Preparation Of ZnO-based Thin Films And Their Applications In Transistors

In today’s society,the ability to interact with and acquire information is particularly important.Thin Film Transistor（TFT）is an important component in the Flat panel display drive circuit,its performance has a significant impact on display technology.At present,metal oxide thin-film transistor has attracted much attention because of its unique structure and characteristics.It has higher performance and higher reliability than traditional silicon-based thin film transistors,among them,zinc oxide（Zn O）based thin film transistors are the leading metal oxide thin-film transistor in the field of flat panel display,which has attracted more and more attention and research,however,the intrinsic defects in Zn O films seriously affect the performance of TFT and limit its application.In order to meet the requirements of TFT for high stability,high mobility and high transmission,researchers are more committed to the study of how to improve the performance of Zn O-based thin film transistors.In this thesis,tungsten（W）doped Zn O thin film transistors（WZO-TFT）were prepared by RF magnetron sputtering and reverse adhesive process,the WZO-TFT is analyzed and optimized.The detailed research contents are as follows:（1）WZO-TFTs were prepared by deposition and growth of WZO films on p-type Si/Si O₂substrates using a counter-gel process and RF magnetron sputtering and by electron beam evaporation of Al electrodes.The effects of different sputtering powers,different argon-to-oxygen ratios and different sputtering pressures on the performance of WZO-TFTs were investigated to investigate the optimal growth conditions of WZO-TFTs,and it was found that at room temperature,when the Zn O sputtering power is 150 W,tray speed is 20 rpm,tungsten sputtering power is 2 W,sputtering pressure is 8 m Torr,argon-to-oxygen ratio is 95:5,the device performance is optimal,the current switching ratio reaches 10⁵,the threshold voltage is 16.89 V,the carrier mobility is 0.157cm²/Vs,the average transmittance of the film in the visible region reaches 90%,and the crystalline quality of the film is The crystalline quality of the film is better and the surface is more flat and dense.（2）To further improve the performance of WZO-TFT based on the above,we performed rapid annealing of WZO under oxygen atmosphere and found that the annealing temperature did not change the meritocratic growth of WZO films along the（002）crystal plane,and the annealing had a better improvement on the electrical properties of WZO-TFT devices.Compared with the unannealed WZO-TFT,the root-mean-square roughness of the annealed WZO film is reduced,and the film surface is flatter and smoother.Secondly,annealing effectively improves the hump effect at the WZO-TFT channel layer interface,and the current switching ratio of the TFT is increased by two orders of magnitude to 7.48×10⁷,with a subthreshold swing of 1.4975 V/decade,and the electrical properties of the device are improved.（3）In order to further study the properties of WZO-TFT,we prepared double channel layer WZO-TFT.The double-channel-layer WZO thin films were prepared by magnetron sputtering from low-resistance layer to high-resistance layer,the total sputtering time of the low resistance layer and the high resistance layer is set to 15 minutes,and the sputtering time of the low resistance layer and the high resistance layer is changed,the effect of double channel layer structure on the performance of WZO-TFT was studied,the growth time of low resistance layer and high resistance layer were 3min and 12 min,4 min and 11 min,5 min and 10 min,6 min and 9 min,7 min and 8 min,respectively.When the sputtering time of low resistance layer is 5 min,and that of high resistance layer is 10 min,the performance of double channel layer WZO-TFT is the best,the switching ratio is 1.37×10⁶,and the swing of sub-threshold is 1.5645 V/decade,the electrical properties are better than single channel layer WZO-TFT.