Study On The Preparation Of WZTO And HAO Precursor Solution By Power Ultrasound And The Performance Of TFT

Among the various manufacturing processes of amorphous oxide semiconductor thin film transistor(AOS TFT),solution process will become a potential method for the preparation of AOS TFT owing to its low cost and simple process.The key factor in the preparation of AOS TFT technology is the stable and high-performance precursor solution.At present,the formation of precursor solution involves several important steps:the complete decomposition of the metal alkoxides in an organic solvent,formation of the homogeneous solution,and formation of stable gel under certain conditions.These processes involve high temperature and long-time water bath treatment and agitation(above 50°C for several hours).Therefore,in order to improve efficiency,it is urgent to develop a rapid and high-effective method for preparing precursor solution.Power ultrasound technology use ultrasound to generate sonochemical reactions in the solution,and then form cavitation bubbles.The formation,oscillation,growth,contraction and rupture of cavitation bubbles will trigger physical and chemical changes.When the cavitation bubbles burst,it will produce transient high temperature and high pressure,which will accelerate the dissolution of the solute and the agitation of the solution.In addition,the use of power ultrasound for preparing the precursor solution does not require additional heating conditions.Moreover,it will provide conditions that are not easily obtained by other conventional methods such as the water bath method,and effectively improve the preparation efficiency of the precursor solution.The main work of this paper is as follows:(1)The tungsten zinc tin oxide(WZTO)precursor solution was prepared by power ultrasound.The influence of the time of power ultrasonic treatment on the WZTO precursor solution was studied,and it was compared with the WZTO precursor solution prepared by traditional water bath treatment.The mobility of WZTO TFT prepared by the precursor solution treated with power ultrasound for 10 min was 2.7 cm²v^-1s^-1,the threshold voltage was 1.2 V,the subthreshold swing was 0.14 V/dec,and the switching ratio was 5.1×10⁷.While the mobility of the WZTO TFT prepared by the precursor solution treated with water bath for 3 h was only 1.2 cm²v^-1s^-1.The results show that the power ultrasound technology can significantly reduce the preparation time of the precursor solution and increase the efficiency by 18 times.(2)The hafnium aluminum oxide(HAO)precursor solution was prepared by power ultrasound.The influence of different annealing temperature on the electrical properties of the HAO film was explored.The results show that the HAO film has good electrical properties.The relative dielectric constant of HAO film was 15.9,the leakage current density was only 9.1×10^-8 A/cm² under the electric field strength of 2 MV/cm,and the breakdown voltage was as high as 5.9 MV/cm.(3)WZTO/HAO TFT devices with two structures,bottom-gate bottom-contact and top-gate bottom-contact,were fabricated by power ultrasound technology.The mobility of the TFT with bottom-gate bottom-contact structure was 18.7 cm²v^-1s^-1,the threshold voltage was-0.47 V,the subthreshold swing was 0.11 V/dec,and the on/off current ratio was 1.2×10⁷.The stability of positive bias stress(PBS)and negative bias stress(NBS)of the TFT device was excellent,and the threshold voltage deviation was0.27 V and-0.39 V,respectively.The mobility of the TFT with top-gate bottom-contact structure was 0.12 cm²v^-1s^-1,the threshold voltage was 1.3 V,the subthreshold swing was 0.95 V/dec,and the on/off current ratio was 2.3×10⁴.Since the HAO film was used as a passivation layer to cover the WZTO film,the influence of water and oxygen in the air on the TFT was reduced.The stability of PBS and NBS was better than TFT device with bottom-gate bottom-contact,and the threshold voltage shift was 0.05 V and-0.17 V,respectively.