Hydrogen sensor based on silicon nano film

Abstract

The invention discloses a hydrogen sensor based on a silicon nano-film. The hydrogen sensor comprises a hydrogen sensitive material, a central mass block, a silicon nano-film piezoresistor, cantilever beams, a metal lead and a frame, the hydrogen-sensitive material is deposited on the central mass block, the central mass block is located in the middle of the four cantilever beams, the central mass block and the four cantilever beams form a cantilever beam structure shaped like a Chinese character'wan ', each beam arm of the four cantilever beams is provided with a silicon nano-film piezoresistor, each cantilever beam is further provided with a metal lead, and the metal lead is connected with the central mass block. The metal lead is connected with the piezoresistor to form a Wheatstone bridge, and the frame supports the periphery of the cantilever beam structure shaped like the Chinese character'wan '. According to the hydrogen sensor based on the silicon nano-film, a nano-porous palladium film is adopted as a hydrogen sensitive material, a silicon nano-film piezoresistor is adopted as a piezoresistor, local narrow thinning is performed on a cantilever beam, and the sensitivity and the response speed of the sensor are improved by utilizing the hydrogen sensitive material-a cantilever beam structure shaped like a Chinese character'wan 'and a silicon nano-film sensitive unit.

Description

Technical Field

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

[0003] There are potential risks of leakage, combustion and explosion in the preparation, storage, transportation, filling and use of hydrogen. Therefore, achieving rapid concentration detection of hydrogen has always been an urgent problem to be solved in the application of hydrogen energy and large-scale commercial promotion.

[0004] With the rise of micro-electromechanical system (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 easy integration. MEMS technology covers a wide range and has been widely used in various fields such as medical, aviation, automobile, microelectronics, mechanical manufacturing and communication. Hydrogen sensors can be divided into catalytic, electrochemical, semiconductor, optical fiber, acoustic, etc. according to the principle. Each has its own advantages and disadvantages. Piezoresistive hydrogen sensors are made based on the piezoresistive effect. When the hydrogen-sensitive film adsorbs hydrogen, the mass changes. The mass change causes the cantilever beam to bend, changing the resistance value of the varistor. 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, but it 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

[0005] In view of this, an object of the present invention is to provide a hydrogen sensor based on silicon nanofilm to solve the problem that the response time of hydrogen sensors in the prior art is not short enough and the sensitivity is not ideal enough.

[0006] To achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a hydrogen sensor based on silicon nanofilm, 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 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 varistors (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 varistors (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).

[0007] 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.

[0008] 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 "ten thousand" cantilever beam structure.

[0009] In a preferred embodiment, 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 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.

[0010] 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, 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:

[0011] In a preferred embodiment, 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.

[0012] In a preferred embodiment, the hydrogen-sensitive material deposited on the central mass block (2) is a nanoporous palladium film.

[0013] 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, local thinning and local narrowing treatment is performed at the root of the beam.

[0014] 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.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] The invention adopts a novel silicon nano-film structure varistor to increase the sensitivity of the sensor based on the giant piezoresistive effect.

[0017] The present invention improves the cantilever beam structure and uses a "Wan"-shaped cantilever beam structure, so that the cantilever beam has a longer length within a limited space, reduces rigidity and increases sensitivity.

[0018] The present invention improves the cantilever beam structure, narrows and thins the root of each cantilever beam so that it has a stress concentration area, thereby improving the sensitivity of the sensor.

[0019] The present invention adopts nanoporous palladium membrane as hydrogen-sensitive material, which has a faster response speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a schematic diagram of a hydrogen sensor based on silicon nanofilm in a preferred embodiment of the present invention;

[0021] Figure 2 is a schematic top view of a hydrogen sensor based on a silicon nanofilm in an embodiment of the present invention;

[0022] Figure ID:

[0023] 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

[0024] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0025] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0026] 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. In addition, 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.

[0027] 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 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 a silicon nanofilm varistor 3 on their beam arms, 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 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.

[0028] 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.

[0029] 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 “ten thousand” cantilever beam structure.

[0030] 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 and finally output as an electrical signal. The change in hydrogen concentration is detected by the change in the voltage signal.

[0031] 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, the resistance of each varistor 3 on the beam is equal, that is, R1=R2=R3=R4; when the varistor 4 on the beam is subjected to the same stress, the resistance change of each varistor 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 energy band structure, the mobility of carriers, and the resistivity and resistance values.

[0032] 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.

[0033] 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.

[0034] The hydrogen-sensitive material deposited on the central mass block 2 is a nanoporous palladium film, and is plated on the silicon central mass block 2 by a DC magnetron sputtering method. The palladium film with a nanoporous structure can improve the response speed of the hydrogen sensor.

[0035] 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 beam, that is, the root of the beam is locally thinned and locally narrowed, and the silicon nanofilm varistor 3 is arranged in the stress concentration area to improve the sensitivity of the sensor. The "Wan" cantilever beam structure allows the cantilever beam to have a longer length within a limited space, reduces stiffness, and increases sensor sensitivity.

[0036] The silicon nanofilm varistor 3 is etched in the stress concentration area of ​​the cantilever beam.

[0037] Finally, it should be noted that the above examples are only examples for clear explanation and should not be regarded as limiting the specific implementation methods. For ordinary technicians in this field, other forms of changes or adjustments can be made based on the above description, but any obvious changes or adjustments are still within the scope of protection 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 varistors (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 varistors (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).

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) and the first cantilever beam (41), the second cantilever beam (42), the third cantilever beam (43) and the fourth cantilever beam (44) form a "ten thousand" cantilever beam structure.

4. The hydrogen sensor based on silicon nanofilm according to claim 3, characterized in that: 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.

5. The hydrogen sensor based on silicon nanofilm according to claim 4, characterized in that: When the deformation of the cantilever beam structure causes the stress on the beam to change, the corresponding resistance of the 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, the resistance of each silicon nanofilm varistor (3) on the beam is equal, that is, R1=R2=R3=R4; when the silicon nanofilm varistor (3) on the beam is subjected to the same stress, the resistance change of each silicon nanofilm varistor (3) on the beam is equal, that is, ΔR1=ΔR2=ΔR3=ΔR4, and the formula is simplified to:

6. 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 varistor (3) and the frame are manufactured on a wafer using silicon micromachining technology combined with semiconductor technology.

7. 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.

8. The 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) form a "ten thousand" beam structure, and stress concentration areas are designed at both ends of the cantilever beams, that is, local thinning and local narrowing treatment is performed at the beam roots.

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

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