Patent ID: 11940264
Assignee: ASML NETHERLANDS B.V.
Field: Measurement (Instruments)
Classification: CPC G | IPC G

Claim 0:
1. A method for calibrating a mirror of an interferometer system configured to measure a position of an object, which interferometer system includes a first interferometer and a second interferometer, wherein the first interferometer is arranged to provide a first position signal representative of a position of the object in a X-direction by directing a first measurement beam on a first mirror, wherein the second interferometer is arranged to provide a second position signal representative of the position of the object in the X-direction by directing a second measurement beam on a second mirror, and wherein the first mirror and the second mirror are arranged on opposite sides of the object and extend in a Y-direction, wherein the method comprises
a. generating a first data set comprising the first position signal and the second position signal for each of a plurality of positions of the object in the Y-direction while the object is in a first rotational orientation and in a first position in a Z-direction;
b. tilting the object to a second rotational orientation about a rotation axis perpendicular to the X-direction;
c. generating a second data set comprising the first position signal and the second position signal for each of a plurality of positions of the object in the Y-direction while the object is in the second rotational orientation and in the first position in the Z-direction; and
d. determining a shape of the first mirror and/or a shape of the second mirror in the Y-direction based on the first data set and the second data set.