SIO2 PRECIPITATION IN HIGHLY SUPERSATURATED OXYGEN-IMPLANTED SINGLE-CRYSTAL SILICON

An extended transmission-electron-microscopy investigation of oxygen-i mplanted silicon has been carried out and has given evidence for a new precipitation mechanism. This mechanism is related to SiO2 precipitat ion of free oxygen involved in dense and hot collisional cascades and produces the largest precipitates in the region where oxygen concentra tion is still high but primary events originating the collisional casc ades are no longer sufficient to guarantee the spatial covering of the silicon. This mechanism prevails at relatively low fluence, while at high fluence the conventional precipitation dominates; in the present experimental conditions (energy = 100 keV, target temperature congruen t-to 250-degrees-C) the oxygen fluence separating these two behaviors is in the interval 1 X 10(16)-1 X 10(17) cm-2.