Stress release and modal coupling mechanism and accelerometer sensitive structure
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- NAT UNIV OF DEFENSE TECH
- Filing Date
- 2025-07-11
- Publication Date
- 2026-07-21
Smart Images
Figure CN122193627B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of microelectromechanical systems manufacturing technology, and in particular to a stress relief and modal coupling mechanism and an accelerometer sensing structure. Background Technology
[0002] With the development of science and the progress of technology, accelerometers, as core inertial devices for measuring the motion parameters of objects, have received increasing attention and research.
[0003] Traditional accelerometer solutions are limited by their large size, excessive weight, and high manufacturing costs, making large-scale application difficult. However, miniature accelerometers based on microelectromechanical systems (MEMS) technology significantly reduce device size and cost through miniaturized design and mass production processes, while maintaining high reliability. They have been widely used in fields such as automotive motion control, image stabilization systems, and industrial machinery monitoring, becoming a key vehicle for the penetration of inertial sensing technology into the consumer market.
[0004] In existing technologies, MEMS accelerometers are mainly classified into piezoresistive, capacitive, and tunneling current types according to their sensing mechanisms. The detection dimensions cover single-axis to three-axis structures, and an appropriate solution needs to be selected according to the application scenario requirements.
[0005] However, despite the advantages of different technological approaches, their performance is still limited by physical principles and structural characteristics. Specifically, MEMS accelerometers employ a multilayer heterogeneous material bonding and packaging process. Mismatch in the thermal expansion coefficients of the various layers can lead to thermal mismatch stress accumulation when temperatures change. This residual stress is transmitted to the sensitive structure through elastic beams, causing drift in structural stiffness parameters and resonant frequency shifts. Consequently, this results in temperature drift in the sensor's output signal, significantly reducing the device's temperature stability and thus affecting detection accuracy. Summary of the Invention
[0006] Therefore, it is necessary to provide a stress relief and modal coupling mechanism and an accelerometer sensing structure to address the above-mentioned technical problems, which can improve the detection accuracy and temperature stability of MEMS accelerometers.
[0007] A stress relief and modal coupling mechanism and an accelerometer sensing structure include: two differential mass blocks and a stress relief component; Two differential mass blocks are distributed symmetrically along an alternate axis to form an air bandgap between them. The central axis of the air bandgap is taken as the first axis of symmetry of the sensitive structure, and an axis perpendicular to the first axis of symmetry and passing through the center of the sensitive structure is taken as the second axis of symmetry of the sensitive structure. The stress relief component is located on the first axis of symmetry and is connected to the two differential mass blocks. The stress relief assembly includes: two or more stress relief beams, two or more elastic connecting beams, four or more elastic support beams, and a compensation anchor point, to achieve stress relief and modal coupling; The stress relief beam has an "H" shaped structure, and the horizontal part of the "H" shaped structure is located on the second axis of symmetry; two or more stress relief beams are divided into two groups and are spaced apart on both sides of the first axis of symmetry. The elastic connecting beam is a strip structure perpendicular to the first axis of symmetry and is divided into two groups so that the two ends of the stress relief beam are respectively connected to the two groups of elastic connecting beams. The elastic support beam is a strip structure arranged between the two sets of stress relief beams along the direction of the first axis of symmetry, and is divided into two groups; the two sets of elastic support beams are respectively connected to the two sets of elastic connecting beams, and are both connected to the center of the stress relief assembly to form a compensation anchor point at the center of the stress relief assembly.
[0008] In one embodiment, the compensation anchor point is a rectangular structure, and the long side of the rectangular structure is parallel to the first axis of symmetry; The ratio of the length of the compensation anchor point to the length of the elastic support beam is 1:2.
[0009] In one embodiment, it further includes: an elastic coupling beam disposed on the differential mass block; The elastic coupling beam is located on the second axis of symmetry and is elastically connected to the stress relief assembly.
[0010] In one embodiment, it further includes: support anchor points and rigid support beams disposed on the differential mass block; The support anchor point is located on the second axis of symmetry and is spaced apart from the elastic coupling beam; The rigid support beam is located on the second axis of symmetry and is connected to the support anchor point, so that the support anchor point is located between the elastic coupling beam and the rigid support beam.
[0011] In one embodiment, the support anchor point is located at the center of the differential mass block.
[0012] In one embodiment, the elastic coupling beam is the same length as the rigid support beam.
[0013] In one embodiment, the differential mass block has a groove perpendicular to the plane of the differential mass block, and the grooves of the two differential mass blocks are centrally symmetrical about the compensation anchor point.
[0014] In one embodiment, a groove recessed toward the stress relief component is provided at the midpoint of the long side of the differential mass block away from the stress relief component.
[0015] In one embodiment, it further includes: a substrate and four detection electrodes arranged in a centrally symmetrical manner; The detection electrodes are disposed on the substrate and are divided into two groups corresponding to the differential mass blocks; the two detection electrodes in the same group are respectively connected to the support anchor points of the corresponding differential mass blocks.
[0016] In one embodiment, the sensitive structure is fabricated based on a monocrystalline silicon substrate or a fused silica substrate.
[0017] This application has the following beneficial effects: the aforementioned stress relief and modal coupling mechanism and accelerometer sensitive structure utilize dual differential mass blocks to achieve mass difference distribution through surface grooves, connected to support anchor points via rigid support beams; the stress relief component connects the two differential mass blocks, releasing thermal stress caused by the mismatch of material thermal expansion coefficients, while its built-in compensation anchor points adjust the torsional stiffness of the constraint system. When acceleration is input, the dual differential mass blocks generate a reverse torque pair, driving the sensitive structure to form a reverse torsional oscillation motion, achieving dual-path differential output. Attached Figure Description
[0018] Figure 1 This is a schematic diagram of the differential mass block and stress relief component of a stress relief and modal coupling mechanism and an accelerometer sensing structure in one embodiment; Figure 2 This is a schematic diagram of the detection electrode and substrate of a stress relief and modal coupling mechanism and an accelerometer sensitive structure in one embodiment.
[0019] Figure label: Differential mass block 1, elastic coupling beam 11, support anchor point 12, rigid support beam 13, groove 14, cut groove 15; Stress relief component 2, stress relief beam 21, elastic connection beam 22, elastic support beam 23, compensation anchor point 24; Detection electrode 3; Substrate 4. Detailed Implementation
[0020] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.
[0021] Furthermore, the use of terms such as "first" and "second" in this application is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of those features. In the description of this application, "multiple sets" means at least two sets, such as two sets, three sets, etc., unless otherwise explicitly specified.
[0022] In this application, unless otherwise expressly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection, an electrical connection, a physical connection, or a wireless communication connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two elements or the interaction between two elements, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.
[0023] This application provides a stress relief and modal coupling mechanism and an accelerometer sensing structure, such as Figure 1 and Figure 2 As shown, in one embodiment, it includes: a differential mass block, a stress relief assembly, a detection electrode, and a substrate.
[0024] The differential mass blocks adopt a rectangular baseline configuration design, and their geometric contours can be adaptively adjusted according to structural parameter requirements. There are two differential mass blocks, arranged in an axisymmetrically spaced manner to form an air band gap between them. The central axis of the air band gap serves as the first axis of symmetry of the sensitive structure, and an axis perpendicular to the first axis of symmetry and passing through the center of the sensitive structure serves as the second axis of symmetry. Both differential mass blocks are axisymmetrically distributed about the first and second axes of symmetry. The differential mass blocks are equipped with elastic coupling beams, support anchor points, rigid support beams, grooves, and slots.
[0025] The elastically coupled beam is located on the second axis of symmetry and is elastically connected to the stress relief assembly.
[0026] The support anchor points are located on the second axis of symmetry and are spaced apart from the elastically coupled beams.
[0027] The rigid support beam is located on the second axis of symmetry and connected to the support anchor point, so that the support anchor point is located between the elastic coupling beam and the rigid support beam, and the differential mass block forms a rigid mechanical connection with the support anchor point through the rigid support beam, and the differential mass block forms an elastic coupling with the stress relief component through the elastic coupling beam.
[0028] There are two grooves, each perpendicularly set on the plane of a differential mass block. The two grooves are centrally symmetrical about the center of the sensitive structure (which is also the intersection of the first axis of symmetry and the second axis of symmetry).
[0029] The groove is set in the non-sensitive direction of the differential mass block, specifically at the midpoint of the long side of the differential mass block away from the stress relief component, and is recessed towards the stress relief component to adjust the moment of inertia. This kind of topology adjustment can achieve synergistic optimization of the dynamic characteristics and structural parameters of the mass block while maintaining the central symmetry constraint, and is compatible with the batch micromachining process requirements such as deep reactive ion etching.
[0030] The stress relief assembly is simultaneously positioned on the first and second axes of symmetry and connected to two differential mass blocks. The stress relief assembly includes two or more stress relief beams, two or more elastic connecting beams, four or more elastic support beams, and a compensation anchor point to construct a multi-level parallel stress buffer unit and form a distributed stress distribution network. This achieves synergistic optimization of stress buffering capacity and distribution uniformity, realizing stress relief and modal coupling. Furthermore, the design of the stress relief assembly can concentrate vibrations on specific modes, thereby improving the sensor's resolution and sensitivity. Adjusting the torsional stiffness of the coupling structure reduces cross-coupling (cross-coupling refers to interference signals between different modes), thus improving the sensor's measurement accuracy and ensuring the accuracy of the measurement results.
[0031] The stress relief beam has an "H" shaped structure, with the horizontal part of the "H" shaped structure located on the second axis of symmetry. There are two or more stress relief beams, which are divided into two groups and symmetrically spaced on both sides of the first axis of symmetry.
[0032] The elastic connecting beam is a strip structure perpendicular to the first axis of symmetry and is divided into two groups so that the two ends of the stress relief beam are connected to the two groups of elastic connecting beams respectively, forming a symmetrical stress transmission path.
[0033] The elastic support beam is a strip structure set between the two sets of stress relief beams along the direction of the first axis of symmetry, and is divided into two sets; the two sets of elastic support beams are symmetrically set on both sides of the second axis of symmetry, respectively connected to the two sets of elastic connecting beams, and both are connected to the center of the stress relief component, so as to form a compensation anchor point at the center of the stress relief component (which is also the center of the sensitive structure) to ensure torsional stiffness.
[0034] There are four detection electrodes, which are centrally symmetrically distributed and integrated onto the surface of the substrate by sputtering or deposition. The four detection electrodes are divided into two groups, each corresponding to a differential mass block. The two detection electrodes in the same group are connected to the support anchor points of the corresponding differential mass blocks, so that the detection electrodes integrated on the substrate surface and the corresponding differential mass blocks form a geometrically identical electrode matching configuration. Each differential mass block is matched with two symmetrically distributed detection electrodes. Each electrode is electrically connected through a single-channel independent wiring, that is, electrically isolated through an independent interconnect channel. The geometric shape parameters of the detection electrodes correspond to and match the projected contour and dynamic displacement of the differential mass blocks to achieve precise coupling between capacitance detection and mechanical motion modes, thereby improving accuracy.
[0035] The substrate serves as a support structure, providing loading space for the detection electrodes and differential mass blocks. The substrate can be made of silicon-based or glass-based materials. The differential mass blocks and stress relief components are bonded to the substrate surface using support anchors and compensation anchors, forming an interface connection conforming to standard microelectromechanical systems (MEMS) processes. This achieves highly reliable integration of the micromechanical structure and the substrate while meeting the compatibility requirements of mass production processes. It is important to note that for different substrate materials, it is crucial to ensure that the stress matching characteristics and process compatibility of the sensitive structure meet the requirements of mass production.
[0036] Preferably, the compensation anchor point is a rectangular structure, with its long side parallel to the first axis of symmetry; the length ratio of the compensation anchor point to the elastic support beam is 1:2. This configuration enhances the fatigue resistance and long-term stability of the overall structure, ensures uniform load transfer from the anchor point to the beam, achieves structural compactness and lightweighting while meeting functional requirements, and provides good process compatibility.
[0037] More preferably, the support anchor point is located at the center of the differential mass block. That is, the spatial coordinates of the support anchor point are embedded within the geometric contour boundary of the differential mass block, and the centroid projection of the support anchor point does not exceed the geometric envelope of the differential mass block (i.e., the centroid projection of the support anchor point is always within the geometric envelope of the differential mass block). This embedded layout of the support anchor point constrains the motion degree of freedom of the differential mass block, ensuring the efficiency of mechanical transmission while avoiding mass distribution imbalance.
[0038] More preferably, the elastic coupling beam and the rigid support beam are of equal length, and both the elastic coupling beam and the rigid support beam are axially symmetrical about the first axis of symmetry; the stress relief beam has a uniform geometric configuration and is axially symmetrical about the second axis of symmetry; all elastic connecting beams are of equal length and are axially symmetrical about the second axis of symmetry to construct a stress relief structure; all elastic support beams are of equal length and are axially symmetrical about the first axis of symmetry to form a symmetrical stress transmission path; the above settings can ensure differential operation and reduce errors.
[0039] More preferably, the elastic coupling beam, rigid support beam, stress relief beam, elastic connection beam, and elastic support beam are all axially symmetrically distributed about the second axis of symmetry to form a symmetrically distributed mechanical transmission path.
[0040] More preferably, differential mass can be precisely controlled by adjusting the depth, area, and contour parameters of the groove.
[0041] In one specific embodiment, the two ends of the two stress relief beams are connected to two elastic connecting beams respectively, forming a symmetrical stress transmission path. The elastic connecting beams are connected to compensation anchor points through four elastic support beams of equal length, realizing multi-level elastic connection and constructing a gradient stress dissipation network. The stress relief component adopts a three-level series flexible stress transmission topology of stress relief beam-elastic connecting beam-elastic support beam. Among them, the stress relief beams serve as primary stress buffer units and also as main stress buffer units, the elastic connecting beams serve as secondary dissipation channels to realize stress redistribution, and the elastic support beams serve as end release nodes to complete end stress dissipation. Finally, the residual stress is introduced into the substrate through the compensation anchor points. Through the stepwise stiffness reduction design, a stress gradient attenuation mechanism is formed, which effectively reduces the coupling interference of thermal stress on the dynamic characteristics of sensitive structures, realizes gradient buffering of stress transmission path, and realizes three-level gradient dissipation and dynamic release of thermal stress along a predetermined path.
[0042] Meanwhile, the stress relief component forms adjustable constraint boundary conditions through compensation anchor points, achieving dynamic matching and real-time control with the torsional stiffness parameters of the sensitive structure (specifically, the compensation anchor points adjust the spatial distribution density and constraint strength of the anchorage area to change the equivalent stiffness matrix of the stress relief component, thereby dynamically matching the torsional stiffness requirements of the sensitive structure under different working conditions), so as to better adjust the parameters, which helps stress relief and further improves accuracy.
[0043] It should be noted that the sensitive structure is based on either a monocrystalline silicon substrate or a fused silica substrate. The monocrystalline silicon substrate is formed with a high aspect ratio through bulk silicon micromachining or deep reactive ion etching, while the fused silica substrate is formed with glass micro / nano processing technology to improve surface precision. Both material systems can be used to construct sensitive structures that meet the design requirements through differentiated process paths.
[0044] In this application, when the sensitive structure is subjected to acceleration, i.e., under acceleration excitation, the differential mass block will generate angular displacement and torsional displacement around the sensitive axis. This torsional motion causes a differential transformation in the distance between the plates of the parallel plate capacitor formed by the lower surface of the differential mass block and the detection electrodes, resulting in a change in the differential capacitance and forming dual-channel differential capacitance modulation signals (ΔC1 and ΔC2). Acceleration sensing is achieved by calculating the change in differential capacitance. Specifically, the sum of the absolute values of the two capacitance changes (|ΔC1|+|ΔC2|) is extracted by a transimpedance amplifier to eliminate nonlinear errors. At the same time, differential operations (ΔC1-ΔC2) are used to suppress common-mode interference. Finally, the acceleration vector is accurately quantized through analog-to-digital conversion and digital calculation. The above sensing mechanism achieves common-mode noise suppression through the synergistic effect of symmetrical torsional motion and dual-channel differential detection, ensuring linear response characteristics over a wide dynamic range.
[0045] The aforementioned stress relief and modal coupling mechanism and accelerometer sensing structure utilize dual differential mass blocks to achieve mass difference distribution through surface grooves, connected to support anchor points via rigid support beams. The stress relief component connects the two differential mass blocks, releasing thermal stress caused by the mismatch in the material's thermal expansion coefficients. Simultaneously, its built-in compensation anchor points adjust the torsional stiffness of the constraint system. When acceleration is input, the dual differential mass blocks generate opposing torque pairs, driving the sensing structure to form a reverse torsional oscillation motion, achieving dual-path differential output.
[0046] The sensitive structure of this application improves the detection accuracy and temperature stability of MEMS accelerometers through the asymmetric (torsional, non-axisymmetric in terms of the detection principle) mass distribution design of dual differential mass blocks and the synergistic optimization of stress relief components, providing a synergistically optimized systematic solution for high-precision inertial sensing. Specifically, through a synchronous differential detection mechanism, symmetrical torsional motion is driven by a reverse torque pair, and the phase reversal characteristics of dual-channel capacitor signals are utilized to eliminate common-mode noise introduced by mechanical vibration coupling and electromagnetic interference at the source of the signal chain, theoretically eliminating the influence of common-mode errors such as interference force and temperature. At the same time, by designing a stress relief structure, the residual thermal stress caused by the difference in the thermal expansion coefficient of materials is directionally released and dynamically dissipated along a preset path, thereby ensuring the consistency of sensor performance and significantly improving the temperature sensitivity of the elastic beam stiffness parameters. In addition, the stress relief component achieves in-situ compensation of the system's torsional stiffness through dynamic adaptation of the compensation anchor point constraint conditions, achieving synergistic optimization in stress relief and stiffness matching in high-precision inertial sensing.
[0047] The contents not described in detail in this specification are existing technologies known to those skilled in the art.
[0048] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0049] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the contents of the appended documents.
Claims
1. A stress relief and modal coupling mechanism and an accelerometer sensing structure, characterized in that, include: Two differential mass blocks and a stress relief assembly; Two differential mass blocks are distributed in an axisymmetric manner to form an air bandgap between the two differential mass blocks. The central axis of the air bandgap is used as the first axis of symmetry of the sensitive structure, and the axis perpendicular to the first axis of symmetry and passing through the center of the sensitive structure is used as the second axis of symmetry of the sensitive structure. The stress relief assembly is located on the first axis of symmetry and is connected to two differential mass blocks; The stress relief assembly includes: two or more stress relief beams, two or more elastic connecting beams, four or more elastic support beams, and a compensation anchor point, to achieve stress relief and modal coupling; The stress relief beam has an "H" shaped structure, and the horizontal part of the "H" shaped structure is located on the second axis of symmetry; two or more stress relief beams are divided into two groups and are spaced apart on both sides of the first axis of symmetry. The elastic connecting beam is a strip structure perpendicular to the first axis of symmetry and is divided into two groups so that the two ends of the stress relief beam are respectively connected to the two groups of elastic connecting beams. The elastic support beam is a strip structure arranged between the two sets of stress relief beams along the direction of the first axis of symmetry, and is divided into two sets; the two sets of elastic support beams are respectively connected to the two sets of elastic connecting beams, and are both connected to the center of the stress relief component to form a compensation anchor point at the center of the stress relief component. It also includes: an elastic coupling beam disposed on the differential mass block; The elastic coupling beam is located on the second axis of symmetry and is elastically connected to the stress relief component; It also includes: support anchor points and rigid support beams provided on the differential mass block; The support anchor point is located on the second axis of symmetry and is spaced apart from the elastic coupling beam; The rigid support beam is located on the second axis of symmetry and is connected to the support anchor point, so that the support anchor point is located between the elastic coupling beam and the rigid support beam.
2. The stress relief and modal coupling mechanism and accelerometer sensing structure according to claim 1, characterized in that, The compensation anchor point is a rectangular structure, and the long side of the rectangular structure is parallel to the first axis of symmetry. The ratio of the length of the compensation anchor point to the length of the elastic support beam is 1:
2.
3. The stress relief and modal coupling mechanism and accelerometer sensing structure according to claim 1 or 2, characterized in that, The support anchor point is located at the center of the differential mass block.
4. The stress relief and modal coupling mechanism and accelerometer sensing structure according to claim 3, characterized in that, The elastic coupling beam is the same length as the rigid support beam.
5. A stress relief and modal coupling mechanism and an accelerometer sensing structure according to claim 1 or 2, characterized in that, The differential mass block has a groove perpendicular to the plane of the differential mass block, and the grooves of the two differential mass blocks are centrally symmetrical about the compensation anchor point.
6. A stress relief and modal coupling mechanism and an accelerometer sensing structure according to claim 1 or 2, characterized in that, The differential mass block has a groove recessed towards the stress relief component at the midpoint of its long side away from the stress relief component.
7. A stress relief and modal coupling mechanism and an accelerometer sensing structure according to claim 1 or 2, characterized in that, Also includes: The substrate and four detection electrodes arranged in a centrally symmetrical manner; The detection electrodes are disposed on the substrate and are divided into two groups corresponding one-to-one with the differential mass blocks; The two detection electrodes in the same group are respectively connected to the support anchor points of the corresponding differential mass blocks.
8. A stress relief and modal coupling mechanism and an accelerometer sensing structure according to claim 1 or 2, characterized in that, The sensitive structure is prepared based on a single-crystal silicon substrate or a fused silica substrate.