Ion beam-assisted planarization of chemically vapor deposited diamond thin films using electron cyclotron resonance plasma

The high inherent surface roughness of as-deposited polycrystalline diamond films has made effective planarization processing of these films essential for most industrial applications. We have investigated the efficacy of ion beam sources for planarization in an electron cyclotron resonance plasma system using both direct substrate biasing and an accelerating grid system. Rough polycrystalline diamond films were synthesized using hot filament chemical vapor deposition. Both the etching rates and the resultant surface roughnesses were found to decrease as the angle of incidence (relative to the substrate surface normal) of the ion beam was increased. In the case of direct biasing of the sample, acicular features were observed following processing at higher incident angles. The use of double ion-extraction grids in conjunction with concomitant sample rotation was found to produce more uniform planarization of the diamond films. The rate of surface roughness reduction was found to be nonlinear and decreased with time. For both ion extraction methods investigated, the average film roughness (R_a) was significantly reduced from 0.2 to 0.05-0.06 μm.