Preparation And Properties Of Fully Transparent A-IGZO Thin Film Transistor

Oxygen thin film transistors(TFT)have a series of advantages,such as high mobility,low temperature preparation,large area preparation,good uniformity,transparency and so on.Therefore,they have great potential in the field of fully transparent display and flexible display.In this work,a series of fully transparent thin film transistors based on a-IGZO material are fabricated according to the high transparency of some oxide films.In this work,the fully transparent TFT is successfully prepared,and the insulating layer and electrode of the transparent device are studied and optimized.The specific contents of this work are as follows:(1)First,the insulating layer of fully transparent devices is studied.In this work,PMMA and PVA are used as insulating layers of transparent devices,and TFT at different rotational speeds of insulating layers are prepared respectively.The results show that the surface morphology of PMMA and PVA films prepared by spin coating is good,but the surface morphology of PMMA films is better,and the overall performance of devices can be improved by increasing the rotation speed.In general,the insulation performance of PVA film is better than that of PMMA film,but because the surface morphology of PVA film is slightly worse,PMMA is chosen as the insulation layer of devices in the follow-up study.(2)After determining the optimum speed of PMMA insulation layer,a series of studies have been carried out on the electrodes of the device.Firstly,the photoelectric properties of ITO and IGZO thin films were studied under different fabrication processes.The resistivity of ITO thin films prepared under 0%oxygen partial pressure,125 W sputtering power,1500 s sputtering time and 1 mTorr cavity pressure is the lowest,which is 1.54×10-4 ?·cm.The resistivity of IGZO thin films prepared under 0%oxygen partial pressure,125 W sputtering power,1500 s sputtering time and 1 mTorr cavity pressure is the lowest.(3)After determining the optimum preparation process of transparent electrode,fully transparent TFT based on IGZO and ITO as transparent electrode was prepared.Both devices show certain performance,and the fully transparent TFT based on ITO electrode has better performance.The TFT switching ratio based on ITO electrode is 1.7×104,the mobility is 6.335 cm2V-1s-1,the threshold voltage is 0.8 V,and the sub-threshold swing is 1.9 V/decade.The TFT switching ratio based on IGZO electrode is 0.696×103,the mobility is 4.101 cm2V-1s-1,the threshold voltage is 3.1 V,and the sub-threshold swing is 6.4 V/decade.(4)In order to improve the overall performance of the device based on IGZO transparent electrode,annealing treatment was also carried out.It was found that annealing can improve the interface defects between the insulating layer and the active layer and improve the carrier mobility.After annealing,the mobility of the device increased to 6.065 cm2V-1s-1,and the threshold voltage decreased from 3.1 V to 1.6 V.In order to further improve the performance of the device,a transparent TFT based on composite insulating layer was prepared.Before the original PMMA insulating layer,a layer of ultra-thin atomic layer deposition(ALD)aluminium oxide was added.The mobility of the composite insulating layer device was 5.99 cm2V-1s-1,the switching ratio was 0.87×104,and the threshold voltage and sub-threshold swing amplitude were 2.6 V and 3.5 V/decade,respectively.