The generation of point defects during the oxidation of silicon

Oxidation of silicon is known to cause the climb of faulted defects and to influence the rate of impurity diffusion. These effects have been related to the. generation of excess point defects at the oxidizing interface. The paper describes experiments designed to determine the point defect concentrations at the oxidizing interface using the loop annealing technique. The loops were initially introduced into silicon slices by ion-implantation and annealing and then the growth or shrinkage of the loops was measured in thin foils following annealing treatments using oxidizing or non-oxidizing atmospheres. Vacuum annealing caused loop shrinkage from which the coefficient of self-diffusion and the extrinsic stacking fault energy were determined. These values are in good agreement with values obtained by other techniques. Comparison of these shrinkage rates with the growth rates obtained during an oxidizing anneal enabled the ratio of the interstitial concentration at the oxidizing interface to the bulk equilibrium interstitial concentration to be determined. This supersaturation ratio decreases with increasing temperature from 2.2 at 900°C to 1.4 at 1140°C. Extrapolation of these results to higher temperatures indicates that the supersaturation ratio becomes less than one at ∼ 1200°C, where loop shrinkage would be expected to occur in both oxidizing and non-oxidizing conditions; this was confirmed qualitatively. These results are discussed in terms of the oxidation mechanism of silicon.