US 12,444,630 B2
Single-material waveplates for pupil polarization filtering
Chong Shen, San Jose, CA (US); Guoheng Zhao, Palo Alto, CA (US); and Bret Whiteside, San Jose, CA (US)
Assigned to KLA Corporation, Milpitas, CA (US)
Filed by KLA Corporation, Milpitas, CA (US)
Filed on May 31, 2022, as Appl. No. 17/829,289.
Claims priority of provisional application 63/289,258, filed on Dec. 14, 2021.
Prior Publication US 2023/0187241 A1, Jun. 15, 2023
Int. Cl. H01L 21/67 (2006.01); G01N 21/88 (2006.01); G01N 21/95 (2006.01); G02B 5/18 (2006.01); G02B 5/30 (2006.01)
CPC H01L 21/67288 (2013.01) [G01N 21/8806 (2013.01); G01N 21/9501 (2013.01); G02B 5/1814 (2013.01); G02B 5/1819 (2013.01); G02B 5/1833 (2013.01); G02B 5/3083 (2013.01); G02B 5/3091 (2013.01); G01N 2021/8848 (2013.01)] 11 Claims
OG exemplary drawing
 
1. An optical inspection system, comprising:
a light source to emit ultraviolet light to illuminate a target;
an objective lens to collect ultraviolet light scattered from the target;
a plurality of single-material gratings to convert a polarization of the ultraviolet light scattered from the target from an elliptical polarization that varies spatially across a collection pupil to a linear polarization that is uniformly oriented across the collection pupil, wherein;
the plurality of single-material gratings has phase retardation that varies spatially across the collection pupil in accordance with the elliptical polarization,
the plurality of single-material gratings comprises a first one-dimensional grating and a second one-dimensional grating,
the first one-dimensional grating has a duty cycle that varies spatially across the collection pupil and an orientation that varies spatially across the collection pupil, and
the second one-dimensional grating has a duty cycle that varies spatially across the collection pupil and an orientation that varies spatially across the collection pupil; and
a linear polarizer to filter out the ultraviolet light having the linear polarization,
wherein the first one-dimensional grating and the second one-dimensional grating are disposed between the objective lens and the linear polarizer.