A Technology Research Of Zinc Oxide Nitride Thin Film Transistor

Though the application of the oxide Thin Film Transistor(TFT) lasts only eight years, it represents megatrend, not only due to the higher mobility than amorphous silicon and organic semiconductor to integrate the drive circuit of display, but also the simple processing in low temperature and vaccum., The high transmittance is another important feature. The oxide semiconductor material has Zinc Oxide(ZnO),Indium Zinc Oxide(IZO),Indium Gallium Zinc Oxide(IGZO).etc. Valence band is formed of 2p orbit in the band structure of oxide semiconductor,the band gap of ZnO is about 3.2eV, but the oxygen vacancies exist beyond the valence band maximum, it will result in the slow decay of current, and then leads to the device instability. So it is important to explore the oxide doped with the larger size anions(N3-, S2-, Se2-, and so on) with higher p orbital energy than oxygen. In the article, the film of Zinc Oxide Nitride(ZnON) is prepared by reactive radio-frequency magnetron sputtering and its performance was tested. An inverted staggered bottom-gate structure was prepared with ZnON film as the active layer and its electrical properties were investigated. There are three main parts in this paperFirstly, the ZnON film was fabricated in the glass substrate by reactive radio-frequency magnetron sputtering. and the element of N, O, Zn was proved through the EDS analysis. The transmittance of the film was tested in the different sputtering power and the flow rate of nitrogen and Oxygen, and the products prepared in different flow rate of nitrogen and oxygen are characterized by SEM and EDS. We found the samples are all direct band gap semiconductor. And the transmittance generally presents a decreasing trend. The morphology has an obvious improvement with the flow of nitrogen increasing. The EDS proves the existence of the O, N and Zn.Secondly, the inverted staggered bottom-gate structure is used in this paper, including that Si as substrate and gate, SiO2 as gate insulator, ZnON as active layer, Mo as the source/drain. we develop and find the specific parameters of the fabrication process. We choose the flow of nitrogen as 50 sccm and sputtering power as 300 w, the detals of lithography is cleaning the substrate, gluing(first speed 800rps/min, last speed 2800rps/min),soft-baking(100℃,5min),development(1.5% NaOH solution,10seconds) and post-baking(120℃,20min),we put NaON into the 5% H2O2 solution until the PH is 8 when begin to etch.At last, We test the electrical properties of prepared TFTs in different sputtering power and different flow rate of nitrogen and oxygen.We find the performance of the prepared TFTs generally are from good to bad. Finally we study the stability of the TFT. we found the shift of the threshold voltage get bigger from the time of the gate voltage increasing,the trend looks like exponential function.