Differential interferometer system and lithographic step-and-scan apparatus provided with such a system
First Claim
1. An interferometer system for measuring a mutual position and movement of a first and a second object in at least one direction, said system comprising, for at least one of all possible mutual directions of movement:
- a first interferometer unit, associated with the first object, provided with a first beam splitter, a first measuring reflector and a plurality of first reflectors, anda second interferometer unit, associated with the second object, provided with a second beam splitter, a second measuring reflector and a plurality of second reflectors, characterized in that, in operation, a measuring beam passes through both the first and the second interferometer unit and is reflected at least once by both the first measuring reflector and the second measuring reflector, in that the first and second interferometer units have the same radiation-sensitive detector, and in that a reference beam associated with the measuring beam traverses the same path as the measuring beam between the first and the second interferometer unit.
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Accused Products
Abstract
A differential interferometer system for measuring the mutual positions and movements of a first object (WH) and a second object (MH). The system comprises a first interferometer unit (1, 2, 3, 4) having a first measuring reflector (RW) and a second interferometer unit (5, 6, 7, 8) having a second measuring reflector (RM). Since a measuring beam (bm) passes through both the first and the second interferometer unit and is reflected by both the first and the second measuring reflector, and since the measuring beam and the reference beam (br) traverse the same path at least between the two interferometer units, accurate measurements can be preformed very rapidly. The interferometer system may be used to great advantage in a step-and-scan-lithographic projection apparatus.
581 Citations
14 Claims
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1. An interferometer system for measuring a mutual position and movement of a first and a second object in at least one direction, said system comprising, for at least one of all possible mutual directions of movement:
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a first interferometer unit, associated with the first object, provided with a first beam splitter, a first measuring reflector and a plurality of first reflectors, and a second interferometer unit, associated with the second object, provided with a second beam splitter, a second measuring reflector and a plurality of second reflectors, characterized in that, in operation, a measuring beam passes through both the first and the second interferometer unit and is reflected at least once by both the first measuring reflector and the second measuring reflector, in that the first and second interferometer units have the same radiation-sensitive detector, and in that a reference beam associated with the measuring beam traverses the same path as the measuring beam between the first and the second interferometer unit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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Specification