Simulation Design Of Electron Optical System For Electron Beam Etching

In recent years,with the rapid development of the chip industry,chips are used in many fields,so the demand for chips is rising rapidly,which also brings new challenges to the processing and manufacturing of chips.At present,chip processing technology is mainly divided into lithography technology and electron beam etching technology,electron beam etching technology started earlier in China and has a certain foundation,which can provide some experience for the research of electron beam etching technology.Studying electron beam etching technology can solve some problems in chip processing theoretically.The research and design of electron beam etching technology need a lot of money and time cost.The electron gun and electron lens of electron beam etching system can be optimized quickly by using electron optics CAD software,which can save time for the design of electron beam etching system.At present,the software MTSS is independently developed by the Computer Simulation Technology Research Institute of UESTC,EOS module is a special electronic optical design software,which can simulate the electron gun comprehensively,quickly and accurately;MFS module is a special permanent magnet system design software,which can simulate the permanent magnet system quickly and accurately.In this thesis,a dual-mode electron gun with low energy dispersion and high flatness is designed.The voltage,current density,energy dispersion and flatness of the dual-mode electron gun refer to the parameters of mapper's multi-electron beam exposure system.Different parallel electron beams can be obtained by changing the voltage of each electrode.The difference of current density between the two modes is more than twice,the energy dispersion is less than 5 e V,and the flatness is less than 5mrad,electron guns with different current densities can be used in different processing environments,and some experience is also summarized in the process of electron gun simulation design.The static field permanent magnet lens is designed on the basis of dual mode electron gun,which has a good focusing compression effect on electron beam.The maximum compression ratio of the multi-beam electron lens is about 250 times,the compression factor of the position with small distortion is about 160 times,the single beam diameter is about 16 nm;the maximum compression factor of the single-beam electron lens is about 290 times,and the single-beam diameter is about 14 nm.The different positions of the multi-electron beam array are subjected to different electric field forces in the electrostatic lens,which tends to distort the multi-electron beam array,comparing the simulation electrostatic lens with the static field permanent magnet lens,the results of simulation and qualitative analysis show that electrostatic lens may not be suitable for electron beam etching system.The parallel electron beam generated by the dual-mode electron gun can form multi-electron beam array only after passing through the micron aperture beam splitter plate,which has high requirements for simulation calculation.Therefore,using three multi-electron beam array construction methods to simulate multi-electron beam array focusing can save calculation time.And it is also verified that the different construction methods of multi-electron beam array have little influence on the simulation results.Mesh and the maximum number of iterative steps will affect the computation time and the accuracy of simulation calculation,in order to ensure the accuracy of the simulation results and avoid the confusion between the errors and the actual distortion of the system,the convergence of the multi-electron beam array focusing simulation results is analyzed from the mesh and the maximum iterative steps.Through simulation comparative analysis,it is determined that the grid adopts segmental encryption,the minimum size is0.8um,and the maximum iteration step number is 25.The current of the multi-electron beam array and the spacing between the centers of the adjacent single electron beam will affect the space charge force and have a great influence on the distortion.Therefore,the influence of the parameters of the multi-electron beam array on the focusing compression of the multi-electron beam array is simulated and analyzed.According to the results of the dual-mode electron gun and the design and analysis of the electronic lens,the matching simulation of the electronic lens is carried out,the simulation of single electron beam electron lens and multi-electron beam electron lens is realized,and the simulation cost,simulation results and distortion after focusing are analyzed.The distortion analysis includes absolute distortion,relative distortion,rotation Angle and compression multiple.Finally,some possible methods to reduce distortion are proposed based on simulation experience.