Patent ID: 7876452
Filing Date: 2011-01-25
Classification: G01B,G03F

Abstract:
1. A process apparatus, comprising: a process tool situated at a process position; a stage that is movable in at least a first movement direction relative to the process tool; a first interferometer system situated relative to the stage to determine a position of the stage in the first movement direction relative to the process position, the first interferometer system comprising a respective measurement interferometer system and a respective reference interferometer system producing data regarding stage position in the first movement direction, the respective reference interferometer system comprising a first reference interferometer and a second reference interferometer, the first reference interferometer producing reference data regarding position of the process tool in the movement direction, and the second reference interferometer being redundant to the first reference interferometer; and a processor coupled to the first interferometer system and configured to determine, from the data produced by the respective measurement interferometer system and the first reference interferometer, a position of the stage in the first movement direction relative to the process tool, and to determine, from the data produced by the first and second reference interferometers, a displacement of the process tool relative to the process position, and thus to determine a position of the stage in the first movement direction relative to the process position.