Pressure sensor

Abstract

The invention relates to a pressure sensor. A pressure sensor (1) is provided with: a pressure receiving body (2) having a diaphragm section (4) that deforms upon receiving pressure on a pressure receiving surface (41), and a rim section (5) that is integrally formed on the outer periphery of the diaphragm section (4) and is formed thicker than the diaphragm section (4); and a semiconductor substrate (3) that is bonded to the rear surface (42) of the pressure receiving surface (41) and detects the strain of the diaphragm section (4) by means of a vibrating strain gauge, the pressure receiving body (2) is formed from a ceramic, and the semiconductor substrate (3) has: a base section (6) that is provided so as to face the rear surface (42); and a joining part (7) having a joining surface (71) protruding from the base part (6) toward the back surface (42) and joined to the back surface (42), the area of the joining part (7) being smaller than the area of the base part (6) when viewed from a direction perpendicular to the back surface (42).

Description

Technical Field

[0001] The present invention relates to a pressure sensor for measuring the pressure applied to a pressure-receiving surface of a diaphragm. Background Art

[0002] A pressure sensor that mainly measures the pressure of a measured body that is a fluid is known. The pressure sensor has a diaphragm. The diaphragm has a pressure-receiving surface to which pressure is applied from the measured body. The pressure sensor measures pressure based on the amount of deformation of the diaphragm caused by the pressure applied to the pressure-receiving surface. For example, as shown in Patent Document 1, such a pressure sensor has a structure in which a diaphragm is formed of metal and a piezoresistance type strain gauge is attached to the diaphragm.

[0003] Patent Document 1: Japanese Patent Application Laid-Open No. 11-94666

[0004] If the object to be measured contains foreign matter, the metal diaphragm may be plastically deformed by the collision of the foreign matter. In addition, when the object to be measured is an acidic or alkaline corrosive fluid, the metal diaphragm may corrode. In addition, when the object to be measured is hydrogen, it may penetrate through the metal diaphragm or become brittle due to hydrogen embrittlement. Summary of the invention

[0005] An object of the present invention is to obtain a pressure sensor capable of achieving increased strength of a diaphragm, improved wear resistance, improved corrosion resistance, and the like, and also capable of achieving improved resolution.

[0006] The pressure sensor involved in the present invention comprises: a pressure-bearing body, which has a diaphragm part and a rim part, the diaphragm part is deformed when it is subjected to pressure on the pressure-bearing surface, and the rim part is formed as an integral part on the outer periphery of the diaphragm part and is formed thicker than the diaphragm part; and a semiconductor substrate, which is bonded to the back side of the pressure-bearing surface and uses a vibration strain gauge to detect the strain of the diaphragm part. The pressure-bearing body is formed of ceramic, and the semiconductor substrate comprises: a base part, which is arranged opposite to the back side; and a bonding part, which has a bonding surface protruding from the base toward the back side and bonded to the back side. At least one vibration strain gauge is arranged on the semiconductor substrate, and when observed from a direction perpendicular to the back side, the area of ​​the bonding part is smaller than the area of ​​the base.

[0007] Effects of the Invention

[0008] According to the pressure sensor of the present invention, it is possible to achieve an effect of increasing the strength of the diaphragm, improving the wear resistance, improving the corrosion resistance, etc., and also achieving an improvement in resolution. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a cross-sectional view of the pressure sensor according to the first embodiment.

[0010] Figure 2 Viewed from the semiconductor substrate side Figure 1 Diagram of the pressure sensor shown.

[0011] Figure 3 This is a diagram showing the pressure sensor according to the first modification of the first embodiment as viewed from the semiconductor substrate side.

[0012] Figure 4 This is a diagram showing the pressure sensor according to the second modification of the first embodiment as viewed from the semiconductor substrate side.

[0013] Figure 5 This is a cross-sectional view of a pressure sensor according to a third modified example of the first embodiment.

[0014] Figure 6 Viewed from the semiconductor substrate side Figure 5 Diagram of the pressure sensor shown.

[0015] Figure 7 This is a cross-sectional view of a pressure sensor according to a fourth modified example of the first embodiment.

[0016] Figure 8 This is a cross-sectional view of a pressure sensor according to a fifth variation of the first embodiment.

[0017] Fig. 9 This is a cross-sectional view of a pressure sensor according to a sixth variation of the first embodiment.

[0018] Fig.10 This is a cross-sectional view of a pressure sensor according to a seventh variation of the first embodiment. DETAILED DESCRIPTION

[0019] Hereinafter, a pressure sensor according to an embodiment of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the embodiment described below.

[0020] [Implementation Method 1]

[0021] Figure 1 It is a cross-sectional view of the pressure sensor according to the first embodiment. Figure 2 Viewed from the semiconductor substrate side Figure 1 FIG. 1 is a diagram of a pressure sensor shown in FIG. 1 . The pressure sensor 1 includes a pressure receiving body 2 and a semiconductor substrate 3. The pressure sensor 1 mainly measures the pressure of a measured body which is a fluid.

[0022] The pressure-receiving body 2 is made of ceramics and includes a diaphragm portion 4 and a rim portion 5 .

[0023] The diaphragm portion 41 is a plate-shaped portion that is thinner than the rim portion 5 and functions as a diaphragm that is deformed by the pressure received from the object to be measured. One surface of the diaphragm portion 4 is a pressure-receiving surface 41 that contacts the object to be measured. The back surface 42 of the diaphragm portion 4 that faces the opposite side of the pressure-receiving surface 41 is a surface that is bonded to the semiconductor substrate 3. In addition, Figure 2 This is a diagram 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.

[0024] The diaphragm 4 is formed into a circular shape when viewed from above. Both the pressure-receiving surface 41 and the back surface 42 of the diaphragm 4 are flat surfaces when not under pressure. The rim 5 is formed into an annular shape surrounding the diaphragm 4. Figure 1 As shown, the rim 5 is formed thicker than the diaphragm 4. In addition, the rim 5 is smoothly connected to the back surface 42 of the diaphragm 4 without any step difference. Thus, the overall shape of the pressure-receiving body 2 is formed in a shape in which a concave portion is formed on the pressure-receiving surface 41 side in the portion where the diaphragm 4 is formed.

[0025] The semiconductor substrate 3 includes a base 6, a bonding portion 7, and a resonator 8. The semiconductor substrate 3 is formed of silicon. The base 6 is provided to face the back surface 42 of the diaphragm portion 4. The base 6 has a square shape in a plan view.

[0026] The engagement portion 7 protrudes from the base portion 6 toward the back surface 42 of the diaphragm portion 4. Figure 2 The dotted line in the figure indicates the joint 7. The joint 7 has a joint surface 71 that is joined to the back surface 42 of the diaphragm 4. The joint 7 and the diaphragm 4 are physically or mechanically connected in a manner that can transmit vibration and deformation. The shape of the joint surface 71 (joint 7) is circular when viewed from above. When viewed from above, the area of ​​the joint 7 is smaller than the area of ​​the base 6.

[0027] In addition, in a plan view, the area of ​​the joint surface 71 is smaller than the area of ​​the diaphragm portion 4, and the entire joint surface 71 is joined to the back surface 42 of the diaphragm portion 4. Here, if 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 joint surface 71 of the present embodiment 1 is summarized, X2>X1>Y1>Y2.

[0028] The vibrator 8 is formed on the base 6. Electrode pads (not shown) are provided on the base 6. The vibrator 8 is excited by applying a voltage through the electrode pads.

[0029] Regarding the pressure sensor 1, the diaphragm 4 is deformed by the pressure received from the measured object, and the semiconductor substrate 3 is also deformed accordingly. The deformation of the semiconductor substrate 3 generates strain in the vibrator 8 and causes the resonance frequency to change. The change in the resonance frequency of the vibrator 8 is detected based on the electrical signal obtained through the electrode pad. Regarding the pressure sensor 1, the pressure value generated in the measured object is detected by pre-understanding the relationship between the pressure applied to the diaphragm 4 and the change in the resonance frequency of the vibrator 8.

[0030] Regarding the pressure sensor 1 described above, the diaphragm portion 4 and the rim portion 5 that are in contact with the measured body are formed of ceramics, so even if a diaphragm formed of metal collides with a foreign object in the measured body, plastic deformation will not occur. In addition, ceramics are corrosion-resistant, so even if the measured body is corrosive to acid or alkaline, the pressure value can be measured. In addition, the hydrogen permeability is lower than that of metals, and it is difficult to produce hydrogen embrittlement, so even if the measured body is hydrogen, the pressure value can be measured.

[0031] It is preferred that the deformation of the semiconductor substrate 3 of the pressure sensor 1 is caused only by the change in the pressure of the measured body. However, the materials of the pressure-receiving body 2 and the semiconductor substrate 3 bonded to each other are different, so when the temperature changes, the semiconductor substrate 3 will be deformed due to the difference in thermal expansion coefficient. That is, when the temperature changes, the resonance frequency of the vibrator 8 changes due to factors other than the change in the pressure of the measured body, which becomes an error factor in the measurement of the pressure value of the pressure sensor 1. In order to reduce the error factor caused by the temperature change, it is necessary to reduce the difference between the thermal expansion coefficient of the pressure-receiving body 2 and the thermal expansion coefficient of the semiconductor substrate 3.

[0032] For example, in a current pressure sensor, a piezoresistive 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 increases, so the metal diaphragm and the piezoresistive strain gauge are bonded via a low-melting-point glass having a thermal expansion coefficient between the two. As a result, the difference in thermal expansion coefficients between the components is reduced compared to a case where the metal diaphragm and the piezoresistive strain gauge are directly bonded, thereby reducing the error factor caused by the temperature difference.

[0033] However, although the difference in thermal expansion coefficient between components can be reduced, low-melting-point glass is a viscoelastic body, so its characteristics drift due to creep. The drift of the characteristics of low-melting-point glass becomes a factor of error in the pressure value measured by the pressure sensor.

[0034] In the present embodiment 1, the diaphragm portion 4 and the rim portion 5 of the pressure-bearing body 2 are formed of ceramics. In addition, the base portion 6 and the joint portion 7 of the semiconductor substrate 3 are formed of silicon. The thermal expansion coefficient of silicon is αs=2.6ppm / K. For example, if silicon nitride having a thermal expansion coefficient αn=3.4ppm / K is used as the ceramic, the difference in thermal expansion coefficient becomes Δα=αn-αs=0.8ppm / K, which can reduce the difference in thermal expansion coefficient. Therefore, even if the diaphragm portion 4 and the semiconductor substrate 3 are joined, the error factor caused by temperature change can be reduced. In addition, it is preferred 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 less than or equal to 2ppm / °C in the range of 0°C to 200°C. In this way, if the difference in thermal expansion coefficient is small in a wide temperature range, the range of the temperature range in which the pressure sensor 1 can be used is also expanded. In addition, if silicon nitride is used as the ceramic, this condition can be met.

[0035] The semiconductor substrate 3 is made of silicon, and its thermal expansion coefficient is different from that of the ceramic material of the diaphragm 4, so the joined portion is deformed due to the bimetallic effect. When the thermal expansion coefficient of the ceramic material is greater than that of silicon, if the temperature rises, the diaphragm 4 formed of the ceramic material expands, and tensile strain is generated in the semiconductor substrate 3 made of silicon. At the same time, the surface of the diaphragm 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 coefficient. At this time, by optimizing the thickness of the semiconductor substrate 3, the thickness of the diaphragm 4, the area of ​​the joint 7, etc., it is possible to design so that the strain caused by the difference in thermal expansion coefficient is eliminated, and the temperature error can be made substantially zero. When the thermal expansion coefficient of the ceramic material is smaller than that of silicon, the relationship between expansion and compression is also opposite, and it is possible to design so that the strain caused by the difference in thermal expansion coefficient is eliminated in the same way.

[0036] In addition, a vibration type strain gauge for detecting changes in the natural frequency of the vibrator 8 is provided on the semiconductor substrate 3. The measurement factor (Gf) indicating the resolution of the vibration type strain gauge is approximately 1000, and the semiconductor substrate 3 shows a very 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.

[0037] In addition, regarding the pressure sensor 1, the diaphragm 4 is sometimes thickened or the outer diameter is reduced in order to achieve high pressure resistance. When such high pressure resistance is achieved, the deformation of the diaphragm 4 when the pressure of the measured body changes is reduced, but if the semiconductor substrate 3 shows high resolution, the pressure value can be detected even with a small deformation. That is, the pressure sensor 1 can achieve both high pressure resistance and high resolution.

[0038] In the semiconductor substrate 3 , a bonding portion 7 having a smaller area than the base 6 in a plan view projects from the base 6 toward the back surface 42 of the diaphragm 4 , and the semiconductor substrate 3 is bonded to the diaphragm 4 at a bonding surface 71 of the bonding portion 7 .

[0039] The semiconductor substrate 3 is manufactured by a dicing process of cutting a semiconductor wafer in which a plurality of semiconductor substrates 3 are arranged as one body using a cutting tool. Sometimes, chips and burrs are formed on the outer edge of the semiconductor substrate 3 that contacts the cutting tool. Sometimes, chips 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 cause poor bonding to the back surface 42.

[0040] On the other hand, regarding the pressure sensor 1 of the first embodiment, the periphery of the portion that will become the joint portion 7 can be removed by etching in advance in the process before the cutting process at the time of the semiconductor wafer. Regarding the removal based on etching, high-precision processing with almost no formation of chips and burrs can be achieved. If the periphery of the portion that will become the joint portion 7 is removed before the cutting process, the cutting tool does not contact the outer edge of the joint surface 71 in the cutting process, so chips and burrs are not formed on the outer edge of the joint surface 71.

[0041] Therefore, by forming the joining portion 7 to have a smaller area than the base portion 6 in a plan view, it is possible to prevent the occurrence of joining defects due to chips and burrs formed on the outer edge of the joining surface 71 .

[0042] In addition, the bonding portion 7 formed with high precision by etching reduces the variation among products. Thus, the variation among products of the resolution of the pressure sensor 1 can be reduced.

[0043] In addition, in order to achieve a high pressure resistance of the pressure sensor 1, the outer diameter of the diaphragm portion 4 is sometimes designed to be smaller. On the other hand, the semiconductor substrate 3 needs to have an area for carrying elements such as electrode pads and sensor elements for extracting electrical signals to achieve the target function. The portion where the elements are carried does not need to be joined to the diaphragm portion 4, and when not joined, the characteristics will not be deteriorated due to deformation of the electrode pads, which is preferred. In the present embodiment 1, the joint 7 is formed with an area required for joining with the back side 42 of the diaphragm portion 4, and the area of ​​the base 6 when viewed from above is larger than the joint 7, so that the mounting portion of the element can be ensured to form a pressure sensor 1 that can measure the pressure value with higher accuracy.

[0044] Figure 3 This is a diagram of a pressure sensor according to a first variant of the first embodiment as viewed from the semiconductor substrate side. Figure 3 As shown, the shape of the base 6 when viewed from above can be circular. Even if the shape of the base 6 is circular, it can be made larger than the area of ​​the bonding portion 7. Figure 1 and Figure 2Similarly to the example shown, it is possible to prevent the occurrence of defective joining due to chips and burrs, and to provide the pressure sensor 1 capable of measuring a pressure value with high accuracy.

[0045] Figure 4 This is a diagram of a pressure sensor according to a second variation of the first embodiment as viewed from the semiconductor substrate side. Figure 4 As shown, the shape of the joint portion 7 when viewed from above may be a polygon. Even if the shape of the joint portion 7 is a polygon, it can be made smaller than the area of ​​the base 6 to be compatible with the base 6. Figure 1 and Figure 2 Similarly to the example shown, it is possible to prevent the occurrence of defective joining due to chips and burrs, and further, to form the pressure sensor 1 capable of measuring a pressure value with high accuracy.

[0046] Figure 5 This is a cross-sectional view of a pressure sensor according to a third modified example of the first embodiment. Figure 6 Viewed from the semiconductor substrate side Figure 5 The pressure sensor is shown in Figure 1. Figure 5 and Figure 6 As shown, in the pressure sensor 1 according to the third modification, the pressure receiving surface 41 and the back surface 42 of the diaphragm 4 are not flat surfaces but are provided with steps so as to bulge toward the back surface 42. Thus, the pressure receiving surface 41 and the back surface 42 of the diaphragm 4 are not limited to flat surfaces.

[0047] Figure 7 This is a cross-sectional view of a pressure sensor according to a fourth modified example of the first embodiment. Figure 7 The cross-section shown is equivalent to Figure 2 The cross-sectional view cut by the dot-dash line is shown in FIG. Figure 7 As shown, the rim 5 can be smoothly connected to the pressure receiving surface 41 of the diaphragm 4 without any step. In the pressure sensor 1 according to the fourth modification, the overall shape of the pressure receiving body 2 is formed in a shape in which a recess is formed on the back surface 42 side of the portion where the diaphragm 4 is formed.

[0048] Figure 8 This is a cross-sectional view of a pressure sensor according to a fifth variation of the first embodiment. Figure 8 The cross-section shown is equivalent to Figure 2 The cross-sectional view cut by the dot-dash line is shown in FIG. Figure 8 As shown, the rim portion 5 is provided with a step difference on both sides of the pressure receiving surface 41 and the back surface 42 of the diaphragm portion 4 and connected. Regarding the pressure sensor 1 according to the fifth modification, the overall shape of the pressure receiving body 2 is formed in a shape in which recesses are 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.

[0049] Fig. 9This is a cross-sectional view of a pressure sensor according to a sixth variation of the first embodiment. Fig. 9 The cross-section shown is equivalent to Figure 2 The cross-sectional view cut by the dotted line is shown in FIG. Fig. 9 As shown in FIG. 1 , the relationship among the outer diameter X11 of the diaphragm 4, the outer diameter X12 of the rim 5, the side length Y11 of the base 6, and the outer diameter Y12 of the joint 7 is X12>Y11>X11>Y12. If no recess is formed on the back surface 42 side of the diaphragm 4, it is possible to Fig. 9 As shown, the side length Y11 of the base 6 is set larger than the outer diameter of the diaphragm 4. When the base 6 is circular, Y11 is the outer diameter, and when it is a polygon larger than or equal to a pentagon, Y11 is the outer diameter of the inscribed circle.

[0050] Fig.10 This is a cross-sectional view of a pressure sensor according to a seventh variation of the first embodiment. Fig.10 The cross-section shown is equivalent to Figure 2 The cross-sectional view cut by the dot-dash line is shown in FIG. Fig.10 As shown in FIG. 1 , the relationship among the outer diameter X21 of the diaphragm 4, the outer diameter X22 of the rim 5, the side length Y21 of the base 6, and the outer diameter Y22 of the joint 7 is X22>Y21>Y22>X11. If no recess is formed on the back surface 42 side of the diaphragm 4, it is possible to Fig.10 As shown in FIG. 1 , the outer diameter Y22 of the joint portion 7 is set larger than the outer diameter of the diaphragm portion 4. In the seventh modification, the outer peripheral portion as a part of the joint surface 71 contacts the rim portion 5. In addition, when the base 6 is circular, Y21 is the outer diameter, and when it is a polygon greater than or equal to a pentagon, Y21 is the outer diameter of the inscribed circle.

[0051] In addition, regarding Figures 1 to 10 In the pressure sensor 1 shown as an example, the back surface 42 and the bonding surface 71 may be bonded directly or through a metal film. Examples of metals used for the metal film include titanium, silver, and gold.

[0052] [other]

[0053] Several examples of combinations of disclosed technical features are described below.

[0054] (1) A pressure sensor comprising: a pressure-bearing body having a diaphragm portion and a rim portion, the diaphragm portion being deformed when subjected to pressure on a pressure-bearing surface, the rim portion being formed integrally with the outer periphery of the diaphragm portion and being formed thicker than the diaphragm portion; and a semiconductor substrate being bonded to the back side of the pressure-bearing surface and detecting the strain of the diaphragm portion, the pressure-bearing body being formed of ceramic, the semiconductor substrate having: a base portion being arranged opposite to the back side; and a bonding portion having a bonding surface protruding from the base portion toward the back side and bonded to the back side, at least one vibration-type strain gauge being provided on the semiconductor substrate, and an area of ​​the bonding portion being smaller than an area of ​​the base portion when viewed from a direction perpendicular to the back side.

[0055] (2) Based on the pressure sensor described in (1), the base and the bonding portion are formed of silicon, and the difference between the thermal expansion coefficient of the base and the bonding portion and the thermal expansion coefficient of the pressure-bearing body is less than or equal to 2 ppm / °C in the range of 0°C to 200°C.

[0056] (3) In the pressure sensor described in (1) or (2), the entirety of the bonding surface is in contact with the diaphragm portion.

[0057] (4) In the pressure sensor described in (1) or (2), a portion of the bonding surface is in contact with the rim portion.

[0058] (5) In the pressure sensor described in any one of (1) to (4), the bonding surface is bonded to the back surface by direct bonding or via a metal film.

[0059] (6) In the pressure sensor described in any one of (1) to (5), the pressure receiving surface side of the pressure receiving body is recessed in a region where the diaphragm portion is provided.

[0060] (7) In the pressure sensor described in any one of (1) to (5), the back surface side of the pressure-receiving body is recessed in a region where the diaphragm portion is provided.

[0061] (8) In the pressure sensor described in any one of (1) to (7), the base portion has a square shape when viewed from a direction perpendicular to the back surface.

[0062] (9) In the pressure sensor described in (8), the side length of the base portion is larger than the outer diameter of the diaphragm portion.

[0063] (10) In the pressure sensor described in any one of (1) to (7), the base portion has a circular shape when viewed from a direction perpendicular to the back surface.

[0064] (11) In the pressure sensor described in (10), an outer diameter of the base portion is larger than an outer diameter of the diaphragm portion.

[0065] (12) In the pressure sensor described in any one of (1) to (11), the bonding surface has a circular shape when viewed from a direction perpendicular to the back surface.

[0066] (13) In the pressure sensor described in any one of (1) to (11), the bonding surface has a polygonal shape when viewed from a direction perpendicular to the back surface.

[0067] Description of the label

[0068] 1. Pressure sensor

[0069] 2 Pressure body

[0070] 3 Semiconductor substrate

[0071] 4 Diaphragm

[0072] 5. Rim

[0073] 6 Base

[0074] 7 Joint

[0075] 8 Vibrator

[0076] 41 Pressure surface

[0077] 42 Back

[0078] 71 Joint surface

Claims

1. A pressure sensor, wherein: The pressure sensor has: A pressure-receiving body having a diaphragm portion and a rim portion, wherein the diaphragm portion is deformed by receiving pressure on a pressure-receiving surface, and the rim portion is integrally formed at an outer periphery of the diaphragm portion and is formed thicker than the diaphragm portion; as well as a semiconductor substrate bonded to the back surface of the pressure receiving surface to detect the strain of the diaphragm portion, The pressure-bearing body is formed of ceramics, The semiconductor substrate comprises: a base portion disposed opposite to the back surface; and a bonding portion having a bonding surface protruding from the base portion toward the back surface and bonding to the back surface, At least one vibration strain gauge is provided on the semiconductor substrate. When viewed from a direction perpendicular to the rear surface, the area of ​​the joining portion is smaller than the area of ​​the base portion.

2. The pressure sensor according to claim 1, wherein: The base and the joint are formed of silicon, The difference between the thermal expansion coefficients of the base portion and the joining portion and the thermal expansion coefficient of the pressure receiving body is less than or equal to 2 ppm / °C within a range of 0°C to 200°C.

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

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

5. The pressure sensor according to claim 1, wherein: The bonding surface is bonded to the back surface by direct bonding or via a metal film.

6. The pressure sensor according to claim 1, wherein: The pressure receiving surface side of the pressure receiving body is recessed 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. The pressure sensor according to claim 1, wherein: When viewed from a direction perpendicular to the back surface, the base has a square shape.

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

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

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

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

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

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