Laser working method

摘要

A converging point of processing laser light is made to accurately follow a laser light irradiation surface of an object to be processed. An object to be processed 1 is irradiated with measuring laser light along a line to cut 5, astigmatism is added to a reflected light component of the measuring laser light reflected by a front face 3 of the object 1 irradiated with the measuring laser light, a displacement sensor signal corresponding to a converged light image of the reflected light component having the astigmatism added thereto is detected, and the displacement sensor signal is made to become a feedback reference value corresponding to the quantity of the reflected light component, so as to locate the converging point of the processing laser light at a predetermined position with respect to the front face 3. This allows tire converging point of the processing laser light to follow the front face 3 of the object 1 reliably and accurately even when an area exhibiting an extremely low reflectance to the measuring laser light exists in a part of the front face 3 and lowers the quantity of the reflected light component of the measuring laser light.

主权项

1. A laser processing method of irradiating a planar object to be processed with processing laser light while locating a converging point within the planar object, so as to form a modified region to become a cutting start point within the planar object along a line to cut the planar object, the method comprising:
a height setting step of irradiating the planar object with a measuring laser light, adding astigmatism to a reflected light component of the measuring laser light reflected by a laser irradiation surface irradiated with the measuring laser light in the planar object, detecting, as a feedback reference value, a displacement sensor signal corresponding to a converged light image of the reflected light component having the astigmatism added thereto, and locating the converging point of the measuring laser light within the object rather than at a front face of the object, so as to entirely move an acquirable range of the displacement sensor signal toward an inside of the planar object; a trace recording step of irradiating with the measuring laser light along the line to cut, adding astigmatism to a reflected light component of the measuring laser light reflected by a laser irradiation surface irradiated with the measuring laser light in the planar object, detecting a displacement sensor signal corresponding to a converged light image of the reflected light component having the astigmatism added thereto, and making the displacement sensor signal become the feedback reference value, so as to perform feedback control for locating the converging point of the processing laser light at a predetermined position with respect to the laser irradiation surface, and recording the control signal of the control; and a modified region forming step for controlling with the control signal, locating the converging point of the processing laser light at a predetermined position with respect to the laser irradiation surface and irradiates the planar object with the processing laser light, so as to form a modified region within the planar object, wherein the displacement sensor signal is a relative value of an astigmatism signal corresponding to displacement of the laser irradiation surface, relative to a total light quantity signal corresponding to a total light quantity of a reflected light component received.