Study On Preparation Of TFT Insulation Layer By Anodization

The screen is the interface of human-computer interaction,and it has become an indispensable role in people's work and life.Amorphous oxide semiconductor thin film transistor(AOS-TFT)with high carrier mobility(1~100cm2V-1s-1),great film uniformity,relatively low process temperature,transparent to visible light and compatible with preparation process of a-Si TFT,is a strong contender for the next generation of display technology.But it is inevitable for AOS-TFT to use high vacuum,high energy and other expensive equipment to deposit thin film.On the one hand,it is difficult to control the oxygen vacancies in the oxide films,on the other hand,it is not conducive for TFT preparing at low temperature,so it can not satisfy the development needs of new display devices of electronic paper,transparent display and so on.The equipment of anodic oxidation is simple and inexpensive,and it can realize the low temperature TFT preparation.This paper is the first time to explore the preparation of complex oxide thin film by anodizing Mg-Al alloy thin film,and studying its structure and insulation performance.The main work as well as results are as follows:1.By comparison of deposition method of electron beam evaporation and magnetron sputtering,we found that the single source electron beam evaporation and magnetron sputtering is difficult to control the atom proportion of Al and Mg in the film,and employing Mg and Al metal targets,the composition ratio of the films can be controlled very well by the dual source electron beam evaporation.2.By EDS and SEM characterization of alloy thin film,it showed that optimizing process parameters of electron beam current,targets and substrate temperature of electron beam evaporation,adjusting electron beam current can obtain desired atom proportion of Mg-Al alloy thin films,and the film quality can be improved by appropriate electron beam current,highly pure Mg and Al particle target and substrate temperature at 180?,obtaining smooth surface morphology and compact alloy thin film.3.About anodic oxidation,we prepared alumina thin film by anodizing aluminum film,obtaining the good performance of alumina insulation layer,in order to verify the feasibility of preparing oxide film by anodizing metal.Based on that,we studied the preparing Mg-Al complex oxide film by anodizing Mg-Al alloy thin film.The study showed that,during anodic oxidation,constant current,constant voltage,the duration of constant voltage and composition ratio of alloy thin film have an effect on insulating properties of the oxide film.Employing appropriate proportion of Mg-Al alloy film and the constant current and constant voltage parameters of 2m A-85 V and 3m A-85 V can obtain high quality oxidation film,and prolonging constant voltage oxidation time properly can further reduced the film defects and the leakage current of the thin film.4.Through annealing,the surface roughness and defects can be reduced,and the leakage current can be reduced further.By optimizing the process parameters,the leakage current of anodic oxidation film is 10-4m A/cm2,the breakdown voltage is about 20 V,and relative dielectric constant is 8.35.Using oxide film as the insulation layer of TFT,the device has somewhat field controlling effect.