Pressure sensor construction and pressure sensor device

Abstract

A pressure sensor structure (1) includes: a sensor main body including a diaphragm plate (32) that functions as a sensing electrode, a base (31) opposite the diaphragm plate (32), and a side wall layer (20) that maintains a gap between the diaphragm plate (32) and the base (31); and a base substrate (10) of electric conductivity for supporting the sensor main body. The side wall layer (20) includes a protective electrode layer (22) and an upper protective electrode insulating layer (21) and a lower protective electrode insulating layer (23) that electrically insulate the protective electrode layer (22). An outer side surface of the diaphragm plate (32) and an outer side surface of the side wall layer (22) are coated with an electrically insulating film (40). A contact area (CT) where a portion of the protective electrode layer (22) provided in the electrically insulating film (40) is connected to the outside air. With such a structure, the influence of external interference can be suppressed, and high-precision pressure measurement can be performed.

Description

Technical Field

[0001] This invention relates to a pressure sensor structure for measuring pressures such as air pressure and water pressure, and a pressure sensor device using the pressure sensor structure. Background Technology

[0002] Pressure sensors can be manufactured using MEMS (Micro-Electro-Mechanical Systems) technology, which applies semiconductor manufacturing techniques. For example, ultra-miniature sensors of approximately 0.5 to 2 square millimeters can be achieved. A typical pressure sensor has a capacitor structure with two electrodes, and can measure pressure by detecting changes in electrostatic capacitance caused by changes in ambient pressure.

[0003] Figure 5 This is a cross-sectional view illustrating an example of a conventional pressure sensor structure. Such a pressure sensor structure, disclosed for example in Patent Document 1, comprises a diaphragm plate 32 functioning as a sensing electrode, a base electrode 31 opposite it, and a sidewall layer 20. The sidewall layer 20 includes a protective electrode layer 22 and electrically insulating layers 21 and 23 disposed above and below it. The substrate 10 is formed of a conductive material and is electrically connected to the base electrode 31. The protective electrode layer 22 and the base electrode 31 are formed in the same layer, sandwiched between the upper diaphragm plate 32 and the lower substrate 10, forming a three-layer electrode structure. This eliminates parasitic electrostatic capacitance independent of pressure changes.

[0004] The upper portion of the pressure sensor structure, namely the outer surface of the diaphragm plate 32 and the sidewall layer 20, is covered by an electrically insulating film 40, which functions as a passivation film, over its entire surface. The electrically insulating film 40 is, for example, made of SiN. x Electrically insulating materials such as SiO2 are used to prevent short circuits between electrodes and protect the structure of the pressure sensor.

[0005] Figure 6 It means that it can be connected to Figure 5 The circuit diagram shown is an example of a capacitance conversion circuit for a pressure sensor configuration. This capacitance conversion circuit includes an operational amplifier OP, a base terminal TB for the base, a sensing terminal TS for the sensing electrode (diaphragm plate), a protection terminal TG for the protection electrode, a voltage source CV, and a reference impedance RA. By using such a capacitance conversion circuit, parasitic electrostatic capacitance is eliminated, suppressing the effects of external interference and obtaining a voltage output representing the electrostatic capacitance between the diaphragm plate and the base.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: International Publication No. 2015 / 107453 Summary of the Invention

[0009] The problem the invention aims to solve

[0010] Figure 5 The pressure sensor shown is constructed by forming multiple chips from a single semiconductor wafer using MEMS technology and then cutting them into individual chips. The resulting chips, along with an integrated circuit for signal processing, are housed together in a synthetic resin housing 50 to complete the pressure sensor device.

[0011] In this configuration, the lower portion of the pressure sensor structure, namely the back and sides of the substrate 10, is in close contact with the housing 50, but the upper portion of the pressure sensor structure is exposed to external air. Therefore, there is a possibility that liquids such as water (LQ) may adhere to the electrically insulating membrane 40 due to condensation, seepage, etc. Such liquids (LQ) typically contain conductive components such as ions, and thus may function as conductors or electrodes. Consequently, the pressure output value changes due to variations in the parasitic capacitance between the diaphragm plate 32 and the substrate 10. Furthermore, the pressure output value changes due to the influence of electromagnetic noise from the outside on the diaphragm plate 32 and the base 31.

[0012] The purpose of this invention is to provide a pressure sensor structure capable of suppressing the influence of external interference and enabling high-precision pressure measurement, and a pressure sensor device using the pressure sensor structure.

[0013] Solution for solving the problem

[0014] One aspect of the present invention is a pressure sensor structure that detects changes in the electrostatic capacitance between electrodes, wherein...

[0015] The pressure sensor is constructed as follows:

[0016] The sensor body includes a diaphragm plate that functions as a sensing electrode, a base electrode opposite the diaphragm plate, and a sidewall layer that maintains the gap between the diaphragm plate and the base electrode; and

[0017] A conductive substrate is used to support the sensor body.

[0018] The sidewall layer includes a protective electrode layer and an upper protective electrode insulating layer and a lower protective electrode insulating layer that electrically insulate the protective electrode layer.

[0019] The outer surface of the diaphragm plate and the outer surface of the sidewall layer are covered with an electrically insulating film.

[0020] The contact area of ​​the electrically insulating film where the protective electrode layer is located is in contact with the external air.

[0021] Another aspect of the pressure sensor device of the present invention includes:

[0022] The pressure sensor described above;

[0023] Housing, which houses the pressure sensor configuration; and

[0024] A capacitance conversion circuit processes the signal from the pressure sensor configuration and eliminates parasitic electrostatic capacitance around the diaphragm plate.

[0025] The effects of the invention

[0026] According to the present invention, the influence of external interference can be suppressed, and high-precision pressure measurement can be performed. Attached Figure Description

[0027] Figure 1 This is a cross-sectional view showing an example of the pressure sensor structure according to Embodiment 1 of the present invention.

[0028] Figure 2 It means that it can be connected to Figure 1 The circuit diagram shown is an example of a capacitive switching circuit constructed from a pressure sensor.

[0029] Figure 3 This is a cross-sectional view showing an example of the pressure sensor structure according to Embodiment 2 of the present invention.

[0030] Figure 4 It means Figure 3 The diagram shows a cross-sectional view of the pressure sensor structure housed within the casing.

[0031] Figure 5 (A) is a cross-sectional view showing an example of the pressure sensor structure 1 according to Embodiment 4 of the present invention. Figure 5 (B) is Figure 5 The top view of the pressure sensor configuration 1 shown in (A) indicates that the electrical insulating film 40 has been removed for ease of understanding.

[0032] Figure 6 It means Figure 5 The diagram shows a cross-sectional view of the pressure sensor structure housed within the casing.

[0033] Figure 7 This is a cross-sectional view showing an example of the construction of a conventional pressure sensor.

[0034] Figure 8 It means that it can be connected to Figure 7 The circuit diagram shown is an example of a capacitive switching circuit constructed from a pressure sensor. Detailed Implementation

[0035] One embodiment of the present invention is a pressure sensor structure that detects changes in electrostatic capacitance between electrodes, wherein,

[0036] The pressure sensor is constructed as follows:

[0037] The sensor body includes a diaphragm plate that functions as a sensing electrode, a base electrode opposite the diaphragm plate, and a sidewall layer that maintains the gap between the diaphragm plate and the base electrode; and

[0038] A conductive substrate is used to support the sensor body.

[0039] The sidewall layer includes a protective electrode layer and an upper protective electrode insulating layer and a lower protective electrode insulating layer that electrically insulate the protective electrode layer.

[0040] The outer surface of the diaphragm plate and the outer surface of the sidewall layer are covered with an electrically insulating film.

[0041] The contact area of ​​the electrically insulating film where the protective electrode layer is located is in contact with the external air.

[0042] According to this structure, even when liquids such as water adhere to the electrical insulating film due to condensation or seepage, the protective electrode layer and the adhered liquid are maintained at the same potential through the contact area of ​​the electrical insulating film. Therefore, it is possible to prevent changes in pressure output value caused by liquid adhesion and to suppress the influence of external interference.

[0043] Alternatively, the contact area may be configured such that a portion of the protective electrode layer is connected to the external air via an opening formed in the diaphragm plate and the upper protective electrode insulating layer.

[0044] Based on this structure, by configuring a contact area CT in a location where liquid is prone to adhere and stagnate, the influence of external interference can be suppressed to achieve high-precision pressure measurement.

[0045] Alternatively, a conductive film may be provided on the electrically insulating film and electrically connected to the protective electrode layer via the contact area.

[0046] According to this structure, even when liquids such as water adhere to the electrically insulating film due to condensation or seepage, the protective electrode layer and the adhered liquid are maintained at the same potential through the contact area between the conductive film and the electrically insulating film. Therefore, it is possible to prevent changes in pressure output value caused by liquid adhesion and to suppress the influence of external interference.

[0047] Alternatively, the conductive film may be formed of Pt, Au, Ag, Al, Cu, Ir, Rh, Pd, Ti, Ni, Cr, Zr, Nb or Si, or an alloy containing at least one of these elements.

[0048] Based on this structure, the corrosion resistance of the conductive film is increased. Therefore, even when the liquid adhering to the electrically insulating film is a corrosive liquid such as chlorine water or seawater, the degradation of the conductive film can be suppressed.

[0049] One aspect of the pressure sensor device of the present invention includes:

[0050] The pressure sensor described above;

[0051] Housing, which houses the pressure sensor configuration; and

[0052] A capacitance conversion circuit processes the signal from the pressure sensor configuration and eliminates parasitic electrostatic capacitance around the diaphragm plate.

[0053] Based on this structure, a pressure sensor device can be realized that can suppress the effects of external interference such as condensation, water seepage, and electromagnetic noise.

[0054] (Implementation Method 1)

[0055] Figure 1 This is a cross-sectional view showing an example of a pressure sensor structure 1 according to Embodiment 1 of the present invention. The pressure sensor structure 1 includes a sensor body and a substrate 10, etc. The sensor body includes a diaphragm plate 32, a base electrode 31 and a sidewall layer 20, and the substrate 10 supports the sensor body.

[0056] The diaphragm plate 32 is formed of conductive materials such as polycrystalline Si, amorphous Si, or monocrystalline Si, and functions as a sensing electrode that can deform according to the surrounding pressure difference. The diaphragm plate 32 is exemplified as a single-layer structure, but it may also contain two or more layers.

[0057] The base 31 is formed of a conductive material such as polycrystalline Si, amorphous Si, or monocrystalline Si, and is disposed opposite to the separator 32. The sidewall layer 20 is provided to maintain the gap G between the separator 32 and the base 31. The gap G is a sealed space relative to the outside, for example, sealed with an inactive gas and maintained at a constant pressure.

[0058] The diaphragm plate 32 and the base 31 constitute a parallel-plate capacitor. The electrostatic capacitance C between the electrodes is expressed by C = ε × S / d, using the dielectric constant ε of the gap G, the electrode area S, and the distance d between the electrodes. When the diaphragm plate 32 elastically deforms according to the pressure difference between the external environment and the gap G, the distance d between the electrodes changes, and the electrostatic capacitance C changes accordingly.

[0059] The sidewall layer 20 is frame-shaped, surrounding the gap G, and consists of at least three layers, including a protective electrode layer 22, an electrically insulating layer 21 disposed below the protective electrode layer 22 and the base 31, and an electrically insulating layer 23 disposed above the protective electrode layer 22. Here, the sidewall layer 20 is shown as a three-layer structure, but it may also contain four or more layers. The protective electrode layer 22 is shown as a single-layer structure, but it may also contain two or more layers. The electrically insulating layers 21 and 23 are shown as single-layer structures, but they may also contain two or more layers.

[0060] The substrate 10 is formed of conductive materials such as polycrystalline Si, amorphous Si, or monocrystalline Si. The substrate 10 can be composed of one or more layers; for example, an electrically insulating layer can be provided on the lower surface of the substrate 10.

[0061] The planar shape of the diaphragm plate 32, the base 31, and the sidewall layer 20 is typically rectangular, but it can also be square, circular, elliptical, polygonal, etc.

[0062] The outer surfaces of the diaphragm plate 32 and the sidewall layer 20 are covered by an electrically insulating film 40, which functions as a passivation film. The electrically insulating film 40 is, for example, made of SiN. x Electrically insulating materials such as SiO2 are used to prevent short circuits between electrodes and protect the structure of the pressure sensor.

[0063] In this embodiment, the electrically insulating film 40 does not cover the entire upper portion of the pressure sensor structure 1. A contact area CT, where a protective electrode layer 22 is provided on the electrically insulating film 40, is partially exposed to the outside and connected to the external air. This contact area CT can be continuously provided along the outer periphery of the protective electrode layer 22, or, for example, it can be provided partially or intermittently, like a dotted line, dashed line, or single-dot-dashed line.

[0064] Next, the function of such a contact area CT will be explained. There is a possibility that liquids such as water may adhere to the electrically insulating membrane 40 due to condensation, seepage, etc. Such liquids typically contain conductive components such as ions, therefore, the pressure output value changes due to variations in the parasitic capacitance between the diaphragm plate 32 and the substrate 10. In this embodiment, by having a contact area CT, even when liquid adheres to the electrically insulating membrane 40, the protective electrode layer 22 and the adhered liquid are maintained at the same potential via the contact area CT. Therefore, changes in the pressure output value due to liquid adhesion can be prevented, and the influence of external interference can be suppressed.

[0065] Figure 2 It means that it can be connected to Figure 1The circuit diagram shown is an example of a capacitance conversion circuit for the pressure sensor configuration 1. This capacitance conversion circuit includes an operational amplifier OP, a base terminal TB for the base electrode, a sensing terminal TS for the sensing electrode (diaphragm plate), a protection terminal TG for the protection electrode, a voltage source CV, and a reference impedance RA. If liquid LQ adheres to the electrically insulating membrane 40, it affects the electrostatic capacitance between the sensing terminal TS and the base terminal TB. However, the protection electrode layer 22 and the adhered liquid are maintained at the same potential via the contact area CT, thus preventing changes in the pressure output value due to the adhesion of liquid LQ.

[0066] exist Figure 2 In this configuration, the base terminal TB is connected to the imaginary ground point VG of the inverting input of the operational amplifier OP, and the protection terminal TG is at ground potential. Therefore, the voltage and current between the protection electrode and the base can be ignored, and the capacitance value measured between the base and the diaphragm plate is substantially unaffected. The sensing terminal TS is connected to the voltage source CV in a manner that ignores the current between the protection electrode and the diaphragm plate and substantially does not affect the capacitance value measured between the diaphragm plate and the base. The electrostatic capacitance between the protection electrode and the base is connected between ground and the imaginary ground point VG, and does not substantially affect the capacitance value measured between the diaphragm plate and the base.

[0067] The capacitance between the base terminal TB and the sensing terminal TS is set as CS, and the capacitance between the base terminal TB and the protection terminal TG is set as CL. Furthermore, the voltage source CV is assumed to be an AC voltage source with an effective voltage Ui, the feedback circuit element RA is assumed to be a capacitor with a capacitance equal to CF, and the open-loop gain of the amplifier OP is assumed to be A. The amplifier's output voltage Uo is expressed as follows.

[0068]

Number 1

[0069]

[0070] Thus, the effect of CL is correspondingly reduced along with the amplifier's open-loop gain A. The electrostatic capacitance between the sensing terminal TS and the protection terminal TG is also connected in parallel with a voltage source Ui, which acts as an ideal voltage source and can supply current to the electrostatic capacitance without changing the voltage, thus having no effect on the output voltage.

[0071] (Implementation Method 2)

[0072] Figure 3 This is a cross-sectional view showing an example of a pressure sensor structure 1 according to Embodiment 2 of the present invention. The pressure sensor structure 1 includes a sensor body and a substrate 10, etc. The sensor body includes a diaphragm plate 32, a base electrode 31, and a sidewall layer 20, and the substrate 10 supports the sensor body. The materials and functions of these components are similar to those of other components. Figure 1 The structures shown are identical, so repeated explanations are omitted.

[0073] In this embodiment, a conductive film 24 is provided on the electrically insulating film 40, which is electrically connected to the protective electrode layer 22 via the contact area CT. The conductive film 24 is provided in such a way that it is in physical contact with the contact area CT and covers the outer wall of the sidewall layer 20. As a result, the probability of conductivity between the liquid LQ and the protective electrode layer 22 is increased. Such a conductive film 24 may also be provided continuously along the outer periphery of the protective electrode layer 22, or, for example, it may be provided partially or intermittently, or it may be provided in a mesh pattern.

[0074] Figure 4 It means Figure 3 The diagram shows a cross-sectional view of the pressure sensor structure 1 housed within the housing 50. The lower portion of the pressure sensor structure 1, i.e., the back and sides of the substrate 10, is in close contact with the housing 50, but the upper portion is exposed to external air. Therefore, there is a possibility that liquids such as water (LQ) may adhere to the electrically insulating membrane 40 due to condensation, seepage, etc. The internal space of the housing 50 is recessed like a bowl, thus liquids (LQ) tend to remain near the outer wall of the sidewall layer 20. The liquids (LQ) are in physical contact with the conductive membrane 24, and the protective electrode layer 22 and the adhered liquids (LQ) are maintained at the same potential through the contact area CT between the conductive membrane 24 and the electrically insulating membrane 40. Therefore, changes in the pressure output value due to liquid adhesion can be prevented, and the influence of external interference can be suppressed.

[0075] The conductive film 24 can also be formed from Pt, Au, Ag, Al, Cu, Ir, Rh, Pd, Ti, Ni, Cr, Zr, Nb, or Si, or alloys containing at least one of these elements, such as stainless steel, aluminum alloys, titanium alloys, nickel alloys, etc. This increases the corrosion resistance of the conductive film 24. Therefore, even when the liquid adhering to the electrically insulating film 40 is a corrosive liquid such as chlorine water or seawater, the deterioration of the conductive film 24 can be suppressed. Examples of methods for forming the conductive film 24 include vapor deposition, sputtering, plating, coating, etc.

[0076] (Implementation Method 3)

[0077] Figure 1 , Figure 3 The pressure sensor structure shown is 1 and Figure 2 The capacitor conversion circuit shown is housed together in Figure 4 The housing 50 shown. Thus, a pressure sensor device capable of suppressing the effects of external interference such as condensation, water seepage, and electromagnetic noise can be realized.

[0078] (Implementation Method 4)

[0079] Figure 5(A) is a cross-sectional view of an example of the pressure sensor structure 1 according to Embodiment 4 of the present invention. Figure 5 (B) is Figure 5 The pressure sensor structure 1 shown in (A) is a top view, indicating the state with the electrically insulating membrane 40 removed for ease of understanding. This pressure sensor structure 1 includes a sensor body and a substrate 10, etc. The sensor body includes a diaphragm plate 32, a base 31, and a sidewall layer 20, and the substrate 10 supports the sensor body. The materials, functions, and other characteristics of these components are described. Figure 1 The structures shown are identical, so repeated explanations are omitted.

[0080] In this embodiment, Figure 1 In the pressure sensor structure shown, the electrically insulating layer 23, diaphragm plate 32, and electrically insulating film 40 are partially removed, and an opening is provided on the upper surface of the protective electrode layer 22 that is partially exposed to external air. The exposed portion of the protective electrode layer 22 functions as a contact area CT connected to the external air. Figure 5 In (B), an example is shown where the contact area CT is a rectangular continuous line. Besides being rectangular, the contact area CT can also be other geometric shapes such as square, circle, or ellipse, and can be partially or intermittently arranged like dotted lines, dashed lines, or single-dot-dashed lines, in addition to being continuous. The electrical insulation layer 23a and the diaphragm plate 32a remain on the outer side of the contact area CT. Thus, by placing the contact area CT in areas where liquid easily adheres and accumulates, the influence of external interference can be suppressed, achieving high-precision pressure measurement.

[0081] Figure 6 It means Figure 5 The diagram shows a cross-sectional view of the pressure sensor structure 1 housed in the housing 50. Similar to Embodiment 2, the pressure sensor structure 1 has a conductive film 24 on the electrically insulating film 40, which is electrically connected to the protective electrode layer 22 via the contact area CT. This conductive film 24 can also be omitted, as in Embodiment 1.

[0082] The lower part of the pressure sensor structure 1, namely the back and sides of the substrate 10, is in close contact with the housing 50, but the upper part of the pressure sensor structure is exposed to the outside air. Therefore, there is a possibility that liquids such as water (LQ) may adhere to the electrically insulating membrane 40 due to condensation, seepage, etc. The internal space of the housing 50 is recessed like a bowl, so there is a tendency for liquid LQ to remain near the outer wall of the sidewall layer 20. The liquid LQ is in physical contact with the conductive membrane 24, and the protective electrode layer 22 and the adhered liquid LQ are maintained at the same potential through the contact area CT between the conductive membrane 24 and the electrically insulating membrane 40. Therefore, changes in the pressure output value due to liquid adhesion can be prevented, and the influence of external interference can be suppressed.

[0083] The conductive film 24 can also be formed from Pt, Au, Ag, Al, Cu, Ir, Rh, Pd, Ti, Ni, Cr, Zr, Nb, or Si, or alloys containing at least one of these elements, such as stainless steel, aluminum alloys, titanium alloys, nickel alloys, etc. This increases the corrosion resistance of the conductive film 24. Therefore, even when the liquid adhering to the electrically insulating film 40 is a corrosive liquid such as chlorine water or seawater, the deterioration of the conductive film 24 can be suppressed. Examples of methods for forming the conductive film 24 include vapor deposition, sputtering, plating, coating, etc.

[0084] (Implementation Method 5)

[0085] Figure 5 The pressure sensor structure shown is 1 and Figure 2 The capacitor conversion circuit shown is housed together in Figure 6 The housing 50 shown. Thus, a pressure sensor device capable of suppressing the effects of external interference such as condensation, water seepage, and electromagnetic noise can be realized.

[0086] The invention has been fully described with reference to the accompanying drawings and preferred embodiments, but various modifications and variations will be apparent to those skilled in the art. It should be understood that such modifications and variations are included therein as long as they do not depart from the scope of the invention as defined by the appended claims.

[0087] Industrial availability

[0088] This invention enables the construction of a pressure sensor that can suppress the influence of external interference and perform high-precision pressure measurement, and is therefore extremely useful in industry.

[0089] Explanation of reference numerals in the attached figures

[0090] 1. Pressure sensor structure; 10. Substrate; 20. Sidewall layer; 21, 23. Electrically insulating layer; 24. Conductive film; 22. Protective electrode layer; 31. Base; 32. Diaphragm plate; 40. Electrically insulating film; 50. Housing; CT. Contact area; G. Gap; LQ. Liquid.

Claims

1. A pressure sensor configuration that detects changes in electrostatic capacitance between electrodes, wherein, The pressure sensor is constructed as follows: The sensor body includes a diaphragm plate that functions as a sensing electrode, a base electrode opposite the diaphragm plate, and a sidewall layer that maintains the gap between the diaphragm plate and the base electrode; and A conductive substrate is used to support the sensor body. The sidewall layer includes a protective electrode layer and an upper protective electrode insulating layer and a lower protective electrode insulating layer that electrically insulate the protective electrode layer. The outer surface of the diaphragm plate and the outer surface of the sidewall layer are covered with an electrically insulating film. In the contact area where the protective electrode layer is located on the electrical insulating film, there is a local area that is connected to the external air. The contact area is configured as a portion of the protective electrode layer that is connected to the outside air via an opening formed in the diaphragm plate and the upper protective electrode insulating layer.

2. The pressure sensor structure according to claim 1, wherein, A conductive film is provided on the electrically insulating film and is electrically connected to the protective electrode layer via the contact area.

3. The pressure sensor structure according to claim 2, wherein, The conductive film is formed of Pt, Au, Ag, Al, Cu, Ir, Rh, Pd, Ti, Ni, Cr, Zr, Nb or Si, or an alloy containing at least one of these elements.

4. A pressure sensor device, wherein, The pressure sensor device includes: The pressure sensor construction according to any one of claims 1 to 3; Housing, which houses the pressure sensor configuration; and A capacitance conversion circuit processes the signal from the pressure sensor configuration and eliminates parasitic electrostatic capacitance around the diaphragm plate.

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