JPH0632849A - P-hydroxystyrene-alpha-methylstyrene block copolymer partially esterified with t-butoxycarbonyl group and its production - Google Patents

Abstract

PURPOSE:To obtain the subject copolymer having a narrow mol.wt. distribution, capable of being developed with an alkali, having a high developing property and a high resolving property, and useful for resist materials, etc., by t- butoxycarbonylating the hydroxyl groups of the polyhydroxystyrene parts in a specific copolymer. CONSTITUTION:The hydroxyl groups of the poly p-hydroxystyrene parts in a singly dispersible p-hydroxystyrene-alpha-methylstyrene block copolymer having a weight-average mol.wt. (Mw)/number-average mol.wt. (Mn) of 1.01-1.5 are partially t-butoxycarbonylated to provide the objective copolymer having repeating units of formulas I, II and III.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is a monodisperse p-hydroxystyrene in which the hydroxyl groups of the poly (p-hydroxystyrene) moiety, which is preferably used as a resist material for LSI, are partially esterified with tert-butoxycarbonyl groups. The present invention relates to an α-methylstyrene block copolymer and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, the problems to be solved by the invention
Functional polymers are often used as base polymers for resist materials used for high-resolution lithography or LSI. In particular, with the recent progress in higher density of LSIs, resist materials are required to have higher resolution and higher developability. As a functional polymer capable of meeting such requirements, novolac resins have hitherto been used. Although it was used in the mainstream, various chemical amplification type resist materials have been studied recently as alternatives.

Of the above-mentioned chemically amplified resist materials, those having a functional group which is easily eliminated by an acid and having different solubilities before and after elimination of the functional group are particularly preferred from the viewpoint of workability. ing. As such a resist material, a polystyrene derivative having excellent plasma resistance is known to be particularly suitable.

When these polymers are used as a base polymer for resist, their molecular weight and molecular weight distribution have a great influence on the developing characteristics and resolution of the resist, but these polymers are usually subjected to a radical polymerization method or a condensation polymerization method. Since it is a polydisperse polymer obtained by, it is not considered from the beginning to control the molecular weight and the molecular weight distribution.Therefore, in order to improve the developability and resolution of the resist, the molecular weight is controlled using a method called fractionation. There is.

However, the method of separation is not only complicated in operation but also has a drawback that it takes time, and it is difficult to sufficiently follow the demanding performance which becomes strict. It could not be a means.

Therefore, it has been desired to develop a high quality polymer suitable as a base polymer for a resist material.

The present invention has been made in order to meet the above-mentioned demand, and has a functional group that is easily eliminated by an acid.
Polyp-, which is useful as a resist material and the like, can be easily developed with an alkali because of its different solubility before and after elimination of the functional group, and has high developability and high resolution.
An object of the present invention is to provide a p-hydroxystyrene-α-methylstyrene block copolymer in which a hydroxyl group of a hydroxystyrene portion is partially esterified with a tert-butoxycarbonyl group, and a method for producing the same.

[0008]

Means and Actions for Solving the Problems As a result of intensive studies for achieving the above object, the present inventor has found that α-methylstyrene represented by the following structural formula (4) and the following structural formula (5)
After the living polymerization with p-tert-butoxystyrene represented by, the tert-butyl group in the molecule is eliminated, or α-methylstyrene represented by the following structural formula (6) and the following structural formula (7) After the living polymerization with p-methoxymethoxystyrene represented by, the methoxymethyl group in the molecule is eliminated, the weight average molecular weight ( _Mw ) / number average molecular weight ( _Mn ) is 1.01 to 1 0.5 of a monodisperse block copolymer of p-hydroxystyrene and α-methylstyrene is obtained, and the hydroxyl groups of the poly-p-hydroxystyrene portion in the block copolymer are partially tert-butoxycarbonyl. To have a repeating unit represented by the following structural formulas (1), (2) and (3), and having a molecular weight distribution of M _w / M _n = 1.
A block copolymer of p-hydroxystyrene and α-methylstyrene, in which the hydroxyl group of the poly-p-hydroxystyrene part of 01 to 1.5 is partially esterified with a tert-butoxycarbonyl group, is obtained. Is easy to control and surely M _w / M _n = 1.01-
In addition to giving a monodisperse block copolymer of 1.5, the monodisperse block copolymer thus obtained has a tert-butoxycarbonyl group which can be easily eliminated by an acid, It can be easily developed with alkali and has high developability and high resolution without the troublesome technique of separation due to monodispersity. The present invention has been completed by finding that it can be suitably used for applications.

[0009]

[Chemical 2]

Therefore, the present invention provides the above structural formula (1),
Poly p-hydroxystyrene having the repeating units represented by (2) and (3) and having a molecular weight distribution of weight average molecular weight (M _w ) / number average molecular weight (M _n ) = 1.01 to 1.5 Part of the hydroxyl group is partially esterified with a tert-butoxycarbonyl group, and a weight average molecular weight ( _Mw ) / number average molecular weight ( _Mn ) of 1.01 to 1.5 The above-mentioned p-hydroxystyrene-α-methylstyrene block copolymer for partially tert-butoxycarbonylating the hydroxyl groups of the poly-p-hydroxystyrene part in the monodisperse block copolymer of p-hydroxystyrene and α-methylstyrene. A method for producing a polymer is provided.

The present invention will be described in more detail below. The block copolymer of the present invention has a repeating unit represented by the following structural formulas (1), (2) and (3). The hydroxyl group of the styrene portion is partially esterified with a tert-butoxycarbonyl group.

[0012]

[Chemical 3]

Here, the above equations (1), (2) and (3)
The repeating unit may be contained at any ratio, but usually the weight fraction is 0.01 ≦ structural formula (1) ≦ 99.98,0.
It is preferable to contain them in a ratio such that 01 ≦ structural formula (2) ≦ 99.98, 0.01 ≦ structural formula (3) ≦ 99.98, and (1) + (2) + (3) = 1. , Particularly when the block copolymer of the present invention is used as a resist material,
From the viewpoint of the difference in solubility during development of the resist, 20 ≦
(1) ≤ 99.98, 0.01 ≤ (2) ≤ 50, 0.0
1 ≦ (3) ≦ 80, more preferably 50 ≦ (1) ≦ 9
9.98, 0.01 ≦ (2) ≦ 20, 0.01 ≦ (3)
It is preferable that ≦ 45.

Further, in the above block copolymer, the ratio of partial esterification of hydroxyl groups in the molecule by t-butoxycarbonyl groups is 0.1 to 80% (weight%, the same applies hereinafter) with respect to poly-p-hydroxystyrene. , Especially 5 to 45%
Is preferred.

The above-mentioned p-hydroxystyrene of the present invention and α
The block copolymer with methylstyrene is a monodisperse polymer having a molecular weight distribution such that _Mw / _Mn is in the range of 1.01 to 1.5, preferably 1.01 to 1.3. . Those having M _w / M _n less than 1.01 are technically difficult to synthesize, and if it exceeds 1.5, it is impossible to obtain a high resolution and a high degree of development that can be used as a resist material. The weight average molecular weight (M _w ) is determined by the light scattering method.
The number average molecular weight (M _n ) can be measured using a membrane osmometer.

Further, the average molecular weight of the above block copolymer is not particularly limited, but when it is used as a resist material, the number average molecular weight is generally 500 to 50.
It is preferably in the range of 30,000, particularly preferably in the range of 3,000 to 300,000. If the number average molecular weight is less than 500, the resist material may not have film strength.
If it exceeds 50,000, there is a problem in developing characteristics and compatibility,
In some cases, high resolution and high development degree cannot be obtained.

The molecular weight distribution can be evaluated by gel permeation chromatography (GPC), and the molecular structure can be easily confirmed by ¹ H-NMR spectrum.

In the present invention, the monodisperse partially esterified p-hydroxystyrene-α-methylstyrene block copolymer described above is a hydroxyl group of the monodisperse p-hydroxystyrene-α-methylstyrene block copolymer as shown below. Can be easily obtained by partially esterifying with a t-butoxycarbonyl group.

First, the monodisperse block copolymer of p-hydroxystyrene and α-methylstyrene is subjected to living polymerization of two kinds of monomers represented by the following structural formulas (4) and (5), and then, It can be obtained by removing the t-butyl group in the molecule.

[0020]

[Chemical 4]

Further, the monodisperse block copolymer of p-hydroxystyrene and α-methylstyrene is subjected to living polymerization of two kinds of monomers represented by the following structural formulas (6) and (7), and then in the molecule. It can also be obtained by removing the methoxymethyl group.

[0022]

[Chemical 5]

In living polymerization of the above-mentioned monomer, it is preferable to use an organometallic compound as a polymerization initiator. Examples of the organometallic compound include n-butyllithium, sec-butyllithium, t-butyllithium, sodium naphthalene, sodium anthracene,
Examples thereof include organic alkali metals such as α-methylstyrene tetramargin sodium, cumyl potassium, and cumyl cesium. The amount of the polymerization initiator added depends on the molecular weight of the produced polymer and is calculated from the molecular weight and the weight of the monomer.

Living polymerization is generally desirably carried out in an organic solvent. Examples of the organic solvent include aromatic hydrocarbons, cyclic ethers, aliphatic hydrocarbon solvents and the like, and specific examples thereof include benzene, toluene, tetrahydrofuran, dioxane, tetrahydropyran, dimethoxyethane, n-hexane and cyclohexane. These organic solvents may be used alone or in combination of two or more. The concentration of both monomers (formula (4) and formula (5) or formula (6) and formula (7)) in the organic solvent is preferably 1 to 50%, more preferably 1 to 30%.

The reaction is preferably carried out under high vacuum or under stirring in an inert gas atmosphere such as argon or nitrogen. The reaction temperature can be freely selected from −100 ° C. to the boiling point temperature of the organic solvent used, but it is particularly preferable to carry out the reaction at −78 ° C. to 0 ° C. with a tetrahydrofuran solvent and at room temperature with a benzene solvent. Also, the reaction is usually about 1
It is suitable to carry out for 0 minutes to 30 hours.

The reaction is stopped by adding a terminating agent such as methanol, water or methyl bromide to the reaction system. Then, the obtained reaction mixture solution is precipitated in a suitable solvent, for example, methanol, washed and dried to purify and isolate the polymer produced by the polymerization reaction. When the living polymerization reaction is carried out in this manner, in the reaction of the monomers of the above formulas (4) and (5), only vinyl groups in both monomers are selectively reacted and polymerized, and the following structural formula (8) And the block copolymer having the repeating units represented by (9) is obtained.

[0027]

[Chemical 6]

Further, also in the reaction of the monomers of the above formulas (6) and (7), only vinyl groups in both monomers selectively react and polymerize, and are represented by the following structural formulas (10) and (11). A block copolymer having repeating units is obtained.

[0029]

[Chemical 7]

The copolymer thus obtained is a monodisperse polymer having a molecular weight distribution M _w / M _n of 1.01 to 1.5.

Since the yield of the polymer in the above reaction is almost 100%, the molecular weight of the obtained polymer can be easily calculated from the weight of the monomer used and the number of moles (number of molecules) of the polymerization initiator.

Next, a t-butyl group in the copolymer having the repeating units represented by the above formulas (8) and (9) or a copolymer having the repeating units represented by the above formulas (10) and (11). By removing the methoxymethyl group in the polymer, a block copolymer of p-hydroxystyrene having a phenol residue structural unit represented by the following structural formulas (12) and (13) and α-methylstyrene was obtained. To be

[0033]

[Chemical 8]

The elimination reaction of the above t-butyl group and methoxymethyl group is carried out by dioxane, acetone, acetonitrile,
This can be easily carried out by dropping an acid such as hydrochloric acid or hydrobromic acid in benzene or the like alone or in a mixed solvent.
In these reactions, the main chain of the polymer is not cleaved and the crosslinking reaction between molecules does not occur,
The molecular weight distribution of the precursor block copolymer of p-t-butoxystyrene or methoxymethoxystyrene and α-methylstyrene is maintained as it is, and monodisperse p-hydroxystyrene and α-methylstyrene having a narrow molecular weight distribution A copolymer can be obtained.

In this case, the addition amount of the acid is poly (pt)
-Butoxystyrene) and an equimolar amount or more.

Further, the reaction for partially t-butoxycarbonylating the hydroxyl groups of the poly-p-hydroxystyrene portion of the block copolymer of monodisperse p-hydroxystyrene and α-methylstyrene described above is carried out by a conventional t reaction. It can be easily carried out in the same manner as in the butoxycarbonylation reaction.

For example, as a t-butoxycarbonylation reagent, t-butyl chloroformate, di-t-butyl carbonate, t-butoxycarbonylthio- (4,6-dimethylpyrazine), t-butylpentachlorophenyl carbonate, 2- (t-butoxycarbonyloxyimino) -2-phenylacetonitrile or the like is used, and pyridine, tetraethylamine or the like is used as an acid trap solvent, and the hydroxyl group of the monodisperse poly-p-hydroxystyrene part is partially t. -Butoxycarbonylation. In this case, dimethylamine, 4-N, N-dimethylaminopyridine or the like may be added to the reaction system as a t-butoxycarbonylation catalyst, if necessary. The amount of t-butoxycarbonylation reagent used is proportional to the t-butoxycarbonylation rate, and the amount of t-butoxycarbonylation catalyst added can be a catalytic amount. Further, the amount of the acid trap solvent used is preferably equimolar to the t-butoxycarbonylation reagent.

The potassium-t-butoxide is used to make a block copolymer of p-hydroxystyrene and α-methylstyrene into a potassium salt, which is then monodispersed by reaction with di-t-butyl dicarbonate. The copolymer of p-hydroxystyrene and α-methylstyrene can be partially t-butoxycarbonylated. The t-butoxycarbonylation reaction in the present invention is not limited to the above reaction.

The t-butoxycarbonylation rate of the partially esterified monodisperse p-hydroxystyrene-α-methylstyrene copolymer of the present invention thus obtained is ¹ H-
It can be easily confirmed by an NMR spectrum. This t-butoxycarbonylation rate is higher than that of poly-p-hydroxystyrene from the viewpoint of the difference in solubility during development of the resist and the control of the crosslinking reaction, as described above. It is preferably in the range of 0.1 to 80%, particularly 5 to 45%.

[0040]

INDUSTRIAL APPLICABILITY The p-hydroxystyrene-α-methylstyrene block copolymer partially esterified with a t-butoxycarbonyl group of the present invention can be alkali-developed and has a narrow molecular weight distribution. It is suitable as a photosensitive polymer material. According to the production method of the present invention, the molecular weight of the block copolymer of the monodisperse t-butoxycarbonyl group partial ester of p-hydroxystyrene and α-methylstyrene can be controlled arbitrarily and easily. It can be manufactured industrially advantageously.

[0041]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[Example] Monodispersed p-hydroxystyrene and α-methylstyrene
Synthesis of Copolymer of 2000 mL of tetrahydrofuran as a solvent and 9 × 1 of n-butyllithium as an initiator in a 3-liter flask.
0 ^-3 mol was charged and mixed. The obtained mixed solution is -7
After cooling to 8 ° C., 95 g of p-tert-butoxystyrene was added to this solution and the polymerization reaction was carried out while stirring for 2 hours, then 5 g of α-methylstyrene was added and the polymerization reaction was carried out while stirring for 5 hours. When it was carried out, the reaction solution turned red. Then, methanol was added to the obtained reaction solution as a reaction terminator to stop the polymerization reaction, and this solution was poured into methanol to precipitate the obtained polymer, which was separated and dried to give a white 100 g of polymer was obtained.

The ¹ H-NMR measurement results of the obtained polymer are as follows.

[0044]

[Chemical 9]

From the ¹ H-NMR measurement result, it was confirmed that the above copolymer was a copolymer composed of 5% α-methylstyrene and 95% p-tert-butoxystyrene. Further, the number average molecular weight was measured by the membrane osmotic pressure measurement method and found to be 1.0 × 10 ⁴ g / mol. Furthermore, it was confirmed from the results of the GPC elution curve that the monodispersity was extremely high ( _Mw / _Mn = 1.11). In addition, GP
The C elution curve is as shown in FIG.

Then, 100 g of the obtained copolymer was added to 1200 ml of acetone to dissolve it, and a small amount of concentrated hydrochloric acid was added at 60 ° C. The resulting solution was stirred for 8 hours, then poured into water, washed and dried.
68 g of polymer were obtained.

The number average molecular weight of this polymer was measured by the membrane osmometry and found to be 6500 g / mol.
Moreover, the result of having evaluated the molecular weight distribution of this polymer by GPC is as shown in FIG. 2, and it was confirmed that it was a copolymer having extremely high monodispersity. Furthermore, from the ¹ H-NMR measurement results of the polymer obtained here, tert-
Since a peak derived from a butyl group was not observed, it was confirmed that the polymer was a copolymer of poly p-hydroxystyrene and poly α-methylstyrene and had no tert-butyl group.

A partial tert-butoxycarbonyl group
Stellized p-hydroxystyrene and α-methylstyrene
Synthesis of Block Copolymer with Ren 50 g of a copolymer of p-hydroxystyrene and α-methylstyrene (molecular weight 6500, molecular weight distribution 1.11) obtained by living polymerization was dissolved in 1 liter of pyridine,
While stirring at 45 ° C, 35 g of di-t-butyl dicarbonate was added. A gas was generated at the same time as the addition, but the reaction was carried out for 1 hour in a N ₂ stream. The reaction solution was added dropwise to 2 liters of water containing 20 g of concentrated hydrochloric acid to obtain a white precipitate. After filtering, the precipitate was dissolved in 50 ml of acetone and added dropwise to 1 liter of water. After filtering the precipitate, it was dried under vacuum at 40 ° C or lower.

The obtained polymer has the above formulas (1) and (2)
And having a repeating unit of (3), ¹ H-NM
Using the peak of the OH group at 8 ppm in R
As a result of obtaining the introduction rate of the -butoxycarbonyl group, 17.
It was 0% and the molecular weight distribution was 1.12.

[Brief description of drawings]

FIG. 1 is a GPC of a block copolymer of p-tert-butoxystyrene and α-methylstyrene obtained in Examples.
It is a graph which shows an elution curve.

FIG. 2 shows p-hydroxystyrene and α obtained in Examples.
It is a graph which shows the GPC elution curve of a block copolymer with methylstyrene.

Continued Front Page (72) Inventor Fujio Yagihashi 3-2-1 Sakado, Takatsu-ku, Kawasaki-shi, Kanagawa Shin-Etsu Chemical Co., Ltd. Corporate Research Center

Claims (2)

[Claims] 1. A repeating unit represented by the following structural formulas (1), (2) and (3), and having a molecular weight distribution of weight average molecular weight (M _w ) / number average molecular weight (M _n ) = 1. 01-
The p-hydroxystyrene-α-methylstyrene block copolymer in which the hydroxyl group of the poly-p-hydroxystyrene part is partially esterified with a tert-butoxycarbonyl group, which is 1.5. [Chemical 1] 2. Poly in a block copolymer of monodisperse p-hydroxystyrene and α-methylstyrene having a weight average molecular weight (M _w ) / number average molecular weight (M _n ) of 1.01 to 1.5. The hydroxyl group of the p-hydroxystyrene part is partially t
The p- according to claim 1, which is ert-butoxycarbonylated.
A method for producing a hydroxystyrene-α-methylstyrene block copolymer.