signal transmission devices

Abstract

To provide a signal transmission device having a capacitor coupler with a structure that can more reliably suppress the influence of a high electric field on a control circuit.SOLUTION: A signal transmission device includes a shield portion 60 that has conductors 61a to 61e to which a low voltage is applied between a lower electrode 40 and an upper electrode 50 and a low voltage circuit area 20. The shield portion 60 includes an eaves portion 63 that is positioned higher than the low voltage circuit area 20 with the stacking direction of the lower electrode 40 and the upper electrode 50 as the height direction, and extends on the side opposite to the lower electrode 40 and the upper electrode 50.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a signal transmission device having a capacitor coupler. [Background technology]

[0002] There is known a signal transmission device having a capacitor coupler that transmits signals between a high-voltage circuit and a low-voltage circuit while electrically isolating and separating them. For example, Patent Document 1 proposes a signal transmission device having a capacitor coupler configured with a lower electrode on the low-voltage side and an upper electrode on the high-voltage side via an insulating film. In this signal transmission device, a shielding section is provided between the capacitor coupler and peripheral elements provided around it, in which conductor vias and conductive interconnect structures are alternately stacked in multiple stages, thereby suppressing the application of a high electric field to the peripheral elements. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Patent Application Publication No. 2019 / 0206981 Summary of the Invention [Problem to be solved by the invention]

[0004] When a signal transmission device having a capacitor coupler is used to control the on / off of a power switching element that controls a high-voltage motor or the like, a high electric field of 1 kVrms is applied between the upper and lower electrodes. When such a high electric field is applied, a high electric field is also applied to the periphery of the capacitor coupler. Therefore, if a shielding section is simply formed by repeatedly stacking conductor vias and conductive interconnect structures in multiple layers, as shown in Patent Document 1, the high electric field will wrap around from above the shielding section, affecting the control circuitry and other components of the peripheral elements. For example, if the peripheral element includes a memory, the high electric field can cause negative charge leakage, resulting in the memory function being disabled. Furthermore, the high electric field can also generate wiring noise.

[0005] In view of the above, it is an object of the present invention to provide a signal transmission device having a capacitor coupler with a structure that can more reliably suppress the influence of a high electric field on a control circuit. [Means for solving the problem]

[0006] To achieve the above object, the signal transmission device having a capacitor coupler according to claim 1 comprises a semiconductor substrate (10), a low-voltage circuit region (20) having a control circuit built into the semiconductor substrate and operating based on a low-voltage reference potential, an insulating film (30) formed on the semiconductor substrate, a lower electrode (40) formed on the semiconductor substrate via the insulating film and to which a control signal from the control circuit is output, an upper electrode (40) arranged opposite the lower electrode via the insulating film, forming a capacitor together with the lower electrode and to which a high potential higher than the low voltage is applied, and a shield section (60) formed at least within the insulating film, arranged between the lower electrode and the upper electrode and the low-voltage circuit region, and having conductors (61a-61e) to which a voltage applied by operation of the control circuit from the low voltage is applied. The shield section is located higher than the low-voltage circuit region with the stacking direction of the lower electrode and the upper electrode as the height direction, and has a canopy section (63) extending to the opposite side of the lower electrode and the upper electrode.

[0007] In this way, the shield is provided with an eave portion, which extends on the opposite side of the lower electrode and upper electrode, i.e., the eave portion made of a conductor, extends toward above the control circuit. Therefore, the eave portion prevents a high electric field from entering the low-voltage circuit area where the control circuit is located, thereby preventing it from affecting the control circuit and other components.

[0008] The reference symbols in parentheses attached to each component indicate an example of the correspondence between the component and the specific components described in the embodiments described below. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a partial cross-sectional view of a signal transmission device having a capacitor coupler according to a first embodiment. [Figure 2] 2 is a diagram showing a top view of the capacitor coupler and the shield part in FIG. 1. FIG. [Figure 3] 10A and 10B are diagrams showing the results of investigating how an electric field is applied near a capacitor coupler when an overhanging portion is provided and when an overhanging portion is not provided. [Figure 4] 10A and 10B are diagrams showing the results of investigating how an electric field is applied near a capacitor coupler when there is no shield portion and when there is a shield portion and the width of the canopy portion is changed. [Figure 5] 10 is a diagram showing the results of investigating how an electric field is applied near a capacitor coupler when the shortest distance L from the upper electrode to the shield part is changed. [Figure 6A] 10 is a partial cross-sectional view of a signal transmission device in which the arrangement of the eave portion is changed, which is explained as a modification of the first embodiment. FIG. [Figure 6B] 10 is a partial cross-sectional view of a signal transmission device in which the arrangement of the eave portion is changed, which is explained as a modification of the first embodiment. FIG. [Figure 6C] 10 is a partial cross-sectional view of a signal transmission device in which the arrangement of the eave portion is changed, which is explained as a modification of the first embodiment. FIG. [Figure 7] 10 is a diagram showing a top view of a capacitor coupler and a shield part in a signal transmission device according to a second embodiment. FIG. [Figure 8] 10 is a diagram showing a top view of a capacitor coupler and a shield part in a signal transmission device according to a third embodiment. FIG. [Figure 9] FIG. 10 is a partial cross-sectional view of a signal transmission device according to a fourth embodiment. [Figure 10] 10 is a diagram showing a top view of the capacitor coupler, the shielding portion, and the floating conductor in FIG. 9. FIG. [Figure 11] 10 is a diagram showing a top view of the capacitor couplers, the shielding portion, and the floating conductor when two capacitor couplers are provided. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following embodiments, parts that are identical or equivalent to each other will be denoted by the same reference numerals.

[0011] (First embodiment) A first embodiment will be described. A signal transmission device having a capacitor coupler described in this embodiment is used, for example, to control a power switching element used to drive a motor or the like, and is configured by integrating the capacitor coupler with low-voltage and high-voltage control circuits on a single chip. For example, a chip on which the low-voltage control circuit and capacitor coupler are formed is provided, and a chip on which the high-voltage control circuit, capacitor coupler, and power switching element drive circuit are formed are provided as separate chips. The capacitor couplers on the low-voltage chip and the high-voltage chip are connected to each other, and when a signal is output from the low-voltage control circuit, signal transmission is performed through the capacitor couplers. Based on this, the power switching element is driven by a drive circuit provided on the high-voltage chip. Note that the following description will use a capacitor coupler formed on the low-voltage chip as an example, but the high-voltage side capacitor coupler can also have a similar structure to the low-voltage side capacitor coupler.

[0012] 1, the signal transmission device is configured to include a low-voltage circuit region 20 on a semiconductor substrate 10, and a capacitor coupler formed of a lower electrode 40 and an upper electrode 50 via an insulating film 30. In addition, a shield section 60 is provided between the lower electrode 40 and the upper electrode 50 and to separate them from the low-voltage circuit region 20.

[0013] The semiconductor substrate 10 is made of, for example, a silicon substrate, and peripheral elements included in the low-voltage circuit region 20, such as an IGBT (insulated gate bipolar transistor) and a MOSFET, are fabricated on the semiconductor substrate 10.

[0014] The low-voltage circuit region 20 is a region in which control circuits for controlling high-voltage driven devices, such as power switching elements and their drive circuits, are formed. The control circuits provided in the low-voltage circuit region 20 are driven based on a low-voltage reference voltage, such as ground potential (hereinafter referred to as GND). Although details of the control circuit are not shown here, peripheral elements are fabricated on the semiconductor substrate 10 through a semiconductor manufacturing process, and wiring sections connected to the peripheral elements are patterned in the insulating film 30 to form an integrated circuit. The peripheral elements that make up the control circuit include memory, and when the signal transmission device is shipped as a product, negative charge is injected into the memory to write data, adjusting the signal transmission device to perform the desired operation.

[0015] The insulating film 30 has a multi-layer laminated structure. Here, an example will be described in which the insulating film 30 has a five-layer structure of films 31 to 35, but the number of layers may be arbitrary. The first film 31 is formed on the surface of the semiconductor substrate 10, and the lower electrode 40 is formed on this first film 31. The second films 32 to 35 are formed between the lower electrode 40 and the upper electrode 50.

[0016] The first film 31 to the fifth film 35 are made of the same insulating material, but may be made of different materials. Here, the first film 31 to the fifth film 35 are made of TEOS (tetraethoxysilane).

[0017] The thicknesses of the first film 31 to the fifth film 35 are arbitrary, but the thicknesses of the second film 32 to the fifth film 35 are determined in order to set the distance between the lower electrode 40 and the upper electrode 50. In addition, in the case of this embodiment, the thicknesses of the first film 31 to the fourth film 34 are determined in order to set the height of the shield part 60, etc.

[0018] The total thickness of the second films 32 to the fifth films 35 determines the formation height of the lower electrode 40 and the upper electrode 50, with the stacking direction of the lower electrode 40 and the upper electrode 50 being the height direction. The total thickness of the second films 32 to the fifth films 35 determines the capacitance value of the capacitor formed by the lower electrode 40 and the upper electrode 50, so the thicknesses of the second films 32 to the fifth films 35 are determined depending on the required capacitance value. For example, the thicknesses of the second films 32 to the fifth films 35 are set so that the distance between the lower electrode 40 and the upper electrode 50 is 4 to 10 μm, preferably 5 to 8 μm.

[0019] The first to fourth films 31 to 34 are alternately and repeatedly formed with the conductors 61a to 61d (described later) that constitute the shield part 60. In the present embodiment, the total thickness of the first to fourth films 31 to 34 is the height of the shield part 60. The thickness of each of the first to fourth films 31 to 34 is set to a thickness that allows the vias 62a to 62d that constitute the shield part 60 together with the conductors 61a to 61d to be satisfactorily embedded.

[0020] The lower electrode 40 is one electrode of a capacitor that constitutes the capacitor coupler. The lower electrode 40 is formed on the first film 21 and is electrically connected to a desired portion of the control circuit through an extraction wiring 41 (shown in FIG. 2) that is also formed on the first film 21. A signal is output from the control circuit to this lower electrode 40, thereby transmitting the signal between the lower electrode 40 and the upper electrode 50. A low voltage is applied to the lower electrode 40 because a control signal is transmitted from the control circuit, which operates based on a low reference voltage.

[0021] 2, the lower electrode 40 is configured in a rectangular shape with rounded corners and sides of 50 to 600 μm, and has a thickness of 0.2 to 1 μm. The constituent material of the lower electrode 40 may be any metal that is used as an electrode material, such as Al (aluminum), W (tungsten), Cu (copper), Ti (titanium), or Ta (tantalum).

[0022] 2, the upper electrode 50 is configured in a rectangular shape with rounded corners and sides of 50 to 600 μm, for example, and is thicker than the lower electrode 40, with a thickness of 3 to 5 μm, for example. The upper electrode 50 is formed on the lower electrode 40 with the second film 32 to the fifth film 35 interposed therebetween. The upper electrode 50 is disposed opposite the lower electrode 40, and in this embodiment, the upper electrode 50 is smaller than the lower electrode 40 in terms of the dimensions in the top view shown in FIG. 2, i.e., the dimensions in the planar direction.

[0023] It is preferable that the sides of the rectangle formed by the upper electrode 50 and the sides of the rectangle formed by the lower electrode 40 are parallel to each other, and that the center of the upper electrode 50 and the center of the lower electrode 40 coincide. However, the sides of the rectangle formed by the upper electrode 50 and the sides of the rectangle formed by the lower electrode 40 do not have to be parallel to each other. Furthermore, as long as the upper electrode 50 is located inside the lower electrode 40 when viewed from the normal direction to the top surface of the upper electrode 50, the center of the upper electrode 50 and the center of the lower electrode 40 do not have to coincide. The material of the upper electrode 50 may be any metal that is used as an electrode material, such as Al, W, Cu, Ti, or Ta. The materials of the upper electrode 50 and the lower electrode 40 may be the same or different.

[0024] The upper electrode 50 is electrically connected to a chip equipped with an external power switching element drive circuit by wire bonding (not shown) on the surface of the upper electrode 50. The upper electrode 50 is connected to a drive circuit or the like that operates at a reference voltage higher than the low voltage that the low-voltage circuit region 20 uses as a reference, and therefore a high voltage is applied to the upper electrode 50.

[0025] The shield section 60 is formed at least within the insulating film 30, and is intended to prevent the high electric field applied to the capacitor coupler from affecting peripheral elements provided in the low-voltage circuit region 20. The shield section 60 is connected to a voltage applied by control circuit operation from a low voltage, for example, to the reference potential point of the low-voltage circuit region 20, in this case, to the GND potential which is the potential of the semiconductor substrate 10. In this embodiment, as shown in Fig. 2, the shield section 60 is arranged to completely surround the lower electrode 40 and upper electrode 50 which constitute the capacitor coupler.

[0026] 1, the shield part 60 is configured to have conductors 61a to 61d and vias 62a to 62d. The conductors 61a to 61d are provided on the surfaces of the first to fourth films 31 to 34, respectively, and are formed by depositing a conductive material on the surfaces of the first to fourth films 31 to 34 and then patterning the deposited material. The vias 62a to 62d are formed by filling via holes formed in the first to fourth films 31 to 34 with a conductive material, for example, a portion of the material constituting the conductors 61a to 61d. The conductors 61a to 61d and the vias 62a to 62d are stacked and connected in the height direction to configure the shield part 60.

[0027] Some of the conductors 61a-61d included in the shield part 60, in this case the topmost conductor 61d closest to the upper electrode 50, are positioned higher than the low-voltage circuit region 20, specifically higher than the peripheral elements included in the low-voltage circuit region 20. The conductor 61d positioned higher than the peripheral elements serves as an overhang part 63, which protrudes more than the other conductors 61a-61c on the side opposite the lower electrode 40 and upper electrode 50, covering the upper parts of the peripheral elements. The overhang part 63 may have a width greater than that of the conductors 61a-61c other than the overhang part 63, i.e., a distance from the end closest to the lower electrode 40 and upper electrode 50 to the end furthest from the lower electrode 40 and upper electrode 50, but it is preferable that the width be 10 μm or more.

[0028] Furthermore, the shield part 60 may be disposed at any location, but the shortest distance L from the upper electrode 50 to the shield part 60 is set to be longer than the distance from the upper electrode 50 to the lower electrode 40. Preferably, the shortest distance L is set to 13 μm or more.

[0029] In this manner, a signal transmission device is configured having a capacitor coupler formed by a capacitor consisting of the lower electrode 40 and the upper electrode 50. In a signal transmission device configured in this manner, a control circuit (not shown) outputs a control signal to the lower electrode 40, which is then transmitted to the upper electrode 50 and then to an external chip via a bonding wire. As a result, a drive circuit provided in the external chip drives a power switching element based on the control signal from the control circuit. This makes it possible to drive a motor or the like.

[0030] In a signal transmission device having such a capacitor coupler, a high electric field of, for example, 1 kVrms is applied between the lower electrode 40 and the upper electrode 50. Furthermore, when determining whether a product is good or bad by screening before shipping, a high electric field of 3 kVrms is applied between the lower electrode 40 and the upper electrode 50. When these high electric fields are applied, a high electric field is also applied to the periphery of the capacitor coupler.

[0031] For this reason, a shielding section consisting of alternating layers of conductor vias and conductive interconnect structures, as shown in Patent Document 1, would allow a high electric field to penetrate from above the shielding section, affecting the control circuits and other components of the peripheral elements. For example, if the peripheral elements include memory, the high electric field can cause negative charge leakage, preventing the memory from functioning properly. The high electric field can also cause wiring noise.

[0032] In contrast, in this embodiment, the shield part 60 is provided with a canopy part 63, and the canopy part 63, which is made up of conductors 61d, extends above the control circuit. Therefore, the canopy part 63 prevents a high electric field from entering the low-voltage circuit area 20 where the control circuit is arranged, thereby preventing the control circuit and other components from being affected.

[0033] Figure 3 shows the results of investigating how an electric field is applied near the capacitor coupler when the shield section 60 does not include a canopy portion 63 and when it does. Figure 4 shows the results of investigating how an electric field is applied near the capacitor coupler when the shield section 60 is not included and when the shield section 60 is included and the width of the canopy portion 63 is changed to 10 μm, 18 μm, and 25 μm. As shown in these figures, when the shield section 60 is not included, a high electric field is applied to the low-voltage circuit region 20, but in the structure with the shield section 60, the high electric field is repelled by the shield section 60.

[0034] In this case, as shown in FIG. 3 , if the shield section 60 does not have a structure that includes the overhanging portion 63, i.e., if the shield section 60 does not extend above the low-voltage circuit region 20, the high electric field will bend toward the low-voltage circuit region 20. However, as shown in FIG. 4 , if the shield section 60 has the overhanging portion 63, the high electric field is prevented from bending toward the low-voltage circuit region 20. For example, when the width of the overhanging portion 63 is 10 μm, the high electric field bends toward the low-voltage circuit region 20 slightly, but almost none of the high electric field bends toward the low-voltage circuit region 20. Furthermore, when the width of the overhanging portion 63 is 18 μm or 25 μm, the high electric field does not bend toward the low-voltage circuit region 20 at all. Although not shown here, simulations were performed by changing the width of the overhanging portion 63 and the distance between the lower electrode 40 and the upper electrode 50. The simulations showed that bending toward the low-voltage circuit region 20 was generally prevented when the width of the overhanging portion 63 was 10 μm or more. In particular, when the width of the overhanging portion 63 was set to 20 to 40 μm, the high electric field hardly reached the low-voltage circuit region 20 side.

[0035] In this way, by providing the shield portion 60 with the overhang portion 63, it is possible to suppress the high electric field from penetrating into the low-voltage circuit region 20, thereby suppressing the influence on the control circuit, etc. As a result, for example, if a memory is provided as a peripheral element, negative charge leakage due to the high electric field is suppressed, and the memory function is prevented from being disabled. In addition, it is possible to suppress the generation of wiring noise due to the high electric field.

[0036] Furthermore, since the shield section 60 is at the same potential as the lower electrode 40, in this case the GND potential, if the distance from the upper electrode 50, which is on the high-voltage side, is too close, electric field concentration may occur at the position of the shield section 60 closest to the upper electrode 50. For this reason, the shortest distance L is made longer than the distance from the upper electrode 50 to the lower electrode 40. This makes it possible to mitigate charge concentration at the position of the shield section 60 closest to the upper electrode 50.

[0037] 5 shows the results of investigating how the electric field is applied near the capacitor coupler when the width of the overhanging portion 63 is set to 25 μm and the shortest distance L is changed to 10 μm, 20 μm, and 28 μm. As shown in this figure, even when the shortest distance L is 10 μm, the high electric field is generally prevented from bending toward the low-voltage circuit region 20. When the shortest distance L is 20 μm or 28 μm, the high electric field does not bend toward the low-voltage circuit region 20 at all.

[0038] Here, the measurement results are shown when the width of the overhanging portion 63 is 25 μm, but similar measurement results were obtained when the width was changed. Analysis of the measurement results revealed that when the distance between the lower electrode 40 and the upper electrode 50 is 4 to 10 μm, if the shortest distance L is 13 μm or more, almost no high electric field leaks into the low-voltage circuit region 20. When the distance between the lower electrode 40 and the upper electrode 50 is 10 μm or more, the high electric field is less likely to leak into the low-voltage circuit region 20. Therefore, when the distance between the lower electrode 40 and the upper electrode 50 is 4 μm or more, it can be said that the shortest distance L should be 13 μm or more. Therefore, it is preferable that the shortest distance L is 13 μm or more.

[0039] Furthermore, in this embodiment, the upper electrode 50 is thicker than the lower electrode 40. When a potential difference is generated between the lower electrode 40 and the upper electrode 50, electric field concentration occurs at the lower end of the upper electrode 50, which is on the lower electrode 40 side, and at the upper end, which is on the opposite side from the lower electrode 40. If the thickness of the upper electrode 50 is thin, the electric field concentration points at the upper and lower ends of the upper electrode 50 become closer, making dielectric breakdown due to electric field concentration more likely to occur. In contrast, if the thickness of the upper electrode 50 is made thicker than that of the lower electrode 40, the electric field concentration points can be separated. This prevents the electric field concentrations occurring at the upper and lower ends of the upper electrode 50 from overlapping, mitigating electric field concentration and further suppressing dielectric breakdown due to electric field concentration.

[0040] (Modification of the first embodiment) In the first embodiment, the case where the eave portion 63 is formed by the conductor 61d located at the highest position in the shield portion 60 has been exemplified, but the eave portion 63 does not have to be formed at the highest position. Also, although the case where the shield portion 60 is formed by a four-layer structure of the conductors 61a to 61d and the vias 62a to 62d has been shown, the number of layers is arbitrary.

[0041] For example, as shown in FIGS. 6A and 6B, the overhang portion 63 may be formed by a conductor 61b or conductor 61c that is not located at the highest position. Furthermore, as shown in FIG. 6C, the shield portion 60 may be configured to extend above the outermost surface of the insulating film 30 by including a conductor 61e on the surface of the fifth film 35 and a via 62e formed in the fifth film 35 and filled with a conductive material in a via hole. In such a configuration, the overhang portion 63 may be formed on the outermost surface of the insulating film 30, as shown in FIG. 6C. Forming the overhang portion 63 on the outermost surface of the insulating film 30 can suppress the intrusion of a high electric field and also suppress creeping discharge through the outermost surface of the insulating film 30. While the overhang portion 63 is configured by one of the multiple conductors 61a-61e, it may be configured by more than one. That is, it is sufficient that the overhang portion 63 is configured by at least one of the multiple conductors 61a-61e.

[0042] (Second embodiment) The second embodiment will be described. This embodiment is different from the first embodiment in that the layout of the shield part 60 is changed, but other aspects are the same as the first embodiment, so only the differences from the first embodiment will be described.

[0043] As shown in FIG. 7, in this embodiment, the shield portion 60 is not disposed so as to completely surround the periphery of the lower electrode 40 and the upper electrode 50, but is formed at a position corresponding to only a part of them.

[0044] That is, when the low-voltage circuit region 20 is arranged only on a portion of the periphery of the lower electrode 40 and the upper electrode 50, the shield section 60 is arranged only between the low-voltage circuit region 20 and the lower electrode 40 and the upper electrode 50. In the present embodiment, the low-voltage circuit region 20 is provided along one side of the rectangular lower electrode 40 and upper electrode 50, and therefore the shield section 60 is arranged between at least that one side and the low-voltage circuit region 20. Then, to prevent a high electric field from wrapping around the shield section 60 from the side and affecting the low-voltage circuit region 20, the shield section 60 is also provided facing that side and portions of two adjacent sides.

[0045] In this way, when the low-voltage circuit region 20 is located in a portion of the periphery of the lower electrode 40 and the upper electrode 50, the shield portion 60 may be provided in a position corresponding to only a portion of the periphery of the lower electrode 40 and the upper electrode 50. Even with such a structure, the same effect as in the first embodiment can be obtained.

[0046] (Third embodiment) The third embodiment will be described. This embodiment is different from the first embodiment in that the layout of the shield part 60 is changed, but other aspects are the same as the first embodiment, so only the parts that are different from the first embodiment will be described.

[0047] In the first embodiment described above, the structure includes one capacitor coupler, but when the structure includes two capacitor couplers as shown in FIG. 8, the two capacitor couplers may be surrounded by one shield portion 60.

[0048] For example, a signal transmission device can be used in a form in which two capacitor couplers form a set to transmit one signal. When the signal transmission device is used to control power switching elements for driving a three-phase motor, a total of six power switching elements provided in each of the upper and lower arms for three phases are controlled. In this case, 12 capacitor couplers are provided. In such a case, a structure is used in which each set of two capacitor couplers used for signal transmission is surrounded by one shield part 60.

[0049] In this way, even if two capacitor couplers are configured to be surrounded by one shield part 60, the same effect as in the first embodiment can be obtained.

[0050] (Fourth embodiment) A fourth embodiment will now be described. This embodiment proposes a structure that can further suppress the effects of a high electric field compared to the first to third embodiments, and is otherwise similar to the first to third embodiments, so only the differences from the first to third embodiments will be described. Note that the following description will be given by taking as an example a case where the structure of this embodiment is applied to a structure in which a shield portion 60 is arranged so as to completely surround the periphery of a capacitor coupler, as in the first embodiment.

[0051] As shown in FIG. 9, a floating conductor 70 is provided between the lower electrode 40 and the upper electrode 50 .

[0052] The float conductor 70 is disposed within the insulating film 30, electrically isolated from the lower electrode 40, the upper electrode 50, and the shield portion 60, and is at a float potential. The float conductor 70 is disposed between the lower electrode 40 and the upper electrode 50, i.e., at a position midway between the heights of the lower electrode 40 and the upper electrode 50. Furthermore, in the top view shown in FIG. 10 , the float conductor 70 is disposed between at least one of the lower electrode 40 and the upper electrode 50 and the shield portion 60. While it is sufficient for the float conductor 70 to be spaced apart from each of the lower electrode 40 and the upper electrode 50, it is preferable for the float conductor 70 to be spaced apart from each of the lower electrode 40 and the upper electrode 50 by a predetermined distance or more. For example, it is preferable for the float conductor 70 to be spaced apart from each of the lower electrode 40 and the upper electrode 50 by 5 μm or more.

[0053] The thickness of the float conductor 70 is arbitrary, but in this embodiment, it is set to be approximately the same as that of the lower electrode 40, for example.

[0054] In this embodiment, the float conductor 70 is configured in a frame shape and is disposed outside the smaller of the lower electrode 40 and the upper electrode 50. Specifically, as shown in FIG. 10 , the float conductor 70 in this embodiment has a rectangular frame shape with rounded corners. The width of the float conductor 70, i.e., the dimension in the surface direction of the semiconductor substrate 10, is arbitrary. Here, the dimension on the inner periphery of the float conductor 70 is larger than the dimension on the outer periphery of the upper electrode 50, and the dimension on the outer periphery is the same as or larger than the dimension on the outer periphery of the lower electrode 40.

[0055] As described above, the signal transmission device of this embodiment includes the float conductor 70. When the float conductor 70 is included, the float conductor 70 has an intermediate potential between the lower electrode 40 and the upper electrode 50, so that the electric field is also directed toward the float conductor 70, and the direction of the electric field at the end of the upper electrode 50, to which a high voltage is applied, is dispersed. This makes it possible to reduce the maximum electric field strength at the end of the upper electrode 50. Therefore, the electric field concentration at the end of the upper electrode 50 is alleviated, making it possible to suppress dielectric breakdown due to the electric field concentration and improve the withstand voltage.

[0056] While the structure of this embodiment has been described above as being applied to a structure in which the shield section 60 is disposed so as to completely surround the periphery of the capacitor coupler, as in the first embodiment, it can also be applied to the structures of the second and third embodiments. For example, when two capacitor couplers are provided as in the third embodiment, as shown in FIG. 11 , the float conductor 70 is disposed so as to surround at least one of the lower electrode 40 and the upper electrode 50 of each capacitor coupler in a top view. Then, both the two capacitor couplers and the float conductor 70 are surrounded by a single shield section 60. This configuration can also be applied to the structure of the third embodiment. Although not shown in the second embodiment, the float conductor 70 can be disposed between the capacitor coupler and the shield section 60 so as to surround at least one of the lower electrode 40 and the upper electrode 50.

[0057] (Other embodiments) Although the present disclosure has been described based on the above-described embodiment, it is not limited to the embodiment and encompasses various modifications and modifications within the equivalent range. In addition, various combinations and forms, as well as other combinations and forms including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure.

[0058] For example, the dimensional relationship between the lower electrode 40 and the upper electrode 50 described in each of the above embodiments is arbitrary, and the lower electrode 40 and the upper electrode 50 may be the same size, or the upper electrode 50 may be larger than the lower electrode 40. In that case, when forming the float conductor 70 as shown in the fourth embodiment, it is sufficient that the float conductor 70 is formed so as to surround at least the smaller of the lower electrode 40 and the upper electrode 50 in a top view. Furthermore, when the lower electrode 40 and the upper electrode 50 are the same size, it is sufficient that the float conductor 70 is formed so as to surround both of them in a top view.

[0059] Furthermore, in the above embodiments, the lower electrode 40 and the upper electrode 50 are configured as a rectangle with rounded corners, but they may be configured as other shapes, such as a circle or other polygonal shapes.

[0060] Furthermore, the first embodiment and its modified example may be combined to form a plurality of eave portions 63 at positions of different heights.

[0061] Furthermore, in each of the above embodiments, the conductors 61a-61e and the vias 62a-62e are arranged linearly in the height direction, but they do not have to be arranged linearly. For example, the conductors 61a-61e and the vias 62a-62e may be arranged so that they are gradually separated from the capacitor coupler as they move higher. Even in this case, it is sufficient to form the overhanging portion 63 by extending only some of the conductors toward the side away from the capacitor coupler.

[0062] In the fourth embodiment, one float conductor 70 is formed for each capacitor coupler, but multiple float conductors may be provided. In addition, the float conductor 70 is formed so as to completely surround at least one of the lower electrode 40 and the upper electrode 50 of the capacitor coupler when viewed from above, but it does not have to completely surround the entire periphery.

[0063] It goes without saying that in each of the above embodiments, the elements constituting the embodiments are not necessarily essential unless they are specifically stated as essential or are clearly considered essential in principle. Furthermore, in each of the above embodiments, when numerical values such as the number, values, amounts, and ranges of the components of the embodiments are mentioned, they are not limited to the specific numbers unless they are specifically stated as essential or are clearly limited to a specific number in principle. Furthermore, in each of the above embodiments, when the shapes, positional relationships, etc. of the components are mentioned, they are not limited to the shapes, positional relationships, etc., unless they are specifically stated or are clearly limited to a specific shape, positional relationship, etc. in principle. [Explanation of symbols]

[0064] 10. Semiconductor substrate 20 Low-Voltage Circuit Area 30 insulating film 40 Lower electrode 50 Upper electrode 60 Shield part 61a~61e Conductors 62a~62e via 63 Eaves 70 Floating Conductor

Claims

1. 1. A signal transmission device having a capacitor coupler, A semiconductor substrate (10); a low-voltage circuit area (20) having a control circuit that operates based on a low-voltage reference potential built into the semiconductor substrate; an insulating film (30) formed on the semiconductor substrate; a lower electrode (40) formed on the semiconductor substrate via the insulating film, to which a control signal from the control circuit is output; an upper electrode (40) disposed opposite the lower electrode via the insulating film, constituting a capacitor together with the lower electrode, and to which a high potential higher than the low voltage is applied; a shield section (60) formed at least within the insulating film, arranged between the lower electrode and the upper electrode and the low-voltage circuit region, and configured to have conductors (61a to 61e) to which a voltage applied by operation of the control circuit from the low voltage is applied; a signal transmission device having a capacitor coupler, wherein the shielding portion is positioned higher than the low-voltage circuit area with the stacking direction of the lower electrode and the upper electrode as the height direction, and has a canopy portion (63) extending on the opposite side from the lower electrode and the upper electrode.

2. the insulating film has a laminated structure of multiple layers, 2. A signal transmission device having a capacitor coupler as described in claim 1, wherein the shield portion is configured by connecting, in the height direction, a plurality of conductors (61a to 61e) formed alternately with each layer of the insulating film configured of the plurality of layers and vias (62a to 62e) arranged in via holes formed in each of the layers, and the eave portion is configured by only a portion of the plurality of conductors extending on the side opposite the lower electrode and the upper electrode.

3. 3. The signal transmission device having a capacitor coupler according to claim 2, wherein the eaves portion is formed by the highest conductor (61d, 61e) among the plurality of conductors.

4. 4. A signal transmission device having a capacitor coupler according to claim 1, wherein the upper electrode is thicker than the lower electrode.

5. 5. A signal transmission device having a capacitor coupler according to claim 1, further comprising a floating conductor (50) disposed within the insulating film at a height intermediate between the heights of the lower electrode and the upper electrode, the floating conductor being at a floating potential.

6. 6. A signal transmission device having a capacitor coupler according to claim 1, wherein the shield portion is set to a ground potential which is the potential of the semiconductor substrate.

7. 7. A signal transmission device having a capacitor coupler according to claim 1, wherein the eave portion has a width of 10 μm or more, which corresponds to the distance from an end closer to the lower electrode and the upper electrode to an end farther from the lower electrode and the upper electrode.

8. 7. A signal transmission device having a capacitor coupler according to claim 1, wherein the eave portion has a width of 20 to 40 μm, which corresponds to the distance from the end closer to the lower electrode and the upper electrode to the end farther from the end.

9. 9. A signal transmission device having a capacitor coupler according to claim 1, wherein the shortest distance (L) of the shield portion from the upper electrode is 13 [mu]m or more.

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