STEPPER OR SCANNER HAVING TWO ENERGY MONITORS FOR A LASER

摘要

A first laser light intensity detector (44) is positioned within a stepper or scanner (20) proximate to a reticle (36) so that attenuation due to stepper optics has already occurred prior to the laser light impinging upon the light intensity detector. Preferably, the first light intensity detector is mounted as closed to the wafer (22) as practical. A second light intensity detector (46) is located at the output of the laser (12). The light intensity detected from the outputs of the first and second light intensity detectors, in conjunction, forms part of a feedback mechanism which adjusts the light output of the laser, during wafer fabrication, so that the light intensity detected by the first light intensity detector is an optimum value.