JPH0222762B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a 2-cyanoacrylic acid ester polymer with good yield and relatively narrow molecular weight distribution with good reproducibility. More specifically, the present invention is mainly used as a radiation-sensitive resist material including electron beams, X-rays, and γ-rays by polymerizing in a solvent using a specific polymerization initiator.
In particular, weight average molecular weight/number average molecular weight (hereinafter Mw/
Abbreviated as Mn. The present invention provides a method for producing a 2-cyanoacrylic acid ester polymer having a narrow molecular weight distribution with a value of approximately 2.0 or less in good yield and with good reproducibility. In the production of large-scale integrated circuits, resist materials with high sensitivity and high resolution are essential, and are particularly suitable for technology that uses radiation to draw ultra-fine patterns with a line width of 1 micron or less at high speed and with good reproducibility. It is desired to develop materials for resists. These resist materials can be broadly classified into negative resists, which undergo preferential cross-linking reactions and become insolubilized by irradiation, and positive resists, which undergo preferential decomposition reactions and become easily soluble by irradiation. The main use of the polymer obtained by the polymerization method of the present invention is as a material for positive resists, in which the polymer cleavage reaction occurs preferentially in the radiation irradiated areas, resulting in The molecular weight of the polymer decreases,
Since it becomes easily soluble in various solvents, the irradiated portion can be selectively dissolved and removed, making it possible to form a positive pattern.
The performance of these resist materials is evaluated in terms of sensitivity to radiation, resolution, etc. Generally, negative resists have high sensitivity but poor resolution, while positive resists have low sensitivity but high resolution. Therefore, the emergence of positive resist materials with high sensitivity and high resolution is desired in large-scale integrated circuit manufacturing technology. The sensitivity of positive resist materials is, for example, Polym.
Eng. and Sci., 17 , 396 (1977), it depends on the molecular weight of the polymer, and the sensitivity increases as the molecular weight increases. On the other hand, the resolution largely depends on the molecular weight distribution of the polymer, and the narrower the molecular weight distribution, the better the resolution. Although 2-cyanoacrylic acid ester polymer has higher sensitivity than methyl methacrylate polymer, which is a typical positive resist, it has the disadvantage that it cannot form patterns with good resolution. , it was not practically satisfactory. Regarding the polymerization method of 2-cyanoacrylic acid ester, see, for example, J.Appl.Polym.Sci., 4 , 231.
(1960) and Makromol.Chem., 182 , 421.
(1981) and other anionic polymerization methods described. It is a well-known fact that it is generally difficult to obtain a polymer with a narrow molecular weight distribution by radical polymerization, and it is not very effective in improving resolution. On the other hand, it is known that anionic polymerization can easily produce polymers with a very narrow molecular weight distribution, as typified by anionic polymerization of styrene, etc.
Due to its extremely high anionic polymerizability in anionic polymerization of cyanoacrylate esters, it is difficult to control the molecular weight and molecular weight distribution compared to anionic polymerization of ordinary monomers, and the anionic polymerization method described in the above-mentioned literature etc. However, it is not possible to produce a polymer having a desired molecular weight and molecular weight distribution with good reproducibility. As mentioned above, it is difficult to produce a 2-cyanoacrylic acid ester polymer having the desired molecular weight and molecular weight distribution using conventional methods, and even if one attempts to produce it, it requires many manipulations such as polymerization conditions. The above limitations were required, and this method was not satisfactory in practice. In general, it is clear from the fact that 2-cyanoacrylic acid esters initiate polymerization even in the presence of weak bases such as water and alcohols, as they are prized as instant adhesives. However, it is difficult to obtain a polymer as a resist material by using these weak bases as a polymerization initiator because the polymerization rate is very slow, and it is difficult to use it practically. On the other hand, when phosphines or amines, which are more nucleophilic and basic, are used as polymerization initiators,
Although polymerization proceeds very rapidly, the molecular weight and molecular weight distribution of the resulting polymer cannot be easily controlled. In other words, in the case of phosphines and amines,
An acid-base reaction occurs between the polymerization solvent and trace water in the monomer, and the resulting OH ^- ions serve as a new initiator, which complicates the polymerization reaction.
In addition, 2-cyanoacrylic acid ester monomers usually contain acidic substances such as sulfur dioxide and propane sultone as anionic polymerization inhibitors, and these may affect the growth reaction of polymerization. is clear. The present inventors focused on the specific anionic polymerizability of the above-mentioned 2-cyanoacrylic acid ester, and the main purpose of the present inventors is to provide a method for producing a polymer useful as a positive resist material with high sensitivity and excellent resolution. As a result of various studies on polymerization methods for 2-cyanoacrylic acid ester, we found that by polymerizing in a solvent using a sulfide compound as a polymerization initiator, the molecular weight distribution of the polymer is relatively narrow, and monomers and The present invention has been completed by discovering a method for producing a 2-cyanoacrylic acid ester polymer that is not significantly affected by the purity of the solvent, that is, has high reproducibility. That is, the present invention relates to a method for producing a 2-cyanoacrylic acid ester polymer, which is characterized in that the polymerization is carried out in a solvent using a sulfide or disulfide compound as a polymerization initiator. The present invention will be explained in more detail below. The present invention relates to a method for producing a 2-cyanoacrylic acid ester polymer, and the 2-cyanoacrylic acid ester used in the present invention is represented by the following general formula. It is something. However, in the formula, R ₃ is an alkyl group, a halogenated alkyl group, a cycloalkyl group, an alkenyl group, an alkoxyalkyl group, an alkynyl group, or an aryl group having 1 to 12 carbon atoms, and specifically, methyl 2 - cyanoacrylate,
Ethyl 2-cyanoacrylate, n-propyl 2
-cyanoacrylate, isopropyl 2-cyanoacrylate, n-butyl 2-cyanoacrylate, isobutyl 2-cyanoacrylate, n-pentyl 2-cyanoacrylate, isoamyl 2-
Cyanoacrylate, n-hexyl 2-cyanoacrylate, n-octyl 2-cyanoacrylate, cyclohexyl 2-cyanoacrylate, 2
-ethylhexyl 2-cyanoacrylate, allyl 2-cyanoacrylate, benzyl 2-cyanoacrylate, methoxyethyl 2-cyanoacrylate, propargyl 2-cyanoacrylate,
These include chloroethyl 2-cyanoacrylate, chloropropyl 2-cyanoacrylate, trifluoroethyl 2-cyanoacrylate, and phenyl 2-cyanoacrylate. These can be obtained by ordinary synthetic methods,
Preferably, the composition contains 5 ppm to 50 ppm of an aeon polymerization inhibitor and 2000 ppm or less of a radical polymerization inhibitor. In the production method of the present invention, it is essential to use a specific polymerization initiator, and the polymerization initiator is a sulfide or disulfide compound represented by the following general formula. R ₁ (-S-)R ₂ In the formula, R ₁ and R ₂ are alkyl, cycloalkyl, alkenyl, alkynyl, aryl, aralkyl groups, etc. having a carbon number ranging from 1 to 16,
It may be substituted with a cyano group, an alkoxycarbonyl group, a cidroxy group, a halogen atom, or the like, or it may be one in which R ₁ and R ₂ are bonded to form a ring. Further, n is 1 or 2. Specific examples of these linear sulfide, disulfide compounds, and cyclic sulfide compounds include dimethyl sulfide, diethyl sulfide, di-n-butyl sulfide, 2,2'-thiodiethanol, β, β'-
Thiodipropionitrile, dimethyl 3,3'-thiodipropionate, diethyl 3,3'-thiodipropionate, di-n-propyl 3,3'-thiodipropionate, dimethyl disulfide, diethyl sulfide , diphenyl disulfide, thiophene, tetrahydrothiophene, thioanisole, etc.
Among these, β,β′-thiodipropionitrile,
Dimethyl 3,3'-thiodipropionate, tetrahydrothiophene, and dimethyl disulfide are more preferred in achieving the object of the present invention. The amount of the sulfide compound added is less than the number of moles of 2-cyanoacrylic acid ester charged, that is, the amount of 2-cyanoacrylic ester charged is 100.
The amount may be 100 mol or less per mole, but in order to obtain a polymer with a desired molecular weight, it is preferable to adjust the amount to be in the range of 0.02 to 20 mol per 100 mol of 2-cyanoacrylic acid ester.
If the amount added is less than 0.02 mol, the polymerization reaction will be very slow and it will take a long time to obtain a good yield, and if it exceeds 20 mol, the polymer will become a low molecular weight polymer, making it unsuitable as a resist material. In order to obtain a polymer with a narrow molecular weight distribution in a good yield with good reproducibility by polymerizing 2-cyanoacrylic acid ester, it is necessary to carry out the polymerization in a solvent where the polymerization reaction can be easily controlled. Examples of the solvent include acetone, methyl ethyl ketone, cyclohexanone, methyl isobutyl ketone, acetonitrile, propionitrile, benzonitrile, or a mixed solvent thereof. benzene,
It is also possible to use a solvent selected from aromatic hydrocarbons such as toluene, acetate ester compounds such as methyl acetate and ethyl acetate, and ether compounds such as tetrahydrofuran, dioxane and dimethoxyethane, but in that case a mixed solvent may be used. and at least one component is acetone, methyl ethyl ketone,
Preferably, it contains cyclohexanone or acetonitrile. These polymerization solvents do not require special purification, and can be purified by a known dehydration method and then subjected to polymerization. By the manufacturing method of the 2-cyanoacrylic acid ester polymer explained above, in particular, the molecular weight is 20,000~20,000~
A 2-cyanoacrylic acid ester polymer with a Mw/Mn value of approximately 2.0 or less, which is a measure of molecular weight distribution, can be obtained with good reproducibility and in good yield, and is useful as a positive resist material. You can get it. The procedure for implementing the polymerization method of the present invention is to introduce a predetermined amount of solvent into a polymerization container, then add and dissolve 2-cyanoacrylic acid ester, and start polymerization of a predetermined amount while stirring the polymerization system sufficiently. Generally, the polymerization reaction is carried out by introducing a chemical agent, but 2
-The order of introducing the cyanoacrylic acid ester, the solvent, and the polymerization initiator is not limited to this. The polymerization temperature is preferably as low as possible, but preferably in the range of -100°C to 60°C in view of the relationship between the polymerization reaction rate and the molecular weight of the resulting polymer. The method of the present invention is applicable regardless of the size of the polymerization scale, and is not limited to the amounts and ratios of the 2-cyanoacrylic acid ester and the solvent. The present invention will be further explained below with reference to Examples. Example 1 After introducing acetone 1 and 20 g of ethyl 2-cyanoacrylate as a polymerization solvent into a normal eggplant-shaped flask, the inside of the reaction vessel was cooled to 0°C. Dimethyl disulfide 1.51 while stirring the system thoroughly.
Of the 10 c.c. of acetone solution containing g, 1 c.c. was introduced to start the polymerization reaction. Two hours after the start of the reaction, the temperature was raised to room temperature and the reaction was continued for 24 hours to obtain a polymer. The yield of the polymer obtained after reprecipitation purification was 85%.
When the molecular weight and molecular weight distribution were measured by gel permeation chromatography (GPC), the Mw was 300,000 and the Mw/Mn was 1.7. Examples 2 to 10 Polymerization of 20 g of various 2-cyanoacrylic acid esters was carried out in almost the same manner as in Example 1 using dimethyl 3,3'-thiodipropionate as a polymerization initiator and acetonitrile 1 as a polymerization solvent. Ta.
The results are summarized in Table-1. By the production method of the present invention, the molecular weight is several hundred thousand and the molecular weight distribution is
It becomes possible to produce a polymer having Mw/Mn in the range of 1.5 to 1.8 with a yield of 80% or more, and it is possible to provide a radiation resist material with excellent performance.

[Table] Examples 11 to 17 20 g of isobutyl 2-cyanoacrylate was polymerized in substantially the same manner as in Example 1 using various sulfide compounds as polymerization initiators. The polymerization solvent is acetone 1. The molecular weight and molecular weight distribution of the polymer were evaluated in the same manner as in Example 1. A table summarizing the results.
Shown in 2. The wide variety of sulfide compounds used have molecular weights and molecular weight distributions in the hundreds of thousands.
A polymer having a relatively narrow molecular weight distribution with Mw/Mn in the range of 1.5 to 2.0 was obtained in good yield.

【table】

[Table] Comparative Examples 1 to 4 20 g of n-hexyl 2-cyanoacrylate was prepared in almost the same manner as in Example 1 using pyridine, N,N-dimethyl P-toluidine, triphenylphosphine, and triethylamine as polymerization initiators. Polymerization was carried out. The results are summarized in Table 3. Molecular weight and molecular weight distribution were evaluated using the same method as in Example 1. From a comparison with the results in Table 2, it is clear that the polymerization method of the present invention provides a polymer with a narrower molecular weight distribution than the comparative example. In addition, in the table, bimodal
indicates that the produced polymer is composed of two components, and the molecular weight indicates the value of each component.

[Table] Examples 18-24 Using dimethyl 3,3'-thiodipropionate as a polymerization initiator, 2-cyanoacrylic acid ester
Polymerization of 20 g of isobutyl 2-cyanoacrylate was carried out in substantially the same manner as in Example 1, with the amount of initiator charged per 100 moles varied within the range of 0.02 to 20 moles. Acetone 1 was used as the polymerization solvent. The results are shown in Table-4. Obviously, the polymerization method of the present invention can produce a polymer having any desired molecular weight by adjusting the amount of polymerization initiator added to the 2-cyanoacrylic acid ester.

【table】

[Table] Example 25 Using tetrahydrothiophene as a polymerization initiator, 20 g of isoamyl 2-cyanoacrylate containing 20 ppm and 50 ppm of sulfur dioxide as a polymerization inhibitor was polymerized in substantially the same manner as in Example 1. The polymerization solvent is methyl ethyl ketone 1.
The amount of the polymerization initiator charged is 1 mole per 100 moles of 2-cyanoacrylic acid ester. Yield is 93% when sulfur dioxide is 20ppm and 85% when 50ppm
The molecular weights evaluated using the same method as in Example 1 are 38.2×10 ⁴ and 36.8×10 ⁴ , respectively.
The value of Mw/Mn was 1.6 in all cases. From this result, it is clear that the polymerization method according to the present invention is a method for producing a 2-cyanoacrylic acid ester polymer with high reproducibility. Example 26 In substantially the same manner as in Example 1, 20 g of ethyl 2-cyanoacrylate was polymerized. The polymerization solvent was a mixed solvent of acetone and tetrahydrofuran in a ratio of 8:2. The polymerization initiator is dimethyl sulfide. The yield was 80%, the molecular weight evaluated using the same method as Example 1 was 230,000, and the molecular weight distribution Mw/
The Mn value was 1.6.

Claims (1)

[Claims] 1. A method for producing a 2-cyanoacrylic acid ester polymer, which comprises polymerizing in a solvent using a sulfide or disulfide compound as a polymerization initiator.