Improved properties of Pt–HfO2 gate insulator–ZnO semiconductor thin film structure by annealing of ZnO layer

Metal-insulator-semiconductor capacitors were fabricated with sputtered ZnO and atomic layer deposited HfO2 as the semiconductor and gate dielectric layers, respectively. From the capacitance–voltage measurements, it was confirmed that pre-deposition annealing of the sputtered ZnO layer at 300 °C in air greatly decreased the interfacial trap density (∼ 2 × 1012 cm− 2 eV− 1). X-ray photoelectron spectroscopy showed a decrease in the OH bonds adsorbed on the ZnO surface after pre-deposition annealing, which improved the interface property. A very small capacitance equivalent thickness of 1.3 nm was achieved, which decreased the operation voltage (< 5 V) of the device significantly.