A hydrogen sensor based on silicon nanomembrane

Abstract

The application discloses a hydrogen sensor based on a silicon nanomembrane, which comprises hydrogen-sensitive material, a center mass block, a silicon nanomembrane pressure-sensitive resistor, a cantilever beam, a metal lead and a frame; the hydrogen-sensitive material is deposited on the center mass block, the center mass block is located in the middle of the four cantilever beams, the center mass block and the four cantilever beams form a 'Wang' character cantilever beam structure, the silicon nanomembrane pressure-sensitive resistor is arranged on each beam arm of the four cantilever beams, the metal lead is further arranged on each cantilever beam, the metal lead is connected with the pressure-sensitive resistor to form a Wheatstone bridge, and the frame supports the periphery of the 'Wang' character cantilever beam structure. The application provides a hydrogen sensor based on a silicon nanomembrane, the hydrogen-sensitive material is a nano-porous palladium membrane, the pressure-sensitive resistor is a silicon nanomembrane pressure-sensitive resistor, the cantilever beam is locally and narrowly thinned, the hydrogen-sensitive material, the 'Wang' character cantilever beam structure and the silicon nanomembrane sensitive unit are utilized to improve the sensitivity and the response speed of the sensor.

Description

Technical Field

[0001] The present invention relates to the technical field of sensors, in particular to a hydrogen sensor based on silicon nanofilm. Background Art

[0002] Hydrogen has potential risks of leakage, combustion and explosion during its preparation, storage, transportation, filling and use. Therefore, achieving rapid hydrogen concentration detection has always been an urgent problem that needs to be solved in the application and large-scale commercial promotion of hydrogen energy.

[0003] With the rise of microelectromechanical systems (MEMS) technology, it has gradually become a hot topic of research due to its advantages such as miniaturized structure, low manufacturing cost, arrayability, mass production, and ease of integration. MEMS technology covers a wide range of fields and has extensive applications in various fields such as medicine, aviation, automobiles, microelectronics, mechanical manufacturing, and communications. Hydrogen sensors can be divided into catalytic, electrochemical, semiconductor, fiber optic, and acoustic types according to their principles. Each has its own advantages and disadvantages. Piezoresistive hydrogen sensors are made based on the piezoresistive effect. When the hydrogen-sensitive film adsorbs hydrogen, its mass changes. This mass change causes the cantilever beam to bend, changing the resistance value of the piezoresistor. The change in hydrogen concentration is detected by detecting the output voltage value caused by the change in resistance value. The piezoresistive hydrogen sensor has a simple process and a small size. When the sensitive unit is subjected to external force, it deforms and the internal resistance changes. At this time, the bridge formed will produce a corresponding output due to imbalance. This type of sensor has the advantages of good linearity and convenient measurement. However, this type of sensor has the disadvantages of slow response speed and low sensitivity. Therefore, it is necessary to select new materials and design new structures of sensors to solve the above technical problems. Summary of the Invention

[0004] In view of this, the object of the present invention is to provide a hydrogen sensor based on silicon nanofilm to solve the problems of insufficient response time and suboptimal sensitivity of hydrogen sensors in the prior art.

[0005] To achieve the above-mentioned purpose, the present invention adopts the following technical solution: a hydrogen sensor based on silicon nanofilm, comprising: a hydrogen-sensitive material (1), a central mass block (2), a silicon nanofilm piezoresistor (3), a first cantilever beam (41), a second cantilever beam (42), a third cantilever beam (43), a fourth cantilever beam (44), a metal lead (5), and a frame (6); the hydrogen-sensitive material (1) is deposited on the central mass block (2), the central mass block (2) is located in the middle of the first cantilever beam (41), the second cantilever beam (42), the third cantilever beam (43), and the fourth cantilever beam (44); the hydrogen-sensitive material (1) is deposited on the central mass block (2), the central mass block (2) is located in the middle of the first cantilever beam (41), the second cantilever beam (42), the third cantilever beam (43), and the fourth cantilever beam (44); The first cantilever beam (41), the second cantilever beam (42), the third cantilever beam (43), and the fourth cantilever beam (44) are all provided with silicon nanofilm piezoresistors (3). The first cantilever beam (41), the second cantilever beam (42), the third cantilever beam (43), and the fourth cantilever beam (44) are also all provided with metal leads (5). The metal leads (5) connect the silicon nanofilm piezoresistors (3) to form a Wheatstone bridge. The frame (6) supports the four sides of the cantilever beam structure composed of the first cantilever beam (41), the second cantilever beam (42), the third cantilever beam (43), and the fourth cantilever beam (44).

[0006] In a preferred embodiment, the first cantilever beam (41), the second cantilever beam (42), the third cantilever beam (43), and the fourth cantilever beam (44) are arranged in rotational symmetry.

[0007] In a preferred embodiment, the central mass block (2) and the first cantilever beam (41), the second cantilever beam (42), the third cantilever beam (43), and the fourth cantilever beam (44) form a "Wan" cantilever beam structure.

[0008] In a preferred embodiment, when the hydrogen sensor adsorbs hydrogen through the hydrogen-sensitive material (1), the mass of the central mass block (2) changes, driving the cantilever beam structure to bend. The deformation of the cantilever beam structure causes a change in the stress of the first cantilever beam (41), the second cantilever beam (42), the third cantilever beam (43), and the fourth cantilever beam (44), and the corresponding resistance value of the piezoresistor (3) changes. The resistance value is then converted into a change in voltage value through a Wheatstone bridge, and finally output as an electrical signal. The change in the voltage signal is used to detect the change in hydrogen concentration.

[0009] In a preferred embodiment, when the deformation of the cantilever beam structure causes a change in the stress on the beam, the corresponding resistance value of the varistor (3) changes, and its output voltage is expressed as: Where V is the output voltage, V CCis the input voltage value, and the resistance values ​​of the silicon nanofilm varistors (3) on the beam are equal, that is, R1=R2=R3=R4; when the varistors (4) on the beam are subjected to the same stress, the resistance changes of the silicon nanofilm varistors (3) on the beam are equal, that is, ΔR1=ΔR2=ΔR3=ΔR4, and the formula is simplified to:

[0010] In a preferred embodiment, the central mass (2), the first cantilever beam (41), the second cantilever beam (42), the third cantilever beam (43), the fourth cantilever beam (44), the silicon nanofilm piezoresistor (3) and the frame are manufactured on a wafer using silicon micromachining technology combined with semiconductor technology.

[0011] In a preferred embodiment, the hydrogen-sensitive material deposited on the central mass (2) is a nanoporous palladium film.

[0012] In a preferred embodiment, the first cantilever beam (41), the second cantilever beam (42), the third cantilever beam (43), and the fourth cantilever beam (44) form a "Wan" beam structure, and stress concentration areas are designed at both ends of the cantilever beams, that is, the beam roots are locally thinned and narrowed.

[0013] In a preferred embodiment, the silicon nanofilm varistor (3) is a silicon nanofilm varistor, which is etched in the stress concentration area of ​​the cantilever beam.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] The present invention adopts a novel silicon nano-film structure piezoresistive resistor and increases the sensitivity of the sensor based on the giant piezoresistive effect.

[0016] The present invention improves the cantilever beam structure and adopts a "Wan"-shaped cantilever beam structure, so that the cantilever beam has a longer length within a limited space, reduces rigidity and increases sensitivity.

[0017] The present invention improves the cantilever beam structure, narrows and thins the root of each cantilever beam to provide a stress concentration area, and improves the sensitivity of the sensor.

[0018] The present invention adopts nanoporous palladium membrane as hydrogen-sensitive material, which has a faster response speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of a hydrogen sensor based on silicon nanofilm in a preferred embodiment of the present invention;

[0020] Figure 2 is a schematic top view of a hydrogen sensor based on a silicon nanofilm in an embodiment of the present invention;

[0021] Figure ID:

[0022] 1-hydrogen-sensitive material, 2-central mass block, 3-silicon nanofilm varistor, 41-first cantilever beam, 42-second cantilever beam, 43-third cantilever beam, 44-fourth cantilever beam, 5-metal lead, 6-frame. DETAILED DESCRIPTION

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0024] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present application belongs.

[0025] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application; as used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form, and it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or their combinations.

[0026] A hydrogen sensor based on silicon nanofilm, reference Figure 1-2 , comprising: a hydrogen-sensitive material 1, a central mass block 2, a silicon nanofilm varistor 3, a first cantilever beam 41, a second cantilever beam 42, a third cantilever beam 43, a fourth cantilever beam 44, a metal lead 5, and a frame 6; the hydrogen-sensitive material 1 is deposited on the central mass block 2, the central mass block 2 is located between the first cantilever beam 41, the second cantilever beam 42, the third cantilever beam 43, and the fourth cantilever beam 44, the first cantilever beam 41, the second cantilever beam 42, the third cantilever beam 43, and the fourth cantilever beam 44 are all provided with a silicon nanofilm varistor 3 on their arms, the first cantilever beam 41, the second cantilever beam 42, the third cantilever beam 43, and the fourth cantilever beam 44 are also all provided with a metal lead 5, the metal lead 5 connects the silicon nanofilm varistor 3 to form a Wheatstone bridge, and the frame 6 supports the four sides of the cantilever beam structure composed of the first cantilever beam 41, the second cantilever beam 42, the third cantilever beam 43, and the fourth cantilever beam 44.

[0027] The first cantilever beam 41 , the second cantilever beam 42 , the third cantilever beam 43 , and the fourth cantilever beam 44 are arranged in rotational symmetry.

[0028] The central mass block 2 and the first cantilever beam 41 , the second cantilever beam 42 , the third cantilever beam 43 and the fourth cantilever beam 44 form a “Wan” cantilever beam structure.

[0029] When the hydrogen sensor adsorbs hydrogen through the hydrogen-sensitive material 1, the mass of the central mass block 2 changes, causing the cantilever beam structure to bend. The deformation of the cantilever beam structure brings about changes in the stress of the first cantilever beam 41, the second cantilever beam 42, the third cantilever beam 43, and the fourth cantilever beam 44. The corresponding resistance value of the varistor 3 changes, which is then converted into a change in voltage value through a Wheatstone bridge circuit and finally output as an electrical signal. The change in the voltage signal is used to detect the change in hydrogen concentration.

[0030] When the deformation of the cantilever beam structure causes the stress on the beam to change, the resistance of the corresponding silicon nanofilm varistor (3) changes, and its output voltage is expressed as: Where V is the output voltage, V CC is the input voltage value, and the resistance of each piezoresistor 3 on the beam is equal, that is, R1=R2=R3=R4; when the piezoresistor 4 on the beam is subjected to the same stress, the resistance change of each piezoresistor 3 on the beam is equal, that is, ΔR1=ΔR2=ΔR3=ΔR4, and the formula is simplified to: For semiconductors, the piezoresistive effect is the application of stress to the surface of the semiconductor material. The stress will cause the material to deform, resulting in corresponding changes in the band structure, the mobility of carriers, and the resistivity and resistance value.

[0031] The resistance change rate can be expressed by the following formula: where π l is the piezoresistive coefficient, σ l The silicon nanofilm of the present invention has a giant piezoresistive effect, which can increase the piezoresistive coefficient of the varistor (3), and the higher the corresponding output voltage, the higher the sensitivity.

[0032] The central mass block 2 , the first cantilever beam 41 , the second cantilever beam 42 , the third cantilever beam 43 , the fourth cantilever beam 44 , the silicon nanofilm varistor 3 and the frame are manufactured on a wafer using silicon micromachining technology combined with semiconductor technology.

[0033] The hydrogen-sensitive material deposited on the central mass block 2 is a nanoporous palladium film, which is plated on the silicon central mass block 2 using a DC magnetron sputtering method. The palladium film with a nanoporous structure can improve the response speed of the hydrogen sensor.

[0034] The first, second, third, and fourth cantilever beams 41, 42, 43, and 44 form a swastika beam structure. Stress concentration areas are designed at both ends of the cantilever beams, where the beam roots are locally thinned and narrowed. Silicon nanofilm varistor 3 is placed in these stress concentration areas to improve sensor sensitivity. The swastika beam structure allows the cantilever beams to extend in a limited space, reducing stiffness and increasing sensor sensitivity.

[0035] The silicon nanofilm varistor 3 is etched in the stress concentration area of ​​the cantilever beam.

[0036] Finally, it should be noted that the above examples are merely illustrative and should not be construed as limiting the specific embodiments. Those skilled in the art will readily appreciate that other variations or adjustments may be made based on the above description, but any such obvious variations or adjustments remain within the scope of the present invention.

Claims

1. A hydrogen sensor based on silicon nanofilm, characterized in that include: A hydrogen-sensitive material (1), a central mass block (2), a silicon nanofilm varistor (3), a first cantilever beam (41), a second cantilever beam (42), a third cantilever beam (43), a fourth cantilever beam (44), a metal lead (5), and a frame (6); the hydrogen-sensitive material (1) is deposited on the central mass block (2); the central mass block (2) is located between the first cantilever beam (41), the second cantilever beam (42), the third cantilever beam (43), and the fourth cantilever beam (44); the first cantilever beam (41), the second cantilever beam (42), the third cantilever beam (43), and the fourth cantilever beam (44); The first cantilever beam (41), the second cantilever beam (42), the third cantilever beam (43), and the fourth cantilever beam (44) are all provided with silicon nanofilm piezoresistors (3); the first cantilever beam (41), the second cantilever beam (42), the third cantilever beam (43), and the fourth cantilever beam (44) are also provided with metal leads (5); the metal leads (5) connect the silicon nanofilm piezoresistors (3) to form a Wheatstone bridge; the frame (6) supports the four sides of the cantilever beam structure composed of the first cantilever beam (41), the second cantilever beam (42), the third cantilever beam (43), and the fourth cantilever beam (44); The central mass block (2) forms a "ten thousand" cantilever beam structure with the first cantilever beam (41), the second cantilever beam (42), the third cantilever beam (43), and the fourth cantilever beam (44); When the hydrogen sensor absorbs hydrogen through the hydrogen-sensitive material (1), the mass of the central mass block (2) changes, driving the cantilever beam structure to bend. The deformation of the cantilever beam structure causes a change in the stress of the first cantilever beam (41), the second cantilever beam (42), the third cantilever beam (43), and the fourth cantilever beam (44). The corresponding resistance value of the silicon nanofilm varistor (3) changes, which is then converted into a change in voltage value through a Wheatstone bridge and finally output as an electrical signal. The change in the voltage signal is used to detect the change in hydrogen concentration. When the deformation of the cantilever beam structure causes the stress on the beam to change, the resistance of the corresponding silicon nanofilm varistor (3) changes, and its output voltage is expressed as: ;in, is the output voltage, is the input voltage value, and the resistance of each silicon nanofilm varistor (3) on the beam is equal, that is, When the silicon nanofilm piezoresistors (3) on the beam are subjected to the same stress, the resistance changes of the silicon nanofilm piezoresistors (3) on the beam are equal, that is, , the formula is simplified to: ; The first cantilever beam (41), the second cantilever beam (42), the third cantilever beam (43), and the fourth cantilever beam (44) form a "Wan" beam structure, and stress concentration areas are designed at both ends of the cantilever beams, that is, the beam roots are locally thinned and narrowed.

2. A hydrogen sensor based on silicon nanofilm according to claim 1, characterized in that: The first cantilever beam (41), the second cantilever beam (42), the third cantilever beam (43), and the fourth cantilever beam (44) are arranged in rotational symmetry.

3. The hydrogen sensor based on silicon nanofilm according to claim 1, characterized in that: The central mass block (2), the first cantilever beam (41), the second cantilever beam (42), the third cantilever beam (43), the fourth cantilever beam (44), the silicon nanofilm piezoresistor (3) and the frame are manufactured on a wafer using silicon micromachining technology combined with semiconductor technology.

4. The hydrogen sensor based on silicon nanofilm according to claim 1, characterized in that: The hydrogen-sensitive material deposited on the central mass block (2) is a nanoporous palladium film.

5. The hydrogen sensor based on silicon nanofilm according to claim 1, characterized in that: A silicon nanofilm varistor (3) is etched in the stress concentration area of ​​the cantilever beam.

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