The B diffusion in strained SiGe, with and without C, was studied by using point defect injection. Interstitial-, vacancy- and non-injection conditions were achieved by annealing capping layers which were either bare, with Si3N4 film or with Si3N4+SiO2 bilayers, respectively. The concentration profiles of B, Ge, and C were obtained by using secondary-ion mass spectrometry, and the diffusion coefficients of B in each type of matrix (figure 7) were deduced by computer simulation. Under inert annealing, it was found that C strongly suppressed B diffusion in SiGe:C. On the other hand, the C only weakly suppressed B diffusion in SiGe:C under interstitial injection. For inert annealing conditions, C reduced the B diffusion coefficient in SiGe:C by factors of 8.4, 5.9 and 8.0 at 940, 1000 and 1050C respectively. For interstitial injection, the corresponding factors were 2.2, 3.4 and 1.6. The degree of B diffusion suppression achieved in SiGe:C depended upon the level of C retained during annealing. Interstitial injection was shown to enhance C diffusion strongly in SiGe:C, and hence decreased the effectiveness of C for B diffusion suppression. The results illustrated that the retarding effect of C upon B diffusion in SiGe:C was strongly reduced when annealing was carried out under conditions where interstitials were injected from the surface.

Effect of Point Defect Injection on Diffusion of Boron in Silicon and Silicon–Germanium in the Presence of Carbon. M.S.A.Karunaratne, A.F.W.Willoughby, J.M.Bonar, J.Zhang, P.Ashburn: Journal of Applied Physics, 2005, 97[11], 113531 (7pp)