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US 4,289,801 AGranted
Method for producing fine grained pyrolytic silicon nitride
AssigneeUnited Technologies Corporation
InventorsFrancis S. Galasso, Malcolm Basche, deceased
Life of this patent
Estimating the term…
Abstract
Novel fine grained pyrolytic silicon nitride is produced by adding a substantial amount of methane to the normal reactant gases. Silicon tetrafluoride and ammonia in ratios of 60:40 to 10:90 may be employed with additions of methane in amounts equal to from 50 to 500% of the sum of silicon tetrafluoride and ammonia. When these reactant gases are passed over a heated substrate at a low pressure pyrolytic silicon nitride with a grain size of less than about 10 microns results.
Claims6
A method for producing fine grain pyrolytic silicon nitride which comprises:
- providing reactant gases which comprise from 40 to 90% ammonia, balance silicon halide and an amount of methane equal to from about 50 to 500% of the reactant gases, mixing these gases and flowing them into a reaction chamber which contains a substrate, said reaction chamber and substrate being heated to from 1200.degree. to 1900.degree. C. and said reaction chamber being maintained at a partial pressure of less than 300 mm of Hg of reactant gases, so that fine grained pyrolytic silicon nitride free of carbon and having a grain size less than about 10 microns is deposited on the substrate.
Dependencies are inferred from the claim text.