An Improved ICP Etching for Mesa-Terminated 4H-SiC p-i-n Diodes

An improved Bosch etching process using inductively coupled plasma system has been investigated for the etching of 4H-silicon carbide (SiC). By optimizing the etch parameters, a mesa structure with nearly vertical sidewall and without microtrench at the bottom corner has been fabricated, and the formation and elimination of the microtrench are preliminarily discussed for the Bosch cycles in this paper. Scanning electron microscopic analysis was used to demonstrate the etched morphology under different etching conditions. Simple mesa-terminated 4H-SiC p-i-n diodes were fabricated. The effect of the improved mesa structure on the dc characteristics of the diodes has been experimentally verified by comparing with the nonoptimized mesa structure with microtrench. The results exhibited a completely consistent forward tendency and a similar reverse leakage level less than -900 V for both diodes, but different blocking performances. A maximum blocking voltage of 1565 V at room temperature was obtained from the nonmicrotrenched device with a mesa height of 4.3 μm, corresponding to 66% of a parallel plane breakdown voltage for the drift layer of 15 μm. Slight microtrench is the main cause of premature breakdown.