Low static pressure error resonance differential pressure sensor for high static pressure environment

Abstract

The invention discloses a low-static-pressure error resonance differential pressure sensor for a high-static-pressure environment, and relates to a micro electro mechanical system. The differential pressure sensor is used for realizing differential pressure measurement of low static pressure error and high sensitivity ratio under the condition of high static pressure. The sensor is of a single resonator structure, and accurate capturing of the fluid pressure difference is achieved through micro-motion driving of the middle film. Especially for static pressure error control in a high static pressure environment, the influence of static pressure on a measurement result is remarkably reduced through the design that the upper and lower pressure sensing layers resist static pressure loads and the main island clamps the middle film. The ratio of the differential pressure sensitivity to the static pressure error of the sensor is high, and excellent measurement performance can be kept in a high static pressure environment. The device is suitable for various high-precision measurement scenes, especially in the fields of petrochemical engineering, aerospace, environmental monitoring, medical equipment and the like, and can provide a reliable and accurate differential pressure measurement solution for users. By adopting an advanced micromachining technology, miniaturization and low-cost production are realized, and meanwhile, long-term stability and repeatability are ensured.

Description

Technical Field

[0001] The 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, micro-electromechanical system (MEMS) resonant pressure sensors have gradually become one of the key technologies in the field of pressure measurement. With the support of MEMS technology, pressure sensors have achieved miniaturization, high precision and low cost. However, with the continuous expansion of application areas, the application of pressure sensors in extreme environments has received more and more attention, especially in high-end equipment, military weapons, aerospace, deep-sea exploration and other fields. In these extreme environments, achieving micro differential pressure detection under high static pressure has become an important technical challenge facing MEMS pressure sensors.

[0003] MEMS pressure sensors can be divided into differential pressure, absolute pressure and gauge pressure types according to the reference standard of the test pressure. Its core sensitive mechanisms include piezoresistive, piezoelectric and resonant types. Resonant pressure sensors are widely favored in the field of pressure measurement due to their advantages of high precision, high sensitivity and stability, and their comprehensive accuracy can be better than 0.01% FS. However, for differential pressure sensors, how to achieve small differential pressure detection under high static pressure background is still a technical challenge. Improving the sensitivity of differential pressure sensors has become the key to improving overall performance.

[0004] In this context, many companies and research teams at home and abroad began to develop related products. Foreign companies such as Druck, YOKOGAWA, Paroscientific and Thales began research and development of such products as early as the 1980s. Some 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 to engage in research in this field in the 1990s. Chengdu Aircraft Industry (Group) Co., Ltd. (Patent document: A micro-differential pressure MEMS sensor in a high static pressure environment and its manufacturing method, patent number: ZL202010123456.9, publication date: 2022-04-05.) A detailed review of the development and application status of MEMS pressure sensor technology shows that there are still huge technical challenges and room for development 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 environment, which is provided with an upper pressure-sensing layer, a balanced silicon island layer, a resonant layer, a lower pressure-sensing layer and a glass layer in sequence from bottom to top;

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

[0009] The balanced silicon island layer comprises an upper main island, a lower main island and an auxiliary island, as well as four electrode holes for electrical connection with the resonance layer; the balanced silicon island layer is tightly combined with the resonance layer to balance the stress changes transmitted by the static pressure and transmit the differential pressure stress changes to the resonance layer; the auxiliary island is on the same side as the lower main island, and the four electrode holes are distributed at the tail end of the layer structure and correspond to the resonance layer electrode structure, and the electrical connection with the resonance layer is achieved through the electrode holes; the release groove of the movable structure of the balanced silicon island layer is used to bond and fix the resonance layer and allow the main beam to have space for free vibration;

[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 grounding electrode. The main beam and the sub-beam are connected to each other. The driving electrode is used to drive the resonant sub-beam to make the main beam generate an initial vibration amplitude. According to different output frequencies under different pressures, the signal is detected by the detection electrode. The balancing mass block is located between the upper pressure membrane and the upper main island, and is used to balance and transmit stress to ensure the stability and accuracy of the sensor in a high static pressure environment.

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

[0012] The glass layer is used to fix the upper pressure-sensitive layer, the balanced silicon island layer, the resonant layer, and the lower pressure-sensitive layer structure. The glass layer is provided with glass layer vents, which are used for the entry of gas (liquid) below, so that the lower pressure-sensitive membrane is sensitive to the medium pressure and produces corresponding displacement changes.

[0013] Furthermore, 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.

[0014] Furthermore, the upper pressure-sensitive layer is made of single-crystal silicon material and may be 500 microns thick; 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 adopts a 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, the electrode holes are made by wet etching technology for connecting to external circuits.

[0020] Furthermore, the electrodes of the resonance 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 can significantly reduce the influence of static pressure on the measurement results and achieve 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. Use advanced micro-machining technology to achieve miniaturization and low-cost production of sensors, while ensuring long-term stability and repeatability. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The figure is a schematic diagram of the overall structure of a low static pressure error resonant differential pressure sensor for a high static pressure environment 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 Front view of the balanced silicon island layer of the low static pressure error resonant differential pressure sensor for high static pressure environment.

[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 facing a high static pressure environment.

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

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

[0036] Fig.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] Fig.11 for Figure 1 The displacement deformation cloud diagram of the balanced silicon island layer and the resonance 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] Fig.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] Fig.13 for Figure 1 The differential pressure sensitivity curve of the low static pressure error resonant differential pressure sensor for high static pressure environment within the differential pressure sensitive range of 0 to 300 kPa.

[0040] exist Figures 1 to 9 In the figure, the markers are:

[0041] 1: electrode hole, 2: upper pressure-sensitive film; 3: upper pressure-sensitive layer, 4: balanced silicon island layer, 5: resonance layer, 6: lower pressure-sensitive layer, 7: glass layer; 8: upper main island, 9: lower main island, 10: secondary island, 11: release groove of movable structure of balanced silicon island layer; 12: balancing mass block, 13: cover plate, 14: resonance main beam; 15: resonance secondary beam, 16: detection electrode, 17: driving electrode, 18: grounding electrode, 19: release groove of movable structure of lower pressure-sensitive layer, 20: lower pressure-sensitive film; 21: ventilation hole of glass layer. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the following embodiments will further illustrate the present invention in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. On the contrary, the present invention covers any substitution, modification, equivalent method and scheme made on the essence and scope of the present invention as defined by the claims.

[0043] See also Figures 1 to 9 , the sensor structure of the low static pressure error resonant differential pressure sensor for high static pressure environment includes an upper pressure-sensitive layer 3, a balanced silicon island layer 4, a resonant layer 5, a lower pressure-sensitive layer 6 and a glass layer 7 arranged in sequence from bottom to top. The upper pressure-sensitive layer 3 is bonded to the upper part of the balanced silicon island layer 4, wherein the upper pressure-sensitive film 2 of the upper pressure-sensitive layer 3 is located on one side, and the position is precisely matched with 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 secondary island 10, and 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 secondary beam 15, a detection electrode 16, a driving electrode 17 and a grounding electrode 18. The resonant secondary beam 15 is driven by the driving electrode 17 to make the resonant main beam 14 generate an initial vibration amplitude. The lower pressure-sensing layer 6 includes a lower pressure film 20 and a lower pressure-sensing layer movable structure release groove 19. The peripheral portion of the lower pressure film 20 is bonded to the glass layer 7 to fix the entire sensor core. The glass layer 7 fixes the above layer structure and allows the gas (liquid) below to pass through the glass layer vent 21, so that the lower pressure-sensing film 20 is sensitive to the medium pressure and produces a corresponding displacement change.

[0044] See also Figures 1 to 8The upper pressure-sensitive layer 3 is made of single crystal silicon material with a thickness of 500 microns. An upper pressure-sensitive film 2 is formed on one side of the upper pressure-sensitive layer. The film has a thickness of tens of microns. Its size and shape are precisely controlled by micromachining technology to improve the sensitivity to pressure changes. The balanced silicon island layer 4 is located below the upper pressure-sensitive layer 3 and is tightly bonded to the upper pressure-sensitive layer by direct bonding technology. This layer includes multiple island structures, each of which is formed by wet etching technology to ensure the stability of the structure. The resonant layer 5 is located below the balanced silicon island layer 4 and includes a resonant main beam 14, a resonant sub-beam 15, and a detection electrode 16 connected thereto. These structures are precisely processed by micro-electromechanical system (MEMS) technology to achieve precise control of the resonant frequency. The resonant main beam 14 and the resonant sub-beam 15 of the resonant layer 6 are formed by micromachining technology. They are mechanically coupled by a specific design so as to produce predictable resonant frequency changes when subjected to pressure changes. When the upper pressure-sensitive layer 3 senses changes in external pressure, the pressure is transmitted to the balanced silicon island layer 4 through the upper pressure-sensitive film 2, and further transmitted to the resonant layer 6. The lower pressure-sensing layer 6 is located below the resonance layer 5 and is tightly bonded to the resonance layer through 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-sensitive layer 3, the balanced silicon island layer 4, the resonant layer 5 and the lower pressure-sensitive layer 6 are tightly combined by high-temperature bonding technology to ensure the integrity and stability of the sensor. Electrode hole production: Electrode holes are formed on the balanced silicon island layer 4 and the lower pressure-sensitive 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 in a high static pressure environment, the upper pressure-sensitive layer 3 and the lower pressure-sensitive layer 6 respectively sense the pressure changes, and the pressure changes are converted into stress changes through the upper pressure-sensitive film 2 and the lower pressure-sensitive film 20. The stress changes are transmitted by the upper main island 8 and the lower main island 9 of the balanced silicon island layer 4 to balance the stress changes transmitted by the static pressure. The secondary island 10 transmits the differential pressure stress changes to the cover plate 13 and drives it to rotate, thereby transmitting the stress changes caused by the differential pressure to the resonant main beam 14. The resonant main beam 14 and the resonant secondary beam 15 generate corresponding vibrations according to the stress changes. The detection electrode 16 outputs the corresponding electrical signal according to the vibration frequency changes of the resonant main beam 14 and the resonant secondary beam 15, and performs signal processing through an external circuit to finally obtain the differential pressure value.

[0047] See also Figures 10 to 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 at 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-sensitive layer 3 and the lower pressure-sensitive layer 6 are optimized to ensure that under high static pressure conditions, 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-sensitive layer increases, the ability of the whole 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-sensitive layer 3 and the lower pressure-sensitive layer 6 should be 500μm, and it is in line with the thickness size of existing common silicon wafers. A special pressure transmission mechanism is designed. By balancing the stepped structure of the silicon island layer 4, the pressure change felt by the upper pressure-sensing layer 3 is effectively converted into the resonant frequency change of the resonance layer 6, thereby improving the differential pressure sensitivity and enhancing the stability and reliability of the sensor in a complex pressure environment. The thickness of the resonance layer 6 is closely related to the differential pressure sensitivity. In order to ensure accurate sensitivity to the differential pressure under high static pressure load, the thickness of the resonance layer 6 can be determined to be in the range of 60 to 70 μm after analysis and optimization. The precise matching of the upper pressure-sensing film 2 and the lower pressure-sensing film 20 not only enhances the consistency of pressure transmission, but also reduces the static pressure error caused by structural asymmetry. In terms of material selection, single crystal silicon is selected as the main material of the upper pressure-sensing layer 3 and the lower pressure-sensing layer 6 due to its excellent mechanical properties and stable chemical properties; its high elastic modulus and low temperature coefficient ensure that the sensor can still maintain high precision and long-term stability under high static pressure environment. The selection of the glass layer 7 takes into account its good sealing and light transmittance. In terms of processing technology, advanced micro-machining technology and MEMS technology are widely used in the manufacturing process of sensors. From the high temperature processing technology of interlayer bonding to the wet etching of electrode holes, we strive for precision, especially the fine processing of the resonance main beam 14, the resonance sub-beam 15, the detection electrode and the driving electrode in the resonance layer 5, which determines the resonance frequency and detection accuracy of the sensor. The application of micro welding technology ensures the reliable connection between the electrode and the external circuit, reducing the 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 of 30MPa and differential pressure of 300kPa, Fig.11 The displacement deformation cloud diagram shown intuitively displays the displacement deformation of the balanced silicon island layer 4 and the resonance layer 5, verifying the effectiveness and rationality of the structural design. Fig.12The static pressure error curve in further proves the low static pressure error characteristics of the sensor under a large static pressure range of 15MPa, indicating that it has good anti-static pressure interference ability. Fig.13 The differential pressure sensitivity curve clearly shows 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 show that the sensor provided by the present invention can sense pressure changes through the upper and lower pressure-sensitive layers in a high static pressure environment, and accurately measure the differential pressure value through the change in the resonant frequency of the resonant layer, while achieving performance optimization of low static pressure error. The sensor of the present invention 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 a reliable and accurate differential pressure measurement solution. By adopting advanced micromachining technology, the sensor of the present invention can be miniaturized and produced at low cost, while ensuring long-term stability and repeatability.

[0050] The above embodiments are only preferred embodiments of the present invention and cannot 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 present invention.

Claims

1. A low static pressure error resonant differential pressure sensor for high static pressure environment, characterized in that An upper pressure-sensitive layer, a balanced silicon island layer, a resonance layer, a lower pressure-sensitive layer and a glass layer are sequentially arranged from bottom to top; The upper pressure-sensitive layer is bonded to the upper part of the balanced silicon island layer, the upper pressure film of the upper pressure-sensitive layer is located on one side, and the upper pressure film of the upper pressure-sensitive layer matches the position of the upper main island of the balanced silicon island layer to ensure the consistency and accuracy of pressure transmission; The balanced silicon island layer comprises an upper main island, a lower main island and an auxiliary island, as well as four electrode holes for electrical connection with the resonance layer; the balanced silicon island layer is tightly combined with the resonance layer to balance the stress changes transmitted by the static pressure and transmit the differential pressure stress changes to the resonance layer; the auxiliary island is on the same side as the lower main island, and the four electrode holes are distributed at the tail end of the layer structure and correspond to the resonance layer electrode structure, and the electrical connection with the resonance layer is achieved through the electrode holes; the release groove of the movable structure of the balanced silicon island layer is used to bond and fix the resonance layer and allow the main beam to have space for free vibration; 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 grounding electrode. The main beam and the sub-beam are connected to each other. The driving electrode is used to drive the resonant sub-beam to make the main beam generate an initial vibration amplitude. According to different output frequencies under different pressures, the signal is detected by the detection electrode. The balancing mass block is located between the upper pressure membrane and the upper main island, and is used to balance and transmit stress to ensure the stability and accuracy of the sensor in a high static pressure environment. The lower pressure-sensing layer includes a lower pressure film and a release groove for a movable structure of the lower pressure-sensing layer. The peripheral portion of the lower pressure film is bonded to the glass layer to fix the entire sensor core, thereby 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 the auxiliary beam of the resonance layer; The glass layer is used to fix the upper pressure-sensitive layer, the balanced silicon island layer, the resonant layer, and the lower pressure-sensitive layer structure. The glass layer is provided with glass layer vents, which are used for the entry of gas (liquid) below, so that the lower pressure-sensitive membrane is sensitive to the medium pressure and produces corresponding displacement changes.

2. A low static pressure error resonant differential pressure sensor for high static pressure environment as claimed in claim 1, characterized in that The upper pressure film of the upper pressure-sensitive 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 environment as claimed in claim 1, characterized in that The upper pressure-sensitive layer is made of single-crystal silicon material with 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 environment 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 environment 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 environment 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 environment as claimed in claim 1, characterized in that High-temperature bonding technology is used to achieve close bonding between the layers, ensuring the integrity and stability of the sensor.

8. A low static pressure error resonant differential pressure sensor for high static pressure environment as claimed in claim 1, characterized in that The electrode hole is made by wet etching technology and is used to connect to an external circuit.

9. A low static pressure error resonant differential pressure sensor for high static pressure environment as claimed in claim 1, characterized in that The electrodes of the resonance layer are connected to an 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 environment as claimed in claim 1, characterized in that The thickness of the resonance layer is between 60 and 70 μm.

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