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Proceedings Paper

A CCD-Based Control System For Crystal Growth
Author(s): Douglas Yates
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Paper Abstract

An automatic crystal growth control system for the edge-defined film-fed growth (EFG) of silicon ribbon is described. The system uses optical sensing with CCD Linear Imaging Devices to determine the process status and to direct control decisions. In EFG, the crystal grows from a film of melt whose shape is controlled by the dimensions of the perimeter of a die. The thickness of the ribbon is determined by the die top thickness and the height of the solid liquid interface above the die top (meniscus height); the position of the ribbon edges is very sensitive to the temperature distribution near the ends of the die. During growth, it is desirable to measure the meniscus height and the position of the edges to make control decisions. An optical image of the growing crystal is formed by a lens system and three CCDs are placed in the image plane to make these measurements. The signals from these CCDs have been used to control the power supplied to small heating elements near the die top. Appropriate selection of the viewing angle and radiation shields will enhance the delineation of the meniscus height and edge positions. Success has been obtained in controlling the edge positions. However, the presence of carbide particles at the die top constitutes a serious source of noise in interface height measurements.

Paper Details

Date Published: 15 December 1977
PDF: 9 pages
Proc. SPIE 0116, Solid-State Imaging Devices, (15 December 1977); doi: 10.1117/12.955645
Show Author Affiliations
Douglas Yates, Mobil Tyco Solar Energy Corporation (United States)

Published in SPIE Proceedings Vol. 0116:
Solid-State Imaging Devices
Jim Campbell, Editor(s)

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