The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jun. 28, 1977
Filed:
Mar. 31, 1975
Gordon Charles Joyce, Malvern, EN;
National Research Development Corporation, London, EN;
Abstract
Automatic control of the growth from the melt of a crystal in the Czochralski technique by weighing the crystal, comparing the weight with its expected value in a comparator and using the difference in a servo-loop as a servo-control signal is known. The servo-control signal modulates the melt heater power which adjusts the temperature isotherms of the melt in order to maintain the crystal cross-sectional area constant. It has been found that a thermal delay which occurs when heat is conducted from the melt crucible to the crystal/melt interface can cause the crystal cross-sectional area to depart from its uniform expected value. The effect of the thermal delay is compensated for by a phase advance circuit which is connected to the output of the servo-loop comparator.