Pressure sensor

Abstract

To obtain a pressure sensor which is excellent in temperature characteristic and enables a diaphragm to have high strength, high wear resistance and high corrosion resistance and furthermore enables improvement of resolution power.SOLUTION: A pressure sensor 1 comprises: a pressure-receiving body 2 having a diaphragm portion 4 which is deformed when receiving pressure on a pressure-receiving surface 41 and a rim portion 5 integrally formed on the outer circumference of the diaphragm portion 4 and formed thicker than the diaphragm portion 4; and a semiconductor substrate 3 which is joined to a reverse side 42 of the pressure-receiving surface 41, and detects strain of the diaphragm portion 4 with a vibratory strain gauge. The pressure-receiving body 2 is formed from ceramic, and the semiconductor substrate 3 includes a base portion 6 disposed facing the reverse side 42, and a joint portion 7 having a joining surface 71 protruding toward the reverse side 42 from the base portion 6 and joined to the reverse side 42, the joint portion 7 having a larger area than the area of the base portion 6 when seen from a direction perpendicular to the reverse side 42.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a pressure sensor that measures a pressure applied to a pressure-receiving surface of a diaphragm. [Background technology]

[0002] There is known a pressure sensor that measures the pressure of a measurement object, which is mainly a fluid. The pressure sensor includes a diaphragm. The diaphragm has a pressure receiving surface to which pressure is applied from the measurement object. The pressure sensor measures the pressure based on the amount of deformation of the diaphragm due to the pressure applied to the pressure receiving surface. For example, as shown in Patent Document 1, such a pressure sensor includes a diaphragm formed of metal and a piezo-resistance type strain gauge attached to the diaphragm. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-94666 Summary of the Invention [Problem to be solved by the invention]

[0004] If the object being measured contains a foreign object, the metal diaphragm will be plastically deformed by the impact of the foreign object. If the object being measured is a corrosive fluid such as an acid or alkali, the metal diaphragm may corrode. If the object being measured is hydrogen, hydrogen may permeate the metal diaphragm or the diaphragm may become brittle due to hydrogen embrittlement.

[0005] An object of the present invention is to provide a pressure sensor that can improve the strength, wear resistance, and corrosion resistance of the diaphragm while also improving the resolution. [Means for solving the problem]

[0006] The pressure sensor of the present invention comprises a pressure receiving body having a diaphragm portion that deforms when pressure is applied to the pressure receiving surface, and a rim portion that is formed integrally with the outer periphery of the diaphragm portion and is thicker than the diaphragm portion, and a semiconductor substrate that is joined to the back surface of the pressure receiving surface and detects the strain of the diaphragm portion with a vibration strain gauge, the pressure receiving body being formed of ceramic, the semiconductor substrate having a base portion facing the back surface and a joint portion that protrudes from the base toward the back surface and has a joint surface that is joined to the back surface, at least one vibration strain gauge is provided on the semiconductor substrate, and when viewed from a direction perpendicular to the back surface, the area of ​​the joint portion is smaller than the area of ​​the base. Effect of the Invention

[0007] According to the pressure sensor of the present invention, it is possible to improve the strength of the diaphragm, improve the wear resistance, improve the corrosion resistance, and the like, while also improving the resolution. [Brief description of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view of a pressure sensor according to a first embodiment. [Diagram 2] 2 is a view of the pressure sensor shown in FIG. 1 as viewed from the semiconductor substrate side. [Diagram 3] 1 is a view of a pressure sensor according to a first modified example of the first embodiment, viewed from the semiconductor substrate side. [Figure 4] 13 is a view of a pressure sensor according to a second modified example of the first embodiment, viewed from the semiconductor substrate side. FIG. [Diagram 5] 13 is a cross-sectional view of a pressure sensor according to a third modified example of the first embodiment. FIG. [Figure 6] 6 is a view of the pressure sensor shown in FIG. 5 as viewed from the semiconductor substrate side. [Figure 7] 13 is a cross-sectional view of a pressure sensor according to a fourth modified example of the first embodiment. FIG. [Figure 8] FIG. 13 is a cross-sectional view of a pressure sensor according to a fifth modified example of the first embodiment. [Figure 9]FIG. 13 is a cross-sectional view of a pressure sensor according to a sixth modified example of the first embodiment. [Figure 10] FIG. 13 is a cross-sectional view of a pressure sensor according to a seventh modified example of the first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, a pressure sensor according to an embodiment of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiment described below.

[0010] [Embodiment 1] Fig. 1 is a cross-sectional view of a pressure sensor according to embodiment 1. Fig. 2 is a view of the pressure sensor shown in Fig. 1 as seen from the semiconductor substrate side. The pressure sensor 1 includes a pressure receiving body 2 and a semiconductor substrate 3. The pressure sensor 1 measures the pressure of a measurement object, which is mainly a fluid.

[0011] The pressure-receiving body 2 is made of ceramic and has a diaphragm portion 4 and a rim portion 5.

[0012] The diaphragm portion 4 is a plate-like portion formed thinner than the rim portion 5, and functions as a diaphragm that deforms when pressure is applied from a measured object. One surface of the diaphragm portion 4 serves as a pressure-receiving surface 41 that contacts the measured object. The back surface 42 of the diaphragm portion 4, which faces the opposite side to the pressure-receiving surface 41, serves as the surface to which the semiconductor substrate 3 is bonded. Note that FIG. 2 is a view of the pressure sensor 1 as viewed from the back surface 42. In the following description, the state in which the pressure sensor 1 is viewed from a direction perpendicular to the back surface 42 is simply referred to as a plan view.

[0013] The diaphragm portion 4 has a circular shape in a plan view. Both the pressure-receiving surface 41 and the back surface 42 of the diaphragm portion 4 are flat when not receiving pressure. The rim portion 5 has an annular shape that surrounds the diaphragm portion 4. As shown in FIG. 1, the rim portion 5 is formed to be thicker than the diaphragm portion 4. The rim portion 5 is also smoothly connected to the back surface 42 of the diaphragm portion 4 without any steps. As a result, the overall shape of the pressure-receiving body 2 has a recess formed on the pressure-receiving surface 41 side in the area where the diaphragm portion 4 is formed.

[0014] The semiconductor substrate 3 has a base 6, a joint 7, and a vibrator 8. The semiconductor substrate 3 is made of silicon. The base 6 is provided opposite to the rear surface 42 of the diaphragm portion 4. In a plan view, the base 6 has a square shape.

[0015] The joint 7 protrudes from the base 6 toward the back surface 42 of the diaphragm portion 4. In Fig. 2, the joint 7 is indicated by a dashed line. The joint 7 has a joint surface 71 that is joined to the back surface 42 of the diaphragm portion 4. In a plan view, the shape of the joint surface 71 (joint 7) is circular. In a plan view, the area of ​​the joint 7 is smaller than the area of ​​the base 6.

[0016] In addition, in a plan view, the area of ​​the bonding surface 71 is smaller than the area of ​​the diaphragm portion 4, and the entire bonding surface 71 is bonded to the rear surface 42 of the diaphragm portion 4. In this embodiment 1, the relationship among the outer diameter X1 of the diaphragm portion 4, the outer diameter X2 of the rim portion 5, the side length Y1 of the base 6, and the outer diameter Y2 of the bonding surface 71 is summarized as X2>X1>Y1>Y2.

[0017] The oscillator 8 is formed on the base 6. Electrode pads (not shown) are provided on the base 6. The oscillator 8 is excited by applying a voltage through the electrode pads.

[0018] In the pressure sensor 1, the diaphragm portion 4 is deformed by the pressure received from the object to be measured, and the semiconductor substrate 3 is also deformed accordingly. The deformation of the semiconductor substrate 3 causes a strain in the vibrator 8, which changes the resonant frequency. The change in the resonant frequency of the vibrator 8 is detected based on an electrical signal obtained through an electrode pad. In the pressure sensor 1, the pressure value generated in the object to be measured is detected by understanding the relationship between the pressure applied to the diaphragm portion 4 and the change in the resonant frequency of the vibrator 8.

[0019] In the pressure sensor 1 described above, the diaphragm portion 4 and the rim portion 5 that come into contact with the object to be measured are made of ceramic, so they are not subject to plastic deformation even if a foreign object strikes the object to be measured, as is the case with diaphragms made of metal. In addition, ceramics are corrosion resistant, so it is possible to measure pressure values ​​even when the object to be measured is corrosive, such as acidic or alkaline. In addition, ceramics have lower hydrogen permeability than metals and are less susceptible to hydrogen embrittlement, so it is possible to measure pressure values ​​even when the object to be measured is hydrogen.

[0020] It is preferable that the deformation of the semiconductor substrate 3 in the pressure sensor 1 occurs only due to changes in pressure of the object to be measured. However, since the pressure receiver 2 and the semiconductor substrate 3, which are bonded together, are made of different materials, the difference in thermal expansion coefficients causes deformation of the semiconductor substrate 3 when the temperature changes. In other words, when the temperature changes, the resonant frequency of the vibrator 8 changes due to factors other than the change in pressure of the object to be measured, which becomes a cause of error in the measurement of the pressure value by the pressure sensor 1. In order to reduce the cause of error caused by temperature changes, it is necessary to reduce the difference between the thermal expansion coefficients of the pressure receiver 2 and the semiconductor substrate 3.

[0021] For example, in a conventional pressure sensor, a piezo-resistance type strain gauge is bonded to a metal diaphragm. In such a pressure sensor, the difference between the thermal expansion coefficient of the metal diaphragm and the thermal expansion coefficient of the strain gauge becomes large, so the metal diaphragm and the piezo-resistance type strain gauge are bonded via low-melting-point glass whose thermal expansion coefficient is a value between the two. This reduces the difference in thermal expansion coefficient between the components compared to when the metal diaphragm and the piezo-resistance type strain gauge are directly bonded, thereby reducing error factors caused by temperature differences.

[0022] However, although the difference in the thermal expansion coefficient between the components can be reduced, the low-melting-point glass is a viscoelastic material, and so its characteristics drift due to the creep phenomenon. The drift in the characteristics of the low-melting-point glass becomes a factor of error in the pressure value measurement by the pressure sensor.

[0023] In the first embodiment, the diaphragm portion 4 and the rim portion 5 of the pressure receiver 2 are made of ceramic. The base portion 6 and the joint portion 7 of the semiconductor substrate 3 are made of silicon. The thermal expansion coefficient of silicon is αs=2.6 ppm / K. For example, if silicon nitride with a thermal expansion coefficient of αn=3.4 ppm / K is used as the ceramic, the thermal expansion coefficient difference is Δα=αn-αs=0.8 ppm / K, and the difference in the thermal expansion coefficient can be reduced. Therefore, even if the diaphragm portion 4 and the semiconductor substrate 3 are joined, the error factor caused by temperature change can be reduced. It is preferable that the difference between the thermal expansion coefficient of the base portion 6 and the joint portion 7 and the thermal expansion coefficient of the diaphragm portion 4 and the rim portion 5 is 2 ppm / °C or less in the range from 0°C to 200°C. In this way, if the difference in the thermal expansion coefficient is small in a wide temperature range, the temperature range in which the pressure sensor 1 can be used is also wide. It is possible to satisfy this condition by using silicon nitride as the ceramic.

[0024] The semiconductor substrate 3 is made of silicon, and has a different thermal expansion coefficient from the ceramic material of the diaphragm part 4, so the joined part deforms due to the bimetal effect. If the thermal expansion coefficient of the ceramic material is larger than that of silicon, the diaphragm part 4 made of ceramic material expands when the temperature rises, generating tensile strain in the semiconductor substrate 3 made of silicon. At the same time, the surface of the diaphragm part 4 becomes convex and the surface of the semiconductor substrate 3 becomes concave, and the surface of the semiconductor substrate 3 shrinks relatively, so that the vibration strain gauge 8 mounted on the surface generates compressive strain due to the difference in thermal expansion coefficients. In this case, by optimizing the thickness of the semiconductor substrate 3, the thickness of the diaphragm part 4, the area of ​​the joint 7, etc., it is possible to design it so that the distortion caused by the difference in thermal expansion coefficients is canceled out, and the temperature error can be reduced to almost zero. If the thermal expansion coefficient of the ceramic material is smaller than that of silicon, the relationship between expansion and compression is reversed, but it is also possible to design it so that the distortion caused by the difference in thermal expansion coefficients is canceled out in the same way.

[0025] Also, a vibration type strain gauge that detects changes in the natural frequency of the vibrator 8 is provided on the semiconductor substrate 3. The vibration type strain gauge has a gauge factor (Gf) indicating resolution of Gf to 1000, and the semiconductor substrate 3 exhibits extremely high resolution, thereby achieving high resolution of the pressure sensor 1. At least one vibration type strain gauge is provided on the semiconductor substrate 3.

[0026] In addition, in the pressure sensor 1, the diaphragm portion 4 may be thickened or the outer diameter may be reduced in order to achieve a high pressure resistance. When such a high pressure resistance is achieved, the amount of deformation of the diaphragm portion 4 when the pressure of the object to be measured changes becomes small, but if the semiconductor substrate 3 exhibits high resolution, it is possible to detect the pressure value even with a small amount of deformation. In other words, the pressure sensor 1 can achieve both high pressure resistance and high resolution.

[0027] In addition, a bonding portion 7 having an area smaller than that of the base portion 6 in a planar view protrudes from the base portion 6 toward the rear surface 42 of the diaphragm portion 4, and the semiconductor substrate 3 is bonded to the diaphragm portion 4 at a bonding surface 71 of the bonding portion 7.

[0028] The semiconductor substrate 3 is manufactured through a dicing process in which a semiconductor wafer, in which a plurality of semiconductor substrates 3 are arranged and integrally formed, is cut with a blade. Chipping and burrs may be formed on the outer edge of the semiconductor substrate 3 that comes into contact with the blade. Chipping and burrs formed on the outer edge of the surface of the semiconductor substrate 3 that is bonded to the back surface 42 of the diaphragm portion 4 may cause poor bonding to the back surface 42.

[0029] On the other hand, in the pressure sensor 1 of the first embodiment, the periphery of the portion that will become the bond 7 at the stage of the semiconductor wafer can be removed by etching in a step prior to the dicing step. Removal by etching enables highly accurate processing with almost no chipping or burrs being formed. If the periphery of the portion that will become the bond 7 is removed before the dicing step, the blade does not come into contact with the outer edge of the bond surface 71 in the dicing step, and therefore no chipping or burrs are formed on the outer edge of the bond surface 71.

[0030] Therefore, by forming the joint 7 having a smaller area than the base 6 in a plan view, it is possible to prevent poor bonding caused by chipping and burrs formed on the outer edge of the joint surface 71.

[0031] Furthermore, the joint 7 formed with high precision by etching has small variations between products, which makes it possible to reduce variations in resolution between pressure sensors 1.

[0032] Furthermore, when the pressure sensor 1 is designed to withstand high pressure, the outer diameter of the diaphragm portion 4 may be designed to be small. On the other hand, the semiconductor substrate 3 needs an area for mounting elements for achieving the intended function, such as electrode pads for extracting electrical signals and sensor elements. The portion for mounting the elements does not need to be bonded to the diaphragm portion 4, and it is preferable that the portions are not bonded to prevent deterioration of characteristics due to deformation of the electrode pads. In this embodiment 1, the bonding portion 7 is formed with an area required for bonding to the back surface 42 of the diaphragm portion 4, while the area of ​​the base portion 6 in a plan view is made larger than that of the bonding portion 7, thereby securing the portion for mounting the elements and making it possible to obtain a pressure sensor 1 that can measure pressure values ​​with higher accuracy.

[0033] Fig. 3 is a view of the pressure sensor according to the first modified example of the embodiment 1 as viewed from the semiconductor substrate side. As shown in Fig. 3, the shape of the base 6 in a plan view may be circular. Even if the shape of the base 6 is circular, by making it larger than the area of ​​the bonding portion 7, it is possible to prevent bonding failure caused by chipping and burrs, as in the examples shown in Figs. 1 and 2, and to provide the pressure sensor 1 that can measure pressure values ​​with high accuracy.

[0034] Fig. 4 is a view of a pressure sensor according to a second modified example of the first embodiment, as viewed from the semiconductor substrate side. As shown in Fig. 4, the shape of the bonding portion 7 in a plan view may be polygonal. Even if the shape of the bonding portion 7 is polygonal, by making it smaller than the area of ​​the base portion 6, it is possible to prevent bonding failure caused by chipping and burrs, as in the examples shown in Figs. 1 and 2, and to provide the pressure sensor 1 that can measure pressure values ​​with high accuracy.

[0035] Fig. 5 is a cross-sectional view of a pressure sensor according to a third modified example of the first embodiment. Fig. 6 is a view of the pressure sensor shown in Fig. 5 as seen from the semiconductor substrate side. As shown in Figs. 5 and 6, in the pressure sensor 1 according to the third modified example, the pressure receiving surface 41 and the back surface 42 of the diaphragm portion 4 are not flat, but have a step protruding toward the back surface 42. In this way, the pressure receiving surface 41 and the back surface 42 of the diaphragm portion 4 are not limited to flat surfaces.

[0036] Fig. 7 is a cross-sectional view of a pressure sensor according to a fourth modified example of the first embodiment. The cross-sectional view shown in Fig. 7 corresponds to the cross-sectional view taken along the dashed line shown in Fig. 2. As shown in Fig. 7, the rim portion 5 may be smoothly connected to the pressure-receiving surface 41 of the diaphragm portion 4 without any step. In the pressure sensor 1 according to the fourth modified example, the overall shape of the pressure-receiving body 2 has a recess formed on the back surface 42 side in the portion where the diaphragm portion 4 is formed.

[0037] Fig. 8 is a cross-sectional view of a pressure sensor according to a fifth modified example of the first embodiment. The cross-sectional view shown in Fig. 8 corresponds to the cross-sectional view cut along the dashed line shown in Fig. 2. As shown in Fig. 8, the rim portion 5 is connected to both the pressure-receiving surface 41 and the back surface 42 of the diaphragm portion 4 by providing a step. In the pressure sensor 1 according to the fifth modified example, the overall shape of the pressure-receiving body 2 is such that a recess is formed on both the pressure-receiving surface 41 side and the back surface 42 side in the portion where the diaphragm portion 4 is formed.

[0038] FIG. 9 is a cross-sectional view of a pressure sensor according to a sixth modified example of the first embodiment. The cross-sectional view shown in FIG. 9 corresponds to the cross-sectional view cut along the dashed line shown in FIG. 2. As shown in FIG. 9, the relationship between the outer diameter X11 of the diaphragm portion 4, the outer diameter X12 of the rim portion 5, the side length Y11 of the base portion 6, and the outer diameter Y12 of the joint portion 7 is X12>Y11>X11>Y12. If no recess is formed on the back surface 42 side of the diaphragm portion 4, the side length Y11 of the base portion 6 can be made larger than the outer diameter of the diaphragm portion 4 as shown in FIG. 9. Note that when the base portion 6 is circular, Y11 is the outer diameter, and when the base portion 6 is a polygon having pentagons or more sides, Y11 is the outer diameter of an inscribed circle.

[0039] FIG. 10 is a cross-sectional view of a pressure sensor according to a seventh modification of the first embodiment. The cross-sectional view shown in FIG. 10 corresponds to the cross-sectional view cut along the dashed line shown in FIG. 2. As shown in FIG. 10, the relationship between the outer diameter X21 of the diaphragm portion 4, the outer diameter X22 of the rim portion 5, the side length Y21 of the base portion 6, and the outer diameter Y22 of the joint portion 7 is X22>Y21>Y22>X11. If no recess is formed on the back surface 42 side of the diaphragm portion 4, the outer diameter Y22 of the joint portion 7 can be made larger than the outer diameter of the diaphragm portion 4 as shown in FIG. 10. In the seventh modification, the outer periphery, which is a part of the joint surface 71, is in contact with the rim portion 5. Note that when the base portion 6 is circular, Y21 is the outer diameter, and when the base portion 6 is a polygon with pentagons or more sides, Y21 is the outer diameter of the inscribed circle.

[0040] 1 to 10, the rear surface 42 and the bonding surface 71 may be bonded directly or via a metal film. Examples of metals used for the metal film include titanium, silver, and gold.

[0041] 〔others〕 Some examples of combinations of the disclosed technical features are set out below.

[0042] (1) A pressure sensor comprising: a pressure receiving body having a diaphragm portion that deforms when pressure is applied to a pressure receiving surface, and a rim portion that is integrally formed on the outer periphery of the diaphragm portion and is thicker than the diaphragm portion; and a semiconductor substrate that is joined to the back surface of the pressure receiving surface and detects strain of the diaphragm portion, wherein the pressure receiving body is formed of ceramic, the semiconductor substrate has a base portion provided opposite the back surface, and a joint portion that protrudes from the base toward the back surface and has a joint surface that is joined to the back surface, at least one vibration type strain gauge is provided on the semiconductor substrate, and when viewed from a direction perpendicular to the back surface, the area of ​​the joint portion is smaller than the area of ​​the base.

[0043] (2) The pressure sensor described in (1), wherein the base and the joint are formed of silicon, and the difference between the thermal expansion coefficient of the base and the joint and the thermal expansion coefficient of the pressure receiving body is 2 ppm / °C or less in the range of 0°C to 200°C.

[0044] (3) The pressure sensor according to (1) or (2), wherein the entire joint surface is in contact with the diaphragm portion.

[0045] (4) The pressure sensor according to (1) or (2), wherein a portion of the joint surface is in contact with the rim portion.

[0046] (5) The pressure sensor according to any one of (1) to (4), wherein the bonding surface is bonded to the back surface directly or via a metal film.

[0047] (6) The pressure sensor according to any one of (1) to (5), wherein the pressure-receiving body is recessed on the pressure-receiving surface side in a region where the diaphragm portion is provided.

[0048] (7) The pressure sensor according to any one of (1) to (5), wherein the pressure receiving body has a recess on the back surface side in a region where the diaphragm portion is provided.

[0049] (8) The pressure sensor according to any one of (1) to (7), wherein the base has a square shape when viewed from a direction perpendicular to the back surface.

[0050] (9) The pressure sensor according to (8), wherein the side length of the base portion is greater than the outer diameter of the diaphragm portion.

[0051] (10) The pressure sensor according to any one of (1) to (7), wherein the base has a circular shape when viewed from a direction perpendicular to the back surface.

[0052] (11) The pressure sensor according to (10), wherein the outer diameter of the base portion is larger than the outer diameter of the diaphragm portion.

[0053] (12) The pressure sensor according to any one of (1) to (11), wherein the bonding surface has a circular shape when viewed from a direction perpendicular to the back surface.

[0054] (13) The pressure sensor according to any one of (1) to (11), wherein the bonding surface has a polygonal shape when viewed from a direction perpendicular to the back surface. [Explanation of symbols]

[0055] 1 Pressure Sensor 2 Pressure receiver 3. Semiconductor Substrate 4 Diaphragm 5 Rim 6 base 7 Joint 8 Transducers 41 Pressure surface 42 Back side 71 Joint surface

Claims

1. a pressure receiving body having a diaphragm portion that deforms when pressure is applied to a pressure receiving surface, and a rim portion that is integrally formed on the outer periphery of the diaphragm portion and is thicker than the diaphragm portion; a semiconductor substrate bonded to a rear surface of the pressure receiving surface and configured to detect a strain of the diaphragm portion, The pressure-receiving body is made of ceramic, the semiconductor substrate has a base portion provided opposite the rear surface, and a bonding portion protruding from the base portion toward the rear surface and having a bonding surface bonded to the rear surface, At least one vibrating strain gauge is provided on the semiconductor substrate; A pressure sensor in which the area of ​​the joint is smaller than the area of ​​the base when viewed from a direction perpendicular to the back surface.

2. the base and the joint are formed of silicon; 2. The pressure sensor according to claim 1, wherein a difference between a thermal expansion coefficient of said base and said joint and a thermal expansion coefficient of said pressure receiver is 2 ppm / .degree. C. or less in the range of 0.degree. C. to 200.degree.

3. 2. The pressure sensor according to claim 1, wherein the entire joint surface is in contact with the diaphragm portion.

4. The pressure sensor according to claim 1 , wherein a portion of the joint surface is in contact with the rim portion.

5. The pressure sensor according to claim 1 , wherein the bonding surface is bonded to the rear surface directly or via a metal film.

6. 2. The pressure sensor according to claim 1, wherein the pressure receiving body is recessed on the pressure receiving surface side in a region where the diaphragm portion is provided.

7. The pressure sensor according to claim 1 , wherein the back surface side of the pressure receiving body is recessed in a region where the diaphragm portion is provided.

8. 2. The pressure sensor according to claim 1, wherein the base has a square shape when viewed from a direction perpendicular to the back surface.

9. The pressure sensor according to claim 8 , wherein a side length of the base portion is greater than an outer diameter of the diaphragm portion.

10. 2. The pressure sensor according to claim 1, wherein the base portion has a circular shape when viewed from a direction perpendicular to the back surface.

11. The pressure sensor according to claim 10 , wherein an outer diameter of the base portion is greater than an outer diameter of the diaphragm portion.

12. 2. The pressure sensor according to claim 1, wherein the bonding surface has a circular shape when viewed from a direction perpendicular to the back surface.

13. 2. The pressure sensor according to claim 1, wherein the bonding surface has a polygonal shape when viewed from a direction perpendicular to the back surface.

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