Radiation Response of Al2O3-based MOS Capacitors Under Different Bias Conditions

We present for the first time real-time gamma-ray (Co-60) radiation response of MOS capacitors with an atomic layer deposited Al2O3 as insulating layer under different bias conditions. Preirradiation electrical characterization showed voltage instability due to tunneling transitions between the substrate and preexisting defects inside the dielectric layer. Real-time capacitance-voltage (C-V) measurements along irradiation showed two distinguishable regions: For short times, the response is strongly bias dependent (positive voltage shift for positive bias and the opposite for negative bias) with a shape linear with log(t), while for long times the voltage shift is always negative with a linear dependence with dose. This behavior can be explained and reproduced by a physical model that takes into account the superposition of a bias-induced electron trapping/detrapping by tunneling transitions with the substrate (as without radiation) and a radiation-induced hole capture.