A scanning electron microscope and a wafer height detection device thereof

Abstract

The utility model relates to the field of semiconductor manufacturing and detection, especially a kind of scanning electron microscope and wafer height detection device thereof.The wafer height detection device includes: light beam emission module, for emitting the convergent detection light beam with target pattern to the wafer surface to be measured, and detection light beam is configured to form convergent focus point after being reflected by wafer surface to be measured;And light beam detection module, set in the position after the reflected light beam of detection light beam passes through convergent focus point, and configured to image reflected light beam.The wafer height detection device of the utility model avoids the condition that the surface topography pattern of wafer to be measured is imaged clearly together with target pattern by offsetting convergent focus point of light beam emission module to wafer to be measured, thereby significantly weaken the influence of surface topography pattern of wafer to be measured on detection accuracy, and then improve the accuracy of wafer height detection.

Description

Technical Field

[0001] This utility model relates to the field of semiconductor manufacturing and testing, and in particular to a scanning electron microscope and its wafer height detection device. Background Technology

[0002] In semiconductor manufacturing processes, the Scanning Electron Microscope (SEM), as an electron beam imaging device, is used for high-resolution topographic observation and defect detection of wafer surfaces. To ensure image clarity, the working distance of the SEM is typically small and requires strict matching of the objective lens focal length. However, due to issues such as local warping of the wafer itself, height differences exist between different points on the wafer surface, causing variations in the SEM working distance, resulting in image defocusing and affecting detection accuracy. Therefore, it is necessary to accurately detect the wafer surface height during SEM inspection to provide a change signal to the sample stage supporting the wafer, thereby facilitating real-time adjustment of the SEM working distance.

[0003] There is currently a wafer height detection method based on optical projection, which projects a preset pattern onto the wafer surface, and the image is received by a detector after reflection. The height change of the wafer surface is inferred by the displacement of the image points of the preset pattern, so as to detect the actual height of each point on the wafer surface.

[0004] However, current solutions typically focus the projected image of the preset pattern onto the wafer surface, causing the actual morphology pattern of the wafer surface to be imaged on the detector surface along with the image from the pattern card. This affects the imaging accuracy of the preset pattern, interferes with algorithm calculations, and consequently reduces the accuracy of wafer height detection. Utility Model Content

[0005] In view of the above problems, this utility model proposes a scanning electron microscope and a wafer height detection device that overcomes or at least partially solves the above problems.

[0006] One objective of this invention is to provide a wafer height detection device for scanning electron microscopes, thereby improving the accuracy of wafer height detection.

[0007] A further objective of this invention is to simplify the optical path design, thereby reducing detection costs.

[0008] Another further objective of this invention is to improve the stability of wafer height detection.

[0009] Specifically, this invention provides a wafer height detection device for scanning electron microscopes, comprising: A beam emitting module is used to emit a converged detection beam with a target pattern onto the surface of a wafer under test, and the detection beam is configured to form a converging focal point after being reflected by the surface of the wafer under test; and The beam detection module is positioned at the point where the reflected beam of the detection beam passes through the convergence focal point, and is configured to image the reflected beams in pairs.

[0010] Optionally, the beam emitting module includes: A light source, used to emit light onto the surface of the wafer under test; A target pattern, located between the light source and the wafer under test, is used to form a detection beam with the target pattern; and The emission focusing lens, located between the chart and the wafer under test, is used to project the detection beam onto the surface of the wafer under test.

[0011] Optionally, the focal points of the emission focusing lens and the emission focusing lens are located on opposite sides of the surface of the wafer under test in the height direction.

[0012] Optionally, the emission focusing lens is configured such that the surface of the wafer under test is outside the depth of focus of the emission focusing lens.

[0013] Optionally, the beam emitting module also includes: A collimator, located between the light source and the chart, is used to collimate the light emitted by the light source and project the collimated light onto the chart.

[0014] Optionally, the beam emitting module is tilted relative to the surface of the wafer under test so that the detection beam is projected onto the surface of the wafer under test at an angle.

[0015] Optionally, the beam detection module includes: A detection focusing lens, positioned in the optical path of the reflected beam and downstream of the converging focal point, is used to receive and converge the reflected beam; and The detector is positioned in the optical path of the reflected beam and downstream of the detection focusing lens. It is used to receive the reflected beam after it has been converged by the detection focusing lens and to generate a detection image based on the reflected beam.

[0016] Optionally, the detection focusing lens is configured to focus the reflected beam onto the imaging surface of the detector.

[0017] According to another aspect of the present invention, a scanning electron microscope is also provided, comprising: The wafer height detection device of any of the above.

[0018] Optionally, the beam emission module is configured such that the projection area of ​​the detection beam on the surface of the wafer under test is coaxial with the detection area of ​​the scanning electron microscope.

[0019] This invention discloses a wafer height detection device. By incorporating a beam emitting module and a beam detection module, the beam emitting module emits a converged detection beam with a target pattern onto the surface of the wafer under test. The detection beam is reflected from the wafer surface to form a converging focal point. The beam detection module is positioned after the reflected beam passes through this focal point and images the reflected beam. Therefore, by shifting the converging focal point of the beam emitting module to the wafer under test, this device reduces the likelihood of the surface morphology pattern of the wafer being imaged by the beam detection module. This avoids the situation where the surface morphology pattern and the target pattern are clearly imaged together, significantly reducing the impact of the surface morphology pattern on detection accuracy, reducing interference with algorithm calculations, and facilitating accurate capture of the image point displacement of the target pattern through the imaging of the reflected beam, thereby improving the accuracy of wafer height detection.

[0020] Furthermore, in the wafer height detection device of this invention, the beam emitting module includes a light source, a pattern card, and a focusing lens. The light source emits light, the pattern card is located between the light source and the wafer and forms a detection beam with a target pattern, and the focusing lens projects the detection beam onto the wafer surface. Thus, the wafer height detection device of this invention achieves a light source focusing effect using a single lens in the beam emitting module, simplifying the optical path design and effectively reducing detection costs. It also achieves precise projection of the detection beam, ensuring the accuracy of the target pattern projection onto the wafer surface, and laying a reliable optical foundation for subsequent imaging and height calculation of the reflected beam.

[0021] Furthermore, in the wafer height detection device of this invention, the emitting focusing lens and its focal point are located on opposite sides of the surface of the wafer under test in the height direction, so that the surface of the wafer under test is naturally outside the focal point of the emitting focusing lens. Therefore, by setting the focal point of the emitting focusing lens outside the surface of the wafer under test, the wafer height detection device of this invention suppresses the interference of the surface morphology pattern of the wafer under test on the imaging of the target pattern, thereby significantly improving the detection accuracy. Simultaneously, by setting the focal point of the emitting focusing lens on the side of the wafer under test away from the emitting focusing lens, the wafer height detection device of this invention ensures that the detection beam can stably form a converging focal point after reflection from the surface of the wafer under test, providing structural protection for the accurate imaging of the beam detection module and further improving the stability of wafer height detection.

[0022] 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

[0023] 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: Figure 1 This is a schematic diagram of the structure of a wafer height detection device in the prior art; Figure 2 This is a schematic diagram of a portion of the structure of a scanning electron microscope according to an embodiment of the present invention; Figure 3 This is a schematic diagram of a wafer height detection device according to an embodiment of the present invention. Detailed Implementation

[0024] Exemplary embodiments of the present invention will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present invention to those skilled in the art.

[0025] Figure 1 This is a schematic diagram of a wafer height detection device in the prior art. (Example:) Figure 1 As shown, in existing wafer height detection methods, the wafer height detection device 2 includes a projection end 3 and a detection end 7.

[0026] like Figure 1 As shown, the projection end 3 focuses the detection light 4 with a preset pattern onto the wafer surface 5, the detection end 7 receives the reflected light 6 of the detection light 4 and forms an image, and infers the height change of the wafer surface 5 by the displacement of the image point of the preset pattern in the imaging result of the detection end 7, so as to detect the actual height of each point on the wafer surface 5.

[0027] Based on this, the wafer height detection device 2 in the prior art focuses the projected image of the preset pattern onto the wafer surface 5, causing the actual shape pattern of the wafer surface 5 to be imaged together with the preset pattern at the detection end, which affects the imaging accuracy of the preset pattern, interferes with the algorithm calculation, and thus reduces the accuracy of wafer height detection.

[0028] To address the aforementioned problems, this utility model provides a scanning electron microscope and a wafer height detection device thereof. Figure 2 This is a schematic diagram of a portion of the structure of a scanning electron microscope according to an embodiment of the present invention. Figure 2 As shown, the scanning electron microscope 1 of this embodiment generally includes a wafer height detection device 10 and an electron beam source 20.

[0029] In this embodiment, the scanning electron microscope 1 is used to scan the surface of the wafer 30 to be tested, which is placed on the sample stage. Figure 2 As shown, the electron beam source 20 can emit an incident electron beam 21 onto the wafer 30 under test, and the incident electron beam 21 is projected onto the surface 31 of the wafer 30 under test to form a detection area 22.

[0030] In addition, the scanning electron microscope 1 is also equipped with a detection component for detecting the emitted electrons formed after the incident electron beam 21 irradiates the surface 31 of the wafer 30 under test, so as to generate a scanning image of the wafer 30 under test, thereby detecting surface defects of the wafer 30 under test, or measuring the critical dimensions of the wafer 30 under test.

[0031] like Figure 2 As shown, the wafer height detection device 10 includes a beam emitting module 100 and a beam detection module 200. The beam emitting module 100 emits a converging detection beam 300 with a target pattern onto the surface 31 of the wafer 30 under test. The beam detection module 200 receives the reflected beam 400 of the detection beam 300 and is configured to image the reflected beam 400 to calculate the height change of the surface 31 of the wafer 30 under test by means of the image point displacement of the target pattern.

[0032] Therefore, the scanning electron microscope 1 of this embodiment utilizes the wafer height detection device 10 to realize real-time detection of wafer height, which facilitates the real-time provision of height change signals to the sample stage, thereby making it easier to adjust the working distance of the SEM in a timely manner, avoiding image defocusing problems caused by wafer height differences, and greatly improving the imaging quality of the SEM.

[0033] In some embodiments, such as Figure 2 As shown, the beam emission module 100 is configured such that the projection area 310 of the detection beam 300 on the surface 31 of the wafer 30 under test is coaxially set with the detection area 22 of the scanning electron microscope 1.

[0034] Specifically, the beam emitting module 100 is configured to adjust the incident angle of the detection beam 300 relative to the surface 31 of the wafer 30 under test according to the detection area 22 of the SEM, so as to adjust the position of the projection area 310 of the detection beam 300 projected on the surface 31 of the wafer 30 under test, thereby making the projection area 310 and the detection area 22 have the same central axis, thereby realizing the coaxial measurement of the detection optical path and the detection area 22 of the SEM.

[0035] In other words, the beam emission module 100 can change the incident angle of the detection beam 300 relative to the surface 31 of the wafer 30 to be measured, so that the projection area 310 of the detection beam 300 is coaxially measured with the SEM detection area 22, so as to accurately measure the wafer height in the SEM field of view in real time.

[0036] Therefore, in the scanning electron microscope 1 of this embodiment, the projection area 310 of the detection beam 300 and the detection area 22 of the SEM are coaxially arranged, ensuring that the wafer height detection point is completely consistent with the SEM detection point. This allows the height detection result to be directly used for SEM working distance adjustment, avoiding adjustment errors caused by misalignment of the detection area 22, and further improving the imaging clarity of the SEM. The following is in conjunction with... Figures 2 to 3 The wafer height detection device 10 of the scanning electron microscope 1 of this embodiment will be described in detail below.

[0037] In some embodiments, such as Figure 2 As shown, the beam emitting module 100 is used to emit a converged detection beam 300 with a target pattern onto the surface 31 of the wafer 30 under test, and the detection beam 300 is configured to form a converged focal point D after being reflected by the surface 31 of the wafer 30 under test.

[0038] It should be noted that the convergence focal point D refers to the equivalent focal point formed when the reflected beam 400 converges to a single point after the detection beam 300 is reflected by the surface 31 of the wafer 30 under test.

[0039] In other words, the wafer height detection device 10 of this utility model adjusts the optical path design to shift the focusing point D of the beam emission module 100 to the surface 31 of the wafer 30 to be measured.

[0040] In addition, the beam detection module 200 is positioned at the point where the reflected beam 400 of the detection beam 300 passes the convergence focal point D, and is configured to image the reflected beam 400.

[0041] Therefore, the wafer height detection device 10 of this invention reduces the possibility of the surface morphology pattern of the wafer 30 being imaged in the beam detection module 200 by shifting the focusing point D of the beam emission module 100 to the wafer 30 under test. This avoids the situation where the surface morphology pattern of the wafer 30 under test and the target pattern are clearly imaged together, thereby significantly reducing the impact of the surface morphology pattern of the wafer 30 under test on the detection accuracy, reducing the interference of algorithm calculation, and facilitating the accurate capture of the image point displacement of the target pattern through the imaging of the reflected beam 400, thereby improving the accuracy of wafer height detection.

[0042] In some embodiments, such as Figure 2 As shown, the beam emitting module 100 may include a light source 110, a pattern card 120, and an emission focusing lens 130. The light source 110 is used to emit light onto the surface 31 of the wafer 30 under test. Specifically, the light source 110 may be configured to emit a monochromatic beam onto the surface 31 of the wafer 30 under test.

[0043] The pattern 120 is located between the light source 110 and the wafer 30 under test, and has a target pattern for forming a detection beam 300 with the target pattern. Specifically, the surface of the pattern 120 is pre-set with a high-precision target pattern, which can be an easily identifiable structure. For example, the target pattern can be set as a specific geometric shape.

[0044] When the light emitted by the light source 110 shines on the pattern card 120, the effective beam carrying the pattern information is filtered out through selective transmission and modulation of the target pattern, thereby forming a detection beam 300 with the target pattern, which provides a stable reference for subsequent wafer surface reflection imaging and image point displacement analysis.

[0045] The emission focusing lens 130 is located between the diagram 120 and the wafer 30 under test, and is used to project the detection beam 300 onto the surface 31 of the wafer 30 under test.

[0046] In other words, the light source 110, the pattern card 120, and the emission focusing lens 130 are arranged sequentially at intervals along the direction pointing to the wafer 30 under test, so that the light emitted by the light source 110 can form a detection beam 300 with the target pattern after passing through the pattern card 120, and the target pattern is projected onto the surface 31 of the wafer 30 under the converging effect of a single emission focusing lens 130.

[0047] Therefore, the wafer height detection device 10 of this utility model can achieve the focusing effect of the light source 110 by using a single lens in the beam emitting module 100. This simplifies the optical path design, thereby effectively reducing the detection cost, and also achieves accurate projection of the detection beam 300, thus ensuring the projection accuracy of the target pattern on the wafer surface 31. This lays a reliable optical foundation for the subsequent imaging and height calculation of the reflected beam 400.

[0048] Figure 3 This is a schematic diagram of a wafer height detection device according to an embodiment of the present invention. Figure 3 As shown, the beam emitting module 100 may also include a collimator 140. The collimator 140 is located between the light source 110 and the diagram 120, and is used to collimate the light emitted by the light source 110 and project the collimated light onto the diagram 120.

[0049] In other words, the wafer height detection device 10 of this utility model can directly use a finished collimator to collimate the light source 110. After the collimated beam hits the pattern card 120, it forms a parallel detection beam 300. After being converged by the emission focusing lens 130, it is projected onto the surface 31 of the wafer 30 to be tested, so as to shape the detection beam 300.

[0050] Therefore, the wafer height detection device 10 of this utility model uses a collimator 140 to project the detection beam 300 onto the pattern card 120 in a parallel or nearly parallel state, effectively eliminating the divergence of the beam emitted by the light source 110, thereby ensuring the projection stability of the target pattern and further improving the detection accuracy and reliability.

[0051] In addition, the wafer height detection device 10 of this invention improves the optical performance of the light source 110 through the collimator 140, making it possible to use a non-ideal light source 110, increasing the flexibility of the overall design, and thus helping to reduce costs.

[0052] In some embodiments, such as Figure 3 As shown, the emission focusing lens 130 and its focal point A can be located on opposite sides of the surface 31 of the wafer 30 under test in the height direction. Specifically, the height direction of the surface of the wafer 30 under test can be the up-down direction of the scanning electron microscope 1 in its normal operating posture, that is, the axial direction of the electron beam source 20.

[0053] In other words, the focal point A of the emission focusing lens 130 is set on the other side of the surface 31 of the wafer 30 to be tested, away from the emission focusing lens 130, so that the detection beam 300 is focused on the converging focal point D after being reflected by the surface 31 of the wafer 30 to be tested.

[0054] Therefore, in the wafer height detection device 10 of this utility model embodiment, the emission focusing lens 130 and its focal point A are respectively located on opposite sides of the surface 31 of the wafer 30 to be tested in the height direction, so that the surface 31 of the wafer 30 to be tested is naturally outside the focal point A of the emission focusing lens 130, suppressing the interference of the surface morphology pattern of the wafer 30 to be tested on the imaging of the target pattern, thereby significantly improving the detection accuracy.

[0055] In addition, the wafer height detection device 10 of this utility model sets the focal point A of the emission focusing lens 130 on the other side of the surface 31 of the wafer 30 to be tested away from the emission focusing lens 130, which ensures that the detection beam 300 can stably form a converging focal point D after being reflected by the surface 31 of the wafer 30 to be tested. This provides a structural guarantee for the accurate imaging of the beam detection module 200 and further improves the stability of wafer height detection.

[0056] In some embodiments, such as Figure 3 As shown, the emission focusing lens 130 is configured to place the surface 31 of the wafer 30 under test outside the focal depth of the emission focusing lens 130, so as to improve the defocusing degree of the surface topography pattern of the wafer 30 under test, thereby utilizing the characteristic of out-of-focus imaging blurring to further reduce the interference of the surface topography pattern of the wafer 30 under test on the imaging results.

[0057] Therefore, the wafer height detection device 10 of this utility model improves the defocusing degree of the surface morphology pattern of the wafer 30 under test through optical path design, avoids the problem of superposition interference between the pattern on the wafer surface 31 and the target pattern image, thereby improving the imaging accuracy of the target pattern, providing a more reliable image basis for height detection, and further improving the accuracy of wafer height detection.

[0058] In some embodiments, such as Figure 2 and Figure 3 As shown, the beam emitting module 100 is tilted relative to the surface 31 of the wafer 30 under test, so that the detection beam 300 is tilted and projected onto the surface 31 of the wafer 30 under test. Specifically, the incident angle of the detection beam 300 of the beam emitting module 100 is adjustable to adjust the position of the projection area 310 of the detection beam 300 on the surface 31 of the wafer 30 under test.

[0059] Therefore, in the wafer height detection device 10 of this utility model, the detection beam 300 is obliquely projected onto the wafer surface 31, which optimizes the incident angle of the detection beam 300, effectively avoids interference between the wafer height detection device 10 and the electron beam optical path of the scanning electron microscope 1, and facilitates the adjustment of the incident angle, thus providing a basis for coaxial measurement of the detection optical path and the SEM detection area 22.

[0060] In some embodiments, such as Figure 2 and Figure 3 As shown, the beam detection module 200 may include a detection focusing lens 210 and a detector 220. The detection focusing lens 210 is disposed in the optical path of the reflected beam 400 and downstream of the converging focal point D, for receiving the reflected beam 400 and converging it. The detector 220 is disposed in the optical path of the reflected beam 400 and downstream of the detection focusing lens 210, for receiving the reflected beam 400 after it has been converged by the detection focusing lens 210, and for generating a detection image based on the reflected beam 400.

[0061] Therefore, the wafer height detection device 10 of this utility model can form an optical imaging measurement system by using a single detection focusing lens 210 and detector 220, which not only reduces the detection cost, but also achieves accurate detection of the reflected beam 400, making it easy to accurately extract the image point displacement of the target pattern through image processing algorithms, and providing data support for the height calculation of the wafer 30 to be measured.

[0062] In some embodiments, such as Figure 2 and Figure 3 As shown, the detection focusing lens 210 can be configured to focus the reflected beam 400 onto the imaging surface 221 of the detector 220.

[0063] Therefore, in the wafer height detection device 10 of this utility model, the detection focusing lens 210 is configured to focus the reflected beam 400 onto the imaging surface 221 of the detector 220, ensuring that the reflected beam 400 with the target pattern can form a clear image on the detector 220, which facilitates accurate identification of the image point displacement of the target pattern, thus providing a basis for high-precision height detection.

[0064] In some embodiments, the wafer height detection device 10 of this invention may further include a control computer connected to the detector 220. The control computer is used to acquire the imaging results of the detector 220 and analyze and calculate the image point displacement of the target pattern based on the imaging results, so as to realize the real-time acquisition of the surface height information of the wafer 30 under test.

[0065] It should be noted that the image point displacement of the target pattern can be the displacement between the image point positions of the target pattern in the imaging result of the detector 220 when the detection beam 300 is projected onto the current projection area 310 and when the preset measurement zero position is reached.

[0066] In addition, the wafer height detection device 10 can flexibly set the measurement zero point. Specifically, the measurement zero point can be changed according to the SEM requirements to ensure that the measurement range is adapted to the SEM requirements.

[0067] Therefore, the wafer height detection device 10 of this utility model uses a control computer to acquire the imaging results of the detector 220 in real time, and calculates the image point displacement between the current projection area 310 and the preset measurement zero position to quickly obtain the wafer surface height information.

[0068] In addition, the measurement zero point of the wafer height detection device 10 of this utility model can be adapted to the working requirements of SEM as needed, flexibly matching the working distance range and detection scenarios of different SEMs, improving the versatility of the wafer height detection device 10, and realizing efficient collaboration between wafer height detection and SEM work.

[0069] Those skilled in the art should understand that, unless otherwise specified, the terms "center," "height," "upper," "lower," "front," "rear," "outer," and "axial" used in the embodiments of this utility model to indicate orientation or positional relationship are merely for the convenience of describing and understanding the technical solution of this utility model, and are not intended to indicate or imply that the device or component referred to must have a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0070] In the description of this embodiment, references to terms such as "some embodiments" indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, 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.

[0071] 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. A wafer height detection device for a scanning electron microscope, characterized in that... include: A beam emitting module is used to emit a converged detection beam with a target pattern onto the surface of a wafer under test, and the detection beam is configured to form a converging focal point after being reflected by the surface of the wafer under test; and A beam detection module is positioned at the point where the reflected beam of the detected beam passes the convergence focal point, and is configured to image the reflected beam.

2. The wafer height detection device according to claim 1, characterized in that, The beam emitting module includes: A light source, used to emit light onto the surface of the wafer under test; A pattern card, located between the light source and the wafer under test, and having the target pattern, is used to form the detection beam with the target pattern; and An emission focusing lens, located between the chart and the wafer under test, is used to project the detection beam onto the surface of the wafer under test.

3. The wafer height detection device according to claim 2, characterized in that, The focal points of the emission focusing lens and the emission focusing lens are located on opposite sides of the surface of the wafer under test in the height direction, forming the converging focal point.

4. The wafer height detection device according to claim 3, characterized in that, The emission focusing lens is configured such that the surface of the wafer under test is outside the focal depth of the emission focusing lens.

5. The wafer height detection device according to claim 2, characterized in that, The beam emitting module also includes: A collimator, located between the light source and the chart, is used to collimate the light emitted by the light source and project the collimated light onto the chart.

6. The wafer height detection device according to claim 2, characterized in that, The beam emitting module is tilted relative to the surface of the wafer under test so that the detection beam is projected onto the surface of the wafer under test at an angle.

7. The wafer height detection device according to claim 2, characterized in that, The beam detection module includes: A detection focusing lens, disposed in the optical path of the reflected beam and downstream of the converging focal point, is used to receive the reflected beam and converge it; and A detector is disposed in the optical path of the reflected beam and downstream of the detection focusing lens, for receiving the reflected beam after it has been converged by the detection focusing lens, and for generating a detection image based on the reflected beam.

8. The wafer height detection device according to claim 7, characterized in that, The detection focusing lens is configured to focus the reflected beam onto the imaging surface of the detector.

9. A scanning electron microscope, characterized in that, include: The wafer height detection device according to any one of claims 1 to 8.

10. The scanning electron microscope according to claim 9, characterized in that, The beam emitting module is configured such that the projection area of ​​the detection beam on the surface of the wafer under test is coaxial with the detection area of ​​the scanning electron microscope.

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