Radiation response of Al2O3-based MOS capacitors under different bias conditions

We present for the first time real-time γ-ray (⁶⁰Co) 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.