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

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 P2O5 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, the31P in SIMS as well as P0 and P2O5 features in XPS were also detected, although the intensities were very weak compared to those at the interface.