Circumferential error signal apparatus for crystal rod pulling

摘要

The circumference of a crystal rod is monitored and controlled during the rod growing process by providing relative rotation between the growing crystal rod and a melt of the crystal material as the rod is being pulled from the melt according to the Czochralski method, and by using a radiation-sensitive control system for adjusting growth conditions of the rod in response to variations in a radiation signal which is indicative of the circumferential dimension of the rod. An electronic circuit integrates the radiation signal over each complete rotation of the rod, thereby eliminating unnecessary adjustment of the growth conditions in response to diametric variations of the rod which recur regularly in each rotation.