JPH1114484A - Pressure sensor and its manufacturing method, and differential transfer device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow a plurality of pressure sensitivity of a semiconductor pressure sensor. SOLUTION: On a differential diaphragm 65, a rigid body 58 is formed annularly along the outside periphery of its central region, while on the side of a p-type diffusion layer 51b, a projection 57 is annularly formed along the outer periphery of the central region of the differential diaphragm 65. When a positive pressure ΔP of a specified value or above is applied, the outside periphery of a central region 65a of the differential diaphragm 65 is constrained by the projection 57 and the rigid body 58, and peaks σ2 and σ1 of tensile stress appear in the vicinity of outside edge part in the central region and that in a peripheral region, respectively, in a stress distribution on the differential diaphragm 65. Here, four piezo resistors are arranged for each of the vicinity or outside edge part in the peripheral region and that in the central region, respectively, on the differential diaphragm 65.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diffusion type pressure sensor utilizing a piezoresistance effect of a diffusion resistance layer formed on a silicon pellet having a diaphragm structure.

[0002]

2. Description of the Related Art As one of diffusion type pressure sensors utilizing the piezoresistance effect of a diffusion resistance layer formed on a silicon pellet having a diaphragm structure, a semiconductor pressure sensor for differential pressure described in Japanese Patent Application Laid-Open No. Hei 8-295085 is known. Have been.
This semiconductor pressure sensor (hereinafter, referred to as a conventional pressure sensor)
In order to suppress the non-linear error, there are two structural measures, namely, (a) formation of a boss in the central region on the diaphragm, and (b) periphery except for the rim where the diffusion layer is formed. The area is made thinner.

[0003]

However, the above-mentioned conventional pressure sensor has a disadvantage that it cannot cover a wide pressure range from low pressure to high pressure because the pressure sensitivity is constant. .

In order to solve this disadvantage, a plurality of diaphragms having mutually different pressure receiving areas, that is, a plurality of pressure sensors having mutually different pressure sensitivities may be mounted on one chip. This time, a new problem of increasing the size of the chip occurs.

Accordingly, an object of the present invention is to provide a small-sized pressure sensor having a plurality of pressure sensitivities. By using the present pressure sensor as a detection end of the differential pressure transmitter, the measurement pressure range of the differential pressure transmitter can be expanded.

[0006]

In order to solve the above-mentioned problems, the present invention is directed to a differential pressure applied to a differential pressure diaphragm by a plurality of strain gauges arranged on a differential pressure diaphragm fixed on a substrate. A differential pressure sensor for detecting distortion of the differential pressure diaphragm displaced in accordance with
The substrate has a support end for supporting the differential pressure diaphragm in a region surrounding a central region on a back surface of the differential pressure diaphragm from a point in time when the diaphragm for differential pressure is displaced by a predetermined displacement amount on the substrate side; Some of the strain gauges are arranged in the peripheral region so as to detect a strain in a peripheral region of the surface of the differential pressure diaphragm, and some of the strain gauges are strain gauges. The present invention provides a differential pressure sensor, wherein the sensor is disposed in a central region of the diaphragm for detecting a distortion in a central region of the diaphragm.

According to such a structure, when the differential pressure applied to the differential pressure diaphragm exceeds a predetermined value, the central region of the differential pressure diaphragm is simply supported. Therefore, when the differential pressure applied to the differential pressure diaphragm exceeds a predetermined value, the stress distribution on the differential pressure diaphragm includes:
The peak value σ of the tensile stress is applied to both the central region and the peripheral region.
₁ and σ ₂ appear (see FIG. 4B). This means that the central region and the peripheral region of the differential pressure diaphragm can each function as an independent diaphragm. To be more specific, the peripheral region the larger peak value sigma ₁ of appears functions as sensitive low pressure diaphragm to changes in the applied pressure difference, the central region appears peak value sigma ₂ The smaller, It functions as a high-pressure diaphragm that is insensitive to changes in the applied differential pressure.

Accordingly, even when only one diaphragm for differential pressure is mounted, a plurality of pressure sensitivities can be achieved as in the case where a plurality of diaphragms for differential pressure are mounted. That is, it is possible to cover a wide pressure range from low pressure to high pressure without the disadvantage of increasing the size of the chip.

For example, if such a differential pressure sensor is mounted as a detection end of the differential pressure transmitter, it is obvious that the measurement pressure range of the differential pressure transmitter is expanded.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

First, the basic structure of the semiconductor pressure sensor according to the present embodiment will be described.

The semiconductor pressure sensor of the present invention has a piezoresistance effect of a p-type diffusion resistance layer (hereinafter referred to as piezoresistance) formed on a diaphragm having a two-layer structure of an insulating film such as SiON and an n-type silicon single crystal film. Is a diffusion type pressure sensor that detects both the differential pressure and the static pressure, that is, a composite sensor. As shown in FIG. 1, the basic structure of the sensor chip 100 includes a differential pressure diaphragm 65 responsive to a differential pressure and a static pressure diaphragm 66 responsive to a static pressure, and a post 59 having a pressure inlet 68 (usually Fe -Ni alloy or other metal), an adhesive layer 60 (usually made of low melting point glass, Pyrex glass or other glass) and the like.

However, in the present embodiment, since the restraining member 58 is formed on the surface of the differential pressure diaphragm 65 because of necessity, the deformation of the differential pressure diaphragm 65 during the differential pressure measurement causes the end face 59a of the post 59 to deform. An initial gap Δt _{0 on the} order of μm is provided between the end face 59 a of the post 59 and the tip of the restraining member 58 so as not to be hindered by the gap.

Incidentally, for industrial reasons and the like, the adhesive layer 6 having a sufficient height to provide such an initial gap Δt ₀ is provided.
In the case where it is difficult to form the post 59, as shown in FIG.
Protrusions 73 having an appropriate height may be formed.

As shown in FIG. 3, the sensor chip 100 has a p-type high-concentration impurity diffusion layer 51 formed by diffusing boron or other impurities on an n-type silicon single crystal substrate 51a.
b (referred to as a p-type diffusion layer 51b). The static pressure diaphragms 66a, 66b, 66c, 66d located at each corner of the sensor chip 100 are p
It is deformed by the difference (static pressure) between the reference pressure inside the cavity 62 formed on the mold diffusion layer 51b side and the pressure applied to its own surface. Further, the differential pressure diaphragm 65 located at the center of the sensor chip 100 has a difference (difference) between the pressure introduced from the pressure introduction port 63 formed in the p-type diffusion layer 51b and the pressure applied to its surface. Pressure).
However, in the present embodiment, in order to suppress the non-linear error and improve the pressure sensitivity, the thickness of the differential pressure diaphragm 65 is not made uniform, and the piezo resistors 31a, 31b, 31c,
Only the peripheral region 67b except for the rib region 67a where the 31d is formed is thinned.

By the way, on the surface of the differential pressure diaphragm 65, a rigid restraining member 58 is formed in an annular shape along the outer periphery of the central region via an insulating layer 37. There is no special restriction on the shape of the restraining member 58. Therefore, as the shape of the restraining member 58, a shape other than the annular shape (for example, a polygon or the like) as shown in FIG. 3 may be adopted. Also, it may be divided on the way.

Similarly, on the side of the p-type diffusion layer 51b, a projection 57 is formed in an annular shape along the outer periphery of the central region 65a of the diaphragm 65 for differential pressure. However, between the tip of the projection 57 and the back of the differential pressure diaphragm 65,
By providing an initial gap Δt ₁ on the order of μm,
In the initial no-load state, it is necessary to prevent the tip of the projection 57 from contacting the back surface of the differential pressure diaphragm 65. There is no special restriction on the shape of the projection 57.

Therefore, when a positive pressure .DELTA.P of a predetermined value or more is applied to the surface of the differential pressure diaphragm 65, as shown in FIG.
The vertical movement of the outer periphery of 5a is completely prevented by the projection 57 and the restraining member 58. According to the force balancing conditions, the stress distribution on the surface of the differential pressure diaphragm 65 at this time has, as shown in FIG.
The peaks σ ₂ and σ _{1 of the} tensile stress given by the following formulas (1) and (2) appear both near the outer edge in the inside and near the outer edge in the peripheral region 65b.

Σ ₁ = 3 × (X ² −Z ² ) × ΔP / (16 × h ² ) (1) σ ₂ = 3 × Y ² × ΔP / (16 × h ² ) (2) Here, X is the outer diameter of the differential pressure diaphragm 65,
Y and Z are the inner and outer diameters of the restraining member 58, h
Is the thickness of the diaphragm 65 for differential pressure.

Therefore, four piezoresistors 3 are provided near the outer edge in the peripheral area 65b on the surface of the differential pressure diaphragm 65.
1a, 31c, 32a, 32c, the longitudinal direction of which is (10
0) is arranged to face the crystal axis <110> direction A ₁ on the crystal surface. Further, four piezoresistors 31b, 31d, 32b, and 32d are provided near the outer edge in the central region 65a on the surface of the differential pressure diaphragm 65, and the longitudinal direction thereof is (10).
0) is arranged to face the crystal axis <110> direction A ₂ on the crystal surface. A Wheatstone that outputs a voltage V ₁ given by the following equation (3) by four piezoresistors 31a, 31b, 31c, and 31d arranged near the outer edge in the peripheral area 65b of the differential pressure diaphragm 65. A bridge 40a is formed, and four piezoresistors 32a, 32b, 32c, 32 arranged near the outer edge in the central region 65a of the differential pressure diaphragm 65 are separately provided.
by d, it is a Wheatstone bridge 40b that outputs a voltage V ₂ given by Equation (4) shown below (see FIG. 5).

V ₁ = (1/2) × π ₄₄ × (1-ν) × σ ₁ × V (3) V ₂ = (1/2) × π ₄₄ × (1-ν) × σ ₂ × V (4) where ν is the Poisson's ratio of the differential pressure diaphragm 65, and π ₄₄ is the piezoresistors 31a, 31b, 31c, 3
Piezoresistive coefficients of shear of 1d, 32a, 32b, 32c, 32d.

From the equation (5) derived from the above equations (1), (2), (3), and (4), by adjusting the three shape parameters X, Y, and Z, the two Wheatstone bridges 40 are adjusted.
It can be seen that the output voltage ratios V ₁ : V ₂ of a and b can be freely changed. In other words, it can be seen that the present semiconductor pressure sensor can detect a differential pressure with two different pressure sensitivities as shown in FIG. 6, even though it has only one differential pressure diaphragm 65.

For example, in order to enable simultaneous detection of a differential pressure based on a predetermined pressure sensitivity S and a pressure sensitivity 4 × S which is four times the predetermined pressure sensitivity S, the output voltage ratio V ₁ : V of the two Wheatstone bridges 40a and 40b. _The three shape parameter ratios X: Y: Z may be set to 5: 2: 3 so that ₂ becomes 4: 1.

V ₁ / V ₂ = (X ² −Z ² ) / Y ² (5) Further, each of the static pressure diaphragms 66a, 66b, 66c, 6
On the surface of 6d, the piezo resistors 33a, 33b,
33c and 33d are arranged respectively. However, piezoresistive 33a, 33c has its longitudinal direction (100) Yes disposed to face the crystal axis <110> direction A ₁ on the crystal surface, piezoresistive 33b, 33d, the longitudinal direction (1
00) is arranged to face the crystal axis <011> direction A ₂ on the crystal surface. And each diaphragm 66 for static pressure
a, 66b, 66c, piezoresistive 33a disposed on the surface of the 66d, 33b, 33c, by 33d, Wheatstone bridge 40c for outputting a voltage V ₃ corresponding to the static pressure
(See FIG. 5).

Further, the silicon chip 100 piezoresistive 34 yet another one is on, so as to be directed in the longitudinal direction (100) crystal axes on the crystal face direction <100> A _3, i.e., ambient temperature changes Therefore, the excitation voltage V is also supplied from a power supply to the piezo resistor 34 (hereinafter, referred to as a temperature sensor 34) (see FIG. 5).

The through holes 64 formed for etching unnecessary sacrificial layers (described later) used for forming the respective static pressure diaphragms 66a, 66b, 66c, 66d are formed at 54a, 54b, 54c, 54d. It is a thick film that closes. Also, 3
5, 36 are lead lines drawn from each piezoresistor to constitute a Wheatstone bridge and the like;
3,4,5,6,7,8,9,10,11,12,13,14,1
Reference numerals 5 and 16 denote contact pads (aluminum) for connecting these lead wires 35 and 36 to each other. Of these lead wires 35 and 36, at least the lead wire 35 laid on the surface of the differential pressure diaphragm 65 in the vicinity of the piezoresistor or other areas where the influence of temperature hysteresis is large, is the diffusion of boron and other impurities. It is preferable that the lead wire 36 laid outside the adhesive layer 74 and in other areas where the influence of the temperature hysteresis is small be made of aluminum or another low-resistance conductor.

Next, a method of manufacturing the present semiconductor pressure sensor will be described with reference to FIG.

First, as shown in FIG. 3A, a p-type diffusion layer 51b is formed on the surface of an n-type silicon single crystal 51a by diffusing boron and other impurities at a high concentration. Further, by implanting phosphorus or other ions partially into the p-type diffusion layer 51b, five n
-Type high-concentration impurity diffusion layers 55a and 55b, that is, an n-type high-concentration impurity diffusion layer 55a (hereinafter, referred to as a first sacrifice layer 55a) to be a base of the differential pressure diaphragm 65, and respective static pressure diaphragms 66a and 66b. , 66c, 66d55b
An n-type high-concentration impurity diffusion layer 55b (hereinafter, referred to as a second sacrifice layer 55b) which is to be a base for is formed. However, due to the formation of the pressure introduction port 63 and the protrusion 57 (see FIG. 1), a device for forming the first sacrificial layer 55a having a different thickness depending on the position, for example, to the p-type diffusion layer 51b. In the ion implantation process, it is necessary to take measures such as switching the acceleration voltage of the accelerator.

After the formation of the first sacrifice layer 55a and the second sacrifice layer 55b is completed in this way, SiON, SiO ₂ , SiN, Al ₂ O _{3 and} other insulators are deposited by CVD. Thus, an insulating film 52 having an appropriate thickness is formed on these two diffusion layers 51b and 55.
Further, after an n-type silicon single crystal substrate is bonded on the insulating film 52, an n-type silicon single crystal substrate having an appropriate thickness is formed by grinding.
It is finished to the type silicon single crystal film 53. Alternatively, the n-type silicon single crystal film 53 may be formed on the insulating film 52 by epitaxial growth of the n-type silicon single crystal, deposition of the n-type silicon single crystal, or the like.

Thereafter, as shown in FIG. 2B, boron and other impurities are diffused into the n-type silicon single crystal film 53 at a high concentration, so that the n-type silicon single crystal film 53 is positioned at a predetermined position on the surface of the n-type silicon single crystal film 53. Piezoresistors 31a, 31b, 31c,
31d, 32a, 32b, 32c, 32d, 33a, 33b,
33c, 33d, and 34 are formed. Specifically, the piezoresistors 33a, 33b, 33c, 33 are respectively provided in the regions to be the static pressure diaphragms 66a, 66b, 66c, 66d.
d is formed one by one. Also, the differential pressure diaphragm 65
The four piezoresistors 31a, 31b, 31c, 31d, and 3 are respectively located near the outer edge of a region that is to be the central region 65a and near the outer edge of the region that is to be the peripheral region 65b.
2a, 32b, 32c and 32d are formed. Further, a piezoresistor 34 to be a temperature sensor is formed in a thick region on the sensor chip 100 where no diaphragm is formed. This is because the change in the gauge resistance value R is shown only in response to a change in ambient temperature.

Further, boron and other impurities are diffused in the n-type silicon single crystal film 53 at a high concentration in a region where the influence of the temperature hysteresis is large so that each Wheatstone bridge shown in FIG. 6 is formed. Thus, the lead wire 35 is formed, and in the other area, the lead wire 3 is formed by depositing aluminum or another low-resistance conductor.
6 is formed. Alternatively, all the lead lines may be formed by diffusion of boron or other impurities.

Thereafter, as shown in FIG. 3C, a resist pattern 56 is formed on the surface of the n-type silicon single crystal film 53 by using a photoresist, and then the resist pattern 5 is formed.
Using n as a mask, n-type silicon single crystal film 53 and insulating film 52 are etched. As a result, a through hole 64 connecting the outside and the second sacrificial layer 55b is formed at a location where the detection accuracy of the static pressure is not adversely affected. And the pressure inlet 63
The first sacrificial layer 55a and the second sacrificial layer 55a are introduced by introducing an etchant (e.g., hydrazine) having a higher etching rate for the n-type silicon single crystal than the SiON or p-type diffusion layer from the portion 63a to be formed and the through hole 64. Two sacrificial layers 55
b) is completely removed. Then, if the unnecessary etchant is recovered, the above-described protrusion 57 and the pressure introducing port 63 are completed.

Thereafter, as shown in FIG. 3D, after the unnecessary resist pattern 56 is removed by washing, an SiO ₂ or other insulating layer is formed in a band along the outer periphery of a region to be the central region 65a of the differential pressure diaphragm 65. 37 is formed.
Then, by filling aluminum or another thick film 54a, 54b, 54c, 54d into the through hole 64, the cavity 62 after the removal of the second sacrificial layer 55b is hermetically sealed. As a result, the aforementioned static pressure diaphragm 66a,
66b, 66c, 66d are completed. In the same step, a thick film 58 is also formed on the surface of the insulating film 37 to complete the restraining member 58 described above.
When a thicker restraining member 58 is required, it is desirable to separately provide a step of forming only the restraining member 58.

Thereafter, as shown in FIG. 7E, if the region to become the peripheral region 65b of the differential pressure diaphragm 65 is partially thinned by etching, the aforementioned differential pressure diaphragm 65, that is, the rib region 67a is formed. The diaphragm 65 for differential pressure in which only the peripheral region 67b except for the above is thinned is completed. If the etching does not leave even a through hole, a part of the n-type silicon single crystal film 53 may be completely removed as shown in FIG. As shown in b), even if the etching reaches the insulating film 52, it does not matter.

As can be seen from the above series of processes, in order to manufacture the semiconductor pressure sensor according to the present embodiment, it is sufficient to utilize only the already established micromachining technology.

By the way, for this semiconductor pressure sensor,
The restraining member 58 on the differential pressure diaphragm 65 is not essential. For example, as shown in FIG. 9, even if the restricting member 58 is not formed on the differential pressure diaphragm 65, even the protrusion 57 that is to be the support end of the differential pressure diaphragm 65 is formed on the p-type diffusion layer 51b. This is because, in the stress distribution on the differential pressure diaphragm 65, peaks of tensile stress appear near both the outer edge of the central region 65a and the outer edge of the peripheral region 65b. However, in such a case, the differential pressure diaphragm 65
Since the stress distribution cannot be as steep as when the restraining member is formed thereon, it is inevitable that the pressure sensitivity will decrease to some extent and the nonlinear error will increase to some extent.

There are several alternative arrangements of the piezoresistor on the differential pressure diaphragm 65.

For example, as shown in FIG. 10, in the peripheral region 56b of the differential pressure diaphragm 65, two piezoresistors are located near the inner edge where the peak of the compressive stress (σ _{3 in} FIG. 4) appears. 31a, 31c, and so that the longitudinal direction thereof arranged (100) to face the crystal axis <110> direction a ₁ on the crystal surface, two resistors 31b, the 31d, the longitudinal direction (100) crystal crystal axes on the plane <011> may be arranged to face the direction a _2.

Alternatively, as shown in FIG. 11, in the peripheral region 65b of the diaphragm 65 for differential pressure, the longitudinal direction is (1) near the inner edge where the peak σ _{3 of the} compressive stress appears.
00) crystal axis <110> direction A 2 pieces of piezoresistance 31b toward the ₁ on the crystal surface, by placing 31d symmetrically, also near the outer edge peak sigma ₁ has appeared in the tensile stress, the longitudinal direction There (100) may be disposed crystal axis <110> direction a 2 pieces of piezoresistance 31a toward the ₁ on the crystal surface, and 31c symmetrically.

Alternatively, as shown in FIG. 12, in the peripheral area 65b of the diaphragm 65 for differential pressure, the longitudinal direction is (1) near the inner edge where the peak σ _{3 of the} compressive stress appears.
00) and the other crystal axis <011> towards the direction A ₂ 2 This piezoresistive 31b on the crystal surface, the 31d arranged symmetrically,
Also near the outer edge of the peak sigma ₁ tensile stress has appeared, its longitudinal direction (100) crystal axes on the crystal plane <011> towards the direction A ₂ 2 This piezoresistive 31a, so as to place the 31c It does not matter.

Finally, typical applications of the present semiconductor pressure sensor will be described.

The present semiconductor pressure sensor can be used as a detection end of a diaphragm type differential pressure transmitter. For this purpose, first, as shown in FIG. 13, it is necessary to incorporate the present semiconductor pressure sensor into the hermetic seal container 75. Specifically, the high-pressure side process connection port 120 of the hermetic seal container 75 is welded or bonded.
After the post 59 of the present semiconductor pressure sensor is fixed, it is necessary to connect a lead wire 77 between the output terminal 76 provided on the hermetic seal container 75 and the contact pad of the present semiconductor pressure sensor.

In this state, as shown in FIG. 14, the diaphragm type differential pressure transmitter is incorporated in a housing 80. However, in the assembled state, the high pressure side process connection port 8 of the housing 80 of the diaphragm type differential pressure transmitter
1b is connected to the high pressure side process connection port 120 of the hermetic seal container 75, and to the low pressure process connection port 81a of the diaphragm type differential pressure transmitter housing 80,
The pressure inlet 63 of the semiconductor pressure sensor is connected. That is, the high pressure side seal diaphragm 82b
Of the semiconductor pressure sensor and the static pressure diaphragms 66a, 66b, 66c, of the semiconductor pressure sensor by the silicone oil or other filling liquid 83b.
The pressure transmitted to each surface of the pressure sensor 66d and applied to the high pressure side seal diaphragm 82a is transmitted to the back surface of the differential pressure diaphragm 65 of the semiconductor pressure sensor by the silicone oil or other filling liquid 83a.

The output voltage of the output terminal 76 of the hermetic seal container 75, that is, the output voltage V _{1 of} the Wheatstone bridge 40a, the Wheatstone bridge 40b
The output voltage V _2, Wheatstone bridge 40c of the output voltage V _3, the output voltage V ₄ of the temperature sensor 34 is input to the signal processing section 93 through the wiring pattern on the flexible printed circuit 85, the signal processing unit 93 First, the multiplexer 86 selects the plurality of input voltages V ₁ ,
While switching between V ₂ , V ₃ and V ₄ , the signal is input to the programmable gain amplifier 87. Then, the input voltages V ₁ , V ₂ , V ₃ , V
₄ is digitally converted by the A / D converter 88 and then input to the microprocessor 89.

Then, the microprocessor 89 sets the RO
With reference to the static pressure correction map stored in M90,
Static pressure data D ₃ corresponding to both of the output voltage V ₃ of the output voltage V ₄ and the Wheatstone bridge 40c of the temperature sensor 34
Is calculated. The static pressure data is stored in a buffer memory.
(Not shown). Here, the static pressure correction map referred, for each temperature, an actual output voltage V ₃ of the Wheatstone bridge 40c, correction processing that has been this is stored in association with static pressure data subjected to temperature compensation Map.

The microprocessor 89 has a ROM
The differential pressure data D ₁ corresponding to both the output voltage V ₄ of the temperature sensor 34 and the output voltage V ₁ of the Wheatstone bridge 40 a are calculated with reference to the differential pressure correction map stored in 34 calculates the output voltage V ₄ and the Wheatstone bridge 40b differential data D ₂ corresponding to both of the output voltage V ₂ of the. It should be noted that the differential pressure correction map referred to here means that the Wheatstone bridge 4
This is a map for correction processing in which actual output voltages V ₁ and V _{2 of} 0a and 40b are associated with differential pressure data subjected to temperature compensation.

Then, the microprocessor 89 sets the RO
With reference to the range threshold data ΔP ₁ stored in M90, according to the magnitude relationship between these two differential pressure data D ₁ , D ₂ and the range threshold data ΔP ₁ , these two differential pressure data D ₁ , D Select the normal differential pressure data from ₂ . Specifically, when these two differential pressure data D ₁ and D ₂ are larger than the range threshold data ΔP ₁ , the differential pressure data D ₂ calculated from the output voltage V ₂ of the Wheatstone bridge 40b.
Is stored in a buffer memory (not shown) as normal differential pressure data. Otherwise, select the differential pressure data D ₁ calculated from the output voltage V ₁ of the Wheatstone bridge 40a, and stored in a buffer memory (not shown) so as normal differential pressure data. That is, Δ
In the high pressure range of P ₁ <ΔP <ΔP ₂ , differential pressure data is calculated from the output voltage V ₂ having good linearity but low pressure sensitivity, and in the low pressure range of 0 ≦ ΔP ≦ ΔP ₁ ,
Linearity is inferior although to calculate the differential pressure data from the output voltages V ₁ high pressure sensitivity. In other words, the pressure sensitivity is automatically switched for each pressure range.

Finally, the microprocessor 89 inputs the static pressure data and the differential pressure data stored in the buffer memory (not shown) to the D / A converter 91. And D
Both data digitally converted by the / A converter 91 are transmitted signals (analog signal, digital signal, superimposed signal of analog and digital signal, etc.) by the subsequent V / I converter 92.
After being converted to, it is output to the transmitting unit.

As described above, when the present semiconductor pressure sensor is employed as a detection end, and the pressure sensitivity is automatically switched for each pressure range, it is possible to cope with pressure measurement from a low pressure range to a high pressure range. Becomes That is, the rangeability of the diaphragm type transmitter can be improved.

As shown in FIGS. 1 and 2, if the outer diameter Z of the restraining member 58 is made larger than the inner diameter D of the pressure inlet 68, the diaphragm for differential pressure is formed by the restraining member 58. 65 excessive deformation is prevented,
A new effect of preventing breakage of the differential pressure diaphragm 65 when introducing an excessive pressure (absorption pressure) can also be achieved. Similarly, it is needless to say that the projection 57 is useful for preventing the differential pressure diaphragm 65 from being broken when an excessive pressure (pressurized) is introduced. Therefore, if this semiconductor pressure sensor is adopted as a detection end, in order to prevent the diaphragm from being destroyed when excessive pressure is introduced, a center diaphragm or the like that may cause a drift of a transmission signal or a hysteresis may be used. There is no need to attach to the housing of the differential pressure transmitter. That is, it can be said that the use of the semiconductor pressure sensor is also useful as a measure for simplifying the manufacturing process of the diaphragm type differential pressure transmitter and a measure for stabilizing the transmission signal of the diaphragm type differential pressure transmitter.

[0051]

According to the present invention, a small semiconductor pressure sensor having a plurality of pressure sensitivities, that is, a small semiconductor pressure sensor covering a wide pressure range from low pressure to high pressure can be provided. Therefore, for example, if the present pressure sensor is mounted as a detection end of the differential pressure transmitter, the measurement pressure range of the diaphragm type differential pressure transmitter can be expanded.

[Brief description of the drawings]

FIG. 1 is an example of a cross-sectional view of a semiconductor pressure sensor according to an embodiment of the present invention.

FIG. 2 is an example of a cross-sectional view of the semiconductor pressure sensor according to the embodiment of the present invention.

FIG. 3A is an example of a top view of a sensor chip of a semiconductor pressure sensor according to an embodiment of the present invention, and FIG.
It is ABCDDE sectional drawing.

4A is a sectional view conceptually showing deformation of a differential pressure diaphragm, and FIG. 4B is a stress distribution diagram on the differential pressure diaphragm at that time.

FIG. 5 is a connection diagram of a piezo resistor.

FIG. 6 is a diagram showing output characteristics of the semiconductor pressure sensor according to the embodiment of the present invention.

FIG. 7 is a view illustrating a method for manufacturing the semiconductor pressure sensor according to the embodiment of the present invention.

FIG. 8 is an example of a cross-sectional view of the sensor chip of the semiconductor pressure sensor according to the embodiment of the present invention, taken along ABCD-DE.

FIG. 9A is an example of a top view of a sensor chip of a semiconductor pressure sensor according to an embodiment of the present invention, and FIG.
It is ABCDDE sectional drawing.

FIG. 10A is an example of a top view of a sensor chip of a semiconductor pressure sensor according to an embodiment of the present invention, and FIG.
Is a cross-sectional view taken along the line ABCDC.

11A is an example of a top view of a sensor chip of a semiconductor pressure sensor according to an embodiment of the present invention, and FIG.
Is a cross-sectional view taken along the line ABCDC.

FIG. 12A is an example of a top view of a sensor chip of a semiconductor pressure sensor according to an embodiment of the present invention, and FIG.
Is a cross-sectional view taken along the line ABCDC.

FIG. 13 is a sectional view of a detection end of the diaphragm type transmitter according to the embodiment of the present invention.

FIG. 14 is a sectional view of a diaphragm-type transmitter according to an embodiment of the present invention.

[Explanation of symbols]

1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16… Contact pads 31a, 31b, 31c, 31d, 32a, 32b, 32c, 32d, 33a, 33b, 33c, 33d…
Piezoresistor 34 Piezoresistor for temperature sensor 35,36 Leader 37 Insulating layer 40a Wheatstone bridge 40b Wheatstone bridge 40c Wheatstone bridge 51a N-type silicon single crystal substrate 51b P-type diffusion Layer 52 ... Insulating film 53 ... N-type silicon single crystal film 54a, 54b, 54c, 54d ... Thick film 55a, 55b ... N-type diffusion layer 56 ... Resist pattern 57 ... Protrusion 58 ... Restriction member 59 ... Post 60 ... Adhesion Layer 62… Cavity of reference pressure 63… Pressure inlet 65… Relative pressure diaphragm 65a… Central area of differential pressure diaphragm 65b… Peripheral area of differential pressure diaphragm 66a, 66b, 66c, 66d… Static pressure diaphragm 67… Differential pressure diaphragm Rib area 68 ... Post pressure inlet 75 ... Hermetic seal container 76 ... Terminal 77 ... Lead wire 80 ... Housing 81a ... Low pressure side process connection port 81b ... High pressure side process connection port 82a ... Low pressure side seal diaphragm 82b ... High pressure side seal diaphragm 83a, 83b ... Filled liquid 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 93 ... Signal processing unit 100 ... Sensor chip 120 ... High-pressure side process connection port

Claims (10)

[Claims] 1. A differential pressure diaphragm for detecting a distortion of a differential pressure diaphragm which is displaced in accordance with a differential pressure applied to the differential pressure diaphragm by a plurality of strain gauges arranged on a differential pressure diaphragm fixed on a substrate. The sensor, wherein the substrate has a support end that supports the diaphragm for differential pressure in a region surrounding a central region on the back surface of the diaphragm for differential pressure from the time when the diaphragm for differential pressure is displaced by a predetermined displacement amount to the substrate side. Having a part of the plurality of strain gauges is arranged in the peripheral region so as to detect a strain in a peripheral region of the surface of the differential pressure diaphragm; A part of the strain gauge is arranged in the central region so as to detect a strain in the central region of the surface of the diaphragm for differential pressure. Capacitors. 2. A differential pressure diaphragm for detecting a distortion of a differential pressure diaphragm which is displaced in accordance with a differential pressure applied to the differential pressure diaphragm by a plurality of strain gauges arranged on a differential pressure diaphragm fixed on a substrate. The sensor, wherein the substrate has a support end that supports the diaphragm for differential pressure in a region surrounding a central region on the back surface of the diaphragm for differential pressure from the time when the diaphragm for differential pressure is displaced by a predetermined displacement amount to the substrate side. In the peripheral area of the surface of the diaphragm for differential pressure, two strain gauges each having a longitudinal direction parallel to the radial direction of the diaphragm and two strain gauges each having a longitudinal direction parallel to the tangential direction of the diaphragm are arranged. A strain gauge whose longitudinal direction is parallel to the radial direction of the diaphragm is provided in a central region of the surface of the diaphragm for differential pressure, Two strain gauges each having a direction parallel to the tangential direction of the diaphragm are arranged two each, and four strain gauges arranged in a central region of the surface of the differential pressure diaphragm, and a periphery of the surface of the differential pressure diaphragm The four strain gauges disposed in the region each form a Wheatstone bridge, wherein the sensor is a differential pressure sensor. 3. The differential pressure sensor according to claim 2, wherein a predetermined gap is provided between the support unit and the differential pressure diaphragm when the differential pressure is not applied to the differential pressure diaphragm. A differential pressure sensor characterized by being formed. 4. The sensor for differential pressure according to claim 2, wherein the diaphragm for differential pressure is supported in a band region surrounding a central region on the back surface of the diaphragm for differential pressure. 5. The differential pressure sensor according to claim 2, wherein the differential pressure is applied to a band region surrounding a central region of a surface of the differential pressure diaphragm by the differential pressure. A differential pressure sensor, wherein a restricting member for pressing a pressure diaphragm against the support end is formed. 6. The sensor for differential pressure according to claim 2, wherein the diaphragm for differential pressure has a peripheral area other than an area where the strain gauge is disposed. A differential pressure sensor characterized by being formed thinner than a region where a strain gauge is arranged. 7. A composite sensor capable of detecting both a differential pressure and a static pressure, wherein the static pressure sensor is mounted on a substrate of the differential pressure sensor according to any one of claims 2, 3, 4, 5, and 6. A static pressure diaphragm having a pressure reference cavity is fixed, and four strain gauges are arranged on the surface of the static pressure diaphragm, and the four strain gauges form a Wheatstone bridge. Features a composite sensor. 8. The composite sensor according to claim 7, further comprising a temperature sensor for detecting a temperature change of the composite sensor. 9. A differential pressure transmitter, comprising a composite sensor according to claim 8 as a detection end, for transmitting a differential pressure detected by said composite sensor to a remote place, wherein said composite sensor is provided for each temperature of said composite sensor. A first storage unit storing a correction value of an output signal value of each Wheatstone bridge of the sensor; and a correction corresponding to a temperature detected by the temperature sensor from the storage unit for each Wheatstone bridge of the composite sensor. The correction means for taking out the respective values, correcting the output signal values of the respective Wheatstone bridges of the composite sensor using the correction values, and the corrected output signal value of the Wheatstone bridge for differential pressure of the composite sensor. Selecting means for selecting any one of the two differential pressure Wheatstone bridges of the composite sensor. As the differential pressure, differential pressure transmitter, characterized in that it comprises a transmitting means for transmitting the output signal value after the correction of one differential pressure Wheatstone bridge which is selected in the selection means. 10. The differential pressure transmitter according to claim 9, wherein: a first seal diaphragm to which a first pressure is applied; and a pressure applied to the first seal diaphragm to a differential pressure diaphragm of the composite sensor. A first chamber for storing a sealed liquid to be transmitted to the surface of the second sensor, a second seal diaphragm to which a second pressure is applied, and a pressure applied to the second seal diaphragm to a surface of a differential pressure diaphragm of the composite sensor. And a second chamber for storing a filled liquid to be transmitted.