Formation of soi by oxidation of silicon with engineered porosity gradient

Abstract

A method is provided for making a silicon-on-insulator substrate. Such method can include epitaxially growing a highly p-type doped silicon-containing layer onto a major surface of an underlying semiconductor region of a substrate. Subsequently, a non-highly p-type doped silicon-containing layer may be epitaxially grown onto a major surface of the p-type highly-doped epitaxial layer to cover the highly p-type doped epitaxial layer. The overlying non-highly p-type doped epitaxial layer can have a dopant concentration substantially lower than the dopant concentration of the highly p-type doped epitaxial layer. The substrate can then be processed to form a buried oxide layer selectively by oxidizing at least portions of the highly p-type doped epitaxial layer covered by the non-highly p-type doped epitaxial layer, the buried oxide layer separating the overlying monocrystalline semiconductor layer from the underlying semiconductor region. Such processing can be performed while simultaneously annealing the non-highly p-type doped epitaxial layer.