Radiation and bias switch-induced charge dynamics in Al2O3-based metal-oxide-semiconductor structures

Abstract

Charge trapping dynamics induced by exposition to γ-ray (60Co) radiation and bias switching in MOS capacitors with atomic layer deposited Al2O3 as insulating layer was studied. Electrical characterization prior to irradiation showed voltage instabilities due to electron tunneling between the substrate and preexisting defects inside the dielectric layer. Real-time capacitance-voltage (C-V) measurements during irradiation showed two distinct regimes: For short times, the response is strongly bias dependent and linear with log(t), consistent with electron trapping/detrapping; for long times, the voltage shift is dominated by the radiation-induced hole capture being always negative and linear with dose. A simple model that takes into account these two phenomena can successfully reproduce the observed results.