Patent ID: 8257496
Filing Date: 2012-09-04
Classification: C30B,Y10T

Abstract:
1. A weighing system for maintaining optimal CZ crystal growth comprising: a crucible provided in a vacuum chamber for holding a quantity of molten material from which a crystal is grown; a feedstock introduction means for replenishing the material in the crucible; a vacuum bearing provided with a central bore for supporting a shaft therein for rotatably moving the crucible, while maintaining a controlled atmosphere in the vacuum chamber; flexure mounts depending from a base of the vacuum chamber for supporting the vacuum bearing; flexible bellows provided between an upper surface of the vacuum bearing and the base of the vacuum chamber for enabling the vacuum bearing and crucible shaft to move while maintaining a vacuum seal to the vacuum bearing; flexures for holding the vacuum bearing to the flexure mounts, the flexures having a stiffness in a horizontal direction that is greater than a stiffness in a vertical direction; a sensor responsive to changes in the vertical distance between the vacuum bearing and the base of the vacuum chamber, such that as melt level falls, the distance between the vacuum bearing and vacuum chamber changes due to a spring effect of the bellows and flexures, and for producing an output signal representative of the vertical distance; a feedstock controller responsive to the sensor output signal and coupled with the feedstock introduction means, for correlating the output signal with the melt level in the crucible, and for introducing an amount of feedstock so as to maintain the melt level constant as the crystal is grown.