CN108318525B - Micro thermal conductivity detector insensitive to flow - Google Patents
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- 229910052710 silicon Inorganic materials 0.000 claims abstract description 71
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Abstract
A micro thermal conductivity detector insensitive to flow belongs to the field of micro electro mechanical systems. Etching a micro-channel in a total-dividing mode on the back surface of the silicon substrate to serve as an air flow channel, penetrating the silicon substrate on the front surface of the silicon substrate by adopting an etching technology to form two micro-cuboid heat conduction pools, forming a net-shaped supporting film on the front surface of the silicon substrate and a thermistor on the net-shaped supporting film and hanging the net-shaped supporting film above the heat conduction pools, and finally bonding the silicon substrate with a glass cover plate and a glass substrate respectively to finish manufacturing. The structure realizes the non-coplanar design of the airflow channel and the thermistor, combines the arrangement of the micro-channels in a branch form, realizes the semi-diffusion design of the airflow channel and the thermal conductivity cell, greatly reduces the influence of the fluctuation of the air flow on the working performance of the thermal conductivity detector, and simultaneously meets the requirement of response speed. In addition, the non-coplanar design avoids the interference of channels on circuit integration in the traditional design, so that the direct integration of the bridge and related circuits on the front surface of the silicon substrate becomes simple and feasible.
Description
Technical Field
The invention relates to the field of micro-electromechanical systems, in particular to a design of a micro thermal conductivity detector insensitive to flow, which can be widely applied to analysis of various mixed gases.
Background
The thermal conductivity detection method is one of the earliest methods applied to gas detection, and the method utilizes the characteristic that the temperature of a thermistor in a thermal conductivity detector changes correspondingly with the volume fraction of the detected gas to realize the detection of different volume fractions of the gas. The thermal conductivity detector has the advantages of simple device, low price and the like, and is a universal detector because of being responsive to almost all gases, so the thermal conductivity detector is widely applied to the field of gas analysis.
The traditional thermal conductivity detector has the problems of low detection sensitivity, large error, large volume, large weight and the like, so that the application range of the thermal conductivity detector is severely limited, and with the development of MEMS (Micro-electro-mechanical-system) technology, the Micro thermal conductivity detector designed and manufactured by adopting the MEMS processing technology has the advantages of reduced volume and weight, reduced power consumption and greatly improved working performance. However, in current thermal conductivity detector designs, the following problems remain:
1. in the current miniature thermal conductivity detector design, almost completely adopt the straight-through structure, namely gas directly flows through the thermal conductivity cell, and this design has guaranteed response speed, but makes the thermal conductivity detector very sensitive to the flow simultaneously, and the flow fluctuation can produce great adverse effect to its working property, and because the air current is to the direct impact of suspension support membrane in the existing design for support membrane stability variation, easy damage. Although a diffusion structure appears in the traditional thermal conductivity detector design, the response speed is greatly sacrificed due to the limitation of the processing technology, and the practical application is less.
2. In the current micro thermal conductivity detector design, the through structure is adopted to enable the air channel to completely penetrate through the surface of the silicon substrate where the air channel and the thermistor are located, so that connection of the wheatstone bridge and related circuits on the surface of the silicon substrate becomes difficult, and only the circuits can be connected outside the silicon substrate generally.
The above-mentioned problems should be a key technical problem to be solved or optimized by researchers in the field in order to obtain a micro thermal conductivity detector with more simplified circuit arrangement and better performance in combination with response speed requirements and flow fluctuation effects.
Disclosure of Invention
In view of the above-mentioned problems, the present invention proposes a design of a micro thermal conductivity detector insensitive to flow, and aims to achieve a simplified circuit arrangement of the micro thermal conductivity detector, and to achieve both response speed and operational performance affected by flow fluctuation, and other beneficial effects. The specific technical scheme of the invention is as follows:
a micro thermal conductivity detector insensitive to flow, comprising: the glass comprises a silicon substrate (1), an upper glass cover plate (2) and a lower glass substrate (3), wherein the lower glass substrate (3) is bonded with the back surface, namely the lower end surface, of the silicon substrate (1), and the upper glass cover plate (2) is bonded with the front surface, namely the upper end surface, of the silicon substrate (1);
the silicon substrate (1) is provided with two cuboid micro heat conduction pools (12), the two cuboid micro heat conduction pools (12) are of cavity structures, the upper end face and the lower end face of the silicon substrate (1) are vertically penetrated, and the two cuboid micro heat conduction pools (12) are on the same straight line along the length direction;
etching a gas inlet channel, an inlet flow dividing channel, a plurality of branch channels, an outlet flow converging channel and a gas outlet channel on the back surface of the silicon substrate (1), namely the lower end surface of the silicon substrate, aiming at each cuboid micro thermal conductivity cell (12) to form a total-division total-type gas channel; an inlet channel is communicated with an inlet flow distribution channel, the length direction of the inlet flow distribution channel is parallel to the length direction of the cuboid miniature thermal conductivity cell (12), an outlet converging channel is parallel to the inlet flow distribution channel, a plurality of branch channels are parallel and are respectively perpendicular to and communicated with the inlet flow distribution channel and the outlet converging channel, and the plurality of branch channels penetrate through the lower part of the corresponding cuboid miniature thermal conductivity cell (12) and are perpendicular to the length direction of the cuboid miniature thermal conductivity cell (12); the outlet confluence channel is connected with the gas outlet channel, and the length direction of the outlet confluence channel at the connection part is vertical to the length direction of the gas outlet channel;
the gas channels of the two cuboid miniature heat conduction tanks (12) are distributed in a central plane symmetry way, one gas channel is used as a gas channel to be tested, and the other gas channel is used as a reference gas channel;
two reticular support films (13) are fixedly arranged at the front surface of the silicon substrate (1), namely at the upper end face of each cuboid miniature heat conduction pool (12), and a thermistor (14) is deposited on the upper surface of each reticular support film (13); the thermistor (14) is of a multi-section folded structure and is connected in parallel and in series to form a planar structure, namely, the thermistor (14) is hung on the upper port of the cuboid miniature thermal conductivity cell (12) through the reticular support film (13); both ends of each thermistor (14) are connected with electrode leads (15), and the electrode leads (15) are positioned on the front surface of the silicon substrate (1); two thermistors (14) in the upper port of each cuboid miniature thermal conductivity cell (12) are arranged along the length direction of the cuboid miniature thermal conductivity cell (12), four thermistors (14) arranged on the silicon substrate (1) sequentially form four resistors R1, R4, R2 and R3, the four resistors are connected by an electrode lead (15), and an electrode bonding pad (16) is arranged at the edge of the front surface of the silicon substrate (1).
R1 and R4 are arranged at the upper port of one cuboid miniature thermal conductivity cell (12), and R2 and R3 are arranged at the upper port of the other cuboid miniature thermal conductivity cell (12); four thermistors (14) are counted in the two heat conduction pools to form four bridge arms of a Wheatstone bridge, and a bridge circuit is directly connected with an insulating layer on the front side of the silicon substrate (1) through electrode leads (15).
It is further preferable that the length direction of the junction of the inlet channel and the inlet split channel is vertical, and a side wall of the inlet split channel opposite to the inlet channel is provided with a sector-shaped groove (11) with a section.
It is further preferable that the thermistor (14) protrudes out of the front surface of the reticular support film (13), and a groove is correspondingly arranged on the upper glass cover plate (2) for matching with the thermistor (14).
The silicon substrate (1) is respectively and electrostatically bonded with the upper glass cover plate (2) and the lower glass substrate (3).
The width of the inlet split flow channel is smaller than that of the outlet converging channel, the width of the gas inlet channel is equal to that of the gas outlet channel, 4 branch channels of a single channel are the smallest in width, the branch channels of 2 edges are correspondingly positioned at the edge of the heat conducting pool, and the 4 branch channels are arranged side by side at equal intervals and are symmetrical to the positions of the gas inlet channel and the gas outlet channel.
The front side of the silicon substrate (1) is etched to penetrate through a cuboid miniature heat conduction pool (12) of the silicon substrate (1), the lower part of the cuboid miniature heat conduction pool is communicated with a branch channel, and a semi-diffusion design is formed by the arrangement of the flow channels and the heat conduction pool. The width of the cuboid miniature heat conducting pool (12) is 2-4 times of the width of each branch channel.
Two reticular support films (13) and thermistors (14) on the reticular support films are arranged above the single cuboid miniature heat conduction pool (12), and the two thermistors (14) are arranged in parallel relative to the lower airflow direction.
The single reticular support film (13) is provided with 4 support beams, wherein the electrode leads (15) and the thermistor (14) are connected on the surfaces of two long support beams, and the two short support beams are used for supporting in an auxiliary mode, so that stability is improved. The thermistor (14) is arranged in a serpentine shape in a right-angle fold line form on the mesh support film (13), and the thermistor (14) is sputter deposited on the surface of the silicon nitride layer of the mesh support film (13) during micromachining. The reticular support film (13) adopts a composite film, the lower layer is a monocrystalline silicon layer and silicon oxide with proper thickness, the upper layer is connected with the thermistor (14) and is silicon nitride, and the thermistor (14) is a Pt thin film resistor with high resistivity and high temperature coefficient of resistance.
As described above, the micro thermal conductivity detector insensitive to flow provided by the invention has the following beneficial effects:
1. the micro-rectangular thermal conductivity cell penetrates through the silicon wafer, the reticular support film and the thermistor are positioned above the thermal conductivity cell, namely the front surface of the silicon wafer, and the width of the thermal conductivity cell is 2-4 times of that of the micro-rectangular thermal conductivity cell, so that the structure realizes non-coplanar design of the airflow channel and the thermistor, and semi-diffusion design of the airflow channel and the micro-rectangular thermal conductivity cell, thereby greatly reducing the influence of the air flow and the pressure fluctuation on the working performance of the thermal conductivity detector, and simultaneously, the design of 4 narrow branch channels and the position arrangement of the thermal conductivity cell ensure the requirement of the thermal conductivity detector on the response speed.
2. The width of the inlet diversion channel is smaller than that of the outlet confluence channel, so that the gas can smoothly flow out of the micro-channel, and the stagnation or the reverse flow is prevented from being formed at the outlet. The arrangement of the fan-shaped grooves in the inlet diversion channel, which are opposite to the position of the airflow inlet, is beneficial to the smooth diversion and outflow of the air.
3. The two thermistors in the single thermal conductivity cell are arranged in parallel relative to the direction of the air flow below, so that adverse effects caused by reduced heat exchange quantity when the air flow passes through the upstream thermistor and is heated and then passes through the downstream thermistor in the general straight-through design are avoided. The thermistor is sputtered and deposited on the surface of the silicon nitride layer of the reticular support film, so that good heat insulation and insulation effects are ensured.
4. The non-coplanar design avoids the defects of the general straight-through design, liberates the front surface of the silicon substrate, and enables the micro thermal conductivity detector bridge and related circuits to be directly connected and completed on the insulating layer on the front surface of the silicon substrate by the electrode leads, thereby being more simplified.
Drawings
FIG. 1 is a schematic view showing the structure of the back surface of a silicon substrate of a micro thermal conductivity detector according to the present invention.
Fig. 2 is a schematic diagram of a front structure of a silicon substrate of the micro thermal conductivity detector according to the present invention, in which four thermistors in total in two thermal conductivity cells form four legs of a wheatstone bridge.
FIG. 3 is a schematic cross-sectional view showing the whole structure of the micro thermal conductivity detector according to the present invention.
FIG. 4 is a schematic diagram of a mesh support film and a thermistor of the micro thermal conductivity detector of the present invention.
Fig. 5 is a schematic diagram of a micro thermal conductivity detector bridge circuit.
FIG. 6 is a schematic diagram showing the processing steps of the micro thermal conductivity detector of the present invention.
FIG. 7 is a schematic diagram showing a three-dimensional structure of a micro thermal conductivity detector according to the present invention.
The reference numerals in the figures illustrate:
the device comprises a silicon base 1, an upper glass cover plate 2, a lower glass substrate 3, a gas inlet channel to be detected 4, a gas outlet channel to be detected 5, a reference gas inlet channel 6, a reference gas outlet channel 7, an inlet shunt channel 8, an outlet confluence channel 9, a branch channel 10, a fan-shaped groove 11, a cuboid miniature heat conduction pool 12, a reticular support membrane 13, a thermistor 14, an electrode lead 15 and an electrode pad 16.
Detailed Description
The invention provides a micro thermal conductivity detector insensitive to flow, which has the following core ideas: the non-coplanar design is realized by processing the reticular support film with the thermistor and the micro-channel in the form of total division on the front and the back of the silicon substrate respectively, meanwhile, the micro-cuboid heat conduction pool penetrates through the silicon substrate, the lower part of the micro-cuboid heat conduction pool is communicated with the branch channels, the semi-diffusion design of the airflow channel and the heat conduction pool is realized, and the integral structure greatly reduces the influence of gas flow and pressure fluctuation on the working performance besides ensuring the requirement of the micro-thermal conductivity detector on the response speed. Meanwhile, the front surface of the silicon substrate is not provided with micro-channels, so that the connection of the bridge and related circuits is simpler and easier to implement. The miniature thermal conductivity detector designed by the design has not been reported at home and abroad at present.
The invention will now be described in detail by way of example with reference to the accompanying drawings.
As shown in fig. 3, a micro thermal conductivity detector insensitive to flow has an overall structure including a silicon base 1, a glass cover plate 2 with grooves, and a glass substrate 3. As shown in fig. 1, the back surface of the silicon substrate 1 is integrated with micro-channels in a form of total component, including a to-be-detected gas inlet channel 4, a to-be-detected gas outlet channel 5, a reference gas inlet channel 6, a reference gas outlet channel 7, an inlet shunt channel 8, an outlet confluence channel 9, a branch channel 10 and a fan-shaped groove 11. As shown in fig. 2, the front surface of the silicon substrate 1 includes a mesh-shaped support film 13, a thermistor 14, an electrode lead 15, and an electrode pad 16 suspended on a rectangular parallelepiped micro thermal conductivity cell 12 penetrating the silicon substrate 1. A schematic three-dimensional structure of the micro thermal conductivity detector is shown in fig. 7.
The branch channel 10 of the micro channel in the form of total division is communicated with the lower part of the rectangular micro thermal conductivity cell 12, the reticular support membrane 13 and the thermistor 14 on the reticular support membrane are hung above the rectangular micro thermal conductivity cell 12, so that a semi-diffusion structure is formed between the airflow channel and the rectangular micro thermal conductivity cell 12, namely, when the gas in the branch channel 10 flows through the lower part of the rectangular micro thermal conductivity cell 12, part of the gas reaches the upper part of the rectangular micro thermal conductivity cell 12 in a convection and diffusion mode to contact with the thermistor 14 and complete gas exchange, the direct impact of the airflow on the reticular support membrane 13 is avoided, the width of the rectangular micro thermal conductivity cell 12 is preferably 0.4mm, which is 2-4 times of the width of the branch channel 10, and the whole structure greatly reduces the influence of flow and pressure fluctuation on the working performance of the micro thermal conductivity detector besides ensuring the requirement of the micro thermal conductivity detector on the response speed.
The width of the inlet distribution channels 8 is preferably 0.4mm and less than the width of the outlet confluence channels 9 is preferably 0.6mm, which allows smooth flow of gas out of the micro-channels without gas stagnation or reflux at the outlet.
A fan-shaped groove 11 is arranged in the inlet diversion channel 8 and is opposite to the air flow inlet, so that the air can be smoothly diverted and flows out.
The arrangement of two thermistors 14 in parallel with respect to the direction of the air flow within the single rectangular parallelepiped micro thermal conductivity cell 12 avoids the adverse effect of reduced heat transfer as the air flow is heated past the upstream thermistor and past the downstream thermistor in a typical pass-through design.
The front surface of the silicon substrate 1 is provided with an insulating layer which is LPCVD silicon oxide with the thickness of 1-2 mu m and LPCVD silicon nitride with the thickness of 0.1-0.4 mu m, and the material of the reticular support film 13 is silicon oxide, silicon nitride and a little incompletely removed silicon, wherein the internal stress of the support film is greatly reduced by adopting silicon oxide and silicon nitride with reasonable thickness. The shape of the thermistor 14 is a serpentine structure in the form of a right-angle fold line, the resistance value is preferably 90 ohms, and the thermistor 14 is sputtered and deposited on the surface of the silicon nitride layer of the reticular support film 13, so that a good heat insulation effect is ensured, and the specific structure is shown in fig. 4.
The net-shaped supporting film 13 is provided with 4 supporting beams which are two long and two short and are suspended in the cuboid miniature heat conduction pool 12, so that the heat isolation is improved well, and the heat loss and the power consumption are reduced greatly. The electrode lead 15 is connected to the thermistor 14 by two long support beams, and the specific structure is shown in fig. 4.
The air flow channel and the thermistor 14 form a non-coplanar design, the defects of the general straight-through design are overcome, the front surface of the silicon substrate 1 is relieved, the micro thermal conductivity detector bridge and related circuits are directly connected and completed on the insulating layer of the front surface of the silicon substrate by the electrode leads 15, and the electrode pads 16 are arranged at the edges, so that the whole is simplified. The wheatstone bridge circuit is shown in fig. 5 and the actual bridge connection on the front side of the silicon substrate 1 is shown in fig. 2.
The micro thermal conductivity detector insensitive to flow is processed by adopting MEMS technology, the processing steps are shown in figure 6, and the processing process comprises the following basic steps:
(a) Selecting a silicon wafer with the thickness of 0.4mm, cleaning the silicon wafer, and thermally oxidizing a layer of silicon oxide with the thickness of 300nm on the front surface and the back surface of the silicon wafer respectively, wherein the bonding requirement of a silicon substrate and glass can be still ensured by the existence of the silicon oxide with the thickness.
(b) A mask plate a comprising an electrode pad 16, an electrode lead 15 and a reticular support film 13 is manufactured, and a 1380nm deep groove is pre-patterned and etched on the front surface of a silicon wafer by using silicon oxide and photoresist as masks by using the mask plate.
(c) LPCVD is carried out on a layer of silicon oxide with the thickness of 1 mu m in the groove, LPCVD is carried out on a layer of silicon nitride with the thickness of 0.1 mu m, and a functional layer formed by two layers of composite films is used as a main material of the thermoelectric insulating layer and the net-shaped supporting film, and the LPCVD silicon oxide and the silicon nitride outside the groove are etched and removed. And manufacturing a mask plate b of the Pt thermistor 14, taking photoresist as a mask, and depositing a Cr/Pt thermistor layer with the thickness of 20nm/150nm on the silicon nitride surface in the groove etched in advance on the front surface of the silicon wafer by adopting a magnetron sputtering technology. And manufacturing a mask plate c of the Au electrode pad 16 and the Au electrode lead 15, taking photoresist as a mask, depositing a Cr/Au electrode layer with the thickness of 30nm/250nm on the silicon nitride surface in the groove etched in advance on the front surface of the silicon wafer by adopting a magnetron sputtering technology, and connecting the Cr/Au electrode layer with a thermistor layer, wherein a smooth surface is formed outside the reticular support film on the front surface of the silicon wafer at the moment, and the subsequent bonding is ensured to be carried out smoothly, wherein the Cr layer is used as an adhesive.
(d) And manufacturing a mask plate d of the cuboid micro thermal conductivity cell 12, etching the micro thermal conductivity cell on the back surface of the silicon wafer by adopting a deep reactive ion etching technology by taking silicon oxide and photoresist as masks, wherein the etching depth of the first step is 195 mu m. And manufacturing a mask plate e of the micro-channel in the form of total component, taking silicon oxide and photoresist as masks, etching the micro-channel with the depth of 200 mu m on the back surface of the silicon wafer by adopting a deep reactive ion etching technology, and simultaneously etching the micro thermal conductivity cell with the depth of 200 mu m, wherein the thickness of 5 mu m is reserved from the front surface of the silicon substrate.
(e) And manufacturing a mask plate f of the cuboid miniature thermal conductivity cell 12 comprising the reticular support film 13, etching and releasing the reticular support film on the front surface of the silicon wafer by taking photoresist as a mask, and manufacturing the cuboid miniature thermal conductivity cell 12 and the reticular support film 13 suspended in the cuboid miniature thermal conductivity cell 12. And a Cr/Au layer is deposited on the surface of the Pyrex7740 glass, a mask plate d of the cuboid miniature thermal conductivity cell 12 is utilized, the Cr/Au layer is combined with photoresist to serve as a mask, a groove with the depth of 100 mu m is formed on the surface of the Pyrex7740 glass by chemical etching, and the glass cover plate 2 is manufactured. Grooves having a depth of 100 μm were also etched in the surface of the glass substrate 3 at positions corresponding to the gas inlet and outlet passages. The silicon substrate 1 is respectively bonded with the glass cover plate 2 and the glass substrate 3 by adopting an electrostatic bonding technology, and stainless steel capillaries with the outer diameter of 0.3mm can be connected at the positions of the gas inlet and outlet channels, so that the manufacturing of the micro thermal conductivity detector is completed.
The processing method of the invention is different from the prior processing method in that a dielectric layer is deposited on the surface of a silicon wafer, a metal layer is arranged on the dielectric layer, and the dielectric layer is etched to remove the bonding area before final bonding. In the processing process of the embodiment, a dielectric layer is deposited in the groove etched in a pre-patterning manner, and a thermistor and an electrode metal layer are deposited on the surface of the dielectric layer in a sputtering manner, so that a smooth surface is formed on the surface of the silicon wafer, and the subsequent bonding process is ensured to be smoothly carried out.
In summary, the above is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (8)
1. A micro thermal conductivity detector insensitive to flow, comprising: the glass comprises a silicon substrate (1), an upper glass cover plate (2) and a lower glass substrate (3), wherein the lower glass substrate (3) is bonded with the back surface, namely the lower end surface, of the silicon substrate (1), and the upper glass cover plate (2) is bonded with the front surface, namely the upper end surface, of the silicon substrate (1);
the silicon substrate (1) is provided with two cuboid micro heat conduction pools (12), the two cuboid micro heat conduction pools (12) are of cavity structures, the upper end face and the lower end face of the silicon substrate (1) are vertically penetrated, and the two cuboid micro heat conduction pools (12) are on the same straight line along the length direction;
etching a gas inlet channel, an inlet flow dividing channel, a plurality of branch channels, an outlet flow converging channel and a gas outlet channel on the back surface of the silicon substrate (1), namely the lower end surface of the silicon substrate, aiming at each cuboid micro thermal conductivity cell (12) to form a total-division total-type gas channel; an inlet channel is communicated with an inlet flow distribution channel, the length direction of the inlet flow distribution channel is parallel to the length direction of the cuboid miniature thermal conductivity cell (12), an outlet converging channel is parallel to the inlet flow distribution channel, a plurality of branch channels are parallel and are respectively perpendicular to and communicated with the inlet flow distribution channel and the outlet converging channel, and the plurality of branch channels penetrate through the lower part of the corresponding cuboid miniature thermal conductivity cell (12) and are perpendicular to the length direction of the cuboid miniature thermal conductivity cell (12); the outlet confluence channel is connected with the gas outlet channel, and the length direction of the outlet confluence channel at the connection part is vertical to the length direction of the gas outlet channel;
the gas channels of the two cuboid miniature heat conduction tanks (12) are distributed in a central plane symmetry way, one gas channel is used as a gas channel to be tested, and the other gas channel is used as a reference gas channel;
two reticular support films (13) are fixedly arranged at the front surface of the silicon substrate (1), namely at the upper end face of each cuboid miniature heat conduction pool (12), and a thermistor (14) is deposited on the upper surface of each reticular support film (13); the thermistor (14) is of a multi-section folded structure and is connected in parallel and in series to form a planar structure, namely, the thermistor (14) is hung on the upper port of the cuboid miniature thermal conductivity cell (12) through the reticular support film (13); both ends of each thermistor (14) are connected with electrode leads (15), and the electrode leads (15) are positioned on the front surface of the silicon substrate (1); two thermistors (14) in the upper port of each cuboid miniature heat conduction pool (12) are arranged along the length direction of the cuboid miniature heat conduction pool (12), four thermistors (14) arranged on a silicon substrate (1) sequentially form four resistors R1, R4, R2 and R3, the four resistors are connected by an electrode lead (15), and an electrode pad (16) is arranged at the edge of the front surface of the silicon substrate (1);
r1 and R4 are arranged at the upper port of one cuboid miniature thermal conductivity cell (12), and R2 and R3 are arranged at the upper port of the other cuboid miniature thermal conductivity cell (12); four thermistors (14) are counted in the two heat conduction pools to form four bridge arms of a Wheatstone bridge, and a bridge circuit is directly connected with an insulating layer on the front side of the silicon substrate (1) through electrode leads (15);
the thermistor (14) protrudes out of the front surface of the reticular support film (13), and a groove is correspondingly arranged on the upper glass cover plate (2) and is used for matching with the thermistor (14).
2. A micro thermal conductivity detector insensitive to flow according to claim 1, characterized in that the length direction of the junction of the inlet channel and the inlet tap channel is vertical, and a sector-shaped groove (11) is provided in the side wall of the inlet tap channel facing the inlet channel.
3. A micro thermal conductivity detector insensitive to flow according to claim 1, characterized in that the silicon substrate (1) is bonded electrostatically to the upper glass cover plate (2) and the lower glass substrate (3), respectively.
4. A micro thermal conductivity detector insensitive to flow according to claim 1, wherein the inlet split channel width is smaller than the outlet manifold channel width, the gas inlet channel width is equal to the gas outlet channel width, the number of the branch channels of a single channel is 4, the width is smallest in the channels, the 2 edge branch channels are correspondingly located at the edge of the thermal conductivity cell, the 4 branch channels are equally spaced side by side, and are symmetrical with respect to the gas inlet and outlet channels.
5. A micro thermal conductivity detector insensitive to flow according to claim 1, characterized in that the width of the rectangular parallelepiped micro thermal conductivity cell (12) is 2-4 times the width of each branch channel.
6. A micro thermal conductivity detector insensitive to flow according to claim 1 characterized in that two mesh support films (13) and thermistors (14) thereon are arranged above a single micro thermal conductivity cell (12), the two thermistors (14) being arranged in parallel with respect to the direction of the air flow below.
7. A micro thermal conductivity detector insensitive to flow according to claim 1, characterized in that the mesh support film (13) is a composite film, the lower layer is a monocrystalline silicon layer and silicon oxide with proper thickness, and the upper layer is connected with the thermistor is silicon nitride; the thickness of the silicon oxide is 1-2 mu m, and the thickness of the silicon nitride is 0.1-0.4 mu m.
8. A micro thermal conductivity detector insensitive to flow according to claim 1, characterized in that the mesh support film (13) has 4 support beams, wherein the electrode leads (15) are connected with the thermistor (14) on the surfaces of two long support beams, two short support beams for supporting assistance, improving stability; the thermistor (14) is arranged in a serpentine shape in a right-angle fold line form on the mesh support film (13), and the thermistor (14) is sputter deposited on the surface of the silicon nitride layer of the mesh support film (13) during micromachining.
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| EP3671195A1 (en) * | 2018-12-17 | 2020-06-24 | Siemens Aktiengesellschaft | Thermoresistive gas sensor |
| CN109752418B (en) * | 2019-01-21 | 2021-11-05 | 中国科学院上海微系统与信息技术研究所 | Miniature thermal conductivity gas sensor |
| CN112034017A (en) * | 2020-09-16 | 2020-12-04 | 电子科技大学 | Wafer-level packaging-based micro thermal conductivity detector and preparation method thereof |
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