EXTRINSIC DISLOCATION LOOP BEHAVIOR IN SILICON WITH A THERMALLY GROWNSILICON-NITRIDE FILM

The effect of a thermally grown silicon nitride (SiNx) film on end-of- range extrinsic dislocation loops in a silicon substrate was investiga ted by transmission electron microscopy. A layer of extrinsic dislocat ion loops was formed by annealing a Si wafer amorphized by a Ge+ ion i mplant. A nitride film was grown on the Si by further annealing in amm onia (NH3) at 810 and 910 degrees 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 showe d no change. The results are explained by a supersaturation of vacanci es caused by the presence of the nitride film, resulting in loop disso lution. By integrating the measured vacancy flux over the distance fro m the nitride/Si :interface to the loop layer, we extract an estimate for the relative supersaturation of vacancies at 910 degrees C, C-v/ C -v similar to 4, where C-v is the concentration of vacancies and the asterisk denotes equilibrium. We. rule out interstitial undersaturatio n-induced loop dissolution based on loop stability with temperature an d oxidation-enhanced loop growth values from a previous report using t he same calculations. A comparison with estimated C-v / C-v processin g equipment and parameters but monitoring the change in Sb diffusivity with nitridation shows excellent agreement. (C) 1997 American Institu te of Physics.