JP7457351B2 - Flow measurement method and pressure type flow controller calibration method - Google Patents

Description

The present invention relates to a method for measuring a flow rate and a method for calibrating a flow rate control device, and particularly relates to a method for measuring a flow rate of hydrogen fluoride gas using a build-down method or the like, and a method for calibrating a pressure type flow rate control device using the same.

In a gas supply system for semiconductor manufacturing equipment, various types of gas are switched and supplied to a process chamber. The flow rate of the supplied gas is controlled by a flow control device provided in each line. Gases supplied to the process chamber include source gas, etching gas, purge gas, and the like. For example, hydrogen fluoride (HF) gas may be used as the etching gas.

In the operation of a flow rate control device, it is desired to check the flow rate accuracy and calibrate the flow rate control device at any time, and the build-up method and build-down method are known as flow rate measurement methods. The build-up method is a method of measuring the flow rate of gas flowing into a build-up volume based on changes in pressure within the build-up volume of known volume. The build-down method is a method of measuring the flow rate of gas flowing out of a build-down volume based on changes in pressure within the build-down volume of known volume.

In the build-down method, the gas present in the build-down capacity installed upstream of the flow control device is allowed to flow out through the flow control device after closing the on-off valve on the upstream side of the build-down capacity. . Then, by measuring the pressure drop rate (ΔP/Δt) and temperature (T) within the build-down capacity at that time, for example, Q=K(ΔP/Δt)×V/RT (K: constant, R : gas constant, V: volume of build-down capacity), the flow rate Q can be calculated by calculation (for example, Patent Documents 1 and 2). The flow rate determined by the build-down method is compared with the flow rate indicated by the flow control device, and can be used for calibrating the flow control device.

International Publication No. WO 2013/179550 US Patent No. 8,667,830 International Publication No. 2004/066048

By the way, when measuring the flow rate using the build-down method, a build-down chamber installed in the flow path is used as the build-down capacity, but when performing flow rate verification at a small flow rate, the pressure drop rate becomes small and the flow rate measurement becomes difficult. It takes time. In addition, hydrogen fluoride gas has the property of being easily adsorbed to the inner surface of channels made of stainless steel, etc., so if a build-down chamber is provided, it may be difficult to clean it afterwards. Ta.

Furthermore, the inventors have discovered that when attempting to measure a small flow rate of hydrogen fluoride gas when using the build-down method, the accuracy of flow rate measurement may decrease depending on the measurement conditions.

The present invention has been made in view of the above-mentioned problems, and provides a flow rate measurement method that uses the build-down method to measure the flow rate of hydrogen fluoride gas with improved accuracy, and a flow rate control using the same. Its main purpose is to provide a method for calibrating equipment.

A flow rate measurement method according to an embodiment of the present invention is a method for measuring the flow rate of hydrogen fluoride gas in a gas system having a flow control device with a control valve, an upstream opening/closing valve provided upstream of the control valve, and a supply pressure sensor that measures the supply pressure between the upstream opening/closing valve and the control valve, and the flow rate measurement is performed in a state in which the flow control device controls the flow of hydrogen fluoride gas at a set flow rate, and includes the steps of closing the upstream opening/closing valve from a state in which the upstream opening/closing valve and the control valve are open, measuring the supply pressure using the supply pressure sensor with the upstream opening/closing valve closed, and calculating the flow rate of the hydrogen fluoride gas using the change in the supply pressure after the supply pressure becomes equal to or lower than a predetermined measurement start pressure at which it is confirmed that the hydrogen fluoride gas does not cluster.

In one embodiment, the rate of decrease in the supply pressure is ΔP/Δt (Torr/sec), the volume of the flow path between the upstream on-off valve and the control valve is Vs(l), and the hydrogen fluoride gas When the temperature is T (℃) and the constant is Kv (=1000・60/760), the flow rate Q (sccm) is based on Q=Kv・(273/(273+T))・Vs・(ΔP/Δt) is required.

In one embodiment, the measurement start pressure is -0.03 to 0.05 MPaG (gauge pressure).

In one embodiment, the volume of the flow path between the upstream on-off valve and the control valve is 0.5 to 20 cc.

In one embodiment, the flow rate control device includes a constriction section, the control valve upstream of the constriction section, an upstream pressure sensor that measures pressure between the control valve and the constriction section, and a control circuit. We are prepared.

In one embodiment, the flow rate control device includes a temperature measurement section, and the flow rate measurement method further includes a step of determining the measurement start pressure using the temperature measured by the temperature measurement section.

A method for calibrating a pressure-type flow rate control device according to an embodiment of the present invention includes a constriction section, a control valve upstream of the constriction section, and an upstream pressure sensor that measures the pressure between the control valve and the constriction section. , a method for calibrating a pressure-type flow rate control device which has a control circuit and feedback-controls the control valve so that the flow rate calculated from the output of the upstream pressure sensor becomes a set flow rate, the pressure-type flow rate control device having a control circuit; The flow rate control device includes an upstream on-off valve provided upstream of the control valve, and a gas system that supplies hydrogen fluoride gas together with a supply pressure sensor that measures the supply pressure between the upstream on-off valve and the control valve. The method includes a step of flowing hydrogen fluoride at a predetermined flow rate using the pressure type flow rate control device, a step of closing the upstream on-off valve while the predetermined flow rate of hydrogen fluoride is flowing, and a step of closing the upstream on-off valve with the predetermined flow rate of hydrogen fluoride flowing. After closing, the supply pressure measured by the supply pressure sensor becomes equal to or less than a predetermined measurement start pressure at which it is confirmed that the hydrogen fluoride gas does not cluster. The method includes a step of calculating the flow rate of hydrogen gas, and a step of changing a calculation formula so that the flow rate calculated from the pressure of the upstream pressure sensor becomes the flow rate calculated by the calculation.

According to the embodiment of the present invention, it is possible to appropriately measure the flow rate of hydrogen fluoride gas.

1 is a schematic diagram showing a fluid control system in which a flow rate measurement method according to an embodiment of the present invention is implemented; 3 is a flowchart related to a flow rate measurement method according to an embodiment of the present invention. 3 is a graph for explaining a flow rate measurement method according to an embodiment of the present invention.

First, an overview of the flow rate measurement method according to the embodiment of the present invention will be explained. As mentioned above, there is a need to measure the flow rate of hydrogen fluoride (HF) gas at a small flow rate. The present inventor has particularly studied a method of measuring the flow rate of HF gas using the configuration of a pressure-type flow rate control device without separately providing a dedicated flow rate measuring device. More specifically, we conducted extensive research on measuring the flow rate of HF gas at a small flow rate by a build-down method using the configuration of an existing gas supply system.

As a result, the pressure between the upstream on-off valve provided on the upstream side of the pressure-type flow control device and the upstream on-off valve and the control valve of the pressure-type flow control device (i.e., the pressure on the upstream side of the pressure-type flow control device) It has been found that small HF gas flow rate measurements can be suitably performed by the build-down method using a supply pressure sensor that measures the supply pressure (supply pressure).

However, after detailed investigation, it was found that when measuring the flow rate of HF gas using the build-down method, the flow rate measurement accuracy can decrease depending on the gas pressure and temperature. It was also found that the cause of this is the formation of clusters of HF gas.

It is known that HF gas clusters depending on conditions such as temperature, pressure, and concentration. For example, Patent Document 3 by the present applicant describes a method for controlling the flow rate of HF gas while preventing clustering. is listed. Here, clustering is a phenomenon in which gas molecules of the same type combine through interaction to form a cluster.

Therefore, in the flow rate measurement method of the present embodiment, the flow rate of HF gas is accurately measured by measuring the change in supply pressure when HF gas flows out under conditions that do not cause clustering in the build-down method. I took it as a thing. In this method, the flow rate of HF gas could be appropriately measured even at a small flow rate by using the configuration of the pressure type flow rate control device without connecting a special device for flow rate measurement.

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 system 100 according to an embodiment of the invention. The gas system 100 is configured to be able to supply gas from the gas supply source 2 to the process chamber 8 of the semiconductor manufacturing equipment via the flow rate control device 10 .

The gas supply source 2 can supply various gases used in semiconductor manufacturing processes, such as raw material gas, etching gas, or purge gas. However, in this embodiment, HF gas is supplied from the gas supply source 2. HF gas is generally used as a cleaning gas or dry etching gas in semiconductor manufacturing processes.

A vacuum pump 9 is connected to the process chamber 8, and can evacuate the inside of the chamber and the flow path connected to the chamber. Although only one gas supply line is shown in FIG. 1, in order to supply various gases, a plurality of gas supply lines, each of which is provided with a flow rate control device 10, share a common line. It may also be connected to the process chamber 8 via.

The flow rate control device 10 used in this embodiment is a pressure-type flow rate control device, and includes a constriction section 14, a control valve 12 on the upstream side of the constriction section, and a pressure between the control valve 12 and the constriction section 14 (i.e., It includes an upstream pressure sensor 17 that measures pressure P1) and a control circuit (not shown). Further, the flow rate control device 10 of the present embodiment includes a downstream pressure sensor 18 that measures a downstream pressure P2 that is the pressure downstream of the throttle portion 14, and a supply pressure sensor that measures the supply pressure P0 upstream of the control valve 12. 16. The flow rate control device 10 may include a temperature sensor (not shown) that measures the temperature between the control valve 12 and the throttle section 14.

The flow rate control device 10 is configured to control the flow rate of gas flowing downstream of the throttle section 14 by adjusting the opening degree of the control valve 12 based on the output of the upstream pressure sensor 17 and the like. As the constriction part 14, an orifice plate, a critical nozzle, a sonic nozzle, or the like can also be used. The diameter of the orifice or nozzle is set to, for example, 10 μm to 2000 μm.

As the control valve 12, for example, a piezo element driven valve is used. In a piezo element-driven valve, the amount of movement of the diaphragm valve element can be adjusted by controlling the voltage applied to the piezo element, and the degree of opening thereof can be adjusted as desired. As the supply pressure sensor 16, the upstream pressure sensor 17, and the downstream pressure sensor 18, a silicon single crystal pressure sensor or a capacitance manometer having a pressure-sensitive diaphragm equipped with a strain gauge is preferably used. As the temperature sensor, a thermistor or a platinum resistance temperature sensor is suitably used.

In the flow control device 10, the control circuit may incorporate a CPU, memory, A/D converter, etc., and may include a computer program configured to execute the operations described below, and may be realized by a combination of hardware and software.

The flow control device 10 controls the flow rate by utilizing the principle that when the critical expansion condition P1/P2≧approximately 2 (where P1 is the upstream pressure, P2 is the downstream pressure, and approximately 2 is the case for nitrogen gas) is satisfied, the flow rate Q is determined by the upstream pressure P1, not by the downstream pressure P2. When the critical expansion condition is satisfied, the flow rate Q is calculated from Q=K1·P1 (where K1 is a constant that depends on the type of fluid and the fluid temperature). Furthermore, when the downstream pressure sensor 18 is provided, even if the critical expansion condition is not satisfied, the flow rate Q can be calculated from Q=K2·P2 ^m (P1−P2) ⁿ (where K2 is a constant that depends on the type of fluid and the fluid temperature, and m and n are exponents derived from the actual flow rate).

When the set flow rate Qs is input to the control circuit, the control circuit calculates the calculated flow rate Qc according to the above formula based on the output of the upstream pressure sensor 17 and the like. Then, the control valve 12 is feedback-controlled so that the calculated flow rate Qc approaches the input set flow rate Qs. The calculated flow rate Qc may be displayed on an external monitor as a flow rate output value.

In the gas system 100 configured to perform flow rate control in this manner, in this embodiment, the upstream on-off valve 4 on the upstream side of the flow rate control device 10 and the downstream on-off valve 6 on the downstream side of the flow rate control device 10 are is provided. The upstream on-off valve 4 is used to control gas supply to the flow rate control device 10, and is also used to measure the flow rate of HF gas by a build-down method, which will be described later. The downstream on-off valve 6 is used to reliably stop the supply of gas to the process chamber 8. When a plurality of gas supply lines are provided, the downstream on-off valve 6 is also used to switch the type of gas to be supplied.

As the upstream on-off valve 4 and the downstream on-off valve 6, on-off valves such as fluid-driven valves such as AOV (Air Operated Valve), electromagnetic valves, or electric valves are preferably used. The downstream opening/closing valve 6 may be built into the flow rate control device 10 as a valve with a built-in orifice formed integrally with the throttle portion 14 . When provided integrally as a valve with a built-in orifice, the downstream opening/closing valve 6 may be placed immediately upstream of the throttle portion 14 .

In the gas system 100 of the present embodiment, the flow rate control device 10 used is not limited to the pressure-type flow rate control device described above, but may include, for example, a thermal type flow rate control device or other types of flow rate control devices. It's okay. However, in order to measure the flow rate by the build-down method described below, the gas system used includes a control valve 12 for controlling the flow rate, an upstream opening/closing valve 4 on the upstream side thereof, and a supply pressure for measuring the supply pressure P0. It is necessary to have a sensor 16.

Hereinafter, a method for measuring the flow rate of HF gas by the build-down method using the gas system 100 will be described.

FIG. 2 shows a flowchart of the flow rate measurement method according to this embodiment. In this embodiment, as shown in step S1, the flow rate measurement is performed by opening the upstream on-off valve 4 (V4), the downstream on-off valve 6 (V6), and the control valve 12 (CV) of the flow rate control device 10 to obtain a desired flow rate. It starts with gas flowing.

At this time, typically, the supply pressure P0 is sufficiently larger than the upstream pressure P1, and the upstream pressure P1 is also sufficiently larger than the downstream pressure P2. The downstream pressure P2 is usually set to a vacuum pressure (for example, 100 Torr or less). When the critical expansion condition is satisfied, the HF gas flows downstream of the throttle section 14 at a desired flow rate by controlling the upstream pressure P1 by adjusting the opening degree of the control valve 12.

Before starting flow measurement, the supply pressure P0 is set, for example, to -0.03 to 0.05 MPaG, and the upstream pressure P1 is set, for example, to 1 to 65 kPaa. The flow rate of the HF gas flowing downstream of the throttle section 14 is set, for example, to 0.2 sccm to 20 sccm.

Next, as shown in step S2, the upstream on-off valve 4 is closed to start the build-down. After the upstream on-off valve 4 is closed, the supply pressure P0 and the upstream pressure P1 decrease as gas flows out through the throttling section 14. Figure 3 shows the decrease in supply pressure P0 after the upstream on-off valve 4 is closed at time t0.

In this embodiment, the flow path between the upstream on-off valve 4 and the control valve 12 is defined as a build-down capacity Vs, and the flow rate of gas flowing out from this build-down capacity Vs via the control valve 12 is determined by the supply pressure sensor 16. Measure based on changes in output over time. The build-down capacity is set, for example, to 0.5 cc to 20 cc, and more preferably to 1 cc to 5 cc.

Using part of the flow path as the build-down volume without providing a build-down tank allows for a smaller size and lower cost, and has the advantage of allowing flow measurement to be performed in a short time. In addition, by setting the build-down volume to a relatively small value, a relatively large pressure drop occurs even with a small amount of gas flowing out, improving the accuracy of flow measurement at small flow rates.

However, as shown in FIG. 3, in this embodiment, the build-down flow rate measurement is not started immediately from the time t0 when the upstream on-off valve 4 is closed, but when the supply pressure P0 reaches a predetermined measurement start pressure P0S. The time t1 is confirmed, and the build-down flow rate measurement is performed from this time t1. The reason is that when the supply pressure P0 is higher than the measurement start pressure P0S, there is a possibility that the HF gas is clustered, and there is a possibility that appropriate flow rate measurement cannot be performed. For this reason, a measurement start pressure P0S that has been confirmed not to cause clustering is set in advance, and the build-down flow rate measurement is performed within a pressure range lower than this measurement start pressure P0S.

For this purpose, as shown in steps S3 and S4 in FIG. 2, the supply pressure P0 after the upstream on-off valve 4 is closed is monitored, and when it reaches the measurement start pressure P0S (YES in step S4), the time (start time) t1 at that time is identified and stored in memory (step S5).

Furthermore, it is known that clustering of HF gas tends to occur even when the gas temperature is low. Therefore, it is also preferable to measure the flow rate after confirming that the gas temperature is equal to or higher than a predetermined temperature. Furthermore, since clustering becomes less likely to occur as the concentration of the HF gas is lower, the flow rate measurement may be performed with the concentration of the HF gas lowered by a diluent gas.

In the build-down in this embodiment, the build-down flow rate is measured under conditions in which the HF gas does not cluster. As the above-mentioned measurement start pressure P0S, different values may be used depending on the measured gas temperature, and different values may be used depending on the gas concentration. As mentioned above, it is considered that the higher the gas temperature and the lower the gas concentration, the less likely clustering will occur, so when the gas temperature is high and/or the gas concentration is low, the measurement starting pressure P0S will be higher. You may also use

The measurement start pressure P0S is set to, for example, 30 to 60 kPaa when the gas temperature is about 60°C. The gas temperature may be measured using a temperature sensor provided separately to measure the temperature of the gas in the flow path (build-down capacity) between the upstream on-off valve 4 and the control valve 12, or may be substituted with the output of a temperature sensor (or temperature measurement unit) that measures the temperature of the flow path between the control valve 12 and the throttling unit 14 provided in a typical flow control device 10.

Then, under conditions in which the HF gas does not cluster, as shown in steps S6 to S8 in FIG. Δt is measured. Then, the flow rate can be measured based on the pressure drop rate ΔP/Δt (the slope of the graph shown in FIG. 3) measured at this time (step S9). When the gas temperature is also measured, the flow rate Q (sccm) of the HF gas can be calculated, for example, based on the following equation.

In the above equation, T is the gas temperature (°C), Vs is the build-down volume (i.e., the volume of the flow path between the upstream on-off valve 4 and the control valve 12), and ΔP/Δt is the is the pressure drop rate determined from the measurement of the supply pressure P0.

In the embodiments shown in FIGS. 2 and 3, the final pressure P0E is set in advance, and the time Δt from the measurement start pressure P0S to the final pressure P0E is measured to calculate the pressure drop rate ΔP/Δt. I'm looking for it. However, the pressure drop rate ΔP/Δt can be determined in various ways as long as the process is performed under conditions in which the HF gas does not cluster. For example, the pressure value P0(t) of the supply pressure is calculated every sampling period from time t1 when the measurement start pressure P0S is reached, until it reaches a predetermined time t2 (the time t1+Δt after a predetermined time Δt has elapsed from the start time t1). The slope ΔP/Δt of the straight line may be determined from the pressure value P0(t) obtained by the method of least squares.

In this way, even for HF gas that clusters, the flow rate can be suitably determined by the build-down method. In addition, by using the flow path between the upstream on-off valve 4 and the control valve 12 as a build-down volume with a relatively small volume, it is possible to measure small flow rates in a short period of time. The flow rate determined in this way can also be used to calibrate the flow control device 10.

The calibration of the pressure-type flow control device 10 can be performed by flowing hydrogen fluoride at a predetermined flow rate through the flow control device 10, closing the upstream on-off valve 4 while hydrogen fluoride is flowing at the predetermined flow rate, calculating the flow rate (build-down flow rate) of hydrogen fluoride gas using the change in supply pressure after the supply pressure P0 measured by the supply pressure sensor 16 falls below a predetermined measurement start pressure P0S (a pressure at which it is confirmed that hydrogen fluoride gas does not cluster), and updating the flow rate calculation formula of the flow control device 10 (for example, the value of K1 in Q = K1 P1) based on the calculated build-down flow rate.

Although the embodiments of the present invention have been described above, various modifications are possible. For example, although the flow rate measurement method using the build-down method based on the temporal change in gas pressure has been described above, a measurement method that also takes into account the change in gas temperature before and after the outflow can also be adopted.

To explain specifically, first, after closing the upstream on-off valve 4, at the time point (time t1) when the supply pressure P0 reaches the measurement start pressure P0S described above, the gas temperature T1 of the HF gas in the build-down capacity is measured. Ru. At this time, the amount of gas (number of moles) n1 in the build-down volume at the start of measurement is calculated as n1 = (P0S・Vs)/(R・T1) from PV=nRT (ideal gas equation of state). can be expressed. Here, R is a gas constant and Vs is a build-down volume.

Then, under non-clustering conditions, the gas flow continues, and when the final pressure P0E is reached (time t2), the amount of gas substance n2 can be expressed as n2 = (P0E Vs) / (R T2) using the gas temperature T2 measured at this time.

Here, since the flow rate (mass flow rate) Q corresponds to the change in the amount of substance per time, it can be expressed as Q=Δn/Δt=(n1−n2)/Δt. Therefore, by measuring the gas temperature at each time t1 and t2 and measuring the time Δt (time from time t1 to time t2), the flow rate Q can be determined based on the following formula.
Q=((P0S・Vs)/(R・T1)−(P0E・Vs)/(R・T2))/Δt
=(Vs/R)・((P0S/T1)-(P0E/T2))/Δt

As described above, it is also possible to determine the flow rate based on the change in gas temperature and the time change in the supply pressure P0 during the build-down process.

In addition, in the above embodiment, the steps up to flow rate measurement using the build-down method have been explained, but after the flow rate measurement is completed, the upstream on-off valve 4 may be opened to allow the gas to flow at a steady flow again. good. Since the upstream opening/closing valve 4 can be opened instantly, the supply pressure P0 can be quickly recovered. In addition, the pressure-type flow rate control device can control the flow rate of gas flowing downstream of the throttle part based on the upstream pressure P1, regardless of slight fluctuations in the supply pressure P0. It is also possible to measure the flow rate by the build-down method based on the change in the supply pressure P0 described above while flowing at a controlled flow rate.

The flow rate measurement method according to the embodiment of the present invention is suitably used to measure the flow rate of hydrogen fluoride gas used in semiconductor manufacturing equipment and the like.

2 Gas supply source 4 Upstream on-off valve 6 Downstream on-off valve 8 Process chamber 9 Vacuum pump 10 Flow rate controller 12 Control valve 14 Throttle section 16 Supply pressure sensor 17 Upstream pressure sensor 18 Downstream pressure sensor 100 Gas system

Claims (5)

a flow rate control device having a control valve; an upstream on-off valve provided upstream of the control valve; a supply pressure sensor that measures supply pressure between the upstream on-off valve and the control valve; A method for measuring the flow rate of hydrogen fluoride gas carried out in a gas system having a temperature measuring section capable of measuring the temperature of the fluid between the control valve and the control valve ,
The flow rate measurement is performed in a state where the flow rate control device controls the hydrogen fluoride gas to flow at a set flow rate,
closing the upstream on-off valve from the state in which the upstream on-off valve and the control valve are open;
measuring the supply pressure using the supply pressure sensor while the upstream on-off valve is closed;
The flow rate of the hydrogen fluoride gas is calculated by using the change in the supply pressure after the supply pressure becomes equal to or lower than a predetermined measurement start pressure at which it is confirmed that the hydrogen fluoride gas does not cluster. The steps you are looking for and
determining the predetermined measurement start pressure using the temperature measured by the temperature measuring section, before calculating the flow rate of the hydrogen fluoride gas using the change in the supply pressure;
Flow measurement methods, including: When the rate of decrease in the supply pressure is ΔP/Δt, the volume of the flow path between the upstream on-off valve and the control valve is Vs, and the temperature of the hydrogen fluoride gas is T, based on the following formula: The flow rate measurement method according to claim 1, wherein the flow rate Q is determined.

3. The flow rate measuring method according to claim 1, wherein the volume of the flow path between the upstream on-off valve and the control valve is 0.5 cc to 20 cc. The flow rate control device includes a throttle section, the control valve upstream of the throttle section, an upstream pressure sensor that measures pressure between the control valve and the throttle section, and a control circuit. The flow rate measuring method according to any one of claims 1 to 3. a constriction section, a control valve upstream of the constriction section, an upstream pressure sensor that measures the pressure between the control valve and the constriction section, and an upstream pressure sensor that measures the temperature of the fluid between the control valve and the constriction section. A pressure-type flow rate control device having a measurable temperature measurement unit and a control circuit, and configured to feedback-control the control valve so that the flow rate calculated from the output of the upstream pressure sensor becomes a set flow rate. A calibration method,
The pressure-type flow rate control device supplies hydrogen fluoride gas together with an upstream on-off valve provided upstream of the control valve and a supply pressure sensor that measures the supply pressure between the upstream on-off valve and the control valve. It consists of a gas system that
flowing hydrogen fluoride at a predetermined flow rate using the pressure type flow rate controller;
closing the upstream on-off valve while a predetermined flow rate of hydrogen fluoride is flowing;
After closing the upstream opening/closing valve, the supply pressure changes after the supply pressure measured by the supply pressure sensor becomes equal to or less than a predetermined measurement start pressure at which it is confirmed that the hydrogen fluoride gas does not cluster. calculating the flow rate of the hydrogen fluoride gas using the
determining the predetermined measurement start pressure using the temperature measured by the temperature measuring section, before calculating the flow rate of the hydrogen fluoride gas using the supply pressure change;
A method for calibrating a pressure-type flow rate control device, comprising: changing a calculation formula so that the flow rate calculated from the pressure of the upstream pressure sensor becomes the flow rate determined by the calculation.

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