Study On Compact Model Of A-IGZO Thin Film Transistor Reflecting Process Change

Amorphous Indium-gallium-zinc-zinc Oxide（a-IGZO）is a new generation of metal oxide semiconductor,which has the advantages of high mobility and low temperature preparation,and has great application potential in the field of flexible electronics.The compact model of a-IGZO Thin Film Transistor（TFT）is a mathematical description of the electrical characteristics of the device.It can be used for circuit simulation based on a-IGZO TFT.It is the basis of developing a-IGZO flexible integrated chip.The electrical characteristics of a-IGZO TFT are directly related to the deposition conditions of a-IGZO film,annealing temperature,gate oxide materials and other process conditions.However,the existing a-IGZO TFT compact model is mostly based on ideal material parameters,which is weakly related to the fabrication process and has little practical application value.Therefore,a-IGZO TFT compact model reflecting the change of fabrication process will be studied in depth.The material properties of a-IGZO film and gate oxide will be changed,and the electrical properties of the device will be affected.This thesis first studies the effects of different a-IGZO film deposition conditions,thermal annealing temperature and types of gate oxide layer on the electrical characteristics of a-IGZO TFT.The flat band voltage(V_FB),threshold voltage(V_TH),field-effect mobility(μ_FE),maximum current(I_max),sub-threshold swing（SS）and other electrical characteristics of the device under different preparation processes were extracted.Secondly,the influence of a-IGZO film and gate oxide layer material characteristics on the electrical characteristics of the device is studied by TCAD simulation.The results show that the Ar/O₂aeration ratio and thermal annealing temperature during the deposition process of a-IGZO film change the distribution of acceptor-like defects and interface defects,and then affect V_FB,V_TH,I_max,SS andμ_FE.The types of gate oxide materials mainly change the interface defect distribution and interface fixed charge,and then affect the V_TH,Imax and SS of the device.Based on the above reasearch,a compact a-IGZO TFT model was established,and the drain current（I_D）was divided into I_above,I_Sub and I_off with V_FB and V_TH as segmentation points.Based on fusing the field-effect mobility of Trap Limited Conduction model and Percolation Conduction model,I_above describes the current equations of carrier tail state and extended state transport.I_Sub contains the diffusion current controlled by the interface state trap and the drift current controlled by the body deep state defect.I_off approximates the diffusion current of V_g at V_FB based on I_Sub.Four kinds of model parameters including macroscopic electrical characteristics,defect state characteristics,barrier characteristics and interface state characteristics are introduced into the model.Finally,a-IGZO TFT current curves under different process conditions were fitted according to the model,and the model error was less than 5%.The model includes four kinds of parameters that can reflect process changes,the relationship between the three process conditions and the model was realized,which has good scalability,and can accurately reflect the process change and the influence on the electrical characteristics of the device.