An Electropolishing Technique for Germanium and Silicon

An electrochemical technique has been developed for polishing germanium and silicon to yield smooth and flat semiconductor surfaces. This technique is based on the anodic dissolution of a semiconductor whose surface is close to a moving cathode. The average surface roughness of electropolished semicon‐ductors was found to be ±25Aå and the deviation from flatness was typically 1 µ/cm. For n‐type samples, the holes necessary to support uniform electrolysis of the surface were injected by illuminating the anode surface. For both n‐ and p‐type anodes the average current efficiencies were found to be between 103 and 105%. Practical current densities are about 0.1 amp/cm 2 . At this value, the etch rates were about 2.2 µ/min for germanium and 1.9 µ/min for silicon.