Patent ID: 9739723
Date: 2017-08-22
CPC Classifications: G01N

Claim:
1. A method of defect inspection for a photomask, the method comprising: obtaining registration errors existing in a field region of the photomask, wherein the photomask includes the field region and a calibration key pattern region; obtaining a first light transmittance of the field region; performing registration correction by irradiating a first laser beam onto the field region; obtaining a first transmittance reduction in the field region by the registration correction; obtaining a second light transmittance in the field region by using the first transmittance reduction; performing light transmittance correction to the calibration key pattern region so that the calibration key pattern region has light transmittance substantially equal to the second light transmittance; performing light calibration using the corrected calibration key pattern region to obtain a light calibration result; and performing defect inspection to the field region by using the light calibration result.