SiC Trench Etch with Varying Aspect Ratio and Rounded Corner

SiC trench etching is one of the most challenging processes in the fabrication of wide-bandgap semiconductor power chips. Etch uniformity can be significantly improved (<2%) by adjusting the Power Source Ratio (PSR) and Gas Source Ratio (GSR). Optimizing the power and ratio of dual-frequency RF power supplies can achieve an etch rate of nearly 1 μm/min for SiC. Through the selection of power and gases, the effective etch selectivity (SiC/OX) can exceed 7, potentially reaching much higher values. The combination of Main Etching (ME) and Over-Etching (OE) can be employed to correct both bottom roundness and sidewall roughness. Furthermore, by refining the sidewall roughness of the initial photoresist through modification and subsequently treating the sidewalls of the oxide hard mask layer post-etching, the sidewall roughness of the oxide trench can be significantly mitigated. This refinement, in turn, minimizes the impact on the sidewall roughness of the SiC trench during the patterning process.