JP2022123546A - Pressure measuring device - Google Patents

Abstract

To provide a pressure measuring device capable of precisely measuring a wide range of pressure.SOLUTION: A pressure measuring device includes a sensor diaphragm 101 that is displaceable, and receives pressure of a measurement object by a pressure reception surface 101a, and a measurement part (non-illustrated) for measuring displacement of the sensor diaphragm 101, and the sensor diaphragm 101 is set to a convex state to a side of the pressure reception surface 101a in a reference state. The sensor diaphragm 101 is disposed in a sensor element 102, includes a reference chamber 102a formed between an inner wall of the sensor element 102 and a surface in a side opposite to the pressure reception surface 101a, and can be displaced in a direction of the reference chamber 102a or in the opposite direction.SELECTED DRAWING: Figure 1

Description

The present invention relates to a pressure measuring device.

For example, a pressure measuring device that measures the pressure value from the amount of deflection of a diaphragm under pressure, that is, the displacement, is widely used in industrial applications including semiconductor equipment. 2. Description of the Related Art In the manufacture of semiconductor devices, various film forming apparatuses using vapor phase epitaxy and dry etching apparatuses are used. Such manufacturing equipment is required to stably form a thin film with a thickness on the order of nanometers with a film thickness accuracy of several percent or less. Therefore, it is important to measure the pressure accurately. A pressure measuring device is used to measure such pressure.

In order to measure the absolute pressure in this type of pressure measuring device, there is a technique in which a vacuum reference chamber is provided on one side of the diaphragm and detection is made based on the displacement of the diaphragm according to the pressure to be measured. Among such pressure measuring devices for measuring absolute pressure, a sealed liquid is widely used as a pressure transmission medium (see Patent Document 1).

Japanese Patent No. 3285971

In the absolute pressure sensor as described above, when the pressure range becomes wider than a certain level, the pressure sensitivity becomes non-linear, and it is difficult to maintain high sensitivity. Moreover, as a result of this, the measurement accuracy is degraded. Therefore, there is currently a demand for a pressure measuring device capable of measuring a wide pressure range with high accuracy and measuring absolute pressure.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the problems described above, and to provide a pressure measuring device capable of measuring a wide pressure range with high accuracy.

A pressure measuring device according to the present invention includes a sensor diaphragm that is displaceable and receives a pressure to be measured on its pressure receiving surface, and a measurement unit that measures the displacement of the sensor diaphragm. It is in a convex state on the side of .

In one configuration example of the above pressure measuring device, the sensor diaphragm is disposed in the sensor element and has a reference chamber formed between the inner wall of the sensor element and the surface opposite to the pressure receiving surface. Alternatively, it can be displaced in the opposite direction.

In one configuration example of the pressure measuring device, the reference chamber is closed, and the reference state is a state in which the pressure in the reference chamber and the pressure received by the pressure receiving surface are the same.

In one configuration example of the pressure measuring device, the measuring section has a movable electrode formed in the movable region of the sensor diaphragm and a fixed electrode formed facing the movable electrode.

In one configuration example of the pressure measurement device, the measurement unit measures strain of the sensor diaphragm.

An example of the configuration of the pressure measuring device further includes a pressure-receiving diaphragm that directly receives the pressure to be measured, and a pressure-transmitting substance that transmits the pressure received by the pressure-receiving diaphragm to the sensor diaphragm. The pressure to be measured is received by the pressure receiving surface.

In one configuration example of the pressure measuring device, the measuring section includes a piezoresistive region formed on the sensor diaphragm.

As described above, according to the present invention, since the sensor diaphragm is convex toward the pressure receiving surface in the standard state, it is possible to provide a pressure measuring device capable of measuring a wide pressure range with high accuracy.

FIG. 1 is a cross-sectional view showing the configuration of a pressure measuring device according to an embodiment of the invention. FIG. 2 is a characteristic diagram showing the state of pressure sensitivity.

A pressure measuring device according to an embodiment of the present invention will be described below with reference to FIG. This pressure measuring device includes a sensor diaphragm 101 that is displaceable and receives a pressure to be measured on a pressure receiving surface 101a, and a measurement unit (not shown) that measures the displacement of the sensor diaphragm 101. The sensor diaphragm 101 is provided with a reference , the pressure-receiving surface 101a is in a convex state.

A sensor diaphragm 101 is arranged in a sensor element 102 . Here, a sensor element 102 is a general term for a mechanism that includes a sensor diaphragm 101, measures the displacement (distortion) of the sensor diaphragm 101, converts it into a pressure value, and outputs the pressure value. For example, the sensor diaphragm 101 is arranged inside a housing that constitutes the sensor element 102 . It also includes a reference chamber 102a formed between the inner wall of the sensor element 102 and the surface of the sensor diaphragm 101 opposite to the pressure receiving surface 101a.

For example, the reference chamber 102a is formed between the inner wall of the area in which the sensor diaphragm 101 is arranged and the surface of the sensor diaphragm 101 opposite to the pressure receiving surface 101a. be able to. The sensor diaphragm 101 can be displaced toward or away from the reference chamber 102a. Note that the reference chamber 102a may be provided in contact with the surface opposite to the pressure receiving surface 101a. For example, the sensor diaphragm 101 has a concave surface when viewed from the reference chamber 102a in the reference state.

Also, the reference chamber 102a is sealed. For example, the reference chamber 102a is hermetically sealed in the state of the reference pressure. This reference pressure can be a pressure close to absolute vacuum. In the reference state described above, the pressure inside the reference chamber 102a and the pressure received by the pressure receiving surface 101a are the same. The reference state can also be a state in which the pressure receiving surface 101a does not receive pressure. A pressure introduction port 102b is formed on the side of the pressure receiving surface 101a of the sensor element 102 .

The measurement unit can be of a capacitance type having a movable electrode formed in the movable region of the sensor diaphragm 101 and a fixed electrode formed facing the movable electrode. The change in capacitance formed between the movable electrode and the fixed electrode measures the pressure received by the sensor diaphragm 101 . A change in the capacitance formed between the movable electrode and the fixed electrode is converted into a pressure value by the measuring device using the set sensor sensitivity and output.

Moreover, the measurement unit can be a strain type that measures the strain of the sensor diaphragm 101 . In this case, the measuring part comprises a piezoresistive area formed in the sensor diaphragm 101 . For example, a piezo element is arranged at each of four locations around the sensor diaphragm 101, four piezo resistance regions of the four piezo elements are bridge-connected, and the four piezo resistance regions accompanying the deformation of the sensor diaphragm 101 under pressure. The pressure can be measured by obtaining the change in the resistance value of as the bridge output.

For example, when the sensor diaphragm 101 is made of silicon, the piezo elements can be formed by diffusion resistors in the sensor diaphragm 101 made of silicon. Moreover, the strain of the sensor diaphragm 101 can be measured by forming the sensor diaphragm 101 from a thin metal plate and forming a metal strain gauge on the sensor diaphragm 101 formed from the metal plate.

The pressure measuring device also comprises a base 111 on which the sensor element 102 is mounted. A pressure-receiving diaphragm 103 is provided in the base portion 111, and a pressure-receiving diaphragm chamber 104, a through hole 105, and an injection hole 106 are formed. In FIG. 1, the pressure-receiving diaphragm 103 is arranged on the side facing the pressure-receiving surface 101a of the sensor diaphragm 101, but it is not limited to this. For example, the through hole 105 can be bent and routed so that the pressure-receiving diaphragm 103 is arranged on the reference chamber 102 a side when viewed from the sensor diaphragm 101 . Alternatively, the through hole 105 may be bent and the pressure receiving diaphragm 103 may be arranged on the side surface of the base portion 111 .

The base 111 is made of SUS316L, for example. The outer shape of the base 111 is circular or rectangular in plan view. The sensor element 102 is provided on the main surface 111a side of the base portion 111 . The pressure receiving diaphragm 103 is formed on the rear surface 111b side of the base 111 . A pressure-receiving diaphragm chamber 104 is formed between the pressure-receiving diaphragm 103 and the base portion 111 . The planar shape of the pressure receiving diaphragm chamber 104 is, for example, circular.

Further, the through hole 105 communicates the pressure introduction port 102b of the sensor element 102 and the pressure receiving diaphragm chamber 104 with each other. Injection hole 106 communicates the outside of base 111 with through hole 105 . Pressure-receiving diaphragm chamber 104 , through-hole 105 , and injection hole 106 are filled with pressure-transmitting substance 107 and sealed with sealing material 108 . After injecting the pressure transmitting substance 107 from the injection hole 106 to fill the pressure receiving diaphragm chamber 104 and the through hole 105 , the inlet of the injection hole 106 is sealed with the sealing material 108 .

The pressure to be measured is received by the pressure receiving diaphragm 103 , and the pressure received by the pressure receiving diaphragm 103 is transmitted to the sensor diaphragm 101 (pressure receiving surface 101 a ) of the sensor element 102 by the pressure transmitting substance 107 . In the embodiment, the pressure to be measured is directly received by the pressure receiving diaphragm 103 , and the sensor diaphragm 101 receives the pressure to be measured on the pressure receiving surface 101 a via the pressure transmitting material 107 . It should be noted that the injection hole 106 can be provided in the housing of the sensor element 102 as long as it allows the area filled with the pressure transmitting substance 107 to communicate with the outside.

According to the pressure measuring device according to the first embodiment, it is possible to maintain the pressure sensitivity in a linear state even in a region where the process pressure is high with respect to the required measurement range. In the pressure measuring device used in the required environment, stainless steel, titanium alloy, nickel alloy, ceramics, etc. are used as the materials of the parts that come into contact with the environment, such as the base 111 and the pressure receiving diaphragm chamber 104 . Incompressible fluid such as silicone oil is used as the pressure transmitting substance 107 .

According to the embodiment, the sensor diaphragm 101 is projected toward the pressure receiving surface 101a in the standard state. become wider. In other words, according to the embodiment, the maximum amount of deflection can be reduced while maintaining the span of the motion range, so high sensitivity can be maintained.

As exemplified in FIG. 2(a), conventionally, in the area surrounded by the dotted line where the process pressure is high with respect to the required measurement range, the change in the output of the sensor element (pressure sensitivity) with respect to the process pressure becomes non-linear. High sensitivity cannot be maintained. On the other hand, as shown in FIG. 2B, according to the embodiment, the pressure sensitivity is obtained in a region wider than the required measurement range, and even in a region where the process pressure is higher than the required measurement range, the pressure It becomes possible to maintain the sensitivity in a linear state. Alternatively, it is possible to maintain the required pressure sensitivity without being perfectly linear.

The filling (injection) and encapsulation of the pressure transmitting substance 107 will now be described. In general, after injecting the pressure-transmitting substance 107 under reduced pressure, the pressure difference (=P _atm -P _ref ) between the pressure P _ref in the reference chamber 102a and the atmospheric pressure P _atm at room temperature (≈reference temperature) causes the sensor While the diaphragm 101 is displaced, the pressure transmitting substance 107 is injected and sealed with the sealing material 108 . After injecting and sealing the pressure transmitting substance 107 in this way, when the process pressure P ₁ to be measured is reduced to P ₁ =P _ref , the displacement of the sensor diaphragm 101 becomes zero. Here, it is considered that the pressure loss due to the rigidity of the pressure-receiving diaphragm is sufficiently small and can be ignored. A flat state (not convex) in which the sensor diaphragm 101 is neither displaced toward the pressure receiving surface 101a nor toward the reference chamber 102a is referred to as a zero displacement state. With this general encapsulation of the pressure-transmitting substance 107, the sensor diaphragm 101 cannot be projected toward the pressure-receiving surface 101a in a non-pressure-receiving state.

On the other hand, first, the temperature (liquid temperature) of the pressure transmitting substance 107 is injected as T° C. (T>reference temperature) higher than the reference temperature, and the pressure difference of P _atm −P _ref is the state in which the sensor diaphragm 101 is displaced. , the sealing material 108 is used for sealing. After injecting the pressure-transmitting substance 107 at room temperature, the pressure-transmitting substance 107 including the base 111 can be sealed at a temperature of T.degree. After sealing, when cooled to the reference temperature, the volume of the sealed pressure transmitting material 107 shrinks according to the temperature change of T° C.-reference temperature.

As the volume of the pressure transmitting substance 107 shrinks, the displacement of the sensor diaphragm 101 is offset in a decreasing direction. From this state, for example, when the process pressure P ₁ is reduced to P ₁ =P _ref , the sensor diaphragm 101 is displaced toward the pressure receiving surface 101a side, in other words, in the direction opposite to the reference chamber 102a by the amount offset during cooling. becomes. The sealing temperature T of the pressure transmitting material 107 can be adjusted according to the desired amount of offset of the sensor diaphragm 101 . In addition, in order to precisely adjust the offset amount of the sensor diaphragm 101 and obtain an output with good reproducibility, the temperature of the entire member including the pressure transmitting material 107 and the base 111 constituting the region in which this is enclosed must be increased. Warming to a constant temperature is preferred. Note that the temperature can be managed based on, for example, a signal from a temperature sensor previously formed in the sensor element 102 .

As described above, according to the present invention, the sensor diaphragm is in a state of being convex toward the pressure-receiving surface side in the standard state. Measurement equipment can be provided. In the above-described embodiment, the method of temperature control during sealing of the pressure transmitting substance 107 was shown, but the present invention is not limited to this. For example, deformation of the sensor diaphragm due to bonding stress or membrane stress of the constituent members can be used.

It should be noted that the present invention is not limited to the embodiments described above, and many modifications and combinations can be implemented by those skilled in the art within the technical concept of the present invention. It is clear.

DESCRIPTION OF SYMBOLS 101... Sensor diaphragm, 101a... Pressure receiving surface, 102... Sensor element, 102a... Reference chamber, 102b... Pressure introduction port, 103... Pressure receiving diaphragm, 104... Pressure receiving diaphragm chamber, 105... Through hole, 106... Injection hole, 107... Pressure Transfer substance 108 Sealing material 111 Base 111a Main surface 111b Back surface.

Claims (7)

a sensor diaphragm that is displaceable and receives the pressure to be measured on its pressure-receiving surface;
a measuring unit that measures the displacement of the sensor diaphragm,
A pressure measuring device according to claim 1, wherein the sensor diaphragm is convex toward the pressure receiving surface side in a reference state. The pressure measuring device according to claim 1,
The sensor diaphragm is disposed in the sensor element, has a reference chamber formed between an inner wall of the sensor element and a surface opposite to the pressure receiving surface, and is displaceable in the direction of the reference chamber or in the opposite direction. A pressure measuring device characterized by: The pressure measuring device according to claim 2,
The pressure measuring device, wherein the reference chamber is sealed, and the reference state is a state in which the pressure in the reference chamber and the pressure received by the pressure receiving surface are the same. In the pressure measuring device according to any one of claims 1 to 3,
The measurement unit
a movable electrode formed in the movable region of the sensor diaphragm;
and a fixed electrode formed to face the movable electrode. In the pressure measuring device according to any one of claims 1 to 3,
The pressure measuring device, wherein the measuring unit measures strain of the sensor diaphragm. The pressure measuring device according to claim 5,
A pressure measuring device, wherein the measuring unit includes a piezoresistive region formed on the sensor diaphragm. In the pressure measuring device according to any one of claims 1 to 6,
a pressure receiving diaphragm that directly receives the pressure to be measured;
a pressure transmitting substance that transmits the pressure received by the pressure receiving diaphragm to the sensor diaphragm,
A pressure measuring device, wherein the sensor diaphragm receives the pressure to be measured on the pressure receiving surface via the pressure transmitting substance.

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