Apparatus of producing silicon single crystal and method of producing silicon single crystal

An apparatus of producing a silicon single crystal by pulling a silicon single crystal from a silicon melt formed in a crucible, comprising:

• an imaging device that takes an image of a region including a surface of the silicon melt from a direction that is inclined with a predetermined angle about a pulling axis of the silicon single crystal;
• a heat shield that is disposed so as to cover a partial surface of the silicon melt and that has a circular opening through which the silicon single crystal during pulling penetrates;
• a first operator that operates the imaging device and takes a real image of the heat shield including the opening and a mirror image of the heat shield reflected on the surface of the silicon melt, measures a spacing between the real image and the mirror image, and calculates a position of the surface of the silicon melt;
• a second operator that operates the imaging device and takes an image of a bright-zone appearing in the vicinity of an interface between the silicon melt and the silicon single crystal, and calculates a position of the surface of the silicon melt based on a center position of the silicon single crystal that is determined based on the image of the bright zone;
• and
• a controller that refers a data of the position of the surface of the silicon melt obtained by the first operator and a data of the position of the surface of the silicon melt obtained by the second operator, and controls the position of the surface of the silicon melt in during the pulling of the silicon single crystal, wherein
• the first operator transforms contours of the real image and the mirror image of the heat shield obtained by the imaging device to project the contours of the real image and the mirror image to a plane corresponding to a lower end position of the heat shield,
• the first operator calculates a center position of the projected real image of the heat shield through circular approximation of the contour of the opening of the real image of the heat shield that appears as an elliptic shape,
• the first operator calculates a center position of the projected mirror image of the heat shield through circular approximation of the contour of the opening of the mirror image of the heat shield, and
• the first operator measures the spacing between the real image and the mirror image based on a spacing between the center positions of the projected real image and the projected mirror image of the heat shield.