Low-stress MEMS resonant accelerometer

Abstract

The invention discloses a low-stress MEMS (Micro Electro Mechanical System) resonant accelerometer which is processed by adopting an SOG (Silicon On Glass) process, the upper layer is an accelerometer micro-mechanical sensitive structure made of monocrystalline silicon and is used for sensing external acceleration, and gold is deposited on the accelerometer micro-mechanical sensitive structure to serve as an electrode and is used for inputting and outputting signals; the lower layer is a glass substrate and is used for supporting the micromechanical sensitive structure of the upper layer. Anchor points for supporting a micro-mechanical sensitive structure and a stress release ring are symmetrically arranged, so that the residual stress generated in the sensitive axis direction of the tuning fork resonator due to mismatching of thermal expansion coefficients of materials in the machining process is reduced. And a thermal deformation matching frame is arranged, so that thermal stress generated on the tuning fork resonator due to inconsistent expansion or contraction deformation of each part of the micro-mechanical sensitive structure in the working temperature change process is reduced. According to the invention, the residual stress generated by processing and the thermal stress generated by the change of the working environment of the sensor are reduced, thereby reducing the influence of the temperature on the output frequency of the resonator, and improving the long-term stability of the output of the resonant accelerometer.

Description

Technical Field

[0001] The present invention belongs to the technical field of micro-electromechanical systems, and in particular relates to a low-stress MEMS resonant accelerometer. Background Art

[0002] MEMS sensors integrate various micromechanical sensitive structures, microsensors, microactuators, and microelectronic devices on a single silicon chip, enabling the measurement of environmental variables in fields such as mechanics, thermals, optics, and chemistry while miniaturizing the device. Compared to traditional sensors, MEMS sensors offer advantages such as small size, high precision, and low cost, playing a crucial role in consumer electronics, automotive engineering, medical equipment, and aerospace. MEMS accelerometers, one of the earliest commercialized sensors, are capable of measuring physical quantities such as acceleration and vibration and are widely used in process industries, aviation equipment, and unmanned systems.

[0003] MEMS accelerometers based on the resonant principle are the future direction of high-precision accelerometer development due to their advantages such as small size, low cost, high precision, and quasi-digital output. Currently, institutions such as Tsinghua University, Peking University, Nanjing University of Science and Technology, and Xi'an Jiaotong University have developed prototype MEMS accelerometers based on the resonant principle. However, because MEMS sensors require multi-layer bonding during processing and involve multiple materials, differences in thermal expansion coefficients between these materials can cause residual stress in the sensitive chip after bonding. In addition, changes in the sensor's operating temperature can also cause thermal mismatch within the structure. This thermal stress can cause serious issues with zero-bias stability and temperature drift, affecting the sensor's temperature consistency and stability. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to address the above-mentioned deficiencies in the prior art and provide a low-stress MEMS resonant accelerometer. This invention is used to address the technical problem of residual stress easily generated in the tuning fork resonator due to mismatched material thermal expansion coefficients during the processing of existing MEMS resonant accelerometers. This invention also reduces the thermal mismatch generated within the structure during operating temperature changes, thereby reducing the temperature drift of the resonant accelerometer output.

[0005] The present invention adopts the following technical solutions: A low-stress MEMS resonant accelerometer, comprising: Glass substrate; A micromechanical sensitive structure is provided on the glass substrate, wherein an electrode is deposited on the surface of the micromechanical sensitive structure; The micromechanical sensitive structure comprises: mass block; a first tuning fork resonator and a second tuning fork resonator arranged symmetrically; a micro-lever amplifying mechanism connecting the mass block and the tuning fork resonator; A first supporting microspring, a second supporting microspring, a third supporting microspring, and a fourth supporting microspring are respectively arranged at the four corners of the mass block; The first anchor point, the second anchor point, the third anchor point, the fourth anchor point, the fifth anchor point, and the sixth anchor point are symmetrically arranged to symmetrically support the micromechanical sensitive structure; The first stress absorbing ring, the second stress absorbing ring, the third stress absorbing ring and the fourth stress absorbing ring are used to reduce the residual stress during processing; The first thermal deformation matching frame, the second thermal deformation matching frame, and the third thermal deformation matching frame are used to reduce thermal stress caused by operating temperature changes; Among them, the first anchor point, the second anchor point, the third anchor point, the fourth anchor point, the fifth anchor point, the sixth anchor point, the first stress absorption ring, the second stress absorption ring, the third stress absorption ring, and the fourth stress absorption ring.

[0006] Preferably, the first tuning fork resonator and the second tuning fork resonator are symmetrically arranged about the sensitive axis to form a differential sensitive structure.

[0007] Preferably, the two ends of the first thermal deformation matching frame and the second thermal deformation matching frame are respectively connected to the first supporting microspring, the second supporting microspring, the third supporting microspring, the fourth supporting microspring and the first anchor point, the third anchor point, the fourth anchor point and the sixth anchor point, so as to match the thermal deformation of the two ends of the supporting microspring in the direction of the sensitive axis.

[0008] Preferably, the first tuning fork resonator and the second tuning fork resonator are arranged at the thermal expansion center of the device to reduce bonding residual stress.

[0009] Preferably, the first stress absorption ring, the second stress absorption ring, the third stress absorption ring, and the fourth stress absorption ring are flexible structures, connecting the first thermal deformation matching frame, the first thermal deformation matching frame, the third thermal deformation matching frame and the first anchor point, the third anchor point, the fourth anchor point, and the sixth anchor point, so as to absorb residual stress and enhance impact resistance.

[0010] Preferably, the first stress absorption ring, the second stress absorption ring, the third stress absorption ring, and the fourth stress absorption ring offset the difference in thermal expansion coefficient between the single crystal silicon and the glass substrate through deformation.

[0011] Preferably, the micro-lever amplification mechanism includes multiple groups of symmetrical first micro-lever amplification structures, second micro-lever amplification structures, third micro-lever amplification structures, and fourth micro-lever amplification structures, and the endpoints of the first force input end, second force input end, third force input end, fourth force input end and the first force output end, second force output end, third force output end, and fourth force output end of each micro-lever are located on the same horizontal line to eliminate frequency drift caused by inconsistent thermal deformation.

[0012] Preferably, the glass substrate and the micromechanical sensitive structure are bonded by a SOG process, and the glass substrate is high borosilicate glass.

[0013] Preferably, the second thermal deformation matching frame connects the first fulcrum end, the second fulcrum end, the third fulcrum end and the fourth fulcrum end of the micro-lever to ensure synchronization of thermal deformation of the fulcrum end, the force input end and the force output end.

[0014] Preferably, the overall structure is symmetrical about the X-axis and the Y-axis, and the sensitive axis is the Y-axis.

[0015] Compared with the prior art, the present invention has at least the following beneficial effects: A low-stress MEMS resonant accelerometer utilizes symmetrically arranged anchor points supporting the micromechanical sensitive structure and stress relief rings to reduce residual stress in the tuning fork resonator's sensitive axis caused by mismatched material thermal expansion coefficients during processing. A thermal deformation matching framework is also provided to minimize thermal stress in the tuning fork resonator caused by inconsistent expansion displacement along the sensitive axis between the microlever input and output, the support spring and mass, and the connection between the support spring and anchor area during operating temperature fluctuations. This reduces the overall impact of temperature on the resonator's output frequency and improves the temperature stability of the resonant accelerometer's output.

[0016] The present application provides a low-stress MEMS resonant accelerometer and its micromechanical sensitive structure, which effectively suppresses the thermal stress caused by processing residual stress and operating temperature changes through symmetrically arranged stress absorption rings, thermal deformation matching frame and micro-lever amplification mechanism, significantly reduces the deterioration of sensor zero bias stability and temperature drift, and has the advantages of improving temperature consistency and long-term stability.

[0017] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings to be used in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0019] Figure 1 Schematic diagram of an accelerometer manufactured based on SOG process; Figure 2 It is a low stress MEMS resonant accelerometer; Figure 3 Schematic diagram of the micro-lever amplification mechanism.

[0020] Wherein: 1. Glass substrate; 2. Micromechanical sensitive structure; 3. Electrode; 2-1. Mass block; 2-2a. First tuning fork resonator; 2-2b. Second tuning fork resonator; 2-3a. First microlever amplifying structure; 2-3a-1. First force input end; 2-3a-2. First fulcrum end; 2-3a-3. First force output end; 2-3b. Second microlever amplifying structure; 2-3b-1. Second force input end; 2-3b-2. Second fulcrum end; 2-3b-3. Second force output end; 2-3c. Third microlever amplifying structure; 2-3c-1. Third force input end; 2-3c-2. Third fulcrum end; 2-3c-3. Third force output end; 2-3d. Fourth microlever amplifying structure; 2-3d -1. Fourth force input end; 2-3d-2. Fourth fulcrum end; 2-3d-3. Fourth force output end; 2-4a. First supporting microspring; 2-4b. Second supporting microspring; 2-4c. Third supporting microspring; 2-4d. Fourth supporting microspring; 2-5a. First thermal deformation matching frame; 2-5b. Second thermal deformation matching frame; 2-5c. Third thermal deformation matching frame; 2-6a. First stress absorption ring; 2-6b. Second stress absorption ring; 2-6c. Third stress absorption ring; 2-6d. Fourth stress absorption ring; 2-7a. First anchor point; 2-7b. Second anchor point; 2-7c. Third anchor point; 2-7d. Fourth anchor point; 2-7e. Fifth anchor point; 2-7f. Sixth anchor point. DETAILED DESCRIPTION

[0021] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0022] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "one side", "one end", "one side" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0023] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0024] It will be understood that when used in this specification and the appended claims, the terms “comprises” and “comprising” indicate the presence of described features, integers, steps, operations, elements and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0025] It should also be understood that the terms used in the present specification are only for the purpose of describing particular embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0026] It should be further understood that the term "and / or" used in the present description and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

[0027] The accompanying drawings illustrate various schematic diagrams of structures according to embodiments disclosed herein. These figures are not drawn to scale; for clarity, some details are exaggerated and some details may be omitted. The shapes of the various regions and layers shown in the figures, as well as their relative sizes and positional relationships, are merely exemplary and may deviate in practice due to manufacturing tolerances or technical limitations. Those skilled in the art may design regions / layers with different shapes, sizes, and relative positions as needed.

[0028] The present invention provides a low-stress MEMS resonant accelerometer. By symmetrically arranging anchor points supporting a micromechanical sensitive structure and a stress relief ring, this reduces residual stress generated along the sensitive axis of the tuning fork resonator due to mismatched material thermal expansion coefficients during processing. A thermal deformation matching frame is also provided to reduce thermal stress on the tuning fork resonator caused by inconsistent expansion or contraction deformation of various parts of the micromechanical sensitive structure during operating temperature changes. This invention reduces residual stress generated during processing and thermal stress caused by changes in the sensor's operating environment, thereby reducing the impact of temperature on the resonator's output frequency and improving the stability and temperature consistency of the resonant accelerometer's output.

[0029] See also Figure 1 The present invention provides a low-stress MEMS resonant accelerometer, comprising a lower glass substrate 1 and an upper micromechanical sensitive structure 2, wherein the glass substrate 1 is used to support the micromechanical sensitive structure 2, the material of the micromechanical sensitive structure 2 being single crystal silicon and being used to sense external acceleration, and gold being deposited thereon as an electrode 3 for signal input and output; a mass block 2-1 of the micromechanical sensitive structure 2 is connected to a microlever amplification structure, and the output end of the microlever is connected to a tuning fork resonator; supporting microsprings are arranged at the four corners of the mass block 2-1 to suspend the mass block 2-1; when there is external acceleration input, the mass block 2-1 is displaced under the action of inertial force, and the inertial force is amplified by the microlever amplification mechanism and acts on the tuning fork resonator, thereby generating a stiffness disturbance on the tuning fork resonator, causing the frequency of its output to change, thereby obtaining the acceleration to be measured.

[0030] The SOG process is used, the upper micromechanical sensitive structure 2 is made using a standard bulk silicon process, and the glass substrate 1 is made of high borosilicate glass. The glass substrate 1 and the micromechanical sensitive structure 2 are bonded via support anchors.

[0031] The center point of the sensitive structure of the MEMS accelerometer sensor is taken as the origin, and a coordinate system is established with the horizontal and vertical axes being the X-axis and the Y-axis respectively. The overall structure of the present invention is symmetrical about the X-axis and the Y-axis, and the sensitive axis is the Y-axis.

[0032] The tuning fork resonators have identical structures and are symmetrical about the X-axis. When an external acceleration input is applied, the natural frequency of one tuning fork resonator increases due to tension, while the natural frequency of the other tuning fork resonator decreases due to compression, forming a differentially sensitive pair of resonators to eliminate common-mode interference.

[0033] See also Figure 2 The micromechanical sensitive structure 2 includes a mass block 2-1, a first tuning fork resonator 2-2a, a second tuning fork resonator 2-2b, a first microlever amplifying structure 2-3a, a second microlever amplifying structure 2-3b, a third microlever amplifying structure 2-3c, a fourth microlever amplifying structure 2-3d, a first supporting microspring 2-4a, a second supporting microspring 2-4b, a third supporting microspring 2-4c, a fourth supporting microspring 2-4d, a first thermal deformation matching frame 2-5a, a second thermal deformation matching frame 2-5b, a third thermal deformation matching frame 2-5c, a first stress absorbing ring 2-6a, a second stress absorbing ring 2-6b, a third stress absorbing ring 2-6c, a fourth stress absorbing ring 2-6d and an anchor point, which are symmetrical about the X-axis and the Y-axis, and the sensitive axis is the Y-axis.

[0034] See also Figure 3 , including two groups of first micro-lever amplifying structures 2-3a, second micro-lever amplifying structures 2-3b, third micro-lever amplifying structures 2-3c, and fourth micro-lever amplifying structures 2-3d with completely identical structures and symmetrical positions. Each amplifying lever structure includes a first force input end 2-3a-1, a second force input end 2-3b-1, a third force input end 2-3c-1, a fourth force input end 2-3d-1, a first fulcrum end 2-3a-2, a second fulcrum end 2-3b-2, a third fulcrum end 2-3c-2, a fourth fulcrum end 2-3d-2, a first force output end 2-3a-3, a second force output end 2-3b-3, a third force output end 2-3c-3, and a fourth force output end 2-3d-3.

[0035] The mass block 2-1 is connected to the first force input end 2-3a-1, the second force input end 2-3b-1, the third force input end 2-3c-1, and the fourth force input end 2-3d-1 of the micro-lever amplification structure, the first force output end 2-3a-3 and the fourth force output end 2-3d-3 are connected to the first tuning fork resonator 2-2a, and the second force output end 2-3b-3 and the third force output end 2-3c-3 are connected to the second tuning fork resonator 2-2b.

[0036] The first supporting microspring 2-4a, the second supporting microspring 2-4b, the third supporting microspring 2-4c and the fourth supporting microspring 2-4d are arranged at the four corners of the sensitive mass block 2-1 to suspend the mass block 2-1.

[0037] When there is acceleration input on the Y-axis, the mass block 2-1 will produce displacement under the action of inertial force, and the inertial force will be amplified by the micro-lever amplification mechanism, acting on the first tuning fork resonator 2-2a and the second tuning fork resonator 2-2b to generate stiffness disturbance, causing the output frequency to change, and thus obtaining the acceleration to be measured.

[0038] The first tuning fork resonator 2-2a and the second tuning fork resonator 2-2b have the same structure and are symmetrical in position; when there is external acceleration input, the natural frequency of one tuning fork resonator increases due to tension, and the natural frequency of the other decreases due to pressure, so that the two resonators form a pair of differential sensitive structures to eliminate common-mode interference.

[0039] The first tuning fork resonator 2-2a and the second tuning fork resonator 2-2b are designed at the sixth anchor point 2-7f, the thermal expansion center of the device, to reduce the residual stress caused by the mismatch of thermal expansion coefficients of the single crystal silicon and the glass substrate after bonding.

[0040] The first, second, and third thermal deformation matching frames 2-5a, 2-5b, and 2-5c are centrally fixed, their ends expanding or contracting with temperature. The centers of the second, sixth, and fifth anchor points 2-7b, 2-7f, and 2-7e are aligned horizontally and on the X-axis of symmetry. This ensures consistent thermal deformation along the sensitive axis at the same horizontal position, thereby reducing thermal stress transmitted to the tuning fork resonator. The first and third thermal deformation matching frames 2-5a, 2-5c are connected to one end of the supporting microspring to match the expansion or contraction deformation in the Y direction at the connection between the other end of the supporting microspring and the mass 2-1.

[0041] The second thermal deformation matching frame 2-5b is connected to the first fulcrum end 2-3a-2, the second fulcrum end 2-3b-2, the third fulcrum end 2-3c-2, and the fourth fulcrum end 2-3d-2 of the amplifying lever. When the operating temperature changes, the expansion or contraction deformation at the connection between the second thermal deformation matching frame 2-5b and the first fulcrum end 2-3a-2, the second fulcrum end 2-3b-2, the third fulcrum end 2-3c-2, and the fourth fulcrum end 2-3d-2 of the amplifying lever is consistent with the expansion or contraction deformation at the connection between the mass block 2-1 and the first force input end 2-3a-1, the second force input end 2-3b-1, the third force input end 2-3c-1, and the fourth force input end 2-3d-1 of the amplifying lever, and the first force output end 2-3a-3, the second force output end 2-3b-3, the third force output end 2-3c-3, and the fourth force output end 2-3d-3 of the micro-lever and the first tuning fork resonator 2-2a and the second tuning fork resonator 2-2b, thereby reducing the inconsistent structural expansion or contraction deformation when the operating temperature of the accelerometer changes, which may lead to changes in the output frequencies of the first tuning fork resonator 2-2a and the second tuning fork resonator 2-2b.

[0042] The first thermal deformation matching frame 2-5a, the third thermal deformation matching frame 2-5c are connected to one end of the first supporting microspring 2-4a, the second supporting microspring 2-4b, the third supporting microspring 2-4c, and the fourth supporting microspring 2-4d, and are used to match the expansion or contraction deformation at the other end of the first supporting microspring 2-4a, the second supporting microspring 2-4b, the third supporting microspring 2-4c, and the fourth supporting microspring 2-4d, so as to reduce the inconsistent expansion or contraction deformation at the two ends of the first supporting microspring 2-4a, the second supporting microspring 2-4b, the third supporting microspring 2-4c, and the fourth supporting microspring 2-4d when the operating temperature of the accelerometer changes, resulting in thermal stress in the first tuning fork resonator 2-2a and the second tuning fork resonator 2-2b, thereby causing the output frequency to change.

[0043] The endpoints of the first force input end 2-3a-1, the second force input end 2-3b-1, the third force input end 2-3c-1, the fourth force input end 2-3d-1, the first fulcrum end 2-3a-2, the second fulcrum end 2-3b-2, the third fulcrum end 2-3c-2, the fourth fulcrum end 2-3d-2, the first force output end 2-3a-3, the second force output end 2-3b-3, the third force output end 2-3c-3 and the fourth force output end 2-3d-3 of each amplifying lever are all on the same horizontal line to reduce the output frequency of the first tuning fork resonator 2-2a and the second tuning fork resonator 2-2b changing with temperature due to inconsistent expansion or contraction deformation of the lever force input end and the force output end when the operating temperature of the accelerometer changes.

[0044] The first stress absorbing ring 2-6a, the second stress absorbing ring 2-6b, the third stress absorbing ring 2-6c and the fourth stress absorbing ring 2-6d are deformable flexible structures.

[0045] The first and third thermal deformation matching frames 2-5a and 2-5c are connected to the first, third, fourth, and sixth anchor points 2-7a, 2-7c, 2-7d, and 2-7f via a stress absorbing ring 2-6a, a second, third, and fourth stress absorbing rings 2-6b, 2-6c, and 2-6d. These rings provide sufficient support for the structure, preventing the mass 2-1, the first and third thermal deformation matching frames 2-5a, 2-5c from collapsing when impacted, thereby enhancing the structure's impact resistance. Furthermore, these rings absorb residual stress caused by the mismatch in thermal expansion coefficients between the single crystal silicon and the glass substrate after bonding, thereby reducing stress on the first and third thermal deformation matching frames 2-5a and 2-5c.

[0046] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0047] Example 1 In existing MEMS accelerometers, residual stresses are generated during the multi-layer bonding process due to differences in material thermal expansion coefficients, and variations in operating temperature lead to structural thermal mismatch. These issues lead to decreased bias stability and temperature drift, affecting measurement accuracy. For example, during the operation of aerospace equipment, internal thermal stress in the sensor can cause abnormal acceleration signal output, resulting in attitude control errors.

[0048] To address these issues, a structure that can effectively absorb residual stress and compensate for thermal deformation is needed. Traditional methods reduce stress by optimizing the bonding process, but this cannot eliminate the dynamic stress caused by temperature fluctuations. Research has found that incorporating flexible elements into the support structure can relieve residual stress, while a matching frame structure can accommodate the thermal expansion differences between different materials. Based on this, a stress-absorbing ring and a thermal deformation matching frame are integrated into the sensitive structure to form a composite stress compensation mechanism.

[0049] Therefore, this application proposes an accelerometer structure comprising a glass substrate, a micromechanical sensitive structure disposed on top, and electrodes deposited on the surface of the structure. The micromechanical sensitive structure comprises a mass, a symmetrical tuning fork resonator, a microlever amplification mechanism connecting the mass and the resonator, supporting microsprings arranged at the four corners, symmetrical anchor points supporting the overall structure, stress-absorbing rings distributed around the anchor points, and a thermal deformation matching frame connecting the supporting microsprings to the anchor points.

[0050] Among them, the glass substrate refers to a bearing layer formed by high borosilicate glass material, which can be bonded to the silicon structure through an anodic bonding process. Its thermal expansion coefficient is close to that of the silicon material and is used to reduce the interfacial thermal stress. The micromechanical sensitive structure refers to a movable mechanical component formed by etching single-crystal silicon, which includes a mass block and a resonator, and is used to convert acceleration into a change in resonant frequency. The supporting microspring refers to an elastic beam structure connecting the mass block and the frame, which can be designed as a folded beam or a serpentine beam to constrain the freedom of movement of the mass block. The stress absorption ring refers to an annular flexible structure surrounding the anchor point, which can be designed as a wavy or spiral geometric configuration to release the residual stress of processing through elastic deformation. The thermal deformation matching frame refers to a transition structure connecting the support spring and the anchor point, which can be designed as a U-shaped or H-shaped layout to coordinate the displacement difference between the two ends of the support spring when the temperature changes.

[0051] Specifically, the mass block displaces along the sensitive axis under the action of acceleration. A microlever amplification mechanism converts this displacement into a change in the axial stress of the tuning fork resonator, causing a shift in the resonant frequency. Four sets of supporting microsprings limit the mass block's movement in non-sensitive directions, and the symmetrical anchor point layout ensures balanced structural stiffness. The stress-absorbing ring offsets the interfacial stress between glass and silicon during the bonding process through flexible deformation, while also buffering external impact loads. A thermal deformation matching frame connects the fixed end of the supporting microspring to the anchor point. When the temperature changes, the frame's expansion and contraction match the thermal expansion of the supporting spring, preventing the spring from twisting and deformation.

[0052] Compared to existing technologies, most accelerometers use rigid anchor points, which results in residual stress concentration at the base of the support structure. This solution uses stress-absorbing rings to disperse interfacial stress and a thermal deformation matching frame to actively compensate for temperature-induced deformation differences. While conventional structures fail to consider the thermal stability of the resonator's position, this solution places the tuning fork resonator in the center of thermal expansion, minimizing the impact of thermal gradients on its performance.

[0053] Through the above technical solution, this application effectively reduces residual stress from machining and thermal stress caused by operating temperature changes, improving resonant frequency stability. The symmetrical layout of the support structure reduces interference from non-sensitive axes, the stress absorption ring enhances shock resistance, and the thermal deformation matching frame maintains the linear deformation characteristics of the support spring, thereby improving the temperature consistency and long-term stability of acceleration measurement.

[0054] Example 2 The present application further proposes that the first tuning fork resonator and the second tuning fork resonator are symmetrically arranged about the sensitive axis to form a differential sensitive structure.

[0055] Axisymmetrical arrangement of the sensitive axis refers to the mirror-symmetric distribution of the two tuning fork resonators along the sensitive axis. This can be achieved by symmetry in geometry, size, and support point locations, ensuring that the two resonators deform in opposite directions when subjected to acceleration. A differential sensing structure involves differential processing of the output signals of the two resonators. This can be achieved using a bridge circuit or frequency difference detection circuit, improving sensitivity by offsetting common-mode interference.

[0056] Specifically, when external acceleration acts along the sensitive axis, the mass, transmitted by the microlever amplification mechanism, displaces the mass, subjecting the first and second tuning fork resonators to tensile and compressive stresses, respectively, resulting in opposite shifts in resonant frequency. By detecting the frequency difference between the two resonators, common-mode errors caused by temperature variations and residual stresses from machining are eliminated, while differential-mode signals caused by acceleration are amplified. The symmetrical layout further ensures that deformations of the two resonators due to thermal expansion or mechanical shock cancel each other out, minimizing the impact of asymmetric stresses on measurement accuracy.

[0057] Compared with existing technologies, existing resonant accelerometers often use a single resonator or an asymmetric layout, which makes it difficult to effectively eliminate temperature drift and residual stress. This solution uses a differential symmetrical design to convert environmental interference into a common-mode signal, significantly reducing its impact on the output.

[0058] Through the above technical solution, the present application can suppress the frequency drift caused by thermal stress and processing residual stress, improve the stability and sensitivity of acceleration measurement, and enhance the anti-interference ability of the sensor in complex temperature environments.

[0059] Example 3 The present application further proposes that the two ends of the first thermal deformation matching frame and the second thermal deformation matching frame are respectively connected to the first supporting microspring, the second supporting microspring, the third supporting microspring, the fourth supporting microspring and the first anchor point, the third anchor point, the fourth anchor point and the sixth anchor point, so as to match the thermal deformation of the two ends of the supporting microspring in the direction of the sensitive axis.

[0060] Among them, the thermal deformation matching frame refers to a connection structure with a specific stiffness, which can be achieved by homogenizing the silicon-based material and the supporting microspring, and achieving deformation coordination through the consistency of the thermal expansion coefficient of the material. The supporting microspring refers to the elastic support component connecting the mass block and the substrate, which can be achieved by a folded beam or a serpentine beam structure, which is used to transmit the inertial force caused by acceleration and allow a small displacement of the mass block. The anchor point refers to a rigid connection point fixed to the substrate, which can be achieved by a boss structure formed by etching high borosilicate glass, which is used to constrain the end displacement of the supporting microspring. The sensitive axis direction refers to the main measurement direction of the accelerometer, which can be defined by the coupling relationship between the freedom of motion of the mass block and the vibration mode of the tuning fork resonator.

[0061] Specifically, when the operating temperature changes, the fixed and free ends of the supporting microspring undergo axial deformation due to the difference in thermal expansion of the materials. The thermal deformation matching frame connects the fixed end of the supporting microspring to the anchor point, ensuring that the deformation of both ends of the supporting microspring remains consistent along the sensitive axis. For example, when the temperature rises, the fixed end of the supporting microspring undergoes thermal expansion displacement due to the substrate constraint, while the free end undergoes an equal amount of synchronous displacement due to the rigid connection of the thermal deformation matching frame, thereby eliminating the thermal stress gradient within the supporting microspring.

[0062] Compared to existing technologies, traditional structures lack a thermal deformation matching frame, resulting in asymmetric deformation of the supporting microsprings at both ends when the temperature changes, causing axial stress accumulation in the resonator. This solution uses a rigid connection frame to enforce the synchronization of the displacements at both ends of the supporting microspring, ensuring that the deformation caused by thermal expansion is evenly distributed along the sensitive axis.

[0063] Through the above technical solution, the present application effectively suppresses the asymmetric deformation of the supporting microspring caused by temperature changes, avoids the local concentration of thermal stress in the resonator area, and thus significantly reduces the temperature drift error of the accelerometer output frequency.

[0064] Example 4 The present application further proposes that the first tuning fork resonator and the second tuning fork resonator are arranged at the thermal expansion center of the device to reduce bonding residual stress.

[0065] The center of thermal expansion refers to the geometrically symmetrical center of deformation of the device's overall structure when the temperature changes. This can be achieved by using finite element simulation to calculate the thermal expansion distribution of the structure and then determining the location where the thermal expansion deformation is minimized. Bonding residual stress refers to the internal stress caused by the difference in thermal expansion coefficients of different materials during the bonding process. This stress can be alleviated by optimizing the structural layout. This stress can cause the resonator frequency to drift.

[0066] Specifically, when the tuning fork resonator is placed at the center of thermal expansion, the displacement of the area in which it is located when the temperature changes is minimized, effectively offsetting the thermal expansion difference between the resonator made of single-crystal silicon material and the glass substrate. When the device undergoes the high-temperature process of the bonding process, the structural deformation of the thermal expansion center area is constrained, avoiding local stress concentration caused by different material shrinkage rates. As a result, the thermal mismatch stress between the anchor end of the resonator and the substrate is reduced, and the stability of the resonant frequency is improved.

[0067] Compared to existing technologies, tuning fork resonators in existing accelerometers are typically placed at the edge of the structure or in an asymmetric position. This results in uneven distribution of residual stress along the resonator's axis after bonding, affecting frequency stability. This solution, by placing the resonator at the center of thermal expansion, achieves spatially symmetrical distribution of thermal stress generated during bonding, achieving self-compensation for stress through the structure's inherent geometric symmetry.

[0068] Through the above technical solution, the present application effectively reduces the impact of residual stress caused by the bonding process on the resonator, avoids the frequency drift of the resonator caused by local stress concentration, and improves the temperature consistency and long-term stability of the accelerometer.

[0069] Example 5 The present application further proposes that the first stress absorption ring, the second stress absorption ring, the third stress absorption ring, and the fourth stress absorption ring are flexible structures, connecting the first thermal deformation matching frame, the third thermal deformation matching frame and the first anchor point, the third anchor point, the fourth anchor point, and the sixth anchor point, so as to absorb residual stress and enhance impact resistance.

[0070] Among them, the flexible structure refers to a mechanical structure with elastic deformation capability, which can be realized by using a folded beam or a serpentine structure, and the internal stress of the structure is released through local deformation. The stress absorption ring refers to an annular component surrounding the sensitive structure, which can be realized by connecting multiple sections of flexible beams in series to form a closed-loop structure, and the interference of residual stress on the resonator is dispersed by deformation. The thermal deformation matching frame refers to a rigid frame that matches the thermal expansion coefficient of the supporting microspring, which can be formed by synchronous processing of single crystal silicon material and supporting microspring, and the internal stress gradient of the structure is reduced by constraining the direction of thermal deformation. The anchor point refers to the support connection point fixed on the substrate, which can be realized by using a boss structure formed by etching high borosilicate glass, and the overall structural stability is maintained by a symmetrical layout.

[0071] Specifically, when residual stress is generated in the sensitive micromechanical structure due to processing or temperature changes, the stress-absorbing ring of the flexible structure absorbs the stress energy through its own elastic deformation, preventing stress concentration from being transmitted to the tuning fork resonator. The rigid connection between the thermal deformation matching frame and the anchor point forms a stable support boundary, while the flexible connection of the stress-absorbing ring allows for micro-displacement between the frame and the anchor point, further offsetting the thermal expansion difference between the single crystal silicon and the glass substrate. When an external impact load acts on the structure, the folded beam structure of the stress-absorbing ring disperses the impact energy through multi-stage deformation, preventing brittle fracture of the microlever amplification mechanism.

[0072] Compared with existing technologies, traditional MEMS accelerometers use rigid anchors to directly support the sensitive structure. This causes residual stress to be transmitted along a rigid path to the resonator, leading to frequency drift. This solution introduces a flexible stress-absorbing ring to create a buffer interface between the anchor and the sensitive structure. This converts the linearly transmitted residual stress into localized deformation of the ring structure, significantly reducing the impact of thermal mismatch stress on the resonator's operating frequency.

[0073] Through the above technical solution, this application effectively blocks the conduction path of processing residual stress and working thermal stress, avoiding the problem of resonant frequency offset caused by stress concentration. While maintaining the overall rigidity of the structure, the flexible stress absorption ring dissipates impact energy through controllable deformation, thereby improving the structural reliability of the accelerometer under complex working conditions. The synergistic effect of the thermal deformation matching frame and the stress absorption ring enables the sensitive structure to maintain a stable mechanical transmission path during temperature fluctuations, thereby improving the temperature stability of the sensor.

[0074] Example 6 The present application further proposes that the first stress absorption ring, the second stress absorption ring, the third stress absorption ring, and the fourth stress absorption ring offset the difference in thermal expansion coefficient between the single crystal silicon and the glass substrate through deformation.

[0075] A stress-absorbing ring is an annular structure with elastic deformation capabilities, specifically a folded beam or serpentine beam structure. It absorbs stress concentrations at material interfaces through localized flexible deformation. Thermal expansion coefficient differentials refer to the differences in linear expansion between materials when exposed to temperature changes. This can be achieved by matching the thermal expansion coefficients of the materials or introducing stress-absorbing structures, using structural deformation to compensate for differences in thermal deformation at the interface.

[0076] Specifically, the stress-absorbing ring is connected between the thermal deformation matching frame and the anchor point. When the single-crystal silicon and glass substrate experience differential thermal expansion due to temperature changes, the stress-absorbing ring releases interfacial shear stress through its own elastic deformation. For example, at high temperatures, the glass substrate expands more than the single-crystal silicon structure, causing the folded beam structure of the stress-absorbing ring to bend and deform, thus preventing stress accumulation caused by a rigid connection. This deformation process dynamically adapts to the material's expansion behavior at different temperatures, eliminating residual stress caused by thermal mismatch.

[0077] Compared to existing technologies, traditional structures use rigid anchor points to directly fix sensitive structures, which cannot effectively mitigate the thermal expansion differences between heterogeneous materials. This solution introduces flexible stress-absorbing rings to convert shear stress at the material interface into controllable deformation of the local structure, achieving active adjustment of the stress path and achieving a higher thermal matching tolerance than fixed connection methods.

[0078] Through the above technical solution, this application effectively reduces bonding residual stress and thermal stress caused by operating temperature changes, avoiding the problem of resonator frequency drift. The elastic deformation characteristics of the stress absorption ring can disperse the impact load energy, improving the structural reliability of the sensor in a vibrating environment while maintaining the symmetry and stability of the sensitive structure.

[0079] Example 7 The present application further proposes that the micro-lever amplification mechanism includes multiple groups of symmetrical first micro-lever amplification structures, second micro-lever amplification structures, third micro-lever amplification structures, and fourth micro-lever amplification structures, and the endpoints of the first force input end, second force input end, third force input end, fourth force input end and the first force output end, second force output end, third force output end, and fourth force output end of each micro-lever are located on the same horizontal line to eliminate frequency drift caused by inconsistent thermal deformation.

[0080] Among them, the micro-lever amplification mechanism refers to a structure that mechanically amplifies the inertial force generated by the mass block through the lever principle. Specifically, it can be achieved by using silicon-based micromachining technology to form a cantilever beam structure with a fixed fulcrum, a force input end and a force output end. Its function is to convert tiny acceleration signals into measurable resonant frequency changes.

[0081] Among them, the force input end refers to the point of action in the micro-lever structure that receives the inertial force transmitted by the mass block. It can be specifically achieved by an anchor point structure rigidly connected to the mass block. Its function is to transmit the displacement caused by acceleration to the lever fulcrum.

[0082] Among them, the force output end refers to the point of action in the micro-lever structure that transmits the amplified force to the tuning fork resonator. It can be specifically achieved by a flexible hinge structure connected to the root of the tuning fork resonator. Its function is to convert the amplified force into the axial stress change of the resonator.

[0083] Among them, the same horizontal line refers to the alignment of the coordinates of the force input end and the force output end in the direction perpendicular to the sensitive axis. Specifically, a geometrically symmetrical layout can be achieved through photolithography mask layout design. Its function is to ensure that the thermal expansion of each connection point remains consistent when the temperature changes.

[0084] Specifically, when external acceleration acts on the mass, the resulting inertial force is transmitted to the tuning fork resonator via four symmetrically distributed microlever amplification structures. Because the force input and output endpoints of each microlever are aligned horizontally, the longitudinal displacements of the various connection points remain synchronized when temperature changes cause the structure to thermally expand, preventing imbalances in the lever arm lengths caused by differences in thermal deformation. As a result, the axial preload applied to the tuning fork resonator is not subject to additional changes due to temperature fluctuations, thereby suppressing drift in the resonant frequency.

[0085] Compared to existing technologies, traditional micro-lever structures often employ asymmetric layouts or geometric alignment that doesn't strictly constrain the force transmission path. This can easily lead to relative displacement deviations between the input and output terminals when the temperature changes, resulting in amplification misalignment and frequency drift. This solution, however, achieves a self-compensation mechanism for thermal deformation by constraining the spatial relationship between the force transmission endpoints.

[0086] Through the above technical solution, the present application effectively suppresses the fluctuation of the lever amplification coefficient caused by temperature changes, eliminates the interference of thermal stress on the stability of the resonant frequency, and thus improves the temperature adaptability and long-term stability of the accelerometer.

[0087] Example 8 The present application further proposes that the glass substrate and the micromechanical sensitive structure are bonded by an SOG process, and the glass substrate is high borosilicate glass.

[0088] Among them, SOG process bonding refers to the bonding of the substrate and the sensitive structure by using a spin-on glass layer as an intermediate dielectric layer. Specifically, it can be achieved by spin-coating and depositing glass materials and then heat-treating them to form a dense bonding layer. This process can reduce the bonding interface stress and increase the bonding strength.

[0089] Among them, high borosilicate glass refers to a type of borosilicate glass with a high boron oxide content. Specifically, it can be achieved by using a type with a thermal expansion coefficient close to that of single crystal silicon material, such as Borofloat 33 or Pyrex 7740. Its thermal expansion coefficient can be controlled within 3.2~3.8×10 -6 / ℃ range, the difference in thermal expansion coefficient from single crystal silicon is less than 10%.

[0090] Specifically, a glass slurry is spin-coated on the surface of a glass substrate to form an intermediate layer, which is then chemically bonded to the single-crystal silicon material of the micromechanical sensitive structure by heating and pressurizing. The thermal expansion coefficient of the borosilicate glass substrate is close to that of single-crystal silicon, and the difference in thermal deformation between the two during temperature changes is small, thereby suppressing stress concentration at the bonding interface due to thermal mismatch. The bonding layer formed by the SOG process has a uniform thickness distribution. For example, a spin-on glass layer with a thickness of 0.5 to 2 microns can be used. The density of the bonding layer is controlled by adjusting the heat treatment temperature and time to avoid structural warping or cracking caused by local stress concentration during the bonding process.

[0091] Compared with the existing technology, the thermal expansion coefficients of the glass substrate and the silicon material are quite different when the traditional method uses the anodic bonding process. For example, the thermal expansion coefficient of ordinary soda-lime glass is about 9×10 -6 / °C, resulting in high residual stress on the interface after bonding. However, this solution uses the SOG process combined with high borosilicate glass to improve the thermal expansion coefficient matching between the bonding layer material and the substrate, while also avoiding the local stress problem caused by uneven electric field distribution during anodic bonding.

[0092] Through the above technical solution, the present application effectively reduces the residual stress at the bonding interface and the thermal stress caused by operating temperature changes, thereby improving the resonant frequency stability of the micromechanical sensitive structure, while reducing the sensor zero bias drift caused by bonding stress, and improving the temperature consistency and long-term stability of the accelerometer.

[0093] Example 9 The present application further proposes a second thermal deformation matching frame connecting the first fulcrum end, the second fulcrum end, the third fulcrum end, and the fourth fulcrum end of the micro-lever to ensure that the thermal deformation of the fulcrum end, the force input end, and the force output end is synchronized.

[0094] Among them, the second thermal deformation matching frame refers to a supporting frame structure made of a material with matching thermal expansion coefficients. Specifically, it can be implemented using a single-crystal silicon material of the same material as the micro-lever fulcrum end, and deformation coordination between structures is achieved through the consistency of the material's thermal expansion coefficient. The fulcrum end refers to the supporting node that transmits the force in the micro-lever mechanism. Specifically, it can be achieved by forming a rigid connection structure through a silicon-based etching process to maintain the motion stability of the lever amplification mechanism. Thermal deformation synchronization refers to the consistency of the deformation amount generated by the structure when the temperature changes. Specifically, it can be achieved through the geometrically symmetrical layout of the frame and the fulcrum end, eliminating stress concentration caused by local thermal expansion differences.

[0095] Specifically, when the ambient temperature changes, synchronized axial expansion and contraction deformation occurs between the second thermal deformation matching frame and the micro-lever fulcrum end. Because the frame and the fulcrum end are made of materials with the same thermal expansion coefficient and are rigidly connected to form an integral structure, the longitudinal thermal expansion of the frame is evenly transmitted to the micro-lever mechanism through the fulcrum end. This synchronized deformation mechanism ensures that the relative position relationship between the input and output ends of the lever remains constant, avoiding changes in the lever ratio caused by fulcrum position offset. Furthermore, the symmetrical layout of the frame can balance the thermal deformation of the fulcrums on both sides, maintaining the movement symmetry of the lever mechanism in the direction of the sensitive axis.

[0096] In some embodiments, the second thermal deformation matching frame can be designed as a rectangular ring structure with a uniform cross-sectional width, with its four connection points rigidly connected to the fulcrum ends of the micro-lever. The geometric center of the frame coincides with the center of symmetry of the micro-lever system, ensuring that thermal expansion caused by temperature gradients is evenly distributed along the frame axis.

[0097] Compared with the existing technology, the traditional MEMS accelerometer does not have a thermal deformation matching frame, and the micro-lever fulcrum end is directly fixed on the base anchor point. When the temperature changes, the difference in thermal expansion between the base material and the lever material will cause the fulcrum position to shift, thereby changing the lever magnification and causing frequency drift. This solution transfers the fixed position of the fulcrum end from the base to the frame structure by introducing an independent thermal deformation matching frame, effectively isolating the thermal expansion difference between the base material and the lever structure. Through the above technical solution, the present application can eliminate the influence of temperature changes on the transmission accuracy of the micro-lever mechanism and maintain the stability of the resonant frequency. The synchronous thermal deformation mechanism of the fulcrum end and the frame can compensate for the difference in thermal expansion coefficient of the materials, avoid the acceleration measurement error caused by the fulcrum position offset, and improve the working reliability of the sensor in a wide temperature range environment.

[0098] Example 10 The present application further proposes a low-stress MEMS resonant accelerometer, the overall structure of which is symmetrical about the X-axis and the Y-axis, with the Y-axis being the sensitive axis.

[0099] The overall structural symmetry about the X and Y axes refers to the mirror symmetry of the micromechanical sensitive structure's geometry, mass distribution, and support anchor point layout along these two axes. This can be achieved by using symmetrically arranged masses, tuning fork resonators, microlever amplification mechanisms, and supporting microsprings. This symmetrical design allows thermal deformation and residual stresses to offset each other within the structure. Having the Y-axis as the sensitive axis means that the acceleration detection direction coincides with the Y-axis. This can be achieved by aligning the vibration mode direction of the tuning fork resonator with the Y-axis, thereby optimizing the stress transfer efficiency along the sensitive axis.

[0100] Specifically, the symmetrical structure balances the differential thermal expansion along the X and Y axes, evenly distributing the thermal stress generated by the micromechanical sensing structure during temperature fluctuations along the symmetry axis. For example, when temperature fluctuations cause differential thermal expansion between the glass substrate and the single-crystal silicon structure, the symmetrically arranged stress-absorbing rings and thermal deformation matching frame simultaneously absorb the deformation, avoiding localized stress concentration. Furthermore, the design of the sensitive axis along the Y axis aligns the force output by the microlever amplification mechanism with the detection direction, reducing the impact of lateral interference on the resonant frequency.

[0101] Compared with existing technologies, traditional MEMS accelerometers often adopt a single-axis symmetric or asymmetric layout, which leads to uneven thermal stress distribution and causes zero-bias drift. The symmetrical structure of this application uses a dual-axis symmetric layout to suppress the effects of thermal deformation and residual stress in both the X-axis and Y-axis directions, significantly reducing the interference of temperature changes on the resonant frequency. In addition, the design of aligning the sensitive axis with the Y-axis further optimizes the transmission path of the acceleration signal and reduces coupling errors in the non-sensitive direction.

[0102] Through the above technical solution, this application effectively solves the problems of poor bias stability and temperature drift caused by uneven thermal stress distribution in traditional MEMS accelerometers. The symmetrical layout offsets thermal deformation within the structure, and the design of the sensitive axis improves the stress transfer efficiency in the detection direction, thereby improving the temperature consistency and long-term stability of the sensor.

[0103] Replacing the glass substrate with a silicon-on-silicon dioxide (SiO2 / Si) composite substrate further reduces residual stress and is compatible with CMOS processes, facilitating integration with ASICs.

[0104] The anchor points (2-7a~2-7f) adopt a radial star array (non-rectangular symmetry), and the center of the anchor point is located at the center of thermal expansion, which is suitable for circular chip packaging. The thermal stress distribution is isotropic and the ability to resist mechanical torsional loads is improved.

[0105] In summary, the low-stress MEMS resonant accelerometer of the present invention, with a symmetrical anchor point layout combined with a flexible stress release ring, will significantly reduce the mismatch of the thermal expansion coefficient of the material during the processing process, resulting in residual stress generated in the sensitive axis direction of the tuning fork resonator, thereby reducing the overall impact of temperature on the output frequency of the resonator and improving the temperature stability of the resonant accelerometer output.

[0106] The above content is only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A low stress MEMS resonant accelerometer, characterized in that: include: Glass substrate (1); A micromechanical sensitive structure (2) is provided on the glass substrate (1), wherein an electrode (3) is deposited on the surface of the micromechanical sensitive structure (2); The micromechanical sensitive structure (2) comprises: Mass (2-1); A first tuning fork resonator (2-2a) and a second tuning fork resonator (2-2b) are symmetrically arranged; a micro-lever amplifying mechanism connecting the mass block (2-1) and the tuning fork resonator; a first supporting microspring (2-4a), a second supporting microspring (2-4b), a third supporting microspring (2-4c), and a fourth supporting microspring (2-4d) respectively arranged at the four corners of the mass block (2-1); A first anchor point (2-7a), a second anchor point (2-7b), a third anchor point (2-7c), a fourth anchor point (2-7d), a fifth anchor point (2-7e), and a sixth anchor point (2-7f) are symmetrically arranged to symmetrically support the micromechanical sensitive structure (2); A first stress absorbing ring (2-6a), a second stress absorbing ring (2-6b), a third stress absorbing ring (2-6c), and a fourth stress absorbing ring (2-6d) are used to reduce residual stress during processing; A first thermal deformation matching frame (2-5a), a second thermal deformation matching frame (2-5b), and a third thermal deformation matching frame (2-5c) are used to reduce thermal stress caused by changes in operating temperature; Among them, the first anchor point (2-7a), the second anchor point (2-7b), the third anchor point (2-7c), the fourth anchor point (2-7d), the fifth anchor point (2-7e), the sixth anchor point (2-7f), the first stress absorption ring (2-6a), the second stress absorption ring (2-6b), the third stress absorption ring (2-6c), and the fourth stress absorption ring (2-6d).

2. The low stress MEMS resonant accelerometer according to claim 1, wherein: The first tuning fork resonator (2-2a) and the second tuning fork resonator (2-2b) are symmetrically arranged about a sensitive axis to form a differential sensitive structure.

3. The low stress MEMS resonant accelerometer according to claim 1, wherein: The two ends of the first thermal deformation matching frame (2-5a) and the second thermal deformation matching frame (2-5b) are respectively connected to the first supporting microspring (2-4a), the second supporting microspring (2-4b), the third supporting microspring (2-4c), the fourth supporting microspring (2-4d) and the first anchor point (2-7a), the third anchor point (2-7c), the fourth anchor point (2-7d), and the sixth anchor point (2-7f), so as to match the thermal deformation of the two ends of the supporting microspring in the direction of the sensitive axis.

4. The low stress MEMS resonant accelerometer according to claim 1, wherein: The first tuning fork resonator (2-2a) and the second tuning fork resonator (2-2b) are arranged at the thermal expansion center of the device to reduce bonding residual stress.

5. The low stress MEMS resonant accelerometer according to claim 1, wherein: The first stress absorption ring (2-6a), the second stress absorption ring (2-6b), the third stress absorption ring (2-6c), and the fourth stress absorption ring (2-6d) are flexible structures, connecting the first thermal deformation matching frame (2-5a), the first thermal deformation matching frame (2-5a), the third thermal deformation matching frame (2-5c) and the first anchor point (2-7a), the third anchor point (2-7c), the fourth anchor point (2-7d), and the sixth anchor point (2-7f) to absorb residual stress and enhance impact resistance.

6. The low stress MEMS resonant accelerometer according to claim 5, characterized in that: The first stress absorption ring (2-6a), the second stress absorption ring (2-6b), the third stress absorption ring (2-6c), and the fourth stress absorption ring (2-6d) offset the difference in thermal expansion coefficient between the single crystal silicon and the glass substrate (1) through deformation.

7. The low stress MEMS resonant accelerometer according to claim 1, wherein: The micro-lever amplification mechanism includes multiple groups of symmetrical first micro-lever amplification structures (2-3a), second micro-lever amplification structures (2-3b), third micro-lever amplification structures (2-3c), and fourth micro-lever amplification structures (2-3d). The endpoints of the first force input end (2-3a-1), second force input end (2-3b-1), third force input end (2-3c-1), fourth force input end (2-3d-1) and the first force output end (2-3a-3), second force output end (2-3b-3), third force output end (2-3c-3), and fourth force output end (2-3d-3) of each micro-lever are located on the same horizontal line to eliminate frequency drift caused by inconsistent thermal deformation.

8. The low stress MEMS resonant accelerometer according to claim 1, wherein: The glass substrate (1) and the micromechanical sensitive structure (2) are bonded via a SOG process, and the glass substrate (1) is high borosilicate glass.

9. The low stress MEMS resonant accelerometer according to claim 1, wherein: The second thermal deformation matching frame (2-5b) connects the first fulcrum end (2-3a-2), the second fulcrum end (2-3b-2), the third fulcrum end (2-3c-2), and the fourth fulcrum end (2-3d-2) of the micro-lever to ensure synchronization of thermal deformation of the fulcrum ends, the force input end, and the force output end.

10. The low stress MEMS resonant accelerometer according to any one of claims 1 to 9, characterized in that: The overall structure is symmetrical about the X-axis and the Y-axis, and the sensitive axis is the Y-axis.

Images