CN114303229A - Electrostatic lens for controlling electron beam - Google Patents
Electrostatic lens for controlling electron beam Download PDFInfo
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- CN114303229A CN114303229A CN202080060729.1A CN202080060729A CN114303229A CN 114303229 A CN114303229 A CN 114303229A CN 202080060729 A CN202080060729 A CN 202080060729A CN 114303229 A CN114303229 A CN 114303229A
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- electrostatic lens
- lens element
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- electrons
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- 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]
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J49/00—Particle spectrometers or separator tubes
- H01J49/44—Energy spectrometers, e.g. alpha-, beta-spectrometers
- H01J49/46—Static spectrometers
- H01J49/48—Static spectrometers using electrostatic analysers, e.g. cylindrical sector, Wien filter
Abstract
It is described an apparatus (100) comprising an electrostatic lens (7) comprising: an optical axis (6); a first electrostatic lens element (1); a second electrostatic lens element (2); and a deflector device comprising a deflector package (5) having a plurality of electrodes (15) arranged circumferentially around the optical axis (6) between a first end (26) of the first electrostatic lens element (1) and a second end (29) of the second electrostatic lens element (2) and arranged to deflect the electron beam in at least a first coordinate direction (x, y) perpendicular to the optical axis (6). The deflector package (5) is arranged such that during operation of the electrostatic lens (7) electrons travelling from the first electrostatic lens element (1) to the second electrostatic lens element (2) pass first through an electric field between the first electrostatic lens element (1) and the deflector package (5) and subsequently through an electric field between the deflector package (5) and the second electrostatic lens element (2).
Description
Technical Field
The invention relates to a device comprising an electrostatic lens for controlling an electron beam. In particular, the invention relates to a device comprising an electrostatic lens for use in a hemispherical deflector type of photo spectrometer.
Background
WO 2013/133739 describes an analyzer device for an electron spectrometer. The analyzer device is arranged to form an electron beam of electrons emitted from the electron emitting sample and to transport the electrons between said electron emitting sample and the entrance slit of the measurement area through a lens system having a substantially straight optical axis. The lens system is arranged to deflect the electron beam at least a first time and a second time in at least a first coordinate direction. By deflecting the electron beam at least twice, it is possible to operate the lens system in an angle-resolved mode such that it deflects the electron beam such that a predetermined portion of the angular distribution of the electrons passes the entrance slit of the measurement region in a direction substantially parallel to the optical axis of the lens system. The main embodiment described in WO 2013/133739 comprises a first deflector package and a second deflector package. The basic explanation of the function of the lens system is as follows. The first deflector package is controlled to deflect the desired predetermined angular distribution of electrons towards the optical axis of the lens system. The second deflector package is controlled to deflect the desired angular distribution of the electrons at the optical axis to provide the electrons with a direction along the optical axis of the lens system.
An advantage of the lens system described in WO 2013/133739 is that the specific angular distribution of electrons emitted from the electron emitting sample can be controlled to enter the entrance slit of the measurement region in a direction substantially parallel to the optical axis of the lens system without the need to tilt the electron emitting sample.
Disclosure of Invention
It is an object of the present invention to provide a device comprising an electrostatic lens for controlling the electron beam entering an electron spectrometer, which device is an alternative to the lens systems described in the prior art.
It is another object of the invention to provide a device comprising an electrostatic lens for controlling an electron beam, the device having only one deflector device with a deflector package comprising a plurality of electrodes, while still allowing electrons entering through a first opening in the same direction with respect to the optical axis to be focused along the optical axis to the same point at the location of a second opening.
It is another object of the invention to provide a device comprising an electrostatic lens for steering an electron beam, the device having as few optical elements as possible, enabling steering of the electrons such that a specific angular distribution of electrons emitted from an electron emitting sample leaves the device at a controllable angle, and such that the electron beam from the device is adapted to enter an electron spectrometer.
At least one of these objects is achieved by an aperture arrangement, an analyzer device or a method according to the independent claims.
Further advantages are achieved by the features of the dependent claims.
The apparatus according to the invention is configured for use with an electron spectrometer and comprises an electrostatic lens having: the electron source includes an internal volume, a first opening for electrons to enter the internal volume, a second opening for electrons to exit from the internal volume, and a substantially straight optical axis extending from the first opening through the internal volume to the second opening. The electrostatic lens is configured to form an electron beam entering through the first opening and transmit the electron beam to the second opening. The electrostatic lens further comprises a first electrostatic lens element having a first end facing the first opening and a second end facing away from the first opening; a second electrostatic lens element having a first end facing the first electrostatic lens element and a second end facing the second opening; and a deflector device comprising a deflector package having a plurality of electrodes arranged circumferentially around the optical axis between a first end of the first electrostatic lens element and a second end of the second electrostatic lens element and arranged to deflect the electron beam in at least a first coordinate direction perpendicular to the optical axis. The device is characterized in that the deflector package is arranged such that, during operation of the electrostatic lens, electrons travelling from the first electrostatic lens element to the second electrostatic lens element pass first through an electric field between the first electrostatic lens element and the deflector package and subsequently through an electric field between the deflector package and the second electrostatic lens element, and wherein the electrodes are electrically separated from each other and from the first electrostatic lens element and the second electrostatic lens element. The apparatus can be controlled such that the electron beam exiting through the second opening is directed along the optical axis of the electrostatic lens.
During operation of the electrostatic lens, voltages are applied to the lens element and to the electrodes of the deflector package. The device is controllable by controlling the voltages to the different lens elements and to the different electrodes of the deflector package.
The electrostatic lens is adapted to enter the electron spectrometer when the electron beam is directed along the optical axis of the electrostatic lens. Therefore, when it is possible to control the electrostatic lens in this way, no direction change is required after the second opening. In other words, all the direction changes needed to adapt the electron beam to enter the electron spectrometer are made before the second opening.
According to the present application, an electrode is considered to be a separate electrode only when it is electrically separated from other electrodes. Thus, two electrodes are considered to be part of the same electrode if they are electrically connected and therefore always at the same potential.
Electrically separated means that the electrodes/lens elements can be set at different voltages independently of each other.
By electrically separating the electrodes from each other and from the first and second electrostatic lens elements, it is possible to apply different voltages to the first and second electrostatic lens elements and different electrodes. The different voltages applied to the electrodes produce a central voltage. Thus, by the first electrostatic lens element, electrons of the deflector package and the second electrostatic lens element will first experience an electric field between the first electrostatic lens element and the deflector package, and second and then experience an electric field between the deflector package and the second electrostatic lens element. These two different electric fields together with the different applied voltages applied to the electrodes effectively result in two deflections of electrons. The device according to the invention thus provides operational freedom with respect to the electron deflection and enables an efficient adjustable control of both deflections in a coordinate direction perpendicular to the optical axis.
The device according to the invention may be controlled such that the specific angular distribution of the electrons emitted from the electron emitting sample may be controlled to exit through the second opening at a controllable angle.
Preferably, the angle of the electrons exiting through the second opening is controlled to be parallel to the optical axis in one of coordinate directions perpendicular to the optical axis. This means that the electrons exiting through the second opening can be controlled to enter the entrance slit of the measurement region in a direction substantially parallel to the optical axis of the lens system.
The device is controlled by means of voltages applied to the electrostatic lens element and the electrodes.
The first electrostatic lens element may be disposed adjacent to the second electrostatic lens element with a gap therebetween. The deflector package may span at least a portion of a gap between the first electrostatic lens element and the second electrostatic lens element. In principle, there is always a gap between the first electrostatic lens element and the second electrostatic lens element. However, if the gap is large enough, there is a risk that external electric fields penetrate the gap and affect the electrons. In order to shield electrons passing through the electrostatic lens from such electric fields, the deflector package spans at least a portion of the gap.
The deflector package may comprise at least 2 electrodes, preferably at least 4 electrodes, most preferably at least 8 electrodes, arranged around the optical axis, wherein n is an integer. Therefore, the minimum number of electrodes is 2. This allows the electrons to be deflected twice.
The deflector package may comprise at least 4 electrodes arranged in a substantially rotationally symmetrical fashion, wherein the electrodes of the deflector package act as deflectors in at least two coordinate directions. By having at least 4 electrodes it is possible to eliminate spherical deformations.
The electrodes in the deflector package may be arranged at a minimum electrode separation distance from the optical axis. Preferably, all electrodes are arranged at the same distance from the optical axis. The closest electrode defines the minimum electrode separation distance if the electrodes are not arranged at the same distance from the optical axis.
The length of the deflector package may be at least 50%, preferably at least 100%, most preferably at least 150% of the minimum electrode separation distance from the optical axis in the deflector package. This is advantageous in that two deflections are achieved at reasonable voltages over the electrodes and the first and second electrostatic lens elements.
A distance parallel to the optical axis between the deflector package and any one of the first and second electrostatic lens elements may be less than 10%, preferably less than 5%, most preferably less than 2% of a minimum electrode separation distance from the optical axis. This limitation is relevant when the deflector package extends over only a part of the gap between the first electrostatic lens element and the second electrostatic lens element.
The deflector device may comprise a metal tube, wherein the deflector package is arranged in the metal tube, and wherein the metal tube is arranged electrically separate from the deflector package, the first electrostatic lens element and the second electrostatic lens element. Such a metal tube may be advantageous for mechanical reasons of ease of attaching the electrode.
The second opening may be elongated in a plane perpendicular to the optical axis, wherein the ratio of the width to the height of the second opening is at least 10:1, preferably at least 30: 1. The advantage of an elongated opening is that it cuts off electrons in a manner suitable for an electron spectrometer.
The first opening may be disposed in the first lens element and the second opening may be disposed in the second lens element. A device comprising only two lens elements is the simplest embodiment.
The apparatus may further comprise a third electrostatic lens element arranged such that the first electrostatic lens element is arranged between the third electrostatic lens element and the second electrostatic lens element; and a fourth electrostatic lens element arranged such that the second electrostatic lens is arranged between the fourth electrostatic lens element and the first electrostatic lens element. By having additional third and fourth lens elements, it is possible to control the electrons with a lower voltage difference between the lens elements. Lower voltage differences are preferred. With the third lens element and the fourth lens element it is also easier to obtain the same focusing properties for different energies of the analyzed electrons. In addition, with the third electrostatic lens element and the fourth electrostatic lens element, when electrons are deflected on their paths from the first opening to the second opening, it is possible to keep the electrons close to the optical axis, which results in smaller aberrations.
The electrostatic lens may be arranged to operate in an angle-resolved mode such that electrons entering through the first opening in the same direction relative to the optical axis are focused to the same point at the location of the second opening along the optical axis, and such that electrons exiting through the second opening exit at a controllable angle relative to the optical axis in at least one coordinate direction perpendicular to the optical axis. This is preferred when the apparatus is used with, for example, a photo-spectrometer for analyzing photoelectrons.
The electrostatic lens may be arranged to operate also in an imaging mode such that electrons entering through the first opening from the same point on the electron emitting sample are focused along the optical axis to the same point at the location of the second opening and such that electrons exiting through the second opening exit at a controllable angle relative to the optical axis in at least one coordinate direction.
Preferably, the angle of the electrons exiting through the second opening is controlled to be substantially zero in one of coordinate directions perpendicular to the optical axis. In the case where the second opening is elongated along the first coordinate direction, it is preferable that the angle of the electrons exiting through the second opening is controlled to be substantially zero in the second coordinate direction.
The device may be configured for use in an analyzer device for determining at least one parameter related to electrons emitted from an electron emitting sample, wherein the device is arranged with a first opening facing the electron emitting sample and a second opening adjacent to an entrance slit of a measurement region of the analyzer for transporting electrons from the electron emitting surface to the entrance slit of the measurement region. This is an advantageous implementation of the device.
The device may further comprise a control unit configured to apply a separate voltage to each of the electrodes of the deflector device. Applying separate voltages enables good control of the electrons.
The control unit may also be configured to apply a separate voltage to each of the electrostatic lens elements. This makes it possible to use only one control unit to supply different voltages to the electrostatic lens element.
Drawings
Preferred embodiments of the present invention will be described below with reference to the accompanying drawings, in which:
fig. 1 shows an analyzer device in which a device comprising an electrostatic lens is arranged to control electrons emitted from an electron emitting sample.
Fig. 2 shows in a perspective cross-sectional view a device comprising an electrostatic lens according to a first embodiment of the invention.
Fig. 3 shows the device shown in fig. 2 in a cross-sectional side view.
Fig. 4 shows in a perspective cross-sectional view a device comprising an electrostatic lens according to a second embodiment of the invention.
Fig. 5 shows in a perspective cross-sectional view a device comprising an electrostatic lens according to a third embodiment of the invention.
Fig. 6 shows, in a cross-sectional side view, a device comprising an electrostatic lens according to a fourth embodiment of the invention.
Fig. 7 shows the device according to the embodiment of fig. 2 to 6 in a cross-sectional view along the optical axis towards the second opening.
Fig. 8 shows in cross-sectional view a device according to an alternative embodiment directed along the optical axis towards the second opening.
Detailed Description
In the following description of the preferred embodiments, the same reference numerals will be used for similar features in different drawings. The figures are not drawn to scale.
Fig. 1 shows a photo-spectrometer 200 of the hemispherical deflector type according to the prior art. The device comprising the electrostatic lens 7 is arranged in the photo spectrometer 200. In the hemispherical deflector type of photo spectrometer 200, the central component is the measurement area 8, where the energy of the electrons is analyzed. The measurement region 8 is formed by two concentric hemispheres 9 mounted on a substrate 10 and between which an electrostatic field is applied. The electrons enter the measurement region 8 through the second opening 21 and continue through the entrance slit 11, the electrons entering the region between the hemispheres 9 in a direction close to perpendicular to the substrate 10 are deflected by the electrostatic field, and those electrons having a kinetic energy within a certain range defined by the deflection field will reach the detector device 12 after having travelled through the hemispheres. In a typical instrument, electrons are transmitted from their source (typically a sample 13 that emits electrons upon excitation with photons, electrons or other particles) through an electrostatic lens 7 comprising a plurality of lens elements 1-4 having a common and substantially straight optical axis 6 and a deflector package 5 to an entrance slit 11 of a hemisphere 9. The electrostatic lens 7 comprises a first opening 20, which in the embodiment shown in fig. 1 faces the sample 13, and a second opening 21 at the opposite end of the electrostatic lens 7. The deflector package comprises a plurality of electrodes 15. In contrast to electrostatic lenses according to the prior art, which comprise a first electrostatic lens element 1 and a second electrostatic lens element 2, in connection with which the deflector package 5 is arranged such that it overlaps the first electrostatic lens element 1 and the second electrostatic lens element 2. The device comprising the electrostatic lens 7 will be described in more detail below with reference to fig. 2 and 3. The electrostatic lens 7 is configured to form an electron beam entering through the first opening 20 and to transmit the electron beam to the second opening 21 and further to the entrance slit 11. The electrons entering through the first opening 20 originate from the sample 13. The third electrostatic lens element 3 and the fourth electrostatic lens element 4 are optional. In the embodiment shown in fig. 1, the third electrostatic lens element 3 may form part of the first electrostatic lens element 1 and the fourth electrostatic lens element 4 may form part of the second electrostatic lens element 2. However, it is advantageous to electrically separate the third electrostatic lens element 3 and the fourth electrostatic lens element 4 from the first electrostatic lens element 1 and the second electrostatic lens element 2, as will be described below.
The detector arrangement 12 typically comprises a multi-channel electron multiplier plate (MCP)14 which is arranged in the same plane as the entrance slit 11 of the hemisphere 9 and which generates a measurable electrical signal at the location of the incoming electrons, which can then be recorded optically by a phosphor screen and a camera 17, or as electrical pulses on, for example, a delay line or a resistive anode detector. Alternatively, some energy-selective electrons, particularly with respect to their spin, may be further analyzed after leaving the hemispherical region through the outlet 16 to the spin detector 18. Of course, the detector device 12 may be arranged in other ways. The MCP 14 and the entrance slit 11 may be arranged in different planes, for example.
Fig. 2 shows a device 100 comprising an electrostatic lens 7 having an inner volume 19, a first opening 20 for electrons to enter the inner volume 19, a second opening 21 for electrons to exit from the inner volume 19, and a substantially straight optical axis 6 extending from the first opening 20 through the inner volume 19 to the second opening 21. The electrostatic lens 7 is configured to form an electron beam entering through the first opening 20 and transmit the electron beam to the second opening 21. The electrostatic lens 7 includes a first electrostatic lens element 1 in which a first opening 20 is arranged, and a second electrostatic lens element 2 in which a second opening 21 is arranged. The electrostatic lens further comprises a deflector device comprising a deflector package 5 having a plurality of electrodes 15 arranged to overlap the first electrostatic lens element 1 and the second electrostatic lens element 2. The deflector package 5 is arranged to deflect the electron beam in at least a first coordinate direction (x, y) perpendicular to the optical axis 6. The electrostatic lens elements 1, 2 are electrically separated from each other and from the deflector package 5, so that different voltages can be applied to each of the electrostatic lens elements 1, 2 and to each of the deflector elements 15 in the deflector package of the deflector package 5. This is achieved by having a gap B between the first electrostatic lens element 1 and the second electrostatic lens element 2 to prevent electrical contact between the first electrostatic lens element 1 and the second electrostatic lens element 2. The gap B between the first electrostatic lens element 1 and the second electrostatic lens element 2 may be filled with an insulating material (not shown in fig. 2). In this way, the electrostatic lens elements 1, 2 are mechanically connected. The electrostatic lens elements 1, 2 and the deflector device may be arranged within a magnetic shield (not shown in fig. 2). The apparatus 100 further comprises a control unit 22 arranged to apply a voltage to each electrode of the electrostatic lens elements 1-4 and the deflector package 5. The deflector package 5 is arranged such that during operation of the electrostatic lens, electrons travelling from the first electrostatic lens element 1 to the second electrostatic lens element 2 pass first through the electric field between the first electrostatic lens element 1 and the deflector package 5 and subsequently through the electric field between the deflector package 5 and the second electrostatic lens element 2. This can be achieved in different ways. In the embodiment of fig. 2, the deflector package extends in the direction of the optical axis 6 across the gap B between the first electrostatic lens element 1 and the second electrostatic lens element 2.
The deflector package 5 comprises electrodes arranged around an optical axis 6. A separate voltage is applied to each electrode of the deflector package 5 to effect deflection in the respective coordinate direction. The electrodes are arranged at a minimum electrode separation distance D from the optical axis. The minimum number of electrodes is 2 to enable deflection so that electrons entering the first opening 20 at a certain angle in the x and y directions with respect to the optical axis enter the second opening 21. The minimum number of electrodes is 4 so that electrons entering the first opening at the same angle in the x-direction with respect to the optical axis 6 can enter the second opening substantially independently of their angle in the y-direction when they enter the first opening. This will be described in more detail below.
In operation, the control unit applies different voltages to the electrostatic lens elements 1, 2 and the deflector package 5. A central voltage is applied to the deflector package 5. A separate deflection voltage is also applied to each electrode 15. The deflection voltage is added to the center voltage. A deflection voltage is applied to the electrodes in order to select which electrons enter the first opening and which will hit the second opening, wherein a positive deflection voltage is applied to one electrode 15 of the pair and a negative deflection voltage is applied to the opposite electrode 15 of the pair. A first voltage is applied across the first lens element 1. When the apparatus is used in a photo spectrometer 200 (fig. 1), the first voltage is the same as the voltage on the sample 13. A different voltage is applied to the second electrostatic lens element 2. The voltage difference between the first voltage and the second voltage and the voltage difference between the central voltage and the first voltage control the focusing of electrons entering the inner volume 19 through the first opening 20. By controlling the voltage it is possible to control the position of the electron focus.
Fig. 3 shows in a cross-sectional side view an electron 25 entering through the first opening 20 at an angle α to the optical axis 6 in the x-direction, i.e. perpendicular to the direction of maximum extension of the second opening. By applying appropriate voltages across the first electrostatic lens element 1, the second electrostatic lens element 2 and the deflector package 5, the electrons will hit the second opening 21 parallel to the optical axis 6. The deflection voltage controls the deflection of the electrons. The deflection voltage together with the difference between the central voltage and the first voltage determines which angular distribution of electrons entering through the first opening 20 will hit the slits constituting the second opening 21. The above factors affect the path of the electrons. The first deflection of the electrons is realized by the difference between the first voltage and the central voltage and the difference between the deflection voltages. The second deflection of the electrons is mainly achieved by the difference between the central voltage and the second voltage. By adjusting the different voltages it is possible to adjust the first deflection and the second deflection to a desired angular distribution of the electrons, so that the electrons travelling in the desired angular distribution can pass through the second opening 21 parallel to the optical axis.
It is desirable that the length L of the deflector package 5 is at least 50%, preferably at least 100%, most preferably at least 150% of the minimum electrode separation distance D in the deflector package 5 to achieve good control of the electrons.
Thus, the electrostatic lens may be operated in an angle-resolved mode such that electrons entering through the first opening in the same direction with respect to the optical axis are focused to the same point at the position of the second opening along the optical axis. Electrons entering the inner volume 19 of the electrostatic lens 7 through the first opening at the same angle in a first plane x but at different angles in a second plane y perpendicular to the first plane form a line when travelling parallel to the optical axis. Such electrons can be controlled to exit through the elongated slit forming the second opening 21.
Fig. 4 shows a device 100 comprising an electrostatic lens 7 having an inner volume 19, a first opening 20 for electrons to enter the inner volume 19, a second opening 21 for electrons to exit from the inner volume 19, and a substantially straight optical axis 6 extending from the first opening 20 through the inner volume 19 to the second opening 21. The electrostatic lens 7 is configured to form an electron beam entering through the first opening 20 and transmit the electron beam to the second opening 21. The electrostatic lens 7 of fig. 4 is similar to the electrostatic lens of fig. 2 and 3, but comprises, in addition to the first electrostatic lens element 1 and the second electrostatic lens element 2, a third electrostatic lens element 3 in which the first opening 20 is arranged. The electrostatic lens 7 further comprises a fourth electrostatic lens element 4 in which the second opening 21 is arranged. The electrostatic lens further comprises a deflector device comprising a deflector package 5 having a plurality of electrodes 15 arranged between the first electrostatic lens element 1 and the second electrostatic lens element 2. The deflector package 5 is arranged to deflect the electron beam at least in a first coordinate direction x, y perpendicular to the optical axis 6, which first coordinate direction x, y extends in the z-direction. The electrostatic lens 7 further comprises a fourth electrostatic lens element 4 arranged between the third electrostatic lens element 3 and the second electrostatic lens element 2. In fig. 5, the second opening 21 is arranged in the sub-electrode 4' of the fourth electrode. The sub-electrode 4' is electrically connected to the fourth electrode 4 via an electrical connection 30. Thus, in the sense of the present application, the fourth electrode and the sub-electrode effectively constitute parts of the same electrode. The sub-electrode 4' is separated from the electrical connection 30 and physically separated from the fourth electrode. The sub-opening 21' is arranged in the fourth electrode 4. The sub-opening 21' is substantially circular. The arrangement with sub-openings 21' and sub-electrodes 4 is advantageous for structural reasons. The electrostatic lens elements 1-4 are electrically separated from each other and from the deflector package 5, so that different voltages can be applied to each of the electrostatic lens elements 1-4 and the deflector package 5. This is illustrated in fig. 4 by the gaps between the electrostatic lens elements 1-4. However, the electrostatic lens elements 1-4 are preferably mechanically connected to non-conductive connecting means (not shown in fig. 4). The apparatus 100 further comprises a control unit 22 arranged to apply a voltage to each electrode of the electrostatic lens elements 1-4 and the deflector package 5. The deflector package 5 is arranged such that during operation of the electrostatic lens 7, electrons travelling from the first electrostatic lens element 1 to the second electrostatic lens element 2 pass first through the electric field between the first electrostatic lens element 1 and the deflector package 5 and subsequently through the electric field between the deflector package 5 and the second electrostatic lens element 2. This can be achieved in different ways. Fig. 5 shows a cross-sectional side view of an apparatus according to another embodiment. In the embodiment of fig. 5, the deflector package 5 extends along the third electrostatic lens element 3 in the direction of the optical axis 6 over substantially the entire gap B between the first electrostatic lens element 1 and the second electrostatic lens element 2. This is basically the only difference between the embodiments of fig. 4 and 5.
The deflector package 5 comprises electrodes arranged in a substantially rotationally symmetric fashion with respect to the optical axis 6. The electrodes of the deflector package 5 serve as deflectors in the respective coordinate direction. The electrodes are arranged at a minimum electrode separation distance D from the optical axis 6.
In fig. 6, a device according to another embodiment is shown in a cross-sectional side view. The only difference between the embodiment of fig. 5 and the embodiment of fig. 6 is that the deflector package 5 is surrounded by a tube 23. The tube 23 is not functioning electrostatically as it is shielded from the interior 19 of the lens.
Fig. 6 shows, in a cross-sectional side view, an electron 25 entering through the first opening 20 at an angle a to the optical axis 6. By applying appropriate voltages across the first electrostatic lens element 1, the second electrostatic lens element 2 and the deflector package 5, the electrons will hit the second opening 21 parallel to the optical axis 6. In operation, the control unit 22 applies different voltages to the electrostatic lens elements 1-4 and the deflector package 5. A central voltage is applied to the deflector package 5. A separate deflection voltage is also applied to each electrode 15. The deflection voltage is added to the center voltage. Different voltages are applied to the first electrostatic lens element 1, the second electrostatic lens element 2, the third electrostatic lens element 3, and the fourth electrostatic lens element 4, respectively. The voltage difference between the third voltage and the first voltage applied across the third electrostatic lens element 3 together with the voltage difference between the first voltage and the central voltage controls the focusing of the electrons entering the inner volume 19 through the first opening 20. By controlling the voltage it is possible to control the position of the electron focus. The deflection voltage controls the deflection of the electrons. The deflection voltage together with the central voltage, the difference between the first voltage and the second voltage determines the angular distribution of electrons entering through the first opening 20 that will hit the slits constituting the second opening 21. The above factors affect the path of the electrons. The first deflection of electrons is realized by the difference between the third voltage and the central voltage and the difference between the deflection voltages. The second deflection of the electrons is mainly achieved by the difference between the central voltage and the fourth voltage. By adjusting the third voltage, the center voltage and the deflection voltage, the first deflection can be adjusted to the desired angular distribution of the electrons. The fourth voltage may then be adjusted to bend the electrons into the desired angular distribution such that they travel parallel to the optical axis and may pass through the second opening.
It is desirable that the length L of the deflector package 5 is at least 50%, preferably at least 100%, most preferably at least 150% of the minimum electrode separation distance D in the deflector package 5 to achieve good control of the electrons.
Thus, the electrostatic lens may be operated in an angle-resolved mode such that electrons entering through the first opening of the first electrostatic lens element 1 in the same direction with respect to the optical axis are focused along the optical axis to the same point at the location of the second opening. Electrons entering the inner volume 19 of the electrostatic lens 7 through the first opening at the same angle in a first plane x but at different angles in a second plane y perpendicular to the first plane form a line when travelling parallel to the optical axis. Such electrons can be controlled to exit through the elongated slit forming the second opening 21. This will be described in more detail below with reference to fig. 7.
By controlling the voltages on the electrostatic lens elements 1-4 and the electrodes 15 differently than how the voltages are controlled in the angle-resolved mode, it is possible to operate the electrostatic lens 7 in the imaging mode. In the imaging mode, the electron emission surface is imaged on the plane of the second opening. Only a part of the image of the electron emission sample impinges on the second opening 21. This portion corresponds to a specific portion of the electron emission sample. It is possible to control the voltages on the electrostatic lens elements 1-4 and the electrode 15 such that different parts of the image hit the second opening 21. It is also possible to control the angle by which the electrons exiting through the second opening exit at a controllable angle in at least one coordinate direction with respect to the optical axis.
In fig. 6, the first electrostatic lens element 1 and the second electrostatic lens element 2 are arranged with a gap B between the first electrostatic lens element 1 and the second electrostatic lens element 2. The deflector package 5 spans a part of the gap between the first electrostatic lens element 1 and the second electrostatic lens element 2. The distance G parallel to the optical axis 6 between the deflector package device and any of the first and second electrostatic lens elements 2 is less than 10%, preferably less than 5%, most preferably less than 2% of the minimum electrode separation distance D from the optical axis 6.
The deflector device comprises a metal tube 23, wherein the deflector package 5 is arranged in the metal tube 23, and wherein the metal tube 23 is arranged electrically separated from the deflector package 5, the first electrostatic lens element 1 and the second electrostatic lens element 2.
Fig. 7 shows a view of the device according to fig. 2 to 6 along the length axis towards the second opening 21, as shown in fig. 3 and 4. The device comprises a deflector package 5 comprising eight electrodes 15a-15 h. The point 24 shows five different electron beams entering through the first opening 20 at an angle a in the x-direction with respect to the optical axis, but having five different angles in the y-direction with respect to the optical axis 6. The main function of the electrodes 15a and 15e is to select the elevation angle through the second opening 21. The main function of the electrodes 15c and 15g is to focus the electron beam 24 in the y-direction. The main function of the electrodes 15b, 15d, 15f and 15h is to eliminate spherical distortions, so that the light beam 24 with the same elevation angle passes through the slit regardless of its angle in the y-direction to the optical axis 6. The electrostatic lens 7 is preferably controlled such that the electrons exit through the second opening substantially parallel to the optical axis in the x-direction. The second opening has a width W and a height H. The ratio of the width W to the height H is greater than 10.
Fig. 8 shows an alternative to the device shown in fig. 7. The device comprises a deflector package 5 comprising two electrodes 15a, 15 b. The point 24 shows five different electron beams entering through the first opening 20 at an angle a in the x-direction with respect to the optical axis, but having five different angles in the y-direction with respect to the optical axis 6. In case of only two electrodes in the deflector package, it is not possible to avoid spherical deformations. This is reflected in fig. 8 in that the side beams 24a, 24e are too high to enter the second opening 21, while the central beam 24c is too low to enter the second opening 21.
The above-described embodiments may be modified in many ways without departing from the scope of the invention, which is limited only by the appended claims.
Claims (16)
1. An apparatus (100) for an electron spectrometer, the apparatus (100) comprising an electrostatic lens (7) having: -an inner volume (19), -a first opening (20) for electrons to enter the inner volume (19), -a second opening (21) for electrons to exit from the inner volume (19), and-a substantially straight optical axis (6) extending from the first opening (20) through the inner volume (19) to the second opening (21), wherein the electrostatic lens (7) is configured to form an electron beam entering through the first opening (20) and to transmit the electron beam to the second opening (21), wherein the electrostatic lens (7) further comprises:
a first electrostatic lens element (1) having a first end (26) facing the first opening (20) and a second end (27) facing away from the first opening (20),
-a second electrostatic lens element (2) having a first end (28) facing the first electrostatic lens element (1) and a second end (29) facing the second opening (21), and
-a deflector device comprising a deflector package (5) having a plurality of electrodes (15) arranged circumferentially around the optical axis (6) between a first end (26) of the first electrostatic lens element (1) and a second end (29) of the second electrostatic lens element (2) and arranged to deflect the electron beam in at least a first coordinate direction (x, y) perpendicular to the optical axis (6), characterized in that the deflector package (5) is arranged such that electrons travelling from the first electrostatic lens element (1) to the second electrostatic lens element (2) during operation of the electrostatic lens (7) first pass an electric field between the first electrostatic lens element (1) and the deflector package (5) and subsequently pass an electric field between the deflector package (5) and the second electrostatic lens element (2), and wherein the electrodes are electrically separated from each other and from the first and second electrostatic lens elements, wherein the apparatus is controllable such that the electron beam exiting through the second opening is directed along the optical axis of the electrostatic lens (7).
2. The device (100) according to claim 1, wherein the first electrostatic lens element (1) is arranged adjacent to the second electrostatic lens element (2) with a gap (B) between the first electrostatic lens element (1) and the second electrostatic lens element (2), and wherein the deflector package (5) spans at least a part of the gap (B) between the first electrostatic lens element (1) and the second electrostatic lens element (2).
3. The device (100) according to claim 1 or 2, wherein the deflector package comprises at least 2 electrodes (15), preferably at least 4 electrodes (15), most preferably at least 8 electrodes (15), arranged around the optical axis (6).
4. The device (100) according to claim 3, wherein the deflector package (5) comprises at least 4 electrodes (15) arranged in a substantially rotationally symmetric fashion, wherein the electrodes (15) of the deflector package (5) act as deflectors in at least two coordinate directions (X, Y).
5. The apparatus (100) according to any of the preceding claims, wherein the electrodes (15) in the deflector package (5) are arranged at a minimum electrode separation distance (D) from the optical axis (6).
6. The device (100) according to claim 5, wherein the length (L) of the deflector package (5) is at least 50%, preferably at least 100%, most preferably at least 150% of the minimum electrode separation distance (D) in the deflector package from the optical axis (6).
7. The device (100) according to claim 5 or 6, wherein a distance (G) parallel to the optical axis (6) between the deflector package and any of the first and second electrostatic lens elements is less than 10%, preferably less than 5%, most preferably less than 2% of the minimum electrode separation distance (D) from the optical axis (6).
8. The device (100) according to any of the preceding claims, wherein the deflector device comprises a metal tube (23), wherein the deflector package (5) is arranged in the metal tube (23), and wherein the metal tube (23) is arranged electrically separated from the deflector package (5), the first electrostatic lens element (1) and the second electrostatic lens element (2).
9. The apparatus (100) according to any one of the preceding claims, wherein the second opening is elongated in a plane perpendicular to the optical axis, wherein the second opening has a width to height ratio of at least 10:1, preferably at least 30: 1.
10. The device (100) according to any one of the preceding claims, wherein the first opening is arranged in the first electrostatic lens element and the second opening is arranged in the second electrostatic lens element.
11. The apparatus (100) according to any one of claims 1 to 9, further comprising
-a third electrostatic lens element (3) arranged such that the first electrostatic lens element (1) is arranged between the third electrostatic lens element (3) and the second electrostatic lens element (2), and
-a fourth electrostatic lens element (4) arranged such that the second electrostatic lens element (2) is arranged between the fourth electrostatic lens element (4) and the first electrostatic lens element (1).
12. The device (100) according to claim 11, wherein the first opening (20) is arranged in the third electrostatic lens element (3) and the second opening (21) is arranged in the fourth electrostatic lens element (4).
13. The apparatus (100) according to any one of the preceding claims, wherein the electrostatic lens (7) is arranged to operate in an angle-resolved mode such that electrons entering through the first opening (20) in the same direction with respect to the optical axis (6) are focused along the optical axis (6) to the same point at the location of the second opening (21) and such that electrons exiting through the second opening exit at a controllable angle with respect to the optical axis.
14. The device (100) according to any of the preceding claims, configured for use in an analyzer device for determining at least one parameter related to electrons emitted from an electron emitting sample (13), wherein the device is arranged with the first opening (20) facing the electron emitting sample (13) and the second opening (21) adjacent to an entrance slit (11) of a measurement region (8) of the analyzer for transporting electrons from an electron emitting surface to the entrance slit (11) of the measurement region (8).
15. The device (100) according to any of the preceding claims, further comprising a control unit (22) configured to apply a separate voltage to each of the electrodes (1-4) of the deflector package (5).
16. The apparatus (100) according to any one of the preceding claims, wherein the control unit (22) is further configured to apply a separate voltage to each of the electrostatic lens elements (1-4).
Applications Claiming Priority (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE1900143A SE543575C2 (en) | 2019-08-30 | 2019-08-30 | Electrostatic lens for controlling beam of charged particles |
| SE1900143-7 | 2019-08-30 | ||
| SE1951077-5 | 2019-09-24 | ||
| SE1951077A SE543641C8 (en) | 2019-08-30 | 2019-09-24 | Electrostatic lens for controlling beam of electrons |
| PCT/SE2020/050824 WO2021040609A1 (en) | 2019-08-30 | 2020-08-27 | Electrostatic lens for controlling beam of electrons |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN114303229A true CN114303229A (en) | 2022-04-08 |
Family
ID=74684879
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202080060729.1A Pending CN114303229A (en) | 2019-08-30 | 2020-08-27 | Electrostatic lens for controlling electron beam |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP4022669A4 (en) |
| CN (1) | CN114303229A (en) |
| WO (1) | WO2021040609A1 (en) |
Family Cites Families (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH071681B2 (en) * | 1990-04-19 | 1995-01-11 | 株式会社日立製作所 | Charged particle beam device |
| EP0462554B1 (en) * | 1990-06-20 | 2000-10-11 | Hitachi, Ltd. | Charged particle beam apparatus |
| DE59711915D1 (en) * | 1997-09-29 | 2004-10-21 | Advantest Corp | objective lens |
| JP2003207470A (en) * | 2002-01-16 | 2003-07-25 | Jeol Ltd | Electron spectroscopic apparatus |
| US7435956B2 (en) * | 2004-09-10 | 2008-10-14 | Multibeam Systems, Inc. | Apparatus and method for inspection and testing of flat panel display substrates |
| US7233008B1 (en) * | 2005-03-14 | 2007-06-19 | Applied Materials, Israel, Ltd. | Multiple electrode lens arrangement and a method for inspecting an object |
| GB0700754D0 (en) * | 2007-01-15 | 2007-02-21 | Oxford Instr Analytical Ltd | Charged particle analyser and method |
| JP5098618B2 (en) * | 2007-12-12 | 2012-12-12 | 富士ゼロックス株式会社 | Information processing apparatus and program |
| ES2687794T3 (en) * | 2012-03-06 | 2018-10-29 | Scienta Omicron Ab | Analyzer arrangement for particle spectrometer |
| JP6238978B2 (en) * | 2012-06-29 | 2017-11-29 | エフ・イ−・アイ・カンパニー | Multi-ion source |
-
2020
- 2020-08-27 WO PCT/SE2020/050824 patent/WO2021040609A1/en unknown
- 2020-08-27 CN CN202080060729.1A patent/CN114303229A/en active Pending
- 2020-08-27 EP EP20856886.5A patent/EP4022669A4/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| EP4022669A1 (en) | 2022-07-06 |
| WO2021040609A1 (en) | 2021-03-04 |
| EP4022669A4 (en) | 2023-10-11 |
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