Electrochemically Thinned N/N+ Epitaxial Silicon—Method and Applications

The method of thinning n/n + epitaxial silicon wafers by selective anodic dissolution of the substrate in aqueous HF is described. Some of the properties of the system are discussed and applications are presented. It appears the technique is best suited for use where the material has not had extensive prior processing, especially n+ diffusions, and/or where the epitaxial layer is of high resistivity. The most promising areas of application appear to be: ( a ) fabrication of thin films for experimental purposes, ( b ) thinning of simple diode arrays, and ( c ) solid dielectric isolated IC fabrication. Considerable impediments to use of the process are the necessity of having epitaxial layers of unusual perfection and the fact that local anodic etching occurs at sites of high carrier generation.