AUTOMATIC CONTROL OF CRYSTAL ROD DIAMETER

摘要

An apparatus for use in a crystal manufacturing system based on a floating zone method or Czochralski method, adapted to control a quantity relating to the diameter of a crystal rod at the crystallization boundary, and designed to reduce hunting in the control of the quantity relating to the crystal diameter so as to prevent disturbance in crystallization and reduce irregularities in the surface of the crystal rod even if there is a discrepancy between a predetermined pattern and the ideal pattern with respect to the quantity to be controlled. The apparatus has a controller provided with: a program setter (72) adapted to output a quantity based on a predetermined pattern written in the controller in response to a detected value of the quantity relating to the crystal diameter at the crystallization boundary (24) or to the length of the crystal rod (18); a first adjuster (84) for performing a PI or PID control action in response to the difference between the detected value and the desired value of the quantity relating to the crystal diameter at the crystallization boundary (24); a second adjuster (76) for performing, in response to the difference between the detected value and the desired value of the quantity relating to the crystal diameter at the crystallization boundary (24), I<2> control action for additional time-integration of a value obtained by time-integration of this difference; and a superposer (78) for outputting, as an adjustment amount, a value of linear combination between the program setter (72), the first adjuster (84), and the second adjuster (76).