Research On Temperature-dependent Model Of FinFETs At Millimeter Wave Frequency Band

In recent years,with the development of the wireless communication industry,semiconductor-related industries have begun to develop rapidly.As the device size gradually scales down,the short-channel effect of planar devices becomes more serious,and its performance gradually becomes difficult to meet the requirements.Therefore,a new structure of Fin Field-Effect Transistor(FinFET)has emerged.Compared with planar devices,FinFETs can effectively improve the short channel effect,enhance the gate control capability and the performance of the device,hence it has received widespread attention.However,the application of FinFET devices in low temperature environments has not been well studied.At low temperatures,the characteristics of semiconductor devices are significantly improved,specifically increased mobility and saturation speed.In addition,cryogenic devices can be widely used in many fields such as space exploration,medical equipment and superconductivity.Therefore,the application of FinFETs is very promising at low temperatures,so it is necessary to study and establish FinFET models at low temperatures.In this thesis,the characteristics of FinFETs in millimeter wave frequency band under dynamic temperature changes are studied.Firstly,this paper proposes an improved compact equivalent circuit model(CECM)of FinFET transistor in millimeter wave frequency band.The mechanism of the magnetic coupling effect between the interconnection line and the silicon-based substrate is analyzed.It can be found that the magnetic coupling effects that occur between interconnection lines and substrates are more significant in the mm-wave frequencies compare with several gigahertz.Therefore,we propose an improved CECM considering magnetic coupling effect and the corresponding parameter extraction method.Compared with the work that does not consider the magnetic coupling effect,the improved model can improve the phase accuracy and can characterize the transistor well in the frequency range of 0.2 GHz to 66.2 GHz.Secondly,after removing the test structure to obtain the small signal parameters of the FinFETs,the parameter extraction method is used to extract the initial values of the components in the CECM within the temperature range(84 K-295 K).Then,the temperature dependence of the external parasitic and intrinsic parameters of the transistor is analyzed.Based on the process and physical characteristics of the device,the variation of component value with temperature is summarized.Finally,to solve the problem that the conventional drain-current model has errors at low temperatures,this thesis proposes an improved drain-current model considering dynamic temperature changes.Based on the classic Poisson's equation,an exact charge density expression is proposed by using the Lambert W function.Furthermore,an improved charge-based drain-current model for FinFETs is proposed.To verify the accuracy of the proposed model,a test structure was constructed based on the 14 nm FinFET process,and the current characteristics of the device in the temperature range of84 K-295 K were measured.Comparing the calculation results of the traditional model and the improved model with the measured results,it is found that the improved model can significantly improve the accuracy of the model,and it can be used in the temperature range of 295 K,250 K,200 K,160 K,120 K,100 K,and 84 K.