Annealing behavior of phosphorus in native oxide films on heavily phosphorus doped silicon

Abstract

Phosphorus redistribution and its chemical structure in the native oxide/Si as well as thermal oxides (∼ 30 nm)/Si were investigated using X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy (SIMS). The Si substrates were both heavily P-doped Si(100) and poly-Si, together with nondoped poly-Si. The in-depth profiles of P obtained by both XPS and SIMS showed that the dopant-P redistributed in the thin native oxide film (NOF) even at room temperature, and the amount of P increased drastically upon annealing. The amount of redistributed P was much larger for Si(100) than for poly-Si. The dominant chemical structure of P was not P 2O 5 but elemental-P and/or Si-P. Clear pileup of P at theNOF/Si interface could not be observed, since the thickness of NOF is very thin and probably P diffused into throughout the NOF. In the case of thermal oxides, both SIMS and XPS profiles exhibited a big pileup-P at the oxide/Si interface. The amount of pileup-P was about two times larger for the Si(100) than for the poly-Si, and it increased with annealing temperature. In the oxide films, the 31P in SIMS as well as P 0 and P 2O 5 features in XPS were also detected, although the intensities were very weak compared to those at the interface.