EP3989260A1 - Vorrichtung zur erzeugung von ionisiertem gasförmigem oder dampfförmigem material - Google Patents

Vorrichtung zur erzeugung von ionisiertem gasförmigem oder dampfförmigem material Download PDF

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Publication number
EP3989260A1
EP3989260A1 EP20203419.5A EP20203419A EP3989260A1 EP 3989260 A1 EP3989260 A1 EP 3989260A1 EP 20203419 A EP20203419 A EP 20203419A EP 3989260 A1 EP3989260 A1 EP 3989260A1
Authority
EP
European Patent Office
Prior art keywords
substrate
electrons
electrode
vapour
enable
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.)
Pending
Application number
EP20203419.5A
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English (en)
French (fr)
Inventor
Gareth Andrew Taylor
John Peter Carr
Paul Farrar
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.)
Evince Technology Ltd
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Evince Technology Ltd
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 Evince Technology Ltd filed Critical Evince Technology Ltd
Priority to EP20203419.5A priority Critical patent/EP3989260A1/de
Priority to PCT/EP2021/079036 priority patent/WO2022084370A1/en
Priority to TW110139052A priority patent/TW202232545A/zh
Publication of EP3989260A1 publication Critical patent/EP3989260A1/de
Pending legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J3/00—Details of electron-optical or ion-optical arrangements or of ion traps common to two or more basic types of discharge tubes or lamps
    • H01J3/02—Electron guns
    • H01J3/021—Electron guns using a field emission, photo emission, or secondary emission electron source
    • H01J3/022—Electron guns using a field emission, photo emission, or secondary emission electron source with microengineered cathode, e.g. Spindt-type
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J27/00—Ion beam tubes
    • H01J27/02—Ion sources; Ion guns
    • H01J27/20—Ion sources; Ion guns using particle beam bombardment, e.g. ionisers
    • H01J27/205—Ion sources; Ion guns using particle beam bombardment, e.g. ionisers with electrons, e.g. electron impact ionisation, electron attachment
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2201/00—Electrodes common to discharge tubes
    • H01J2201/30—Cold cathodes
    • H01J2201/304—Field emission cathodes
    • H01J2201/30403—Field emission cathodes characterised by the emitter shape
    • H01J2201/30407—Microengineered point emitters
    • H01J2201/30415—Microengineered point emitters needle shaped
    • 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
    • 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
    • H01J2237/06341—Field emission
    • H01J2237/0635—Multiple source, e.g. comb or array
    • 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
    • H01J2237/08—Ion sources

Definitions

  • the present invention relates to an apparatus for generating ionised gaseous material or vapour.
  • ionic gas species is utilised in a plurality of applications that include, but are not limited to, analysis of gas species using spectroscopic techniques, materials deposition, etching of materials, and propulsion. In all such cases, the lower the ambient pressure, the more difficult the generation of ionic gas species becomes.
  • a known method of generating ionised gas species consists of the provision of a discrete electron source, which may be thermionic or utilise field emission, and a geometric arrangement of electrodes and/or magnetic fields so as to create a constrained local electromagnetic environment that facilitates the creation of an avalanche condition that leads to the ionisation of the target gas species.
  • the initial source of the ionisation process i.e. the electron source
  • the efficiency of such sources becomes dependent on the effectiveness of the initial confinement method to propagate the initial avalanche process.
  • US 9194379 discloses an ion thruster comprising a permeable substrate which is formed of arrays of carbon nanotubes (CNTs), W-nanorods, ⁇ -siC nanorods, Zn-O nanopencils, other nanowires, and/or other nano - materials, singly or in combination, to accomplish the production of positive ions from a propellant gas by field ionization.
  • a permeable substrate is formed of an array of carbon nanotubes with open spaces or apertures between the carbon nanotubes.
  • ⁇ 's high field enhancement factors
  • carbon nanotubes are grown with selected optimum height and spacings.
  • ⁇ s of over 2000 are utilized in order to establish the high electric local fields needed for field ionization while the field in the overall gap (V/d) remains below vacuum breakdown.
  • International patent application WO2019/020588 discloses an arrangement in which a field emission structure is embedded within a diamond substrate.
  • This arrangement may be formed, for example, using a metal catalyst to effect the creation of a hole feature that can be filled with a conductive material to create a region of high electric field sufficient to initiate field emission of electrons into diamond.
  • the efficiency of the emitter structure may be further enhanced through the incorporation of additional layers and terminations so as to yield Fowler-Nordheim Tunnelling, as described in international patent application WO 2018/172029 .
  • the field emission tip is in this way protected from ion bombardment.
  • This embedded structure may thus form a suitable basis for an ion source which overcomes many of the problems of Spindt or other exposed nanostructure field emitters while also being amenable to highly reproducible integrated circuit manufacturing techniques.
  • Preferred embodiments of the present invention seek to provide an improved apparatus for generating ionised gaseous material or vapour.
  • an apparatus for generating an ionised gaseous material or ionised vapour comprising:
  • this provides the advantage of enabling ionisation at lower pressures by enabling the gaseous material and the emitted electrons to be located in close proximity to each other. Also, this enables the efficiency of ionisation to be improved since a plurality of conductors and apertures can be distributed across the substrate.
  • this provides the advantage of protecting the second end of the conductor from degradation by collision with ions, and enables heat to be conducted away from the second end of the conductor through the substrate.
  • At least one said electrode may be adapted to increase the emission of electrons from at least one said second end.
  • At least one said electrode may be adapted to apply an electric field to electrons adjacent at least one said first end.
  • the voltage that needs to be applied to stimulate the emission of electrons is kept to a minimum and electric fields can be precisely controlled.
  • At least one said electrode may be adapted to accelerate electrons emitted from said second surface.
  • This provides the advantage of improving control of the resulting distribution of the emitted electrons from the second surface both in terms of energy distribution and scatter.
  • At least one said electrode may be adapted to resist movement of ionised gaseous material or vapour towards said second surface.
  • This provides the further advantage of deterring ions generated in the proximity of the apparatus from travelling back towards the negatively biased elongate source of electrons and reducing their energy if they do, thereby minimising the probability of damage caused by their collision with the said source of electrons.
  • At least one said electrode may be encapsulated within the apparatus.
  • This provides the advantages of preventing the electrons emitted from a second end from flowing to a said electrode, thereby creating a leakage path, and ensures that the electric field between the said electrode and the elongate conductors is maintained completely within a solid dielectric ensuring that the maximum possible field is generated at the second end of the elongate conductor.
  • the encapsulated electrodes can by brought into closer proximity to the point of electron generation, whereby the magnitude of the applied voltages can be greatly reduced while still achieving the same electric field intensity.
  • the electrodes can also provide a combined means of focusing the distribution of the emitted electrons, thereby improving subsequent ionisation efficiency.
  • the advantage is also provided of reducing the overall structure to a single die produced using semiconductor fabrication techniques. Also, potential erosion of said electrodes by the action of a plasma during manufacture of the apparatus is minimised, and the overall efficiency of the source is improved by removing any electrical leakage path to the electrodes.
  • At least one said electrode may be encapsulated within said crystalline material.
  • At least one said electrode may be encapsulated within said crystalline material doped with nitrogen.
  • the apparatus may further comprise temperature control means for controlling the temperature of the gaseous material or vapour.
  • the crystalline material may be a group IV material.
  • the group IV material may be diamond.
  • At least one said recess may be formed by means of catalytic etching.
  • At least one said aperture may be formed by means of catalytic etching.
  • the method may further comprise encapsulating at least one said electrode within the apparatus.
  • a method of generating ionised gas or vapour using an apparatus as defined above comprising:
  • the method may further comprise controlling the temperature of the substrate.
  • an apparatus 2 for generating an ionised gaseous material comprises a substrate 4 of crystalline material in the form of as diamond in the example shown in Figure 2 , and a controlled field emission electron source structure in the form of a plurality of elongate metallic electrical conductors 6 formed in elongate recesses 8 extending from a first surface 10 of the substrate 4 such that distal ends 12 of the conductors 6 are embedded in the substrate 4 near a second surface 14 of the substrate 4.
  • the conductors 6 are connected to cathodes 16 formed on the first surface 10 of the substrate 4.
  • the apparatus 2 also has a microfluidic structure having apertures in the form of fluid flow channels 18 through which a target gas species 20 can pass.
  • the fluid flow channels 18 extend through the substrate 4 from the first surface 10 of the substrate to the second surface 14.
  • the fluid flow channels 18 have diameter typically 3 ⁇ m or less and the field emission conductors 6 have diameter 1 ⁇ m or more and aspect ratios of greater than 5: 1.
  • the conductors 6 and flow channels 18 can be distributed throughout the bulk of the substrate 4 in a regular array, which enables generation of free electrons 22 ( Figure 2 ) over a larger area of the second surface 14 of the substrate 4, and enables the free electrons 22 to interact with flowing gas 20 so that both ionisation and overall directional flow move the resulting ionised gaseous species 24 into a larger area and away from the source of initial ionisation at the second surface 14 of the substrate 4.
  • the conductors 6 can be formed by using a lithographically patterned metal catalyst to effect a controlled etch of the diamond to form the recesses 8 of aspect ratios of at least 5:1.
  • a thin film (not shown) of metal such as nickel, cobalt or iron is deposited on the first surface 10 of the substrate 8 in selective small areas, and the diamond substrate 4 is then heated in a reducing atmosphere to around 1,000°C to 1,200°C such that the catalyst selectively attacks certain crystal planes of the diamond (if single crystal).
  • the catalyst can be tuned to preferentially react with a single crystal plane.
  • a hole feature can be created adjusting the temperature so that metal catalyst preferentially reacts with the ⁇ 111 ⁇ planes it is in contact with enabling an elongate square sided hole feature to be created whose sides are defined by the ⁇ 110 ⁇ planes and the base of the hole by the ⁇ 111 ⁇ planes.
  • Those skilled in the art will be able to apply surface treatments and metallise the elongate hole features using suitable deposition techniques in order to create one or more ordered field emission structures in the form of conductors 6.
  • microfluidic channels 18 for gas flow through the substrate 4 can be created by means of similar use of a metal catalyst etch process as is used to form the recesses 8 for the conductors 6, but allowing the catalyst to completely etch through the diamond substrate 4 from the first surface 10 to the second surface 14, creating a generally square section channel if similar process conditions to those already described are used.
  • a metal catalyst etch process as is used to form the recesses 8 for the conductors 6, but allowing the catalyst to completely etch through the diamond substrate 4 from the first surface 10 to the second surface 14, creating a generally square section channel if similar process conditions to those already described are used.
  • those skilled in the art can utilise lithographic techniques combined with low pressure reactive ion etch processes to create microfluidic channels 18.
  • the cathodes 16 connected to the electrical conductors 6 at the first surface 10 of the substrate 4 enable connection of the conductors 6 to a voltage source for applying an electric field to the conductors 6.
  • the cathode structure 16 may be encapsulated, which would provide the advantage of protecting the circuit path of the cathode 16 in the event that the species 20 to be ionised is capable of precipitating onto the cathode 16 surface and/or is capable of conducting electricity in the neutral state.
  • the species 20 to be ionised is passed through the flow channels 18 from the first surface 10 to the second surface 14.
  • an electrical bias is applied between the cathode 16 and emission control electrode 26 such that the resultant electric field between the elongate conductors 6 causes electrons to be emitted from the distal ends 12 of the conductors 6 into the substrate 4.
  • positively biased with respect to cathode 16 electrons 22 are emitted from the substrate 4 through the surface 14 into the ambient atmosphere where they interact with the target species 20 resulting in the creation of ions 24.
  • FIG. 3 A typical arrangement of the flow channels 18 and field emission features 6 is shown in Figure 3 .
  • This interdigitated approach has the advantage that a larger percentage of ions 24 are generated in the initial wave as a result of the higher number density of atoms or molecules of the target species 20 in proximity to the immediate source of electrons 22, i.e. the distal ends 12 of the conductors 6, which in turn leads to a larger overall ionisation efficiency.
  • Figure 4 shows an exemplar apparatus 102 of a second embodiment of the structure described in Figures 2 and 3 , whereby a substrate 8, which incorporates the apparatus 2 is mounted in assembly that permits additional electrical biases to be applied by the use one or more external control grids as exemplified by 32 and 36 shown, which are electrically isolated using insulating spacers 34 and 38 respectively, to enhance the ionisation of the target species 20 to form ions 24.
  • external control grids as exemplified by 32 and 36 shown, which are electrically isolated using insulating spacers 34 and 38 respectively, to enhance the ionisation of the target species 20 to form ions 24.
  • the first external control grid 32 is used to attract and accelerate electrons produced by the apparatus 2 so ensure that they have sufficient energy to ionise the target species 20.
  • a second optional additional external control grid 36 may be employed to subsequently accelerate ions 24 away from the apparatus 102.
  • the electrical biasing of this external control grid 36 will be negative with respect to external control grid 32, thereby reversing the direction of the electric field.
  • different regimes of electrical biasing and a plurality of additional electrodes 36 along with their spacing and shape may be employed.
  • an apparatus 202 of a third embodiment is shown.
  • the apparatus 202 shown in Figure 5 differs from the apparatus 102 of Figure 4 in that the first additional electrode 32 and the second additional electrode 36 are integrated into the diamond substrate structure along with the control gate 26 in the form of a multilayer control electrode structure 40. Since the gaseous material 20 to be ionised would generally be neutrally charged during its passage through the fluidic channels 18, the application of various biases to the control electrodes 40 should have no impact on gas flow through the structure 202.
  • This third embodiment offers several advantages over the second embodiment.
  • the control electrodes can provide a combined means of focusing the distribution of the emitted electrons improving subsequent ionisation efficiency.
  • Thirdly this provides the advantage of reducing the overall structure to a single die produced using semiconductor fabrication techniques.
  • the arrangement of Figure 5 also includes current suppression regions 44 of nitrogen doped diamond material for suppressing flow of electrons between the elongate electrical conductors 6 and the electrodes 26, 32, 36.
  • the nitrogen doped layers of the current suppression regions are lightly doped (10 16 to 10 18 atoms per cm 3 ) so, with some, but far fewer, vacancies electrons become trapped and hence electron mobility is inhibited, thereby enabling the nitrogen doped layers to acts as more effective insulators than undoped diamond.
  • a structure can be achieved by using conventional semiconductor manufacturing processes whereby alternate lithographically patterned layers of a conductive metal such as copper, silver or aluminium and an electrically insulating material such a silicon dioxide or silicon nitride are deposited so as to achieve the desired structure.
  • a conductive metal such as copper, silver or aluminium
  • an electrically insulating material such as silicon dioxide or silicon nitride
  • the insulating material may instead be nitrogen doped diamond whose nitrogen concentration is in the range 10 16 to 10 18 atoms per cm -3 deposited using a plasma assisted chemical vapour deposition process (PA-CVD).
  • PA-CVD plasma assisted chemical vapour deposition process
  • the choice of metals will be more restricted to ensure both adhesion to the diamond, compatibility with the typical 750C to 850C conditions encountered during the PA-CVD growth process and to ensure lattice compatibility so that the deposited nitrogen-doped diamond material is predominantly single crystal. Achieving this is likely to require the deposition of multiple metals to create each electrode, for example an initial layer of 30nm titanium which carbides with the diamond to ensure adhesion followed by 100nm- 250nm of silver or copper to provide bulk electrical conduction and finally 5nm of iridium to provide close lattice constant matching to ensure heteroepitaxial single crystal growth.
  • control electrode 26 will still be biased with reference to the cathode 16 so as to stimulate and regulate the generation of electrons.
  • the next control electrode 32 will be biased positively with respect to the control electrode 26 so as to provide a means of accelerating the electrons out of the diamond.
  • the final control electrode 36 may be biased positively or negatively with respect to the control electrode 32. This has the advantage of providing better control of the resulting distribution of the emitted electrons 22 from the structure 202 in terms of energy distribution and scatter thereby providing more effective ionisation of the target species 20.
  • an apparatus 302 of a fourth embodiment is shown, which differs from the apparatus 202 of Figure 5 in that a thermal management system 42 is brought into proximity with the substrate 4 containing the ionisation source structure in order to effect heating or cooling of the substrate 4.
  • a thermal management system 42 is brought into proximity with the substrate 4 containing the ionisation source structure in order to effect heating or cooling of the substrate 4.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Combustion & Propulsion (AREA)
  • Physical Or Chemical Processes And Apparatus (AREA)
EP20203419.5A 2020-10-22 2020-10-22 Vorrichtung zur erzeugung von ionisiertem gasförmigem oder dampfförmigem material Pending EP3989260A1 (de)

Priority Applications (3)

Application Number Priority Date Filing Date Title
EP20203419.5A EP3989260A1 (de) 2020-10-22 2020-10-22 Vorrichtung zur erzeugung von ionisiertem gasförmigem oder dampfförmigem material
PCT/EP2021/079036 WO2022084370A1 (en) 2020-10-22 2021-10-20 Apparatus for generating ionised gaseous or vapour material
TW110139052A TW202232545A (zh) 2020-10-22 2021-10-21 用於產生電離氣體或蒸氣材料的設備

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP20203419.5A EP3989260A1 (de) 2020-10-22 2020-10-22 Vorrichtung zur erzeugung von ionisiertem gasförmigem oder dampfförmigem material

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EP3989260A1 true EP3989260A1 (de) 2022-04-27

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EP20203419.5A Pending EP3989260A1 (de) 2020-10-22 2020-10-22 Vorrichtung zur erzeugung von ionisiertem gasförmigem oder dampfförmigem material

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TW (1) TW202232545A (de)
WO (1) WO2022084370A1 (de)

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3852595A (en) * 1972-09-21 1974-12-03 Stanford Research Inst Multipoint field ionization source
US9194379B1 (en) 2010-02-10 2015-11-24 The United States Of America As Represented By The Secretary Of The Navy Field-ionization based electrical space ion thruster using a permeable substrate
US20180051679A1 (en) * 2015-02-20 2018-02-22 Commonwealth Of Australia As Represented By Defen- Ce Science And Technology Group Of The Department Thruster
WO2018172029A1 (en) 2017-03-22 2018-09-27 Evince Technology Ltd Diamond semiconductor device
WO2019020588A1 (en) 2017-07-28 2019-01-31 Evince Technology Limited DEVICE FOR CONTROLLING ELECTRON FLOW AND METHOD OF MANUFACTURING THE DEVICE

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3852595A (en) * 1972-09-21 1974-12-03 Stanford Research Inst Multipoint field ionization source
US9194379B1 (en) 2010-02-10 2015-11-24 The United States Of America As Represented By The Secretary Of The Navy Field-ionization based electrical space ion thruster using a permeable substrate
US20180051679A1 (en) * 2015-02-20 2018-02-22 Commonwealth Of Australia As Represented By Defen- Ce Science And Technology Group Of The Department Thruster
WO2018172029A1 (en) 2017-03-22 2018-09-27 Evince Technology Ltd Diamond semiconductor device
WO2019020588A1 (en) 2017-07-28 2019-01-31 Evince Technology Limited DEVICE FOR CONTROLLING ELECTRON FLOW AND METHOD OF MANUFACTURING THE DEVICE

Also Published As

Publication number Publication date
WO2022084370A1 (en) 2022-04-28
TW202232545A (zh) 2022-08-16

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