Resonant micro-differential pressure sensor and preparation method thereof

Abstract

The invention provides a resonant micro-differential pressure sensor and a preparation method thereof, the resonant micro-differential pressure sensor comprises a packaging layer, a pressure sensitive film layer, a resonator layer, a sealing layer and an assembly layer which are arranged in sequence from top to bottom, and the pressure sensitive film layer is provided with a sensitive film; the packaging layer is provided with an air inlet channel, and the packaging layer and the sensitive film are stacked; the resonator layer comprises two resonators and an electrode structure, the two resonators are located in the middle area and the edge area of the sensitive film respectively, and the electrode structure is arranged on the same side of the two resonators; an air inlet structure is arranged on the assembly layer, and at least part of the air inlet structure is overlapped with the two resonators in the free direction from top to bottom; wherein the sealing layer and the resonator layer are connected through a silicon-silicon bonding process, and the sealing layer and the assembly layer are connected through an anodic bonding process; the problems that in the prior art, sensitivity is limited in the manufacturing process of a micro differential pressure sensor, thermal stress and residual stress are caused after packaging, and vacuum packaging of a resonator cannot be achieved through a silicon-silicon bonding technology are solved.

Description

Technical Field

[0001] This application relates to the field of sensor technology, and more specifically, to a resonant differential pressure sensor and its fabrication method. Background Technology

[0002] Significant progress has been made in the field of MEMS (Micro-Electro-Mechanical Systems) sensors, especially in the design and fabrication of differential pressure sensors, in recent years. Silicon resonant pressure sensors, due to their high precision, excellent stability, and near-digital output characteristics, have shown broad application prospects in various fields such as drones, airships, environmental monitoring, and medical equipment.

[0003] However, the main problems faced by existing technologies in the design and fabrication of silicon resonant differential pressure sensors are concentrated in two aspects: First, the differential pressure sensitivity is limited. Traditional packaging methods, such as using composite thin-film structures, not only bring the resonator too close to the neutral plane of the composite film, reducing stress changes, but also increase the overall thickness of the sensitive film. These two factors combined lead to a decrease in the sensor's responsivity when detecting small differential pressures, making it difficult to achieve the required high-precision measurement. Second, the packaging process introduces thermal stress and residual stress. Using techniques such as glass anodic bonding or metal eutectic bonding introduces heterogeneous materials into the core areas of the resonator and sensitive film. Due to the difference in thermal expansion coefficients, additional thermal stress and difficult-to-eliminate residual stress are generated during temperature changes. This seriously affects the accuracy and long-term stability of the resonator, limiting the overall performance of the sensor. Simultaneously, the vacuum level of silicon-silicon bonding processes is insufficient to ensure the normal operation of the resonator. Summary of the Invention

[0004] The main objective of this invention is to provide a resonant differential pressure sensor and its fabrication method, in order to solve the problems of limited sensitivity during the fabrication process of existing differential pressure sensors, thermal stress and residual stress after packaging, and insufficient vacuum in silicon-silicon bonding.

[0005] To achieve the above objectives, according to one aspect of the present invention, a resonant differential pressure sensor is provided, comprising, from top to bottom, an encapsulation layer, a pressure-sensitive membrane layer, a resonator layer, a sealing layer, and an assembly layer, wherein a sensitive membrane is disposed on the pressure-sensitive membrane layer;

[0006] An air intake channel is provided on the encapsulation layer, which is free from top to bottom. The encapsulation layer is stacked with the sensitive film so that a first pressure is applied to the first side of the sensitive film through the air intake channel.

[0007] The resonator layer includes two resonators and an electrode structure. The two resonators are located in the middle and edge regions of the sensitive film, respectively. The electrode structure is set on the same side of the two resonators to drive the two resonators to vibrate and detect the vibration frequency.

[0008] An air intake structure is provided on the assembly layer. In a free top-to-bottom direction, at least a portion of the air intake structure is stacked with two resonators to apply a second pressure to the two resonators and the second side of the sensitive membrane.

[0009] The sealing layer and the resonator layer, as well as the sealing layer and the assembly layer, are connected by a silicon-silicon bonding process.

[0010] Furthermore, the sealing layer is provided with air intake holes, and the assembly layer is provided with an adsorption area. The adsorption area is used to hold getter, and the adsorption area is connected to the air intake holes to adsorb the air between the resonator layer and the sealing layer through the air intake holes.

[0011] Furthermore, an air guide groove is provided on the sealing layer, and an adsorption hole is located on one side of the air guide groove to guide the air between the resonator layer and the sealing layer to the air intake hole through the air guide groove.

[0012] Furthermore, the intake structure includes a perforated structure, a flow channel, and a pressure hole arranged in sequence. At least a portion of the flow channel is arranged around the outer periphery of the adsorption zone. The sealing layer is also provided with a sealing perforated structure. In a free top-to-bottom direction, the sealing perforated structure is stacked with the perforated structure to apply a second pressure to the second side of the resonator and the sensitive membrane through the pressure hole.

[0013] Furthermore, at least two hollow structures are provided on the resonator layer, with the at least two hollow structures located on both sides of the two resonators respectively. Among them, there are at least two sealed hollow structures, and the at least two sealed hollow structures are provided in a one-to-one correspondence with the at least two hollow structures and are interconnected with each other.

[0014] Furthermore, two resonant cavities are provided on the resonator layer, with each cavity corresponding to one of the two resonators. Each cavity provides space for vibration of its corresponding resonator, and the two resonant cavities are connected by an electrode wire.

[0015] Furthermore, the electrode structure includes a driving electrode and a detection electrode. The driving electrode is located on the same side of the two resonators, and the detection electrode is located on the other side of the two resonators, so as to drive the two resonators to vibrate through the driving electrode and detect the vibration frequency of the two resonators through the detection electrode.

[0016] Furthermore, the pressure-sensitive membrane layer includes a buried oxide layer, which is in contact with the resonator layer, wherein the material of the buried oxide layer is silicon oxide.

[0017] Furthermore, a micro-capping layer is disposed on the resonator layer, a resonant cavity is disposed on the micro-capping layer, and a silicon oxide insulating layer is formed on the micro-capping layer, so as to form the resonant cavity by etching on the silicon oxide insulating layer.

[0018] According to another aspect of the present invention, a method for fabricating a resonant differential pressure sensor is provided, for fabricating the above-mentioned resonant differential pressure sensor, the method comprising:

[0019] S1. A first bonding component is provided, the first bonding component includes a first substrate and a pressure-sensitive film layer and a resonator layer stacked on the first substrate. The pressure-sensitive film layer has a sensitive film, and the resonator layer includes two resonators and an electrode structure. The two resonators are located in the middle region and the edge region of the sensitive film, respectively, and the electrode structure is disposed on the same side of the two resonators.

[0020] S2. A second component to be bonded is provided, wherein the second component to be bonded includes a second substrate and a sealing layer stacked on the second substrate;

[0021] S3. Using the surface of the resonator layer away from the pressure-sensitive film layer and the surface of the sealing layer away from the second substrate as the bonding interface, the first component to be bonded and the second component to be bonded are bonded, and the second substrate of the bonded structure is removed to obtain the first intermediate component.

[0022] S4. Provide a third component to be bonded, the third component to be bonded including a third substrate and an assembly layer located on the third substrate, the assembly layer having an air intake structure, at least a portion of the air intake structure being stacked with two resonators;

[0023] S5. Using the surface of the assembly layer away from the third substrate and the surface of the sealing layer away from the resonator layer as bonding surfaces, bond the third component to be bonded and the first intermediate component to obtain the resonant differential pressure sensor chip.

[0024] By applying the technical solution of this invention, through the stacked design of the encapsulation layer, pressure-sensitive film layer, resonator layer, sealing layer, and assembly layer, and by using silicon-silicon bonding technology to achieve precise connections between each layer, the measurement accuracy and reliability of the sensor are significantly improved. The combination of the sensitive film on the pressure-sensitive film layer and the air intake channel of the encapsulation layer ensures effective loading and monitoring of the first pressure, while the air intake structure of the assembly layer precisely applies a second pressure to the two resonators, achieving bidirectional vibration detection under differential pressure. The unique layout of the two resonators, located in the middle and edge regions of the sensitive film respectively, combined with the precise driving and frequency detection of the electrode structure, greatly enhances the sensor's sensitivity to minute pressure changes and frequency response characteristics. The use of silicon-silicon bonding technology not only effectively reduces the thermal stress and residual stress caused by the introduction of heterogeneous materials, ensuring the long-term stability and accuracy of the sensor, but also achieves high-vacuum encapsulation through secondary bonding, significantly reducing the impact of air damping on resonator vibration and improving the sensor's Q value and sensitivity. Furthermore, this design optimizes the signal transmission path and enhances the electric field coupling between the electrodes and resonators, thereby improving the overall signal quality and detection efficiency. Attached Figure Description

[0025] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0026] Figure 1 An exploded view of the resonant differential pressure sensor according to an embodiment of this application is shown;

[0027] Figure 2 A schematic diagram of the resonator layer structure according to an embodiment of this application is shown;

[0028] Figure 3 A schematic diagram of the sealing layer structure according to an embodiment of this application is shown;

[0029] Figure 4 A side view of a resonant differential pressure sensor according to an embodiment of this application is shown from a first perspective;

[0030] Figure 5 An embodiment of this application is shown. Figure 4 A magnified view of a portion of the image;

[0031] Figure 6 This illustration shows a side view of the resonant differential pressure sensor according to an embodiment of this application from a first-person perspective;

[0032] Figure 7 An embodiment of this application is shown. Figure 6 A magnified view of a portion of the image.

[0033] The above figures include the following reference numerals:

[0034] 100. Pressure-sensitive membrane layer; 110. Sensitive membrane; 210. Resonator layer; 211. Resonator; 213. Electrode structure; 220. Sealing layer; 221. Resonant cavity; 214. Buried oxide layer; 223. Gas guide groove; 224. Gas intake hole; 300. Assembly layer; 310. Pressure hole; 320. Flow channel; 330. Adsorption region; 340. Hollow structure; 222. Micro-sealing layer; 225. Silicon oxide insulating layer. Detailed Implementation

[0035] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0036] Significant progress has been made in the field of MEMS (Micro-Electro-Mechanical Systems) sensors, especially in the design and fabrication of differential pressure sensors, in recent years. Silicon resonant pressure sensors, due to their high precision, excellent stability, and near-digital output characteristics, have shown broad application prospects in various fields such as drones, airships, environmental monitoring, and medical equipment.

[0037] However, the main problems faced by existing technologies in the design and fabrication of silicon resonant differential pressure sensors are concentrated in two aspects: First, the differential pressure sensitivity is limited. Traditional packaging methods, such as using composite thin film structures, not only bring the resonator too close to the neutral plane of the composite film, reducing stress changes, but also increase the overall thickness of the sensitive film. The combined effect of these two factors leads to a decrease in the sensor's responsiveness when detecting small differential pressures, making it difficult to achieve the required high-precision measurement. Second, there are problems with thermal stress and residual stress caused by the packaging process. Using techniques such as glass anodic bonding or metal eutectic bonding, heterogeneous materials are introduced into the core area of ​​the resonator and the sensitive film. Due to the difference in thermal expansion coefficients, additional thermal stress and residual stress that are difficult to eliminate are generated when the temperature changes. This seriously affects the accuracy and long-term stability of the resonator and limits the overall performance of the sensor.

[0038] Therefore, the main objective of this invention is to provide a resonant differential pressure sensor to solve the problems of limited sensitivity during the fabrication process of existing differential pressure sensors, as well as the thermal stress and residual stress caused after packaging.

[0039] To address the aforementioned issues, this technical solution first provides a resonant differential pressure sensor, comprising, from top to bottom, an encapsulation layer, a pressure-sensitive membrane layer 100, a resonator layer 210, a sealing layer 220, and an assembly layer 300, wherein a sensitive membrane 110 is disposed on the pressure-sensitive membrane layer 100.

[0040] An air intake channel is provided on the encapsulation layer, which is free from top to bottom. The encapsulation layer is stacked with the sensitive film 110 so as to apply a first pressure to the first side of the sensitive film 110 through the air intake channel.

[0041] The resonator layer 210 includes two resonators 211 and an electrode structure 213. The two resonators 211 are located in the middle region and the edge region of the sensitive film 110, respectively. The electrode structure 213 is disposed on the same side of the two resonators 211 to drive the two resonators 211 to vibrate and detect the vibration frequency.

[0042] An air intake structure is provided on the assembly layer 300. In a free top-to-bottom direction, at least part of the air intake structure is stacked with two resonators 211 to apply a second pressure to the two resonators 211 and the second side of the sensitive membrane 110.

[0043] The sealing layer 220 and the resonator layer 210, and the sealing layer 220 and the assembly layer 300 are connected by silicon-silicon bonding process.

[0044] The structural layout adopted in this technical solution, especially the relative position design of the resonator layer 210 and the sensitive film 110, ensures that the resonator 211 is far away from the neutral surface of the sensitive film 110, increasing the degree of deformation under small differential pressure, thereby significantly improving the detection accuracy of the micro differential pressure sensor. The silicon-silicon bonding process is used to connect the sealing layer 220 and the resonator layer 210, as well as the sealing layer 220 and the assembly layer 300, avoiding the problem of thermal expansion coefficient mismatch caused by the introduction of heterogeneous materials. At the same time, the vacuum encapsulation of the assembly layer solves the problem of insufficient vacuum degree of low-stress silicon-silicon bonding, significantly reducing the thermal stress and residual stress level during the encapsulation process, ensuring the long-term stability and measurement accuracy of the resonator 211.

[0045] By designing two resonators 211 and placing them in the middle and edge regions of the sensitive membrane 110 respectively, and combining them with a specific air intake structure and driving electrode, the sensor can achieve bidirectional measurement of positive and negative pressure differences through the frequency changes of the two resonators 211, thus broadening the application range of the sensor.

[0046] By incorporating an air intake channel within the encapsulation layer, which works in conjunction with the air intake structure on the assembly layer 300, this invention achieves a high-vacuum seal within the resonator 211 region. This high-vacuum encapsulation environment not only reduces the impact of dielectric damping on the vibration of the resonator 211 and improves the sensor's response speed, but also enhances the overall stability of the sensor due to vibration stability under low-pressure conditions.

[0047] The silicon-to-silicon bonding process not only provides highly reliable packaging but also enhances the overall structural stability of the sensor by strengthening the connections between layers. This reinforced structural connection ensures reliable operation of the sensor under complex environmental conditions, extends its lifespan, and simplifies the sensor packaging process, avoiding the complex handling of heterogeneous materials required in traditional bonding technologies, thereby reducing the difficulty and cost of the packaging process.

[0048] Furthermore, the sealing layer 220 is provided with an air intake hole 224, and the assembly layer 300 is provided with an adsorption area 330. The adsorption area 330 is used to hold the getter, and the adsorption area 330 is connected to the air intake hole 224 so as to adsorb the air between the resonator layer 210 and the sealing layer 220 through the air intake hole 224.

[0049] This invention achieves efficient vacuuming of the space between the resonator layer 210 and the sealing layer 220 by providing an air intake hole 224 on the sealing layer 220 and effectively connecting it with the adsorption area 330 on the assembly layer 300. The high vacuum environment significantly reduces the damping effect of air molecules on the vibration of the resonator 211, improves the Q value of the resonator, and thus enhances the sensitivity and response speed of the sensor.

[0050] The design of the suction port 224 and the adsorption region 330, combined with the silicon-silicon bonding process, effectively avoids thermal stress and residual stress that are difficult to eliminate due to the introduction of foreign materials during the packaging process. This optimized packaging strategy ensures the structural stability and measurement accuracy of the resonator layer 210 under temperature changes, and extends the service life of the sensor.

[0051] The presence of the suction port 224 not only facilitates vacuum sealing but also enhances the structural seal between the resonator layer 210 and the sealing layer 220. This further improves the sensor's airtightness, prevents external gas interference, and ensures the sensor's stability and reliability in harsh environments.

[0052] The continuous action of the getter in adsorption zone 330 continuously adsorbs residual gas, maintaining a high vacuum state in the resonator region. This long-term vacuum environment optimizes the operating conditions of the resonator, significantly improving the long-term stability and measurement consistency of the sensor.

[0053] The efficient vacuuming mechanism is achieved through a simple suction port 224 and adsorption zone 330, reducing reliance on expensive vacuum packaging equipment. This not only lowers the packaging cost of the sensor but also simplifies the manufacturing process, improving production efficiency and yield.

[0054] Furthermore, the sealing layer 220 is also provided with an air guide groove 223, and the air intake hole 224 is located on one side of the air guide groove 223, so as to guide the air between the resonator layer 210 and the sealing layer 220 to the air intake hole 224 through the air guide groove 223.

[0055] This technical solution significantly optimizes the sensor's packaging process and performance by combining the air guide groove 223 and the suction port 224 on the sealing layer 220. The clever design of the air guide groove 223 guides residual air between the resonator layer 210 and the sealing layer 220, effectively directing it to the suction port 224, thus promoting the rapid formation and stable maintenance of a high vacuum state. This design not only greatly improves the sensor's sensitivity and reduces air damping effects, making the resonator's frequency response more acute under micro-differential pressure, but also effectively reduces thermal stress and residual stress during the packaging process, ensuring the long-term accuracy and stability of the resonator. Simultaneously, the combined design of the air guide groove 223 and the suction port 224 simplifies the sensor's vacuum packaging process, reduces production costs, and improves the consistency and efficiency of mass production.

[0056] Furthermore, the intake structure includes a perforated structure 340, a flow channel 320, and a pressure hole 310 arranged in sequence. At least a portion of the flow channel 320 is arranged around the outer periphery of the adsorption region 330. The sealing layer 220 is also provided with a sealing perforated structure. In the direction from top to bottom, the sealing perforated structure is superimposed on the perforated structure 340 to apply a second pressure to the second side of the resonator 211 and the sensitive membrane 110 through the pressure hole 310.

[0057] This application achieves efficient and accurate application of a second pressure to the resonator 211 by setting an air intake structure, including a hollow structure 340, a flow channel 320, and a pressure hole 310, and precisely superimposing a sealing hollow structure on the sealing layer 220. This design not only ensures uniform pressure distribution on the resonator, improving the differential pressure detection accuracy of the sensor, but also effectively isolates different pressure sources and avoids interference through the layout of the flow channel 320 around the adsorption region 330. In addition, the combination of the hollow structure 340 and the sealing hollow structure not only simplifies the pressure transmission mechanism, but also enhances the structural stability and airtightness of the entire sensor, thereby ensuring measurement reliability and long-term stability under complex environmental conditions.

[0058] Furthermore, at least two hollowed-out structures 212 are provided on the resonator layer 210. The at least two hollowed-out structures 212 are located on both sides of the two resonators 211 respectively. There are at least two sealing hollowed-out structures. The at least two sealing hollowed-out structures are provided in a one-to-one correspondence with the at least two hollowed-out structures 212 and are interconnected with each other.

[0059] This application achieves effective control and optimization of the environment surrounding the resonator 211 by setting at least two hollowed-out structures 212 on the resonator layer 210 and correspondingly setting at least two sealed hollowed-out structures on the sealing layer 220. The one-to-one correspondence of these hollowed-out and sealed hollowed-out structures not only significantly improves the mechanical stress level of the resonator and enhances the response sensitivity to differential pressure changes, but also reduces vibration inertia by decreasing the material mass near the resonator, thereby improving the frequency response speed and measurement accuracy of the sensor. Furthermore, this design moves the resonator away from the neutral plane of the composite film, further optimizing the stress distribution and ensuring high-precision detection capability under minute differential pressure changes. The interconnected design of the sealed hollowed-out structures and hollowed-out structures 212 also strengthens airflow control inside the sensor, improving airtightness and overall stability.

[0060] Furthermore, two resonant cavities 221 are provided on the resonator layer 210, and the two resonant cavities 221 correspond one-to-one with the two resonators 211. Each resonant cavity 221 is used to provide a space for vibration of its corresponding resonator 211. The two resonant cavities 221 are connected by an electrode wire.

[0061] This application employs a carefully designed system with two resonant cavities 221 on the resonator layer 210, forming a one-to-one correspondence with the two resonators 211. This provides ample vibration space for the resonators 211, significantly optimizing the sensor's micro-differential pressure detection performance. The presence of the resonant cavities 221 significantly reduces the damping of the resonators 211 during vibration, increasing their Q value and thus enhancing the sensor's sensitivity to minute pressure changes and frequency response speed. Furthermore, the two resonant cavities 221 are connected by electrode lines, enabling precise control and monitoring of the resonator 211's vibration state. This strengthens signal stability and reliability, allowing the sensor to accurately capture and distinguish between positive and negative pressure differences, further improving the measurement range and accuracy. This layout also effectively isolates the resonators 211 from the surrounding materials, reducing the impact of thermal stress and residual stress, ensuring the sensor's stability during long-term use.

[0062] Furthermore, the electrode structure 213 includes a driving electrode and a detection electrode. The driving electrode is located on the same side of the two resonators 211, and the detection electrode is located on the other side of the two resonators 211, so as to drive the two resonators 211 to vibrate through the driving electrode and detect the vibration frequency of the two resonators 211 through the detection electrode.

[0063] This application, through the designed electrode structure 213—a separate layout of the driving electrode and the detection electrode—achieves precise driving of two resonators 211 and independent detection of their vibration frequencies, significantly improving the measurement accuracy and dynamic response characteristics of the micro differential pressure sensor. The driving electrode, positioned on the same side of the two resonators 211, synchronously and evenly excites the resonators 211 to vibrate, ensuring the purity and consistency of the vibration mode and reducing measurement errors caused by non-differential pressure factors. The detection electrode, located on the other side, can capture the vibration state of the resonators 211 without interference. By comparing the frequency differences between the two resonators 211, it accurately reflects changes in differential pressure, achieving high-sensitivity detection even in extremely low differential pressure environments. This electrode structure 213 design also effectively isolates electromagnetic interference during the driving and detection processes, improving the sensor's signal quality and noise immunity. The clear division of labor between the driving and detection electrodes ensures the reliability and accuracy of the sensor in bidirectional differential pressure detection, providing strong technical support for precision instruments and high-end applications.

[0064] Furthermore, the pressure-sensitive membrane layer 100 includes a buried oxide layer 214, which is in contact with the resonator layer 210, wherein the material of the buried oxide layer 214 is silicon oxide.

[0065] This application significantly enhances the performance and reliability of the micro differential pressure sensor by integrating a buried oxide layer 214 made of silicon oxide into the pressure-sensitive membrane layer 100 and ensuring close contact with the resonator layer 210. The use of silicon oxide, with its excellent chemical and thermal stability, effectively protects the resonator layer 210 and reduces the impact of external environmental factors such as temperature changes on sensor accuracy. The contact design between the buried oxide layer 214 and the resonator layer 210 optimizes the pressure transmission path, ensuring that the stress generated when the sensitive membrane 110 deforms can be efficiently and directly transmitted to the resonator layer 210, improving the sensor's sensitivity and response speed to minute pressure changes. Furthermore, the high dielectric constant of silicon oxide enhances the electric field coupling between electrodes, improving the signal efficiency of the driving and detection electrodes, further enhancing the sensor's measurement accuracy and stability.

[0066] Furthermore, a micro-capping layer 222 is provided on the resonator layer 210, a resonant cavity 221 is provided on the micro-capping layer 222, and a silicon oxide insulating layer 225 is formed on the micro-capping layer 222, so that the resonant cavity 221 is formed by etching on the silicon oxide insulating layer 225.

[0067] This application significantly improves the structural precision and functional integration of the silicon resonant differential pressure sensor by adding a micro-capping layer 222 to the resonator layer 210 and precisely forming a silicon oxide insulating layer 225 and a resonant cavity 221 thereon. The introduction of the silicon oxide insulating layer, with its insulating properties and mechanical stability, effectively isolates the resonator 211 from direct contact with the external environment, reducing the interference of environmental factors such as humidity and impurities on the performance of the resonator 211, and enhancing the long-term stability and reliability of the sensor. The design of the resonant cavity 221 not only provides the necessary vibration space for the resonator 211, but also achieves high precision and low stress in the cavity structure through precise etching of the silicon oxide insulating layer, ensuring efficient vibration and accurate frequency response of the resonator 211 during differential pressure detection. Furthermore, the combination of the micro-capping layer 222 and the silicon oxide insulating layer 225 further optimizes the sensor's packaging process, improves the vacuum sealing effect, and reduces thermal stress and residual stress during the packaging process, playing a crucial role in improving the overall accuracy and long-term stability of the sensor.

[0068] Example 2

[0069] This application also provides a method for fabricating a resonant differential pressure sensor, used to manufacture the above-mentioned resonant differential pressure sensor. The fabrication method includes:

[0070] S1. A first bonding component is provided, which includes a first substrate and a pressure-sensitive film layer 100 and a resonator layer 210 stacked on the first substrate. The pressure-sensitive film layer 100 has a sensitive film 110. The resonator layer 210 includes two resonators 211 and an electrode structure 213. The two resonators 211 are located in the middle region and the edge region of the sensitive film 110, respectively. The electrode structure 213 is disposed on the same side of the two resonators 211.

[0071] S2. A second component to be bonded is provided, wherein the second component to be bonded includes a second substrate and a sealing layer 220 stacked on the second substrate;

[0072] S3. Using the surface of the resonator layer 210 away from the pressure-sensitive film layer 100 and the surface of the sealing layer 220 away from the second substrate as the bonding interface, the first component to be bonded and the second component to be bonded are bonded, and the second substrate of the bonded structure is removed to obtain the first intermediate component.

[0073] S4. Provide a third component to be bonded, the third component to be bonded includes a third substrate and an assembly layer 300 located on the third substrate, the assembly layer 300 has an air intake structure, at least a portion of the air intake structure is stacked with two resonators 211.

[0074] S5. Using the surface of the assembly layer 300 away from the third substrate and the surface of the sealing layer 220 away from the resonator layer 210 as bonding surfaces, the third component to be bonded and the first intermediate component are bonded to obtain the resonant differential pressure sensor chip.

[0075] First, an SOI silicon insulator substrate is selected, the structure of which includes a first substrate layer, a buried oxide layer and a device layer. Then, a region of the sensitive film 110 is formed in the device layer using dry etching technology. This region will serve as the core part of the pressure-sensitive film layer 100.

[0076] Two resonators 211 and corresponding electrode structures 213 are formed by etching on the device layer. The two resonators 211 are positioned in the middle and edge regions of the sensitive film 110, respectively, to achieve bidirectional differential pressure measurement.

[0077] The electrode structure 213 includes a driving electrode and a detection electrode, which are disposed on the same side of the two resonators 211 for driving the resonators 211 to vibrate and detecting their vibration frequency.

[0078] Another SOI substrate is selected as the second substrate, which will be used as the base for the second bonding component. A silicon oxide insulating layer 225 with a thickness of about 1 micrometer is formed on the device layer by thermal oxidation. The silicon oxide insulating layer 225 is patterned and etched to form a resonant cavity 221 corresponding to the resonator 211 region, as well as structures such as gas guide groove 223 and resonator 211, for subsequent vacuum packaging.

[0079] The side of the resonator layer 210 of the first component to be bonded that is away from the pressure-sensitive film layer 100 and the side of the sealing layer 220 of the second component to be bonded that is away from its substrate layer are used as the bonding interface. The two SOI wafers are cleaned, mega-scanned, and spun dry. After the bonding surface is activated by plasma, silicon-silicon bonding is completed at 400°C. After bonding is completed, the substrate layer of the second component to be bonded is removed by chemical mechanical polishing and other techniques to obtain the first intermediate component. At this time, the resonator layer and the sealing layer form a stable bonding structure.

[0080] BF33 glass was selected as the third substrate, on which a layer of Cr / Au metal was sputtered. Subsequently, a hollow structure 340, an adsorption region 330, and a flow channel 320 were formed through patterning and HF gas etching for secondary bonding to achieve vacuum encapsulation. Pressure holes 310 were cut out by laser processing to ensure that the getter deposition area is connected to the outside atmosphere.

[0081] Using the surface of the assembly layer 300 away from the third substrate and the surface of the sealing layer 220 away from the resonator layer 210 as bonding surfaces, the assembly layer is bonded to the first intermediate through an anodic bonding process. After the bonding process is completed, it is kept at 450°C for 40 minutes to activate the getter and promote the absorption of internal gases, thereby achieving vacuum encapsulation of the resonator 211 region, ensuring the structural integrity of the assembly layer 300 and the sealing layer 220, and finally forming a resonant differential pressure sensor chip.

[0082] Metal (such as aluminum) is evaporated in the electrode hole area to extract the electrical signal of the resonator 211 and form a connection with the external circuit. The wafer is then diced to cut it into individual sensor chips, thus completing the fabrication of the resonant differential pressure sensor.

[0083] This fabrication method ensures the precision of the sensor structure and the absence of foreign material introduction through silicon-silicon bonding technology, significantly reducing the impact of thermal and residual stress. Simultaneously, high-vacuum encapsulation is achieved through secondary bonding technology, ensuring the long-term stability and high sensitivity of the sensor. The entire process combines advanced material handling and microfabrication techniques, providing a reliable and efficient process for manufacturing high-performance resonant differential pressure sensors.

[0084] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0085] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0086] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0087] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0088] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0089] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A resonant differential pressure sensor, comprising, from top to bottom, a packaging layer, a pressure sensitive membrane layer (100), a resonator layer (210), a sealing layer (220) and an assembly layer (300), characterized in that, the pressure sensitive membrane layer (100) is provided with a sensitive membrane (110); the packaging layer is provided with an air inlet channel, in a free top-to-bottom direction, and is superimposed with the sensitive membrane (110) to apply a first pressure to a first side of the sensitive membrane (110) through the air inlet channel; the resonator layer (210) comprises two resonators (211) and an electrode structure (213), the two resonators (211) are respectively located in the middle region and the edge region of the sensitive membrane (110), and the electrode structure (213) is arranged on the same side of the two resonators (211) to drive the two resonators (211) to vibrate and detect the vibration frequency; the assembly layer (300) is provided with an air inlet structure, in a free top-to-bottom direction, and at least part of the air inlet structure is superimposed with the two resonators (211) to apply a second pressure to the second side of the two resonators (211) and the sensitive membrane (110); wherein the sealing layer (220) and the resonator layer (210), and the sealing layer (220) and the assembly layer (300) are connected by a silicon-silicon bonding process.

2. The resonant differential pressure sensor of claim 1, wherein, The sealing layer (220) is provided with an air suction hole (224), and the assembly layer (300) is provided with an adsorption area (330) for containing an air suction agent, and the adsorption area (330) is in communication with the air suction hole (224) to adsorb the air between the resonator layer (210) and the sealing layer (220) through the air suction hole (224).

3. The resonant differential pressure sensor of claim 2, wherein, The sealing layer (220) is further provided with a gas guide groove (223), and the air suction hole (224) is located on one side of the gas guide groove (223) to guide the air between the resonator layer (210) and the sealing layer (220) to the air suction hole (224) through the gas guide groove (223).

4. The resonant differential pressure sensor of claim 2, wherein, The air inlet structure comprises a hollow structure (340), a flow channel (320) and a pressure hole (310) arranged in sequence, and at least part of the flow channel (320) is arranged around the outer periphery of the adsorption area (330), wherein the sealing layer (220) is further provided with a sealing hollow structure, in a free top-to-bottom direction, and the sealing hollow structure is superimposed with the hollow structure (340) to apply the second pressure to the second side of the resonator (211) and the sensitive membrane (110) through the pressure hole (310).

5. The resonant differential pressure sensor of claim 4, wherein, The resonator layer (210) is further provided with at least two hollow structures (212), and the at least two hollow structures (212) are respectively located on both sides of the two resonators (211), wherein the sealing hollow structure is at least two, and the at least two sealing hollow structures are arranged one by one and in communication with the at least two hollow structures (212).

6. The resonant differential pressure sensor of claim 5, wherein, The resonator layer (210) is provided with two resonant cavities (221), and the two resonant cavities (221) correspond to the two resonators (211) one by one, and each resonant cavity (221) is used for providing a vibration space for the resonator (211) corresponding thereto, wherein the two resonant cavities (221) are connected through an electrode line.

7. The resonant differential pressure sensor of claim 1, wherein, The electrode structure (213) comprises a driving electrode and a detection electrode, the driving electrode is located on the same side of the two resonators (211), and the detection electrode is located on the other side of the two resonators (211), so as to drive the two resonators (211) to vibrate through the driving electrode and detect the vibration frequency of the two resonators (211) through the detection electrode.

8. The resonant differential pressure sensor of claim 1, wherein, The pressure-sensitive membrane layer (100) comprises a buried oxygen layer (214), and the buried oxygen layer (214) is in contact with the resonator layer (210), wherein the material of the buried oxygen layer (214) is silicon oxide.

9. The resonant differential pressure sensor of claim 6, wherein, The resonator layer (210) is provided with a micro-capping layer (222), the micro-capping layer (222) is provided with the resonant cavity (221), and a silicon oxide insulation layer (225) is formed on the micro-capping layer (222), so as to form the resonant cavity (221) by etching on the silicon oxide insulation layer (225).

10. A method for manufacturing a resonant micro differential pressure sensor according to any one of claims 1 to 9, characterized in that The preparation method comprises: S1, providing a first to-be-bonded part, the first to-be-bonded part comprising a first substrate and a pressure-sensitive membrane layer (100) and a resonator layer (210) stacked on the first substrate, the pressure-sensitive membrane layer (100) having a sensitive membrane (110) thereon, the resonator layer (210) comprising two resonators (211) and an electrode structure (213), the two resonators (211) being located at the middle region and the edge region of the sensitive membrane (110) respectively, and the electrode structure (213) being arranged on the same side of the two resonators (211); S2, providing a second to-be-bonded part, the second to-be-bonded part comprising a second substrate and a sealing layer (220) stacked on the second substrate; S3, taking the surface of the resonator layer (210) away from the pressure-sensitive membrane layer (100) and the surface of the sealing layer (220) away from the second substrate as a bonding interface, bonding the first to-be-bonded part and the second to-be-bonded part, and removing the second substrate of the bonded structure to obtain a first intermediate part; S4, providing a third to-be-bonded part, the third to-be-bonded part comprising a third substrate and an assembly layer (300) located on the third substrate, the assembly layer (300) having an air inlet structure, and at least part of the air inlet structure being stacked with the two resonators (211); S5, taking the surface of the assembly layer (300) away from the third substrate and the surface of the sealing layer (220) away from the resonator layer (210) as a bonding surface, bonding the third to-be-bonded part and the first intermediate part to obtain a resonant micro differential pressure sensor chip.

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