Charged particle gun and charged particle beam device

Abstract

Provided is a charged particle gun capable of increasing the number of charged particles contained in one pulse. A charged particle gun that releases a charged particle beam comprises: an emitter (10); an extraction electrode (12) that extracts the charged particle beam from the emitter (10); a capacitor (50), one end of which is connected to the extraction electrode (12); a bias 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 switching circuit (30) that switches whether the second voltage or the reference potential is supplied to the other end of the capacitor (50) on the basis of the reference pulse signal.

Description

Technical Field

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

[0002] As an electron source used in electron microscopes such as a scanning electron microscope and a transmission electron microscope, Patent Document 1 discloses a pulse electron source capable of irradiating a pulsed electron beam.

[0003] As a method of realizing a pulse electron source, there is a method of using a blanker to quickly blank the electron beam released from an electron gun to make the electron beam pulsed. In this method, a high-brightness pulse electron source can be obtained by using a high-brightness Schottky electron gun or a cold cathode electric field emission electron gun.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2000-208080 Summary of the invention

[0007] Problem that the invention aims to solve

[0008] However, in the above-mentioned method of emitting an electron beam in a pulse form using a blanker, the number of electrons included in one pulse is small.

[0009] Solutions for solving problems

[0010] One embodiment of the charged particle gun of the present invention is a charged particle gun for releasing a charged particle beam, comprising:

[0011] Transmitter;

[0012] an extraction electrode that extracts the charged particle beam from the emitter;

[0013] A capacitor, one end of which is connected to the lead-out electrode;

[0014] a first power source that supplies a first voltage to the one end of the capacitor via a resistor;

[0015] a second power supply that outputs a second voltage; and

[0016] The switch circuit switches whether to supply the second voltage or the reference potential to the other end of the capacitor based on the reference pulse signal.

[0017] In such a charged particle gun, the voltage applied to the extraction electrode can be changed in a pulsed manner by switching the other end of the capacitor from the reference potential to the second voltage based on the reference pulse signal from the state where the first voltage is supplied to one end of the capacitor and the reference potential is supplied to the other end of the capacitor, thereby increasing the number of charged particles contained in one pulse.

[0018] One embodiment of a charged particle device according to the present invention includes the charged particle gun described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a diagram showing the structure of the electron gun according to the first embodiment.

[0020] Figure 2 This is a graph showing emission current EC of an electron beam emitted from the electron gun according to the first embodiment.

[0021] Figure 3 This is a graph showing emission current EC of an electron beam emitted from the electron gun according to the first embodiment.

[0022] Figure 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 release mode.

[0023] Figure 5 is a graph showing the reference continuous signal SAc, the inversion signal SB, the voltage signal SC, the emission current EC0, and the emission current EC in the continuous release mode.

[0024] Figure 6 This is a diagram showing a comparative example of a method of emitting an electron beam in a pulsed state.

[0025] Figure 7 It is a diagram showing the structure of an electron gun according to the second embodiment.

[0026] Figure 8 It is a graph showing the emission current EC of the electron beam according to the second embodiment.

[0027] Fig. 9 : is a graph showing the reference pulse signal SAp, the inversion signal SB, the voltage signal SC, the emission current EC0, and the emission current EC in the pulse release mode.

[0028] Fig.10 : is a graph showing the reference pulse signal SAp, the reverse signal SB, the voltage signal SC, the emission current EC0, and the emission current EC in a modification of the pulse release mode.

[0029] Fig.11 It is a diagram showing the structure of an electron microscope according to a third embodiment.

[0030] Description of Reference Numerals

[0031] 10…emitter, 12…lead-out 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…bias 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…camera device. DETAILED DESCRIPTION

[0032] Hereinafter, preferred embodiments of the present invention will be described in detail using the accompanying drawings. Moreover, the embodiments described below are not intended to unduly limit the contents of the present invention as described in the claims. In addition, all the structures described below are not necessarily essential components of the present invention.

[0033] Hereinafter, an electron gun that emits an electron beam is described as an example of the charged particle gun of the present invention, but the charged particle gun of the present invention may also be a gun that emits a charged particle beam (such as an ion beam) other than an electron beam.

[0034] 1. First Implementation Method

[0035] 1.1. Electron gun composition

[0036] First, an electron gun according to a first embodiment will be described with reference to the drawings. Figure 1 It is a diagram showing the structure of the electron gun 100 according to the first embodiment.

[0037] like Figure 1 As shown, 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 pulse 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 pulse emission mode for emitting an electron beam in a pulsed state and a continuous emission mode for emitting an electron beam with a constant emission current.

[0038] The emitter 10 is a source of electron emission, that is, a cathode. For example, a tungsten tip having a nanometer-order diameter at the tip can be used as the emitter 10. The emitter 10 is connected to a reference potential.

[0039] The extraction electrode 12 is an electrode for extracting electrons from the emitter 10. Between the emitter 10 and the extraction electrode 12, an extraction voltage which is a positive high voltage for generating a strong electric field on the surface of the emitter 10 is applied.

[0040] The electron gun 100 is a field release type electron gun that forms a strong electric field at the tip of the emitter 10 and releases electrons using the tunnel effect. Alternatively, 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 releases electrons using the Schottky effect.

[0041] The blanker 14 blanks 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. Thus, the emission and non-emission of the electron beam can be switched at high speed.

[0042] The blanker 14 is disposed between the extraction electrode 12 and the sample 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 integrated in the irradiation optical system of the electron microscope, for example.

[0043] The reference signal generator 20 generates a reference signal SA. The reference signal generator 20 generates a reference pulse signal as the reference signal SA in the pulse release mode and generates a reference continuous signal as the reference signal SA in the continuous release mode. The reference signal SA is input to the switch circuit 30 and the blanking signal generation circuit 70.

[0044] The switch circuit 30 switches whether to supply the pulse voltage output from the pulse power supply 40 or the reference potential (ground potential) to the capacitor 50 based on the reference signal SA.

[0045] The switch circuit 30 includes a first switch 32, a second switch 34, and an inverter 36. One end of the first switch 32 is connected to a pulse power source 40, and the other end of the first switch 32 is connected to a capacitor 50. One end of the second switch 34 is connected to a reference potential, and the other end of the second switch 34 is connected to the capacitor 50.

[0046] The first switch 32 is input with the inversion signal SB obtained by inverting the logic level of the reference signal SA by the inverter 36. The second switch 34 is directly input with the reference signal SA. Therefore, the first switch 32 and the second switch 34 operate mutually exclusively. That is, when the first switch 32 is turned on, the second switch 34 is turned off, and when the first switch 32 is turned off, the second switch 34 is turned on. In the switch circuit 30, when the first switch 32 is turned 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.

[0047] The pulse power source 40 outputs a pulse voltage (second voltage). One end of the pulse power source 40 is connected to the switch circuit 30, and the other end of the pulse power source 40 is connected to a reference potential. The pulse voltage can be set to an arbitrary value.

[0048] 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. The extraction electrode 12 is applied with a voltage signal SC.

[0049] The bias power supply 60 supplies a bias voltage (first voltage) to one end of the capacitor 50 via the resistor 52. One end of the bias power supply 60 is connected to one end of the capacitor 50 via the resistor 52, and the other end of the bias power supply 60 is connected to a reference potential. The bias voltage can be set to any value.

[0050] 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 the user's 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 according to the blanking signal SD.

[0051] The control unit 80 receives instructions from the user and controls the blanking signal generating circuit 70 according to the instructions from the user. 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 program by the processor.

[0052] 1.2. Action

[0053] 1.2.1. Release of electron beam

[0054] Figure 2 and Figure 31 is a graph showing the emission current EC of the electron beam released from the electron gun 100. The electron gun 100 can be switched as follows. Figure 2 The continuous emission mode of releasing electron beams at a constant emission current as shown in FIG. Figure 3 In the pulse release mode, the electron beam is emitted in a pulsed state as shown in FIG. In the continuous release mode, the electron beam can be irradiated to the sample with a constant emission current. In the pulse release mode, for example, the electron beam can be irradiated to the sample in a pulsed state with a period of microseconds. The peak intensity of the emission current EC in the pulse release mode, i.e., the current Ip (Ip≠0), is greater than the current value of the emission current EC in the continuous release mode, i.e., the current Ic (Ic≠0).

[0055] 1.2.2. Pulse release mode

[0056] Figure 4 1 is a graph showing a reference pulse signal SAp, an inversion signal SB, a voltage signal SC, an emission current EC0, a blanking signal SD, and an emission current EC in a pulse release mode. The emission current EC0 is an electron current released from the emitter 10, and is an emission current before the electron beam is incident on the blanker 14. The emission current EC is an emission current of the post-stage of the blanker 14. That is, the emission current EC is an emission current of the electron beam released from the electron gun 100.

[0057] In the pulse release mode, the switch circuit 30 switches the supply of the pulse voltage Vp or the reference potential to the other end of the capacitor 50 supplied with the bias voltage Vo based on the reference pulse signal SAp, so that the voltage signal SC applied to the extraction electrode 12 changes in a pulsed manner. As a result, the emission current EC0 changes in a pulsed manner.

[0058] The blanker 14 performs blanking according to the blanking signal SD synchronized with the reference pulse signal SAP to extract a part of the pulse of the emission current EC0. As a result, the electron gun 100 emits an electron beam in a pulsed state.

[0059] Hereinafter, the operation of the electron gun 100 in one cycle C from time t1 to time t5 will be described in detail.

[0060] At time t1, the reference signal generator 20 switches the logic level of the reference pulse signal SAp from a high level to a low level. As a result, the inverter 36 is input with the reference pulse signal SAp of a low level. The reference pulse signal SAp is inverted in its logic level by the inverter 36. Therefore, the first switch 32 is input with the inversion signal SB of a high level. As a result, the first switch 32 is turned on. In addition, the second switch 34 is directly input with the reference pulse signal SAp of a low level. As a result, the second switch 34 is turned off.

[0061] By turning on the first switch 32 and turning off the second switch 34, the 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. On the other hand, since one end of the capacitor 50 is connected to the bias power supply 60 via the resistor 52, the bias voltage Vo is supplied to one end of the capacitor 50. By switching the voltage applied to the other end of the capacitor 50 from the reference potential to the pulse voltage Vp, the voltage value of the voltage signal SC gradually increases from the bias voltage Vo according to the time constant determined by the capacitance of the capacitor 50 and the resistance value of the first switch 32, and is constant at the sum of the bias voltage Vo and the pulse voltage Vp, Vo+Vp.

[0062] For example, when the pulse voltage Vp is set to 1.2 kV and the bias voltage Vo is set to 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.

[0063] In addition, at this time, although the voltage value of the voltage signal SC is ideally constant at Vo+Vp, it will gradually decrease due to the charge accumulated in the capacitor 50 being released via the resistor 52. However, if it is a sufficiently short time compared to 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 will not change significantly, and the voltage value of the voltage signal SC can also be considered 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 sufficiently long time compared to the pulse width of the reference pulse signal SAp.

[0064] By making the voltage value of the voltage signal SC applied to the extraction electrode 12 the sum Vo+Vp, the current value of the emission current EC0 of the electron beam discharged from the emitter 10 becomes the current Ip.

[0065] 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.

[0066] At time t2 after a predetermined time Δt has passed from time t1, the blanking signal generating circuit 70 switches the logic level of the blanking signal SD from a high level to a low level. Furthermore, the blanking signal generating circuit 70 maintains the low level for a constant period P from time t2. Thus, the blanker 14 does not blank the electron beam during the constant period P from time t2. As a result, during the constant period P from time t2, the current value of the emission current EC becomes the current Ip.

[0067] At time t3 after a constant period P has passed from time t2, the blanking signal generating circuit 70 switches the logic level of the blanking signal SD from low level to high level. As a result, the blanker 14 starts blanking the electron beam at time t3. As a result, at time t3, the current value of the emission current EC becomes zero.

[0068] The blanking signal generating circuit 70 includes, for example, a delay circuit for controlling the time Δt and a control circuit for controlling a constant period P corresponding to the pulse width. The time Δt and the constant period P can be set to arbitrary values, and are set based on the instructions of the user received by the control unit 80. For example, by setting the time Δt to be longer than the time from the time t2 to the time when the voltage value of the voltage signal SC stabilizes at Vo+Vp, an electron beam pulse with a stable peak intensity can be obtained. In addition, by setting the constant period P to the microsecond level, an electron beam pulse with a pulse width of the microsecond level can be obtained.

[0069] At time t4, the reference signal generator 20 switches the logic level of the reference pulse signal SAp from a low level to a high level. As a result, the inverter 36 is input with the reference pulse signal SAp of a high level. The reference pulse signal SAp is inverted in its logic level by the inverter 36. Therefore, the first switch 32 is input with the inversion signal SB of a low level. As a result, the first switch 32 is turned off. In addition, the second switch 34 is directly input with the reference pulse signal SAp of a high level. As a result, the second switch 34 is turned on.

[0070] By turning off the first switch 32 and turning on the second switch 34, the other end of the capacitor 50 is supplied with a reference potential. That is, the voltage applied to the other end of the capacitor 50 is switched from the pulse voltage Vp to the reference potential. On the other hand, the bias voltage Vo is supplied to one end of the capacitor 50. By switching the voltage applied to the other end of the capacitor 50 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 the time constant determined by the capacitance of the capacitor 50 and the resistance value of the resistor 52, and is constant at the bias voltage Vo.

[0071] For example, when the pulse voltage Vp is set to 1.2 kV and the bias voltage Vo is set to 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.

[0072] The bias voltage Vo is set so that the emission current EC0 becomes the current Ic. Therefore, by supplying the voltage signal SC of the bias voltage Vo to the extraction electrode 12, the emission current EC0 of the electron beam emitted from the emitter 10 becomes the current Ic.

[0073] At time t5, the reference signal generator 20 switches the logic level of the reference pulse signal SAp from a high level to a low level. As a result, the first switch 32 is input with the high-level inversion signal SB via the inverter 36, and thus the first switch 32 is turned on. In addition, the second switch 34 is directly input with the low-level reference pulse signal SAp, and thus the second switch 34 is turned off.

[0074] By turning on the first switch 32 and turning off the second switch 34, the voltage applied to the other end of the capacitor 50 is switched from the reference potential to the pulse voltage Vp. By switching the voltage applied to the other end of the capacitor 50 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 of the bias voltage Vo and the pulse voltage Vp, Vo+Vp. By making the voltage value of the voltage signal SC the sum Vo+Vp, the current value of the emission current EC0 of the electron beam released from the emitter 10 becomes the current Ip.

[0075] 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, during the period from time t3 to time t5, the blanker 14 blanks the electron beam. As a result, during the period from time t3 to time t5, the current value of the emission current EC becomes zero.

[0076] Time t5 corresponds to time t1, and the electron gun 100 operates from time t1 to time t5 as one cycle C. The electron gun 100 emits one electron beam pulse in one cycle C from time t1 to time t5. By repeating this cycle C, the electron gun 100 emits an electron beam in a pulsed state.

[0077] In addition, 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, in the electron gun 100, electron beam pulses can be released at a desired period. In addition, for example, by changing the duty ratio of the reference pulse signal SAp, the pulse width of the emission current EC0 can be changed.

[0078] In addition, the bias voltage Vo and the pulse voltage Vp can be set to arbitrary values. Therefore, in the electron gun 100, it is possible to emit an electron beam pulse having a desired peak intensity.

[0079] 1.2.3. Continuous release mode

[0080] Figure 5 is a graph showing the reference continuous signal SAc, the inversion signal SB, the voltage signal SC, the emission current EC0, and the emission current EC in the continuous release mode.

[0081] In the continuous release mode, the reference signal generator 20 generates the reference continuous signal SAc as the reference signal SA. In the continuous release mode, the blanker 14 does not operate.

[0082] The reference signal generator 20 continuously outputs the high-level reference continuous signal SAc. Therefore, the first switch 32 is continuously turned off, and the second switch 34 is continuously turned on. As a result, the other end of the capacitor 50 is continuously supplied with the reference potential. Therefore, the voltage value of the voltage signal SC is constant at the bias voltage Vo. As a result, the current value of the emission current EC0 of the electron beam released from the emitter 10 is constant at the current Ic.

[0083] 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.

[0084] 1.3. Effect

[0085] The electron gun 100 includes: an emitter 10; an extraction electrode 12, which extracts an electron beam from the emitter 10; a capacitor 50, one end of which is connected to the extraction electrode 12; a bias power supply 60, which supplies a bias voltage Vo to one end of the capacitor 50 via a resistor 52; a pulse power supply 40, which outputs a pulse voltage Vp; and a switch circuit 30, which switches whether to supply the pulse voltage Vp or the reference potential to the other end of the capacitor 50 based on a reference pulse signal SAp.

[0086] In the electron gun 100, since one end of the capacitor 50 is connected to the bias voltage Vo and the other end of the capacitor 50 is connected to the reference potential, a charge corresponding to the difference between the bias voltage Vo and the reference potential is accumulated in the capacitor 50, and the other end of the capacitor 50 is switched from the reference potential to the pulse voltage Vp based on the reference pulse signal SAp, so that the voltage applied to the extraction electrode 12 can be changed in a pulsed manner. As a result, the emission current EC0 can be changed in a pulsed manner, and the number of electrons contained in one pulse can be increased.

[0087] In addition, 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 bias 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.

[0088] Figure 6 This is a diagram showing a comparative example of a method of emitting an electron beam in a pulsed state.

[0089] For example, in the existing Schottky type electron gun or cold cathode electric field release type electron gun, Figure 6 As shown, by making the emission current EC0 of the electron beam released from the emitter 10 constant at the current Ip and blanking the electron beam by the blanker 14, a pulsed electron beam with a peak intensity of the current Ip can be released. By increasing the emission current using a Schottky type electron gun or a cold cathode electric field release type electron gun, the number of electrons contained in one pulse can be increased.

[0090] However, when the electron beam emission current EC0 is made constant at the current Ip, the electron beam with a large emission current is irradiated to the electrode etc. for a long time, so the amount of gas released by the electron beam irradiating the electrode etc. increases. Furthermore, when the emission current is increased, a large current flows through the tip of the emitter, so the temperature of the emitter itself rises, the shape of the tip of the emitter changes, etc.

[0091] In contrast, in the electron gun 100, if Figure 4 As shown in FIG. 1 , the emission current EC0 of the electron beam released from the emitter 10 is changed in a pulsed manner by taking the current Ip as the peak current value. Therefore, for example, Figure 6 Compared with the case where the current value of the emission current EC0 is made constant at the current Ip shown in the figure, the time during which the electron beam is irradiated to the electrode, etc. can be shortened, thereby reducing the amount of gas released due to the electron beam being irradiated to the electrode, etc. In addition, in the electron gun 100, the time during which a large current flows through the tip of the emitter 10 can be shortened, thereby reducing the temperature rise of the emitter itself and the change in the shape of the tip of the emitter. For example, by making Figure 4 The duty cycle of the reference pulse signal SAP shown in the figure becomes smaller, and the pulse width of the emission current EC0 can be reduced. As a result, the time for the electron beam to be irradiated to the electrode etc. can be shortened. In addition, the time for a large current to flow through the tip of the emitter 10 can be shortened.

[0092] In the electron gun 100, for example, the extraction voltage required to obtain the desired emission current, that is, the voltage value of the voltage signal SC, may increase due to degradation of the emitter 10. Even in this case, the electron gun 100 can easily obtain the desired emission current EC0 by increasing the bias voltage Vo and superimposing the pulse voltage Vp.

[0093] The electron gun 100 includes a blanker 14 for blanking the electron beam. The blanker 14 blanks the electron beam according to a blanking signal SD synchronized with the reference pulse signal SAP. Therefore, when the emission current EC0 increases in the electron gun 100, the electron beam can be taken out 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.

[0094] The electron gun 100 includes a blanking signal generating circuit 70 that generates a blanking signal SD. In addition, 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. In addition, 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. In addition, the blanking signal generating circuit 70 switches the blanking signal SD from a high level to a low level after a predetermined time Δt has passed since the logic level of the reference pulse signal SAp is switched from a high level to a low level, and maintains the low level for a constant period P.

[0095] Therefore, in the electron gun 100, when the emission current EC0 that changes in a pulse shape increases, the electron beam can be taken out by blanking to obtain an electron beam pulse. Therefore, in the electron gun 100, the number of electrons included in one pulse can be increased.

[0096] In addition, the above-mentioned logic level is an example and is not limited to this. The switch circuit 30 supplies the pulse voltage Vp during the period when the reference pulse signal SAp is at the first logic level, and supplies the reference potential during the period when the reference pulse signal SAp is at the second logic level. In addition, the blanker 14 blanks the electron beam during the period when the blanking signal SD is at the third logic level, and does not blank the electron beam during the period when the blanking signal SD is at the fourth logic level. In addition, 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 constant for a period P after a predetermined time Δt has passed since the logic level of the reference pulse signal SAp is switched from the second logic level to the first logic level. At this time, as long as the first logic level and the second logic level are different logic levels, the third logic level and the fourth logic level are different logic levels.

[0097] In the electron gun 100, the blanking signal generating circuit 70 sets the predetermined time Δt and the constant period P to the time specified by the user. Therefore, in the electron gun 100, the blanker 14 can be used to extract an electron beam pulse of a desired pulse width at a desired timing from the electron beam whose emission current EC0 changes in a pulsed manner.

[0098] In addition, in the above-mentioned embodiment, the blanking signal generating circuit 70 sets the prescribed time Δt and the constant period P to the time specified by the user, but the blanking signal generating circuit 70 may set at least one of the prescribed time Δt and the constant period P to the time specified by the user.

[0099] 2. Second Implementation Method

[0100] 2.1. Electron gun

[0101] Next, an electron gun according to a second embodiment will be described with reference to the drawings. Figure 7 1 is a diagram showing the structure of an electron gun 200 according to the second embodiment. In the electron gun 200 according to the second embodiment, components having the same functions as those of the components of the electron gun 100 according to the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

[0102] In the above-mentioned electron gun 100, if Figure 4 As shown, the electron beam is pulsed out from the electron beam emitted from the emitter 10 by using the blanker 14, and the electron beam is emitted in a pulsed state.

[0103] In contrast, in the electron gun 200, the blanker 14 is not used, and the electron beam is emitted from the emitter 10 in a pulsed state. Figure 7 As shown, the electron gun 200 does not include the blanker 14 and the blanking signal generating circuit 70 .

[0104] 2.2. Action

[0105] 2.2.1. Release of electron beam

[0106] Figure 8 2 is a graph showing the emission current EC of the electron beam released from the electron gun 200. The electron gun 200 can be switched as follows. Figure 2 The continuous release mode of releasing an electron beam with a constant current Ic as shown in FIG. Figure 8 As shown in the figure, the pulse emission mode emits an electron beam in a pulsed state at a constant period.

[0107] 2.2.2. Pulse release mode

[0108] Fig. 9 : is a graph showing the reference pulse signal SAp, the inversion signal SB, the voltage signal SC, the emission current EC0, and the emission current EC in the pulse release mode.

[0109] In the pulse release mode, the switch circuit 30 switches whether to supply a pulse voltage Vp or a reference potential to the other end of the capacitor 50 to which the bias voltage Vo is supplied based on the reference pulse signal SAp, so that the voltage signal SC changes in a pulsed manner. As a result, the emission current EC0 changes in a pulsed manner. Therefore, the electron gun 200 releases an electron beam in a pulsed manner.

[0110] Hereinafter, the operation of the electron gun 200 in one cycle C from time t10 to time t12 will be described.

[0111] At time t10, the reference signal generator 20 switches the logic level of the reference pulse signal SAp from a high level to a low level. As a result, the first switch 32 is input with the high-level inversion signal SB via the inverter 36, and thus the first switch 32 is turned on. In addition, the second switch 34 is directly input with the low-level reference pulse signal SAp, and thus the second switch 34 is turned off.

[0112] By turning on the first switch 32 and turning off the second switch 34, the voltage applied to the other end of the capacitor 50 is switched from the reference potential to the pulse voltage Vp. By switching the voltage applied to the other end of the capacitor 50 from the reference potential to the pulse voltage Vp, the voltage value of the voltage signal SC gradually increases from the bias 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 is constant at the sum of the bias voltage Vo and the pulse voltage Vp, Vo+Vp. By making the voltage value of the voltage signal SC the sum Vo+Vp, the current value of the emission current EC0 becomes the current Ip.

[0113] Since the electron gun 200 does not have the blanker 14, the electron beam discharged from the emitter 10 is directly discharged from the electron gun 200. Therefore, the emission current EC is equal to the emission current EC0.

[0114] At time t11, the reference signal generator 20 switches the logic level of the reference pulse signal SAp from a low level to a high level. As a result, the first switch 32 is input with the low-level inversion signal SB via the inverter 36, and thus the first switch 32 is turned off. In addition, the second switch 34 is directly input with the high-level reference pulse signal SAp, and thus the second switch 34 is turned on.

[0115] By turning off the first switch 32 and turning on the second switch 34, the other end of the capacitor 50 is supplied with a reference potential. That is, the voltage applied to the other end of the capacitor 50 is switched from the pulse voltage Vp to the reference potential. On the other hand, the bias voltage Vo is supplied to one end of the capacitor 50. By switching the voltage applied to the other end of the capacitor 50 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 is constant at the bias voltage Vo.

[0116] Here, in the electron gun 100 described above, the bias voltage Vo is set to a voltage value that makes the current value of the emission current EC0 equal to the voltage value of the current Ic. In contrast, in the electron gun 200, the bias voltage Vo is set to a voltage value lower than the voltage required to release the electron beam from the emitter 10. Therefore, by supplying the voltage signal SC having the voltage value of the bias voltage Vo to the extraction electrode 12, the current value of the emission current EC0 becomes zero.

[0117] At time t12, the reference signal generator 20 switches the logic level of the reference pulse signal SAp from a high level to a low level. As a result, the first switch 32 is input with the high-level inversion signal SB via the inverter 36, and thus the first switch 32 is turned on. In addition, the second switch 34 is directly input with the low-level reference pulse signal SAp, and thus the second switch 34 is turned off.

[0118] By turning on the first switch 32 and turning off the second switch 34, the voltage applied to the other end of the capacitor 50 is switched from the reference potential to the pulse voltage Vp. By switching the voltage applied to the other end of the capacitor 50 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 of the bias voltage Vo and the pulse voltage Vp, Vo+Vp. By making the voltage value of the voltage signal SC the sum Vo+Vp, the current value of the emission current EC0 becomes the current Ip.

[0119] Time t12 corresponds to time t10, and the electron gun 200 operates from time t10 to time t12 as one cycle C. The electron gun 200 emits one electron beam pulse in one cycle C from time t10 to time t12. By repeating this cycle C, the electron gun 200 emits an electron beam in a pulsed state.

[0120] 2.2.3. Continuous release mode

[0121] The operation of the electron gun 200 in the continuous release mode is the same as that described above. Figure 5 The operation of the electron gun 100 in the continuous emission mode shown is the same, and the description thereof is omitted.

[0122] 2.3. Effect

[0123] The electron gun 200 includes: an emitter 10; an extraction electrode 12, which extracts an electron beam from the emitter 10; a capacitor 50, one end of which is connected to the extraction electrode 12; a bias power supply 60, which supplies a bias voltage Vo to one end of the capacitor 50 via a resistor 52; a pulse power supply 40, which outputs a pulse voltage Vp; and a switch circuit 30, which switches whether to supply the pulse voltage Vp or the reference potential to the other end of the capacitor 50 based on a reference pulse signal SAp.

[0124] Therefore, the electron gun 200 can increase the number of electrons contained in one electron beam pulse, similarly to the electron gun 100. Moreover, the electron gun 200 can reduce the amount of gas released when the electron beam is irradiated to the electrode, etc., similarly to the electron gun 100. Moreover, the electron gun 200 can reduce the temperature rise of the emitter itself and the change in the shape of the tip of the emitter, similarly to the electron gun 100.

[0125] 2.4. Modifications

[0126] Fig.10 : is a graph showing the reference pulse signal SAp, the reverse signal SB, the voltage signal SC, the emission current EC0, and the emission current EC in a modification of the pulse release mode.

[0127] In the second embodiment described above, the bias voltage Vo is set to a voltage value lower than the voltage required to emit electrons from the emitter 10. Therefore, in the electron gun 200, when the voltage value of the voltage signal SC is the bias voltage Vo, the current value of the emission current EC0 is zero. Fig. 9 In the example shown, the electron gun 200 emits an electron beam that periodically repeats irradiation and non-irradiation.

[0128] In contrast, the bias voltage Vo may be a voltage that causes the emitter 10 to emit an electron beam with an emission current of current Id (Id≠0). Thus, when the voltage signal SC becomes the bias voltage Vo, the current value of the emission current EC0 becomes current Id instead of zero.

[0129] As a result, the electron gun 200 can emit an electron beam that repeats strong and weak periods of time.

[0130] 3. Third Implementation Method

[0131] Next, an electron microscope according to a third embodiment will be described. Fig.11 It is a diagram showing the structure of an electron microscope 300 according to the third embodiment.

[0132] like Fig.11 As shown, the electron microscope 300 includes the electron gun 100 . In addition, although the case where the electron microscope 300 includes the electron gun 100 is described here, the electron microscope 300 may include the electron gun 200 .

[0133] like Fig.11 As shown, the electron microscope 300 includes the 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 an imaging device 320 .

[0134] The electron gun 100 emits an electron beam. The electron gun 100 can be switched as follows: Figure 2 The continuous emission mode of releasing electron beams at a constant emission current as shown in FIG. Figure 3 Therefore, in the electron microscope 300 , it is possible to irradiate the sample S with an electron beam having a constant emission current or irradiate the sample S with a pulsed electron beam.

[0135] The irradiation optical system 302 includes a plurality of lenses for irradiating the sample S with electron beams. The irradiation optical system 302 converges the electron beams and irradiates the sample S. The irradiation optical system 302 may include an aperture, a deflector, etc. in addition to the plurality of lenses. In addition, the blanker 14 may be integrated into the irradiation optical system 302 .

[0136] The sample stage 304 holds the sample S. The sample stage 304 includes a moving mechanism for moving the sample S horizontally or vertically and a tilting mechanism for tilting the sample S. By moving the sample S using the sample stage 304 , the field of view of the transmission electron microscope image (TEM image) can be moved.

[0137] The objective lens 306 forms a TEM image using 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.

[0138] The imaging device 320 captures a TEM image formed by the imaging optical system. The imaging device 320 is, for example, a CCD (Charge Coupled Device) camera, a CMOS (Complementary metal-oxide-semiconductor) camera, or the like.

[0139] In the electron microscope 300, the electron beam emitted from the electron gun 100 can be focused by the irradiation optical system 302 to form an electron probe, and the electron beam can be deflected by a deflector (not shown) to scan the sample S with the electron probe, and a scanning transmission electron microscope image (STEM image) can be obtained by detecting electrons transmitted through the sample S. That is, the electron microscope 300 also functions as a scanning transmission electron microscope.

[0140] In the above description, the electron gun 100 is applied to a transmission electron microscope, but the electron gun 100 can also be applied to other charged particle beam devices. Examples of such charged particle beam devices include scanning electron microscopes, electron probe microanalyzers, Auger microprobes, and electron beam imaging devices.

[0141] 4. Modifications

[0142] In addition, the present invention is not limited to the above-mentioned embodiment, and various modifications can be made within the scope of the gist of the present invention.

[0143] For example, in the first and second embodiments described above, the charged particle gun of the present invention is an electron gun that emits an electron beam, but the charged particle gun of the present invention may also be a charged particle gun that emits a charged particle beam (such as an ion beam) other than an electron beam. Figure 1 The polarity of the emitter 10 and the extraction electrode 12 shown enables an ion gun to be implemented that releases an ion beam.

[0144] In the third embodiment described above, the charged particle beam device of the present invention is described as an electron microscope having an electron gun 100, but the charged particle beam device of the present invention may also be a charged particle beam device having an ion gun. As such a charged particle beam device, for example, a focused ion beam device can be cited.

[0145] The present invention is not limited to the above-mentioned embodiments, and various modifications can be further made. For example, the present invention includes a configuration that is substantially the same as the configuration described in the embodiment. The so-called substantially the same configuration refers to, for example, a configuration with the same function, method and result, or a configuration with the same purpose and effect. In addition, the present invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that has the same effect as the configuration described in the embodiment, or a configuration that can achieve the same purpose. In addition, the present invention includes a configuration in which a known technology is added to the configuration described in the embodiment.

Claims

1. A charged particle gun that releases a charged particle beam, characterized in that: Include: Transmitter; an extraction electrode that extracts the charged particle beam from the emitter; A capacitor, one end of which is connected to the lead-out electrode; a first power source that supplies a first voltage to the one end of the capacitor via a resistor; a second power supply which outputs a second voltage; as well as The switch circuit switches whether to supply the second voltage or the reference potential to the other end of the capacitor based on the reference pulse signal.

2. The charged particle gun according to claim 1, wherein: comprising a blanker for performing blanking of the charged particle beam, The blanker performs blanking of the charged particle beam according to a blanking signal synchronized with the reference pulse signal.

3. The charged particle gun according to claim 2, wherein: comprising 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 in which the blanking signal is at a third logic level, and does not blank the charged particle beam during a period in which the blanking signal is at a fourth logic level. The blanking signal generating circuit switches the blanking signal from the third logic level to the fourth logic level and maintains the fourth logic level for a constant period after a predetermined time has passed since the logic level of the reference pulse signal was switched from the second logic level to the first logic level.

4. The charged particle gun according to claim 3, wherein: The blanking signal generating circuit sets at least one of the predetermined time and the constant period to a time specified by a user.

5. The charged particle gun according to claim 1, wherein: The switch circuit changes the emission current of the charged particle beam emitted from the emitter in a pulsed manner by switching whether to supply the second voltage or the reference potential to the other end of the capacitor based on the reference pulse signal.

6. The charged particle gun according to claim 1, wherein: The first voltage is set to a voltage value lower than a voltage required to release a charged particle beam from the emitter.

7. A charged particle beam device, characterized in that: A charged particle gun comprising the charged particle gun according to any one of claims 1 to 6.

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