Comparison of F-2 plasma chemistries for deep etching of SiC

A number of F-2-based plasma chemistries (NF3, SF6, PF5, and BF3) were investigated for high rate etching of SiC. The most advantageous of these is SF6, based on the high rate (0.6 mum min-l) it achieves and its relatively low cost compared to NF3. The changes in electrical properties of the near-surface region are relatively minor when the incident ion energy is kept below approximately 75 eV. At a process pressure of 5 mtorr, the SiC etch rate falls-off by similar to 15% in 30 mum diameter via holes compared to larger diameter holes (>60 mum diameter) or open areas on the mask. We also measured the effect of exposed SiC area on the etch rate of the material.