JPH06186106A - Electrostatic capacity-type pressure sensor - Google Patents

Abstract

PURPOSE:To measure a pressure with high accuracy and with high reliability by a method wherein a pressure range from a very small pressure up to a high pressure can be measured in an electrostatic capacity manner without being affected by a change in atmospheric surroundings including the problem of dew condensation and dust particles and an error caused by a change in the surroundings is suppressed. CONSTITUTION:The title sensor is provided with a cylindrical frame body 1, with a first diaphragm 2 and a second diaphragm 3 formed at both end parts of the frame body 1 so as to be faced, with a beam part 4 which is connected and fixed to opposite faces of the first diaphragm 2 and the second diaphragm 3 and with a movable electrode support plate 5 which is supported by the beam 4 so as to face the first diaphragm 2 and the second diaphragm 3 and in which a movable electrode 6 has been formed on one face. In addition, the inner wall surface of the diaphragm support part 1 is provided with the movable electrode 6 which faces the movable electrode support plate 5 and which is supported in such a way that the beam 4 is inserted and passed and with a fixed electrode support playe 7 in which a fixed electrode 8 has been formed on an opposite face via a gap G. The frame body 1 is separted from the outside, and a capacitor structure C is formed between the movable electrode 6 and the fixed electrode 8.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, as a capacitance type pressure sensor of this type, a fixed electrode 31 is provided in a recess as shown in a cross section in FIG.
Cover glass 3 made of Pyrex etc.
2 and a silicon wafer 34 having a movable electrode 33 formed in a concave portion on the front surface, the electrode surfaces of which are opposed to each other, and peripheral portions thereof are joined by a joining portion 35 by anodic joining to form a diaphragm portion D. Element 36 has been proposed. Note that P1 is the measurement pressure and P2 is the atmospheric pressure.

In the capacitance type pressure sensor constructed as described above, when the measured pressure P1 increases, the diaphragm portion D is deformed and the gap G between the fixed electrode 31 and the movable electrode 33 changes (in this case, Becomes smaller), the capacitance value of the capacitor composed of the fixed electrode 31 and the movable electrode 33 changes, and the measured pressure P1 can be detected by measuring this capacitance value.

[0004]

However, in the electrostatic capacitance type pressure sensor having such a structure, when the environment such as the humidity of the atmospheric pressure changes, the fixed electrode 31 and the movable electrode 33 are separated from each other. There is an error factor that the permittivity of the air in the gap G changes in response to a change in humidity, which causes the capacitor capacitance value to change due to factors other than the measured pressure.

As a solution to such a problem,
There has been proposed an electrostatic capacitance type pressure sensor provided with a reference capacitor in order to eliminate an error factor caused by a change in environment such as humidity (Japanese Unexamined Patent Publication No. 63-308529). This capacitance type pressure sensor includes a sensing capacitor whose capacitance value changes according to the measured pressure and a reference capacitor whose capacitance value does not change even when the measured pressure changes. Since the same atmosphere is introduced into the gap between the reference capacitor and both electrodes, it is possible to eliminate an error factor caused by a change in environment such as humidity.

However, the capacitance type pressure sensor constructed as described above has a problem that it is not possible to eliminate an error factor when dew condensation occurs on the surface of the capacitor electrode or when fine dust is mixed into the capacitor electrode. there were. In addition, the occurrence of dew condensation is an unavoidable phenomenon when the temperature of the medium whose pressure is measured is lower than the atmospheric temperature, and dust contamination is an unavoidable problem as long as there is a pressure introduction hole for atmospheric pressure. is there. Therefore, these problems cause an error in pressure measurement, which makes it impossible to perform highly accurate and reliable pressure measurement.

Therefore, the present invention has been made in order to solve the above-mentioned conventional problems, and its purpose is to reduce the influence of minute pressure without being affected by changes in the atmospheric environment including the problems of dew condensation and dust. An object of the present invention is to provide an electrostatic capacitance type pressure sensor capable of electrostatically measuring a pressure range up to high pressure. Another object of the present invention is to provide an electrostatic capacitance type pressure sensor capable of suppressing the occurrence of an error due to a change in environment and enabling highly accurate and highly reliable pressure measurement.

[0008]

In order to achieve such an object, a first aspect of the present invention is directed to a diaphragm supporting portion which is formed in a substantially cylindrical shape, and which opposes each other so as to close both ends of the diaphragm supporting portion. A first diaphragm portion and a second diaphragm portion, which are formed as follows, and a first diaphragm portion and a second diaphragm portion which are connected to the facing surfaces of the first diaphragm portion and the second diaphragm portion. A beam part to be fixed, and the first diaphragm part and the second beam part on the beam part.
And a movable electrode supporting portion having a movable electrode formed on at least one surface thereof, the movable electrode supporting portion being opposed to the diaphragm portion, and being supported on the inner wall surface of the diaphragm supporting portion by facing the movable electrode supporting portion and inserting the beam portion. And a fixed electrode support portion having a fixed electrode formed on at least one surface facing the movable electrode via a cavity, and the inside of the diaphragm support portion is isolated from the outside and between the movable electrode and the fixed electrode. The capacitor structure is formed on. Also, the second
According to another aspect of the present invention, there is provided a diaphragm support portion formed in a substantially tubular shape, a first diaphragm portion formed to face each other so as to close both ends of the diaphragm support portion, and having a thick portion on at least one of the facing surfaces, A beam that is connected to the opposing surface of the second diaphragm portion and the first diaphragm portion and the second diaphragm portion that have a thick portion on at least one side, and that fixes the first diaphragm portion and the second diaphragm portion. Part, a movable electrode formed on at least one thick part of the first diaphragm part and the second diaphragm part, and an inner wall surface of the diaphragm support part facing the first diaphragm part and the second diaphragm part. And a fixed electrode support portion having a fixed electrode formed on at least one surface facing the movable electrode through the beam portion while being supported through the beam portion. , The diaphragm supporting portion is made by forming a capacitor structure between the movable electrode and the fixed electrode while being isolated from the outside.

[0009]

In the present invention, the measurement pressure (for example, atmospheric pressure)
P1 is applied to the first diaphragm portion, and the measured pressure P2
Is applied to the second diaphragm portion to generate a pressure difference between the measured pressure P1 and the measured pressure P2, the first diaphragm portion and the second diaphragm portion and the beam portion are integrated. Displacement, the gap size of the cavity between the movable electrode and the fixed electrode changes, and the capacitance value of the capacitor structure composed of the movable electrode and the fixed electrode changes.Measurement by measuring this capacitance value You can know the pressure.

[0010]

Embodiments of the present invention will be described in detail below with reference to the drawings. (Embodiment 1) FIGS. 1A and 1B are views showing the configuration of an embodiment of an electrostatic capacity type pressure sensor according to the present invention. FIG. 1A is a plan view and FIG. 1B is FIG. 1A. 3 is a cross-sectional view taken along line BB ′ of FIG. In the figure, 1 is a frame body as a diaphragm support body formed in a substantially rectangular tube shape, and 2 and 3 are thin-walled first frames formed so as to be closed at both open end portions of the frame body 1, respectively. The second diaphragm. The frame 1, the first diaphragm 2 and the second diaphragm 3 are made of, for example, sapphire glass.

Reference numeral 4 denotes a beam for connecting and fixing the first diaphragm 2 and the second diaphragm 3 in the frame 1.
Is a movable electrode support plate which is supported and fixed on the beam 4 so as to face the first diaphragm 2 and the second diaphragm 3, and 6
Is a movable electrode made of a conductive thin film formed on the upper surface of the movable electrode supporting plate 5, and 7 is a fixed electrode which is supported on the inner wall surface of the frame body 1 so as to face the movable electrode supporting plate 5 and pass through the beam 4. It is a support plate.

The beams 4, the movable electrode supporting plate 5, and the fixed electrode supporting plate 6 are also made of, for example, sapphire glass. Further, 8 is a gap G between electrodes (about 1 μm) on the surface of the fixed electrode support plate 7 facing the movable electrode 6.
It is a fixed electrode composed of a conductive thin film formed through the above.

Further, the movable electrode 6 and the fixed electrode 8 are arranged so as to face each other with an interelectrode gap G formed therebetween to form a capacitor structure C to form a capacitive sensor element. Further, the inside of the frame 1 in which the capacitor structure C is formed is completely sealed by being isolated from the external environment, and a vacuum or gas is enclosed inside the frame.

In the capacitance type pressure sensor constructed as described above, the measured pressure (for example, atmospheric pressure) P1 of the environment 1 is applied to the first diaphragm 2, and the measured pressure P2 of the environment 2 is applied to the second diaphragm 3. Set to be applied to. As a result, when the measurement pressure P2 is applied to the second diaphragm 3 and a pressure difference occurs between the measurement pressure P1 and the measurement pressure P2, the first diaphragm 2 and the second diaphragm 3 and the beam 4 are integrated. When the movable electrode 6 is displaced, the gap G of the cavity between the movable electrode 6 and the fixed electrode 8 changes.
The capacitance value of the capacitor structure C composed of the fixed electrode 8 and the fixed electrode 8 changes, and the measured pressure can be detected by measuring this capacitance value.

2 (a) to 2 (e) are sectional views of respective steps for explaining the method of manufacturing the capacitance type pressure sensor shown in FIG. First, as shown in FIG. 2A, the first sapphire substrate 21 having a relatively large thickness is subjected to groove processing by dry etching to form a groove 21a having a desired shape on one surface. Next, as shown in FIG. 2B, a second sapphire substrate 22 having a relatively thin plate is bonded onto the sapphire substrate 21 having the groove 21a formed therein. In this case, the direct bonding without the bonding material of the mirror-like substrates is well known in the silicon substrates, but the sapphire substrates 21 and 22 are well known.
Similarly, the direct joining is possible. Ie the first
After bonding the sapphire substrate 21 and the second sapphire substrate 22 at room temperature, a high temperature heat treatment is performed to strengthen the bond.

Next, as shown in FIG. 2C, an opening H communicating with the groove 21a of the first sapphire substrate 21 is formed in the second sapphire substrate 22 by dry etching or the like. Next, a conductive thin film is formed on the surface of the second sapphire substrate 22 and patterned to form the movable electrode 6 having a desired shape.
To form. The conductive thin film can be formed by a dry film forming method such as CVD, vapor deposition, or sputtering, which is used in ordinary semiconductor processes. Next, as shown in FIG. 2 (d), a groove process by dry etching is performed on one surface by a process similar to the above-described process to form grooves 23a and 23b having a desired shape.
Further, a conductive thin film is formed on the bottom surface of the groove 23a, and patterning is performed to form the fixed electrode 8 having a desired shape.
The sapphire substrate 23 is attached to the surface side of the second sapphire substrate 22 so that both electrode surfaces face each other and is bonded by the above-mentioned direct bonding method.

Next, after polishing the opposite surface side of the third sapphire substrate 23 bonded to the second sapphire substrate 22 to the position shown by the broken line, as shown in FIG.
The sapphire substrate 23 of FIG.
As shown in FIG. 1A, the fourth sapphire substrate 24 having the groove 24a formed in the same shape as that in FIG.
The sensor structure as shown in FIG.

In the electrostatic capacitance type pressure sensor constructed as described above, the gap G between the movable electrode 6 and the fixed electrode 8 constituting the capacitor structure C whose capacitance value changes according to the measured pressure is the frame body 1, The first diaphragm 2 and the second diaphragm 3 are completely sealed by being isolated from the external environment,
Since a vacuum or a gas is sealed inside and is isolated from the outside atmosphere and the like, an error caused by environmental changes such as humidity is eliminated. Further, no dew condensation occurs on the electrode surfaces of the movable electrode 6 and the fixed electrode 8 forming the capacitor structure C, and fine dust is not mixed between the movable electrode 6 and the fixed electrode 8. There is no error caused by dust.

Further, according to this structure, when the measured pressure is zero and the pressure P1 = the pressure P2 = the atmospheric pressure, when the atmospheric pressure fluctuates, the distance between the first diaphragm 2 and the second diaphragm 3 is increased. When the inside of the cavity is vacuum, the first diaphragm 2 and the second diaphragm 3 change in accordance with the pressure difference between the first diaphragm 2 and the second diaphragm 3 and the outside, except for the portion bonded to the beam 4. However, since the beam 4 does not change even when the first diaphragm 2 and the second diaphragm 3 are displaced, the gap G between the movable electrode 6 and the fixed electrode 8 does not change.
In principle, the capacitance value of the capacitor structure C whose capacitance value changes according to the measured pressure is not affected by atmospheric pressure fluctuation.

Further, according to such a configuration, when the cavity is filled with gas, the change in the pressure in the cavity due to the temperature change is changed by the first diaphragm other than the portion bonded to the beam 4. 2 and the second diaphragm 3, the gap G between the movable electrode 6 and the fixed electrode 8 does not change, so the capacitance value of the capacitor structure C whose capacitance value changes according to the measured pressure is the first diaphragm. The change in the cavity internal pressure between the second diaphragm 2 and the second diaphragm 3 is hardly affected. That is, the error caused by the change in the pressure inside the closed cavity due to the temperature change is eliminated.

(Embodiment 2) FIG. 3 is a diagram showing the construction of another embodiment of the capacitance type pressure sensor according to the present invention.
3A is a plan view, and FIG. 3B is a sectional view taken along the line BB ′ in FIG. 3A. The same parts as those in FIG. To do. In FIG. 3, reference numeral 9 denotes a fixed electrode support plate which is arranged substantially in parallel between the movable electrode support plate 5 and the second diaphragm 3 and which is supported and fixed to the inner wall surface of the frame body 1 by inserting the beam 4 therein. Is a movable electrode made of a conductive thin film formed on the opposite surface side of the movable electrode 6 formed on the movable electrode supporting plate 5, and 11 is an interelectrode gap G on the surface of the fixed electrode supporting plate 9 facing the movable electrode 10. The movable electrode 10 and the fixed electrode 11 are opposed to each other via an interelectrode gap G to form a capacitor structure.

Therefore, in this sensor structure,
The movable electrode 6 and the fixed electrode 8 form a first capacitor structure C1.
Is formed, the second capacitor structure C2 is formed by the movable electrode 10 and the fixed electrode 11, and the inside of the frame body 1 in which these capacitor structures C1 and C2 are formed is completely sealed by being isolated from the external environment. Then, a vacuum or gas is enclosed in the interior thereof to form a capacitive sensor element.

The capacitance type pressure sensor constructed as described above has a measurement pressure P1 of environment 1 and a measurement pressure P2 of environment 2.
A first capacitor structure C1 that changes according to the pressure difference between
Since the second capacitor structure C2 and the second capacitor structure C2 are formed, the pressure difference between the first capacitor structure C1 and the second capacitor structure C2 is output to output the base capacitance value (capacity when there is no pressure difference). Value) is not included, and only the amount of change in the capacity value according to the pressure difference is included. For this reason, the dynamic range becomes large, and more accurate measurement becomes possible.

(Embodiment 3) FIGS. 4A and 4B are views showing the configuration of a capacitance type pressure sensor according to still another embodiment of the present invention. FIG. 4A is a plan view and FIG. 4B is FIG. B- in (a)
FIG. 2 is a cross-sectional view taken along line B ′, and the same parts as those in FIG. In FIG.
The difference from FIG. 1 is that the first diaphragm 2 ′ is formed with a thick portion 2 a protruding inward, and the thick portion 2 a has an interelectrode gap G on the surface facing the fixed electrode 8. The movable electrode 6 is formed therethrough. A beam 4 is connected to and fixed to the thick portion 2a. In this case as well, the movable electrode 6 and the fixed electrode 8 are arranged so as to face each other with the interelectrode gap G interposed therebetween to form the capacitor structure C.

Even with such a structure, the same effect as that of the first embodiment can be obtained. Also, the first diaphragm 2 '
Since the thick portion 2a is provided in the above, it is easier in terms of manufacturing technology to manufacture the thick diaphragm than the structure of the movable electrode 6 fixed to the beam 4 in the first embodiment.
Manufacturing of the capacitive sensor element is simple and easy.

5 (a) to 5 (d) are cross-sectional views of respective steps for explaining the method of manufacturing the capacitance type pressure sensor shown in FIG. First, as shown in FIG. 5A, the first sapphire substrate 25 having a relatively large plate thickness is subjected to groove processing by dry etching to form a groove 25a having a desired shape on one surface. Next, as shown in FIG. 5B, on one surface of the sapphire substrate 25 having the groove 25a formed therein, a groove is formed by dry etching on one surface by a process similar to that described above to form the groove 26a, 26b having a desired shape. The formed second sapphire substrate 26 is made to face each other with the groove forming surfaces facing each other, and is bonded by the direct bonding method described above.

Next, after polishing the surface side of the second sapphire substrate 26 opposite to the bonding surface to the position shown by the broken line,
As shown in FIG. 5C, this second sapphire substrate 26
A conductive thin film is formed on the polished surface side of and patterned to form the fixed electrode 8 having a desired shape.

Next, as shown in FIG. 5 (d), a groove is formed by dry etching on one surface by a process similar to the above-described process to form grooves 27a and 27b having a desired shape, and the bottom surface of the groove 27b is further formed. Forming a conductive thin film on
The third sapphire substrate 27 on which the movable electrode 6 having a desired shape is formed by patterning is used as the second sapphire substrate 2
Both electrode surfaces are made to face each other on the front surface side of 6 and bonded by the above-mentioned direct bonding method, whereby the sensor structure as shown in FIG. 4 is completed.

(Embodiment 4) FIGS. 6A and 6B are views showing the configuration of a capacitance type pressure sensor according to still another embodiment of the present invention. FIG. 6A is a plan view and FIG. 6B is FIG. B- in (a)
FIG. 4 is a cross-sectional view taken along line B ′, and the same parts as those in FIG. In FIG.
4 is different from FIG. 4 in that the second diaphragm 3'is formed with a thick portion 3a protruding inward, and between the thick portion 3a and the thick portion 2a of the first diaphragm 2 '. The beam 4 is connected to and fixed to.

The thick wall portion 3 of the second diaphragm 2 '
The movable electrode 10 is formed on a, and the inter-electrode gap G is formed on the back side of the fixed electrode support plate 7 facing the movable electrode 10.
The fixed electrode 11 made of a conductive thin film is formed through the via to form a capacitor structure.

Therefore, in this sensor structure,
The movable electrode 6 and the fixed electrode 8 form a first capacitor structure C1.
Is formed, the second capacitor structure C2 is formed by the movable electrode 10 and the fixed electrode 11, and the inside of the frame body 1 in which these capacitor structures C1 and C2 are formed is completely sealed by being isolated from the external environment. Then, a vacuum or gas is enclosed in the interior thereof to form a capacitive sensor element.

Even with such a configuration, the same effect as that of the above-described third embodiment can be obtained, and the first diaphragm 2'and the second diaphragm 3'can be formed by the same member, so that the capacitive sensor The fabrication of the device becomes easier and easier.

In the embodiment described above, the frame 1, the first diaphragm 2, the second diaphragm 3, the beam 4, the movable electrode support plate 5, the fixed electrode support plate 7 and the fixed electrode support plate 7 are used. The case of using sapphire has been described, but the same structure can be obtained by using silicon, Pyrex, quartz glass, or the like.

Further, in the above-described embodiment, the case where the first diaphragm 2 and the second diaphragm 3 have a quadrangular shape has been described. However, the shape may be the same with a round shape or another shape.

[0035]

As described above, according to the present invention,
Since the hollow portion between the movable electrode and the fixed electrode forming the capacitor structure whose capacitance value changes according to the measured pressure is isolated from the external environment, the following effects can be obtained. No errors are generated due to environmental changes such as humidity. No dew condensation occurs on the surfaces of the movable electrode and the fixed electrode, and fine dust is not mixed between these electrodes, so that there is no error caused by the dew condensation or dust. Almost unaffected by fluctuations in atmospheric pressure. An error caused by a change in the cavity internal pressure between the sealed first diaphragm part and the second diaphragm part due to a temperature change hardly occurs. Therefore, it is possible to completely eliminate all error factors caused by changes in the atmospheric environment, so it is possible to measure the pressure range from low pressure to high pressure without being affected by environmental changes, and with high accuracy and reliability. It is possible to obtain extremely excellent effects such as high pressure measurement.

[Brief description of drawings]

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

FIG. 2 is a cross-sectional view of a step illustrating a method for manufacturing the capacitance type pressure sensor shown in FIG.

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

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

5A to 5D are cross-sectional views of steps for explaining a method of manufacturing the capacitance type pressure sensor shown in FIG.

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

FIG. 7 is a cross-sectional view illustrating a configuration of a conventional capacitance type pressure sensor.

[Explanation of symbols]

 1 frame 2 first diaphragm 2a thick part 2'first diaphragm 3 second diaphragm 3'second diaphragm 3a thick part 4 beam 5 movable electrode support plate 6 movable electrode 7 fixed electrode support plate 8 fixed Electrode 9 Fixed electrode support plate 10 Movable electrode 11 Fixed electrode 12 Fixed electrode support plate 13 Fixed electrode support plate C1 First capacitor structure C2 Second capacitor structure P1 Measured pressure P2 Measured pressure G Gap

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takaro Kuroiwa 1-12-2 Kawana, Fujisawa-shi, Kanagawa Yamatake Honeywell Co., Ltd. Fujisawa Plant (72) Inventor Takashi Masuda 1-12-2 Kawana, Fujisawa-shi, Kanagawa Yamatake Honeywell Co., Ltd. Fujisawa Factory

Claims (2)

[Claims] 1. A diaphragm support portion formed in a substantially cylindrical shape, a first diaphragm portion and a second diaphragm portion formed to face each other so as to close both ends of the diaphragm support portion, and the first diaphragm portion and the second diaphragm portion. The first diaphragm portion and the second diaphragm portion are connected to the facing surfaces of the first diaphragm portion and the second diaphragm portion.
A beam portion for fixing the diaphragm portion to a movable electrode supporting portion having a movable electrode formed on at least one surface thereof and supported by the beam portion so as to face the first diaphragm portion and the second diaphragm portion. A fixed electrode is formed on at least one surface of the diaphragm supporting portion that faces the movable electrode supporting portion and is supported by inserting the beam portion through the inner wall surface of the diaphragm supporting portion and the movable electrode and the cavity portion. And a fixed electrode support part, wherein the inside of the diaphragm support part is isolated from the outside and a capacitor structure is formed between the movable electrode and the fixed electrode. 2. A diaphragm support portion formed in a substantially cylindrical shape, and a first diaphragm formed to face each other so as to close both ends of the diaphragm support portion and having a thick portion on at least one of the facing surfaces. And a second diaphragm part, and a first diaphragm part and a second diaphragm part, which are connected to the facing surfaces of the first diaphragm part and the second diaphragm part having a thick part on at least one of the first diaphragm part and the second diaphragm part. A movable electrode formed on a thick wall portion of at least one of the first diaphragm portion and the second diaphragm portion, and a beam portion for fixing the first diaphragm portion and the first diaphragm portion on the inner wall surface of the diaphragm support portion. The second electrode is fixed to at least one surface that faces the diaphragm portion and that is supported by inserting the beam portion and that faces the movable electrode through the cavity portion. A fixed electrode supporting plate portion on which an electrode is formed, wherein the inside of the diaphragm supporting portion is isolated from the outside, and a capacitor structure is formed between the movable electrode and the fixed electrode. Pressure sensor.