JPH0665323A - Monodisperse copolymer and its production - Google Patents

Abstract

PURPOSE:To produce a monodisperse copolymer comprising two kinds of structural units and meeting the requirements of a polymer for a resist material by subjecting two specific monomers to anionic copolymn. CONSTITUTION:This monodisperse copolymer comprising structural units of formulas II and IV is obtd. by subjecting monomers of formulas I and II to anionic copolymn. In the anionic copolymn., a known living anionic polymn. initiator, esp. an organometallic compd.(e.g. n-butyllithium), is pref. used to improve the monodisperseness, The copolymn. is pref. carried out in an org. solvent (e.g. tetrahydrofuran) to facilitate the control of reaction rate. The obtd. copolymer meets the requirements of a polymer for a high-resolution resist material.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a novel copolymer and a method for producing the same, and more particularly to a monodisperse copolymer excellent as a functional polymer and a method for producing the same.

[0002]

2. Description of the Related Art Functional polymers are widely used as polymers for high-resolution lithography resist materials when manufacturing LSIs (Large Scale Integrated Circuits) used in computers and the like. 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 a high resolution and a high developability capable of coping with the higher density has been demanded.

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).
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. 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. On the other hand, a chemically amplified resist material having a functional group that is easily eliminated by an acid and having different solubilities before and after the elimination of the functional group is excellent in workability.
Various studies have been conducted to improve the production efficiency of I and the like. As such a chemically amplified resist material polymer, a styrene derivative polymer having excellent plasma resistance has been known.

[0005]

However, since the polymer of the styrene derivative used as the polymer for the resist material is conventionally produced by the radical polymerization method or the condensation polymerization method, it is difficult to control the molecular weight and the molecular weight distribution. Therefore, it is difficult to produce a monodisperse styrene derivative polymer that sufficiently satisfies the required performance as a polymer for a resist material.

Therefore, as a result of diligent studies on polymers of styrene derivatives, the present inventors found a novel monodisperse copolymer satisfying the required performance as a polymer for resist materials and a method for producing the same, and arrived at the present invention. did. Therefore, the first object of the present invention is to provide a novel monodisperse copolymer which satisfies the required performance as a polymer for resist materials. A second object of the present invention is to provide a novel method for producing a monodisperse copolymer which can satisfy the required performance as a polymer for a resist material and can be controlled to an arbitrary molecular weight.

[0007]

The above-mentioned various objects of the present invention are achieved by a monodisperse copolymer comprising a unit represented by the following chemical formula 5 and a unit represented by the following chemical formula 6, and a method for producing the same. Was done.

[Chemical 5]

[Chemical 6] In the formula, R is a hydrogen atom or a methyl group.

In the present invention, the monodispersity means the ratio M _W / M of the weight average molecular weight M _W and the number average molecular weight M _n of the copolymer.
It means that _n is 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 can be easily confirmed by infrared absorption (IR) spectrum or ¹ H-NMR spectrum.

The monodisperse copolymer composed of the units represented by the chemical formulas 5 and 6 of the present invention is obtained by anionic polymerization of the monomer represented by the following chemical formula 7 and the monomer represented by the following chemical formula 8. It can be easily manufactured.

[Chemical 7]

[Chemical 8] In the formula, R is a hydrogen atom or a methyl group.

In the present invention, it is preferable to use a living anion initiator in the anionic polymerization of the monomer represented by Chemical formula 7 and the monomer represented by Chemical formula 8 from the viewpoint of improving monodispersibility. It is particularly preferred to use organometallic compounds. Preferred organic metal compounds include, for example, n-butyllithium, sec-butyllithium, tert-butyllithium, sodium naphthalene, potassium naphthalene, sodium anthracene, α
—Organic alkali metal compounds such as methylstyrene tetramargin sodium, cumyl potassium, cumyl cesium, and the like.

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.

All monomers in the organic solvent during the polymerization reaction (monomers represented by Chemical formula 7 and monomers represented by Chemical formula 8)
The concentration is preferably 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 10 minutes to 30 hours, a monodisperse copolymer having the units of Chemical formulas 5 and 6 can be obtained. The termination of the polymerization reaction can be carried out by adding a terminating agent such as methanol, water or methyl bromide, whereby a copolymer having a desired molecular weight can be easily obtained. In this case, since the active terminal during the polymerization reaction has a color peculiar to the anion, the termination of the polymerization reaction can be easily confirmed by the presence or absence of this color.

When a block polymer is obtained as a copolymer, one monomer is polymerized, the other monomer is added, and the polymerization reaction is carried out again. A random copolymer is used as the copolymer. When it is obtained, the monomer represented by Chemical formula 7 and the monomer represented by Chemical formula 8 may be mixed in advance, and the obtained mixture may be polymerized. When living anionic polymerization is carried out, the monomer reacts 100%, so the molecular weight of 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. Can be controlled appropriately.

The molecular weight distribution of the copolymer thus obtained is monodisperse (M _w / M _n = 1.01 to 1.5).
0). In the present invention, the number average molecular weight of the copolymer is 5
It may be in the range of 00 to 500,000, but 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 5 or 6 in an arbitrary ratio can be produced, but usually, (the repeating unit represented by the Chemical formula 5) / ( The molar ratio of the repeating units represented is (0.01-9)
The range is 9.99) / (99.99 to 0.01).

[0016]

Since the novel copolymer of the present invention has a narrow molecular weight distribution and is monodisperse, it satisfies the required performance as a polymer for a resist material having high resolution. Particularly, the block copolymer of the polymer represented by Chemical formula 5 and the polymer represented by Chemical formula 6 is suitable as a polymer for a resist material. Further, according to the production method of the present invention, the molecular weight can be controlled as desired, so that a monodisperse copolymer having physical properties suitable for the intended use can be easily produced.

[0017]

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 liter flask was charged with 1800 ml of tetrahydrofuran as a solvent and 9 × 10 ⁻³ mol of n-butyllithium as an initiator, mixed and cooled to −78 ° C., and then 5 g of styrene was added. After polymerizing for 1 hour, p-methoxymethoxy-α-
When 95 g of methyl styrene was added and the polymerization reaction was carried out while stirring for 20 hours, the reaction liquid turned red. Then, 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 obtain a white polymer. 100 g was obtained.

From the ¹ H-NMR spectrum, the obtained polymer was found to contain 5% styrene and p-methoxymethoxy-.
It was confirmed to be a block copolymer having 95% of α-methylstyrene portion. Furthermore, from the GPC elution curve (FIG. 1), the monodisperse copolymer (M _W / M _n = 1.1
It was confirmed to be 1).

The results of the above ¹ H-NMR are as follows. 1.4～2.2Ppm :( broad, 3H, -C H ₂ -
CH-) 1.4~1.8ppm :( broad, 2H, -C H ₂ C
(CH ₃₎ -) 1.5~2.0ppm :( broad, 3H, -CH ₂ C
_{(C H 3) -) 1.3~1.6ppm} :( broad, 9H, OC (C H
₃ ) ₃ 3.5-4.0 ppm: (broad, 3H, -OC
H ₃₎ 5.0~5.5ppm :( broad, 2H, -OC H ₂
O-) 6.0~7.0ppm :( broad, 4H, C ₆ H ₄₎ The number-average molecular weight measured by membrane osmometry is
It was 5.5 × 10 ⁴ g / mol.

EXAMPLE 2 To a 2.2 liter flask were charged 1.5 liters of tetrahydrofuran as a solvent and 1 × 10 ^-3 mol of cumylcesium as an initiator, mixed and cooled to -78 ° C., and then 20 g of styrene was added, The polymerization reaction was carried out while stirring for 1 hour. Next, when 20 g of p-methoxymethoxy-α-methylstyrene was added and the polymerization reaction was carried out while stirring for 5 hours, the reaction solution turned red. Then, methanol was added to the reaction solution as a reaction terminator to stop the polymerization reaction, and then the solution was poured into methanol to precipitate the polymer, which was separated and dried to obtain 40 g of a white polymer. Obtained.

From the ¹ H-NMR spectrum of the obtained polymer, the same characteristic absorption as in Example 1 was observed, and a block copolymer having 50% styrene and 50% p-methoxymethoxy-α-methylstyrene was obtained. It was confirmed to be a polymer. Further, from the GPC elution curve (Fig. 2), the obtained copolymer was a monodisperse copolymer ( _Mw / _Mn =
1.14) was confirmed. The number average molecular weight of the copolymer measured by the membrane osmometry is 3.5.
It was × 10 ⁴ g / mol.

Example 3 A 3.2 liter flask was charged with 1,000 ml of tetrahydrofuran as a solvent and 2 × 10 ⁻³ mol of n-butyllithium as an initiator, mixed and cooled to −20 ° C., and then α-methyl. 10 g of styrene
Was added and the reaction was started for 1 hour.
The mixture was cooled to room temperature, and the polymerization reaction was carried out while stirring for 8 hours. Then, 30 g of p-methoxymethoxy-α-methylstyrene
Was added and the polymerization reaction was carried out with stirring for 20 hours, and the reaction solution turned red. Next, methanol was added as a reaction terminator to the obtained reaction solution to stop the polymerization reaction, and then the solution was poured into methanol to precipitate the obtained polymer, which was separated and dried to obtain a white polymer. 40 g was obtained.

From the ¹ H-NMR spectrum, it was confirmed that the obtained polymer was a block copolymer having 25% of α-methylstyrene moiety and 75% of p-methoxymethoxy-α-methylstyrene moiety. . Furthermore, GPC
From the elution curve (FIG. 3), it was confirmed that the obtained polymer was a monodisperse copolymer (M _W / M _n = 1.11). The number average molecular weight measured by the membrane osmometry was 1.8 × 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.

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

FIG. 3 The polymer obtained in Example 3 (number average molecular weight 1
8,000 g / mol) GPC elution curve.

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 2] In the formula, R is a hydrogen atom or a methyl group. 2. The monodisperse copolymer according to claim 1, wherein the copolymer is a block copolymer of a repeating unit represented by the chemical formula 1 and a repeating unit represented by the chemical formula 2. 3. The method for producing a monodisperse copolymer according to claim 1, wherein the monomer represented by the following chemical formula 3 and the monomer represented by the following chemical formula 4 are anionically polymerized. 3] [Chemical 4] In the formula, R is a hydrogen atom or a methyl group. 4. The method according to claim 3, wherein one monomer is polymerized and then the other monomer is added to polymerize.
The method for producing the monodisperse copolymer according to 1.