Research On The Application Of InGaZnO-based Thin Film Transistors In Logic Circuits

The oxide semiconductor thin film transistors represented by InGaZnO have many advantages,such as excellent mobility,low off-current,strong stability,good uniformity,visible transparency and low-temperature processing.They are expected to replace traditional amorphous silicon and low-temperature poly-silicon as the next-generation mainstream thin film transistor.Circuits based on InGaZnO thin film transistors can be applied not only to the display field,but also to flexible electronics,sensors and many other fields.Since the electrial performance of p-type oxide thin film transistors is generally poor,it is difficult to match the electrical performance of n-type oxide thin film transistors.Therefore,most of the currently reported circuits based on InGaZnO thin film transistors are based on their own unipolar logic circuits,which lag behind CMOS circuits based on n-type and p-type oxide thin film transistors in many aspects,such as power consumption,anti-interference ability,preparation area,voltage gain and so on.From this,this paper prepared and optimized InGaZnO thin film transistors at first,and built CMOS inverters with p-type SnO thin film transistor.At the same time,in order to solve the problems of p-type SnO thin film transistor preparation difficulties and narrow process window,this research proposed to use high-resistance SnO_x thin film transistors as resistive loads to construct resistive load inverters,which will be an alternative to CMOS inverters.The specific contents are as follows:1.InGaZnO thin film is prepared by magnetron sputtering and InGaZnO thin film transistor is prepared.The internal mechanisms between film thickness,sputtering atmosphere,annealing conditions,gate oxide material as well as thickness and the performance of InGaZnO thin film transistors were explored,and prepared high performance InGaZnO thin films transistor.The saturation mobility of the device was10.27 cm²/Vs,and the on/off current ratio was higher than 10⁷.By annealing at 200? for 30 minutes in a nitrogen environment,the saturation mobility of the device increased to 14.99 cm²/Vs.The excellent electrical performance of InGaZnO thin film transistors had laid a good foundation for the design of subsequent circuits.2.p-type SnO thin-film transistor was used as PMOS load to construct CMOS inverters with n-type InGaZnO thin-film transistors.At the same time,electrical tests were carried out on thin films transistors and CMOS inverters.The saturation mobility of SnO thin-film transistors was 0.82 cm²/Vs,and current ratio reached 10³.Then the CMOS inverters with different values of K were studied and it showed that when K was20,the overall performance of the CMOS inverter had reached the best:the maximum voltage gain was-30.7 V/V,the logic threshold was approximately equal to V_DD/2,the effective input ratio had reached 88%,but the voltage gain still had certain gap compared with the international leading level.3.By using high-resistance SnO_x thin film transistors as the resistive load to construct a resistive load inverter with InGaZnO thin film transistor,this research solved the problems of the large area of resistive load inverters and the inability to integrate,and finally achieved full swing output,and obtained voltage gain of-11.8 V/V,which was better than general resistive load inverter.At the same time,a resistance load inverter with simple preparation and high stability can be used as an alternative to the CMOS inverter.