DEPOSITION OF SMOOTH, ORIENTED DIAMOND FILMS USING MICROWAVE PLASMA CHEMICAL VAPOR-DEPOSITION

The use of low pressure and high gas flow conditions in a microwave plasma diamond chemical vapor deposition reactor resulted in films with small grain size and with a (110) preferred orientation on silicon substrates. The diamond films were deposited at 23 Torr total pressure, with gas composition of 1% CH4 in H2, and total gas flow rate of 25-800 standard cm3 min-1. An intermediate layer of microcrystalline diamond was also effective in reducing the grain size and increasing the degree of preferred orientation. Flow modeling of the reactor showed a qualitative change in convective flow pattern over our range of experimental conditions. Recirculation vortices formed at the low flow conditions, but mostly disappeared at the higher gas flow rates. The modest increase in deposition rate which we observed is consistent with the loss of vortex structure. The results are compared with those of a previous study of diamond films deposited at 40 Torr.