MEMS inertial device capable of inhibiting static negative stiffness
By introducing a limit structure into a MEMS inertial device and designing it symmetrically, the potentials of the MEMS structure and the substrate are equal, the problem of electrostatic negative stiffness is solved, device performance is improved and design is simplified.
Patent Information
- Application Number
- CN202421558469.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-03
- Publication Date
- 2025-04-18
- Estimated Expiration
- 2034-07-03
AI Technical Summary
The existing MEMS inertial devices have electrostatic negative stiffness problems in their design, resulting in adverse factors such as improved structural sensitivity, decreased actual stiffness and possible nonlinear vibration.
By introducing a limit structure between the substrate and the cover plate of the MEMS inertial device, and designing the limit structure symmetrically with the first trace layer with respect to the MEMS structure, the potentials of the MEMS structure and the substrate are equal, and the potential difference and electrostatic negative stiffness are eliminated.
The electrostatic negative stiffness is eliminated, and the performance of MEMS inertial devices is improved. The overall design is simple, avoiding the adverse impact of electrostatic negative stiffness on the device.
Smart Images
Figure CN222774001U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of MEMS inertial devices, in particular to a MEMS inertial device capable of suppressing electrostatic negative stiffness. Background Art
[0002] In general, MEMS inertial devices can be regarded as a spring-damped mass resonant system (such as Figure 1 As shown). There is a voltage U between the mass block M and the lower plate with a spacing of h. D is the damping of the mass block M during resonance (generally, the compression mold damping and sliding film damping of the air, the thermoelastic damping of the anchor point, etc. are mainly considered), and K is the spring force received by the mass block M during resonance (mainly affected by the structural design). F is the external force received by the mass block M. When there is a resultant force F (cause of generation: electrostatic force, external acceleration angular velocity, etc.), the mass block M moves downward a distance u under the influence of the force F. By detecting the capacitance of the mass block M and the lower plate after the displacement u, the displacement u of the mass block M can be obtained, and then the size of F can be deduced according to the dynamic formula to obtain the current acceleration and angular velocity. In order to realize functions such as capacitance detection, there is often a voltage difference between the mass block M and the lower plate. This voltage difference will generate an electrostatic force F el According to Hooke's law F = kx, when the mass block M moves the same displacement, due to the electrostatic force F el , the other forces required by the mass block M are reduced. In other words, the mechanical stiffness k becomes smaller, that is, electrostatic negative stiffness is generated. In the design of inertial devices, the effect of electrostatic negative stiffness must be considered. On the one hand, electrostatic negative stiffness can reduce the modal resonance frequency of the inertial device through tuning, thereby achieving modal matching of the gyroscope (a design idea that the gyroscope drive frequency and the detection frequency are very close, thereby achieving high sensitivity and high precision of the gyroscope); on the other hand, since electrostatic negative stiffness increases the sensitivity of the structure, the decrease in the actual stiffness of the inertial device may cause the device to attract, produce nonlinear vibrations and other unfavorable factors.
[0003] At present, the method to suppress electrostatic negative stiffness is to detect capacitance through low-voltage and high-frequency signals, so as to reduce the voltage difference between the mass block M and the plate, thereby reducing the influence of electrostatic negative stiffness. However, its disadvantage is that the circuit design is complex and difficult to implement. In the current common MEMS process, there are two mainstream lead schemes, the side lead type and the TSV type. In the side lead type, it is common to have leads under the structure and the package cover directly above the structure. Usually, the cover (CAPWAFER) is grounded (GND) together with the bonding ring, and the MEMS structure and GND are not at the same potential. The MEMS structure is very close to the substrate and far away from the cover, which makes the potential difference between the MEMS structure and the cover generate electrostatic force and generate electrostatic negative stiffness. In the TSV type solution, the metal or silicon traces are led through the cover (CAP Wafer). Although the size of the chip is reduced, the potential of the MEMS structure and the substrate are not equal, which will generate a potential difference and electrostatic negative stiffness.
[0004] Therefore, it is necessary to provide a MEMS inertial device design technical solution that is simple in design and can make the potential of the MEMS structure and the substrate equal and eliminate the potential difference and the electrostatic negative stiffness. Utility Model Content
[0005] In order to solve the above technical problems, the utility model provides a MEMS inertial device capable of suppressing electrostatic negative stiffness.
[0006] The utility model provides a MEMS inertial device capable of suppressing electrostatic negative stiffness, comprising: a substrate, a cover plate arranged on the upper surface of the substrate, and a MEMS structure located in the cover plate;
[0007] A first wiring layer is provided on the inner surface of the cavity constructed by the cover plate and the substrate;
[0008] The cover plate is provided with an opening for the first wiring layer to connect to the outside;
[0009] A limited position structure is arranged in the cavity;
[0010] The limiting structure and the first wiring layer are symmetrical with respect to the MEMS structure.
[0011] In a possible implementation manner, the area of the limiting structure is the same as the area of the mass block in the MEMS structure, and both are smaller than the area of the first wiring layer.
[0012] In a possible implementation manner, the area of the first wiring layer is the same as the area of the limiting structure, and both are larger than the area of the mass block in the MEMS structure.
[0013] In a possible implementation manner, a second wiring layer is provided on a side of the limiting structure close to the first wiring layer.
[0014] In a possible implementation manner, the MEMS structure is a structural layer of a gyroscope or an accelerometer.
[0015] In a possible implementation, the opening is provided on the bottom surface of the cover plate;
[0016] The first wiring layer is located on the inner surface of the bottom surface of the cover plate.
[0017] In a possible implementation, the opening is provided on a side surface of the cover plate;
[0018] The first wiring layer is located on the upper surface of the substrate.
[0019] The technical solution provided by the utility model has at least the following beneficial effects:
[0020] By adding a limiting structure and designing the limiting structure and the first wiring layer symmetrically about the MEMS structure, the potential of the MEMS structure and the substrate can be equalized, eliminating the potential difference and electrostatic negative stiffness, improving the performance of the MEMS inertial device, and simplifying the overall design. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 1 A schematic diagram of an embodiment of the utility model that considers a MEMS inertial device in the prior art as a spring damping mass resonance system;
[0022] Figure 2 A schematic diagram of a first cross-sectional structure of a MEMS inertial device capable of suppressing electrostatic negative stiffness provided by an embodiment of the utility model;
[0023] Figure 3 A schematic diagram of a second cross-sectional structure of a MEMS inertial device capable of suppressing electrostatic negative stiffness provided by an embodiment of the utility model;
[0024] Figure 4 A schematic diagram of a third cross-sectional structure of a MEMS inertial device capable of suppressing electrostatic negative stiffness provided by an embodiment of the utility model;
[0025] Figure 5 A schematic diagram of a fourth cross-sectional structure of a MEMS inertial device capable of suppressing electrostatic negative stiffness provided by an embodiment of the utility model;
[0026] In the accompanying drawings, 11, substrate; 12, cover plate; 13, MEMS structure; 14, cavity; 15, first wiring layer; 16, opening; 17, limiting structure; 18, second wiring layer. DETAILED DESCRIPTION
[0027] In order to deepen the understanding of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. The embodiments are only used to explain the present invention and do not limit the protection scope of the present invention.
[0028] Please refer to Figures 2 to 5 The utility model provides a MEMS inertial device capable of suppressing electrostatic negative stiffness, comprising: a substrate 11, a cover plate 12 disposed on the upper surface of the substrate 11, and a MEMS structure 13 located in the cover plate 12;
[0029] The inner surface of the cavity 14 formed by the cover plate 12 and the substrate 11 is provided with a first wiring layer 15;
[0030] The cover plate 12 is provided with an opening 16 for the first wiring layer 15 to connect to the outside;
[0031] A limiting structure 17 is provided in the cavity 14;
[0032] The limiting structure 17 and the first wiring layer 15 are symmetrical with respect to the MEMS structure 13 .
[0033] In this embodiment, the lead scheme adopted by the MEMS inertial device can be a side lead type or a TSV type. The first wiring layer 15 is a conventional wiring layer in the MEMS inertial device.
[0034] When using the side lead type lead solution, such as Figure 2 , the limiting structure 17 is located on the inner surface of the cover plate 12, and its area is the same as the area of the mass block in the MEMS structure 13. The limiting structure 17 and the cover plate 12 are at the same potential, and the distance above the MEMS structure 13 to the same potential is shortened. At the same time, through the circuit design of the first wiring layer 15, the area below the MEMS structure 13 can be set to a ground potential (GND). When the distance between the newly added limiting structure 17 above the MEMS structure 13 and the substrate 11 below is equal, although there is an electrostatic difference and an electrostatic force above and below the MEMS structure 13, the two forces are equal and opposite in magnitude, and the resultant force is 0. Therefore, the MEMS structure 13 is not affected by the negative electrostatic stiffness. Among them, the limiting structure 17 can be made of the same material as the cover plate 12, and the specific selection is made according to actual needs.
[0035] When using the TSV lead solution, such as Figure 3, the limiting structure 17 is located on the upper surface of the substrate 11, and its area corresponds to the area of the first wiring layer 15 set inside the cover plate 12. The limiting structure 17 and the substrate 11 are at the same potential, and the distance below the MEMS structure 13 to the same potential is shortened. At the same time, through the circuit design of the first wiring layer 15, the area above the MEMS structure 13 can be set to a ground potential (GND). When the distance between the newly added limiting structure 17 below the MEMS structure 13 and the upper cover plate 12 is equal, although there is an electrostatic difference and an electrostatic force above and below the MEMS structure 13, the two forces are equal and opposite in magnitude, so that the resultant electrostatic force of the MEMS structure 13 on the upper and lower sides is 0, so that the MEMS structure 13 is not affected by the negative electrostatic stiffness. Among them, the limiting structure 17 can be made of the same material as the substrate 11, and the specific selection is made according to actual needs.
[0036] In one possible implementation, Figure 2 and Figure 4 The area of the limiting structure 17 is the same as the area of the mass block in the MEMS structure 13 , and both are smaller than the area of the first wiring layer 15 .
[0037] In this embodiment, the MEMS inertial device adopts a side lead type lead solution. At this time, the area of the limiting structure 17 needs to correspond to the area of the mass block in the MEMS structure 13.
[0038] In one possible implementation, Figure 3 and Figure 5 The area of the first wiring layer 15 is the same as the area of the limiting structure 17 , and both are larger than the area of the mass block in the MEMS structure 13 .
[0039] In this embodiment, the MEMS inertial device adopts a TSV type lead solution. In this case, the area of the limiting structure 17 needs to correspond to the area of the first wiring layer 15 .
[0040] In one possible implementation, Figure 4 and Figure 5 A second wiring layer 18 is disposed on one side of the limiting structure 17 close to the first wiring layer 15 .
[0041] In this embodiment, the second wiring layer 18 is a conventional wiring layer in a MEMS inertial device.
[0042] When using the side lead type lead solution, such as Figure 4The second wiring layer 18 is arranged on the lower surface of the limiting structure 17. The second wiring layer 18 can achieve equipotential with the MEMS structure 13 through electrical connection. At the same time, the first wiring layer 15 above the substrate 11 is also connected to the MEMS structure 13 at the same potential, so that the MEMS structure 13 and the upper and lower components can achieve 0 potential difference, fundamentally eliminating the influence of electrostatic negative stiffness.
[0043] When using the TSV lead solution, such as Figure 5 The second wiring layer 18 is arranged on the upper surface of the limiting structure 17. The second wiring layer 18 can achieve equipotential with the MEMS structure 13 through electrical connection. At the same time, the first wiring layer 15 under the cover plate 12 is also connected to the MEMS structure 13 at the same potential, so that the MEMS structure 13 and the upper and lower components can achieve 0 potential difference, fundamentally eliminating the influence of electrostatic negative stiffness.
[0044] Preferably, the combined layer formed by the limiting structure 17 and the second wiring layer 18 and the first wiring layer 15 may be designed symmetrically with respect to the MEMS structure 13 .
[0045] In a possible implementation, the MEMS structure 13 is a structural layer of a gyroscope or an accelerometer.
[0046] In this embodiment, the MEMS structure 13 adopts the structure of the structural layer of a conventional gyroscope or accelerometer. Assuming that the MEMS structure 13 is the structural layer of the accelerometer, the MEMS structure 13 can be composed of a movable mass block, a torsion wiggling elastic beam, an anchor point, etc. The movable mass block is supported by the torsion wiggling elastic beam, and the torsion wiggling elastic beam is fixed to the substrate 11 through the anchor point. A detection capacitor plate is also provided on the first wiring layer 15. A differential capacitor is formed between the detection capacitor plate and the movable mass block.
[0047] In one possible implementation, Figure 3 and Figure 5 , the opening 16 is provided on the bottom surface of the cover plate 12;
[0048] The first wiring layer 15 is located on the inner surface of the bottom surface of the cover plate 12 .
[0049] In this embodiment, the MEMS inertial device adopts a side lead type lead solution.
[0050] In one possible implementation, Figure 2 and Figure 4 , the opening 16 is provided on the side of the cover plate 12;
[0051] The first wiring layer 15 is located on the upper surface of the substrate 11 .
[0052] In this embodiment, the MEMS inertial device adopts a TSV type lead solution.
[0053] The above embodiments should not limit the present invention in any way, and any technical solutions obtained by equivalent replacement or equivalent conversion shall fall within the protection scope of the present invention.
Claims
1. A MEMS inertial device capable of suppressing electrostatic negative stiffness, characterized in that: include: A substrate, a cover plate disposed on an upper surface of the substrate, and a MEMS structure located in the cover plate; A first wiring layer is provided on the inner surface of the cavity constructed by the cover plate and the substrate; The cover plate is provided with an opening for the first wiring layer to connect to the outside; A limited position structure is arranged in the cavity; The limiting structure and the first wiring layer are symmetrical with respect to the MEMS structure.
2. The MEMS inertial device according to claim 1, characterized in that: The area of the limiting structure is the same as the area of the mass block in the MEMS structure, and both are smaller than the area of the first wiring layer.
3. The MEMS inertial device according to claim 1, characterized in that: The area of the first wiring layer is the same as the area of the limiting structure, and both are larger than the area of the mass block in the MEMS structure.
4. The MEMS inertial device according to claim 1, characterized in that: A second wiring layer is arranged on a side of the limiting structure close to the first wiring layer.
5. The MEMS inertial device according to claim 1, characterized in that: The MEMS structure is a structural layer of a gyroscope or an accelerometer.
6. The MEMS inertial device according to claim 1, characterized in that: The opening is arranged on the bottom surface of the cover plate; The first wiring layer is located on the inner surface of the bottom surface of the cover plate.
7. The MEMS inertial device according to claim 1, characterized in that: The opening is arranged on the side of the cover plate; The first wiring layer is located on the upper surface of the substrate.