Self-adaptive temperature compensation thermopile type flow sensor chip and manufacturing method thereof

Abstract

The invention provides a self-adaptive temperature compensation thermopile type flow sensor chip and a manufacturing method thereof.The chip comprises a substrate, a flow detection thermopile and at least one detection correction thermocouple set, the flow detection thermopile and the detection correction thermocouple set are located above the substrate, and the flow detection thermopile comprises an upstream thermopile and a downstream thermopile which are arranged at intervals in the first direction; the detection and correction thermocouple group and the flow detection thermopile are arranged at intervals in the second direction, and the two ends of the detection and correction thermocouple group are located in the second direction of the area where the cold end of the upstream thermopile is located and the area where the cold end of the downstream thermopile is located so as to detect the temperature difference between the cold end of the upstream thermopile and the cold end of the downstream thermopile. Therefore, the output voltage of the flow detection thermopile is corrected to improve the flow detection precision. According to the sensor chip, the output voltage is increased by adopting a hardware compensation method, extra noise is not introduced, the space utilization rate is higher while the signal-to-noise ratio is increased, and the cost is effectively reduced. The manufacturing method can realize large-scale low-cost batch manufacturing.

Description

Technical Field

[0001] The present invention relates to the technical field of micro-electromechanical systems and sensors, in particular to an adaptive temperature compensation thermopile flow sensor chip and a manufacturing method thereof. Background Art

[0002] MEMS flow sensor is a silicon-based sensor based on micro-electromechanical system. It is mainly divided into thermal flow sensor and thermopile flow sensor. Among them, thermal flow sensor causes temperature deviation on the uniform and stable spatial thermal field according to the flow rate, so that the temperature sensitive resistor changes with the temperature, thereby detecting the resistance change to detect the flow rate; thermopile flow sensor is based on the thermoelectric effect. The flow rate causes temperature deviation on the uniform and stable spatial thermal field, which changes the temperature difference between the hot end and the cold end of the thermopile, causing the thermopile output voltage to change, thereby realizing flow detection. Please refer to Figure 1 , which is a simplified structural diagram of a general sensor based on the thermoelectric effect. The thermoelectric effect (Seebeck effect) refers to the flow of carriers in the thermocouple material from the hot end to the cold end under a temperature gradient (by setting a heat source at one end of the thermocouple to generate a temperature gradient), forming a potential difference, under the action of which a reverse current is generated. After a dynamic balance is reached between the thermal current and the reverse current, a stable potential difference V is formed at both ends of the thermocouple. ab =β(T hot -T cold ), where β is the Seebeck coefficient of the thermocouple material, T hot is the temperature of the hot end of the thermocouple, T cold is the temperature of the cold end of the thermocouple.

[0003] The noise voltage of a conventional thermopile flow sensor is proportional to the resistance of the thermopile. Its detection sensitivity depends on the output voltage of the thermopile at the same flow rate. The larger the output of the thermopile, the higher the sensitivity. In order to improve its sensitivity and signal-to-noise ratio, the following three methods are usually used: (1) Make more pairs of thermocouples to increase the output voltage of the thermopile. However, this method increases the noise while increasing the output voltage, and occupies a larger chip area, which is not conducive to sensor miniaturization and production cost; (2) Thin the thickness of the thermopile support film to reduce the heat dissipated through the support film. While increasing the output voltage, it will not increase any noise. However, this method increases the difficulty of the manufacturing process, and the risk of damage to the support film during use increases dramatically; (3) Select materials with higher thermoelectric effect efficiency as thermocouple materials to achieve high-precision detection, but this method is relatively expensive.

[0004] Therefore, how to solve the problems of increased test noise, increased production cost, increased volume and increased process difficulty caused by increasing the output voltage of the sensor chip in the prior art has become an important technical problem that needs to be solved urgently by technical personnel in this field.

[0005] It should be noted that the above introduction to the technical background is only for the convenience of providing a clear and complete description of the technical solutions of the present invention and for the convenience of understanding by those skilled in the art. It cannot be considered that the above technical solutions are well known to those skilled in the art simply because these solutions are described in the background technology section of the present invention. Summary of the invention

[0006] In view of the shortcomings of the prior art described above, the purpose of the present invention is to provide an adaptive temperature compensated thermopile flow sensor chip and a method for manufacturing the same, so as to solve the problems of increased noise, increased cost or increased process difficulty generated by the method of improving the detection sensitivity of the flow sensor in the prior art.

[0007] To achieve the above objectives and other related objectives, the present invention provides an adaptive temperature compensation thermopile flow sensor chip, comprising:

[0008] substrate;

[0009] a flow detection thermopile, located above the substrate, the flow detection thermopile comprising an upstream thermopile and a downstream thermopile spaced apart in a first direction, the upstream thermopile comprising an upstream cold end and an upstream hot end arranged oppositely, the downstream thermopile comprising a downstream cold end and a downstream hot end arranged oppositely, the upstream cold end and the downstream cold end being opposite to each other, and the upstream hot end and the downstream hot end being opposite to each other;

[0010] At least one detection and correction thermocouple group is located above the substrate, the detection and correction thermocouple group is spaced apart from the flow detection thermopile in a second direction, the second direction is perpendicular to the first direction, the detection and correction thermocouple group includes a first end and a second end that are relatively arranged in the first direction, the first end is in the second direction of the area where the upstream cold end is located, and the second end is in the second direction of the area where the downstream cold end is located.

[0011] Optionally, the sensor chip further includes an insulating cavity buried in the substrate, a portion of the substrate located above the insulating cavity constitutes a support film, at least a portion of the upstream thermopile is located on the support film, and at least a portion of the downstream thermopile is located on the support film.

[0012] Optionally, the sensor chip further comprises a heating resistor extending in the second direction, wherein the heating resistor is located above the supporting film and between the upstream hot end and the downstream hot end.

[0013] Optionally, the sensor chip further comprises a first thermal insulation groove, which vertically penetrates the support film to communicate with the thermal insulation cavity, and the first thermal insulation groove is located between the detection and correction thermocouple group and the flow detection thermopile in the second direction.

[0014] Optionally, the sensor chip further includes a second thermal insulation groove, which vertically penetrates the support film to communicate with the thermal insulation cavity, and the second thermal insulation groove is located between the upstream thermopile and the downstream thermopile.

[0015] Optionally, the upstream thermopile and the downstream thermopile are symmetrically distributed with respect to the second direction.

[0016] Optionally, the upstream thermopile includes a plurality of upstream thermocouples arranged at intervals in the second direction and connected in series, and the downstream thermopile includes a plurality of downstream thermocouples arranged at intervals in the second direction and connected in series.

[0017] Optionally, the sensor chip includes two detection and correction thermocouple groups, and the two detection and correction thermocouple groups are symmetrically arranged on both sides of the flow detection thermopile.

[0018] Optionally, the detection and correction thermocouple group includes a plurality of detection and correction thermocouple groups, and the plurality of detection and correction thermocouple groups are arranged at intervals in the second direction.

[0019] Optionally, the detection and correction thermocouple group includes a first thermocouple, wherein the first thermocouple is respectively connected to a first metal and a second metal at both ends in a first direction, at least a portion of the first metal is located between the first thermocouple and the upstream thermopile, and at least a portion of the second metal is located between the first thermocouple and the downstream thermopile.

[0020] Optionally, the detection and correction thermocouple group also includes a second thermocouple, which is located on the side of the first thermocouple away from the flow detection thermopile, and the second thermocouple is respectively connected to a third metal and a fourth metal at both ends in the first direction, the third metal extends to the side of the upstream thermopile away from the downstream thermopile, and the fourth metal extends to the side of the downstream thermopile away from the upstream thermopile, and the first metal and the second metal are located between the third metal and the fourth metal.

[0021] The present invention also provides a method for manufacturing an adaptive temperature compensation thermopile flow sensor chip, comprising the following steps:

[0022] providing a substrate;

[0023] forming a flow detection thermopile above the substrate, the flow detection thermopile comprising an upstream thermopile and a downstream thermopile spaced apart in a first direction, the upstream thermopile comprising an upstream cold end and an upstream hot end arranged oppositely, the downstream thermopile comprising a downstream cold end and a downstream hot end arranged oppositely, the upstream cold end and the downstream cold end being opposite to each other, and the upstream hot end and the downstream hot end being opposite to each other;

[0024] At least one detection and correction thermocouple group is formed above the substrate, the detection and correction thermocouple group is spaced apart from the flow detection thermopile in a second direction, the second direction is perpendicular to the first direction, the detection and correction thermocouple group includes a first end and a second end that are relatively arranged in the first direction, the first end is located in the second direction of the area where the upstream cold end is located, and the second end is located in the second direction of the area where the downstream cold end is located.

[0025] As described above, the adaptive temperature compensation thermopile flow sensor chip of the present invention adopts a hardware compensation method (setting a detection and correction thermocouple group), which can increase the final output voltage without setting more thermocouples or reducing the thickness of the support film or replacing high-efficiency thermocouple materials. At the same time, no additional noise is introduced and even the detection noise is reduced. The signal-to-noise ratio is effectively improved, the structural stability is high and the space utilization rate is relatively higher, which effectively reduces the cost. In addition, the materials used in each structure of the sensor chip are conventional semiconductor materials, without precious metals, and the process is relatively mature, the risk of production defects is reduced, and the production cost is further reduced. The method for making the adaptive temperature compensation thermopile flow sensor chip of the present invention can produce a flow sensor chip with high detection accuracy and stable structure, the production process is mature and the cost is low, and large-scale low-cost batch production can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Shown is a simplified schematic diagram of a general sensor based on the thermoelectric effect.

[0027] Figure 2 Shown is a schematic diagram of a top view of the structure of the adaptive temperature compensation thermopile flow sensor chip of the present invention.

[0028] Figure 3 Display as Figure 2 The schematic diagram of the top view of the upstream thermopile in the adaptive temperature compensation thermopile flow sensor chip is shown.

[0029] Figure 4Shown is another schematic top view of the structure of the adaptive temperature compensation thermopile flow sensor chip of the present invention.

[0030] Figure 5 Shown is a flow chart of the manufacturing steps of the adaptive temperature compensation thermopile flow sensor chip of the present invention.

[0031] Component number description

[0032] 101 Thermocouple

[0033] 101a Hot End

[0034] 101b Cold end

[0035] 102 Heat Source

[0036] 1 Substrate

[0037] 11 Support film

[0038] 2 Flow detection thermopile

[0039] 21 Upstream Thermopile

[0040] 210 Upstream thermocouple

[0041] 211 Upstream cold end area

[0042] 22 Downstream Thermopile

[0043] 220 Downstream thermocouple

[0044] 221 Downstream cold end area

[0045] 3. Detection and calibration of thermocouple group

[0046] 31 First thermocouple

[0047] 311 First Metal

[0048] 312 Second Metal

[0049] 32 Second thermocouple

[0050] 321 Third Metal

[0051] 322 Fourth Metal

[0052] 4 Insulation cavity

[0053] 5 Heating resistor

[0054] 6 First insulation tank

[0055] 7 Second insulation tank

[0056] Steps S1 to S3 DETAILED DESCRIPTION

[0057] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0058] See also Figures 2 to 5 It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner, and the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0059] The measurement principle of a conventional thermopile flow sensor is as follows: two thermopiles are set in the flow sensor - an upstream thermopile and a downstream thermopile, and the flow sensor is placed in a flow detection environment. The flow causes a temperature shift in the space where the temperature distribution is originally relatively balanced, and brings the heat from the upstream to the downstream, causing the hot end temperature of the upstream thermopile to decrease and the hot end temperature of the downstream thermopile to increase, causing the output voltage of the upstream thermopile to decrease and the output of the downstream thermopile to increase. The output difference of the two is used to obtain an output voltage that is proportional to the flow rate. After analyzing the factors that affect the detection accuracy of the flow sensor, the inventor found that since the flow sensor is based on heat induction to react to the gas flow rate, it is more sensitive to the temperature of the working environment. A small temperature difference may produce a large measurement error. When the temperature of the two cold ends is inconsistent, the difference between the output voltages of the two thermopiles will drift (that is, the output voltage is not only related to the gas flow, but also to the temperature difference between the two cold ends). When the sensor is working under different ambient temperatures, the temperature of the cold end of the upstream thermopile is not completely consistent with the temperature of the cold end of the downstream thermopile, so that the output voltage of the sensor has temperature drift, which will have an adverse effect on the flow detection sensitivity. The inventor adopts the following technical solution to solve the problem of interference caused by the temperature difference between the cold end temperature of the upstream thermopile and the cold end of the downstream thermopile on the detection sensitivity, thereby achieving high-precision flow detection. Please refer to the following content for detailed solutions.

[0060] Embodiment 1

[0061] This embodiment provides an adaptive temperature compensation thermopile flow sensor chip. Figure 2 , which is a schematic diagram of the top view structure of the sensor chip, including a substrate 1, a flow detection thermopile 2 and at least one set of detection and correction thermocouple groups 3.

[0062] Specifically, Figure 2 As shown, the flow detection thermopile 2 and the detection correction thermocouple group 3 are both located above the substrate 1, wherein the flow detection thermopile 2 includes a first direction ( Figure 2 The upstream thermopile 21 and the downstream thermopile 22 are arranged at intervals in the Y direction (the Y direction is the flow direction of the airflow), and the upstream thermopile 21 includes an upstream cold end ( Figure 2 Not marked in) and upstream hot end ( Figure 2 The downstream thermopile 22 includes a relatively arranged downstream cold end ( Figure 2 Not marked in) and downstream hot end ( Figure 2 The upstream cold end is opposite to the downstream cold end, and the upstream hot end is opposite to the downstream hot end; the detection and correction thermocouple group 3 is in the second direction ( Figure 2 The detection correction thermocouple group 3 is spaced apart from the flow detection thermopile 2 in the X direction (as shown in the X direction), and the second direction is perpendicular to the first direction. The detection correction thermocouple group 3 includes a first end and a second end that are relatively arranged in the first direction, the first end is in the second direction of the area 211 where the upstream cold end is located, and the second end is in the second direction of the area 221 where the downstream cold end is located.

[0063] Please note that Figure 3 , which is a schematic diagram of the overall structure of the upstream thermopile. In general, the thermopile is composed of multiple thermocouples, and each thermocouple has a relatively arranged cold end (the end with a lower temperature) and a hot end (the end with a higher temperature) in its extension direction. Due to factors such as arrangement, morphology or process accuracy, the cold ends of the multiple thermocouples are not completely flush (i.e., on the same straight line), but are in the same area. The first end and the second end of the detection and correction thermocouple group 3 mentioned here are respectively located in the second direction of the area 211 where the upstream cold end is located and the area 221 where the downstream cold end is located ( Figure 3 The arrow points to the interval) means that the first end is nearly flush with the upstream cold end (the temperature of the first end and the upstream cold end is almost equal) and the second end is nearly flush with the downstream cold end (the temperature of the second end and the downstream cold end is almost equal), so that the temperature difference between the upstream cold end and the downstream cold end can be detected, and the output result of the flow detection thermopile 2 is subsequently corrected to improve the detection accuracy. In addition, the substrate 1 includes a front side and a back side that are relatively arranged, and the flow detection thermopile 2 and the detection correction thermocouple group 3 are both located on the front side of the substrate 1. In addition, Figure 2 and Figure 3All of these are for the purpose of fully demonstrating the specific structure of the sensor chip and the thermopile, which is actually equivalent to enlarging the local structure. In fact, the sizes of the upstream cold end area and the downstream cold end area in the first direction are much smaller than those shown in the figure. Therefore, it can be regarded as that the first end is nearly flush with the upstream cold end and the second end is nearly flush with the downstream cold end.

[0064] As an example, Figure 2 As shown, the sensor chip also includes an insulating cavity 4, which is buried in the substrate 1, and the portion of the substrate 1 located above the insulating cavity 4 constitutes a support film 11. At least a portion of the upstream thermopile 21 is located on the support film 11, and at least a portion of the downstream thermopile 22 is located on the support film 11. The thickness of the support film 11 is set based on actual needs and is set as small as possible while ensuring structural stability (no damage during use) to avoid excessive heat consumption on the support film 11.

[0065] As an example, the insulation cavity 4 is obtained by dry etching the back side of the substrate 1. Due to the process characteristics, the insulation cavity 4 in this embodiment is hexagonal. In other embodiments, other suitable methods can be used to form the insulation cavity 4, such as front side wet etching.

[0066] As an example, the sensor chip further includes a heating resistor 5 extending in the second direction, wherein the heating resistor 5 is located above the supporting film 11 and between the upstream hot end and the downstream hot end.

[0067] Specifically, most of the structures of the upstream thermopile 21 and the downstream thermopile 22 are located on the support film 11, and a heating resistor 5 is arranged on the support film 11 to heat the hot end of the upstream thermopile 21 (i.e., the upstream hot end) and the hot end of the downstream thermopile 22 (i.e., the downstream hot end), so that a potential difference is generated between the cold end and the hot end of the upstream thermopile 21 due to the temperature difference, and a potential difference is generated between the cold end and the hot end of the downstream thermopile 22 due to the temperature difference. The setting of the insulation cavity 4 can prevent the heat generated by the heating resistor 5 from being dissipated to the back side of the substrate 1, thereby improving thermal efficiency and detection sensitivity.

[0068] As an example, the upstream thermopile 21 and the downstream thermopile 22 are symmetrically distributed about the second direction. Since the upstream thermopile 21 and the downstream thermopile 22 are spaced apart in the first direction, that is, at least a portion of the upstream thermopile 21 is aligned with at least a portion of the downstream thermopile 22 in the second direction, the hot end of the upstream thermopile 21, that is, the hot end of the downstream thermopile 22, absorbs substantially the same amount of heat generated by the heating resistor 5 when there is no airflow passing through, so that the temperature is almost the same. In the process of airflow flowing from upstream to downstream, the heat will be brought to the downstream. If the upstream thermopile 21 and the downstream thermopile 22 are not symmetrically distributed about the second direction (different sizes or not completely aligned), part of the heat of the upstream hot end will not be absorbed by the downstream hot end, resulting in a waste of thermal efficiency and loss of detection sensitivity.

[0069] As an example, the upstream thermopile 21 includes a plurality of upstream thermocouples 210 spaced apart and connected in series in the second direction, and the downstream thermopile 22 includes a plurality of downstream thermocouples 220 spaced apart and connected in series in the second direction. Preferably, the various parameters of the upstream thermocouple 210 (for example, the quantity, length, width, the spacing between two adjacent thermocouples, the position and the arrangement method, etc.) are consistent with the various parameters of the downstream thermocouple 220, which can reduce the difficulty of production and avoid unnecessary noise effects caused by structural differences. In addition, since the voltage signal output by the thermopile is obtained by summing up the potential difference of multiple thermocouples, the more the number of thermocouples, the more sensitive the detection accuracy, but the production cost and volume are relatively large. Figure 2 The number of thermocouples (including the upstream thermocouple 210 and the downstream thermocouple 220 ) shown in the figure is only an example. In actual application, the number of thermocouples is reasonably set based on actual needs and is not specifically limited here.

[0070] Further, a plurality of the upstream thermocouples 210 are arranged flush, and a plurality of the downstream thermocouples 220 are arranged flush; or, a plurality of the upstream thermocouples 210 are arranged in a staggered manner, and a plurality of the upstream thermocouples 210 are arranged in a staggered manner; or, a plurality of the upstream thermocouples 210 constitute an upstream thermocouple group, a plurality of the upstream thermocouple groups are arranged in a staggered manner, a plurality of the downstream thermocouples 220 constitute a downstream thermocouple group, and a plurality of the upstream thermocouple groups are arranged in a staggered manner. Flush arrangement means that both ends of each thermocouple are kept flush, and staggered arrangement means that the two ends of two adjacent thermocouples are staggered by a preset distance. In the case of flush arrangement, the two ends of the detection and correction thermocouple group 3 (i.e., the first end and the second end) are preferably kept flush with the upstream cold end and the downstream cold end, respectively. In this embodiment, a plurality of the upstream thermocouple groups are arranged in a staggered manner. It should be noted that, Figure 2The upstream thermopile and the downstream thermopile shown in the figure each include 9 thermocouple groups and each thermocouple group includes 3 thermocouples. In actual application, the above number can be adjusted based on actual needs (for example, Figure 4 (shown)

[0071] As an example, the sensor chip includes two detection and correction thermocouple groups 3, which are symmetrically arranged on both sides of the flow detection thermopile 2, and can occupy a smaller area under the premise of ensuring sensitive detection of the temperature difference between the upstream cold end and the downstream cold end. In other embodiments, the number of the detection and correction thermocouple groups 3 can be one group or more groups, which are reasonably set based on actual needs by comprehensively considering factors such as production cost, sensor occupied space and performance requirements of the sensor. For example, in applications where the sensor occupied space is strictly required but the sensor accuracy is slightly loose, only one group of the detection and correction thermocouple groups 3 can be set, and in applications where the sensor detection accuracy is higher, multiple groups of the detection and correction thermocouple groups 3 can be set.

[0072] As an example, the two detection and correction thermocouple groups 3 are connected in series to obtain a better temperature difference detection effect.

[0073] As an example, the detection correction thermocouple group 3 includes a plurality of detection correction thermocouples, which are arranged at intervals in the second direction. Since the temperature will be different due to the different distances from the support film 11 in the first direction, the thermocouples with different distances from the support film 11 in the first direction can avoid the detection noise generated thereby as much as possible and ensure the detection sensitivity to the greatest extent. In actual application, the number of the thermocouples is considered comprehensively by factors such as detection accuracy, production cost and occupied area. It should be noted that when the detection and correction thermocouple group 3 includes multiple detection and correction thermocouples, similar to the arrangement of the upstream thermocouple 210 and the downstream thermocouple 220, multiple detection and correction thermocouples are arranged in parallel or staggered (but it is not mandatory to keep the arrangement of the detection and correction thermocouples consistent with the arrangement of the upstream / downstream thermocouples), and in any arrangement, the first end of each detection and correction thermocouple in the first direction is located in the second direction of the area 211 where the upstream cold end is located, and the second end of each detection and correction thermocouple in the first direction is located in the second direction of the area 221 where the downstream cold end is located, thereby ensuring the correction effect of the detection and correction thermocouple group 3 on the temperature difference between the upstream cold end and the downstream cold end.

[0074] As an example, a plurality of the detection and correction thermocouples are connected in series in sequence, thereby achieving accurate detection of small temperature differences.

[0075] As an example, the detection and correction thermocouple group includes a first thermocouple 31, and the first thermocouple 31 is connected to a first metal 311 and a second metal 312 at two ends in the first direction, respectively. At least a portion of the first metal 311 is located between the first thermocouple 31 and the upstream thermopile 21, and at least a portion of the second metal 312 is located between the first thermocouple 31 and the downstream thermopile 22. In a single sensor chip, the area for accommodating the above-mentioned metals is limited, and the larger the metal area, the more favorable it is for the temperature detection sensitivity. Therefore, it is necessary to set the above-mentioned metal with a larger area as much as possible in the limited vacant area. Since the insulation cavity 4 is hexagonal, the support film 11 located above the insulation cavity 4 is naturally hexagonal, so that there is a blank area between the edge of the support film 11 and the first thermocouple 31. The blank area can be used to accommodate the first metal 311 and the second metal 312, thereby improving the detection accuracy and space utilization.

[0076] Furthermore, the portion of the first metal 311 extending into between the first thermocouple 31 and the upstream thermopile 21 and the portion of the second metal 312 extending into between the first thermocouple 31 and the downstream thermopile 22 are arranged in a wedge shape or a serpentine shape. In this embodiment, the above structure is wedge-shaped. Since the temperature distribution on the substrate 1 is relatively random, setting the above structure in a wedge shape can sense the temperatures at more locations, thereby more accurately reflecting the temperature difference between the cold ends of the upstream and downstream thermopile 22. In other embodiments, the above structure can also be set to other morphologies that can achieve similar effects, such as a serpentine shape. It should be noted that the purpose of connecting metal at both ends of the detection and correction thermocouple is to reflect the temperature difference between the cold ends of the upstream and downstream thermoelectric piles as much as possible to improve the temperature detection sensitivity. From a conventional perspective, each metal should extend as close to the upstream cold end or the downstream cold end as possible to maximize the reflection of the actual temperature at the upstream cold end and the downstream cold end. However, the temperature difference between the upstream cold end and the downstream cold end is uneven from a microscopic perspective, and changes at any time with factors such as ambient temperature. Therefore, by analyzing the ambient temperature of the insulation cavity, setting the first metal and the second metal to a wedge shape or a snake shape can make the two ends of the detection and correction thermocouple as close to the actual temperature of the upstream hot end and the downstream hot end as possible to achieve more accurate temperature difference detection.

[0077] As an example, the detection and correction thermocouple group also includes a second thermocouple 32, which is located on the side of the first thermocouple 31 away from the flow detection thermopile 2, and the two ends of the second thermocouple 32 in the first direction are respectively connected to a third metal 321 and a fourth metal 322, the third metal 321 extends to the side of the upstream thermopile 21 away from the downstream thermopile 22, the fourth metal 322 extends to the side of the downstream thermopile 22 away from the upstream thermopile 21, and the first metal 311 and the second metal 312 are located between the third metal 321 and the fourth metal 322.

[0078] Specifically, the role of metals connected to the opposite ends of the first thermocouple and the two ends of the second thermocouple is that the thermal conductivity of metal materials is higher than that of other materials, and the temperature difference between the upstream cold end and the downstream cold end can be better detected, thereby improving the accuracy of the detection result. Therefore, when the number of detection and correction thermocouples in the detection and correction thermocouple group 3 is greater than 2, a third thermocouple 33 is also included, and the third thermocouple 33 is located between the first thermocouple 31 and the second thermocouple 32, and the two ends of the third thermocouple 33 in the first direction are also connected to metals, and the metals to which they are connected are respectively located between the metals connected to the two ends of the first thermocouple 31 and the metals connected to the two ends of the second thermocouple 32.

[0079] As an example, the area of ​​the first metal 311 is larger than the area of ​​the third metal 321, and the area of ​​the second metal 312 is larger than the area of ​​the fourth metal 322, that is, the metal area connected at both ends of the first thermocouple 31 is larger than the metal area connected at both ends of the second thermocouple 32. The reason for this setting is that the closer to the support film 11, the higher the temperature, and the corresponding temperature difference is also finer. The larger the metal area, the higher the temperature conduction efficiency. Therefore, the metal at both ends of the thermocouple (the first thermocouple 32) relatively close to the support film 11 is set larger, which is beneficial to improving the temperature detection sensitivity (that is, when the detection correction thermocouple group 3 includes multiple detection correction thermocouples, as the distance between the detection correction thermocouple and the flow detection thermopile 2 increases, the area of ​​the metal connected at both ends decreases accordingly). It should be noted that Figure 2 The figure only illustrates the connection relationship of each metal. In fact, the area distribution of each metal may not be as shown. Figure 2 shown.

[0080] As an example, the upstream thermocouple 210, the downstream thermocouple 220, and the detection and correction thermocouple (including the first thermocouple 31 and the second thermocouple 32) are made of the same material, all including polysilicon and Al, and are preferably composed of a pair of P-type polysilicon thermocouple strips and N-type polysilicon thermocouple strips. The P-type polysilicon thermocouple strips and the N-type polysilicon thermocouple strips can be arranged in parallel or stacked up and down, and connected in series. The use of polysilicon material to make thermocouples can be fully compatible with semiconductor manufacturing processes, reducing manufacturing difficulty and manufacturing costs. When the above-mentioned thermocouple materials are consistent, the above-mentioned thermocouples can be made in the same manufacturing step, saving process steps and reducing manufacturing costs. The above-mentioned thermocouple structure is preferably stacked up and down (with an isolation layer in the middle), which can increase the integration to achieve miniaturization and meet multiple occasions. In addition, it should be noted that in the present embodiment, the above-mentioned thermocouples are all in the shape of strips. In actual application, the morphology of each thermocouple is not limited to the strip shape, and can be reasonably set based on actual needs. In addition, the material of the heating resistor 5 is preferably consistent with the material of each thermocouple.

[0081] It should be noted that when the detection and correction thermocouple group 3 includes multiple detection and correction thermocouples, each of the detection and correction thermocouples is connected in series in sequence, and the detection and correction thermocouple itself includes two thermocouple bars connected in series. Taking the detection and correction thermocouple group 3 including the first thermocouple 31 and the second thermocouple 32 as an example, the first thermocouple 31 includes a first P-type polysilicon thermocouple bar and a first N-type polysilicon thermocouple bar, and the second thermocouple 32 includes a second P-type polysilicon thermocouple bar and a second N-type polysilicon thermocouple bar, wherein the downstream end of the first P-type polysilicon thermocouple bar is electrically connected to the downstream end of the first N-type polysilicon thermocouple bar to form the first thermocouple 31, and the downstream end of the second P-type polysilicon thermocouple bar is electrically connected to the downstream end of the second N-type polysilicon thermocouple bar to form the second thermocouple. 32 (the "upstream end" and "downstream end" mentioned here are defined based on the direction of airflow), the upstream end of the first P-type polysilicon thermocouple strip is electrically connected to the upstream end of the second N-type polysilicon thermocouple strip to realize the series connection of the first thermocouple 31 and the second thermocouple 32, the upstream end of the first N-type polysilicon thermocouple strip and the upstream end of the second P-type polysilicon thermocouple strip are respectively electrically led out to output voltage signals or connected to other structures (such as when two detection and correction thermocouple groups are provided, they can be used to realize the series connection between the two detection and correction thermocouple groups). At this time, the connection between the above-mentioned first metal to the fourth metal and the corresponding thermocouple pair must be reasonably set on the premise of satisfying the series connection between the two thermocouple strips of the thermocouple pair itself and the series connection between adjacent thermocouple pairs. For example, the first metal 311 (or the third metal 321) can be electrically connected to either the P-type polysilicon thermocouple bar or the N-type polysilicon thermocouple bar of the first thermocouple pair 31 (or the second thermocouple pair 31) but not both of them at the same time, and the second metal 312 (or the fourth metal 322) can be electrically connected to either the P-type polysilicon thermocouple bar or the N-type polysilicon thermocouple bar of the first thermocouple pair 31 (or the second thermocouple pair 32) or both of them at the same time, so that the problem of parallel connection affecting the test accuracy due to an error in the electrical connection relationship of a certain metal will not occur.

[0082] As an example, the materials of the first metal 311, the second metal 312, the third metal 321 and the fourth metal 322 include at least one of Au, Ag, Cu and Al, preferably Cu, which has a relatively high thermal conductivity, is a conventional semiconductor material and is inexpensive.

[0083] As an example, the sensor chip further includes a first thermal insulation groove 6, which vertically penetrates the support film 11 to communicate with the thermal insulation cavity 4, and the first thermal insulation groove 6 is located between the detection and correction thermocouple group 3 and the flow detection thermopile 2 in the second direction. The aforementioned thermal insulation cavity 4 is used to achieve vertical (perpendicular to the first direction and the second direction) thermal isolation of the hot end of the upstream thermopile 21, the hot end of the downstream thermopile 22 and the heating resistor 5 from the substrate 1, and here the first thermal insulation groove 6 is used to achieve lateral (including the first direction and the second direction) thermal isolation of the above structure from the substrate 1, further improving the detection accuracy.

[0084] Furthermore, the first thermal insulation groove 6 is in the form of a right-angled trapezoid, which can achieve maximum isolation between the above structures (further away from the substrate 1) while maintaining consistency with the thermal insulation cavity 4 in shape, so that less heat from the heating resistor 5 is dissipated from the side, thereby maintaining higher thermal efficiency. Preferably, when the thermal insulation cavity 4 is in the form of a regular hexagon, the smaller angle of the right-angled trapezoid is 60°, which is consistent with the outline of the thermal insulation cavity 4.

[0085] Furthermore, the number of the first thermal insulation grooves 6 ranges from 2 to 4, preferably in pairs and symmetrically arranged about the heating resistor 5, which can ensure detection accuracy. In this embodiment, the number of the first thermal insulation grooves 6 is 4.

[0086] As an example, the sensor chip further includes a second thermal insulation groove 7, which vertically penetrates the support film 11 to communicate with the thermal insulation cavity 4, and the second thermal insulation groove 7 is located between the upstream thermopile 21 and the downstream thermopile 22. Further, the second thermal insulation groove 7 is located between the upstream thermopile 21 and the heating resistor 5 and / or between the downstream thermopile 22 and the heating resistor 5. When the upstream thermocouples 210 and the downstream thermocouples 220 are arranged in an alternating manner, there is a gap between half of the upstream thermocouples 210 and half of the downstream thermocouples 220 and the heating resistor 5, and the second thermal insulation groove 7 opens from the gap and extends vertically, which is equivalent to the second thermal insulation groove 7 being located between the thermocouple (upstream thermocouple 210 or downstream thermocouple 220) and the heating resistor 5 in the first direction, and between two adjacent thermocouples in the second direction, which can further improve space utilization. The setting of the second thermal insulation groove 7 can prevent the heat generated by the heating resistor 5 from being conducted in the lateral direction (which will cause the sensor to take too long to reach thermal equilibrium), thereby ensuring that the heat is preferentially conducted in the direction of the thermocouple, effectively shortening the response time. In addition, during the operation of the sensor chip, the airflow moves from upstream to downstream, thereby bringing the upstream heat to the downstream. The second thermal insulation groove 7 can reduce the heat provided by the heating resistor 5 to the upstream hot end while not causing any loss to the heat brought to the downstream hot end by the airflow, thereby reducing the output voltage of the upstream thermopile 21 and increasing the output voltage of the downstream thermopile 22, thereby increasing the output voltage of the final sensor chip, greatly improving the thermal efficiency and reducing the power consumption in the non-working state.

[0087] Furthermore, the number of the second thermal insulation grooves 7 includes a plurality of grooves, preferably in pairs and symmetrically arranged about the heating resistor 5. The number and position of the second thermal insulation grooves 7 are reasonably set based on the number and arrangement of the thermocouple strips in the flow detection thermopile 2, and are not necessarily limited to the same. Figure 2 The number (6) and shape (rectangular) of the insulation grooves shown in FIG.

[0088] Specifically, the working principle of the flow sensor chip is as follows: Assume that when the sensor is working (i.e., there is flow passing through the sensor), the temperature of the hot end of the upstream thermopile 21 is T uph , the cold end temperature is T upc , the hot end temperature of the downstream thermopile 22 is T downh , the cold end temperature is T downc , and the two thermopiles are axially symmetrically distributed and have the same Seebeck coefficient (β), and the heating resistor 5 (R heat ) so that a temperature difference is generated between the cold end and the hot end of the two thermopiles, thereby generating a potential difference, wherein the output voltage of the upstream thermopiles 21 is V up , V up=β(T uph -T upc ), the output voltage of the downstream thermopile 22 is V down , V down =β(T downh -T downc ), the output voltage of the sensor is V out =V up -V down =β(T uph -T upc )-β(T downh -T downc )=β[(T uph -T downh )+(T downc -T upc )], and V out It is proportional to the flow rate. Generally, the cold end temperature of the upstream thermopile 21 and the downstream thermopile 22 is assumed to be approximately equal to the ambient temperature (i.e., T downc -T upc =0), at this time, V out =β[(T uph -T downh )+(T downc -T upc )]=β(T uph -Td ownh ), that is, the output voltage of the default sensor is not affected by the temperature difference between the cold ends of the two thermopiles. However, in actual applications, due to the certain difference in the cold end temperature of the upstream and downstream thermopiles (i.e., T downc -T upc ≠0), so that at different ambient temperatures, the output of the upstream thermopile 21 and the output of the downstream thermopile 22 both change nonlinearly, so it is necessary to adjust V out To compensate for the noise interference caused by the temperature difference between the cold ends of the upstream and downstream thermopile 22, a detection and correction thermocouple group 3 is provided in the present invention, which is specially used to test the temperature difference between the cold ends of the upstream and downstream thermopile 22, and its output voltage is set to V cref , and the material of the detection and correction thermocouple group 3 is the same as that of the upstream and downstream thermopiles 22, so its Seebeck coefficient is also the same as that of the upstream and downstream thermopiles 22, then V cref =β(T downc -T upc ), when the ambient temperature changes, the cold end temperatures of the upstream thermopile 21 and the downstream thermopile 22 change differently. cref As the temperature changes, V out =β[(T uph -T downh )+(T downc -T upc)], assuming the output voltage after temperature compensation is V outf , then V outf =V out -V cref =β(T uph -T downh ), the result is no longer affected by the cold end temperature of the upstream and downstream thermopile 22. When the ambient temperature changes, the output of the flow sensor is only related to the flow rate, thereby improving the detection sensitivity of the flow sensor to the flow rate.

[0089] The adaptive temperature compensation thermopile flow sensor chip of the present embodiment includes a flow detection thermopile and a detection correction thermocouple group. The flow detection thermopile is used for conventional flow detection, and the detection correction thermocouple group is used to correct the detection noise caused by the ambient temperature when the flow detection thermopile is working. Specifically, when there is a temperature difference between the upstream cold end and the downstream cold end of the flow detection thermopile, the detection correction thermocouple group adaptively eliminates the interference of the temperature difference on the detection result, which greatly reduces the difficulty of back-end calibration and improves the detection sensitivity, and increases the practicality of the sensor chip in complex environments. Compared with the method for improving detection sensitivity introduced in the background technology, the sensor chip adopts a hardware compensation method (setting a detection correction thermocouple group). There is no need to set more thermocouples or reduce the thickness of the support film or replace the high-efficiency thermocouple material, so that the final output voltage can be increased. At the same time, no additional noise is introduced and even the detection noise is reduced. The signal-to-noise ratio is effectively improved, the structural stability is high and the space utilization rate is relatively higher, which effectively reduces the cost. In addition, the materials used in each structure of the sensor chip are conventional semiconductor materials, without precious metals, and the process is relatively mature, the risk of production defects is reduced, and the production cost is further reduced.

[0090] Embodiment 2

[0091] This embodiment provides a method for manufacturing an adaptive temperature compensation thermopile flow sensor chip, which can be used to manufacture the sensor chip as described in the first embodiment or other chips with similar structures. Figure 5 , which is a flowchart of the steps of the production method, comprising the following steps:

[0092] S1: providing a substrate;

[0093] S2: forming a flow detection thermopile above the substrate, the flow detection thermopile comprising an upstream thermopile and a downstream thermopile spaced apart in a first direction, the upstream thermopile comprising an upstream cold end and an upstream hot end arranged oppositely, the downstream thermopile comprising a downstream cold end and a downstream hot end arranged oppositely, the upstream cold end and the downstream cold end are opposite to each other, and the upstream hot end and the downstream hot end are opposite to each other;

[0094] S3: forming at least one detection and correction thermocouple group above the substrate, wherein the detection and correction thermocouple group is spaced apart from the flow detection thermopile in a second direction, the second direction is perpendicular to the first direction, and the detection and correction thermocouple group includes a first end and a second end that are relatively arranged in the first direction, the first end is located in the second direction of the area where the upstream cold end is located, and the second end is located in the second direction of the area where the downstream cold end is located;

[0095] The forming of the flow detection thermopile on the substrate and the forming of at least one set of detection and calibration thermocouples on the substrate are performed simultaneously or in steps.

[0096] First, see Figure 2 , perform step S1, provide a substrate 1, the substrate 1 adopts a conventional semiconductor substrate, such as a Si substrate, a SiGe substrate, a SiC substrate or an SOI substrate, etc., the substrate 1 includes a front side and a back side that are relatively arranged, and subsequent steps are performed based on the front side of the substrate 1.

[0097] Please see again Figure 2 , execute step S2 and step S3 to form a flow detection thermopile 2 and at least one detection correction thermocouple group 3 above the substrate 1, the flow detection thermopile 2 includes an upstream thermopile 21 and a downstream thermopile 22 spaced apart in a first direction, and the detection correction thermocouple group 3 is spaced apart from the flow detection thermopile 2 in a second direction, wherein step S2 and step S3 can be performed simultaneously or in steps, preferably simultaneously, which can effectively save process steps and costs, and in other embodiments, the above two steps can also be performed in steps for other factors.

[0098] As an example, the detection and correction thermocouple group 3 includes a plurality of detection and correction thermocouples, and the plurality of detection and correction thermocouples are arranged at intervals in the second direction and connected in series.

[0099] As an example, the method further includes forming a metal layer above the substrate and patterning the metal layer.

[0100] As an example, the detection and correction thermocouple group 3 includes a first thermocouple 31, and the patterned metal layer includes a first metal 311 and a second metal 312, the first metal 311 and the second metal 312 are respectively located at the two ends of the first thermocouple 31 in the first direction, at least a portion of the first metal 311 is located between the first thermocouple 31 and the upstream thermopile 21, and at least a portion of the second metal 312 is located between the first thermocouple 31 and the downstream thermopile 22.

[0101] As an example, the detection and correction thermocouple group 3 also includes a second thermocouple 32, which is located on the side of the first thermocouple 31 away from the flow detection thermopile 2, and the patterned metal layer also includes a third metal 321 and a fourth metal 322, which are respectively located at the two ends of the second thermocouple 32 in the first direction, and the third metal 321 extends to the side of the upstream thermopile 21 away from the downstream thermopile 22, and the fourth metal 322 extends to the side of the downstream thermopile 22 away from the upstream thermopile 21, and the first metal 311 and the second metal 312 are located between the third metal 321 and the fourth metal 322.

[0102] Specifically, the conventional thermopile manufacturing process usually includes the steps of forming a metal layer and patterning the metal layer. However, the purpose of patterning the metal layer in the conventional process is to connect the two thermocouple bars in the same thermocouple pair in series through metal and to connect adjacent thermocouples in series through metal. In the present embodiment, the metal layer is patterned to achieve series connection between the thermocouples, and at the same time, metals connected to the two ends of the thermocouples included in the detection and correction thermocouple group are formed, thereby effectively improving the flow detection accuracy of the sensor chip manufactured while saving process steps and costs.

[0103] As an example, the step of forming a heating resistor 5 above the substrate 1 is also included. When the material of the heating resistor 5 is the same as that of the thermocouple, the step of forming the heating resistor 5 can be performed simultaneously with or separately from step S2 (step S3), preferably simultaneously to save process steps.

[0104] As an example, it also includes the steps of forming the heat-insulating cavity 4, the first heat-insulating groove 6, and the second heat-insulating groove 7. The above structures can all be formed by dry etching, wherein the heat-insulating cavity 4 is etched based on the back side of the substrate 1, and the first heat-insulating groove 6 and the second heat-insulating groove 7 are etched based on the front side of the substrate 1, which is conducive to reducing the process difficulty. For the specific position of the above structure, please refer to the relevant content in Example 1, which will not be repeated here.

[0105] The method for manufacturing the adaptive temperature compensation thermopile flow sensor chip of this embodiment can manufacture a flow sensor chip with high detection accuracy and stable structure. The manufacturing process is mature and the cost is low, and large-scale and low-cost batch production can be achieved.

[0106] In summary, the adaptive temperature compensation thermopile flow sensor chip of the present invention adopts a hardware compensation method (setting a detection and correction thermocouple group), and the final output voltage can be increased without setting a larger number of thermocouples or reducing the thickness of the support film or replacing high-efficiency thermocouple materials. At the same time, no additional noise is introduced and even the detection noise is reduced. The signal-to-noise ratio is effectively improved, the structural stability is high, and the space utilization rate is relatively higher, which effectively reduces the cost. In addition, the materials used in each structure of the sensor chip are conventional semiconductor materials, without precious metals, and the process is relatively mature, the risk of production defects is reduced, and the production cost is further reduced. The method for making the adaptive temperature compensation thermopile flow sensor chip of the present invention can produce a flow sensor chip with high detection accuracy and stable structure, the manufacturing process is mature and the cost is low, and large-scale low-cost batch production can be achieved. Therefore, the present invention effectively overcomes the various shortcomings in the prior art and has a high industrial utilization value.

[0107] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. An adaptive temperature compensation thermopile flow sensor chip, characterized in that: include: substrate; a flow detection thermopile, located above the substrate, the flow detection thermopile comprising an upstream thermopile and a downstream thermopile spaced apart in a first direction, the upstream thermopile comprising an upstream cold end and an upstream hot end arranged oppositely, the downstream thermopile comprising a downstream cold end and a downstream hot end arranged oppositely, the upstream cold end and the downstream cold end being opposite to each other, and the upstream hot end and the downstream hot end being opposite to each other; At least one detection and correction thermocouple group is located above the substrate, the detection and correction thermocouple group is spaced apart from the flow detection thermopile in a second direction, the second direction is perpendicular to the first direction, the detection and correction thermocouple group includes a first end and a second end that are relatively arranged in the first direction, the first end is in the second direction of the area where the upstream cold end is located, and the second end is in the second direction of the area where the downstream cold end is located.

2. The adaptive temperature compensation thermopile flow sensor chip according to claim 1, characterized in that: The sensor chip also includes an insulation cavity buried in the substrate, a portion of the substrate located above the insulation cavity constitutes a support film, at least a portion of the upstream thermopile is located on the support film, and at least a portion of the downstream thermopile is located on the support film.

3. The adaptive temperature compensation thermopile flow sensor chip according to claim 2, characterized in that: The sensor chip further includes a heating resistor extending in a second direction, the heating resistor being located above the supporting film and between the upstream hot end and the downstream hot end.

4. The adaptive temperature compensation thermopile flow sensor chip according to claim 2, characterized in that: The sensor chip further includes a first thermal insulation groove, which vertically penetrates the support film to communicate with the thermal insulation cavity, and is located between the detection and correction thermocouple group and the flow detection thermopile in the second direction.

5. The adaptive temperature compensation thermopile flow sensor chip according to claim 2, characterized in that: The sensor chip further includes a second thermal insulation groove, which vertically penetrates the support film to communicate with the thermal insulation cavity, and is located between the upstream thermopile and the downstream thermopile.

6. The adaptive temperature compensation thermopile flow sensor chip according to claim 1, characterized in that: The upstream thermopile and the downstream thermopile are symmetrically distributed with respect to the second direction.

7. The adaptive temperature compensation thermopile flow sensor chip according to claim 1, characterized in that: The upstream thermopile includes a plurality of upstream thermocouples arranged at intervals in the second direction and connected in series, and the downstream thermopile includes a plurality of downstream thermocouples arranged at intervals in the second direction and connected in series.

8. The adaptive temperature compensation thermopile flow sensor chip according to claim 1, characterized in that: The sensor chip includes two detection and correction thermocouple groups, and the two detection and correction thermocouple groups are symmetrically arranged on both sides of the flow detection thermopile.

9. The adaptive temperature compensation thermopile flow sensor chip according to claim 1, characterized in that: The detection and correction thermocouple group includes a plurality of detection and correction thermocouples, and the plurality of detection and correction thermocouples are arranged at intervals in the second direction.

10. The adaptive temperature compensation thermopile flow sensor chip according to claim 9, characterized in that: The detection and correction thermocouple group includes a first thermocouple, wherein the first thermocouple is respectively connected to a first metal and a second metal at both ends in a first direction, at least a portion of the first metal is located between the first thermocouple and the upstream thermopile, and at least a portion of the second metal is located between the first thermocouple and the downstream thermopile.

11. The adaptive temperature compensation thermopile flow sensor chip according to claim 10, characterized in that: The detection and correction thermocouple group also includes a second thermocouple, which is located on a side of the first thermocouple away from the flow detection thermopile, and the second thermocouple is connected to a third metal and a fourth metal at both ends in the first direction, respectively, the third metal extends to a side of the upstream thermopile away from the downstream thermopile, the fourth metal extends to a side of the downstream thermopile away from the upstream thermopile, and the first metal and the second metal are located between the third metal and the fourth metal.

12. A method for manufacturing an adaptive temperature compensation thermopile flow sensor chip, characterized in that: The following steps are involved: providing a substrate; forming a flow detection thermopile above the substrate, the flow detection thermopile comprising an upstream thermopile and a downstream thermopile spaced apart in a first direction, the upstream thermopile comprising an upstream cold end and an upstream hot end arranged oppositely, the downstream thermopile comprising a downstream cold end and a downstream hot end arranged oppositely, the upstream cold end and the downstream cold end being opposite to each other, and the upstream hot end and the downstream hot end being opposite to each other; At least one detection and correction thermocouple group is formed above the substrate, the detection and correction thermocouple group is spaced apart from the flow detection thermopile in a second direction, the second direction is perpendicular to the first direction, the detection and correction thermocouple group includes a first end and a second end that are relatively arranged in the first direction, the first end is located in the second direction of the area where the upstream cold end is located, and the second end is located in the second direction of the area where the downstream cold end is located; The forming of the flow detection thermopile on the substrate and the forming of at least one detection calibration thermocouple set on the substrate are performed simultaneously or in steps.

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