WO1999044399A1 - Apparatus for the investigation of surface chemistry - Google Patents

Apparatus for the investigation of surface chemistry Download PDF

Info

Publication number
WO1999044399A1
WO1999044399A1 PCT/GB1999/000517 GB9900517W WO9944399A1 WO 1999044399 A1 WO1999044399 A1 WO 1999044399A1 GB 9900517 W GB9900517 W GB 9900517W WO 9944399 A1 WO9944399 A1 WO 9944399A1
Authority
WO
WIPO (PCT)
Prior art keywords
test piece
plasma
probe means
laser
probe
Prior art date
Application number
PCT/GB1999/000517
Other languages
French (fr)
Inventor
Stewart Robert Chesterfield
Christopher Budd
Original Assignee
Matra Bae Dynamics (Uk) 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 Matra Bae Dynamics (Uk) Limited filed Critical Matra Bae Dynamics (Uk) Limited
Priority to AU25392/99A priority Critical patent/AU2539299A/en
Priority to EP99905096A priority patent/EP1059018A1/en
Priority to JP54326999A priority patent/JP2002509614A/en
Publication of WO1999044399A1 publication Critical patent/WO1999044399A1/en

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
    • G01N21/71—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light thermally excited
    • G01N21/718—Laser microanalysis, i.e. with formation of sample plasma
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H1/00—Generating plasma; Handling plasma
    • H05H1/0006—Investigating plasma, e.g. measuring the degree of ionisation or the electron temperature
    • H05H1/0012—Investigating plasma, e.g. measuring the degree of ionisation or the electron temperature using electromagnetic or particle radiation, e.g. interferometry
    • H05H1/005—Investigating plasma, e.g. measuring the degree of ionisation or the electron temperature using electromagnetic or particle radiation, e.g. interferometry by using X-rays or alpha rays

Abstract

A test piece (1) such as a sheet of metal is irradiated by a high power laser (4) in a vacuum chamber (2). The electromagnetic properties of the plasma formed at the irradiated metal surface are measured by three probes (5, 6, 7), these properties being indicative of the chemical nature of the irradiated surface.

Description

APPARATUS FOR THE INVESTIGATION OF SURFACE CHEMISTRY
This Invention relates to apparatus for Investigating the chemical composition of a surface.
It has been observed that when the surface of a test piece, a sheet of metal for example, Is Irradiated with a high powered laser beam, a plasma Is formed In the vicinity of point of Impact of the beam and metal surface. The plasma (or lonlsatlon) results from the Intense local heating of the metal surface by the laser beam.
Associated with the plasma are electric and magnetic fields, the Intensities of which depend upon the surface chemistry of the test piece. Thus by measuring these fields, Information regarding the chemical composition of these surface can be Inferred. For Instance, It Is possible, from field Intensity measurements to ascertain to what extent a metal surface has suffered oxidation.
Accordingly the present invention comprises apparatus for investigating the chemical composition of a surface; the apparatus including; a laser for irradiating the surface of a test piece and thereby initiating lonlsatlon of a part of the surface to form a plasma, -2-
and probe means located adjacent to said part of the surface and being responsive to the electro-magnetic properties of the plasma.
The probe means can comprise an electric field monopole having a central conductor which protrudes through an opening in the test piece.
Alternatively or additionally the probe means can be a magnetic field probe comprising a conductive loop.
As a further alternative, the probe means can be arranged to measure the conductivity of the plasma which results from the lonlsatlon process.
Some embodiments of the invention will now be described, by way of example only, with reference to the drawings of which:
Figure 1 is a schematic diagram of apparatus for investigating the surface chemistry of a test piece, and Figure 2 is a sectional view of the test piece of Figure 1 incorporating three different types of probe.
In Figure 1, a test piece comprising a metal sheet 1 whose surface chemistry is to be investigated, is located in an evacuated chamber 2. The chamber 2 incorporates an infra-red transmissive window 3, through which is projected -3-
a laser beam generated by a higher power Neodynium-YAG laser 4.
The test piece is fitted with an electric field probe 5, a magnetic field probe 6 and a plasma conductivity sensor 7. The output signals from the three probes (5,6,7) are fed to electrical measurement equipment 8 located outside the chamber 2.
A description of each of the probes (5,6,7) now follows with reference to Figure 2.
The electric field probe 5 comprises an SMA connector whose central conductor 9 is pushed through a hole which is drilled through the test piece 1. The central conductor 9 is not in electrical contact with the test piece 1, but protrudes through it into the region of plasma formation. The outer conductor 10 of the SMA connector is fixed in electrical contact with the reverse side of the test piece i.e. that side remote from the surface to be irradiated. The electric field probe 5 acts as a monopole antenna, receptive to any electric field which may be generated in an lonlsatlon process.
The magnetic field probe 6 is similar to the electric field probe 5 previously described in that it comprises an SMA connector whose central conductor 11 pushed through a -4-
hole in the test piece yet not in direct electrical contact therewith, and whose outer conductor 12 is in electrical contact with the reverse side of the test piece. A conductor loop is formed by linking the tip of the central conductor 11 with the irradiated surface of the test piece 1 by a short piece of wire 13. Any magnetic field generated in an lonlsatlon process and threading the loop will give rise to a current measurable by the equipment 8.
The plasma conductivity sensor 7 comprises a twinax cable whose two inner conductors 14, 15 protrude through a hole in the test piece 1 into the vicinity of plasma generation. Each conductors 14, 15 is isolated from the other and from the test piece by an epoxy plug 16. The outer conductor 17 of the twinax cable is in electrical contact with the reverse side of the test piece 1. In this example the conductor designated 14 is raised to a potential +V and the conductor designed 15 is fixed at a potential -V with respect to the outer conductor 17 and test piece 1. By measuring the current flowing through the inner conductors 14, 15, the conductivity of any plasma generated at the surface of the test piece 1 can be ascertained.
In operation, a pulse of infra-red laser radiation from the NdYAG laser 4 irradiates a point on the surface of the -5-
test piece 1. As a result of the intense heat generated, an lonlsatlon process occurs which results in a plasma being generated close to the surface of the test piece at the point of irradiation. The associated electric field, magnetic field and conductivity of the plasma are detected and measured by the probes 5, 6 and 7 respectively in conjunction with the electrical measurement equipment 8.
The magnitudes of the currents generated in each probe give an indication of the strength of electric and magnetic fields and of the conductivity of the plasma close to the irradiated surface. From these measurements, the chemical composition of the surface, prior to heating and lonlsatlon can be inferred.

Claims

-6-CLAIMS
1. Apparatus for investigating the chemical composition of a surface, the apparatus including: a laser for irradiating the surface of a test piece and thereby initiating lonlsatlon of a part of the surface to form a plasma, and probe means located adjacent to said part of the surface and being responsive to the electro-magnetic properties of the plasma.
2. Apparatus according to claim 1 in which the probe means protrudes through an opening in the test piece into the vicinity of plasma formation.
3. Apparatus according to claim 2 in which the probe means comprises an electric monopole.
4. Apparatus according to claim 2 in which the probe means comprises a magnetic loop sensor.
5. Apparatus according to claim 2 in which the probe means comprises a conductivity sensor comprising a pair of conductors each with a DC voltage bias, balanced relative to the test piece, between them.
6. Apparatus according to any preceding claim in which the laser is a Neodymium YAG laser. -7-
7. Apparatus according to any preceding claim in which the test piece and probes are enclosed in a vacuum chamber.
8. Apparatus for investigating the chemical composition of a surface substantially as hereinbefore described with reference to the drawings.
PCT/GB1999/000517 1998-02-26 1999-02-18 Apparatus for the investigation of surface chemistry WO1999044399A1 (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
AU25392/99A AU2539299A (en) 1998-02-26 1999-02-18 Apparatus for the investigation of surface chemistry
EP99905096A EP1059018A1 (en) 1998-02-26 1999-02-18 Apparatus for the investigation of surface chemistry
JP54326999A JP2002509614A (en) 1998-02-26 1999-02-18 Equipment for testing surface chemistry

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9803932.4 1998-02-26
GBGB9803932.4A GB9803932D0 (en) 1998-02-26 1998-02-26 Apparatus for the investigation of surface chemistry

Publications (1)

Publication Number Publication Date
WO1999044399A1 true WO1999044399A1 (en) 1999-09-02

Family

ID=10827547

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1999/000517 WO1999044399A1 (en) 1998-02-26 1999-02-18 Apparatus for the investigation of surface chemistry

Country Status (5)

Country Link
EP (1) EP1059018A1 (en)
JP (1) JP2002509614A (en)
AU (1) AU2539299A (en)
GB (1) GB9803932D0 (en)
WO (1) WO1999044399A1 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2384303A (en) * 2001-09-24 2003-07-23 Pure Wafer Ltd Detection of metals in semiconductor wafers
US7186981B2 (en) * 2003-07-29 2007-03-06 Thermal Wave Imaging, Inc. Method and apparatus for thermographic imaging using flash pulse truncation

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0719077A1 (en) * 1994-12-21 1996-06-26 Adolf-Slaby-Institut, Forschungsgesellschaft für Plasmatechnologie, und Mikrostrukturierung mbH Method and apparatus for determining of absolute plasma parameters
EP0887835A2 (en) * 1997-06-24 1998-12-30 Applied Materials, Inc. Diagnostic pedestal assembly for a semiconductor wafer processing system

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0719077A1 (en) * 1994-12-21 1996-06-26 Adolf-Slaby-Institut, Forschungsgesellschaft für Plasmatechnologie, und Mikrostrukturierung mbH Method and apparatus for determining of absolute plasma parameters
EP0887835A2 (en) * 1997-06-24 1998-12-30 Applied Materials, Inc. Diagnostic pedestal assembly for a semiconductor wafer processing system

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
C.G. MORGAN: "Laser-induced plasmas and resonance ionisation spectroscopies", IEE PROCEEDINGS: SCIENCE, MEASUREMENT AND TECHNOLOGY, vol. 141, no. 2, March 1994 (1994-03-01), INSTITUTION OF ELECTRICAL ENGINEERS, GB, pages 83 - 88, XP000434098, ISSN: 1350-2395 *
J. BRCKA ET AL: "Investigation of plasma expansion in the PLD process by means of an electrical probe", PLASMA SOURCES, SCIENCE AND TECHNOLOGY, vol. 3, no. 2, May 1994 (1994-05-01), Bristol, GB, pages 128 - 133, XP002110403 *
N. NAKANO ET AL: "Computational and experimental studies on spontaneous magnetic field generation associated with laser-produced plasmas in vacuum", JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, vol. 46, no. 3, March 1979 (1979-03-01), pages 960 - 969, XP002110404 *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2384303A (en) * 2001-09-24 2003-07-23 Pure Wafer Ltd Detection of metals in semiconductor wafers
US7186981B2 (en) * 2003-07-29 2007-03-06 Thermal Wave Imaging, Inc. Method and apparatus for thermographic imaging using flash pulse truncation

Also Published As

Publication number Publication date
AU2539299A (en) 1999-09-15
GB9803932D0 (en) 1998-04-22
EP1059018A1 (en) 2000-12-13
JP2002509614A (en) 2002-03-26

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