High resolution Auger sputter profiling study of the effect of phosphorus pileup on the Si–SiO2 interface morphology

We have used Auger electron spectroscopy in conjunction with sputter etching and crater-edge profiling to study the distribution of phosphorus near the Si–SiO2 interface and the effect of the phosphorus distribution on the width of the interface transition region. The samples studied consisted of thermal oxides approximately 1000-Å-thick grown on Si (111) substrates with initial phosphorus concentrations up to 6×1020 cm−3. Phosphorus pileup at the Si–SiO2 interface was observed with the phosphorus peak (after correcting for electron escape depth effects) on the Si side within 5 Å of the interface. The 10%–90% width of the Si–SiO2 transition region as measured by the SiLVV transition varies from 25 (low doping limit) to 38 Å (bulk doping level of 6×1020 cm−3). Results are interpreted in terms of a recently proposed model for the Si–SiO2 interface.