This paper discusses the intrusion of H into a-Si layers during solid phase epitaxy and the effect of this H on the growth kinetics. We show that during annealing in the presence of water vapor, H is continuously generated at the oxidizing a-Si surface and diffuses into the amorphous layer, where it causes a reduction in the epitaxial growth rate. The measured variation of growth rate with the depth of the amorphous/crystal interface is correlated with the concentration of H at the interface. The diffusion coefficient for H in a-Si is determined by comparing measured depth profiles with calculated values. Hydrogen intrusion is observed even in layers annealed in vacuum and in inert gas ambients. Thin (<;5000 Åthick) a-Si layers are especially susceptible to this effect, but we show that in spite of the presence of H the activation energy for SPE derived earlier from thin-layer data is in good agreement with the intrinsic value obtained from thick, hydrogen-free layers.
Boron diffusion in polycrystalline Si-on-single crystal Si systems has been studied by secondary ion mass spectrometry. The extrapolated B-diffusion profiles in polycrystalline Si and in the single crystal Si substrate reveal a discontinuity at the polycrystalline Si-single crystal Si interface. The discontinuity in the B profiles is believed to occur due to the blockage of B-defect complexes by the interfacial oxide between polycrystalline Si and the single-crystal Si substrate, as well as the immobility of these defect complexes in single crystal Si. The B in the implant peak region above the B solid solubility limit is found to be immobile in single crystal Si during annealing due to the formation of electrically inactive B-defect complexes. In polycrystalline Si, however, our results show that the B in the peak region spreads out more rapidly than in single crystal Si possibly due to the diffusion of B-defect complexes along grain boundaries. The B-defect complexes are electrically inactive as determined by spreading resistance analysis. If the B concentration is lowered below the solid solubility limit, either by decreasing the dose or by raising the anneal temperature, no discontinuity is observed in the B profile across the polycrystalline Si-single crystal Si interface.
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