Flow ratio controller and gas distribution system using same

Abstract

A disclosed example flow ratio controller includes an inlet configured to receive an input process gas stream; an inlet pressure sensor configured to measure an inlet pressure; a first outlet and a second outlet configured to output a first portion and a second portion of an input process gas stream; a first flow valve and a second flow valve configured to control a flow of input process gas to the first outlet and the second outlet; a first position sensor and a second position sensor configured to measure valve positions of the first flow valve and the second flow valve; a first outlet pressure sensor and a second outlet pressure sensor configured to measure outlet pressures of the first outlet and the second outlet; and control circuitry configured to control the first flow valve and the second flow valve using a valve flow model and based on a predetermined flow ratio of the first outlet and the second outlet, the inlet pressure, the first valve position and the second valve position, and the first outlet pressure and the second outlet pressure.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 553,958, entitled “FLOW RATIO CONTROLLERS AND GASDISTRIBUTION SYSTEMS UTILIZING FLOW RATIO CONTROLLERS,” filed on February 15, 2024. The entire contents of U.S. Provisional Patent Application Serial No. 63 / 553,958 are expressly incorporated herein by reference. Technical Field

[0003] The present disclosure relates generally to flow control and, more particularly, to flow ratio controllers and gas distribution systems utilizing the same. Background Art

[0004] A flow ratio controller receives a flow of one or more gases and distributes the flow among multiple outputs according to defined ratios. Summary of the Invention

[0005] A flow ratio controller and a gas distribution system utilizing the same are disclosed, substantially as illustrated by and described in conjunction with at least one of the Figures, as more fully set forth in the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] These and other features, aspects, and advantages of the present disclosure will be better understood when the following detailed description is read with reference to the accompanying drawings, in which like reference numerals represent like parts throughout, wherein:

[0007] Figure 1 is a block diagram of certain example gas distribution systems including multiple gas sources and a flow ratio controller for controlling gas distribution according to aspects of the present disclosure.

[0008] Figure 2 It can be used to implement Figure 1 Schematic diagram of an example flow valve for each flow valve in a flow ratio controller.

[0009] Figure 3 Describes the elements of a traffic model that can be Figure 1 The control circuit system uses to control Figure 2 flow valve and / or determine the flow through a flow valve without using a dedicated flow meter.

[0010] Figure 4A and Figure 4Bis a plot of example valve flow models that can be obtained from Figure 1 The control circuit system uses to control Figure 2 flow valve and / or determine the flow through a flow valve without using a dedicated flow meter.

[0011] Figure 5 is a flowchart representing example machine readable instructions that may be executed to implement Figure 1 control circuit system to provide controlled gas distribution.

[0012] The accompanying drawings are not necessarily drawn to scale. Where appropriate, similar or identical reference numbers are used to designate similar or identical components. DETAILED DESCRIPTION

[0013] To promote an understanding of the principles of the claimed technology and to present its best currently understood mode of operation, reference will now be made to the embodiments illustrated in the drawings, and specific language will be used to describe these embodiments. It will be understood, however, that no limitation of the scope of the claimed technology is intended thereby, as such alterations and further modifications of the illustrated apparatus and such further applications of the principles of the claimed technology as illustrated herein are within the ordinary scope of those skilled in the art to which the claimed technology pertains.

[0014] Flow ratio controllers are used in applications such as semiconductor manufacturing to deliver precise ratios of gas to different areas of a wafer. In addition to cost-effectiveness, these semiconductor manufacturing applications benefit from faster response times, repeatable results, and consistent results. Traditional flow ratio controllers, which include inlet and outlet pressure sensors for each channel, as well as mass flow meters and control valves, can introduce errors in flow ratio distribution due to variations between the sensors.

[0015] Compared to conventional flow ratio controllers, the disclosed example flow ratio controllers offer increased stability and accuracy, as well as improved response time to flow rate changes. The disclosed example flow ratio controllers utilize piezoelectric valves and an inlet pressure sensor shared across all outlet channels of the flow ratio controller to provide accurate and repeatable gas distribution to multiple channels without the use of flow sensors for flow detection. Instead, the disclosed example utilizes valve flow models, inlet and outlet pressure sensors, and valve position sensors to determine the flow rate through each channel.

[0016] The disclosed example flow ratio controller includes: an inlet configured to receive an input process gas flow; an inlet pressure sensor configured to measure an inlet pressure of the input process gas flow; a first outlet configured to output a first portion of the input process gas flow; a second outlet configured to output a second portion of the input process gas flow; a first flow valve configured to control a flow of the input process gas to the first outlet; a second flow valve configured to control a flow of the input process gas to the second outlet; and a first position sensor configured to To measure a first valve position of a first flow valve; a first outlet pressure sensor, which is configured to measure a first outlet pressure of the first outlet; a second position sensor, which is configured to measure a second valve position of a second flow valve; a second outlet pressure sensor, which is configured to measure a second outlet pressure of the second outlet; and a control circuit system, which is configured to use a valve flow model and control the first flow valve and the second flow valve based on a predetermined flow ratio of the first outlet and the second outlet, the inlet pressure, the first valve position, the second valve position, the first outlet pressure and the second outlet pressure.

[0017] In some example flow ratio controllers, the control circuitry is configured to: determine a first flow rate at a first outlet based on an inlet pressure, a first outlet pressure, and a first valve position in the absence of a flow meter; determine a second flow rate at a second outlet based on an inlet pressure, a second outlet pressure, and a second valve position in the absence of a flow meter; and control at least one of a first flow valve and a second flow valve based on the first flow rate, the second flow rate, and a predetermined flow ratio. In some example flow ratio controllers, the control circuitry is configured to: control the first flow valve to generate a sonic flow condition through the first flow valve when the first flow valve is open; and control the second flow valve to generate a sonic flow condition through the second flow valve when the second flow valve is open.

[0018] In some example flow ratio controllers, a first flow valve includes a first loss region and a second loss region connected in series with each other, wherein the control circuitry is configured to control the first flow valve based on calculating a first laminar flow through the first loss region and calculating a first sonic flow through the second loss region. In some example flow ratio controllers, a second flow valve includes a third loss region and a fourth loss region connected in series with each other, and the control circuitry is configured to control the second flow valve based on calculating a second laminar flow through the third loss region and calculating a second sonic flow through the fourth loss region.

[0019] In some examples, the flow ratio controller includes three or more flow valves, the three or more flow valves including the first flow valve and the second flow valve, each of the three or more flow valves having an orifice, a position sensor, and an outlet pressure sensor, wherein the control circuit system is configured to calculate the flow through each of the three or more flow valves and control each of the three or more flow valves to meet a predetermined diversion ratio.

[0020] In some example flow ratio controllers, the first flow valve and the second flow valve each comprise a piezoelectric valve. In some example flow ratio controllers, the first position sensor and the second position sensor each comprise at least one of a capacitive position sensor, a strain gauge position sensor, a Hall effect position sensor, or an optical position sensor. In some example flow ratio controllers, the valve flow model is a predetermined model that relates valve position, flow rate, input pressure, and output pressure for each of the first and second flow valves.

[0021] Some example flow ratio controllers further include a manifold configured to distribute the input process gas flow to the first flow valve and the second flow valve, wherein the inlet pressure sensor is configured to measure the inlet pressure in the manifold. In some example flow ratio controllers, the control circuitry is configured to: determine a rate of change of the inlet pressure based on a measurement result from the inlet pressure sensor; and control the first flow valve and the second flow valve based on the inlet pressure and the rate of change of the inlet pressure to maintain the inlet pressure within a predetermined range of the predetermined inlet pressure.

[0022] The disclosed example precision gas distribution system includes: a plurality of mass flow controllers configured to control the flow of corresponding gases to corresponding outlets; and a flow ratio controller configured to: receive gas from the mass flow controllers via an inlet; and control the plurality of flow valves by using a valve flow model and based on an inlet pressure at the inlet, valve positions of the plurality of flow valves, and outlet pressures of the plurality of outlets of the flow ratio controller, thereby controlling the delivery of corresponding portions of the gas to the plurality of outlets of the flow ratio controller according to predetermined flow ratios of the plurality of outlets.

[0023] In some example precision gas distribution systems, a flow ratio controller includes an inlet pressure sensor configured to measure an inlet pressure of an input process gas flow, the input process gas flow including gas at an inlet, wherein a plurality of outlets includes a first outlet configured to output a first portion of the input process gas flow and a second outlet configured to output a second portion of the input process gas flow, and a plurality of flow valves includes a first flow valve configured to control a flow of the input process gas to the first outlet and a second flow valve configured to control a flow of the input process gas to the second outlet. The flow ratio controller further includes: a first position sensor, which is configured to measure a first valve position of the first flow valve; a first outlet pressure sensor, which is configured to measure a first outlet pressure of the first outlet; a second position sensor, which is configured to measure a second valve position of the second flow valve; a second outlet pressure sensor, which is configured to measure a second outlet pressure of the second outlet; and a control circuit system, which is configured to use a valve flow model and control the first flow valve and the second flow valve based on a predetermined flow ratio of the first outlet and the second outlet, the inlet pressure, the first valve position, the second valve position, the first outlet pressure and the second outlet pressure.

[0024] In some example precision gas distribution systems, the control circuitry is configured to: control the first flow valve to generate a sonic flow pattern through the first flow valve when the first flow valve is open; and control the second flow valve to generate a sonic flow pattern through the second flow valve when the second flow valve is open. In some example precision gas distribution systems, the first flow valve includes a first loss region and a second loss region connected in series, wherein the control circuitry is configured to control the first flow valve based on calculating a first laminar flow through the first loss region and calculating a first sonic flow through the second loss region.

[0025] In some example precision gas distribution systems, the first flow valve and the second flow valve each comprise a piezoelectric valve. In some example precision gas distribution systems, the first position sensor and the second position sensor each comprise at least one of a capacitive position sensor, a strain gauge position sensor, a Hall effect position sensor, or an optical position sensor. In some example precision gas distribution systems, the valve flow model is a predetermined model that relates valve position, flow rate, input pressure, and output pressure for each of the first and second flow valves.

[0026] Some example precision gas distribution systems further include a manifold configured to distribute the input process gas flow to the first flow valve and the second flow valve, wherein the inlet pressure sensor is configured to measure an inlet pressure in the manifold. In some example precision gas distribution systems, the control circuitry is configured to: determine a rate of change of the inlet pressure based on a measurement result from the inlet pressure sensor; and control the first flow valve and the second flow valve based on the inlet pressure and the rate of change of the inlet pressure to maintain the inlet pressure within a predetermined range of a predetermined inlet pressure.

[0027] Some example precision gas distribution systems further include a temperature sensor configured to measure a temperature of the input process gas flow, the control circuitry configured to control the first flow valve and the second flow valve based on the temperature.

[0028] Figure 1 1 is a block diagram of an example gas distribution system 100 that includes a plurality of gas sources 102a-102n and a flow ratio controller 104 for controlling the distribution of the gases 102a-102n (e.g., a predetermined mixture of two or more gases in the gases 102a-102n). The gases 102a-102n can be different types of process gases, such as process gases used in semiconductor manufacturing.

[0029] The example gas distribution system 100 includes a set of mass flow controllers 106a-106n that control the flow rate of each gas 102a-102n. The mass flow controllers 106a-106n output the corresponding gas 102a-102n to a manifold 108 or other mixing volume and feed it into an inlet 110 of a flow ratio controller 104.

[0030] Figure 1An example flow ratio controller 104 receives respective portions (e.g., as a mixture) of inlet process gas flows (e.g., gases 102a-102n) via an inlet 110 and controls delivery of the input process gas flows to a set of outlets 112a-112m. As disclosed in greater detail below, the flow ratio controller 104 controls delivery of the input process gas flows according to a predetermined flow ratio of the plurality of outlets 112a-112m by controlling the plurality of flow valves using a valve flow model based on an inlet pressure at the inlet 110, valve positions of the plurality of flow valves, and outlet pressures of the plurality of outlets 112a-112m. The inlet 110 and the outlets 112a-112m can be any single or combination of types of disconnectable or permanent gas connections, such as threaded connections, quick-connect connections, welded or brazed connections, and / or any other suitable type of connection. The outlets 112a-112m may be coupled (eg, via hoses, pipes, conduits, and / or any other rigid, semi-rigid, and / or flexible conduits) to corresponding outlet locations 114a-114m to which the input process gas flow is to be output.

[0031] The example flow ratio controller 104 includes a set of flow valves 116a-116m, each of which controls the flow from a shared inlet 110 to a corresponding outlet 112a-112m. The inlet pressure at the inlet 110 (also the inlet pressure at the inlet of the flow valves 116a-116m) is measured via an inlet pressure sensor 118. Figure 2 As discussed in greater detail, each flow valve 116a - 116m includes a position sensor 120a - 120m to measure a valve position of the corresponding flow valve 116a - 116m.

[0032] In some examples, the flow ratio controller 104 includes a manifold for distributing the input process gas flow to the first flow valve and the second flow valve, wherein the inlet pressure sensor is configured to measure the inlet pressure in the manifold.

[0033] Each gas path from the inlet 110 to one of the outlets 112a-112m is referred to herein as an "outlet channel." Each outlet channel 126a-126m includes a corresponding flow valve 116a-116m (with a corresponding position sensor 120a-120m), a corresponding outlet 112a-112m, and a corresponding outlet pressure sensor 122a-122m. The outlet pressure sensor 122a-122m (e.g., between the outlet of the flow valve 116a-116m and the outlet 112a-112m) measures the outlet pressure of the corresponding outlet 112a-112m.

[0034] The example flow ratio controller 104 further includes a control circuit system 124 for controlling the flow valves 116a-116m to output gas to two or more outlet channels in the outlet channels 126a-126m. The example control circuit system 124 can be an integrated processing system, a programmable logic controller, a general-purpose computer, a laptop computer, a tablet computer, and / or any other type of processing system configured to communicate with the sensors 120a-120m, 122a-122m and the flow valves 116a-116m of the flow ratio controller 104. For example, the control circuit system 124 includes a processor 128, a memory 130, and a storage device 132. The example processor 128 can be any general-purpose central processing unit (CPU) from any manufacturer. In some other examples, the processor 128 can include one or more dedicated processing units, such as a RISC processor with an ARM core, a graphics processing unit, a digital signal processor, and / or a system on a chip (SoC). The processor 128 executes machine-readable instructions 134, which may be stored locally at the processor (e.g., in an included cache or SoC), in memory (e.g., random access memory or other volatile memory, read-only memory, or other non-volatile memory such as flash memory), and / or in storage 132. Example storage 132 may be a hard disk drive, a solid-state storage drive, a hybrid drive, a RAID array, and / or any other mass data storage device.

[0035] exist Figure 1 In the example of FIG, the control circuit system 124 uses a predetermined (e.g., stored, received) flow ratio to control the flow valves 116a-116m. The predetermined flow ratio can be stored in the memory 130 and / or the storage device 132, and / or received at the processor from an external control system (e.g., via the communication circuit system).

[0036] exist Figure 1 In the example, the flow ratio controller 104 does not have a flow sensor that directly measures the outlet flow through the outlet passages 126a-126m. Instead, the example control circuit system 124 controls the flow valves 116a-116m according to one or more valve flow models. The valve flow models can be stored in a memory or other storage device of the control circuit system 124. The example valve flow models that can be used by the control circuit system 124 relate valve position, inlet pressure, outlet pressure, and flow rate for each example flow valve 116a-116m. Because, for example, different flow valves 116a-116m have different configurations, the control circuit system 124 can use different valve flow models for different flow valves 116a-116m.

[0037] The example flow ratio controller 104 further includes a temperature sensor 136 for measuring the temperature of the gas received via the inlet 110 and / or a plurality of temperature sensors configured to measure the temperature of the gas distributed through the flow valves 116a-116m. Although in many cases the temperature of the gas distributed to the different outlet channels 126a-126m is substantially equal, the control circuit system 124 can use the measured temperature to compensate for or correct for flow and / or pressure variations.

[0038] Figure 2 is a schematic diagram of an example flow valve 200 that can be used to implement Figure 1 The flow ratio of each flow valve 116a-116m in the controller 104. Figure 2 The example flow valve 200 is a piezoelectric valve including a stack of piezoelectric actuators 202 coupled to a control board 204 to control a valve inlet 206 in a base 210 (e.g., coupled to a Figure 1 The size of the gas passage between the inlet 110 of the flow valve 200 and the valve outlet 208 (eg, coupled to the outlet 112). The valve inlet 206 and the valve outlet 208 are selectively coupled to the housing 214 of the flow valve 200 via the flow channel 212.

[0039] The example piezoelectric flow valve 200 is a normally open valve, allowing gas to be vented to a desired location in the event of a power outage rather than being trapped within the gas distribution system 100. In other examples, the flow valve 200 is a normally closed valve.

[0040] Flow channel 212 can be adjusted by controlling piezoelectric actuator 202 to move control plate 204. For example, control plate 204 can move away from base 210 to increase the size of flow channel 212 and toward base 210 to decrease the size of flow channel 212 and / or close flow channel 212.

[0041] The piezoelectric actuator 202 is coupled to the control board 204 via a valve stem 216, a rod, or other rigid coupling. To detect the position of the flow valve 200, the example position sensor 120 detects the distance between the position sensor 120 and a target member 218 coupled to the valve stem 216. When the valve stem 216 is actuated to move by the piezoelectric actuator 202, the target member 218 moves toward and away from the position sensor 120. The position sensor 120 can be a capacitive position sensor, a strain gauge position sensor, an optical position sensor, a Hall effect sensor, and / or any other type of position sensor, and the target member 218 can be of a type suitable for the type of position sensor 120.

[0042] The example control circuitry 124 may include multiple elements in a flow model for the valve 200. For example, the flow model may represent multiple sources of flow constraints, such as a first pressure loss region (e.g., a viscous flow region) and a second loss region (e.g., an inviscid flow region). Figure 3 Describes the elements of a traffic model that can be Figure 1 The control circuit system 124 is used to control Figure 2 The flow valve 200 and / or determining the flow through the flow valve without using a dedicated flow meter.

[0043] Figure 2 and Figure 3 The flow valve 200 and elements 302-308 can be reflected as Figure 1 Each example flow valve 116a-116m.

[0044] like Figure 3 As shown, the distance between the control plate 204 and the valve seat 302 controls the size of the viscous flow region 304 and the size of the non-viscous flow region 306. An example non-viscous flow region 306 may include an orifice 308 that is located at Figure 1 The flow rates of the different flow valves 116a-116m may be different.

[0045] The control circuit system 124 controls the position of the valve 200 (e.g., the position of the control plate 204 as measured by the position sensor 120), the inlet pressure ... Figure 1 The flow rate through the viscous flow region 304 and the non-viscous flow region 306, thereby determining the flow rate through the valve 200, is determined by the inlet pressure sensor 118 (measured by the outlet pressure sensor 118), the outlet pressure (measured by the outlet pressure sensor 122 connected to the valve outlet 208), the size of the orifice 308, and the properties of the gas being transmitted (e.g., the viscosity of the gas, the temperature, the density of the gas).

[0046] Control circuitry 124 determines the first pressure drop across viscous flow region 304 using Equation 1 to determine the intermediate pressure P x and the corresponding flow Q vis .

[0047]

[0048] In Equation 1, Q vis is the mass flow rate through the viscous flow region 304, P1 is the inlet pressure (as measured by the inlet pressure sensor 118), and P xis the intermediate pressure between the viscous flow region 304 and the inviscid flow region 306, H is the distance between the control plate 204 and the valve seat 302, μ is the dynamic viscosity of the gas, w is the width of the viscous flow region 304, L is the length of the flow path of the viscous flow region 304, and R is the gas constant.

[0049] Control circuitry 124 further determines a second pressure drop across inviscid flow region 306 using Equation 2 (for sonic flow regime) or Equation 3 (for subsonic flow regime).

[0050]

[0051] In equations 2 and 3, C d is the discharge coefficient, k is the gas specific heat ratio, M is the gas molecular weight, T is the gas temperature, Dia is the orifice diameter 308, T ref is the reference temperature, P ref is the reference pressure, R u is the universal gas constant, and h is the distance between the control plate 204 and the valve seat 302 .

[0052] When the condition expressed by Equation 4 is true, sonic flow occurs.

[0053]

[0054] During sonic flow, a standing shock wave forms that can restrict flow through the orifice even if the upstream pressure increases further relative to the downstream pressure. By operating the flow valve 200 in the sonic flow regime, the control circuitry 124 can more reliably determine the flow through the flow valve 200.

[0055] Using equations 1-4, the control circuitry 124 determines the pressure at which Q is to be used based on the P1 (inlet pressure) measurement and the P2 (outlet pressure of the passage 126) measurement. vis and Q inv Equal intermediate pressure value P x For the same intermediate pressure P x value, so that Q vis and Q inv Equal flows are those through the valve 200 and therefore through the corresponding outlet channels.

[0056] In some examples, when the flow valves 116a-116m are open, the control circuit system 124 controls the flow valves 116a-116m to operate uniformly in the sonic flow regime, such as by controlling the pressure drop across the flow valve 200 to satisfy Equation 4. In some other examples, the control circuit system 124 can control the flow valves 116a-116m to operate in the subsonic flow regime. However, operating in the subsonic flow regime may require additional computational effort on the part of the control circuit system 124.

[0057] Figure 4A and Figure 4B are plots of example valve flow models 400, 402 that may be represented by Figure 1 The control circuit system 124 is used to control Figure 2 The flow valve 200 and / or the flow rate through the flow valve 200 can be determined without using a dedicated flow meter. For example, the valve flow model 400, 402 can be stored in Figure 1 The example valve flow model 400 relates the valve position (e.g., the distance between the control plate 204 and the valve seat 302) to the flow through the valve 200 for a given orifice size, inlet pressure, and outlet pressure. Similarly, the valve flow model 400 relates the valve position to the flow through the valve 200 for larger orifice sizes, inlet pressures, and outlet pressures. Figure 1 The example memory 130 and / or storage device 132 may include additional sets of inlet pressures and outlet pressures for each orifice size and / or multiple sets of flow rates for different combinations of valve positions, inlet pressures and outlet pressures for each orifice size present in the set of flow valves 116a-116m.

[0058] return Figure 1 In some examples, control circuitry 124 is further configured to compensate for changes in inlet pressure caused by changes in inlet flow from gases 102a to 102n (e.g., via MFCs 106a to 106n). In conventional flow control systems, as gas mass accumulates in pipes, conduits, manifolds, and / or other gas carriers, changes in flow result in corresponding changes in inlet pressure. Conventional systems that respond to stable pressure may need to wait a considerable amount of time to respond and make any necessary flow control adjustments, thereby reducing the response time of the overall gas distribution system.

[0059] The example control circuit system 124 improves response time when a flow change occurs at the inlet 110 by both monitoring the inlet pressure (measured by the inlet pressure sensor 118) and determining the rate of change of the inlet pressure based on the measurement of the inlet pressure sensor 118. If the rate of change of the inlet pressure increases above a predetermined threshold, the control circuit system 124 responds to maintain the inlet pressure within a predetermined range of a predetermined inlet pressure. The predetermined inlet pressure can be a pressure determined by the control circuit system 124 to maintain a sonic flow regime through the flow valves 116a-116m (e.g., using Equation 4) and / or any other target pressure determined by the control circuit system 124 to achieve a desired flow ratio. In some examples, the predetermined range of the rate of change of the inlet pressure is selected to avoid variations due to noise, but to maintain sufficient sensitivity to pressure variations caused by flow changes.

[0060] For example, if the MFCs 106a-106n increase their flow rate (e.g., due to a change in process or recipe), the resulting increase in flow will cause a corresponding increase in the pressure measured by the inlet pressure sensor 118. The control circuitry 124 detects that the rate of change of the inlet pressure is increasing and determines a corresponding change in the position of each flow valve 116a-116m to maintain both the predetermined flow ratio and the target pressure. For example, for a higher rate of change of pressure, the control circuitry 124 may determine a larger change in valve position. Conversely, for a lower rate of change of pressure, the control circuitry may determine a smaller change in valve position.

[0061] Figure 5 is a flow chart representing example machine readable instructions 500 that may be executed to implement Figure 1 The control circuit system 124 provides controlled distribution of gas from the outlet passages 126a-126m. Figure 1 The gas distribution system 100 and Figure 2 The example instructions 500 are described with reference to the valve 200 .

[0062] At block 502, the control circuitry 124 determines flow ratios for the outlet channels 126a-126m. The flow ratios may be stored in the memory 130 or storage device 132 and / or received via the I / O interface and / or communication circuitry.

[0063] At block 504, the control circuitry 124 determines whether gas distribution has begun. For example, the control circuitry 124 may detect that an input process gas flow is being received from the MFCs 106a-106n based on a change in inlet pressure (e.g., as measured by the inlet pressure sensor 118). If gas distribution has not yet begun (block 504), control returns to block 502.

[0064] When gas distribution begins (block 504), at block 506, the control circuit system 124 determines a target flow valve position for each flow valve 116a-116m based on the flow valve orifice size, the inlet pressure, and the target outlet pressure to output a target flow rate for each outlet channel 126a-126m that matches the flow ratio. For example, the control circuit system 124 can refer to the valve flow models 400, 402 and / or equations 1-4 to set the desired flow rate specified by the flow ratio for each outlet channel so that the total flow through the outlet channels 126a-126m is equal to the flow rate at the inlet 110. In some examples, the control circuit system 124 can control the flow valves 116a-116m to set a sonic flow regime to reduce the complexity of calculating the target valve positions.

[0065] At block 508, the control circuit system 124 controls the flow valves 116a-116m based on the corresponding determined valve positions. For unused outlet channels 126a-126m, the control circuit system 124 controls the corresponding flow valves 116a-116m to close. The control circuit system 124 can use closed-loop control of the piezoelectric actuator 202 based on position feedback from the position sensors 120a-120m to control the flow valves 116a-116m to the correct valve positions.

[0066] At block 510, the control circuitry 124 determines the inlet pressure and the rate of change of the inlet pressure. For example, the control circuitry 124 may receive inlet pressure data from the inlet pressure sensor 118 and calculate the rate of change of the inlet pressure. At block 512, the control circuitry 124 determines whether the inlet pressure and / or the rate of change are greater than a threshold value. If the rate of change of the inlet pressure is greater than the threshold value (block 512), then at block 514, the control circuitry 124 adjusts the flow valve positions of all open flow valves 116a-116m to limit the rate of change of the inlet pressure. For example, the flow valve positions may be adjusted to maintain a predetermined flow ratio at each outlet channel 126a-126m and reduce the settling time of the flow change.

[0067] After adjusting the flow valve position (block 514), or if the rate of change of the inlet pressure is not greater than the threshold value (block 512), the control circuitry 124 determines whether the flow ratio has changed at block 516. If the flow ratio has changed (block 516), control returns to block 506 to determine a new target flow valve position.

[0068] If the flow ratio has changed (block 516), the control circuitry 124 determines whether gas distribution is complete at block 518. If gas distribution is to continue (block 518), control returns to block 508 to continue controlling the flow valves 116a-116m. When gas distribution is complete (block 518), the example instructions 500 end.

[0069] As used herein, “and / or” refers to any one or more of the multiple items connected by “and / or” in a list. As an example, “x and / or y” refers to any element in the three-element set {(x), (y), (x, y)}. In other words, “x and / or y” refers to “one or both of x and y”. As another example, “x, y and / or z” refers to any element in the seven-element set {(x), (y), (z), (x, y), (x, z), (y, z), (x, y, z)}. In other words, “x, y and / or z” refers to “one or more of x, y and z”. As used herein, the term “exemplary” refers to serving as a non-limiting example, instance, or diagram. As used herein, the terms “e.g.,” and “for example” introduce a list of one or more non-limiting examples, instances, or diagrams.

[0070] Although the present method and / or system has been described with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the present method and / or system. For example, the frames and / or components of the disclosed examples may be combined, split, rearranged and / or otherwise modified. In addition, many modifications may be made to adapt specific circumstances or materials to the teachings of the present disclosure without departing from the scope of the present disclosure. Therefore, the present method and / or system is not limited to the specific embodiments disclosed. Rather, the present method and / or system will include all embodiments that fall within the scope of the appended claims, both literally and according to the doctrine of equivalents.

Claims

1. A flow ratio controller, comprising: an inlet configured to receive an input process gas flow; an inlet pressure sensor configured to measure an inlet pressure of the input process gas flow; a first outlet configured to output a first portion of the input process gas flow; a second outlet configured to output a second portion of the input process gas flow; a first flow valve configured to control a flow of an input process gas to the first outlet; a second flow valve configured to control a flow of the input process gas to the second outlet; a first position sensor configured to measure a first valve position of the first flow valve; a first outlet pressure sensor configured to measure a first outlet pressure of the first outlet; a second position sensor configured to measure a second valve position of the second flow valve; a second outlet pressure sensor configured to measure a second outlet pressure of the second outlet; as well as A control circuit system is configured to control the first flow valve and the second flow valve using a valve flow model and based on a predetermined flow ratio of the first outlet and the second outlet, the inlet pressure, the first valve position, the second valve position, the first outlet pressure, and the second outlet pressure.

2. The flow ratio controller according to claim 1, wherein: The control circuit system is configured to: determining a first flow rate at the first outlet based on the inlet pressure, the first outlet pressure, and the first valve position without a flow meter; determining a second flow rate at the second outlet based on the inlet pressure, the second outlet pressure, and the second valve position without a flow meter; as well as At least one of the first flow valve and the second flow valve is controlled based on the first flow rate, the second flow rate, and the predetermined flow rate ratio.

3. The flow ratio controller according to claim 1, wherein: The control circuit system is configured to: When the first flow valve is open, controlling the first flow valve to generate a sonic flow state passing through the first flow valve; as well as When the second flow valve is open, the second flow valve is controlled to generate a sonic flow regime through the second flow valve.

4. The flow ratio controller according to claim 1, wherein: The first flow valve includes a first loss region and a second loss region connected in series with each other, wherein the control circuit system is configured to control the first flow valve based on calculating a first laminar flow through the first loss region and calculating a first choked flow through the second loss region.

5. The flow ratio controller according to claim 1, wherein: The flow ratio controller includes three or more flow valves, the three or more flow valves including the first flow valve and the second flow valve, each of the three or more flow valves having an orifice, a position sensor and an outlet pressure sensor, wherein the control circuit system is configured to calculate the flow through each of the three or more flow valves and control each of the three or more flow valves to meet a predetermined diversion ratio.

6. The flow ratio controller according to claim 1, wherein: The first flow valve and the second flow valve each include a piezoelectric valve.

7. The flow ratio controller according to claim 1, wherein: The first position sensor and the second position sensor each include at least one of a capacitive position sensor, a strain gauge position sensor, a Hall effect position sensor, or an optical position sensor.

8. The flow ratio controller according to claim 1, wherein: The valve flow model is a predetermined model that relates valve position, flow, input pressure, and output pressure for each of the first flow valve and the second flow valve.

9. The flow ratio controller of claim 1 , further comprising a manifold configured to distribute the input process gas flow to the first flow valve and the second flow valve, wherein The inlet pressure sensor is configured to measure an inlet pressure in the manifold.

10. The flow ratio controller according to claim 1, wherein: The control circuit system is configured to: determining a rate of change of the inlet pressure based on measurements from the inlet pressure sensor; as well as Based on the inlet pressure and the rate of change of the inlet pressure, the first flow valve and the second flow valve are controlled to maintain the inlet pressure within a predetermined range of a predetermined inlet pressure.

11. A precision gas distribution system comprising: a plurality of mass flow controllers configured to control the flow of respective gases to respective outlets; as well as A flow ratio controller, wherein the flow ratio controller is configured to: receiving the gas from the mass flow controller via an inlet; as well as The plurality of flow valves are controlled using a valve flow model based on an inlet pressure at the inlet, valve positions of the plurality of flow valves, and outlet pressures of the plurality of outlets of the flow ratio controller, thereby controlling delivery of corresponding portions of the gas to the plurality of outlets according to predetermined flow ratios of the plurality of outlets.

12. The precision gas distribution system of claim 11, wherein: The flow ratio controller comprises: an inlet pressure sensor configured to measure an inlet pressure of an input process gas flow comprising gas at the inlet; wherein the plurality of outlets includes a first outlet configured to output a first portion of the input process gas flow and a second outlet configured to output a second portion of the input process gas flow; The plurality of flow valves include a first flow valve configured to control the flow of the input process gas to the first outlet and a second flow valve configured to control the flow of the input process gas to the second outlet, and the flow ratio controller further includes: a first position sensor configured to measure a first valve position of the first flow valve; a first outlet pressure sensor configured to measure a first outlet pressure of the first outlet; a second position sensor configured to measure a second valve position of the second flow valve; a second outlet pressure sensor configured to measure a second outlet pressure of the second outlet; and A control circuit system is configured to control the first flow valve and the second flow valve using a valve flow model and based on a predetermined flow ratio of the first outlet and the second outlet, the inlet pressure, the first valve position, the second valve position, the first outlet pressure, and the second outlet pressure.

13. The precision gas distribution system of claim 12, wherein: The control circuit system is configured to: When the first flow valve is open, controlling the first flow valve to generate a sonic flow state passing through the first flow valve; and When the second flow valve is open, the second flow valve is controlled to generate a sonic flow regime through the second flow valve.

14. The precision gas distribution system of claim 12, wherein: The first flow valve includes a first loss region and a second loss region connected in series, wherein the control circuit system is configured to control the first flow valve based on calculating a first laminar flow through the first loss region and calculating a first sonic flow through the second loss region.

15. The precision gas distribution system of claim 12, wherein: The first flow valve and the second flow valve each include a piezoelectric valve.

16. The precision gas distribution system of claim 12, wherein: The first position sensor and the second position sensor each include at least one of a capacitive position sensor, a strain gauge position sensor, a Hall effect position sensor, or an optical position sensor.

17. The precision gas distribution system of claim 12, wherein: The valve flow model is a predetermined model that relates valve position, flow, input pressure, and output pressure for each of the first flow valve and the second flow valve.

18. The precision gas distribution system of claim 12, further comprising a manifold configured to distribute the input process gas flow to the first flow valve and the second flow valve, wherein The inlet pressure sensor is configured to measure an inlet pressure in the manifold.

19. The precision gas distribution system of claim 12, wherein: The control circuit system is configured to: determining a rate of change of the inlet pressure based on measurements from the inlet pressure sensor; as well as Based on the inlet pressure and the rate of change of the inlet pressure, the first flow valve and the second flow valve are controlled to maintain the inlet pressure within a predetermined range of a predetermined inlet pressure.

20. The precision gas distribution system of claim 12, further comprising a temperature sensor configured to measure a temperature of the input process gas flow, the control circuitry configured to control the first and second flow valves based on the temperature.

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