JP2021163410A - Flow rate measurement method and method for calibrating pressure type flow rate controller - Google Patents

Abstract

To appropriately measure the flow rate of hydrogen fluoride gas.SOLUTION: A hydrogen fluoride gas flow rate measurement method is performed in a state where hydrogen fluoride gas is controlled to flow at a preset flow rate in a gas system comprising: a flow rate controller 10 which has a control valve 12; an upstream on-off valve 4 which is provided upstream of the control valve; and a supply pressure sensor 16 which measures a supply pressure between the upstream on-off valve and the control valve. The hydrogen fluoride gas flow rate measurement method comprises: a step of closing the upstream on-off valve from a state where the upstream on-off valve and the control valve are open; a step of measuring the supply pressure by using the supply pressure sensor while the upstream on-off valve is closed; and a step of obtaining the flow rate of the hydrogen fluoride gas based on a change in the supply pressure after the hydrogen fluoride gas becomes less than or equal to a predetermined measurement start pressure where the hydrogen fluoride gas is confirmed not to be clustered.SELECTED DRAWING: Figure 1

Description

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

In the gas supply system of a semiconductor manufacturing apparatus, various types of gas are switched and supplied to the process chamber. The flow rate of the supplied gas is controlled by a flow rate control device provided in each line. The gas supplied to the process chamber includes a raw material gas, an etching gas, a purge gas and the like. As the etching gas, for example, hydrogen fluoride (HF) gas may be used.

In the operation of the 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 the build-down method are known as the flow rate measurement methods. The build-up method is a method of measuring the flow rate of gas flowing into the build-up capacity based on the change in pressure in the build-up capacity of a known volume. The build-down method is a method of measuring the flow rate of gas flowing out of the build-down capacity based on a change in pressure in the build-down capacity of a known volume.

In the build-down method, the gas existing inside the build-down capacity provided on the upstream side of the flow control device is discharged via 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 the temperature (T) in the builddown capacity at that time, for example, Q = K (ΔP / Δt) × V / RT (K: constant, R). The flow rate Q can be obtained by calculation from: gas constant, V: volume of builddown capacity) (for example, Patent Documents 1 and 2). The flow rate obtained by the build-down method is compared with the flow rate indicated by the flow control device and can be used for calibration of the flow control device.

International Publication No. 2013/179550 U.S. Pat. No. 8,667,830 International Publication No. 2004/066048

By the way, as the builddown capacity when measuring the flow rate by the builddown method, a builddown chamber or the like provided in the flow path is used, but when performing a flow rate test of a small flow rate, the pressure drop rate becomes small and the flow rate is measured. It takes time. Further, since hydrogen fluoride gas has a property of being easily adsorbed on the inner surface of a flow path made of stainless steel or the like, if a build-down chamber or the like is provided, there may be a problem that it is difficult to clean the gas thereafter. rice field.

Furthermore, the present inventor has found that when a small flow rate measurement of hydrogen fluoride gas is performed when the build-down method is used, the accuracy of the flow rate measurement may decrease depending on the measurement conditions.

The present invention has been made in view of the above problems, and is a flow rate measuring method capable of measuring the flow rate of hydrogen fluoride gas with higher accuracy by using the build-down method, and a flow rate control using the method. Its main purpose is to provide a method of calibrating the device.

The flow rate measuring method according to the embodiment of the present invention measures the supply pressure between the flow rate control device having a control valve, the upstream on-off valve provided on the upstream side of the control valve, and the upstream on-off valve and the control valve. It is a method of measuring the flow rate of hydrogen fluoride gas performed in a gas system having a supply pressure sensor for measuring, and the flow rate measurement is a state in which the flow control device controls the flow of hydrogen fluoride gas at a set flow rate. In the step of closing the upstream on-off valve from the state where the upstream on-off valve and the control valve are opened, and the state where the upstream on-off valve is closed, the supply pressure is measured by using the supply pressure sensor. Using the step to measure and the change in the supply pressure after the supply pressure becomes equal to or lower than the predetermined measurement start pressure at which it is confirmed that the hydrogen fluoride gas does not cluster, the hydrogen fluoride gas is used. Includes a step of calculating the flow rate of.

In one embodiment, the rate of drop of 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 of is T (° C.) 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 certain embodiments, the measurement start pressure is −0.03 to 0.05 MPaG (gauge pressure).

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

In certain embodiments, the flow control device comprises a throttle portion, the control valve on the upstream side of the throttle portion, an upstream pressure sensor for measuring the pressure between the control valve and the throttle portion, and a control circuit. I have.

In certain embodiments, the flow rate control device comprises a temperature measuring unit, and the flow rate measuring method further includes a step of determining the measurement start pressure using the temperature measured by the temperature measuring unit.

The method of calibrating the pressure type flow control device according to the embodiment of the present invention includes a throttle portion, a control valve on the upstream side of the throttle portion, and an upstream pressure sensor for measuring the pressure between the control valve and the throttle portion. , A method for calibrating a pressure type flow control device having a control circuit and feedback-controlling the control valve so that the flow rate calculated from the output of the upstream pressure sensor becomes a set flow rate. The flow control device is a gas system that supplies hydrogen fluoride gas together with an upstream on-off valve provided on the upstream side of the control valve and a supply pressure sensor that measures the supply pressure between the upstream on-off valve and the control valve. The step of flowing a predetermined flow of hydrogen fluoride by the pressure type flow control device, the step of closing the upstream on-off valve while the predetermined flow of hydrogen fluoride is flowing, and the upstream on-off valve. After closing, the fluorination using the supply pressure change after the supply pressure measured by the supply pressure sensor becomes equal to or lower than the predetermined measurement start pressure at which it is confirmed that the hydrogen fluoride gas does not cluster. It includes a step of calculating the flow rate of hydrogen gas by calculation and a step of changing the 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, the flow rate of hydrogen fluoride gas can be appropriately measured.

It is a schematic diagram which shows the fluid control system which carries out the flow rate measurement method by embodiment of this invention. It is a flowchart which concerns on the flow rate measurement method by embodiment of this invention. It is a graph for demonstrating the flow rate measurement method by embodiment of this invention.

First, an outline of the flow rate measuring method according to the embodiment of the present invention will be described. As described above, there is a request to measure the flow rate of hydrogen fluoride (HF) gas at a small flow rate. In particular, the present inventor has studied a method of measuring the flow rate of HF gas by using the configuration of the pressure type flow rate control device without separately providing a dedicated flow rate measuring device. More specifically, we have made diligent studies on measuring the flow rate of HF gas at a small flow rate by the build-down method using the configuration of the 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 control valve between the upstream on-off valve and the control valve of the pressure-type flow control device (that is, on the upstream side of the pressure-type flow control device). It was found that a small flow rate of HF gas flow rate can be suitably measured by the build-down method using a supply pressure sensor that measures (supply pressure).

However, as a result of detailed examination, it was found that when the flow rate of HF gas is measured by the build-down method, the flow rate measurement accuracy may decrease depending on the pressure and temperature of the gas. Then, it was found that the cause was that the HF gas was clustered.

It is known that HF gas is clustered depending on conditions such as temperature, pressure, and concentration. For example, in Patent Document 3 by the applicant, a method of controlling the flow rate of HF gas while preventing clustering. Is described. Here, clustering is a phenomenon in which gas molecules of the same type are combined by interaction to form a mass.

Therefore, in the flow rate measuring method of the present embodiment, in the build-down method, the flow rate of the HF gas is accurately measured by measuring the change in the supply pressure when the HF gas is discharged under the condition of not clustering. I made it. In this method, the flow rate of HF gas can be appropriately measured even with a small flow rate by utilizing the configuration of the pressure type flow rate control device without connecting a special device for flow rate measurement.

Hereinafter, embodiments of the present invention will be described 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 present invention. The gas system 100 is configured so that the gas from the gas supply source 2 can be supplied to the process chamber 8 of the semiconductor manufacturing apparatus via the flow rate control device 10.

Various gases used in the semiconductor manufacturing process, such as a raw material gas, an etching gas, or a purge gas, can be supplied from the gas supply source 2. However, in the present embodiment, the HF gas is supplied from the gas supply source 2. HF gas is generally used as a gas for cleaning or a gas for dry etching in a semiconductor manufacturing process.

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

The flow control device 10 used in the present embodiment is a pressure type flow control device, and is a pressure type flow control device, and the pressure between the throttle portion 14, the control valve 12 on the upstream side of the throttle portion, and the pressure between the control valve 12 and the throttle portion 14 (that is, upstream). It includes an upstream pressure sensor 17 for measuring the pressure P1) and a control circuit (not shown). Further, the flow control device 10 of the present embodiment has a downstream pressure sensor 18 that measures the downstream pressure P2, which is the pressure on the downstream side of the throttle portion 14, and a supply pressure sensor 18 that measures the supply pressure P0 on the upstream side of the control valve 12. It has 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 portion 14.

The flow rate control device 10 is configured to control the flow rate of the gas flowing downstream of the throttle portion 14 by adjusting the opening degree of the control valve 12 based on the output of the upstream pressure sensor 17 or the like. As the throttle portion 14, an orifice plate, a critical nozzle, a sound velocity 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 drive type valve is used. In the piezo element drive type valve, the amount of movement of the diaphragm valve body can be adjusted by controlling the voltage applied to the piezo element, and the opening degree thereof can be arbitrarily adjusted. As the supply pressure sensor 16, the upstream pressure sensor 17, and the downstream pressure sensor 18, a pressure sensor or a capacitance manometer made of a silicon single crystal having a pressure-sensitive diaphragm provided with a strain gauge is preferably used. As the temperature sensor, a thermistor or a platinum resistance temperature detector is preferably used.

In the flow control device 10, the control circuit may include a computer program having a built-in CPU, memory, A / D converter, etc. and configured to execute an operation described later, and is realized by a combination of hardware and software. Can be done.

When the flow rate control device 10 satisfies the critical expansion condition P1 / P2 ≥ about 2 (where P1 is the upstream pressure, P2 is the downstream pressure, and about 2 is the nitrogen gas), the flow rate Q depends on the downstream pressure P2. The flow rate is controlled using the principle that it is determined by the upstream pressure P1. When the critical expansion condition is satisfied, the flow rate Q is calculated from Q = K1 · P1 (K1 is a constant depending on the type of fluid and the fluid temperature). Further, when the downstream pressure sensor 18 is provided, even if the critical expansion condition is not satisfied, the flow rate Q is set to Q = K2 · P2 ^m (P1-P2) ⁿ (where K2 is the type of fluid and the fluid temperature. The dependent constants m and n can be calculated from the exponent derived from the actual flow rate).

When the set flow rate Qs is input to the control circuit, the control circuit obtains the calculated flow rate Qc according to the above equation 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 control the flow rate in this way, in the present 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 used. Is provided. The upstream on-off valve 4 is used for controlling the gas supply to the flow rate control device 10, and is also used for executing the flow rate measurement of HF gas by the build-down method 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 for switching the supply gas type.

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

In the gas system 100 of the present embodiment, the flow rate control device 10 is not limited to the pressure type flow rate control device described above, and is, for example, a thermal flow rate control device or another type of flow rate control device. You may. However, in order to measure the flow rate by the build-down method described below, the gas system used is a control valve 12 for flow control, an upstream on-off 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, which is performed using the gas system 100, will be described.

FIG. 2 shows a flowchart of the flow rate measuring method according to the present embodiment. In the present 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 from the state where the gas flows at.

At this time, typically, the supply pressure P0 is sufficiently larger than the upstream pressure P1, and the upstream pressure P1 is 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 upstream pressure P1 is controlled by adjusting the opening degree of the control valve 12, so that the HF gas flows to the downstream side of the throttle portion 14 at a desired flow rate.

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

Next, as shown in step S2, the builddown is started by closing the upstream on-off valve 4. After closing the upstream on-off valve 4, the supply pressure P0 and the upstream pressure P1 decrease as the gas flows out through the throttle portion 14. FIG. 3 shows a drop in the supply pressure P0 after the upstream on-off valve 4 is closed at time t0.

In the present embodiment, the flow path between the upstream on-off valve 4 and the control valve 12 is a build-down capacity Vs, and the flow rate of the gas flowing out from the build-down capacity Vs through the control valve 12 is measured by the supply pressure sensor 16. Measure based on the time variation of the output. The builddown capacity is set to, for example, 0.5 cc to 20 cc, and more preferably 1 cc to 5 cc.

By using a part of the flow path as the builddown capacity without providing the builddown tank, it is possible to realize miniaturization and cost reduction, and it is possible to obtain the advantage that the flow rate can be measured in a short time. Further, by setting the builddown capacity to be relatively small, the pressure drops relatively large even if the gas flows out at a small flow rate, so that the accuracy of the flow rate measurement at the time of a small flow rate can be improved.

However, as shown in FIG. 3, in the present embodiment, the supply pressure P0 reaches a predetermined measurement start pressure P0S instead of immediately starting the builddown flow rate measurement from the time t0 when the upstream on-off valve 4 is closed. The time t1 is confirmed, and the builddown flow rate measurement is performed from this time t1. The reason is that when the supply pressure P0 is larger than the measurement start pressure P0S, the HF gas may be clustered and an appropriate flow rate measurement may not be possible. Therefore, the measurement start pressure P0S confirmed that clustering does not occur is set in advance, and the build-down flow rate measurement is performed within a pressure range lower than the measurement start pressure P0S.

Therefore, as shown in steps S3 to S4 of FIG. 2, when the supply pressure P0 after closing the upstream on-off valve 4 is monitored and reaches the measurement start pressure P0S (YES in step S4), , The time (start time) t1 at that time is specified and stored in the memory (step S5).

It is also known that clustering of HF gas is likely to occur even when the gas temperature is low. Therefore, it is also preferable to measure the flow rate in a state where it is confirmed that the gas temperature is equal to or higher than a predetermined temperature. Further, the lower the concentration of the HF gas, the less likely it is that clustering will occur. Therefore, the flow rate may be measured in a state where the concentration of the HF gas is lowered by the diluting gas.

In the builddown in this embodiment, the builddown flow rate is measured under the condition that the HF gas does not cluster. As the measurement start pressure P0S, a different value may be used depending on the measured gas temperature, or a different value may be used depending on the gas concentration. As described above, it is considered that clustering is less likely to occur as the gas temperature is higher and the gas concentration is lower. Therefore, when the gas temperature is high and / or the gas concentration is low, the measurement start pressure P0S is higher. May be used.

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 separately provided so as to measure the temperature of the gas in the flow path (builddown capacity) between the upstream on-off valve 4 and the control valve 12. , The output of a temperature sensor (or temperature measuring unit) for measuring the temperature of the flow path between the control valve 12 and the throttle unit 14 provided in the general flow control device 10 may be substituted.

Then, under the condition that the HF gas does not cluster, the builddown time corresponding to the builddown pressure ΔP (here, the difference between the measurement start pressure P0S and the final pressure P0E) is shown in steps S6 to S8 of FIG. Δt is measured. Then, the flow rate can be measured based on the pressure drop rate ΔP / Δt (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 obtained by calculation based on, for example, the following formula.

In the above equation, T is the gas temperature (° C.), Vs is the builddown volume (that is, the volume of the flow path between the upstream on-off valve 4 and the control valve 12), and ΔP / Δt is as described above. It is a pressure drop rate obtained from the measurement of the supply pressure P0.

In the embodiment 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 measure the pressure drop rate ΔP / Δt. I'm looking for it. However, the pressure drop rate ΔP / Δt can be obtained in various modes as long as the operation is carried out under the condition that the HF gas does not cluster. For example, the pressure value P0 (t) of the supply pressure is obtained for each sampling cycle from the time t1 when the measurement start pressure P0S is reached, and until the predetermined time t2 (the time of t1 + Δt after the lapse of the predetermined time Δt from the start time t1) is reached. The slope of a straight line ΔP / Δt may be obtained from the pressure value P0 (t) obtained in 1) by the minimum square method.

As described above, even if the HF gas is clustered, the flow rate can be suitably determined by the build-down method. Further, by using the flow path between the upstream on-off valve 4 and the control valve 12 as a build-down capacity having a relatively small volume, it is possible to measure a small flow rate in a short time. The flow rate thus obtained can also be used for calibration of the flow rate control device 10.

To calibrate the pressure type flow control device 10, a predetermined flow rate of hydrogen fluoride is flowed by the flow rate control device 10, the upstream on-off valve 4 is closed, and the upstream on-off valve 4 is closed while the predetermined flow rate of hydrogen fluoride is flowing. After that, the supply pressure change after the supply pressure P0 measured by the supply pressure sensor 16 becomes equal to or lower than the predetermined measurement start pressure P0S (pressure confirmed that hydrogen fluoride gas does not cluster) is used. The flow rate of hydrogen fluoride gas (build-down flow rate) is calculated by calculation, and the flow rate calculation formula (for example, the value of K1 in Q = K1 and P1) of the flow rate control device 10 is updated based on the obtained build-down flow rate. Can be done by

Although the embodiments of the present invention have been described above, various modifications can be made. For example, although the flow rate measuring method by the build-down method based on the time change of the gas pressure has been described above, the measuring method may also take into consideration the change in the gas temperature before and after the outflow.

Specifically, first, after closing the upstream on-off valve 4, when the supply pressure P0 reaches the above-mentioned measurement start pressure P0S (time t1), the gas temperature T1 of the HF gas in the builddown capacity is measured. NS. At this time, the amount of substance (number of moles) n1 of the gas in the builddown capacity at the start of measurement is n1 = (P0S · Vs) / (RT1) from PV = nRT (ideal gas state equation). Can be represented. Here, R is the gas constant and Vs is the builddown volume.

After that, when the outflow of gas progresses under the condition of not clustering and the final pressure P0E is reached (time t2), the amount of substance n2 of the gas is n2 = (P0E) using the temperature T2 of the gas measured at this time. -Vs) / (R / T2) can be expressed.

Here, since the flow rate (mass flow rate) Q corresponds to the change in the amount of substance per hour, it can be expressed as Q = Δn / Δt = (n1-n2) / Δt. Therefore, the flow rate Q can be obtained based on the following equation by measuring the gas temperature at each time t1 and t2 and measuring the time Δt (time from time t1 to time t2).
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 obtain the flow rate based on the change in the gas temperature and the time change in the supply pressure P0 during the build-down process.

Further, in the above embodiment, the process of measuring the flow rate by the build-down method has been described, but after the flow rate measurement is completed, the upstream on-off valve 4 may be opened so that the gas flows again in a steady flow. good. Since the upstream on-off valve 4 can be opened instantaneously, the supply pressure P0 can be quickly recovered. Further, since the pressure type flow rate control device can control the flow rate of the gas flowing downstream of the throttle portion based on the upstream pressure P1 regardless of the slight fluctuation of the supply pressure P0, the gas flows to the downstream side of the throttle portion. It is also possible to measure the flow rate by the build-down method based on the above-mentioned change in the supply pressure P0 while keeping the flow rate at the controlled flow rate.

The flow rate measuring method according to the embodiment of the present invention is suitably used for measuring the flow rate of hydrogen fluoride gas used in a semiconductor manufacturing apparatus or the like.

2 Gas supply source 4 Upstream on-off valve 6 Downstream on-off valve 8 Process chamber 9 Vacuum pump 10 Flow control device 12 Control valve 14 Squeezing part 16 Supply pressure sensor 17 Upstream pressure sensor 18 Downstream pressure sensor 100 Gas system

Claims (7)

In a gas system having a flow rate control device having a control valve, an upstream on-off valve provided on the upstream side of the control valve, and a supply pressure sensor for measuring the supply pressure between the upstream on-off valve and the control valve. It is a method of measuring the flow rate of hydrogen fluoride gas, which is performed.
The flow rate measurement is performed in a state where the flow rate control device controls the flow of hydrogen fluoride gas at a set flow rate.
From the state where the upstream on-off valve and the control valve are opened, the step of closing the upstream on-off valve and
With the upstream on-off valve closed, the step of measuring the supply pressure using the supply pressure sensor, and
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 the predetermined measurement start pressure at which it is confirmed that the hydrogen fluoride gas does not cluster. Including the required steps
Flow rate measurement method. When the drop rate of 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 equation. The flow rate measuring method according to claim 1, wherein the flow rate Q is obtained.

The flow rate measuring method according to claim 1 or 2, wherein the measurement starting pressure is −0.03 to 0.05 MPaG. The flow rate measuring method according to any one of claims 1 to 3, 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 control device includes a throttle portion, a control valve on the upstream side of the throttle portion, an upstream pressure sensor for measuring the pressure between the control valve and the throttle portion, and a control circuit. The flow rate measuring method according to any one of claims 1 to 4. The flow rate measuring method according to any one of claims 1 to 5, wherein the flow rate control device includes a temperature measuring unit and further includes a step of determining the measurement start pressure using the temperature measured by the temperature measuring unit. .. It has a throttle portion, a control valve on the upstream side of the throttle portion, an upstream pressure sensor for measuring the pressure between the control valve and the throttle portion, and a control circuit, and is calculated from the output of the upstream pressure sensor. It is a calibration method of a pressure type flow control device configured to feedback control the control valve so that the set flow rate becomes the set flow rate.
The pressure type flow control device supplies hydrogen fluoride gas together with an upstream on-off valve provided on the upstream side of the control valve and a supply pressure sensor for measuring the supply pressure between the upstream on-off valve and the control valve. Consists of a gas system
A step of flowing a predetermined flow rate of hydrogen fluoride by the pressure type flow rate control device, and
The step of closing the upstream on-off valve while a predetermined flow rate of hydrogen fluoride is flowing,
After closing the upstream on-off valve, the supply pressure changes after the supply pressure measured by the supply pressure sensor becomes equal to or lower than the predetermined measurement start pressure at which it is confirmed that the hydrogen fluoride gas does not cluster. The step of calculating the flow rate of the hydrogen fluoride gas by calculation and
A method for calibrating a pressure type flow rate control device, which includes a step of changing the calculation formula so that the flow rate calculated from the pressure of the upstream pressure sensor becomes the flow rate obtained by the calculation.

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