JPH0128937B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a positive radiation resist material that is sensitive to radiation such as electron beams, X-rays, gamma rays, and far ultraviolet rays. The present invention relates to positive radiation resist materials. There are two types of radiation resists: negative type, in which bridge chips become insolubilized by exposure to radiation, and positive type, in which the exposed areas disintegrate and are dissolved and removed during development.Generally, negative type has high sensitivity but poor resolution; Although it has excellent resolution, it has the disadvantage of low sensitivity. Currently, development efforts are focused on increasing the sensitivity of positive resists, which have excellent resolution.
Many positive radiation resists have been proposed in the past, but none are known that simultaneously satisfy the basic characteristics necessary for a resist, such as sensitivity, resolution, and dry etching resistance. For example, polymethyl methacrylate (hereinafter abbreviated as PMMA), which has been most widely studied and put into practical use in some areas, has excellent resolution, but its sensitivity to electron beams is 5 × 10 ^-5
It has a low defect of ~1×10 ^-4 coulomb/cm ² .
Sensitivity here is the minimum amount of radiation exposure necessary for 100% of the resist film coated on the substrate to be removed by a developing operation. For this reason, many methods have been investigated to improve sensitivity without sacrificing the advantages of PMMA. The first is to increase the sensitivity by increasing the molecular weight of PMMA, that is, by increasing the molecular weight, the rate of decrease in molecular weight due to electron beam exposure is increased. Kuroda et al. wrote in ``Proceedings of the Autumn Academic Conference of the Japan Society of Applied Physics,'' p. 233 (1971) that a mixed solvent was prepared by mixing ethyl acetate and isoaluminium acetate in a volume ratio of 2:8 using PMMA with a molecular weight of 4 million. It has been reported that the sensitivity increased by 3 digits to 5×10 ^-8 clones/cm ² when used as a developer. However, it is not clear whether the resolution was maintained in this case. Usually, high molecular weight polymers cannot be filtered through a submicron diameter filter, so the coating properties are extremely deteriorated due to mixed dust. In addition, many other disadvantages occur at the same time, such as significant swelling during development and a decrease in resolution. The second method is to increase sensitivity by copolymerizing methyl methacrylate as a main component with a vinyl compound. The introduction of materials with a large G-value for cleavage or materials that are easily thermally decomposed is known, such as methacrylic acid, isobutylene, α-chloroacrylate, α-cyanoacrylate, acrylonitrile, and copolymers of isobutyl methacrylate and methyl methacrylate. ing. The sensitivity of these materials is certainly one to two orders of magnitude higher than that of PMMA. However, the glass transition temperature
It also has serious drawbacks as a resist, such as significantly lower heat resistance than PMMA, and resolution that causes pattern flow during heat treatment similar to that of PMMA. The third method is a method of increasing sensitivity by introducing a component that breaks the bridge when heated. Since this method maintains the bridge chip structure in the unexposed area, it can be expected not only to increase sensitivity but also to develop in a short time. There are three known types of this method. One is that the polymer itself forms intermolecular bridge cracks when heated; methyl methacrylate-methacrylic acid copolymer and polymethacrylamide polymer are known, and these are -COOH, -, respectively.
It becomes three-dimensional through a dehydration reaction between COOH and a deammonization reaction between -CONH ₂ and -CONH ₂ . However, although these have high sensitivity, they have very poor resolution, and furthermore, it is difficult to control the density of bridge chips at a constant level, so they have the disadvantage that they cannot be provided as stable resists. The second method involves adding additives to the polymer to create intermolecular bridges, such as adding a diepoxy compound to the methyl methacrylate-methacrylic acid copolymer and adding neopentyl glycol to the methyl methacrylate-methacrylic acid chloride copolymer. things are known. However, these reactions also have the disadvantage that it is difficult to control the bridge chipping density, and unreacted substances cause film burr. The third method is to mix two types of polymers, and the reactive groups of one polymer combine with the reactive groups of the other polymer to create a three-dimensional structure. A method is known in which a copolymer of methyl methacrylate and methacrylic acid chloride and a copolymer of methyl methacrylate and methacrylic acid are mixed. However, methacrylic acid chloride has extremely high reactivity and reacts with water in the air, causing great difficulties in stable storage and handling during use. The present invention was made to improve the above-mentioned drawbacks, and provides a positive radiation resist material that has higher sensitivity than PMMA, has a resolution comparable to PMMA, is easy to handle, and can be stored for a long time. This is what we provide. That is, the present invention provides (a) general formula

A group consisting of 97 to 70 mol% of a methacrylic acid ester represented by the formula (wherein R is an alkyl group or a cycloalkyl group and may contain a halogen substituent), and (b) acrylic acid and methacrylic acid. A copolymer composed of 3 to 30 mol% of at least one selected from
100 parts of metal acetylacetonate containing divalent or higher valence metal ions and soluble in the solvent of the above copolymer.
This is a positive radiation resist material containing 0.1 to 20 parts. The positive radiation resist material of the present invention is made by copolymerizing a methacrylic acid ester as a main component and adding a component consisting of at least one of acrylic acid and methacrylic acid, which partially participates in bridge chipping, and to this copolymer, a novel bridge chipping agent is added. A metal acetylacetonate containing a multivalent metal ion of divalent or higher valence is added. One component of the copolymer used in the present invention has the general formula:

It is a methacrylic acid ester represented by the formula: (R is an alkyl group or a cycloalkyl group, and may contain a halogen substituent). The alkyl group and cycloalkyl group are preferably lower-grade ones, and the alkyl group preferably has 4 or less carbon atoms, and the cycloalkyl group preferably has 6 or less carbon atoms. These may be used alone or in combination in any proportion. Specific examples include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, and methacrylic acid.
Examples include iso-propyl, n-butyl methacrylate, iso-butyl methacrylate, sec-butyl methacrylate, and cyclohexyl methacrylate.Other examples containing halogen include 2,2,2-trifluoroethyl methacrylate, 2, 2,2-
Trichloroethyl methacrylate, 2,2,2-
trifluoro-iso-propyl methacrylate,
Examples include 2,2,2-trichloro-iso-propyl methacrylate. Other components of the copolymer are acrylic acid and methacrylic acid, which may also be used alone or in combination. The composition of the polymer synthesized by these combinations is 97 to 70 mol% for the former and 3 to 30 mol% for the latter.
It can be used up to a certain extent. The reason for this is that if the latter is too small, the bridge chipping density will decrease and the solvent resistance will not be sufficient, and if it is too large, the amount of exposure to bring the bridge chipping density within the gelling limit will increase, resulting in a decrease in sensitivity. Because it will lead you.
However, in this case, although the amount of the bridging agent can be adjusted to some extent, it is not preferable to add a large amount of copolymer components because the original properties of the main components will be lost. The most effective range is a copolymerization composition of 95 to 85 mol% for the former and 5 to 15 mol% for the latter. The polymerization may be a commonly used radical polymerization. Next, the bridge chipping agent used in the present invention has a valence of 2 or more, and since it is applied to the substrate by dissolving it in a solvent together with the copolymer, butyl acetate, isoamyl acetate, isobutyl acetate, methyl cellosolve acetate, dimethyl A metal acetylacetonate soluble in the solvent of the copolymer, such as formamide, dimethyl sulfoxide, methyl isobutyl ketone, methyl ethyl ketone, chlorobenzene, toluene, etc., is used. Specific examples include nickel acetylacetonate,
Iron acetylacetonate, lead acetylacetonate, cobalt acetylacetonate (divalent and trivalent), copper acetylacetonate, chromium acetylacetonate (divalent and trivalent),
Examples include, but are not limited to, manganese acetylacetonate, calcium acetylacetonate, magnesium acetylacetonate, zinc acetylacetonate, titanium acetylacetonate, cadmium acetylacetonate, barium acetylacetonate, aluminum acetylacetonate, and the like. Depending on the type of organic solvent, these may be difficult to dissolve, but even in such cases, if a highly polar solvent such as dimethyl sulfoxide or dimethyl formamide is used, a sufficient amount to produce the effects of the present invention can be obtained. Can be dissolved. Regarding the amount of metal acetylacetonate added, it is desirable that the total amount of the number of carboxyl groups in the copolymer and the valence of the metal ion is 1:1,
The weight ratio of the metal acetylacetonate is 0.1 to 20 parts per 100 parts of the copolymer, and a particularly preferable range is 0.5 to 5 parts. Further, the radiation resist in the present invention does not form bridge chips when it is applied onto a substrate, but is caused to chip by heating in the pre-baking stage. The heating temperature at this time is preferably in the range of 100°C to 200°C. In other words, if the temperature is lower than 100℃, it will take a very long time to form a bridge chip, and if the temperature is higher than 200℃, a dehydration reaction will occur between the carboxyl groups that are copolymerized components, causing the bridge to chip, making it difficult to control the bridge chip density. It becomes difficult. Furthermore, it is not preferable that the molecular weight of the copolymer used in the present invention is very high. That is, although the solubility of this resist is reduced by forming bridge chips, it is desirable that the solubility be as high as possible once exposed to light. For this purpose, the weight average molecular weight of the copolymer is preferably 10,000 to 700,000. Although the mechanism of action of the present invention is not clear, it is thought that the following reaction probably occurs. That is, upon heating, the metal acetylacetonate and the carboxylic acid react to form an ionic bond between the polyvalent metal ion and the carboxylic acid. According to experiments conducted by the present inventors, the amount of film reduction before and after pre-baking is proportional to the amount of metal acetylacetonate added. From this, it is considered that most of the main reaction components other than metal ions are dispersed outside the resist film. The present invention will be explained below with reference to Examples. However, these do not define the content of the present invention. Example 1 Methyl methacrylate and methacrylic acid were radically polymerized by a conventional method to obtain a copolymer containing 80 mol% of the former and 20 mol% of the latter. The weight average molecular weight at this time was 42,000. Next, for this copolymer,
Add 1.22 weight percent iron acetylacetonate (containing trivalent iron ions) and dissolve in methyl cellosolve acetate. The concentration at this time was 16.1%. Next, this resist solution was filtered through a 0.45μ membrane filter, and then spin coating was performed. When the spinner was rotated for 1 minute at 1000 rpm, a film having a thickness (d) x refractive index (n) of 10000 Å was obtained. (Hereinafter, this value of n·d will be treated as the film thickness.) Next, this resist film was prebaked at 170° C. for 60 minutes. At this stage, the difference in film thinning rate between those with and without a bridge chipping agent was 50 Å/min for the former and 290 Å/min for the latter, clearly indicating that bridge chips were formed (Figure 1). reference). After prebaking, the samples were exposed to electron beams with various exposure times, developed with methyl isobutyl ketone, and measured. The results are shown in FIG. For exposure, an electron beam exposure device JEBX-2B manufactured by JEOL Ltd. was used, and the acceleration voltage was 30 KV. As a result, when developing for 5 minutes, the film loss rate in the non-exposed area was 3% and the sensitivity was 3.2 x 10 ^-5 coulombs/
cm ² , contrast was 2.84, and sensitivity was 9.8 x 10 ^-6 coulombs/cm ² contrast 2.23 with 15% film loss in non-exposed areas after 20 minutes of development. From this, it can be seen that the contrast is almost the same as that of PMMA, and the sensitivity is improved by 5 to 10 times. Example 2 To the copolymer obtained in Example 1, 1.41% by weight of nickel acetylacetonate (containing divalent nickel ions) was added and dissolved in methyl cellosolve acetate. Next, this was coated in the same manner as in Example 1, and heat treated at 150°C for 60 minutes.
As a result, the film reduction rate was 125 Å/min, confirming that bridge chips were still formed. This was subjected to the same operations as in Example 1 to determine the resist characteristics. When the film loss was 10%, the sensitivity was 9.2×10 ^-6 coulombs/cm ² and the contrast was 2.35. Example 3 Iso-propyl methacrylate and acrylic acid were radically polymerized in a conventional manner to obtain a copolymer containing 91 mol% of the former and 9 mol% of the latter. The weight average molecular weight at this time was 180,000. To this copolymer, 2.85 weight percent of cobalt acetylacetonate (containing trivalent cobalt ions) was added and dissolved in methyl cellosolve acetate. Next, this is Example 1
After coating in the same manner as above and pre-baking at 170℃ for 60 minutes,
The same operations as in Example 1 were performed to determine resist characteristics. When the film loss was 13%, the sensitivity was 1.0×10 ^-5 coulombs/cm ² and the contrast was 2.33. Example 4 Radical polymerization of n-butyl methacrylate and methacrylic acid was carried out in a conventional manner to obtain a copolymer containing 84 mol% of the former and 13 mol% of the latter. The weight average molecular weight is
It was 330,000. 1.5% by weight of copper acetylacetonate was added to this copolymer and dissolved in methyl cellosolve acetate. Next, this was coated, and after pre-baking at 170°C for 60 minutes, the same operation as in Example 1 was performed. The film reduction rate was 13%, and the sensitivity was 1.0×10 ^-6 coulombs/cm ² and the contrast was 2.0. Example 5 Cyclohexyl methacrylate and acrylic acid were radically polymerized to obtain a copolymer containing 83 mol% of the former and 17 mol% of the latter. The weight average molecular weight was 150,000. To this copolymer, 5.1% by weight of iron acetylacetonate (trivalent iron ion) was added and dissolved in methyl cellosolve acetate. Next, this was coated, and after prebaking at 150°C for 60 minutes, the same operation as in Example 1 was performed. Sensitivity 7.7× when film reduction rate is 16%
It was 10 ^-6 coulombs/cm ² and the contrast was 1.76. Example 6 2,2,2-trichloroethyl methacrylate and methacrylic acid were radically polymerized in a conventional manner to obtain a copolymer containing 87 mol% of the former and 13 mol% of the latter. The weight average molecular weight was 270,000. 5.5% by weight of aluminum acetylacetonate was added to this copolymer and dissolved in methyl cellosolve acetate. Next, coat this with
After prebaking at 200°C for 60 minutes, it was exposed and developed with ethyl cellosolve. Sensitivity is 2.1× when film reduction rate is 11%
It had a value of 10 ^-6 coulombs/cm ² and a contrast of 2.8.

[Brief explanation of drawings]

Figure 1 shows a copolymer of methyl methacrylate and methacrylic acid, with a molar ratio of 100 for the former to 100 for the latter.
25 (hereinafter referred to as (copolymer−
1) versus iron acetylacetonate (Fe
(AA) ₃ ) and nickel acetylacetonate (Ni(AA) ₂ ) are added to the film. Figure 2 shows copolymer-1
This is a sensitivity characteristic curve obtained when 1.22 weight percent of iron acetylacetonate was added to the sample. Measurements were made with four different developing times, and A is 5.
Film reduction rate is 3.0% after minute development, B is 6.0% after 8 minutes development, C is 10% after 15 minutes development, D is 20 minutes.
This is a sensitivity characteristic curve when the film reduction rate is 15% during minute development.

Claims (1)

[Scope of Claims] 1 (a) 97 to 70 mol% of a methacrylic acid ester represented by the general formula [Formula] (wherein R is an alkyl group or a cycloalkyl group and may contain a halogen substituent); (b) A copolymer composed of 3 to 30 mol% of at least one selected from the group consisting of acrylic acid and methacrylic acid.
100 parts of metal acetylacetonate containing divalent or higher valence metal ions and soluble in the solvent of the above copolymer.
A positive radiation resist material containing 0.1 to 20 parts.