Jeol Ltd.

Kunihiko Uchida

Atsushi Yamada

Tsutomu Negishi

Mitsuru Yamada

Susumu Takashima

Kouichi Suefuji

Method and an apparatus for automatically moving the focal plane of the electron beam produced by a scanning electron microscope to the position of specimen surface. An auxiliary coreless coil of a low inductance is disposed close to the objective lens. The exciting current fed to the coil is varied to move the focal plane of the electron beam toward the optical axis. At each of discrete positions of the focal plane, a specimen is scanned with the electron beam. The resulting secondary electrons are detected by a detector. Individual output signals from the detector are compared to select the maximum signal. Then, only the objective lens is excited. The exciting current fed to the objective lens is modified to move the focal plane along the position closest to the specimen surface.

Method and apparatus for automatic focusing of scanning electron

There is disclosed a conical electromagnetic lens whose spherical aberration and chromatic aberration coefficients can be made small if the apex angle of the conical lens is small. The lens comprises a conical bobbin through which a beam of charged particles passes and a coil wound on the outer periphery of the bobbin. The number of turns of the coil per unit length along the axis of the lens is increased from the inlet end toward the exit end of the lens.

Growing community of inventors

Tokyo, Japan

Kunihiko Uchida