US 7,321,432 B2 | ||
Measurement and compensation of errors in interferometers | ||
Henry A. Hill, Tucson, Ariz. (US) | ||
Assigned to Zygo Corporation, Middlefield, Conn. (US) | ||
Filed on Sep. 09, 2003, as Appl. No. 10/659,103. | ||
Claims priority of provisional application 60/409285, filed on Sep. 09, 2002. | ||
Prior Publication US 2004/0085546 A1, May 06, 2004 | ||
Int. Cl. G01B 11/14 (2006.01) |
U.S. Cl. 356—500 | 59 Claims |
1. A method for determining the location of an alignment mark on a stage, the method comprising:
measuring a location, x1, of a stage along a first measurement axis using an interferometer;
measuring a location, x2, of the stage along a second measurement axis substantially parallel to the first measurement axis; and
determining a location of the alignment mark along a third axis substantially parallel to the first measurement axis based
on x1, x2, and a correction term, ψ3,
wherein the interferometer comprises interferometer optics configured to direct a measurement beam to reflect from a mirror
where the interferometer optics or the mirror are attached to the stage, and ψ3 is calculated from predetermined information comprising information characterizing imperfections in the interferometer optics.
|