WO2024189799A1 - Electron beam control circuit, electron gun, electron light source device, electron beam measurement method, and electron beam trajectory control method - Google Patents

Abstract

An electron beam control circuit according to the present invention controls the voltage applied to a lead-out electrode of an electron gun and thereby changes the switching of an electron beam emitted from a cathode of the electrode gun between an ON state and an OFF state. The electron beam control circuit comprises an amplifier that supplies forward bias voltage to the lead-out electrode, a power supply that supplies reverse bias voltage to the lead-out electrode, and a switch circuit that performs switching such that the amplifier and the lead-out electrode are connected when the electron beam is put into the ON state and the power supply and the lead-out electrode are connected when the electron beam is put into the OFF state.

Description

Electron beam control circuit, electron gun, electron light source device, electron beam measurement method, and electron beam trajectory control method

The present invention relates to an electron beam control circuit, an electron gun, an electron light source device, an electron beam measurement method, and an electron beam trajectory control method.

The electron gun used is a pierce-type electron gun that has an electron emission surface that emits electrons, an extraction electrode that generates an electric field between the electron emission surface and the electron emission surface to cause electrons to be emitted from the electron emission surface, and a cone-shaped electrode that has the same potential as the electron emission surface and is arranged around the electron emission surface (Patent Document 1).

U.S. Pat. No. 6,642,657

One aspect of the present invention is a control circuit that changes the on and off states of an electron beam emitted from a cathode of an electron gun having an extraction electrode by controlling the voltage applied to the extraction electrode, and is an electron beam control circuit that includes an amplifier that supplies a forward bias voltage to the extraction electrode, a power supply that supplies a reverse bias voltage to the extraction electrode, and a switch circuit that connects the amplifier to the extraction electrode when the electron beam is in the on state and switches to connect the power supply to the extraction electrode when the electron beam is in the off state.

One aspect of the present invention is an electron gun comprising an extraction electrode that controls the amount of electron beam emitted from a cathode, an anode that accelerates the electron beam emitted from the cathode, a modification electrode that is provided between the extraction electrode and the anode and changes the opening angle of the electron beam passing through it, an extraction electrode control amplifier that applies a voltage to the extraction electrode based on an electron beam command that specifies the amount of the electron beam, and a modification electrode control amplifier that applies a voltage to the modification electrode based on the electron beam command.

One aspect of the present invention is an electron light source device having a power supply path extending from an insulator base, comprising a filament power supply unit for applying a voltage to a cathode that emits an electron beam, an extraction electrode for controlling the amount of the electron beam from the cathode, and a cathode protector for blocking the path of electrons from the extraction electrode to the power supply path when the extraction electrode is controlled to reduce the amount of the electron beam.

One aspect of the present invention is an electron beam measurement method that includes: scanning an electron beam from an electron light source unit on a first aperture having a first current sensor using a first beam deflector capable of changing the deflection angle of the electron beam; measuring a first beam current distribution of the electron beam on a first arrangement surface of the first aperture using a first output from the first current sensor of the first aperture; scanning the electron beam from the electron light source unit on a second aperture arranged on the exit side of the first aperture and having a second current sensor using a second beam deflector arranged on the exit side of the first aperture and capable of changing the deflection angle of the electron beam; measuring a second beam current distribution of the electron beam on a second arrangement surface of the second aperture using a second output from the second current sensor of the second aperture; and determining a light source size and an opening angle of the electron beam from the electron light source unit based on the beam current distribution measured using the first output of the first current sensor and the beam current distribution measured using the second output of the second current sensor.

One aspect of the present invention is a laser scanning electron microscope comprising an extraction electrode for controlling the amount of an electron beam emitted from a cathode, a focusing lens unit including a focusing lens for converging the electron beam by a magnetic field, a first deflector provided between the extraction electrode and the focusing lens for deflecting the trajectory of the electron beam, a second deflector provided between the first deflector and the focusing lens for deflecting the trajectory of the electron beam deflected by the first deflector, an extraction electrode control amplifier for applying a voltage to the extraction electrode based on an electron beam command that specifies the amount of the electron beam, and a focusing lens unit for focusing the electron beam. The electron gun includes a first control unit that outputs an excitation current to the first deflector based on a voltage command or a current command based on an electron beam command, and a second control unit that outputs an excitation current to the second deflector based on a voltage command or a current command based on the electron beam command, where the first control unit controls the first deflector so that the trajectory of the electron beam from the first deflector is directed toward the center of the second deflector, and the second control unit controls the second deflector so that the trajectory of the electron beam from the second deflector is along the optical axis or parallel to the optical axis.

One aspect of the present invention is an electron beam trajectory control method that includes deflecting an electron beam from an electron light source unit with a first beam deflector, deflecting the electron beam from the first beam deflector with a second beam deflector, and changing the beam current of the electron beam from the electron light source unit, where the deflecting with the first beam deflector includes deflecting the electron beam such that a first trajectory of the electron beam from the first beam deflector does not change when the beam current changes, and the deflecting with the second beam deflector includes deflecting the electron beam such that a second trajectory of the electron beam from the second beam deflector does not change when the beam current changes.

FIG. 2 is a cross-sectional view showing an example of the configuration of the electron gun 2 according to the present embodiment. 2 is a cross-sectional view showing an example of the configuration of a lens barrel portion 3 according to the present embodiment. FIG. FIG. 2 is a diagram showing an example of the configuration of an extraction electrode control circuit 210 according to the embodiment. 2 is an example of an enlarged cross-sectional view showing the vicinity of a focusing electrode 20 of the electron gun 2 according to the embodiment. FIG. 2 is an example of an enlarged cross-sectional view showing the vicinity of a focusing electrode 20 of the electron gun 2 according to the embodiment. FIG. FIG. 2 is an example of an exploded perspective view showing the configuration of a cathode unit 10, a cathode protector 70, and a focusing electrode 20 according to the embodiment. 3 is a diagram showing an example of the configuration of an aperture angle adjustment/differential exhaust mechanism 4 according to the embodiment; FIG. 1 is a diagram showing an example of the spread of an electron beam in a conventional electron gun 2a according to an embodiment when the beam current of the electron beam is large. FIG. 1 is a diagram showing an example of the spread of an electron beam in a conventional electron gun 2a according to an embodiment of the present invention when the beam current of the electron beam is small. FIG. 3 is a diagram showing an example of the spread of an electron beam in the electron gun 2 according to the embodiment. FIG. FIG. 2 is a diagram showing an example of the configuration of a high-speed beam alignment system 5 according to the embodiment. FIG. 2 is a diagram showing an example of the configuration of a high-speed beam modulation mechanism 6 according to the embodiment. 5A to 5C are diagrams illustrating an example of an electron beam measurement method according to an embodiment. 11 is a diagram showing an example of an output from a current sensor by scanning an electron beam EB1 on an aperture according to the embodiment. FIG. 11A and 11B are diagrams illustrating an example of measurement of the source size of the electron beam EB1 according to the embodiment. 6A to 6C are diagrams illustrating an example of a method for measuring a spot diameter on a modeling surface according to an embodiment. FIG. 2 is a diagram illustrating an example of the configuration of a beam measurement sensor 180 according to the embodiment.

(Embodiment)
Hereinafter, the embodiments will be described in detail with reference to the drawings.
[Configuration of the electron lens barrel 1]
The configuration of an electron barrel 1 according to this embodiment will be described with reference to Figures 1 and 2. The electron barrel 1 includes an electron gun 2 and a lens barrel section 3. Figure 1 is a cross-sectional view showing an example of the configuration of the electron gun 2 according to this embodiment. Figure 2 is a cross-sectional view showing an example of the configuration of the lens barrel section 3 according to this embodiment.

For ease of explanation, the drawings show an XYZ Cartesian coordinate system, which is a three-dimensional Cartesian coordinate system. In the XYZ Cartesian coordinate system, the direction of the Z axis is vertically downward. In the following explanation, the direction parallel to the Z axis is also referred to as the up-down direction. The direction of the Z axis is also referred to as the downward direction. The direction opposite to the direction of the Z axis is also referred to as the upward direction. The positive side of the direction of the Z axis is also referred to as the downward side, and the negative side of the direction of the Z axis is also referred to as the upward side.
The direction parallel to the Z axis is also referred to as the optical axis direction. The positive side of the Z axis is also referred to as the target side, and the negative side of the Z axis is also referred to as the cathode side.
The direction parallel to the Y-axis is also called the depth direction. The positive side of the Y-axis is also called the front side, and the negative side of the Y-axis is also called the back side. The direction parallel to the X-axis is also called the left-right direction. The positive side of the X-axis is also called the right side, and the negative side of the X-axis is also called the left side.

The electron gun 2 comprises a cathode unit 10, a focusing electrode 20, an extraction electrode 30, a changing electrode 40, a shield electrode 50, an anode 60, a cathode protector 70, and a high-voltage control unit 200. The cathode unit 10, the focusing electrode 20, the extraction electrode 30, the changing electrode 40, and the cathode protector 70 are provided inside the shield electrode 50. The shield electrode 50 constitutes part of the housing of the electron gun 2.

The cathode unit 10, focusing electrode 20, extraction electrode 30, deflection electrode 40, shield electrode 50, and anode 60 are arranged along the optical axis AX1. The optical axis AX1 extends in the Z direction, which is the central axis.

The cathode unit 10, focusing electrode 20, extraction electrode 30, change electrode 40, shield electrode 50, anode 60, and cathode protector 70 all have a shape that is rotationally symmetrical with respect to the optical axis AX1 in the portions close to the optical axis AX1.

The cathode unit 10, focusing electrode 20, extraction electrode 30, and changing electrode 40 are each electrically insulated and held by a shield electrode 50. The cathode unit 10 is housed in a cathode protector 70 and is electrically insulated from the surroundings. The cathode protector 70 is surrounded by the focusing electrode 20.

The cathode unit 10 includes a cathode 101 , a filament power supply portion 102 , and an insulator base 104 .
The filament power supply 102 applies a voltage to the cathode 101. The filament power supply 102 has a power supply path 103 through which a current from a heating power supply flows. The power supply path 103 extends from an insulator base 104. The cathode 101 emits an electron beam when a voltage is applied by the filament power supply 102. The electron beam emitted by the cathode 101 is a flow of thermoelectrons emitted from the cathode 101 by heating from the power supply path 103.

The extraction electrode 30 controls the amount of electron beam EB1 emitted from the cathode 101. The extraction electrode 30 controls the amount of thermoelectrons (the magnitude of the current of the electron beam EB1) by a control voltage applied by the high voltage control unit 200.

The focusing electrode 20 focuses the thermoelectrons extracted by the extraction electrode 30 so that they pass through the extraction electrode 30. The focusing electrode 20 is provided to surround an axis (i.e., the optical axis AX1) along the direction in which the electron beam EB1 is emitted from the cathode 101. Here, the focusing electrode 20 has a structure that includes and fixes the power supply path 103 while maintaining electrical insulation. In this embodiment, this structure is realized by storing a cathode protector 70 inside the focusing electrode 20. The configuration of the focusing electrode 20 will be described in detail later.

The anode 60 accelerates the electron beam EB1 emitted from the cathode 101. Here, the anode 60 accelerates the electron beam EB1 focused by the focusing electrode 20 to a desired speed.

The modification electrode 40 is provided between the extraction electrode 30 and the anode 60. The modification electrode 40 changes the opening angle of the electron beam EB1 passing through it. In other words, the modification electrode 40 focuses the electron beam EB1 passing through it.

The orifice 80 is provided on the emission side of the anode 60. The orifice 80 is provided so that the electron beam EB1 that has passed through an opening in the anode 60 passes through it. The orifice 80 creates a difference in the degree of vacuum between the electron gun 2 and the lens barrel section 3, which is the area below the electron gun 2. The length of the orifice 80 is longer than that of orifices provided in conventional electron barrels. The inner diameter and length of the orifice 80 are determined based on the conditions (passage conditions and differential pumping conditions) described below.

The shield electrode 50 shields the electric field inside and outside the shield electrode 50 so as to prevent discharge from each of the cathode 101, the focusing electrode 20, the extraction electrode 30, and the changing electrode 40. As described above, the shield electrode 50 constitutes a part of the housing of the electron gun 2, and the focusing electrode 20, the extraction electrode 30, and the changing electrode 40 are disposed inside the shield electrode 50. Note that it is sufficient that at least a part of the shield electrode 50 is provided between the changing electrode 40 and the anode 60.
The shield electrode 50 has an opening through which the electron beam EB1 passes and converges the electron beam EB1, thereby adjusting the output shape of the electron beam.

The controller 190 controls the high voltage control unit 200 .
The high voltage control unit 200 includes an extraction electrode control circuit 210 , a changing electrode control amplifier 220 , and a shield electrode control amplifier 230 .

The controller 190 transmits an electron beam command I to the extraction electrode control circuit 210. The electron beam command I indicates the magnitude of the beam current of the electron beam EB1. The extraction electrode control circuit 210 supplies a control voltage to the extraction electrode 30 based on the electron beam command I.

The extraction electrode control circuit 210 is a control circuit that changes the switching between the on and off states of the electron beam EB1 by controlling the voltage applied to the extraction electrode 30. The extraction electrode control circuit 210 has a MOSFET switch and a high-speed high-voltage amplifier. The MOSFET switch switches between a forward bias voltage and a reverse bias voltage to switch the electron beam EB1 between the on and off states. The high-speed high-voltage amplifier supplies a forward bias control voltage to the extraction electrode 30 so as to change the magnitude of the electron beam EB1. The configuration of the extraction electrode control circuit 210 will be described in detail later.
In the following description, switching between the on and off states of the electron beam EB1 may be referred to as on/off switching.

The controller 190 transmits a modified electrode voltage command G to the modified electrode control amplifier 220. The modified electrode voltage command G indicates a control voltage for controlling the modified electrode 40 at high speed and high voltage. The modified electrode control amplifier 220 supplies a control voltage to the modified electrode 40 based on the modified electrode voltage command G.

The controller 190 transmits a shield electrode voltage command S to the shield electrode control amplifier 230. The shield electrode voltage command S indicates a control voltage for controlling the shield electrode 50 at high speed and high voltage. The shield electrode control amplifier 230 supplies a control voltage to the shield electrode 50 based on the shield electrode voltage command S.

The beam deflector 90 is provided around the orifice 80. The beam deflector 90 generates a deflection field that changes the direction of the electron beam EB1 passing through the orifice 80. As a result, the beam deflector 90 changes the beam trajectory so that the electron beam EB1 does not hit the inside of the orifice 80. The beam deflector 90 may be an air-core coil to change the magnetic field under high frequency. In this embodiment, as an example, the beam deflector 90 includes a first air-core coil 91 and a second air-core coil 92.

The description of the configuration of the electron lens barrel 1 will continue with reference to FIG.
The lens barrel unit 3 includes a focusing lens unit 100, a first beam deflector 130, a first aperture 140, a second beam deflector 150, a second aperture 160, a deflector 170, a beam measurement sensor 180, a controller 190, a first deflector control amplifier 300, a second deflector control amplifier 310, a focusing lens unit control amplifier 320, and a deflector control amplifier 330. The controller 190 is shared by the electron gun 2 and the lens barrel unit 3. The lens barrel unit 3 is provided inside a housing, but the housing is not shown in FIG. 2.

The focusing lens unit 100 focuses the electron beam EB1 that has passed through the deflecting electrode 40. The focusing lens unit 100 includes a focusing lens 110 and an adjusting lens 120.
The focusing lens 110 converges the electron beam EB1 by a magnetic field. The focusing lens 110 is an objective lens for focusing the electron beam EB1 at the irradiation position on the target.
The adjusting lens 120 uses a magnetic field to change the degree of convergence of the electron beam EB1 by the condenser lens 110. The adjusting lens 120 is an electrostatic or magnetic dynamic lens for adjusting the beam diameter of the electron beam EB1 at the irradiation position on the target.

The first beam deflector 130 is provided between the extraction electrode 30 and the focusing lens 110. The first beam deflector 130 deflects the trajectory of the electron beam EB1. In other words, the first beam deflector 130 can change the deflection angle of the electron beam EB1. The second beam deflector 150 is provided between the first beam deflector 130 and the focusing lens 110. The second beam deflector 150 deflects the trajectory of the electron beam EB1 deflected by the first beam deflector 130. In other words, the second beam deflector 150 can change the deflection angle of the electron beam EB1.

The first beam deflector 130 and the second beam deflector 150 each generate a deflection field that corrects the beam axis deviation and tilt that change according to the beam current of the electron beam EB1. The first beam deflector 130 and the second beam deflector 150 are, for example, four-pole or eight-pole magnetic or electrostatic deflectors.

The first aperture 140 allows the electron beam EB1 deflected by the first beam deflector 130 to pass through. The first aperture 140 is equipped with a first current sensor 141. The first current sensor 141 measures the magnitude of the beam current of the electron beam EB1 that strikes the first aperture 140.

The second aperture 160 is through which the electron beam EB1 passes after passing through the first aperture 140 and being deflected by the second beam deflector 150. The second aperture 160 is equipped with a second current sensor 161. The second current sensor 161 measures the magnitude of the beam current of the electron beam EB1 that collides with the second aperture 160.

With this configuration, the first aperture 140 and the second aperture 160 each use a current sensor to measure the beam diameter, divergence angle, axis misalignment, and amount of tilt, which change according to the beam current of the electron beam EB1.

Deflector 170 is provided on the target side of focusing lens unit 100. Deflector 170 deflects electron beam EB1 converged by focusing lens unit 100. Deflector 170 is a 4-pole or 8-pole magnetic or electrostatic deflector that generates a deflection field that determines the beam position (left-right and depth positions) of electron beam EB1 at the irradiation position on the target.

Beam measurement sensor 180 measures the beam diameter (also called spot diameter) of electron beam EB1 at the irradiation position on the target. Beam measurement sensor 180 includes, for example, a Faraday cup and a measurement chart.

The controller 190 controls the first deflector control amplifier 300, the second deflector control amplifier 310, the focusing lens section control amplifier 320, and the deflector control amplifier 330.

The controller 190 transmits a first deflection field command DA1 to the first deflector control amplifier 300. The first deflection field command DA1 is a command for controlling the first beam deflector 130 at high speed. The first deflection field command DA1 indicates a control voltage for controlling the first beam deflector 130 at high speed and high voltage, or a control current for controlling the first beam deflector 130 at high speed and high current. The first deflector control amplifier 300 supplies a control current to the first beam deflector 130 based on the first deflection field command DA1. The deflection field of the first beam deflector 130 is controlled by the control current.

The controller 190 transmits a second deflection field command DA2 to the second deflector control amplifier 310. The second deflection field command DA2 is a command for controlling the second beam deflector 150 at high speed. The second deflection field command DA2 indicates a control voltage for controlling the second beam deflector 150 at high speed and high voltage, or a control current for controlling the second beam deflector 150 at high speed and high current. The second deflector control amplifier 310 supplies a control current to the second beam deflector 150 based on the second deflection field command DA2. The deflection field of the second beam deflector 150 is controlled by the control current.

Here, the controller 190 synchronizes the first deflection field command DA1 and the second deflection field command DA2 with the electron beam command I.

The controller 190 transmits an adjustment lens control command C to the focusing lens section control amplifier 320. The adjustment lens control command C indicates a control current for controlling the adjustment lens 120 at high speed and with a high current. The focusing lens section control amplifier 320 supplies a control current to the adjustment lens 120 based on the adjustment lens control command C. The electric field or magnetic field of the adjustment lens 120 is controlled by the control current.
Furthermore, the condenser lens section control amplifier 320 supplies a control current to the condenser lens 110. The electric field or magnetic field of the condenser lens 110 is controlled by the control current.

The controller 190 transmits a beam deflection command D to the deflector control amplifier 330. The beam deflection command D indicates a control current for controlling the deflector 170. The deflector control amplifier 330 supplies a control current to the deflector 170 based on the beam deflection command D. The deflection field of the deflector 170 is controlled by the control current.

Here, the controller 190 synchronizes the adjustment lens control command C with the electron beam command I and the beam deflection command D.

[Configuration of extraction electrode control circuit 210]
In controlling the electron microscope, in order to control the metal solidification phenomenon that occurs on a millisecond time scale, it is preferable to be able to control the beam current (heat input) at a sub-millisecond speed, which is at least 10 times faster. On the other hand, when the shape of the object is taken into consideration, it is necessary to quickly switch the electron beam on and off at the boundary of the object, for example.

In this case, particularly when the beam deflection speed is fast, not only is it necessary to set the voltage of the electron gun electrode (Mod Anode, extraction electrode 30 in this embodiment) that controls the beam current quickly, but it is also necessary to have even faster rise and fall times to the set voltage. For example, if a beam with a diameter of 100 μm is deflected at the melt surface at a speed of 10 m/s, the rise and fall times for switching the electron beam on and off in a section of less than 10% of the beam diameter will be 1 μs or less. A rapid charge and discharge circuit is required to drive the Mod Anode at this speed.

On the other hand, a high-voltage amplifier capable of directly controlling the electrode voltage at a speed of 1 μs in an environment floating at a high voltage of 60 kV or more not only becomes large, but also causes a rise in temperature of the floating section due to increased power consumption and an increase in the power transmission load to the floating section.
In view of the above, the challenge is to achieve sub-millisecond beam current modulation speeds and microsecond on/off switching of the electron beam while preventing the device from becoming too large and consuming too much power.

FIG. 3 is a diagram showing an example of the configuration of the extraction electrode control circuit 210 according to this embodiment. The extraction electrode control circuit 210 includes an extraction electrode control amplifier 211, a reverse bias voltage supply source 212, a switch circuit 213, a charging capacitor 214, a charging power supply 215, and an emitter follower 216. Note that in FIG. 3, the circuit configuration of the extraction electrode 30 shown in FIG. 1 is shown as an extraction electrode 217.

The extraction electrode control amplifier 211 supplies a forward bias voltage to the extraction electrode 217. The extraction electrode control amplifier 211 is a high-speed, high-voltage amplifier that applies a forward bias voltage of a predetermined voltage or higher at a predetermined speed or higher. The forward bias voltage applied by the extraction electrode control amplifier 211 is controlled based on the electron beam command I.

The reverse bias voltage supply source 212 supplies a reverse bias voltage to the extraction electrode 217. Here, the reverse bias voltage supply source 212 supplies a reverse bias voltage to the extraction electrode 217 when the electron beam EB1 is switched from the on state to the off state. Note that the reverse bias voltage supply source 212 may be a constant voltage power supply.

The switch circuit 213 connects the extraction electrode control amplifier 211 to the extraction electrode 217 when the electron beam EB1 is turned on, and switches to connect the reverse bias voltage supply source 212 to the extraction electrode 217 when the electron beam EB1 is turned off. The switch circuit 213 may be, for example, a MOSFET switch or a high-voltage, high-speed MOSFET.

The charging capacitor 214 charges the extraction electrode 217 when the electron beam EB1 is turned on. Here, the extraction electrode 217 is rapidly charged by the charging capacitor 214. One example of the charging capacitor 214 is a capacitor bank. A capacitor bank is a collection of multiple capacitors connected in parallel.

The charging power supply 215 charges the charging capacitor 214. The charging power supply 215 may be a constant voltage power supply.

The emitter follower 216 includes a transistor whose base is connected to the extraction electrode control amplifier 211, whose emitter is connected in parallel to the charging capacitor 214 and the charging power supply 215, and whose collector is connected to the switch circuit 213. The emitter follower 216 is configured by connecting multiple such transistors in parallel. The 1a transistor 2161a, the 2a transistor 2162a, the 3a transistor 2163a, and the 4a transistor 2164a are examples of the multiple transistors connected in parallel.

In this embodiment, the collector of the transistor is connected to the switch circuit 213 via another transistor. The collector of the transistor and the emitter of the other transistor are connected to each other. The first b transistor 2161b, the second b transistor 2162b, the third b transistor 2163b, and the fourth b transistor 2164b are each an example of the other transistor.

Therefore, the emitter follower 216 includes multiple transistors whose collectors and emitters are connected to each other. In other words, the emitter follower 216 uses a Darlington connection. With this configuration, the emitter follower 216 can control a large collector current with a small base current. Note that the emitter follower 216 does not necessarily have to use a Darlington connection.

The capacitance of the charging capacitor 214 is, for example, 2 nF or more. Note that the configuration of the charging capacitor 214 is not limited to a configuration in which multiple capacitors are connected in parallel, as long as it has a sufficient capacitance.

The electron beam EB1 is switched on and off by switching between the forward bias voltage of the extraction electrode control amplifier 211 and the reverse bias voltage of the reverse bias voltage supply source 212 at high speed by the switch circuit 213. At this time, when switched to the on state, the beam current of the electron beam EB1 is the beam current specified by the electron beam command I. Alternatively, the forward bias voltage is controlled by the extraction electrode control amplifier 211 so that the electron beam EB1 can be continuously modulated while maintaining the on state.

If the current capacity of the extraction electrode control amplifier 211 is small, or if the floating capacitance of the extraction electrode 217 including the wiring is large, the amount of current required for rapid charging of the extraction electrode 217 may exceed the current capacity. This causes a voltage drop in the extraction electrode control amplifier 211, resulting in a significant delay in the time until the beam current specified by the electron beam command I is established. This significant delay in the time until the specified beam current is established is particularly noticeable when there is a sudden change from the reverse bias voltage to the forward bias voltage when the electron beam EB1 is switched from the off state to the on state.

Then, the extraction electrode control circuit 210 employs an emitter follower 216 in which a charging capacitor 214, which is a capacitor bank with a large capacitance on the emitter side, a constant voltage power supply with a large current capacity, and a charging power supply 215 are connected in parallel, an extraction electrode control amplifier 211 is connected to the base, and the collector side is connected to a switch circuit 213. The configuration of the extraction electrode control circuit 210 makes it possible to realize the following regarding charging while maintaining the relationship in which the forward bias voltage is the output value of the extraction electrode control amplifier 211. In other words, while maintaining this relationship, when the electron beam EB1 is switched from the off state to the on state, or when the electron beam EB1 is continuously modulated at high speed while maintaining the on state, the charging capacitor 214 is responsible for rapid charging of the extraction electrode 217. On the other hand, while maintaining this relationship, the charging capacitor 214 can be charged by the charging power supply 215 when the voltage of the extraction electrode 217 is steady.

In addition, the charging capacitor 214, the charging power supply 215, and the emitter follower 216 may be omitted from the configuration of the extraction electrode control circuit 210.

As described above, the electron beam control circuit of this embodiment (in this embodiment, the extraction electrode control circuit 210) is a control circuit that changes the switching between the on state and the off state of the electron beam EB1 emitted from the cathode 101 of the electron gun 2 equipped with the extraction electrode 30 by controlling the voltage applied to the extraction electrode 30, and includes an amplifier (in this embodiment, the extraction electrode control amplifier 211), a power supply (in this embodiment, the reverse bias voltage supply source 212), and a switch circuit 213.
The amplifier (in this embodiment, the extraction electrode control amplifier 211 ) supplies a forward bias voltage to the extraction electrode 30 .
A power supply (in this embodiment, a reverse bias voltage supply 212 ) supplies a reverse bias voltage to the extraction electrode 30 .
The switch circuit 213 switches between connecting an amplifier (in this embodiment, the extraction electrode control amplifier 211) and the extraction electrode 30 when the electron beam EB1 is turned on, and between connecting a power source (in this embodiment, the reverse bias voltage supply source 212) and the extraction electrode 30 when the electron beam EB1 is turned off.

With this configuration, the electron beam control circuit according to this embodiment (in this embodiment, the extraction electrode control circuit 210) can switch the electron beam EB1 on and off, making it easy to control the electron beam EB1.

If the electron beam is left on without being switched on and off, temperature control will be required when the electron beam is moved away from the target, so electron beam control must be designed in advance.

In the extraction electrode control circuit 210, it is particularly preferable that the extraction electrode control amplifier 211 is a high-speed, high-voltage amplifier, the switch circuit 213 is a high-voltage, high-speed MOSFET, and the charging capacitor 214 is a large-capacity capacitor for rapid charging. This enables the extraction electrode control circuit 210 to stably switch the electron beam on and off at high speed to the voltage specified by the extraction electrode control amplifier 211, and to perform continuous, high-speed beam current modulation when the electron beam EB1 is in the on state.

[Configuration of focusing electrode 20]
In the electron microscope column 1 according to this embodiment, the thermionic electron source is driven in the space charge limited region to modulate the beam current and to switch it on and off. In order to drive the thermionic electron source in the space charge limited region, the thermionic electron source needs to be heated to a high temperature of about 1500° C. Therefore, in order to suppress the power consumption required to heat the thermionic electron source, the cathode 101 is configured to have a small heat capacity by sandwiching the material between carbon filaments.

Due to this configuration, the cathode 101 is exposed not only on the emission surface but also on the sides and bottom. This exposure causes the surrounding electric field to emit electrons from the sides and bottom. The emission of electrons from the sides and bottom can lead to charging up of the surrounding insulators, creepage and space discharge, instability of the electrode voltage due to absorption by the filament power supply 102, and a slowdown in the speed at which the electrodes are charged. In high-speed beam current modulation, preventing creepage and space discharge and stabilizing the electrode voltage are issues.

Now, with reference to Figures 4 to 6, the configuration of the focusing electrode 20 and the cathode protector 70 will be described. The focusing electrode 20 and the cathode protector 70 together are also referred to as a focusing electrode unit. Figures 4 and 5 are each an example of a cross-sectional view showing an enlarged view of the vicinity of the focusing electrode 20 of the electron gun 2 according to this embodiment. Figure 6 is an example of an exploded perspective view showing the configuration of the cathode unit 10, the cathode protector 70, and the focusing electrode 20 according to this embodiment.

Note that the up-down direction in Figures 5 and 6 is opposite to that in other figures such as Figure 4. Therefore, only when referring to Figures 5 and 6, the direction of the Z axis is also referred to as the upward direction. The direction opposite to the direction of the Z axis is also referred to as the downward direction. The positive side of the direction of the Z axis is also referred to as the upper side, and the negative side of the direction of the Z axis is also referred to as the lower side.

The focusing electrode 20 includes a fitting portion 21 , a converging portion 22 , and a housing portion 23 .
The insulator base 104 fits into the fitting portion 21 from above and below. In Fig. 6, the fitting portion 21 is provided below the focusing electrode 20. The fitting portion 21 has a shape that allows the cathode unit 10 to be inserted from below. As a result, the insulator base 104 fits into the fitting portion 21, and the cathode 101 and the filament power supply portion 102 are inserted inside the focusing electrode 20. Note that the insulator base 104 is covered by the fitting portion 21 when fitted into the fitting portion 21.

The converging portion 22 has a curved surface for converging the thermoelectrons emitted from the cathode 101. The curved surface is provided in a portion of the focusing electrode 20 that faces the fitting portion 21 in the up-down direction. In FIG. 6, the curved surface is provided on the upper side of the focusing electrode 20.

The storage section 23 is provided between the fitting section 21 and the converging section 22 in the vertical direction. The storage section 23 stores the cathode protector 70.

The cathode protector 70 consists of protector member 701-1 and protector member 701-2. Protector member 701-1 and protector member 701-2 face each other. Protector member 701-1 and protector member 701-2 are inserted into storage section 23 from the side (depth direction in FIG. 6) while facing each other. After being stored in storage section 23, protector member 701-1 and protector member 701-2 are fixed in contact with each other by inserting screws 703-1 and 703-2.

The cathode protector 70 has a groove 702 that surrounds the power supply path 103 of the filament power supply unit 102 without contact. Here, protector member 701-1 has groove 702-1 as the groove in question. Protector member 701-2 has groove 702-2 as the groove in question. The cathode protector 70 surrounds the power supply path 103 of the filament power supply unit 102 without contact by sandwiching the power supply path 103 of the filament power supply unit 102 between protector member 701-1 and protector member 701-2.

As a result, when the insulator base 104 is engaged with the engagement portion 21, the side and bottom surfaces of the cathode 101 are covered by the focusing electrode 20. As a result, the insulator base 104 and other electrodes cannot be seen from the side and bottom surfaces of the cathode 101.

Here, the cathode protector 70 blocks the path of electrons from the extraction electrode 30 to the power supply path 103 when the extraction electrode 30 is controlled to reduce the amount of the electron beam EB1. The cathode protector 70 also blocks the path of electrons from the extraction electrode 30 to the insulator base 104 when the extraction electrode 30 is controlled to reduce the amount of the electron beam EB1.

As described above, the electron light source device according to this embodiment (the electron gun 2 in this embodiment) includes the filament power supply unit 102, the extraction electrode 30, and the cathode protector 70.
The filament power supply unit 102 has a power supply path 103 extending from an insulator base 104, and is a member for applying a voltage to the cathode 101 that emits the electron beam EB1.
The extraction electrode 30 controls the amount of the electron beam EB 1 from the cathode 101 .
The cathode protector 70 blocks the path of electrons from the extraction electrode 30 to the power supply path 103 when the extraction electrode 30 is controlled to reduce the amount of the electron beam EB1.

With this configuration, the electron light source device according to this embodiment (electron gun 2 in this embodiment) can prevent electrons emitted from the side and bottom surfaces of the cathode 101 from colliding with insulators and other electrodes. It can also prevent creeping and spatial discharges and electrode response delays that occur when the electrons collide with insulators and other electrodes.

[Opening angle adjustment/differential exhaust mechanism 4]
When using a cathode made of lanthanum hexaboride (Lab6) or the like, a small-diameter orifice is used that establishes differential evacuation between the electron gun region and the lower part in order to keep the electron gun region at an ultra-high vacuum. However, when drawing out a high-current beam current for additive manufacturing, an electrostatic lens with sufficient focusing power is used in front of the output aperture (cathode side) because the drawn beam expands beyond the output aperture diameter.

On the other hand, when the beam current is rapidly modulated and switched on/off, the trajectory of the electron beam may become distorted during the rise process, causing it to collide with the output aperture. When this happens, the reflected electrons or secondary electrons generated by the electron beam colliding with the aperture are trapped in the magnetic field of the magnetic lens in the previous stage (cathode side) and form an electron cloud. When an electron cloud is formed, it has the effect of dispersing the subsequent electron beam and encouraging the beam to collide with the output aperture.

There is a risk that these effects will cause delays in beam settling time. The challenge is to avoid this risk while enabling differential pumping to ensure the cathode's lifespan.

Below, with reference to FIG. 7, the aperture angle adjustment/differential pumping mechanism 4, which is a mechanism provided in the electron lens barrel 1 for adjusting the aperture angle of the electron beam EB1 and performing differential pumping, will be described. FIG. 7 is a diagram showing an example of the configuration of the aperture angle adjustment/differential pumping mechanism 4 according to this embodiment. FIG. 7 shows the configuration of the electron lens barrel 1 shown in FIGS. 1 and 2 that is necessary for explaining the aperture angle adjustment/differential pumping mechanism 4.

The aperture angle adjustment/differential pumping mechanism 4 comprises an extraction electrode 30, a changing electrode 40, a shield electrode 50, an anode 60, an orifice 80, a beam deflector 90, a controller 190, and a high voltage control unit 200. The high voltage control unit 200 comprises an extraction electrode control circuit 210, a changing electrode control amplifier 220, and a shield electrode control amplifier 230. The beam deflector 90 comprises a first air core coil 91 and a second air core coil 92.

First, the opening angle adjustment will be described.
The aperture angle of the electron beam EB1 extracted by the voltage applied to the extraction electrode 30 varies depending on the beam current. Therefore, the aperture angle of the electron beam EB1 is adjusted so that the electron beam EB1 does not collide with the orifice 80 arranged on the target side of the electron gun output section (cathode unit 10, focusing electrode 20, extraction electrode 30, deflection electrode 40, and shield electrode 50) and on the cathode side of the focusing lens 110. In the electron lens barrel 1, the aperture angle is adjusted by the lens effect caused by applying voltages to the deflection electrode 40 and the shield electrode 50 arranged on the target side of the extraction electrode 30.

As described above, the extraction electrode control amplifier 211 provided in the extraction electrode control circuit 210 applies a voltage to the extraction electrode 30 based on the electron beam command I that specifies the amount of the electron beam EB1.
In order to adjust the aperture angle, the modifying electrode control amplifier 220 and the shield electrode control amplifier 230 each need to follow the modulation speed of the beam current of the electron beam EB1 by the extraction electrode control circuit 210. For this reason, the modifying electrode control amplifier 220 and the shield electrode control amplifier 230 each need to be a high-speed, high-voltage amplifier that follows the modulation speed of the beam current.

The modified electrode voltage command G transmitted from the modified electrode control amplifier 220 to the modified electrode 40 is determined depending on the electron beam command I transmitted from the controller 190 to the extraction electrode 30. Therefore, the modified electrode control amplifier 220 applies a voltage to the modified electrode 40 based on the electron beam command I. The timing of changing the voltage applied to the extraction electrode 30 by the extraction electrode control amplifier 211 is equal to the timing of changing the voltage applied to the modified electrode 40 by the modification electrode control amplifier 220. The speed of changing the voltage applied to the extraction electrode 30 by the extraction electrode control amplifier 211 is equal to the speed of changing the voltage applied to the modified electrode 40 by the modification electrode control amplifier 220.

Here, the modification electrode control amplifier 220 applies a voltage to the modification electrode 40 to adjust the divergence of the electron beam EB1 passing through the modification electrode 40 according to the magnitude of the beam current of the electron beam EB1.

In addition, the shield electrode voltage command S sent from the shield electrode control amplifier 230 to the shield electrode 50 is determined depending on the electron beam command I. Therefore, the shield electrode control amplifier 230 applies a voltage to the shield electrode 50 based on a voltage command based on the electron beam command I.

Next, the differential pumping mechanism will be described.
The inner diameter and length of the orifice 80 are determined based on the passage conditions and the differential pumping conditions.
The passing condition is a condition that the electron beam EB1 whose opening angle has been adjusted by the changing electrode 40 and the shield electrode 50 can completely pass through the inside of the orifice 80. The passing condition may also be a condition that the electron beam EB1 whose opening angle has been adjusted by the changing electrode 40 can pass through the inside of the orifice 80.

Differential pumping conditions are conditions that allow differential pumping so that the electron gun chamber reaches the required vacuum level. Therefore, the inner diameter and length of the orifice 80, along with the passage conditions, are determined based on the conductance that allows differential pumping so that the space in which the cathode 101 is located (the electron gun chamber) reaches a predetermined vacuum level.

The inner diameter of the orifice 80 determined based on the above passage conditions and differential pumping conditions is larger than that of the conventional orifice, and the length is longer than that of the conventional orifice. Therefore, in the electron lens barrel 1, the spread of the electron beam EB1 is controlled by the deflection electrode 40, which functions as an electrostatic lens having a sufficient focusing power.
The inner diameter and length of the orifice 80 may be determined based on at least the passage conditions.

The controller 190 also adjusts the deflection field of the beam deflector 90. Here, an inclination of the electron beam EB1 may occur due to an error in the installation position of the extraction electrode 30, etc. In such a case, the controller 190 adjusts the deflection field of the beam deflector 90 so that the electron beam EB1 does not collide with the inside of the orifice 80.

Here, with reference to Figs. 8 to 10, the control of the spread of the electron beam EB1 will be described in comparison with a conventional example. Figs. 8 and 9 are each a diagram showing an example of the spread of the electron beam in a conventional electron gun 2a. Fig. 8 shows an example when the beam current of the electron beam is large. Fig. 9 shows an example when the beam current of the electron beam is small. Fig. 10 is a diagram showing an example of the spread of the electron beam in the electron gun 2 according to this embodiment.

The electron gun 2a includes five electrodes: a cathode 101a, a focusing electrode 20a, an extraction electrode 30a, a shield electrode 50a, and an anode 60a.
The focusing lens L1a shows the lens effect produced by the focusing electrode 20a. The extraction electrode lens L2a shows the lens effect produced by the extraction electrode 30a. The extraction electrode/base lens L3a shows the lens effect produced by the extraction electrode 30a and the shield electrode 50a. The base/anode lens L4a shows the lens effect produced by the shield electrode 50a and the anode 60a.

When the beam current is large, electron gun 2a generates space charge divergence lens SL1a, space charge divergence lens SL2a, and space charge divergence lens SL3a. On the other hand, when the beam current is small, electron gun 2a generates space charge divergence lens SL1b, space charge divergence lens SL2b, and space charge divergence lens SL3b.

Here, the lens effect of the electrodes changes depending on the beam current. For example, the effect of the space charge divergence lens SL3b shown in FIG. 9 is smaller than the effect of the space charge divergence lens SL3a shown in FIG. 8 because the current density of electron beam EB1b is lower than that of electron beam EB1a. When the beam current is small, the lens effect of the electrodes exceeds the space charge effect. As a result, electron beam EB1b follows a diverging trajectory after forming a crossover.

On the other hand, as shown in FIG. 10, the electron gun 2 according to this embodiment includes six electrodes: a cathode 101 , a focusing electrode 20 , an extraction electrode 30 , a deflection electrode 40 , a shield electrode 50 , and an anode 60 .
The focusing lens L1 shows a lens effect produced by the focusing electrode 20. The extraction electrode lens L2 shows a lens effect produced by the extraction electrode 30. The deflection electrode lens L3 shows a lens effect produced by the extraction electrode 30, the deflection electrode 40, and the shield electrode 50. The base-anode lens L4 shows a lens effect produced by the shield electrode 50 and the anode 60.

In the electron gun 2, even if the beam current is small, the lens principal plane and focal length can be directly controlled by the deflection electrode 40. Therefore, in the electron gun 2, even if the beam current is small, the electron beam EB1 can be controlled to suppress its spread.

As described above, the electron gun according to this embodiment (in this embodiment, the aperture angle adjustment/differential pumping mechanism 4) includes the extraction electrode 30, the anode 60, the modifying electrode 40, an extraction electrode control amplifier (in this embodiment, the extraction electrode control amplifier 211 provided in the extraction electrode control circuit 210), and the modifying electrode control amplifier 220.
The extraction electrode 30 controls the amount of the electron beam EB 1 emitted from the cathode 101 .
The anode 60 accelerates the electron beam EB 1 emitted from the cathode 101 .
The changing electrode 40 is provided between the extraction electrode 30 and the anode 60, and changes the aperture angle of the electron beam EB1 passing therethrough.
An extraction electrode control amplifier (in this embodiment, an extraction electrode control amplifier 211 provided in the extraction electrode control circuit 210) applies a voltage to the extraction electrode 30 based on an electron beam command I that specifies the amount of the electron beam EB1.
The modifying electrode control amplifier 220 applies a voltage to the modifying electrode 40 based on the electron beam command I.

With this configuration, the electron gun according to this embodiment (in this embodiment, the opening angle adjustment/differential pumping mechanism 4) can change the opening angle of the electron beam EB1 by applying a voltage to the changing electrode 40 based on the amount of the electron beam EB1, thereby preventing delays in the beam settling time.

In addition, in the electron gun according to this embodiment (in this embodiment, the opening angle adjustment/differential pumping mechanism 4), the inner diameter and length of the orifice 80 are determined based on the passage conditions as well as the conductance that enables differential pumping so that the space in which the cathode 101 is located reaches a predetermined degree of vacuum.

With this configuration, the electron gun according to this embodiment (in this embodiment, the opening angle adjustment/differential pumping mechanism 4) can perform differential pumping while satisfying the passage condition that the electron beam EB1, whose opening angle has been adjusted by the changing electrode 40, can pass through the inside of the orifice 80, thereby extending the life of the electron gun.

[High-speed beam alignment system 5]
In order to set the beam current to a desired value, the voltage of the extraction electrode 30 is set to a voltage corresponding to the desired value. At this time, the emission direction of the electron beam EB1 changes due to an installation error between the cathode 101 and the extraction electrode 30. Due to this change, the electron beam EB1 is incident on the focusing lens 110 with a deviation in the emission angle and a deviation in the optical axis. As a result, off-axis aberration and a deviation in the beam irradiation position due to the change in beam current may occur on the melt surface.

Even if the beam current changes, it is necessary to suppress the shift in the beam irradiation position and the change in the beam shape due to off-axis aberration. Therefore, the challenge is to correct the shift in the emission angle of the electron beam EB1 and the optical axis shift in synchronization with the change in the beam current.

Below, with reference to FIG. 11, the high-speed beam alignment system 5 provided in the electron barrel 1 to correct the emission angle of the electron beam EB1 and its deviation from the optical axis AX1 will be described. FIG. 11 is a diagram showing an example of the configuration of the high-speed beam alignment system 5 according to this embodiment. FIG. 11 shows the configuration of the electron barrel 1 shown in FIGS. 1 and 2 that is necessary for explaining the high-speed beam alignment system 5.

The high-speed beam alignment system 5 includes an extraction electrode 30, a first beam deflector 130, a second beam deflector 150, a first aperture 140, a second aperture 160, a focusing lens unit 100, a beam measurement sensor 180, a controller 190, an extraction electrode control circuit 210, a first deflector control amplifier 300, and a second deflector control amplifier 310. The focusing lens unit 100 includes a focusing lens 110 and an adjustment lens 120.

The emission angle of electron beam EB1 and its position relative to optical axis AX1 change depending on the beam current of electron beam EB1 extracted by extraction electrode 30. Here, the position relative to optical axis AX1 refers to the position in the direction perpendicular to optical axis AX1 (depth direction and left-right direction). The deviation of the position of electron beam EB1 relative to optical axis AX1 is sometimes referred to as optical axis deviation.

In FIG. 11, beam trajectory T1 indicates the trajectory of electron beam EB1. The portion of beam trajectory T1 from the installation position of first beam deflector 130 to the installation position of second beam deflector 150 is called first trajectory T11. The portion of beam trajectory T1 from the installation position of second beam deflector 150 to the installation position of focusing lens unit 100 is called second trajectory T12.

The first beam deflector 130 is provided between the extraction electrode 30 and the focusing lens 110. The first beam deflector 130 deflects the beam trajectory T1. Here, the first beam deflector 130 generates a deflection field that directs the beam trajectory T1 (first trajectory T11) toward the center of the second beam deflector 150.

The second beam deflector 150 is provided between the first beam deflector 130 and the focusing lens 110. The second beam deflector 150 deflects the beam trajectory T1 deflected by the first beam deflector 130. Here, the second beam deflector 150 generates a deflection field that makes the beam trajectory T1 (second trajectory T12) parallel to the optical axis.

The extraction electrode control circuit 210 applies a voltage to the extraction electrode 30 based on an electron beam command I that specifies the amount of the electron beam EB1.
The first deflector control amplifier 300 outputs an excitation current to the first beam deflector 130 based on a voltage command or a current command based on the electron beam command I. The first deflector control amplifier 300 controls the first beam deflector 130 so that the beam trajectory T1 (first trajectory T11) from the first beam deflector 130 is directed toward the center of the second beam deflector 150.
The second deflector control amplifier 310 outputs an excitation current to the second beam deflector 150 based on a voltage command or a current command based on the electron beam command I. The second deflector control amplifier 310 controls the second beam deflector 150 so that the beam trajectory T1 (second trajectory T12) from the second beam deflector 150 is aligned along the optical axis AX1 or parallel to the optical axis AX1.

The first deflector control amplifier 300 and the second deflector control amplifier 310 respectively control the first beam deflector 130 and the second beam deflector 150 so as to maintain the beam trajectory T1 from the second beam deflector 150 constant when the amount of the electron beam EB1 specified by the electron beam command I changes.

When the amount of electron beam EB1 specified by electron beam command I changes, the first deflector control amplifier 300 changes the excitation current output to the first beam deflector 130 so that the trajectory (first trajectory T11) of the electron beam EB1 from the first beam deflector 130 heads toward the center of the second beam deflector 150.
When the amount of electron beam EB1 specified by electron beam command I changes, the second deflector control amplifier 310 changes the excitation current output to the second beam deflector 150 so that the trajectory (second trajectory T12) of the electron beam EB1 from the second beam deflector 150 is along the optical axis AX1 or parallel to the optical axis AX1.

As described above, the emission angle and optical axis deviation of the electron beam EB1 are corrected by the deflection field generated by the first beam deflector 130 and the deflection field generated by the second beam deflector 150. Therefore, the first deflector control amplifier 300 that drives the first beam deflector 130 and the second deflector control amplifier 310 that drives the second beam deflector 150 must each be a high-speed, high-voltage amplifier that tracks the modulation speed of the beam current, or a high-speed current amplifier.

The first deflection field command DA1 sent from the first deflector control amplifier 300 to the first beam deflector 130 is determined depending on the electron beam command I sent from the controller 190 to the extraction electrode 30. Note that the first deflection field command DA1 indicates a control voltage when the first deflector control amplifier 300 is a high-speed, high-voltage amplifier. The first deflection field command DA1 indicates a control current when the first deflector control amplifier 300 is a high-speed current amplifier. Therefore, the first deflector control amplifier 300 applies a current or voltage to the first beam deflector 130 based on the electron beam command I.

The second deflection field command DA2 sent from the second deflector control amplifier 310 to the second beam deflector 150 is determined depending on the electron beam command I. The second deflection field command DA2 indicates a control voltage when the second deflector control amplifier 310 is a high-speed, high-voltage amplifier. The second deflection field command DA2 indicates a control current when the second deflector control amplifier 310 is a high-speed current amplifier. Therefore, the second deflector control amplifier 310 applies a current or voltage to the second beam deflector 150 based on the electron beam command I.

Here, the adjustment of the first deflection field command DA1 and the second deflection field command DA2 is performed by a set of the extraction electrode 30, the first beam deflector 130 arranged on the target side of the extraction electrode 30, and the first aperture 140, and a set of the second beam deflector 150 arranged on the target side of the first aperture 140, and the second aperture 160, or a set of the second beam deflector 150, the focusing lens 110 or the adjustment lens 120, and the beam measurement sensor 180.
A method for adjusting the beam trajectory T1 (a beam trajectory control method) by the first beam deflector 130 and the second beam deflector 150 will be described later.

As described above, the electron gun according to this embodiment (in this embodiment, the high-speed beam alignment system 5) includes the extraction electrode 30, the focusing lens section 100, a first deflector (in this embodiment, the first beam deflector 130), a second deflector (in this embodiment, the second beam deflector 150), an extraction electrode control amplifier (in this embodiment, the extraction electrode control circuit 210), a first control section (in this embodiment, the first deflector control amplifier 300), and a second control section (in this embodiment, the second deflector control amplifier 310).
The extraction electrode 30 controls the amount of the electron beam EB 1 emitted from the cathode 101 .
The focusing lens unit 100 includes a focusing lens 110 that focuses the electron beam EB1 by a magnetic field.
The first deflector (in this embodiment, the first beam deflector 130) is provided between the extraction electrode 30 and the focusing lens 110, and deflects the trajectory of the electron beam EB1.
The second deflector (in this embodiment, the second beam deflector 150) is provided between the first deflector (in this embodiment, the first beam deflector 130) and the focusing lens 110, and deflects the trajectory of the electron beam EB1 deflected by the first deflector (in this embodiment, the first beam deflector 130).
An extraction electrode control amplifier (in this embodiment, the extraction electrode control circuit 210) applies a voltage to the extraction electrode 30 based on an electron beam command I that specifies the amount of the electron beam EB1.
The first control unit (in this embodiment, the first deflector control amplifier 300) outputs an excitation current to the first deflector (in this embodiment, the first beam deflector 130) based on a voltage command or a current command (in this embodiment, the first deflection field command DA1) based on the electron beam command I.
The second control unit (in this embodiment, the second deflector control amplifier 310) outputs an excitation current to the second deflector (in this embodiment, the second beam deflector 150) based on a voltage command or a current command (in this embodiment, the second deflection field command DA2) based on the electron beam command I.
The first control unit (in this embodiment, the first deflector control amplifier 300) controls the first deflector (in this embodiment, the first beam deflector 130) so that the trajectory of the electron beam EB1 from the first deflector (in this embodiment, the first beam deflector 130) heads toward the center of the second deflector (in this embodiment, the second beam deflector 150).
The second control unit (in this embodiment, the second deflector control amplifier 310) controls the second deflector (in this embodiment, the second beam deflector 150) so that the trajectory of the electron beam EB1 from the second deflector (in this embodiment, the second beam deflector 150) is along the optical axis or parallel to the optical axis.

This configuration allows the electron gun of this embodiment (in this embodiment, the high-speed beam alignment system 5) to correct deviations in the emission angle and optical axis of the electron beam EB1 in response to changes in the beam current, thereby suppressing changes in the beam shape.

[Method of controlling electron beam trajectory using a beam deflector]
An error in the shape or installation position of an electrode such as the extraction electrode 30 may cause the beam trajectory T1 to bend, which may prevent the electron beam EB1 from reaching the modeling surface. In addition, this error may cause the beam trajectory T1 to deviate significantly from the optical axis AX1, causing the electron beam EB1 to enter the focusing lens 110 and resulting in large aberration. Meanwhile, in the electron lens barrel 1, the voltage of the electrodes such as the extraction electrode 30 is modulated at high speed, so that the deviation of the beam trajectory T1 (emission angle and optical axis deviation) also changes at high speed.

In the electron beam trajectory control method, the electron beam EB1 from the electron gun 2 is deflected by the first beam deflector 130. The electron beam EB1 from the first beam deflector 130 is deflected by the second beam deflector 150. The beam current of the electron beam EB1 from the electron gun 2 is changed. Here, deflecting by the first beam deflector 130 includes deflecting the electron beam EB1 such that the first trajectory T11 of the electron beam EB1 from the first beam deflector 130 does not change when the beam current changes. Deflecting by the second beam deflector 150 includes deflecting the electron beam EB1 such that the second trajectory T12 of the electron beam EB1 from the second beam deflector 150 does not change when the beam current changes. Below, methods for achieving these controls will be described.

In the electron beam trajectory control method, the beam trajectory is corrected at high speed using the first beam deflector 130 and the first aperture 140, and the second beam deflector 150 and the second aperture 160. The first beam deflector 130 and the second beam deflector 150 can each change the deflection field (magnetic field) at a frequency equivalent to that of the extraction electrode 30, etc. For this reason, it is preferable that the first beam deflector 130 and the second beam deflector 150 are each, for example, an air-core coil.

The first beam deflector 130 is used to change the beam trajectory T1 to scan the first aperture 140. In this scan, the position where the electron beam EB1 passes through the first aperture 140 in a direction perpendicular to the optical axis AX1 is measured based on the measurement result of the first current sensor 141. Based on the scan result, the center of the first aperture 140 is determined to be the center of the second beam deflector 150. The first beam deflector 130 is adjusted so that the first trajectory T11 passes through the center of the second beam deflector 150.

Thus, deflecting by the first beam deflector 130 includes deflecting the electron beam EB1 so that the first trajectory T11 passes through the center of the second beam deflector 150.

Next, the second beam deflector 150 is used to change the beam trajectory T1 to scan the second aperture 160. In this scan, the position where the electron beam EB1 passes through the second aperture 160 in a direction perpendicular to the optical axis AX1 is measured based on the measurement result of the second current sensor 161. Based on the scan result, the center of the second aperture 160 is determined to be the center of the focusing lens 110. The second beam deflector 150 is adjusted so that the second trajectory T12 passes through the center of the focusing lens 110.

Therefore, deflection by the second beam deflector 150 includes deflecting the electron beam EB1 so that the second trajectory T12 is along the optical axis of the focusing lens unit 100 or along an axis parallel to the optical axis AX1. This causes the electron beam EB1 from the second beam deflector 150 to be incident on the focusing lens unit 100.

Then, the focal center is determined. The focal center is determined by changing the excitation of the focusing lens 110 or the adjustment lens 120 (wobbling) and determining the excitation current of the second beam deflector 150 at which the irradiation position of the electron beam EB1 on the modeling surface does not change. In other words, while changing the excitation of the focusing lens unit 100, the position of the electron beam via the focusing lens unit 100 on the plane intersecting with the optical axis AX1 is measured as the focal center. The irradiation position of the electron beam EB1 on the modeling surface is measured by the beam measurement sensor 180.

As described above, the electron beam trajectory control method according to this embodiment includes deflecting the electron beam EB1 from the electron light source unit (in this embodiment, the electron gun 2) by the first beam deflector 130, deflecting the electron beam EB1 from the first beam deflector 130 by the second beam deflector 150, and changing the beam current of the electron beam EB1 from the electron light source unit.
Deflecting by the first beam deflector 130 includes deflecting the electron beam EB1 such that the position of the first trajectory of the electron beam EB1 from the first beam deflector 130 at the center of the second beam deflector 150 does not change when the beam current of the electron beam EB1 changes.
Deflecting by the second beam deflector 150 includes deflecting the electron beam EB1 such that the second trajectory of the electron beam EB1 from the second beam deflector 150 does not change when the beam current of the electron beam EB1 changes.

With this configuration, the electron beam trajectory control method according to this embodiment can correct deviations in the emission angle and optical axis of the electron beam EB1 in response to changes in the beam current, thereby suppressing changes in the beam shape.

[High-speed beam modulation mechanism 6]
When the beam current is changed, the divergence effect due to the space charge effect also changes, and the characteristics of the electronic light source, such as the light source size, divergence angle, and light source position, also change. Therefore, there is a problem that the aberration and magnification of the focusing lens located on the target side of the light source change in conjunction with the change in beam current. In order to obtain a desired beam diameter at any beam deflection position on the melt surface without being affected by the change in beam current, the challenge is to control the beam diameter in synchronization with the beam current and beam deflection.

Below, with reference to FIG. 12, we will explain the high-speed beam modulation mechanism 6 provided in the electron tube 1 to adjust for changes in the light source characteristics (also called electron gun performance) of the electron gun 2, which change depending on the beam current. FIG. 12 is a diagram showing an example of the configuration of the high-speed beam modulation mechanism 6 according to this embodiment. FIG. 12 shows the configuration of the electron tube 1 shown in FIGS. 1 and 2 that is necessary for explaining the high-speed beam modulation mechanism 6.

The high-speed beam modulation mechanism 6 includes an extraction electrode 30, a changing electrode 40, a shield electrode 50, an adjustment lens 120, a deflector 170, a first beam deflector 130, a first aperture 140, a second beam deflector 150, a second aperture 160, a focusing lens 110, a beam measurement sensor 180, a controller 190, a high-voltage control unit 200, a focusing lens section control amplifier 320, and a deflector control amplifier 330. The high-voltage control unit 200 includes an extraction electrode control circuit 210, a changing electrode control amplifier 220, and a shield electrode control amplifier 230.

When modulating the beam diameter, the light source characteristics of the electron gun 2, which change depending on the beam current extracted by the extraction electrode 30, are adjusted to appropriate values. To adjust the light source characteristics of the electron gun 2, a conversion electrode 40 and a shield electrode 50 are placed on the target side of the extraction electrode 30 and on the cathode side of the focusing lens 110.

The main lens power as a focusing lens is provided by the focusing lens 110. Meanwhile, the final focusing of the electron beam EB1 is determined by correction by the adjustment lens 120 arranged inside the focusing lens 110. The adjustment lens 120 performs correction to focus the electron beam EB1, as well as correction of defocus that depends on the amount of deflection by the deflector 170. The deflector 170 is arranged on the target side of the adjustment lens 120.

In order to adjust the light source characteristics of the electron gun 2, the extraction electrode control circuit 210 that drives the extraction electrode 30, the change electrode control amplifier 220 that drives the change electrode 40, the shield electrode control amplifier 230 that drives the shield electrode 50, and the focusing lens section control amplifier 320 that drives the adjustment lens 120 must each be a high-speed, high-voltage amplifier or a high-speed current amplifier that tracks the modulation speed and deflection speed of the beam current.

The modified electrode voltage command G sent from the modified electrode control amplifier 220 to the modified electrode 40 is determined depending on the electron beam command I sent from the controller 190 to the extraction electrode 30. Therefore, the modified electrode control amplifier 220 applies a voltage to the modified electrode 40 based on the electron beam command I.

The shield electrode voltage command S sent from the shield electrode control amplifier 230 to the shield electrode 50 is determined depending on the electron beam command I. Therefore, the shield electrode control amplifier 230 applies a voltage to the shield electrode 50 based on a voltage command based on the electron beam command I.

The adjustment lens control command C sent from the focusing lens unit control amplifier 320 to the adjustment lens 120 is determined depending on the electron beam command I, the beam deflection command D, and the beam diameter command F. Therefore, the focusing lens unit control amplifier 320 controls the focusing lens unit 100 based on a voltage command or a current command based on the electron beam command I, the beam deflection command D, and the beam diameter command F. The focusing lens unit control amplifier 320 only needs to apply a current or a voltage to the focusing lens unit 100 based on at least the electron beam command I, or the electron beam command I and the beam deflection command D. Here, the focusing lens unit control amplifier 320 applies a current or a voltage to the adjustment lens 120.

The deflector control amplifier 330 outputs a current to the deflector 170 based on the beam deflection command D.

The first beam deflector 130 or the second beam deflector 150 may be used as an astigmatism corrector. In that case, the first deflection field command DA1 sent from the first deflector control amplifier 300 (not shown in FIG. 12) to the first beam deflector 130, or the second deflection field command DA2 sent from the second deflector control amplifier 310 (not shown in FIG. 12) to the second beam deflector 150, is determined depending on the electron beam command I, the beam deflection command D, and the beam diameter command F, similar to the adjustment lens control command C.

As described below, the adjustment of the modified electrode voltage command G and the shield electrode voltage command S is performed by the extraction electrode 30, modified electrode 40, shield electrode 50, and a set of a first beam deflector 130 and a first aperture 140 arranged on the target side of the shield electrode 50, and a set of a second beam deflector 150 and a second aperture 160 arranged on the target side of the first aperture 140.

The adjustment lens control command C is adjusted by the extraction electrode 30, the change electrode 40, the shield electrode 50, the deflector 170, and the beam measurement sensor 180. The beam measurement sensor 180 is disposed on the target side of the deflector 170 and has an opening on the melt surface.

These modified electrode voltage command G, shield electrode voltage command S, and adjustment lens control command C are adjusted by measuring the light source characteristics of the electron gun 2, which change depending on the beam current, inside the lens barrel 3.

As described above, the electron gun according to this embodiment (in this embodiment, the beam high-speed modulation mechanism 6) comprises the extraction electrode 30, the anode 60, the modifying electrode 40, an extraction electrode control amplifier (in this embodiment, the extraction electrode control amplifier 211 provided in the extraction electrode control circuit 210), and the modifying electrode control amplifier 220.
The extraction electrode 30 controls the amount of the electron beam EB 1 emitted from the cathode 101 .
The anode 60 accelerates the electron beam EB 1 emitted from the cathode 101 .
The changing electrode 40 is provided between the extraction electrode 30 and the anode 60, and changes the aperture angle of the electron beam EB1 passing therethrough.
An extraction electrode control amplifier (in this embodiment, an extraction electrode control amplifier 211 provided in the extraction electrode control circuit 210) applies a voltage to the extraction electrode 30 based on an electron beam command that specifies the amount of the electron beam EB1.
The modifying electrode control amplifier 220 applies a voltage to the modifying electrode 40 based on the electron beam command I.

With this configuration, the electron gun according to this embodiment (in this embodiment, the high-speed beam modulation mechanism 6) can change the opening angle of the electron beam EB1 by applying a voltage to the changing electrode 40 based on the amount of the electron beam EB1, so that adjustments can be made to obtain the desired beam diameter on the modeling surface even if the beam current is changed.

[Electron beam measurement method]
The beam diameter (spot diameter) of the electron beam EB1 on the modeling surface needs to be modulated at high speed during modeling. At that time, the beam diameter is adjusted to a desired value using the adjustment lens 120 while the voltages of the extraction electrode 30, the deflection electrode 40, and the shield electrode 50 are fixed at arbitrary values. To ensure accuracy, it is necessary to create a correction function for correcting the excitation by the adjustment lens 120 by measuring the spot diameter on the modeling surface.

In addition, the light source characteristics of the electron gun 2 gradually change during operation, making it necessary to modify the above correction function. However, in the past, it was difficult to measure the light source characteristics of the electron gun 2 on the printing surface in real time during printing.

In this embodiment, the voltages of the extraction electrode 30, the change electrode 40, and the shield electrode 50 are changed in order to measure the light source characteristics of the electron gun 2 in real time and obtain the desired performance. Therefore, there is no need to change the excitation by the adjustment lens 120 or the correction function.

FIG. 13 is a diagram showing an example of an electron beam measurement method according to this embodiment.
In order to measure the light source characteristics of the electron gun 2, an edge profile is acquired by scanning the first aperture 140 and the second aperture 160. The first aperture 140 has a first current sensor 141, and is placed on a first placement plane PZ1 on the target side of the first beam deflector 130.
The second beam deflector 150 is disposed on the emission side of the first aperture 140. The second aperture 160 has a second current sensor 161, and is disposed on a second arrangement plane PZ2 on the target side of the second beam deflector 150. The first arrangement plane PZ1 and the second arrangement plane PZ2 are each a plane perpendicular to the optical axis direction.

The electron beam EB1 from the electron gun 2 is scanned on a first aperture 140 having a first current sensor 141 by changing the deflection angle of the electron beam EB1 using a first beam deflector 130. Here, in scanning on the first aperture 140, the electron beam EB1 scans the edge of an opening 142 of the first aperture 140.
The electron beam EB1 from the electron gun 2 is scanned over a second aperture that is disposed on the exit side of the first aperture 140 and has a second current sensor, using the second beam deflector 150. In scanning over the second aperture 160, the electron beam EB1 scans the edge of an opening 162 of the second aperture 160.

FIG. 14 shows an example of the output from the current sensor (the first output from the first current sensor 141, or the second output from the second current sensor 161) when the electron beam EB1 is scanned over the aperture. As an example, FIG. 14 shows the output when the electron beam EB1 is scanned in the X-axis direction (left-right direction). In FIG. 14, the horizontal axis indicates the position of the electron beam EB1 in the X-axis direction. The vertical axis indicates the signal strength output from the current sensor. The signal strength indicates the magnitude of the beam current of the electron beam EB1 blocked by the aperture.

The edge profile EP1 indicates the signal intensity when the electron beam EB1 is scanned in the X-axis direction. The line spread function LSF1 is obtained by differentiating the edge profile EP1 with respect to the position in the X-axis direction. Region R1 indicates the region in the line spread function LSF1 where the electron content of the electron beam EB1 at a predetermined position in the optical axis direction (the position of the first placement surface PZ1 or the second placement surface PZ2) is a predetermined percentage (50 percent).

Based on the first output from the first current sensor 141, an edge profile is obtained at the position of the first placement surface PZ1. Based on the second output from the second current sensor 161, an edge profile is obtained at the position of the second placement surface PZ2. In other words, an edge profile is obtained for each of the two positions in the optical axis direction (positions in the Z direction).

Beam current distribution with an arbitrary electron content ratio is measured for each of the two positions in the optical axis direction using the edge profile. In other words, the beam current distribution on the first placement plane PZ1 is calculated from a profile signal indicating the magnitude of the first output of the first current sensor 141 for the position on the first placement plane PZ1. The beam current distribution on the second placement plane PZ2 is calculated from a profile signal indicating the magnitude of the second output of the second current sensor 161 for the position on the second placement plane PZ2.

Therefore, the first output from the first current sensor 141 is used to measure the beam current distribution of the electron beam EB1 on the first placement surface PZ1. The second output from the second current sensor 161 is used to measure the beam current distribution of the electron beam EB1 on the second placement surface PZ2 of the second aperture 160.

Next, the source size and aperture angle of the electron beam EB1 from the electron gun 2 are determined based on the beam current distribution measured using the first output of the first current sensor 141 and the beam current distribution measured using the second output of the second current sensor 161.

Here, from the beam current distribution on the first placement surface PZ1, it is possible to determine the beam diameter at which the ratio of the total electrons contained in the electron beam EB1 on the first placement surface PZ1 is a predetermined ratio. From the beam current distribution on the second placement surface PZ2, it is possible to determine the beam diameter at which the ratio of the total electrons contained in the electron beam EB1 on the second placement surface PZ2 is a predetermined ratio.

FIG. 15 is a diagram showing an example of the measurement of the source size of the electron beam EB1 according to this embodiment. FIG. 15 shows the change in beam current distribution with respect to the position in the Z-axis direction. In FIG. 15, the opening angle for the region with an electron content of 30 percent is shown as opening angle W30, the opening angle for the region with an electron content of 50 percent is shown as opening angle W50, and the opening angle for the region with an electron content of 90 percent is shown as opening angle W90. Also, in FIG. 15, the opening angle for the region with an electron content of 90 percent is shown as the total electron content opening angle DT1.

As described above, the beam current distribution is measured for each of the two optical axis positions on the first placement surface PZ1 and the second placement surface PZ2. Therefore, the source size SP1 can be obtained by drawing a straight line to connect the beam diameters that have the same electron content at two points. In other words, the source size of the electron beam EB1 can be measured by projecting the measured beam diameter back onto the electron gun 2.

Therefore, the light source size SP1 and the opening angles W30, W50, W90, and DT1 having the desired electron content are calculated using the first profile signal obtained from the first output of the first current sensor 141, the second profile signal obtained from the second output of the second current sensor 161, and information regarding the distance between the first placement surface PZ1 and the second placement surface PZ2.

In the electron beam measurement method according to this embodiment, the first beam deflector 130 and the second beam deflector 150 can be modulated at high speed, so that the light source characteristics of the electron gun 2 can be measured in real time during modeling.

Next, we will explain how to measure the spot diameter on the modeling surface and how to create a correction function to correct the excitation by the adjustment lens 120. Note that the correction function can be created using the method described in Patent Document 2, for example.

FIG. 16 is a diagram showing an example of a method for measuring the spot diameter on the printing surface according to this embodiment. FIG. 17 is a diagram showing an example of the configuration of a beam measurement sensor 180 according to this embodiment. To measure the spot diameter on the printing surface, the beam measurement sensor 180 is installed on the printing surface. The beam measurement sensor 180 includes a Faraday cup 181 and a measurement chart 182. The diameter of the Faraday cup 181 is equal to the size of the printing range. When installed on the printing surface, the measurement chart 182 has multiple openings 183 provided in a plane approximately perpendicular to the optical axis AX1.

The measurement chart 182 is scanned by the deflector 170, and the electron beam EB1 that passes through the opening 183 provided in the measurement chart 182 is detected by the Faraday cup 181. Based on the detection results by the Faraday cup 181, the edge profile is measured and the spot diameter on the modeling surface is calculated.

The measurement chart 182 is made of a metal (e.g., tungsten) that can withstand the heat of the incident electron beam EB1, and another type of metal (e.g., copper) is attached to the back side. The shape of the apertures 183 is octagonal. This is so that the shape of the spot can be measured in each of the X-axis direction, Y-axis direction, and 45-degree rotation direction. The width of one aperture 183 and the spacing between adjacent apertures 183 are determined based on the condition that a spot shape of up to 1.5 mm can be correctly estimated. For example, the width of the apertures 183 is 3 mm or more, and the spacing between adjacent apertures 183 is 2.5 mm or more.

The correction function is calculated based on the relationship between the spot diameter and deflection amount measured by the beam measurement sensor 180 and the excitation by the adjustment lens 120.

As described above, the electron beam measurement method according to this embodiment includes scanning the electron beam EB1 from the electron light source unit (electron gun 2 in this embodiment) over the first aperture 140 having a first current sensor 141 using a first beam deflector 130 that can change the deflection angle of the electron beam EB1, measuring a first beam current distribution of the electron beam EB1 on the first placement plane PZ1 of the first aperture 140 using a first output from the first current sensor 141 of the first aperture 140, and scanning the electron beam EB1 from the electron light source unit (electron gun 2 in this embodiment) over the first aperture 140 having a first current sensor 141 using a first output from the first current sensor 141 of the first aperture 140. The method includes scanning a second aperture 160, which is disposed on the exit side of the first aperture 140 and has a second current sensor 161, using a changeable second beam deflector 150, measuring a second beam current distribution of the electron beam EB1 on a second placement surface PZ2 of the second aperture 160 using a second output from the second current sensor 161 of the second aperture 160, and determining the light source size and opening angle of the electron beam EB1 from the electron light source unit (electron gun 2 in this embodiment) based on the beam current distribution measured using the first output of the first current sensor 141 and the beam current distribution measured using the second output of the second current sensor 161.

With this configuration, the electron beam measurement method according to this embodiment can control the beam diameter based on the determined light source size and opening angle even when the beam current changes, making it possible to obtain the desired beam diameter on the printing surface.

The electron lens barrel 1 may include at least one of the configurations of the extraction electrode control circuit 210, the configuration of the focusing electrode 20, the configuration of the aperture angle adjustment/differential exhaust mechanism 4, the high-speed beam alignment system 5, and the configuration of the high-speed beam modulation mechanism 6 described in this embodiment. Therefore, in the configuration of the electron lens barrel 1, the configuration of the extraction electrode control circuit 210, the configuration of the focusing electrode 20, the configuration of the aperture angle adjustment/differential exhaust mechanism 4, the high-speed beam alignment system 5, and the high-speed beam modulation mechanism 6 may each be configured in a manner other than that described in this embodiment.
Furthermore, in the electron lens column 1, the electron beam trajectory control method and the electron beam measurement method described in this embodiment do not necessarily have to be used.

Although one embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to that described above, and various design changes can be made without departing from the spirit of the present invention.

1 Electron barrel 2 Electron gun 3 Lens barrel section 4 Angle adjustment/differential pumping mechanism 5 High-speed beam alignment system 6 High-speed beam modulation mechanism 10 Cathode unit 20 Focusing electrode 21 Fitting section 22 Converging section 23 Storage section 30 Extraction electrode 40 Changing electrode 50 Shield electrode 60 Anode 70 Cathode protector 80 Orifice 90 Beam deflector 91 First air-core coil 92 Second air-core coil 100 Focusing lens section 101 Cathode 102 Filament power supply section 103 Power supply path 104 Insulator base 110 Focusing lens 120 Adjustment lens 130 First beam deflector 140 First aperture 141 First current sensor 142 Opening 150 Second beam deflector 160 Second aperture 161 Second current sensor 162 Opening 170 Deflector 180 Beam measurement sensor 181 Faraday cup 182, measurement chart 183, opening 190, controller 200, high voltage control unit 210, extraction electrode control circuit 211, extraction electrode control amplifier 212, reverse bias voltage supply source 213, switch circuit 214, charging capacitor 215, charging power supply 216, emitter follower 217, extraction electrode 220, modification electrode control amplifier 230, shield electrode control amplifier 300, first deflector control amplifier 310, second deflector control amplifier 320, focusing lens unit control amplifier 330, deflector control amplifier 701-1, protector member 701-2, protector member 702, groove I, electron beam command C, adjustment lens control command S, shield electrode voltage command D, beam deflection command DA1, first deflection field command DA2, second deflection field command G, modification electrode voltage command EB1, electron beam PZ1, first arrangement surface PZ2, second arrangement surface SP1, light source size T1 Beam orbit T11 First orbit T12 Second orbit

Claims (30)

A control circuit for changing the switching between an on state and an off state of an electron beam emitted from a cathode of an electron gun having an extraction electrode by controlling a voltage applied to the extraction electrode,
an amplifier for supplying a forward bias voltage to the extraction electrode;
a power source for supplying a reverse bias voltage to the extraction electrode;
a switch circuit that switches between connecting the amplifier and the extraction electrode when the electron beam is in the on state and connecting the power supply and the extraction electrode when the electron beam is in the off state;
An electron beam control circuit comprising: a charging capacitor for charging the extraction electrode when the electron beam is turned on;
a charging power source for charging the charging capacitor;
an emitter follower including a transistor having a base connected to the amplifier, an emitter connected in parallel to the charging capacitor and the charging power supply, and a collector connected to the switch circuit;
The electron beam control circuit of claim 1 further comprising: The electron beam control circuit according to claim 2 , wherein the emitter follower includes a plurality of transistors whose collectors and emitters are connected to each other. an extraction electrode for controlling the amount of the electron beam emitted from the cathode;
an anode for accelerating the electron beam emitted from the cathode;
a deflection electrode provided between the extraction electrode and the anode for deflecting an aperture angle of the electron beam passing therethrough;
an extraction electrode control amplifier that applies a voltage to the extraction electrode based on an electron beam command that specifies the amount of the electron beam;
a modifying electrode control amplifier that applies a voltage to the modifying electrode based on the electron beam command;
An electron gun comprising: 5. The electron gun according to claim 4, wherein said modifying electrode control amplifier applies a voltage to said modifying electrode so as to adjust the divergence of said electron beam passing through said modifying electrode in accordance with the magnitude of the beam current of said electron beam. a shield electrode that is provided at least partially between the deflection electrode and the anode, has an opening through which the electron beam passes, and focuses the electron beam;
The electron gun according to claim 4 or 5, further comprising: a shield electrode control amplifier that applies a voltage to the shield electrode based on a voltage command based on the electron beam command. a focusing lens portion for focusing the electron beam having passed through the deflecting electrode;
7. The electron gun according to claim 4, further comprising: a condenser lens section control amplifier that applies a current or a voltage to the condenser lens section based on at least the electron beam command. a deflector provided closer to a target than the focusing lens unit and configured to deflect the electron beam converged by the focusing lens unit;
a deflector control unit that outputs a current to the deflector based on a beam deflection command,
8. The electron gun according to claim 7, wherein the condenser lens section control amplifier controls the condenser lens section based on a voltage command or a current command based on the electron beam command and the beam deflection command. the focusing lens unit includes a focusing lens that focuses the electron beam by a magnetic field, and an adjusting lens that changes the degree of convergence of the electron beam by the focusing lens by a magnetic field or an electric field,
9. The electron gun according to claim 7, wherein the focusing lens section control amplifier applies the current or the voltage to the adjustment lens. 10. The electron gun according to claim 4, wherein a timing for changing the voltage applied to the extraction electrode by the extraction electrode control amplifier is equal to a timing for changing the voltage applied to the modification electrode by the modification electrode control amplifier. 11. The electron gun according to claim 4, wherein a rate at which the voltage applied to the extraction electrode by the extraction electrode control amplifier is changed is equal to a rate at which the voltage applied to the modification electrode by the modification electrode control amplifier is changed. an orifice provided on the emission side of the anode so that the electron beam passing through the opening of the anode passes through;
12. The electron gun according to claim 4, wherein an inner diameter and a length of the orifice are determined based on a passing condition under which the electron beam, the opening angle of which has been adjusted by the deflecting electrode, can pass through the inside of the orifice. 13. The electron gun according to claim 12, wherein an inner diameter and a length of the orifice are determined based on the passage condition and a conductance that enables differential evacuation so that a space in which the cathode is located reaches a predetermined vacuum level. 14. The electron gun according to claim 12 or 13, further comprising a beam deflector disposed around the orifice and configured to generate a deflection field for changing the direction of the electron beam passing through the orifice. a filament power supply having a power supply path extending from an insulator base for applying a voltage to a cathode that emits an electron beam;
an extraction electrode for controlling the amount of the electron beam from the cathode;
a cathode protector that blocks a path of electrons from the extraction electrode to the power supply path when the extraction electrode is controlled to reduce the amount of the electron beam. 16. The electron light source device according to claim 15, wherein the cathode protector blocks a path of electrons from the extraction electrode toward the insulator base when the extraction electrode is controlled to reduce an amount of the electron beam. a focusing electrode provided to surround an axis along a direction in which the electron beam is emitted from the cathode;
The focusing electrode is
a fitting portion into which the insulator base is fitted from a first direction;
a converging portion having a curved surface for converging thermoelectrons emitted from the cathode, the curved surface being provided in a portion facing the fitting portion in the first direction;
a housing portion for housing the cathode protector, the housing portion being provided between the fitting portion and the converging portion in the first direction;
The electronic light source device according to claim 15 or 16, comprising: The electron light source device according to claim 15 , wherein the cathode protector has a groove surrounding the power supply path of the filament power supply part in a non-contact manner. the cathode protector is made up of two opposing portions, each having the groove;
The electronic light source device according to claim 18 , wherein the cathode protector surrounds the power supply path of the filament power supply part without contacting the power supply path of the filament power supply part by sandwiching the power supply path of the filament power supply part with the cathode protector. scanning an electron beam from an electron light source unit over a first aperture having a first current sensor by using a first beam deflector capable of changing a deflection angle of the electron beam;
measuring a first beam current distribution of the electron beam at a first placement plane of the first aperture using a first output from the first current sensor of the first aperture;
scanning the electron beam from the electron light source unit over a second aperture disposed on an exit side of the first aperture and having a second current sensor, by using a second beam deflector disposed on an exit side of the first aperture and capable of changing a deflection angle of the electron beam;
measuring a second beam current distribution of the electron beam at a second placement plane of the second aperture using a second output from the second current sensor of the second aperture;
determining a light source size and an opening angle of the electron beam from the electron light source unit based on a beam current distribution measured using a first output of the first current sensor and a beam current distribution measured using a second output of the second current sensor. scanning the first aperture includes scanning an edge of an opening of the first aperture with the electron beam;
The electron beam metrology method of claim 20 , wherein scanning over the second aperture includes causing the electron beam to scan an edge of an opening of the second aperture. the first beam current distribution is calculated from a profile signal indicating a magnitude of the first output with respect to a position on the first arrangement surface;
The beam measurement method according to claim 20 or 21, wherein the second beam current distribution is calculated from a profile signal indicating a magnitude of the second output with respect to a position on the second placement surface. a beam diameter, the ratio of which to all electrons contained in the electron beam on the first arrangement plane is a predetermined ratio, is calculated from the first beam current distribution;
The beam measurement method according to claim 22 , further comprising: calculating a beam diameter, the ratio of which to all electrons contained in the electron beam on the second placement plane being a predetermined ratio, from the second beam current distribution. 24. The beam measurement method according to claim 20, wherein, in determining the light source size and the opening angle, the light source size and the opening angle are calculated using a first profile signal obtained from the first output, a second profile signal obtained from the second output, and information regarding a distance between a surface on which the first aperture is disposed and a surface on which the second aperture is disposed. an extraction electrode for controlling the amount of the electron beam emitted from the cathode;
a focusing lens unit including a focusing lens that focuses the electron beam by a magnetic field;
a first deflector provided between the extraction electrode and the focusing lens and configured to deflect a trajectory of the electron beam;
a second deflector provided between the first deflector and the focusing lens, for deflecting a trajectory of the electron beam deflected by the first deflector;
an extraction electrode control amplifier that applies a voltage to the extraction electrode based on an electron beam command that specifies the amount of the electron beam;
a first control unit that outputs an excitation current to the first deflector based on a voltage command or a current command based on the electron beam command;
a second control unit that outputs an excitation current to the second deflector based on a voltage command or a current command based on the electron beam command;
Equipped with
the first control unit controls the first deflector so that a trajectory of the electron beam from the first deflector is directed toward a center of the second deflector;
The second control unit controls the second deflector so that a trajectory of the electron beam from the second deflector is along an optical axis or parallel to the optical axis. 26. The electron gun of claim 25, wherein the first controller and the second controller control the first deflector and the second deflector, respectively, to maintain a constant trajectory of the electron beam from the second deflector when the amount of the electron beam specified by the electron beam command changes. When the amount of the electron beam specified by the electron beam command is changed,
the first control unit changes the excitation current output to the first deflector so that a trajectory of the electron beam from the first deflector is directed toward a center of the second deflector;
27. The electron gun according to claim 25 or 26, wherein the second control unit changes the excitation current output to the second deflector so that a trajectory of the electron beam from the second deflector is along the optical axis or parallel to the optical axis. deflecting an electron beam from an electron light source unit by a first beam deflector;
deflecting the electron beam from the first beam deflector with a second beam deflector;
changing a beam current of the electron beam from the electron light source unit;
and deflecting with the first beam deflector includes deflecting the electron beam such that a first trajectory of the electron beam from the first beam deflector does not change when the beam current changes;
The method of controlling an electron beam trajectory, wherein the deflecting by the second beam deflector includes deflecting the electron beam such that a second trajectory of the electron beam from the second beam deflector does not change when the beam current changes. The method further includes causing the electron beam from the second beam deflector to be incident on a focusing lens unit;
deflecting with the first beam deflector includes deflecting the electron beam such that the first trajectory of the electron beam passes through a center of the second beam deflector;
The electron beam trajectory control method of claim 28, wherein deflecting by the second beam deflector includes deflecting the electron beam so that the second trajectory of the electron beam is along an optical axis of the focusing lens section or along an axis parallel to the optical axis. 30. The electron beam trajectory control method according to claim 29, further comprising: measuring a position of the electron beam, via the condenser lens section, on a plane intersecting the optical axis while changing excitation of the condenser lens section.

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