Thermal flow sensor

Abstract

The utility model relates to a thermal flow sensor. A barrier layer is arranged on the back surface of the substrate; a supporting structure layer; an upstream thermopile lower-layer thermocouple, a downstream thermopile lower-layer thermocouple and a central heat source structure; a first insulating layer; an upstream thermopile upper thermocouple and a downstream thermopile upper thermocouple; the upstream thermopile lower-layer thermocouple and the upstream thermopile upper-layer thermocouple form an upstream temperature measuring element thermopile, and the downstream thermopile lower-layer thermocouple and the downstream thermopile upper-layer thermocouple form a downstream temperature measuring element thermopile; a second insulating layer; the cold and hot end connecting structure comprises an upstream thermopile structure hot junction region, a first upstream thermopile structure cold junction region, a second upstream thermopile structure cold junction region, a downstream thermopile structure hot junction region, a first downstream thermopile structure cold junction region and a second downstream thermopile structure cold junction region; and the back release cavity penetrates through the barrier layer and extends to the supporting structure layer. The utility model has the characteristics of fast speed, high sensitivity and stable structure.

Description

Technical Field

[0001] The utility model relates to the technical field of flow sensors, in particular to a thermal flow sensor. Background Art

[0002] Thermal flow sensors measure flow by supplying constant voltage to a heating resistor and measuring the temperature difference between upstream and downstream temperature measuring elements at different flow rates. Depending on the type of temperature measuring resistor, they can be divided into thermistor flow sensors and thermopile flow sensors. However, existing thermopile flow sensors have problems such as slow response speed, low sensitivity, and complex structure. An improved thermal flow sensor is urgently needed to overcome these technical defects. Summary of the invention

[0003] To this end, the utility model provides a thermal flow sensor, which has the characteristics of fast speed, high sensitivity and stable structure.

[0004] In order to solve the above technical problems, the utility model provides a thermal flow sensor, comprising:

[0005] A substrate having a barrier layer disposed on the back side thereof;

[0006] A support structure layer is arranged on the front surface of the substrate;

[0007] The upstream thermopile lower layer thermocouple, the downstream thermopile lower layer thermocouple and the central heat source structure are respectively arranged on the surface of the supporting structure layer;

[0008] A first insulating layer covers the surfaces of the upstream thermopile lower layer thermocouple, the downstream thermopile lower layer thermocouple and the central heat source structure respectively;

[0009] The upper thermocouple of the upstream thermopile and the upper thermocouple of the downstream thermopile are respectively arranged on the surface of the first insulating layer above the lower thermocouple of the upstream thermopile and the lower thermocouple of the downstream thermopile; the lower thermocouple of the upstream thermopile and the upper thermocouple of the upstream thermopile constitute an upstream temperature measuring element thermopile, and the lower thermocouple of the downstream thermopile and the upper thermocouple of the downstream thermopile constitute a downstream temperature measuring element thermopile;

[0010] a second insulating layer, covering the surfaces of the upper thermocouple of the upstream thermopile, the upper thermocouple of the downstream thermopile and a portion of the first insulating layer;

[0011] a hot and cold end connection structure, which penetrates the first insulating layer and / or the second insulating layer, and includes an upstream thermopile structure hot junction area connected between the upstream thermopile lower layer thermocouple and the upstream thermopile upper layer thermocouple, a first upstream thermopile structure cold junction area connected to the upstream thermopile lower layer thermocouple, a second upstream thermopile structure cold junction area connected to the upstream thermopile upper layer thermocouple, a downstream thermopile structure hot junction area connected between the downstream thermopile lower layer thermocouple and the downstream thermopile upper layer thermocouple, a first downstream thermopile structure cold junction area connected to the downstream thermopile lower layer thermocouple, and a second downstream thermopile structure cold junction area connected to the downstream thermopile upper layer thermocouple;

[0012] The back release cavity penetrates the barrier layer and extends to the support structure layer to release the hot end position of the upstream temperature measuring element thermopile, the hot end position of the downstream temperature measuring element thermopile and the position of the central heat source structure.

[0013] In one embodiment of the present invention, the portion of the back release cavity located in the substrate is in an isosceles inverted trapezoidal shape.

[0014] In one embodiment of the present invention, the barrier layer is made of silicon oxide with a thickness of 0.01-1 μm.

[0015] In one embodiment of the present invention, the support structure layer includes a silicon oxide support layer and a silicon nitride support layer which are sequentially arranged on the surface of the substrate.

[0016] In one embodiment of the present invention, the thickness of the silicon oxide support layer is 0.1-5 μm.

[0017] In one embodiment of the present invention, the thickness of the silicon nitride support layer is 0.01-0.5 μm.

[0018] In one embodiment of the present invention, a silicon oxide passivation layer covering the front side of the chip is also included.

[0019] In one embodiment of the present invention, the central heat source structure adopts a platinum thin film resistor with a thickness of 0.05-0.5 μm.

[0020] In one embodiment of the present utility model, the second insulating layer includes a second insulating layer 1 covering the upper thermocouple of the upstream thermopile, a second insulating layer 2 covering the upper thermocouple of the downstream thermopile, and a second insulating layer 3 covering the surface of the first insulating layer located above the central heat source structure;

[0021] Two ends of the hot junction area of ​​the upstream thermopile structure respectively penetrate the first insulating layer and the second insulating layer 1;

[0022] Two ends of the hot junction area of ​​the downstream thermopile structure respectively penetrate the first insulating layer and the second insulating layer 2;

[0023] The cold junction area of ​​the first upstream thermopile structure sequentially penetrates the first insulating layer and the second insulating layer and extends to the low step surface of the second insulating layer 1, and the cold junction area of ​​the second upstream thermopile structure penetrates and extends to the high step surface of the second insulating layer 1;

[0024] The first downstream thermopile structure cold junction area sequentially penetrates the first insulating layer and the second insulating layer 2 and extends to the low step surface of the second insulating layer 2, and the second downstream thermopile structure cold junction area penetrates and extends to the high step surface of the second insulating layer 2.

[0025] In one embodiment of the present invention, it also includes a heat source wire structure that runs through the second insulation layer three and the first insulation layer and is connected to the central heat source structure.

[0026] The above technical solution of the utility model has the following advantages compared with the prior art:

[0027] The thermal flow sensor described in the utility model can significantly improve the response speed of the sensor, quickly respond to flow rate changes, and improve measurement efficiency by optimizing the thermopile structure and heat source configuration. The combined design of the thermopile and the central heat source improves the sensitivity of the sensor to flow rate changes and can more accurately detect tiny flow rate changes.

[0028] The utility model uses multi-layer insulation materials and a back release cavity design to improve the thermal stability and durability of the sensor, ensure stable operation in complex environments, enable the temperature measuring element to more accurately sense changes in fluid flow rate, and improve the accuracy of flow measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to make the content of the utility model more clearly understood, the utility model is further described in detail below based on specific embodiments of the utility model in combination with the accompanying drawings.

[0030] Figure 1 It is a structural schematic diagram of the thermal flow sensor of the utility model.

[0031] Description of the Figures in the Specification:

[0032] 1. Substrate;

[0033] 2. Silicon oxide support layer;

[0034] 3. Silicon nitride support layer;

[0035] 4. Central heat source structure;

[0036] 5a, thermocouple of the lower layer of the upstream thermopile; 5b, thermocouple of the lower layer of the downstream thermopile;

[0037] 6a, first insulating layer; 6b, second insulating layer; 61, second insulating layer one; 62, second insulating layer two; 63, second insulating layer three;

[0038] 7a, upper thermocouple of upstream thermopile; 7b, upper thermocouple of downstream thermopile;

[0039] 81. hot junction area of ​​upstream thermopile structure; 82. cold junction area of ​​first upstream thermopile structure; 83. cold junction area of ​​second upstream thermopile structure; 84. hot junction area of ​​downstream thermopile structure; 85. cold junction area of ​​first downstream thermopile structure; 86. cold junction area of ​​second downstream thermopile structure; 87. heat source wire structure;

[0040] 9. Passivation layer;

[0041] 10. Barrier layer;

[0042] 11. Back release cavity. DETAILED DESCRIPTION

[0043] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0044] In the present invention, if directions (up, down, left, right, front and back) are described, it is only for the convenience of describing the technical solution of the present invention, and does not indicate or imply that the technical features referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention.

[0045] In the present utility model, "several" means one or more, "multiple" means more than two, "greater than", "less than", "exceed" and the like are understood to exclude the number itself; "above", "below", "within" and the like are understood to include the number itself. In the description of the present utility model, if there is a description of "first" or "second", it is only used for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0046] In the present invention, unless otherwise clearly defined, the words "set", "install", "connect" and the like should be understood in a broad sense, for example, they can be directly connected or indirectly connected through an intermediate medium; they can be fixedly connected or detachably connected or integrally formed; they can be mechanically connected or electrically connected or able to communicate with each other; they can be the internal connection of two elements or the interaction relationship between two elements. Those skilled in the art can reasonably determine the specific meanings of the above words in the present invention in combination with the specific content of the technical solution.

[0047] Reference Figure 1 As shown, a thermal flow sensor of the utility model comprises:

[0048] A substrate 1, a barrier layer 10 is provided on the back side thereof;

[0049] A supporting structure layer is arranged on the front surface of the substrate 1;

[0050] The upstream thermopile lower layer thermocouple 5a, the downstream thermopile lower layer thermocouple 5b and the central heat source structure 4 are respectively arranged on the surface of the supporting structure layer;

[0051] The first insulating layer 6a covers the surfaces of the upstream thermopile lower layer thermocouple 5a, the downstream thermopile lower layer thermocouple 5b and the central heat source structure 4 respectively;

[0052] The upstream thermopile upper thermocouple 7a and the downstream thermopile upper thermocouple 7b are correspondingly arranged on the surface of the first insulating layer 6a above the upstream thermopile lower thermocouple 5a and the downstream thermopile lower thermocouple 5b respectively; the upstream thermopile lower thermocouple 5a and the upstream thermopile upper thermocouple 7a constitute an upstream temperature measuring element thermopile, and the downstream thermopile lower thermocouple 5b and the downstream thermopile upper thermocouple 7b constitute a downstream temperature measuring element thermopile;

[0053] A second insulating layer 6b covers the surfaces of the upstream thermopile upper thermocouple 7a, the downstream thermopile upper thermocouple 7b and part of the first insulating layer 6a;

[0054] The hot and cold end connection structure penetrates the first insulating layer 6a and / or the second insulating layer 6b, and includes an upstream thermopile structure hot junction area 81 connected between the upstream thermopile lower layer thermocouple 5a and the upstream thermopile upper layer thermocouple 7a, a first upstream thermopile structure cold junction area 82 connected to the upstream thermopile lower layer thermocouple 5a, a second upstream thermopile structure cold junction area 83 connected to the upstream thermopile upper layer thermocouple 7a, a downstream thermopile structure hot junction area 84 connected between the downstream thermopile lower layer thermocouple 5b and the downstream thermopile upper layer thermocouple 7b, a first downstream thermopile structure cold junction area 85 connected to the downstream thermopile lower layer thermocouple 5b, and a second downstream thermopile structure cold junction area 86 connected to the downstream thermopile upper layer thermocouple 7b;

[0055] The back release cavity 11 penetrates the barrier layer 10 and extends to the support structure layer to release the hot end position of the upstream temperature measuring element thermopile, the hot end position of the downstream temperature measuring element thermopile and the position of the central heat source structure 4.

[0056] In one embodiment, the portion of the back release cavity 11 located in the substrate 1 is in the shape of an isosceles inverted trapezoid. By providing a release cavity on the back of the substrate 1, the hot end of the thermopile can release heat more quickly, thereby reducing thermal hysteresis and enabling the sensor to respond to flow changes more quickly. The isosceles inverted trapezoid shape facilitates etching and enhances the efficiency of heat release.

[0057] In one embodiment, the barrier layer 10 is made of silicon oxide with a thickness of 0.01-1 μm, which is used as a release etching window to etch the back release cavity 11. The silicon oxide material has good thermal stability and corrosion resistance, ensuring the structural stability of the back release cavity 11.

[0058] In one embodiment, the support structure layer includes a silicon oxide support layer 2 and a silicon nitride support layer 3 which are sequentially disposed on the surface of the substrate 1 .

[0059] Specifically, the thickness of the silicon oxide support layer 2 is 0.1-5 μm, and the thickness of the silicon nitride support layer 3 is 0.01-0.5 μm. The double-layer support structure layer can improve the stress of the support film layer through the reverse stress of silicon nitride and silicon oxide.

[0060] In one embodiment, a silicon oxide passivation layer 9 covering the front side of the chip is also included, which can effectively isolate different temperature zones, reduce heat loss, and improve measurement accuracy and sensitivity.

[0061] In one embodiment, the central heat source structure 4 uses a platinum thin film resistor with a thickness of 0.05-0.5 μm. The central heat source structure 4 uses a platinum thin film resistor, which has high thermal conductivity and fast heating characteristics, and can reach the required temperature in a very short time, ensuring the rapid response of the sensor to flow changes.

[0062] In one embodiment, the second insulating layer 6b includes a second insulating layer 1 61 covering the upper thermocouple 7a of the upstream thermopile, a second insulating layer 2 62 covering the upper thermocouple 7b of the downstream thermopile, and a second insulating layer 3 63 covering the surface of the first insulating layer 6a located above the central heat source structure 4;

[0063] Two ends of the upstream thermopile structure hot junction region 81 respectively penetrate the first insulating layer 6a and the second insulating layer 1 61;

[0064] Two ends of the downstream thermopile structure hot junction region 84 respectively penetrate the first insulating layer 6a and the second insulating layer 2 62;

[0065] The first upstream thermopile structure cold junction area 82 sequentially penetrates the first insulating layer 6a and the second insulating layer 6b and extends to the low step surface of the second insulating layer 61, and the second upstream thermopile structure cold junction area 83 penetrates and extends to the high step surface of the second insulating layer 61;

[0066] The first downstream thermopile structure cold junction area 85 sequentially penetrates the first insulating layer 6a and the second insulating layer 62 and extends to the low step surface of the second insulating layer 62 , and the second downstream thermopile structure cold junction area 86 penetrates and extends to the high step surface of the second insulating layer 62 .

[0067] In one embodiment, it also includes a heat source wire structure 87 that penetrates the second insulation layer 3 63, the first insulation layer 6a and is connected to the central heat source structure 4.

[0068] By optimizing the structure of the hot junction area and the cold junction area, the resistance and energy loss are reduced, and the response speed and measurement accuracy of the sensor are improved.

[0069] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the utility model rather than to limit it. Although the utility model has been described in detail with reference to examples, ordinary technicians in the field should understand that the technical solution of the utility model can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the utility model, which should be included in the scope of the claims of the utility model.

Claims

1. A thermal flow sensor, characterized in that: include: A substrate (1), a barrier layer (10) being provided on the back side thereof; A supporting structure layer, arranged on the front surface of the substrate (1); The upstream thermopile lower layer thermocouple (5a), the downstream thermopile lower layer thermocouple (5b) and the central heat source structure (4) are respectively arranged on the surface of the support structure layer; A first insulating layer (6a) covers the surfaces of the upstream thermopile lower layer thermocouple (5a), the downstream thermopile lower layer thermocouple (5b) and the central heat source structure (4); The upstream thermopile upper thermocouple (7a) and the downstream thermopile upper thermocouple (7b) are correspondingly arranged on the surface of the first insulating layer (6a) above the upstream thermopile lower thermocouple (5a) and the downstream thermopile lower thermocouple (5b); the upstream thermopile lower thermocouple (5a) and the upstream thermopile upper thermocouple (7a) constitute an upstream temperature measuring element thermopile, and the downstream thermopile lower thermocouple (5b) and the downstream thermopile upper thermocouple (7b) constitute a downstream temperature measuring element thermopile; a second insulating layer (6b), covering the surfaces of the upper thermocouple (7a) of the upstream thermopile, the upper thermocouple (7b) of the downstream thermopile and a portion of the first insulating layer (6a); a hot and cold end connection structure, penetrating the first insulating layer (6a) and / or the second insulating layer (6b), comprising an upstream thermopile structure hot junction area (81) connected between the upstream thermopile lower layer thermocouple (5a) and the upstream thermopile upper layer thermocouple (7a), a first upstream thermopile structure cold junction area (82) connected to the upstream thermopile lower layer thermocouple (5a), a second upstream thermopile structure cold junction area (83) connected to the upstream thermopile upper layer thermocouple (7a), a downstream thermopile structure hot junction area (84) connected between the downstream thermopile lower layer thermocouple (5b) and the downstream thermopile upper layer thermocouple (7b), a first downstream thermopile structure cold junction area (85) connected to the downstream thermopile lower layer thermocouple (5b), and a second downstream thermopile structure cold junction area (86) connected to the downstream thermopile upper layer thermocouple (7b); A back release cavity (11) penetrates the barrier layer (10) and extends to the support structure layer, so as to release the hot end position of the upstream temperature measuring element thermopile, the hot end position of the downstream temperature measuring element thermopile and the position of the central heat source structure (4).

2. A thermal flow sensor according to claim 1, characterized in that: The portion of the back release cavity (11) located in the substrate (1) is in the shape of an isosceles inverted trapezoid.

3. A thermal flow sensor according to claim 1, characterized in that: The barrier layer (10) is made of silicon oxide with a thickness of 0.01 to 1 μm.

4. A thermal flow sensor according to claim 3, characterized in that: The support structure layer comprises a silicon oxide support layer (2) and a silicon nitride support layer (3) which are sequentially arranged on the surface of the substrate (1).

5. A thermal flow sensor according to claim 4, characterized in that: The thickness of the silicon oxide support layer (2) is between 0.1 and 5 μm.

6. A thermal flow sensor according to claim 4, characterized in that: The thickness of the silicon nitride support layer (3) is between 0.01 and 0.5 μm.

7. A thermal flow sensor according to claim 1, characterized in that: It also includes a silicon oxide passivation layer (9) covering the front side of the chip.

8. A thermal flow sensor according to claim 1, characterized in that: The central heat source structure (4) uses a platinum thin film resistor with a thickness of 0.05-0.5 μm.

9. A thermal flow sensor according to claim 1, characterized in that: The second insulating layer (6b) comprises a second insulating layer 1 (61) covering the upper thermocouple (7a) of the upstream thermopile, a second insulating layer 2 (62) covering the upper thermocouple (7b) of the downstream thermopile, and a second insulating layer 3 (63) covering the surface of the first insulating layer (6a) located above the central heat source structure (4); Two ends of the upstream thermopile structure hot junction region (81) respectively penetrate the first insulating layer (6a) and the second insulating layer 1 (61); Two ends of the downstream thermopile structure hot junction region (84) respectively penetrate the first insulating layer (6a) and the second insulating layer (62); The first upstream thermopile structure cold junction area (82) sequentially penetrates the first insulating layer (6a) and the second insulating layer (6b) and extends to the low step surface of the second insulating layer one (61), and the second upstream thermopile structure cold junction area (83) penetrates and extends to the high step surface of the second insulating layer one (61); The first downstream thermopile structure cold junction area (85) sequentially penetrates the first insulating layer (6a) and the second insulating layer 2 (62) and extends to the low step surface of the second insulating layer 2 (62), and the second downstream thermopile structure cold junction area (86) penetrates and extends to the high step surface of the second insulating layer 2 (62).

10. A thermal flow sensor according to claim 9, characterized in that: It also includes a heat source wire structure (87) that penetrates the second insulation layer three (63), the first insulation layer (6a) and is connected to the central heat source structure (4).

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