Characterization of arsenic dose loss at the Si/SiO2 interface

Abstract

Careful sample preparation and secondary ion mass spectroscopy have been used to characterize arsenic dose loss to the silicon–oxide interface. Using high resolution x-ray photoelectron spectroscopy for microprofiling, we have directly observed the pileup of arsenic at the silicon dioxide–silicon interface. At least half of the pileup is shown to be on the silicon side of the interface in the first monolayer of silicon. Monolayer chemical oxidation and etching are successfully used to profile this pileup in silicon. This pileup contains most of the arsenic dose loss that occurs during transient enhanced diffusion. This result is crucial to correctly model the dose loss and provides physical justification for using a trap/detrap model at the interface, which is necessary to account for the fact that the arsenic surface concentration remains constant during an anneal and the fact that the dose loss is partially reversible. Finally, we have found that normal etching of the oxide in dilute hydroflouric acid and subsequent rinsing in water and exposure to air causes a permanent loss in arsenic dose.