JP2006126127A - Capacitance type pressure sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-sensitivity capacitance type pressure sensor hardly influenced by an acceleration resulting from a centrifugal force or the like. <P>SOLUTION: This capacitance type pressure sensor 1 is equipped with a diaphragm 3 and a fixed electrode arranged oppositely to the diaphragm 3 through a gap. The sensor 1 is characterized by being provided with at least one or more linear beam parts 8a, 8b on the diaphragm 3. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a capacitive pressure sensor, and more particularly to a capacitive pressure sensor with high sensitivity and less error.

  Capacitance-type pressure sensors are small in size and simple in structure, and have recently become widespread in various fields. As an example, a capacitive pressure sensor has begun to be adopted as a means for monitoring the air pressure of a tire of an automobile.

11 and 12 show a conventional capacitive pressure sensor. As shown in FIGS. 11 and 12, the conventional capacitive pressure sensor 101 includes a diaphragm 103 formed by thinning a part of the Si substrate 102, and a fixed electrode 104 disposed so as to face the diaphragm 103. The fixed electrode 104 and the support substrate 105 that supports the Si substrate 102 are mainly configured. A gap 106 is provided between the diaphragm 103 and the fixed electrode 104, and the gap 106 serves as a dielectric to form a kind of electrostatic capacity.
In this capacitance type pressure sensor 101, the gap amount is changed by the bending of the diaphragm 103 in response to the change in the pressure of the fluid, and the change in the gap amount can be detected by the change in the capacitance so that the pressure can be detected. It has become.

  However, in the conventional capacitive pressure sensor shown in FIGS. 11 and 12, as shown by the one-dot chain line in FIG. 12, when the pressure is applied to the diaphragm 103, the diaphragm 103 itself elastically deforms. While the central portion of 103 is greatly bent, the amount of bending is reduced in the peripheral portion. For this reason, the total amount of deflection of the diaphragm 103 is averaged by the central portion and the peripheral portion, and as a result, the amount of deflection is reduced, and as a result, the change in capacitance is also reduced and the pressure detection sensitivity is lowered. There was a problem to do.

Therefore, Patent Document 1 below discloses a pressure sensor that improves the linearity of pressure sensitivity by providing a diaphragm with a frustum-shaped mesa portion.
JP 7-209121 A (paragraph 0002, FIG. 1)

  However, when the pressure sensor described in Patent Document 1 is used to measure the air pressure of the above-described automobile tire, the following problem occurs. That is, the pressure sensor of Patent Document 1 is provided with a mesa portion protruding from the diaphragm, and this mesa portion may be inclined with respect to the fixed electrode due to the centrifugal force accompanying the rotation of the tire. In this case, although the pressure has not changed, the change in the capacitance is caused by the inclination of the mesa portion, and there is a possibility that the pressure change is erroneously detected.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a capacitive pressure sensor that has high sensitivity and is less affected by acceleration due to centrifugal force or the like.

In order to achieve the above object, the present invention employs the following configuration.
The capacitance-type pressure sensor of the present invention includes a diaphragm and a fixed electrode disposed so as to be opposed to the diaphragm via a gap, and at least one linear beam portion is provided on the diaphragm. Is provided apart from the outer peripheral portion surrounding the diaphragm.

  According to the above configuration, since the partial elastic deformation of the central portion of the diaphragm is prevented by the beam portion and the entire diaphragm is displaced, the capacitance change due to the pressure change becomes large, and the capacitance type pressure sensor Can increase the sensitivity. Further, since the beam portion is relatively less susceptible to acceleration, there is no possibility of erroneously detecting a pressure change even when subjected to acceleration.

In the capacitive pressure sensor of the present invention, it is preferable that the beam portion is formed radially from the center of the diaphragm in plan view.
Moreover, in the capacitive pressure sensor of the present invention, it is preferable that the beam portion is formed so as to pass through the central portion of the diaphragm in plan view.
In the capacitive pressure sensor of the present invention, it is preferable that the beam portion is formed in a substantially cross shape in a plan view.

  With these configurations, the maximum displacement area of the diaphragm can be secured widely, and the sensitivity of the capacitive pressure sensor can be further increased.

  The capacitive pressure sensor according to the present invention is the capacitive pressure sensor described above, wherein the diaphragm is formed in a circular shape in plan view, and the width of the beam portion is 5% or more of the diameter of the diaphragm. The dimension is 15% or less, and the length of the beam part is 50% or more and 80% or less of the diameter of the diaphragm.

  According to said structure, the maximum displacement area at the time of the pressure application with respect to the whole area of a diaphragm can be 50% or more, and a sensitivity can be improved.

  Further, the capacitive pressure sensor of the present invention is the capacitive pressure sensor described above, wherein the thickness of the beam portion is thinner than the thickness of the outer peripheral portion surrounding the diaphragm. Features.

  With this configuration, the beam portion is less susceptible to acceleration, and the risk of erroneously detecting a pressure change is reduced.

  According to the capacitive pressure sensor of the present invention, pressure can be detected with high sensitivity, and pressure can be accurately detected by eliminating the influence of acceleration and the like.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 to 9 show an embodiment of the capacitive pressure sensor of the present invention. These drawings are for explaining the configuration of the capacitive pressure sensor, and each part shown in the figure is illustrated. The size, thickness, dimensions, and the like do not necessarily match the actual dimensional relationship of the capacitive pressure sensor.

[First Embodiment]
Hereinafter, a first embodiment will be described with reference to the drawings. FIG. 1 is a schematic plan view showing the configuration of the capacitive pressure sensor of the present embodiment, and FIG. 2 is a schematic cross-sectional view corresponding to the line AA ′ in FIG.

  A capacitive pressure sensor 1 shown in FIG. 1 and FIG. 2 includes a diaphragm 3 formed by thinning a part of a Si substrate 2, a fixed electrode 4 opposed to the diaphragm 3, a fixed electrode 4 and It is mainly composed of a support substrate 5 that supports the Si substrate 2. A gap 6 is provided between the diaphragm 3 and the fixed electrode 4, and this gap 6 serves as a dielectric to form a kind of electrostatic capacity. In this capacitive pressure sensor 1, the gap amount varies as the diaphragm 3 bends in response to a fluid pressure change, and the change in the gap amount can be detected by a change in the capacitance to detect a pressure change. It is like that.

  The support substrate 5 is made of glass or the like. The Si substrate 2 is cut from single crystal silicon. The Si substrate 2 and the support substrate 5 are joined by anodic bonding.

A first recess 7 a that partitions the gap 6 is provided on the fixed electrode 4 side of the diaphragm 3. As shown in FIG. 1, the first recess 7a is formed in a substantially circular shape in plan view. A fixed electrode 4 made of Au, Al, Cr, Pt or the like is disposed on the support substrate 5 so as to face the first recess 7a. The fixed electrode 4 also has a substantially circular shape in plan view corresponding to the shape of the first recess 7a. Around the first concave portion 7a, a joint portion 10 is provided so as to protrude toward the support substrate 3 side. The support substrate 5 and the Si substrate 2 are anodically bonded via the bonding portion 10.
A second recess 7 b is provided on the upper surface 3 a of the diaphragm 3 opposite to the fixed electrode 4. As shown in FIG. 1, the second recess 7b is formed in a rectangular shape in plan view. By providing the first concave portion 7 a and the second concave portion 7 b on both surfaces of the Si substrate 2, the thickness of the diaphragm 3 is formed thinner than the original thickness of the Si substrate 2.

A beam portion 8 is formed on the upper surface 3 a of the diaphragm 3. As shown in FIG. 1, the beam portion 8 is formed in a substantially cross shape in plan view.
Further, an outer peripheral portion 9 that partitions the second concave portion 7 b is formed on the outer periphery of the Si substrate 2. The outer peripheral portion 9 is formed thicker than the beam portion 8 in the second recess 7b. The beam portion 8 is provided so as to be spaced apart from the outer peripheral portion 9 at a predetermined interval.

  The beam portion 8 is formed in a substantially cross shape in plan view when the linear first beam portion 8a and the second beam portion 8b intersect each other at an angle of 90 ° in the center portion of the diaphragm 3 in plan view. ing. The first beam portion 8a is formed in the vertical direction in FIG. 1, and the second beam portion 8b is formed in the horizontal direction in FIG. Each of the beam portions 8 a and 8 b is formed so as to pass through the central portion O in plan view of the diaphragm 3. With this configuration, the beam portion 8 is formed in a radial shape when viewed from the central portion O in the plan view of the diaphragm 3.

The first beam portion 8a is inclined portion 8a which connects the upper surface portion 8a ₁ projecting from the upper surface 3a of the diaphragm 3, and the upper surface 3a of the upper surface portion 8a ₁ is formed around the upper surface portion 8a ₁ and the diaphragm ₂ . Similarly, the second beam portion 8b includes a top portion 8b _1, and a sloped portion 8b ₂ which connects the upper surface 3a of the upper surface portion 8b top portion 8b ₁ is formed around the ₁ and the diaphragm . Further, the beam portions 8a and 8b are formed at substantially the same height, whereby the upper surface portions 8a ₁ and 8b ₁ form the same surface at substantially the center of the diaphragm.

The Si substrate 2 is cut out from a Si single crystal, and the diaphragm 3 and the beam portion 8 are formed by anisotropically etching the Si single crystal. The upper surface portions 8a ₁ and 8b _{1 of} the first and second beam portions 8a and 8b are Si (100) surfaces, and the inclined portions 8a ₂ and 8b _{2 of} the first and second beam portions 8a and 8b are Si. (111) plane. The upper surface 3a of the diaphragm 3 is also a (100) surface of Si. Accordingly, the inclination angle of the inclined portion _8a 2, 8b ₂ with respect to the upper surface portion _8a 1, 8b ₁ and the upper surface 3a is set to 54.7 °.

The thickness t ₁ of the diaphragm 3 excluding the beam portion 8 is set in a range of 10 to 60 μm. The thickness _{t 2} of the beam portion 8 is set in a range of 50 to 100 [mu] m. Thus, the thickness _t 3 of the diaphragm 3 including the beam portion _{8 (= t 1 + t 2} ) is set in a range of 60～160Myuemu.

Next, as shown in FIG. 1, the diameter of the diaphragm 3 and _{d 1,} the first, second beam portions 8a, when 8b width of the _w 1, _{w 2, respectively,} w 1, _{w 2,} respectively, 15% 5% or more of the diameter _{d 1} of the diaphragm 3 are the following dimensions. In addition, when the lengths of the first and second beam portions 8a and 8b are m ₁ and m ₂ , respectively, m ₁ and m ₂ have dimensions of 50% or more and 80% or less of the diameter d ₁ of the diaphragm 3 respectively. Has been. With this configuration, the first and second beam portions 8 a and 8 b are prevented from protruding outside the diaphragm 3. Here, the diameter d ₁ of the diaphragm 3 is defined as the distance between the first recess 7 a and the joint 10 through the center of the diaphragm 3 from an arbitrary point on the boundary line between the first recess 7 a and the joint 10. This is the length of a straight line connecting up to another point on the boundary line. The widths w ₁ and w ₂ and the lengths m ₁ and m ₂ of the first and second beam portions 8a and 8b are dimensions including the inclined portions 8a ₂ and 8b ₂ .

Next, the outer peripheral portion 9 of the Si substrate 2, an upper surface portion 9a ₁ projecting from the upper surface 3a of the diaphragm 3, and a top portion 9a ₁ and the upper surface 3a is formed between the upper surface portion 9a ₁ and the upper surface 3a and a inclined portion 9a ₂ which connects. Upper surface portion 9a ₁ is formed to protrude from the upper surface portion _8a 1, 8b ₁ of the beam portion 8. Thereby, the thickness of the beam portion 8 is formed thinner than the thickness of the outer peripheral portion 9. The upper surface portion 9a ₁ of the outer peripheral portion is the (100) plane of Si, the inclined portion 9a ₂ is a (111) plane of Si. Accordingly, the inclination angle of the inclined portion 9a ₂ with respect to the upper surface portion 9a _1, and is set to 54.7 °.

  Next, the operation of the capacitive pressure sensor 1 will be described. The diaphragm 3 is disposed on the fixed electrode 4 of the support substrate 5 through the gap 6 with the joint 10 as a fixed end. The diaphragm 3 is in contact with the fluid to be measured on the second recess 7b side. When the pressure of the fluid to be measured increases, the diaphragm 3 is bent toward the fixed electrode 4 and the gap 6 is reduced. At this time, since the periphery of the diaphragm 3 is fixed by the joint portion 10, the central portion is deformed more greatly than the peripheral portion of the diaphragm and tends to bend toward the fixed electrode. However, the diaphragm 3 is provided with a substantially cross-shaped beam portion 8, and the strength of the central portion of the diaphragm 3 is reinforced by the beam portion 8, so that only the central portion of the diaphragm 3 is not greatly bent. The almost entire diaphragm is displaced toward the fixed electrode 4 side. As a result, the amount of change in the gap 6 is larger than that in the case where the beam portion 8 is not provided, and the change in capacitance is increased, thereby improving the pressure sensitivity.

Further, since the first and second beam portions 8a and 8b always pass through the central portion O of the diaphragm 3 and extend to the peripheral portion, only the central portion O of the diaphragm does not bend, and almost the entire diaphragm is fixed. Displacement to the electrode 4 side improves pressure sensitivity.
Furthermore, since the beam portion 8 is formed in a substantially cross shape in plan view, the strength of a wide portion from the center portion O to the peripheral portion of the diaphragm 3 can be reinforced. As a result, a wide displacement area of the diaphragm 3 that is displaced when subjected to pressure can be secured widely, whereby the change in capacitance can be increased and pressure sensitivity can be improved.
In particular, by setting the dimensions w ₁ , w ₂ , m _1, and m ₂ of the beam portion 8 with respect to the diaphragm diameter d ₁ within the above range, the displacement area when applying pressure to the entire area of the diaphragm 3 is 50% or more. The sensitivity can be further improved.

  In addition, since the thickness of the beam portion 8 is set lower than the thickness of the peripheral portion 9, the volume of the entire beam portion 8 becomes small and is hardly affected by acceleration or the like. Thereby, the influence of acceleration can be eliminated as much as possible, and malfunction of the pressure sensor can be prevented.

Next, a manufacturing method of the capacitive pressure sensor 1 of the present embodiment will be described.
First, as shown in FIG. 3A, a single crystal Si substrate 2 is prepared. The upper surface 2a of the Si substrate 2 is a (100) surface of Si. Then, as shown in FIG. 3A, the first recess 7 a is formed by wet etching or dry etching on the lower surface 2 b side of the Si substrate 2. The first recess 7a becomes a gap 6 when the Si substrate 2 and the support substrate 5 are joined. The depth _{d 3} of the first recess 7a is preferably about 0.5 to 2.0 [mu] m. Depth d ₃ is in contact with the diaphragm and the fixed electrode at the time of bonding between less than 0.5μm and the supporting substrate gap is too narrow, there is a possibility that sticking undesirably. The change in the gap to pressure changes when the depth d ₃ exceeds 2.0μm is reduced, undesirable sensitivity decreases.

Next, as shown in FIG. 3B, the second recess 7b is formed by wet etching with a mask (not shown) overlapped on the upper surface 2a side of the Si substrate 2. As an etching solution, it is preferable to use a potassium hydroxide aqueous solution, a 3 methylammonium hydroxide (TMAH) aqueous solution, an ethylenediamine pyrocatechol (EDP) aqueous solution, or the like. The Si substrate 2 is anisotropically etched by performing etching using these etching solutions. The bottom surface 7b _{1 of the} formed second recess 7b is a (100) surface of Si, and the inclined portion 7b ₂ surrounding the bottom surface 7b ₁ is a (111) surface of Si. The inclined portion 7b ₂ becomes the inclined portion 9a ₂ of the outer peripheral portion 9 later. The depth _{d 4} of the second recess is preferably about 50 to 200 [mu] m.

Next, as shown in FIG. 3C, by wet etching in a laminated state not shown in the mask on the bottom portion 7b ₁ of the second recess 7b, first, second beam portions 8a, viewed substantially cross consisting 8b A shaped beam portion 8 is formed. It is preferable to use a potassium hydroxide aqueous solution, a TMAH aqueous solution, or an EDP aqueous solution as the etching solution. The Si substrate 2 is anisotropically etched by performing etching using these etching solutions. The formed beam portion 8 has upper surface portions 8a ₁ and 8b _{1 which} are Si (100) surfaces, and the inclined portions 8a ₂ and 8b ₂ which surround these upper surface portions 8a ₁ and 8b ₁ are Si (111) surfaces and Become. The thickness _{t 2} of the beam portion 8 is preferably about 50 to 100 [mu] m. The thickness _{t 1} of the diaphragm surrounding the beam portion 8 is preferably about 10 to 60 [mu] m.

  Then, after the fixed electrode 4 is formed on the support substrate 5 and the etched Si substrate 2 is overlaid on the support substrate 5, the Si substrate 2 and the support substrate 5 are anodic bonded in a vacuum. In this way, a capacitive pressure sensor 1 as shown in FIGS. 1 and 2 is obtained.

[Second Embodiment]
Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a schematic plan view showing the configuration of the capacitive pressure sensor 21 according to the second embodiment of the present invention, and FIG. 5 is a schematic cross-sectional view corresponding to the line BB ′ in FIG. is there. Of the components shown in FIGS. 4 and 5, the same components as those of the capacitive pressure sensor of the first embodiment shown in FIGS. The description is omitted.

The difference between the present embodiment and the first embodiment is that a single linear beam portion 28 is provided instead of the beam portion having a substantially cross shape in plan view.
That is, as shown in FIGS. 4 and 5, the beam portion 28 is formed in a substantially I shape in plan view. The beam portion 28 is formed so as to pass through the central portion O of the diaphragm 3 in plan view. With this configuration, the beam portion 28 is formed radially and symmetrically as viewed from the center of the diaphragm 3 in plan view. The beam portion 28 is provided so as to be spaced apart from the outer peripheral portion 9 at a predetermined interval.

Further, the beam portion 28 includes a top surface portion 28a ₁ projecting from the upper surface 3a of the diaphragm 3, an inclined portion 28a ₂ which connects the upper surface 3a of the formed around the upper surface portion 28a ₁ and the upper surface portion 28a ₁ and the diaphragm It is composed of
The Si substrate 2 is cut from a Si single crystal, and the diaphragm 3 and the beam portion 28 are formed by anisotropically etching the Si single crystal. Thus the upper surface portion 28a ₁ of the beam portion 28 is the (100) plane of Si, the inclined portion 28a ₂ there is a (111) plane of Si. The upper surface 3a of the diaphragm 3 is also a (100) surface of Si. Thus, the inclination angle of the inclined portion 28a ₂ with respect to the upper surface portion 28a ₁ and the upper surface 3a is set to 54.7 °.

The thickness t ₁ of the diaphragm 3 excluding the beam portion 28 is set in a range of ₁₀ to 60 μm, the thickness t ₂ of the beam portion 28 is set in a range of 50 to ₁₀₀ μm, and the thickness of the diaphragm 3 including the beam portion 28 is set. t ₃ (= t ₁ + t ₂ ) is set in a range of 60 to 160 μm.

Next, as shown in FIG. 4, when the diameter of the diaphragm 3 is d ₁ and the width of the beam portion 28 is w ₃ , w ₃ has a dimension of 5% to 15% of the diameter d ₁ . . Further, when the length of the beam portion 28 is m ₃ , m ₃ has a dimension of 50% to 80% of the diameter d ₁ . With this configuration, the beam portion 28 is prevented from protruding outside the diaphragm 3. The width w ₃ and the length m ₃ of the beam portion 28 are dimensions including the inclined portion 28a ₂ .

  According to the capacitive pressure sensor 21 of the present embodiment, the same effect as the capacitive pressure sensor of the first embodiment can be obtained.

[Third Embodiment]
Hereinafter, a third embodiment of the present invention will be described with reference to the drawings. FIG. 6 is a schematic plan view showing a configuration of a capacitive pressure sensor 31 according to the third embodiment of the present invention, and FIG. 7 is a schematic cross-sectional view corresponding to the line CC ′ in FIG. is there. Of the components shown in FIGS. 6 and 7, the same reference numerals are used for the same components as those of the capacitive pressure sensor 1 of the first embodiment shown in FIGS. The description is omitted.

The difference between this embodiment and the first embodiment is that, in addition to the beam portion having a substantially cross shape in plan view, a third beam portion surrounding the beam portion in the cross shape is formed, thereby forming a lattice shape in plan view. This is the point where the beam portion 38 is provided.
That is, as shown in FIGS. 6 and 7, the beam portion 38 includes linear first beam portions 38 a and second beam portions 38 b that intersect each other at an angle of 90 ° in the center portion of the diaphragm 3 in plan view. And a third beam portion 38c surrounding the first and second beam portions 38a and 38b. The third beam portion 38c is in contact with the first and second beam portions 38a and 38b at an angle of 90 °. With this configuration, the beam portion 38 is formed radially and symmetrically as viewed from the central portion O in the plan view of the diaphragm 3. Further, the beam portions 38 a to 38 c are provided with a certain distance from the outer peripheral portion 9.

  According to the capacitive pressure sensor 31 of the present embodiment, the same effect as that of the capacitive pressure sensor 1 of the first embodiment can be obtained.

[Fourth Embodiment]
Hereinafter, a fourth embodiment of the present invention will be described with reference to the drawings. FIG. 8 is a schematic plan view showing the configuration of a capacitive pressure sensor 51 according to the fifth embodiment of the present invention. FIG. 9 is a schematic cross-sectional view corresponding to the line EE ′ in FIG. is there. Of the components shown in FIGS. 8 and 9, the same components as those of the capacitive pressure sensor 1 of the first embodiment shown in FIGS. The description is omitted.

The capacitive pressure sensor 51 of the present embodiment is common to the first embodiment in that a beam portion 58 having a substantially cross shape in plan view is formed, while the height of the beam portion 58 is set to the outer peripheral portion 59 of the Si substrate. The point which made it the same as the height of is different.
That is, as shown in FIGS. 8 and 9, in the beam portion 58 of the present embodiment, the linear first beam portion 58 a and the second beam portion 58 b are 90 to each other at the central portion O in the plan view of the diaphragm 3. By intersecting at an angle of °, it is formed in a substantially cross shape in plan view. Each of the beam portions 58a and 58b is formed so as to pass through the central portion O of the diaphragm 3 in plan view. With this configuration, the beam portion 58 is formed symmetrically when viewed from the center of the diaphragm 3 in plan view. Further, the first and second beam portions 58 a and 58 b do not protrude outside the diaphragm 3. The dimensional relationship between the diameter of the diaphragm 3 and the width and length of the first and second beam portions 58a and 58b is the same as that in the first embodiment. Further, the beam portions 58a and 58b are provided with a certain distance from the outer peripheral portion 59.

The first beam portion 58a has a top surface portion 58a ₁ projecting from the upper surface 3a of the diaphragm 3, the side wall portion 58a which is formed around the upper surface portion 58a ₁ by connecting the upper surface 3a of the upper surface portion 58a ₁ and the diaphragm ₂ . Similarly, the second beam portion 58b includes an upper surface portion 58b _1, and a side wall portion 58b ₂ which connects the upper surface 3a of the upper surface portion 58b upper surface portion 58b ₁ is formed around the ₁ and the diaphragm . Further, the beam portions 58a and 58b are formed at substantially the same height, so that the upper surface portions 58a ₁ and 58b ₁ form the same surface at substantially the center of the diaphragm.

The Si substrate 2 is cut out from the Si single crystal, and the diaphragm 3 and the beam portion 58 are formed by dry etching the Si single crystal. Thereby, the inclination angle of the side wall portions 58a ₂ and 58b ₂ with respect to the upper surface portions 58a ₁ and 58b ₁ and the upper surface 3a is set to 90 °.

The thickness t ₄ of the diaphragm 3 excluding the beam portion 58 is set in a range of 10 to 60 μm. The thickness _{t 5} of the beam part 8 is set in a range of 190～500Myuemu. Thus, the thickness _t 6 of the diaphragm 3 including the beam portion _{8 (= t 4 + t 5} ) is set in a range of 200～550Myuemu.

Next, the outer peripheral portion 59 of the Si substrate 2, an upper surface portion 59a ₁ projecting from the upper surface 3a of the diaphragm 3, an upper surface portion 59a ₁ and the upper surface 3a is formed between the upper surface portion 59a ₁ and the upper surface 3a and a connecting side wall portion 59a ₂ Prefecture. The upper surface portion 59a ₁ is formed at substantially the same height as the upper surface portion _58a 1, 58b ₁ of the beam portion 58. Thereby, the thickness of the beam part 58 is made the same as the thickness of the outer peripheral part 59. Further, the inclination angle of the side wall 59a ₂ with respect to the upper surface portion 59a _1, and is set to 90 °.

In addition, the manufacturing method of the electrostatic capacitance type pressure sensor 51 of this embodiment is as follows. First, a mask is placed on the upper surface of the Si substrate 2 and then dry etching is performed to form a beam portion 58 having a substantially cross shape in plan view. At this time, continued dry etching to a thickness _{t 4} of the diaphragm is in the range of 10 m to 50 m. When the etching is completed, the etched Si substrate is anodically bonded to the support substrate 5 in a vacuum. In this way, the capacitive pressure sensor 51 of the present embodiment is obtained.

According to the capacitive pressure sensor 51 of the present embodiment, the same effect as the capacitive pressure sensor 1 of the first embodiment can be obtained.
Furthermore, according to the capacitive pressure sensor 51 of this embodiment, since the Si substrate 2 is dry-etched to form the beam portion 58, an inclined portion is formed in the beam portion as in the first to fourth embodiments. Thus, the beam portion can be reduced, and the capacitance type pressure sensor 51 can be downsized.

The gap thickness is 0.5 μm, the diaphragm diameter d ₁ is 1000 μm, the diaphragm thickness t ₁ is 50 μm, the beam portion thickness t ₂ is 50 μm, and the diaphragm thickness t ₃ including the beam portion is 100 μm, The widths w ₁ and w ₂ of the first and second beam portions with respect to the diameter d ₁ are set to 10%, and the lengths m ₁ and m ₂ of the first and second beam portions are set to 70%. The sensor of Example 1 having the same configuration as the capacitance type pressure sensor of the first embodiment shown in FIG.

By setting the gap thickness to 0.7 μm, the diaphragm diameter d ₁ to 1000 μm, and the diaphragm thickness t ₁ to 50 μm, the configuration is the same as that of the conventional capacitive pressure sensor shown in FIGS. The sensor of Comparative Example 1 was manufactured.

Next, a capacitive pressure sensor of Comparative Example 2 as shown in FIGS. 13 and 14 was manufactured. The capacitive pressure sensor shown in FIG. 13 and FIG. 14 is formed by forming an annular beam 68 on the diaphragm 3. The gap thickness is 0.5 μm, the diaphragm diameter d ₁ is 1000 μm, the diaphragm thickness t ₇ is 50 μm, the beam thickness t ₈ is 100 μm, and the diaphragm thickness t ₉ including the beam 68 is The outer diameter of the annular beam portion 68 was 500 μm, and the width of the beam portion 68 was 50 μm.

For the capacitance type pressure sensors of Example 1 and Comparative Examples 1 and 2, the change in capacitance when the pressure was increased to 0 to 500 kPa was investigated. FIG. 10 shows the relationship between pressure and capacitance.
As shown in FIG. 10, it can be seen that the capacitance type pressure sensor of Example 1 has a larger amount of change in capacitance with respect to pressure change than Comparative Examples 1 and 2. On the other hand, it can be seen that the sensor of Comparative Example 1 has a small capacitance itself at 0 kPa, and further, the amount of change in the capacitance with respect to the pressure change is smaller than that in Example 1. This is presumably because the pressure sensor of Example 1 is provided with a cross-shaped beam portion, so that the area of the displacement portion of the diaphragm when pressure is applied is increased, and the change in capacitance is increased. .
Next, as shown in FIG. 10, the capacitance type pressure sensor of Comparative Example 2 is substantially the same in capacitance at 0 to 100 kPa as in Example 1, but the capacitance exceeds 100 kPa. It can be seen that the amount of change is smaller than Example 1. This is because the shape of the beam portion of Comparative Example 2 is annular, so that the beam portion is not formed at the center portion of the diaphragm, and the diaphragm cannot be reinforced by the beam portion. This is considered to be because the amount of deflection only at the central portion is increased, the area of the displaced portion of the diaphragm when pressure is applied is reduced, and the change in capacitance remains small.

  The technical scope of the present invention is not limited to the above embodiment. For example, in the fourth embodiment, the shape of the beam portion is not limited to the cross shape, but may be linear or radial.

FIG. 1 is a schematic plan view showing the configuration of a capacitive pressure sensor according to a first embodiment of the present invention. FIG. 2 is a schematic cross-sectional view corresponding to the line A-A ′ of FIG. 1. FIG. 3 is a process diagram for explaining a method of manufacturing the capacitive pressure sensor according to the first embodiment of the present invention. FIG. 4 is a schematic plan view showing the configuration of the capacitive pressure sensor according to the second embodiment of the present invention. FIG. 5 is a schematic cross-sectional view corresponding to the line B-B ′ of FIG. 4. FIG. 6 is a schematic plan view showing the configuration of a capacitive pressure sensor according to a third embodiment of the present invention. FIG. 7 is a schematic cross-sectional view corresponding to the line C-C ′ of FIG. 6. FIG. 8 is a schematic plan view showing a configuration of a capacitive pressure sensor according to a fourth embodiment of the present invention. FIG. 9 is a schematic cross-sectional view corresponding to the line E-E ′ of FIG. 8. FIG. 10 is a graph showing the relationship between the pressure and capacitance of the capacitive pressure sensors of Example 1 and Comparative Examples 1 and 2. FIG. 11 is a schematic plan view showing the configuration of a conventional capacitance type pressure sensor. 12 is a schematic cross-sectional view corresponding to the line F-F ′ in FIG. 11. FIG. 13 is a schematic plan view showing the configuration of a capacitive pressure sensor of Comparative Example 2. 14 is a schematic cross-sectional view corresponding to the line G-G ′ of FIG. 13.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Capacitance type pressure sensor, 3 ... Diaphragm, 4 ... Fixed electrode, 6 ... Gap, 8a, 8b ... Beam part, 9 ... Outer peripheral part

Claims (6)

  A diaphragm and a fixed electrode disposed opposite to each other through a gap are provided, and at least one or more linear beam portions are separated from an outer peripheral portion surrounding the diaphragm on the diaphragm. A capacitance-type pressure sensor characterized by being provided.   The capacitive pressure sensor according to claim 1, wherein the beam portion is formed radially from the center of the diaphragm in plan view.   The capacitive pressure sensor according to claim 1 or 2, wherein the beam portion is formed so as to pass through a central portion of the diaphragm in plan view.   4. The capacitive pressure sensor according to claim 1, wherein the beam portion is formed in a substantially cross shape in a plan view.   The diaphragm is formed in a circular shape in plan view, the width of the beam portion is set to a dimension of 5% to 15% of the diameter of the diaphragm, and the length of the beam portion is 50% to 80% of the diameter of the diaphragm. 5. The capacitance type pressure sensor according to claim 1, wherein the capacitance type pressure sensor has the following dimensions. 6. The capacitive pressure sensor according to claim 1, wherein a thickness of the beam portion is formed thinner than a thickness of the outer peripheral portion surrounding the diaphragm.

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