US 12,261,014 B2
Scanning electron microscope and objective lens
Motohiro Nakamura, Tokyo (JP); and Takeyuki Kobayashi, Tokyo (JP)
Assigned to JEOL Ltd., Tokyo (JP)
Filed by JEOL Ltd., Tokyo (JP)
Filed on Jul. 7, 2022, as Appl. No. 17/859,399.
Claims priority of application No. 2021-113476 (JP), filed on Jul. 8, 2021.
Prior Publication US 2023/0014270 A1, Jan. 19, 2023
Int. Cl. H01J 37/14 (2006.01); H01J 37/28 (2006.01)
CPC H01J 37/14 (2013.01) [H01J 37/28 (2013.01)] 9 Claims
OG exemplary drawing
 
1. A scanning electron microscope comprising:
an electron gun for emitting an electron beam;
an objective lens for focusing the emitted electron beam onto a sample; and
a sample chamber in which the sample is housed;
wherein the objective lens comprises an inner polepiece comprising an inner surface that defines an inner space through which the electron beam passes, an outer polepiece disposed outside the inner polepiece and facing the sample chamber, at least one through-hole extending through the inner and outer polepieces, and at least one cover member that closes off the through-hole;
wherein the objective lens causes leakage of magnetic field from an opening between the inner and outer polepieces toward the sample;
wherein the sample chamber has a degree of vacuum lower than that in an inner space that forms an electron beam path inside the inner polepiece; and
wherein one opening of the at least one through-hole is formed in the inner surface of the inner polepiece and another opening of the at least one through-hole is formed in an outer surface of the outer polepiece, the outer surface facing the sample chamber.