Cvd, Incorporated

Joseph T Keeley

Michael A Pickering

Raymond L Taylor

Jitendra Singh Goela

A process is disclosed by which the finish and figure of polished preshaped structures (such as mirrors) can be replicated directly by chemical vapor deposition, with only minor polishing of the replica being required to obtain a final product, and with the original substrate being reusable for further replication. Relevant conditions under which the process can be carried out are given. Featured in the process is a pretreatment step prior to the deposition of a layer of silicon carbide to form the replica, which pretreatment step involves the formation on the polished substrate of an oxide layer and a carbon layer of high finish and uniform thickness. The carbon layer allows easy separation of the substrate and replica which otherwise would be bound together.

Chemical vapor deposition process to replicate the finish and figure of

A fluid dynamic method and apparatus effects the isolation of a predetermined deposition area in a hot-walled chemical vapor deposition chamber and limits the deposition to that area. The disclosed technique reduces stress and cracking in materials produced by chemical vapor deposition, prevents backside growth, and has particular utility in the fabrication by the chemical vapor deposition process of large, lightweight mirrors.

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Woburn, MA, United States of America

Joseph T Keeley