Ebara Solar, Inc.

John R Easoz

Barry Munshower

Takashi Isobe

A method and system for controlling the thickness of a pair of dendrites in a dendritic silicon web growth process to improve dendritic silicon web production. An image of each dendrite in a web emerging from a silicon melt in a furnace is produced by a pair of cameras focused on the dendrite pair. The dendrite images are digitized, the average thickness of the dendrites is calculated, and compared to set point parameters. The average difference between the dendrite thicknesses and the set point parameters is used to control the overall furnace temperature, while the differences between the thickness of each pair are used to control the lateral temperature distribution in the furnace in order to maintain the dendrite thickness within predetermined limits. The method can be used in a closed loop configuration to automatically control the furnace temperature and lateral temperature distribution; or in an open loop configuration to provide visible feedback information to an operator who manually adjusts the furnace temperature conditions.

Silicon ribbon growth dendrite thickness control system

The amount of silicon feed material supplied to a silicon melt furnace in a silicon crystal web growing installation is controlled by providing a melt level reference signal, generating a melt level signal representative of the level of the molten silicon in the silicon melt furnace, and providing a feed rate control signal representative of the difference between the melt level signal and the melt level reference signal. The feed rate control signal is used in a open loop mode to advise an operator of the amount of adjustment needed to correct the melt level; and is used in a closed loop mode to control the feed rate of the silicon feed material to the furnace. The laser beam reflected off the melt surface is passed through a narrow bandpass filter to remove noise due to thermal radiation from the furnace. The melt level signals generated by a position detector are averaged and digitally filtered to eliminate erroneous data caused by mechanical vibrations and other noise sources.

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McMurray, PA, United States of America

John R Easoz