公开(公告)号：US12270647B2

公开(公告)日：2025-04-08

申请号：US17920751

申请日：2021-03-22

Applicant: ASML Netherlands B.V.

Inventor： Maarten Jozef Jansen ,  Ping Liu

IPC: G01B9/02055 ,  G01B9/02001 ,  G01B9/02003 ,  G01B9/02004 ,  G01B9/02015 ,  G01B9/02056 ,  G03F7/00

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.