JP2862720B2 - Narrowly dispersible polyhydroxystyrene partially esterified with t-butoxycarbonyl group and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a narrowly dispersible polyhydroxystyrene derivative preferably used as a resist material for LSIs, and more particularly to a narrowly dispersible polyhydroxystyrene having a hydroxyl group partially esterified with a t-butoxycarbonyl group. The present invention relates to styrene and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, functional polymers have been frequently used as base polymers for resist materials used for high resolution lithography or LSI.
In particular, with the recent progress of high density in LSI, resist materials are required to have higher resolution and higher developability. Conventionally, to answer such a request,
Novolak resin is used, but recently,
As a substitute for this, various chemically amplified resist materials have been studied.

Among the chemically amplified resist materials, those having a functional group which is easily removed by an acid from the viewpoint of workability and having different solubility before and after the removal of the functional group have been awarded. I have. As such a resist material, a polystyrene derivative having excellent plasma resistance is known as a particularly suitable material.

When these polymers are used as a base polymer for a resist, their molecular weight and molecular weight distribution greatly affect the development characteristics and resolution of the resist. However, these polymers are polydisperse polymers obtained by a usual radical polymerization method or polycondensation method, and consideration is not given to controlling the molecular weight and molecular weight distribution from the beginning. In order to increase the molecular weight, the molecular weight is controlled using a method called fractionation.

[0005] However, the separation method has a disadvantage that not only the operation is complicated but also it takes time.
Since it is difficult to sufficiently keep up with the demanding performance, it cannot be an essential means for solving the problem.

[0006]

In view of the above, polyhydroxystyrene having narrow dispersibility has been attracting attention from the beginning of production in recent years (JP-A-59-199705 and Preprints of the Society of Polymer Science, vol. 31, p. 1149). However, since this polymer does not have a group that can be removed by an acid,
As it is, it cannot be used as a resist material. Thus, the present inventors have conducted intensive studies on narrowly dispersible polystyrene derivatives that can be used as resist materials. As a result, polyhydroxystyrene having narrow dispersibility and partially esterified with a t-butoxycarbonyl group has high functionality. The present inventors have found that the present invention is extremely promising as a molecule, and have reached the present invention.

Incidentally, the technique of using polyhydroxystyrene partially esterified with a t-butoxycarbonyl group as a base polymer for a resist is described in Journal of Photopolymer Science and Technology, Vol. 4, No. 3, pp. 469-472. (1991)
In this publication, the molecular weight and the molecular weight distribution are not taken into consideration, and the above-mentioned problems relating to polydispersion have not been solved. Further, there is no known synthesis example of narrow-dispersion polyhydroxystyrene partially esterified with a t-butoxycarbonyl group.

Accordingly, a first object of the present invention is to provide a narrowly dispersible polyhydroxystyrene derivative which can be developed with an acid and has high resolution and is promising as a resist material. A second object of the present invention is to provide a novel method for producing a narrowly dispersible polyhydroxystyrene derivative.

[0009]

SUMMARY OF THE INVENTION The above objects of the present invention are attained by providing a narrow dispersion partially esterified with a t-butoxycarbonyl group having a repeating unit represented by the following structural formulas (Formula 3) and (Formula 4). The present invention has been achieved by a hydrophilic polyhydroxystyrene and a method for producing the same.

[0010]

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In the present invention, the term "narrow dispersibility" means that the molecular weight distribution is narrow ( _Mw / _Mn = 1.03 to 1.50). Here, _Mw is the weight average molecular weight of the polymer, and _Mn is the number average molecular weight. Here, the weight average molecular weight can be measured by a light scattering method, and the number average molecular weight can be measured by a membrane osmometer.

The molecular weight distribution of the narrow-dispersion polyhydroxystyrene partially esterified with a t-butoxycarbonyl group of the present invention (hereinafter referred to as "partially esterified narrow-dispersion polyhydroxystyrene") is 1.03-1. It must have a narrow dispersion of .50. This is because if the molecular weight distribution exceeds 1.50, high resolution and high degree of development cannot be achieved as a resist material, and if the molecular weight distribution is 1.03 or less, there is great technical difficulty.

The above molecular weight distribution can be evaluated by gel permeation chromatography (GPC), and the molecular structure can be easily confirmed by ¹ H-NMR spectrum. Although the average molecular weight of the partially esterified narrow-dispersion polyhydroxystyrene of the present invention is not particularly limited, when it is used as a resist material, it is generally preferably in the range of 10,000 to 50,000.

The partially esterified narrow-dispersion polyhydroxystyrene of the present invention can be easily obtained by partially esterifying the hydroxyl group of the narrow-dispersion polyhydroxystyrene with a t-butoxycarbonyl group as shown below.

The narrowly dispersible polyhydroxystyrene used in the present invention is obtained, for example, by subjecting a monomer represented by the following formula (5) or (6) to living polymerization, and then removing the dimethylphenylcarbinylsilyl group in the former case. And in the latter case, by removing the t-butyl group.

[0016]

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In the living polymerization of the above monomers, an organometallic compound is used as a polymerization initiator. Examples of such organometallic compounds include organic alkali metals such as n-butyllithium, sec-butyllithium, t-butyllithium, sodium naphthalene, sodium anthracene, sodium α-methylstyrene tetramer, cumyl potassium, and cumyl cesium.

The living polymerization of the above monomers generally comprises
Performed in an organic solvent. The organic solvent used in this case is an aromatic hydrocarbon, a cyclic ether, an aliphatic hydrocarbon solvent or the like, and specific examples thereof include, for example, benzene,
Examples include toluene, tetrahydrofuran, dioxane, tetrahydropyran, dimethoxyethane, n-hexane, cyclohexane and the like. These organic solvents may be used alone or in combination of two or more.

The concentration of the monomer in the polymerization is preferably 1 to 50% by weight, more preferably 1 to 30% by weight. The reaction is carried out with stirring under a high vacuum or in an atmosphere of an inert gas such as argon or nitrogen. The reaction temperature can be freely selected from −100 ° C. to the boiling point of the organic solvent used, but it is particularly preferable to react at −78 ° C. to 0 ° C. for a tetrahydrofuran solvent and room temperature for a benzene solvent.

The above polymerization reaction is usually carried out for about 10 minutes to 7 hours. As a result, only the vinyl group in the compound of the above (Chemical Formula 5) or (Chemical Formula 6) selectively reacts and polymerizes, and in the former case, the polymer represented by the following structural formula (Chemical Formula 7)
In the latter case, a polymer represented by the following (Formula 8) is obtained.

[0021]

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The termination of the reaction can be carried out, for example, with methanol, water,
The reaction is performed by adding a terminator such as methyl bromide to the reaction system. Next, the polymer produced by the polymerization reaction can be purified and isolated by precipitating the obtained reaction mixture solution in a suitable solvent, for example, methanol, washing and drying.

[0023] The molecular weight distribution of the polymer thus obtained is narrow dispersion _{(M w / M n = 1.03~1} . 50). Incidentally, the yield of the polymer in the above reaction is approximately 10%.
Since it is 0%, 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, the dimethylphenylcarbinylsilyl group in the polymer represented by the above formula (7) or the t-butyl group in the polymer represented by the formula (8) is eliminated,
Polyhydroxystyrene having a phenol residue structural unit represented by the following (Formula 9) is obtained.

[0025]

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The cleavage of the ether bond in the above elimination reaction can be easily carried out by adding an acid such as hydrochloric acid, hydrobromic acid or the like in a single or mixed solvent of dioxane, acetone, acetonitrile, benzene or the like. it can. In these reactions, the main chain of the polymer is cut,
Since no cross-linking reaction occurs between the molecules, the molecular weight distribution of the precursor, for example, t-butoxypolystyrene, is maintained as it is, and narrow-dispersion polyhydroxystyrene having a narrow molecular weight distribution can be obtained.

In the present invention, the reaction for partially converting hydroxyl groups of narrowly dispersed polyhydroxystyrene to t-butoxycarbonyloxy can be easily carried out by a usual t-butoxycarbonyloxylation reaction.

To explain this concretely, for example, t-
As a butoxycarbonyloxylating reagent, chloroformic acid-
t-butyl, di-t-butyl carbonate, t-butoxycarbonylthio- (4,6-dimethylpyridine), t-butyl
-Butylpentachlorophenyl carbonate, 2- (t
-Butoxycarbonyloxyimino) -2-phenylacetonitrile and the like, and using pyridine, tetraethylamine and the like as an acid trapping solvent, the hydroxyl groups of narrowly dispersed polyhydroxystyrene are partially t-butoxycarbonyloxylated. In this case, if necessary, dimethylamine, 4-N, N-dimethylaminopyridine or the like may be added to the reaction system as a t-butoxycarbonyloxylation catalyst.

Further, using potassium-t-butoxide,
Polyhydroxystyrene is converted to a potassium salt, which is
The hydroxyl group of narrowly dispersed polyhydroxystyrene can also be partially t-butoxycarbonyloxylated by a method of reacting with t-butyl dicarbonate.
However, the t-butoxycarbonyloxylation reaction in the present invention is not limited to the above reaction.

The t-butoxycarbonyloxylation rate is preferably in the range of 1 to 60%, particularly preferably in the range of 5 to 45%, from the viewpoint of the difference in solubility during development of the resist and the control of the crosslinking reaction. Is preferred. The t-butoxycarbonyloxylation rate of the partially esterified narrowly dispersible polyhydroxystyrene of the present invention thus obtained can be easily confirmed by a ¹ H-NMR spectrum.

[0031]

The partially esterified narrowly dispersible polyhydroxystyrene of the present invention has a narrow molecular weight distribution and can be controlled to an arbitrary molecular weight, so that it is suitable as a photosensitive polymer material such as a high-resolution resist material. is there. Further, the present invention is extremely significant because acid development can be performed and production is easy.

[0032]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto.

Synthesis Example 1 Synthesis of Narrowly Dispersible Polyhydroxystyrene In a reactor, p-vinylphenol and dimethylphenylcarbinyldimethylchlorosilane in an equimolar amount were added, and in the presence of imidazole in a dimethylformamide solvent at room temperature. The reaction was carried out for 6 hours.

The product was distilled under reduced pressure to give 70% of p-vinylphenoxydimethylphenylcarbinyldimethylsilane.
In a yield of The boiling point of the obtained p-vinylphenoxydimethylphenylcarbinyldimethylsilane was 130 ° C /
The boiling point was 0.1 mmHg. Purification was performed using a purifying agent such as CaH ₂ and sodium benzophenone in order to remove impurities such as moisture from the monomer, and distillation was performed.

Next, 550 ml of tetrahydrofuran as a solvent and n as a polymerization initiator are placed in a 1-liter flask.
After charging 8.5 × 10 ^-4 mol of -butyllithium, 30 g of p-vinylphenoxydimethylphenylcarbinyldimethylsilane diluted with 50 ml of tetrahydrofuran was added to this mixed solution at -78 ° C., followed by polymerization for 1 hour. The solution turned red. The polymerization was terminated by adding methanol to the reaction solution.

The reaction mixture was poured into methanol, and the resulting polymer was precipitated, separated and dried to obtain 24.5 g of a white polymer. 20 g of the obtained poly (p-vinylphenoxydimethylphenylcarbinyldimethylsilane)
Was dissolved in 250 ml of acetone, a small amount of concentrated hydrochloric acid was added at 60 ° C., and the mixture was stirred for 6 hours, then poured into water, and the polymer was precipitated, washed and dried to obtain 8 g of a polymer. The number average molecular weight of the obtained polymer is 14,000,
From the PC elution curve, it was confirmed that the polymer had a very narrow dispersibility. The molecular weight distribution was 1.1.

Synthesis Example 2 Synthesis Example 1 of narrowly dispersed polyhydroxystyrene was prepared by using pt-butoxystyrene monomer as a raw material.
After dehydration and purification in the same manner as described above, 1,500 tetrahydrofuran was added as a solvent to a 2 liter flask.
ml and n × butyl lithium as an initiator at 8 × 10 ^−3.
Mole charged. To this mixed solution was added pt-butoxystyrene diluted with 50 ml of tetrahydrofuran at -78 ° C.
When 100 g was added and polymerization was carried out for 2 hours, the solution turned red.

After confirming that the desired degree of polymerization has been reached,
The polymerization reaction was terminated by adding methanol to the reaction solution,
Then, the reaction mixture was poured into methanol to precipitate the obtained polymer, which was separated and dried to obtain 80 g of a white polymer.

Next, 20 g of the obtained poly (pt-butoxystyrene) was dissolved in 250 ml of acetone.
Then, a small amount of concentrated hydrochloric acid was added thereto, and the mixture was stirred for 6 hours, then poured into water to precipitate a polymer, and washed and dried to obtain 13 g of a polymer. The number average molecular weight of the obtained polymer is 9,00
It was 0. From the GPC elution curve, it was confirmed that the polymer was very narrow in dispersibility. The molecular weight distribution was 1.1.

Embodiment 1 Polyhydroxystyrene obtained in Synthesis Example 1 (molecular weight 14,000, molecular weight distribution 1.
1) 10 g was dissolved in 90 ml of pyridine, and 2 g (about 20 mol%) of di-t-butyl dicarbonate was stirred at 45 ° C.
Was added. A gas was generated at the same time as the addition, but the reaction was allowed to proceed for 1 hour in a nitrogen stream.
Was added dropwise to 1.5 liters of water containing, to obtain a white precipitate.

After the precipitate was filtered, the precipitate was dissolved in 50 ml of acetone and added dropwise to 1.5 l of water. After the precipitate was filtered, the precipitate was vacuum dried at 40 ° C. or lower. The molecular weight distribution of the narrow-dispersion polyhydroxystyrene partially esterified with the t-butoxycarbonyl group thus obtained is shown in FIG.
, The dispersion is very narrow, and M _w / M _n is 1.1
It was 0.

From the ¹ H-NMR spectrum (Table 1), the hydroxyl groups of the polyhydroxystyrene were partially changed to t-
Butoxycarbonyloxylation was confirmed, and the integration ratio revealed that the introduction ratio of t-butoxycarbonyl group was 19%.

[Table 1]

Embodiment 2 FIG. Polyhydroxystyrene obtained in Synthesis Example 2 (molecular weight 9,000, molecular weight distribution 1.4)
10 g was dissolved in 90 ml of pyridine, and 4 g (about 40 mol%) of di-t-butyl dicarbide was added while stirring at 45 ° C. A gas was generated at the same time as the addition. After reacting for 1 hour in a nitrogen stream, the reaction solution was dropped into 1.5 liter of water containing 40 g of concentrated hydrochloric acid to obtain a white precipitate.
Filtered.

Then, it is dissolved in 100 ml of acetone,
After dripping into 1.5 liters of water and filtering the precipitate,
Vacuum dried at 40 ° C. or less. The t thus obtained
The molecular weight distribution of the narrow-dispersion polyhydroxystyrene partially esterified with -butoxycarbonyl group was very narrow-dispersion as shown in FIG. 2, and M _w / M _n was 1.12.

[Brief description of the drawings]

FIG. 1 is a GPC molecular weight distribution curve of a narrowly dispersed polyhydroxystyrene partially esterified with a t-butoxycarbonyl group obtained in Example 1.

FIG. 2 is a GPC molecular weight distribution curve of the narrow-dispersion polyhydroxystyrene partially esterified with a t-butoxycarbonyl group obtained in Example 2.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Motoyuki Yamada 100-1 Sakado, Takatsu-ku, Kawasaki-shi, Kanagawa Kanagawa Science Park R & D Building A12F Shin-Etsu Chemical Co., Ltd. Corporate Research Center (72) Invention Person Keijun Tanaka 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Inventor Koji Ban 1-6-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Inventor Yoshio Kawai 1-6, Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (58) Field surveyed (Int. Cl. ⁶ , DB name) C08F 8/14 C08F 12/00-12/24 C08F 212 / 00-212/14

Claims (2)

(57) [Claims] [Claim 1] have a repeating unit represented by the following structural formula (Formula 1) and (Formula 2), along with being partially esterified with t- butoxycarbonyl group, the number average molecular weight M _n
The ratio M _w / M _{n of the} weight average molecular weight M _{w to} the weight average molecular weight M _w is 1.03 to
1. A narrowly dispersible polyhydroxystyrene having a ratio of 1.50 . Embedded image Embedded image Wherein the weight average molecular to number average molecular weight M _n
Narrowly dispersible polyhydroxystyrene having a ratio _Mw / _Mn of 1.03 to 1.50 in an amount _Mw is partially esterified with a t-butoxycarbonyl group. A method for producing a partially esterified narrowly dispersible polyhydroxystyrene.