Research Of Process Variations Of 3 Nm Gate All Around Field Effect Transistor And The Performance Of Unit Circuits

In the past half century,the semiconductor industry has developed rapidly along the path of Moore’s Law.With the development of integrated circuit manufacturing process towards 3 nm or even smaller nodes,Nanosheet Field Effect Transistor(NSFET)has become one of the current research and development hotspots due to its excellent gate control performance,short channel effect suppression ability and small leakage current.However,due to the small size and complex preparation process,the electrical characteristics of NSFET are more significantly affected by the random fluctuation of the process.For this reason,this paper has carried out the research work on the process fluctuation of NSFET under the 3 nm node,including the research on the impact of process fluctuation on the electrical characteristics of NSFET,the establishment of an intensive model of process fluctuation of NSFET,and based on the proposed volatility model,it has deeply explored the influence of process fluctuation on the circuit performance of NSFET related units.The main research work and achievements are as follows:(a)The NSFET device structures with different gate lengths(12～18 nm)under the3 nm process node were built using the Technology Computer Aided Design(TCAD)tool,and their electrical characteristics were simulated and analyzed to extract key electrical parameters;based on the Berkeley Short-channel Insulated-Gate Field-Effect Transistor Model-Common Multi Gate(BSIM-CMG),the paper has completed the extraction of NSFET global model parameters including temperature effects,and the fitting accuracy has reached the industry standard.(b)Aiming at the random process fluctuations commonly existing in deep,micro and nano sized devices,TCAD simulation tool was used to study the influence of workfunction variation,line edge roughness and gate edge roughness on the electrical parameters of NSFET devices,such as threshold voltage,opening current,subthreshold swing and closing current.It is found that the work-function variation has a significant impact on the threshold voltage,subthreshold swing and off state current fluctuation of the device.The line edge roughness will cause a large fluctuation of the device’s opening current.The influence of the gate edge roughness is far weaker than the workfunction variation and the line edge roughness,and only has a significant effect on the opening current and subthreshold swing.(c)According to the existing modeling method of process fluctuation model and the extracted BSIM-CMG global model,the NSFET device structure is reasonably optimized,and the device intensive model with process fluctuation is established;the established volatility model is imported into the circuit network list of the H-Simulation Program with Integrated Circuit Emphasis(HSPICE).The simulation results show that the electrical characteristics of NSFET are affected by process fluctuations and are compared with TCAD simulation results.It can be found that the simulation results of the volatility model can accurately predict the impact of device electrical characteristics on process fluctuations within the acceptable error range;the possible causes of model errors are described and the corresponding optimization scheme is proposed.(d)When the accuracy of the above volatility model is verified,the volatility model is introduced into HSPICE to explore the impact of process fluctuations on the circuit performance of NSFET related units,and the fluctuations caused by the three process fluctuations in the circuit energy consumption delay characteristics are discussed respectively.Comparing the effects of the three,the results show that the fluctuation of circuit performance caused by the fluctuation of work-function variation is the most severe,the influence of line edge roughness is slightly weaker than that of work-function variation,and the fluctuation caused by the roughness of gate edge is far weaker than that of the other two processes,which is consistent with the device simulation results,indicating that the fluctuation model can provide some help for evaluating the influence of process fluctuation on the performance of NSFET related circuits.This paper systematically carried out NSFET device structure construction,BSIMCMG global model parameter extraction,NSFET device level process fluctuation analysis,NSFET fluctuation model establishment and analysis verification,and NSFET unit circuit performance affected by process fluctuation.The research results can provide some guidance for the optimization of NSFET devices and practical circuit applications in the future.