Band offsets and charge storage characteristics of atomic layer deposited high- k Hf O₂ Ti O₂ multilayers

The band offsets and charge storage characteristics of atomic layer deposited high- k Hf O2 Ti O2 multilayers with ten periods in p-SiSi O2 (Hf O2 Ti O2) Al2 O3 structure have been investigated. The thickness of high- k Hf O2 or Ti O2 film is ∼0.5 nm for each layer, before and after annealing treatment of 900 °C for 1 min in N2 ambient. High-resolution transmission electron microscopy, x-ray photoelectron spectroscopy, and ultraviolet photoelectron spectroscopy measurements on high- k Hf O2 Ti O2 multilayers confirm the layer-by-layer structure after annealing treatment, suggesting the Hf O2 Ti O2 multilayer quantum wells. The valence band offsets of Hf O2 and Ti O2 films are found to be ∼3.1 and ∼1.5 eV, respectively. The conduction band offsets are found to be ∼1.7 eV for Hf O2 films and ∼0.9 eV for Ti O2 films. The high- k Hf O2 Ti O2 multilayers in p-SiSi O2 (Hf O2 Ti O2) Al2 O3 /aluminum memory capacitor show a large capacitance-voltage hysteresis memory window of ∼5 V at gate voltage of ±5 V, due to the charge storage in multilayer quantum wells. The hysteresis memory window of ∼1.3 V at small gate voltage of ±1 V is also observed. The high- k Hf O2 Ti O2 multilayer memory structure can be used in future nanoscale flash memory device applications.