A gas sensor, a sensor manufacturing method, and a detection method

Abstract

The application provides a gas sensor, belonging to the field of micro-electro-mechanical systems, comprising a silicon substrate, an insulating medium support layer, a signal generating source, a signal receiving source and an insulating medium passivation layer, the insulating medium support layer is arranged on the upper surface of the silicon substrate, at least one signal generating source and at least one signal receiving source are arranged on the upper surface of the insulating medium support layer, the insulating medium support layer is arranged as a cantilever beam with both ends fixed, the signal generating source and the signal receiving source are deposited on the cantilever beam, there is a spacing between the signal generating source and the signal receiving source, and the insulating medium passivation layer is arranged on the upper surface of the signal generating source, the signal receiving source and the insulating medium support layer, and a preparation method and a detection method of the gas sensor are also provided; signal extraction is carried out by using the heat transfer time of the gas medium, the signal generating source is mainly gas heat conduction, the response time delay and noise interference of solid heat conduction in traditional detection are avoided, and the problems of slow heat signal transmission and slow response of the sensor are solved.

Description

Technical Field

[0001] This invention relates to the field of microelectromechanical systems technology, and in particular to a gas sensor, a sensor preparation method, and a detection method. Background Technology

[0002] Binary gas mixture detection is widely used in hydrogen energy equipment, new energy vehicles, and air conditioning and refrigeration. Currently, there are many types of gas sensors on the market, such as laser, infrared, photoionization, electrochemical, catalytic, semiconductor, solid electrolyte, and thermal conductivity sensors. Different gas media have different thermal conductivity coefficients. Thermal conductivity gas sensors detect gases by detecting the differences in heat energy propagation under different gas components. The thermal conductivity detection principle is a purely physical detection mechanism. These gas sensors are more reliable than electrochemical and semiconductor sensors, and have significant advantages in the detection of binary gas mixtures.

[0003] Traditional thermal conductivity gas sensors are often large, power-consuming, have low sensitivity, and exhibit significant temperature drift. Therefore, miniaturization, high reliability, and high sensitivity development of thermal conductivity gas sensors are crucial. The paper "Working Principle and Improved Detection Method of Thermal Conductivity Gas Sensors" (Du Binxian, Chen Jinrun, Yin Jun, School of Automation, Chongqing University, PLA, Chemical Engineering and Equipment) describes the traditional detection method of thermal conductivity gas sensors. The gas to be measured is introduced into a gas chamber, where a thermistor, platinum wire, or tungsten wire is located. Heating the thermistor to a certain temperature allows heat to dissipate more easily from the thermistor when the thermal conductivity of the gas is high, reducing its resistance. This changing resistance is converted into an unbalanced voltage output through signal conditioning and conversion circuitry. The change in output voltage reflects the change in the thermal conductivity of the gas, thus enabling the detection of gas concentration. However, this detection method relies on the temperature change of the thermistor itself. Since the thermistor's structure primarily relies on solid-state heat transfer, directly measuring its resistance change results in a certain response time delay and noise interference, leading to slow thermal signal transmission, slow sensor response, and low sensitivity. Summary of the Invention

[0004] The technical problem to be solved by this invention is how to solve the problem of slow thermal signal transmission and slow sensor response when using traditional detection methods for thermal conductivity gas sensors.

[0005] The present invention solves the above-mentioned technical problems through the following technical solution: a gas sensor, comprising a silicon substrate, an insulating dielectric support layer, a signal generator, a signal receiver, and an insulating dielectric passivation layer, wherein the insulating dielectric support layer is disposed on the upper surface of the silicon substrate, at least one signal generator and at least one signal receiver are disposed on the upper surface of the insulating dielectric support layer, a cantilever beam fixed at both ends is configured on the insulating dielectric support layer, and the signal generator and signal receiver are deposited on the cantilever beam, wherein there is a gap between the signal generator and the signal receiver, and the insulating dielectric passivation layer is disposed on the upper surface of the signal generator, the signal receiver, and the insulating dielectric support layer.

[0006] This invention utilizes a gaseous medium to transfer heat and extracts gas sensor signals based on the heat transfer time. Since the heat dissipation from the signal source is primarily due to gas thermal conduction, it avoids the response time delay and noise interference issues inherent in traditional detection methods that directly measure the signal source from solid thermal conduction. This solves the problems of slow thermal signal transmission and slow sensor response in thermal conductivity gas sensors. The sensitive materials for both the signal source and receiver are deposited on a cantilever beam structure, reducing the sensor's solid area, thereby lowering power consumption and improving heat utilization.

[0007] Preferably, one signal generator and one signal receiver are provided, and they are symmetrically arranged on both sides of the diagonal of the silicon substrate.

[0008] Preferably, one signal generating source is provided, and multiple signal receiving sources are provided. The signal generating source is located at the center of the upper surface of the silicon substrate, and the multiple signal receiving sources are arranged around the signal generating source with different spacing from the signal generating source.

[0009] Preferably, multiple signal generating sources and multiple signal receiving sources are provided, and the multiple signal generating sources form a polygonal structure, with the signal receiving sources arranged at equal or unequal intervals around the signal generating sources.

[0010] Preferably, the insulating dielectric support layer, the signal generator, the signal receiver, and the insulating passivation layer form a multi-layer "laminated" structure.

[0011] Preferably, the insulating dielectric support layer is a single-layer or multi-layer "laminated" structure.

[0012] Preferably, a sensitive material is deposited on the signal generating source and the signal receiving source. The sensitive material is a conductive, heat-generating metal or semiconductor.

[0013] Preferably, the signal generator is connected to an external control circuit, and the signal receiver is connected to an external measurement circuit.

[0014] This invention also provides a method for preparing a gas sensor, comprising the following steps:

[0015] Step 1: Deposit an insulating dielectric support layer on the surface of a silicon substrate;

[0016] Step 2: Pattern photoresist on the surface of the insulating dielectric support layer, and prepare the signal generator and signal receiver.

[0017] Step 3: Deposit an insulating dielectric passivation layer on the upper surface of the signal generator, signal receiver, and insulating dielectric support layer;

[0018] Step 4: Etch the Pad window and wet release window using RIE;

[0019] Step 5: Wet etching to form a cantilever beam structure.

[0020] The present invention also provides a detection method for a gas sensor, comprising the following steps:

[0021] Step 1: Calibrate the sensor using a standard gas to obtain the time constant output value for different mixed gas concentrations, and store the data in the MCU of the test circuit;

[0022] Step 2: Power the control circuit and measurement circuit of the sensor. The sensor's signal generator emits a stable pulse signal, and the measurement circuit outputs a pulse voltage signal from the signal receiver.

[0023] Step 3: Inject background gas into the sensor test chamber, and then inject the gas to be tested sequentially according to the concentration ratio of 0-100%.

[0024] Step 4: The peripheral detection circuit can detect the concentration of the injected gas by detecting the time displacement of the signal receiving source.

[0025] The advantages provided by this invention are:

[0026] 1. This invention uses a gas medium to transfer heat and utilizes the heat transfer time to extract gas sensor signals. The heat dissipation of the signal source temperature is mainly due to gas thermal conduction, which avoids the problems of response time delay and noise interference caused by solid thermal conduction when directly measuring the signal source in traditional detection methods. This solves the problems of slow thermal signal transmission and slow sensor response of thermal conduction gas sensors.

[0027] 2. The sensitive materials for both the signal generator and receiver are deposited on the cantilever beam structure, which reduces the solid area of ​​the sensor, thereby lowering power consumption and improving heat utilization. Utilizing the flexibility of the cantilever structure, arrayed gas sensors with multiple cantilever beams at varying spacings can be fabricated, resulting in high sensitivity and reliability.

[0028] 3. This invention utilizes a pulse excitation source, resulting in lower sensor power consumption.

[0029] 4. This invention utilizes MEMS process technology to fabricate sensors, resulting in small individual sensor sizes, enabling mass production and low cost per unit. Attached Figure Description

[0030] Figure 1 A schematic diagram of a gas sensor provided for an embodiment of the present invention;

[0031] Figure 2 A schematic diagram of an extended structure of a gas sensor provided in an embodiment of the present invention;

[0032] Figure 3 A schematic diagram of an extended structure two of the gas sensor provided in an embodiment of the present invention;

[0033] Figure 4 A detection circuit diagram of a gas sensor provided for an embodiment of the present invention;

[0034] In the figure: 1 silicon substrate, 2 insulating dielectric support layer, 3 signal generator, 4 signal receiver, 5 insulating dielectric passivation layer. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0036] like Figure 1 As shown, the present invention provides a gas sensor, including a silicon substrate 1, an insulating dielectric support layer 2, a signal generator 3, a signal receiver 4, and an insulating dielectric passivation layer 5. The insulating dielectric support layer 2 is disposed on the upper surface of the silicon substrate 1. The signal generator 3 and the signal receiver 4 are both disposed on the upper surface of the insulating dielectric support layer 2. A specific area of ​​the insulating dielectric support layer 2 is configured as a cantilever beam with both ends fixed. The signal generator 3 and the signal receiver 4 are deposited on the cantilever beam. There is a certain gap between the signal generator 3 and the signal receiver 4. The insulating dielectric passivation layer 5 is disposed on the upper surface of the signal generator 3, the signal receiver 4, and the insulating dielectric support layer 2.

[0037] Combination Figure 4Before actual use, the gas sensor of this invention needs to be calibrated using a standard gas to obtain the time constant output value for different mixed gas concentrations, and the data is stored in the MCU of the test circuit. The signal generator 3 is controlled by a peripheral control circuit providing pulse excitation. The signal generator 3 emits a stable pulse signal, causing its own temperature to rise to a certain value, injecting background gas into the sensor test chamber, and then sequentially injecting the gas medium to be tested according to a certain concentration ratio. The signal generator 3 transfers heat to the signal receiver 4 through the gas medium. When different components or concentrations of gas medium are injected into the chamber, the heat sensed by the signal receiver 4 will change accordingly, and the time it takes to sense the heat will also change accordingly. The peripheral measurement circuit is connected to the signal receiver 4 to output the pulse voltage signal of the signal receiver 4. By detecting the time displacement of the signal receiver 4, the composition or concentration of the injected gas medium can be detected.

[0038] This invention utilizes a gaseous medium to transfer heat and extracts gas sensor signals based on the heat transfer time. Since the heat dissipation from the signal source is primarily due to gas thermal conduction, it avoids the response time delay and noise interference issues inherent in traditional detection methods that directly measure the signal source from solid thermal conduction. This solves the problems of slow thermal signal transmission and slow sensor response in thermal conductivity gas sensors. The sensitive materials for both the signal source and receiver are deposited on a cantilever beam structure, reducing the sensor's solid area, thereby lowering power consumption and improving heat utilization.

[0039] Furthermore, one signal generator 3 and one signal receiver 4 are each provided, and they are symmetrically arranged on both sides of the diagonal of the silicon substrate 1.

[0040] Furthermore, the insulating dielectric support layer 2, the signal generator 3, the signal receiver 4, and the insulating passivation layer 5 form a multi-layer "laminated" structure.

[0041] Furthermore, the insulating dielectric support layer 2 is a single-layer or multi-layer "laminate" structure, which can reduce the intrinsic stress and thermal stress of the thin film structure.

[0042] Furthermore, a sensitive material is deposited on the signal generating source 3 and the signal receiving source 4. The sensitive material can be a conductive, heat-generating metal or a semiconductor. The metal can be platinum, nickel, etc., and the semiconductor can be polycrystalline silicon.

[0043] Furthermore, in combination Figure 2 One signal generator 3 is provided, and multiple signal receivers 4 are provided. The signal generator 3 is located at the center of the upper surface of the silicon substrate 1, and the multiple signal receivers 4 are arranged around the signal generator 3 with different spacing from the signal generator 3. Specifically, four signal receivers 4 can be provided, arranged around the perimeter, with the spacing controlled by a cantilever beam structure.

[0044] Furthermore, in combination Figure 3 Multiple signal generators (3) and signal receivers (4) are provided, forming a polygonal structure. The signal receivers (4) are arranged around the signal generators (3) at equal or unequal intervals. Specifically, four signal generators (3) are provided, each corresponding to one signal receiver (4). Each signal generator (3) has a different size, specifically a different resistance value, and a different width of its resistance bar. The signal generators (3) can be arranged in a polygonal layout, such as triangles, pentagons, or hexagons.

[0045] Furthermore, signal generator 3 is connected to an external control circuit, and signal receiver 4 is connected to an external measurement circuit. The duty cycle of the pulse signal can be selected not only at 50% but also at 70%. By setting the high-level time longer, it is easier to acquire the signal.

[0046] This invention also provides a method for preparing a gas sensor, comprising the following steps:

[0047] Step 1: The silicon substrate 1 can be made of single-crystal silicon. An insulating dielectric support layer 2 is deposited on the surface of the silicon substrate 1. The insulating dielectric layer 2 can be made of silicon nitride-silicon oxide.

[0048] Step 2: Pattern photoresist on the surface of insulating dielectric support layer 2, and prepare signal generator 3 and signal receiver 4;

[0049] Step 3: Deposit an insulating dielectric passivation layer 5 on the upper surface of the signal generator 3, the signal receiver 4 and the insulating dielectric support layer 2. The insulating dielectric passivation layer 5 can be made of silicon nitride.

[0050] Step 4: Etch the Pad window and wet release window using RIE;

[0051] Step 5: Wet etching to form a cantilever beam structure.

[0052] The present invention also provides a gas sensor detection method, comprising the following steps:

[0053] Step 1: Calibrate the sensor using a standard gas to obtain the time constant output value for different mixed gas concentrations, and store the data in the MCU of the test circuit;

[0054] Step 2: Power the control circuit and measurement circuit of the sensor. The sensor's signal generator 3 emits a stable pulse signal, and the measurement circuit outputs the pulse voltage signal from the signal receiver 4.

[0055] Step 3: Inject background gas (compressed air or nitrogen) into the sensor test chamber, and then inject the gas to be tested (e.g., hydrogen) in sequence according to the concentration ratio of 0-100%.

[0056] Step 4: The peripheral detection circuit can detect the concentration of the injected gas by detecting the time displacement of the signal receiving source 4.

[0057] Working Principle: The sensor signal generator 3 is controlled by pulse excitation provided by the external circuit, causing its own temperature to rise to a certain value. The signal receiver 4 senses the temperature of the signal generator 3 after a certain lag, as this temperature is transmitted from the signal generator 3 to the signal receiver 4 through the gas medium. By changing the gas composition, the time it takes for the signal receiver 4 to sense the temperature will vary due to the different thermal conductivity coefficients between different gases. Different gas concentrations result in different time constants. The signal receiver 4 is a temperature-sensitive element; its resistance value corresponds one-to-one with the temperature value. By connecting the signal receiver 4 to the external circuit, the resistance change signal caused by the temperature change is extracted, and the change in the phase shift time constant of the resistance is obtained. Thus, the concentration of the binary gas mixture can be correlated with its time constant.

[0058] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A gas sensor characterized by: The device includes a silicon substrate (1), an insulating dielectric support layer (2), a signal generator (3), a signal receiver (4), and an insulating dielectric passivation layer (5). The insulating dielectric support layer (2) is disposed on the upper surface of the silicon substrate (1). At least one signal generator (3) and at least one signal receiver (4) are disposed on the upper surface of the insulating dielectric support layer (2). The insulating dielectric support layer (2) is configured with cantilever beams fixed at both ends. The signal generator (3) and the signal receiver (4) are deposited on the cantilever beams. There is a gap between the signal generator (3) and the signal receiver (4). The insulating dielectric passivation layer (5) is disposed on the upper surface of the signal generator (3), the signal receiver (4), and the insulating dielectric support layer (2). The signal generator (3) emits a stable pulse signal and its temperature rises. Background gas is injected, and then the gas medium to be tested is injected in sequence. The signal generator (3) transfers heat to the signal receiver (4) through the gas medium. The composition or concentration of the gas medium to be tested is detected by detecting the time displacement of the signal receiver (4).

2. The gas sensor according to claim 1, characterized by: One signal generator (3) and one signal receiver (4) are each provided and are symmetrically arranged on both sides of the diagonal of the silicon substrate (1).

3. The gas sensor according to claim 1, characterized in that: One signal generator (3) is provided, and multiple signal receivers (4) are provided. The signal generator (3) is located at the center of the upper surface of the silicon substrate (1), and multiple signal receivers (4) are arranged around the signal generator (3) with different spacing from the signal generator (3).

4. The gas sensor according to claim 1, characterized in that: Multiple signal generators (3) and multiple signal receivers (4) are provided. Multiple signal generators (3) form a polygonal structure, and the signal receivers (4) are arranged around the signal generators (3) at equal or unequal intervals.

5. The gas sensor according to claim 2, 3, or 4, characterized in that: The insulating dielectric support layer (2), signal generator (3), signal receiver (4), and insulating dielectric passivation layer (5) form a multi-layer "laminated" structure.

6. The gas sensor according to claim 5, characterized in that: The insulating dielectric support layer (2) is a single-layer or multi-layer "laminated plate" structure.

7. The gas sensor according to claim 2, 3, or 4, characterized in that: Sensitive materials are deposited on the signal generating source (3) and the signal receiving source (4). The sensitive materials are conductive, heat-generating metals or semiconductors.

8. The gas sensor according to claim 7, characterized in that: The signal generator (3) is connected to an external control circuit, and the signal receiver (4) is connected to an external measurement circuit.

9. A method for preparing a gas sensor as described in any one of claims 1-8, characterized in that: Includes the following steps: Step 1: Deposit an insulating dielectric support layer (2) on the surface of a silicon substrate (1); Step 2: Pattern photoresist on the surface of the insulating dielectric support layer (2) and prepare signal generator (3) and signal receiver (4). Step 3: Deposit an insulating dielectric passivation layer (5) on the upper surface of the signal generator (3), the signal receiver (4) and the insulating dielectric support layer (2); Step 4: Etch the Pad window and wet release window using RIE; Step 5: Wet etching to form a cantilever beam structure.

10. A detection method of a gas sensor as described in any one of claims 1-8, characterized in that: Includes the following steps: Step 1: Calibrate the sensor using a standard gas to obtain the time constant output value for different mixed gas concentrations, and store the data in the MCU of the test circuit; Step 2: Power the control circuit and measurement circuit of the sensor. The sensor's signal generator (3) emits a stable pulse signal, and the measurement circuit outputs the pulse voltage signal from the signal receiver (4). Step 3: Inject background gas into the sensor test chamber, and then inject the gas to be tested sequentially according to the concentration ratio of 0-100%. Step 4: The peripheral detection circuit can detect the concentration of the injected gas by detecting the time displacement of the signal receiving source (4).

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