US2241432A - Electron scanning microscope - Google Patents

Electron scanning microscope Download PDF

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Publication number
US2241432A
US2241432A US228776A US22877638A US2241432A US 2241432 A US2241432 A US 2241432A US 228776 A US228776 A US 228776A US 22877638 A US22877638 A US 22877638A US 2241432 A US2241432 A US 2241432A
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United States
Prior art keywords
electron
scanning
layer
recording
spot
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Expired - Lifetime
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US228776A
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English (en)
Inventor
Ardenne Manfred Von
Borries Bodo Von
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/02—Details
    • H01J37/22—Optical, image processing or photographic arrangements associated with the tube
    • H01J37/224—Luminescent screens or photographic plates for imaging; Apparatus specially adapted therefor, e. g. cameras, TV-cameras, photographic equipment or exposure control; Optical subsystems specially adapted therefor, e. g. microscopes for observing image on luminescent screen
    • D—TEXTILES; PAPER
    • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
    • D04B—KNITTING
    • D04B15/00—Details of, or auxiliary devices incorporated in, weft knitting machines, restricted to machines of this kind
    • D04B15/66—Devices for determining or controlling patterns ; Programme-control arrangements
    • D04B15/68—Devices for determining or controlling patterns ; Programme-control arrangements characterised by the knitting instruments used
    • D04B15/78—Electrical devices
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/02—Details
    • H01J37/20—Means for supporting or positioning the object or the material; Means for adjusting diaphragms or lenses associated with the support
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/26—Electron or ion microscopes; Electron or ion diffraction tubes
    • H01J37/28—Electron or ion microscopes; Electron or ion diffraction tubes with scanning beams
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
    • H01J2237/26—Electron or ion microscopes
    • H01J2237/28—Scanning microscopes
    • H01J2237/2802—Transmission microscopes

Definitions

  • the invention relates to electron microscopes and more particularly to such microscope in which the object to be tested is scanned by an electron beam of small diameter and the electrons, passing through the object, or the electrons diffracted, dispersed or reflected on by the object, or the secondarily released electrons are employed to compose the image of the object from individual points.
  • the electron energy modulated in the above-mentioned manner by the structure of the object is directly recorded with the aid of a photographic layer which, during the scanning movement of the electron beam, efiects a proportional movement of greater amplitude.
  • the advantage is attained that not only the stream of the electrons but also the electron power comes into action which in the case of a scanning microscope may assume relatively high values owing to the application of anode voltages of several thousand volts.
  • the invention presents the further advantage that the recording is highly sensitive and permits an integration for considerable periods.
  • the electron beam is sharply concentrated onto the object by means of an electron-optical reduction system whose pole pieces are arranged but a few millimeters away from the object.
  • the invention further provides that the movable photographic layer is arranged directly behind the object to be tested, or that a suitably screened auxiliary lens is placed between the object and the photographic layer in order to reconcentrate the electrons.
  • the latter method leads to great chromatic aberrations, since the speed of the electrons after they have passed through the object is non-homogeneous.
  • an auxiliary lens between the object and the electron indicator has not only the advantage of rendering the construction simpler but also oifers the important advantage that an additional after-acceleration is brought about in order to increase the kinetic energy of the electrons, so that the electron speed is again homogenized.
  • an afteracceleration of the modulated electron beam may be advantageous for the last-mentioned reason.
  • an image of the object may also be directly obtained if as in the case of picture transmission the position of the photographic layer to be recorded is so changed with respect to the electron spot or also the position of the electron spot to be recorded is so changed by means of auxiliary deviating fields with respect to the photosensitive layer that an undistorted image of the structure of the object under observation is directly produced on the photosensitive layer.
  • the amplitudes of deflection for the X and Y direction must have a proper ratio with respect to each other and must also maintain certain absolute magnitudes in order that an undistorted proper image be recorded.
  • Fig. 1 represents a sectional elevation of the electron-optical magnifying and recording system of an electron scanning microscope accord ing to the invention
  • Fig. 2 shows a diagram of an entire arrangement according tothe invention, including the electric circuits necessary for producing the scanning movement of the beam and for simultaneously and proportionally operating the movable recording means.
  • the vacuum vessel of the microscope is designated by 30. It contains a source 3
  • the object to be examined is located at 5.
  • the beam after having passed through the object so as to be modified thereby, leaves the vacuum vessel through a Lenard window 6 and impinges upon a recording drum I I carrying a photosensitive layer.
  • An optical lens system 33 serves to concentrate the beam so as to produce a sharp scanning spot in the plane of incidence of the object, this spot being considerably much smaller than the entire object surface so as to cover only a small fraction of the whole surface.
  • Scanning electrodes and I9 serve to move the beam and the scanning spot over the object surface so as to compose a point-for-point and line-for-line image.
  • pole piece I of the lens system 33 By designing the pole piece I of the lens system 33 in a novel manner it is possible to arrange the object 2 in the immediate neighborhood of the center of gravity of the optical system and at the same time to dispense with constructional elements laterally of the object which would prevent the arrangement of large photographic plates or of drums provided with photosensitive material.
  • the photosensitive layer should be arranged outside the vacuum chamber, which is not absolutely necessary for carrying out the invention, it is preferable to choose said bore as well as the diameter of the object very small; for instance, T 5 mm. in diameter in order that the Lenard window necessary in this case presents a thickness as small as possible. Practical tests have shown that it is preferable to employ a Lenard window 5 consisting of a collodion film of l0 to 10* mm.
  • the collodion film Immediately behind the collodion film follows the diaphragm 6, which may under given circumstances be omitted, and then the photosensitive layer 1 arranged on a drum as shown in Fig, 1. If the photosensitive layer is not arranged in a vacuum chamber but is exposed to the open air it is important that this layer be guided with very great mechanical precision so that it remains as close as possible to the Lenard window in order to attain high electron densities as well as to avoid absorption losses. If this layer is arranged in the vacuum chamber the foil 5 then serves only as an object holder and may therefore be thinner than the above-mentioned him by l to 2 orders of magnitude.
  • a very important problem in the photographic recording is the control of the focussing of the electron spot on the plane of the object under examination. This control which would otherwise only be possible after the development of the photographic film, is facilitated by the use of an auxiliary fluorescent screen 8, an optical mirror 9 and a microscope it as shown in Fig. 1 in dotted lines.
  • This focussing unit is employed before placing the photosensitive layer in the path of the electron beam to recognise the variations of the amounts of electrons when slowly scanning the object from the fluctuations of the fluorescence. The more marked the fluctuations appear with a constant scanning speed and a constant fine structure of the object, the sharper the electron spot is adjusted on the object.
  • a Wollaston wire of, for instance, A; microns in thickness is arranged in the plane of the section through the object, 1. e., on the supporting foil of the object across the field of view and the degree of the darkening must be measured when the electron spot passes over the wire.
  • the coloring agent or the protection against light must be so chosen that a subsequent removal thereof is rendered possible so that the blackening brought about by the electron efiects becomes perceptible.
  • the electrons have even in the case of the aforem ntioned light screening still approximately the full penetrating power at the prevailing voltages of the scanning microscope, so that the sensitivity of the actinic layer to the electron effects is not materially impaired by the screening.
  • the application of the light-sensitive material to a drum has the advantage over the plane arrangement that the recording direction of the image is always the same and that in the case of a spiral advancement of the drum both image point coordinates are simultaneously controlled by a single drive. This rigid coupling is also the reason why the recording on a drum has come into extensive use in image telegraphy.
  • Fig. 2 shows by way of example the electrical connection for photographic drum recording in connection with an electron scanning microscope.
  • the drum ll provided with the photographic layer is driven by means of a motor I2 in such a manner that upon each rotation the drum advances by the width of a line in front of the electron focal point of the scanning microscope.
  • On the driving shaft of the drum is arranged a contact wheel l3 which during each rotation short-circuits the capacitor l4 only once and always at exactly the same phase angle.
  • the capacitor l4 and the beam deflecting plates l5 of the scanning microscope are arranged in parallel relation to and connected with a direct current source 2!.
  • An adjustable resistor I6 is par allel-connected with the capacitor. When a contact is made at disk l3, capacitor I4 is shortcircuited and discharged.
  • the capacitor is supplied with a constant current through resistor l6 and gradually charged thereby.
  • the voltage between the deflecting plates l5 increases accordingly so that the electron beam is gradually deflected until the next discharge of capacitor l4 occurs.
  • the contact of the potentiometer resistance I8 is moved by the drum drive rigidly coupled therewith through the reduction gear H the movement occurring in accordance with the number of lines.
  • the potentiometer contact advances by a further step and consequently controls the voltage for the slow ordinate deflection plates I9 of the microscope deflecting system.
  • the ratio of the XY deflections with respect to each other is so adjusted that no distortion is brought about.
  • Figs. 1 and 2 show only one of the several possible forms of the invention.
  • the use of an auxiliary lens in connection with after-acceleration and the use of auxiliary deflecting plates in front of the photographic layer ln connection with the recording on a plane photographic layer represent advantageous forms of the invention.
  • the advantage is obtained that no mechanically moved parts are employed and that a completely rigid coupling of the image point coordinates is attained by a simple electric parallel connection of the deflecting voltages or deflecting currents for either deflecting system XY.
  • Another way of recording consists in projecting the luminous spot of a fluorescent screen arranged directly behind the object by means of an optical system having a great luminous intensity on a light-sensitive layer and in then changing the position for the image synthesis.
  • This method is, however, limited to the use of considerable streams of electrons and limited due to the fact that a correspondingly smaller resolving power is involved owing to the losses due to the fluorescence and to the optical projection.
  • Electron scanning microscope having means for producing an electron beam, means for supporting an object in the path of the beam, means for concentrating said beam so as to produce a scanning spot on the object, means for moving said beam to scan the surface of the object, a recording member for accommodating a photosensitive layer, said recording member being arranged in the path of said beam behind the object and movable transversely to said beam, and mechanical control means connected with said recording member for moving said member in proportional relation to the scanning movements of said beam, yet with an amplitude greater than that of said movements, whereby an enlarged image of the object is produced upon said layer.
  • Electron scanning microscope having means for producing an electron beam, means for supporting an object in the path of the beam, means for concentrating said beam so as to produce a scanning spot on the object, scanning means for moving said beam to scan the surface of the 0bj ect, a movable recording member for accommodating a photosensitive layer, said member being disposed directly behind the object in the direction of the beam travel, means for directing the beam, modulated by the structure of the object, onto said sensitive layer to be recorded there, and mechanical control means connected with said recording member for moving said member relatively to said object in proportional relation to the scanning movements of said beam, yet with an amplitude greater than that of said scanning movements, said control means being electrically connected with said scanning means so as to operate in synchronism therewith, whereby an enlarged image of the object is produced upon said layer.
  • Electron beam scanning microscope comprising means for holding an object to be examined, means for producing an electron beam having a diameter of the order of 10- mm. in the plane of incidence at the object to be examined, scanning means for moving said beam to scan the surface of the object, a movable recording member for accommodating a photosensitive layer, means for directing the beam, modulated by the structure of the object, onto said sensitive layer, mechanical control means connected with said recording member for moving said member relatively to said object in proportional relation to the scanning movements of said beam, yet with an amplitude greater than that of said scanning movements, said control means being electrically connected with said scanning means so as to operate in synchronism therewith, whereby an enlarged image of the object is produced upon said layer, and an electric auxiliary field arranged between the object and said sensitive layer, for accelerating the electrons.
  • Electron beam scanning microscope comprising means for holding an object to be examined, means for producing an electron beam having a diameter of the order of 10- mm. at the object to be examined, electrostatic scanning means for deflecting said beam in perpendicular directions to scan the surface of the object, means for accommodating a photosensitive layer disposed behind the object in the direction of the beam travel, means for directing said beam, modulated by the structure of the object, onto said sensitive layer to be recorded there, mechanical control means for moving said layer relative to the object and transverse to the path of the beam, and electric control means for synchronously operating said electrostatic scanning means and said control means so as to move said photosensitive layer in proportional relation to the travel of the beam on said object, yet with an amplitude greater than said travel, whereby an enlarged image of the object is produced upon said layer.
  • Electron beam scanning microscope com prising a vacuum vessel, means in said vessel for producing an electron beam, means for holding an object to be examined, means for concentrating said beam so as to produce a scanning spot on the object to be examined, means for moving said beam to scan the surface of the object, an object carrier comprising a supporting film for the object disposed across the path of the beam and forming a Lenard window closing said vacuum vessel, a movable recording member arranged outside of said vessel for accommodating a photosensitive layer, said member being disposed in the path of said beam behind said ob ject carrier, and mechanical control means connected with said recording member for moving said member relatively to said object in propor tional relation to the scanning movements of said beam, yet with an amplitude greater than that of said scanning movements, said control means being electrically connected with said scanning means so as to operate in synchronism therewith, whereby an enlarged image of the object is produced upon said layer.
  • Electron beam scanning microscope com prising means for holding an object to be examined, means for producing an electron beam having a diameter of the order of 10* mm. at the object to be examined, scanning means for moving said beam to scan the surface of the object, a recording member for accommodating a photosensitive layer, said member being arranged in the path of said beam behind the object, mechanical control means connected with said recording member for moving said member relatively to said object in proportional relation to the scanning movements of said beam yet with an amplitude greater than that of said movemerits, said control means being electrically connected with said scanning means to operate in synchronism therewith in order to produce an enlarged image of the object on said layer, and electron-optical concentrating lens means disposed between said object and said sensitive layer.

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  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Textile Engineering (AREA)
  • Analysing Materials By The Use Of Radiation (AREA)
US228776A 1937-09-11 1938-09-07 Electron scanning microscope Expired - Lifetime US2241432A (en)

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Application Number Priority Date Filing Date Title
DE518951X 1937-09-11

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BE (1) BE430092A (en)van)
FR (1) FR843213A (en)van)
GB (1) GB518951A (en)van)
NL (1) NL53866C (en)van)

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2527562A (en) * 1945-08-02 1950-10-31 Raymond E Mccormick Apparatus for recording oscilloscopic signal traces
US2680815A (en) * 1950-12-28 1954-06-08 High Voltage Engineering Corp Method of and apparatus for treating substances with high energy electrons
US2680669A (en) * 1947-11-26 1954-06-08 Jr Ward Shepard Cathode ray multisignal measuring and recording apparatus
US2729748A (en) * 1950-08-17 1956-01-03 High Voltage Engineering Corp Apparatus for sterilizing foods, drugs and other substances by scanning action of high-energy electrons
US2839602A (en) * 1951-10-09 1958-06-17 Julius Cato Vredenburg Inglesb Method of and apparatus for recording pictures
US2894160A (en) * 1954-09-09 1959-07-07 Sheldon Edward Emanuel Electron microscopes
US2901627A (en) * 1953-02-19 1959-08-25 Leitz Ernst Gmbh Method of and apparatus for the electronic magnification of objects
US2932549A (en) * 1953-11-20 1960-04-12 Technicon Instr Method and apparatus for recording vectorcardiographs
US3025125A (en) * 1957-08-06 1962-03-13 Texaco Inc Method and apparatus for photographing oscilloscopic sweep magnified signals
US3346736A (en) * 1964-09-22 1967-10-10 Applied Res Lab Inc Electron probe apparatus having an objective lens with an aperture for restricting fluid flow
US3845305A (en) * 1972-05-12 1974-10-29 Max Planck Gesellschaft Microbeam probe apparatus
EP0022356A1 (en) * 1979-07-03 1981-01-14 Unisearch Limited Scanning electron microscope and detection configuration therefor
US20070111617A1 (en) * 2005-11-17 2007-05-17 Oxford Instruments Analytical Oy Window membrane for detector and analyser devices, and a method for manufacturing a window membrane
US20080095309A1 (en) * 2006-10-17 2008-04-24 Oxford Instruments Analytical Oy Compensation for fluctuations over time in the radiation characteristics of the X-ray source in an XRF analyser

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2527562A (en) * 1945-08-02 1950-10-31 Raymond E Mccormick Apparatus for recording oscilloscopic signal traces
US2680669A (en) * 1947-11-26 1954-06-08 Jr Ward Shepard Cathode ray multisignal measuring and recording apparatus
US2729748A (en) * 1950-08-17 1956-01-03 High Voltage Engineering Corp Apparatus for sterilizing foods, drugs and other substances by scanning action of high-energy electrons
US2680815A (en) * 1950-12-28 1954-06-08 High Voltage Engineering Corp Method of and apparatus for treating substances with high energy electrons
US2839602A (en) * 1951-10-09 1958-06-17 Julius Cato Vredenburg Inglesb Method of and apparatus for recording pictures
US2901627A (en) * 1953-02-19 1959-08-25 Leitz Ernst Gmbh Method of and apparatus for the electronic magnification of objects
US2932549A (en) * 1953-11-20 1960-04-12 Technicon Instr Method and apparatus for recording vectorcardiographs
US2894160A (en) * 1954-09-09 1959-07-07 Sheldon Edward Emanuel Electron microscopes
US3025125A (en) * 1957-08-06 1962-03-13 Texaco Inc Method and apparatus for photographing oscilloscopic sweep magnified signals
US3346736A (en) * 1964-09-22 1967-10-10 Applied Res Lab Inc Electron probe apparatus having an objective lens with an aperture for restricting fluid flow
US3845305A (en) * 1972-05-12 1974-10-29 Max Planck Gesellschaft Microbeam probe apparatus
EP0022356A1 (en) * 1979-07-03 1981-01-14 Unisearch Limited Scanning electron microscope and detection configuration therefor
US20070111617A1 (en) * 2005-11-17 2007-05-17 Oxford Instruments Analytical Oy Window membrane for detector and analyser devices, and a method for manufacturing a window membrane
US7618906B2 (en) 2005-11-17 2009-11-17 Oxford Instruments Analytical Oy Window membrane for detector and analyser devices, and a method for manufacturing a window membrane
US20080095309A1 (en) * 2006-10-17 2008-04-24 Oxford Instruments Analytical Oy Compensation for fluctuations over time in the radiation characteristics of the X-ray source in an XRF analyser
US7474730B2 (en) 2006-10-17 2009-01-06 Oxford Instruments Analytical Oy Compensation for fluctuations over time in the radiation characteristics of the X-ray source in an XRF analyser

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Publication number Publication date
NL53866C (en)van)
GB518951A (en) 1940-03-12
BE430092A (en)van)
FR843213A (fr) 1939-06-28

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