Mechanical centering device and electron microscope

Abstract

The present invention discloses a mechanical alignment device and an electron microscope using the device. The device comprises: a laser emitter, disposed within a sample chamber of the electron microscope, emitting a laser beam toward the electron source of the electron microscope; a half-reflecting half-mirror, disposed within the lens barrel of the electron microscope, between the electron source and the aperture of the electron microscope, and located on the irradiation path of the laser beam emitted by the laser emitter, with the reflective surface of the half-reflecting half-mirror tilted downward; and an image sensor, mounted on the lens barrel, receiving the laser beam reflected by the half-reflecting half-mirror. The present invention uses a laser beam that overlaps with the electron beam as a reference for mechanical pre-alignment of the electron microscope. The relative position of the aperture is adjusted by observing the laser beam spot, and the relative position of the electron source is adjusted by observing the reflection of the laser beam at the tip of the electron source gun. Rapid mechanical alignment of the electron microscope is achieved safely and quickly without the need for high voltage or vacuum.

Description

Technical Field

[0001] The present invention relates to the technical field of electron microscopes, and in particular to a mechanical centering device and an electron microscope having the mechanical centering device. Background Art

[0002] Electron microscopes (EM), also known as electron microscopes (EM), are categorized by structure and purpose into transmission electron microscopes, scanning electron microscopes, reflection electron microscopes, and emission electron microscopes. Their basic principle is that an electron source emits an electron beam, which is modulated by a lens system and then strikes the sample being observed, stimulating various physical signals. These signals are detected by a detector and then processed and modulated to form an image. The electron source is located within the microscope barrel, while the sample is supported by a sample stage within the sample chamber.

[0003] The alignment and co-ordination of electron microscopes are the foundation and guarantee of good imaging. Currently known methods for electron microscope alignment and co-ordination generally require observing the electron beam spot or the pattern formed on the detector by a specific sample to determine whether the mechanical axis, optical axis, and magnetic axis in the electron microscope coincide and make adjustments accordingly. This type of alignment and co-ordination method has the following disadvantages: the method must ensure the normal emission of the electron source, so the entire system must be operated and adjusted under high vacuum and high voltage conditions; the method relies on an invisible electron beam as a signal source, and the adjustments of multiple system axes are coupled to each other. The effect is relatively good for high-precision adjustment, but the efficiency is very low when the initial alignment of the system is poor, and it is impossible to quickly and accurately achieve the initial mechanical pre-alignment of the system. Summary of the Invention

[0004] In order to overcome the deficiencies of the prior art, the present invention provides a mechanical centering device for an electron microscope and an electron microscope having the mechanical centering device, so as to achieve the purpose of quickly and accurately realizing the initial mechanical pre-centering of the system.

[0005] To achieve the above object, the present invention first provides a mechanical centering device, comprising:

[0006] A laser emitter, the laser emitter being arranged in a sample chamber of an electron microscope and emitting a laser beam toward an electron source of the electron microscope;

[0007] A half-reflecting half-mirror, the half-reflecting half-mirror being arranged in a lens barrel of an electron microscope, being located between an electron source and an aperture of the electron microscope when the laser emitter emits a laser beam, and being located on an irradiation path of the laser beam emitted by the laser emitter, with a reflective surface of the half-reflecting half-mirror being arranged to tilt downward;

[0008] An image sensor is mounted on the lens barrel and receives the laser beam reflected by the half-reflecting half-mirror lens.

[0009] Optionally, a lens system is further included for adjusting the beam spot diameter of the laser beam emitted by the laser emitter.

[0010] Optionally, the reflecting surface of the half-reflecting half-mirror lens forms an angle of 45 degrees with the irradiation direction of the laser beam emitted by the laser emitter.

[0011] Optionally, the direction of the line connecting the center of the reflective surface of the half-reflecting half-mirror and the center of the image sensor is consistent with the irradiation direction of the laser beam reflected by the half-reflecting half-mirror.

[0012] Optionally, the image sensor is a CCD sensor.

[0013] Optionally, the image sensor is a CMOS sensor.

[0014] Optionally, a half-reflective half-mirror moving mechanism is also included.

[0015] Optionally, the laser emitter is mounted on a sample stage of an electron microscope.

[0016] Secondly, the present invention provides an electron microscope, which includes any one of the above-mentioned mechanical centering devices.

[0017] The mechanical centering device provided by the present invention uses a laser beam that coincides with the electron beam as a reference for mechanical pre-centering of the electron microscope. The relative position of the aperture is adjusted by observing the laser beam spot, and the relative position of the electron source is adjusted by observing the reflection of the laser beam at the tip of the electron source gun. Without the need for high voltage electricity and maintaining vacuum, the rapid mechanical centering of the electron microscope can be safely and quickly achieved.

[0018] Based on the following detailed description of specific embodiments of the present invention in conjunction with the accompanying drawings, those skilled in the art will become more aware of the above and other objects, advantages and features of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Hereinafter, some specific embodiments of the present invention will be described in detail in an exemplary and non-limiting manner with reference to the accompanying drawings. The same reference numerals in the accompanying drawings indicate the same or similar components or parts. It should be understood by those skilled in the art that these drawings are not necessarily drawn to scale. In the accompanying drawings:

[0020] Figure 1 Schematic diagram of the structure of the mechanical centering device in an embodiment of the present invention.

[0021] Figure 2 This is a schematic diagram of the image formed by the laser beam when the aperture is not centered.

[0022] Figure 3 It is a schematic diagram of the image formed by the laser beam when the aperture is centered.

[0023] Figure 4 This is a schematic diagram of the reflection of the laser beam at the gun tip when the electron source is not centered.

[0024] Figure 5 This is a schematic diagram of the reflection of the laser beam at the gun tip when the electron source is centered.

[0025] Reference numerals:

[0026] 1. Mirror barrel, 2. Sample chamber, 3. Sample stage, 4. Electron source, 5. Aperture, 6. Laser emitter, 7. Half-reflective half-mirror lens, 8. Image sensor, 9. Push-pull mechanism. DETAILED DESCRIPTION

[0027] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0028] The present invention is described using a scanning electron microscope as an example. The scanning electron microscope mainly includes the following components:

[0029] Electron optical system, which includes an electron gun (electron source) and a lens system. The function of the electron gun is to generate an electron illumination source. The functions of the lens system are: (1) to reduce the size of the virtual light source from tens of microns to 5nm (or smaller), and to continuously change it from tens of microns to several nanometers; (2) to control the opening angle of the electron beam, which can be changed in the range of 10-2 to 10-3rad; (3) the formed focused electron beam can be raster-scanned on the surface of the sample, and the scanning angle range is variable. In order to obtain the above-mentioned scanning electron beam, the lens system usually includes an electromagnetic lens, a scanning coil and an aperture. The electromagnetic lens is used to focus the electron beam. The function of the scanning coil is to deflect the electron beam and make a regular sweep on the sample surface. The function of the aperture includes filtering out the far-axis electrons in the electron beam and adjusting the image depth of field.

[0030] The mechanical system consists of a support and a sample chamber. The sample chamber contains a sample stage and has several windows on its four walls. In addition to the electron detector, other detectors and a spectrometer can also be installed.

[0031] Vacuum system is very important in electron optical instruments because electron beams can only be generated and manipulated under vacuum. Commonly used high vacuum systems include dry pump systems, turbomolecular pump systems, and ion pump systems.

[0032] The signal collection, processing, and display system of a scanning electron microscope (SEM) involves focusing the electron beam emitted by the electron gun into a point source. This point source, under an accelerating voltage, generates a high-energy electron beam. This high-energy electron beam is then focused into a tiny spot by an electromagnetic lens. After passing through a final electromagnetic lens equipped with a scanning coil, the electron beam strikes the sample surface point by point in a raster-like scanning pattern, simultaneously stimulating physical signals at varying depths. These signals are received by various detectors and synchronously transmitted to a computer display via an amplifier, resulting in real-time imaging. The incident electron beam generates various physical signals in the sample, including Auger electrons (AuE), secondary electrons (SE), backscattered electrons (BSE), X-rays (characteristic X-rays and continuous X-rays), cathodoluminescence (CL), absorbed electrons (AE), and transmitted electrons. Different physical signals require different detection systems, broadly classified into three categories: electron detectors, cathodoluminescence detectors, and X-ray detectors.

[0033] The electron optical system is generally located in the lens barrel above the sample chamber. The signal detector is usually located in the sample chamber or the lens barrel. The electron gun, lens system and signal detector are connected to an external power supply. The vacuum system provides a vacuum environment for the lens barrel and sample chamber.

[0034] like Figure 1 As shown, the mechanical centering device in the embodiment of the present invention includes a laser emitter 6, a half-reflecting half-mirror 7 and an image sensor 8. The laser emitter 6 is arranged in the sample chamber 2, and in this embodiment is specifically arranged on the sample stage 3. When performing the centering operation, the laser emitter 6 is placed at the system origin, for example, by adjusting the position of the sample stage 3 or adjusting the position of the laser emitter 6 on the sample stage 3. The system origin here refers to the system reference point of the centering. The half-reflecting half-mirror 7 is arranged in the lens barrel 1, below the electron source 4 and above the aperture 5, that is, between the electron source 4 and the aperture 5, and is located on the irradiation path of the laser beam emitted by the laser emitter 6. The reflective surface of the half-reflecting half-mirror 7 is tilted downward, so that after the laser beam emitted from the laser emitter 6 is irradiated on the reflective surface of the half-reflecting half-mirror 7, a portion is reflected toward the side wall of the lens barrel 1, and the other portion passes through the half-reflecting half-mirror 7 and irradiates the electron source 4. Image sensor 8 is mounted on the lens barrel and located in the illumination path of light reflected by semi-reflecting mirror 7, so that it can receive the laser beam reflected by semi-reflecting mirror 7. Preferably, the reflective surface of semi-reflecting mirror 7 forms a 45-degree angle with the illumination direction of the laser beam emitted by laser emitter 6, and / or preferably, the direction of the line connecting the center of the reflective surface of semi-reflecting mirror 7 and the center of image sensor 8 is consistent with the illumination direction of light reflected by semi-reflecting mirror 7. Image sensor 8 can be a CCD (charge coupled device) sensor or a CMOS (complementary metal oxide semiconductor) sensor, etc.

[0035] In this embodiment, the mechanical centering device may further include a laser irradiation lens system for adjusting the beam spot diameter of the laser beam emitted by the laser emitter 6 to match the size of the aperture 5. Those skilled in the art will appreciate that the aperture 5 may be one or more than one aperture 5 disposed along the optical path.

[0036] In this embodiment, the half-reflecting mirror 7 is movable so as to be removed from the optical path after the centering operation is completed. For example, a push-pull mechanism 9 can be provided for the half-reflecting mirror 7, to which the half-reflecting mirror 7 is fixed. The push-pull mechanism 9 enables the half-reflecting mirror 7 to be moved from the side wall of the lens barrel 1 toward the center of the lens barrel 1 or vice versa. The above examples are merely illustrative; in actual applications, any suitable mechanism can be selected to achieve the movement of the half-reflecting mirror 7.

[0037] Taking a scanning electron microscope as an example, when mechanical alignment is performed, the laser emitter 6 is first placed at the system origin (for example, by moving the sample stage). The laser emitter 6 then emits a parallel laser beam in the direction of the electron source 4. The lens system can then be adjusted to better match the size of the aperture 5. The laser beam passes through each aperture 5 in the electron microscope in sequence and hits the half-reflecting half-mirror 7 below the electron source 4. A portion of the laser light is reflected toward the side wall of the lens barrel 1 and is received by the image sensor 8, which displays the resulting image on a display device (such as a computer monitor). By observing parameters such as the roundness and concentricity of the resulting image, it is determined whether the laser beam is blocked by the aperture 5. Based on this, the position of the aperture 5 is adjusted to achieve mechanical alignment of the aperture in the electron microscope lens system. The other part passes through the half-reflecting half-mirror 7 and hits the electron source 4, specifically the gun tip of the electron source 4, and is diffusely reflected by the gun tip of the electron source 4. The operator can observe the diffuse reflection of this part of the laser through the observation window on the side wall of the lens barrel 1, and judge whether the electron source 4 meets the centering requirements according to the brightness of the light spot on the gun tip, and make adjustments based on this.

[0038] If the aperture 5 is offset relative to the beam axis, the laser beam is partially blocked by the aperture 5, and the image formed is as follows: Figure 2 As shown, the operator can observe the movement and changes of the image formed by the laser beam while adjusting the position of the diaphragm 5 in a targeted manner until the center of the diaphragm 5 is basically aligned with the beam axis. At this time, the image is as shown in FIG. Figure 3 shown.

[0039] If the electron source 4 is offset relative to the beam axis, the reflection of the laser beam on the gun tip will be as follows: Figure 4 As shown, the operator can adjust the position of the electron source 4 in a targeted manner while observing the changes in the intensity and direction of the laser beam reflected by the gun tip to achieve the effect of pre-centering. At this time, the reflection of the laser beam on the gun tip is as shown in FIG. Figure 5 shown.

[0040] The mechanical centering device provided in the embodiment of the present invention can be removed after the mechanical pre-centering of the electron microscope is completed, and then the electron microscope is subsequently assembled, or it can be retained in the electron microscope for standby use.

[0041] The mechanical centering device provided by the present invention uses a laser beam that coincides with the electron beam as a reference for mechanical pre-centering of the electron microscope. The relative position of the aperture is adjusted by observing the laser beam spot, and the relative position of the electron source is adjusted by observing the reflection of the laser beam at the tip of the electron source gun. Without the need for high voltage electricity and maintaining vacuum, the rapid mechanical centering of the electron microscope can be safely and quickly achieved.

[0042] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A mechanical centering device, characterized in that: include: A laser emitter, the laser emitter being arranged in a sample chamber of an electron microscope and emitting a laser beam toward an electron source of the electron microscope; A half-reflecting half-mirror, the half-reflecting half-mirror being arranged in a lens barrel of an electron microscope, being located between an electron source and an aperture of the electron microscope when the laser emitter emits a laser beam, and being located on an irradiation path of the laser beam emitted by the laser emitter, with a reflective surface of the half-reflecting half-mirror being arranged to tilt downward; An image sensor, the image sensor being mounted on the lens barrel and receiving the laser beam reflected by the half-reflecting half-mirror lens; The reflective surface of the half-reflecting half-mirror forms an angle of 45 degrees with the irradiation direction of the laser beam emitted by the laser emitter, and the direction of the line connecting the center of the reflective surface of the half-reflecting half-mirror and the center of the image sensor is consistent with the irradiation direction of the laser beam reflected by the half-reflecting half-mirror; Also included is a lens system for adjusting the beam spot diameter of the laser beam emitted by the laser emitter; The image of the reflected laser beam received by the image sensor is used to determine whether the aperture blocks the laser beam based on the roundness and concentricity of the image, and the aperture position is adjusted based on the determination to achieve mechanical centering of the aperture; and the electron source is judged to be offset based on the change in brightness of the diffusely reflected light spot through the diffuse reflection of the laser beam that passes through the half-reflecting half-mirror and irradiates the electron source gun tip, and the electron source position is adjusted based on the determination to achieve mechanical centering of the electron source.

2. The mechanical centering device according to claim 1, characterized in that: The image sensor is a CCD sensor.

3. The mechanical centering device according to claim 1, characterized in that: The image sensor is a CMOS sensor.

4. The mechanical centering device according to claim 1, characterized in that: It also includes a half-reflective half-mirror moving mechanism.

5. The mechanical centering device according to claim 1, characterized in that: The laser emitter is installed on the sample stage of the electron microscope.

6. An electron microscope, characterized in that It comprises a mechanical centering device according to any one of claims 1-5.

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