Pressure sensor structure and pressure sensor device

Abstract

This pressure sensor structure 1 comprises: a sensor main body including a diaphragm plate 32 which functions as a sensing electrode, a base electrode 31 facing the diaphragm plate 32, and a sidewall layer 20 that maintains a gap between the diaphragm plate 32 and the base electrode 31; and a conductive base substrate 10 for supporting the sensor main body. The sidewall layer 20 includes a guard electrode layer 22, and upper and lower guard electrode insulating layers 21, 23 which electrically insulate the guard electrode layer 22. An outer surface of the diaphragm plate 32 and an outer surface of the sidewall layer 20 are covered with an electrically insulating film 40. The electrically insulating film 40 is provided with a contact region CT in which a part of the guard electrode layer 22 is connected to external air. This configuration makes it possible to suppress the influence of a disturbance and perform a pressure measurement with high accuracy.

Description

[Technical Field]

[0001] The present invention relates to a pressure sensor structure for measuring pressure such as atmospheric pressure or water pressure, and a pressure sensor device using the same. [Background technology]

[0002] Pressure sensors can be manufactured using MEMS (microelectromechanical systems) technology, which applies semiconductor manufacturing technology, making it possible to create ultra-small sensors measuring, for example, approximately 0.5 to 2 mm square. A typical pressure sensor has a capacitor structure with two electrodes, and can measure pressure by detecting changes in capacitance caused by changes in ambient pressure.

[0003] figure 7 is a cross-sectional view showing an example of a conventional pressure sensor structure. This pressure sensor structure is disclosed, for example, in Patent Document 1, and is composed of a diaphragm plate 32 that functions as a sense electrode, a base electrode 31 facing it, and a sidewall layer 20. The sidewall layer 20 includes a guard electrode layer 22 and electrical insulating layers 21 and 23 arranged above and below it. The base substrate 10 is formed of a conductive material and is electrically connected to the base electrode 31. The guard electrode layer 22 is formed in the same layer as the base electrode 31 and is sandwiched between the upper diaphragm plate 32 and the lower base substrate 10 to form a three-layer electrode structure. This makes it possible to cancel stray capacitance unrelated to pressure changes.

[0004] The upper portion of the pressure sensor structure, i.e., the outer surfaces of the diaphragm plate 32 and the sidewall layer 20, are entirely covered with an electrically insulating film 40 which functions as a passivation film. x It is made of an electrically insulating material such as SiO2 to prevent short circuits between electrodes and protect the pressure sensor structure.

[0005] figure 8 The figure 71 is a circuit diagram showing an example of a capacitance conversion circuit that can be connected to the pressure sensor structure shown in FIG. This capacitance conversion circuit includes an operational amplifier OP, a base terminal TB for the base electrode, a sense terminal TS for the sense electrode (diaphragm plate), a guard terminal TG for the guard electrode, a voltage source CV, and a reference impedance RA. By using such a capacitance conversion circuit, a voltage output indicative of the capacitance between the diaphragm plate and the base electrode can be obtained while canceling stray capacitance and suppressing the effects of external disturbances. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2015 / 107453 Summary of the Invention [Problem to be solved by the invention]

[0007] The pressure sensor structure shown in Fig. 5 is obtained by forming a large number of chips on a single semiconductor wafer using MEMS technology and then cutting them into individual chips. The obtained chips are housed in a synthetic resin housing 50 together with an integrated circuit that performs signal processing, completing the pressure sensor device.

[0008] In this case, the lower portion of the pressure sensor structure, i.e., the back and side surfaces of the base substrate 10, are in close contact with the housing 50, but the upper portion of the pressure sensor structure is exposed to the outside air. Therefore, liquid LQ, such as water, may adhere to the electrical insulating film 40 due to condensation or water intrusion. Because such liquid LQ generally contains conductive components such as ions, it can function as a conductor or an electrode. This can change the stray capacitance between the diaphragm plate 32 and the base substrate 10, causing a shift in the pressure output value. Furthermore, the diaphragm plate 32 and the base electrode 31 may be affected by external electromagnetic noise, causing a shift in the pressure output value.

[0009] An object of the present invention is to provide a pressure sensor structure that can suppress the influence of disturbances and perform high-precision pressure measurement, and a pressure sensor device using the same. [Means for solving the problem]

[0010] One aspect of the present invention is a pressure sensor structure that detects a change in capacitance between electrodes, comprising: a sensor body including a diaphragm plate that functions as a sense electrode, a base electrode facing the diaphragm plate, and a sidewall layer that maintains a gap between the diaphragm plate and the base electrode; a conductive base substrate for supporting the sensor body; the sidewall layer includes a guard electrode layer and upper and lower guard electrode insulating layers that electrically insulate the guard electrode layer; an outer surface of the diaphragm plate and an outer surface of the sidewall layer are coated with an electrically insulating film; The electrical insulating film is provided with a contact region where a part of the guard electrode layer is connected to the outside air.

[0011] A pressure sensor device according to another aspect of the present invention comprises the above pressure sensor structure and a housing that contains the pressure sensor structure; a capacitance conversion circuit that processes signals from the pressure sensor structure and cancels stray capacitance around the diaphragm plate. [Effects of the Invention]

[0012] According to the present invention, the influence of disturbances can be suppressed and high-precision pressure measurement can be performed. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a cross-sectional view showing an example of a pressure sensor structure according to a first embodiment of the present invention. [Figure 2] 2 is a circuit diagram showing an example of a capacitance conversion circuit that can be connected to the pressure sensor structure shown in FIG. 1. [Figure 3] FIG. 6 is a cross-sectional view showing an example of a pressure sensor structure according to a second embodiment of the present invention. [Figure 4] 4 is a cross-sectional view showing a state in which the pressure sensor structure shown in FIG. 3 is housed in a housing. [Figure 5] Fig. 5(A) is a cross-sectional view showing an example of a pressure sensor structure 1 according to embodiment 4 of the present invention. Fig. 5(B) is a plan view of the pressure sensor structure 1 shown in Fig. 5(A), showing a state in which the electrical insulating film 40 has been removed for ease of understanding. [Figure 6] 6 is a cross-sectional view showing a state in which the pressure sensor structure shown in FIG. 5 is housed in a housing. [Figure 7] FIG. 1 is a cross-sectional view showing an example of a conventional pressure sensor structure. [Figure 8] 8 is a circuit diagram showing an example of a capacitance conversion circuit that can be connected to the pressure sensor structure shown in FIG. 7. DETAILED DESCRIPTION OF THE INVENTION

[0014] One aspect of the present invention is a pressure sensor structure that detects a change in capacitance between electrodes, comprising: a sensor body including a diaphragm plate that functions as a sense electrode, a base electrode facing the diaphragm plate, and a sidewall layer that maintains a gap between the diaphragm plate and the base electrode; a conductive base substrate for supporting the sensor body; the sidewall layer includes a guard electrode layer and upper and lower guard electrode insulating layers that electrically insulate the guard electrode layer; an outer surface of the diaphragm plate and an outer surface of the sidewall layer are coated with an electrically insulating film; The electrical insulating film is provided with a contact region where a part of the guard electrode layer is connected to the outside air.

[0015] With this configuration, even if liquid such as water adheres to the electrical insulating film due to condensation or water intrusion, the guard electrode layer and the adhered liquid are maintained at the same potential via the contact area of the electrical insulating film, thereby preventing a shift in the pressure output value due to the adherence of liquid and suppressing the effects of disturbances.

[0016] The contact region may be provided so that a portion of the guard electrode layer is connected to the outside air via an opening formed in the diaphragm plate and the upper guard electrode insulating layer.

[0017] According to this configuration, by arranging the contact area CT in a location where liquid is likely to adhere and accumulate, it is possible to suppress the influence of disturbances and achieve highly accurate pressure measurement.

[0018] A conductive film electrically connected to the guard electrode layer via the contact region may be provided on the electrical insulating film.

[0019] With this configuration, even if liquid such as water adheres to the electrical insulating film due to condensation or water intrusion, the guard electrode layer and the adhered liquid are maintained at the same potential via the contact area between the conductive film and the electrical insulating film, thereby preventing a shift in the pressure output value due to the adherence of liquid and suppressing the effects of external disturbances.

[0020] 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.

[0021] This configuration improves the corrosion resistance of the conductive film, thereby preventing deterioration of the conductive film even when the liquid adhering to the electrical insulating film is a corrosive liquid such as chlorine water or seawater.

[0022] A pressure sensor device according to one aspect of the present invention includes the above pressure sensor structure and a housing that contains the pressure sensor structure; a capacitance conversion circuit that processes signals from the pressure sensor structure and cancels stray capacitance around the diaphragm plate.

[0023] This configuration makes it possible to realize a pressure sensor device that can suppress the influence of disturbances such as condensation, water ingress, and electromagnetic noise.

[0024] (Embodiment 1) 1 is a cross-sectional view showing an example of a pressure sensor structure 1 according to a first embodiment of the present invention. The pressure sensor structure 1 includes a sensor body including a diaphragm plate 32, a base electrode 31, and a sidewall layer 20, and a base substrate 10 that supports the sensor body.

[0025] The diaphragm plate 32 is formed of a conductive material such as polycrystalline silicon, amorphous silicon, or single crystal silicon, and functions as a sense electrode that is deformable in response to a pressure difference between the surroundings. Although a single-layer structure is illustrated, the diaphragm plate 32 may include two or more layers.

[0026] The base electrode 31 is formed of a conductive material such as polycrystalline silicon, amorphous silicon, or single-crystalline silicon, and is disposed opposite the diaphragm plate 32. The sidewall layer 20 is provided to maintain a gap G between the diaphragm plate 32 and the base electrode 31. The gap G is a space sealed from the outside, and is filled with, for example, an inert gas and maintained at a constant pressure.

[0027] The diaphragm plate 32 and the base electrode 31 form a parallel-plate capacitor. The capacitance C between the electrodes is expressed as C = ε × S / d, where ε is the dielectric constant of the gap G, S is the electrode area, and d is the inter-electrode distance. When the diaphragm plate 32 elastically deforms in response to the pressure difference between the outside and the gap G, the inter-electrode distance d changes, and the capacitance C also changes accordingly.

[0028] The sidewall layer 20 is disposed in a frame shape so as to surround the gap G and is composed of at least three layers, including a guard electrode layer 22, an electrical insulating layer 21 disposed below the guard electrode layer 22 and the base electrode 31, and an electrical insulating layer 23 disposed above the guard electrode layer 22. Here, a three-layer configuration is exemplified for the sidewall layer 20, but it may include four or more layers. A single-layer configuration is exemplified for the guard electrode layer 22, but it may include two or more layers. A single-layer configuration is exemplified for the electrical insulating layers 21 and 23, but it may include two or more layers.

[0029] The base substrate 10 is formed of a conductive material such as polycrystalline Si, amorphous Si, single crystal Si, etc. The base substrate 10 can be configured with one or more layers, and for example, an electrically insulating layer may be provided on the lower surface of the base substrate 10.

[0030] The planar shape of the diaphragm plate 32, base electrode 31 and sidewall layer 20 is typically rectangular, but may also be square, circular, elliptical, polygonal or the like.

[0031] The outer surface of the diaphragm plate 32 and the outer surface of the sidewall layer 20 are covered with an electrically insulating film 40 that functions as a passivation film. The electrically insulating film 40 is made of, for example, SiN x It is made of an electrically insulating material such as SiO2 to prevent short circuits between electrodes and protect the pressure sensor structure.

[0032] In this embodiment, the electrical insulating film 40 does not cover the entire upper portion of the pressure sensor structure 1, and a contact region CT that exposes a part of the guard electrode layer 22 to the outside and is connected to the outside air is provided in the electrical insulating film 40. Such a contact region CT may be provided continuously along the outer periphery of the guard electrode layer 22, or may be provided partially or intermittently, for example, as indicated by a dotted line, a dashed line, or a dash-dot line.

[0033] Next, the function of the contact area CT will be explained. Liquids such as water may adhere to the electrical insulating film 40 due to condensation, water intrusion, and the like. Such liquids generally contain conductive components such as ions, which can change the stray capacitance between the diaphragm plate 32 and the base substrate 10 and cause a shift in the pressure output value. In this embodiment, the presence of the contact area CT ensures that even if liquid adheres to the electrical insulating film 40, the guard electrode layer 22 and the adhered liquid are maintained at the same potential via the contact area CT. This makes it possible to prevent a shift in the pressure output value due to the adhesion of liquid, and suppress the effects of external disturbances.

[0034] 2 is a circuit diagram showing an example of a capacitance conversion circuit that can be connected to the pressure sensor structure 1 shown in FIG. This capacitance conversion circuit includes an operational amplifier OP, a base terminal TB for the base electrode, a sense terminal TS for the sense electrode (diaphragm plate), a guard terminal TG for the guard electrode, a voltage source CV, and a reference impedance RA. When liquid LQ adheres to the electrically insulating film 40, it affects the capacitance between the sense terminal TS and the base terminal TB. However, because the guard electrode layer 22 and the adhered liquid are maintained at the same potential via the contact region CT, a shift in the pressure output value due to the adhesion of liquid LQ can be prevented.

[0035] In Figure 2, the base terminal TB is connected to the virtual ground VG of the inverting input of the operational amplifier OP, and the guard terminal TG is at ground potential. Therefore, the voltage and current between the guard electrode and the base electrode are negligible and have no substantial effect on the capacitance measured between the base electrode and the diaphragm plate. The sense terminal TS is connected to a voltage source CV so that the current between the guard electrode and the diaphragm plate is negligible and has no substantial effect on the capacitance measured between the diaphragm plate and the base electrode. The capacitance between the guard electrode and the base electrode is connected between ground and the virtual ground VG and has no substantial effect on the capacitance measured between the diaphragm plate and the base electrode.

[0036] Let CS be the capacitance between the base terminal TB and the sense terminal TS, and CL be the capacitance between the base terminal TB and the guard terminal TG. Assume also that the voltage source CV is an AC voltage source with an effective voltage Ui, the feedback circuit element RA is a capacitor with a capacitance equal to CF, and the open-loop gain of the amplifier OP is A. The output voltage Uo of the amplifier can be expressed as follows:

[0037]

number

[0038] Thus, the effect of CL is reduced by the amount of amplifier open-loop gain A. The capacitance between the sense terminal TS and the guard terminal TG also has no effect on the output voltage, since it is connected in parallel with the voltage source Ui, which, as an ideal voltage source, can supply current to this capacitance without changing the voltage.

[0039] (Embodiment 2) 3 is a cross-sectional view showing an example of a pressure sensor structure 1 according to a second embodiment of the present invention. This pressure sensor structure 1 includes a sensor body including a diaphragm plate 32, a base electrode 31, and a sidewall layer 20, and a base substrate 10 that supports the sensor body. The materials and functions of these components are the same as those of the structure shown in FIG. 1, so a repeated description will be omitted.

[0040] In this embodiment, a conductive film 24 is provided on the electrical insulating film 40, and is electrically connected to the guard electrode layer 22 via the contact region CT. The conductive film 24 is provided so as to cover the outer wall of the sidewall layer 20 while being in physical contact with the contact region CT. This increases the probability of electrical conduction between the liquid LQ and the guard electrode layer 22. Such a conductive film 24 may be provided continuously along the outer periphery of the guard electrode layer 22, or may be provided partially or intermittently, for example, or may be provided in a mesh shape.

[0041] FIG. 4 is a cross-sectional view showing the pressure sensor structure 1 shown in FIG. 3 housed in a housing 50. The lower portion of the pressure sensor structure 1, i.e., the back and side surfaces of the base substrate 10, are in close contact with the housing 50, but the upper portion of the pressure sensor structure is exposed to the outside air. Therefore, liquid LQ, such as water, may adhere to the electrical insulating film 40 due to condensation or water intrusion. Because the internal space of the housing 50 is recessed like a bowl, the liquid LQ tends to accumulate near the outer wall of the sidewall layer 20. The liquid LQ comes into physical contact with the conductive film 24, and the guard electrode layer 22 and the adhered liquid LQ are maintained at the same potential via the contact region CT of the conductive film 24 and the electrical insulating film 40. This prevents a shift in the pressure output value due to the adhesion of liquid, and suppresses the effects of external disturbances.

[0042] The conductive film 24 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, such as stainless steel, an aluminum alloy, a titanium alloy, or a nickel alloy. This increases the corrosion resistance of the conductive film 24. Therefore, even if the liquid adhering to the electrical insulating film 40 is a corrosive liquid such as chlorine water or seawater, deterioration of the conductive film 24 can be suppressed. The conductive film 24 can be formed by, for example, vapor deposition, sputtering, plating, or coating.

[0043] (Embodiment 3) The pressure sensor structure 1 shown in Figures 1 and 3 is housed in a housing 50 as shown in Figure 4 together with the capacitance conversion circuit shown in Figure 2. This makes it possible to realize a pressure sensor device that can suppress the influence of external disturbances such as condensation, water intrusion, and electromagnetic noise.

[0044] (Embodiment 4) Fig. 5(A) is a cross-sectional view showing an example of a pressure sensor structure 1 according to a fourth embodiment of the present invention. Fig. 5(B) is a plan view of the pressure sensor structure 1 shown in Fig. 5(A), showing a state in which the electrical insulating film 40 has been removed for ease of understanding. This pressure sensor structure 1 comprises a sensor body including a diaphragm plate 32, a base electrode 31, and a sidewall layer 20, and a base substrate 10 that supports the sensor body. The materials and functions of these components are the same as those of the structure shown in Fig. 1, so a repeated explanation will be omitted.

[0045] In this embodiment, the electrical insulating layer 23, the diaphragm plate 32, and the electrical insulating film 40 are partially removed from the pressure sensor structure shown in FIG. 1 to provide an opening that exposes a portion of the upper surface of the guard electrode layer 22 to the outside air. The exposed portion of the guard electrode layer 22 functions as a contact region CT that connects to the outside air. FIG. 5B illustrates an example in which the contact region CT is a rectangular continuous line. The contact region CT may have other geometric shapes, such as a square, a circle, or an ellipse, and may be provided partially or intermittently as a dotted line, a dashed line, or a dashed-dotted line, instead of a continuous line. The electrical insulating layer 23a and the diaphragm plate 32a remain outside the contact region CT. By locating the contact region CT in a location where liquid is likely to adhere and accumulate, the influence of external disturbances can be suppressed, enabling high-precision pressure measurement.

[0046] 6 is a cross-sectional view showing a state in which the pressure sensor structure 1 shown in FIG. 5 is housed in a housing 50. In the pressure sensor structure 1, as in the second embodiment, a conductive film 24 is provided on the electrical insulating film 40 and electrically connected to the guard electrode layer 22 via the contact region CT. As in the first embodiment, this conductive film 24 may be omitted.

[0047] The lower portion of the pressure sensor structure 1, i.e., the back and side surfaces of the base substrate 10, are in close contact with the housing 50, but the upper portion of the pressure sensor structure is exposed to the outside air. As a result, liquid LQ such as water may adhere to the electrical insulating film 40 due to condensation or water intrusion. Because the internal space of the housing 50 is recessed like a bowl, the liquid LQ tends to accumulate near the outer wall of the sidewall layer 20. The liquid LQ comes into physical contact with the conductive film 24, and the guard electrode layer 22 and the adhered liquid LQ are maintained at the same potential via the contact region CT of the conductive film 24 and the electrical insulating film 40. As a result, a shift in the pressure output value due to the adhesion of liquid can be prevented, and the effects of external disturbances can be suppressed.

[0048] The conductive film 24 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, such as stainless steel, an aluminum alloy, a titanium alloy, or a nickel alloy. This increases the corrosion resistance of the conductive film 24. Therefore, even if the liquid adhering to the electrical insulating film 40 is a corrosive liquid such as chlorine water or seawater, deterioration of the conductive film 24 can be suppressed. The conductive film 24 can be formed by, for example, vapor deposition, sputtering, plating, or coating.

[0049] (Embodiment 5) The pressure sensor structure 1 shown in Fig. 5 is housed in a housing 50 as shown in Fig. 6 together with the capacitance conversion circuit shown in Fig. 2. This makes it possible to realize a pressure sensor device that can suppress the influence of disturbances such as condensation, water ingress, and electromagnetic noise.

[0050] Although the present invention has been fully described in connection with the preferred embodiments with reference to the accompanying drawings, various changes and modifications will become apparent to those skilled in the art, and it is to be understood that such changes and modifications are included within the scope of the present invention as defined by the appended claims unless they depart therefrom. [Industrial Applicability]

[0051] The present invention is extremely useful industrially because it can realize a pressure sensor structure that can suppress the influence of disturbances and perform high-precision pressure measurement. [Explanation of symbols]

[0052] 1 Pressure sensor structure 10 Base board 20 Sidewall layer 21,23 Electrical insulating layer 24 Conductive film 22 Guard electrode layer 31 Base electrode 32 Diaphragm plate 40 Electrical insulating film 50 Housing CT contact area G gap LQ Liquid

Claims

1. A pressure sensor structure that detects a change in capacitance between electrodes, comprising: a sensor body including a diaphragm plate that functions as a sense electrode, a base electrode facing the diaphragm plate, and a sidewall layer that maintains a gap between the diaphragm plate and the base electrode; a conductive base substrate for supporting the sensor body; the sidewall layer includes a guard electrode layer and upper and lower guard electrode insulating layers that electrically insulate the guard electrode layer; an outer surface of the diaphragm plate and an outer surface of the sidewall layer are coated with an electrically insulating film; a contact region in which a part of the guard electrode layer is connected to the outside air is provided in the electrical insulating film; The contact region is provided so that a portion of the guard electrode layer is connected to the outside air via an opening formed in the diaphragm plate and the upper guard electrode insulating layer.

2. 2. The pressure sensor structure according to claim 1, further comprising a conductive film provided on the electrical insulating film and electrically connected to the guard electrode layer via the contact region.

3. 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.

4. a pressure sensor structure according to any one of claims 1 to 3; a housing that contains the pressure sensor structure; a capacitance conversion circuit that processes a signal from the pressure sensor structure and cancels stray capacitance around the diaphragm plate.

Images