US3736423A - Electron lens of magnetic field type for an electron microscope and the like - Google Patents

Electron lens of magnetic field type for an electron microscope and the like Download PDF

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Publication number
US3736423A
US3736423A US00142606A US3736423DA US3736423A US 3736423 A US3736423 A US 3736423A US 00142606 A US00142606 A US 00142606A US 3736423D A US3736423D A US 3736423DA US 3736423 A US3736423 A US 3736423A
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United States
Prior art keywords
coils
compensating
electron
electron lens
lens according
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Expired - Lifetime
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US00142606A
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English (en)
Inventor
S Katagiri
S Kasai
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Hitachi Ltd
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Hitachi Ltd
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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
    • H01J37/04—Arrangements of electrodes and associated parts for generating or controlling the discharge, e.g. electron-optical arrangement or ion-optical arrangement
    • H01J37/153—Electron-optical or ion-optical arrangements for the correction of image defects, e.g. stigmators
    • 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
    • H01J37/10—Lenses
    • H01J37/14—Lenses magnetic

Definitions

  • undesirable deflecting magnetic fields occur in the area of contacting portions between the pole pieces and magnetic path members in said lens to deflect an electron beam therein.
  • the image produced by the beam is distorted, and further it is impossible to observe said image within a constant viewing field since the image is shifted therefrom so that the ability of an electron microscope and the like using said lens to produce an acceptable image is unsatisfactory and manipulation thereof becomes complicated.
  • compensating coils are disposed in the vacuum space of the pole piece opening or beam passage in said lens so as to eliminate said astigmatism and undesirable deflection of the electron beam.
  • such an'arrangement is undesirable since the lead lines of said compensating coils must be taken out from said vacuum space without producing leakage and it is required to insulate between said compensating coils and the magnetic circuit of said lens.
  • FIG. la is a longitudinal section showing an embodiment of this invention.
  • FIGS. 1b and 1c are cross sections of respective embodiments of compensating coil arrangements taken along line lb, c lb, c in FIG. la;
  • FIG. 2 is a partial sectional view showing the location of compensating coils in another embodiment of this invention.
  • FIG. 3a is a partial sectional view showing the main part of a further embodiment of this invention.
  • FIG. 3b is a section taken along line IIIb IIIb in FIG. 3a;
  • FIG. 4a is a longitudinal section showing a still further embodiment of this embodiment
  • FIG. 4b is a cross section taken along line IVb .IVb of FIG. 4a;
  • FIG. 5a is a longitudinal section showing the main part of a still further embodiment of this invention.
  • FIG. 5b is a cross section taken along line Vb Vb of FIG. 5a;
  • FIG. 6a is a longitudinal section showing still another embodiment of this invention.
  • FIG. 6b is a cross section taken along line Vlb Vlb of FIG. 6a;
  • FIG. 7 is a circuit diagram showing a circuit for supplying a compensating current to said compensating coils.
  • an electron lens includes an upper magnetic pole piece 1, a lower magnetic pole piece 2, an upper magnetic path member 3, a lower magnetic path member 4, an exciting lens coil 5 wound in an annular shape to surround the electron beam passage, and a spacer 6 made of non-magnetic'material.
  • the upper and lower magneticpole pieces 1 and 2 and the upper and lower magnetic path members 3 and 4 constitute a magnetic cover disposed to cover the exciting lens coil 5.
  • These are well known elements which constitute a conventional electron lens structure of magnetic field type. In such an electron lens, the spacer 6 is not always used.
  • the electron lens further includes a compensating coil device 7 having four coils A to D, as shown in FIG. lb, which are wound on the lower magnetic path member 4 through holes formed therein.
  • the respective coils are disposed to have an angle of formed between two transverse center axes of said coils adjoining each other, as shown in FIG. lb.
  • the compensating coils may be recessed in the cover body so as not to protrude therefrom.
  • the coil A is connected to coil C with an opposite sense thereto in series and the coil B is connected to coil D in the same manner.
  • Compensating currents are supplied to said coils ,in such a manner that magnetic flux a, and flux da produced by said coils A and C are in the direction of an electron beam axis E, and magnetic flux and flux (1),, produced by said coils B and D are in the opposite direction thereof so as to compensate for astigmatism and undesirable deflection of the electron beam.
  • the compensating coil device may be constructed by eight coils-A to H, e.g., as shown in FIG. lc.
  • the respective coils are wound on the lower magnetic path member 4 through holes formed therein as in the foregoing, and they are disposed in such am manner that the angle defined by the central axes of the adjacent two coils is 45.
  • the coils A, C, E and G are connected in series with the sense of alternate coils being the same. Thus, they are energized in such a manner that, as in the above description, d), and 41 which are among the magnetic fluxes produced by the respective coils opposing each other, are directed towards the electron beam axis E; whereas, and are directed away from the axis.
  • the coils B, D, F and H are connected in series, and are energizedas described above.
  • the compensating coil device in FIG. comprises in combination two sets of the one in FIG. 1b.
  • the compensating current which is caused to flow through one set of the coils,
  • A, C, E and G is made so as to differ in phase by 90 with respect to the compensating current which is caused to flow through the other set of the coils B, D, F and IL.
  • the current through one set of the coils is varied in accordance with the cosine of the angle, so that the resultant magnetic field may rotate by 360. In this manner, in whichever direction astigmatism appears, it may be corrected.
  • FIG. 6b Even if eight coils are not used, astigmatism generated in any direction may be corrected with only four coils A, A, B and B insofar as they are arranged as illustrated in FIG. 6b.
  • the mutually opposing coils A and A, and B and B' are connected in series, respectively, while they are disposed in such a manner that the central axes of the coils of the set consisting of A and A and those of the coils of the set consisting of B and B define an angle of 45, respectively.
  • FIG. 2 is a modification of the embodiment in FIG. 1a, and has the deflecting coil embedded in the lower magnetic path member 4.
  • the feature of this embodiment is that the leakage magnetic field from the magnetic cover may be reduced.
  • the deflecting coil 7 Since the deflecting coil 7 is wound into the iron core in each of the embodiments shown in FIGS. 1a and 2, the magnetic reluctance through which the magnetic flux permeates is low, and the correcting effect is strong. Therefore, even when the deflecting coil 7 is provided at that part of the lower magnetic path member 4 which is considerably distant from the electron lens gap, its effect may be sufficiently utilized.
  • FIGS. 3a and 3b illustrate a further embodiment with the deflecting coil 7 mounted on the lower pole piece 2.
  • numeral 8 designates a protecting tube. The feature of this embodiment resides in that, since the compensating coil device 7 is assembled in the vicinity of the electron lens gap, the correcting effect is strong and hence it may accomplish the object of the invention satisfactorily even in case where only a small amount of excitation is provided.
  • FIGS. 4a and 4b A still further embodiment shown in FIGS. 4a and 4b has the deflecting coil 7 installed at that part of the magnetic path member which is at a position as distant from the electron beam axis as possible.
  • the figures illustrate a structure wherein four coils A, B, C and D constituting the deflecting coil 7 are provided so as to enable the correction of incorrect deflection of an electron beam and astigmatism in a specific direction, it is also possible to construct the deflecting coil so as to correct astigmatism in any direction by providing eight coils, as seen in FIG. lc.
  • compensating coil device 7 is assembled in the magnetic cover in the vicinity of the electron lens gap, and yet, it is disposed so as not to appear within the vacuum space of the electron beam path.
  • the compensating coil device A to'D in FIG. 1b may be connected to the lens coil 5 through resistors R and R and variable resistors R and R thereby to supply predetermined currents from an exciting power source 9 to both of the coils.
  • an electron lens of the magnetic field type for an electron microscope and the like comprising an exciting lens coil wound in an annular shape, a magnetic cover disposed to cover said lens coil and composed of an upper magnetic path member, a lower magnetic path member and upper and lower magnetic pole pieces, the improvement which comprises a plurality of compensating coils each being wound on different portions of said magnetic cover through holes provided therein, supply means for supplying compensating currents to said compensating coils and adjusting means for adjusting said compensating currents whereby astigmatism and undesired deflection of an electron beam passing through said lens can be eliminated.
  • An electron lens according to claim 1 characterized by eight compensating coils, which are respectively arranged such that the central axes of adjacent coils define an angle of 45 therebetween.
  • An electron lens according to claim 1 characterized in that said compensating coils are embedded in said magnetic cover.
  • An electron lens according to claim 1 characterized by four compensating coils, the central axes of one pair of coils opposing each other defining an angle of 7 45 with those of the other pair of coils opposing each other.
  • said compensating coils are provided in said lower magnetic path member.

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  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Electron Beam Exposure (AREA)
  • Particle Accelerators (AREA)
  • Electron Sources, Ion Sources (AREA)
US00142606A 1970-05-13 1971-05-12 Electron lens of magnetic field type for an electron microscope and the like Expired - Lifetime US3736423A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP45040630A JPS4929089B1 (fr) 1970-05-13 1970-05-13

Publications (1)

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US3736423A true US3736423A (en) 1973-05-29

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US00142606A Expired - Lifetime US3736423A (en) 1970-05-13 1971-05-12 Electron lens of magnetic field type for an electron microscope and the like

Country Status (4)

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US (1) US3736423A (fr)
JP (1) JPS4929089B1 (fr)
DE (1) DE2123576B2 (fr)
GB (1) GB1355252A (fr)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3984687A (en) * 1975-03-17 1976-10-05 International Business Machines Corporation Shielded magnetic lens and deflection yoke structure for electron beam column
DE2856782A1 (de) * 1978-01-03 1979-07-12 Thomson Csf Elektronenoptik-objektiv
US4393308A (en) * 1980-03-20 1983-07-12 Siemens Aktiengesellschaft High current electron source
US20120037813A1 (en) * 2010-08-11 2012-02-16 Ict Integrated Circuit Testing Gesellschaft Fur Halbleiterpruftechnik Mbh Multi-axis lens, beam system making use of the compound lens, and method of manufacturing the compound lens
EP2827356A1 (fr) * 2013-07-18 2015-01-21 Fei Company Lentille magnétique permettant de focaliser un faisceau de particules chargées
US20200043698A1 (en) * 2018-08-03 2020-02-06 Nuflare Technology, Inc. Electron optical system and multi-beam image acquiring apparatus

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL7804035A (nl) * 1978-04-17 1979-10-19 Philips Nv Elektronenmikroskoop.

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3046397A (en) * 1959-06-17 1962-07-24 Tesla Np Device for compensating axial astigmatism of electron-optical systems
US3150258A (en) * 1962-07-05 1964-09-22 Philips Electronic Pharma Electromagnetic stigmators for correcting electron-optical deficiencies in the lenses of electron beam instruments

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3046397A (en) * 1959-06-17 1962-07-24 Tesla Np Device for compensating axial astigmatism of electron-optical systems
US3150258A (en) * 1962-07-05 1964-09-22 Philips Electronic Pharma Electromagnetic stigmators for correcting electron-optical deficiencies in the lenses of electron beam instruments

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3984687A (en) * 1975-03-17 1976-10-05 International Business Machines Corporation Shielded magnetic lens and deflection yoke structure for electron beam column
DE2856782A1 (de) * 1978-01-03 1979-07-12 Thomson Csf Elektronenoptik-objektiv
US4330709A (en) * 1978-01-03 1982-05-18 Thomson-Csf Electronic optical objective
US4393308A (en) * 1980-03-20 1983-07-12 Siemens Aktiengesellschaft High current electron source
US20120037813A1 (en) * 2010-08-11 2012-02-16 Ict Integrated Circuit Testing Gesellschaft Fur Halbleiterpruftechnik Mbh Multi-axis lens, beam system making use of the compound lens, and method of manufacturing the compound lens
US8481958B2 (en) * 2010-08-11 2013-07-09 Ict Integrated Circuit Testing Gesellschaft Fur Halbleiterpruftechnik Gmbh Multi-axis lens, beam system making use of the compound lens, and method of manufacturing the compound lens
EP2827356A1 (fr) * 2013-07-18 2015-01-21 Fei Company Lentille magnétique permettant de focaliser un faisceau de particules chargées
US9595359B2 (en) 2013-07-18 2017-03-14 Fei Company Magnetic lens for focusing a beam of charged particles
US20200043698A1 (en) * 2018-08-03 2020-02-06 Nuflare Technology, Inc. Electron optical system and multi-beam image acquiring apparatus
US11621144B2 (en) * 2018-08-03 2023-04-04 Nuflare Technology, Inc. Electron optical system and multi-beam image acquiring apparatus

Also Published As

Publication number Publication date
GB1355252A (en) 1974-06-05
DE2123576A1 (de) 1971-12-02
DE2123576B2 (de) 1976-10-07
JPS4929089B1 (fr) 1974-08-01

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