The chemical composition changes of silicon and phosphorus in the process of native oxide formation of heavily phosphorus doped silicon

The chemical composition changes of silicon and phosphorus in the process o f native oxide formation of both heavily phosphorus-doped Si(1 0 0) and pol ycrystalline Si prepared by BF-treatment were monitored for a period of 1 y ear, using angle dependent X-ray photoelectron spectroscopy (XPS). Right af ter HF-treatment, significant amounts of unoxidized-P (P*) and a new chemic al state of Si (Si*) having an unstable bond were detected in the surface r egion of heavily P-doped Si. With decreasing depth, the concentration of P* increased, whereas the Si* decreased. The surface segregated P* was larger for P-doped Si(1 0 0) than for P-doped poly-Si. During the growth of nativ e oxide, the distributions of P* and Si* in the underlying Si surface did n ot change largely with oxide thickness. A part of P atoms also reacted with oxygen and incorporated into Si-O-P network in the native oxide, and the a mount of P-oxide increased with the progress of oxidation. The decomposed S i 2p spectra of growing oxide films on both heavily P-doped Si showed that the dominant component was not the Si4+, but Si3+ state until the oxide thi ckness went up to over about 1.5 nm, while that for the low P-content Si wa s Si4+, except at the very narrow interface. (C) 2001 Elsevier Science B.V. All rights reserved.