Amorphous Indium Zinc Oxide Thin Film Transistor

Thin film transistors (TFTs) based on indium zinc oxide as channel layer were studied in this thesis.The channel layer and dielectric layer were fabricated and characterized, respectively. Thin film transistors were fabricated with shadow mask. The performance of device was improved by optimizing the deposition parameter of channel layer and configuration of TFTs.Firstly, indium zinc oxide (IZO) thin films were deposited on glass substrates by DC reactive magnetron sputtering at room temperature. The structure of IZO films is amorphous, and the surface of IZO films is smooth. The resistivity of the thin films can be adjusted from 10-3 to 106 Q-cm through the proper control of the oxygen pressure during the deposition process.As-deposited amorphous IZO (a-IZO) films show high optical transmission, the average transmittance in the visible region is about 87%,and the optical band gap exhibits from 3.34 eV to 3.62 eV, which is between zinc oxide and indium oxide. a-IZO films deposited by DC reactive magnetron sputtering show good semi-conductive and optical properties which can satisfy the requirements of TFTs.Secondly, SiO2 films were deposited on glass substrates by pulsed plasma deposition (PPD) at room temperature. For the SiO2 films deposited at oxygen pressure of 2.4×10-2 Pa,2.6×10-2 Pa and 2.8×10-2 Pa, the relative dielectric constant was 3.82,3.88 and 3.92,respectively. SiO2 films also show high optical transmission, the average transmittance in the visible region is about 87%.SiO2 films deposited by PPD show good dielectric and optical properties, which have potential application in TFT as insulator layer.Finally, TFTs were fabricated using shadow mask based on the studies of channel layer and dielectric layer. The dependence of performance on the deposition parameter of channel layer and configuration of TFTs were investigated in detail. The main results show that:1) TFTs with a-IZO channel layer which were deposited at oxygen pressure of 5.0×10-2 Pa show the best output characteristics with distinct saturation and the largest output current at the same bias voltage. Oxygen pressure of 5.0×10-2 Pa was considered as the optimal parameter to depositα-IZO channel layer.2) With smoother interface between channel layer and dielectric layer, the performance of top-gated TFT was better than bottom-gated TFT. The top-gated TFT operated in n-type enhancement mode with a field-effect mobility of 4.08 cm2V-1s-1, an on-off current ratio of 103 and a threshold voltage of 0.57.