US 11,703,771 B2
Variable diffraction grating
Ali Alsaqqa, Trumbull, CT (US); Fadi El-Ghussein, Holmdel, NJ (US); Lambertus Gerardus Maria Kessels, Clifton Park, NY (US); Roxana Rezvani Naraghi, Easton, CT (US); Krishanu Shome, Cheshire, CT (US); Timothy Allan Brunner, Ridgefield, CT (US); and Sergei Sokolov, Eindhoven (NL)
Assigned to ASML Holding N.V., Veldhoven (NL); and ASML Netherlands B.V., Veldhoven (NL)
Appl. No. 17/773,003
Filed by ASML Holding N.V., Eindhoven (NL); and ASML Netherlands B.V., Eindhoven (NL)
PCT Filed Oct. 12, 2020, PCT No. PCT/EP2020/078615
§ 371(c)(1), (2) Date Apr. 28, 2022,
PCT Pub. No. WO2021/083649, PCT Pub. Date May 6, 2021.
Claims priority of provisional application 62/927,206, filed on Oct. 29, 2019.
Prior Publication US 2022/0390861 A1, Dec. 8, 2022
Int. Cl. G03F 7/20 (2006.01); G03F 9/00 (2006.01)
CPC G03F 9/7019 (2013.01) [G03F 9/7076 (2013.01)] 17 Claims
OG exemplary drawing
 
1. A calibration system comprising:
a plate adjacent to a wafer alignment mark disposed on a wafer;
a fixed alignment mark disposed on the plate and configured to act as a reference mark for an initial calibration of the calibration system; and
a variable diffraction grating disposed on the plate and comprising a plurality of unit cells configured to form a plurality of variable alignment marks,
wherein the variable diffraction grating is configured to match the wafer alignment mark in order to calibrate a shift-between-orders of one of the variable alignment marks and the fixed alignment mark.