Studies of radiation effects in Al₂O₃-based metal-oxide-semiconductor structures induced by Si heavy ions

The radiation effects of metal-oxide-semiconductor (MOS) capacitors based on an Al₂O₃ gate dielectric were studied using 30 MeV Si heavy ions. To give insights into the types of defects induced by Si ion irradiation in the gate oxide, synergistic experiments involving γ-ray irradiation and Si ion irradiation were carried out. The results revealed that the defects in the as-grown Al₂O₃ layer were found to be hole trapping centers, whereas Si ion induced new defects were electron trapping centers. The experimental and simulation data of current density-voltage (J-V) curves confirmed that the transmission mechanism of leakage current in the Al₂O₃ layer was mainly dominated by the Frenkel-Poole mechanism. In detail, the variations of leakage current were mainly due to the attributions of the local built-in electric field-assisted current leakage and the conductive path-assisted current leakage and were found to be dependent on the irradiation condition and Al₂O₃ thickness. Lastly, the decrease of the gate oxide capacitance of MOS capacitors was attributed to the increase of the series resistance and leakage current in MOS capacitors.