Low temperature fabrication of high performance ZnO thin film transistors with high-k dielectrics

We report on the study of the low-temperature fabrication of ZnO thin film transistors on high-k gate dielectrics: Al2O3, HfO2 and ZrO2. All gate dielectrics were grown by atomic layer deposition at 150 °C and the ZnO semiconductors were grown by rf magnetron sputtering at room temperature. The electrical characteristics and device performance have been investigated systematically, along with the thin film structural properties by X-ray diffraction and atomic force microscopy. Highly (0 0 0 2)-oriented ZnO thin films were observed and their surface morphology revealed similar microstructures regardless of the bottom gate oxides. The fabricated thin film transistors showed high on/off ratio larger than 105 and low subthreshold voltage swing. The discrepancy of the device performance in these combinations indicated a significant gate dielectrics and interface dependence.