(736g) Simulations of Chemical Vapor Deposition of Silicon in a Fluidized Bed Reactor with Detailed Reaction Kinetics

Title: Simulations of Chemical Vapor Deposition of Silicon in a Fluidized Bed Reactor with Detailed Reaction Kinetics

Authors: Caixia Chen[1], Youwen Fan

Organization: Key Laboratory of Coal Gasification and Energy Chemical Engineering of Ministry of Education, East China University of Science and Technology, Shanghai 200237, China

Abstract:

Fluidized bed reactor for silane deposition is an important technology for solar-grade silicon production. A problem that hinders a continuous operation of the FB-CVD reactor is the clogging of reactor internals because of undesired fine dusts production mainly due to homogeneous decomposition. In this presentation, we report a comprehensive numerical model for silicon deposition in fluidized bed reactors with detailed reaction kinetics. A reaction mechanism based on detailed gas phase reaction and a set of semi-empirical surface reactions was validated against published experimental data obtained in a temperature range similar to a FB-CVD reactor using a boundary layer reaction module of CHEMKIN. The results showed Hoâ??s gas and surface mechanisms were suitable for FB-CVD.

The TFM-KTGF two-fluid model coded in Ansys Fluent platform was employed in the simulation of the gas-solid fluid dynamics at a fluidized bed silicon CVD-reactor. A 0.5 m ID cylindrical silicon fluidized bed was simulated with computational grids of 200 times particle size. The Matlab image processing toolbox was used for the post-processing of the simulation data and the bubble size distributions were obtained. The classical Gidaspow drag force model and a literature reported sub grid scale model (SGS) were compared, and the deviation of the bubble size predicted by using the SGS model is 12.6% comparing with Mori-Wenâ??s equation, which is smaller than the deviation of 21.4% obtained from Gidaspow model.

The reaction model has been coupled with the TFM-KTGF simulation, the preliminary results showed that the predicted silicon deposition rate was in consistence with Hsuâ??s experimental data. Further work will be performed to investigate the effects of operating conditions such as the temperature, pressure, silane/hydrogen ratio on the deposition process. The effects of bubble size distributions on fine dusts formation will be discussed.

Key words: FB-CVD, bubble size distribution, detail reaction mechanism, TFM-KTGF simulation