Out-diffusion of nitrogen from float-zone silicon measured by dislocation locking

A measurement of nitrogen out-diffusion from nitrogen-doped float-zone silicon made using a dislocation locking technique is presented. Specimens containing a well-defined array of dislocation half-loops are subjected to identical anneals at 750 degrees C, during which nitrogen diffuses both to the surface and to the dislocations. The specimens are then chemically etched so as to remove different thicknesses of material from the surface. The stress required to move the dislocations away from the nitrogen is then measured. The variation in this unlocking stress with thickness of material removed allows some measure of nitrogen diffusivity to be deduced. The result obtained is consistent with an extrapolation of SIMS out-diffusion measurements previously performed at higher temperatures, but indicates a different activation energy for out-diffusion to that associated with dislocation locking by nitrogen. (C) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.