Patent ID: 8610028
Filing Date: 2013-12-17
Classification: B23K

Abstract:
1. A laser processing apparatus for irradiating a planar object to be processed with processing laser light while locating a converging point within the object, so as to form modified regions to become a cutting start point within the object along a cutting line to cut the object, the apparatus comprising: a mount table for mounting the object; a processing laser light source for emitting the processing laser light as linearly polarized light; a measuring laser light source for emitting measuring laser light for irradiating the object; a first half-wave plate for changing a polarization direction of the processing laser light emitted from the processing laser light source; a polarizing plate for splitting the processing laser light transmitted through the first half-wave plate into a processing laser light component having a polarization direction in a predetermined direction and a processing laser light component having a polarization direction in a direction intersecting the predetermined direction; a second half-wave plate for changing the polarization direction of the processing laser light component, split by the polarizing plate, having the polarization direction in the direction intersecting the predetermined direction into the predetermined direction; a first converging lens for converging the processing laser light component, split by the polarizing plate, having the polarization direction in the predetermined direction and the measuring laser light emitted from the measuring laser light source toward the object; a second converging lens having an optical axis that is arranged in parallel with an optical axis of the first converging lens along the predetermined direction and separated from the first converging lens by a predetermined distance, for converging the processing laser light component, transmitted through the second half-wave plate, having the polarization direction in the predetermined direction toward the object; control arrangement that detects a reflected light component of the measuring laser light reflected by a laser light irradiation surface irradiated with the measuring laser light in the object so as to regulate a distance between the laser light irradiation surface and the second converging lens such that a converging point of the processing laser light converged by the second converging lens is located at a predetermined position with reference to the laser light irradiation surface; and moving arrangement that relatively moves at least one of a pair of the first and second converging lenses and the mount table along the cutting line in a state where the predetermined direction substantially coincides with the cutting line, wherein the control arrangement executes: first control for operating the first converging lens such that the first converging lens is separated from the laser light irradiation surface by a constant distance and, while acquiring operation information concerning the operation, operating the second convergent lens according to the operation information and the predetermined distance; and second control for operating the first converging lens according to the operation information and operating the second converging lens according to the operation information and the predetermined distance, the first and second control being performed by arranging the first and the second converging lenses along the cutting line and moving the first and second converging lenses together along the cutting line relative to the object, at the operation of the first control, irradiating the object with the measuring laser light by using the first converging lens, detecting the reflected light of the measuring laser, and while acquiring operation information concerning the operation, operating the first converging lens such that the first converging lens is separated from the laser light irradiation surface by a constant distance; from the time at which the optical axis of the second converging lens reaches the end of the object, irradiating the object with the processing laser light by using the second converging lens while operating the second converging lens according to the operation information and the predetermined distance to form a first modified region within the object, and at the operation of the second control, from the time at which the optical axis of the second converging lens reaches the other end of the object, irradiating the object with the processing laser light by using the second converging lens while operating the second converging lens according to the operation information and the predetermined distance to form a second modified region within the object; from the time at which the optical axis of the first converging lens reaches the other end of the object, irradiating the object with the processing laser light by using the first converging lens while operating the first converging lens according to the operation information and the predetermined distance to form a third modified region within the object.