Study On The Preparation And Interface Modification Of Indi?m Galli?m Zinc Oxide Thin Film Transistor

With the development of smartphones,TVs and wearables,display technology is playing an increasingly important role.Thin-Film Transistor?TFT?is the core device of display technology.Traditional thin film transistors have been unable to meet the requirements of modern display technology.Due to their excellent properties such as high mobility and good light transmittance,indi?m galli?m zinc oxide thin film transistor?IGZO-TFT?has become the panel company headed by Visionox in China.The technology that is vigorously developed has higher requirements on the quality and performance of thin film transistors.The thin film transistor prepared by using the IGZO thin film as the channel layer has special advantages:good transparency,high carrier mobility,and can be prepared at normal temperature,thereby opening up a wave of research on a new generation of display technology.In this paper,the effects of different oxygen and argon ratios on the light transmittance and electrical properties of IGZO films,the effects of annealing atmosphere and temperature on the properties of IGZO-TFTs,and the effects of interfacial modification on the performance of IGZO-TFTs were investigated,which laid a foundation for the industrial application of IGZO-TFT.By studying the light transmittance of IGZO film,it is found that the IGZO film prepared under different oxygen-argon ratios has a light transmittance of more than83%,because the IGZO film prepared by magnetron sputtering at room temperature is amorphous.The state can reduce the scattering of incident light,and because the surface of the IGZO film is smooth and has little effect on scattering,the IGZO film has a good light transmission effect in the visible light range.The light transmittance of the IGZO film is closely related to the optical band gap?eV?.When the oxygen to argon ratio is 1.05:8,the optical band gap of the IGZO film is 3.48 eV.When the oxygen content is too much,the oxygen vacancies in the IGZO film are reduced,and the effective electron quantity is reduced.Under the experimental conditions,the results show that the performance of the prepared IGZO thin film transistor is optimal when the oxygen to argon ratio is 1.05:8.IGZO thin film transistors were prepared under different annealing atmospheres?Ar,Air,O₂?at 300°C,and their stability and electrical properties were tested.The results show that the IGZO-TFT prepared by annealing under oxygen has a carrier mobility of 10.5 cm²/V·s,a switching current ratio(I_on/I_off)of 3.9×10⁷,and a threshold voltage of 2.2 V.The difference between air annealing and oxygen annealing is small.The carrier mobility after annealing in air is 10.1 cm²/V·s,the switching current ratio(I_on/I_off)is 3.7×10⁷,and the threshold voltage is 2.3 V.Taken together,air annealing can not only improve the quality of thin film transistors,but also save costs.By studying the properties of IGZO thin film transistors after annealing at different annealing temperatures in air?300°C,350°C,400°C,respectively?,it is found that the stability and electrical properties of IGZO thin film transistors are better when the temperature is 350°C.The carrier mobility reached 12.5 cm²/V·s,the switching current ratio was 5.0×10⁸,and the threshold voltage was 2.4 V.In order to improve the stability and electrical properties of the IGZO thin film transistor,it is necessary to modify its interface.Since the sputtering insulating layer generates defects during the preparation of the IGZO thin film transistor,the leakage current of the IGZO thin film transistor is increased,the threshold voltage is increased,and the carrier mobility is lowered.In this experiment,three layers of superposed insulating layers of HfO_x N_y/HfO₂/HfO_x N_y were prepared by magnetron sputtering.The results show that the optimum ratio of oxygen and argon nitrogen is 1.05:8:0.5 when sputtering HfO_xN_y.The passivation layer HfO_xN_y acts as a package defect,which reduces the defects when the insulating layer contacts the interface,and improves the thin film transistor's stability.By studying the effect of the thickness of passivation layer HfO_xN_y on the electrical properties of IGZO thin film transistors,the designed thicknesses are 0 nm,1 nm,2 nm,and 3 nm,respectively.The results show that when the passivation layer thickness is 2 nm.The threshold voltage(V_th)is a minimum of1.7 V,the hysteresis(?V_th)is 0.18 V,and the carrier mobility(?_sat)is 35.24 cm²/V·s.This is because when the thickness is 2 nm,the interface defects are better encapsulated and passivated,and the stability of the prepared IGZO thin film transistor is better.In this thesis,plasma bombardment experiments were carried out on the channel layer of IGZO thin film transistor with argon gas.The bombardment time was 0 s,10 s,20 s,30 s,respectively.The carrier mobility was found at 10 s bombardment time,the carrier mobility??sat?reached 62.13 cm²/V·s,the threshold voltage(V_th)was 1.25 V,and the switching current ratio(I_on/I_off)was 5.6×10⁸.Finally,by comparing the performance difference of IGZO thin film transistors prepared by different electrode materials of Cu,Al and Ti,a suitable electrode backup material was selected.After testing,it was found that Al is more suitable as an electrode material,and finally an IGZO thin film transistor having a switching current ratio of 9.5×10⁸ is prepared.