Patent ID: 7126083

Claim:
A method of calibrating a marking position of a chip scale marker including a laser system for emitting a laser beam, a wafer holder having a hole and adapted to support, over the hole, a wafer to be processed, a camera connected to an X-Y stage for translating the camera over and across the wafer holder and operative to monitor the wafer supported on the wafer holder, a laser beam power density reducing unit removably arranged on the optical path of the laser beam to reduce the power density of the laser beam during calibration, the method comprising the steps of: providing a screen that has a front and a rear surface and operative to generate, on the front surface, a beam point when a laser beam is directed onto the rear surface, the beam point corresponding to the location where the laser beam intersects the rear surface mounting the screen over the hole of the wafer holder; directing the laser beams using the laser system, through the hole onto the rear surface of the screen so as to form a beam point on the front surface of the screen; capturing an image of the beam point by use of the camera, the camera including a reference image point; measuring the deviation of the captured image of the beam point from the reference image point; and calibrating the laser system based on the measured deviation.