High-temperature mass flow controller and mass flow sensor

Abstract

Providing thermal mass flow sensors and mass flow controllers. [Solution] The illustrated thermal mass flow sensor disclosed comprises a flow tube having a layer of inorganic insulator on its outer surface, two or more wires wound around the flow tube for a corresponding length so as to cover the inorganic insulator, a heating controller configured to control the heating of one or more of the two or more wires, and a mass flow measuring circuit configured to determine the mass flow through the flow tube based on the measurement of the temperatures of two or more of the two or more wires.

Description

TECHNICAL FIELD

[0001] [RELATED APPLICATIONS] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 781,744, filed on April 1, 2025, entitled "HIGH-TEMPERATURE MASS FLOW CONTROLLERS AND MASS FLOW SENSORS". The entirety of U.S. Provisional Patent Application No. 63 / 781,744 is expressly incorporated herein by reference in its entirety.

[0002] The present disclosure relates to control and measurement of mass flow (mass flow rate), and more specifically, relates to high-temperature mass flow controllers and mass flow sensors.

BACKGROUND ART

[0003] A mass flow controller (MFC) is a device for controlling the flow rate of a fluid through a flow path based on a desired flow and a real-time feedback measurement value of the fluid flow rate. To control this process and maintain the desired flow rate, the mass flow controller electromechanically controls the opening and closing of a valve to achieve the desired flow rate according to the feedback measurement value.

SUMMARY OF THE INVENTION

[0004] High-temperature mass flow controllers and mass flow sensors are disclosed as being substantially illustrated by at least one of the drawings and described with respect to at least one of the drawings.

[0005] The benefits and advantages of the present disclosure will become more readily apparent to those skilled in the art after reviewing the following detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] [Figure 1] 1 is a block diagram of an exemplary mass flow controller according to aspects of the present disclosure.

[0007] [Figure 2A] This figure shows an example of a flow tube and wire that can be used to implement the thermal mass flow sensor shown in Figure 2A. [Figure 2B] Figure 2B shows an example of a flow tube and wire that can be used to implement the thermal mass flow sensor.

[0008] [Figure 3] This is a block diagram of an exemplary computing device that can be used to implement the valve control circuit section of Figure 1. [Modes for carrying out the invention]

[0009] The drawings are not necessarily to exact scale. Where appropriate, similar or identical reference numerals are used to refer to similar or identical components.

[0010] Mass flow controllers are used to measure and control the flow of gases, such as those used in the manufacture of semiconductor devices. The diverse processes for semiconductor manufacturing continue to evolve, moving towards reducing size and cost while improving performance. To this end, semiconductor manufacturing is progressing towards the use of materials that involve the use of higher temperatures and / or lower pressures for use in vapor form. Therefore, mass flow control at lower pressures and higher temperatures than the operating range of conventional MFCs is required.

[0011] Conventional MFCs use one of two main technical classifications to measure mass flow. The first technical classification includes thermal-based techniques that measure mass flow by the energy required to heat the gas flow. As mass flow increases, more energy is required to heat the flowing gas. The second technical classification is pressure-based techniques that measure mass flow by measuring the temperature and pressure of the gas before and after a characterized throttling. Pressure-based MFCs require much higher pressures than thermal-based MFCs. Due to the large pressure drop required during measurement, the use of pressure-based MFCs at the lower pressures required for large amounts of steam is limited.

[0012] Thermal MFCs have lower pressure drop requirements for measuring mass flow. When combined with a control valve with a larger, lower pressure drop, thermal MFCs have an extended practical operating pressure range. However, conventional MFCs have a limited operating temperature range, which limits their use with materials that require higher temperatures for evaporation. Conventional MFCs use components insulated with organic electrical insulators, which limits the operating temperature range of conventional MFCs. While the organic electrical insulators used in some conventional MFCs can withstand temperatures up to 200°C, the additional heating (e.g., about 80°C above ambient temperature) provided by the heating coil or heating wire (electrical wire) of a thermal mass flow sensor exceeds the temperature limit of the organic electrical insulator in high-temperature applications (e.g., ambient temperature of 200°C), leading to the breakdown of the electrical insulator and instability of the MFC.

[0013] The illustrated mass flow sensors and MFCs disclosed offer a higher operating temperature range than conventional MFCs and mass flow sensors. In the illustrated examples, the characterized flow tube comprises a layer of inorganic electrical insulation, thereby preventing short circuits between the flow tube and the windings used for heating and / or sensing. Conventional MFCs and mass flow sensors would suffer from the breakdown or other failure of the organic (e.g., polyimide) insulation used to electrically insulate the windings and / or flow tube.

[0014] Figure 1 is a block diagram of an exemplary mass flow controller (MFC) 100. The exemplary MFC 100 comprises a base unit 102, a mass flow meter 104, and a valve assembly 106. The mass flow meter 104 and the valve assembly 106 are mounted on the base unit 102. The base unit 102 may further comprise a fluid inlet 114 and a fluid outlet 116. The MFC controls the flow of gas from the fluid inlet 114 to the fluid outlet 116. The exemplary MFC 100 is shown having the mass flow meter 104 upstream of the valve assembly 106 (for example, the mass flow meter 104 is positioned between the valve assembly 106 and the valve inlet 114).

[0015] The exemplary valve assembly 106 comprises a valve 108 and an actuator 110. The valve 108 is actuated by the actuator 110 to control the flow of gas from a fluid inlet 114 to a fluid outlet 116. The exemplary valve assembly 106 can be a normally open valve or a normally closed valve. Since the MFC 100 is configured to operate at ambient temperatures of 200°C, 240°C, 300°C or higher, the actuator 110 can be thermally isolated from the ambient environment and / or may be provided with liquid cooling.

[0016] The MFC100 includes an upstream pressure transducer 120 configured to measure pressure at an upstream position (e.g., upstream of the flow sensor 126 and the bypass throttling device 125) and a downstream pressure transducer 122 configured to measure pressure at a downstream position (e.g., downstream of the flow sensor 126 and the bypass throttling device 125).

[0017] The exemplary MFC 100 further comprises a valve control circuit unit 118 communicatively coupled to a mass flow meter 104 and a valve assembly 106. The valve control circuit unit 118 comprises a processor which may be a general-purpose central processing unit (CPU). In some examples, the valve control circuit unit 118 may be implemented using or comprising one or more dedicated processing units such as an FPGA, a RISC processor with an ARM core, an image processing unit, a digital signal processor, and / or a system on a chip (SoC). The valve control circuit unit 118 executes machine-readable instructions which may be stored locally in the valve control circuit unit 118 (e.g., in an internal cache or SoC), in random access memory (or other volatile memory), in read-only memory (or other non-volatile memory such as flash memory), and / or in a mass storage device. Exemplary mass storage devices include hard drives, solid-state storage drives, hybrid drives, RAID arrays, and / or any other mass data storage devices.

[0018] The illustrated mass flow meter 104 is a thermal flow meter. The illustrated mass flow meter 104 in Figure 1 comprises a bypass channel 124 through which a portion of the fluid flows, which has a bypass throttling device 125, and another channel through which a smaller portion of the fluid flows, which has a flow sensor 126. The valve control circuit 118 receives a measurement signal from the mass flow meter 104 (for example, a signal representing the flow rate, or a signal representing temperature or power that can be used to calculate the flow rate).

[0019] During operation, as the fluid passes through the flow sensor 126, the flow sensor 126 measures real-time flow data (e.g., temperature data, power data, etc.) and supplies it to the valve control circuit 118. The fluid flow rate is susceptible to influences, and multiple operating conditions, including the type of fluid, upstream and downstream pressures, temperature, flow rate setpoint, and valve operating characteristics, all affect the fluid flow rate, potentially causing a deviation from the desired set flow rate. The valve control circuit 118 controls the operation of the valve assembly 106 (e.g., in real time) by supplying an error correction drive signal to the valve actuator 110 to adjust the position of the valve 108. The flow rate is controlled by the change in the position of the valve 108. The valve control circuit 118 may use factors such as the type of fluid, readings from the upstream and downstream pressure transducers, flow rate setpoint, valve specifications, and / or valve calibration data to control the operation of the valve 108. In some examples, the valve control circuit 118 uses closed-loop control such as proportional control, integral control, proportional-integral (PI) control, differential control, proportional-derivative (PD) control, integral-derivative (ID) control, proportional-integral-derivative (PID) control, and / or any other type of closed-loop or feedback-based control to control the fluid flow in the MFC 100.

[0020] The exemplary flow sensor 126 can be a two-wire or three-wire flow sensor. Examples of exemplary two-wire thermal flow sensors include a current-controlled (e.g., target current, target power) mass flow sensor that measures flow rate based on the temperature (or voltage) difference between two windings, and a temperature-controlled (e.g., target temperature) mass flow sensor that measures flow rate based on the current or power consumed to maintain the upstream and downstream windings at a target temperature or temperature gradient. A current-controlled thermal mass flow sensor may comprise a small-diameter capillary tube having a temperature-sensitive coil formed from wires wound at two positions around the tube. When current is supplied to the coil, the coil self-heats, thereby increasing both the temperature of the coil and the temperature of a local portion of the flow tube. As gas flows through the sensor, the gas has a preferential cooling effect on the upstream coil because it is mostly heated by the warmer tube closer to the upstream coil. The temperature difference between the upstream and downstream coils indicates the flow (flow rate) through the tube. A larger flow rate results in a greater cooling effect and a larger resulting signal. A temperature-controlled mass flow sensor varies the power supplied to each winding to maintain both coils at an average constant target temperature. The difference in power supplied to the two coils is proportional to the flow, and this power difference is used to measure the mass flow. An example of an embodiment of a two-wire thermal flow sensor is described in U.S. Patent No. 6,845,659 (John Michael Lull). U.S. Patent No. 6,845,659 in its entirety constitutes part of this application by reference.

[0021] The exemplary three-wire thermal flow sensor features a central winding that provides heating, and the flow rate is measured based on the temperature difference between the upstream and downstream windings. An example of an embodiment of the three-wire thermal flow sensor is described in U.S. Patent No. 5,944,048 (Bump et al.). U.S. Patent No. 5,944,048 in its entirety constitutes part of this application by reference.

[0022] In some examples, the flow sensor 126 uses a hybrid technique for determining mass flow, where the target wire temperature is based on the ambient temperature. The mass flow is determined by the power required to maintain the target temperature across different flows. The hybrid technique adjusts the target temperature to account for varying air conductivity, flow tube material, and / or wire material, which may affect heat transfer from the wire(s) to the flowing fluid and / or from the fluid to the sensing wire.

[0023] In some examples, the valve control circuitry 118 includes an operator interface (e.g., one or more operator input devices and / or operator output devices) and / or a communication interface (e.g., wired and / or wireless communication circuitry) to receive commands, configuration variables, setpoints (e.g., flow rate setpoints), gas properties, and / or other data. The operator interface and / or communication interface can further output data for viewing by an operator and / or output data to one or more external devices.

[0024] Although the mass flow meter 104 of Figure 1 is part of the MFC 100, in other examples, the mass flow meter 104 may be a separate device configured to measure mass flow through a flow tube and output the measured mass flow to an external device.

[0025] Figure 2A shows an exemplary flow tube 202 and windings 204, 206 that can be used to implement the flow sensor 126 of Figure 1. Figure 2B is a more detailed view of a portion of the exemplary flow tube and winding 206. Although the exemplary flow tube 202 and windings 204, 206 are shown as a two-wire thermal mass flow sensor, the illustrated example can be adapted to a three-wire thermal mass flow sensor.

[0026] To improve the operating temperature range of the flow tube to exceed that of conventional mass flow sensors, the outer surface of the exemplary flow tube 202 is coated with a layer 208 of inorganic insulator. The inorganic insulator layer 208 can be a ceramic such as a silica-based ceramic material. However, the inorganic insulator layer 208 can be implemented using alumina-based ceramics, inorganic aerogels, fiberglass, mica, and / or any other inorganic thermal insulator that enables the desired thickness and electrical insulation. The inorganic insulator layer 208 can be applied to the flow tube 202 via plasma jet spraying or any other suitable application method.

[0027] The windings 204, 206 of Figures 2A and 2B are bare wires wound directly on the inorganic insulator layer 208. The windings 204, 206 can be wound at a pitch of 1.3 times the diameter used for the windings 204, 206. In other examples, the windings 204, 206 can be wound at a small pitch of 1.1 times the diameter used for the windings 204, 206 (e.g., based on the control level of the winding process to avoid short circuits between turns), or at a large pitch of 2 times or more the diameter used for the windings 204, 206. In some examples, the flow tube 202 or the inorganic insulator layer 208 can be formed with helical grooves to guide the winding process and to reduce or eliminate movement of the windings 204, 206 that could cause short circuits between turns of one of the windings 204, 206. Additionally or alternatively, the windings 204, 206 can be bonded to the inorganic insulator layer 208 using a high-temperature adhesive to reduce or prevent movement of the windings 204, 206.

[0028] In some examples, windings 204 and 206 have organic insulators at the time of the winding process. The exemplary flow tube 202 and windings 204 and 206 can then be heat-treated at a high temperature (e.g., 500°C), which burns off the insulation of the wire and obtains the desired winding pitch without adversely affecting the inorganic insulator layer 208. Heat treatment can also relieve stress within windings 204 and 206 and reduce movement. Even without heat treatment of windings 204 and 206, the inorganic insulator layer 208 prevents failure of the thermal mass flow sensor if the organic insulation of the wire fails during operation.

[0029] Compared to conventional thermal mass flow sensors, the disclosed exemplary flow sensor 126, which includes an inorganic insulating layer 208, is capable of continuous use at ambient temperatures of at least 200°C. Some such flow sensors 126 are capable of continuous use at ambient temperatures of at least 240°C and / or at least 300°C, taking into account additional heating of the inorganic insulating layer 208 by one or more of the windings 204, 206 above ambient temperature.

[0030] The exemplary windings 204 and 206 can be coupled to a heating controller (control device) 210 to control the heating of one or more of the windings 204 and 206 (for example, one of both windings 204 and 206 of a two-wire sensor, or one of the windings 204 and 206 of a three-wire sensor with a third wire). The exemplary windings 204 and 206 are further coupled to a mass flow measurement circuit 212. The mass flow measurement circuit 212 determines the mass flow through the flow tube 202 based on the measurement of the heating of the windings 204 and 206 using the two-wire or three-wire sensor technology described above.

[0031] Figure 3 is a block diagram of an exemplary computing device 300 that can be used to implement the valve control circuit unit 118 of Figure 1. The exemplary computing device 300 can be a general-purpose computer, a laptop computer, a tablet computer, a mobile device, a server, an all-in-one computer, and / or any other type of computing device. The computing device 300 of Figure 3 comprises a processor 302, which can be a general-purpose central processing unit (CPU). In some examples, the processor 302 can include one or more dedicated processing units such as an FPGA, a RISC processor with an ARM core, an image processing unit, a digital signal processor, and / or a system on a chip (SoC). The processor 302 executes machine-readable instructions 304 that can be stored locally in the processor (e.g., in an internal cache or SoC), in random access memory 306 (or other volatile memory), in read-only memory 308 (or other non-volatile memory such as flash memory), and / or in a mass storage device 310. The illustrated mass storage device 310 can be a hard drive, a solid-state storage drive, a hybrid drive, a RAID array, and / or any other mass data storage device. The bus 312 enables communication between the processor 302, RAM 306, ROM 308, mass storage device 310, network interface 314, and / or input / output interface 316.

[0032] The illustrated network interface 314 includes hardware, firmware, and / or software that connects the computing device 300 to a communication network 318, such as the Internet. For example, the network interface 314 may include IEEE 802.X compliant wireless and / or wired communication hardware for transmitting and / or receiving communications.

[0033] The illustrative I / O interface 316 in Figure 3 includes hardware, firmware, and / or software that connects one or more input / output devices 320 to the processor 302 to provide input to the processor 302 and / or output from the processor 302. For example, the I / O interface 316 may include an image processing device for interface connection with a display device, a universal serial bus port for interface connection with one or more USB-compliant devices, FireWire®, a fieldbus, and / or any other type of interface. The illustrative computing device 300 may include a display device 324 (e.g., an LCD screen) coupled to the I / O interface 316. Other illustrative I / O devices 320 may include a keyboard, keypad, mouse, trackball, pointing device, microphone, audio speaker, display device, optical media drive, multitouch touchscreen, gesture recognition interface, magnetic media drive, and / or any other type of input and / or output device.

[0034] The computing device 300 can access the non-temporary machine-readable media 322 via the I / O interface 316 and / or one or more I / O devices 320. Examples of the machine-readable media 322 in Figure 3 include optical discs (e.g., Compact Discs (CDs), Digital Versatile / Video Discs (DVDs), Blu-ray® discs, etc.), magnetic media (e.g., floppy disks), portable storage media (e.g., portable flash drives, Secure Digital (SD) cards, etc.), and / or any other type of removable and / or installed machine-readable media.

[0035] The method and system can be implemented in hardware, software, and / or a combination of hardware and software. The method and / or system can be implemented centrally in at least one computing system, or distributedly, with different elements distributed across several interconnected computing systems. Any type of computing system or other device adapted to perform the method described herein is suitable. A typical combination of hardware and software may include a general-purpose computing system, along with a program or other code that, once loaded and executed, controls the computing system to perform the method described herein. Another typical embodiment may include an application-specific integrated circuit or chip. Some embodiments may include a non-temporary machine-readable (e.g., computer-readable) medium (e.g., flash drive, optical disk, magnetic storage disk, etc.) which stores one or more lines of machine-executable code, thereby causing a machine to perform a process such as that described herein. As used herein, the term “non-temporary machine-readable medium” includes all types of machine-readable storage media and is defined to exclude propagated signals.

[0036] As used in this application, the terms “circuit” and “circuits” refer to physical electronic components (i.e., hardware) and any software and / or firmware ("code") that can constitute the hardware, that the hardware can execute, and / or that can otherwise be associated with the hardware. As used in this application, for example, a particular processor and memory may include a first “circuit” when executing one or more first lines of code, and a second “circuit” when executing one or more second lines of code. As used in this application, “and / or” means any one or more items in the list linked by “and / or”. For example, “x and / or y” means any element of the set of three elements {(x), (y), (x,y)}. In other words, “x and / or y” means “one or both of x and y”. As another example, “x, y and / or z” means any element of the seven-element set {(x), (y), (z), (x,y), (x,z), (y,z), (x,y,z)}. In other words, “x, y and / or z” means “one or more of x, y and z.” As used in this application, the term “exemplary” means to serve as an unrestrictive example, case, or illustration. As used in this application, the term “for example” means to begin a list of one or more unrestrictive examples, cases, or illustrations. As used in this application, whenever circuits include the hardware and code (if any of which are required) necessary to perform a certain function, the circuits are “operable” to perform that function, regardless of whether the performance of that function is disabled or not (e.g., by user-configurable settings, factory trim, etc.).

[0037] While the Method and / or System has been described with reference to certain specific embodiments, those skilled in the art will understand that various modifications and substitutions can be made without departing from the scope of the Method and / or System. In addition, many modifications can be made without departing from the scope of the Disclosure to adapt the teachings of the Disclosure to specific circumstances or materials. For example, the systems, blocks and / or components of the disclosed examples can be combined, divided, rearranged, and / or otherwise modified. Therefore, the Method and / or System is not limited to the specific embodiments disclosed. Rather, the Method and / or System includes all embodiments that fall within the scope of the appended claims, either literally or under the doctrine of equivalents.

Claims

1. A thermal mass flow sensor, A flow tube having a layer of inorganic insulator on its outer surface, Two or more wires are wound around the flow tube for a corresponding length so as to cover the inorganic insulator, A heating controller configured to control the heating of one or more of the two or more wires, A mass flow measurement circuit is configured to determine the mass flow passing through the flow tube based on the measurement of the temperature of two or more of the two or more wires, A thermal mass flow sensor equipped with the following features.

2. The thermal mass flow sensor according to claim 1, wherein the two or more wires are uninsulated wires directly wound on the inorganic insulator.

3. The thermal mass flow sensor according to claim 1, wherein the inorganic insulator is capable of continuous use at an ambient temperature of at least 200°C.

4. The thermal mass flow sensor according to claim 3, wherein the inorganic insulator is capable of continuous use at an ambient temperature of at least 240°C.

5. The thermal mass flow sensor according to claim 4, wherein the inorganic insulator is capable of continuous use at an ambient temperature of at least 300°C.

6. The thermal mass flow sensor according to claim 1, wherein the inorganic insulator has a helical groove, and at least one of the first wire and the second wire is disposed within the helical groove.

7. The thermal mass flow sensor according to claim 1, wherein the inorganic insulator includes ceramic.

8. The thermal mass flow sensor according to claim 1, wherein the mass flow measurement circuit is configured to determine the mass flow based on at least one of the temperature difference between two or more of the two or more wires, or the difference in power consumed to maintain two or more of the two or more wires at a target temperature.

9. It is a mass flow controller, A thermal mass flow sensor, A flow tube having a layer of inorganic insulator on its outer surface, Two or more wires are wound around the flow tube for a corresponding length so as to cover the inorganic insulator, A heating controller configured to control the heating of one or more of the two or more wires, A mass flow measurement circuit is configured to determine the mass flow passing through the flow tube based on the measurement of the heating of two or more of the two or more wires, A thermal mass flow sensor equipped with, A flow valve configured to control the flow between the flow tube and at least one of the inlet or outlet based on the mass flow determined by the thermal mass flow sensor, A mass flow controller equipped with the following features.

10. The mass flow controller according to claim 9, wherein the two or more wires are uninsulated wires directly wound on the inorganic insulator.

11. The mass flow controller according to claim 10, wherein the first wire of the two or more wires is wound at a pitch of at least 1.1 times the diameter of the first wire, and the second wire of the two or more wires is wound at a pitch of at least 1.1 times the diameter of the second wire.

12. The mass flow controller according to claim 9, wherein the inorganic insulator is capable of continuous use at an ambient temperature of at least 200°C.

13. The mass flow controller according to claim 12, wherein the inorganic insulator is capable of continuous use at an ambient temperature of at least 240°C.

14. The mass flow controller according to claim 13, wherein the inorganic insulator is capable of continuous use at an ambient temperature of at least 300°C.

15. The mass flow controller according to claim 9, wherein the mass flow measurement circuit is configured to determine the mass flow based on at least one of the temperature difference between the first wire and the second wire, or the difference in power consumed to maintain the first wire and the second wire at a target temperature.

16. The mass flow controller according to claim 9, wherein the flow valve comprises an actuator that is thermally insulated from the surrounding environment.

17. The mass flow controller according to claim 9, wherein the inorganic insulator has a helical groove, and at least one of the first wire and the second wire is disposed within the helical groove.

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