Polysilicon produced by a fluid bed process

Details Polysilicon produced by a fluid bed process Polysilicon produced by a fluid bed process

1987-01-16

1989-04-11

Doll, John

Stock material or miscellaneous articles

Coated or structually defined flake, particle, cell, strand,...

Particulate matter

423349, 427213, 428405, 437 81, 437225, 437233, B32B 516, B05D 700, C01B 3302

Patent

active

048205877

ABSTRACT:
Silicon of high purity is made by decomposing silane in a fluidized bed reactor. To obtain good process economics, two modes of operation are used. In a first mode, the reactor is operated under high productivity conditions which also result in co-production of silicon dust or fines. The dust on the particles can cause problems in handling. For example, in bagging the particles, or removing the particles from a bag, the dust can become airborne from the larger particle surfaces and form an objectionable cloud of silicon dust. The invention provides a method for uniting dust to the larger silicon particles. In a second process mode, a thin (0.1-5.0 micron) layer of high purity silicon is deposited on the dust laden particles. This second mode is most preferably carried out by (a) treating the dust-laden particles with a deposition gas comprising 1 to 5 mole % silicon admixed with an inert carrier gas such as hydrogen, (b) in a fluidized bed reactor, and (c) at a process temperature of 620.degree.650.degree. C. The product polysilicon is composed of free flowing, approximately spherical particles having a size distribution of 150-1500 microns, an average size of 650-750 microns and has a particle bulk density of 2.3 grams per cubic centimeter, a bulk density of about 1360 kg/m.sup.3 and a silicon surface dust content of less than about 0.08 wt. %.

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VLSI Fabrication Principles Silicon and Gallium Arsenide Ghandhi, 7/1984, pp. 517-520.
G. Hsu et al, Fines in Fluidized Bed Silane Pyrolysis, J. Electrochem Soc., vol. 131, No. 3, pp. 660-163, Mar. 1984.
G. Hsu et al, Fluidized Bed Silicon Deposition, Eighteenth IEEE Photovoltaic Specialists Conference, 1984, pp. 553-557.
F. C. Eversteijn, Gas-Phase Decomposition of Silane in a Horizontal Epitaxial Reactor, Philips Res. Reports 26, 134-144, 1971.

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