Thickness measuring device for semiconductor wafer determines thickness of workpiece from distance between specified points at which laser beam reflected from top and bottom surface of workpiece fall on imaging unit

摘要

An imaging unit (22) captures the laser beam reflected from the top surface of the workpiece (40) and a ray of laser beam reflected from the bottom surface of the workpiece after passing through the workpiece. A processor (23) determines the thickness of the workpiece from the distance between two points at which reflected laser beams fall on the imaging unit.