Flow sensing device based on thermopile

Abstract

The present invention is entitled "Flow Sensing Apparatus Based on Thermopile." Example systems, apparatuses, and methods are disclosed herein for sensing a flow rate of a fluid using a flow sensing apparatus based on a thermopile. An example apparatus includes a flow sensing apparatus including a heating structure having a centerline. The flow sensing apparatus can further include a thermopile. At least a portion of the thermopile can be disposed on the heating structure. The thermopile can include a first thermocouple having a first thermocouple junction disposed upstream of the centerline of the heating structure. The thermopile can further include a second thermocouple having a second thermocouple junction disposed downstream of the centerline of the heating structure.

Description

[0001] This application is a divisional application of the invention patent application filed on April 20, 2020, with application number 202010311039.0 and invention title "Flow Sensing Device Based on Thermopile". Technical Field

[0002] The exemplary embodiments disclosed herein relate generally to sensors, and more specifically to flow sensors. Background Technology

[0003] Flow sensors are increasingly used in industrial and commercial applications to measure and control the mass flow rate of gases and liquids. Conventional flow sensor designs typically exhibit drift characteristics that reduce their measurement sensitivity.

[0004] The applicant has identified numerous defects and problems associated with conventional flow sensors. Through effort, ingenuity, and innovation, many of these identified problems have been addressed by the developed solutions, including those described in the embodiments of this disclosure, and numerous examples of these solutions are detailed herein. Summary of the Invention

[0005] This document discloses systems, apparatus, methods, and computer program products for providing thermopile-based flow sensing devices with low or no drift characteristics, which in some cases are compatible with complementary metal-oxide-semiconductor (CMOS) processing.

[0006] In one exemplary embodiment, an apparatus for sensing fluid flow rate is provided. The apparatus may include a flow sensing device comprising a heating structure having a centerline. The flow sensing device may further include a thermopile. At least a portion of the thermopile may be disposed on the heating structure. The thermopile may include a first thermocouple having a first thermocouple junction disposed upstream of the centerline of the heating structure. The thermopile may further include a second thermocouple having a second thermocouple junction disposed downstream of the centerline of the heating structure.

[0007] In another example embodiment, a method for manufacturing a device for sensing fluid flow rate is provided. The method may include providing a heating structure having a centerline. The method may further include disposing at least a portion of a thermoelectric stack on the heating structure. The thermoelectric stack may include a first thermocouple having a first thermocouple junction disposed upstream of the centerline of the heating structure. The thermoelectric stack may further include a second thermocouple having a second thermocouple junction disposed downstream of the centerline of the heating structure.

[0008] In yet another example embodiment, an apparatus for sensing fluid flow rate is provided. The apparatus may include a flow sensing device comprising a heating structure having a centerline. The flow sensing device may further include a first thermopile comprising a first plurality of thermocouples disposed upstream of the centerline of the heating structure. The first plurality of thermocouples may include a first subset of the first plurality of thermocouples aligned generally parallel to the centerline of the heating structure. The first plurality of thermocouples may further include a second subset of the first plurality of thermocouples aligned generally perpendicular to the centerline of the heating structure. The flow sensing device may further include a second thermopile comprising a second plurality of thermocouples disposed downstream of the centerline of the heating structure. The second plurality of thermocouples may include a third subset of the second plurality of thermocouples aligned generally parallel to the centerline of the heating structure. The second plurality of thermocouples may further include a fourth subset of the second plurality of thermocouples aligned generally perpendicular to the centerline of the heating structure.

[0009] In yet another example embodiment, a method for manufacturing a device for sensing fluid flow rate is provided. The method may include providing a heating structure having a centerline. The method may further include disposing a first thermopile upstream of the centerline of the heating structure. The first thermopile may include a first plurality of thermocouples disposed upstream of the centerline of the heating structure. The first plurality of thermocouples may include a first subset of the first plurality of thermocouples aligned generally parallel to the centerline of the heating structure. The first plurality of thermocouples may further include a second subset of the first plurality of thermocouples aligned generally perpendicular to the centerline of the heating structure. The method may further include disposing a second thermopile downstream of the centerline of the heating structure. The second thermopile may include a second plurality of thermocouples disposed downstream of the centerline of the heating structure. The second plurality of thermocouples may include a third subset of the second plurality of thermocouples aligned generally parallel to the centerline of the heating structure. The second plurality of thermocouples may further include a fourth subset of the second plurality of thermocouples aligned generally perpendicular to the centerline of the heating structure.

[0010] The foregoing description of the invention is provided merely to outline some exemplary embodiments and to provide a basic understanding of some aspects of this disclosure. Therefore, it should be understood that the above embodiments are merely illustrative and should not be construed as limiting the scope or substance of this disclosure in any way. It should be understood that, in addition to those summarized herein, the scope of this disclosure covers many other possible embodiments, some of which will be further described below. Attached Figure Description

[0011] Some exemplary embodiments of this disclosure have been described in general terms above. Reference will now be made to the accompanying drawings, which illustrate exemplary embodiments and features of this disclosure and are not necessarily drawn to scale. It should be understood that the components and structures shown in the drawings may or may not be present in the various embodiments of this disclosure described herein. Therefore, some embodiments or features of this disclosure may include fewer or more components or structures than those shown in the drawings without departing from the scope of this disclosure.

[0012] Figure 1 An example layout of a thermopile-based flow sensing device according to some example implementations described herein is shown.

[0013] Figure 2A and Figure 2B Example temperature contours are shown for an example flow sensing device based on a thermopile according to some example embodiments described herein.

[0014] Figure 3 Another example layout of a thermopile-based flow sensing device according to some example implementations described herein is shown.

[0015] Figure 4 Another example layout of a thermopile-based flow sensing device according to some example implementations described herein is shown.

[0016] Figure 5 Another example layout of a thermopile-based flow sensing device according to some example implementations described herein is shown.

[0017] Figure 6 Another example layout of a thermopile-based flow sensing device according to some example implementations described herein is shown.

[0018] Figure 7 Another example layout of a thermopile-based flow sensing device according to some example implementations described herein is shown.

[0019] Figure 8 Another example layout of a thermopile-based flow sensing device according to some example implementations described herein is shown.

[0020] Figure 9A , Figure 9B , Figure 9C , Figure 9D , Figure 9E , Figure 9F , Figure 9G , Figure 9H , Figure 9I , Figure 9J , Figure 9K , Figure 9L , Figure 9M , Figure 9N , Figure 9O , Figure 9P , Figure 9Q , Figure 9R , Figure 9S and Figure 9T An example process flow is shown for manufacturing an example flow sensing device based on a thermopile according to some example embodiments described herein.

[0021] Figure 10 Another example layout of a thermopile-based flow sensing device according to some example implementations described herein is shown.

[0022] Figure 11 An example table of thermocouple materials for example flow sensing devices based on thermopile, according to some example embodiments described herein, is shown.

[0023] Figure 12 An example flowchart is shown, illustrating example methods according to some example implementations described herein.

[0024] Figure 13 An example flowchart is shown, illustrating another example method based on some example implementations described herein. Detailed Implementation

[0025] The following description should be read with reference to the accompanying drawings, in which similar reference numerals throughout the views denote similar elements. The detailed description and drawings illustrate several embodiments intended to illustrate the disclosure. It should be understood that any designations of the disclosed features (e.g., first, second, etc.) and / or directional terms used with the disclosed features (e.g., front, back, lower, upper, etc.) are relative terms indicating illustrative relationships between related features. The word "example" is used herein to mean "serving as an example, instance, or illustration." Any embodiment described herein as an "example" is not necessarily more preferred or advantageous than other embodiments.

[0026] First, it should be understood that although illustrative embodiments of one or more aspects are shown below, the disclosed components, systems, and methods can be implemented using a variety of techniques. This disclosure should in no way be limited to the exemplary embodiments, drawings, and techniques shown below, but modifications can be made within the scope of the appended claims and their equivalents. While dimensional values ​​for various elements are disclosed, the drawings may not be drawn to scale.

[0027] Typically, the output of a hot-wire anemometer flow sensor die drifts when powered. In these hot-wire anemometer flow sensors, which typically use platinum as the resistive material, the drift in the sensor is due to stress relaxation in the platinum layer and changes in stress in the silicon nitride layer surrounding the platinum, which forms an air bridge, partly because platinum has piezoresistive properties that vary with its resistive stress. In other words, the drift in these hot-wire anemometer flow sensors is generally due to stress relaxation in the platinum layer and is influenced by residual stress in the air bridge (also known as a microbridge). For example, drift has been directly correlated with stress in the plasma-enhanced chemical vapor deposition (PECVD) silicon nitride layer on the surface of the microbridge. This stress in the PECVD silicon nitride layer changes over time as the air bridge is continuously heated by a resistance heater, which is an integral part of the flow sensor. Experimentally, this drift value has reached as high as 40 µV per day at empty flow rates. Therefore, there is a need for a flow sensor exhibiting low drift characteristics that can be used with both gases and liquids.

[0028] The exemplary embodiments described herein provide systems, apparatus, and methods for reducing or eliminating drift experienced by conventional flow sensors by providing various arrangements for thermopile-based flow sensing devices. In some embodiments, the signal generated by the thermopile-based flow sensing device disclosed herein is a voltage source and has minimal response to membrane resistance, achieved by using a thermocouple or thermopile. Without membrane resistance sensitivity, other sensitivities (such as stress or magnetoresistance changes) are negligible. An additional thermocouple can provide additional voltage, signal, and sensitivity, an advantage that conventional resistive flow sensors do not offer in terms of sensitivity. In some cases, the thermopile structure can be fabricated on a microbridge structure or membrane structure. In some embodiments, the membrane structure disclosed herein can provide the same thermopile structure as a microbridge, as well as other structures that a microbridge cannot provide.

[0029] In some implementations, the general process for manufacturing thermopile flow sensors is as follows:

[0030] 1. Growth of thermal silica.

[0031] 2. Deposit the bottom silicon nitride. In some implementations, silicon dioxide can be used instead of all silicon nitride dielectrics, such as PECVD, tetraethoxysilane (TEOS), or sputter deposition, to reduce thermal conductivity.

[0032] 3. Deposit and pattern the resistance heater structure. The heater structure can be made of materials such as: silicon (including polycrystalline silicon); platinum; nickel-chromium alloys; permalloy; PtSi and other silicides; W; TiN; AlN; WN; any other suitable material; or any combination thereof.

[0033] 4. Deposit silicon nitride interlayer dielectric.

[0034] 5. Deposit and pattern the first thermocouple material. (Refer to...) Figure 11 Various thermocouple materials that can be used for the first thermocouple are discussed in more detail.

[0035] 6. Deposit interlayer dielectric. In some cases, depending on the materials used, this step may be optional but can result in higher yields. In some cases, if an interlayer dielectric is used, it must be patterned to open vias to the underlying thermocouple material.

[0036] 7. Deposit and pattern the second thermocouple material. (Refer to...) Figure 11 Various thermocouple materials that can be used for a second thermocouple are discussed in more detail.

[0037] 8. Deposit interlayer dielectrics, patterns, and open vias onto the heater and thermopile connections.

[0038] 9. Deposit metal (such as Al / 1% Cu) and pattern it to form lead-out lines and bonding pads.

[0039] 10. Deposit and pattern a silicon nitride overlay to open up the bonding pad area.

[0040] 11. Pattern the back side of the wafer and use deep reactive ion etching (DRIE) to create a cavity beneath the thermopile structure.

[0041] In some implementation schemes, such as reference Figure 1 Figure 2 Figure 3 , Figure 4 , Figure 5 , Figure 6 Figure 9 Figure 10 and Figure 12 The heater structure discussed may be located below a single set of thermocouples (e.g., a thermopile), with one side upstream and the other downstream of the heater structure. In these arrangements, the thermocouples are not located on the silicon die. Instead, the thermocouples are suspended on the cavity or reside on the membrane structure. In some embodiments, the set of thermocouples may be collectively referred to as a thermopile. In some embodiments, the thermopile may be placed on a thermally insulating structure (such as a bridge or membrane) where opposing thermocouples (e.g., cold junctions, hot junctions) are oriented such that one set of junctions is upstream and the other set is downstream of the heating element centerline.

[0042] In some implementation schemes, such as reference Figure 7 , Figure 8 and Figure 13The heater structure under discussion can be located between two sets of thermocouples (e.g., two thermopile structures), with one set of thermocouples located upstream of the heater structure and the other set downstream. In these arrangements, parasitic effects exist, and each set of thermocouples has one side on the bulk silicon die that fluctuates in temperature.

[0043] In some implementations, the following formula can be used to characterize

[0044] The flow sensing device based on thermopile disclosed in this article:

[0045] ΔV = nΔS(ΔT)

[0046] Where ΔV = potential difference; n = number of thermocouples; S = Seebeck coefficient (also known as thermal power, thermoelectric power (TE) or thermoelectric sensitivity); ΔS = TE1 - TE2 (thermoelectric power of the first thermoelectric material - thermoelectric power of the second thermoelectric material); T = temperature; and ΔT = T1 - T ref (Measured temperatures at (multiple) thermojunctions - temperatures at (multiple) reference thermojunctions). In some cases, such as Figure 7 As shown, T1 can be measured on the film structure 716 using downstream thermocouple 712, and on bulk silicon using downstream thermocouple 713. In other cases, such as in Figure 6 As shown, the relative temperature difference ΔT can be measured on the membrane structure 716 using the upstream thermocouple 608 and the downstream thermocouple 610 without using a reference temperature.

[0047] The embodiments disclosed herein have many advantages, such as: (1) providing low-drift or drift-free devices (e.g., as referenced) Figure 1 Figure 2 Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8 Figure 9 Figure 10 , Figure 12 and Figure 13 (as discussed); (2) providing potential compatibility with CMOS processing through a unique combination of thermocouple materials (e.g., as referenced). Figure 11 (As discussed).

[0048] Although this disclosure describes the features of the thermopile-based flow sensing device disclosed herein with reference to flow sensors, the thermopile-based flow sensing device disclosed herein can be used in the testing or application of any suitable sensor, detector, gauge, instrument, utilizing precise heating or temperature detection, or other applications where such use is required.

[0049] Figure 1An example layout of a thermopile-based example flow sensing device 100 according to some example embodiments described herein is shown. In some embodiments, the thermopile-based example flow sensing device 100 may be provided for sensing the flow rate of fluid 101 (e.g., the flow rate of a gas or liquid). In some embodiments, the thermopile-based example flow sensing device 100 may include a heating structure 102 having a centerline 104. In some embodiments, the thermopile-based example flow sensing device 100 may further include a thermopile 106. In some embodiments, at least a portion of the thermopile 106 may be disposed on the heating structure 102.

[0050] In some embodiments, the thermopile 106 may include a plurality of thermocouples having a plurality of thermocouple junctions. In some embodiments, the plurality of thermocouples may have a plurality of upstream thermocouple junctions 108 (e.g., nineteen upstream thermocouple junctions) disposed upstream of the centerline 104 of the heating structure 102. In some embodiments, the plurality of thermocouples may have a plurality of downstream thermocouple junctions 110 (e.g., nineteen downstream thermocouple junctions) disposed downstream of the centerline 104 of the heating structure 102. In some embodiments, the plurality of upstream thermocouple junctions 108 and the plurality of downstream thermocouple junctions 110 may be disposed on the heating structure 102. In some embodiments, the number of upstream thermocouple junctions 108 and the number of downstream thermocouple junctions 110 may be the same. In some embodiments, the number of upstream thermocouple junctions 108 and the number of downstream thermocouple junctions 110 may depend on the Seebeck coefficient of the thermocouple material in the thermocouples and the desired output voltage (e.g., may be a function of them).

[0051] In some embodiments, the thermopile-based example flow sensing device 100 may further include a plurality of upstream sample temperature sensing thermocouples 112 (e.g., two upstream sample temperature sensing thermocouples) disposed upstream of the centerline 104 of the heating structure 102. In some embodiments, the thermopile-based example flow sensing device 100 may further include a plurality of downstream sample temperature sensing thermocouples 114 (e.g., two downstream sample temperature sensing thermocouples) disposed downstream of the centerline 104 of the heating structure 102. In some embodiments, the plurality of upstream sample temperature sensing thermocouples 112 and the plurality of downstream sample temperature sensing thermocouples 114 may be disposed on the heating structure 102.

[0052] In some embodiments, each of the plurality of upstream thermocouple junctions 108, the plurality of downstream thermocouple junctions 110, the plurality of upstream sample temperature sensing thermocouple junctions 112, and the plurality of downstream sample temperature sensing thermocouple junctions 114 may include a corresponding interface between a first thermocouple material and a second thermocouple material, as shown in reference to Figure 11 More detailed description.

[0053] In some implementation schemes, such as Figure 1 As shown, an example flow sensing device 100 based on a thermopile may include a substrate defining a membrane structure 116. In some embodiments, a portion of a heating structure 102 may be disposed on the membrane structure 116. In some embodiments, a thermopile 106, a plurality of thermocouples, a plurality of upstream thermocouple junctions 108, a plurality of downstream thermocouple junctions 110, a plurality of upstream sample temperature sensing thermocouple junctions 112, a plurality of downstream sample temperature sensing thermocouple junctions 114, or one or more portions thereof, or combinations thereof, may be disposed on the membrane structure 116. In some embodiments, the membrane structure 116 may provide thermal isolation from a bulk (e.g., silicon) die that may have high thermal conductivity. In some embodiments, the shape of the membrane structure 116 may be rectangular, square, circular, elliptical, or any other suitable shape or combination thereof.

[0054] In other implementation schemes (for brevity, in...), Figure 1 (Not shown in the image), the example flow sensing device 100 based on a thermopile may include a substrate defining a microbridge structure. In some embodiments, a portion of the heating structure 102 may be disposed on the microbridge structure. In some embodiments, a thermopile 106, a plurality of thermocouples, a plurality of upstream thermocouple junctions 108, a plurality of downstream thermocouple junctions 110, a plurality of upstream sample temperature sensing thermocouple junctions 112, a plurality of downstream sample temperature sensing thermocouple junctions 114, one or more portions thereof, or combinations thereof, may be disposed on the microbridge structure.

[0055] Figure 2A Example temperature contour lines 220 (e.g., including, but not limited to, temperature contour line 220A, maximum temperature difference contour line 220B (extending through temperature contour lines near the location where the maximum temperature difference occurs) for an example flow sensing device 200 based on a few example embodiments described herein) are shown.

[0056] In some implementation schemes, such as Figure 2A and Figure 2B As shown, an example thermopile-based flow sensing device 200 can be provided for sensing the flow rate of a fluid 201 (e.g., the flow rate of a gas or liquid). In some embodiments, the thermopile-based example flow sensing device 200 may include a heating structure 202 having a centerline 204 and an axis 205 arranged perpendicular to the centerline 204. In some embodiments, the thermopile-based example flow sensing device 200 may further include a thermopile. In some embodiments, at least a portion of the thermopile may be disposed on the heating structure 202.

[0057] In some implementation schemes, such as Figure 2A and Figure 2B As shown, a thermopile may include multiple thermocouples having multiple thermocouple junctions. In some embodiments, the multiple thermocouples may have multiple upstream thermocouple junctions 208 (e.g., seventeen upstream thermocouple junctions) disposed upstream of the centerline 204 of the heating structure 202. In some embodiments, the multiple thermocouples may have multiple downstream thermocouple junctions 210 (e.g., seventeen downstream thermocouple junctions) disposed downstream of the centerline 204 of the heating structure 202. In some embodiments, the number of upstream thermocouple junctions 208 and the number of downstream thermocouple junctions 210 may be the same. In some embodiments, the number of upstream thermocouple junctions 208 and the number of downstream thermocouple junctions 210 may depend on the Seebeck coefficient of the thermocouple material in the thermocouple and the desired output voltage (e.g., it may be a function of them).

[0058] In some implementation schemes, such as Figure 2A and Figure 2B As shown, each of the plurality of upstream thermocouples 208 and the plurality of downstream thermocouples 210 can be generated along a maximum temperature difference contour line 220B (e.g., a temperature contour line extending through the vicinity of the minimum temperature difference location 222 and the maximum temperature difference location 224), wherein the farthest upstream thermocouple of the plurality of upstream thermocouples 208 occurs near the minimum temperature difference location 222, and wherein the farthest downstream thermocouple of the plurality of downstream thermocouples 210 occurs near the maximum temperature difference location 224. For example, the maximum temperature difference can be defined by the minimum temperature difference location 222 upstream of the centerline 204 and the maximum temperature difference location 224 downstream of the centerline 204. The plurality of upstream thermocouples 208 can be disposed near multiple locations on the maximum temperature difference contour line 220B. In other words, the plurality of upstream thermocouples 208 can be disposed upstream of the centerline 204 near a first plurality of points on the upstream portion of the maximum temperature difference contour line 220B extending through the minimum temperature difference location 222. Multiple downstream thermocouples 210 may be located downstream of the centerline 204 near a second plurality of points on the downstream portion of the maximum temperature difference contour line 220B extending through the maximum temperature difference location 224. In some embodiments, multiple upstream thermocouples 208 and multiple downstream thermocouples 210 may not be located on the heating structure 202.

[0059] Figure 2B An example minimum temperature contour line 223 is shown, set around the minimum temperature difference location 222. Figure 2B An example maximum temperature contour line 225 is further shown around the maximum temperature difference location 224.

[0060] In some implementation schemes, such as Figure 2A and Figure 2BAs shown, the minimum temperature difference location 222 can be located approximately 135 micrometers upstream of the centerline 204. In some embodiments, such as Figure 2A and Figure 2B As shown, the maximum temperature difference location 224 can be located approximately 137 micrometers downstream of the centerline 204. The locations of the minimum temperature difference location 222 and the maximum temperature difference location 224 can vary with changes in the membrane structure 216 (e.g., shape, thickness), the heating structure 202 (e.g., shape, thickness, (multiple) materials), the voltage applied to the heating structure 202, and other structures.

[0061] In some embodiments, each of the plurality of upstream thermocouple junctions 208 and the plurality of downstream thermocouple junctions 210 may include a corresponding interface between a first thermocouple material and a second thermocouple material, as shown in reference 1. Figure 11 A more detailed description.

[0062] In some implementation schemes, such as Figure 2A and Figure 2B As shown, an example flow sensing device 200 based on a thermopile may include a substrate defining a membrane structure 216. In some embodiments, a portion of a heating structure 202 may be disposed on the membrane structure 216. In some embodiments, a thermopile, a plurality of thermocouples, a plurality of upstream thermocouple junctions 208, a plurality of downstream thermocouple junctions 210, one or more portions thereof, or combinations thereof may be disposed on the membrane structure 216. In some embodiments, the membrane structure 216 may provide thermal isolation from a bulk (e.g., silicon) die that may have high thermal conductivity. In some embodiments, the shape of the membrane structure 216 may be rectangular, square, circular, elliptical, or any other suitable shape or combination thereof.

[0063] In other implementation schemes (for brevity, in...), Figure 2A or Figure 2B (Not shown in the image), the example flow sensing device 200 based on a thermopile may include a substrate defining a microbridge structure. In some embodiments, a portion of the heating structure 202 may be disposed on the microbridge structure. In some embodiments, a thermopile, a plurality of thermocouples, a plurality of upstream thermocouple junctions 208, a plurality of downstream thermocouple junctions 210, one or more portions thereof, or combinations thereof may be disposed on the microbridge structure.

[0064] Figure 3An example layout of a thermopile-based example flow sensing device 300 according to some example embodiments described herein is shown. In some embodiments, the thermopile-based example flow sensing device 300 may be provided for sensing the flow rate of fluid 301 (e.g., the flow rate of a gas or liquid). In some embodiments, the thermopile-based example flow sensing device 300 may include a heating structure 302 having a centerline 304. In some embodiments, the thermopile-based example flow sensing device 300 may further include a thermopile 306. In some embodiments, at least a portion of the thermopile 306 may be disposed on the heating structure 302.

[0065] In some embodiments, the thermopile 306 may include a plurality of thermocouples having a plurality of thermocouple junctions. In some embodiments, the plurality of thermocouples may have a plurality of upstream thermocouple junctions 308 (e.g., nineteen upstream thermocouple junctions) disposed upstream of the centerline 304 of the heating structure 302. In some embodiments, the plurality of thermocouples may have a plurality of downstream thermocouple junctions 310 (e.g., nineteen downstream thermocouple junctions) disposed downstream of the centerline 304 of the heating structure 302. In some embodiments, the plurality of upstream thermocouple junctions 308 and the plurality of downstream thermocouple junctions 310 may be disposed on the heating structure 302. In some embodiments, the number of upstream thermocouple junctions 308 and the number of downstream thermocouple junctions 310 may be the same. In some embodiments, the number of upstream thermocouple junctions 308 and the number of downstream thermocouple junctions 310 may depend on the Seebeck coefficient of the thermocouple material in the thermocouples and the desired output voltage (e.g., may be a function of them).

[0066] In some embodiments, the thermopile-based example flow sensing device 300 may further include a plurality of upstream sample temperature sensing thermocouples 312 (e.g., two upstream sample temperature sensing thermocouples) disposed upstream of the centerline 304 of the heating structure 302. In some embodiments, the thermopile-based example flow sensing device 300 may further include a plurality of downstream sample temperature sensing thermocouples 314 (e.g., two downstream sample temperature sensing thermocouples) disposed downstream of the centerline 304 of the heating structure 302. In some embodiments, the plurality of upstream sample temperature sensing thermocouples 312 and the plurality of downstream sample temperature sensing thermocouples 314 may be disposed on the heating structure 302.

[0067] In some embodiments, each of the plurality of upstream thermocouple junctions 308, the plurality of downstream thermocouple junctions 310, the plurality of upstream sample temperature sensing thermocouple junctions 312, and the plurality of downstream sample temperature sensing thermocouple junctions 314 may include a corresponding interface between a first thermocouple material and a second thermocouple material, as shown in reference to Figure 11 More detailed description.

[0068] In some implementation schemes, such as Figure 3 As shown, an example flow sensing device 300 based on a thermopile may include a substrate defining a membrane structure 316. In some embodiments, a portion of a heating structure 302 may be disposed on the membrane structure 316. In some embodiments, a thermopile 306, a plurality of thermocouples, a plurality of upstream thermocouple junctions 308, a plurality of downstream thermocouple junctions 310, a plurality of upstream sample temperature sensing thermocouple junctions 312, a plurality of downstream sample temperature sensing thermocouple junctions 314, or one or more portions thereof, or combinations thereof, may be disposed on the membrane structure 316. In some embodiments, the membrane structure 316 may provide thermal isolation from a bulk (e.g., silicon) die that may have high thermal conductivity. In some embodiments, the shape of the membrane structure 316 may be rectangular, square, circular, elliptical, or any other suitable shape or combination thereof.

[0069] In other implementation schemes (for brevity, in...), Figure 3 (Not shown in the image), the example flow sensing device 300 based on a thermopile may include a substrate defining a microbridge structure. In some embodiments, a portion of the heating structure 302 may be disposed on the microbridge structure. In some embodiments, a thermopile 306, a plurality of thermocouples, a plurality of upstream thermocouple junctions 308, a plurality of downstream thermocouple junctions 310, a plurality of upstream sample temperature sensing thermocouple junctions 312, a plurality of downstream sample temperature sensing thermocouple junctions 314, one or more portions thereof, or combinations thereof, may be disposed on the microbridge structure.

[0070] Figure 1 An example layout of a thermopile-based example flow sensing device 400 according to some example embodiments described herein is shown. In some embodiments, the thermopile-based example flow sensing device 400 may be provided for sensing the flow rate of fluid 401 (e.g., the flow rate of a gas or liquid). In some embodiments, the thermopile-based example flow sensing device 400 may include a heating structure 402 having a centerline 404. In some embodiments, the thermopile-based example flow sensing device 400 may further include a thermopile 406. In some embodiments, at least a portion of the thermopile 406 may be disposed on the heating structure 402.

[0071] In some embodiments, the thermopile 406 may include a plurality of thermocouples having a plurality of thermocouple junctions. In some embodiments, the plurality of thermocouples may have a plurality of upstream thermocouple junctions 408 (e.g., nineteen upstream thermocouple junctions) disposed upstream of the centerline 404 of the heating structure 402. In some embodiments, the plurality of thermocouples may have a plurality of downstream thermocouple junctions 410 (e.g., nineteen downstream thermocouple junctions) disposed downstream of the centerline 404 of the heating structure 402. In some embodiments, the plurality of upstream thermocouple junctions 408 and the plurality of downstream thermocouple junctions 410 may be disposed on the heating structure 402. In some embodiments, the number of upstream thermocouple junctions 408 and the number of downstream thermocouple junctions 410 may be the same. In some embodiments, the number of upstream thermocouple junctions 408 and the number of downstream thermocouple junctions 410 may depend on the Seebeck coefficient of the thermocouple material in the thermocouples and the desired output voltage (e.g., may be a function of them).

[0072] In some embodiments, the thermopile-based example flow sensing device 400 may further include a plurality of upstream sample temperature sensing thermocouples 412 (e.g., two upstream sample temperature sensing thermocouples) disposed upstream of the centerline 404 of the heating structure 402. In some embodiments, the thermopile-based example flow sensing device 400 may further include a plurality of downstream sample temperature sensing thermocouples 414 (e.g., two downstream sample temperature sensing thermocouples) disposed downstream of the centerline 404 of the heating structure 402. In some embodiments, the plurality of upstream sample temperature sensing thermocouples 412 and the plurality of downstream sample temperature sensing thermocouples 414 may be disposed on the heating structure 402.

[0073] In some embodiments, each of the plurality of upstream thermocouple junctions 408, the plurality of downstream thermocouple junctions 410, the plurality of upstream sample temperature sensing thermocouple junctions 412, and the plurality of downstream sample temperature sensing thermocouple junctions 414 may include a corresponding interface between a first thermocouple material and a second thermocouple material, as shown in reference to Figure 11 More detailed description.

[0074] In some implementation schemes, such as Figure 4As shown, an example flow sensing device 400 based on a thermopile may include a substrate defining a membrane structure 416. In some embodiments, a portion of a heating structure 402 may be disposed on the membrane structure 416. In some embodiments, a thermopile 406, a plurality of thermocouples, a plurality of upstream thermocouple junctions 408, a plurality of downstream thermocouple junctions 410, a plurality of upstream sample temperature sensing thermocouple junctions 412, a plurality of downstream sample temperature sensing thermocouple junctions 414, one or more portions thereof, or combinations thereof, may be disposed on the membrane structure 416. In some embodiments, the membrane structure 416 may provide thermal isolation from a bulk (e.g., silicon) die that may have high thermal conductivity. In some embodiments, the shape of the membrane structure 416 may be rectangular, square, circular, elliptical, or any other suitable shape or combination thereof.

[0075] In other implementation schemes (for brevity, in...), Figure 4 (Not shown in the image), the example flow sensing device 400 based on a thermopile may include a substrate defining a microbridge structure. In some embodiments, a portion of the heating structure 402 may be disposed on the microbridge structure. In some embodiments, a thermopile 406, a plurality of thermocouples, a plurality of upstream thermocouple junctions 408, a plurality of downstream thermocouple junctions 410, a plurality of upstream sample temperature sensing thermocouple junctions 412, a plurality of downstream sample temperature sensing thermocouple junctions 414, one or more portions thereof, or combinations thereof, may be disposed on the microbridge structure.

[0076] Figure 5 An example layout of a thermopile-based example flow sensing device 500 according to some example embodiments described herein is shown. In some embodiments, the thermopile-based example flow sensing device 500 may be provided for sensing the flow rate of fluid 501 (e.g., the flow rate of a gas or liquid). In some embodiments, the thermopile-based example flow sensing device 500 may include a heating structure 502 having a centerline 504. In some embodiments, the thermopile-based example flow sensing device 500 may further include a thermopile 506. In some embodiments, at least a portion of the thermopile 506 may be disposed on the heating structure 502.

[0077] In some embodiments, the thermopile 506 may include a plurality of thermocouples having a plurality of thermocouple junctions. In some embodiments, the plurality of thermocouples may have a plurality of upstream thermocouple junctions 508 (e.g., nineteen upstream thermocouple junctions) disposed upstream of the centerline 504 of the heating structure 502. In some embodiments, the plurality of thermocouples may have a plurality of downstream thermocouple junctions 510 (e.g., nineteen downstream thermocouple junctions) disposed downstream of the centerline 504 of the heating structure 502. In some embodiments, the number of upstream thermocouple junctions 508 and the number of downstream thermocouple junctions 510 may be the same. In some embodiments, the number of upstream thermocouple junctions 508 and the number of downstream thermocouple junctions 510 may depend on the Seebeck coefficient of the thermocouple material in the thermocouples and the desired output voltage (e.g., it may be a function of them).

[0078] In some embodiments, each of the plurality of upstream thermocouples 508 and the plurality of downstream thermocouples 510 may be aligned parallel to the centerline 504 and along the path through the location of minimum temperature difference (e.g., Figure 2A and Figure 2B The upstream vertical line near the minimum temperature difference location 222 shown and through the maximum temperature difference location (e.g., Figure 2A and Figure 2B The maximum temperature difference location (224) shown in the diagram appears downstream of a vertical line. For example, the maximum temperature difference can occur from a first location upstream of the centerline 504 (e.g., Figure 2A and Figure 2B The minimum temperature difference at the minimum temperature difference location 222 shown and the second location downstream of the centerline 504 (e.g., Figure 2A and Figure 2B The maximum temperature difference is defined at the maximum temperature difference location 224 shown; a plurality of upstream thermocouples 508 may be disposed upstream of the center line 504 near a first plurality of points on a first line extending through the vicinity of the first location and generally parallel to the center line 504; and a plurality of downstream thermocouples 510 may be disposed downstream of the center line 504 near a second plurality of points on a second line extending through the vicinity of the second location and generally parallel to the center line 504. In some embodiments, the plurality of upstream thermocouples 508 and the plurality of downstream thermocouples 510 may not be disposed on the heating structure 502.

[0079] In some embodiments, the thermopile-based example flow sensing device 500 may further include a plurality of upstream sample temperature sensing thermocouples 512 (e.g., two upstream sample temperature sensing thermocouples) disposed upstream of the centerline 504 of the heating structure 502. In some embodiments, the thermopile-based example flow sensing device 500 may further include a plurality of downstream sample temperature sensing thermocouples 514 (e.g., two downstream sample temperature sensing thermocouples) disposed downstream of the centerline 504 of the heating structure 502. In some embodiments, the plurality of upstream sample temperature sensing thermocouples 512 and the plurality of downstream sample temperature sensing thermocouples 514 may be disposed on the heating structure 502.

[0080] In some embodiments, each of the plurality of upstream thermocouple junctions 508, the plurality of downstream thermocouple junctions 510, the plurality of upstream sample temperature sensing thermocouple junctions 512, and the plurality of downstream sample temperature sensing thermocouple junctions 514 may include a corresponding interface between a first thermocouple material and a second thermocouple material, as shown in reference to Figure 11 More detailed description.

[0081] In some implementation schemes, such as Figure 5 As shown, an example flow sensing device 500 based on a thermopile may include a substrate defining a membrane structure 516. In some embodiments, a portion of a heating structure 502 may be disposed on the membrane structure 516. In some embodiments, a thermopile 506, a plurality of thermocouples, a plurality of upstream thermocouple junctions 508, a plurality of downstream thermocouple junctions 510, a plurality of upstream sample temperature sensing thermocouple junctions 512, a plurality of downstream sample temperature sensing thermocouple junctions 514, one or more portions thereof, or combinations thereof, may be disposed on the membrane structure 516. In some embodiments, the membrane structure 516 may provide thermal isolation from a bulk (e.g., silicon) die that may have high thermal conductivity. In some embodiments, the shape of the membrane structure 516 may be rectangular, square, circular, elliptical, or any other suitable shape or combination thereof.

[0082] In other implementation schemes (for brevity, in...), Figure 5 (Not shown in the image), the example flow sensing device 500 based on a thermopile may include a substrate defining a microbridge structure. In some embodiments, a portion of a heating structure 502 may be disposed on the microbridge structure. In some embodiments, a thermopile 506, a plurality of thermocouples, a plurality of upstream thermocouple junctions 508, a plurality of downstream thermocouple junctions 510, a plurality of upstream sample temperature sensing thermocouple junctions 512, a plurality of downstream sample temperature sensing thermocouple junctions 514, one or more portions thereof, or combinations thereof, may be disposed on the microbridge structure.

[0083] Figure 6An example layout of a thermopile-based example flow sensing device 600 according to some example embodiments described herein is shown. In some embodiments, the thermopile-based example flow sensing device 600 may be provided for sensing the flow rate of fluid 601 (e.g., the flow rate of a gas or liquid). In some embodiments, the thermopile-based example flow sensing device 600 may include a heating structure 602 having a centerline 604. In some embodiments, the thermopile-based example flow sensing device 600 may further include a thermopile 606. In some embodiments, at least a portion of the thermopile 606 may be disposed on the heating structure 602.

[0084] In some embodiments, the thermopile 606 may include a plurality of thermocouples having a plurality of thermocouple junctions. In some embodiments, the plurality of thermocouples may have a plurality of upstream thermocouple junctions 608 (e.g., nineteen upstream thermocouple junctions) disposed upstream of the centerline 604 of the heating structure 602. In some embodiments, the plurality of thermocouples may have a plurality of downstream thermocouple junctions 610 (e.g., nineteen downstream thermocouple junctions) disposed downstream of the centerline 604 of the heating structure 602. In some embodiments, the number of upstream thermocouple junctions 608 and the number of downstream thermocouple junctions 610 may be the same. In some embodiments, the number of upstream thermocouple junctions 608 and the number of downstream thermocouple junctions 610 may depend on the Seebeck coefficient of the thermocouple material in the thermocouples and the desired output voltage (e.g., it may be a function of them).

[0085] In some implementations, each of the plurality of upstream thermocouples 608 and the plurality of downstream thermocouples 610 may be aligned along contour lines of maximum temperature difference (e.g., Figure 2A and Figure 2B The maximum temperature difference contour line 220B shown appears, where the farthest upstream thermocouple among the multiple upstream thermocouples 608 is at the location of minimum temperature difference (e.g., Figure 2A and Figure 2B The minimum temperature difference location (222) is shown, and the furthest downstream thermocouple of the plurality of downstream thermocouples 610 is at the maximum temperature difference location (e.g., Figure 2A and Figure 2B The maximum temperature difference occurs at location 224, as shown. For example, the maximum temperature difference can occur at a first location upstream of centerline 604 (e.g., Figure 2A and Figure 2B The minimum temperature difference at the minimum temperature difference location 222 shown and the second location downstream of the centerline 604 (e.g., Figure 2A and Figure 2B The maximum temperature difference is limited at the maximum temperature difference location 224 shown; and multiple upstream thermocouples 608 can be arranged along the maximum temperature difference contour (e.g., Figure 2A and Figure 2B The multiple upstream thermocouples 608 may be located near multiple points on a first portion (e.g., the upstream portion) of the maximum temperature difference contour line extending through the first location, upstream of the centerline 604; and the multiple downstream thermocouples 610 may be located near multiple points on a second portion (e.g., the downstream portion) of the maximum temperature difference contour line extending through the second location, downstream of the centerline 604. In some embodiments, the multiple upstream thermocouples 608 and the multiple downstream thermocouples 610 may not be located on the heating structure 602.

[0086] In some embodiments, the thermopile-based example flow sensing device 600 may further include a plurality of upstream sample temperature sensing thermocouples 612 (e.g., two upstream sample temperature sensing thermocouples) disposed upstream of the centerline 604 of the heating structure 602. In some embodiments, the thermopile-based example flow sensing device 600 may further include a plurality of downstream sample temperature sensing thermocouples 614 (e.g., two downstream sample temperature sensing thermocouples) disposed downstream of the centerline 604 of the heating structure 602. In some embodiments, the plurality of upstream sample temperature sensing thermocouples 612 and the plurality of downstream sample temperature sensing thermocouples 614 may not be disposed on the heating structure 602.

[0087] In some embodiments, each of the plurality of upstream thermocouple junctions 608, the plurality of downstream thermocouple junctions 610, the plurality of upstream sample temperature sensing thermocouple junctions 612, and the plurality of downstream sample temperature sensing thermocouple junctions 614 may include a corresponding interface between a first thermocouple material and a second thermocouple material, as shown in reference to Figure 11 More detailed description.

[0088] In some implementation schemes, such as Figure 6 As shown, an example flow sensing device 600 based on a thermopile may include a substrate defining a membrane structure 616. In some embodiments, a portion of a heating structure 602 may be disposed on the membrane structure 616. In some embodiments, a thermopile 606, a plurality of thermocouples, a plurality of upstream thermocouple junctions 608, a plurality of downstream thermocouple junctions 610, a plurality of upstream sample temperature sensing thermocouple junctions 612, a plurality of downstream sample temperature sensing thermocouple junctions 614, or one or more portions thereof, or combinations thereof, may be disposed on the membrane structure 616. In some embodiments, the membrane structure 616 may provide thermal isolation from a bulk (e.g., silicon) die that may have high thermal conductivity. In some embodiments, the shape of the membrane structure 616 may be rectangular, square, circular, elliptical, or any other suitable shape or combination thereof.

[0089] In other implementation schemes (for brevity, in...), Figure 6 (Not shown in the image), an example flow sensing device 600 based on a thermopile may include a substrate defining a microbridge structure. In some embodiments, a portion of a heating structure 602 may be disposed on the microbridge structure. In some embodiments, a thermopile 606, a plurality of thermocouples, a plurality of upstream thermocouple junctions 608, a plurality of downstream thermocouple junctions 610, a plurality of upstream sample temperature sensing thermocouple junctions 612, a plurality of downstream sample temperature sensing thermocouple junctions 614, one or more portions thereof, or combinations thereof, may be disposed on the microbridge structure.

[0090] Figure 7 An example layout of a thermopile-based example flow sensing device 700 according to some example embodiments described herein is shown. In some embodiments, the thermopile-based example flow sensing device 700 may be provided for sensing the flow rate of fluid 701 (e.g., the flow rate of a gas or liquid). In some embodiments, the thermopile-based example flow sensing device 700 may include a heating structure 702 having a centerline 704. In some embodiments, the thermopile-based example flow sensing device 700 may further include a first thermopile 706 and a second thermopile 710.

[0091] In some embodiments, the first thermopile 706 may include a plurality of upstream thermocouples having a first plurality of upstream thermocouple junctions 708 (e.g., nineteen upstream thermocouple junctions) disposed upstream of the centerline 704 of the heating structure 702 and a second plurality of upstream thermocouple junctions 709 (e.g., nineteen upstream thermocouple junctions) disposed further upstream of the centerline 704 of the heating structure 702. In some embodiments, the number of the first plurality of upstream thermocouple junctions 708 and the number of the second plurality of upstream thermocouple junctions 709 may be the same. In some embodiments, the number of the first plurality of upstream thermocouple junctions 708 and the number of the second plurality of upstream thermocouple junctions 709 may depend on the Seebeck coefficient of the thermocouple material in the thermocouple and the desired output voltage (e.g., it may be a function of them).

[0092] In some embodiments, the first plurality of upstream thermocouples 708 and the second plurality of upstream thermocouples 709 may not be provided on the heating structure 702. For example, the maximum temperature difference may be caused by a first location located upstream of the centerline 704 (e.g., Figure 2A and Figure 2B The minimum temperature difference at the minimum temperature difference location 222 shown and the second location downstream of the centerline 704 (e.g., Figure 2A and Figure 2BThe maximum temperature difference is defined at the maximum temperature difference location 224 shown; a first plurality of upstream thermocouples 708 may be located upstream of the center line 704 near a first plurality of points on a first line extending through the vicinity of the first location and aligned substantially parallel to the center line 704; and a second plurality of upstream thermocouples 709 may be located further upstream of the center line 704 near a second plurality of points on a second line aligned substantially parallel to the center line 704.

[0093] In some embodiments, the second thermopile 710 may include a plurality of downstream thermocouples having a first plurality of downstream thermocouple junctions 712 (e.g., nineteen downstream thermocouple junctions) disposed downstream of the centerline 704 of the heating structure 702 and a second plurality of downstream thermocouple junctions 713 (e.g., nineteen downstream thermocouple junctions) disposed further downstream of the centerline 704 of the heating structure 702. In some embodiments, the number of the first plurality of downstream thermocouple junctions 712 and the number of the second plurality of downstream thermocouple junctions 713 may be the same. In some embodiments, the number of the first plurality of downstream thermocouple junctions 712 and the number of the second plurality of downstream thermocouple junctions 713 may depend on the Seebeck coefficient of the thermocouple material in the thermocouple and the desired output voltage (e.g., it may be a function of them).

[0094] In some embodiments, each of the first plurality of upstream thermocouples 708 and the first plurality of downstream thermocouples 712 may be aligned parallel to the centerline 704 and along the path through the location of minimum temperature difference (e.g., Figure 2A and Figure 2B The vertical line upstream of the minimum temperature difference location (222) and through the maximum temperature difference location (e.g., Figure 2A and Figure 2B A vertical line appears downstream of the location of the maximum temperature difference (224). For example, the maximum temperature difference can occur from a first location upstream of the centerline 704 (e.g., Figure 2A and Figure 2B The minimum temperature difference at the minimum temperature difference location 222 shown and the second location downstream of the centerline 704 (e.g., Figure 2A and Figure 2B The maximum temperature difference is defined at the maximum temperature difference location 224 shown; a plurality of first downstream thermocouples 712 may be disposed near a third plurality of points on a third line extending through the second location and aligned substantially parallel to the center line 704 downstream of the center line 704; and a plurality of second downstream thermocouples may be disposed near a fourth plurality of points on a fourth line aligned substantially parallel to the center line 704 further downstream of the center line 704. In some embodiments, the first plurality of downstream thermocouples 712 and the second plurality of downstream thermocouples may not be disposed on the heating structure 702.

[0095] In some embodiments, each of the first plurality of upstream thermocouple junctions 708, the second plurality of upstream thermocouple junctions 709, the first plurality of downstream thermocouple junctions 712, the second plurality of downstream thermocouple junctions 713, the plurality of upstream sample temperature sensing thermocouple junctions, and the plurality of downstream sample temperature sensing thermocouple junctions may include a corresponding interface between a first thermocouple material and a second thermocouple material, as shown in reference to Figure 11 More detailed description.

[0096] In some implementation schemes, such as Figure 7 As shown, an example flow sensing device 700 based on a thermopile may include a substrate defining a membrane structure 716. In some embodiments, a portion of a heating structure 602 may be disposed on the membrane structure 616. In some embodiments, a first thermopile 706, a plurality of upstream thermocouples, a first plurality of upstream thermocouple junctions 708, a second plurality of upstream thermocouple junctions 709, a second thermopile 710, a plurality of downstream thermocouples, a first plurality of downstream thermocouple junctions 712, a second plurality of downstream thermocouple junctions 713, a plurality of upstream sample temperature sensing thermocouple junctions, a plurality of downstream sample temperature sensing thermocouple junctions, one or more portions thereof, or combinations thereof may be disposed on the membrane structure 716. For example, as Figure 7 As shown, a portion of the first thermopile 706 can be disposed on the membrane structure 716, such that the first plurality of upstream thermocouples 708 can be disposed on the membrane structure 716, while the second plurality of upstream thermocouples 709 may not be disposed on the membrane structure 716. In another example, as... Figure 7 As shown, a portion of the second thermopile 710 may be disposed on the membrane structure 716, such that the first plurality of downstream thermocouples 712 may be disposed on the membrane structure 716, while the second plurality of downstream thermocouples 713 may not be disposed on the membrane structure 716. In some embodiments, the membrane structure 716 may provide thermal isolation from a bulk (e.g., silicon) die that may have high thermal conductivity. In some embodiments, the shape of the membrane structure 716 may be rectangular, square, circular, elliptical, or any other suitable shape or combination thereof.

[0097] Figure 8 An example layout of a thermopile-based example flow sensing device 800 according to some example embodiments described herein is shown. In some embodiments, the thermopile-based example flow sensing device 800 may be provided for sensing the flow rate of fluid 801 (e.g., the flow rate of a gas or liquid). In some embodiments, the thermopile-based example flow sensing device 800 may include a heating structure 802 having a centerline 804 and an axis 805 arranged perpendicular to the centerline 804. In some embodiments, the thermopile-based example flow sensing device 800 may further include a first thermopile 806 and a second thermopile 826.

[0098] In some embodiments, the first thermopile 806 may include a plurality of upstream thermocouples disposed upstream of the centerline 804 of the heating structure 802. In some embodiments, the plurality of upstream thermocouples may include a first subset of a plurality of upstream thermocouples aligned generally parallel to the centerline 804 of the heating structure 802, such as a first plurality of upstream parallel thermocouples 808 having a first plurality of upstream thermocouple junctions 810 (e.g., six thermocouple junctions) and a second plurality of upstream thermocouple junctions 812 (e.g., seven thermocouple junctions). In some embodiments, the plurality of upstream thermocouples may further include a second subset of a plurality of upstream thermocouples aligned generally perpendicular to the centerline 804 of the heating structure 802, such as a plurality of upstream vertical thermocouples 814 having a third plurality of upstream thermocouple junctions 816 (e.g., eleven thermocouple junctions) and a fourth plurality of upstream thermocouple junctions 818 (e.g., twelve thermocouple junctions). In some embodiments, the plurality of upstream thermocouples may include a third subset of a plurality of upstream thermocouples aligned generally parallel to the centerline 804 of the heating structure 802, such as a second plurality of upstream parallel thermocouples 820 having a fifth plurality of upstream thermocouple junctions 822 (e.g., six thermocouple junctions) and a sixth plurality of upstream thermocouple junctions 824 (e.g., six thermocouple junctions). In some embodiments, the first thermopile 806 may not be disposed on the heating structure 802. In some embodiments, the number of the first plurality of upstream thermocouple junctions 810, the second plurality of upstream thermocouple junctions 812, the third plurality of upstream thermocouple junctions 816, the fourth plurality of upstream thermocouple junctions 818, the fifth plurality of upstream thermocouple junctions 822, and the sixth plurality of upstream thermocouple junctions 824 may depend on the Seebeck coefficient of the thermocouple material in the thermocouples and the desired output voltage (e.g., it may be a function of them).

[0099] In some embodiments, the second thermopile 826 may include a plurality of downstream thermocouples disposed downstream of the centerline 804 of the heating structure 802. In some embodiments, the plurality of downstream thermocouples may include a first subset of a plurality of downstream thermocouples aligned generally parallel to the centerline 804 of the heating structure 802, such as a first plurality of downstream parallel thermocouples 828 having a first plurality of downstream thermocouple junctions 830 (e.g., six thermocouple junctions) and a second plurality of downstream thermocouple junctions 832 (e.g., seven thermocouple junctions). In some embodiments, the plurality of downstream thermocouples may further include a second subset of a plurality of downstream thermocouples aligned generally perpendicular to the centerline 804 of the heating structure 802, such as a plurality of downstream vertical thermocouples 834 having a third plurality of downstream thermocouple junctions 836 (e.g., eleven thermocouple junctions) and a fourth set of a plurality of downstream thermocouple junctions 838 (e.g., twelve thermocouple junctions). In some embodiments, the plurality of downstream thermocouples may include a third subset of a plurality of downstream thermocouples aligned generally parallel to the centerline 804 of the heating structure 802, such as a second plurality of downstream parallel thermocouples 840 having a fifth plurality of downstream thermocouple junctions 842 (e.g., six thermocouple junctions) and a sixth plurality of downstream thermocouple junctions 844 (e.g., six thermocouple junctions). In some embodiments, the second thermopile 826 may not be disposed on the heating structure 802. In some embodiments, the number of the first plurality of downstream thermocouple junctions 830, the second plurality of downstream thermocouple junctions 832, the third plurality of downstream thermocouple junctions 836, the fourth plurality of downstream thermocouple junctions 838, the fifth plurality of downstream thermocouple junctions 842, and the sixth plurality of downstream thermocouple junctions 844 may depend on the Seebeck coefficient of the thermocouple material in the thermocouples and the desired output voltage (e.g., it may be a function of them).

[0100] In some implementations, each of the second plurality of upstream thermocouples 812, the fourth plurality of upstream thermocouples 818, the sixth plurality of upstream thermocouples 824, the second plurality of downstream thermocouples 832, the fourth plurality of downstream thermocouples 838, and the sixth plurality of downstream thermocouples 844 may be disposed above a bulk substrate (e.g., bulk silicon) and may be at the same temperature, and thus may be used as a reference for measurement.

[0101] In some embodiments, each of the first plurality of upstream thermocouple junctions 810, the second plurality of upstream thermocouple junctions 812, the third plurality of upstream thermocouple junctions 816, the fourth plurality of upstream thermocouple junctions 818, the fifth plurality of upstream thermocouple junctions 822, the sixth plurality of upstream thermocouple junctions 824, the first plurality of downstream thermocouple junctions 830, the second plurality of downstream thermocouple junctions 832, the third plurality of downstream thermocouple junctions 836, the fourth plurality of downstream thermocouple junctions 838, the fifth plurality of downstream thermocouple junctions 842, and the sixth plurality of downstream thermocouple junctions 844 may include a corresponding interface between the first thermocouple material and the second thermocouple material, as shown in reference to Figure 11 A more detailed description.

[0102] In some implementation schemes, such as Figure 8 As shown, an example flow sensing device 800 based on a thermopile may include a substrate defining a membrane structure 816. In some embodiments, a portion of a heating structure 802 may be disposed on the membrane structure 856. In some embodiments, a plurality of upstream thermocouples, a first subset of a plurality of upstream thermocouples, a first plurality of upstream parallel thermocouples 808, a first plurality of upstream thermocouple junctions 810, a second plurality of upstream thermocouple junctions 812, a second subset of a plurality of upstream thermocouples, a plurality of upstream vertical thermocouples 814, a third plurality of upstream thermocouple junctions 816, a fourth plurality of upstream thermocouple junctions 818, a third subset of a plurality of upstream thermocouples, a second plurality of upstream parallel thermocouples 820, a fifth plurality of upstream thermocouple junctions 822, a sixth plurality of upstream thermocouple junctions 824, a second thermopile 826, and a plurality of downstream... Thermocouples, a first subset of multiple downstream thermocouples, a first plurality of downstream parallel thermocouples 828, a first plurality of downstream thermocouple junctions 830, a second plurality of downstream thermocouple junctions 832, a second subset of multiple downstream thermocouples, downstream vertical thermocouples 834, a third plurality of downstream thermocouple junctions 836, a fourth plurality of downstream thermocouple junctions 838, a third subset of multiple downstream thermocouples, a second plurality of downstream parallel thermocouples 840, a fifth plurality of downstream thermocouple junctions 842, a sixth plurality of downstream thermocouple junctions 844, and one or more portions thereof, or combinations thereof, may be disposed on the membrane structure 856. For example, as... Figure 8 As shown, a portion of the first thermopile 806 can be disposed on the membrane structure 856, such that: a first plurality of upstream thermocouples 810 can be disposed on the membrane structure 856, while a second plurality of upstream thermocouples 812 may not be disposed on the membrane structure 856; a third plurality of upstream thermocouples 816 can be disposed on the membrane structure 856, while a fourth plurality of upstream thermocouples 818 may not be disposed on the membrane structure 856; and a fifth plurality of upstream thermocouples 822 can be disposed on the membrane structure 856, while a sixth plurality of upstream thermocouples 824 may not be disposed on the membrane structure 856. In another example, as... Figure 8As shown, a portion of the second thermopile 826 may be disposed on the membrane structure 856 such that: a first plurality of downstream thermocouples 830 may be disposed on the membrane structure 856, and a second plurality of downstream thermocouples 832 may not be disposed on the membrane structure 856; a third plurality of downstream thermocouples 836 may be disposed on the membrane structure 856, while a fourth plurality of downstream thermocouples 838 may not be disposed on the membrane structure 856; and a fifth plurality of downstream thermocouples 842 may be disposed on the membrane structure 856, while a sixth plurality of downstream thermocouples 844 may not be disposed on the membrane structure 856. In some embodiments, the membrane structure 856 may provide thermal isolation from a bulk (e.g., silicon) die that may have high thermal conductivity. In some embodiments, the shape of the membrane structure 856 may be rectangular, square, circular, elliptical, or any other suitable shape or combination thereof.

[0103] Figure 9A , Figure 9B , Figure 9C , Figure 9D , Figure 9E , Figure 9F , Figure 9G , Figure 9H , Figure 9I , Figure 9J , Figure 9K , Figure 9L , Figure 9M , Figure 9N , Figure 9O , Figure 9P , Figure 9Q , Figure 9R , Figure 9S and Figure 9T An example process flow is shown for manufacturing an example flow sensing device based on a thermopile according to some example embodiments described herein.

[0104] like Figure 9A As shown, at step 900, the process flow may begin by fabricating a silicon dioxide (SiO2) layer 932A on the top surface of a substrate 930 (e.g., a silicon die or wafer) and a silicon dioxide layer 932B on the bottom surface of the substrate 930 (e.g., by thermal oxidation).

[0105] like Figure 9B As shown, at step 902, the process flow can continue to fabricate (e.g., by deposition, such as by sputtering) a silicon nitride layer 936 (e.g., Si3N4) on the top surface of the silicon dioxide layer 932A.

[0106] like Figure 9CAs shown, at step 904, the process flow can continue to fabricate (e.g., by deposition and patterning) a heater layer (e.g., TaN / NiFe / TaN) defining the heating structure 938 on the top surface of the silicon nitride layer 936.

[0107] Figure 9D An example layout of a thermopile-based example flow sensing device 905 manufactured at step 904 is shown. In some embodiments, the thermopile-based example flow sensing device 905 may be provided for sensing the flow rate of fluid 942 (e.g., the flow rate of a gas or liquid). In some embodiments, the thermopile-based example flow sensing device 905 may include a heating structure 938 having a centerline 940.

[0108] like Figure 9E As shown, at step 906, the process flow can continue to fabricate (e.g., by deposition, such as by sputtering) a silicon nitride layer 944A (e.g., Si3N4) on the top surface of the silicon nitride layer 936 and the heater layer defining the heating structure 938.

[0109] like Figure 9F As shown, at step 908, the process flow can continue to fabricate (e.g., by deposition and patterning) a first thermocouple material layer 946 (e.g., 60:40NiFe, 80:20NiFe) on the top surface of the silicon nitride layer 944A.

[0110] Figure 9G An example layout of an example flow sensing device 909 based on a thermopile, manufactured at step 908, is shown.

[0111] like Figure 9H As shown, at step 910, the process flow can continue to fabricate (e.g., by deposition, such as by sputtering and patterning) a silicon nitride layer 944B (e.g., Si3N4) on the top surface of the silicon nitride layer 944A and the first thermocouple material layer 946, and to open contact vias in the silicon nitride layer 944B to provide access to the top surface of the first thermocouple material layer 946.

[0112] Figure 9I An example layout of an example flow sensing device 911 based on a thermopile, manufactured at step 910, is shown.

[0113] like Figure 9J As shown, at step 908, the process flow can continue to fabricate (e.g., by deposition and patterning) a second thermocouple material layer 948 (e.g., Cr) on the top surface of the first thermocouple material layer 946 by contacting a window that opens in the silicon nitride layer 944B.

[0114] Figure 9KAn example layout of a thermopile-based example flow sensing device 913 manufactured at step 912 is shown. In some embodiments, the thermopile-based example flow sensing device 913 may be provided for sensing the flow rate of fluid 942 (e.g., the flow rate of a gas or liquid). In some embodiments, the thermopile-based example flow sensing device 913 may include a heating structure 938 having a centerline 940. In some embodiments, the thermopile-based example flow sensing device 913 may further include a thermopile 950. In some embodiments, at least a portion of the thermopile 950 may be disposed on the heating structure 938.

[0115] In some embodiments, the thermopile 950 may include a plurality of thermocouples having a plurality of thermocouple junctions. In some embodiments, the plurality of thermocouples may have a plurality of upstream thermocouple junctions 952 (e.g., nineteen upstream thermocouple junctions) disposed upstream of the centerline 940 of the heating structure 938. In some embodiments, the plurality of thermocouples may have a plurality of downstream thermocouple junctions 954 (e.g., nineteen downstream thermocouple junctions) disposed downstream of the centerline 940 of the heating structure 938. In some embodiments, the number of upstream thermocouple junctions 952 and the number of downstream thermocouple junctions 954 may be the same. In some embodiments, the number of upstream thermocouple junctions 952 and the number of downstream thermocouple junctions 954 may depend on (e.g., may be) the Seebeck coefficient of the first thermocouple material layer 946, the Seebeck coefficient of the second thermocouple material layer 948, and the desired output voltage (e.g., may be a function of them).

[0116] In some embodiments, each of the plurality of upstream thermocouples 952 and the plurality of downstream thermocouples 954 may be aligned parallel to the centerline 940 and along the path through the location of minimum temperature difference (e.g., Figure 2A and Figure 2B The upstream vertical line near the minimum temperature difference location 222 shown and through the maximum temperature difference location (e.g., Figure 2A and Figure 2B The maximum temperature difference location (224) shown in the diagram appears downstream of a vertical line. For example, the maximum temperature difference can occur from a first location upstream of the centerline 940 (e.g., Figure 2A and Figure 2B The minimum temperature difference at the minimum temperature difference location 222 shown and the second location downstream of the centerline 940 (e.g., Figure 2A and Figure 2BThe maximum temperature difference is defined at the maximum temperature difference location 224 shown; a plurality of upstream thermocouples 952 may be disposed upstream of the centerline 940 near a first plurality of points on a first line extending through the vicinity of the first location and generally parallel to the centerline 940; and a plurality of downstream thermocouples 945 may be disposed downstream of the centerline 940 near a second plurality of points on a second line extending through the vicinity of the second location and generally parallel to the centerline 940. In some embodiments, the plurality of upstream thermocouples 952 and the plurality of downstream thermocouples 954 may not be disposed on the heating structure 938.

[0117] In some embodiments, the thermopile-based example flow sensing device 913 may further include a plurality of upstream sample temperature sensing thermocouples 956 (e.g., two upstream sample temperature sensing thermocouples) disposed upstream of the centerline 940 of the heating structure 938. In some embodiments, the thermopile-based example flow sensing device 913 may further include a plurality of downstream sample temperature sensing thermocouples 958 (e.g., two downstream sample temperature sensing thermocouples) disposed downstream of the centerline 940 of the heating structure 938. In some embodiments, the plurality of upstream sample temperature sensing thermocouples 956 and the plurality of downstream sample temperature sensing thermocouples 958 may not be disposed on the heating structure 938.

[0118] In some embodiments, each of the plurality of upstream thermocouple junctions 952, the plurality of downstream thermocouple junctions 954, the plurality of upstream sample temperature sensing thermocouple junctions 956, and the plurality of downstream sample temperature sensing thermocouple junctions 958 may include a corresponding interface between a first thermocouple material and a second thermocouple material, as shown in reference to Figure 9J and Figure 11 More detailed description.

[0119] like Figure 9L As shown, at step 914, the process flow can continue to fabricate (e.g., by deposition, such as by sputtering and patterning) a silicon nitride layer 944C (e.g., Si3N4) on the top surface of the silicon nitride layer 944B and the second thermocouple material layer 948, and to open contact vias in the silicon nitride layer 944C to provide access to the top surface of the second thermocouple material layer 948.

[0120] Figure 9M An example layout of an example flow sensing device 915 based on a thermopile, manufactured at step 914, is shown.

[0121] like Figure 9NAs shown, at step 916, the process flow can continue to fabricate (e.g., by deposition and patterning) an electrical contact layer 960 (e.g., TiW / Al, TiW / 2%Al-Cu) on the top surface of the second thermocouple material layer 948 through contact vias that open in the silicon nitride layer 944C.

[0122] Figure 9O An example layout of an example flow sensing device 917 based on a thermopile, manufactured at step 916, is shown.

[0123] like Figure 9P As shown, at step 918, the process flow can continue to fabricate (e.g., by plasma-enhanced chemical vapor deposition (PECVD)) a silicon nitride overlay 962 (e.g., Si) on the top surface of the silicon nitride layer 944C and the electrical contact layer 960. x N y -H) and openings in the contact vias in the silicon nitride outer layer 962 to provide access to the top surface of the electrical contact layer 960.

[0124] Figure 9Q An example layout of an example flow sensing device 919 based on a thermopile, manufactured at step 918, is shown.

[0125] like Figure 9R As shown, at step 920, the process flow can continue to fabricate the film structure by forming (e.g., via DRIE) a cavity 964 that passes through the silicon dioxide layer 932B and the substrate 930 until the bottom surface of the silicon dioxide layer 932A is reached. At step 920, the process flow may include forming (e.g., via DRIE) one or more side cavities 966 that pass through a portion (e.g., through 70% of the thickness of the substrate 930) of the silicon dioxide layer 932B and the substrate 930.

[0126] Figure 9S An example layout of an example thermopile-based flow sensing device 921 fabricated at step 920 is shown. In some embodiments, the thermopile-based example flow sensing device 921 may include a substrate defining a membrane structure 968. In some embodiments, a portion of a heating structure 938 may be disposed on the membrane structure 968. In some embodiments, a thermopile 950, a plurality of thermocouples, a plurality of upstream thermocouple junctions 952, a plurality of downstream thermocouple junctions 954, a plurality of upstream sample temperature sensing thermocouple junctions 956, a plurality of downstream sample temperature sensing thermocouple junctions 958, one or more portions thereof, or combinations thereof, may be disposed on the membrane structure 968. In some embodiments, the membrane structure 968 may provide thermal isolation from a substrate 930, which may have high thermal conductivity. In some embodiments, the shape of the membrane structure 968 may be rectangular, square, circular, elliptical, or any other suitable shape or combination thereof.

[0127] In other embodiments (not shown in FIG. 9 for simplicity), the example flow sensing device 921 based on a thermopile may include a substrate defining a microbridge structure. In some embodiments, a portion of a heating structure 938 may be disposed on the microbridge structure. In some embodiments, a thermopile 950, a plurality of thermocouples, a plurality of upstream thermocouple junctions 952, a plurality of downstream thermocouple junctions 954, a plurality of upstream sample temperature sensing thermocouple junctions 956, a plurality of downstream sample temperature sensing thermocouple junctions 958, one or more portions thereof, or combinations thereof, may be disposed on the microbridge structure.

[0128] Figure 9T References are shown Figure 9A , Figure 9B , Figure 9C , Figure 9E , Figure 9F , Figure 9H , Figure 9J , Figure 9L , Figure 9N , Figure 9P and Figure 9R Legends describing the various example layers.

[0129] Figure 10 An example layout of a thermopile-based example flow sensing device 1000 according to some example embodiments described herein is shown. In some embodiments, the thermopile-based example flow sensing device 1000 may be provided for sensing the flow rate of fluid 1001 (e.g., the flow rate of a gas or liquid). In some embodiments, the thermopile-based example flow sensing device 1000 may include a heating structure 1002 having a centerline 1004. In some embodiments, the thermopile-based example flow sensing device 1000 may further include a thermopile 1006. In some embodiments, at least a portion of the thermopile 1006 may be disposed on the heating structure 1002.

[0130] In some embodiments, the thermopile 1006 may include a plurality of thermocouples having a plurality of thermocouple junctions. In some embodiments, the plurality of thermocouples may have a plurality of upstream thermocouple junctions 1008 (e.g., nineteen upstream thermocouple junctions) disposed upstream of the centerline 1004 of the heating structure 1002. In some embodiments, the plurality of thermocouples may have a plurality of downstream thermocouple junctions 1010 (e.g., nineteen downstream thermocouple junctions) disposed downstream of the centerline 1004 of the heating structure 1002. In some embodiments, the plurality of upstream thermocouple junctions 1008 and the plurality of downstream thermocouple junctions 1010 may not be disposed on the heating structure 1002. In some embodiments, the number of upstream thermocouple junctions 1008 and the number of downstream thermocouple junctions 1010 may be the same. In some embodiments, the number of upstream thermocouple junctions 1008 and the number of downstream thermocouple junctions 1010 may depend on the Seebeck coefficient of the thermocouple material in the thermocouples and the desired output voltage (e.g., it may be a function of them).

[0131] In some embodiments, the thermopile-based flow sensing device 1000 may further include a plurality of upstream sample temperature sensing thermocouples 1012 (e.g., two upstream sample temperature sensing thermocouples) disposed upstream of the centerline 1004 of the heating structure 1002. In some embodiments, the thermopile-based flow sensing device 1000 may further include a plurality of downstream sample temperature sensing thermocouples 1014 (e.g., two downstream sample temperature sensing thermocouples) disposed downstream of the centerline 1004 of the heating structure 1002. In some embodiments, the plurality of upstream sample temperature sensing thermocouples 1012 and the plurality of downstream sample temperature sensing thermocouples 1014 may not be disposed on the heating structure 1002.

[0132] In some embodiments, each of the plurality of upstream thermocouple junctions 1008, the plurality of downstream thermocouple junctions 1010, the plurality of upstream sample temperature sensing thermocouple junctions 1012, and the plurality of downstream sample temperature sensing thermocouple junctions 1014 may include a corresponding interface between a first thermocouple material and a second thermocouple material, as shown in reference to Figure 11 More detailed description.

[0133] In some implementation schemes, such as Figure 10As shown, an example flow sensing device 1000 based on a thermopile may include a substrate defining a membrane structure 1016. In some embodiments, a portion of a heating structure 1002 may be disposed on the membrane structure 1016. In some embodiments, a thermopile 1006, a plurality of thermocouples, a plurality of upstream thermocouple junctions 1008, a plurality of downstream thermocouple junctions 1010, a plurality of upstream sample temperature sensing thermocouple junctions 1012, a plurality of downstream sample temperature sensing thermocouple junctions 1014, one or more portions thereof, or combinations thereof, may be disposed on the membrane structure 1016. In some embodiments, the membrane structure 1016 may provide thermal isolation from a bulk (e.g., silicon) die that may have high thermal conductivity. In some embodiments, the shape of the membrane structure 1016 may be rectangular, square, circular, elliptical, or any other suitable shape or combination thereof.

[0134] In other implementation schemes (for brevity, in...), Figure 10 (Not shown in the image), the example flow sensing device 1000 based on a thermopile may include a substrate defining a microbridge structure. In some embodiments, a portion of the heating structure 1002 may be disposed on the microbridge structure. In some embodiments, a thermopile 1006, a plurality of thermocouples, a plurality of upstream thermocouple junctions 1008, a plurality of downstream thermocouple junctions 1010, a plurality of upstream sample temperature sensing thermocouple junctions 1012, a plurality of downstream sample temperature sensing thermocouple junctions 1014, one or more portions thereof, or combinations thereof, may be disposed on the microbridge structure.

[0135] Figure 11 Example Table 1100 illustrates thermocouple materials for an example thermopile-based flow sensing device according to some example embodiments described herein. For example, the thermocouple materials shown in Example Table 1100 can be used to provide a thermocouple junction including an interface between a first thermocouple material and a second thermocouple material. In some embodiments, the number of thermocouple junctions in the thermopile of the example thermopile-based flow sensing device disclosed herein can depend on the Seebeck coefficients of the thermocouple materials in the thermocouples and the desired output voltage (e.g., it can be a function of them). The term "dS" refers to the difference between the Seebeck coefficients of the thermocouple materials in the thermocouples.

[0136] In some embodiments, the first thermocouple material may include polycrystalline silicon, and the second thermocouple material may include aluminum. In some embodiments, the first and second thermocouple materials may include polycrystalline silicon with different doping (e.g., n-type and p-type polycrystalline silicon). For example, the first thermocouple material may include n-type polycrystalline silicon (nPoly Si), and the second thermocouple material may include p-type polycrystalline silicon (pPoly Si). In another example, the first thermocouple material may include p-type polycrystalline silicon (pPoly Si), and the second thermocouple material may include n-type polycrystalline silicon (nPoly Si).

[0137] In some embodiments, the first thermocouple material may include a nickel-iron alloy (e.g., 60:40NiFe, 80:20NiFe), and the second thermocouple material may include chromium (Cr), wherein dS is about 65 μV / C for 60:40NiFe and Cr or about 53 μV / C for 80:20NiFe and Cr. In some embodiments, the first thermocouple material may include a nickel-iron alloy (e.g., 60:40NiFe, 80:20NiFe), and the second thermocouple material may include chromium disilicide (CrSi2), wherein dS is about 105 μV / C for 60:40NiFe and CrSi2 or about 93 μV / C for 80:20NiFe and CrSi2. In some embodiments, the first thermocouple material may include a nickel-iron alloy (e.g., 60:40NiFe, 80:20NiFe), and the second thermocouple material may include rhenium disilicide (ReSi2).

[0138] In some embodiments, the first thermocouple material may include chromium nitride (e.g., CrN), and the second thermocouple material may include copper (Cu), wherein the dS is about 146 μV / C for CrN and Cu. In some embodiments, the first thermocouple material may include chromium nitride (e.g., CrN), and the second thermocouple material may include aluminum (Al), wherein the dS is about 138 μV / C for CrN and Al. In some embodiments, the first thermocouple material may include chromium nitride (e.g., CrN), and the second thermocouple material may include p-type polycrystalline silicon (pPoly Si), wherein the dS is about 270 μV / C for CrN and pPoly Si.

[0139] In some embodiments, the first thermocouple material may include copper (Cu), and the second thermocouple material may include a copper-nickel alloy (e.g., constantan).

[0140] In some implementations, the thermopile-based flow sensing devices disclosed herein may include any combination of the components, structures, and features discussed with reference to the example thermopile-based flow sensing devices 100, 200, 300, 400, 500, 600, 700, and 800, as well as any of the example thermopile-based flow sensing devices described with reference to FIG9 (e.g., example thermopile-based flow sensing devices 913, 915, 917, 919, and 921) (including the addition or omission of components, structures, and features).

[0141] Specific components of the example device involved in this disclosure have already been described, and will be discussed below in conjunction with... Figure 12 and Figure 13 This describes an example process for providing a thermopile-based flow sensing device.

[0142] Figure 12 Example flowchart 1200 is shown, which includes example operation of a device (e.g., device 100, 200, 300, 400, 500, 600, 913, 915, 917, 919, 921, 1000) for manufacturing or otherwise providing a means for sensing fluid flow according to some example embodiments described herein.

[0143] As shown in operation 1202, example flowchart 1200 can be started by providing heating structures (e.g., heating structures 102, 202, 302, 402, 502, 602, 938, 1002) with centerlines (e.g., centerlines 104, 204, 304, 404, 504, 604, 940, 1004).

[0144] As shown in operation 1204, example flowchart 1200 can proceed to arrange at least a portion of a thermopile (e.g., thermopile 106, 206, 306, 406, 506, 606, 950, 1006) on the heating structure. The thermopile may include a first thermocouple having a first thermocouple junction (e.g., one of one or more upstream thermocouple junctions 108, 308, 408, 508, 608, 952, 1008) disposed upstream of the centerline of the heating structure. The thermopile may further include a second thermocouple having a second thermocouple junction (e.g., one of one or more downstream thermocouple junctions 110, 310, 410, 510, 610, 954, 1010) disposed downstream of the centerline of the heating structure. In some implementations, the number of upstream and downstream thermocouple junctions in the thermopile can depend on the Seebeck coefficient of the thermocouple material and the desired output voltage (e.g., it can be a function of them).

[0145] In some implementations, operations 1202 and 1204 may not necessarily be performed using... Figure 12 The sequence described in the text occurs. In some implementations, Figure 12 One or more of the operations described herein can occur substantially simultaneously. In some implementations, in Figure 12 One or more additional operations may be involved before, after, or in between any of the operations shown.

[0146] Figure 13 An exemplary flowchart 1300 is shown, which includes exemplary operation of a device (e.g., device 700, 800) for manufacturing or otherwise providing a means for sensing fluid flow according to some exemplary embodiments described herein.

[0147] As shown in operation 1302, example flowchart 1300 can begin by providing a heating structure (e.g., heating structure 702, 802) with a centerline (e.g., centerline 704, 804).

[0148] As shown in operation 1304, example flowchart 1300 can proceed to position a first thermopile (e.g., thermopile 706, 806) upstream of the centerline of the heating structure. The first thermopile may include a first plurality of thermocouples positioned upstream of the centerline of the heating structure. In some embodiments, the first plurality of thermocouples may include a first subset of the first plurality of thermocouples aligned generally parallel to the centerline of the heating structure (e.g., upstream parallel thermocouples 808, 820). In some embodiments, the first plurality of thermocouples may further include a second subset of the first plurality of thermocouples aligned generally perpendicular to the centerline of the heating structure (e.g., upstream vertical thermocouple 814). In some cases, the first thermopile may be positioned above the heating structure, such as in a layer above but not on the heating structure.

[0149] As shown in operation 1306, example flowchart 1300 can proceed to position a second thermopile (e.g., thermopile 710, 826) downstream of the centerline of the heating structure. The second thermopile may include a second plurality of thermocouples positioned downstream of the centerline of the heating structure. In some embodiments, the second plurality of thermocouples may include a third subset (e.g., downstream parallel thermocouples 828, 840) of a second plurality of thermocouples aligned generally parallel to the centerline of the heating structure. In some embodiments, the second plurality of thermocouples may further include a fourth subset (e.g., downstream vertical thermocouple 834) of a second plurality of thermocouples aligned generally perpendicular to the centerline of the heating structure. In some cases, the second thermopile may be positioned above the heating structure, such as in a layer above but not on the heating structure.

[0150] In some implementations, operations 1302, 1304, and 1306 may not necessarily be performed using... Figure 13 The sequence described in the text occurs. In some implementations, Figure 13 One or more of the operations described herein can occur substantially simultaneously. In some implementations, in Figure 13 One or more additional operations may be involved before, after, or in between any of the operations shown.

[0151] therefore, Figure 12 and Figure 13 Example flowcharts describing operations performed according to exemplary embodiments of the present disclosure are shown. It should be understood that each block of the flowchart, and combinations of blocks in the flowchart, can be implemented by various means, such as devices including hardware, firmware, one or more processors, and / or circuitry associated with the execution of software including one or more computer program instructions. In some embodiments, one or more of the above-described processes can be performed by executing program code instructions. For example, one or more of the above-described processes can be executed by a material handling apparatus (e.g., a robotic arm, servo motor, motion controller, etc.) and computer program instructions residing on a non-transitory computer-readable storage memory. In this regard, program code instructions that, when executed, cause the execution of the above-described processes can be stored by a non-transitory computer-readable storage medium (e.g., memory) of a computing device and executed by a processor of the computing device. In this respect, computer program instructions embodying the above-described processes can be stored by the memory of a device employing embodiments of the present disclosure and executed by a processor of the device. It is understood that any such computer program instructions can be loaded onto a computer or other programmable device (e.g., hardware) to produce a machine such that the resulting computer or other programmable device provides an implementation of the functions specified in flowcharts 1200 and 1300. When executed, the instructions stored in a computer-readable storage memory produce an article of art configured to implement the various functions specified in flowcharts 1200 and 1300. The program code instructions can also be loaded onto a computer or other programmable device to cause a series of operations to be performed on the computer or other programmable device to produce a computer-implemented process, such that the instructions executing on the computer or other programmable device provide operations for implementing the functions specified in the operations of flowcharts 1200 and 1300. Furthermore, executing the computer or other processing circuitry to perform the various functions transforms the computer or other processing circuitry into a specific machine configured to perform the exemplary embodiments of this disclosure.

[0152] Reference Figure 12 and Figure 13The flowchart operations described support combinations of devices for performing a specified function and combinations of operations for performing the specified function. It will be understood that one or more operations of the flowchart, and combinations of operations within the flowchart, can be implemented by a computer system based on dedicated hardware, or a combination of dedicated hardware and computer instructions, to perform the specified function.

[0153] In some example implementations, some of the operations described herein may be modified or further amplified as described below. Furthermore, in some implementations, additional optional operations may be included. It should be understood that each of the modifications, optional additions, or amplifications described herein may be included in the operations herein, either individually or in combination with any other feature described herein.

[0154] The foregoing method descriptions and process flowcharts are provided as illustrative examples only and are not intended to require or imply that the steps of the various embodiments must be performed in the presented order. As those skilled in the art will understand, the order of steps in the above embodiments can be performed in any order. Words such as “after,” “then,” “next,” and similar terms are not intended to limit the order of steps; these words are merely used to guide the reader through the description of the method. Furthermore, any reference to singular claim elements, for example, using the articles “a,” “an,” or “the,” should not be construed as limiting the element to the singular and, in some cases, may be interpreted in the plural form.

[0155] As described above, and based on this disclosure, it will be appreciated that embodiments of this disclosure can be configured as systems, apparatuses, methods, mobile devices, back-end network devices, computer program products, other suitable devices, and combinations thereof. Therefore, embodiments may include a variety of apparatuses, including entirely hardware or any combination of software and hardware. Furthermore, embodiments may take the form of a computer program product on at least one non-transitory computer-readable storage medium having computer-readable program instructions (e.g., computer software) embodied in the storage medium. Any suitable computer-readable storage medium may be utilized, including non-transitory hard disks, CD-ROMs, flash memory, optical storage devices, or magnetic storage devices. It should be understood that any computer program instructions and / or other types of code described herein may be loaded onto the circuitry of a computer, processor, or other programmable device to produce a machine, such that the computer, processor, or other programmable circuitry executing the code on that machine forms means for implementing various functions (including those described herein). In some embodiments, features of this disclosure may include or be communicatively coupled to an application-specific integrated circuit (ASIC) configured to convert differential output voltages from one or more thermopiles (e.g., in a single-chip or two-chip configuration).

[0156] Although various embodiments based on the principles disclosed herein have been shown and described above, modifications can be made by those skilled in the art without departing from the teachings of this disclosure. The embodiments described herein are representative only and not intended to be limiting. Many variations, combinations, and modifications are possible and are within the scope of this disclosure. Alternative embodiments resulting from the merging, integration, and / or omission of features of one or more embodiments are also within the scope of this disclosure. Therefore, the scope of protection is not limited by the description given above, but is defined by the following claims, which include all equivalents of the subject matter of the claims. Each claim is incorporated into the specification as further disclosure, and the claims are embodiments of this disclosure. Furthermore, any of the foregoing advantages and features may relate to specific embodiments, but the application of such published claims should not be limited to methods and structures that achieve any or all of the above advantages or have any or all of the above features.

[0157] Furthermore, the section headings used herein are intended to align with or provide organizational clues for the recommendations of 37 C. FR § 1.77. These headings should not limit or characterize the disclosure set forth in any of the claims published in this disclosure. For example, the description of the technology in the “Background Art” section should not be construed as an admission that a particular technology is prior art to any disclosure in this disclosure. Nor should “Summary of the Invention” be considered a limiting characterization of the disclosure set forth in the published claims. Furthermore, any reference in this disclosure to the singular forms of “Disclosure” or “Simplification” should not be used to prove that there is only one novel point in this disclosure. Multiple embodiments of this disclosure may be set forth according to the limitations of the multiple claims published in this disclosure, and such claims accordingly define the disclosure protected by them and their equivalents. In all cases, the scope of these claims should be considered in accordance with the advantages of the claims themselves, and should not be limited by the headings set forth herein.

[0158] Furthermore, without departing from the scope of this disclosure, the systems, subsystems, apparatuses, techniques, and methods described and illustrated in various embodiments in a discrete or separate manner can be combined or integrated with other systems, modules, techniques, or methods. Other devices or components shown or discussed as being interconnected or communicating with each other can be indirectly interconnected through some intermediate devices or components, whether such interconnection is made electrically, mechanically, or otherwise. Other examples of variations, substitutions, and modifications that can be identified by those skilled in the art without departing from the scope of this disclosure are also provided.

[0159] Those skilled in the art to which these embodiments pertain will recognize numerous modifications and other embodiments of the disclosure set forth herein, which benefit from the teachings presented in the foregoing description and associated drawings. Although the drawings show only certain components of the apparatuses and systems described herein, various other components may be used in conjunction with the components and structures disclosed herein. Therefore, it should be understood that this disclosure is not limited to the specific embodiments disclosed, and modifications and other embodiments are intended to be included within the scope of the appended claims. For example, various elements or components may be combined, rearranged, or integrated into another system, or certain features may be omitted or not implemented. Furthermore, the steps in any of the methods described above may not necessarily occur in the order depicted in the drawings, and in some cases, one or more of the depicted steps may occur substantially simultaneously, or additional steps may be involved. Although specific terminology is used herein, it is used only in a general and descriptive sense and not for limiting purposes.

Claims

1. A device for sensing fluid flow rate, the device comprising: Flow sensing device, the flow sensing device comprising: A heating structure having a centerline defining upstream and downstream sections of the flow sensing device; Membrane structure; A first thermopile, wherein at least a portion of the first thermopile is disposed on the membrane structure, and wherein the first thermopile comprises: The first plurality of upstream thermocouples disposed on the membrane structure, and A second plurality of upstream thermocouple junctions deviating from the membrane structure; and A second thermopile, wherein at least a portion of the second thermopile is disposed on the membrane structure, and wherein the second thermopile comprises: The first plurality of downstream thermocouple junctions disposed on the membrane structure, and No second or more downstream thermocouple junctions are disposed on the membrane structure. The maximum temperature difference is defined by the minimum temperature difference at a first position upstream of the centerline and the maximum temperature difference at a second position downstream of the centerline, wherein the upstream thermocouple is located near the first position and the downstream thermocouple is located near the second position.

2. The apparatus of claim 1, further comprising a substrate defining a microbridge structure, wherein a portion of the heating structure is disposed on the microbridge structure.

3. The apparatus of claim 1, wherein the first plurality of upstream thermoelectric couplings disposed on the membrane structure are disposed upstream of the centerline.

4. The apparatus of claim 1, wherein the second plurality of upstream thermoelectric couplings disposed on the membrane structure are disposed further upstream of the centerline.

5. The apparatus of claim 1, wherein the first plurality of downstream thermocouples disposed on the membrane structure are disposed downstream of the centerline.

6. The apparatus of claim 1, wherein the second plurality of downstream thermocouples disposed on the membrane structure are disposed further downstream of the centerline.

7. The apparatus of claim 1, wherein the upstream thermocouple and the downstream thermocouple are disposed near multiple locations on the maximum temperature difference contour line.

8. The apparatus of claim 1, wherein the first and second plurality of upstream thermocouples and the first and second plurality of downstream thermocouples are disposed at a plurality of locations on the maximum temperature difference contour line.

9. The apparatus of claim 1, wherein the first and second plurality of upstream thermocouple junctions comprise an interface between a first thermocouple material and a second thermocouple material, wherein the first thermocouple material comprises polycrystalline silicon, and wherein the second thermocouple material comprises aluminum.

10. The apparatus of claim 1, wherein the first and second plurality of upstream thermocouple junctions comprise an interface between a first thermocouple material and a second thermocouple material, wherein the first thermocouple material comprises n-type polycrystalline silicon, and wherein the second thermocouple material comprises p-type polycrystalline silicon.

11. The apparatus of claim 1, wherein the first and second plurality of upstream thermocouple junctions comprise an interface between a first thermocouple material and a second thermocouple material, wherein the first thermocouple material comprises p-type polycrystalline silicon, and wherein the second thermocouple material comprises n-type polycrystalline silicon.

12. The apparatus of claim 1, wherein the first and second plurality of upstream thermocouple junctions comprise an interface between a first thermocouple material and a second thermocouple material, wherein the first thermocouple material comprises a nickel-iron alloy, and wherein the second thermocouple material comprises chromium.

13. The apparatus of claim 1, wherein the first and second plurality of upstream thermocouple junctions comprise an interface between a first thermocouple material and a second thermocouple material, wherein the first thermocouple material comprises a nickel-iron alloy, and wherein the second thermocouple material comprises chromium disilicide.

14. The apparatus of claim 1, wherein the first and second plurality of upstream thermocouple junctions comprise an interface between a first thermocouple material and a second thermocouple material, wherein the first thermocouple material comprises a nickel-iron alloy, and wherein the second thermocouple material comprises rhenium disilicide.

15. The apparatus of claim 1, wherein the first and second plurality of upstream thermocouple junctions comprise an interface between a first thermocouple material and a second thermocouple material, wherein the first thermocouple material comprises chromium nitride, and wherein the second thermocouple material comprises copper.

16. The apparatus of claim 1, wherein the first and second plurality of upstream thermocouple junctions comprise an interface between a first thermocouple material and a second thermocouple material, wherein the first thermocouple material comprises chromium nitride, and wherein the second thermocouple material comprises aluminum.

17. The apparatus of claim 1, wherein the first and second plurality of upstream thermocouple junctions comprise an interface between a first thermocouple material and a second thermocouple material, wherein the first thermocouple material comprises chromium nitride, and wherein the second thermocouple material comprises p-type polycrystalline silicon.

18. A method of manufacturing an apparatus for sensing fluid flow rate, the method comprising: A heating structure is provided, the heating structure having a centerline defining upstream and downstream sections of a flow sensing device; Membrane structure; A first thermopile, wherein at least a portion of the first thermopile is disposed on the membrane structure, and wherein the first thermopile comprises: The first plurality of upstream thermocouples disposed on the membrane structure, and A second plurality of upstream thermocouple junctions deviating from the membrane structure; and A second thermopile, wherein at least a portion of the second thermopile is disposed on the membrane structure, and wherein the second thermopile comprises: The first plurality of downstream thermocouple junctions disposed on the membrane structure, and No second or more downstream thermocouple junctions are disposed on the membrane structure. The maximum temperature difference is defined by the minimum temperature difference at a first position upstream of the centerline and the maximum temperature difference at a second position downstream of the centerline, wherein the upstream thermocouple is located near the first position and the downstream thermocouple is located near the second position.

19. An apparatus for sensing fluid flow rate, the apparatus comprising: Flow sensing device, the flow sensing device comprising: A heating structure having a centerline defining upstream and downstream sections of the flow sensing device; Membrane structure; A first thermopile, comprising a first plurality of thermocouples disposed upstream of the centerline. The first plurality of thermocouples includes a first subset of the first plurality of thermocouples aligned parallel to the centerline, including at least one thermocouple junction disposed on the membrane structure; and The first plurality of thermocouples includes a second subset of the first plurality of thermocouples aligned perpendicular to the centerline, including at least one thermocouple junction disposed on the membrane structure; and The second thermopile includes a second plurality of thermocouples disposed downstream of the centerline. The second plurality of thermocouples includes a third subset of the second plurality of thermocouples aligned parallel to the centerline, comprising at least one thermocouple junction disposed on the membrane structure; and The second plurality of thermocouples includes a fourth subset of the second plurality of thermocouples aligned perpendicular to the centerline, comprising at least one thermocouple junction disposed on the membrane structure. The maximum temperature difference is defined by the minimum temperature difference at a first position upstream of the centerline and the maximum temperature difference at a second position downstream of the centerline, wherein the thermocouple junctions of the first plurality of thermocouples are disposed near the first position, and wherein the thermocouple junctions of the second plurality of thermocouples are disposed near the second position.

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