<title>Formation of oxygen-related donors during transition from thermal donors to new donors in CZ-silicon</title>

Abstract

CZ-Si has been subjected to different heating schedules in an effort to have a deeper insight about the appearance and disappearance of thermal donors, generation of new donors and thermal acceptors along with the amount of oxygen and carbon precipitated. Annealing of the oxygen rich silicon samples in the temperature range 465 - 540 degrees Celsius for 26 hours demonstrated the three OD stages -- growth region followed by annihilation of TDs and subsequently ND generation. Samples with low oxygen content pre-annealed at 455 degrees Celsius for 24 hrs and annealed at 470 degrees Celsius for varying annealing duration showed the complete absence of the first stage of rapid growth of TDs, but the pre-annealed samples with both low and high oxygen contents and subsequently annealed in the temperature range 430 - 630 degrees Celsius for short duration exhibited the dominance of thermal acceptors beyond the annealing temperature corresponding to maximum ND generation. The pattern of oxygen and carbon precipitation for such samples is also different. Activation energy for oxygen diffusion and self interstitials in silicon come out to be 0.6 eV and 0.4 eV respectively and the diffusion coefficient of oxygen in the pre-annealed samples and annealed at 470 degrees Celsius for different durations to be 6.18 by 10<SUP>-19</SUP> cm<SUP>2</SUP>s<SUP>-1</SUP>. Oxygen reduction is governed by second order kinetics.