Study Of Hafnium Aluminum Oxide Composite Dielectric Film And Thin Film Transistor With High Mobility Of Zinc Indium Tin Oxide Semiconductor

Recently, thin film transistors(TFTs) based on transparent oxide semiconductor have potential applications in the next flat panel displays due to its high transmittance and high mobility and attract considerable attention. Nowdays, most of the TFTs are prepared by vacuum process, and obtain good performance. But the vacuum process has many shortcomings. Compared with the vacuum method, the solution method is a promising mothod with some advantages, such as low cost, simple equitment, and the composition of the film can be cotrolled accurately. The study of TFT prepared by solution mothed is increasing year by year,In this paper, Hf O2, Al2O3 and HAO films are prepared by solution mothed to be dielectric materials and ZITO is also prepared by solution mothed to be semiconductor materials. Base on the study, low voltage operating TFTs with bottom gate top gate(BGTC) structure are fabricated, and the performances of the TFTs are investaged.The works in this paper are as follows: 1. The dielectric layer is investaged ahead. The structural and optoelectronic properties of Hf O2 and Al2O3 films annealed at different temperatures are first studied. The results show that Hf O2 films have high leakage current, low breakdown electric field and high dielectric constant. On the contrary, Al2O3 films have low leakage current, high breakdown electric field and low dielectric constant. HAO is a promising gate dielectric material, which can leverage the advantages of high dielectric constant of Hf O2 with low leakage current of Al2O3. The results show that the HAO film with Hf/Al=2:1 annealed at 500 oC have relative permittivity of 12.1 and the leakage current density of the HAO f ilm is 1.69 × 10-7 A /cm2 when the electric field is 2 MV / cm. 2. ZITO film is also prepared by solution method. The annealing temperature on the effects of ZITO film is studied and the films are charactized by XPS, AFM. To fabricated TFT devices with BGTC structure, the etching rate of ZITO film annealed at different temperatures in PAN and oxalic is studied. The results show that the etching rate of ZITO film annealed at 350 oC in the PAN with 35 oC is almost negligible. 3. On the basis of successfully fabrication of insulating layer and the active layer by solution method, the low temperature voltage operating TFT devices with BGTC structure are fabricated. We focus on the ZITO-HAO TFTs. ZITO-HAO TFT device annealed at 500 oC showed a saturated field effect mobility of 13.5 cm2/Vs, a subthreshold swing of 87 m V/decade, an on-to-off current ratio of 7.2×106 and a threshold voltage of-0.6 V. The TFT device showed excellent stability against the PBS, which was related to the good ZITO semiconductor layer and interface between the ZITO channel and HAO gate dielectric.