Method for detecting the thickness of a non-metallic film

Abstract

The present application relates to the field of test and test technology, and more particularly to a kind of non-metal film thickness detection method, comprising the following steps: S1, preparation micropore scale;S2, the micropore scale and sputtering non-metal film sample are placed in the sample holder of scanning electron microscope;S3, using scanning electron microscope at first high pressure to the micropore is scanned, determine the critical thickness a of charge effect disappearance;S4, at first high pressure to execute sample detection, and the first high pressure of sample surface is obtained by gathering secondary electron image;S5, using scanning electron microscope at second high pressure to the micropore is scanned, determine the critical thickness b of charge effect disappearance;S6, at second high pressure to execute sample detection, and the second high pressure of sample surface is obtained by gathering secondary electron image;S7, to the secondary electron image of first high pressure, the secondary electron image of second high pressure is handled, determines the area of non-metal film thickness in a to b range.

Description

Technical Field

[0001] This invention relates to the field of testing and measurement technology, and in particular to a method for detecting the thickness of non-metallic thin films. Background Technology

[0002] Non-metallic thin films are sputtered onto the surfaces of aircraft engine parts to bond functional films. The thickness of the non-metallic film is required to be in the range of a few micrometers. To improve the bonding strength between the non-metallic film and the part, the surface of the part needs to be roughened. After sputtering the non-metallic film onto the roughened surface, the non-metallic film is thicker in the recesses and thinner in the protrusions.

[0003] To determine the thickness of non-metallic thin films, metallographic samples need to be prepared for measurement. However, metallographic methods for measuring micron-sized non-metallic thin films can only detect the thickness of a single cross-section, limiting the detection range. It cannot detect the area occupied by the thickness of a non-metallic film within a specific range. Furthermore, proper edge protection is required during sample preparation.

[0004] To address the challenges of limited detection range and difficulty in edge protection in non-metallic film testing, and to improve the efficiency of large-scale non-metallic film thickness detection, there is an urgent need for a method for detecting the thickness of non-metallic films. Summary of the Invention

[0005] The main objective of this invention is to provide a method for detecting the thickness of non-metallic thin films, thereby addressing the aforementioned technical problems.

[0006] To achieve the above objectives, this invention proposes a method for detecting the thickness of non-metallic thin films, comprising the following steps:

[0007] S1. Prepare a micron-hole scale, the surface of which is arrayed with micron-holes of progressively increasing depth, and the micron-holes are filled with the same material as the non-metallic film, the material filling the scale surface flush with the surface;

[0008] S2. Place the micron aperture scale and the sputtered non-metallic thin film sample together in the sample holder of the scanning electron microscope;

[0009] S3. Use a scanning electron microscope to scan the micron-holes under the first high voltage, acquire secondary electron images of each micron-hole, and determine the critical thickness a at which the charge effect disappears.

[0010] S4. Acquire secondary electron images of the sample surface under the first high pressure;

[0011] S5. Using a scanning electron microscope to scan the micron-holes under the second high voltage, secondary electron images of each micron-hole are acquired to determine the critical thickness b at which the charge effect disappears.

[0012] S6. Under the second high pressure, a secondary electron image of the sample surface under the second high pressure is acquired.

[0013] S7. Process the secondary electronic images under the first high voltage and the secondary electronic images under the second high voltage to determine the area occupied by the non-metallic film thickness in the range of a to b within the control range from the first high voltage to the second high voltage.

[0014] Preferably, in steps S3 and S5, the critical thickness is determined by selecting the minimum depth of the micron-sized hole corresponding to the white color in the acquired secondary electron image as the critical thickness.

[0015] Preferably, in steps S3 to S6, the working distance, magnification, and scanning speed of the scanning electron microscope remain consistent.

[0016] Preferably, in steps S3 to S6, the magnification is 100x and the scanning speed is 2.6 frames / second.

[0017] Preferably, the first high voltage is 15kV and the second high voltage is 30kV.

[0018] Preferably, the micrometer aperture scale has a length of 20 mm, a width of 1 mm, and a thickness of 0.1 mm; the material is 1Cr18Ni9Ti.

[0019] Preferably, the micro-pores are countersunk holes, numbering 20, arranged in 4 rows and 5 columns; the diameter of the micro-pores is 0.1 mm, and the spacing between two adjacent micro-pores is 0.05 mm.

[0020] Preferably, the depths of the micron-sized holes in the first row are 1 μm, 2 μm, 3 μm, 4 μm, and 5 μm, respectively.

[0021] The depths of the micron-sized holes in the second row are 6μm, 7μm, 8μm, 9μm, and 10μm, respectively.

[0022] The depths of the micron-sized holes in the third row are 11μm, 12μm, 13μm, 14μm, and 15μm, respectively.

[0023] The depths of the micron-sized holes in the fourth row are 16μm, 17μm, 18μm, 19μm, and 20μm, respectively.

[0024] Preferably, in step S7, the secondary electron image under the first high voltage and the secondary electron image under the second high voltage are binarized, the two images are subtracted to obtain a difference image, the difference image is Gaussian blurred and binarized to optimize the image.

[0025] Preferably, in step S2, the micron-sized scale and the sample are both connected to the sample holder through a conductive medium, which is conductive tape or copper wire.

[0026] Due to the adoption of the above technical solution, the beneficial effects of the present invention are as follows:

[0027] (1) The detection method provided by the present invention does not require grinding of the sample, thus avoiding the problem of difficult protection of the sample edge. When detecting whether the thickness of the non-metallic film is within the required range, it is only necessary to collect two secondary electron images under different high voltages to determine whether the film is within the required range, and the detection efficiency is high.

[0028] (2) The method of the present invention utilizes the charging effect of scanning electron microscope to detect the thickness of non-metallic thin films by scanning materials with poor conductivity, thus expanding the application of scanning electron microscope.

[0029] (3) Scanning electron microscopes take less time to acquire secondary electron images, which greatly improves detection efficiency. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of the front of the micrometer aperture scale;

[0032] Figure 2 This is a cross-sectional view of the first row of micron-sized pores;

[0033] Figure 3 Secondary electron images of non-metallic thin films under high voltages of 15KV and 30KV;

[0034] Figure 4 The image shows the difference image and the optimized difference image.

[0035] The following are the symbols in the attached figures: 1. Micrometer aperture scale; 2. Micrometer aperture. Detailed Implementation

[0036] 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 a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0037] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0038] Furthermore, the use of terms such as "first" and "second" in this invention is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed by this invention.

[0039] Referring to the attached figures, a method for detecting the thickness of a non-metallic thin film includes the following steps:

[0040] S1. A micro-aperture scale 1 is prepared, the surface of which is arrayed with micro-apertures 2 of progressively increasing depth. The micro-apertures 2 are filled with the same material as the non-metallic thin film, and the material fills the scale surface flush with the surface. Specifically, the material of the micro-aperture scale 1 is 1Cr18Ni9Ti, its length is 20 mm, its width is 1 mm, and its thickness is 0.1 mm. The non-metallic thin film is mainly composed of silicon oxide.

[0041] The micron-holes 2 are countersunk holes, numbering 20, arranged in 4 rows and 5 columns; the diameter of the micron-holes 2 is 0.1 mm, and the spacing between two adjacent micron-holes 2 is 0.05 mm.

[0042] The depths of the first row of micron-sized holes 2 are 1μm, 2μm, 3μm, 4μm, and 5μm, respectively.

[0043] The depths of the second row of micron-sized holes 2 are 6μm, 7μm, 8μm, 9μm, and 10μm, respectively.

[0044] The depths of the micron-sized holes 2 in the third row are 11μm, 12μm, 13μm, 14μm, and 15μm, respectively.

[0045] The depths of the micron-sized holes 2 in the fourth row are 16μm, 17μm, 18μm, 19μm, and 20μm, respectively.

[0046] S2. Place the micron-sized aperture scale 1 and the sputtered non-metallic thin film sample together in the sample holder of the scanning electron microscope; before placement, the sample needs to be cleaned and dried. The micron-sized aperture scale 1 and the sample are connected to the sample holder through a conductive medium, which is conductive tape or copper wire.

[0047] S3. After preparing the scanning electron microscope (SEM), move the micron aperture scale 1 directly below the SEM objective and adjust it to a suitable working distance. Scan the micron aperture 2 using the SEM under a first high voltage (15 kV). Specifically, scan 20 micron apertures 2 at a magnification of 100x and a scanning speed of 2.6 frames / second. After the secondary electron images show no change, acquire secondary electron images of the 20 micron apertures 2 to determine the critical thickness 'a' at which the charging effect disappears. In the acquired secondary electron images, micron apertures 2 with a depth greater than or equal to 'a' will appear white due to the charging effect, while micron apertures 2 with a depth less than 'a' will appear grayish-black. Therefore, the minimum depth of the micron aperture 2 corresponding to the white color in the image is selected as the critical thickness 'a'.

[0048] S4. Perform sample testing under the first high voltage (15kV) and acquire a secondary electron image of the sample surface under the first high voltage. Specifically, without changing the working distance of the scanning electron microscope, move the field of view of the scanning electron microscope and scan the test surface of the sample under the parameters of 100x magnification and 2.6 frames / second scanning speed. After the secondary electron image has no change, acquire a secondary electron image of the test surface of the sample. Then, the thickness of the non-metallic film in the white area of ​​the secondary electron image is greater than or equal to a, and the thickness of the non-metallic film in the gray-black area is less than a.

[0049] S5. Using the same method, scan the micron-holes 2 under a second high voltage using a scanning electron microscope (SEM) to acquire secondary electron images of each micron-hole 2 and determine the critical thickness b at which the charging effect disappears. Specifically, the first high voltage is 30 kV, and 20 micron-holes 2 are scanned at a magnification of 100x and a scanning speed of 2.6 frames / second. After the secondary electron images show no change, secondary electron images of the 20 micron-holes 2 are acquired to determine the critical thickness b at which the charging effect disappears. In the acquired secondary electron images, micron-holes 2 with a depth greater than or equal to b will appear white due to the charging effect, while micron-holes 2 with a depth less than b will appear grayish-black. Therefore, the minimum depth of the micron-hole 2 corresponding to the white color in the image is selected as the critical thickness b.

[0050] S6. Perform sample testing under the second high voltage (30kV) and acquire a secondary electron image of the sample surface under the second high voltage. Specifically, without changing the working distance of the scanning electron microscope, move the field of view of the scanning electron microscope and scan the test surface of the sample under test at a magnification of 100x and a scanning speed of 2.6 frames / second. After the secondary electron image has no change, acquire a secondary electron image of the test surface of the sample under test. Then, the thickness of the non-metallic film in the white area of ​​the secondary electron image is greater than or equal to b, and the thickness of the non-metallic film in the gray-black area is less than b.

[0051] Compare the images of the same location on the sample under test at 15kV and 30kV high voltage, see details below. Figure 3 As shown, the thickness of the non-metallic film in the area where the white area of ​​the 15KV image is reduced compared to the white area of ​​the 30KV image is a to b.

[0052] S7. Process the secondary electron images under the first and second high voltages to determine the region occupied by the non-metallic film thickness within the range of a to b. Specifically, in the image processing software, the secondary electron images under the first high voltage (15KV) and the second high voltage (30KV) are binarized at an appropriate threshold. The two images are subtracted to obtain a difference image. A Gaussian blur with appropriate parameters is applied to the difference image, and it is binarized again at an appropriate threshold to optimize the image. The non-metallic film thickness in the white area of ​​the obtained image is a to b. See [link to details]. Figure 4 .

[0053] In this embodiment, the 15KV and 30KV high voltages used are determined based on the values ​​of a and b. The values ​​of a and b are determined based on the minimum and maximum values ​​required for the thickness of the non-metallic thin film. Secondary electronic images of the micron aperture scale 1 under different high voltages are collected in advance to obtain the high voltages corresponding to a and b of the shallowest micron aperture 2 that makes the micron aperture scale 1 appear white.

[0054] The principle of the charge effect utilized by the scanning electron microscope is as follows:

[0055] When scanning materials with poor conductivity with a scanning electron microscope, the material surface appears as white or black striped areas in the secondary electron image due to charge accumulation. This phenomenon is often referred to as the charging effect. Thin coatings of powder particles with poor conductivity can eliminate the charging effect, that is, the charging effect will be eliminated when the thickness of the poor conductivity material is reduced to a certain value. Further experiments have found that the higher the voltage of the scanning electron microscope, the thicker the material can be to eliminate the charging effect of the poor conductivity material.

[0056] By utilizing this phenomenon, secondary electron images of the micron-sized aperture scale 1 under different high voltages can be pre-acquired to obtain the minimum thickness required to eliminate the charging effect of poorly conductive materials corresponding to different high voltages. The non-metallic thin film sputtered on the part needs to be controlled within a certain range. Based on the minimum and maximum values ​​of this range, two corresponding high voltage values ​​are obtained. Then, two secondary electron images of the same location on the sample or part with the sputtered non-metallic thin film are acquired at these two high voltage values. By comparing the difference in the charging effect area in the two images, the area occupied by the non-metallic thin film within the controlled thickness range can be obtained.

[0057] Multiple secondary electron images under different high voltages can be continuously acquired and processed by image processing software to generate a 3D contour map of the thickness of non-metallic thin films.

[0058] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for detecting the thickness of a non-metallic thin film, characterized in that, Includes the following steps: S1. Prepare a micro-hole scale (1), the surface of which is arrayed with micro-holes (2) of progressively increasing depth, and the micro-holes (2) are filled with the same material as the non-metallic film, the material filling the surface of the scale; S2. Place the micron aperture scale (1) and the sputtered non-metallic thin film sample together in the sample holder of the scanning electron microscope; S3. Using a scanning electron microscope to scan the micron-hole (2) under the first high voltage, the secondary electron images of each micron-hole (2) are acquired to determine the critical thickness a at which the charge effect disappears. S4. Acquire secondary electron images of the sample surface under the first high pressure; S5. Using a scanning electron microscope to scan the micron-hole (2) under the second high voltage, the secondary electron images of each micron-hole (2) are acquired to determine the critical thickness b at which the charge effect disappears. S6. Acquire secondary electron images of the sample surface under the second high pressure; S7. Process the secondary electron images under the first high voltage and the secondary electron images under the second high voltage to determine the area occupied by the non-metallic film thickness in the range of a to b. In steps S3 and S5, the critical thickness is determined as follows: in the acquired secondary electron image, the minimum depth of the micron-sized hole (2) corresponding to the white color in the image is selected as the critical thickness. In step S7, the secondary electron image under the first high voltage and the secondary electron image under the second high voltage are binarized, the two images are subtracted to obtain a difference image, Gaussian blur is applied to the difference image, and then binarized to optimize the image. The first high voltage and the second high voltage used are determined based on the values ​​of a and b. The values ​​of a and b are determined based on the minimum and maximum values ​​required for the thickness of the non-metallic film. Secondary electronic images of the micron aperture scale (1) under different high voltages are collected in advance, and then the high voltage corresponding to the values ​​of a and b of the shallowest micron aperture (2) that makes the micron aperture scale (1) appear white is obtained.

2. The detection method as described in claim 1, characterized in that, In steps S3 to S6, the working distance, magnification, and scanning speed of the scanning electron microscope remain consistent.

3. The detection method as described in claim 2, characterized in that, In steps S3 to S6, the magnification is 100x and the scanning speed is 2.6 frames / second.

4. The detection method as described in claim 1, characterized in that, The first high voltage is 15kV, and the second high voltage is 30kV.

5. The detection method as described in claim 1, characterized in that, The micrometer aperture scale (1) has a length of 20 mm, a width of 1 mm, and a thickness of 0.1 mm; the material is 1Cr18Ni9Ti.

6. The detection method as described in claim 1, characterized in that, The micro-holes (2) are countersunk holes, numbering 20, arranged in 4 rows and 5 columns; the diameter of the micro-holes (2) is 0.1 mm, and the distance between two adjacent micro-holes (2) is 0.05 mm.

7. The detection method as described in claim 6, characterized in that, The depths of the first row of micron-sized holes (2) are 1 μm, 2 μm, 3 μm, 4 μm, and 5 μm, respectively; The depths of the micron-sized holes (2) in the second row are 6μm, 7μm, 8μm, 9μm, and 10μm, respectively; The depths of the micron-sized holes (2) in the third row are 11 μm, 12 μm, 13 μm, 14 μm, and 15 μm, respectively; The depths of the micron-sized holes (2) in the fourth row are 16μm, 17μm, 18μm, 19μm, and 20μm, respectively.

8. The detection method as described in claim 1, characterized in that, In step S2, the micron-sized aperture scale (1) and the sample are both connected to the sample holder through a conductive medium, which is conductive tape or copper wire.

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