Crystallographic defects in thermally oxidized wafer bonded silicon on insulator (SOI) substrates

The crystalline quality of wafer bonded (WB) silicon on insulator (SOI) structures thermal treated in dry oxygen ambients has been investigated by means of transmission electron microscopy and defect etching. The main crystallographic defects present in the SOI layers are dislocations, amorphous precipitates, and oxidation induced stacking faults (OISF). The evolution of the OISFs with time and temperature has also been investigated. The main feature observed is that the OISF in WB SOI structures undergo a retrogrowth process at temperatures around T = 1195°C for times of t = 2h. This result is very similar to that recently reported for oxygen implanted SOI (SIMOX) but considerably different from that observed in bulk silicon. The experimental data fits nicely a model recently proposed for the retrogrowth of OISF in thin SOI layers. This model considers that the self-interstitial supersaturation is considerably reduced compared to bulk silicon due to the relative fast point defect recombination inside the top silicon layer.