Unconventional-shaped eddy current detection coil and optimization method

Abstract

The invention provides an eddy current detection coil with an unconventional shape and an optimization method. The eddy current detection coil can be used for detecting the thickness of a micro-nano metal film. The axial section shapes of the coils are two unconventional shapes of a right trapezoid and a parallelogram, the right trapezoid coil comprises four structures according to the difference of the acute angle positions of the axial section, and the parallelogram coil comprises two structures according to the difference of the acute angle positions of the axial section; according to the invention, by optimizing the section shape and the characteristic parameters of the detection coil, the detection sensitivity and the spatial resolution of the coil are effectively considered.

Description

Technical Field

[0001] The invention belongs to the field of micro-nano detection technology, and specifically relates to an eddy current detection coil with an unconventional shape and an optimization method. Background Art

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

[0003] Existing micro-nano metal film thickness eddy current sensor detection coils mostly adopt rectangular cross-section shapes (i.e. cylindrical coils). While continuously optimizing the basic parameters of rectangular coils to improve thickness sensitivity, there are problems such as difficulty in properly taking into account spatial resolution. Summary of the invention

[0004] To solve the above problems, the present invention provides an eddy current detection coil with an unconventional shape and an optimization method, which take into account both thickness sensitivity and spatial resolution to improve the detection performance of the eddy current sensor.

[0005] An eddy current detection coil of an unconventional shape can be used to detect the thickness of a micro-nano-scale metal film. 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, and the detection sensitivity and spatial resolution of the coil are different. The orientation of the acute angle of the right-angled trapezoid includes the lower inner side of the cross-sectional area, the upper inner side of the cross-sectional area, the lower outer side of the cross-sectional area, and the upper outer side of the cross-sectional area.

[0006] When the axial cross-section is a parallelogram, the detection sensitivity and spatial resolution of the coil are different depending on the position of the acute angle of the parallelogram, and the positions of the acute angle of the parallelogram include the upper inner side and the lower inner side of the cross-section.

[0007] Furthermore, when the axial cross-sectional shape is a right-angled trapezoid and the acute angle of the right-angled trapezoid is located at the lower inner side of the cross-sectional area, the diameter of the top circle on the inner side of the coil is greater than the diameter of the bottom circle, and the diameter of the top circle on 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 remains unchanged, the smaller the acute angle of the right-angled trapezoid, the more turns of the coil, the greater the detection sensitivity, and the better the spatial resolution.

[0008] Furthermore, when the axial cross-sectional shape is a right-angled trapezoid, and the acute angle of the right-angled trapezoid is located at the upper inner side of the cross-sectional area, the diameter of the top circle on the inner side of the coil is smaller than the diameter of the bottom circle, and the diameter of the top circle on 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 remains unchanged, the smaller the acute angle of the right-angled trapezoid, the more turns of the coil, the greater the detection sensitivity, and the better the spatial resolution.

[0009] Furthermore, when the axial cross-sectional shape is a right-angled trapezoid and the acute angle of the right-angled trapezoid is located at the bottom of the outer side of the cross-section, the diameter of the top circle on the inner side of the coil is the same as the diameter of the bottom circle, and the diameter of the top circle on the outer side of the coil is smaller 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-angled trapezoid, the more turns of the coil, the greater the detection sensitivity, and the worse the spatial resolution.

[0010] Furthermore, when the axial cross-sectional shape is a right-angled trapezoid and the acute angle of the right-angled trapezoid is located above the outer side of the cross-section, the diameter of the top circle on the inner side of the coil is the same as the diameter of the bottom circle, and the diameter of the top circle on the outer side of 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-angled trapezoid, the more turns of the coil, the greater the detection sensitivity, and the worse the spatial resolution.

[0011] Furthermore, when the axial cross-sectional shape is a parallelogram and the acute angle of the parallelogram is located at the upper inner side of the cross-sectional area, the diameter of the top circle on the inner side of the coil is smaller than the diameter of the bottom circle, and the diameter of the top circle on the outer side of the coil is smaller than the diameter of the bottom circle. At this time, the number of coil turns remains unchanged, the smaller the acute angle of the parallelogram, the greater the detection sensitivity of the coil, and the worse the spatial resolution.

[0012] Furthermore, when the axial cross-sectional shape is a parallelogram and the acute angle of the parallelogram is located at the lower inner side of the cross-sectional area, the diameter of the top circle on the inner side of the coil is greater than the diameter of the bottom circle, and the diameter of the top circle on the outer side of the coil is greater than the diameter of the bottom circle. At this time, the number of coil turns remains unchanged, the smaller the acute angle of the parallelogram, the greater the detection sensitivity of the coil, and the worse the spatial resolution.

[0013] Furthermore, an optimization method for an unconventional shaped eddy current detection coil is provided. The relative change degree of the detection sensitivity and spatial resolution of any unconventional shaped coil whose axial cross-section is a right-angled trapezoid or a parallelogram relative to the basic coil is defined as a comparison coefficient, and the calculation method thereof is:

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

[0015] The basic coil is a conventional coil with a rectangular axial cross section, c is the comparison coefficient, △S Lis the change in detection sensitivity of the irregular shape 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 in the eddy current radius of the unconventional coil relative to the eddy current radius of the basic coil, r e is the eddy current domain radius of the basic coil;

[0016] When c<0, it means S L and r e The change direction is opposite; when c>0, it means S L and r e The change direction of is the same. Among them, when S L and r e When increasing at the same time, the larger the c, the greater the S L The faster the increase speed is, or the slower the spatial resolution is, the slower the decrease speed is. L and r e When c decreases at the same time, the smaller the c, the faster the spatial resolution increases, or S L The descent speed is relatively slower.

[0017] Furthermore, by comparing the size of the coefficient c, the axial cross-sectional shape, the position of the acute angle and the acute angle of the coil are optimized, wherein the optimal axial cross-sectional shape of the unconventional coil is a right-angled trapezoid, the acute angle is below the outer side of the cross-section and the acute angle is within the range of [15°, 21°].

[0018] Beneficial effects:

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

[0020] 2. The present invention provides an optimization method for unconventional shaped eddy current detection coils, which uses a comparison coefficient as an evaluation index and calculates the comparison coefficient by the ratio of the detection sensitivity change rate to the eddy current domain radius change rate, and then obtains the unconventional coil with the best performance by measuring the size of the comparison coefficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A schematic diagram of the structure of the eddy current basic coil provided by the present invention;

[0022] Figure 2 A schematic diagram of the structure of an eddy current right-angle trapezoidal coil provided by the present invention;

[0023] Figure 3 This is a schematic diagram of the structure of the eddy current parallelogram coil provided by the present invention. DETAILED DESCRIPTION

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

[0025] For micro-nano metal film thickness measurement, detection sensitivity S L The spatial resolution is the radius r of the eddy current domain corresponding to the radial eddy current intensity on the metal film surface dropping to 1 / e of the maximum value. e The size of the eddy current is characterized by the range of [0,r e ] is the effective detection range, and the eddy current domain radius r e The larger the thickness, the lower the spatial resolution. It is difficult for conventional coils to achieve both detection sensitivity and spatial resolution during parameter optimization, that is, the improvement of detection sensitivity will significantly increase the eddy current domain radius, resulting in a significant decrease in spatial resolution. The present invention takes both thickness sensitivity and spatial resolution into consideration, and by changing the cross-sectional shape of the detection coil, the detection sensitivity of the coil is improved while taking into consideration the spatial resolution performance, thereby achieving high sensitivity and strong spatial resolution of the eddy current sensor.

[0026] In view of this, the present invention provides an eddy current detection coil of unconventional shape. Aiming at micro-nano detection, the cross-section of the unconventional coil is different from the conventional coil with a rectangular cross-section, and the cross-section of the unconventional coil is a right-angled trapezoid and a parallelogram, and the coil performance is optimized by changing the cross-sectional shape of the detection coil.

[0027] Specifically, an eddy current detection coil of an unconventional shape can be used to detect the thickness of a micro-nano-scale metal film, wherein the axial cross-sectional shape of the coil is a right-angled trapezoid or a parallelogram, wherein when the axial cross-sectional shape is a right-angled trapezoid, the orientation of the acute angle of the right-angled trapezoid is different, and 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 lower inner side of the cross section, the upper inner side of the cross section, the lower outer side of the cross section, and the upper outer side of the cross section;

[0028] When the axial cross-section is a parallelogram, the detection sensitivity and spatial resolution of the coil are different depending on the position of the acute angle of the parallelogram, and the positions of the acute angle of the parallelogram include the upper inner side and the lower inner side of the cross-section.

[0029] When the axial cross-section is a right-angled trapezoid, and the acute angle of the right-angled trapezoid is located at the lower inner side of the cross-section, the diameter of the top circle on the inner side of the coil is greater than the diameter of the bottom circle, and the diameter of the top circle on 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 remains unchanged, the smaller the acute angle of the right-angled trapezoid, the more turns of the coil, the greater the detection sensitivity, and the better the spatial resolution.

[0030] When the axial cross-section is a right-angled trapezoid, and the acute angle of the right-angled trapezoid is located at the upper inner side of the cross-section, the diameter of the top circle on the inner side of the coil is smaller than the diameter of the bottom circle, and the diameter of the top circle on 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 remains unchanged, the smaller the acute angle of the right-angled trapezoid, the more turns of the coil, the greater the detection sensitivity, and the better the spatial resolution.

[0031] When the axial cross-section is a right-angled trapezoid, and the acute angle of the right-angled trapezoid is located below the outer side of the cross-section, the diameter of the top circle on the inner side of the coil is the same as the diameter of the bottom circle, and the diameter of the top circle on the outer side of the coil is smaller 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-angled trapezoid, the more turns of the coil, the greater the detection sensitivity, and the worse the spatial resolution.

[0032] When the axial cross-section is a right-angled trapezoid, and the acute angle of the right-angled trapezoid is located above the outer side of the cross-section, the diameter of the top circle on the inner side of the coil is the same as the diameter of the bottom circle, and the diameter of the top circle on the outer side of 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-angled trapezoid, the more turns the coil has, the greater the detection sensitivity, and the worse the spatial resolution.

[0033] When the axial cross-section shape is a parallelogram, and the acute angle of the parallelogram is located at the upper inner side of the cross-section, the diameter of the top circle on the inner side of the coil is smaller than the diameter of the bottom circle, and the diameter of the top circle on the outer side of the coil is smaller than the diameter of the bottom circle. At this time, the number of coil turns remains unchanged, the smaller the acute angle of the parallelogram, the greater the coil detection sensitivity, and the worse the spatial resolution.

[0034] When the axial cross-section shape is a parallelogram, and the acute angle of the parallelogram is located at the lower inner side of the cross-section, the diameter of the top circle on the inner side of the coil is greater than the diameter of the bottom circle, and the diameter of the top circle on the outer side of the coil is greater than the diameter of the bottom circle. At this time, the number of coil turns remains unchanged, the smaller the acute angle of the parallelogram, the greater the coil detection sensitivity, and the worse the spatial resolution.

[0035] It should be noted that if Figure 1 The figure is a schematic diagram of the structure of the eddy current basic coil provided by the embodiment of the present invention. The axial cross-section of the basic coil is a rectangle. The basic parameters of the basic coil can refer to the following example: wire diameter 100 μm, inner diameter 3 mm, aspect ratio 4, number of turns 100.

[0036] That is to say, compared with the basic coil with a rectangular cross section, the present invention proposes two unconventional coils with a right-angled trapezoidal cross section and a parallelogram cross section. Figure 2 A schematic diagram of a right-angle trapezoidal coil structure provided by an embodiment of the present invention. The axial cross-section of the coil is a right-angle trapezoid. The present invention defines a structural parameter α, which is the angle corresponding to the acute angle of the coil. Figure 1 Based on the basic coil shown, the deformation can obtain four different structures of right-angle trapezoidal coils, namely coil 1 to coil 4. That is, compared with the basic coil, the right-angle trapezoidal coil includes four different structures according to the different acute angle positions.

[0037] Figure 3 Schematic diagram of the parallelogram coil structure provided by an embodiment of the present invention. The axial cross-section of the coil is a parallelogram. The present invention defines a structural parameter β, which is the angle corresponding to the acute angle of the coil. Figure 1 Based on the basic coil shown, deformation can obtain coil 5 and coil 6, two parallelogram coils with different structures. In other words, compared with the basic coil, the parallelogram coil includes two different structures according to the different acute angle positions.

[0038] It should be noted that the shape parameters of the unconventional coil have a significant impact on its sensitivity and spatial resolution. The calculation method for the relative change in the detection sensitivity and spatial resolution of any unconventional coil with an axial cross-section of a right-angle trapezoid or a parallelogram relative to the basic coil is:

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

[0040] Among them, the basic coil is a conventional coil with a rectangular axial cross-section shape, c is the comparison coefficient, △S L is the change in detection sensitivity of the irregular shape 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 in the eddy current radius of the unconventional coil relative to the eddy current radius of the basic coil, r e is the eddy current domain radius of the basic coil;

[0041] When c<0, it means S L and r e The change direction is opposite; when c>0, it means S L and r e The change direction of is the same. Among them, when S L and r e When increasing at the same time, the larger the c, the greater the S LThe faster the increase speed is, or the slower the spatial resolution is, the slower the decrease speed is. L and r e When c decreases at the same time, the smaller the c, the faster the spatial resolution increases, or S L The descent speed is relatively slower.

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

[0043] Based on the above analysis, the comparison coefficients of coils 1 to 6 are further discussed according to the comparison coefficients proposed in the present invention as a measurement indicator. When α=β, the comparison coefficients are sorted according to the size of the comparison coefficients, and it is found that the comparison coefficient of coil 3 is the largest, which means that coil 3 can significantly improve the detection sensitivity under the condition of a small reduction in spatial resolution. Compared with the basic coil, when α is about 18°, the comparison coefficient of coil 3 is the largest, which further leads to the conclusion that the structure and performance of coil 3 are the best.

[0044] That is to say, by comparing the sizes of the coefficients, the present invention can determine the axial cross-sectional shape of the coil, the position of the acute angle and the angle of the acute angle, wherein an unconventional-shaped coil whose axial cross-sectional shape is a right-angled trapezoid, whose acute angle is below the outer side of the cross-section and whose acute angle is within the range of [15°, 21°] corresponds to the optimal detection sensitivity while minimizing the decrease in spatial resolution.

[0045] It should be noted that the above 6 types of coil structures of different unconventional shapes obtained by deformation on the basic coil all belong to the protection content of the present invention, among which the coil structure shown in coil 3 has the best performance. Compared with other unconventional coils, coil 3 can quickly improve the detection sensitivity under the condition of less sacrifice of spatial resolution.

[0046] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art may certainly make various corresponding changes and modifications based on the present invention, but these corresponding changes and modifications should all fall within the scope of protection of the claims attached to the present invention.

Claims

1. An eddy current detection coil of unconventional shape can be used to detect the thickness of micro-nano metal films, characterized in that: The axial cross-sectional shape of the coil is a right-angled trapezoid or a parallelogram, wherein when the axial cross-sectional shape is a right-angled trapezoid, the orientation of the acute angle of the right-angled trapezoid is different, and 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 lower inner side of the cross-sectional area, the upper inner side of the cross-sectional area, the lower outer side of the cross-sectional area, and the upper outer side of the cross-sectional area; When the axial cross-section is a parallelogram, the detection sensitivity and spatial resolution of the coil are different depending on the position of the acute angle of the parallelogram, and the positions of the acute angle of the parallelogram include the upper inner side and the lower inner side of the cross-section.

2. The eddy current detection coil of an unconventional shape as claimed in claim 1, characterized in that: When the axial cross-section is a right-angled trapezoid, and the acute angle of the right-angled trapezoid is located at the lower inner side of the cross-section, the diameter of the top circle on the inner side of the coil is greater than the diameter of the bottom circle, and the diameter of the top circle on 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 remains unchanged, the smaller the acute angle of the right-angled trapezoid, the more turns of the coil, the greater the detection sensitivity, and the better the spatial resolution.

3. The eddy current detection coil of an unconventional shape as claimed in claim 1, characterized in that: When the axial cross-section is a right-angled trapezoid, and the acute angle of the right-angled trapezoid is located at the upper inner side of the cross-section, the diameter of the top circle on the inner side of the coil is smaller than the diameter of the bottom circle, and the diameter of the top circle on 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 remains unchanged, the smaller the acute angle of the right-angled trapezoid, the more turns of the coil, the greater the detection sensitivity, and the better the spatial resolution.

4. The eddy current detection coil of an unconventional shape as claimed in claim 1, characterized in that: When the axial cross-section is a right-angled trapezoid, and the acute angle of the right-angled trapezoid is located below the outer side of the cross-section, the diameter of the top circle on the inner side of the coil is the same as the diameter of the bottom circle, and the diameter of the top circle on the outer side of the coil is smaller 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-angled trapezoid, the more turns of the coil, the greater the detection sensitivity, and the worse the spatial resolution.

5. The eddy current detection coil of an unconventional shape as claimed in claim 1, characterized in that: When the axial cross-section is a right-angled trapezoid, and the acute angle of the right-angled trapezoid is located above the outer side of the cross-section, the diameter of the top circle on the inner side of the coil is the same as the diameter of the bottom circle, and the diameter of the top circle on the outer side of 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-angled trapezoid, the more turns the coil has, the greater the detection sensitivity, and the worse the spatial resolution.

6. The eddy current detection coil of an unconventional shape as claimed in claim 1, characterized in that: When the axial cross-section shape is a parallelogram, and the acute angle of the parallelogram is located at the upper inner side of the cross-section, the diameter of the top circle on the inner side of the coil is smaller than the diameter of the bottom circle, and the diameter of the top circle on the outer side of the coil is smaller than the diameter of the bottom circle. At this time, the number of coil turns remains 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 eddy current detection coil of an unconventional shape as claimed in claim 1, characterized in that: When the axial cross-section shape is a parallelogram, and the acute angle of the parallelogram is located at the lower inner side of the cross-section, the diameter of the top circle on the inner side of the coil is greater than the diameter of the bottom circle, and the diameter of the top circle on the outer side of the coil is greater than the diameter of the bottom circle. At this time, the number of coil turns remains unchanged, the smaller the acute angle of the parallelogram, the greater the detection sensitivity of the coil, and the worse the spatial resolution.

8. A method for optimizing an eddy current detection coil of an irregular shape as claimed in claim 1, characterized in that: The relative change degree of detection sensitivity and spatial resolution of any unconventional coil with a right-angle trapezoid or parallelogram axial cross-section relative to the basic coil is defined as the comparison coefficient, which is calculated as follows: c=(△S L / S L ) / (△r e / r e ) The basic coil is a conventional coil with a rectangular axial cross section, c is the comparison coefficient, △S L is the change in detection sensitivity of the irregular shape 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 in the eddy current radius of the unconventional coil relative to the eddy current radius of the basic coil, r e is the eddy current domain radius of the basic coil; When c<0, it means S L and r e The change direction is opposite; when c>0, it means S L and r e The change direction of is the same. Among them, when S L and r e When increasing at the same time, the larger the c, the greater the S L The faster the increase speed is, or the slower the spatial resolution is, the slower the decrease speed is. L and r e When c decreases at the same time, the smaller the c, the faster the spatial resolution increases, or S L The descent speed is relatively slower.

9. The method for optimizing an eddy current detection coil of an unconventional shape as claimed in claim 8, characterized in that: By comparing the size of the coefficient c, the axial cross-sectional shape, the position of the acute angle and the angle of the acute angle of the coil are optimized. Among them, the optimal axial cross-sectional shape of the unconventional coil is a right-angled trapezoid, the acute angle is below the outer side of the cross-section and the acute angle is in the range of [15°, 21°].

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