PECVD and PIID processing of diamondlike carbon

Amorphous hydrogenated carbon (a-C:H) films are deposited on silicon substrates by microwave plasma enhanced chemical vapor deposition (PECVD), from pure C2H2 using two different modes to bias the substrate, namely RF at 13.56 MHz (PECVD process) and pulsed DC (PIID process). The pulsed-bias voltage is varied from −50 to −300 V with fixed pulse width and pulse frequency of 20 μs and 10 kHz, respectively. Significant variations in terms of growth rate and carbon hybridization type were observed. The influence of bias waveform on the carbon material structure is discussed using mainly FTIR and Raman analyses. One advantage of the PIID process over the conventional PECVD process is also pointed out by studying the ion energy distribution: the incident power deposited onto the substrate can be modified by changing the duty factor of the DC pulse without modifying the ion energy.