A method for measuring the thickness of a thin film by low-power microscope assisted atomic force microscope

Abstract

The application discloses a kind of low-power optical microscope assisted atomic force microscope measurement film thickness method, first with the aid of low-power optical microscope, atomic force microscope probe tip and the step of to-be-measured sample is pre-aligned, then control needle tip to drop to the first height of step surface.Real-time monitoring lifts up needle tip, so that it is in the focal plane range of low-power optical microscope with sample surface, adjust probe position, let needle tip projection be located directly above step to complete accurate positioning.Start linear scanning mode, single row scanning in the direction of vertical step extension, dynamically adjust scanning range parameters, until scanning curve presents step-like characteristics, switch to line-by-line scanning mode after adjusting to field center to obtain three-dimensional topography data, and obtain the film thickness of to-be-measured sample based on the three-dimensional topography data.The method optimizes probe and sample positioning process, reasonably sets scanning parameters and data processing method, effectively solves the problem of long time consumption and low accuracy of atomic force microscope film thickness measurement under the assistance of low-power optical microscope.

Description

Technical Field

[0001] This invention belongs to the field of thin film thickness measurement technology, and relates to a method for measuring thin film thickness using an atomic force microscope assisted by a low-magnification optical microscope. Background Technology

[0002] Precise measurement of thin film thickness is a core component supporting modern high-end manufacturing and cutting-edge technology development, playing an irreplaceable role in semiconductors, display technology, optical coating, photovoltaics, and flexible electronics. With the trend towards miniaturization and functional integration of devices, the precision of thin film thickness control is directly related to the electrical performance, optical characteristics, and reliability of devices. For example, in semiconductor manufacturing, a thickness error exceeding the sub-nanometer level in the gate oxide layer of a transistor will lead to a surge in leakage current and device failure; in the display field, a thickness deviation of only a few nanometers between the emissive layer and the electron transport layer in an OLED screen can significantly affect luminous efficiency and color uniformity. It is particularly important to note that in the measurement of nanometer-scale (1~100 nm) and submicron-scale (100~1000 nm) thin films, which involve core parameter ranges in many fields, high-precision, high-efficiency, and non-destructive measurement of the thickness of such thin films is crucial.

[0003] Atomic force microscopy (AFM) is a commonly used technique for measuring thin film thickness. This technique directly obtains the height difference between the thin film and the substrate by scanning the surface morphology with a probe. Its core advantage lies in the nanometer-level resolution of the three-dimensional morphology (vertical resolution up to 0.1 nm). It can directly measure the step height of any material (including insulators), and is especially suitable for non-transparent, low-roughness, or heterogeneous interface thin films. At the same time, AFM has high repeatability (accuracy better than 1%), making it authoritative in nanometer-level thin film measurement.

[0004] However, when using atomic force microscopy (AFM) to test film thickness, the probe tip of the AFM needs to be positioned at the step. Because the probe is extremely small, typically on the micrometer scale, an optical microscope is required for magnification and assistance in positioning to accurately measure the morphology at the step. However, for AFMs equipped with optical microscopes with low magnification (e.g., maximum magnification of tens of times), manual positioning relies on the operator's experience, a time-consuming process that significantly impacts testing efficiency. Furthermore, during the auxiliary positioning process, the probe surface is susceptible to contamination or mechanical wear, leading to morphological distortion and affecting the accuracy of the test. Summary of the Invention

[0005] To address the problems existing in the prior art, the present invention provides a method for measuring thin film thickness using an atomic force microscope assisted by a low-magnification microscope, thereby solving the technical problems of long time consumption and low accuracy when measuring thin film thickness using an atomic force microscope with the assistance of a low-magnification microscope in the prior art.

[0006] This invention is achieved through the following technical solution: A method for measuring thin film thickness using a low-magnification atomic force microscope includes the following steps: S1: By observing with a low-power optical microscope, the probe tip of the atomic force microscope is pre-aligned with the step of the sample to be tested, and then the probe tip is controlled to descend to a position at the first height on the surface of the step. S2: Raise the probe tip so that the probe tip and the surface of the sample to be tested are within the focal plane of the low-power optical microscope. Under the real-time monitoring of the low-power optical microscope, adjust the position of the probe so that the projection of the probe tip is directly above the step of the sample to be tested, thus completing the precise positioning. S3: Start the linear scanning mode of the atomic force microscope, perform a single-line scan along the direction perpendicular to the extension of the step, dynamically adjust the scanning range parameters until the step-like feature appears in the real-time feedback scanning curve, and adjust the area corresponding to the step-like feature to the center of the scanning field of view, then switch to the line-by-line scanning mode to obtain three-dimensional morphological data. S4: Obtain the film thickness of the sample to be tested based on the three-dimensional morphology data.

[0007] Preferably, the first height is 5~20 nm.

[0008] Preferably, the first height is 10~15 nm.

[0009] Preferably, in step S2, the probe tip is raised so that the probe tip and the sample surface are within the focal plane of the low-power optical microscope. Specifically, the probe tip is raised so that the distance between the probe tip and the sample surface is 100~300μm, so that the probe tip and the sample surface are within the focal plane of the low-power optical microscope.

[0010] Preferably, in step S2, the probe tip is raised so that the probe tip and the sample surface are within the focal plane of the low-power optical microscope. Specifically, the probe tip is raised so that the distance between the probe tip and the sample surface is 100~200μm, so that the probe tip and the sample surface are within the focal plane of the low-power optical microscope.

[0011] Preferably, in step S3, the scanning range parameter is dynamically adjusted as follows: first, the initial scanning range is set to 5% to 10% of the probe tip movement limit, and a linear scan is performed. Then, the scanning range is gradually increased until the upper and lower platforms of the step of the sample to be tested are fully displayed in the scanning curve.

[0012] Preferably, during the process of gradually increasing the scanning range, the increase in the scanning range each time does not exceed 50% of the current value.

[0013] Preferably, during the process of gradually increasing the scanning range, if the height difference of the step-like features in the scanning curve changes by more than 10% after two consecutive increases in the scanning range, the scan range is reverted to the previous scan range and manual intervention is triggered.

[0014] Preferably, in step S3, when performing linear scanning mode, if the scanning range exceeds 50% of the range of the atomic force microscope scanner, the scanning range is reduced to 30%~40% of the scanner range, and it is ensured that the upper and lower platforms of the step of the sample to be tested are both within the scanning field of view.

[0015] Preferably, in step S4, the film thickness of the sample to be tested is obtained based on the three-dimensional morphology data. Specifically, the three-dimensional morphology data is first leveled and noise lines are removed. Then, at least 3 to 10 measurement points are selected to measure the step height respectively, and the average value is taken as the film thickness.

[0016] Compared with the prior art, the present invention has the following beneficial technical effects: This invention discloses a method for measuring thin film thickness using a low-magnification optical microscope-assisted atomic force microscopy. The method first performs pre-alignment through observation using a low-magnification optical microscope. Then, the probe tip is lowered to a position at a first height from the stepped surface. Under real-time monitoring of the low-magnification optical microscope, the probe tip is raised to achieve confocal focusing of the probe tip and the sample surface under the microscope, followed by fine positioning. This method of lowering the probe to an appropriate height before fine positioning ensures that the probe tip and sample surface are clearly focused simultaneously under the optical microscope, and the probe tip movement does not scratch the sample surface. The positioning process is more efficient, avoiding repeated attempts due to positioning difficulties, thus reducing positioning time. Regarding parameter settings, the initial value of the scanning range (Size) is set relatively small to protect the probe and sample. After lowering the probe, it scans back and forth along a line, gradually adjusting the parameters. Once the cross-sectional shape of the scan line appears stepped and the step position is adjusted to the center, line-by-line scanning is then performed. This gradual parameter adjustment method avoids repeated scanning caused by blindly setting parameters, enabling the finding of suitable scanning parameters more quickly, thereby shortening the scanning time and improving measurement efficiency. This method effectively solves the technical problems of long time consumption and low accuracy when measuring film thickness using atomic force microscopy with low magnification under the assistance of a low magnification microscope in the prior art by optimizing the probe and sample positioning process, reasonably setting scanning parameters and data processing methods.

[0017] Furthermore, in step S2, the probe tip is raised so that the probe tip and the sample surface are within the focal plane of the low-power microscope. Specifically, the probe tip is raised so that the distance between the probe tip and the sample surface is 100~300μm. This ensures that both the probe and the sample surface can be clearly imaged under the low-power microscope, facilitating precise positioning and adjustment, and improving measurement efficiency. Within this range, a suitable height difference between the probe tip and the sample can be ensured, while avoiding inaccurate positioning or probe deviation during descent due to excessive height, thereby improving measurement accuracy and efficiency.

[0018] Furthermore, in step S3, the scanning range parameters are dynamically adjusted. Specifically, the initial scanning range is first set to 5% to 10% of the probe tip's movement limit, and a linear scan is performed. Then, the scanning range is gradually increased until the upper and lower platforms of the step of the sample to be tested are completely displayed in the scanning curve. Setting the initial scanning range can protect the probe and the sample, avoiding damage to the probe or sample due to an excessively large initial scanning range. At the same time, gradually increasing the scanning range can more accurately find a suitable scanning range, ensuring that the upper and lower platforms of the step can be completely scanned, laying the foundation for obtaining accurate three-dimensional morphology data in the future.

[0019] Furthermore, during the gradual increase of the scanning range, the increase in the scanning range each time does not exceed 50% of the current value. This limitation can prevent the scanning range from increasing too quickly, which could lead to distortion of the scanning curve or failure to accurately capture step-like features. By controlling the magnitude of each increase, the scanning process can be made more stable and accurate, thereby improving the reliability of the measurement results.

[0020] Furthermore, during the process of gradually increasing the scanning range, if the height difference of the step-like feature in the scanning curve changes by more than 10% after two consecutive increases in the scanning range, the process will revert to the previous scanning range and trigger manual intervention. This process can promptly detect any abnormalities that may occur during the scanning process, such as unreasonable scanning range settings or interference on the sample surface that cause abnormal height difference changes. By reverting to the previous scanning range and triggering manual intervention, inaccurate measurement results due to abnormalities can be avoided, thus ensuring the quality of the measurement.

[0021] Furthermore, in step S3, when performing linear scanning mode, if the scanning range exceeds 50% of the atomic force microscope scanner's range, the scanning range is reduced to 30%~40% of the scanner's range. This ensures that both the upper and lower platforms of the step on the sample are within the scanning field of view. This process protects the scanner and prevents inaccurate measurement results due to an excessively large scanning range. At the same time, ensuring that both the upper and lower platforms of the step are within the scanning field of view guarantees the acquisition of complete step morphology data, providing an accurate basis for subsequent film thickness calculation. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the probe structure of the atomic force microscope used in Embodiment 2 of the present invention, wherein (a) is a top view and (b) is a side view; Figure 2 This is a photograph of the precisely aligned sample step and probe microcantilever under a low-power microscope, as described in the prior art. Figure 3 The image shows the sample step and probe microcantilever after needle insertion in the existing technology under a low-power microscope. Figure 4 The sample profile line obtained after precise alignment in existing technology; Figure 5 This is a two-dimensional morphology image of the sample to be tested, obtained using existing technology; Figure 6 This is a photograph of the sample step and probe microcantilever after pre-alignment using the method of the present invention in Embodiment 2 of the present invention, taken under a low-power microscope. Figure 7 The image shows the probe tip and the sample under a low-power optical microscope when the probe tip is raised to a distance of 100 μm from the sample surface after the probe is inserted using the method of the present invention. Figure 8 This is a schematic diagram of how the probe tip projection is positioned directly above the step of the sample under test in Embodiment 2 of the present invention. Figure 9 The image shows the probe and sample step under a low-power optical microscope after fine alignment using the method of the present invention. Figure 10 A cross-sectional view of the sample to be tested after fine alignment using the method of the present invention; Figure 11 The image shows the morphology of the step of the sample under test obtained by the method of the present invention, wherein (a) is a two-dimensional morphology of the sample and (b) is a three-dimensional morphology of the sample. Figure 12 In order to be in Figure 11 Four measurement points were selected on the two-dimensional topography map to measure the subsequent step thickness. Figure 13 for Figure 12 Test results of the step thickness between points A and B; Figure 14 for Figure 12 Test results of the step thickness between points C and D; Figure 15 for Figure 12 Test results of the step thickness between points E and F; Figure 16 for Figure 12 The test results of the step thickness between points G and H.

[0024] Among them, 1. cantilever, 2. probe tip, and 3. step. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0026] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0027] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0028] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Furthermore, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0029] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0030] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; 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; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0031] The present invention will now be described in further detail with reference to the accompanying drawings: This invention discloses a method for measuring thin film thickness using a low-magnification atomic force microscope, comprising the following steps: S1: By observing with a low-power optical microscope, the probe tip of the atomic force microscope is pre-aligned with the step of the sample to be tested, and then the probe tip is controlled to descend to a position at the first height on the surface of the step. In a preferred embodiment, the first height is 5~20 nm, preferably 10~15 nm, and more preferably 10 nm.

[0032] S2: Raise the probe tip so that the probe tip and the surface of the sample to be tested are within the focal plane of the low-power optical microscope. Under the real-time monitoring of the low-power optical microscope, adjust the position of the probe tip so that the projection of the probe tip is directly above the step of the sample to be tested, thus completing the precise positioning. In one specific embodiment, the probe tip is raised so that the distance between the probe tip and the sample surface is 100~300μm, so that the probe tip and the sample surface are within the focal plane range of the low magnification lens. The preferred elevation distance is 100~200μm, and more preferably 100μm.

[0033] S3: Start the linear scanning mode of the atomic force microscope, perform a single-line scan along the direction perpendicular to the extension of the step, dynamically adjust the scanning range parameters until the step-like feature appears in the real-time feedback scanning curve, and adjust the area corresponding to the step-like feature to the center of the scanning field of view, then switch to the line-by-line scanning mode to obtain three-dimensional morphological data. When dynamically adjusting the scanning range parameters, the specific steps are as follows: first, set the initial scanning range to 5%~10% of the probe tip movement limit, perform a linear scan, and then gradually increase the scanning range until the upper and lower platforms of the step of the sample to be tested are fully displayed in the scanning curve.

[0034] During the gradual increase of the scanning range, the increase in scanning range each time shall not exceed 50% of the current value. In addition, if the height difference of the step-like feature in the scanning curve changes by more than 10% after two consecutive increases in scanning range, the scan range shall be reverted to the previous scan range and manual intervention shall be triggered.

[0035] When performing linear scanning mode, if the scanning range exceeds 50% of the atomic force microscope scanner's range, the scanning range should be reduced to 30%~40% of the scanner's range, and it should be ensured that both the upper and lower platforms of the step of the sample under test are within the scanning field of view.

[0036] S4: The three-dimensional topography data is leveled and noise filtered. Multiple measurement points in the stepped area are selected to calculate the average height difference, thus obtaining the film thickness result. 3 to 10 measurement points can be selected here, with 5 being preferred.

[0037] Example 2 To further explain the technical solution of the present invention, the method is illustrated using a Brook NCHV-A type atomic force microscope probe as an example. The structure of the Brook NCHV-A type atomic force microscope probe is as follows: Figure 1 As shown, the Bruker NCHV-A atomic force microscope probe includes a cantilever 1 and a probe tip 2 located at the free end of the cantilever 1. The cantilever 1 and the probe tip 2 are designed as a single unit. The specific testing process is as follows: S1: Pre-alignment. Specifically, this involves pre-aligning the tip of probe 2 of the atomic force microscope with the step of the sample under test using a low-power optical microscope. In existing technologies, pre-alignment, also known as fine alignment, during testing mainly involves bringing the probe as close as possible to the sample step under a low-power microscope before insertion. Figure 2 As shown.

[0038] In this invention, pre-alignment involves roughly aligning the sample steps with the sample. First, ensure the Shimadzu SPM-9700HT atomic force microscope is in normal working order. Place the sample to be tested on the sample stage and secure it to prevent movement during the test. Turn on the low-magnification optical microscope and observe the step structure on the sample surface through the microscope's eyepiece or the connected display screen. Adjust the focal length, magnification, brightness, and other parameters of the low-magnification optical microscope to achieve clear imaging. Simultaneously, adjust the low-magnification microscope so that the probe enters the field of view to observe the relative position of the probe tip and the sample steps.

[0039] Then, based on the observed positions of the probe tip and the step, the sample is moved and adjusted so that the step of the sample is closer to the probe tip, such as... Figure 6 The location.

[0040] S2: Fine alignment. Current technology performs pre-alignment, or precise alignment, before the probe is inserted, thus completing the alignment process. Figure 2 The operation is similar, but in the existing technology, the pre-aligned probe after insertion and the sample step are shown in the low-power microscope image. Figure 3 It is evident that in existing technologies, the tip of the probe microcantilever cannot effectively align with the sample step after insertion. Under such circumstances, the obtained sample profile line during testing is as follows: Figure 4 As shown in the figure, the step surface of the sample cannot be effectively observed under the test window. Furthermore, the morphology image obtained during this test also fails to effectively observe the step surface of the sample. Figure 5 As shown.

[0041] The precise alignment process of this invention is as follows: After pre-alignment, the probe tip is precisely controlled to descend to a position 5-20 nm above the step surface using the atomic force microscope's control system (the fast approach process of the atomic force microscope). The height sensor or height feedback function in the control system of the atomic force microscope can be used to monitor the height change of the probe tip in real time, ensuring its accurate descent to the 5-20 nm height. Then, the probe tip is raised so that the distance between the probe tip and the sample surface is 100 μm. The image of the probe and sample step under a low-magnification optical microscope at this point is shown below. Figure 7 At this point, the sample step and the probe can be focused simultaneously. Then, under real-time monitoring with a low-power optical microscope, the relative positions of the probe tip and the step are precisely adjusted so that the projection of the probe tip is directly above step 3 of the sample to be tested. Figure 8 As shown, the probe has been precisely positioned. The image of the aligned probe and sample step under a low-power optical microscope is shown below. Figure 9 ,Depend on Figure 9 As can be seen, the above operations effectively achieved rapid and accurate alignment of the probe and the sample step.

[0042] In step S2, with the help of real-time monitoring by a low-power optical microscope, the control system of the atomic force microscope is operated to slowly raise the probe tip so that the distance between the probe tip and the surface of the sample to be tested reaches 100 μm.

[0043] Once the probe tip is raised to a height of 100 μm, the relative position of the probe tip and the step of the sample is observed again using a low-power optical microscope. At this point, due to the suitable height difference between the probe tip and the sample surface, both can be clearly imaged under the optical microscope. Based on the observed image, the probe tip is finely moved and adjusted using the control system of the atomic force microscope so that its projection is directly above the step of the sample. This adjustment process requires great patience and precision, as even small deviations can lead to inaccurate subsequent measurement results. The fine-tuning function of the control system can be used to gradually move the probe tip while observing the changes in the image under the low-power optical microscope until the projection of the probe tip is accurately positioned directly above the step. During the adjustment process, it is necessary to operate slowly to avoid collision between the probe tip and the sample surface. During the movement, the image under the low-power optical microscope is continuously observed to ensure that the probe tip does not deviate from the expected movement path.

[0044] This process ensures that the height difference between the needle tip and the sample surface is only 100μm, allowing both to be clearly focused simultaneously under an optical microscope. Furthermore, the needle tip will not scratch the sample surface when moved. Most importantly, the needle tip and sample positions are aligned before insertion, and the needle tip will not deviate significantly during its descent. However, if the needle tip is aligned when it is far from the sample surface, firstly, the needle tip and sample surface cannot be clearly focused simultaneously. Even if the needle tip is moved to the step position on the sample surface, the probe will deviate from the step position when it hits the sample surface because the probe does not move vertically downwards when it approaches the sample surface, thus making it impossible to obtain the step height. S3: Parameter settings and needle insertion test. Start the linear scanning mode of the atomic force microscope and perform a single-line scan along the direction perpendicular to the step extension. Dynamically adjust the scanning range parameters until a step-like feature appears in the real-time feedback scanning curve, such as... Figure 10 As shown, after adjusting the area corresponding to the stepped feature to the center of the scanning field of view, the scanning mode is switched to obtain three-dimensional topographic data. For step S3, first, activate the scanning function of the atomic force microscope and set the initial value of the scanning range Size to a small value, such as about 10% of the probe tip's movement limit. The main purpose of this setting is to protect the probe and sample, preventing damage to the probe or sample surface due to an excessively large scanning range during the initial scan. Simultaneously, set other relevant scanning parameters, such as scanning speed and scanning frequency. The scanning speed should not be too fast to avoid affecting the scanning accuracy; the scanning frequency should be reasonably selected based on the sample characteristics and measurement requirements.

[0045] Then, control the probe tip to descend to the sample surface and begin single-line scanning. During the scanning process, observe the changes in the scanning curve or image in real time. The scanning data can be viewed through the software interface to observe whether a step-like feature appears in the cross-sectional shape of the scan line. If no obvious step-like feature appears in the cross-sectional shape of the scan line, or if the step is not in the center, the scanning parameters need to be adjusted. The value of the scan range (Size) can be gradually adjusted to increase the scan range until a clear step shape can be seen on the cross-sectional line. Once the step shape is visible, begin adjusting the value of offset X. Adjusting offset X is to position the step in the middle of the cross-sectional line, thus obtaining more accurate step height information. By fine-tuning the value of offset X, observe the change in the step position on the cross-sectional line until the step is in the middle position.

[0046] After adjusting offset X, consider whether further reducing the scan range is necessary. If the current scan range is large, exceeding half of the scanner's measurement range, the Size value needs to be reduced. When reducing the Size value, ensure that the upper and lower platforms of the step are fully visible to guarantee the integrity of the measurement data. Once all parameters are adjusted to appropriate positions, switch the scanning mode to progressive scan mode. During progressive scan, the atomic force microscope will scan the sample surface line by line according to the set scan range and parameters, acquiring complete three-dimensional morphological image data. The morphological image of the step on the sample under test is shown below. Figure 11 As shown. During the scanning process, it is essential to continuously monitor the scanning progress and the accuracy of the data. If any abnormalities occur, such as distorted scanning curves or large data fluctuations, the scanning should be stopped immediately. Check the parameter settings and equipment status, troubleshoot the problem, and then continue scanning.

[0047] S4: Process the data to obtain the step height, i.e., the film thickness. This requires using data processing software to perform flattening, noise removal, and other operations. Then, select multiple locations, measure the step height separately, and take the average value.

[0048] For step S4, the saved 3D topographic image data is imported into data processing software. This software can be the software included with the atomic force microscope or a third-party professional data processing software. In the data processing software, the data is first flattened. The purpose of flattening is to remove any overall topographic changes such as tilting or bending that may exist on the sample surface, making the data more accurately reflect the height information of the steps. Appropriate flattening methods, such as planar flattening or polynomial flattening, can be selected using the flattening function in the software to process the data.

[0049] After calibration, noise lines are removed from the data. Noise lines, which may be caused by equipment noise, environmental interference, or other factors, can affect the accuracy of step height measurements. Filtering functions in data processing software, such as Gaussian filtering and median filtering, can be used to filter the data and remove noise lines. During filtering, appropriate filter parameters should be selected based on the characteristics of the data and the type of noise to avoid over-filtering that could lead to data distortion.

[0050] After removing noise lines, select multiple measurement points in the stepped area, such as... Figure 12 As shown, four measurement points were selected. The selection of measurement points should be representative, covering different locations on the steps to ensure the accuracy of the measurement results. The height of each measurement point was measured separately, as shown below. Figures 13-16 As shown, the height value of each measurement point can be obtained through the measurement function in the data processing software. Then, the average value of these height values ​​is calculated, and this average value is the height of the step, which is also the thickness of the membrane.

[0051] After obtaining the film thickness results, the results are analyzed and verified. The measured results can be compared with theoretical values ​​and results obtained by other measurement methods to check if the results are within a reasonable range. If there is a large deviation in the measurement results, possible causes should be analyzed, such as unreasonable parameter settings, improper data processing methods, or defects on the sample surface. Based on the analysis results, the testing process and data processing methods should be adjusted and improved accordingly, and measurements should be repeated until accurate and reliable measurement results are obtained.

[0052] The comparison of Example 2 effectively demonstrates the high efficiency of the technical solution of the present invention. On the one hand, the existing technology cannot guarantee whether the step surface can be tested, and the test takes a long time. However, through the optimization of the test process by the present invention, the accurate test of the sample step surface can be effectively achieved within ten minutes, which greatly improves the efficiency and accuracy of the test.

[0053] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for measuring thin film thickness using a low-power microscope-assisted atomic force microscope, characterized in that, Includes the following steps: S1: By observing with a low-power optical microscope, the probe tip of the atomic force microscope is pre-aligned with the step of the sample to be tested, and then the probe tip is controlled to descend to a position at a first height on the surface of the step; the first height is 5~20nm; S2: Raise the probe tip so that the probe tip and the surface of the sample to be tested are within the focal plane of the low-power optical microscope. Under the real-time monitoring of the low-power optical microscope, adjust the position of the probe so that the projection of the probe tip is directly above the step of the sample to be tested, thus completing the precise positioning. S3: Start the linear scanning mode of the atomic force microscope, perform a single-line scan along the direction perpendicular to the extension of the step, dynamically adjust the scanning range parameters until the step-like feature appears in the real-time feedback scanning curve, and adjust the area corresponding to the step-like feature to the center of the scanning field of view, then switch to the line-by-line scanning mode to obtain three-dimensional morphological data. S4: Obtain the film thickness of the sample to be tested based on the three-dimensional morphology data.

2. The method for measuring thin film thickness using a low-magnification atomic force microscope according to claim 1, characterized in that, The first height is 10~15 nm.

3. The method for measuring thin film thickness using a low-magnification atomic force microscope according to claim 1, characterized in that, In step S2, the probe tip is raised so that the probe tip and the sample surface are within the focal plane of the low-power optical microscope. Specifically, the probe tip is raised so that the distance between the probe tip and the sample surface is 100~300μm, so that the probe tip and the sample surface are within the focal plane of the low-power optical microscope.

4. The method for measuring thin film thickness using a low-magnification atomic force microscope according to claim 1, characterized in that, In step S2, the probe tip is raised so that the probe tip and the sample surface are within the focal plane of the low-power optical microscope. Specifically, the probe tip is raised so that the distance between the probe tip and the sample surface is 100~200μm, so that the probe tip and the sample surface are within the focal plane of the low-power optical microscope.

5. The method for measuring thin film thickness using a low-magnification atomic force microscope according to claim 1, characterized in that, In step S3, the scanning range parameters are dynamically adjusted. Specifically, the initial scanning range is first set to 5% to 10% of the probe tip movement limit, and a linear scan is performed. Then, the scanning range is gradually increased until the upper and lower platforms of the step of the sample to be tested are fully displayed in the scanning curve.

6. The method for measuring thin film thickness using a low-magnification atomic force microscope according to claim 5, characterized in that, During the process of gradually increasing the scanning range, the increase in scanning range each time shall not exceed 50% of the current value.

7. The method for measuring thin film thickness using a low-magnification atomic force microscope according to claim 5, characterized in that, If, during the process of gradually increasing the scanning range, the height difference of the step-like features in the scanning curve changes by more than 10% after two consecutive increases in the scanning range, the scan range is reverted to the previous scan range and manual intervention is triggered.

8. The method for measuring thin film thickness using a low-magnification atomic force microscope according to claim 1, characterized in that, In step S3, when performing linear scanning mode, if the scanning range exceeds 50% of the range of the atomic force microscope scanner, the scanning range is reduced to 30%~40% of the scanner range, and it is ensured that the upper and lower platforms of the step of the sample under test are both within the scanning field of view.

9. The method for measuring thin film thickness using a low-magnification atomic force microscope according to claim 1, characterized in that, In step S4, the film thickness of the sample to be tested is obtained based on the three-dimensional topography data. Specifically, the three-dimensional topography data is first leveled and noise lines are removed. Then, at least 3 to 10 measurement points are selected to measure the step height respectively, and the average value is taken as the film thickness.

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