CN117723780A - Acceleration sensor based on graphene suspension mass block and preparation method thereof - Google Patents
Acceleration sensor based on graphene suspension mass block and preparation method thereof Download PDFInfo
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Abstract
The invention discloses an acceleration sensor based on a graphene suspension mass block, and the sensing mechanism of the acceleration sensor comprises a capacitance type sensor and a transconductance type sensor. The capacitive acceleration sensor structure comprises a graphene film layer serving as an upper polar plate of a capacitor, a deposited Ti/Au electrode layer and Si/SiO 2 Mass block, siO 2 An insulating layer, an intermediate bonding layer, and a highly conductive Si substrate layer as a lower plate of the capacitor. The transconductance acceleration sensor structure comprises a graphene film layer, a drain electrode layer, a source electrode layer and Si/SiO 2 Mass block, siO 2 An insulating layer, an intermediate bonding layer, and a highly conductive Si substrate layer as a gate electrode. The invention also discloses a preparation method of the acceleration sensor based on the graphene suspension mass block. The capacitive and transconductance acceleration sensor disclosed by the invention has higher sensitivity, better resolution and higher precision, is less influenced by temperature, and has the characteristics of devicesCan be greatly improved.
Description
Technical Field
The invention belongs to the field of micro-nano sensor manufacturing, and particularly relates to an acceleration sensor of a graphene suspended mass block and a preparation method thereof.
Background
Acceleration sensors have been an important tool in the scientific and industrial fields for the past few decades. The NEMS acceleration sensor has the advantages of small volume, low cost, low power consumption, good stability and the like, is widely applied to the testing of acceleration, vibration, impact, inclination angle and the like in the fields of military, medical treatment, automobile and industrial control, and is a core component of a miniaturized inertial measurement unit. Silicon-based acceleration sensors have been widely manufactured and used in recent decades, however, existing acceleration sensors still have some technical difficulties, such as large volume, low sensitivity, and insufficient signal-to-noise ratio. Accordingly, researchers have been seeking new materials and techniques to improve the performance of acceleration sensors.
In recent years, graphene has attracted a great deal of attention as an emerging material. Graphene has a plurality of unique properties such as high conductivity, high scalability, ultrathin structure and the like, becomes an ideal material applied to micro-nano electromechanical sensors, and has been subjected to concept verification in the fields of nano electromechanical resonators, pressure sensors and other devices. Aiming at the difficult problem that the miniaturization and high performance of the current acceleration sensor are difficult to be compatible, the prototype device of the miniature and high-sensitivity piezoresistive nano electromechanical acceleration sensor based on the graphene film is subjected to conceptual verification by utilizing the excellent and unique mechanical and electrical characteristics of the graphene. In the acceleration sensor based on graphene, the graphene film is used as a sensitive structure film of the sensor, and due to the piezoresistive effect of the graphene, the graphene film generates a variable resistance when stressed, and researchers can measure the acceleration by utilizing the change of the resistance. In addition, the preparation and integration techniques of graphene have also been greatly advanced, such as mechanical exfoliation, chemical vapor deposition, and the like. These techniques provide process support for the fabrication of graphene-based acceleration sensors.
The graphene film is adopted as a sensitive structure of the acceleration sensor, and an advanced micro-nano preparation technology is utilized, so that the size of the sensitive structure of the sensor can be obviously reduced, and the performance of the acceleration sensor is improved. It has the advantages of high sensitivity, quick response speed, wide working temperature range, high resolution for small acceleration change, etc. NEMS acceleration sensor can be divided into capacitive type, piezoresistive type, resonant type, transconductance type and other types according to different detection principles, and has the advantages of low cost, high sensitivity, low cost and high sensitivityThe medium capacitance detection and the transconductance detection have higher sensitivity, precision and resolution, and have important research value in the application of the acceleration sensor. In the prior fabrication of NEMS acceleration sensors based on graphene suspended masses, silicon-on-insulator (SOI) materials were used, which required first etching of trenches to form the mass. Then inverting the SOI to realize back etching, and leaving a layer of SiO after back Si substrate layer etching 2 The layer supports the mass. And then carrying out graphene transfer and patterning etching to integrate the graphene with the prefabricated SOI substrate. To release the mass on the suspended graphene film, reactive ion beam etching (RIE) is used to remove most of the SiO 2 Sacrificial layer is etched by gas phase HF to remove residual SiO 2 And finally realizing release of the mass block to obtain the graphene suspension mass block sensitive structure. However, the piezoresistive graphene acceleration sensor still has the problems of insufficient detection resolution, limited precision, relatively low device yield and the like.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, and provides an acceleration sensor based on a graphene suspended mass block and a preparation method thereof, wherein the sensing mechanism of the acceleration sensor is capacitive and transconductance type, and the performances of the acceleration sensor such as sensitivity, resolution, precision and the like are further improved, and the yield of the device is further improved.
The invention is realized by the following technical scheme: the structure of the acceleration sensor comprises a graphene film layer, an electrode layer, a Si/SiO2 mass block, a SiO2 insulating layer, an intermediate bonding layer and a high-conductivity Si substrate layer which are sequentially arranged from top to bottom. The acceleration sensor comprises two acceleration sensor structures, wherein one acceleration sensor is a capacitive graphene suspension mass acceleration sensor, and the other acceleration sensor is a transconductance graphene suspension mass acceleration sensor. The capacitive acceleration sensor structure comprises a graphene film layer serving as an upper polar plate of a capacitor, a deposited Ti/Au electrode layer and Si/SiO 2 Mass block, siO 2 Insulating layer, intermediate bonding layer and processA highly conductive Si substrate layer that is the bottom plate of the capacitor. The transconductance acceleration sensor structure comprises a graphene film layer, a drain electrode layer, a source electrode layer and Si/SiO 2 Mass block, siO 2 An insulating layer, an intermediate bonding layer, and a highly conductive Si substrate layer as a gate electrode.
For the capacitive acceleration sensor, the graphene film layer is used as an upper polar plate of the capacitor, the high-conductivity Si substrate layer is used as a lower polar plate of the capacitor, when the acceleration sensor moves, the graphene film can deviate up and down, so that the capacitance between the upper polar plate and the lower polar plate is changed, and the current acceleration can be calculated by detecting the change of the capacitance.
For the transconductance type acceleration sensor, the basic principle is that a graphene film is used as a transconductance layer, when the acceleration sensor moves, the suspended graphene film can deviate up and down, so that the distance between the graphene film and a gate electrode at the bottom of the graphene film is changed, the charge concentration in the graphene layer is changed, the current of the graphene film is changed, and the acceleration of the sensor can be calculated by detecting the current of the graphene film. The acceleration sensor has the advantages of high sensitivity, quick response, low power consumption and the like.
The suspended graphene film is a graphene film (0-200 nm) which is single-atomic layer, double-atomic layer, three-atomic layer, four-atomic layer, five-atomic layer, six-atomic layer, seven-atomic layer, eight-atomic layer, nine-atomic layer, ten-atomic layer and thicker. The suspended graphene film also comprises a heterogeneous layer of graphene and other two-dimensional films, including graphene/molybdenum disulfide (MoS 2 ) Graphene/tungsten disulfide (WS) 2 ) Graphene/molybdenum diselenide (MoSe) 2 ) Graphene/tungsten diselenide (WSe) 2 ) Graphene/platinum diselenide (PtSe) 2 ) Graphene/molybdenum ditelluride (MoTe) 2 ) Graphene/tungsten ditelluride (WTe) 2 ) Graphene/vanadium diselenide (VSe) 2 ) Graphene/chromium disulfide (CrS) 2 ) Graphene/chromium diselenide (CrSe) 2 ) Graphene/other transition metal sulfurChemical compound (TMDC), graphene/black phosphorus (P), graphene/MXene, graphene/hexagonal boron nitride (h-BN). The suspended graphene film also comprises the composite of graphene and other nano thin layers, including the composite of graphene and metals (such as gold, silver, copper and aluminum), metal oxides (such as aluminum oxide), organic polymers (such as Polydimethylsiloxane (PDMS), polymethyl methacrylate (PMMA) and poly (bisphenol A) carbonate (PC)). Sources of graphene include chemical vapor deposition synthesis, mechanical exfoliation, liquid phase exfoliation, epitaxial growth, and reduction oxidation.
The preparation method of the acceleration sensor based on the graphene suspension mass block comprises the following steps:
(1) Step 1:
and cleaning the silicon wafer, and putting the silicon wafer into a cleaning solution with a certain concentration for cleaning so as to remove impurities and pollutants on the surface.
(2) Step 2:
and (3) performing heat treatment, namely placing the cleaned silicon wafer into a heat treatment furnace, performing heat treatment at high temperature and in a specific environment, taking out the silicon wafer after the heat treatment is finished, and cooling with distilled water. This step helps to remove the oxide layer from the surface.
(3) Step 3:
and (3) performing thermal oxidation, placing the silicon wafer into a heat treatment furnace, and introducing oxygen or mixed gas of oxygen and steam into a furnace chamber to react the surface of the silicon with the oxygen so as to form a silicon dioxide film.
(4) Step 4:
the silicon dioxide is etched, a photoresist is coated first, a layer of photoresist is spin coated on the surface of the silicon substrate, and then Ultraviolet (UV) exposure is used to map the pattern on the photoresist. The photoresist is developed and the exposed portions are dissolved in a developer. And then etching, namely placing the silicon wafer into an etching groove, etching by using proper etching solution (hydrofluoric acid), and controlling etching time and solution concentration at the same time so as to achieve the required etching thickness. The photoresist is then removed.
(5) Step 5:
and (3) preparing an electrode, namely placing the cleaned substrate into a vacuum coating machine, and selecting targets of evaporating materials titanium (Ti) and gold (Au). And setting parameters such as vacuum degree, evaporation power and the like according to the required film thickness. Through vacuum coating, a Ti film is deposited on the surface of the substrate, and then an Au film is deposited. And after evaporation, cooling the substrate to normal temperature, and taking the substrate out of the vacuum coating machine to obtain the Ti/Au electrode.
(6) Step 6:
after the electrode is prepared, back etching is needed, photoresist is spun on the back, ultraviolet exposure is then needed, and development is performed. The silicon dioxide layer is then etched by RIE (reactive ion etching) process, the Si is then etched by Deep Reactive Ion Etching (DRIE) process, and finally the photoresist residue is removed by oxygen plasma etching.
(7) Step 7:
and the next step is to carry out the process flow of the second silicon substrate, so as to prepare the silicon substrate.
(8) Step 8:
then forming a through hole cavity by etching the Si substrate, firstly patterning through a mask, spin-coating photoresist, printing the pattern on the photoresist by ultraviolet exposure, and developing the photoresist, wherein the exposed part is dissolved in a developer. The Si substrate is then subjected to Deep Reactive Ion Etching (DRIE) and the photoresist residue is removed by oxygen plasma etching.
(9) Step 9:
bonding the two processed silicon substrates, and coating a bonding adhesive on the silicon substrates to be bonded, wherein the bonding adhesive can be an adhesive or other adhesives suitable for silicon-based materials. The two silicon substrates are aligned so that their surfaces are in intimate contact. And the two silicon substrates are pressed together by using a pressure method or a hot pressing method, so that the uniform pressing force is ensured, and the bonding quality is ensured.
(10) Step 10:
next, graphene transfer is performed by first preparing graphene grown on a copper foil, spin-coating a polymethyl methacrylate (PMMA) solutionSpin-coating on graphene at 500 rpm for 5 seconds followed by 1800 rpm for 30 seconds, then baking on a 85 ℃ hotplate for 5 minutes (about 200nm thick for solvent evaporation and PMMA curing), then placing copper foil on ferric chloride (FeCl) 3 ) In solution to effect etching of copper. After etching, the copper-free PMMA/graphene layer is transferred to the deionized water (DI) surface with the aid of a silicon wafer, and then transferred to a dilute HCI solution (to remove residual Fe) 3+ ) Finally, returning to deionized water for cleaning, and respectively removing FeCl 3 Residual and chloride ion residual. The PMMA/graphene layer was then transferred onto a silicon substrate and the silicon substrate was baked on a heated platen for 10 minutes (45℃.) to dry and improve the graphene film and SiO 2 Adhesion between surfaces. Then placed in acetone for 24 hours to remove PMMA, and finally placed in isopropanol for 5 minutes to remove acetone residues.
(11) Step 11:
and after the graphene is transferred, carrying out patterning etching on the graphene. And (3) spin coating a photoresist layer, exposing and developing, and finally performing RIE etching on the graphene.
(12) Step 12:
in order to etch the silicon dioxide layer of the first silicon substrate, gas phase HF is needed to etch to realize self-suspension of the graphene film, and because gas phase HF is used to etch to enable gas to reach the silicon dioxide layer below the graphene film, a through hole cavity is formed when the second silicon substrate is manufactured, so that gas can pass through the through hole to etch silicon dioxide above.
Compared with the prior acceleration sensor, the capacitive and transconductance acceleration sensor has the following advantages:
firstly, the invention uses two silicon substrates to process (one is the substrate for forming the mass block and the other is the substrate for forming the through hole by etching), and the mass block is suspended by bonding the two silicon substrates.
Secondly, the process adopted by the invention is to transfer the graphene film onto a flat silicon dioxide substrate, and then etch the silicon dioxide layer by using gas phase HF, so that the self-suspension of the graphene film is realized, and meanwhile, the high-quality suspended graphene film is obtained. Compared with the traditional method for directly transferring graphene onto the cavity, the method can avoid the problems of wrinkling, folding, local fracture and the like of the graphene film to a great extent, thereby greatly improving the yield and performance of the device.
Thirdly, the acceleration sensor adopts two structures of a capacitive structure and a transconductance structure, so that the acceleration sensor has higher sensitivity, better resolution and higher precision and is less affected by temperature. The capacitive acceleration sensor measures acceleration based on a change in capacitance value, and the transconductance acceleration sensor measures acceleration based on a change in current output. Compared with a resistance type acceleration sensor, the structure can detect acceleration change more rapidly and accurately, so that sensitivity, resolution and accuracy are improved greatly.
Fourth, the acceleration sensor of the present invention can be better applied to more fields such as electronic equipment, medical treatment, automobiles, aerospace, etc. due to higher sensitivity, resolution, precision, etc.
Drawings
Fig. 1 is a process cross-sectional view of a transconductance graphene suspended mass acceleration sensor.
Fig. 2 is a process cross-sectional view of a capacitive graphene suspended mass acceleration sensor.
Fig. 3 is a three-dimensional structure diagram of a transconductance-type graphene suspended mass acceleration sensor.
Fig. 4 is a three-dimensional structural diagram of a capacitive graphene suspended mass acceleration sensor.
Detailed Description
The invention is further explained below with reference to the drawings:
the preparation method of the graphene suspension mass acceleration sensor comprises the following steps:
(1) Step 1:
and cleaning the silicon wafer, and putting the silicon wafer into a cleaning solution with a certain concentration for cleaning so as to remove impurities and pollutants on the surface.
(2) Step 2:
and (3) performing heat treatment, namely placing the cleaned silicon wafer into a heat treatment furnace, performing heat treatment at high temperature and in a specific environment, taking out the silicon wafer after the heat treatment is finished, and cooling with distilled water. This step helps to remove the oxide layer from the surface.
(3) Step 3:
and (3) performing thermal oxidation, placing the silicon wafer into a heat treatment furnace, and introducing oxygen or mixed gas of oxygen and steam into a furnace chamber to react the surface of the silicon with the oxygen, so as to form a silicon dioxide film with the thickness of 1.4 mu m.
(4) Step 4:
the silicon dioxide is etched to a depth of 15 μm, photoresist coating is performed first, a layer of photoresist is spin-coated on the surface of the silicon substrate, and then Ultraviolet (UV) exposure is used to map the pattern on the photoresist. The photoresist is developed and the exposed portions are dissolved in a developer. And then etching, namely placing the silicon wafer into an etching groove, etching by using proper etching solution (hydrofluoric acid), and controlling etching time and solution concentration at the same time so as to achieve the required etching thickness. The photoresist is then removed.
(5) Step 5:
the preparation of the electrodes (the size of the deposited electrode is 10 μm by 3 μm) is carried out, the cleaned substrate is put into a vacuum coating machine, and targets of evaporating materials titanium (Ti) and gold (Au) are selected. And setting parameters such as vacuum degree, evaporation power and the like according to the required film thickness. Through vacuum coating, a Ti film is deposited on the surface of the substrate, and then an Au film is deposited. After evaporation, the substrate is cooled to normal temperature and can be taken out from the vacuum coating machine, so that a Ti/Au electrode layer is formed.
(6) Step 6:
after the electrode is prepared, back etching is needed, photoresist is spun on the back, ultraviolet exposure is then needed, and development is performed. Silicon dioxide layer (15 μm thick) is then etched by RIE (reactive ion etching) process, si is then etched by Deep Reactive Ion Etching (DRIE) process, and finally photoresist residues are removed by oxygen plasma etching.
(7) Step 7:
and next, carrying out a second silicon substrate process flow, and preparing a second silicon substrate.
(8) Step 8:
then forming a through hole cavity by etching the Si substrate, specifically, firstly patterning through a mask, then spin-coating photoresist, printing the pattern on the photoresist by ultraviolet exposure, developing the photoresist, and dissolving the exposed part in a developer. Thereafter, the Si substrate was subjected to DRIE etching (etching depth: 15 μm), and the photoresist residue was removed by oxygen plasma etching.
(9) Step 9:
bonding the two processed silicon substrates, and coating a bonding adhesive on the silicon substrates to be bonded, wherein the bonding adhesive can be an adhesive or other adhesives suitable for silicon-based materials. The two silicon substrates are aligned so that their surfaces are in intimate contact. And the two silicon substrates are pressed together by using a pressure method or a hot pressing method, so that the uniform pressing force is ensured, and the bonding quality is ensured.
(10) Step 10:
following transfer of graphene, graphene grown on a copper foil was first prepared, polymethyl methacrylate (PMMA) solution was spin coated on graphene, spin coated at 500 rpm for 5 seconds, followed by 1800 rpm for 30 seconds, then baked on a hot plate at 85 ℃ for 5 minutes (about 200nm thick for solvent evaporation and PMMA curing), and then the copper foil was placed on iron trichloride (FeCl 3 ) In solution to effect etching of copper. After etching, the copper-free PMMA/graphene layer is transferred to the deionized water (DI) surface with the aid of a silicon wafer, and then transferred to a dilute HCI solution (to remove residual Fe) 3+ ) Finally return toCleaning in deionized water to remove FeCl respectively 3 Residual and chloride ion residual. The PMMA/graphene layer was then transferred onto a silicon substrate and the silicon substrate was baked on a heated platen for 10 minutes (45℃.) to dry and improve the graphene film and SiO 2 Adhesion between surfaces. Then placed in acetone for 24 hours to remove PMMA, and finally placed in isopropanol for 5 minutes to remove acetone residues.
(11) Step 11:
and after the graphene is transferred, carrying out patterning etching on the graphene. And (3) spin coating a photoresist layer, exposing and developing, and finally etching the graphene by RIE (reactive ion).
(12) Step 12:
in order to etch the silicon dioxide layer of the first silicon substrate, gas phase HF is needed to etch to realize self-suspension of the graphene film, and because gas phase HF is used to etch to enable gas to reach the silicon dioxide layer below the graphene film, a through hole cavity is formed when the second silicon substrate is manufactured, so that gas can pass through the through hole to etch silicon dioxide above.
The structure of the acceleration sensor prepared by the method comprises a graphene film layer, an electrode layer, a Si/SiO2 mass block, a SiO2 insulating layer, an intermediate bonding layer and a high-conductivity Si substrate layer which are sequentially arranged from top to bottom.
The acceleration sensor comprises two structures, wherein one structure is a capacitive graphene suspension mass acceleration sensor, and the other structure is a transconductance type graphene suspension mass acceleration sensor. The capacitive acceleration sensor structure comprises a graphene film layer serving as an upper polar plate of a capacitor, a deposited Ti/Au electrode layer and Si/SiO 2 Mass block, siO 2 An insulating layer, an intermediate bonding layer, and a highly conductive Si substrate layer as a bottom plate of the capacitor. The transconductance acceleration sensor structure comprises a graphene film layer, a drain electrode layer, a source electrode layer and Si/SiO 2 Mass block, siO 2 An insulating layer, an intermediate bonding layer, and a highly conductive Si substrate layer as a gate electrode.
For the capacitive acceleration sensor, the graphene film layer is used as an upper polar plate of the capacitor, the high-conductivity Si substrate layer is used as a lower polar plate of the capacitor, when the acceleration sensor moves, the graphene film can deviate up and down, so that the capacitance between the upper polar plate and the lower polar plate is changed, and the current acceleration can be calculated by detecting the change of the capacitance.
For the transconductance type acceleration sensor, the basic principle is that a graphene film is used as a transconductance layer, when the acceleration sensor moves, the suspended graphene film can deviate up and down, so that the distance between the graphene film and a gate electrode at the bottom of the graphene film is changed, the charge concentration in the graphene layer is changed, the current of the graphene film is changed, and the acceleration of the sensor can be calculated by detecting the current of the graphene film. The acceleration sensor has the advantages of high sensitivity, quick response, low power consumption and the like.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.
Claims (8)
1. A preparation method of an acceleration sensor based on a graphene suspension mass block is characterized by comprising the following steps of: the method is realized by adopting the following processes:
step 1:
firstly, preparing a first silicon substrate, cleaning a silicon wafer, and putting the silicon wafer into a cleaning solution with a certain concentration for cleaning so as to remove impurities and pollutants on the surface;
step 2:
carrying out heat treatment, namely placing the cleaned silicon wafer into a heat treatment furnace, carrying out heat treatment in a high-temperature environment, taking out the silicon wafer after the heat treatment is finished, and cooling with distilled water;
step 3:
performing thermal oxidation, putting a silicon wafer into a heat treatment furnace, and introducing oxygen or mixed gas of oxygen and steam into a furnace chamber to react the surface of the silicon with the oxygen so as to form a silicon dioxide film;
step 4:
etching silicon dioxide, firstly coating photoresist, spin-coating a layer of photoresist on the surface of a silicon substrate, and then exposing by Ultraviolet (UV) light to map a pattern on the photoresist; developing the photoresist, the exposed portions being dissolved in a developer; then etching, namely placing the silicon wafer into an etching groove, etching by using proper etching solution (hydrofluoric acid), and controlling etching time and solution concentration at the same time so as to achieve the required etching thickness; then removing the photoresist;
step 5:
preparing an electrode, namely placing the cleaned substrate into a vacuum coating machine, and selecting target materials of evaporating materials titanium (Ti) and gold (Au); setting parameters such as vacuum degree, evaporation power and the like according to the required film thickness; depositing a Ti film on the surface of a substrate through vacuum coating, and then depositing an Au film; after evaporation, cooling the substrate to normal temperature, and taking the substrate out of the vacuum coating machine to obtain a Ti/Au electrode;
step 6:
after the electrode is prepared, back etching is needed, photoresist is spun on the back, ultraviolet exposure is then carried out, and development is carried out; etching the silicon dioxide layer by using an RIE (reactive ion etching) process, etching Si by using a Deep Reactive Ion Etching (DRIE) process, and finally removing photoresist residues by using an oxygen plasma etching process;
step 7:
performing a second silicon substrate process flow to prepare a silicon substrate;
step 8:
forming a through hole cavity by etching the Si substrate, firstly patterning through a mask, spin-coating photoresist, printing the pattern on the photoresist by using ultraviolet exposure, and developing the photoresist, wherein the exposed part is dissolved in a developer; then, deep Reactive Ion Etching (DRIE) is carried out on the Si substrate, and oxygen plasma etching is used for removing photoresist residues;
step 9:
bonding the two processed silicon substrates, coating a layer of bonding adhesive on the silicon substrates to be bonded, aligning the two silicon substrates to enable the surfaces of the two silicon substrates to be in close contact, pressurizing the two silicon substrates together by using a pressure method or a hot pressing method, and ensuring uniform pressurizing force;
step 10:
transferring graphene, preparing graphene grown on a copper foil, spin-coating a polymethyl methacrylate (PMMA) solution on the graphene, spin-coating at a speed of 500 rpm for about 5 seconds, spin-coating at a speed of 1800 rpm for about 30 seconds, baking on a hot plate at about 85 ℃ for about 5 minutes, evaporating the solvent, solidifying the PMMA, and placing the copper foil on ferric trichloride (FeCl) 3 ) In solution; transferring the PMMA/graphene layer without copper to the surface of deionized water (DI) with the assistance of a silicon wafer after etching, transferring the PMMA/graphene layer into a diluted HCI solution, and finally returning to the deionized water for cleaning; then transferring PMMA/graphene layer onto silicon substrate, baking the silicon substrate on heating table for about 10 min to 45 deg.C, drying, and improving graphene film and SiO 2 Adhesion between surfaces; then placed in acetone for 24 hours to remove PMMA, and finally placed in isopropanol for 5 minutes to remove acetone residues;
step 11:
after transferring the graphene, carrying out patterning etching on the graphene, also spin-coating a layer of photoresist, carrying out exposure development, and finally carrying out RIE etching on the graphene;
in the above steps, when the silicon dioxide layer of the first silicon substrate is etched, gas phase HF is adopted for etching, and the second silicon substrate is a through hole cavity.
2. Acceleration sensor based on graphite alkene suspended mass piece, its characterized in that: the structure of the acceleration sensor comprises a graphene film layer, an electrode layer, a Si/SiO2 mass block, a SiO2 insulating layer, an intermediate bonding layer and a high-conductivity Si substrate layer which are sequentially arranged from top to bottom.
3. An acceleration sensor based on a graphene suspension mass according to claim 2, characterized in that: the electrode layer is divided into a drain electrode layer and a source electrode layer, and the high-conductivity Si substrate layer is used as a gate electrode to form the transconductance acceleration sensor.
4. An acceleration sensor based on a graphene suspension mass according to claim 2, characterized in that: the electrode layer is a deposited Ti/Au electrode layer, wherein the graphene film layer is used as an upper electrode plate of the capacitor, and the high-conductivity Si substrate layer is used as a lower electrode plate of the capacitor to form the capacitive acceleration sensor.
5. An acceleration sensor based on a graphene suspension mass according to claim 2, characterized in that: the suspended graphene film is a single atomic layer, a double atomic layer, three atomic layers, four atomic layers, five atomic layers, six atomic layers, seven atomic layers, eight atomic layers, nine atomic layers, ten atomic layers and thicker graphene film (0-200 nm); the suspended graphene film also comprises a heterogeneous layer of graphene and other two-dimensional films, including graphene/molybdenum disulfide (MoS 2 ) Graphene/tungsten disulfide (WS) 2 ) Graphene/molybdenum diselenide (MoSe) 2 ) Graphene/tungsten diselenide (WSe) 2 ) Graphene/platinum diselenide (PtSe) 2 ) Graphene/molybdenum ditelluride (MoTe) 2 ) Graphene/tungsten ditelluride (WTe) 2 ) Graphene/vanadium diselenide (VSe) 2 ) Graphene/chromium disulfide (CrS) 2 ) Graphene/chromium diselenide (CrSe) 2 ) Graphene/other transition metal sulfides (TMDC), graphene/black phosphorus (P), graphene/MXene, graphene/hexagonal boron nitride (h-BN); the suspended graphene film also comprises the composite of graphene and other nano thin layers, including graphene and metals (such as gold, silver, copper and aluminum), metal oxides (such as aluminum oxide) and organic polymers(e.g., polydimethylsiloxane (PDMS), polymethyl methacrylate (PMMA), poly (bisphenol a) carbonate (PC)); sources of graphene include chemical vapor deposition synthesis, mechanical exfoliation, liquid phase exfoliation, epitaxial growth, and reduction oxidation.
6. The method for preparing the acceleration sensor based on the graphene suspension mass block according to claim 1, wherein the method comprises the following steps: the transfer method of graphene includes wet transfer, i.e., a transfer method using PMMA as a supporting layer and a non-supporting layer transfer method, an electrostatic force transfer method, a bubbling transfer method, i.e., an electrochemical reaction transfer method and a non-electrochemical bubbling auxiliary transfer method, a heat release tape method, a Polydimethylsiloxane (PDMS) printing method, and dry transfer, i.e., a roll-to-roll transfer method, and a metal auxiliary peeling method.
7. An acceleration sensor based on a graphene suspension mass according to claim 2, characterized in that: the shape of the suspended graphene film comprises a film with four circumferences fully covering the cavity and the mass block and a strip with parts covering the cavity and the mass block; the width of the graphene is 100 nanometers to 2 millimeters; the shape of the suspended mass block comprises square, cuboid, cylinder and hexagonal; the side dimensions of the suspended mass range from nanometer scale (100 nm) to millimeter scale (1 mm); the height dimensions of the suspended mass range from nanometer scale (100 nm) to millimeter scale (1 mm); the hanging mass blocks are located below the graphene, and the number of the hanging mass blocks is at least 1.
8. An acceleration sensor based on a graphene suspension mass according to claim 2, characterized in that: the thickness of the upper layer silicon wafer is 1~500/>The thickness of the lower layer silicon wafer is 1 +.>~500/>The materials suspended from the graphene mass include silicon, silicon dioxide, silicon nitride, polysilicon, organic polymers (such as polydimethylsiloxane, polymethyl methacrylate, poly (bisphenol A) carbonate, benzocyclobutene), photoresists (such as SU-8), metals (such as gold, silver, copper, aluminum), and the electrode materials include gold, silver, copper, aluminum, titanium, and their composites.
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