Microscale pattern etch of 4H–SiC by inductively coupled plasma

Abstract

SiC is commonly used in the field of high temperature, high frequency, high power and radiation-resistant semiconductor devices and ultraviolet photodetectors due to its excellent photoelectric characteristics. Plasma etching is one of the key processes in the fabrication of SiC devices. However, it is difficult to obtain a smooth and vertical etch profile due to the subtrench effect when the conventional inductively coupled plasma (ICP) is used to etch SiC with small-size patterns (such as 1 μm holes or trenches), thus affecting the subsequent process and device performance. To study microscale pattern etch of 4H–SiC, we used different mask and etch gas systems for ICP etching. The etch profile was characterized using SEM. When the chlorine gas was used, there was no subtrench but a very inclined angle between the SiC bottom and sidewalls, which is hard to improve. When we used photoresist (PR) mask–HBr system, sidewall deposition happened. SiO₂ mask–HBr/Ar system could help to etch different angles but has a limitation angle of up to 80°. Compared to above systems, the etching profile was much more vertical when HBr/SF₆/O₂ was used. After many rounds of process debugging, we obtain a good etching profile with flat and vertical sidewalls, no subtrench in the bottom and no damage of the SiO₂ mask. Our work shows a good way of microscale pattern SiC etching by ICP.