Manufacturing method of single crystals

A manufacturing method of a single crystal by the Czochralski method, comprising:

• measuring a space between a melt surface and a lower end of a seed crystal provided above a melt,
• lowering the seed crystal based on the space and bringing the seed crystal into contact with the melt, and
• growing the single crystal at the lower end of the seed crystal by pulling the seed crystal while maintaining a state of contact with the melt, wherein
• the measuring of the space between the melt surface and the lower end of the seed crystal:
• captures an image of the seed crystal and the melt surface using a camera installed diagonally above the melt surface,
• generates a real-image edge approximation circle by approximating a circle from an approximately arc-shaped edge pattern at a lower end portion of a real image of the seed crystal shown in the image captured by the camera and also generates a mirror-image edge approximation circle by approximating a circle from an approximately arc-shaped edge pattern at an upper end portion of a mirror image of the seed crystal reflected on the melt surface, and calculates the space between the melt surface and the lower end of the seed crystal based on the distance from the center coordinates of the real-image edge approximation circle to the center coordinates of the mirror-image edge approximation circle,
• the seed crystal further includes a tapered portion provided below the straight-trunk portion,
• the lower end of the seed crystal is the lower end of the tapered portion, and the taper angle of the tapered portion is greater than the installation angle of the camera, and
• the manufacturing method further comprises measuring a length of the tapered portion in advance before measuring the space between the melt surface and the lower end of the seed crystal, and the measuring of the space between the melt surface and the lower end of the seed crystal includes subtracting the length of the tapered portion from the space between the melt surface and the lower end of the straight-trunk portion of the seed crystal.