An unconventional shape eddy current detection coil and optimization method

Abstract

The application provides a non-conventional shape eddy current detection coil and an optimization method, which can be used for detecting the thickness of a micro-nano metal film; the axial cross-sectional shape of the coil is a right trapezoid and a parallelogram, wherein the right trapezoid coil includes four structures according to different positions of the axial cross-sectional acute angle, and the parallelogram coil includes two structures according to different positions of the axial cross-sectional acute angle; the application effectively considers the detection sensitivity and spatial resolution of the coil by optimizing the cross-sectional shape and characteristic parameters of the detection coil.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of micro-nano detection, and particularly relates to a non-conventional shape eddy current detection coil and an optimization method. BACKGROUND

[0002] Metal thin films are widely used in aerospace, integrated circuits (IC), and other fields due to their excellent performance. Thickness is a key parameter of metal thin films, directly determining the performance of the thin films. Therefore, the thickness of the thin films should be detected online during the manufacturing process to achieve precise control. There are various methods available for measuring the thickness of metal thin films, including the four-probe method, optical method, eddy current method, and ultrasonic method. Among them, the eddy current method has high application potential in online measurement of the thickness of micro-nano metal thin films due to its simple structure, fast response speed, and strong anti-interference ability.

[0003] Existing micro-nano metal thin film thickness eddy current sensor detection coils mostly adopt a rectangular cross-sectional shape (i.e., a cylindrical coil). While continuously optimizing the basic parameters of the rectangular coil to improve the thickness sensitivity, it is difficult to properly balance the spatial resolution. SUMMARY

[0004] To solve the above problems, the present application provides a non-conventional shape eddy current detection coil and an optimization method, which balances the thickness sensitivity and spatial resolution to improve the detection performance of the eddy current sensor.

[0005] A non-conventional shape eddy current detection coil can be used to detect the thickness of micro-nano metal thin films. The axial cross-sectional shape of the coil is a right-angled trapezoid or a parallelogram. When the axial cross-sectional shape is a right-angled trapezoid, the orientation of the acute angle of the right-angled trapezoid is different, the detection sensitivity and spatial resolution of the coil are different, and the orientation of the acute angle of the right-angled trapezoid includes the inside lower side of the cross section, the inside upper side of the cross section, the outside lower side of the cross section, and the outside upper side of the cross section.

[0006] When the axial cross-sectional shape is a parallelogram, the orientation of the acute angle of the parallelogram is different, the detection sensitivity and spatial resolution of the coil are different, and the orientation of the acute angle of the parallelogram includes the inside upper side of the cross section and the inside lower side of the cross section.

[0007] Further, when the axial cross-sectional shape is a right-angled trapezoid, and the orientation of the acute angle of the right-angled trapezoid is the inside lower side of the cross section, the diameter of the top circle inside the coil is greater than the diameter of the bottom circle, and the diameter of the top circle outside the coil is the same as the diameter of the bottom circle. At this time, the outer diameter of the coil remains unchanged, the smaller the acute angle of the right-angled trapezoid, the more the number of turns of the coil, the greater the detection sensitivity, and the better the spatial resolution.

[0008] Further, when the axial cross-sectional shape is a right trapezoid, and the acute angle of the right trapezoid is on the inside of the cross section, the diameter of the top circle on the inside of the coil is smaller than the diameter of the bottom circle, and the diameter of the top circle on the outside of the coil is the same as the diameter of the bottom circle, at this time, the coil outer diameter is unchanged, the smaller the acute angle of the right trapezoid, the more the number of turns of the coil, the greater the detection sensitivity, and the better the spatial resolution.

[0009] Further, when the axial cross-sectional shape is a right trapezoid, and the acute angle of the right trapezoid is on the inside of the cross section, the diameter of the top circle on the inside of the coil is smaller than the diameter of the bottom circle, and the diameter of the top circle on the outside of the coil is the same as the diameter of the bottom circle, at this time, the coil outer diameter is unchanged, the smaller the acute angle of the right trapezoid, the more the number of turns of the coil, the greater the detection sensitivity, and the better the spatial resolution.

[0010] Further, when the axial cross-sectional shape is a right trapezoid, and the acute angle of the right trapezoid is on the inside of the cross section, the diameter of the top circle on the inside of the coil is smaller than the diameter of the bottom circle, and the diameter of the top circle on the outside of the coil is the same as the diameter of the bottom circle, at this time, the coil outer diameter is unchanged, the smaller the acute angle of the right trapezoid, the more the number of turns of the coil, the greater the detection sensitivity, and the better the spatial resolution.

[0011] Further, when the axial cross-sectional shape is a right trapezoid, and the acute angle of the right trapezoid is on the inside of the cross section, the diameter of the top circle on the inside of the coil is smaller than the diameter of the bottom circle, and the diameter of the top circle on the outside of the coil is the same as the diameter of the bottom circle, at this time, the coil outer diameter is unchanged, the smaller the acute angle of the right trapezoid, the more the number of turns of the coil, the greater the detection sensitivity, and the better the spatial resolution.

[0012] Further, when the axial cross-sectional shape is a right trapezoid, and the acute angle of the right trapezoid is on the inside of the cross section, the diameter of the top circle on the inside of the coil is smaller than the diameter of the bottom circle, and the diameter of the top circle on the outside of the coil is the same as the diameter of the bottom circle, at this time, the coil outer diameter is unchanged, the smaller the acute angle of the right trapezoid, the more the number of turns of the coil, the greater the detection sensitivity, and the better the spatial resolution.

[0013] Further, an optimization method of a non-conventional shape eddy current detection coil, the relative change degree of the detection sensitivity and the spatial resolution of any one axial cross-sectional shape of a non-conventional shape coil which is a right trapezoid or a parallelogram relative to a basic coil is defined as a comparison coefficient, and the calculation method is:

[0014] c=(△S L / S L ) / (△r e / r e )

[0015] Wherein, the basic coil is a regular coil with a rectangular axial cross section, c is the comparison coefficient, △S LS is a change amount of the detection sensitivity of the unconventional shape coil relative to the detection sensitivity of the base coil L △r is the detection sensitivity of the base coil e r is a change amount of the eddy current field radius of the unconventional shape coil relative to the eddy current field radius of the base coil e r is the eddy current field radius of the base coil

[0016] When c < 0, it indicates that the change direction of S L and r e is opposite; when c > 0, it indicates that the change direction of S L and r e is the same. Wherein, when S L and r e increase at the same time, the greater c indicates that the increase speed of S L is relatively faster, or the decrease speed of spatial resolution is relatively slower; when S L and r e decrease at the same time, the smaller c indicates that the increase speed of spatial resolution is relatively faster, or the decrease speed of S L is relatively slower.

[0017] Further, by comparing the size of the coefficient c, the axial cross-sectional shape of the coil, the position of the acute angle and the acute angle are optimized, wherein the preferred unconventional shape coil axial cross-sectional shape is a right trapezoid, the acute angle is below the outside of the cross section and the acute angle is in the range of [15°, 21°].

[0018] Advantages:

[0019] 1. The present application provides an unconventional shape eddy current detection coil, which belongs to a right trapezoidal and parallelogram cross-sectional shape unconventional shape eddy current detection coil, wherein the right trapezoidal coil includes four structures according to the different positions of the acute angle, and the parallelogram coil includes two structures according to the different positions of the acute angle; the present application effectively considers the coil detection sensitivity and spatial resolution by changing the cross-sectional shape of the detection coil.

[0020] 2. The present application provides an optimization method for an unconventional shape eddy current detection coil, which takes a comparison coefficient as an evaluation index, calculates the comparison coefficient by the ratio of the detection sensitivity change rate and the eddy current field radius change rate, and then obtains the unconventional coil with the optimal performance by measuring the size of the comparison coefficient. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The present application provides an eddy current base coil structure schematic diagram;

[0022] Figure 2 The present application provides an eddy current right trapezoidal coil structure schematic diagram;

[0023] Figure 3 The electric eddy current parallel quadrilateral coil structure schematic diagram provided by the application. DETAILED DESCRIPTION

[0024] In order to enable personnel in the art to better understand the scheme of the present application, the technical scheme in the embodiments of the present application will be clearly and completely described below in combination with the drawings in the embodiments of the present application.

[0025] For micro-nano metal thin film thickness measurement, detection sensitivity S L and spatial resolution are two important indicators for measuring the performance of the detection coil, wherein the spatial resolution is characterized by the size of the eddy current domain radius r e when the radial eddy current intensity on the surface of the metal thin film decreases to 1 / e of the maximum value, and the effective detection range is in the eddy current domain range [0, r e ]. The larger the eddy current domain radius r e , the lower the spatial resolution. The conventional shape coil is difficult to realize the balance of detection sensitivity and spatial resolution in the parameter optimization process, that is, the increase of the detection sensitivity will significantly increase the eddy current domain radius, resulting in a significant decrease of the spatial resolution. The present application balances the thickness sensitivity and the spatial resolution, changes the cross-sectional shape of the detection coil, improves the detection sensitivity of the coil, and balances the spatial resolution performance, so as to realize high sensitivity and strong spatial resolution of the electric eddy current sensor.

[0026] Therefore, the present application provides a non-conventional shape electric eddy current detection coil. For micro-nano detection, the cross section of the non-conventional shape coil is a right trapezoid and a parallelogram, which is different from the cross section of the conventional shape coil which is a rectangle. The cross-sectional shape of the detection coil is changed to realize the optimization of the coil performance.

[0027] Specifically, a non-conventional shape electric eddy current detection coil can be used to detect the thickness of a micro-nano metal thin film. The axial cross-sectional shape of the coil is a right trapezoid or a parallelogram. When the axial cross-sectional shape is a right trapezoid, the orientation of the acute angle of the right trapezoid is different, and the detection sensitivity and the spatial resolution of the coil are different. The orientation of the acute angle of the right trapezoid includes the lower inside of the cross section, the upper inside of the cross section, the lower outside of the cross section, and the upper outside of the cross section.

[0028] When the axial cross-sectional shape is a parallelogram, the orientation of the acute angle of the parallelogram is different, and the detection sensitivity and the spatial resolution of the coil are different. The orientation of the acute angle of the parallelogram includes the upper inside of the cross section and the lower inside of the cross section.

[0029] When the axial cross-sectional shape is a right-angled trapezoid, and the acute angle of the right-angled trapezoid is located at the inner side of the cross section, the diameter of the top circle of the inner side of the coil is smaller than the diameter of the bottom circle, and the diameter of the top circle of the outer side of the coil is the same as the diameter of the bottom circle, at this time, the outer diameter of the coil is unchanged, the smaller the acute angle of the right-angled trapezoid, the more the number of turns of the coil, the greater the detection sensitivity, and the better the spatial resolution.

[0030] When the axial cross-sectional shape is a right-angled trapezoid, and the acute angle of the right-angled trapezoid is located at the inner side of the cross section, the diameter of the top circle of the inner side of the coil is smaller than the diameter of the bottom circle, and the diameter of the top circle of the outer side of the coil is the same as the diameter of the bottom circle, at this time, the outer diameter of the coil is unchanged, the smaller the acute angle of the right-angled trapezoid, the more the number of turns of the coil, the greater the detection sensitivity, and the better the spatial resolution.

[0031] When the axial cross-sectional shape is a right-angled trapezoid, and the acute angle of the right-angled trapezoid is located at the inner side of the cross section, the diameter of the top circle of the inner side of the coil is smaller than the diameter of the bottom circle, and the diameter of the top circle of the outer side of the coil is the same as the diameter of the bottom circle, at this time, the outer diameter of the coil is unchanged, the smaller the acute angle of the right-angled trapezoid, the more the number of turns of the coil, the greater the detection sensitivity, and the better the spatial resolution.

[0032] When the axial cross-sectional shape is a right-angled trapezoid, and the acute angle of the right-angled trapezoid is located at the inner side of the cross section, the diameter of the top circle of the inner side of the coil is smaller than the diameter of the bottom circle, and the diameter of the top circle of the outer side of the coil is the same as the diameter of the bottom circle, at this time, the outer diameter of the coil is unchanged, the smaller the acute angle of the right-angled trapezoid, the more the number of turns of the coil, the greater the detection sensitivity, and the better the spatial resolution.

[0033] When the axial cross-sectional shape is a right-angled trapezoid, and the acute angle of the right-angled trapezoid is located at the inner side of the cross section, the diameter of the top circle of the inner side of the coil is smaller than the diameter of the bottom circle, and the diameter of the top circle of the outer side of the coil is the same as the diameter of the bottom circle, at this time, the outer diameter of the coil is unchanged, the smaller the acute angle of the right-angled trapezoid, the more the number of turns of the coil, the greater the detection sensitivity, and the better the spatial resolution.

[0034] When the axial cross-sectional shape is a right-angled trapezoid, and the acute angle of the right-angled trapezoid is located at the inner side of the cross section, the diameter of the top circle of the inner side of the coil is smaller than the diameter of the bottom circle, and the diameter of the top circle of the outer side of the coil is the same as the diameter of the bottom circle, at this time, the outer diameter of the coil is unchanged, the smaller the acute angle of the right-angled trapezoid, the more the number of turns of the coil, the greater the detection sensitivity, and the better the spatial resolution.

[0035] It should be noted that, as shown in Figure 1 The basic coil axial cross-sectional shape is a rectangle. The basic parameters of the basic coil can refer to the following examples: wire diameter 100 μm, inner diameter 3 mm, width-height ratio 4, and number of turns 100.

[0036] That is, compared with the basic coil with rectangular cross section, the present application proposes two kinds of unconventional coils with right-angled trapezoidal and parallelogram cross sections. Among them, Figure 2 The right-angled trapezoidal coil structure schematic diagram provided for the embodiment of the present application. The axial cross section shape of the coil is right-angled trapezoidal. The present application defines the structure parameter α, that is, the angle corresponding to the acute angle of the coil. In the present application, the acute angle of the coil is defined as the angle between the horizontal line and the tangent line of the coil at the acute angle position. Figure 1 On the basis of the basic coil shown, the transformation can obtain the coil 1~coil 4, four different structures of right-angled trapezoidal coils. That is, compared with the basic coil, the right-angled trapezoidal coil includes 4 different structures according to the different positions of the acute angle.

[0037] Figure 3 The parallelogram coil structure schematic diagram provided for the embodiment of the present application. The axial cross section shape of the coil is parallelogram. The present application defines the structure parameter β, that is, the angle corresponding to the acute angle of the coil. In the present application, the acute angle of the coil is defined as the angle between the horizontal line and the tangent line of the coil at the acute angle position. Figure 1 On the basis of the basic coil shown, the transformation can obtain the coil 5 and coil 6, two different structures of parallelogram coils. That is, compared with the basic coil, the parallelogram coil includes 2 different structures according to the different positions of the acute angle.

[0038] It should be noted that the shape parameter of the unconventional coil shape has a significant influence on its sensitivity and spatial resolution. The calculation method of the relative change degree of the detection sensitivity and the spatial resolution of any unconventional coil with axial cross section shape of right-angled trapezoidal or parallelogram relative to the basic coil is as follows:

[0039] c=(△S L / S L ) / (△r e / r e )

[0040] Wherein, the basic coil is a conventional coil with rectangular axial cross section shape, c is the comparison coefficient, △S L is the change amount of the detection sensitivity of the unconventional coil relative to the detection sensitivity of the basic coil, S L is the detection sensitivity of the basic coil, △r e is the change amount of the vortex domain radius of the unconventional coil relative to the vortex domain radius of the basic coil, r e is the vortex domain radius of the basic coil;

[0041] When c<0, it means that the change directions of S L and r e are opposite; when c>0, it means that the change directions of S L and r e are the same. Among them, when S L and r e increase at the same time, the larger c means that S LThe faster the increase in speed, or the slower the decrease in spatial resolution; when S L and r e The smaller c indicates the faster the increase in speed, or the slower the decrease in spatial resolution; when S L decreases.

[0042] For coil 1 and coil 2, c<0, and as α decreases, S L increases, and r e decreases; for coil 3 and coil 4, c>0, and as α decreases, S L increases, and r e also increases; for coil 5 and coil 6, c>0, and as β decreases, S L increases, and r e also increases.

[0043] Based on the above analysis, the comparative coefficients of coil 1 to coil 6 are further discussed according to the comparative coefficient as a measurement index. When α=β, the comparative coefficients are ranked in descending order, and the comparative coefficient of coil 3 is the largest, which means that coil 3 can significantly improve the detection sensitivity with a small decrease in spatial resolution. Compared with the basic coil, the comparative coefficient of coil 3 is the largest when α is about 18°, which further means that coil 3 has the optimal structure performance.

[0044] That is, the axial cross-sectional shape of the coil, the position of the acute angle, and the angle of the acute angle can be determined by the size of the comparative coefficient, wherein the axial cross-sectional shape is a right trapezoid, the acute angle of the right trapezoid is at the lower outside of the cross section, and the acute angle is in the range of [15°, 21°], and the irregularly shaped coil corresponds to the optimal detection sensitivity, while the decrease in spatial resolution is minimized.

[0045] It should be noted that the above-mentioned six different irregularly shaped coils obtained by deforming the basic coil all belong to the protection content of the present application, wherein the coil 3 has the optimal performance, and compared with other irregular coils, coil 3 can quickly improve the detection sensitivity with a small sacrifice of spatial resolution.

[0046] Of course, the present application can have other various embodiments, and those skilled in the art can certainly make various corresponding changes and modifications according to the present application without departing from the spirit and essence of the present application, but these corresponding changes and modifications should all belong to the protection scope of the claims attached to the present application.

Claims

1. An unconventional eddy current detection coil, used for detecting the thickness of nanoscale metal thin films, characterized in that, The axial cross-sectional shape of the coil is either a right trapezoid or a parallelogram. When the axial cross-sectional shape is a right trapezoid, the detection sensitivity and spatial resolution of the coil vary depending on the location of the acute angle of the right trapezoid. The locations of the acute angle of the right trapezoid include the lower inside of the cross-section, the upper inside of the cross-section, the lower outside of the cross-section, and the upper outside of the cross-section. The number of turns of the coil, the location of the acute angle, and the angle of the acute angle are determined according to the required detection sensitivity and spatial resolution. When the axial cross-section is a parallelogram, the detection sensitivity and spatial resolution of the coil vary depending on the orientation of the acute angle of the parallelogram. The orientation of the acute angle of the parallelogram includes the upper part of the inner side of the cross-section and the lower part of the inner side of the cross-section. The number of turns of the coil, the orientation of the acute angle of the coil, and the angle of the acute angle are determined according to the required detection sensitivity and spatial resolution.

2. The unconventional eddy current detection coil as described in claim 1, characterized in that, When the axial cross-section is a right trapezoid and the acute angle of the right trapezoid is located below the inside of the cross-section, the diameter of the top circle inside the coil is larger than the diameter of the bottom circle, and the diameter of the top circle outside the coil is the same as the diameter of the bottom circle. At this time, the outer diameter of the coil remains unchanged. The smaller the acute angle of the right trapezoid, the more coil turns, the greater the detection sensitivity, and the better the spatial resolution.

3. The unconventional eddy current detection coil as described in claim 1, characterized in that, When the axial cross-section is a right trapezoid and the acute angle of the right trapezoid is located above the inner side of the cross-section, the diameter of the top circle inside the coil is smaller than the diameter of the bottom circle, and the diameter of the top circle outside the coil is the same as the diameter of the bottom circle. At this time, the outer diameter of the coil remains unchanged. The smaller the acute angle of the right trapezoid, the more coil turns, the greater the detection sensitivity, and the better the spatial resolution.

4. The unconventional eddy current detection coil as described in claim 1, characterized in that, When the axial cross-section is a right trapezoid and the acute angle of the right trapezoid is located below the outer side of the cross-section, the diameter of the top circle inside the coil is the same as the diameter of the bottom circle, and the diameter of the top circle outside the coil is smaller than the diameter of the bottom circle. In this case, the inner diameter of the coil remains unchanged. The smaller the acute angle of the right trapezoid, the more coil turns, the greater the detection sensitivity, and the worse the spatial resolution.

5. The unconventional eddy current detection coil as described in claim 1, characterized in that, When the axial cross-section is a right trapezoid and the acute angle of the right trapezoid is located above the outer side of the cross-section, the diameter of the top circle inside the coil is the same as the diameter of the bottom circle, and the diameter of the top circle outside the coil is greater than the diameter of the bottom circle. At this time, the inner diameter of the coil remains unchanged. The smaller the acute angle of the right trapezoid, the more coil turns, the greater the detection sensitivity, and the worse the spatial resolution.

6. The unconventional eddy current detection coil as described in claim 1, characterized in that, When the axial cross-section is a parallelogram and the acute angle of the parallelogram is located above the inside of the cross-section, the diameter of the top circle inside the coil is smaller than the diameter of the bottom circle, and the diameter of the top circle outside the coil is smaller than the diameter of the bottom circle. In this case, with the number of coil turns unchanged, the smaller the acute angle of the parallelogram, the greater the detection sensitivity of the coil and the worse the spatial resolution.

7. The unconventional eddy current detection coil as described in claim 1, characterized in that, When the axial cross-section is a parallelogram and the acute angle of the parallelogram is located below the inside of the cross-section, the diameter of the top circle inside the coil is larger than the diameter of the bottom circle, and the diameter of the top circle outside the coil is larger than the diameter of the bottom circle. At this time, with the number of coil turns unchanged, the smaller the acute angle of the parallelogram, the greater the detection sensitivity of the coil and the worse the spatial resolution.

8. An optimization method for an unconventional eddy current detection coil as described in claim 1, characterized in that, Based on the relative change in detection sensitivity and spatial resolution of an unconventional coil with an axial cross-section of a right trapezoid or parallelogram relative to a base coil, a comparison coefficient is defined, and its calculation method is as follows: The base coil is a conventional coil with a rectangular axial cross-section. For comparison coefficients, This represents the change in detection sensitivity of an unconventional coil relative to the detection sensitivity of a basic coil. Based on the detection sensitivity of the base coil, This represents the change in the radius of the eddy current domain of an unconventional shaped coil relative to the radius of the eddy current domain of the base coil. The radius of the eddy current domain of the base coil; when c When <0, it means S L and r e The direction of change is opposite; when c When >0, it means S L and r e The directions of change are the same; among them, when S L and r e When increasing simultaneously, c Larger means S L The faster the increase in speed, or the slower the decrease in spatial resolution; when S L and r e When both decrease, c The smaller the value, the faster the spatial resolution increases, or S L The slower the descent, the better.

9. The optimization method for an unconventional eddy current detection coil as described in claim 8, characterized in that, By comparing coefficients c The size of the coil is optimized by considering the axial cross-sectional shape, the location of the acute angle, and the angle of the acute angle. Among these, the preferred non-conventional coil axial cross-sectional shape is a right trapezoid with the acute angle located below the outer side of the cross-section and within the range of [15º, 21º].

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