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Proceedings Paper

Plasma etching and deposition as a method of polishing CVD diamond
Author(s): Ian Paul Llewellyn; Robert Carnegie Chittick; Rudolf August Heinecke
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Paper Abstract

As grown, CVD diamond windows have low infra-red absorption, but are highly scattering in transmission due to the presence of crystalline facets on the material surface. Conventionally, these facets are removed by mechanical polishing techniques which are slow, not easily adapted to complex shapes, and which can lead to mechanical damage and loss of strength. In this work, an attempt has been made to use a patented plasma etching and deposition method to polish CVD diamond window material optically flat. Low pressure radio frequency (rf) discharges of a variety of plasma etchant gases (Ar, H2 CCl4, SF6, CO2) have been used to etch the diamond surface. Etch rates of 2000 angstroms/minute can be obtained using carefully optimized etch chemistries. It has been shown that plasma etching the diamond window under conditions which give a high self-induced dc bias causes preferential sputtering of the edges of microcrystallites and hence polishes the diamond surface flat. Certain plasma chemistries, notably those involving chlorine, have also been found to flatten the surface by preferentially removing the crystalline facets. By plasma depositing silicon oxide on the window material it is possible to planarize the surface prior to a plasma etch stage and then plasma etch away the silicon oxide and diamond in a subsequent etch stage so smoothing the diamond surface. The affect of these polishing methods on a variety of CVD diamond films is discussed and the limitations of the technique addressed.

Paper Details

Date Published: 28 September 1994
PDF: 7 pages
Proc. SPIE 2286, Window and Dome Technologies and Materials IV, (28 September 1994); doi: 10.1117/12.187341
Show Author Affiliations
Ian Paul Llewellyn, BNR Europe Ltd. (United Kingdom)
Robert Carnegie Chittick, BNR Europe Ltd. (United Kingdom)
Rudolf August Heinecke, BNR Europe Ltd. (United Kingdom)

Published in SPIE Proceedings Vol. 2286:
Window and Dome Technologies and Materials IV
Paul Klocek, Editor(s)

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