JP3136549B2 - Capacitive pressure sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitive sensor having a diaphragm structure for detecting a change in pressure to be measured in a capacitive manner.

[0002]

2. Description of the Related Art Conventionally, as a pressure sensor of this type, a cover glass 42 made of Pyrex or the like having a fixed electrode 41 as shown in a cross section in FIG. A sensor element 46 is formed by arranging a silicon wafer 44 on which a movable electrode 43 is formed and an electrode surface thereof facing each other, and joining a peripheral portion thereof by a joining portion 45 by anodic bonding.
6 is fixed to the base 48 by the joint 47. In addition, 49 is a pressure introduction port.

[0003]

However, the capacitance type pressure sensor constructed as described above has the following problem.
Due to the difference in the coefficient of thermal expansion between the material of the base 6 and the material of the base 48, when the ambient temperature changes, stress is applied to the sensor element 6. If the stress is large, there is a problem that an error in the temperature characteristic of the sensor element 46 occurs. In addition, in the joint portion 47 between the sensor element 46 and the base 48, a joint that generates heat at the time of joining, such as soldering, is widely performed. In this case as well, the sensor element 4 is not used due to the temperature difference between the time of joining and the time of use.
6, a residual stress is generated, and the stress changes with time. This causes an error in pressure measurement, and there has been a problem that highly accurate and highly reliable pressure measurement cannot be performed.

Accordingly, the present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to significantly reduce the stress of a sensor element generated by joining the sensor element and a base. The capacitance-type pressure sensor, which greatly reduces the temperature characteristic of the measured pressure-capacitance value characteristic of the sensor element due to this stress and its temporal change, and enables highly accurate and highly reliable pressure measurement. To provide.

[0005]

In order to achieve the above object, the present invention provides a substrate having a first electrode formed on one surface and a second substrate formed on a surface facing the first electrode. A diaphragm plate on which electrodes are formed is opposed to each other with a gap therebetween to form a sensor element, and a pressure measuring section is formed on one end side including the first electrode and the second electrode in the length direction of the sensor element. A fixed portion that does not contribute to pressure measurement is formed on the other end side, and a pressure vessel is fixedly arranged on at least one surface of the fixed portion. In another aspect of the present invention, a substrate having a first electrode formed on one surface and a diaphragm plate having a second electrode formed on a surface facing the first electrode include a first electrode. A stopper plate having a second gap formed on a surface opposed to the other end of the diaphragm plate in which a second electrode of the stopper plate is formed on the outer surface of the diaphragm plate and opposed to each other with a gap therebetween. And a pressure measuring portion is formed at one end of the sensor element in the longitudinal direction, and a fixing portion not contributing to pressure measurement is formed at the other end, and a pressure vessel is provided at one of the fixing portions. Are fixedly arranged.

[0006]

According to the present invention, since the sensor element is fixed to the pressure vessel at a fixed portion other than the pressure measurement section, the transmission of measurement error factors generated in the fixed section to the pressure measurement section by fixing the pressure vessel is reduced. You.

[0007]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a view showing a configuration of an embodiment of a capacitance type pressure sensor according to the present invention. FIG. 1 (a) is a plan view, FIG. 1 (b) is a sectional view taken along line BB of FIG. (C) is a plan view of the line CC. In the figure, reference numeral 11 denotes a substrate formed of, for example, quartz glass or the like, and 12 denotes a substrate 1
A groove as a gap 12g for arranging a lead wire formed on the upper surface side of the 1 and having a constant depth so that the overall shape is substantially square and the cross section is concave, and 13 is formed on the bottom surface in the groove 12. A fixed electrode made of a conductive thin film.

Reference numeral 14 denotes a diaphragm plate made of, for example, quartz glass, which is fixedly bonded to the peripheral surface of the substrate 11, and reference numeral 15 denotes a movable thin film formed of a conductive thin film formed on the surface of the diaphragm plate 14 facing the fixed electrode 13. Electrodes 16 are lead wires of the fixed electrode 13 formed to penetrate the end side of the diaphragm plate 14, and 17 are electrode terminals thereof, which are formed on the fixed electrode 13 formed on the substrate 11 and the diaphragm plate 14. The movable electrode 15 thus arranged is opposed to the movable electrode 15 with a gap 12g therebetween to form a capacitor structure, thereby forming a capacitive sensor element 18.

In addition, the sensor element 1 thus configured
As shown in FIGS. 1A and 1B, a diaphragm sensing portion 14a, a diaphragm connecting portion 14b, and a diaphragm joining portion 14c are formed on the diaphragm plate 14 side, and the substrate 11 is formed on the substrate 11 side. Regions of the sensing part 11a, the board connecting part 11b, and the board bonding part 11c are respectively formed.

The sensor element 1 constructed as described above
8 is a diaphragm joint 14c of the diaphragm plate 14.
A pressure vessel 19 having an opening 19a so as to surround the electrode terminal 17 provided therein is fixedly joined at the opening 19a. In other words, the diaphragm joint 14c that does not contribute to the sensing of the sensor element 18 is fixed to the pressure vessel 19 at the portion thereof, and is arranged in the pressure vessel 19. The fixing to the pressure vessel 19 may be performed at the substrate bonding portion 11c.

In such a configuration, the distance between the movable electrode 15 and the fixed electrode 13 is changed by the displacement of the diaphragm sensing portion 14a of the diaphragm plate 14 due to the pressure in the pressure vessel 19, and the pressure value is reduced. It can be detected as a capacitance value between both electrodes. Further, even if the substrate sensing part 11a of the substrate 11 is displaced, the diaphragm plate 1
4 and the substrate 11 may be displaced. The opening 19a
There may be a pressure inlet opening communicating with the groove 12. Further, the example in which the fixed electrode 13 is constituted by two sheets electrically insulated has been described, but it is needless to say that the present invention can be implemented with one sheet. Further, the shape of the fixed electrode 13 is a rectangular shape, but may be a circular shape or another polygonal shape.

According to such a configuration, the sensor element 18
From the sensing part 14a to the diaphragm connecting part 14
Since the diaphragm joint 14c is fixed and held at the opening 19a in the pressure vessel 19 by the diaphragm joint 14c, the transmission of the measurement error factor caused by the fixing of the pressure vessel 19 to the sensing part 14a at the diaphragm joint 14c is performed. Can be reduced. Further, the substrate 11 and the diaphragm plate 14 are made of the same material, and it is possible to join them without providing an adhesive layer. In this case, an error factor caused by the presence of the dissimilar material adhesive layer (thermal stress Etc.).

FIG. 2 is a diagram showing a configuration of a capacitance type pressure sensor according to still another embodiment of the present invention.
2A is a plan view, FIG. 2B is a cross-sectional view taken along the line BB,
FIG. 2C is a plan view of the line CC, and the same parts as those in the above-mentioned figures are denoted by the same reference numerals. 1 differs from FIG. 1 in that a stopper plate 20 having a gap 20g and a pressure introducing hole 20h communicating with the gap 20g is joined and fixed on the diaphragm plate 14 on a surface facing the diaphragm plate 14. The lead wire 16 of the fixed electrode 13 is inserted through the stopper plate 20, and the electrode terminal 17 is provided on the surface of the stopper plate 20 to constitute the sensor element 18A.

As shown in FIG. 2B, the sensor element 18A constructed as described above has a stopper sensing portion 20a and a stopper connecting portion 20b on the stopper plate 20 side.
And a region of the stopper joint 20c are formed, respectively. A pressure vessel 19 having an opening 19a is joined and fixed so as to surround the electrode terminal 17 provided in the stopper joint 20c, and the sensor element 18A is accommodated therein. I have. That is, the pressure vessel 19 is fixed at the stopper joining portion 20c that does not contribute to the sensing of the sensor element 18A,
It is configured to be arranged inside the pressure vessel 19. In addition,
The fixing to the pressure vessel 19 may be performed at the substrate bonding portion 11c.

In such a configuration, the distance between the fixed electrode 13 and the movable electrode 15 is changed by the displacement of the diaphragm sensing portion 14a or the substrate sensing portion 11a of the diaphragm plate 14 due to the pressure in the pressure vessel 19. Then, the pressure value can be detected as a capacitance value between both electrodes. Further, even if the substrate sensing part 11a of the substrate 11 is displaced, the diaphragm plate 14 and the substrate 11 may be displaced.

In such a configuration as well, the transmission of measurement error factors caused by fixing of the pressure vessel 19 at the stopper connecting portion 20c to the substrate sensing portion 11a or the diaphragm sensing portion 14a can be reduced. Further, by providing the stopper plate 20 on the diaphragm plate 14, the rigidity of the diaphragm plate 14 is reinforced, and the occurrence of warpage of the sensor element 18A due to the fixed position with the offset pressure vessel 19 can be reduced. Further, it serves as a stopper when the diaphragm sensing portion 14a is displaced toward the stopper plate 20 side. Further, there may be a pressure introduction port communicating with the groove 12 from the opening 19a.

FIG. 3 is a view showing the configuration of another embodiment of the capacitance type pressure sensor according to the present invention. FIG. 3 (a) is a plan view and FIG. 3 (b) is a cross section taken along the line BB. Figure, Figure 3
(C) is a plan view of the line CC, and the same parts as those in the above-mentioned figures are denoted by the same reference numerals. 2 is different from FIG. 2 in that U-shaped depressions 11d and 20d are formed on the outer surfaces of the substrate connecting portion 11b and the stopper connecting portion 20c of the substrate 11, respectively. The stopper connecting portion 20b of the stopper plate 20 is also formed with a groove 20d having a U-shaped cross section over three outer surfaces. Further, although not shown, the diaphragm plate 14 also has a groove 11d and a groove having the same structure that communicates with the groove 20d in the diaphragm connecting portion 14b to form the sensor element 18B.

Although these grooves are formed so as to make one turn around the sensor element 18B, one turn is not a mast, and the same effect can be obtained even if the grooves are formed in pairs on two opposing outer surfaces. . The shape of the groove is not limited to a U-shape, and may be a V-shape, a square groove, or a trapezoidal groove.

In such a structure, the same effect as described above can be obtained, and the connection between the sensor element 18B and the recess 11d and the groove 20d can be provided, so that the pressure vessel 19 and the fixed sensor element 18B can be joined together. Part 18
The transmission of the measurement error factor occurring in c to the sensing unit 18a can be more reliably reduced.

FIG. 4 is a diagram showing the configuration of another embodiment of the capacitance type pressure sensor according to the present invention. FIG. 4 (a) is a plan view, and FIG. 4 (b) is a cross section taken along line BB. Figure, Figure 4
(C) is a plan view of the line CC, and the same parts as those in the above-mentioned figures are denoted by the same reference numerals. 2 is different from FIG. 2 in that the sensor element 18A is formed such that the length L _C of the connection portion 18b thereof is longer than the length L _S of the sensing portion 18a (L _C > L _S ).

According to such a configuration, the sensor element 18
By making the length of the connecting portion 18b of A longer than the length of the sensing portion 18a, the sensing portion 18 of the measurement error factor generated at the joint portion 18c to which the pressure vessel 19 is fixed is provided.
a can be more reliably reduced.

FIG. 5 is a view showing a configuration of another embodiment of the capacitance type pressure sensor according to the present invention. FIG. 5 (a) is a plan view and FIG. 5 (b) is a cross section taken along the line BB. Figure, Figure 5
(C) is a plan view of the line CC, and the same parts as those in the above-mentioned figures are denoted by the same reference numerals. 2 is different from FIG. 2 in that the sensor element 18B is fixed to the pressure vessel 19 by joining a joint 18c thereof and an opening 19a of the pressure vessel 19 via a spacer plate 21.

In such a configuration, the same effect as described above is obtained, and the coefficient of thermal expansion (α) of the spacer plate 21 is determined by the coefficient of thermal expansion of the joining member in contact with the spacer plate 21 and the container member of the pressure vessel 19. , The stress applied to the substrate 11 when the temperature changes due to the difference in the thermal expansion coefficient between the substrate 11 and the pressure vessel 19 is reduced, the reliability of bonding is increased, and the sensing of the sensor element 18B is performed. Part 18
The measurement error factor transmitted to a can be reduced. For example, the sensor element 18B is made of quartz glass (α = 0.6 × 10 ⁻⁶ / ° C.)
And the pressure vessel 19 is made of stainless steel (α = 18 × 1
0 ^-6 / ° C), the thermal expansion coefficient of the joining member is selected to be a value between these values.

FIGS. 6A and 6B are diagrams showing a configuration of another embodiment of the capacitance type pressure sensor according to the present invention. FIG. 6A is a plan view, and FIG. Figure, Figure 6
(C) is a plan view of the line CC, and the same parts as those in the above-mentioned figures are denoted by the same reference numerals. 5 is different from FIG. 5 in that a reference fixed electrode 22 having substantially the same area as the fixed electrode 13 is independently formed in the groove 12 at the joint portion 11c of the substrate 11, and the reference fixed electrode 22 is further provided via a gap 12g. A reference counter electrode 23 is formed on the diaphragm plate 14 facing the fixed electrode 22 to form a sensor element 18D.

In such a configuration, the pressure vessel 19
Of the movable electrode 15 and the fixed electrode by displacing the movable diaphragm in the diaphragm sensing portion 14a by a differential pressure between the pressure in the pressure vessel 19 and the pressure guided from the pressure introducing hole 11h. 13, the pressure value can be detected as the capacitance value between the two electrodes, and the distance between the reference fixed electrode 22 and the reference counter electrode 23 does not change depending on the pressure difference. The capacitance value between the electrodes is also unchanged.

In such a configuration, the same effect as described above can be obtained, and the sensing capacitor composed of the movable electrode 15 and the fixed electrode 13 and the reference fixed electrode 2
Since the same measurement gas or the same atmosphere enters the reference capacitor composed of the reference electrode 2 and the reference counter electrode 23, the same influence is given to environmental factors such as humidity, and the differential pressure is differently affected. The pressure values corrected for environmental factors can be detected by the outputs of both capacitors.

FIGS. 7A and 7B are diagrams showing a configuration of another embodiment of the capacitance type pressure sensor according to the present invention. FIG. 7A is a plan view, and FIG. 7B is a cross section taken along the line BB. Figure, Figure 7
(C) is a plan view of the line CC, and the same parts as those in the above-mentioned figures are denoted by the same reference numerals. 2 is different from that of FIG.
7 is formed on the joint portion 14a of the diaphragm plate 14 in the electrode extraction hole 20e to form the sensor element 18K.

With such a configuration, the same effect as described above can be obtained. In addition, the movable electrode 15 or the fixed electrode 13
By shortening the vertical connection length from the lead wire 16 to the electrode terminal 17 to the electrode terminal 17, the electrode take-out portion can be easily manufactured.

FIG. 8 is a view showing the configuration of another embodiment of the capacitance type pressure sensor according to the present invention. FIG. 8 (a) is a plan view and FIG. 8 (b) is a cross section taken along line BB. FIG. 8
(C) is a plan view of the line CC, and the same parts as those in the above-mentioned figures are denoted by the same reference numerals. 7 is different from FIG. 7 in that a signal processing semiconductor chip 26 connected to a wire 25 from an electrode terminal 17 is disposed on a pressure vessel 19.

In such a configuration, the same effects as described above can be obtained, and the configuration is separated from the measuring body. Further, the reliability of the signal processing unit is ensured by providing the signal processing semiconductor chip 26 near the measuring unit. And the elimination of stray capacitance.

FIGS. 9 to 18 are plan views showing steps for explaining an embodiment of a method of manufacturing a capacitance type pressure sensor according to the present invention. In the figure, first, as shown in FIG.
A mask is formed on one surface of the substrate sensing portion 11a and a portion where the wiring is routed by a known printing technique, and then a groove 12 is formed as a gap having a concave cross section.

Next, as shown in FIG. 10, after a metal film for an electrode is formed on the substrate 11 on which the groove 12 is formed, a fixed electrode 13 having a desired shape and the fixed electrode 13 are formed in the groove 12 by a known engraving technique. Form wiring.

Next, as shown in FIG.
The movable electrode 15 is formed in the required shape on the surface facing the substrate 11 in the same manner as the fixed electrode 13.

Next, as shown in FIG. 12, a substantially elliptical electrode extraction hole 31 is formed by hydrofluoric acid etching at a predetermined position on the back side of the diaphragm plate 14 so that the bottom 30 penetrates.

Next, as shown in FIG. 13, a metal film 32 is formed on the entire surface of the diaphragm plate 14 where the holes 31 are formed.

Next, as shown in FIG.
The surface on which the metal film 32 of No. 4 is formed is polished to a desired thickness. As a result, a structure in which the lead wires 16 pass through the diaphragm plate 14 is formed.

Next, as shown in FIG. 15, a gap 20g and a pressure introduction hole 20h are formed in the stopper sensing portion on the side of the stopper plate 20 bonded to the diaphragm plate 14.

Next, as shown in FIG. 16, a hole 34 through which the bottom part 33 penetrates the stopper plate 20 is formed by hydrofluoric acid etching at the stopper joint on the back side where the gap 20g and the pressure introducing hole 20h are provided. I do.

Next, as shown in FIG.
After bonding and bonding the stopper 4 and the stopper plate 20, a metal film is formed on the surface of the stopper plate 20 where the holes 34 are formed, and the electrode terminals 17 are formed by a known engraving technique.

Next, as shown in FIG. 18, the pressure vessel 19 is joined to a predetermined position on the stopper plate 20 to complete the process.

In the above-described embodiment, the case where the material of the substrate, the diaphragm plate, and the stopper plate is quartz glass has been described. However, other materials such as ceramic, silicon, and glass other than quartz glass are used. Is also good.

[0042]

As described above, according to the present invention,
By fixing the pressure vessel to the fixed part of the sensor element, it becomes difficult for measurement error factors such as stress generated in the fixed part of the sensor element to be transmitted to the pressure measuring unit, so that highly accurate and highly reliable pressure measurement can be performed. An extremely excellent effect, such as being possible, can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a capacitance type pressure sensor according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of another embodiment of the capacitance type pressure sensor according to the present invention.

FIG. 3 is a diagram showing a configuration of a capacitance type pressure sensor according to still another embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of another embodiment of the capacitance type pressure sensor according to the present invention.

FIG. 5 is a diagram showing a configuration of another embodiment of the capacitance type pressure sensor according to the present invention.

FIG. 6 is a diagram showing a configuration of another embodiment of the capacitance type pressure sensor according to the present invention.

FIG. 7 is a diagram showing a configuration of another embodiment of the capacitance type pressure sensor according to the present invention.

FIG. 8 is a diagram showing a configuration of another embodiment of the capacitance type pressure sensor according to the present invention.

FIG. 9 is a plan view of a step for explaining the method for manufacturing the capacitive pressure sensor according to the present invention.

FIG. 10 is a plan view of a step following FIG. 9;

FIG. 11 is a plan view of a step following FIG. 10;

FIG. 12 is a plan view of a step following FIG. 11;

FIG. 13 is a plan view of a step following FIG. 12;

FIG. 14 is a plan view of a step following FIG. 13;

FIG. 15 is a plan view of a step following FIG. 14;

FIG. 16 is a plan view of a step following FIG. 15;

FIG. 17 is a plan view of a step following FIG. 16;

FIG. 18 is a plan view of a step following FIG. 17;

FIG. 19 is a cross-sectional view illustrating an example of the configuration of a conventional capacitive pressure sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Substrate 12 Groove 13 Fixed electrode 14 Diaphragm board 14a Diaphragm sensing part 14b Diaphragm connection part 14c Diaphragm junction part 15 Movable electrode 16 Lead wire 17 Electrode terminal 18 Sensor element 18A Sensor element 18B Sensor element 18D Sensor element 18K Sensor element 18A Sensor element Part 18b Sensor element connecting part 18c Sensor element connecting part 19 Pressure vessel 19a Opening 19b Electrode taking-out hole 20 Stopper plate 20a Stopper plate sensing part 20b Stopper plate connecting part 20c Stopper plate connecting part 20d Groove 20e Electrode taking-out hole 21 Spacer plate 22 Reference fixed electrode 23 Reference counter electrode 24 Spacer plate 25 Wire 26 Semiconductor chip

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-134570 (JP, A) JP-A-63-305229 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01L 9/12

Claims (2)

(57) [Claims] 1. A sensor in which a substrate having a first electrode formed on one surface and a diaphragm plate having a second electrode formed on a surface opposed to the first electrode are arranged to face each other with a gap therebetween. A pressure measuring portion is formed at one end including the first and second electrodes in the length direction of the sensor element, and a fixing portion not contributing to pressure measurement is formed at the other end; A pressure sensor in which a pressure vessel is fixedly arranged on at least one surface of the portion. 2. A substrate having a first electrode formed on one surface and a diaphragm plate having a second electrode formed on a surface facing the first electrode via a first gap. A stopper plate having a second gap formed on a surface of the diaphragm plate having a second electrode formed on the outer surface of the diaphragm plate and having a second electrode formed on the outer surface of the diaphragm plate is opposed to the sensor element. A pressure measuring unit is formed at one end in the length direction of the sensor element and a fixing unit that does not contribute to pressure measurement is formed at the other end, and a pressure vessel is fixedly arranged at one of the fixing units. A capacitance type pressure sensor characterized by the above-mentioned.