Laser conversion of high purity silicon powder to densified granular forms

摘要

The present invention relates to a direct method to convert fine and ultra fine silicon powder from polysilicon manufacturing sources such as fluid bed and free space reactors into densified granular forms. This conversion process is effected by the use of lasers of selective wavelengths from solid state diode or optically-pumped YAG sources to locally heat, melt and densify a controlled quantity of silicon powder, and comprises the steps of distributing dry silicon powder on an inert substrate, subjecting the silicon charge to a focused laser beam to realize melted and densified granular forms, and discharging the product. When adapted to high purity silicon powder, the end use for the densified silicon granular forms is primarily as feedstock for silicon-based semiconductor and photovoltaic manufacturing industries. The process, suitably modified, is adaptable to form other silicon body shapes and components.

主权项

1. A method for converting high purity silicon powder into a polysilicon granule of a desired size and of a desired shape, the method comprising:
(a) providing a dry source of high purity silicon powder; (b) providing a process substrate comprising a recess having a defined size and shape, the defined size and shape being the size and shape required to form the polysilicon granule of the desired size and the desired shape; (c) feeding a selected amount of dry silicon powder into the recess of the process substrate, the selected amount of dry silicon powder being the amount required to form the polysilicon granule of the desired size and the desired shape; (d) heating the dry silicon powder disposed in the recess with a laser emitting light at a wavelength in the range of ultraviolet to near infrared for a selected time and at a selected power so as to cause local melting, densification and solidification, whereby to form a polysilicon granule of the desired size and the desired shape, wherein the polysilicon granule has a diameter greater than 0.75 mm and less than 5 mm; and (e) discharging the polysilicon granule from the process substrate.