The fabrication of thin film transistors with ZnO as active channel layer

Bottom-gate thin film transistors with ZnO as the active channel layer were fabricated on (100) silicon wafer or ITO glass by lift-off and rf sputtering method. The ZnO films deposited on insulator layer were characterized by X-ray diffractometry and atomic force microscopy. Thermally oxidized SiO₂ film was served as insulator in ZnO-TFT fabricated on silicon wafer, and aluminum metal was used for source and drain contacts. The device operated in n channel enhancement mode with the threshold voltage, current on/off ratio, channel mobility of 8V, 5 × 10³ and 0.61 cm²/(V·s), respectively. The SiO₂, Al₂O₃, SiN_x, PbTiO₃ films were used as gate insulators in transparent ZnO-TFTs fabricated on ITO glass. It was found that the ZnO films all have high c-axis preferential orientation on different insulators and the average optical transmittance of transparent ZnO-TFTs was 85% approximately.