Sputtered silicon carbide thin films as protective coating for MEMS applications

Abstract

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 −1400MPa to +100MPa. 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 (−100MPa) SiC thin films. No degradation of the protective layer has been observed after 3h in KOH at 80°C.