POSITION MEASUREMENT UNIT, MEASUREMENT SYSTEM, AND LITHOGRAPHIC APPARATUS COMPRISING SUCH POSITION MEASUREMENT UNIT

摘要

PROBLEM TO BE SOLVED: To provide a compact position measurement unit for a lithographic apparatus or the like.

SOLUTION: A measurement unit to measure a position in first and second dimensions includes a diffraction type encoder and an interferometer. The diffraction type encoder measures by means of a diffraction on first and second diffraction gratings (G1, G2) the position in the first dimension of the second grating (G2) with respect to the first grating (G1). The interferometer measures the position in the second dimension of a mirror (MI). The measurement unit includes a combined optical unit (COU) to transfer an encoder measurement beam (EMB) as well as an interferometer measurement beam (IMB). Further, the measurement unit may include a combined light source for the encoder as well as the interferometer. One of the first and second diffraction gratings (G1, G2) may further show some degree of zero order reflection to provide the mirror (MI) of the interferometer.

COPYRIGHT: (C)2007,JPO&INPIT