A silicon-based resonant pressure sensor based on a folded beam structure

Abstract

A silicon-based resonant pressure sensor based on a folded beam structure is disclosed. The sensor utilizes an electrostatically excited piezoresistive detection method and includes a pressure diaphragm layer, a pressure-sensing layer, a resonant structure layer, and a base layer. The pressure-sensing layer and resonator layer are made of silicon, while the base layer is made of BF33 borosilicate glass. The pressure-sensing layer primarily bears the load pressure. When subjected to load pressure, the pressure diaphragm deforms, causing displacement of the silicon islands on the diaphragm. These islands, connected by silicon-silicon bonding, transmit the lateral displacement to the resonator layer, generating axial internal stress in the resonant beam. This alters the stiffness of the main resonant beam, thereby changing the resonant frequency of the resonator and characterizing the pressure. The base layer serves as an encapsulation layer, forming a high-vacuum sealed cavity. This design reduces stress concentration caused by thermal expansion, ensuring good temperature characteristics of the sensor.

Description

Technical Field

[0001] This invention relates to a pressure sensor, and more particularly to a silicon-based resonant pressure sensor based on a folded beam structure that facilitates the release of thermal expansion, and a method for manufacturing the same. Background Technology

[0002] Pressure sensors based on microelectromechanical systems (MEMS) originated in the early 1980s. Due to their small size, high accuracy, and good stability, they have been widely used in industrial measurement and aerospace. Because of their huge demand, they have received increasing attention in recent years, especially pressure sensors for high-precision applications such as weaponry, atmospheric data acquisition, and industrial process control.

[0003] There are many types of pressure sensors, mainly including piezoresistive, piezoelectric, and resonant types. Among them, the resonant pressure sensor, which has the highest accuracy, has an overall accuracy better than 0.01%FS. It indirectly measures pressure by detecting changes in the natural frequency of the resonator, and outputs a quasi-digital signal. It can be directly connected to a computer or easily integrated into an instrument that directly displays digital data. However, the complex structural design and high manufacturing difficulty of high-precision resonant pressure sensors have resulted in the lack of mature products in China, making it entirely dependent on imports. To break through foreign technological blockades, major domestic laboratories are currently in the imitation stage. Improving the working accuracy of resonant pressure sensors, increasing the Q value of the sensors, and stabilizing the Q value are the key focuses and hot topics in the field of pressure sensing.

[0004] Resonant pressure sensors have a wide range of applications and excellent measurement performance, and many companies or research teams at home and abroad have begun to develop related products. Foreign countries started earlier, and many companies began to develop such products in the 1980s. At present, the companies that can produce high-performance products in this field are mainly: Druck, Yokogawa Electric Corporation of Japan, Paroscientific of the United States, Thales of France, etc. Some domestic research institutions and universities also began research in this field in the 1990s. Representative teams include: Institute of Electronics of Chinese Academy of Sciences, Beijing University of Aeronautics and Astronautics, University of Electronic Science and Technology of China, Xiamen University, Northwestern Polytechnical University, etc. Reference (Yuan Weizheng, Ren Sen, Deng Jinjun, et al. Development of silicon micromechanical resonant pressure sensor technology [J]. Journal of Mechanical Engineering, 2013, 49(20):2-9.).

[0005] When the temperature changes, the sensor core, heated and unable to expand freely, generates thermal stress. This thermal stress on the resonant detection structure causes a change in its resonant frequency, resulting in frequency errors that reduce the sensor's measurement accuracy. Current research on reducing temperature drift primarily employs temperature-insensitive materials to fabricate the sensor's sensitive structure or uses temperature compensation to reduce temperature drift. However, the impact of temperature on sensor performance still exists. Therefore, a novel MEMS silicon-based resonant pressure sensor structure is needed to mitigate the temperature effect and achieve excellent temperature characteristics for the resonant pressure sensor chip. Summary of the Invention

[0006] The purpose of this invention is to solve the problem of the influence of thermal stress caused by thermal expansion due to temperature changes on the resonant frequency of a resonator, and to provide a silicon-based resonant pressure sensor based on a folded beam structure that facilitates the release of thermal expansion and its manufacturing method.

[0007] The present invention relates to a silicon-based resonant pressure sensor with a folded beam structure, which consists of a glass base layer, a middle resonant sensitive layer, and an upper pressure-sensing layer from bottom to top.

[0008] The pressure-sensing layer is the layer in which the sensor directly contacts the pressure to be measured. The pressure-sensing layer includes a pressure membrane, silicon islands, and electrode holes. The pressure membrane and the cavity in which the silicon islands are placed are located at the center of the pressure-sensing layer. The silicon islands are located at the center of the pressure membrane and are symmetrically distributed. The electrode holes are located around the perimeter of the pressure-sensing layer.

[0009] The pressure-sensitive layer and the resonant sensitive layer are connected by silicon-silicon bonding; the resonant sensitive layer is used to convert pressure changes into detectable vibration frequency changes, and supports vibration and modulation signals, outputting the detected frequency change; the resonant sensitive layer consists of a resonant main beam, a resonant secondary beam, a resonator mass plate, a silicon island cover plate, a driving end fixed tooth, a driving electrode, a resonant secondary beam moving tooth, a detection piezoresistive beam, a detection electrode, and a ground electrode, forming a resonator structure.

[0010] The resonant main beam and the resonant secondary beam are interconnected. The moving tooth of the resonant secondary beam is integral with the resonant secondary beam and connected to the resonant main beam. The fixed tooth at the driving end is connected to the driving electrode. The resonant secondary beam is connected to the piezoresistive detection beam and the grounding electrode through its end. One end of the resonant main beam is connected to the silicon island cover plate, and the other end of the resonant main beam is connected to the anchor point on the resonator mass plate. The resonator mass plate is located at the center of the resonant structure, with only one end connected to the silicon island cover plate and the other end unfixed. The resonator mass plate also serves as a bonding area to fix the resonator structure. The silicon island cover plates are symmetrically distributed and connected to the resonators. The piezoresistive strips are symmetrically distributed and connected, and all are connected to the detection electrode.

[0011] The glass base layer is used to support the resonant structure layer. The center of the glass base layer has a pressure cavity groove for the device glass base layer and a release groove for the movable structure of the glass base layer corresponding to the resonant layer.

[0012] The pressure diaphragm is rectangular or rectangular in shape.

[0013] The silicon islands are symmetrically distributed in a pair on the pressure membrane.

[0014] The resonant main beam, resonant secondary beam, and detection piezoresistive strip are symmetrically distributed on both sides of the resonator structure layer. The two ends of the resonant main beam are connected to the silicon island cover plate and the mass plate, respectively. The mass plate is connected to the silicon island cover plate on only one side, and there is no fixed resonator structure similar to a single-end fixed support on the other side.

[0015] The electrode holes are four in number, evenly distributed on the pressure-sensitive layer, and correspond to the positions of the detection and driving electrodes of the resonant layer.

[0016] The fabrication method of the silicon-based MEMS resonant pressure sensor includes the following steps:

[0017] 1) Take a 400μm double-sided polished silicon wafer, and use wet etching on the lower surface to obtain a 100μm high-pressure film silicon island and a 20μm movable structure release groove for the resonant main beam and resonant secondary beam to vibrate freely, thus obtaining a pressure-sensitive layer. Then, oxidize both sides of the silicon wafer to obtain a 1μm oxide layer (the oxide layer is not a structure, but only a material formed during the process).

[0018] 2) Take another 400μm double-sided polished silicon wafer and oxidize it. Then, perform silicon-silicon bonding with the silicon wafer oxidized in step 1) and reduce the thickness of the silicon wafer after bonding to the thickness of 50μm required for the resonant structure layer to obtain the resonant structure layer without the resonant structure.

[0019] 3) The resonant layer pattern is transferred onto the silicon wafer on which the resonant structure layer is fabricated using photolithography, and then the entire structure on the resonant structure layer is fabricated using deep reactive ion etching.

[0020] 4) Take a 400μm BF33 glass substrate and etch out the pressure cavity groove and movable structure release groove of the device glass substrate layer. Then, anoly bond the vacuum-encapsulated glass substrate layer with the silicon wafer obtained in step 3) to the upper surface. Use hydrofluoric acid (BHF) to etch out a 20μm pressure cavity groove and movable structure release groove on the glass substrate. Sputter a getter to ensure vacuum encapsulation of the core within the pressure cavity groove and movable structure release groove, and then anoly bond it with the silicon wafer with the prepared resonant structure layer obtained in step 3).

[0021] 5) Electrode vias are created using deep reactive ion etching. These vias expose the detection electrode, excitation electrode, and ground electrode on the resonant structure layer, providing a window for subsequent connection of the resonant structure layer 2 to external circuits via leads.

[0022] The beneficial effects of this invention are:

[0023] 1) The design of the folded beam structure is to overcome the stress concentration problem caused by temperature changes in the core. A structure with one end fixed and the other end folded back is adopted. This allows the thermal expansion displacement of the beam caused by temperature changes to be released, reducing the stress concentration caused by thermal expansion, reducing the influence of temperature on frequency, and ensuring good temperature characteristics of the sensor.

[0024] 2) A resonator with the same folded beam structure can be used for differential output, which can eliminate the common mode temperature signal of the sensor, greatly reduce the temperature sensitivity of the sensor core, and ensure excellent temperature characteristics.

[0025] 3) The process employs silicon-silicon bonding technology and anodic bonding technology, which greatly reduces the complexity of the process. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the overall structure of an embodiment of the silicon-based resonant pressure sensor with a folded beam structure according to the present invention.

[0027] Figure 2 for Figure 1 Exploded view of the three-layer structure of the silicon-based resonant pressure sensor.

[0028] Figure 3 for Figure 1 A front view of the overall structure of the pressure-sensing layer of the silicon-based resonant pressure sensor.

[0029] Figure 4 for Figure 1 The overall structure front view of the resonant structure layer.

[0030] Figure 5 for Figure 4 Enlarged view of part A of the resonant layer structure.

[0031] Figure 6 for Figure 5 Enlarged view of the partially resonant comb structure B.

[0032] Figure 7 for Figure 1 Front view of the overall structure of the glass base layer of the silicon-based resonant pressure sensor.

[0033] Figure 8 for Figure 1 The main process flow of the silicon-based resonant pressure sensor

[0034] Figure 9 for Figure 1 Temperature drift comparison curves of whether the silicon-based resonant pressure sensor uses a folded beam

[0035] The markings in the diagram are as follows:

[0036] 1. Pressure-sensing layer; 2. Resonant structure layer; 3. Glass base layer; 4. Silicon island, 4A. First silicon island, 4B. Second silicon island; 5. Pressure membrane; 6. Electrode through-hole, 6A. First electrode through-hole, 6B. Second electrode through-hole, 6C. Third electrode through-hole, 6D. Fourth electrode through-hole; 7. Movable structure release groove of pressure-sensing layer; 8A. First silicon island cover plate; 8B. Second silicon island cover plate; 9A. First driving electrode; 9B. Second driving electrode; 10. Detection electrode; 11. Grounding electrode; 12. Resonant mass plate; 13. Resonant main beam; 14. Resonant secondary beam; 15. Folded beam fixing anchor point; 16. Detection pressure resistance strip; 17. Driving electrode fixed tooth; 18. Resonant secondary beam moving tooth; 19. Glass base layer pressure cavity groove; 20. Glass base layer movable structure release groove. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the following embodiments will be used in conjunction with the accompanying drawings to further illustrate the invention. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0038] See Figures 1-9 The silicon-based resonant pressure sensor based on a folded beam structure described in this embodiment of the invention is provided with a glass base layer 3, a middle resonant structure layer 2 and an upper pressure-sensing layer 1 from bottom to top.

[0039] The pressure-sensing layer 1 is the layer in which the sensor directly contacts the pressure to be measured. The pressure-sensing layer 1 is connected to the resonant structure layer 2 by silicon-silicon bonding. The resonant structure layer 2 is used to convert pressure changes into detectable vibration frequency changes and supports vibration and modulation signals, outputting the detected frequency changes. The glass base layer 3 is used to support the resonant structure layer and ensure the vacuum degree of the internal structure of the core.

[0040] A pressure film 5 is provided on the bonding surface between the pressure-sensitive layer 1 and the resonant structure layer 2. The pressure-sensitive layer 1 is used to withstand load pressure, and the pressure-sensitive layer 1 and the resonant structure layer 2 form a vibration system that can be sensitive to pressure loads.

[0041] The pressure membrane 5 on the pressure-sensitive layer 1 and the pressure cavity groove of the glass base layer 3 form a cavity for placing the first silicon island 4A and the second silicon island 4B in parallel. The pressure membrane 5 and the cavity for placing the first silicon island 4A and the second silicon island 4B are located at the upper center of the pressure-sensitive layer 1. The first silicon island 4A and the second silicon island 4B are located at the center of the pressure membrane 5 and are symmetrically distributed on the pressure membrane 5. The tops of the first silicon island 4A and the second silicon island 4B are connected to the first silicon island cover plate 8A and the second silicon island cover plate 8B on the resonant structure layer 2, forming a sensitive pressure... In a vibration system subjected to force load, when subjected to load pressure, the pressure diaphragm 5 deforms under pressure, thereby causing the first silicon island 4A and the second silicon island 4B on the pressure diaphragm 5 to displace. The deformation of the first silicon island 4A and the second silicon island 4B is transmitted to the resonant main beam 13 on the resonant structure layer 2 through the first silicon island cover plate 8A and the second silicon island cover plate 8B on the resonant structure layer 2. The stiffness of the resonant main beam 13 changes, resulting in a change in its natural frequency. The change in frequency has a certain linear relationship with the applied pressure load. By detecting the frequency change, the pressure information can be calculated.

[0042] The pressure-sensitive layer 1 has a first electrode through hole 6A, a second electrode through hole 6B, a third electrode through hole 6C, and a fourth electrode through hole 6D. The first electrode through hole 6A and the third electrode through hole 6C correspond to the first driving electrode 9A and the second driving electrode 9B on the resonant structure layer 2. The second electrode through hole 6B corresponds to the ground electrode 11 on the resonant structure layer 2. The fourth electrode through hole 6D corresponds to the detection electrode 10 on the resonant structure layer 2. The first to fourth electrode through holes 6A, 6B, 6C, and 6D are used to connect to external circuits to excite and detect the vibrating elements in the resonant structure layer.

[0043] The first electrode through-hole 6A, the second electrode through-hole 6B, the third electrode through-hole 6C, and the fourth electrode through-hole 6D are located around the pressure-sensitive layer 1 and are used to connect the leads to the external circuit. Leads are led out from the first electrode through-hole 6A, the second electrode through-hole 6B, the third electrode through-hole 6C, and the fourth electrode through-hole 6D so that the external AC drive signal can be applied to the first drive electrode 9A and the second drive electrode 9B, causing the resonant main beam 13 and the resonant secondary beam 14 to vibrate at their natural frequencies. The vibration causes the detection piezoresistive strip 16 to undergo alternating deformation at the same frequency as the vibration, causing the resistance of the detection piezoresistive strip 16 to change alternately. The detection piezoresistive strip 16 is connected to the external circuit through the detection electrode 10 and the ground electrode 11 via the leads led out from the second electrode through-hole 6B and the fourth electrode through-hole 6D. The circuit can convert the alternating changes in resistance into a voltage signal at the same frequency as the natural frequency, thereby measuring and outputting the pressure.

[0044] The resonant structure layer 2 includes a first driving electrode 9A, a second driving electrode 9B, a detection electrode 10, a ground electrode 11, a resonant mass plate 12, a resonant main beam 13, a resonant secondary beam 14, a detection piezoresistive strip 16, fixed teeth 17 of the driving electrode, and movable teeth 18 of the resonant secondary beam symmetrically distributed around the centerline of the resonant structure layer 2. The movable teeth 18 of the resonant secondary beam are connected to the resonant secondary beam 14, and the resonant secondary beam 14 is connected to the resonant main beam 16. One end of the resonant main beam 13 is connected to the first silicon via two fixed anchor points 15. Island cover plate 8A and second silicon island cover plate 8B are connected and fixed at one end. The other end of the resonant main beam 13 is connected to the resonator mass plate 12 through folded beam anchor point 15, forming a folded beam structure. The resonator mass plate 12 is connected to the second silicon island cover plate 8B at only one end, and the other end of the resonator mass plate 12 is the folded beam anchor point 15, which is not fixed. The bottom of the resonant secondary beam 14 is connected to the detection piezoresistive strip 16. The detection piezoresistive strip 16 is symmetrically distributed and connected, and is connected to the detection electrode 10. To ensure that the pressure membrane 5 deforms symmetrically when subjected to pressure load, the first silicon island cover plate 8A and the second silicon island cover plate 8B are symmetrically distributed with the center line of the short side of the rectangular pressure membrane 5 on the pressure-sensitive layer 1 as the axis of symmetry.

[0045] The pressure-sensitive layer 1 has a movable structure release groove 7, which provides vibration space for the resonant main beam 13, resonant secondary beam 14, detection pressure resistance strip 16, and resonant secondary beam moving tooth 18. If the movable structure release groove is not opened, the resonant main beam 13, resonant secondary beam 14, detection pressure resistance strip 16, and resonant secondary beam moving tooth 18 on the resonant structure layer 2 will be completely fixed and thus cannot vibrate, and cannot be pressure sensitive.

[0046] The glass base layer 3 is made of BF33 borosilicate glass and has a glass base layer pressure cavity groove 19 and a glass base layer movable structure release groove 20, which are made by BHF etching.

[0047] The pressure membrane 5 has a certain thickness and is rectangular in shape. The thickness of the pressure membrane 5 can be adjusted within the allowable range of the process according to the measurement range and sensitivity requirements.

[0048] When the main resonant beam 13 vibrates, it drives the secondary resonant beam 14 to vibrate. The secondary resonant beam 14 vibrates in-plane around its bottom support point, which in turn drives the detection pressure strip 16 connected to the secondary resonant beam 14 to vibrate. The detection pressure strip 16 is continuously subjected to compression and tension, causing its resistance value to change periodically. Under these conditions, the natural frequencies of the main resonant beam 13 and the secondary resonant beam 14 decrease as the pressure increases, and the vibration frequency of the detection pressure strip 16 decreases accordingly. The periodic frequency of the resistance value also decreases. By detecting the change in electrical quantity caused by the change in the resistance value of the pressure strip, the corresponding resonant frequency is obtained.

[0049] Reference Figure 5The silicon-based resonant pressure sensor designed in this invention employs a folded beam structure to release stress concentration caused by thermal expansion. When the ambient temperature rises, the resonant structure layer 2 expands due to heat, and the resonant main beam 13 expands due to heat, increasing in volume and generating longitudinal displacement. The resonant main beam 13 is connected to the second silicon island cover plate 8B through the resonant beam fixing anchor point 15. Therefore, the longitudinal displacement direction of the resonant main beam 13 due to thermal expansion is the side of the resonant main beam 13 away from the resonant beam fixing anchor point 15. Since the other side of the resonant main beam 13 is connected to the resonator mass plate 12 through the folded beam anchor point 15, and the resonator mass plate 12 is only connected to the second silicon island cover plate 8B at one end, with the other end unconstrained, the displacement caused by thermal expansion is released on the unconstrained side, thereby releasing the stress concentration caused by thermal expansion of the resonant main beam 13. The stiffness change of the resonant main beam 13 due to stress is small, which reduces the frequency change caused by temperature. Since the sensor calculates pressure by changing the resonant frequency, the small frequency change caused by temperature is beneficial to improving the accuracy of the sensor, thus giving the designed silicon-based resonant pressure sensor good temperature characteristics.

[0050] Reference Figure 8 The key steps in fabricating the silicon-based resonant pressure sensor with a folded beam structure include the following:

[0051] 1) Take a 400μm double-sided polished silicon wafer, and use wet etching on the lower surface to obtain a 100μm high silicon island 4. A 20μm pressure-sensitive layer movable structure release groove is used to make the resonant main beam and resonant secondary beam vibrate freely, to obtain pressure-sensitive layer 1. Then, oxidize the silicon wafer on both sides to obtain a 1μm oxide layer.

[0052] 2) Take another 400μm double-sided polished silicon wafer and oxidize it. Then, perform silicon-silicon bonding with the silicon wafer oxidized in step 1) and reduce the thickness of the silicon wafer after bonding to the thickness of 50μm required for the resonant structure layer to obtain the resonant structure layer 2 without the resonant structure.

[0053] 3) The resonant layer pattern is transferred to the silicon wafer on which the resonant structure layer 2 is prepared by photolithography, and then the entire structure on the resonant structure layer 2 is fabricated by deep reactive ion etching. A silicon island cover plate is then prepared on top of the silicon island.

[0054] 4) Take a 400μm BF33 glass disc (glass substrate layer 3), and use hydrofluoric acid (BHF) to etch a 20μm pressure cavity groove and a movable structure release groove into the glass disc used to prepare the glass substrate layer. Sputter getter to ensure vacuum sealing of the core into the pressure cavity groove and the movable structure release groove. Then, perform anodic bonding with the silicon wafer with the prepared resonant structure layer obtained in step 3).

[0055] 5) Electrode vias are created using deep reactive ion etching. Electrode vias 6 expose the driving electrode, detection electrode, and ground electrode on the resonant structure layer, providing a window for the subsequent resonant structure layer to be connected to external circuits via leads.

[0056] like Figure 9 As shown in the figure, the experiment shows that the temperature drift of the sensor without the folded beam structure is 3.19599 Hz / ℃, while the temperature drift of the sensor with the folded beam structure is 0.896692 Hz / ℃. The temperature coefficient is reduced by a factor of four, which significantly reduces the influence of temperature on the sensor and achieves good temperature characteristics of the resonant pressure sensor.

[0057] The above embodiments are merely preferred embodiments of the present invention and should not be considered as limiting the scope of the present invention. All equivalent variations and improvements made within the scope of the present invention should still fall within the patent coverage of the present invention.

Claims

1. A silicon-based resonant pressure sensor based on a folded beam structure, characterized in that, From bottom to top, the structure consists of a glass base layer, a middle resonant sensitive layer, and an upper pressure-sensitive layer. The pressure-sensing layer is the layer in which the sensor directly contacts the pressure to be measured. The pressure-sensing layer includes a pressure membrane, silicon islands, and electrode holes. The pressure membrane and the cavity in which the silicon islands are placed are located at the center of the pressure-sensing layer. The silicon islands are located at the center of the pressure membrane and are symmetrically distributed. The electrode holes are located around the perimeter of the pressure-sensing layer. The pressure-sensitive layer and the resonant sensitive layer are connected by silicon-silicon bonding; the resonant sensitive layer is used to convert pressure changes into detectable vibration frequency changes, and supports vibration and modulation signals, outputting the detected frequency change. The resonant sensitive layer consists of a resonant main beam, a resonant secondary beam, a resonator mass plate, a silicon island cover plate, a driving end fixed tooth, a driving electrode, a resonant secondary beam moving tooth, a detection piezoresistive beam, a detection electrode, and a grounding electrode, forming a resonator structure. The resonant main beam and the resonant secondary beam are interconnected. The moving tooth of the resonant secondary beam is integral with the resonant secondary beam and connected to the resonant main beam. The fixed tooth of the driving end is connected to the driving electrode. The resonant secondary beam is connected to the piezoresistive detection beam and the grounding electrode at its end; one end of the resonant main beam is connected to the silicon island cover plate, and the other end of the resonant main beam is connected to the anchor point on the resonator mass plate; the resonator mass plate is located at the center of the resonant structure, with only one end connected to the silicon island cover plate and the other end unfixed. The resonator mass plate also serves as a bonding area to fix the resonator structure; the silicon island cover plates are symmetrically distributed and connect the resonators. The piezoresistive strips are symmetrically distributed and connected, and all are connected to the detection electrode; The glass base layer is used to support the resonant structure layer. The center of the glass base layer has a pressure cavity groove for the device glass base layer and a release groove for the movable structure of the glass base layer corresponding to the resonant layer.

2. The silicon-based resonant pressure sensor based on a folded beam structure as described in claim 1, characterized in that... The pressure diaphragm is rectangular or rectangular in shape.

3. The silicon-based resonant pressure sensor based on a folded beam structure as described in claim 1, characterized in that... The silicon islands are symmetrically distributed in pairs on the pressure membrane with the center line of the short side of the rectangle as the axis of symmetry.

4. The silicon-based resonant pressure sensor based on a folded beam structure as described in claim 1, characterized in that... The resonant main beam, resonant secondary beam, and detection piezoresistive strip are all symmetrically distributed on both sides of the resonator with the overall center line as the axis of symmetry.

5. The silicon-based resonant pressure sensor as described in claim 1, characterized in that... The two ends of the resonant main beam are connected to the silicon island cover plate and the resonator mass plate, respectively. The mass plate is connected to the silicon island cover plate on only one side, and the other side is not fixed.

6. The silicon-based resonant pressure sensor based on a folded beam structure as described in claim 1, characterized in that: The electrode holes are four in number, evenly distributed on the pressure-sensitive layer, and correspond to the positions of the detection electrode and the driving electrode of the resonant structure layer.

7. The silicon-based resonant pressure sensor based on a folded beam structure as described in claim 1, characterized in that: The glass base layer is made of BF33 borosilicate glass.

8. A method for fabricating a silicon-based resonant pressure sensor based on a folded beam structure as described in any one of claims 1 to 7, characterized in that... Includes the following steps: 1) Take a 400μm double-sided polished silicon wafer, and use wet etching on the lower surface to obtain a 100μm high-pressure film silicon island and a 20μm movable structure release groove for the resonant main beam and resonant secondary beam to vibrate freely, to obtain a pressure-sensitive layer, and oxidize the silicon wafer on both sides to obtain a 1μm oxide layer. 2) Take another 400μm double-sided polished silicon wafer and oxidize it. Then, perform silicon-silicon bonding with the silicon wafer oxidized in step 1) and reduce the thickness of the silicon wafer after bonding to the thickness of 50μm required for the resonant structure layer to obtain the resonant structure layer without the resonant structure. 3) The resonant layer pattern is transferred onto the silicon wafer on which the resonant structure layer is fabricated using photolithography, and then the entire structure on the resonant structure layer is fabricated using deep reactive ion etching. 4) Take a 400μm BF33 glass substrate and use hydrofluoric acid (BHF) to etch a 20μm pressure cavity groove and a movable structure release groove into the glass substrate. Sputter a getter to ensure vacuum sealing of the core in the pressure cavity groove and the movable structure release groove. Then, perform anodic bonding with the silicon wafer with the prepared resonant structure layer obtained in step 3). 5) Electrode holes are created using deep reactive ion etching. These holes expose the detection electrode, excitation electrode, and ground electrode on the resonant structure layer, providing a window for the subsequent resonant structure layer to be connected to external circuits via leads.

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