JPH0632840A - Singly dispersible copolymer and its production - Google Patents

Abstract

PURPOSE:To obtain a novel singly dispersible copolymer satisfying requirements as a polymer for resist materials having high resolution degrees by anion- polymerizing p-hydroxy-alpha-methylstyrene with styrene. CONSTITUTION:A monomer of formula I (R<1> is H, 1-12C alkyl; R<2>, R<3> are 1-12C alkyl)(e.g. p-t-butoxy-alpha-methylstyrene) is anion-copolymerized with styrene monomer, followed by releasing the group of formula: C(R<1>)(R<2>)(R<3>) from the copolymer to produce the objective copolymer comprising the block copolymer having repeating units of formulas II and III. The anion polymerization is preferably performed in the monomer concentration of 1-14wt.% in the presence of a living anion polymerization initiator such as n-butyl lithium in THF at -78 to 0 deg.C for 10min to 30hr. For the release of the group of the formula: C(R<1>)(R<2>)(R<3>), the copolymer is dissolved in a solvent such as acetone and subsequently dropwisely mixed with an acid such as hydrobromic acid.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel copolymer and a method for producing the same, which is particularly excellent as a functional polymer.
The present invention relates to a monodisperse copolymer of -hydroxy-α-methylstyrene and styrene, and a method for producing the same.

[0002]

2. Description of the Related Art Functional polymers are often used as polymers for resist materials for high-resolution lithography when manufacturing LSI (Large Scale Integrated Circuit) used for computers and the like. Further, in recent years, with the development of LSI manufacturing technology, the degree of integration of LSI has become higher and higher, and a resist material having high resolution and high developability capable of coping with such higher density is required.

To increase the resolution of the resist material,
It is theoretically known that it is effective to narrow the molecular weight distribution of the polymer used (monodispersity). Conventionally, novolac resin has been used as such a polymer for a resist material, but in this case, a method called fractionation has been performed to control the molecular weight distribution (for example,
(Japanese Patent Laid-Open No. 62-121754).

However, such a method of classification has the drawback that the operation is complicated and it takes time, and it is difficult to sufficiently follow the demanding performance that becomes strict. Problem solving is desired. Controlling the polymer to an arbitrary molecular weight is also effective when compatibilizing the polymer as a blending agent, controlling the mechanical properties of the polymer, or adjusting the viscosity of the polymer solution. It is a means.

By the way, a styrene derivative has attracted attention as a polymer whose molecular weight is relatively easy to control. Among them, polyhydroxystyrene is particularly promising because it has excellent development resistance and plasma resistance. It is being noticed and considered.

Conventionally, poly (p-hydroxystyrene) has been produced by a radical polymerization method (Journal of Polymer Science, No. 4, 1949, 703).
Page) and a method for producing narrowly dispersible poly (p-hydroxystyrene), JP-A-59-199705 and Proceedings of the Polymer Society of Japan (Vol. 31, 1982, 11).
P. 49). Furthermore, regarding the method for producing a copolymer of p-hydroxystyrene and styrene, Journal of Polymer Science (A-1, Vol. 7,
1969, pp. 2175 to 2184).

[0007]

However, a polymer for a resist material using monodisperse polyhydroxystyrene has not been industrially produced. Therefore,
While the inventors of the present invention diligently studied the industrial production method of polyhydroxystyrene, they found that a copolymer of p-hydroxy-α-methylstyrene and styrene can be easily made monodisperse, and the present invention was found. Arrived

Therefore, a first object of the present invention is to provide a novel monodisperse copolymer satisfying the required performance as a polymer for a resist material. A second object of the present invention is to provide an industrial production method of a novel monodisperse copolymer which satisfies the required performance as a polymer for a resist material.

[0009]

The above-mentioned various objects of the present invention are achieved by a monodisperse copolymer (p-hydroxy-α-) comprising a unit represented by the following chemical formula 4 and a unit represented by the following chemical formula 5. (Copolymer of methylstyrene and styrene), and a method for producing the same.

[Chemical 4]

[Chemical 5]

In the present invention, the monodispersity means the ratio M _W / M _n of the weight average molecular weight M _W and the number average molecular weight M _n of the copolymer of p-hydroxy-α-methylstyrene and styrene.
Means 1.01 to 1.50. In the case of living polymerization, the weight average molecular weight can be easily calculated by calculating from the weight of the monomer and the number of moles of the initiator, or by using the light scattering method. Further, the number average molecular weight is easily measured using a membrane osmometer.

The molecular weight distribution can be evaluated by gel permeation chromatography (GPC), and the molecular structure is infrared absorption (IR) spectrum or ¹ H.
-It can be easily confirmed by the NMR spectrum. The copolymer of p-hydroxy-α-methylstyrene and styrene of the present invention is obtained by anionically polymerizing a monomer represented by the following chemical formula 6 and a styrene monomer, and then -C
It can be easily produced by removing the groups represented by (R ¹ ) (R ² ) (R ³ ).

[0012]

[Chemical 6] In the above formula, R ¹ is a hydrogen atom or an alkyl group having 1 to 12 carbon atoms, and R ² and R ³ are alkyl groups having 1 to 12 carbon atoms.

In the present invention, it is preferable to use a known living anion initiator from the viewpoint of obtaining a monodisperse copolymer when anionically polymerizing the monomer represented by Chemical formula 6 and the styrene monomer. It is particularly preferred to use organometallic compounds. Preferred organometallic compounds include, for example, n-butyllithium and sec-
Examples thereof include organic alkali metal compounds such as butyl lithium, tert-butyl lithium, sodium naphthalene, sodium anthracene, sodium α-methylstyrene tetrameride, cumyl potassium and cumyl cesium.

In the present invention, the anionic polymerization can be carried out in a non-solvent system, but it is particularly preferably carried out in an organic solvent from the viewpoint of easy adjustment of the reaction rate. Preferred organic solvents include benzene, aromatic hydrocarbon solvents such as toluene, tetrahydrofuran, dioxane, cyclic ether solvents such as tetrahydropyran,
Aliphatic hydrocarbon solvents such as dimethoxyethane, n-hexane, cyclohexane and the like can be mentioned. These organic solvents may be used alone or in combination, but tetrahydrofuran is particularly preferably used.

Monomers (Chemical Formula 6) in an organic solvent for polymerization
The concentration of monomer and styrene monomer represented by is 1
It is preferably about 40% by weight. The polymerization reaction is preferably carried out under high vacuum or in the presence of an inert gas such as nitrogen from the viewpoint of preventing reaction with oxygen and the like. The reaction temperature can be appropriately selected in the range of -100 ° C to the boiling temperature of the reaction solution, but in the case of using a tetrahydrofuran solvent, the range of -78 ° C to 0 ° C and in the case of using a benzene solvent. Room temperature is preferred.

By carrying out the polymerization reaction for about 10 minutes to 30 hours, a copolymer composed of the units represented by the following chemical formulas 7 and 8 can be obtained.

[Chemical 7]

[Chemical 8]

When a block copolymer is obtained as a copolymer, it is preferable to polymerize one monomer and then add the other monomer to carry out the polymerization reaction again. The termination of the polymerization reaction can be carried out by adding a terminating agent such as methanol, water or methyl bromide.

When the living anion polymerization reaction is carried out, the monomers react 100%, so that the amount of the monomer used and the number of moles (number of molecules) of the living anion initiator to be added can be adjusted to obtain a monomer. The molecular weight of the polymer obtained can be controlled appropriately. The molecular weight distribution of the copolymer thus obtained is monodisperse (M _w /
M _n = 1.01-1.50).

Next, --C (R
¹ ) By removing the groups represented by (R ² ) and (R ³ ), the monodisperse copolymer of the present invention can be obtained.
The reaction of cleaving the ether group for eliminating the group represented by --C (R ¹ ) (R ² ) (R ³ ) is carried out by diluting the copolymer with dioxane, acetone, acetonitrile, benzene,
It can be easily carried out by dissolving in a solvent such as water or a mixed solvent thereof and then dropping an acid such as hydrobromic acid. Further, this reaction does not break the main chain of the polymer or cause a cross-linking reaction between the molecules, so that a monodisperse copolymer can be obtained.

In the present invention, the number average molecular weight of the copolymer can be in the range of 500 to 500,000, but it is particularly preferably in the range of 3,000 to 300,000. Further, a copolymer containing the repeating unit represented by the above Chemical formula 4 or 5 can be produced in an arbitrary ratio, but usually (the repeating unit represented by the Chemical formula 4)
/ (The repeating unit represented by Chemical formula 5) has a molar ratio of (0.0
The range is 1 to 99.99) / (99.99 to 0.01). In particular, when the copolymer of the present invention is used as a resist material, the above molar ratio is (60-99.99) / (40-0.
01) is preferable.

[0021]

EFFECT OF THE INVENTION Since the novel copolymer of p-hydroxy-α-methylstyrene and styrene of the present invention has a narrow molecular weight distribution and is monodisperse, it has the required performance as a polymer for a resist material of high resolution. Fulfill. In particular, a block copolymer of p-hydroxy-α-methylstyrene and styrene is suitable as a polymer for a resist material. Further, according to the production method of the present invention, the molecular weight can be arbitrarily controlled, so that the copolymer of the present invention having the physical properties suitable for the application can be industrially produced.

[0022]

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

Example 1 A 1,2-liter flask was charged with 1800 ml of tetrahydrofuran as a solvent and 9 × 10 ^-3 mol of n-butyllithium as an initiator, mixed, cooled to -78 ° C., and then pt-butoxy. -95 g of α-methylstyrene was added, the initiation reaction was carried out while stirring at -20 ° C for 2 hours, and the reaction system was further cooled to -78 ° C to carry out a growth reaction for 10 hours. Next, when 5 g of styrene was added and the polymerization reaction was carried out while stirring for 2 hours, the reaction liquid turned red.

Methanol was added to the obtained reaction solution as a reaction terminator to stop the polymerization reaction, and then the solution was poured into methanol to precipitate the obtained polymer, which was separated and dried to give a white polymer. 39g of coalescence was obtained. The polymer obtained had a styrene content of 5% from the ¹ H-NMR spectrum shown below.
And pt-butoxy-α-methylstyrene 95% was confirmed to be a copolymer having each block chain.

1.4-2.2 ppm: (broad,
_{3H, -C H 2 -C H -} ) 1.4~1.8ppm: ( broad, 2H, -C H
_{2 -C (CH 3) -)} 1.5~2 ppm: ( broad, 3H, -CH
_{2 -C (C H 3) -} ) 1.3~1.6ppm: ( broad, 9H, OC
_{(C H 3) 3) 6~7ppm} : ( broad, 4H, C ₆ H
₄ )

From the GPC elution curve (FIG. 1), it was confirmed that the copolymer had extremely high monodispersity (M _W / M _n = 1.11). The number average molecular weight measured by the membrane osmometry was 1.0 × 10 ⁴ g / mol. Then, 20 g of the obtained copolymer was added to acetone 300
After adding to ml and dissolving, a small amount of concentrated hydrochloric acid was added at 60 ° C. and stirred for 6 hours. The solution was poured into water, washed and dried to obtain 14 g of the polymer of the present invention.

Since no peak derived from t-butyl group was observed in the ¹ H-NMR spectrum of the obtained polymer, the polymer had no poly-p-containing t-butyl group.
It was confirmed to be a copolymer having each block chain of -hydroxy-α-methylstyrene and polystyrene.
In addition, it was confirmed from the GPC elution curve (FIG. 2) that the copolymer was extremely monodisperse. The number average molecular weight measured by the membrane osmometry was 7,000 g / mol.

EXAMPLE 2 A 2.2 liter flask was charged with 1.9 liters of tetrahydrofuran as a solvent and 2 × 10 ^-3 mol of cumylcesium as an initiator, mixed and cooled to -78 ° C., pt-butoxy- 80 g of α-methylstyrene was added. After reacting for 5 hours, a solution prepared by dissolving 20 g of styrene in 200 ml of a tetrahydrofuran solvent was added, and a polymerization reaction was carried out while further stirring for 2 hours. As a result, the reaction solution turned red. Next, methanol was added to the reaction solution as a reaction terminator to stop the polymerization reaction, and the mixture was poured into methanol to precipitate the obtained polymer, which was separated and dried to obtain 80 g of a white polymer. Obtained.

From the ¹ H-NMR spectrum of the obtained polymer, characteristic absorption similar to that in Example 1 was observed, and styrene 2
0% and p-t-butoxy-α-methylstyrene 80%
Was confirmed to be a copolymer having each block chain. Further, from the GPC elution curve (FIG. 3), the obtained copolymer has extremely high monodispersity (M _W / M _n =
1.11) It was confirmed to be a copolymer. The number average molecular weight of the copolymer measured by the membrane osmometry was 4.5 × 10 ⁴ g / mol.

Then, 10 g of the obtained copolymer was added to 100
After dissolving in ml of acetone, a small amount of concentrated hydrochloric acid was added at 60 ° C., and the mixture was stirred for 8 hours, then the obtained solution was poured into water, washed and dried to obtain 7 g of a polymer. From the ¹ H-NMR spectrum of the obtained polymer, no peak derived from t-butyl group was observed.
It was confirmed to be a copolymer having each block chain of poly-p-hydroxy-α-methylstyrene and polystyrene having no butyl group. Further, it was confirmed from the GPC elution curve (FIG. 4) that the copolymer had extremely high monodispersity. The number average molecular weight of the copolymer measured by the membrane osmometry was 3.2 × 10 ⁴ g / mol.

[Brief description of drawings]

FIG. 1 shows the polymer obtained in Example 1 (number average molecular weight 1
(G / mol) GPC elution curve.

2 is a GPC elution curve of the polymer (number average molecular weight of 7,000 g / mol) obtained in Example 1. FIG.

FIG. 3 The polymer obtained in Example 2 (number average molecular weight 4
(5,000 g / mol) is a GPC elution curve.

FIG. 4 The polymer obtained in Example 2 (number average molecular weight 3
2,000 g / mol) GPC elution curve.

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 (4)

[Claims] 1. A monodisperse copolymer comprising a unit represented by the following chemical formula 1 and a unit represented by the following chemical formula 2. [Chemical 1] [Chemical 2] 2. The monodisperse copolymer according to claim 1, wherein the copolymer is a block copolymer comprising a repeating unit represented by the chemical formula 1 and a repeating unit represented by the chemical formula 2. 3. Anionic polymerization of a monomer represented by the following chemical formula 3 and a styrene monomer, followed by —C (R ¹ )
The method for producing a monodisperse copolymer according to claim 1, wherein the groups represented by (R ² ) and (R ³ ) are eliminated. In the formula, R ¹ is a hydrogen atom or an alkyl group having 1 to 12 carbon atoms, and R ² and R ³ are alkyl groups having 1 to 12 carbon atoms. 4. The method for producing a monodisperse copolymer according to claim 3, wherein one monomer is polymerized and then the other monomer is added and polymerized.