JPH0632839A - Singly dispersible copolymer and its production - Google Patents

Abstract

PURPOSE:To readily obtain a novel single dispersible copolymer useful as a polymer for resist materials having high resolution degrees by copolymerizing p-hydroxystyrene with p-hydroxy-alpha-methylstyrene and subsequently subjecting the copolymer to a specific treatment. 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-butoxystyrene) is anion-copolymerized with a monomer of formula II (e.g. p-t-butoxy-alpha-methylstyrene), the copolymer to produce the objective copolymer consisting of units of formulae III and IV polymerization is preferably performed in the presence of a living anion polymerization initiator in THF at -78 to 0 deg.C for 1-30hr. 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 hydrochloric acid. n-Butyl lithium, etc., is preferable as the living anion polymerization initiator.

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.
A monodisperse copolymer of hydroxystyrene and p-hydroxy-α-methylstyrene and a method for producing the same.

[0002]

2. Description of the Related Art Functional polymers are often used as high-resolution resist materials for lithography when manufacturing LSIs (large-scale integrated circuits) used in computers and the like. In recent years, with the development of LSI manufacturing technology, LSI
The degree of integration is further increased, and there is a demand for a resist material having high resolution and high developability that can cope with such higher density.

On the other hand, it is theoretically known that narrowing the molecular weight distribution of the polymer used (making it monodisperse) is effective for increasing the resolution of the resist material. 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, JP-A-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 polyhydroxystyrene is described in JP-A-59-199705 and Proceedings of Polymer Society of Japan (Vol. 31, 1982, p. 1149). Furthermore, for the method for producing a copolymer of p-hydroxystyrene and styrene, see Journal of Polymer Science (A-1, Vol. 7, 1969).
, Pages 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-hydroxystyrene and p-hydroxy-α-methylstyrene can be easily made monodisperse, The present invention has been reached.

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 a method for industrially producing 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-hydroxystyrene and p-copolymer) comprising units represented by the following chemical formula 5 and units represented by the following chemical formula 6. -Hydroxy-α-methylstyrene copolymer), and a method for producing the same.

[Chemical 5]

[Chemical 6]

In the present invention, the monodispersity means the weight average molecular weight M _W and the number average molecular weight M _{n of the} copolymer of p-hydroxystyrene and p-hydroxy-α-methylstyrene.
The ratio M _w / M _n of 1.01 to 1.50 is meant. 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-hydroxystyrene and p-hydroxy-α-methylstyrene of the present invention undergoes anionic polymerization of a monomer represented by the following chemical formula 7 and a monomer represented by the following chemical formula 8 and then -C ( It can be easily produced by eliminating the group represented by R ¹ ) (R ² ) (R ³ ).

[0012]

[Chemical 7]

[Chemical 8] In the above chemical formulas 7 and 8, 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, a known living anion initiator is used in view of obtaining a monodisperse copolymer when anionically polymerizing the monomer represented by Chemical formula 7 and the monomer represented by Chemical formula 8. Preference is given to using, especially organometallic compounds.

Preferred organic metal compounds include, for example, n-butyllithium, sec-butyllithium and ter.
Examples thereof include organic alkali metal compounds such as t-butyllithium, sodium naphthalene, anthracene sodium, α-methylstyrenetetramage sodium, cumyl potassium and cumyl cesium.

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

Monomers (Chemical Formula 7) in an organic solvent for polymerization
It is preferable that the concentration of the monomer represented by and the total amount of the monomer represented by Chemical formula 8) is 1 to 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 1 to 30 hours, a copolymer composed of the units represented by the following chemical formulas 9 and 10 can be obtained.

[Chemical 9]

[Chemical 10]

When a block copolymer is obtained as the copolymer, one of the monomers represented by the chemical formula 7 is polymerized, then the other monomer represented by the chemical formula 8 is added, and the polymerization reaction is carried out again. Good. The termination of the polymerization reaction can be carried out by adding a terminating agent such as methanol, water or methyl bromide.

When living anionic polymerization is carried out, 100% of the monomers react, so the polymer obtained by adjusting the amount of the monomer used and the number of moles (number of molecules) of the living anion initiator added. The molecular weight of 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 for eliminating the group represented by --C (R ¹ ) (R ² ) (R ³ ) is carried out by using the copolymer as a solvent such as dioxane, acetone, acetonitrile, benzene, water or a mixed solvent thereof. It can be easily carried out by adding acid such as hydrochloric acid or hydrobromic acid after the solution is dissolved. 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. A copolymer containing the unit represented by the chemical formula 9 or the chemical formula 10 at an arbitrary ratio can be produced, but usually, the unit represented by the chemical formula 9 / (the chemical formula 10) The unit) has a molar ratio of (0.01-99.99) /
The range is (99.99 to 0.01).

[0022]

The p-hydroxystyrene and p- of the present invention
Since the novel copolymer with hydroxy-α-methylstyrene has a narrow molecular weight distribution and is monodisperse, it satisfies the required performance as a high-resolution polymer for resist materials. Particularly, a block copolymer of poly (p-hydroxystyrene) and poly (hydroxy-α-methylstyrene) is suitable as a polymer for a resist material. Further, according to the production method of the present invention, since the molecular weight can be arbitrarily controlled, the copolymer of the present invention having physical properties suitable for the application,
It can be manufactured industrially.

[0023]

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 2-liter flask was charged with 700 ml of tetrahydrofuran as a solvent and 2 × 10 ⁻³ mol of n-butyllithium as an initiator, mixed and cooled to −78 ° C., and then pt-butoxy. Styrene 20
g was added and the polymerization reaction was carried out while stirring for 2 hours.
Then, 20 g of p-t-butoxy-α-methylstyrene
Was added and the polymerization reaction was carried out with stirring for 20 hours, and the reaction solution turned red.

After adding methanol as a reaction terminator to the obtained reaction solution to terminate the polymerization reaction, the solution is poured into methanol to precipitate the polymer, which is separated and dried to obtain a white polymer. 40 g was obtained. The polymer obtained is a copolymer having 50% of pt-butoxystyrene and 50% of pt-butoxy-α-methylstyrene having each block chain from the ¹ H-NMR spectrum below. It was confirmed.

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 a very high monodispersity (M _W / M _n = 1.11). The number average molecular weight measured by the membrane osmometry was 1.8 × 10 ⁴ g / mol. Then, 20 g of the obtained copolymer was added to acetone 300
After adding to ml to dissolve, a small amount of concentrated hydrochloric acid was added at 60 ° C. and the mixture was stirred for 6 hours. The solution was poured into water, washed and dried to obtain 13 g of the polymer of the present invention.

From the ¹ H-NMR spectrum of the obtained polymer, no peak derived from t-butyl group was observed, so that the polymer had no t-butyl group and poly (p-hydroxystyrene) and poly (p-hydroxystyrene) were not contained. It was confirmed to be a copolymer having each block chain of (p-hydroxy-α-methylstyrene). 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 12,000 g / mol.

EXAMPLE 2 A 2.2 liter flask was charged with 1.5 liters of tetrahydrofuran as a solvent and 1 × 10 ^-3 mol of cumylcesium as an initiator, mixed and cooled to -78 ° C., pt-butoxystyrene. 80 g was added. After reacting for 2 hours, pt-butoxy-α
A solution of 20 g of methylstyrene dissolved in 200 ml of a tetrahydrofuran solvent was added, and the polymerization reaction was carried out while stirring for 20 hours. The reaction solution turned red. Next, methanol was added to the reaction solution as a reaction terminator to stop the polymerization reaction, and then the mixture was poured into methanol to precipitate the obtained polymer, which was separated and dried to obtain 100 g of a white polymer. Obtained.

From the ¹ H-NMR spectrum of the obtained polymer, characteristic absorption similar to that of Example 1 was observed, and p-t-
It was confirmed to be a copolymer having 80% butoxystyrene and 20% pt-butoxy-α-methylstyrene and having each block chain. In addition, it was confirmed from the GPC elution curve (FIG. 3) that the obtained copolymer was a copolymer having extremely high monodispersity (M _W / M _n = 1.14).

The number average molecular weight of the copolymer measured by the membrane osmometry was 10 × 10 ⁴ g / mol. Then, 10 g of the obtained copolymer was dissolved in 100 ml of acetone, a small amount of concentrated hydrochloric acid was added at 60 ° C., and the mixture was stirred for 8 hours. Pour the obtained solution into water and wash
After drying, 6 g of polymer was obtained.

From the ¹ H-NMR spectrum of the obtained polymer, no peak derived from t-butyl group was observed, so that the polymer was identified as poly (p-hydroxystyrene) having no t-butyl group. It was confirmed to be a copolymer having each block chain of poly (p-hydroxy-α-methylstyrene). In addition, 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 6.5 × 10 ⁴ g / mol.

[Brief description of drawings]

FIG. 1 shows the polymer obtained in Example 1 (number average molecular weight 1
8,000 g / mol) GPC elution curve.

FIG. 2 The polymer obtained in Example 1 (number average molecular weight 1
2,000 g / mol) GPC elution curve.

FIG. 3 The polymer obtained in Example 2 (number average molecular weight 10
(G / mol) GPC elution curve.

FIG. 4 The polymer obtained in Example 2 (number average molecular weight 6
(5,000 g / mol) is a 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. Anionically polymerizing a monomer represented by the following chemical formula 3 and a monomer represented by the following chemical formula 4, and then -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. [Chemical 4] In the chemical formulas 3 and 4, R ¹ is a hydrogen atom or a carbon atom number 1 to
12 alkyl groups, R ² and R ³ have 1 carbon atom
~ 12 alkyl groups. 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.