ASML Holding N.V.
Position measurement system, zeroing method, lithographic apparatus and device manufacturing method

Abstract:

A position measurement system configured to measure a position of an object, the system including: a displacement interferometer having a first capture range; a time-of-flight sensor having a second capture range that is larger than the first capture range and having an inaccuracy that is smaller than the first capture range; and a processing unit, wherein the position measurement system has a zeroing mode in which the processing unit is configured to determine a coarse position of the object within the second capture range based on an output from the time-of-flight sensor, and in which the processing unit is configured to determine a fine position of the object based on the determined coarse position and an output from the displacement interferometer.