The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Feb. 13, 2001
Filed:
Aug. 11, 1998
Michael Gordon, Lincolndale, NY (US);
Scott Messick, Pleasant Valley, NY (US);
Chris Robinson, Hyde Park, NY (US);
James Rockrohr, Hopewell Junction, NY (US);
Nikon Corporation, Tokyo, JP;
Abstract
Temperature dependency on magnetic field strength of an electron optical element in an electron beam system due to variation of permeability with temperature of a ferromagnetic pole piece subject to radiant heating from another electron optical element is corrected by measurement of pole piece temperature and closed loop control of excitation current of a correction element which may be provided as a portion of a lens, stigmator, deflector or the like. A correction function may be computed to extrapolate correction values from empirically determined correction values or correction values may be retrieved from a memory such as a look-up table. Performance of the electron beam system is improved and constraints on choice of pole piece materials, mounting geometry, relative positioning of electron optical column elements and electron optical column length are relaxed since temperature dependencies of many electron optical elements can be corrected.