Position measurement system, interferometer and lithographic apparatus

A position measurement system includes an interferometer to determine a position of an object. The interferometer is arranged to generate a first, second and third signals representative of the position by irradiating respective first, second and third areas of a reflective surface of the object. Al...

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Hauptverfasser: Van Der Pasch, Engelbertus Antonius Fransiscus, Van Leeuwen, Robbert Edgar
Format: Patent
Sprache:eng
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Zusammenfassung:A position measurement system includes an interferometer to determine a position of an object. The interferometer is arranged to generate a first, second and third signals representative of the position by irradiating respective first, second and third areas of a reflective surface of the object. Along a line, the first and second areas are at a first distance relative to each other, the second and third areas are at a second distance relative to each other, and the first and third areas are at a third distance relative to each other. The interferometer is arranged to provide a rotation signal representative of a rotation of the object along an axis based on the first, second and third signals. The axis is parallel to the reflective surface and perpendicular to the line.