Numerical Simulation And Optimization Of Polycrystalline Silicon Directional Solidification Process

Polysilicon is the raw material of silicon target material and one of the important raw materials for the development of electronic information industry.However,since the whole production process is completed in the ingot furnace,people can’t check the status of polysilicon in the ingot process with the naked eye.They can only evaluate the influence of technological parameters on the quality of polysilicon in the production process through a large number of experiments,continuous adjustment of technological parameters,and detection of finished products.With the continuous development of computer simulation technology,it has become an effective new method to study the influence of parameters in directional solidification process by using simulation analysis.This paper achieves the purpose of optimizing the ingot process by numerical simulation.By studying the principle and key control technology of polysilicon directional solidification process,the structure of polysilicon directional solidification equipment was analyzed,and the mathematical model of polysilicon directional solidification process was established.The route of simulation analysis was determined,and the melting process before the directional solidification process was simulated.The thermal field distribution and phase transformation process after the melting were obtained,which were used as the initial field of the directional solidification process for calculation.Based on the analysis of the thermal field results during the directional solidification process of polysilicon,the variation law of the thermal field distribution with time and section position was obtained,that is,the average temperature along the X axis of the YZ plane decreased from high,and then increased after reaching the middle region.The solid-liquid distribution law of directional solidification process is studied.The stud y shows that the solidification starts from the bottom of polysilicon and gradually solidifies upward.In the middle stage of solidification,a convex solid-liquid distribution interface shape is gradually presented.The stress distribution law in different solidification stages is studied to confirm the influencing factors of stress.The stress distribution can be used as the target value for subsequent optimization to control.The effects of different chamfering radius of crucible on various physical fields under R=0 mm,R=20 mm,R=30 mm and R=40 mm were compared.It was confirmed that increasing the crucible bottom fillet radius had certain improvement effect on the stress and temperature at the initial solidification stage.The effect of the pull-down speed of three different insulation floor on each physical field is compared.It is confirmed that accelerating the pull-down speed of insulation floor is conducive to improving the shape of solid-liquid interface and making the interface more gentle.However,if the speed of insulation floor is too fast,concave solid-liquid interface will be produced.The original scheme and optimization scheme were selected for production verification,and the temperature at the bottom of the heat exchange platform was tested by thermocouple,and the experimental test temperature was compared with the simulation analysis temperature to confirm that the simulation analysis error was within the engineering acceptable range,and the reliability of the simulation analysis method was confirmed.At the same time,b y comparing the actual production of polysilicon crystal morphology,It is confirmed that the crystal growth of the polysilicon generated by the optimization scheme is basically in the vertical state,which is better than the divergent distribution morphology of the original scheme.The crystal morphology distribution corresponds to the solid-liquid interface in the simulation analysis,which further verifies the accuracy of the analysis method and also provides certain guiding significance for the production.