Improvement of charge trapping characteristics of Al2O3/Al-rich Al2O3/SiO2 stacked films by thermal annealing

Thin film Al2O3/Al-rich Al2O3/SiO2 structures were fabricated on p-Si substrates. Radio-frequency magnetron co-sputtering was used to form Al-rich Al2O3 thin film as the charge-trapping layer of nonvolatile Al2O3 memory. Capacitance-voltage measurements showed a large hysteresis due to charge trapping in the Al-rich Al2O3 layer. The charge trap density was estimated to be 42.7 × 1018 cm− 3, which is the largest value ever reported for an Al-rich Al2O3 layer; it is six times larger than that of a conventional metal-nitride-oxide-silicon memory. Thermal annealing was found to reduce the leakage current of the Al2O3 blocking layer, thereby providing this structure with better data retention at room temperature than an as-deposited one. In addition, the annealed structure was found to exhibit good data retention even at 100 °C.