The Preparation Of Nitrogen Oxygen Zinc Thin Film And Research Of Its Optical And Electrical Characteristics

In recent years, during the rapid development of the semiconductor device,semiconductor thin film materials have been widely used in many fields, such as energy,the information industry and national defense. Especially in the field of flat panel display and solar cell, they contain much great value of using. Thin film material is one of the important bases, which can support the development of science and technology information industry. It will get a more broad space to develop. As a representative of new oxide thin films, ZnON thin films have become the research focus,which have many advantages, such as high carrier mobility, the excellent optical and electrical properties, high stability, clean, abundant raw materials. In this paper, during making ZnON thin films, the best process parameters and preparation conditions are explored,and the performance of ZnON thin films is tested. Then ZnON based thin film transistor(ZnON-TFT) ,which uses ZnON thin films as the active layer, is made. TFT preparation process is finished. The measurement of ZnON-TFT electrical characteristics is obtained. We explore the impact of different preparation conditions on the electrical properties of ZnON-TFT. Specific content is divided into the following three parts:Firstly, ZnON thin films are prepared by radio-frequency magnetron sputtering.The parameters such as the ratio of oxygen and nitrogen, the sputtering power and the distance between target and substrate are changed.The optical properties, square resistance and SEM of the films are characterized. The results show that the ratio of nitrogen has a great influence on the transmittance of the films. With the crease of the nitrogen flow rate, the nitrogen content in the films increases, the transmittance decreases and the band gap decreases. At the same time, the transmittance of ZnON thin films is also related to the sputtering power and the target-substrate distance.The sputtering power increases, the transmittance decreases. The target-substrate distance increases, and the transmittance increases. In addition, the square resistance decreases with the increase of the nitrogen content. The SEM images show that the surface of ZnON thin films is smooth.Secondly, ZnON-TFT is prepared including that ZnON as active layer, Si as gate,SiO2 as gate insulator and Mo as source drain electrode. The heavily doped P type Si which contains a SiO2 layer is used as the substrate. Using RF magnetron sputtering to prepare a 80nm thick ZnON thin film, then using DC magnetron sputtering to prepare a 100nm thick Mo thin film. After photolithography and etching, ZnON-TFT is obtained.Finally, the electrical properties of ZnON-TFT under different preparation parameters are tested. The transfer characteristic curve and the output characteristic curve of TFT are measured by using the semiconductor tester. The data are drawn into the graph to extract the characteristic parameters. The results show that with the increase of nitrogen flow rate and sputtering power, the carrier mobility and the switching ratio of ZnON-TFT increases at the beginning and then decreases, the subthreshold swing decreases at the beginning and then increases.With the increases of the target-substrate distance, the mobility and the switching ratio decreases and the subthreshold swing increases.The optimal preparation parameters are nitrogen flow 30sccm, sputtering power 120W, target-substrate distance 9cm. Under these parameters,the carrier mobility is 6.12 cm2/V·s,the switching ratio is 1.14×105, the subthreshold swing is 1.5 V/dec, and the threshold voltage is 8.5V. The threshold voltage is positive indicating that ZnON-TFT is N channel enhancement made TFT device.