Radiation-induced back-channel leakage in SiGe CMOS on silicon-on-sapphire (SOS) technology

We report the first results of a high-energy gamma irradiation experiment on SiGe CMOS on silicon-on-sapphire (SOS) technology. In contrast to bulk Si CMOS, with increasing total dose the pFETs develop a significant off-state leakage, while the nFETs show a reduction in the leakage, which we attribute to negative charge trapping at the back Si-sapphire interface. Both the Si and SiGe pFETs showed the enhancement in leakage, suggesting that the leakage mechanism was not related to the SiGe channel. When the devices were cooled to liquid-nitrogen temperature, the leakage disappears completely, suggesting that the trapping mechanism is strongly temperature dependent.