Effect of surface proximity on end-of-range loop dissolution in silicon

The effect of surface proximity on the dissolution of end-of-range dislocation loops in silicon was investigated by transmission electron microscopy (TEM). A layer of dislocation loops was formed at a depth of 2600 Å by annealing a Si wafer amorphized by a $1015 cm−2,$ 120 keV, and a $1015 cm−2,$ 30 keV dual $Si+$ implant for 30 min at 850 °C. The wafer was diced into $1 cm×1 cm$ pieces and polished by a chemical–mechanical polishing technique to decrease the loop depth to 1800 and 1000 Å. The samples were then furnace annealed at 900 and 1000 °C in $N2$ gas. Quantitative TEM analysis revealed that the density of small loops decreases as the loop band is brought closer to the surface. The flux of interstitials to the surface varied inversely with loop depth, indicating that the loop dissolution is diffusion limited. Assuming that the loops maintain a supersaturation of interstitials $(CIL)$ around them, and by integrating the measured interstitial flux from the loop layer to the surface, the relative supersaturation of interstitials near the loop layer $(CIL/CI*)$ was extracted 900 and 1000 °C.