A magnetic induction device and a manufacturing method thereof

Abstract

A magnetic induction device and a manufacturing method thereof, comprising a substrate, a first metal layer, a first insulating layer and a second metal layer; at least one first groove is formed on a first surface of the substrate, and the second metal layer, the first insulating layer and the first metal layer are sequentially arranged in the at least one first groove; the first insulating layer is arranged between the first metal layer and the second metal layer. By arranging multiple metal layers in the groove, the effective cross-sectional area of the metal line is increased without increasing the thickness / width ratio of the metal line, thereby reducing the AC resistance of the magnetic induction device.

Description

Technical Field

[0001] The present invention relates to a magnetic induction device and a manufacturing method thereof. Background Art

[0002] Magnetic induction devices are widely used in fields such as radio frequency circuits and power management. Reducing the AC resistance of magnetic induction devices plays an important role in improving the performance of magnetic induction devices. Increasing the cross-sectional area of the metal lines of the metal winding is a common method to reduce the resistance. The DC resistance of the metal winding is inversely proportional to the cross-sectional area of the metal lines. However, when the operating frequency is very high, affected by the skin effect, the effective cross-sectional area of the metal lines related to the AC resistance is only the part of the metal surface with a depth not exceeding the skin depth. When both the width and thickness of the metal lines are significantly greater than the skin depth, increasing the cross-sectional area of the metal lines will no longer significantly reduce the AC resistance. Therefore, a reasonable design will set one of the width and thickness of the metal lines to be about twice the skin depth to ensure that the cross-sectional area of the metal lines is the effective cross-sectional area, and reduce the AC resistance by increasing the other dimension of the width and thickness. The skin depth δ is given by δ = [ρ / (πfμ)] 1 / 2 where ρ is the resistivity of the metal lines, f is the operating frequency, and μ is the magnetic permeability of the metal lines. If the metal lines are made of copper, the skin depth is about 6.6 microns at 100 MHz and about 2.1 microns at 1 GHz.

[0003] As Figure 1 shown, it is a cross-sectional view of an existing magnetic induction device, including a substrate and a metal winding. A first metal layer is provided on the first surface of the substrate. The metal winding of the magnetic induction device is disposed on the first metal layer. The first metal layer is disposed above the first surface of the substrate. The width of the metal lines of the first metal layer is much larger than the thickness of the metal lines. This magnetic induction device suppresses the skin effect by restricting the thickness of the metal lines. To reduce the AC resistance, it is necessary to increase the width of the metal lines, but this will significantly reduce the metal line density and thus reduce the inductance density.

[0004] As Figure 2 shown, it is a cross-sectional view of another existing magnetic induction device, including a substrate and a metal winding. At least one first groove is provided on the first surface of the substrate. A first metal layer is provided in the first groove. The metal winding of the magnetic induction device is disposed on the first metal layer. The thickness of the metal lines of the first metal layer is significantly larger than the width of the metal lines. This magnetic induction device suppresses the skin effect by restricting the width of the metal lines. To reduce the AC resistance, it is only necessary to increase the thickness of the metal lines. However, since the preparation of the embedded metal lines requires etching of corresponding-shaped grooves and metal filling on the first surface of the substrate, a too large thickness / width ratio of the metal lines will cause difficulties in the process preparation. Therefore, the width of the metal lines is limited by the skin depth, and the thickness is limited by the process capabilities, and the cross-sectional area of the metal lines is restricted. Summary of the Invention

[0005] The object of the present invention is to propose a novel magnetic induction device in view of the defects existing in the background art. By arranging multiple metal layers in the groove, the effective cross-sectional area of the metal line is increased without increasing the thickness / width ratio of the metal line, thereby reducing the AC resistance of the magnetic induction device.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A magnetic induction device, characterized in that it includes a substrate, a first metal layer, a first insulating layer and a second metal layer; at least one first groove is formed on the first surface of the substrate, and the second metal layer, the first insulating layer, and the first metal layer are sequentially arranged in the at least one first groove; the first insulating layer is arranged between the first metal layer and the second metal layer.

[0008] Further, the first groove is a spiral groove, and the first metal layer and the second metal layer form a spiral metal winding matching the spiral groove.

[0009] Further, the first metal layer and the second metal layer are connected externally to form a parallel relationship.

[0010] Further, the cross-section of the first groove is rectangular or trapezoidal; the cross-section of the second metal layer is nearly "concave" shaped; the cross-section of the first metal layer is rectangular or trapezoidal.

[0011] Further, the magnetic induction device further includes a first filling area, the cross-section of the first groove is rectangular or trapezoidal; the cross-section of the second metal layer is nearly "concave" shaped; the cross-section of the first metal layer is nearly "concave" shaped; the first filling area is arranged inside the first groove to fill the concave part of the first metal layer, and its cross-section is rectangular.

[0012] Further, the depth of the first groove is greater than the opening width.

[0013] Further, the magnetic induction device further includes a second insulating layer, and the second insulating layer is arranged between the second metal layer and the substrate.

[0014] Further, the materials of the first metal layer and the second metal layer are copper, and the substrate is high-resistance silicon or glass.

[0015] The present invention also provides a manufacturing method of a magnetic induction device, including the following steps:

[0016] Form a first groove on the substrate that extends from the substrate surface to the inside;

[0017] Sputter a seed layer on the substrate surface and in the first groove, and then electroplate to form a second metal layer, where the second metal layer does not completely fill the first groove;

[0018] Form a first insulating layer on the surface of the second metal layer, where the first insulating layer does not completely fill the groove;

[0019] Sputter a seed layer on the surface of the first insulating layer, and then electroplate to form a first metal layer;

[0020] Grind or etch to remove the metal material and insulating material on the substrate surface, leaving the first metal layer, second metal layer, and first insulating layer located in the groove.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] A novel magnetic induction device provided by the present invention increases the effective cross-sectional area of the metal line without increasing the thickness / width ratio of the metal line by arranging multiple metal layers in the groove, thereby reducing the AC resistance of the magnetic induction device. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 FIG. is a cross-sectional view of an existing magnetic induction device;

[0024] Figure 2 FIG. is a cross-sectional view of another existing magnetic induction device;

[0025] Figure 3 FIG. is a cross-sectional view of a magnetic induction device provided by the present invention;

[0026] Figure 4 FIG. is a top view of the first groove;

[0027] Figure 5 FIG. is a cross-sectional view of a magnetic induction device provided in Embodiment 2;

[0028] Figures 6a to 6e FIG. is a preparation flow chart of a magnetic induction device provided in Embodiment 1. DETAILED DESCRIPTION OF THE INVENTION

[0029] The technical solutions of the present invention will be described in detail below with reference to the drawings and embodiments.

[0030] The present invention provides a magnetic induction device, and its cross-sectional view is as shown in Figure 3As shown, it includes a substrate, a first metal layer, a first insulating layer, and a second metal layer; at least one first groove is formed on the first surface of the substrate, and the second metal layer, the first insulating layer, and the first metal layer are sequentially arranged in the at least one first groove; the second metal layer is arranged between the first metal layer and the surface of the first groove, and the first insulating layer is arranged between the first metal layer and the second metal layer; the first metal layer and the second metal layer are connected in parallel through an external connection to form the metal wires of a metal winding. Since a first insulating layer is arranged between the first metal layer and the second metal layer, the eddy current that generates the skin effect is blocked, and the effective cross-sectional area of the metal wire is approximately the sum of the effective cross-sectional area when the first metal layer exists alone and the effective cross-sectional area when the second metal layer exists alone. Under the same process capabilities, the first metal layer of the present invention can have the same wire thickness and width as the first metal layer in the prior art II, that is, the same effective cross-sectional area, and the second metal layer provides an additional effective cross-sectional area, thus significantly reducing the AC resistance. Under reasonable design, the width w of the metal winding of the first metal layer is approximately twice the skin depth, that is, 2δ. Assuming that the thickness of the first metal layer allowed by the process capabilities is t, the effective cross-sectional area of the first metal layer is 2δt; the second metal layer has a "concave" cross-section. Assuming that the second metal layer uniformly covers the surface of at least one first groove (for example, it can be achieved by copper electroplating using conformal electroplating solution), the width d of the metal winding of the second metal layer is also approximately twice the skin depth, that is, 2δ, then the effective cross-sectional area of the second metal layer is 2δ(2t + 6δ), and the total effective cross-sectional area is 6δ(t + 2δ), which is more than 3 times that of the case with only the first metal layer. Therefore, the novel magnetic induction device provided by the present invention can significantly reduce the AC resistance. In the case of only having the first metal layer, the groove depth-width ratio of the first groove is t / 2δ. After introducing the second metal layer, the groove depth-width ratio is (t + 2δ) / 6δ, which is smaller than the case of only having the first metal layer. Therefore, introducing the second metal layer will not increase the difficulty of groove preparation and filling. According to a similar principle, the novel magnetic induction device proposed by the present invention can also further increase the effective cross-sectional area of the metal wire and reduce the AC resistance by arranging more metal layers between the second metal layer and the surface of at least one first groove of the substrate.

[0031] A novel magnetic induction device provided by the present invention includes a substrate, a first metal layer, a first insulating layer, and a second metal layer; at least one first groove is formed on the first surface of the substrate, and the second metal layer, the first insulating layer, and the first metal layer are sequentially arranged in the at least one first groove; the second metal layer is arranged between the first metal layer and the surface of the first groove, and the first insulating layer is arranged between the first metal layer and the second metal layer. Generally, the at least one first groove is a spiral first groove, and the top view from above the substrate surface is as Figure 4As shown, the first metal layer and the second metal layer form a spiral metal winding that matches the spiral first groove. The first metal layer and the second metal layer are in a parallel relationship through external connection and jointly form the metal winding of the magnetic induction device. The cross-section of the first groove is rectangular or trapezoidal; the cross-section of the second metal layer is nearly "concave" shaped; the cross-section of the first metal layer is rectangular or trapezoidal. The depth of the first groove is greater than the opening width. Preferably, the depth of the first groove is greater than twice the opening width. Preferably, the depth of the first groove is greater than 20 microns. Preferably, the thickness of the second metal layer is less than 20 microns. The first metal layer and the second metal layer can be copper, the first insulating layer can be silicon oxide, and the substrate can be high-resistance silicon or glass. When the loss factor of the substrate is large, a second insulating layer can be provided between the second metal layer and the first surface of the substrate, and the second insulating layer can be silicon oxide.

[0032] Embodiment 1

[0033] For the magnetic induction device described in Embodiment 1, the cross-section is as Figure 3 shown. The cross-section of the first groove is rectangular; the cross-section of the second metal layer is nearly "concave" shaped; the cross-section of the first metal layer is rectangular; the depth of the first groove is greater than 20 microns; the thickness of the second metal layer is less than 20 microns. The first metal layer and the second metal layer are copper, the first insulating layer is silicon oxide, and the substrate is high-resistance silicon.

[0034] Embodiment 2

[0035] For the magnetic induction device described in Embodiment 2, the cross-section is as Figure 5 shown, and it further includes a first filling area. The cross-section of the first groove is rectangular; the cross-section of the second metal layer is nearly "concave" shaped; the cross-section of the first metal layer is nearly "concave" shaped and does not completely fill the first groove; the first filling area fills the sunken part of the "concave" shape of the first metal layer, thereby completely filling the first groove. The first filling area is an insulating material, such as epoxy resin. The nearly "concave" shaped cross-section is beneficial to increasing the effective cross-sectional area of the first metal layer and reducing the process difficulty of electroplating filling. Preferably, the thickness of the first metal layer is less than 20 microns.

[0036] Embodiment 3

[0037] As shown in Figure 6, the manufacturing method of the magnetic induction device of the present invention includes the following steps: forming a first groove extending from the substrate surface to the inside on the substrate, as Figure 6a shown; sputtering a seed layer on the substrate surface and inside the first groove, and then electroplating with a metal material to form a second metal layer. The seed layer and the second metal layer sequentially cover the surface of the groove, and the second metal layer does not completely fill the first groove, asFigure 6b as shown; a first insulating layer is formed on the surface of the second metal layer, and the first insulating layer does not completely fill the groove, as Figure 6c shown; a seed layer is sputtered on the surface of the first insulating layer, and then a first metal layer is formed by electroplating, as Figure 6d shown; grinding or etching is performed to remove the metal material and the insulating material on the surface of the substrate, and the first metal layer, the second metal layer, and the first insulating layer located in the groove are retained, as Figure 6e shown. The groove extending from the surface of the substrate to the interior of the substrate can be formed by a reactive ion etching process. The sputtered seed layer can be titanium / copper or titanium tungsten / copper. The electroplating of the second metal layer can be conformal copper electroplating (i.e., electroplating a uniform thickness on the surface of the seed layer). The formation of the first insulating layer can be achieved by chemical vapor deposition, such as plasma enhanced chemical vapor deposition. The electroplating of the first metal layer can be super-filling copper electroplating (i.e., mainly electroplating at the bottom of the groove until it is filled) to completely fill the groove and form a cross-section similar to a rectangle or a trapezoid, or conformal copper electroplating can be used to form a "concave" shaped cross-section.

Claims

1. A magnetic induction device, characterized in that, it includes a substrate, a first metal layer, a first insulating layer and a second metal layer; at least one first groove is formed on the first surface of the substrate, and the second metal layer, the first insulating layer, and the first metal layer are sequentially arranged in the at least one first groove; the first metal layer and the second metal layer are connected externally to form a parallel relationship; the cross-section of the first groove is rectangular or trapezoidal; the cross-section of the second metal layer is nearly "concave" shaped; the cross-section of the first metal layer is rectangular or trapezoidal.

2. The magnetic induction device according to claim 1, characterized in that, the first groove is a spiral groove, and the first metal layer and the second metal layer form a spiral metal winding matching the spiral groove.

3. The magnetic induction device according to claim 1, characterized in that, the depth of the first groove is greater than the opening width.

4. The magnetic induction device according to claim 1, characterized in that, the magnetic induction device further includes a second insulating layer, and the second insulating layer is arranged between the second metal layer and the substrate.

5. The magnetic induction device according to claim 1, characterized in that, the materials of the first metal layer and the second metal layer are copper, and the substrate is high-resistance silicon or glass.

6. A manufacturing method of the magnetic induction device according to claim 1, comprising the following steps: forming a first groove extending from the substrate surface to the inside on the substrate; sputtering a seed layer on the substrate surface and in the first groove, and then electroplating to form a second metal layer, and the second metal layer does not completely fill the first groove; forming a first insulating layer on the surface of the second metal layer; sputtering a seed layer on the surface of the first insulating layer, and then electroplating to form a first metal layer; grinding or etching to remove the metal material and insulating material on the substrate surface, and retaining the first metal layer, the second metal layer and the first insulating layer located in the groove.

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