Simulation Of Gradient Doping Distribution On Silicon Surface Based On Ion Implantation

With the continuous progress of science and technology,low light level night vision devices are gradually developing to digital direction.As a new type of digital low light level night vision imaging device,electron bombardment CMOS(EBCMOS)has many advantages,such as small size,light weight,low power consumption,high sensitivity and can work under ultra-low illumination.Therefore,in recent years,the research of EBCMOS devices has gradually become one of the hot topics in the field of low light level night vision.Different from the photoelectric conversion process in the solid-state imaging devices(such as low illumination CMOS)when single photon transforms into a single electron,the electron multiplication layer(P-type silicon substrate)in EBCMOS can further transform single photon into a large number of secondary electrons.The structure design of electron multiplication layer is very important to improve the gain and resolution characteristics of EBCMOS.In order to improve the gain and resolution characteristics of EBCMOS,gradient doping in multiplication layer can be used to improve the charge collection efficiency.However,there are few reports about how to design the surface structure of electron multiplier layer to improve the charge collection efficiency of EBCMOS devices.Therefore,the gradient doping mechanism on the surface of EBCMOS electron multiplication layer is a key problem to be solved.Therefore,this paper firstly carried out the simulation of the influence of different parameters on the silicon surface structure under single ion implantation.Then,based on the above research,the structure design of gradient doping on silicon surface was realized by various energy injection modes,and the corresponding charge collection efficiency of multiplication layer was discussed.In the simulation work of the influence of different parameters on the silicon surface structure under single ion implantation,the influence of different implantation conditions on doping distribution was simulated by the a simulation software,TRIM(the Transport of Ions in Matter),which is based on the longitudinal distribution theory of implanted ions in the target.And then,the influence of implantation energy,masking layer type and thickness,and implantation angle on the average projection range and standard deviation was revealed.It provides theoretical support for gradient doping simulation.In the study of the influence of different energy implantation modes on the gradient doping and charge collection efficiency of silicon surface,different kinds and thickness of masking layer,implantation angle,implantation energy,implantation energy and dose are selected to carry out various ion implantation on the surface layer of EBCMOS electron multiplier layer.The influence of various parameters on the surface structure parameters of the electron multiplication layer was analyzed to realize the surface gradient doping distribution.Finally,based on the carrier transport theory and Monte Carlo method,the influence of the corresponding surface structure on the electric field distribution and charge collection efficiency of EBCMOS devices is simulated and analyzed.The research content of this paper solves some key problems in the structure design of electron multiplier layer in electron impact imaging devices,such as the selection of ion implantation conditions,the selection of masking layer's type and thickness,the selection of implantation energy and dose,the influence of different implantation modes on the doping distribution of electron multiplier layer.Furthermore,the influence mechanism of surface doping distribution on the charge collection efficiency of the electron multiplier layer is explored,and a new structure design method of gradient doping on the surface of the electron multiplier layer of high gain EBCMOS is proposed,which provides a theoretical basis for the preparation of high gain EBCMOS.