A resonant differential pressure sensor with low static pressure error for high static pressure environments

Abstract

A low static pressure error resonant differential pressure sensor for high static pressure environments, involving a micro-electromechanical system. It is used to achieve differential pressure measurement with low static pressure error and high sensitivity ratio under high static pressure conditions. The sensor adopts a single resonator structure and accurately captures the fluid pressure difference through micro-drive of the intermediate membrane. In particular, the static pressure error control in high static pressure environments significantly reduces the influence of static pressure on the measurement results by using the upper and lower pressure-sensing layers to resist the static pressure load and the main island to clamp the intermediate membrane. The sensor has a high ratio of differential pressure sensitivity to static pressure error and can maintain excellent measurement performance even in high static pressure environments. It is suitable for a variety of high-precision measurement scenarios, especially in the fields of petrochemicals, aerospace, environmental monitoring, and medical equipment, and can provide users with reliable and accurate differential pressure measurement solutions. By adopting advanced micromachining technology, miniaturization and low-cost production are achieved while ensuring long-term stability and repeatability.

Description

Technical Field

[0001] The present invention relates to the technical field of micro-electromechanical systems (MEMS), and in particular to a low static pressure error resonant differential pressure sensor for high static pressure environments. Background Art

[0002] Since the early 1980s, microelectromechanical system (MEMS) resonant pressure sensors have gradually become a key technology in the field of pressure measurement. MEMS technology has enabled miniaturization, high precision, and low cost of pressure sensors. However, as applications continue to expand, pressure sensors in extreme environments are gaining increasing attention, particularly in high-end equipment, military weaponry, aerospace, and deep-sea exploration. In these extreme environments, achieving micro differential pressure detection under high static pressure has become a major technical challenge for MEMS pressure sensors.

[0003] MEMS pressure sensors can be categorized as differential, absolute, and gauge pressure depending on the reference pressure used for the test. Their core sensing mechanisms include piezoresistive, piezoelectric, and resonant. Resonant pressure sensors are widely favored in the pressure measurement field due to their high precision, high sensitivity, and stability, with overall accuracy exceeding 0.01% FS. However, for differential pressure sensors, achieving small differential pressure detection under high static pressure conditions remains a technical challenge. Improving the sensitivity of differential pressure sensors is crucial for improving overall performance.

[0004] Against this backdrop, many companies and research teams at home and abroad have begun developing related products. Foreign companies such as Druck, YOKOGAWA, Paroscientific, and Thales began developing these products as early as the 1980s. Domestic research institutions and universities, such as the Institute of Electronics of the Chinese Academy of Sciences, Beijing University of Aeronautics and Astronautics, University of Electronic Science and Technology of China, Xiamen University, and Northwestern Polytechnical University, began research in this field in the 1990s. Chengdu Aircraft Industry (Group) Co., Ltd. (Patent Document: A Micro-Differential Pressure MEMS Sensor for High Static Pressure Environments and Its Manufacturing Method, Patent No.: ZL202010123456.9, Publication Date: 2022-04-05) provides a detailed review of the development and application status of MEMS pressure sensor technology, demonstrating that significant technical challenges and room for development remain in the field of high static pressure micro-differential pressure detection. Summary of the Invention

[0005] The object of the present invention is to provide a low static pressure error resonant differential pressure sensor for high static pressure environments, which can achieve low static pressure error and high sensitivity ratio in high static pressure environments.

[0006] In order to achieve this object, the present invention adopts the following technical solutions:

[0007] A low static pressure error resonant differential pressure sensor for high static pressure environments, which is sequentially arranged from bottom to top with an upper pressure-sensing layer, a balanced silicon island layer, a resonant layer, a lower pressure-sensing layer, and a glass layer;

[0008] The upper pressure-sensitive layer is bonded to the upper portion of the balancing silicon island layer, and the upper pressure film of the upper pressure-sensitive layer is located on one side. The upper pressure film of the upper pressure-sensitive layer matches the position of the upper main island of the balancing silicon island layer to ensure consistency and accuracy of pressure transmission;

[0009] The balancing silicon island layer comprises an upper main island, a lower main island, and a secondary island, as well as four electrode holes for electrical connection to the resonant layer. The balancing silicon island layer is tightly integrated with the resonant layer to balance stress changes caused by static pressure and transmit differential pressure stress changes to the resonant layer. The secondary island and the lower main island are on the same side, and the four electrode holes are distributed at the tail end of the layer structure and correspond to the electrode structure of the resonant layer. The electrode holes achieve electrical connection to the resonant layer. The release groove of the movable structure of the balancing silicon island layer is used to bond and fix the resonant layer and allow space for the main beam to vibrate freely.

[0010] The resonant layer includes a balancing mass block, a cover plate, a main beam, a sub-beam, a detection electrode, a driving electrode, and a ground electrode. The main beam and the sub-beam are interconnected. The driving electrode is used to drive the resonant sub-beam to make the main beam generate an initial vibration amplitude. The output frequency varies under different pressures, and the signal is detected by the detection electrode. The balancing mass block is located between the upper pressure membrane and the upper main island to balance and transmit stress, ensuring the stability and accuracy of the sensor in a high static pressure environment.

[0011] The lower pressure-sensing layer includes a lower pressure membrane and a movable structure release groove for the lower pressure-sensing layer. The peripheral portion of the lower pressure membrane is bonded to the glass layer to fix the entire sensor core, ensuring the structural stability and long-term reliability of the sensor. The movable structure release groove of the lower pressure-sensing layer is used to release the vibration of the main beam and auxiliary beam of the resonance layer.

[0012] The glass layer is used to fix the upper pressure-sensing layer, the balanced silicon island layer, the resonant layer, and the lower pressure-sensing layer structure. The glass layer is provided with a glass layer vent hole, which is used for the gas (liquid) below to enter, so that the lower pressure-sensing membrane is sensitive to the medium pressure and produces a corresponding displacement change.

[0013] Furthermore, the upper pressure film of the upper pressure-sensing layer is made of a highly elastic silicon material to improve the response speed and sensitivity of the sensor to pressure changes.

[0014] Furthermore, the upper pressure-sensitive layer is made of single-crystal silicon material and may be 500 microns thick; and the upper pressure-sensitive film may be 2 microns thick.

[0015] Furthermore, the upper main island and the lower main island of the balanced silicon island layer form a stable mechanical structure to reduce static pressure errors.

[0016] Furthermore, the balancing mass block of the resonance layer is made of high-rigidity silicon material to improve the resonance stability of the resonance layer.

[0017] Furthermore, the bonding between the lower pressure film of the lower pressure-sensing layer and the glass layer is made of highly sealing silicon material to ensure the sealing performance of the sensor in a high static pressure environment.

[0018] Furthermore, high-temperature bonding technology is used to achieve close bonding between the layers, ensuring the integrity and stability of the sensor.

[0019] Furthermore, electrode holes are made by wet etching technology for connecting to external circuits.

[0020] Furthermore, the electrodes of the resonant layer are connected to the external circuit through micro-welding technology to ensure accurate signal transmission.

[0021] Furthermore, the thickness of the resonance layer is closely related to the differential pressure sensitivity. To ensure accurate sensitivity to the differential pressure under high static pressure load, the thickness of the resonance layer is determined to be optimally in the range of 60 to 70 μm through analysis and optimization.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The design of the upper and lower pressure-sensitive layers resisting the static pressure load and the main island clamping the intermediate film significantly reduces the influence of static pressure on the measurement results and achieves low static pressure error.

[0024] 2. The ratio of the sensor's differential pressure sensitivity to static pressure error is very high, which improves measurement accuracy.

[0025] 3. Suitable for a variety of high-precision measurement scenarios, especially in high static pressure environments, such as petrochemical, aerospace, environmental monitoring and medical equipment.

[0026] 4. Advanced micromachining technology is used to achieve miniaturization and low-cost production of sensors while ensuring long-term stability and repeatability. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the overall structure of a low static pressure error resonant differential pressure sensor for high static pressure environments according to an embodiment of the present invention.

[0028] Figure 2 for Figure 1 An exploded view of the three-layer structure of the low static pressure error resonant differential pressure sensor for high static pressure environments.

[0029] Figure 3 for Figure 1 A front view of the upper pressure-sensing layer of the low static pressure error resonant differential pressure sensor for high static pressure environments.

[0030] Figure 4 for Figure 1 A front view of the balanced silicon island layer of the low static pressure error resonant differential pressure sensor for high static pressure environments.

[0031] Figure 5 for Figure 1 Back view of the balanced silicon island layer of the low static pressure error resonant differential pressure sensor for high static pressure environments.

[0032] Figure 6 for Figure 1 A front view of the resonant layer of the low static pressure error resonant differential pressure sensor for high static pressure environments.

[0033] Figure 7 for Figure 1 A front view of the lower pressure-sensing layer of the low static pressure error resonant differential pressure sensor for high static pressure environments.

[0034] Figure 8 for Figure 1 Back view of the lower pressure-sensing layer of the low static pressure error resonant differential pressure sensor for high static pressure environments.

[0035] Figure 9 for Figure 1 Front view of the glass layer of the low static pressure error resonant differential pressure sensor for high static pressure environments.

[0036] Figure 10 for Figure 1 A front view of the resonant layer operating mode of the low static pressure error resonant differential pressure sensor for high static pressure environments.

[0037] Figure 11 for Figure 1 Displacement deformation cloud diagram of the equilibrium silicon island layer and the resonant layer of the low static pressure error resonant differential pressure sensor for high static pressure environment at a static pressure of 30 MPa and a differential pressure of 300 kPa.

[0038] Figure 12 for Figure 1 The static pressure error curve of the low static pressure error resonant differential pressure sensor for high static pressure environment under a large static pressure range of 15 MPa.

[0039] Figure 13 for Figure 1 The differential pressure sensitivity curve of the low static pressure error resonant differential pressure sensor for high static pressure environment is within the differential pressure sensitive range of 0 to 300 kPa.

[0040] exist Figures 1 to 9 In the , each mark is:

[0041] 1: Electrode hole, 2: Upper pressure-sensing film; 3: Upper pressure-sensing layer, 4: Balanced silicon island layer, 5: Resonant layer, 6: Lower pressure-sensing layer, 7: Glass layer; 8: Upper main island, 9: Lower main island, 10: Auxiliary island, 11: Release slot for the movable structure of the balanced silicon island layer; 12: Balancing mass block, 13: Cover plate, 14: Resonant main beam; 15: Resonant auxiliary beam, 16: Detection electrode, 17: Driving electrode, 18: Ground electrode, 19: Release slot for the movable structure of the lower pressure-sensing layer, 20: Lower pressure-sensing film; 21: Vent hole in the glass layer. DETAILED DESCRIPTION

[0042] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the following embodiments will be further described with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention. On the contrary, the present invention encompasses any alternatives, modifications, equivalent methods, and solutions made within the spirit and scope of the present invention as defined by the claims.

[0043] See also Figures 1 to 9 The sensor structure of a low static pressure error resonant differential pressure sensor for high static pressure environments includes an upper pressure-sensing layer 3, a balanced silicon island layer 4, a resonant layer 5, a lower pressure-sensing layer 6, and a glass layer 7, which are arranged in sequence from bottom to top. The upper pressure-sensing layer 3 is bonded to the upper part of the balanced silicon island layer 4, wherein the upper pressure-sensing film 2 of the upper pressure-sensing layer 3 is located on one side and precisely matches the position of the upper main island 8 of the balanced silicon island layer 4 to ensure the consistency and accuracy of pressure transmission. The balanced silicon island layer 4 includes an upper main island 8, a lower main island 9, and a sub-island 10, as well as electrode holes 1 distributed at the tail end to achieve electrical connection with the resonant layer 5. The resonant layer 5 includes a balancing mass block 12, a cover plate 13, a resonant main beam 14, a resonant sub-beam 15, a detection electrode 16, a driving electrode 17, and a grounding electrode 18. The resonant sub-beam 15 is driven by the driving electrode 17 to cause the resonant main beam 14 to generate an initial vibration amplitude. The lower pressure-sensing layer 6 includes a lower pressure membrane 20 and a release groove 19 for the lower pressure-sensing layer's movable structure. The periphery of the lower pressure membrane 20 is bonded to the glass layer 7, securing the entire sensor core. The glass layer 7 secures this layered structure and allows the inflow of gas (or liquid) below through glass vents 21. This allows the lower pressure-sensing membrane 20 to sense the medium's pressure and generate corresponding displacement changes.

[0044] See also Figures 1 to 8The upper pressure-sensing layer 3 is made of single-crystal silicon and is 500 microns thick. On one side of the layer is formed an upper pressure-sensing membrane 2, which is tens of microns thick and whose size and shape are precisely controlled using micromachining techniques to enhance sensitivity to pressure changes. The balancing silicon island layer 4 is located beneath the upper pressure-sensing layer 3 and is tightly bonded to the upper pressure-sensing layer via direct bonding. This layer comprises multiple island structures, each formed using wet etching to ensure structural stability. The resonant layer 5, located beneath the balancing silicon island layer 4, includes a resonant main beam 14, a resonant sub-beam 15, and connected detection electrodes 16. These structures are precisely machined using micro-electromechanical systems (MEMS) technology to achieve precise control of the resonant frequency. The resonant main beam 14 and resonant sub-beam 15 of the resonant layer 6 are formed using micromachining techniques and are mechanically coupled through a specific design to produce predictable resonant frequency changes when subjected to pressure changes. When the upper pressure-sensing layer 3 senses a change in external pressure, the pressure is transmitted through the upper pressure-sensing membrane 2 to the balancing silicon island layer 4 and further to the resonant layer 6. The lower pressure-sensing layer 6 is located below the resonant layer 5 and is tightly bonded to the resonant layer via silicon-silicon bonding technology. The lower pressure-sensing layer includes a lower pressure-sensing film 20, whose shape and thickness match those of the upper pressure-sensing film 2 to achieve balanced pressure transmission.

[0045] See also Figures 1 to 8 The sensor manufacturing process is implemented as follows. Interlayer bonding: The upper pressure-sensing layer 3, the balancing silicon island layer 4, the resonant layer 5 and the lower pressure-sensing layer 6 are tightly bonded by high-temperature bonding technology to ensure the integrity and stability of the sensor. Electrode hole production: Electrode holes are formed on the balancing silicon island layer 4 and the lower pressure-sensing layer 6 by wet etching technology for connecting to external circuits. Electrode connection: The driving electrode 17, the ground electrode 18 and the detection electrode 16 of the resonant layer 5 are connected to the external circuit by micro-welding technology to ensure accurate signal transmission.

[0046] When the sensor is exposed to high static pressure, the upper and lower pressure-sensing layers 3 and 6 respectively sense pressure changes, converting these pressure changes into stress changes through the upper and lower pressure-sensing membranes 2 and 20. These stress changes are balanced by the upper and lower main islands 8 and 9 of the balancing silicon island layer 4, which balance the stress changes caused by the static pressure. The secondary island 10 transmits the differential pressure stress changes to the cover plate 13, driving its rotation. This, in turn, transmits the stress changes caused by the differential pressure to the resonant main beam 14. The resonant main beam 14 and resonant secondary beam 15 generate corresponding vibrations based on the stress changes. The detection electrode 16 outputs an electrical signal based on the vibration frequency changes of the resonant main beam 14 and resonant secondary beam 15. This signal is processed by an external circuit to ultimately determine the differential pressure value.

[0047] See also Figures 10-13The present invention achieves an optimized ratio of high differential pressure sensitivity and low static pressure error by comprehensively considering the structural design, material properties and processing technology of the sensor. Multiple rounds of experimental tests and performance evaluations are carried out to determine the optimal sensor design parameters so that the differential pressure sensitivity reaches the maximum and the static pressure error is kept to the minimum within a given static pressure range. In terms of structural design, the overall structural design of the sensor is carefully planned to maximize performance. Through simulation and experimental verification, the geometric dimensions and layout of the upper pressure-sensing layer 3 and the lower pressure-sensing layer 6 are optimized to ensure that under high static pressure environments, pressure changes can be evenly transmitted to the resonant layer 6, thereby reducing the static pressure error caused by structural asymmetry. As the thickness of the pressure-sensing layer increases, the ability of the entire machine to resist static pressure is enhanced. In order to ensure that the yield strength of the silicon material of 7GPa is not exceeded under large static pressure loads, combined with the requirements for the overall sensitivity of the sensor, it can be determined through analysis and optimization that the thickness of the upper pressure-sensing layer 3 and the lower pressure-sensing layer 6 should be 500μm, and is in line with the thickness size of existing common silicon wafers. A unique pressure transmission mechanism is designed. By balancing the stepped structure of the silicon island layer 4, pressure changes sensed by the upper pressure-sensing layer 3 are effectively converted into resonant frequency changes in the resonant layer 6, thereby improving differential pressure sensitivity and enhancing the sensor's stability and reliability in complex pressure environments. The thickness of the resonant layer 6 is closely related to differential pressure sensitivity. To ensure accurate differential pressure sensitivity under high static pressure loads, the optimal thickness of the resonant layer 6 has been determined to be between 60 and 70 μm. The precise matching of the upper and lower pressure-sensing membranes 2 and 20 not only enhances pressure transmission consistency but also reduces static pressure errors caused by structural asymmetry. Single-crystal silicon was chosen as the primary material for the upper and lower pressure-sensing layers 3 and 6 due to its excellent mechanical properties and stable chemical properties. Its high elastic modulus and low temperature coefficient ensure that the sensor maintains high accuracy and long-term stability even in high static pressure environments. The glass layer 7 was selected for its excellent sealing and light transmittance. Advanced micromachining and MEMS processes are widely used in the sensor's manufacturing process. From high-temperature processing techniques for interlayer bonding to wet etching of electrode holes, precision is paramount. In particular, the meticulous processing of the resonant main beam 14 and resonant sub-beam 15 in the resonant layer 5, as well as the detection and drive electrodes, determines the sensor's resonant frequency and detection accuracy. Micro-welding technology ensures a reliable connection between the electrodes and external circuitry, reducing interference and loss in signal transmission.

[0048] Through multiple rounds of experimental tests and performance evaluation, the optimal design parameters of the sensor were determined. Under extreme conditions of static pressure 30MPa and differential pressure 300kPa, Figure 11 The displacement deformation cloud diagram shown intuitively displays the displacement deformation of the balanced silicon island layer 4 and the resonant layer 5, verifying the effectiveness and rationality of the structural design. Figure 12The static pressure error curve in further proves the low static pressure error characteristic of the sensor under a large static pressure range of 15MPa, indicating that it has good anti-static pressure interference ability. Figure 13 The differential pressure sensitivity curve clearly demonstrates the high sensitivity of the sensor in the differential pressure sensitive range of 0 to 300 kPa, ensuring its accuracy and reliability in various application scenarios.

[0049] Experiments have shown that the sensor provided by the present invention can sense pressure changes in high static pressure environments through its upper and lower pressure-sensing layers, accurately measure differential pressure values ​​through changes in the resonant frequency of the resonant layer, and achieve performance optimization with low static pressure errors. The sensor of the present invention is suitable for a variety of high-precision measurement scenarios, particularly in the fields of petrochemicals, aerospace, environmental monitoring, and medical equipment, providing users with a reliable and accurate differential pressure measurement solution. By utilizing advanced micromachining techniques, the sensor of the present invention achieves miniaturization and low-cost production while ensuring long-term stability and repeatability.

[0050] The above embodiments are only preferred embodiments of the present invention and should not be considered to limit the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent of the present invention.

Claims

1. A low static pressure error resonant differential pressure sensor for high static pressure environment, characterized by From bottom to top, an upper pressure-sensitive layer, a balanced silicon island layer, a resonant layer, a lower pressure-sensitive layer and a glass layer are sequentially arranged; The upper pressure-sensitive layer is bonded to the upper portion of the balancing silicon island layer, and the upper pressure film of the upper pressure-sensitive layer is located on one side. The upper pressure film of the upper pressure-sensitive layer matches the position of the upper main island of the balancing silicon island layer to ensure consistency and accuracy of pressure transmission; The balancing silicon island layer comprises an upper main island, a lower main island, and a secondary island, as well as four electrode holes for electrical connection to the resonant layer. The balancing silicon island layer is tightly integrated with the resonant layer to balance stress changes caused by static pressure and transmit differential pressure stress changes to the resonant layer. The secondary island and the lower main island are on the same side, and the four electrode holes are distributed at the tail end of the layer structure and correspond to the electrode structure of the resonant layer. The electrode holes achieve electrical connection to the resonant layer. The release groove of the movable structure of the balancing silicon island layer is used to bond and fix the resonant layer and allow space for the main beam to vibrate freely. The resonant layer includes a balancing mass block, a cover plate, a main beam, a sub-beam, a detection electrode, a driving electrode, and a ground electrode. The main beam and the sub-beam are interconnected. The driving electrode is used to drive the resonant sub-beam to make the main beam generate an initial vibration amplitude. The output frequency varies under different pressures, and the signal is detected by the detection electrode. The balancing mass block is located between the upper pressure membrane and the upper main island to balance and transmit stress, ensuring the stability and accuracy of the sensor in a high static pressure environment. The lower pressure-sensing layer includes a lower pressure membrane and a release groove for the movable structure of the lower pressure-sensing layer. The peripheral portion of the lower pressure membrane is bonded to the glass layer to fix the entire sensor core, ensuring the structural stability and long-term reliability of the sensor. The release groove of the movable structure of the lower pressure-sensing layer is used to release the vibration of the main beam and auxiliary beam of the resonance layer; The glass layer is used to fix the upper pressure-sensing layer, the balanced silicon island layer, the resonant layer, and the lower pressure-sensing layer structure. The glass layer is provided with a glass layer vent hole, which is used for the gas or liquid below to enter, so that the lower pressure-sensing membrane is sensitive to the medium pressure and produces a corresponding displacement change.

2. A low static pressure error resonant differential pressure sensor for high static pressure environments as claimed in claim 1, characterized in that The upper pressure film of the upper pressure-sensing layer is made of highly elastic silicon material to improve the response speed and sensitivity of the sensor to pressure changes.

3. A low static pressure error resonant differential pressure sensor for high static pressure environments as claimed in claim 1, characterized in that The upper pressure-sensitive layer is made of single-crystal silicon material and has a thickness of 500 μm; the thickness of the upper pressure-sensitive film is 2 μm.

4. A low static pressure error resonant differential pressure sensor for high static pressure environments as claimed in claim 1, characterized in that The upper main island and the lower main island of the balanced silicon island layer form a stable mechanical structure to reduce static pressure error.

5. A low static pressure error resonant differential pressure sensor for high static pressure environments as claimed in claim 1, characterized in that The balancing mass block of the resonance layer is made of high-rigidity silicon material to improve the resonance stability of the resonance layer.

6. A low static pressure error resonant differential pressure sensor for high static pressure environments as claimed in claim 1, characterized in that The bonding between the lower pressure film of the lower pressure-sensing layer and the glass layer adopts a highly sealing silicon material to ensure the sealing performance of the sensor in a high static pressure environment.

7. A low static pressure error resonant differential pressure sensor for high static pressure environments as claimed in claim 1, characterized in that The layers are tightly bonded through high-temperature bonding technology to ensure the integrity and stability of the sensor.

8. A low static pressure error resonant differential pressure sensor for high static pressure environments as claimed in claim 1, characterized in that The electrode holes are made by wet etching technology and are used to connect to external circuits.

9. A low static pressure error resonant differential pressure sensor for high static pressure environments as claimed in claim 1, characterized in that The electrodes of the resonance layer are connected to the external circuit through micro-welding technology to ensure accurate signal transmission.

10. A low static pressure error resonant differential pressure sensor for high static pressure environments as claimed in claim 1, characterized in that The thickness of the resonance layer is 60-70 μm.

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