Stacking faults in (100) epitaxial silicon caused by HF and thermal oxidation and effects on p-n junctions

Abstract

Extrinsic stacking faults form in (100) epitaxial silicon as the result of HF attack of the surface followed by thermal oxidation. The fault density after steam oxidation at 1100 °C is typically greater than 10⁴ faults cm⁻², whereas one or two orders of magnitude fewer faults occur during dry O₂ oxidation or O₂‐steam‐O₂ oxidation following attack by HF. The fault density after steam oxidation may be reduced by etching or by anodizing the (100) epitaxial surface prior to steam oxidation. These effects may also be obtained with heat‐treated (100) bulk silicon, when exposed to HF and thermally oxidized. The interpretation is that HF attacks and disorders the (100) surface, causing a fault which propagates during subsequent steam oxidation. These effects occur seldom if at all on (111) silicon. The HF‐oxidation‐induced faults can be the sites of microplasmas in diffused p‐n junctions, and data are reported which shows that improved junctions are obtained with processing that avoids the formation of these faults.