Patent ID: 7825350

Claim:
A method of cutting a wafer-like object to be processed along a line along which the object is intended to be cut, the object being made of semiconductor material and comprising a first surface and a second surface, the first surface comprising a laser light entrance surface, the method comprising: irradiating the object with laser light so as to form multiple light-converging points at respective locations within the object that are each spaced from the first surface and the second surface, wherein the irradiation to form the light-converging points results in the formation of a molten processed spot at the location of each light-converging point which is one of a spot which is obtained by changing material of the object from single crystal structure to amorphous structure, a spot which is obtained by changing material of the object from single crystal structure to polycrystalline structure, and a spot including a spot which is obtained by changing material of the object from single crystal structure to amorphous structure and polycrystalline structures, such that after formation of the molten processed spots, the object comprises a molten processed region including the molten processed spots that are formed along the line along which the object is intended to be cut and a non-molten region which is not molten, with the non-molten region existing above and/or below the molten processed region such that the molten processed region does not extend continuously through the object from the first surface to the second surface, each molten processed spot being formed so that it is not formed in the laser light entrance surface of the object, and the molten processed region functioning as a starting point for cutting the object along the line along which the object is intended to be cut; and causing a crack to form which extends from the starting point toward the first surface and/or the second surface of the object, with the crack facilitating cutting of the object.