JP2896728B2 - 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 capacitance type pressure sensor having a diaphragm structure for detecting a change in measured pressure in a capacitive manner.

[0002]

2. Description of the Related Art Conventionally, as a capacitive 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 or the like on which is formed
2 and a silicon wafer 34 in which a movable electrode 33 is formed in a concave portion on the front surface, the electrode surfaces of which are arranged to face each other, and a peripheral portion thereof is 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 measurement pressure P1 increases, the diaphragm D is deformed, and the gap G between the fixed electrode 31 and the movable electrode 33 changes (in this case, the gap G is changed). Becomes smaller), and the capacitance value of the capacitor composed of the fixed electrode 31 and the movable electrode 33 changes. By measuring this capacitance value, the measured pressure P1 can be detected.

[0004]

However, the capacitance type pressure sensor configured as described above has a problem in that the environment between the fixed electrode 31 and the movable electrode 33 is changed when an environmental change such as atmospheric pressure humidity occurs. There is an error factor that the permittivity of the air in the gap G changes in response to the change in humidity, thereby changing the capacitor capacitance value due to factors other than the measured pressure.

[0005] As a solution to such a problem,
An electrostatic capacitance type pressure sensor provided with a reference capacitor for removing an error factor generated by a change in environment such as humidity has been proposed (Japanese Patent Application Laid-Open No. 63-308529). This capacitance type pressure sensor has a sensing capacitor whose capacitance value changes according to a 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 two electrodes with the reference capacitor, it is possible to eliminate an error factor caused by an environmental change such as humidity.

However, the capacitance type pressure sensor configured as described above has a problem that it cannot remove an error factor when dew condensation on the capacitor electrode surface or minute dust enters the capacitor electrode. there were. In addition, the occurrence of dew condensation is an inevitable phenomenon when the temperature of the medium for measuring pressure is lower than the atmospheric temperature, and the intrusion of dust is an inevitable problem since the presence of a pressure introduction hole for atmospheric pressure. is there. Therefore, these problems cause an error in pressure measurement, and have a problem in that highly accurate and highly reliable pressure measurement cannot be performed.

[0007] Accordingly, the present invention has been made to solve the above-mentioned conventional problems, and its object is to reduce the pressure from a small pressure without being affected by changes in the atmospheric environment including the problem of condensation and dust. An object of the present invention is to provide a capacitance type pressure sensor capable of measuring a pressure range up to a high pressure capacitively. Another object of the present invention is to provide a capacitance type pressure sensor capable of suppressing occurrence of an error due to a change in environment and enabling highly accurate and highly reliable pressure measurement.

[0008]

According to a first aspect of the present invention, there is provided a diaphragm support having a substantially cylindrical shape and opposing each other so as to close both ends of the diaphragm support. A first diaphragm portion and a second diaphragm portion formed by the first diaphragm portion and a first diaphragm portion and a second diaphragm portion which are connected to the opposing surfaces of the first diaphragm portion and the second diaphragm portion. A beam portion to be fixed, and the first diaphragm portion and the second
A movable electrode support portion which is supported opposite to the diaphragm portion and has a movable electrode formed on at least one surface, and which is supported on the inner wall surface of the diaphragm support portion by facing the movable electrode support portion and passing the beam portion. And a fixed electrode support having a fixed electrode formed on at least one surface facing the movable electrode via the cavity, wherein the inside of the diaphragm support is isolated from the outside and between the movable electrode and the fixed electrode. In which a capacitor structure is formed. Also, the second
The invention provides a diaphragm support portion formed in a substantially cylindrical shape, a first diaphragm portion formed to face both ends of the diaphragm support portion so as to close both ends thereof, and having a thick portion on at least one of the facing surfaces. A beam that is connected to a second diaphragm portion and a facing surface of the first diaphragm portion and the second diaphragm portion having at least one thick portion and that fixes the first diaphragm portion and the second diaphragm portion. A movable electrode formed on a thick portion of at least one of the first diaphragm portion and the second diaphragm portion; and a first diaphragm portion and a second diaphragm portion facing the inner wall surface of the diaphragm support portion. A movable electrode and a fixed electrode support having a fixed electrode formed on at least one surface opposed to the movable electrode via the cavity. , 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 measured pressure (for example, atmospheric pressure)
P1 is applied to the first diaphragm section and the measured pressure P2
Is set to be applied to the second diaphragm section, when a pressure difference occurs between the measurement pressure P1 and the measurement pressure P2, the first diaphragm section, the second diaphragm section, and the beam section are integrated. The gap 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.This capacitance value is measured. You can know the pressure.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings. (Embodiment 1) 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, and FIG. 1 (b) is FIG. 1 (a). 3 is a sectional view taken along line BB ′ of FIG. In the figure, reference numeral 1 denotes a frame as a diaphragm support formed in a substantially cylindrical shape, and reference numerals 2 and 3 denote first thin-walled first portions formed at both open end portions of the frame 1, respectively. And the second diaphragm. The frame 1, the first diaphragm 2, and the second diaphragm 3 are formed 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.
A movable electrode support plate 6 supported and fixed to the beam 4 so as to face the first diaphragm 2 and the second diaphragm 3;
Is a movable electrode formed of a conductive thin film formed on the upper surface of the movable electrode support plate 5; 7 is a fixed electrode which is supported on the inner wall surface of the frame 1 by being opposed to the movable electrode support plate 5 and through the beam 4. It is a support plate.

The beam 4, the movable electrode support plate 5 and the fixed electrode support plate 6 are similarly formed of, for example, sapphire glass. Reference numeral 8 denotes an inter-electrode gap G (about 1 μm) on a surface of the fixed electrode support plate 7 facing the movable electrode 6.
) Is a fixed electrode made of a conductive thin film formed through the film.

The movable electrode 6 and the fixed electrode 8 are opposed to each other with a gap G between the electrodes to form a capacitor structure C, thereby forming a capacitive sensor element. Further, the inside of the frame body 1 in which the capacitor structure C is formed is completely sealed, being isolated from the external environment, and a vacuum or gas is sealed therein.

In the capacitance type pressure sensor configured 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 changed to the second diaphragm 3. Set to be applied to As a result, the measurement pressure P2 is applied to the second diaphragm 3, and when a pressure difference occurs between the measurement pressure P1 and the measurement pressure P2, the first diaphragm 2, the second diaphragm 3, and the beam 4 are integrated. And 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 capacitor and the fixed electrode 8 changes. By measuring this capacitance value, the measured pressure can be detected.

FIGS. 2A to 2E are cross-sectional views of respective steps for explaining a 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 processed by dry etching to form grooves 21a having a desired shape on one surface. Next, as shown in FIG. 2B, a second sapphire substrate 22 having a relatively small thickness is laminated on the sapphire substrate 21 having the groove 21a formed thereon. In this case, the direct bonding without the bonding material between the mirror substrates is well known among the silicon substrates, but the sapphire substrates 21 and 22 are well known.
Can also be directly joined. That is, the first
After the sapphire substrate 21 and the second sapphire substrate 22 are bonded at room temperature, a high-temperature heat treatment is performed to strengthen the bonding.

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 is patterned to form a 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 a normal semiconductor process. Next, as shown in FIG. 2D, a groove is formed by dry etching on one surface by a process similar to the above-described process to form desired grooves 23a and 23b.
Further, a conductive thin film is formed on the bottom surface of the groove 23a and is patterned to form the fixed electrode 8 having a desired shape.
The sapphire substrate 23 is bonded to the surface side of the second sapphire substrate 22 with the two electrode surfaces facing each other and bonded by the direct bonding method described above.

Next, the opposite surface of the third sapphire substrate 23 bonded to the second sapphire substrate 22 is polished to a position shown by a broken line, and then the third sapphire substrate 23 is polished as shown in FIG.
The sapphire substrate 23 of FIG.
The fourth sapphire substrate 24 in which the groove 24a is processed in the same shape as that of FIG.
Is completed.

In the capacitance type pressure sensor having the above-described configuration, 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 defined by the frame 1, A first diaphragm 2 and a second diaphragm 3 that are completely sealed and isolated from the external environment;
Since a vacuum or gas is sealed in the inside and is isolated from the outside atmosphere or the like, errors due to environmental changes such as humidity do not occur. In addition, there is no dew condensation on the electrode surfaces of the movable electrode 6 and the fixed electrode 8 constituting the capacitor structure C, and no minute dust is mixed between the movable electrode 6 and the fixed electrode 8. Error caused by dust and dust is eliminated.

According to such a configuration, when the measured pressure is zero and the pressure P1 = the pressure P2 = the atmospheric pressure, when the atmospheric pressure fluctuates, the pressure between the first diaphragm 2 and the second diaphragm 3 is changed. When the inside of the cavity is a vacuum, the first diaphragm 2 and the second diaphragm 3 change according to the pressure difference with the outside except for the portion joined to the beam 4. However, since the beam 4 does not change even if 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.
The capacitance value of the capacitor structure C whose capacitance value changes according to the measurement pressure is not affected by the atmospheric pressure fluctuation in principle.

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

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

Therefore, in this sensor structure,
The first capacitor structure C1 is composed of the movable electrode 6 and the fixed electrode 8.
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 1 on which these capacitor structures C1 and C2 are formed is completely sealed off from the external environment. A vacuum or gas is sealed in the inside to form a capacitive sensor element.

The capacitance type pressure sensor configured as described above has a measurement pressure P1 of the environment 1 and a measurement pressure P2 of the environment 2
The first capacitor structure C1 that changes according to the pressure difference
And the second capacitor structure C2 is formed, so that the pressure difference between the first capacitor structure C1 and the second capacitor structure C2 is output, so that the output value has a base capacitance value (capacity when there is no pressure difference). Value) is included, and only the change in the capacitance value according to the pressure difference is included. For this reason, the dynamic range is increased, and more accurate measurement is possible.

(Embodiment 3) FIGS. 4 (a) and 4 (b) show a configuration of a capacitance type pressure sensor according to still another embodiment of the present invention, wherein FIG. 4 (a) is a plan view and FIG. (A) B-
FIG. 3 is a cross-sectional view taken along the 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 projecting inward from the first diaphragm 2 ′. The movable electrode 6 is formed through the interposition. Further, the beam 4 is connected and fixed to the thick portion 2a. Also in this case, the movable electrode 6 and the fixed electrode 8 are opposed to each other with the inter-electrode gap G therebetween to form the capacitor structure C.

With such a configuration, substantially the same effects as in the first embodiment can be obtained. Also, the first diaphragm 2 '
Since the thick portion 2a is provided in the first embodiment, it is easier in terms of manufacturing technology to manufacture a thick diaphragm than the structure of the movable electrode 6 fixed to the beam 4 in the first embodiment.
The production of the capacitive sensor element is simple and easy.

FIGS. 5A to 5D are cross-sectional views of respective steps for explaining a 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 thickness is processed by dry etching to form grooves 25a having a desired shape on one surface. Next, as shown in FIG. 5B, on the sapphire substrate 25 on which the groove 25a is formed, a groove is formed by dry etching on one surface by a process similar to the above-described process, thereby forming grooves 26a and 26b having desired shapes. The formed second sapphire substrate 26 is bonded to each other with the groove forming surfaces facing each other and by the direct bonding method described above.

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

Next, as shown in FIG. 5D, 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 desired shapes, and further, the bottom surface of the groove 27b is formed. A conductive thin film is formed on
The third sapphire substrate 27 on which the movable electrode 6 having the required shape is formed by patterning is replaced with the second sapphire substrate 2
By making the two electrode surfaces face each other on the front surface side of 6 and bonding them together by the direct bonding method described above, the sensor structure as shown in FIG. 4 is completed.

(Embodiment 4) FIGS. 6 (a) and 6 (b) show a configuration of a capacitance type pressure sensor according to still another embodiment of the present invention. FIG. 6 (a) is a plan view and FIG. (A) B-
FIG. 5 is a cross-sectional view taken along the line B ′, in which the same parts as those in FIG. In FIG.
The difference from FIG. 4 is that the second diaphragm 3 'has a thick portion 3a protruding inward from the thick portion 3a and the thick portion 2a of the first diaphragm 2'. Has a structure in which the beam 4 is connected and fixed.

The thick portion 3 of the second diaphragm 2 '
a, a movable electrode 10 is formed on the back surface of the fixed electrode support plate 7 facing the movable electrode 10.
A fixed electrode 11 made of a conductive thin film is formed through the substrate to form a capacitor structure.

Therefore, in this sensor structure,
The first capacitor structure C1 is composed of the movable electrode 6 and the fixed electrode 8.
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 1 on which these capacitor structures C1 and C2 are formed is completely sealed off from the external environment. A vacuum or gas is sealed in the inside to form a capacitive sensor element.

In such a structure, the same effect as that of the third embodiment can be obtained, and the first diaphragm 2 'and the second diaphragm 3' can be formed of the same member. The manufacture of the device is simpler and easier.

In the above-described embodiment, 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 provided. Although the case of forming using sapphire has been described, a similar configuration can be made 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 are square is described. However, the same configuration can be applied to the case of a round shape or another shape.

[0035]

As described above, according to the present invention,
Since the cavity between the movable electrode and the fixed electrode forming the capacitor structure whose capacitance value changes in accordance with the measured pressure is configured to be isolated from the external environment, the following effects can be obtained. There is no error caused by environmental changes such as humidity. There is no dew condensation on the surfaces of the movable electrode and the fixed electrode, and no minute dust is mixed between these electrodes. Therefore, there is no error caused by the dew or dust. Hardly affected by fluctuations in atmospheric pressure. Almost no error occurs due to a change in the internal pressure of the cavity between the sealed first diaphragm portion and the second diaphragm portion due to a temperature change. Therefore, all error factors caused by changes in the atmospheric environment can be completely removed, enabling measurement of pressure ranges from micro pressure to high pressure without being affected by environmental changes, and high accuracy and reliability. An extremely excellent effect, such as a high pressure measurement, 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 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 embodiment 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.

FIG. 5 is a cross-sectional view of a step for explaining the method for manufacturing the capacitive pressure sensor shown in FIG.

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 cross-sectional view illustrating a configuration of a conventional capacitive pressure sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Frame 2 1st diaphragm 2a Thick part 2 '1st diaphragm 3 2nd diaphragm 3' 2nd 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 Measurement pressure P2 Measurement pressure G gap

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takaro Kuroiwa 1-12-2 Kawana, Fujisawa-shi, Kanagawa Prefecture Inside the Fujisawa Plant of Yamatake Honeywell Co., Ltd. (72) Inventor Takashi Masuda 1-12-2 Kawana, Fujisawa-shi, Kanagawa Prefecture No. Takeshi Yamatake Honeywell Co., Ltd. Fujisawa Plant (56) References JP-A-58-44324 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01L 9/12 G01L 19/06

Claims (2)

(57) [Claims] 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; The first diaphragm portion and the second diaphragm portion are connected to opposing surfaces of the first diaphragm portion and the second diaphragm portion.
A beam portion for fixing the diaphragm portion to the movable electrode supporting portion, the movable electrode supporting portion being supported by the beam portion to face the first diaphragm portion and the second diaphragm portion, and having a movable electrode formed on at least one surface thereof; A fixed electrode is formed on at least one surface of the diaphragm supporting portion which is opposed to the movable electrode supporting portion on the inner wall surface of the diaphragm supporting portion and inserted through the beam portion, and is opposed to the movable electrode via a cavity. A fixed electrode support portion, wherein the inside of the diaphragm support portion is isolated from the outside, and a capacitor structure is formed between the movable electrode and the fixed electrode. 2. A first diaphragm having a substantially cylindrical shape, and a first diaphragm formed to face both ends of the diaphragm support so as to close both ends thereof and having a thick portion on at least one of the opposed surfaces. And a second diaphragm portion, which are connected to opposing surfaces of the first diaphragm portion and the second diaphragm portion each having a thick portion on at least one of the first diaphragm portion and the second diaphragm portion. A movable electrode formed on at least one thick portion of the first diaphragm portion and the second diaphragm portion; and a first diaphragm portion and a second portion on an inner wall surface of the diaphragm support portion. 2 and is fixed to at least one surface facing the movable electrode through the hollow portion while being supported by being inserted through the beam portion. A fixed electrode support plate portion on which electrodes are formed, wherein the inside of the diaphragm support portion is isolated from the outside and a capacitor structure is formed between the movable electrode and the fixed electrode. Pressure sensor.