DE2915203A1 - ELECTRON MICROSCOPE - Google Patents

Description

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11/12/1978 * 1 PHN 9090

"Electron microscope"

The invention relates to an electron microscope with an electron gun for generating an electron beam, with an electron optical lens system, a slide, an electron detector and an image recording arrangement.

Such an electron microscope is known from US Pat

3 889 11 ^ known.

When one is separated in such an electron microscope a phase image and an amplitude image, it is necessary to generate a number of images one after the other generate or a possible radiographic grid method where several images can be generated at the same time. When using a transmission scanning electron microscope Although several images can be recorded at the same time and thus both phase contrast as well as amplitude contrast can be recorded, but one The disadvantage here is that radiographic raster images generally have a lower quality. if Radiographic and raster images combined must be, the quality of a composite image to be generated is in fact due to the comparatively inadequate Radiographic raster image determined. There is also generally the influence of product spoilage due to contamination larger in a transmission scanning electron microscope than in a scanning electron microscope.

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There is also the disadvantage that a user who has a high-resolution scanning electron microscope often not also using an equivalent scanning electron microscope disposes. In an electron microscope operating in raster mode, it is only possible to use images generated one after the other, both in phase contrast and in can also be recorded in amplitude contrast. An essential one The disadvantage here is that because of the temporally separated image recordings, for example due to contamination, 'vibrations, thermal displacements, etc. the images are unequal, as a result of which in the Composition large image errors occur. Also, it is nowhere near easy to get the pictures in as required to bring good recording (overlay) on top of each other, while the finally sought images always later can be generated and thus the possibility of on-line operation is excluded.

The invention is based on the object of creating an electron microscope with which on-line- ! Phase and amplitude images can be generated. The task is achieved in an electron microscope of the type mentioned in that between the electron gun and a beam tilting arrangement for intermittently switching the electron beam between the slide fixed adjustable angle positions with respect to an object to be exposed recorded and the image recording arrangement is arranged to merge images generated at each of the angular positions.

Since the beam in an inventive electron * "" microscope quickly, for example, between two positions can be switched, Bildex 'can be generated from both directions, for example by an integrating Effect of the recording arrangement can be put together.

™ . In a preferred embodiment according to the invention, the beam can be switched between two fixed positions and the image recording arrangement contains a television circuit, the image frequency of which is the switching frequency for the

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Electron beam corresponds. Adding or subtracting, the latter by broadcasting one of the image signals via a Inverse stage, - takes place through inertia in the television monitor or by the indolence of the eye.

In a further preferred embodiment, in particular for image subtraction an image subtraction arrangement with a nematic liquid crystal was added, whereby relatively large image areas can be processed. Such an arrangement describes, for example, the

^ publication "IEEE Transactions an Electronic Devices", Vol.ED 22, pp. 775 ... 783.

In a preferred embodiment according to the invention are two television monitors, one for phase contrast by subtracting individual images and one for amplitude contrast

' ⁵ trast by adding individual images, recorded. This means that both images can be seen at the same time. By using a color television circle, it is also possible to discriminate in terms of color, which results in easier visual perception.

Some preferred embodiments of electron microscopes according to the invention are explained in more detail below with reference to the drawing.

An electron microscope according to the scheme in the drawing contains an electron emitter 1 with an anode 2, a beam alignment system 3 (beam alignment) and a diaphragm h, a condenser system with a first condenser lens 6 and a condenser diaphragm 7> an objective with a first objective pole-8 and a second objective pole 9 »an object space 11, a diffraction lens 12 with a diffraction diaphragm

13> an intermediate lens 14, a projection system with a first projection lens 15 and a second projection lens 16, a film camera 17 and a detector 18. All these parts are in a housing 20 with an electrical lead 21 for the electron gun and an insight

window 22 added. A binocular loupe 23, a ventilation device? .H and a disk camera 25 are connected to the housing. According to the invention, there is now a beam tilting arrangement 26 in this electron microscope

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recorded, with the help of which the exposing electron beam can be switched between two positions in which each about half of the exposure diaphragm area is filled with incoherent radiation. This is, as it were, a raster analog differential detection in transmission raster mode according to the description in "Optik", 41 (i97 ^) Pp. 452 ... 456, realized. The beam tilting arrangement can also 26 be designed and mounted in such a way that with their help the electron beam between two in the objective

'"hide diametrically oriented positions for each oblique exposure of an object can be switched. Other methods can also be used if just taken care of that the exposure between two shots is between positions symmetrically located in the lens diaphragm is tilted. By exciting the beam tilting arrangement, preferably with a rectangular signal, the aforementioned are Disadvantages for a scanning electron microscope are eliminated and can be achieved with a sufficiently rapid change in the direction of the beam as measured in the radiographic grid mode.

The image signals generated can be viewed on a television monitor 3I are shown, which is also normally assigned to a scanning electron microscope. The monitor is there matched to an image frequency that corresponds to the tilt frequency, so that the same image is always displayed in turn

will. By integrating the eye or the phosphor of the television monitor, a total image is generated. To a To generate the difference image between the two partial images the images taken by one of the directional positions of the exposing Beam are generated via a reverse circuit

fed to the monitor. As a result, the images are shown in turn with positive and negative contrast. Intensity modulations from phase objects that are opposed without contrast reversal in two successive images would be through the contrast inversion in successive Images the same and visible during the image integration. By using a relatively high Image flickering can be avoided by tilting frequency or a relatively sluggish monitor phosphor.

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Instead of contrast reversal and a black and white monitor In another preferred embodiment according to the invention, the image is displayed with the aid of a color television monitor and generate complementary color signals for each of the partial images. In the successive fields For example, a red image with an unmodulated blue and a green signal and a blue and green image modulated together with an unmodulated red signal. Intensity modulations without this color modulation opposite in two consecutive images would now be visible in the same color because For example, an increase in the red signal in an image has the same discoloration as a decrease in the blue and green. Signal in the second picture. Other color combinations can also be selected for the color modulation. In general, the method with color modulation is more sensitive because discoloration against a white background are visually perceptible earlier than gray fluctuations in one Black and white image. For other than visual perceptions, however, this does not always have to be the case.

To tilt the exposing electron beam, in a preferred embodiment a beam tilting arrangement in the embodiment according to US Pat. No. 3,777,211 into the electron microscope between the electron beam and the objective lens, preferably not too close to the condenser lens. By the way, many electron microscopes are anyway executed with a beam directing element, such as a wobbler or a beam lifting element; these elements can can readily be used in connection with the invention.

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Claims (1)

T2-11.1978 1 PHN 9090 PATENT CLAIMS 1.) Electron microscope with an electron gun to generate an electron beam, with an electron optical Lens system, a slide, an electron detector and an image recording arrangement, characterized in that between the electron gun and a beam tilting arrangement (26) for intermittently switching the electron beam between the slide recorded fixed adjustable angular positions with respect to an object to be exposed and the image recording arrangement is arranged to merge images generated at each of the angular positions. 2. Electron microscope according to claim 1, characterized in that the beam tilting arrangement is designed in this way and that the electron beam can be excited in two angular positions is adjustable, with an objective diaphragm in mutually symmetrical parts in turn about halfway is exposed. 3 · Electron microscope according to claim 1, characterized in that that the tilting arrangement is set up and excitable in such a way that the electron beam is thus between two Angular positions can be switched, with the electron beam in two symmetrical positions in an objective diaphragm forms a narrowest diameter. H. Electron microscope according to one of the preceding claims, characterized in that the image recording 909843 / 0-913 11/12/78. 2 PHN 9090 arrangement contains a television monitor, the frame rate of which is adapted to the beam tilting frequency. 5. Electron microscope according to claim k, characterized in that the image signals can be fed to the television monitor as amplitude modulation. 6. Electron microscope according to claim k, characterized in that the television monitor is a «- color television monitor and the image signals can be displayed as color modulation on this monitor. 7. Electron microscope according to one of the preceding claims, characterized in that the detection arrangement is assigned an inversion stage for the phase inversion of one of the signals.
8. Electron microscope according to one of the preceding claims, characterized in that this electron microscope is assigned an image subtraction arrangement with a nematic liquid crystal. 9 · Electron microscope according to one of the preceding claims, characterized in that the image recording arrangement contains an image integrating element. 10. Electron microscope according to one of the preceding claims, characterized in that the image recording arrangement contains a separately readable memory for each of the two beam positions. 909843/0913