US3619607A - Electron microscope including an electromagnetic electron energy analyzing lens - Google Patents

Electron microscope including an electromagnetic electron energy analyzing lens Download PDF

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Publication number
US3619607A
US3619607A US49575A US3619607DA US3619607A US 3619607 A US3619607 A US 3619607A US 49575 A US49575 A US 49575A US 3619607D A US3619607D A US 3619607DA US 3619607 A US3619607 A US 3619607A
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lens
electron
energy
electron beam
cylindrical lens
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US49575A
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English (en)
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Takeo Ichinokawa
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J49/00—Particle spectrometers or separator tubes
    • H01J49/44—Energy spectrometers, e.g. alpha-, beta-spectrometers
    • H01J49/46—Static spectrometers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
    • H01J29/84—Traps for removing or diverting unwanted particles, e.g. negative ions, fringing electrons; Arrangements for velocity or mass selection
    • H01J29/845—Traps for removing or diverting unwanted particles, e.g. negative ions, fringing electrons; Arrangements for velocity or mass selection by means of magnetic systems
    • 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
    • H01J37/04—Arrangements of electrodes and associated parts for generating or controlling the discharge, e.g. electron-optical arrangement or ion-optical arrangement
    • H01J37/05—Electron or ion-optical arrangements for separating electrons or ions according to their energy or mass

Definitions

  • Apparatus for analyzing the energy of an electron beam in an electron microscope includes a cylindrical 4 Chums 4 Drawing Figs' lens of the magnetic field type inserted additionally or in place [52] U.S. Cl i. 250/49.5 A, of a conventional intermediate lens, and a slit member 250/49.5D cooperating with said cylindrical lens. said cylindrical lens [5] Int. Cl H0 lj 37/26 being excited under preselected conditions.
  • the present invention relates to an apparatus for analyzing the energy of an electron beam in an electron microscope or the like.
  • the analysis of the energy of an electron beam which has passed through a thin membrane or film of a sample, or of the beam which is scattered from a thick sample is useful for many applications such as analysis of the image produced in an electron microscope, measurement of scattering and absorption of electrons in a solid material, identification of material of an extremely small quantity, etc.
  • a cylindrical lens of the electrostatic type is used as the means for analyzing the energy of the electron beam.
  • the conventional apparatus of this kind has encountered many practical difficulties.
  • the electron beam analyzer lens occupies a great space due to its extremely large bulk and it is difiicult to install the lens in the column of the electron microscope.
  • the maintenance and the operation is not only difficult, but also the operation of the electron microscope becomes difficult, owing to the use of the electrostatic lens.
  • the apparatus can not be employed practically in applications where an electron accelerating voltage higher than 50 kv. is required.
  • the present invention contemplates the elimination of the difficulties to which the prior apparatus has been subject.
  • an important object of this invention is to provide a novel and improved apparatus for analyzing the energy of an electron beam in an electron microscope or the like.
  • Another object of this invention is to provide an apparatus for analyzing the energy of an electron beam, in which is employed under certain conditions a cylindrical analyzer lens of magnetic field type in place of the conventional electrostatic cylindrical lens.
  • the above object can be accomplishedcd by providing an apparatus for analyzing the energy of electrons scattered from or having passed through the sample.
  • said apparatus comprising an electromagnetic cylindrical lens interposed between an objective lens and a projection lens of the electron microscope and adapted to have applied thereto a strong excitation, and a slit member disposed in front of said cylindrical lens.
  • FIGS. 1A and B schematically show electron optical systems of an embodiment according to this invention under different excitations.
  • FIG. 2 is a schematic perspective view of a cylindrical lens portion employed in the optical systems shown in FIGS. IA and B, and
  • FIG. 3 is a graph to illustrate the relation between lens strength (excitation strength) of the cylindrical lens and offaxial chromatic aberration.
  • FIGS. IA and B the principle of this invention will be first explained.
  • Reference numeral 5 indicates an electron source which emits electron beam (e) of uniform energy.
  • the electron beam e thus emitted is thereafter collimated by a condenser lens 6 to form a narrow collimated beam.
  • a sample 7 is illuminated by this collimated electron beam and the image of the sample 7 is produced by an objective lens (8) on the plane of a slit member 4. The image thus produced is then formed by the lenses 3 and 9 on a fluorescent screen 11.
  • the velocity 83 electrons in the beam which has 64 through the sample 7 will be varied owing to the loss of energy such as caused by the inelastic scattering in the sample 7.
  • an analyzer lens 3 which cooperates with the slit member 4 to project that portion e, of the electron beam e which has passed through the slit 4 on the fluorescent screen 11 by way of the projecting lens 9, whereby the energy loss spectra, namely the image limited by the slit 4, are produced on the screen 11 depending on the variation of the amount of the energy loss.
  • the analyzer lens 3 of this invention is disposed in place of a conventional intermediate lens, and is composed of magnetic pole pieces 1, l and 2, 2 which are contoured and arranged so as to form a cylindrical configuration as a whole, as is clearly shown in FIG. 2.
  • This analyzer lens 3 is magnetically excited by the power source of the conventional intermediate lens.
  • the slit 4 is disposed normally to the refraction plane X of the electron beam.
  • FIG. 3 shows graphically the relation between the coefficient of off-axial chromatic aberration Cch of the magnetic cylindrical lens 3 and the lens strength or the excitation strength.
  • the chromatic aberration coefficient Cch is taken along the ordinate, while taken along the abscissa is the value Nl/ V whereinV is the voltage for accelerating the electron beam, N is the number of turns of the exciting coil and l is current.
  • eHoa in the circular symmetrical 8mVr lens or imaging lens wherein e charge of an electron m mass of an electron H0 maximum strength of magnetic field along the lens axis a a half-width of the magnetic field, and
  • the point B in the coordinates of FIG. 3 corresponds to the lens strength when k is three-fourths. This also corresponds to the lens strength when k is 3 in case of a circular symmetrical lens.
  • FIG. 1A shows the corresponding optical system attained when the excitation strength is smaller than at the point A
  • FIG. 18 shows the corresponding optical system when the excitation is stronger than that of the point B.
  • magnifications in the plane X, andin the plane Y perpendicular thereto, of the electron-microscopic image become equal to each other by selecting the area of the image.
  • the astigmatic aberration of the image in the planes X and Y will remain substantially negligible in practice, since the depth of focus of the objective lens 8 which produces the image on the slit member 4, is very large due to the inherent nature of the electron microscope. Accordingly, if the slit member 4 is removed, an image similar to that obtained by a conventional electron microscope is projected on the fluorescent screen 11. When observing such image, if the slit member 4 is inserted in parallel to the plane Y by utilizing a suitable device such as the image selecting aperture device usually mounted on a conventional electron microscope, the image limited by the slit is projected on the fluorescent screen l I.
  • This electron beam e is dispersed depending on the energy thereof, as shown in FIG. 2, because of the chromatic aberration of the lens 3. This operation is very simple and easily carried out as in the case of selected area difiraction.
  • the above dispersion 6 of the electron beam can be mathematically expressed as follows:
  • M is the magnification of the analyzer lens
  • r is distance from the axis of the magnetic cylindrical lens to the slit
  • Vr is the electron beam accelerating voltage corrected by the relativistic factor
  • AV is loss of energy of the electron beam in the sample.
  • pole pieces of a magnetic cylindrical lens are employed in place of those of the conventional circular lens when electron microscopic images are analyzed.
  • the present invention it is also possible to produce the electron-microscopic image by means of no loss electrons or loss electrons, using the energy selecting microscope method of the scanning type.
  • the present invention provides an apparatus for, analyzing the energy of the electron beam, which can be easily constructed simply by replacing the pole pieces of a conventional circular lens by the inventive cylindrical lens or by inserting additionally the analyzer lens. It has been experimentally confirmed already that the apparatus according to this invention exhibits an energy resolution of l ev. at accelerating voltage higher than 50 kv. The apparatus of this invention can be successfully applied to an ultrahigh voltage electron microscopev.
  • the present invention has been described with reference to preferably embodiments selected only by way of example. However, this invention is not restricted to such embodiment, and should be therefore broadly interpreted within the scope and spirit of the invention as defined in the claims.
  • apparatus for analyzing the energy of an electron beam in an electron microscope and having an electron source means for applying an accelerating voltage to electrons generated by said source, an objective lens, a projection lens and an intermediate lens between the objective and projection lenses; the improvement comprising an electromagnetically energized cylindrical lens; a slit member positioned in advance of said electromagnetically energized lens; and energizing means exciting said electromagnetically energized cylindrical lens with an excitation such that the square of the excitation parameter k is substantially three-fourths, which parameter k is given by the following expression lens.
  • said electromagnetically energized cylindrical lens includes two pairs of magnetizable pole pieces, each pole piece being semicylindrical and said pole pieces being arranged to form a substantially complete cylinder for passage of the electron beam between facing pole faces of the pole pieces of both pairs.

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  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Analysing Materials By The Use Of Radiation (AREA)
  • Electron Tubes For Measurement (AREA)
  • Electron Sources, Ion Sources (AREA)
US49575A 1967-03-30 1970-06-24 Electron microscope including an electromagnetic electron energy analyzing lens Expired - Lifetime US3619607A (en)

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JP1953467 1967-03-30

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US3619607A true US3619607A (en) 1971-11-09

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US49575A Expired - Lifetime US3619607A (en) 1967-03-30 1970-06-24 Electron microscope including an electromagnetic electron energy analyzing lens

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US (1) US3619607A (enrdf_load_stackoverflow)
DE (1) DE1639280C3 (enrdf_load_stackoverflow)
FR (1) FR1558166A (enrdf_load_stackoverflow)
GB (1) GB1226872A (enrdf_load_stackoverflow)
NL (1) NL153718B (enrdf_load_stackoverflow)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3863069A (en) * 1973-01-31 1975-01-28 Jeol Ltd Electron microscope with energy analyzer
US4068123A (en) * 1973-07-27 1978-01-10 Nihon Denshi Kabushiki Kaisha Scanning electron microscope
US4929838A (en) * 1988-02-16 1990-05-29 Fujitsu Limited Magnetic object lens for an electron beam exposure apparatus which processes a wafer carried on a continuously moving stage

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3256433A (en) * 1962-03-27 1966-06-14 Hitachi Ltd Energy-selecting electron microscope using electron optics
US3374346A (en) * 1964-07-15 1968-03-19 Hitachi Ltd Spectroscopic electron microscope wherein a specimen is irradiated with x-rays and the electrons emitted are energy analyzed

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3256433A (en) * 1962-03-27 1966-06-14 Hitachi Ltd Energy-selecting electron microscope using electron optics
US3374346A (en) * 1964-07-15 1968-03-19 Hitachi Ltd Spectroscopic electron microscope wherein a specimen is irradiated with x-rays and the electrons emitted are energy analyzed

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
Scanning Electron Diffraction with Energy Analysis, Denbigh et al., Journal of Scientific Instruments Vol. 42 No. 5, May 1965 *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3863069A (en) * 1973-01-31 1975-01-28 Jeol Ltd Electron microscope with energy analyzer
US4068123A (en) * 1973-07-27 1978-01-10 Nihon Denshi Kabushiki Kaisha Scanning electron microscope
US4929838A (en) * 1988-02-16 1990-05-29 Fujitsu Limited Magnetic object lens for an electron beam exposure apparatus which processes a wafer carried on a continuously moving stage

Also Published As

Publication number Publication date
DE1639280B2 (de) 1973-07-12
NL153718B (nl) 1977-06-15
FR1558166A (enrdf_load_stackoverflow) 1969-02-21
DE1639280A1 (de) 1972-03-16
NL6804435A (enrdf_load_stackoverflow) 1968-10-01
GB1226872A (enrdf_load_stackoverflow) 1971-03-31
DE1639280C3 (de) 1974-01-31

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