Differential-pressure-based flow meters

Abstract

SOLUTION: Various embodiments include apparatuses and methods for forming the apparatus. In one embodiment, the apparatus is a flow meter having inlet and outlet portions for transporting fluid along a flow path. A flow-restrictor element is formed within the flow path to impart a pressure drop to the fluid. A flow sensor has a first surface of the flow sensor in direct fluid communication with the fluid flowing upstream of the flow-restrictor element, and a second surface, on a portion of the flow sensor opposite to the first surface, in direct fluid communication with the fluid flowing downstream of the flow-restrictor element. The flow sensor senses a differential pressure in the fluid due to the at least one flow-restrictor element. Other apparatuses and systems are disclosed.SELECTED DRAWING: Figure 3A

Description

[Technical field]

[0001] Claiming priority This application claims the benefit of priority to U.S. patent application Ser. No. 62 / 796,969, entitled "DIFFERENTIAL-PRESSURE-BASED FLOW METERS," filed Jan. 25, 2019, which is hereby incorporated by reference in its entirety. The subject matter disclosed herein relates to various types of equipment used in the semiconductor and related industries. More specifically, the subject matter disclosed herein relates to an apparatus for determining either a volumetric flow rate of a fluid or a mass flow rate of a fluid, both based on a differential pressure sensor. [Background technology]

[0002] Many industrial processes require accurate and precise measurement and control of various process fluids. Certain processes, such as the measurement of incompressible fluids (e.g., liquids), require volumetric flow rates (e.g., liters per minute (lpm), standard cubic centimeters per minute (sccm), or cubic meters per second (m 3 For most processes, only the mass flow rate (e.g., milligrams per minute (mg / m), or kilograms per second (kg / s)) needs to be measured. However, other processes, such as measurements of compressible fluids (e.g., gases), often require measurements of mass flow (e.g., milligrams per minute (mg / m), or kilograms per second (kg / s)). Thus, for compressible fluids, discussion of the volumetric mass density (also referred to simply as mass density herein) of a fluid may be considered to be a function of absolute pressure and temperature. For example, in the semiconductor and related industries, mass flow meters and mass flow controllers are used to accurately and precisely measure and control the mass of process fluids introduced into a process chamber. A wide variety of techniques can measure flow rates in devices such as thermal devices, ultrasonic time-of-flight devices, Coriolis devices, and pressure-based devices.

[0003] Pressure-based flow meters utilize a defined flow restriction to provide a pressure drop corresponding to the measured flow rate. When a pressure-based flow meter is deployed as a mass flow meter or mass flow controller, the flow meter also calculates the mass flow rate using a temperature measurement, the resulting pressure drop, and (for compressible fluids) a measurement of absolute pressure, combining knowledge of both the fluid properties and the flow restriction.

[0004] Referring to FIG. 1, a cross-sectional view of a prior art differential pressure based flow meter 100 is shown. The differential pressure based flow meter 100 includes a fluid inlet 109 and a fluid outlet 111 for fluid flowing in a flow path 113, and a restrictive element 107. A first cavity 103A and a second cavity 103B are coupled to the flow path 113 by a first pressure port 105A and a second pressure port 105B, respectively. The first cavity 103A is in fluid pressure communication with a first side 101A of the differential pressure sensor 101, and the second cavity 103B is in fluid pressure communication with a second side 101B of the differential pressure sensor 101. As fluid flows through the flow path 113, the restrictive element 107 creates a greater pressure on the upstream side (the side of the fluid inlet 109) such that the pressure of the fluid is greater than the pressure on the downstream side (the side of the fluid outlet) of the restrictive element 107. As a result, the higher fluid pressure (upstream of the restrictive element 107) is transmitted to the first cavity 103A through the first pressure port 105A. Similarly, the lower pressure (downstream of the restrictive element 107) is transmitted to the second cavity 103B through the second pressure port 105B. Thus, the first side 101A of the differential pressure sensor 101 experiences a higher pressure than the second side 101B of the differential pressure sensor 101. Although the cavities 103A, 103B are coupled to the flow path by the pressure ports 105A, 105B, the cavities are not directly coupled to the fluid flowing through the flow path 113. Thus, the cavities 103A, 103B experience a change in pressure on either side of the restrictive element 107.

[0005] Those skilled in the art understand the operation of the differential pressure sensor 101. In general, however, the differential pressure sensor 101 may be considered a type of flexible diaphragm. When the pressure on the first side 101A of the differential pressure sensor 101 is greater than the pressure on the second side 101B of the differential pressure sensor 101, the differential pressure sensor 101 deflects or bends. This deflection generates an electrical signal that is proportional to the difference between the two pressures. Thus, the differential pressure sensor 101 can be calibrated for a flow rate of a fluid based on the generated electrical signal.

[0006] However, a significant concern with the differential pressure based flow meter 100 is that the first cavity 103A and the second cavity 103B each contain a "dead volume" that is not flushed during operation of the differential pressure based flow meter 100. As a result, various types of contaminants can become trapped within either of the cavities 103A, 103B and eventually be released into the fluid flow in the flow path 113. In the case of a differential pressure based flow meter 100 used in semiconductor process operations, the contaminants can cause defects in one or more integrated circuits being fabricated. Such defects can cause one or more integrated circuits to be inoperable, which can result in significant loss of revenue for the companies that fabricate the integrated circuits.

[0007] Thus, in various embodiments described herein, the disclosed subject matter discloses several types of differential pressure-based flow meters that have no dead volume.

[0008] The information described in this section is provided to provide one of ordinary skill in the art with a context for the subject matter disclosed below and should not be construed as admitted prior art. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 shows a cross-sectional view of a prior art differential pressure based flow meter.

[0010] [Diagram 2]FIG. 2 illustrates a cross-sectional view of one embodiment of a differential pressure-based flow meter in accordance with the subject matter of this disclosure.

[0011] [Figure 3A] FIG. 3A illustrates a cross-sectional view of another embodiment of a differential pressure-based flow meter in accordance with the subject matter of the present disclosure.

[0012] [Figure 3B] FIG. 3B shows a section of the differential pressure-based flow meter embodiment of FIG. 3A.

[0013] [Figure 4A] FIG. 4A is a cross-sectional view of another embodiment of a differential pressure-based flow meter in accordance with the subject matter of the present disclosure.

[0014] [Figure 4B] FIG. 4B shows details of a flow sensor carrier used in the differential pressure-based flow meter embodiment of FIG. 4A.

[0015] [Figure 4C] FIG. 4C illustrates a cross-sectional view of another embodiment of a differential pressure-based flow meter in accordance with the subject matter of the present disclosure.

[0016] [Figure 4D] FIG. 4D shows details of a flow sensor carrier used in the differential pressure-based flow meter embodiment of FIG. 4C. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The subject matter of the present disclosure will now be described in detail with reference to several general and specific embodiments shown in various accompanying drawings. In the following description, numerous specific details are set forth to provide a thorough understanding of the subject matter of the present disclosure. However, it will be apparent to one skilled in the art that the subject matter of the present disclosure may be practiced without some or all of these specific details. In other instances, well-known process steps, construction techniques, or structures have not been described in detail in order not to obscure the subject matter of the present disclosure.

[0018] In each of the embodiments described herein, the various differential pressure based flow meters may be considered volumetric flow meters. However, based on reading and understanding the subject matter of this disclosure, one of ordinary skill in the art will recognize how to convert each of the various embodiments of the volumetric flow meters of the present disclosure into a mass flow meter or mass flow controller. Such techniques are also described in more detail below.

[0019] Referring now to FIG. 2, a cross-sectional view of one embodiment of a differential pressure based flow meter 200 in accordance with the subject matter of the present disclosure is shown. The differential pressure based flow meter 200 is shown to include a fluid inlet 201 and a fluid outlet 203 for fluid to flow through a flow path 205. FIG. 2 is also shown to include a flow sensor 207 having a first side 207A and a second side 207B, as well as a flow restricting element 211 and a flow meter body 215. Because the fluid flowing through the flow path 205 is in direct hydraulic or pneumatic communication with the flow sensor 207, there is no need for the first and second pressure ports 105A, 105B of FIG. 1 to relay pressure to the first and second cavities 103A, 103B as required by prior art differential pressure based flows. As a result, there is no dead volume that can trap and later release contaminants, since the pressure ports 105A, 105B and cavities 103A, 103B are not required in various embodiments of the subject matter of the present disclosure. Additionally, because the flow path is continuous, the differential pressure based flow meter 200 is continuously flushed during operation.

[0020] The flow restricting element 211 is located between a first bend 209 in the flow path 205 and a second bend 213 in the flow path 205. The first and second bends 209, 213 allow fluid flowing through the flow path 205 to flow past opposing sides of the flow sensor 207 (i.e., first side 207A and second side 207B). The flow restricting element 211 may comprise any type of flow restriction device such that the fluid flowing through the flow path 205 has a higher pressure upstream of the flow restricting element 211 than downstream of the flow restricting element 211. (In certain embodiments, the design of the differential pressure based flow meter 200 is bidirectional; therefore, the pressure difference on opposing sides of the flow sensor 207 may be reversed.) Such flow restricting devices may include, for example, orifices machined or otherwise formed in a plate disposed across the flow path 205, or laminar flow elements. In other embodiments, the flow restricting element 211 can provide a reduced cross-sectional area in the area of ​​the flow passage 205 to increase the pressure of the fluid flowing upstream of the reduced area flow passage. Such devices and techniques are known in the art.

[0021] In one embodiment, the flow sensor 207 comprises a differential pressure sensor that senses a pressure difference perceived as a pressure difference between the fluid pressures on a first side 207A and a second side 207B of the flow sensor 207. In this embodiment, the flow sensor 207 can be considered a type of flexible diaphragm.

[0022] As known to those skilled in the art, differential pressure sensors can measure a much wider range of fluid flow rates than other flow sensors known in the art. The range of detectable fluid flow rates is known as the "turndown ratio." Turndown ratio is also referred to as "rangeability" and indicates the range over which a flow meter can accurately measure the flow rate of a fluid. Thus, the turndown ratio represents the upper limit of the measurement range and the lower limit of the measurement range and is expressed as a ratio of the upper limit to the lower limit. In each of the various embodiments of the flow meters disclosed herein, the turndown ratio may be at least about 100:1 or greater.

[0023] In various embodiments, as shown in FIG. 2, the flow sensor 207 is positioned to measure the flow rate of fluid flowing in directions about 180° apart relative to each other on opposite sides of the flow sensor 207 (i.e., the inlet and outlet flows on opposite sides of the flow sensor 207 are substantially parallel to each other, but in opposite directions). However, the fluids at the fluid inlet 201 and the fluid outlet 203 need not flow substantially parallel to each other. That is, the fluid flowing from the fluid inlet 201 need not flow toward the fluid outlet 203 in approximately opposite directions. The fluid inlet 201 and the fluid outlet 203 may be positioned at an angle, for example, about 0° to about 45° apart. In other embodiments, the fluid inlet 201 and the fluid outlet 203 may be positioned at an angle, for example, about 45° to about 60° apart. In still other embodiments, the fluid inlet 201 and the fluid outlet 203 may be positioned at an angle, for example, about 60° to about 90° or more apart. As a result, in embodiments where it is desirable for the fluid flow proximate the flow sensor to flow in a laminar flow regime, the fluid inlet 201 and fluid outlet 203 may be positioned at various angles and be considered within the scope of the subject matter of this disclosure.

[0024] For example, each of the various fluid inlet 201 and fluid outlet 203 directional scenarios described above may flow at approximately 180° to one another on opposite sides of the flow sensor 207 in the portion of the flow path proximate the flow sensor 207. However, distal to the flow sensor 207 (e.g., upstream and downstream of the flow sensor 207 at a suitable distance to accommodate a laminar flow regime near the flow sensor 207, as described in more detail below), the flow paths can be positioned at any relative angle to one another as described above for convenience in mounting couplers or fittings on the differential pressure based flow meter 200.

[0025] With continued reference to FIG. 2, the first bend 209 and the second bend are on opposite sides of the flow restricting element 211. However, for a given embodiment of the differential pressure based flow meter 200, if it is desired that the fluid flow be in a laminar regime, at least one of the first bend 209 and the second bend 213 may each be located at least 5-7 diameters (based on the internal dimensions and assuming the cross section of the flow channel is circular) upstream and downstream of the flow restricting element 211, respectively. Alternatively, or in addition to increasing the path length to at least 5-7 diameters, various flow straightener devices known in the art may be used within the flow channel 205 as well. Based on basic principles of fluid mechanics, one skilled in the art will recognize how to position and size the flow channel 205 to accommodate laminar fluid flow. For example, if the flow channel 205 does not have a circular cross-sectional area, another relevant internal characteristic length dimension, such as, for example, hydraulic diameter for a flow channel having a rectangular cross section, the length of the channel upstream and downstream of the bends 209, 213, may be selected to restore laminar flow. Based on reading and understanding the subject matter of this disclosure, one of ordinary skill in the art will recognize how to determine the length of a flow path (e.g., before or after a bend) to create laminar flow for a given fluid flow rate, fluid density, and dynamic viscosity of the fluid.

[0026] Instead of having a laminar fluid flow, in other embodiments, the flow sensor 207 may be calibrated for a turbulent or transitional flow regime where the variation in flow rate is fairly stable. The acceptable variation in flow may be determined empirically for a given fluid and flow rate of interest, or may be determined in advance using computational fluid dynamics (CFD) analysis as known in the art. For example, one skilled in the art may determine that a turbulent flow rate may be within a given tolerance range if the flow does not vary by more than, for example, ±10% of the nominal flow rate. Such calibration techniques are known in the relevant art.

[0027] Overall, the differential pressure based flow meter 200 may be constructed by various means known in the art. For example, in various embodiments, the differential pressure based flow meter 200 may be constructed from one or more laminations of material, with each lamination being at least partially machined or otherwise formed (e.g., molded) prior to final assembly. In certain exemplary embodiments, a first lamination portion may be machined from 316L stainless. A second lamination portion, which substantially mirrors the first lamination portion, is also machined. The flow sensor 207 and flow restricting element 211 are then placed and bonded (e.g., welded, chemically bonded, or otherwise coupled) to one of the lamination portions. The two lamination portions are then welded or coupled together.

[0028] In other embodiments, the flow meter body 215 may have parts that are cast, molded, sintered, or otherwise formed and joined together. In still other embodiments, the flow meter body may be partially or completely manufactured using additive manufacturing techniques (e.g., printed from a 3D printer). Such techniques, and others, are known in the art.

[0029] The meter body 215 may be formed from one or more of a number of materials known in the art. For example, if the differential pressure based flow meter 200 is expected to carry caustic or corrosive fluids, various types of ceramic materials (e.g., aluminum oxide (Al 2 O 3 ), zirconium dioxide (ZrO 2 ), or beryllium oxide (BeO), or stainless steel (e.g., types 304 or 316L). In other applications, various types of machinable and / or moldable polymers and high performance plastics may be selected to form at least a portion of the flowmeter body 215.

[0030] 3A illustrates a cross-sectional view of another embodiment of a differential pressure-based flow meter 300 in accordance with the subject matter of the present disclosure. When used to measure fluid flow in the laminar flow regime, the long flow path reduces or eliminates the possibility of viscous impingement of the fluid on the face of the flow sensor 309, thus reducing or eliminating measurement errors due to transient or turbulent flows. However, as discussed in more detail below, the differential pressure-based flow meter 300 can also be calibrated for use in transient and turbulent flow regime flows.

[0031] The differential pressure based flow meter 300 of Figure 3 is shown to include a fluid inlet 301 and a fluid outlet 303 for fluid flowing through a flow path 307. Figure 3 is shown to include a flow sensor 309 having a first side 309A and a second side 309B, and a sensor wire 315 that couples the flow sensor 309 to an external device such as a flow controller or microprocessor (not shown). Figure 3 is also shown to include a first laminar flow element 305, a second laminar flow element 313, a flow restricting element 311, and a flow meter body 317.

[0032] In various embodiments, at least one of the first laminar flow element 305 and the second laminar flow element 313 is optional. Whether the laminar flow elements 305, 313 are optional depends at least in part on whether the flow sensor 309 is positioned to measure a flow rate of a fluid in a laminar flow regime, a transitional flow regime, or a turbulent flow regime, as discussed with reference to the differential pressure-based flow meter 200 of FIG.

[0033] Another consideration as to whether the laminar flow elements 305, 313 are optional depends at least in part on the physical location (distance) of the first side 309A of the flow sensor 309 relative to the fluid inlet 301, as well as the physical location (distance) of the second side 309B of the flow sensor 309 relative to the flow restricting element 311. For example, the differential pressure based flow meter 300 may be constructed such that the flow sensor 309 is a sufficient distance away from the fluid inlet 301, or the combination of tubes, channels, or other tubing that conveys the fluid to the differential pressure based flow meter 300 may be constructed to have a sufficient length such that the first velocity profile of the fluid is in the laminar flow regime, at least immediately before the fluid passes the upstream end of the flow sensor 309 on the first side 309A. Such determinations and calculations are well understood by those skilled in the art. Similarly, the physical distance from the downstream side of the flow restricting element 311 to the upstream end of the flow sensor 309 on the second side 309B may be constructed such that the second velocity profile of the fluid is in the laminar flow regime.

[0034] Thus, one or more laminar flow elements 305, 313 may be used in the differential pressure based flow meter 300. For example, for various embodiments and configurations of the differential pressure based flow meter 300, more than two laminar flow elements (only two shown) may be used. In addition, multiple flow restriction elements 311 (only one shown) may be used for flow of a particular type of fluid or a particular range of fluids. For example, when measuring low flow rates, multiple flow restriction elements 311 may be used to increase the pressure differential, in which case the flow sensor 309 is selected as the differential pressure sensor.

[0035] Similar to the differential pressure based flowmeter 200 of Figure 2, because the fluid flowing through the flow path 205 is in direct hydraulic or pneumatic communication with the pressure sensor, there is no need for first and second pressure ports 105A, 105B to relay pressure to the first and second cavities 103A, 103B as required by the prior art differential pressure based flowmeter of Figure 1. As a result, there is no dead volume that could trap and later release contaminants, since pressure ports 105A, 105B and cavities 103A, 103B are not required in various embodiments of the presently disclosed subject matter.

[0036] As discussed with respect to flow restricting element 211 of Figure 2, flow restricting element 311 of Figure 3 may comprise various types of flow restriction devices. For example, flow restricting element 311 may be a laminar flow element, a plate configured transverse to the direction of fluid flow with one or more orifices drilled or otherwise formed therethrough, or a restrictive bend in the flow path without a separate flow restriction device. Also, flow sensor 309 may comprise one or more types of flow sensors, as described above with reference to flow sensor 207 of Figure 2. For ease of understanding the subject matter of the disclosure provided herein, flow sensor 309 may be considered a differential pressure sensor.

[0037] Also, as discussed with reference to FIG. 2, the flow sensor 309 is positioned to measure the flow rate of fluid flowing in directions that are approximately 180° apart on opposite sides of the flow sensor 309 (i.e., the inlet and outlet flows on opposite sides of the flow sensor 309 are substantially parallel to each other, but in opposite directions). However, it is not necessary that the fluids at the fluid inlet 301 and the fluid outlet 303 flow substantially parallel to each other. That is, the fluids flowing from the fluid inlet 301 need not flow toward the fluid outlet 303 in approximately opposite directions. The fluid inlet 301 and the fluid outlet 303 may be positioned at an angle, for example, between about 0° and about 45° apart. In other embodiments, the fluid inlet 301 and the fluid outlet 303 may be positioned at an angle, for example, between about 45° and about 60° apart. In still other embodiments, the fluid inlet 301 and the fluid outlet 303 may be positioned at an angle, for example, between about 60° and about 90° or more apart. As a result, in embodiments where it is desirable for the fluid flow proximate the flow sensor to flow in a laminar flow regime, the fluid inlet 301 and fluid outlet 303 may be positioned at various angles and be considered within the scope of the subject matter of this disclosure.

[0038] For example, each of the various fluid inlet 301 and fluid outlet 303 directional scenarios described above may flow at approximately 180° to one another on opposite sides of the flow sensor 309 in the portion of the flow path proximate the flow sensor 309. However, distal to the flow sensor 309 (e.g., upstream and downstream of the flow sensor 309 at a suitable distance to accommodate a laminar flow regime near the flow sensor 309 as described in more detail herein), the flow paths can be positioned at any relative angle to one another as described above for convenience in mounting couplers or fittings on the differential pressure based flow meter 300.

[0039] 3A, the flow restricting element 311 is located between a first laminar flow element 305 in the flow path 307 and a second laminar flow element 313 in the flow path 307. As a result, the first and second laminar flow elements 305, 313 allow fluid flowing through the flow path 307 to flow past opposing sides (first side 309A and second side 309B) of the flow sensor 309. When used with a differential pressure sensor based flow sensor 309, the flow restricting element 311 may comprise any type of flow restriction device such that the fluid flowing through the flow path 307 has a higher pressure upstream of the flow restricting element 311 than downstream of the flow restricting element 311. Such a flow restricting device may include, for example, an orifice machined or otherwise formed in a plate disposed across the flow path 307. In various embodiments, the flow restricting element 311 may also comprise additional laminar flow elements. (It is known in the art that laminar flow elements cause a pressure drop across the length of the laminar flow element.) In other embodiments, as discussed with reference to FIG. 2, the cross-sectional area of ​​the flow channel 307 may be reduced to increase the pressure of the fluid flowing upstream of the reduced area flow channel. In various embodiments, the diameter d of the flow channel 307 may be reduced to 1000 mm. 1 is the diameter d of the second portion of the flow passage 307 2 (See FIG. 3B.) Such devices and techniques are known in the art.

[0040] Figure 3B illustrates section 330 (at section AA of Figure 3A) of an embodiment of the differential pressure-based flowmeter 300 of Figure 3A. Based on reading and understanding the subject matter of this disclosure, one of ordinary skill in the art will recognize that the differential pressure-based flowmeter 300 of Figures 3A and 3B may be constructed using, for example, any of the materials or techniques described above with reference to Figure 2.

[0041] 4A illustrates a cross-sectional view of another embodiment of a differential pressure-based flow meter 400 in accordance with the subject matter of this disclosure. Although the differential pressure-based flow meter 400 is described as being based on a differential pressure sensor, the differential pressure-based flow meter 400 can use any of a variety of flow sensors known in the art. Thus, the term "differential pressure-based flow meter" is primarily used for ease of understanding the various embodiments of FIG. 4A, as described below.

[0042] The differential pressure based flow meter 400 of Figure 4 is shown to include a fluid inlet 401, a fluid outlet 403, an upstream partial flow path 405L, a downstream partial flow path 405R, a first enclosure portion 407L, a second enclosure portion 407R, and a flow sensor carrier 409. The upstream partial flow path 405L and the downstream partial flow path 405R are upstream and downstream, respectively, of the flow sensor carrier 409. The flow sensor carrier 409 has an upstream side 413A and a downstream side 413B.

[0043] Figure 4B shows details of the flow sensor carrier 409 used in the embodiment of the differential pressure based flow meter 400 of Figure 4A. With simultaneous reference to Figures 4A and 4B, the flow sensor carrier 409 is shown to include a differential pressure sensor 413, as well as a first through hole 411, a second through hole 417, and a third through hole 419. The through holes 411, 417, 419 are formed through the flow sensor carrier 409 in substantially the same direction and include orifices through which fluid can flow from the upstream partial flow path 405L through the flow sensor carrier 409 to the downstream partial flow path 405R.

[0044] Upon reading and understanding the subject matter of this disclosure, one skilled in the art will recognize that at least two of the first, second, and third through holes 411, 417, 419 are optional and only a single through hole in the flow sensor carrier 409 is required. In other embodiments, there may be more than three through holes (e.g., four or more). Additionally, any through hole may be formed in various diameters and shapes through various techniques independently known in the art. Such techniques include laser drilling, mechanical drilling, electrical discharge machining (EDM), or other subtractive machining operations known in the art. For example, at least one of the through holes 411, 417, 419 may have a conical or tapered inlet and / or outlet, and may have a circular, elliptical, or other cross-sectional hole. In other embodiments, the entire flow sensor carrier 409 may be formed from additive machining techniques as described above. Once formed, the differential pressure sensor 413 may be press-fit, welded, chemically bonded, or otherwise coupled to the flow sensor carrier 409 by techniques independently known in the art.

[0045] In a particular exemplary embodiment, as shown, the first enclosure portion 407L comprises an inlet pipe structure having two ends: a first end (including the fluid inlet 401) and a second end positioned to receive the flow sensor carrier 409. The first end may be flared to a VCR® metal-to-metal seal feature or welded to a male VCR® pipe stub, for example, as known in the art. In other embodiments, the first end may be formed as a VCO® O-ring type face seal fitting, for example (VCR® and VCO® seal fittings are registered trademarks of Swagelok Corporation, Solon, Ohio, USA). One skilled in the art will recognize that other types of fittings may be used as well.

[0046] The remaining end (i.e., the second end) of the inlet pipe structure may be flared substantially in one direction (e.g., the positive y-direction). The substantially unidirectional flaring leaves the lower portion (e.g., the inlet pipe) of the first enclosure portion 407L substantially undeformed and the lower portion (e.g., the outlet pipe) of the second enclosure portion 407R substantially undeformed, thereby forming an elliptical cross-sectional area at the interface region 415. The substantially unidirectional flaring creates a first interface feature 421 and a second interface feature 423, as shown in FIG. 4A.

[0047] Continuing with this particular exemplary embodiment, the second enclosure portion 407R includes an outlet tube, beginning with a flared portion of the upstream portion of the outlet tube forming a second interface feature 423 and mating with the first interface feature 421. The outlet tube terminates at a downstream portion of the outlet tube with a coupling feature that connects the outlet tube to, for example, a proportional valve block (not shown, but known in the art). Either the outlet end of the outlet tube or the proportional valve block terminates in, for example, a VCR® or VCO® seal fitting feature. The flow sensor carrier 409 is then placed, formed, or otherwise mounted between the inlet and outlet tubes at the interface features 421, 423. The inlet and outlet tubes are then bonded together at the interface region 415, substantially collinear with one another (e.g., by orbital laser welding, interference or press fit, chemical adhesives, combinations thereof, or other techniques known in the art).

[0048] The first enclosure portion 407L, the second enclosure portion 407R, and the flow sensor carrier 409 may be constructed using any of the materials or techniques described above with reference to Figure 2. Alternatively, the first enclosure portion 407L and the second enclosure portion 407R may be constructed using various types of tubing materials known in the art, including, for example, stainless steel tubing, copper tubing, polymer-based tubing, or other materials. The tubing is selected at least in part based on fluid flow considerations (e.g., the corrosiveness of the fluid as well as the pressure at which the fluid is conveyed), contamination considerations, and other considerations known in the art.

[0049] In another particular exemplary embodiment, the first enclosure portion 407L and the second enclosure portion 407R may comprise a tube structure. As known in the art, the tube structure may be formed, for example, from a thin-walled tube that may not be able to withstand the operating pressures encountered during fluid transport by itself. However, the tube structure may be backed up with one or more structural components, such as an outer mold of each of the tube structures, to ensure that the tubes do not deform during operation. The back-up components may include, for example, fiber-reinforced polymers, ceramics, polymers, metals, or other suitable materials known in the art. In addition, because the back-up components are non-wetted, there are limited or no purity requirements for the components. As a result, the function of structure is separated from the function of maintaining the purity of the fluid. The thin-walled tubes may be selected from materials known to resist chemical properties and formed to reduce or eliminate particle trapping. Additionally, the tubes may be formed using operations such as hydroforming, pneumatic forming, or mechanical flaring, as known in the art.

[0050] Depending on factors such as fluid velocity, fluid density, and fluid kinematic viscosity, the velocity impingement on the upstream side 413A of the flow sensor carrier 409, and thus the differential pressure sensor 413, can be large. Additionally, the drag force generated by the flow sensor carrier 409 can also be large. Thus, the differential pressure based flow meter 400 may need to be calibrated for each of the different types of fluids conveyed therein. However, the differential pressure based flow meter 400 of FIG. 4A can be constructed less expensively than the differential pressure based flow meters 200, 300 of FIGS. 2 and 3A.

[0051] Similar in at least some respects to the differential pressure-based flow meter 400 of FIGS. 4A and 4B, FIG. 4C illustrates a cross-sectional view of another embodiment of a differential pressure-based flow meter 430 in accordance with the subject matter of the present disclosure.

[0052] The differential pressure based flow meter 430 of Figure 4C is shown to include a fluid inlet 431, a fluid outlet 433, an upstream flow path portion 435L, a downstream flow path portion 435R, a first enclosure portion 437L, a second enclosure portion 437R, and a flow sensor carrier 439. The upstream flow path portion 435L and the downstream flow path portion 435R are upstream and downstream, respectively, of the flow sensor carrier 439. The flow sensor carrier 439 has an upstream side 443A and a downstream side 443B.

[0053] Figure 4D shows details of the flow sensor carrier 439 used in the embodiment of the differential pressure based flow meter 430 of Figure 4C. With simultaneous reference to Figures 4C and 4D, the flow sensor carrier 439 is shown to include a differential pressure sensor 443 and a plurality of through holes 441. The plurality of through holes 441 are formed through the flow sensor carrier 439 in substantially the same direction and include orifices through which fluid can flow from the upstream partial flow path 435L through the flow sensor carrier 439 to the downstream partial flow path 435R.

[0054] Upon reading and understanding the subject matter of this disclosure, one skilled in the art will recognize that flow sensor carrier 439 need only have a single through hole of plurality of through holes 441. Additionally, one skilled in the art will recognize that additional through holes beyond the number shown in Figure 4D may be used. The plurality of through holes 441, as well as flow sensor carrier 439, may be formed from a variety of materials and have a variety of shapes, as discussed above with reference to Figures 4A and 4B.

[0055] Differential pressure-based flowmeter 430 of Figure 4C differs from differential pressure-based flowmeter 400 of Figure 4A in that interface region 445 of Figure 4C has a substantially round cross-sectional area as compared to the substantially elliptical cross-sectional area at interface region 415 of Figure 4C. That is, first interface feature 447 and second interface feature 449 of Figure 4C may be flared substantially in three directions (e.g., in the positive x, y, and z directions).

[0056] 4C are flared, the flow sensor carrier 439 is then placed, formed, or otherwise mounted between the first enclosure portion 437L and the second enclosure portion 437R at the interface features 447, 449. The first enclosure portion 437L and the second enclosure portion 437R are then bonded together at the interface region 445 and are substantially collinear with one another (e.g., by orbital laser welding, interference or press fit, chemical adhesives, combinations thereof, or other techniques known in the art).

[0057] As can be appreciated by those skilled in the art, each of the various embodiments of the differential pressure-based volumetric flow meters described herein can be formed into a mass flow meter or mass flow controller by adding additional components. As known in the art, a mass flow controller is arranged to automatically control the flow rate of a fluid according to a set flow rate transmitted as an electrical signal in the form of a predetermined set value. In particular, when the fluid is a gas, the mass flow controller is substantially unaffected by changes in gas pressure due to temperature changes or other factors, as these factors can be measured and considered separately. For example, a mass flow controller also includes the various volumetric flow meters described above, as well as all of the control valves, valve actuators, and controllers coupled to the volumetric flow meters. Based on reading and understanding the subject matter of the present disclosure, a person skilled in the art will readily recognize which components are necessary and how to couple those components to the various volumetric flow meters described herein to form various types of mass flow meters.

[0058] In general, the subject matter of the present disclosure contained herein generally describes or relates to flow meter components operable and usable to control part of the operation of a "tool" in a semiconductor fabrication environment (fab). Such tools can include various types of deposition (including plasma-based tools such as ALD (atomic layer deposition), CVD (chemical vapor deposition), PECVD (plasma enhanced CVD)) and etching tools (e.g., reactive ion etching (RIE) tools), as well as various types of thermal furnaces (e.g., rapid thermal annealing and oxidation), ion implantation, and various other process and metrology tools found in various fabs and known to those skilled in the art. However, the subject matter of the present disclosure is not limited to semiconductor environments, but can be used in numerous machine tool environments, such as robotic assembly, manufacturing, and fluid control operations in machining environments (including, for example, operations using physical vapor deposition (PVD) tools), as well as various other environments. Upon reading and understanding the disclosure provided herein, those skilled in the art will recognize that various embodiments of the subject matter of the present disclosure may be used with other types of processes and a wide variety of tools and components.

[0059] As used herein, the term "or" may be interpreted in an inclusive or exclusive sense. Furthermore, other embodiments will be understood by those skilled in the art based on reading and understanding the present disclosure provided. Furthermore, based on reading and understanding the present disclosure provided herein, those skilled in the art will readily understand that all of the various combinations of the techniques and examples provided herein may be applied in various configurations.

[0060] Although various embodiments are discussed separately, these separate embodiments are not intended to be considered as independent techniques or designs. As indicated above, each of the various portions may be related to each other, and each may be used separately or in combination with other embodiments discussed herein. For example, although various embodiments of methods, operations, and processes have been described, these methods, operations, and processes may be used separately or in various combinations.

[0061] As a result, many modifications and variations can be made, as would be apparent to one skilled in the art upon reading and understanding the present disclosure provided herein. For example, each of the various embodiments is shown and described as using a single differential pressure sensor. However, based on reading and understanding the subject matter of the present disclosure, one skilled in the art would recognize that two or more differential pressure sensors may be used in each of the embodiments, for example, depending on the viscosity of the fluid expected to be conveyed through the respective flow meter. Additionally, one or more flow restricting elements may be used with each of the various embodiments described herein to increase the differential pressure drop measured by the various differential pressure sensors. When measuring low fluid flow rates (e.g., less than 1 sccm), a higher pressure drop may be used, and the higher the pressure drop, the greater the accuracy of the flow meter at low flow rates.

[0062] Moreover, functionally equivalent methods and devices within the scope of the present disclosure, in addition to those recited herein, will be apparent to those skilled in the art from the foregoing description. Portions and features of some embodiments, materials, and construction techniques may be included in or substituted for other embodiments. Such modifications and variations are intended to be included within the scope of the appended claims. Accordingly, the present disclosure is to be limited only by the terms of the appended claims and the full scope of equivalents to which such claims are entitled. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting.

[0063] The Abstract of the present disclosure is provided to allow the reader to quickly ascertain the nature of the technical disclosure. The Abstract is submitted with the understanding that it will not be used to interpret or limit the scope of the claims. It can also be understood that in the foregoing Detailed Description, various features may be grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of disclosure should not be construed as limiting the scope of the claims. Accordingly, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate embodiment.

Claims

1. 1. A flow meter comprising: a flow path having an inlet and an outlet and configured to transport a fluid; at least one flow restricting element within the flow passage and disposed between the inlet and the outlet of the flow passage and configured to provide a pressure drop to the fluid; a flow sensor disposed between the inlet and outlet portions of the flow path, a first surface of the flow sensor configured to be in direct fluid communication with the fluid flowing upstream of the at least one flow restricting element, a second surface of a portion of the flow sensor opposite the first surface of the flow sensor configured to be in direct fluid communication with the fluid flowing downstream of the at least one flow restricting element, and the flow sensor configured to sense a differential pressure of the fluid across the at least one flow restricting element.

2. 2. The flow meter of claim 1, The at least one flow restricting element comprises a laminar flow element.

3. 2. The flow meter of claim 1, The at least one flow restricting element comprises an orifice.

4. 2. The flow meter of claim 1, The at least one flow restricting element comprises a plurality of orifices.

5. 2. The flow meter of claim 1, A flow meter, wherein the inlet and outlet portions of the flow passage are disposed substantially parallel to one another.

6. 2. The flow meter of claim 1, The flow meter, wherein the inlet and outlet of the flow passage are disposed at an angle between about 0° and about 45° apart.

7. 2. The flow meter of claim 1, The flow meter, wherein the inlet and outlet of the flow passage are disposed at an angle between about 45° and about 60° apart.

8. The flow meter of claim 1 further comprises: A flow meter comprising a first bend in the flow path upstream of the at least one flow restricting element and a second bend downstream of the at least one flow restricting element.

9. 2. The flow meter of claim 1, A flow meter, wherein at least one of the first bend and the second bend is at least 5 to 7 characteristic length dimensions away from the at least one flow restricting element, the characteristic length dimensions being based on an internal dimension of the flow path.

10. 2. The flow meter of claim 1, The flow meter, wherein the flow sensor is a differential pressure sensor.

11. 2. The flow meter of claim 1, The flow meter wherein the turndown ratio of the flow meter is at least about 100:

1.

12. 1. A flow meter comprising: a flow path having an inlet and an outlet and configured to transport a fluid, the flow path having a single bend formed therein; at least one flow restricting element within the flow passage and disposed between the inlet and the outlet of the flow passage and configured to provide a pressure drop to the fluid; at least one flow sensor having a first surface and a second surface opposite the first surface, wherein the first surface of the flow sensor is configured to be in direct fluid communication with the fluid flowing upstream of the at least one flow restricting element and the second surface is configured to be in direct fluid communication with the fluid flowing downstream of the at least one flow restricting element, and the flow sensor is configured to sense a differential pressure of the fluid across the at least one flow restricting element.

13. 13. The flow meter of claim 12, The at least one restrictive element is located within the single bend in the flow path.

14. 13. The flow meter of claim 12, The at least one flow restricting element is a laminar flow element.

15. 13. The flow meter of claim 12, The flow meter, wherein the at least one flow restriction is a plate configured transverse to a direction of fluid flow having at least one orifice formed therethrough.

16. 13. The flow meter of claim 12, A flow meter comprising: a flow passage having a single bend in the flow passage having a reduced cross-sectional area compared to a cross-sectional area of ​​a remainder of the flow passage; and wherein the at least one flow restriction comprises the reduced cross-sectional area.

17. 13. The flow meter of claim 12, A flow meter, wherein a cross-sectional area of ​​the inlet portion of the flow passage is greater than a cross-sectional area of ​​the outlet portion of the flow passage.

18. 13. The flow meter of claim 12, A flow meter, wherein a cross-sectional area of ​​the outlet portion of the flow passage is greater than a cross-sectional area of ​​the inlet portion of the flow passage.

19. 13. The flow meter of claim 12, The flow meter is configured to have no dead volume therein.

20. 1. A flow meter comprising: an upstream portion and a downstream portion for conveying a fluid, the upstream portion and the downstream portion being substantially collinear with each other; a flow sensor carrier disposed transversely to the direction of the transported fluid between the upstream and downstream partial flow paths; at least one orifice formed through the flow sensor carrier in substantially the same direction as the flow of the fluid, the at least one orifice providing a pressure drop between the upstream and downstream partial flow paths; a flow sensor formed within the flow sensor carrier and having a first surface and a second surface opposite the first surface, the first surface of the flow sensor configured to be in direct fluid communication with the fluid flowing upstream of the flow sensor carrier and the second surface of the flow sensor configured to be in direct fluid communication with the fluid flowing downstream of the flow sensor carrier, and the flow sensor configured to sense a differential pressure of the fluid across the at least one orifice.

Images