Electron-optical column and electron beam inspection apparatus having the same
By introducing an imaging grating into the electron optical lens barrel, the sample height is directly fed back based on changes in the grating image, thus solving the error problem introduced by external hardware and achieving the effects of simplifying the structure and improving measurement accuracy.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-16
- Publication Date
- 2026-06-19
AI Technical Summary
Existing methods for measuring the height of electro-optical telescopes require external hardware, resulting in complex structures and significant errors that affect measurement accuracy.
An imaging grating is placed on the return path of the electron beam. The sample height change is determined by analyzing the changes in the image of the imaging grating and then compensated for, avoiding the use of external hardware such as capacitive sensors or triangular reflection optical path devices.
This achieves a simplified structure and improves the accuracy and speed of height measurement without introducing additional errors, ensuring that the electron beam is always kept at the optimal focus on the sample surface.
Smart Images
Figure CN224384246U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of electron beam detection equipment technology, and in particular to an electron optical lens barrel and an electron beam detection device having the same. Background Technology
[0002] Electron beam inspection equipment is widely used in the semiconductor industry. For example, scanning electron microscopes (SEMs) are commonly used for defect detection in manufactured objects such as chips. The main principle of an SEM is to use a beam of charged particles to bombard the surface of the object under test, and to detect the secondary electron signals generated in the bombarded area to obtain various physical and chemical information about the sample, such as morphology, composition, and characteristic distribution. Typical applications of electron beam inspection equipment include the detection of microscopic patterns and measurement of critical dimensions on semiconductor silicon wafers and photomasks using electron beams in a vacuum, and the detection of open-circuit and short-circuit defects in CMOS integrated circuits.
[0003] The electron optical tube is a core component of electron beam detection equipment, characterized by high precision and high compositeness. When the electron optical tube is in operation, its optical depth of field is very small, typically on the order of tens of nanometers to a few micrometers. If the height difference of the sample exceeds the depth of field range of the electron optical tube, the sample image will become out of focus, resulting in a suboptimal resolution image. Therefore, ensuring the electron beam operates at the optimal focal plane is crucial. In industries such as semiconductors, the electron beam operates under fixed conditions for image stability, meaning the focusing capability of the electron optics is constant. Therefore, for cases where the sample surface height varies, it is necessary to measure the sample surface height and then compensate for the height difference using a separate height control system based on the measurement results.
[0004] Common height measurement methods include capacitance measurement, triangular reflection measurement, and grating measurement. Capacitance measurement utilizes a capacitive sensor placed on a pole piece; when the height between the sensor and the sample changes, the sensor signal changes. This signal change drives a moving structure to perform rapid height compensation, achieving high-speed measurement and compensation. Triangular reflection measurement uses changes in the height of the optical reflective surface to indicate changes in the position of the reflected light spot, thus reflecting the height change and driving a moving structure to perform rapid height compensation. Grating measurement builds upon triangular reflection by transforming the light spot shape into a grating shape. Algorithms detect changes in the grating lines relative to the height to reflect changes in the sample surface height, offering superior detection accuracy compared to light spot reflection. Existing height measurement methods all require external hardware, such as capacitance sensor structures and triangular reflection optical path devices, which not only increase structural complexity but also introduce additional errors, affecting the accuracy of height measurement. Utility Model Content
[0005] In view of the above problems, this utility model is proposed to provide an electron optical tube and an electron beam detection device having the same, which overcomes or at least partially solves the above problems. It can realize height measurement function without the aid of external hardware, has a simple structure, and can prevent the introduction of additional errors as much as possible, thereby improving measurement accuracy.
[0006] Specifically, this utility model provides an electron optical lens barrel for an electron beam detection device, comprising:
[0007] A cylindrical body, the interior of which is used for the passage of an electron beam; the electron beam is configured to act on a sample such that the sample generates a return electron signal under the action of the electron beam.
[0008] A detector is disposed inside the cylinder and configured to receive the returned electronic signal;
[0009] An imaging grating is disposed inside the cylinder and on the side of the detector that receives the returned electron signal; the imaging grating is configured to block part of the returned electron signal so that the image generated by the electron beam detection device based on the returned electron signal received by the detector is superimposed with the image of the imaging grating.
[0010] Optionally, the imaging grating includes:
[0011] A shielding frame having a connecting hole for forming a forward path of the electron beam;
[0012] At least one blocking rod is disposed outside the path of the electron beam.
[0013] Optionally, the blocking frame is an annular frame or a square frame, and the annular frame or the square frame surrounds the communicating hole.
[0014] Optionally, one end of each of the shielding bars is connected to the outside of the shielding frame.
[0015] Optionally, there are multiple blocking bars, which are arranged at intervals along the circumference of the blocking frame.
[0016] Optionally, the plurality of the shielding bars are evenly distributed along the circumference of the shielding frame.
[0017] Optionally, the electron optical lens barrel further includes:
[0018] The mounting frame is disposed on the cylinder, the shielding frame is disposed inside the mounting frame, and the shielding rod is disposed between the mounting frame and the shielding frame.
[0019] Optionally, the detector is provided with an electron beam passage hole;
[0020] The connecting hole is coaxially arranged with the electron beam through hole;
[0021] The connecting hole is a circular hole, and the diameter of the connecting hole is greater than or equal to the diameter of the hole through which the electron beam passes.
[0022] Optionally, the electron optical lens barrel further includes:
[0023] A condenser lens is disposed inside the cylinder and is located on the side of the detector opposite to the imaging grating;
[0024] The objective lens is disposed inside the tube and is located on the side of the imaging grating opposite to the detector.
[0025] This utility model also provides an electron beam detection device, which includes any of the above-mentioned electron optical lens tubes.
[0026] In the electron optical tube and electron beam detection device of this invention, an imaging grating is incorporated. This grating is positioned on the return path of the electron beam, blocking the returning electron signal. This results in the image generated by the electron beam detection device being superimposed with the image of the imaging grating. Then, the degree of defocusing of the grating image is determined based on changes in the grating image, which in turn allows for feedback on the change in sample height. Height compensation is then applied based on this change, ensuring that the electron beam focus point remains consistently on the sample surface.
[0027] The electron optical tube and electron beam detection device of this invention directly compensate for height based on the imaging of the imaging grating. It does not require the introduction of external hardware such as capacitive sensor structure or triangular reflection optical path device, nor does it introduce additional errors caused by external hardware. This reduces the complexity of the structure, makes it simple, and ensures the accuracy of the height change obtained, thereby ensuring the accuracy of the results obtained by the electron beam detection device.
[0028] The above and other objects, advantages and features of this utility model will become more apparent to those skilled in the art from the following detailed description of specific embodiments of this utility model in conjunction with the accompanying drawings. Attached Figure Description
[0029] The following sections will describe some specific embodiments of the present invention in a detailed manner by way of example and not limitation, with reference to the accompanying drawings. The same reference numerals in the drawings denote the same or similar parts or components. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings:
[0030] Figure 1 This is a schematic structural diagram of an electron optical lens barrel according to an embodiment of the present invention;
[0031] Figure 2 This is a schematic internal structure diagram of an electron optical lens barrel according to an embodiment of the present invention;
[0032] Figure 3 This is a schematic imaging diagram of an electron optical lens barrel according to an embodiment of the present invention;
[0033] Figure 4 This is a schematic imaging diagram of an electron optical lens tube according to another embodiment of the present invention;
[0034] Figure 5 This is a schematic imaging diagram of an electron optical lens tube according to another embodiment of the present invention;
[0035] Figure 6 This is a schematic structural diagram of an imaging grating in an electron optical lens barrel according to an embodiment of the present invention;
[0036] Figure 7 This is a schematic structural diagram of an imaging grating in an electron optical lens barrel according to another embodiment of the present invention;
[0037] Figure 8 This is a schematic structural diagram of an imaging grating in an electron optical lens barrel according to another embodiment of the present invention;
[0038] Figure 9 This is a schematic structural diagram of an imaging grating in an electron optical lens barrel according to another embodiment of the present invention;
[0039] Figure 10 This is a schematic structural diagram of an imaging grating in an electron optical lens barrel according to yet another embodiment of the present invention.
[0040] In the attached image:
[0041] 10. Cylinder body 11. Electron beam 12. Returning electron signal 12. Detector 20. Imaging grating 30. Shielding frame 31. Connecting hole 32. Shielding rod 33. Mounting frame 34. Condenser lens 40. Objective lens 50. Sample 80. Detailed Implementation
[0042] The following reference Figures 1 to 10This invention describes an electron optical tube and an electron beam detection device having the same, according to embodiments of the present invention. In this description, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature, that is, include one or more of that feature. In the description of the present invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified. When a feature "includes or contains" one or more of the features it encompasses, unless otherwise specifically described, this indicates that other features are not excluded and may be further included.
[0043] Unless otherwise expressly specified and limited, the terms "set," "install," "connect," "link," "fix," and "couple" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art should be able to understand the specific meaning of the above terms in this utility model according to the specific circumstances.
[0044] Furthermore, in the description of this embodiment, "above" or "below" the second feature can include direct contact between the first and second features, or it can include contact between the first and second features through another feature between them. That is, in the description of this embodiment, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," or "below" of the second feature can mean the first feature is directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.
[0045] In the description of this embodiment, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this utility model. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.
[0046] Figure 1This is a schematic structural diagram of an electron optical lens barrel according to an embodiment of the present invention, as shown below. Figure 1 As shown, and refer to Figures 2 to 10 This utility model provides an electron optical tube for an electron beam detection device, which includes a tube body 10, a detector 20, and an imaging grating 30.
[0047] The cylinder 10 is used for the passage of an electron beam 11. The electron beam 11 is configured to act on a sample 80, causing the sample 80 to generate a return electron signal 12 under the action of the electron beam 11. A detector 20 is disposed inside the cylinder 10 and configured to receive the return electron signal 12. An imaging grating 30 is disposed inside the cylinder 10 and is located on the side of the detector 20 that receives the return electron signal 12. The imaging grating 30 is configured to partially block the return electron signal 12, so that the image generated by the electron beam 11 detection device based on the return electron signal 12 received by the detector 20 is superimposed with the image of the imaging grating 30.
[0048] In this embodiment of the electron optics tube, during operation, the electron beam 11, after passing through the through-hole on the on-axis detector 20, is focused onto the sample surface, forming a nanoscale electron beam spot. Due to the interaction between electrons and the sample 80, a return electron signal 12 is generated on the sample surface. These sputtered electron signals will pass back through the imaging grating 30. Since the sputtered electron beam 11 is divergent, the imaging grating 30 partially blocks the return electron signal 12. The return electron signal 12 passing through the imaging grating 30 strikes the detector 20 and is converted into an electrical signal for imaging.
[0049] Because the returned electronic signal 12 is partially blocked by the imaging grating 30, the image acquired by the detector 20 contains not only the information of the sample 80 but also the image of the imaging grating 30 superimposed on it. Moreover, the images acquired at different locations are all images of the sample 80 superimposed with the image of the imaging grating 30.
[0050] When the topography of sample 80 changes, the image acquired by detector 20 will become out of focus accordingly. Since sample 80 and imaging grating 30 are not on the same image plane, and the electron beam 11 focuses near the sample surface, the image of imaging grating 30 will be more severely out of focus than the image of sample 80 in the final image acquired by detector 20. Figures 3 to 5 As shown.
[0051] Furthermore, the image of the imaging grating 30 in the image is extracted and analyzed. Based on the degree of defocusing of the image of the imaging grating 30, the change in the height of the sample 80 is fed back, thereby driving the motion structure to perform height compensation. This can change the height of the sample 80 or the electron optical tube, so as to achieve the goal that the focus point of the electron beam 11 is always on the sample surface.
[0052] like Figure 3 , Figure 4 , Figure 5 As shown, this is used to compare the focus and out-of-focus conditions of 30 images from the imaging grating. Figure 3 This is a diagram showing the focal position. Figure 4 This is a schematic diagram of the 30 images of the imaging grating with a slight change in height. Figure 5 This is a schematic diagram of the imaging grating 30 where the height has changed more significantly. The relationship between different degrees of defocus and height changes can be detected and acquired in advance, and then stored in tables, etc., to facilitate the subsequent acquisition of the change in height of sample 80 based on the determined degree of defocus, that is, to obtain the height compensation amount.
[0053] In other words, in the electron optical tube of this embodiment, when the height of the sample 80 changes, the imaging distance of the electron beam 11 changes. However, the focusing capability of the electron optical tube remains fixed. Due to the change in height, the image of the electron beam 11 becomes out of focus. The returning electron beam 11 also passes through the imaging grating 30, creating a shadow effect on the electron signal image. However, because the height of the sample surface changes, the diameter and beam density of the returning electron beam 11 change, resulting in different degrees of obstruction of the returning signal electrons and different imaging effects. Furthermore, the imaging grating 30 is positioned higher, closer to the detector 20, and its obstruction of the returning electron signal 12 is greater. Therefore, in the final image acquired by the detector 20, the image of the imaging grating 30 is more severely out of focus than the image of the sample 80. Since the physical dimensions of the imaging grating 30 are fixed, its out-of-focus, focused, and over-focus images maintain the basic layout of the imaging grating 30, facilitating image recognition. The image of the imaging grating 30 in the final image is extracted and analyzed. Based on the degree of defocusing of the image of the imaging grating 30, the change in the height of the sample 80 can be fed back, thereby driving the sample 80 to perform height compensation, so as to achieve the goal that the focus point of the electron beam 11 is always on the sample surface.
[0054] In other words, in the electron optical tube of this embodiment, because it has an imaging grating 30, which is positioned on the return path of the electron beam 11 and blocks the returned electron signal 12, the image generated by the electron beam 11 detection device is superimposed with the image of the imaging grating 30. Then, based on the changes in the image of the imaging grating 30, the degree of defocusing of the grating image is determined, thereby providing feedback on the change in the height of the sample 80. Height compensation is then performed based on this change to ensure that the focus point of the electron beam 11 is always on the sample surface, guaranteeing that the electron beam 11 always operates in positive focus. Furthermore, by directly compensating for height based on the imaging of the imaging grating 30, external hardware such as capacitive sensor structures and triangular reflection optical path devices is not required, and additional errors caused by external hardware are avoided. This reduces structural complexity, simplifies the structure, and ensures the accuracy of the obtained height change, thereby guaranteeing the accuracy of the results obtained by the electron beam 11 detection device. Moreover, this embodiment can quickly measure the height change of the sample surface.
[0055] In some embodiments of this utility model, such as Figure 6-9 As shown, the imaging grating 30 may include a blocking frame 31, which has a connecting hole 32 for forming the path of the electron beam 11. The electron beam 11 can advance onto the sample surface through the connecting hole 32 in the middle of the blocking frame 31. The connecting hole 32 does not obstruct the electron beam 11. The blocking frame 31 can obstruct the returned electron signal 12. The image of the blocking frame 31 is simple and occupies a small area, which facilitates the analysis and acquisition of the defocusing degree of the imaging grating 30. Due to its simple structure, the blocking frame 31 does not obstruct the returned electron signal 12 over a large area, ensuring the accuracy of the sample 80 information contained in the acquired image.
[0056] Similarly, in some embodiments of this utility model, such as Figure 6-10 As shown, the imaging grating 30 may include at least one blocking rod 33, disposed outside the forward path of the electron beam 11. The image of the blocking rod 33 is also simple and occupies a small area, which facilitates the analysis of the degree of defocusing of the imaging grating 30, and will not obstruct the return electron signal 12 over a large area, thus ensuring the accuracy of the sample information contained in the acquired image.
[0057] In some preferred embodiments of this invention, the imaging grating 30 may simultaneously include a blocking frame 31 and at least one blocking rod 33, with one end of each blocking rod 33 connected to the outside of the blocking frame 31. In this embodiment, the entire imaging grating 30 is a simple structure with a central opening and an external perforation, which can also be referred to as a fine grating structure.
[0058] In some preferred embodiments of this invention, the shielding frame 31 is an annular frame or a square frame, which encloses the communicating hole 32. Multiple shielding rods 33 may be arranged sequentially at intervals along the circumference of the shielding frame 31. For example, multiple shielding rods 33 may be evenly distributed along the circumference of the shielding frame 31. Of course, in some alternative embodiments, the multiple shielding rods 33 may not be evenly distributed along the circumference of the shielding frame 31. The arrangement of the shielding rods 33 can be adaptively designed according to the condition of the sample surface, and can be aligned with locations where there is less information on the sample surface.
[0059] In some embodiments of this utility model, to facilitate the installation of the imaging grating 30, the electro-optical lens barrel further includes a mounting frame 34, which is disposed on the barrel body 10. A shielding frame 31 is disposed inside the mounting frame 34, and a shielding rod 33 is disposed between the mounting frame 34 and the shielding frame 31. Preferably, the shielding rod 33, the mounting frame 34, and the shielding frame 31 can be integrally formed.
[0060] In some embodiments of this invention, the detector 20 is provided with an electron beam passage hole. A connecting hole 32 is coaxially arranged with the electron beam passage hole. The connecting hole 32 is a circular hole, and its diameter is greater than or equal to the diameter of the electron beam passage hole to prevent obstruction of the electron beam 11 passing through the electron beam passage hole. The electron optical tube also includes a condenser lens 40 and an objective lens 50. The condenser lens 40 is disposed inside the tube body 10 and is located on the side of the detector 20 opposite to the imaging grating 30. The objective lens 50 is disposed inside the tube body 10 and is located on the side of the imaging grating 30 opposite to the detector 20.
[0061] An electron beam 11 emitted from a filament (such as a tungsten filament or thermal field emission) travels along the optical axis. After passing through a condenser lens, the divergent electron beam 11 is gradually converged under the influence of a magnetic field. It then passes through a detector 20. The electron beam through-hole at the center of the detector 20 is approximately 100 micrometers in diameter. Electron beams 11 with a diameter larger than this through-hole are blocked, while those smaller pass through the detector 20. The electron beam 11 then passes through an imaging grating 30. Since the electron beam 11 is still focused at this point, it passes through the central aperture of the imaging grating 30, i.e., through the connecting aperture 32. The imaging grating 30 does not obstruct the electron beam 11. Finally, under the focusing effect of the objective lens, the electron beam 11 is focused onto the sample surface, forming a nanometer-scale electron beam spot.
[0062] This utility model also provides an electron beam 11 detection device, which includes any of the aforementioned electron optical tubes. The electron beam 11 detection device can be a charged particle beam imaging device. This device controls the focusing state of charged particles, causing them to interact with the semiconductor sample 80 (such as a wafer). By capturing secondary particles, transmitted particles, and other particle signals, it performs imaging, characterizing the morphology, structure, composition, and other information of the sample 80. The charged particle beam imaging device is typically a scanning electron microscope. When using the electron beam 11 detection device of this application embodiment, the image generated from the returned electron signal 12 received by the detector 20 is superimposed with the image of the imaging grating 30. The degree of defocusing of the grating image can be determined based on the changes in the image of the imaging grating 30, thereby feeding back the change in the height of the sample 80. Based on this change, height compensation is performed to ensure that the electron beam 11 focus point is always on the sample surface, guaranteeing that the electron beam 11 always operates in a positive-focus state.
[0063] Therefore, those skilled in the art should recognize that although many exemplary embodiments of the present invention have been shown and described in detail herein, many other variations or modifications conforming to the principles of the present invention can be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the present invention. Therefore, the scope of the present invention should be understood and recognized as covering all such other variations or modifications.
Claims
1. An electron-optical column of an electron beam inspection apparatus, characterized by, include: A cylindrical body, the interior of which is used for the passage of an electron beam; the electron beam is configured to act on a sample such that the sample generates a return electron signal under the action of the electron beam. A detector is disposed inside the cylinder and configured to receive the returned electronic signal; An imaging grating is disposed inside the cylinder and on the side of the detector that receives the returned electron signal; the imaging grating is configured to block part of the returned electron signal so that the image generated by the electron beam detection device based on the returned electron signal received by the detector is superimposed with the image of the imaging grating.
2. The electron optical lens barrel according to claim 1, characterized in that, The imaging grating includes: A shielding frame having a connecting hole for forming a forward path of the electron beam; At least one blocking rod is disposed outside the path of the electron beam.
3. The electron optical lens barrel according to claim 2, characterized in that, The obstruction frame is an annular frame or a square frame, and the annular frame or the square frame encloses the connecting hole.
4. The electron optical lens barrel according to claim 2, characterized in that, One end of each of the shielding bars is connected to the outside of the shielding frame.
5. The electron optical lens barrel according to claim 4, characterized in that, There are multiple blocking rods, which are arranged at intervals along the circumference of the blocking frame.
6. The electron optical lens barrel according to claim 5, characterized in that, The plurality of the shielding rods are evenly distributed along the circumference of the shielding frame.
7. The electron-optical barrel of claim 2, wherein Also includes: The mounting frame is disposed on the cylinder, the shielding frame is disposed inside the mounting frame, and the shielding rod is disposed between the mounting frame and the shielding frame.
8. The electron optical lens barrel according to claim 2, characterized in that, The detector is provided with an electron beam passage hole; The connecting hole is coaxially arranged with the electron beam through hole; The connecting hole is a circular hole, and the diameter of the connecting hole is greater than or equal to the diameter of the hole through which the electron beam passes.
9. The electron-optical barrel of claim 1, wherein, Also includes: A condenser lens is disposed inside the cylinder and is located on the side of the detector opposite to the imaging grating; The objective lens is disposed inside the tube and is located on the side of the imaging grating opposite to the detector.
10. An electron beam detecting apparatus characterized by comprising: Includes the electro-optical lens tube as described in any one of claims 1 to 9.