Fully isothermal activated hydrogen sensor and preparation method thereof

Abstract

The invention belongs to the field of electronics and sensors, and particularly provides a full-isothermal activated hydrogen sensor and a preparation method thereof, which are used for solving the problems of poor activation effect of a sensitive layer, limited effect rate, difficulty in responding to gas at the optimal working temperature and the like caused by non-uniform heating of an unheated plate of an existing hydrogen sensor. According to the invention, the heating electrode with an arc-edge rectangular structure is creatively provided, the insulating layer and the sensitive layer are sequentially deposited on the heating layer, and the temperature distribution of the heating area is regulated and controlled by adjusting the curvature radius of the arc edge of the arc-edge rectangular structure, so that the temperatures of different heating areas of the heating electrode are basically consistent, and the full isothermal activation of the sensitive layer is realized; the problem of insufficient gas-sensitive performance caused by non-uniform heating of a micro heater of a traditional hydrogen sensor is effectively solved; moreover, the preparation process of the full-isothermal activated hydrogen sensor is simple, wafer-level preparation of the low-power-consumption hydrogen sensor is realized on the premise that an etching process is not needed, and industrial production is facilitated.

Description

Technical Field

[0001] The present invention belongs to the field of electronics and sensors, and particularly provides an isothermal-activated hydrogen sensor and a preparation method thereof. Background Art

[0002] With the development of technology, the use of energy fuels in fields such as chemical operations, aerospace, and transportation is becoming increasingly widespread. The problems of the stock of traditional fossil fuels and environmental issues are becoming increasingly serious. Under this premise, hydrogen has been widely used due to its advantages such as being clean, pollution-free, and renewable. However, in actual applications, since hydrogen is a colorless and odorless gas that cannot be perceived by humans and has the characteristics of being flammable and explosive, there is a potential danger of causing great harm to production facilities, personnel safety, and the surrounding environment. Therefore, it is necessary to use a hydrogen sensor to monitor the environment to prevent accidents such as gas leakage, explosion, and fire.

[0003] Currently, the commonly used sensitive materials for mainstream hydrogen sensors are noble metals, semiconductor metal oxides, etc. With the continuous development of energy utilization, the requirements for the response rate and wide detection limit detection performance of hydrogen sensors are constantly increasing, and the heating operation of hydrogen sensors has gradually been studied. Relevant reports have pointed out that heating the sensitive materials of noble metals or semiconductor metal oxides can effectively activate the materials and improve the performance. On the one hand, the increase in temperature can effectively promote the dissociation, adsorption, and desorption processes of gases on the material surface. On the other hand, it can increase the diffusion rate of gas molecules inside the material, thereby shortening the response time of the hydrogen sensor and improving the sensitivity of the hydrogen sensor.

[0004] Traditional hydrogen sensors are composed of a micro-heating plate, an insulating layer, a sensitive layer, etc. The sensitive electrode is heated by the micro-heating plate to improve the performance. However, the conventional heating method using a micro-heating plate does not consider the uniformity of temperature distribution. There is a certain temperature difference in the sensitive material in different heating regions, resulting in different activation effects in each region of the sensitive layer, leading to a lag in gas response and affecting the response time and detection range of the sensor. For example, the patent document with the publication number CN 109060895A discloses a resistive metal thin film hydrogen sensor operating in a temperature-rising mode. By controlling the heating device, the working temperature of the metal thin film sensitive electrode is set within the range of 50°C to 100°C, effectively improving the response speed and sensitivity of the hydrogen sensor. However, this structure does not consider the heating uniformity of the micro-heating plate, resulting in the response rate of the sensor still being affected. Summary of the Invention

[0005] The object of the present invention is to provide a fully isothermal activated hydrogen sensor and its preparation method, so as to solve the problems of poor activation effect of the sensitive layer, limited effect rate, and difficulty in responding to gases at the optimal working temperature caused by uneven heating of the unheated plate in the existing hydrogen sensors. The present invention creatively proposes a heating electrode with an arc-edge rectangular structure, which effectively optimizes the temperature distribution in the heating area of the heating layer, realizes the fully isothermal activation of the sensitive layer by the heating layer, thereby improving the gas sensing performance of the hydrogen sensor, and has a wide application background in the fields of energy development, industrial environment monitoring, etc.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A fully isothermal activated hydrogen sensor, comprising: a substrate 101, a heating layer 102, an insulating layer 103, and a sensitive layer 104. Among them, the heating layer is disposed on the surface of the substrate, the insulating layer is disposed on the surface of the heating layer and completely covers the heating area of the heating layer, and the sensitive layer is disposed on the surface of the insulating layer and directly above the heating area of the heating layer. Its characteristic lies in that the heating area of the heating layer adopts an arc-edge rectangular heating electrode.

[0008] Furthermore, the arc-edge rectangular heating electrode is composed of splicing 1 rectangular heating area and 2 bow-shaped heating areas. The 2 bow-shaped heating areas are spliced along the long side of the rectangular heating area, and the arc-edge rectangular heating electrode is axially symmetric along the midline of the rectangular heating area.

[0009] Even further, the sensitive layer is located directly above the arc-edge rectangular heating electrode and is arranged along the long side direction of the arc-edge rectangular heating electrode. The length of the sensitive layer is x, and the arc curvature radius of the bow-shaped heating area is y. Then x and y satisfy: y = ax + b, where the value range of a is -250 to -150, and the value range of b is 50 to 150.

[0010] Furthermore, the substrate adopts polyimide or other low-thermal conductivity materials with a thermal conductivity less than 0.05 W / (m·°C), and the thickness is 100 μm to 500 μm.

[0011] Furthermore, the heating layer adopts a metal material such as gold, nickel, aluminum, silver, or copper, and the thickness is 100 nm to 400 nm.

[0012] Furthermore, the insulating layer adopts silicon oxide or aluminum oxide, and the thickness is 100 nm to 300 nm.

[0013] Furthermore, the sensitive layer adopts a metal material palladium, or a composite material composed of a metal material palladium and one of the metal materials nickel, gold, ruthenium, cobalt, and copper, or a semiconductor metal oxide tin oxide or tungsten oxide. The thickness of the sensitive layer is 20 nm to 50 nm.

[0014] Further, a method for preparing a fully isothermal-activated hydrogen sensor includes the following steps:

[0015] Step 1: Implement the patterning of the heating layer by lithography. Deposit the heating layer on the substrate through electron beam evaporation, and strip the photoresist after deposition.

[0016] Step 2: Implement the patterning of the insulating layer by lithography. Deposit the insulating layer on the heating layer through electron beam evaporation, and strip the photoresist after deposition.

[0017] Step 3: Implement the patterning of the sensitive layer by lithography. Deposit the sensitive layer on the insulating layer through electron beam evaporation, and strip the photoresist after deposition.

[0018] Step 4: Implement the patterning of the pins of the sensitive layer by lithography. Deposit the pins of the sensitive layer on the insulating layer through electron beam evaporation, and strip the photoresist after deposition.

[0019] Based on the above technical solution, the beneficial effects of the present invention are as follows:

[0020] The present invention provides a fully isothermal-activated hydrogen sensor based on a vertical heat transfer structure and a preparation method thereof. In the fully isothermal-activated hydrogen sensor, a specific arc-edge rectangular heating layer is deposited on a low-thermal-conductivity substrate, and an insulating layer and a sensitive layer are sequentially deposited in the isothermal heating region of the heating layer. By adjusting the arc-edge curvature radius of the arc-edge rectangle, the temperature distribution in the heating region is regulated. The arc-edge curvature radius and the length of the heating region are in an inverse proportional relationship through fitting design. When the length of the heating region becomes larger, a temperature difference appears between the central part and the two side parts of the heating electrode, and the central temperature is higher than the two side temperatures. It is necessary to reduce the arc-edge curvature radius to eliminate the temperature difference and ensure that the temperatures in different heating regions of the heating electrode are basically the same, so as to achieve the full isothermal activation of the sensitive layer, and vice versa. Thus, the present invention solves the problem of insufficient gas-sensing performance caused by uneven heating of the micro-heater in traditional hydrogen sensors. Moreover, the preparation process of the fully isothermal-activated hydrogen sensor is simple. Without the need for an etching process, the wafer-level preparation of a low-power hydrogen sensor is realized, which is beneficial to industrial production. Description of the Drawings

[0021] Figure 1 It is a schematic structural diagram of a fully isothermal-activated hydrogen sensor in Embodiment 1 of the present invention.

[0022] Figure 2 It is a schematic structural diagram of a hydrogen sensor based on traditional heating in Comparative Example 1 of the present invention.

[0023] Figure 3 It is a temperature distribution curve of the two-dimensional cross-section of the heating region in Embodiment 1 and Comparative Example 1 of the present invention. Detailed Embodiments

[0024] To make the objectives, technical solutions and beneficial effects of the present invention more clear and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0025] Embodiment 1

[0026] This embodiment provides a hydrogen sensor with full isothermal activation, and its structure is as Figure 1 shown, specifically including: a substrate 101, a heating layer 102, an insulating layer 103, and a sensitive layer 104, where:

[0027] The substrate material is made of polyimide, with a thickness of 200 microns, a length of 2 millimeters, and a width of 2 millimeters;

[0028] The heating layer material is made of metallic gold, with a thickness of 100 nanometers. The specific structure includes: 2 rectangular pads on both sides and 1 arc-edge rectangular heating electrode in the middle. Among them, the length of the rectangular pad is 300 microns and the width is 400 microns. The length of the arc-edge rectangular heating electrode is 600 microns and the width is 10 microns. According to the relationship between the arc curvature radius y and the heating region length x: y = ax + b, where a = -204.3 and b = 105.2; when the calculated heating length is 300 microns, the curvature radii of the 2 arc edges are 40 microns; it should be noted that the arc-edge rectangle described in the present invention is composed of 1 rectangle and 2 bow-shaped parts spliced together. The 2 bow-shaped parts are spliced along the long side of the rectangle, and the arc-edge rectangle is an axisymmetric figure along the middle line of the rectangle. The length and width of the arc-edge rectangle refer to the length and width of the rectangle, and the heating length refers to the length of the vertical projection of the sensitive layer on the heating layer.

[0029] The insulating layer material is silicon oxide, and the distribution area completely covers the heating area of the heating electrode, with a thickness of 200 nanometers;

[0030] The sensitive layer material is palladium metal material. The thickness of the sensitive layer is 20 nanometers, the length is 300 microns, and the width is 5 microns; moreover, both ends of the sensitive layer are led out through pins.

[0031] Furthermore, the hydrogen sensor with full isothermal activation is prepared by the following steps:

[0032] Step 1: Use photolithography to pattern the heating layer. Deposit the heating layer on the substrate through electron beam evaporation, and strip the photoresist after deposition;

[0033] Step 2: Use photolithography to pattern the insulating layer. Deposit the insulating layer on the heating layer through electron beam evaporation, and strip the photoresist after deposition;

[0034] Step 3: Implement the patterning of the sensitive layer using photolithography. Deposit the sensitive layer on the insulating layer through electron beam evaporation. After deposition, strip the photoresist.

[0035] Step 4: Implement the patterning of the sensitive layer pins using photolithography. Deposit the sensitive layer pins on the insulating layer through electron beam evaporation. After deposition, strip the photoresist.

[0036] The fully isothermal activated hydrogen sensor described in this embodiment is simulated and modeled by software. The actual heating effect is simulated by setting the boundary conditions of current and solid heat transfer.

[0037] The beneficial effects of the present invention will be described in detail below in combination with the simulation results. To more intuitively illustrate the beneficial effects of the present invention, the present invention also provides a Comparative Example 1. The hydrogen sensor based on the traditional heating method in Comparative Example 1 is as Figure 2 shown. The only difference from Example 1 is that the heating electrode is rectangular, with a length of 600 microns and a width of 10 microns. In addition, it should be noted that: Figure 1 and Figure 2 are only the structural schematic diagrams of the fully isothermal activated hydrogen sensor in Example 1 and the hydrogen sensor based on the traditional heating method in Comparative Example 1. To make the structures of the heating layer and the sensitive layer clearly visible, Figure 1 the rectangular pads of the heating layer, the arc-edge rectangular heating electrodes, the sensitive layer, and Figure 2 the rectangular pads and the rectangular heating electrode sensitive layer in

[0038] are not drawn strictly according to the scale. Figure 3 Perform a simulation test on the surface heating temperature distribution of the heating electrode structures in Example 1 and Comparative Example 1. Set the initial current to 0.025 amperes, and take the center of the heating layer as the coordinate origin. The temperature distribution curves of the two-dimensional cross-sections of the heating regions in Example 1 and Comparative Example 1 are obtained by simulation, as

[0039] In summary, the present invention provides a fully isothermal activated hydrogen sensor based on vertical heat transfer and a preparation method thereof. A specific arc-edge rectangular heating layer is deposited on a low-thermal-conductivity substrate. By adjusting the structure of the arc-edge rectangle of the heating layer, the temperature distribution of the heating area of the heating layer is controlled, so as to achieve the full isothermal activation of the sensitive layer by the heating layer, accelerate the response speed of the hydrogen sensor, and solve the problem that it is difficult for traditional heating structures to make materials respond to gases at the optimal working temperature.

[0040] As described above, the above is only a specific implementation manner of the present invention. Any feature disclosed in this specification, unless specifically described, can be replaced by other equivalent or similar-purpose alternative features; all the features disclosed, or all the steps in any method or process, except for mutually exclusive features and / or steps, can be combined in any way.

Claims

1. A fully isothermally activated hydrogen sensor, comprising: A substrate (101), a heating layer (102), an insulating layer (103), and a sensitive layer (104), wherein the heating layer is arranged on the surface of the substrate, the insulating layer is arranged on the surface of the heating layer and completely covers the heating area of ​​the heating layer, and the sensitive layer is arranged on the surface of the insulating layer and is located directly above the heating area of ​​the heating layer; and the characteristic is that the heating area of ​​the heating layer adopts an arc-edged rectangular heating electrode.

2. The fully isothermally activated hydrogen sensor according to claim 1, characterized in that: The arc-edge rectangular heating electrode is composed of a rectangular heating zone and two arc-shaped heating zones, the two arc-shaped heating zones are spliced ​​along the long sides of the rectangular heating zone, and the arc-edge rectangular heating electrode is an axisymmetric structure along the center line of the rectangular heating zone.

3. The fully isothermally activated hydrogen sensor according to claim 1, characterized in that: The sensitive layer is located directly above the arc-edge rectangular heating electrode and is arranged along the long side direction of the arc-edge rectangular heating electrode. The length of the sensitive layer is x, and the arc-edge curvature radius of the bow-shaped heating zone is y, then x and y satisfy: y=ax+b, wherein the value range of a is -250 to -150, and the value range of b is 50 to 150.

4. The fully isothermally activated hydrogen sensor according to claim 1, characterized in that: The substrate is made of polyimide or other low thermal conductivity materials with a thermal conductivity of less than 0.05 W / m degrees Celsius, and has a thickness of 100 microns to 500 microns.

5. The fully isothermally activated hydrogen sensor according to claim 1, characterized in that: The heating layer is made of metal material such as gold, nickel, aluminum, silver or copper, and has a thickness of 100 nanometers to 400 nanometers.

6. The fully isothermally activated hydrogen sensor according to claim 1, characterized in that: The insulating layer is made of silicon oxide or aluminum oxide, and has a thickness of 100 nanometers to 300 nanometers.

7. The fully isothermally activated hydrogen sensor according to claim 1, characterized in that: The sensitive layer is made of metal material palladium, or a composite material composed of metal material palladium and one of metal materials nickel, gold, ruthenium, cobalt, and copper, or semiconductor metal oxide tin oxide and tungsten oxide. The thickness of the sensitive layer is 20 nanometers to 50 nanometers.

8. The method for preparing a fully isothermally activated hydrogen sensor according to claim 1, characterized in that: The following steps are involved: Step 1: Use photolithography to pattern the heating layer, deposit the heating layer on the substrate by electron beam evaporation, and peel off the photoresist after deposition; Step 2: Patterning the insulating layer using a photolithography process, depositing the insulating layer on the heating layer using an electron beam evaporation process, and stripping the photoresist after the deposition is completed; Step 3: Use photolithography to pattern the sensitive layer, deposit the sensitive layer on the insulating layer by electron beam evaporation, and peel off the photoresist after deposition; Step 4: Use photolithography to pattern the pins of the sensitive layer, deposit the pins of the sensitive layer on the insulating layer through electron beam evaporation, and peel off the photoresist after deposition.

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