JPH1114482A - Electrostatic capacity pressure sensor and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrostatic capacity pressure sensor wherein a floating capacity is small while plastic deformation at a diaphragm part subject to a pressure is suppressed for high-precision pressure diaphragm. SOLUTION: A diaphragm 111 is of such brittle material as of impurity- diffused single-crystalline silicon, which is immune to plastic deformation and forms a stable pressure receiving structure body. An oxide film 103 is formed between the diaphragm 111 and a moving electrode 104b, which reduces a floating capacity between the moving electrode 104b and a substrate 101 and the moving electrode 104b and an impurities diffusion layer 102. The oxide film 103 and the moving electrode 104b are divided into a plurality of regions, and on each region of the oxide film 103, each region of the moving electrode 104b is formed. Thus, a stress strain due to difference in thermal expansion coefficient among the diaphragm 111, the oxide film 103, and the moving electrode 104b is reduced. A fixed electrode 107 is covered with a fixed electrode structure body 108 of such insulating polycrystalline silicon film where no impurity is doped, so that the stiffness of the electrode 107 is strengthened for reduced leak current.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure sensor for detecting pressure, and more particularly to a capacitance type pressure sensor used for controlling an engine of an automobile and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventional capacitance type pressure sensors include:
For example, there is a pressure sensor described in Japanese Patent Publication No. 7-50789. The capacitance-type pressure sensor described in this publication has a first type by impurity diffusion on a single crystal silicon substrate.
Is formed, and a second electrode opposed to the first electrode via a gap is formed of conductive polycrystalline silicon in a diaphragm shape.

[0003] When pressure is applied to the diaphragm-shaped second electrode, the applied pressure displaces the diaphragm-shaped second electrode. The displacement of the second electrode changes the capacitance between the first electrode and the second electrode, and the pressure is detected by detecting the change.

[0004]

However, in the above-mentioned prior art, since the first electrode is formed by diffusion, the junction capacitance with the silicon substrate is very large.
Since the stray capacitance between the first electrode and the second electrode becomes large, pressure detection accuracy is low, and high-precision pressure detection cannot be performed.

Further, since the second electrode has a structure in which it comes into direct contact with air as a medium to be measured, a leak current occurs when dirty air mixed with gasoline or the like comes into contact with the second electrode. However, it is difficult to accurately detect the capacitance, and high-precision pressure detection cannot be performed.

[0006] Further, since the diaphragm which is displaced by pressure is made of polycrystalline silicon, it tends to be plastically deformed, and the correspondence between the applied pressure and the change of the capacitance may fluctuate. For this reason, there has been a problem that accuracy of pressure detection is reduced and reliability is poor.

An object of the present invention is to realize a capacitance type pressure sensor which has a small floating capacitance, suppresses plastic deformation of a diaphragm portion subjected to pressure, and is capable of detecting pressure with high accuracy, and a method of manufacturing the same. is there.

[0008]

[Means for Solving the Problems]

(1) The present invention is configured as follows to achieve the above object. That is, in the capacitance type pressure sensor, a diaphragm which is a single crystal silicon substrate and is displaced by an applied pressure, an insulating film formed on the diaphragm, and a first electrode formed on the insulating film And a distance between the first electrode and the second electrode is changed by a pressure applied to the second electrode formed opposite to the first electrode via a gap and the diaphragm. Means for detecting a change in capacitance between the first electrode and the second electrode, and converting the change into a voltage.

(2) Preferably, in the above (1),
The insulating film is divided into at least two parts.

(3) Preferably, in the above (2), the first electrode is divided into at least two or more.

(4) Preferably, in the above (3), the area of the first electrode is smaller than the area of the insulating film.

(5) Preferably, in the above (1) to (4), a part of the space between the first electrode and the silicon substrate is hollow.

(6) Preferably, in the above (1) to (5), the first electrode is made of polycrystalline silicon.

(7) Preferably, in the above (1) to (6), the pressure sensor is integrated with a signal processing circuit for processing a signal of the pressure sensor, and a MOS transistor included in the signal processing circuit is provided. The material of the gate electrode and the material of the first electrode are the same.

An insulating film is formed between the diaphragm and the first electrode, and a stray capacitance generated between the first electrode and the single crystal silicon substrate and between the first electrode and the impurity is generated. Reduced.

If the insulating film and the first electrode are formed so as to be finely divided, that is, divided into a plurality of regions, the diaphragm, the insulating film, the first electrode, and the mutual heat can be formed. It is possible to reduce stress strain caused by a difference in expansion coefficient. That is, in the case where the first electrode and the insulating film are divided into a plurality, the stress strain caused by the difference in the coefficient of thermal expansion can be reduced as compared with the case where the first electrode and the insulating film are not divided into a plurality.

When the first electrode of the pressure sensor is made of polycrystalline silicon, the material of the gate electrode of the MOS transistor of the signal processing circuit for processing the signal of the pressure sensor is also made of polycrystalline silicon. Therefore, the pressure sensor and the signal processing circuit can be integrally configured.

(8) In the method of manufacturing the capacitance type pressure sensor, a step of doping the single crystal silicon substrate with an impurity, a step of forming an oxide film on a predetermined portion on the impurity, and Forming a conductive polycrystalline silicon film serving as an electrode on the oxide film and patterning, forming a sacrificial layer on at least the first electrode;
Patterning, forming a conductive polycrystalline silicon film serving as a second electrode on at least the sacrificial layer, and forming an insulated polycrystalline silicon film on the second electrode; Patterning, removing the sacrificial layer, forming a protective film on the insulated polycrystalline silicon film, and the opposite side of the surface of the single crystal silicon substrate doped with the impurities. Etching a predetermined portion of the surface to form a diaphragm made of the impurity.

The first electrode is made of polycrystalline silicon, and the signal processing circuit MO for processing the signal of the pressure sensor is provided.
When the material of the gate electrode of the S transistor is also made of polycrystalline silicon, the pressure sensor and the signal processing circuit can be integrated and manufactured at the same time.

(9) In the capacitance type pressure sensor, a diaphragm which is a single crystal silicon substrate and is displaced by an applied pressure, and a first diaphragm formed on the diaphragm and divided into at least two or more. Electrodes and
A second electrode formed to face the first electrode via a gap.
The distance between the first electrode and the second electrode is changed by the pressure applied to the first electrode and the diaphragm, and the capacitance between the first electrode and the second electrode is changed. Means for detecting that the voltage changes, and converting the voltage into a voltage;
A capacitance type pressure sensor comprising:

(10) Preferably, in the above (9), the first electrode is made of polycrystalline silicon.

(11) Preferably, in the above (9) or (10), the pressure sensor is integrated with a signal processing circuit for processing a signal of the pressure sensor, and a MOS transistor of the signal processing circuit is provided. The material of the gate electrode and the material of the first electrode are the same.

Since the first electrode is formed by being divided into a plurality of regions, it is possible to reduce stress distortion caused by a difference in thermal expansion coefficient between the diaphragm and the first electrode.

(12) In the method of manufacturing a capacitance type pressure sensor, a step of doping an impurity into a single crystal silicon substrate and a step of forming a conductive polycrystalline silicon film serving as a first electrode on the impurity Forming a predetermined portion and patterning into a plurality of divided regions; forming a sacrificial layer on at least the first electrode and patterning; forming a conductive layer to be a second electrode; Forming a crystalline silicon film on at least the sacrificial layer, forming an insulated polycrystalline silicon film on the second electrode and patterning, removing the sacrificial layer, Forming on the insulated polycrystalline silicon film, and etching a predetermined portion of a surface of the single crystal silicon substrate opposite to the surface doped with the impurity, thereby removing the impurity. And a step of forming a diaphragm made of.

The first electrode is made of polycrystalline silicon, and the MO of the signal processing circuit for processing the signal of the pressure sensor is provided.
When the material of the gate electrode of the S transistor is also made of polycrystalline silicon, the pressure sensor and the signal processing circuit can be integrated and manufactured at the same time.

[0026]

FIG. 1 is a sectional view of a capacitance type pressure sensor according to a first embodiment of the present invention, and FIG.
FIG. 2 is a plan view of the first embodiment. 1 and 2, a capacitance type pressure sensor according to the first embodiment includes a single crystal silicon substrate 101, an impurity diffusion layer 102,
Oxide film layer (insulating film) 103, fixed electrode wiring 104a, movable electrode (first electrode) 104b, protective film 105, fixed electrode (second electrode) 107, fixed electrode structure 108, gap 109, protective film 110, a diaphragm 111, and a pressure introducing hole 112.

The air to be measured is supplied to the pressure introducing hole 11.
2 is introduced. When the air introduced into the pressure introduction hole 112 applies pressure to the diaphragm 111, the diaphragm 111 is displaced according to the magnitude of the pressure.

When the diaphragm 111 is displaced, a gap 109 between the movable electrode 104b and the fixed electrode 107 formed on the diaphragm 111 changes.
When the distance between the movable electrode 104b and the fixed electrode 107 changes, the capacitance formed between the electrodes changes. The pressure can be detected by detecting the change in the capacitance.

Since the diaphragm 111 is a brittle material made of single-crystal silicon in which impurities are diffused,
It forms a reliable and stable pressure passive structure without plastic deformation.

An oxide film 103 is formed between the diaphragm 111 and the movable electrode 104b.
The stray capacitance generated between the semiconductor substrate 04b and the substrate 101 and between the movable electrode 104b and the impurity diffusion layer 102 is reduced. Further, as shown, the oxide film 103 is formed by being finely divided, that is, divided into a plurality of regions (in this example, 16 regions).

The movable electrode 104b is also formed of the oxide film 103.
In the same manner as described above, it is finely divided, that is, divided into a plurality of regions, and each region is electrically connected. The movable electrode 104 is formed on the oxide film 103 above each region.
Each of the plurality of regions b is formed.

As a result, it is possible to reduce stress distortion caused by a difference in the coefficient of thermal expansion between the diaphragm 111, the oxide film 103, and the movable electrode 104b. That is, in the case where the movable electrode 104b and the oxide film 103 are divided into a plurality, the stress strain caused by the difference in the coefficient of thermal expansion can be reduced as compared with the case where the movable electrode 104b and the oxide film 103 are not divided into a plurality.

The upper portion of the fixed electrode 107 is covered with a fixed electrode structure 108 made of an insulating polycrystalline silicon film not doped with impurities, and the rigidity of the fixed electrode 107 is enhanced. In addition, by completely covering the surface of the fixed electrode 107 with an insulator, leakage current can be reduced.

As described above, according to the capacitance type pressure sensor of the first embodiment of the present invention, the diaphragm 11
1 is a brittle material made of single crystal silicon in which impurities are diffused, and the movable electrode 104b and the diaphragm 1
An oxide film 103 is disposed between the movable electrode 104 and the movable electrode 104 and the movable electrode 104b and the oxide film 103 are divided into a plurality of regions.

Further, the upper portion of the fixed electrode 107 is covered with a fixed electrode structure 108 made of an insulating polycrystalline silicon film not doped with impurities.
Therefore, it is possible to realize a highly accurate and highly reliable electrostatic capacitance type pressure sensor in which the pressure passive structure is stable, the deformation due to thermal strain is small, the floating capacitance and the leak current are small.

Next, a method of manufacturing the above-described capacitance type pressure sensor according to the first embodiment of the present invention will be described. FIG.
FIG. 6 to FIG. 6 are diagrams illustrating each step of the manufacturing method.
In FIG. 3, a single-crystal silicon substrate 101 for IC production
The same impurity diffusion layer 1 as that for forming the well of the CMOS circuit.
02 is formed by ion implantation and thermal diffusion. This impurity is P-well if the substrate is N-sub and P-sub is
Then, it is N-well (step (a) in FIG. 3)
(B)).

On the impurity diffusion layer 102, the same oxide film 103 as that for LOCOS formation is selectively formed by thermal diffusion (formed at a predetermined portion). Alternatively, after an oxide film is formed on the entire surface, patterning may be performed by dry etching (step (c) in FIG. 3).

Next, referring to FIG. 4, polycrystalline silicon doped with impurities for forming the fixed electrode wiring 104a and the movable electrode 104b is formed on the oxide film 103 and patterned (steps in FIG. 4). (D)). In this case, since the material of the gate electrode of the CMOS circuit (or MOS circuit) described later is often polycrystalline silicon,
The CMOS circuit (or MO circuit)
S circuit) can also be formed integrally.

After covering a protective film 105 such as a nitride film on the movable electrode 104b, a sacrificial layer 106 such as an oxide film or a PSG film is formed.
Is subjected to patterning by photo-etching (steps (e) and (f) in FIG. 4).

Next, steps (g), (h) and (i) of FIG.
Then, a polycrystalline silicon film doped with an impurity to be a fixed electrode 107 and a non-doped polycrystalline silicon film 108 are deposited and patterned.

Subsequently, in FIG. 6, the sacrificial layer is wet-etched with hydrofluoric acid or the like. Thereafter, a protective film 110 such as a nitride film is formed, and the single crystal silicon substrate 101 is formed.
Is anisotropically wet-etched with KOH or the like from the back surface (step (j) in FIG. 6). At this time, by etching while applying a voltage between the single crystal silicon substrate 101 and the diffusion layer 102, the single crystal silicon substrate 1
Only 01 is etched, and the impurity diffusion layer 102 can be left without being etched. Thereby, the diaphragm 110 and the pressure introducing hole 111 can be formed simultaneously (step (k) in FIG. 6).

According to the method of manufacturing the capacitance type pressure sensor according to the first embodiment of the present invention, the sensor can be manufactured integrally with a COMOS circuit (MOS circuit) on the same substrate. A method for manufacturing a pressure sensor having stable characteristics can be realized.

FIG. 7 is a sectional view of a capacitance type pressure sensor according to a second embodiment of the present invention, and FIG.
It is a top view of an embodiment. 7 and 8, a capacitance type pressure sensor according to the second embodiment includes a single crystal silicon substrate 201, an impurity diffusion layer 202, an oxide film layer 203, a fixed electrode wiring 204a, a movable electrode 204b, and a fixed electrode. 206, fixed electrode structure 207, void 208,
Protective film 209, diaphragm 210, pressure introduction hole 211
It has.

The air to be measured is supplied to the pressure introducing holes 21.
Introduced to 1. When the air introduced into the pressure introducing hole 211 applies pressure to the diaphragm 210, the diaphragm 210 is displaced according to the magnitude of the pressure. When the diaphragm 210 is displaced, the gap 208 between the movable electrode 204b and the fixed electrode 206 formed on the diaphragm 210 changes, that is, by changing the distance between the movable electrode 204b and the fixed electrode 206, The capacitance formed between both electrodes changes, and pressure can be detected. Diaphragm 210 is a brittle material made using impurity-diffused single crystal silicon.

An oxide film 203 is formed between the diaphragm 210 and the movable electrode 204b.
The stray capacitance generated between the semiconductor substrate 04b and the substrate 201 and between the movable electrode 204b and the impurity diffusion layer 202 is reduced.

Further, the oxide film 203 is finely divided and formed in an overhanging manner on top of it, that is, the area of each divided region of the movable electrode 204b is smaller than the area of each divided region of the oxide film 203. By forming the movable electrode 204b so as to be large, it is possible to greatly reduce stress distortion caused by a difference in thermal expansion coefficient between the diaphragm 210, the oxide film 203, and the movable electrode 204b.

The same effect as in the first embodiment can be obtained in the capacitance type pressure sensor according to the second embodiment of the present invention. Furthermore, in the second embodiment, the movable electrode 204b is formed so that each area of each divided region of the movable electrode 204b is larger than each area of each divided region of the oxide film 203. The stress distortion caused by the difference in the coefficient of thermal expansion between the diaphragm 210, the oxide film 203, and the movable electrode 204b can be greatly reduced.

Next, a method of manufacturing the above-described capacitance type pressure sensor according to the second embodiment of the present invention will be described. FIG.
FIG. 12 to FIG. 12 are diagrams illustrating each step of the above manufacturing method. In FIG. 9, a single crystal silicon substrate 2 for IC production is shown.
In FIG. 1, the same impurity diffusion layer 202 as that for forming the well of the CMOS circuit (MOS circuit) is ion-implanted and formed by thermal diffusion. This impurity layer is P-well if the substrate is N-sub and N-well if the substrate is P-sub (FIG. 9).
Steps (a) and (b)).

The same oxide film 203 as that for LOCOS formation is selectively formed on the impurity diffusion layer 202 by thermal oxidation (step (c) in FIG. 9). Alternatively, patterning may be performed by dry etching after forming an entire surface oxide film.

Next, in FIG. 10 and FIG. 11, the fixed electrode wiring 204a and the movable electrode 240
A film of polycrystalline silicon doped with an impurity for forming b is formed and patterned (step (d) in FIG. 10).

The fixed electrode wiring 204a and the movable electrode 240
Then, a sacrificial layer 205 such as an oxide film or a PSG film is deposited and patterned by photoetching (step (e) in FIG. 10).

Thereafter, a polycrystalline silicon film doped with an impurity to be a fixed electrode 206 and a non-doped polycrystalline silicon film 207 are deposited and patterned (step (f) in FIG. 10 and step in FIG. 11). (G)).

Next, the sacrificial layer 205 and a part of the oxide film 203 are wet-etched with hydrofluoric acid or the like (FIG. 1).
Step 1 (h)).

Subsequently, in FIG. 12, a protective film 209 such as a nitride film is formed on the polycrystalline silicon film 207 (step (i) in FIG. 12). The wet etching is performed (step (j) in FIG. 12). At this time, the single crystal silicon substrate 2
By etching while applying a voltage between the first diffusion layer 202 and the diffusion layer 202, only the single crystal silicon substrate 201 is etched, and the impurity diffusion layer 202 can be left without being etched. Thereby, the diaphragm 2
10 and the pressure introduction hole 211 can be formed simultaneously.

According to the method of manufacturing the capacitance type pressure sensor according to the second embodiment of the present invention described above, the sensor can be manufactured integrally with the CMOS circuit on the same substrate, and it is small, inexpensive, and has stable characteristics. A method for manufacturing a pressure sensor can be realized.

FIG. 13 is a configuration diagram of a signal processing circuit applied to signal processing of an output signal from the capacitance type pressure sensor of the present invention. 13, this signal processing circuit includes a signal application unit 231, a pressure detection unit 232, a capacity detection unit 233, and an output adjustment unit 234.

The signal application section 231 includes a power supply VDD and analog switches SW1 and SW2. The pressure detecting section 232 includes one capacitor CS, which is a capacitor as a pressure detecting element formed by the movable electrodes (104b, 204b) and the fixed electrodes (107, 206).

The capacitance detecting section 233 includes an analog switch S
It is composed of W3, SW4, SW5, operational amplifier OP1, capacitors CR, CT, CF. Output adjustment unit 23
4 is a power supply VDD, an operational amplifier OP2, resistors R4, R
5, R6, R7 and a capacitor C4.

The signal application unit 231, the pressure detection unit 232, and the capacitance detection unit 233 have a switched capacitor circuit configuration, and an output proportional to the capacitance value is obtained by the on / off operation of each switch. Assuming that the output voltage (output of OP1) of the capacitance detection unit 233 is Vo, the operation of this circuit is expressed by the following equation (1). However, CF, CT, C
S and CR are capacitors CF, CT, CS, and C, respectively.
Let R be the capacitance value. CF ・ Vo (n) = CF ・ Vo (n-1)-CT ・ Vo (n-1)-CS ・ VDD + CR ・ VDD --- (1) Finally, the following equation (2) is used. Become a relationship. Vo = ((CR-CS) / CF) · VDD −−− (2) Therefore, pressure is applied to the detection element, and the capacitor C
A change in the capacitance value of S can be converted to a voltage output.

This output voltage is adjusted by the output adjusting section 234 to a predetermined offset voltage and sensitivity. With this circuit configuration, the pressure signal can be relatively easily converted into the voltage signal.

The above-described signal processing circuit is constituted by a CMOS circuit. If the gate electrode of this CMOS circuit is made of polycrystalline silicon, the CMOS circuit and the pressure sensor main body can be integrally formed.

FIG. 14 is a sectional view of a capacitance type pressure sensor according to a third embodiment of the present invention, and FIG. 15 is a plan view of the third embodiment. 14 and 15, the capacitance type pressure sensor according to the third embodiment includes a single crystal silicon substrate 301, an impurity diffusion layer 302,
Oxide film layer 303a, fixed electrode wiring 304a, movable electrode 3
04b, fixed electrode 307, structure for fixed electrode 308, gap 309, protective film 310, diaphragm 311a, groove 3
11b, a pressure introduction hole 312 is provided.

The air to be measured is supplied to the pressure introducing hole 31.
When pressure is applied to the diaphragm 311,
The diaphragm 311a is displaced according to the magnitude of the pressure. When the diaphragm 311a is displaced, a gap 309 between the movable electrode 304b and the fixed electrode 307 formed on the diaphragm 311a changes, whereby the capacitance formed between the electrodes changes, and the pressure decreases. Can be detected.

Since the diaphragm 311a is made of a single-crystal silicon which is a brittle material and is diffused with impurities, it forms a reliable and stable pressure passive structure without plastic deformation.

The diaphragm 311a is formed by finely dividing the groove 311b in the substrate 301 and forming the movable electrode 304b only on the upper portion other than the groove 311b. It is possible to reduce stress strain.

The upper portion of the fixed electrode 307 is covered with a fixed electrode structure 308 made of an insulating polycrystalline silicon film which is not doped with an impurity, thereby enhancing the rigidity of the fixed electrode 307 and the surface of the fixed electrode 307. Is completely covered with an insulator to reduce leakage current.

As described above, according to the capacitance type pressure sensor of the third embodiment of the present invention, the diaphragm 31
1a is made of a brittle material made of single-crystal silicon with impurity diffusion, and these movable electrodes 304b are divided into a plurality of regions. Further, the upper portion of the fixed electrode 307 is covered with a fixed electrode structure 308 made of an insulating polycrystalline silicon film not doped with impurities. Therefore, it is possible to realize a highly accurate and highly reliable capacitance type pressure sensor in which the pressure passive structure is stable, the deformation due to the thermal strain is small, and the leak current is small.

Next, a method of manufacturing the capacitance type pressure sensor according to the third embodiment of the present invention will be described. FIG.
6 to 19 are diagrams illustrating each step of the manufacturing method. In FIG. 16, the same impurity diffusion layer 302 as that for forming a well of a CMOS circuit is ion-implanted into a single-crystal silicon substrate 301 for IC manufacture and formed by thermal diffusion (steps (a) and (b) in FIG. 16). This impurity is P-well if the substrate is N-sub and N-we if the substrate is P-sub.
ll.

On the impurity diffusion layer 302, the same oxide films 303a and 303b as those for forming the LOCOS are selectively formed by thermal oxidation (step (c) in FIG. 16). Alternatively, patterning may be performed by dry etching after forming an entire surface oxide film.

Next, referring to FIG. 17, on the oxide film 303a and the impurity diffusion layer 302, polycrystalline silicon doped with impurities for forming the fixed electrode wiring 304a and the movable electrode 304b is formed and patterned. (Step (d) in FIG. 17).

Then, a sacrificial layer 306 such as an oxide film or a PSG film is deposited on the movable electrode 340b and the like and patterned by photoetching (step (e) in FIG. 17).

After that, a polycrystalline silicon film doped with an impurity to be a fixed electrode 307 and a non-doped polycrystalline silicon film 308 are deposited and patterned (step (f) in FIG. 17, FIG. 18). Step (g)).

After that, the sacrificial layer 306 and the oxide film 303b are wet-etched with hydrofluoric acid or the like, and
9 and the groove 311b are formed simultaneously (step (h) in FIG. 18). Thereafter, a protective film 310 such as a nitride film is formed (step (i) in FIG. 19), and anisotropic wet etching is performed from the back surface of the single crystal silicon substrate 301 with KOH or the like (step (j) in FIG. 19). .

At this time, by etching while applying a voltage between the single crystal silicon substrate 301 and the diffusion layer 302, only the single crystal silicon substrate 301 is etched and the impurity diffusion layer 302 is left without being etched. Can be. Thereby, the diaphragm 311
a and the pressure introduction hole 312 can be formed simultaneously.

According to the method of manufacturing the capacitance type pressure sensor according to the third embodiment of the present invention described above, the sensor can be manufactured integrally with the COMOS circuit on the same substrate, and it is small, inexpensive, and has stable characteristics. A method for manufacturing a pressure sensor can be realized.

In the above example, the movable electrodes (104b, 204b, 304b) and the oxide films (103,
Although the number of divisions of 203 is set to 16, the number of divisions is not limited to 16, and may be a number of divisions that can obtain a distortion reduction effect according to necessary specifications, and the number may be a value of 2 or more divisions.

Further, the capacitance type pressure sensor of the present invention
It is suitable as a pressure sensor for controlling an engine for a car, but is not limited to a car and may be applied to any other sensor that detects pressure.

[0078]

Since the present invention is configured as described above, it has the following effects. The diaphragm is made of brittle material made of single-crystal silicon with impurity diffusion, and an oxide film is placed between the movable electrode and the diaphragm, reducing stray capacitance and enabling high-precision pressure detection It is possible to realize a simple capacitance type pressure sensor.

Further, if the movable electrode and the oxide film are configured so as to be divided into a plurality of regions, the diaphragm, the oxide film,
It is possible to reduce the stress strain caused by the difference in the coefficient of thermal expansion between the movable electrodes, and to realize a capacitance type pressure sensor capable of detecting pressure with high accuracy.

If the upper portion of the fixed electrode is configured to be covered with a fixed electrode structure made of an insulating polycrystalline silicon film which is not doped with impurities, deformation due to thermal strain is small, and leakage current is reduced. It is possible to realize a high-accuracy and highly-reliable capacitance-type pressure sensor with less noise.

Further, it is possible to realize an electrostatic capacitance type pressure sensor which has no plastic deformation of a structure subjected to pressure and has a stable characteristic which is hardly subjected to distortion due to intrinsic stress during thermal stress film formation.

Further, since the semiconductor device can be manufactured by using a general IC manufacturing process, it can be integrated with the circuit portion into one chip, and a manufacturing method that can be reduced in size and cost can be realized.

[Brief description of the drawings]

FIG. 1 is a sectional view of a capacitive pressure sensor according to a first embodiment of the present invention.

FIG. 2 is a plan view of the first embodiment of the present invention.

FIG. 3 is a diagram illustrating a method of manufacturing the capacitance type pressure sensor according to the first embodiment of the present invention.

FIG. 4 is a diagram illustrating a method of manufacturing the capacitance type pressure sensor according to the first embodiment of the present invention.

FIG. 5 is a diagram illustrating a method of manufacturing the capacitance type pressure sensor according to the first embodiment of the present invention.

FIG. 6 is a diagram illustrating a method of manufacturing the capacitance type pressure sensor according to the first embodiment of the present invention.

FIG. 7 is a sectional view of a capacitance type pressure sensor according to a second embodiment of the present invention.

FIG. 8 is a plan view of a second embodiment of the present invention.

FIG. 9 is a diagram illustrating a method of manufacturing a capacitance type pressure sensor according to a second embodiment of the present invention.

FIG. 10 is a diagram illustrating a method of manufacturing a capacitance type pressure sensor according to a second embodiment of the present invention.

FIG. 11 is a diagram illustrating a method of manufacturing the capacitance type pressure sensor according to the second embodiment of the present invention.

FIG. 12 is a diagram illustrating a method of manufacturing the capacitance type pressure sensor according to the second embodiment of the present invention.

FIG. 13 is a configuration diagram of a signal processing circuit applied to the capacitance type pressure sensor of the present invention.

FIG. 14 is a sectional view of a capacitance type pressure sensor according to a third embodiment of the present invention.

FIG. 15 is a plan view of a third embodiment of the present invention.

FIG. 16 is a diagram illustrating a method of manufacturing the capacitance type pressure sensor according to the third embodiment of the present invention.

FIG. 17 is a diagram illustrating a method of manufacturing the capacitance type pressure sensor according to the third embodiment of the present invention.

FIG. 18 is a diagram illustrating a method of manufacturing the capacitance type pressure sensor according to the third embodiment of the present invention.

FIG. 19 is a diagram illustrating a method of manufacturing the capacitance type pressure sensor according to the third embodiment of the present invention.

[Explanation of symbols]

 101, 201, 301 Single-crystal silicon substrate 102, 202, 302 Impurity diffusion layer 103, 203 Oxide film layer 104a, 204a, 304a Fixed electrode wiring 104b, 204b, 304b Movable electrode 105 Protective film 106, 205, 306 Sacrificial layer 107, 206, 307 Fixed electrode 108, 207, 308 Fixed electrode structure 109, 208, 309 Void 110, 209, 310 Protective film 111, 210, 311a Diaphragm 112, 211, 312 Pressure introducing hole 231 Signal applying unit 232 Pressure detecting unit 233 Capacity detection unit 234 Output adjustment unit VDD Power supply SW1, SW2, SW3 Analog switch SW4, SW5 Analog switch CS Capacitor OP1, OP2 Operational amplifier CR, CT, CF capacitor VDD Power supply R4, R5, R6 R7 resistance C4 capacitor

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Satoshi Shimada 7-1-1, Omikacho, Hitachi City, Ibaraki Prefecture Inside Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Kiyomitsu Suzuki 7-1 Omikacho, Hitachi City, Ibaraki Prefecture No. 1 Inside Hitachi, Ltd.Hitachi Research Laboratory (72) Inventor Akihiko Saito 7-1-1, Omikacho, Hitachi City, Ibaraki Prefecture Inside Hitachi, Ltd.Hitachi Research Laboratory Co., Ltd. (72) Inventor Masahiro Matsumoto Hitachi, Ibaraki Prefecture 7-1-1, Omika-cho Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Atsushi Miyazaki 2520 Ojitakaba, Hitachinaka-shi, Ibaraki Pref., Ltd.Automotive Equipment Division, Hitachi, Ltd. (72) Inventor Norio Ichikawa, Ibaraki Prefecture 2477 Takaba, Hitachinaka City Hitachi Car Engineering Co., Ltd. (72) Inventor Junichi Horie Hitachi, Ibaraki Naka Oaza high field 2520 address Co., Ltd. Hitachi automotive equipment business unit (72) inventor Seiji Kurio Hitachinaka City, Ibaraki Prefecture Takaba 2477 address stock company Hitachi car in Engineering

Claims (12)

[Claims] 1. A single crystal silicon substrate, a diaphragm which is displaced by an applied pressure, an insulating film formed on the diaphragm, a first electrode formed on the insulating film, And a second electrode formed facing the first electrode.
The first electrode by the pressure applied to the diaphragm.
Means for detecting a change in capacitance between the first electrode and the second electrode due to a change in the distance between the first electrode and the second electrode, and converting the change into a voltage. A capacitive pressure sensor, comprising: 2. The capacitance type pressure sensor according to claim 1, wherein said insulating film is divided into at least two parts. 3. A capacitance type pressure sensor according to claim 2, wherein said first electrode is divided into at least two or more. 4. The capacitance type pressure sensor according to claim 3, wherein the area of said first electrode is smaller than the area of said insulating film. 5. The capacitance type pressure sensor according to claim 1, wherein a part of the space between the first electrode and the silicon substrate is hollow. Capacitive pressure sensor. 6. A capacitance type pressure sensor according to claim 1, wherein said first electrode is made of polycrystalline silicon. Sensor. 7. A capacitance type pressure sensor according to claim 1, wherein the pressure sensor is integrated with a signal processing circuit for processing a signal of the pressure sensor.
A capacitance type pressure sensor, wherein the material of the gate electrode of the MOS transistor and the material of the first electrode included in the signal processing circuit are the same. 8. A step of doping a single-crystal silicon substrate with an impurity, a step of forming an oxide film on a predetermined portion on the impurity, and a step of oxidizing a conductive polycrystalline silicon film to be a first electrode. Forming a pattern on the film and patterning; forming a sacrificial layer on at least the first electrode and patterning; forming a conductive polycrystalline silicon film serving as a second electrode at least Forming a sacrificial layer, forming an insulated polycrystalline silicon film on the second electrode and patterning, removing the sacrificial layer, and forming a protective film on the insulated polycrystalline silicon film. Forming on a crystalline silicon film, etching a predetermined portion of a surface of the single crystal silicon substrate opposite to the surface on which the impurity is doped to form a diaphragm made of the impurity; Capacitive pressure method for manufacturing a sensor, comprising the steps, a to. 9. A single crystal silicon substrate, a diaphragm which is displaced by an applied pressure, a first electrode formed on the diaphragm and divided into at least two or more, and a first electrode through a gap. The second electrode formed facing the electrode of
The first electrode by the pressure applied to the diaphragm.
Means for detecting a change in capacitance between the first electrode and the second electrode due to a change in the distance between the first electrode and the second electrode, and converting the change into a voltage. A capacitive pressure sensor, comprising: 10. The capacitance type pressure sensor according to claim 9, wherein said first electrode is made of polycrystalline silicon. 11. A capacitance type pressure sensor according to claim 9, wherein said pressure sensor is integrated with a signal processing circuit for processing a signal of said pressure sensor, and a gate of a MOS transistor included in said signal processing circuit. The material of the electrode and the material of the first electrode are the same material. 12. A step of doping an impurity into a single crystal silicon substrate, and forming a conductive polycrystalline silicon film to be a first electrode at a predetermined portion on the impurity, and forming a plurality of divided regions on the impurity. Patterning; forming a sacrificial layer on at least the first electrode; and patterning; forming a conductive polycrystalline silicon film to be a second electrode on at least the sacrificial layer. Forming an insulated polycrystalline silicon film on the second electrode and patterning; removing the sacrificial layer; forming a protective film on the insulated polycrystalline silicon film And a step of etching a predetermined portion of the surface of the single crystal silicon substrate opposite to the surface doped with the impurity to form a diaphragm made of the impurity. A method for manufacturing a capacitance-type pressure sensor, comprising: