JPS6227535B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for developing high-resolution electron beam resist, and more specifically to the creation of minute patterns such as selective diffusion and selective etching in the semiconductor industry; When this pattern is created using an electron beam resist in a submicron image recording device that retains recorded information by converting it into surface irregularities, such as that seen in the production of video disks, as is known in Japanese Patent Application Laid-open No. 47-37415, etc. , relates to a method for developing an electron beam resist.

[Conventional technology]

Since positive electron beam resists are indispensable for submicron microfabrication technology, various resists have been devised. Among them, polymethyl methacrylate (RMMA) is known to have the best resolution, but its drawback is low sensitivity. Therefore, many studies have been reported in recent years to improve the sensitivity of positive electron beam resists, such as polybutyl methacrylate, copolymers of methyl methacrylate and methacrylic acid, copolymers of methacrylic acid and acrylonitrile, Positive electron beam resists such as copolymers of methyl methacrylate and isobutylene, polybutene-1-sulfone, polyisopropenyl ketone, polymethacrylamide, polycyanoacrylates, and fluorine-containing polymethacrylates have been announced; However, it is difficult to say that this resist fully satisfies both sensitivity and resolution.

In order to solve the above-mentioned drawbacks, the present inventors
As a result of various research on electron beam resist,
General formula below: [However, in the formula, X is the same or different and represents a cyano group (-
CN) or a carbamoyl group ( _-CONH2 ), R is the same or different and represents a lower alkyl group such as methyl, ethyl, propyl, etc., and n represents a positive integer. ] We have proposed an electron beam resist whose main component is polyα-cyanoacrylate, polyα-carbamoyl acrylate, or a copolymer of both. This relates to the improvement of PMMA like the above-mentioned exemplified polymers (Japanese Patent Application No. 71535/1983). Incidentally, R in the above general formula is preferably a lower alkyl group, because a lower alkyl group lowers the glass transition and makes it difficult to dry. The polymer represented by the above general formula can be obtained, for example, by the following method (see Japanese Patent Application No. 71535/1983).

40 parts of α-cyanoethyl acrylate monomer is dissolved in 320 parts of acetonitrile, 0.1 part of dimethylformamide is added dropwise as a polymerization initiator, and anionic polymerization is carried out for 2 hours with stirring at room temperature. Thereafter, the polymer is precipitated into a large amount of methanol and dried under vacuum. The higher the molecular weight of the polymer used at this time, the better, and preferably about 1 million to 3 million.

[Problem that the invention seeks to solve]

However, electron beam resists containing the polymer represented by the above general formula as a main component have higher sensitivity than PMMA, but are inferior in resolution.

For example, poly α-cyanoethyl acrylate (weight average molecular weight w = 400,000) is dissolved in cyclohexanone at a concentration of 5%, and this solution is spin-coated at about 300 rpm onto a glass substrate with chromium vapor deposited to form a 4000A thick film. After forming a film of
After heat treatment at 130℃ for 15 minutes, the irradiation dose was approximately 4.
×16 ^-6 clones/cm ² , irradiated with an electron beam at an accelerating voltage of 15 KV, then developed at room temperature using a mixed solvent of ethyl acetate and methyl isobutyl ketone, and then washed with isopropyl alcohol and dried. You can get results like this. That is,
At this time, when the two patterns after development with a development time of 20 seconds and 60 seconds were observed at a magnification of 10,000 times using an electron microscope, the bottom of the resist film did not come through in the pattern with a development time of 20 seconds, and the bottom surface of the irradiated area was very dark. A rough surface with severe unevenness was observed, and although the development time was 60 seconds, the development was done to the bottom, but the developed side was rough and whiskers were seen on the bottom. Note that when PMMA is used, this kind of surface roughening phenomenon is hardly observed.

The present inventors believe that the poor resolution of electron beam resists using this polycyanoacrylate is due to
It was thought that this occurred during the development-rinsing process.

In other words, an electron beam resist whose main component is a polymer represented by the above general formula is irradiated with an electron beam to simultaneously cleave the main chain and simultaneously produce dicyanoglutarate, α-cyanoacrylic acid, α-carbamoyl acrylic acid, etc. Something that dissolves in water or swells in water is produced. However, conventional electron beam resists made of polymers such as polycyanoacrylates are solvents that are insoluble in acetone, ethyl acetate, cyclohexanone, tetrahydrofuran, and methyl isobutyl ketone, which are solvents in which resist materials are well soluble. Since the image was developed using an organic solvent such as a mixed solvent with cyclohexane, n-hexane, methyl alcohol, etc. (organic solvents do not contain water), it is necessary to remove substances that dissolve or swell in the water. This resulted in poor resolution.

As a result of intensive research to solve this development problem, the present inventors have completed the present invention, believing that development with a water-containing developer washes away the irradiated area, improving resolution.

[Means for solving problems]

That is, the developing method of the present invention has the following general formula: (However, in the formula, X is the same or different and represents a cyano group or a carbamoyl group, R is the same or different and represents a lower alkyl group, and n represents a positive integer.) After electron beam irradiation is performed on an electron beam resist whose main component is polyα-carbamoyl acrylate or a copolymer of both, development is performed using a developer consisting of water and a solvent soluble in the electron beam resist. It is characterized by

The water-containing developer used in the present invention is composed of water and an organic solvent. It must be a polar solvent that can be mixed in a proportion of . For example, dimethylformamide (DMF), dimethyl sulfoxide, acetonitrile, acetone,
N-methylpyrrolidone, diacetone alcohol,
Examples include γ-butyrolactone and methyl cellosolve acetate. The mixing ratio of water and these solvents varies depending on the resist-dissolving power of the solvent, but it is preferable to use, for example, DMF:water = 3:1 and γ-butyrolactone:water = 4:5. At this time, if you develop with DMF alone, the unirradiated areas will easily melt, which is undesirable.

After development with the developer, post-treatment may be performed using water. In this case, a surfactant may be mixed with the post-processing water so that the developer is mixed and dissolved immediately.

In addition to the above-mentioned water, the post-treatment liquid includes a mixture of alcohols such as methanol, ethanol, and isopropanol, glycols such as methyl cellosolve, and methyl carbitol, and water.

〔Example〕

The present invention will be explained below with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

Example 1 4% polyα-cyanoethyl acrylate (weight average molecular weight w = 2.4 million) in cyclohexanone
The resulting solution was applied onto a substrate made of glass with chromium vapor-deposited at approximately 1500 rpm using a spin coating method.
A resist film with a thickness of 5000A° was formed.

After that, the film was heat-treated at 130°C for 15 minutes, and the irradiation amount was 4×10 ^-6 coulombs/cm ² and the accelerating voltage was
An electron beam with a beam width of 1.3μ was scanned at 13KV.

After irradiation, the sample was taken out of the irradiation device and immersed in a first developer solution consisting of ethyl acetate: methyl isobutyl ketone (1:1) for 90 seconds at room temperature, and then immersed in a second developer solution consisting of isopropanol:water (3:1). to
It was immersed for 30 seconds, developed, and then dried.

The obtained developed surface was examined using an electron microscope at a magnification of 1
When I observed it under 10,000x magnification, I could see a bottomless line with no whiskers.

Example 2 A resist film obtained in the same manner as in Example 1 was coated with a chromium vapor deposition mask irradiated with an electron beam in the same manner as in Example 1.
The film was developed by immersing it in a developer consisting of DMF:water (3:1) for 60 seconds, followed by washing with water for 15 seconds and drying.

When the obtained developed surface was similarly observed under an electron microscope at a magnification of 10,000 times, it was found that the irradiated area had eluted at 4000A, and no surface roughness was observed at the bottom. The electron micrograph is shown in Fig. 1.

Example 3 α-Cyano and α-carbamoylethyl acrylate copolymer (molecular weight Mw = 2.6 million) was dissolved in cyclohexanone to a concentration of 4%, and the resulting solution was applied onto a chrome substrate by spin coating at approximately 1500 rpm.
A resist film with a thickness of 6000A° was formed.

After that, the film was heat-treated at 130°C for 15 minutes,
An electron beam with a beam width of 1.3 μm was scanned at an irradiation dose of 4×10 ⁻⁶ coulombs/cm ² and an acceleration voltage of 13 KV. After irradiation, the sample was taken out from the irradiation device and immersed in a first developer solution consisting of ethyl acetate: methyl isobutyl ketone (1:1) for 45 seconds at room temperature, and after drying, it was placed in a second developer solution consisting of DMF:water (3:1). After immersion for 30 seconds and development, the film was washed with water and dried. When the obtained developed surface was similarly observed under an electron microscope at a magnification of 10,000 times, the irradiated area was found to have eluted at 4500A, and no surface roughness was observed at the bottom.

Comparative Example A chromium vapor deposition mask irradiated with an electron beam obtained in the same manner as in Example 1 was immersed in a developer consisting of ethyl acetate: methyl isobutyl ketone (1:1) for 60 seconds, then washed with isopropanol for 15 seconds and dried. .

When the obtained developed surface was observed with an electron microscope at a magnification of 10,000 times, the irradiated area was found to have eluted at 2700A°.
A rough surface was observed on the bottom. The electron micrograph is shown in Fig. 2.

〔Effect of the invention〕

As described above, the present invention enables water-soluble or water-swellable components to be produced by electron beam irradiation by specifying polymer components in polymer-based electron beam resists, which have conventionally been conventionally developed using organic solvents. This method is based on the knowledge that, by simply adding water to the developer, an excellent developed relief can be easily obtained.

[Brief explanation of the drawing]

FIG. 1 is an electron micrograph (×10,000) showing the grain structure of the developed relief surface according to the present invention, and FIG. 2 is an electron micrograph (×10,000) showing the grain structure of the developed relief surface according to the conventional method.

Claims (1)

[Claims] 1. General formula: (However, in the formula, X is the same or different and represents a cyano group or a carbamoyl group, R is the same or different and represents a lower alkyl group, and n represents a positive integer.) After electron beam irradiation is performed on an electron beam resist whose main component is polyα-carbamoyl acrylate or a copolymer of both, development is performed using a developer consisting of water and a solvent soluble in the electron beam resist. A method for developing an electron beam resist, characterized by: