Novel time-modulated chemical vapor deposition process for growing diamond films

Smooth polycrystalline diamond films were deposited onto silicon substrates using a newly developed time-modulated chemical vapor deposition (TMCVD) process. The distinctive feature of the TMCVD process involves pulsing the hydrocarbon gas, methane, at different flow rates for varying durations into the vacuum reactor during the chemical vapor deposition (CVD) process. Generally, CVD diamond films display nonuniformity in the crystal sizes and surface roughness along the film growth profile. The TMCVD method was specifically developed to (i) deposit smooth films, (ii) control film microstructure and morphology, and (iii) improve film reliability. We show that the TMCVD process produces diamond films with improved surface smoothness as compared to films of similar thickness produced by conventional CVD method under similar conditions. Surprisingly perhaps, the TMCVD method gave growth rates much higher than the conventional CVD method without reducing the film quality as revealed by the SEM micrographs and micro-Raman spectra.