Study On Coupling Technology Of Electronic Grade Polysilicon Growth Reactor Based On Numerical Simulation

Crystalline silicon is the basic material of semiconductor devices and solar cells.It can be divided into solar grade and electronic grade according to different uses,and the latter has more higher requirements for the preparation process.Modified Siemens method is the mainstream technology for the preparation of polysilicon.In the reduction section,chemical vapor deposition reaction?CVD?occurs on the surface of high temperature silicon filament,then crystal silicon deposits and filament growths.Although China's total production has ranked the first in the world,the annual import of electronic grade polysilicon is still more than100,000 tons.Electron-grade polysilicon products require higher deposition quality.In practice,decreasing deposition rate is usually adopted to achieve uniform deposition,but at the same time,the conversion ratio will be reduced and the unit energy consumption will be greatly increased.In this paper,electronic grade polysilicon reactor of 9 pairs rods are selected to study the deposition conditions of crystal silicon in the reactor.The optimization scheme is proposed and verified by experiments.The coupling scheme of the reactor is proposed to achieve tail gas recovery.The main research contents are as follows:Modeling of reactor and reduction process was studied by using simulation technology.With the help of PolySim^TM software based on computational fluid dynamics?CFD?,which is developed by STR,the reduction process was modeled,including gas turbulence?based on k-model?,heat transfer between silicon rod and gas,thermal radiation,current heating of silicon rod,surface growth of silicon rod,etc.The Navier-Stokes equation,enthalpy equation and turbulence equation are solved by built-in calculator and after ten thousands iterations,convergence values of different parameters and its distributions in the reactor are obtained.Based on PolySim^TM software,the process modeling of reactor has been completed.Distribution characteristics of flow field and temperature field and so on have been studied and analyzed.The optimization scheme of reactor structure has been put forward and verified by experiments,and the expected optimization effect has been achieved.By modeling and fitting the whole process,the effects of flow rate,ratio of TCS and H₂,temperature of polysilicon deposition area,surface velocity of silicon rod and emissivity of reactor wall on total output of polysilicon,deposition rate,energy consumption and conversion ratio of TCS under typical operating conditions were compared and analyzed.Based on the existing reactor modeling,the structure scheme of single reactor under coupling modes was put forward and modeled.The temperature field,flow field and boundary layer thickness under each scheme were compared and analyzed,and 15/9 scheme was selected finally.After fixed the realization scheme of the coupling reactor,the modeling of the two reactors and pipelines under coupling mode is compeleted.Finally,the anticipated process characteristics are obtained by calculation.Through the study of the above problems,the theoretical guidance is provide d for systematically understanding the characteristics of reduction process,improving the quality of deposition,and further developing consumption reducing methods,which has a strong reference significance for the optimization of preparation process and the realization of coupling process of electronic grade polysilicon.