Carbon segregation in silicon

Carbon doping strongly suppresses the diffusion of boron. This is very important for later high temperature processing steps, e.g. for the fabrication of a high doped SiGe-base in a heterojunction bipolar transistor. We investigated (with a novel method) the segregation of C in Si (100) at growth temperatures between 500 and 700 degreesC. A C-doped Si layer was grown by MBE under constant C and Si fluxes. The growth temperature was switched between 300 degreesC and the investigated growth temperature. As the temperature was switched, the surface-accumulated C concentration was perturbed, causing a spike or depression in the SIMS depth profile. The surface segregation at a given temperature was measured by the amount of adlayer density in the spike. Clear evidence of the surface segregation of carbon in Si is found by these experiments. (C) 2000 Elsevier Science B.V. All rights reserved.