Microstructural changes in oxygen implanted SOI material at intermediate annealing steps in thermal ramping

The authors report on the microstructural changes in HT (high-temperature-implanted) SIMOX (separation by implanted oxygen) at various stages in the ramping process by simulating the thermal treatment with two-hour anneals at intermediate temperatures. The wafers studied were implanted to 1.8*10/sup 18/ cm/sup -2/ at 200 keV at a temperature of 620 degrees C. To simulate the effect of the thermal ramping cycle, wafers were annealed for 2 hours at 50 degrees C intervals from 800 degrees C to 1100 degrees C. Cross section samples were studied with conventional transmission electron microscopy (TEM) techniques at 200 keV. Major microstructural changes are shown to occur in SIMOX during the thermal ramping cycle between temperatures of 900 degrees C and 1100 degrees C. These changes strongly affect, possibly even control, the final defect density and buried oxide microstructure, even prior to the final high temperature anneal. Dislocation formation in SIMOX occurs during thermal ramping, probably between 1000 degrees C and 1100 degrees C. This suggests that it may be possible to further reduce dislocation densities of 10/sup 6/ cm/sup -2/, as found in HT SIMOX, by altering the thermal ramping cycle.<
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