公开(公告)号：US20230168077A1

公开(公告)日：2023-06-01

申请号：US17920751

申请日：2021-03-22

Applicant: ASML Netherlands B.V.

Inventor： Maarten Jozef JANSEN ,  Ping LIU

IPC: G01B9/02055 ,  G01B9/02056 ,  G01B9/02001 ,  G03F7/20

CPC classification number: G01B9/02072 ,  G01B9/02059 ,  G01B9/02007 ,  G03F7/70516

Abstract: The invention provides a method for calibration of an optical measurement system, which may be a heterodyne interferometer system, wherein a first optical axis and a second optical axis have a different optical path length, the method comprises: ∘measuring a first measurement value along the first optical axis using a first measurement beam, ∘measuring a second measurement value along the second optical axis using a second measurement beam, ∘changing a wavelength of the first measurement beam and the second measurement beam, ∘measuring a further first measurement value along the first optical axis using the first measurement beam with changed wavelength, measuring a further second measurement value along the second optical axis using the second measurement beam with changed wavelength, ∘determining a cyclic error of the optical measurement system on the basis of the measured values, and ∘storing a corrective value based on the cyclic error.