Paramagnetic defect centers in BESOI and SIMOX buried oxides

Electron paramagnetic resonance (EPR) and capacitance-voltage measurements have been combined to identify the chemical nature and charge state of defects in BESOI (bonded and etchback silicon-on-insulator) and SIMOX (separation by implantation of oxygen) 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 postimplantation, 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. A relatively new class of defects in SiO ₂, delocalized spin centers, are found to be hole traps in both SIMOX and BESOI materials