Electron beam energy analyzer

Abstract

The invention relates to the technical field of electron gun equipment, and discloses an electron beam energy analyzer which comprises a focusing electrode, a speed reduction grid electrode, a voltage equalizing plate, a Faraday cup, a direct-current power supply and a picoammeter, the focusing electrode, the speed reduction grid electrode, the voltage equalizing plate and the Faraday cup are sequentially arranged on the same optical axis, and the focusing electrode is arranged behind a beam limiting diaphragm of an electron gun; the picoammeter is connected with the Faraday cup and is grounded. The DC power supply is connected with the focusing electrode, the deceleration grid electrode and the voltage-sharing plate. The electron beams are converged and collimated through the focusing electrode, so that the influence of transverse divergence on the test resolution is reduced; screening electrons with kinetic energy greater than grid potential through the deceleration grid; potential distribution near the gate holes is smoothly reduced through the voltage equalizing plate, and the resolution ratio of electron beam energy detection is improved. The analyzer provided by the invention is simple in structure, the measurement precision reaches dozens of millivolts, and the analyzer can be used for electron beam energy analysis of a high-brightness electron gun.

Description

Technical Field

[0001] The present invention relates to the technical field of electron gun equipment, in particular to an electron beam energy analyzer. Background Art

[0002] Reducing electron beam energy dispersion plays an important role. For example, in scanning electron microscopes, smaller electron beam energy dispersion improves the focusing characteristics of the electron beam, thereby improving imaging resolution. In the field of electron beam processing, smaller energy dispersion means a more concentrated electron beam energy distribution, which enables more precise control of the processing process. For example, in electron beam lithography, reducing energy dispersion can improve lithographic resolution and pattern accuracy. Therefore, studying electron beam energy dispersion is of great significance to promoting the development of electron beam components and equipment.

[0003] Devices for measuring charged particle energy distribution primarily include deflection-type energy analyzers and retarding-field energy analyzers. The former utilizes the different deflection trajectories of charged particles of different energies in an electric (or magnetic) field to analyze their energy distribution. However, this approach suffers from low resolution. Improving resolution requires a large number of collimating and focusing lenses, significantly increasing the device size and making it difficult to directly measure the energy spectrum of electron beams from existing electron guns (such as SEMs and EBLs). Electrostatic retarding-field energy analyzers analyze the energy distribution of electron beams by regulating the retarding grid voltage to select electrons within a specific energy range. Their advantages are their small size, simple structure, and direct compatibility with electron gun architectures. For high-brightness electron beam measurement equipment such as scanning electron microscopes, the energy distribution of the electron beam is generally within a few eV. For Schottky and cold-field electron guns, the beam energy spread is particularly limited to 0.3-0.7 eV. This requires an energy spread measurement device with a resolution of less than 50 meV. However, existing energy spread measurement devices fail to meet these resolution requirements. Summary of the Invention

[0004] In view of this, the present invention provides an electron beam energy analyzer to solve the problem of resolution of energy dispersion measurement devices in the related art.

[0005] The present invention provides an electron beam energy analyzer, which includes: a focusing electrode, a deceleration grid, a voltage balancing plate, a Faraday cup, a DC power supply and a picoammeter, wherein:

[0006] The focusing electrode, the deceleration grid, the equalizing plate, and the Faraday cup are sequentially arranged on the same optical axis. The focusing electrode is placed behind the beam limiting aperture of the electron gun. The picoammeter is connected to the Faraday cup and grounded. The DC power supply is respectively connected to the focusing electrode, the deceleration grid, and the equalizing plate.

[0007] The focusing electrode is used to converge and collimate the electron beam emitted by the electron gun, and the potential of the focusing electrode is lower than the kinetic energy of the electron beam;

[0008] The deceleration grid is used to screen electrons whose energy is greater than the deceleration grid potential;

[0009] The voltage balancing plate is used to smooth the potential near the deceleration grid hole, and the potential of the voltage balancing plate is lower than the potential of the deceleration grid;

[0010] The Faraday cup is used to collect electrons passing through the deceleration grid;

[0011] The picoammeter is used to measure the beam current entering the Faraday cup;

[0012] The DC power supply is used to apply voltage to the focusing electrode, the deceleration grid, and the voltage balancing plate.

[0013] The present invention provides an electron beam energy analyzer, which converges and collimates the electron beam through a focusing electrode to reduce the influence of lateral divergence on the test resolution; screens electrons with kinetic energy greater than the grid potential through a deceleration grid; and smoothes the potential near the deceleration grid hole through a voltage equalizing plate to improve the resolution of electron beam energy detection.

[0014] In an optional embodiment, the focal position is changed by adjusting the voltage applied by the DC power supply to the focusing electrode.

[0015] In an optional embodiment, the current received by the Faraday cup is regulated by adjusting the voltage applied by the DC power supply to the deceleration grid.

[0016] In an optional embodiment, the electron beam energy analyzer further comprises: a ceramic plate, and the focusing electrode, the deceleration grid, the balancing plate and the Faraday cup are separated by the ceramic plate and brazed into a coaxial integral component.

[0017] In an optional embodiment, the electron beam energy analyzer further includes: a vacuum chamber, wherein the focusing electrode, the deceleration grid, the voltage balancing plate, the Faraday cup and the ceramic plate are all located in the vacuum chamber.

[0018] In an optional embodiment, the focusing electrode, the deceleration grid, the voltage balancing plate and the Faraday cup are all made of non-magnetic materials.

[0019] In an optional embodiment, the ceramic plate is at least one of aluminum oxide and aluminum nitride.

[0020] In an optional embodiment, the focusing electrode, the deceleration grid, the voltage balancing plate and the ceramic plate are in a circular shape.

[0021] In an optional embodiment, the Faraday cup is a cup with a lid, and the lid is provided with holes.

[0022] In an optional embodiment, the vacuum environment of the vacuum chamber is 1E-6Pa-1E-7Pa. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 is a schematic diagram of an electron beam energy analyzer provided in an embodiment of the present invention;

[0025] Figure 2 1 is a schematic structural diagram of another electron beam energy analyzer provided by an embodiment of the present invention;

[0026] Figure 3 The electron beam energy analyzer of the embodiment of the present invention is used to simulate the change of the electron beam trajectory with the deceleration grid voltage under the ideal Schottky electron gun;

[0027] Figure 4 This is the relationship between the receiving current and the deceleration grid voltage obtained by simulating an ideal Schottky electron gun used in the electron beam energy analyzer of an embodiment of the present invention. DETAILED DESCRIPTION

[0028] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative efforts shall fall within the scope of protection of the present invention.

[0029] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0030] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; internal connections between two components; wireless connections or wired connections. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0031] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0032] To perform energy spectrum analysis of low-energy electron beams, the present invention provides an electron beam energy analyzer. This analyzer is positioned behind the beam-limiting aperture of the electron optical system. Its specific installation location is determined by the electron beam divergence angle and kinetic energy. For example, the analyzer can be positioned 10-30 mm behind the beam-limiting aperture of the electron optical system.

[0033] like Figure 1 As shown, the electron beam energy analyzer includes: a focusing electrode 100, a deceleration grid 200, a voltage balancing plate 300, a Faraday cup 400, a DC power supply 500, and a picoammeter 600. The focusing electrode 100, the deceleration grid 200, the voltage balancing plate 300, and the Faraday cup 400 are arranged in sequence along the optical axis. The focusing electrode 100 is placed behind the beam-limiting aperture of the electron gun. The picoammeter 600 is connected to the Faraday cup 400 and grounded. The DC power supply 500 is connected to the focusing electrode 100, the deceleration grid 200, and the voltage balancing plate 300, respectively. The focusing electrode 100 is used to converge and collimate the electron beam emitted by the electron gun. The potential of the focusing electrode 100 is lower than the kinetic energy of the electron beam. The deceleration grid 200 is used to filter electrons with energy greater than the potential of the deceleration grid. The voltage balancing plate 300 is used to smooth the potential near the deceleration grid aperture. The potential of the voltage balancing plate 300 is lower than the potential of the deceleration grid. The Faraday cup 400 is used to collect electrons that pass through the deceleration grid 200. The picoammeter 600 is used to measure the beam current entering the Faraday cup 400. The DC power supply 500 is used to apply voltage to the focusing electrode 100, the deceleration grid 200, and the voltage equalizing plate 300.

[0034] Specifically, the electron beam after being scraped by the beam-limiting aperture enters the tester, is decelerated by the deceleration electric field of the focusing electrode 100, and converges toward the optical axis near the exit of the hole. The potential V1 of the focusing electrode 100 is lower than the kinetic energy of the electron beam, and all electrons can pass through the focusing electrode 100. The potential V2 of the deceleration grid 200 is approximately the kinetic energy of the electrons. The electrons are still decelerated in front of the deceleration grid 200. At this time, only electrons with energy greater than the voltage of the deceleration grid 200 can pass through the deceleration grid hole. The equalizing plate 300 is 0.5-3mm behind the deceleration grid 200. The absolute value of the potential V3 of the equalizing plate 300 is slightly lower than the kinetic energy of the electrons, which plays a role in smoothing the potential distribution of the deceleration grid hole, thereby improving the resolution of the test instrument. The Faraday cup 400 is placed 20-50mm behind the equalizing plate 300, and the transcutaneous ammeter 600 is grounded to collect electrons passing through the deceleration grid 200. The DC power supply 500 outputs three adjustable negative high voltages, which serve as the voltage for the focusing electrode 100, the deceleration grid 200, and the voltage for the voltage balancing plate 300. The energy distribution of the electron beam can be determined by analyzing the differential relationship between the current received by the Faraday cup 400 and the voltage of the deceleration grid 200.

[0035] The present invention provides an electron beam energy analyzer, which converges and collimates the electron beam through a focusing electrode to reduce the influence of lateral divergence on the test resolution; screens electrons with kinetic energy greater than the grid potential through a deceleration grid; and smoothes the potential near the deceleration grid hole through a voltage equalizing plate to improve the resolution of electron beam energy detection.

[0036] In an optional embodiment, the focal position is changed by adjusting the voltage applied to the focusing electrode 100 by the DC power supply 500 .

[0037] Specifically, by adjusting the voltage applied to the focusing electrode 100 by the DC power supply 500, the potential V1 of the focusing electrode 100 can be changed, and the focus position can be adjusted to ensure that the electron beam is as focused and collimated as possible before entering the deceleration grid 200.

[0038] In an optional embodiment, the current received by the Faraday cup 400 is regulated by adjusting the voltage applied by the DC power supply 500 to the deceleration grid 200 .

[0039] Specifically, by adjusting the voltage applied by the DC power supply 500 to the deceleration gate 200, the potential V2 of the deceleration gate 200 can be changed, thereby screening electrons in a specific energy range, so that only electrons with kinetic energy greater than the gate potential pass through and enter the Faraday cup 400, causing the current received by the Faraday cup 400 to change accordingly.

[0040] Among them, the three-way high-voltage output power supply is an integrated unit, and three sets of discrete negative high-voltage power supplies can also be used. During installation, the output of the DC power supply 500 is fed into the vacuum chamber through the high-voltage electrode flange, and is connected to the wiring pins of each component on the analyzer through a vacuum high-voltage insulated wire (such as a polyimide-coated wire) in the chamber. The focusing electrode 100, the deceleration grid 200, and the equalizing plate 300 are respectively powered by the same power supply, which supports independent adjustment of the potential of each component to meet the needs of electron beam analysis in different energy ranges (such as wide energy band scanning or fixed threshold detection). The potential gradient can dynamically match the kinetic energy and beam size of the electron beam, and is compatible with different types of electron guns (such as thermal emission guns and field emission guns) without hardware modification, and has strong scalability.

[0041] In an optional embodiment, as Figure 2 As shown, the electron beam energy analyzer further includes: a ceramic plate, and the focusing electrode 100, the deceleration grid 200, the equalizing plate 300 and the Faraday cup 400 are separated by the ceramic plate and brazed into a coaxial integral component.

[0042] Specifically, the ceramic plate is composed of three ceramic rings (701, 702, 703). The focusing electrode 100, the deceleration grid 200, the equalizing plate 300, and the Faraday cup 400 are separated by ceramic rings and welded into an integral component in a vacuum furnace. The deceleration grid 200, the equalizing plate 300, and the Faraday cup 400 must ensure high finish, and the center hole must be strictly coaxial with the electron beam to be tested. The focusing electrode 100, the deceleration grid 200, the equalizing plate 300, and the Faraday cup 400 are arranged in sequence along the same optical axis to ensure the linearity of the electron beam transmission path, reduce scattering loss, and improve energy analysis efficiency. The focusing electrode 100, the deceleration grid 200, and the equalizing plate 300 all have protruding terminal pins (which can be equipped with nuts). The terminal pins are staggered at a certain angle to prevent lead interference; the Faraday cup 400 is welded with terminal studs. The picoammeter 600 is connected to the terminal posts on the Faraday cup 400 via an air plug or vacuum electrode. Grounding the Picoammeter 600 allows for low-noise current detection (picoampere level) to match weak beam signals (such as electron beams in extremely high vacuum environments), improving the signal-to-noise ratio and measurement sensitivity.

[0043] In an optional embodiment, the electron beam energy analyzer further includes: a vacuum chamber, wherein the focusing electrode 100, the deceleration grid 200, the voltage equalizing plate 300, the Faraday cup 400 and the ceramic plate are all located in the vacuum chamber.

[0044] Specifically, the structural components of the electron beam energy analyzer are partially placed in a vacuum chamber, which provides the analyzer with a high vacuum environment better than 10-5 Pa. Exemplarily, the vacuum environment of the vacuum chamber is 1E-6 Pa to 1E-7 Pa.

[0045] In an optional embodiment, the focusing electrode 100, the deceleration grid 200, the voltage balancing plate 300 and the Faraday cup 400 are all made of non-magnetic materials. The ceramic plate is at least one of aluminum oxide and aluminum nitride.

[0046] Specifically, non-magnetic materials include copper, molybdenum, and 316 stainless steel. The focusing electrode 100, deceleration grid 200, voltage-equalizing plate 300, and ceramic plate are annular in shape. The Faraday cup 400 is a cup with a lid and a hole. The aperture of the hole is as small as possible while ensuring full electron beam transmission. The Faraday cup 400 uses a fully absorbing electron collection method to avoid interference from reflected electrons and ensure beam measurement integrity.

[0047] In a specific embodiment of the present invention, the focusing electrode 100, the deceleration grid 200, and the equalizing plate 300 have a diameter of 50 mm and a thickness of 1 mm, and the apertures are 2 mm, 0.8 mm, and 0.5 mm, respectively. The inter-electrode spacing is 2 mm and 0.9 mm. The electron beam to be measured is a Schottky electron gun, with an ideal electron beam of 20 nA and 5 keV passing through a 100 μm aperture. The voltage V1 on the focusing electrode 100 is set to -4850 V, the voltage V3 on the equalizing plate 300 is -4999.5 V, and the voltage V2 on the deceleration grid 200 is adjusted. The electron beam trajectory changes as follows: Figure 3 As shown, the current I received by the Faraday cup 400 changes as Figure 4 As shown. Figure 3 and Figure 4 It can be seen that when the retarding grid voltage is -5017.410V, the electron beam completely passes through the grid aperture and enters Faraday cup 400. When the retarding grid voltage is -5017.433V, all electrons are intercepted by the retarding grid, and no electrons are received by Faraday cup 400. Differentiating the receiving current I with respect to the retarding grid voltage yields the energy distribution spectrum of the electron beam. The full width at half maximum (FWHM) of this distribution spectrum is 11 meV, representing the energy spread, which is also the theoretical resolution of the energy analyzer and meets the requirements for testing high-brightness electron beams with energy spreads of a few tenths of an electron volt.

[0048] Although the embodiments of the present invention have been described with reference to the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention. Such modifications and variations are all within the scope defined by the appended claims.

Claims

1. An electron beam energy analyzer, characterized in that The electron beam energy analyzer includes: a focusing electrode, a deceleration grid, a voltage balancing plate, a Faraday cup, a DC power supply and a picoammeter, wherein: The focusing electrode, the deceleration grid, the equalizing plate, and the Faraday cup are sequentially arranged on the same optical axis. The focusing electrode is placed behind the beam limiting aperture of the electron gun. The picoammeter is connected to the Faraday cup and grounded. The DC power supply is respectively connected to the focusing electrode, the deceleration grid, and the equalizing plate. The focusing electrode is used to converge and collimate the electron beam emitted by the electron gun, and the potential of the focusing electrode is lower than the kinetic energy of the electron beam; The deceleration grid is used to screen electrons whose energy is greater than the deceleration grid potential; The voltage balancing plate is used to smooth the potential near the deceleration grid hole, and the potential of the voltage balancing plate is lower than the potential of the deceleration grid; The Faraday cup is used to collect electrons passing through the deceleration grid; The picoammeter is used to measure the beam current entering the Faraday cup; The DC power supply is used to apply voltage to the focusing electrode, the deceleration grid, and the voltage balancing plate.

2. The electron beam energy analyzer according to claim 1, characterized in that The focus position is changed by adjusting the voltage applied to the focusing electrode by the DC power supply.

3. The electron beam energy analyzer according to claim 1, characterized in that The current received by the Faraday cup is regulated by adjusting the voltage applied by the DC power supply to the deceleration grid.

4. The electron beam energy analyzer according to claim 1, characterized in that The electron beam energy analyzer further includes a ceramic plate, through which the focusing electrode, the deceleration grid, the voltage balancing plate and the Faraday cup are separated and brazed into a coaxial integral component.

5. The electron beam energy analyzer according to claim 4, characterized in that The electron beam energy analyzer further includes a vacuum chamber, wherein the focusing electrode, the deceleration grid, the voltage balancing plate, the Faraday cup and the ceramic plate are all located in the vacuum chamber.

6. The electron beam energy analyzer according to claim 1, characterized in that The focusing electrode, the deceleration grid, the voltage balancing plate and the Faraday cup are all made of non-magnetic materials.

7. The electron beam energy analyzer according to claim 4, characterized in that The ceramic plate is at least one of aluminum oxide and aluminum nitride.

8. The electron beam energy analyzer according to claim 4, characterized in that The focusing electrode, the deceleration grid, the voltage balancing plate and the ceramic plate are in the shape of a circular ring.

9. The electron beam energy analyzer according to claim 4, characterized in that The Faraday cup is a cup with a lid, and the lid is provided with holes.

10. The electron beam energy analyzer according to claim 5, characterized in that The vacuum environment of the vacuum chamber is 1E-6Pa-1E-7Pa.

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