Charged particle beam apparatus

Abstract

The purpose of the present invention is to provide a charged particle beam device that: has an electrode short-circuit mechanism with which a change in lens action that occurs between accelerating electrodes during a change in an acceleration voltage can be suppressed; and is capable of operating with the acceleration voltage applied as-is to the electrode short-circuit mechanism. The charged particle beam device according to the present invention controls the potential difference between a short electrode and a first multi-stage accelerating electrode to the extent that discharge does not occur with the acceleration voltage applied as-is to a first accelerating electrode, and connects the first multi-stage accelerating electrode and the short electrode which are at the potential difference.

Description

Technical Field

[0001] The present invention relates to an electrode short - circuit mechanism provided in a charged particle beam device.

Background Art

[0002] The electron gun mounted on an electron microscope is provided with an acceleration electrode that gives a predetermined energy (hereinafter described as acceleration voltage) to electrons generated from an electron source. In a device with a high acceleration voltage to be applied (for example, an acceleration voltage of 200 kV or more), energy is given to electrons step - by - step by a plurality of multi - stage acceleration electrodes arranged via voltage - dividing resistors.

[0003] In an electron gun, when the acceleration voltage is changed, the lens action generated between the multi - stage acceleration electrodes changes. In particular, when the acceleration voltage is set low, the lens action becomes weak, so the aberration coefficient generated in the electron gun tends to increase, which is a factor degrading the performance of the electron microscope.

[0004] Patent Document 1 describes a method of short - circuiting any one of the multi - stage acceleration electrodes according to the acceleration voltage to be set in order to suppress the change in the lens action when the acceleration voltage is changed.

[0005] Patent Document 2 describes a method of suppressing the change in the lens action when the acceleration voltage is changed by adding a new control power supply under the acceleration voltage potential and using this to change the potential of the multi - stage acceleration electrodes.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] In the electron microscope described in Patent Document 1, when operating the step switching switch during acceleration voltage change, the application of the acceleration voltage must be stopped. When the application of the acceleration voltage is stopped, it takes a certain amount of time until the acceleration voltage is applied again and the electron gun operates stably. In particular, in the case of a Schottky type electron gun, since it is necessary to lower the heating temperature of the electron source in conjunction with the stop operation, the time required until the electron gun operates stably becomes even longer.

[0008] Patent Document 2 describes a method for suppressing a change in the lens action between acceleration electrodes that occurs during acceleration voltage change without stopping the acceleration voltage. However, in order to implement this method, it is necessary to newly add a control power supply under the acceleration voltage potential and provide a structure for supplying a voltage controlled by the control power supply to the acceleration electrodes. The newly added control power supply requires high stability because it is necessary to keep the potential of the acceleration electrodes constant during the use of the electron microscope. In addition, since the structure for supplying the voltage from the newly added control power supply to the acceleration electrodes is always incorporated inside the apparatus, it is necessary to have an insulation structure corresponding to high voltage so as not to cause dielectric breakdown with other potential structures even when a high acceleration voltage is applied. Therefore, in order to implement Patent Document 2, a significant change in the existing electron gun structure is required, and an increase in manufacturing cost due to the complexity of the structure and an increase in the discharge risk of the withstand voltage structure can be considered.

[0009] The present invention has been made in view of the above problems, and has an electrode short-circuit mechanism capable of suppressing a change in the lens action between acceleration electrodes that occurs during acceleration voltage change, and an object thereof is to provide a charged particle beam apparatus that can operate while applying an acceleration voltage to the electrode short-circuit mechanism.

Means for Solving the Problems

[0010] The charged particle beam apparatus according to the present invention controls the potential difference between the short electrode and the first multi-stage acceleration electrode to such an extent that no discharge occurs while applying an acceleration voltage to the first acceleration electrode, and connects the first multi-stage acceleration electrode having the potential difference and the short electrode.

Effects of the Invention

[0011] The charged particle beam device according to the present invention has an electrode short - circuit mechanism for suppressing changes in the lens action between acceleration electrodes that occur when the acceleration voltage is changed, and can be operated while applying an acceleration voltage to the electrode short - circuit mechanism. As a result, the acceleration voltage can be changed in a short time without degrading the performance of the electron gun, and the operability of the electron microscope can be greatly improved.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Modes for Carrying Out the Invention

[0013] <Embodiment 1> FIG. 1 is a configuration diagram of an electron microscope 1 according to Embodiment 1 of the present invention. For convenience of description, only the peripheral portion of the electron source 101 is shown. The electron microscope 1 includes the following: an electron source 101 that generates electrons; a first acceleration electrode 102 to which a first acceleration voltage for accelerating the electrons emitted from the electron source 101 is applied; a voltage dividing resistor group 103 located at the subsequent stage of the first acceleration electrode 102 for dividing the voltage between the first acceleration electrode 102 and the ground; a multi-stage acceleration electrode group 120 to which voltage dividing resistors are respectively connected; a first acceleration power source 104 that supplies a voltage to be applied to the electron source 101 and the first acceleration electrode 102; a second acceleration power source 105 that supplies a voltage to be applied to the first acceleration electrode 102 by controlling the voltage at the potential supplied by the first acceleration power source 104; an acceleration tube 106 that holds the electron source 101, the first acceleration electrode 102, and the multi-stage acceleration electrode group 120; a short electrode 107 for grounding the potential of at least one electrode among the multi-stage acceleration electrodes to the ground; a short electrode power source 108 that supplies a voltage to be applied to the short electrode 107; a control device 109 that supplies the voltages to be applied to the first acceleration power source 104, the second acceleration power source 105, and the short electrode power source 108, and controls the operation of the short electrode 107; and an electron gun housing 110 that holds the acceleration tube 106 and the short electrode 107.

[0014] In the present embodiment, each acceleration electrode constituting the multi-stage acceleration electrode group 120 is called as follows in the order of increasing distance from the first acceleration electrode 102: a multi-stage acceleration electrode 121, a multi-stage acceleration electrode 122, a multi-stage acceleration electrode 123, a multi-stage acceleration electrode 124, and a multi-stage acceleration electrode 125. The multi-stage acceleration electrode 125 is grounded. In the present embodiment, the inside of the acceleration tube 106 is a high-vacuum region (for example, a gas pressure of 1×10 -6 Pa or less), and the space between the acceleration tube 106 and the electron gun housing 110 is filled with an inert gas (for example, sulfur hexafluoride) for the purpose of improving the discharge voltage.

[0015] FIG. 2 shows an operation example when the electron microscope 1 transitions from the high acceleration voltage observation state (for example, acceleration voltage of 200 kV) to the low acceleration voltage observation state (for example, acceleration voltage of 80 kV). In this embodiment, the case where the short electrode 107 is connected to the multi-stage acceleration electrode 122 will be taken as an example for explanation. Although the potential information of each structure is described in the following explanation, the values shown below are just examples and do not limit the scope of the rights of the present invention.

[0016] In the high acceleration voltage observation state shown in FIG. 2, by the first acceleration power supply 104, the potential (V0) of the electron source 101 is controlled to -200 kV. To the first acceleration electrode 102, a potential difference of 20 kV is supplied to the electron source 101 by the second acceleration power supply 105, thereby accelerating the electrons. Since the potential difference of the second acceleration power supply 105 is superimposed on the potential of the electron source 101 for the potential (V1) of the first acceleration electrode 102, it becomes -180 kV. In this embodiment, assuming that each resistance value R of the voltage dividing resistor group 103 is set equal, the potentials (V2 to V6) from the multi-stage acceleration electrode 121 to the multi-stage acceleration electrode 125 are respectively the values shown in Table 1. Since the short electrode power supply 108 is used when connecting the short electrode 107, it is stopped in the observation state. Therefore, the potential (Vs) of the short electrode 107 becomes 0 kV.

[0017] [Table 1]

[0018] From the content described in Patent Document 1, in order to suppress the change in the lens action between the acceleration electrodes that occurs when the acceleration voltage is changed, it is required to make the lens action that occurs between the acceleration electrodes located in the upper stage closer to the state before the acceleration voltage change. In this embodiment, when transitioning from the high acceleration voltage observation state to the low acceleration voltage observation state, the purpose is to suppress the change in the lens action that occurs between the first acceleration electrode 102 and the multi-stage acceleration electrode 121, and between the multi-stage acceleration electrode 121 and the multi-stage acceleration electrode 122.

[0019] Table 2 shows the potential differences between the electrodes in the high-acceleration voltage observation state. The potential differences between V1 - V2 and V2 - V3 are both 36 kV. The potential difference between the multi-stage acceleration electrode 122 (V3) and the short electrode 107 is 108 kV. However, in this state, since the distance L between the multi-stage acceleration electrode 122 and the short electrode 107 is sufficiently ensured (for example, 12 mm or more), no discharge occurs between these electrodes.

[0020]

Table 2

[0021] Figure 3 shows the control flow of the acceleration voltage switching state when switching from the high-acceleration voltage observation state to the low-acceleration voltage observation state. In this embodiment, in order to reduce the risk of discharge during the operation of the short electrode 107, the potential state in S302 is passed through during acceleration voltage switching. This flowchart is implemented by the control device 109 controlling each part of the electron microscope 1.

[0022] The initial state is a state where -200 kV is applied to the V0 potential and -180 kV is applied to the V1 potential (step 301). In step 302, the control device 109 controls the first acceleration power supply 104 and the second acceleration power supply 105, and sets the potential of the electron source 101 and the potential of the first acceleration electrode 102 to -30 kV and -29 kV, respectively. By this control, the potential of each electrode and the potential difference between each electrode become the values shown in Table 3 and Table 4, respectively. -30 kV is a provisional potential set to temporarily reduce the potential difference from the ground so that excessive damage does not occur even when trouble occurs around the electron source 101. Other values than -30 kV may be used as long as the same effect can be achieved. V1 may be a potential closer to the ground potential than V0.

[0023]

Table 3

[0024]

Table 4

[0025] In step 303, the control device 109 changes the potential set value of the short electrode 107. Step 303 is repeated until the determination shown in step 304 is satisfied. In step 304, the potential difference between the short electrode 107 and the multi-stage acceleration electrode 122 is set to be within ±K. Here, K is a potential difference at which no discharge occurs between the short electrode 107 and the multi-stage acceleration electrode 122, referring to the Paschen curve described in "Discharge Handbook, edited by the Discharge Handbook Publishing Committee of the Institute of Electrical Engineers of Japan, pp192" (reference document). K can be the value derived and stored in advance by the control device 109, or it can be derived each time this step is executed.

[0026] In this embodiment, the potential of the short electrode 107 is set to Vs = -17.4 kV by passing the determination in step 304 (step 305). Thereby, the potential difference between the short electrode 107 and the multi-stage acceleration electrode 122 becomes 0 kV, and no discharge occurs even if the distance L between the two electrodes is brought close until they contact. If no discharge occurs, the potential difference between the short electrode 107 and the multi-stage acceleration electrode 122 does not necessarily have to be 0 kV.

[0027] In step 306, the control device 109 operates a short electrode drive mechanism (for example, an air cylinder) to connect the short electrode 107 to the multi-stage acceleration electrode 122. After the short electrode 107 and the multi-stage acceleration electrode 122 are connected, the control device 109 controls the short electrode power supply 108 to change the potential of the multi-stage acceleration electrode 122 to the ground potential (step 307). In this embodiment, in order to reduce the noise generated from the short electrode power supply 108, the short electrode 107 is connected to a grounding point different from that of the short electrode power supply 108 (step 308).

[0028] In step 309, the control device 109 controls the first acceleration power source 104 and the second acceleration power source 105 to change the potentials of the electron source 101 and the first acceleration electrode 102 to the set values in the low-acceleration voltage observation state, and ends the control of the acceleration voltage switching (step 310).

[0029] By the switching control of FIG. 3, without stopping the application of the acceleration voltage to the electron source 101, it is possible to operate an electrode short-circuit mechanism that can suppress the change in the lens action between the acceleration electrodes that occurs when the acceleration voltage is changed as described in Patent Document 1. According to this flowchart, the potential of each electrode and the potential difference between the electrodes become the values shown in Tables 5 to 6.

[0030] [Table 5]

[0031] [Table 6]

[0032] FIG. 4 is a configuration diagram around the short electrode power source 108 in Embodiment 1. A potential measuring device 301, a switching switch 302, and a protection resistor 303 are arranged between the short electrode power source 108 and the short electrode 107. The switching switch 302 has three or more terminals and is connected to a structure leading to the short electrode 107, a structure leading to the short electrode power source 108, and a structure 304 leading to the ground potential, respectively. The protection resistor (described as R1. For example, 1 MΩ) is provided between the switching switch 302 and the short electrode power source 108.

[0033] FIG. 5 shows a circuit diagram when each resistance value of the voltage dividing resistor group 103 is R2 (for example, 1.7 GΩ). Although not shown in the figure, only in step 306 and step 3071 described later, the short electrode 107 and the multi-stage acceleration electrode 122 are in a non-contact state (Note 1).

[0034] FIG. 6 is a flowchart for explaining the details of step 307. In the initial state (step 306), the output (Vps) of the short electrode power supply 108 is 0 kV, and the potential (Vs) of the short electrode 107 is also 0 kV. The switching switch 302 is in a state where power is being supplied between the short electrode 107 and the short electrode power supply 108 (SWs = ON), and is in a non-contact state with the terminal leading to the ground structure (SWg = OFF).

[0035] In steps 3071 to 3072, the control device 109 controls the short electrode power supply 108 and changes it so that the potential of the multi-stage acceleration electrode 122 (in this embodiment, the value of the potentiometer 301 is being monitored) is within the ground potential ± variable Kg. The variable Kg is derived and determined with reference to the Paschen curve described in the reference document, similar to the variable K, so as to obtain a potential difference at which no discharge occurs between the ground potential structure and the short electrode 107. In this embodiment, the output (Vps) of the short electrode power supply 108 in this step is about 8.9 V. Therefore, the specification of the short electrode power supply 108 required in this embodiment is that it can output a voltage of about -20 kV to 10 V.

[0036] Since the switching switch 302 operates in, for example, an atmospheric environment, Kg in this flowchart is a value different from K. This is because the periphery of the electron source 101 operates in, for example, an inert gas environment.

[0037] In step 3073, the control device 109 operates the switching switch 302 to ground the structure between the protection resistor 303 and the short electrode 107 to the ground potential. At this time, the switching switch 302 must always be structured to be connected to the protection resistor 303. This is because if the switching switch 302 is opened, the short electrode 107 may become disconnected from the ground potential. Therefore, in this embodiment, a structure at the ground potential is operated (for example, an air cylinder is used in the drive system), and the switch is switched by bringing it into contact with the structure between the protection resistor 303 and the short electrode 107.

[0038] After the potential of the short electrode 107 reaches the ground potential, in step 3074, the control device 109 stops the output of the short electrode power supply 108. Thus, the process of connecting the short electrode 107 to a grounding point different from the short electrode power supply 108 (step 307) is completed.

[0039] This flowchart also has the following significance. Since the short electrode power supply 108 is arranged to suppress discharge, it is desirable to stop it when it is unnecessary so that it is not used for other purposes. According to the flowchart of FIG. 6, the short electrode power supply 108 will be connected to and supply power to the short electrode 107 only when necessary, so the short electrode power supply 108 can be protected from unexpected operations.

[0040] With the configuration described above, it becomes possible to protect the short electrode power supply 108 from overcurrent due to discharge. Also, by grounding the structure between the protection resistor 303 and the short electrode 107 to the ground potential, it becomes possible to ignore the influence of the voltage drop by the protection resistor 303, and the short electrode power supply 108 can be stopped in the observation state. That is, since the short electrode power supply 108 only needs to operate when the short electrode 107 operates, the power consumption of the device can be reduced. Also, by stopping the short electrode power supply 108, it becomes possible to prevent noise generated from the same power supply from flowing into the device.

[0041] In this embodiment, the potential of the short electrode 107 was set and the short electrode 107 was operated. Instead of this, the control device 109 may calculate the electric field between the short electrode 107 and the multi-stage acceleration electrode 122 from the distance L between the short electrode 107 and the multi-stage acceleration electrode 122 and the potential of the short electrode 107, store the result, and control the drive system of the short electrode power supply 108 and the short electrode 107 so that the electric field is within a range where discharge does not occur.

[0042] In this embodiment, after connecting the short electrode 107, the structure between the short electrode 107 and the short electrode power supply 108 was grounded at a grounding point different from that of the short electrode power supply 108, but the control by the short electrode power supply 108 may be continued.

[0043] <Embodiment 1: Summary> The electron microscope 1 according to the first embodiment controls the potential of the short electrode 107 so that a potential difference is generated between the short electrode 107 and the multi-stage acceleration electrode 122 that does not cause discharge, connects the short electrode 107 to the multi-stage acceleration electrode 122, and then controls the short electrode power supply 108 so that the potential of the short electrode 107 becomes the ground potential. Thereby, the electrode short-circuit mechanism can be operated while applying an acceleration voltage to the electron source 101.

[0044] <Embodiment 2> In Embodiment 1, it was described that the potential of the short electrode 107 is controlled to such an extent that no discharge occurs using the short electrode power supply 108. In Embodiment 2 of the present invention, instead of using the short electrode power supply 108, a configuration example for suppressing discharge is described by controlling the potential of the first acceleration electrode 102 (and the potential generated in the multi-stage acceleration electrode 122 by dividing the potential).

[0045] FIG. 7 is a configuration diagram of the electron microscope 1 in the second embodiment. Compared with FIG. 1, it is different in that it does not include the short electrode power supply 108. Since other configurations are the same as those in FIG. 1, the differences from Embodiment 1 will be mainly described below.

[0046] FIG. 8 is a configuration diagram around the short electrode 107 in the second embodiment. Using FIG. 8, the operation when shifting from the high acceleration voltage observation state (for example, acceleration voltage 200 kV) to the low acceleration voltage observation state (for example, acceleration voltage 80 kV) will be described.

[0047] In the high-acceleration voltage observation state shown in FIG. 8, the potential (V0) of the electron source 101 is controlled to -200 kV by the first acceleration power supply 104. A potential difference of 20 kV is supplied to the first acceleration electrode 102 with respect to the electron source 101 by the second acceleration power supply 105 to accelerate electrons. Since a potential difference of 20 kV is superimposed on the potential of the first acceleration electrode 102 (V1) with respect to the potential of the electron source 101, it becomes -180 kV. The configuration of the voltage dividing resistor group 103 is the same as that in the first embodiment, and the potentials (V2 to V6) of the respective multi-stage acceleration electrodes are the values shown in Table 1, respectively. Since the short electrode is grounded to the ground potential, the potential (Vs) of the short electrode is 0 kV. The potential differences between the respective multi-stage acceleration electrodes are the values shown in Table 2.

[0048] FIG. 9 shows a control flow of the acceleration voltage switching state through which the electron microscope switches from the high-acceleration voltage observation state to the low-acceleration voltage observation state. In the present embodiment, in order to reduce the discharge risk during the operation of the short electrode 107, the potential state in S902 is passed through during the acceleration voltage switching. This flowchart is implemented by the control device 109 controlling each part of the electron microscope 1.

[0049] The initial state is a state in which -200 kV is applied to the V0 potential and -180 kV is applied to the V1 potential (step 901). In step 902, the control device 109 controls the first acceleration power supply 104 and the second acceleration power supply 105 to set the potential of the electron source 101 and the potential of the first acceleration electrode 102 to -30 kV and -29 kV, respectively. As a result, the potentials of the respective electrodes and the potential differences between the respective electrodes become the values shown in Table 3 and Table 4, respectively.

[0050] In step 903, the control device 109 controls the second acceleration power supply 105 to change the potential of the first acceleration electrode 102. The change in the potential of the first acceleration electrode 102 is repeated until the determination shown in step 904 is satisfied. In step 904, it is assumed that the value A shown in Equation 1 below is within the ground potential ± variable K. Similar to Embodiment 1, the variable K is the potential difference between two electrodes in the air (for example, sulfur hexafluoride) such that discharge does not occur, with reference to the Paschen curve described in the reference document. In this embodiment, K = 0.6 kV. The variable N in Equation 1 indicates the number of acceleration electrodes (for example, in this embodiment, N = 6). The variable Ns indicates the number of stages of the multi-stage acceleration electrode to which the short electrode 107 is connected (for example, if it is the multi-stage acceleration electrode 122, Ns = 2). The variable Ri indicates the resistance value of the voltage-dividing resistor connected between the i-th stage and the (i + 1)-th stage of the acceleration electrodes (for example, when i = 3, it is the resistance value of the voltage-dividing resistor provided between the multi-stage acceleration electrode 123 and the multi-stage acceleration electrode 124).

[0051]

Number

[0052] In this embodiment, the case where the value A in Equation 1 is the same as the determination value Gnd - K will be taken as an example for explanation. Substituting the potential (V0) of the electron source, the number of acceleration electrodes (N), and the number of stages (Ns) of the multi-stage acceleration electrode to which the short electrode 107 is connected in this embodiment into Equation 1, in order for A to satisfy the condition shown in step 904 as a result, the potential (V1) of the first acceleration electrode 102 needs to be controlled within ±1 kV. The potentials and potential differences of each electrode when A is the same as the determination value Gnd - K are the values shown in Table 7 and Table 8. Through the above control, the potential difference between the short electrode 107 and the multi-stage acceleration electrode 122 becomes 0.6 kV, and a state is achieved where discharge does not occur even when the distance L between the two electrodes is brought close until they touch.

[0053]

Table 7

[0054]

Table 8

[0055] In step 905, the short - electrode driving mechanism (for example, an air cylinder) is operated to connect the short electrode 107 to the multi - stage acceleration electrode 122. After the short electrode 107 and the multi - stage acceleration electrode 122 are connected, the first acceleration power supply 104 and the second acceleration power supply 105 are controlled to change the potentials of the electron source 101 and the first acceleration electrode 102 to the set values in the low - acceleration - voltage observation state, and the control of the acceleration - voltage switching is terminated (step 906). After connecting the short electrode 107 to the multi - stage acceleration electrode 122 after step 905, the control device 109 performs control so that the potential of the multi - stage acceleration electrode 122 is maintained. That is, while it is necessary to maintain the multi - stage acceleration electrode 122 at the ground potential, each part is controlled so that its potential state is maintained. For example, the connection between the short electrode 107 and the multi - stage acceleration electrode 122 may be maintained.

[0056] By the switching control of FIG. 9, without stopping the application of the acceleration voltage, an electrode short - circuit mechanism capable of suppressing the change in the lens action between the acceleration electrodes that occurs during the acceleration - voltage change as described in Patent Document 1 can be operated. Note that, as described above, the potential of each electrode and the potential difference between the electrodes become the values shown in Tables 5 and 6.

[0057] FIG. 10 shows the simulation results of the electron - beam trajectory. The upper part of FIG. 10 is the result when the potential (V0) of the electron source 101 is set to - 30 kV in the acceleration - voltage switching state. The lower part of FIG. 10 is the result when the potential (V0) of the electron source 101 is set to - 10 kV. The simulation results assume a Schottky - type electron source, and the extraction voltage of the electron beam is 2.5 kV both in the upper and lower parts. The configuration of the electron microscope 1 may be any of Embodiments 1 to 2.

[0058] When the potential (V0) of the electron source 101 is set to -30 kV, the trajectory 1001 of the electron beam is focused, and many electron beams are irradiated onto the electron gun aperture section 1003 located at the rear stage of the ground potential structure 1002 provided in the acceleration tube 106. On the other hand, when the potential (V0) of the electron source 101 is set to -10 kV, the trajectory 1004 of the electron beam tends to diverge, and many electron beams are irradiated onto the surface of the structure 1002. Generally, since alumina is used as the material of the acceleration tube provided in the electron gun, it is not preferable that electron beams are irradiated onto the surface of the structure 1002 as in the case where the potential (V0) of the electron source 101 is -10 kV. This is because when secondary electrons or scattered primary electrons generated from the electron beams irradiated onto the surface of the structure 1002 are irradiated onto alumina, a large amount of outgassing occurs from the alumina. Since outgassing is highly likely to be a cause of discharge and charging in the acceleration tube, such a situation can be said to be not preferable.

[0059] In the present embodiment, the potential of the first acceleration electrode 102 was set and the short electrode 107 was operated. Instead of this, the control device 109 may calculate the electric field between the short electrode 107 and the multi-stage acceleration electrode 122 from the distance L between the short electrode 107 and the multi-stage acceleration electrode 122 and the potential of the multi-stage acceleration electrode 122, and control the drive systems of the second acceleration power source 105 and the short electrode 107 so that the electric field is within a range where discharge does not occur.

[0060] <Regarding the modification of the present invention> In the above embodiment, the potential (V0) of the electron source 101 at the time of accelerating voltage switching was set to -30 kV, but this potential changes the optimum value depending on the structure of the electron gun and the voltage applied to each electrode. Therefore, the setting conditions of the potential (V0) of the electron source 101 at the time of accelerating voltage switching are preferably set based on the simulation results and experimental values of the electron beam trajectory.

[0061] In the above embodiments, a flow of transitioning from a high-acceleration voltage observation state to a low-acceleration voltage observation state has been described. However, a transition from a low-acceleration voltage observation state to a high-acceleration voltage observation state can also be implemented according to this embodiment. Although the description of the processing flow is omitted, when switching the state of the switching switch 302 and when switching the state of the short electrode 107, similar to the above processing, the short electrode power supply 108 (Embodiment 1) or the second acceleration power supply 105 (Embodiment 2) may be controlled so that discharge does not occur between the structures.

[0062] In the above embodiments, the short electrode 107 is provided within the electron gun housing 110, but it may also be provided outside the electron gun housing 110.

[0063] In the above embodiments, the resistance values of the voltage-dividing resistor group 103 are the same, but they may each have individual resistance values.

[0064] In the above embodiments, the short electrode 107 is connected to the multi-stage acceleration electrode 122, but the connection destination multi-stage acceleration electrode may be changed according to the applied acceleration voltage.

[0065] In the above embodiments, there is one short electrode 107, but a plurality of short electrodes 107 may be provided.

[0066] In the above embodiments, the control device 109 can be configured by hardware such as a circuit device that implements its functions, or can also be configured by software that implements its functions being executed by an arithmetic device such as a CPU (Central Processing Unit).

[0067] In the above embodiments, it has been described that the multi-stage acceleration electrode is set to the ground potential (grounded), but the present invention can be similarly applied even when a reference potential other than the ground potential is used. In this case, the ground potential in the above embodiments may be appropriately read as that reference potential for application.

[0068] In the above embodiment, the electron microscope 1 was described as an example of a charged particle beam apparatus. However, the present invention can also be used in a short-circuit mechanism of multi-stage acceleration electrodes in other charged particle beam apparatuses.

Explanation of Signs

[0069] 101 Electron source 102 First acceleration electrode 103 Voltage dividing resistor group 104 First acceleration power supply 105 Second acceleration power supply 106 Acceleration tube 107 Short circuit electrode 108 Short circuit electrode power supply 109 Control device 110 Electron gun housing 120 Multi-stage acceleration electrode group 121 Multi-stage acceleration electrode 122 Multi-stage acceleration electrode 123 Multi-stage acceleration electrode 124 Multi-stage acceleration electrode 125 Multi-stage acceleration electrode 401 Potential measuring device 402 Switching switch 403 Protection resistor

Claims

1. A charged particle beam device that irradiates a sample with a charged particle beam, comprising: a charged particle source that emits the charged particle beam; a first acceleration electrode to which a first acceleration voltage for accelerating the charged particle beam is applied; a multi-stage acceleration electrode group disposed between a stage on which the sample is placed and the first acceleration electrode; a short electrode connected to a first multi-stage acceleration electrode of the multi-stage acceleration electrode group at a reference potential; a control unit that controls the potential of the first acceleration electrode and the potential of the multi-stage acceleration electrode group; The control unit controls the potential difference between the short electrode and the first multi-stage acceleration electrode so as not to cause discharge while applying an acceleration voltage to the charged particle source, After interconnecting the first multi-stage acceleration electrode having the potential difference of the value and the short electrode, the control unit controls the potential of the first multi-stage acceleration electrode to be the reference potential. A charged particle beam device characterized by the above.

2. The charged particle beam device further includes a short electrode power supply that supplies a voltage to the short electrode, The control unit controls the short electrode power supply so that the potential difference becomes the value, After interconnecting the first multi-stage acceleration electrode having the potential difference of the value and the short electrode, the control unit controls the short electrode power supply so that the first multi-stage acceleration electrode becomes the reference potential. The charged particle beam device according to claim 1, characterized by the above.

3. The charged particle beam device further includes a switching switch that switches whether to connect the short electrode to either the short electrode power supply or the reference potential, After controlling the short electrode power supply so that the first multi-stage acceleration electrode becomes the reference potential, the control unit operates the switching switch so as to connect the short electrode to the reference potential. The charged particle beam device according to claim 2, characterized by the above.

4. When operating the switching switch so as to connect the short electrode to the reference potential, the control unit controls the switching switch so as to connect the short electrode to the reference potential while maintaining the connection between the short electrode and the short electrode power supply. The charged particle beam device according to claim 3, characterized by the above.

5. When operating the switching switch so as to connect the short electrode to the reference potential, the control unit controls the short electrode power supply so that no discharge occurs in the switching switch. ​ The charged particle beam device according to claim 4, characterized in that.

6. The charged particle beam device further includes a drive mechanism for changing the distance between the short electrode and the first multi-stage acceleration electrode, The control unit stores the result of deriving the electric field between the short electrode and the first multi-stage acceleration electrode from the distance and the potential of the short electrode, The control unit controls the drive mechanism and the short electrode power supply so that the derived electric field is within a range where discharge does not occur. The charged particle beam device according to claim 2, characterized in that.

7. The multi-stage acceleration electrode group includes a second multi-stage acceleration electrode between the first acceleration electrode and the first multi-stage acceleration electrode, Before interconnecting the first multi-stage acceleration electrode and the short electrode, the control unit controls the potential difference between the first acceleration electrode and the second multi-stage acceleration electrode to be a first potential difference, and controls the potential difference between the second multi-stage acceleration electrode and the first multi-stage acceleration electrode to be the first potential difference, After interconnecting the first multi-stage acceleration electrode and the short electrode, the control unit controls the potential difference between the first acceleration electrode and the second multi-stage acceleration electrode to be a second potential difference, and controls the potential difference between the second multi-stage acceleration electrode and the first multi-stage acceleration electrode to be the second potential difference. The charged particle beam device according to claim 1, characterized in that.

8. During the process of switching the first acceleration voltage between a high acceleration voltage and a low acceleration voltage, the control unit sets the potential of the first acceleration electrode to a provisional potential closer to the reference potential than the low acceleration voltage, The control unit performs control to obtain the first potential difference or the second potential difference by distributing the provisional potential between the respective acceleration electrodes of the multi-stage acceleration electrode group. The charged particle beam device according to claim 7, characterized in that.

9. The charged particle beam device further includes a voltage dividing resistor for dividing the first acceleration voltage between the respective acceleration electrodes of the multi-stage acceleration electrode group, The control unit controls the first acceleration voltage so that the potential of the first multi-stage acceleration electrode generated by the voltage dividing resistor dividing the first acceleration voltage approaches the reference potential to an extent where discharge does not occur, After making the potential of the first multi-stage acceleration electrode approach the reference potential, the control unit interconnects the first multi-stage acceleration electrode and the short electrode. The charged particle beam device according to claim 1, characterized in that...

10. The charged particle beam device further includes a drive mechanism for changing the distance between the short electrode and the first multi-stage acceleration electrode. The control unit stores the result of deriving the electric field between the short electrode and the first multi-stage acceleration electrode from the distance and the potential of the short electrode. The control unit controls the drive mechanism so that the derived electric field is within a range where no discharge occurs. The charged particle beam device according to claim 1, characterized in that...

Images