The diffusion of B in polycrystal-on-monocrystal samples was studied by using secondary ion mass spectrometry. The extrapolated diffusion profiles in polycrystalline material and in the monocrystalline substrate revealed a discontinuity at their interface. This discontinuity was attributed to the blockage of B-defect complexes by an interfacial oxide between the polycrystalline and monocrystalline materials, as well as to the immobility of these defect complexes in monocrystalline Si. The B in the implant peak region above the B solid solubility limit was found to be immobile in monocrystalline Si during annealing, due to the formation of electrically inactive B-defect complexes. However, in polycrystalline material the B in the peak region spread out more rapidly than it would in monocrystalline material; due possibly to the diffusion of B-defect complexes along grain boundaries. The latter complexes were electrically inactive, according to spreading resistance data. If the B concentration was decreased to below the solid solubility limit, either by decreasing the dose or by increasing the annealing temperature, no discontinuity was observed (in the B profile) across the polycrystalline/monocrystalline interface.

S.Batra, M.Manning, C.Dennison, A.Sultan, S.Bhattacharya, K.Park, S.Banerjee, M.Lobo, G.Lux, C.Kirschbaum, J.Norberg, T.Smith, B.Mulvaney: Journal of Applied Physics, 1993, 73[8], 3800-4