Flow rate ratio control device, control program for flow rate ratio control device, and control method for flow rate ratio control device

Abstract

To provide a flow ratio controller allowing for smooth change-over upon changing over a branch flow passage the greatest in flow rate.SOLUTION: A flow ratio controller comprises at least two branch flow passages that are branched from a main flow passage, a first fluid control valve that has a sensor to detect a position of a valve body and a second fluid control valve that is provided on the other of the branch flow passages, a storage unit that stores a reference position of the valve body to distribute a flow passing through the main flow passage at a predetermined flow ratio to the first and second branch flow passages, and a flow ratio control unit that position-controls the first fluid control valve such that the valve body thereof comes to the reference position and controls the flow ratio of the second fluid control valve such that the flow becomes a target flow. The flow ratio control unit, when the valve body of the second fluid control valve under flow control reaches the reference position, changes over the control in position and flow of the fluid control valve so that the second fluid control valve is position-controlled such that the valve body thereof comes to the reference position and the first fluid control valve is flow-controlled such that a flow thereof becomes a target flow.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a flow rate ratio control device that controls the flow rate ratio of fluids flowing through multiple branch flow paths branching off from a main flow path, a control program used in the flow rate ratio control device, and a control method for the flow rate ratio control device. [Background technology]

[0002] A conventional flow rate ratio control device (also called a flow splitter), as shown in Patent Document 1, for example, is considered to be one in which a fluid control valve is provided in each of a plurality of branch flow paths branched off from a main flow path, and the fluid control valve of the branch flow path that has the largest flow rate is controlled to control the flow rate, and the fluid control valves of the other branch flow paths are controlled to control the flow rate, thereby controlling the flow rate ratio of fluids flowing through the plurality of branch flow paths. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2018 / 047644 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned flow rate ratio control device, it is considered that the flow rate ratio of the fluids flowing through the multiple branch flow paths can be controlled by fully opening the fluid control valve of the branch flow path with the largest flow rate (hereinafter referred to as fluid control valve A) and controlling the flow rates of the fluid control valves of the other branch flow paths (hereinafter referred to as fluid control valve B). With this configuration, it is only necessary to fully open fluid control valve A, making the control easy.

[0005] Here, when switching the branch flow path with the highest flow rate, it is possible to gradually increase the flow rate of fluid control valve B, and after fluid control valve B is fully open, switch fluid control valve A to flow control and maintain fluid control valve B in the fully open state. In other words, when the branch flow path with the highest flow rate is switched, both fluid control valves A and B are fully open.

[0006] However, due to differences in conductance among the multiple branch flow paths, even when both fluid control valves A and B are fully open, the flow rate is not distributed equally among the multiple branch flow paths. This creates a problem: the point at which the branch flow path with the highest flow rate switches (switching point) is not achieved when the flow rates of the multiple branch flow paths are equal. Furthermore, the fluid control valves installed in the multiple branch flow paths vary from one to another, and inputting a drive signal (voltage signal) to fully open these fluid control valves does not necessarily result in the same flow rate. As a result, when switching from the branch flow path with the highest flow rate to another, a sudden change (spike) occurs in the flow rate through the branch flow path, preventing smooth branch flow path switching. As a result, problems arise when a flow rate ratio control device that performs the above control is used, for example, in semiconductor manufacturing processes.

[0007] The present invention has been made in consideration of the above-mentioned problems, and its main objective is to enable a flow ratio control device to switch branch flow paths with the largest flow rate while keeping the flow rates of multiple branch flow paths uniform, and to smoothly switch branch flow paths without causing a sudden change (spike) in the flow rate flowing through the branch flow paths. [Means for solving the problem]

[0008] That is, a flow rate ratio control device according to the present invention comprises at least first and second branch flow paths branching off from a main flow path, a first fluid control valve provided in the first branch flow path and having a position sensor for detecting the position of a valve element, a second fluid control valve provided in the second branch flow path and having a position sensor for detecting the position of the valve element, a memory unit for storing, in each of the fluid control valves, a reference position of the valve element for distributing the flow rate through the main flow path to the first branch flow path and the second branch flow path at a predetermined flow rate ratio, and a flow rate ratio control unit that controls the flow rate ratio of at least the first and second branch flow paths by position-controlling the first fluid control valve so that the position of its valve element is at the reference position and by flow-controlling the second fluid control valve so that the flow rate becomes a target flow rate, and is characterized in that, when the valve element of the second fluid control valve that it controls the flow rate reaches the reference position, the flow rate ratio control unit switches between position control and flow rate control of each of the fluid control valves, and position-controls the second fluid control valve so that its valve element is at the reference position and flow-controls the first fluid control valve so that the flow rate becomes the target flow rate.

[0009] With such a flow ratio control device, the reference position of the valve body for flowing a predetermined reference flow rate in each fluid control valve is stored, and the first fluid control valve and the second fluid control valve are switched based on this reference position.Therefore, when the flow ratio control device switches the branch flow path with the largest flow rate, the flow rates of the multiple branch flow paths can be switched evenly, and the branch flow paths can be switched smoothly without causing a sudden change (spike) in the flow rate flowing through the branch flow paths.

[0010] Specifically, by normalizing the reference position of the valve element of the fluid control valve provided in each of the multiple branch flow paths based on the reference position of the valve element of the fluid control valve provided in the branch flow path with the lowest conductance among the multiple branch flow paths, the flow rate of the multiple branch flow paths can be switched evenly when the flow ratio control device switches the branch flow path with the highest flow rate. Furthermore, this normalization allows the lowest possible differential pressure to be maintained throughout the system, thereby shortening the time it takes for gas to reach, for example, a process chamber from the flow ratio control device. Furthermore, according to the present invention, the conductance of the multiple branch flow paths from the fluid control valves to, for example, a process chamber can be normalized, thereby canceling system fluctuations that occur in downstream components, such as filters in the flow paths or showerheads in the chamber.

[0011] As a specific example of the operation of the flow rate ratio control device, it is conceivable to continuously switch the branch flow paths through which the fluid flows from the first branch flow path to the second branch flow path without changing the flow rate of the fluid flowing through the main flow path. In this case, it is desirable that the flow rate ratio control unit gradually displaces the valve element of the second fluid control valve that controls the flow rate from the fully closed position to the reference position, and when the position of the valve element reaches the reference position, switch the position control and flow rate control of each of the fluid control valves, position control the second fluid control valve so that its valve element is at the reference position, and flow rate control the first fluid control valve so that the flow rate gradually becomes zero.

[0012] Specifically, the predetermined flow rate ratio may be a ratio that divides the flow rate through the main flow path equally between the first branch flow path and the second branch flow path. In this case, it is desirable that the reference position is a position that is set as a fully open position of the fluid control valve.

[0013] It is desirable that the first fluid control valve, together with a flow sensor provided in the first branch flow path, constitute a first fluid control device, and the second fluid control valve, together with a flow sensor provided in the second branch flow path, constitute a second fluid control device.

[0014] Furthermore, a control program for a flow ratio control device according to the present invention is a control program used in a flow ratio control device including at least first and second branch flow paths branched from a main flow path, a first fluid control valve provided in the first branch flow path and having a position sensor for detecting the position of a valve element, and a second fluid control valve provided in the second branch flow path and having a position sensor for detecting the position of the valve element, wherein each of the fluid control valves includes a memory unit for storing a reference position of the valve element for distributing a flow rate flowing through the main flow path to the first branch flow path and the second branch flow path at a predetermined flow rate ratio, and a control program for storing a reference position of the first fluid control valve. and a flow ratio control unit that controls the position of the first fluid control valve so that its valve element is at the reference position and controls the flow rate of the second fluid control valve so that its flow rate becomes a target flow rate, thereby controlling the flow rate ratio of the at least first and second branch flow paths, and the flow ratio control unit switches between position control and flow rate control of the fluid control valves when the valve element of the second fluid control valve to be flow-controlled reaches the reference position, and controls the position of the second fluid control valve so that its valve element is at the reference position and controls the flow rate of the first fluid control valve so that its flow rate becomes the target flow rate. By installing such a control program in an existing flow ratio control device, it can be made to exhibit the same functions as the flow ratio control device of the present invention described above.

[0015] Furthermore, a control method for a flow ratio control device according to the present invention is a control method for a flow ratio control device comprising at least first and second branch flow paths branched from a main flow path, a first fluid control valve provided in the first branch flow path and having a position sensor for detecting the position of a valve element, and a second fluid control valve provided in the second branch flow path and having a position sensor for detecting the position of the valve element, the control method comprising the steps of: storing, in each of the fluid control valves, a reference position of the valve element for distributing a flow rate flowing through the main flow path to the first branch flow path and the second branch flow path at a predetermined flow rate ratio; and a flow rate ratio control step of controlling the flow rate ratio of at least the first and second branch flow paths by position-controlling the first fluid control valve so that its valve body is at the reference position and by flow-controlling the second fluid control valve so that the flow rate becomes a target flow rate, wherein the flow rate ratio control step switches between position control and flow rate control of the fluid control valves when the valve body of the second fluid control valve that controls the flow rate reaches the reference position, and controls the position of the second fluid control valve so that its valve body is at the reference position and controls the flow rate of the first fluid control valve so that the flow rate becomes the target flow rate. [Effects of the Invention]

[0016] According to the present invention described above, when switching the branch flow path with the largest flow rate in the flow ratio control device, the flow rates of the multiple branch flow paths can be switched evenly, and the branch flow paths can be switched smoothly without causing a sudden change (spike) in the flow rate flowing through the branch flow paths. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is an overall schematic diagram of a flow ratio control device according to an embodiment of the present invention; [Figure 2] FIG. 2 is a schematic diagram showing the flow rate control device of the same embodiment. [Figure 3] FIG. 10 is a diagram showing a procedure of flow normalization according to the embodiment. [Figure 4]3A and 3B are schematic diagrams showing the control contents of the fluid control valve and the flow rates of branched flow paths in the embodiment; DETAILED DESCRIPTION OF THE INVENTION

[0018] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A flow ratio control device according to an embodiment of the present invention will be described below with reference to the drawings.

[0019] <1.Device configuration> As shown in FIG. 1, the flow rate ratio control device 100 of this embodiment is used, for example, in a semiconductor manufacturing process, and is used to introduce gases for semiconductor processing into a vacuum chamber 200 that houses a wafer through multiple inlets of the vacuum chamber 200 at predetermined flow rate ratios.

[0020] Specifically, the flow rate ratio control device 100 includes a main flow path ML, a plurality of branch flow paths BL1 to BL4 branching off from the main flow path L1, a plurality of fluid control devices MFC1 to MFC4 provided in each of the plurality of branch flow paths BL1 to BL4, and a master controller COM that oversees the control of the plurality of fluid control devices MFC1 to MFC4, and is configured to control the flow rate ratio of the gas flowing through each of the branch flow paths BL1 to BL4 to a target flow rate ratio.

[0021] The main flow path ML has its upstream end connected to a gas source 300 that supplies gas for semiconductor processes, and a plurality of branch flow paths BL1 to BL4 connected to its downstream end. Although Fig. 1 shows an example in which four branch flow paths BL1 to BL4 are connected, the number of branch flow paths BL is not particularly limited as long as there are two or more branch flow paths BL.

[0022] 2, each of the fluid control devices MFC1 to MFC4 is a so-called mass flow controller, and includes a block 2 in which an internal flow path communicating with the branch flow paths BL1 to BL4 is formed, a fluid control valve 3 provided in the block 2 for controlling the flow rate of the internal flow path, a flow sensor 4 provided in the block 2 and provided on the upstream or downstream side of the fluid control valve 3 in the internal flow path, and a valve control unit 5 for controlling the fluid control valve 3. In the following, when distinguishing between the components of each of the fluid control devices MFC1 to MFC4, they will be referred to as a first fluid control valve 31, a second fluid control valve 32, etc.

[0023] The fluid control valve 3 has a valve seat 31 provided midway through the internal flow path, a valve element 32 that moves toward and away from the valve seat 31, and an actuator 33 made of, for example, a piezoelectric element that moves the valve element 32. The fluid control valve 3 may be of a normally open type that is in a fully open state when the actuator 33 is not driven, or may be of a normally closed type that is in a fully closed state when the actuator 33 is not driven.

[0024] The fluid control valve 3 further includes a position sensor 6 that detects the position of the valve element 32 relative to the valve seat 31. The position sensor 6 is, for example, an eddy current non-contact displacement sensor. The detected position obtained by the position sensor 6 is output to the valve control unit 5.

[0025] The flow rate sensor 4 is, for example, a pressure type and includes a laminar flow element 41 provided in the internal flow path, an upstream pressure sensor 42 that detects the pressure upstream of the laminar flow element 41, a downstream pressure sensor 43 that detects the pressure downstream of the laminar flow element 41, and a flow rate output circuit 44 that outputs a flow rate based on the detected pressures detected by the pressure sensors 42, 43. The flow rate output circuit 44 calculates the flow rate of the fluid from the differential pressure between the detected pressures of the upstream pressure sensor 42 and the downstream pressure sensor 43 and outputs the calculated flow rate to the valve control unit 5. Note that the flow rate sensor 4 may also be a thermal type.

[0026] Based on commands from the master controller COM, the valve control unit 5 controls the flow rate or position of the fluid control valve 3. In addition, the valve control unit 5, together with the master controller COM, functions as a flow rate ratio control unit 8, which will be described later.

[0027] When the valve control unit 5 controls the flow rate of the fluid control valve 3, it performs flow rate feedback control based on the deviation between a target position for achieving a preset target flow rate and the detected position detected by the position sensor 6 so as to reduce the deviation (flow rate control mode). In this case, the valve control unit 5 controls the voltage applied to the fluid control valve 3 based on the deviation between the target position and the detected position so that the measurement position of the position sensor 6 becomes the detected position. Note that the valve control unit 5 may also perform flow rate feedback control based on the deviation between a preset target flow rate and the measured flow rate measured by the flow sensor 4 so as to reduce the deviation. In this case, it calculates a target opening based on the deviation between the target flow rate and the measured flow rate, and controls the voltage applied to the fluid control valve 3 so that the opening indicated by the position sensor 6 becomes the target opening.

[0028] Furthermore, when the valve control unit 5 controls the position of the fluid control valve 3, it performs position feedback control (position control mode) based on the deviation between a preset target position and the detected position detected by the position sensor 6 so as to reduce the deviation. In other words, when controlling the position of the fluid control valve 3, the valve control unit 5 does not perform feedback control using the measured flow rate measured by the flow rate sensor 4.

[0029] In this embodiment, the valve control unit 5 of the fluid control device MFC1 provided in the master line, which is the branch flow path with the largest target flow rate ratio (here, the first branch flow path BL1), operates in the position control mode. On the other hand, the valve control units 5 of the fluid control devices MFC2 to MFC4 provided in the slave lines, which are the branch flow paths BL2 to BL4 other than the master line, operate in the flow rate control mode.

[0030] Here, the target position in the position control mode will be described. The flow rate ratio control device 100 of this embodiment has a memory unit 7 that stores a reference position of the valve element 32 for distributing the flow rate through the main flow path ML to the plurality of branch flow paths BL1 to BL4 at a predetermined flow rate ratio in each fluid control valve 3. The memory unit 7 may be provided individually in the memory of each fluid control device MFC1 to MFC4, as shown in Fig. 2, or may be provided collectively in the memory of the master controller COM.

[0031] The storage unit 7 stores a reference position of the valve element 32 for distributing the flow rate through the main flow path ML to the branch flow paths BL1 to BL4 at a predetermined flow rate ratio in each fluid control valve 3. The reference position of the valve element 32 set for each fluid control valve 3 is a position set as the fully open position of the fluid control valve 3. This reference position becomes the target position in the position control mode.

[0032] The predetermined flow rate ratio in this embodiment is obtained by equally dividing the flow rate (for example, 4 L) flowing through the main flow path ML into the branch flow paths BL1 to BL4 (the flow rate of each of the branch flow paths BL1 to BL4 is 1 L).

[0033] <2. How to set the reference position> Here, the reference position is determined in advance by, for example, the following flow normalization procedure, as shown in FIG.

[0034] A drive signal (voltage signal) is input to each of the multiple fluid control valves 3 provided in the first to fourth branch flow paths BL1 to BL4 to physically place them in a fully open state, and the position (fully open position) of the valve body 32 detected by the position sensor 6 at that time is obtained (step S1).

[0035] In addition, a drive signal (voltage signal) is input to each of the multiple fluid control valves 3 provided in the first to fourth branch flow paths BL1 to BL4 to physically place them in a fully closed state, and the position (fully closed position) of the valve body 32 detected by the position sensor 6 at that time is obtained (step S2).

[0036] Then, the fluid control valve 3 is fully opened so that the diversion ratio of the fluid flowing through the first to fourth branch flow paths BL1 to BL4 becomes a predetermined diversion ratio (here, the diversion ratio is the same (25%) for each), and the diversion ratio of the fluid flowing through the first to fourth branch flow paths BL1 to BL4 at that time is calculated (step S3).

[0037] The flow division ratio calculated in step S3 is compared with the predetermined flow division ratio (step S4), and if the difference between them is greater than a predetermined threshold, the fully open position of one of the fluid control valves 3 provided in the first to fourth branch flow paths BL1 to BL4 is changed (step S5). For example, the fully open position of the fluid control valve 3 provided in the branch flow path with the largest difference is changed.

[0038] Then, using the changed fully open position, the process returns to step S3, and the change of the fully open position of the fluid control valve 3 is repeated until the difference between the diversion ratio of the fluid flowing through the first to fourth branch flow paths BL1 to BL4 and the predetermined diversion ratio becomes less than the predetermined threshold value. The fully open positions of each fluid control valve 3 thus determined are stored in the memory unit 7 as reference positions (step S6).

[0039] The master controller COM inputs commands to each of the fluid control devices MFC1-MFC4 based on the target flow rate ratio of the gas flowing through each of the branch flow paths BL1-BL4 received from the user, causing the fluid control device MFC1 provided in the branch flow path BL1, which is the master line, to execute a position control mode for performing position control, and inputs individual target flow rates calculated from the target flow rate ratios into the fluid control devices MFC2-MFC4 provided in the other branch flow paths BL2-BL4 to execute a flow rate control mode. Note that the master controller COM and the valve control units 5 of each of the flow rate control devices MFC1-MFC4 work together to function as a flow rate ratio control unit 8 described below.

[0040] At this time, the flow rate ratio control unit 8 controls the position of the fluid control valve 3 of the fluid control device MFC1 provided in the branch flow path BL1, which is the master line, based on the detected position detected by the position sensor 6 so that the position of its valve body 32 becomes a reference position, and controls the flow rate of the fluid control valves 3 of the fluid control devices MFC2 to MFC4 provided in the branch flow paths BL2 to BL4, which are slave lines, so that the flow rate becomes a target flow rate, thereby controlling the flow rate ratios of the multiple branch flow paths BL1 to BL4.

[0041] <3. Master line switching operation> The flow rate ratio control unit 8 may successively switch the branch flow path (master line) with the largest target flow rate ratio from the first branch flow path BL1 to the second branch flow path BL2 without changing the flow rate of the fluid flowing through the main flow path ML. Note that, although the case of switching between the first branch flow path BL1 and the second branch flow path BL2 is illustrated here as an example, the same applies to switching between other branch flow paths.

[0042] In this case, the flow ratio control unit 8 gradually displaces the valve element 32 of the second fluid control valve 3 provided in the second branch flow path BL2 from the fully closed position to the reference position in the flow control mode, as shown in Fig. 4. Here, the valve element 32 is gradually displaced so that the flow rate through the second branch flow path BL2 increases linearly.

[0043] When the position of the valve element 32 of the second fluid control valve 3 provided in the second branch flow path BL2 reaches the reference position, the second fluid control valve 3 is switched from flow rate control to position control, and the second fluid control valve 3 is position-controlled so that its valve element 32 is at the reference position. The first fluid control valve 3 provided in the first branch flow path BL1 is flow-controlled so that the flow rate of the first branch flow path BL1 gradually decreases to zero. Here, the valve element 32 is gradually displaced so that the flow rate through the first branch flow path BL1 decreases linearly. In a series of operations that continuously switch from the first branch flow path BL1 to the second branch flow path BL2, the flow rate through the first branch flow path BL1 decreases linearly, and the flow rate through the second branch flow path BL2 increases linearly. This allows the branch flow path (master line) with the highest target flow rate ratio to be continuously switched from the first branch flow path BL1 to the second branch flow path BL2. Note that Figure 4 illustrates an example in which the master line is switched from the "first branch flow path BL1" to the "second branch flow path BL2," and then the master line is switched again from the "second branch flow path BL2" to the "first branch flow path BL1."

[0044] 4, it is also possible to evaluate the performance of the operation of switching the branch flow paths BL1 and Bl2 of the flow ratio control device 100. That is, the performance of the flow ratio control device 100 can be evaluated by determining whether or not a sudden change (spike) occurs in the flow rate through the branch flow paths BL1 and Bl2 at the mutual switching point between the first branch flow path BL1 and the second branch flow path BL2.

[0045] <4. Effects of this embodiment> According to the flow rate ratio control device 100 of this embodiment configured as described above, the reference position of the valve body for flowing a predetermined reference flow rate in each fluid control valve 3 is stored, and the first fluid control valve 3 and the second fluid control valve 3 are switched based on this reference position.Therefore, when switching the branch flow path with the largest flow rate in the flow rate ratio control device 100, the flow rates of the multiple branch flow paths BL1 to BL4 can be switched in an equal state, and the branch flow paths can be switched smoothly without causing a sudden change (spike) in the flow rate flowing through the branch flow paths BL1 and BL2.

[0046] Specifically, by normalizing the reference position of the valve element 32 of the fluid control valve 3 provided in each of the branch flow paths BL1 to BL4 based on the reference position of the valve element 32 of the fluid control valve 3 provided in the branch flow path with the lowest conductance among the branch flow paths BL1 to BL4, the flow rate of the branch flow paths BL1 to BL4 can be uniformly switched when the flow rate ratio control device 100 switches the branch flow path with the highest flow rate. Furthermore, by normalizing the flow rate ratio in this manner, the differential pressure can be maintained as low as possible throughout the entire system, thereby shortening the time it takes for gas to reach, for example, a process chamber from the flow rate ratio control device 100. Furthermore, according to this embodiment, the conductance of the flow paths from the fluid control valve 3 to, for example, a process chamber can be normalized in the branch flow paths BL1 to BL4, thereby canceling system fluctuations that occur in downstream components, such as filters installed in the flow paths or showerheads installed in the chambers.

[0047] For example, in the case of a plurality of branch flow paths BL1 to BL4 connected to a vacuum chamber 200 used in a semiconductor process, when switching between a master-slave relationship between a branch flow path connected to the center of the vacuum chamber 200 and a branch flow path connected to the outer periphery of the vacuum chamber 200, the switching can be performed smoothly, thereby improving the quality of the semiconductor manufacturing process. An example of switching the master-slave relationship is when transitioning from process control, in which a high flow rate is directed to the outer periphery of the vacuum chamber 200, to purge control, in which a high flow rate is directed to the center of the vacuum chamber 200.

[0048] <5. Other embodiments> The present invention is not limited to the above-described embodiment.

[0049] In the above embodiment, the reference position is the position of the valve element 32 for allowing flow rates with the same branch ratio (equally distributed flow rates). However, the reference position may also be the position of the valve element 32 for allowing flow rates with different branch ratios. In the example of FIG. 4 , the reference position may be the position of the valve element 32 for allowing flow rates with a branch ratio of, for example, 49:51 or 52:48 between the first branch flow path BL1 and the second branch flow path BL2, rather than the same branch ratio (50:50) between the first branch flow path BL1 and the second branch flow path BL2. Alternatively, the reference position may have a certain range by providing a certain range for the predetermined reference flow rate within the resolution (e.g., 0.2% of full scale) of the fluid control valve 3. The reference position in the above embodiment may be set to a position of the valve element 32 where the reference flow rate has this range. In other words, the timing at which the fluid control valve 3 switches between position control and flow rate control may not be a single point, but may have a certain range.

[0050] 4, the timing for switching control between the first branch flow path BL1 and the second branch flow path BL2 may be varied. In this case, when the master line is switched from the first branch flow path BL1 to the second branch flow path BL2, after a period in which both the first fluid control valve 3 and the second fluid control valve 3 are position-controlled (or flow-rate-controlled), the first fluid control valve 3 becomes flow-rate-controlled and the second fluid control valve becomes position-controlled.

[0051] In the above embodiment, the fluid control device MFC is a packaged mass flow controller, but other fluid control devices may be provided in each branch flow path. For example, a fluid control valve and a flow rate sensor that are not packaged like a mass flow controller may be treated as a fluid control device.

[0052] In the above embodiment, the position of the fluid control valve provided in the branch flow path with the highest fluid flow rate is controlled based on the target flow rate ratio. However, for example, the branch flow path with the second or third highest fluid flow rate may be set as the master line, and the other branch flow paths may be set as slave lines, and the position of the fluid control valve provided in the master line may be controlled.

[0053] Furthermore, in the above embodiment, an example was shown in which the flow rate ratio control device was used in a semiconductor manufacturing process, but it can also be used for other purposes.

[0054] In addition, various modifications and combinations of the embodiments may be made as long as they do not go against the spirit of the present invention. [Explanation of symbols]

[0055] 100 Flow ratio control device ML: Main flow path BL1 to BL4: Branching channels 3. Fluid control valve 32 Valve body 6. Position sensor 7...Storage section 8. Flow ratio control section

Claims

1. At least first and second branch flow paths branched from the main flow path; a first fluid control valve provided in the first branch flow path and having a position sensor that detects the position of a valve element; a second fluid control valve provided in the second branch flow path and having a position sensor that detects the position of a valve element; a storage unit configured to store, in each of the fluid control valves, a reference position of the valve element for distributing a flow rate of the main flow path to the first branch flow path and the second branch flow path at a predetermined flow rate ratio; a flow rate ratio control unit that controls the position of the first fluid control valve so that its valve element is at the reference position and controls the flow rate of the second fluid control valve so that the flow rate becomes a target flow rate, thereby controlling the flow rate ratio of at least the first and second branch flow paths, a flow ratio control device, wherein when the position of the valve element of the second fluid control valve that controls the flow rate reaches the reference position, the flow rate ratio control unit switches between position control and flow rate control of each of the fluid control valves, performs position control of the second fluid control valve so that its valve element is at the reference position, and performs flow rate control of the first fluid control valve so that its flow rate becomes a target flow rate.

2. 2. The flow rate ratio control device according to claim 1, wherein the flow rate ratio control section gradually displaces a valve element of the second fluid control valve that controls the flow rate from a fully closed position to the reference position, and when the position of the valve element reaches the reference position, switches between position control and flow rate control of each of the fluid control valves, thereby controlling the position of the second fluid control valve so that its valve element is at the reference position, and controlling the flow rate of the first fluid control valve so that the flow rate gradually becomes zero.

3. the predetermined flow rate ratio is a ratio at which the flow rate flowing through the main flow path is equally distributed to the first branch flow path and the second branch flow path, The flow ratio control device according to claim 1 or 2, wherein the reference position is a position set as a fully open position of the fluid control valve.

4. the first fluid control valve constitutes a first fluid control device together with a flow rate sensor provided in the first branch flow path, 4. The flow ratio control device according to claim 1, wherein the second fluid control valve and a flow sensor provided in the second branch flow path constitute a second fluid control device.

5. A control program used in a flow ratio control device including at least first and second branch flow paths branched from a main flow path, a first fluid control valve provided in the first branch flow path and having a position sensor that detects the position of a valve element, and a second fluid control valve provided in the second branch flow path and having a position sensor that detects the position of the valve element, a storage unit configured to store, in each of the fluid control valves, a reference position of the valve element for distributing a flow rate of the main flow path to the first branch flow path and the second branch flow path at a predetermined flow rate ratio; a computer is provided with a function as a flow rate ratio control unit that controls the position of the first fluid control valve so that its valve element is at the reference position, and controls the flow rate of the second fluid control valve so that the flow rate becomes a target flow rate, thereby controlling the flow rate ratio of at least the first and second branch flow paths, a control program for a flow rate ratio control device, wherein when the valve element of the second fluid control valve that controls the flow rate reaches the reference position, the flow rate ratio control unit switches between position control and flow rate control of each of the fluid control valves, performs position control of the second fluid control valve so that the position of its valve element becomes the reference position, and performs flow rate control of the first fluid control valve so that the flow rate becomes a target flow rate.

6. A control method for a flow ratio control device comprising at least first and second branch flow paths branched from a main flow path, a first fluid control valve provided in the first branch flow path and having a position sensor that detects the position of a valve element, and a second fluid control valve provided in the second branch flow path and having a position sensor that detects the position of the valve element, a storing step of storing a reference position of the valve element for distributing a flow rate of the main flow path to the first branch flow path and the second branch flow path at a predetermined flow rate ratio in each of the fluid control valves; a flow rate ratio control step of controlling the position of the first fluid control valve so that its valve element is at the reference position and controlling the flow rate of the second fluid control valve so that the flow rate becomes a target flow rate, thereby controlling the flow rate ratio of at least the first and second branch flow paths, The flow rate ratio control step is a control method for a flow rate ratio control device, in which, when the valve element of the second fluid control valve that controls the flow rate reaches the reference position, position control and flow rate control of each of the fluid control valves are switched, the second fluid control valve is position-controlled so that the position of its valve element becomes the reference position, and the first fluid control valve is flow-controlled so that the flow rate becomes a target flow rate.

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