Flow rate control device

Abstract

A flow rate control device (10) comprises: a pressure control valve (12) that can be opened freely; a flow rate control valve (14) provided on the downstream side of the pressure control valve; a throttle section (16) provided between the pressure control valve and the flow rate control valve; an upstream pressure sensor (18) that measures the pressure between the pressure control valve and the throttle section; and a control circuit (13). The pressure control valve (12) is configured so that feedback control is performed on the basis of the output of the upstream pressure sensor and a pulse gas is supplied by opening / closing control of the flow rate control valve (14). The control circuit (13) is configured so as to change the feedback control of the pressure control valve (12) in accordance with the opening / closing state of the flow rate control valve (14), or to perform additional control of the feedback control of the pressure control valve (12) when switching the opening / closing of the flow rate control valve (14).

Description

Flow Control Device

[0001] The present invention relates to a flow rate control device, and more particularly to a flow rate control device configured to be able to supply gas in a pulsed manner.

[0002] In gas supply systems for semiconductor manufacturing equipment and chemical plants, various types of flow rate control devices are used to control the flow of material gases, etching gases, etc. Among these, pressure-type flow rate control devices are widely used because they can control the flow rate of various fluids with high precision using a relatively simple mechanism that combines a control valve and a restrictor (e.g., an orifice plate) (see, for example, Patent Document 1).

[0003] A pressure-type flow rate control device is configured to control the fluid pressure upstream of a throttle section (hereinafter sometimes referred to as upstream pressure P1 or control pressure P1) by adjusting the opening of a control valve, and to cause fluid to flow downstream of the throttle section at a flow rate corresponding to the upstream pressure P1, or the upstream pressure P1 and downstream pressure P2 (fluid pressure downstream of the throttle section). Pressure-type flow rate control devices have excellent flow rate control characteristics, allowing stable flow rate control even in situations where the primary supply pressure, i.e., the fluid pressure upstream of the control valve, fluctuates greatly.

[0004] Furthermore, in recent years, there has been a demand for flow control devices to be applied to, for example, ALD (Atomic Layer Deposition), ALE (Atomic Layer Etching), etc. In such applications, it is required to open and close a control valve using a high-speed (very short-period) pulse-shaped control signal to quickly switch the flow rate within a short period of time.

[0005] The applicant has disclosed a flow rate control device that can also accommodate pulsed gas supply in Patent Document 2. The flow rate control device described in Patent Document 2 is configured such that when controlling a continuous flow, the pressure upstream of the throttle section is controlled by a pressure control valve to control the flow rate in the same way as a pressure-type flow rate control device, and when controlling an intermittent, pulsating flow, the flow rate is controlled by opening and closing a flow rate control valve provided downstream of the throttle section.

[0006] JP 2004-138425 A International Publication No. 2019 / 107215

[0007] However, the inventors of the present application have found that when opening and closing a flow control valve located downstream of a throttling section, simply opening and closing the flow control valve in a pulsed manner while controlling the pressure upstream of the throttling section using a control valve, as in the past, can result in a decrease in the responsiveness of the flow control.

[0008] The present invention has been made to solve the above problems, and a main object of the present invention is to provide a flow rate control device that can respond to pulse gas supply with improved responsiveness.

[0009] A flow control device according to an embodiment of the present invention comprises a pressure control valve that can be freely opened, a flow control valve provided downstream of the pressure control valve, a throttling section provided between the pressure control valve and the flow control valve, an upstream pressure sensor that measures the pressure between the pressure control valve and the throttling section, and a control circuit that controls the operation of at least the pressure control valve, wherein the pressure control valve is feedback-controlled based on the output of the upstream pressure sensor and is configured to supply pulse gas by controlling the opening and closing of the flow control valve, and the control circuit is configured to change the feedback control of the pressure control valve depending on the opening and closing state of the flow control valve.

[0010] In one embodiment, the control circuit is configured to perform PID control of the pressure control valve, and is configured to change a control variable for the PID control of the pressure control valve depending on whether the flow rate control valve is open or closed.

[0011] A flow control device according to an embodiment of the present invention comprises a pressure control valve that can be opened or closed freely, a flow control valve provided downstream of the pressure control valve, a throttling section provided between the pressure control valve and the flow control valve, an upstream pressure sensor that measures the pressure between the pressure control valve and the throttling section, and a control circuit that controls the operation of at least the pressure control valve, wherein the pressure control valve is feedback-controlled based on the output of the upstream pressure sensor and is configured to supply pulsed gas by controlling the opening and closing of the flow control valve, and the control circuit is configured to perform additional control to the feedback control of the pressure control valve at least when the flow control valve is switched from open to closed and when it is switched from closed to open.

[0012] In one embodiment, the pressure control valve is configured to be PID controlled, and the control circuit is configured to additionally perform control to reset an integral amount in the PID control of the pressure control valve at least when the flow control valve is switched from open to closed or when the flow control valve is switched from closed to open.

[0013] In one embodiment, the control circuit is configured to additionally control the pressure control valve to close when the flow control valve is switched from open to closed, without referring to the output of the upstream pressure sensor.

[0014] In one embodiment, the control circuit is configured to feedback-control the pressure control valve by amplifying a control amount for a predetermined period when the flow control valve is switched from closed to open.

[0015] According to the flow rate control device of the embodiment of the present invention, pulse gas can be appropriately supplied with good responsiveness.

[0016] 1 is a schematic diagram showing the configuration of a fluid supply system including a flow control device according to an embodiment of the present invention. FIG. 2 is a diagram showing a flow control device according to an embodiment of the present invention. FIG. 3 is a graph showing the upstream pressure, pulsed opening and closing control of a flow control valve, and flow rate output of a supply gas when a pulsed gas supply is performed. FIG. 4 shows the upstream pressure, pulsed opening and closing control of a flow control valve, and PID control of a pressure control valve during an on-off period of a pulsed gas supply in a comparative example. FIG. 5 shows the upstream pressure, pulsed opening and closing control of a flow control valve, and PID control of a pressure control valve during an on-off period of a pulsed gas supply in an example. FIG. 6 shows the upstream pressure, pulsed opening and closing control of a flow control valve, and PID control of a pressure control valve during an on-off period of a pulsed gas supply in another example. FIG. 7 shows PID control of a pressure control valve with special control inserted therein during an on-off period of a pulsed gas supply in yet another example.

[0017] 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.

[0018] 1 shows a gas supply system 100 including a flow rate control device 10 according to an embodiment of the present invention. The gas supply system 100 is configured to supply a gas G from a gas supply source 2 to a process chamber 6 via the flow rate control device 10. The gas supplied from the gas supply source 2 may be any of various raw material gases or etching gases.

[0019] A vacuum pump 8 is connected to the process chamber 6, and it is possible to evacuate the chamber and the flow path upstream of it. A stop valve 4 is provided between the flow rate control device 10 and the process chamber 6, and the supply of gas to the process chamber 6 can be stopped using the stop valve 4.

[0020] Furthermore, in the gas supply system 100 of this embodiment, a line for supplying a purge gas G' from the purge gas supply source 3 via a stop valve 5 is connected downstream of the stop valve 4. In this configuration, the gas G from the gas supply source 2 can be supplied to the process chamber 6 in a pulsed manner, or the purge gas G' can be supplied during a period when the supply of the gas G is stopped, thereby enabling an ALD process or an ALE process to be performed.

[0021] 1 shows an embodiment in which one type of gas G and purge gas G' are supplied, a plurality of gas supply lines for supplying various gases may be commonly connected to the process chamber 6. In this case, a flow rate control device 10 and a stop valve 4 are provided in each gas supply line. In a multi-line embodiment, the stop valve 4 can be used to switch the gas supplied to the process chamber 6 and to control the flow rate of each gas.

[0022] 2 shows the configuration of the flow control device 10 of this embodiment. The flow control device 10 includes a pressure control valve 12 provided upstream, a flow control valve 14 provided downstream of the pressure control valve 12, and a throttle unit 16 provided between the pressure control valve 12 and the flow control valve 14.

[0023] The flow control device 10 also includes an upstream pressure sensor 18 that detects the pressure P1 between the pressure control valve 12 and the restriction portion 16, a downstream pressure sensor 19 that measures the pressure P2 downstream of the flow control valve 14, and an inflow pressure sensor 17 that detects the pressure P0 upstream of the pressure control valve 12. However, in other aspects, the flow control device 10 does not need to include the downstream pressure sensor 19 or the inflow pressure sensor 17. The upstream pressure sensor 18, the downstream pressure sensor 19, and the inflow pressure sensor 17 are configured, for example, by capacitance manometers.

[0024] The throttle portion 16 is formed, for example, by an orifice plate. The pressure control valve 12 is a valve whose opening can be freely adjusted, and is formed, for example, by a piezoelectric element-driven valve (hereinafter sometimes referred to as a piezo valve). A piezo valve is a proportional valve whose diaphragm valve element can be opened to any opening by controlling the voltage applied to a piezo actuator.

[0025] On the other hand, the flow control valve 14 only needs to have at least the function of an on / off valve, and any type of on / off valve can be used, for example, an AOV (air-operated valve), a solenoid valve, an electric valve, etc. However, a valve whose opening can be freely adjusted may also be used as the flow control valve 14, and for example, as described in Patent Document 2, a piezo valve configured so that a strain sensor or the like is attached to a piezo element and its opening can be directly measured and adjusted may be used.

[0026] In the flow control device 10, the opening of the pressure control valve 12 is feedback-controlled (more specifically, PID-controlled) by a control circuit 13 based on the output of an upstream pressure sensor 18 so that the upstream pressure P1 on the upstream side of the restriction unit 16 is maintained at a desired value. On the other hand, the flow control valve 14 is controlled to open and close in accordance with a predetermined pulse signal by a control circuit 15 in order to supply pulsed gas in the ALD process or the ALE process.

[0027] The control circuits 13, 15 may have built-in CPUs, memories, A / D converters, etc., and may include computer programs configured to execute control operations or arithmetic processing operations described below, and may be realized by a combination of hardware and software. Specific flow rate control procedures using the flow rate control device 10 will be described later.

[0028] 3 shows the upstream pressure P1, the pulsed opening and closing control of the flow control valve 14, and the flow rate output of the supplied gas when a pulsed gas supply is performed using the flow control device 10. As shown in FIG. 3, the upstream pressure P1 on the upstream side of the throttle unit 16 is maintained at a constant pressure corresponding to the set flow rate by feedback control of the pressure control valve 12 provided upstream of the throttle unit 16. During this period, the flow control valve 14 provided downstream of the throttle unit is controlled to turn on and off in a pulsed manner, and as a result, gas is supplied in a pulsed manner at the set flow rate downstream of the flow control valve 14.

[0029] The flow rate of gas flowing downstream through the throttle unit 16 while the downstream flow control valve 14 is open is determined by the magnitude of the upstream pressure P1 controlled using the pressure control valve 12. In a pressure-type flow control device that controls the upstream pressure P1 of the throttle unit 16, when the critical expansion condition P1 / P2≧approximately 2 (where P1 is the upstream pressure on the upstream side of the throttle unit, P2 is the downstream pressure on the downstream side of the throttle unit, and approximately 2 is for nitrogen gas) is satisfied, flow rate control is performed using the principle that the flow rate Q is determined by the upstream pressure P1, regardless of the downstream pressure P2.

[0030] When the critical expansion condition is satisfied, the flow rate Q follows the equation Q = K1 x P1 (K1 is a constant that depends on the opening area of ​​the throttle portion, the type of fluid, and the fluid temperature). Furthermore, if the downstream pressure sensor 19 is provided, the flow rate Q can be calculated even if the critical expansion condition is not satisfied, and the flow rate Q follows the equation Q = K2 x P2. ｍ (P1-P2) ｎ (where K2 is a constant that depends on the opening area of ​​the throttle portion, the type of fluid, and the fluid temperature, and m and n are exponents derived based on the actual flow rate).

[0031] However, it has been found that simply performing the feedback operation of the pressure control valve 12 to maintain the upstream pressure P1 at a constant pressure corresponding to the desired flow rate and simply opening and closing the flow control valve 14 (on-off valve) in a pulsed manner as described above may not actually result in appropriate flow rate control, especially when switching between opening and closing. This will be explained in detail below.

[0032] 4 shows the flow rate setting input (In), the upstream pressure or flow rate output (Out), the opening and closing operation (V1) of the pressure control valve 12, and the opening and closing operation (V2) of the flow rate control valve 14 in a comparative example when a pulsed opening and closing operation of the flow rate control valve 14 is performed. The flow rate setting input (In) is maintained at a substantially constant value.

[0033] 4, during the ON period of the pulse gas supply, i.e., during the open period of the flow control valve 14 (the ON period of the opening / closing operation V2), feedback control of the pressure control valve 12 is performed based on the output of the upstream pressure sensor 18. This keeps the upstream pressure approximately constant during the ON period, allowing gas to flow at an approximately constant flow rate corresponding to the flow rate setting input (In).

[0034] However, when the downstream flow control valve 14, which is comprised of an AOV or the like, closes at the falling edge of the opening / closing operation V2 shown in the figure, and the pulse gas supply switches from the ON period to the OFF period, the flow of gas is suddenly cut off. At this time, feedback control of the upstream pressure control valve 12 does not shut off the pressure control valve 12 instantaneously, but rather closes over a period of time with a delay from the closing of the flow control valve 14, as shown by opening / closing operation V1. As a result, the gas flowing in through the pressure control valve 12 causes the upstream pressure P1 to rise significantly beyond the set value. This causes a relatively large deviation d1 between the flow rate setting input (In) and the flow rate output (Out).

[0035] In this state, although gas is not actually flowing, the pressure control valve 12 remains closed because it is determined that the flow rate has increased based on the output of the upstream pressure sensor 18. During this time, in the sealed space formed by the upstream pressure control valve 12 and the downstream flow rate control valve 14 being both closed, the upstream pressure P1 (and the flow rate output determined from the upstream pressure P1) is maintained at a constant value exceeding the set value.

[0036] If the PID control of the pressure control valve 12 continues during this period, the upstream pressure P1 will exceed the target value, i.e., the deviation d1 will continue. Therefore, the integral amount of the deviation of the PID control (the integral amount that prompts the valve to close) will continue to accumulate over the OFF period.

[0037] Next, when the flow rate control valve 14 opens and the pulse gas supply is switched on, the pressure control valve 12 remains closed for a while, and the gas in the sealed space having an upstream pressure P1 exceeding the target value is suddenly discharged downstream, resulting in an undershoot state. Because a relatively large integral amount of PID control accumulated during the pulse gas supply off period remains as described above, even if the undershoot state occurs, the pressure control valve 12 does not immediately open to restore the upstream pressure P1, but instead begins to open after the accumulated integral amount is consumed. During this delay period, gas is not supplied at the desired flow rate, making it difficult to supply the desired amount (volume) of gas per pulse.

[0038] Therefore, in this embodiment, the control of the upstream pressure control valve 12 is changed or additionally controlled in accordance with the open / closed state and switching timing of the flow control valve 14, thereby improving the responsiveness of the pressure control valve 12 immediately after the flow control valve 14 switches from closed to open, shortening the undershoot period, and enabling pulsed gas to be supplied at a more desired rate. Specific control will be described below.

[0039] 5 shows the results of another example of PID control in which the control constants of the PID control of the pressure control valve 12 are changed between the open period (on period) and the closed period (off period) of the operation V2 of the flow control valve 14. Here, normal PID control suitable for flow control is performed on the pressure control valve 12 during the on period, and PID control in which the control variables are changed to improve responsiveness is performed during the off period. More specifically, the P gain (proportional gain) value in the PID control is set larger during the off period.

[0040] In this embodiment, the control constant is switched at timing t1 when the flow control valve 14 is switched from open to closed and at timing t2 when the flow control valve 14 is switched from closed to open in operation V2. At timing t1, the control is switched to control with a larger P gain, and at timing t2, the control is switched to control with the original P gain.

[0041] As a result, when the system switches to the off period, the pressure control valve 12 is closed more quickly, thereby reducing the degree of the upward deviation d2 of the upstream pressure (output flow rate) during the off period. This also reduces the integral amount of deviation accumulated during the off period, so that even if normal PID control is restored when the system switches to the on period, the valve opens with higher responsiveness, as shown by operation V1, and the undershoot period can be shortened. Note that during the off period, the control variable may be changed so that the I gain (integral gain) in PID control becomes smaller.

[0042] FIG. 6 shows another example in which control is performed as additional control to forcibly reset the integral amount of PID control to zero when switching from an on period to an off period, more specifically, at each of the timings t1 and t2 when the open / closed state of the flow control valve 14 changes.

[0043] As shown in the figure, when the integral amount is reset at timing t1 when the flow control valve 14 switches from open to closed (the falling edge of the opening / closing operation V2), the pressure control valve 12 momentarily closes as shown by operation V1. Thereafter, the pressure control valve 12 opens slightly, and then closes by feedback control to eliminate the upward deviation. However, because the pressure control valve 12 momentarily closes and the flow output Out also falls below the target value at this time, it is possible to reduce the degree of deviation d3 during the off period and the integral amount accumulated during the off period.

[0044] Furthermore, at timing t2 when the OFF period switches to the ON period, the accumulated amount of integral I is reset, so that the pressure control valve 12 starts opening without waiting for the accumulated amount to be consumed, thereby shortening the undershoot period. Furthermore, with this control, when the flow control valve 14 is opened at timing t2, the drop in the flow output Out is suppressed, the undershoot period is shortened, and normal PID control can be restored with good responsiveness.

[0045] 7 shows yet another embodiment in which special control different from the normal PID control of the pressure control valve 12 is inserted for a predetermined period of time when the open / close state of the flow control valve 14 changes. In the illustrated embodiment, a high-speed closing process C1 of the pressure control valve 12 is added for a certain period of time when the on period switches to the off period. The high-speed closing process C1 additionally performs control to forcibly close the pressure control valve 12 without referring to the output of the upstream pressure sensor 18. This makes it possible to reduce the degree of deviation during the off period.

[0046] Furthermore, at the timing of switching from the OFF period to the ON period, a process C2 is added to amplify the control amount of the pressure control valve 12 for a certain period of time. This allows the integral amount of PID control accumulated during the OFF period to be consumed more quickly, shortening the undershoot period and improving responsiveness.

[0047] In this way, the flow control device 10 can supply pulsed gas with good responsiveness by changing the PID control of the upstream pressure control valve 12 depending on the open / close state of the flow control valve 14 downstream of the throttling section, which switches the pulsed gas supply on and off, or by performing special control or additional control of the PID control at the timing of the open / close switch.

[0048] The timing of the control change or additional control may be determined by referring to the signal that controls the opening and closing operation of the flow control valve 14. In addition to this, control different from the normal PID control when the flow control valve 14 is on may be performed when the deviation between input and output exceeds a certain threshold or when a certain time has elapsed since the flow control valve 14 was switched on or off.

[0049] The control systems (pressure control, pulse control, flow control) of the pressure control valve 12 and the flow control valve 14 may be integrated or separate. For example, a control system for the pressure control valve 12 may be provided separately from the control system for the flow control valve 14.

[0050] The present invention is not limited to the above-described embodiment, and various modifications are possible. For example, although the above description has been given of an embodiment in which the throttle unit 16 and the flow control valve 14 are provided separately, it is also possible to use a flow control valve 14 that incorporates the throttle unit 16.

[0051] The flow rate control device according to the embodiment of the present invention is preferably used to appropriately supply pulsed gas.

[0052] 2 Gas supply source 4 Stop valve 6 Process chamber 8 Vacuum pump 10 Flow rate control device 12 Pressure control valve 13, 15 Control circuit 14 Flow rate control valve 16 Throttle section 18 Upstream pressure sensor 100 Gas supply system

Claims

1. A flow control device comprising: a pressure control valve that can be freely opened; a flow control valve provided downstream of the pressure control valve; a throttle section provided between the pressure control valve and the flow control valve; an upstream pressure sensor that measures the pressure between the pressure control valve and the throttle section; and a control circuit that controls the operation of at least the pressure control valve, wherein the pressure control valve is feedback-controlled based on the output of the upstream pressure sensor and is configured to supply pulsed gas by controlling the opening and closing of the flow control valve, and wherein the control circuit is configured to change the feedback control of the pressure control valve depending on the opening and closing state of the flow control valve.

2. The flow control device according to claim 1, wherein the control circuit is configured to PID control the pressure control valve and to change a control variable of the PID control of the pressure control valve depending on the open / closed state of the flow control valve.

3. A flow rate control device comprising: a pressure control valve whose opening angle can be freely adjusted; a flow rate control valve provided downstream of the pressure control valve; a throttle section provided between the pressure control valve and the flow rate control valve; an upstream pressure sensor that measures the pressure between the pressure control valve and the throttle section; and a control circuit that controls the operation of at least the pressure control valve, wherein the pressure control valve is feedback-controlled based on the output of the upstream pressure sensor and pulse gas is supplied by controlling the opening and closing of the flow rate control valve, and wherein the control circuit is configured to perform additional control to the feedback control of the pressure control valve at least when the flow rate control valve is switched from open to closed and when it is switched from closed to open.

4. The flow control device according to claim 3, wherein the control circuit is configured to perform PID control of the pressure control valve and is configured to additionally perform control to reset an integral amount in the PID control of the pressure control valve at least when the flow control valve is switched from open to closed or when it is switched from closed to open.

5. The flow control device according to claim 3, wherein the control circuit is configured to additionally perform control to forcibly close the pressure control valve when the flow control valve is switched from open to closed, without referring to the output of the upstream pressure sensor.

6. A flow control device according to claim 3 or claim 5, wherein the control circuit is configured to amplify the control amount for a predetermined period of time when the flow control valve is switched from closed to open, thereby feedback controlling the pressure control valve.

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