Single-channel micro-thermal conductivity detector and its preparation method

Abstract

The present invention provides a single-channel microthermal conductivity detector and a preparation method thereof. A conductive connection member is integrated in a substrate to replace an external lead wire, avoiding the formation of contact resistance and reducing the zero-point error and noise interference of the detector; the reference channel is cancelled, and the thermistor of the reference channel is directly prepared in the substrate, avoiding the noise formed by the gas flow disturbance in the reference channel. At the same time, the requirement for one-way carrier gas is reduced, and the gas supply burden of the gas chromatography system is reduced; the microthermal conductivity detector of the present invention has a simple structure, can effectively improve the detection sensitivity of the detector, and at the same time reduce the gas supply burden of the gas chromatography system, which is beneficial to portable applications and can further promote the miniaturization of the gas chromatography system.

Description

Technical Field

[0001] The present invention belongs to the field of microelectromechanical systems and relates to a single-channel microthermal conductivity detector and a preparation method thereof. Background Art

[0002] A thermal conductivity detector is a concentration-type and non-destructive sensor, which realizes detection based on the difference in thermal conductivity of different gases. The miniaturized microthermal conductivity detector has a small volume, low power consumption and light weight, and can meet the needs of miniaturization of gas chromatography systems.

[0003] The microthermal conductivity detector forms a Wheatstone bridge with four thermistors. Among them, two thermistors are arranged in the reference channel, and the other two thermistors are arranged in the test channel. When only the carrier gas passes through the two channels, the bridge is balanced and no output signal is generated; when the carrier gas in the test channel carries the component gas to be detected, the change in thermal conductivity will cause the resistance value of the thermistor to change, so that the bridge is unbalanced and an electrical signal is output, and then the chromatogram of the gas to be detected is obtained.

[0004] At present, the microthermal conductivity detector generally forms a Wheatstone bridge by means of external leads, which will inevitably introduce contact resistance. On the one hand, the inconsistency of the contact resistance will cause the Wheatstone bridge to be unbalanced, resulting in zero-point error. On the other hand, the contact resistance will also introduce interference signals; the double-channel gas path structure with a test channel and a reference channel is prone to generate noise due to unstable air flow in the reference channel, reducing the signal-to-noise ratio of the detector; the double-channel gas path structure requires two carrier gases, which will increase the gas supply burden of the gas chromatography system and is not conducive to application scenarios such as on-site analysis.

[0005] Therefore, it is necessary to provide a single-channel microthermal conductivity detector and a preparation method thereof. Summary of the Invention

[0006] In view of the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a single-channel microthermal conductivity detector and a preparation method thereof, which are used to solve the problems of reduced signal-to-noise ratio and large carrier gas consumption caused by the structure of the microthermal conductivity detector in the prior art.

[0007] To achieve the above purpose and other related purposes, the present invention provides a single-channel microthermal conductivity detector, and the single-channel microthermal conductivity detector includes:

[0008] A substrate, in which a microchannel is provided;

[0009] Thermistors, the thermistors include a first thermistor and a fourth thermistor arranged on the substrate, and a second thermistor and a third thermistor suspended in the microchannel through a support structure;

[0010] A conductive connection member, which is disposed on the substrate and connected to the thermistor to form a Wheatstone bridge structure;

[0011] A cover plate, which is bonded to the substrate, and the microchannel is covered by the cover plate to form a closed microchannel.

[0012] Optionally, the support structure is in a mesh shape; the support structure includes a first dielectric layer on the lower surface of the thermistor and a second dielectric layer on the upper surface of the thermistor.

[0013] Optionally, the pads in the conductive connection member are exposed on the cover plate; the conductive connection member and the thermistor are made of the same material.

[0014] Optionally, the cover plate is disposed on opposite sides of the substrate, or the cover plate is only disposed on one side of the substrate; a cover plate accommodation groove corresponding to the microchannel is provided on the side of the cover plate adjacent to the substrate.

[0015] Optionally, the substrate includes a silicon substrate, a silicon-on-insulator substrate, a ceramic substrate or a glass substrate; the cover plate includes a silicon cover plate, a silicon-on-insulator cover plate, a ceramic cover plate or a glass cover plate.

[0016] The present invention also provides a preparation method for a single-channel microthermal conductivity detector, including the following steps:

[0017] Provide a substrate;

[0018] Form a thermistor, a conductive connection member and a support structure on the substrate, the thermistor includes a first thermistor, a second thermistor, a third thermistor and a fourth thermistor, wherein the conductive connection member connects the thermistors to form a Wheatstone bridge structure;

[0019] Provide an upper cover plate and bond the upper cover plate to the upper surface of the substrate;

[0020] Pattern the substrate from the lower surface of the substrate to form a microchannel, and the second thermistor and the third thermistor are suspended in the microchannel through the support structure;

[0021] Provide a lower cover plate and bond the lower cover plate to the lower surface of the substrate, and combine the upper cover plate and the lower cover plate to cover the microchannel to form a closed microchannel.

[0022] The present invention also provides a preparation method for a single-channel microthermal conductivity detector, including the following steps:

[0023] Provide a substrate;

[0024] A thermistor, a conductive connection member, and a support structure are formed on the substrate. The thermistor includes a first thermistor, a second thermistor, a third thermistor, and a fourth thermistor. Among them, the conductive connection member connects the thermistors to form a Wheatstone bridge structure;

[0025] The substrate is patterned to form microchannels with bottoms located in the substrate, and the second thermistor and the third thermistor are suspended in the microchannels through the support structure;

[0026] An upper cover plate is provided and bonded to the upper surface of the substrate, and the microchannels are covered by the upper cover plate to form closed microchannels.

[0027] Optionally, when bonding, the substrate has a substrate accommodation groove, and / or the upper cover plate has a cover plate accommodation groove.

[0028] Optionally, the formed support structure is a mesh structure.

[0029] Optionally, the conductive connection member is prepared while preparing the thermistor, and the pads in the conductive connection member are exposed on the upper cover plate.

[0030] As described above, the single-channel micro-thermal conductivity detector and its preparation method of the present invention integrate a conductive connection member in the substrate to replace the external lead wire, avoiding the formation of contact resistance, reducing the zero-point error and noise interference of the detector; canceling the reference channel, and directly preparing the thermistor of the reference channel in the substrate, avoiding the noise formed by the gas flow disturbance in the reference channel. At the same time, the demand for one-way carrier gas is reduced, and the gas supply burden of the gas chromatography system is reduced.

[0031] The micro-thermal conductivity detector of the present invention has a simple structure, can effectively improve the detection sensitivity of the detector, and at the same time reduce the gas supply burden of the gas chromatography system, which is beneficial to portable applications and can further promote the miniaturization of the gas chromatography system. Description of the Drawings

[0032] Figure 1 Shown is a three-dimensional structural schematic diagram of the single-channel micro-thermal conductivity detector based on a silicon substrate in Embodiment 1 and Embodiment 2 of the present invention.

[0033] Figure 2 Shown as Figure 1 The structural schematic diagram of the thermistor and the support structure in

[0034] Figures 3 - 4 Shown as Figure 1 The layout schematic diagram of the Wheatstone bridge structure in

[0035] Figure 5It shows the process flow chart of preparing a single-channel micro-thermal conductivity detector in Embodiment 1 of the present invention.

[0036] Figures 6 - 10 It shows the structural schematic diagram presented by each step of preparing a single-channel micro-thermal conductivity detector based on a silicon substrate in Embodiment 1 of the present invention.

[0037] Figure 11 It shows the process flow chart of preparing a single-channel micro-thermal conductivity detector in Embodiment 2 of the present invention.

[0038] Figures 12a - 13 It shows the structural schematic diagram presented by each step of preparing a single-channel micro-thermal conductivity detector based on a silicon substrate in Embodiment 2 of the present invention.

[0039] Figures 14 - 18 It shows the structural schematic diagram presented by each step of preparing a single-channel micro-thermal conductivity detector based on a silicon-on-insulator substrate in Embodiment 3 of the present invention.

[0040] Figures 19a - 20 It shows the structural schematic diagram presented by each step of preparing a single-channel micro-thermal conductivity detector based on a silicon-on-insulator substrate in Embodiment 4 of the present invention.

[0041] Explanation of reference numerals

[0042] 100 Silicon substrate

[0043] 110 Silicon oxide layer

[0044] 120 Substrate accommodation groove

[0045] 210 Glass upper cover plate

[0046] 211 Cover plate accommodation groove

[0047] 220 Glass lower cover plate

[0048] 300 Closed micro-channel

[0049] 301 Micro-channel

[0050] 400 Thermistor

[0051] 401 First thermistor

[0052] 402 Second thermistor

[0053] 403 Third thermistor

[0054] 404 Fourth thermistor

[0055] 500 Conductive connection member

[0056] 501 Lead

[0057] 502 Pad

[0058] 601 First dielectric layer

[0059] 602 Second dielectric layer

[0060] 111 Silicon-on-insulator substrate

[0061] 101 Bottom silicon

[0062] 102 Buried oxide layer

[0063] 103 Top silicon

[0064] 700 Protective layer Specific implementation manner

[0065] The following uses specific specific examples to illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0066] When detailing the embodiments of the present invention, for the convenience of description, the cross-sectional views showing the device structure will be enlarged locally in a non-general proportion, and the schematic diagrams are only examples, and they should not limit the scope of protection of the present invention here. In addition, in actual production, three-dimensional spatial dimensions including length, width, and depth should be included.

[0067] For the convenience of description, spatial relationship terms such as "beneath", "below", "lower than", "under", "above", "on", etc. may be used here to describe the relationship between an element or feature shown in the drawings and other elements or features. It will be understood that these spatial relationship terms are intended to include other directions of the device in use or operation, in addition to the directions depicted in the drawings. Embodiments in which the first and second features are formed in direct contact can be included, and embodiments in which additional features are formed between the first and second features can also be included, such that the first and second features may not be in direct contact. Additionally, when a layer is referred to as being "between" two layers, it can be the only layer between the two layers, or one or more intervening layers may also exist.

[0068] It should be noted that the diagrams provided in this embodiment only illustrate the basic concept of the present invention in a schematic manner. Therefore, only the components related to the present invention are shown in the diagrams, rather than being drawn according to the number, shape, and size of the components in actual implementation. The type, quantity, and ratio of each component in actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0069] Embodiment 1

[0070] Referring to Figures 1 - 10 , this embodiment provides a single-channel micro-thermal conductivity detector, and the single-channel micro-thermal conductivity detector includes: a substrate, a thermistor 400, a conductive connecting member 500, and a cover plate. A micro-channel 301 is provided in the substrate; the thermistor 400 includes a first thermistor 401 and a fourth thermistor 404 disposed on the substrate, and a second thermistor 402 and a third thermistor 403 suspended in the micro-channel 301 through a support structure; the conductive connecting member 500 is disposed on the substrate and connects the thermistor 400 to form a Wheatstone bridge structure; the cover plate is bonded to the substrate, and the micro-channel 301 is covered by the cover plate to form a closed micro-channel 300.

[0071] Specifically, referring to Figures 1 - 4 , in this embodiment, the conductive connecting member 500 is located on the substrate and includes a lead 501 and a pad 502. The lead 501 connects the thermistor 400 to form the Wheatstone bridge structure. The thermistor 400 is used as a measuring element for the gas thermal conductivity to perform thermal conductivity detection. Among them, the first thermistor 401 is represented by R1, the second thermistor 402 is represented by R2, the third thermistor 403 is represented by R3, the fourth thermistor 404 is represented by R4. The second thermistor 402 and the third thermistor 403 are located in the support structure in the micro-channel 301 and are suspended in the micro-channel 301 through the support structure. The resistance values of the second thermistor 402 and the third thermistor 403 change with the gas flowing through the micro-channel 301. The other two thermistors R1 and R4, that is, the first thermistor 401 and the fourth thermistor 404, are located on the surface of the substrate. The pads 502 connected to the Wheatstone bridge structure are denoted as Pad1, Pad2, Pad3, and Pad4. Among them, Pad1 and Pad4 are used as power supply terminals, and Pad2 and Pad4 are used as signal terminals.

[0072] In this embodiment, since the conductive connecting member 500 is integrated in the substrate, it can replace the external lead for electrical connection, avoid the formation of contact resistance, and reduce the noise interference of the detector; the micro-thermal conductivity detector only has a single channel, that is, the reference channel is cancelled, and the thermistors of the reference channel, that is, the first thermistor 401 and the fourth thermistor 404, are directly provided in the substrate, so as to avoid the noise formed by the air flow disturbance in the reference channel. At the same time, the demand for one-way carrier gas is reduced, and the gas supply burden of the gas chromatography system is reduced.

[0073] As an example, the substrate may include a silicon substrate 100, a silicon-on-insulator substrate, a ceramic substrate, or a glass substrate; the cover plate may include a silicon cover plate, a silicon-on-insulator cover plate, a ceramic cover plate, or a glass cover plate.

[0074] Specifically, referring to Figures 1 - 10 , in this embodiment, the substrate uses the silicon substrate 100, the cover plate uses a glass cover plate, and the cover plate is disposed on opposite sides of the substrate, that is, it includes an upper glass cover plate 210 and a lower glass cover plate 220. However, the selection of the material of the single-channel microthermal conductivity detector is not limited thereto. For example, according to needs, the silicon substrate 100 can also be replaced with a silicon-on-insulator substrate, a ceramic substrate, a glass substrate, etc. The upper glass cover plate 210 can also be replaced with a silicon upper cover plate, a silicon-on-insulator upper cover plate, a ceramic upper cover plate, etc. The lower glass cover plate 220 can also be replaced with a silicon lower cover plate, a silicon-on-insulator lower cover plate, a ceramic lower cover plate, etc.

[0075] As an example, a cover plate accommodation groove 211 corresponding to the support structure and the thermistor 400 is provided on a side of the cover plate adjacent to the substrate.

[0076] Specifically, referring to Figure 10 , according to needs, the upper glass cover plate 210 is provided with the cover plate accommodation groove 211 corresponding to the support structure on a side adjacent to the silicon substrate 100 to provide sufficient space for the support structure. However, it is not limited thereto. When the silicon substrate 100 can provide sufficient space for the support structure, the cover plate accommodation groove 211 may not be provided in the upper glass cover plate 210.

[0077] As an example, the support structure is in a mesh structure.

[0078] Specifically, referring to Figure 2 and Figure 3 , the support structure is suspended in the microchannel 301, and preferably the support structure is suspended in the center of the microchannel 301 and placed parallel to the air flow direction. When the support structure adopts a mesh structure, the contact area of the second thermistor 402 and the third thermistor 403 located on the support structure can be increased, and the sensitivity can be increased. Of course, according to needs, the support structure can also adopt other morphologies, and no excessive limitation is made here.

[0079] As an example, the support structure includes a first dielectric layer 601 and a second dielectric layer 602 stacked from bottom to top.

[0080] In this embodiment, the support structure is composed of the first dielectric layer 601 and the second dielectric layer 602. Among them, the first dielectric layer 601 serves as the support layer, and the second dielectric layer 602 serves as the protective layer. The first dielectric layer 601 may include one or a combination of a silicon oxide layer and a silicon nitride layer, and the second dielectric layer 602 may include one or a combination of a silicon oxide layer and a silicon nitride layer, which can be specifically selected according to needs.

[0081] As an example, the conductive connector 500 and the thermistor 400 are made of the same material, or different materials can also be used according to needs.

[0082] In this embodiment, the conductive connector 500 is formed on the upper surface of the silicon substrate 100 and is insulated from the silicon substrate 100 through the first dielectric layer 601. The material used for the thermistor 400 may include one of a Pt / Ti stack, a Ni / Cr stack, a W / Ti stack, and a W / Re stack, which can be specifically selected according to needs. The material used for the conductive connector 500 may include one of a Pt / Ti stack, a Ni / Cr stack, a W / Ti stack, a W / Re stack, an Al / Ti stack, and an Au / Ti stack. Preferably, the conductive connector 500 and the thermistor 400 are made of the same material to simplify the process, which can be specifically selected according to needs.

[0083] As an example, the pad 502 in the conductive connector 500 is preferably exposed on the cover plate for easy electrical connection, but it is not limited thereto.

[0084] Refer to Figures 5 - 10 , this embodiment also provides a method for manufacturing a single-channel microthermal conductivity detector, including the following steps:

[0085] S1: Provide a substrate;

[0086] S2: Form a thermistor 400, a conductive connector 500, and a support structure on the substrate. The thermistor 400 includes a first thermistor 401, a second thermistor 402, a third thermistor 403, and a fourth thermistor 404. Among them, the conductive connector 500 connects the thermistor 400 to form a Wheatstone bridge structure;

[0087] S3: Provide an upper cover plate and bond the upper cover plate to the upper surface of the substrate;

[0088] S4: Pattern the substrate from the lower surface of the substrate to form a microchannel 301, and the second thermistor 402 and the third thermistor 403 are suspended in the microchannel 301 through the support structure;

[0089] S5: Provide a lower cover plate, bond the lower cover plate to the lower surface of the substrate, and cover the microchannel 301 with the upper cover plate and the lower cover plate to form a closed microchannel 300.

[0090] The preparation of the single-channel microthermal conductivity detector described above can adopt this method, but is not limited thereto. The following will further introduce the preparation of the single-channel microthermal conductivity detector in this embodiment in conjunction with Figures 6 - 10 , and make a further introduction to the preparation of the single-channel microthermal conductivity detector in this embodiment.

[0091] First, refer to Figure 5 and Figure 6 , and perform step S1 to provide a substrate.

[0092] Specifically, in this embodiment, the substrate uses a silicon substrate 100, but is not limited thereto. For example, according to needs, the substrate can also be replaced with a silicon-on-insulator substrate, a ceramic substrate, a glass substrate, etc. Regarding the selection of the material and size of the substrate, no excessive restrictions are made here.

[0093] Next, refer to Figures 5 - 9b , and perform step S2 to form a thermistor 400, a conductive connection member 500, and a support structure on the substrate. The thermistor 400 includes a first thermistor 401, a second thermistor 402, a third thermistor 403, and a fourth thermistor 404. Among them, the conductive connection member 500 connects the thermistor 400 to form a Wheatstone bridge structure.

[0094] In this embodiment, the support structure may include a first dielectric layer 601 and a second dielectric layer 602 stacked from bottom to top. The thermistor 400 is located between the first dielectric layer 601 and the second dielectric layer 602. The preparation steps may include:

[0095] First, as Figure 6 , first form a silicon oxide layer 110 on the upper surface of the silicon substrate 100.

[0096] Next, as Figure 7 , after photolithography, use a Buffered Oxide Etchant (BOE) to remove the exposed silicon oxide layer 110, remove the photoresist, and use the silicon oxide layer 110 as a mask to etch the exposed silicon substrate 100 with a KOH etchant to form a substrate accommodation groove 120 to provide an accommodation space for the subsequent prepared support structure, thermistor 400, and conductive connection member 500, facilitating subsequent bonding. However, it is not limited thereto. For example, a cover plate accommodation groove 211 for accommodating the support structure can also be formed only in the subsequent upper cover plate, or corresponding accommodation grooves can be formed in both the silicon substrate 100 and the upper cover plate. No excessive limitations are made here.

[0097] Next, as shown in Figure 7 , after removing the mask formed by the silicon oxide layer 110, the first dielectric layer 601 is prepared on the upper surface of the silicon substrate 100, such as a stack of a silicon oxide (SiOx) layer and a silicon nitride (SiNx) layer, or a single-layer silicon oxide layer or a silicon nitride layer.

[0098] Next, as shown in Figure 8 , the thermistor 400 is formed on the first dielectric layer 601. Among them, the method of forming the thermistor 400 can adopt the sputtering method. For example, a Pt / Ti stack, a Ni / Cr stack, a W / Ti stack, or a W / Re stack can be prepared as the thermistor 400. After lithography, the ion beam etching process (IBE) is used to etch and pattern the thermistor 400 to prepare the required thermistor 400, that is, the first thermistor 401, the second thermistor 402, the third thermistor 403, and the fourth thermistor 404.

[0099] In this embodiment, while preparing the thermistor 400, the conductive connection member 500 is prepared to reduce the process steps. That is, the conductive connection member 500 is made of the same material as the thermistor 400, including one of a Pt / Ti stack, a Ni / Cr stack, a W / Ti stack, and a W / Re stack. Among them, the conductive connection member 500 includes a lead 501 to connect the thermistor 400 to form a Wheatstone bridge structure. Since the conductive connection member 500 is integrated in the substrate, it can replace the external lead for electrical connection, avoid the formation of contact resistance, and reduce the noise interference of the detector. Combining with Figure 10 , it is preferred that the pad 502 in the conductive connection member 500 is exposed on the upper cover plate for easy electrical connection.

[0100] Next, as shown in Figure 8 , the second dielectric layer 602 is prepared on the surface of the thermistor 400, such as a stack of a silicon oxide (SiOx) layer and a silicon nitride (SiNx) layer, or a single-layer silicon oxide layer or a silicon nitride layer, for protecting the thermistor 400.

[0101] Next, as shown in Figure 9a and Figure 9b, perform photolithography, and the second dielectric layer 602 and the first dielectric layer 601 can be etched by a reactive ion etching (RIE) process to remove the dielectric layer in the bonding region and the pad 502 region, facilitating the subsequent bonding process and exposing the pad 502 for subsequent packaging welding, and etching the dielectric layer inside the support structure to form the support structure in a mesh structure, so as to increase the contact area between the support structure and the sample and improve the sensitivity.

[0102] Next, refer to Figure 5 and Figure 10 , perform step S3, provide an upper cover plate, and bond the upper cover plate to the upper surface of the substrate.

[0103] In this embodiment, the upper cover plate uses a glass upper cover plate 210, but it is not limited thereto. For example, the upper cover plate can also use a silicon-on-insulator upper cover plate, a ceramic upper cover plate, or a silicon upper cover plate, etc. The selection of the material and size of the upper cover plate is not overly restricted here. The glass upper cover plate 210 and the silicon substrate 100 can be anodically bonded.

[0104] Next, refer to Figure 5 and Figure 10 , perform step S4, pattern the substrate from the lower surface of the substrate to form a microchannel 301, and the second thermistor 402 and the third thermistor 403 are suspended in the microchannel 301 through the support structure.

[0105] Specifically, perform photolithography from the back surface of the silicon substrate 100, and the silicon substrate 100 can be etched by a deep reactive ion etching (DRIE) process to form the microchannel 301 to release the support structure, so that the second thermistor 402 and the third thermistor 403 are suspended in the microchannel 301 through the support structure.

[0106] Next, refer to Figure 5 and Figure 10 , perform step S5, provide a lower cover plate, and bond the lower cover plate to the lower surface of the substrate, and combine the upper cover plate and the lower cover plate to cover the microchannel 301 to form a closed microchannel 300.

[0107] In this embodiment, the lower cover plate uses a glass lower cover plate 220, but it is not limited thereto. For example, the lower cover plate can also use a silicon-on-insulator lower cover plate, a ceramic lower cover plate, or a silicon lower cover plate, etc. The selection of the material and size of the lower cover plate is not overly restricted here. Among them, the glass lower cover plate 220 and the silicon substrate 100 can be anodically bonded.

[0108] Finally, dicing and packaging steps can also be performed to complete the preparation of the single-channel microthermal conductivity detector.

[0109] Embodiment 2

[0110] Refer to Figures 11 - 13 , this embodiment also provides another single-channel microthermal conductivity detector based on a silicon substrate and its preparation method. The above preparation of the single-channel microthermal conductivity detector can adopt this method, but is not limited thereto. The main difference between this embodiment and Embodiment 1 is: Refer to Figure 13 , a cover plate is only provided on one side of the substrate to form a closed microchannel 300, so as to reduce the number of cover plates used.

[0111] Regarding the preparation method of the single-channel microthermal conductivity detector, the following steps can be included:

[0112] S1: Provide a substrate;

[0113] S2: Form a thermistor 400, a conductive connection member 500 and a support structure on the substrate. The thermistor 400 includes a first thermistor 401, a second thermistor 402, a third thermistor 403 and a fourth thermistor 404. Among them, the conductive connection member 500 connects the thermistor 400 to form a Wheatstone bridge structure;

[0114] S3: Pattern the substrate to form a microchannel 301 with the bottom located in the substrate, and the second thermistor 402 and the third thermistor 403 are suspended in the microchannel 301 through the support structure;

[0115] S4: Provide an upper cover plate and bond the upper cover plate to the upper surface of the substrate, and cover the microchannel 301 through the upper cover plate to form a closed microchannel 300.

[0116] Regarding the types of the substrate and the cover plate in the single-channel microthermal conductivity detector, etc., no limitations are made here. Refer to Embodiment 1. Regarding the preparation steps S1 and S2 of the single-channel microthermal conductivity detector, refer to the preparation of Figures 6 - 9b in Embodiment 1, which will not be elaborated here. Only the different steps S3 and S4 will be described below.

[0117] Specifically, as Figure 11 , Figure 12a and Figure 12b , when performing step S3, after forming the support structure, TMAH or KOH wet etching solution can be directly used, or dry etching agents such as SF6 or XeF2 can be used to remove a part of the silicon substrate 100 located below the support structure to release the support structure and form the microchannel 301; or asFigure 12a and Figure 12b As shown in Figure 12b , using photolithography, first use the DRIE process to etch the silicon substrate 100 to a certain depth. After removing the photoresist, then use a wet etching solution such as TMAH or KOH, or use a dry etchant such as SF6 or XeF2 to remove a part of the silicon substrate 100 located below the support structure, so as to release the support structure.

[0118] Then, as shown in Figure 11 and Figure 13 , perform step S4, and bond the glass upper cover plate 210 and the silicon substrate 100 by using, for example, anodic bonding.

[0119] Finally, the steps of dicing and packaging can also be performed to complete the preparation of the single-channel microthermal conductivity detector.

[0120] Embodiment III

[0121] Referring to Figures 14 - 18 , this embodiment also provides a single-channel microthermal conductivity detector based on a silicon-on-insulator substrate and a preparation method thereof. The above preparation of the single-channel microthermal conductivity detector can adopt this method, but is not limited thereto. The main difference between this embodiment and Embodiment I is that the substrate uses a silicon-on-insulator substrate 111 having a bottom silicon layer 101, a buried oxide layer 102, and a top silicon layer 103. For the single-channel microthermal conductivity detector and its preparation method, reference can be made to Embodiment I, which will not be elaborated here. Only the differences will be described below.

[0122] Compared with Embodiment I, in this embodiment, after etching the support structure by using the RIE process, the top silicon layer 103 is etched by using photolithography DRIE, and then the exposed buried oxide layer 102 is etched by using the RIE process; then the upper cover plate is bonded to the top silicon layer 103 of the silicon-on-insulator substrate 111; then, photolithography and etching are performed from the lower surface of the silicon-on-insulator substrate 111 to form the microchannel 301 to release the support structure; then the lower cover plate is bonded to the silicon-on-insulator substrate 111; dicing and packaging are performed to complete the preparation of the microthermal conductivity detector.

[0123] Embodiment IV

[0124] Referring to Figures 19a - 20 , this embodiment also provides another single-channel microthermal conductivity detector based on a silicon-on-insulator substrate and a preparation method thereof. The above preparation of the single-channel microthermal conductivity detector can adopt this method, but is not limited thereto. The main difference between this embodiment and Embodiment I is that the substrate uses a silicon-on-insulator substrate 111 having a bottom silicon layer 101, a buried oxide layer 102, and a top silicon layer 103. For the single-channel microthermal conductivity detector and its preparation method, reference can be made to Embodiment I, which will not be elaborated here. Only the differences will be described below.

[0125] In this embodiment compared with the first embodiment, after the second dielectric layer 602 and the first dielectric layer 601 are etched by the RIE process in photolithography, the top silicon 103 can be etched by the DRIE process after photolithography again, and then the buried oxide layer 102 exposed is etched by the RIE process, as Figure 19a ; then a protective layer 700 is deposited, such as one or a stack of SiNx layer and SiOx layer, to protect the side walls of the thermistor 400 and the top silicon 103; the dielectric layer in the gap of the thermistor 400 is etched by the RIE process after photolithography, and then the bottom silicon 101 is etched to a certain depth by the DRIE process, as shown in Figure 19b ; then a wet etching solution such as TMAH or KOH, or a dry etchant such as SF6 or XeF2 is used to remove a part of the bottom silicon 101 located below the support structure to release the support structure, as Figure 20 ; the protective layer 700 in the bonding area of the top silicon 103, the pad 502 area and the second dielectric layer 602 area is etched by the RIE process to facilitate bonding and electrical connection, and then the upper cover plate and the top silicon 103 are bonded by anodic bonding, as Figure 20 ; finally, dicing and packaging are completed to prepare the single-channel micro-thermal conductivity detector.

[0126] In summary, in the single-channel micro-thermal conductivity detector and its preparation method of the present invention, a conductive connecting piece is integrated in the substrate to replace an external lead, avoiding the formation of contact resistance, reducing the zero-point error and noise interference of the detector; the reference channel is cancelled, and the thermistor of the reference channel is directly prepared in the substrate, avoiding the noise formed by the gas flow disturbance in the reference channel, and at the same time, reducing the demand for one-way carrier gas and reducing the gas supply burden of the gas chromatography system; the micro-thermal conductivity detector of the present invention has a simple structure, can effectively improve the detection sensitivity of the detector, and at the same time reduce the gas supply burden of the gas chromatography system, which is beneficial to portable applications and can further promote the miniaturization of the gas chromatography system.

[0127] The above embodiments are only illustrative of the principles and effects of the present invention, and are not used to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A single-channel micro-thermal conductivity detector, characterized in that The single-channel micro-thermal conductivity detector includes: A substrate, in which a micro-channel is provided; Thermistors, including a first thermistor and a fourth thermistor disposed on the substrate, and a second thermistor and a third thermistor suspended in the micro-channel through a support structure, so as to cancel the reference channel and directly fabricate the first thermistor and the fourth thermistor corresponding to the reference channel on the substrate; Conductive connectors, disposed on the substrate and connecting the thermistors to form a Wheatstone bridge structure; A cover plate, bonded to the substrate, and covering the micro-channel through the cover plate to form a closed micro-channel; Wherein, the support structure is in a mesh shape; the support structure includes a first dielectric layer located on the lower surface of the thermistor and a second dielectric layer located on the upper surface of the thermistor; the pads in the conductive connectors are exposed on the cover plate; the cover plate is disposed on opposite sides of the substrate, or the cover plate is only disposed on one side of the substrate; a cover plate accommodation groove corresponding to the micro-channel is provided on the side of the cover plate adjacent to the substrate.

2. The single-channel micro-thermal conductivity detector according to claim 1, wherein: The conductive connectors and the thermistors are made of the same material.

3. The single-channel micro-thermal conductivity detector according to claim 1, characterized in that: The substrate includes a silicon substrate, a silicon-on-insulator substrate, a ceramic substrate or a glass substrate; the cover plate includes a silicon cover plate, a silicon-on-insulator cover plate, a ceramic cover plate or a glass cover plate.

4. A preparation method of a single-channel micro-thermal conductivity detector, characterized in that, It includes the following steps: Provide a substrate; Form thermistors, conductive connectors and a support structure on the substrate. The thermistors include a first thermistor, a second thermistor, a third thermistor and a fourth thermistor. Among them, the conductive connectors connect the thermistors to form a Wheatstone bridge structure; Provide an upper cover plate and bond the upper cover plate to the upper surface of the substrate; Pattern the substrate from the lower surface of the substrate to form a micro-channel, and the second thermistor and the third thermistor are suspended in the micro-channel through the support structure; Provide a lower cover plate and bond the lower cover plate to the lower surface of the substrate, and combine the upper cover plate and the lower cover plate to cover the micro-channel to form a closed micro-channel; Wherein, the single-channel micro-thermal conductivity detector cancels the reference channel and directly fabricates the first thermistor and the fourth thermistor corresponding to the reference channel on the substrate.

5. A preparation method of a single-channel micro-thermal conductivity detector, characterized in that, It includes the following steps: Provide a substrate; Form thermistors, conductive connectors and a support structure on the substrate. The thermistors include a first thermistor, a second thermistor, a third thermistor and a fourth thermistor. Among them, the conductive connectors connect the thermistors to form a Wheatstone bridge structure; Pattern the substrate to form a micro-channel with the bottom located in the substrate, and the second thermistor and the third thermistor are suspended in the micro-channel through the support structure; Provide an upper cover plate and bond the upper cover plate to the upper surface of the substrate, and cover the micro-channel through the upper cover plate to form a closed micro-channel; Wherein, the single-channel micro-thermal conductivity detector cancels the reference channel and directly fabricates the first thermistor and the fourth thermistor corresponding to the reference channel on the substrate.

6. The preparation method of the single-channel micro-thermal conductivity detector according to claim 4 or 5, characterized in that: During bonding, the substrate has a substrate accommodation groove, and / or the upper cover plate has a cover plate accommodation groove.

7. The preparation method of the single-channel micro-thermal conductivity detector according to claim 4 or 5, characterized in that: The formed support structure is a mesh structure.

8. The preparation method of the single-channel micro-thermal conductivity detector according to claim 4 or 5, characterized in that: The conductive connecting member is prepared while the thermistor is being prepared, and the pads in the conductive connecting member are exposed on the upper cover plate.

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