Sputtered silicon carbide thin films as protective coating for MEMS applications

There is a need for chemically resistant coatings that protect the exposed surface of microfluidics components. Pinhole free films with low stress and a good uniformity on flat and inclined surfaces are required. In this study, amorphous silicon carbide (SiC) thin films have been deposited by RF magnetron sputtering on flat surfaces and into micromachined cavities of Si (100). The variation of RF power, deposition pressure and substrate bias voltage have been studied. Depending on the deposition conditions, the film stress can be adjusted from −1400 MPa to +100 MPa. Modifications of the deposition rate and the morphology between normal and inclined (54.7°) planes have been observed. Optimal chemical stability was found with slightly compressive (−100 MPa) SiC thin films. No degradation of the protective layer has been observed after 3 h in KOH at 80°C.