Control of Trenching and Surface Roughness in Deep Reactive Ion Etched 4H and 6H SiC

An optimized deep reactive ion etching (DRIE) process for the fabrication of SiC microstructures has been developed. The optimized process enables the etching of 4H and 6H SiC to depths > 100 μm with the required characteristics of (1) high rate (>0.5 μm/min), (2) vertical sidewalls, (3) minimal microtrenching at the sidewall base, and (4) smooth etched surfaces. The optimized process was determined based on the results of an experiment (full factorial design) which determined how the etch characteristics are affected by four important process parameters: temperature of the wafer chuck, pressure within the chamber, and concentrations of O2 and Ar in a gas flow comprised of O2, Ar and SF6. This study is believed to be the first systematic investigation of the effect of temperature on SiC DRIE characteristics; substrate heating was found to be a key in producing the desired etch properties.