| 摘要 |
PROBLEM TO BE SOLVED: To produce a high-quality single crystal with few crystal defects by improving control performance for a moving average value of a pulling-up speed having a causal relationship to quality of a single crystal.SOLUTION: A target value of a pulling-up speed of a single crystal for each predetermined pulling-up length is set before pulling-up the single crystal. A moving average value of the pulling-up speed is calculated using an actual pulling-up speed between the start time of pulling-up of the predetermined pulling-up length and the present time. The revised target value of the pulling-up speed at the present time is calculated and the single crystal is drawn-up based on the revised value. A pulling-up length (α+β) for calculating the revised value of the target pulling-up speed is changed according to an actual diameter value of the single crystal, where α is a pulling-up length in the past for calculating the actual moving average value of the pulling-up speed and β is a pulling-up length in the future.SELECTED DRAWING: Figure 1 |
