OPTICAL-EMISSION DIAGNOSTICS AND FILM GROWTH DURING MICROWAVE-PLASMA-ASSISTED DIAMOND CVD

High-resolution spectroscopy of atomic and molecular lines in a hydrog en-methane-argon plasma was used for the investigation of the gas temp erature and the atomic hydrogen concentration as a function of process parameters (power, pressure, and methane concentration) during microw ave-plasma-assisted CVD of oriented diamond films on silicon(100) subs trates. Translational temperatures were derived from the Doppler broad ening of H-2 lines and the H-alpha line. Rotational temperatures of H- 2 as calculated from the Q-branch of the Fulcher-alpha system yield mu ch lower temperatures which can be explained by theoretical considerat ions. Information about the changes in hydrogen concentration is obtai ned by actinometry, i.e. by relating the intensity of the Balmer lines to an argon line. The results are relatively independent of the choic e of the Balmer and actinometer lines, except when varying the methane concentration. The diamond films show distinct changes in morphology with increasing microwave power or methane concentration. From the gro wth rate at constant methane content, limits for the activation energy of diamond growth have been derived by using a simple growth law whic h takes into account the influence of substrate temperature and gas ph ase activation. Microstructure formation at high temperatures is contr olled by the growth competition between {100} and {111} facets, while twinning dominates in the low-temperature range.