Etching of 4H–SiC in a NF3/CH4 inductively coupled plasma

Abstract

In this study, SiC was etched in a NF3/CH4 inductively coupled plasma. Process parameters and experimental ranges are radio frequency (rf) source power 700–900 W, bias power 50–150 W, pressure 6–12 mTorr, and NF3 percentage 20%–100%. The etch rate and profile angle were examined as a function of process parameters. For optimization, effects of various parameter combinations were investigated by means of a 24 full factorial experiment. Main effect analysis revealed that the etch rate is the most significantly affected by NF3 percentage. In contrast, the source power effect was the most insignificant for both etch rate and profile. For the dc bias less than about 385 V, the etch rate was strongly correlated to the dc bias induced by the source power. This correlation was observed for variations in other parameters. This reveals that the dc bias played an important role in determining the etch rate. For variations in NF3 percentage, both etch rate and profile angle behaved in a conflicting way. The highest etch rate optimized by the experimental design is 450 nm/min, obtained at 700 W source power, 150 W bias power, 12 mTorr, and 100% NF3 percentage.