JP2895262B2 - Composite sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite sensor, and more particularly to a composite sensor having a differential pressure sensor and a static pressure sensor and capable of obtaining a differential pressure signal and a static pressure signal with high accuracy and high output. is there.

[0002]

2. Description of the Related Art With regard to a differential pressure sensor for measuring a differential pressure, a multi-function type sensor (hereinafter, referred to as a composite sensor) or a sensor similar thereto which can simultaneously detect a differential pressure signal, a static pressure signal, and a temperature signal, includes: Conventionally, there are many disclosed examples. For example, JP-A-61-240134 or JP-B-2-970
No. 4, etc. In each of these disclosed examples, a resistor group sensitive to a differential pressure or a static pressure, and a resistor sensitive to a temperature exist on a thin portion called a diaphragm, and these resistances are determined by a semiconductor diffusion method or an ion implantation method. Are formed on the substrate at the same time, and are joined to the fixing table.

In the above-described composite sensor, static pressure (line pressure)
The change in the zero point of the differential pressure sensor (which is the main sensor) caused by temperature and temperature is positively compensated based on the output signal of the static pressure sensor and the auxiliary sensor of the temperature sensor installed on this main sensor. Thus, a highly accurate differential pressure signal is obtained.

The static pressure signal disclosed in Japanese Patent Publication No. Hei 2-9704 is based on a bending strain generated based on a difference in longitudinal elastic modulus between a semiconductor substrate and a fixed base when a static pressure is applied.
Since it is detected, it is a very small signal.

On the other hand, in the disclosure of Japanese Patent Application Laid-Open No. 61-240131, since a differential pressure and a static pressure are detected by providing a pressure sensing portion, the obtained static pressure signal is a differential pressure signal. This signal is considerably larger than that of the above signal.

However, in either of the above two prior arts, the static pressure sensor for detecting the static pressure has a sensitivity direction (a direction most sensitive to the static pressure) with respect to the differential pressure. They are arranged so as to coincide with the direction in which the sensitivity becomes maximum. Therefore, the sensitivity direction of the static pressure sensor and the sensitivity direction of the differential pressure sensor (the direction most sensitive to the differential pressure) are arranged to be exactly the same. Therefore, when a differential pressure is applied to the differential pressure sensor, the differential pressure simultaneously affects a static pressure sensor disposed in the vicinity in the same sensitivity direction. For this reason, in the conventional composite sensor,
It is necessary to correct the sensor output of each of the differential pressure sensor and the static pressure sensor using a complicated correction procedure, and to obtain an accurate differential pressure.

As another prior art, a semiconductor pressure converter (Japanese Patent Application Laid-Open No. 1-184433) previously filed by the present applicant has been disclosed.
No.) exists. The semiconductor pressure converter has a rigid portion in the center, a fixed portion in the periphery, and an annular diaphragm between the rigid portion and the fixed portion. Then, the differential pressure gauge is attached to the diaphragm, and the static pressure gauge is attached to the fixed portion in the tangential direction and the central rigid portion in the radial direction. Since the static pressure gauge is disposed in the central rigid portion where a constant stress is generated, a stable static pressure output can be obtained by this configuration. Therefore, it is possible to obtain a differential pressure signal with little influence of static pressure.

[0008]

In the prior art other than the semiconductor pressure converter proposed by the present applicant, when a load due to a differential pressure is applied to the differential pressure sensor, it is disposed near the differential pressure sensor. Because the load affects the static pressure sensor,
In consideration of the influence, it is necessary to correct the output signal of the static pressure sensor. An object of the present invention is to provide a complex sensor including a differential pressure sensor and a static pressure sensor with a sensor configuration method capable of obtaining a high-output static pressure signal without affecting the static pressure sensor due to a differential pressure. It is an object of the present invention to provide a composite sensor that obtains information of various types of differential pressure and static pressure. It is another object of the present invention to provide a small and inexpensive composite sensor with good productivity.

[0009]

SUMMARY OF THE INVENTION A composite sensor according to the present invention comprises a sensor substrate having a differential pressure detecting diaphragm at the center and a fixed portion at the periphery, and a plurality of differential pressure detecting diaphragms disposed on the diaphragm. It has a sensing element and a plurality of sensing elements for static pressure detection arranged on the fixed part, and the sensing element for static pressure detection,
It has a configuration in which it is arranged in a direction that is not affected by a tensile stress generated in a region where the static pressure detecting sensitive element is provided based on a differential pressure applied to the diaphragm. That is, in the arrangement of the differential pressure gauge and the static pressure gauge arranged on the surface of the sensor substrate,
The arrangement positions of the plurality of static pressure gauges are determined to be predetermined positions which are not affected by the tensile stress caused by the differential pressure. More specifically, in the composite sensor according to the present invention, each of the plurality of sensing elements for static pressure detection is placed on the sensor substrate in an area where the sensing elements for static pressure detection are arranged based on the differential pressure applied to the diaphragm. It is arranged on the line in the direction not affected by the generated tensile stress, and the sensitivity direction of each of the plurality of sensing elements for detecting static pressure is directed to the direction most affected by the tensile stress generated by the static pressure. It is arranged. Further, the composite sensor according to the present invention further provides a reference direction having an angle of 0 degrees when the direction most affected by the tensile stress is defined as:
The line in the direction not affected by the tensile stress was set to have an angle of 45 degrees or -45 degrees with respect to the reference direction. In each of the above structures, the sensor substrate can be formed of a p-type (100) plane silicon single crystal,
In this case, the direction not affected by the tensile stress is:
<001> Axial direction. In each of the above configurations ,
In order to increase the output of the static pressure sensor, a diaphragm for detecting static pressure may be formed, and all or a part of the sensitive element for detecting static pressure may be arranged on the diaphragm. Further, when performing the processing of the sensor substrate by etching is anisotropic etching or isotropic etching are used.

[0010]

In the composite sensor according to the present invention, based on the arrangement structure described above, the tensile stress due to the differential pressure applied to the differential pressure sensor portion does not affect the sensitive element for the static pressure sensor, and the sensitive element for the static pressure sensor. Operates with high sensitivity only to static pressure.
Therefore, a highly accurate static pressure can be detected.
Compensation for the differential pressure based on the subsequent signal processing is simplified, and a highly accurate differential pressure can be measured. In a composite sensor provided with a static pressure detecting diaphragm separately from the differential pressure detecting diaphragm, a large static pressure signal can be obtained because the gauge resistance value on the diaphragm changes according to the static pressure.
Also, by processing the sensor substrate by etching, the diaphragm is formed in the sensor substrate, the anisotropic etching is improved machining accuracy of the diaphragm, in the isotropic etching breakdown voltage is improved since the roundness attaches to the diaphragm.
Further, since a large number of diaphragms can be formed at the same time, productivity is improved.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a plan view showing a first embodiment of a composite sensor according to the present invention, and FIG. 2 is a sectional view of a main part thereof. 1 is p
A sensor substrate 2 made of a semiconductor material made of a (100) plane silicon single crystal of a mold is a fixing base for fixing the sensor substrate 1. The planar shapes of the sensor substrate 1 and the fixed base 2 are round. As is apparent from FIGS. 1 and 2, a concave portion 3 is formed in the center of the sensor substrate 1, whereby a circular diaphragm 4 is formed in the upper surface portion, and a ring-shaped fixing portion 5 is formed in the peripheral portion. It is formed. The diaphragm 4 has front and rear surfaces as pressure receiving surfaces, and detects a pressure difference between two pressures Ps + ΔP and Ps applied to the front and rear pressure receiving surfaces. The fixing base 2 is formed of borosilicate glass whose linear expansion coefficient is close to that of silicon in order to maintain electrical insulation from the sensor substrate 1 and to reduce thermal distortion due to a difference in linear expansion coefficient. The sensor board 1 and the fixed base 2 are
It is joined by an anodic joining method or the like. A hole 6 is formed in the center of the fixing base 2. The hole 6 communicates with the recess 3 of the sensor substrate 1, and a fluid with a pressure Ps is introduced into the surface of the diaphragm 4 on the recess 3 side through the hole 6.

As shown in FIG. 1, differential pressure gauges 111 to 114 are formed on the surface of the sensor substrate 1 by doping impurities by ion implantation or thermal diffusion. These differential pressure gauges 111 to 114 have two pressures Ps + ΔP,
This gauge responds to a differential pressure ΔP generated in the diaphragm 4 by Ps. The differential pressure gauges 111 to 114 are arranged in the vicinity of the fixed portion 5 where the stress in the radial direction and the circumferential direction in the area of the diaphragm 4 becomes maximum in order to detect the differential pressure. Each of the differential pressure gauges 111 to 114 is arranged so that its sensitivity direction (longitudinal direction in the example shown in FIG. 1) is oriented in the <110> axis direction of p-type (100) plane silicon.

On the surface of the fixed part 5 around the diaphragm 4, four static pressure gauges 121 to 124 are formed in a dispersed state as shown in the figure. Static pressure gauge 121-
Reference numeral 124 denotes a gauge that responds to the static pressure Ps. The static pressure gauge is formed in the same manner as the differential pressure gauge. The static pressure gauges 121 to 124 have a sensitivity direction in the longitudinal direction. The four static pressure gauges 121 to 124 are arranged on lines 7 and 8 indicated by alternate long and short dash lines. That is, the static pressure gauges 121 to 124 are arranged in the direction not affected by the tensile stress generated by the differential pressure applied to the diaphragm 4, for example, in the <001> axial lines 7 and 8 in the p-type (100) silicon. Arranged above. The four static pressure gauges are formed on the lines 7 and 8 at positions equidistant from their intersection. Further, as is clear from FIG.
In order to obtain a static pressure signal, 21 to 124 are <1 in the direction in which the sensitivity to static pressure increases, for example, in the (100) plane.
10> It is arranged so that its sensitivity direction coincides with the axial direction.

Reference numeral 9 denotes a temperature gauge formed on the surface of the fixed portion 5, which is <001 in a direction in which sensitivity to stress generated by differential pressure or static pressure is small, for example, in the (100) plane.
> It is arranged in the axial direction. The temperature gauge 9 functions as a temperature sensor in which the resistance value does not change even when subjected to stress, and the resistance value changes only due to a change in temperature.

Differential pressure gauges 111 to 114 and static pressure gauges 121 to 1 forming a gauge group on the surface of the sensor substrate 1
24, the temperature gauge 9 is configured as a bridge circuit as shown in FIG. Differential pressure gauge 111-
114 a differential pressure signal E _D as differential pressure sensor, constituting a static pressure signal E _S hydrostatic gauges 121 to 124 as a static pressure sensor, as the temperature gauge 9 of the temperature signal E _T as a temperature sensor, respectively output Have been.

By configuring the composite sensor as described above, the tensile stress (σ _m ) generated when a differential pressure is applied does not affect the static pressure gauges 121 to 124. The static pressure gauges 121 to 124 can obtain a change in resistance value by a stress generated by a deformation based on a difference in elastic modulus between the sensor substrate 1 and the fixed base 2 at the time of a static pressure load. That is, a composite sensor including a static pressure sensor that is not affected by the differential pressure can be configured.

Next, the tensile stress (σ
_m ) does not affect the static pressure gauges 121 to 124 in principle. The diaphragm 4 formed substantially at the center of the sensor substrate 1 has a differential pressure ΔP
Responds to and deforms. In order to detect the differential pressure ΔP, as described above, each differential pressure gauge 111 is moved in the crystal axis direction in which the sensitivity to the stress generated in the diaphragm 4 due to the differential pressure is maximized.
To 114 are oriented in the longitudinal direction. Regarding the static pressure gauges 121 to 124, the lines 7 and 8 in the crystal axis direction at which the sensitivity to the tensile stress generated by the differential pressure is minimized.
Placed on top (this is the same direction as the direction in which the temperature gauge 9 is placed) and the static pressure gauge 1 to obtain a static pressure signal.
The directions 21 to 124 (longitudinal directions) are arranged in a direction in which the sensitivity to the stress generated by the static pressure is maximized. Therefore,
The static pressure gauges 121 to 124 do not respond to the tensile stress generated by the differential pressure, but act so as to be sensitive only to the tensile stress generated by the static pressure. That is, the tensile stress generated when the differential pressure is applied is
4 is not affected.

The above will be specifically described with reference to an example of p-type silicon having a (100) plane. On the (100) plane, as shown in FIGS. 4 and 5A, the piezoresistance coefficient is large in the <110> axis direction, and high sensitivity can be obtained. Therefore, as shown in FIG. 5 (B), the differential pressure gauges 111 to 114 are positioned at the positions where the stresses σl and σt generated in the diaphragm 4 are maximum and the longitudinal direction thereof is made coincident with the maximum stress generation direction. Be placed. Static pressure gauges 121 to 12
4 as well as the differential pressure gauge,
0> A large output can be obtained by arranging in the axial direction. However, since the effect of the tensile stress generated by the differential pressure is great, the piezoresistance coefficient is arranged on the <001> axial line which is almost zero, and the static pressure To obtain output only by the stress generated at
<110> Static pressure gauges 121 to 124 are formed in the axial direction. As a result, the same output is obtained from the static pressure gauge as when it is arranged in the <110> axis direction, and the output is not affected by the differential pressure. <001> Tensile stress σ _m generated by differential pressure ΔP by arranging on axial line 7
Influence on the static pressure gauges 121 to 124, that is, the rate of change ΔR / R of the gauge resistance is

[0019]

ΔR / R = πl σl + πt σt (1) Here, referring to FIG. 6, πl: piezoresistance coefficient in the longitudinal direction πt: piezoresistance coefficient σl in the lateral direction: acting in the longitudinal direction .Tau.t: stress acting in the lateral direction. "L" is the lowercase letter of the alphabet L.

In the <110> axial direction,

[0021]

[Number 2] _{πl = π 44/2 ··· (} 2) πt = -π 44/2 ··· (3) wherein, [pi _44: arranging the gauge piezoresistance coefficient <001> axial shear Σt and σt at this time are as shown in FIG.

[0022]

Equation 3] _{σl = σ m cos45 ° ··· (} 4) σt = σ m sin45 ° ··· (5) above equation (2) to (5), are substituted into Equation (1),

[0023]

(Equation 4)

Therefore, on the line in the <001> axial direction, the static pressure gauge 121 is oriented in the <110> axial direction.
The effect of the tensile stress σ _{m on} the static pressure gauges 121 to 124 becomes almost zero by arranging them in the longitudinal direction of 〜124.

Next, a second embodiment of the present invention will be described with reference to FIGS. Reference numerals 111 to 114 denote the differential pressure gauges, which are provided on the differential pressure detecting diaphragm 4 in the vicinity of the fixed portion where the stress in the radial direction and the circumferential direction becomes maximum, as in the first embodiment. On the other hand, the static pressure gauges 121 to 1
24 is formed on the static pressure detection diaphragm 10 provided separately from the differential pressure detection diaphragm 4. The diaphragm 10 is formed by providing a recess 11 in the sensor substrate 1. The static pressure gauges 121 to 124 are arranged in the same crystal axis direction as the temperature gauge, and are arranged with their longitudinal directions oriented in the same crystal axis direction as the differential pressure gauges 111 to 114. Similarly to the differential pressure gauges 111 to 114, the pressure gauges are provided near the fixed portion where the radial and circumferential stresses generated on the static pressure detection diaphragm 10 are maximum. In this embodiment, two static pressure detecting diaphragms 10 are formed, and a pair of static pressure gauges 121, 123, 122 and 124 are arranged on each of the diaphragms 10. There is no problem even if the number of the diaphragms 10 is one. In this case, the four static pressure gauges 121 to 124
Are disposed on the three diaphragms 10. The temperature gauge 9
The electrodes are arranged in the crystal axis direction (<001> direction) at which the resistance does not change due to the differential pressure or the static pressure and exhibit the minimum sensitivity of the piezoresistance coefficient. As described above, the differential pressure gauges 111 to 114, the static pressure gauges 121 to 124, and the temperature gauge 9, which are the above-described gauge groups, are assembled as a bridge circuit as shown in FIG. Are configured to obtain

The fixed base 2 of the sensor substrate 1 is
As in the case of the embodiment, it is formed of borosilicate glass having a linear expansion coefficient similar to that of silicon. However, in the present embodiment, a method is employed in which the static pressure is detected by the stress generated based on the deformation of the static pressure detection diaphragm 10,
The fixing base 2 may be made of silicon having an oxide film provided on a bonding surface.

When the sensor substrate 1 and the fixing base 2 are joined by an anodic joining method or the like, the recesses 3 and 11 each form a cavity. The cavity formed by the recess 3 is the same as that of the first embodiment. However, the cavity formed by the recess 11 is completely sealed at the time of joining with the fixed base 2, so that the cavity is completely separated from the static pressure. It operates as a reference pressure chamber having a pressure of Generally, an appropriate pressure between vacuum and atmospheric pressure is selected as the pressure in the reference pressure chamber. As a result, the static pressure detecting diaphragm 10 becomes a flexure element responsive to the static pressure, and operates in response to the pressure difference between the reference pressure chamber pressure and the static pressure.

By configuring the composite sensor as described above,
The tensile stress σ _m generated at the time of differential pressure load is
Since the resistance change is obtained by the stress generated on the static pressure detection diaphragm 10 at the time of the static pressure load without affecting the static pressure, the composite sensor capable of taking out the high output static pressure signal without the influence of the differential pressure is provided. Can be configured.

Next, a third embodiment of the present invention will be described with reference to FIG. Similar to the second embodiment of the, two static pressure detecting diaphragm 10 is provided, the static pressure gauge 121,12 4 arranged on each diaphragm 10, further to the fixed portion 5 of the first embodiment Static pressure gauge 12 as in the case
It is arranged 2, 12 3. As shown in FIG. 5, the effect of the tensile stress σm generated on the diaphragm 4 due to the differential pressure is not always zero even in the <001> axis direction of the (100) plane. Static pressure gauges 121 to 12
4 is a static pressure gauge 12 on the static pressure detecting diaphragm 10
1,12 static pressure gauges 12 on the fixed portion 5 from the fourth variation
As it is taken out by subtracting the 2, 12 3 variation of FIG. 3
The output of the static pressure sensor which does not fluctuate due to the differential pressure can be obtained by configuring the bridge circuit shown in FIG. Here, the static pressure gauge 12 on the static pressure detection diaphragm 10 is used.
1,12 4 outputs, static pressure gauges 12 on the fixed portion 5
A configuration of subtracting the 2, 12 3 of the output, the output of the static pressure gauge 121,12 4 on diaphragm 10 exits static pressure is the output of the static pressure gauge 122,12 3 on the fixed part Since an output ten times or more can be obtained, a large static pressure output can be obtained even if the difference is subtracted.

Next, a fourth embodiment of the present invention will be described with reference to FIG. In this embodiment, the sensor substrate 1 is
In one embodiment, the shape is square, while the shape is square. Differential pressure gauge 111-114, static pressure gauge 1
If the temperature gauges 21 to 124 and the temperature gauge 9 are arranged in the same manner as in the above-described embodiments, a composite sensor having a static pressure sensor which is not affected by a differential pressure can be configured. Here, an example is shown in which the static pressure gauges 121 to 124 are provided on the static pressure detection diaphragm 10 and the fixed portion 5 as in the third embodiment.

When the sensor substrate 1 is formed into a round shape in a planar shape as described above, it is necessary to cut out one semiconductor substrate one by one into a round shape by machining or the like, and to join the semiconductor substrate 1 to the fixed base 2. On the other hand, when the sensor substrate 1 is formed in a rectangular shape, one semiconductor substrate and the fixing table 2 are first joined by an anodic bonding method or the like, and then cut by dicing. A sensor can be formed,
It greatly improves productivity and cost performance.

In each of the above embodiments, as described with reference to FIG. 4, p-type silicon of the (100) plane is used. When p-type silicon of the (100) plane is used, as described above, the differential pressure gauge group is arranged in the <110> axial direction where the piezoresistance coefficient is the maximum, and the static pressure gauge group is determined to have the minimum piezoresistance coefficient. <001> axis direction.
In general, n-type silicon is not used in composite sensors because of its poor nonlinearity. However, in the present invention, by using (001) n-type silicon, the differential pressure gauge group is arranged in the crystal axis direction in which the piezoresistance coefficient is maximum, and the static pressure gauge group is minimized in the piezoresistance coefficient. By arranging in the direction of the crystal axis on the line in the direction of the crystal axis, an n-type composite sensor having a static pressure sensor free from the influence of the differential pressure can be configured. The temperature gauge is arranged in the direction of the crystal axis where the piezoresistance coefficient is minimized. The piezoresistance coefficient in the axial direction where the n-type (011) plane silicon differential pressure gauge group is arranged is smaller than the piezoresistance coefficient in the axial direction where the p-type (100) plane silicon differential pressure gauge group is arranged. And 10%
Since the sensitivity is high, the use of the n-type (011) plane silicon has an effect of obtaining a larger differential pressure output than the case of using the p-type (100) plane silicon. As described above, when the n-type silicon is applied to the composite sensor, the non-linearity is deteriorated. However, such a deterioration in the non-linearity is not a problem today when a correction algorithm for the sensor output is established.

FIG. 11 is a sectional view showing a case where the sensor substrate 1 of the composite sensor according to the present invention is processed by etching. If processing is performed by isotropic etching such as dry etching, a rounded portion R is formed at the contact portion between the diaphragm 4 and the fixed portion 5 as shown in FIG. And has the effect of improving the breakdown voltage. Also, if processing is performed by anisotropic etching such as alkali etching, the diaphragm 4 is formed of a silicon single crystal plane as shown in FIG. distillate Ri is improved. In either case of isotropic or anisotropic, if processing is performed by etching, a large number of diaphragms 4 (or 10) can be simultaneously formed on one semiconductor substrate, so that mass productivity is improved and inexpensive. The sensor substrate 1 can be manufactured.

Further, the composite sensor of the present invention can form a differential pressure sensor and a static pressure sensor on a single semiconductor chip, and has a simple structure.

FIG. 12 shows an example in which the composite sensor according to the present invention is incorporated in a differential pressure transmitter. The differential pressure transmitter 14 measures a differential pressure ΔP between both ends of an orifice 13 provided in a pipeline 12 of a chemical plant or the like, obtains a flow rate flowing through the pipeline 12, and transmits it to a control device. Since measuring the differential pressure accurately leads to more efficient operation of the plant, the role of the differential pressure transmitter is great.

FIG. 13 is a block diagram of the differential pressure transmitter 14.
Shown in The differential pressure output from the differential pressure sensor DPS, the static pressure output from the static pressure sensor SPS, and the temperature output from the temperature sensor TS in the composite sensor 15 are represented by a multiplexer (MPX).
16 and a programmable gain amplifier (PG
A) It is amplified at 17. Next, an A / D converter (A / D) 1
The digital signal is converted into a digital signal at 8 and transmitted to a microcomputer (MPU) 19. The memory (M) 20 stores the characteristics of each sensor of differential pressure, static pressure, and temperature. The microcomputer 19 uses the data to correct the sensor output and detect the differential pressure with high accuracy. The detected differential pressure is converted into an analog signal again by a D / A converter (D / A) 21 and output.

Using the composite sensor according to the present invention, the processing in the microcomputer 19 can be roughly described first.
The temperature sensor output removes the temperature effect of the differential pressure sensor output,
Next, the influence of temperature is removed from the output of the static pressure sensor by the output of the temperature sensor, and this is used to remove the influence of static pressure from the output of the differential pressure sensor. Thus, accurate differential pressure information can be obtained. In the conventional composite sensor, since the output of the static pressure sensor includes the influence of the differential pressure, a process for removing the influence of the differential pressure is required. On the other hand, in the composite sensor of the present invention, since the differential pressure does not affect the static pressure sensor, accurate differential pressure data can be obtained with simpler correction.

[0038]

As apparent from the above description, the present invention has the following effects. On the surface of the sensor substrate formed of a semiconductor, according to the type of semiconductor crystal, the static pressure detecting sensitive element is arranged in a direction that is not affected by the tensile stress due to the differential pressure. A static pressure signal having no influence can be obtained, and a highly accurate differential pressure measurement value can be obtained with simpler correction. In addition, if the diaphragm for detecting static pressure is provided separately from the diaphragm for detecting differential pressure, a static pressure signal having a high output and no influence of differential pressure can be obtained, so that the accuracy of differential pressure measurement can be improved. The static pressure signal can also be used as a sensor for process pressure. Furthermore,
The sensor substrate is processed by etching, improves walking stops <br/>, reliability, rich in economy.

[Brief description of the drawings]

FIG. 1 is a plan view of a composite sensor according to a first embodiment of the present invention.

FIG. 2 is a sectional view of the composite sensor according to the first embodiment of the present invention.

FIG. 3 is a connection diagram of each gauge of the composite sensor.

FIG. 4 is a distribution diagram showing a distribution of the number of piezoresistors in p-type silicon.

FIG. 5 is a diagram showing a resistance change and a stress distribution on a diaphragm.

FIG. 6 is a diagram for explaining stress acting on a static pressure gauge of a p-type (100) plane silicon substrate.

FIG. 7 is a plan view of a composite sensor according to a second embodiment of the present invention.

8 is a sectional view taken along line VIII-VIII in FIG.

FIG. 9 is a plan view of a composite sensor according to a third embodiment of the present invention.

FIG. 10 is a plan view of a composite sensor according to a fourth embodiment of the present invention.

FIG. 11 is a sectional view of a main part of a composite sensor formed by isotropic etching and anisotropic etching on a sensor substrate.

FIG. 12 is a diagram illustrating an example of use of a differential pressure transmitter.

FIG. 13 is a block diagram showing a specific configuration of a differential pressure transmitter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sensor board 2 Fixed base 4 Diaphragm for differential pressure detection 5 Fixed part 7, 8 line 9 Temperature gauge 10 Diaphragm for static pressure detection 14 Differential pressure transmitter 111-114 Differential pressure gauge 211-214 Static pressure gauge

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Satoshi Shimada 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Seiichi Ukai 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture Hitachi, Ltd. (56) References JP-A-3-44079 (JP, A) JP-A-1-184433 (JP, A) JP-A-64-27275 (JP, A) JP-A-61-240134 (JP, A) JP-A-56-40735 (JP, A) Japanese Patent Publication No. 2-9704 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01L 9/04 101

Claims (7)

(57) [Claims] 1. A sensor substrate comprising a central diaphragm for detecting a differential pressure and a peripheral fixed part, a plurality of differential pressure detecting sensitive elements disposed on the diaphragm, and a plurality of static elements disposed on the fixed part. In the composite sensor including the pressure detecting sensitive element, the static pressure detecting sensitive element is in a direction not affected by a tensile stress generated in an arrangement area of the static pressure detecting sensitive element based on a differential pressure applied to the diaphragm. A composite sensor, comprising: a sensor; 2. A sensor board comprising a central diaphragm for detecting differential pressure and a peripheral fixed portion; a plurality of differential pressure detecting sensitive elements disposed on the diaphragm; and a plurality of differential elements disposed on the fixed portion. In the composite sensor including the static pressure detecting sensitive element, each of the plurality of static pressure detecting sensitive elements is provided on the sensor substrate based on a differential pressure applied to the diaphragm. The sensitivity directions of the plurality of sensing elements for detecting static pressure are arranged on a line in a direction not affected by the tensile stress generated in the direction, and the sensitivity direction of each of the plurality of sensing elements for detecting static pressure is most affected by the tensile stress generated by the static pressure. A composite sensor, wherein the composite sensor is arranged to face. 3. The composite sensor according to claim 2 , wherein, when the direction most affected by the tensile stress is a reference direction having an angle of 0 degrees, the line in a direction not affected by the tensile stress is the line. 45 degrees or -4 with respect to the reference direction
A composite sensor having an angle of 5 degrees. 4. The composite sensor according to claim 3 , wherein the number of said static pressure detecting sensitive elements is four, and said static pressure detecting sensitive elements are two lines of 45 degrees and -45 degrees. A composite sensor, which is distributed and disposed at positions equidistant from the intersection of the two. 5. The composite sensor according to claim 1 , wherein the sensing element for detecting static pressure is formed in a part of the fixed portion.
The static pressure detecting diaphragm is disposed on the formed static pressure detecting diaphragm, a part of the static pressure detecting sensitive element is disposed on the static pressure detecting diaphragm, and the remaining static pressure detecting sensitive element is fixed. A composite sensor, wherein the composite sensor is disposed on a unit. In integrated sensor 6. The method of claim 1 or 2, wherein the sensor substrate is formed of p-type (100) plane silicon single crystal, the direction which is not affected by the tensile stress <
001> axial direction. 7. The composite sensor according to claim 6 , wherein the processing of the sensor substrate is performed by using one of anisotropic etching and isotropic etching.