Effect of Point Defect Injection on B diffusion in C containing Si and SiGe
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B8.6.1
Effect of Point Defect Injection on B diffusion in C containing Si and SiGe Mudith S. A. Karunaratne1, Janet M. Bonar2, Jing Zhang3 and Arthur F. W. Willoughby1 1 Materials Research Group, School of Engineering Sciences and 2 School of Electronics & Computer Science, University of Southampton, Highfield, Southampton SO17 1BJ, UK 3 Blackett Laboratory, Department of Physics, Imperial College London, Prince Consort Road, London SW7 2BW UK ABSTRACT In this paper, we compare B diffusion in epitaxial Si, Si with 0.1%C, SiGe with 11% Ge and SiGe:C with 11%Ge and 0.1%C at 1000°C under interstitial, vacancy and non-injection annealing conditions. Diffusion coefficients of B in each material were extracted by computer simulation, using secondary ion mass spectroscopy (SIMS) profiles obtained from samples before and after annealing. Interstitial injection enhances B diffusion considerably in all materials compared to inert annealing. In samples which experienced vacancy injection, B diffusion was suppressed. The results are consistent with the view that B diffusion in these materials occurs primarily via interstitialcy type defects. INTRODUCTION Processes such as dry oxidation can strongly perturb the equilibrium concentrations of point defects and alter the diffusion rates of dopants. During high temperature oxidation of a Si surface, interstitials are injected [1, 2]. Since Boron diffuses mainly via interstitialcy type defects in Si [1] the diffusion is enhanced as a result of interstitial supersaturation in the material [1, 2]. Annealing of a silicon nitride film on the other hand injects vacancies which cause an undersaturation of interstitials in the bulk material [3-5]. Boron diffusion is retarded in this case. Surfaces masked with double layered SiO2-Si3N4 films undergo no injection when annealed [4]. By annealing samples with either a bare, Si3N4 film or SiO2-Si3N4 layered surface in an O2 ambient, it is possible to create interstitial injection, vacancy injection or inert (non-injection) conditions respectively, in a single experiment [6]. By comparing diffusion behavior of a dopant under different injection conditions, valuable insight into diffusion mechanisms can be gained. In this paper we have examined the diffusion behavior of B in Si, Si with 0.1% C, SiGe with 11%Ge and SiGe:C with 11%Ge and 0.1% C, under the different defect injection conditions described above. In view of recent technological interest in the SiGe heterojunction bipolar transistor (HBT) [7-9] there is considerable demand for developing process models incorporating dopant diffusion in SiGe and SiGe:C materials. Hence, there is a requirement to generate diffusion data and also to expand our understanding of diffusion mechanisms in these material systems. The experiments described here form part of a wider study aimed at producing such data and understanding the mechanisms of the C effect.
B8.6.2
Out-diffusion of B from the base region into collector and emitter regions during thermal processing is one of the factors which limit the h
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