The Fabrication And Characteristics Study Of IZO TFT With Ta₂O₅Insulated Gate

Oxide thin film transistors (Metal Oxide TFT) have superior electricalproperties that include wide band gap, high uniformity, high stability and high carriermobility compared with that of conventional Si and organic TFTS. The indium zincoxide(IZO) is becoming the focus of oxide TFT technology due to its non-toxic, lowtemperature process preparation, high transparency in the visible range. In this paper,Ta2O5, IZO films were prepared and analyzed, thin film transistors with differentstructure were also prepared which took IZO as the active layer, Ta2O5as the gatedielectric, PbPc as the modification layer, Al as the source/drain electrode and thegrid electrode. The main contents are as follows:Tantalum oxide film was formed by using radio frequency magnetron sputtering,using tantalum oxide ceramic as a target with purity of99.99%, the atoms weresputtered and deposited on quartz glass substrates in argon glow discharge process.Multiple groups of thin film were prepared in different working pressure, sputteringpower and gas flow rate, whose thickness were tested by step tester, then therelationship between the sputtering rate and the process parameters were analyzed.The results show when the working pressure is0.5Pa, the sputtering power is250W,argon flow rate is12sccm Ta2O5the sputtering rate is optimal. We used method ofRF magnetron reactive sputtering, we obtained IZO thin film with purity of99.99%indium zinc alloy as a target and with using argon as working gas, oxygen as reactivegas, surface morphology of film was tested using atomic force microscope.Bottom gate thin film transistor and the top gate thin films transistors withdifferent thickness of dielectric layer were prepared and tested with the aboveprocess. The test results show, thin film transistors operate in the depletion mode,because of the flat interface of channel layer-insulating layer, under the same biasvoltage, the output current of the top gate thin film transistor is greater than thebottom gate thin film transistor. Compared with top gate device of different thicknessof dielectric layer, when the thickness of dielectric layer decreases, working currentof the device increases significantly, from microampere to milliampere level.