US3479505A - Method of operating an ion microprobe using secondary elections - Google Patents

Method of operating an ion microprobe using secondary elections Download PDF

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Publication number
US3479505A
US3479505A US561997A US3479505DA US3479505A US 3479505 A US3479505 A US 3479505A US 561997 A US561997 A US 561997A US 3479505D A US3479505D A US 3479505DA US 3479505 A US3479505 A US 3479505A
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United States
Prior art keywords
specimen
ion
ion beam
image
operating
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US561997A
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English (en)
Inventor
Helmut J Liebl
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APPLIED RES LAB
APPLIED RESEARCH LAB Inc
EIDP Inc
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APPLIED RES LAB
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Priority claimed from DE19691919880 external-priority patent/DE1919880A1/de
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Assigned to JAMES TALCOTT, INC., LLOYDS BANK INTERNATIONAL LIMITED reassignment JAMES TALCOTT, INC. SECURITY INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: APPLIED RESEARCH LABORATORIES, INC., ARL APPLIED RESEARCH LABORATORIES, S.A.
Assigned to E.I. DU PONT DE NEMOURS AND COMPANY reassignment E.I. DU PONT DE NEMOURS AND COMPANY ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: BUCKFELDER, JOHN J., SCHLEINITZ, HENRY M.
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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
    • H01J37/26—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
    • 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
    • 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
    • H01J37/252—Tubes for spot-analysing by electron or ion beams; Microanalysers
    • 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
    • H01J37/252—Tubes for spot-analysing by electron or ion beams; Microanalysers
    • H01J37/256—Tubes for spot-analysing by electron or ion beams; Microanalysers using scanning beams
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J49/00—Particle spectrometers or separator tubes
    • H01J49/02—Details
    • H01J49/10—Ion sources; Ion guns
    • H01J49/14—Ion sources; Ion guns using particle bombardment, e.g. ionisation chambers
    • H01J49/142—Ion sources; Ion guns using particle bombardment, e.g. ionisation chambers using a solid target which is not previously vapourised

Definitions

  • an ion probe of the type with which the present invention is concerned includes an ion source, means for accelerating ions away from the source toward a specimen to be analyzed, means for focusing the ions so accelerated into a relatively narrow beam so that they impinge only upon a very small area of the specimen, and usually an ion analyzer for analyzing ions sputtered from the surface of the specimen by the ion beam.
  • Instruments of this type are capable of great sensitivity in the chemical analysis of materials. They have been shown to be able to detect elements that are present in a specimen material in amounts of only a few parts per billion.
  • the ion beam may be scanned in a raster pattern over a limited portion of the surface of a specimen, while a similar pattern is produced synchronously upon the face of an oscilloscope.
  • An electrical signal is produced indicative of the instantaneous ion emission at a selected mass and energy from the surface of the specimen, and is applied in amplified form to modulate the intensity of the electron beam of the oscilloscope.
  • the oscilloscope thus produces a light image indicating the variations in concentration of a particular element, which image can, in many cases, be matched with an image of the surface of the specimen as seen through a microscope.
  • an important object of the present invention is to improve the operation of an ion microprobe of the stated type, and to facilitate the determination of the point at which the ion beam imjinges upon a specimen at any given moment.
  • the number of electrons emitted by the specimen in response to ion bombardment greatly exceeds the number of ions emitted of any given mass and energy. For a given beam current, therefore, a larger electrical signal can be obtained from the electron emission than from the emission of only selected ions. This is particularly true in those cases where the selected ions are those of elements that are present in the specimen only in very small proportions.
  • the electron emission is also a function of the composition of the surface, and has been found to vary with fully adequate sensitivity to enable ready matching of the oscilloscope image with the image in the microscope.
  • the practice of the invention is expected to find its greatest utilization in connection with use of the ion probe for work other than ion analysis such as, for example, when the probe is used for etching a material by sputtering, or for depositing a layer of a material from the ion beam upon a selected area of a body, or when it is used for inspecting bodies such as miniature semiconductor devices for defects.
  • Different materials in or on the surface of the specimen emit electrons at different respective rates in response to ion bombardment of a given magnitude.
  • Compositional irregularities such as grain boundaries in materials, for example, emit electrons at different rates from other portions of the specimen, and thus show up in the electrically produced image. Many such irregularities are also visible when the surface is viewed through a microscope, so that an observer is enabled to locate very precisely the position of the ion beam at any given moment.
  • a selected material different from the major constituent materials of the specimen may be applied to the surface of the specimen in accordance with a predetermined pattern to provide positively identifiable reference points or areas.
  • FIGURE 1 is a fragmentary, schematic diagram of a portion of an ion microprobe arranged for the practice of the presently preferred embodiment of the invention.
  • FIGURE 2 is a similar view to that of FIGURE 1, but showing the microprobe arranged for the practice of an alternative form of the invention.
  • FIGURE 1 shows only that portion of the microprobe which must be modified for the practice of the present invention from the arrangement shown in my hereinabove identified copending application, and that application may be referred to for a complete description of an operative ion microprobe of the kind with which the present invention is primarily concerned.
  • a beam 10 of ions generated by any desired means is directed toward a specimen material 12 and impinges thereon in a spot of microscopic dimensions.
  • the beam 10 passes between two pairs of deflection plates 14 and 16, respectively, and is then focused by a uni-potential lens 18 upon the surface of the specimen 12.
  • Means are provided for applying deflection voltages to the plates 14 and 16 to cause the beam 16 to scan across a pre-selected area of the surface of the specimen. Such scanning may be in the manner of a television raster, or, alternatively, under manual control, as in a manually driven cross-slide.
  • the outer plates 20 and 21 of the uni-potential lens which serves as the objective lens for focusing the ion beam, are grounded, and the specimen is biased positively about 2 /2 kv. with respect to ground.
  • Positive ions sputtered from the surface of the specimen 12 are collected by a grounded tubular electrode 28, and directed into a double focusing mass spectrometer for analysis.
  • the specimen is biased negatively with respect to ground by a few hundred volts, and the electrode 21 of the objective lens 18 nearest the specimen 12 is ungrounded and connected to the input of a DC amplifier 24.
  • a DC amplifier 24 receives electrons emitted by the specimen from the specimen.
  • the current thus produced constitutes an electrical signal representative of the instantaneous rate of electron emission.
  • the signal is amplified by the amplifier 24 and applied to the control grid of an oscilloscope 26 for modulating the intensity of its trace.
  • the electron beam of the oscilloscope 26 is detected synchronously with the deflection of the ion beam 10, but, of course, across a much wider range so that the raster on the oscilloscope, when raster scanning is used, represents a greatly enlarged image of the scanned portion of the surface of the specimen.
  • the image produced by the oscilloscope is then compared with the optical image produced by a microscope (not shown) aimed at the specimen, thus enabling precise determination of the position of the ion beam at any given moment.
  • Image's produced by the oscilloscope in the practice of the invention are sharp and clear even with currents of 10- ampere in the ion probe. It is also possible, by using methods of accelerating the electrons from the specimen, and by having them impinge on a scintillation crystal, the output of which is fed to a photomultiplier, to obtain useful images on the oscilloscope when the current in the ion beam is even smaller than 10" ampere.
  • One such arrangement for accelerating the electrons and using a scintillation crystal is described in an article by T, E.
  • the secondary electrons from the specimen 12 are collected by the electrode 28 that is normally used for accelerating positive ions from the specimen into mass spectrometer 30.
  • the front element 21 of the objective lens is left grounded, and the collecting electrode 28 is ungrounded and connected to the input of the amplifier 24.
  • the specimen again is biased a few hundred volts negatively. Substantially the same results are achieved in this as in the first embodiment of the invention.
  • the selection of an electrode for collecting the electrons is largely a matter of convenience.
  • Method of operating an ion probe of the type wherein a beam of ions is focussed upon a microscopically small area of a specimen and scanned across the specimen to bombard successive incremental portions thereof to facilitate determination of the points of impingement of the beam on the specimen comprising the steps of collecting electrons emitted by the specimen in response to bombardment by the ion beam, producing an electrical signal indicative of variations in the numbers of electrons emitted from the successive incremental portions as the beam is scanned, and producing a visual display in response to the electrical signal so produced, thereby enabling a comparison between the visual display and an optically produced image of a portion of the specimen.
  • Method of determining the point of impingement of an ion beam upon the surface of a specimen comprising the steps of scanning a sharply focussed ion beam across a selected portion of the specimen, producing an electrical signal responsively to electrons emitted by the surface in response to the ion beam, the electrical signal being indicative of the instantaneous rate of electron emission from the specimen, and producing a visual display in response to the electrical signal so produced, thereby enabling a comparison between the visual display and an optically produced image of the selected portion of the specimen.

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  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Analysing Materials By The Use Of Radiation (AREA)
US561997A 1966-06-30 1966-06-30 Method of operating an ion microprobe using secondary elections Expired - Lifetime US3479505A (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US56199766A 1966-06-30 1966-06-30
FR6911444A FR2041865A5 (enrdf_load_stackoverflow) 1966-06-30 1969-04-14
DE19691919880 DE1919880A1 (de) 1969-04-14 1969-04-18 Verfahren zum Betreiben einer Ionensonde

Publications (1)

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US3479505A true US3479505A (en) 1969-11-18

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US (1) US3479505A (enrdf_load_stackoverflow)
FR (1) FR2041865A5 (enrdf_load_stackoverflow)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3686499A (en) * 1969-05-16 1972-08-22 Hitachi Ltd Ion micro-analyzer
JPS5129437B1 (enrdf_load_stackoverflow) * 1970-08-19 1976-08-25
US4629898A (en) * 1981-10-02 1986-12-16 Oregon Graduate Center Electron and ion beam apparatus and passivation milling

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2624854B2 (ja) * 1989-10-23 1997-06-25 株式会社日立製作所 ２次イオン質量分析装置

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3103584A (en) * 1963-09-10 Electron microanalyzer system
US3219817A (en) * 1961-11-09 1965-11-23 Trub Tauber & Co A G Electron emission microscope with means to expose the specimen to ion and electron beams

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3103584A (en) * 1963-09-10 Electron microanalyzer system
US3219817A (en) * 1961-11-09 1965-11-23 Trub Tauber & Co A G Electron emission microscope with means to expose the specimen to ion and electron beams

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3686499A (en) * 1969-05-16 1972-08-22 Hitachi Ltd Ion micro-analyzer
JPS5129437B1 (enrdf_load_stackoverflow) * 1970-08-19 1976-08-25
US4629898A (en) * 1981-10-02 1986-12-16 Oregon Graduate Center Electron and ion beam apparatus and passivation milling

Also Published As

Publication number Publication date
FR2041865A5 (enrdf_load_stackoverflow) 1971-02-05

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Owner name: JAMES TALCOTT, INC., NEW YORK

Free format text: SECURITY INTEREST;ASSIGNORS:APPLIED RESEARCH LABORATORIES, INC.;ARL APPLIED RESEARCH LABORATORIES, S.A.;REEL/FRAME:004326/0899

Effective date: 19840828

Owner name: LLOYDS BANK INTERNATIONAL LIMITED, NEW YORK

Free format text: SECURITY INTEREST;ASSIGNORS:APPLIED RESEARCH LABORATORIES, INC.;ARL APPLIED RESEARCH LABORATORIES, S.A.;REEL/FRAME:004326/0899

Effective date: 19840828

Owner name: E.I. DU PONT DE NEMOURS AND COMPANY, DELAWARE

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:BUCKFELDER, JOHN J.;SCHLEINITZ, HENRY M.;REEL/FRAME:004326/0513

Effective date: 19840925

Owner name: JAMES TALCOTT, INC., 1633 BROAWAY NEW YORK, NY 10

Free format text: SECURITY INTEREST;ASSIGNORS:APPLIED RESEARCH LABORATORIES, INC., A MA CORP.;ARL APPLIED RESEARCH LABORATORIES, S.A. A SWITZERLAND CORP.;REEL/FRAME:004326/0899

Effective date: 19840828

Owner name: LLOYDS BANK INTERNATIONAL LIMITED, ONE SEAPORT PLA

Free format text: SECURITY INTEREST;ASSIGNORS:APPLIED RESEARCH LABORATORIES, INC., A MA CORP.;ARL APPLIED RESEARCH LABORATORIES, S.A. A SWITZERLAND CORP.;REEL/FRAME:004326/0899

Effective date: 19840828

Owner name: E.I. DU PONT DE NEMOURS AND COMPANY, WILMINGTON, D

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNORS:BUCKFELDER, JOHN J.;SCHLEINITZ, HENRY M.;REEL/FRAME:004326/0513

Effective date: 19840925