Total-Ionizing-Dose Effects on 3-D Sequentially Integrated FDSOI Ring Oscillators

Total-ionizing-dose (TID) responses are investigated for fully depleted silicon-on-insulator (FDSOI) ring oscillators (ROs) in 3-D architectures. Operational frequencies decrease after irradiation in these devices due primarily to threshold voltage shifts and transconductance degradation due to interface-trap buildup in the pull-up $p$ MOSFETs. 3-D sequentially integrated FDSOI ROs fabricated in the bottom layer of the 3-D structure show the most significant frequency degradation. The ac-bias irradiation leads to greater shifts than static-bias irradiation in these devices due to enhanced interface-trap buildup. Circuit simulations reinforce the relative importance of transconductance degradation in pull-up $p$ MOSFETs to the TID response of these ROs.