JPH10132682A - Semiconductor pressure sensor, its manufacture, and compound transmitter using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a semiconductor pressure sensor with an excessive pressure protection mechanism, which can be manufactured easily, in which a residual strain to a diaphragm can be suppressed, and which can also be applied to an object with a single rigid body part. SOLUTION: A substrate 51 in n-type face single-crystal silicon, and a rigid body part 23 is machined into an octagonal shape within a diaphragm 21 for detection differential pressure. A plate material 24 made of a silicon n-type high-concentration impurity layer is formed at the tip of the rigid body part 23 via a film 25 of SiN. The hole diameter of a pressure introduction port 29 is smaller than the maximum diameter of the plate material 24, thus generating a pressure difference between the upper and lower surfaces of the diaphragm 21 and causing the plate material 24 to contact post material 28 as a stopper when an excessive pressure is applied from an upper surface side. When an excessive pressure is applied from the lower surface side of the diaphragm 21, the plate material 24 hits against the support thick part of the diaphragm 21 for enabling the plate material 24 to operate as a stopper by reducing the diameter of the plate material 24 smaller than the minimum diameter of the lower surface side opening of a thick part for supporting the diaphragm 21 and increasing it larger than the maximum diameter of the diaphragm 21.

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 used for measuring pressure and the like in various plants, a method of manufacturing the same, and a composite transmitter using the same.

[0002]

2. Description of the Related Art It is widely known to construct a pressure sensor using a piezoresistor as a strain-sensitive gauge on a silicon diaphragm which is displaced under the pressure of an object to be measured. If excessive pressure is applied to this pressure sensor and exceeds the breaking strength of silicon, the diaphragm will be broken and the pressure sensor will be broken. Therefore, it is necessary to provide some kind of protection mechanism in the event that excessive pressure is applied.

In a pressure transmitter, a protection mechanism is often provided in a transmitter body in which the pressure sensor is incorporated so that an excessive pressure is not applied to the pressure sensor. However, providing a protection mechanism in the pressure transmitter body not only increases the size of the pressure transmitter itself, but also causes mechanical strain caused by incorporating the protection mechanism to cause drift and hysteresis of the transmitter output. Adversely affect properties. Therefore, it is desirable to provide a protection mechanism against excessive pressure in the pressure sensor itself.

[0004] As an example in which a protection mechanism against excessive pressure is provided in the pressure sensor itself, there is a semiconductor pressure sensor described in Japanese Patent Publication No. 6-29819. In this semiconductor pressure sensor, a cap having a cap on the front side of the diaphragm and a base having a projection on the lower side are fixed to the silicon substrate, so that the positive excessive pressure applied from the front side of the diaphragm and the lower side of the diaphragm A stopper is formed for both positive and negative overpressures of the negative overpressure applied from the side. Thus, by providing the pressure sensor itself with the excessive pressure protection mechanism, it is possible to reduce the size of the pressure transmitter and prevent the output characteristics of the transmitter from deteriorating.

Japanese Patent Application Laid-Open No. 6-313743 discloses an example in which a protection mechanism against excessive pressure is provided in the pressure sensor itself.
There is a semiconductor pressure sensor described in Japanese Unexamined Patent Publication (Kokai) No. H10-26095. In this semiconductor pressure sensor, two bosses projecting downward from a diaphragm of a semiconductor chip are provided separately from each other. In addition, a pedestal disposed opposite to the semiconductor chip has a first protrusion protruding between the two bosses and a pair of second protrusions opposing each other with the two bosses interposed therebetween. Have been.

When excessive pressure is applied from the diaphragm side to the pedestal side, the diaphragm is deformed,
The two bosses contact the pair of second protrusions, and further deformation of the diaphragm is prevented. Further, when an excessive pressure is applied from the pedestal side to the diaphragm side, the diaphragm is deformed, and the two bosses come into contact with the first projecting portion, and further deformation of the diaphragm is prevented.

[0007]

However, the above-mentioned Tokuho 6
In the semiconductor pressure sensor described in JP-A-298819, a cap functioning as a protection mechanism against excessive pressure from the negative side is fixed to the substrate on which the diaphragm is formed, and residual strain caused by the fixing, that is, the fixing. Therefore, there is a problem that the residual distortion due to thermal expansion or the like is directly transmitted to the diaphragm, the diaphragm is deformed, and the output signal offset of the pressure sensor when no load is applied becomes large.

Further, in the semiconductor pressure sensor described in Japanese Patent Application Laid-Open No. 6-313743, there is a problem that a plurality of bosses must be formed on the pedestal, which complicates the manufacturing process. Further, in the semiconductor pressure sensor described in this publication, only those in which two or more bosses are formed on the diaphragm are applicable, and only a single protrusion (boss) is formed at the center of the diaphragm. There was also a problem that it could not be applied to what was not done.

It is an object of the present invention to be easy to manufacture and
To realize a semiconductor pressure sensor having an excessive pressure protection mechanism in which residual strain on a diaphragm is suppressed and which can be applied to a sensor having a single protrusion or a rigid body, a method of manufacturing the semiconductor pressure sensor, and a composite transmitter using the same. It is.

[0010]

[Means for Solving the Problems]

(1) In order to achieve the above object, the present invention is configured as follows. That is, a single-crystal silicon substrate is hollowed out from the back side to form an opening on the back side, a diaphragm thin part and a thick part supporting the diaphragm are formed on the front side, and a pressure-receiving element is formed on the surface of the diaphragm. A piezoresistor is disposed, and in a region adjacent to the diaphragm thin portion, a rigid body having a thicker plate than the thin portion, and a metal base having a pressure inlet in the substrate are applied to the diaphragm. In the semiconductor pressure sensor for detecting a pressure, a plate member is bonded to a surface of the rigid body opposite to the thin-walled diaphragm.

When an excessive pressure is applied from the surface of the diaphragm, the plate material comes into contact with the base, so that the plate material can act as a mechanical stopper. When an excessive pressure is applied from the back side of the diaphragm, the plate material comes into contact with the thick portion and the rigid portion due to the deformation of the diaphragm, so that the plate material can act as a mechanical stopper. (2) Preferably In the above (1), the rigid portion is formed at the center of the diaphragm, and the shape of the plate is similar to the shape of the diaphragm. (3) Also, preferably, in the above (2), the diameter of the diaphragm is smaller than the diameter of the opening formed on the back surface side, and the diameter of the opening increases from the back surface side toward the diaphragm. , Gradually getting smaller.

(4) Preferably, in the above (3), the maximum diameter of the plate is smaller than the minimum diameter of the opening on the back surface. (5) Preferably, in the above (3), the minimum diameter of the plate member is larger than the maximum diameter of the diaphragm thin portion.

(6) Preferably, the above (1) to (1)
In (5), the thick portion supporting the diaphragm is fixed to a post member having a pressure inlet, and the diameter of the pressure inlet of the post member is equal to the maximum diameter of the plate member on a surface facing the thin portion of the diaphragm. And the surface opposite to the surface facing the diaphragm thin portion is smaller than the maximum diameter of the plate material.

(7) Preferably, the above (1) to
In (5), the thick portion supporting the diaphragm is fixed to a post material having a pressure inlet, and the thickness of the rigid portion, the thickness of the plate material, and the thickness of these adhesive layers are added. The plate thickness is smaller than the thickness of the thick portion supporting the diaphragm, and the maximum diameter of the plate material is larger than the hole diameter of the pressure inlet of the post material.

(8) Preferably, the above (1) to
In (7), an electrode is formed on a surface of the plate member opposite to a surface to be bonded to the rigid portion, a thick portion supporting the diaphragm is fixed, and a post member having a pressure inlet is provided with an electrode of the plate member. An electrode is formed on the surface facing the substrate, and a capacitor is formed between these two electrodes.

(9) Preferably, in (8) above, a change in the capacitance of the capacitor is detected, and based on the change in capacitance, the capacitor is used as differential pressure detecting means for detecting the pressure applied to the diaphragm. . In accordance with the deformation of the diaphragm, the distance between the two electrodes fluctuates and the capacitance value of the capacitor also changes. Therefore, if this change in the capacitance value is detected, the capacitor can be used as a differential pressure detecting means.

(10) Preferably, in (8) above, a change in the capacitance of the capacitor is detected, and the capacitor is used as acceleration detecting means for detecting an acceleration applied to the semiconductor pressure sensor based on the change in capacitance. Can be The diaphragm is deformed according to the acceleration applied to the semiconductor pressure sensor, and the distance between the two electrodes fluctuates according to the deformation of the diaphragm, so that the capacitance value of the capacitor also changes. For example, a capacitor can be used as acceleration detecting means.

(11) Preferably, the above (1) to
In (10), a temperature sensor is formed on the same substrate as the diaphragm thin portion.

(12) Preferably, the above (1) to (1)
In (11), another diaphragm separate from the above-mentioned diaphragm is provided on the same substrate as the above-mentioned diaphragm thin portion, and a piezo resistor for detecting static pressure is arranged on this other diaphragm to form a static pressure sensor. .

(13) In the composite transmitter, the semiconductor pressure sensor described in (1) to (10), the temperature detecting means, the static pressure detecting means, and the output signal of the static pressure detecting means are used as the temperature detecting means. And a signal processing means for correcting the differential pressure output signal detected by the semiconductor pressure sensor using the corrected output signals of the static pressure detecting means and the temperature detecting means.

(14) Preferably, in the above (13), the signal processing means comprises a memory and a microprocessor, and outputs the output signal of the static pressure detecting means with respect to the temperature change and the differential pressure output signal to the memory. The relationship and the relationship between the differential pressure output signal and the static pressure change are stored, and the detection signal from the semiconductor pressure sensor is corrected using the microprocessor based on the data stored in the memory.

(15) Preferably, (13)
Wherein the signal processing means comprises a memory and a microprocessor, and the memory has a relation between an output signal of the static pressure detecting means and a differential pressure output signal with respect to a temperature change, and an output of the static pressure detecting means due to the influence of acceleration. The relationship between the signal and the differential pressure output signal and the relationship between the differential pressure output signal and the static pressure change are stored, and the detection signal from the semiconductor pressure sensor is converted into data stored in the memory using the microprocessor. Correct based on

(16) Further, in the composite transmitter, the semiconductor pressure sensor, the temperature detecting means, the static pressure detecting means and the signal processing means of the above (9) are provided, and the signal processing means comprises a memory and a micro-processor. A memory for storing the relationship between the output signal of the static pressure detecting means and the differential pressure output signal with respect to the temperature change and the relationship between the differential pressure output signal with respect to the static pressure change in the memory; From the data stored in the memory using the microprocessor, a predetermined differential pressure threshold is stored in the memory, and the differential pressure output signal is When the differential pressure output signal is less than or equal to, the differential pressure output signal by the piezo resistor is selected,
When the pressure difference exceeds the threshold value, a differential pressure detecting means using a capacitor is selected and output.

(17) Preferably, the above (13)
-In (16), a first pressure receiving chamber in which a first pressure transmitting fluid for directly transmitting pressure to one surface side of the diaphragm of the semiconductor pressure sensor is sealed, and a second diaphragm is provided. A second pressure receiving chamber filled with a second pressure transmitting fluid for directly transmitting pressure to the other surface of the diaphragm, a first measurement pressure is applied to the first diaphragm, and a second pressure receiving chamber is applied to the second diaphragm. Two measurement pressures are applied, and the difference between the first and second measurement pressures is detected by a semiconductor pressure sensor.

(18) In the method of manufacturing a semiconductor pressure sensor, a step of forming a piezoresistor on the surface of the diaphragm supporting substrate made of single crystal silicon, and an etching mask on the back surface side of the diaphragm supporting substrate. A step of forming a predetermined pattern, a step of forming a predetermined pattern by etching on the back side of the diaphragm support substrate, and a step of forming a predetermined pattern by etching after connecting a plate material to the back side of the diaphragm support substrate Forming an opening on the back side of the diaphragm support substrate, and forming a thin portion on the front surface and a thick portion for supporting the same, and the side surface of the thick portion is formed on the back surface of the diaphragm support substrate. The side opening is wide and the side where the diaphragm is formed is tapered so as to be narrow. Forming a rigid portion thicker than the thin portion in a region adjacent to the diaphragm thin portion, forming the plate material into a predetermined shape, and a pressure introduction port communicating with the opening. A metal substrate having
And fixing to the back surface of the diaphragm support substrate.

(19) Preferably, in the above (18), a step of forming an electrode on the surface of the plate member facing the base, and a step of forming an electrode on the base opposite to the electrode formed on the plate member And further provided.

[0027]

FIG. 1 is a schematic top view of a semiconductor pressure sensor according to a first embodiment of the present invention, and FIG. 2 is a schematic sectional view taken along line AOB of FIG. It is.
1 and 2, a substrate 51 is made of n-type (100) plane single crystal silicon, and a rigid body (projection) 23 is formed in a diaphragm 21 for detecting a differential pressure by using, for example, an alkali anisotropic etching technique. To form an octagon.
Alternatively, it may be processed into a circular shape by isotropic etching.

Outside the differential pressure detecting diaphragm 21,
The two static pressure detecting diaphragms 22 are simultaneously formed by alkali anisotropic etching. A plate member 24 made of a silicon p-type high-concentration impurity layer is formed at the tip of the rigid portion 23 via a SiN film 25.

The shape of the plate member 24 is octagon in FIGS. 1 and 2, but may be a circular shape or any other shape. It is more appropriate to make the shape similar to the shape of the diaphragm. 27 is a low melting point glass, 28 is a post material (base) made of, for example, Fe—Ni having a pressure inlet 29. Piezoresistors 31a to 31d and 32a to 32d for detecting stress when the diaphragm is deformed by receiving pressure on the diaphragms 21 and 22 and a temperature sensor 33
Are formed. 34 is a wiring of a p-type high concentration impurity layer,
35 is an aluminum wiring, and 1 to 12 are aluminum contact pads.

Here, the rigid portion 23 is
The area in contact with the differential pressure detecting diaphragm 21 is larger than the area of the surface of the post member 28 facing the pressure inlet 29, and has a shape that becomes thinner toward the post member 28. The diameter of the differential pressure detecting diaphragm 21 is smaller than the diameter of the opening of the substrate 51 facing the pressure inlet 29 of the post member 28. That is, the diameter of the opening increases from the differential pressure detecting diaphragm 21 toward the post member 28.

FIG. 3 is a view showing a manufacturing process of the semiconductor pressure sensor shown in FIGS. 1 and 2. Hereinafter, the manufacturing process will be described with reference to FIG. First, in FIG. 3A, boron is diffused on the upper surface (surface) of a diaphragm support substrate 51 made of n-type (100) plane single-crystal silicon to form piezoresistors 31a to 31d and a p-type high-concentration impurity layer. Wiring 34, aluminum wiring 35, and contact pads 1 to 12 are formed.

Next, in FIG. 3B, an SiN film 25 is deposited on the lower surface (back surface) side of the single crystal silicon substrate 51 by, for example, CVD, and a pattern serving as a mask at the time of alkali anisotropic etching is formed. It is formed by photolithography and etching.

Subsequently, as shown in FIG. 3 (c), a Si
An O2 film 26 is deposited, and a pattern is formed by photolithography and etching.

Next, in FIG. 3D, after the above-described steps (a) to (c), a silicon p-type high concentration impurity layer is deposited on the lower surface side of the single crystal silicon substrate 51 by, for example, CVD. After connecting the plate material 24 to the lower surface of the substrate 51, a pattern is formed by photolithography and etching.

Next, in FIG. 3E, after etching the SiO 2 film 26, the diaphragms 21, 2 are etched by alkali anisotropic etching with hydrazine.
2. The rigid body 23 and the plate 24 are formed. Hydrazine is p-type high-concentration impurity silicon for n-type silicon, S
Since the selectivity of iN is large, it is possible to selectively remove n-type silicon by etching.

At this time, the side surface of the thick portion supporting the diaphragm 21 has a wide opening on the lower surface side of the silicon substrate 51.
It is formed in a tapered shape so that the side on which the diaphragm 21 is formed becomes narrow. Finally, the post material 28 made of Fe—Ni or the like is fixed to the silicon substrate 51 via the low-melting glass 27. At this time, the diaphragm 21 communicating with the pressure inlet 29 is a diaphragm for detecting a differential pressure, and the diaphragm 22 not communicating with the pressure inlet 29 is a diaphragm for detecting a static pressure.

If the sum of the thickness of the projection 23, the thickness of the SiN film, and the thickness of the plate material 24 is substantially equal to or greater than the thickness of the thick film supporting the diaphragm 21, FIG.
The hole 3 having a diameter E larger than the maximum diameter D of the plate member 24 is formed on the surface of the post member 28 facing the plate member 24 as shown in FIG.
By forming 0, a displacement area of the diaphragm 21 when pressure is applied to the diaphragm 21 can be secured.

If the sum of the thickness of the projection 23, the thickness of the SiN film, and the thickness of the plate material 24 is smaller than the thickness of the thick film supporting the diaphragm 21, pressure is applied from the upper surface of the diaphragm. If the diaphragm displacement area at the time can be sufficiently ensured, the surface of the post member 28 facing the plate member 24 can be made flat as shown in FIG.

In any case, the hole diameter d of the pressure introduction port 29 is set smaller than the maximum diameter D of the plate member 24. 4 and 5, the plate member 24 and the post member 28 come into contact with each other when an excessive pressure is applied from the upper surface of the diaphragm, so that a mechanical stopper can be formed. The dimension of the hole 30 in the depth direction is, for example, 10 microns to 50 microns.

The p-type piezoresistors 31a-31d, 32a-32 formed near the respective surfaces of the differential pressure detecting diaphragm 21 and the four static pressure detecting diaphragms 22 are formed.
32d is formed in the <110> direction, which is most sensitive to stress by diffusing boron or the like. The piezo resistance increases when a tensile stress acts in the longitudinal direction. Gauges arranged in this direction are called L gauges.

The piezoresistive resistance decreases when a tensile stress acts in the lateral direction. Gauges arranged in this direction are called T gauges. In the example of FIG. 1, all four piezoresistors 31 a to 31 d on the differential pressure detecting diaphragm 21 are arranged near the support of the diaphragm 21, and two L gauges whose longitudinal direction is parallel to the radial direction of the diaphragm 21. Two T gauges 31b and 31d whose longitudinal directions are parallel to the tangential direction of the diaphragm 21 are arranged.

On the static pressure detecting diaphragm 22, L gauges 32a, 32c and T gauges 32b, 32d are arranged. The method of arranging the piezoresistors is, in addition to the example of FIG. 1, a method of arranging two L gauges and two T gauges all near the rigid body part, two L gauges near the diaphragm support part and two L gauges near the rigid body part. There is a method of arranging two T gauges in the vicinity of the diaphragm support and two in the vicinity of the rigid body. The piezoresistors 31a to 31d and 32a to 32d form two sets of Wheatstone bridge circuits as shown in FIG.

Here, a portion composed of a bridge circuit of the differential pressure detecting diaphragm 21 and the piezoresistors 31a to 31d is called a differential pressure sensor, and the static pressure detecting diaphragm 22
A portion constituted by a bridge circuit including the piezoresistors 32a to 32d is referred to as a static pressure sensor. Diaphragm 21 or 2
When pressure is applied to each of the diaphragms 2,
Each of the bridge circuits formed by the piezoresistors formed on the diaphragms 21 and 22 generates sensor outputs V1 and V2 that are substantially proportional to the pressure difference between the upper and lower surfaces of the diaphragms 21 and 22. .

Here, the differential pressure sensor measures the pressure difference (differential pressure) between the upper surface and the lower surface of the diaphragm 21, while the static pressure sensor measures the pressure difference between the upper surface of the diaphragm 22 and the sealed constant pressure portion. (Static pressure) will be measured.

On the other hand, the temperature sensor 33 integrated on the same substrate as the diaphragms 21 and 22 is similarly formed by diffusing boron or the like, but shows almost no change in resistance to stress change. By arranging in the direction,
Make it sensitive only to temperature. The temperature sensor 33 is connected to the piezoresistive bridge circuit of the differential pressure sensor and the static pressure sensor as shown in FIG.

Piezo resistors 31a-31d, 32a-32
d between arrangements and aluminum contact pad 1
For the wiring to -12, a p-type impurity diffusion layer 34 in which boron or the like is diffused at a higher concentration and an aluminum wiring 35 are used in combination. In this embodiment, the diaphragms 21, 2
2 and piezoresistors 31a to 31d, 32a to 32d
Where the effect of temperature hysteresis is relatively small, such as at a distance from the equipment, aluminum wiring with a small resistance value is used. Is also possible.

Next, the operation of the sensor when pressure is applied to the diaphragm 21 will be described with reference to FIGS. When a pressure difference occurs between the upper surface and the lower surface of the diaphragm 21 and the upper surface side has a higher pressure, FIG.
The diaphragm 21 is deformed as shown in FIG. When the diaphragm 21 is deformed, the stress generated in the vicinity of the surface of the diaphragm 21 in which the piezoresistor is built is shown in FIG.
The result is as shown in FIG. That is, on the diaphragm 21, the maximum tensile stress σ1 is generated in the vicinity of the support portion of the diaphragm 21, and the maximum compression stress is generated in the vicinity of the rigid body.

As shown in FIG. 7A, if the outer diameter of the diaphragm 21 is X, the outer diameter of the rigid portion 23 is Y, and the thickness of the diaphragm is h, when the differential pressure ΔP is applied, The maximum tensile stress σ1 is represented by the following equation (1). σ1 = 3 (X ² −Y ² ) ΔP / (16h ² ) (1) As shown in FIG. 1, when two L gauges and two T gauges are arranged near the support of the diaphragm 21, respectively. , The output V1 of the differential pressure sensor is expressed by the following equation (2). _{V1 = (1/2) · π 44} (1-ν) σ1 · V --- (2) where, [nu is Poisson's ratio, [pi ₄₄ is piezoresistance coefficient of shear, V is the excitation voltage.

Next, the operation when an excessive pressure is applied from the lower surface side of the diaphragm 21 will be described. When an excessive pressure is applied from the lower surface side of the diaphragm 21, the diaphragm 21 deforms as shown in FIG. At this time, by making the diameter of the plate member 24 smaller than the minimum diameter of the back-side opening of the thick portion supporting the diaphragm 21 and larger than the maximum diameter of the diaphragm 21 as shown in FIG. The plate member 24 hits the tapered portion of the thick portion supporting the diaphragm 21 formed during the alkali anisotropic etching, and the plate member 24 can function as a mechanical stopper.

As described above, according to the first embodiment of the present invention, since the plate member 24 is connected to the distal end face of the rigid portion 23 facing the post member 28, a single protrusion or rigid portion 23 is provided.
And a semiconductor pressure sensor having an excessive pressure protection mechanism applicable to those having a pressure sensor.

In the step (d) of FIG.
In step (e), the connection between the plate 23 and the substrate 51 except for the connection with the distal end surface of the rigid part 23 is caused by the residual strain on the base 51 caused by joining the plate 24 to the base 1. Most are released by being removed. As a result, there is no deformation of the diaphragm 21 due to the residual strain, and the output offset can be kept small.

As described with reference to FIG. 3, the manufacturing process is provided with an excessive pressure protection mechanism only by adding a simple process such as connection of the plate member 24 to the distal end surface of the rigid member 23. Semiconductor pressure sensors can be manufactured.

Therefore, according to the first embodiment of the present invention, it is easy to manufacture, the residual strain on the diaphragm is suppressed, and the excessively large size can be applied to the one having a single protrusion or a rigid body. A semiconductor pressure sensor having a pressure protection mechanism and a method for manufacturing the same can be realized.

FIG. 9 is a schematic sectional view of a semiconductor pressure sensor according to a second embodiment of the present invention. Since the upper surface is the same as the example shown in FIG. The example of FIG. 9 corresponds to a cross section taken along line AOB of the top view of FIG.

As shown in FIG. 9, in the second embodiment, an electrode 41 is provided on the surface of the plate member 24 facing the post member 28, and an electrode 42 is provided on the surface of the post member 28 facing the plate member 24. And a capacitor is formed between the two electrodes 41 and 42.

The wiring from the capacitor is performed by forming n-type high-concentration impurity layers 43 and 44 on an n-type silicon substrate 51. Other configurations are the same as those in the example shown in FIG.

FIG. 10 is a view showing a manufacturing process of the semiconductor pressure sensor according to the second embodiment shown in FIG. Hereinafter, the manufacturing process will be described with reference to FIG. In FIG. 10A, the diaphragm support substrate 51
Piezoresistors 31a to 31d, 32a to 32d, p-type high-concentration impurity layer wiring 34 and aluminum wiring 35,
Contact pads 1 to 12, n-type high concentration impurity layer 43,
44 is formed.

Next, as shown in FIG. 10B, an SiN film 25 is deposited on the lower surface of the single crystal silicon substrate 51, and a pattern to be used as a mask at the time of alkali anisotropic etching and a contact for extracting an electrode are formed. Holes are formed by photolithography and etching.

Subsequently, in FIG. 10C, an SiO 2 film 26 is deposited on the lower surface of the single crystal silicon substrate 51, and a pattern is formed by photolithography and etching.

Next, in FIG. 10D, after the above-described steps (a) to (c), the plate material 24 is bonded to the lower surface side of the single crystal silicon substrate 51 to form a silicon p-type high concentration impurity layer. Is deposited and a pattern is formed, for example, Pt / C
The r electrode 41 is formed on the surface of the plate member 24 by vapor deposition.

Then, in (e) of FIG.
After the etching of 2, the diaphragms 21 and 22 were subjected to alkali anisotropic etching with hydrazine.
The rigid part 23 and the plate 24 are formed. Finally, the post material 28 having the electrode 42 is fixed to the substrate 51 via the low-melting glass 27.

The capacitor composed of the electrodes 41 and 42 formed as described above can be used as a capacitive pressure sensor. That is, as shown in FIG. 11, the projection 23 is displaced in accordance with the deformation of the diaphragm 21 generated when receiving the pressure, and at the same time, the plate 24 is displaced in parallel. As shown by a curve P in FIG. 12, the output V1 of the piezoresistive bridge circuit increases in nonlinearity and decreases in sensitivity as the displacement of the diaphragm increases. Is inversely proportional to the distance, the greater the displacement of the diaphragm, the higher the sensitivity.

Therefore, assuming that when the differential pressure ΔP exceeds the differential pressure ΔP1, the nonlinearity of the output V1 of the piezoresistive bridge circuit becomes large, the differential pressure ΔP becomes 0 ≦ ΔP ≦ ΔP1
Is measured with a piezoresistive pressure sensor and the differential pressure
By measuring the range of P up to ΔP1 <ΔP ≦ ΔP2 with a capacitive pressure sensor, a wide pressure range can be measured with high accuracy.

When the pressure sensor is used in a dynamic place such as a car, for example, it is used not only as a differential pressure sensor using a piezoresistor but also as a capacitive acceleration sensor using the above-mentioned capacitor. can do. That is, as shown in FIG. 13, when the positive-side acceleration G is applied to the sensor in addition to the positive-side differential pressure ΔP, the plate 2
Numeral 4 causes a deformation due to the acceleration in addition to a parallel displacement corresponding to the deformation of the diaphragm 21 generated when receiving the pressure. The deformation of the plate material due to the acceleration causes an increase in the capacitance value of the capacitor.

Therefore, as shown in FIG. 13, when the positive differential pressure and the acceleration are received, the capacitance value of the capacitor becomes larger as shown in FIG. By reading the change in capacitance, the pressure component and the acceleration component can be separated.

As described above, by forming the electrode 41 on the plate member 24 and the electrode 42 on the post member 28, a capacitive pressure sensor and a capacitive acceleration sensor can be formed. By combining with, more accurate pressure measurement becomes possible.

As shown in FIG. 13, there is a possibility that not only the positive side acceleration but also the negative side acceleration may be received. However, it is possible to determine whether the acceleration is the positive side acceleration or the negative side acceleration. It is possible. That is, as shown in FIG. 13, when the plate member 24 receives the positive side differential pressure and receives the positive side acceleration, the plate member 24 is deformed in the direction of the post member 28, so that the plate member 24 is not deformed. The capacitance value becomes larger in comparison.

On the other hand, as shown in FIG. 15, when receiving the positive side differential pressure and receiving the negative side acceleration, the plate member 24 is deformed in a direction away from the post member 28, so that the plate member 24 is deformed. The capacitance value is smaller than that in a state where no signal is received.

Accordingly, if the relationship between the positive side differential pressure and the capacitance value is known in advance in a state where the plate member 24 is not deformed, that is, in a state where the plate material 24 is not subjected to acceleration, how much smaller is the capacitance value. Calculating the positive or negative capacitance value, it is possible to detect how much positive acceleration or negative acceleration has been received.

Further, as shown in FIG. 16, when a negative pressure difference is applied and a positive acceleration is applied, the plate material 24 is deformed in the direction of the post material 28, so that the plate material 24 is deformed. The capacitance value is larger than in the state without the capacitance.

On the other hand, as shown in FIG. 17, when receiving a negative pressure difference and receiving a negative acceleration, the plate material 24 is deformed in a direction away from the post material 28, so that the plate material 24 is deformed. The capacitance value is smaller than that in a state where no signal is received.

Therefore, if the relationship between the negative differential pressure and the capacitance value in a state where the plate member 24 is not deformed, that is, in a state where the plate material 24 is not subjected to acceleration, is known in advance, how much smaller is the capacitance value. Calculating the capacity value of the negative side or the large value, it is possible to detect how much positive side acceleration has been received and how much negative side acceleration has been received. As described above, even when the vehicle receives the differential pressure on the positive side and the negative side and receives the acceleration, it is possible to determine whether the vehicle has received the acceleration on the positive side or the acceleration on the negative side.

After the step (e) in FIG. 10, the semiconductor pressure sensor is welded or adhered to an output take-out fitting (seal fitting) 75 as shown in FIG. The take-out terminal 76 is connected by a lead wire 77. The metal fitting 75 has an airtight structure by a hermetic seal.

As described above, according to the second embodiment of the present invention, the following effects are obtained in addition to the effects of the first embodiment. That is, the electrode 41 and the plate member 2 of the post member 28 are provided on the surface of the plate member 24 facing the post member 28.
An electrode 42 is formed on the surface side facing 4 and both electrodes 41 and 4
2 and a capacitor is formed between them, so that the differential pressure range where the linearity of the output of the piezoresistive bridge circuit is good is measured with a piezoresistive pressure sensor, and the nonlinearity of the output of the piezoresistive bridge circuit is measured. By measuring the differential pressure range in which is large with a capacitive pressure sensor, it is possible to measure a wide pressure range with high accuracy.

Further, when the semiconductor pressure sensor is used in a dynamic place such as a car, for example, the above-mentioned capacitor is used not only as a differential pressure sensor utilizing piezoresistance but also as a capacitive acceleration sensor. Can be.

FIG. 19 is a schematic sectional view of a composite transmitter according to a third embodiment of the present invention. In FIG. 19, the semiconductor pressure sensor having the configuration shown in FIG. 4, FIG. 5, or FIG. 9 incorporated in the seal fitting 75 is incorporated in the pressure receiving section 81 of the composite transmitter.

The pressure applied to the high pressure side seal diaphragm 82a and the low pressure side seal diaphragm 82b is transmitted to the sensor chip 84 through a pressure transmission fluid 83 such as silicone oil.

The output of the semiconductor sensor is transmitted to a signal processing unit through an FPC (flexible printed circuit) 85. In the case of the composite transmitter according to the present invention, three of differential pressure, static pressure, and temperature are used.
The kinds of output signals are selectively taken in through an MPX (multiplexer) 86.

Next, the output signal is amplified by a PGA (programmable gain amplifier) 87 and the A / D converter 88
The digital signal is converted into a digital signal and transmitted to an MPU (microprocessor) 89. MPU (Signal Processing Means) 89
Calculates and corrects the sensor output based on the data in the ROM 90 in which the characteristics of the differential pressure, static pressure, and temperature sensors and the characteristics of the capacitive pressure sensor, the differential pressure threshold value, and the acceleration characteristics are stored. Calculate each value of pressure, temperature and acceleration.

At this time, the differential pressure applied to the sensor is
It is determined whether the pressure difference is equal to or less than the differential pressure threshold value ΔP1, and when the differential pressure is equal to or less than ΔP1, the output of the piezoresistive pressure sensor is output. Use the output of the sensor. In this way, a highly sensitive sensor output can be obtained over a wide pressure range.

The value thus obtained is again converted into an analog signal by a D / A converter 91, and a high-precision analog signal, digital signal or a signal in which an analog or digital signal is superimposed via a V / I converter 92. Is output.

In a conventional composite transmitter which does not have a mechanical stopper against excessive pressure in the sensor chip itself, it is necessary to take measures such as forming a center diaphragm which serves as a mechanical stopper in the transmitter body. Was. That is, if excessive pressure applied to the seal diaphragms 82a and 82b is directly transmitted to the sensor chip via the pressure transmitting fluid, the sensor chip may be damaged, so that the seal diaphragms 82a and 82b and the sensor It is necessary to arrange the center diaphragm between the chip and the chip so that the pressure applied to the seal diaphragms 82a and 82b is transmitted to the sensor chip via the center diaphragm.

Providing such a center diaphragm in the transmitter body not only complicates the manufacturing process but also causes main factors such as drift of the transmitter output and temperature hysteresis.

On the other hand, in the semiconductor pressure sensor according to the present invention, since the pressure sensor itself has a mechanical stopper for both positive and negative excessive pressures, the center diaphragm protects the sensor chip when excessive pressure is applied. It is not necessary to provide a special structure such as the above in the transmitter main body, the manufacture becomes easy, and the output characteristics as the transmitter can be further stabilized.

As described above, according to the composite transmitter in one embodiment of the present invention, since the semiconductor pressure sensor having the structure shown in FIG. 4, FIG. 5, or FIG. 9 is provided, the center for protecting the sensor chip is provided. There is no need to provide a special structure such as a diaphragm in the transmitter main body, the manufacture becomes easy, and the output characteristics of the transmitter can be made more stable.

[0086]

Since the present invention is configured as described above, it has the following effects. Easy to manufacture,
In addition, a semiconductor pressure sensor having an excessive pressure protection mechanism in which residual strain on a diaphragm is suppressed and which can be applied to a sensor having a single protrusion or a rigid body, a method of manufacturing the same, and a composite transmitter using the same are realized. can do.

Further, by using this protection mechanism, it is possible to realize a highly accurate semiconductor pressure sensor with an excessive pressure protection mechanism. In addition, by forming two electrodes facing each other using this protection mechanism to constitute a capacitive sensor, a wide pressure range can be measured with high accuracy, and a pressure component and an acceleration component can be separated. It becomes possible.

Further, since the pressure sensor itself can be provided with a mechanical stopper for both positive and negative excessive pressures, the structure of the transmitter body can be simplified, and a highly accurate composite transmitter having stable output characteristics can be realized. it can.

[Brief description of the drawings]

FIG. 1 is a schematic top view of a semiconductor pressure sensor according to a first embodiment of the present invention.

FIG. 2 is a schematic sectional view taken along the line AOB of FIG.

FIG. 3 is a view showing a manufacturing process of the semiconductor pressure sensor shown in FIGS. 1 and 2;

FIG. 4 is a schematic sectional view showing an example of the shape of a post material.

FIG. 5 is a schematic sectional view showing another example of the shape of the post material.

FIG. 6 is a connection diagram of a piezo resistor.

FIG. 7 is a diagram showing deformation and stress distribution of a diaphragm when pressure is applied.

FIG. 8 is a diagram showing deformation of the diaphragm when excessive pressure is applied from the lower surface of the diaphragm.

FIG. 9 is a schematic sectional view of a semiconductor pressure sensor according to a second embodiment of the present invention.

FIG. 10 is a view showing a manufacturing process of the semiconductor pressure sensor shown in FIG. 9;

11 is a diagram showing deformation of a diaphragm when pressure is applied to the semiconductor pressure sensor shown in FIG.

12 is a graph showing a relationship between a bridge output and a change in capacitance with respect to a differential pressure in the semiconductor pressure sensor shown in FIG.

13 is a diagram showing deformation when a positive-side differential pressure and acceleration are simultaneously applied to the semiconductor pressure sensor shown in FIG. 9;

14 is a graph showing a relationship between a differential pressure and a change in a capacitance value when only a differential pressure is applied to the semiconductor pressure sensor shown in FIG. 9 and when a differential pressure and an acceleration are simultaneously applied. .

FIG. 15 is a diagram showing deformation when a positive differential pressure and a negative acceleration are simultaneously applied to the semiconductor pressure sensor shown in FIG. 9;

16 is a diagram showing deformation when a negative differential pressure and a positive acceleration are simultaneously applied to the semiconductor pressure sensor shown in FIG. 9;

FIG. 17 is a diagram showing deformation when a negative differential pressure and acceleration are simultaneously applied to the semiconductor pressure sensor shown in FIG. 9;

FIG. 18 is a schematic cross-sectional view showing a state where the semiconductor pressure sensor according to the second embodiment is incorporated in an output take-out fitting (seal fitting).

FIG. 19 is a schematic sectional view of a composite transmitter according to a third embodiment of the present invention.

[Explanation of symbols]

1-12 Aluminum contact pad for taking out output of composite sensor 21 Diaphragm for differential pressure detection 22 Diaphragm for static pressure detection 23 Rigid portion 24 Plate 25 Adhesive layer between rigid portion and plate 26 Oxide film used as sacrificial layer at etching 27 Low melting point Glass 28 Post material 29 Pressure inlet 30 Hole having a diameter larger than the maximum diameter of the plate material 31a to 31d Piezo resistance on diaphragm for detecting differential pressure 32a to 32d Piezo resistance on diaphragm for detecting static pressure 33 Gauge for temperature sensor 34 p Type high concentration impurity layer wiring 35 Aluminum wiring 41 Plate material side electrode 42 Post material side electrode 43 Plate material side silicon n type high concentration impurity layer 44 Substrate surface side silicon n type high concentration impurity layer 51 n type single crystal silicon substrate 75 Hermetic seal 76 Output extraction terminal 77 Lead wire 81 Differential pressure transmitter pressure receiving part 82a High pressure side seal diaphragm 82b Low pressure side seal diaphragm 83 Pressure transmitting fluid 84 Sensor chip 85 Flexible printed circuit 86 Multiplexer 87 Programmable gain amplifier 88 A / D converter 89 Microprocessor 90 ROM 91 D / A converter 92 V / I converter

Claims (7)

[Claims] 1. A single-crystal silicon substrate is hollowed out from the back side to form an opening on the back side, a thin-walled diaphragm and a thick-walled portion for supporting the same are formed on the front-side, and a single-crystal silicon substrate is formed on the front surface of the diaphragm. A piezoresistor is disposed as a pressure-receiving element, a rigid portion having a thickness greater than the thin portion in a region adjacent to the thin portion of the diaphragm, and a metal base having a pressure inlet in the substrate. A semiconductor pressure sensor for detecting a pressure applied to a rigid body, comprising a plate bonded to a surface of the rigid body opposite to a side of the diaphragm thin portion. 2. The semiconductor pressure sensor according to claim 1, wherein said rigid portion is formed at a central portion of said diaphragm, said plate has a shape similar to that of said diaphragm, and said diaphragm has a diameter of said diaphragm. A semiconductor pressure sensor, wherein the diameter of the opening is smaller than the diameter of the opening formed on the back surface, and the diameter of the opening gradually decreases from the back surface toward the diaphragm. 3. A semiconductor pressure sensor according to claim 2, wherein a maximum diameter of said plate is smaller than a minimum diameter of said opening at said back surface, and a minimum diameter of said plate is smaller than a maximum diameter of said diaphragm thin portion. Semiconductor pressure sensor characterized in that it is also large. 4. The semiconductor pressure sensor according to claim 1, wherein an electrode is formed on a surface of the plate member opposite to a surface to be bonded to the rigid portion, and the thick plate supports the diaphragm. The part is fixed, on the post material having a pressure inlet, an electrode is formed on the surface of the plate material facing the electrode,
A semiconductor pressure sensor wherein a capacitor is formed between these two electrodes. 5. A semiconductor pressure sensor according to claim 1, wherein said semiconductor pressure sensor comprises: a temperature detecting means; a static pressure detecting means; and an output signal of said static pressure detecting means. Signal processing means for correcting the differential pressure output signal detected by the semiconductor pressure sensor using the corrected output signals of the static pressure detection means and the temperature detection means. Composite transmitter. 6. A method of manufacturing a semiconductor pressure sensor, comprising the steps of: forming a piezoresistor on the surface of a diaphragm supporting substrate made of single crystal silicon; and forming a predetermined pattern serving as an etching mask on the back surface of the diaphragm supporting substrate. Forming a predetermined pattern by etching on the back side of the diaphragm support substrate; and connecting a plate material to the back side of the diaphragm support substrate, and then forming a predetermined pattern by etching. Forming an opening on the back side of the diaphragm support substrate,
A thin portion of the diaphragm on the front side and a thick portion supporting the same, such that the side surface of the thick portion has a wide opening on the back side of the diaphragm support substrate and a narrow side on which the diaphragm is formed. Forming a tapered shape, forming a rigid portion thicker than the thin portion in a region adjacent to the diaphragm thin portion, forming the plate material into a predetermined shape, and communicating with the opening portion A method for manufacturing a semiconductor pressure sensor, comprising: a metal base having a pressure introduction port; and a step of fixing to a back surface of the diaphragm support substrate. 7. A method of manufacturing a semiconductor pressure sensor according to claim 6, wherein an electrode is formed on a surface of said plate material facing said base, and an electrode facing said electrode formed on said plate material is provided on said base. Forming a semiconductor pressure sensor.