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:
Mar. 25, 1997
Filed:
Mar. 18, 1996
Atsushi Kobaru, Hitachinaka, JP;
Tadashi Otaka, Hitachinaka, JP;
Tatsuya Maeda, Hitachinaka, JP;
Katsuhiro Sasada, Hitachinaka, JP;
Hitachi, Ltd., Tokyo, JP;
Abstract
An electron beam is focused on a specimen by a focusing lens. A light beam is incident on the position of irradiation of the specimen with the electron beam and the reflected light beam is detected by a linear light detector. The output of the detector is used to measure the height of the specimen at the position of irradiation of the electron beam. The specimen is moved in a plane perpendicular to an optical axis of the focusing lens. A specimen height measuring device carries out the height measurement of the specimen at a position to be observed on the specimen and at positions thereon which are in the vicinity of the position to be observed, when those positions are located at the position of irradiation of the electron beam. The specimen height measuring device averages the measured values so as to produce a focusing correction signal on the basis thereof and controls the focusing lens on the basis of the focusing correction signal.