Metal film hydrogen sensor and preparation method thereof

Abstract

The invention provides a metal film hydrogen sensor and a preparation method thereof. The sensor comprises a substrate structure, a measuring electrode and a hydrogen sensitive laminated structure which are sequentially arranged from bottom to top, the hydrogen sensitive laminated structure can be combined with hydrogen to change the resistance value of the hydrogen sensitive laminated structure, the hydrogen sensitive laminated structure at least comprises a hydrogen storage layer and a hydrogen adsorption diffusion layer, the hydrogen adsorption diffusion layer is arranged above the hydrogen storage layer, and the hydrogen adsorption diffusion layer is used for adsorbing the hydrogen and enabling the hydrogen to be diffused in the hydrogen adsorption diffusion layer; the measuring electrode is electrically connected with the hydrogen sensitive laminated structure. Compared with a traditional palladium alloy film, the hydrogen storage layer can remarkably improve the hydrogen storage capacity of the sensor, so that the resistance type hydrogen sensor has a wider dynamic response range, through structural design, three functions of the sensing unit are achieved through the two metal film layers respectively, and the application range of the resistance type hydrogen sensor is widened. Therefore, each layer of metal film is optimized, and the overall performance of the hydrogen sensor is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor sensors, and particularly to a metal thin film hydrogen sensor and a preparation method thereof. Background Art

[0002] Hydrogen energy is a secondary energy source with rich sources, green and low-carbon, and wide applications, and is gradually becoming one of the important carriers for the global energy transformation and development. However, hydrogen is an inflammable and explosive dangerous gas, and hydrogen leakage may cause fire and explosion accidents, resulting in heavy casualties and property losses. Since hydrogen is colorless, odorless, has strong penetration ability, and is inflammable and explosive, it has become increasingly important to monitor the leakage risk in the production, storage, transportation and use of hydrogen in real time. Hydrogen sensors are the key core technology for hydrogen leakage detection. Semiconductor hydrogen sensors have the advantages of high sensitivity, small size, high stability, high integration, etc., and are an ideal solution for hydrogen leakage detection in the field of hydrogen energy. Metal thin film resistive hydrogen sensors with palladium metal or palladium alloy as the core have the characteristics of simple device structure, good selectivity, and strong anti-interference ability, and are currently widely used in the fields of hydrogen production, hydrogen storage and hydrogen transportation in the hydrogen energy field.

[0003] The core of traditional palladium alloy thin film resistive hydrogen sensors is a palladium and its alloy sensitive thin film. Hydrogen molecules dissociate and adsorb, diffuse and solid-phase dissolve on the surface of the thin film to form palladium hydride compounds, thereby changing the resistance of the thin film and generating a hydrogen response. However, due to the surface oxidation and hydrogen embrittlement effects of palladium and its alloys, this type of sensor has the following disadvantages or pain points: The sensitive thin film with palladium and its alloy thin film as the core is easily saturated by hydrogen adsorption and dissolution due to the limitation of the thin film volume, resulting in a small dynamic range of the sensor response and cannot be applied to the detection of high-concentration hydrogen. Summary of the Invention

[0004] In view of this, the embodiments of the present invention provide a metal thin film hydrogen sensor and a preparation method thereof to eliminate or improve one or more defects existing in the prior art.

[0005] The first aspect of the present invention provides a metal thin film hydrogen sensor, including: a substrate structure, a measurement electrode, and a hydrogen-sensitive laminated structure arranged in sequence from bottom to top;

[0006] The measurement electrode is fixedly arranged on the substrate structure and electrically connected to the hydrogen-sensitive laminated structure;

[0007] The hydrogen-sensitive laminated structure can combine with hydrogen to change its resistance value. The hydrogen-sensitive laminated structure at least includes a hydrogen storage layer and a hydrogen adsorption and diffusion layer. The hydrogen adsorption and diffusion layer is disposed above the hydrogen storage layer. The hydrogen adsorption and diffusion layer is used for adsorbing hydrogen and enabling hydrogen to diffuse inside it. The hydrogen storage layer is used for combining with the hydrogen in the hydrogen adsorption and diffusion layer and storing it in the form of metal hydride.

[0008] In some embodiments of the present invention, the hydrogen-sensitive laminated structure further includes a structure buffer layer. The structure buffer layer is fixedly disposed between the substrate structure and the hydrogen storage layer. The structure buffer layer can combine with the material of the substrate structure to form a stable connection, so as to improve the mechanical stability of the hydrogen-sensitive laminated structure.

[0009] In some embodiments of the present invention, the metal thin film hydrogen sensor further includes a thin film passivation layer. The thin film passivation layer is disposed above the hydrogen-sensitive laminated structure. The thin film passivation layer can enable hydrogen to pass through and can block oxygen, water molecules, and interfering gas molecules from passing through.

[0010] In some embodiments of the present invention, the structure buffer layer includes a metal thin film formed by one or more of titanium, aluminum, palladium, or chromium. The thickness of the structure buffer layer is 20 - 60 nanometers;

[0011] The hydrogen storage layer includes a metal thin film formed by one or more of magnesium, titanium, nickel, or iron. The thickness of the hydrogen storage layer is 80 - 150 nanometers;

[0012] The hydrogen adsorption and diffusion layer includes a metal thin film formed by one or more of palladium, platinum, ruthenium, iridium, or their alloys. The thickness of the hydrogen adsorption and diffusion layer is 20 - 50 nanometers;

[0013] The thin film passivation layer includes a film layer formed by one or more of silicon oxide, silicon nitride, aluminum oxide, titanium oxide, polytetrafluoroethylene, or polyimide. The thickness of the thin film passivation layer is 30 - 70 nanometers.

[0014] In some embodiments of the present invention, the structure buffer layer is a metal titanium thin film with a thickness of 40 nanometers; the hydrogen storage layer is a metal magnesium thin film with a thickness of 100 nanometers; the hydrogen adsorption and diffusion layer is a metal palladium thin film with a thickness of 30 nanometers; the thin film passivation layer is a polyimide thin film with a thickness of 50 nanometers.

[0015] In some embodiments of the present invention, the measurement electrode covers a part of the structure of the substrate structure. The measurement electrode is disposed on the left and right sides of the substrate structure. The hydrogen-sensitive laminated structure is disposed on the front and back sides of the substrate structure. The hydrogen-sensitive laminated structure has a square wave pulse type structure.

[0016] In some embodiments of the present invention, the substrate structure includes an insulating substrate layer, a thin-film heater, and an insulating dielectric layer stacked in sequence. The edge of the insulating dielectric layer is in contact with the insulating substrate layer, and the middle part of the insulating dielectric layer completely covers the thin-film heater.

[0017] In some embodiments of the present invention, the thin-film heater includes heating electrodes and a thin-film resistance layer, and the heating electrodes are arranged on the left and right sides of the thin-film resistance layer;

[0018] The heating electrode includes a metal thin film formed of one of gold, platinum, and silver. The thin-film resistance layer includes a film layer formed of one of a metal material, a metal oxide semiconductor, and a compound semiconductor. The thicknesses of both the heating electrode and the thin-film resistance layer are 100 - 150 nanometers.

[0019] The second aspect of the present invention provides a method for preparing a metal thin-film hydrogen sensor for preparing the metal thin-film hydrogen sensor, and the method includes the following steps:

[0020] Prepare an insulating substrate layer by using any one of magnetron sputtering process, thin-film thermal evaporation, laser thin-film deposition, or screen printing process;

[0021] Deposit a thin-film heater on the insulating substrate layer by using any one of magnetron sputtering process, thin-film thermal evaporation, laser thin-film deposition, or screen printing process;

[0022] Deposit an insulating dielectric layer on the thin-film heater by using any one of screen printing process, spin coating method, chemical vapor deposition, or magnetron sputtering process;

[0023] Deposit a measurement electrode on the insulating dielectric layer by using any one of screen printing process, magnetron sputtering process, or thin-film thermal evaporation process;

[0024] Deposit a hydrogen storage layer on the insulating dielectric layer and the measurement electrode by using any one of magnetron sputtering process, thin-film thermal evaporation, chemical vapor deposition, or laser deposition;

[0025] Deposit a hydrogen adsorption and diffusion layer on the hydrogen storage layer by using any one of magnetron sputtering process, thin-film thermal evaporation, or laser deposition.

[0026] The third aspect of the present invention provides a method for preparing a metal thin-film hydrogen sensor for preparing the metal thin-film hydrogen sensor, and the method includes the following steps:

[0027] Prepare an insulating substrate layer by using any one of magnetron sputtering process, thin-film thermal evaporation, laser thin-film deposition, or screen printing process;

[0028] Deposit a thin-film heater on an insulating substrate layer using any one of magnetron sputtering, thin-film thermal evaporation, laser thin-film deposition, or screen printing processes;

[0029] Deposit an insulating dielectric layer on the thin-film heater using any one of screen printing, spin coating, chemical vapor deposition, or magnetron sputtering processes;

[0030] Deposit a measurement electrode on the insulating dielectric layer using any one of screen printing, magnetron sputtering, or thin-film thermal evaporation processes;

[0031] Deposit a structural buffer layer on the insulating dielectric layer and the measurement electrode using any one of magnetron sputtering, thin-film thermal evaporation, chemical vapor deposition, or laser deposition;

[0032] Deposit a hydrogen storage layer on the structural buffer layer using any one of magnetron sputtering, thin-film thermal evaporation, chemical vapor deposition, or laser deposition;

[0033] Deposit a hydrogen adsorption and diffusion layer on the hydrogen storage layer using any one of magnetron sputtering, thin-film thermal evaporation, or laser deposition;

[0034] Deposit a thin-film passivation layer on the hydrogen adsorption and diffusion layer using any one of screen printing, spin coating, chemical vapor deposition, or magnetron sputtering processes.

[0035] In the metal thin-film hydrogen sensor and its preparation method of the present invention, the substrate structure has good insulation properties and chemical inertness, does not react with hydrogen, and at the same time has good thermal stability and surface flatness. Hydrogen molecules can undergo dissociative adsorption, dissolution, and diffusion behaviors on the surface of the hydrogen adsorption and diffusion layer, and the hydrogen storage layer can form metal hydrides with hydrogen atoms and can dissolve a large amount of hydrogen. Compared with traditional palladium alloy thin films, the hydrogen storage layer can significantly increase the hydrogen storage capacity of the sensor, so that the resistive hydrogen sensor has a wider dynamic response range. Through structural design, the present invention realizes the three functions of the sensitive unit using two metal thin-film layers respectively, so as to optimize each metal thin-film layer respectively and improve the overall performance of the hydrogen sensor.

[0036] The additional advantages, objectives, and features of the present invention will be partially described below and will become partially apparent to those of ordinary skill in the art after studying the following text, or can be learned according to the practice of the present invention. The objectives and other advantages of the present invention can be achieved and obtained through the structure specifically pointed out in the specification and the drawings.

[0037] Those skilled in the art will understand that the objectives and advantages that can be achieved by the present invention are not limited to the above specifically described, and it will be more clearly understood from the following detailed description that the above and other objectives that the present invention can achieve. Description of the Drawings

[0038] The drawings described herein are provided to further understand the present invention, form a part of this application, and do not limit the present invention. The components in the drawings are not drawn to scale, but are only for showing the principles of the present invention. To facilitate showing and describing some parts of the present invention, corresponding parts in the drawings may be enlarged, that is, may become larger relative to other components in the exemplary device actually manufactured according to the present invention. In the drawings:

[0039] Figure 1 It is a schematic cross-sectional structure diagram of a metal thin film hydrogen sensor in an embodiment of the present invention.

[0040] Figure 2 It is a schematic structure diagram of a substrate structure in an embodiment of the present invention.

[0041] Figure 3 It is a schematic structure diagram of a hydrogen storage layer, a hydrogen adsorption and diffusion layer, and a structure buffer layer in an embodiment of the present invention.

[0042] Figure 4 It is a top view of a metal thin film hydrogen sensor in an embodiment of the present invention.

[0043] Figure 5 It is a cross-sectional electron micrograph of a metal thin film hydrogen sensor in an embodiment of the present invention.

[0044] Figure 6 It is an electron micrograph of a thin film passivation layer in an embodiment of the present invention.

[0045] Figure 7 It is a hydrogen response result diagram of a metal thin film hydrogen sensor in an embodiment of the present invention.

[0046] Figure 8 It is a flowchart of a preparation method of a metal thin film hydrogen sensor in an embodiment of the present invention.

[0047] Figure 9 It is a flowchart of a preparation method of a metal thin film hydrogen sensor in another embodiment of the present invention.

[0048] Reference numerals: 11, insulating substrate layer; 12, thin film heater; 13, insulating dielectric layer; 121, heating electrode; 122, thin film resistance layer; 21, hydrogen storage layer; 22, hydrogen adsorption and diffusion layer; 23, structure buffer layer; 24, thin film passivation layer; 25, measuring electrode. Detailed Description of the Invention

[0049] To make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below in conjunction with the embodiments and the drawings. Herein, the illustrative embodiments of the present invention and the descriptions thereof are used to explain the present invention, but not to limit the present invention.

[0050] Herein, it should also be noted that in order to avoid obscuring the present invention with unnecessary details, only the structures and / or processing steps closely related to the solution according to the present invention are shown in the drawings, while other details less related to the present invention are omitted.

[0051] It should be emphasized that the term "comprising / including" when used herein refers to the presence of features, elements, steps or components, but does not exclude the presence or addition of one or more other features, elements, steps or components.

[0052] Herein, it should also be noted that if not otherwise specified, the term "connection" in this article can not only refer to direct connection, but also represent indirect connection with intermediates.

[0053] In the following, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same reference numerals represent the same or similar components, or the same or similar steps.

[0054] To solve the technical problems in the prior art that the traditional palladium alloy thin film resistance type hydrogen sensor is prone to hydrogen adsorption and dissolution to form saturation, resulting in a small dynamic range of the sensor response and being unable to be applied to the detection of high-concentration hydrogen, the embodiments of the present invention provide a metal thin film hydrogen sensor, and the hydrogen storage layer of the sensor increases the hydrogen dissolution ability, improving the dynamic detection range of the sensor.

[0055] It should be noted that the gas sensor herein refers to an electronic component capable of sensing the types and concentration information of gases in the working environment. The semiconductor gas sensor refers to a sensor device with a sensitive material as the core and the output signal of the device being an electrical parameter, and belongs to a kind of gas sensor. The resistive gas sensor refers to a kind of semiconductor gas sensor, and the sensor relies on the resistance change of the sensitive material to generate a gas recognition signal. Selectivity refers to the ability of the sensor to identify a single target in the presence of multiple targets. The metal thin film refers to a metal solid state layer made of a metal material with a thickness much smaller than the area. The micro-nano process refers to the semiconductor material and device manufacturing technology mainly based on modern silicon process, such as basic process flows like photolithography, film coating and etching.

[0056] Referring to Figure 1 , the first aspect of the present invention provides a metal thin film hydrogen sensor, including: a substrate structure, a measurement electrode 25 and a hydrogen sensitive laminated structure arranged in sequence from bottom to top.

[0057] The measuring electrode 25 is disposed between the insulating dielectric layer 13 and the hydrogen storage layer 21 and is electrically connected to the hydrogen-sensitive laminated structure. Structurally, the measuring electrode 25 is composed of a metal conductive thin film. Functionally, it collects the electrical signals of the hydrogen-sensitive laminated structure. Specifically, the electrical signals can be any one of resistance, current, voltage, capacitance, and work function, or a combined output thereof. The measuring electrode 25 has high electrical conductivity and stable chemical and physical properties at high temperatures. For example, a platinum metal thin film with a thickness of 60 nm can be selected as the measuring electrode 25. It can maintain high conductivity characteristics and chemical inertness under high-temperature and atmosphere conditions, making the heating power stable and ensuring the stability of the sensor output signal. The material of the measuring electrode 25 can also be any one of gold, platinum, silver, polysilicon, or copper.

[0058] The hydrogen-sensitive laminated structure can combine with hydrogen to change its resistance value. The hydrogen-sensitive laminated structure at least includes a hydrogen storage layer 21 and a hydrogen adsorption and diffusion layer 22. The hydrogen adsorption and diffusion layer 22 is disposed above the hydrogen storage layer 21. The hydrogen adsorption and diffusion layer 22 is used to adsorb hydrogen and allow hydrogen to diffuse inside it. The hydrogen storage layer 21 is used to combine with the hydrogen in the hydrogen adsorption and diffusion layer 22 and store it in the form of metal hydride. Hydrogen molecules can undergo dissociation adsorption, dissolution, and diffusion behaviors on the surface of the hydrogen adsorption and diffusion layer 22. The hydrogen storage layer 21 can form metal hydride with hydrogen atoms and can dissolve a large amount of hydrogen. Compared with the traditional palladium alloy thin film, the hydrogen storage layer 21 can significantly increase the hydrogen storage capacity of the sensor, thereby enabling the resistive hydrogen sensor to have a wider dynamic response range.

[0059] The core sensitive element of the traditional palladium alloy thin film resistive hydrogen sensor is the palladium alloy thin film, which also serves as the functions of hydrogen adsorption, diffusion, and storage. Therefore, it is impossible to simultaneously meet the requirements of these three functions. Through structural design in the embodiments of the present invention, the three functions of the sensitive unit are realized separately by two metal thin film layers, so as to optimize each metal thin film layer respectively and improve the overall performance of the hydrogen sensor.

[0060] In some embodiments, referring to Figure 3 and Figure 5, the hydrogen-sensitive laminated structure further includes a structural buffer layer 23. The structural buffer layer 23 is fixedly disposed between the substrate structure and the hydrogen storage layer 21. The structural buffer layer 23 can combine with the material of the substrate structure to form a stable connection, so as to improve the mechanical stability of the hydrogen-sensitive laminated structure. In traditional palladium alloy thin film resistive hydrogen sensors, after hydrogen molecules come into contact with palladium and its alloy thin films and undergo a solid solution reaction to form palladium hydride compounds, the volume of the thin film expands significantly, resulting in cracks and detachment of palladium and its alloy thin films, causing sensor damage. After the sensor responds to hydrogen, it cannot recover, and the signal drifts severely, thus posing a risk of sensor reading failure. To solve this technical problem, the material of the structural buffer layer 23 in this embodiment can form an alloy material with the insulating dielectric layer 13. For example, when the insulating dielectric layer 13 is made of silicon oxide, the material of the structural buffer layer 23 can form a silicon alloy material with silicon, so it has good adhesion and can effectively improve the mechanical stability of the hydrogen-sensitive laminated structure. At the same time, the structural buffer layer 23 can form an alloy substance with the hydrogen storage layer 21 to eliminate the stress inside the hydrogen-sensitive laminated structure film, improving the long-term stability of the sensor, and thus solving the problems of film detachment and cracks caused by hydrogen embrittlement of the sensor.

[0061] In some embodiments, the metal thin film hydrogen sensor further includes a thin film passivation layer 24. The thin film passivation layer 24 is disposed above the hydrogen-sensitive laminated structure. The thin film passivation layer 24 can allow hydrogen to pass through and can block oxygen, water molecules, and interfering gas molecules from passing through. Structurally, the thin film passivation layer 24 is composed of a continuous organic or inorganic thin film. Functionally, it prevents environmental pollutants, humidity, and interfering gases from coming into contact with the metal thin film laminated structure and generating cross-interference responses. In traditional palladium alloy thin film resistive hydrogen sensors, palladium and its alloys are prone to surface oxidation in an air environment to form a palladium oxide thin film, thus losing their activity to hydrogen molecules. Therefore, when the sensor is placed in the atmospheric environment for a long time, it is likely to cause abnormal responses to low-concentration hydrogen and reduce the response speed of the sensor. To solve this technical problem, the thin film passivation layer 24 in this embodiment has no sensitive characteristics to hydrogen and can effectively isolate the contact between oxygen, water molecules, interfering molecules, and non-organic volatile gas molecules in the environment and the hydrogen-sensitive laminated structure, thereby significantly improving the specificity and sensitivity of the hydrogen sensor. For example, a polyimide thin film can be selected as the thin film passivation layer 24. The polyimide thin film has the advantages of low cost and high stability, and at the same time has good hydrogen permeability. By regulating the thin film passivation material, thin film structure, and growth process, the performance of the resistive hydrogen sensor can be effectively improved. Refer to Figure 6 , which is an electron micrograph of the thin film passivation layer 24 magnified 80,000 times. The thin film passivation layer 24 has a dense structure and can prevent large molecule gases from entering (large molecule gases refer to gas molecules with a larger volume than hydrogen molecules), while hydrogen molecules have a small diameter and can selectively pass through.

[0062] A continuous thin film passivation layer 24 is deposited on the surface of the hydrogen-sensitive laminated structure for passivation. Utilizing the characteristic of the small diameter of hydrogen molecules, hydrogen molecules are selectively passed through while oxygen, water molecules, and large interfering gas molecules with larger molecular diameters are isolated. Thereby, the oxidation and poisoning effects on the surface of the hydrogen-sensitive laminated structure are inhibited, and the response speed of the sensor is improved. Compared with traditional palladium alloy resistive devices, the treatment of the thin film passivation layer 24 in this embodiment enables the sensor to have a longer lifespan and a faster response speed.

[0063] The metal thin film hydrogen sensor in the above embodiment overcomes the disadvantages of hydrogen embrittlement effect, slow surface film oxidation response speed, easy saturation of hydrogen adsorption, and narrow dynamic response range of traditional platinum metal thin film resistive hydrogen sensors through the orderly stacking of metal thin films with different functions. In the above embodiment, a metal thin film laminated structure design is adopted, and the device structure is simple. The laminated structure can be compatible with the growth of metal thin films with different processes, so the process is simple and the manufacturing cost of the device is significantly reduced.

[0064] Aiming at the technical disadvantages of traditional palladium alloy thin film resistive sensors, the metal thin film hydrogen sensor proposed in the embodiment of the present invention can effectively avoid the oxidation behavior of palladium metal thin films through the metal thin film laminated design, and improve the sensitivity and response speed of the sensor. By introducing a metal thin film with high hydrogen storage alloy capacity through the metal thin film stack, the present invention can avoid the expansion and hydrogen embrittlement effect of palladium metal dissolving hydrogen on the one hand, and can also increase the hydrogen adsorption and dissolution capacity to improve the dynamic response range of hydrogen on the other hand.

[0065] In some embodiments, the hydrogen-sensitive laminated structure includes multiple hydrogen adsorption and diffusion layers 22 or hydrogen storage layers 21. For example, the hydrogen-sensitive laminated structure includes a structure buffer layer 23, a first hydrogen storage layer, a first hydrogen adsorption and diffusion layer, and a second hydrogen storage layer arranged in sequence from bottom to top. After hydrogen is adsorbed in the second hydrogen storage layer, it will spontaneously diffuse to the first hydrogen adsorption and diffusion layer according to the concentration gradient and combine with the first hydrogen storage layer until saturation. When the first hydrogen storage layer is saturated, the second hydrogen storage layer begins to adsorb and store hydrogen. Such a multi-layer structure can increase the hydrogen storage capacity. Another example is that the hydrogen-sensitive laminated structure includes a structure buffer layer 23, a first hydrogen storage layer, a first hydrogen adsorption and diffusion layer, and a second hydrogen adsorption and diffusion layer arranged in sequence from bottom to top. Such an arrangement can form the effect of multi-layer hydrogen storage or multi-layer hydrogen adsorption and diffusion.

[0066] In some embodiments, the structure buffer layer 23 includes a metal thin film formed by one or more of titanium, aluminum, palladium, or chromium, and the thickness of the structure buffer layer 23 is 20 - 60 nanometers, optionally 40 nanometers.

[0067] The hydrogen storage layer 21 includes a metal thin film formed by one or more of magnesium, titanium, nickel, or iron, and the thickness of the hydrogen storage layer 21 is 80 - 150 nanometers, optionally 100 nanometers.

[0068] The hydrogen adsorption and diffusion layer 22 comprises a metal thin film formed of one or more of palladium, platinum, ruthenium, iridium or their alloys. The thickness of the hydrogen adsorption and diffusion layer 22 is 20 - 50 nanometers, and 30 nanometers is optional.

[0069] The thin film passivation layer 24 comprises a film layer formed of one or more of silicon oxide, silicon nitride, aluminum oxide, titanium oxide, polytetrafluoroethylene or polyimide. The thickness of the thin film passivation layer 24 is 30 - 70 nanometers, and 50 nanometers is optional.

[0070] In a specific embodiment, the structural buffer layer 23 is a titanium metal thin film with a thickness of 40 nanometers. The titanium metal thin film can form an alloy material with the insulating dielectric layer 13, has good adhesion, and can effectively improve the mechanical stability of the hydrogen-sensitive laminated structure; the hydrogen storage layer 21 is a magnesium metal thin film with a thickness of 100 nanometers. The magnesium metal thin film can form metal hydrides with hydrogen atoms and can dissolve a large amount of hydrogen; the hydrogen adsorption and diffusion layer 22 is a palladium metal thin film with a thickness of 30 nanometers. Hydrogen molecules can undergo dissociative adsorption, dissolution and diffusion on the surface of the palladium metal thin film; the thin film passivation layer 24 is a polyimide thin film with a thickness of 50 nanometers. The polyimide thin film has no sensitive characteristics to hydrogen and can effectively isolate the contact between oxygen, water molecules, interfering molecules and non-organic volatile gas molecules in the environment and the hydrogen-sensitive laminated structure, thereby significantly improving the specificity and sensitivity of the hydrogen sensor.

[0071] In some embodiments, referring to Figure 4 , the measurement electrode 25 covers a part of the substrate structure. The measurement electrode 25 is disposed at the left and right positions of the substrate structure, and the hydrogen-sensitive laminated structure is disposed at the front and back positions of the substrate structure. The hydrogen-sensitive laminated structure has a square-wave pulse type configuration. Both ends of the hydrogen-sensitive laminated structure are connected to the measurement electrodes 25 on the left and right sides. The measurement electrodes 25 are disposed on the left and right sides of the substrate structure, which is convenient for connecting leads to external test equipment. The square-wave pulse type hydrogen-sensitive laminated structure enables a hydrogen-sensitive laminated structure with a long enough length to be deposited on the substrate structure per unit area, thereby increasing the contact area with hydrogen and improving the sensitivity and detection range of the sensor.

[0072] In some embodiments, referring to Figure 2, the base structure includes an insulating substrate layer 11, a thin-film heater 12, and an insulating dielectric layer 13 that are sequentially stacked. The edge of the insulating dielectric layer 13 is in contact with the insulating substrate layer 11, and the middle part of the insulating dielectric layer 13 completely covers the thin-film heater 12. The insulating substrate layer 11 is made of an insulating material and is a block structure that serves as the support for the overall sensor. The insulating substrate layer 11 has good insulating properties and chemical inertness and does not chemically react with hydrogen; at the same time, it has good thermal stability and surface flatness. The insulating substrate layer 11 can be made of materials such as alumina, silica, alumina ceramics, polymers, quartz, and aluminum nitride. In a specific embodiment, a 500-micron alumina ceramic sheet is selected as the insulating substrate layer 11, which has the advantages of low cost and good thermal stability.

[0073] The thin-film heater 12 provides a suitable operating temperature for the hydrogen-sensitive laminated structure. Usually, the operating temperature is 70 - 150 degrees Celsius. The hydrogen-sensitive laminated structure needs to be at a certain temperature to have sufficient adsorption capacity for hydrogen. Hydrogen molecules can fully diffuse in the hydrogen-sensitive laminated structure, causing a change in the resistance value of the hydrogen-sensitive laminated structure, achieving the accuracy of measuring the resistance change. The thin-film heater 12 is made of a metal material with a high stability coefficient, a metal-oxide semiconductor, and a compound semiconductor, or a combination of different types of materials above. The thin-film heater 12 can convert electrical energy into heat energy and maintain a relatively high temperature. For example, the material of the thin-film heater 12 can be selected from gold, platinum, silver, polysilicon, palladium-silver alloy, and ruthenium oxide, etc.

[0074] The insulating dielectric layer 13 is used to physically isolate the thin-film heater 12 and the hydrogen-sensitive laminated structure, achieve electrical isolation between the layer structures, and prevent interference. The insulating dielectric layer 13 has no sensitive characteristics to gases and has stable insulating properties at high temperatures. The insulating dielectric layer 13 can be any one of silica, silicon nitride, alumina, aluminum nitride, or tantalum oxide, or a combination thereof. For example, silicon nitride can be selected. The silicon nitride thin-film insulating dielectric layer has the advantages of low cost and low process temperature. A relatively thick insulating dielectric layer can prevent gas molecules from directly contacting the thin-film heater 12.

[0075] In some embodiments, referring to Figure 2 , the thin-film heater 12 includes heating electrodes 121 and a thin-film resistance layer 122. The heating electrodes 121 are arranged on the left and right sides of the thin-film resistance layer 122. The heating electrodes 121 include a metal thin film formed by one of gold, platinum, and silver. The thin-film resistance layer 122 includes a film layer formed by one of a metal material, a metal-oxide semiconductor, and a compound semiconductor. After the heating electrodes 121 are energized, the current is conducted to the thin-film resistance layer 122, and the thin-film resistance layer 122 generates heat under the thermal effect of the resistance. The heating electrodes 121 and the thin-film resistance layer 122 have good thermal stability and a high temperature coefficient.

[0076] Referring to Figure 7, The hydrogen response result diagram of the metal thin film hydrogen sensor in an embodiment of the present invention. The percentage above the curve in the figure is the hydrogen concentration. The curve consists of multiple continuous curves that first rise and then fall. The lowest point of each curve is the hydrogen injection point, and the highest point of each curve is the hydrogen withdrawal point. It can be seen from the figure that the resistance change of the sensor is used as the signal output. After the sensor contacts hydrogen in the working environment, the resistance rises rapidly; after the hydrogen disappears, the resistance value of the sensor decreases. Compared with the prior art solutions, the metal thin film hydrogen sensor provided by the present invention has a fast response speed, that is, after contacting hydrogen, the resistance value rises rapidly. At the same time, the sensor also exhibits good stability, that is, the sensor can experience multiple response and recovery processes in a short time without being damaged.

[0077] In the above embodiment of the present invention, the metal thin film hydrogen sensor uses the hydrogen-sensitive laminated structure as the hydrogen-sensitive unit, and does not solely rely on palladium or palladium alloy thin films in the prior art to simultaneously complete the adsorption, dissociation, diffusion, and dissolution behaviors of hydrogen molecules. Metal thin films with different functions respectively undertake the functions of hydrogen adsorption, dissolution, diffusion, and storage. Therefore, the present invention can effectively solve the problems faced by traditional palladium alloy resistive hydrogen sensors in principle. The metal thin film hydrogen sensor in the above embodiment of the present invention has the following advantages and effects:

[0078] 1. The hydrogen storage layer in the hydrogen-sensitive laminated structure increases the hydrogen dissolution ability and improves the dynamic detection range of the sensor. Compared with traditional palladium alloy thin films, the present invention introduces a hydrogen storage metal thin film through the metal thin film laminated structure, significantly increasing the hydrogen storage capacity of the sensitive thin film, thereby enabling the resistive hydrogen sensor to have a wider dynamic response range.

[0079] 2. The structure buffer layer in the hydrogen-sensitive laminated structure increases the adhesion between the thin film and the substrate, and at the same time can eliminate the stress inside the thin film, improving the long-term stability of the sensor. Traditional palladium alloy thin films expand after dissolving hydrogen, causing internal stress release, resulting in cracks and peeling of the thin film, and even damage to the sensor. The present invention increases the adhesion between the thin film and the substrate by introducing a structure buffer layer to avoid thin film peeling. At the same time, the structure buffer layer eliminates the stress between the thin films, inhibits the generation of thin film cracks, and improves the stability of the sensor.

[0080] 3. The thin film passivation layer isolates the environmental oxygen and water molecules from acting on the sensitive unit, avoiding the oxidation of the hydrogen adsorption and diffusion layer, and improving the response speed of the hydrogen sensor. In the present invention, a thin film passivation layer is deposited on the surface of the hydrogen-sensitive laminated structure. This thin film layer utilizes the selective passing ability of small hydrogen molecules to avoid direct contact between oxygen, water molecules, and large molecule interfering gases in the environment and the metal thin film, thereby improving the response speed of the hydrogen sensor.

[0081] Refer to Figure 8, the second aspect of the present invention provides a method for preparing a metal thin film hydrogen sensor for preparing a metal thin film hydrogen sensor. The method includes the following steps:

[0082] S11. Prepare an insulating substrate layer 11 by using any one of magnetron sputtering process, thin film thermal evaporation, laser thin film deposition or screen printing process. The insulating substrate layer 11 is made of insulating material, and materials such as alumina, silica, alumina ceramic sheet, quartz and aluminum nitride can be selected. In a specific embodiment, a 500-micron alumina ceramic sheet is selected as the insulating substrate layer 11, which has the advantages of low cost and good thermal stability.

[0083] S12. Deposit a thin film heater 12 on the insulating substrate layer 11 by using any one of magnetron sputtering process, thin film thermal evaporation, laser thin film deposition or screen printing process; the thin film heater 12 is made of a metal material with high electrical conductivity, such as gold, platinum and silver. In a specific embodiment, a 120-nanometer platinum metal thin film is deposited on the insulating substrate layer 11 by magnetron sputtering as the thin film heater 12.

[0084] S13. Deposit an insulating dielectric layer 13 on the thin film heater 12 by using any one of screen printing process, spin coating method, chemical vapor deposition, magnetron sputtering process; the material of the insulating dielectric layer 13 can be selected from any one of silica, silicon nitride, alumina, aluminum nitride or tantalum oxide. The above materials have good electrical insulation properties and at the same time prevent gas molecules from penetrating the insulating dielectric layer 13 and contacting the thin film heater 12. In a specific embodiment, a silicon nitride thin film is grown on the thin film heater 12 by chemical vapor deposition as the insulating dielectric layer 13, and the thickness is not less than 100 nanometers.

[0085] S14. Deposit a measurement electrode 25 on the insulating dielectric layer 13 by using any one of screen printing process, magnetron sputtering process and thin film thermal evaporation process; the material of the deposited measurement electrode 25 can be selected from any one of gold, platinum, silver, polysilicon or copper. The above materials have high electrical conductivity and stable chemical and physical properties at high temperatures. In a specific embodiment, a 60-nanometer-thick platinum metal thin film is grown on the dielectric insulating dielectric layer 13 by magnetron sputtering as the measurement electrode 25. Platinum metal has high electrical conductivity and good chemical stability at high temperatures.

[0086] S15. Deposit a hydrogen storage layer 21 on the insulating dielectric layer 13 and the measurement electrode 25 by using any one of magnetron sputtering process, thin film thermal evaporation, chemical vapor deposition and laser deposition; the material of the hydrogen storage layer 21 can be selected from any one of magnesium, titanium, nickel or iron. The above materials can form metal hydrides with hydrogen atoms and can dissolve a large amount of hydrogen. In a specific embodiment, a 100-nanometer-thick magnesium metal thin film is grown on the measurement electrode 25 and the insulating dielectric layer 13 as the hydrogen storage layer 21.

[0087] S16. Deposit a hydrogen adsorption and diffusion layer 22 on the hydrogen storage layer 21 by using any one of magnetron sputtering, thin film thermal evaporation, and laser deposition. The hydrogen adsorption and diffusion layer 22 can be a thin film composed of palladium or a palladium alloy, or it can be platinum, ruthenium, or iridium. Hydrogen molecules can undergo dissociative adsorption, dissolution, and diffusion on the surface of the above materials. In a specific embodiment, a 30-nanometer-thick palladium metal thin film is grown on the hydrogen storage layer 21 by using the magnetron sputtering process as the hydrogen adsorption and diffusion layer 22.

[0088] It should be noted that magnetron sputtering, thin film thermal evaporation, laser thin film deposition, screen printing, chemical vapor deposition, and spin coating are all prior arts and will not be elaborated here.

[0089] Refer to Figure 9 , the third aspect of the present invention provides a method for preparing a metal thin film hydrogen sensor for preparing a metal thin film hydrogen sensor, and the method includes the following steps:

[0090] S21. Prepare an insulating substrate layer 11 by using any one of magnetron sputtering, thin film thermal evaporation, laser thin film deposition, or screen printing;

[0091] S22. Deposit a thin film heater 12 on the insulating substrate layer 11 by using any one of magnetron sputtering, thin film thermal evaporation, laser thin film deposition, or screen printing;

[0092] S23. Deposit an insulating dielectric layer 13 on the thin film heater 12 by using any one of screen printing, spin coating, chemical vapor deposition, or magnetron sputtering;

[0093] S24. Deposit a measurement electrode 25 on the insulating dielectric layer 13 by using any one of screen printing, magnetron sputtering, and thin film thermal evaporation processes;

[0094] S25. Deposit a structural buffer layer 23 on the insulating dielectric layer 13 and the measurement electrode 25 by using any one of magnetron sputtering, thin film thermal evaporation, chemical vapor deposition, and laser deposition;

[0095] S26. Deposit a hydrogen storage layer 21 on the structural buffer layer 23 by using any one of magnetron sputtering, thin film thermal evaporation, chemical vapor deposition, and laser deposition;

[0096] S27. Deposit a hydrogen adsorption and diffusion layer 22 on the hydrogen storage layer 21 by using any one of magnetron sputtering, thin film thermal evaporation, and laser deposition;

[0097] S28. Deposit a thin-film passivation layer 24 on the hydrogen adsorption and diffusion layer 22 by any one of screen printing process, spin coating method, chemical vapor deposition, and magnetron sputtering process.

[0098] Compared with the preparation method of the metal thin-film hydrogen sensor in the above embodiment, the preparation method of the metal thin-film hydrogen sensor in this embodiment adds step S25 and step S28.

[0099] In step S25, the structural buffer layer 23 is selected from metals such as titanium, aluminum, palladium, or chromium. In a specific embodiment, a 40-nanometer-thick metal titanium thin film is grown on the measurement electrode 25 and the insulating dielectric layer 13 as the structural buffer layer 23.

[0100] In step S28, the thin-film passivation layer 24 can be an inorganic thin-film material such as silicon oxide, silicon nitride, aluminum oxide, or titanium oxide, or an organic thin-film material such as polytetrafluoroethylene or polyimide. In a specific embodiment, a 50-nanometer-thick polyimide thin film is grown on the hydrogen adsorption and diffusion layer 22 by chemical vapor deposition process as the thin-film passivation layer 24.

[0101] It should be clear that the present invention is not limited to the specific configurations and processes described above and shown in the figures. For the sake of brevity, the detailed description of known methods is omitted here. In the above embodiments, several specific steps are described and shown as examples. However, the method process of the present invention is not limited to the specific steps described and shown. Those skilled in the art can make various changes, modifications, and additions, or change the order between steps after understanding the spirit of the present invention.

[0102] In the present invention, the features described and / or illustrated for one embodiment can be used in the same way or in a similar way in one or more other embodiments, and / or combined with the features of other embodiments or replace the features of other embodiments.

[0103] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, various changes and modifications can be made to the embodiments of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A metal thin film hydrogen sensor, characterized in that: include: A base structure, a measuring electrode (25) and a hydrogen sensitive stacked structure are sequentially arranged from bottom to top; The measuring electrode (25) is fixedly arranged on the base structure and electrically connected to the hydrogen sensitive stacked structure; The hydrogen-sensitive stacked structure can combine with hydrogen to change its resistance value. The hydrogen-sensitive stacked structure at least comprises a hydrogen storage layer (21) and a hydrogen adsorption diffusion layer (22). The hydrogen adsorption diffusion layer (22) is arranged above the hydrogen storage layer (21). The hydrogen adsorption diffusion layer (22) is used to adsorb hydrogen and diffuse hydrogen inside the hydrogen storage layer (21). The hydrogen storage layer (21) is used to combine with the hydrogen in the hydrogen adsorption diffusion layer (22) and store it in the form of metal hydride.

2. The metal thin film hydrogen sensor according to claim 1, characterized in that: The hydrogen-sensitive stacked structure further comprises a structural buffer layer (23), wherein the structural buffer layer (23) is fixedly arranged between the base structure and the hydrogen storage layer (21), and the structural buffer layer (23) can be combined with the material of the base structure to form a stable connection, so as to improve the mechanical stability of the hydrogen-sensitive stacked structure.

3. The metal thin film hydrogen sensor according to claim 1 or 2, characterized in that: The metal thin film hydrogen sensor also includes a thin film passivation layer (24), which is arranged above the hydrogen sensitive stacked structure. The thin film passivation layer (24) can allow hydrogen to pass through but can block oxygen, water molecules and interfering gas molecules from passing through.

4. The metal thin film hydrogen sensor according to claim 3, characterized in that: The structural buffer layer (23) comprises a metal film formed by one or more of titanium, aluminum, palladium or chromium, and the thickness of the structural buffer layer (23) is 20-60 nanometers; The hydrogen storage layer (21) comprises a metal film formed of one or more of magnesium, titanium, nickel or iron, and the thickness of the hydrogen storage layer (21) is 80-150 nanometers; The hydrogen adsorption diffusion layer (22) comprises a metal film formed by one or more of palladium, platinum, ruthenium, iridium or alloys thereof, and the thickness of the hydrogen adsorption diffusion layer (22) is 20-50 nanometers; The thin film passivation layer (24) comprises a film layer formed by one or more of silicon oxide, silicon nitride, aluminum oxide, titanium oxide, polytetrafluoroethylene or polyimide, and the thickness of the thin film passivation layer (24) is 30-70 nanometers.

5. The metal thin film hydrogen sensor according to claim 3, characterized in that: The structural buffer layer (23) is a metal titanium film with a thickness of 40 nanometers; the hydrogen storage layer (21) is a metal magnesium film with a thickness of 100 nanometers; the hydrogen adsorption diffusion layer (22) is a metal palladium film with a thickness of 30 nanometers; and the film passivation layer (24) is a polyimide film with a thickness of 50 nanometers.

6. The metal thin film hydrogen sensor according to claim 1, characterized in that: The measuring electrode (25) covers part of the structure of the base structure. The measuring electrode (25) is arranged on the left and right sides of the base structure. The hydrogen sensitive stacked structure is arranged on the front and back sides of the base structure. The hydrogen sensitive stacked structure has a square wave pulse structure.

7. The metal thin film hydrogen sensor according to claim 1, characterized in that: The base structure comprises an insulating substrate layer (11), a thin film heater (12) and an insulating medium layer (13) which are stacked in sequence, the edge of the insulating medium layer (13) being in contact with the insulating substrate layer (11), and the middle of the insulating medium layer (13) completely covering the thin film heater (12).

8. The metal thin film hydrogen sensor according to claim 7, characterized in that: The thin film heater (12) comprises a heating electrode (121) and a thin film resistance layer (122), wherein the heating electrode (121) is arranged on the left and right sides of the thin film resistance layer (122); The heating electrode (121) comprises a metal thin film formed of one of gold, platinum and silver, and the thin film resistor layer (122) comprises a film layer formed of one of metal materials, metal oxide semiconductors and compound semiconductors. The thickness of the heating electrode (121) and the thin film resistor layer (122) are both 100-150 nanometers.

9. A method for preparing a metal thin film hydrogen sensor, used for preparing the metal thin film hydrogen sensor according to any one of claims 1 to 8, characterized in that: The method comprises the following steps: preparing an insulating substrate layer (11) by using any one of a magnetron sputtering process, a thin film thermal evaporation process, a laser thin film deposition process or a screen printing process; Depositing a thin film heater (12) on the insulating substrate layer (11) by using any one of a magnetron sputtering process, a thin film thermal evaporation process, a laser thin film deposition process or a screen printing process; Depositing an insulating dielectric layer (13) on the thin film heater (12) by using any one of a screen printing process, a spin coating method, a chemical vapor deposition method, and a magnetron sputtering process; Depositing a measuring electrode (25) on the insulating dielectric layer (13) by any one of a screen printing process, a magnetron sputtering process and a thin film thermal evaporation process; Depositing a hydrogen storage layer (21) on the insulating dielectric layer (13) and the measuring electrode (25) by using any one of a magnetron sputtering process, thin film thermal evaporation, chemical vapor deposition and laser deposition; A hydrogen adsorption diffusion layer (22) is deposited on the hydrogen storage layer (21) by using any one of magnetron sputtering, thin film thermal evaporation and laser deposition.

10. A method for preparing a metal thin film hydrogen sensor, used for preparing the metal thin film hydrogen sensor according to any one of claims 1 to 8, characterized in that: The method comprises the following steps: preparing an insulating substrate layer (11) by using any one of a magnetron sputtering process, a thin film thermal evaporation process, a laser thin film deposition process or a screen printing process; Depositing a thin film heater (12) on the insulating substrate layer (11) by using any one of a magnetron sputtering process, a thin film thermal evaporation process, a laser thin film deposition process or a screen printing process; Depositing an insulating dielectric layer (13) on the thin film heater (12) by using any one of a screen printing process, a spin coating method, a chemical vapor deposition method, and a magnetron sputtering process; Depositing a measuring electrode (25) on the insulating dielectric layer (13) by using any one of a screen printing process, a magnetron sputtering process and a thin film thermal evaporation process; Depositing a structural buffer layer (23) on the insulating dielectric layer (13) and the measuring electrode (25) by using any one of a magnetron sputtering process, thin film thermal evaporation, chemical vapor deposition and laser deposition; Depositing a hydrogen storage layer (21) on the structural buffer layer (23) by using any one of a magnetron sputtering process, thin film thermal evaporation, chemical vapor deposition and laser deposition; Depositing a hydrogen adsorption diffusion layer (22) on the hydrogen storage layer (21) by using any one of a magnetron sputtering process, thin film thermal evaporation and laser deposition; A thin film passivation layer (24) is deposited on the hydrogen adsorption diffusion layer (22) by using any one of a screen printing process, a spin coating method, a chemical vapor deposition method, and a magnetron sputtering process.

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