Patent ID: 8212227
Filing Date: 2012-07-03
Classification: B82Y,H01J

Abstract:
1. An electron beam apparatus equipped with a height detection system configured to assess a height of a specimen during use, comprising: an electron beam unit having an electron beam source for emitting an electron beam, an objective lens for controlling the electron beam, a table for setting a specimen, and a detector for detecting secondary charged particles emanated from the specimen by the irradiation of the electron beam emitted from the electron beam source and controlled by the objective lens; and a height detection system for detecting height of the specimen set on the table; wherein the height detection system includes: an illumination system configured to direct a first and a second beam of light through a mask with a multi-slit pattern to a surface of the specimen at substantially opposite azimuth angles and at substantially equal angles of incidence; first and second detectors, wherein the first detector is configured to detect a first multi-slit image by the first beam of light reflected from the surface of the specimen and to generate an output signal responsive to the detected first multi-slit image, and wherein the second detector is configured to detect a second multi-slit image by the second beam of light reflected from the surface of the specimen and to generate an output signal responsive to the detected second multi-slit image; and a device configured to receive the output signals from the first and second detectors and to generate a comparison signal from the output signals, the comparison signal being responsive to the height of the specimen; wherein the objective lens is controlled so as to focus the electron beam on the specimen by adjusting a focus control current or a focus control voltage of the objective lens in accordance with the comparison signal.