Simulation of TID Effects in a High Voltage Ring Oscillator

Oscillation frequency of a high voltage ring oscillator is observed to change non-linearly with increasing dose. The change in oscillation is caused by buildup of oxide-trapped charge in both gate and isolation oxides post-radiation. A simulation methodology is described and implemented which successfully re-creates oscillator response by way of radiation-enabled simulation. Implementation of radiation-enabled simulation of ring oscillator is discussed. Simulation allows projection of oscillator response in-situ, allowing designers to anticipate changes in oscillation and implement radiation hardening as required. Alternatively, implementation of a ring oscillator as a reliability monitor in a large-scale circuit allows easily detectable observation of total dose effects on transistors.