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Rescanning Technique To Improve Mask Inspection Throughput

IP.com Disclosure Number: IPCOM000048602D
Original Publication Date: 1982-Feb-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Davis, DE: AUTHOR [+3]

Abstract

It has been shown that rescanning of defect locations, detected during E-beam inspection of optical photomasks, achieves higher throughputs by allowing a higher number of false alarms (not missed defects) resulting from increased scan speed. The time saved by scanning at a higher speed is much greater than the time spent eliminating the false alarms, resulting in a significant decrease in inspection time.

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Rescanning Technique To Improve Mask Inspection Throughput

It has been shown that rescanning of defect locations, detected during E- beam inspection of optical photomasks, achieves higher throughputs by allowing a higher number of false alarms (not missed defects) resulting from increased scan speed. The time saved by scanning at a higher speed is much greater than the time spent eliminating the false alarms, resulting in a significant decrease in inspection time.

The detection of a defect (or a false alarm) results in the retaining of information that defines the location (X, Y address) and type (clear or opaque) of the defect. These defect addresses are used to generate rescan patterns, such that rescanning can be accomplished at the rectangle, subfield, field, or mask level. The technique involves rescanning only those locations where defects (preponderantly false alarms) were detected, reducing the rescan overhead to an absolute minimum. The number of rescans required to insure elimination of false alarms can be calculated from the system signal to noise ratio and input as a parameter to the test system. Locations that consistently register as defects are true defects and are saved for later repair.

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