Depth profiling of vacancy defects and their thermal stability in N-implanted Si: a positron annihilation study

Abstract

Depth-resolved positron annihilation studies have been carried out on nitrogen-implanted Si to investigate defect evolution and thermal stability. Si(1 0 0) wafers have been implanted with 60 keV N+ ions to a fluence of 1 × 1014 and 1 × 1015 ions/cm2. From positron diffusion analysis of defect-sensitive S-parameter profiles, it is found that the higher dose sample undergoes a two-step annealing process consisting of annealing of deep level defects, followed by vacancy agglomeration near the surface at 873 K. For the low dose sample, however, nitrogen vacancy complexes are the only major defects remaining at 873 K. Annealing at 1073 K is sufficient to remove all kinds of open volume defects present in the samples.