Electrochemical Etching of 6H-SiC Using Aqueous KOH Solutions with Low Surface Roughness

Commercially available n-type 6H-SiC wafers were etched in aqueous KOH solutions by an electrochemical method. We varied the etching conditions, such as KOH concentration, temperature, UV light illumination and current density, and observed the morphologies of the etched surfaces and etching rates. Etching proceeds with oxide film growth and its peeling off or with continuous dissolution of silicon oxide depending on the conditions. Although the etching under all the conditions roughens the surfaces at a current density of 5 mA/cm 2 , we obtained the flattest etched surface at a current density of 1 mA/cm 2 in 1 wt% KOH concentration at temperature of 50–55°C with UV light illumination. We also fabricated a patterned structure under this etching condition with evaporated Ni metal as a mask.