High temperature mass flow controller and mass flow sensor

Abstract

A disclosed example thermal mass flow sensor includes a flow tube having a layer of inorganic insulating material on an outer surface thereof, two or more wires wrapped on respective lengths of the flow tube on the inorganic insulating material, a heating controller configured to control heating of one or more of the two or more wires, and mass flow measurement circuitry configured to determine a mass flow through the flow tube based on measuring temperatures of two or more of the two or more wires.

Description

[0001] Related applications

[0002] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 781,744, filed April 1, 2025, entitled “HIGH-TEMPERATURE MASS FLOW CONTROLLERS AND MASS FLOW SENSORS”. The entire contents of U.S. Provisional Patent Application Serial No. 63 / 781,744 are expressly incorporated herein by reference. Technical Field

[0003] This disclosure relates to mass flow control and measurement, and more specifically, to a high-temperature mass flow controller and a mass flow sensor. Background Technology

[0004] A mass flow controller (MFC) is a device that controls the flow of fluid through a flow path based on a desired flow rate and real-time feedback measurements of the fluid velocity. To control the process and maintain the desired flow rate, the mass flow controller electromechanically controls the opening and closing of valves to achieve the desired flow rate based on feedback measurements. Summary of the Invention

[0005] A high-temperature mass flow controller and a mass flow sensor are disclosed, substantially as shown in at least one of the accompanying drawings and described in conjunction with at least one of the accompanying drawings. Attached Figure Description

[0006] The benefits and advantages of this disclosure will become more apparent to those skilled in the art after reading the following detailed description and accompanying drawings, in which:

[0007] Figure 1 This is a block diagram of an example mass flow controller based on various aspects of this disclosure.

[0008] Figure 2A and Figure 2B This shows what can be used to implement Figure 2A and Figure 2B Example flow tube and wires for a thermal mass flow sensor.

[0009] Figure 3 It can be used to achieve Figure 1 A block diagram of an example computing device for a valve control circuit system.

[0010] The accompanying drawings are not necessarily drawn to scale. Where appropriate, similar or identical reference numerals are used to refer to similar or identical parts. Detailed Implementation

[0011] Mass flow controllers are used to measure and control the flow rate of gases, such as those used in the manufacture of semiconductor devices. Various processes used in semiconductor manufacturing continue to evolve towards smaller size and lower cost while improving performance. To this end, semiconductor manufacturing is shifting towards the use of materials that are used in vapor form at higher temperatures and / or lower pressures. Therefore, mass flow control is required at lower pressures and higher temperatures than the operating range of conventional mass flow controllers (MFCs).

[0012] Conventional MFCs use one of two main types of techniques to measure mass flow rate. The first type involves heat-based techniques, which measure mass flow rate by the energy required to heat the gas flow. As the mass flow rate increases, more energy is needed to heat the flowing gas. The second type is pressure-based techniques, which measure mass flow rate by measuring the gas temperature and pressure before and after characteristic limits. Pressure-based MFCs require significantly higher pressures than heat-based MFCs. The pressure drop required during measurement and its magnitude limit the use of pressure-based MFCs at the lower pressures required for many vapors.

[0013] Thermal mass flow meters (MFCs) have lower pressure drop requirements for measuring mass flow rates. When combined with larger, low-pressure-drop control valves, thermal MFCs offer an extended practical operating pressure range. However, conventional MFCs have a limited operating temperature range, which restricts their use with materials requiring higher temperatures for evaporation. Conventional MFCs use components insulated with organic electrical insulation, which limits their operating temperature range. While the organic electrical insulation used in some conventional MFCs can withstand temperatures up to 200°C, the additional heating provided by the heating coils or wires of the thermal mass flow sensor (e.g., approximately 80°C above ambient temperature) exceeds the temperature limits of the organic electrical insulation (e.g., ambient temperature of 200°C) in high-temperature applications, leading to insulation breakdown and MFC instability.

[0014] The disclosed example mass flow sensor and MFC offer a higher operating temperature range than conventional MFCs and mass flow sensors. In the disclosed example, the characteristic flow tube includes an inorganic electrical insulation layer that prevents short circuits between the flow tube and the lead windings used for heating and / or sensing. Conventional MFCs and mass flow sensors will suffer breakdown or other failures of the organic (e.g., polyimide) insulation used to electrically insulate the lead windings and / or flow tube.

[0015] Figure 1This is a block diagram of an example mass flow controller (MFC) 100. The example MFC 100 includes a base 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 102. The base 102 may also include a fluid inlet 114 and a fluid outlet 116. The MFC controls the gas flow from the fluid inlet 114 to the fluid outlet 116. Although the example MFC 100 is shown as having a mass flow meter 104 upstream of the valve assembly 106 (e.g., the mass flow meter 104 is positioned between the valve assembly 106 and the valve inlet 114).

[0016] Example valve assembly 106 includes a valve 108 and an actuator 110. Valve 108 is actuated by actuator 110 to control the flow of gas from fluid inlet 114 to fluid outlet 116. Example valve assembly 106 may be a normally open or normally closed valve. Because MFC 100 is configured to operate at ambient temperatures of 200°C, 240°C, 300°C, or higher, actuator 110 may be thermally insulated from the ambient environment and / or include liquid cooling.

[0017] MFC 100 includes an upstream pressure transducer 120 and a downstream pressure transducer 122, the upstream pressure transducer being configured to measure pressure at an upstream location (e.g., upstream of rate sensor 126 and bypass limiter 125), and the downstream pressure transducer being configured to measure pressure at a downstream location (e.g., downstream of rate sensor 126 and bypass limiter 125).

[0018] Example MFC 100 also includes a valve control circuitry 118 communicatively coupled to mass flow meter 104 and valve assembly 106. Valve control circuitry 118 includes a processor, which may be a general-purpose central processing unit (CPU). In some examples, valve control circuitry 118 may be implemented using or include one or more dedicated processing units, such as an FPGA, a RISC processor with an ARM core, a graphics processing unit, a digital signal processor, and / or a system-on-a-chip (SoC). Valve control circuitry 118 executes machine-readable instructions, which may be stored locally at valve control circuitry 118 (e.g., in an included cache or SoC), in random access memory (or other volatile memory), read-only memory (or other non-volatile memory such as flash memory), and / or in mass storage devices. Example mass storage devices include hard disk drives, solid-state drives, hybrid drives, RAID arrays, and / or any other mass data storage device.

[0019] Example mass flow meter 104 is a heat flow meter. Figure 1The example mass flow meter 104 includes a bypass channel 124 with a bypass limiter 125 and another channel with a flow rate sensor 126, through which a portion of the fluid flows and through the other channel. A valve control circuit system 118 receives measurement signals (e.g., signals indicating flow rate, or signals indicating temperature or power that can be used to calculate the flow rate) from the mass flow meter 104.

[0020] During operation, as fluid flows past flow velocity sensor 126, the flow velocity sensor 126 measures and provides real-time flow velocity data (e.g., temperature data, power data, etc.) to valve control circuitry system 118. Fluid flow velocity can be sensitive, and many operating conditions, including fluid type, upstream and downstream pressure, temperature, flow velocity setpoint value, and valve operating characteristics, can affect fluid flow velocity, causing it to deviate from the desired setpoint rate. Valve control circuitry system 118 controls the operation of valve assembly 106 (e.g., real-time control) by providing an error correction drive signal to valve actuator 110 to adjust the position of valve 108. Changes in the position of valve 108 control the flow velocity. Valve control circuitry system 118 can use factors such as fluid type, upstream and downstream pressure transducer readings, flow velocity setpoint value, valve specifications, and / or valve calibration data to control the operation of valve 108. In some examples, the valve control circuit system 118 uses closed-loop control, such as proportional control, integral control, proportional-integral (PI) control, derivative control, proportional-derivative (PD) control, integral-derivative (ID) control, proportional-integral-derivative (PID) control and / or any other type of closed-loop control or feedback-based control, to control the flow of fluid in the MFC 100.

[0021] Example flow rate sensor 126 can be a two-wire or three-wire flow rate sensor. Example two-wire thermal flow rate sensors can include current-controlled (e.g., target current, target power) mass flow rate sensors and temperature-controlled (e.g., target temperature) mass flow rate sensors. Current-controlled mass flow rate sensors measure flow rate as a function of the temperature (or voltage) difference between two conductor windings, while temperature-controlled mass flow rate sensors measure flow rate as a function of the current or power consumed to maintain the upstream and downstream conductor windings at a target temperature or temperature gradient. Current-controlled thermal mass flow rate sensors can include a small-diameter capillary with a temperature-sensitive coil formed by winding conductors around the tube at two locations. When current is supplied to the coil, the coil self-heats, thereby raising the temperature of the coil and a localized section of the flow tube. When gas flows through the sensor, the gas has a preferential cooling effect on the upstream coil because it is primarily heated by the localized warming of the upstream coil. The temperature difference between the upstream and downstream coils indicates the flow rate through the tube. Higher flow rates produce a greater cooling effect and a larger resulting signal. A temperature-controlled mass flow sensor alters the power of each wire winding to maintain both coils at a constant average target temperature. The power difference supplied to the two coils is proportional to the flow rate, and this power difference is used to measure the mass flow rate. An exemplary embodiment of a biwire-type heat flow sensor is described in U.S. Patent No. 6,845,659 (John Michael Lull). The entire contents of U.S. Patent No. 6,845,659 are incorporated herein by reference.

[0022] An example three-wire heat flow sensor includes a central lead winding that provides heating, and the flow rate is measured as a function of the temperature difference between the upstream and downstream lead windings. An example embodiment of a three-wire heat flow sensor is described in U.S. Patent No. 5,944,048 (Bump et al.). The entire contents of U.S. Patent No. 5,944,048 are incorporated herein by reference.

[0023] In some examples, the flow rate sensor 126 uses a hybrid approach to determine the mass flow rate, where the target conductor temperature is a function of the ambient temperature. The power required to maintain the target temperature at different flow rates determines the mass flow rate. The hybrid approach adjusts the target temperature by taking into account variations in the conductivity of the air, the flow tube material, and / or the conductor material, which may affect heat transfer from the conductor to the flowing fluid and / or from the fluid to the sensing conductor.

[0024] 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., a wired and / or wireless communication circuitry) to receive commands, configuration variables, setpoints (e.g., flow rate setpoints), gas characteristics, and / or other data. The operator interface and / or communication interface may also output data for operator viewing and / or to one or more external devices.

[0025] Although Figure 1 The mass flow meter 104 is part of the MFC 100, but in other examples, the mass flow meter 104 may be a separate device configured to measure the mass flow rate through the flow tube and output the measured mass flow rate to an external device.

[0026] Figure 2A This shows what can be used to implement Figure 1 Example flow tube 202 and wire windings 204, 206 of flow velocity sensor 126. Figure 2B A more detailed illustration is provided of a portion of the example flow tube and wire winding 206. Although the example flow tube 202 and wire windings 204, 206 are shown as a two-wire type thermal mass flow sensor, the example shown can be adapted to a three-wire type thermal mass flow sensor.

[0027] To improve the operating temperature range of the flow tube compared to conventional mass flow sensors, the outer surface of the example flow tube 202 is coated with an inorganic insulating material layer 208. The inorganic insulating material layer 208 can be ceramic, such as a silica-based ceramic material. However, the inorganic insulating material layer 208 can be implemented using alumina-based ceramics, inorganic aerogels, glass fibers, mica, and / or any other inorganic thermal insulator that allows for the desired thickness, and electrical insulation can be used. The inorganic insulating material layer 208 can be applied to the flow tube 202 by plasma jet spraying or any other application method.

[0028] Figure 2A and Figure 2BThe conductor windings 204 and 206 are bare conductors wound directly on the inorganic insulating layer 208. The conductor windings 204 and 206 can be wound with a pitch of 1.3 times the diameter used in the conductor windings 204 and 206. In other examples, the conductor windings 204 and 206 can be wound with a pitch as low as 1.1 times the diameter used in the conductor windings 204 and 206 (e.g., based on a level of control in the winding process to avoid inter-turn short circuits) or as high as 2 times or more the diameter used in the conductor windings 204 and 206. In some examples, the flow tube 202 or the inorganic insulating layer 208 can be formed with helical grooves to guide the conductor winding process and reduce or eliminate displacement of the conductor windings 204 and 206, which could lead to inter-turn short circuits in one of the conductor windings 204 and 206. Alternatively or additionally, the conductor windings 204 and 206 may be coupled to the inorganic insulating layer 208 using a high-temperature adhesive to reduce or prevent displacement of the conductor windings 204 and 206.

[0029] In some examples, the wire windings 204, 206 have organic insulation during the winding process. The example flow tube 202 and the wire windings 204, 206 can then be heat-treated at a high temperature (e.g., 500°C), which burns away the wire insulation to produce the desired winding pitch without adversely affecting the inorganic insulation layer 208. The heat treatment also reduces stress in the wire windings 204, 206 to minimize displacement. Even without heat treatment, the inorganic insulation layer 208 prevents thermal mass flow sensor failure in the event of organic wire insulation failure during operation.

[0030] Compared to conventional thermal mass flow sensors, the disclosed example flow sensor 126, including the inorganic insulating layer 208, is capable of continuous operation at ambient temperatures of at least 200°C. Considering the additional heating of the inorganic insulating layer 208 to above ambient temperature by one or more of the wire windings 204, 206, some of these flow sensors 126 are capable of continuous operation at ambient temperatures of at least 240°C, and / or at least 300°C.

[0031] Example wire windings 204, 206 can be coupled to heating controller 210 to control the heating of one or more of the wire windings 204, 206 (e.g., two wire windings 204, 206 in a two-wire sensor, or one of the wire windings 204, 206 in a three-wire sensor including a third wire). Example wire windings 204, 206 are further coupled to mass flow measurement circuitry 212. Mass flow measurement circuitry 212 determines the mass flow rate through flow tube 202 based on measuring the heating of wire windings 204, 206 using the two-wire or three-wire sensor technology discussed above.

[0032] Figure 3 It can be used to achieve Figure 1 A block diagram of an example computing device 300 with valve control circuitry system 118. The example computing device 300 may be a general-purpose computer, laptop computer, tablet computer, mobile device, server, all-in-one computer, and / or any other type of computing device. Figure 3 The computing device 300 includes a processor 302, which may be a general-purpose central processing unit (CPU). In some examples, the processor 302 may include one or more dedicated processing units, such as an FPGA, 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 302 executes machine-readable instructions 304, which may be stored locally at the processor (e.g., in the included 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. Example mass storage device 310 may be a hard disk drive, a solid-state drive, a hybrid drive, a RAID array, and / or any other mass data storage device. A 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.

[0033] Example network interface 314 includes hardware, firmware, and / or software for connecting computing device 300 to a communication network 318 such as the Internet. For example, network interface 314 may include IEEE 802.X compliant wireless and / or wired communication hardware for sending and / or receiving communications.

[0034] Figure 3 Example I / O interface 316 includes hardware, firmware, and / or software for connecting one or more input / output devices 320 to processor 302, thereby providing input to and / or output from processor 302. For example, I / O interface 316 may include a graphics processing unit for interfacing with a display device, a universal serial bus port for interfacing with one or more USB-compatible devices, FireWire, fieldbus, and / or any other type of interface. Example computing device 300 may include a display device 324 (e.g., an LCD screen) coupled to I / O interface 316. Other example I / O devices 320 may include a keyboard, keypad, mouse, trackball, pointing device, microphone, audio speaker, display device, optical media driver, multi-touch screen, gesture recognition interface, magnetic media driver, and / or any other type of input and / or output device.

[0035] The computing device 300 can access the non-transitory machine-readable medium 322 via the I / O interface 316 and / or the I / O device 320. Figure 3 Examples of machine-readable media 322 include optical discs (e.g., compact discs (CDs), digital multifunction / 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 installable machine-readable media.

[0036] The method and system can be implemented using 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 distributed in a distributed manner with different components distributed across several interconnected computing systems. Any kind of computing system or other device suitable for performing the methods described herein is appropriate. A typical combination of hardware and software may include a general-purpose computing system having a program or other code that, when loaded and executed, controls the computing system to perform the methods described herein. Another typical implementation may include an application-specific integrated circuit or chip. Some implementations may include a non-transitory machine-readable (e.g., computer-readable) medium (e.g., a flash drive, optical disc, magnetic disk, etc.) storing one or more lines of code that can be executed by a machine to perform the processes described herein. As used herein, the term "non-transitory machine-readable medium" is defined to include all types of machine-readable storage media and excludes propagating signals.

[0037] As used herein, the terms “circuit” and “circuit system” refer to physical electronic components (i.e., hardware) and any software and / or firmware (“code”) that can configure, be executed by, and / or otherwise associate with the hardware. As used herein, for example, a particular processor and memory may constitute a first “circuit” when executing a first line or more of code, and a second “circuit” when executing a second line or more of code. As used herein, “and / or” means any one or more items in a list connected by “and / or”. As an example, “x and / or y” means any element in the three-element set {(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 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" means "one or more of x, y, and z". As used herein, the term "exemplary" means used as a non-limiting example, instance, or illustration. As used herein, the terms "such as" and "for example" introduce one or more lists of non-limiting examples, instances, or illustrations. As used herein, a circuit system is "operable" to perform a function whenever it includes the hardware and code necessary to perform the function, if necessary, regardless of whether the performance of the function is disabled or not enabled (e.g., through user-configurable settings, factory settings, etc.).

[0038] While this method and / or system has been described with reference to certain embodiments, those skilled in the art will understand that various changes and substitutions can be made without departing from the scope of this method and / or system. Furthermore, many modifications can be made to adapt particular situations or materials to the teachings of this disclosure without departing from the scope of this disclosure. For example, the systems, blocks, and / or other components of the disclosed examples can be combined, divided, rearranged, and / or otherwise modified. Therefore, this method and / or system is not limited to the specific embodiments disclosed. Rather, this method and / or system will include all embodiments that fall within the scope of the appended claims, both literally and under the principle of equivalents.

Claims

1. A thermal mass flow sensor, comprising: A flow tube having an inorganic insulating material layer on its outer surface; Two or more wires, said two or more wires being wound around the inorganic insulating material along the corresponding length of the flow tube; A heating controller configured to control the heating of one or more of the two or more wires; and A mass flow measurement circuit system configured to determine the mass flow rate through the flow tube based on measuring the temperature of two or more of the two or more conductors.

2. The thermal mass flow sensor as claimed in claim 1, wherein the two or more wires are non-insulated wires directly wound on the inorganic insulating material.

3. The thermal mass flow sensor as claimed in claim 1, wherein the inorganic insulating material is capable of continuous use at an ambient temperature of at least 200 degrees Celsius.

4. The thermal mass flow sensor as claimed in claim 3, wherein the inorganic insulating material is capable of continuous use at an ambient temperature of at least 240 degrees Celsius.

5. The thermal mass flow sensor as claimed in claim 4, wherein the inorganic insulating material is capable of continuous use at an ambient temperature of at least 300 degrees Celsius.

6. The thermal mass flow sensor as claimed in claim 1, wherein the inorganic insulating material comprises a spiral groove, and at least one of the first wire and the second wire is disposed within the spiral groove.

7. The thermal mass flow sensor as claimed in claim 1, wherein the inorganic insulating material comprises ceramic.

8. The thermal mass flow sensor of claim 1, wherein the mass flow measurement circuitry is configured to determine the mass flow rate based on at least one of the temperature difference between two or more of the two or more conductors or the power difference required to maintain the two or more of the two or more conductors at a target temperature.

9. A mass flow controller, comprising: Thermal mass flow sensor, the thermal mass flow sensor comprising: A flow tube having an inorganic insulating material layer on its outer surface; Two or more wires, said two or more wires being wound around the inorganic insulating material along the corresponding length of the flow tube; A heating controller configured to control the heating of one or more of the two or more wires; and A mass flow measurement circuit system configured to determine the mass flow rate through the flow tube based on measuring the heating of two or more of the two or more conductors; and A flow valve configured to control the flow rate between the flow tube and at least one of the inlet or outlet based on the mass flow rate determined by the thermal mass flow sensor.

10. The mass flow controller of claim 9, wherein the two or more wires are non-insulated wires directly wound on the inorganic insulating material.

11. The mass flow controller of claim 10, wherein the first conductor of the two or more conductors is wound with a pitch of at least 1.1 times the diameter of the first conductor, and the second conductor of the two or more conductors is wound with a pitch of at least 1.1 times the diameter of the second conductor.

12. The mass flow controller of claim 9, wherein the inorganic insulating material is capable of continuous use at an ambient temperature of at least 200 degrees Celsius.

13. The mass flow controller of claim 12, wherein the inorganic insulating material is capable of continuous use at an ambient temperature of at least 240 degrees Celsius.

14. The mass flow controller of claim 13, wherein the inorganic insulating material is capable of continuous use at an ambient temperature of at least 300 degrees Celsius.

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

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

17. The mass flow controller of claim 9, wherein the inorganic insulating material comprises a spiral groove, and at least one of the first wire and the second wire is disposed within the spiral groove.

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