The Formation of Porous Silicon and its Applications to Dielectric Isolation

Abstract

ABSTRACTPorous silicon is formed by the anodic dissolution of p-type silicon in aqueous hydrofluoric acid. Because of its very high porosity, this material can be rapidly cKidized to form thick (˜10 μn) oxide layers with minimal stress on the underlying silicon wafer. A remarkable property of porous silicon is that preserves the crystalline orientation of the substrate despite removal of more than half of the silicon in the etched region, providing a suitable surface for the growth of epitaxial layers. Several schemes for dielectric isolation have been suggested which take advantage of these unique properties. In this paper, the mechanism of porous silicon formation will be presented and the relative advantages and disadvantages for practical device applications will be discussed.