Low stress PECVD amorphous silicon carbide for MEMS applications

In this work we present a characterization of PECVD (plasma-enhanced chemical vapour deposition) amorphous silicon carbide films for MEMS/BioMEMS applications. For this applications a high deposition rate and a controllable value of the residual stress is required. The influence of the main parameters is analyzed. Due to annealing effect, the temperature can decrease the compressive value of the stress. The RF frequency mode presents a major influence on residual stress: in low frequency mode a relatively high compressive stress is achieved due to ion bombardment and, as a result, densification of the layer achieved. The PECVD amorphous silicon carbide layers presents a low etching rate in alkaline solutions (around 13 A/min in KOH 30% at 80°C) while in HF 49% the layer is practically inert. Amorphous silicon carbide can be used as masking layer for dry etching in XeF2 reactors (etching rate of 7 A/min). Finally, applications of PECVD amorphous silicon carbide layers for MEMS/BioMEMS applications are presented.