US 11,927,549 B2
Shielding strategy for mitigation of stray field for permanent magnet array
Qian Zhang, San Jose, CA (US); Wayne Chiwoei Lo, Campbell, CA (US); Joseph Maurino, Milpitas, CA (US); and Tomas Plettner, Milpitas, CA (US)
Assigned to KLA CORPORATION, Milpitas, CA (US)
Filed by KLA Corporation, Milpitas, CA (US)
Filed on Sep. 9, 2021, as Appl. No. 17/470,183.
Prior Publication US 2023/0076175 A1, Mar. 9, 2023
Int. Cl. G01N 23/20 (2018.01); G01N 23/20008 (2018.01); H01F 7/02 (2006.01); H05K 9/00 (2006.01)
CPC G01N 23/20008 (2013.01) [H01F 7/0273 (2013.01); H05K 9/0075 (2013.01); G01N 2223/052 (2013.01); G01N 2223/20 (2013.01); G01N 2223/30 (2013.01)] 20 Claims
OG exemplary drawing
 
1. An inspection system comprising:
an array of electron beam columns, each comprising an electron source configured to emit electrons toward a stage;
a first permanent magnet array configured to condense the electrons from each electron source into an array of electron beams, wherein the first permanent magnet array is arranged at a first end of the array of electron beam columns; and
a plurality of shielding plates extending across the array of electron beam columns downstream of the first permanent magnet array in a direction of electron emission;
wherein the plurality of shielding plates each comprise a plurality of apertures and have a thickness between 1 μm and 1 mm, and the array of electron beams pass through the plurality of apertures; and
whereby the plurality of shielding plates reduce stray magnetic field in a radial direction of the array of electron beams.