Total dose radiation and annealing responses of the back transistor of Silicon-On-Insulator pMOSFETs

Abstract

The total dose radiation and annealing responses of the back transistor of Silicon-On-Insulator (SOI) pMOSFETs have been studied by comparing with those of the back transistor of SOI nMOSFETs fabricated on the same wafer. The transistors were irradiated by 60Co γ-rays with various doses, and the front transistors are biased in a Float-State and Off-State, respectively, during irradiation. The total dose radiation responses of the back transistors are characterized by their threshold voltage shifts. The results show that the total dose radiation response of the back transistor of SOI pMOSFETs, similar to that of SOI nMOSFETs, depends greatly on their bias conditions during irradiation. However, with the Float-State bias, rather than the Off-State bias, the back transistors of SOI pMOSFETs reveal a much higher sensitivity to total dose radiation, which is contrary to those of SOI nMOSFETs. In addition, it is also found that the total dose radiation effect of the back transistor of SOI pMOSFETs irradiated with Off-State bias, as well as that of the SOI nMOSFETs, exhibits an increasing trend as the channel length decreases. The annealing response of the back transistors after irradiation at room temperature without bias, characterized by their threshold voltage shifts, indicates that there is a relatively complex annealing mechanism associated with channel length and type, bias condition during irradiation. In particular, for all the transistors irradiated with Off-State bias, their back transistors show an abnormal annealing effect during early annealing. All the results have been discussed and analyzed in detail by the aid of simulation.