Heat exchanger-ingot casting/slicing process. Silicon sheet growth development for the large area silicon sheet task of the Low Cost Silicon Solar Array Project. Sixth quarterly progress report, December 17, 1976--March 21, 1977
Efforts in crystal casting during this quarter were directed towards developing a crucible to prevent cracking and establish parameters for achieving the maximum growth rate for single crystal ingot solidification. Emphasis was placed on reducing the furnace superheat to increase growth rate and to cast SiO/sub 2/ liners directly in graphite crucibles. Fast growth rates were achieved by reducing the furnace temperature as close to the melt point as the instrumentation would allow--3/sup 0/C. Good single crystal growth was achieved on top of the seed by this technique, but the periphery of the seed was too cool to seed single crystal growth. Ingots were quenched from 1000/sup 0/C with helium to shatter the crucible; this did not prevent cracking of the ingot. Low density fused silica bodies were fabricated. The wetting characteristics of liquid silicon in a vacuum atmosphere was sufficient to cause penetration into open paths such as cracks and voids. Slicing tests were performed to determine: (1) the effectiveness of grooved support rollers in reducing blade wander, (2) the effectiveness of slow, nonsynchronous and stationary workpiece motions on slicing performance; and (3) the performance and life of diamond plated tungsten wire. With grooved rollers positioned on either side of the workpiece, blade wander and wafer taper were reduced an order of magnitude. For a stationary workpiece, twice the blade force was required to obtain cutting rates comparable with rocked workpieces. This resulted in wire breakage, deterioration of cutting rate, and waviness of wafer surfaces. Slow non-synchronous rocking of the workpiece dramatically improved the surface quality. Wafers could be sliced at 0.2 lb., 90 gm, instead of 0.15 lb., 68 gm, force per wire and still produce high surface quality.
- Research Organization:
- Crystal Systems, Inc., Salem, MA (USA)
- DOE Contract Number:
- NAS-7-100-954373
- OSTI ID:
- 7105765
- Report Number(s):
- ERDA/JPL/954373-77/6
- Country of Publication:
- United States
- Language:
- English
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Heat exchanger-ingot casting/slicing process. Silicon sheet growth development for the large area silicon sheet task of the low cost silicon solar array project. Seventh quarterly progress report, March 22, 1977--June 30, 1977
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