Extrinsic dislocation loop behavior in silicon with a thermally grown silicon nitride film

Abstract

The effect of a thermally grown silicon nitride (SiNx) film on end-of-range extrinsic dislocation loops in a silicon substrate was investigated by transmission electron microscopy. A layer of extrinsic dislocation loops was formed by annealing a Si wafer amorphized by a Ge+ ion implant. A nitride film was grown on the Si by further annealing in ammonia (NH3) at 810 and 910 °C for 30–180 min. Wafers with a loop layer were also annealed in argon (Ar) at the same conditions as the NH3-annealed wafers to determine loop behavior in an inert environment. Samples annealed in NH3 had a significant decrease in the net number of interstitials bound by the loops, while those annealed in Ar showed no change. The results are explained by a supersaturation of vacancies caused by the presence of the nitride film, resulting in loop dissolution. By integrating the measured vacancy flux over the distance from the nitride/Si interface to the loop layer, we extract an estimate for the relative supersaturation of vacancies at 910 °C, CV/CV*∼4, where CV is the concentration of vacancies and the asterisk denotes equilibrium. We rule out interstitial undersaturation-induced loop dissolution based on loop stability with temperature and oxidation-enhanced loop growth calculations. A comparison with estimated CV/CV* values from a previous report using the same processing equipment and parameters but monitoring the change in Sb diffusivity with nitridation shows excellent agreement.