Device for detecting the relative position between opposed first

Details Device for detecting the relative position between opposed first Device for detecting the relative position between opposed first

1992-02-12

1992-11-03

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Photocell controls its own optical systems

356401, G01N 2186

Patent

active

051608480

ABSTRACT:
A device, usable with first and second opposed objects each having at least one diffraction grating, for detecting a positional relationship between those objects in a direction perpendicular to the direction in which they are opposed, is disclosed. The device includes a light source for projecting light to a diffraction grating of one of the first and second objects and a first detecting system for detecting, in a first plane, first light diffracted by diffraction gratings of the first and second objects. The position of incidence of the first light on the first plane is changeable with a change in the relative position of the first and second objects in the perpendicular direction. A second detecting system detects, in a second plane, second light diffracted by a diffraction grating of the first and second objects, wherein a change in the position of incidence of the second light on the second plane due to a change in the relative position of the first and second objects in the perpendicular direction is different from the change in the position of incidence of the first light. A position detecting system detects the relative position of the first and second objects, in accordance with the detection by the first and second detecting systems; wherein the first and second lights are those lights having been diffracted, at different orders, by the same diffraction grating of one of the first and second objects.

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Kinoshita, et al., "A Dual Grating Alignment Technique for X-Ray Lithography", J. Vac. Sci. Technol. B1(4), Oct.-Dec. 1983, pp. 1276-1279.
Itoh, et al., "Optical-Heterodyne Detection of Mask-to-Wafer Displacement for Fine Alignment", 362 Japanese Journal of Applied Physics No. 8, Parts 2, pp. L684-L686, Aug. 1986.

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