High-sensitivity miniature thermal conductivity detector and manufacturing method thereof

Abstract

The invention relates to a high-sensitivity miniature thermal conductivity detector and a manufacturing method thereof. The high-sensitivity miniature thermal conductivity detector comprises a detection substrate and a thermosensitive element, the thermo-sensitive elements comprise a first thermo-sensitive element, a second thermo-sensitive element, a third thermo-sensitive element and a fourth thermo-sensitive element which are arc-shaped or serpentine-shaped, and the first thermo-sensitive element and the second thermo-sensitive element are arranged in the first gas channel in an overlapping manner, so that gas flow in the first gas channel vertically passes through the planes of the first thermo-sensitive element and the second thermo-sensitive element; the third thermosensitive element and the fourth thermosensitive element are arranged in the second gas channel in an overlapped mode so that gas flow in the second gas channel can vertically pass through the plane of the third thermosensitive element and the plane of the fourth thermosensitive element. According to the high-sensitivity miniature thermal conductivity detector, the two thermosensitive elements are overlapped in the gas channel, and the planes of the two thermosensitive elements are perpendicular to the gas flow direction of the gas pipeline, so that the volume of a thermal conductivity cell is reduced, the heat transfer efficiency is improved, and the sensitivity is improved.

Description

Technical Field

[0001] The present application relates to the technical field of gas detection, and in particular to a high-sensitivity micro thermal conductivity detector and a manufacturing method thereof. Background Art

[0002] In the gas chromatography system, the detector is the core component of the system, and it is also the part with the most complex structure and the most difficult to make. The quality of its performance plays a decisive role in the performance of the entire system. Among them, the thermal conductivity detector TCD is one of the most widely used and frequently used detection devices in the gas chromatography system, and has a good development prospect. The thermal conductivity detector TCD detects the concentration and type of the sample based on the difference in thermal conductivity between the reference gas and the sample gas. The thermal conductivity detector TCD also has high sensitivity and stability. Since the thermal conductivity coefficients of different gases are different, the range of detected gases includes almost all volatile substances. The biggest feature of the thermal conductivity detector TCD is that there is no requirement for the type of sample to be detected, including organic and inorganic substances, and it has good versatility. Moreover, the thermal conductivity detector TCD can detect almost all volatile or semi-volatile substances without damaging the sample, which is unmatched by other detectors. Therefore, thermal conductivity detectors have more advantages in applications than other common detectors. They are the earliest, most widely used and most common type of gas chromatograph detectors. They can be used to analyze hydrogen, oxygen, nitrogen, chlorine, argon, ammonia, carbon monoxide, carbon dioxide, sulfur dioxide and other gases. They can also analyze organic pollutants and are widely used in the fields of petroleum, chemical industry, environmental protection, scientific research, etc. Therefore, thermal conductivity detectors have good development prospects.

[0003] The micro thermal conductivity detector (Micro TCD) manufactured using MEMS technology has become increasingly mature and has made great progress. MEMS technology has made new breakthroughs in reducing the volume of thermal conductivity detection cells. The volume of the thermal conductivity cell inside the device can be reduced to one percent or even one thousandth of the original, making the micro gas chromatography system based on MEMS technology also have higher sensitivity, increasing the sensitivity of the device by one to two orders of magnitude. It can also reduce the power consumption of the equipment. The micro thermal conductivity detector can be more easily integrated into the gas chromatography system, providing more space support for the design of the gas chromatography system, while greatly improving the integration of multiple parameters, and the scope of application has been further improved, such as online monitoring, portable integrated design, etc.

[0004] The thermal conductivity detector uses a Wheatstone bridge as the detection circuit. Four thermistors are distributed on the Wheatstone bridge. When the resistance values ​​of the four thermistors satisfy a certain relationship, the bridge is in a balanced state, and the output voltage is zero. Otherwise, it is not zero. Inside the micro thermal conductivity detector, four thermistors with exactly the same resistance are located in the center of the reference gas channel and the first gas channel, and are used to detect the temperature changes of the two gas flow channels respectively. When the thermal conductivity detector is working, the four thermistors are energized to generate Joule heat, and the heat is transmitted outward through the gas in the channel. Such a structure can effectively reduce the cell volume and heat loss, and improve the sensitivity of the device in the thermal conductivity detector. Inside the micro thermal conductivity detector, the core detection part of the gas adopts a Wheatstone bridge structure, and four thermistors constitute a bridge, which is distributed in the center of the two gas flow channels respectively. The four thermistors are made under the same conditions, so the resistance value difference of each element is small.

[0005] In the design of a micro thermal conductivity detector, reducing the volume of the cell in the thermal conductivity cell cavity is an important aspect of optimizing performance. Improving the sensitivity of a thermal conductivity detector can be achieved by reducing the cell volume and heat loss. Dead volume refers to areas in the thermal conductivity cell where gas molecules cannot flow freely. The gas molecules in these areas will not exchange heat with the thermistor, thereby affecting the detector's response speed and sensitivity. The larger the cell volume of the micro thermal conductivity detector, the larger the dead volume. As the cell volume increases, the heat exchange rate between the gas molecules and the thermistor slows down, reducing the detector's response speed and sensitivity. The common defects of existing thermal conductivity detectors are: First, thermal conductivity detectors usually have a large cell volume, generally 100-500μL, and some are even larger. Their internal structure is relatively complex, consisting of a thermistor and a cell body. The thermistor is mostly a hot wire, such as a tungsten wire, a platinum wire, a rhenium wire, etc. The hot wire is installed in the channel of the cell body in the thermal conductivity detector. The cell body material was mostly copper in the early days, but now it is mostly stainless steel, which has the disadvantages of short life, low sensitivity, large volume, and high power consumption. Second, the air flow channels of existing thermal conductivity detectors often adopt straight channels. In each channel, two thermistors are located at the front and rear ends of the channel respectively. Such a distribution brings a larger pool volume, and the two thermistors are not in the same position. The air flow flows through the two thermistors successively, which will cause the temperature difference of the two thermistors, which is not conducive to signal detection; third, the shape of the thermistors of the thermal conductivity detector is mostly a broken line shape, and the resistance width at the corner position is different. After this structure is powered on and heated, uneven temperature and deformation distribution may occur at the corner position, which may affect the life and performance of the entire thermal conductivity detector. Summary of the invention

[0006] The present application provides a high-sensitivity micro thermal conductivity detector and a manufacturing method thereof, which are used to solve the technical problems that the existing thermal conductivity detectors have large volume and low sensitivity due to the use of zigzag-type thermistor elements.

[0007] In order to achieve the above objectives, this application provides the following technical solutions:

[0008] In one aspect, a highly sensitive micro thermal conductivity detector is provided, comprising:

[0009] A detection substrate is provided with a thermal conductivity cell perpendicular to a base surface of the detection substrate, wherein the thermal conductivity cell includes a first gas channel and a second gas channel;

[0010] A thermal sensitive element is parallel to the detection substrate and is suspended in the thermal conductivity cell;

[0011] Wherein, the thermosensitive element includes a first thermosensitive element, a second thermosensitive element, a third thermosensitive element and a fourth thermosensitive element in an arc shape or a serpentine shape, the first thermosensitive element and the second thermosensitive element overlap to form a thermosensitive module arranged in the first gas channel, so that the airflow in the first gas channel passes vertically through the planes of the first thermosensitive element and the second thermosensitive element, and the first thermosensitive element and the second thermosensitive element are separated by a first insulating medium; the third thermosensitive element and the fourth thermosensitive element overlap to form a thermosensitive module arranged in the second gas channel, so that the airflow in the second gas channel passes vertically through the planes of the third thermosensitive element and the fourth thermosensitive element, and the third thermosensitive element and the fourth thermosensitive element are separated by a second insulating medium.

[0012] Preferably, the thermistor module includes a first dielectric layer, a first metal layer, an intermediate insulating layer, a second metal layer and a second dielectric layer, the first metal layer is arranged on the first dielectric layer, the intermediate insulating layer is arranged on the first metal layer, the second metal layer is arranged on the intermediate insulating layer, and the second dielectric layer is arranged on the second metal layer.

[0013] Preferably, the first dielectric layer, the intermediate insulating layer and the second dielectric layer are all made of one or more insulating dielectric materials selected from silicon nitride, silicon oxide and silicon carbide.

[0014] Preferably, the first metal layer and the second metal layer are both made of platinum, tungsten, titanium, aluminum or nickel.

[0015] Preferably, the thickness of the intermediate insulating layer is 10 nm to 1000 nm, and the thickness of the second dielectric layer is 100 nm to 1000 nm.

[0016] Preferably, the first gas channel and the second gas channel are both provided with a gas inlet and a gas outlet.

[0017] Preferably, at least four connection points connected to the thermosensitive element are provided in the first gas channel and the second gas channel, and the thermosensitive element is connected to the thermal conductivity pool through the connection points; and / or, corresponding to the connection lines of the thermosensitive element, connection holes are opened in the first gas channel and the second gas channel.

[0018] Preferably, the detection substrate comprises an upper substrate and a lower substrate abutting against the lower end surface of the upper substrate.

[0019] On the other hand, a method for manufacturing a high-sensitivity micro-thermal conductivity detector is provided, which is applied to the high-sensitivity micro-thermal conductivity detector described above, and the manufacturing method comprises the following steps:

[0020] Acquire material data of the detection substrate and the thermal sensitive module, wherein the material data includes an upper substrate, a lower substrate, a first dielectric layer, a first metal layer, an intermediate insulating layer, a second metal layer, and a second dielectric layer;

[0021] Performing metal stripping and etching on the upper substrate, the first dielectric layer, the first metal layer, the intermediate insulating layer, the second metal layer and the second dielectric layer to obtain a composite structure having a mesh-shaped micro-bridge pattern;

[0022] Performing photolithography and etching on the lower substrate to obtain a capping substrate having connection points and grooves;

[0023] Placing the micro-bridge pattern of the composite structure in the groove of the capping substrate and aligning it with the connection point of the capping substrate and then performing bonding processing to obtain an initial detector;

[0024] The upper substrate of the initial detector is corroded by using KOH or TMAH corrosive solution to obtain a high-sensitivity micro thermal conductivity detector with a suspended microbridge structure.

[0025] Preferably, the upper substrate, the first dielectric layer, the first metal layer, the intermediate insulating layer, the second metal layer and the second dielectric layer are subjected to metal stripping and etching to obtain a composite structure having a mesh-shaped microbridge pattern, which includes:

[0026] Depositing the first dielectric layer on the surface of the upper substrate to obtain a first substrate sample;

[0027] Depositing the first metal layer on the surface of the first dielectric layer in the first substrate sample, and then processing the first metal layer by metal stripping technology or etching technology to obtain a second substrate sample having a serpentine or mesh structure thermosensitive element;

[0028] Depositing the intermediate insulating layer on the surface of the first metal layer in the second substrate sample to obtain a third substrate sample;

[0029] Depositing the second metal layer on the surface of the intermediate insulating layer in the third substrate sample, and obtaining a fourth substrate sample having a serpentine or mesh structure thermosensitive element by metal stripping technology or etching technology on the second metal layer, wherein the thermosensitive elements of the first metal layer and the second metal layer of the fourth substrate sample overlap each other;

[0030] Depositing the second dielectric layer on the surface of the second metal layer in the fourth substrate sample to obtain a fifth substrate sample;

[0031] The surface of the fifth substrate sample is subjected to photolithography treatment to obtain a sixth substrate sample with a mesh microbridge pattern; then the first dielectric layer and the middle insulating layer of the sixth substrate sample are etched away using reactive ion etching technology to obtain a composite structure with a mesh-shaped microbridge pattern.

[0032] The high-sensitivity micro thermal conductivity detector and its manufacturing method, the high-sensitivity micro thermal conductivity detector, comprising a detection substrate, a thermal conductivity cell perpendicular to the detection substrate base surface, the thermal conductivity cell comprising a first gas channel and a second gas channel; a thermal element parallel to the detection substrate base surface and suspended in the thermal conductivity cell; the thermal element comprising a first thermal element, a second thermal element, a third thermal element and a fourth thermal element in an arc shape or a serpentine shape, the first thermal element overlaps with the second thermal element to form a thermal module arranged in the first gas channel, so that the airflow in the first gas channel passes perpendicularly through the planes of the first thermal element and the second thermal element, and the first thermal element and the second thermal element are separated by a first insulating medium; the third thermal element overlaps with the fourth thermal element to form a thermal module arranged in the second gas channel, so that the airflow in the second gas channel passes perpendicularly through the planes of the third thermal element and the fourth thermal element, and the third thermal element and the fourth thermal element are separated by a second insulating medium.

[0033] It can be seen from the above technical scheme that the present application has the following advantages: the high-sensitivity micro-thermal conductivity detector not only reduces the volume of the thermal conductivity cell, but also improves the heat transfer efficiency and the sensitivity of the high-sensitivity micro-thermal conductivity detector by placing two thermistors overlapping in the gas channel and the planes of the two thermistors are perpendicular to the airflow direction of the gas pipeline; the use of arc-shaped or serpentine-shaped thermistors instead of traditional zigzag thermistors makes the temperature and stress distribution of each position of the thermistor more uniform, and the life and stability of the thermistor are higher. At the same time, without increasing the surface area of ​​the thermal conductivity cell, the length of the thermistor can be made as long as possible to increase the resistance value of the thermistor and improve the sensitivity; the technical problems of the existing thermal conductivity detector being large in volume and having low sensitivity due to the use of zigzag thermistors are solved.

[0034] The manufacturing method of the high-sensitivity micro thermal conductivity detector adopts a wet etching process to prepare a gas flow channel, replacing the traditional back-side dry etching release, which can reduce the cavity depth of the gas channel and the cell volume of the thermal conductivity cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0036] Figure 1 This is a schematic diagram of the structure of a high-sensitivity micro thermal conductivity detector described in an embodiment of the present application;

[0037] Figure 2 This is a schematic side view of the structure of the high-sensitivity micro thermal conductivity detector described in an embodiment of the present application;

[0038] Figure 3 This is a schematic diagram of the top view of the high-sensitivity micro thermal conductivity detector described in an embodiment of the present application;

[0039] Figure 4 Schematic diagram of the steps of the method for manufacturing the high-sensitivity micro thermal conductivity detector described in an embodiment of the present application. DETAILED DESCRIPTION

[0040] In order to make the purpose, features, and advantages of the invention of this application more obvious and easy to understand, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the embodiments described below are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0041] In the description of the embodiments of the present application, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present application, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0042] In the embodiments of the present application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0043] Patent term explanation:

[0044] The embodiment of the present application provides a high-sensitivity micro thermal conductivity detector and a manufacturing method thereof, which solves the technical problems that the existing thermal conductivity detectors are large in size and have low sensitivity due to the use of zigzag-shaped thermistors.

[0045] Embodiment 1:

[0046] Figure 1 This is a schematic diagram of the structure of the high-sensitivity micro thermal conductivity detector described in an embodiment of the present application.

[0047] like Figure 1 As shown, an embodiment of the present application provides a high-sensitivity micro-thermal conductivity detector, including a detection substrate and a thermal sensitive element arranged on the detection substrate.

[0048] In the embodiment of the present application, the detection substrate is provided with a thermal conductivity cell perpendicular to the detection substrate surface, and the thermal conductivity cell includes a first gas channel 5 and a second gas channel 2. The detection substrate includes an upper substrate 1 and a lower substrate 7 abutting against the lower end surface of the upper substrate 1.

[0049] It should be noted that the detection substrate is used as the base of the high-sensitivity micro thermal conductivity detector to support the thermal conductivity cell and the thermosensitive element. In this embodiment, the upper substrate 1 is made of a silicon wafer, and the lower substrate 7 can be made of a glass substrate. The high-sensitivity micro thermal conductivity detector is prepared on the upper substrate 1 using semiconductor manufacturing technology (such as micro-electromechanical system (MEMS) technology), which reduces the volume of the traditional detector by several times, and the cell volume of the high-sensitivity micro thermal conductivity detector is reduced to less than μL. In addition, the high-sensitivity micro thermal conductivity detector can be mass-produced with lower cost and good consistency. Among them, the upper substrate 1 made of silicon wafer and the lower substrate 7 made of glass substrate are sealed to form a closed cavity, and used as a gas channel to reduce the cell volume of the thermal conductivity cell, avoid redundant dead volume, and speed up the response of the high-sensitivity micro thermal conductivity detector.

[0050] In the embodiment of the present application, the thermosensitive element is parallel to the base surface of the detection substrate and is suspended in the thermal conductivity pool. Among them, the thermosensitive element includes a first thermosensitive element 31, a second thermosensitive element 41, a third thermosensitive element 3 and a fourth thermosensitive element 4 in an arc shape or a serpentine shape. The first thermosensitive element 31 and the second thermosensitive element 41 overlap to form a thermosensitive module arranged in the first gas channel 5, so that the airflow in the first gas channel 5 passes vertically through the plane of the first thermosensitive element 31 and the second thermosensitive element 41, and the first thermosensitive element 31 and the second thermosensitive element 41 are separated by a first insulating medium; the third thermosensitive element 3 and the fourth thermosensitive element 4 overlap to form a thermosensitive module arranged in the second gas channel 2, so that the airflow in the second gas channel 2 passes vertically through the plane of the third thermosensitive element 3 and the fourth thermosensitive element 4, and the third thermosensitive element 3 and the fourth thermosensitive element 4 are separated by a second insulating medium.

[0051] It should be noted that the thermistor can be selected as thermistor. The first insulating medium and the second insulating medium can be made of one or more insulating medium materials selected from silicon nitride, silicon oxide, and silicon carbide. In this embodiment, the high-sensitivity micro thermal conductivity detector is realized by overlapping two thermistors in the same gas channel, and the two thermistors are separated by an insulating medium, so that the volume of the thermal conductivity cell is halved on the basis of placing the two thermistors in front and behind, thereby improving the sensitivity of the high-sensitivity micro thermal conductivity detector. The high-sensitivity micro thermal conductivity detector adopts the airflow direction of the gas channel to be perpendicular to the plane of the thermistor. After the airflow enters the thermal conductivity cell from the air inlet of the gas channel, it flows vertically through the surface of the thermistor, which can improve the heat transfer efficiency, thereby improving the sensitivity of the high-sensitivity micro thermal conductivity detector. The high-sensitivity micro thermal conductivity detector uses an arc-shaped or snake-shaped thermistor to replace the traditional zigzag thermistor, so that the temperature and stress distribution at each position of the thermistor is more uniform, the life and stability of the thermistor are higher, and at the same time, without increasing the surface area of ​​the thermal conductivity cell, the length of the thermistor can be made as long as possible to increase the resistance value of the thermistor and improve the sensitivity.

[0052] In the embodiment of the present application, both the first gas channel 5 and the second gas channel 2 are provided with an air inlet and an air outlet 6 .

[0053] It should be noted that the highly sensitive micro thermal conductivity detector has two holes (such as an air inlet and an air outlet 6) on the upper substrate 1 as openings of two gas channels of the sensitive micro thermal conductivity detector. The air flows in from the air inlet direction of the two gas channels. Two thermosensitive elements are distributed in the middle of each gas channel. The two thermosensitive elements are placed overlappingly, and there is an insulating medium between the two thermosensitive elements as an insulating layer. When the gas enters the gas channel from the air inlet, it flows vertically through the surface of the thermosensitive element and flows out from the air outlet 6.

[0054] The present application provides a high-sensitivity micro thermal conductivity detector, comprising a detection substrate, a thermal conductivity cell perpendicular to the base surface of the detection substrate, the thermal conductivity cell comprising a first gas channel and a second gas channel; a thermosensitive element parallel to the base surface of the detection substrate and suspended in the thermal conductivity cell; the thermosensitive element comprises a first thermosensitive element, a second thermosensitive element, a third thermosensitive element and a fourth thermosensitive element in an arc or serpentine shape, the first thermosensitive element overlaps with the second thermosensitive element to form a thermosensitive module arranged in the first gas channel, so that the airflow in the first gas channel passes vertically through the planes of the first thermosensitive element and the second thermosensitive element, and the first thermosensitive element and the second thermosensitive element are separated by a first insulating medium; the third thermosensitive element overlaps with the fourth thermosensitive element to form a thermosensitive module arranged in the second gas channel, so that the airflow in the second gas channel passes vertically through the planes of the third thermosensitive element and the fourth thermosensitive element, and the third thermosensitive element and the fourth thermosensitive element are separated by a second insulating medium. The high-sensitivity micro-thermal conductivity detector not only reduces the volume of the thermal conductivity cell, but also improves the heat transfer efficiency and the sensitivity of the high-sensitivity micro-thermal conductivity detector by placing two thermally sensitive elements overlapping each other in the gas channel and with the planes of the two thermally sensitive elements perpendicular to the gas flow direction of the gas pipeline; the use of arc-shaped or serpentine-shaped thermally sensitive elements instead of traditional zigzag-shaped thermistors makes the temperature and stress distribution of each position of the thermally sensitive element more uniform, and the life and stability of the thermally sensitive element are higher. At the same time, without increasing the surface area of ​​the thermally sensitive cell, the length of the thermally sensitive element can be made as long as possible to increase the resistance value of the thermally sensitive element and improve the sensitivity; the technical problems of the existing thermal conductivity detector being large in volume and having low sensitivity due to the use of zigzag-shaped thermally sensitive elements are solved.

[0055] Figure 2 This is a schematic side view of the structure of the high-sensitivity micro thermal conductivity detector described in an embodiment of the present application.

[0056] like Figure 2 As shown, in one embodiment of the present application, the thermistor module includes a first dielectric layer 13, a first metal layer 12, an intermediate insulating layer 11, a second metal layer 10 and a second dielectric layer 9, the first metal layer 12 is arranged on the first dielectric layer 13, the intermediate insulating layer 11 is arranged on the first metal layer 12, the second metal layer 12 is arranged on the intermediate insulating layer 11, and the second dielectric layer 9 is arranged on the second metal layer 10.

[0057] It should be noted that the first dielectric layer 13, the intermediate insulating layer 11 and the second dielectric layer 9 can all be made of one or more insulating dielectric materials selected from silicon nitride, silicon oxide and silicon carbide. The first metal layer 12 and the second metal layer 10 can all be made of platinum, tungsten, titanium, aluminum or nickel. The thickness of the intermediate insulating layer 11 can be selected to be 10nm~1000nm, and the thickness of the second dielectric layer 9 can be selected to be 100nm~1000nm. In this embodiment, the first insulating medium and the second insulating medium of the high-sensitivity micro thermal conductivity detector refer to the intermediate insulating layer 11. The entire thermistor module is suspended in the middle of the gas channel of the thermal conductivity cell. The thermistor module is composed of a multilayer structure including a first dielectric layer 13, a first metal layer 12, an intermediate insulating layer 11, a second metal layer 10, and a second dielectric layer 9. The pattern of the thermistor module is a mesh, wherein the first dielectric layer 13 serves as the main support of the entire thermistor module, so that the entire thermistor module structure is stably suspended in the middle of the gas channel. The first metal layer 12 and the second metal layer 10 serve as thermistors of the thermistor module. The second metal layer 10 overlaps the first metal layer 12. When the gas channel airflow of the upper substrate flows through the thermistor, the detection function is achieved; the intermediate insulating layer 11 serves as an insulating layer between the first metal layer 12 and the second metal layer 10 to achieve the function of isolation and insulation; the second dielectric layer 9 serves as a protective layer for the metal layer to prevent erosion and oxidation by water vapor and corrosive gases in the airflow.

[0058] Figure 3 This is a schematic diagram of the top view of the high-sensitivity micro thermal conductivity detector described in an embodiment of the present application.

[0059] like Figure 3 As shown, in one embodiment of the present application, at least four connection points 8 connected to the thermistor are provided in the first gas channel 5 and the second gas channel 2, and the thermistor is connected to the thermal conductivity pool through the connection points 8; and / or, corresponding to the connection lines of the thermistor, connection holes are opened in the first gas channel 5 and the second gas channel 2.

[0060] It should be noted that the connection point 8 can be selected as an anchor point. Figure 1 and Figure 3As shown, a thermosensitive element is distributed in each gas channel, and the entire thermosensitive module is distributed between the first gas channel 5 and the second gas channel 2 of the thermal conductivity cell. The thermosensitive element is connected to the upper substrate 1 through a connection point 8 to reduce the heat transfer between the thermosensitive element and the upper substrate 1 and reduce heat loss. The shape of the entire thermosensitive module is circular, so that the heating area of ​​the circular thermosensitive element is concentrated as much as possible in the center of the thermal conductivity cell; and the pattern of the thermosensitive element is spiral or serpentine, and the arc-shaped thermosensitive element is used to replace the traditional zigzag thermistor, so that the temperature and stress distribution of each position of the thermosensitive element is more uniform, the life and stability of the thermosensitive element are higher, and at the same time, without increasing the surface area of ​​the thermal conductivity cell, the length of the thermosensitive element can be made as long as possible to increase the resistance value of the thermosensitive element and improve the sensitivity.

[0061] In the embodiment of the present application, the structure of the high-sensitivity micro thermal conductivity detector is more compact and simple, the dead volume is small, and the peak broadening of the thermal sensitive element can be effectively reduced. In addition, the high-sensitivity micro thermal conductivity detector has higher sensitivity, is suitable for the detection of lower concentration substances, has lower power consumption, smaller size, and higher integration.

[0062] Embodiment 2:

[0063] Figure 4 Schematic diagram of the steps of the method for manufacturing the high-sensitivity micro thermal conductivity detector described in an embodiment of the present application.

[0064] like Figure 4 As shown, the embodiment of the present application provides a method for manufacturing a high-sensitivity micro-thermal conductivity detector, which is applied to the high-sensitivity micro-thermal conductivity detector described above. The manufacturing method includes the following steps:

[0065] S1. Acquire material data of the detection substrate and the thermal sensing module, the material data including an upper substrate, a lower substrate, a first dielectric layer, a first metal layer, an intermediate insulating layer, a second metal layer, and a second dielectric layer.

[0066] It should be noted that the content of the high-sensitivity micro thermal conductivity detector has been described in the first embodiment, and the content of the high-sensitivity micro thermal conductivity detector will not be repeated in this embodiment. In step S1, the materials required for making the high-sensitivity micro thermal conductivity detector are obtained. In this embodiment, the upper substrate is a substrate made of a silicon wafer, and the lower substrate can be a substrate made of a glass substrate.

[0067] S2. Perform metal stripping and etching on the upper substrate, the first dielectric layer, the first metal layer, the intermediate insulating layer, the second metal layer and the second dielectric layer to obtain a composite structure having a mesh-shaped microbridge pattern. The process of performing metal stripping and etching on the upper substrate, the first dielectric layer, the first metal layer, the intermediate insulating layer, the second metal layer and the second dielectric layer to obtain a composite structure having a mesh-shaped microbridge pattern includes:

[0068] Depositing a first dielectric layer on the surface of the upper substrate to obtain a first substrate sample;

[0069] Depositing a first metal layer on the surface of the first dielectric layer in the first substrate sample, and then processing the first metal layer by metal stripping technology or etching technology to obtain a second substrate sample having a serpentine or mesh structure thermosensitive element;

[0070] Depositing an intermediate insulating layer on the surface of the first metal layer in the second substrate sample to obtain a third substrate sample;

[0071] Depositing a second metal layer on the surface of the middle insulating layer in the third substrate sample, and obtaining a fourth substrate sample having a serpentine or mesh structure thermosensitive element by metal stripping or etching the second metal layer, wherein the thermosensitive element of the first metal layer of the fourth substrate sample overlaps with the thermosensitive element of the second metal layer;

[0072] Depositing a second dielectric layer on the surface of the second metal layer in the fourth substrate sample to obtain a fifth substrate sample;

[0073] The surface of the fifth substrate sample is photolithographically processed to obtain a sixth substrate sample with a mesh microbridge pattern; then the first dielectric layer and the middle insulating layer of the sixth substrate sample are etched away using reactive ion etching technology to obtain a composite structure with a mesh-shaped microbridge pattern.

[0074] It should be noted that, in the process of obtaining the first substrate sample, a first dielectric layer 13 is deposited on the surface of the cleaned upper substrate. This first dielectric layer 13 can be used as both an insulating layer and a supporting layer. The material of the first dielectric layer 13 is selected from one or more dielectric materials such as silicon nitride, silicon oxide, silicon carbide and other insulating materials to keep the surface of the first dielectric layer 13 flat. In the process of obtaining the second substrate sample, a first metal layer 12 (such as a metal film) is deposited on the surface of the first dielectric layer 13. The material of the first metal layer 12 is selected from materials with high resistance temperature coefficients such as platinum, tungsten, titanium, aluminum, nickel, etc. to improve the sensitivity of the high-sensitivity micro-thermal conductivity detector. After coating, the first metal layer 12 is processed by metal stripping technology or etching technology to obtain a serpentine or mesh structure as a thermal element. In the process of obtaining the third substrate sample, an intermediate insulating layer 11 is deposited on the surface of the first metal layer 12. The material of the intermediate insulating layer is one or more insulating materials such as silicon nitride, silicon oxide, silicon carbide and the like. The thickness of the intermediate insulating layer is 10nm-1000nm to ensure the insulation between the metal resistors. In the process of obtaining the fourth substrate sample, a second metal layer 10 is deposited on the surface of the intermediate insulating layer 11, and the second metal layer 10 is processed by metal stripping technology or etching technology under the same conditions as the first metal layer 12 to obtain a serpentine or mesh-shaped thermistor. The thermistor made of the first metal layer overlaps with the thermistor made of the second metal layer, and is separated by the intermediate insulating layer. In the process of obtaining the fifth substrate sample, a second dielectric layer 9 is deposited on the second metal layer. The material of the second dielectric layer 9 is one or more insulating materials such as silicon nitride, silicon oxide, and silicon carbide. In the process of obtaining a composite structure with a mesh-shaped microbridge pattern, a mesh microbridge pattern is obtained on the surface of the fifth substrate sample by photolithography; and then the first dielectric layer and the intermediate insulating layer are etched away by reactive ion etching technology to obtain a composite structure of a microbridge structure pattern.

[0075] S3. Perform photolithography and etching on the lower substrate to obtain a capping substrate with connection points and grooves.

[0076] It should be noted that step S3 is to obtain a capping substrate that matches the composite structure. In this embodiment, the gas channel and the electrode area pattern that matches the microbridge structure pattern are photoetched on the surface of the lower substrate made of a glass wafer of the same size as the upper substrate 1, and a groove with a depth of 1 μm-500 μm is etched using a BOE solution or an HF solution to prepare a matching capping base.

[0077] S4. Place the micro-bridge pattern of the composite structure in the groove of the capping substrate and align it with the connection point of the capping substrate and then perform bonding processing to obtain an initial detector.

[0078] It should be noted that in step S4, the composite structure is tightly combined with the composite structure to obtain a closed gas channel. In this embodiment, in the process of obtaining the initial detector, a puncher is used to punch an air inlet and an air outlet on the surface or side of the cap substrate to connect with the external gas path, and it is aligned with the microbridge pattern of the composite structure and tightly combined by bonding.

[0079] S5. The upper substrate of the initial detector is corroded with KOH or TMAH etching solution to obtain a highly sensitive micro thermal conductivity detector with a suspended microbridge structure.

[0080] It should be noted that in step S5, a high-sensitivity micro thermal conductivity detector with a suspended micro-bridge structure is manufactured based on step S4. In this embodiment, two insulating layers and one metal film of the initial detector after the processing in step S4 are used as masks, KOH or TMAH (tetramethylammonium hydroxide) is used as an etching solution, and the substrate is etched downward to form a cavity, and the suspended micro-bridge structure is released to complete the manufacture of a high-sensitivity micro thermal conductivity detector with a suspended micro-bridge structure.

[0081] In the embodiment of the present application, the manufacturing method of the high-sensitivity micro thermal conductivity detector adopts a wet etching process to prepare the gas flow channel, replacing the traditional back-side dry etching release, which can reduce the cavity depth of the gas channel and reduce the cell volume of the thermal conductivity cell.

[0082] As described above, the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A highly sensitive micro thermal conductivity detector, characterized in that: include: A detection substrate is provided with a thermal conductivity cell perpendicular to a base surface of the detection substrate, wherein the thermal conductivity cell includes a first gas channel and a second gas channel; A thermal sensitive element is parallel to the detection substrate and is suspended in the thermal conductivity cell; Wherein, the thermosensitive element includes a first thermosensitive element, a second thermosensitive element, a third thermosensitive element and a fourth thermosensitive element in an arc shape or a serpentine shape, the first thermosensitive element and the second thermosensitive element overlap to form a thermosensitive module arranged in the first gas channel, so that the airflow in the first gas channel passes vertically through the planes of the first thermosensitive element and the second thermosensitive element, and the first thermosensitive element and the second thermosensitive element are separated by a first insulating medium; the third thermosensitive element and the fourth thermosensitive element overlap to form a thermosensitive module arranged in the second gas channel, so that the airflow in the second gas channel passes vertically through the planes of the third thermosensitive element and the fourth thermosensitive element, and the third thermosensitive element and the fourth thermosensitive element are separated by a second insulating medium.

2. The high-sensitivity micro thermal conductivity detector according to claim 1, characterized in that: The thermistor module includes a first dielectric layer, a first metal layer, an intermediate insulating layer, a second metal layer and a second dielectric layer, wherein the first metal layer is arranged on the first dielectric layer, the intermediate insulating layer is arranged on the first metal layer, the second metal layer is arranged on the intermediate insulating layer, and the second dielectric layer is arranged on the second metal layer.

3. The high-sensitivity micro thermal conductivity detector according to claim 2, characterized in that: The first dielectric layer, the middle insulating layer and the second dielectric layer are all made of one or more insulating dielectric materials selected from silicon nitride, silicon oxide and silicon carbide.

4. The high-sensitivity micro thermal conductivity detector according to claim 2, characterized in that: The first metal layer and the second metal layer are both made of platinum, tungsten, titanium, aluminum or nickel.

5. The high-sensitivity micro thermal conductivity detector according to claim 2, characterized in that: The thickness of the intermediate insulating layer is 10 nm to 1000 nm, and the thickness of the second dielectric layer is 100 nm to 1000 nm.

6. The high-sensitivity micro thermal conductivity detector according to any one of claims 1 to 5, characterized in that: The first gas channel and the second gas channel are both provided with a gas inlet and a gas outlet.

7. The high-sensitivity micro thermal conductivity detector according to any one of claims 1 to 5, characterized in that: At least four connection points connected to the thermosensitive element are provided in the first gas channel and the second gas channel, and the thermosensitive element is connected to the thermal conductivity pool through the connection points; and / or, corresponding to the connection lines of the thermosensitive element, connection holes are opened in the first gas channel and the second gas channel.

8. The high-sensitivity micro thermal conductivity detector according to any one of claims 1 to 5, characterized in that: The detection substrate comprises an upper substrate and a lower substrate abutting against the lower end surface of the upper substrate.

9. A method for manufacturing a high-sensitivity micro thermal conductivity detector, applied to the high-sensitivity micro thermal conductivity detector according to any one of claims 1 to 8, characterized in that: The manufacturing method comprises the following steps: Acquire material data of the detection substrate and the thermal sensitive module, wherein the material data includes an upper substrate, a lower substrate, a first dielectric layer, a first metal layer, an intermediate insulating layer, a second metal layer, and a second dielectric layer; Performing metal stripping and etching on the upper substrate, the first dielectric layer, the first metal layer, the intermediate insulating layer, the second metal layer and the second dielectric layer to obtain a composite structure having a mesh-shaped microbridge pattern; Performing photolithography and etching on the lower substrate to obtain a capping substrate having connection points and grooves; Placing the micro-bridge pattern of the composite structure in the groove of the capping substrate and aligning it with the connection point of the capping substrate and then performing bonding processing to obtain an initial detector; The upper substrate of the initial detector is corroded by using KOH or TMAH corrosive solution to obtain a high-sensitivity micro thermal conductivity detector with a suspended microbridge structure.

10. The method for manufacturing a highly sensitive micro thermal conductivity detector according to claim 9, characterized in that: The composite structure having a mesh-shaped microbridge pattern is obtained by performing metal stripping and etching on the upper substrate, the first dielectric layer, the first metal layer, the intermediate insulating layer, the second metal layer and the second dielectric layer. The composite structure includes: Depositing the first dielectric layer on the surface of the upper substrate to obtain a first substrate sample; Depositing the first metal layer on the surface of the first dielectric layer in the first substrate sample, and then processing the first metal layer by metal stripping technology or etching technology to obtain a second substrate sample having a serpentine or mesh structure thermosensitive element; Depositing the intermediate insulating layer on the surface of the first metal layer in the second substrate sample to obtain a third substrate sample; Depositing the second metal layer on the surface of the intermediate insulating layer in the third substrate sample, and obtaining a fourth substrate sample having a serpentine or mesh structure thermosensitive element by metal stripping technology or etching technology on the second metal layer, wherein the thermosensitive elements of the first metal layer and the second metal layer of the fourth substrate sample overlap each other; Depositing the second dielectric layer on the surface of the second metal layer in the fourth substrate sample to obtain a fifth substrate sample; The surface of the fifth substrate sample is subjected to photolithography treatment to obtain a sixth substrate sample with a mesh microbridge pattern; then the first dielectric layer and the middle insulating layer of the sixth substrate sample are etched away using reactive ion etching technology to obtain a composite structure with a mesh-shaped microbridge pattern.

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