Residue-free reactive ion etching of β-SiC in CHF3/O2 with H2 additive

Longer term CHF3/O2 reactive ion etching of β-SiC thin films on Si required for heterostructure fabrication results in the formation of columnar residues in the etched regions which prevent proper device operation. Using Auger electron spectroscopy, the formation of the residues has been correlated with the sputter deposition of Al particles from the plasma electrode onto the SiC surface and the subsequent micromasking effect. A low-level (∼10%) addition of H2 gas to the CHF3/O2 plasma was found to completely prevent the formation of residues in the etched regions. Possible mechanisms responsible for the prevention of residues include the formation of volatile Al-H compounds and the enhanced etching of the C-rich surface.