Automatically controlled crystal growth

Details Automatically controlled crystal growth Automatically controlled crystal growth

1975-03-31

1977-02-15

Gruber, Felix D.

Registers

Transfer mechanism

Traveling pawl

23273SP, 23515112, B01J 1718, G06G 766

Patent

active

040083870

ABSTRACT:
The Czochralski growth of a crystal may be automatically controlled to provide uniform crystal cross-sectional area by weighing the crucible containing the melt from which the crystal is grown and deriving a weight signal which is compared with its expected value to produce a feedback loop control signal to control the melt heater power. However a magnetic field will be associated with the melt heater current and the interaction of this field on the crucible can produce a levitation force which is recorded erroneously as part of the weight signal. This unwanted force can make the closed-loop control unstable. The error component in the weight signal is cancelled in the invention by deriving an equal and opposite component by monitoring the current supplied to the melt heater and adding the derived component to the weight signal in the feedback loop.

REFERENCES:
patent: 2686864 (1954-08-01), Wroughton et al.
patent: 2686865 (1954-08-01), Kelly, Jr.
patent: 2908004 (1959-10-01), Levinson
patent: 3284172 (1966-11-01), Binder
patent: 3617392 (1971-11-01), Locke, Jr.
patent: 3621213 (1971-11-01), Jen et al.
patent: 3832626 (1974-08-01), Stut

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