Fines in Fluidized Bed Silane Pyrolysis

Silicon deposition on silicon seed particles by silane pyrolysis in a fluidized bed reactor is being investigated as a low cost, high throughput method to produce high purity polysilicon for solar cell applications. Studies of fines, particles 0.1–10μ diam, initiated from homogeneous decomposition in the reactor were conducted using 2 and 6 in. diam fluidized beds. The studies show functional dependences of fines elutriation on operating parameters such as silane feed concentration, temperature, gas velocity, and bubble size. The observation that the fines elutriation is generally below 10% of the silicon‐in‐silane feed is explained using a concept of scavenging by large particles in an environment of less free space for homogeneous nucleation. Preliminary results suggest that, with proper conditions and distributor design, high silane concentration ( in ) feed may be used for silicon production in fluidized bed reactors.