Thermal flow sensor and preparation method thereof

Abstract

The invention provides a thermal flow sensor and a preparation method thereof.The thermal flow sensor comprises a substrate, a partition plate, a measurement structure, a protection layer, a first bonding pad, a second bonding pad and an output bonding pad, and a cavity is formed in the substrate; the partition plate is positioned on the upper surface of the substrate and above the opening of the cavity; the measuring structure is located on the upper surface of the partition plate and comprises temperature-sensitive resistors, a main temperature measuring element, a heating element and an isolating layer, the main temperature measuring element is located above the cavity and is symmetrical about the center line, perpendicular to the Y direction, of the cavity, the heating element is located above the cavity and is symmetrical about the center line, perpendicular to the Y direction, of the cavity, and the temperature-sensitive resistors are located on the two sides of the main temperature measuring element; the protective layer covers the exposed upper surface of the measurement structure; the first bonding pad, the second bonding pad and the output bonding pad are electrically connected with the two ends of the temperature-sensitive resistor, the heating element and the main temperature measuring element respectively. The main temperature measuring element and the heating element which are symmetrical about the center line, perpendicular to the Y direction, of the cavity are arranged over the cavity, and the influence of external heat radiation is avoided.

Description

Technical Field

[0001] The invention belongs to the field of sensor manufacturing and relates to a thermal flow sensor and a preparation method thereof. Background Art

[0002] Flow measurement and control are of great significance in the fields of industry, medicine, bioengineering, etc. Among them, MEMS thermal flow sensors have been widely used due to their small size, high precision, low power consumption, and fast response speed. For example, in the automotive field, the control of the engine air intake flow rate guides the effective combustion of fuel; in the medical field, the high-precision control requirements of oxygen flow for Chinese home ventilators, oxygen concentrators, etc. At present, most of the thermal flow sensors on the market belong to the three-element thermal temperature difference structure, which is mainly composed of a heating resistor, an upstream temperature measuring element, and a downstream temperature measuring element; the temperature measuring element is generally composed of a thermopile or a thermistor; the heating resistor is located in the center of the chip, and the upstream temperature measuring element and the downstream temperature measuring element are located on both sides of the heating resistor. When the fluid passes through, the temperature balance between the upstream temperature measuring element and the downstream temperature measuring element is broken, resulting in a temperature difference, and then the flow value can be judged by the size of the temperature difference.

[0003] In the thermal flow sensor disclosed in the patent with publication number CN114577288A, the upstream thermistor and the downstream thermistor of the sensor are separately arranged on the surface of the substrate, and the heating resistor is arranged on the surface of the substrate and is located between the upstream thermistor and the downstream thermistor. This structure can solve the problem that the thermal flow sensor affects the measurement accuracy due to uneven heat diffusion, and at the same time can improve the sensitivity of the sensor. However, the structure is composed of three parts: a heating resistor, an upstream thermopile temperature measuring element, and a downstream thermopile temperature measuring element. The two groups of thermopiles are symmetrically arranged on the upstream and downstream sides of the heating resistor, respectively, making the size of the sensor relatively large and the structure relatively complex. In addition, the sensor of this structure ignores the radiation effect of the temperature measuring element on the fluid environment temperature. In the process of fluid flow, in addition to the temperature difference caused by the movement of the fluid, the temperature in the fluid channel will also generate radiation. Its radiation reaches the surface of the chip and also generates a response, which is easy to cause partial measurement errors, and its measurement accuracy is not high.

[0004] Therefore, there is an urgent need to find a thermal flow sensor that simplifies the measurement structure, improves the measurement accuracy and avoids the influence of external thermal radiation. Summary of the invention

[0005] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a thermal flow sensor and a preparation method thereof, so as to solve the problems of the thermal flow sensor in the prior art, such as complex structure, poor measurement accuracy and great influence of external thermal radiation.

[0006] To achieve the above objectives and other related objectives, the present invention provides a thermal flow sensor, comprising:

[0007] A substrate having a cavity extending through the substrate;

[0008] a partition plate, located on the upper surface of the substrate and above the opening of the cavity;

[0009] A measuring structure, located on the upper surface of the partition, the measuring structure comprising a temperature-sensitive resistor, a main temperature measuring element, a heating element and an isolation layer located between the heating element and the main temperature measuring element, the main temperature measuring element is located above the cavity opening and is symmetrical about the center line of the cavity perpendicular to the Y direction, the dimensions of the main temperature measuring element in the X direction and the Y direction are both smaller than the dimensions of the cavity opening, the heating element is located above the cavity opening and is symmetrical about the center line of the cavity perpendicular to the Y direction, the dimension of the heating element in the X direction is not smaller than the dimension of the main temperature measuring element and is not larger than the dimension of the cavity opening, the dimension of the heating element in the Y direction is smaller than the dimension of the main temperature measuring element, the temperature-sensitive resistor is located above the substrate on both sides of the main temperature measuring element along the Y direction, and the X direction and the Y direction are perpendicular to each other;

[0010] a protective layer covering the exposed upper surface of the measurement structure;

[0011] A first pad, a second pad and an output pad, wherein the first pad is electrically connected to the two ends of the temperature-sensitive resistor, the second pad is electrically connected to the two ends of the heating element, and the output pad is electrically connected to the two ends of the main temperature measuring element.

[0012] Optionally, the main temperature measuring element comprises a plurality of thermocouples arranged at intervals along the X direction, and the plurality of thermocouples in the main temperature measuring element are connected in series to form a thermopile.

[0013] Optionally, the thermocouple is provided with two electric couple arms spaced apart along the X direction, the electric couple arms of the thermocouple include any two of a P-type arm extending along the Y direction, an N-type arm extending along the Y direction, and a metal arm extending along the Y direction, and the thermocouple is also provided with a connecting portion for connecting two different electric couple arms.

[0014] Optionally, the main temperature measuring element is located directly above the heating element, the heating element is located on the upper surface of the partition, and the isolation layer covers the exposed surface of the heating element and the exposed upper surface of the partition; or the heating element is located directly above the main temperature measuring element, the main temperature measuring element is located on the upper surface of the partition, and the isolation layer covers the exposed surface of the main temperature measuring element and the exposed upper surface of the partition.

[0015] Optionally, a heat-resistant groove opening from the upper surface of the protective layer is provided directly above the opening of the cavity, the heat-resistant groove is located on both sides of the main temperature measuring element along the Y direction, and the size of the heat-resistant groove along the X direction is not less than the size of the heating element along the X direction.

[0016] Optionally, the heat-resisting groove is further provided with end portions at both ends along the X direction, the end portions extend in a direction close to the heating element, and the end portions are spaced a preset distance from a center line of the heating element perpendicular to the Y direction.

[0017] Optionally, at least one auxiliary temperature measuring element is provided on both sides of the main temperature measuring element along the Y direction and is spaced apart from the main temperature measuring element by a preset distance.

[0018] Optionally, the auxiliary temperature measuring element includes a first portion and a second portion located on both sides of the main temperature measuring element along the Y direction, and the first portion and the second portion are symmetrical about a center line of the cavity perpendicular to the Y direction.

[0019] Optionally, a plurality of the auxiliary temperature measuring elements are provided in the thermal flow sensor, and the hot end and the cold end of the first part farthest from the center line of the cavity perpendicular to the Y direction are respectively located directly above the cavity and the substrate, and the hot end and the cold end of the second part farthest from the center line of the cavity perpendicular to the Y direction are respectively located directly above the cavity and the substrate.

[0020] Optionally, the auxiliary temperature measuring element comprises a plurality of thermocouples arranged at intervals along the X direction, and the plurality of thermocouples in the auxiliary temperature measuring element are connected in series to form a thermopile.

[0021] Optionally, a heat-resistant groove opening from the upper surface of the protective layer is further provided between the main temperature measuring element and the auxiliary temperature measuring element, and the heat-resistant groove is spaced apart from the main temperature measuring element and the auxiliary temperature measuring element by a preset distance, respectively. The size of the heat-resistant groove along the X direction is not smaller than the size of the main temperature measuring element and the auxiliary temperature measuring element and is smaller than the size of the cavity.

[0022] Optionally, a third soldering pad is further provided in the thermal flow sensor, and two ends of the auxiliary temperature measuring element are electrically connected to the third soldering pad respectively.

[0023] The present invention also provides a method for preparing a thermal flow sensor, comprising the following steps:

[0024] Providing a substrate, forming a partition with a preset thickness on the upper surface of the substrate, and defining a functional area on the upper surface of the partition;

[0025] A measuring structure is formed on the upper surface of the partition, the measuring structure comprising a temperature-sensitive resistor, a main temperature measuring element, a heating element, and an isolation layer between the heating element and the main temperature measuring element, the main temperature measuring element is located above the functional area and is symmetrical about a center line of the functional area perpendicular to the Y direction, the dimensions of the main temperature measuring element in the X direction and the Y direction are both smaller than the dimensions of the functional area, the heating element is located above the functional area and is symmetrical about a center line of the functional area perpendicular to the Y direction, the dimension of the heating element in the X direction is not smaller than the dimension of the main temperature measuring element and is not larger than the dimension of the functional area, the dimension of the heating element in the Y direction is smaller than the dimension of the main temperature measuring element, the temperature-sensitive resistor is located above the substrate on both sides of the main temperature measuring element along the Y direction, and the X direction and the Y direction are perpendicular to each other;

[0026] forming a protective layer covering the exposed upper surface of the measurement structure;

[0027] Forming a first pad, a second pad and an output pad, wherein the first pad is electrically connected to both ends of the temperature-sensitive resistor, the second pad is electrically connected to both ends of the heating element, and the output pad is electrically connected to both ends of the main temperature measuring element;

[0028] A cavity penetrating the substrate is formed directly below the functional area, and the size and shape of the cavity are the same as those of the functional area.

[0029] As described above, the thermal flow sensor and preparation method thereof of the present invention improves the temperature measuring structure in the sensor, and sets the main temperature measuring element and the heating element separated by the isolation layer just above the cavity, and the main temperature measuring element and the heating element are symmetrical about the center line of the cavity perpendicular to the Y direction, so that when the fluid flow rate in the Y direction of the sensor is zero, the temperature distribution of the cold end and the hot end of the main temperature measuring element along the Y direction is the same, which avoids the influence of the thermal radiation of the external environment on the measurement of the fluid flow rate in a medium and high temperature environment, improves the measurement accuracy of the sensor, and adopts one main temperature measuring element to measure the temperature difference, reduces the number of temperature measuring elements, simplifies the structure of the sensor, and sets at least one auxiliary temperature measuring element on both sides of the main temperature measuring element along the Y direction. The temperature measuring element is provided in the form of a temperature sensor, and the auxiliary temperature measuring elements are symmetrically distributed about the center line of the cavity perpendicular to the Y direction, so that the sensor can realize multi-range flow measurement, reduce the number of the temperature measuring elements, and then reduce the number of temperature difference signal output ports in the sensor, reduce the manufacturing cost, reduce the size of the sensor, and effectively simplify the use method, simplify the back-end signal processing steps, and can also be applied to application scenarios with limited number of temperature measuring elements, and the application scenarios are more abundant and flexible; by forming the heat-resistant groove in the laminated structure composed of the partition, the isolation layer and the protective layer, the heat loss of the heating element is reduced, the measurement accuracy is further improved, the power consumption of the heating element is reduced, and then the power consumption of the device is reduced, the performance of the sensor is improved, and it has a high industrial utilization value. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Shown is a schematic structural diagram of the thermal flow sensor of the present invention.

[0031] Figure 2 Display as Figure 1 Schematic diagram of the cross-sectional structure of a medium-heat flow sensor.

[0032] Figure 3 Display as Figure 1 A structural schematic diagram of a thermal flow sensor with a heat-resistant groove arranged therein.

[0033] Figure 4 Display as Figure 3 Schematic diagram of the cross-sectional structure of a medium-heat flow sensor.

[0034] Figure 5 Display as Figure 3 Another schematic diagram of the structure of a medium-heat flow sensor.

[0035] Figure 6 Display as Figure 1 Schematic diagram of the three-dimensional structure of a thermal flow sensor with auxiliary temperature measuring elements arranged on both sides of the main temperature measuring element.

[0036] Figure 7 Display as Figure 6 Schematic diagram of the partial structure of the medium-heat flow sensor.

[0037] Figure 8 Display as Figure 6 Schematic diagram of the structure of a medium-heat flow sensor.

[0038] Fig. 9 Display as Figure 6 Schematic diagram of the cross-sectional structure of a medium-heat flow sensor.

[0039] Fig.10 Display as Figure 6 Schematic diagram of the structure of a thermal flow sensor with a heat-resistant groove.

[0040] Fig.11 Display as Fig.10 Schematic diagram of the cross-sectional structure of a medium-heat flow sensor.

[0041] Fig.12 It is a schematic diagram showing the cross-sectional structure after forming a partition in the preparation method of the thermal flow sensor of the present invention.

[0042] Fig.13 It shows a schematic diagram of a cross-sectional structure after forming a temperature measuring structure in the preparation method of the thermal flow sensor of the present invention.

[0043] Fig.14 Another schematic diagram of a cross-sectional structure after forming a temperature measuring structure in the preparation method of the thermal flow sensor of the present invention is shown.

[0044] Fig.15 It shows a schematic diagram of a cross-sectional structure after forming a protective layer in the preparation method of the thermal flow sensor of the present invention.

[0045] Fig.16 Another schematic diagram of the cross-sectional structure after forming a protective layer in the preparation method of the thermal flow sensor of the present invention is shown.

[0046] Description of Figure Numbers

[0047] 1 substrate

[0048] 11 Cavity

[0049] 2 partitions

[0050] 3 Measurement structure

[0051] 31 Thermistor

[0052] 32 Main temperature measuring element

[0053] 321 temperature measuring element

[0054] 33 Heating elements

[0055] 34 Isolation Layer

[0056] 4 protective layers

[0057] 41 heat-resistant groove

[0058] 5First pad

[0059] 51 Second pad

[0060] 52 output pads

[0061] 53 Third pad DETAILED DESCRIPTION

[0062] 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.

[0063] See also Figures 1 to 16 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.

[0064] Embodiment 1

[0065] This embodiment provides a thermal flow sensor, such as Figure 1 and Figure 2As shown, they are respectively a schematic diagram of the structure of the thermal flow sensor and a schematic diagram of the cross-sectional structure of the thermal flow sensor, comprising a substrate 1, a partition 2, a measuring structure 3, a protective layer 4, a first pad 5, a second pad 51 and an output pad 52, wherein the substrate 1 is provided with a cavity 11 penetrating the substrate 1; the partition 2 is located on the upper surface of the substrate 1 and above the opening of the cavity 11; the measuring structure 3 is located on the upper surface of the partition 2, the measuring structure 3 comprises a temperature-sensitive resistor 31, a main temperature measuring element 32, a heating element 33 and an isolation layer 34 located between the heating element 33 and the main temperature measuring element 32, the main temperature measuring element 32 is located above the opening of the cavity 11 and is symmetrical about the center line of the cavity 11 perpendicular to the Y direction, and the dimensions of the main temperature measuring element 32 in the X direction and the Y direction are both smaller than the The size of the opening of the cavity 11, the heating element 33 is located above the opening of the cavity 11 and is symmetrical about the center line of the cavity 11 perpendicular to the Y direction, the size of the heating element 33 in the X direction is not less than the size of the main temperature measuring element 32 and not greater than the size of the opening of the cavity 11, the size of the heating element 33 in the Y direction is smaller than the size of the main temperature measuring element 32, the temperature-sensitive resistor 31 is located above the substrate 1 on both sides of the main temperature measuring element 32 along the Y direction, and the X direction is perpendicular to the Y direction; the protective layer 4 covers the exposed upper surface of the measuring structure 3; the first pads 5 are electrically connected to the two ends of the temperature-sensitive resistor 31, the second pads 51 are electrically connected to the two ends of the heating element 33, and the output pads 52 are electrically connected to the two ends of the main temperature measuring element 32.

[0066] Specifically, under the condition of ensuring the performance of the sensor, the thickness, size and shape of the substrate 1 can be selected according to actual conditions and are not limited here.

[0067] Specifically, under the condition of ensuring the performance of the sensor, the opening size, position and shape of the cavity 11 can be selected according to actual conditions, and no limitation is given here. In this embodiment, the shape of the opening of the cavity 11 is a rectangle.

[0068] Specifically, during the operation of the sensor, the cavity 11 is configured to reduce the excessive loss of heat generated by the heating element 33 through conduction through the substrate 1, thereby reducing the loss of heat generated by the heating element 33, and reducing the power consumption of the heating element 33 while ensuring the accuracy of the sensor.

[0069] Specifically, under the condition of ensuring the performance of the sensor, the thickness of the partition 1 can be selected according to actual conditions and is not limited here.

[0070] Specifically, the thermistor 31 located above the partition 2 on both sides of the cavity 11 along the Y direction is used to measure the ambient temperature and temperature difference upstream and downstream of the sensor. The electrical performance parameters and dimensions of the thermistors 31 on both sides of the cavity 11 along the Y direction are the same, and the distances between the thermistors 31 on both sides of the cavity 11 along the Y direction and the edge of the area directly above the cavity 11 are the same.

[0071] As an example, the main temperature measuring element 32 includes a plurality of thermocouples (not shown) arranged at intervals along the X direction, and the plurality of thermocouples in the main temperature measuring element 32 are connected in series to form a thermopile.

[0072] Specifically, under the condition of ensuring the performance of the sensor, the number of the thermocouples in the main temperature measuring element 32 and the size of the main temperature measuring element 32 can be selected according to the actual situation, and are not limited here. The size here refers to the size of the main temperature measuring element 32 in the XY plane.

[0073] Specifically, the thermocouple is composed of two conductive materials with different Seebeck coefficients. Due to the different Seebeck coefficients of the conductive materials, when a temperature difference is generated between the hot end and the cold end of the thermocouple, a potential difference is generated between the cold end and the hot end of the thermocouple, and the greater the difference in Seebeck coefficients of the conductive materials constituting the thermocouple, the greater the potential difference between the cold end and the hot end of the thermocouple.

[0074] As an example, the thermocouple is provided with two thermocouple arms (not shown) spaced apart along the X direction, and the thermocouple arms include any two of a P-type arm extending along the Y direction, an N-type arm extending along the Y direction, and a metal arm extending along the Y direction, and the thermocouple is also provided with a connecting portion (not shown) for connecting two different thermocouple arms. That is, the thermocouple arms in the thermocouple can be a combination of a P-type arm and a metal arm, a combination of an N-type arm and a metal arm, or a combination of a P-type arm and an N-type arm.

[0075] Specifically, when the thermocouple is composed of an N-type arm and a metal arm, the material of the N-type arm includes N-type polysilicon or other suitable semiconductor materials whose Seebeck coefficient differs from that of the metal arm, and the material of the metal arm includes aluminum or other suitable metal materials whose Seebeck coefficient differs from that of the N-type arm; when the thermocouple is composed of a P-type arm and a metal arm, the material of the P-type arm includes P-type polysilicon or other suitable semiconductor materials whose Seebeck coefficient differs from that of the metal arm, and the material of the metal arm includes aluminum or other suitable metal materials whose Seebeck coefficient differs from that of the P-type arm; when the thermocouple is composed of an N-type arm and a P-type arm, the material of the N-type arm includes N-type polysilicon or other suitable semiconductor materials whose Seebeck coefficient differs from that of the P-type arm, and the material of the P-type arm includes P-type polysilicon or other suitable semiconductor materials whose Seebeck coefficient differs from that of the N-type arm.

[0076] Specifically, under the condition of ensuring the performance of the sensor, the size and thickness of each thermocouple arm in the thermocouple can be selected according to actual conditions and are not limited here.

[0077] Specifically, under the condition of ensuring the performance of the sensor, the distance between the two thermocouple arms in the thermocouple can be selected according to actual conditions and is not limited here.

[0078] Specifically, the thermocouple arm of the main temperature measuring element 32 is parallel to the Y direction, the hot end and the cold end of the thermocouple are located at both ends of the thermocouple along the Y direction, and in the Y direction, the distances between the hot end and the cold end of the thermocouple and the edge of the cavity 11 are the same, and in the X direction, the distances between the temperature measuring element 33 and the edge of the cavity 11 are the same.

[0079] Specifically, the connecting portion is used to electrically connect two adjacent thermocouples and two thermocouple arms in the thermocouple.

[0080] Specifically, while ensuring the performance of the sensor, the shape and size of the connecting portion can be selected according to actual conditions and are not limited here.

[0081] Specifically, the heating element 33 includes at least one heating resistor, and the heating element 33 is symmetrically arranged with the center line of the cavity 11 perpendicular to the Y direction as the symmetry axis, and the number of heating resistors in the heating element 33 can be selected according to actual conditions while ensuring the performance of the sensor, and is not limited here. In this embodiment, the heating element 33 is two heating resistors with the center line of the cavity 11 perpendicular to the Y direction as the symmetry axis, the two heating resistors are at a preset distance from the center line and are evenly distributed on both sides of the center line, and the shape of the heating resistor is a long strip extending along the X direction.

[0082] Specifically, the material of the heating element 33 includes polysilicon, platinum, nickel, copper, iron, iron-nickel alloy or other thermal resistance conductive materials that are compatible with MEMS technology.

[0083] Specifically, while ensuring the performance of the sensor, the size and thickness of the heating element 33 can be selected according to actual conditions and are not limited here.

[0084] Specifically, the material of the isolation layer 34 includes silicon oxide, silicon nitride, silicon oxynitride or other suitable dielectric materials.

[0085] Specifically, under the condition of ensuring the performance of the sensor, the thickness of the isolation layer 34 can be selected according to actual conditions and is not limited here.

[0086] As an example, the main temperature measuring element 32 is located directly above the heating element 33 , the heating element 33 is located on the upper surface of the partition 2 , and the isolation layer 34 covers the exposed surface of the heating element 33 and the exposed upper surface of the partition 2 .

[0087] As an example, the heating element 33 is located directly above the main temperature measuring element 32 , the main temperature measuring element 32 is located on the upper surface of the partition 2 , and the isolation layer 34 covers the exposed surface of the main temperature measuring element 32 and the exposed upper surface of the partition 2 .

[0088] Specifically, the material of the protection layer 4 includes silicon oxide, silicon nitride, silicon oxynitride or other suitable dielectric materials.

[0089] Specifically, under the condition of ensuring the performance of the sensor, the thickness of the protective layer 4 can be selected according to actual conditions and is not limited here.

[0090] Specifically, by arranging the measuring structure 3 between the protective layer 4 and the partition 2, and the main temperature measuring element 32 and the heating element 33 are both located between the partition 2 and the protective layer 4 directly above the cavity 11, the cold and hot ends of the thermocouple in the main temperature measuring element 32 maintain the same thermal capacity and thermal conductivity, so as to achieve the same good thermal insulation performance between the cold and hot ends of the thermocouple and the substrate 1.

[0091] Specifically, in order to ensure the performance of the sensor, the thickness of the laminated structure composed of the partition 2, the measuring structure 3 and the protective layer 4 needs to be as thin as possible, and the laminated structure also needs to have good mechanical stability.

[0092] As an example, Figure 3 and Figure 4 As shown, they are a structural schematic diagram of the thermal flow sensor provided with the heat-resistance groove 41 and Figure 3 Schematic diagram of the cross-sectional structure of the thermal flow sensor, a heat-resistant groove 41 opening from the upper surface of the protective layer 4 is provided directly above the opening of the cavity 11, and the heat-resistant groove 41 is located on both sides of the main temperature measuring element 32 along the Y direction, and the size of the heat-resistant groove 41 along the X direction is not less than the size of the heating element 33 along the X direction.

[0093] Specifically, the heat-resistance groove 41 is symmetrical about the center line of the cavity 11 perpendicular to the Y direction. Under the condition of ensuring the performance of the sensor, the distance between the heat-resistance groove 41 and the main temperature measuring element 32 can be selected according to actual conditions, and is not limited here; the opening size and shape of the heat-resistance groove 41 can be selected according to actual conditions, and are not limited here. In this embodiment, the heat-resistance groove 41 is parallel to the heating resistor in the adjacent heating element 33, and the opening shape of the heat-resistance groove 41 is rectangular.

[0094] Specifically, by setting the heat-resistant groove 41, the thermal conductivity between the cold end and the hot end of the main temperature measuring element 32 and the substrate 1 can be reduced, so that the heat exchange between the cold end and the hot end of the main temperature measuring element 32 and the substrate 1 is reduced, and the heat loss is reduced, thereby improving the efficiency of heat exchange when the heat in the laminated structure and the fluid move.

[0095] Specifically, the partition 2, the measuring structure 3 and the protective layer 4 form a laminated structure. Under the condition of ensuring that the heat loss of the sensor is small and the laminated structure has good mechanical stability, the heat-resistant groove 41 may or may not penetrate the laminated structure.

[0096] As an example, Figure 5As shown, it is a schematic diagram of the structure of the thermal flow sensor in which the end portion is provided in the heat-resistant groove 41. The heat-resistant groove 41 is also provided with an end portion at both ends along the X direction. The end portion extends in a direction close to the heating element 33, and the end portion is spaced a preset distance from the center line of the heating element 33 perpendicular to the Y direction.

[0097] Specifically, while ensuring the performance of the sensor, the distance between the end and the heating element 33 can be selected according to actual conditions, and is not limited here. In this embodiment, the distance between the end located on both sides of the heating element 33 along the Y direction and the heating element 33 is the same.

[0098] Specifically, in the X direction, the distances between the four ends and the two ends of the adjacent heating element 33 are the same, so as to ensure uniform thermal conductivity of the sensor.

[0099] Specifically, while ensuring the performance of the sensor, the angle between the end and the portion of the heat-resistant groove 41 parallel to the heating element 33 can be selected according to actual conditions, and is not limited here. In this embodiment, the angle between the end and the portion of the heat-resistant groove 41 parallel to the heating element 33 is 90°.

[0100] As an example, Figure 6 , Figure 7 , Figure 8 and Fig. 9 As shown in the figure, they are respectively a three-dimensional structural schematic diagram of a thermal flow sensor in which the auxiliary temperature measuring elements 321 are arranged on both sides of the main temperature measuring element 32 along the Y direction, Figure 6 Partial structural diagram of the thermal flow sensor described in Figure 6 The structural diagram of the thermal flow sensor described in Figure 6 Schematic diagram of the cross-sectional structure of the thermal flow sensor, the main temperature measuring element 32 is further provided with at least one auxiliary temperature measuring element 321 spaced apart from the main temperature measuring element 32 by a preset distance on both sides along the Y direction.

[0101] As an example, the auxiliary temperature measuring element 321 includes a first portion and a second portion located on both sides of the main temperature measuring element 32 along the Y direction, and the first portion and the second portion are symmetrical about a center line of the cavity 11 perpendicular to the Y direction.

[0102] Specifically, under the condition of ensuring the performance of the device, the number of the auxiliary temperature measuring elements 321 can be selected according to the actual situation, and is not limited here. In this embodiment, only one auxiliary temperature measuring element 321 is provided in the thermal flow sensor.

[0103] Specifically, when there are multiple auxiliary temperature measuring elements 321, the first parts of all the auxiliary temperature measuring elements 321 are located on the same side of the main temperature measuring element 32, and the second parts of all the auxiliary temperature measuring elements 321 are located on the same side of the main temperature measuring element 32. The first parts are arranged at intervals along the Y direction, and the distance between the hot end of the first part and the second part of each auxiliary temperature measuring element 321 and the main temperature measuring element 32 is greater than the distance between the cold end and the main temperature measuring element 32.

[0104] Specifically, while ensuring the performance of the sensor, the distance between two adjacent first parts can be selected according to actual conditions and is not limited here.

[0105] As an example, the thermal flow sensor is provided with a plurality of auxiliary temperature measuring elements 321, the hot end and the cold end of the first part farthest from the center line of the cavity 11 perpendicular to the Y direction are respectively located directly above the cavity 11 and the substrate 1, and the hot end and the cold end of the second part farthest from the center line of the cavity 11 perpendicular to the Y direction are respectively located directly above the cavity 11 and the substrate 1.

[0106] Specifically, when a plurality of auxiliary temperature measuring elements 321 are provided on both sides of the main temperature measuring element 32 along the Y direction, the size of the auxiliary temperature measuring element 321 along the X direction may be the same as or different from the size of the main temperature measuring element 32 along the X direction. Under the condition of ensuring the performance of the sensor, the size of the first part along the Y direction in each of the auxiliary temperature measuring elements 321 may be selected according to actual conditions, and is not limited here. In this embodiment, the size of the first part along the Y direction and the size along the X direction in each of the auxiliary temperature measuring elements 321 are the same.

[0107] As an example, the auxiliary temperature measuring element 321 includes a plurality of thermocouples arranged at intervals along the X direction, and the plurality of thermocouples in the auxiliary temperature measuring element 321 are connected in series to form a thermopile.

[0108] Specifically, the first part and the second part of each of the auxiliary temperature measuring elements 321 are composed of the thermocouples that are the same in number and size and are symmetrical about the center line of the cavity 11 perpendicular to the Y direction.

[0109] Specifically, while ensuring the performance of the sensor, the number of the thermocouples in the auxiliary temperature measuring element 321 can be selected according to actual conditions, and is not limited here; the size of the thermocouple along the Y direction can be selected according to actual conditions, and is not limited here; the type of the electric couple arm in the thermocouple can be selected according to actual conditions, and is not limited here. In this embodiment, the type of the electric couple arm in each of the auxiliary temperature measuring elements 321 is the same as the type of the electric couple arm in the main temperature measuring element 32.

[0110] Specifically, the two adjacent thermocouples in the auxiliary temperature measuring element 321 and the thermocouple arms in the thermocouple are electrically connected to an electrical connector (not shown). While ensuring the performance of the sensor, the material, shape and size of the electrical connector can be selected according to actual conditions and are not limited here. In this embodiment, the material, shape and size of the electrical connector are the same as those of the connecting portion.

[0111] As an example, Fig.10 and Fig.11 As shown, they are Figure 6 The thermal flow sensor described in the embodiment is provided with the heat-resistance groove 41 and Fig.10 A schematic diagram of the cross-sectional structure of the thermal flow sensor described in the figure, wherein a heat-resistant groove 41 opening from the upper surface of the protective layer 4 is further provided between the main temperature measuring element 32 and the auxiliary temperature measuring element 321, and the heat-resistant groove 41 is spaced apart from the main temperature measuring element 32 and the auxiliary temperature measuring element 321 by a preset distance, respectively, and the size of the heat-resistant groove 41 along the X direction is not less than the size of the main temperature measuring element 32 and the auxiliary temperature measuring element 321 and is smaller than the size of the cavity 11.

[0112] Specifically, when the main temperature measuring element 32 is provided with a plurality of auxiliary temperature measuring elements 321 on both sides along the Y direction, and the heat-resistant groove 41 is provided above the cavity 11, the heat-resistant groove 41 is symmetrical about the center line of the cavity 11 perpendicular to the Y direction. While ensuring the performance of the sensor, the number of the heat-resistant grooves 41 can be selected according to actual conditions and is no longer restricted here.

[0113] Specifically, when a plurality of auxiliary temperature measuring elements 321 are provided on both sides of the main temperature measuring element 32 along the Y direction, the thermal conductivity between the center temperature of the device and the substrate 1 is reduced through the provision of the heat-resistant groove 41, so that the heat exchange between the temperature measuring end of the temperature measuring element and the substrate 1 is reduced, and the heat loss is reduced, thereby improving the efficiency of heat exchange between the heat in the laminated structure composed of the partition 2, the isolation layer 34 and the protective layer 4 and the moving fluid. By utilizing the improvement of the heat exchange efficiency, the potential difference generated by the temperature measuring element can be adjusted, and then the flow test range of the device can be adjusted.

[0114] Specifically, when no fluid passes through, an electric load is applied to the heating element 33 to generate heat, and the temperature of the temperature measuring end (cold end and hot end) of the main temperature measuring element 32 is the same, and no potential difference is generated; the temperature of the temperature measuring end of the auxiliary temperature measuring element 321 on both sides of the main temperature measuring element 32 along the Y direction is the same, and the same potential difference is generated. When fluid passes through, the temperature of the temperature measuring end of the main temperature measuring element 32 (i.e., the upstream and downstream of the sensor) is no longer the same, and a potential difference is generated; the temperature measuring ends of the first part and the second part symmetrical about the center line of the heating element 33 perpendicular to the Y direction have different temperature differences, resulting in different potential differences, and the purpose of flow test can be achieved based on the potential difference signal.

[0115] Specifically, since the measuring range of the sensor is related to the distance between the temperature measuring end of the temperature measuring element and the heating element 33, the greater the distance between the temperature measuring end of the temperature measuring element and the heating element 33, the smaller the measuring range of the temperature measuring element is. By respectively adjusting the distance from the temperature measuring end of the main temperature measuring element 32 and the auxiliary temperature measuring element 321 located on both sides of the main temperature measuring element 32 along the Y direction to the heating element 33, the measuring range of the sensor can be adjusted.

[0116] Specifically, since the distances between the temperature measuring ends (cold end and hot end) of the main temperature measuring element 32 and the auxiliary temperature measuring element 321 and the heating element 33 are different, the measurement of fluid flow rates of different ranges can be achieved. The temperature measuring end of the main temperature measuring element 32 is closer to the heating element 33, so that a larger range of fluid flow can be measured. The two auxiliary temperature measuring elements 321 located on both sides of the main temperature measuring element 32 along the Y direction and symmetrically distributed are farther away from the heating element 33, so that a smaller range of fluid flow can be measured.

[0117] As an example, the thermal flow sensor is further provided with a third pad 53, and both ends of the auxiliary temperature measuring element 321 are electrically connected to the third pad 53. That is, both ends of the first part and the second part are electrically connected to different third pads 53, respectively.

[0118] Specifically, when a plurality of the auxiliary temperature measuring elements 321 are provided in the sensor, both ends of the first portion and the second portion of each of the auxiliary temperature measuring elements 321 are electrically connected to different third pads 53 , respectively.

[0119] Specifically, the material of the first pad 5 includes titanium, titanium nitride, silver, gold, copper, tungsten, nickel, platinum, aluminum or other suitable conductive materials; the material of the second pad 51 includes titanium, titanium nitride, silver, gold, copper, tungsten, nickel, platinum, aluminum or other suitable conductive materials; the material of the output pad 52 includes; the material of the third pad 53 includes titanium, titanium nitride, silver, gold, copper, tungsten, nickel, platinum, aluminum or other suitable conductive materials.

[0120] Specifically, while ensuring the performance of the sensor, the size, shape and position of the first pad 5 can be selected according to actual conditions and are no longer restricted here; the size, shape and position of the second pad 51 can be selected according to actual conditions and are no longer restricted here; the size, shape and position of the output pad 52 can be selected according to actual conditions and are no longer restricted here; the size, shape and position of the third pad 53 can be selected according to actual conditions and are no longer restricted here.

[0121] Specifically, the first pad 5 , the second pad 51 , the third pad 53 and the output pad 52 are electrically connected to corresponding device structures through conductive wires, respectively.

[0122] Specifically, by improving the temperature measuring structure 3 of the thermal flow sensor, the isolation layer 34 is used to separate the main temperature measuring element 32 and the heating element 33. At the same time, the main temperature measuring element 32 and the heating element 33 are symmetrical about the center line of the cavity 11 perpendicular to the Y direction. The upstream and downstream temperatures of the device are measured only by a thermopile constituting the main temperature measuring element 32, which relatively simplifies the structure of the device, reduces the size of the device, and also reduces the number of output ports in the device.

[0123] Specifically, since the main temperature measuring element 32 and the heating element 33 are symmetrical about the center line of the cavity 11 perpendicular to the Y direction, when the fluid flow velocity in the Y direction of the sensor is zero, the temperature distribution of the cold end and the hot end of the main temperature measuring element 32 are the same, so that when no fluid flow occurs, the potential difference generated by the main temperature measuring element 32 receiving unnecessary external radiation remains zero and no response is generated. When fluid flow occurs above the sensor along the Y direction to take away heat, a temperature difference is generated between the cold end and the hot end of the main temperature measuring element 32, and the main temperature measuring element 32 responds, thereby improving the accuracy of the sensor, avoiding the heat in the medium and high temperature environment from radiating to the surface of the device and generating a temperature difference signal of non-fluid flow, thereby avoiding the interference of external thermal radiation, reducing the number of temperature measuring elements, simplifying the structure of the sensor, and improving the measurement accuracy of the sensor.

[0124] Specifically, by setting the auxiliary temperature measuring element 321, utilizing the special arrangement of a small number of the auxiliary temperature measuring elements 321, and combining with the main temperature measuring element 32, accurate measurement of a variety of flow ranges in different complex environments can be achieved, effectively simplifying the usage method and reducing costs. At the same time, it can also be suitable for application scenarios that limit the number of temperature measuring elements, and the application scenarios are more abundant and flexible.

[0125] Specifically, by providing the heat-resistant groove 41 in the laminated structure composed of the partition 2, the isolation layer 34 and the protective layer 4, the heat loss generated by the heating element 33 is reduced, the measurement accuracy is further improved, the power consumption of the heating element 33 is reduced, and then the power consumption of the device is reduced, thereby improving the performance of the sensor.

[0126] The thermal flow sensor of this embodiment improves the structure of the measuring structure 3, places the main temperature measuring element 32 and the heating element 33 directly above the cavity 11, and uses the isolation layer 34 to isolate the main temperature measuring element 32 and the heating element 33, and the main temperature measuring element 32 and the heating element 33 are symmetrical about the center line of the cavity 11 perpendicular to the Y direction, so that when the fluid flow rate in the Y direction of the sensor is zero, the temperature distribution of the cold end and the hot end of the main temperature measuring element 32 is the same, so that the main temperature measuring element 32 does not respond, and only when the fluid flow rate in the Y direction of the sensor is not zero and takes away the heat generated in the sensor, a temperature difference is generated between the cold end and the hot end of the main temperature measuring element 32, and then a temperature difference signal response is generated, thereby avoiding the heat in the environment radiating to the device surface in a medium or high temperature environment, causing a temperature difference between the cold end and the hot end of the temperature measuring element, thereby generating a non-fluid flow temperature difference signal, which affects the measurement. The invention has the advantages of high precision and only one main temperature measuring element 32 is needed to measure the fluid flow rate, which reduces the number of temperature measuring elements, simplifies the structure of the sensor, and improves the measurement precision of the sensor; by arranging the auxiliary temperature measuring elements 321 on both sides of the main temperature measuring element 32 along the Y direction, utilizing the special arrangement of fewer auxiliary temperature measuring elements 321, and combining the auxiliary temperature measuring elements 321 with the main temperature measuring element 32, it is possible to achieve accurate measurement of various flow ranges under different complex environments, effectively simplify the use method, reduce costs, and also be applicable to application scenarios where the number of temperature measuring elements is limited, and the application scenarios are more abundant and flexible; by arranging the heat-resistant groove 41 in the laminated structure composed of the partition 2, the isolation layer 34 and the protective layer 4, the heat loss of the heating element 33 is reduced, the measurement precision is further improved, the power consumption of the heating element 33 is reduced, and then the power consumption of the device is reduced, thereby improving the performance of the sensor.

[0127] Embodiment 2

[0128] This embodiment provides a method for preparing a thermal flow sensor, comprising the following steps:

[0129] S1: providing a substrate, forming a partition with a preset thickness on the upper surface of the substrate, and defining a functional area on the upper surface of the partition;

[0130] S2: forming a measurement structure on the upper surface of the partition, the measurement structure comprising a temperature-sensitive resistor, a main temperature measuring element, a heating element and an isolation layer between the heating element and the main temperature measuring element, the main temperature measuring element is located above the functional area and is symmetrical about the center line of the functional area perpendicular to the Y direction, the dimensions of the main temperature measuring element in the X direction and the Y direction are both smaller than the dimensions of the functional area, the heating element is located above the functional area and is symmetrical about the center line of the functional area perpendicular to the Y direction, the dimension of the heating element in the X direction is not smaller than the dimension of the main temperature measuring element and is not larger than the dimension of the functional area, the dimension of the heating element in the Y direction is smaller than the dimension of the main temperature measuring element, the temperature-sensitive resistor is located above the substrate on both sides of the main temperature measuring element along the Y direction, and the X direction and the Y direction are perpendicular to each other;

[0131] S3: forming a protective layer covering the exposed upper surface of the measurement structure;

[0132] S4: sequentially forming a first pad, a second pad and an output pad, wherein the first pad is electrically connected to both ends of the temperature-sensitive resistor, the second pad is electrically connected to both ends of the heating element, and the output pad is electrically connected to both ends of the main temperature measuring element;

[0133] S5: forming a cavity penetrating the substrate directly below the functional area, wherein the size and shape of the cavity are the same as those of the functional area.

[0134] See also Figure 12 to Figure 14 , performing the step S1 and the step S2: providing a substrate 1, forming a partition 2 of a preset thickness on the upper surface of the substrate 1, and defining a functional area (not shown) on the upper surface of the partition 2; forming a measurement structure 3 on the upper surface of the partition 2, the measurement structure 3 comprising a temperature-sensitive resistor 31, a main temperature measuring element 32, a heating element 33 and an isolation layer 34 located between the heating element 33 and the main temperature measuring element 32, the main temperature measuring element 32 being located above the functional area and symmetrical about a center line of the functional area perpendicular to the Y direction, the main temperature measuring element 32 being located above the functional area and symmetrical about a center line of the functional area perpendicular to the Y direction, The dimensions of the temperature element 32 in the X direction and the Y direction are both smaller than the dimension of the functional area. The heating element 33 is located above the functional area and is symmetrical about the center line of the functional area perpendicular to the Y direction. The dimension of the heating element 33 in the X direction is not smaller than the dimension of the main temperature measuring element 32 and not larger than the dimension of the functional area. The dimension of the heating element 33 in the Y direction is smaller than the dimension of the main temperature measuring element 32. The thermistors 31 are located above the substrate 1 on both sides of the main temperature measuring element 33 along the Y direction. The X direction and the Y direction are perpendicular to each other.

[0135] Specifically, the substrate 1 is made of silicon, glass or other suitable materials.

[0136] Specifically, Fig.12 , which is a schematic diagram of the cross-sectional structure after the partition 2 is formed. The method of forming the partition 2 includes chemical vapor deposition, physical vapor deposition, thermal oxidation or other suitable methods.

[0137] Specifically, the material of the partition 2 includes silicon oxide, silicon nitride, silicon oxynitride or other suitable dielectric materials.

[0138] Specifically, under the condition of ensuring the performance of the sensor, the size, position and shape of the functional area on the upper surface of the substrate 1 can be selected according to actual conditions, and are not limited here. In this embodiment, the functional area is rectangular in shape.

[0139] Specifically, the material of the thermistor 31 includes one of metal, ceramic, single crystal semiconductor, temperature-sensitive glass and temperature-sensitive plastic, or other suitable temperature-sensitive materials. The method of forming the thermistor 31 is a commonly used method for forming a thermistor in a sensor, which will not be repeated here.

[0140] Specifically, Fig.13 and Fig.14 As shown, they are respectively a schematic diagram of a cross-sectional structure after the temperature measuring structure 3 is formed and another schematic diagram of a cross-sectional structure after the temperature measuring structure 3 is formed. The heating element 33 can be located directly above the main temperature measuring element 32, or directly below the main temperature measuring element 32, that is, the main temperature measuring element 32 is located on the upper surface of the partition 2, the isolation layer 34 covers the exposed surface of the main temperature measuring element 32 and the exposed upper surface of the partition 2, and the heating element 33 is located on the upper surface of the isolation layer 34 directly above the temperature measuring element 32, or the heating element 32 is located on the upper surface of the partition 2, the isolation layer 34 covers the exposed surface of the heating element 33 and the exposed upper surface of the partition 2, and the main temperature measuring element 32 is located on the upper surface of the isolation layer 34 directly above the heating element 33.

[0141] Specifically, the thermistor 31 is used to measure the ambient temperature of the environment in which the sensor is located. The thermistor 31 can be located on the upper surface of the partition 2 or on the upper surface of the isolation layer 34 .

[0142] Specifically, in the process of forming the temperature measuring structure 3, after the temperature-sensitive resistor 31 and the heating element 33 are formed on the upper surface of the partition 2, the isolation layer 34 and the main temperature measuring element 32 are formed in sequence; after the heating element 33 is formed on the upper surface of the partition 2, the isolation layer 34 and the main temperature measuring element 32 and the temperature-sensitive resistor 31 located on the upper surface of the isolation layer 34 are formed; after the temperature-sensitive resistor 31 and the main temperature measuring element 32 are formed on the upper surface of the partition 2, the isolation layer 34 and the heating element 33 are formed in sequence; or after the main temperature measuring element 32 is formed on the upper surface of the partition 2, the isolation layer 34 and the heating element 33 and the temperature-sensitive resistor 31 located on the upper surface of the isolation layer 34 are formed.

[0143] Specifically, the method for forming the heating element 33 is a conventional method for forming a thermal resistor, which will not be described in detail here.

[0144] Specifically, the main temperature measuring element 32 includes a plurality of thermocouples arranged at intervals along the X direction, and the plurality of thermocouples in the main temperature measuring element 32 are connected in series to form a thermopile; the thermocouple is provided with two electric couple arms, and the electric couple arms of the thermocouple include any two of a P-type arm extending along the Y direction, an N-type arm extending along the Y direction, and a metal arm extending along the Y direction.

[0145] Specifically, the method of forming the isolation layer 34 includes chemical vapor deposition, physical vapor deposition or other suitable methods; the method of forming the main temperature measuring element 32 includes chemical vapor deposition, physical vapor deposition, atomic layer deposition, magnetron sputtering, metal compound vapor deposition, molecular beam epitaxy, atomic vapor deposition or other suitable methods.

[0146] Specifically, the main temperature measuring element 32 is also provided with a connecting portion for electrically connecting two adjacent thermocouples and electrically connecting the thermocouple arms in the thermocouple.

[0147] Specifically, the material of the connecting part includes titanium, titanium nitride, silver, gold, copper, tungsten, nickel, platinum, aluminum or other suitable conductive materials; the method of forming the connecting part includes chemical vapor deposition, physical vapor deposition, atomic layer deposition, magnetron sputtering, metal compound vapor deposition, molecular beam epitaxy, atomic vapor deposition or other suitable methods.

[0148] Specifically, the temperature measuring structure 3 is also formed with at least one auxiliary temperature measuring element 321 located on both sides of the main temperature measuring element 32 along the Y direction, the main temperature measuring element 32 and the auxiliary temperature measuring element 321 are located on the same horizontal plane, the auxiliary temperature measuring element 321 includes a first part and a second part, the first part and the second part are located on different sides of the main temperature measuring element 32 along the Y direction, and the first part and the second part are symmetrical about the center line of the functional area perpendicular to the Y direction.

[0149] Specifically, the auxiliary temperature measuring element 321 includes a plurality of thermocouples arranged at intervals along the X direction, and the plurality of thermocouples in the auxiliary temperature measuring element 321 are connected in series to form a thermopile, and the electric couple arms of the thermocouples in the auxiliary temperature measuring element 321 may be of the same type as or different from the electric couple arms in the main temperature measuring element 32. In this embodiment, the electric couple arms of the thermocouples in the auxiliary temperature measuring element 321 are of the same type as the electric couple arms in the main temperature measuring element 32.

[0150] Please see again Figure 15 to Figure 16 , perform the steps S3, S4 and S5: form a protective layer 4 covering the exposed upper surface of the measuring structure 3; form a first pad 5, a second pad 51 and an output pad 52, the first pad 51 is electrically connected to the two ends of the temperature-sensitive resistor 31, the second pad 51 is electrically connected to the two ends of the heating element 33, and the output pad 52 is electrically connected to the two ends of the main temperature measuring element 32; and form a cavity 11 that passes through the substrate 1 directly below the functional area, and the size and shape of the cavity 11 are the same as those of the functional area.

[0151] Specifically, Fig.15 and Fig.16 The figures show a schematic diagram of a cross-sectional structure after the protective layer 4 is formed and another schematic diagram of a cross-sectional structure after the protective layer 4 is formed. The protective layer 4 is used to protect the temperature measuring structure 3 to prevent the temperature measuring structure 3 from being damaged by external force to ensure the performance of the sensor.

[0152] Specifically, the method of forming the protective layer 4 includes chemical vapor deposition, physical vapor deposition or other suitable methods.

[0153] Specifically, after forming the protective layer 4 and before forming the first solder pad 5, the second solder pad 51, and the output solder pad 52, it also includes a step of forming a heat-resistant groove 41 located on both sides of the heating element 33 along the Y direction and spaced a preset distance from the main temperature measuring element 32. The size of the heat-resistant groove 41 in the X direction is larger than the size of the main temperature measuring element 32 and is parallel to the heating element 33. The heat-resistant groove 41 is symmetrical about the center line of the functional area perpendicular to the Y direction. The heat-resistant groove 41 may penetrate the laminated structure formed by the partition 2, the isolation layer 34 and the protective layer 4, or may not penetrate the laminated structure.

[0154] Specifically, the heat-resisting groove 41 is further provided with ends at both ends along the X direction, the ends extend in a direction close to the heating element 33 , and the ends are spaced a preset distance from a center line of the heating element 33 perpendicular to the Y direction.

[0155] Specifically, when the auxiliary temperature measuring element 321 is provided in the sensor, the heat-resistant groove 41 can be located between the main temperature measuring element 32 and the auxiliary temperature measuring element 321, or can be located between two adjacent auxiliary temperature measuring elements 321 on the same side of the main temperature measuring element 32; when a plurality of auxiliary temperature measuring elements 321 are provided in the sensor, a plurality of heat-resistant grooves 41 located above the cavity 11 can also be formed on both sides of the main temperature measuring element 32 along the Y direction, and the heat-resistant grooves 41 are respectively spaced apart from the main temperature measuring element 32 and the auxiliary temperature measuring element 321 by a preset distance.

[0156] Specifically, the method for forming the first pad 5 includes chemical vapor deposition, physical vapor deposition, atomic layer deposition, magnetron sputtering, metal compound vapor deposition, molecular beam epitaxy, atomic vapor deposition or other suitable methods; the method for forming the second pad 51 includes chemical vapor deposition, physical vapor deposition, atomic layer deposition, magnetron sputtering, metal compound vapor deposition, molecular beam epitaxy, atomic vapor deposition or other suitable methods; the method for forming the output pad 52 includes chemical vapor deposition, physical vapor deposition, atomic layer deposition, magnetron sputtering, metal compound vapor deposition, molecular beam epitaxy, atomic vapor deposition or other suitable methods. In this embodiment, the first pad 5, the second pad 51 and the output pad 52 are formed simultaneously.

[0157] Specifically, when the auxiliary temperature measuring element 321 is formed in the sensor, a third welding pad 53 is also formed in the sensor, and the method of forming the third welding pad 53 includes chemical vapor deposition, physical vapor deposition, atomic layer deposition, magnetron sputtering, metal compound vapor deposition, molecular beam epitaxy, atomic vapor deposition or other suitable methods.

[0158] Specifically, a conductive lead is also formed in the sensor, and the conductive lead electrically connects the first pad 5 and the thermistor 31, the second pad 51 and the heating element 33, the output pad 52 and the main temperature measuring element 32, and when an auxiliary temperature measuring element is formed in the sensor, the conductive lead also electrically connects the third pad 53 and the auxiliary temperature measuring element 321.

[0159] Specifically, the conductive lead is made of the same material as the connecting portion, and a method for forming the conductive lead includes chemical vapor deposition, physical vapor deposition, atomic layer deposition, magnetron sputtering, metal compound vapor deposition, molecular beam epitaxy, atomic vapor deposition or other suitable methods.

[0160] Specifically, the method of forming the cavity 11 includes dry etching, wet etching or other suitable methods.

[0161] Specifically, by forming the main temperature measuring element 32 and the heating element 33 which are symmetrical about the center line of the cavity 11 perpendicular to the Y direction, the temperature distribution of the hot end and the cold end (the two ends along the Y direction) of the main temperature measuring element 32 is made the same, thereby avoiding the influence of external environmental radiation, and forming the auxiliary temperature measuring elements 321 on both sides of the main temperature measuring element 32, so as to realize multi-range flow measurement.

[0162] Specifically, by combining the main temperature measuring element 32 with the auxiliary temperature measuring element 321, fewer temperature measuring elements are used to meet the testing requirements of different flow ranges, reducing the number of temperature measuring elements, and then reducing the number of temperature difference signal output ports, thereby lowering the manufacturing cost, reducing the size of the sensor, and simplifying the back-end signal processing steps.

[0163] The preparation method of the thermal flow sensor of this embodiment forms the main temperature measuring element 32 and the heating element 33 symmetrically about the center line of the cavity 11 perpendicular to the Y direction, so that the temperature distribution of the hot end and the cold end of the main temperature measuring element 32 are the same, thereby avoiding the influence of external environmental radiation; by forming the auxiliary temperature measuring element 321 on both sides of the main temperature measuring element 32, multi-range flow measurement is realized, the number of temperature measuring elements is reduced, and then the number of temperature difference signal output ports is reduced, the manufacturing cost is lowered, the size of the sensor is reduced, and the back-end signal processing steps are simplified.

[0164] In summary, the thermal flow sensor and the preparation method thereof of the present invention improve the temperature measuring structure, and the main temperature measuring element and the heating element are arranged just above the cavity, and the main temperature measuring element and the heating element are symmetrical about the center line of the cavity perpendicular to the Y direction, so that when the fluid flow rate in the Y direction of the sensor is zero, the temperature distribution at both ends of the main temperature measuring element along the Y direction is the same, thereby avoiding the influence of the thermal radiation of the external environment on the measurement, improving the measurement accuracy of the sensor, and only one main temperature measuring element is required to realize the measurement of the temperature difference, reducing the number of temperature measuring elements, simplifying the structure of the sensor, and at least one pair of temperature measuring elements are arranged on both sides of the main temperature measuring element along the Y direction. , and the auxiliary temperature measuring element is symmetrical about the center line of the cavity perpendicular to the Y direction, realizing multi-range flow measurement, reducing the number of temperature measuring elements, and then reducing the number of temperature difference signal output ports, reducing the manufacturing cost, reducing the size of the sensor, and effectively simplifying the use method, simplifying the back-end signal processing steps, and can also be applied to application scenarios that limit the number of temperature measuring elements, expanding the scope of application; by setting a heat-resistant groove in the laminated structure composed of the partition, the isolation layer and the protective layer, the heat loss of the heating element is reduced, the measurement accuracy is further improved, the power consumption of the heating element is reduced, and then the power consumption of the device is reduced, and the performance of the sensor is improved. Therefore, the present invention effectively overcomes the various shortcomings in the prior art and has a high industrial utilization value.

[0165] 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. A thermal flow sensor, characterized in that: include: A substrate having a cavity extending through the substrate; a partition plate, located on the upper surface of the substrate and above the opening of the cavity; A measuring structure, located on the upper surface of the partition, the measuring structure comprising a temperature-sensitive resistor, a main temperature measuring element, a heating element and an isolation layer located between the heating element and the main temperature measuring element, the main temperature measuring element is located above the cavity opening and is symmetrical about the center line of the cavity perpendicular to the Y direction, the dimensions of the main temperature measuring element in the X direction and the Y direction are both smaller than the dimensions of the cavity opening, the heating element is located above the cavity opening and is symmetrical about the center line of the cavity perpendicular to the Y direction, the dimension of the heating element in the X direction is not smaller than the dimension of the main temperature measuring element and is not larger than the dimension of the cavity opening, the dimension of the heating element in the Y direction is smaller than the dimension of the main temperature measuring element, the temperature-sensitive resistor is located above the substrate on both sides of the main temperature measuring element along the Y direction, and the X direction and the Y direction are perpendicular to each other; a protective layer covering the exposed upper surface of the measurement structure; A first pad, a second pad and an output pad, wherein the first pad is electrically connected to the two ends of the temperature-sensitive resistor, the second pad is electrically connected to the two ends of the heating element, and the output pad is electrically connected to the two ends of the main temperature measuring element.

2. The thermal flow sensor according to claim 1, characterized in that: The main temperature measuring element comprises a plurality of thermocouples arranged at intervals along the X direction, and the plurality of thermocouples in the main temperature measuring element are connected in series to form a thermopile.

3. The thermal flow sensor according to claim 2, characterized in that: The thermocouple is provided with two thermocouple arms spaced apart along the X direction, and the thermocouple arms include any two of a P-type arm extending along the Y direction, an N-type arm extending along the Y direction, and a metal arm extending along the Y direction. The thermocouple is also provided with a connecting portion for connecting two different thermocouple arms.

4. The thermal flow sensor according to claim 1, characterized in that: The main temperature measuring element is located directly above the heating element, the heating element is located on the upper surface of the partition, and the isolation layer covers the exposed surface of the heating element and the exposed upper surface of the partition; or the heating element is located directly above the main temperature measuring element, the main temperature measuring element is located on the upper surface of the partition, and the isolation layer covers the exposed surface of the main temperature measuring element and the exposed upper surface of the partition.

5. The thermal flow sensor according to claim 1, characterized in that: A heat-resistant groove opening from the upper surface of the protective layer is also provided directly above the opening of the cavity. The heat-resistant groove is located on both sides of the main temperature measuring element along the Y direction, and the size of the heat-resistant groove along the X direction is not less than the size of the heating element along the X direction.

6. The thermal flow sensor according to claim 5, characterized in that: The heat-resisting groove is further provided with end portions at both ends along the X direction, the end portions extend in a direction close to the heating element, and the end portions are spaced a preset distance from a center line of the heating element perpendicular to the Y direction.

7. The thermal flow sensor according to claim 1, characterized in that: At least one auxiliary temperature measuring element is provided on both sides of the main temperature measuring element along the Y direction and is spaced a preset distance from the main temperature measuring element.

8. The thermal flow sensor according to claim 7, characterized in that: The auxiliary temperature measuring element includes a first portion and a second portion located at two sides of the main temperature measuring element along the Y direction, and the first portion and the second portion are symmetrical about a center line of the cavity perpendicular to the Y direction.

9. The thermal flow sensor according to claim 8, characterized in that: The thermal flow sensor is provided with a plurality of auxiliary temperature measuring elements, the hot end and the cold end of the first part farthest from the center line of the cavity perpendicular to the Y direction are respectively located directly above the cavity and the substrate, and the hot end and the cold end of the second part farthest from the center line of the cavity perpendicular to the Y direction are respectively located directly above the cavity and the substrate.

10. The thermal flow sensor according to claim 7, characterized in that: The auxiliary temperature measuring element includes a plurality of thermocouples arranged at intervals along the X direction, and the plurality of thermocouples in the auxiliary temperature measuring element are connected in series to form a thermopile.

11. The thermal flow sensor according to claim 7, characterized in that: A heat-resistant groove opening from the upper surface of the protective layer is also provided between the main temperature measuring element and the auxiliary temperature measuring element. The heat-resistant groove is spaced apart from the main temperature measuring element and the auxiliary temperature measuring element by a preset distance, respectively. The size of the heat-resistant groove along the X direction is not less than the size of the main temperature measuring element and the auxiliary temperature measuring element and is smaller than the size of the cavity.

12. The thermal flow sensor according to claim 7, characterized in that: The thermal flow sensor is also provided with a third soldering pad, and both ends of the auxiliary temperature measuring element are electrically connected to the third soldering pad respectively.

13. A method for preparing a thermal flow sensor, characterized in that: The following steps are involved: Providing a substrate, forming a partition with a preset thickness on the upper surface of the substrate, and defining a functional area on the upper surface of the partition; A measuring structure is formed on the upper surface of the partition, the measuring structure comprising a temperature-sensitive resistor, a main temperature measuring element, a heating element, and an isolation layer between the heating element and the main temperature measuring element, the main temperature measuring element is located above the functional area and is symmetrical about a center line of the functional area perpendicular to the Y direction, the dimensions of the main temperature measuring element in the X direction and the Y direction are both smaller than the dimensions of the functional area, the heating element is located above the functional area and is symmetrical about a center line of the functional area perpendicular to the Y direction, the dimension of the heating element in the X direction is not smaller than the dimension of the main temperature measuring element and is not larger than the dimension of the functional area, the dimension of the heating element in the Y direction is smaller than the dimension of the main temperature measuring element, the temperature-sensitive resistor is located above the substrate on both sides of the main temperature measuring element along the Y direction, and the X direction and the Y direction are perpendicular to each other; forming a protective layer covering the exposed upper surface of the measurement structure; Forming a first pad, a second pad and an output pad, wherein the first pad is electrically connected to both ends of the temperature-sensitive resistor, the second pad is electrically connected to both ends of the heating element, and the output pad is electrically connected to both ends of the main temperature measuring element; A cavity penetrating the substrate is formed directly below the functional area, and the size and shape of the cavity are the same as those of the functional area.

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