Secondary defect formation in bonded silicon-on-insulator after boron implantation

Silicon-on-insulator (SOT) has proven to be a viable alternative to traditional bulk silicon for fabrication of complementary metal-oxide-semiconductor devices. However, a number of unusual phenomena with regards to diffusion and segregation of dopants in SOI have yet to be explained. In the present study, SOITEC wafers were thinned to 700 and 1600 Angstrom using oxidation and etching. Ion implantation was performed into SOI and bulk silicon wafers using B-11(+) ions at 6.5 and 19 keV with a dose of 3 X 10(14) cm(-2). Thermal processing occurred in a furnace at 750 degreesC for times ranging from 5 min to 8 h under an inert ambient. Using quantitative transmission electron microscopy it was observed that the concentration of trapped interstitials and density of {311} defects was significantly reduced in SOI compared to the bulk. Hall effect was used to monitor the activation process of boron in SOI and bulk silicon. Significantly less activation was observed in SOI compared to the bulk and was dependent on the surface silicon thickness. For the first time, a decrease in the trapped interstitial concentration is observed in SOI even with minimal dose loss to the buried oxide. It is hypothesized that the formation of boron-interstitial clusters may be more pronounced in SOI, leading to a reduction in the trapped interstitial population and {311} defect density. (C) 2004 American Vacuum Society.