公开(公告)号：US20180224757A1

公开(公告)日：2018-08-09

申请号：US15748644

申请日：2016-07-29

Applicant: ASML NETHERLANDS B.V.

Inventor： Engelbertus Antonius Fransiscus VAN DER PASCH ,  Robert Edgar VAN LEEUWEN

IPC: G03F7/20 ,  G01B11/02 ,  G01B11/26 ,  G01B9/02

CPC classification number: G03F7/70775 ,  G01B9/02061 ,  G01B11/026 ,  G01B11/26 ,  G03F7/70716 ,  G03F7/7085

Abstract: A position measurement system includes an interferometer to determine a position of an object. The interferometer is arranged to generate a first, second and third signals representative of the position by irradiating respective first, second and third areas of a reflective surface of the object. Along a line, the first and second areas are at a first distance relative to each other, the second and third areas are at a second distance relative to each other, and the first and third areas are at a third distance relative to each other. The interferometer is arranged to provide a rotation signal representative of a rotation of the object along an axis based on the first, second and third signals. The axis is parallel to the reflective surface and perpendicular to the line.