A hydrogen sensor and a method for preparing the same

Abstract

The invention discloses a hydrogen sensor and a preparation method thereof, which belongs to the field of sensor technology and is used to solve the technical problem that the current hydrogen sensor has weak anti-interference performance. The hydrogen sensor specifically comprises a silicon wafer substrate, a thin film electrical isolation layer is provided on the silicon wafer substrate, a heating resistor, a temperature measuring resistor and a hydrogen sensitive resistor are provided on the thin film electrical isolation layer, the heating resistor, the temperature measuring resistor and the hydrogen sensitive resistor are all provided with lead terminals, and an organic polymer thin film layer is provided above the hydrogen sensitive resistor. The invention has the advantages of stable performance, long life, low cost, good anti-interference performance, etc.

Description

Technical Field

[0001] The present invention mainly relates to the technical field of hydrogen sensors, and in particular to a hydrogen sensor and a preparation method thereof. Background Art

[0002] Hydrogen is an important flammable, explosive, and highly efficient renewable energy source. When the concentration of hydrogen leaked in the air reaches 4.0%-74.5%, it may cause a strong explosion when exposed to open flames. Hydrogen has important applications in both military and civilian applications. In order to ensure safe use, hydrogen sensors are mainly used in the military to prevent hydrogen leakage, fire, explosion, and environmental monitoring in equipment. The main applications in the civilian field include petrochemical refineries and petrochemical production enterprises, industrial gas production enterprises such as chlor-alkali, hydrogen and chlorine, semiconductor industry, nuclear energy, power plants and other energy plants, fuel cell technology-related enterprises, etc. In the military, it is mainly used for aerospace boosters, fuel cell fuel energy and environmental gas concentration monitoring in military operating environments.

[0003] There are currently seven main types of hydrogen sensors, namely palladium (Pd) or Pd alloy thin film type, surface acoustic wave type, catalytic combustion type, thermal conductivity type, electrochemical type, thermoelectric thin film type, and oxide semiconductor field effect transistor type. All types of hydrogen sensors have an important disadvantage, which is that they are easily interfered by other gases, thus affecting the accuracy of the sensor. In addition, the mainstream hydrogen sensors on the market now use electrochemical, catalytic combustion and other methods, which generally have the disadvantages of short life and poor stability.

[0004] Pd alloy hydrogen sensors have the advantages of stable performance and long life, and are currently the most promising hydrogen sensors. However, the sensors are easily affected by other gases in the environment, which reduces the accuracy of the sensors. Taking 1% H2 and 99% N2 mixed gas (hereinafter referred to as 1% H2 / N2) and 1% H2 and 99% Air mixed gas (hereinafter referred to as 1% H2 / Air) as examples, the sensor response amplitudes of these two gases differ by more than 50%, which greatly affects the response accuracy of the sensor in different environments, that is, the sensor's anti-interference ability is very poor. Summary of the invention

[0005] The technical problem to be solved by the present invention is: in view of the problems existing in the prior art, the present invention provides a hydrogen sensor with strong anti-interference performance and a preparation method thereof.

[0006] In order to solve the above technical problems, the technical solution proposed by the present invention is:

[0007] A hydrogen sensor comprises a silicon wafer substrate, a thin film electrical isolation layer is provided on the silicon wafer substrate, a heating resistor, a temperature measuring resistor and a hydrogen sensitive resistor are provided on the thin film electrical isolation layer, the heating resistor, the temperature measuring resistor and the hydrogen sensitive resistor are all provided with lead terminals, and an organic polymer thin film layer is provided above the hydrogen sensitive resistor.

[0008] As a further improvement of the above technical solution:

[0009] The temperature measuring resistor and the hydrogen sensitive resistor are both located in the area enclosed by the heating resistor.

[0010] The heating resistor is rectangular, and the temperature measuring resistor and the hydrogen sensitive resistor are both S-shaped and are located in a rectangular area enclosed by the heating resistor.

[0011] The organic polymer film layer is made of PMMA or PTFE high molecular organic polymer.

[0012] The hydrogen sensitive resistor is composed of Pd 1-x -Ni x , Pd 1-x -Ag x , Pd 1-x -Cr x or Pd 1-x -Cu x Made of materials.

[0013] The thin film electrical isolation layer is a SiO2 thin film electrical isolation layer.

[0014] The present invention also discloses a method for preparing the hydrogen sensor as described above, comprising the steps of:

[0015] S1, cleaning the silicon wafer substrate;

[0016] S2, preparing a thin film electrical isolation layer on a silicon wafer substrate;

[0017] S3, preparing a heating resistor and a temperature measuring resistor on the thin film electrical isolation layer;

[0018] S4, preparing a hydrogen sensitive resistor on the thin film electrical isolation layer;

[0019] S5, preparing an organic polymer thin film layer on the entire chip surface;

[0020] S6. Prepare lead ends to obtain a hydrogen sensor, wherein the lead ends include a heating resistor lead end, a temperature measuring resistor lead end and a hydrogen sensitive resistor lead end.

[0021] As a further improvement of the above technical solution:

[0022] After step S6, the performance test of the hydrogen sensor is performed again.

[0023] In step S2, the thickness of the SiO2 thin film electrical isolation layer is 0.5 μm to 5 μm, and the preparation method is PVD, CVD or evaporation.

[0024] The thickness of the heating resistor and the temperature measuring resistor is 100nm to 500nm, and the preparation method is PVD or evaporation; the thickness of the hydrogen sensitive resistor is 50nm to 200nm, and the preparation method is PVD or evaporation; the thickness of the organic polymer film layer ranges from 10nm to 150nm, and the preparation method is chemical bath deposition or PVD.

[0025] Compared with the prior art, the advantages of the present invention are:

[0026] The present invention heats the hydrogen sensor chip through a Pt heating resistor to increase the chip temperature, and measures the chip temperature through a Pt temperature measuring resistor. When the temperature reaches a set value, the chip stops heating; when the chip temperature drops below the set temperature, it starts heating again, and finally reaches a balance so that the chip temperature is stabilized at the set value, thereby reducing the impact of ambient temperature changes on the response of the hydrogen sensitive resistor and improving the accuracy of the hydrogen sensor.

[0027] The thin film electrical isolation layer in the present invention electrically isolates the silicon wafer substrate from the Pt heating resistor, the Pt temperature measuring resistor, and the Pd alloy hydrogen sensitive resistor to avoid leakage current that affects the accuracy of the sensor.

[0028] The organic polymer film layer in the present invention is made of PMMA or PTFE material. Since H2 molecules are much smaller than other gas molecules such as O2 and N2, H2 molecules can easily pass through the PMMA or PTFE film, while other gas molecules such as O2 and N2 are blocked outside the film, thereby reducing the contact between other molecules except H2 molecules and the Pd alloy hydrogen sensitive resistor 5, thereby improving the anti-interference performance of the hydrogen sensor.

[0029] The Pt heating resistor of the present invention surrounds the Pt temperature measuring resistor and the Pd alloy hydrogen sensitive resistor, which can effectively ensure the uniformity of the chip surface temperature and further avoid the influence of ambient temperature fluctuation on the response of the hydrogen sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 FIG. 1 is a top view of the structure of a hydrogen sensor according to an embodiment of the present invention.

[0031] Figure 2 FIG. 4 is a cross-sectional structural diagram of a hydrogen sensor according to an embodiment of the present invention.

[0032] Figure 3 The flowchart of the method for preparing a hydrogen sensor of the present invention is shown in an embodiment.

[0033] Figure 4This is a comparison diagram of the test response curves of the hydrogen sensor of the present invention.

[0034] Legend: 1. Silicon wafer substrate; 2. Thin film electrical isolation layer; 3. Heating resistor; 4. Temperature measuring resistor; 5. Hydrogen sensitive resistor; 6. Organic polymer thin film layer; 7. Heating resistor lead end; 8. Temperature measuring resistor lead end; 9. Hydrogen sensitive resistor lead end. DETAILED DESCRIPTION

[0035] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0036] like Figure 1 and Figure 2 As shown, the hydrogen sensor of the embodiment of the present invention includes a silicon wafer substrate 1, a thin film electrical isolation layer 2 is provided on the silicon wafer substrate 1, a Pt heating resistor 3, a Pt temperature measuring resistor 4 and a Pd alloy hydrogen sensitive resistor 5 are provided on the thin film electrical isolation layer 2, the Pt heating resistor 3, the Pt temperature measuring resistor 4 and the Pd alloy hydrogen sensitive resistor 5 are all provided with lead terminals, which are respectively a heating resistor lead terminal 7, a temperature measuring resistor lead terminal 8 and a hydrogen sensitive resistor lead terminal 9, and an organic polymer thin film layer 6 is provided above the hydrogen sensitive resistor 5.

[0037] When the hydrogen sensor is working, the hydrogen sensor chip is heated by the Pt heating resistor 3 to increase the chip temperature, and the chip temperature is measured by the Pt temperature measuring resistor 4. When the temperature reaches the set value, the chip stops heating; when the chip temperature drops below the set temperature, it starts heating again, and finally reaches a balance so that the chip temperature is stabilized at the set value, thereby reducing the impact of ambient temperature changes on the response of the hydrogen sensitive resistor 5 and improving the accuracy of the hydrogen sensor.

[0038] The thin film electrical isolation layer 2 is a SiO2 electrical isolation layer, which is used to electrically isolate the silicon wafer substrate 1 from the Pt heating resistor 3, the Pt temperature measuring resistor 4, and the Pd alloy hydrogen sensitive resistor 5 to avoid leakage current, thereby affecting the accuracy of the sensor.

[0039] The organic polymer film layer 6 is made of PMMA or PTFE material. Since H2 molecules are much smaller than other gas molecules such as O2 and N2, H2 molecules can easily pass through the PMMA or PTFE film, while other gas molecules such as O2 and N2 are blocked outside the film, thereby reducing the contact between other molecules except H2 molecules and the Pd alloy hydrogen sensitive resistor 5, thereby improving the anti-interference performance of the hydrogen sensor.

[0040] In a specific embodiment, the Pt heating resistor 3 is rectangular, and the Pt temperature measuring resistor 4 and the Pd alloy hydrogen sensitive resistor 5 are both S-shaped and located in the rectangular area enclosed by the heating resistor 3. The Pt heating resistor 3 surrounds the Pt temperature measuring resistor 4 and the Pd alloy hydrogen sensitive resistor 5, which can effectively ensure the uniformity of the chip surface temperature and further avoid the influence of ambient temperature fluctuations on the response of the hydrogen sensor. Of course, the shapes of the above-mentioned Pt heating resistor 3, Pt temperature measuring resistor 4 and Pd alloy hydrogen sensitive resistor 5 are not limited here, and other shapes can also be adopted in other embodiments.

[0041] like Figure 3 As shown, the embodiment of the present invention also discloses a method for preparing the hydrogen sensor as described above, comprising the steps of:

[0042] S1, cleaning the silicon wafer substrate 1;

[0043] S2, preparing a thin film electrical isolation layer 2 on the silicon wafer substrate 1;

[0044] S3, preparing a heating resistor 3 and a temperature measuring resistor 4 on the thin film electrical isolation layer 2;

[0045] S4, preparing a hydrogen sensitive resistor 5 on the thin film electrical isolation layer 2;

[0046] S5, preparing an organic polymer thin film layer 6 on the entire chip surface;

[0047] S6. Prepare lead ends to obtain a hydrogen sensor, wherein the lead ends include a heating resistor lead end 7, a temperature measuring resistor lead end 8 and a hydrogen sensitive resistor lead end 9.

[0048] The above preparation method has a simple process flow, and the prepared hydrogen sensor has the characteristics of stable performance, long life, low cost, good anti-interference performance, etc.

[0049] The present invention is further described in detail below in conjunction with a complete specific embodiment:

[0050] S1, prepare an n-type 4-inch silicon wafer substrate 1, and use acetone and alcohol to ultrasonically clean it for 10 to 15 minutes respectively;

[0051] S2, then prepare a SiO2 thin film electrical isolation layer 2 on the silicon wafer substrate 1, as an electrical isolation layer between the Pd alloy hydrogen sensitive resistor 5, the Pt temperature measuring resistor 4 and the Pt heating resistor 3 and the silicon wafer substrate 1; wherein the thickness of the SiO2 thin film electrical isolation layer 2 is 0.5μm to 5μm, and the preparation method is PVD, CVD, evaporation, etc.; if an ion beam sputtering coating process is adopted, the sputtering coating process is a voltage of 550V and a current of 50mA, and the thickness of the prepared SiO2 film is 1μm;

[0052] S3, preparing a Pt heating resistor 3 and a Pt temperature measuring resistor 4 by a lift-off process; the preparation method is ion beam sputtering coating, the sputtering coating process is a voltage of 700V and a current of 70mA, and the thickness of the prepared Pt film is 100nm; wherein the thickness of the Pt heating resistor 3 and the Pt temperature measuring resistor 4 can be selected between 100nm and 500nm;

[0053] S4, prepare Pd alloy hydrogen sensitive resistor 5 by lift-off process; the material of Pd alloy hydrogen sensitive resistor 5 is Pd 1-x -Ni x , Pd 1-x -Ag x , Pd 1-x -Cr x , Pd 1-x -Cu x The preparation method is ion beam sputtering coating, the sputtering coating process is 650V voltage and 60mA current, and the prepared Pd 0.9 Ni 0.1 The film thickness is 100nm, where the thickness is selected between 50nm and 200nm;

[0054] S5, then prepare an organic polymer layer on the entire chip surface; the polymer is PMMA, PTFE, etc., the preparation method is an ion beam sputtering coating process, the process is a voltage of 450V, a current of 45mA, the prepared film thickness is 15nm, and the thickness range can be selected between 10nm and 150nm;

[0055] S6. Lead terminals are prepared by lift-off process, including Pt heating resistor lead terminal 7, Pt temperature measuring resistor lead terminal 8, and Pd alloy hydrogen sensitive resistor lead terminal 9; the lead terminal materials are Au, Al, etc., and the preparation method is ion beam sputtering coating. The sputtering coating process has a voltage of 750V and a current of 75mA. The thickness of the prepared Al film is 700nm, and the thickness can be selected between 100nm and 900nm.

[0056] Finally, the prepared hydrogen sensor was subjected to a performance test using a mixture of 1% H2 and 99% N2 (1% H2 / N2) and a mixture of 1% H2 and 99% air (1% H2 / Air). Figure 4 The hydrogen sensor test response curve shown in the figure shows that the response amplitudes under the two gases are basically consistent, indicating that the hydrogen sensor has good anti-interference performance.

[0057] The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims

1. A hydrogen sensor, characterized in that: The device comprises a silicon wafer substrate (1), a thin film electrical isolation layer (2) being provided on the silicon wafer substrate (1), a heating resistor (3), a temperature measuring resistor (4) and a hydrogen sensitive resistor (5) being provided on the thin film electrical isolation layer (2), the heating resistor (3), the temperature measuring resistor (4) and the hydrogen sensitive resistor (5) being all provided with lead terminals, and an organic polymer thin film layer (6) being provided above the hydrogen sensitive resistor (5); The organic polymer film layer (6) is made of PMMA or PTFE high molecular organic polymer; The thin film electrical isolation layer (2) is a SiO2 thin film electrical isolation layer; The hydrogen sensitive resistor (5) is made of Pd 1-x -Ni x , Pd 1-x -Ag x , Pd 1-x -Cr x or Pd 1-x -Cu x Made of materials; The thickness of the organic polymer thin film layer (6) is in the range of 10 nm to 150 nm and is deposited by an ion beam sputtering coating process with a sputtering voltage of 450 V and a sputtering current of 45 mA.

2. The hydrogen sensor according to claim 1, characterized in that: The temperature measuring resistor (4) and the hydrogen sensitive resistor (5) are both located within the area enclosed by the heating resistor (3).

3. The hydrogen sensor according to claim 2, characterized in that: The heating resistor (3) is rectangular, and the temperature measuring resistor (4) and the hydrogen sensitive resistor (5) are both S-shaped and are located within the rectangular area enclosed by the heating resistor (3).

4. A method for preparing a hydrogen sensor as claimed in any one of claims 1 to 3, characterized in that: Includes steps: S1, cleaning the silicon wafer substrate (1); S2, preparing a thin film electrical isolation layer (2) on the silicon wafer substrate (1); S3, preparing a heating resistor (3) and a temperature measuring resistor (4) on the thin film electrical isolation layer (2); S4, preparing a hydrogen sensitive resistor (5) on the thin film electrical isolation layer (2); S5, preparing an organic polymer thin film layer (6) on the entire chip surface; S6. Prepare lead ends to obtain a hydrogen sensor, wherein the lead ends include a heating resistor lead end (7), a temperature measuring resistor lead end (8) and a hydrogen sensitive resistor lead end (9).

5. The preparation method according to claim 4, characterized in that: After step S6, the performance test of the hydrogen sensor is performed again.

6. The preparation method according to claim 4 or 5, characterized in that: In step S2, the thickness of the SiO2 thin film electrical isolation layer (2) is in the range of 0.5 μm to 5 μm, and the preparation method is PVD, CVD or evaporation.

7. The preparation method according to claim 4 or 5, characterized in that: The thickness of the heating resistor (3) and the temperature measuring resistor (4) ranges from 100 nm to 500 nm, and the preparation method is PVD or evaporation; the thickness of the hydrogen sensitive resistor (5) ranges from 50 nm to 200 nm, and the preparation method is PVD or evaporation.

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