Abstract

The efficiency and cost effectiveness of plasma enhanced CVD has been observed experimentally to scale with microwave power. The microwave energy couples directly to the electron plasma and from the electrons to the background gas. With hydrogen as the background gas the dominant electron processes at typical operating parameters are (1) vibrational excitation, which couples to the translational modes and heats the gas, and (2) electron impact dissociation, which generates the atomic hydrogen needed for the deposition of high quality diamond. Using a first principles Boltzmann solver to determine the electron energy distribution, we find that the primary parameter that determines which process predominates is the electric field strength. By pulsing the microwave field it is possible to substantially enhance hydrogen atom production relative to a cw process of the same average power output, resulting in a more efficient, high quality deposition and lower gas temperature.

© 1995 Optical Society of America