Study On Source/Drain Resistance Of MOSFET In Source And Drain Region With Nonuniform Doping

With the development of modern integrated circuit technology and the continuous improvement of semiconductor manufacturing,increasing the performance of MOSFET devices has become an urgent demand in the current stage.As a result of the continuous progress and transformation of semiconductor device manufacturing technology,the size of the device has been developed from micron to nanometer,thus the integration of integrated circuits has been improved.MOSFET device feature size reduced to the field of nanometer size,resulting in a decrease in carrier mobility,so the source and drain resistance will increase,which caused serious degradation of drive current of the MOSFET device.As the physical size of the MOSFET device becomes smaller,the effective channel length of the device will be shortened,however,the effective channel length is one of the important parameters that affect the electrical characteristics of the device.The decrease of effective channel length will bring short channel effect,and affect the electrical characteristics,such as conduction current and switch characteristics of the device.As the channel length can not be reduced by the same proportion,the control of the resistance of the source/drain region becomes an important factor for improving the device performance without short channel effect.This paper mainly analyzes the research significance of MOSFET source/drain resistance.In order to improve the characteristics of the device and reduce the source/drain resistance,the source and drain regions adopt non-uniform doping method.For the study of source/drain resistance of MOSFET with uniform doping,two research methods are mainly introduced:extraction method and modeling method.The extraction method mainly introduces the channel resistance method(CRM),analyzing the principle and the extraction method of the channel resistance method.The modeling methods mainly includes numerical method,analytical method and semi-analytical method,which advantages and disadvantages are introduced,and the applicability of the three modeling methods is illustrated.By studying the modeling method of MOSFET source/drain resistance in uniformly doped source/drain regions,numerical modeling is more effective for studying the source/drain resistance of MOSFETs in non-uniformly doped source/drain regions,this method can be calculated by computer aided software,although there is no exact analytical expression,it is quicker and easier to solve practical problems.Based on the existing research methods,a MOSFET source/drain resistance model of numerical modeling is proposed.This paper mainly studies two kinds of non uniformly doped MOSFET devices,one is Gaussian doped source and drain region of MOSFET,and the other is a Gaussian doped source and drain of MOSFET with silicide.According to the analysis of the physical characteristics of the semiconductor,the differential model of the numerical modeling is used to approximate the potential of the source and drain regions.The doping concentration in the vertical direction of the source and drain regions conforms to Gaussian function distribution,and the concentration of the horizontal direction is constant.Due to the concentration of source and drain regions in the vertical direction is Gaussian function distribution gradient,there are drifting and diffusion motions in the source and drain regions.According to the basic theory of drift-diffusion,the partial differential equations satisfying the potential of the source and drain regions can be obtained,and the differential method is used to solve the partial differential equations.The carriers have diffusion and drift motions in the y direction and no carrier movement in the x direction.The current density can be integrated by selecting a cross section in the source and drain regions to obtain the on-state current of the source and drain regions.Applied voltage between the drain and the gate stack,using MATLAB program can solve the source/drain resistance.In order to verify the correctness of the model,the SILVACO simulation is used to extract the source/drain resistance of the MOSFET with heterogeneous doping.By comparing a large number of data,the results of the differential model calculation and SILVACO extraction error smaller.The main factors influencing the source/drain resistance of MOSFETs in non-uniformly doped source and drain regions are the peak concentration of Gaussian doping,the deviation of Gaussian distribution,the junction depth of the source and drain regions and the length of the conductive channel from the electrode.Analysis of the source/drain resistance of the source and drain of the Gaussian doped doped silicide reveals that the influence of the Gaussian distribution deviation on the source and drain resistance is relatively small,and the silicide concentration has a great influence on the source/drain resistance of the source and drain of the Gaussian doped source and drain,So a more in-depth understanding of heterogeneous doped source and drain regions.