JPH0667980B2 - Method for producing α-cyanoacrylic acid ester polymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing a monodisperse polymer of an α-cyanoacrylate having a good yield and an extremely sharp molecular weight distribution with good reproducibility. is there.

More specifically, the present invention uses a specific polymerization initiator and polymerizes in a solvent at a specific reaction temperature, and as a main component of a radiation sensitive resist having an extremely high resolution, particularly a weight average molecular weight / number average molecular weight (hereinafter _w / It is intended to provide a method for producing an α-cyanoacrylic acid ester polymer having a sharp molecular weight distribution such that the value of (abbreviated as _n ) is approximately 1 in good yield and with good reproducibility.

[Background of technology]

In the field of manufacturing large-scale semiconductor integrated circuits, patterns of functional regions, electrode contact windows, wirings, etc. are mostly formed by a dry etching method using a pattern made of a photosensitive resin as a mask.

As semiconductor integrated circuits have become highly integrated, there has been an increasing tendency to frequently use a radiation drawing technique capable of obtaining a submicron high resolution for pattern formation using the photosensitive resin.

Electron beam direct writing, X-ray lithography, and focused ion beam exposure techniques are being realized as lithography techniques with a line width of 0.5 μm or less, which is the limit of optical exposure, but practically usable resists are very few. These resist materials undergo a cross-linking reaction when exposed to radiation, and a negative type that becomes insoluble in the developer and the main polymer of the resist undergoes a main chain splitting reaction when exposed to radiation, making them positively soluble in the developer. There is a mold. The characteristics of the negative resist are high sensitivity and excellent etching resistance, but low resolution. On the other hand, the positive resist is characterized by high resolution, but low sensitivity and poor etching resistance. The demands of the industry for high integration of semiconductor large-scale integrated circuits have been escalated more and more recently, and negative resists with high sensitivity and excellent etching resistance are also fatally inferior in resolution and forced to retreat. However, positive resists are becoming the mainstream instead.

[Conventional technology and problems]

Polymethylmethacrylate (P-MMA) is well known as a representative base polymer of the positive type radiation sensitive resist. The resolution of this polymer is 0.3-0.5 μm
Although it is said to be suitable as a submicron resist, the sensitivity is extremely low at 5 × 10 ⁻⁵ C / cm ² and the etching resistance is poor, so many proposals for improving sensitivity and etching resistance have been made. Although it has been done, very few have reached the level of practical application.

To improve the sensitivity, methods such as introduction of electron withdrawing groups such as Cl, F, Br, N, O, S and increasing the molecular weight have been taken. However, there are many cases where the etching resistance is lowered and sufficient results have not been obtained. Not up. Further, although various proposals have been made for improving etching resistance, very few have been put to practical use.

Although the industry has already entered the era of sub-micron resists, the sensitivity and etching resistance of positive resists are far from practical use, so we are focusing on these two major characteristics. Since the resolution is not always sufficient as a resist for large-scale integrated circuits after 64 Mbit D-RAM, improving the resolution is one of the main themes that must be resolved.

[Object of the Invention]

It is an object of the present invention to introduce a monodisperse polymer into α-cyanoacrylic acid ester, which has an extremely excellent sensitivity to radiation, and thereby has a high sensitivity and a high sensitivity suitable for semiconductor large scale integrated circuits after 64 Mbit D-RAM. It is intended to provide a method for producing a base polymer of a resist for forming a positive type pattern of resolution.

[Structure of Invention]

The present invention uses α-cyanoacrylic acid ester at 20 to −120 ° C.
Polymerization in the presence of an anionic polymerization initiator obtained by mixing one kind or two or more kinds of weak anions such as organic amine, organic amide, phosphine, thiourea, thioalcohol, and ether while cooling to It is characterized in that a dispersion polymer is obtained.

Regarding the polymerization method of α-cyanoacrylic acid ester, J,
As described in Apple, Polym, Sci., 4 , 231 (1960), Yugo 27 , 280 (1969), there are radical polymerization method and anion polymerization method.

Generally, it is a well-known fact that it is difficult to obtain a polymer having an extremely narrow molecular weight distribution by the radical polymerization method,
It has little effect on resolution improvement.

On the other hand, it is known that the anionic polymerization method can obtain a polymer having a very narrow molecular weight distribution as represented by anionic polymerization of styrene, p-dimethylaminomethylstyrene, isoprene and the like. Due to its extremely high anionic polymerizability in anionic polymerization, it is extremely difficult to control the molecular weight and the molecular weight distribution as compared with the anionic polymerization of ordinary monomers. A polymer having a predetermined molecular weight and molecular weight distribution cannot be produced with good reproducibility.

Moreover, even if an attempt was made to produce this polymer, it was necessary to limit the operational conditions such as polymerization, and it was impossible to obtain reproducibility in practice.

Generally, α-cyanoacrylic acid ester initiates polymerization even with a weak base such as water or alcohol,
Instant adhesives containing this as the main ingredient are used as one-component universal adhesives due to the ability to instantaneously anionically polymerize at a room temperature using a very small amount of water adhering to the surface of the adherend as a curing agent. It is clear from this.

In anionic polymerization, there is theoretically no termination reaction, so by adjusting the amount of polymerization initiator, a polymer with a specified molecular weight and a very narrow molecular weight distribution (theoretically the same molecular weight) should be obtained. However, there are many cases in which side reactions such as a termination reaction caused by impurities and the like occur together.

When a weak base such as water or alcohol is used as the anionic polymerization initiator of α-cyanoacrylic acid ester,
Its polymerization rate is extremely slow, and it can be used when handling very small amounts of monomers such as instant adhesives, but this polymerization reaction is easily affected by trace impurities and productivity is poor, so it is unsuitable as an industrial production method. .

On the other hand, when phosphines and amines with higher nucleophilicity and higher basicity are used as the polymerization initiator, under normal conditions, the polymerization rate is extremely fast, and a runaway reaction occurs to cause a side reaction,
The molecular weight and molecular weight distribution of the produced polymer cannot be easily controlled.

Further, in addition to the above, an acidic substance such as sulfur dioxide or propane sultone is usually added as a polymerization inhibitor to the α-cyanoacrylic acid ester to maintain the storage stability of the α-cyanoacrylic acid ester. However, it is clear that the co-occurrence of termination reactions by these influences the growth reaction of polymerization.

The present inventors focused on the specific anionic polymerizability of the above α-cyanoacrylic acid ester, and provided a method for producing a polymer useful as a positive resist material having high sensitivity and excellent resolution. As a main purpose, as a result of various studies on the polymerization method of α-cyanoacrylic acid ester, since the anionic property of these monomers is extremely high, the α-cyanoacrylic acid ester is cooled to a reaction temperature of its freezing point or lower. , Suppress its molecular motion,
Organic amides that are more active than extremely weak anions such as water,
Phosphine, organic amine, thiourea, thioalcohol,
By reproducing in the presence of a polymerization initiator such as ether, it is possible to suppress side reactions that occur concurrently with water and other impurities in the system, and polymerization termination reactions due to acidic substances such as sulfur dioxide and propane sultone. The present invention has been completed by finding a method for producing a monodisperse polymer having excellent properties.

Hereinafter, the present invention will be described in more detail. The present invention relates to a method for producing an α-cyanoacrylic acid ester polymer, and the α-cyanoacrylic acid ester used in the present invention is represented by the following general formula. It is what is done.

However, in the formula, R is an alkyl group having 1 to 12 carbon atoms, a halogenated alkyl group, a cycloalkyl group, an alkenyl group, an alkoxyalkyl group, an alkynyl group, an allyl group or the like, and specifically, α- Methyl cyanoacrylate, α-cyanoacrylic acid ethyl, α-cyanoacrylic acid n-propyl, α-cyanoacrylic acid isopropyl, α-cyanoacrylic acid n-butyl, α-cyanoacrylic acid isobutyl, α-cyanoacrylic acid n -Pentyl, isoamyl α-cyanoacrylate, n-hexyl α-cyanoacrylate, n-octyl α-cyanoacrylate, cyclohexyl α-cyanoacrylate, 2-ethylhexyl α-cyanoacrylate, allyl α-cyanoacrylate , Benzyl α-cyanoacrylate, 2-methoxyethyl α-cyanoacrylate alpha-cyanoacrylic acid propargyl, alpha-cyanoacrylic acid trichloroethyl, alpha
-Tetrachloropropyl cyanoacrylate, trifluoroethyl α-cyanoacrylate, phenyl α-cyanoacrylate and the like.

These may be those obtained by an ordinary synthesis method, as long as they contain 5 to 50 ppm of an anionic polymerization inhibitor and 2000 ppm or less of a radical polymerization inhibitor.

In the production method of the present invention, control of the reaction temperature with a specific anionic polymerization initiator is an essential condition, and the polymerization initiator is an organic amine, organic amide, phosphine, thiourea,
Weak anions such as thioalcohol and ether or mixtures thereof, preferably diethylamine, dimethyl para-toluidine, aniline, dimethylformamide, diphenylphosphine, 2.5-xylidine, thiosemicarbazide, thiourea, 1.3-diphenyl Thiourea, 1
-Propanethiol, 15 crown 5 ether and the like.

The addition amount of these polymerization initiators is not particularly limited, but is preferably 0.01 to 2.0 mol% with respect to the monomer.

The reaction temperature is close to the freezing point of each monomer, or a temperature lower than that is required, the polymerization rate of the monomer is controlled, and side reactions are suppressed, which is an essential condition of the present invention.
The reaction temperature that can be used is -30 ° C to -120 ° C, preferably -30 to -100 ° C.

As the solvent used for this purpose, acetone, methyl ethyl ketone, ethyl acetate, cyclohexanone, methyl isobutyl ketone, acetonitrile, propionitrile,
It is a mixed solvent of trichlorethylene, THF, and the like.

In any case, the solvent used must be a good solvent for the poly α-cyanoacrylic acid ester, and must be a solvent that does not precipitate the poly α-cyanoacrylic acid ester at a predetermined low temperature. As these solvents, those purified by a known dehydration method can be used.

As described above, according to the method for producing a monodisperse polymer of α-cyanoacrylic acid ester, a monodisperse polymer having an arbitrary molecular weight of 20,000 to 1,000,000 can be obtained with good reproducibility and in good yield.

As a means for carrying out the polymerization method of the present invention, a predetermined amount of a predetermined solvent is introduced into a polymerization vessel, and then a predetermined amount of a predetermined polymerization initiator is added and cooled to a predetermined temperature.

It is a general method to stir the polymerization initiator solution while adding a predetermined solvent containing a predetermined amount of a predetermined α-cyanoacrylate while maintaining the temperature at a predetermined temperature or lower, and to carry out the reaction, but it is particularly limited to this order. It is not something that will be done.

The method of the present invention is applicable regardless of the scale of polymerization.

〔The invention's effect〕

The present invention provides a method for obtaining a monodisperse polymer of α-cyanoacrylic acid ester extremely economically and efficiently using a specific anionic polymerization initiator and a specific reaction temperature and a solvent.

The α-cyanoacrylic acid ester monodisperse polymer thus obtained is extremely excellent when used as a main component of a radiation resist because of its high sensitivity and good pattern accuracy. It is suitable for forming ultra-high density patterns such as electron beam and X-ray linography processes in the production of integrated circuits, and makes a great contribution to the improvement of semiconductor technology and semiconductor production.

Examples 1 to 11 As shown in Table 1, a predetermined amount of a predetermined anionic polymerization initiator was added to 800 ml of a predetermined solvent, and the system temperature was cooled to -30 to -90 ° C. After sufficiently stirring the inside of the system, 100 ml of a predetermined solvent containing 0.1 mol of a predetermined α-cyanoacrylic acid ester containing 50 ppm of an anionic polymerization inhibitor SO ₂ was gradually added so as not to exceed the predetermined reaction temperature and reacted. The reaction was stopped by adding an anionic polymerization terminator to obtain a polymer. This polymer was purified by the reprecipitation method. The molecular weight of the obtained polymer was determined by gel permeation chromatography (GPC) one-light scattering method, and the results shown in Table 1 were obtained.

Comparative Examples 1 to 5 As shown in Table 2, after introducing 800 ml of an acetone solution containing a predetermined amount of a predetermined anionic polymerization initiator into the flask, the temperature in the system was kept at 30 ° C. while sufficiently stirring the system. , 100 ml of an acetone solution containing 0.1 mol of ethyl α-cyanoacrylate was gradually added and reacted to obtain a polymer.
After the polymer was purified by the reprecipitation method and the molecular weight was determined by the GPC light scattering method, the results shown in Table 2 were obtained.

Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display area H01L 21/027

Claims (1)

[Claims] 1. A solvent which is a good solvent for poly .alpha.-cyanoacrylic acid ester and which does not precipitate poly .alpha.-cyanoacrylic acid ester at a predetermined low temperature, at -30.degree. C. to -120.
Α-Cyanoacryl which is polymerized in the presence of a weak anion such as an organic amine, an organic amide, a phosphine, a thiourea, a thioalcohol and an ether, or an anionic polymerization initiator of a mixed system thereof while cooling to ℃. Method for producing acid ester polymer.