Chemistry of inorganic compounds – Carbon or compound thereof – Elemental carbon
Patent
1992-08-21
1995-01-10
Lewis, Michael
Chemistry of inorganic compounds
Carbon or compound thereof
Elemental carbon
427249, 4272551, C01B 3165
Patent
active
053805160
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a process for synthesizing diamond by chemical vapor deposition process which allows production of diamond having high purity, high crystallizability and high versatility at low cost and at high speed.
BACKGROUND ART
An artificial diamond was heretofore been synthesized under high-temperature, high-pressure thermodynamically equilibrium conditions. But recently a process for synthesizing diamond in a vapor phase has been developed.
In the vapor deposition process, hydrocarbon gas diluted with an over ten times larger volume of hydrogen is excited by a plasma or a hot filament to form a layer of diamond on a substrate in a reaction chamber.
As another prior art method, it is known to introduce a preheated material gas onto a heated substrate to pyrolytically decompose hydrocarbon to separate diamond (Japanese Patent No. 1272728).
Any prior art method for synthesizing diamond in a vapor phase requires basically a large amount of hydrogen, though it considers various methods for introducing neat to start a chemical reaction. Thus the cost for the material gas tends to be high. Moreover, hydrogen tends to be trapped in the diamond, thus lowering its purity and crystallizability. Also this will set limitations on the synthesis conditions of diamond, the speed of synthesis, the area of synthesis and the material of the substrate.
It is an object of the present invention to obviate these problems.
DISCLOSURE OF THE INVENTION
The present inventors have given consideration to various gas conditions to find out that a stable plasma can be produced and diamond having a good crystallizability can be produced at a high speed over a large area under the following conditions where no hydrogen is used except for the hydrogen which may be contained in the compound gas. The conditions of gas can be classified into two groups.
Namely, in the first method of the present invention, a mixture of oxygen gas and a carbon-containing compound gas or a mixture further containing an inert gas is introduced into a reaction vessel and a plasma is generated by an electromagnetic field, thereby producing diamond on a substrate placed in the vessel.
In the second method of the present invention, a gas mixture of one or two or more of fluorine gas, chlorine gas, a nitrogen oxide gas and a sulfur dioxide gas, or a mixture of the gas mixture with oxygen gas and a carbon-containing compound gas, or a mixture further containing an inert gas is introduced into a reaction vessel, and a plasma is generated by use of an electromagnetic field, thereby producing diamond on a substrate placed in the vessel.
With these methods, diamond develops uniformly and several times faster than with any prior art chemical vapor deposition (CVD) process, in which an expensive hydrogen gas is used in great amounts, and the diamond thus obtained contains no hydrogen over a large area (several tens of square millimeters) and has a high purity and a high crystallizability.
Either a direct current or alternating current electromagnetic field may be used to produce a plasma. In the latter case, it should be a high-frequency wave or a microwave having a frequency of over 1 KH.sub.Z for better controllability.
In order to produce a film of diamond of high purity and high crystallizability while preventing the deposition of non-diamond carbon, the gases should be mixed in the first method so that the ratio between the oxygen atoms and the carbon atoms in the material gas (oxygen/carbon) is 5-0.05 and preferably 2-0.1 and if the carbon compound contains hydrogen, the ratio among the oxygen, carbon and hydrogen atoms (oxygen/(carbon+hydrogen)) is 4-0.01 and preferably 1-0.05.
If an inert gas is used in the first method, the ratio of atoms among the inert gas, oxygen and carbon (inert gas/(oxygen+carbon)) should be 100-0 and preferably 20-0.02.
In the second method, the gases used should be mixed so that the ratio of atoms among fluorine (F), chlorine (Cl), oxygen (O) and carbon ((F+Cl+O)/C) in the material gas is 5-0.0
REFERENCES:
patent: 4767608 (1988-08-01), Matsumoto et al.
patent: 4938940 (1990-07-01), Hirose et al.
patent: 4985227 (1991-01-01), Ito et al.
patent: 4992298 (1991-02-01), Deutchmann et al.
English Translation of JP 61-15889, Jul. 18, 1986.
Chen, "Materials Research Ball.", 24(1) 87-94 (Jan. 1989).
Chang et al., "J. Appl. Phys.", 63(5) 1744-1748 (Mar., 1988).
"Patent Abst. of Japan", 11(63) (C-406) [2510] Feb. 26, 1987 Abstracting JP-A-61222915.
"Patent Abst. of Japan", 12(110) (C-486) [2957] Apr. 8, 1988 abstracting JP-A-62 235295.
"Patent Abst. of Japan", 10(362) (C-389) [2419] Dec. 4, 1986 abstracting JP-A-61 158899.
Meyer et al., "Proc. SPIE", 1146 21-25 (1989).
Meyer et al., "Proc. 1st Int. Symp. on Diamond and Diamond-like Films", 89(12) 494-499 (1989).
Fujimori Naoji
Imai Takahiro
Tanabe Keiichiro
Kalinchak Stephen G.
Lewis Michael
Sumitomo Electric Industries Ltd.
LandOfFree
Process for synthesizing diamond in a vapor phase does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for synthesizing diamond in a vapor phase, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for synthesizing diamond in a vapor phase will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-849367