Semiconductor device and semiconductor module

Abstract

The purpose is to provide a semiconductor device that can determine the withstand voltage characteristics and reduce costs. The semiconductor device includes a semiconductor substrate, a first electrode, a second electrode and an insulating film. The semiconductor substrate includes a semiconductor element on the surface and a back electrode on the back surface for controlling the operation of the semiconductor element. The first electrode and the second electrode are arranged in an end region, which is formed at the periphery of the semiconductor substrate and is located outside the active region where the semiconductor element is formed. The insulating film is arranged between the first electrode and the second electrode. The second electrode is arranged on an insulating interlayer film arranged on the surface of the semiconductor substrate. The first electrode is in contact with the surface of the semiconductor substrate and is arranged on the end side of the semiconductor substrate compared to the second electrode. The first electrode is electrically connected to the back electrode.

Description

Technical Field

[0001] The present invention relates to a semiconductor device and a semiconductor module. Background Art

[0002] Power semiconductor devices that are applied with high voltages require high withstand voltage leakage characteristics. This withstand voltage leakage characteristic is sometimes reduced due to the influence of humidity (moisture). However, the adverse conditions caused by humidity cannot be identified before the main withstand voltage is reduced, and in most cases they are identified through system errors. In the worst case, the reduction in withstand voltage will cause damage to the power semiconductor device and its system.

[0003] Patent Document 1 proposes a semiconductor chip for detecting moisture absorbed by a low-k material or peeling of the low-k material caused by the moisture. The semiconductor chip includes a plurality of capacitor electrodes between a guard ring and a circuit element or outside the guard ring. The semiconductor chip can detect changes in electrostatic capacitance between the capacitor electrodes to identify the damaged portion of the guard ring caused by moisture or peeling.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2005-228854 Summary of the invention

[0005] When a capacitor is formed in the terminal region, two or more openings are required as the area for wiring the two electrodes forming the capacitor. In particular, when a wire is connected to these electrodes, the opening needs to have an area corresponding to the wire diameter. Therefore, the size of the semiconductor device increases, and the cost increases.

[0006] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a semiconductor device capable of determining withstand voltage characteristics and reducing costs.

[0007] The semiconductor device to which the present invention relates comprises a semiconductor substrate, a first electrode, a second electrode and an insulating film. The semiconductor substrate comprises a semiconductor element on the surface and a back electrode on the back surface for controlling the operation of the semiconductor element. The first electrode and the second electrode are arranged in an end region, which is formed at the periphery of the semiconductor substrate and is located outside the active region where the semiconductor element is formed. The insulating film is arranged between the first electrode and the second electrode. The second electrode is arranged on an insulating interlayer film arranged on the surface of the semiconductor substrate. The first electrode is in contact with the surface of the semiconductor substrate, and the first electrode is arranged on the end side of the semiconductor substrate compared with the second electrode, and the first electrode is electrically connected to the back electrode.

[0008] Effects of the Invention

[0009] According to the present invention, it is possible to provide a semiconductor device that can achieve determination of withstand voltage characteristics and cost reduction.

[0010] The objects, features, aspects, and advantages of the present invention will become more apparent from the following detailed description and accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a cross-sectional view showing the structure of the semiconductor device according to the first embodiment.

[0012] Figure 2 It is a plan view showing the structure of the semiconductor device according to the first embodiment.

[0013] Figure 3 FIG. 1 is a plan view showing an example of the structure of a packaged semiconductor device.

[0014] Figure 4 Yes means Figure 3 A cross-section of the structure and a diagram of the electrical circuit are shown.

[0015] Figure 5 This is a block diagram showing the structure of the semiconductor module according to the first embodiment.

[0016] Figure 6 This is a diagram showing an example of the relationship between the withstand voltage of a capacitor and a semiconductor device and humidity.

[0017] Figure 7 This is a flowchart showing a method for measuring the withstand voltage characteristics of the semiconductor device according to the first embodiment.

[0018] Figure 8 It is a cross-sectional view showing the structure of a semiconductor device according to a modification of the first embodiment.

[0019] Fig. 9 It is a plan view showing the structure of a semiconductor device according to a modification of the first embodiment.

[0020] Fig.10 It is a plan view showing the structure of a semiconductor device according to the second embodiment.

[0021] Fig.11 It is a plan view showing the structure of a semiconductor device according to a modification of the second embodiment. DETAILED DESCRIPTION

[0022] <Implementation Method 1>

[0023] Figure 1 and Figure 2 Each of them is a cross-sectional view and a plan view showing the structure of the semiconductor device 1 according to the first embodiment. Figure 1 Show Figure 2 The cross section at AA' is shown. Figure 3 FIG. 1 is a plan view showing an example of the structure of the packaged semiconductor device 1 .

[0024] The semiconductor device 1 includes a semiconductor substrate 2 , a semiconductor element (not shown), a front electrode 3 , a back electrode 4 , a first electrode 10 , a second electrode 20 , an insulating film 5 , a protective film 6 , a packaging material 11 , and electrode terminals 12 .

[0025] The semiconductor element is arranged on the surface of the semiconductor substrate 2 and is located below the surface electrode 3. The semiconductor element is formed of, for example, a semiconductor such as Si, or a so-called wide-bandgap semiconductor such as SiC, GaN, etc. The semiconductor element is, for example, an IGBT (Insulated Gate Bipolar Transistor), a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), a diode, etc. The semiconductor element is, for example, a semiconductor element for power (power semiconductor element). The semiconductor substrate 2 and the semiconductor element involved in the first embodiment are formed of a wide-bandgap semiconductor.

[0026] The surface electrode 3 is provided on the surface of the semiconductor substrate 2 corresponding to the active region where the semiconductor element is formed. The surface electrode 3 controls the operation of the semiconductor element. The operation is, for example, the on-off operation of IGBT, MOSFET, etc.

[0027] The back electrode 4 is provided on the back side of the semiconductor substrate 2. The back electrode 4 controls the operation of the semiconductor element. When the semiconductor element is an IGBT, the surface electrode 3 includes two electrode pads (not shown) connected to the gate electrode and the emitter electrode, respectively, and the back electrode 4 corresponds to the electrode pad connected to the collector electrode. When the semiconductor element is a MOSFET, the surface electrode 3 includes two electrode pads (not shown) connected to the gate electrode and the source electrode, respectively, and the back electrode 4 corresponds to the electrode pad connected to the drain electrode. When the semiconductor element is a diode, the surface electrode 3 is an electrode pad connected to the anode, and the back electrode 4 is an electrode pad connected to the cathode.

[0028] The first electrode 10 and the second electrode 20 are provided in the terminal region 8 outside the active region where the semiconductor element is formed. The terminal region 8 is formed outside the surface electrode 3, that is, the outer periphery of the semiconductor substrate 2. The second electrode 20 is provided on the insulating interlayer film 7 provided on the surface of the semiconductor substrate 2. The first electrode 10 is in contact with the surface of the semiconductor substrate 2, and is provided on the end side of the semiconductor substrate 2 compared with the second electrode 20. The first electrode 10 may also be provided on the surface of the semiconductor substrate 2 via a contact electrode (not shown) provided on the surface of the semiconductor substrate 2. It is preferred that the first electrode 10 is provided near the end (end face) of the semiconductor substrate 2. The first electrode 10 and the second electrode 20 are away from the surface electrode 3 and the semiconductor element to such an extent that they do not participate in the operation of the semiconductor element. That is, the first electrode 10 and the second electrode 20 are independent. The first electrode 10 is electrically connected to the back electrode 4 via a small resistor at the end face of the semiconductor substrate 2. In addition, the first electrode 10 and the second electrode 20 involved in the first embodiment are formed of the same material as the surface electrode 3. The first electrode 10 , the second electrode 20 , and the surface electrode 3 are formed of, for example, Al, AlSi, or the like.

[0029] like Figure 3 As shown, the first electrode 10 and the second electrode 20 are provided in a region of the outer periphery of the semiconductor substrate 2 in a direction in which the electrode terminal 12 protrudes outward. In other words, the first electrode 10 and the second electrode 20 are provided on the root end 12A side of the electrode terminal 12 in the outer periphery of the semiconductor substrate 2.

[0030] The insulating film 5 is provided between the first electrode 10 and the second electrode 20. The first electrode 10, the second electrode 20 and the insulating film 5 form a capacitor structure in the end region 8. The capacitance thereof changes according to the degree of moisture absorption of the insulating film 5.

[0031] The protective film 6 has insulating properties and covers the surface of the semiconductor substrate 2. The protective film 6 has two openings. A portion 20A of the second electrode 20 and the surface electrode 3 are respectively exposed from the two openings. On the other hand, the first electrode 10 is covered by the protective film 6, and the first electrode 10 is not exposed. The insulating film 5 and the protective film 6 involved in the first embodiment are formed of the same material. For example, the insulating film 5 and the protective film 6 are formed of polyimide.

[0032] Packaging material 11 pairs Figure 1 The structure shown in the figure, that is, the structure including the semiconductor substrate 2, the first electrode 10, the second electrode 20 and the insulating film 5, etc. is encapsulated. The semiconductor device 1 involved in the first embodiment is encapsulated by the encapsulation material 11, and the encapsulation is a molded encapsulation of resin encapsulation. However, the encapsulation is not limited to this structure, and it can also be a structure in which the semiconductor substrate 2 and the like contained in the housing are encapsulated.

[0033] The electrode terminal 12 is connected to any of the second electrode 20, the front electrode 3, and the back electrode 4 in the packaging material 11. Figure 3 In the figure, the detailed structure of the internal wiring 13 inside the packaging material 11 is omitted, but for example, Figure 3 One end of the electrode terminal 12 located in the center is connected to a portion 20A of the second electrode 20 via an internal wiring 13 such as a wire. Figure 3 One end of the electrode terminal 12 located at the bottom is connected to the back electrode 4 via the internal wiring 13. The other end of each electrode terminal 12 protrudes to the outside of the packaging material 11. The other end can be connected to an external circuit, for example, to a control unit 16 described later. Figure 4 Yes means Figure 3 The first electrode 10 is connected to the back electrode 4 via a small resistor at the end surface of the semiconductor substrate 2.

[0034] Figure 5 1 is a block diagram showing the structure of a semiconductor module 15 according to Embodiment 1. The semiconductor module 15 includes the semiconductor device 1 described above and a control unit 16 .

[0035] The control unit 16 stores in advance the relationship between the capacitance between the first electrode 10 and the second electrode 20 and the humidity, and the relationship between the withstand voltage of the semiconductor device 1 and the humidity, respectively, in a memory or the like. Figure 6 1 is a diagram showing an example of the relationship between the capacitance and the withstand voltage of the semiconductor device 1 and humidity. The control unit 16 determines the humidity at which the semiconductor device 1 loses the withstand voltage function based on the relationship between the withstand voltage of the semiconductor device 1 and humidity. Moreover, the control unit 16 sets the capacitance at the humidity at which the withstand voltage function is lost as a threshold value based on the relationship between the capacitance between the first electrode 10 and the second electrode 20 and humidity. The control unit 16 determines the withstand voltage function of the semiconductor device 1 based on the threshold value and the detection capacitance between the first electrode 10 and the second electrode 20 obtained by applying a voltage between the second electrode 20 and the back electrode 4. For example, the control unit 16 outputs an error before the detection capacitance exceeds the threshold value, that is, when the detection capacitance shows a value within a predetermined range relative to the threshold value.

[0036] The functions of the control unit 16 are realized by a processing circuit (not shown). The processing circuit includes, for example, a processor and a memory. The functions of the control unit 16 are realized by the processor executing a program stored in the memory.

[0037] Next, a method for measuring the withstand voltage characteristics of the semiconductor device 1 by the control unit 16 of the semiconductor module 15 will be described. Figure 7 This is a flowchart showing a method for measuring the withstand voltage characteristics of the semiconductor device 1 according to the first embodiment.

[0038] In step S1, the control unit 16 applies a voltage between the second electrode 20 and the back electrode 4. The voltage is applied, for example, through the electrode terminal 12 connected to the second electrode 20 and the electrode terminal 12 connected to the back electrode 4. Since the first electrode 10 is electrically connected to the back electrode 4 via a small resistor at the end surface of the semiconductor substrate 2, if the voltage drop caused by the small resistor is excluded, the first electrode 10 and the back electrode 4 are short-circuited. That is, the potentials of the two are regarded as the same potential (common potential). The control unit 16 regards the first electrode 10 and the back electrode 4 as being at the same potential and obtains the capacitance (detection capacitance) between the first electrode 10 and the second electrode 20. Alternatively, in the case where other resistances or capacitances are included between the first electrode 10 and the back electrode 4, these resistances and capacitances are also predetermined as design values ​​of the semiconductor device 1. The control unit 16 obtains the capacitance (detection capacitance) between the first electrode 10 and the second electrode 20 based on the result of applying the voltage between the second electrode 20 and the back electrode 4 and these design values.

[0039] The capacitance measurement is performed when the semiconductor device 1 is not in operation. In addition, the capacitance measurement can be performed when the semiconductor device 1 is not packaged, but since the direction and degree of water intrusion are important parameters related to the withstand voltage characteristics, it is preferred that the capacitance measurement be performed when the semiconductor device 1 is packaged.

[0040] In step S2, the control unit 16 determines the relationship between the capacitance between the first electrode 10 and the second electrode 20 and the withstand voltage of the semiconductor device 1 and the humidity ( Figure 6 ), the detection capacitance between the first electrode 10 and the second electrode 20, and the withstand voltage function of the semiconductor device 1 is determined. Here, the control unit 16 outputs an error before the detection capacitance exceeds the threshold value, that is, when the detection capacitance shows a value within a predetermined range relative to the threshold value. The error indicates that moisture has penetrated into the package and the withstand voltage function of the semiconductor device 1 cannot be ensured. Since the error is output before the detection capacitance exceeds the threshold value, the damage of the semiconductor device 1 can be prevented.

[0041] In summary, the semiconductor device 1 according to the first embodiment includes a semiconductor substrate 2, a first electrode 10, a second electrode 20, and an insulating film 5. The semiconductor substrate 2 includes a semiconductor element on the surface and includes a back electrode 4 for controlling the operation of the semiconductor element on the back surface. The first electrode 10 and the second electrode 20 are provided in an end region 8 formed on the outer periphery of the semiconductor substrate 2. The end region 8 is located outside the active region where the semiconductor element is formed. The insulating film 5 is provided between the first electrode 10 and the second electrode 20. The second electrode 20 is provided on an insulating interlayer film 7 provided on the surface of the semiconductor substrate 2. The first electrode 10 is in contact with the surface of the semiconductor substrate 2 and is provided on the end side of the semiconductor substrate 2 compared with the second electrode 20. The first electrode 10 is electrically connected to the back electrode 4.

[0042] The semiconductor device 1 according to the first embodiment includes an insulating protective film 6 covering the surface of the semiconductor substrate 2. A portion 20A of the second electrode 20 is exposed from an opening of the protective film 6. The first electrode 10 is covered with the protective film 6.

[0043] With such a structure, by applying a voltage between the second electrode 20 and the back electrode 4, the capacitance between the first electrode 10 and the second electrode 20 is detected. The capacitance is appropriately monitored, and the moisture intrusion condition is determined based on the change in capacitance. When it is determined that the moisture intrusion is excessive, a preventive measure is taken, such as stopping the semiconductor device 1 or the system using the semiconductor device 1. Since the damage of the semiconductor device 1 is prevented in advance, its reliability is improved. In addition, the voltage for capacitance measurement is applied between the second electrode 20 and the back electrode 4. Therefore, the semiconductor device 1 does not require an opening for connecting the internal wiring to the first electrode 10. In addition, the wiring connecting the first electrode 10 and the back electrode 4 is also not required. As a result, the size of the semiconductor device 1 is miniaturized and the cost is reduced. In this way, the semiconductor device 1 involved in embodiment 1 achieves the determination of the withstand voltage characteristics and the reduction of costs.

[0044] In addition, the first electrode 10 , the second electrode 20 , and the surface electrode 3 of the semiconductor device 1 according to Embodiment 1 are formed of the same material. In addition, the insulating film 5 and the protective film 6 are formed of the same material.

[0045] With such a structure, the first electrode 10, the second electrode 20, and the surface electrode 3 are manufactured by the same process. Similarly, the insulating film 5 and the protective film 6 are manufactured by the same process. Therefore, the manufacturing cost is reduced.

[0046] The semiconductor device 1 according to the first embodiment includes a packaging material 11 and an electrode terminal 12. The packaging material 11 packages the semiconductor substrate 2, the first electrode 10, the second electrode 20, and the insulating film 5. One end of the electrode terminal 12 is connected to any one of the second electrode 20, the back electrode 4, and the surface electrode 3 inside the packaging material 11, and the other end protrudes to the outside of the packaging material 11. The first electrode 10 and the second electrode 20 are provided on the side of the root end portion 12A of the electrode terminal 12 protruding from the packaging material 11 in the outer periphery of the semiconductor substrate 2.

[0047] Moisture easily enters the inside of the packaging material 11 from the root end 12A of the electrode terminal 12. By providing the first electrode 10 and the second electrode 20 forming the capacitor in the direction of the root end 12A of the electrode terminal 12, the detection sensitivity of moisture is improved.

[0048] In addition, the semiconductor substrate 2 according to the first embodiment is formed of a wide-gap semiconductor.

[0049] Since the first electrode 10 and the second electrode 20 are metal, when the first electrode 10 and the second electrode 20 are arranged in the terminal region 8, a detailed electric field strength design is required. Depending on the structure of the first electrode 10 and the second electrode 20, the function of the semiconductor device 1 may be reduced, thereby causing a reduction in quality. If manufacturing fluctuations, etc. are taken into consideration, it is necessary to design the terminal structure with a margin in advance. In the case where the semiconductor substrate 2 involved in embodiment 1 is formed of a wide bandgap semiconductor (SiC, GaN, etc.), even if the electric field strength inside the semiconductor substrate 2 is increased by the second electrode 20, the effect is small. Therefore, the design becomes easy and low cost is achieved.

[0050] In addition, the semiconductor module 15 according to the first embodiment includes the semiconductor device 1 and the control unit 16. The control unit 16 determines the withstand voltage function of the semiconductor device 1 based on the capacitance between the first electrode 10 and the second electrode 20 and the relationship between the withstand voltage of the semiconductor device 1 and humidity, and the detection capacitance between the first electrode 10 and the second electrode 20 obtained by applying a voltage between the second electrode 20 and the back electrode 4.

[0051] Such a semiconductor module 15 outputs an error based on a predetermined determination standard for the detection capacitance. Since an error is output before the withstand voltage function of the semiconductor device 1 cannot be ensured, the reliability of the semiconductor device 1 is improved.

[0052] (Variation of Implementation Example 1)

[0053] Figure 8 and Fig. 9 Each of them is a cross-sectional view and a plan view showing the structure of a semiconductor device 1A according to a modification of the first embodiment. Figure 8 Show Fig. 9 The cross section at BB' is shown.

[0054] The insulating film 5A according to the modification of the first embodiment is formed of a material different from that of the protective film 6. The insulating film 5A is made of, for example, CaF 2 、Al 2 O 3 and Si 3 N 4 The protective film 6 is formed of polyimide.

[0055] The capacitance in normal state is adjusted by selecting the material of the insulating film 5A. In other words, the detection sensitivity of the capacitance change caused by humidity is adjusted by selecting the material. As a result, erroneous operation such as excessive detection is prevented.

[0056] <Implementation Method 2>

[0057] A semiconductor device and a semiconductor module according to Embodiment 2 will be described. Embodiment 2 is a subordinate concept of Embodiment 1, and the semiconductor device according to Embodiment 2 includes the structures of the semiconductor device 1 according to Embodiment 1. The description of the same structures and operations as those of Embodiment 1 will be omitted.

[0058] Fig.10 1 is a plan view showing the structure of a semiconductor device 1B according to Embodiment 2. The first electrode 10 and the second electrode 20 are provided in a ring shape along the outer periphery of the semiconductor substrate 2. In other words, the first electrode 10 and the second electrode 20 are arranged on the entire outer periphery.

[0059] With such a structure, the cross-sectional area that determines the capacitance between the first electrode 10 and the second electrode 20 becomes larger. The cross-sectional area is obtained by the product of the film thickness of the first electrode 10 or the second electrode 20 and the length of the first electrode 10 or the second electrode 20. In addition, when the dielectric constant of the insulating film 5 is set to ε, the cross-sectional area is set to S, and the distance between the first electrode 10 and the second electrode 20 is set to d, the capacitance C is represented by C=ε×S / d. By configuring the first electrode 10 and the second electrode 20 on the entire periphery of the semiconductor substrate 2, the cross-sectional area S increases and the capacitance C becomes larger. As a result, the detection sensitivity becomes higher.

[0060] In addition, according to the cross-sectional area S and the distance d, the semiconductor device 1B can be designed to have a detection sensitivity corresponding to the application. Since the detection sensitivity can be adjusted as needed, it is possible to prevent malfunctions such as excessive detection. For example, it is preferred that the film thickness of the first electrode 10 and the second electrode 20 is a value that satisfies ±50% relative to the film thickness of the surface electrode 3. It is preferred that the interval between the first electrode 10 and the second electrode 20 is less than or equal to one third of the width of the terminal region 8.

[0061] (Variation of Implementation Example 2)

[0062] Fig.11 1 is a top view showing the structure of a semiconductor device 1C according to a modified example of Embodiment 2. A portion 20A of the second electrode 20 connected to the electrode terminal 12 does not need to be provided on the root end portion 12A side of the electrode terminal 12. In addition, the size of the region is arbitrary. Even with such a structure, the same effect as described above is achieved.

[0063] In addition, the present invention can freely combine the various embodiments, and can appropriately modify or omit the various embodiments.

[0064] Although the present invention has been described in detail, the above description is in all aspects illustrative and the present invention is not limited thereto. It should be understood that numerous modifications not shown and exemplified are conceivable without departing from the scope of the present invention.

[0065] Description of the label

[0066] 1 semiconductor device, 1A semiconductor device, 1B semiconductor device, 1C semiconductor device, 2 semiconductor substrate, 3 surface electrode, 4 back electrode, 5 insulating film, 5A insulating film, 6 protective film, 7 interlayer film, 8 terminal region, 10 first electrode, 11 packaging material, 12 electrode terminal, 12A root end portion, 13 internal wiring, 15 semiconductor module, 16 control unit, 20 second electrode, 20A part of the second electrode.

Claims

1. A semiconductor device comprising: A semiconductor substrate including a semiconductor element on the surface and a back electrode on the back surface for controlling the operation of the semiconductor element; A first electrode and a second electrode, which are provided in an end region formed at the periphery of the semiconductor substrate and located outside an active region where the semiconductor element is formed; an insulating film disposed between the first electrode and the second electrode; as well as an insulating protective film covering the surface of the semiconductor substrate, The second electrode is provided on an insulating interlayer film provided on the surface of the semiconductor substrate. The first electrode is in contact with the surface of the semiconductor substrate, and is provided on an end side of the semiconductor substrate compared to the second electrode, and is electrically connected to the back electrode. The first electrode is covered by the protective film, A portion of the second electrode is exposed from the opening of the protective film.

2. The semiconductor device according to claim 1, wherein The insulating film includes any of polyimide, CaF2, Al2O3 and Si3N4.

3. The semiconductor device according to claim 1 or 2, wherein: The first electrode, the second electrode, and a surface electrode are formed of the same material, the surface electrode is provided on the surface of the semiconductor substrate and controls the operation of the semiconductor element. The insulating film and the protective film are formed of the same material.

4. The semiconductor device according to claim 1 or 2, wherein: The semiconductor device further comprises: A packaging material that packages the semiconductor substrate, the first electrode, the second electrode, and the insulating film; as well as an electrode terminal, one end of which is connected to any one of the second electrode, the back electrode, and the surface electrode inside the packaging material, and the other end of which protrudes to the outside of the packaging material, and the surface electrode is provided on the surface of the semiconductor substrate and controls the operation of the semiconductor element, The first electrode and the second electrode are provided on the side of a root end portion of the electrode terminal protruding from the sealing material in the outer peripheral portion of the semiconductor substrate.

5. The semiconductor device according to claim 1 or 2, wherein: The first electrode and the second electrode are provided in a ring shape along the outer periphery of the semiconductor substrate.

6. The semiconductor device according to claim 1 or 2, wherein: The semiconductor substrate is formed of a wide bandgap semiconductor.

7. A semiconductor module comprising: The semiconductor device according to any one of claims 1 to 6; and A control unit determines the withstand voltage function of the semiconductor device based on the capacitance between the first electrode and the second electrode and the relationship between the withstand voltage of the semiconductor device and humidity, and the detected capacitance between the first electrode and the second electrode obtained by applying a voltage between the second electrode and the back electrode.

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