Materials properties and carrier recombination lifetimes in thin epi-less bond-etch silicon on insulator (EL-BESOI)

The use of MeV boron implantation as an etch stop for epi-less bond etch silicon on insulator (EL-BESOI) has recently been reported. In that work a 490-nm device film was demonstrated with thickness uniformity on the order of 8 nm. Details on the characterization of materials properties and carrier recombination lifetimes in the device material were not presented. Since the device film will have had a high energy (2.5 MeV) boron beam pass through it as part of the etch stop processing, such a study is needed to confirm that, after annealing, the material is not left in a damaged or defective state. In the present work the authors study these properties with the objective of examining such SOI layers with nominal 250-nm thickness. A significant amount of the materials characterization can be accomplished prior to bonding since the device wafer can be deep implanted at 2.5 MeV and then examined near its surface where the final device material will reside. The final SOI material is evaluated relative to electronic defect states by way of minority carrier recombination lifetime measurements done in a side-by-side comparison of MOSFET devices in the SOI material relative to similar bulk monitor devices. Material quality is determined relative to benchmark lifetimes that are above and below 20 μs