Melt surface change measurement under different crucible rotations in Czochralski furnace using an image-processing method

Abstract

Effect of different crucible rotations on the silicon melt surface in Czochralski furnace is studied using an image-based measurement system. The mathematical model on the relationship between the target feature in the image and the melt level is discussed. A new improved approach based on Otsu method is applied to segment the feature area from the imperfect image due to uneven illumination. The calibration experiment indicates that the measurement system has resolution of 0.00371 mm. The effectiveness experiment shows that system measurements are very accurate. The surfaces of silicon melt with different crucible rotation rates are measured and analyzed. The result reveals that the melt surface becomes a paraboloid shape with crucible rotation. Moreover, crucible rotations cause more fluctuation on the melt surface under less silicon melt mass. This work may provide us with an effective method to monitor the melt surface change during crystal growth.