Electron microscope and method of using the same

Abstract

The present invention relates to an electron microscope and a method for using the same, belonging to the technical field of electron microscopes. The electron microscope can integrate magnetic lens functions and electrostatic lens functions, and realizes the conversion of the two lens functions by adjusting the position of an annular pole shoe and the potential difference. The operation is simple and the implementation is convenient. The electron microscope comprises: an electron source; an electron accelerating electrode; an objective lens arranged below the electron accelerating electrode; an inner pole shoe arranged on the inner side surface of the inner end of an upper shell of the objective lens and arranged in contact with the inner side surface of the upper shell; an outer pole shoe arranged on the inner side of the inner end of a lower shell of the objective lens and arranged longitudinally; a motion control device arranged on the inner side of the objective lens and below the inner pole shoe; an annular pole shoe or a deflection device or an electron detector arranged on the motion control device and realizing up and down movement under the action of the motion control device; the annular pole shoe is electrically connected to a voltage regulator; and a sample stage is located at the bottom.

Description

Technical Field

[0001] The present invention relates to the technical field of electron microscopes, and in particular to an electron microscope and a method for using the electron microscope. Background Art

[0002] The scanning electron microscope (SEM) is an observation method intermediate between the transmission electron microscope and the optical microscope. It uses a narrow, focused, high-energy electron beam to scan a sample. The interaction between the beam and the material stimulates various physical information, which is then collected, amplified, and re-imaged to characterize the microscopic morphology of the material. The electron optical system is its core component, and the electron lens (electrostatic and magnetic lenses are collectively referred to as the electron lens) is another core component of the electron optical system. The objective lens is the most critical component of the electron lens. Electron lenses have a certain resolution and aberrations. Aberrations can be corrected to a large extent.

[0003] There are two types of electron lenses: electrostatic lenses and magnetic lenses. The characteristics of electrostatic lenses are: no image rotation angle, relatively light, low voltage stability requirements, easy to focus the electron beam (directly changing the acceleration voltage during use can change the focal length and magnification), and relatively energy-saving (it consumes energy when used for imaging, but does not consume energy when normally connected to a high-voltage lens). The characteristics of magnetic lenses are: small imaging aberrations, no need for high-voltage excitation, and considering the problem of dielectric materials being polarized under the action of electrostatic lenses, immersion lenses can be made. When in use, the current intensity can only be changed by changing the coil, which can control the focal length and magnification.

[0004] Electrostatic lenses focus ion beams quickly, an advantage that magnetic lenses currently cannot replace. However, both have their own drawbacks. Electrostatic lenses have the following three drawbacks: 1. Focus and magnification are difficult to control, requiring a potential difference of thousands or even several kilovolts to significantly alter the focal length and magnification, and the magnification adjustment range is narrow, typically only a few times. 2. During operation, I is very low, but the voltage is very high. Once the vacuum level drops, it can easily cause sparking between the electrodes, leading to breakdown and burning. 3. Although small (thin), the imaging aberrations are significant. Magnetic lenses have the following three drawbacks: 1. Focal length can be controlled by changing the runoff coil I, and the magnification adjustment range can be several to dozens of times. 2. They are large and require a cooling system, making them difficult to incorporate into small instruments. 3. Maintaining operation requires a constant current flow, consuming energy.

[0005] In summary, electrostatic lenses and magnetic lenses have their own scope of application. Electrostatic lenses are better for low-voltage electron beams, but for high-voltage electron beams, the focusing ability of electrostatic lenses will be greatly reduced. On the contrary, magnetic lenses are less affected. Therefore, low-voltage electrostatic lenses are mostly used now. Some electron microscopes now also need to be equipped with focused ion beams (FIBs). FIBs accelerate the ion beam generated by an ion source (mostly Ga, but some equipment also has He and Ne ion sources) through an ion gun, focus it, and then act on the sample surface. Functions: (1) Generate secondary electron signals to obtain electron images, which is similar to SEM (scanning electron microscope); (2) Use high-current ion beams to remove surface atoms to complete micro- and nano-scale surface morphology processing. FIBs use ions. Considering the charge-to-mass ratio, ions are much larger than electrons. If magnetic lenses are used to focus, a large magnetic field is required, which is not possible with current technology. Using electrostatic lenses instead requires several sets of electrodes with a load voltage of several to more than ten kilovolts to achieve this.

[0006] Therefore, the present invention provides a new structure to effectively combine the two, which can form a new electron microscope with good detection effect for various samples. Summary of the Invention

[0007] In view of this, the present invention provides an electron microscope and a method for using the same, which can integrate the magnetic lens function and the electrostatic lens function, and realize the conversion of the two lens functions by adjusting the position of the annular pole shoe and the potential difference. The operation is simple and the implementation is convenient.

[0008] In one aspect, the present invention provides an electron microscope comprising:

[0009] An electron source is placed on top of the electron microscope and is used to generate an electron beam for scanning by the electron microscope;

[0010] an electron accelerating electrode, disposed below the electron source and used to increase the speed of the electron beam;

[0011] an objective lens, disposed below the electron accelerating electrode and used for focusing the electron beam;

[0012] An inner pole shoe is provided on the inner side surface of the inner end of the upper shell of the objective lens (the inner end is the end close to the electron beam, and the inner side is the side facing the lower shell), and is arranged in close contact with the inner side surface of the upper shell;

[0013] An outer pole shoe is arranged on the inner side of the inner end of the lower shell of the objective lens (the inner end is the end close to the electron beam, and the inner side is the side facing the upper shell), and is arranged longitudinally;

[0014] a motion control device, arranged on the inner side of the objective lens (the side close to the electron beam) and located below the inner pole shoe;

[0015] an annular pole shoe or a deflection device or an electronic detector, which is arranged on the motion control device and moves up and down under the action of the motion control device; the annular pole shoe is electrically connected to the voltage regulator;

[0016] The sample stage is set at the bottom of the electron microscope and is used to place the sample.

[0017] According to the above aspects and any possible implementation, there is further provided an implementation, wherein the motion control device includes a vertically arranged movable gear shaft, at least two gears meshing with the movable gear shaft, a motor connected to the gears, and a motion control end; the number of motors and gears may correspond one to one or one to two;

[0018] In a one-to-two arrangement, one of the motors is connected to one of the two gears, the gear forming the driving wheel and the other gear being the driven wheel.

[0019] The motor is fixedly arranged inside the objective lens, and the motor is electrically connected to the motion control end;

[0020] The rotating shaft of the motor is fixedly connected to the center of the corresponding gear;

[0021] All the gears are arranged longitudinally in sequence and mesh with the side surfaces of the movable gear shaft provided with teeth, and rotate to drive the movable gear shaft to move up and down;

[0022] The movable gear shaft is fixedly connected to the annular pole shoe or the deflection device or the electronic detector.

[0023] According to the above aspects and any possible implementation, there is further provided an implementation, wherein the motion control device further includes a housing, the housing being disposed outside the gear and the motor;

[0024] A longitudinal slot is provided on one side wall of the housing close to the electron beam; the movable gear shaft is embedded in the longitudinal slot and is slidably connected with the slot wall of the longitudinal slot.

[0025] According to the above aspects and any possible implementation manner, an implementation manner is further provided, wherein the movable gear shaft is in the shape of a rod with a square or trapezoidal cross section.

[0026] According to the above aspects and any possible implementation, an implementation is further provided, wherein upper and lower ends of the movable gear shaft are respectively provided with limit members for limiting the upper and lower movement limits of the movable gear shaft.

[0027] According to the above aspects and any possible implementation, an implementation is further provided, wherein the deflection device comprises: a non-powered annular pole shoe and a deflector provided inside the annular pole shoe.

[0028] According to the aspects described above and any possible implementation method, an implementation method is further provided, in which the inner end of the upper shell and the inner end of the lower shell of the objective lens have a horizontal spacing for the longitudinal movement of the annular pole shoe or the deflection device or the electron detector, and the inner end of the upper shell of the objective lens is closer to the electron beam than the inner end of the lower shell.

[0029] According to the above aspects and any possible implementation, there is further provided an implementation in which the inner ring of the annular pole shoe is longitudinally aligned with the inner end of the upper shell of the objective lens.

[0030] According to the above aspects and any possible implementation, there is further provided an implementation, wherein the annular pole piece, the deflection device, or the electron detector has three movable positions:

[0031] The first position is: the position of the lower surface of the inner pole shoe;

[0032] The second position is: the position where the inner end portion of the lower housing of the objective lens extends;

[0033] The third position is between the objective lens and the sample to be measured.

[0034] In another aspect, the present invention provides a method for using an electron microscope as described above, the method comprising:

[0035] The annular pole shoe is moved to a first position by a motion control device, and a voltage regulator is adjusted to put the annular pole shoe in a non-powered state, so that the annular pole shoe exhibits an immersion magnetic lens function;

[0036] The annular pole shoe is moved to a second position by a motion control device, and a voltage regulator is adjusted to place the annular pole shoe in a non-powered state, so that the annular pole shoe exhibits a non-immersed magnetic lens function;

[0037] The annular pole shoe is moved to a third position by a motion control device, and a voltage regulator is adjusted to put the annular pole shoe in a powered state, so that the annular pole shoe exhibits an electrostatic lens function;

[0038] The deflection device is moved to the first position, the second position or the third position by a motion control device to achieve electron beam focusing functions in different ranges;

[0039] The electron detector is moved to the first position, the second position or the third position by a motion control device to collect backscattered electrons in different areas.

[0040] Compared with the prior art, one of the above technical solutions has the following advantages or beneficial effects: moving the annular pole shoe to the first position and the second position can form an immersion magnetic lens and a non-immersion magnetic lens; moving the annular pole shoe to the third position and applying a potential difference can form an electrostatic lens, thereby meeting the microscopic imaging requirements of different samples; and applying a voltage to the annular pole shoe in the third position can further focus the electron beam and obtain an image with higher resolution;

[0041] Another technical solution among the above technical solutions has the following advantages or beneficial effects: the present invention can realize scanning for scanning fields of different heights by means of a longitudinally movable deflection device;

[0042] Another technical solution among the above technical solutions has the following advantages or beneficial effects: the present invention can collect backscattered electrons with different scattering angles through a longitudinally movable electron detector, thereby solving the problem that backscattered electrons are difficult to collect accurately due to their wide distribution range.

[0043] Of course, any product implementing the present invention does not necessarily need to achieve all of the above-mentioned technical effects at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0045] Figure 1 This is a schematic diagram of the principle structure of an electron microscope provided in Example 1 of the present invention;

[0046] Figure 2 This is a schematic diagram of the principle structure of an electron microscope provided in Example 2 of the present invention;

[0047] Figure 3 This is a schematic diagram of the detection range of an electron microscope provided in Example 2 of the present invention;

[0048] Figure 4 This is a schematic diagram of the principle structure of an electron microscope provided in Example 3 of the present invention;

[0049] Figure 5 This is a schematic diagram of the detection range of an electron microscope provided in Example 3 of the present invention;

[0050] Figure 6 is a side structural diagram of the motion control device in Example 1 of the present invention;

[0051] Figure 72 is a schematic top view of the structure of the motion control device in Example 1 of the present invention.

[0052] Among them, in the figure:

[0053] 1. Electron source; 2. Electron accelerating electrode; 3. Electron beam; 4. Objective lens; 5. Inner pole shoe; 6. Outer pole shoe; 7. Motion control device; 8. Annular pole shoe; 9. Voltage regulator; 10. Sample to be tested; 11. Sample stage; 12. Deflection device; 13. Electron detector; 14. Gear rotation module; 15. Housing; 16. Motion control terminal. DETAILED DESCRIPTION

[0054] In order to better understand the technical solution of the present invention, the embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0055] It should be understood that the embodiments described are only a portion of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative work are within the scope of protection of the present invention.

[0056] In order to overcome the shortcomings of the prior art, the present invention provides an electron microscope, the position of which is controlled by motion to move the annular pole shoe so as to realize the switching of the electron microscope between an electrostatic lens and a magnetic lens. The magnetic lens can also be switched between an immersion lens and a non-immersion lens to observe magnetic / non-magnetic test samples, as well as test samples that require focused ion beam (FIB) processing, and high-quality images can be obtained. The annular pole shoe can also be replaced with a deflection device or an electron detector to meet the customer's needs for onlooker testing of different materials. Specifically, the electron microscope includes:

[0057] Electron source: used to generate the electron beam used for electron microscope scanning;

[0058] Electron accelerating electrode: It is set below the electron source and is used to increase the speed of the electron beam. There is a light hole in the middle of the electron accelerating electrode for the electron beam to pass through.

[0059] Objective lens: arranged below the electron accelerating electrode, used to focus the electron beam;

[0060] Inner pole shoe: set on the inner side of the inner end of the upper shell of the objective lens, and set in close contact with the inner side of the upper shell;

[0061] Outer pole shoe: arranged on the inner side of the inner end of the lower shell of the objective lens, arranged longitudinally;

[0062] Annular pole shoe: movable up and down and arranged between the inner pole shoe and the sample to be tested;

[0063] There is a certain gap between the inner end of the upper shell of the objective lens and the inner end of the lower shell in the horizontal direction, and this gap provides space for the longitudinal movement of the annular pole shoe; preferably, the width of the annular pole shoe ring (that is, the difference between the outer edge radius and the inner edge radius) is not greater than the horizontal spacing between the inner end of the upper shell of the objective lens and the inner end of the lower shell; and preferably, the inner end of the annular pole shoe is longitudinally aligned with the inner end face of the upper shell of the objective lens.

[0064] Motion control device: The annular pole shoe is provided on the motion control device and is used to drive the annular pole shoe to achieve longitudinal movement; the motion control device drives the annular pole shoe to move between a first position, a second position, and a third position, wherein the first position is the lower surface position of the inner pole shoe, the second position is the extended position of the end of the lower housing of the objective lens, and the third position is below the objective lens and above the sample to be measured;

[0065] The motion control device moves the annular pole shoe from the lower surface position of the inner pole shoe to the outer pole shoe pointing connection position; and also controls the annular pole shoe to move from the lower surface position of the inner pole shoe to the position between the objective lens and the sample to be measured;

[0066] In some optional embodiments, the annular pole piece may also be replaced by a deflection device or an electronic detector.

[0067] Example 1:

[0068] like Figure 1 As shown, the present invention provides an electron microscope, which includes an electron source 1, an electron accelerating electrode 2, an electron beam 3, an objective lens 4, an inner pole shoe 5, an outer pole shoe 6, a motion control device 7, an annular pole shoe 8, a voltage regulator 9, a sample to be measured 10 and a sample stage 11.

[0069] Specifically, electron source 1 is used to generate an electron beam. Electron source 1 is classified into field emission sources and thermal emission sources. Field emission sources are further classified into hot field and cold field sources. Thermal emission sources include tungsten filaments, lanthanum hexaboride, and the like. In the present invention, electron source 1 can be any type of electron source 1 for generating an electron beam.

[0070] The electron accelerating electrode 2 is an anode, which is arranged along the emission direction of the electron beam and is used to form an electric field to increase the movement speed of the electron beam.

[0071] The objective lens 4 is used to focus the electron beam onto the sample 10 to be measured.

[0072] The annular pole shoe 8 is used to change the direction of motion of the electron beam before it is incident on the sample to be tested 10, and can generate a scanning field with any deflection direction. The annular pole shoe 8 is connected to the voltage regulator 9, which is adjusted so that the annular pole shoe is in two states: no power applied and power applied, forming a magnetic deflection device and an electric deflection device respectively. The scanning electron beam acting on the sample to be tested 10 will generate secondary electrons, backscattered electrons, cathode fluorescence, etc. The annular pole shoe 8 is set on the motion control device 7, which is vertically arranged at the inner end of the objective lens 4. The motion control device 7 drives the annular pole shoe 8 to move up and down.

[0073] Motion control device 7 such as Figure 6 and Figure 7 As shown, it comprises a gear rotation module 14, a housing 15 and a motion control end 16. The gear rotation module 14 comprises a vertically arranged mobile pinion, at least two gears meshing with the mobile pinion and two motors connected to the gear. The outer periphery of the gear and the motor is covered with the housing 15 to protect the gear and the motor. The motion control end 16 can be arranged inside the housing 15 and connected to the motor to control the work of the motor and change the rotation state, rotation direction and rotation speed of the motor. The motor and the housing 15 are fixedly arranged on the inner side of the objective lens, and the motor drives the gear to rotate, thereby making the mobile pinion move up and down. The mobile pinion is a rod-shaped with a square cross section or a trapezoidal cross section, and its outer side is provided with teeth that can mesh with the gear, and this outer side is a side away from the annular pole shoe 8. Slide rails are provided on the two side surfaces connected to the outer side surface; a vertical slot is provided on the inner side wall of the housing 15, and the slot is square or trapezoidal, and sliders are provided on both side walls of the slot. The movable gear shaft is embedded in the slot, and the slide rails on both side surfaces thereof are respectively slidably connected to the sliders on the two side walls of the slot. The fourth side surface of the movable gear shaft, that is, the inner side surface, is fixedly connected to the annular pole shoe 8, so that the annular pole shoe 8 can move between the first position, the second position and the third position as the gear in the motion control device 7 moves up and down. Limiting members are provided at the upper and lower ends of the movable gear shaft, respectively, for limiting the upper and lower movement limits of the movable gear shaft. The limiting members are arranged horizontally. When the gear contacts the lower surface of the upper limit member or the upper surface of the lower limit member, the movable gear shaft can no longer move further, thereby playing a limiting role.

[0074] In a specific embodiment of the present invention, two gears are controlled by a motor, one of which is the active gear and the other is the driven gear. The rotation direction of the gears is adjusted by the forward and reverse rotation of the motor.

[0075] When the motion control device 7 moves the annular pole shoe 8 to the first position, the annular pole shoe 8 is below the inner pole shoe 5, and the sample stage rises to near the focus (located within the field), so it is a magnetic immersion lens at this time; and at this time the annular pole shoe 8 plays the role of thickening the inner pole shoe below the inner pole shoe 5, and at the same time can increase the magnetic lines of force, so that higher resolution images can be obtained.

[0076] In an immersion electron microscope, when the sample 10 is within the focused magnetic field formed by the objective lens 4, the objective lens has a small aberration coefficient and a short focal length, resulting in high electron microscope image resolution. As the distance between the region of maximum magnetic field intensity and the sample 10 decreases, the aberration decreases, the focal length decreases, and the electron microscope image resolution increases. Immersion lenses are also suitable for non-magnetic samples.

[0077] When the motion control device 7 moves the annular pole shoe 8 to the second position, the annular pole shoe 8 is located at the inner end of the outer pole shoe 6 (the inner end refers to the end close to the electron beam), and the sample stage rises to the vicinity of the annular pole shoe 8. At this time, it is a magnetic non-immersion lens, which is suitable for the detection of magnetic samples.

[0078] When motion control device 7 moves annular pole shoe 8 to the third position, it is now below objective lens 4 and above sample 10. The sample stage rises to the vicinity of annular pole shoe 8, and a voltage is applied to annular pole shoe 8, forming an electrostatic lens. Because annular pole shoe 8 is connected to voltage regulator 9, voltage regulator 9 is adjusted to maintain an applied voltage on the annular pole shoe. Since magnetic lenses have a fixed number of turns in their coils, their use is limited by the number of turns and their zoom speed is relatively slow. Therefore, applying a potential difference to annular pole shoe 8 allows for rapid zoom speed control, resulting in higher-resolution images.

[0079] When the annular pole shoe 8 is in the third position, it forms an electrostatic lens, which is suitable for the new electron microscope equipped with a focused ion beam (FIB). FIB uses ions. Considering the charge-to-mass ratio, ions are much larger than electrons. If a magnetic lens is used to focus, a large magnetic field is required, which cannot be achieved with the current technology level. If an electrostatic lens is used instead, it can be achieved with several groups of electrodes with a load voltage of several to more than ten kilovolts.

[0080] Example 2:

[0081] The difference between this embodiment and embodiment 1 is that the annular pole shoe 8 is replaced by a deflection device 12, as shown in FIG. Figure 2 shown.

[0082] When the motion control device 7 moves the deflection device 12 to the first position, the second position, and the third position, the deflection device plays the role of focusing the electron beam. Figure 3As shown, the deflection device 12 can be moved to three positions using the motion control device 7. The three positions have different detection ranges. The image signal quality of the three positions is collected, and the position with the best signal is selected to capture the final desired image. This can produce higher quality image signals and higher resolution images.

[0083] The deflection device 12 may be constructed by adding a deflector to the inner side of the annular pole shoe 8 , and the annular pole shoe and the added deflector together constitute the deflection device.

[0084] Example 3:

[0085] The difference between this embodiment and embodiment 1 is that the annular pole piece 8 is replaced with an electronic detector 13, as shown in FIG. Figure 4 shown.

[0086] After the incident electron beam impacts the surface of the sample 10 under test, it escapes from the sample 10 after undergoing elastic and inelastic collisions. The backscattered electrons are emitted from a depth of approximately 10 nm to 1 μm below the sample surface, revealing structural information deeper within the sample. Because the energy of the backscattered electrons is higher than 50 eV, their escape directions from the surface of the sample 10 are irregular, and their number depends on the incident angle of the electrons and the average atomic number Z of the sample material under test. The larger the Z, the more incident electrons are scattered, so the backscattered electrons can reflect the elemental distribution of the sample. The yield of backscattered electrons is also affected by the sample surface topography, so the backscattered electron signal simultaneously reflects the sample surface topography and compositional contrast.

[0087] As mentioned above, since the backscattered electrons escape from the surface of the sample 10 in irregular directions and have different average atomic numbers, the number of scattered electrons is also different, and the distribution range is wide, it is difficult for the electron detector to detect and collect backscattered electrons from all directions at the same time. Figure 5 As shown, it can be seen that the angles of the backscattered electrons (BSE) collected are different depending on the height of the detector. When the detector is close to the sample, that is, at the third position, it collects mainly backscattered electrons (BSE) from a small part of the θ2 (medium angle) and most of the θ3 (high angle) area; when the detector is at the second position, it collects mainly backscattered electrons (BSE) from the majority of the θ2 (medium angle) and a small part of the θ1 (low angle) area; when the detector is at the first position, it collects mainly backscattered electrons (BSE) from the majority of the θ1 (low angle) area. It can be seen that by moving the electron detector 13 by the motion control device 7, it can be moved to three positions respectively. The detection ranges of the three positions are different, and the number of collected signals is also different.

[0088] For different materials, the image signal quality of three locations needs to be collected separately, and then the location with the best signal is selected to collect the final required image. This can ensure a higher quality image signal.

[0089] The above describes in detail an electron microscope and its method of use provided in the embodiments of the present application. The description of the above embodiments is only intended to help understand the method and core concept of the present application; at the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present application. In summary, the contents of this specification should not be construed as limiting the present application.

Claims

1. An electron microscope, characterized in that The electron microscope comprises: Electron source: located at the top of the electron microscope, used to generate the electron beam used for electron microscope scanning; Electron accelerating electrode: arranged below the electron source, used to increase the speed of the electron beam; Objective lens: arranged below the electron accelerating electrode, used for focusing the electron beam; Inner pole shoe: arranged on the inner side surface of the inner end of the upper shell of the objective lens, and arranged in close contact with the inner side surface of the upper shell; Outer pole shoe: arranged on the inner side of the inner end of the lower shell of the objective lens, arranged longitudinally; A motion control device is arranged inside the objective lens and below the inner pole shoe; An annular pole shoe or deflection device: provided on the motion control device and capable of moving up and down under the action of the motion control device; the annular pole shoe is electrically connected to the voltage regulator; Sample stage: set at the bottom of the electron microscope, used to place samples; The annular pole piece or the deflection device has three movement positions: The first position is: the position of the lower surface of the inner pole shoe; The second position is: the position where the inner end portion of the lower housing of the objective lens extends; The third position is between the objective lens and the sample to be measured; The annular pole shoe is moved to a first position by a motion control device, and a voltage regulator is adjusted to put the annular pole shoe in a non-powered state, so that the annular pole shoe exhibits an immersion magnetic lens function; The annular pole shoe is moved to a second position by a motion control device, and a voltage regulator is adjusted to place the annular pole shoe in a non-powered state, so that the annular pole shoe exhibits a non-immersed magnetic lens function; The annular pole shoe is moved to a third position by a motion control device, and a voltage regulator is adjusted to put the annular pole shoe in a powered state, so that the annular pole shoe exhibits an electrostatic lens function; The deflection device is moved to the first position, the second position or the third position by the motion control device to achieve electron beam focusing functions in different ranges.

2. The electron microscope according to claim 1, characterized in that The motion control device includes a vertically arranged movable gear shaft, at least two gears meshing with the movable gear shaft, a motor connected to the gears, and a motion control end; The motor is fixedly arranged inside the objective lens, and the motor is electrically connected to the motion control end; The rotating shaft of the motor is fixedly connected to the center of the corresponding gear; All the gears are arranged longitudinally in sequence and mesh with the side surfaces of the movable gear shaft provided with teeth, and rotate to drive the movable gear shaft to move up and down; The movable gear shaft is fixedly connected to the annular pole shoe or the deflection device.

3. The electron microscope according to claim 2, characterized in that The motion control device further comprises a housing, wherein the housing is arranged outside the gear and the motor; A longitudinal slot is provided on one side wall of the housing close to the electron beam; the movable gear shaft is embedded in the longitudinal slot and is slidably connected with the slot wall of the longitudinal slot.

4. The electron microscope according to claim 2, characterized in that The movable gear shaft is in the shape of a rod with a square or trapezoidal cross section.

5. The electron microscope according to claim 2, characterized in that The upper and lower ends of the movable gear shaft are respectively provided with limit pieces for limiting the upper and lower movement limits of the movable gear shaft.

6. The electron microscope according to claim 1, characterized in that The deflection device comprises: a non-powered annular pole shoe and a deflector arranged inside the annular pole shoe.

7. The electron microscope according to claim 1, characterized in that The inner end of the upper shell of the objective lens and the inner end of the lower shell have a horizontal distance that can be used to set the annular pole shoe or the deflection device, and the inner end of the upper shell of the objective lens is closer to the electron beam than the inner end of the lower shell.

8. The electron microscope according to claim 7, characterized in that The inner ring of the annular pole shoe is longitudinally aligned with the inner end of the upper housing of the objective lens.

Images