Capacitance type pressure sensor

Abstract

To prevent deposition on a diaphragm while simplifying a structure of a baffle.SOLUTION: A capacitance type pressure sensor includes a housing 7 that forms a measurement chamber S so as to surround a pressure receiving surface 2a of a diaphragm 2 and has a gas introduction port 7a that introduces a gas to the measurement chamber S formed therein, and a baffle member 8 provided in the measurement chamber S. The baffle member 8 includes an opposite surface part 81 opposite to the gas introduction port 7a, and a surrounding surface part 82 that is provided on a side of the gas introduction port 7a of the opposite surface part 81 and surrounds the periphery of the gas introduction port 7a. The surrounding surface part 82 has a flowing part 83 that allows a gas introduced from the gas introduction port 7a to flow from an end on the side of the gas introduction port to a side of the diaphragm 2.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a capacitive pressure sensor. [Background technology]

[0002] A capacitance type pressure sensor measures pressure by detecting a change in capacitance between a diaphragm that is displaced by pressure and a fixed electrode.

[0003] This capacitance type pressure sensor can be used, for example, to measure the pressure of gas during a semiconductor manufacturing process. Here, gases used in semiconductor manufacturing processes are often highly reactive and have high temperatures. If the temperature difference between the gas and the diaphragm during the semiconductor manufacturing process is large, gas components and decomposed gas components will accumulate on the diaphragm, adversely affecting the sensor output.

[0004] For this reason, a conventional method has been proposed in which a baffle is disposed between the diaphragm and a gas inlet of the housing in which the diaphragm is disposed.

[0005] Specifically, the baffle shown in Patent Document 1 and Patent Document 2 have been considered. The baffle in Patent Document 1 has a baffle orifice formed between an inner baffle structure and an outer baffle structure. This baffle is configured so that the inflowing gas hits the inner baffle structure and the outer baffle structure and passes through the baffle orifice. The baffle in Patent Document 2 is flat and configured so that the gas hits the center of the plate surface, is detouring, and passes through gaps formed around the periphery.

[0006] However, none of the above baffles can fully secure the path for the inflowing gas, and therefore cannot fully exert the effect of reducing the amount of deposition on the diaphragm. It is also possible to make the baffle into a complex flow path such as a labyrinth shape, but this may cause clogging due to deposition, resulting in poor responsiveness. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Special Publication No. 2023-525634 Summary of the Invention [Problem to be solved by the invention]

[0008] Therefore, the present invention has been made to solve the above-mentioned problems, and an object of the present invention is to prevent deposition on the diaphragm while simplifying the baffle structure. [Means for solving the problem]

[0009] That is, the capacitance type pressure sensor of the present invention is a capacitance type pressure sensor that measures pressure by detecting changes in capacitance between a diaphragm that is displaced by pressure and a fixed electrode, and is characterized in that it comprises a housing that surrounds the pressure-receiving surface of the diaphragm to form a measurement chamber and has a gas inlet for introducing gas into the measurement chamber, and a baffle member provided in the measurement chamber, the baffle member having an opposing surface portion that faces the gas inlet and a surrounding surface portion that is provided on the gas inlet side of the opposing surface portion and surrounds the periphery of the gas inlet, and the surrounding surface portion has a flow portion that allows gas introduced from the gas inlet to flow from the end on the gas inlet side to the diaphragm side.

[0010] In such a capacitance type pressure sensor, the gas introduced from the gas inlet hits the opposing surface and reverses its direction of travel, and flows from the flow section formed at the end of the surrounding surface on the gas inlet side to the diaphragm side. As a result, the path of the introduced gas is sufficiently secured, and gas components or decomposed gas components can be deposited mainly on the opposing surface and the surrounding surface, thereby reducing deposition on the diaphragm. In addition, the baffle member is a bottomed tubular member consisting of the opposing surface and the surrounding surface, which simplifies the baffle structure and makes it extremely unlikely that the responsiveness will deteriorate due to clogging with deposits, etc. Furthermore, since the baffle member is a bottomed tubular member, it is possible to accumulate more deposits.

[0011] As a specific embodiment of the flow passage portion, it is preferable that a plurality of the flow passage portions are provided in the circumferential direction of the surrounding surface portion. With this configuration, gas can be made to flow toward the diaphragm from multiple flow sections, improving the responsiveness of pressure measurement. Also, by providing multiple flow sections, the size of each flow section can be reduced, and the gas flow path can be made complex, improving the deposition effect on the baffle member.

[0012] The baffle member has a joint protrusion for joining to an inner surface of the housing, and the joint protrusion is desirably provided to correspond to the gas flow section when viewed from the gas inlet. Here, a surface of the joint protrusion facing the gas inlet serves as a flow change surface for changing the flow of gas flowing from the gas flow section to the diaphragm side. With this configuration, the gas flowing from the flow passage to the diaphragm side hits the joint protrusion, and the gas components and decomposed gas components can be deposited on the joint protrusion, which also reduces deposition on the diaphragm.

[0013] It is preferable that the housing has a flat surface portion on which the gas inlet is formed, and an end portion of the surrounding surface portion on the gas inlet side is provided in contact with the flat surface portion. With this configuration, the introduced gas flows through the flow passage without fail after hitting the opposing surface portion and changing its flow direction, thereby improving the deposition effect at the baffle member.

[0014] It is desirable that the housing has an inward protruding portion that protrudes inward beyond the baffle member on the opposite side of the baffle member from the gas inlet port. With this configuration, gas that flows through the flow section of the baffle member toward the diaphragm hits the inner protrusion, and the gas components and decomposed gas components can be deposited on the inner protrusion, which also reduces deposition on the diaphragm.

[0015] Moreover, it is preferable that the capacitance type pressure sensor of the present invention further comprises a baffle plate provided separately from the baffle member and interposed between the baffle member and the gas inlet. With this configuration, gas components and decomposed gas components can be deposited not only on the baffle member but also on the baffle plate, which can further reduce deposition on the diaphragm.

[0016] As a specific embodiment of the baffle plate, it is preferable that the baffle plate has a plurality of slits formed therein.

[0017] In order to complicate the path along which the gas flows passing through the slits in the baffle plate, it is desirable that the plurality of slits be formed at positions different from the flow passage portions in the circumferential direction. Effect of the Invention

[0018] Thus, according to the present invention, it is possible to prevent deposition on the diaphragm while simplifying the baffle structure. [Brief description of the drawings]

[0019] [Figure 1]1 is a cross-sectional view showing a schematic configuration of a capacitance type pressure sensor according to an embodiment of the present invention. [Diagram 2] FIG. 4 is a partially enlarged cross-sectional view of the baffle member of the embodiment. [Diagram 3] FIG. 2A is an upper perspective view of a baffle member according to the embodiment, and FIG. [Figure 4] FIG. 4 is a partially enlarged cross-sectional view showing a schematic diagram of a gas flow in the embodiment. [Diagram 5] FIG. 11 is a cross-sectional view showing a schematic configuration of a capacitive pressure sensor according to a modified embodiment. [Figure 6] FIG. 13 is a top perspective view of a baffle plate according to a modified embodiment. [Figure 7] FIG. 11 is a cross-sectional view showing a schematic configuration of a capacitive pressure sensor according to a modified embodiment. [Figure 8] 10 is a cross-sectional view showing the positional relationship between the slits of the baffle plate and the flow passages of the baffle member in a modified embodiment. FIG. [Figure 9] FIG. 11 is a cross-sectional view showing a schematic configuration of a capacitive pressure sensor according to a modified embodiment. [Figure 10] FIG. 13 is a plan view of a baffle member integrated with a housing in an alternative embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a capacitive pressure sensor according to the present invention will be described below with reference to the drawings. In addition, in any of the drawings shown below, for the purpose of easy understanding, some parts are omitted or exaggerated in schematic form as appropriate. The same components are denoted by the same reference numerals and the description thereof is omitted as appropriate.

[0021] <Basic configuration of the capacitance type pressure sensor 100> The capacitance type pressure sensor 100 according to this embodiment measures pressure by detecting a change in capacitance between a diaphragm 2 that is displaced by pressure and a fixed electrode 3.

[0022] The capacitance type pressure sensor 100 is used, for example, in a semiconductor manufacturing process to measure the pressure of gas during the semiconductor manufacturing process. Note that the capacitance type pressure sensor 100 can be used not only in the semiconductor manufacturing process but also in other processes.

[0023] Specifically, as shown in FIG. 1, the capacitance type pressure sensor 100 has a diaphragm 2 having a pressure-receiving surface 2a that receives gas pressure, a fixed electrode 3 arranged to form a gap with a surface 2b (hereinafter, back surface 2b) opposite the pressure-receiving surface 2a of the diaphragm 2, and a support 4 that supports the diaphragm 2 and the fixed electrode 3.

[0024] The diaphragm 2 is a metal thin plate that is elastically deformed by minute pressure changes received by the pressure receiving surface 2a and has excellent corrosion resistance and heat resistance. The diaphragm 2 of this embodiment can be formed from a Ni-Co alloy containing nickel and cobalt as main components and tungsten, molybdenum, titanium, chromium, etc. The diaphragm 2 may also be formed from a Ni alloy containing nickel as main component and iron, chromium, niobium, etc., or may be formed from stainless steel. The diaphragm 2 has a disk shape in its natural state, and its thickness can be, for example, 5 μm or more and 200 μm or less in order to improve sensitivity to gas pressure changes.

[0025] The fixed electrode 3 constitutes a capacitor together with the diaphragm 2. The fixed electrode 3 is provided such that its tip surface 3a faces the back surface 2b of the diaphragm 2 with a predetermined gap formed therebetween. A signal output section 5 such as a lead wire for detecting a change in capacitance is connected to the upper end section of the fixed electrode 3 (the end section opposite the diaphragm 2). This signal output section 5 is connected to an arithmetic circuit (not shown) that converts the amount of change in capacitance into a pressure signal and outputs it.

[0026] The support 4 supports the diaphragm 2 so that a predetermined gap is formed between the rear surface 2b of the diaphragm 2 and the tip surface 3a of the fixed electrode 3. In this embodiment, the support 4 has a cylindrical tip 4a, to which the peripheral edge of the rear surface 2b of the diaphragm 2 is joined. A fixing portion 4b for fixing the fixed electrode 3 is provided inside the support 4, and the fixed electrode 3 is fixed to the fixing portion 4b. In addition, a getter material 6 made of a material that adsorbs excess gas and maintains the degree of vacuum is provided inside the support 4.

[0027] As shown in FIG. 1, the capacitance type pressure sensor 100 of this embodiment is provided with a housing 7 that surrounds the pressure receiving surface 2a of the diaphragm 2 to form a measurement chamber S and has a gas inlet port 7a for introducing gas into the measurement chamber S, and a baffle member 8 that is provided in the measurement chamber S to cover the gas inlet port 7a.

[0028] The housing 7 has a cylindrical tip 7b, to which the peripheral edge of the diaphragm 2 on the side of the pressure-receiving surface 2a is joined. This forms a measurement chamber S surrounding the pressure-receiving surface 2a. The housing 7 also has a gas inlet 7a formed in a position facing the pressure-receiving surface 2a of the diaphragm 2. The housing 7 has a flat portion 71 in which the gas inlet 7a is formed. The housing 7 also has a gas inlet pipe 72 for introducing gas into the gas inlet 7a, and the gas inlet pipe 72 is connected to an external gas piping (not shown).

[0029] The baffle member 8 reduces deposition on the diaphragm 2 by obstructing the flow of gas introduced into the measurement chamber S from the gas inlet 7a.

[0030] Specifically, as shown in Figures 1 to 4, the baffle member 8 has an opposing surface portion 81 that faces the gas inlet 7a, and a surrounding surface portion 82 that is located on the gas inlet 7a side of the opposing surface portion 81 and surrounds the periphery of the gas inlet 7a.

[0031] Here, the opposing surface portion 81 has, for example, a flat plate shape, and the surrounding surface portion 82 has, for example, a cylindrical shape or other tubular shape. The opposing surface portion 81 and the surrounding surface portion 82 are provided continuously, and the connection portion between the opposing surface portion 81 and the surrounding surface portion 82 has a structure with no gaps. The baffle member 8 of this embodiment has, for example, a bottomed tubular shape such as a bottomed cylindrical shape, and its bottom wall portion becomes the opposing surface portion 81, and its side wall portion becomes the surrounding surface portion 82.

[0032] The surrounding surface portion 82 has a flow passage portion 83 at an end portion 82a on the gas inlet 7a side, which allows the gas introduced from the gas inlet 7a to flow toward the diaphragm 2. A plurality of flow passage portions 83 are provided in the circumferential direction of the surrounding surface portion 82 (see FIG. 2). Specifically, the flow passage portion 83 is configured as a recess recessed toward the diaphragm 2 at the end portion 82a on the gas inlet 7a side of the surrounding surface portion 82 (see FIG. 3).

[0033] 1 to 4, the baffle member 8 has a plurality of joining protrusions 84 for joining to the inner side surface 7c of the housing 7. The plurality of joining protrusions 84 are formed to protrude outward from the surrounding surface portion 82, and contact the inner side surface 7c of the housing 7 when housed in the housing 7. When the joining protrusions 84 are joined to the inner side surface 7c of the housing 7, the end portion 82a of the surrounding surface portion 82 on the gas inlet 7a side is fixed in a state of contact with the flat surface portion 71 of the housing 7. As a result, the gas introduced from the gas inlet 7a flows out from between the concave portion, which is the flow passage portion 83, and the flat surface portion 71 to the periphery of the surrounding surface portion 82.

[0034] Further, as shown in FIG. 1 and FIG. 4, the multiple joint protrusions 84 are formed on the surrounding surface portion 82 closer to the diaphragm 2 than the flow passage portion 83. Here, the multiple joint protrusions 84 are formed on the end portion 82b opposite to the end portion 82a on the surrounding surface portion 82. As shown in FIG. 2 and FIG. 3, the multiple joint protrusions 84 are provided corresponding to the multiple flow passage portions 83 as viewed from the gas inlet 7a. That is, the joint protrusions 84 and the flow passage portions 83 are provided at the same position in the circumferential direction as viewed from the gas inlet 7a. Here, being provided at the same position in the circumferential direction means that the joint protrusions 84 and the flow passage portions 83 are provided overlapping each other in the circumferential direction as viewed from the gas inlet 7a. In this embodiment, the circumferential dimension of the joint protrusions 84 is larger than the circumferential dimension of the corresponding flow passage portion 83. This makes it easier for the gas flowing out of the flow passage portion 83 to hit the joint protrusions 84.

[0035] 1 and 4, the housing 7 of this embodiment has an inner protrusion 73 that protrudes inward from the baffle member 8 on the side opposite the gas inlet 7a (the diaphragm 2 side) with respect to the baffle member 8. This inner protrusion 73 is provided on the entire circumference of the inner side surface 7c of the housing 7, and obstructs the flow of gas that flows from the periphery of the surrounding surface portion 82 of the baffle member 8 toward the diaphragm 2 side.

[0036] Next, the flow of gas introduced into the measurement chamber S in this embodiment will be described with reference to FIG.

[0037] The gas introduced from the gas inlet 7a hits the opposing surface portion 81 of the baffle member 8, flows radially outward toward the surrounding surface portion 82, and flows along the surrounding surface portion 82 in the opposite direction to the opposing surface portion 81. In other words, the direction of gas flow is reversed inside the baffle member 8. Then, the gas flows from the flow portion 83 to the outside of the surrounding surface portion 82, and flows toward the diaphragm 2 between the surrounding surface portion 82 and the inner side surface 7c of the housing 7. At this time, the gas hits the joint protrusion portion 84. After that, the gas hits the inner protrusion portion 73 formed on the housing 7, and flows toward the center of the baffle member 8, and reaches the diaphragm 2.

[0038] <Effects of this embodiment> Thus, according to the capacitance type pressure sensor 100 of this embodiment, the gas introduced from the gas inlet 7a hits the opposing surface portion 81 and reverses its direction of movement, and flows from the flow passage portion 83 formed at the end of the surrounding surface portion 82 on the gas inlet 7a side to the diaphragm 2 side. As a result, the path of the introduced gas is sufficiently secured, and the gas components or the decomposed gas components can be deposited mainly on the opposing surface portion 81 and the surrounding surface portion 82, and the deposition on the diaphragm 2 can be reduced. In addition, the baffle member 8 is a bottomed tubular member consisting of the opposing surface portion 81 and the surrounding surface portion 82, so that the configuration of the baffle member 8 can be simplified, and the possibility of the response being deteriorated due to clogging by the deposits is extremely low. Furthermore, since the baffle member 8 is a bottomed tubular member, more deposits can be stored.

[0039] <Other embodiments> For example, the flow section 83 in the above embodiment is composed of a recess formed by cutting out the end of the surrounding surface section 82 in a rectangular shape, but the shape of the recess is not limited to this and may be cut out in a partial circular shape or a polygonal shape such as a triangular shape.

[0040] Moreover, the flow passage 83 may be composed of a through hole formed in the surrounding surface portion 82. In this case, the flow passage 83 composed of a through hole is provided on the gas inlet side of the surrounding surface portion 82 in order to sufficiently secure a gas path.

[0041] Although the flow passages 83 in the above embodiment are formed at equal intervals in the circumferential direction, they do not have to be provided at equal intervals in the circumferential direction.

[0042] Furthermore, in addition to the baffle member 8 of the embodiment, a configuration including a baffle plate 9 may be used as shown in Figs. 5 and 6. Specifically, the baffle plate 9 is provided separately from the baffle member 8 and is provided between the baffle member 8 and the gas inlet 7a. This baffle plate 9 is provided so as to block the gas inlet 7a. The baffle plate 9 is, for example, disc-shaped, and has a plurality of slits 9S formed therein. Here, the plurality of slits 9S are formed radially, but the formation mode of the plurality of slits 9S is not limited to this. With this configuration, not only the baffle member 8 described above, but also gas components and decomposed gas components can be deposited on the baffle plate 9. As a result, deposition on the diaphragm 2 can be further reduced.

[0043] In addition, in the configuration with the baffle plate 9, as shown in Figs. 7 and 8, it is desirable to form the multiple slits 9S at positions different from the flow passage 83 in the circumferential direction. These multiple slits 9S are not provided at positions corresponding to the flow passage 83, and the gas introduced from the gas inlet 7a does not pass through the gas inlet 7a, the slits 9S, and the flow passage 83 in a straight line as viewed from the introduction direction, as shown in Fig. 8. With this configuration, the gas introduced from the gas inlet 7a meanders in the radial direction as viewed from the introduction direction while flowing from the slits 9S to the flow passage 83. As a result, the path through which the gas passes through the slits 9S of the baffle plate 9 can be made complex, and the accumulation effect in the baffle member can be improved.

[0044] Moreover, in the above embodiment, the baffle member 8 and the housing 7 are separate members, but as shown in Figures 9 and 10, the baffle member 8 and the housing 7 may be integrally configured. That is, the outer wall portion 70 welded to the flat portion 71 where the gas inlet 7a of the housing 7 is formed may be integrally configured with the baffle member 8. Here, the flow passage portion 83 of the baffle member 8 is composed of a plurality of through holes formed in the surrounding surface portion 82. By integrally configuring the housing 7 and the baffle member 8 in this manner, the structure can be simplified while maintaining a complex flow path. In addition, various modifications and combinations of the embodiments may be made as long as they do not go against the spirit of the present invention. [Explanation of symbols]

[0045] 100···Capacitive pressure sensor 2. Diaphragm 2a Pressure-receiving surface 3...Fixed electrode S...Measurement room 7. Housing 7a Gas inlet 71 ···Plane part 73...Inner protrusion 8 Baffle member 81... Opposite surface part 82 ... Surrounding surface part 83...Flow section 84...Joining protrusion 9 Baffle plate 9S ···Slit

Claims

1. A capacitance-type pressure sensor that measures pressure by detecting a change in capacitance between a diaphragm that is displaced by pressure and a fixed electrode, a housing surrounding the pressure receiving surface of the diaphragm to form a measurement chamber, the housing having a gas inlet for introducing a gas into the measurement chamber; a baffle member provided in the measurement chamber, The baffle member is an opposing surface portion facing the gas inlet; a surrounding surface portion provided closer to the gas inlet than the facing surface portion and surrounding the periphery of the gas inlet, The surrounding surface portion has a flow portion that allows gas introduced from the gas inlet to flow from the end portion on the gas inlet side to the diaphragm side, in a capacitance type pressure sensor.

2. The capacitance type pressure sensor according to claim 1 , wherein the flow passage portion is provided in a plurality of portions in a circumferential direction of the surrounding surface portion.

3. The baffle member has a joining protrusion for joining to an inner surface of the housing, 3. The capacitance type pressure sensor according to claim 1, wherein the joint protrusion is provided in a position corresponding to the gas flow portion when viewed from the gas inlet.

4. the housing has a flat surface on which the gas inlet is formed, 4. The capacitance type pressure sensor according to claim 1, wherein an end of said surrounding surface portion on said gas inlet side is provided in contact with said flat portion.

5. 5. The capacitance type pressure sensor according to claim 1, wherein the housing has an inward protruding portion that protrudes inward beyond the baffle member on a side opposite to the gas inlet with respect to the baffle member.

6. 6. The capacitance type pressure sensor according to claim 1, further comprising a baffle plate provided separately from the baffle member and interposed between the baffle member and the gas inlet.

7. 7. The capacitance type pressure sensor according to claim 6, wherein the baffle plate has a plurality of slits formed therein.

8. The capacitance type pressure sensor according to claim 7 , wherein the plurality of slits are formed at positions different from the flow passage portion in the circumferential direction.

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