JPH0675196B2 - Positive electron beam resist - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a high-sensitivity, high-resolution positive electron beam resist. More specifically, it is an object of the present invention to provide a resist for selective etching or selective diffusion in manufacturing a photomask in the semiconductor industry and manufacturing a semiconductor by direct writing on a silicon wafer.

[Prior art and its problems] Polymethylmethacrylate (PMMA) is known as a typical example of a positive electron beam resist, but its sensitivity is as low as 50 μC / cm ² and the throughput of the electron beam lithography system becomes a problem. , A lot of research has been done to increase the sensitivity.

It is generally known that the introduction of an electron withdrawing group such as a cyano group or a halogen atom into the molecule improves the sensitivity, and the α-methyl group of the methacrylic acid ester polymer is replaced with a cyano group. The 2-cyanoacrylic acid ester polymer has a high sensitivity of 1 μC / cm ² (accelerating voltage 20 kV). Furthermore, when the ester group of 2-cyanoacrylic acid ester is a cyclic alkyl group, heat resistance and solvent resistance are also high. However, since the edge roughness of the resist pattern is large, the resolution is low, and sensitivity and resolution have not been satisfied at the same time.

In addition, the butyl methacrylate polymer in which the methyl group, which is the ester group of PMMA, is replaced with a butyl group has a high glass transition temperature of 15 ° C with a high sensitivity of 0.5 μC / cm ² , so it has almost no heat resistance and sufficient resolution. Is not obtained, and this resist has not yet satisfied both sensitivity and resolution at the same time.

[Problems to be Solved by the Invention] It is an object of the present invention to provide a positive type electron beam resist having high sensitivity and high resolution at the same time for a large scale integrated circuit after 16 megabit DRAM.

[Means for Solving the Problems] The present invention provides a positive type electron beam resist containing a 2-cyanoacrylic acid ester-methacrylic acid ester copolymer represented by the formula (a) as a main component and simultaneously satisfying high sensitivity and high resolution. To do.

The 2-cyanoacrylic acid ester-methacrylic acid ester copolymer according to the present invention is obtained by radically polymerizing a 2-cyanoacrylic acid ester monomer and a methacrylic acid ester monomer. The molecular weight of the obtained copolymer is generally 10,000 to 3,000,000. However, if the molecular weight is too high, the coatability is lowered, and if the molecular weight is too low, the sensitivity is lowered. Those having a molecular weight of 10,000 to 1,000,000 are preferable.

The 2-cyanoacrylic acid ester monomer used in the present invention is represented by the following formula (b).

However, R ₁ in the formula is a cyclic alkyl group having 5 to 8 carbon atoms, and specifically, cyclopentyl 2-cyanoacrylate, cyclohexyl 2-cyanoacrylate, cycloheptyl 2-cyanoacrylate, 2- Cyclooctyl cyanoacrylate.

The methacrylic acid ester monomer is represented by the following formula (c).

However, R ₂ in the formula is an alkyl group having 1 to 8 carbon atoms or a cyclic alkyl group having 3 to 8 carbon atoms, and specifically, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate. , N-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-pentyl methacrylate, isoamyl methacrylate, n-hexyl methacrylate, cyclohexyl methacrylate, n-octyl methacrylate and the like.

The copolymerization ratio is 2-cyanoacrylic acid ester: methacrylic acid ester = 5: 95 to 95: 5, preferably 10:90 to 90:10. When the content of 2-cyanoacrylate is high, the sensitivity is high but the resolution is low. On the contrary, when the content of methacrylic acid ester (excluding butyl methacrylate) is high, the resolution is high but the sensitivity is low. . In the case of a methacrylic acid ester having 6 or more carbon atoms in the ester group, when the content thereof is high, the glass transition temperature is low, so that there is no heat resistance and the resolution is lowered.

FIG. 1 is a residual film sensitivity curve showing a comparison between PMMA and a 2-cyanoacrylic acid cyclohexyl-methyl methacrylate copolymer of the present invention. The acceleration voltage of the irradiation electron beam is 20 kV.
The development conditions after irradiation are as follows: developer (copolymer) methyl isobutyl ketone: 2-propanol = 40:60 (PMMA) methyl isobutyl ketone: 2
-Propanol = 50:50 Development time ... (copolymer) 5 minutes (PMMA) 10 minutes Development temperature ... 20 ° C. As can be seen from this figure, the positive type electron beam resist of the present invention is remarkably improved in sensitivity. When the resist pattern was observed with an electron microscope, a sharp pattern without edge roughness was observed.

[Example 1] 10 g of cyclohexyl 2-cyanoacrylate, 10 g of methyl methacrylate, 2 g of acetic acid, 0.1 of azobisisobutyronitrilo
g was charged in a glass sealed tube (copolymerization ratio 50:50), and reacted in a nitrogen stream at 60 ° C. for 10 hours. This was poured into petroleum ether to precipitate the reaction product, which was a white powdery copolymer.
18: 3g was obtained. The molecular weight of this copolymer was 380,000 (GPC
According to polystyrene).

A 5% by weight solution of this copolymer in cyclohexanone was prepared, and a resist film of 4900A thickness was formed at 1200rpm by spin coating method on a glass substrate on which chromium was vapor-deposited at 1000A thickness, and heat treated at 120 ° C for 30 minutes. Then, electron beam irradiation was performed at an irradiation amount of ² μC / cm ² and an acceleration voltage of 20 kV. After electron beam irradiation, 2 with a mixed solvent of methyl isobutyl ketone: 2-propanol = 40:60
A positive resist pattern was obtained by dipping at 0 ° C. for 5 minutes, rinsing in 2-propanol and drying. Furthermore, after heat treatment at 120 ° C for 30 minutes, dipping it in a cerium ammonium nitrate and perchloric acid chromium etching solution for 50 seconds, the chromium layer of 1000A is etched, and the resist film is removed with acetone. A chromium pattern having a line width of 0.5 μm was obtained.

[Comparative Example 1] PMMA was coated on a chrome blank to a thickness of 5000A.
After prebaking at 70 ° C. for 30 minutes, irradiation with an electron beam of 1 to 100 μC / cm ² was performed. After electron beam irradiation, methyl isobutyl ketone: 2-
It was immersed in a mixed solvent of propanol = 50: 50 at 20 ° C. for 10 minutes, then rinsed with 2-propanol and dried. The electron dose at which the resist in the electron beam irradiated area was completely removed, that is, the residual film sensitivity was 50 μC / cm ² . This electron dose is 25 times that of the copolymer according to the invention.

[Example 2] 12 g of cyclopentyl 2-cyanoacrylate, 8 g of cissopropyl methacrylate, 2 g of acetic acid and 0.1 g of azobisisobutyronitrilo were charged in a glass sealed tube (copolymerization ratio 60:40), and the same as in Example 1. The reaction and treatment were carried out to obtain 15.5 g of a copolymer. The molecular weight of this copolymer was 320,000.

A 5 wt% cyclohexanone solution of this copolymer was prepared,
A film was formed in the same manner as in Example 1, and after heat treatment, ² μC / cm ²
It was irradiated with an electron beam. After irradiation with electron beam, the mixture was mixed with 2-methoxyethanol: 2-propanol-30: 70 mixed solvent at 20 ° C for 3 times.
Soak for a minute, then rinse with 2-purpanol and dry. When the obtained resist pattern was observed by SEM, a very sharp pattern without edge roughness was observed.

[Comparative Example 2] A 4 wt% cyclohexanone solution of 2-cyanoacrylate cyclopentyl polymer having a molecular weight of 510,000 was prepared, and a film was formed on a chromium blank by a spin coating method, prebaked at 120 ° C for 30 minutes, and then at 2 µC / Irradiation with electron beam was performed at cm ² . After electron beam irradiation, methyl isobutyl ketone: 2-propanol = 60: 4
It was developed with a mixed solvent of 0 for 5 minutes and processed in the same manner as in Example 1, and the obtained resist pattern was observed with an electron microscope. As a result, the edge roughness was large.

Example 3 Cyclooctyl 2-cyanoacrylate 14 g, isobutyl methacrylate 6 g, acetic acid 2 g, azoisobutyronitrilo 0.07
g was charged in a glass sealed tube (copolymerization ratio 70:30), reacted at 60 ° C. for 15 hours, and treated in the same manner as in Example 1 to obtain 18.1 g of a copolymer. The molecular weight of this copolymer was 500,000.

Make a 4 wt% cyclohexanone solution of this copolymer,
A film was formed in the same manner as in Example 1, and after heat treatment, electron beam irradiation was performed at ² μC / cm ² . After electron beam irradiation, it was immersed in a mixed solvent of 2-butoxyethanol: 2-propanol = 95: 5 for 20 minutes at 20 ° C, then rinsed with 2-propanol and dried. Furthermore, it is heat-treated at 120 ° C for 30 minutes, and it is treated with a cerium ammonium nitrate and perchloric acid chromium etching solution to 50
When immersed for 1000 seconds, the chromium layer of 1000A is etched,
Removing the resist coating with acetone leaves the glass substrate
A chromium pattern having a line width of 0.5 μm was obtained.

[Comparative Example 3] A 5% by weight solution of n-butyl methacrylate polymer in ethyl cellosolve was prepared, and a film was formed on a chromium blank by a spin coating method, prebaked at 120 ° C for 30 minutes, and then at 2 µC / c.
It was irradiated with an electron beam at m ² . After the electron beam irradiation, it was dipped in 2-propanol for 3 minutes to obtain a resist pattern. Post-baking must be performed to wet etch chromium using this resist pattern, but it must be treated at 50 ° C. or higher to obtain sufficient adhesion. However, since the glass transition temperature was low at that temperature, resist flow occurred and the resist pattern was deformed.

[Advantage of the Invention] From the above, by using the resist of the present invention, it is possible to form a positive resist pattern with high sensitivity and high resolution, and it is possible to bring about a great effect on high productivity and cost reduction in semiconductor manufacturing. You can

[Brief description of drawings]

FIG. 1 is a residual film sensitivity curve showing a comparison between the 2-cyanoacrylic acid cyclohexyl-methyl methacrylate copolymer of the present invention and PMMA.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mizen Sato 1 Funami-cho, Minato-ku, Nagoya-shi, Aichi 1 Toa Gosei Chemical Industry Co., Ltd. (72) Inventor Yoshiaki Fujimoto Funami-cho, Minato-ku, Nagoya-shi, Aichi No. 1 No. 1 Toagosei Chemical Industry Co., Ltd. Research Institute (72) Inventor Kaoru Kimura No. 1 Funami-cho, Minato-ku Nagoya City, Aichi Prefecture No. 1 Toagosei Chemical Industry Co., Ltd. In-house Examiner Kayoko Yasuda (56) References JP-A-1-154146 (JP, A) JP-A-1-217341 (JP, A)

Claims (1)

[Claims] 1. A general formula (a) (However, R ₁ in the formula is a cyclic alkyl group having 5 to 8 carbon atoms,
R ₂ is an alkyl group having 1 to 8 carbon atoms or a cyclic alkyl group having 3 to 8 carbon atoms, and m and n are positive integers) 2-cyanoacrylic acid ester-methacrylic acid ester copolymer A positive type electron beam resist, characterized in that