A study of silicon interstitial kinetics using silicon membranes: Applications to 2D dopant diffusion

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Abstract
The kinetics of silicon interstitial generation, recombination, and diffusion in floatzone (FZ) and Czochralski (CZ) silicon were studied during oxidation at 1100 °C using thin silicon membranes as test structures. One side of the membrane was oxidized to inject interstitials and the other side was covered with films of pad-oxide and silicon nitride. The interstitial concentration was monitored at both sides of the membrane simultaneously to determine the interface and transport kinetics of interstitials. The interstitial supersaturation at the oxidizing side was found to be insensitive to both the thickness variation and to the interface condition of the other side of the membrane. A model for this effect is proposed. At the interface opposite the oxidizing side, a delayed buildup of interstitials was observed. Using these results for FZ Si and assuming that there was no bulk recombination, an effective interstitial diffusivity of 9×10−10 cm2/s and an effective interface recombination rate of 3×10−7 cm/s for a silicon/pad-oxide interface were obtained. Interstitial transport across the CZ Si membranes during oxidation was slower than that across FZ membranes. The parameters extracted from these studies have been used to successfully model 2D dopant diffusion.