Lloyd W Denney

US Patent:

46635254, May 5, 1987

Filed:

Jul 8, 1985

Appl. No.:

6/752547

Inventors:

Mitsuo Ohtsuki - Sunnyvale CA
Lloyd W. Denney - Menlo Park CA

Assignee:

Nanometrics Incorporated - Sunnyvale CA

International Classification:

G01N 2300

US Classification:

250307

Abstract:

In an electron microscope employing a multi-element electrostatic lens and a position adjustable electron emission gun, the gun tip must be in precise alignment with the very small apertures in the lens elements for high resolution imaging. If the tip is precisely aligned, there will be no variations in displacement of an image if the lens element potentials are varied; if there is misalignment, the image displacement will vary with voltage variations. Thus, proper alignment of the gun tip is easily and rapidly achieved by varying the lens element potential with an oscillator while adjusting the position of the gun tip to a zero image variation.