JP2023163311A - Flow rate measurement device, flow rate measurement method, and calibration method of flow rate control device - Google Patents

Abstract

To provide a flow rate measurement device that can measure a gas flow rate controlled by a flow rate control device in reduced time.SOLUTION: A flow rate measurement device 20, which is connected to a flow path interposed between a downstream valve V0 provided on the downstream side of a flow rate control device 10 and a gas using device, comprises: a gas inlet Gin communicating with the flow path on the downstream side of the downstream valve; a gas outlet Gout communicating with an exhaust system; a first built-in valve AV1 for build-up provided in the flow path between the gas inlet and the gas outlet; a second built-in valve AV2 provided between the first built-in valve and the gas outlet; a first pressure sensor 21 and a first temperature sensor 23 for measuring the pressure and temperature of the first built-in valve on the upstream side; a second pressure sensor 22 and a second temperature sensor 24 for measuring the pressure and temperature between the first built-in valve and the second built-in valve; and a control circuit 25.SELECTED DRAWING: Figure 1

Description

The present invention relates to a flow rate measuring device for measuring the flow rate of gas controlled by a flow rate controlling device used in semiconductor manufacturing equipment, drug manufacturing equipment, chemical plants, etc., a flow rate measuring method, and calibration of a flow rate controlling device using the same. Regarding the method.

BACKGROUND ART In semiconductor manufacturing equipment, chemical plants, etc., it is required to supply gas at an appropriate flow rate to gas-using devices such as process chambers. As gas flow rate control devices, mass flow controllers (thermal mass flow rate control devices) and pressure type flow rate control devices are known.

In a flow rate control device, the flow rate needs to be managed with high precision, and it is preferable to check the flow rate accuracy and calibrate the flow rate control device from time to time. For example, a build-up method is known as a flow rate measurement method for measuring the flow rate of gas controlled by a flow rate control device. The build-up method is a method of measuring the flow rate by detecting changes in the pressure of gas flowing into a known volume (build-up volume).

The build-up method involves flowing gas into a pipe or tank with a known volume (V) installed downstream of a flow rate control device, and measuring the gas pressure increase rate (ΔP/Δt) and gas temperature (T) at that time. This method allows accurate flow rate determination without the need for connecting an expensive flow rate standard. More specifically, in the build-up method, when the gas constant is R, the flow rate Q can be determined according to, for example, Q=22.4×(ΔP/Δt)×V/RT.

Patent Document 1 discloses a method in which a flow rate measurement device as a flow rate reference device is connected to the downstream side of a flow rate control device incorporated in a gas supply system, and the flow rate is measured by a build-up method using this device. . In this method, gas from a flow rate control device flows into a tank included in a flow rate measurement device, and the flow rate is measured by measuring the rate of pressure rise within the tank. By measuring the flow rate in this way, you can check the flow rate accuracy of the flow control device at any time, so if the accuracy has decreased, you can calibrate the flow control device and maintain a reliable flow control device for a long time. It is possible to provide

International Publication No. 2012/014375 International Publication No. 2018/147354 JP 2019-120617 Publication International Publication No. 2020/026784 JP 2021-21677 Publication

In recent years, for supplying various gases, a plurality of gas supply lines equipped with flow rate control devices are connected to a process chamber via a common line. However, in gas supply systems where multiple flow control devices are connected, line dependence of gas flow and pressure loss may occur due to differences in piping diameter from each flow control device to the flow measurement device. . As a result, when a flow rate is measured using the build-up method, there may be a difference in measurement accuracy depending on the flow rate control device to be measured.

On the other hand, Patent Document 2 discloses that a pressure measurement value in a gas-sealed state after simultaneously closing a downstream valve on the downstream side of a flow rate control device and a valve in a flow rate measuring device is used for measurement in a build-up method. Techniques have been described to correct flow rates to reduce line dependence.

Further, in a gas supply system in which a large number of gas supply lines are provided, the length of piping used as part of the build-up capacity may exceed 10 m. In such long piping, temperature distribution often occurs. In particular, recently there has been an increase in applications that handle high-temperature gases, and the piping from the flow control device to the process chamber may be heated to a relatively high temperature by a heater, so the piping temperature and environmental temperature tend to vary depending on location. . In this way, if the details of the temperature of the entire piping cannot be confirmed, when measuring the flow rate using the build-up method, the temperature of the build-up capacity cannot be ascertained, making it difficult to accurately determine the gas flow rate. There is a problem with becoming.

Furthermore, gas supply systems that have a large number of gas supply lines vary in the number of lines and piping design depending on the application, and the configuration may change during use, so it is used as a build-up capacity. It is not easy to determine the total volume of piping without error. In reality, it is quite difficult to accurately determine the total volume of the piping based on the piping dimensions and flow path configuration.

To address these problems, Patent Document 3 and Patent Document 4 disclose a flow rate method that allows accurate flow rate measurement even when the actual temperature and volume value in the piping section during build-up flow rate measurement cannot be determined. A measuring device is disclosed.

7 and 8 are for explaining a conventional flow rate measurement method using a build-up method using a conventional flow rate measurement device 90 having a configuration similar to that described in Patent Document 3 and Patent Document 4. This is a diagram. Although FIG. 7(a) shows only one gas supply line to be measured for simplicity, in reality, multiple gas supply lines are connected to the pipe 5a, and each gas supply line is connected to the pipe 5a. A flow rate control device and a downstream valve V0 are provided in the gas supply line.

As shown in FIG. 7(a), in the gas supply system, a conventional flow rate measurement device 90 is connected to the flow rate control device 10 and the piping 5a downstream of the downstream valve V0. Further, the downstream side of the flow rate measuring device 90 is connected to an exhaust system provided with a vacuum pump or the like via a cutoff valve V4.

The flow measuring device 90 includes a first built-in valve AV1' for build-up, a second built-in valve AV2' upstream thereof, two pressure sensors 91a and 91b for measuring gas pressure between these, and a temperature sensor. 93. The two pressure sensors 91a and 91b are a large flow rate pressure sensor 91a (for example, rated at 100 Torr) and a small flow rate pressure sensor 91b (for example, rated at 20 Torr), which have different pressure measurement ranges, and either one can be selected depending on the flow rate or build-up pressure. The output of the pressure sensor is used. However, the present invention is not limited to this, and the number of pressure sensors may be only one, or two pressure sensors of the same standard may be installed to improve accuracy.

The difference between the flow rate measuring device 90 and the past flow rate measuring devices described in Patent Document 1 and the like is that it includes a second built-in valve AV2' on the upstream side, and also includes a second built-in valve AV2' on the upstream side and a flow rate measuring device 90 from the second built-in valve AV2' to the first built-in valve AV1'. The point is that the volume Vb of the flow path is accurately determined in advance. The flow rate measuring device 90 uses the second built-in valve AV2' to perform the partial pressure method described later, thereby making the flow rate measurement by the build-up method more accurate without requiring the measured values of the gas temperature and volume in the pipe 5a. It is configured so that it can be executed.

A method for measuring the volume Vb of the flow path (hereinafter sometimes referred to as internal capacity) from the second built-in valve AV2' to the first built-in valve AV1' in the flow rate measuring device 90 is described in Patent Document 5, for example. ing. The volume Vb of the flow rate measuring device 90 can be measured in advance before connecting to the gas supply system and stored in a memory within the device. The volume Vb is not limited to a constant value; as disclosed in Patent Documents 4 and 5, the environmental temperature at the time of flow measurement and the magnitude of the pressure after build-up (volume change inside the pressure sensor due to diaphragm deformation) Different values may be used depending on the

FIG. 7(b) shows a flow rate measurement procedure performed using the flow rate measurement device 90. FIG. 7(b) shows the gas pressure P within the device measured by the pressure sensors 91a and 91b, as well as the opening and closing of the downstream valve V0, the first built-in valve AV1', the second built-in valve AV2', and the downstream cutoff valve V4. Operation is shown. Note that the cutoff valve V4 does not necessarily need to be provided for flow rate measurement.

First, in order to suppress line dependence of flow rate measurement accuracy, the downstream valve V0 and the first built-in valve AV1' are simultaneously closed from a state in which gas is flowing through the flow rate measurement device 90 at the flow rate controlled by the flow rate control device 10. By this, the pressure P ₀ at the time of simultaneous sealing is measured.

Next, from a state in which gas is flowing through the flow rate measuring device 90 at a controlled flow rate, first, by closing only the first built-in valve AV1' inside the flow rate measuring device 90, the piping 5a and the internal capacity (second built-in valve AV1') are closed. Gas is stored in the build-up capacity including the flow path from valve AV2' to first built-in valve AV1'. By building up in this way, the gas pressure P increases linearly with time.

Then, after the build-up time Δt has elapsed, the downstream valve V0 on the flow control device 10 side is closed, and the pressure _P1 after the build-up is measured in a state where the pressure is stable. Here, in this example, the flow rate is measured using the simultaneous sealing pressure P ₀ to suppress the line dependence, so as described in Patent Documents 2 to 4, the build-up pressure ΔP The value of ΔP=(P ₁ −P ₀ ) is used as ΔP=(P 1 −P 0 ), thereby eliminating line dependence and obtaining the pressure increase rate (ΔP/Δt) required for flow rate calculation.

Note that the pressure increase rate (ΔP/Δt) may be obtained by measuring the pressure P 1 after the predetermined build-up time Δt has elapsed as described above, or by measuring the pressure P ₁ after the build-up reaches the predetermined pressure P ₁ . It may also be obtained by measuring the build-up time Δt until reaching the point.

In order to prevent a decrease in measurement accuracy due to unclear temperature of the piping 5a, the flow measuring device 90 is capable of measuring the temperature Ta and volume value Va of the piping during flow measurement using the partial pressure method. It is possible to describe the flow rate using the temperature Tb and the volume value Vb within, thereby realizing flow rate measurement that is not easily influenced by temperature.

Specifically, after the build-up, the downstream valve V0 and the first built-in valve AV1' are closed, and from the state where the pressure between them is maintained at _P1 (see FIG. 8(a)), the second built-in valve AV2 is closed. ' is closed. Then, while maintaining the pressure on the upstream side at _P1 , the first built-in valve AV1' is temporarily opened, and the gas on the downstream side of the second built-in valve AV2' is exhausted to lower the pressure. In addition, if the shutoff valve V4 is provided, it is also maintained in the open state, or if it is closed at the time of sealing after build-up, it is changed to the open state.

As a result, as shown in FIG. 8(b), the pressure on the downstream side of the second built-in valve AV2' decreases from _P1 to _P2 . Note that the pressure may be reduced to _P2 by specifying the temporary opening time of the first built-in valve AV1', or by monitoring the pressure _P2 and opening the first built-in valve AV1' when it reaches a predetermined pressure. You can also close it.

After the first built-in valve AV1' is closed, the upstream side of the second built-in valve AV2' is maintained at pressure _P1 , and the downstream side of the second built-in valve AV2' is maintained at pressure _P2 . is realized. Thereafter, by opening the second built-in valve AV2' while keeping the downstream valve V0 and the first built-in valve AV1' closed, the pressure difference between the upstream pressure _P1 and the downstream pressure _P2 is eliminated. As a result, as shown in FIG. 8(c), the pressure within the entire build-up capacity from the downstream valve V0 to the first built-in valve AV1' is equalized to _P3 .

Here, since the downstream valve V0 and the first built-in valve AV1' remain closed, the downstream valve V0 and the first built-in valve AV1' are closed before and after the second built-in valve AV2' is opened. The total amount of gaseous matter between them is the same. Therefore, applying the Boyle-Charles law, we obtain the following equation:
P ₁・Va/Ta+P ₂・Vb/Tb=P ₃・Va/Ta+P ₃・Vb/Tb

In the above formula, Va is the volume value of the pipe 5a, Ta is the gas temperature in the pipe 5a, Vb is the volume value of the internal volume in the flow rate measuring device, and Tb is the internal volume that can be measured by the temperature sensor 93. gas temperature. Note that in the above equation, it is assumed that the temperature Ta and the temperature Tb do not change between the time of _P2 measurement and the time of _P3 measurement in the flow rate measurement device 90, based on the actual environment.

Also, rearranging the above formula, from (P ₁ - P ₃ )Va・Tb=(P ₃ -P ₂ )Vb・Ta, Va/Ta=(P ₃ -P ₂ )/(P ₁ -P ₃ ) ×Vb/Tb is derived. That is, Va/Ta can be described using Vb/Tb and P ₁ , P ₂ , and P ₃ by using the partial pressure method.

On the other hand, in the build-up method, the flow rate Q corresponds to the rate of increase in the amount of gas Δn/Δt flowing into the build-up volume having the volume V. Here, if Δna is the amount of gas substance increased in the pipe 5a during build-up and Δnb is the amount of gas substance increased by the internal capacity of the flow rate measuring device during build-up, applying the gas equation of state, the volume conversion The flow rate Q (sccm) is expressed by the following formula.
Q=22.4×Δn/Δt
=22.4×(Δna+Δnb)/Δt
=22.4×(ΔP・Va/R・Ta+ΔP・Vb/R・Tb)/Δt
=22.4×(ΔP/R・Δt)×(Va/Ta+Vb/Tb)

In the above equation, ΔP corresponds to the pressure increase due to build-up (in this case, ΔP=P ₁ −P ₀ ), and Δt corresponds to build-up time (time required for build-up). Note that R is a gas constant, and the above equation shows a case where the unit of pressure is (Pa) and the unit of temperature is (K). When the unit of pressure is (Torr), it is expressed as Q=(22.4/760)×(ΔP/RΔt)×(Va/Ta+Vb/Tb).

Since the relationship Va/Ta=(P ₃ -P ₂ )/(P ₁ -P ₃ )×Vb/Tb is obtained by the above-mentioned partial pressure method, the volumetric flow rate Q is Q=22.4. It is obtained from ×(ΔP/RΔt)×(Vb/Tb)×((P ₃ −P ₂ )/(P ₁ −P ₃ )+1). In this way, if the partial pressure method is applied, the measured values ΔP (= P ₁ - _{P 0} )/Δt, P ₁ , P ₂ , P ₃ , and Tb, and the known volume read out from the memory Using the value Vb, the flow rate Q can be determined by calculation while reducing the line dependence and the influence of the pipe temperature, without the need to measure the volume Va of the pipe 5a and the gas temperature Ta.

However, in the build-up method using the conventional flow rate measuring device 90, in order to implement the partial pressure method, after the build-up by closing the first built-in valve AV1', the downstream valve V0 and the second built-in valve AV2' are closed. It will be done. Furthermore, after that, it is necessary to temporarily open the first built-in valve AV1' to create a pressure difference between the pressure _P1 and the pressure _P2 between the upstream side and the downstream side of the second built-in valve AV2'.

For this reason, although the above-mentioned method allows highly accurate flow measurement by reducing line dependence and temperature effects, it requires a relatively long working time. In particular, in the above flow measurement method, a certain amount of waiting time is provided in each sealing state in order to measure pressure and temperature in a stable gas state, and this waiting time is required multiple times (four times in the above example). ) It is necessary to repeat the sealing process in sequence, which increases the working time.

The present invention has been made in view of the above-mentioned problems, and provides a flow rate measuring device and a flow rate measuring device capable of measuring gas flow rate in a relatively short time with high accuracy using a build-up method or a partial pressure method. The main purpose of this paper is to provide a measurement method and a method for calibrating a flow rate control device using the measurement method.

A flow rate measurement device according to an embodiment of the present invention includes a flow rate control device, a downstream valve provided downstream of the flow rate control device, and a gas usage device connected to a flow path downstream of the downstream valve. The gas supply system is connected to a flow path between the downstream valve and the gas usage device, and is configured to measure the flow rate of the gas controlled by the flow rate control device, and is configured to measure the flow rate of the gas controlled by the flow rate control device, a gas inlet communicating with the flow path, a gas outlet communicating with the exhaust system, a first built-in valve for build-up provided in the flow path between the gas inlet and the gas outlet, and the first built-in valve. a second built-in valve provided between the first built-in valve and the gas outlet; a first pressure sensor and a first temperature sensor that measure the pressure and temperature upstream of the first built-in valve; a second pressure sensor and a second temperature sensor that measure pressure and temperature between the second built-in valve, the first built-in valve, the second built-in valve, the first pressure sensor, the first temperature sensor, and the second built-in valve; a second pressure sensor and a control circuit connected to the second temperature sensor, the pressure and temperature on the upstream side of the first built-in valve can be measured with the first built-in valve closed; , the pressure and temperature downstream of the first built-in valve can also be measured.

In one embodiment, the control circuit controls gas pressure P ₁ upstream of the first built-in valve, which is measured with the downstream valve and the first built-in valve closed, and the first built-in valve. The gas pressure _P2 on the downstream side of the first built-in valve is measured with the second built-in valve closed, and the downstream valve and the second built-in valve are closed and the first built-in valve is open. The flow rate is calculated based on the pressure _P3 on the upstream side or the downstream side of the first built-in valve, which is measured under the condition that the first built-in valve is in the upstream side or the downstream side.

In one embodiment, the flow rate measurement device further includes a capacity expansion chamber of known volume provided in the flow path between the first built-in valve and the second built-in valve.

In one embodiment, the flow rate measuring device further includes a third built-in valve provided upstream of the first pressure sensor and the first temperature sensor.

A flow rate measurement method according to an embodiment of the present invention includes a flow rate control device, a downstream valve provided downstream of the flow rate control device, and a gas usage device connected to a flow path downstream of the downstream valve. In a gas supply system, a flow rate measured using a flow rate measurement device connected to a flow path between the downstream valve and the gas usage device and configured to measure the flow rate of gas controlled by the flow rate control device. In the measurement method, the flow rate measuring device includes a gas inlet communicating with a flow path on the downstream side of the downstream valve, a gas outlet communicating with an exhaust system, and a flow path between the gas inlet and the gas outlet. A first built-in valve provided for build-up, a second built-in valve provided between the first built-in valve and the gas outlet, and pressure and temperature on the upstream side of the first built-in valve are measured. A first pressure sensor, a first temperature sensor, and a second pressure sensor and a second temperature sensor that measure pressure and temperature between the first built-in valve and the second built-in valve, and the downstream valve , with the first built-in valve and the second built-in valve open, the gas flows from the gas inlet to the gas outlet of the flow rate measurement device at a flow rate controlled by the flow rate control device; the upstream side of the first built-in valve in a sealed state in which the downstream valve is closed after a predetermined time has elapsed after the first built-in valve is closed in a state where the downstream valve and the first built-in valve are closed after build-up; measuring a gas pressure _P1 using the first pressure sensor; and closing the second built-in valve, and the first built-in valve in a sealed state with the first built-in valve and the second built-in valve closed. using the second pressure sensor to measure gas pressure _P2 on the downstream side of the gas pressure sensor; The gas pressure _P3 in a sealed state where only the valve is opened to communicate from the downstream valve to the second built-in valve, and the downstream valve and the second built-in valve are closed is measured by the first pressure sensor and the second pressure. The method includes a step of measuring using at least one of the sensors, and a step of calculating a gas flow rate based on the measured gas pressure P ₁ , gas pressure P ₂ , and gas pressure P ₃ .

In one embodiment, the flow rate measurement method includes at least one of a sealed state in which the first built-in valve and the second built-in valve are closed, or a sealed state in which the downstream valve and the second built-in valve are closed. further comprising _the step of measuring _a gas temperature Tc on the downstream side of the first built-in valve using _the second temperature sensor; The gas flow rate is calculated based on the temperature Tc and the known volume value Vc of the capacity between the first built-in valve and the second built-in valve.

In one embodiment, the flow rate measurement method includes supplying gas at a flow rate controlled by the flow rate control device to the flow rate measurement device while the downstream valve, the first built-in valve, and the second built-in valve are open. When the gas is flowing from the gas inlet to the gas outlet, the downstream valve and the first built-in valve are simultaneously closed, and the gas pressure P ₀ on the upstream side of the first built-in valve in the sealed state is measured by the first pressure sensor. The gas flow rate is calculated based on the gas pressure P ₀ in addition to the gas pressure P ₁ , gas pressure P ₂ , and gas pressure P ₃ .

In one embodiment, the step of measuring the gas pressure _P2 using the second pressure sensor is performed at a point downstream of the first built-in valve during a period in which the first built-in valve is closed to perform build-up. The second built-in valve is closed from a state in which the side is evacuated, and the pressure _P2 is then measured in a sealed state in which the first built-in valve and the second built-in valve are closed.

A flow rate calibration method according to an embodiment of the present invention includes the steps of: measuring the flow rate of gas controlled by the flow rate control device using the flow rate measurement device according to any of the flow rate measurement methods described above; , a step of comparing the flow rate outputted by the flow rate control device, and a step of calibrating the flow rate control device based on the comparison result in the comparing step.

By using the flow rate measurement device according to the embodiment of the present invention, it is possible to accurately measure the flow rate of the gas controlled by the flow rate control device in a relatively short time, and the flow rate can be controlled based on the measurement result. Equipment can be calibrated.

FIG. 1 is a schematic diagram showing a gas supply system connected to a flow rate measuring device according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing a specific configuration example of the flow rate control device shown in FIG. 1. FIG. 1 is a schematic diagram showing a configuration example from a flow rate control device to a flow rate measurement device in a system in which a flow rate measurement method according to an embodiment of the present invention is implemented. It is a diagram showing a flow rate measurement sequence when carrying out a flow rate measurement method, with the horizontal axis representing time, the gas pressure P within the device measured by a pressure sensor provided in the flow rate measurement device, the downstream valve V0, and the first built-in gas pressure P. The opening and closing operations of valve AV1, second built-in valve AV2, and third built-in valve AV3 are shown. FIG. 4 is a diagram for explaining the procedure of the partial pressure method in the flow rate measurement method of the embodiment, in which (a) shows the sealed space upstream of the first built-in valve AV1 and the downstream side of the first built-in valve AV1 after build-up; (b) shows a state in which the first built-in valve AV1 is subsequently opened to eliminate the pressure difference. An example of the configuration of a system from a flow rate control device to a flow rate measuring device in another embodiment is shown. It is a figure for explaining the conventional flow measurement method using a build-up method performed using the conventional flow measurement device, (a) shows the structure from the flow control device to the flow measurement device, and (b) is the gas pressure P within the device measured by the pressure sensor installed in the flow rate measuring device, and the downstream valve V0, the first built-in valve AV1', the second built-in valve AV2', and the cutoff valve V4, with the horizontal axis being time. Shows opening/closing operation. It is a figure which shows the procedure of the partial pressure method in the conventional flow measurement method, (a) shows the sealing state after build-up, (b) is after that closing the second built-in valve AV2' and closing the first built-in valve AV1. ' is opened to exhaust the downstream side of the second built-in valve AV2', and (c) then closes the first built-in valve AV1' and opens the second built-in valve AV2' to eliminate the pressure difference. Indicates the state in which

Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to the following embodiments.

FIG. 1 shows a gas supply system 100 to which a flow measurement device 20 according to an embodiment of the invention is connected. The gas supply system 100 is configured to be able to supply gas from a plurality of gas supply lines to a process chamber (gas usage device) 6 of a semiconductor manufacturing device via an on-off valve 4 provided in a common line. A vacuum pump 8 is connected to the process chamber 6, and can evacuate the inside of the chamber and the flow path connected thereto. The flow rate measuring device 20 may be detachably connected to the gas supply system 100.

Each gas supply line is provided with a gas supply source 2, a flow rate control device 10, and a downstream valve V0. The gas from the gas supply source 2 is supplied to the process chamber 6 after its flow rate is controlled by the flow rate control device 10 . The gas supply source 2 stores various arbitrary gases such as material gas, etching gas, and purge gas. The downstream valve V0 is used to switch the lines for supplying gas, and by controlling the opening and closing of the downstream valve V0 of each line, any type of gas can be supplied to the process chamber 6.

FIG. 2 is a diagram showing a specific configuration example of the flow rate control device 10. As shown in FIG. Although the type of flow rate control device 10 that is calibrated using the flow rate measurement method of this embodiment is not particularly limited, in this embodiment, a known pressure-type flow rate control device is used as the flow rate control device 10. ing.

The flow rate control device 10 includes a constriction section 12 having a fine opening, a control valve 14 provided upstream of the constriction section 12, an upstream pressure sensor 16 provided between the constriction section 12 and the control valve 14, and a temperature sensor 16 provided between the constriction section 12 and the control valve 14. A sensor 17 and a downstream pressure sensor 18 provided on the downstream side of the constriction section 12 are provided. In other embodiments, downstream pressure sensor 18 may not be provided. Further, the upstream pressure sensor 16, temperature sensor 17, and downstream pressure sensor 18 are connected to the CPU of the control circuit 15 via an AD converter, and the control circuit 15 controls the opening and closing of the control valve 14 based on the output of each sensor. The degree can be controlled. An external device 19 for a user to input a target flow rate may be connected to the control circuit 15.

As the constriction part 12, an orifice plate, a critical nozzle, a sonic nozzle, or the like is used. The diameter of the orifice or nozzle is set to, for example, 10 μm to 2000 μm. As the control valve 14, for example, a piezo element driven valve is used. A piezo element-driven valve can adjust the amount of movement of a diaphragm valve element by controlling the voltage applied to the piezo element, and can arbitrarily adjust its opening degree with good responsiveness. Further, as the upstream pressure sensor 16 and the downstream pressure sensor 18, for example, a silicon single crystal pressure sensor having a pressure sensitive diaphragm provided with a strain gauge or a capacitance manometer is used. Further, as the temperature sensor 17, for example, a thermistor or a platinum resistance temperature sensor is used.

The flow rate control device 10 performs flow rate control using the principle that when the critical expansion condition: PU/PD≧about 2 is satisfied, the flow rate Q is determined by the upstream pressure PU and not by the downstream pressure PD. Here, PU is the gas pressure (upstream pressure) on the upstream side of the throttle part, PD is the gas pressure (downstream pressure) on the downstream side of the throttle part, and about 2 is for nitrogen gas. When the critical expansion condition is satisfied, the flow rate Q on the downstream side of the throttle part is given by Q=K1·PU (K1 is a constant depending on the type of fluid and the fluid temperature). In addition, when the downstream pressure sensor 18 is provided, even if the critical expansion condition is not satisfied, based on the measured upstream pressure PU and downstream pressure PD, Q=K2・PD ^m (PU-PD) ⁿ (here The flow rate Q can be calculated from K2 (K2 is a constant depending on the type of fluid and fluid temperature, and m and n are indices derived based on the actual flow rate).

In order to control the flow rate, a set flow rate is input to the control circuit 15, and the control circuit 15 calculates the flow rate Q according to the above formula based on the output of the pressure sensor 42, etc., and sets the flow rate to the input setting. The control valve 14 is feedback-controlled to approach the flow rate. The flow rate determined by the calculation may be displayed on an external monitor as a flow rate output value.

However, in the pressure-type flow rate control device 10, the relationship between the upstream pressure PU and the flow rate Q (the above constant K1 and constant K2) may change. However, since the pressure-type flow rate control device 10 does not normally have a mechanism that can directly measure the flow rate, even if there is a change in the relationship as described above, especially an abnormality in the throttle section 12, It is difficult to detect this immediately.

In contrast, in this embodiment, as described later, the actual flow rate can be measured using the flow rate measurement device 20, and the flow rate control device 10 can be calibrated based on the measurement result. Therefore, even if the pressure-type flow rate control device 10 is used, calibration is performed by updating the above-mentioned constants K1 and K2 in order to correspond to changes in the state of the throttle section 12. 100, accurate flow rate control can be performed continuously over a long period of time.

Further, in the example shown in FIG. 2, the downstream valve V0 is provided outside the flow rate control device 10, but the downstream valve V0 may be incorporated inside the flow rate control device 10. The downstream valve V0 may be configured integrally with the throttle portion 12 inside the flow rate control device 10, and may constitute a so-called orifice-built-in valve as described in International Publication No. 2018/021277, for example. In this case, the volume between the orifice through which the flow rate-controlled gas flows downstream and the downstream valve V0 is designed to be extremely small, so even if this volume is not included in the build-up capacity described later, it will have little effect on flow measurement accuracy. I won't. In addition, in the flow rate control device 10, when the downstream pressure sensor 18 is arranged downstream of the valve with a built-in orifice, this downstream pressure sensor 18 is the output of the first pressure sensor 21 in the flow rate measurement device 20 when measuring the build-up flow rate. There is a possibility that it can be used for confirmation or as a substitute for the first pressure sensor 21.

Referring again to FIG. 1, the flow rate measuring device 20 will be described. A flow rate measuring device 20 for measuring flow rate by a build-up method is connected to the downstream side of the flow rate control device 10 and the downstream valve V0. In the gas supply system 100, the flow rate measurement device 20 is connected to the flow path between the downstream valve V0 and the process chamber 6, and is configured to measure the flow rate of the gas controlled by the flow rate control device 10. There is.

In this embodiment, the flow rate measurement device 20 is connected to the gas supply path via the on-off valve 5 so as to be able to communicate with all the flow rate control devices 10. In this configuration, gas whose flow rate is controlled by the flow rate control device 10 can flow through the flow rate measurement device 20 from any line, and thereby the flow rate of the gas flowing through any gas line can be measured. The flow rate measuring device 20 may be provided in the middle of the common gas line before the process chamber 6 in other embodiments.

The downstream side of the flow rate measuring device 20 is connected to an exhaust system provided with a vacuum pump 28. Note that in the embodiment shown in FIG. 1, a vacuum pump 28 is provided that is separate from the vacuum pump 8 connected to the process chamber 6, but the invention is not limited to this. The downstream side of the flow rate measuring device 20 may be connected to an exhaust system provided with a vacuum pump 8 connected to the process chamber 6, without providing the vacuum pump 28. However, in this case, it is preferable that each exhaust line is provided with an on-off valve so that exhaust from the process chamber 6 and exhaust from the flow rate measuring device 20 can be switched.

The specific configuration of the flow rate measuring device 20 will be described below. The flow rate measuring device 20 is provided in a gas inlet Gin communicating with the flow path on the downstream side of the downstream valve V0, a gas outlet Gout communicating with the exhaust system, and a flow path between the gas inlet Gin and the gas outlet Gout. It includes a first built-in valve AV1 for build-up, and a second built-in valve AV2 provided between the first built-in valve AV1 and the gas outlet Gout.

In the illustrated embodiment, the flow rate measuring device 20 further includes a third built-in valve AV3 provided upstream of the first pressure sensor 21 and the first temperature sensor 23. However, the third built-in valve AV3 is provided because it may be necessary when the flow rate control device 10 is attached to and detached from the gas supply system 100, but in order to implement the flow rate measurement method described later. Not necessarily necessary. Therefore, in the flow rate measuring device 20, the third built-in valve AV3 may be omitted.

The flow measuring device 20 also includes a first pressure sensor 21 and a first temperature sensor 23 that measure the pressure Pb and temperature Tb on the upstream side of the first built-in valve AV1, and the first built-in valve AV1 and the second built-in valve AV2. A second pressure sensor 22 and a second temperature sensor 24 are provided to measure the pressure Pc and temperature Tc between. The flow measuring device 20 can measure the pressure Pb and temperature Tb on the upstream side of the first built-in valve AV1 with the first built-in valve AV1 closed, and can measure the pressure Pc on the downstream side of the first built-in valve AV1. It is configured so that it can also measure temperature Tc.

As the first built-in valve AV1, the second built-in valve AV2, the third built-in valve AV3, and the downstream valve V0 near the flow rate control device 10, for example, an AOV (Air Operated Valve) is suitable as a highly responsive opening/closing valve. used for. However, the present invention is not limited to this, and other on-off valves such as electromagnetic valves and electric valves can also be used. Further, as the first pressure sensor 21 and the second pressure sensor 22, for example, a capacitance manometer or a silicon single crystal pressure sensor having a pressure-sensitive diaphragm provided with a strain gauge is preferably used. Further, as the first temperature sensor 23 and the second temperature sensor 24, for example, a thermistor or a platinum resistance temperature sensor is used.

Note that, similar to the flow rate measurement device 90 shown in FIG. 7(a), the first pressure sensor 21 of the flow rate measurement device 20 may be configured by two first pressure sensors. In this case, one of them functions for high pressure and the other for low pressure, and if a pressure sensor of the same range is used, it can also be used for double checking. The number of first pressure sensors 21 may be arbitrary. Similarly, any number of second pressure sensors 22 may be provided for any purpose.

The flow measuring device 20 further includes a control circuit 25 connected to the first built-in valve AV1, the second built-in valve AV2, the first pressure sensor 21, the first temperature sensor 23, the second pressure sensor 22, and the second temperature sensor 24. It is equipped with The control circuit 25 typically includes a CPU, a memory (storage unit) such as ROM or RAM, an A/D converter, etc., and runs a computer program configured to execute a flow rate measurement operation to be described later. may be implemented by a combination of hardware and software.

Although the control circuit 25 is built into the flow rate measuring device 20 in this embodiment, it may be provided as an external device. The control circuit 25 may be configured to control the operations of the first built-in valve AV1 and the second built-in valve AV2 based on the signal indicating the opening/closing operation of the downstream valve V0, or may be configured to control the operation of the first built-in valve AV1 and the second built-in valve AV2 based on the output of each sensor. may be configured to output an opening/closing instruction signal to the downstream valve V0.

In the flow measuring device 20 having the above configuration, the first built-in valve AV1 is a build-up on-off valve that is always closed when performing a build-up process to be described later. In this embodiment, the flow rate measurement by the build-up method is performed by closing the on-off valve 4 provided in the flow path leading to the process chamber 6, opening the on-off valve 5 provided in the piping 5a leading to the flow rate measuring device 20, and Only the downstream valve V0 of the gas line in which the flow rate control device 10 that is the target of flow rate measurement is installed is opened, and the downstream valves V0 of the other gas lines are closed, and the flow rate is controlled by the target flow rate control device 10. The process starts with the gas flowing through the flow rate measuring device 20.

In this embodiment, the flow path portion shown in bold line in FIG. is formed.

Note that, strictly speaking, the build-up capacity also includes the capacity of the flow path between the throttle section 12 in the flow rate control device 10 and the downstream valve V0. However, since this capacity is small compared to the entire build-up capacity, it can be almost ignored when measuring the flow rate. In particular, when the throttle part 12 and the downstream valve V0 are provided close to each other (here, this refers to the case where the volume is 0.1% or less of the total build-up volume), the measurement accuracy is almost reduced. It can be ignored and treated as something that should not be allowed. However, in order to perform more accurate measurement, fixed values may be used for the volume Vst and the gas temperature Tst of the capacity and incorporated into the calculation formula for measuring the flow rate. For the volume Vst, it is sufficient to use an approximate known volume estimated from the design, and for the gas temperature Tst, it is sufficient to substitute, for example, the output of the temperature sensor 17 included in the flow rate control device 10. In any case, it is preferable that the downstream valve V0 is located close to the flow control device 10.

Hereinafter, with reference to FIGS. 3 to 5, a flow rate measurement method using the flow rate measurement device 20 will be specifically described.

FIG. 3 is a diagram schematically showing a simplified system from the flow rate control device 10 to the flow rate measuring device 20, which is the object of measurement. In FIG. 3, the build-up capacity forming portion between the downstream valve V0 and the third built-in valve AV3 of the flow rate measurement device 20 in this system is shown as a pipe 5a (gas temperature Ta) having a volume Va, and the flow rate measurement device 20 The flow path (build-up capacity forming part) between the third built-in valve AV3 and the first built-in valve AV1 is shown as a first internal capacity having a volume Vb, and the first built-in valve AV1 and the second built-in valve AV2 are The flow path between them is shown as a second internal volume having a volume Vc.

Gas pressure Pb and gas temperature Tb in the first internal volume can be measured at all times using a sensor, and gas pressure Pc and gas temperature Tc in the second internal volume can also be measured at all times using a sensor. On the other hand, it is not easy to accurately determine the volume Va of the pipe 5a, and the gas temperature Ta in the pipe 5a is difficult to measure because of the presence of temperature distribution. For this reason, in the flow rate measurement method of this embodiment as well, the build-up method and the partial pressure method are also applied to measure the flow rate without using the gas temperature Ta or volume Va in the pipe 5a.

Further, in this embodiment, the volume Vc of at least the second internal capacity in the flow rate measuring device 20 is accurately measured in advance before being incorporated into the gas supply system 100, and the known volume Vc is stored in the memory of the control circuit 25, etc. is stored in. Similar to the conventional flow rate measuring device 90 described above, the volume Vc can be measured in advance before shipping using the method described in Patent Document 5, for example. As the volume Vc, not only a constant value but also a variable value corresponding to the environmental temperature at the time of flow rate measurement or the magnitude of the pressure after build-up (volume change inside the pressure sensor due to diaphragm deformation) may be used.

In the flow rate measurement procedure, first, as shown in FIG. 4, at time t1, all the valves shown in the figure are opened, and the flow rate measurement device 20 receives a steady flow of gas whose flow rate is controlled by the target flow rate control device 10. It starts from a state of flowing flow. In the graph of pressure P in FIG. 4, the solid line indicates the pressure Pb indicated by the first pressure sensor 21, the broken line indicates the pressure Pc indicated by the second pressure sensor 22, and the double line indicates the pressure Pc indicated by the first pressure sensor 21. This indicates that the pressure Pb output by the second pressure sensor 21 and the pressure Pc indicated by the second pressure sensor 22 are the same.

After that, at time t2, the downstream valve V0 and the first built-in valve AV1 are closed simultaneously, and in the sealed state (between V0 and AV1) from time t2 to time t3, the simultaneous sealing pressure P corresponding to the line dependence ₀ is measured using the first pressure sensor 21. This simultaneous sealing pressure P ₀ measurement does not necessarily need to be performed before the build-up process, but after the build-up process and the partial pressure method application process, a state in which the gas flows through the flow rate measuring device 20 in a steady flow is formed. You can run it afterwards.

Thereafter, at time t3, the downstream valve V0 and the first built-in valve AV1 are opened, and between times t3 and t4, the gas whose flow rate is controlled by the target flow rate control device 10 is supplied to the flow rate measuring device 20 as a steady flow. It flows again.

Thereafter, at time t4, the first built-in valve AV1 for build-up is closed, thereby starting a build-up process in which gas is flowed at a controlled flow rate from the flow rate control device 10 into the build-up capacity having the volume Va+Vb. The build-up process continues from the time when the first built-in valve AV1 is closed at time t4 until time t5 when a predetermined build-up time Δt has elapsed. During this build-up period, the pressure Pb within the build-up volume increases linearly with time.

On the other hand, in this embodiment, even after the first built-in valve AV1 is closed at time t4, the second built-in valve AV2 remains open, so that the gap between the first built-in valve AV1 and the second built-in valve AV2 is Gas is exhausted from the second internal volume via the gas outlet Gout. As a result, as shown in FIG. 4, the pressure Pc indicated by the second pressure sensor 22 decreases to a pressure _P2 lower than the pressure when the flow is steady. In the illustrated example, the pressure _P2 is, for example, a vacuum pressure of 100 Torr or less, and after rapidly decreasing immediately after time t4, the first built-in valve AV1 is closed and the second built-in valve AV1 connected to the exhaust system is opened. When valve AV2 is open, a substantially constant vacuum pressure is maintained.

Thereafter, at time t5, the downstream valve V0 is closed, thereby forming a sealed state (between V0 and AV1) after build-up. Then, when the pressure and temperature of the gas settle down in the sealed state, the gas pressure _P1 and gas temperature Tb after build-up are measured.

Furthermore, by closing the second built-in valve AV2 before reaching time t6, the first built-in valve AV1 and the second built-in valve AV2 are also sealed, and the pressure Pc between them is equal to the value of _P2. will be maintained. Note that the second built-in valve AV2 may be closed, for example, at time t5 when the downstream valve V0 is closed upon completion of build-up.

In this way, by simultaneously reducing the pressure on the downstream side during the build-up period, at time t6, the sealed space on the upstream side of the first built-in valve AV1 and the sealed space on the downstream side of the first built-in valve AV1 are already sealed. A pre-partial pressure state (FIG. 5(a)) is formed in which a pressure difference occurs between the space and the space. Furthermore, since a pressure sensor and a temperature sensor are provided corresponding to each internal volume, it is possible to measure the pressures P ₁ and P ₂ and the temperatures Tb and Tc in each sealed space in this state.

Therefore, after the conventional sealed state after build-up as shown in FIG. 7(b), the reduced pressure can be measured by closing the second built-in valve AV2' and temporarily opening the first built-in valve AV1'. The steps of forming a space and measuring its pressure can be omitted. Thereby, the working time required for flow rate measurement can be shortened.

Note that, although the above description describes a mode in which the second built-in valve AV2 is maintained in an open state at time t4, the downstream side of the first built-in valve AV1 is exhausted, and the second built-in valve AV2 is closed after time t5. It is not limited to this. For example, at time t4, the second built-in valve AV2 may be closed simultaneously with or immediately after closing the first built-in valve AV1. In this case, the pressure _P2 between the first built-in valve AV1 and the second built-in valve AV2 does not decrease to vacuum pressure, but can be maintained at a pressure similar to the pressure when a steady flow is flowing.

It is also possible to close the second built-in valve AV2 at the build-up start time t4 shown in FIG. 4, that is, a little before closing the first built-in valve AV1. By closing the second built-in valve AV2 first, the pressure upstream and downstream of the first built-in valve AV1 similarly begins to rise linearly. By closing the first built-in valve AV1 in the middle of the process to officially start the build-up, a build-up method can be performed using the capacity between the downstream valve V0 and the first built-in valve AV1.

In this case, if the build-up time from the time when the first built-in valve AV1 is closed until the downstream valve V0 is closed is Δt, and the pressure increase width during this period is ΔP, the pressure increase rate ΔP/Δt is calculated as follows: ΔP/Δt= It is given by (P ₁ - P ₂ )/Δt. Therefore, it is possible to determine the flow rate by the build-up method. Furthermore, even if the second built-in valve AV2 is closed first, the pressure P1 in the sealed space upstream of the first built-in valve AV1 and the pressure _P2 in the sealed space downstream of the first built-in valve AV1 _are changed before the partial pressure method. can be made to be different from each other, and flow rate correction using the partial pressure method can be performed without any problem.

Note that when the second built-in valve AV2 is closed first as described above, the pressure _P2 that rises during the predetermined time until the first built-in valve AV1 is closed to officially start the build-up reflects line dependence. It could be something like that. Therefore, when determining the build-up flow rate using (P ₁ - P ₂ )/Δt as described above, it is possible to reduce line dependence while omitting the step of measuring pressure P ₀ by simultaneous sealing. There is sex.

As can be seen from the above description, as long as it is possible to start build-up by closing the first built-in valve AV1, the second built-in valve AV2 can be closed at any timing before the partial pressure method. Along with this, after build-up, the pressure P ₂ between the first built-in valve AV1 and the second built-in valve AV2, which is maintained constant before the partial pressure method (pressure at the time of sealing measured by the second pressure sensor 22 ) can take any value as long as it is smaller than the pressure _P1 on the upstream side of the first built-in valve AV1 after build-up.

Thereafter, at time t6, by opening the first built-in valve AV1 while maintaining the downstream valve V0 and the second built-in valve AV2 in the closed state, the pressure difference is eliminated as shown in FIG. 5(b). The pressure is maintained at a uniform pressure _P3 after time t7 shown in FIG. At this time, it is possible to measure the pressure P3 using at least one of the first pressure sensor 21 and the second pressure sensor 22, and also to measure the pressure _P3 using the first temperature sensor 23 and the second temperature sensor 24. , gas temperature Tb and gas temperature Tc can be measured.

Then, before and after the partial pressure, each sensor included in the flow rate measuring device 20 is used to calculate the gas pressure _P1 on the upstream side of the first built-in valve AV1 and the gas temperature Tb at the first internal capacity from time t5 to t6, and the gas temperature Tb at the first internal capacity at time t5. The gas pressure P ₂ and gas temperature Tc in the second internal capacity on the downstream side of the first built-in valve AV1 at ~t6, and the gas pressure _P3 and gas temperatures Tb, Tc at times t7-t8 are obtained as measured values, respectively. .

Here, also in the flow rate measuring method of the present embodiment, the total amount of gas substance between the downstream valve V0 and the second built-in valve AV2 is Since it is invariant, applying the Boyle-Charles law yields the following relational expression.

In the above formula, R is a gas constant, Va and Ta are the volume value and gas temperature in the pipe 5a, which are difficult to measure, and the other P ₁ , P ₂ , P ₃ , Tb, and Tc are the above Measurable pressure and temperature values. Also, in this equation, considering the actual environment, it is assumed that the temperatures Ta, Tb, and Tc of each flow path section remain unchanged and the same in each state shown in FIGS. 5(a) and (b). It is assumed that

Then, by transforming the above equation, the following equation is obtained.

As can be seen from the above, Va/Ta, which is difficult to actually measure, is determined by the pressures P ₁ , P ₂ , P ₃ and temperatures Tb, Tc obtained by measurement, and the It can be seen that it can be described using the volume Vb of the first internal capacitor and the volume Vc of the second internal capacitor.

Also in this measurement method, the flow rate Q determined in the build-up method corresponds to the rate of increase in the amount of gas Δn/Δt flowing into the build-up volume having the volume value V (= Va + Vb). When the equation of state is applied, the volume-converted flow rate Q (sccm) can be expressed by the following equation.
Q=22.4×Δn/Δt
=22.4×(ΔP・Va/R・Ta+ΔP・Vb/R・Tb)/Δt
=22.4×(ΔP/R・Δt)×(Va/Ta+Vb/Tb)

In the above equation, ΔP corresponds to the pressure increase due to build-up (in this case, ΔP=P ₁ −P ₀ ), and Δt corresponds to build-up time (time required for build-up). Note that R is a gas constant, and the above equation shows a case where the unit of pressure is (Pa) and the unit of temperature is (K). When the unit of pressure is (Torr), it is expressed as Q=(22.4/760)×(ΔP/RΔt)×(Va/Ta+Vb/Tb).

Then, by using the partial pressure method described above, the relationship Va/Ta=(Vc/Tc)×(P ₃ - P ₂ )/(P ₁ -P ₃ )-Vb/Tb is obtained, so by substituting this, , the volumetric flow rate Q can be determined by calculation based on the following formula.
Q=22.4×((P ₁ - P ₀ )/RΔt)×(P ₃ -P ₂ )/(P ₁ -P ₃ )×(Vc/Tc)

In this way, this measurement method eliminates the need to measure the volume Va and gas temperature Ta of the pipe 5a, and uses the measured values and the capacitance value read from the memory to eliminate the influence of line dependence and pipe temperature. The flow rate Q can be determined by calculation while reducing the working time through a simplified process.

The flow rate measurement device 20 and the flow rate measurement method according to the embodiment of the present invention have been described above, but in other aspects, the flow rate measurement device 20 includes a second internal valve between the first built-in valve AV1 and the second built-in valve AV2. The volume may include a volume expansion chamber for increasing the volume.

FIG. 6 shows a modified flow rate measuring device 20A provided with the above-mentioned capacity expansion chamber 5c. By providing the capacity expansion chamber 5c with a known volume, the rate of variation in the volume Vc that may occur depending on the magnitude of the gas pressure is reduced, and the accuracy of flow rate measurement can be further improved. Furthermore, by providing the capacity expansion chamber 5c with a known volume, in the partial pressure method, the volume Vc on the downstream side of the first built-in valve AV1 is smaller than the volume (Va+Vb) from the downstream valve V0 to the first built-in valve AV1. Therefore, even after partial pressure, the entire pressure becomes almost the same as the pressure _P1 after build-up, which can prevent an increase in measurement error.

In addition, as a result of measuring the flow rate of the gas controlled by the flow rate control device 10 to be measured using the flow rate measurement device 20 as described above, the output flow rate of the flow rate control device 10 and the amount measured by the flow rate measurement device 20 If the measured flow rate is significantly different, it is considered that a flow rate control failure has occurred in the flow rate control device 10. For this reason, it is preferable to compare the output flow rate of the flow rate control device 10 and the measured flow rate, and calibrate the flow rate control device 10 if the difference exceeds a threshold value.

For example, when the flow rate control device 10 is a pressure-type flow rate control device, when the measured flow rate of the flow rate measurement device 20 is sufficiently small compared to the output flow rate of the flow rate control device 10, the constriction section 12 of the flow rate control device 10 is clogged. Therefore, it can be determined that the gas cannot flow at an accurate flow rate just by referring to the upstream pressure PU. In this case, by updating the constant K1 of Q=K1·PU, which is the flow rate formula of the flow rate control device 10, to a smaller value corresponding to the measured flow rate, it is possible to flow the gas at an accurate control flow rate. can be calibrated to

A flow rate measuring device, a flow rate measuring method, and a method for calibrating a flow rate control device according to an embodiment of the present invention include measuring the flow rate of gas flowing at a flow rate controlled by the flow rate control device using a build-down method, and adjusting the flow rate control device. Properly used to calibrate.

2 Gas supply source 4 On-off valve 5 On-off valve 5a Piping 6 Process chamber (gas usage equipment)
8 Vacuum pump 10 Flow rate control device 12 Throttle section 14 Control valve 16 Upstream pressure sensor 17 Temperature sensor 18 Downstream pressure sensor 20 Flow rate measurement device 21 First pressure sensor 22 Second pressure sensor 23 First temperature sensor 24 Second temperature sensor 25 Control Circuit 28 Vacuum pump 100 Gas supply system AV1 First built-in valve AV2 Second built-in valve AV3 Third built-in valve V0 Downstream valve

Claims (9)

A gas supply system including a flow rate control device, a downstream valve provided downstream of the flow rate control device, and a gas usage device connected to a flow path downstream of the downstream valve, wherein the downstream valve and the gas A flow rate measurement device connected to a flow path between the device used and configured to measure the flow rate of gas controlled by the flow rate control device,
a gas inlet communicating with a flow path on the downstream side of the downstream valve;
a gas outlet communicating with the exhaust system;
a first built-in valve for build-up provided in a flow path between the gas inlet and the gas outlet;
a second built-in valve provided between the first built-in valve and the gas outlet;
a first pressure sensor and a first temperature sensor that measure the pressure and temperature upstream of the first built-in valve;
a second pressure sensor and a second temperature sensor that measure pressure and temperature between the first built-in valve and the second built-in valve;
A control circuit connected to the first built-in valve, the second built-in valve, the first pressure sensor, the first temperature sensor, the second pressure sensor, and the second temperature sensor,
With the first built-in valve closed, the pressure and temperature on the upstream side of the first built-in valve can be measured, and the pressure and temperature on the downstream side of the first built-in valve can also be measured. A flow rate measuring device. The control circuit controls gas pressure _P1 on the upstream side of the first built-in valve, which is measured when the downstream valve and the first built-in valve are closed, and the first built-in valve and the second built-in valve. A gas pressure P2 on the downstream side of the first built-in valve is measured when the first built-in valve is closed, and a gas pressure _P2 is measured when the downstream valve and the second built-in valve are closed and the first built-in valve is open. The flow rate measuring device according to claim 1, wherein the flow rate is calculated based on a pressure _P3 on the upstream side or downstream side of the first built-in valve. The flow rate measuring device according to claim 1 or 2, further comprising a capacity expansion chamber with a known volume provided in a flow path between the first built-in valve and the second built-in valve. The flow rate measuring device according to claim 1 or 2, further comprising a third built-in valve provided upstream of the first pressure sensor and the first temperature sensor. A gas supply system including a flow rate control device, a downstream valve provided downstream of the flow rate control device, and a gas usage device connected to a flow path downstream of the downstream valve, wherein the downstream valve and the gas A flow rate measurement method performed using a flow rate measurement device connected to a flow path between the device used and configured to measure the flow rate of gas controlled by the flow rate control device,
The flow rate measurement device includes a gas inlet communicating with a flow path on the downstream side of the downstream valve, a gas outlet communicating with an exhaust system, and a build-up device provided in the flow path between the gas inlet and the gas outlet. a first built-in valve, a second built-in valve provided between the first built-in valve and the gas outlet, a first pressure sensor that measures pressure and temperature upstream of the first built-in valve; a second pressure sensor and a second temperature sensor that measure pressure and temperature between the first built-in valve and the second built-in valve,
flowing gas from the gas inlet to the gas outlet of the flow rate measurement device at a flow rate controlled by the flow rate control device while the downstream valve, the first built-in valve, and the second built-in valve are open;
The first built-in valve is closed after a predetermined time has elapsed after closing the first built-in valve in a state where gas is flowing, and the first built-in valve is in a sealed state in which the downstream valve and the first built-in valve are closed after build-up. using the first pressure sensor to measure a gas pressure _P1 on the upstream side of the
Close the second built-in valve, and measure gas pressure _P2 downstream of the first built-in valve in a sealed state with the first built-in valve and the second built-in valve closed using the second pressure sensor. step and
From the state in which the downstream valve, the first built-in valve, and the second built-in valve are closed, only the first built-in valve is opened to communicate from the downstream valve to the second built-in valve, and the downstream valve is closed. and a step of measuring gas pressure _P3 in a sealed state in which the second built-in valve is closed, using at least one of the first pressure sensor and the second pressure sensor;
A method for measuring a flow rate, comprising: calculating a gas flow rate based on the measured gas pressure P ₁ , gas pressure P ₂ , and gas pressure P ₃ . In at least one of a sealed state where the first built-in valve and the second built-in valve are closed or a sealed state where the downstream valve and the second built-in valve are closed, the second temperature sensor is used to measure the temperature of the first built-in valve. further comprising the step of measuring a gas temperature Tc downstream of the built-in valve;
In addition to the gas pressure P ₁ , gas pressure P ₂ , and gas pressure P ₃ , based on the gas temperature Tc and a known volume value Vc of the capacity between the first built-in valve and the second built-in valve. 6. The flow rate measurement method according to claim 5, wherein the gas flow rate is calculated by With the downstream valve, the first built-in valve, and the second built-in valve open, gas is flowing from the gas inlet to the gas outlet of the flow rate measurement device at a flow rate controlled by the flow rate control device. further comprising the step of simultaneously closing the downstream valve and the first built-in valve and measuring the gas pressure P ₀ upstream of the first built-in valve in a sealed state using the first pressure sensor,
The flow rate measuring method according to claim 5 or ₆ , wherein the gas flow rate is calculated based on the gas pressure P 0 as well as the gas pressure P ₁ , gas pressure P ₂ , and gas pressure P ₃ . The step of measuring the gas pressure _P2 using the second pressure sensor is performed during a period in which the first built-in valve is closed to perform build-up, while the downstream side of the first built-in valve is being exhausted. The flow rate measurement according to claim 5 or 6, comprising the step of closing the second built-in valve from a state and then measuring the pressure _P2 in a sealed state in which the first built-in valve and the second built-in valve are closed. Method. According to the flow rate measurement method according to claim 5 or 6, measuring the flow rate of the gas controlled by the flow rate control device using the flow rate measurement device;
Comparing the measured flow rate with the flow rate output by the flow rate control device;
A method for calibrating a flow rate control device, comprising: calibrating the flow rate control device based on the comparison result in the comparing step.

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