Method for measuring thickness of a layer of a metal compound by scanning electron microscopy

Abstract

The application relates to a scanning electron microscope measurement method for the thickness of a metal compound layer, which comprises the following steps: obtaining a cross section containing the compound layer by wire cutting, and polishing after inlaying; observing under a scanning electron microscope, selecting a copper-tin alloy compound layer to be measured, selecting a backscattering electron probe to obtain a composition contrast image, adjusting the image contrast so that the measured object and the matrix have obvious differences; selecting a magnification of 2500 times matching the thickness of the metal compound layer, obtaining a high-definition backscattering electron image at a scanning speed of 28 seconds / frame; and quantitatively and finely measuring the thickness of the metal compound layer by using ImageJ software. The advantages of the application are as follows: the metal compound layer is extracted by using the ImageJ image processing software, the area is calculated to obtain the average thickness of the film thickness measurement method, not only the accurate alloy layer thickness information is obtained, but also the standard deviation value of the measured object is obtained to evaluate the uniformity of the measured object; the measurement method improves the accuracy and can be applied to detection and analysis practices.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of material detection and analysis, in particular to a scanning electron microscope measurement method for the thickness of a metal compound layer. BACKGROUND

[0002] The thickness of the intermetallic compound layer is very uneven, and the traditional measurement method is to measure N groups and then calculate the arithmetic mean value. This method is relatively true and reliable for measuring relatively uniform thin layers, but for uneven objects, sometimes the thickness and uniformity of the measured object cannot be correctly evaluated.

[0003] A microanalysis method for the thickness of a chromium-free passivation film on an aluminum-zinc plated sheet, published as CN109975340A, and a measurement method for the thickness of a surface treatment on a circuit board, published as CN111220103A, both involve applying a conductive coating or protective layer to the surface to be detected to ensure accurate measurement results, but do not address optimization of thickness measurement.

[0004] A thickness detection method for silver-tin interfacial metal intermetallic compound layers, published as CN113670236A, uses a suitable etching solution to etch the silver-tin sample, making the boundaries in the silver-tin sample clearly exposed and observable by a scanning electron microscope, thereby achieving measurement of the thickness of the interfacial metal intermetallic compound layer in the silver-tin sample, but only involves simple length measurement several times to calculate the arithmetic mean value.

[0005] A method for measuring the thickness of a steel wire coating, published as CN109974635A, mainly uses a long and short axis measurement to eliminate the size effect of the steel wire, which is prone to tilting during the preparation process. The main purpose of this invention is to use the long and short axis average value to eliminate the measurement error of the tilted thin wire, which is also a simple length average algorithm. SUMMARY

[0006] The purpose of the present application is to provide a scanning electron microscope measurement method for the thickness of a metal compound layer, which not only obtains accurate alloy layer thickness information, but also obtains the standard deviation value of the measured object to evaluate the uniformity of the measured object.

[0007] To achieve the above-mentioned purpose, the present application realizes the following technical solutions:

[0008] A scanning electron microscope measurement method for the thickness of a metal compound layer, specifically comprising the following steps:

[0009] S1, wire cutting to cut a sample cross section containing a metal compound, and then embedding, grinding, and polishing to remove contaminants remaining on the surface of the sample;

[0010] S2, select the metal compound layer to be measured by scanning electron microscope, obtain the composition contrast image by backscattered electron probe, adjust the contrast of the image, and distinguish the measured object from the substrate;

[0011] S3, a magnification matching the thickness of the metal compound layer is used, the scanning speed is greater than 15 seconds / frame, and a high-definition backscattered image is obtained;

[0012] S4, the thickness of the metal compound layer is quantitatively measured by using ImageJ software, and the measured object is extracted by adjusting the appropriate threshold value of the binary image;

[0013] S5, check and improve the segmented image;

[0014] S6, the measured object is equally divided, the area of each segmented body is measured, the average width of each segmented body is obtained, and after multi-view field measurement, the average thickness and standard deviation of the measured alloy layer are obtained.

[0015] In step S4, image binarization is to assign the pixel point gray value greater than or equal to a given threshold T in the entire image to 1, and assign the pixel point gray value less than the given threshold T to 0, to obtain a black and white image with only two gray values of 0 and 1.

[0016] The given threshold T is to divide the pixel set according to the gray level, and each subset obtained forms a region corresponding to the real metal compound layer, which is used for data analysis and processing.

[0017] In step S5, the segmented image includes an over-segmented image and an unsegmented image, the unsegmented image is artificially filled, and the over-segmented image is artificially restored.

[0018] In step S2, the working parameters of the scanning electron microscope are as follows: acceleration voltage 15-25kV, working distance 10-15mm, diaphragm 30-60μm, and the substrate is the attachment main body of the metal alloy layer.

[0019] Compared with the prior art, the beneficial effects of the present application are:

[0020] The film thickness measurement method for calculating the area to obtain the average thickness by extracting the metal compound layer through the ImageJ image processing software not only obtains accurate alloy layer thickness information, but also obtains the standard deviation value of the measured object, which is used to evaluate the uniformity of the measured object. This measurement method improves the accuracy compared with the commonly used multi-point equidistant measurement average method, and can be applied to detection and analysis practice. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a metal compound layer thickness measurement diagram. DETAILED DESCRIPTION

[0022] The application will be described in detail below with reference to the accompanying drawings, but it should be pointed out that the implementation of the application is not limited to the following embodiments.

[0023] The following examples are implemented on the premise of the technical solutions of the application, and detailed embodiments and specific operation processes are given, but the protection scope of the application is not limited to the following examples. The methods used in the following examples are all conventional methods unless otherwise specified.

[0024] [Example 1]

[0025] See Figure 1 A scanning electron microscope measurement method for the thickness of a metal compound layer specifically includes the following steps:

[0026] S1, after copper-tin simulation welding, a cross section containing the compound layer is obtained by wire cutting, and then inlaying, grinding and polishing are performed.

[0027] S2, under the scanning electron microscope, the copper-tin alloy compound layer to be measured is selected, the working parameters are selected as an acceleration voltage of 20 kV, a working distance of 10 mm, and an aperture of 60 μm, a backscattered electron probe is selected to obtain a composition contrast image, and the image contrast is adjusted so that the measured object is distinguished from the matrix.

[0028] S3, a magnification of 2500 times matching the thickness of the metal compound layer is selected, and a high-definition backscattered electron image is obtained at a scanning speed of 28 seconds / frame.

[0029] S4, ImageJ software is used to quantitatively and finely measure the thickness of the metal compound layer; under the interface of the ImageJ software, the measured object is extracted by adjusting a suitable threshold value to binarize the image; according to a given threshold value T, the pixel point gray value of the entire image greater than or equal to the given threshold value T is assigned as 1, and the pixel point gray value less than T is assigned as 0, so that a black-and-white image with only 0 and 1 gray values is obtained; threshold value selection is the most important part of image processing and analysis, and the purpose is to divide the pixel set according to the gray level, so that each subset forms a region corresponding to the real object, and each region has consistent properties, thereby realizing data analysis and processing functions.

[0030] S5, the image after computer segmentation is checked and improved, the unsegmented interface is manually filled, and the over-segmented is manually restored.

[0031] S6, the copper-tin compound layer 10 to be measured is equally divided into ten parts, the area of each segmented body is measured, the average width of each segment is calculated by dividing the height, and the average thickness and standard deviation of the measured object are obtained by data processing after multi-field measurement, as shown in Table 1.

[0032] Table 1 Average thickness and standard deviation of measured objects

[0033] Examples Average thickness pm Standard deviation pm 1 3.73 1.31 2 2.11 0.75 3 1.77 0.53

[0034] The present application extracts the metal compound layer by using the ImageJ image processing software, calculates the area to obtain the average thickness of the film thickness measurement method, not only obtains the accurate alloy layer thickness information, but also obtains the standard deviation value of the measured object, which is used to evaluate the uniformity of the measured object; this measurement method is more accurate than the commonly used multi-point equidistant measurement average method, and can be applied to detection and analysis practice.

Claims

1. A method of scanning electron microscope measurement of the thickness of a layer of a metal compound, characterized in that Specifically comprising the following steps: S1, linear cutting intercepts a sample cross section containing metal compounds, and after inlaying, grinding and polishing, removes the surface contaminants of the sample; S2, selects the metal compound layer to be measured by a scanning electron microscope, obtains a composition contrast image using a backscattered electron probe, adjusts the contrast of the image, and distinguishes the measured object from the matrix; S3, a magnification matching the thickness of the metal compound layer is used, and the scanning speed is greater than 15 seconds / frame, to obtain a high-definition backscattered image; S4, quantitatively measures the thickness of the metal compound layer using ImageJ software, adjusts the appropriate threshold to binarize the image to extract the measured object; S5, checks and improves the segmented image; S6, equally divides the measured object, measures the area of each segmented body, and obtains the average width of each segmented body, and after multi-view field measurement, obtains the average thickness and standard deviation of the measured alloy layer; The segmented image includes an over-segmented image and an unsegmented image, the unsegmented image is artificially filled, and the over-segmented image is artificially restored.

2. The method of claim 1, wherein the metal compound layer is a metal oxide layer. In step S4, the image binarization is to assign the pixel point gray value greater than or equal to a given threshold T in the entire image to 1, and assign the pixel point gray value less than the given threshold T to 0, to obtain a black and white image with only two gray values of 0 and 1.

3. The method of claim 2, wherein the metal compound layer is a metal oxide layer. The given threshold T is to divide the pixel set according to the gray level, and each subset obtained forms a region corresponding to the real metal compound layer, for data analysis and processing.

4. The method of claim 1, wherein the metal compound layer is a metal oxide layer. In step S2, the working parameters of the scanning electron microscope are: acceleration voltage 15-25kV, working distance 10-15mm, and diaphragm 30-60μm, and the matrix is the attachment body of the metal alloy layer.

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