Process for producing silicon carbide layers and an article

Details Process for producing silicon carbide layers and an article Process for producing silicon carbide layers and an article

1995-07-13

1997-12-16

Beck, Shrive

Coating processes

Coating by vapor, gas, or smoke

Carbon or carbide coating

4272551, 4272557, 427345, C23C 1632

Patent

active

056982615

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The invention relates to chemical engineering, more particularly to a process for depositing silicon carbide layers from a gas phase and also to an article manufactured by this process. The use of this process in microelectronics makes it possible to substantially improve the quality of superlarge integrated circuits having a memory capacity of greater than 1 mbit.
Known in the art is a process for producing silicon carbide layers by deposition from a gas phase containing methyl trichlorosilane and hydrogen. The deposition process is carried out on a tungsten substrate at a temperature of 1200.degree. to 1500.degree. C. at a pressure of 10 to 700 mm Hg and a hydrogen flow rate of 500 cm/min (see British Patent 1031833, Class C23C 11/00, 1964).
This process is disadvantageous in that it cannot produce nonporous silicon carbide having a dense structure, has low deposition rate, high energy consumption and it causes the contamination of the environment by reaction products.
Also known is a process for producing silicon carbide layers by deposition from the gas phase. The process comprises precleaning the original components such as methyl trichlorosilane and hydrogen, mixing them at a methyl trichlorosilane to hydrogen concentration of 0.5 to 1.5 g/l (the molar ratio is 1:13.5-4.5), feeding the mixture into a reactor at a gas stream volumetric rate of 6 to 10 1/hr (the feed density is 0.13-0.22 g/cm.sup.2.hr), thermal decomposition on a graphite filament heated to 1400.degree.-1500.degree. C. to produce silicon carbide layers (see L. P. Ivanova et al, "Preparation of Polycrystalline Silicon Carbide by Thermal Decomposition of Methyl Trichlorosilane", "Silicon Carbide", Kiev, Naukovo Dumka Publishers, 1966, p.151).
The process is disadvantageous in that it has high specific capacity and low efficiency and this makes it impossible to use it on an industrial scale. The process also provides no measures to make it ecologically pure, as the decomposition products (such as hydrogen chloride, hydrogen, organochlorosilanes, silicon chlorides) which cause contamination of the environment cannot be utilized.
Known in the art is a process for manufacturing silicon carbide articles by mixing liquid carbon compounds (liquid hydrocarbons) and liquid silicon compounds (organochlorosilanes) and depositing silicon carbide on a carbanaceous mandrel at a temperature higher than 1000.degree. C. The mixing of the original components, vapor pressure and the composition of the gas-vapor mixture (GVM) than these components are fed into the reactor and are regulated so that the molar fraction of the silicon compound in vapors exceeds the molar traction of the carbon compound (see Japanese Patent Application No. 56-5686, class CO1 B 31/36, 1981).
The article and the process are disadvantageous in that the articles having the stoichiometric composition without inclusion of second phases and high density without internal mechanical stresses cannot be produced.
Known in the art are a process and an article produced from silicon carbide by deposition from the gas phase. The process comprises feeding a gas-vapor mixture of alkyl chlorosilane and hydrogen into a reactor at a molar ratio of 1:(1-3), respectively, depositing silicon carbide onto a mandrel heated to 1200.degree.-1250.degree. C. and removing the mandrel (see British Patent No. 1100407, class CO1 B 31/36, 1965).
The process and the resulting articles are disadvantageous in that it is impracticable to produce nonporous articles having theoretical density of the stoichiometric composition which contains no second phases. Besides, the process does not envisage measures aimed at protecting the environment from outgoing gases, and the yield of alkylchlorosilane into silicon carbide does not exceed 30%.


DESCRIPTION OF THE INVENTION

The object of the invention is basically to provide a process for producing silicon carbide layers that enable one to produce silicon carbide which has a stoichiometric composition, contains no second phases, has high density

REFERENCES:
patent: 3091517 (1963-05-01), Short et al.
patent: 4131697 (1978-12-01), Randon et al.
patent: 4491604 (1985-01-01), Lesk et al.
patent: 4980202 (1990-12-01), Brennan et al.
patent: 4997678 (1991-03-01), Taylor et al.
patent: 5118485 (1992-06-01), Arvidson et al.
patent: 5154862 (1992-10-01), Reagan et al.
patent: 5462800 (1995-10-01), Yamazaki et al.

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