Dry etching of porous silicon in high density plasmas

Dry etching processes routinely used for plasma etching of crystalline Si (c-Si) are evaluated as potential means for removal of porous Si (PS). Etching rates for PS and the selectivity with respect to c-Si are determined for a variety of plasma conditions and material parameters. We find that PS etching rates depend on the plasma conditions, and more importantly on PS material properties such as porosity and degree of oxidization. In addition, the selectivity varies from high to very low values, depending on the porosity and the thermal treatment of PS. The developed dry etching processes are compatible with the fabrication of devices where PS is used both as a sacrificial layer and as a patternable active material.