Apparatus for detecting or collecting secondary electrons, charg

Details Apparatus for detecting or collecting secondary electrons, charg Apparatus for detecting or collecting secondary electrons, charg

1998-02-03

1999-11-09

Westin, Edward P.

Radiant energy

Inspection of solids or liquids by charged particles

Electron probe type

250397, H01J 3728

Patent

active

059819472

ABSTRACT:
Apparatus and methods are disclosed for performing highly precise mark detection by obtaining a large signal as a result of the efficient capture of secondary electrons (SEs) emitted from a surface of a specimen. A charged-particle beam is directed at a location (e.g., a mark) on the specimen (e.g., reticle or wafer). SEs emitted from the location are detected using one or more secondary-electron collectors or detectors. To guide the SEs toward the secondary-electron collectors or detectors, a magnetic flux is created that extends radially outward in the vicinity of the surface of the specimen. E.g., an objective lens is situated above the specimen adjacent the specimen surface, and an electromagnetic lens is placed below the specimen adjacent the lower surface of the specimen. The magnetic fields produced by these lenses can be mutually repulsive to form a resultant magnetic flux near the upper surface of the specimen that extends radially outward parallel with the upper surface of the specimen. Thus, electrons can escape only radially outward parallel to the sample surface to the secondary-electron collectors or detectors. The apparatus provides a stable charged-particle beam without charging because the SE collector or detector removes SEs from the vicinity of the optical axis.

REFERENCES:
patent: 5412210 (1995-05-01), Todokoro et al.
patent: 5594245 (1997-01-01), Todokoro et al.
patent: 5872358 (1999-02-01), Todokoro et al.
Kato et al., "A Beam Drift Reduction Device for the X-Ray Mask E-Beam Writer, EB-X2," Jpn. J. Appl. Phys. 35:6429-6434 (1996).
Kato et al., "Beam Position Stabilization by Suppression of Electrons Reentering the Electron-Beam Column," J. Vac. Sci. Technol. 13:2450-2454 (1995).

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