Silicon isotopic tracing with the Si-29(p, gamma) narrow resonance near 415 keV

Atomic transport of silicon during the formation of modified surface layers on silicon single crystal wafers has often been evoked in processes such a s SIMOX or thermal oxidation but has never been directly observed. Recently , observations of substantial oxygen exchange at the SiO2/Si interface duri ng dry thermal oxidation indicate diffusion of oxygen-containing species fr om the interface to the gas phase, one candidate being the molecule SiO. Si licon isotopic tracing studies could contribute decisive new information to help understand these and other processes. Preparation of single crystal S i enriched in one of the rare isotopes has so far proven to be difficult. I n this paper we report on the preparation of about 400 Angstrom thick epita xial layers enriched in Si-29 to over 30 at.% by ion implantation. After am orphisation and high dose implantation, the solid phase epitaxial regrowth rate is much reduced compared to low dose implants because of significant o xygen contamination due to recoil implantation of oxygen, but channeling in the enriched layer shows a chi(min) of a few percent, indicating good epit axial regrowth. Our first application of silicon isotopic tracing is to the study of the dry thermal oxidation of silicon. We have found significant s ilicon loss during this process. (C) 2000 Elsevier Science B.V. All rights reserved.