JPH07174652A - Semiconductor pressure sensor and its manufacture as well as pressure detection method - Google Patents

Abstract

PURPOSE:To provide a semiconductor pressure sensor which can detect a change in the pressure of a high-pressure fluid. CONSTITUTION:A large-area diaphragm 1a and a small-area diaphragm are supported by a square frame-shaped frame 2, and a movable electrode 13 is formed on the surface of the small-area diaphragm. A glass cover 3 is superposed on, and bonded to, the frame 2, a hollow 4 is formed at the inside of the cover 3 so as to face the diaphragm 1a and the small-area diaphragm, and a fixed electrode 14 is formed in the hollow 4 so as to face the moving electrode 13. At this time, a deep hollow 4a is formed on the diaphragm 1a, a shallow hollow 4b is formed $ the small-area diaphragm, and a liquid (preferably, a noncompressive liquid) 11 is filled into the hollow 4. Another galss cover 9 is superposed up on, and bonded to, the rear surface of the frame 2, an airtight space 10 is formed on the rear surface of the small-area diaphragm, a gas 12 is filled so as to keep the airtight space 10 at a definite pressure, and a pressure sensor E is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor pressure sensor, a manufacturing method thereof and a pressure detecting method. In particular,
The present invention relates to a semiconductor pressure sensor for detecting the pressure of a fluid such as air or gas, a manufacturing method thereof, and a pressure detection method.

[0002]

2. Description of the Related Art Conventionally, two types of pressure sensors called a capacitance type pressure sensor and a piezoresistive type pressure sensor have been developed and put into practical use as semiconductor pressure sensors. These semiconductor pressure sensors detect pressure fluctuations of a fluid such as air or liquid under a minute pressure, and measure the pressure of the applied fluid (absolute pressure or relative pressure with respect to a reference pressure).

In these pressure sensors, when a fluid pressure is applied to a thin diaphragm, the diaphragm bends according to the magnitude of the applied pressure. Therefore, the amount of applied pressure is detected by detecting the amount of deflection of this diaphragm as the change in the value of the electrostatic capacitance formed between the movable electrode formed on the diaphragm and the fixed electrode formed on the inner surface of the fixed substrate. You can know the size of. Further, the magnitude of the pressure can be known by detecting the change in the resistance value of the strain detecting element such as the piezoresistive element formed on the diaphragm.

[0004]

However, as the pressure applied to the diaphragm increases, the pressure applied to the diaphragm and the amount of flexure of the diaphragm are not directly proportional, and the linearity of the pressure sensor is poor. Further, in order to improve the linearity of the pressure sensor, it is conceivable that two pressure sensors having different detection sensitivities are used and the output difference between the two pressure sensors is measured to obtain a differential output. It was very difficult to apply the same pressure to the two simultaneously, and the wiring for measuring the output difference of the pressure sensor was complicated.

Further, since the diaphragm bends toward the inner surface of the fixed substrate due to the applied pressure, the diaphragm and the inner surface of the fixed substrate come into contact with each other as the applied pressure increases, and the diaphragm can bend further. However, the detection range was narrow.

On the other hand, as shown in FIG. 10, the pressure introducing port 23 is formed from the upper surface of the diaphragm 22 supported by the supporting substrate 21.
The pressure sensor G configured so that the diaphragm 22 separates from the inner surface of the fixed substrate 24 in accordance with the pressure applied through the diaphragm.
However, in such a pressure sensor G, it is necessary to open the pressure introduction port 23 in the fixed substrate 24 made of a glass substrate or the like, which makes the production of the pressure sensor G very difficult. It was Further, in the pressure sensor G having such a structure, there is a problem that moisture or the like enters the pressure chamber 25 to damage the diaphragm 22, or the sensitivity is lowered due to dust or the like. . Also,
There is also a problem in that the dielectric constant between the electrodes 26, 26 changes due to moisture in the pressure chamber 25 and the like, which causes measurement errors and variations in the measurement pressure.

Further, since the diaphragm 22 is formed in a thin film shape, it is impossible to measure the pressure under high pressure, and if the pressure is to be measured under high pressure, the diaphragm 22 must be formed thick, and It was difficult to measure minute pressure fluctuations below. Further, recently, there is an increasing need for a pressure sensor that can measure pressure fluctuations under high pressure.

The present invention has been made in view of the above-mentioned drawbacks of the conventional examples, and an object thereof is to widen the detection range of the pressure sensor and improve the linearity. Another object of the present invention is to provide a pressure sensor that can detect minute pressure fluctuations in high-pressure fluid.

[0009]

The semiconductor pressure sensor of the present invention is a semiconductor pressure sensor in which a fixed substrate is bonded to at least one surface of a supporting substrate supporting the diaphragm, and two diaphragms are supported by the fixed substrate and the supporting substrate. It is characterized in that the pressure detection means having different detection sensitivities is configured on each of the diaphragms so as to be supported by the supporting substrate so as to face the same closed space provided between the substrate and the substrate.

Further, the areas of the diaphragms may be different, and the thicknesses of the diaphragms may be different. Furthermore, the distance between each diaphragm and the fixed substrate may be different. These supporting substrate and diaphragm can be made of silicon, and the fixed substrate can be made of glass.

A pressure detecting method according to the present invention is a method for detecting pressure by the pressure sensor, which is characterized by detecting a difference between outputs of the pressure detecting means provided on the two diaphragms and having different detection sensitivities. I am trying.

A second pressure sensor of the present invention is a semiconductor pressure sensor in which a fixed substrate is bonded to one surface of a support substrate supporting a diaphragm, and two diaphragms are provided between the fixed substrate and the support substrate. The same closed space provided between them is supported by the supporting substrate, the closed space is filled with a fluid having a constant pressure, and the closed space forming substrate is bonded to the remaining surface of the supporting substrate. A closed space is formed between one of the diaphragms and the closed space forming substrate, and the pressure in the closed space is maintained at substantially the same pressure as the pressure in the closed space to form the closed space. The diaphragm is characterized in that a pressure detecting means is provided.

Further, a closed space forming substrate having a pressure introducing device for guiding pressure to the pressure sensor may be bonded.

Further, in the second pressure sensor, the support substrate and the diaphragm are made of silicon, and the fixed substrate and the closed space forming substrate are made of glass, and a glass / silicon / glass substrate is formed. It may have a three-layer structure.

The method of manufacturing the pressure sensor of the present invention is
A second method for manufacturing a semiconductor pressure sensor according to the present invention is characterized in that the closed space forming substrate is joined under a constant pressure to form the closed space.

Further, in the first and second pressure sensors of the present invention, the pressure is measured by measuring a change in electrostatic capacitance between a movable electrode provided on the diaphragm and a fixed electrode provided on the fixed substrate. The pressure detecting means may be configured as the detecting means, or the pressure detecting means may be configured by measuring the change in the resistance value of the strain detecting element provided on the diaphragm.

[0017]

In the first semiconductor pressure sensor of the present invention,
Since the two diaphragms support the pressure detection means having different detection sensitivities facing the same closed space on the support substrate, the differential pressure can be detected by one pressure sensor by detecting the output difference between the two pressure detection means. A pressure sensor having an output can be created. Therefore, the pressure introducing device for obtaining the differential output is not complicated unlike the conventional pressure sensor, and it is not necessary to lay out the wiring for connecting the two pressure sensors. Further, since the diaphragm provided with the pressure detection means faces the same closed space, the reference pressures can be the same and the measurement error can be reduced. Therefore, in the first pressure sensor of the present invention, the linearity is improved, and the pressure can be measured accurately in a wide pressure range. Further, the pressure sensor can be downsized.

For this purpose, for example, by supporting diaphragms having different areas, it is possible to construct pressure detecting means having different detection sensitivities. Further, the pressure detection means having different detection sensitivities can be configured by supporting the diaphragms having different thicknesses or by making the distance between the diaphragms and the fixed substrate different.

For this purpose, for example, the support substrate and the diaphragm can be made of silicon, and the fixed substrate can be made of glass. Further, if the support substrate and the diaphragm are made of silicon, the support substrate and the diaphragm can be easily made integrally by a semiconductor manufacturing technique or the like, and the detection circuit and the like can be easily made.

In the second semiconductor pressure sensor of the present invention, since the two diaphragms face the same closed space and are supported by the supporting substrate, and the closed space is filled with the fluid, the pressure detecting means is The provided diaphragm can be displaced in the direction away from the fixed substrate. Therefore, even if the pressure is increased, the diaphragm does not come into contact with the fixed substrate, so that the measurement range of the pressure sensor can be widened. Further, since a closed space is formed between the diaphragm and the fixed substrate, moisture and dust do not enter from the outside, and the diaphragm is not damaged and the sensitivity is not lowered. Moreover, since the dielectric constant in the closed space is always constant, stable pressure measurement can be performed. Further, since it is not necessary to form the pressure introducing port on the fixed substrate, the manufacturing process can be simplified.

Further, since the closed space formed by the diaphragm provided with the pressure detecting means and the closed space forming substrate is maintained at a pressure almost equal to that of the fluid filled in the closed space, the diaphragm is It is possible to measure the pressure fluctuation under high pressure by displacing according to the pressure difference with the pressure filled in the closed space.

Further, in this pressure sensor, if a closed space forming substrate provided with a pressure introducing device is joined to a support substrate to form a closed space, pressure can be easily introduced into the pressure sensor, and a mounting substrate, etc. Can be easily attached to. Further, since a pressure introducing device is not required separately from the pressure sensor, it is possible to reduce the cost.

Further, the fixed substrate, the support substrate, and the closed space forming substrate are made of glass, silicon, and glass, respectively, and the pressure sensor has a three-layer structure of glass / silicon / glass, so that the thermal expansion coefficient is different. It is possible to alleviate the distortion caused by the above and improve the temperature characteristics.

According to the manufacturing method of the present invention, it is possible to easily maintain a constant pressure in the closed space.

[0025]

1 (a) and 1 (b) shows a pressure sensor A according to an embodiment of the present invention, in which FIG. 1 (a) is a sectional view thereof and FIG. 1 (b) is a plan view thereof. It is a figure. Pressure sensor A
Is a thin film diaphragm 1 having a large elastic area
a and a thin film diaphragm 1b having a small area are supported at their peripheral portions by a frame 2 having a rectangular frame shape. The diaphragm 1a, the diaphragm 1b, and the frame 2 are integrally formed from a silicon substrate (silicon wafer) by a semiconductor manufacturing technique. Diaphragm 1a
A conductive layer is formed on almost the entire upper surface of the substrate by ion implantation to form a movable electrode 5a. In addition, a conductive layer is formed on almost the entire upper surface of the diaphragm 1b by ion implantation, and a movable electrode 5b is formed. These two movable electrodes 5a and 5b are insulated and separated from each other by a pn junction or the like formed around the conductive layer.
The movable electrodes 5a and 5b are connected to the respective diaphragms 1
Alternatively, a metal thin film such as Al may be formed on the upper surfaces of a and 1b.

A glass cover 3 is provided on the upper surface of the frame 2.
And the peripheral portion of the cover 3 is joined to the frame 2 by an anodic joining method or the like. Further, a large recess 4 is formed on the inner surface of the cover 3 so that the diaphragm 1a and the diaphragm 1b can be elastically deformed freely in the thickness direction thereof so as to face the respective diaphragms 1a and 1b. Is filled with a gas 8 such as air having a constant pressure and serves as a reference pressure. A fixed electrode 6a is formed on the inner surface of the cover 3 so as to face the movable electrode 5a with a small gap therebetween, and a capacitor C _A is formed between the movable electrode 5a and the fixed electrode 6a. Further, a fixed electrode 6b is formed facing the movable electrode 5b with a small gap therebetween, and a capacitor C _B is formed between the movable electrode 5b and the fixed electrode 6b. Further, the same pressure can be simultaneously introduced to the lower surface of the diaphragm 1a and the lower surface of the diaphragm 1b.

Thus, the diaphragm 1 of the pressure sensor A
When pressure is applied to a and the diaphragm 1b, the diaphragm 1a and the diaphragm 1b are elastically deformed by the applied pressure, and the diaphragm 1a and the diaphragm 1b are displaced toward the inner surface of the cover 3 depending on the magnitude of the pressure. To do. Diaphragm 1a and diaphragm 1
b narrows each gap between the fixed electrode 6b gap and the movable electrode 5b of the displaced movable electrode 5a and the fixed electrode 6a, 2 two capacitors C _A configured in the pressure sensor A, the value of the capacitance of C _B Respectively change according to the magnitude of the applied pressure.

FIG. 2 shows the diaphragm 1a and the diaphragm.
Condensed between the frame 1b and the cover 3
SA C_A, C_BShows the relationship between the capacitance value of the
ing. Curve a is formed on the diaphragm 1a with a large area
Between the movable electrode 5a and the fixed electrode 6a
Indexer C_AThe change in the capacitance of
The movable electrode 5b formed on the diaphragm 1b and the fixed electrode
Capacitor C constructed between poles 6b_BChange the capacitance of
Is shown. A diaphra with a large area as shown in curve a.
Capacitor C configured in the frame 1a_AThe capacitance of
It increases in response to the applied pressure and then increases rapidly.
On the other hand, a controller configured on the diaphragm 1b having a small area
Densa C_BCapacitance of capacitor C_ACapacitance change
Although it is more gradual than
It is getting bigger. However, for example, these two condens
SA C_A, C_BThe capacitance of the
Frequency f by conversion circuit (Cf circuit)₁, F₂Converted to
After that, the difference between them (Δf = f 1-f₂) As
It is possible to know the magnitude of the applied pressure by
Two capacitors C with different detection characteristics_A, C_B
The linearity of the pressure sensor A
Can be improved. Moreover, this pressure sensor A
In that case, the diaphragm 1a and the diaphragm 1b are
Created from one silicon wafer by semiconductor manufacturing technology
The differential pressure sensor can be manufactured with a simple structure.
Can be made. Also, two conventional types with different sensitivities
Obtain a differential output by measuring the output difference of the pressure sensor
However, according to the pressure sensor A of the present invention, two
Pressure detection means with different detection sensitivities in one pressure sensor
Because it is configured,
Two pressure introducing devices are provided for each pressure sensor.
For connecting the output from the pressure sensor of
There is no need for complicated wiring work. Moreover, the reference pressure
Since the (pressure inside the depression 4) is common, the individual pressure
Smaller measurement error compared to configuring a reference pressure in the sensor
You can do it. Also, line up two pressure sensors
Space saving compared with the case of pressure sensor
Can be miniaturized.

Further, like the pressure sensor B shown in FIG. 3, strain detecting elements 7a and 7b such as piezoresistive elements and strain gauges whose resistance values change due to the strain generated on the upper surfaces of the two diaphragms 1a and 1b. Set up 2
It is also possible to detect the difference in change in resistance value caused by the displacement of the two diaphragms 1a and 1b.

FIG. 4 (a) is a sectional view showing a pressure sensor C which is still another embodiment of the present invention, and FIG. 4 (b) is a plan view thereof. The pressure sensor C has two equal areas. The diaphragm 1a and the diaphragm 1b are supported by the frame 2 at their peripheral portions. A cover 3 made of glass is stacked on the frame 2, and the peripheral portion of the cover 3 is anodically bonded to the frame 2. One large recess 4 is formed on the inner surface of the cover 3 so that the two diaphragms 1a and 1b can be elastically deformed freely in the thickness direction thereof. The recess 4 is formed into a deep recess 4a with a large gap from one of the diaphragms 1a and a shallow recess 4b with a small gap from the remaining diaphragm 1b.

Then, pressure is applied to the pressure sensor C.
And the respective diaphragm 1a and diaphragm 1b
Is displaced according to the applied pressure. Diaphragm 1a
And when the diaphragm 1b is displaced, the movable electrodes 5a, 5b
And the gap between the fixed electrodes 6a and 6b change.
It Here, the gap between the movable electrode 5a and the fixed electrode 6a
Is large, the movable electrode 5a and the fixed electrode 6a are not configured.
Capacitor C_AThe capacitance of is shown by the curve a in FIG.
So that it gradually increases. On the other hand, the movable electrode 5a and the fixed
Capacitor C configured with pole 6b_BFigure 5 shows the capacitance of
It rapidly increases as shown by the curve b. But the first
As in the embodiment, these two capacitors C_A, C_BCapacitance of
For example, the frequency f₁, F₂Output as
Wave number f₁, F Difference of 2 (Δf = f₁-F₂) Is detected, the
A differential output with good linearity can be obtained.

FIG. 6 is a sectional view showing a pressure sensor D according to still another embodiment of the present invention. Although the areas of the diaphragm 1a and the diaphragm 1b of the pressure sensor D are equal, the diaphragm 1a is thick and the diaphragm 1b is large. Is made thin. Therefore, the capacitance of the capacitor C _A formed in the diaphragm 1a gradually increases as the pressure P increases as shown by the curve _A in FIG. 7, and the capacitance of the capacitor C _B formed in the diaphragm 1b increases. The capacity rapidly increases as the pressure P increases, as shown by the curve B in FIG. In this way, the differential pressure sensor D can be produced by supporting the diaphragms 1a and 1b having different thicknesses. Further, a strain detecting element such as a piezoresistive element may be formed on the diaphragm.

As described above, two output characteristics are different.
A pressure sensor is formed by exposing two diaphragms 1a and 1b to one depression 4 and detecting a difference between sensor signals generated in the two diaphragms 1a and 1b as a differential output type linear sensor. It is possible to improve the sex.

FIG. 8 shows a sectional view of a pressure sensor E which is still another embodiment of the present invention. The pressure sensor E is provided with a diaphragm 1a having a large area and a diaphragm 1b having a small area so as to face the recess 4 provided in the cover 3 and the peripheral portions of the diaphragm 1a are supported by the frame 2. The recess 4 has a deep recess 4a separated from the diaphragm 1a by a large gap and the remaining diaphragm 1b.
And a shallow recess 4b with a small gap therebetween. Another glass cover 9 is attached to the lower surface of the frame 2.
Are joined together, and a closed space 10 is formed by the cover 9 on the lower surface of the diaphragm 1b. A conductive layer is formed on the diaphragm 1b having a small area by ion implantation or the like, and the upper surface thereof serves as the movable electrode 13. Also,
A fixed electrode 14 is formed on the inner surface of the cover 9 with a small gap from the movable electrode 13, and a capacitor C is formed between the movable electrode 13 and the fixed electrode 14.

A liquid 11 (preferably an incompressible fluid) is filled in the recess 4 of the cover 3, and the closed space 10 is filled.
Is filled with the gas 12 so as to have a reference pressure P near the measured pressure (P + ΔP). For example, 2 kg / cm ²
When it is desired to measure a minute pressure fluctuation in the vicinity, the gas 12 may be filled so that the pressure in the closed space 10 becomes ² kg / cm ² . At this time, it is necessary to fill the closed space 10 with the gas 12 with high pressure accuracy, but if the frame 2 and the cover 9 are joined to form the closed space 10 in a desired constant pressure container, the gas 12 can be accurately fed. 12 can be filled.

Thus, the diaphragm 1 of the pressure sensor E
When the measured pressure (P + ΔP) is introduced into a, since the liquid 11 having the pressure P is filled in the depression 4, the pressure of P + ΔP is also transmitted to the diaphragm 1b. When the pressure of P + ΔP is transmitted to the diaphragm 1b, the diaphragm 1b
Is displaced in a direction away from the inner surface of the cover 3, and the capacitance of the capacitor C is a fluctuation of the applied pressure (P + ΔP−P =
ΔP). Therefore, by detecting a change in the capacitance of the capacitor C, it is possible to know the pressure fluctuation applied to the pressure sensor E under high pressure. At this time, the diaphragm 1a to which the measurement pressure is applied
Since a large gap is formed between the fixed substrate 3 and the fixed substrate 3, the diaphragm 1a does not contact the fixed substrate 3 even when a large pressure is applied. Further, since the closed space 10 is so large that the diaphragm 1b does not come into contact with the cover 9 even when the diaphragm 1b is displaced, it is possible to measure a high pressure without lowering the measurement sensitivity.

Further, in the pressure sensor E, since the liquid 4 is filled in the depression 4, the dielectric constant between the movable electrode 13 and the fixed electrode 14 is always kept constant, and the air to be measured is kept. It is possible to perform pressure measurement with little measurement error or variation without being affected by humidity and the like.

Further, in this pressure sensor E, since the glass cover 3 and the cover 9 are bonded to the upper and lower surfaces of the silicon frame 2, the distortion due to heating and temperature change at the time of bonding is small, and the pressure is reduced. The temperature characteristics of the sensor E can also be made excellent.

The pressure sensor F shown in FIG.
Another glass cover 15 is placed on the entire lower surface of the frame 2, and a pressure chamber 16 is formed on the lower surface of the diaphragm 1a having a large area. A closed space 10 is formed on the lower surface of the diaphragm 1b having a small area, and the closed space 10 is filled with a gas 12. Also,
The inside of the depression 4 is filled with the liquid 11. In the pressure sensor F, the cover 15 is integrally provided with the introduction pipe 17, and the pressure can be introduced into the pressure chamber 16 through the introduction pipe 17. In this way, the introduction pipe 1
If the cover 15 integrally molded with 7 is joined to the frame 2, an introducing device for introducing pressure to the pressure sensor F and a cover 15 for forming the closed space 10 on the lower surface of the diaphragm 1a can be simultaneously formed. Moreover, the structure of the pressure sensor F is simplified, and the manufacturing process can be simplified. Further, since the introduction pipe 17 is provided in advance in the pressure sensor F, the pressure chamber 16 and the mounting board can be mounted on the mounting board or the like without strictly aligning them.

Incidentally, like the pressure sensor B shown in FIG. 3, a strain detecting element may be provided on the upper surface or the lower surface of the diaphragm 1b to detect the pressure fluctuation.

[0041]

According to the first pressure sensor of the present invention,
Since one pressure sensor is equipped with two pressure detection means having different detection sensitivities, the connection wiring to the introduction device and the detection circuit for the differential output type can be simplified, and the differential pressure sensor can be used. It can be easily configured. Therefore, it is possible to accurately measure pressure in a wide measurement range, and it is possible to provide a small-sized pressure sensor having excellent linearity.

Further, in the second pressure sensor of the present invention, since the diaphragm is supported by the supporting substrate so as to face the same closed space, the diaphragm is displaced in the direction away from the fixed substrate by the applied pressure. Can be made.
Therefore, even if the pressure increases, the diaphragm does not come into contact with the fixed substrate, and the measurement range of the pressure sensor can be expanded. Also, the dielectric constant in the closed space does not change,
It is possible to provide a pressure sensor with less measurement error and variation. Moreover, since moisture and dust do not enter the closed space, the diaphragm is not damaged and the sensitivity is not lowered. Moreover, since it is not necessary to open the pressure introducing port in the fixed substrate, the manufacturing process can be simplified.

Further, since substantially the same pressure is applied to the upper and lower surfaces of the diaphragm, the pressure fluctuation can be measured under a high pressure.

If this pressure sensor has a three-layer structure of glass / silicon / glass, the strain due to the difference in the coefficient of thermal expansion can be relaxed and the temperature characteristics of the pressure sensor can be improved.

In this pressure sensor, if the substrate provided with the pressure introducing device is joined to the supporting substrate to form the sealed space, the pressure can be easily introduced to the pressure sensor and the mounting on the mounting substrate is easy. become. Further, the manufacturing cost can be reduced by reducing the number of parts.

Also, according to the manufacturing method of the present invention, it is possible to easily maintain a constant pressure in the closed space.

[Brief description of drawings]

1A is a sectional view of a pressure sensor according to an embodiment of the present invention, and FIG. 1B is a plan view thereof.

FIG. 2 is a sensitivity curve diagram of two diaphragms in the pressure sensor of the above.

FIG. 3 is a cross-sectional view of a pressure sensor that is another embodiment of the present invention.

FIG. 4A is a sectional view of a pressure sensor which is still another embodiment of the present invention, and FIG. 4B is a plan view thereof.

5 is a sensitivity curve diagram of two diaphragms in the pressure sensor of FIG.

FIG. 6 is a cross-sectional view of a pressure sensor which is still another embodiment of the present invention.

FIG. 7 is a sensitivity curve diagram of two diaphragms in the pressure sensor of FIG.

FIG. 8 is a cross-sectional view of a pressure sensor that is still another embodiment of the present invention.

FIG. 9 is a cross-sectional view of a pressure sensor that is still another embodiment of the present invention.

FIG. 10 is a cross-sectional view of a conventional pressure sensor.

[Explanation of symbols]

 1a, 1b Diaphragm 4 Dimples 5a, 5b Movable electrodes 6a, 6b Fixed electrodes 7a, 7b Strain detection element 10 Sealed space 11 Liquid 17 Introduction pipe

Claims (12)

[Claims] 1. A semiconductor pressure sensor in which a fixed substrate is bonded to at least one surface of a support substrate supporting a diaphragm, and two diaphragms are provided in the same closed space provided between the fixed substrate and the support substrate. The semiconductor pressure sensor is characterized in that the diaphragm is supported by the support substrate, and pressure detection means having different detection sensitivities are formed on the respective diaphragms. 2. The semiconductor pressure sensor according to claim 1, wherein the areas of the diaphragms are different from each other. 3. The semiconductor pressure sensor according to claim 1, wherein the diaphragms have different thicknesses. 4. The semiconductor pressure sensor according to claim 1, wherein the distance between each diaphragm and the fixed substrate is different. 5. The semiconductor pressure sensor according to claim 1, 2, 3 or 4, wherein the support substrate and the diaphragm are made of silicon, and the fixed substrate is made of glass. 6. A method for detecting pressure by the semiconductor pressure sensor according to claim 1, wherein the output of the pressure detection means provided on two diaphragms and having different detection sensitivities. A pressure detection method characterized by detecting the difference between 7. A semiconductor pressure sensor in which a fixed substrate is bonded to one surface of a support substrate supporting a diaphragm, wherein two diaphragms are provided in the same closed space provided between the fixed substrate and the support substrate. The closed space is filled with a fluid having a constant pressure, and the closed space forming substrate is joined to the remaining surface of the support substrate to face at least one of the diaphragm and the closed space. A closed space is formed between the space forming substrate, the pressure in the closed space is maintained at a pressure substantially the same as the pressure in the closed space, and the diaphragm forming the closed space is provided with pressure detection means. A semiconductor pressure sensor characterized in that 8. The semiconductor pressure sensor according to claim 7, wherein a sealed space forming substrate having a pressure introducing device for introducing pressure to the pressure sensor is bonded to the pressure sensor. 9. The supporting substrate and the diaphragm are made of silicon, and the fixed substrate and the closed space forming substrate are made of glass to have a three-layer structure of glass / silicon / glass. The semiconductor pressure sensor according to claim 7 or 8. 10. A method for manufacturing the semiconductor pressure sensor according to claim 7, 8 or 9, wherein the sealed space forming substrate is bonded under a constant pressure to form the sealed space. A method for manufacturing a semiconductor pressure sensor having a feature. 11. The pressure detecting means detects pressure by measuring a change in electrostatic capacitance between a movable electrode provided on the diaphragm and a fixed electrode provided on the fixed substrate. Claims 1, 2, 3, 4, 5, 7,
8. The semiconductor pressure sensor according to 8 or 9. 12. The pressure detecting means detects pressure by measuring a change in resistance value of a strain detecting element provided on the diaphragm.
The semiconductor pressure sensor according to 3, 4, 5, 7, 8 or 9.