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:
Mar. 08, 1994
Filed:
Aug. 20, 1991
Dieter Drechsel, Bruchkobel, DE;
Leybold Aktiengesellschaft, Hanau, DE;
Abstract
A method and an apparatus are proposed for pulling crystals from the melt. The recharging of the melt (4) is performed such that the crucible (3) is raised and lowered with respect to the crystal pulling system while keeping the position of the melt surface (25) constant with respect to the crystal pulling system. In particular it is proposed that, during a first time interval (34) the amount of recharge (37) per unit time be greater than the average amount of recharge (38, 39) per unit time that would be necessary in order to make up for the consumption of material by the growing crystal (5), that during a second time interval (45) the amount of recharge (46) per unit time be less than the average recharge amount per unit time that would be necessary in order to make up for the consumption of material by the growing crystal, that during the first time interval the crucible (3) be lowered to keep the melt surface constant with respect to the crystal pulling apparatus, that during the second time interval the crucible (3) be raised to keep the melt surface constant with respect to the crystal pulling apparatus. By the invention, erosion ring grooves on the inside wall of the crucible are prevented and thus the useful life of the crucible is considerably lengthened. The method according to the invention can be practiced on existing apparatus.