroxide, t-butylcumyl peroxide, α, α′-bis (t-butylperoxy-m-isopropyl) benzene, Dialkyl peroxides such as 2,5-di (t-butylperoxy) hexyne-3, t-butylperoxybenzoate, t-butylperoxyacetate, 2,5-dimethyl-2,5-di (benzoylper) Peroxyesters such as oxy) hexane, ketone peroxides such as cyclohexanone peroxide, 3,3,5-trimethylcyclohexanone peroxide, methylcyclohexanone peroxide, 2,2-bis (4,4-di-t- Butylperoxycyclohexyl) propane, 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane, 1,1-bis (t-butylperoxy) cyclohexane, n-butyl-4,4-bis (t-butylperoxy) valate, and the like. Oxyketals, cumene hydroperoxide, diisopropylbenzene hydroperoxide, hydroperoxides such as 2,5-dimethylcyclohexane-2,5-dihydroperoxide, benzoyl peroxide, decanoyl peroxide, lauroyl peroxide, Organic peroxide radical polymerization initiators such as diacyl peroxides such as 2,4-dichlorobenzoyl peroxide and peroxydicarbonates such as bis (t-butylcyclohexyl) peroxydicarbonate can be used. Particularly preferred is AIBN which is easy to obtain and handle.

The agent added to obtain a polymer having a narrow degree of dispersion is not particularly limited, but the RAFT reagent is particularly preferably used for this purpose. The RAFT reagent is not particularly limited as long as it is a polymer represented by the above general formula (2) or (3) and can control polymerization, but in the case of polymerization of a (meth) acrylate monomer, Compounds represented by formulas (4) to (11).

The form of polymerization of the polymer according to the present invention is not particularly limited, such as bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization, etc., but a solvent that dissolves the copolymer produced from the convenience of handling the polymer. It is preferable to carry out the reaction by solution polymerization using. Examples of solvents used for solution polymerization include ethers and ketones, preferably ethers having a boiling point near or above the polymerization temperature, more preferably 1,4-dioxane, tetrahydrofuran and the like. . Although the monomer concentration at the time of polymerization is not particularly limited, it is preferably in the range of 10 to 70% by weight, more preferably 20 to 60% by weight for convenience of handling. Although the polymerization reaction temperature depends on the type of monomer used and the type of initiator, it is preferably a general radical polymerization temperature of 0 ° C. or higher and 150 ° C. or lower, at which the monomer does not decompose.

There is no particular limitation on the free radical source to be input for polymer end group conversion as long as it can activate the dormant species. For example, radical polymerization initiation such as the above-mentioned azo compound or organic peroxide is started. The agent can be used. The amount used is preferably 0.1% by weight to 50% by weight with respect to the entire contents of the reaction system, but is preferably 0.1% by weight to 20% by weight in consideration of the purification step of the polymer. The timing of introducing the free radical source may be the time when the residual monomer is as small as possible after the start of the polymerization reaction, but it is preferable that the polymer purified by performing post-treatment such as reprecipitation is dissolved again in the solvent. About the reaction temperature at the time of injection | throwing-in or after injection | throwing, what is necessary is just the temperature which a radical generate | occur | produces from a free radical source.

（式中Ｒ_５は炭素数１〜２０のアルキル基） Similarly, the chain transfer agent to be introduced for polymer end group conversion is not particularly limited as long as it can induce a chain reaction by a radical, but the substituent does not impair the transmittance by contact with the polymer active radical end. Is preferably bonded to the polymer terminal, and a chain transfer agent represented by the following general formula (12) can be used.

(Wherein R ₅ is an alkyl group having 1 to 20 carbon atoms)

Specific examples of the chain transfer agent represented by the formula (12) include t-dodecyl mercaptan, 2-butanethiol, 1-butanethiol, 1-octanethiol, 1-decanethiol, cyclohexanethiol, 2-methyl-1 -Propanethiol etc. can be used. Particularly preferred is t-dodecyl mercaptan which is easy to obtain and handle. The amount used is preferably 0.1% by weight to 50% by weight with respect to the entire contents of the reaction system, but is preferably 0.1% by weight to 20% by weight in consideration of the purification step of the polymer. There is no particular limitation on the timing of the charging, but it is preferably at the same time as or before the free radical source to be charged for polymer end group conversion.

The reaction time for terminal conversion is not particularly limited, but a time longer than the free radical source half-life is preferred. After the reaction, the polymer of the present invention can be isolated by performing a post-treatment operation such as reprecipitation and purifying it.

（プロトンＮＭＲ測定における、末端基に由来するシグナルの積分値をＡ、末端基以外で重合体全体のプロトンシグナルに由来するシグナルの積分値をＢ、ＲＡＦＴ試薬由来の末端残基１個あたりのプロトン数をＲ、重合体中の計算上のプロトン数（ＧＰＣ測定によるＭｎの値より導いた重合度とカーボンＮＭＲ測定による求まる重合体の平均分子組成より算出する）をＰとする。） About the effect of this invention, it can judge from the light absorbency change of the peak derived from a terminal group in visible and ultraviolet absorption spectrum measurement. Further, when the signal derived from the terminal structure does not overlap with a signal other than the terminal structure in the polymer, the ratio X (%) at which the residue derived from the RAFT reagent is present at the terminal can be calculated from the NMR measurement by the following formula.

(In proton NMR measurement, the integrated value of the signal derived from the terminal group is A, the integrated value of the signal derived from the proton signal of the whole polymer other than the terminal group is B, and the proton per terminal residue derived from the RAFT reagent. The number is R, and the number of protons calculated in the polymer is P (calculated from the degree of polymerization derived from the Mn value by GPC measurement and the average molecular composition of the polymer obtained by carbon NMR measurement).

  If analysis by proton NMR is difficult, the terminal structure can be quantified by measuring the sulfur content by combustion flask-ion chromatography analysis. In this case, the ion content of the polymer combustion product completely burned in the closed flask is dissolved in pure water, and the sulfate ion in the aqueous solution is determined by ion chromatography.

By repeatedly performing the conversion reaction in the present invention, the terminal conversion rate can be further increased. For example, the radical source and the chain transfer agent may be directly added to the reaction solution after the first conversion reaction to start the second reaction, or between the first conversion reaction and the second conversion reaction. A purification step such as reprecipitation may be interposed. However, it is usually possible to obtain a polymer having a clear difference from the polymer before conversion in one reaction.

Although the mechanism by which the polymer processing method according to the present invention gives a highly transparent polymer in a specific ultraviolet light region is not completely clarified, it is generally considered as follows.
First, radicals generated from a free radical source are added to the sulfur atom of the thiocarbonyl structure at the polymer terminal represented by the general formula (1), whereby the RAFT terminal is reactivated and detached from the polymer chain. At this time, the polymer terminal from which the RAFT terminal has been detached is an active radical, and has the possibility of reacting with various substances in the reaction system. To illustrate,
・ First, inactivation due to dissolved oxygen.
Second, chain transfer to solvent.
Third, reaction with the remaining polymerizable monomer.
-Recombination with radicals generated from a fourth source of free radicals.
・ Fifth, chain transfer to chain transfer agent.
Sixth, recombination with the chain transfer agent radical that became active as the reaction progressed.
• Seventh active recombination of polymer ends.
• Re-added to the RAFT reagent structure that was eighth reactivated and detached from the polymer chain.
These are the main possibilities.
Of these, the first to third possibilities can be avoided to some extent by methods such as nitrogen substitution, use of solvent species that do not easily cause chain transfer, and polymer purification.
The fourth possibility corresponds to the reaction described above (Patent Document 3), and in order to make this possibility dominant, the condition for instantaneously decomposing a large amount of free radicals, that is, a thermally decomposable radical When the generator is used, a large amount of free radical source is used at a temperature at which the half-life is shortened. This is very wasteful and not efficient. Furthermore, in order to satisfy the transmittance, which is the purpose of this study, a free radical source with a limited structure must be selected.
Therefore, this researcher came up with the fifth and sixth possibilities. Examples of chain transfer agents include mercaptans, carbon tetrahalides, diphenyl disulfides, tetraalkylthiuram disulfides, and the like. Any chain transfer agent having the ability to undergo chain transfer from a polymer terminal radical can be used. However, when considering the transmittance of the polymer and stability over time, mercaptans give the best effect when used as a resist resin.
The seventh and eighth possibilities can be ignored by making the chain transfer agent present in excess.
The above is considered to be the reason why the efficient transmittance can be improved, and forms the basis of the present invention.

EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not restrict | limited at all by these examples. In addition, the physical property etc. in an Example and a comparative example were measured with the following method.

(Number average molecular weight)
A sample solution obtained by dissolving 20 mg of the copolymer in 5 ml of tetrahydrofuran and filtered through a 0.5 μm membrane filter was measured using a gel permeation chromatography chromatography GPC-101 manufactured by Shodex. Separation column is ShodexGPC
KF-G, KF-805, KF-803, KF-802 are used in series, the solvent is tetrahydrofuran, the flow rate is 1.0 ml / min, the detector is a differential refractometer, the measurement temperature is 40 ° C., the injection amount is 0.1 ml, Styrene was used as the standard polymer.

(Polymer terminal structure)
^It calculated | required by the measurement of < ¹ > H-NMR. This measurement was carried out 64 times by placing about 15% by mass of deuterated chloroform in a 5 mm diameter tube using JNM-AL400 FT-NMR manufactured by JEOL.

(Absorbance measurement)
A polymer cyclohexanone solution was spin-coated on a 1 mm thick quartz plate and baked at 90 ° C. for 90 seconds to form a 1 μm thick polymer film on the quartz plate. The UV absorbance of the polymer film sample having a wavelength of 193 nm was measured using a UV-visible spectrophotometer model V-570 manufactured by JASCO Corporation, with reference to a quartz plate to which no polymer film was applied.

Synthesis Example (Production of polymer having additive residue in terminal group)
2-methyl-2-adamantyl methacrylate 96.4 g, α-hydroxy-γ-butyrolactone methacrylate 35.0 g, 3-hydroxy-1-adamantyl methacrylate 48.6 g, azobisisobutyronitrile 4.3 g, pyrrole-1- A reactor was charged with 7.5 g of thiocarbonyl disulfide and 270 g of dioxane, and after deaeration treatment, a polymerization reaction was carried out at a reaction temperature of 70 ° C. for 12 hours. Next, the reaction solution was diluted with 740 g of tetrahydrofuran, and then poured into 9000 g of a hexane / tetrahydrofuran mixed solvent (weight ratio 9: 1), and the resulting precipitate was filtered off for purification. The collected precipitate was dried under reduced pressure, dissolved in tetrahydrofuran, and purification was repeated to obtain 160 g of a desired resin.

Example 1 [Terminal group treatment using a chain transfer agent]
4.0 g of the polymer synthesized in the above synthesis example was dissolved in 6.0 g of dioxane, charged into a reactor, degassed, heated, and when heated to 75 ° C., 0.43 g of t-dodecyl mercaptan, azobisisobutyronitrile. 0.35 g was added and reacted at 75 ° C. for 7 hours. Next, the reaction solution was diluted with 17 g of tetrahydrofuran, and then poured into 200 g of a mixed solvent of hexane / tetrahydrofuran (weight ratio 9: 1), and the resulting precipitate was filtered off for purification. The collected precipitate was dried under reduced pressure, dissolved in 16 g of tetrahydrofuran, poured into 180 g of methanol, and the resulting precipitate was filtered off again to obtain 3.5 g of the desired resin. GPC analysis of the recovered polymer revealed that Mn (number average molecular weight) was 8000 and Mw / Mn (molecular weight distribution) was 1.2. The proportion having a pyrrole structure in the terminal group determined from the above-mentioned ¹ H-NMR integration ratio was 19%, and the absorbance per 1 μm of the resin film thickness was 0.28.

Example 2 [Repeated end group treatment with chain transfer agent]
2.0 g of the polymer treated in Example 1 was dissolved in 3.0 g of dioxane, charged into a reactor, degassed, heated and reached 75 ° C., 0.22 g of t-dodecyl mercaptan, azobisisobutyro 0.18 g of nitrile was added and the reaction was carried out at 75 ° C. for 7 hours. Next, the reaction solution was diluted with 8.5 g of tetrahydrofuran and then poured into 100 g of a mixed solvent of hexane / tetrahydrofuran (weight ratio 9 to 1), and the resulting precipitate was filtered off for purification. The collected precipitate was dried under reduced pressure, dissolved in 8.0 g of tetrahydrofuran, poured into 90 g of methanol, and the resulting precipitate was filtered off again to obtain 1.8 g of the desired resin. GPC analysis of the recovered polymer revealed that Mn (number average molecular weight) was 8000 and Mw / Mn (molecular weight distribution) was 1.2. The proportion having a pyrrole structure in the terminal group determined from the ¹ H-NMR integration ratio described above was 12%, and the absorbance per 1 μm of the resin film thickness was 0.27.

Comparative Example 1 [Normal radical polymerization]
A reaction vessel was charged with 14 g of dioxane, and 9.6 g of 2-methyl-2-adamantyl methacrylate, 3.5 g of α-hydroxy-γ-butyrolactone methacrylate, 4.9 g of 3-hydroxy-1-adamantyl methacrylate, azobisiso 1.4 g of butyronitrile and 14 g of dioxane were charged, and after deaeration treatment, the reaction vessel was kept at 70 ° C. and dropped from the dropping layer in 2 hours. After aging for 4 hours, the reaction solution was diluted with 74 g of tetrahydrofuran and then poured into 900 g of a hexane / tetrahydrofuran mixed solvent (weight ratio 9 to 1), and the resulting precipitate was purified by filtration. The collected precipitate was dried under reduced pressure, dissolved in tetrahydrofuran and purified repeatedly to obtain 14 g of the desired resin. GPC analysis of the recovered polymer revealed that Mn (number average molecular weight) was 5000 and Mw / Mn (molecular weight distribution) was 1.9. The proportion having a pyrrole structure in the terminal group determined from the above-mentioned ¹ H-NMR integration ratio was 0%, and the absorbance per 1 μm of the resin film thickness was 0.26.

Comparative Example 2 [Production of polymer without end group conversion treatment]
4.0 g of the polymer synthesized in Synthesis Example 1 is diluted with 6.0 g of dioxane and 17 g of tetrahydrofuran and then poured into 200 g of a mixed solvent of hexane / tetrahydrofuran (weight ratio 9 to 1), and the resulting precipitate is filtered off. Purification was performed. The collected precipitate was dried under reduced pressure, dissolved in 16 g of tetrahydrofuran, poured into 180 g of methanol, and the resulting precipitate was filtered off again to obtain 3.6 g of the desired resin. GPC analysis of the recovered polymer revealed that Mn (number average molecular weight) was 8000 and Mw / Mn (molecular weight distribution) was 1.2. The ratio of having a pyrrole structure in the terminal group determined from the above-mentioned ¹ H-NMR integration ratio was 61%, and the absorbance per 1 μm of the resin film thickness was 0.36.

Comparative Example 3 [End group treatment without chain transfer agent]
4.0 g of the polymer synthesized in Synthesis Example 1 was dissolved in 6.0 g of dioxane, charged into a reactor, degassed, heated, and when it reached 75 ° C., 0.35 g of azobisisobutyronitrile was added and 75 ° C. The reaction was carried out for 7 hours. Next, the reaction solution was diluted with 17 g of tetrahydrofuran, and then poured into 200 g of a mixed solvent of hexane / tetrahydrofuran (weight ratio 9: 1), and the resulting precipitate was filtered off for purification. The collected precipitate was dried under reduced pressure, dissolved in 16 g of tetrahydrofuran, poured into 180 g of methanol, and the resulting precipitate was filtered off again to obtain 3.5 g of the desired resin. GPC analysis of the recovered polymer revealed that Mn (number average molecular weight) was 8000 and Mw / Mn (molecular weight distribution) was 1.2. The proportion having a pyrrole structure in the terminal group determined from the integration ratio of ¹ H-NMR described above was 23%, and the absorbance per 1 μm of the resin film thickness was 0.31.

Comparative Example 4 [Repeated end group treatment without chain transfer agent]
2.0 g of the polymer treated in Comparative Example 3 was dissolved in 3.0 g of dioxane, charged into a reactor, degassed, heated and reached 75 ° C., and 0.18 g of azobisisobutyronitrile was added. The reaction was carried out at 7 ° C. for 7 hours. Next, the reaction solution was diluted with 8.5 g of tetrahydrofuran and then poured into 100 g of a mixed solvent of hexane / tetrahydrofuran (weight ratio 9 to 1), and the resulting precipitate was filtered off for purification. The collected precipitate was dried under reduced pressure, dissolved in 8.0 g of tetrahydrofuran, poured into 90 g of methanol, and the resulting precipitate was filtered off again to obtain 1.8 g of the desired resin. GPC analysis of the recovered polymer revealed that Mn (number average molecular weight) was 8000 and Mw / Mn (molecular weight distribution) was 1.2. The proportion having a pyrrole structure in the terminal group determined from the ¹ H-NMR integration ratio described above was 14%, and the absorbance per 1 μm film thickness of the resin was 0.30.

Comparative Example 5 [End group treatment without chain transfer agent]
3.5 g of resin was obtained by the same operation except that the amount of azobisisobutyronitrile used in Comparative Example 3 was doubled. GPC analysis of the recovered polymer revealed that Mn (number average molecular weight) was 8000 and Mw / Mn (molecular weight distribution) was 1.2. The proportion having a pyrrole structure in the terminal group determined from the above-mentioned ¹ H-NMR integration ratio was 22%, and the absorbance per 1 μm of the resin film thickness was 0.30.

Comparative Example 6 [Terminal Group Treatment without Chain Transfer Agent]
3.5 g of resin was obtained by the same operation except that the amount of azobisisobutyronitrile used in Comparative Example 3 was doubled using the resin obtained in Comparative Example 5. GPC analysis of the recovered polymer revealed that Mn (number average molecular weight) was 8000 and Mw / Mn (molecular weight distribution) was 1.2. The proportion having a pyrrole structure in the terminal group determined from the above-mentioned ¹ H-NMR integration ratio was 15%, and the absorbance per 1 μm film thickness of the resin was 0.30.

Example 3 [End group treatment continuously with polymerization]
2-methyl-2-adamantyl methacrylate 48.2 g, α-hydroxy-γ-butyrolactone methacrylate 17.5 g, 3-hydroxy-1-adamantyl methacrylate 24.3 g, azobisisobutyronitrile 2.1 g, pyrrole-1- A reactor was charged with 3.7 g of thiocarbonyl disulfide and 135 g of dioxane, and after deaeration treatment, a polymerization reaction was performed at a reaction temperature of 70 ° C. for 12 hours. Subsequently, 9.7 g of t-dodecyl mercaptan and 7.8 g of azobisisobutyronitrile were added and further reacted at 75 ° C. for 7 hours. Next, the reaction solution was diluted with 370 g of tetrahydrofuran, poured into 4500 g of a hexane / tetrahydrofuran mixed solvent (weight ratio of 9: 1), and the resulting precipitate was separated by filtration for purification. The recovered precipitate was dried under reduced pressure, dissolved in tetrahydrofuran, poured into 180 g of methanol, and the resulting precipitate was filtered off again to obtain a desired resin of 82 g. GPC analysis of the recovered polymer revealed that Mn (number average molecular weight) was 8000 and Mw / Mn (molecular weight distribution) was 1.2. The proportion having a pyrrole structure in the terminal group determined from the ¹ H-NMR integration ratio described above was 22%, and the absorbance per 1 μm of the resin film thickness was 0.28.

As shown in Table 1, the absorbance at a wavelength of 193 nm per 1 μm film thickness of the polymer end-treated with a free radical source and a chain transfer agent is 0.27 to 0.28 (Examples 1 to 3). Since it is not used, the absorbance of the polymer which is not narrowly dispersed (0.26, Comparative Example 1) is comparable. On the other hand, 0.36 was not subjected to terminal treatment (Comparative Example 2), and only 0.30 was treated with a free radical source (Comparative Examples 3 to 6).

Claims (10)

  A method of converting the terminal structure of a polymer by adding at least one chain transfer agent and at least one free radical source to the polymer and reacting them. The method according to claim 1, wherein the polymer has a terminal structure represented by the following general formula (1).

(Wherein R ₁ represents a substituted or unsubstituted alkyl group, alkenyl group, aryl group, saturated or unsaturated carbocyclic or heterocyclic ring, alkoxy group, or a heterocyclic ring bonded via a nitrogen atom.) Initiation of polymerization reaction in a radical polymerization system comprising at least one type of ethylenically unsaturated monomer, at least one type of free radical source, and at least one type selected from RAFT reagents represented by the following general formula (2) or (3) Later, the terminal structure by adding at least one kind of free radical source (which may be the same as or different from the one used earlier) and at least one kind of chain transfer agent to react with each other is obtained. How to convert.

(Wherein R ₂ and R ₃ may be the same or different and each represents a substituted or unsubstituted alkyl group, alkenyl group, aryl group, saturated carbocyclic ring, unsaturated carbocyclic ring, aromatic group, heterocyclic ring, alkoxy group) Represents a heterocyclic ring bonded through a nitrogen atom.)

(R ₂ is the same as in formula (2), and R ₄ represents a substituted or unsubstituted alkyl group, aryl group, saturated carbocyclic ring, unsaturated carbocyclic ring or alkoxy group.) The method according to any one of claims 1 to 3, wherein the free radical source is an azo compound or an organic peroxide. The method according to any one of claims 1 to 4, wherein the chain transfer agent is represented by the following general formula (4).

(Wherein R ₅ is an alkyl group having 1 to 20 carbon atoms) The method according to any one of claims 3 to 5, wherein at least one of the ethylenically unsaturated monomers is a (meth) acrylic acid ester compound.   The polymer which converted the terminal structure by the method of any one of Claims 1-6.   The molecular weight distribution (Mw / Mn) obtained by converting the terminal structure by the method according to any one of claims 1 to 6 is 1.4 or less, and the absorbance of ultraviolet rays having a wavelength of 193 nm per 1 μm film thickness is 0.00. A polymer of 3 or less.   The polymer according to claim 7 or 8, having a weight average molecular weight of 2,000 to 300,000. Use of the polymer according to any one of claims 7 to 9 as a resist resin.