EP0058137A2 - Appareil à rayons X - Google Patents

Appareil à rayons X Download PDF

Info

Publication number
EP0058137A2
EP0058137A2 EP82810049A EP82810049A EP0058137A2 EP 0058137 A2 EP0058137 A2 EP 0058137A2 EP 82810049 A EP82810049 A EP 82810049A EP 82810049 A EP82810049 A EP 82810049A EP 0058137 A2 EP0058137 A2 EP 0058137A2
Authority
EP
European Patent Office
Prior art keywords
enclosure
rays
wall
opening
target
Prior art date
Legal status (The legal status 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 status listed.)
Withdrawn
Application number
EP82810049A
Other languages
German (de)
English (en)
Other versions
EP0058137A3 (fr
Inventor
Philip J. Mallozzi
Harold M. Epstein
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Battelle Development Corp
Original Assignee
Battelle Development Corp
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 Battelle Development Corp filed Critical Battelle Development Corp
Publication of EP0058137A2 publication Critical patent/EP0058137A2/fr
Publication of EP0058137A3 publication Critical patent/EP0058137A3/fr
Withdrawn legal-status Critical Current

Links

Images

Classifications

    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21G—CONVERSION OF CHEMICAL ELEMENTS; RADIOACTIVE SOURCES
    • G21G4/00—Radioactive sources

Definitions

  • This invention relates to apparatus for providing X-rays to an object that may be in an ordinary environment such as air at approximately atmospheric pressure.
  • Apparatus according to the present invention is especially useful for applications wherein it is expensive, time consuming, or otherwise inconvenient to move objects that are to receive soft X-rays into and out of a special environment, such as a vacuum chamber in which the X-rays are produced.
  • Typical applications of this type include laser produced X-ray systems for high resolution lithography, for extended X-ray absorption fine structure (EXAFS) spectroscopy, and for X-ray microscopy.
  • X-rays usually are produced in a vacuum, but for many purposes it is desirable to apply them in air.
  • soft X-rays especially those having photon energies of less than about 5 keV, a problem arises in bringing the X-rays from the vacuum into air, because a window that is thick enough and strong enough to withstand the pressure difference between the vacuum and the air is opaque to the X-rays, except in very small windows.
  • the problem is especially serious in X-ray lithography, where it is desirable to illuminate large areas.
  • the present invention provides simple, inexpensive, convenient means for overcoming the problem.
  • the X-ray pattern produced with iron targets irradiated with about 100-joule laser pulses at a 45 degree angle of incidence is substantially omnidirectional.
  • the conversion efficiency of greater than 25 percent refers to X-rays which are radiated away from the slab and pass perpendicularly through 3000 Angstroms of plastic (paraline) coated with 2000 Angstroms of aluminum. This conversion efficiency is thus a lower bound and refers only to the portion of the spectrum above about 300 electron volts. Most of the observed X-rays lie between about 0.3 and 1.5 keV, with a small but useful fraction having energies as high as 10 to 100 keV.
  • Apparatus according to the present invention typically employs X-ray producing means of the type described above. It may, however, use other somewhat similar means, such as equipment that uses an electron beam, rather than a laser beam, for producing the X-rays.
  • X-ray producing means of the type described above. It may, however, use other somewhat similar means, such as equipment that uses an electron beam, rather than a laser beam, for producing the X-rays.
  • the energy directing means comprises means for directing energy from a laser onto the target, as by focusing the energy onto a spot on the target having a diameter of about 1 to 200 micrometers.
  • the opening in the common wall portion is about 0.2 to 2 millimeters in diameter, and the distance between the opening and the spot on the target is about 0.2 to 5 centimeters.
  • the gas conveyed into the second enclosure is helium, hydrogen, or a hydrocarbon; preferably helium; maintained, at least in the vicinity of the highly transparent portion of the wall thereof, at a pressure of about 0.9 to 1 atmosphere.
  • the highly transparent portion of the wall of the second enclosure comprises a thin foil that typically comprises essentially beryllium or a plastic material. The thickness of the foil typically is about 2 to 20 micrometers.
  • the X-rays produced at the target typically have energies predominantly of about 0.3 to 2 keV.
  • the highly transparent portion of the wall of the second enclosure may comprise an opening therein; and the gas inside the second enclosure can be substantially separated from the air around it; either by a gas curtain passing along the opening; or by the object to which the X-rays are to be provided, or a component associated with the object, placed against the wall and covering the opening.
  • the second enclosure may have an intermediate compartment between the common wall portion and the wall having the highly transparent portion; the gas in the intermediate compartment being maintained at a pressure less than the pressure in the vicinity of the highly transparent portion of the wall of the second enclosure and greater than the pressure in the first enclosure.
  • Apparatus according to the invention for obtaining EXAFS data of a material typically comprises also spectral dispersive means in the second enclosure so located as to receive X-rays that pass through the opening and to direct the spectrally resolved X-rays on toward the highly transparent portion of the wall adjacent to the object to which the X-rays are to be provided, and the object typically comprises recording means.
  • Such apparatus typically comprises also means for positioning a sample of material in the optical path of the X-rays, either in the second enclosure or outside of the second enclosure and between the highly transparent portion of the wall and the recording means.
  • Figure 1 is a schematic plan view of typical apparatus according to the present invention.
  • Figure 2 is a similar view of a typical embodiment of the invention for obtaining EXAFS data of a material. CARRYING OUT THE INVENTION
  • typical apparatus for providing X-rays 11 to an object 12 that may be in an ordinary environment such as air at approximately atmospheric pressure comprises means such as a lens 13 for directing energy 14 onto a target 15 to produce X-rays 11 of a selected spectrum and intensiry at the target 15, a substantially fluid-tight first enclosure 16 around the target 15, means as indicated by the arrow 17 (such as a vacuum pump, not shown) for reducing the quantity of gas in the first enclosure 16 to maintain the pressure therein substantially below atmospheric pressure (typically less than about 1 torr), a substantially fluid-tight second enclosure 18 adjoining the first enclosure 16, with the two enclosures 16,18 having at least a portion of one wall 19 in common, the common wall portion 19 having therein an opening 20 large enough to permit X-rays 11 to pass through it (20) and yet small enough that the pressure reducing means can evacuate gas 21 from the first enclosure 16 at least as fast as it enters through the opening 20, the target 15 being located close enough to the opening 20
  • a mask 26 may be placed between the highly transparent portion 25 of the wall 22 and the object 12 to block,the X-rays proceeding toward the other regions of the object 12.
  • the energy directing means typically comprises a lens 13 for directing energy 14, passing through a window 29 in the first enclosure 16, from a laser 27, onto the target 15, as by focusing the energy 14 onto a spot 28 on the target 15 having a diameter of about 1 to 200 micrometers.
  • the opening 20 in the common wall portion 19 is about 0.2 to 2 millimeters in diameter, and the distance between the opening 20 and the spot 28 on the target 15 is about 0.2 to 5 centimeters.
  • the gas 24 conveyed into the second enclosure 18 is helium, hydrogen, or a hydrocarbon, such as methane; maintained at a pressure of about 0.9 to 1 atmosphere,at least in the vicinity of the highly transparent portion of the wall thereof.
  • the gas 24 comprises essentially helium, which is known to be highly transparent to X-rays as well as substantially inert.
  • the highly transparent portion 25 of the wall 22 of the second enclosure 18 comprises a thin foil 25 that typically comprises essentially beryllium or a plastic material.
  • the thickness of the foil 25 typically is about 2 to 20 micrometers. Other materials, preferably having atomic numbers of not more than about 8, may also be used. Where a less transparent material is used it must be very thin.
  • the X-rays 11 produced at the target 15 typically have energies predominantly of about 0.3 to 2 keV.
  • the highly transparent portion 25 of the wall 22 may be very thin, because the pressure on each side of it is approximately the same. It may even comprise only a gas curtain, rather than a solid material; or the mask 26 in Figure 1 or the sample 32 in Figure 2 may be placed against the thick "frame" formed by the wall 22 to substantially separate the gas 24 inside the second enclosure 18 from the air around it. Where an adjacent mask or sample is not used, the object 12 may be placed against the wall 22 to substantially separate the gas 24 inside the second enclosure 18 from the air around it.
  • At least one intermediate compartment 34 in the second enclosure 18 may be desirable to form at least one intermediate compartment 34 in the second enclosure 18, as shown in Figure 1 between the wall 19' (having an opening 20' therein for the X-rays 11 to pass through) and the wall 19.
  • the pressure in each such compartment is maintained between the pressures in the adjacent enclosed regions.
  • means such as a vacuum pump can maintain the proper pressure.
  • a differential evacuation system of the type used for the emission of electron beams into the atmosphere may be desirable.
  • the highly transparent portion 25 of the wall 22 of the second enclosure 18 may comprise an opening therein; and the gas 24 inside the second enclosure 18 can be substantially separated from the air around it; either by a gas curtain passing along the opening at 25; or by the object 12 to which the X-rays 11 are to be provided, or a component associated with the object 12 (such as the mask 26 in Figure 1 or the sample 32 in Figure 2), placed against the wall 22 and covering the opening at 25.
  • the second enclosure 18 may have an intermediate compartment 34, as in Figure 1, between the common wall portion 19 and the wall 22 having the highly transparent portion 25; the gas in the intermediate compartment 34 being maintained at a pressure less than the'pressure in the vicinity of the highly transparent portion 25 of the wall 22 of the second enclosure 18-and greater than the pressure in the first enclosure 16.
  • typical apparatus for obtaining EXAFS data of a material comprises also spectral dispersive means such as a monochromator 30 in the second enclosure 18 so located as to receive X-rays 11 that pass through the opening and to direct the spectrally resolved X-rays llR on toward the highly transparent portion 25 of the wall 22 adjacent to the object 12 to which the X-rays llR are to be provided, and the object 12 typically comprises recording means such as a photographic film 12.
  • spectral dispersive means such as a monochromator 30 in the second enclosure 18 so located as to receive X-rays 11 that pass through the opening and to direct the spectrally resolved X-rays llR on toward the highly transparent portion 25 of the wall 22 adjacent to the object 12 to which the X-rays llR are to be provided
  • the object 12 typically comprises recording means such as a photographic film 12.
  • Such apparatus typically comprises also means such as a support (not shown) for positioning a sample of material 31 in the optical path of the X-rays 11,11R, either in the second enclosure 18 as indicated by the dashed line 31, or outside of the second enclosure 18 and between the highly transparent portion 25 of the wall 22 and the recording means 12, as indicated at 32.
  • the latter position 32 usually is more convenient than positions (such as 31) in the second enclosure 18.
  • the radiant energy 14 is directed to the target 15 in a single pulse in such manner as to produce soft X-rays 11 from the target 15 in a single pulse in such manner as to produce soft X-rays 11 from the target 15 suitable for obtaining the EXAFS spectrum of the material 32, which typically is an element having an atomic number of less than 40.
  • EXAFS apparatus as in Figure 2 may comprise also means for moving the surface of the target 15 typically in a rotating and advancing motion (not shown) to provide a helical locus of points on a cylindrical surface of the target 15 travelling through the location of the focal spot 28 where the laser light energy 14 strikes the surface.
  • the energy 14 typically is directed to the moving target surface at 28 in a series of pulses in such manner as to produce soft X-rays 11 from the target 15 suitable for obtaining the EXAFS spectrum of the material 32.
  • the X-rays from the target 15 preferably comprise continuum radiation in a selected EXAFS spectral regime of the sample 32.
  • the target 15 comprises essentially an element having a continuum just above the L-lines that includes a selected EXAFS spectral regime of the sample 32.
  • the target 15 may comprise a plurality of elements whose lines are spaced closely enough to form virtually a continuum in a selected EXAFS spectral regime of the sample 11.
  • Such a target 15 typically comprises a mixture of elements of adjacent atomic numbers.
  • the radiant energy typically comprises a laser pulse 14 with a power density of at least about 1 0 13 watts per square 'centimeter, and the target 15 typically comprises a solid (typically metal) surface, whereby a surface plasma is formed and raised to the kilovolt temperature regime.
  • Some EXAFS can be obtained, however, in the ultraviolet and ultrasoft X-ray regime using lower power densities down to about 10 11 watts per square centimeter.
  • the laser pulse 14 typically is focused to strike the focal spot 28 on the taget 15 about 1 to 200 micrometers in diameter.
  • a typical method of producing X-rays for use in the present invention comprises directing radiant energy from a laser onto a target, and conversion efficiency of at least about 3 percent is obtained by providing the radiant energy in a low-power precursor pulse of approximately uniform effective intensity focused onto the surface of the target for about 1 to 30 nanoseconds so as to generate an expanding unconfined coronal plasma having less than normal solid density throughout and comprising a low-density (underdense) region wherein the plasma frequency is less than the laser radiation frequency and a higher-density (overdense) region wherein the plasma frequency is greater than the laser radiation frequency and, about 1 to 30 nanoseconds after the precursor pulse strikes the target, a higher-power main pulse focused onto the plasma for about 10 -3 to 30 nanoseconds and having such power density and total energy that the radiant energy is absorbed in the underdense region and conducted into the overdense region to heat it and thus to produce X-
  • the target typically consists essentially of an element having a high atomic number Z, i.e., an atomic number Z greater than 10.
  • the target consists essentially of iron, calcium, chromium, nickel, aluminum, lead, tungsten, or gold.
  • the amplitude, duration, and shape of the precursor pulse typically are adjusted to control the intensity and spectral content of the X-rays.
  • the precursor pulse typically comprises about 0.01 to 5 joules (about 10 10 to 10 12 watts per square centimeter) in about 1 to 30 nanoseconds, and strikes the target at an angle of about 20 to 70 degrees from its surface.
  • the main pulse typically comprises at least 0.1 joule, preferably about 10 to 200 joules in about 1 to 3 nanoseconds.
  • the target consists essentially of iron and the duration of the precursor pulse is about 8 to 10 nanoseconds.
  • the electron density in the low-density region of the plasma typically is about 10 16 to 10 21 per cubic centimeter, and in the higher-density region about 10 19 to 10 25 per cubic centimeter.
  • the radiant energy typically is focused onto a spot on the target having a diameter of about 1 to 1000 micrometers.
  • the volume of the plasma typically is about 10 -6 to 10 -3 cubic centimeter, the thickness of the plasma in any direction being about 0.001 to 0.1 centimeter.
  • the X-rays are emitted predominantly in the form of spectral lines.
  • the radiant energy may be focused onto a spot on the target having a diameter of about 1 to 100 micrometers, generating a plasma of about the same diameter, to form substantially a point source of X-rays and thus to provide substantially the advantages of stimulated emission of X-rays.
  • composition of the target and the temperature of the plasma are selected to provide a substantial amount of stimulated emission of X-rays.
  • X-rays are directed to impinge upon a fluorescent target so as to remove inner shell electrons from atoms thereof and thereby create a population inversion.
  • the required population inversion is not established by the pumping mechanism alone, but by the combined action of the pumping mechanism and a quenching mechanism that extinguishes the lower laser level at a rate sufficient to establish and continuously maintain the inversion.
  • the pumping mechanism typically comprises excitation by collisions of electrons and ions or by dielectronic recombination.
  • the quenching mechanism typically comprises Auger transitions, Coster-Krohig transitions, or collisions.
  • the radiant energy may be from a laser, or it may comprise a beam of electrons.
  • the pumping mechanism may comprise a beam of electrons.
  • Apparatus according to the present invention is especially useful for applications wherein it is expensive, time consuming, or otherwise inconvenient to move objects that are to receive soft X-rays into and out of a special environment, such as a vacuum chamber in which the X-rays are produced.
  • Typical applications of this type include laser produced X-ray systems for high resolution lithography, for extended X-ray absorption fine structure (EXAFS) spectroscopy, and for X-ray microscopy.
  • X-rays usually are produced in a vacuum, but for many purposes it is desirable to apply them in air.
  • soft X-rays especially those having photon energies of less than about 5 keV, a problem arises in bringing the X-rays from the vacuum into air, because a window that is thick enough and strong enough to withstand the pressure difference between the vacuum and the air is opaque to the X-rays, except in very small windows.
  • the problem is especially serious in X-ray lithography, where it is desirable to illuminate large areas.
  • the present invention provides simple, inexpensive convenient means for overcoming the problem of providing X-rays to an object that may be in an ordinary environment such as air at approximately atmospheric pressure.
  • Apparatus according to this invention is useful and advantageous not only in X-ray lithography but also in laser EXAFS, and especially in fast EXAFS spectroscopy with a single pulse of laser-produced X-rays,.or with a plurality of such pulses.
  • EXAFS Extended X-ray Absorption Fine Structure
  • the EXAFS spectrum of aluminum has been measured with a nanosecond pulse of soft X-rays generated by a laser-produced plasma. This technique provides a practical alternative to synchrotron radiation for the acquisition of EXAFS data. It also provides a unique capability for the analysis of molecular structure in highly transient chemical species.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • High Energy & Nuclear Physics (AREA)
  • X-Ray Techniques (AREA)
  • Analysing Materials By The Use Of Radiation (AREA)
  • Exposure Of Semiconductors, Excluding Electron Or Ion Beam Exposure (AREA)
EP82810049A 1981-02-09 1982-02-05 Appareil à rayons X Withdrawn EP0058137A3 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US23277481A 1981-02-09 1981-02-09
US232774 1981-02-09

Publications (2)

Publication Number Publication Date
EP0058137A2 true EP0058137A2 (fr) 1982-08-18
EP0058137A3 EP0058137A3 (fr) 1983-03-16

Family

ID=22874523

Family Applications (1)

Application Number Title Priority Date Filing Date
EP82810049A Withdrawn EP0058137A3 (fr) 1981-02-09 1982-02-05 Appareil à rayons X

Country Status (3)

Country Link
EP (1) EP0058137A3 (fr)
JP (1) JPS57150000A (fr)
CA (1) CA1184675A (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4484339A (en) * 1981-02-09 1984-11-20 Battelle Development Corporation Providing X-rays
EP0181193A2 (fr) * 1984-11-08 1986-05-14 Hampshire Instruments, Inc Dispositif d'irradiation par rayons X
US4692934A (en) * 1984-11-08 1987-09-08 Hampshire Instruments X-ray lithography system

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6119752U (ja) * 1984-07-11 1986-02-05 理学電機株式会社 Ｘ線誘導筒
JPH01140100A (ja) * 1987-11-26 1989-06-01 Nec Corp Ｘ線取出し方法

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3870882A (en) * 1973-05-23 1975-03-11 Gca Corp Esca x-ray source
US4119855A (en) * 1977-07-08 1978-10-10 Massachusetts Institute Of Technology Non vacuum soft x-ray lithographic source

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS4852075A (fr) * 1971-10-29 1973-07-21

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3870882A (en) * 1973-05-23 1975-03-11 Gca Corp Esca x-ray source
US4119855A (en) * 1977-07-08 1978-10-10 Massachusetts Institute Of Technology Non vacuum soft x-ray lithographic source

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4484339A (en) * 1981-02-09 1984-11-20 Battelle Development Corporation Providing X-rays
EP0181193A2 (fr) * 1984-11-08 1986-05-14 Hampshire Instruments, Inc Dispositif d'irradiation par rayons X
US4692934A (en) * 1984-11-08 1987-09-08 Hampshire Instruments X-ray lithography system
EP0181193A3 (en) * 1984-11-08 1988-04-13 Hampshire Instruments, Inc X-ray irradiation system

Also Published As

Publication number Publication date
JPS57150000A (en) 1982-09-16
EP0058137A3 (fr) 1983-03-16
CA1184675A (fr) 1985-03-26

Similar Documents

Publication Publication Date Title
Zamponi et al. Femtosecond hard X-ray plasma sources with a kilohertz repetition rate
US6333966B1 (en) Laser accelerator femtosecond X-ray source
US4484339A (en) Providing X-rays
Bollanti et al. Soft X-ray plasma source for atmospheric-pressure microscopy, radiobiology and other applications
EP0105261B1 (fr) Production de rayons x
US3360733A (en) Plasma formation and particle acceleration by pulsed laser
Harilal et al. Temporal and spatial evolution of laser ablated plasma from YBa2Cu3O7
EP0058137A2 (fr) Appareil à rayons X
Bollanti et al. Development and characterisation of an XeCl excimer laser-generated soft-X-ray plasma source and its applications
JP2006078470A (ja) ３次元微細領域元素分析方法及び３次元微細領域元素分析装置
Cullman et al. Comparison of different x‐ray sources using the same printing process parameters
US20030219097A1 (en) X-ray microscope having an X-ray source for soft X-ray
US3886366A (en) Compton back-scattered radiation source
JPS58225636A (ja) Ｘ線を対象物に照射する装置
US3870882A (en) Esca x-ray source
US3821579A (en) X ray source
JPH0760654B2 (ja) イオンビ−ム発生方法および装置
JPS6078400A (ja) プラズママイクロチヤンネルを用いた強いｘ線源
US4857730A (en) Apparatus and method for local chemical analyses at the surface of solid materials by spectroscopy of X photoelectrons
USH1200H (en) Method or creating x-rays from a pulsed laser source using a gaseous medium
Batani et al. L-shell x-ray spectroscopy of laser-produced plasmas in the 1-keV region
Martin et al. Imaging x‐ray fluorescence spectroscopy using microchannel plate relay optics
Mallozzi et al. Providing X-rays
EP0093970A1 (fr) Générateur de rayons X mous
Bollanti et al. Characteristics of a soft X-ray plasma source for different pumping laser configurations and spectral analysis

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Designated state(s): AT BE CH DE FR GB IT LU NL SE

PUAL Search report despatched

Free format text: ORIGINAL CODE: 0009013

AK Designated contracting states

Designated state(s): AT BE CH DE FR GB IT LI LU NL SE

17P Request for examination filed

Effective date: 19830907

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION HAS BEEN WITHDRAWN

18W Application withdrawn

Withdrawal date: 19831216

RIN1 Information on inventor provided before grant (corrected)

Inventor name: EPSTEIN, HAROLD M.

Inventor name: MALLOZZI, PHILIP J.