It was recalled that the C-doping of Si was of great interest because, at high concentrations (greater than 1018/cm3), the C could reduce or suppress undesirable B diffusion in Si-based bipolar transistors. In order to understand this macroscopic behavior, the processes of point-defect interaction between dopants, vacancies and self-interstitials was analyzed. The reduction in B diffusion by C was known to be due to the creation of a self-interstitial undersaturation. The influence of an over-saturation of vacancies, which was also produced by a high C concentration during annealing, was considered. Experiments on a vacancy-diffusing dopant (Sb) were used to prove this effect. Thus, in a C-rich sample, the Sb diffusivity was enhanced by about 8 times as compared with samples with a much lower C concentration. An investigation was also made of C co-precipitation with O. This affinity was explained in terms of an exchange of point defects, and volume compensation.

Engineering the Diffusion Behavior of Dopants (B, Sb) in Silicon by Incorporation of Carbon. P.Lavéant, P.Werner, N.Engler, U.Gösele: Nuclear Instruments and Methods in Physics Research B, 2002, 186[1-4], 292-7

Table 18

Effect of CoSi2 Coating on Sb Diffusion in Si