Planarization of diamond thin film surfaces by ion beam etching at grazing incidence angle

S. Ilias, G. Sené, P. Möller, V. Stambouli, J. Pascallon, D. Bouchier, A. Gicquel (1), A. Tardieu (1), E. Anger (1), M.F. Ravet (2)

Institut d'Electronique Fondamentale, URA CNRS 22, Bat. 220, Université Paris-Sud, F-91405 Orsay, cedex, France.
(1) Laboratoire d'Ingénierie des Matériaux et des Hautes Pressions, CNRS, Université Paris-Nord, Avenue J.B. Clément, F-93430 Villetaneuse, France
(2) Laboratoire de Microstructures et de Microélectronique, CNRS, 196 Avenue H. Ravera, BP 107, F-92225 Bagneux, France.

ABSTRACT

Ion beam etching at grazing incidence angle has been used to reduce the surface roughness of polycrystalline diamond thin films, 1 ± 0.2 micron thick, deposited by microwave plasma chemical vapor deposition (MWPCVD). Different reactive etching conditions have been tested for a beam energy of 1 keV with various ion beam and gas atmosphere compositions: pure Ar+, mixture of  Ar+ + N2+ and Ar+ under a controlled oxygen partial pressure. Their influence on the etching kinetics, roughness and morphology evolutions of the film, crystalline quality have been studied using SEM, AFM and Raman spectroscopy. The optical transmittance has also meseared. The ion beam processes studied result in a drastic reduction of the film surface roughness with a slightly better efficiency for the Ar+ and oxygen gas mixture. The roughness decrease leads to an increase in the optical transmittance without any change in the crystalline quality of the film. This planarizing method should be particularly well-adapted for thicker films taking into account the balance between the initial values of thickness and roghness on the one hand, and the material loss on the other. Furthermore, it could be usefully applied to produce large-area membranes.

Article published in Diamond and Related Materials 5 (1996) 835-839.