JPH0641240A - Monodisperse copolymer and its production - Google Patents

Abstract

PURPOSE:To obtain a monodisperse copolymer excellent as a functional polymer by subjecting two specific styreninc or styrene deriv. monomers to an anionic polymn. CONSTITUTION:A monomer of formula I (wherein R is H or methyl) and a monomer of formula II are subjected to an anionic polymn. to give a monodisperse coplymer comprising units of formula II and units of formula IV. The anionic polymn., though it can be carried out in the absence of any solvent, is pref. conducted in an org. solvent, pref. in tetrahydrofuran, because the reaction rate can be easily controlled in the solvent. The obtd. copolymer, being monodisperse i.e., having a narrow mol.wt. distribution, satisfies the requirements of a resist material having a high resolving power.

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 resist materials used in high resolution lithography 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 resins have been used as such polymers for resist materials. In this case,
A method called fractionation has been used 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 not only the operation is complicated but also that it takes time, and it is difficult to adequately follow the demanding performance that becomes strict, so that an essential problem solving is not possible. 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, and therefore the manufacturing efficiency of LSI and the like is improved. Various studies have been conducted to improve the quality. As such a chemically amplified polymer for a resist material, a styrene derivative polymer having excellent plasma resistance is known.

[0006]

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 capable of sufficiently satisfying the required performance as a polymer for a resist material. Therefore,
The present inventors have conducted intensive studies on polymers of styrene derivatives, and have found a novel monodisperse copolymer that satisfies the required performance as a polymer for resist materials and a method for producing the same, and arrived at the present invention.

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 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.

[0008]

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] However, R in the chemical formula 5 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), the molecular structure of which is infrared absorption (IR) spectrum or ¹ H.
-It can be easily confirmed by the NMR spectrum. Further, the randomness of the copolymer can be easily confirmed by the value of Tg (glass transition point) measured using DSC.

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] However, R in the chemical formula 7 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 preferable to carry out the polymerization reaction 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.

The concentration of all the monomers (the monomer represented by Chemical formula 7 and the monomer represented by Chemical formula 8) in the organic solvent in the polymerization reaction 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 performed 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 monomers react 100%, so that it can be obtained by adjusting the amount of the monomer used and the number of moles (number of molecules) of the living anion initiator to be added. The molecular weight of the polymer can be controlled appropriately. The molecular weight distribution of the copolymer thus obtained is monodisperse (M _w /
M _n = 1.01-1.50).

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 chemical formula 5 or 6 in an arbitrary ratio can be produced, but in general, (the repeating unit represented by the chemical formula 5)
/ (The repeating unit represented by Chemical formula 6) has a molar ratio of (0.0
The range is 1 to 99.99) / (99.99 to 0.01).

[0019]

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.

[0020]

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 2500 ml of tetrahydrofuran as a solvent and 1 × 10 ⁻² mol of n-butyllithium as an initiator were charged in a 3-liter flask, mixed and cooled to −78 ° C., and then 5 g of styrene was added. After carrying out the polymerization reaction for 1 hour, 95 g of pt-butoxy-α-methylstyrene was further added, and the polymerization reaction was carried out while stirring for 20 hours. The reaction solution 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% by weight of styrene and pt-butoxy-.
It was confirmed to be a block copolymer having 95% by weight of α-methylstyrene portion. Furthermore, from the GPC elution curve (FIG. 1), the monodisperse copolymer (M _W / M _n = 1.
11) was confirmed.

The results of ¹ H-NMR are as follows. 1.4～2.2Ppm :( broad, 3H, -C H ₂ -
C H −) 1.4 to 1.8 ppm: (broad, 2 H, −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)} 6.0~7.0ppm :( broad, 4H, C ₆ H ₄₎ The number-average molecular weight measured by membrane osmometry is
It was 9,000 g / mol.

Example 2.2 A 2.2 liter flask was charged with 1.5 liters of tetrahydrofuran as a solvent and 1 x 10 ^-3 mol of cumylcesium as an initiator, mixed and cooled to -78 ° C, and then 20 g of styrene was added. 1
After carrying out the polymerization reaction with stirring for 20 hours, 20 g of pt-butoxy-α-methylstyrene was further added and the polymerization reaction was carried out with stirring for 10 hours, and 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 solution was poured into methanol to precipitate the obtained 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, a characteristic absorption similar to that in Example 1 was observed, and a block having 50% by weight of a styrene portion and 50% by weight of a pt-butoxy-α-methylstyrene portion was observed. It was confirmed to be a copolymer. Further, from the GPC elution curve (Fig. 2), the obtained copolymer was a monodisperse copolymer ( _Mw / _Mn =
It was confirmed to be 1.08). The number average molecular weight of the copolymer measured by the membrane osmometry is 37,
It was 000 g / mol.

Example 3 A 3.2 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 −20 ° C., and 20 g of α-methylstyrene was added. After the addition and polymerization reaction for 1 hour, the reaction system was cooled to −78 ° C., and the polymerization reaction was carried out for 8 hours while stirring. Then p-t
-Butoxy-α-Methylstyrene 20 g was added,
When the polymerization reaction was carried out with stirring for a time, the reaction solution turned red.

Then, 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,
After separation and drying, 40 g of a white polymer was obtained. The ¹ H-NMR spectrum confirmed that the obtained polymer was a block copolymer having 50% by weight of α-methylstyrene portion and 50% by weight of p-butoxy-α-methylstyrene portion.

From the GPC elution curve (FIG. 3), it was confirmed that the copolymer was a monodisperse copolymer (M _W / M _n = 1.05). The number average molecular weight measured by the membrane osmometry was 19,000 g / mol.

[Brief description of drawings]

1 shows the polymer obtained in Example 1 (number average molecular weight 9,
(000 g / mol) GPC elution curve.

FIG. 2 shows the polymer obtained in Example 2 (number average molecular weight: 3).
(7,000 g / mol) GPC elution curve.

FIG. 3 The polymer obtained in Example 3 (number average molecular weight 1
(9,000 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 Formula 1, 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 chemical formula 3, 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.