Paramagnetic defect centers in BESOI and SIMOX buried oxides

The authors have combined electron paramagnetic resonance and capacitance-voltage measurements to identify the chemical nature and charge state of defects in BESOI and SIMOX materials. The four types of defect centers observed, charged oxygen vacancies, delocalized hole centers, amorphous-Si centers, and oxygen-related donors, are strikingly similar. In the BESOI materials, the radiation-induced EPR centers are located at or near the bonded interface. Therefore, the bonded interface is a potential hole trap site and may lead to radiation-induced back-channel leakage. In SIMOX materials it is found that all of the defects in the buried oxide are due to excess-Si. The results using poly-Si/thermal oxide/Si structures strongly suggest that it is the post-implantation, high temperature anneal processing step in SIMOX that leads to their existence. The anneal leads to the out-diffusion of oxygen from the buried oxide creating excess-Si related defects in the oxide and O-related donors in the underlying Si substrates. Last, the study has elucidated a number of interesting aspects regarding the physical nature of a relatively new class of defects in SiO2: delocalized spin centers. The authors find that they are hole traps in both SIMOX and BESOI materials