WO2007017621A1 - Dispositif optique à électrons - Google Patents

Dispositif optique à électrons Download PDF

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Publication number
WO2007017621A1
WO2007017621A1 PCT/GB2006/002306 GB2006002306W WO2007017621A1 WO 2007017621 A1 WO2007017621 A1 WO 2007017621A1 GB 2006002306 W GB2006002306 W GB 2006002306W WO 2007017621 A1 WO2007017621 A1 WO 2007017621A1
Authority
WO
WIPO (PCT)
Prior art keywords
electron
optical apparatus
imaging optics
sample holder
specimen
Prior art date
Application number
PCT/GB2006/002306
Other languages
English (en)
Inventor
Joseph Ernest Morgan
David Stanley Harding
Original Assignee
Cambridge Image Technology Limited
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 Cambridge Image Technology Limited filed Critical Cambridge Image Technology Limited
Publication of WO2007017621A1 publication Critical patent/WO2007017621A1/fr

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Classifications

    • 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
    • G01N23/22—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 measuring secondary emission from the material
    • G01N23/225—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 measuring secondary emission from the material using electron or ion
    • 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
    • H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
    • H01J2237/02—Details
    • H01J2237/0216—Means for avoiding or correcting vibration effects
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
    • H01J2237/06—Sources
    • H01J2237/063—Electron sources
    • H01J2237/06325—Cold-cathode sources
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
    • H01J2237/16—Vessels

Definitions

  • This invention relates to electron-optical apparatus, such as those using electron beams and ion beams, and in particular an electron probe microanalyser for assessing specimens using optical cathode luminescence, X-ray analysis and associated techniques.
  • Electron-optical apparatus such as an electron probe microanalyser, is used to obtain information about specimens in a variety of different scientific fields, including the biological, chemical, geological and geophysical fields.
  • Microanalysers generate electron and optical beams which are used to obtain information about the distribution and shape of particles within specimens, for example using cathode luminescence.
  • Microanalysisrs also allow for X-ray analysis on non-luminescent material, for example ores and specimens obtained from ocean dredging.
  • Specimens undergoing analysis are placed within a sealed vacuum chamber.
  • the vacuum chamber incorporates transparent windows and is placed beneath a microscope which images the specimen from radiation modified by the specimen surface.
  • the quality of image obtained depends on the amount of radiation collected, which is in turn dependent on the distance between the microscope objective and the sample. Long exposure times are used to compensate for the distance between the microscope and the sample. However the image can alter during exposure, for example due to vibration, so affecting the image quality.
  • This is a particular problem where a microanalyser is being used in an environment which cannot be precisely controlled, for example on board a survey ship or in a field laboratory. It is an aim of the present invention to provide an electron-optical apparatus that allows images to be obtained using shorter exposure times, so reducing the impact of the external environment on the image.
  • an electron-optical apparatus such as an electron probe microanalyser, comprising means for generating an electron beam, a sample holder and imaging optics, wherein the apparatus further comprises a vacuum chamber containing and surrounding both the sample holder and the imaging optics.
  • the apparatus further comprises a vacuum chamber containing and surrounding both the sample holder and the imaging optics.
  • the imaging optics typically comprise a magnifying lens and a focussing lens, with additional polarisers, filters, analysers, beam restricters, beam splitters within the chamber as required.
  • the means for generating the electron beam is also contained and surrounded by the vacuum chamber.
  • the means for generating an electron beam may be a cold cathode electron source, otherwise known as a plasma electron source, which generates electrons by ionising the surrounding gaseous environment, so releasing electrons for imaging purposes and analysis.
  • the means for generating an electron beam may generate a wide, or flood, beam which is incident upon an aperture which reduces the beam diameter. With an aperture of suitable size to restrict the flood beam to 100 microns in diameter, a 300-400 micron working distance between the imaging optics and the sample holder is obtainable.
  • the sample holder is moveable along three independent orthogonal axes and is motorised for ease of adjustment.
  • the apparatus may further comprise a sample transfer means to allow specimens to be placed into the vacuum or removed from the vacuum.
  • a micro-drill may be provided within the chamber, manouverable to drill small samples from a specimen being analysed.
  • the drill By placing the drill within the chamber, the drill can be positioned directly over an area of interest which has already been identified by analysis, and the vacuum switched off whilst the micro-drill obtains small samples for further analysis. This improves the accuracy of obtaining supplementary samples from an existing specimen as the drill can be positioned whilst the specimen is being imaged.
  • Typical light sources such as lasers
  • Apparatus for assessing the radiation from the specimen for example spectrometers, mass spectrometers, can be placed external to or inside the chamber.
  • the critical distance for imaging specimens is the distance between the imaging optics and the specimen on the sample stage, this working distance needing to be as small as possible if exposure times are to be kept as short as possible.
  • the distance from the imaging optics to the elements external the chamber, for example a cooled CCD camera and a spectrometer, is not critical to the exposure time as beyond the imaging optics the optical beam is parallel, i.e. infinity optics.
  • the electron probe microanalyser of Figure 1 comprises a plurality of elements within an envelope formed by vacuum chamber 10, these elements being surrounded and contained by the vacuum chamber.
  • the analyser at around 0.027m 3 total volume is more compact than a conventional system and, by inclusion of all the elements within a sealed unit, is more robust.
  • Analysis and recording equipment for example spectrometer 12, mass spectrometer 14, cooled CCD camera 16 and also light sources 18, 20 are external to the analyser and do not form part of the present invention, although are used in combination with the present invention. If desired, the mass spectrometer 14, spectrometer 12, and light sources 18, 20 can be placed in the vacuum chamber 10.
  • a specimen stage 22 which is moveable in the x, y and z axes by motors, carries a specimen 24.
  • the specimen 24 is positioned at a working distance x from imaging optics 26 normal to the optical axis and which consist of two lenses, one of which magnifies and one of which focusses the beam.
  • Light path 30 defines the light optical axis through the microanalyser with the focussed part 32 of the image beam being a parallel beam and so directed to infinity.
  • the distance from the chamber of the external elements, i.e. the spectrometer 12, the light sources 18, 20, mass spectrometer 14, and cooled camera 16, does not affect the imaging capabilities of the apparatus as beam 32 is a parallel beam.
  • the working distance x depends on the diameter of a beam 34 from a cold cathode electron gun 36 or alternative beam source such as a hot cathode.
  • the cold cathode electrode gun 36 is a plasma electron source which ionises the partial vacuum of between 5xlO "2 Torr and 10 "6 Torr, so releasing electrons which can be targeted obliquely towards the sample in beam 34, intersecting the specimen beneath the optics 26.
  • the beam has a wide diameter, known as a flood beam, and can be reduced in diameter by beam restricter and X-ray target selector 38 if required so that a beam of 100 microns is incident upon the specimen 24.
  • the narrower the beam diameter the smaller the working distance x, so increasing optical sensitivity. With a 100 micron diameter beam, a working distance of around 300-400 microns is obtainable. With a larger beam diameter, the working distance increases, but one is able to look at a larger area of the specimen.
  • the working distance is able to be reduced more than would be possible if the imaging optics were outside the vacuum chamber and thus the exposure time required to obtain an image of sufficient resolution is reduced. This is due to the inverse square law for radiant energy, where for a given collection area, if you double the distance of the collection area away from the, emission point, the light received is reduced by a quarter.
  • the imaging optics 26 closer to the specimen 24, more light is obtained in a shorter exposure time, so obtaining the same quality image in a shorter time than for a system where the optics are further away, because they are outside the vacuum.
  • the sample image can change slightly during exposure, for example due to vibration or beam damage to the sample which can alter the spectra seen from the sample. Therefore reducing the exposure time is of particular advantage where the data is being acquired outside a normal laboratory, for example on board a ship during acquisition of sample for analysis by sedimentologists.
  • a rotating motorised polariser 40 and motorised filter 42 are of use in certain analysis techniques, and a solenoid controlled analyser 44 can be placed within the chamber.
  • An energy dispersive X-ray (EDX) detector 46 can be placed within the chamber for when X-ray analysis is required.
  • a motorised filter 42' in front of one or more of the light sources 18, 20 is sometimes desirable.
  • a micro-drill 48 can also be positioned within the chamber, so that small samples can be drilled directly from the main specimen 24 without needing to remove the specimen 24 from the chamber 10. This allows more accurate selection and acquisition of small supplementary samples.
  • a sample collection transfer device 50 is also provided to assist with placing the specimen 24 into and out of the chamber 10. This may incorporate a disposable cover slip to protect the objective lens within optics 26.
  • the light source 18 is a laser beam directed through the optical axis 30 to achieve laser ablation of the specimen for analysis by mass spectrometers 14. Raman spectrometry is also possible.
  • the analyser is appropriate for use in areas where on-site analysis is required, for example in forensic science.
  • the analyser is suitable for use anywhere where a conventional microanalysisr is over-specified as far as resolution is concerned.
  • a conventional microanalysisr is over-specified as far as resolution is concerned.
  • many conventional probes use a very fine beam which is de-focussed to give a spatial resolution at 1 micron. For many purposes this is too small a resolution, and being able to resolve to a spatial resolution of around 100 microns is quite sufficient.
  • the microanalyser enables direct optical observation or measurement simultaneously with the action of the applied beam, providing minimum optical working distance for optimum optical performance. Where any other process does not require or allow simultaneous optical observation or measurement, the objective lens or specimen can be positioned in an alternative position.
  • Other physical parameters can be varied at the sample simultaneously or separately while maintaining optical performance, for example the electroluminesce can be adjusted depending on an applied voltage. Differential vacuum levels permit all vacuum-dependent excitation and analytical techniques to be used.

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  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Analysing Materials By The Use Of Radiation (AREA)

Abstract

La présente invention concerne un microanalyseur optique à électrons, comprenant un faisceau d'électrons de cathode à froid, un support d'échantillon (22), et des optiques d'imagerie, le dispositif comprenant en outre une chambre à vide (10) contenant, et entourant à la fois le support d'échantillon (22) et les optiques d’imagerie (26). En plaçant les optiques d’imagerie (26) et le support d’échantillon à l’intérieur de la chambre à vide (10), la distance physique entre les optiques d’imagerie (26) et l’échantillon est réduite (24). Cela permet de réduire les temps d’exposition nécessaires à l’obtention d’une image ou d'un spectre de même qualité qu'avec les systèmes de l'art antérieur présentant des distances supérieures entre les optiques d'imagerie et les supports d'échantillons/ Les effets de vibration sont sensiblement réduits en raison de la réduction des temps d'exposition nécessaires.
PCT/GB2006/002306 2005-08-05 2006-06-22 Dispositif optique à électrons WO2007017621A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB0516098.1 2005-08-05
GB0516098A GB0516098D0 (en) 2005-08-05 2005-08-05 Electron-optical apparatus

Publications (1)

Publication Number Publication Date
WO2007017621A1 true WO2007017621A1 (fr) 2007-02-15

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB2006/002306 WO2007017621A1 (fr) 2005-08-05 2006-06-22 Dispositif optique à électrons

Country Status (2)

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GB (1) GB0516098D0 (fr)
WO (1) WO2007017621A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109324062A (zh) * 2017-07-31 2019-02-12 台湾积体电路制造股份有限公司 极紫外光容器检查方法
CN115616017A (zh) * 2022-09-30 2023-01-17 南方科技大学 一种电子光学测试平台装置

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1260575B (de) * 1962-09-04 1968-02-08 United Aircraft Corp Verfahren zur zerstoerungsfreien Pruefung elektronischer Bauteile
JPS60247140A (ja) * 1984-05-22 1985-12-06 Shimadzu Corp カソ−ドルミネツセンス装置

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1260575B (de) * 1962-09-04 1968-02-08 United Aircraft Corp Verfahren zur zerstoerungsfreien Pruefung elektronischer Bauteile
JPS60247140A (ja) * 1984-05-22 1985-12-06 Shimadzu Corp カソ−ドルミネツセンス装置

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
CARLSSON L ET AL: "An efficient apparatus for studying cathodoluminescence in the scanning electron microscope", JOURNAL OF PHYSICS E: SCIENTIFIC INSTRUMENTS 1974, vol. 7, no. 2, 1974, pages 98 - 100, XP002409517 *
HERMAN M A ET AL: "HETEROINTERFACES IN QUANTUM WELLS AND EPITAXIAL GROWTH PROCESSES: EVALUATION BY LUMINESCENCE TECHNIQUES", JOURNAL OF APPLIED PHYSICS, AMERICAN INSTITUTE OF PHYSICS. NEW YORK, US, vol. 70, no. 2, 15 July 1991 (1991-07-15), pages R1 - R52, XP000241733, ISSN: 0021-8979 *
ROBINS L H ET AL: "CATHODOLUMINESCENCE OF DEFECTS IN DIAMOND FILMS AND PARTICLES GROWNBY HOT-FILAMENT CHEMICAL-VAPOR DEPOSITION", PHYSICAL REVIEW, B. CONDENSED MATTER, AMERICAN INSTITUTE OF PHYSICS. NEW YORK, US, vol. 39, no. 18, 15 June 1989 (1989-06-15), pages 13367 - 13377, XP000036119, ISSN: 0163-1829 *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109324062A (zh) * 2017-07-31 2019-02-12 台湾积体电路制造股份有限公司 极紫外光容器检查方法
CN109324062B (zh) * 2017-07-31 2024-02-09 台湾积体电路制造股份有限公司 极紫外光容器检查方法
CN115616017A (zh) * 2022-09-30 2023-01-17 南方科技大学 一种电子光学测试平台装置
CN115616017B (zh) * 2022-09-30 2023-11-10 南方科技大学 一种电子光学测试平台装置

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