Nonuniformity of the macropore etching front in thin n-Si wafers

Abstract

A factor responsible for the appearance of a dome-shaped front of macropore etching in thin silicon wafers during their photoelectrochemical etching in a cell with a ring anode has been established. It is shown that the formation of a dome-shaped front is related to a radial voltage drop in the substrate, which leads to a decrease in the current density in the central part of the etched wafer. The effect of applied voltage on the shape of the front has been studied. We suggest monitoring of the development of nonuniformity in the course of etching using a change (i) in the temporal variation of the adjusted intensity of illumination and (ii) in the current-voltage characteristic. Various methods intended to provide deep uniform macropores are considered.