Research On Device And Circuit Analytical Model For Amorphous Semiconductor Thin-Film Transistor

In recent years,amorphous semiconductor thin-film transistors have become the focus of academic research and industrial application due to their good mechanical flexibility,compatibility with arbitrary substrate,low cost and large area processability at low temperature.It is widely used in wearable sensors,medical patches,flexible displays and disposable RFID tags.The design complexity of TFT technology is much less than that of silicon integrated circuit.However,the existing commercial EDA tools are usually developed for complex silicon integrated circuits.And due to the difference in material properties,the electrical characteristics of TFT are quite different from that of metal-oxide-field semiconductor effect transistor(MOSFET),so the traditional MOSFET model is not suitable for TFT.Therefore,the current TFT circuit design is mainly achieved by manual design,which is often time-consuming and cannot achieve the optimal performance of the circuit.In order to improve the efficiency of TFT technology circuit design,a set of design tools for various TFT technologies is needed,including TFT compact device model,circuit analytical model.At present,the research of TFT device and circuit analytical model is focused on the above-threshold region.With the rapid increase of energy demand,low-power design technology has become an increasingly important demand.This puts forward higher requirements for accurate modeling of TFT operating in subthreshold region.In this paper,the subthreshold current is divided into two parts:diffusion current which is exponentially related to gate voltage and drift current which is power-law related to gate voltage.The two parts are derived respectively and then combined into a continuous closed-form expression with a transition function.Finally,a TFT compact device model with higher accuracy in subthreshold region is established.Based on the device model,the input-output models of two kinds of unipolar inverters are established and the important performance indexes of the inverters are calculated,such as noise margin,voltage gain and propagation delay.A circuit analytical model which can describe the relationship between the circuit performance and the process and design parameters is obtained.At last,the accuracy and practicability of the device model and circuit analytical model are verified by comparing with experimental data and simulation results.This two model can effectively guide the circuit design,and are significant for the wide application of TFT technology.