HERSTELLUNG VON POLYKRISTALLINEM SILIZIUM DURCH PYROLYSE VON SILAN.

摘要

A polysilicon process is disclosed in which the fines which are inherently produced in a fluid bed deposition type operation using silicon seed particles and a silane feed are in effect glued on to the product particles so as to reduce the undesirable effect of the silicon fines. The process comprises operating a fluid bed in two modes. In the first mode, high productivity is favored at the expense of producing fines which are produced by homogeneous decomposition of the silane feed. In the second mode, the fines are in effect glued on to the particles to which they are adhered by means of deposition of a thin layer of silicon. In the second mode, the concentration of the silane in the feed gases is reduced thus favoring hetergeneous deposition of the silicon on the silicon particles in the bed. The process can be operated using a single fluid bed reactor by alternating cycles or in a more continuous manner utilizing two fluid bed reactors, the first reactor being operated at the high productivity rate with the second reactor taking the silicon particles from the first reactor and operated at the gluing on conditions.