Method of producing a wafer from an ingot including a peel-off detecting step

A method of producing a wafer from a hexagonal single-crystal ingot, comprising the steps of:

• forming a peel-off layer in the hexagonal single-crystal ingot by applying a laser beam having a wavelength transmittable through the hexagonal single-crystal ingot while positioning a focal point of the laser beam in the hexagonal single-crystal ingot at a depth corresponding to a thickness of a wafer to be produced from an end face of the hexagonal single-crystal ingot;
• generating ultrasonic waves from an ultrasonic wave generating unit positioned in facing relation to the wafer to be produced across a water layer interposed therebetween, thereby to break the peel-off layer;
• and
• positioning an image capturing unit sideways of the wafer to be produced and detecting when the wafer to be produced is peeled off the hexagonal single-crystal ingot
• wherein the image capturing unit is configured and arranged to capture an image of a gap between the wafer to be produced and an upper surface of a remaining portion of the hexagonal single-crystal ingot.