US3597607A - Electron probe employing three secondary emission detectors whose outputs are combined to minimize error - Google Patents

Electron probe employing three secondary emission detectors whose outputs are combined to minimize error Download PDF

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US3597607A
US3597607A US706001A US3597607DA US3597607A US 3597607 A US3597607 A US 3597607A US 706001 A US706001 A US 706001A US 3597607D A US3597607D A US 3597607DA US 3597607 A US3597607 A US 3597607A
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detectors
specimen
path
mixing circuit
signals
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US706001A
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Alistair John Campbell
Andrew D G Stewart
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Leica Microsystems Inc
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Cambridge Instruments Inc
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
    • G01N23/20—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by using diffraction of the radiation by the materials, e.g. for investigating crystal structure; by using scattering of the radiation by the materials, e.g. for investigating non-crystalline materials; by using reflection of the radiation by the materials
    • G01N23/203—Measuring back scattering

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  • This invention relates to electron beam apparatus in which an electron beam is caused to impinge on the surface of a specimen and the backscattered electrons which emerge from the specimen are observed by appropriately placed detecting instruments.
  • the degree of back scattering is dependent on the atomic number of the element scanned, and by synchronizing a display on a cathode ray tube screen or on a two-coordinate plotter with the scanning of the electron probe over an area of the specimen surface it is possible to produce a picture of the element distributions.
  • the distribution of the backscattered electrons depends not only on the distribution of the elements but also on the topography of the specimen surface. Accordingly it has recently been proposed to distinguish between the influences of these two factors by providing two electron detectors spaced apart symmetrically on opposite sides of the electron beam and both receiving backscattered electrons from the same scanned spot on the specimen surface. Their outputs are added to produce a signal dependent on atomic number that is at least partially independent of topography and are subtracted to produce a signal that depends on the topography but is independent of atomic number.
  • the objects of the present invention is to provide means for detecting topographical features which run in any direction simultaneously and without moving either the specimen or the detectors.
  • a further object is to provide improved means for displaying atomic number distributions.
  • the outputs of the detectors are connected to one or more mixing circuits which allows these outputs to be combined in a manner such that the topographical display, derived from the circuit, has the appearance of being illuminated from substantially any desired direction at will.
  • the outputs of the detectors are connected to a mixing circuit which combines these outputs in a manner such that the display, derived from the circuit, shows all the topographical features of the specimen, whatever their direction, but does not distinguish between hills and valleys.
  • the output of all the detectors can be added to produce a signal that is dependent on atomic number but independent of topography and, in fact, this should be achieved with much greater success than in the known arrangement with only two detectors.
  • FIG. 1 is a diagrammatic perspective view showing the use of three detectors
  • FIG. 2 is a plan view corresponding to FIG. 1;
  • FIG. 3 is a diagram to assist in an understanding of the mathematical relationships.
  • FIG. 4 is aplan view showing the use of four detectors.
  • a finely focused electron beam or so-called probe B is caused in a known manner to impinge on the surface of a specimen S of which the nature, both chemical composition and surface quality or topography, are to be analyzed.
  • the impingement of the electrons causes the emission of backscattered electrons, which may be partially secondary electrons and partially the impinging electrons reversed in direction. These are picked up by electron detectors.
  • the electron beam B will normally be scanned laterally in a raster in two mutually perpendicular directions parallel to the surface of the specimen, so as to cover a small selected area, and the outputs of the detectors are fed to the brightness control of a cathode-ray tube, of which the beam is scanned in synchronism with that of the beam B, so that there is displayed on the screen of the cathode ray tube a picture of the distribution of the electron backscatter behavior over the scanned area.
  • the distribution of the backscattered electrons is, for reasons of symmetry, uniform about the axis of the beam 8, and the degree of back scattering is dependent on the atomic number, being greater for the elements of higher atomic number.
  • the surface is undulating, as by the formation of microcrystals having exposed surfaces in planes which are inclined to the overall plane of the whole surface, then the backscattered electrons will tend to be distributed asymmetrically.
  • FIGS. 1 and 2 we show the use of three detectors D D and D distributed uniformly apart as viewed in the direction of the impinging electron beam.
  • the electrical output signals obtained from the three detectors are fed to a mixing circuit M. Where one is interested in knowing the nature of the elements present in the region under analysis these three outputs are simply added, and the resultant signal is dependent on atomic number, but is independent of the surface topography. Where the surface topography is the important thing, one combines the three outputs (1 ,11 and d to produce an output D in accordance with the equation:
  • Either of these signals l) or 0 will give a topographical display which, like the earlier version, is independent of the atomic number of the elements being scanned, but in this version there is no distinction between hills and valleys.
  • the signals D and I) may be obtained equally well where there are more than three detectors but cannot be obtained with fewer than three.
  • an electron-probe microanalyzing instrument can be equipped with switches allowing the immediate selection of any ofthe signals D, D or I) as well as a knob controlling the angle of apparent illumination and a switch allowing the selection of the atomic number signal (d +d,+d,) instead.
  • the proposal according to the invention to use three or more detectors has an important advantage over the use of two detectors, even where their outputs are simply being added together to produce the atomic number signal. Where there are only two detectors a scratch or surface irregularity extending in a direction parallel to the line joining the two detectors will not be apparent but may have an equal effect on the signals in both detectors and thus introduce an apparent variation in composition that is not actually present. This is eliminated by the use of three or more detectors.
  • Electron beam apparatus comprising means for causing an electron beam to impinge on the surface of a specimen placed in the path of said beam, an array ofn electron detectors, n being at least three, spaced symmetrically around the path of said beam in positions to pick up resultant backscattered electrons from said specimen surface, said detectors producing electrical signals dependent on the backscattered electrons picked up, means for causing relative lateral scanning between said beam and said specimen surface, and
  • an electric mixing circuit said mixing circuit being arranged to produce an output where d,,, d, d,, are the electric signals from said detectors, and 6 is the angle between an arbitrary direction lying in a plane normal to the beam and the projection, onto said plane, of a line joining the path of the beam to that detector which produces the output d,,.
  • the apparatus of claim 1 including switching means associated with said mixing circuit to allow selection at will of a signal representing the sum of the outputs of all said detectors.
  • dd I+[d d [+]d d where d' l/n(d,,+d,+ +d,,,,).
  • a method of determining the topography of the surface of a specimen comprising causing an electron beam to impinge on said surface, detecting the resultant electrons back scattered from said surface by means of an array of n separate detectors, n being at least three, symmetrically spaced around the path of said beam, causing relative lateral scanning between said beam and said specimen surface, deriving from the detectors at least three corresponding electrical signals and deriving from said signals an output signal 360 COS 3 10.
  • a method of determining the topography of the surface of a specimen comprising causing an electron beam to impinge on said surface, detecting thevresultant electrons back scattered from said surface by means of an array of n separate detectors, n being at least three, symmetrically spaced around the path of said beam.

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  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
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  • Analysing Materials By The Use Of Radiation (AREA)
US706001A 1967-02-16 1968-02-16 Electron probe employing three secondary emission detectors whose outputs are combined to minimize error Expired - Lifetime US3597607A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB7463/67A GB1195271A (en) 1967-02-16 1967-02-16 Electron Beam Apparatus

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US3597607A true US3597607A (en) 1971-08-03

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US (1) US3597607A (enrdf_load_stackoverflow)
DE (1) DE1673847B2 (enrdf_load_stackoverflow)
FR (1) FR1568135A (enrdf_load_stackoverflow)
GB (1) GB1195271A (enrdf_load_stackoverflow)

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3876879A (en) * 1973-11-09 1975-04-08 Calspan Corp Method and apparatus for determining surface characteristics incorporating a scanning electron microscope
US4219731A (en) * 1977-11-24 1980-08-26 Vlsi Technology Research Association Method for detecting object picture by electron beam
US4426577A (en) 1980-02-15 1984-01-17 International Precision Incorporated Electron microscope of scanning type
US4600839A (en) * 1983-03-09 1986-07-15 Hitachi, Ltd. Small-dimension measurement system by scanning electron beam
US4733074A (en) * 1985-04-17 1988-03-22 Hitachi, Ltd. Sample surface structure measuring method
US4751384A (en) * 1986-02-17 1988-06-14 Hitachi, Ltd. Electron beam metrology system
US4912313A (en) * 1987-11-27 1990-03-27 Hitachi Ltd. Method of measuring surface topography by using scanning electron microscope, and apparatus therefor
US20030147484A1 (en) * 2001-11-08 2003-08-07 Olshansky Yury Iosiphovich Method for detecting an explosive in an object under investigation
US20090242792A1 (en) * 2008-03-31 2009-10-01 Hitachi High-Technologies Corporation Electron microscopy
US20110095001A1 (en) * 2009-10-23 2011-04-28 Thorsten Loewer Thermal Material-Processing Method
US20120217392A1 (en) * 2011-02-28 2012-08-30 Tsutomu Murakawa Pattern-height measuring apparatus and pattern-height measuring method

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2285169A (en) * 1993-12-21 1995-06-28 Secretary Trade Ind Brit Scanning electron microscope grain imaging

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3193679A (en) * 1962-04-24 1965-07-06 Ti Group Services Ltd Electron probe apparatus for counting the number of inclusions in a specimen
US3204095A (en) * 1960-12-21 1965-08-31 Hitachi Ltd Electron probe microanalyzer with means to eliminate the effect of surface irregularities
US3329813A (en) * 1964-08-25 1967-07-04 Jeol Ltd Backscatter electron analysis apparatus to determine elemental content or surface topography of a specimen

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3204095A (en) * 1960-12-21 1965-08-31 Hitachi Ltd Electron probe microanalyzer with means to eliminate the effect of surface irregularities
US3193679A (en) * 1962-04-24 1965-07-06 Ti Group Services Ltd Electron probe apparatus for counting the number of inclusions in a specimen
US3329813A (en) * 1964-08-25 1967-07-04 Jeol Ltd Backscatter electron analysis apparatus to determine elemental content or surface topography of a specimen

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3876879A (en) * 1973-11-09 1975-04-08 Calspan Corp Method and apparatus for determining surface characteristics incorporating a scanning electron microscope
US4219731A (en) * 1977-11-24 1980-08-26 Vlsi Technology Research Association Method for detecting object picture by electron beam
US4426577A (en) 1980-02-15 1984-01-17 International Precision Incorporated Electron microscope of scanning type
US4600839A (en) * 1983-03-09 1986-07-15 Hitachi, Ltd. Small-dimension measurement system by scanning electron beam
US4733074A (en) * 1985-04-17 1988-03-22 Hitachi, Ltd. Sample surface structure measuring method
US4751384A (en) * 1986-02-17 1988-06-14 Hitachi, Ltd. Electron beam metrology system
US4912313A (en) * 1987-11-27 1990-03-27 Hitachi Ltd. Method of measuring surface topography by using scanning electron microscope, and apparatus therefor
US6928131B2 (en) * 2001-11-08 2005-08-09 Ratec, Ltd. Method for detecting an explosive in an object under investigation
US20030147484A1 (en) * 2001-11-08 2003-08-07 Olshansky Yury Iosiphovich Method for detecting an explosive in an object under investigation
US20090242792A1 (en) * 2008-03-31 2009-10-01 Hitachi High-Technologies Corporation Electron microscopy
US8044352B2 (en) * 2008-03-31 2011-10-25 Hitachi High-Technologies Corporation Electron microscopy
US20110095001A1 (en) * 2009-10-23 2011-04-28 Thorsten Loewer Thermal Material-Processing Method
CN102039483A (zh) * 2009-10-23 2011-05-04 波宾股份公司 材料热加工方法
US8314358B2 (en) * 2009-10-23 2012-11-20 Pro-Beam Ag & Co. Kgaa Thermal material-processing method
US20120217392A1 (en) * 2011-02-28 2012-08-30 Tsutomu Murakawa Pattern-height measuring apparatus and pattern-height measuring method
US8604431B2 (en) * 2011-02-28 2013-12-10 Advantest Corp. Pattern-height measuring apparatus and pattern-height measuring method

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Publication number Publication date
GB1195271A (en) 1970-06-17
DE1673847A1 (de) 1971-12-30
DE1673847B2 (de) 1976-08-12
FR1568135A (enrdf_load_stackoverflow) 1969-05-23

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