Patent ID: 7710582

Claim:
A laser processing apparatus in which liquid is supplied to a surface of a substrate held in a horizontal position by a substrate-holding unit, forming a film of liquid on the surface, and a processing laser beam is applied to the surface through the film of liquid, thereby cutting and removing a part of a surface region of the substrate, said apparatus comprising: a light-applying section which has a laser source that emits the processing laser beam and a focusing unit that focuses the processing laser beam on the surface of the substrate held by the substrate-holding unit; a drive mechanism which moves the substrate-holding unit and the light-applying section relative to each other so as to move the substrate to align an axis of the processing laser beam with a point on the surface of the substrate; a lift mechanism which moves the focusing unit up from or, down toward, the surface of the substrate held by the substrate-holding unit; height-map acquiring means having a first laser displacement meter which applies a first distance-measuring laser beam to the surface of the substrate, thereby to measure a height of the surface of the substrate, and having a second laser displacement meter which applies a second distance-measuring laser beam at a back of the processing beam, thereby to detect the second distance-measuring laser beam reflected from the surface of the substrate and determines a depth to which the surface region of the substrate has been cut and removed with the processing laser beam, and configured to measure distances between the focusing unit and a plurality of points on the surface of the substrate held by the substrate-holding unit and acquire, from the distances measured, a height map of the surface of the substrate; and a control unit which sets a plurality of measuring points on the surface of the substrate, causes the drive mechanism to move the substrate, thereby to align each measuring point with an axis of the first distance-measuring laser beam, causes the first laser displacement meter to apply the first distance-measuring laser beam to each measuring point and to measure the height of the surface of the substrate at each measuring point, and causes the lift mechanism to move the focusing section, thereby to correct the distance between the focusing unit and the surface of the substrate, causes the light-applying section to emit the processing laser beam, thereby to cut and remove a part of the surface region of the substrate, and causes the second laser displacement meter to measure the depth of which the surface region of the substrate has been cut and removed with the processing laser beam.