Simulation And Optimization Of Polysilicon Reduction Process

A CVD model of polysilicon in hydrogen-trichlorosilane system is established forreduction system of polysilicon chlorosilane，coupling gas phase reactions andsurface reactions by Chemkin4.0，then numerical solution by CFD softwareFluent6.3.26is made.The reaction mechanism of chemical vapor deposition in hydrogen-trichlorosilanesystem is determined by analysis of the thermodynamic properties in the Siemensreactor，addressing reaction Gibbs free energy and equilibrium constants with CVDin the Siemens reactor，next the equilibrium partial pressure of eight gas componentin the Siemens reactor as well as the conversion rate of trichlorosilane and the yieldof polysilicon are calculated， in comparation to literature experimental data，thenthe reliability of thermodynamic data is ensured；CVD in hydrogen-trichlorosilanesystem by equilibrium model, planar shear flow model and cylindrical shear flowmodel of Chemkin4.0is simulated，analysising balance data of CVD，temperaturedistribution，velocity distribution，silicon deposition rate and conversion rate oftrichlorosilane.At last，the simulation of the polysilicon CVD model in hydrogen-trichlorosilanesystem by Fluent6.3.23is made，addressing silicon growth rate with gas inlettemperature， velocity of gas inlet，gas composition，surface temperature andreaction pressure，calculated results of the CVD model with were compared toexperimental data and calculated data obtained from literature in order to verify theCVD model,what is more，the silicon deposition efficiency is calculated，as a result，assuming all other conditions constant，silicon growth rate increases with increase ofsurface temperature，reactor pressure as well as gas inlet temperature，whenhydrogen mole fraction is less than0.8，silicon growth rate is proportional tohydrogen mole fraction，when more than0.8，silicon growth rate is on the contrary，the silicon deposition efficiency can reach up to about11%；Furthermore，thestructure of the Siemens reactor is reserched，specifically discussing the commonforms of the nozzle the Siemens reactor，the geometric model of the nozzle isestablished and meshed，simulation of the flow field of the nozzle by Fluent6.3.23ismade to determine that the expansion nozzle is the best form.