Effects of annealing temperature on buried oxide precipitates in He and O co-implanted Si

The effects of the processing conditions on the formation of buried oxide precipitates in He and O co-implanted Si were investigated by the combination of Fourier transform infrared (FTIR) absorption spectroscopy, depth-resolved positron annihilation Doppler spectroscopy, and transmission electron microscopy (TEM). Silicon wafers were implanted with 50 keV He ions at a fluence of 2 × 1016 cm−2 and subsequent 150 keV O ions at a fluence of 2 × 1017 cm−2. For comparison, reference Si wafers were only implanted with 150 keV O ions. The Si–O–Si stretching frequency increases while the peak width of the Si–O–Si stretching absorption band decreases with an increase in annealing temperature. After the same annealing, the peak width of the Si–O–Si stretching absorption band in the He and O co-implanted sample is significantly larger than that in the reference sample. Two kinds of vacancy-type defects are observed by positrons, i.e., vacancy-type defects and vacancy-oxygen complexes. The characteristic S values of vacancy-type defects and vacancy-type complexes in the He and O co-implanted sample are smaller than those of the reference sample. In addition, the thickness of the buried oxide layer in the He and O co-implanted sample is smaller than that in the reference sample. After annealing at 1473 K, the O content is larger in the He and O co-implanted sample compared to that in the reference sample.

► As-implantation, He-induced vacancy-type defects enhance the formation of oxide precipitates.
► After annealing, He-induced vacancy-type defects reduce the thickness of the buried oxide layer.
► The O content increases in the He and O co-implanted sample.