Influence of the Masking Material and Geometry on the 4H-SiC RIE Etched Surface State
The roughness of etched SiC surfaces must be minimized to obtain surfaces with a smooth aspect, avoiding micromasking artifacts originating from re-deposited particles during the etching process. Four varieties of masks, Al, Ni, Si and C, were deposited on the SiC surface by photolithographic process. The C structures were formed by annealing conversion of patterned thick photoresist. On these surfaces, dry etching was performed with an SF6/O2 plasma produced in a Reactive-Ion-Etching (RIE) reactor. Although a better aspect of the surface is obtained with Ni in comparison with Al mask, micromasking could also occur even with Ni if the mask design was not enough spaced out. With C and Si masks, which produce fluorides species with negative boiling temperature, smooth etched surface was obtained without micromasking, even for tight masks covering up to 90% of the SiC surface.
Edouard V. Monakhov, Tamás Hornos and Bengt. G. Svensson
M. Lazar et al., "Influence of the Masking Material and Geometry on the 4H-SiC RIE Etched Surface State", Materials Science Forum, Vols. 679-680, pp. 477-480, 2011