US3731094A - Electron beam apparatus with means for generating a rotation-symmetrical magnetic field - Google Patents

Electron beam apparatus with means for generating a rotation-symmetrical magnetic field Download PDF

Info

Publication number
US3731094A
US3731094A US00173045A US17304571A US3731094A US 3731094 A US3731094 A US 3731094A US 00173045 A US00173045 A US 00173045A US 17304571 A US17304571 A US 17304571A US 3731094 A US3731094 A US 3731094A
Authority
US
United States
Prior art keywords
electron beam
magnetic field
beam apparatus
rotation
electron
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US00173045A
Other languages
English (en)
Inventor
Poole J Le
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
US Philips Corp
Original Assignee
US Philips Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by US Philips Corp filed Critical US Philips Corp
Application granted granted Critical
Publication of US3731094A publication Critical patent/US3731094A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • 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
    • 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
    • H01J29/46—Arrangements of electrodes and associated parts for generating or controlling the ray or beam, e.g. electron-optical arrangement
    • H01J29/56—Arrangements for controlling cross-section of ray or beam; Arrangements for correcting aberration of beam, e.g. due to lenses
    • 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
    • H01J37/06—Electron sources; Electron guns
    • H01J37/063—Geometrical arrangement of electrodes for beam-forming
    • 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
    • H01J37/06—Electron sources; Electron guns
    • H01J37/067—Replacing parts of guns; Mutual adjustment of electrodes
    • 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
    • H01J37/145—Combinations of electrostatic and magnetic lenses
    • 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
    • H01J41/00—Discharge tubes for measuring pressure of introduced gas or for detecting presence of gas; Discharge tubes for evacuation by diffusion of ions
    • H01J41/02—Discharge tubes for measuring pressure of introduced gas or for detecting presence of gas
    • H01J41/04—Discharge tubes for measuring pressure of introduced gas or for detecting presence of gas with ionisation by means of thermionic cathodes

Definitions

  • An apparatus for generating an electrostatic space charge in a rotation-symmetrical magnetic field in [30] Forms Apphcanon Pnomy Data which an electron beam from an electron gun which is Aug.21, 1970 Netherlands ..7012387 arranged laterally on the field space generates the space charge in the field space.
  • the electron beam [52] U.S. Cl. ..250/49.5 D, 250/495 A may be adjusted by mechanical adjustment of the gun [51] Int.
  • the invention relates to an electron beam apparatus comprising an electron source for generating an electron beam and means for generating a rotation-symmetrical magnetic field.
  • An electron beam apparatus of this kind is known from the British Pat. Specification No. 578,273, in which it serves to reduce the spherical aberration of electromagnetic lenses.
  • electrons emitted by an electron source form an electrostatic space charge which exerts a compensating effect on the spherical aberration of an electron beam which is axially injected into the lens field.
  • the electron source used for this purpose consists of an annular cathode, which is coaxially provided near an axial extremity of the electromagnetic lens field.
  • This set-up has the drawback that the rotation symmetry of the lens field for the image forming electrons is readily disturbed by the annular cathode and in particular by supply lines to the cathode.
  • the resultant rotation-symmetry errors result in image defects for the image-forming electron beam.
  • an electron beam apparatus of the kind set forth according to the invention is characterized in that the electron source consists of an electron gun which is situated near an axial extremity of the rotation symmetrical magnetic field and at the side of the continuation of thesymmetry axis thereof, a principal direction of the electron gun being directed towards the magnetic field for the electron beam and crossing the magnetic field at an angle of no more than approximately
  • the electron source can be situated such that it has no effect on the rotation symmetry of the magnetic field, while at the same time the control possibility for the electron beam is enhanced-The latter applies to the current intensity, to the energy with which and the angle at which the electrons are injected into the magnetic field.
  • the angle of incidence and the velocity of the electrons are adapted to the magnetic field strength of the rotation-symmetrical magnetic field so that these electrons describe a helix of very small pitch therein.
  • the space charge in the magnetic field is not formed exclusively, or even mainly, by electrons from the injected electron beam, but by secondary electrons which are produced by ionization of gas present in the magnetic field. Consequently, a gas pressure between approximately 10 and 10- Torr is to prevail in the field space.
  • a cylindrical conductor which is coaxially arranged in the magnetic field and whose potential is adjustable may be of assistance for the purposeyboth in order to force the ions produced out of the field space and to co-determine the angle of incidence of the primary beam.
  • the angle of incidence can also be controlled by means of a hinged arrangement of the gun.
  • FIG. I is a diagrammatic view of an electron beam apparatus according to the invention.
  • FIG. 2 is a diagrammatic view of an electron gun suitable for use as an electron source in an electron beam apparatus according to the invention
  • FIG. 3 is a diagrammatic view of an electron microscope, one of the electromagnetic projector lenses of which forms part of an electron beam apparatus according to the invention
  • FIG. 4 is a diagrammatic view of a micro-analyzer one objective lens, constructed as a tube lens, of which forms part of an electron beam apparatus according to the invention, and
  • FIG. 5 is a diagrammatic view of an ionization manometer, an ionization measuring chamber of which as a rotation-symmetrical field space forms part of an electron beam apparatus according to the invention.
  • a rotation-symmetrical magnetic field is generated in a field space I by an electromagnetic coil 2 having windings 3, a ferromagnetic shielding 4 and an air-gap 5.
  • This electromagnetic coil may be replaced by a permanent magnet or may be formed by pole shoes of an electro magnet.
  • an electron'beam 6 is shown, which is used, for example, for an electronoptical image in an electron microscope, a scanning micro-analyzer, an electron beam machining apparatus or another apparatus of this kind, where an electron beam having satisfactory projection properties is desired.
  • an electron gun 7 having a cathode-9 provided with filaments 8, a control electrode I0 andv an anode 11.
  • a magnetic lens 13 is mounted in the anode I I.
  • the electron beam I2 if injected into the magnetic field under an angle of no more than approximately 30 and crossing the symmetry axis, will follow a helix 14.
  • the pitch of this helix is determined by the intensity of the magnetic field and the energy of the injected electrons.
  • a sleeve I5 of non-ferromagnetic electrically conducting material is situated around the field space I.
  • this sleeve 15 When this sleeve 15 is at a positive potential, it will push away the ions produced by the electron beam and a negative space charge can build up in the magnetic field.
  • the direction in which the electron beam 12 is injected can be adjusted by varying the preferably positive potential of the sleeve 15.
  • An energy for the electrons from the electron beam 12 corresponding to approximately 500 to 1,000 eV produces a maximum active section area for ionizing a gas in the space passed by the beam.
  • a preferred embodiment of an electron gun for such an electron beam apparatus includes, besides the already mentioned filaments 8, cathode 9, control electrode 10, anode Ill and lens 13, means for a mechanical adjustment possibility for the electron beam 12.
  • control electrode 10 for example between the control electrode and the anode deformable rings 16 are provided, and around the anode a deformable ring 17 is provided, so that, for example by externally operable adjusting screws, not shown, the gun can be realigned after mounting.
  • FIG. 3 shows a preferred embodiment of an electron beam apparatus which forms part of an electron microscope.
  • an electron gun 18 having a cathode 19, a control electrode 20 and an anode 21, a condenser lens 22, a main lens formed by the electromagnetic coil 2, a projector lens 23 and a target screen 24.
  • the electron gun 7 is mounted between the main lens 2 and the projector lens 23.
  • the diagrammatic representation of an electron microscope serves merely for the purpose of illustration.
  • an electron beam apparatus according to the invention can be incorporated.
  • FIG. 4 shows another embodiment of an electron beam apparatus according to the invention.
  • the means for generating a rotation-symmetrical magnetic field are formed therein by an objective lens 25 of the type such as is described, for example, in US. Pat. No. 3,394,254, which can be used, for example, in a scanning micro-analyzer.
  • An elongated magnetic coil 26 which is characteristic of this type of lens and which is enclosed in a cooling body 27 forms a magnetic field which is particularly suitable for using a space charge according to the invention so as to compensate for spherical aberration.
  • the spherical aberration coefficient of a magnetic lens may readily be reduced by a factor of by using a space charge according to the invention.
  • the resolving power is determined by the fourth root of the spherical aberration coefficient, so that the gain, though noticeable, is not appreciable.
  • the free operating distance is determined by the focal distance of the last lens and this can be chosen a factor of 5 larger in said example while maintaining proper focussing. It was found possible to achieve a focus size of l um with a normal beam, apertures of one-thirtieth radian and a free working distance having a length of 50 mm.
  • the space charge is mainly built up by secondary electrons as a result of ionization, said electrons being kept in the lens space by the composite electrical field of the sleeve 15 and the rotation-symmetrical field, it will be less critical as regards the angle of injection and the energy of the electron beam, and a smaller beam current will be sufficient.
  • a beam current of l u A produces a space charge offering sufficient compensation.
  • a desired ratio between the contributions of each of the processes to the total space charge can be selected in particular by varying the potential ofthe sleeve 15.
  • the secondary electrons produces by ionization of a residual gas can escape from the field only by colliding with gas molecules. Hence, the production of secondary electrons and the probability of their escape are proportional to the gas pressure. As a result, the build up of a space charge cloud of secondary electrons is not very critical for the pressure in the field space.
  • FIG. 5 shows a preferred embodiment which is suitable for this purpose.
  • An airtight envelope 30 comprises, as in known ionization manometers, an aperture 31 for connection to a space in which the gas pressure is to be measured, a collector 32 and an anode 33.
  • means are provided for generating the rotation-symmetrical mag netic field, which means in the embodiment shown take the form of an electromagnetic coil 2, while an electron gun 7, which in this case may be provided with a threeelectrode electrostatic lens 34 for collimating the electron beam 12, extends into the envelope 30.
  • an electron beam apparatus is to be provided merely with means for separating the ions from the primary and/or secondary electrons and with means for collimating and deflecting the ion beam. All this can be realized by known means so that in a comparatively small space having a small electron current a comparatively large ion production is obtainable.
  • An electron beam apparatus comprising an electron gun for generating an electron beam and means for generating a rotation-symmetrical magnetic field, said electron gun being arranged near an axial end of the rotation-symmetrical magnetic field and at the side of a continuation of the symmetry axis thereof, a principal direction for the electron beam of said electron gun being directed towards the magnetic field and crossing the axis of the magnetic field under an angle of at the most approximately 30 2.
  • An electron beam apparatus as claimed in claim 2, wherein the means for adjusting the electron beam consist of a cylindrical electrical conductor which is coaxially arranged in the rotation-symmetrical magnetic field. 7
  • An electron beam apparatus as claimed in claim 1, wherein the means for generating a rotation-symmetrical magnetic field comprise an electromagnetic lens for focusing a beam of image-forming electrons which is axially injected into the magnetic field.
  • a scanning electron microscope provided with an electron beam apparatus as claimed in claim 6, wherein the electromagnetic lens is an imaging lens of the scanning electron microscope which is situated nearest to the location of an object to be scanned.
  • An electron beam machining apparatus provided with an electron beam apparatus as claimed in claim 6, wherein the electromagnetic lens is a convergence lens of the electron beam machining apparatus.
  • a scanning micro-analyzer provided with an electron beam apparatus as claimed in claim 6, wherein the magnetic lens is an electromagnetic lenses of the scanning micro-analyzer.
  • An electron beam apparatus as claimed in claim 1 wherein during operation a gas pressure of between 10" and 10" Torr prevails at the area of the rotationsymmetrical magnetic field.
  • An ionization manometer provided with an ionization measuring space and an electron beam apparatus as claimed in claim 1 wherein the rotation-symmetrical magnetic field of the electron beam apparatus extends at least partially into the ionization-measuring space of the ionization manometer.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Electron Sources, Ion Sources (AREA)
  • Electron Beam Exposure (AREA)
  • Analysing Materials By The Use Of Radiation (AREA)
US00173045A 1970-08-21 1971-08-19 Electron beam apparatus with means for generating a rotation-symmetrical magnetic field Expired - Lifetime US3731094A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
NL7012387A NL7012387A (de) 1970-08-21 1970-08-21

Publications (1)

Publication Number Publication Date
US3731094A true US3731094A (en) 1973-05-01

Family

ID=19810827

Family Applications (1)

Application Number Title Priority Date Filing Date
US00173045A Expired - Lifetime US3731094A (en) 1970-08-21 1971-08-19 Electron beam apparatus with means for generating a rotation-symmetrical magnetic field

Country Status (8)

Country Link
US (1) US3731094A (de)
BE (1) BE771537A (de)
CA (1) CA937340A (de)
CH (1) CH536026A (de)
FR (1) FR2104603A5 (de)
GB (1) GB1367360A (de)
NL (1) NL7012387A (de)
SE (1) SE377001B (de)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3912930A (en) * 1973-09-26 1975-10-14 Physics Int Co Electron beam focusing system
US5045705A (en) * 1989-09-15 1991-09-03 U.S. Philips Corp. Charged particle beam apparatus with charge-up compensation

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ATA4694A (de) * 1994-01-13 1994-11-15 Ims Ionen Mikrofab Syst Projektionssystem fuer geladene teilchen

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2233264A (en) * 1938-12-27 1941-02-25 Rca Corp Electron lens
GB578273A (en) * 1943-03-03 1946-06-21 British Thomson Houston Co Ltd Improvements in electron optical systems
US2452919A (en) * 1945-08-28 1948-11-02 Gen Electric Electron optical system
US2890342A (en) * 1954-09-29 1959-06-09 Gen Electric System for charge neutralization
US3100260A (en) * 1961-11-15 1963-08-06 Philips Electronic Pharma Electron lens for reduction of spherical aberration
US3209147A (en) * 1963-03-05 1965-09-28 Centre Nat Rech Scient Electron lens spherical aberration correcting device comprising a current carrying wire section on the lens axis

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2233264A (en) * 1938-12-27 1941-02-25 Rca Corp Electron lens
GB578273A (en) * 1943-03-03 1946-06-21 British Thomson Houston Co Ltd Improvements in electron optical systems
US2452919A (en) * 1945-08-28 1948-11-02 Gen Electric Electron optical system
US2890342A (en) * 1954-09-29 1959-06-09 Gen Electric System for charge neutralization
US3100260A (en) * 1961-11-15 1963-08-06 Philips Electronic Pharma Electron lens for reduction of spherical aberration
US3209147A (en) * 1963-03-05 1965-09-28 Centre Nat Rech Scient Electron lens spherical aberration correcting device comprising a current carrying wire section on the lens axis

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3912930A (en) * 1973-09-26 1975-10-14 Physics Int Co Electron beam focusing system
US5045705A (en) * 1989-09-15 1991-09-03 U.S. Philips Corp. Charged particle beam apparatus with charge-up compensation

Also Published As

Publication number Publication date
DE2138892B2 (de) 1977-03-24
CA937340A (en) 1973-11-20
FR2104603A5 (de) 1972-04-14
DE2138892A1 (de) 1972-02-24
NL7012387A (de) 1972-02-23
BE771537A (fr) 1972-02-21
SE377001B (de) 1975-06-16
GB1367360A (en) 1974-09-18
CH536026A (de) 1973-04-15

Similar Documents

Publication Publication Date Title
Crewe et al. A high‐resolution scanning transmission electron microscope
US4255661A (en) Electrostatic emission lens
US6194729B1 (en) Particle beam apparatus
JP3268583B2 (ja) 粒子線装置
US4713543A (en) Scanning particle microscope
JP4176149B2 (ja) 粒子光学機器の色収差を補正する補正装置
US3801792A (en) Electron beam apparatus
US4214162A (en) Corpuscular beam microscope for ring segment focusing
JP3324282B2 (ja) カラー受像管装置
US2486856A (en) Electron lens
US2580675A (en) Correction device for microscopes of the reflection mirror type
JP2934707B2 (ja) 走査電子顕微鏡
JP3558325B2 (ja) 銃レンズ及び粒子線装置
JP3325557B2 (ja) 帯電粒子ビーム装置
US3731094A (en) Electron beam apparatus with means for generating a rotation-symmetrical magnetic field
US6653632B2 (en) Scanning-type instrument utilizing charged-particle beam and method of controlling same
US4020387A (en) Field emission electron gun
US3286187A (en) Ion source utilizing a spherically converging electric field
US3931519A (en) Field emission electron gun
US2420560A (en) Electron microscope
US3931517A (en) Field emission electron gun
US3303345A (en) Image amplifier with magnification grid
US2499545A (en) Rotary x-ray tube
US2632115A (en) Focusing device for electron microscopes
US3925664A (en) Field emission electron gun