Defect formation in silicon at a mask edge during crystallization of an amorphous implantation layer

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Abstract
Implantation defects under a mask edge were studied by cross-sectional transmission electron microscopy. An arsenic implantation with a dose of 5×1015 cm−2 as used for source/drain implantations in metal-oxide-semiconductor transistor structures completely amorphizes a 63-nm-thick silicon surface layer and produces a sharply curved amorphous/crystalline interface under the mask edge. Annealing at 900 °C results in the formation of vacancy-type dislocation half-loops or microtwinning on {111} planes under the mask edge. Partial crystallization of the amorphous layer at 500 °C revealed a notch in the amorphous/crystalline interface which is shown to be due to the different epitaxial regrowth rates on the various lattice planes. On further annealing, the above-mentioned defects are generated when the crystallization fronts on both sides of the notch join.