Browse Prior Art Database

Mask Inspection Device

IP.com Disclosure Number: IPCOM000080156D
Original Publication Date: 1973-Nov-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 2 page(s) / 29K

Publishing Venue

IBM

Related People

Kosanke, K: AUTHOR [+3]

Abstract

Inspection is accomplished by comparing two masks, a master mask and the mask to be inspected, or two chipsites. The two patterns 4 to be compared are illuminated by coherent radiation, e.g., by a laser beam 1 exiting from laser L and passing incoherator 2 and beam expander 3, 3', and are imaged by optical system 5.

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Mask Inspection Device

Inspection is accomplished by comparing two masks, a master mask and the mask to be inspected, or two chipsites. The two patterns 4 to be compared are illuminated by coherent radiation, e.g., by a laser beam 1 exiting from laser L and passing incoherator 2 and beam expander 3, 3', and are imaged by optical system 5.

A biprism 6, arranged between frequency plane FP and image plane IP of optical system 5, superimposes both images in the image plane. Since the rays forming the two superimposed images are incident from two different directions a fringe pattern, i.e., a light pattern having an AC component, is formed in areas where identical light patterns are brought to coincidence.

In areas where only one pattern is imaged, i.e., where pattern zones out of registration or pattern zones having a defect are imaged, a luminous DC signal is formed since only a ray from one direction is incident in such areas. Areas where no pattern is imaged are dark, i.e., their DC component is equal to zero. By scanning the image plane with a light-beam deflector or a vidicon tube 7 error signals are derived, amplified by 8 and recorded at 9 if a DC signal other than zero is sensed.

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