US3845304A - Ion microanalyzer - Google Patents

Ion microanalyzer Download PDF

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Publication number
US3845304A
US3845304A US00343019A US34301973A US3845304A US 3845304 A US3845304 A US 3845304A US 00343019 A US00343019 A US 00343019A US 34301973 A US34301973 A US 34301973A US 3845304 A US3845304 A US 3845304A
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United States
Prior art keywords
specimen
ion
voltage
microanalyzer
shield electrode
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Expired - Lifetime
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US00343019A
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English (en)
Inventor
H Tamura
K Nakamura
T Kondo
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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
    • H01J49/00—Particle spectrometers or separator tubes
    • H01J49/26—Mass spectrometers or separator tubes
    • H01J49/28—Static spectrometers
    • H01J49/32—Static spectrometers using double focusing
    • 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

Definitions

  • the ion microanalyzer of the prior art has a problem in that it is significantly hard to discriminate between the secondary ions emitted from atoms of the specimen and those from vapor phase or absorption layer. This results in reduction of accuracy or difficulty in identifying elements. Therefore, this problem should, by all means, be solved when considering microanalysis of element and analysis of thin film or surface of material.
  • Another object of this invention is to provide an ion microanalyzer of a single focusing type ease rarefiecriminating between the secondary ions emitted from the specimen and those from the vapor phase.
  • FIG. 1 is a schematic diagram of an ion microanalyzer of the prior art.
  • FIG. 2 is aschematic diagram of one embodiment of the ion microanalyzer in accordance with the present invention.
  • FIG. 3 is a schematic diagram of another embodiment of this invention.
  • FIGS. 4a and 4b show the relationship between secondary ion energy and mass spectrum.
  • FIG. 1 there is shown an ion microanalyzer of the prior art.
  • the prior art analyzer is composed of a primary ion irradiation device 1 including an ion source, means for focussing an ion beam 2, and means for deflecting the ion beam (not shown); a specimen 3; an electrode 4 for attraction of secondary ions; at mass spectrometer 5, 6, 7 and 8; a secondary ion detector 9; and a recorder 10.
  • Conventional massspectromete'rs are usually divided into a single focussing type which is provided with only the sector magnetic field device 7, and a double focusing type one which is provided with the sector electric field device and with the sector magnetic field device 7.
  • the former type one is used in such a case that a relatively poor resolution is permitted because it cannot perform an energy selection of the secondary ions emitted from the specimen.
  • the latter type one is used in case a high resolution is required.
  • a voltage of several KV or less is applied to the specimen while a voltage of about 10 percent of that applied to the specimen is applied to both the upper and lower electrodes of the sector electric field device.
  • a secondary ion acceleration voltage Va and the voltage iVd to be applied to the sector electric device are supplied by individually independent voltage sources 12, 13 and 14.
  • the voltages are variable while keeping the ratio therebetween constant.
  • the secondary ion acceleration voltage i.e., the specimen potential Va is maintained constant, and the energy selection of the secondary ions is made by changing the voltage forming the sector electric field.
  • the secondary ion acceleration voltage Va and the sector potential iVd are concurrently changed so that energy selection of the secondary ion cannot be done.
  • the former microanalyzer is capable of energy selection, but has a difficulty in maintaining the absolute value of the secondary ion energy constant.
  • the ion microanalyzer of the prior art has inherently a problem when a high accuracy is required in identifying elements and in quantitative analysis.
  • This invention is directed to solving the problem and to achieving an improvement in the ion microanalyzer.
  • the specimen is shielded by a shielding body which is formed of a conductive mesh or perforated conductor electrode, and an appropriate voltage is applied between the specimen and the electrode;
  • the specimen voltage i.e., the secondary ion acceleration voltage Va can be made variable independent of the voltage for the sector electric field.
  • the ion microanalyzer in accordance with the present invention will operatein two modes: I.
  • the one is such that only the secondary ions having energy larger than apredetermined energy are guided to the mass spectrometer by applying the electric field between the specimen and the shield body electrode for
  • An embodiment of the latter mode will first be described with reference to the schematic diagram in FIG. 2.
  • Si and GaAs single crystals were employed as the specimen '3.
  • the specimen chamber is evacuated to l X 10' Torr, and then air was introduced therein until the degree of vacuum in the chamber reaches 1 X 10 Torr.
  • the specimen was irradiated by ion beams wherein ion current was lU uA, the acceleration voltage was KV, and argon ions Ar were used as primary ions.
  • THe specimen voltage, i.e., the secondary ion acceleration voltage Va was set at 3 KV while the output of the mass spectrometer was adjusted equal to the mass peak of the sealed-in gas, i.e. 0+ or N+.
  • the sector electrical field and the sector magnetic field then are adjusted so as to minimize the 0 or N
  • the measurement was made of the mass spectrum of the secondary ions emitted from gas phase in such a manner that after such adjustment, only the exciting current for the sector magnetic field is changed with the other portion being fixed.
  • the acceleration voltage of the secondary ion is reduced so that the ions of high energy alone may be introduced into the mass spectrometer.
  • the mass spectrum of the bulk is measured by changing the exciting current for the sector magnetic field.
  • FIG. 3 shows another embodiment of this invention in which this invention is applied to the mass spectrometer of a single focusing type.
  • the mass-spectrometer of this kind in the prior art has inherently no ability to select the energy of the secondary ions, but has a high utility value in that the secondary ions are utilized in high efficiency and the device is simple in the construction. Thus, a gross effect will be expected if the single focusing type could be capable of selecting the energy of secondary ions.
  • the energy selection of the secondary ions is achieved by changing the potential of the electrode relative to the specimen by tVg which is supplied through a switch 17 from a voltage source 16.
  • the potential ofthe electrode 15 is made higher by Vg than the specimen potential. Accordingly, the secondary ions having an initial energy of less than Vg (eV) can not pass through the electrode 15 while the ions of Vg (eV) or larger are permitted to pass therethrough into the mass spectrometer.
  • FIGS. 4a and 4b show the results of the experiment.
  • the mass spectrum as shown in FIG. 4a is observed in the detection of the secondary ions of relativelylow energy (10 KV). It can be seen from the drawing that the mass spectrum of C*, CH, N*, 0 0*, etc. emitted from the gas phase are found, and that of the atom of the specimen (Si) is not found. The observed spectrum is not changed even when the specimen is substituted by others. Thus, it is. apparent that this spectrum shows the secondary ions from the gass phase.
  • the present invention provides an improved ion microanalyzer which is capable of remarkable discrimination between the secondary ions emitted from the specimen and the gas phase ions of low energy.
  • An ion microanalyzer comprising: means for generating an ion beam, means for directing said beam to a desired portion of a specimen, a mass spectrometer for analyzing secondary ions emitted from said speci- 20 men, a variable electric source for applying a voltage to said specimen, and a shield body which encloses said specimen and to which said voltage is applied.
  • An ion microanalyzer comprising:
  • An ion microanalyzer comprising:
  • a mass spectrometer for analyzing secondary ions emitted from said specimen; an electric source for applying a voltage to said specimen;
  • said third means includes an electric source applying a voltage between said specimen and said shield electrode.
  • said mass spectrometer is of a double focusing type provided with a sector electric field device, a sector magnetic field device, and a variable electric source for applying a voltage to said sector electric field de- 9.
  • said shield electrode is a perforated conductive electrode.
  • an ion microanalyzer having first means for generating an ion beam and directing said ion beam onto a desired portion of a specimen;
  • a massspectrometer for analyzing secondary ions emitted from said specimen as a result of said ion beam being directed thereon;

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  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Analysing Materials By The Use Of Radiation (AREA)
US00343019A 1972-03-21 1973-03-20 Ion microanalyzer Expired - Lifetime US3845304A (en)

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JP47027386A JPS5214999B2 (ja) 1972-03-21 1972-03-21

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4036777A (en) * 1975-07-25 1977-07-19 Compagnie D'applications Mecaniques A L'electronique Au Cinema Et A L'atomistique (C.A.M.E.C.A.) Ion current measuring arrangement
US4058724A (en) * 1975-06-27 1977-11-15 Minnesota Mining And Manufacturing Company Ion Scattering spectrometer with two analyzers preferably in tandem
US6765198B2 (en) 2001-03-20 2004-07-20 General Electric Company Enhancements to ion mobility spectrometers

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3646344A (en) * 1969-01-02 1972-02-29 Graham Plows Scanning electron beam apparatus for viewing potential distribution on specimen surfaces
US3686499A (en) * 1969-05-16 1972-08-22 Hitachi Ltd Ion micro-analyzer

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3646344A (en) * 1969-01-02 1972-02-29 Graham Plows Scanning electron beam apparatus for viewing potential distribution on specimen surfaces
US3686499A (en) * 1969-05-16 1972-08-22 Hitachi Ltd Ion micro-analyzer

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4058724A (en) * 1975-06-27 1977-11-15 Minnesota Mining And Manufacturing Company Ion Scattering spectrometer with two analyzers preferably in tandem
US4036777A (en) * 1975-07-25 1977-07-19 Compagnie D'applications Mecaniques A L'electronique Au Cinema Et A L'atomistique (C.A.M.E.C.A.) Ion current measuring arrangement
US6765198B2 (en) 2001-03-20 2004-07-20 General Electric Company Enhancements to ion mobility spectrometers

Also Published As

Publication number Publication date
DE2313852A1 (de) 1973-10-04
JPS4895887A (ja) 1973-12-08
DE2313852B2 (de) 1975-08-28
JPS5214999B2 (ja) 1977-04-26

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