Plasma etching and deposition as a method of polishing CVD diamond

Ian Paul Llewellyn; Robert Carnegie Chittick; Rudolf August Heinecke

doi:10.1117/12.187341

28 September 1994 Plasma etching and deposition as a method of polishing CVD diamond

Ian Paul Llewellyn, Robert Carnegie Chittick, Rudolf August Heinecke

Proceedings Volume 2286, Window and Dome Technologies and Materials IV; (1994) https://doi.org/10.1117/12.187341
Event: SPIE's 1994 International Symposium on Optics, Imaging, and Instrumentation, 1994, San Diego, CA, United States

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.

Citation Download Citation

Ian Paul Llewellyn, Robert Carnegie Chittick, and Rudolf August Heinecke "Plasma etching and deposition as a method of polishing CVD diamond", Proc. SPIE 2286, Window and Dome Technologies and Materials IV, (28 September 1994); https://doi.org/10.1117/12.187341

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