Charged particle beam device

Abstract

A charged particle beam device according to the present disclosure comprises: a high-voltage power supply; a charged particle source; one or more cables that electrically connect the high-voltage power supply and the charged particle source; and one or more current sensors that are installed on the cable and are capable of detecting a high-frequency component of a current due to discharge.

Description

charged particle beam equipment

[0001] The present disclosure relates to a charged particle beam device.

[0002] Charged particle beam devices have high-voltage locations, such as cables, electron guns, and ion sources, where discharges can occur. In particular, in scanning electron microscopes, which require highly accurate beam irradiation, minute discharges (partial discharges) can cause the voltage controlling the beam to fluctuate, potentially resulting in performance degradation. Furthermore, continuous partial discharges can lead to insulation breakdown due to deterioration and charging of insulators. Therefore, it is necessary to detect partial discharges occurring in high-voltage locations and determine their locations.

[0003] The abstract of Patent Document 1 states, "A charged particle beam device capable of accurately detecting abnormal discharge in a charged particle source is provided. The charged particle beam device includes a charged particle source 12, an acceleration voltage source 3 that applies an acceleration voltage to the charged particle source 12, a transformer 30 having a gap G in a core C and a primary winding connected between the acceleration voltage source 3 and the charged particle source 12, a primary current detection circuit that detects the current flowing in the primary winding N1 based on the current flowing in or voltage generated by a secondary winding N2 of the transformer, and a discharge detection circuit that detects discharge based on the output of the primary current detection circuit." This makes it possible to detect the current when a breakdown occurs and shut down the device.

[0004] The abstract of Patent Document 2 states, "In a charged particle beam device, the position where a discharge has occurred is detected with a simple configuration. The charged particle beam system includes a charged particle beam device 101 and a detection circuit 114. The charged particle beam device 101 has a first antenna 102 having a first resonant frequency and a second antenna 103 having a second resonant frequency. The detection circuit 114 has a first amplitude detection unit 110 that detects a first amplitude of a signal after passing through a first filter 107, a second amplitude detection unit 111 that detects a second amplitude of the signal after passing through a second filter 108, and an amplitude comparison unit 113 that compares the first amplitude with the second amplitude."

[0005] JP 2010-232129 A JP 2020-47476 A

[0006] However, while the purpose of Patent Document 1 is to detect dielectric breakdown and it is an effective detection method for large currents, it is thought that it has low sensitivity to minute discharges such as partial discharges.

[0007] The technique of Patent Document 2 can detect discharges occurring inside the housing, such as in the electron gun, but it is difficult to detect partial discharges occurring in cables, power supplies, and the like.

[0008] Therefore, the present disclosure provides a technique capable of detecting discharge at a location where a high voltage is applied in a charged particle beam device.

[0009] In order to solve the above problems, the charged particle beam device disclosed herein is characterized by comprising a high-voltage power supply, a charged particle source, one or more cables electrically connecting the high-voltage power supply and the charged particle source, and one or more current sensors installed on the cables and capable of detecting high-frequency components of current due to discharge.

[0010] Further features related to the present disclosure will become apparent from the description of this specification and the accompanying drawings. Also, aspects of the present disclosure are achieved and realized by the elements and combinations of various elements and the aspects of the following detailed description and the appended claims. The description of this specification is merely exemplary and does not limit the scope or application of the claims of the present disclosure in any way.

[0011] According to the technique of the present disclosure, it is possible to detect discharge at a location where a high voltage is applied in a charged particle beam device. Problems, configurations, and effects other than those described above will become clear from the description of the following embodiments.

[0012] Fig. 1 is a schematic diagram showing a partial configuration of a charged particle beam device according to a first embodiment; Fig. 2 is a schematic diagram showing an overall configuration of a charged particle beam device according to the first embodiment; Fig. 3 is a schematic diagram showing a partial configuration of a charged particle beam device according to a second embodiment; Fig. 4 is a flowchart showing a method for determining a discharge position according to the second embodiment; Fig. 5 is a schematic diagram showing a partial configuration of a charged particle beam device according to a third embodiment; Fig. 6 is a flowchart showing a method for determining a discharge position according to the third embodiment.

[0013] First Embodiment <Configuration Example of Charged Particle Beam Device> Fig. 1 is a schematic diagram showing the configuration of a portion of a charged particle beam device 1000 according to a first embodiment. The charged particle beam device 1000 includes a high-voltage power supply 1, a current sensor 10, a cable 20, and an electron gun 30 (charged particle source). The electron gun 30 and the high-voltage power supply 1 are electrically connected via the cable 20. The high-voltage power supply 1 includes an acceleration power supply 2 and an extraction power supply 3. The electron gun 30 includes an electron source 31 and an extraction electrode 32. A DC voltage is supplied to the electron source 31 from the acceleration power supply 2. A DC voltage is supplied to the extraction electrode 32 from the extraction power supply 3. If power for a suppressor electrode, a heater, or the like is required depending on the structure of the electron gun 30, the power may be supplied from the high-voltage power supply 1 in the same manner, or from a separate, independent power supply.

[0014] The current sensor 10 is installed in the cable 20. The current sensor 10 can be one that can detect only high-frequency components of 1 kHz or more, which are the main components of partial discharge, excluding the DC current component. An example of such a current sensor is a high-frequency CT.

[0015] When a partial discharge occurs, regardless of the location of the occurrence, such as the high-voltage power supply 1, the cable 20, or the electron gun 30, a high-frequency component associated with the partial discharge flows in the cable 20 superimposed on the DC current. The current sensor 10 installed in the cable 20 detects this high-frequency component, thereby detecting the partial discharge.

[0016] The cable 20 may be, for example, a single-core cable, a coaxial cable, or a multi-core cable. A coaxial cable has a center conductor to which a high voltage is applied and a shield wire connected to ground. Using such a coaxial cable reduces the risk of discharge due to high voltage and avoids the risk of discharge near the current sensor 10.

[0017] FIG. 2 is a schematic diagram showing the overall configuration of a charged particle beam device 1000 according to the first embodiment. The charged particle beam device 1000 further includes a housing 40, an ion pump 50, a recording unit 90, a control device 80, and a signal processing unit 100. The housing 40 contains a focusing lens 33, a scanning coil 34, an objective lens 35, and a stage 36. The focusing lens 33 focuses the electron beam emitted from the electron source 31 to reduce the diameter of the electron beam. The scanning coil 34 scans the electron beam. When a coil current is applied to the objective lens 35, the objective lens 35 focuses the electron beam to form an electron beam with a diameter of approximately several nanometers, which is then irradiated onto a sample S placed on a stage 36. The electron beam moves over the sample S due to a voltage applied to the scanning coil 34. The ion pump 50 evacuates the housing 40. Although only one ion pump 50 is shown, multiple ion pumps 50 may be provided.

[0018] Although the connection lines are not shown, the stage 36 and the ion pump 50 are each connected to the high-voltage power supply 1 by cables (not shown), and a high voltage is applied to them. Current sensors 10 are also installed on the cable connecting the high-voltage power supply 1 and the stage 36, and on the cable connecting the high-voltage power supply 1 and the ion pump 50.

[0019] The control device 80 can be configured, for example, by a computer system. The computer system includes a processor, a memory, a storage device, an input device, a display device, etc. The control device 80 performs processing to control the entire charged particle beam device 1000 and each part thereof in accordance with instructions input by a user via a GUI screen or the like displayed on a display device (not shown). Specifically, the control device 80 controls the operations of the high-voltage power supply 1, the focusing lens 33, the scanning coil 34, and the objective lens 35. The control device 80 also performs processing related to measurement and inspection of the sample S.

[0020] The signal processing unit 100 can be configured with, for example, any processor. The signal processing unit 100 receives an input of a detection signal from the current sensor 10 and processes the detection signal. The signal processing unit 100 analyzes the amplitude, frequency, frequency, detection time, and position of partial discharge from the detection signal of the current sensor 10, and stores the results in the recording unit 90. If the amplitude of partial discharge is equal to or greater than a predetermined value and there is a risk of affecting the accuracy of measurement and inspection or of insulation breakdown, the signal processing unit 100 feeds back a warning to the control device 80. When the control device 80 receives the warning feedback from the signal processing unit 100, it can take measures such as displaying an alert on a display device or shutting down the high-voltage power supply 1.

[0021] The recording unit 90 can be configured by a storage device such as a memory, an internal storage, an external storage, etc. When a signal having a predetermined value or more is input to the signal processing unit 100, the recording unit 90 stores the partial discharge signal as log data.

[0022] If the amplitude, frequency, frequency, detection time, etc. of partial discharges are characteristic depending on the location where the partial discharge occurs, a previously acquired discharge pattern can be stored as a database in the recording unit 90. In this case, the signal processing unit 100 can detect the discharge location by comparing the input signal with the database and the applied voltage sequence. For example, if the partial discharge value detected by the current sensor 10 increases when the output voltage of the extraction power supply 3 is increased, it can be determined that the partial discharge occurred at the high-voltage power supply 1. If the partial discharge value detected by the current sensor 10 increases when the voltage on the electron gun 30 side is increased, it can be determined that the partial discharge occurred at the electron gun 30. If the partial discharge continues to occur, it can be determined that a discharge is occurring in space. If the partial discharge stops immediately, it can be determined that the discharge is due to charging of an insulator.

[0023] Although the control device 80 and the signal processing unit 100 are configured separately, the functions of the signal processing unit 100 may be executed by a processor or the like of the control device 80. The recording unit 90 may also be built into the control device 80 or the signal processing unit 100.

[0024] Summary of First Embodiment As described above, the charged particle beam device 1000 according to the first embodiment includes the high-voltage power supply 1, the electron gun 30 (charged particle source), one or more cables 20 that electrically connect the high-voltage power supply 1 and the electron gun 30, and one or more current sensors 10 that are installed on the cable 20 and can detect high-frequency components of a current due to a discharge. With this configuration, it is possible to detect a partial discharge that occurs in the high-voltage power supply 1, the electron gun 30, or the cable 20.

[0025] Second Embodiment In the first embodiment, it has been described that partial discharges can be detected and their locations determined by installing one current sensor 10 in the cable 20. In the second embodiment, a case will be described in which multiple (two) current sensors are installed.

[0026] 3 is a schematic diagram showing a partial configuration of a charged particle beam device 2000 according to the second embodiment. As shown in FIG. 3, in the second embodiment, two current sensors 10, a first current sensor 11 and a second current sensor 12, are installed on a cable 20. The first current sensor 11 is installed on the high-voltage power supply 1 side. The second current sensor 12 is installed on the electron gun 30 side. The other configuration of the charged particle beam device 2000 according to the second embodiment is similar to that of the charged particle beam device 1000 according to the first embodiment.

[0027] The first current sensor 11 may be built into the high-voltage power supply 1. The second current sensor 12 may be built into the electron gun 30. By building in at least one of the multiple current sensors in this way, the size of the device can be reduced. Also, if a multi-core cable is used as the cable 20, it is difficult to provide a current sensor for each line. In such cases, building in the current sensors makes installation easier.

[0028] When a partial discharge occurs, the signal processing unit 100 can determine the position of the discharge by comparing the times at which the signals of the first current sensor 11 and the second current sensor 12 are detected.

[0029] 4 is a flowchart showing a method for determining a discharge position according to the second embodiment. In step S101, when a partial discharge occurs, the signal processing unit 100 acquires signals detected by the first current sensor 11 and the second current sensor 12. In step S102, the signal processing unit 100 calculates the arrival time T １ is calculated from the signal waveform of the second current sensor 12, and the arrival time T ２ Calculate.

[0030] In step S103, the signal processing unit 100 calculates the arrival time T １ and T ２ and the threshold T ｔｈ Compare with the threshold T ｔｈ is set by referring to experimental values. １ and T ２ The time difference is the threshold T ｔｈ In the following cases, the process proceeds to step S105: In step S105, the signal processing unit 100 determines that the discharge position is inside the cable 20, and stores the determination result in the recording unit 90.

[0031] Arrival time T １ and T ２ The time difference is the threshold T ｔｈ If the arrival time T １ and arrival time T ２ The arrival time T ２ The arrival time T １ If it is greater, the process proceeds to step S106. In step S106, the signal processing unit 100 determines that the discharge position is at the high voltage power supply 1, and stores the determination result in the recording unit 90.

[0032] Arrival time T １ The arrival time T ２If it is greater, the process proceeds to step S107. In step S107, the signal processing unit 100 determines that the discharge position is the electron gun 30, and stores the determination result in the recording unit 90.

[0033] Summary of Second Embodiment As described above, the charged particle beam device 2000 according to the second embodiment includes two current sensors: the first current sensor 11 and the second current sensor 12. The signal processing unit 100 determines the location of a partial discharge based on the arrival times of signals due to discharge detected by the two current sensors. In this way, the location of the discharge can be identified.

[0034] Third Embodiment In the first and second embodiments, the high-voltage power supply 1 and the electron gun 30 are connected by one cable 20. In the third embodiment, a case where multiple (two) cables are used will be described.

[0035] 5 is a schematic diagram showing a partial configuration of a charged particle beam device 3000 according to the third embodiment. As shown in FIG. 5 , in the third embodiment, two cables, a first cable 21 and a second cable 22, are connected to the high-voltage power supply 1 and the electron gun 30. A first current sensor 11 is provided for the first cable 21. A second current sensor 12 is provided for the second cable 22. Although the number of cables is two in FIG. 5 , the number varies depending on the number of electrodes of the electron gun 30 and the high-voltage power supply 1. The number of current sensors also varies depending on the number of cables. The other configuration of the charged particle beam device 3000 according to the third embodiment is similar to that of the charged particle beam device 1000 according to the first embodiment.

[0036] When a partial discharge occurs, the signal processing unit 100 can determine the position of the discharge based on the amplitude of the signals from the first current sensor 11 and the second current sensor 12 .

[0037] 6 is a flowchart showing a method for determining a discharge position according to the third embodiment. In step S201, when a partial discharge occurs, the signal processing unit 100 acquires signals detected by the first current sensor 11 and the second current sensor 12. In step S202, the signal processing unit 100 calculates an amplitude A from the signal waveform of the first current sensor 11. １ and calculates the amplitude A from the signal waveform of the second current sensor 12. ２ Calculate.

[0038] In step S203, the signal processing unit 100 calculates the amplitude A １ and A ２ Among them, the maximum value A ｍａｘ In step S204, the signal processing unit 100 acquires the amplitude A １ and A ２ α・A ｍａｘ Compared with α・A ｍａｘ The larger signal is extracted. α represents the variation in amplitude between the first cable 21 and the second cable 22, and is set with reference to experimental values.

[0039] In step S205, the signal processing unit 100 calculates α·A ｍａｘ The cable of the larger signal source is determined as the discharge location and stored in the recording unit 90. Specifically, １ The value of α・A ｍａｘ If the amplitude A is greater than the amplitude A, it is determined that a partial discharge has occurred in the first cable 21 in which the first current sensor 11 is installed. ２ The value of α・A ｍａｘ If the amplitude A is greater than the amplitude A, it is determined that a partial discharge has occurred in the second cable 22 in which the second current sensor 12 is installed. １ and A ２ Both values ​​of α・A ｍａｘ If it is greater than this, it is determined that a partial discharge has occurred between the first cable 21 and the second cable 22.

[0040] Summary of Third Embodiment As described above, in the charged particle beam device 3000 according to the third embodiment, the high-voltage power supply 1 and the electron gun 30 are connected by two cables: the first cable 21 and the second cable 22. The first current sensor 11 is installed on the first cable 21, and the second current sensor 12 is installed on the second cable 22. The signal processing unit 100 determines the location of a partial discharge based on the amplitude of the signals due to the discharge detected by the two current sensors. In this way, the location of the discharge can be identified.

[0041] [Modifications] The present disclosure is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present disclosure, and it is not necessary to include all of the described configurations. Furthermore, a part of one embodiment can be replaced with a configuration of another embodiment. Furthermore, a configuration of another embodiment can be added to a configuration of one embodiment. Furthermore, a part of the configuration of each embodiment can be added to, deleted from, or substituted for a part of the configuration of another embodiment.

[0042] REFERENCE SIGNS LIST 1 High voltage power supply 2 Acceleration power supply 3 Extraction power supply 10 Current sensor 11 First current sensor 12 Second current sensor 20 Cable 21 First cable 22 Second cable 30 Electron gun 31 Electron source 32 Extraction electrode 33 Focusing lens 34 Scanning coil 35 Objective lens 36 Stage 40 Housing 50 Ion pump 80 Control device 90 Recording unit 100 Signal processing unit S Sample

Claims

1. A charged particle beam device, comprising: a high-voltage power supply; a charged particle source; one or more cables electrically connecting the high-voltage power supply and the charged particle source; and one or more current sensors installed in the cable and capable of detecting a high-frequency component of a current due to discharge.

2. The charged particle beam device according to claim 1, further comprising a processor that processes a signal output from the current sensor, wherein the processor outputs a warning when an amplitude of the signal is equal to or greater than a predetermined value.

3. The charged particle beam device according to claim 2, further comprising a recording unit that stores the signal processed by the processor, wherein a database of patterns of the signal corresponding to positions where the discharge has occurred, acquired in advance, is stored in the recording unit, and the processor compares a signal newly output from the current sensor with the database to determine a position where the discharge has occurred.

4. The charged particle beam device according to claim 1, wherein the cable is a coaxial cable having a central conductor to which a high voltage is applied and a shield wire connected to ground.

5. The charged particle beam device according to claim 1, wherein the one or more current sensors include a first current sensor and a second current sensor, the first current sensor is installed on the high-voltage power supply side of the cable, and the second current sensor is installed on the charged particle source side of the cable.

6. The charged particle beam device according to claim 5, further comprising a processor that processes signals output from the first current sensor and the second current sensor, wherein the processor determines a position where the discharge has occurred based on a difference between arrival times of signals from the first current sensor and the second current sensor.

7. The charged particle beam device according to claim 5, wherein the first current sensor is built in the high-voltage power supply.

8. The charged particle beam device according to claim 5, wherein the second current sensor is installed inside the charged particle source.

9. The charged particle beam device according to claim 1, wherein the one or more cables include a plurality of cables electrically connected to each electrode of the charged particle source, the one or more current sensors include a plurality of current sensors, and the plurality of current sensors are each installed in one of the plurality of cables. A charged particle beam device characterized by this.

10. The charged particle beam device according to claim 9, further comprising a processor that processes signals output from the plurality of current sensors, wherein the processor determines the position where the discharge has occurred based on the amplitudes of the signals of the plurality of current sensors. A charged particle beam device characterized by this.

11. The charged particle beam device according to claim 1, wherein the cable is a multi-core cable including a plurality of conductors and an insulating coating for each conductor, and the plurality of conductors are connected to each electrode of the charged particle source. A charged particle beam device characterized by this.

12. The charged particle beam device according to claim 1, further comprising an ion pump connected in the housing of the charged particle source, wherein the cable includes a plurality of cables electrically connected to a high voltage power source that drives the ion pump, and the current sensor is installed in each of the plurality of cables. A charged particle beam device characterized by this.

Images