Pressure sensor

Abstract

To obtain a wider measurement range by suppressing degradation of measurement accuracy.SOLUTION: The pressure sensor has a first sensor element 121a and a second sensor element 121b. The pressure in a first reference room 103a of the first sensor element 121a is higher than the pressure in a second reference room 103b of the second sensor element 121b. The pressure of the first reference room 103a is set to a vacuum (0 Pa), for example.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Pressure sensors such as capacitance-type diaphragm vacuum gauges attach a sensor chip containing a diaphragm (membrane) to a pipe through which the gas to be measured flows, and output a pressure value from the amount of deflection of the diaphragm when pressure is applied. For example, in the capacitance type, the amount of deflection (displacement) of the diaphragm is converted into a capacitance value, and a pressure value is calculated from the capacitance value and output. This type of pressure sensor has little dependency on the type of gas, and is therefore widely used in industrial applications, including semiconductor equipment (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-109484 A Summary of the Invention [Problem to be solved by the invention]

[0004] In diaphragm gauges, the thickness and planar size (diameter) of the diaphragm change depending on the measurement range. When the measurement range that can be covered is exceeded, a vacuum gauge with a diaphragm configured for a larger measurement range is used for measurement. In a vacuum gauge with a larger measurement range, the diaphragm is less likely to deform than in a vacuum gauge with a smaller measurement range, so the sensitivity to the same pressure is lower and the measurement accuracy deteriorates.

[0005] The present invention has been made to solve the above problems, and has an object to suppress deterioration of measurement accuracy and to obtain a wider measurement range. [Means for solving the problem]

[0006] The pressure sensor of the present invention comprises a first base, a first diaphragm spaced apart from the surface of the first base and facing the first base, a first reference chamber formed between the first base and the first diaphragm and sealed, a first measurement circuit configured to determine a pressure value received by the first diaphragm based on the displacement of the first diaphragm, a second base, a second diaphragm spaced apart from the surface of the second base and facing the second base, a second reference chamber formed between the second base and the second diaphragm and sealed at a higher pressure than the first reference chamber, and a second measurement circuit configured to determine a pressure value received by the second diaphragm based on the displacement of the second diaphragm.

[0007] In one configuration example of the pressure sensor, the first diaphragm and the second diaphragm have the same shape.

[0008] In one configuration example of the above pressure sensor, there is provided a first movable electrode provided on the opposing surface of a first diaphragm facing the first base, a first fixed electrode provided on the surface of the first base and facing the first movable electrode, a second movable electrode provided on the opposing surface of a second diaphragm facing the second base, and a second fixed electrode provided on the surface of the second base and facing the second movable electrode, and a first measurement circuit converts a change in capacitance between the first movable electrode and the first fixed electrode due to displacement of the first diaphragm into a pressure value and outputs it, and a second measurement circuit converts a change in capacitance between the second movable electrode and the second fixed electrode due to displacement of the second diaphragm into a pressure value and outputs it.

[0009] In one configuration example of the pressure sensor, the first reference chamber is in a vacuum. Effect of the Invention

[0010] As described above, according to the present invention, the pressure in the second reference chamber is made higher than that in the first reference chamber, so that deterioration of measurement accuracy is suppressed and a wider measurement range can be obtained. [Brief description of the drawings]

[0011] [Figure 1]FIG. 1 is a cross-sectional view showing the configuration of a pressure sensor according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a characteristic diagram showing the characteristics of the pressure sensor according to the embodiment of the present invention. [Diagram 3] FIG. 3 is a characteristic diagram showing the characteristics of a conventional pressure sensor. [Figure 4] FIG. 4 is a cross-sectional view showing the configuration of another pressure sensor according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] A pressure sensor according to an embodiment of the present invention will be described below with reference to Fig. 1. This pressure sensor includes two sensor elements, a first sensor element 121a and a second sensor element 121b. This pressure sensor can be used as, for example, a vacuum gauge.

[0013] The first sensor element 121a includes a first base 101a, a first diaphragm 102a, a first reference chamber 103a, and a first measurement circuit 110a. The first diaphragm 102a is disposed facing the first base 101a at a distance from the surface of the first base 101a. The first base 101a can be made of an insulator such as sapphire or alumina ceramic.

[0014] The first diaphragm 102a is supported on the first base 101a by a first support portion 106a provided so as to surround the periphery of the first diaphragm 102a. The first diaphragm 102a is displaceable in the normal direction of the plane of the first base 101a. The first diaphragm 102a is displaced by receiving pressure from the measurement object. The first diaphragm 102a and the first support portion 106a can be made of an insulator such as sapphire or alumina ceramic. The first diaphragm 102a can be, for example, circular in plan view.

[0015] The first reference chamber 103a is formed between the first base 101a and the first diaphragm 102a and is sealed. The first reference chamber 103a can be, for example, a vacuum (0 Pa). The first reference chamber 103a is a sealed space defined by the opposing surfaces of the first base 101a and the first diaphragm 102a and the inner peripheral surface of the first support portion 106a.

[0016] The first measurement circuit 110a determines the pressure value received by the first diaphragm 102a based on the displacement of the first diaphragm 102a. For example, the first sensor element 121a includes a first movable electrode 104a provided on the facing surface of the first diaphragm 102a facing the first base 101a, and a first fixed electrode 105a provided on the surface of the first base 101a facing the first movable electrode 104a. The first measurement circuit 110a converts the change in capacitance between the first movable electrode 104a and the first fixed electrode 105a due to the displacement of the first diaphragm 102a into a pressure value and outputs it.

[0017] The second sensor element 121b includes a second base 101b, a second diaphragm 102b, a second reference chamber 103b, and a second measurement circuit 110b. The second diaphragm 102b is disposed facing the second base 101b at a distance from the surface of the second base 101b. The second base 101b can be made of an insulator such as sapphire or alumina ceramic. For example, the second diaphragm 102b can have the same shape as the first diaphragm 102a. Note that the second diaphragm 102b does not need to have the same shape as the first diaphragm 102a as long as pressure sensitivity sufficient to maintain the required measurement accuracy can be obtained.

[0018] The second diaphragm 102b is supported on the second base 101b by a second support portion 106b provided so as to surround the periphery of the second diaphragm 102b. The second diaphragm 102b is displaceable in the normal direction of the plane of the second base 101b. The second diaphragm 102b is displaced by receiving pressure from the measurement object. The second diaphragm 102b and the second support portion 106b can be made of an insulator such as sapphire or alumina ceramic. The second diaphragm 102b can be, for example, circular in plan view.

[0019] The second reference chamber 103b is formed between the second base 101b and the second diaphragm 102b and is sealed. The second reference chamber 103b has a higher pressure than the first reference chamber 103a. The second reference chamber 103b is a sealed space defined by the opposing surfaces of the second base 101b and the second diaphragm 102b and the inner peripheral surface of the second support portion 106b.

[0020] The second measurement circuit 110b determines the pressure value received by the second diaphragm 102b based on the displacement of the second diaphragm 102b. For example, the second sensor element 121b includes a second movable electrode 104b provided on the opposing surface of the second diaphragm 102b facing the second base 101b, and a second fixed electrode 105b provided on the surface of the second base 101b facing the second movable electrode 104b. The second measurement circuit 110b converts the change in capacitance between the second movable electrode 104b and the second fixed electrode 105b due to the displacement of the second diaphragm 102b into a pressure value and outputs it.

[0021] For example, the first sensor element 121a and the second sensor element 121b are disposed adjacent to each other. The first base 101a and the second base 101b can be integrally formed. The first sensor element 121a and the second sensor element 121b do not need to be disposed adjacent to each other.

[0022] As described above, the pressure in the second reference chamber 103b is higher than that in the first reference chamber 103a. For example, when the first diaphragm 102a is placed in a vacuum, the first diaphragm 102a is parallel to the facing surface of the first base 101a, but the second diaphragm 102b is convex outward from the state in which it is parallel to the facing surface of the second base 101b. If the sensor value output when the diaphragm is parallel to the facing surface of the base is 0, the sensor value output from the first sensor element 121a is 0 in a vacuum as shown in FIG. 2(a), but no sensor value is output from the second sensor element 121b as shown in FIG. 2(b). As shown in FIG. 2(b), the pressure at which the sensor value output from the second sensor element 121b is 0 is higher than the vacuum.

[0023] On the other hand, in the conventional technology in which the thickness and size of the diaphragm are changed according to the measurement range, as shown in Fig. 3, both the sensor element (a) with a low measurement range and the sensor element (b) with a high measurement range output a sensor value of 0 in a vacuum. However, as is clear from a comparison between Fig. 2(b) and Fig. 3(b), the second sensor element 121b has a large change in sensor value relative to a change in pressure, and is more sensitive to the same pressure than the conventional sensor element. Thus, according to the embodiment, a wider measurement range can be obtained while suppressing deterioration in measurement accuracy.

[0024] In addition, by using values ​​outside the measurement range of each sensor element (area without linearity), it is possible to check the soundness of the measurement values ​​of each sensor element within the measurement range, making it possible to detect failures in the sensor elements, etc.

[0025] For example, a pressure value at which the change in the sensor value output from the first sensor element 121a accompanying a pressure rise starts to decrease can be obtained in advance by experiment or the like, and this pressure value can be set as the switching value. In actual use, when the sensor value output from the first measurement circuit 110a reaches the switching value, the sensor value output from the second measurement circuit 110b can be switched to the sensor value output from the pressure sensor.

[0026] Incidentally, in the above description, an example in which two sensor elements are provided has been described, but the present invention is not limited to this. The number of sensor elements may be three or more. For example, as shown in FIG. 4, a configuration may be provided in which four sensor elements are provided: a first sensor element 121a, a second sensor element 121b, a third sensor element 121c, and a fourth sensor element 121d. The first sensor element 121a and the second sensor element 121b are the same as those described above.

[0027] The third sensor element 121c includes a third base (not shown), a third diaphragm 102c, a third reference chamber 103c, and a third measurement circuit (not shown). The third diaphragm 102c is disposed facing the third base at a distance from the surface of the third base. The third base may be made of an insulator such as sapphire or alumina ceramic. For example, the third diaphragm 102c may have the same shape as the first diaphragm 102a.

[0028] The third diaphragm 102c is supported on the third base by a third support portion 106c provided so as to surround the periphery of the third diaphragm 102c. The third diaphragm 102c is displaceable in the normal direction of the plane of the third base. The third diaphragm 102c is displaced by receiving pressure from the measurement object. The third diaphragm 102c and the third support portion 106c can be made of an insulator such as sapphire or alumina ceramic. The third diaphragm 102c can be, for example, circular in plan view.

[0029] The third reference chamber 103c is formed between the third base and the third diaphragm 102c and is sealed. The third reference chamber 103c has a higher pressure than the second reference chamber 103b. The third reference chamber 103c is a sealed space defined by the opposing surfaces of the third base and the third diaphragm 102c and the inner peripheral surface of the third support portion 106c.

[0030] The third measurement circuit determines the pressure value received by the third diaphragm 102c based on the displacement of the third diaphragm 102c. For example, the third sensor element 121c includes a third movable electrode 104c provided on the facing surface of the third diaphragm 102c facing the third base, and a third fixed electrode (not shown) provided on the surface of the third base facing the third movable electrode 104c. The third measurement circuit converts a change in capacitance between the third movable electrode 104c and the third fixed electrode due to the displacement of the third diaphragm 102c into a pressure value and outputs the pressure value.

[0031] The fourth sensor element 121d includes a fourth base (not shown), a fourth diaphragm 102d, a fourth reference chamber 103d, and a fourth measurement circuit (not shown). The fourth diaphragm 102d is disposed facing the fourth base at a distance from the surface of the fourth base. The fourth base may be made of an insulator such as sapphire or alumina ceramic. For example, the fourth diaphragm may have the same shape as the first diaphragm 102a.

[0032] The fourth diaphragm 102d is supported on the fourth base by a fourth support portion 106d provided so as to surround the periphery of the fourth diaphragm 102d. The fourth diaphragm 102d is displaceable in the normal direction of the plane of the fourth base. The fourth diaphragm 102d is displaced by receiving pressure from the measurement object. The fourth diaphragm 102d and the fourth support portion 106d can be made of an insulator such as sapphire or alumina ceramic. The fourth diaphragm 102d can be, for example, circular in plan view.

[0033] The fourth reference chamber 103d is formed between the fourth base and the fourth diaphragm 102d and is sealed. The fourth reference chamber 103d has a higher pressure than the third reference chamber 103c. The fourth reference chamber 103d is a sealed space defined by the opposing surfaces of the fourth base and the fourth diaphragm 102d and the inner peripheral surface of the fourth support portion 106d.

[0034] The fourth measurement circuit determines the pressure value received by the fourth diaphragm 102d based on the displacement of the fourth diaphragm 102d. For example, the fourth sensor element 121d includes a fourth movable electrode 104d provided on the facing surface of the fourth diaphragm 102d facing the fourth base, and a fourth fixed electrode (not shown) provided on the surface of the fourth base facing the fourth movable electrode 104d. The fourth measurement circuit converts a change in capacitance between the fourth movable electrode 104d and the fourth fixed electrode due to the displacement of the fourth diaphragm 102d into a pressure value and outputs the pressure value.

[0035] The first sensor element 121a, the second sensor element 121b, the third sensor element 121c, and the fourth sensor element 121d can be disposed adjacent to each other as shown in Fig. 4. Each base can be integrally formed. The sensor elements do not need to be disposed adjacent to each other.

[0036] As described above, according to the present invention, the pressure in the second reference chamber is made higher than that in the first reference chamber, so that deterioration of measurement accuracy can be suppressed and a wider measurement range can be obtained.

[0037] It should be noted that the present invention is not limited to the above-described embodiments, and it is apparent that many modifications and combinations can be made by a person having ordinary knowledge in the art within the technical concept of the present invention. [Explanation of symbols]

[0038] 101a...first base, 101b...second base, 102a...first diaphragm, 102b...second diaphragm, 103a...first reference chamber, 103b...second reference chamber, 104a...first movable electrode, 104b...second movable electrode, 105a...first fixed electrode, 105b...second fixed electrode, 106a...first support portion, 106b...second support portion, 121a...first sensor element, 121b...second sensor element.

Claims

1. A first base; a first diaphragm spaced apart from a surface of the first base and facing the first base; a first reference chamber formed between the first base and the first diaphragm and sealed; A first measurement circuit configured to determine a pressure value received by the first diaphragm based on a displacement of the first diaphragm; A second base; a second diaphragm spaced apart from a surface of the second base and facing the second base; a second reference chamber formed between the second base and the second diaphragm, the second reference chamber being pressurized higher than the first reference chamber and sealed; a second measurement circuit configured to determine a pressure value received by the second diaphragm based on the displacement of the second diaphragm; A pressure sensor comprising:

2. 2. The pressure sensor according to claim 1, The first diaphragm and the second diaphragm have the same shape.

3. 2. The pressure sensor according to claim 1, a first movable electrode provided on a surface of the first diaphragm facing the first base; a first fixed electrode provided on a surface of the first base and facing the first movable electrode; a second movable electrode provided on a surface of the second diaphragm facing the second base; a second fixed electrode provided on a surface of the second base and facing the second movable electrode; Equipped with the first measurement circuit converts a change in capacitance between the first movable electrode and the first fixed electrode due to a displacement of the first diaphragm into a pressure value and outputs the pressure value; The second measurement circuit converts a change in capacitance between the second movable electrode and the second fixed electrode due to a displacement of the second diaphragm into a pressure value and outputs the pressure value. Pressure sensor.

4. The pressure sensor according to any one of claims 1 to 3, The first reference chamber is a vacuum pressure sensor.

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