Accurate measurements of the intrinsic diffusivities of boron and phosphorus in silicon

All activity in modeling transient diffusion behavior relies on knowledge o f the inert intrinsic diffusivities of dopants in Si. The measurements upon which these values are based were conducted over 15 years ago. Since then, the quality of wafers used in industrial applications has significantly ch anged. This will affect the effective diffusivity through changes in trap c oncentrations. The reliability of measurement techniques has also changed d ramatically from tracer and staining methods to secondary ion mass spectrom etry (SIMS) measurements that are dominant today. Finally, our understandin g of diffusion behavior has changed significantly. For example, we now unde rstand that the extraction of diffusivities from implanted samples with no pre-anneal includes a significant transient effect. We have measured the in ert intrinsic diffusivities of As, B, P, and Sb in different substrates in defect-free Czochralski and float zone wafers and epitaxially grown layers. All samples underwent a 30 min anneal at 1000 degrees C in dry oxygen in o rder to grow a cap oxide and eliminate transient enhanced diffusion. We per formed SIMS analysis on an initial batch of samples to evaluate the differe nt factors that may affect the diffusivity in a nonideal manner and conclud ed that there are no transient effects but that surface effects are importa nt. Hence, for the fast moving dopants (B, P) we restrict our data extracti on to the deep implants. Our data show that B and P diffusivities are diffe rent than the values commonly assumed in the literature at low temperatures . We compare our results to previously published data in light of the facto rs mentioned here. (C) 2000 American Institute of Physics. [S0003-6951(00)0 4039-0].