Stability And Mechanism Of ZnO-TFT Based On NbLaO Gate Dielectric

Zinc oxide thin film transistor?ZnO-TFT?has broad application prospects in high performance flat panel display,wearable flexible electronics,integrated sensors,etc.due to its high mobility,simple preparation process,good light transmission and large area preparation.Has become an important research direction of TFT technology.In order to further reduce the working voltage of ZnO-TFT,a high-k NbLaO film is used as the gate dielectric of ZnO-TFT,and four kinds of ZnO-TFTs with different stacked gate dielectric structures are prepared.Their electrical properties and gate bias stress.The stability is compared and the bias stress stability and thermal stability of NbLaO/SiO₂ double-layer gate dielectric ZnO-TFT are discussed deeply.The main research contents and results are as follows:ZnO-TFTs with the gate dielectric of the four different components of NbLaO?NbLaO/SiO₂?NbLaO/Al₂O₃?SiO₂/NbLaO/SiO₂ were manufactured by magnetic control sputtering using the main gate dielectric material of NbLaO.The research found that the four structural devices showed excellent electrical properties.The ratios of the switching current reached up to 7×10⁶.The swing of the sub-threshold value was less than 0.2 V/dec and the mobility was greater than 3 cm²/Vs.The main reason of the improvements in electrical properties of the the laminated gate dielectric is that to use SiO₂ thin film as the transition layer of the NbLaO gate dielectric that can perfect the roughness of the surface of the NbLaO thin film,improve the film formation quality of the ZnO active layer,and reduce the defective density of the interface of the active layer/gate dielectric layer.The electrical properties stability of ZnO-TFT with the gate dielectric of NbLaO/SiO₂under bias stress was studied.The result showed that,under the positive grid bias or the negative leakage bias stress,the device has distinct instability.The dominating changes were reflected in the device threshold voltage drifted into the the direction of the negative gate voltage and the off-state current increased gradually.A mass of empty holes captured by the the gate dielectric layer and its interface and abundant electrons captured by the trap state of the active layer both resulted in these changes.Besides,the degradation of the device is slight and the stress stability is good under the negative grid bias or the positive leakage bias stress.The stability of ZnO-TFT with gate dielectric of NbLaO/SiO₂ under different working temperatures was investigated.The results showed that when the operating temperature rises from 293 K to 353 K,the threshold voltage of the device decreases from 3.23 V to 2.06 V,and the saturation mobility increases from 28.28 cm²/Vs to 96.92 cm²/Vs,mainly due to the ZnO film near room temperature.The main reason is that the donor impurities in the ZnO thin film near the room temperature are not completely ionized,and the ionization increases as the temperature increases,and the bulk carriers increase.When the operating temperature drops to the initial temperature,the electrical characteristics of the device are substantially restored to the initial state,which indicates that the thermal effect does not cause a change in the internal microstructure of the device to generate a new defect state within the test temperature range.