Multilayer palladium-based micro-thermal hydrogen sensor based on MEMS technology and preparation method thereof

Abstract

The application belongs to the technical field of MEMS, material and sensor, and relates to a hydrogen sensor, and particularly provides a multilayer palladium-based micro-thermal hydrogen sensor based on a MEMS process and a preparation method thereof, so as to realize the technical targets of miniaturization, high heating efficiency, fast response time, accurate temperature control and good circuit compatibility. In the application, a temperature measuring electrode, a temperature measuring-heating electrode isolation layer, a heating electrode, a heating-hydrogen sensitive electrode isolation layer and a hydrogen sensitive electrode are sequentially stacked on a substrate to form a multilayer overlapping structure, the same isolation layer is arranged between the heating electrode and the hydrogen sensitive electrode and the temperature measuring electrode stacked above and below the heating electrode, the temperature measuring electrode and the hydrogen sensitive electrode are in the same temperature region, the heating efficiency is improved, the accurate temperature control is realized, and the applicability of the palladium-based micro-thermal hydrogen sensor in different application scenarios is improved. In addition, a hollow structure is formed in the multilayer overlapping structure to form a heat resistance region, so that the heating efficiency can be further improved and the device power consumption can be reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of MEMS technology, materials and sensors, and relates to a hydrogen sensor, and particularly provides a multilayer palladium-based micro-thermal hydrogen sensor based on a MEMS process and a preparation method thereof. BACKGROUND

[0002] Hydrogen is widely used in industrial production (such as automobiles, aviation, power generation, etc.) as a clean fuel, which can solve the problems of insufficient reserves, non-sustainability and serious pollution compared with traditional fuels. However, at the same time, there are also safety factors such as low explosion limit and easy leakage, which need to be detected by hydrogen sensors. At present, the mainstream hydrogen sensor is composed of a micro-heating plate, an isolation layer and a sensitive layer. On the one hand, the high heating temperature and the insufficient heating efficiency cause high heating power consumption, resulting in low integration; on the other hand, the detection limit of the hydrogen sensor after heating is narrow, which is not conducive to detecting hydrogen in a high concentration environment. Therefore, a hydrogen sensor with low power consumption, high integration and wide detection limit has become a research focus.

[0003] In the 1970s, with the discovery of the hydrogen-sensitive properties of palladium, a new solution was provided for the field of hydrogen sensors, which proved to be a hydrogen-sensitive material capable of achieving low power consumption and fast response. In recent years, research results of palladium-based hydrogen sensors have been reported. For example, the patent document with publication number CN 101482528B discloses an integrated dense nanoparticle single-layer film hydrogen sensor. Due to the hydrogen absorption lattice expansion of palladium nanoparticles, new electrical connection points are formed between the nanoparticles, causing the electrical conductivity between the comb-shaped electrodes to increase, thereby detecting changes in hydrogen concentration. For example, the patent document with publication number CN 101968461B discloses a room temperature hydrogen sensor based on a palladium-nano tin dioxide film-shaped electrode. However, the above two devices have the following problems: due to insufficient film thickness or uneven nanoparticle distribution, the process has uncontrollable factors affecting the batch consistency and repeatability of the device; if a thick film is deposited as a hydrogen-sensitive electrode to improve consistency, the response time will increase, which is not conducive to rapid detection, and a micro-heating plate must be used for heating, and precise temperature control is required for application in different external temperature environments. Therefore, it is of great significance to introduce a micro-heating plate to heat the thick film to achieve a hydrogen sensor with wide detection range, rapid detection and device batch consistency.

[0004] At present, there are also a small number of reports on palladium-based micro-thermal hydrogen sensors. For example, the patent document with publication number CN 109060895 A discloses a resistance type metal thin film hydrogen sensor that works in a temperature rising mode. However, this structure does not have a temperature measuring electrode for temperature monitoring and temperature control, and cannot adapt to different external temperature environments. In addition, this structure is based on a planar design, and there is excess heat loss during heating, resulting in more energy loss. SUMMARY

[0005] The present application aims to provide a multi-layer palladium-based micro-hot hydrogen sensor based on MEMS technology and a preparation method thereof, to achieve the technical goals of miniaturization, high heating efficiency, fast response time, accurate temperature control, and good circuit compatibility, and to improve the working ability of the palladium-based micro-hot hydrogen sensor in different environments, which has wide application potential in energy development, industrial safety, military, and other fields.

[0006] To achieve the above-mentioned purpose, the technical solution adopted by the present application is:

[0007] A multi-layer palladium-based micro-hot hydrogen sensor based on MEMS technology, comprising: a substrate 101, a temperature measuring electrode 102, a temperature measuring-heating electrode isolation layer 103, a heating electrode 104, a heating-hydrogen sensitive electrode isolation layer 105, and a hydrogen sensitive electrode 106; characterized in that:

[0008] The substrate 101 is provided with a hollow structure on the back, a patterned support layer is formed in the center area of the top of the substrate, a heat blocking area 107 is formed in the hollow area around the patterned support layer, and a pin area 108 is formed in the area connected to both sides of the patterned support layer;

[0009] The temperature measuring electrode 102 is arranged on the patterned support layer, the heating-temperature measuring electrode isolation layer 103 is arranged on the temperature measuring electrode, the heating electrode 104 is arranged on the heating-temperature measuring electrode isolation layer, the temperature measuring-hydrogen sensitive electrode isolation layer 105 is arranged on the heating electrode, and the hydrogen sensitive electrode 106 is arranged on the temperature measuring-hydrogen sensitive electrode isolation layer; the temperature measuring electrode 102, the temperature measuring-heating electrode isolation layer 103, the heating electrode 104, the heating-hydrogen sensitive electrode isolation layer 105, and the hydrogen sensitive electrode 106 adopt the same pattern structure as the patterned support layer;

[0010] The temperature measuring electrode 102, the temperature measuring-heating electrode isolation layer 103, the heating electrode 104, the heating-hydrogen sensitive electrode isolation layer 105, and the hydrogen sensitive electrode 106 are connected to the pin area 108 of the substrate and the isolation layer between adjacent pins.

[0011] Further, the temperature measuring electrode, the temperature measuring-heating electrode isolation layer, the heating electrode, the heating-hydrogen sensitive electrode isolation layer, and the hydrogen sensitive electrode all adopt a serpentine structure.

[0012] Further, the hydrogen sensitive electrode adopts palladium-nickel, palladium-cobalt, or palladium-ruthenium alloy, and the thin film thickness is 5-30 nm.

[0013] Further, the heating electrode adopts common heating electrodes such as metal nickel, gold, and gold-nickel alloy, and the thin film thickness is 50-100 nm.

[0014] Further, the temperature measuring electrode adopts common temperature measuring electrodes such as metal nickel, gold, gold-nickel alloy, and the film thickness is 20-40 nm.

[0015] Further, the temperature measuring-heating electrode isolation layer and the heating-hydrogen sensitive electrode isolation layer adopt the same material, specifically insulating materials such as aluminum oxide, silicon oxide, silicon nitride; and the temperature measuring-heating electrode isolation layer and the heating-hydrogen sensitive electrode isolation layer have the same thickness, specifically 200-300 nm.

[0016] Further, the patterned support layer has a thickness of 10-50 μm.

[0017] Further, the preparation method of the multilayer palladium-based micro-thermal hydrogen sensor based on the MEMS process comprises the following steps:

[0018] Step 1: realizing the patterning of the temperature measuring electrode and its pin by using a photolithography process, depositing the temperature measuring electrode and its pin on the silicon substrate by using an electron beam evaporation process, and stripping the photoresist after the deposition is completed;

[0019] Step 2: realizing the patterning of the heating-temperature measuring electrode isolation layer by using a photolithography process, depositing the temperature measuring-heating electrode isolation layer on the temperature measuring electrode and its electrode by using an electron beam evaporation process, and stripping the photoresist after the deposition is completed;

[0020] Step 3: realizing the patterning of the heating electrode and its pin by using a photolithography process, depositing the heating electrode and its pin on the temperature measuring-heating electrode isolation layer by using an electron beam evaporation process, and stripping the photoresist after the deposition is completed;

[0021] Step 4: realizing the patterning of the heating-hydrogen sensitive electrode isolation layer by using a photolithography process, depositing the heating-hydrogen sensitive electrode isolation layer on the heating electrode and its pin by using an electron beam evaporation process, and stripping the photoresist after the deposition is completed;

[0022] Step 5: realizing the patterning of the hydrogen sensitive electrode and its pin by using a photolithography process, depositing the hydrogen sensitive electrode and its pin on the heating-hydrogen sensitive electrode isolation layer by using an electron beam evaporation process, and stripping the photoresist after the deposition is completed;

[0023] Step 6: realizing the patterning of the etching region by using a photolithography process, using a wet etching process to perform isotropic etching on the back of the silicon substrate by using TMAH and hydrofluoric acid solution in sequence, and forming the snake-shaped support layer and the hollow structure around the snake-shaped support layer.

[0024] Based on the above technical solution, the application has the following beneficial effects:

[0025] The application provides a multilayer palladium-based micro-thermal hydrogen sensor based on a MEMS process and a preparation method thereof. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 It is a three-dimensional structure schematic diagram of the multilayer palladium-based hydrogen sensor based on the MEMS process in the application.

[0027] Figure 2 It is a sectional structure schematic diagram of the multilayer palladium-based hydrogen sensor based on the MEMS process in the application.

[0028] Figure 3 It is a preparation flowchart of the multilayer palladium-based hydrogen sensor based on the MEMS process in the application. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical scheme and beneficial effects of the application clearer, the application is further described in detail below in combination with the drawings and examples.

[0030] The embodiment provides a multilayer palladium-based micro-thermal hydrogen sensor based on a MEMS process, and the structure is as shown in Figure 1 、 Figure 2 The embodiment provides a multilayer palladium-based micro-thermal hydrogen sensor based on a MEMS process, and the structure is as shown in

[0031] The substrate 101 is made of silicon material or aluminum oxide, a hollow structure is formed on the back of the substrate by etching, a serpentine support layer is formed in the center area of the top of the substrate, and a heat resistance area 107 is formed in the hollow area around the serpentine support layer, and the two side areas connected with the serpentine support layer form a pin area 108;

[0032] The temperature measuring electrode 102 is arranged on the serpentine support layer and is made of gold or nickel with a thickness of 50 nanometers;

[0033] The heating-temperature measuring electrode isolation layer 103 is arranged on the temperature measuring electrode, adopts alumina or silicon dioxide, and has a thickness of 200 nanometers;

[0034] The heating electrode 104 is arranged on the heating-temperature measuring electrode isolation layer, adopts gold or nickel, has a line width of 20 micrometers, and has a thickness of 100 nanometers;

[0035] The temperature measuring-hydrogen sensing electrode isolation layer 105 is arranged on the heating electrode, adopts alumina or silicon dioxide, and has a thickness of 200 nanometers;

[0036] The hydrogen sensing electrode 106 is arranged on the temperature measuring-hydrogen sensing electrode isolation layer, adopts palladium-nickel, palladium-cobalt or palladium-ruthenium alloy, and has a thickness of 20 nanometers;

[0037] The temperature measuring electrode 102, the temperature measuring-heating electrode isolation layer 103, the heating electrode 104, the heating-hydrogen sensing electrode isolation layer 105, the hydrogen sensing electrode 106 and the serpentine support layer adopt the same serpentine structure;

[0038] The temperature measuring electrode 102, the temperature measuring-heating electrode isolation layer 103, the heating electrode 104, the heating-hydrogen sensing electrode isolation layer 105, the hydrogen sensing electrode 106 are led out from the pin area 108 of the substrate, and the isolation layer between adjacent pins, that is, the temperature measuring electrode and the pin thereof are completely isolated from the heating electrode and the pin thereof through the temperature measuring-heating electrode isolation layer, and the heating electrode and the pin thereof are completely isolated from the hydrogen sensing electrode and the pin thereof through the heating-hydrogen sensing electrode isolation layer; and in order to facilitate the leading out of each electrode and ensure the complete separation between adjacent pins, the areas of the temperature measuring electrode pin, the temperature measuring-heating electrode isolation layer, the heating electrode pin, the heating-hydrogen sensing electrode isolation layer and the hydrogen sensing electrode pin are sequentially reduced from bottom to top in the pin area 108.

[0039] The above multi-layer palladium-based micro-thermal hydrogen sensor can be prepared by using the MEMS process. Taking a silicon substrate as an example, the heating, temperature measuring and hydrogen sensing electrodes and the isolation layer between the electrodes are deposited on the wafer by using the method of multiple photolithography-film plating-peeling / etching, mainly including the steps of photolithography, deposition and peeling / etching of the heating, temperature measuring and hydrogen sensing electrodes and the isolation layer between the electrodes, as shown in Figure 3 The method comprises the following steps:

[0040] Step 1: Selecting an oxygen-silicon-110 silicon substrate, realizing the patterning of the temperature measuring electrode and the pin thereof by using a photolithography process, depositing a 10-nm chromium layer and a 40-nm gold layer on the silicon substrate by using an electron beam evaporation process, and using the two layers as the temperature measuring electrode, and then placing the sample with completed deposition into NMP solution for ultrasonic photoresist peeling to complete the preparation of the temperature measuring electrode and the pin thereof;

[0041] Step 2: The heating-temperature measuring electrode isolation layer is patterned by a photolithography process, 200nm of aluminum oxide is deposited on the temperature measuring electrode and the electrode by an electron beam evaporation process as a temperature measuring-heating electrode isolation layer, and the sample after deposition is placed in an NMP solution for ultrasonic photoresist stripping to complete the preparation of the temperature measuring-heating electrode isolation layer;

[0042] Step 3: The heating electrode and its pins are patterned by a photolithography process, 20nm of chromium and 80nm of gold are deposited on the temperature measuring-heating electrode isolation layer by an electron beam evaporation process, which are used as a heating electrode, the sample after deposition is placed in an NMP solution for ultrasonic photoresist stripping to complete the preparation of the heating electrode and its pins;

[0043] Step 4: The heating-hydrogen sensitive electrode isolation layer is patterned by a photolithography process, 200nm of aluminum oxide is deposited on the heating electrode and its pins by an electron beam evaporation process as a heating-hydrogen sensitive electrode isolation layer, and the sample after deposition is placed in an NMP solution for ultrasonic photoresist stripping to complete the preparation of the heating-hydrogen sensitive electrode isolation layer;

[0044] Step 5: The hydrogen sensitive electrode and its pins are patterned by a photolithography process, 20nm of palladium or palladium alloy is deposited on the heating-hydrogen sensitive electrode isolation layer by an electron beam evaporation process as a hydrogen sensitive electrode, and the sample after deposition is placed in an NMP solution for ultrasonic photoresist stripping to complete the preparation of the hydrogen sensitive electrode and its pins;

[0045] Step 6: The etching area is patterned by a photolithography process, and the back of the silicon substrate is isotropically etched by using TMAH and hydrofluoric acid solution in sequence by a wet etching process to form a snake-shaped support layer and a hollow structure around the support layer, wherein the thickness of the support layer is 30-50μm.

[0046] In summary, the application provides a multi-layer palladium-based micro-thermal hydrogen sensor based on a MEMS process and a preparation method thereof, which uses a multi-layer superposition structure to greatly improve the heating efficiency to achieve low power consumption, and the temperature measuring electrode can realize accurate temperature control, the working temperature of the hydrogen sensitive electrode using palladium-nickel, palladium-cobalt or palladium-ruthenium as the material is controlled within the optimal working temperature range, so that it can adapt to different external temperature working environments.

[0047] The above is only a specific embodiment of the application, any feature disclosed in the specification can be replaced by other equivalent or similar purpose alternative features unless specifically described; all features disclosed, or steps in all methods or processes, except for mutually exclusive features and / or steps, can be combined in any way.

Claims

1. A multilayer palladium-based micro-hot-hydrogen sensor based on MEMS technology, comprising: The base (101), the temperature measuring electrode (102), the temperature measuring-heating electrode isolation layer (103), the heating electrode (104), the heating-hydrogen sensitive electrode isolation layer (105) and the hydrogen sensitive electrode (106); characterized in that: The back of the base (101) is provided with a hollow structure, and a patterned support layer is formed in the central area of the top of the base, the hollow area around the patterned support layer forms a heat resistance area (107), and the areas connected to the patterned support layer on both sides form a pin area (108); The temperature measuring electrode (102) is arranged on the patterned support layer, the temperature measuring-heating electrode isolation layer (103) is arranged on the temperature measuring electrode, the heating electrode (104) is arranged on the temperature measuring-heating electrode isolation layer, the heating-hydrogen sensitive electrode isolation layer (105) is arranged on the heating electrode, and the hydrogen sensitive electrode (106) is arranged on the heating-hydrogen sensitive electrode isolation layer, and the temperature measuring electrode (102), the temperature measuring-heating electrode isolation layer (103), the heating electrode (104), the heating-hydrogen sensitive electrode isolation layer (105) and the hydrogen sensitive electrode (106) adopt the same pattern structure as the patterned support layer; The temperature measuring electrode (102), the temperature measuring-heating electrode isolation layer (103), the heating electrode (104), the heating-hydrogen sensitive electrode isolation layer (105) and the hydrogen sensitive electrode (106) are arranged on the pin area (108) of the substrate and the isolation layer between adjacent pins.

2. The multi-layered palladium-based micro-hot-hydrogen sensor based on MEMS process according to claim 1, wherein, The temperature measuring electrode, the temperature measuring-heating electrode isolation layer, the heating electrode, the heating-hydrogen sensitive electrode isolation layer and the hydrogen sensitive electrode all adopt a serpentine structure.

3. The multi-layered palladium-based micro-hot-hydrogen sensor based on MEMS process according to claim 1, wherein, The hydrogen sensitive electrode adopts palladium-nickel, palladium-cobalt or palladium-ruthenium alloy, and the thickness is 5-30 nm.

4. The multi-layered palladium-based micro-hot-hydrogen sensor based on MEMS process according to claim 1, wherein, The thickness of the heating electrode is 50-100 nm.

5. The multi-layer palladium-based micro-hot-hydrogen sensor based on MEMS process according to claim 1, wherein, The thickness of the temperature measuring electrode is 20-40 nm.

6. The multi-layer palladium-based micro-hot-hydrogen sensor based on MEMS process according to claim 1, wherein, The temperature measuring-heating electrode isolation layer and the heating-hydrogen sensitive electrode isolation layer adopt the same material, specifically aluminum oxide, silicon oxide or silicon nitride insulating material, and the thickness of the temperature measuring-heating electrode isolation layer and the heating-hydrogen sensitive electrode isolation layer is the same, specifically 200-300 nm.

7. The multi-layer palladium-based micro-hot-hydrogen sensor based on MEMS process according to claim 1, wherein, The thickness of the patterned support layer is 10-50 μm.

8. The method of claim 1, wherein the multi-layered palladium-based micro-hot hydrogen sensor is prepared by a MEMS process. The method comprises the following steps: Step 1: The temperature measuring electrode and its pins are patterned by a photolithography process, the temperature measuring electrode and its pins are deposited on the silicon substrate by an electron beam evaporation process, and the photoresist is stripped after deposition; Step 2: The temperature measuring-heating electrode isolation layer is patterned by a photolithography process, the temperature measuring-heating electrode isolation layer is deposited on the temperature measuring electrode and the electrode by an electron beam evaporation process, and the photoresist is stripped after deposition; Step 3: The heating electrode and its pins are patterned by a photolithography process, the heating electrode and its pins are deposited on the temperature measuring-heating electrode isolation layer by an electron beam evaporation process, and the photoresist is stripped after deposition; Step 4: The heating-hydrogen sensitive electrode isolation layer is patterned by a photolithography process, the heating-hydrogen sensitive electrode isolation layer is deposited on the heating electrode and its pins by an electron beam evaporation process, and the photoresist is stripped after deposition; Step 5: The hydrogen-sensitive electrode and its pin are patterned by using a photolithography process, and the hydrogen-sensitive electrode and its pin are deposited on the heated hydrogen-sensitive electrode isolation layer by an electron beam evaporation process; after the deposition is completed, the photoresist is stripped; Step 6: The etching area is patterned by using a photolithography process, and the silicon substrate back is etched by using a wet etching process to form a serpentine support layer and a hollow structure around the serpentine support layer.

Images