Patent ID: 7363180
Filing Date: 2008-04-22
Classification: B23K

Abstract:
1. A method for calibrating a workpiece processing system that includes a workpiece containing fiducial points with known locations, a chuck for holding the workpiece, a laser emitting a laser beam and optics for directing the laser beam to the workpiece, a material handling subsystem, and a control subsystem for commanding the material handling system, the optics, or both, to direct a particular point along the laser beam to a particular point on the workpiece to compensate for systematic errors in the relationship between the laser beam and the workpiece, comprising: performing 3D measurements of a workpiece at multiple positions to construct 3D map data corresponding to the workpiece; correcting errors in X and Y locations by comparing the measured locations of fiducial points on the 3D map to their known locations; calculating a first best fit surface to the 3D map data; removing a first error by first surface subtraction that includes subtracting the first best fit surface from the 3D map data to form a first residual; calculating a second best fit surface to the first residual formed by the first surface subtraction; removing a second error by second surface subtraction that includes subtracting the second best fit surface from the first residual to form a second residual; dividing the second residual formed by the second surface subtraction into multiple smaller, adjacent regions; calculating a regional best fit surface to each of the multiple regions to form corresponding regional surfaces; combining the X and Y location corrections, the first best fit surface, the second best fit surface, and the regional surfaces into a calibration map; using the calibration map to estimate errors in the relationship between the laser beam and the workpiece; and storing the calibration map for use in calibrating subsequent workpieces, thereby to enable correction of systematic errors introduced by the system.