For very deep etching of SIG, up to and exceeding 100 mum, which would be required for selected applications, no suitable process has been reported. The ideal process would optimize a combination of fast etch rate, absence of residue, good mask selectivity, sidewall control, and reproducibility. In this work, we compare five SiC etches used in commercial Reactive Ion Etch (RIE) systems with regard to the above criteria, and demonstrate the first 80 mum via etch in SiC using a Ni-alloy mask. The SiC etches examined are residue-free, and possess etch rates ranging from 8 nm/minute up to 235 nm/minute. The etches utilize one or more of the following fluorinated gases: NF3, SF6, or CHF3. Several inorganic and organic mask materials have been evaluated with SiC:mask etch selectivity ranging fi om 10:1 to 160:1.