Pulse potential confined electrochemical polishing on gallium arsenide wafer

Free of tool wear, residual stress, and surface damage, electrochemistry plays a significant role in precision machining. We report here a semiconductor polishing technique based on electrochemically induced chemical etching, in which the concentration distribution of electrogenerated etchant between the tool electrode and the semiconductor workpiece can be precisely controlled by the pulse frequency of the potential applied to the tool electrode. A theoretical model is established, and the finite element analysis shows that the concentration difference of the electrogenerated etchant at the peak and valley of the rough surface of the semiconductor workpiece is dependent on the frequency of the potential pulse. Consequently, the diffusion distance and concentration distribution of electrogenerated etchant at the tool electrode/electrolyte interface can be controlled effectively by tuning the frequency of pulse potential. Under a mechanical motion mode, the roughness of a raw GaAs workpiece can be reduced efficiently from 700 nm to 5.1 nm. This technique is ideal for the electrochemical polishing of semiconductor wafers.