Electrically isolated resonant micromechanical accelerometer
By setting an electrically isolated structure on the outside of the mass block of the resonant micromechanical accelerometer, the interference of bias electrostatic force is eliminated, which improves the accuracy and linearity of acceleration detection and solves the nonlinearity problem caused by electrostatic force in traditional designs.
Patent Information
- Application Number
- CN202610397693.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2025-07-14
- Filing Date
- 2026-03-30
- Publication Date
- 2026-05-15
AI Technical Summary
Traditional resonant micromechanical accelerometers are susceptible to interference from bias electrostatic forces at high accelerations, leading to nonlinearity and decreased detection accuracy.
An electrical isolation structure is set on the outside of the mass block to ensure electrical isolation and the same potential as the mass block, eliminating the bias electrostatic force caused by the potential difference, and transmitting the inertial force to the resonant unit through the force transmission component, thereby improving the linearity of the acceleration-frequency conversion.
It effectively blocks the interference of bias electrostatic force on the displacement of the mass block, improves the accuracy and linearity of acceleration detection, and reduces zero bias temperature drift.
Smart Images
Figure CN122043006A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of microelectromechanical technology, and in particular to an electrically isolated resonant micromechanical accelerometer. Background Technology
[0002] Resonant micromechanical accelerometers have attracted much attention in high-performance inertial navigation, geological exploration, and precision control fields due to their advantages such as direct frequency signal output, strong anti-interference capability, and large dynamic range. The core principle of resonant micromechanical accelerometers is to convert the input acceleration into the characteristic frequency shift of the resonant unit for detection.
[0003] In the design of traditional resonant micro-mechanical accelerometers, the micromechanical structure is typically constructed using deep silicon etching. To ensure etching tolerance, the etching gap is often limited, which can easily lead to a potential difference between the resonant micro-mechanical accelerometer and the surrounding fixed area, resulting in unintended bias electrostatic forces. In particular, as the input acceleration increases, the mass structure in the resonant micro-mechanical accelerometer deviates from its initial equilibrium position, and the electrostatic forces on both sides cannot completely cancel each other out. This generates additional bias forces, causing nonlinearity. Summary of the Invention
[0004] To address the existing technical problems, this application provides an electrically isolated resonant micromechanical accelerometer that can effectively eliminate bias electrostatic interference and improve measurement accuracy and linearity.
[0005] This application provides an electrically isolated resonant micromechanical accelerometer, comprising: Substrate; An anchoring platform is disposed above the substrate, and the anchoring platform is connected to the substrate through an anchoring part; A mass block is connected to the anchoring platform via a cantilever support assembly, which suspends the mass block above the substrate. An acceleration detection component includes a resonant unit and an electrode group corresponding to the resonant unit; A force transmission component connects the mass block and the resonant unit; An electrical isolation structure is disposed on the outside of the mass block and is electrically isolated from the mass block, wherein the electrical isolation structure has the same potential as the mass block. The mass block generates an X-axis displacement under the action of acceleration. The force transmission component transmits the X-axis displacement of the mass block to the resonant unit to change the Y-axis vibration frequency of the resonant unit. The acceleration is determined based on the vibration frequency of the resonant unit.
[0006] The electrically isolated resonant micromechanical accelerometer provided in the above embodiments, by setting an electrically isolated structure on the outside of the mass block, is electrically isolated from the mass block and has the same potential as the mass block. In this way, the electrically isolated structure can eliminate the parasitic bias electrostatic force generated by the potential difference between the mass block and external fixed structures, such as electrodes, substrates, ground planes, or silicon structures housing the electrically isolated resonant micromechanical accelerometer, so as to avoid the bias electrostatic force interfering with the displacement of the mass block and physically blocking the interference path. Since the bias electrostatic force is eliminated, the displacement of the mass block can be dominated by inertial force only. The axial force transmitted to the resonant unit through the force transmission component can correspond to the acceleration more accurately, thereby improving the linearity of acceleration-frequency conversion and thus improving the detection accuracy. Attached Figure Description
[0007] Figure 1 This is a top view of an electrically isolated resonant micromechanical accelerometer provided in one embodiment.
[0008] Figure 2 for Figure 1 The diagram shows a three-dimensional view of an electrically isolated resonant micromechanical accelerometer.
[0009] Figure 3 for Figure 1 The figure shows a three-dimensional cross-sectional view of an electrically isolated resonant micromechanical accelerometer.
[0010] Figure 4 This is a schematic diagram of the structure of a cantilever support assembly provided in one embodiment.
[0011] Figure 5 for Figure 4 The displacement distribution diagram of the cantilever support assembly is shown.
[0012] Figure 6 This is a schematic diagram of the force transmission component provided in one embodiment.
[0013] Figure 7 for Figure 6 A schematic diagram of the lever section in the force transmission assembly shown.
[0014] Figure 8 for Figure 7 The displacement distribution diagram of the lever section is shown.
[0015] Figure 9 This is a schematic diagram of the structure of the resonant unit in the acceleration detection component in one embodiment.
[0016] Figure 10 This is a schematic diagram of the acceleration detection component in one embodiment.
[0017] Figure 11 for Figure 10 The displacement distribution diagram of the acceleration detection component is shown.
[0018] Figure 12 This is a diagram showing the axial sensitive mode displacement distribution of an electrically isolated resonant micromechanical accelerometer in one embodiment.
[0019] Figure 13 This is a top view of an electrically isolated resonant micromechanical accelerometer in another embodiment.
[0020] Figure 14 for Figure 13 The displacement distribution diagram of the acceleration detection component in the electrically isolated resonant micromechanical accelerometer is shown.
[0021] Figure 15 for Figure 13 The diagram shows the structure of the acceleration detection component in the electrically isolated resonant micromechanical accelerometer.
[0022] Figure 16 This is a schematic diagram of an electrically isolated structure in one embodiment.
[0023] Figure 17 This is a schematic diagram of the electrical isolation structure in another embodiment.
[0024] Figure 18 This is a top view of an electrically isolated resonant micromechanical accelerometer in another embodiment.
[0025] Figure 19 This is a top view of an electrically isolated resonant micromechanical accelerometer in another embodiment. Detailed Implementation
[0026] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.
[0027] To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings. The described embodiments should not be regarded as limitations on this application. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0028] In the following description, the phrase "some embodiments" refers to a subset of all possible embodiments. It should be noted that "some embodiments" can be the same subset or different subsets of all possible embodiments, and can be combined with each other without conflict.
[0029] In the following description, the terms "first, second, and third" are used merely to distinguish similar objects and do not represent a specific ordering of objects. It is understood that "first, second, and third" may be interchanged in a specific order or sequence where permitted, so that the embodiments of this application described herein can be implemented in an order other than that illustrated or described herein.
[0030] In the design process of the micromechanical accelerometer, the inventors of this application conducted the following research to address the shortcomings of existing micromechanical accelerometers: In existing technologies, micromechanical accelerometers are primarily constructed using deep silicon etching. The mass block, serving as the main movable structure of the micromechanical accelerometer, is connected to a DC bias potential. A potential difference exists between the mass block and the surrounding fixed area, resulting in an unexpected bias electrostatic force. Whether using a symmetrically distributed single-mass or dual-mass structure, at zero input acceleration, because the applied bias forces are equal in magnitude and opposite in direction, zero bias is not generated. However, as the input acceleration increases, the mass block often deviates from its equilibrium position, and the bias electrostatic forces on both sides cannot completely cancel each other out. This generates additional bias force, easily leading to nonlinearity. For dual-mass structures, the bias electrostatic force can also cause a large zero bias, significantly interfering with the mass block's displacement response along the sensitive axis, thus affecting the linearity and detection accuracy of the acceleration-frequency conversion. The inventors of this application propose setting an equipotential, electrically isolated structure on the outside of the mass block. This equipotentiality eliminates the parasitic bias electrostatic force generated by the potential difference in the mass block, physically blocking the interference path to the mass block's displacement response.
[0031] Please see Figure 1 and Figure 2 One embodiment of this application provides an electrically isolated resonant micromechanical accelerometer, comprising: a substrate 10; an anchoring platform 20 disposed above the substrate 10, the anchoring platform 20 being connected to the substrate 10 via an anchoring part 21; a mass block 50 connected to the anchoring platform 20 via a cantilever support assembly 40, the cantilever support assembly 40 suspending the mass block 50 above the substrate 10; an acceleration detection assembly 70, including a resonant unit 703 and an electrode group 704 corresponding to the resonant unit 703; a force transmission assembly 60 connecting the mass block 50 and the resonant unit 703; and an electrically isolated structure 80 disposed outside the mass block 50 and electrically isolated from the mass block 50, the electrically isolated structure 80 having the same applied potential as the mass block 50. The mass block 50 generates an X-axis displacement under acceleration, and the force transmission assembly 60 transmits the X-axis displacement of the mass block 50 to the resonant unit 703 to change the Y-axis vibration frequency of the resonant unit 703, thereby determining the acceleration based on the vibration frequency of the resonant unit 703.
[0032] The substrate 10 serves as the supporting structure for the electrically isolated resonant micromechanical accelerometer. Anchoring platform 20 is located above substrate 10. Anchoring portion 21 and anchoring platform 20 are situated on the same structural layer. Anchoring platform 20 is connected to substrate 10 via anchoring portion 21, forming a rigid platform structure suspended above substrate 10. In this embodiment, anchoring portion 21 is a single-point anchoring region located at the geometric center of anchoring platform 20. The planar area of anchoring platform 20 is not less than five times the planar area of anchoring portion 21. The single-point anchoring portion 21 on anchoring platform 20 avoids uneven mechanical stress distribution. During temperature changes, the overall structure of the electrically isolated resonant micromechanical accelerometer can thermally expand almost freely within the plane, uniformly releasing thermal stress, reducing zero-bias temperature drift, and minimizing zero-bias error. Furthermore, it overcomes the structural asymmetry introduced by the manufacturing process tolerance of multi-anchor-point architectures, resulting in greater overall rigidity of anchoring platform 20 and more effective isolation of external mechanical strain.
[0033] Please see Figure 3 The substrate 10 includes a support base 11 and a support column 12 disposed on the support base 11. The support column 12 is connected between the anchoring part 21 and the substrate 10. The anchoring platform 20 is anchored to the substrate 10 only through the support column 12, and is suspended above the substrate 10.
[0034] An electrical isolation structure 80 is disposed on the outside of the mass block 50, electrically isolating the mass block 50 from the external fixed structure 90, and is connected to the same potential as the mass block 50 to eliminate the bias electrostatic force generated by the potential difference in the mass block 50. In an optional example, both the electrical isolation structure 80 and the mass block 50 are silicon structures. The electrical isolation structure 80 can be formed on the outside of the mass block 50 by etching a hollow space that penetrates the upper and lower surfaces of the mass block 50 along its thickness direction. The electrical isolation structure 80 can be connected to the same DC bias current as the mass block 50, thereby maintaining equipotential with the mass block 50.
[0035] In the above embodiments, the electrically isolated resonant micromechanical accelerometer has an electrically isolated structure 80 on the outside of the mass block 50. The electrically isolated structure 80 is electrically isolated from the mass block 50 and has the same potential as the mass block 50. In this way, the electrically isolated structure 80 can eliminate the parasitic bias electrostatic force generated by the potential difference between the mass block 50 and the external fixed structure 90, such as electrodes, substrates, ground planes, or silicon structures housing the electrically isolated resonant micromechanical accelerometer, so as to avoid the bias electrostatic force interfering with the displacement of the mass block 50 and physically block the interference path. Since the bias electrostatic force is eliminated, the displacement of the mass block 50 can be dominated by inertial force only. The axial force transmitted to the resonant unit 703 through the force transmission component 60 can correspond to the acceleration more accurately, thereby improving the linearity of the acceleration-frequency conversion and thus improving the detection accuracy.
[0036] In some embodiments, the mass block 50 is arranged around the periphery of the anchoring platform 20; multiple cantilever support assemblies 40 are symmetrically arranged on opposite sides of the anchoring platform 20. The anchoring platform 20 and the mass block 50 are arranged at inner and outer intervals, and multiple cantilever support assemblies 40 are located on the outer periphery of the anchoring platform 20, connecting the anchoring platform 20 and the mass block 50. Each cantilever support assembly 40 can be various known beam structures, such as straight beams, bent beams, or folded beams. In this embodiment, there are four cantilever support assemblies 40, respectively located at the four corners of the outer periphery of the anchoring platform 20. The mass block 50 has corresponding notches at the positions of the cantilever support assemblies 40, and the cantilever support assemblies 40 are located within the notches and connected between the anchoring platform 20 and the mass block 50.
[0037] Please refer to the following: Figure 4 and Figure 5Each cantilever support assembly 40 includes anchor beams 41 and movable beams 42 spaced apart from each other, a node beam 43 connecting one end of the anchor beams 41 and movable beams 42, and an output beam 44 extending outward from the end of the movable beam 42 away from the node beam 43. The anchor beams 41 and movable beams 42 extend along the Y-axis, the end of the anchor beam 41 away from the node beam 43 is connected to the anchoring platform 20, and the output beam 44 is connected to the mass block 50. There can be one or more anchor beams 41 and movable beams 42, which are arranged parallel and spaced apart. The node beam 43 connects the same end of the anchor beams 41 and movable beams 42, forming a U-shape. In this embodiment, there are two anchor beams 41 and two movable beams 42. The movable beams 42 are arranged outside the anchor beams 41. The output beams 44 bend outward from the end of the movable beams 42 away from the node beams 43. The two middle anchor beams 41 are connected to the anchoring platform 20, and the two output beams 44 on both sides extend vertically outward from the ends of the movable beams 42. The output beams 44 are parallel to the node beams 43 and are connected to the mass blocks 50 respectively. When an axial acceleration is input, the displacement distribution of the cantilever support assembly 40 is as follows: Figure 6 As shown, the displacement response at the location of the output beam 44, which is directly connected to the mass block 50, is the maximum value, while the displacement response at the end of the anchor beam 41, which is connected to the anchoring platform 20, transmitted to the anchoring platform 20 through the cantilever support assembly 40, is the minimum value. Therefore, the cantilever support assembly 40 allows the mass block 50 to be suspended relative to the substrate 10 and controls the sensitive axis direction of the mass block 50, which is the X-axis. Under the same acceleration, the displacement response of the mass block 50 along the X-axis is much greater than that along the Y-axis.
[0038] The mass block 50 is connected to the anchoring platform 20 via the cantilever support assembly 40 and is configured to generate a displacement response along the X-axis under the action of acceleration in the X-axis direction. This displacement is converted into an axial force by the force transmission assembly 60 and transmitted to the acceleration detection assembly 70.
[0039] In some embodiments, the acceleration detection component 70 includes a first acceleration detection component 71 and a second acceleration detection component 72 symmetrically disposed on both sides of the anchoring portion 21; in each acceleration detection component 70, the resonant unit 703 includes a resonant beam extending along the X-axis direction, and electrode groups 704 are disposed on both sides of the resonant beam and parallel to the resonant beam, the electrode groups 704 and the resonant unit 703 forming a variable capacitor structure. The resonant beam can refer to a single beam or a combination of multiple beams; it can be a straight beam or a bent beam; it can be various resonator structures that generate resonance by deforming in the Y-axis direction under the action of the axial force transmitted by the force transmission component 60 based on the X-axis displacement of the mass block 50, thereby realizing the conversion of acceleration to frequency.
[0040] Please refer to the following: Figure 6 and Figure 7 The force transmission component 60 includes a first force transmission component 61 corresponding to the first acceleration detection component 71 and a second force transmission component 62 corresponding to the second acceleration detection component 72. Each force transmission component 60 includes a resonant beam support 601 and two levers 602 connected to both ends of the resonant beam support 601. Each lever 602 includes a lever arm 6021, a lever input beam 6022, a lever output beam 6023, and a lever anchoring beam 6024 disposed on the lever arm 6021. The lever anchoring beam 6024 connects the lever arm 6021 to the resonant beam support 601, the lever input beam 6022 connects the lever arm 6021 to the mass block 50, and the lever output beam 6023 connects the lever arm 6021 to the anchoring platform 20. Taking the first force transmission component 61 as an example, ... Figure 7 As shown, the first force transmission component 61 includes two symmetrically arranged lever parts 602 and a resonant beam support part 601. Figure 7 As shown, each lever portion 602 includes a lever arm 6021 constituting the main body of the lever portion 602. The lever input beam 6022, lever output beam 6023, and lever anchoring beam 6024 are all located on the same side of the lever arm 6021 (the same side in the Y-axis direction). Specifically, the lever portion 602 and the resonant beam support portion 601 are arranged along the Y-axis direction. The lever input beam 6022 and the lever output beam 6023 are located at opposite axial ends of the lever arm 6021. The lever input beam 6022 is connected to the mass block 50, and the lever output beam 6023 is connected to the resonant beam support platform. The resonant beam support platform serves as a transition structure between the lever portion 602 and the resonant unit 703 in the acceleration detection assembly 70. In each force transmission assembly 60, the two lever portions 602 are symmetrically arranged, which can counteract Y-axis displacement and avoid applying additional Y-axis force to the resonant unit 703. The lever anchor beam 6024 is positioned between the lever input beam 6022 and the lever output beam 6023 along the length of the lever arm 6021, i.e. along the Y-axis, and is fixed by the anchoring platform 20. The width of the lever arm 6021 is significantly greater than the widths of the lever input beam 6022, the lever anchor beam 6024, and the lever output beam 6023.
[0041] When an axial acceleration is input, the displacement of the lever 602 is as follows: Figure 8 As shown, the X-axis displacement of mass block 50 is converted into an axial force acting on the resonant beam support platform. The formula for calculating the magnitude of the axial force transmitted from the X-axis displacement to the resonant unit 703 by force transmission component 60 is shown in Formula 1 below: (Formula 1) Among them, F out L represents the magnitude of the axial force. in The distance L between the lever anchor beam 6024 and the lever input beam 6022 outThe distance L between the lever anchor beam 6024 and the lever output beam 6023 is specified. In the force transmission assembly 60, the structural design of the lever portion 602 amplifies the force by adjusting the distance L between the lever anchor beam 6024 and the lever input beam 6022. in The distance L between the lever anchor beam 6024 and the lever output beam 6023. out It can change the magnitude of the axial force applied to the resonant unit 703 in the acceleration detection component 70.
[0042] The first acceleration detection component 71 and the second acceleration detection component 72 are arranged symmetrically with respect to the anchoring part 21. Please refer to the following reference. Figures 9 to 11 Taking the first acceleration detection component 71 as an example, the resonant unit 703 includes a resonant beam arranged along the X-axis direction. Its first end along the X-axis direction is fixed to the anchoring platform 20, and its second end is connected to the mass block 50 through the force transmission component 60. The electrode group 704 is arranged correspondingly to the resonant unit 703, including a driving electrode 7041 and a detection electrode 7042. The total effective facing area of the detection electrode 7042 and the resonant beam is greater than the total effective facing area of the driving electrode 7041 and the resonant beam.
[0043] like Figure 9 and Figure 11As shown, the resonant beam includes a first resonant beam 7031, a second resonant beam 7032 disposed on both sides of the first resonant beam 7031 and parallel to the first resonant beam 7031, and a central boss 7034 connecting the first resonant beam 7031 and the second resonant beam 7032; the opposite ends of the first resonant beam 7031 are respectively connected to the force transmission component 60 and the anchoring platform 20. The resonant unit 703 also includes a first comb portion 7033 disposed on the second resonant beam 7032, the first comb portion 7033 including a plurality of first teeth 7035 extending outward from the second resonant beam 7032 along the Y-axis direction, and arranged at intervals along the length direction of the second resonant beam 7032. Electrode group 704 includes a second comb tooth portion 7043 corresponding to the first comb tooth portion 7033. The second comb tooth portion 7043 includes second teeth 7045 that are interleaved and spaced apart from the first teeth 7035. The second comb tooth portion 7043 on the detection electrode corresponds to the first comb tooth portion 7033 at both ends of the second resonant beam 7032, and the second comb tooth portion 7043 on the driving electrode 7041 corresponds to the first comb tooth portion 7033 in the middle of the second resonant beam 7032. In this embodiment, the resonant beam is formed as a composite structure, and its central region is configured with a comb tooth array composed of multiple first teeth 7035. The aspect ratio of the first resonant beam 7031 is ≥80:1. The comb tooth array is composed of no less than 10 (N≥10) thin beams arranged periodically along the X-axis direction. Each comb-tooth beam is oriented along the Y-axis with an aspect ratio ≥ 5:1. The spacing between adjacent beams (i.e., adjacent first teeth 7035) is 5~20 μm. The comb array is fixed on the second resonant beam 7032, thus the second resonant beam 7032 can serve as the ridge of multiple first teeth 7035. The ridge is connected to the central boss 7034 of the first resonant beam 7031. Sliding comb arrays are arranged on both opposite sides of the resonant beam. The vibration displacement distribution of the resonant unit is as follows: Figure 12 As shown.
[0044] The resonant frequency f0 of the resonant unit 703 can be calculated using the following formula: (Formula 2) Wherein, keff is the effective stiffness of the resonant unit 703, which is related to the dimensional parameters of the resonant beam (thickness t, width w, length l) and is modulated by the axial external force Fx. It should be noted that the axial external force here refers to the magnitude F of the axial force F that the force transmission component 60 transmits the X-axis displacement to the resonant unit 703. out When the resonant beam is subjected to tensile axial force, keff increases (positive in Formula 2); when subjected to compressive axial force, keff decreases (negative in Formula 2). meff is the effective mass, which is related to the size parameters of the resonant beam, the material density ρ, and the total top-view projected area Sc of the resonant beam (first resonant beam 7031, central boss 7034, comb ridge and comb tooth array).
[0045] Mass block 50 is a single integral structure, and changes in its axial displacement generate axial forces that act synchronously on all resonant units 703. The displacement distribution of the axially sensitive modes of mass block 50 is as follows: Figure 12 As shown, the length changes of the resonant unit 703 in the first acceleration detection component 71 and the resonant unit 703 in the second acceleration detection component 72 are always opposite, thus causing their resonant frequencies to change in opposite directions. The frequencies of the resonant units 703 in the first acceleration detection component 71 and the second acceleration detection component 72 are subtracted, and the resonant frequency difference is used in conjunction with the axial input acceleration. a in Establish a connection. The acceleration calculation formula, based on the vibration frequency of the resonant unit 703, is shown in Formula 3 below: (Formula 3) Where λ represents the sensitivity coefficient. λ1 is the sensitivity coefficient of the resonant unit 703 in the first acceleration detection component 71, λ2 is the sensitivity coefficient of the resonant unit 703 in the second acceleration detection component 72, f01 is the resonant frequency of the resonant unit 703 in the first acceleration detection component 71, f02 is the resonant frequency of the resonant unit 703 in the second acceleration detection component 72, and Δ f For the resonant frequency difference, a in It is acceleration.
[0046] By characterizing the resonant frequency difference Δf between the resonant unit 703 in the first acceleration detection component 71 and the resonant unit 703 in the second acceleration detection component 72, the sensitivity to acceleration can be improved, the second-order nonlinear coefficient can be reduced, and common-mode errors such as residual stress and temperature drift can be eliminated.
[0047] When there is no acceleration input and the resonant frequencies of the two resonant units 703 in the first acceleration detection component 71 and the second acceleration detection component 72 are similar, a zero-position self-locking phenomenon is likely to occur. That is, when the input axial acceleration is small, the differential frequency Δf hardly changes with the input acceleration. In some embodiments, during the design phase, a resonant frequency difference is created between the two resonant units 703 in the first acceleration detection component 71 and the second acceleration detection component 72, thereby shifting the self-locking region (dead zone) to the non-working area or low-probability area of the input acceleration range.
[0048] In each acceleration detection component 70, electrode groups 704 are disposed on both sides of the corresponding resonant beam, forming a variable capacitor structure with the resonant beam. For example... Figure 10In the resonant unit 703, which is equipped with a sliding diaphragm comb tooth array (first comb tooth portion 7033), the electrode group 704 has periodically arranged finger-like / comb-like fine beams (second comb tooth portion 7043), which are arranged in an alternating parallel configuration with the comb tooth fine beams of the resonant unit 703 to realize the sliding diaphragm damping drive and detection functions. For ease of description, the comb tooth fine beams in the resonant unit 703 are referred to as the first tooth 7035, and the comb teeth of the electrode group 704 are referred to as the second tooth 7045. The electrode gap 705 between the second tooth 7045 of the electrode group 704 and the first tooth 7035 of the resonant unit 703 is formed by deep reactive ion etching process. The width of the electrode gap 705 is in the range of 2~4 μm, the aspect ratio is ≥20:1, the sidewall perpendicularity deviation of the tooth is ≤1°, and the dimensional standard deviation of the electrode gap 705 is within the range of ±0.3 μm.
[0049] The electrode group 704 adopts differential driving and differential detection. Accordingly, the driving electrode 7041 includes a positive driving electrode and a negative driving electrode respectively disposed on opposite sides of the middle of the resonant beam; the detection electrode 7042 includes two groups, respectively disposed at both ends of the resonant beam, and each group of detection electrodes 7042 includes a positive detection electrode and a negative detection electrode respectively disposed on opposite sides of the resonant beam.
[0050] by Figure 10 Taking the comb array as an example, the positive and negative driving electrodes are the positive and negative terminals of the sliding diaphragm driving electrode, respectively. The driving electrical signals applied to the positive and negative terminals of the sliding diaphragm driving electrode are out of phase, forming a differential driving electrode pair. These differential driving electrode pairs are located on opposite sides of the center line of the resonant beam. Similarly, the positive and negative detection electrodes are the positive and negative terminals of the sliding diaphragm detection electrode, respectively. The detection electrical signals extracted from the positive and negative terminals of the sliding diaphragm detection electrode are out of phase, forming a differential detection electrode pair. These differential detection electrode pairs are located on opposite sides of both ends of the resonant beam. The total number of comb teeth / electrode beams in the differential detection electrode pair is greater than the total number of comb teeth / electrode beams in the differential driving electrode pair.
[0051] Please refer to the following: Figures 13 to 15Taking the resonant unit 703, which uses a pressure-film vibrating beam, as an example, the resonant unit 703 also includes a movable electrode disposed on a single resonant beam 7037. The electrode group 704 is configured as a structure of multiple electrode pairs parallel to and opposite to the single resonant beam 7037 to realize the extrusion film damping drive and detection. The micron-level gap 7038 between the electrode group 704 and the resonant unit 703 is formed by deep reactive ion etching. The width of the micron-level gap 7038 is in the range of 2~4 μm, the aspect ratio is ≥20:1, the sidewall verticality deviation is ≤1°, and the dimensional standard deviation of the micron-level gap 7038 is ≤0.3 μm. The electrode group 704 adopts differential drive and differential detection. The drive electrode 7041 includes a positive drive electrode and a negative drive electrode disposed on opposite sides of the middle of the resonant beam. The positive drive electrode and the negative drive electrode are respectively the positive electrode and the negative electrode of the pressure-film drive electrode. The drive electrical signals applied to the positive electrode and the negative electrode of the pressure-film drive electrode are out of phase, forming a differential drive electrode pair. The detection electrodes 7042 comprise two sets, respectively located at both ends of the single resonant beam 7037. Each set of detection electrodes 7042 includes a positive detection electrode and a negative detection electrode located on opposite sides of the single resonant beam 7037. The positive and negative detection electrodes are respectively the positive and negative terminals of the pressure film detection electrode. The detection signals extracted by the positive and negative terminals of the pressure film detection electrode are out of phase, forming a differential detection electrode pair. Each differential driving electrode pair is located on both sides of the single resonant beam 7037. The total effective facing area of the differential detection electrode pair and the single resonant beam 7037 is greater than the total effective facing area of the differential driving electrode pair and the single resonant beam 7037. Compared to the sliding film drive-detection scheme, the pressure film drive-detection scheme, by adjusting the voltage difference between the electrode set 704 and the single resonant beam 7037 to control the resonant frequency, is more direct and easier to compensate for or balance the effects caused by non-ideal factors such as process errors and residual stress.
[0052] An electrical isolation structure 80 is located on the outside of the mass block 50. It can be a single unit or composed of multiple separate parts. The potential of the electrical isolation structure 80 is the same as that of the mass block 50 to prevent the external fixing structure 90 from applying an electrostatic bias force to the mass block 50.
[0053] In some embodiments, please refer to Figure 16 The electrical isolation structure 80 is an annular frame structure formed around the periphery of the mass block 50. This annular electrical isolation structure 80 isolates the entire outer periphery of the mass block 50 from the external fixing structure 90, preventing the external fixing structure 90 from applying electrostatic bias forces to the mass block 50. Optionally, the electrical isolation structure 80 can also be a separate structure; please refer to [reference needed]. Figure 17The electrically isolated structure 80 includes a first isolation part 81 and a second isolation part 82, which are respectively disposed at opposite ends in the sensitive axis direction of the mass block 50. The resonant frequency of the resonant unit is mainly affected by the displacement in the sensitive axis direction of the mass block 50, i.e., the X-axis direction. By separately disposing the first isolation part 81 and the second isolation part 82 at opposite ends in the sensitive axis direction of the mass block 50, the electrostatic bias force in the sensitive axis direction can be reduced or eliminated, and the overall size of the electrically isolated resonant micromechanical accelerometer can be reduced.
[0054] In some embodiments, such as Figure 18 As shown, the mass block 50 has an isolation groove 30 in the middle, dividing the mass block 50 into two symmetrical parts, such as a first sub-mass block 51 and a second sub-mass block 52. The mass block 50 is physically divided into two sub-mass blocks by the isolation groove 30. At this time, the resonant frequency of the resonant unit 703 in the first acceleration detection component 71 is mainly affected by the axial displacement of the first sub-mass block 51 to which it is connected, and the resonant frequency of the resonant unit 703 in the second acceleration detection component 72 is mainly affected by the axial displacement of the second sub-mass block 52 to which it is connected. In this way, the mechanical coupling strength between the resonant units 703 in the two acceleration detection components 70 is weakened, which helps to narrow the self-locking acceleration range.
[0055] In other embodiments, such as Figure 19 As shown, an isolation groove 30 is provided in the middle of the anchoring platform 20, the mass block 50, and the anchoring part 21. The anchoring platform 20, the mass block 50, and the anchoring part 21 are divided into a symmetrical first part and a second part by the isolation groove 30. For example, the mass block 50 is divided into a first sub-mass block 51 and a second sub-mass block 52; the anchoring platform 20 is divided into a first anchoring sub-platform 22 and a second anchoring sub-platform 23; and the anchoring part 21 is divided into a first sub-anchoring part 211 and a second sub-anchoring part 212. The mass block 50, the anchoring platform 20, and the anchoring part 21 are all physically separated by the isolation groove 30, compared to... Figure 18 In the structure of the embodiment shown, the coupling strength between the resonant units 703 in the first acceleration detection component 71 and the second acceleration detection component 72 is further weakened, and the self-locking range is further reduced.
[0056] It should be noted that, in an optional example, in this electrically isolated resonant micromechanical accelerometer, the anchoring platform 20, cantilever support assembly 40, mass block 50, force transmission assembly 60, and acceleration detection assembly 70 are all made of monocrystalline silicon (Si). Thus, this electrically isolated resonant micromechanical accelerometer, through a geometrically symmetrical layout and stiffness gradient design (anchoring part 21 > support column 12 > resonant unit 703), combined with monocrystalline silicon integrated molding technology, allows the single-anchor-point structure to expand freely, uniformly releasing thermal stress and reducing the zero-bias temperature coefficient to 0.5 ppm / ℃. The anchoring platform 20 is a rigid platform, effectively isolating 99% of external mechanical strain. This design overcomes the limitations of multi-anchor-point architectures and has significant application value in high-precision fields such as aerospace.
[0057] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.
Claims
1. An electrically isolated resonant micromechanical accelerometer, characterized in that, include: Substrate; An anchoring platform is disposed above the substrate, and the anchoring platform is connected to the substrate through an anchoring part; A mass block is connected to the anchoring platform via a cantilever support assembly, which suspends the mass block above the substrate. An acceleration detection component includes a resonant unit and an electrode group corresponding to the resonant unit; A force transmission component connects the mass block and the resonant unit; An electrical isolation structure is disposed on the outside of the mass block and is electrically isolated from the mass block, wherein the electrical isolation structure has the same potential as the mass block. The mass block generates an X-axis displacement under the action of acceleration. The force transmission component transmits the X-axis displacement of the mass block to the resonant unit to change the Y-axis vibration frequency of the resonant unit. The acceleration is determined based on the vibration frequency of the resonant unit.
2. The electrically isolated resonant micromechanical accelerometer according to claim 1, characterized in that, The mass block is arranged in a ring around the periphery of the anchoring platform; The cantilever support assembly comprises multiple components, symmetrically arranged on opposite sides of the anchoring platform.
3. The electrically isolated resonant micromechanical accelerometer according to claim 2, characterized in that, Each cantilever support assembly includes an anchor beam and a movable beam spaced apart from each other, a node beam connected to one end of the anchor beam and the movable beam, and an output beam extending outward from the end of the movable beam away from the node beam; The anchoring beam and the movable beam extend along the Y-axis, the end of the anchoring beam away from the node beam is connected to the anchoring platform, and the output beam is connected to the mass block.
4. The electrically isolated resonant micromechanical accelerometer according to claim 1, characterized in that, The acceleration detection assembly includes a first acceleration detection assembly and a second acceleration detection assembly symmetrically disposed on both sides of the anchoring portion; In each of the acceleration detection components, the resonant unit includes a resonant beam extending along the X-axis direction, and the electrode group is disposed on both sides of the resonant beam and parallel to the resonant beam. The electrode group and the resonant unit constitute a variable capacitor structure.
5. The electrically isolated resonant micromechanical accelerometer according to claim 4, characterized in that, The electrode assembly includes a driving electrode and a detection electrode; The total effective facing area of the detection electrode and the resonant beam is greater than the total effective facing area of the driving electrode and the resonant beam.
6. The electrically isolated resonant micromechanical accelerometer according to claim 5, characterized in that, The resonant beam includes a first resonant beam, a second resonant beam disposed on both sides of the first resonant beam and parallel to the first resonant beam, and a central boss connecting the first resonant beam and the second resonant beam; the opposite ends of the first resonant beam are respectively connected to the force transmission component and the anchoring platform. The resonant unit further includes a first comb tooth portion disposed on the second resonant beam. The first comb tooth portion includes a plurality of first teeth extending outward from the second resonant beam along the Y-axis direction and arranged at intervals along the length direction of the second resonant beam. The electrode assembly includes a second comb portion corresponding to the first comb portion. The second comb portion includes second teeth that are interleaved and spaced apart from the first teeth. The second comb portion on the detection electrode corresponds to the first comb portions at both ends of the second resonant beam. The second comb portion on the driving electrode corresponds to the first comb portion in the middle of the second resonant beam.
7. The electrically isolated resonant micromechanical accelerometer according to claim 6, characterized in that, An electrode gap is formed between the first tooth and the second tooth; The width of the electrode gap ranges from 2 to 4 μm, and the aspect ratio is ≥20:
1.
8. The electrically isolated resonant micromechanical accelerometer according to claim 5, characterized in that, The resonant unit also includes a movable electrode disposed on the resonant beam; The driving electrode includes a positive driving electrode and a negative driving electrode disposed on opposite sides of the middle of the resonant beam; the detection electrode includes two sets disposed at both ends of the resonant beam, and each set of the detection electrode includes a positive detection electrode and a negative detection electrode disposed on opposite sides of the resonant beam.
9. The electrically isolated resonant micromechanical accelerometer according to claim 4, characterized in that, The force transmission component includes a first force transmission component corresponding to the first acceleration detection component and a second force transmission component corresponding to the second acceleration detection component; Each of the force transmission components includes a resonant beam support and two levers connected to both ends of the resonant beam support. Each lever includes a lever arm, a lever input beam, a lever output beam, and a lever anchoring beam disposed on the lever arm. The lever anchoring beam connects the lever arm to the resonant beam support, the lever input beam connects the lever arm to the mass block, and the lever output beam connects the lever arm to the anchoring platform.
10. The electrically isolated resonant micromechanical accelerometer according to claim 9, characterized in that, The formula for calculating the magnitude of the axial force by which the force transmission component transmits the X-axis displacement to the resonant unit is as follows: Among them, F out L represents the magnitude of the axial force. in The distance L between the lever anchor beam and the lever input beam. out The distance between the lever anchor beam and the lever output beam; The formula for calculating acceleration based on the vibration frequency of the resonant unit is as follows: ； Where λ1 is the sensitivity coefficient of the resonant unit in the first acceleration detection component, λ2 is the sensitivity coefficient of the resonant unit in the second acceleration detection component, f01 is the resonant frequency of the resonant unit in the first acceleration detection component, f02 is the resonant frequency of the resonant unit in the second acceleration detection component, and Δ f For the resonant frequency difference, a in It is acceleration.
11. The electrically isolated resonant micromechanical accelerometer according to any one of claims 1 to 10, characterized in that, The electrical isolation structure is disposed around the periphery of the mass block; or, The electrical isolation structure includes a first sub-isolation structure and a second sub-isolation structure respectively located at opposite ends of the sensitive axis direction of the mass block.
12. The electrically isolated resonant micromechanical accelerometer according to any one of claims 1 to 10, characterized in that, The mass block has an isolation groove in its middle, dividing the mass block into two symmetrical parts; or, An isolation groove is provided in the middle of the anchoring platform, the mass block and the anchoring part, and the anchoring platform, the mass block and the anchoring part are divided into a symmetrical first part and a second part by the isolation groove.