Fast and slow lifetime degradation in boron-doped Czochralski silicon described by a single defect

A demonstration that boron-oxygen related degradation in boron-doped Czochralski silicon could be caused by a single defect with two trap energy levels is presented. In this work, the same two-level defect can describe the fast and slow lifetime decay with a capture cross-section ratio of electrons and holes for the donor level of sigma(n)/sigma(p) = 19 +/- 4. A model is proposed for the multi-stage degradation involving a single defect, in which the product of the slow reaction is a reactant in the fast reaction. After thermal processing, a population of interstitial oxygen (O-i) exists in a certain state (the precursor state) that can rapidly form defects (fast degradation) and another population of Oi exists in a state that is required to undergo a slow transformation into the precursor state before defect formation can proceed (slow degradation). Kinetic modelling is able to adequately reproduce the multi-stage degradation for experimental data. Dark annealing is also shown to impact the extent of 'fast' degradation. By decreasing the dark annealing time on pre-degraded wafers, a more severe 'fast' degradation of the samples can be enabled during subsequent illumination, consistent with this theory. The paper then discusses possible candidates for the chemical species involved. (C) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim