INFLUENCE OF PHOSPHORUS ADDITION ON DIAMOND CVD

Phosphorus-containing diamond films were deposited on Si(100) by hot-filament CVD using a Ta filament and mixtures of hydrogen, methane and phosphine. The phosphorus concentration in the gas phase was varied between 330 and 5280 ppm PH3/CH4. The P additions led to important modifications in the diamond morphology, growth rate, growth orientation, film quality and homogeneity. These modifications were similar to those which are observed in a growth environment leading away from optimal growth conditions for diamond. The P additions, however, seemed to influence the growth kinetics due primarily to surface reactions rather than to changes in the gas activation (i.e. atomic hydrogen and carbon growth species). A comparison between experimental results and thermodynamic calculations suggested that methinophosphide (HCP) - an unstable and highly reactive phosphorus species - is probably responsible for the deleterious P influences. Qualitative secondary-ion mass spectrometry measurements showed the presence of P in all diamond films prepared with PH3 added to the reaction gases.