Fluidized Bed Process with Silane

Abstract

Silane-based fluidized-bed technology is used to produce polysilicon for solar cells by decomposing silane onto silicon particles suspended in a heated stream of silane and hydrogen. Silane-based fluidized-bed reactors potentially provide a lower cost method to produce polysilicon than the current Siemens reactors that dominate the silicon market. Production of silicon in a fluidized bed requires 80–90% less electrical energy than the currently favored Siemens process and converts a batch process into a more economical continuous process. The spherical granular silicon product from fluidized-bed reactors is preferred to the polysilicon rods produced by the Siemens process for downstream processing. Production of silicon by fluidized beds has been carried on for over 20 years, but the simpler Siemens process has dominated polysilicon production because of the high purity of its polysilicon product and the availability of low-cost electricity. The economics of the silane-based fluidized-bed technology has improved significantly due to advances in reactor design, process modeling, and operational experience. Fluidized-bed technology is the leading candidate to eventually provide less expensive polysilicon for solar cells.