isolator

Abstract

An isolation device according to an embodiment includes a first coil on a primary side, a second coil on a secondary side, a first insulating film, and a primary side conductor electrically connected to the primary side. The second coil is disposed above the first coil and magnetically coupled to the first coil. The first insulating film is disposed on the first coil, and the second coil is embedded in a surface of the first insulating film on a side opposite the first coil. The primary side conductor is embedded in a position separate from the second coil on the surface side of the first insulating film. The first insulating film has a plurality of island-shaped protrusions disposed between the second coil and the primary side conductor on the surface side. The plurality of island-shaped protrusions are configured so that a creepage distance along a surface of the first insulating film, that is, a creepage distance in any direction from the second coil to the primary side conductor, is longer than a straight-line distance in the direction from the second coil to the primary side conductor.

Description

[0001] Related applications

[0002] This application enjoys priority based on Japanese Patent Application No. 2022-0048 (filed on March 16, 2022). This application incorporates the entire contents of the basic application by reference. Technical Field

[0003] The implementation involves isolators. Background Technology

[0004] In isolators that transmit signals via magnetic coupling between two coils, it is important to maintain a high insulation breakdown withstand voltage between the primary and secondary sides. Summary of the Invention

[0005] The embodiment provides an isolator that improves the insulation breakdown withstand voltage between the primary and secondary sides.

[0006] The isolator of this embodiment includes a first coil on a primary side, a second coil on a secondary side, a first insulating film, and a primary conductor electrically connected to the primary side. The second coil is disposed above the first coil and magnetically coupled to it. The first insulating film is disposed on the first coil, and the second coil is embedded in a surface of the first insulating film opposite to the first coil side. The primary conductor is embedded on the surface side of the first insulating film at a position separate from the second coil. The first insulating film has a plurality of island-shaped protrusions on its surface side disposed between the second coil and the primary conductor. The plurality of island-shaped protrusions are configured such that the creepage distance along the surface of the first insulating film, i.e., the creepage distance in any direction from the second coil to the primary conductor, is longer than the straight-line distance in that direction from the second coil to the primary conductor. Attached Figure Description

[0007] Figure 1 This is a schematic cross-sectional view of the isolator in the embodiment.

[0008] Figure 2 This is a schematic diagram showing the structure of the isolator in the implementation method.

[0009] Figure 3 This is a schematic top view showing the isolator in the implementation method.

[0010] Figure 4 (a) to (c) are schematic cross-sectional views showing the manufacturing process of the isolator according to the implementation method.

[0011] Figure 5 (a) to (c) are schematic top views showing the structure of the isolator in a modified embodiment.

[0012] Figure 6 This is a schematic top view of an isolator, illustrating another variation of the implementation method.

[0013] Figure 7 This is a schematic cross-sectional view of an isolator, representing another variation of the implementation.

[0014] Figure 8 This is a schematic top view of the isolator representing a comparative example. Detailed Implementation

[0015] Hereinafter, the embodiments will be described with reference to the accompanying drawings. The same reference numerals will be used to denote the same parts in the drawings, and detailed descriptions will be omitted where appropriate; different parts will be described separately. Furthermore, the drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the ratio of the sizes between parts, etc., may not be the same as in reality. Also, even when showing the same parts, there may be cases where the dimensions and ratios of each part are shown differently according to the drawings.

[0016] Furthermore, the configuration and structure of each part are explained using the X, Y, and Z axes shown in the figures. The X, Y, and Z axes are orthogonal to each other, representing the X, Y, and Z directions, respectively. Additionally, sometimes the Z direction is described as the top, and its opposite direction as the bottom.

[0017] Figure 1 This is a schematic cross-sectional view showing the isolator 1 according to an embodiment. The isolator 1 includes a first coil 10 on the primary side, a second coil 20 on the secondary side, and a primary conductor 30 electrically connected to the primary side circuit including the first coil 10. The isolator 1 transmits signals from the primary side to the secondary side via magnetic coupling between the first coil 10 and the second coil 20. The first coil 10 and the second coil 20 are spiral-shaped planar coils (see reference). Figure 3 ).

[0018] The primary conductor 30 is configured at the same level as the second coil 20 in the direction from the first coil 10 toward the second coil 20, for example, in the Z direction. The primary conductor 30 is provided, for example, as an external terminal for supplying a reference potential to the primary circuit.

[0019] like Figure 1 As shown, the isolator 1 also includes a primary conductor 40, a first insulating film 50, a second insulating film 60, a third insulating film 70, and a semiconductor substrate SS. The semiconductor substrate SS is, for example, silicon. The first insulating film 50, the second insulating film 60, and the third insulating film 70 are stacked on the semiconductor substrate SS.

[0020] The primary conductor 40 is positioned at the same level as the first coil 10 in the Z direction. The primary conductor 40 is, for example, via wiring or a circuit not shown (see reference). Figure 7 The primary conductor 40 is electrically connected to the first coil 10. The primary conductor 40 is electrically connected to the primary conductor 30 on the surface side via the connecting conductor 35.

[0021] A first insulating film 50 is disposed on the first coil 10. The first insulating film 50 is, for example, a silicon oxide film. The first insulating film 50 is disposed between the first coil 10 and the second coil 20. The first insulating film 50 has a film thickness that electrically insulates the second coil 20 from the first coil 10 and imparts a desired insulation breakdown withstand voltage between the first coil 10 and the second coil 20. The first insulating film 50 extends between the primary conductor 30 and the primary conductor 40. A connecting conductor 35 is, for example, a contact plug extending within the first insulating film 50. The connecting conductor 35 is, for example, a conductor containing a metal such as copper.

[0022] The second coil 20 is disposed on the surface of the first insulating film 50 opposite to the first coil. The second coil 20 is, for example, embedded in the first insulating film 50. The second coil is, for example, a conductor containing a metal such as copper.

[0023] A second insulating film 60 is disposed on the first insulating film 50. The second insulating film 60 covers the second coil 20 and the primary conductor 30. The second insulating film 60 is, for example, a silicon oxide film. Alternatively, the second insulating film 60 may have a different composition than the first insulating film 50.

[0024] A third insulating film 70 is disposed between the semiconductor substrate SS and the first insulating film 50. The third insulating film 70 is, for example, a silicon oxide film. The first coil 10 and the primary conductor 40 are respectively embedded in the third insulating film 70 between the first insulating film 50 and the third insulating film 70. The first coil 10 and the primary conductor 40 are, for example, conductors containing metals such as copper.

[0025] like Figure 1 As shown, the first coil 10 and the primary side circuit (not shown) are electrically insulated from the secondary side second coil 20 by the first insulating film 50. The insulation breakdown withstand voltage between the primary and secondary sides is ensured by increasing the distance VD from the first coil 10 to the second coil 20 and the straight-line distance HD from the primary side conductor 30 to the second coil 20.

[0026] However, when there is a low-resistance interface between the first insulating film 50 and the second insulating film 60, the insulation breakdown withstand voltage between the primary and secondary sides decreases. For example, if there are adverse conditions such as foreign matter or mobile ions present between the first insulating film 50 and the second insulating film 60 due to the manufacturing process, or initial deposits during the formation of the second insulating film 60 causing a decrease in the insulation breakdown withstand voltage, the insulation breakdown withstand voltage between the primary and secondary sides will decrease.

[0027] For example, in insulating films deposited using CVD (Chemical Vapor Deposition), there may be initial deposits of approximately tens of nm thickness with different compositions and crystallinity, leading to a decrease in the dielectric breakdown voltage. Such initial deposits can be identified, for example, by comparing the contrast of a TEM (Transmission Electron Microscope) image of the insulating film cross-section.

[0028] In contrast, in the isolator 1 of this embodiment, a plurality of island-shaped protrusions IP are provided between the second coil 20 and the primary conductor 30. The island-shaped protrusions IP are provided, for example, on the surface of the first insulating film 50. As a result, the creepage distance from the second coil 20 along the surface of the first insulating film 50 to the primary conductor 30 is longer than the straight-line distance HD, thereby increasing the resistance at the interface between the first insulating film 50 and the second insulating film 60.

[0029] Figure 2 This is a schematic diagram showing the structure of isolator 1 in the embodiment. Figure 2 This is a schematic top view showing the shape and configuration of the island-shaped protrusions IP in a plane parallel to the boundaries of the first insulating film 50 and the second insulating film 60.

[0030] like Figure 2 As shown, the planar shape of the island protrusion IP is, for example, a regular hexagon. By arranging adjacent island protrusion IPs as close as possible, planar filling can be achieved in the area where multiple island protrusions are provided. Furthermore, the planar shape of the island protrusions in this embodiment is not limited to this example; for example, it can also be a polygon other than a regular hexagon or a circle.

[0031] Figure 3 This is a schematic top view showing the isolator 1 in the embodiment. Figure 3 This is a schematic diagram showing the surface of the first insulating film 50.

[0032] like Figure 3As shown, the second coil 20 is a spiral-shaped planar coil. The second coil 20 has connection pads 23 and 25 at its two ends. The second coil 20 is electrically connected to an external circuit or other secondary coils, for example, via metal wires bonded to the connection pads 23 and 25. Additionally, the first coil 10 is also a planar coil, having the same shape as the second coil 20 below it. Furthermore, the planar shape of the second coil 20 is not limited to a circle; for example, it could be a polygon.

[0033] Multiple island-shaped protrusions IP are disposed, for example, in the region surrounding the second coil 20. The primary conductor 30 can be disposed at any position P1 to P3 outside the region where the island-shaped protrusions IP are located. The island-shaped protrusions IP enable the creepage distance from the second coil 20 to any position P1 to P3 where the primary conductor 30 is disposed to be longer than the straight-line distance HD between them. That is, as shown... Figure 3 As indicated by the middle arrow, in any direction along the surface of the first insulating film 50, the creepage distance from the second coil 20 to the respective placement positions P1 to P3 can be made longer than the straight-line distance HD. The primary conductor 30 can also be arranged, for example, to surround the second coil 20 (see [reference]). Figure 6 ).

[0034] Figure 4 (a) to (c) are schematic cross-sectional views showing the manufacturing process of the isolator according to the implementation method. Figure 4 (a) to (c) are schematic diagrams illustrating the formation process of island-shaped protrusions.

[0035] like Figure 4 As shown in (a), after the second coil 20 is formed in the first insulating film 50, an etching mask EM is formed on the surface of the first insulating film 50. In addition, the primary conductor 30 is formed in a portion not shown.

[0036] The etching mask EM is, for example, a photoresist. The etching mask EM is patterned, for example, using photolithography. In the region where the island-shaped protrusion IP is formed, the etching mask EM is patterned, for example, into a regular hexagon.

[0037] like Figure 4 As shown in (b), the first insulating film 50 is selectively etched to form island-shaped protrusions IP. The first insulating film 50 is selectively removed, for example, by dry etching. During this process, the etching mask EM is also etched, and the island-shaped protrusions IP are configured, for example, to have sloping sides.

[0038] like Figure 4As shown in (c), the etch mask EM is removed. The etch mask EM is removed, for example, by ashing. The height of the island protrusion IP is, for example, lower than the thickness TC in the Z direction of the second coil 20. In addition, the inclination angle θ of the side of the island protrusion IP relative to the plane including the bottom surface between adjacent island protrusion IPs is, for example, greater than 45°. As a result, the creepage distance SD along the surface of the first insulating film 50 can be extended.

[0039] Furthermore, the manufacturing method of the island-shaped protrusion IP is not limited to the examples described above. For example, fine island-shaped protrusions can also be formed by roughening the surface of the first insulating film 50. For example, by liquid phase etching or the like, irregular and random-shaped bumps and depressions can be formed on the surface of the insulating film. Such bump and depression structures preferably have a step difference of several hundred nm, and the area ratio of the protrusions is approximately 50%. In addition, bump and depression structures with a step difference of tens of nm are also effective, complementing the improved adhesion described later, and resulting in good insulation breakdown withstand voltage.

[0040] Figure 5 (a) to (c) are schematic top views showing the structure of the isolator in a modified embodiment. Figure 5 (a) and (b) are schematic diagrams illustrating the configuration examples of the island-shaped protrusion IP involved in the comparative example. Figure 5 (c) is a schematic diagram showing an example of the configuration of the island protrusion IP in the embodiment.

[0041] exist Figure 5 In the example shown in (a), island protrusions IP with a quadrilateral planar shape are configured. Multiple island protrusions IP are arranged at equal intervals, for example, in the X and Y directions. Therefore, between adjacent island protrusions IP, straight short-circuit paths SPX and SPY exist in the X and Y directions, respectively. Short-circuit paths SPX and SPY do not intersect with any island protrusion IP. Therefore, the creepage distance along short-circuit paths SPX and SPY is the same as the straight-line distance HD.

[0042] Figure 5 The example shown in (b) illustrates a configuration in which the phases of the island protrusions IP arranged periodically in the X direction are staggered. That is, the periodic arrangement of the island protrusions IP in the X direction is configured to be alternately staggered in the Y direction. As a result, the short-circuit path SPY in the Y direction can be eliminated, but the short-circuit path in the X direction remains.

[0043] like Figure 5 As shown in (c), island protrusions IP of polygonal shapes with different sizes can also be configured. That is, in Figure 5 In the configuration shown in (b), a large island-shaped protrusion IP in the Y direction is added. This also eliminates the short-circuit path SPX in the X direction.

[0044] In this way, by configuring multiple island-shaped protrusions IP with planar shapes of polygons of different sizes, it is possible to achieve a configuration where the creepage distance in any direction is longer than the straight-line distance HD.

[0045] Figure 6 This is a schematic top view of isolator 2, which represents another variation of the implementation method. Figure 6 This is a schematic diagram showing the surface of the first insulating film 50. In this example, a plurality of second coils 20 are disposed on the secondary side. The plurality of second coils 20 are connected in series, for example, via metal wire (not shown). In addition, the plurality of second coils 20 are magnetically coupled to the plurality of first coils 10 disposed below. Furthermore, the second coils 20 may also be configured such that their outermost circumferences are connected to the respective coils, and the winding directions are the same or opposite.

[0046] exist Figure 6 The document describes four second coils 20, but is not limited to this. The number of second coils 20 disposed on the secondary side is arbitrary, but at least two second coils 20 are provided.

[0047] like Figure 6 As shown, the primary conductor 30 is arranged to surround a plurality of second coils 20. A plurality of island-shaped protrusions IP (not shown) are provided between the primary conductor 30 and each of the second coils 20. Figure 3 The island protrusions IP are configured such that the creepage distance from each of the second coil 20 to the primary conductor 30 is longer in any direction than the straight-line distance between them.

[0048] For example, Figure 8 This is a schematic top view of isolator 3, a comparative example. In isolator 3, a plurality of slots 50G are provided on the surface side of the first insulating film 50. The plurality of slots 50G are arranged in a manner that surrounds the plurality of second coils 20 between each of the plurality of second coils 20 and the primary conductor 30. In this structure, the creepage distance from each second coil 20 to the primary conductor 30 can also be made longer than the straight-line distance HD. However, in order to provide a plurality of slots 50G between each second coil 20 and the primary conductor 30, a large area is required.

[0049] In the isolator 2 of this embodiment, multiple island-shaped protrusions IP can be provided without expanding the space between each second coil and the primary conductor 30. Furthermore, the arrangement of the island-shaped protrusions IP is independent of the shape and arrangement of the second coil 20 and the primary conductor 30. That is, the island-shaped protrusions IP of this embodiment are suitable for miniaturization of the isolator 2 and offer a high degree of flexibility in their arrangement.

[0050] Figure 7 This is a schematic cross-sectional view of isolator 2, which represents another variation of the implementation. Figure 7 It is along Figure 6The cross-sectional view of line AA shown.

[0051] like Figure 7 As shown, the first insulating film 50 has a laminated structure comprising a first film 51, a second film 53, a third film 55, and a fourth film 57. The second insulating film 60 includes a first film 61, a second film 63, and a third film 65. The third insulating film 70 includes a first film 73 and a second film 75.

[0052] The first membrane 51 of the first insulating membrane 50 is, for example, a silicon nitride (SiCN) membrane formed using PCVD (Plasma-enhanced Chemical Vapor Deposition). The first membrane 51 is disposed on the third insulating membrane 70. The first membrane 51 inhibits the diffusion of metal atoms from the first coil 10 and the primary conductor 40 into the first insulating membrane 50.

[0053] The second film 53 is, for example, a silicon oxide film formed using CVD (Chemical Vapor Deposition). The second film 53 is disposed on the first film 51. The second film 53 is located between the first coil 10 and the second coil 20, and has a film thickness sufficient to ensure the insulation breakdown withstand voltage between them. The second film 53 has a film thickness of, for example, 5 micrometers or more in the Z direction.

[0054] The third film 55 is, for example, a silicon nitride film formed using PCVD. The third film 55 is disposed on the second film 53. And, a fourth film 57 is disposed on the third film 55. The fourth film 57 is, for example, a silicon oxide film formed using PCVD.

[0055] The second coil 20 is embedded in the fourth film 57. During the formation of the second coil 20, the third film 55 functions as an etch stop film. That is, when a groove for embedding the second coil 20 and the primary conductor 30 is formed in the fourth film 57, the third film 55 prevents excessive etching from reaching the second film 53.

[0056] The first film 61 of the second insulating film 60 is disposed on the first insulating film 50. The first film 61 is, for example, a SiCN film. The first film 61 suppresses the diffusion of metal atoms in the second coil 20 and the primary conductor 30.

[0057] A second film 63 is disposed on the first film 61. The second film 63 is, for example, a silicon oxide film formed using CVD. The second film 63 is formed in such a way that it covers the second coil 20.

[0058] A third film 65 is disposed on the second film 63 and the first film 61. The third film 65 is disposed in contact with the first film 61 between the second coil 20 and the primary conductor 30. The third film 65 is, for example, a silicon oxide film formed using PCVD.

[0059] The first film 73 of the third insulating film 70 is disposed on the semiconductor substrate SS. The first film 73 is, for example, a silicon oxide film formed by CVD. The first film 73 is formed as an interlayer insulating film.

[0060] A second film 75 is disposed on the first film 73. The second film 75 is, for example, a silicon oxide film formed using PCBD. The first coil 10 and the primary conductor 40 are embedded in the second film 75.

[0061] like Figure 7 As shown, isolator 2 also includes a drive circuit DC. The drive circuit DC actuates the first coil 10. The drive circuit DC is disposed on the surface side of the semiconductor substrate SS. The first film 73 of the third insulating film 70 includes multilayer wiring of the drive circuit DC. The primary conductor 40 is electrically connected to the first coil 10, for example, via the drive circuit DC.

[0062] In isolator 2, island-shaped protrusions IP are provided on the surface of the fourth membrane 57 of the first insulating membrane 50. This allows the creepage distances at the interfaces between the fourth membrane 57 of the first insulating membrane 50 and the first membrane 61 of the second insulating membrane 60, and between the first membrane 61 of the second insulating membrane 60 and the third membrane 65 of the second insulating membrane 60, to be longer than the straight-line distance HD. This, in turn, increases the insulation breakdown voltage between the second coil 20 and the primary conductor 30.

[0063] Furthermore, the improved adhesion at the interface between the fourth film 57 of the first insulating film 50 and the first film 61 of the second insulating film 60 allows for stress dispersion caused by the sealing resin during repeated temperature tests such as TCT. In other words, the creepage distance can be extended through the multiple protrusions, and the stability of the interface due to the improved adhesion can be ensured. Additionally, since the coefficient of linear expansion of the first film 61 configured as the second insulating film 60 is smaller than that of the third film 65 of the second insulating film and the fourth film 57 of the first insulating film 50, and the thickness of the first film 61 configured as the second insulating film 60 is thinner than that of the third film 65 and the fourth film 57 of the first insulating film 50, the stress mitigation effect at the interface between the fourth film 57 of the first insulating film 50 and the first film 61 of the second insulating film 60, and at the interface between the first film 61 of the second insulating film 60 and the third film 65 of the second insulating film 60, is improved. That is, by adopting a structure in which a thinner film (the first film 61 of the second insulating film 60) is sandwiched between a thicker film (the fourth film 57 of the first insulating film 50 and the third film 65 of the second insulating film) with a different coefficient of linear expansion, a higher insulation breakdown voltage can be obtained, which complements the increase in creepage distance and the improvement in tightness of the island structure.

[0064] Several embodiments of the present invention have been described, but these embodiments are provided as examples and are not intended to limit the scope of the invention. These new embodiments can be implemented in various other ways, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included within the scope or spirit of the invention, and are included within the scope of the invention as described in the claims and its equivalents.

Claims

1. An isolator, comprising: The first coil on the primary side; The second coil on the secondary side is disposed above the first coil and is magnetically coupled to the first coil; A first insulating film is disposed on the first coil, and a second coil is embedded in the surface of the first insulating film opposite to the side of the first coil; and The primary conductor is embedded on the surface side of the first insulating film at a position separate from the second coil, and is electrically connected to the primary coil. The first insulating film has a plurality of island-shaped protrusions on its surface side disposed between the second coil and the primary conductor. The plurality of island protrusions are configured such that the creepage distance in any direction from the second coil to the primary conductor is longer than the straight-line distance in that direction from the second coil to the primary conductor, the creepage distance being along the surface of the first insulating film.

2. The isolator according to claim 1, wherein, The plurality of island-shaped protrusions are arranged to surround the second coil.

3. The isolator according to claim 1, wherein, It has multiple pairs consisting of the first coil and the second coil. The primary conductor is arranged to surround a plurality of the second coils.

4. The isolator according to claim 1, wherein, The plurality of island-shaped protrusions have planar shapes of polygons of different sizes in a plane along the surface of the first insulating film.

5. The isolator according to claim 1, wherein, The plurality of island-shaped protrusions each have a hexagonal planar shape in a plane along the surface of the first insulating film and are arranged as close as possible to each other.

6. The isolator according to claim 1, wherein, The first insulating film includes: a first film disposed between the first coil and the second coil; and a second film disposed on the first film. The second coil is embedded in the second membrane.

7. The isolator according to claim 1, wherein, It also has a second insulating film that covers at least a portion of the second coil and the primary conductor.

8. The isolator according to claim 7, wherein, It also includes a third insulating film, which is disposed between the first insulating film and the second insulating film and has a different composition from the first insulating film and the second insulating film. The first insulating film and the second insulating film have the same composition.

9. The isolator according to claim 1, wherein, In the direction from the first coil toward the second coil, the height of the island-shaped protrusion is smaller than the thickness of the second coil.

10. The isolator according to claim 1, wherein, It also has: Semiconductor substrates; and A fourth insulating film disposed on the semiconductor substrate The fourth insulating film is disposed between the semiconductor substrate and the first insulating film. The first coil is embedded in the fourth insulating film.

11. The isolator according to claim 10, wherein, It also includes a driving circuit, which is disposed on the semiconductor substrate between the semiconductor substrate and the fourth insulating film. The first coil and the primary conductor are electrically connected to the driving circuit.

12. The isolator according to claim 1, wherein, The reference potential of the primary side is supplied via the primary side conductor.

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