Patent ID: 8773637

Claim:
A lithographic apparatus arranged to transfer a pattern from a patterning device onto a substrate, the apparatus comprising: a patterning subsystem for receiving said patterning device and applying said pattern to the substrate held at a patterning location; a substrate support for holding the substrate while said pattern is applied; at least one positioning subsystem for moving said substrate support relative to said patterning subsystem and said patterning device such that said pattern is applied at an accurately known location on the substrate; and a measuring subsystem for measuring the location of said substrate relative to the patterning location, and for supplying measurement results to said positioning subsystem, wherein said measuring subsystem includes at least one sensor for receiving radiation projected from an alignment mark, the sensor and the alignment mark being associated one with the patterning device and the other with the substrate support, and a processor for receiving and processing signals from the sensor to resolve spatial information in the projected alignment mark to establish a reference position for measuring positional relationships between said substrate support and said patterning location, wherein said sensor comprises an array of photodetector elements separated in at least one dimension and arranged in a line, the line being oriented at a non-zero angle to the orientation of a line in the projected alignment mark such that the sensor and the processor are operable to perform at least a final step in establishing the reference position while holding the substrate support and patterning device stationary with respect to one another and the processor calculating from signals of said array a reference position in a dimension perpendicular to the line in the projected alignment mark.