Total dose response of Al2O3-based MOS structure under gamma-ray irradiation

The effect of gamma irradiation upon Al/Al2O3/Si MOS structure under different doses of ⁶⁰Co is studied in this article as a function of total dosage. Al2O3 MOS capacitors with a gate dielectric thickness of 4nm and electrode diameter of Φ 1mm are prepared on the p-Si substrate using atomic layer deposition. The MOS capacitors are under zero bias during irradiation under ⁶⁰Co gamma ray with total dose of 300Krad(Si)/500Krad (Si)/1Mrad (Si) and dose rate of 50rad (Si)/s. The high frequency Capacitor-Voltage (C-V) and Current-Voltage (I–V) characteristic are measured at room temperature before and after irradiation for each sample. In addition, Atomic Force Microscopy (AFM), Grazing Incidence X-ray Diffraction (GIXRD), and X-ray Photoelectron Spectroscopy (XPS) are also applied to determine the surface morphology, physical and mechanical properties under different doses of radiation. The oxide trapped charge calculated from the high frequency C-V characteristics is in the order of 10¹¹ cm⁻² and increases with the applied total dose. The XRD spectrum shows several phases of Al2O3 variation under each total dose. The XPS result shows that different total dosage leads to the drift of binding energy peak to a different degree, which indicates the influence of irradiation on the valence state of the elements attributed to the gamma-ray induced interface states.