Oxygen-free dry etching of α-SiC using dilute SF6:Ar in an asymmetric parallel plate 13.56 MHz discharge

Abstract

Etch rates of up to 2200 Å/min have been achieved on hexagonal silicon carbide (SiC) using dilute mixtures of SF6:Ar in a standard 13.56 MHz asymmetric parallel plate discharge. Furthermore, these etch rates have been realized with excellent pattern anisotropy profiles of approximately 1 at pressures in the range of 100–350 mTorr and the SF6 fraction at or below 50%. An understanding of the mechanisms responsible for the high etch rates in this simple, dilute, gas mixture can be achieved by considering the electrical characteristics of the radio frequency plasma. The conditions defining maximum etch rates are associated with peak fluorine ion and/or radical production, and can be defined entirely in terms of the relative current–voltage phase shift leading to optimal plasma impedance conditions and ultimately to maximal power deposition into the plasma. In addition, this study shows that the pervasive practice of utilizing oxygenated gas chemistries for SiC etching is not required, as previously thought, for carbon saturation and removal in order to obtain high etch rates, good surface morphology, and reliable pattern definition on SiC.