Anodic Etching of Silicon

The report discusses the use of an electrochemical technique, termed anodic etching, to delineate electrically active defects and doping density differences in silicon wafers. The method can be applied to starting or processed wafers. Specifically if p-type wafers characteristic of NMOS processing are anodically biased at +.9V in a 5% solution of HF regions of different doping density appear as different colors through the formation of a porous silicon film.