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This paper presents a novel metal-oxide-nitride-oxide-silicon (MONOS)-type nonvolatile memory structure using hafnium oxide (HfO2) as tunneling and blocking layer and tantalum pentoxide (Ta2O5) as the charge trapping layer. The superiorities of such devices to traditional SiO2-Si3N4-SiO2 stack devices in obtaining a better tradeoff between faster programming and better retention are illustrated based on a band engineering analysis. The experimental results demonstrate that the fabricated devices can be programmed as fast as 1 μs and erased from 10 ns at an 8-V gate bias. The retention decay rate of this device is improved by a factor more than three as compared to the conventional MONOS/SONOS type devices. Excellent endurance and read disturb performance are also demonstrated.
Date of Publication: April 2004