Charged particle gun and charged particle beam device

Abstract

To provide a charged particle gun capable of increasing the number of charged particles contained in one pulse.SOLUTION: A charged particle gun emits a charged particle beam, and includes an emitter 10, an extraction electrode 12 that extracts the charged particle beam from the emitter 10, a capacitor 50 having one end connected to the extraction electrode 12, an offset power supply 60 that supplies a first voltage to one end of the capacitor 50 via a resistor 52, a pulse power supply 40 that outputs a second voltage, and a switch circuit 30 that switches between supplying the second voltage or a reference potential to the other end of the capacitor 50 on the basis of a reference pulse signal.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a charged particle gun and a charged particle beam device. [Background technology]

[0002] 2. Description of the Related Art As an electron source used in electron microscopes such as scanning electron microscopes and transmission electron microscopes, Patent Document 1 discloses a pulsed electron source capable of emitting a pulsed electron beam.

[0003] One method for realizing a pulsed electron source is to use a blanker to blank the electron beam emitted from an electron gun at high speed to make the electron beam pulsed. In this method, a high-brightness pulsed electron source can be obtained by using a high-brightness Schottky type electron gun or a cold-cathode field emission type electron gun. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2000-208080 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the above-mentioned method of emitting an electron beam in pulses using a blanker, the number of electrons contained in one pulse is small. [Means for solving the problem]

[0006] One aspect of the charged particle gun according to the present invention is to A charged particle gun that emits a charged particle beam, The emitter and an extraction electrode that extracts the charged particle beam from the emitter; a capacitor having one end connected to the extraction electrode; a first power supply that supplies a first voltage to the one end of the capacitor via a resistor; a second power supply that outputs a second voltage; a switch circuit that switches between supplying the second voltage or a reference potential to the other end of the capacitor based on a reference pulse signal; Includes.

[0007] In such a charged particle gun, a first voltage is supplied to one end of a capacitor, and a reference potential is supplied to the other end of the capacitor, so that a charge corresponding to the difference between the first voltage and the reference potential is accumulated in the capacitor. By switching the other end of the capacitor from the reference potential to a second voltage based on a reference pulse signal, the voltage applied to the extraction electrode can be changed to a pulsed state. This makes it possible to change the emission current to a pulsed state, and increase the number of charged particles contained in one pulse.

[0008] One aspect of a charged particle device according to the present invention includes the above-described charged particle gun. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing the configuration of an electron gun according to a first embodiment. [Diagram 2] 4 is a graph showing an emission current EC of an electron beam emitted from the electron gun according to the first embodiment. [Diagram 3] 4 is a graph showing an emission current EC of an electron beam emitted from the electron gun according to the first embodiment. [Figure 4] 13 is a graph showing a reference pulse signal SAp, an inverted signal SB, a voltage signal SC, an emission current EC0, a blanking signal SD, and an emission current EC in a pulse emission mode. [Diagram 5] Graphs showing the reference continuous signal SAc, the inverted signal SB, the voltage signal SC, the emission current EC0, and the emission current EC in the continuous emission mode. [Figure 6] FIG. 13 is a diagram showing a comparative example of a method for emitting an electron beam in a pulsed manner. [Figure 7] FIG. 13 is a diagram showing the configuration of an electron gun according to a second embodiment. [Figure 8]10 is a graph showing an emission current EC of an electron beam according to the second embodiment. [Figure 9] 5 is a graph showing a reference pulse signal SAp, an inverted signal SB, a voltage signal SC, an emission current EC0, and an emission current EC in a pulse emission mode. [Figure 10] 11 is a graph showing a reference pulse signal SAp, an inverted signal SB, a voltage signal SC, an emission current EC0, and an emission current EC in a modified pulse emission mode. [Figure 11] FIG. 13 is a diagram showing the configuration of an electron microscope according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Preferred embodiments of the present invention will be described in detail below with reference to the drawings. Note that the embodiments described below do not unduly limit the contents of the present invention described in the claims. In addition, not all of the configurations described below are necessarily essential components of the present invention.

[0011] In the following, an electron gun that emits an electron beam will be used as an example of a charged particle gun according to the present invention, but the charged particle gun according to the present invention may also be a gun that emits a charged particle beam (such as an ion beam) other than an electron beam.

[0012] 1. First embodiment 1.1. Electron gun configuration First, an electron gun according to a first embodiment will be described with reference to the drawings. Fig. 1 is a diagram showing the configuration of an electron gun 100 according to the first embodiment.

[0013] 1, the electron gun 100 includes an emitter 10, an extraction electrode 12, a blanker 14, a reference signal generator 20, a switch circuit 30, a pulsed power supply 40 (an example of a second power supply), a capacitor 50, a resistor 52, an offset power supply 60 (an example of a first power supply), and a blanking signal generating circuit 70. The electron gun 100 has a pulsed emission mode in which an electron beam is emitted in a pulsed manner, and a continuous emission mode in which an electron beam is emitted with a constant emission current.

[0014] The emitter 10 is an electron emission source, that is, a cathode. For example, a tungsten tip having a tip diameter on the order of nanometers can be used as the emitter 10. The emitter 10 is connected to a reference potential.

[0015] The extraction electrode 12 is an electrode for extracting electrons from the emitter 10. A positive high voltage, that is, an extraction voltage, is applied between the emitter 10 and the extraction electrode 12 in order to create a strong electric field on the surface of the emitter 10.

[0016] The electron gun 100 is a field emission type electron gun that forms a strong electric field at the tip of the emitter 10 and emits electrons by the tunnel effect. Note that the electron gun 100 may be a Schottky type electron gun that forms a strong electric field at the tip of the emitter 10 and emits electrons by the Schottky effect.

[0017] The blanker 14 performs blanking of the electron beam emitted from the emitter 10. The blanker 14 blocks the electron beam by deflecting the electron beam. An electrostatic deflection plate that can be switched ON / OFF at high speed is used as the blanker 14. This allows high speed switching between emission and non-emission of the electron beam.

[0018] The blanker 14 is disposed between the extraction electrode 12 and a sample to be irradiated with the electron beam. The position of the blanker 14 is not particularly limited as long as it is between the extraction electrode 12 and the sample. The blanker 14 may be incorporated, for example, in the irradiation optical system of the electron microscope.

[0019] The reference signal generator 20 generates a reference signal SA. In the pulse emission mode, the reference signal generator 20 generates a reference pulse signal as the reference signal SA, and in the continuous emission mode, the reference signal generator 20 generates a reference continuous signal as the reference signal SA. The reference signal SA is input to the switch circuit 30 and the blanking signal generation circuit 70.

[0020] The switch circuit 30 switches between supplying the capacitor 50 with the pulse voltage output from the pulse power supply 40 or with the reference potential (ground potential) based on the reference signal SA.

[0021] The switch circuit 30 includes a first switch 32, a second switch 34, and an inverter 36. A pulse power supply 40 is connected to one end of the first switch 32, and a capacitor 50 is connected to the other end of the first switch 32. A reference potential is connected to one end of the second switch 34, and the capacitor 50 is connected to the other end of the second switch 34.

[0022] An inverted signal SB, in which the logical level of the reference signal SA is inverted by an inverter 36, is input to the first switch 32. The reference signal SA is directly input to the second switch 34. Therefore, the first switch 32 and the second switch 34 operate exclusively. That is, when the first switch 32 is on, the second switch 34 is off, and when the first switch 32 is off, the second switch 34 is on. In the switch circuit 30, when the first switch 32 is on, the second switch 34 is not turned on. The first switch 32 and the second switch 34 can be realized by using, for example, a push-pull circuit or a relay circuit.

[0023] The pulse power supply 40 outputs a pulse voltage (second voltage). One end of the pulse power supply 40 is connected to the switch circuit 30, and the other end of the pulse power supply 40 is connected to a reference potential. The pulse voltage can be set to any value.

[0024] One end of the capacitor 50 is connected to the extraction electrode 12. The other end of the capacitor 50 is connected to the switch circuit 30. To the extraction electrode 12, a voltage signal SC is applied.

[0025] The offset power supply 60 supplies an offset voltage (first voltage) to one end of the capacitor 50 via a resistor 52. One end of the offset power supply 60 is connected to one end of the capacitor 50 via the resistor 52, and the other end of the offset power supply 60 is connected to a reference potential. The offset voltage can be set to any value.

[0026] The blanking signal generating circuit 70 generates a blanking signal SD synchronized with the reference signal SA. The blanking signal generating circuit 70 generates the blanking signal SD based on a user instruction received by the control unit 80. The blanking signal SD generated by the blanking signal generating circuit 70 is input to the blanker 14. The blanker 14 operates in response to the blanking signal SD.

[0027] The control unit 80 receives a user instruction and generates a blanking signal in response to the user instruction. The control unit 80 controls the signal generating circuit 70. The control unit 80 includes, for example, a processor such as a CPU (Central Processing Unit) and a storage device such as a RAM (Random Access Memory) and a ROM (Read Only Memory). The storage device stores programs and data for performing various controls. The functions of the control unit 80 can be realized by executing the programs in the processor.

[0028] 1.2. Operation 1.2.1. Electron beam emission 2 and 3 are graphs showing the emission current EC of the electron beam emitted from the electron gun 100. The electron gun 100 can switch between a continuous emission mode in which the electron beam is emitted at a constant emission current as shown in FIG. 2, and a pulse emission mode in which the electron beam is emitted in a pulsed manner as shown in FIG. 3. In the continuous emission mode, the electron beam can be irradiated onto a sample at a constant emission current. In the pulse emission mode, the electron beam can be irradiated onto a sample in a pulsed manner with a period on the order of microseconds, for example. The current Ip (Ip≠0), which is the peak intensity of the emission current EC in the pulse emission mode, is greater than the current Ic (Ic≠0), which is the current value of the emission current EC in the continuous emission mode.

[0029] 1.2.2. Pulsed emission mode 4 is a graph showing the reference pulse signal SAp, the inversion signal SB, the voltage signal SC, the emission current EC0, the blanking signal SD, and the emission current EC in the pulse emission mode. The emission current EC0 is the electron current emitted from the emitter 10, and is the emission current before the electron beam is incident on the blanker 14. The emission current EC is the emission current at the rear stage of the blanker 14. In other words, the emission current EC is the emission current of the electron beam emitted from the electron gun 100.

[0030] In the pulse emission mode, the switch circuit 30 switches between supplying a pulse voltage Vp or a reference potential to one end of the capacitor 50, the other end of which is supplied with an offset voltage Vo, based on the reference pulse signal SAp, and changes the voltage signal SC applied to the extraction electrode 12 into a pulse shape. This causes the emission current EC0 to change into a pulse shape.

[0031] The blanker 14 extracts a part of the pulse of the emission current EC0 by performing blanking in response to a blanking signal SD synchronized with the reference pulse signal SAp, causing the electron gun 100 to emit an electron beam in a pulsed manner.

[0032] The operation of the electron gun 100 for one cycle C from time t1 to time t5 will be described in detail below.

[0033] At time t1, the reference signal generator 20 switches the logical level of the reference pulse signal SAp from high to low. As a result, the low-level reference pulse signal SAp is input to the inverter 36. The logical level of the reference pulse signal SAp is inverted by the inverter 36. Therefore, the high-level inverted signal SB is input to the first switch 32. As a result, the first switch 32 is turned on. Also, the low-level reference pulse signal SAp is directly input to the second switch 34. As a result, the second switch 34 is turned off.

[0034] When the first switch 32 is turned on and the second switch 34 is turned off, a pulse voltage Vp is supplied to the other end of the capacitor 50. That is, the voltage applied to the other end of the capacitor 50 is switched from the reference potential to the pulse voltage Vp. Meanwhile, since the offset power supply 60 is connected to one end of the capacitor 50 via the resistor 52, an offset voltage Vo is supplied to one end of the capacitor 50. As the voltage applied to the voltage signal SC switches from the reference potential to the pulse voltage Vp, the voltage value of the voltage signal SC gradually increases from the offset voltage Vo in accordance with a time constant determined by the capacitance of the capacitor 50 and the resistance value of the first switch 32, and becomes constant at the sum of the offset voltage Vo and the pulse voltage Vp, Vo+Vp.

[0035] For example, if the pulse voltage Vp is 1.2 kV and the offset voltage Vo is 3.0 kV, the voltage value of the voltage signal SC applied to the extraction electrode 12 gradually increases from 3.0 kV and becomes constant at 4.2 kV.

[0036] At this time, the voltage value of the voltage signal SC is ideally constant at the sum Vo+Vp, but the charge stored in the capacitor 50 gradually decreases as it is released via the resistor 52. However, if the time is sufficiently shorter than the time constant determined by the capacitance of the capacitor 50 and the resistance value of the resistor 52, the charge of the capacitor 50 does not change significantly and the voltage value of the voltage signal SC can be considered to be constant. Therefore, the time constant determined by the capacitance of the capacitor 50 and the resistance value of the resistor 52 is set to a time sufficiently longer than the pulse width of the reference pulse signal SAp.

[0037] When the voltage value of the voltage signal SC applied to the extraction electrode 12 becomes the sum Vo+Vp, the current value of the emission current EC0 of the electron beam emitted from the emitter 10 becomes the current Ip.

[0038] At time t1, the blanking signal generating circuit 70 maintains the logic level of the blanking signal SD at a high level. Therefore, at time t1, the blanker 14 blanks the electron beam, and the current value of the emission current EC of the electron beam emitted from the electron gun 100 becomes zero.

[0039] At time t2, a predetermined time Δt after time t1, the blanking signal generation circuit 70 switches the logic level of the blanking signal SD from high to low. The blanking signal generation circuit 70 then maintains the low level for a fixed period P from time t2. As a result, the blanker 14 does not blank the electron beam for the fixed period P from time t2. As a result, the current value of the emission current EC becomes the current Ip for the fixed period P from time t2.

[0040] At time t3, a certain period P after time t2, the blanking signal generating circuit 70 switches the logic level of the blanking signal SD from low to high. This causes the blanker 14 to start blanking the electron beam at time t3. As a result, the current value of the emission current EC becomes zero at time t3.

[0041] The blanking signal generating circuit 70 includes, for example, a delay circuit that controls the time Δt, and a control circuit that controls a fixed period P that corresponds to the pulse width. The time Δt and the fixed period P can be set to any value, and are set based on a user's instruction received by the control unit 80. For example, an electron beam pulse with a stable peak intensity can be obtained by setting the time Δt to be longer than the time from time t2 until the voltage value of the voltage signal SC stabilizes at the sum Vo+Vp. Also, an electron beam pulse with a pulse width on the order of microseconds can be obtained by setting the fixed period P to the order of microseconds.

[0042] At time t4, the reference signal generator 20 switches the logic level of the reference pulse signal SAp from low to high. As a result, the high-level reference pulse signal SAp is input to the inverter 36. The logic level of the reference pulse signal SAp is inverted by the inverter 36. Therefore, the low-level inverted signal SB is input to the first switch 32. As a result, the first switch 32 is turned off. In addition, the second switch 34 The high-level reference pulse signal SAp is directly input to the second switch 34. As a result, the second switch 34 is turned on.

[0043] When the first switch 32 is turned off and the second switch 34 is turned on, the reference potential is supplied to the other end of the capacitor 50. That is, the voltage applied to the other end of the capacitor 50 switches from the pulse voltage Vp to the reference potential. Meanwhile, an offset voltage Vo is supplied to one end of the capacitor 50. When the voltage applied to the other end of the capacitor 50 switches from the pulse voltage Vp to the reference potential, the voltage value of the voltage signal SC applied to the extraction electrode 12 gradually decreases from the sum Vo+Vp according to a time constant determined by the capacitance of the capacitor 50 and the resistance value of the resistor 52, and becomes constant at the offset voltage Vo.

[0044] For example, if the pulse voltage Vp is 1.2 kV and the offset voltage Vo is 3.0 kV, the voltage value of the voltage signal SC applied to the extraction electrode 12 gradually decreases from 4.2 kV and becomes constant at 3.0 kV.

[0045] The offset voltage Vo is set to a voltage value that makes the emission current EC0 have a current Ic. Therefore, when a voltage signal SC of the offset voltage Vo is supplied to the extraction electrode 12, the emission current EC0 of the electron beam emitted from the emitter 10 has a current Ic.

[0046] At time t5, the reference signal generator 20 switches the logic level of the reference pulse signal SAp from high to low. As a result, the first switch 32 receives the high-level inverted signal SB via the inverter 36, and the first switch 32 is turned on. In addition, the second switch 34 receives the low-level reference pulse signal SAp directly, and the second switch 34 is turned off.

[0047] When the first switch 32 is turned on and the second switch 34 is turned off, the voltage applied to the other end of the capacitor 50 switches from the reference potential to the pulse voltage Vp. When the voltage applied to the other end of the capacitor 50 switches from the reference potential to the pulse voltage Vp, the voltage value of the voltage signal SC gradually increases and becomes constant at the sum Vo+Vp of the offset voltage Vo and the pulse voltage Vp. When the voltage value of the voltage signal SC becomes the sum Vo+Vp, the current value of the emission current EC0 of the electron beam emitted from the emitter 10 becomes the current Ip.

[0048] From time t3 to time t5, the blanking signal generating circuit 70 maintains the logic level of the blanking signal SD at a high level. Therefore, from time t3 to time t5, the blanker 14 blanks the electron beam. As a result, from time t3 to time t5, the current value of the emission current EC becomes zero.

[0049] Time t5 corresponds to time t1, and electron gun 100 operates with time t1 to time t5 as one cycle C. Electron gun 100 emits one electron beam pulse in one cycle C from time t1 to time t5. Electron gun 100 repeats this cycle C to emit the electron beam in pulses.

[0050] The period of the reference pulse signal SAp generated by the reference signal generator 20 and the duty ratio of the reference pulse signal SAp can be set to any value. Therefore, the electron gun 100 can emit electron beam pulses at a desired period. Also, for example, the pulse width of the emission current EC0 can be changed by changing the duty ratio of the reference pulse signal SAp.

[0051] Moreover, the offset voltage Vo and the pulse voltage Vp can be set to any value, so that the electron gun 100 can emit an electron beam pulse with a desired peak intensity.

[0052] 1.2.3. Continuous emission mode FIG. 5 is a graph showing the reference continuous signal SAc, the inverted signal SB, the voltage signal SC, the emission current EC0, and the emission current EC in the continuous emission mode.

[0053] In the continuous emission mode, the reference signal generator 20 generates a reference continuous signal SAc as the reference signal SA. In the continuous emission mode, the blanker 14 is not operated.

[0054] The reference signal generator 20 continues to output a high-level reference continuous signal SAc. Therefore, the first switch 32 continues to be in the OFF state, and the second switch 34 continues to be in the ON state. This causes the reference potential to be continuously supplied to the other end of the capacitor 50. Therefore, the voltage value of the voltage signal SC becomes constant at the offset voltage Vo. As a result, the current value of the emission current EC0 of the electron beam emitted from the emitter 10 becomes constant at the current Ic.

[0055] In the continuous emission mode, the blanker 14 does not operate, so the current value of the emission current EC is constant at the current Ic. Thus, in the continuous emission mode, the electron gun 100 emits an electron beam with a constant emission current.

[0056] Effects The electron gun 100 includes an emitter 10, an extraction electrode 12 that extracts an electron beam from the emitter 10, a capacitor 50 having one end connected to the extraction electrode 12, an offset power supply 60 that supplies an offset voltage Vo to one end of the capacitor 50 via a resistor 52, a pulse power supply 40 that outputs a pulse voltage Vp, and a switch circuit 30 that switches between supplying the pulse voltage Vp or the reference potential to the other end of the capacitor 50 based on a reference pulse signal SAp.

[0057] In the electron gun 100, an offset voltage Vo is connected to one end of the capacitor 50, and a reference potential is connected to the other end of the capacitor 50, so that a charge corresponding to the difference between the offset voltage Vo and the reference potential is stored in the capacitor 50. Then, the other end of the capacitor 50 is switched from the reference potential to a pulse voltage Vp based on a reference pulse signal SAp, so that the voltage applied to the extraction voltage can be changed to a pulsed voltage. This makes it possible to change the emission current EC0 to a pulsed current, thereby increasing the number of electrons contained in one pulse.

[0058] Furthermore, in the electron gun 100, an extraction voltage higher than the withstand voltage of the switch circuit 30 can be applied to the extraction electrode 12. For example, even if the withstand voltage of the switch circuit 30 is 1.5 kV, by setting the pulse voltage Vp to 1.2 kV and the offset voltage Vo to 3.0 kV, the voltage applied to the extraction electrode 12 becomes 4.2 kV. In this way, in the electron gun 100, an extraction voltage higher than the withstand voltage of the switch circuit 30 can be applied to the extraction electrode 12.

[0059] FIG. 6 is a diagram showing a comparative example of a method for emitting an electron beam in a pulsed manner.

[0060] For example, in a conventional Schottky electron gun or cold cathode field emission electron gun, as shown in Fig. 6, a pulsed electron beam with a peak intensity of current Ip can be emitted by setting the emission current EC0 of the electron beam emitted from the emitter 10 constant at a current Ip and blanking the electron beam with a blanker 14. By using a Schottky electron gun or a cold cathode field emission electron gun to increase the emission current, the number of electrons contained in one pulse can be increased.

[0061] However, when the electron beam emission current EC0 is kept constant at the current Ip, an electron beam with a large emission current is irradiated onto an electrode, etc. for a long period of time, which increases the amount of gas emitted by the electron beam irradiating the electrode, etc. Furthermore, when the emission current is increased, a large current flows through the tip of the emitter, which may cause the temperature of the emitter itself to rise and the shape of the tip of the emitter to change.

[0062] In contrast, in the electron gun 100, as shown in FIG. 4, the emission current EC0 of the electron beam emitted from the emitter 10 is changed in a pulse shape with the current Ip as the peak current value. Therefore, for example, compared with the case where the current value of the emission current EC0 shown in FIG. 6 is constant at the current Ip, the time during which the electron beam is irradiated to the electrode or the like can be shortened, and the amount of gas emitted by the electron beam being irradiated to the electrode or the like can be reduced. Furthermore, in the electron gun 100, the time during which a large current flows through the tip of the emitter 10 can be shortened, and therefore the temperature rise of the emitter itself and the change in the tip shape of the emitter can be reduced. For example, the pulse width of the emission current EC0 can be reduced by reducing the duty ratio of the reference pulse signal SAp shown in FIG. 4. This allows the time during which the electron beam is irradiated to the electrode or the like to be shortened. Furthermore, the time during which a large current flows through the tip of the emitter 10 can be shortened.

[0063] Furthermore, in the electron gun 100, the extraction voltage required to obtain a desired emission current, i.e., the voltage value of the voltage signal SC, increases due to, for example, deterioration of the emitter 10. Even in this case, in the electron gun 100, the desired emission current EC0 can be easily obtained by increasing the offset voltage Vo and superimposing the pulse voltage Vp.

[0064] The electron gun 100 includes a blanker 14 that blanks the electron beam, and the blanker 14 blanks the electron beam in response to a blanking signal SD synchronized with a reference pulse signal SAp. Therefore, when the emission current EC0 increases, the electron gun 100 can extract the electron beam by blanking to obtain an electron beam pulse. Therefore, the electron gun 100 can increase the number of electrons contained in one pulse.

[0065] The electron gun 100 includes a blanking signal generating circuit 70 that generates a blanking signal SD. The switch circuit 30 supplies a pulse voltage Vp during a period when the reference pulse signal SAp is at a low level, and supplies a reference potential during a period when the reference pulse signal SAp is at a high level. The blanker 14 blanks the electron beam during a period when the blanking signal SD is at a high level, and does not blank the electron beam during a period when the blanking signal SD is at a low level. The blanking signal generating circuit 70 switches the blanking signal SD from a high level to a low level and maintains the low level for a certain period P after a predetermined time Δt has elapsed since the logic level of the reference pulse signal SAp was switched from a high level to a low level.

[0066] Therefore, in the electron gun 100, when the emission current EC0 that changes in a pulse shape increases, the electron beam can be extracted by blanking to obtain an electron beam pulse. Therefore, in the electron gun 100, the number of electrons contained in one pulse can be increased.

[0067] The above logic levels are merely examples, and are not limiting. The switch circuit 30 supplies a pulse voltage Vp during a period when the reference pulse signal SAp is at a first logic level, and supplies a reference potential during a period when the reference pulse signal SAp is at a second logic level. The blanker 14 blanks the electron beam during a period when the blanking signal SD is at a third logic level, and does not blank the electron beam during a period when the blanking signal SD is at a fourth logic level. The blanking signal generating circuit 70 switches the blanking signal SD from the third logic level to the fourth logic level and maintains the fourth logic level for a certain period P after a predetermined time Δt has elapsed since the logic level of the reference pulse signal SAp was switched from the second logic level to the first logic level. At this time, the first logic level The first logic level and the second logic level may be different logic levels, and the third logic level and the fourth logic level may be different logic levels.

[0068] In the electron gun 100, the blanking signal generating circuit 70 sets the predetermined time Δt and the fixed period P to times specified by the user. Therefore, in the electron gun 100, it is possible to extract an electron beam pulse of a desired pulse width at a desired timing using the blanker 14 from the electron beam whose emission current EC0 changes in a pulsed manner.

[0069] In the above embodiment, the blanking signal generating circuit 70 sets the predetermined time Δt and the fixed period P to times specified by the user, but the blanking signal generating circuit 70 may also set at least one of the predetermined time Δt and the fixed period P to times specified by the user.

[0070] 2. Second embodiment 2.1. Electron gun Next, an electron gun according to a second embodiment will be described with reference to the drawings. Fig. 7 is a diagram showing the configuration of an electron gun 200 according to the second embodiment. Hereinafter, in the electron gun 200 according to the second embodiment, components having the same functions as those of the electron gun 100 according to the first embodiment are given the same reference numerals, and detailed description thereof will be omitted.

[0071] In the above-described electron gun 100, as shown in FIG. 4, an electron beam pulse is extracted from the electron beam emitted from the emitter 10 by using the blanker 14, thereby emitting the electron beam in a pulsed manner.

[0072] In contrast to this, the electron gun 200 emits an electron beam in pulses from the emitter 10 without using the blanker 14. The electron gun 200 does not have the blanker 14 and the blanking signal generating circuit 70, as shown in FIG.

[0073] 2.2. Operation 2.2.1. Electron beam emission Fig. 8 is a graph showing the emission current EC of the electron beam emitted from the electron gun 200. The electron gun 200 can switch between a continuous emission mode in which the electron beam is emitted at a constant current Ic as shown in Fig. 2, and a pulse emission mode in which the electron beam is emitted in a pulsed manner at a constant cycle as shown in Fig. 8.

[0074] 2.2.2. Pulsed emission mode FIG. 9 is a graph showing the reference pulse signal SAp, the inverted signal SB, the voltage signal SC, the emission current EC0, and the emission current EC in the pulse emission mode.

[0075] In the pulse emission mode, the switch circuit 30 switches between supplying a pulse voltage Vp or a reference potential to one end of the capacitor 50, the other end of which is supplied with an offset voltage Vo, based on the reference pulse signal SAp, and changes the voltage signal SC to a pulsed state. This causes the emission current EC0 to change to a pulsed state. Therefore, the electron gun 200 emits an electron beam in a pulsed state.

[0076] The operation of the electron gun 200 for one cycle C from time t10 to time t12 will be described below.

[0077] At time t10, the reference signal generator 20 switches the logic level of the reference pulse signal SAp from high to low. As a result, the first switch 32 is Since the inverted signal SB of high level is input via 36, ​​the first switch 32 is turned on. Moreover, since the reference pulse signal SAp of low level is directly input to the second switch 34, the second switch 34 is turned off.

[0078] When the first switch 32 is turned on and the second switch 34 is turned off, the voltage applied to the other end of the capacitor 50 switches from the reference potential to the pulse voltage Vp. When the voltage applied to the other end of the capacitor 50 switches from the reference potential to the pulse voltage Vp, the voltage value of the voltage signal SC gradually increases from the offset voltage Vo according to a time constant determined by the capacitance of the capacitor 50 and the resistance value of the first switch 32, and becomes constant at the sum Vo+Vp of the offset voltage Vo and the pulse voltage Vp. When the voltage value of the voltage signal SC becomes the sum Vo+Vp, the current value of the emission current EC0 becomes the current Ip.

[0079] Since the electron gun 200 does not have a blanker 14, the electron beam emitted from the emitter 10 is emitted directly from the electron gun 200. Therefore, the emission current EC is equal to the emission current EC0.

[0080] At time t11, the reference signal generator 20 switches the logic level of the reference pulse signal SAp from low to high. As a result, the first switch 32 receives the low-level inverted signal SB via the inverter 36, and the first switch 32 is turned off. In addition, the high-level reference pulse signal SAp is directly input to the second switch 34, and the second switch 34 is turned on.

[0081] When the first switch 32 is turned off and the second switch 34 is turned on, the reference potential is supplied to the other end of the capacitor 50. That is, the voltage applied to the other end of the capacitor 50 switches from the pulse voltage Vp to the reference potential. Meanwhile, an offset voltage Vo is supplied to one end of the capacitor 50. When the voltage applied to the other end of the capacitor 50 switches from the pulse voltage Vp to the reference potential, the voltage value of the voltage signal SC gradually decreases from the sum Vo+Vp according to a time constant determined by the capacitance of the capacitor 50 and the resistance value of the resistor 52, and becomes constant at the offset voltage Vo.

[0082] Here, in the above-described electron gun 100, the offset voltage Vo is set to a voltage value at which the current value of the emission current EC0 becomes the current Ic. In contrast to this, in the electron gun 200, the offset voltage Vo is set to a voltage value lower than the voltage required to emit an electron beam from the emitter 10. Therefore, by supplying the voltage signal SC, whose voltage value is the offset voltage Vo, to the extraction electrode 12, the current value of the emission current EC0 becomes zero.

[0083] At time t12, the reference signal generator 20 switches the logic level of the reference pulse signal SAp from high to low. As a result, the first switch 32 receives the high-level inverted signal SB via the inverter 36, and the first switch 32 is turned on. In addition, the low-level reference pulse signal SAp is directly input to the second switch 34, and the second switch 34 is turned off.

[0084] When the first switch 32 is turned on and the second switch 34 is turned off, the voltage applied to the other end of the capacitor 50 switches from the reference potential to the pulse voltage Vp. When the voltage applied to the other end of the capacitor 50 switches from the reference potential to the pulse voltage Vp, the voltage value of the voltage signal SC gradually increases and becomes constant at the sum Vo+Vp of the offset voltage Vo and the pulse voltage Vp. When the voltage value of the voltage signal SC becomes the sum Vo+Vp, the current value of the emission current EC0 becomes the current Ip.

[0085] Time t12 corresponds to time t10, and electron gun 200 operates with time t10 to time t12 as one cycle C. Electron gun 200 emits one electron beam pulse in one cycle C from time t10 to time t12. Electron gun 200 repeats this cycle C to emit the electron beam in a pulsed manner.

[0086] 2.2.3. Continuous emission mode The operation of the electron gun 200 in the continuous emission mode is similar to the operation of the electron gun 100 in the continuous emission mode shown in FIG. 5 described above, and therefore a description thereof will be omitted.

[0087] 2.3. Effects The electron gun 200 includes an emitter 10, an extraction electrode 12 that extracts an electron beam from the emitter 10, a capacitor 50 having one end connected to the extraction electrode 12, an offset power supply 60 that supplies an offset voltage Vo to one end of the capacitor 50 via a resistor 52, a pulse power supply 40 that outputs a pulse voltage Vp, and a switch circuit 30 that switches between supplying the pulse voltage Vp or the reference potential to the other end of the capacitor 50 based on a reference pulse signal SAp.

[0088] Therefore, like the electron gun 100, the electron gun 200 can increase the number of electrons contained in one electron beam pulse. Furthermore, like the electron gun 100, the electron gun 200 can reduce the amount of gas emitted when an electrode or the like is irradiated with an electron beam. Furthermore, like the electron gun 100, the electron gun 200 can reduce the temperature rise of the emitter itself and the change in the tip shape of the emitter.

[0089] 2.4. Variations FIG. 10 is a graph showing the reference pulse signal SAp, the inverted signal SB, the voltage signal SC, the emission current EC0, and the emission current EC in a modified pulse emission mode.

[0090] In the second embodiment described above, the offset voltage Vo is set to a voltage value lower than the voltage required to emit electrons from the emitter 10. Therefore, when the voltage value of the voltage signal SC is the offset voltage Vo, the current value of the emission current EC0 of the electron gun 200 is zero. Therefore, in the example shown in Fig. 9, the electron gun 200 emits an electron beam that periodically repeats irradiation and non-irradiation.

[0091] On the other hand, the offset voltage Vo may be a voltage that causes the emitter 10 to emit an electron beam with an emission current of a current Id (Id≠0). As a result, when the voltage signal SC becomes the offset voltage Vo, the current value of the emission current EC0 becomes the current Id and does not become zero.

[0092] As a result, the electron gun 200 can emit an electron beam that periodically changes in intensity.

[0093] 3. Third embodiment Next, an electron microscope according to a third embodiment will be described. Fig. 11 is a diagram showing the configuration of an electron microscope 300 according to the third embodiment.

[0094] 11, the electron microscope 300 includes an electron gun 100. Note that, although a case in which the electron microscope 300 includes the electron gun 100 will be described here, the electron microscope 300 may also include an electron gun 200.

[0095] As shown in FIG. 11, the electron microscope 300 includes an electron gun 100, an irradiation optical system 302, a sample stage 304, an objective lens 306, an intermediate lens 308, a projection lens 310, and and an imaging device 320.

[0096] The electron gun 100 emits an electron beam. The electron gun 100 can switch between a continuous emission mode in which the electron beam is emitted at a constant emission current as shown in Fig. 2 and a pulse emission mode in which the electron beam is emitted in a pulsed manner as shown in Fig. 3. Therefore, the electron microscope 300 can irradiate the sample S with an electron beam at a constant emission current or irradiate the sample S with a pulsed electron beam.

[0097] The irradiation optical system 302 includes a plurality of lenses for irradiating the sample S with an electron beam. The irradiation optical system 302 converges the electron beam and irradiates the sample S. The irradiation optical system 302 may include a diaphragm, a deflector, and the like in addition to the plurality of lenses. The blanker 14 may be incorporated in the irradiation optical system 302.

[0098] The sample stage 304 holds the sample S. The sample stage 304 is equipped with a movement mechanism for moving the sample S in the horizontal and vertical directions, and a tilt mechanism for tilting the sample S. By moving the sample S on the sample stage 304, the field of view of a transmission electron microscope image (TEM image) can be moved.

[0099] The objective lens 306 forms a TEM image with the electron beam transmitted through the sample S. The intermediate lens 308 and the projection lens 310 project the image formed by the objective lens 306 onto the imaging device 320. The objective lens 306, the intermediate lens 308, and the projection lens 310 constitute an imaging optical system for forming a TEM image.

[0100] The imaging device 320 captures a TEM image formed by an imaging optical system. The imaging device 320 is, for example, a charge coupled device (CCD) camera, a complementary metal-oxide-semiconductor (CMOS) camera, or the like.

[0101] In the electron microscope 300, the electron beam emitted from the electron gun 100 is focused by the irradiation optical system 302 to form an electron probe, and the electron beam is deflected by a deflector (not shown) to scan the sample S with the electron probe, and the electrons transmitted through the sample S are detected to obtain a scanning transmission electron microscope image (STEM image). That is, the electron microscope 300 also functions as a scanning transmission electron microscope.

[0102] Although the above description has been given of the case where the electron gun 100 is applied to a transmission electron microscope, the electron gun 100 can also be applied to other charged particle beam devices, such as a scanning electron microscope, an electron probe microanalyzer, an Auger microprobe, and an electron beam lithography device.

[0103] 4. Modifications The present invention is not limited to the above-described embodiment, and various modifications are possible within the scope of the present invention.

[0104] For example, in the above-mentioned first and second embodiments, the charged particle gun according to the present invention is described as an electron gun that emits an electron beam, but the charged particle gun according to the present invention may be a charged particle gun that emits a charged particle beam (such as an ion beam) other than an electron beam. For example, an ion gun that emits an ion beam can be realized by changing the polarity of the emitter 10 and the extraction electrode 12 shown in FIG.

[0105] In the above-described third embodiment, the charged particle beam device according to the present invention is an electron microscope equipped with the electron gun 100. However, the charged particle beam device according to the present invention may be an ion gun. The charged particle beam device may be a charged particle beam device equipped with a focused ion beam device, for example.

[0106] The present invention is not limited to the above-described embodiment, and various modifications are possible. For example, the present invention includes a configuration that is substantially the same as the configuration described in the embodiment. A substantially identical configuration is, for example, a configuration that has the same function, method, and result, or a configuration that has the same purpose and effect. The present invention also includes a configuration in which non-essential parts of the configuration described in the embodiment are replaced. The present invention also includes a configuration that has the same action and effect as the configuration described in the embodiment, or a configuration that can achieve the same purpose. The present invention also includes a configuration in which publicly known technology is added to the configuration described in the embodiment. [Explanation of symbols]

[0107] 10...emitter, 12...extraction electrode, 14...blanker, 20...reference signal generator, 30...switch circuit, 32...first switch, 34...second switch, 36...inverter, 40...pulse power supply, 50...capacitor, 52...resistor, 60...offset power supply, 70...blanking signal generating circuit, 80...control unit, 100...electron gun, 200...electron gun, 300...electron microscope, 302...irradiation optical system, 304...sample stage, 306...objective lens, 308...intermediate lens, 310...projection lens, 320...imaging device

Claims

1. A charged particle gun that emits a charged particle beam, The emitter and an extraction electrode that extracts the charged particle beam from the emitter; a capacitor having one end connected to the extraction electrode; a first power supply that supplies a first voltage to the one end of the capacitor through a resistor; a second power supply that outputs a second voltage; a switch circuit that switches between supplying the second voltage or a reference potential to the other end of the capacitor based on a reference pulse signal; A charged particle gun comprising:

2. In claim 1, a blanker for blanking the charged particle beam; The blanker performs blanking of the charged particle beam in response to a blanking signal synchronized with the reference pulse signal.

3. In claim 2, a blanking signal generating circuit for generating the blanking signal; the switch circuit supplies the second voltage during a period when the reference pulse signal is at a first logic level, and supplies the reference potential during a period when the reference pulse signal is at a second logic level; the blanker blanks the charged particle beam during a period when the blanking signal is at a third logic level and does not blank the charged particle beam during a period when the blanking signal is at a fourth logic level; a blanking signal generating circuit that switches the blanking signal from the third logic level to the fourth logic level and maintains the fourth logic level for a certain period of time after a predetermined time has elapsed since the logic level of the reference pulse signal switches from the second logic level to the first logic level.

4. In claim 3, A charged particle gun, wherein the blanking signal generating circuit sets at least one of the predetermined time period and the fixed period to a time period designated by a user.

5. In claim 1, the switch circuit switches between supplying the second voltage or the reference potential to the other end of the capacitor based on the reference pulse signal, thereby changing the emission current of the charged particle beam emitted from the emitter into a pulsed form.

6. In claim 1, The first voltage is set to a voltage value lower than a voltage required for emitting a charged particle beam from the emitter.

7. A charged particle beam device comprising the charged particle gun according to any one of claims 1 to 6.

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