Study of trenching formation during SF6/O2 reactive ion etching of 4H-SiC

An accurate and reproducible SF6/O-2 reactive ion etching process in 4H-SIC has been defined, to realise deep and vertical trenches with a high selectivity Ti/Ni mask, and tilted sidewalls with a controlled angle by etching using a SiO2 mask. The trenching issues have been eliminated by increasing the plasma power. Smooth etched surfaces are obtained with a slightly tapered transition at the bottom of the sidewalls associated with a slight narrowing of the lower-end of the walls. Controlling the trench angle, very flat profiles are obtained for low pressure and plasma flow rates, and more vertical sidewalls by increasing these parameters.