EP3891774A1 - Method and arrangement for distance control between a sample and an aperture - Google Patents

Method and arrangement for distance control between a sample and an aperture

Info

Publication number
EP3891774A1
EP3891774A1 EP19821307.6A EP19821307A EP3891774A1 EP 3891774 A1 EP3891774 A1 EP 3891774A1 EP 19821307 A EP19821307 A EP 19821307A EP 3891774 A1 EP3891774 A1 EP 3891774A1
Authority
EP
European Patent Office
Prior art keywords
sample
aperture
pressure
low
sample surface
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
EP19821307.6A
Other languages
German (de)
French (fr)
Inventor
Peter Amann
Anders Nilsson
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.)
Scienta Omicron AB
Original Assignee
Scienta Omicron AB
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 Scienta Omicron AB filed Critical Scienta Omicron AB
Publication of EP3891774A1 publication Critical patent/EP3891774A1/en
Pending legal-status Critical Current

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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
    • G01N23/227—Measuring photoelectric effect, e.g. photoelectron emission microscopy [PEEM]
    • G01N23/2273—Measuring photoelectron spectrum, e.g. electron spectroscopy for chemical analysis [ESCA] or X-ray photoelectron spectroscopy [XPS]
    • 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
    • G01N23/227—Measuring photoelectric effect, e.g. photoelectron emission microscopy [PEEM]
    • 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
    • H01J37/02—Details
    • H01J37/04—Arrangements of electrodes and associated parts for generating or controlling the discharge, e.g. electron-optical arrangement, ion-optical arrangement
    • H01J37/05—Electron or ion-optical arrangements for separating electrons or ions according to their energy or mass
    • 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
    • H01J37/26—Electron or ion microscopes; Electron or ion diffraction tubes
    • H01J37/285—Emission microscopes, e.g. field-emission microscopes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J49/00—Particle spectrometers or separator tubes
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2223/00—Investigating materials by wave or particle radiation
    • G01N2223/07—Investigating materials by wave or particle radiation secondary emission
    • G01N2223/085—Investigating materials by wave or particle radiation secondary emission photo-electron spectrum [ESCA, XPS]
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2223/00—Investigating materials by wave or particle radiation
    • G01N2223/30—Accessories, mechanical or electrical features
    • G01N2223/34—Accessories, mechanical or electrical features sensing means for gap between source and detector
    • 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
    • H01J2237/18—Vacuum control means
    • H01J2237/182—Obtaining or maintaining desired pressure
    • 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
    • H01J2237/18—Vacuum control means
    • H01J2237/188—Differential pressure
    • 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
    • H01J2237/20—Positioning, supporting, modifying or maintaining the physical state of objects being observed or treated
    • H01J2237/202—Movement
    • H01J2237/20221—Translation
    • H01J2237/20235—Z movement or adjustment
    • 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
    • H01J2237/26—Electron or ion microscopes
    • H01J2237/2602—Details
    • H01J2237/2605—Details operating at elevated pressures, e.g. atmosphere
    • 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
    • H01J2237/26—Electron or ion microscopes
    • H01J2237/285—Emission microscopes
    • H01J2237/2855—Photo-emission

Definitions

  • the present invention relates to a method and an arrangement for controlling a distance between a sample and an aperture. More specifically, the present invention relates to a method for controlling a distance between an aperture, in a wall separating a sample region from a low-pressure chamber which is vacuum pumped, and a sample surface, facing the aperture.
  • APXPS Ambient Pressure Photoemission Spectroscopy
  • APPES Ambient Pressure Photo Emission Spectroscopy
  • APPES is performed in three ways; 1) a sample is put in a chamber and the whole chamber is raised to ambient pressures in the mbar range, this is known as the backfill approach; 2) is a variant of the backfill approach where different chambers are sued for different set of experiments and the chambers are exchanged, hence this method is called the exchangeable chamber approach; and 3) an in situ gas cell encapsulate the sample with the front aperture of the analyser. All these three ways could be operated in flow mode, where the gas is let in and simultaneously pumped out via an outlet or the gas is only pumped out via the front cone and the pumping arrangement of the analyser.
  • Electrons have a very small mean free path in gas at ambient pressure. Thus, to enable the electrons to travel from a sample and pass the gas and enter the lens system, the distance between the aperture and the sample must be kept small.
  • the distance between the sample surface and the aperture has been controlled by manually observing the gap between the sample and the aperture by eye, using the scale of the manipulator, or with a camera microscope.
  • An object of the present invention is to provide a method and a computer program for controlling a distance between an aperture, in a wall separating a sample region from a low-pressure chamber which is vacuum pumped, and a sample surface, facing the aperture, which method and computer program are alternatives to the methods and computer programs of the prior art.
  • Another object of the present invention is to provide an arrangement in which a distance between an aperture, in a wall separating a sample region from a low-pressure chamber which is vacuum pumped, and a sample surface, facing the aperture, may be controlled, which method and computer program are alternatives to the methods and computer programs of the prior art.
  • the method and computer program according to the invention are primarily intended to be used for an analyser arrangement for determining at least one parameter related to charged particles emitted from a particle emitting sample.
  • the analyser arrangement is an electron spectrometer.
  • a method for controlling a distance d between an aperture, in a wall separating a sample region from a low-pressure chamber which is vacuum pumped, and a sample surface, facing the aperture, of a sample placed in the sample region at the distance from the aperture.
  • the distance d between the sample surface and the aperture may be controlled with a positioning system.
  • the method is characterized in that the method comprises the steps of
  • the method according to the first aspect provides a very precise distance control. Especially at small distances the method according to the first aspect is extremely precise and is better than the methods of the prior art where an optical microscope is used to control the distance. At distances of below 50 pm, the contrast in optical microscopes is often very poor and a reliable distance measurement is difficult.
  • the method according to the first aspect of the invention may be used to compensate for movement of the sample surface in relation to the aperture due to, e.g., thermal expansion of the sample.
  • the method requires the flow of gas to be kept constant.
  • the term wall should be interpreted broadly.
  • the wall in which the aperture is formed may have any shape.
  • a constant distance may be maintained between the sample and the aperture.
  • the method is based on the discovery that the pressure between the sample surface and the aperture for a constant flow of gas increases with a decreasing distance between the sample surface and the aperture, and that the pressure inside the low-pressure chamber, located behind/inside the aperture, increases with an increasing pressure on the outside of the aperture.
  • the correct distance may be set initially by an absolute measurement. Such an absolute measurement may be performed in many different ways. It may be possible to calibrate the pressure to different distances. Thus, it might be possible to move the sample surface to a position where the pressure in the low pressure chamber corresponds to an earlier determined pressure for the wanted distance.
  • the pressure in the low-pressure chamber may be in the interval between 10 4 to 10 2 mbar, preferably lower than 2xl0 3 mbar.
  • a low pressure is necessary for many applications such as when the low-pressure chamber is an electrostatic lens arranged to focus electrons into an electron beam.
  • the sample pressure may be provided to be higher than 1 mbar, preferably higher than 10 mbar.
  • the sample pressure may be as high as several bars.
  • a substantial pressure difference should be maintained between the interior of the low-pressure chamber and the pressure at the sample, i.e., the sample pressure.
  • a substantial pressure difference is necessary to be able to detect a pressure difference inside the low-pressure chamber for small apertures.
  • the aperture may have a largest dimension in the plane of the end surface being smaller than 1 mm.
  • the largest dimension of the aperture in the plane of the end surface is preferably smaller than 300 pm and may be smaller than 100 pm.
  • the largest dimension is equal to the diameter of the aperture.
  • a small aperture is necessary to be able to have a small distance between the aperture and the sample, which is particularly desirable for a photoelectron spectrometer at high sample pressures.
  • the diameter of the aperture determines the minimum achievable distance between the aperture and the sample surface if a high pressure is to be maintained at the sample surface.
  • a distance between the sample surface and the aperture being twice the diameter of the aperture enables a pressure at the sample surface of 99 % of the pressure at a very large distance from the aperture, when a vacuum is present on the opposite side of the aperture.
  • the pressure is 95 % of the pressure at a large distance from the aperture.
  • the possible distance between the aperture and the sample surface is approximately equal to the diameter of the aperture to maintain a reasonable pressure at the sample surface. For a very small distance between the sample surface and the aperture, a very small diameter of the aperture is necessary.
  • the distance between the sample and the aperture should preferably be kept at no more than 3 times the diameter of the aperture for the method to function with very high precision.
  • the low-pressure chamber may be an electrostatic lens for focusing electrons.
  • a computer program for controlling a distance between an aperture in a wall, separating a sample region from a low-pressure chamber, which is vacuum pumped, and a sample surface, facing the aperture, of a sample placed in the sample region at the distance from the aperture.
  • the distance between the sample surface and the aperture may be controlled with a positioning system.
  • At least one gas outlet connected to a gas supply device, is arranged to direct gas into a volume between the wall and the sample surface.
  • Said computer program comprises instructions which, when executed by at least one processor cause the at least one processor to carry out the steps of
  • the computer program gives the advantages as were described in relation to the method according to the first aspect of the present invention.
  • the term wall should be interpreted broadly.
  • the wall in which the aperture is formed may have any shape.
  • a computer-readable storage medium carrying a computer program according to the second aspect for controlling a distance between an aperture and a sample surface is provided.
  • an arrangement for collecting charged particles from a sample surface of a sample.
  • the arrangement comprises a sample holder, for holding the sample in a sample region, a low-pressure chamber, comprising an aperture, in a wall separating the sample region from the low-pressure chamber, wherein the aperture is arranged to face the sample surface of the sample, when it is placed in the sample holder, in order to collect charged particles from the sample surface into the low-pressure chamber.
  • the arrangement also comprise a positioning system for controlling the position of the sample holder and, thus, the distance between the sample surface and the aperture, and means for vacuum pumping of the low-pressure chamber.
  • the arrangement is characterized in that it comprises at least one gas outlet arranged to direct gas into a volume between the wall and the sample surface, gas supply device for providing a constant flow of gas from said at least one gas outlet, to supply a sample pressure, means for measuring the pressure inside the low-pressure chamber, a control unit connected to the means for measuring the pressure and to the positioning means and arranged to measure the pressure, with the means for measuring the pressure, at predetermined time intervals and to control the positioning system in a closed loop control to keep the pressure inside the low-pressure chamber constant, thereby keeping the distance between the aperture and the sample surface constant.
  • the low-pressure chamber may be an electrostatic lens system comprising a first end, at which the aperture is arranged, and a second end, wherein the lens system is arranged to form a particle beam of charged particles, emitted from the sample surface and entering through the aperture at the first end, and to transport the charged particles to the second end.
  • the low-pressure chamber may be other types of chambers but the arrangement is especially suitable to be implemented with an electrostatic lens.
  • the pressure in the low-pressure chamber may be in the interval between 10 4 to 10 2 mbar, preferably lower than 2xl0 3 mbar.
  • a low pressure is necessary for many applications such as when the low-pressure chamber is an electrostatic lens arranged to focus electrons into an electron beam.
  • the means for providing a constant flow of gas is arranged to provide a sample pressure higher than 1 mbar, preferably higher than 10 mbar.
  • a substantial pressure difference should be maintained between the interior of the low-pressure chamber and the pressure at the sample, i.e., the sample pressure.
  • a substantial pressure difference is necessary to be able to detect a pressure difference inside the low-pressure chamber for small apertures.
  • the pressure in the low pressure chamber is typically measured with a pressure gauge having a logarithmic sensitivity. The lower the pressure on the vacuum side, the better is the sensitivity of such a pressure gauge
  • the arrangement may comprise a measurement region for determining at least one parameter related to charged particles emitted from a sample surface of a particle emitting sample, said measurement region comprising an entrance allowing at least a part of said particles to enter the measurement region, wherein the second end is arranged at the entrance of the measurement region.
  • the pressure should decrease in the direction outwards from the volume between the sample and the aperture.
  • the sample may be placed in ambient pressure.
  • the sample and the wall should be arranged in a chamber, which is vacuum-pumped to provide a pressure gradient outwards from the volume between the aperture and the sample surface.
  • the arrangement may comprise a vacuum chamber, wherein the sample and the wall are arranged in the chamber, and wherein the vacuum chamber is vacuum pumped to provide a pressure gradient outwards from the volume between the aperture and the sample surface.
  • Fig. 1 shows partly in cross section an arrangement for determining at least one parameter related to charged particles emitted from a sample surface of a particle emitting sample.
  • Fig. 2 shows in larger detail the sample and an aperture between which the distance to be controlled is present.
  • Fig. 3 shows a flow diagram illustrating the method and the computer program according to the invention.
  • Fig. 1 shows partly in cross section an arrangement 100 for collecting charged particles from a sample surface Ss of a particle emitting sample 1 and for determining at least one parameter related to the charged particles.
  • the arrangement 100 comprises a sample holder 10, for holding the sample 1 in a sample region 2.
  • the arrangement also comprises a low-pressure chamber 4, comprising an aperture 3, in a wall 6 separating the sample region 2 from the low-pressure chamber 4, wherein the aperture 3 is arranged facing the sample surface Ss of the sample 1 placed in the sample holder 10, in order to collect charged particles from the sample surface Ss into the low-pressure chamber 4.
  • a heater 18 is also arranged on the sample holder 10 and is arranged to heat the sample 1.
  • the arrangement also comprises a positioning system Ps for controlling the position of the sample holder 10 and, thus, the distance d between the sample surface Ss and the aperture 3.
  • the arrangement also comprises a vacuum chamber 11 which encloses the aperture 3, the sample holder 10 and the positioning system Ps.
  • the arrangement also comprises first pump means 12 for vacuum pumping of the low-pressure chamber 4.
  • the arrangement 100 comprises at least one gas outlet 5 arranged to direct gas into a volume between the wall 6 and the sample surface Ss, and gas supply device 20 for providing a flow of gas from said at least one gas outlet 5, to provide a sample pressure.
  • the arrangement 100 also comprises means G for measuring the pressure inside the low-pressure chamber 4, and a control unit CU.
  • the control unit CU is connected to the first pressure measuring means G1 for measuring the pressure and to the positioning means and arranged to measure the pressure, with the first pressure measuring means G1 for measuring the pressure, at predetermined time intervals and to control the positioning system Ps in a closed loop control to keep the pressure inside the low-pressure chamber 4 constant, thereby keeping the distance d between the aperture 3 and the sample surface Ss constant.
  • the control unit comprises an input 19 for an input signal, which may be used to control the positioning system Ps.
  • the arrangement 100 also comprises a second pump means 22 for vacuum pumping of the vacuum chamber 11 and a second pressure measuring means G2 for measuring the pressure in the vacuum chamber 11.
  • the second pump means and the second pressure measuring means G2 are both connected to the control unit CU.
  • the low-pressure chamber 4 is an electrostatic lens system comprising a first end 16, at which the aperture 3 is arranged, and a second end 37 at which an aperture 8 is arranged.
  • the lens system 13 is arranged to form a particle beam from charged particles, emitted from the sample surface Ss and entering through the aperture 3 at the first end 16, and to transport the charged particles to the second end 17.
  • the arrangement 100 a measurement region 3 for determining at least one parameter related to the charged particles emitted from the sample surface Ss of the particle emitting sample 1.
  • the measurement region 3 comprising an entrance 8 allowing at least a part of said particles to enter the measurement region 3.
  • the second end 37 is arranged at the entrance of the measurement region 3.
  • the first pump means 12 for vacuum pumping in the low-pressure chamber 4 is arranged to maintain a pressure of less than 1 mbar, preferably less than 10 2 bar, in the low-pressure chamber 4.
  • a typical pressure in the electrostatic lens system 4 is 10 3 mbar.
  • the means 20 for providing a constant flow of gas is typically arranged to provide a sample pressure of 1-100 mbar.
  • the vacuum chamber is vacuum pumped by a separate vacuum pump (not shown).
  • the background pressure in the vacuum chamber 11 is typically maintained at 10 1 to 10 mbar, but should be considerably lower than the sample pressure.
  • the sample pressure is thus a local pressure in the volume between the sample surface Ss and the aperture 3.
  • Fig. 2 shows in larger detail the sample and an aperture between which the distance d to be controlled is present.
  • Fig. 2 six gas outlets 5 are arranged symmetrically around the aperture 3, of which only two are shown in the cross section in Fig. 2.
  • the length axis L is shown to extend through the aperture
  • a method for controlling a distance d between an aperture 3 and a sample surface Ss will be described with reference to Fig. 3.
  • the vacuum chamber 11 is vacuum pumped with the second pump means 22.
  • the pressure in the vacuum chamber 11 is monitored with the second pressure measuring means G2 connected to the control unit CU.
  • the pressure in the vacuum chamber is kept substantially lower than the sample pressure.
  • the low pressure chamber is vacuum pumped with the first pump means 12.
  • the pressure in the low pressure chamber 4 is monitored with the first pressure measuring means G1 and is preferably kept between 10 4 to 10 2 mbar, preferably lower than 2xl0 3 mbar.
  • a first step 101 at least one gas outlet 5 is provided and arranged to direct gas into a volume between the wall 6 and the sample surface Ss.
  • a constant sample pressure is provided by supplying a constant flow of gas from said at least one gas outlet 5.
  • the constant flow of gas is provided by the gas supply device 20, which is controlled by the control unit CU.
  • the control unit CU controls the positioning system to position the sample at a position determined by, e.g., an input signal on the input 19. Such positioning may be performed in real-time by a user observing the sample 1 and the first end 16 from the side using a microscope. In this way a desired gap may be set.
  • An alternative is to first calibrate pressure readings with different distances determined with the microscope. Such calibration may be done for one or many different gas flows. After having performed such calibration one never needs to use the microscope again but can set the correct distance d based on pressure in the low pressure chamber 4, and the gas flow.
  • the control unit CU may control the distance d between the sample 1 and the aperture 3 automatically.
  • a third step 103 the pressure in the low- pressure chamber 4 is measured at predetermined time intervals by the means G for measuring the pressure. The pressure is registered in the control unit CU. If the sample 1 is heated using the heater 10 the sample will increase in volume. This will lead to a decreasing distance d between the sample 1 and the aperture 3. The decreased distance d will lead to a higher pressure in the low-pressure chamber 4.
  • the control unit CU controls in a forth step 104 the positioning system Ps to move the sample away from aperture 3. The control of the positioning system Ps and the measurement of the pressure in the low pressure chamber
  • the method described above is preferably implemented in a computer program.
  • the computer program may be run on a central processing unit CPU in the control unit CU.
  • the computer program When the computer program is run on the central processing unit CPU it will control the control unit CU to perform the method described above.
  • the low-pressure chamber must not be an electrostatic lens for focusing electrons. It is possible that the low-pressure chamber is a different kind of chamber.

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  • 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)
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  • Spectroscopy & Molecular Physics (AREA)
  • Analysing Materials By The Use Of Radiation (AREA)

Abstract

A method is provided for controlling a distance (d) between an aperture (3), in a wall (6) separating a sample region (2) from a low-pressure chamber (4) which is vacuum pumped, and a sample surface (Ss), facing the aperture (3), of a sample (1) placed in the sample region (2) at the distance (d) from the aperture (3). The distance (d) between the sample surface (Ss) and the aperture (3) may be controlled with a positioning system (Ps). The method comprises the steps of providing at least one gas outlet (5) arranged to direct gas into a volume between the wall (6) and the sample surface (Ss), providing a sample pressure by supplying a constant flow of gas from said at least one gas outlet (5), measuring at predetermined time intervals the pressure inside the low-pressure chamber (4), and controlling in a closed loop the positioning system (Ps) to keep the pressure inside the low-pressure chamber (4) constant, thereby keeping the distance(d)between the aperture (3) and the sample surface (Ss) constant.

Description

METHOD AND ARRANGEMENT FOR DISTANCE CONTROL BETWEEN A SAMPLE AND AN APERTURE
TECHNICAL FIELD
The present invention relates to a method and an arrangement for controlling a distance between a sample and an aperture. More specifically, the present invention relates to a method for controlling a distance between an aperture, in a wall separating a sample region from a low-pressure chamber which is vacuum pumped, and a sample surface, facing the aperture.
BACKGROUND ART
In the prior art systems for Ambient Pressure Photoemission Spectroscopy (APXPS) and Ambient Pressure Photo Emission Spectroscopy (APPES) a high pressure is provided at a sample while radiating the sample to provide, e.g., photoelectrons or electrons originating from Auger processes. The photoelectrons are collected in an electrostatic lens system which is differentially pumped. The electrostatic lens system focuses the photoelectrons onto an entrance to a measurement region. To enable a high vacuum in the electrostatic lens system, the aperture into the electrostatic lens system has to be small.
In prior art APPES is performed in three ways; 1) a sample is put in a chamber and the whole chamber is raised to ambient pressures in the mbar range, this is known as the backfill approach; 2) is a variant of the backfill approach where different chambers are sued for different set of experiments and the chambers are exchanged, hence this method is called the exchangeable chamber approach; and 3) an in situ gas cell encapsulate the sample with the front aperture of the analyser. All these three ways could be operated in flow mode, where the gas is let in and simultaneously pumped out via an outlet or the gas is only pumped out via the front cone and the pumping arrangement of the analyser.
Electrons have a very small mean free path in gas at ambient pressure. Thus, to enable the electrons to travel from a sample and pass the gas and enter the lens system, the distance between the aperture and the sample must be kept small.
The general prior art of pressure estimation originates from Ogletree et al. ", Rev. Sci. Instrum. (2002) 73, 3872", where the pressure profile between the sample chamber and electrostatic lens chamber through an aperture is estimated using a simple analytical function. The pressure profile is also discussed in H. Bluhm, "J. Electron. Spectrosc. Relat. Phenom., 177 (2010), 71-84, and in J. Kahk et al.
"J. Electron. Spectrosc. Relat. Phenom., 205 (2015) 57-65". In said articles it is estimated that the pressure at the sample surface is 95 % of the pressure measured in the sample chamber with a distance of 1 aperture diameter between the sample surface and the aperture and 98 % of the pressure measured in the sample chamber with a distance of 2 aperture diameters between the sample surface and the aperture. Kahk et al. have also calculated that the pressure at the sample surface is varying with pressure. The higher the pressure the more accurate the pressure reading for 1 diameter distance, but for low pressures 2 diameters will be more accurate. The distance from the sample to the cone is related to the pressure of the sample surface as described said articles.
It is, thus, of great importance to keep the correct distance between the sample surface and the aperture, especially in APPES. In the prior art the distance between the sample surface and the aperture has been controlled by manually observing the gap between the sample and the aperture by eye, using the scale of the manipulator, or with a camera microscope.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method and a computer program for controlling a distance between an aperture, in a wall separating a sample region from a low-pressure chamber which is vacuum pumped, and a sample surface, facing the aperture, which method and computer program are alternatives to the methods and computer programs of the prior art.
Another object of the present invention is to provide an arrangement in which a distance between an aperture, in a wall separating a sample region from a low-pressure chamber which is vacuum pumped, and a sample surface, facing the aperture, may be controlled, which method and computer program are alternatives to the methods and computer programs of the prior art.
Favourable solutions to these objects are presented in the independent claims.
Further advantages are provided with the features of the dependent claims.
The method and computer program according to the invention are primarily intended to be used for an analyser arrangement for determining at least one parameter related to charged particles emitted from a particle emitting sample. Primarily, the analyser arrangement is an electron spectrometer.
According to a first aspect of the present invention a method is provided for controlling a distance d between an aperture, in a wall separating a sample region from a low-pressure chamber which is vacuum pumped, and a sample surface, facing the aperture, of a sample placed in the sample region at the distance from the aperture. The distance d between the sample surface and the aperture may be controlled with a positioning system. The method is characterized in that the method comprises the steps of
a) providing at least one gas outlet, connected to a gas supply device, arranged to direct gas into a volume between the wall and the sample surface,
b) providing a sample pressure by supplying, with the gas supply device, a constant flow of gas from said at least one gas outlet,
c) measuring at predetermined time intervals the pressure inside the low-pressure chamber, and d) controlling in a closed loop the positioning system to keep the pressure inside the low-pressure chamber constant, thereby keeping the distance between the aperture and the sample surface constant.
The method according to the first aspect provides a very precise distance control. Especially at small distances the method according to the first aspect is extremely precise and is better than the methods of the prior art where an optical microscope is used to control the distance. At distances of below 50 pm, the contrast in optical microscopes is often very poor and a reliable distance measurement is difficult.
The method according to the first aspect of the invention may be used to compensate for movement of the sample surface in relation to the aperture due to, e.g., thermal expansion of the sample.
The method requires the flow of gas to be kept constant.
The term wall should be interpreted broadly. The wall in which the aperture is formed may have any shape.
With the method according to the first aspect of the invention, a constant distance may be maintained between the sample and the aperture. The method is based on the discovery that the pressure between the sample surface and the aperture for a constant flow of gas increases with a decreasing distance between the sample surface and the aperture, and that the pressure inside the low-pressure chamber, located behind/inside the aperture, increases with an increasing pressure on the outside of the aperture. The correct distance may be set initially by an absolute measurement. Such an absolute measurement may be performed in many different ways. It may be possible to calibrate the pressure to different distances. Thus, it might be possible to move the sample surface to a position where the pressure in the low pressure chamber corresponds to an earlier determined pressure for the wanted distance.
One example of a situation in which the distance between the sample and the aperture has to be controlled is when the sample is heated. Due to expansion of the sample when it is heated, the sample surface will move towards the aperture, resulting in a decreasing distance. The method according to the present invention is very precise for small distances between the sample and the aperture but loses its precision for larger distances. The pressure in the low-pressure chamber may be in the interval between 104 to 10 2 mbar, preferably lower than 2xl03 mbar. A low pressure is necessary for many applications such as when the low-pressure chamber is an electrostatic lens arranged to focus electrons into an electron beam.
The sample pressure may be provided to be higher than 1 mbar, preferably higher than 10 mbar. The sample pressure may be as high as several bars. A substantial pressure difference should be maintained between the interior of the low-pressure chamber and the pressure at the sample, i.e., the sample pressure. A substantial pressure difference is necessary to be able to detect a pressure difference inside the low-pressure chamber for small apertures.
The aperture may have a largest dimension in the plane of the end surface being smaller than 1 mm. The largest dimension of the aperture in the plane of the end surface is preferably smaller than 300 pm and may be smaller than 100 pm. For circular apertures the largest dimension is equal to the diameter of the aperture. A small aperture is necessary to be able to have a small distance between the aperture and the sample, which is particularly desirable for a photoelectron spectrometer at high sample pressures. The diameter of the aperture determines the minimum achievable distance between the aperture and the sample surface if a high pressure is to be maintained at the sample surface. According to established theories a distance between the sample surface and the aperture being twice the diameter of the aperture enables a pressure at the sample surface of 99 % of the pressure at a very large distance from the aperture, when a vacuum is present on the opposite side of the aperture. At a distance being equal to the diameter of the aperture the pressure is 95 % of the pressure at a large distance from the aperture. Thus, the possible distance between the aperture and the sample surface is approximately equal to the diameter of the aperture to maintain a reasonable pressure at the sample surface. For a very small distance between the sample surface and the aperture, a very small diameter of the aperture is necessary.
The distance between the sample and the aperture should preferably be kept at no more than 3 times the diameter of the aperture for the method to function with very high precision.
The low-pressure chamber may be an electrostatic lens for focusing electrons.
For the method to function properly the pressure should decrease in the direction outwards from the volume between the sample and the aperture. For sample pressures above 1 bar the sample may be placed in ambient pressure. Flowever, for lower sample pressures the sample and the wall should be arranged in a chamber, which is vacuum pumped to provide a pressure gradient outwards from the volume between the aperture and the sample surface. According to a second aspect of the present invention a computer program is provided for controlling a distance between an aperture in a wall, separating a sample region from a low-pressure chamber, which is vacuum pumped, and a sample surface, facing the aperture, of a sample placed in the sample region at the distance from the aperture. The distance between the sample surface and the aperture may be controlled with a positioning system. At least one gas outlet, connected to a gas supply device, is arranged to direct gas into a volume between the wall and the sample surface. Said computer program comprises instructions which, when executed by at least one processor cause the at least one processor to carry out the steps of
a) controlling the gas supply device (20) to supply a constant flow of gas to said at least one gas outlet
(5),
b) receiving at predetermined time intervals the pressure values for the pressure inside the low- pressure chamber (4), and
c) controlling, in a closed loop, the positioning system to keep the pressure values constant, thereby keeping the distance (d) between the aperture (3) and the sample surface (Ss) constant.
The computer program gives the advantages as were described in relation to the method according to the first aspect of the present invention.
The term wall should be interpreted broadly. The wall in which the aperture is formed may have any shape.
According to a third aspect of the present invention a computer-readable storage medium carrying a computer program according to the second aspect for controlling a distance between an aperture and a sample surface is provided.
According to a fourth aspect of the present invention an arrangement is provided, for collecting charged particles from a sample surface of a sample. The arrangement comprises a sample holder, for holding the sample in a sample region, a low-pressure chamber, comprising an aperture, in a wall separating the sample region from the low-pressure chamber, wherein the aperture is arranged to face the sample surface of the sample, when it is placed in the sample holder, in order to collect charged particles from the sample surface into the low-pressure chamber. The arrangement also comprise a positioning system for controlling the position of the sample holder and, thus, the distance between the sample surface and the aperture, and means for vacuum pumping of the low-pressure chamber. The arrangement is characterized in that it comprises at least one gas outlet arranged to direct gas into a volume between the wall and the sample surface, gas supply device for providing a constant flow of gas from said at least one gas outlet, to supply a sample pressure, means for measuring the pressure inside the low-pressure chamber, a control unit connected to the means for measuring the pressure and to the positioning means and arranged to measure the pressure, with the means for measuring the pressure, at predetermined time intervals and to control the positioning system in a closed loop control to keep the pressure inside the low-pressure chamber constant, thereby keeping the distance between the aperture and the sample surface constant. The advantages with the arrangement are the same as has been discussed above for the first aspect of the present invention.
The low-pressure chamber may be an electrostatic lens system comprising a first end, at which the aperture is arranged, and a second end, wherein the lens system is arranged to form a particle beam of charged particles, emitted from the sample surface and entering through the aperture at the first end, and to transport the charged particles to the second end.
The low-pressure chamber may be other types of chambers but the arrangement is especially suitable to be implemented with an electrostatic lens.
The pressure in the low-pressure chamber may be in the interval between 104 to 10 2 mbar, preferably lower than 2xl03 mbar. A low pressure is necessary for many applications such as when the low-pressure chamber is an electrostatic lens arranged to focus electrons into an electron beam.
The means for providing a constant flow of gas is arranged to provide a sample pressure higher than 1 mbar, preferably higher than 10 mbar. A substantial pressure difference should be maintained between the interior of the low-pressure chamber and the pressure at the sample, i.e., the sample pressure. A substantial pressure difference is necessary to be able to detect a pressure difference inside the low-pressure chamber for small apertures. The pressure in the low pressure chamber is typically measured with a pressure gauge having a logarithmic sensitivity. The lower the pressure on the vacuum side, the better is the sensitivity of such a pressure gauge
The aperture size and sample to aperture distance that was discussed above for the first aspect of the invention are valid also for the arrangement.
The arrangement may comprise a measurement region for determining at least one parameter related to charged particles emitted from a sample surface of a particle emitting sample, said measurement region comprising an entrance allowing at least a part of said particles to enter the measurement region, wherein the second end is arranged at the entrance of the measurement region. This is a particularly suitable technical field for implementation of the invention.
For the arrangement to function properly the pressure should decrease in the direction outwards from the volume between the sample and the aperture. For sample pressures above 1 bar the sample may be placed in ambient pressure. Flowever, for lower sample pressures the sample and the wall should be arranged in a chamber, which is vacuum-pumped to provide a pressure gradient outwards from the volume between the aperture and the sample surface. To this end the arrangement may comprise a vacuum chamber, wherein the sample and the wall are arranged in the chamber, and wherein the vacuum chamber is vacuum pumped to provide a pressure gradient outwards from the volume between the aperture and the sample surface.
In the following preferred embodiments of the invention will be described with reference to the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 shows partly in cross section an arrangement for determining at least one parameter related to charged particles emitted from a sample surface of a particle emitting sample.
Fig. 2 shows in larger detail the sample and an aperture between which the distance to be controlled is present.
Fig. 3 shows a flow diagram illustrating the method and the computer program according to the invention.
DETAILED DESCRIPTION
Fig. 1 shows partly in cross section an arrangement 100 for collecting charged particles from a sample surface Ss of a particle emitting sample 1 and for determining at least one parameter related to the charged particles. The arrangement 100 comprises a sample holder 10, for holding the sample 1 in a sample region 2. The arrangement also comprises a low-pressure chamber 4, comprising an aperture 3, in a wall 6 separating the sample region 2 from the low-pressure chamber 4, wherein the aperture 3 is arranged facing the sample surface Ss of the sample 1 placed in the sample holder 10, in order to collect charged particles from the sample surface Ss into the low-pressure chamber 4. A heater 18 is also arranged on the sample holder 10 and is arranged to heat the sample 1. The arrangement also comprises a positioning system Ps for controlling the position of the sample holder 10 and, thus, the distance d between the sample surface Ss and the aperture 3. The arrangement also comprises a vacuum chamber 11 which encloses the aperture 3, the sample holder 10 and the positioning system Ps. The arrangement also comprises first pump means 12 for vacuum pumping of the low-pressure chamber 4. Furthermore, the arrangement 100 comprises at least one gas outlet 5 arranged to direct gas into a volume between the wall 6 and the sample surface Ss, and gas supply device 20 for providing a flow of gas from said at least one gas outlet 5, to provide a sample pressure. The arrangement 100 also comprises means G for measuring the pressure inside the low-pressure chamber 4, and a control unit CU. The control unit CU is connected to the first pressure measuring means G1 for measuring the pressure and to the positioning means and arranged to measure the pressure, with the first pressure measuring means G1 for measuring the pressure, at predetermined time intervals and to control the positioning system Ps in a closed loop control to keep the pressure inside the low-pressure chamber 4 constant, thereby keeping the distance d between the aperture 3 and the sample surface Ss constant. The control unit comprises an input 19 for an input signal, which may be used to control the positioning system Ps. The arrangement 100 also comprises a second pump means 22 for vacuum pumping of the vacuum chamber 11 and a second pressure measuring means G2 for measuring the pressure in the vacuum chamber 11. The second pump means and the second pressure measuring means G2 are both connected to the control unit CU.
The low-pressure chamber 4 is an electrostatic lens system comprising a first end 16, at which the aperture 3 is arranged, and a second end 37 at which an aperture 8 is arranged. The lens system 13 is arranged to form a particle beam from charged particles, emitted from the sample surface Ss and entering through the aperture 3 at the first end 16, and to transport the charged particles to the second end 17. The arrangement 100 a measurement region 3 for determining at least one parameter related to the charged particles emitted from the sample surface Ss of the particle emitting sample 1. The measurement region 3 comprising an entrance 8 allowing at least a part of said particles to enter the measurement region 3. The second end 37 is arranged at the entrance of the measurement region 3. The electrons enter the measurement region 3 through an entrance 8 and electrons entering the region between the hemispheres 25 with a direction close to perpendicular to the base plate 7 are deflected by an electrostatic field applied between the hemispheres 25, and those electrons having a kinetic energy within a certain range defined by the electrostatic field will reach a detector arrangement 9 after having travelled through a half circle.
The first pump means 12 for vacuum pumping in the low-pressure chamber 4, is arranged to maintain a pressure of less than 1 mbar, preferably less than 10 2 bar, in the low-pressure chamber 4. A typical pressure in the electrostatic lens system 4 is 103 mbar. The means 20 for providing a constant flow of gas is typically arranged to provide a sample pressure of 1-100 mbar.
The vacuum chamber is vacuum pumped by a separate vacuum pump (not shown). The background pressure in the vacuum chamber 11 is typically maintained at 10 1 to 10 mbar, but should be considerably lower than the sample pressure. The sample pressure is thus a local pressure in the volume between the sample surface Ss and the aperture 3.
Fig. 2 shows in larger detail the sample and an aperture between which the distance d to be controlled is present. In Fig. 2 six gas outlets 5 are arranged symmetrically around the aperture 3, of which only two are shown in the cross section in Fig. 2. The length axis L is shown to extend through the aperture
3 essentially perpendicular to the end surface S of the wall 6.
A method for controlling a distance d between an aperture 3 and a sample surface Ss will be described with reference to Fig. 3. During the method the vacuum chamber 11 is vacuum pumped with the second pump means 22. The pressure in the vacuum chamber 11 is monitored with the second pressure measuring means G2 connected to the control unit CU. The pressure in the vacuum chamber is kept substantially lower than the sample pressure. The low pressure chamber is vacuum pumped with the first pump means 12. The pressure in the low pressure chamber 4 is monitored with the first pressure measuring means G1 and is preferably kept between 104 to 10 2 mbar, preferably lower than 2xl03 mbar. In a first step 101 at least one gas outlet 5 is provided and arranged to direct gas into a volume between the wall 6 and the sample surface Ss. In a second step 102, a constant sample pressure is provided by supplying a constant flow of gas from said at least one gas outlet 5. The constant flow of gas is provided by the gas supply device 20, which is controlled by the control unit CU. The control unit CU controls the positioning system to position the sample at a position determined by, e.g., an input signal on the input 19. Such positioning may be performed in real-time by a user observing the sample 1 and the first end 16 from the side using a microscope. In this way a desired gap may be set. An alternative is to first calibrate pressure readings with different distances determined with the microscope. Such calibration may be done for one or many different gas flows. After having performed such calibration one never needs to use the microscope again but can set the correct distance d based on pressure in the low pressure chamber 4, and the gas flow.
After having set the desired distance d the control unit CU may control the distance d between the sample 1 and the aperture 3 automatically. To this end, in a third step 103 the pressure in the low- pressure chamber 4 is measured at predetermined time intervals by the means G for measuring the pressure. The pressure is registered in the control unit CU. If the sample 1 is heated using the heater 10 the sample will increase in volume. This will lead to a decreasing distance d between the sample 1 and the aperture 3. The decreased distance d will lead to a higher pressure in the low-pressure chamber 4. To compensate for the decreased distance d between the sample 1 and the aperture 3 the control unit CU controls in a forth step 104 the positioning system Ps to move the sample away from aperture 3. The control of the positioning system Ps and the measurement of the pressure in the low pressure chamber
4 with the first pressure measuring means G1 is performed using a closed loop control such as PID- control.
The method described above is preferably implemented in a computer program. The computer program may be run on a central processing unit CPU in the control unit CU. When the computer program is run on the central processing unit CPU it will control the control unit CU to perform the method described above.
The above described embodiments may be amended in many ways without departing from the scope of the invention, which is limited only by the appended claims. The low-pressure chamber must not be an electrostatic lens for focusing electrons. It is possible that the low-pressure chamber is a different kind of chamber.

Claims

1. A method for controlling a distance (d) between an aperture (3), in a wall (6) separating a sample region (2) from a low-pressure chamber (4) which is vacuum pumped, and a sample surface (Ss), facing the aperture (3), of a sample (1) placed in the sample region (2) at the distance (d) from the aperture (3),
- wherein the distance (d) between the sample surface (Ss) and the aperture (3) may be controlled with a positioning system (Ps),
characterized in that the method comprises the steps of
a) providing (101) at least one gas outlet (5), connected to a gas supply device (20), arranged to direct gas into a volume between the wall (6) and the sample surface (Ss),
b) providing a sample pressure (102) by supplying, with the gas supply device (20), a constant flow of gas from said at least one gas outlet (5),
c) measuring (103) at predetermined time intervals the pressure inside the low-pressure chamber (4), and
d) controlling (104) in a closed loop the positioning system (Ps) to keep the pressure inside the low- pressure chamber (4) constant, thereby keeping the distance (d) between the aperture (3) and the sample surface (Ss) constant.
2. The method according to claim 1, wherein a pressure of between 104 to 10 2 bar, preferably lower than 2xl03 bar, is maintained in the low-pressure chamber (4).
3. The method according to claim 1, wherein the sample pressure is provided to be higher than lmbar, preferably higher than 10 mbar.
4. The method according to any one of the preceding claims, wherein the low-pressure chamber (4) is an electrostatic lens for focusing of electrons.
5. The method according to any one of the preceding claims, wherein the sample (1) and the wall (6) are arranged in a chamber (11), which is vacuum pumped to provide a pressure gradient outwards from the volume between the aperture (3) and the sample surface (Ss).
6. A computer program for controlling a distance (d) between an aperture (3) in a wall (6), separating a sample region (2) from a low-pressure chamber (4) which is vacuum pumped, and a sample surface (Ss), facing the aperture (3), of a sample (1) placed in the sample region (2) at the distance (d) from the aperture (3),
- wherein the distance (d) between the sample surface (Ss) and the aperture (3) may be controlled with a positioning system (Ps),
- wherein at least one gas outlet (5), connected to a gas supply device (20), is arranged to direct gas into a volume between the wall (6) and the sample surface (Ss),
said computer program comprising instructions which, when executed by at least one processor cause the at least one processor to carry out the steps of
a) controlling the gas supply device (20) to supply a constant flow of gas to said at least one gas outlet
(5),
b) receiving at predetermined time intervals the pressure values for the pressure inside the low- pressure chamber (4), and
c) controlling, in a closed loop, the positioning system to keep the pressure values constant, thereby keeping the distance (d) between the aperture (3) and the sample surface (Ss) constant.
7. Computer-readable storage medium carrying a computer program for controlling a distance (d) between an aperture (3) and a sample surface (Ss), according to claim 6.
8. An arrangement (100) for collecting charged particles from a sample surface (Ss) of a sample (1), comprising
- a sample holder (10), for holding the sample (1) in a sample region (2),
a low-pressure chamber (4), comprising an aperture (3), in a wall (6) separating the sample region (2) from the low-pressure chamber (4), wherein the aperture (3) is arranged to face the sample surface (Ss) of the sample (1), when it is placed in the sample holder, in order to collect charged particles from the sample surface (Ss) into the low-pressure chamber (4),
- a positioning system (Ps) for controlling the position of the sample holder (10) and, thus, the distance (d) between the sample surface (Ss) and the aperture (3), and
- means for vacuum pumping of the low-pressure chamber (4),
characterized in that the arrangement (100) comprises
- at least one gas outlet (5) arranged to direct gas into a volume between the wall (6) and the sample surface (Ss),
- gas supply device (20) for providing a constant flow of gas from said at least one gas outlet (5), to supply a sample pressure,
- means (G) for measuring the pressure inside the low-pressure chamber (4), and
- a control unit (CU) connected to the means (G) for measuring the pressure and to the positioning means and arranged to measure the pressure, with the means (G) for measuring the pressure, at predetermined time intervals and to control the positioning system (Ps) in a closed loop control to keep the pressure inside the low-pressure chamber (4) constant, thereby keeping the distance (d) between the aperture (3) and the sample surface (Ss) constant.
9. The arrangement (100) according to claim 8, wherein the low-pressure chamber (4) is an electrostatic lens system comprising a first end (16), at which the aperture (3) is arranged, and a second end (37), wherein the lens system (13) is arranged to form a particle beam from charged particles, emitted from the sample surface (Ss) and entering through the aperture (3) at the first end (16), and to transport the charged particles to the second end (37).
10. The arrangement (100) according to claim 8, wherein the means for vacuum pumping in the low- pressure chamber (4), is arranged to maintain a pressure of between 104 to 102 bar, preferably between 5xl04 to 2xl0-3 bar, in the low-pressure chamber (4).
11. The arrangement (100) according to claim 8, 9 or 10, wherein the means for providing a constant flow of gas is arranged to provide a sample pressure, higher than 1 mbar, preferably higher than 10 mbar.
12. The arrangement (100) according to any one of claims 8-11, comprising:
- a measurement region (3) for determining at least one parameter related to charged particles emitted from a sample surface (Ss) of a particle emitting sample (1), said measurement region (3) comprising an entrance (8) allowing at least a part of said particles to enter the measurement region (3), wherein the second end (37) is arranged at the entrance of the measurement region (3).
13. The arrangement according to any one of claims 8-12, comprising a chamber (11) wherein the sample (1) and the wall (6) are arranged in the chamber (11), and wherein the chamber (11) is vacuum pumped to provide a pressure gradient outwards from the volume between the aperture (3) and the sample surface (Ss).
EP19821307.6A 2018-12-07 2019-12-06 Method and arrangement for distance control between a sample and an aperture Pending EP3891774A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE1851528A SE542904C2 (en) 2018-12-07 2018-12-07 Method and arrangement for distance control between a sample and an aperture
PCT/SE2019/051242 WO2020117124A1 (en) 2018-12-07 2019-12-06 Method and arrangement for distance control between a sample and an aperture

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US4528451A (en) * 1982-10-19 1985-07-09 Varian Associates, Inc. Gap control system for localized vacuum processing
US4560880A (en) * 1983-09-19 1985-12-24 Varian Associates, Inc. Apparatus for positioning a workpiece in a localized vacuum processing system
US5103102A (en) * 1989-02-24 1992-04-07 Micrion Corporation Localized vacuum apparatus and method
JP3148353B2 (en) 1991-05-30 2001-03-19 ケーエルエー・インストルメンツ・コーポレーション Electron beam inspection method and system
US6300630B1 (en) * 1999-12-09 2001-10-09 Etec Systems, Inc. Annular differential seal for electron beam apparatus using isolation valve and additional differential pumping
JP3360115B2 (en) 2000-03-17 2002-12-24 東京大学長 Angle-resolved electron spectrometer with diffraction plane aperture transmission energy control system and analysis method using this spectrometer
GB201317026D0 (en) 2013-09-25 2013-11-06 Oxford Instr Nanotechnology Tools Ltd X-ray analysis in air
JP6097863B2 (en) 2016-05-16 2017-03-15 株式会社日立ハイテクノロジーズ Charged particle beam apparatus, sample image acquisition method, and program recording medium

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SE1851528A1 (en) 2020-06-08
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SE542904C2 (en) 2020-09-15

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