A photoacoustic and photothermal sensor

Abstract

The present application provides a photoacoustic and photothermal sensor, which relates to the field of gas detection technology. The shell of the photoacoustic and photothermal sensor is hollow to form a detection cavity, and the infrared radiation module and the detection module are accommodated in the detection cavity; the shell is provided with at least one air hole connected to the detection cavity; the infrared radiation module is used to emit infrared rays to the gas in the detection cavity, and the infrared ray band corresponds to the type of gas to be detected; the detection module is used to detect sound waves and the temperature of the gas in the detection cavity to detect the concentration of the gas to be detected, and the changes in sound waves and temperature are generated by the gas to be detected based on the emitted infrared rays. The embodiment of the present application can expand the detection range of gas concentration by adding photothermal detection, and can perform gas detection through another detection method when one of the detection methods fails or has limited performance, effectively reducing the scenarios where the sensor cannot detect or detects erroneous data, and improving the stability and reliability of the sensor.

Description

Technical Field

[0001] The present application relates to the technical field of gas detection, and in particular, to a photoacoustic and photothermal sensor. Background Art

[0002] In order to detect the type and concentration of gas in the environment, sensors are often used to detect the composition and content of the gas. Sensors used for gas detection include portable gas detection sensors, handheld gas detection sensors, fixed gas detection sensors, online gas detection sensors and many other types.

[0003] Existing sensors often use photoacoustic detection (detecting sound waves generated when the gas is irradiated with infrared light of a specific band at a specific frequency) to detect gas. However, the detection range of gas concentration is limited under this method, and it is easy for the photoacoustic detection to fail (such as failure of the component used to detect sound waves), resulting in failure to detect or erroneous detection data, which reduces the stability and reliability of the sensor. Summary of the invention

[0004] The present application provides a photoacoustic and photothermal sensor, which can solve the problems of the existing sensors' limited gas concentration detection range and single detection method, which are prone to failure to detect or detection data errors, and low stability and reliability. To achieve this purpose, the present application provides the following solutions.

[0005] According to one aspect of an embodiment of the present application, a photoacoustic and photothermal sensor is provided, comprising: a housing, an infrared radiation module, and a detection module, wherein the housing is hollow to form a detection cavity, and the infrared radiation module and the detection module are accommodated in the detection cavity;

[0006] The housing is provided with at least one air hole communicating with the detection cavity;

[0007] The infrared radiation module is used to emit infrared rays to the gas in the detection chamber, and the wavelength band of the infrared rays corresponds to the type of the gas to be detected;

[0008] The detection module is used to detect the sound wave and the temperature of the gas in the detection chamber to detect the concentration of the gas to be detected. The changes in the sound wave and the temperature are generated by the gas to be detected based on the infrared rays emitted.

[0009] In a possible implementation, a connecting plate is included, the connecting plate divides the detection cavity, and the infrared radiation module and the detection module are installed on the connecting plate;

[0010] The connecting plate is provided with a first through hole and a second through hole, wherein the first through hole is opposite to the infrared radiation module, and the detection module is opposite to the second through hole.

[0011] In a possible implementation, the infrared radiation module includes an infrared radiation element, a first filter, and a second filter. The first filter is installed in the first through hole, and the second filter is installed on a side of the infrared radiation element away from the first filter.

[0012] In a possible implementation, the infrared radiation element includes a substrate layer, a first supporting layer, a resistor layer, and a first electrode layer, wherein the substrate layer, the first supporting layer, and the resistor layer are stacked in sequence, and the first electrode layer at least partially covers the resistor layer;

[0013] The substrate layer is fixed to the connecting plate at a side away from the first supporting layer.

[0014] In a possible implementation manner, the substrate layer includes a first etched groove, the first etched groove penetrates the substrate layer, and the first etched groove is opposite to the first through hole.

[0015] In a possible implementation, the step of manufacturing the infrared radiation element includes:

[0016] A substrate layer is formed by using a silicon substrate, and a first supporting layer is formed on one side of the substrate layer;

[0017] forming a conductive film on a side of the first supporting layer away from the substrate layer, and etching the conductive film to form a resistance layer;

[0018] forming a first electrode layer partially covering the resistance layer;

[0019] The substrate layer is pattern-etched to form a first etched groove.

[0020] In a possible implementation, the detection module includes a sound detection element and a temperature detection element. The sound detection element is fixed to the connection plate, and the temperature detection element is integrated on a side of the sound detection element away from the connection plate.

[0021] In a possible implementation, the detection module includes at least one second electrode layer and a base layer, a diaphragm layer, a second support layer, a back plate layer, a protective layer, and a temperature measurement layer stacked in sequence, and the diaphragm layer, the back plate layer, and the temperature measurement layer are connected to different second electrode layers;

[0022] The side of the base layer away from the diaphragm layer is fixed to the connecting plate.

[0023] In one possible implementation, the temperature measuring layer includes a thermocouple layer, the second electrode layer includes a first sub-electrode layer and a second sub-electrode layer, the thermocouple layer is located on the side of the protective layer away from the back electrode layer, the first sub-electrode layer is connected to one end of the thermocouple layer, and the second sub-electrode layer is connected to the other end of the thermocouple layer.

[0024] In a possible implementation, the manufacturing process of the detection module includes:

[0025] A base layer is formed by using a silicon base, and an isolation layer is formed on one side of the base layer;

[0026] forming a diaphragm layer on a side of the isolation layer away from the base layer, and forming a second supporting layer covering the diaphragm layer;

[0027] A dielectric layer, a back plate layer, and a protective layer are sequentially stacked on the side of the second supporting layer away from the diaphragm layer, wherein the protective layer covers the back plate layer, the dielectric layer, and the second supporting layer;

[0028] Forming a temperature measuring layer on the side of the protective layer away from the back plate layer, etching the protective layer and the second supporting layer to form electrode holes, wherein the electrode holes connect the diaphragm layer and the back plate layer;

[0029] The electrode holes are used to form a second electrode layer, and the protective layer, the back electrode layer, and the dielectric layer are etched to form a porous structure;

[0030] Preset areas of the base layer, the isolation layer and the second supporting layer are etched, wherein the preset areas are opposite to the diaphragm layer.

[0031] The beneficial effects of the technical solution provided by the embodiment of the present application are:

[0032] In the photoacoustic and photothermal sensor provided by the present application, a detection cavity is provided in the shell, and an infrared radiation module and a detection module are accommodated in the detection cavity; at least one air hole connected to the detection cavity is provided on the shell; the infrared radiation module is used to emit infrared rays to the gas in the detection cavity, and the type and band of the infrared rays correspond to the type of gas to be detected; the detection module is used to detect sound waves and the temperature of the gas in the detection cavity, and the changes in sound waves and temperature are generated by the gas to be detected based on the emitted infrared rays. The embodiment of the present application realizes the concentration detection of the gas to be detected by combining photoacoustic and photothermal methods, and can expand the detection range of gas concentration by adding photothermal detection. When one of the detection methods fails or the performance is limited, gas detection can be performed by another detection method, which effectively reduces the scenarios where the sensor cannot detect or detects erroneous data, and improves the stability and reliability of the sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following is a brief introduction to the drawings required for use in describing the embodiments of the present application.

[0034] Figure 1 A structural diagram of the photoacoustic and photothermal sensor provided in an embodiment of the present application;

[0035] Figure 2 A three-dimensional diagram of a partial structure of a photoacoustic and photothermal sensor provided in an embodiment of the present application;

[0036] Figure 3 A structural diagram of an infrared radiation element provided in an embodiment of the present application;

[0037] Figure 4 An exploded view of an infrared radiation element provided in an embodiment of the present application;

[0038] Figure 5 A flowchart of manufacturing an infrared radiation element provided in an embodiment of the present application;

[0039] Figure 6 A schematic diagram of a first supporting layer formed in an infrared radiation element provided in an embodiment of the present application;

[0040] Figure 7 Another schematic diagram of a first supporting layer formed in an infrared radiation element provided in an embodiment of the present application;

[0041] Figure 8 A schematic diagram of a resistance layer formed in an infrared radiation element provided in an embodiment of the present application;

[0042] Fig. 9 A schematic diagram of a passivation layer formed in an infrared radiation element provided in an embodiment of the present application;

[0043] Fig.10 A schematic diagram of a first electrode layer formed in an infrared radiation element provided in an embodiment of the present application;

[0044] Fig.11 A schematic diagram of etching a substrate layer in an infrared radiation element provided in an embodiment of the present application;

[0045] Fig.12 A structural diagram of a detection module provided in an embodiment of the present application;

[0046] Fig.13 An exploded view of the detection module provided in the embodiment of the present application;

[0047] Fig.14 A flowchart of making a detection module provided in an embodiment of the present application;

[0048] Fig.15A schematic diagram of an isolation layer and a diaphragm layer formed in a detection module provided in an embodiment of the present application;

[0049] Fig.16 A schematic diagram of a second supporting layer formed in a detection module provided in an embodiment of the present application;

[0050] Fig.17 A schematic diagram of a dielectric layer formed in a detection module provided in an embodiment of the present application;

[0051] Fig.18 A schematic diagram of a back electrode layer formed in a detection module provided in an embodiment of the present application;

[0052] Fig.19 A schematic diagram of a protective layer formed in a detection module provided in an embodiment of the present application;

[0053] Fig. 20 A schematic diagram of a temperature measurement layer formed in a detection module provided in an embodiment of the present application;

[0054] Fig.21 A schematic diagram of an electrode hole formed in a detection module provided in an embodiment of the present application;

[0055] Fig. 22 A schematic diagram of a second electrode layer formed in a detection module provided in an embodiment of the present application;

[0056] Fig.23 A schematic diagram of a porous structure formed in a detection module provided in an embodiment of the present application;

[0057] Fig.24 A schematic diagram of a first etching groove formed in a detection module provided in an embodiment of the present application;

[0058] Fig.25 Schematic diagram of etching the isolation layer and the second supporting layer of the detection module provided in an embodiment of the present application.

[0059] Description of Figure Numbers:

[0060] 1. Shell; 11. Air hole; 2. Connecting plate;

[0061] 3. Detection module; 301. Base layer; 302. Diaphragm layer; 303. Second support layer; 304. Back plate layer; 305. Protective layer; 306. Second electrode layer; 307. Temperature measurement layer; 308. Second etching groove; 309. Isolation layer; 310. Dielectric layer; 311. Electrode hole; 312. Porous structure;

[0062] 4. Infrared radiation module; 41. First filter; 42. Infrared radiation element; 421. Substrate layer; 422. First support layer; 423. Resistance layer; 424. First electrode layer; 425. Passivation layer; 426. First etching groove; 43. Second filter. DETAILED DESCRIPTION

[0063] The embodiments of the present application are described below in conjunction with the drawings in the present application. It should be understood that the implementation methods described below in conjunction with the drawings are exemplary descriptions for explaining the technical solutions of the embodiments of the present application and do not constitute a limitation on the technical solutions of the embodiments of the present application.

[0064] It will be understood by those skilled in the art that, unless specifically stated, the singular forms "one", "said", and "the" used herein may also include plural forms. It should be further understood that the terms "including" and "comprising" used in the embodiments of the present application refer to that the corresponding features can be implemented as the presented features, information, data, steps, operations, elements and / or components, but do not exclude the implementation of other features, information, data, steps, operations, elements, components and / or combinations thereof supported by the technical field. It should be understood that when we say that an element is "connected" or "coupled" to another element, the one element may be directly connected or coupled to the other element, or it may refer to that the one element and the other element establish a connection relationship through an intermediate element. In addition, the "connection" or "coupling" used herein may include wireless connection or wireless coupling. The term "and / or" used herein indicates at least one of the items defined by the term, for example, "A and / or B" indicates that it is implemented as "A", or is implemented as "A", or is implemented as "A and B".

[0065] In order to make the objectives, technical solutions and advantages of the present application clearer, the implementation methods of the present application will be further described in detail below in conjunction with the accompanying drawings.

[0066] The following describes several exemplary embodiments to illustrate the technical solutions of the embodiments of the present application and the technical effects produced by the technical solutions of the present application. It should be noted that the following embodiments can refer to, draw on or combine with each other, and the same terms, similar features and similar implementation steps in different embodiments will not be described repeatedly.

[0067] The present application provides a photoacoustic and photothermal sensor, which aims to solve at least one technical problem existing in the prior art.

[0068] A photoacoustic and photothermal sensor is provided in an embodiment of the present application. The photoacoustic and photothermal sensor can be used for CO2, CO, NO, NO2, CH4, NH3 and other gases that can generate sound waves or temperature changes after absorbing infrared radiation energy in a specific band.

[0069] Alternatively, if Figure 1-Figure 25 As shown, the photoacoustic and photothermal sensor includes a housing 1, an infrared radiation module 4, and a detection module 3. The housing 1 is hollow to form a detection cavity, and the infrared radiation module 4 and the detection module 3 are accommodated in the detection cavity. The housing 1 is provided with at least one air hole 11 connected to the detection cavity. The infrared radiation module 4 is used to emit infrared rays to the gas in the detection cavity, and the type and band of the infrared rays correspond to the type of the gas to be detected. The detection module 3 is used to detect the sound waves and the temperature of the gas in the detection cavity to detect the concentration of the gas to be detected. The changes in the sound waves and the temperature are generated by the gas to be detected based on the emitted infrared rays. The gas enters the detection cavity through the air hole 11 on the housing 1 and is irradiated by the infrared rays emitted by the infrared radiation module 4 in the detection cavity. The gas to be detected in the gas is affected by the infrared rays to generate sound waves or temperature changes, and the sound waves or temperature are detected by the detection module 3. The concentration of the gas to be detected in the gas is determined according to the detection result.

[0070] In one embodiment, Figure 1 As shown, the number of the air holes 11 can be 4, and the air holes 11 can be arranged on the two sides of the housing 1 opposite to the detection module 3 and the infrared radiation module 4. The number of the air holes 11 can also be 0.0 ...

[0071] Optionally, the detection cavity may be rectangular, square, circular, or other regular or irregular shapes, and the specific shape of the detection cavity may be determined according to actual needs or application environment.

[0072] Optionally, to reduce the mention of sensors, e.g. Figure 2 ( Figure 2 For ease of display, part of the housing 1 and the pores 11 are indicated by dotted lines), as shown in the detection module 3, the elements for detecting sound waves and for detecting temperature can be integrated together. Specifically, the two can be integrated in a chip using MEMS (Micro-Electro-Mechanical System) technology, through which the functions of sound wave measurement and temperature acquisition are simultaneously completed. This method not only further reduces the size of the sensor, but also enhances its degree of integration, making the sensor more compact and suitable for use in space-constrained application scenarios. This design improves the overall performance and functionality of the sensor, and provides strong support for efficient detection.

[0073] Optionally, the sensor also includes a connecting plate 2, which divides the detection cavity, and the infrared radiation module 4 and the detection module 3 are installed on the connecting plate 2; a first through hole and a second through hole are provided on the connecting plate 2, the first through hole is opposite to the infrared radiation module 4, and the detection module 3 is opposite to the second through hole.

[0074] In one embodiment, the connecting board 2 can be an integrated circuit board, a PCB board, or other structure capable of supporting the infrared radiation module 4, the detection module 3, and carrying power and / or signal transmission to the detection module 3 and the infrared radiation module 4.

[0075] Optionally, the connecting plate 2 divides the detection cavity into at least two parts, and the divided cavities exchange gas through the first through hole and / or the second through hole, thereby ensuring the balance of air pressure between different cavities.

[0076] Optionally, a portion of the connecting plate 2 may be exposed outside the shell 1 , and the sensor may transmit signals with the detection module 3 and the infrared radiation module 4 or supply power to the detection module 3 and the infrared radiation module 4 through the exposed portion of the connecting plate 2 .

[0077] Optionally, the infrared radiation module 4 includes an infrared radiation element 42, a first filter 41, and a second filter 43. The first filter 41 is installed in the first through hole, and the second filter 43 is installed on the side of the infrared radiation element 42 away from the first filter 41. Through the action of the first filter 41 and the second filter 43, the infrared radiation element 42 emits infrared rays into the detection cavity as infrared rays of a specific wavelength.

[0078] In one embodiment, the infrared radiation element 42 can emit infrared light, the gas to be detected is carbon dioxide, and the first filter 41 and the second filter 43 are 4.3 μm special filters related to carbon dioxide. When the type of the gas to be detected changes, the type of the first filter 41 and the second filter 43 can be changed according to the type to achieve detection of different gases. The infrared radiation element 42 can be a MEMS infrared light source.

[0079] In one embodiment, the sensor is used for carbon dioxide detection, such as Figure 2 , Figure 3 As shown, the housing 1 of the photoacoustic and photothermal sensor is rectangular, and is provided with at least four air holes 11, and the cavities on both sides of the connecting plate 2 are connected to at least one air hole 11. The detection module 3 and the infrared radiation module 4 are fixed on both sides of the connecting plate 2. Through the coordinated work of the detection module 3 and the infrared radiation module 4, the sensor can efficiently detect the concentration of carbon dioxide, and the overall performance and detection accuracy are improved by combining the photoacoustic and photothermal effects.

[0080] Optionally, the acoustic signal generated by the detection module 3 according to the acoustic wave can be transmitted to a phase-locked amplifier for processing, and the sensor obtains the concentration information of the gas to be detected according to the processed signal. In addition, the detected temperature signal can be transmitted to a data acquisition device in the sensor or connected to the sensor, and the sensor or the device connected to the sensor obtains the concentration information of the gas to be detected according to the signal collected by the data acquisition device. After obtaining the concentration information of the gas to be detected through the acoustic signal and the temperature signal, the final concentration of the gas to be detected is determined by combining these two concentration information.

[0081] Alternatively, if Figure 3 , Figure 4 (To avoid obstruction and facilitate display, Figure 3 , Figure 4 As shown in the figure, the first supporting layer 422 is represented by a dotted line, when the infrared radiation element 42 is a MEMS element, the infrared radiation element 42 adopts a cantilever beam structure, which may include a substrate layer 421, a first supporting layer 422, a resistor layer 423, and a first electrode layer 424. The substrate layer 421, the first supporting layer 422 and the resistor layer 423 are stacked in sequence, and the first electrode layer 424 at least partially covers the resistor layer 423; the substrate layer 421 is fixed to the connecting plate 2 on the side away from the first supporting layer 422.

[0082] The infrared radiation element 42 can function as an infrared emission source in the sensor, generating thermal radiation by heating the gas to be detected in the detection cavity. Its advantages are small size and low power consumption.

[0083] Optionally, in order to improve the heat dissipation effect of the infrared radiation element 42 and to enable both sides of the infrared radiation element 42 to emit infrared rays, the substrate layer 421 includes a first etching groove 426, the first etching groove 426 penetrates the substrate layer 421, and the first etching groove 426 is opposite to the first through hole. The substrate layer 421 on the side of the first etching groove 426 is fixed to the connecting board 2. The silicon wafer can be etched by DSI (Deep Silicon Etching) or wet etching to form the first etching groove 426. The size of the first etching groove 426 can be determined according to the heat loss balance and structural stability of the infrared radiation element 42.

[0084] Optionally, the first support layer 422 is used for the infrared radiation element 42, and the material can be silicon dioxide, silicon nitride, polysilicon or other commonly used materials for chip support. The resistor layer 423 uses common MEMS resistor materials such as platinum, tungsten, etc. It can be designed as a double electrode, a single electrode or an array, and the resistor shape can also be designed as a spiral, a square, etc. according to the light emitting requirements.

[0085] Alternatively, if Figure 3 , Figure 4As shown, to protect the resistance layer 423, the infrared radiation element 42 may further include a passivation layer 425 ( Figure 3 The passivation layer 425 is indicated by a dotted line in the figure), and the passivation layer 425 is located on the side of the first support layer 422 away from the substrate layer 421, and partially covers the resistance layer 423. The passivation layer 425 can be made of silicon dioxide, silicon nitride, silicon carbide or other materials that can protect the chip. The first electrode layer 424 can be connected to a power source, a signal source or a signal transmission line, and can be made of gold or other conductive materials that can be used for chip manufacturing.

[0086] In one embodiment, the first electrode layer 424 and the passivation layer 425 cover different regions of the resistor layer 423. The first electrode layer 424 may be disposed on four corners of the resistor layer 423, and the passivation layer 425 may be circular and cover the middle region of the resistor layer 423.

[0087] Alternatively, if Figure 5-Figure 11 As shown, the steps of making the infrared radiation element 42 include:

[0088] S101 : forming a substrate layer 421 using a silicon substrate, and generating a first supporting layer 422 on one side of the substrate layer 421 .

[0089] Optionally, in order to improve the mechanical strength, optimize thermal performance and manage thermal stress of the infrared radiation element 42, the first support layer 422 can be a composite structure of two or more layers. The composite structure provides stronger support to prevent deformation or cracking, and different layers can also be made of different materials. By combining different materials, the influence of thermal stress on the infrared radiation element 42 is reduced, thereby increasing the service life.

[0090] In one embodiment, the first support layer 422 may be a double-layer structure, and the first support layer 422 may be manufactured by one or more methods such as thermal oxidation, PECVD (plasma enhanced chemical vapor deposition), and LPCVD (low pressure chemical vapor deposition). Specifically, a silicon dioxide layer may be first grown on the substrate layer 421 by a thermal oxidation method as the first layer structure of the first support layer 422, and then a silicon nitride layer may be deposited on the silicon dioxide layer by PECVD, and the silicon dioxide layer and the silicon nitride layer may be used as a composite layer of the first support layer 422. Silicon carbide may also be used to manufacture the first support layer 422.

[0091] S102 : forming a conductive film on a side of the first support layer 422 away from the substrate layer 421 , and etching the conductive film to form a resistance layer 423 .

[0092] Optionally, a tungsten (W) film may be deposited as a conductive film on the side of the first support layer 422 away from the substrate layer 421 by sputtering technology. The conductive film may be patterned by wet etching to obtain the resistor layer 423. Other thin film deposition techniques or materials such as platinum (Pt) and polysilicon may also be used as the material of the resistor layer 423.

[0093] S103 : forming a first electrode layer 424 that partially covers the resistance layer 423 .

[0094] Optionally, gold (Au) may be deposited by sputtering technology as the first electrode layer 424 to facilitate subsequent connection of the device to a power source or other driving signals.

[0095] Optionally, to protect the resistor layer 423, a passivation layer 425 may be formed before forming the first electrode layer 424, and the passivation layer 425 covers the middle of the resistor layer 423 and covers the part of the resistor layer 423 with a complex structure. After forming the resistor layer 423, silicon nitride may be deposited as the passivation layer 425 by a PECVD method, or other materials capable of protecting the resistor layer 423 may be used.

[0096] S104 : pattern-etching the substrate layer 421 to form a first etched groove 426 .

[0097] Optionally, the substrate layer 421 may be subjected to deep silicon etching by using DSI or wet etching, so that the silicon substrate is completely etched to form the first etching groove 426 .

[0098] Optionally, the detection module 3 includes a sound detection element and a temperature detection element. The sound detection element is fixed to the connecting plate 2 , and the temperature detection element is integrated on a side of the sound detection element away from the connecting plate 2 .

[0099] In one embodiment, the detection module 3 may be a temperature-measurable microphone, which is not only used to detect the sound signal, but also to monitor the temperature in the cavity. The sound detection element in the temperature-measurable microphone may be a capacitive microphone, and the temperature detection element may be a thermocouple.

[0100] Alternatively, if Fig.12 , Fig.13 As shown, the detection module 3 includes at least one second electrode layer 306 and a base layer 301, a diaphragm layer 302, a second support layer 303, a back plate layer 304, a protective layer 305, and a temperature measuring layer 307 stacked in sequence, wherein the diaphragm layer 302, the back plate layer 304, and the temperature measuring layer 307 are connected to different second electrode layers 306; the base layer 301 is fixed to the connecting plate 2 on the side away from the diaphragm layer 302.

[0101] Optionally, the temperature measuring layer 307 includes a thermocouple layer, the second electrode layer 306 includes a first sub-electrode layer 3061 and a second sub-electrode layer 3062, the thermocouple layer is located on the side of the protective layer 305 away from the back electrode layer 304, the first sub-electrode layer 3061 is connected to one end of the thermocouple layer, and the second sub-electrode layer 3062 is connected to the other end of the thermocouple layer. The electrical signal generated by the thermocouple layer is transmitted through the first sub-electrode layer 3061 and the second sub-electrode layer 3062.

[0102] In one embodiment, the thermocouple layer may include a thermocouple made of two graphene segments with different widths, and the temperature of the gas in the detection chamber is detected by using the thermocouple.

[0103] Optionally, the base layer 301 includes a second etched groove 308, which is opposite to the diaphragm layer 302 and penetrates the base layer 301. The size of the second etched groove 308 corresponds to the size of the diaphragm layer 302. The second etched groove 308 ensures that the diaphragm layer 302 can vibrate freely. The second etched groove 308 can be formed by etching in a DSI manner.

[0104] The diaphragm layer 302 may be made of polysilicon, and serves as one electrode of the capacitor in the detection module 3. The diaphragm layer 302 is deformed under the action of sound waves, thereby causing a change in capacitance value.

[0105] The area of ​​the second supporting layer 303 opposite to the diaphragm layer 302 is removed to ensure that there is a gap between the two plates of the capacitor (the diaphragm layer 302 and the back plate layer 304), so as to achieve normal capacitance change.

[0106] Optionally, the back plate layer 304, as the other pole of the capacitor, can be composed of silicon nitride and polysilicon. The presence of silicon nitride acts as an insulator to prevent the two poles of the capacitor from conducting, thereby ensuring the normal operation of the capacitor. The back plate layer can be designed as a porous structure 312 to balance the atmospheric pressure on both sides of the back plate layer, so that the diaphragm layer 302 is easier to vibrate and the sensitivity of sound wave detection is improved.

[0107] Optionally, the material of the protective layer 305 can be silicon nitride, and the protective layer 305 provides an insulating base for the temperature measuring layer 307 while protecting and fixing the back plate layer 304. The thermocouple layer measures temperature changes based on the Seebeck effect, and the optional materials include graphene. The thermocouple material can also be selected from materials that can be used for temperature detection, such as platinum and tungsten.

[0108] Optionally, the second electrode layer 306 may be formed by depositing a conductive material (such as gold), and the second electrode layer 306 is connected to a corresponding structure in the detection module 3 to achieve driving and temperature signal measurement.

[0109] Alternatively, if Figure 14-Figure 25As shown, the production process of the detection module 3 includes:

[0110] S201 : forming a base layer 301 using a silicon base, and forming an isolation layer 309 on one side of the base layer 301 .

[0111] Optionally, a silicon dioxide layer may be deposited on the silicon substrate of the seat substrate layer 301 by using a PECVD method as the isolation layer 309 .

[0112] S202 : forming a diaphragm layer 302 on a side of the isolation layer 309 away from the base layer 301 , and forming a second supporting layer 303 covering the diaphragm layer 302 .

[0113] Optionally, a layer of amorphous silicon is deposited on a side of the isolation layer 309 away from the base layer 301 , the amorphous silicon is converted into polycrystalline silicon by a rapid annealing technique, and the polycrystalline silicon is patterned to serve as the diaphragm layer 302 .

[0114] Optionally, the second supporting layer 303 may be formed by depositing silicon dioxide using a PECVD method, wherein the second supporting layer 303 covers the side of the diaphragm layer 302 away from the isolation layer 309 and extends to the portion of the isolation layer 309 not covered by the diaphragm layer 302 .

[0115] S203 : forming a dielectric layer 310 , a back plate layer 304 , and a protective layer 305 stacked in sequence on a side of the second support layer 303 away from the diaphragm layer 302 .

[0116] Optionally, the size of the dielectric layer 310 can be consistent with the diaphragm layer 302, and the silicon nitride film can be deposited by PECVD as the dielectric layer 310. The dielectric layer 310 serves to isolate the two plates of the capacitor to prevent the two plates of the capacitor from contacting after the silicon dioxide support layer is released.

[0117] Optionally, the material of the back plate layer 304 can be the same as that of the diaphragm layer 302. The back plate layer 304 can be formed on the side of the dielectric layer 310 away from the second support layer 303. When forming the back plate layer 304, an amorphous silicon layer can be deposited first, and the amorphous silicon layer can be converted into polycrystalline silicon by rapid annealing technology, and the polycrystalline silicon can be patterned to serve as the back plate layer 304 of the capacitor. The area of ​​the back plate layer 304 can be smaller than the area of ​​the dielectric layer 310.

[0118] Optionally, the protective layer 305 covers the back plate layer 304 , the dielectric layer 310 and the second support layer 303 . The protective layer 305 covers the side of the back plate layer 304 away from the dielectric layer 310 , and extends to the portion of the second support layer 303 not covered by the dielectric layer 310 .

[0119] Optionally, a PECVD method may be used to deposit a silicon nitride film as a passivation layer 425 , which can protect the back electrode layer 304 and provide insulation and support for subsequent processing steps.

[0120] S204 : forming a temperature measuring layer 307 on the side of the protective layer 305 away from the back plate layer 304 , etching the protective layer 305 and the second supporting layer 303 to form an electrode hole 311 , and the electrode hole 311 connects the diaphragm layer 302 and the back plate layer 304 .

[0121] Optionally, when forming the temperature measuring layer 307 , a layer of graphene film may be transferred onto the passivation layer 425 by using a wet transfer technique, and then the graphene film may be etched by an etching process to complete the manufacture of the thermocouple in the temperature measuring layer 307 .

[0122] S205 : forming a second electrode layer 306 by using the electrode holes 311 , and etching the protection layer 305 , the back electrode layer 304 , and the dielectric layer 310 to form a porous structure 312 .

[0123] Optionally, the electrode hole 311 may be etched out by wet etching so that the diaphragm layer 302 and the back plate layer 304 have exposed portions through the electrode hole 311 , so as to be connected to an external circuit using the exposed portions.

[0124] Optionally, a gold layer may be deposited in the electrode hole 311 by sputtering technology to form the second electrode layer 306 , and the second electrode layer 306 is used as an electrode for the back plate layer 304 , the diaphragm layer 302 and the temperature measurement layer 307 .

[0125] Optionally, when forming the porous structure 312 , the protective layer 305 , the back plate layer 304 and the dielectric layer 310 may be etched into a porous form with consistent upper and lower structures to ensure that the upper and lower air pressures of the back plate layer 304 are balanced.

[0126] S206 : etching the predetermined areas of the base layer 301 , the isolation layer 309 and the second support layer 303 .

[0127] Optionally, the preset area is opposite to the diaphragm layer 302. The second etching groove 308 can be etched on the base layer 301 by DSI technology. The size of the bottom of the second etching groove 308 can correspond to the size of the second through hole on the connecting plate 2.

[0128] After forming the second etching groove 308 , the isolation layer 309 and the area of ​​the second supporting layer 303 opposite to the diaphragm layer 302 may be etched by wet etching to form cavities on both sides of the diaphragm layer 302 , thereby improving the vibration sensitivity of the diaphragm.

[0129] In the photoacoustic and photothermal sensor provided in the embodiment of the present application, a detection cavity is provided in the shell, and an infrared radiation module and a detection module are accommodated in the detection cavity; at least one air hole connected to the detection cavity is provided on the shell; the infrared radiation module is used to emit infrared rays to the gas in the detection cavity, and the type and band of the infrared rays correspond to the type of gas to be detected; the detection module is used to detect sound waves and the temperature of the gas in the detection cavity, and the changes in sound waves and temperature are generated by the gas to be detected based on the emitted infrared rays. The embodiment of the present application realizes the concentration detection of the gas to be detected by combining photoacoustic and photothermal methods, and can expand the detection range of gas concentration by adding photothermal detection. When one of the detection methods fails or the performance is limited, gas detection can be performed by another detection method, which effectively reduces the scenarios where the sensor cannot detect or detects erroneous data, and improves the stability and reliability of the sensor.

[0130] The terms "first", "second", "third", "fourth", "1", "2", etc. (if any) in the specification and claims of this application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than that shown or described in the drawings.

[0131] It should be understood that, although each operation step is indicated by arrows in the flowchart of the embodiment of the present application, the implementation order of these steps is not limited to the order indicated by the arrows. Unless clearly stated herein, in some implementation scenarios of the embodiment of the present application, the implementation steps in each flowchart can be performed in other orders according to demand. In addition, some or all of the steps in each flowchart may include multiple sub-steps or multiple stages based on actual implementation scenarios. Some or all of these sub-steps or stages may be executed at the same time, and each sub-step or stage in these sub-steps or stages may also be executed at different times respectively. In different scenarios of execution time, the execution order of these sub-steps or stages may be flexibly configured according to demand, and the embodiment of the present application does not limit this.

[0132] The above is only an optional implementation method for some implementation scenarios of the present application. It should be pointed out that for ordinary technicians in this technical field, without departing from the technical concept of the solution of the present application, other similar implementation methods based on the technical ideas of the present application are also within the protection scope of the embodiments of the present application.

Claims

1. A photoacoustic and photothermal sensor, characterized in that: include: A shell, an infrared radiation module, a detection module, and a connecting plate, wherein the shell is hollow to form a detection cavity, and the infrared radiation module and the detection module are accommodated in the detection cavity; The housing is provided with at least one air hole communicating with the detection cavity; The infrared radiation module is used to emit infrared rays to the gas in the detection chamber, and the wavelength band of the infrared rays corresponds to the type of the gas to be detected; The detection module is used to detect the sound wave and the temperature of the gas in the detection chamber to detect the concentration of the gas to be detected, and the changes of the sound wave and the temperature are generated by the gas to be detected based on the emitted infrared rays; The connecting plate divides the detection cavity, and the infrared radiation module and the detection module are installed on the connecting plate; The connecting plate is provided with a first through hole and a second through hole, the first through hole is opposite to the infrared radiation module, and the detection module is opposite to the second through hole; The infrared radiation module comprises an infrared radiation element, a first filter, and a second filter, wherein the first filter is installed in the first through hole, and the second filter is installed on a side of the infrared radiation element away from the first filter; The infrared radiation element comprises a substrate layer, a first supporting layer, a resistor layer, and a first electrode layer, wherein the substrate layer, the first supporting layer, and the resistor layer are stacked in sequence, and the first electrode layer at least partially covers the resistor layer; The substrate layer is fixed to the connecting plate at a side away from the first supporting layer; The detection module includes at least one second electrode layer and a base layer, a diaphragm layer, a second support layer, a back plate layer, a protective layer, and a temperature measurement layer stacked in sequence, wherein the diaphragm layer, the back plate layer, and the temperature measurement layer are connected to different second electrode layers; The side of the base layer away from the diaphragm layer is fixed to the connecting plate.

2. The photoacoustic and photothermal sensor according to claim 1, characterized in that: The substrate layer includes a first etched groove, the first etched groove penetrates the substrate layer, and the first etched groove is opposite to the first through hole.

3. The photoacoustic and photothermal sensor according to claim 2, characterized in that: The steps of manufacturing the infrared radiation element include: A substrate layer is formed by using a silicon substrate, and a first supporting layer is formed on one side of the substrate layer; forming a conductive film on a side of the first supporting layer away from the substrate layer, and etching the conductive film to form a resistance layer; forming a first electrode layer partially covering the resistance layer; The substrate layer is pattern-etched to form a first etched groove.

4. The photoacoustic and photothermal sensor according to claim 1, characterized in that: The detection module includes a sound detection element and a temperature detection element. The sound detection element is fixed to the connection plate, and the temperature detection element is integrated on a side of the sound detection element away from the connection plate.

5. The photoacoustic and photothermal sensor according to claim 1, characterized in that: The temperature measuring layer includes a thermocouple layer, the second electrode layer includes a first sub-electrode layer and a second sub-electrode layer, the thermocouple layer is located on the side of the protective layer away from the back electrode layer, the first sub-electrode layer is connected to one end of the thermocouple layer, and the second sub-electrode layer is connected to the other end of the thermocouple layer.

6. The photoacoustic and photothermal sensor according to claim 1, characterized in that: The production process of the detection module includes: A base layer is formed by using a silicon base, and an isolation layer is formed on one side of the base layer; forming a diaphragm layer on a side of the isolation layer away from the base layer, and forming a second supporting layer covering the diaphragm layer; A dielectric layer, a back plate layer, and a protective layer are sequentially stacked on the side of the second supporting layer away from the diaphragm layer, wherein the protective layer covers the back plate layer, the dielectric layer, and the second supporting layer; Forming a temperature measuring layer on the side of the protective layer away from the back plate layer, etching the protective layer and the second supporting layer to form electrode holes, wherein the electrode holes connect the diaphragm layer and the back plate layer; The electrode holes are used to form a second electrode layer, and the protective layer, the back electrode layer, and the dielectric layer are etched to form a porous structure; Preset areas of the base layer, the isolation layer and the second supporting layer are etched, wherein the preset areas are opposite to the diaphragm layer.

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