Generation of shallow nitrogen-oxygen donors as a method for studying nitrogen diffusion in silicon

Abstract

The nitrogen concentration distribution C(z) obtained after diffusion of nitrogen from the bulk of a sample toward the surface is determined with a high accuracy through subsequent heat treatment at moderate temperatures (for example, at 650°C). This process leads to the formation of shallow thermal donors (nitrogen-oxygen complexes) with a concentration distribution over the depth z of the sample that corresponds to the nitrogen concentration profile C(z) and, therefore, makes it possible to calculate this profile. The proposed method is used to determine the nitrogen concentration profiles C(z) after homogenizing annealing at 950, 1000, and 1050°C. At high oxygen concentrations, the nitrogen transport is promoted by high-rate dissociation of nitrogen dimers. On the other hand, the nitrogen transport is slightly hindered by partial oxidation of nitrogen monomers. The results obtained indicate that the latter effect is not very strong, because the dimeric nitrogen species predominate over the monomeric nitrogen species in the sample and the diffusion profile is determined by the product D1K1/2, where D1 is the diffusion coefficient of nitrogen monomers and K is the dissociation constant.