JPH05289338A - Positive electron beam resist - Google Patents

Abstract

PURPOSE:To obtain a resist free from the generation of cracks of a resist pat tern on silicon dioxide, high in sensitivity and excellent in dry etching resistance by containing a specific 2-cyanoacrylic alkyl cyclohexyl polymer as a main component. CONSTITUTION:The 2-cyanoacrylic alkyl cyclohexyl polymer expressed by the formula is contained as a main component. In the formula, R is a lower alkyl group and is preferably 1-4C. When the carbon number of alkyl group of substituted group is >=5, the deterioration of sensitivity and negative inversion is generated because cross-linking reaction in side chain occurs preferentially by principal chain severance reaction. The number and position of alkyl substituted group is not restricted. In this case, the positive electron beam resist is obtained by the anion polymerization or the radical polymerization of 2- cyanoacrylic alkyl cyclohexyl monomer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positive type electron beam resist having high sensitivity, good dry etching resistance and adaptable to silicon dioxide. More specifically, it is an object of the present invention to provide a resist pattern for selective etching and diffusion in semiconductor manufacturing by manufacturing a phase shift mask in the semiconductor industry and directly writing on a silicon wafer.

[0002]

2. Description of the Related Art With the miniaturization of semiconductor elements in the manufacture of semiconductor integrated circuits, direct exposure of electron beams and exposure methods using phase shift masks are considered promising because of the limit of resolution of conventional ultraviolet exposure. Both methods require electron beam lithography to process silicon dioxide, and this silicon dioxide can be processed by either wet etching or dry etching.

However, wet etching is not suitable for fine processing because it is isotropic etching. On the other hand, in dry etching such as reactive ion etching, fine patterns can be processed because of anisotropic etching. Therefore, dry etching is advantageous for processing a fine pattern, but the dry etching resistance of the resist poses a problem.

The sensitivity of a positive electron beam resist and the resistance to dry etching are in a trade-off relationship. A resist having high sensitivity tends to have low dry etching resistance, and a resist having high dry etching resistance tends to have low sensitivity. For example, P
Positive resists such as BS (trade name manufactured by Chisso Co., Ltd.), EBR-9 (trade name manufactured by Toray Co., Ltd.), and FBM-120 (trade name manufactured by Daikin Industries, Ltd.) have high sensitivity,
The dry etching resistance is low, and is not more than 1/2 that of the methyl methacrylate polymer which is the standard of positive type electron beam resist. In addition, positive electron beam resists containing a benzene ring such as φ-MAC (trade name of Daikin Industries, Ltd.) and MP2400 (trade name of Shipley, USA) have high dry etching resistance but low sensitivity, and 20 μC / There is a problem that the throughput is low because an electron beam dose of cm ² or more is required.

[0005]

The sensitivity of cyclohexyl 2-cyanoacrylate polymer as a positive electron beam resist is as high as ^{2 to} 10 μC / cm ² (accelerating voltage 20 kV),
Further, it has a higher dry etching resistance than other acrylic electron beam resists and PBS, and has almost the same dry etching resistance as a resist containing a benzene ring. This cyclohexyl 2-cyanoacrylate polymer causes no problem when a film is formed on a metal such as chromium, aluminum, or silicon, and is subjected to development treatment after electron beam irradiation, but cracks occur in the resist pattern on silicon dioxide. There was a problem that it would end up.

It is an object of the present invention to provide a resist having high sensitivity and good dry etching resistance in which a resist pattern does not crack even on silicon dioxide.

[0007]

The present invention is a positive-type electron beam resist containing a 2-cyanoalkyl acrylate cyclohexyl polymer represented by the chemical formula 1 as a main component. In the formula, R represents a lower alkyl group and preferably has 1 to 4 carbon atoms. When the alkyl group of the substituent has 5 or more carbon atoms, the side chain cross-linking reaction has priority over the main chain breaking reaction, resulting in decreased sensitivity and negative reversal. The number m and the position of the alkyl substituent are not particularly limited.

[0008]

[Chemical 1]

The positive type electron beam resist according to the present invention is 2-
It is obtained by anionic or radical polymerization of an alkylcyclohexyl acrylate monomer. The alkyl 2-cyclohexylacrylate cyclohexyl monomer used in the present invention is represented by (Chemical Formula 2).
R in the formula is a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group or the like.

[0010]

[Chemical 2]

Although the radical polymerization method is used, the initiators used in ordinary radical polymerization include benzoyl peroxide and azobisisobutyronitrile, which are bulk polymerization or solution polymerization. Is possible. As a polymerization solvent used for solution polymerization, benzene, toluene,
Examples include organic solvents such as xylene, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, tetrahydrofuran, and methyl cellosolve acetate.
Although the polymerization temperature and the polymerization time naturally vary depending on the type and amount of the polymerization initiator and the polymerization solvent used, the polymerization temperature is preferably 40 to 80 ° C., and the polymerization time is preferably 1 to 24 hours.

As an initiator for the anionic polymerization method, an organic amine which is a weak base is preferable. Specific examples thereof include aniline, diethylamine, N, N-dimethyl-p-toluidine and the like. The reaction temperature is preferably 20 to -100 ° C in order to control the polymerization rate of the monomer and suppress side reactions. The same polymerization solvent as that used in radical polymerization can be used.

The molecular weight is from 10,000 to 3,000,000, but if the molecular weight is too high, the coating property is lowered, and if the molecular weight is too low, the sensitivity is lowered.

[0014]

When the cyclohexyl 2-cyanoacrylate polymer is coated on silicon dioxide and irradiated with an electron beam and then developed, a crack occurs in the resist pattern.
It is considered that this is because the six-membered ring has a high stereoregularity and internal stress was applied to the cracks. However, the 2-cyanoacrylic acid ester polymer having a cyclohexyl group substituted with an alkyl group of the present invention has a low stereoregularity and therefore has a characteristic that cracks do not occur even on silicon dioxide. Further, since it does not contain an aromatic group such as a benzene ring and further has a cyano group, the sensitivity is not lowered and the dry etching resistance is also satisfied.

Table 1 shows a comparison between the 2-cyanoalkyl acrylate cyclohexyl polymer of the present invention and the 2-cyanoacrylate cyclohexyl polymer. As is apparent from Table 1, the 2-cyanoacrylic acid ester polymer having an alkylcyclohexyl group of the present invention has excellent sensitivity and dry etching resistance, and further has compatibility with silicon dioxide.

[0016]

[Table 1]

[0017]

【Example】

<Example 1> 2-cyanoacrylic acid-4-methylcyclohexyl monomer 0.1 mol, azobisisobutyronitrile
0.001 mol, 1 ml of acetic acid in a nitrogen stream at 80 ℃ 12
Reacted for hours. This was poured into methanol to precipitate the reaction product, and 13.4 g of a white powdery polymer was obtained. The molecular weight of this polymer was 240,000 (polystyrene conversion by GPC).

2-Cyanoacrylic acid having a molecular weight of 240,000-4-
A cyclohexanone solution of 5% by weight of a methylcyclohexyl polymer was prepared, and chromium was deposited to a thickness of 80 nm, and silicon dioxide was sputtered to a thickness of 400 nm on the glass substrate. Resist film is formed and heat-treated at 120 ° C for 30 minutes, then the irradiation dose is 0.8-40 μC / cm ² (accelerating voltage
It was irradiated with an electron beam at 20 kV).

After electron beam irradiation, methyl isobutyl ketone:
A resist pattern was obtained by immersing in a mixed solvent of isopropyl alcohol = 65: 35 (volume ratio) at 20 ° C. for 1 minute, rinsing in isopropyl alcohol and drying.

The residual film sensitivity was as high as 2.0 μC / cm ² , and the obtained resist pattern was not cracked at all.

Next, using a reactive ion etching device, a mixed gas of CF ₄ (45 SCCM) and oxygen (5 SCCM) was used to
Silicon dioxide was dry-etched at 0.03 Torr and power of 300 W for 18 minutes. When the resist film was removed with acetone and the etching shape of silicon dioxide was observed by an electron microscope, a vertical cross-sectional shape pattern without taper was confirmed. The etching rate of silicon dioxide is 24.6 nm / min, while the etching rate of methyl 2-cyclohexylacrylate is 15.9 nm / min.
It had a sufficient selectivity.

<Example 2> N, N-dimethyl-p-toluidine
Using 0.0002 mol of the polymerization initiator, 0.1 mol of 2-cyanoacrylic acid-4-ethylcyclohexyl monomer was reacted in 200 ml of tetrahydrofuran at -70 ° C for 10 hours. This was poured into petroleum ether to precipitate the reaction product, and 11 g of a white powdery polymer was obtained. The molecular weight of this polymer was 330,000.

2-Cyanoacrylic acid having a molecular weight of 330,000-4-
A cyclohexanone solution of 5% by weight of an ethylcyclohexyl polymer was prepared, and a film was formed on a substrate on which silicon dioxide was sputtered in the same manner as in Example 1, and electron beam irradiation was performed. After the electron beam irradiation, it was dipped in a mixed solvent of methyl isobutyl ketone: isopropyl alcohol = 50: 50 at 20 ° C. for 40 seconds and rinsed in isopropyl alcohol to obtain a resist pattern.

The residual film sensitivity was 2.7 μC / cm ² , and cracks did not occur in the resist pattern. Further Example 1
As a result of performing dry etching in the same manner as in (1), a vertical cross-sectional silicon dioxide pattern without a taper was obtained. The dry etching rate of cyclohexyl 2-cyanoacrylate polymer was 16.2 nm / min, whereas the dry etching rate of ethyl 2-cyanoacrylate cyclohexyl was 15.6 nm / min, and dry etching resistance was improved. ..

Example 3 To 200 ml of toluene was added 2-cyanoacrylic acid-4-isobutylcyclohexyl monomer.
1 mol, acetic acid 1 ml, azobisisobutyronitrile 0.002 mol
Was added, and the mixture was reacted at 60 ° C. for 10 hours in a nitrogen stream.
It was poured into petroleum ether to precipitate the reaction product,
15.4 g of a white powdery copolymer was obtained. The molecular weight of this polymer was 210,000.

2-Cyanoacrylic acid having a molecular weight of 210,000-4-
A film of isobutylcyclohexyl polymer was formed on a substrate in the same manner as in Example 1 and irradiated with an electron beam. After electron beam irradiation, methyl isobutyl ketone: isopropyl alcohol = 3
Immerse in 5:65 mixed solvent at 20 ° C. for 30 seconds,
After the development processing, dry etching was performed.

The residual film sensitivity was 3.8 μC / cm ² , and no crack was found in the resist pattern. The dry etching rate was as good as 15.0 nm / min.

<Comparative Example 1> A 5 wt% cyclohexanone solution of a cyclohexyl 2-cyanoacrylate polymer having a molecular weight of 300,000 was prepared, and a film was formed on a substrate on which silicon dioxide was sputtered in the same manner as in Example 1 to obtain an electron. Radiation was performed. After electron beam irradiation, a resist pattern was obtained by immersing in a mixed solvent of methyl isobutyl ketone: isopropyl alcohol = 60: 40 at 20 ° C. for 3 minutes, rinsing in isopropyl alcohol and drying. However, countless cracks were generated in the obtained resist pattern.

[0029]

INDUSTRIAL APPLICABILITY The positive electron beam resist containing the 2-cycloalkylalkylcyclohexyl polymer of the present invention as a main component does not crack even on silicon dioxide by introducing a lower alkyl group into the cyclohexyl group. The characteristics are shown. Further, since it does not contain an aromatic group such as a benzene ring and further has a cyano group, the sensitivity is not lowered and the dry etching resistance is also satisfied. As described above, the positive electron beam resist of the present invention is extremely excellent in practical use because it can be applied to silicon dioxide without lowering the sensitivity and the dry etching resistance.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical indication location H01L 21/027 (72) Inventor Mizen Sato 1 East of 1 Funami-cho, Minato-ku, Nagoya-shi, Aichi Prefecture Synthetic Chemical Industry Co., Ltd. Nagoya Research Institute (72) Inventor Toshio Okuyama 1-1 Funami-cho, Minato-ku, Nagoya-shi, Aichi Toago Synthetic Chemical Industry Co., Ltd. Nagoya Research Institute

Claims (2)

[Claims] 1. A positive electron beam resist containing a 2-cycloalkylalkylcyclohexyl polymer as a main component. 2. The positive type electron beam resist according to claim 1, wherein the alkyl group substituted on the cyclohexyl group is a lower alkyl group having 1 to 4 carbon atoms.