Ceos Corrected Electron Optical Systems Gmbh

Other

Siemens Aktiengesellschaft

Joachim Zach

Harald Rose

Burkhard Lischke

Stephan Uhlemann

Matthias Kallenbach

Harald Prof Rose

A corrector () for an electron microscope is proposed which is less sensitive to fluctuations of the electrical power supply if a stigmatic intermediate image () of the axial fundamental rays (x, y) is produced in the quadrupole field (') of a first quadrupole element () and this quadrupole field (&#x2032;) is set such that astigmatic intermediate images () of the off-axial fundamental rays (x, y) are produced in the region of the center of the quadrupole fields (&#x2032;) of a third () and fourth multipole element () and there also, due to the setting of the quadrupole field (&#x2032;) of a second quadrupole element (), the axial fundamental rays (x, y) of the same section (x, y) as that, in which the intermediate images () of the off-axial fundamental rays (x, y) are located, each exhibit a maximum.

Corrector

The invention concerns a corrector () for chromatic and aperture aberration correction in an electron microscope with six multipoles () which are disposed in the optical path () one after the other symmetrically with respect to a symmetry plane () for generating quadrupole fields (') and octupole fields, wherein the quadrupole fields (&#x2032;) of all six multipoles () are consecutively rotated through 90&#xb0; with respect to one another, thereby generating a mirror-symmetrical exchange symmetry of the axial fundamental rays (x&#x3b1;, y&#x3b2;). In accordance with the invention, the following is provided for correcting azimuthal coma:

According to the invention, the image contrast in electron optics can be improved without causing aberrations that are no longer tolerable by using, for production and correction of the at least one anamorphic image, quadrupole fields before and after this image whose extent in the direction of the optical axis is equal to at least twice their focal length, and wherein at least one of the axial rays, by an appropriate choice of the magnification M of the intermediate image, enters the quadrupole field before the at least one anamorphic image at a slope 1/M such that a length of the anamorphic image is achieved at which any aberrations caused are still within a tolerable range. The invention also relates to devices for implementing this method.

Method for producing image contrast by phase shifting in electron optics

The invention concerns a phase plate for electron optical imaging, wherein the zero beam () is phase-shifted in order to obtain an image with optimum contrast through interference with the diffracted electron beams (). The shading of diffracted electron beams () is kept to a minimum and shading that cannot be reconstructed from the obtained image data is prevented. This is achieved in that the electrode () is designed as a shielded conductor (), which is disposed to extend from a mounting () in a substantially radial direction towards the area of the zero beam (), wherein the shielded conductor () has an end () in front of the area of the zero beam () such that a field () is formed between the conductor () and the shielding () surrounding it, which overlaps this area. The invention also concerns an imaging method for complete reconstruction of the image and an electron microscope () which is provided with the phase plate ().

Phase plate, imaging method, and electron microscope

A corrector () for the axial and off-axial beam path of a particle-optical system, comprises a first () and a second () correction piece, which are disposed one behind the other in the beam path () on an optical axis (). Each correction piece () comprises four successive multipole elements () disposed symmetrically with respect to a center plane () and with the following fields: wherein the first () and the fourth () multipole elements of the multipole elements () are used to generate quadrupole fields (') and the second () and third () are used to generate octupole fields (&#x2032;&#x2033;) and quadrupole fields (&#x2032;), wherein the latter are superposed magnetic () and electric fields (&#x2033;), wherein the quadrupole fields (&#x2032;) of all four multipole elements () are rotated from one to the next through 90&#xb0;. An astigmatism of third order is corrected by a central multipole element disposed in the center plane and generating an octupole field.

Corrector for axial and off-axial beam paths

Multipole coils () for influencing particle beams have at least two coils () which concentrically enclose an imaginary axis (), wherein a winding () made from a flexible circuit board () is formed by means of conducting paths () disposed thereon for each coil () and the circuit boards () are rolled into at least one circuit board layer (). Multipole coils of this kind () are utilized for aberration correction in particle optics, wherein the windings () of the multipole coils () form windows () whose width in the peripheral direction is chosen in such a fashion that no secondary interfering fields occur and whose length in the axial direction corresponds at least to its width.

Multipole coils

The invention concerns a corrector () for chromatic and aperture aberration correction in a scanning electron microscope or a scanning transmission electron microscope, comprising four multipole elements () which are consecutively disposed in the optical path (), the first () and fourth () of which are used to generate quadrupole fields () and the second () and third () of which are used to generate octupole fields () and quadrupole fields (), wherein the latter are superposed magnetic () and electric () fields, and wherein the quadrupole fields () of all four multipole elements () are successively rotated with respect to one another through 90&#xb0;. Elimination of errors up to fifth order can be realized with a corrector () of this type in that the second () and the third () multipole elements are designed as twelve-pole elements, and an additional twelve-pole element () is inserted between the second () and the third () multipole element, and is loaded with current and/or voltage, such that an octupole field () is generated that is superposed by a twelve-pole field ().

The invention relates to a method for determining geometrical-optical aberrations up to and including 3rd order in particle-optical, probe-forming systems, in particular scanning electron microscopes, comprising an essentially punctiform source, lenses, an object, and a detector, the image being recorded, the process being repeated with an overfocussed and an underfocussed beam, the images being transformed in Fourier space, the transformation of the overfocussed image, and the underfocussed image is divided by the transformed focussed image. The results are reverse transformed, and the brightness profiles of the probes, the images of the source, are determined in overfocus and underfocus. The asymmetry, the width and/or the curvature of the profile being determined in the center, and the image aberration being determined from the differences.

Method for detecting geometrical-optical aberrations

In a high resolution imaging system for close inspection of sub-micrometer structures, a scanning electron microscope includes a detector objective essentially composed of an immersion lens and an annular detector which is arranged between a source side electrode lying at a positive potential and a middle electrode of the immersion lens which likewise lies at a variable positive potential and is arranged concentrically relative to a beam axis of a scanning microscope. The middle electrode and the source side electrode are preferrably formed as truncated cones. The two-stage deflection element for positioning the primary electron beam on the specimen is preferrably integrated into the source side electrode of the immersion lens, the source side electrode being composed of an annular diaphragm and a hollow cylinder.

Detector objective for scanning microscopes

An electron beam apparatus has a primary beam directed onto a point of a specimen to generate emerging secondary electrons that proceed to a detector after traversing an electrical extraction field. The extraction field is provided between electrodes arranged in a plane perpendicular to the optical axis of the electron beam device and a magnetic field is provided perpendicular to the electrical extraction field to compensate for the forces of the extraction field exerted on the primary beam yet to promote extraction of the secondary electrons.

Arrangement for detecting secondary and/or backscatter electrons in an

In a corpuscular-optical beam path, the generation of short electron pulses with steep leading edges is to be effected without a probe movement in the probe plane taking place. For this purpose, the particle beam blanking system comprises at least two deflection systems and a knife edge arranged between two deflection systems in an intermediate image plane, the operating parameters of the deflection systems and the knife edge being matched to the energy distribution of the particles in such a fashion that shifting of the particle beam in the probe plane disappears.

Growing community of inventors

Oestringen, Germany

Joachim Zach