| US 7,532,305 B2 | ||
| Lithographic apparatus and device manufacturing method using overlay measurement | ||
| Arie Jeffrey Den Boef, Waalre (Netherlands); Everhardus Cornelis Mos, Best (Netherlands); Maurits Van Der Schaar, Veldhoven (Netherlands); and Stefan Carolus Jacobus Antonius Keij, Breda (Netherlands) | ||
| Assigned to ASML Netherlands B.V., Veldhoven (Netherlands) | ||
| Filed on Mar. 28, 2006, as Appl. No. 11/390,416. | ||
| Prior Publication US 2007/0229785 A1, Oct. 04, 2007 | ||
| Int. Cl. G03B 27/68 (2006.01) | ||
| U.S. Cl. 355—52 [355/53; 356/399] | 11 Claims |
| 1. A lithographic apparatus arranged to transfer a pattern from a patterning device onto a substrate, comprising:
a reference set of gratings in the substrate, the reference set consisting of two reference gratings having line elements
in a first direction, and one reference grating having line elements in a second direction, the second direction being substantially
perpendicular to the first direction;
a measurement set of gratings on top of the reference set of gratings, the measurement set consisting of three measurement
gratings similar to the reference gratings, in which two of the measurement gratings are oppositely biased in the second direction
relative to the respective two reference gratings and one of the measurement gratings is not biased in the first direction
relative to the respective one reference grating; and
an overlay measurement device, the overlay measurement device being configured to measure asymmetry of the three gratings
in the reference set and the measurement set, and to derive from the measured asymmetry the overlay in both the first and
second direction.
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