Electron microscope

Abstract

Electron microscope, which features: a chamber (1) for electron-optical lenses in which a sample (13) is irradiated with a primary electron beam (19), charged secondary particles generated by the irradiation with the primary electron beam (19) are detected and an image signal is output on the basis of the results of the detection of the charged secondary particles; a substructure (2) that supports the chamber (1) for electron-optical lenses; a sample holder (4) comprising a sample holder (15) for attaching the sample (13) to the sample holder (4) and having one function being to apply a voltage to the sample holder (15); a sample stage (3) for moving the sample (13), wherein the sample stage (3) is attached to the chamber (1) for electron-optical lenses, and the sample holder (4) is designed for applying a high voltage to the sample holder (15) attached to the sample holder (4) in order to be inserted into the sample stage (3); a voltage source (7) that supplies the voltage applied to the sample holder (15) and is arranged within the substructure (1); a first voltage cable (5) which is connected at one of its ends to the sample holder (4); and a relay unit (6) to which the other end of the first voltage cable (5) is connected, the relay unit (6) being arranged on the base (5); a second voltage cable (8) for feeding the voltage generated by the voltage source (7) into the relay unit (6) arranged on the base (2), wherein the length (l) of the first voltage cable (5) is less than the length (L) of the sample holder (4), so that attaching the sample holder (4) to the sample stage (3) requires that the sample holder (4) be attached before the first voltage cable (5) is connected to the relay unit (6).

Description

TECHNICAL FIELD

[0001] The invention relates generally to electron microscopes and, more particularly, to an electron microscope comprising a system configured to safely apply a high voltage to a sample. STATE OF THE ART

[0002] An electron microscope uses electromagnetic lenses to focus a primary electron beam emitted from an electron gun onto a sample, where it captures electrically charged secondary particles from the sample and produces a magnified image of the sample. A scanning electron microscope is an advanced type of electron microscope that also includes the ability to scan the primary electron beam across the sample surface using electromagnetic or electrostatic deflectors above the objective lenses.

[0003] In scanning electron microscopy, the sample under investigation is generally electrically grounded. However, a voltage can also be applied to the sample to view the sample image. Recently, the most commonly used method for observing the sample image is beam deceleration. The deceleration method is a technique used to examine the image of a sample in which a negative voltage of approximately several hundred kilovolts to several kilovolts is applied to the sample as a deceleration voltage, and a primary electron beam is decelerated immediately in front of the sample.

[0004] In the deceleration method, if an accelerating voltage applied to the electron gun for accelerating the primary electron beam is expressed as Vacc and the deceleration voltage applied to the sample is expressed as Vr, the irradiation voltage (also called impact energy) Vi obtained when the primary electron beam reaches the sample is given as Vi = Vacc - Vr. When the deceleration method is performed, high image quality can be obtained even with the same irradiation level compared to that obtained without using the deceleration method (i.e., when the sample is electrically grounded). For example, even though the irradiation voltage obtained when Vacc = 1 kV and Vr = 0.5 kV is the same as that obtained when Vacc = 0.5 kV and Vr = 0.0 kV, in the former case, the optical resolution, that is, how clearly or sharply details of the sample are imaged, is improved compared to the latter case.By using a delay device, the sample image can also be viewed at a lower irradiation voltage (e.g., Vi = 0.1 kV) compared to the minimum acceleration voltage achievable with the electron gun (e.g., Vacc = 0.5 kV). This allows for topographical examination of the topmost sample surface at high resolution. Examination using the delay method has many other advantages, such as preventing the buildup of electrical charges in the sample and reducing sample damage.

[0005] Scanning electron microscopes can be divided into outside-the-lens type, semi-inside-the-lens type, and inside-the-lens type according to the specific design relationship between the objective lenses and the sample. In the outside-the-lens type, the sample is placed in a position completely removed from the magnetic fields of the objective lenses; in the inside-the-lens type, the sample is placed within the magnetic fields of the objective lenses. In the semi-inside-the-lens type, which lies somewhere between the outside-the-lens type and the inside-the-lens type, the sample is placed in a position where the magnetic fields of the objective lenses are partially present. Of the three types of scanning electron microscopes, the inside-the-lens type of scanning electron microscope, which can best utilize the optical performance of the objective lenses, is the most advantageous because it can obtain high-resolution images.

[0006] In the inside-the-lens scanning electron microscope (hereinafter referred to simply as an inside-the-lens SEM), a sample must be placed between the magnetic poles of the lenses to accommodate the requirement of exposing the sample to the magnetic fields of the lenses. Therefore, the sample is mounted on one end of a special sample holder and placed between the objective lenses to view a magnified image of the sample.

[0007] The deceleration method, an examination technique that involves applying a voltage of the same level (of the same magnitude) as the accelerating voltage to the primary electron beam, has the characteristic that the sample is mounted at one end of a special sample holder and then placed between the magnetic poles of the objective lenses. This is likely to cause discharges and pose safety concerns. For this reason, the deceleration method has not been used in the past with inside-the-lens SEMs.

[0008] On the other hand, there are conventional methods in which a voltage, although not as high as the acceleration voltage, is applied to a sample stage for other purposes, especially in the field of transmission electron microscopes or scanning electron microscopes. For example, Patent Document 1 cited below discloses an electron microscope in which a sample stage on which multiple samples are mounted also has a memory mounted on the sample stage to distinguish between the individual samples. An external power supply serving as the operating power supply for the memory is connected to the sample stage via a cable.

[0009] According to Patent Document 1, a cable connection sensor that detects whether the cable is connected is attached to a high-voltage terminal as a measure to ensure safety in conjunction with the application of high voltage. Therefore, the application of voltage to the sample holder is prevented if the cable connection sensor fails to detect the connected state of the cable, or if the main body of the electron microscope fails to recognize the memory on the sample holder. The document US 2005 / 0230636 A1 discloses an electron microscope according to the preamble of claim 1. PRIOR ART DOCUMENTS PATENT DOCUMENT

[0010] Patent document 1: JP 2005 / 327 710 A (US patent US 7 381 968 B2) BRIEF DESCRIPTION OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0011] For the application of the delay method to an inside-the-lens SEM, due to the examination setup in which the specimen holder is inserted between the objective lenses, it is mandatory to connect the high-voltage cable to the specimen holder and apply a delay voltage to the holder. A power supply for scanning electron microscopes is usually housed in a mounting fixture or arranged independently of the main body of the microscope as a power supply unit. For inside-the-lens SEMs that use the delay method, the long high-voltage cable must be connected by routing it from the inside of the mounting fixture or the independent unit to the specimen holder.

[0012] On the other hand, in such an inside-the-lens SEM, since the sample holder can be removed from the main body of the SEM even during operation when the long cable is connected to the sample holder, it may happen that the body of a person operating the device gets entangled in the cable, causing the sample holder to be accidentally pulled out from the main body of the SEM during operation.

[0013] Removing the sample holder with high voltage applied to it poses the risk of electric shock to the operator or damage to the equipment due to a discharge inside the electron optical lens chamber.

[0014] Patent Document 1 discusses issues related to the connected state of the sample holder (connector) and cable in a non-energized state, but the safety of the device during operation is not addressed. However, when the delay process is performed in the inside-the-lens SEM, operator safety must be considered with greater care than in a conventional electron microscope, because a significantly higher voltage is applied to the sample holder than in a conventional electron microscope.

[0015] An object of the present invention is to provide a scanning electron microscope in which the device can be operated more safely than conventional scanning electron microscopes even during an operation of the device in which a delay process is carried out in the scanning electron microscope whose sample holder is inserted into a chamber for electron optical lenses for examining the sample surface. SOLUTION TO THE PROBLEM

[0016] To solve the problems described above, the invention proposes an electron microscope having the features of claim 1. Such an electron microscope according to an embodiment of the present invention comprises a sample holder whose function is to apply a voltage to a sample holder configured to receive a sample, a voltage source that supplies the voltage applied to the sample holder, a voltage cable that is connected at one of its ends to the sample holder, and a relay unit to which the other end of the voltage cable is connected and which is arranged either on a base supporting a lens barrel of the electron microscope or within a cover.

[0017] In this case, it is desirable for the voltage cable to be shorter than that of the sample holder. The voltage cable length can be shorter than that of the sample holder if the relay unit is placed within a circle whose radius, starting from one end of the sample holder when inserted into the electron-optical lens chamber, is smaller than the length of the sample holder. EFFECT OF THE INVENTION

[0018] Accordingly, the relay unit is placed either on the base or in the cover, eliminating the need to route the high-voltage cable from a power supply and reducing the risk of the sample holder being accidentally pulled out of the microscope during operation of the device.

[0019] Furthermore, the sample holder can be prevented from being inserted into the electron-optical lens chamber when the delay voltage is applied if the length of the cable is selected to be shorter than the length of the sample holder.

[0020] As set forth above, according to the present invention, there is provided a scanning electron microscope which causes less frequent electric shocks when a delay process is performed for the observation of the sample surface in the electron microscope whose sample holder is inserted into an electron optical lens chamber, as compared with conventional scanning electron microscopes. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an overall external view of an electron microscope according to a first embodiment. Fig. 2A is an explanatory diagram showing a sample holder and sample stage of the first embodiment. Fig. 2B is a plan view showing a position of a relay unit when the sample holder of the first embodiment is inserted. Fig. 3A is an explanatory diagram detailing an example of the periphery of the relay unit of the first embodiment. Fig. 3B is an explanatory diagram detailing another example of the periphery of the relay unit of the first embodiment. Fig. 4 is a perspective view showing an electrical circuit inside the relay unit according to the Fig. 3B shows the example shown in detail. Fig. 5 is an overall external view of an electron microscope according to a second embodiment. Fig. 6 is an explanatory diagram showing the positioning of a relay unit according to the second embodiment. Fig. 7 is an overall external view of an electron microscope according to a third embodiment. Fig. 8 is a diagram showing the relative positions of a sample stage and objective lenses in the electron microscope according to the third embodiment. EMBODIMENTS OF THE INVENTION (First Embodiment)

[0021] Embodiments of the present invention will be explained in detail below with reference to the accompanying drawings. An exemplary configuration of an electron microscope with a side-insertable sample holder (sample holder) will be explained in the description of the embodiments.

[0022] Fig. 1 is a schematic view of a first embodiment of the present invention showing an electron microscope configured to load a sample into a sample holder located at one end of the sample stage, wherein a voltage can be applied to the sample holder via the sample holder.

[0023] An electron-optical lens chamber 1, in which the sample is irradiated with a primary electron beam and charged secondary particles are output as an image signal after detecting the electrically charged secondary particles generated by the irradiation with the primary electron beam, is supported on an upper surface of a base 2. A sample stage 3 for moving the sample is attached to the electron-optical lens chamber 1, and the sample holder 4 for applying a high voltage to the sample holder mounted on the sample holder 4 is inserted into the sample stage 3.

[0024] A high-voltage source 7 is arranged within the base to supply the voltage to be applied to the sample, so that an operator cannot directly touch the high-voltage source 7.

[0025] The voltage generated by the high-voltage source 7 is first fed from the high-voltage source 7 to a relay unit 6 arranged on the base 2 via a voltage cable 8. The voltage is then fed from the relay unit 6 to the sample holder 4 via a voltage cable 5 and applied to the sample located on the sample holder. The relay unit 6 includes a connector for receiving the voltage cable 5, wherein the voltage cable 5 is connected to the relay unit 6 when the sample is observed using the delay method.

[0026] Fig. 2A shows how the sample holder 4 is inserted into the sample stage 3. The sample holder 4 is attached to the side-mounted sample stage, which is laterally inserted into the electron-optical lens chamber 1 via a vacuum feedthrough. The sample holder 4 includes a handle 11, an O-ring 12 for insertion into the electron-optical lens chamber 1 when placed under high vacuum, a guide pin 14 for guiding the direction in which the sample holder 4 is inserted, the sample holder 15 for fixing the sample 13 thereto, and a shaft 16 for isolating the sample holder 15 from the sample holder 4 and the electron-optical lens chamber 1.

[0027] The voltage cable 5 extends from the handle 11, with a BNC connector A (male) 17 for connecting the relay unit being arranged at one end of the cable. The high voltage applied via the BNC connector A 17 is applied to the sample holder 15 via a high-voltage line 18 running inside the holder, including the handle, whereby the high voltage acts as a delay voltage on the primary electron beam 19. As shown in Fig. 2A, the length L of the sample holder 4 from an end face of the handle 11 to an end face of the sample holder 15 is greater than the length “l” of the tension cable 5; that is, the relationship “L > l” exists between the two dimensions.

[0028] When the length L of the sample holder 4 and the length "l" of the voltage cable 5 satisfy the relationship "L > l" as described above, attaching the sample holder 4 to the sample stage 3 requires that the sample holder 4 be attached before connecting the voltage cable 5 to the relay unit 6. This is because the sample holder 4 cannot be attached to the sample stage 3 if the connection of the voltage cable 5 to the relay unit 6 is made beforehand, because the length of the voltage cable 5 is shorter than that of the sample holder.

[0029] In order for L and “l” to satisfy the relationship “L > l”, the position of the relay unit 6 on the base frame requires appropriate measures. Fig. 2B shows a plan view of the electron microscope with the sample holder 4 inserted into position. As shown, the sample holder 4 is arranged such that one end occupies a substantially central position in the electron-optical lens chamber 1, and the other end, or the terminal between the handle 11 and the power cable 5, protrudes outward from the electron-optical lens chamber 1 by the length of the handle 11. The relationship "L > l" is satisfied when the relay unit 6 (or more precisely, the terminal for connecting to the cable) is positioned on the base so as to lie within a circle of radius L, the center of which lies at a projection point of the above-mentioned protruding position projected onto the base.

[0030] In practice, the voltage cable 5 must have a certain amount of slack. Therefore, to satisfy the relationship "L > l," it is necessary to position the relay unit 6 significantly close to the electron-optical lens chamber 1.

[0031] Next, with reference to the Fig. 3 and Fig. 4 Details of the relay unit 6 are described.

[0032] Fig. 3A is an explanatory diagram detailing an example of the periphery of the relay unit of the first embodiment. Fig. 3A specifically shows electrical wiring between electrical connections within the relay unit 6 and the sample holder 4. The relay unit 6 includes a switch 24 for detecting connector attachment, and the high-voltage source 7 inside the base includes a power supply 31. The power supply 31 is a device for supplying electrical energy for generating high voltage. The high-voltage source 7 is a high-voltage device that generates high voltage based on a supply voltage from the power supply 31, and the high-voltage source 7 is arranged together with or separately from the power supply 31.

[0033] An electrical connection between the sample holder 4 and the high voltage source 7 is controlled by the high voltage control device 32, which operates as a high voltage control unit.

[0034] The connector attachment detection switch 24 operates as a connection detector synchronously with the power supply 31 of the high-voltage source 7. When the connector attachment detection switch 24 is activated (no attachment detected), the high-voltage control device 32 interrupts the electrical connection between the power supply 31 of the high-voltage source 7 and the BNC connector or the sample holder 4.

[0035] The high-voltage control device 32 also operates synchronously with a vacuum monitoring device 33, which monitors the vacuum situation of the sample stage 3 and interrupts the electrical connection between the power supply 31 of the high-voltage source 7 and the sample holder 4 if the vacuum level does not reach a threshold value. This prevents the delay voltage from being applied when the vacuum level in the insertion channel for the sample holder 4 or the electron-optical lens chamber is insufficient, thus preventing a discharge-related accident.

[0036] The connector attachment detection switch 24 may operate synchronously with the high voltage control device 32.

[0037] Even if the voltage cable 5 is connected to the relay unit 6 before attaching the sample holder 4, the vacuum monitoring device 33 interrupts the electrical connection of the high-voltage control device 32 because the sample holder 4 is not attached to the sample stage 3. However, when the sample holder 4 is removed from the sample stage 3, it is necessary to disconnect the voltage cable 5 from the relay unit 6 beforehand. This prevents the sample holder 4 from being removed from the sample stage 3 while high voltage is applied to the sample holder 4.

[0038] At the Fig. 3A, the delay voltage as described above is not applied to the cable terminal of the relay unit 6 when the power cable 5 is not correctly connected to the relay unit 6, thus eliminating the possibility of an accident due to electric shock due to improper electrical connection between the relay unit 6 and the power cable 5.

[0039] Fig. Fig. 3B is an explanatory diagram detailing another example of the periphery of the relay unit of the first embodiment, and Fig. 4 is a perspective view showing an electrical circuit inside the relay unit according to the Fig. 3B shows the example shown in detail.

[0040] The Fig. 3B and Fig. Figure 4 shows example configurations of the relay unit that incorporate high-voltage protection to further improve safety. First, the appearance of the example configurations is described below.

[0041] Fig. Figure 4 is a perspective view of the relay unit with high-voltage protection. The BNC connector A 17 on the power cable 5 is connected to a BNC connector B (female) 22 of the relay unit 6 via a hole in the high-voltage protection 21. A rotary knob 25 attached to the high-voltage protection 21 has a front end that serves as a front screw connection 26. Rotation of the rotary knob 25 allows the front screw connection 26 to directly engage a screw connection 27 of the relay unit 6, thus securing the high-voltage protection 21 to the relay unit 6.

[0042] When the BNC connector A 17 is mounted (connected) to the BNC connector B 22, a switch plate 23 is actuated to activate the connector attachment detection switch 24. Furthermore, when the front screw connection 26 is attached to the screw connection 27, a pin 28 on the high-voltage protector 21 is inserted into a hole formed directly above the screw connection 27, thereby activating a high-voltage protector attachment detection switch 29, which serves as a second switch on the relay unit 6.

[0043] Fig. Figure 3B shows the electrical wiring between the electrical connections within the relay unit 6 and the sample holder 4. The high-voltage protection attachment detection switch 29 operates synchronously with the high-voltage control device 32, which controls the status of the high-voltage source 7 and other high-voltage areas. When the high-voltage protection attachment detection switch 29 is activated (the high-voltage protection attachment is not detected), the electrical connection between the high-voltage source 7 and the corresponding BNC connector is interrupted by the high-voltage control device 32.

[0044] In the Fig. 3b and Fig. In the configurations shown in Figure 4, the connector attachment detection switch 24 and the high-voltage protection attachment detection switch 29 are required to detect the attachment of the respective relevant areas, and the vacuum monitoring device 33 detects that the sample holder 4 is inserted into the sample stage 3 and the vacuum has reached a certain level. At this time, the power supply 31 of the high-voltage source 7 and the high-voltage control device 32 output a desired high voltage from the high-voltage source 7. When the output high voltage reaches the BNC connector A 17 via the power cable 8, the high voltage is supplied to the sample holder 4.

[0045] The following describes a case in which the BNC connector A 17 of the power cable 5 coming from the sample holder 4 is disconnected from the relay unit while high voltage is applied to the sample holder 4. Before disconnecting the BNC connector A 17, it is necessary to remove the high-voltage protector 21 from the relay unit 6. If the high-voltage protector 21 is not attached, the high-voltage control device 32 is turned off, which in turn turns off the high voltage. The high-voltage protector 21 is attached with screw connections, so a certain amount of time is required for removal. Therefore, during the period in which the screw connection is loosened, the electrical potential at the sample holder 4 is dissipated. This can reduce the potential hazard caused by contact with high-voltage areas during the disconnection of the BNC connector A 17.

[0046] As described above, the high voltage can be switched off even if the configuration of Fig. 3A, a high voltage is applied to the sample holder 4 by disconnecting the connector A 17. In this case, the electrical charge stored on the sample holder 4 can still cause an electric shock by discharging to a part of the operator's body, such as a hand. When configuring the Fig. 3B, however, the high voltage can be interrupted by removing the high-voltage protector 21 before disconnecting the connector A 17. By interrupting the high voltage, the charge on the sample holder 4 can be dissipated, thus preventing an electric shock. In short, after the high voltage is interrupted after removing the high-voltage protector 21, the charge on the sample holder 4 can be dissipated by a time difference between the interruption and the removal of the connector A 17, thus preventing an electric shock.

[0047] With the above-described configuration, contact with a high-voltage area can be avoided when inserting and removing the sample holder 4 from the sample stage 3. Even with such a sample holder that involves or requires direct contact by an operator, a safe system for applying high voltage to the sample holder 15 can be provided.

[0048] Even if in the Fig. 3A and Fig. 3B shows an example of an electrical connection diagram for the relay unit 6. Elements with which the connector attachment detection switch and the high-voltage protection attachment detection switch operate synchronously may be the same and are not limited to the examples. Switch structures and parts of the relay unit 6 are shown in Fig. 4, however, the switches are not limited to mechanical switch types, they can also be formed by magnetic sensors or optical switches. (Second embodiment)

[0049] Fig. 5 is an overall external view of an electron microscope according to a second embodiment. In addition to the functions corresponding to those of the electron microscope described in the first embodiment, the electron microscope of the second embodiment includes a cover 41 covering the electron optical lens chamber 1 and the base 2.

[0050] In electron microscopes, the primary electron beam can oscillate due to a particular air flow, resulting either from ambient noise or air conditioning, causing a noise signal to appear in the sample image. Furthermore, expansion / contraction of the electron-optical lens chamber or the stage due to a change in ambient temperature can lead to drift (destruction) of the sample image. These phenomena occur considerably more frequently during the acquisition of higher-resolution images. Because, as in Fig. By providing a cover 41 as shown in Figure 5, changes in air flow due to ambient noise or air conditioning and changes in ambient temperature are prevented, and the adverse effects of these changes are thus effectively eliminated. Attaching the cover is therefore suitable for beam deceleration using the deceleration method frequently used for high-magnification image acquisition.

[0051] In the present embodiment, the cover 41 includes a first door 42 used to remove the sample holder 4 from the sample stage 3, and a second door 43 used for accessing the electron-optical lens chamber 1 from the front for maintenance work, such as mechanical adjustment of the electron-optical axis. The relay unit 6 is arranged inside the cover and, if possible, on the base 2 near the door 42. Opening the first door 42 enables connector assembly and other operations. The power supply cable 5 from the sample holder 4 is connected to the BNC connector B 22 of the relay unit 6. The relay unit 6 is suitably placed on the base 2 so that a mounting surface of the BNC connector B 22 is parallel to the first door 42 or the second door 43 in the cover 41 (ie,, to an open area of ​​the door when the door is open) to improve work efficiency during connector installation / removal and other operations. In the example of the . Fig. 5, the relay unit 6 is arranged such that the mounting surface of the BNC connector B 22 faces the second door 43 and is mounted in a position close to the door 42 so that the connector is easily accessible from the door 42 and can be easily connected to and removed from the relay unit 6. Even if the relay unit 6 is in Fig. 5 is box-shaped, the relay unit 6 can be mounted as shown in Fig. 6 shown examples, be embedded in a wall formed within the cover 41. The BNC connector B 22 shows in Fig. 6(a) in the same direction as the Fig. 5, the BNC connector B 22 may also be connected to an upper surface of the relay unit 6 as shown in Fig. 6(b). (Third embodiment)

[0052] In a third embodiment, an example of a structure of an inside-the-lens SEM is described.

[0053] Fig. Figure 7 is an overall external view of an electron microscope according to this embodiment. In addition to the functions similar to those of the electron microscope described in the first embodiment, the electron microscope of the third embodiment includes a cover 41 covering the electron optical lens chamber 1 and the base 2.

[0054] The cover 41 includes a first door 42 used to remove the sample holder 4 from the sample stage 3, and a second door 43 used for access to the electron-optical lens chamber 1 from the front for maintenance work, such as the mechanical adjustment of the electron-optical axis. The cover 41 further includes a third door 44 to facilitate confirmation on an operation screen 45 through the second door 43 during maintenance work. When the display unit with the operation screen 45 is used, the display unit is displayed on a Fig. 7, and the orientation of the screen can be changed as shown in the figure. By opening the third door 44, an operator can, if he or she is Fig. 7, represented by an arrow, accesses the REM chamber through the second door 43, receive visual confirmation on the screen.

[0055] The relay unit 6 is placed on the base near the first door 42, and the connector is connected to the relay unit, for example.

[0056] Fig. 8 shows relative positions of the sample holder and objective lenses in the electron microscope after insertion into the electron-optical lens chamber 1 according to the third embodiment. The objective lenses with pole pieces are located in the electron-optical lens chamber 1. The pole pieces each include a lower magnetic pole 51 and an upper magnetic pole 52. The sample stage 3 is further arranged on the side of the electron-optical lens chamber 1, and the sample holder 4 with a sample 13 positioned on the holder is placed between the lower magnetic pole 51 and the upper magnetic pole 52 of each objective lens. Therefore, the inside-lens SEM can achieve strong excitation with a short focus, making it suitable for high-resolution specimen examination.The high voltage generated by the high voltage source 7 at this time is led by the voltage cable 5 via the voltage line 18 within the sample holder 4 to the sample holder 15 and acts on the primary electron beam 19.

[0057] In this way, the example shown in one of the Fig. 5 to Fig. 7, a high-resolution examination using the retardation method, which is both safe and easy to perform at a low irradiation voltage, is possible. Furthermore, the combination with the inside-the-lens SEM, as in the example of Fig. 8 , an ultra-high-resolution study using the delay method performed at a low irradiation voltage. List of reference symbols 1 chamber for electron-optical lenses 2 Substructure 3 Side-mounted rehearsal stage (rehearsal stage) 4 Sample holder 5 Power cables (power supply cables) 6 Relay unit 7 High voltage source 8 voltage cables 11 Handle 12 O-ring 13 Sample 14 Guide pin 15 sample holders 16 shaft 17 Connector A (BNC connector A) 18 high-voltage line 19 Primary electron beam 21 High-voltage protection 22 BNC connector B 23 Switch plate 24 switches for detecting the connector fastening 25 Rotary knob 26 of the front screw connection (screw connection at the front end of the rotary knob) 27 Screw connection 28 pin 29 Switch for detecting the high-voltage protection attachment 31 Power supply 32 High-voltage control device (high-voltage control unit) 33 Vacuum monitoring device 41 Cover 42 First Door 43 Second Door 44 Third Door 45 Operating screen 51 Upper magnetic pole 52 Lower magnetic pole

Claims

[1] Electron microscope that has: an electron-optical lens chamber (1) in which a sample (13) is irradiated with a primary electron beam (19), charged secondary particles generated by the irradiation with the primary electron beam (19) are detected, and an image signal is output based on the results of the detection of the charged secondary particles; a base (2) supporting the chamber (1) for electron-optical lenses; a sample holder (4) comprising a sample holder (15) for attaching the sample (13) to the sample holder (4) and having a function of applying a voltage to the sample holder (15); a sample stage (3) for moving the sample (13), wherein the sample stage (3) is attached to the electron-optical lens chamber (1), and the sample holder (4) is designed to apply a high voltage to the sample holder (15) attached to the sample holder (4) to be inserted into the sample stage (3); a voltage source (7) which supplies the voltage applied to the sample holder (15) and which is arranged within the base (1); a first voltage cable (5) connected at one of its ends to the sample holder (4); and a relay unit (6) to which the other end of the first voltage cable (5) is connected, the relay unit (6) being arranged on the base (5); a second voltage cable (8) for feeding the voltage generated by the voltage source (7) into the relay unit (6) arranged on the base (2), wherein the length (l) of the first voltage cable (5) is less than the length (L) of the sample holder (4), so that the attachment of the sample holder (4) to the sample stage (3) requires that the sample holder (4) is attached before the first voltage cable (5) is connected to the relay unit (6). [2] An electron microscope according to claim 1, wherein a terminal for connecting the first power cable (5) to the relay unit (6) is arranged at the other end of the first power cable (5). [3] An electron microscope according to claim 1, wherein the relay unit (6) comprises means for detecting the connection of the first voltage cable (5). [4] An electron microscope according to claim 1, wherein the relay unit (6) comprises a first switch (24) for establishing and interrupting an electrical connection between the sample holder (15) and the voltage source (7). [5] An electron microscope according to claim 4, wherein the relay unit (6) comprises a second switch (29) which activates and deactivates the voltage source (7). [6] An electron microscope according to claim 5, wherein the relay unit (6) comprises a first BNC connector; and the first power cable (5) has a second BNC connector at an end portion of the first power cable (5), the end portion facing the relay unit (6) when the first power cable is connected to the relay unit (6). [7] Electron microscope according to claim 7, wherein the second switch (2) is arranged on the back of the BNC connector of the relay unit (6); the first switch (24) is arranged near the BNC connector of the relay unit (6); and ring-shaped attachments are provided for fastening the BNC connectors of the relay unit (6) and the first voltage cable (5) so that the first switch (24) and the second switch (29) can be activated. [8] An electron microscope according to claim 1, further comprising: a polyhedral cover (41) covering the chamber (1) for electron-optical lenses and the substructure (2); and a door (43) arranged on one side of the cover (41). [9] An electron microscope according to claim 8, further comprising: a first door (42) and a second door (43), each mounted on different sides of the cover (41). [10] An electron microscope according to claim 8, wherein a connecting surface provided on the relay unit (6) for receiving the first power cable (5) is a surface different from the back of the relay unit (6). [11] Electron microscope according to one of the preceding claims, wherein the electron microscope is designed as a scanning electron microscope, wherein in the chamber for electron optical lenses a sample surface is scanned with a primary electron beam, charged secondary particles generated by the scanning with the primary electron beam are detected and an image signal is output on the basis of the results of the detection of the charged secondary particles. [12] Electron microscope according to claim 11, wherein the sample holder (4) is guided laterally into the chamber (1) for electron-optical lenses via the laterally mounted sample stage (3) via a vacuum feedthrough. [13] An electron microscope according to claim 11, wherein the electron optical lens chamber comprises inside-the-lens type objective lenses.

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