An Analytical Study of the Effect of Total Ionizing Dose on Body Current in 130-nm PDSOI I/O nMOSFETs

Abstract

This paper investigates the effect of total ionizing dose (TID) on body current in 130-nm partially depleted (PD) silicon-on-insulator input–output nMOSFETs. As the TID increases, the body current lowers and the peak point of body current shifts left. By deeply theoretical analyses, we give a comprehensive interpretation. As TID increases, more positive charges are nonuniformly trapped in the buried oxide (BOX) layer. As a result, the PD silicon film changes to partially fully depleted silicon film, which induces the coupling effect between front gate and back gate. Consequently, radiation-induced trapped charges in the BOX layer lower the threshold voltage of the front gate and increase the characteristic length. The decrease of the threshold voltage of the front gate and the increase of the characteristic length both lower the maximum lateral field. Hence, the impact ionization is weakened as TID increases. Finally, the body current lowers and the peak point of body current shifts left. Pass-gate (PG) and ON irradiation bias cases are compared. Due to more trapped charge in the BOX layer under the PG bias, the body current lowers more significantly and the peak point of body current shift more left under the PG bias. A 3-D TCAD simulation is applied to verify our theoretical analyses, and good agreement is observed between simulation and theories.