US 12,326,670 B2
Lithographic apparatus, metrology system, and intensity imbalance measurement for error correction
Earl William Ebert, Oxford, CT (US); and Roxana Rezvani Naraghi, Easton, CT (US)
Assigned to ASML HOLDING N.V., Veldhoven (NL)
Appl. No. 18/023,162
Filed by ASML Holding N.V., Veldhoven (NL)
PCT Filed Jul. 24, 2021, PCT No. PCT/EP2021/070766
§ 371(c)(1), (2) Date Feb. 24, 2023,
PCT Pub. No. WO2022/042966, PCT Pub. Date Mar. 3, 2022.
Claims priority of provisional application 63/070,553, filed on Aug. 26, 2020.
Prior Publication US 2023/0324817 A1, Oct. 12, 2023
Int. Cl. G03F 9/00 (2006.01); G03F 7/00 (2006.01)
CPC G03F 9/7088 (2013.01) [G03F 7/70625 (2013.01); G03F 7/70633 (2013.01); G03F 7/706851 (2023.05)] 20 Claims
OG exemplary drawing
 
1. A metrology system comprising:
a beam splitter configured to split scattered radiation scattered by a target into first and second portions of radiation;
a first sensor configured to receive the first portion;
a second sensor configured to receive the second portion after the second portion propagates along a path, wherein the second portion comprises plural beams; and
an optical system, disposed between a pupil image and the second sensor, comprising first and second optical elements configured to process the beams, each of the first and the second optical elements comprising a plurality of wedge surfaces, wherein:
the first and the second optical elements are arranged in series along the path and the wedge surfaces of the first element face the wedge surfaces of the second element,
the wedge surfaces of the first optical element are configured with a concave exit surface to diverge the beams to thereby increase lateral separation between the beams, and
the wedge surfaces of the second optical element are configured to collimate the beams before being transmitted to the second sensor.