Patent ID: 7592238

Claim:
A laser processing method for processing an object to be processed, the object comprising a first surface and a second surface, the method comprising: repeatedly irradiating the object with pulsed laser light elliptically polarized with an ellipticity of other than 1 so as to form a plurality of first light-converging points of the pulsed laser light each at a location within the object spaced from the first surface and the second surface, a major axis of an ellipse indicative of the elliptical polarization of pulsed laser light being aligned with each of a plurality of first lines, extending in a first direction, along which the object is intended to be cut, with multiple occurrences of the first light-converging points being formed along each of the plurality of first lines; forming at least one first modified region within the object at the locations of the first light-converging points so as to form at least one first modified region along each of the plurality of first lines, each at least one first modified region having, when viewed from a laser incident direction, a first length in a direction along the first line along which it is formed, and a second length in a direction perpendicular to the direction of the first length, the first length being longer than the second length; repeatedly irradiating the object with pulsed laser light elliptically polarized with an ellipticity of other than 1 so as to form a plurality of second light-converging points of the pulsed laser light each at a location within the object spaced from the first surface and the second surface, a major axis of an ellipse indicative of the elliptical polarization of the pulsed laser light being aligned with each of a plurality of second lines, extending in a second direction crossing the first direction, along which the object is intended to be cut, with multiple occurrences of the second light-converging points being formed along each of the plurality of second lines; and forming at least one second modified region within the object at the locations of the second light-converging points so as to form at least one second modified region along each of the plurality of second lines, each at least one second modified region having, when viewed from a laser incident direction, a first length in a direction along the second line along which it is formed, and a second length in a direction perpendicular to the direction of the first length, the first length being longer than the second length; wherein each of the at least one first and second modified regions is configured to function as at least one starting point for cutting the object along the line along which it is formed.