Acoustic spectroscopy and electrical characterization of Si/NAOS-SiO2/HfO2 structures

The MOS structure prepared on n-type Si substrate with SiO2/HfO2 gate dielectric layers was formed by 5 nm HfO2 oxide deposited by atomic layer deposition on 0.6 nm SiO2 oxide film prepared with nitric acid oxidation of Si (NAOS) in ∼100% HNO3 vapor. The set of this MOS structure was annealed in N2 atmosphere at 200, 300 and 400 °C for 10 min to stabilize the structure, to decrease the interface states density and leakage current density. The both acoustic deep level transient spectroscopy (A-DLTS) and acoustoelectric response signal versus gate voltage dependence (Uac–Ug characteristics) were used to characterize the interface states and the role of annealing treatment, except ordinary electrical investigation represented by current–voltage and capacitance–voltage measurements. The main interface deep centers with activation energies ∼0.30 eV typical for dangling-bond type defects were observed as well as a particular influence of annealing treatment on the interface states. The obtained results are analyzed and discussed.