Preparation And Stability Of Zinc Oxide Based Thin Film Transistors

The market share of thin film transistor?TFT?in consumer electronic products is gradually expanding,and the demand for resolution and refresh rate of display devices is increasing.The market potential of using TFT for pixel unit drive and control is huge.At present,the equipment driven by oxide thin film transistors has a high cost and has not been widely used in the general consumer market.ZnO material has abundant natural reserves,low price,environmental protection and non-toxic.The production of thin film transistor with ZnO material can reduce the industrial cost.However,the instability of ZnO thin film transistors restricts its industrialization and marketization.In this paper,the reason of hysteresis in the transfer characteristic curve of ZnO thin film transistor and the method to reduce the hysteresis are analyzed.In the experiment,ZnO thin film was prepared by RF magnetron sputtering as channel layer,Si O₂ as gate dielectric layer,Al or Pt as source/drain electrode by electron beam evaporation or thermal evaporation platform,and the thin film transistor was patterned by wet etching.The analysis and optimization are carried out from three aspects:channel layer semiconductor,channel layer surface and channel layer/gate dielectric layer interface:1.ZnO TFT was prepared and annealing atmosphere was changed.N₂,O₂ and air were used for annealing at 300?for 15 minutes,and one TFT was not annealed.The hysteresis of TFT annealed in nitrogen is the smallest,and the threshold voltage deviation?V_TH is 0.2V.2.The ZnO channel layer films were prepared by the treatment of 3%hydrogen peroxide solution.The treatment time was 0s,5s,15s and 30s respectively.The defects of oxygen vacancy on the surface of the ZnO films after treatment were obviously reduced,and the binding sites of O₂ adsorption were reduced,so as to reduce the carrier capture caused by oxygen adsorption.The phenomenon of clockwise hysteresis of transfer characteristic curve is weakened.3.By changing the oxygen partial pressure during sputtering,ZnO thin film TFT with rich oxygen and low oxygen was prepared.By inserting an oxygen rich ZnO thin layer into the channel layer/gate dielectric layer interface as the carrier transport channel,and due to the gradient of carrier concentration in the upper and lower layers,the non-equilibrium carrier filled charge trap reduces the clockwise hysteresis of the transfer characteristic curve.