Analysis of defect classification and sizing information with a dedicated white-light/laser-confocal microscope review station

An integrated white light and laser confocal microscope system for photomask defect review and analysis is presented. Various sized NIST traceable latex spheres a well as defects on an industry standard VERIMASK are used to calibrate and characterize the performance of the system. It is demonstrated that the laser confocal microscope is capable of measuring features as small as 0.2 micrometer in size while the limit for the white light microscope is approximately 0.5 micrometer. Applications of the extended XY resolution and the sub-one-tenth micron depth sensitivity of the laser confocal microscope in defect classification and repair monitoring are explored and illustrated with examples taken from 6-inch conventional and phase-shift photomasks.