U.S. Philips Corporation

Carl-zeiss-stiftung

Ralf Degenhardt

Harald Rose

Karel D Van Der Mast

Dirk Preikszas

An electron beam apparatus is provided with an energy selective device which enables spectrometric measurements together with imaging. The energy selective device has its main electron beam trajectory in a plane outside the optical axis of the electron beam apparatus, thereby substantially reducing the overall length of the apparatus. Preferably the energy selective device has double symmetry such that the energy dispersion has a maximum value in a central plane of symmetry where a selective slit can be introduced. Full symmetry facilitates full compensation of optical aberrations in the device. Adding quadruples in a second plane of symmetry enables imaging of spectra at a location outside the device.

Electron beam apparatus

The invention relates to an imaging system for charged particles having a correction unit for correcting an objective lens. The correction unit essentially includes a beam deflector and a mirror which reflects the incoming particle beam. A first symmetry plane of the deflector is imaged in the mirror. The mirror images this first symmetry plane at an imaging scale of 1:1 in a second symmetry plane of the deflector. At the same time, the symmetry planes are either intermediate image planes or diffraction planes. With the high symmetry of the imaging system, the condition is achieved that the aberrations of the second order caused by a one-time passthrough through the deflector are cancelled after the second passthrough. The mirror can be so adjusted that its negative chromatic aberration compensates for the chromatic aberration of the objective lens and the other lenses. The spherical aberration can be compensated independently thereof with the aid of a hexapole which is centered in a diffraction plane.

Growing community of inventors

Offenbach, Germany

Ralf Degenhardt