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Browse Prior Art Database

Use of Random Patterns and Grilles for Mask Alignment in X Ray Lithography

IP.com Disclosure Number: IPCOM000088949D
Original Publication Date: 1977-Aug-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 2 page(s) / 52K

Publishing Venue

IBM

Related People

Hunziker, HE: AUTHOR

Abstract

A mask-alignment method for use in X-ray lithography uses certain large area patterns which have the property of giving a single, sharp, and unique superposition signal, as well as search ramp signals, when moved relative to each other. These patterns are either random arrays or optical zone plates called "grilles." For alignment, they are used in pairs whose patterns are either identical or complementary. One member of the pair has a pattern consisting of X-ray absorbing and transmitting sections, the other member's pattern is made from active and passive target material. "Active" here refers to the sensing technique used. Superposition signals are sensed by several techniques, used singly or in combinations, including X-ray transmission, X-ray absorption, X-ray fluorescence, X-ray photoemission, and Auger emission.

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Use of Random Patterns and Grilles for Mask Alignment in X Ray Lithography

A mask-alignment method for use in X-ray lithography uses certain large area patterns which have the property of giving a single, sharp, and unique superposition signal, as well as search ramp signals, when moved relative to each other. These patterns are either random arrays or optical zone plates called "grilles." For alignment, they are used in pairs whose patterns are either identical or complementary. One member of the pair has a pattern consisting of X-ray absorbing and transmitting sections, the other member's pattern is made from active and passive target material. "Active" here refers to the sensing technique used. Superposition signals are sensed by several techniques, used singly or in combinations, including X-ray transmission, X-ray absorption, X-ray fluorescence, X-ray photoemission, and Auger emission.

A preferred embodiment is shown in Figs. 1 and 2. The mask contains the random pattern (Fig. 1) which consists of X-ray transmitting sections 10 (clear) and X-ray absorbing sections 11 (hatched). On the substrate is located the pattern (Fig. 2) whose active areas 13 (hatched) consist of an X-ray fluorescent material while passive areas 14 are nonfluorescent. In this embodiment, the random patterns consist of squares with side length l, which corresponds to the alignment tolerance. Irradiation from the mask side with X-rays will produce a fluorescent emission of intensity I fro...