JPS5872938A - Positive type resist resin for far ultraviolet rays - Google Patents

Abstract

PURPOSE:To obtain a resist with high sensitivity to far ultraviolet rays by using monomers including 4-methyl phenyl vinyl ketone to prepare a polymer having a composition contg. at least 10mol% 4-methyl phenyl vinyl ketone units. CONSTITUTION:50 Parts by weight of 4-methyl phenyl vinyl ketone are mixed with 50 parts methyl methacrylate, and after adding 0.1 part polymn. catalyst and carrying out nitrogen substitution, the mixture is polymerized to prepare a polymer contg. at least 10mol% 4-methyl phenyl vinyl ketone units. The polymer is dissolved in methylcellosolve acetate to 6wt% concn. This soln. is applied to a silicon substrate under rotation with a spinner and dried to obtain a resist resin film. This film has high sensitivity to far ultraviolet rays whose wavelengths are shorter than the wavelengths of conventional ultraviolet rays, and it is used as a positive type resist film capable of being dry etched with gaseous CF4.

Description

[Detailed description of the invention] The present invention relates to a deep ultraviolet positive resist resin.

The main development goal of the semiconductor industry, which has been rapidly developing in recent years, is to improve the integration density of electronic circuits.

In the formation of this high-density integrated circuit technology, the most important and fundamental technology is the formation technology of finely processed evaporators.

Photolithography technology using visible light or ultraviolet rays has traditionally been used to form finely processed evaturns, but in recent years electron beams and The development of lithography technology using lines has been progressing. However, although such a method significantly improves processing accuracy, it requires large-scale equipment and requires extremely high investment.

Against this background, microfabrication with a processing accuracy slightly higher than that of conventional photolithography, that is, an accuracy of 1 to 2 micrometers, is achieved using so-called deep ultraviolet light, which has a shorter wave length than the conventionally used ultraviolet light. Therefore, attempts have been made to do this at a low cost with a relatively low investment.

Polymethyl methacrylate, polymethyl isopropenyl ketone, etc. are used as deep UV positive resists used in this deep UV lithography, but while these resists have superior resolving power compared to negative resists, It has the drawbacks of low sensitivity and poor dry etching resistance.

In view of this situation, the inventors of the present invention conducted intensive studies to develop a positive resist for deep UV rays that has high sensitivity and dry etching resistance. The inventors have discovered that the above problems can be solved all at once by using the present invention, and have completed the present invention.

That is, the gist of the present invention is a deep ultraviolet positive resist resin comprising a polymer containing at least 10 moles of 4-methylphenyl vinyl ketone units. The resist resin of the present invention is characterized by introducing into the resist resin a 4-methylphenyl vinyl ketone structure having a ketone group with high selective decomposition properties against deep ultraviolet rays and an aromatic ring with dry etching resistance in the side chain. That's the point.

The deep ultraviolet resist resin according to the present invention consists of a homopolymer or polymer containing at least 10 moles of 4-methylphenyl vinyl ketone units. Specific examples of monomers copolymerizable with 4-methylphenyl vinyl ketone include phenyl vinyl ketone, methyl methacrylate, phenyl methacrylate, t-butyl methacrylate, be/zyl methacrylate, methyl isogropenyl ketone, and styrene. These include, but are not limited to: These monomers are copolymerized with 4-methylphenylvinyl ketone, either singly or in combination, within a range not exceeding 90 mol in terms of monomer molar ratio. If the content of 4-methylphenyl vinyl ketone units in the polymer is less than 10 moles, problems such as a decrease in dry etching resistance, a decrease in sensitivity, and a decrease in polymerization stability are undesirable.

Although there are no particular limitations on the molecular weight and molecular weight distribution KII of the polymer or copolymer constituting the resist resin of the present invention,
If the number average molecular weight (Mn) is less than 4.000 as determined by the polystyrene conversion method using the G, P, C method, it will be difficult to form a homogeneous film during film formation;
If it exceeds Q, OO, or Q, the workability during resist solution filtration will deteriorate, so it is preferable to set it to satisfy the range of 4.000≦Mn≦500,000. Also G, P
, the ratio of the weight average molecular weight (MY) and the number average molecular weight (Mn) determined by the polystyrene conversion method using the C method (
When the value of MWAin ) becomes 5.0 or more, the resolution tends to decrease. Therefore, it is better to select polymerization conditions so that (MvAin) is less than 40.

Solvents used in forming the film of the positive resist resin for deep ultraviolet of the present invention include methyl cellosolve acetate, ethyl acetate, isobutyl acetate, isopropyl acetate, and the like.

As the liquid solution for the resist resin according to the present invention, methyl cellosolve, ethyl cellosolve, methyl isobutyl ketone, methyl ethyl ketone, and mixtures thereof with poor solvents such as isopropanol are preferably used.
Other solvents can be used as long as they have a large difference in dissolution rate in the unirradiated area, so a solvent system suitable for the resist film should be selected and determined as appropriate.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 4-methylphenylvinylketo/ was synthesized using the Mann1ch reaction as shown below.

134.2 parts by weight of 4-methylacetophenone, 897 parts by weight of dimethylamine hydrochloride, and 45 parts by weight of nokuraformaldehyde were dissolved in 200 parts by weight of isobutyl alcohol, and the mixture was reacted with stirring under reflux for 5 hours, and then the reaction solution was heated at 50°C.
The mixture was diluted with 2,000 parts by weight of acetone and cooled to 0° C. to precipitate Mannich salt. The mixture was then dried for one filtration and then subjected to pyrolysis distillation to obtain 80 parts by weight of 4-methylphenyl vinyl ketone. 50 parts by weight of this 4-methylphenyl vinyl ketone and 1 part of azobisisobutyronitrile
05 parts by weight was placed in a glass ampoule, and after purging with nitrogen, the ampoule was sealed with a gas burner and placed in a rotating polymerization tank at 60°C, and polymerized for 15 hours.
After dissolving in 500 parts by weight of N-dimethylacetamide,
It was reprecipitated in distilled water, and the precipitated polymer was filtered with a glass filter and dried to obtain BoQ 4-methylphenyl vinyl ketone 40ml118. This polymer has a tetrano-
The intrinsic viscosity [η] measured using hydrofuran is α60
It was at/9. This poly-4-methylphenyl vinyl λ ketone was dissolved in methyl cellosolve acetate to a concentration of 7.4% by weight, and spin-coated onto a silicon substrate using a spinner. The film thickness after drying was 195μ. The sensitivity of the resist was determined by pre-baking at 120°C for 30 minutes and then using a Canon PL 520 F Deep UV exposure system with a cold mirror CM250 (as shown in Figure 3). Judgment was made by immersing the sample in a 20°C current solution containing a ratio of 4:1 for 3 minutes.

Although this resist resin has a film thickness of zero in the irradiated area, it is
It required an exposure amount of seconds. Furthermore, commercially available 0DUR1014 (manufactured by Tokyo Ohka Corporation), which was measured under the same conditions, required an exposure amount of 60 seconds. When this resist film was dry etched using CF4 gas plasma, the etching rate was 27S, which is 0DUR1014.

Example 2 50 parts by weight of 4-methylphenyl vinyl ketone, 50 parts by weight of methyl methacrylate, and 11 parts by weight of azobisisobutyronitrile synthesized in the same manner as in Example 1 were charged into a glass ampoule and replaced with nitrogen gas. The tube was sealed with a burner, placed in a rotating polymerization tank at 60°C, and polymerized for 5 hours. After dissolving the polymer in 500 parts by weight of NN-dimethylacetamide, it was reprecipitated in distilled water, and the precipitated polymer was filtered once through a glass filter and dried to obtain 60 parts by weight of the polymer. The intrinsic viscosity [η] of this polymer measured using tetrahydrofuran was t2dt/f. Next, this polymer was dissolved in methyl cellosolve acetate to a concentration of 6% by weight, and then spin-coated onto a silicon substrate using a spinner and dried to form a film with a thickness of 1 μm. When the sensitivity was examined in the same manner as in Example 1, it was found that an exposure time of 58 seconds was required. Furthermore, the etching rate in CF4 gas plasma was 3/4 that of commercially available 0DUR1014.

Example 5 4-methylphenyl vinyl ketone so weight s, phenylvinyl@hen 50 weight parts and azopis isoptiloni) hJα0 5 weight parts synthesized in the same manner as in Example 1 were charged into a glass ampoule and replaced with nitrogen. After that, the tube was sealed with a gas burner, and the tube was placed in a rotating polymerization tank at 60° C. and polymerized for 5 hours. The polymer was converted into N,N-dimethylacetamide 50
After dissolving the polymer to 0 parts by weight, it was reprecipitated in distilled water, and the precipitated polymer was filtered with a glass filter and dried to obtain Polymer 46.
Parts by weight were obtained. The intrinsic viscosity of this polymer measured using tetrahydrofuran is αb s dt/l
Met. This polymer was dissolved in methyl cellosolve acetate to a concentration of 7.4% by weight, and then spin-coated onto a silicon substrate using a spinner. Film thickness after drying is cL96μ
Met. When the sensitivity was examined in the same manner as in Example 1, it was found that an exposure time of 32 seconds was required.

In addition, the etching rate in CF and gas plasma is commercially available.
It was 215 of DUR1014.

Claims (1)

[Claims] At least 10 4-methylphenyl vinyl ketone units
Far-UV positive resist resin made of polymer with molar ratio