US 12,270,647 B2
Method for calibration of an optical measurement system and optical measurement system
Maarten Jozef Jansen, Casteren (NL); and Ping Liu, Eindhoven (NL)
Assigned to ASML NETHERLANDS B.V., Veldhoven (NL)
Appl. No. 17/920,751
Filed by ASML Netherlands B.V., Veldhoven (NL)
PCT Filed Mar. 22, 2021, PCT No. PCT/EP2021/057292
§ 371(c)(1), (2) Date Oct. 21, 2022,
PCT Pub. No. WO2021/213750, PCT Pub. Date Oct. 28, 2021.
Claims priority of application No. 20171037 (EP), filed on Apr. 23, 2020.
Prior Publication US 2023/0168077 A1, Jun. 1, 2023
Int. Cl. G01B 9/02055 (2022.01); G01B 9/02001 (2022.01); G01B 9/02003 (2022.01); G01B 9/02004 (2022.01); G01B 9/02015 (2022.01); G01B 9/02056 (2022.01); G03F 7/00 (2006.01)
CPC G01B 9/02072 (2013.04) [G01B 9/02003 (2013.01); G01B 9/02004 (2013.01); G01B 9/02007 (2013.01); G01B 9/02027 (2013.01); G01B 9/02059 (2013.01); G03F 7/70516 (2013.01); G03F 7/70775 (2013.01)] 20 Claims
OG exemplary drawing
 
1. A method for calibration of an optical measurement system comprising a first optical axis associated with first interferometer optics and a second optical axis associated with second interferometer optics, wherein the first optical axis and second optical axis have a different optical path length, the method for the calibration comprising:
measuring a first measurement phase value along the first optical axis using a first measurement beam and a first reference beam;
measuring a second measurement phase value along the second optical axis using a second measurement beam and a second reference beam;
changing a wavelength of the first measurement beam, the first reference beam, the second measurement beam, and the second reference beam;
measuring a further first measurement phase value along the first optical axis using the first measurement beam with changed wavelength and the first reference beam with changed wavelength;
measuring a further second measurement phase value along the second optical axis using the second measurement beam with changed wavelength and the second reference beam with changed wavelength;
determining a cyclic error of the optical measurement system on the basis of the first measurement phase value, the second measurement phase value, the further first measurement phase value and the further second measurement phase value; and
storing a corrective value based on the cyclic error.