SPICE Model Parameter Extraction And Circuit Simulation Of Metal Oxide Thin Film Transistors

With the development of portable mobile devices and corresponding display and sensing technologies,people have increasing demand for the miniaturization,portability and security of electronic devices.Therefore,demands for devices other than traditional silicon-based thin film transistor(TFT)devices start to emerge in cutting-edge portable products.Particularly,glass-based circuits using novel transparent TFTs can enable the integration of more human-machine interactive methods into displays.Innovative technologies including transparent fingerprint sensing have become one of the strategic directions in the industries of intelligent mobile devices.The core component of glass-based transparent electronics is metal-oxide TFTs with high semiconductor bandgaps.TFT devices based on IGZO have already been used in active matrix display circuits.But they are still limited by problems including low mobilities,sensitivity to visible light,and drift of characteristics.The basis of this thesis are ZnO TFT devices based on in-house fabrication processes developed by our groups.They have good transparency,transistor performance,and stability.In order to use these devices for realizing various digital or analog circuits,their accurate SPICE model becomes indispensible,and this is the main research aim of the thesis.This work includes three major parts.The first one is a detailed study on currently available SPICE models,including amorphous silicon devices and low-temperature polysilicon(LTPS)devices.The research in this part includes DC and AC device equations,the physics meaning of important parameters therein,and their impact on the overall device characteristics.Based on this study,we conclude that LTPS TFT SPICE model can be applicable to our ZnO TFTs.In the second part,the DC and AC curves of the ZnO TFT devices are experimentally measured.The third part is based on the first two and make numerical fitting for the measured DC and AC curves using the LTPS SPICE model,thus extracting corresponding SPICE parameters.On this basis,we simulate basic circuits including inverters and ring oscillators and compare the simulated results with measurement results,confirming that our SPICE model can be used for practical circuit designs.