Manufacturing method of gallium nitride substrate

A manufacturing method of a gallium nitride substrate from a gallium nitride ingot having a first surface and a second surface on a side opposite to the first surface, the method comprising:

• a holding step of holding the gallium nitride ingot,
• a peeling layer forming step of forming a peeling layer at a depth, which corresponds to a thickness of the gallium nitride substrate to be manufactured, by splitting a laser beam of a wavelength, which transmits through gallium nitride to form a plurality of focal points, such that each of the plurality of focal points contribute to formation of the peeling layer, and relatively moving the gallium nitride ingot and the plurality of focal points, with the focal points positioned inside the gallium nitride ingot from the first surface;
• and
• a peeling step of peeling the gallium nitride substrate from the gallium nitride ingot using the peeling layer as a start point, wherein:
• the peeling layer forming step is set such that the laser beam is split to form the plurality of focal points and straight lines connecting the individual split focal points each extend along a direction parallel to the direction of the crystal orientation represented by a below-described formula (1), wherein at least one of the straight lines is oriented obliquely with respect to the direction of relative movement between the gallium nitride ingot and the plurality of focal points
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• 2
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• Formula
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• (
• 1
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