US3920990A - Device for analysing a surface layer by means of ion scattering - Google Patents

Device for analysing a surface layer by means of ion scattering Download PDF

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Publication number
US3920990A
US3920990A US466220A US46622074A US3920990A US 3920990 A US3920990 A US 3920990A US 466220 A US466220 A US 466220A US 46622074 A US46622074 A US 46622074A US 3920990 A US3920990 A US 3920990A
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United States
Prior art keywords
surface layer
ions
ion beam
ion
detector
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Expired - Lifetime
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US466220A
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English (en)
Inventor
Nieuwland Jacob Maria Van
Nicolaas Hazewindus
Adrianus Martinus Maria Otten
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US Philips Corp
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US Philips Corp
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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
    • H01J37/252—Tubes for spot-analysing by electron or ion beams; Microanalysers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J49/00—Particle spectrometers or separator tubes
    • H01J49/44—Energy spectrometers, e.g. alpha-, beta-spectrometers
    • H01J49/46—Static spectrometers
    • H01J49/48—Static spectrometers using electrostatic analysers, e.g. cylindrical sector, Wien filter
    • H01J49/482—Static spectrometers using electrostatic analysers, e.g. cylindrical sector, Wien filter with cylindrical mirrors

Definitions

  • the invention relates to a device for analysing a surface layer by means of ion scattering and comprising: means to produce a primary substantially monoenergetic ion beam, a diaphragm aperture for passing ions which are scattered at the surface layer at a previously determined angle with respect to the axis of the primary ion beam, and an electrostatic analyser and a detector to determine the kinetic energy of the scattered ions passed through the diaphragm.
  • Such a device is known from the US. Pat. Specification No. 3,480,774.
  • the surface layer to be examined is bombarded with a primary ion beam.
  • the ions of said beam collide with the atoms of the surface layer, which collisions may in certain conditions be considered as being elastic. This means that the kinetic energy of an ion after the collision may be calculated by means of the laws of conservation of energy and momentum.
  • the energy of the passed ions is measured in an energy analyser.
  • a given voltage at the electrodes of the energy analyser only scattered ions of a given energy E can pass the analyser. Given m E and 0, said energy is therewith characteristic of the mass m of atoms in the surface layer which are hit by the primary beam.
  • a spectrum can be obtained of the types of atoms occurring in the surface layer.
  • a peak in the signal is obtained which the detector supplies.
  • the values of the peak is a measure of the relative quantity of the relevant atoms and the voltage on the analyser associated with the peak is a measure of the mass of the relevant atoms.
  • angle 0 must be accurately determined and the aperture in the diaphragm should therefore be so small that only few scattered ions are passed.
  • 6 should be determined to an accuracy of 1 to 2 by the diaphragm, which has for its result for the known device that only scattered ions within a space angle of 2 X 2 can be accepted so that only a very small signal is formed.
  • an energy analyser having two coaxial cylindrical electrodes.
  • Such an analyser has the advantage that the paths of the scattered ions which enclose a given angle with the axis of the analyser, with which axis the axis of the primary beam coincides, lie on a conical surface.
  • an annular diaphragm having a gap which is 2 wide and has a circumference of 360, 180 times as many ions are accepted by the analyser as by the analyser which is used in the device described in the US. Pat. Specification No. 3,480,774.
  • a device of the type mentioned in the first paragraph is characterized in that the electrostatic analyser comprises two substantially cylindrical hollow coaxial electrodes, that the axis of the primary ion beam coincides substantially with the axis of the analyser, that the diaphragm aperture is substantially annular and is coaxial with the analyser and has a position to pass ions which are scattered over an angle exeeding and that the detector is substantially annular and coaxial with the analyser and surrounds the primary ion beam.
  • the ions are preferably detected at an average angle of scattering between 137 and With said angles of scattering it is possible to make a second order focus of the scattered ions on the detector without the scattered ions first passing the axis of the analyser.
  • a second order focus has the advantage that ions from a comparatively wide region around the average angle of scattering are focused on the detector.
  • FIG. 1 is a perspective view, partially broken away, of a cylindrical analyser for a device according to the invention.
  • FIG. 2 is a diagrammatic sectional view of a device according to the invention.
  • a'primary, substantially monoenergetic ion beam 1 impinges upon a target 2 with an energy of, for example, a few hundred eV.
  • the ions should be selected for mass, charge and energy, which may be carried out with means which are known from the prior art and which need no further explanation.
  • Rare gas ions for example helium or neon ions, are preferably used.
  • An advantage of said ions is their large ionisation energy; this results in a fair chance of their charge being neutralised during the collision, which, it is true, results in a small number of scattering ions but also reduces the possibility of detection of multiple collisions which spoil the measurement.
  • a device according to the invention has just the property that also in the case of a small number of scattered ions sufficient signal is still produced by the detector.
  • the axis of the primary ion beam 1 coincides with the axis of an energy analyser 3.
  • the energy analyser 3 comprises two coaxial cylindrical electrodes 4 and 5.
  • the ions of the beam 1 collide against atoms in the sur-.
  • the energy analyser 3 measures said loss of energy for a given angle (FIG. 2) which exceeds 90. So here we have to do with back scattering.
  • the angle 6 may be. for example. 141 so that the ions accepted by the energy analyser describe paths over the surface of a cone with an apex of 78.
  • the angle 0 is determined by the position of the diaphragm aperture 6 in the cylindrical electrode 4 relative to the target 2. In the radial electric field between the electrodes 4 and 5 the scattered ions describe quasi-parabolic paths. a few of which are denoted by 7, 8. 9 and 10.
  • the energy analyser 3 focuses ion paths which start in the point 12 on the target 2 in an annular focus behind the diaphragm aperture 11.
  • an annular detector 13 is arranged to detect the scattered ions. Said annular detector 13 surrounds the primary ion beam 1 so that same can reach the target 2 without hindrance.
  • F IG. 2 shows for further explanation a sectional view of a device according to the invention namely along a plane through the axis of the primary ion beam 1.
  • the beam 1 is produced by an ion source 14 extracted by an extraction electrode 15, focused by focusing electrodes 16 and 17 and selected for mass by a mass filter 18.
  • the energy analyser 3 has the same reference numerals as in FIG. 1.
  • the electric field between the electrodes 6 and 7 should be everywhere equal to the field between two infinitely long coaxial cylinders. Since the cylinders in practice have a restricted length. electrodes should be provided so as to establish the boundary conditions for the field and possibly slightly correct the field. For that purpose the cylinders 4 and 5 are closed by means of the plates 19 and 20 which are not shown in FIG. 1 for clarity. The plates 19 and 20 introduce an average potential between that of the cylinders 4 and 5. It is also possible to divide the plates 19 and 20 into several electrodes having different potentials so as to obtain a better approximation of the required electric field. The plates may also be manufactured from a material having a large electric resistance and be connected to the cylinders 4 and 5 so as to obtain a uniformly varying potential.
  • a device according to the invention operates with back scattering. Although fewer ions are scattered in the backward direction than in the forward direction, the device according to the invention is just very suitable to detect small quantities of ions.
  • the described back scattering on the contrary has important advantages. First. when the primary beam impinges upon the target approximately perpendicularly, the possibility of sputtering is so much smaller so that the surface layer of the sample is less damaged by the primary beam. At an angle of incidence of 90, sputtering often occurs only at eV, while at an angle of incidence of 45 10 eV is already sufficient. Second, the possibility of multiple collisions which spoil the measured result is much smaller with an approximately perpendicular incidence of the primary beam on the target than with angles of incidence smaller than 90.
  • a low-energy electron gun or a filament may be arranged near the target so as to ensure in known manner for space charge compensation. It is furthermore possible to slowly peel the target layer by layer by means of a separate ion beam or by means of the primary beam with increased intensity, so as to be able to-thus analyse deeper situated layers also.
  • the inner diameter of the electrode 5 in the device shown in the drawing is 125 mm and the outer diameter of the electrode 4 is 50 mm.
  • the distance between the point 12 on the target 2 and the centre of the annular detector 13 is mm.
  • the angle 6 is 141.
  • the electrode 4 is earthed in connection with the transport of the primary ion beam 1. For selecting ions with an energy of V electron volt the potential of the electrode 5 (relative to the electrode 4) should then be V volt.
  • the ion source 14 supplies a flow of ions of the order of magnitude of a few nanoamperes to a few microamperes with an energy which is adjustable from a few tens of volts to a few kilovolts.
  • an energy which is adjustable from a few tens of volts to a few kilovolts rather high requirements are imposed upon the energy spreading of the ions which emerge from the ion source. In practice this should be between 0.1 and 1.0 eV, which is possible with ion sources known from the prior art.
  • the mass filter 18 preferably consists of the known Wien filter.
  • this filter the beam is subjected to the influence of an electric and a magnetic field the directions of which extend perpendicular to each other and to the axis of the beam. This has for its result that of the substantially mono-energetic ion beam only ions having one given mass are not deflected and can pass the filter. The other ions are deflected indeed and are intercepted at some distance from the mass filter by means of a diaphragm.
  • the detector 13 must detect such a small ion flow that direct current measurement is not possible with sufficient accuracy.
  • a so-called channel plate is used as a detector which consists of a plate having a very large number of extremely thin secondary emitting channels.
  • Per incident ion which after passing the diaphragm aperture 11 is post-accelerated to an energy of a few kilovolts by giving the detector a suitable potential relative to the electrode 4, such a channel plate supplies 10 to 10 electrons at the output. Per ion said electrons form an electron pulse.
  • the pulse frequency is measured with known electric means and thus forms a measure of the number of ions entering the detector per second and hence of the ion flow.
  • a device for analyzing a surface layer by means of ion scattering comprising:
  • a substantially annular diaphragm aperture adapted to pass said ions scattered at said surface layer at a predetermined angle with respect to the axis of said ion beam, said angle exceeding 90 with respect to the original direction of said primary ion beam;
  • an electrostatic analyzer comprising two substand. detector means for determining the kinetic energy of those of said scattered ions passing through said diaphragm aperture, said detector means comprising a substantially annular detector element that is coaxial with said analyzer and extends around said 7 primary. ion beam axis, said detector being removed from said surface layer in the direction of said. ion source.

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  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Electron Tubes For Measurement (AREA)
  • Analysing Materials By The Use Of Radiation (AREA)
US466220A 1973-05-08 1974-05-02 Device for analysing a surface layer by means of ion scattering Expired - Lifetime US3920990A (en)

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NL7306378A NL7306378A (xx) 1973-05-08 1973-05-08

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US3920990A true US3920990A (en) 1975-11-18

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US (1) US3920990A (xx)
JP (1) JPS5514504B2 (xx)
DE (1) DE2420275C3 (xx)
FR (1) FR2229064B1 (xx)
GB (1) GB1470847A (xx)
NL (1) NL7306378A (xx)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2929911A1 (de) * 1978-09-01 1980-03-13 Physical Electronics Ind Inc Augerelektronenspektroskop mit einem augeranalysator mit magnetischer linse
US4224518A (en) * 1978-12-21 1980-09-23 Varian Associates, Inc. Multistage cylindrical mirror analyzer incorporating a coaxial electron gun
US4588890A (en) * 1984-12-31 1986-05-13 International Business Machines Corporation Apparatus and method for composite image formation by scanning electron beam
US4633084A (en) * 1985-01-16 1986-12-30 The United States Of America As Represented By The United States Department Of Energy High efficiency direct detection of ions from resonance ionization of sputtered atoms
US4941980A (en) * 1989-02-17 1990-07-17 Opal, Inc. System for measuring a topographical feature on a specimen
US5032724A (en) * 1990-08-09 1991-07-16 The Perkin-Elmer Corporation Multichannel charged-particle analyzer
US5095208A (en) * 1988-06-24 1992-03-10 Hitachi, Ltd. Charged particle generating device and focusing lens therefor
US5813862A (en) * 1994-12-08 1998-09-29 The Regents Of The University Of California Method and device for enhancing the recognition of speech among speech-impaired individuals
US20050274902A1 (en) * 2004-03-25 2005-12-15 Bruker Daltonik Gmbh Ion-optical phase volume compression
WO2012007267A3 (en) * 2010-07-13 2012-06-07 Shimadzu Corporation Charged particle energy analysers and methods of operating charged particle energy analysers

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3041914A1 (de) * 1980-11-06 1982-06-16 Vdo Adolf Schindling Ag, 6000 Frankfurt Einrichtung zur kapazitiven fuellstandsmessung
JPS57194446A (en) * 1981-05-22 1982-11-30 Shimadzu Corp Charged particle energy analyzer
DE3803424C2 (de) * 1988-02-05 1995-05-18 Gsf Forschungszentrum Umwelt Verfahren zur quantitativen, tiefendifferentiellen Analyse fester Proben
JPH0299828A (ja) * 1988-10-06 1990-04-11 Iseki & Co Ltd 流量測定器

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3480774A (en) * 1967-05-26 1969-11-25 Minnesota Mining & Mfg Low-energy ion scattering apparatus and method for analyzing the surface of a solid
US3783280A (en) * 1971-03-23 1974-01-01 Ass Elect Ind Method and apparatus for charged particle spectroscopy

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3735128A (en) * 1971-08-27 1973-05-22 Physical Electronics Ind Inc Field termination plate

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3480774A (en) * 1967-05-26 1969-11-25 Minnesota Mining & Mfg Low-energy ion scattering apparatus and method for analyzing the surface of a solid
US3783280A (en) * 1971-03-23 1974-01-01 Ass Elect Ind Method and apparatus for charged particle spectroscopy

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4205226A (en) * 1978-09-01 1980-05-27 The Perkin-Elmer Corporation Auger electron spectroscopy
DE2929911A1 (de) * 1978-09-01 1980-03-13 Physical Electronics Ind Inc Augerelektronenspektroskop mit einem augeranalysator mit magnetischer linse
US4224518A (en) * 1978-12-21 1980-09-23 Varian Associates, Inc. Multistage cylindrical mirror analyzer incorporating a coaxial electron gun
US4588890A (en) * 1984-12-31 1986-05-13 International Business Machines Corporation Apparatus and method for composite image formation by scanning electron beam
US4633084A (en) * 1985-01-16 1986-12-30 The United States Of America As Represented By The United States Department Of Energy High efficiency direct detection of ions from resonance ionization of sputtered atoms
US5095208A (en) * 1988-06-24 1992-03-10 Hitachi, Ltd. Charged particle generating device and focusing lens therefor
US4941980A (en) * 1989-02-17 1990-07-17 Opal, Inc. System for measuring a topographical feature on a specimen
US5032724A (en) * 1990-08-09 1991-07-16 The Perkin-Elmer Corporation Multichannel charged-particle analyzer
US5813862A (en) * 1994-12-08 1998-09-29 The Regents Of The University Of California Method and device for enhancing the recognition of speech among speech-impaired individuals
US20050274902A1 (en) * 2004-03-25 2005-12-15 Bruker Daltonik Gmbh Ion-optical phase volume compression
US7276688B2 (en) * 2004-03-25 2007-10-02 Bruker Daltonik Gmbh Ion-optical phase volume compression
WO2012007267A3 (en) * 2010-07-13 2012-06-07 Shimadzu Corporation Charged particle energy analysers and methods of operating charged particle energy analysers
US8866103B2 (en) 2010-07-13 2014-10-21 Shimadzu Corporation Charged particle energy analysers and methods of operating charged particle energy analysers

Also Published As

Publication number Publication date
FR2229064A1 (xx) 1974-12-06
JPS5514504B2 (xx) 1980-04-16
GB1470847A (en) 1977-04-21
DE2420275B2 (de) 1980-09-25
DE2420275C3 (de) 1981-07-09
DE2420275A1 (de) 1974-11-28
FR2229064B1 (xx) 1977-06-24
JPS5028393A (xx) 1975-03-22
NL7306378A (xx) 1974-11-12

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