Research On Preparation Of ZnO-based Thin Film Transistor

As a key component of liquid crystal display(LCD)and Active-matrix organic light-emitting diode(AMOLED)display panels,the importance of thin film transistors(TFT)is increasing with the expansion of the consumer market.Thanks to their excellent optical and electrical properties,metal oxide thin film transistors have attracted people's attention.Compared with traditional silicon thin film transistors,they show stronger competitiveness.At present,there are a large number of researches based on zinc oxide(Zn O).Among them,indium gallium zinc oxide thin film transistor(IGZO-TFT)has became a commonly used material due to its excellent performance,but its reliability and sustainability still need to be in doubt,it is mainly due to the high cost and toxicity of indium(In).The search for an alternative is still continuing.Aluminum(Al)has become an alternative material and option.As the most abundant metal element in nature,aluminum can significantly reduce the cost of oxide thin film transistors.After effective Al doping into Zn O,aluminum zinc oxide thin film transistor(AZO-TFT)also has excellent performance.The research of this paper will focus on the influence of different preparation conditions on the performance of AZO-TFT under low temperature process and the method to improve the performance of AZO-TFT through the dual-channel layer structure.In the experiment,a p-type silicon wafer with a 200 nm thick silicon dioxide(Si O₂)insulating layer was used as the substrate,and aluminum zinc oxide(AZO)was prepared by radio frequency magnetron sputtering as the channel layer,and the channel layer was wetted by a photolithography machine.After patterning by method etching,an electron beam evaporation method is used to prepare Al with a thickness of 50 nm as source and drain electrodes.The effects of different channel layer thicknesses,different aluminum doping amounts,and different channel layer structures on the performance of AZO-TFT are discussed separately,and the contents are as follows:1.Deposit AZO films of different thicknesses and use them as the channel layer to prepare AZO-TFT.The method is to control the thickness by controlling the deposition time of RF magnetron sputtering.The Zn O sputtering power is set to 100W and Al doped.The power was set to 5 W,and the deposition time was set to 5 min,10 min,15 min,and 20 min.When the deposition time is set to 15 min,the AZO channel layer thickness is 50 nm,the AZO-TFT switching ratio reaches 3.45×10⁶,the threshold voltage is-1 V,the subthreshold swing is 1.05 V/decade,and the mobility is0.07 cm²/(V?s).2.Prepare AZO thin films with different aluminum doping levels and use this as the channel layer to prepare AZO-TFT.The method of adjusting the Al doping amount is to control the sputtering power of the aluminum target.Generally speaking,high-power sputtering means high doping amount.The deposition time is set to 15min,and the Zn O doping power is set to 100 W,and the Al doping power is set to 10W,15 W,20 W,and 25 W,respectively.When the doping power of Al is 15W,that is,the mass ratio of Al is 7.96%,the threshold voltage of AZO-TFT reaches-4 V,the current switching ratio is 1.84×10⁶,the subthreshold swing is 1.94 V/decade,and the mobility is 0.10 cm²/(V?s).3.A high-resistance AZO film layer and a low-resistance AZO film layer are selected respectively,and a double-layer AZO film is prepared by depositing a low-resistance layer first and then a high-resistance layer.The high-resistance layer and the low-resistance layer of the four sets of samples are total deposited Time15min,by changing the deposition thickness of the two to study the effect of different active layer structure on the performance of the dual-channel layer AZO-TFT,the four sets of experimental low-R layer and high-R layer deposition time are:1 min and14 min,3 min and 12 min,5 min and 10 min,7.5 min and 7.5 min.Among them,the low-R layer deposition time is 2 min,and the high-R deposition time is 12 min.AZO-TFT shows the best electrical performance.Its switching ratio reaches 1.67×10⁷,the threshold voltage is-3 V,and the sub-threshold swing is 1.59 V./decade,the mobility is 0.13 cm²/(V?s),the electrical performance is better than that of the single-channel layer AZO-TFT,and it shows a better output characteristic curve.