Abstract: A high resolution scanning electron microscope collects secondary Auger electrons through its objective lens to sensitively determine the chemical make-up with extremely fine positional resolution. The system uses a magnetic high resolution objective lens, such as a snorkel lens or a dual pole magnetic lens which provides an outstanding primary electron beam performance. The Auger electrons are deflected from the path of the primary beam by a transfer spherical capacitor. The primary beam is shielded, by a tube or plates, as it traverses the spherical capacitor to prevent aberration of the primary beam and the external wall of the shield maintains a potential gradient related to that of the spherical capacitor to reduce aberration of the primary electron beam. The coaxial configuration of the primary electron beam and the collected secondary electron beam allows the Auger image to coincide with the SEM view.

Abstract: The current of secondary electrons emanating from the specimen 14 in an ESEM is amplified by an avalanche-like ionization of the molecules 41 of the gas atmosphere. However, in order to achieve an adequate number of successive ionizations, a comparatively high voltage is required at the detector electrode 30 and, because of the risk of electric breakdowns, the distance between the specimen and the detector may not be smaller than a comparatively large minimum distance. Consequently, the number of successive ionizations is limited and hence also the current amplification. In order to achieve a higher amplification, the invention proposes the application of an additional magnetic field B in the ionization space. The path length of the secondary electrons is thus substantially increased so that a significantly larger number of ionizations takes place and hence a higher amplification is achieved.

Abstract: A high resolution scanning electron microscope collects secondary Auger electrons through its objective lens to sensitively determine the chemical make-up with extremely fine positional resolution. The system uses a magnetic high resolution objective lens, such as a snorkel lens or a dual pole magnetic lens which provides an outstanding primary electron beam performance. The Auger electrons are deflected from the path of the primary beam by a transfer spherical capacitor. The primary beam is shielded, by a tube or plates, as it traverses the spherical capacitor to prevent aberration of the primary beam and the external wall of the shield maintains a potential gradient related to that of the spherical capacitor to reduce aberration of the primary electron beam. The coaxial configuration of the primary electron beam and the collected secondary electron beam allows the Auger image to coincide with the SEM view.

Abstract: Amplification of the current of secondary electrons emanating from the specimen 14 is realized in an ESEM by avalanche-like ionization of the molecules 41 of the gas atmosphere. However, in order to achieve an adequate number of successive ionizations, a comparatively high value of the electric field at the detector electrode 46 is required and, because of the risk of electric breakdowns, the distance between the specimen and the detector electrode may not be smaller than a comparatively large minimum distance. The number of successive ionizations, and hence the current amplification, is thus limited. The invention proposes to configure the electric field of the detector 46, 50, co-operating with the magnetic field 52 of the immersion lens 8 already present in the ionization space, as an electric multipole field. In the case of electric multipoles, at a given field strength on the optical axis the electric field strength outside the optical axis may be substantially higher.

Abstract: In an electron microscope it is sometimes important that specimens can be studied at a very low temperature (for example, that of liquid helium). In the case of known specimen holders the specimen is cooled by supplying the cooling medium via a bore in the specimen holder; this causes thermal drift of the removed specimen holder each time when a specimen is exchanged, and also an acoustic coupling (i.e. transfer of vibrations) exists with the dewar vessel connected to the specimen holder. In accordance with the invention, the specimen is arranged on the end 20 of the specimen holder 7 by means of a separate transport unit 13, 36 so that it is not necessary to remove the specimen holder 7 in order to exchange a specimen, with the result that the specimen holder is not heated. Moreover, the coupling to the cold source 22, 28 can take place via a flexible cooling conduit 30 which extends directly to the end 20 to be cooled and may be permanently connected thereto, thus avoiding the transfer of vibrations.

Abstract: Particle-optical rotationally symmetrical lenses inevitably have chromatic aberration. This lens fault determines the limit of the resolution of known particle-optical apparatus at a comparatively low acceleration voltage (0.5 kV to 5 kV) of the particle beam. This lens fault cannot be eliminated by compensation by means of rotationally symmetrical fields. In order to enhance the resolution of the particle-optical apparatus nevertheless, it has already been proposed to mitigate said lens fault by means of a Wien type corrector. Such a known configuration is provided with a number of electrical and magnetic multipoles. In order to achieve easier adjustment of the various multipole fields, the pole faces (30-i) governing the multipole fields according to the invention have a specific length L=(2.pi..sup.2 n.sup.2)/(K.sub.obj.sup.2 C.sub.c,obj), in which K.sub.obj is the strength of the focusing lens to be corrected and C.sub.c,obj is the coefficient of chromatic aberration of this lens.

Abstract: The focusing device 8 for the primary beam in a scanning electron microscope (SEM) consists in known manner of a combination of a magnetic gap lens 34 and a monopole lens 38. The secondary electrons released from the specimen are detected in accordance with the invention by a detector whose deflection unit 52, or the actual detector 64, 66, is arranged in a field-free space between the gap lens and the monopole lens. This space is rendered field-free by a screening plate 44 arranged underneath the gap lens. In order to achieve a high detector efficiency and a large field of vision, the pole tip of the focusing device 8 is provided with an attraction electrode 42 whose potential is higher than that of the specimen.

Abstract: 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.

Abstract: A method and apparatus for selecting the spatial energy spread of an electron beam for producing an image of an object, as in an electron microscope. An energy-dispersive member is arranged in the vicinity of the electron beam source to widen the electron beam in a dispersion direction. Selection of an energy dispersion within the beam is achieved by selecting a number of pixels having such a local energy dispersion in the image plane of the object.

Abstract: In an electron microscope correction of spherical and chromatic aberration can be achieved in a number of freely adjustable directions by using a multipole correction element whereby a magnetic or electrostatic octupole field, rotatable about the optical axis, or a combined rotatable magnetic and electrostatic quadrupole field is generated. A corrected overall image can be obtained by combination of images successively corrected in different directions. In the case of holographic images, correction in the direction perpendicular to the line direction in the hologram enhances the accuracy of phase determination. A correction element of this kind, having comparatively small dimensions of from 1 to 2 cm, can be simply mounted, notably in a transmission electron microscope, in a space provided for the stigmator.

Abstract: A charged-particle beam apparatus comprises a beam splitting/alignment system whereby individual beams or groups of individual beams can be independently aligned so that they can be brought out of focus in a focal plane of the individual beams, so that a beam limiting diaphragm arranged at that area is irradiated more uniformly with a smaller beam loss.

Abstract: A Variable Axis Lens system comprises at least two lenses which are arranged to be radially offset with respect to an optical axis of the apparatus. Because the lenses do not contain iron, the occurrence of disturbing eddy currents can be prevented. The lenses for axis displacement are preferably constructed as single ring conductors, a number of which can be readily arranged in one plane in a partly overlapping fashion. Such a system can also be arranged behind the object. For the lenses for axis displacement use is preferably made of a ceramic superconducting material having a comparatively high temperature coefficient and a comparatively high specific heat in the superconducting phase, so that they can be simply cooled from the outside.

Abstract: An electron image projector for transferring mask patterns onto a semiconductor wafer comprises a patterned photo-emissive cathode mask (1) and a target (3) such as a semiconductor wafer (11) coated with an electron sensitive resist (10). Accelerated by a uniform electric field E and focussed by a uniform magnetic field H a patterned electron beam is projected from the cathode onto the target with unity magnification. The electric field E is at least mainly established between the cathode and the target A foil is provided for protecting the photocathode against poisoning by gas liberated from the target upon electron beam bombardement. To avoid adversely influencing the imaging electron beams the foil may be constituted as a metal foil with a thickness of about 0,1 .mu.m for 25 kV electrons.

Abstract: An electron beam apparatus comprising a semiconductor electron emitter whose emissive surface dimensions are determined by dimensions of a p-n junction provided in the semiconductor element. By optimizing the dimensions of the emissive surface in relation to the electron-optical properties of the apparatus, an emitter is realized which combines optimum beam formation or imaging with a sufficiently large beam current and a high beam current density as required by the apparatus.

Abstract: In a beam shaper superpositions of a deformed first diaphragm and a deformed or non-deformed second diaphragm can be realized by means of a quadrupole system. As a result of this a great freedom for adapting the spot cross-section to the patterns to be formed is obtained, as a result of which the number of writing pulses per pattern and hence the writing time for, for example, a chip can be considerably reduced and in particular non-orthogonal and non-linear transistions in the patterns can be written with greater definition.

Abstract: By using, in beam path correction, a three-point adjustment of the beam wobbler, the beam path can be optimized for realizing minimum picture errors in the apparatus. For different lens energizations a picture-shifting correction can simply be carried out dynamically.

Abstract: An apparatus for energy-selective visualization of a beam of charged particles emerging from an object is equipped with a double-focusing energy analyzer which is provided with a two-dimensional entrance diaphragm. For visualization of both an image and a spectrum, an optical imaging system behind the analyzer is preferably equipped with one or more quadrapole lenses. An illumination system for an object to be examined is preferably equipped with a system for a sequential partial illumination of the object.

Abstract: In a semiconductor cathode, the electron-emitting part of a pn junction is provided in the tip of a projecting portion of the semiconductor surface which is situated within an opening in an insulating layer on which an acceleration electrode is disposed. Due to the increased electric field near the tip, a reduction of the work function (Schottky effect) is obtained. As a result, cathodes can be realized in which a material reducing the work function, such as caesium, may be either dispensed with or replaced, if required, by another material, which causes lower work function, but is less volatile. The field strength remains so low that no field emission occurs and serarate cathodes can be driven individually, which is favorable for applications in electron microscopy and electron lithography.

Abstract: In order to find criteria for the adjustment of an optimum focus, lens correction, specimen shift and the like, measurements are performed by means of a beam wobbler and the corresponding generation of a variable F(s)=.THETA..vertline.(Xi-Yi+s).vertline.* in order to determine that s-value for which F(s) is a minimum. Using this image shift value is then used to make a correction preferably automatically.

Abstract: A switchable auxiliary lens is arranged in the vicinity of the objective lens of an electron microscope to enable switching between TEM mode and STEM mode. The auxiliary lens may be formed by an interruption in the magnetic circuit of one of the poles of the main lens, and may include an electromagnetic coil which can be excited in a reversable manner.