An Etch-stop Utilizing Selective Etching Of N-type Silicon By Pulsed Potential Anodization

A new dopant selective etching technique, which uses pulsed anodizing voltages applied to silicon samples in KOH: H/sub 2/O solutions, has been developed. The use of pulsed anodization causes passivation of p4ype silicon while n-type silicon continues to etch, making It possible to selectively etch-stop on p-type material. These results are consistent with a process which Is rate limited by holes in the semiconductor. To demonstrate this technique, a 12-.spl mu/m-thick p-type inembrant was formed. This method differs from the conventional p-n junction etch-stop in that the performance of the etch-stop does not depend on the rectifying characteristics of the diode or on the magnitude of Its leakage current. This paper presents data on the passivation of p-type and n-type silicon under pulsed anodization conditions for a broad range of KOH concentra tions and temperatures. Additionally. the application for etch stepping is presented.