Role of metallic contamination in the formation of ’’saucer’’ pit defects in epitaxial silicon

Abstract

Metallic contamination present in silicon wafers prior to epitaxy or introduced during epitaxial processing were found to be responsible for microdefect formation in epitaxial silicon. Such contamination is often due to use of stainless‐steel tweezers. The defects as revealed by Secco etching appeared as shallow saucer pits (s‐pits). High densities of s‐pits were found to affect the surface carrier concentration of the epitaxial layer as measured by the high frequency MOS technique. The s‐pits were found to nucleate oxidation‐induced stacking faults (OSF) on (100) material during subsequent processing. Neutron activation analysis was used to identify the elements causing s‐pits, and transmission electron microscopy analysis was done to identify the defect as a dislocation loop. Several means of reducing s‐pit densities are also presented.