Effect of implant dose on formation of buried-oxide Si islands in low-dose SIMOX

The effect of implant dose on the microstructural changes found during Si island formation in low-dose SIMOX was studied. It was found that, for 0.225E18 cm^-2 sample, a continuous BOX did not form, whereas for the 0.45E18 cm^-2 and 0.675E18 cm^-2 samples, lateral coalescence of banded oxide layers was sufficient to form a continuous BOX. However, for the 0.675E18 cm^-2 sample, there were 3 to 4 banded layers of oxide at 1200°C, which coalescence into two thicker banded layers at 1275°C. These two layers evidently trapped isolated regions of Si during their coalescence, which resulted in the formation of a high density of Si islands in the BOX. Conversely, in the 0.45E18 cm^-2 sample, the 1 to 2 banded layers at 1200°C coalesced into a single banded layer at 1275°C, which then annealed into a single continuous film with very low density of Si islands.