Flow ratio control device and its control method, storage medium

Abstract

This invention provides a flow ratio control device, a control method thereof, and a storage medium. The device comprises: at least two branch channels branching from a main flow channel; first and second fluid control valves, each disposed in one of the two branch channels and having a position sensor; a storage unit for storing reference positions of valve bodies that distribute the flow rate through the main flow channel to the first and second branch channels at a predetermined flow ratio; and a flow ratio control unit for performing position control on the first fluid control valve to bring its valve body to the reference position, and performing flow control on the second fluid control valve to bring the flow rate to the target flow rate, thereby controlling the flow ratio of the at least two branch channels. If the position of the valve body of the second fluid control valve, which is subject to flow control, reaches the reference position, the flow ratio control unit switches between position control and flow control on each fluid control valve, performing position control on the second fluid control valve to bring its valve body to the reference position, and performing flow control on the first fluid control valve to bring the flow rate to the target flow rate.

Description

Technical Field

[0001] The present invention relates to a flow ratio control device for controlling the flow ratio of fluid flowing through multiple branch channels branching from a main channel, a control program for the flow ratio control device, and a control method for the flow ratio control device. Background Technology

[0002] As a conventional flow ratio control device (also known as a flow divider), for example as shown in Patent Document 1, a device can be considered that provides fluid control valves on multiple branch channels branching from the main flow channel, controls the flow rate of the fluid control valve of the branch channel with the largest flow rate, and controls the flow rate of the fluid control valves of the other branch channels, thereby controlling the flow ratio of the fluid flowing through the multiple branch channels.

[0003] Existing technical documents

[0004] Patent Document 1: International Publication No. 2018 / 047644

[0005] In the aforementioned flow ratio control device, it is possible to fully open the fluid control valve (hereinafter referred to as fluid control valve A) of the branch flow channel with the largest flow rate, and control the flow rate of the fluid control valves (hereinafter referred to as fluid control valve B) of the other branch flow channels, thereby controlling the flow ratio of the fluid flowing through multiple branch flow channels. In this configuration, it is only necessary to keep fluid control valve A fully open, thus making its control easy.

[0006] Here, when switching to the branch flow channel with the largest flow rate, it is advisable to gradually increase the flow rate of fluid control valve B. After fluid control valve B becomes fully open, switch fluid control valve A to flow control while keeping fluid control valve B fully open. That is, at the timing of switching to the branch flow channel with the largest flow rate, both fluid control valves A and B are fully open.

[0007] However, due to the different flow conductances of the multiple branch channels, even when both fluid control valves A and B are fully open, the flow rate cannot be evenly distributed among the branch channels. Therefore, the following problem exists: the switching point (switching point) for the branch channel with the highest flow rate cannot be achieved when the flow rates of the multiple branch channels are equal. Furthermore, the fluid control valves installed on the multiple branch channels have individual differences, so even if a drive signal (voltage signal) is input to make these fluid control valves fully open, the flow rate is not limited to the same level. This results in the following problem: when switching from the branch channel with the highest flow rate to another, the flow rate through the branch channel changes drastically (spiking), making the switching of branch channels difficult. Consequently, adverse situations may occur in applications such as semiconductor manufacturing processes where flow rate ratio control devices performing the aforementioned control are used. Summary of the Invention

[0008] The present invention was made in view of the above-mentioned problems. The main objective of the present invention is to enable the switching of multiple branch channels when switching the branch channel with the largest flow rate in the flow rate ratio control device, so that the flow rate through the branch channel does not produce abrupt changes (peaks), thereby enabling smooth switching of the branch channel.

[0009] That is, the flow ratio control device of the present invention is characterized by comprising: at least a first branch flow channel and a second branch flow channel branching from a main flow channel; a first fluid control valve disposed on the first branch flow channel and having a position sensor for detecting the position of the valve body; a second fluid control valve disposed on the second branch flow channel and having a position sensor for detecting the position of the valve body; a storage unit for storing reference positions of the valve bodies of each of the fluid control valves for distributing the flow rate flowing through the main flow channel to the first branch flow channel and the second branch flow channel at a predetermined flow ratio; and a flow ratio control unit for controlling the flow ratio of the at least first branch flow channel and the second branch flow channel by performing position control on the first fluid control valve so that its valve body position is the reference position, and performing flow control on the second fluid control valve so that its flow rate is a target flow rate. If the valve body of the second fluid control valve under flow control reaches the reference position, the flow ratio control unit switches between position control and flow control of each of the fluid control valves, performing position control on the second fluid control valve so that its valve body is the reference position, and performing flow control on the first fluid control valve so that its flow rate is a target flow rate.

[0010] If it is such a flow ratio control device, the reference position of the valve body of each fluid control valve that flows through the specified reference flow is stored in advance. Based on the reference position, the first fluid control valve and the second fluid control valve are switched. Therefore, in the flow ratio control device, when switching the branch flow channel with the largest flow, the switching can be carried out in the state that the flow of multiple branch flow channels is equal, so that the flow of the branch flow channel does not produce abrupt changes (peaks), thus smoothly switching the branch flow channel.

[0011] In detail, based on the reference position of the valve body of the fluid control valve located in the branch flow channel with the lowest flow conductance among multiple branch flow channels, the reference positions of the valve bodies of the fluid control valves located in each of the multiple branch flow channels are standardized. This allows the flow rate ratio control device to switch to the branch flow channel with the highest flow rate while ensuring that the flow rates in all branch flow channels are equal. Furthermore, this standardization maintains the lowest possible pressure differential in the overall system, thereby shortening the arrival time of gas supply from the flow rate ratio control device to, for example, the processing chamber. Moreover, according to the present invention, since the flow conductance of the flow channel from the fluid control valve to, for example, the processing chamber can be standardized in multiple branch flow channels, system variations occurring downstream of components such as filters located in the flow channels and nozzles located in the chambers can be eliminated.

[0012] As an example of the operation of a specific flow ratio control device, one could consider keeping the flow rate of the fluid flowing through the main channel constant while continuously switching the branch flow channels of the fluid flow from a first branch channel to a second branch channel. In this case, it is preferable that if the valve body of the second fluid control valve, which controls the flow rate, is gradually displaced from a fully closed position to the reference position, so that the position of the valve body reaches the reference position, then the flow ratio control unit switches between position control and flow control for each of the fluid control valves, performing position control on the second fluid control valve so that its valve body reaches the reference position, and performing flow control on the first fluid control valve so that the flow rate gradually becomes zero.

[0013] Specifically, the specified flow rate ratio can be considered as the ratio of the flow rate through the main flow channel to the flow rate of the first branch flow channel and the second branch flow channel. In this case, the reference position is preferably set as the fully open position of the fluid control valve.

[0014] Preferably, the first fluid control valve and the flow sensor disposed on the first branch flow channel together constitute a first fluid control device, and the second fluid control valve and the flow sensor disposed on the second branch flow channel together constitute a second fluid control device.

[0015] Furthermore, the storage medium of the present invention storing a control program for a flow ratio control device is characterized in that the flow ratio control device comprises: at least a first branch channel and a second branch channel branching from a main channel; a first fluid control valve disposed on the first branch channel and having a position sensor for detecting the position of the valve body; and a second fluid control valve disposed on the second branch channel and having a position sensor for detecting the position of the valve body. A computer, by executing the control program for the flow ratio control device, functions as both a storage unit and a flow ratio control unit. The storage unit stores information from each of the fluid control valves for distributing the flow rate flowing through the main channel to the first branch channel and the second branch channel at a predetermined flow ratio. The flow ratio control unit controls the flow ratio of at least the first and second branch channels by controlling the position of the valve body of the first fluid control valve so that its valve body is at the reference position, and controlling the flow of the second fluid control valve so that the flow rate is the target flow rate. If the valve body of the second fluid control valve, which is subject to flow control, reaches the reference position, the flow ratio control unit switches between position control and flow control of each fluid control valve, controlling the position of the second fluid control valve so that its valve body is at the reference position, and controlling the flow of the first fluid control valve so that the flow rate is the target flow rate. Installing such a control program onto an existing flow ratio control device allows it to perform the same function as the flow ratio control device of the present invention described above.

[0016] Furthermore, the control method of the flow ratio control device of the present invention is characterized in that the flow ratio control device comprises: at least a first branch flow channel and a second branch flow channel branching from the main flow channel; a first fluid control valve disposed on the first branch flow channel and having a position sensor for detecting the position of the valve body; and a second fluid control valve disposed on the second branch flow channel and having a position sensor for detecting the position of the valve body. The control method of the flow ratio control device includes: a storage step of storing a reference position of the valve body of each of the fluid control valves for distributing the flow rate flowing through the main flow channel to the first branch flow channel and the second branch flow channel at a predetermined flow ratio; and so on. The flow ratio control process involves position control of the first fluid control valve so that its valve body is at the reference position, and flow control of the second fluid control valve so that the flow rate is the target flow rate. The flow ratio of the at least first branch flow channel and the second branch flow channel is controlled. If the valve body of the second fluid control valve, which is subject to flow control, reaches the reference position, the flow ratio control unit switches between position control and flow control of each fluid control valve. Position control of the second fluid control valve is performed so that its valve body is at the reference position, and flow control of the first fluid control valve is performed so that the flow rate is the target flow rate.

[0017] According to the present invention described above, when switching the branch channel with the largest flow rate in the flow rate ratio control device, the switching can be performed when the flow rates of multiple branch channels are equal, so that the flow rate through the branch channel does not change drastically (peak), thereby smoothly switching the branch channel. Attached Figure Description

[0018] Figure 1 This is an overall schematic diagram of a flow ratio control device according to one embodiment of the present invention.

[0019] Figure 2 This is a schematic diagram showing a flow control device according to the same implementation method.

[0020] Figure 3 This is a diagram illustrating the steps of traffic standardization in the same implementation method.

[0021] Figure 4 This is a schematic diagram showing the control contents of the fluid control valve in the same embodiment and the flow rate of the branch flow channel.

[0022] Explanation of reference numerals in the attached figures

[0023] 100··· Flow ratio control device

[0024] ML...the mainstream path

[0025] BL1~BL4···Branch Flow Channels

[0026] 3. Fluid control valve

[0027] 32···Valve body

[0028] 6. Position sensor

[0029] 7. Storage Department

[0030] 8. Flow Ratio Control Department Detailed Implementation

[0031] Hereinafter, a flow ratio control device according to one embodiment of the present invention will be described with reference to the accompanying drawings.

[0032] <1. Device Composition>

[0033] like Figure 1 As shown, the flow rate control device 100 of this embodiment is used, for example, in a semiconductor manufacturing process, for introducing semiconductor processing gas from a plurality of inlets of the vacuum chamber 200 into the vacuum chamber 200 containing the wafer at a predetermined flow rate ratio.

[0034] Specifically, the flow ratio control device 100 is configured to include: a main flow channel ML; multiple branch flow channels BL1 to BL4 branching from the main flow channel ML; multiple fluid control devices MFC1 to MFC4 respectively installed on the multiple branch flow channels BL1 to BL4; and a main controller COM that controls the multiple fluid control devices MFC1 to MFC4 in a manner that the flow ratio of the gas flowing through each branch flow channel BL1 to BL4 is a target flow ratio.

[0035] The upstream end of the main flow channel ML is connected to a gas source 300 that supplies gas for semiconductor processing, and the downstream end is connected to multiple branch channels BL1 to BL4. Figure 1 The example shown is a connection with four branch channels BL1 to BL4, but there are no special restrictions as long as there are two or more branch channels BL.

[0036] The fluid control devices MFC1 to MFC4 are devices known as mass flow controllers, such as... Figure 2 As shown, the device includes: a block 2 having an internal flow channel communicating with branch flow channels BL1 to BL4; a fluid control valve 3 for controlling the flow rate of the internal flow channel provided in the block 2; a flow sensor 4 provided in the block 2, positioned on the upstream or downstream side of the fluid control valve 3 in the internal flow channel; and a valve control unit 5 for controlling the fluid control valve 3. Furthermore, in the following description, when distinguishing the constituent components of each fluid control device MFC1 to MFC4, they will be referred to as the first fluid control valve 3-1, the second fluid control valve 3-2, etc.

[0037] The fluid control valve 3 includes: a valve seat 31 disposed in the middle of an internal flow path; a valve body 32 engaged or disengaged relative to the valve seat 31; and an actuator 33, which is composed of, for example, a piezoelectric element that moves the valve body 32. Furthermore, the fluid control valve 3 can be a normally open type valve that is fully open when the actuator 33 is not activated, or a normally closed type valve that is fully closed when the actuator 33 is not activated.

[0038] In addition, the fluid control valve 3 also has a position sensor 6, which detects the position of the valve body 32 relative to the valve seat 31. The position sensor 6 is, for example, an eddy current type non-contact displacement sensor. The detected position obtained by the position sensor 6 is output to the valve control unit 5.

[0039] The flow sensor 4 is, for example, a pressure type, and includes: a laminar flow element 41 disposed in an internal flow channel; 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 output circuit 44 that outputs the flow rate based on the detected pressures by each pressure sensor 42, 43. Furthermore, the flow output circuit 44 calculates the fluid flow rate based on the pressure difference between the detected pressures of the upstream pressure sensor 42 and the downstream pressure sensor 43, and outputs this calculation to the valve control unit 5. Alternatively, a thermal type flow sensor 4 can also be used.

[0040] The valve control unit 5 performs flow control or position control on the fluid control valve 3 based on instructions from the main controller COM. Furthermore, the valve control unit 5, together with the main controller COM, functions as the flow ratio control unit 8, which will be described later.

[0041] When the valve control unit 5 performs flow control on the fluid control valve 3, flow feedback control (flow control mode) is performed to minimize the deviation between the target position (used to achieve a preset target flow rate) and the detection position detected by the position sensor 6. In this case, the valve control unit 5 controls the applied voltage to the fluid control valve 3 to make the measured position of the position sensor 6 the detection position based on the deviation between the target position and the detection position. Alternatively, the valve control unit 5 can also perform flow feedback control to minimize the deviation between a preset target flow rate and the measured flow rate measured by the flow sensor 4. In this case, a target opening degree is calculated based on the deviation between the target flow rate and the measured flow rate, and the applied voltage to the fluid control valve 3 is controlled to make the opening degree indicated by the position sensor 6 the target opening degree.

[0042] Furthermore, when the valve control unit 5 performs position control on the fluid control valve 3, position feedback control (position control mode) is performed to reduce the deviation between the preset target position and the detection position detected by the position sensor 6. That is, when the valve control unit 5 performs position control on the fluid control valve 3, it does not perform feedback control using the measured flow rate measured by the flow sensor 4.

[0043] In this embodiment, the valve control unit 5 of the fluid control device MFC1, which is located on the branch channel with the largest target flow rate ratio (here, the first branch channel BL1), i.e., the main pipeline, operates in position control mode. On the other hand, the valve control units 5 of the fluid control devices MFC2 to MFC4, which are located on the branch channels BL2 to BL4, i.e., the subordinate pipelines, other than the main pipeline, operate in flow control mode.

[0044] Here, the target position in position control mode will be explained.

[0045] The flow ratio control device 100 of this embodiment has a storage unit 7, which stores the reference positions of the valve bodies 32 of each fluid control valve 3 for distributing the flow rate through the main flow channel ML to the multiple branch flow channels BL1 to BL4 at a predetermined flow ratio. Additionally, as... Figure 2 As shown, the storage unit 7 can be individually installed in the memory of each fluid control device MFC1 to MFC4, or it can be collectively installed in the memory of the main controller COM.

[0046] Furthermore, the storage unit 7 stores reference positions for the valve bodies 32 of each fluid control valve 3, which are used to distribute the flow rate through the main flow channel ML to the multiple branch flow channels BL1 to BL4 at a predetermined flow rate ratio. Here, the reference position of the valve body 32 set for each fluid control valve 3 is a position set as the fully open position of the fluid control valve 3. Moreover, this reference position becomes the target position in the position control mode.

[0047] The flow rate ratio specified in this embodiment is the flow rate ratio that distributes the flow rate (e.g., 4L) flowing through the main channel ML to the multiple branch channels BL1 to BL4 (each branch channel BL1 to BL4 has a flow rate of 1L).

[0048] <2. Method for setting the reference position>

[0049] Here, as Figure 3 As shown, the reference position is determined in advance, for example, through the following flow normalization steps, and stored in the storage unit 7 according to each fluid control valve 3.

[0050] A drive signal (voltage signal) for physically fully opening is input to a plurality of fluid control valves 3 installed on the first branch flow channel to the fourth branch flow channel BL1 to BL4, and the position of the valve body 32 (fully open position) detected by the position sensor 6 is obtained at this time (step S1).

[0051] In addition, drive signals (voltage signals) for physically closing the multiple fluid control valves 3 installed on the first branch flow channel to the fourth branch flow channel BL1 to BL4 are input respectively, and the position of the valve body 32 (fully closed position) detected by the position sensor 6 at this time is obtained (step S2).

[0052] Furthermore, by making the flow ratio of the fluid flowing through the first branch channel to the fourth branch channel BL1 to BL4 a predetermined flow ratio (where the flow ratio is the same (25% each)), the fluid control valve 3 is made fully open, and the flow ratio of the fluid flowing through the first branch channel to the fourth branch channel BL1 to BL4 at this time is calculated (step S3).

[0053] The flow split ratio obtained in step S3 is compared with the predetermined flow split ratio (step S4). If the difference between them is greater than the predetermined threshold, the fully open position of any one of the multiple fluid control valves 3 installed on the first branch flow channel to the fourth branch flow channel BL1 to BL4 is changed (step S5). For example, the fully open position of the fluid control valve 3 installed on the branch flow channel with the largest difference is changed.

[0054] Furthermore, using the modified fully open position, return to step S3 above, and repeatedly change the fully open position of the fluid control valve 3 until the difference between the flow ratio of the fluid flowing through the first branch channel to the fourth branch channel BL1 to BL4 and the predetermined flow ratio becomes less than the predetermined threshold. The fully open position of each fluid control valve 3 obtained thereby is stored as a reference position in the storage unit 7 (step S6).

[0055] The main controller COM, based on the target flow rate ratio of the gas flowing through each branch channel BL1 to BL4 received from the user, inputs commands to each fluid control device MFC1 to MFC4. This causes the fluid control device MFC1, located in the branch channel BL1 which becomes the main pipeline, to execute a position control mode for position control. It also inputs individual target flow rates calculated based on the target flow rate ratios to the fluid control devices MFC2 to MFC4 located in the other branch channels BL2 to BL4, causing them to execute flow control modes. Furthermore, the main controller COM, in cooperation with the valve control units 5 of each flow control device MFC1 to MFC4, functions as a flow rate control unit 8, as shown below.

[0056] At this time, the flow ratio control unit 8 performs position control on the fluid control valve 3 of the fluid control device MFC1 installed on the branch flow channel BL1, which becomes the main pipeline, so that the position of its valve body 32 is the reference position, based on the detection position detected by the position sensor 6. It also performs flow control on the fluid control valve 3 of the fluid control devices MFC2 to MFC4 installed on the branch flow channels BL2 to BL4, which become subordinate pipelines, so that the flow rate is the target flow rate, thereby controlling the flow ratio of the multiple branch flow channels BL1 to BL4.

[0057] <3. Switching Actions of the Main Pipeline>

[0058] Furthermore, it is possible that the flow ratio control unit 8 does not change the flow rate of the fluid flowing through the main flow channel ML, but continuously switches the branch channel (main pipe) with the largest target flow ratio from the first branch channel BL1 to the second branch channel BL2. In addition, the case of switching between the first branch channel BL1 and the second branch channel BL2 is illustrated here, but the same applies to switching between other branch channels.

[0059] In this case, such as Figure 4 As shown, the flow ratio control unit 8 causes the second fluid control valve 3, which is installed on the second branch flow channel BL2, to gradually move its valve body 32 from the fully closed position to the reference position through the flow control mode. Here, the valve body 32 is gradually moved in such a way that the flow rate through the second branch flow channel BL2 increases linearly.

[0060] Furthermore, if the valve body 32 of the second fluid control valve 3 installed on the second branch channel BL2 reaches the reference position, the second fluid control valve 3 is switched from flow control to position control. Position control is performed on the second fluid control valve 3 so that its valve body 32 is at the reference position, and flow control is performed on the first fluid control valve 3 installed on the first branch channel BL1 so that the flow rate of the first branch channel BL1 gradually decreases and becomes zero. Here, the valve body 32 is gradually displaced so that the flow rate flowing through the first branch channel BL1 decreases linearly. In addition, in a series of actions that continuously switch from the first branch channel BL1 to the second branch channel BL2, the flow rate flowing through the first branch channel BL1 decreases linearly, and the flow rate flowing through the second branch channel BL2 increases linearly. Thus, the branch channel (main pipe) with the largest target flow rate ratio continuously switches from the first branch channel BL1 to the second branch channel BL2. In addition, Figure 4 The example illustrates the case where, after switching the main pipe from "first branch channel BL1" to "second branch channel BL2", the main pipe is then switched back from "second branch channel BL2" to "first branch channel BL1".

[0061] In addition, by conducting Figure 4The same switching action can also be used to evaluate the performance of the switching action of the branch channels BL1 and BL2 of the flow ratio control device 100. That is, by determining whether the flow rate through the branch channels BL1 and BL2 changes drastically (peaks) at the switching point between the first branch channel BL1 and the second branch channel BL2, the performance of the flow ratio control device 100 can be evaluated.

[0062] <4. Effects of this implementation method>

[0063] The flow ratio control device 100 of this embodiment, configured in this way, stores in advance the reference position of the valve body for allowing a predetermined reference flow rate to pass through each fluid control valve 3. Based on this reference position, the first fluid control valve 3 and the second fluid control valve 3 are switched. Therefore, when switching the branch flow channel with the largest flow rate in the flow ratio control device 100, the switching can be performed with the flow rates of multiple branch flow channels BL1 to BL4 being equal, and the flow rates flowing through branch flow channels BL1 and BL2 can be prevented from changing drastically (spiking), thereby enabling smooth switching of branch flow channels.

[0064] In detail, by standardizing the reference positions of the valve bodies 32 of the fluid control valves 3 installed on the branch channels BL1 to BL4, which have the lowest flow conductance among the multiple branch channels BL1 to BL4, the switching can be performed when the flow rate of the branch channel with the highest flow rate is switched in the flow ratio control device 100, with the flow rates of the multiple branch channels BL1 to BL4 being equal. Furthermore, by standardizing in this way, the lowest possible pressure differential can be maintained in the overall system, and the arrival time of the gas supply from the flow ratio control device 100 to, for example, the processing chamber can be shortened. Moreover, according to this embodiment, since the flow conductance of the flow path from the fluid control valves 3 to, for example, the processing chamber can be standardized in the multiple branch channels BL1 to BL4, system variations occurring downstream of components such as filters installed in the flow paths and nozzles installed in the chambers can be eliminated.

[0065] In the multiple branch channels BL1 to BL4 connected to, for example, a vacuum chamber 200 for semiconductor processing, the master-slave relationship (master-slave relationship) between the branch channel connected to the central part of the vacuum chamber 200 and the branch channel connected to the outer periphery of the vacuum chamber 200 can be switched smoothly, thereby improving the quality of the semiconductor manufacturing process. Furthermore, the situation where, for example, the flow rate control shifts from a process with a higher flow rate towards the outer periphery of the vacuum chamber 200 to a purge control with a higher flow rate towards the central part of the vacuum chamber 200 conforms to the aforementioned master-slave relationship switching.

[0066] <5. Other Implementation Methods>

[0067] Furthermore, the present invention is not limited to the embodiments described herein.

[0068] The reference position in the described embodiment is the position of the valve body 32 through which flow rates with the same split ratio (equally distributed flow rates) flow, but it can also be the position of the valve body 32 through which flow rates with different split ratios flow. That is, if in Figure 4 In the example given, the flow rate through the valve body 32 may not be the same (50:50) as the flow split ratio of the first branch channel BL1 and the second branch channel BL2, but rather the flow split ratio of the first branch channel BL1 and the second branch channel BL2 may be, for example, 49:51 or 52:48. Furthermore, the specified reference flow rate may be ranged to a degree that the fluid control valve 3 enters within the resolution range (e.g., 0.2% of full scale). The reference position in the above embodiment is ranged by making the valve body 32 a position that has a reference flow rate within that range. That is, the timing of the switching between position control and flow control of the fluid control valve 3 may be ranged rather than occurring at a single point.

[0069] Additionally, if in Figure 4 In the example, the timing for switching the control of the first branch flow channel BL1 and the second branch flow channel BL2 can be ranged. In this case, when the main pipeline is switched from the first branch flow channel BL1 to the second branch flow channel BL2, after both the first fluid control valve 3 and the second fluid control valve 3 have gone through the period of position control (or flow control), the first fluid control valve 3 becomes flow control and the second fluid control valve becomes position control.

[0070] Furthermore, in the described embodiment, the fluid control device MFC is an integrated mass flow controller, but other fluid control devices can also be installed on each branch flow channel. For example, fluid control valves and flow sensors that are not integrated like a mass flow controller can also be treated as fluid control devices.

[0071] In the embodiment described above, the position control valve installed on the branch channel with the highest fluid flow rate is controlled based on the target flow rate ratio. However, for example, the branch channel with the second or third highest fluid flow rate can be used as the main channel, and the other branch channels can be used as subordinate channels, and the position control valve installed on the main channel can be controlled.

[0072] Furthermore, the embodiment described herein illustrates an example of using the flow ratio control device in a semiconductor manufacturing process, but it can also be used for other purposes.

[0073] Furthermore, various modifications and combinations of implementation methods are possible as long as they do not violate the spirit of this invention.

Claims

1. A flow ratio control device, characterized in that, The flow ratio control device includes: At least the first branch channel and the second branch channel branching from the main channel; A first fluid control valve is disposed on the first branch flow channel and has a position sensor for detecting the position of the valve body; The second fluid control valve is installed on the second branch flow channel and has a position sensor that detects the position of the valve body. The storage unit stores the reference position of the valve body of each of the fluid control valves for distributing the flow rate through the main flow channel to the first branch flow channel and the second branch flow channel at a predetermined flow rate ratio; and The flow ratio control unit controls the first fluid control valve and the second fluid control valve, thereby controlling the flow ratio of the at least first branch flow channel and the second branch flow channel. The flow ratio control unit is configured to switch between position control and flow control of the first fluid control valve and the second fluid control valve. Before switching, the flow ratio control unit simultaneously performs position control of the first fluid control valve to make the valve body position of the first fluid control valve the reference position, and flow control of the second fluid control valve to make the flow rate of the second fluid control valve the target flow rate. The switching occurs when the valve body of the second fluid control valve, which is subject to flow control, reaches the reference position. After switching, the flow ratio control unit simultaneously performs position control of the second fluid control valve to make the position of the valve body of the second fluid control valve the reference position, and flow control of the first fluid control valve to make the flow rate of the first fluid control valve the target flow rate.

2. The flow ratio control device according to claim 1, characterized in that, If the valve body of the second fluid control valve, which controls the flow rate, is gradually displaced from the fully closed position to the reference position, so that the position of the valve body reaches the reference position, then the flow rate ratio control unit switches between position control and flow control for each of the fluid control valves. Position control is performed on the second fluid control valve so that its valve body reaches the reference position, and flow control is performed on the first fluid control valve so that the flow rate gradually becomes zero.

3. The flow ratio control device according to claim 1, characterized in that, The specified flow rate ratio is the ratio of the flow rate that is equally distributed between the first branch channel and the second branch channel when the flow rate through the main channel is used. The reference position is a position set as the fully open position of the fluid control valve.

4. The flow ratio control device according to claim 1, characterized in that, The first fluid control valve, together with the flow sensor installed on the first branch flow channel, constitutes the first fluid control device. The second fluid control valve, together with the flow sensor installed on the second branch flow channel, constitutes the second fluid control device.

5. A storage medium storing a control program for a flow rate control device, characterized in that, The flow ratio control device includes: at least a first branch flow channel and a second branch flow channel branching from the main flow channel; a first fluid control valve disposed on the first branch flow channel and having a position sensor for detecting the position of the valve body; and a second fluid control valve disposed on the second branch flow channel and having a position sensor for detecting the position of the valve body. The computer, by executing the control program for the flow ratio control device, functions as both a storage unit and a flow ratio control unit. The storage unit stores the reference position of the valve body of each of the fluid control valves for distributing the flow rate through the main flow channel to the first branch flow channel and the second branch flow channel at a predetermined flow rate ratio. The flow ratio control unit controls the first fluid control valve and the second fluid control valve, thereby controlling the flow ratio of at least the first branch flow channel and the second branch flow channel. The flow ratio control unit is configured to switch between position control and flow control of the first fluid control valve and the second fluid control valve. Before switching, the flow ratio control unit simultaneously performs position control of the first fluid control valve to make the valve body position of the first fluid control valve the reference position, and flow control of the second fluid control valve to make the flow rate of the second fluid control valve the target flow rate. The switching occurs when the valve body of the second fluid control valve, which is subject to flow control, reaches the reference position. After switching, the flow ratio control unit simultaneously performs position control of the second fluid control valve to make the position of the valve body of the second fluid control valve the reference position, and flow control of the first fluid control valve to make the flow rate of the first fluid control valve the target flow rate.

6. A control method for a flow ratio control device, characterized in that, The flow ratio control device includes: at least a first branch flow channel and a second branch flow channel branching from the main flow channel; a first fluid control valve disposed on the first branch flow channel and having a position sensor for detecting the position of the valve body; and a second fluid control valve disposed on the second branch flow channel and having a position sensor for detecting the position of the valve body. The control method of the flow ratio control device includes: The storage process includes storing the reference position of the valve body in each of the fluid control valves for distributing the flow rate through the main flow channel to the first branch flow channel and the second branch flow channel at a predetermined flow rate ratio; and The flow ratio control process controls the first fluid control valve and the second fluid control valve, thereby controlling the flow ratio of the at least first branch flow channel and the second branch flow channel. The flow ratio control process switches between position control and flow control of the first fluid control valve and the second fluid control valve. Before switching, the flow ratio control process simultaneously performs position control of the first fluid control valve to make the valve body position of the first fluid control valve the reference position, and flow control of the second fluid control valve to make the flow rate of the second fluid control valve the target flow rate. The switching occurs when the valve body of the second fluid control valve, which is subject to flow control, reaches the reference position. After the flow ratio control process is switched, it simultaneously performs position control of the second fluid control valve to make the valve body position of the second fluid control valve the reference position, and flow control of the first fluid control valve to make the flow rate of the first fluid control valve the target flow rate.

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