Formation Process of Stacking Faults with Ringlike Distribution in CZ-Si Wafers

In some large diameter CZ-Si wafers, stacking faults with ringlike distribution are observed after thermal oxidation. Although the stacking faults are formed through wafer thickness from surface into bulk after dry O 2 or steam oxidation, no stacking faults are observed after N 2 annealing or HCl+dry O 2 oxidation. All the stacking faults, even in bulk, are therefore considered to be formed by the condensation of silicon self-interstitials generated at the surface during oxidation. The ringlike distribution is found to originate from grown-in oxygen precipitates observed right in the center of the stacking faults by transmission electron microscope.