Exhaust structure and method for flow rate control device, and gas supply system and gas supply method equipped with the same

Abstract

An exhaust structure for a flow rate control device 10 is provided with: the flow rate control device 10, which comprises a main body 11 in which a main body flow path 13 connecting a fluid inlet 13i to a fluid outlet 13o is formed, a control valve 12 provided in the main body flow path, an orifice part 14 provided downstream of the control valve, and a pressure sensor 16 for measuring the pressure between the control valve and the orifice part; a gas source 2 that supplies gas to the flow rate control device; and an exhaust path 4 branching at a branch point A on the gas supply path between the gas source and the flow rate control device. A first valve V1 is disposed in a gas supply path 3 upstream of the branch point, and a second valve V2 is disposed in the exhaust path. When the flow rate control device switches from controlling a first flow rate to controlling a second flow rate, the first valve V1 is closed and the second valve V2 is opened with the control valve 12 being open, thereby discharging the gas retained between the control valve and the orifice part via the exhaust path 4.

Description

[Technical Field]

[0001] The present invention relates to an exhaust structure and an exhaust method for a flow rate control device used in semiconductor manufacturing facilities, chemical plants, etc., and a gas supply system and a gas supply method using the same. [Background technology]

[0002] In semiconductor manufacturing equipment and chemical plants, various flow meters and flow control devices are used to control the flow rates of material gases, etching gases, etc. Among these, pressure-type flow control devices are widely used because they can control the mass flow rate of various fluids with high precision using a relatively simple mechanism that combines a control valve and a restrictor (for example, an orifice plate or critical flow nozzle).Unlike thermal-type flow control devices, pressure-type flow control devices have excellent flow control characteristics, allowing stable flow rate control even when the primary supply pressure, i.e., the pressure upstream of the control valve, fluctuates greatly.

[0003] Some pressure-type flow control devices adjust the flow rate by controlling the fluid pressure upstream of the throttle (hereinafter sometimes referred to as the upstream pressure P1). When the critical expansion condition (upstream pressure P1 / downstream pressure P2 ≧ approximately 2: in the case of argon gas) is met, the flow velocity of the gas through the throttle is fixed at the speed of sound, regardless of the magnitude of the downstream pressure P2 downstream of the throttle, and the mass flow rate of the gas flowing downstream of the throttle is proportional to the upstream pressure P1. Therefore, by appropriately controlling the upstream pressure P1 using a control valve installed upstream of the throttle, it is possible to precisely control the flow rate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2015 / 064035 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-231460 Summary of the Invention [Problem to be solved by the invention]

[0005] However, because pressure-type flow rate control devices are configured to allow gas to flow through the fine holes in the throttle section, even after the control valve's opening is reduced to reduce the flow rate, the pressure of the residual gas between the control valve and the throttle section does not decrease suddenly, and it may take a relatively long time, for example, about one second, for the residual gas to flow out. For this reason, pressure-type flow rate control devices have had the challenge of having to discharge the residual gas as quickly as possible to improve responsiveness when reducing the flow rate, that is, when changing the controlled flow rate from a high flow rate to a low flow rate.

[0006] In response to this, Patent Document 1 discloses a technique for more quickly reducing the gas pressure between the control valve and the throttle unit when performing so-called flow rate step-down control, which reduces the gas supply amount in a stepwise manner. In the pressure-type flow rate control device described in Patent Document 1, an exhaust path is connected as a branch path between the control valve and the throttle unit, and when performing a flow rate step-down, an exhaust valve provided in the exhaust path is opened for a short period of time to more quickly reduce the upstream pressure P1.

[0007] However, the method described in Patent Document 1 requires the provision of an exhaust path and an exhaust valve between the control valve and the throttle section of the pressure type flow control device, which inevitably leads to a problem that the internal structure of the pressure type flow control device tends to become complicated. Also, with the method described in Patent Document 1, it is not easy to provide an additional exhaust function by modifying an existing pressure type flow control device, so a redesigned pressure type flow control device was often used.

[0008] The present invention has been made in consideration of the above-mentioned problems, and its main object is to provide an exhaust structure and exhaust method for a flow control device that can improve the responsiveness of flow rate step-down while utilizing the configuration of an existing flow control device, as well as a gas supply system and gas supply method using the same. [Means for solving the problem]

[0009] An exhaust structure of a flow control device according to an embodiment of the present invention comprises: a main body forming a main flow path connecting a fluid inlet and a fluid outlet; a control valve provided on the main flow path; a throttling section provided downstream of the control valve; and a flow control device having a pressure sensor for measuring the pressure of the main flow path between the control valve and the throttling section; a gas source for supplying gas to the flow control device; and an exhaust path branching at a branch point on the gas supply path between the gas source and the flow control device. A first valve is provided in the gas supply path upstream of the branch point, and a second valve is provided in the exhaust path. The control unit has a controller for controlling the operation of the first valve, the second valve, and the control valve. When changing from a state in which a first flow rate is controlled to a state in which a second flow rate is controlled, the controller closes the first valve and opens the second valve with the control valve open, thereby discharging the gas accumulated between the control valve and the throttling section from the exhaust path.

[0010] In one embodiment, when the flow rate is changed from the first flow rate to the second flow rate, before exhausting the gas between the control valve and the throttle section, the first valve is closed, the second valve is opened, and the control valve is temporarily closed, thereby exhausting the gas between the first valve and the control valve in advance.

[0011] In one embodiment, the exhaust structure of the above-mentioned flow control device further includes a supply pressure sensor that measures the pressure in the flow path between the control valve and the first valve, and is configured to control the opening and closing operation of the control valve based on the output of the supply pressure sensor when changing the flow rate from the first flow rate to the second flow rate.

[0012] In one embodiment, the exhaust structure of the flow control device further includes a relaxation portion disposed between the control valve and the branch point.

[0013] In one embodiment, the device includes a plurality of gas supply paths and a corresponding plurality of flow rate control devices, and the first valve is provided in each of the plurality of gas supply paths, while the exhaust path having the second valve is commonly connected to the plurality of gas supply paths.

[0014] In one embodiment, the system includes a plurality of the gas supply paths and a corresponding plurality of the flow rate control devices, the plurality of gas supply paths and the exhaust path are formed within a single flow path block, and the first valve and the second valve are fixed to the single flow path block.

[0015] A gas supply system according to an embodiment of the present invention includes an exhaust structure of a flow control device described above, and is configured to exhaust the gas between the control valve and the throttling section until a pressure corresponding to a second flow rate is reached, then close the second valve, open the first valve and the control valve, and control the flow rate at the second flow rate.

[0016] An exhaust method for a flow control device according to an embodiment of the present invention is a method for exhausting a flow control device that uses an exhaust structure for a flow control device comprising: a main body forming a main body flow path that connects a fluid inlet and a fluid outlet, a control valve provided on the main body flow path, a throttling section provided downstream of the control valve, and a pressure sensor that measures the pressure of the main body flow path between the control valve and the throttling section; a gas source that supplies gas to the flow control device; and an exhaust path that branches off at a branch point on the gas flow path between the gas source and the flow control device, wherein a first valve is provided in the gas supply path upstream of the branch point and a second valve is provided in the exhaust path, and the method comprises the steps of: outputting a signal to change from a state in which a first flow rate is controlled to a state in which a second flow rate is controlled; closing the first valve and opening the second valve while the control valve is open; and exhausting the fluid that has accumulated between the control valve and the throttling section to the exhaust device.

[0017] In one embodiment, the exhaust method for the above-mentioned flow rate control device includes, after the step of outputting a signal to change from controlling the first flow rate to controlling the second flow rate, a step of closing the first valve, opening the second valve, and temporarily closing the control valve before exhausting the gas between the control valve and the throttling section, thereby exhausting the gas between the first valve and the control valve in advance and then opening the control valve.

[0018] A gas supply method according to an embodiment of the present invention includes the above-described exhaust method for a flow control device, and includes a step of closing the second valve, opening the first valve and the control valve, and controlling at a second flow rate after a step of exhausting the fluid accumulated between the control valve and the throttling portion to the exhaust device. [Effects of the Invention]

[0019] According to a gas supply system using the exhaust structure of a flow rate control device and a gas supply method using the exhaust method according to an embodiment of the present invention, it is possible to improve responsiveness when a flow rate step-down occurs. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a schematic diagram showing a gas supply system using an exhaust structure of a flow rate control device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram illustrating an example of the configuration of a flow rate control device provided in the gas supply system. [Figure 3] FIG. 10 is a schematic diagram showing a gas supply system using an exhaust structure of a flow rate control device according to another embodiment of the present invention. [Figure 4] 10A to 10D are diagrams showing the valve opening and closing operations when performing a flow rate step-down operation according to this embodiment, with (a) to (d) showing sequential steps. [Figure 5] 10 is a graph showing changes over time in upstream pressure P1 and control valve opening CV when a flow rate step-down operation according to the present embodiment is performed. [Figure 6]FIG. 10 is a diagram showing an example of each signal when a flow rate is stepped down. [Figure 7] 5 is a flowchart showing a gas supply operation including an exhaust operation of the flow rate control device according to the embodiment of the present invention. [Figure 8] FIG. 10 is a diagram showing an embodiment in which one common exhaust path is provided for a plurality of gas supply lines. [Figure 9] 1A and 1B are diagrams showing an embodiment in which gas supply paths and exhaust paths for a plurality of gas supply lines are formed within a single metal block, where (a) is a cross-sectional view and (b) is a plan view. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings, but the present invention is not limited to the embodiments described below.

[0022] 1 shows a gas supply system 100 according to this embodiment. The gas supply system 100 can supply gas G from a gas source 1 to a process chamber 24 via a pressure-type flow controller 10 provided in a gas supply path 3. A shutoff valve 22 is provided downstream of the pressure-type flow controller 10, which can stop the gas supply to the process chamber 24. A vacuum pump 26 is also connected to the process chamber 24, which can evacuate the process chamber 24 and the flow path during gas supply. The shutoff valve 22 can be, for example, an air-operated valve (AOV) or a solenoid valve, and may be built into the pressure-type flow controller 10.

[0023] The pressure type flow control device 10 of this embodiment includes a throttle section 14 provided in the flow path, a control valve 12 provided upstream of the throttle section 14, a pressure sensor 16 that detects an upstream pressure P1 between the throttle section 14 and the control valve 12, and a temperature sensor 18 that detects the temperature between the throttle section 14 and the control valve 12. The pressure type flow control device 10 may further include a pressure sensor (not shown) that measures a downstream pressure P2 downstream of the throttle section 14. The pressure sensor that measures the downstream pressure P2 may be provided integrally with the pressure type flow control device 10, or may be provided separately from the pressure type flow control device 10.

[0024] The pressure sensor 16 may be, for example, a semiconductor piezo-resistance diffusion pressure sensor or a capacitance manometer, and the temperature sensor 18 may be, for example, a resistance temperature detector or a thermistor. The control valve 12 may be, for example, a piezo-element-driven valve (hereinafter sometimes referred to as a piezo valve) in which a metal diaphragm valve element is opened and closed by a piezo actuator. A piezo valve is a valve (for example, a proportional valve) that can be opened to any desired degree by adjusting the drive voltage applied to the piezo element.

[0025] Furthermore, for example, an orifice plate or a sonic nozzle is used as the restrictor 14, and the opening diameter of the restrictor 14 is set to, for example, 10 to 2000 μm. As the restrictor 14, any flow resistor, that is, one that imposes restrictions on the flow, pressure, etc. of the fluid, is used.

[0026] 2 shows an exemplary configuration of a pressure-type flow control device 10. The pressure-type flow control device 10 is configured using a main body 11 in which a main body flow passage 13 is formed, which connects a fluid inlet 13i and a fluid outlet 13o. The main body 11 is formed from a metal block made of stainless steel, for example, and the main body flow passage 13 is formed by combining elongated holes drilled in the metal block. Main body flow passage 13A control valve 12 and a throttle section 14 are provided on top of the main body 11. A pressure sensor 16 is also attached to the main body 11 to measure the pressure in the main body flow path 13 between the control valve 12 and the throttle section 14. Note that although the temperature sensor 18 and other components shown in FIG. 1 are omitted in FIG. 2, the temperature sensor 18 is disposed, for example, in a bottomed micropore drilled to the vicinity of the main body flow path 13.

[0027] 1, the pressure type flow rate control device 10 also includes a control circuit 20 connected to the pressure sensor 16, the temperature sensor 18, and the control valve 12. The control circuit 20 incorporates a CPU, memory, A / D converter, etc., which are provided on a circuit board, and includes a computer program for executing the operations described below, and is realized by a combination of hardware and software.

[0028] When gas is supplied to the process chamber 24, the control circuit 20 uses the output of the pressure sensor 16 to determine the flow rate and controls the control valve 12 so that the flow rate passing through the throttle section 14 becomes the set flow rate. More specifically, when the critical expansion condition (P1 / P2≧approximately 2: in the case of argon gas) is satisfied, the calculated flow rate is determined from the output of the pressure sensor 16 according to the relationship of flow rate Q=K1P1 (K1 is a proportionality coefficient that depends on the type of fluid and the fluid temperature), and the control valve 12 is feedback-controlled so that the calculated flow rate becomes the same as the set flow rate. Furthermore, if a pressure sensor (not shown) that measures the downstream pressure P2 is provided, the flow rate Q=K2P2 can be calculated even under non-critical expansion conditions. m (P1-P2) n (K2 is a proportionality coefficient that depends on the type of fluid and the fluid temperature, and the exponents m and n are values ​​derived from the actual flow rate.) The flow rate determined by the calculation may be displayed as a flow rate output value on the display unit of the external control device.

[0029] Furthermore, in the gas supply system 100 of this embodiment, a gas supply path 3 having a first valve (gas supply valve) V1 is provided upstream of the pressure-type flow control device 10 between the gas source 1 and the pressure-type flow control device 10. An exhaust path 4 having a second valve (exhaust valve) V2 is connected to a branch point A between the first valve V1 provided on the gas supply path 3 and the pressure-type flow control device 10. The exhaust path 4 is connected to an exhaust device 2, and gas exhaust E from the gas supply path 3 can be performed by opening the second valve V2. As the first valve V1 and the second valve V2, on-off valves with good responsiveness, such as AOVs (air-operated valves), solenoid valves, or motor-operated valves, are preferably used, but valves with adjustable opening, such as piezo valves, can also be used.

[0030] Furthermore, a supply pressure sensor 28 for measuring the supply pressure P0 is provided in the gas supply path 3 between the first valve V1 and the pressure-type flow control device 10. The supply pressure sensor 28 is used to confirm whether the supply pressure P0 is maintained at a sufficiently high value during normal gas supply, and is also used to monitor the supply pressure P0 during a flow rate step-down, which will be described later. As with the pressure sensor 16, the supply pressure sensor 28 may be, for example, a semiconductor piezo-resistance diffusion pressure sensor or a capacitance manometer, and may be incorporated into the pressure-type flow control device 10, unlike the embodiment shown in FIG. 1.

[0031] FIG. 3 shows a gas supply system 100a according to another embodiment. If gas between the gas supply path 3, the control valve 12, and the throttle unit 14 is suddenly exhausted through the exhaust path 4, the pressure P1 downstream of the control valve 12 will suddenly fluctuate, resulting in unstable control and potentially unstable flow rate control. To prevent this situation, as shown in FIG. 3, a pressure relief unit 29 may be provided between the pressure-type flow control device 10 or the control valve 12 and the branch point A to moderate (restrict) the gas flow during exhaust to some extent. This suppresses sudden pressure fluctuations in the upstream pressure P1, enabling smooth flow rate control. The pressure relief unit 29 may have a larger opening area than the orifice or sonic nozzle used in the throttle unit 14.

[0032] The operation of the gas supply system 100 when performing a flow rate step-down will now be described with reference to FIGS.

[0033] 4A to 4D are diagrams sequentially showing the opening and closing operations of the first valve V1, the second valve V2, and the control valve 12 when the flow rate is stepped down from the first flow rate QH to the lower second flow rate QL. In FIG. 4, the open valves indicate that the valves are open, and the solid black valves indicate that the valves are closed. For simplicity, the supply pressure sensor 28, the temperature sensor 18, and the control circuit 20 shown in FIG. 1 are omitted from FIG. 4.

[0034] It should be noted that some or all of the components of the control circuit 20 may be provided outside the pressure type flow control device 10. The control circuit 20 that controls the control valve 12 may be provided inside the pressure type flow control device 10, and the control of the first valve V1 and the second valve V2 may be performed by another external control circuit, or everything, including the control of the control valve 12 of the pressure type flow control device 10, may be controlled externally. It should be noted that a communication function or a linking function may be provided so that the control circuit 20 built into the pressure type flow control device 10 can link with control circuits that perform other controls, and the entire system may be controlled as a control unit including the control circuit 20 and other control circuits.

[0035] 5 shows the time change in the upstream pressure P1 and the time change in the opening degree CV of the control valve 12, corresponding to each state shown in Figures 4(a) to (d). Here, as described above, in the pressure type flow rate control device 10, the upstream pressure P1 is proportional to the flow rate, and therefore can be considered to indicate the flow rate Q.

[0036] First, as shown in section (a) of Figures 4 and 5, second valve V2 is closed, and first valve V1 and control valve 12 are open, allowing gas to flow at a first flow rate QH (e.g., 100% flow rate). The flow rate can be expressed as a ratio, with the rated flow rate being 100%. At this time, the upstream pressure P1 also indicates a high value corresponding to the first flow rate QH. The opening CV of control valve 12 is also opened to a corresponding large opening.

[0037] Furthermore, while the gas is flowing at the first flow rate, the supply pressure P0 on the upstream side of the control valve 12 is maintained at a value sufficiently greater than the upstream pressure P1. On the other hand, the downstream pressure P2 on the downstream side of the throttle unit 14 is typically maintained at a vacuum pressure (for example, 100 Torr or less), and the gas is supplied to the process chamber 24 at the first flow rate.

[0038] Next, at time t1 shown in Figure 5, when a command is issued to change from the first flow rate QH to a lower second flow rate QL, the first valve V1 is closed, the gas supply is stopped, and the second valve V2 is opened to start exhaust E, as shown in Figure 4(b) and section (b) of Figure 5.

[0039] In this embodiment, the control valve 12 is also closed when the flow rate step-down begins. That is, before exhausting the gas between the control valve 12 and the throttle unit 14, the control valve 12 is temporarily closed to pre-exhaust the gas between the first valve V1 and the control valve 12. In this way, the flow paths between the first valve V1, the second valve V2, and the control valve 12 are exhausted from the exhaust path 4, resulting in a rapid drop in supply pressure P0. On the other hand, even when the control valve 12 is closed, residual gas between the control valve 12 and the throttle unit 14 flows downstream through the throttle unit 14, and the upstream pressure P1 also drops accordingly.

[0040] As shown in Fig. 5, the opening degree CV of the control valve 12 during pre-exhaust may be decreased linearly. Also, before opening the second valve V2 for pre-exhaust, all valves, i.e., the first valve V1, the second valve V2, and the control valve 12, may be closed, and then the second valve V2 may be opened.

[0041] Then, when the supply pressure P0 has become sufficiently low, the control valve 12 is opened at time t2 shown in Fig. 5. As a result, as shown in Fig. 4(c) and section (c) of Fig. 5, the residual gas between the control valve 12 and the throttle unit 14 not only flows downstream through the throttle unit 14 but is also exhausted from the exhaust path 4 via the control valve 12. Therefore, the upstream pressure P1 decreases more rapidly, and at the same time, the flow rate of the gas flowing downstream can also be reduced more rapidly.

[0042] In order to effectively promote the reduction of the upstream pressure P1 using the exhaust path 4 in this way, it is possible to widen the control valve 12 during exhaust, and it is preferable to make the opening (flow path cross-sectional area) of the control valve 12 at least larger than the cross-sectional opening area of ​​the throttle section 14. However, if the control valve 12 is opened too wide, it may take time to adjust the opening of the control valve 12 when gas is subsequently flowed at the second flow rate QL, which may cause undershoot. Taking these factors into consideration, the opening of the control valve 12 during the exhaust operation may be set arbitrarily depending on the magnitude of the first flow rate and the second flow rate. For example, ramp function control may be employed in which the opening gradually increases linearly as shown in section (c) of FIG. 5.

[0043] Next, as shown in Fig. 5, at time t3, when it is confirmed that the upstream pressure P1 has dropped sufficiently, the operation is switched to normal operation in which the gas flows at the second flow rate QL. That is, as shown in Fig. 4(d), the first valve V1 is opened to resume the supply of gas from the gas source 2, and the second valve V2 is closed to close the exhaust path 4. As a result, the supply pressure P0 on the upstream side of the control valve 12 is rapidly restored.

[0044] Furthermore, the control valve 12 shifts to feedback control based on the output of the pressure sensor 16, and the opening is adjusted so that the upstream pressure P1 is maintained at a pressure corresponding to the second flow rate QL. As a result, as shown in section (d) of Figure 5, it is possible to continue to flow gas at the second flow rate QL downstream of the throttle unit 14 even after time t3. In the above-described flow rate step-down, the upstream pressure P1 can be reduced more quickly using the exhaust path 4, thereby improving its responsiveness.

[0045] FIG. 6 is a graph showing an example of a flow control operation sequence including a flow step-down from a first flow rate (here, 100% flow rate) to a second flow rate (here, 30% flow rate). In FIG. 6, V1 and V2 indicate the opening and closing operations of the first valve V1 and the second valve V2, and P0 indicates the supply pressure P0 upstream of the control valve. Furthermore, IN and OUT indicate the input signal (set flow rate signal) and output signal (calculated flow rate signal based on the measured upstream pressure P1) to the pressure-type flow control device 10. Furthermore, CVV indicates the piezo drive voltage applied to the normally closed piezo valve that constitutes the control valve 12, and P1 indicates the upstream pressure P1 between the control valve 12 and the throttle section 14.

[0046] 6, the control valve 12 is closed with the piezo drive voltage CVV=0V, and at time t0, from a 0% flow rate control state where gas supply is stopped, a signal to flow gas at 100% flow rate is input to the pressure-type flow control device 10. At this time, the first valve V1 is kept open, the second valve V2 is kept closed, and the supply pressure P0 is kept at a sufficiently high pressure (here, 250 kPa gauge pressure or higher).

[0047] Meanwhile, an initial voltage is applied to the piezo drive voltage CVV, and here, the piezo drive voltage CVV also gradually increases in accordance with ramp function control or first-order lag control of the target upstream pressure P1. By performing such control, it is possible to suppress the occurrence of flow rate overshoot due to the sudden opening of the control valve 12. Note that other methods, such as feedback control from the beginning, may also be used as a control method for the control valve 12.

[0048] Thereafter, through feedback control of the control valve 12, an input signal IN is given to the pressure type flow control device 10 to reduce the flow rate from a state in which the upstream pressure P1 is maintained at a constant pressure (here, 300 kPa absolute pressure) and gas is flowing at 100% flow rate to 30% flow rate at time t1.

[0049] In this example, first valve V1 is closed and second valve V2 is opened, reducing supply pressure P0. Piezo drive voltage CVV is momentarily set to 0 to close control valve 12, momentarily evacuating any gas remaining in gas supply path 3. Then, the voltage is restored to its original level, opening control valve 12, and gradually decreasing its opening. Because control valve 12 is open at this time, residual gas between control valve 12 and throttle section 14 is rapidly evacuated via exhaust path 4 via control valve 12 and second valve V2.

[0050] Then, at time t3, when the upstream pressure P1 reaches a pressure corresponding to the second flow rate (here, 90 kPa absolute pressure), the control valve 12 is returned to feedback control to maintain the pressure corresponding to the second flow rate. At the same time, the first valve V1 is opened and the second valve V2 is closed, so that the supply pressure P0 is restored to a sufficiently high pressure, and the gas can then continue to flow at the second flow rate.

[0051] 7 is a flowchart showing an example of flow rate step-down control. First, as shown in step S1, with the first valve V1, which is a gas supply valve, open and the second valve V2, which is an exhaust valve, closed, the control valve opening CV is adjusted to an opening corresponding to the first flow rate, and gas flows downstream of the throttle unit 14 at the first flow rate.

[0052] When a command to change the flow rate to a second flow rate that is smaller than the first flow rate and not zero is received as the set flow rate signal, the first valve V1 is closed and the second valve V2 is opened to perform an exhaust operation, as shown in step S2. Here, the control valve opening CV is also closed, and pre-exhaust of the upstream flow path between the first valve V1 and the control valve 12 is performed. Note that the first valve V1 may be closed for the final short period of time during which gas is flowing at the first flow rate. As long as the upstream pressure P1 between the control valve 12 and the throttle unit 14 can be maintained at the desired value, it is also possible to supply gas at the first flow rate just before stepping down to the second flow rate by closing the first valve V1 and reducing the supply pressure P0.

[0053] Next, in step S3, it is determined whether the supply pressure P0 has dropped sufficiently by comparing it with the upstream pressure P1. If the supply pressure P0 is lower than the upstream pressure P1, it can be confirmed that the situation is sufficient to exhaust the residual gas upstream by opening the control valve 12. In this way, by controlling the opening and closing operation of the control valve 12 during the flow rate step-down based on the output of the supply pressure sensor 28, exhaust to the upstream side can be more reliably and effectively performed.

[0054] However, step S3 is not necessarily required. In cases where it is confirmed that the supply pressure P0 drops rapidly in a short time due to pre-evacuation, such as when the flow path volume between the first valve V1 and the control valve 12 is relatively small, the control valve 12 may be controlled to close for a predetermined short period of time without performing a pressure comparison. Also, the supply pressure P0 does not necessarily need to fall below the upstream pressure P1, and it may be determined whether or not pre-evacuation is complete based on whether the supply pressure P0 has dropped to a predetermined pressure. Furthermore, steps S2 and S3, in which the control valve 12 is temporarily closed to perform pre-evacuation, may be omitted altogether.

[0055] Next, as shown in step S4, the control valve 12 is opened to exhaust residual gas between the control valve 12 and the throttle unit 14 via the upstream exhaust path 4. This allows the upstream pressure P1 and the flow rate of gas flowing downstream to be rapidly reduced. In step S4, the control valve 12 may be opened to a predetermined opening in one go, or may be opened gradually over time. Furthermore, feedback control based on the upstream pressure P1 may be continuously performed on the control valve 12. This is because, even when residual gas is being exhausted upstream, the control valve 12 is likely to remain open until the measured upstream pressure P1 decreases to a pressure value corresponding to the second flow rate.

[0056] Then, as shown in step S5, it is determined whether the upstream pressure P1 has decreased to the upstream pressure threshold Pth corresponding to the second flow rate. This threshold Pth may be the value of the upstream pressure P1 corresponding to the second flow rate itself, or may be a threshold set to a different value. If the threshold Pth is set smaller, the upstream exhaust time becomes longer, and the upstream pressure P1 can be decreased more quickly. However, when gas is subsequently flowed at the second flow rate, an undershoot may occur due to insufficient supply pressure P0. Therefore, the threshold Pth may be set to a value somewhat higher than the upstream pressure P1 corresponding to the second flow rate.

[0057] Next, when it is confirmed that the upstream pressure P1 has dropped sufficiently, the first valve V1 is opened and the second valve V2 is closed, as shown in step S6, to restore the supply pressure P0 and prepare the gas supply on the upstream side, and then the control valve opening CV is controlled to an opening corresponding to the second flow rate. Specifically, by feedback-controlling the control valve 12 based on the output of the pressure sensor 16 that measures the upstream pressure P1, gas can be made to flow at the second flow rate downstream of the throttle unit 14.

[0058] By performing a flow rate step-down using the exhaust path 4 provided upstream in the above manner, it is possible to accelerate the decrease in the upstream pressure P1 and improve responsiveness. Furthermore, since it is relatively easy to add the exhaust path 4 to the gas supply path 3 upstream of the pressure type flow control device 10 by modifying it, it is possible to use the existing pressure type flow control device 10 as is and additionally provide the effect of improving responsiveness.

[0059] Gas supply systems according to other embodiments will be described below. Fig. 8 shows an embodiment in which a single common exhaust path 4 is provided for multiple gas supply lines L1 to L3. In the gas supply system shown in Fig. 8, a pressure-type flow control device 10 is provided in the gas supply path 3 of each gas supply line, enabling different types of gas to be supplied to a process chamber at desired flow rates. Note that while gas is being supplied through one gas supply line, the first valve V1 and the control valve 12 are normally closed on the other gas supply lines.

[0060] On the other hand, the exhaust path 4 is commonly connected to a branch point between the first valve V1 and the control valve 12 in each gas supply path 3. The exhaust path 4 can be used to exhaust the gas upstream of any of the gas supply lines L1 to L3 when the flow rate is stepped down, thereby improving responsiveness.

[0061] By providing a common exhaust path 4 in this way, only one exhaust device 2, one exhaust path 4, and one second valve V2 are required, which simplifies the system configuration and reduces costs. Also, even if a supply pressure sensor (not shown) is provided, it may be sufficient to provide only one sensor in the exhaust path 4 or one of the gas supply paths 3.

[0062] 1 can be used as the exhaust device 2, instead of providing a separate exhaust device 2. In this case, the gas supply lines L1 to L3 are connected to the same process chamber 24, and the common exhaust path 4 for exhausting from the upstream side is connected to an exhaust system including the vacuum pump 26 connected to this process chamber 24. Furthermore, it goes without saying that the vacuum pump 26 connected to the chamber can be used as the exhaust device 2 not only in the case of having multiple gas supply lines L1 to L3 as in this embodiment, but also in the single gas supply system shown in FIG.

[0063] 9(a) and (b) show an embodiment in which gas supply paths 3 and exhaust paths 4 for multiple gas supply lines L1 to L3 are provided in one flow path block 5. The flow path block corresponding to multiple gas supply lines is disclosed in, for example, Patent Document 2, and is used to form an integrated gas supply system.

[0064] In this embodiment, each flow path is formed by drilling holes using a drill in a block made of metal (for example, stainless steel) that serves as the flow path block 5. Note that although U-shaped flow paths are shown in Fig. 9(a), it is not easy to form such flow paths by drilling holes. In practice, each flow path can be easily formed by sealing the openings of holes drilled from the end face of the block with sealing plugs, or by drilling V-shaped holes that extend diagonally downward from the top face.

[0065] 9(a) and 9(b), a first valve V1 and a second valve V2 are fixed to the flow path block 5, and the gas supply path 3 and the exhaust path 4 connected at the branch point A can be formed compactly for multiple lines. By providing such a flow path block 5 in the upstream stage of a flow path block provided with a flow control device, it is possible to supply gas G through multiple lines without any problems while also exhausting gas E from the upstream side, and it is possible to improve the responsiveness of the flow rate step-down in each line.

[0066] Although the above describes an embodiment of the present invention, various modifications are possible. For example, the first flow rate QH is set to 100%, but this is not limiting. Similarly, the second flow rate QL is not limited to 30%. The first flow rate QH and the second flow rate QL may be set to any value as long as residual pressure is generated when the flow rate setting is changed from the first flow rate QH to the second flow rate QL. Furthermore, while FIGS. 9(a) and 9(b) illustrate an embodiment in which multiple exhaust paths 4 and second valves V2 corresponding to multiple gas supply lines L1 to L3 are provided in one flow path block 5, it is also possible to provide a single common exhaust path 4 and a single common second valve V2, as shown in FIG. 8, in one flow path block 5 by forming an exhaust path 4 extending in the width direction and commonly connected to each gas supply path 3. [Industrial Applicability]

[0067] The exhaust structure and exhaust method of the flow rate control device according to the embodiment of the present invention, and the gas supply system and gas supply method using them, are used for gas supply in, for example, semiconductor manufacturing equipment. [Explanation of symbols]

[0068] 1. Gas Source 2. Exhaust system 3 Gas supply line 4 Exhaust duct 5 Flow path block 10 Pressure-type flow control device 11 Main unit 12 Control valve 13 Main body flow path 13i fluid inlet 13o fluid outlet 14. Constriction section 16 Pressure Sensor 18 Temperature Sensor 20 Control circuit (control section) 22 Shut-off valve 24 process chambers 26 Vacuum pump 28 Supply pressure sensor 29 Relaxation part V1 First valve (gas supply valve) V2 Second valve (exhaust valve) 100 Gas Supply System

Claims

1. a flow control device including a main body forming a main body flow path that communicates a fluid inlet and a fluid outlet, a control valve provided on the main body flow path, a throttle portion provided downstream of the control valve, and a pressure sensor that measures the pressure of the main body flow path between the control valve and the throttle portion; a gas source that supplies gas to the flow control device; an exhaust path branching at a branch point on a gas supply path between the gas source and the flow rate control device; a first valve is disposed in the gas supply path upstream of the branch point, and a second valve is disposed in the exhaust path; a control unit that controls operations of the first valve, the second valve, and the control valve; when the control unit changes from controlling a first flow rate to controlling a second flow rate, the control unit closes the first valve and opens the second valve while the control valve is open, thereby discharging the gas accumulated between the control valve and the throttle unit from the exhaust path; An exhaust structure of a flow control device, comprising a plurality of the gas supply paths and a corresponding plurality of the flow control devices, wherein the first valve is provided in each of the plurality of gas supply paths, while the exhaust path having the second valve is commonly connected to the plurality of gas supply paths, and only one exhaust path and one second valve are provided.

2. 2. The exhaust structure of a flow control device according to claim 1, wherein, when changing the flow rate from the first flow rate to the second flow rate, before exhausting the gas between the control valve and the throttle section, the first valve is closed, the second valve is opened, and the control valve is temporarily closed, thereby exhausting the gas between the first valve and the control valve in advance.

3. a supply pressure sensor for measuring the pressure in a flow path between the control valve and the first valve; 3. The exhaust structure of a flow rate control device according to claim 1, wherein when the flow rate is changed from the first flow rate to the second flow rate, the opening and closing operation of the control valve is controlled based on the output of the supply pressure sensor.

4. The exhaust structure of a flow rate control device according to claim 1 or 2, further comprising a buffer portion disposed between the control valve and the branch point.

5. 3. The exhaust structure of a flow control device according to claim 1, wherein the plurality of gas supply paths and the exhaust path are formed within a single flow path block, and the first valve and the second valve are fixed to the single flow path block.

6. 3. A gas supply system including the exhaust structure of the flow control device according to claim 1, wherein the gas between the control valve and the throttling portion is exhausted until a pressure corresponding to a second flow rate is reached, and then the second valve is closed and the first valve and the control valve are opened to control the flow rate at the second flow rate.

7. a flow control device including a main body forming a main body flow path that communicates a fluid inlet and a fluid outlet, a control valve provided on the main body flow path, a throttle portion provided downstream of the control valve, and a pressure sensor that measures the pressure of the main body flow path between the control valve and the throttle portion; a gas source that supplies gas to the flow control device; an exhaust path branching at a branch point on the gas flow path between the gas source and the flow rate control device; an exhaust method for a flow control device, which is performed using an exhaust structure of a flow control device, the exhaust structure being configured by arranging a first valve in a gas flow path upstream of the branch point and arranging a second valve in the exhaust path, and comprising a plurality of the gas supply paths and a corresponding plurality of the flow control devices, wherein the first valve is provided in each of the plurality of gas supply paths, while the exhaust path having the second valve is commonly connected to the plurality of gas supply paths, and only one exhaust path and one second valve are provided; outputting a signal to change from controlling the first flow rate to controlling the second flow rate; closing the first valve and opening the second valve while the control valve is open; exhausting gas accumulated between the control valve and the throttle portion; A method for exhausting a flow control device, comprising:

8. 8. The exhaust method for a flow control device according to claim 7, further comprising the step of: after the step of outputting a signal to change from controlling the first flow rate to controlling the second flow rate, before exhausting the gas between the control valve and the throttling portion, closing the first valve, opening the second valve, and temporarily closing the control valve, thereby exhausting the gas between the first valve and the control valve in advance, and then opening the control valve.

9. 9. A gas supply method including the exhaust method of a flow rate control device according to claim 7 or 8, comprising, after a step of exhausting gas accumulated between the control valve and a throttling portion, a step of closing the second valve, opening the first valve and the control valve, and controlling at a second flow rate.

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