Optimizing chemical resistance of PECVD amorphous silicon carbide thin films

Amorphous silicon carbide thin films have been shown to be an appealing passivation strategy for biomedical implants due to their great chemical resistance and biocompatibility. This study investigates the chemical etching resistance of amorphous silicon carbide thin films grown by plasma-enhanced chemical vapor deposition (PECVD) with silane and ethylene gas precursors using varying deposition parameters. The chemical resistance is tested with an accelerated aging treatment in phosphate buffered saline. The films’ etching rate variation is shown to be highly dependent on the deposition conditions. Indeed, the results emphasize the main role of the ratio of silicon and carbon-containing gas precursors, the deposition temperature and the formation of Si-C bonds. High-quality, long-lifetime films are achieved using high-temperature, silane-rich deposition conditions, resulting in accelerated etch rates as low as 0.03 nm/day. The amorphous SiC structure is confirmed using Raman spectroscopy, FTIR, and XPS, and outliers are explained in terms of their composition and chemical bonding. High chemical resistance is associated with high Si-C bonding and eventually nanocrystalline silicon regions in the films.