A hydrogen sensor for measuring hydrogen concentration in a high humidity environment

Abstract

The application discloses a hydrogen sensor for measuring hydrogen concentration in a high-humidity environment, comprising a functional part and a packaging part, wherein the functional part comprises a first thin film layer, an electrode layer and a silicon substrate which are sequentially stacked; the first thin film layer is a silicon compound thin film and is used for protecting the electrode layer; the electrode layer is used for generating a detection signal for detecting hydrogen concentration according to the change of thermal conductivity in the gas; the packaging part is provided with an inner electrode and an outer electrode, the inner electrode is connected with the electrode layer to receive the detection signal of the electrode layer, and the outer electrode is connected with an external circuit to output the detection signal; the hydrogen sensor is provided with reference and compensation resistors, the detection precision and the detection range of the sensor are increased; the measurement resistance wire is fully contacted with the surrounding air through the structural arrangement, the hydrogen concentration change is rapidly detected; and the sensor can be stably applied in the high-humidity environment by adopting the multilayer protective film and the air-permeable and water-repellent film.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of hydrogen sensors, in particular to a hydrogen sensor for measuring hydrogen concentration in a high humidity environment. BACKGROUND

[0002] Hydrogen (H2) is an invisible, inaudible, odorless flammable and explosive gas. The production, manufacturing, transportation and storage processes of various related industries may involve hydrogen release and leakage problems. If a spark and oxygen are encountered, an explosion may occur, which may seriously endanger life and property safety. Therefore, it is very important to monitor the concentration of hydrogen in various related industries, and the core of monitoring and detection is a hydrogen sensor.

[0003] Hydrogen sensors can be mainly divided into electrochemical principle, electrical principle, thermal conductivity principle, etc. according to different principles. Different principles are integrated into various gas detectors, gas analyzers, gas alarms, gas monitoring systems or products themselves according to different detection environments and requirements, playing an important role in hydrogen alarm and hydrogen early warning. The main application industries include mining industry, steel and metallurgy industry, natural gas industry and new energy vehicle industry, etc. At present, in the process of electrolytic water hydrogen production, due to high humidity and strong alkalinity inside the pipeline, the performance of many hydrogen sensors is affected, resulting in reduced detection accuracy, prolonged response time, reduced sensor life, greatly increased detection cost, and reduced safety. Therefore, hydrogen sensor detection technology with small size, low cost and high precision and capable of working in high humidity environment needs to be developed to provide timely early warning for more people in the production operation engineering that may encounter explosion, fire and other sudden conditions, and provide protection. SUMMARY

[0004] The purpose of the present application is to solve the problems in the prior art.

[0005] The technical scheme adopted by the present application to solve its technical problems is to provide a hydrogen sensor for measuring hydrogen concentration in a high humidity environment, comprising:

[0006] A functional part comprising a first thin film layer, an electrode layer and a silicon substrate stacked in sequence; the first thin film layer is a silicon compound thin film for protecting the electrode layer; the electrode layer is used to generate a detection signal for detecting hydrogen concentration according to the change of thermal conductivity in the gas;

[0007] A packaging part provided with an inner electrode and an outer electrode, the inner electrode being connected with the electrode layer to receive the detection signal of the electrode layer, and the outer electrode being connected with an external circuit to output the detection signal.

[0008] Preferably, the electrode layer comprises a first resistor and a second resistor, the first resistor being used for heating and outputting the detection signal, and the second resistor being used for reference and compensation.

[0009] Preferably, the first thin film layer is provided with openings at positions corresponding to the first and second resistance PAD regions, and the electrode layer is connected to the inner electrode of the packaging part through the PAD regions.

[0010] Preferably, the silicon substrate is provided with a cylindrical overhanging structure at a position corresponding to the first resistance through deep silicon etching.

[0011] Preferably, the first resistance adopts a meander-shaped resistance wire, and the second resistance adopts a serpentine-shaped resistance wire.

[0012] Preferably, a second thin film layer and a third thin film layer are further provided between the silicon substrate and the electrode layer, for supporting and protecting the first resistance.

[0013] Preferably, the meander-shaped resistance wire and the serpentine-shaped resistance wire are formed through magnetron sputtering of platinum and photolithographic patterning.

[0014] Preferably, the first thin film layer, the second thin film layer and the third thin film layer all adopt silicon nitride or silicon oxide as raw materials and are formed through chemical vapor deposition.

[0015] Preferably, the packaging part comprises a first packaging layer and a second packaging layer, the first packaging layer is a packaging cover plate provided with an air inlet hole, and the second packaging layer is a packaging base provided with a recess for placing the functional part.

[0016] Preferably, the air inlet hole of the first packaging layer is provided with a gas-permeable and water-repellent film.

[0017] The present application has the following beneficial effects:

[0018] (1) The serpentine-shaped platinum resistance wire serves as a reference and compensation, increases the detection accuracy and detection range of the sensor, and makes the sensor applicable to high-concentration (hydrogen concentration greater than 20000ppm) hydrogen measurement;

[0019] (2) The silicon substrate is provided with a cylindrical overhanging structure through deep silicon etching, so that the measurement resistance wire fully contacts the surrounding air and quickly detects the change of hydrogen concentration.

[0020] (3) The thin film layer avoids direct contact between the electrode layer and the air, avoids corrosion of the electrode layer in a high-humidity environment, and the first packaging layer is provided with an air inlet hole with a gas-permeable and water-repellent film, which effectively avoids water vapor from contacting the sensitive chip without affecting the air permeability, so that the sensor can be stably applied in a high-humidity environment.

[0021] The present application will be further described in detail in conjunction with the accompanying drawings and examples, but the present application is not limited to the examples. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1A functional part structure expansion view of the embodiment of the present application;

[0023] Figure 2 A functional part side view of the embodiment of the present application;

[0024] Figure 3 A functional part top view of the embodiment of the present application;

[0025] Figure 4 A first resistor and a second resistor schematic view of the embodiment of the present application;

[0026] Figure 5 A first encapsulation layer physical view of the embodiment of the present application;

[0027] Figure 6 A second encapsulation layer physical view of the embodiment of the present application. DETAILED DESCRIPTION

[0028] The hydrogen sensor for measuring hydrogen concentration in high humidity environment comprises a functional part and an encapsulation part. The functional part comprises a first thin film layer, an electrode layer and a silicon substrate which are stacked in sequence. The first thin film layer is a silicon compound thin film for protecting the electrode layer. The electrode layer is used for generating a detection signal for detecting hydrogen concentration according to the change of thermal conductivity in the gas. The encapsulation part is provided with an inner electrode and an outer electrode. The inner electrode is connected with the electrode layer to receive the detection signal of the electrode layer. The outer electrode is connected with an external circuit to output the detection signal.

[0029] Referring to Figure 1 and Figure 2 , the functional part structure expansion view and the side view of the embodiment of the present application are shown. The functional part comprises a first thin film layer, an electrode layer, a second thin film layer, a third thin film layer and a silicon substrate which are stacked in sequence.

[0030] Specifically, the first thin film layer, the second thin film layer and the third thin film layer all use silicon nitride or silicon oxide as raw materials and are formed by chemical vapor deposition.

[0031] Specifically, the first thin film layer of the embodiment is silicon nitride and is deposited by PECVD.

[0032] Specifically, the electrode layer of the embodiment is a platinum electrode. After the platinum is deposited on the electrode layer by magnetron sputtering, photoresist is applied. After the photoresist is developed, IBE etching is performed to pattern the platinum.

[0033] Specifically, the second thin film layer and the third thin film layer of the embodiment are silicon nitride and silicon oxide respectively and are deposited on the silicon substrate by PECVD.

[0034] Specifically, the silicon substrate of the embodiment is mainly processed after the above-mentioned thin film layer and the electrode layer are processed. Deep silicon etching is performed on the silicon substrate to form a circular back cavity,

[0035] Specifically, the first thin film layer, the second thin film layer and the third thin film layer can also adopt other silicon compound films.

[0036] Referring to Figure 3 As shown in the figure, it is a functional part top view of the embodiment of the present application, the electrode layer is suspended in the middle, two U-shaped platinum resistors are arranged at the suspended structure, the silicon substrate is etched into a cylindrical suspended structure in the middle, two first resistors are arranged at the place of the electrode layer corresponding to the cylindrical suspended structure, and two second resistors are arranged on both sides of the first resistors.

[0037] The first thin film layer is patterned by photoetching to form an opening at the position corresponding to the PAD area of the electrode layer, so that the PAD area is exposed for wire bonding with the second packaging layer. The purpose of etching a circular back cavity in the silicon substrate is to make the electrode layer fully contact with the environment, so that it can quickly perceive the change of the thermal conductivity of the gas in the environment, thereby more sensitively measuring the hydrogen concentration. Since the silicon substrate is suspended in the middle, the first resistor in the middle of the electrode layer is prone to collapse, so the second thin film layer and the third thin film layer mainly play a supporting and protecting role.

[0038] Specifically, the first thin film layer is deposited by PECVD, then photoresist is applied, and after photoetching and development, RIE etching is performed to pattern the thin film. The silicon nitride film avoids direct contact of the U-shaped resistor in the middle of the electrode layer and the serpentine resistors on both sides with air, so that it can quickly measure the change of the thermal conductivity of the gas in the environment, and also avoid corrosion of the electrode layer in a high humidity environment, so that it can work in a high humidity environment. At the same time, the PAD area is exposed to facilitate the output of the detection signal.

[0039] Specifically, referring to Figure 4 As shown in the figure, it is a first resistor and a second resistor schematic diagram of the embodiment of the present application, two U-shaped resistor wires are arranged in the middle of the electrode layer as the first resistors, and serpentine resistor wires are arranged on both sides of the first resistors as the second resistors.

[0040] Referring to Figure 5 and Figure 6 As shown in the figure, it is a first packaging layer and a second packaging layer of the embodiment of the present application, the first packaging layer is a packaging cover plate with an air inlet hole, and the second packaging layer is a packaging substrate with a groove for placing the functional part. The second packaging layer is provided with an inner electrode and an outer electrode, the inner electrode is connected with the electrode layer to receive the detection signal of the electrode layer, and the outer electrode is connected with an external circuit to output the detection signal.

[0041] Specifically, two back-shaped resistors constitute one side bridge arm of a Wheatstone bridge connected by an external circuit, which is used for heating and measurement, and two serpentine platinum resistors constitute the other side bridge arm of the Wheatstone bridge connected by an external circuit, which is used for reference and compensation. In the specific hydrogen detection process, when the hydrogen concentration changes, due to the high thermal conductivity of hydrogen and the change of the thermal conductivity of the mixed gas, the temperature of the two back-shaped resistors of the middle suspended structure changes rapidly, and the resistance changes, while the temperature of the two serpentine platinum resistors on the two sides does not change, and the resistance does not change. At this time, the Wheatstone bridge is unbalanced, and the change of the hydrogen concentration can be measured through the external signal output circuit. The electrode layer of the embodiment increases the number of temperature compensation resistors and middle back-shaped resistors compared with the electrode layer of other products, increases the detection precision and detection range, and makes it applicable to the measurement of high-concentration hydrogen (hydrogen concentration greater than 20000ppm).

[0042] Specifically, the first packaging layer has 9 gas inlet holes, which facilitate the entry of hydrogen for measurement, and the gas inlet holes have a gas-permeable and water-repellent film, which can effectively prevent water vapor from contacting the sensitive chip and affecting the performance of the sensor, so that the sensor can stably work in a high-humidity environment.

[0043] When the embodiment works, different thermal conductivities of different concentrations of gas are used for detection, the sensitive element is heated to a certain temperature, when the gas to be measured enters, the temperature of the sensor changes, and the resistance of the internal resistance wire also changes correspondingly. The changed resistance is converted into a corresponding voltage signal, and the concentration of the gas to be measured is judged by measuring the size of the voltage signal change. It can be seen that the thermal conductivity type hydrogen sensor proposed in the present application has the advantages of simple structure, low price, convenient use and maintenance, and good stability compared with other principle sensors, and is especially suitable for detection in high-humidity environment.

[0044] The above is only a preferred embodiment of the present application, and is not used to limit the present application, any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A hydrogen sensor for measuring a hydrogen concentration in a high humidity environment, characterized by, The application relates to a hydrogen sensor. The functional part comprises a first thin film layer, an electrode layer and a silicon substrate which are stacked in sequence; the first thin film layer is a silicon compound thin film and is used for protecting the electrode layer; the electrode layer is used for generating a detection signal for detecting the hydrogen concentration according to the thermal conductivity change in the gas; The packaging part is provided with an inner electrode and an outer electrode; the inner electrode is connected with the electrode layer to receive the detection signal of the electrode layer; and the outer electrode is connected with an external circuit to output the detection signal; The electrode layer comprises a first resistor and a second resistor; the first resistor is used for heating and outputting the detection signal; and the second resistor is used for reference and compensation; The first thin film layer is provided with openings at the positions corresponding to the PAD areas of the first resistor and the second resistor; and the electrode layer is connected with the inner electrode of the packaging part through the PAD areas of the first resistor and the second resistor; The silicon substrate is formed into a cylindrical suspended structure through deep silicon etching at the position corresponding to the first resistor; The packaging part comprises a first packaging layer and a second packaging layer; the first packaging layer is a packaging cover plate provided with an air inlet hole; and the second packaging layer is a packaging substrate provided with a recess for placing the functional part; The air inlet hole of the first packaging layer is provided with a gas-permeable and water-repellent thin film.

2. The hydrogen sensor for measuring a hydrogen concentration in a high humidity environment according to claim 1, wherein The first resistor adopts a meander-shaped resistor wire; and the second resistor adopts a serpentine-shaped resistor wire.

3. The hydrogen sensor for measuring a hydrogen concentration in a high humidity environment according to claim 1, wherein The silicon substrate and the electrode layer are further provided with a second thin film layer and a third thin film layer for supporting and protecting the first resistor.

4. The hydrogen sensor for measuring a hydrogen concentration in a high humidity environment according to claim 2, wherein The meander-shaped resistor wire and the serpentine-shaped resistor wire are formed through magnetron sputtering of platinum and photolithography patterning.

5. The hydrogen gas sensor for measuring a hydrogen gas concentration in a high humidity environment according to claim 3, wherein The first thin film layer, the second thin film layer and the third thin film layer all adopt silicon nitride or silicon oxide as raw materials and are formed through chemical vapor deposition.

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