A backside hole type integrated micro infrared gas sensor

Abstract

The application provides a back hole type on-chip integrated miniature infrared gas sensor, which comprises: an infrared detection chip, which is provided with an infrared light source, an infrared detector, and a gas-permeable heat insulation structure between the infrared light source and the infrared detector; a miniature optical cover, which is located on the upper surface of the infrared detection chip, and is provided with a reflecting surface on the miniature optical cover, and the miniature optical cover and the infrared detection chip jointly form a closed optical chamber; the infrared light emitted by the infrared light source is reflected to the infrared detector; a signal processing chip, which is integrated on one side of the infrared detection chip close to the infrared detector; the miniature optical cover, the infrared detection chip and the signal processing chip are packaged and connected by using a MEMS processing technology; the miniature infrared gas sensor adopts a back hole and on-chip integrated method, effectively reduces the volume of the infrared gas sensor, solves the internal thermal interference problem of the miniature infrared gas sensor, and realizes a folding type reflection design, and the optical path is lengthened.

Description

Technical Field

[0001] This application relates to the field of gas sensor technology, and in particular to an on-chip integrated miniature infrared gas sensor. Background Technology

[0002] With the advancement of technology and economic development, society is gradually entering the era of the Internet of Things. The number of sensing nodes is increasing, leading to a growing demand for sensors. Infrared gas sensors have received widespread attention and research due to their advantages such as high accuracy, long lifespan, good selectivity, and non-toxicity, resulting in the development of a series of infrared gas sensors.

[0003] An infrared gas sensor is a miniature spectral analysis device that detects the concentration of a gas by measuring the intensity of its characteristic spectral absorption. Compared with other types of gas sensors, such as electrochemical, catalytic combustion, and semiconductor sensors, it offers a range of advantages, including wider application, longer lifespan, higher sensitivity, better stability, less susceptibility to environmental interference, non-poisoning, oxygen independence, suitability for a variety of gases, high cost-effectiveness, low maintenance costs, and the ability to perform online analysis. It is widely used in petrochemical, metallurgical, mining, air pollution monitoring, agriculture, and medical and health fields.

[0004] With the development of the Internet of Things (IoT) technology, the demand for sensors is trending towards miniaturization and integration. Currently, most commercially available infrared gas sensors use heating wires or incandescent lamps as infrared light sources and TO-packaged detectors as sensing elements. They detect gas components through signal detection and processing, but their large size makes it difficult to meet the needs of miniaturized gas sensors in certain specific applications. Summary of the Invention

[0005] The purpose of this invention is to provide a back-hole type on-chip integrated miniature infrared gas sensor to solve the technical problem of excessive size of existing infrared gas sensors.

[0006] To address the aforementioned technical problems, this invention provides a back-hole type on-chip integrated miniature infrared gas sensor, comprising: an infrared detection chip having an infrared light source, an infrared detector spaced apart from the infrared light source, and a breathable-heat-insulating structure located between the infrared light source and the infrared detector; a miniature optical cover located on the upper surface of the infrared detection chip, the miniature optical cover having at least one reflective surface, and the miniature optical cover and the infrared detection chip together forming a closed optical cavity; the miniature optical cover being configured to reflect infrared light emitted by the infrared light source to the infrared detector through its reflective surface within the optical cavity; and a signal processing chip integrated on the infrared detection chip near the infrared detector and electrically connected to the infrared detector; the back-hole type on-chip integrated miniature infrared gas sensor employs chip-level packaging, and the miniature optical cover, infrared detection chip, and signal processing chip are packaged and connected using MEMS fabrication technology.

[0007] The infrared detection chip has a second auxiliary reflective surface located between the infrared light source and the infrared detector. The micro optical cover includes a first auxiliary reflective surface disposed opposite to the second auxiliary reflective surface, and a first main reflective surface and a second main reflective surface located on both sides of the first auxiliary reflective surface. The optical cavity is defined by the first auxiliary reflective surface, the first main reflective surface, the second main reflective surface, and the second auxiliary reflective surface.

[0008] The first auxiliary reflective surface, the first primary reflective surface, and the second primary reflective surface are all fabricated by coating the lower surface of the micro-optical mask. The second auxiliary reflective surface is fabricated by coating the substrate between the infrared light source and the infrared detector of the infrared detection chip. The coating material is a material with high reflectivity in the infrared band.

[0009] The number of infrared light sources is one, and the number of infrared detectors is at least one. The shapes of the first auxiliary reflective surface and the second auxiliary reflective surface vary with the shape, layout and number of the infrared light source and the infrared detector, which can assist the propagation of infrared light and can match the shape of the infrared light path.

[0010] The breathable-heat-insulating structure includes a breathable hole structure penetrating the infrared detection chip and a breathable hole structure penetrating the micro optical cover, or only includes a breathable hole structure penetrating the infrared detection chip; the breathable hole structure is at least one of polygonal hole, circular hole and strip hole structure.

[0011] At least one of the infrared light source and infrared detector has a surface made of a filter material, which includes a narrowband filter or a metastructure material.

[0012] The infrared light source includes a MEMS light source or an LED light source; the infrared detector includes a thermoelectric detector chip or a photoelectric detector chip.

[0013] The back-hole type on-chip integrated miniature infrared gas sensor also includes a thermistor disposed near the infrared detector; the thermistor is integrated on the miniature optical cover, infrared detection chip or signal processing chip, or externally attached to the back-hole type on-chip integrated miniature infrared gas sensor; the thermistor is made of platinum metal, semiconductor or ceramic.

[0014] The material of the micro-optical cover is aluminum, copper, plastic, resin, ABS, silicon, or glass; the fabrication method of the micro-optical cover is micromachining, lamination process, 3D printing technology, or MEMS processing technology.

[0015] The signal processing chip consists of a power supply module, a signal processing module, and a digital logic unit; the power supply module is configured to provide voltage to the infrared light source, the thermistor, the signal processing module, and the digital logic unit; the digital logic unit includes a storage unit and logic circuits.

[0016] The back-hole type on-chip integrated miniature infrared gas sensor of this invention employs chip-level packaging. The miniature optical cover, infrared detection chip, and signal processing chip are packaged and connected using MEMS fabrication technology, thereby effectively reducing the size of the infrared gas sensor. Furthermore, a breathable-heat-insulating structure is located between the infrared light source and the infrared detector of the infrared detection chip. The sensor's heat-insulating structure replaces the upper vent, achieving a back-hole design with dual functions. Combining the breathable and heat-insulating structures effectively reduces internal thermal interference problems after miniaturization. Additionally, the back-hole type on-chip integrated miniature infrared gas sensor of this invention forms an optical chamber through its reflective surface and the reflective surface of the infrared detection chip, enabling a folded reflective structure in the optical path of the optical chamber, minimizing the sensor's thickness. This folded reflective design increases the optical path length. In other words, compared to a design without reflection where the infrared light source and infrared detector face each other, this folded reflective design increases the optical path length. In NDIR gas detectors, increased optical path length facilitates full absorption by the gas molecules, increasing the attenuation of infrared light reaching the infrared detector and thus improving sensitivity. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the structure of a back-hole type on-chip integrated miniature infrared gas sensor according to an embodiment of the present invention;

[0019] Figure 2 This is a schematic diagram of the disassembled structure of a back-hole type on-chip integrated miniature infrared gas sensor according to an embodiment of the present invention;

[0020] Figure 3 This is a schematic diagram of the structure of an infrared detection chip for a back-hole type on-chip integrated miniature infrared gas sensor according to an embodiment of the present invention.

[0021] Figure 4 This is a schematic diagram of the optical path of a back-hole type on-chip integrated miniature infrared gas sensor according to an embodiment of the present invention;

[0022] Figure 5 This is a schematic diagram of the signal processing chip of a back-hole type on-chip integrated miniature infrared gas sensor according to an embodiment of the present invention;

[0023] Figure 6 Temperature distribution diagram of cross section for an on-chip integrated miniature infrared gas sensor without thermal insulation structure;

[0024] Figure 7 A cross-sectional temperature distribution diagram of a back-hole type on-chip integrated micro infrared gas sensor with a circular hole heat insulation structure according to an embodiment of the present invention;

[0025] Figure 8 A cross-sectional temperature distribution diagram of a back-hole type on-chip integrated micro infrared gas sensor with a strip-shaped perforated heat insulation structure according to an embodiment of the present invention;

[0026] Figure 9 Comparison of the cross-sectional temperature distribution of an on-chip integrated micro infrared gas sensor without thermal insulation structure, and a back-hole type on-chip integrated micro infrared gas sensor with circular hole thermal insulation structure and strip hole thermal insulation structure according to two different embodiments of the present invention.

[0027] The following is supplementary explanation of the attached figures:

[0028] 1-Miniature optical cover; 2-Infrared detection chip; 3-Signal processing chip; 4-Thermistor; 21-Infrared light source; 22-Infrared detector; 23-Second auxiliary reflective surface; 24-Breathable and heat-insulating structure; 11-First auxiliary reflective surface; 12-First main reflective surface; 13-Second main reflective surface; 31-Power supply module; 32-Signal processing module; 33-Digital logic unit; 331-Storage unit; 332-Logic circuit. Detailed Implementation

[0029] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0030] The term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of this application. In the description of this application, it should be understood that the terms "upper," "lower," "top," "bottom," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Moreover, the terms "first," "second," etc., are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein.

[0031] Figure 1 This is a schematic diagram of the structure of a back-hole type on-chip integrated miniature infrared gas sensor according to an embodiment of this application. Figure 2 This is a schematic diagram showing the disassembled structure of a back-hole type on-chip integrated miniature infrared gas sensor according to an embodiment of this application. Please refer to... Figure 1 and combined Figure 2 The back-hole type on-chip integrated miniature infrared gas sensor includes a miniature detection and processing chip and a miniature optical cover 1 disposed on the upper surface of the miniature detection and processing chip. The miniature detection and processing chip includes an infrared detection chip 2 and a signal processing chip 3 located on the same plane and electrically connected to each other. The miniature optical cover 1 is located on the upper surface of the infrared detection chip 2, preferably aligned with it. In this embodiment, the infrared detection chip 2 is a miniature, highly integrated MEMS chip with an infrared detector 22 for detecting infrared signals. The signal processing chip 3 is an ASIC chip, integrated on the infrared detection chip 2 near the infrared detector 22 and electrically connected to it to provide signal processing functions.

[0032] Figure 3 This is a schematic diagram of the infrared detection chip of a back-hole type on-chip integrated miniature infrared gas sensor according to an embodiment of the present invention. Figure 3 As shown, the infrared detection chip 2 is provided with an infrared light source 21, an infrared detector 22 spaced apart from the infrared light source 21, a second auxiliary reflective surface 23 disposed between the infrared light source 21 and the infrared detector 22, and a breathable-heat-insulating structure 24.

[0033] The infrared light source 21 can be, but is not limited to, a MEMS light source or an LED light source. Compared to traditional infrared light sources that are separately fabricated, packaged, and then assembled into infrared gas sensors, such as TO-packaged heating wires or tungsten bulbs, the MEMS or LED light source used in this invention is small in size and can be fabricated and packaged together with the infrared detector, eliminating the need for a separate packaging shell, thus resulting in a smaller size. In this embodiment, the infrared light source 21 on the infrared detection chip 2 is a MEMS light source, implemented using MEMS fabrication technology.

[0034] At least one of the surfaces of the infrared light source 21 and the infrared detector 22 is made of a filter material, which can be, but is not limited to, narrowband filters or metastructure materials. Taking the detection of CO2 gas as an example, CO2 gas molecules specifically absorb 4.26µm infrared light, and the infrared detector 22 needs to sense the intensity of the transmitted 4.26µm wavelength infrared light to determine the CO2 concentration. Therefore, in this patent, at least one of the surfaces of the infrared light source 21 and the infrared detector 22 needs to be provided with a narrowband filter to filter the emitted 4.26µm wavelength infrared light; or, a metastructure material can be used to filter the emitted 4.26µm wavelength infrared light. In addition, when the surface of the infrared detector 22 is made of a filter material, the surface of the infrared light source 21 can also be made of a metastructure material used only to improve the infrared light emissivity (note that in this case, the light source emits broadband light, so the corresponding infrared detector 22 must have a filtering function to achieve the detection of only 4.26µm wavelength infrared light). Thus, the infrared light source 21 can radiate a broadband or corresponding narrowband infrared spectrum.

[0035] In this embodiment, the infrared light source 21 on the infrared detection chip 2 is a MEMS light source, which is realized by MEMS processing technology, and its surface is coated with a superstructure material, and its radiated infrared spectrum is broadband.

[0036] The infrared detector 22 can be, but is not limited to, a thermoelectric detector chip or a photoelectric detector chip. A thermoelectric detector chip can be, for example, a thermopile detector, whose surface film absorbs infrared light and converts it into heat, which is then converted into thermoelectricity by the Seebeck effect. The number of infrared detectors 22 on the infrared detection chip 2 can be, but is not limited to, two. For example, in this embodiment, there are two infrared detectors 22, which are thermoelectric detector chips fabricated using MEMS technology. To correspond to the broadband infrared light emitted by the infrared light source 21 selected in this embodiment, the surface of the infrared detector 22 uses a MIM (Metal Infrared Microstructure) material to achieve corresponding narrowband infrared light detection.

[0037] The back-hole type on-chip integrated miniature infrared gas sensor of the present invention also includes a thermistor 4. The thermistor 4 can be, but is not limited to, integrated on the miniature optical cover 1, the infrared detection chip 2, the signal processing chip 3, or externally attached to the back-hole type on-chip integrated miniature infrared gas sensor, and is positioned close to the infrared detector 22. The thermistor 4 is positioned near the infrared detector 22 to improve the accuracy of temperature measurement by the infrared detector 22, thereby providing an accurate ambient temperature correction coefficient. For example, in this embodiment, the thermistor 4 is integrated near the infrared detector 22 on the infrared detection chip 2, specifically positioned between two infrared detectors 22. The material of the thermistor 4 can be, but is not limited to, platinum, semiconductor, or ceramic. In this embodiment, the thermistor 4 is made of platinum, and its resistance is, but is not limited to, 100KΩ, enabling it to provide an ambient temperature correction coefficient for the signal from the infrared detector 22.

[0038] Because the infrared detection chip 2 is a miniaturized, highly integrated MEMS chip, when the thermistor 4 is integrated into the infrared detection chip 2, the infrared light source 21, infrared detector 22, second auxiliary reflective surface 23, gas-permeable-heat-insulating structure 24, and the thermistor 4 are fabricated on the same substrate using MEMS processing technology and nanofabrication methods. This integrated manufacturing method further enables the infrared gas sensor to have a higher degree of integration. The substrate is made of silicon material, and preferably a wafer substrate.

[0039] In this embodiment, the miniature optical cover 1, the infrared detection chip 2, and the signal processing chip 3 are packaged and connected using MEMS fabrication technology. The MEMS fabrication technology used for packaging and connection includes at least one of TSV, TGV, wire bonding, thermoforming, and flip-chip bonding. TSV technology is used for electrical interconnection. Therefore, the back-hole type on-chip integrated miniature infrared gas sensor of this invention uses chip-level packaging, and the thickness of the fabricated infrared gas sensor can be less than 1.5 mm.

[0040] The miniature optical cover 1 has at least one reflective surface, and the miniature optical cover 1 and the infrared detection chip 2 together form a closed optical cavity; the miniature optical cover 1 is configured to reflect the infrared light emitted by the infrared light source 21 to the infrared detector 22 through its reflective surface within the optical cavity. Figure 4As shown, the infrared detection chip 2 is equipped with an infrared light source 21 and an infrared detector 22, as well as a second auxiliary reflective surface 23 located between the infrared light source 21 and the infrared detector 22. The miniature optical cover 1 includes a first auxiliary reflective surface 11 disposed opposite to the second auxiliary reflective surface 23, and a first main reflective surface 12 and a second main reflective surface 13 located on both sides of the first auxiliary reflective surface 11. Thus, the optical cavity is defined by the first auxiliary reflective surface 11, the first main reflective surface 12, the second main reflective surface 13, and the second auxiliary reflective surface 23, thereby reflecting the infrared light emitted by the infrared light source 21 to the infrared detector 22 within the optical cavity. The first auxiliary reflective surface 11, the first main reflective surface 12, and the second main reflective surface 13 form an arched structure; at least a portion of the first main reflective surface 12 is located directly above the infrared light source 21, and at least a portion of the second main reflective surface 13 is located directly above the infrared detector 22.

[0041] The first auxiliary reflective surface 11, the first primary reflective surface 12, and the second primary reflective surface 13 are all fabricated by coating the lower surface of the micro optical cover 1. The second auxiliary reflective surface 23 is fabricated by coating the substrate between the infrared light source 21 and the infrared detector 22 of the infrared detection chip 2. The coating material is, but is not limited to, gold film, silver film (AgI / Ag), or other materials with high reflectivity in the infrared band. Thus, a high-reflectivity optical cavity is formed after coating, reducing the transmission loss of infrared light signals inside the enclosed optical cavity.

[0042] In this embodiment, there is one infrared light source 21 and two infrared detectors 22 arranged side by side. The light beam is emitted from the infrared light source 21 and dispersed in a trapezoidal shape to reach the parallel infrared detectors 22. Therefore, the beam is narrower at the infrared light source and wider at the infrared detectors. Overall, the shape of the first auxiliary reflective surface 11 and the second auxiliary reflective surface 23 (i.e., the shape of the film area after coating) is a trapezoid with a narrower shape at the infrared light source and a wider shape at the infrared detectors. It should be noted that the first auxiliary reflective surface 11 can be a plane or a cylindrical curved surface, and the second auxiliary reflective surface 23 is a horizontal plane. The two main reflective surfaces of the first main reflective surface 12 and the second main reflective surface 13 are ellipsoidal arc surfaces or inclined planes (the angle between the inclined plane and the horizontal plane is 30-90°), which can realize the reflection and propagation of the light beam.

[0043] Furthermore, in other embodiments, the shapes of the first and second auxiliary reflective surfaces vary with the shape, layout, and number of the infrared light source and infrared detectors, enabling them to assist in the propagation of infrared light and to match the shape of the infrared light path. The number of infrared light sources 21 is one, and the number of infrared detectors 22 is at least one. For example, when there is one infrared light source and one infrared detector, the shape of the reflective surface can be rectangular, parallelogram, or circular; when there is one infrared light source and two infrared detectors, the shape can be trapezoidal, triangular, elliptical, etc.; specifically, when the light source is a rectangular structure and there are two infrared detectors, the shape can be rectangular, parallelogram, or circular.

[0044] In this embodiment, Figure 4 A schematic diagram of the optical path of the optical cavity is given. The optical path of the optical cavity is a folded reflective structure. The cross section of the optical path in the optical channel is set perpendicular to the infrared detection chip 2. The infrared light source 21 emits infrared light at the light input end of the optical cavity. The infrared light signal is reflected by the first primary reflective surface 12 and propagates in the direction of the infrared detector 22. During the propagation process, it directly reaches the second primary reflective surface 13 or reaches the second primary reflective surface 13 after being reflected by at least one of the first auxiliary reflective surface 11 and the second auxiliary reflective surface 23. The second primary reflective surface 13 can reflect the projected infrared light signal to the infrared detector 22 at the light output end of the optical cavity.

[0045] In this embodiment, the fabrication process of the micro-optical cover 1 can be selected from, but is not limited to, micromachining, lamination, 3D printing, or MEMS fabrication; the material of the micro-optical cover 1 can be selected from, but is not limited to, aluminum, copper, plastic, resin, ABS, silicon, or glass; for example, the micro-optical cover 1 provided in this embodiment uses silicon material and is fabricated using MEMS technology, which can achieve wafer-level packaging with the infrared detection chip 2.

[0046] In this embodiment, the breathable-heat-insulating structure 24 is fabricated on the infrared detection chip 2, providing a gas exchange channel for the miniature optical cover 1. Simultaneously, the breathable-heat-insulating structure 24 is fabricated between the infrared light source 21 and the infrared detector 22, solving the thermal interference problem faced by most miniaturized infrared gas sensors. It effectively blocks the high temperature of the infrared light source 21 from propagating to the infrared detector 22, the thermistor 4, and the signal processing chip 3, providing thermal isolation for the signal processing chip 3. The breathable-heat-insulating structure 24 includes, but is not limited to, a breathable hole structure penetrating the infrared detection chip 2. This breathable hole structure can be a polygonal hole, a circular hole, or a strip-shaped hole. The breathable-heat-insulating structure 24 can also be a single combination or multiple arrangements of the above hole structures; for example, in this embodiment... Figure 7 A breathable-insulating structure 24 with an array of circular holes is provided. Figure 8 A breathable-heat-insulating structure 24 is provided, featuring an array of strip-shaped holes. Furthermore, in addition to the infrared detection chip, the miniature optical cover may also have a breathable hole structure.

[0047] The second auxiliary reflective surface 23 and the breathable-heat-insulating structure 24 are both disposed on the substrate between the infrared light source 21 and the infrared detector 22, and the breathable-heat-insulating structure 24 passes through the second auxiliary reflective surface 23. Therefore, the breathable-heat-insulating structure 24 can provide gas exchange function for the optical chamber, and the second auxiliary reflective surface 23 will not affect the gas exchange function.

[0048] During measurement, the gas to be measured enters the optical chamber through natural diffusion. This invention's back-hole type on-chip integrated miniature infrared gas sensor can be used as a standalone module to measure the concentration of a gas in the air, or it can be installed in other gas analysis equipment.

[0049] Figure 7 and Figure 8 Cross-sectional temperature distribution diagrams of a back-hole type on-chip integrated miniature infrared gas sensor according to two different embodiments of the present application are given. In these two different embodiments, a circular hole ventilation-insulation structure and a strip hole ventilation-insulation structure are used as ventilation-insulation structure 24, respectively. Figure 6 This is a cross-sectional temperature distribution diagram of an on-chip integrated miniature infrared gas sensor under the condition of a non-permeable-insulating structure 24. Figure 9 Comparison of the cross-sectional temperature distribution of a back-hole type on-chip integrated micro infrared gas sensor with a circular hole insulation structure and a strip hole insulation structure, according to two different embodiments of this application. Figure 9 The temperature distribution results show that the present invention adds a breathable-heat insulation structure 24, which enables the infrared detection chip 2 to effectively reduce or block the heat propagation from the infrared light source 21 to the signal processing chip 3.

[0050] Figure 4 A schematic diagram of the signal processing chip 3 is given. The signal processing chip 3 consists of a power supply module 31, a signal processing module 32, and a digital logic unit 33.

[0051] The power supply module 31 is configured to provide, but not limited to, 2.8V, 3V, 3.3V, 4V, 4.5V or 5V voltages to the infrared light source 21, the thermistor 4, the signal processing module 32 and the digital logic unit 33 respectively.

[0052] The signal processing module 32 is configured to acquire, amplify, filter, and convert the signal from at least one signal channel of the infrared detector 22 into a digital signal, thereby providing a digital signal to the digital logic unit 33. In this embodiment, the signal processing module 32 has at least two signal channels, and the amplification factor is provided, but is not limited to, 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, or 2048, and the filtering frequency band is selected, but is not limited to, 0.5 to 2 Hz.

[0053] The digital logic unit 33 includes a storage unit 331 and a logic circuit 332. The digital logic unit 33 can be, but is not limited to, an FPGA chip. The storage unit 331 can be, but is not limited to, 1M, 2M, or 4M in size. It is suitable for storing digital signals provided by the signal processing module 32, and can also store data actively written by the user, including calibration data, factory parameters, sensor serial numbers, etc. The logic circuit 332 can realize logic control and communication. Specifically, the logic circuit 332 is configured to control the switching of the infrared light source 21 at a certain frequency, communicate with external devices such as a PC, receive signals from external devices to determine the frequency of switching the infrared light source, receive external data and assist in writing it into the storage module 331, and receive digital signals provided by the signal processing module 32, perform digital filtering, and implement digital signal addition, subtraction, multiplication, and division operations, ultimately converting the digital signal into the concentration value of the measured gas and outputting it.

[0054] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A back-hole type on-chip integrated miniature infrared gas sensor, characterized in that, include: An infrared detection chip includes an infrared light source, an infrared detector spaced apart from the infrared light source, and a breathable-heat-insulating structure located between the infrared light source and the infrared detector. A miniature optical cover, located on the upper surface of an infrared detection chip, has at least one reflective surface, and the miniature optical cover and the infrared detection chip together form a closed optical cavity; the miniature optical cover is configured to reflect infrared light emitted by an infrared source to the infrared detector through its reflective surface within the optical cavity; and The signal processing chip is integrated on the infrared detection chip, close to the infrared detector, and electrically connected to the infrared detector. The back-hole type on-chip integrated miniature infrared gas sensor adopts chip-level packaging, and the miniature optical cover, infrared detection chip and signal processing chip are packaged and connected using MEMS processing technology. The breathable-heat-insulating structure serves two purposes, combining a breathable structure with a heat-insulating structure, which can effectively reduce internal thermal interference problems after miniaturization; the breathable hole structure is an array structure of strip holes.

2. The back-hole type on-chip integrated miniature infrared gas sensor according to claim 1, characterized in that, The infrared detection chip has a second auxiliary reflective surface located between the infrared light source and the infrared detector. The micro optical cover includes a first auxiliary reflective surface disposed opposite to the second auxiliary reflective surface, and a first main reflective surface and a second main reflective surface located on both sides of the first auxiliary reflective surface. The optical cavity is defined by the first auxiliary reflective surface, the first main reflective surface, the second main reflective surface, and the second auxiliary reflective surface, realizing a folded reflection design and increasing the optical path.

3. The back-hole type on-chip integrated miniature infrared gas sensor according to claim 2, characterized in that, The first auxiliary reflective surface, the first primary reflective surface, and the second primary reflective surface are all fabricated by coating the lower surface of the micro-optical mask. The second auxiliary reflective surface is fabricated by coating the substrate between the infrared light source and the infrared detector of the infrared detection chip. The coating material is a material with high reflectivity in the infrared band.

4. The back-hole type on-chip integrated miniature infrared gas sensor according to claim 2, characterized in that, The number of infrared light sources is one, and the number of infrared detectors is at least one. The shapes of the first auxiliary reflective surface and the second auxiliary reflective surface vary with the shape, layout and number of the infrared light source and the infrared detector, which can assist the propagation of infrared light and can match the shape of the infrared light path.

5. The back-hole type on-chip integrated miniature infrared gas sensor according to claim 1, characterized in that, The breathable-heat-insulating structure includes a breathable hole structure penetrating the infrared detection chip and a breathable hole structure penetrating the micro optical cover, or it may only include a breathable hole structure penetrating the infrared detection chip.

6. The back-hole type on-chip integrated miniature infrared gas sensor according to claim 1, characterized in that, At least one of the infrared light source and infrared detector has a surface made of a filter material, which includes a narrowband filter or a metastructure material.

7. The back-hole type on-chip integrated miniature infrared gas sensor according to claim 1, characterized in that, The infrared light source includes a MEMS light source or an LED light source; the infrared detector includes a thermoelectric detector chip or a photoelectric detector chip.

8. The back-hole type on-chip integrated miniature infrared gas sensor according to claim 1, characterized in that, It also includes a thermistor disposed near the infrared detector; the thermistor is integrated on the miniature optical cover, infrared detection chip or signal processing chip, or externally attached to the back-hole type on-chip integrated miniature infrared gas sensor; the thermistor is made of platinum metal, semiconductor or ceramic.

9. The back-hole type on-chip integrated miniature infrared gas sensor according to claim 1, characterized in that, The material of the micro-optical cover is aluminum, copper, plastic, resin, ABS, silicon, or glass; the fabrication method of the micro-optical cover is micromachining, lamination process, 3D printing technology, or MEMS processing technology.

10. The back-hole type on-chip integrated miniature infrared gas sensor according to claim 8, characterized in that, The signal processing chip consists of a power supply module, a signal processing module, and a digital logic unit; the power supply module is configured to provide voltage to the infrared light source, the thermistor, the signal processing module, and the digital logic unit; the digital logic unit includes a storage unit and logic circuits.

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