Novel silicon resonance accelerometer structure based on lever difference
By designing a novel silicon resonant accelerometer structure based on lever differential, and employing a three-layer structure and differential force mechanism, the problem of thermal stress influence under extreme temperature change conditions was solved, thereby improving the performance stability and engineering application capability of the accelerometer.
Patent Information
- Application Number
- CN202423139915.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-18
- Publication Date
- 2026-01-23
- Estimated Expiration
- 2034-12-18
AI Technical Summary
Existing silicon resonant accelerometers exhibit poor performance stability under extreme temperature variations and are severely affected by thermal stress, making it difficult to meet the engineering application requirements of high-precision inertial navigation systems.
A novel silicon resonant accelerometer structure based on lever differential is designed, employing a three-layer structure including a middle layer of micromechanical structure, an upper glass cover, and a lower glass cover. The central stress isolation frame and amplification lever structure are used to reduce the impact of thermal stress on the resonator, and the scaling factor and stability are improved through differential force mechanism.
It effectively suppresses the effects of thermal stress, improves the zero-bias stability and scaling factor of the accelerometer, reduces the difficulty of the manufacturing process, and enhances its engineering application capabilities.
Smart Images
Figure CN223827697U_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of precision sensor technology, and in particular refers to a novel silicon resonant accelerometer structure based on lever differential designed for navigation-grade engineering applications. Background Technology
[0002] A silicon resonant accelerometer is a micromechanical inertial device based on the principle of resonance. It outputs an acceleration signal by measuring the change in the resonant frequency of a resonator caused by acceleration. Compared with traditional capacitive accelerometers, silicon resonant accelerometers have higher zero-bias stability and scale factor stability, and are smaller, cheaper, easier to integrate, and more resistant to interference. Therefore, they have broad application prospects in high-precision inertial navigation systems, especially in the defense and military fields.
[0003] The micromechanical structure of a silicon resonant accelerometer typically consists of a sensitive mass, an amplifying lever structure, a resonator, a support mechanism, a drive mechanism, and a detection mechanism. Its working principle is as follows: the drive mechanism drives the resonator to resonate. When there is an external acceleration input, the sensitive mass senses the acceleration and converts it into inertial force. This inertial force is transmitted to the resonator through the amplifying lever structure, causing the resonator to be subjected to tension or compression, thereby changing its resonant frequency. The detection mechanism determines the magnitude of the input acceleration by detecting the change in the resonant frequency.
[0004] However, a major challenge facing silicon resonant accelerometers in practical applications is their environmental adaptability, particularly their performance stability under extreme temperature variations. Changes in ambient temperature can cause thermal expansion mismatch at the support anchor points, generating thermal stress that affects the accelerometer's performance stability and measurement accuracy. To mitigate the impact of thermal stress, two main methods exist: one is to achieve structural compensation through the rational distribution of multiple support anchor points and the design of meandering beams; however, this method struggles to precisely adjust the anchor point positions, resulting in incomplete control over thermal stress elimination. The second method employs a single-anchor-point support structure based on a stress-isolation frame. While this effectively suppresses thermal stress, the stress-isolation frame requires significant support stiffness, limiting the resonator layout area, increasing manufacturing complexity, and restricting its engineering applications.
[0005] Therefore, it is particularly important to design a silicon resonant accelerometer structure that can effectively suppress the effects of thermal stress, while also being simple to manufacture, compact in structure, and easy to apply in engineering. This invention addresses this need by proposing a novel silicon resonant accelerometer structure based on lever differential. Through an innovative design, it solves the problems existing in the prior art and improves the performance stability and engineering application capabilities of the silicon resonant accelerometer. Summary of the Invention
[0006] To address the aforementioned issues, this invention provides a novel silicon resonant accelerometer structure based on lever differential, designed for navigation-grade engineering applications. This structure is particularly suitable for high-precision inertial navigation systems, aiming to improve the performance stability of the accelerometer under extreme temperature variations through innovative mechanical structure design, reduce the impact of thermal stress on the resonator, and enhance the zero-bias stability and scaling factor of the accelerometer, thereby meeting the urgent needs of the defense and military sectors for high-performance, high-reliability sensors.
[0007] The technical solution adopted in this invention is: a novel silicon resonant accelerometer structure based on lever differential. The novel silicon resonant accelerometer structure consists of three layers: the middle layer is the micromechanical structure of the accelerometer, and its material is single-crystal silicon; the upper layer is a glass cover plate, which is bonded to the support anchor point, outer frame and electrodes of the middle layer, and contains metal wires for extracting frequency signals; the lower glass cover plate is bonded to the silicon outer frame of the middle layer to achieve vacuum encapsulation; the middle micromechanical structure includes a mass block, an amplifying lever structure, a double-ended fixed tuning fork resonator, a central stress isolation frame, driving detection comb teeth, a central anchor point, a mass block support anchor point, a mass block support beam and an outer frame.
[0008] The aforementioned double-ended fixed tuning fork resonator consists of two identical structural dimensions, symmetrically distributed along the non-acceleration-sensitive direction, and centrally distributed along the acceleration-sensitive direction; each double-ended fixed tuning fork resonator is connected at both ends to the output beam of the amplifying lever structure; the fulcrum beam of the amplifying lever structure is connected to the central stress isolation frame, and the geometric center of the central stress isolation frame is connected to the central anchor point.
[0009] The amplifying lever structure includes two forms with different force transmission directions. In the first form, the fulcrum beam is located between the input beam and the output beam, and in the second form, the fulcrum beam is located at the very end of the lever body. When the accelerometer is subjected to external acceleration, the differential force effect of the resonator is achieved through the two forms of amplifying lever structure.
[0010] The mass block is connected to the mass block support anchor point via a mass block support beam, and the inside of the mass block is connected to the input beam of the amplification lever structure; the mass block support beam is designed as a U-shaped beam to reduce stiffness along the acceleration-sensitive direction.
[0011] The central anchor point and the mass block support anchor point are bonded to the upper glass cover plate to provide support for the double-ended fixed tuning fork resonator, the amplifying lever structure and the mass block; the outer frame is bonded to the upper glass cover plate and the lower glass cover plate respectively to ensure that the middle micromechanical structure layer is suspended above the lower glass. The lower glass cover plate is coated with a getter to provide a sealed vacuum cavity for the structure layer.
[0012] The mass block support anchor points are symmetrically distributed at the top left, bottom left, top right, and bottom right centers, with the central anchor point located at the geometric center of the accelerometer. When the ambient temperature changes, the influence of thermal stress on the double-ended fixed tuning fork resonator is reduced through two forms of amplification lever structure and a central stress isolation frame design.
[0013] The driving detection comb, the double-ended fixed tuning fork resonator, the central stress isolation frame and the central anchor point are located inside the mass block. The driving detection comb is located on both sides of the double-ended fixed tuning fork resonator and is symmetrically distributed with the resonator as the central axis. It is used to drive the resonator to resonate and detect the resonant frequency.
[0014] The drive detection comb teeth include fixed comb teeth and movable comb teeth. The movable comb teeth are connected to the middle of the resonant beam, and the fixed comb teeth are bonded to the upper glass cover plate through electrodes to form a drive capacitor and a detection capacitor, thereby realizing the driving and frequency detection of the resonator.
[0015] The double-ended fixed tuning fork resonator includes two resonant beams distributed along the acceleration-sensitive direction. Each resonant beam is connected to the output beam of the amplifying lever structure at both ends. The magnitude of acceleration is characterized by detecting the frequency change of the resonant beams.
[0016] The two double-ended fixed tuning fork resonators produce differential changes when subjected to force; one resonator is subjected to pressure, and the other to tension. By detecting the frequency difference change between the two resonators, the scaling factor and stability of the silicon resonant accelerometer can be improved.
[0017] The advantages of this invention over the prior art are as follows:
[0018] (1) The present invention designs a novel silicon resonant accelerometer structure based on lever differential, distributing the support anchor points at the geometric center and four corners of the accelerometer, and using the central stress isolation frame to support the amplification lever structure. Based on the small thermal stress of the central anchor points and the buffering effect of the mass block support beam, the thermal stress transmitted to the double-ended fixed tuning fork resonator along the acceleration sensitive direction of each anchor point is minimized.
[0019] (2) The present invention designs a novel silicon resonant accelerometer structure based on lever differential. It adopts two amplification lever structures with different force transmission directions to realize the differential force of the resonator and makes the resonator symmetrically distributed along the non-acceleration and non-sensitive direction. This not only ensures the support stiffness of the central stress isolation frame, but also reduces the support area and increases the area of the mass block, thereby improving the scaling factor of the accelerometer.
[0020] (3) The present invention designs a novel silicon resonant accelerometer structure based on lever differential, which has fewer support anchor points, reduces the bonding area between glass and silicon, reduces thermal stress introduced by the processing technology, and greatly reduces the area of the central stress isolation frame, which reduces the processing difficulty and improves the survival rate of the accelerometer. Attached Figure Description
[0021] Figure 1 This is a schematic diagram of the intermediate structure layer of the novel silicon resonant accelerometer in this invention;
[0022] Figure 2 This is a schematic diagram of the mass block supporting beam structure in this invention;
[0023] Figure 3 This is a schematic diagram of an enlarged lever structure with the fulcrum beam in the middle in this invention;
[0024] Figure 4 This is a schematic diagram of the enlarged lever structure at the end of the fulcrum beam in this invention;
[0025] Figure 5 This is a schematic diagram of the forces acting on the resonator in this invention;
[0026] Figure 6 This is a schematic diagram of the double-ended fixed tuning fork resonator structure in this invention;
[0027] Figure 7 This is a schematic diagram of the drive detection comb structure in this invention. Detailed Implementation
[0028] To better understand the purpose, technical solution, and advantages of this invention, the invention will be further described in detail below with reference to the accompanying drawings and simulation data.
[0029] Combination Figure 1 This invention relates to a novel silicon resonant accelerometer structure based on lever differential, which consists of three layers: the middle layer is the micromechanical structure of the accelerometer, made of single-crystal silicon; the upper layer is a glass cover plate, bonded to the support anchor points, outer frame, and electrodes of the middle layer, with internal metal wires for extracting frequency signals; the lower glass cover plate is bonded to the silicon outer frame of the middle layer to achieve vacuum encapsulation. The middle micromechanical structure includes a mass block (1), an amplifying lever structure (2a, 2b, 2c, 2d), a double-ended fixed tuning fork resonator (3a, 3b), a central stress isolation frame (4), driving detection comb teeth (5a, 5b, 5c, 5d), a central anchor point (6), mass block support anchor points (7a, 7b, 7c, 7d), mass block support beams (8a, 8b, 8c, 8d), and an outer frame (9).
[0030] The two double-ended fixed tuning fork resonators (3a, 3b) are acceleration-sensitive structures with identical structural dimensions, symmetrically distributed along the Y direction, and centrally distributed along the X acceleration-sensitive direction. The two ends (13a, 13b, 14a, 14b) of each double-ended fixed tuning fork resonator (3a, 3b) are connected to the output beams (11a, 11b, 11c, 11d) of the amplifying lever structure (2a, 2b, 2c, 2d), respectively. The fulcrum beams (12a, 12b, 12c, 12d) of the amplifying lever structure (2a, 2b, 2c, 2d) are connected to the central stress isolation frame (4), and the geometric center of the central stress isolation frame (4) is connected to the central anchor point (6). The central anchor point and the central stress isolation frame not only ensure the fixation of the resonator and reduce the number of supporting anchor points, but also simplify the structural layout of the resonator.
[0031] The mass block (1) occupies the largest area of the accelerometer. Its four corners (upper left, lower left, upper right, and lower right) are connected to the mass block support anchor points (7a, 7b, 7c, 7d) through the mass block support beams (8a, 8b, 8c, 8d). Figure 2 To ensure that the mass block support beams (8a, 8b, 8c, 8d) have a buffering effect along the acceleration-sensitive direction, their structure is designed as a U-shaped beam to reduce their stiffness along the acceleration-sensitive direction. The mass block (1) is internally connected to the input beams (10a, 10b, 10c, 10d) of the amplified lever structures (2a, 2b, 2c, 2d) distributed symmetrically in the upper left, lower left, upper right, and lower right directions. To achieve force differential, the amplified lever structures (2a, 2b, 2c, 2d) are designed with two force transmission forms, combined with Figure 3 The fulcrum beams (12a, 12c) of the amplified lever structure (2a, 2c) are located between the input beams (10a, 10c) and the output beams (11a, 11c); combined with Figure 4 The fulcrum beams (12b, 12d) of the enlarged lever structure (2b, 2d) are located at the very end of the lever body. Combined with... Figure 5 When the accelerometer is subjected to an external acceleration in the positive X direction, the mass block (1) generates an inertial force F in the positive X direction. mThe mass block support beams (8a, 8b, 8c, 8d) provide support and buffer for the mass block (1). The input beams (10a, 10b, 10c, 10d) transmit the force to the amplifying lever structure (2a, 2b, 2c, 2d). Due to the different positions of the fulcrum beams in the two types of amplifying lever structures, the directions of the force transmitted by the levers are different. Therefore, the two ends (13a, 14a) of the resonator (3a) are subjected to pressure, and the two ends (13b, 14b) of the resonator (3b) are subjected to tension. Similarly, when there is acceleration in the opposite direction of X, the two ends (13a, 14a) of the resonator (3a) are subjected to tension, and the two ends (13b, 14b) of the resonator (3b) are subjected to pressure. The differential effect of the force on the resonant beams (3a, 3b) is achieved through the two types of levers. Figure 6 When a resonator is subjected to pressure, its force-frequency characteristic is expressed as follows:
[0032]
[0033] In the formula, f F Let be the resonant frequency of the resonant beams (15a, 15b, 16a, 16b) after being subjected to force, E be the Young's modulus of monocrystalline silicon, w be the width of the resonant beams (15a, 15b, 16a, 16b), and L be the resonant frequency of the resonant beams (15a, 15b, 16a, 16b). f Let be the length of the resonant beams (15a, 15b, 16a, 16b), h be the thickness of the intermediate layer, F be the pressure exerted on a single resonant beam (15a, 15b, 16a, 16b), ρ be the density of monocrystalline silicon, and m be the mass of the movable comb teeth (17a, 17b, 17c, 17d) connected to the resonant beams (15a, 15b, 16a, 16b). Therefore, when the resonant beams of the two double-ended fixed tuning fork resonators (3a, 3b) are subjected to inertial forces, the resonant frequency of the resonators can be obtained by eliminating higher-order terms through Taylor expansion:
[0034]
[0035] In the formula, f n The resonant frequencies f of the resonant beams (15a, 16a) and (15b, 16b) when they are not subjected to tensile or compressive stress. Fa f is the resonant frequency of the resonant beams (15a, 16a) of the double-ended fixed tuning fork resonator (3a) after being subjected to pressure. Fb Let be the resonant frequency of the resonant beam (15b, 16b) of the double-ended fixed tuning fork resonator (3b) after being subjected to tension. As can be seen from the above formula, the two resonators have a differential effect under stress. By differentiating the output frequencies of the two resonators, the scaling factor of the silicon resonant accelerometer can be improved, common-mode error can be eliminated, and the stability of the accelerometer can be enhanced.
[0036] The central anchor point (6) and the mass block support anchor points (7a, 7b, 7c, 7d) are bonded to the upper glass cover plate, providing support for the double-ended fixed tuning fork resonator (3a, 3b), the amplifying lever structure (2a, 2b, 2c, 2d), and the mass block (1). The outer frame (9) is bonded to the upper and lower glass cover plates respectively, ensuring that the intermediate micromechanical structure layer is suspended above the lower glass. The lower glass cover plate is coated with a getter to provide a sealed vacuum cavity for the structure layer, thereby improving the Q value of the resonant mode.
[0037] The mass block support anchor points (7a, 7b, 7c, 7d) are symmetrically distributed at the upper left, lower left, upper right, and lower right centers, with the central anchor point (6) located at the geometric center of the accelerometer. When the ambient temperature changes, the intermediate structural layer undergoes thermal expansion. Based on the two forms of amplified lever structure (2a, 2b, 2c, 2d) and the central stress isolation frame (4), the connection between the double-ended fixed tuning fork resonator (3a, 3b) and the mass block (1) consists only of the central anchor point (1) and the mass block support anchor points (7a, 7b, 7c, 7d) at the four corners. The thermal stress generated by the central anchor point (1) in the X and Y directions is very small and is transferred to the double-ended fixed tuning fork resonator through the central stress isolation frame (4). The thermal stress of the resonators (3a, 3b) is very small; the thermal stress of the mass block support anchor points (7a, 7b, 7c, 7d) along the X-acceleration sensitive direction is buffered and released through the mass block support beams (8a, 8b, 8c, 8d), so the thermal stress transmitted to the resonators along the X-acceleration sensitive direction through the amplification lever structure (2a, 2b, 2c, 2d) is very small; the acceleration sensitive structure of the entire intermediate layer is close to the free thermal expansion state, and the thermal stress has a minimal impact on the double-ended fixed tuning fork resonators (3a, 3b).
[0038] Combination Figure 7The driving detection comb teeth (5a, 5b, 5c, 5d), the double-ended fixed tuning fork resonators (3a, 3b), and the central stress isolation frame (4) are located inside the mass block (1). The driving detection comb teeth (5a, 5b, 5c, 5d) are symmetrically distributed on both sides of the double-ended fixed tuning fork resonators (3a, 3b) with the resonators as the central axis. Among them, the movable comb teeth (17a, 17b, 17c, 17d) are connected to the middle of the resonant beams (15a, 15b, 16a, 16b) respectively, and the fixed comb teeth (18a, 19a, 20a) are bonded to the upper glass cover plate through electrodes (21a, 22a, 23a) to achieve electrode fixation. The fixed comb teeth (19a) and the movable comb teeth (17a) form a driving capacitor. The fixed comb teeth (19a) apply an electrostatic force to the movable comb teeth (17a) to drive their movement, thereby causing the resonant beam (15a) to resonate. At the same time, the fixed comb teeth (18a, 20a) and the movable comb teeth (17a) form a detection capacitor. The fixed comb teeth (18a, 20a) detect the change in capacitance, thereby measuring the resonant frequency of the resonant beam (15a). Similarly, the driving detection method for the other three resonant beams (15b, 16a, 16b) is the same. Since the four resonant beams (15a, 15b, 16a, 16b) have the same size, the resonant frequency changes of the resonant beams (15a, 16a) and (15b, 16b) are consistent. Finally, the difference between the frequencies of the double-ended fixed tuning fork resonator (3a) and the double-ended fixed tuning fork resonator (3b) is used to characterize the magnitude of the acceleration.
[0039] The above is merely the design structure of this invention and does not constitute any limitation on the scope of protection of this invention; all technical solutions formed by equivalent transformation or equivalent substitution fall within the scope of protection of this invention; the parts of this invention not described in detail are common knowledge to those skilled in the art.
Claims
1. A novel silicon resonant accelerometer structure based on lever differential, characterized in that: The novel silicon resonant accelerometer structure consists of three layers: upper, middle, and lower. The middle layer is the micromechanical structure of the accelerometer, and its material is single-crystal silicon. The upper layer is a glass cover plate, which is bonded to the mass block support anchor point, outer frame and electrodes of the middle layer, and contains metal wires for extracting frequency signals; the lower glass cover plate is bonded to the silicon outer frame of the middle layer to achieve vacuum encapsulation; the middle micromechanical structure includes a mass block, an amplifying lever structure, a double-ended fixed tuning fork resonator, a central stress isolation frame, driving detection comb teeth, a central anchor point, a mass block support anchor point, a mass block support beam and an outer frame.
2. The novel silicon resonant accelerometer structure based on lever differential as described in claim 1, characterized in that: The aforementioned double-ended fixed tuning fork resonator consists of two identical structural dimensions, symmetrically distributed along the non-acceleration-sensitive direction, and centrally distributed along the acceleration-sensitive direction; each double-ended fixed tuning fork resonator is connected at both ends to the output beam of the amplifying lever structure; the fulcrum beam of the amplifying lever structure is connected to the central stress isolation frame, and the geometric center of the central stress isolation frame is connected to the central anchor point.
3. The novel silicon resonant accelerometer structure based on lever differential as described in claim 2, characterized in that: The amplifying lever structure includes two forms with different force transmission directions. In the first form, the fulcrum beam is located between the input beam and the output beam, and in the second form, the fulcrum beam is located at the very end of the lever body. When the accelerometer is subjected to external acceleration, the differential force effect of the resonator is achieved through the two forms of amplifying lever structure.
4. The novel silicon resonant accelerometer structure based on lever differential as described in claim 1, characterized in that: The mass block is connected to the mass block support anchor point via a mass block support beam, and the inside of the mass block is connected to the input beam of the amplification lever structure; the mass block support beam is designed as a U-shaped beam to reduce stiffness along the acceleration-sensitive direction.
5. The novel silicon resonant accelerometer structure based on lever differential as described in claim 1, characterized in that: The central anchor point and the mass block support anchor point are bonded to the upper glass cover plate to provide support for the double-ended fixed tuning fork resonator, the amplifying lever structure and the mass block; the outer frame is bonded to the upper glass cover plate and the lower glass cover plate respectively to ensure that the middle micromechanical structure layer is suspended above the lower glass. The lower glass cover plate is coated with a getter to provide a sealed vacuum cavity for the structure layer.
6. The novel silicon resonant accelerometer structure based on lever differential as described in claim 1, characterized in that: The mass block support anchor points are symmetrically distributed at the top left, bottom left, top right, and bottom right centers, with the central anchor point located at the geometric center of the accelerometer. When the ambient temperature changes, the influence of thermal stress on the double-ended fixed tuning fork resonator is reduced through two forms of amplification lever structure and a central stress isolation frame design.
7. The novel silicon resonant accelerometer structure based on lever differential as described in claim 1, characterized in that: The driving detection comb, the double-ended fixed tuning fork resonator, the central stress isolation frame and the central anchor point are located inside the mass block. The driving detection comb is located on both sides of the double-ended fixed tuning fork resonator and is symmetrically distributed with the resonator as the central axis. It is used to drive the resonator to resonate and detect the resonant frequency.
8. A novel silicon resonant accelerometer structure based on lever differential as described in claim 7, characterized in that: The drive detection comb teeth include fixed comb teeth and movable comb teeth. The movable comb teeth are connected to the middle of the resonant beam, and the fixed comb teeth are bonded to the upper glass cover plate through electrodes to form a drive capacitor and a detection capacitor, thereby realizing the driving and frequency detection of the resonator.
9. A novel silicon resonant accelerometer structure based on lever differential as described in claim 1, characterized in that: The double-ended fixed tuning fork resonator includes two resonant beams distributed along the acceleration-sensitive direction. Each resonant beam is connected to the output beam of the amplifying lever structure at both ends. The magnitude of acceleration is characterized by detecting the frequency change of the resonant beams.
10. A novel silicon resonant accelerometer structure based on lever differential as described in claim 9, characterized in that: Two fixed-end tuning fork resonators produce differential changes when subjected to force; one resonator is subjected to pressure, and the other to tension. The scaling factor and stability of the silicon resonant accelerometer are improved by detecting the frequency difference changes between the two resonators.