A tri-axial capacitive micro-electromechanical accelerometer

Abstract

The application discloses a triaxial capacitive micro-electro-mechanical accelerometer. By integrating a long strip in-plane detection unit, a Y-axis detection unit for detecting acceleration in a second in-plane direction perpendicular to each other and a torsional Z-axis detection unit with unbalanced mass distribution and / or unbalanced force arm distribution on the same substrate, a triaxial detection structure combining in-plane differential capacitive detection and out-of-plane differential capacitive detection is constructed, triaxial detection integration under limited layout area is realized, displacement response capability in the in-plane direction is enhanced, the clarity and flexibility of the structural layout are improved, and the detection sensitivity in the Z-axis direction is improved by increasing the effective action arm of the Z-axis detection unit.

Description

Technical Field

[0001] This application relates to the field of microelectromechanical systems (MEMS) inertial sensor technology, and more particularly to a triaxial capacitive MEMS accelerometer. Background Technology

[0002] With the increasing demand for miniaturized, low-power, and highly integrated inertial sensors in applications such as consumer electronics, automotive electronics, industrial control, attitude recognition, and inertial navigation, triaxial accelerometers, as key devices for acquiring acceleration information in three mutually perpendicular directions in space, typically require the integration of multi-axis detection structures within a limited chip area. Microelectromechanical accelerometers (MEMS) based on the capacitance sensing principle have advantages such as miniaturization, low power consumption, and easy compatibility with integrated circuits, and are therefore widely used in triaxial inertial sensing devices. For such devices, how to achieve triaxial detection integration on the same substrate while ensuring structural feasibility has become a continuous focus of related technologies.

[0003] In practice, triaxial capacitive microelectromechanical accelerometers typically employ a scheme integrating two in-plane detection structures and one out-of-plane detection structure on the same substrate to achieve acceleration detection in two in-plane directions and one direction perpendicular to the substrate, respectively. The in-plane detection structure often uses a movable mass and a fixed electrode to form a differential capacitance detection unit, while the out-of-plane detection structure often uses a suspended mass and a bottom electrode to form a capacitance detection unit. Some schemes also utilize a torsional support structure to achieve the rotational response of the mass around a predetermined axis. To meet the requirements of triaxial integration, the relevant detection modules are usually arranged in parallel, partially nested, enclosed in slots, or other planar layouts on the same chip layout to complete multi-axis detection functions within a single device.

[0004] However, when the above design integrates a triaxial acceleration detection structure on the same substrate, it often suffers from a large layout footprint, resulting in insufficient structural utilization within the limited chip area. The boundary relationships of each detection unit in the layout are not clear enough, which can easily cause the structural regions corresponding to different detection functions to intersect, affecting the clarity of the overall structural organization. The layout coordination between the in-plane and out-of-plane detection structures is insufficient, causing each detection module to restrict each other in terms of size configuration and position arrangement, which is not conducive to balancing integration and performance requirements. In particular, for the Z-axis detection unit, due to the limited structural arrangement, it is easy to cause insufficient response capability and limited change in the corresponding differential capacitance, thereby affecting the detection sensitivity in the out-of-plane direction. Summary of the Invention

[0005] In view of the above-mentioned actual situation, this application proposes a triaxial capacitive microelectromechanical accelerometer to solve the problems of large layout occupation, unclear structural boundaries of each detection unit, insufficient layout coordination between in-plane and out-of-plane detection structures, and limited response capability and differential capacitance change of the Z-axis detection unit when integrating triaxial acceleration detection structures on the same substrate in the prior art.

[0006] A triaxial capacitive microelectromechanical accelerometer includes a substrate, an in-plane detection unit, a Y-axis detection unit, and a Z-axis detection unit disposed on the substrate; The in-plane detection unit includes a first movable mass block, a first anchor point, a first spring beam, a second spring beam, a first forward fixed electrode, a second forward fixed electrode, a first reverse fixed electrode, and a second reverse fixed electrode. The first movable mass block is elongated, and the first anchor point is located in the middle region of the first movable mass block. The first spring beam and the second spring beam are respectively located on opposite sides of the first movable mass block and connected to the first anchor point, so that the first movable mass block can be displaced relative to the first anchor point along a first in-plane direction. The first forward fixed electrode and the second forward fixed electrode are located on the first side of the first anchor point, and the first reverse fixed electrode and the second reverse fixed electrode are located on the second side of the first anchor point, forming a differential capacitance detection structure with the first movable mass block. The Y-axis detection unit is a differential capacitance detection unit used to detect the acceleration in a second in-plane direction that is perpendicular to the detection direction of the in-plane detection unit; The Z-axis detection unit includes a mass block, a central anchor point, a first torsion spring beam, a second torsion spring beam, a first bottom electrode, and a second bottom electrode. The mass block includes a first mass region and a second mass region located on opposite sides of the central anchor point. The first torsion spring beam and the second torsion spring beam are respectively connected between the central anchor point and the mass block, enabling the mass block to rotate around the torsion axis. The first bottom electrode and the second bottom electrode are disposed below the mass block and respectively form a detection capacitor with the mass block. The first mass region and the second mass region have an unbalanced mass distribution and / or an unbalanced lever arm distribution, so that the mass block tilts around the torsion axis under the action of acceleration in the Z-axis direction, thereby causing the detection capacitors corresponding to the first bottom electrode and the second bottom electrode to change in opposite directions. The in-plane detection unit, the Y-axis detection unit, and the Z-axis detection unit are all disposed on the same substrate.

[0007] Furthermore, the first movable mass block, the mass block, the first spring beam, the second spring beam, the first anchor point, the first torsion spring beam, the second torsion spring beam, and the center anchor point are formed from the same device layer and are at the same level in the thickness direction.

[0008] Furthermore, the Y-axis detection unit and the in-plane detection unit are isomorphic, and the in-plane detection unit is formed by rotating the in-plane detection unit 90° around an axis perpendicular to the substrate.

[0009] Furthermore, the first anchor point extends along a direction perpendicular to the length of the first movable mass block and is disposed in the middle region of the first movable mass block; the first spring beam and the second spring beam extend on both sides along the length of the first movable mass block; the first positive fixed electrode and the second positive fixed electrode are respectively disposed in the region corresponding to the first set of plate electrodes of the first movable mass block; and the first negative fixed electrode and the second negative fixed electrode are respectively disposed in the region corresponding to the second set of plate electrodes of the first movable mass block.

[0010] Furthermore, the first forward fixed electrode, the second forward fixed electrode, the first reverse fixed electrode, and the second reverse fixed electrode are all plate-shaped fixed electrodes, and have inclined edge portions and / or convergent edge portions formed on the side facing the first movable mass block.

[0011] Furthermore, the first mass region is a mass region with a large solid retention area, and the second mass region is provided with at least one weight reduction area, so that the mass of the first mass region is greater than the mass of the second mass region, and / or the distance from the center of mass of the first mass region to the torsion axis is greater than the distance from the center of mass of the second mass region to the torsion axis.

[0012] Furthermore, the first bottom electrode and the second bottom electrode are positioned below the mass block with the central anchor point as the center of symmetry; when there is no acceleration in the Z-axis direction, the initial distance between the first bottom electrode and the mass block is equal to or substantially equal to the initial distance between the second bottom electrode and the mass block, so that the corresponding initial detection capacitances are equal to or substantially equal.

[0013] Furthermore, the in-plane detection unit and the Y-axis detection unit are respectively arranged along two mutually perpendicular in-plane directions, and are arranged side by side with the Z-axis detection unit on the substrate; wherein, the Z-axis detection unit is arranged in the remaining layout area formed by the arrangement of the in-plane detection unit and the Y-axis detection unit.

[0014] Furthermore, a reserved area is provided within the first mass region, and at least a portion of the structure of the in-plane detection unit is disposed within the reserved area; the reserved area is a local layout accommodating area disposed within the first mass region, the boundary of which is enclosed by the solid portion of the first mass region and does not penetrate the entire mass block.

[0015] Furthermore, the reserved area is located on the side away from the central anchor point, and the in-plane detection unit is embedded within the reserved area, while the Y-axis detection unit is disposed outside the Z-axis detection unit, so as to increase the effective arm of the first mass area relative to the torsional axis. The triaxial capacitive microelectromechanical accelerometer proposed in this application realizes triaxial acceleration detection integration on the same substrate. By using an elongated in-plane detection structure, an isomorphic Y-axis detection structure, and a torsional Z-axis detection structure with unbalanced mass distribution and / or unbalanced lever arm distribution, it balances layout clarity and layout utilization. At the same time, by increasing the effective working arm of the Z-axis detection unit through embedded arrangement, it improves the tilt response and differential capacitance change in the Z-axis direction. Attached Figure Description

[0016] Figure 1 This is a top view of the detection unit in the elongated surface in an embodiment of this application.

[0017] Figure 2 This is a schematic diagram showing the coplanar structural relationship between the in-plane detection unit and the Z-axis detection unit in an embodiment of this application.

[0018] Figure 3 This is a top view of the Z-axis detection unit in an embodiment of this application.

[0019] Figure 4 This is a schematic diagram illustrating the working principle of the Z-axis detection unit in an embodiment of this application, wherein... Figure 4 (a) is a schematic diagram of the initial equilibrium state. Figure 4 (b) is a schematic diagram of the tilt state after being subjected to acceleration in the Z-axis direction.

[0020] Figure 5 This is a schematic diagram of the triaxial integrated structure of arrangement method 1 in this application embodiment.

[0021] Figure 6 This is a schematic diagram of the embedded structure of arrangement method 2 in the embodiments of this application.

[0022] Explanation of reference numerals in the attached figures 100, Triaxial capacitive MEMS accelerometer; 110, Substrate; 200, In-plane detection unit / X-axis detection unit; 210, First movable mass block; 220, First spring beam; 221, Second spring beam; 230, First anchor point; 240, First forward fixed electrode; 241, Second forward fixed electrode; 250, First reverse fixed electrode; 251, Second reverse fixed electrode; 300, Y-axis detection unit; 400, Z-axis detection unit; 410, Mass block; 411, First mass region; 412, Second mass region; 420, Center anchor point; 430, First torsion spring beam; 431, Second torsion spring beam; 440, First bottom electrode; 441, Second bottom electrode; 450, Reserved area Tz; 460, Torsion axis. Detailed Implementation

[0023] The technical solution of this application will be further described in detail below with reference to the accompanying drawings. It should be understood that the embodiments described below are only for illustrating this application and are not intended to limit the scope of protection of this application. Where there is no conflict, the various embodiments of this application and the technical features of each embodiment can be combined with each other. Equivalent substitutions, conventional changes, and customary adjustments made by those skilled in the art after reading this specification without departing from the technical concept of this application should all be considered to fall within the scope of protection of this application.

[0024] It should be noted that, for ease of description, in this application, the two mutually perpendicular detection directions located in the plane of the substrate 110 are respectively referred to as the first in-plane direction and the second in-plane direction, wherein the second in-plane direction may correspond to the Y-axis direction; the detection direction perpendicular to the plane of the substrate 110 is referred to as the Z-axis direction. The first in-plane direction, the second in-plane direction, and the Z-axis direction are mutually perpendicular. The positional relationships such as up, down, left, right, inside, outside, away, and near shown in the accompanying drawings are mainly used to illustrate the technical solution of this application in conjunction with the accompanying drawings, and do not necessarily constitute a limitation on the scope of protection of this application.

[0025] Reference Figures 1 to 6In some embodiments, this application provides a triaxial capacitive microelectromechanical accelerometer 100, which includes a substrate 110, an in-plane detection unit 200, a Y-axis detection unit 300, and a Z-axis detection unit 400 disposed on the substrate 110. The in-plane detection unit 200 detects acceleration in a first in-plane direction, the Y-axis detection unit 300 detects acceleration in a second in-plane direction perpendicular to the detection direction of the in-plane detection unit 200, and the Z-axis detection unit 400 detects acceleration along a direction perpendicular to the substrate 110. Thus, the in-plane detection unit 200, the Y-axis detection unit 300, and the Z-axis detection unit 400 correspond to three mutually perpendicular detection directions, thereby jointly achieving triaxial acceleration detection.

[0026] In some embodiments, this application integrates a plate-type differential capacitance detection structure for in-plane orientation detection and a torsional differential capacitance detection structure for out-of-plane orientation detection on the same substrate 110, forming a parallel arrangement and an embedded arrangement. Unlike the integration method that places multiple detection modules in the same through-hole enclosure, this application emphasizes the layout organization, structural boundary relationships, and local containment relationships between the detection units. In particular, it emphasizes the enhancement effect on the effective arm of the Z-axis detection unit 400 after forming a single-sided embedded structure by setting a local reserved area Tz450 within the first mass region 411. Through the above arrangement, it is possible to balance triaxial detection integration, clear structural regions, and improved Z-axis direction detection sensitivity within a smaller layout area.

[0027] Reference Figure 1 In some embodiments, the in-plane detection unit 200 includes a first movable mass block 210, a first anchor point 230, a first spring beam 220, a second spring beam 221, a first forward fixed electrode 240, a second forward fixed electrode 241, a first reverse fixed electrode 250, and a second reverse fixed electrode 251. The first movable mass block 210 is generally elongated, with its length dimension greater than its width dimension. The first anchor point 230 is located in the middle region of the first movable mass block 210. The first spring beam 220 and the second spring beam 221 are respectively located on opposite sides of the first movable mass block 210 and connected to the first anchor point 230, so that the first movable mass block 210 can be displaced relative to the first anchor point 230 along a first in-plane direction.

[0028] Specifically, in some embodiments, the first anchor point 230 may extend along a direction perpendicular to the length direction of the first movable mass block 210 and be located in the middle region of the first movable mass block 210. The first spring beam 220 and the second spring beam 221 may extend along both sides of the length direction of the first movable mass block 210 and be connected to the first anchor point 230. With the above arrangement, the first movable mass block 210 can achieve relative displacement in a predetermined in-plane direction under the constraint of the first anchor point 230, while suppressing excessive offset in non-target directions, thereby facilitating the formation of a more stable in-plane detection degree of freedom. In some embodiments, the first spring beam 220 and the second spring beam 221 are mirror images of the first anchor point 230 and are respectively connected to corresponding positions on both sides of the middle of the length direction of the first movable mass block 210. With the above arrangement, the first movable mass block 210 can maintain a more stable translational response during displacement in the first in-plane direction and reduce the additional rotational component about the direction perpendicular to the substrate 110.

[0029] In some embodiments, the first positive fixed electrode 240 and the second positive fixed electrode 241 are disposed on the first side of the first anchor point 230, and the first negative fixed electrode 250 and the second negative fixed electrode 251 are disposed on the second side of the first anchor point 230, respectively forming a differential capacitance detection structure with the first movable mass block 210. Further, the first movable mass block 210 may form a first set of plate-shaped electrode corresponding regions corresponding to the first positive fixed electrode 240 and the second positive fixed electrode 241, and a second set of plate-shaped electrode corresponding regions corresponding to the first negative fixed electrode 250 and the second negative fixed electrode 251. Taking the first anchor point 230 located in the middle region as an example, the first set of plate-shaped electrode corresponding regions and the second set of plate-shaped electrode corresponding regions may be located in the plate-shaped sensing regions on opposite sides of the first anchor point 230, respectively. Thus, when the first movable mass block 210 undergoes in-plane displacement, a differential detection relationship with opposite capacitance change directions can be formed on the first side and the second side. In some embodiments, the first positive fixed electrode 240 and the second positive fixed electrode 241 are spaced apart along the length direction of the first movable mass block 210, and the first negative fixed electrode 250 and the second negative fixed electrode 251 are spaced apart along the length direction of the first movable mass block 210. The fixed electrode located on the first side of the first anchor point 230 and the fixed electrode located on the second side of the first anchor point 230 form a mirror image relationship with respect to the first anchor point 230. In some embodiments, the first positive fixed electrode 240, the second positive fixed electrode 241, and the corresponding regions of the first set of plate-shaped electrodes at least partially correspond in the projection perpendicular to the substrate 110, and the first negative fixed electrode 250, the second negative fixed electrode 251, and the corresponding regions of the second set of plate-shaped electrodes at least partially correspond in the projection perpendicular to the substrate 110. Through the above arrangement, a relatively stable differential capacitance response relationship can be formed on the positive fixed electrode side and the negative fixed electrode side during the displacement of the first movable mass block 210 in the first plane direction.

[0030] In some embodiments, the first forward fixed electrode 240, the second forward fixed electrode 241, the first reverse fixed electrode 250, and the second reverse fixed electrode 251 can all be configured as plate-shaped fixed electrodes. Taking the plate-shaped fixed electrode forming a non-parallel edge profile on the side facing the first movable mass block 210 as an example, the plate-shaped fixed electrode can be provided with an inclined edge portion and / or a converging edge portion. Specifically, the inclined edge portion can be an edge portion that forms an angle with the corresponding side of the first movable mass block 210, and the converging edge portion can be an edge profile that gradually narrows along the detection direction in the first plane or along a projection direction related to the detection direction in the first plane. Through the above edge profile configuration, the local electric field distribution, capacitance change gradient, and output linear range during the displacement process of the first movable mass block 210 can be adjusted, thereby facilitating the design of structural parameters based on target sensitivity, target range, and target linear characteristics. Taking the plate-shaped fixed electrode as an example of an inclined edge portion, the inclined edge portion can form a predetermined angle with respect to the corresponding side of the first movable mass block 210; taking the plate-shaped fixed electrode as an example of a converging edge portion, its projected width along the detection direction in the first surface can gradually decrease along the predetermined displacement direction. Through the above settings, the slope of capacitance change and the linear output range can be further adjusted.

[0031] Furthermore, in different embodiments, the inclined edge portion and the converging edge portion can appear individually or in combination; the edge contours of the first positive fixed electrode 240, the second positive fixed electrode 241, the first negative fixed electrode 250, and the second negative fixed electrode 251 can also be set to be the same or different. Taking a symmetrical design as an example, the fixed electrodes located on both sides of the first anchor point 230 can adopt mirrored edge contours; taking an asymmetrical design as an example, different edge contours can also be set for the fixed electrodes on different sides according to the slope of the target capacitance change, the displacement range, or process limitations. As long as the differential capacitance detection relationship between the first movable mass block 210 and the positive fixed electrode side and the negative fixed electrode side can be maintained, it can fall within the technical concept of this application.

[0032] In some embodiments, when the substrate 110 experiences acceleration input along the first in-plane direction, the first movable mass block 210 undergoes relative displacement in the corresponding direction relative to the first anchor point 230 under inertia, thereby causing the detection capacitors corresponding to the first positive fixed electrode 240 and the second positive fixed electrode 241 to change in opposite directions to the detection capacitors corresponding to the first negative fixed electrode 250 and the second negative fixed electrode 251. After reading the differential capacitance change, the detection circuit can obtain the acceleration information corresponding to the first in-plane direction. The specific differential capacitance signal reading, capacitance-to-voltage conversion, signal amplification, and subsequent processing methods can all be implemented using methods well-known to those skilled in the art, and will not be elaborated upon here.

[0033] In some embodiments, the first movable mass block 210 adopts an elongated structure, and the first spring beam 220 and the second spring beam 221 are respectively located on both sides of the length direction of the first movable mass block 210. With this arrangement, within a limited layout area, the first spring beam 220 and the second spring beam 221 can achieve a relatively long effective elastic length, which helps to reduce structural stiffness, increase inertial response displacement, and improve in-plane detection sensitivity. Simultaneously, the first anchor point 230 is located in the central region, which also facilitates the formation of a clearer left-right partition structure at the layout level, making it easier to arrange corresponding forward and reverse fixed electrodes on both sides of the first anchor point 230.

[0034] In some embodiments, the Y-axis detection unit 300 and the in-plane detection unit 200 are isomorphic. That is, the Y-axis detection unit 300 can maintain a basically consistent structure with the in-plane detection unit 200 in terms of mass block configuration, anchor point arrangement, elastic support method, and differential capacitance detection mechanism, except that its detection direction is rotated 90° relative to the in-plane detection unit 200. Specifically, the Y-axis detection unit 300 can be considered as formed by rotating the in-plane detection unit 200 90° around an axis perpendicular to the substrate 110. Thus, without changing the basic process route and basic unit topology, the detection of acceleration in another in-plane direction can be achieved. In some embodiments, the mass block, anchor points, spring beams, and fixed electrodes in the Y-axis detection unit 300 correspond one-to-one with the corresponding components in the in-plane detection unit 200 in terms of structural topology, and after rotating 90°, the basic arrangement of the anchor points being located in the central region, the elastic support structure being located on opposite sides of the mass block, and the fixed electrodes being placed on both sides of the anchor points is maintained.

[0035] Furthermore, in some embodiments, the Y-axis detection unit 300 and the in-plane detection unit 200 can adopt the same structural parameters to form two relatively symmetrical detection units in the in-plane direction. In other embodiments, the Y-axis detection unit 300 can also adapt and adjust local parameters such as the mass block size, spring beam length, spring beam width, electrode spacing, and electrode area while maintaining the consistency of the basic detection mechanism, so as to meet the different design requirements of the two in-plane directions for sensitivity, natural frequency, range, or layout occupancy. Thus, the "isomorphic structure" does not require the two in-plane detection units to be completely identical in all geometric parameters, but emphasizes the correspondence between the two in the basic structural relationship and basic detection mechanism.

[0036] Figure 5 and Figure 6 In this diagram, the Y-axis detection unit 300 is primarily shown as a whole, with the focus on illustrating its relative arrangement within the triaxial integrated layout. Those skilled in the art will understand that the Y-axis detection unit 300 can internally employ mass blocks, anchor points, elastic support structures, and differential capacitor-fixed electrodes corresponding to the in-plane detection unit 200 to achieve acceleration detection in another in-plane direction. The specific implementation method is something that those skilled in the art can directly determine based on the aforementioned isomorphic relationship.

[0037] Reference Figure 2 In some embodiments, the first movable mass block 210, the mass block 410, the first spring beam 220, the second spring beam 221, the first anchor point 230, the first torsion spring beam 430, the second torsion spring beam 431, and the center anchor point 420 are preferably formed from the same device layer and are at the same level in the thickness direction. In other words, this application does not rely on setting the three detection modules in multiple independent device layers, but preferably forms a coplanar device layer structure on the same substrate 110, and forms the corresponding suspended movable structure through a subsequent release process. In some embodiments, the first movable mass block 210 and the mass block 410 are patterned from the same device layer and can maintain material continuity before release; after release, their corresponding upper and / or lower surfaces can be located at substantially the same height level. Through the above arrangement, it is beneficial to further ensure the layer consistency of different detection units during the manufacturing process.

[0038] Specifically, refer to Figure 2 On the left side, the first movable mass block 210 in the in-plane detection unit 200 is connected to the first anchor point 230 via the first spring beam 220 and the second spring beam 221; (refer to...) Figure 2On the right side, the mass block 410 in the Z-axis detection unit 400 is connected to the center anchor point 420 through the first torsion spring beam 430 and the second torsion spring beam 431. Figure 2 The key point is that the main movable structure and support structure in the in-plane detection unit 200 and the Z-axis detection unit 400 can be located in the same device layer, thereby maintaining consistency in layout organization and process implementation.

[0039] By employing the aforementioned method of forming layers in the same plane and setting them on the same surface, it is beneficial to simplify device layer design, patterning processes, and release processes, reducing the process complexity caused by multi-layer stacking. Furthermore, it helps maintain the layer consistency, release consistency, and structural correspondence of each detection unit during processing, thereby reducing structural deviations that may be caused by interlayer misalignment, interlayer stress differences, or multi-layer registration errors. The microelectromechanical processing methods such as device layer deposition, photolithography, etching, sacrificial layer removal, and release processes can all be implemented using conventional MEMS processes well-known to those skilled in the art, and will not be elaborated upon here.

[0040] Reference Figure 3 In some embodiments, the Z-axis detection unit 400 includes a mass block 410, a central anchor point 420, a first torsion spring beam 430, a second torsion spring beam 431, a first bottom electrode 440, and a second bottom electrode 441. The mass block 410 includes a first mass region 411 and a second mass region 412 located on opposite sides of the central anchor point 420. The first torsion spring beam 430 and the second torsion spring beam 431 are respectively connected between the central anchor point 420 and the mass block 410, enabling the mass block 410 to torsion about the torsion axis 460. The first bottom electrode 440 and the second bottom electrode 441 are disposed below the mass block 410 and respectively form a detection capacitance with the mass block 410. In some embodiments, the first torsion spring beam 430 and the second torsion spring beam 431 are symmetrically arranged relative to the central anchor point 420 and are located on opposite sides of the torsion axis 460. With the above configuration, the mass block 410 can form a relatively stable torsional response around the torsion axis 460 under the action of acceleration in the Z-axis direction. In some embodiments, the first torsion spring beam 430 and the second torsion spring beam 431 are symmetrically arranged with respect to the central anchor point 420 and are respectively located on both sides of the torsion axis 460; the connection positions of the first torsion spring beam 430 and the second torsion spring beam 431 with the mass block 410 are correspondingly distributed with respect to the central anchor point 420. With the above configuration, the mass block 410 can form a relatively stable torsional response around the torsion axis 460 under the action of acceleration in the Z-axis direction.

[0041] In some embodiments, the first mass region 411 is preferably a mass region with a larger solid retention area, and the second mass region 412 is preferably provided with at least one weight-reducing region, thereby making the mass of the first mass region 411 greater than the mass of the second mass region 412, and / or making the distance from the center of mass of the first mass region 411 to the torsion axis 460 greater than the distance from the center of mass of the second mass region 412 to the torsion axis 460. In other words, an unbalanced mass distribution and / or an unbalanced lever arm distribution is formed between the first mass region 411 and the second mass region 412. With the above configuration, when there is an acceleration input along the Z-axis direction, the mass block 410 can tilt outward around the torsion axis 460 under the action of inertia.

[0042] Furthermore, in different embodiments, the unbalanced mass distribution and the unbalanced lever arm distribution can appear individually or in combination. Taking the unbalanced mass distribution appearing alone as an example, this can be achieved by increasing the solid area retained by the first mass region 411, decreasing the solid area retained by the second mass region 412, or setting a weight-reduction region in the second mass region 412. Taking the unbalanced lever arm distribution appearing alone as an example, this can be achieved by adjusting the geometric positions of the first mass region 411 and the second mass region 412 relative to the torsion axis 460, making the distances from their centers of mass to the torsion axis 460 different. In other embodiments, a composite unbalanced structure can also be formed simultaneously through mass differences and differences in center of mass position. Through these various implementation methods, greater freedom can be provided for subsequent structural designs under different sensitivities, ranges, and layout areas.

[0043] In some embodiments, the number, shape, location, and arrangement of the weight-reducing regions can be adjusted according to the target mass difference, the target centroid location, and structural strength requirements. Taking the second mass region 412 as an example, the weight-reducing regions can be hollowed-out regions, partially perforated regions, partially thinned regions, or partially material-removed regions. Only one weight-reducing region can be provided, or multiple weight-reducing regions can be provided; multiple weight-reducing regions can be arranged regularly or irregularly; the weight-reducing regions can appear alone or in combination with local contour relief structures. As long as an unbalanced mass distribution and / or unbalanced lever arm distribution can be formed between the first mass region 411 and the second mass region 412, it can fall within the technical solutions of this application. In some embodiments, the first mass region 411 is preferably maintained as a continuous solid structure, and the weight-reducing regions in the second mass region 412 are preferably arranged to avoid the connection area between the central anchor point 420 and the first torsion spring beam 430 and the second torsion spring beam 431, so as to balance the formation of mass differences and the structural strength of the torsion support area.

[0044] In some embodiments, the first bottom electrode 440 and the second bottom electrode 441 are positioned below the mass block 410 with the central anchor point 420 as the center of symmetry. When there is no acceleration in the Z-axis direction, the initial distance between the first bottom electrode 440 and the mass block 410 is equal to or substantially equal to the initial distance between the second bottom electrode 441 and the mass block 410, so that the corresponding initial detection capacitances are equal to or substantially equal. This arrangement provides a relatively stable initial reference state for subsequent differential detection. Figure 3 In this diagram, the first bottom electrode 440 and the second bottom electrode 441 can be shown as projected regions, primarily used to express the planar correspondence between the bottom electrodes and the mass block 410, as well as their relative arrangement with the central anchor point 420, the first torsion spring beam 430, and the second torsion spring beam 431. In some embodiments, the first bottom electrode 440 and the first mass region 411 at least partially correspond in projection perpendicular to the substrate 110, and the second bottom electrode 441 and the second mass region 412 at least partially correspond in projection perpendicular to the substrate 110. This arrangement allows the mass block 410 to more effectively generate differential capacitance changes on both sides during tilting. In some embodiments, the first bottom electrode 440 and the first mass region 411 at least partially correspond in projection perpendicular to the substrate 110, and the second bottom electrode 441 and the second mass region 412 at least partially correspond in projection perpendicular to the substrate 110. With the above settings, the mass block 410 can form a spacing change corresponding to the bottom electrode position on the first mass region 411 side and the second mass region 412 side respectively during the tilting process around the torsion axis 460, thereby improving the stability of the differential capacitance change.

[0045] Reference Figure 4 , Figure 4 (a) shows a schematic diagram of the mass block 410 in its initial equilibrium state. Figure 4 (b) shows a schematic representation of the state of mass block 410 after it has undergone torsional tilting under the action of acceleration in the Z-axis direction. Figure 4 In the state shown in (a), the mass block 410 remains basically horizontal, and the capacitances formed between the first bottom electrode 440 and the mass block 410, and between the second bottom electrode 441 and the mass block 410, are in an initial equilibrium state. Figure 4 In the state shown in (b), due to the unbalanced mass distribution and / or unbalanced lever arm distribution between the first mass region 411 and the second mass region 412, the mass block 410 tilts around the torsion axis 460, so that one side is relatively close to the bottom electrode below it, and the other side is relatively far away from the bottom electrode below it.

[0046] In some implementations, with Figure 4 Taking the state shown in (b) as an example, one side of the first mass region 411 is relatively closer to the first bottom electrode 440, which reduces the corresponding electrode spacing and increases the detection capacitance; the other side of the second mass region 412 is relatively farther away from the second bottom electrode 441, which increases the corresponding electrode spacing and decreases the detection capacitance. Since the changes in the detection capacitance on both sides are in opposite directions, the Z-axis acceleration signal can be read differentially. Thus, the Z-axis detection unit 400 can achieve sensitive detection of outward acceleration through the cooperation between the unbalanced mass region and the torsional support structure.

[0047] Reference Figure 5 In some embodiments, this application provides a triaxial integrated structure arranged in parallel. Specifically, the in-plane detection unit 200 and the Y-axis detection unit 300 are respectively arranged along two mutually perpendicular in-plane directions, and are arranged in parallel with the Z-axis detection unit 400 on the substrate 110. Optionally, the in-plane detection unit 200 is arranged along a first in-plane direction, the Y-axis detection unit 300 is arranged along a second in-plane direction, and the Z-axis detection unit 400 is arranged in the remaining layout area formed by the arrangement of the in-plane detection unit 200 and the Y-axis detection unit 300.

[0048] Specifically, in the parallel arrangement described above, two elongated in-plane detection units can be first arranged orthogonally in the substrate plane to achieve detection functions for the two in-plane axes respectively. Based on this, the Z-axis detection unit 400 is independently arranged in the remaining layout area defined by the two in-plane detection units. This structural layout ensures clear physical boundaries between detection units, facilitating the differentiation of structural areas for different detection function modules during process implementation. Furthermore, since each detection unit is relatively independent on the layout, its structural dimensions can be adjusted according to the different requirements for sensitivity, frequency characteristics, and layout area occupied by the corresponding detection direction. In some embodiments, the in-plane detection unit 200, the Y-axis detection unit 300, and the Z-axis detection unit 400 are separated from each other in their main structural areas on the substrate 110, and adjacent detection units do not form a continuous nesting relationship. This arrangement makes the structural boundaries corresponding to different detection functions clearer. In some embodiments, the in-plane detection unit 200, the Y-axis detection unit 300, and the Z-axis detection unit 400 are separated from each other in their main functional structural regions on the substrate 110, and adjacent detection units do not form a through-type nesting relationship. This arrangement makes the structural boundaries corresponding to different detection functions clearer and facilitates relatively independent parameter configuration of each detection unit during the layout design stage.

[0049] Furthermore, the parallel arrangement described above reduces the degree of nesting between different detection units at the layout level, facilitating independent optimization of the mass block size, spring beam parameters, electrode spacing, and sensing area of ​​each detection unit during the structural design phase. Simultaneously, since the Z-axis detection unit 400 is located in the remaining layout area, it also helps improve the integration of the three-axis detection function under the condition of limited overall chip area. The specific shape, area, and position of the remaining layout area can be adjusted according to the size parameters of the two in-plane detection units and the overall chip boundary conditions; those skilled in the art can perform conventional design according to actual needs. In some embodiments, the boundary of the remaining layout area at least partially defines the external arrangement range of the Z-axis detection unit 400, and the central anchor point 420 is located inside the remaining layout area.

[0050] Reference Figure 6 In other embodiments, this application provides an embedded triaxial integrated structure. Specifically, a reserved area Tz450 is provided within the first mass region 411, at least a portion of the structure of the in-plane detection unit 200 is disposed within the reserved area Tz450, and the Y-axis detection unit 300 is disposed outside the Z-axis detection unit 400. It should be noted that the reserved area Tz450 is preferably a partial layout accommodating area disposed within the first mass region 411, its boundary being enclosed by the solid portion of the first mass region 411, and not penetrating the entire mass block 410. That is to say, the embedded structure described in this application emphasizes the partial embedding of the in-plane detection unit 200 on one side of the first mass region 411, rather than forming a nested structure that encloses multiple detection modules in the same through slot.

[0051] Furthermore, in some embodiments, the reserved area Tz450 is located on the side away from the central anchor point 420. Taking the in-plane detection unit 200 embedded in the reserved area Tz450 and the Y-axis detection unit 300 disposed outside the Z-axis detection unit 400 as an example, the effective working arm length of the first mass region 411 relative to the torsion axis 460 can be increased. For the torsion Z-axis detection unit 400, under the same Z-axis acceleration input condition, a larger effective working arm means a larger torsional load, thereby enabling the mass block 410 to produce a more obvious tilting response and further increasing the differential change in the detection capacitance corresponding to the first bottom electrode 440 and the second bottom electrode 441, thus improving the detection sensitivity in the Z-axis direction. Furthermore, in some embodiments, after the in-plane detection unit 200 is embedded in the reserved area Tz450, the equivalent mass distribution on one side of the first mass region 411 is retained and / or strengthened in the region away from the torsion axis 460, thereby generating a larger torsional torque under Z-axis acceleration input conditions. In some embodiments, after the in-plane detection unit 200 is embedded in the reserved region Tz450, the distribution relationship of the solid mass of the first mass region 411 on the side away from the torsion axis 460 in the overall layout is preserved and / or enhanced, thereby generating a larger torsional moment under acceleration input conditions in the Z-axis direction. As a result, the mass block 410 can obtain a more obvious tilt response and further improve the amplitude of the differential capacitance change corresponding to the first bottom electrode 440 and the second bottom electrode 441.

[0052] In some embodiments, the reserved area Tz450 can be formed by partial material removal, partial retraction, partial layout clearance, or partial accommodating structure. Taking the first mass region 411 as an overall solid retention area as an example, the reserved area Tz450 can form a partially recessed layout space within the first mass region 411 to accommodate at least a portion of the structure of the in-plane detection unit 200. The "at least a portion of the structure" can be one or more of the following: at least a portion of the layout area of ​​the in-plane detection unit 200, at least a portion of the movable mass block area, at least a portion of the elastic support area, and the corresponding electrode area. Through the above arrangement, the mass characteristic of the first mass region 411 as the heavier side can be maintained, and a partial embedding relationship between the in-plane detection unit 200 and the first mass region 411 can be achieved. In some embodiments, the first mass region 411 retains a continuous solid force transmission area between the reserved area Tz450 and the central anchor point 420, so that while forming a partial accommodating relationship, the first mass region 411 can still maintain effective mass action and force transmission continuity relative to the torsional axis 460. In some embodiments, the reserved area Tz450 is preferably positioned to avoid the central anchor point 420, the first torsion spring beam 430, and the second torsion spring beam 431, so as to avoid adversely affecting the main torsional support path of the Z-axis detection unit 400. In some embodiments, the first mass area 411 retains a continuous solid force transmission area between the reserved area Tz450 and the central anchor point 420, so that the first mass area 411 can maintain effective mass action and force transmission continuity relative to the torsion axis 460 while forming a local containment relationship. Through the above arrangement, it is beneficial to form a local embedding relationship between the in-plane detection unit 200 and the first mass area 411, and also beneficial to maintain the basic torsional response path of the Z-axis detection unit 400. In some embodiments, the reserved area Tz450 is preferably disposed to avoid the center anchor point 420, the first torsion spring beam 430, and the second torsion spring beam 431; further, the reserved area Tz450 does not overlap with the center anchor point 420, the first torsion spring beam 430, and the second torsion spring beam 431 in its projection perpendicular to the direction of the substrate 110. Through the above arrangement, the reserved area Tz450 can be prevented from adversely affecting the main torsion support path of the Z-axis detection unit 400.

[0053] In some embodiments, the outline of the reserved area Tz450 can be set as a rectangle, a strip, a partially open shape, or other outlines suitable for forming a local containment relationship; the depth, proportion, and position of the in-plane detection unit 200 embedded in the reserved area Tz450 can also be adjusted according to the target layout area, target sensitivity, and structural strength requirements. Taking different embedding depths as an example, shallower embedding can take into account the solid continuity of the first mass region 411, while deeper embedding is more conducive to forming a more obvious local containment relationship and an effective arm extension effect. As long as the reserved area Tz450 is located within the first mass region 411 and on the side away from the central anchor point 420, and can increase the effective arm of the first mass region 411 relative to the torsion axis 460 after embedding the in-plane detection unit 200, it can be considered to fall within the technical concept of this application. In some embodiments, the outline boundary of the reserved area Tz450 is at least partially surrounded in the circumferential direction by the solid portion of the first mass region 411, and a continuous solid connecting band is maintained between the reserved area Tz450 and the outer boundary of the first mass region 411. With this arrangement, while forming a local containment relationship, the overall solid continuity of the first mass region 411 can be maintained, and it is beneficial to maintain the effective mass effect on the side away from the torsion axis 460.

[0054] In different implementations, the reserved area Tz450 can exist alone as a local accommodating area, or it can appear in combination with the local weight reduction structure, local yielding structure, or local contour adjustment structure in the first mass area 411. Furthermore, the formation of the reserved area Tz450 and the unbalanced mass distribution and / or unbalanced lever arm distribution between the first mass area 411 and the second mass area 412 can also be set individually or in combination. Through the above settings, while ensuring that the basic mechanism of Z-axis detection remains unchanged, greater design space can be provided for layout optimization and sensitivity adjustment.

[0055] In some embodiments, the in-plane detection unit 200 and the Y-axis detection unit 300 may have the same dimensions; in other embodiments, an asymmetric design may be used based on performance requirements in both in-plane directions. Similarly, the imbalance between the first mass region 411 and the second mass region 412 can be achieved in various ways, such as through differences in solid area, differences in the number of weight-reducing regions, differences in the position of the weight-reducing regions, differences in the center of mass offset, or differences in the action arm relative to the torsion axis 460. For this application, the key is not to limit a unique geometric shape, but to maintain the overall technical solution constituted by the above-mentioned elongated in-plane detection structure, isomorphic Y-axis detection structure, torsion-type Z-axis detection structure, and parallel / embedded layout organization.

[0056] It should be noted that the detection circuits, signal reading circuits, differential processing circuits, packaging structures, and insulating layers, conductive layers, and lead connection structures that cooperate with the substrate 110 for the in-plane detection unit 200, the Y-axis detection unit 300, and the Z-axis detection unit 400 can all be implemented in ways well known to those skilled in the art. As long as the core structural relationships and detection mechanisms described in this application are not affected, the implementation of the technical solution of this application will not be affected.

[0057] In summary, this application achieves triaxial acceleration detection integration on the same substrate 110 through a combination of elongated plate-type in-plane detection units, isomorphic Y-axis detection units, coplanar Z-axis torsional differential detection units, parallel arrangement, and embedded arrangement. Specifically, the elongated in-plane detection units are beneficial for improving in-plane response capability within a limited area; the Z-axis detection units with unbalanced mass distribution and / or unbalanced lever arm distribution are beneficial for forming stable out-of-plane differential capacitance detection; the parallel arrangement facilitates clear layout relationships, well-defined functional areas, and separate parameter adjustments; and the embedded arrangement further enhances Z-axis direction detection sensitivity by increasing the effective lever arm of the first mass region 411 relative to the torsional axis 460.

[0058] The technical features in the above embodiments of this application can be combined arbitrarily. In order to make the description concise, not all possible combinations of the above technical features are described one by one; however, as long as there is no contradiction in the combination of these technical features, they should all be considered as the scope of this specification.

Claims

1. A triaxial capacitive microelectromechanical accelerometer, characterized in that, It includes a substrate (110), an in-plane detection unit (200), a Y-axis detection unit (300), and a Z-axis detection unit (400) disposed on the substrate (110). The in-plane detection unit (200) includes a first movable mass block (210), a first anchor point (230), a first spring beam (220), a second spring beam (221), a first forward fixed electrode (240), a second forward fixed electrode (241), a first reverse fixed electrode (250), and a second reverse fixed electrode (251). The first movable mass block (210) is elongated, and the first anchor point (230) is located in the middle region of the first movable mass block (210). The first spring beam (220) and the second spring beam (221) are respectively located in the middle region of the first movable mass block (210). A movable mass block (210) is positioned on opposite sides and connected to the first anchor point (230) so that the first movable mass block (210) can be displaced relative to the first anchor point (230) in a first in-plane direction; the first positive fixed electrode (240) and the second positive fixed electrode (241) are disposed on the first side of the first anchor point (230), and the first reverse fixed electrode (250) and the second reverse fixed electrode (251) are disposed on the second side of the first anchor point (230), and respectively form a differential capacitance detection structure with the first movable mass block (210); The Y-axis detection unit (300) is a differential capacitance detection unit used to detect the acceleration in a second in-plane direction that is perpendicular to the detection direction of the in-plane detection unit (200); The Z-axis detection unit (400) includes a mass block (410), a center anchor point (420), a first torsion spring beam (430), a second torsion spring beam (431), a first bottom electrode (440), and a second bottom electrode (441). The mass block (410) includes a first mass region (411) and a second mass region (412) located on opposite sides of the center anchor point (420). The first torsion spring beam (430) and the second torsion spring beam (431) are respectively connected between the center anchor point (420) and the mass block (410), so that the mass block (410)... 10) Capable of rotating about the torsion axis (460); the first bottom electrode (440) and the second bottom electrode (441) are disposed below the mass block (410) and respectively form a detection capacitor with the mass block (410). The first mass region (411) and the second mass region (412) have an unbalanced mass distribution and / or an unbalanced lever arm distribution, so that the mass block (410) tilts about the torsion axis (460) under the action of acceleration in the Z-axis direction, thereby causing the detection capacitors corresponding to the first bottom electrode (440) and the second bottom electrode (441) to change in opposite directions; The in-plane detection unit (200), the Y-axis detection unit (300), and the Z-axis detection unit (400) are all disposed on the same substrate (110).

2. The triaxial capacitive microelectromechanical accelerometer according to claim 1, characterized in that, The first movable mass block (210), the mass block (410), the first spring beam (220), the second spring beam (221), the first anchor point (230), the first torsion spring beam (430), the second torsion spring beam (431), and the center anchor point (420) are formed from the same device layer and are at the same level in the thickness direction.

3. The triaxial capacitive microelectromechanical accelerometer according to claim 1, characterized in that, The Y-axis detection unit (300) and the in-plane detection unit (200) are isomorphic, and the in-plane detection unit (200) is formed by rotating the in-plane detection unit (200) 90° around an axis perpendicular to the substrate (110).

4. The triaxial capacitive microelectromechanical accelerometer according to claim 3, characterized in that, The first anchor point (230) extends in a direction perpendicular to the length of the first movable mass block (210) and is disposed in the middle region of the first movable mass block (210). The first spring beam (220) and the second spring beam (221) extend on both sides along the length of the first movable mass block (210). The first positive fixed electrode (240) and the second positive fixed electrode (241) are respectively disposed in the region corresponding to the first set of plate electrodes of the first movable mass block (210). The first reverse fixed electrode (250) and the second reverse fixed electrode (251) are respectively disposed in the region corresponding to the second set of plate electrodes of the first movable mass block (210).

5. The triaxial capacitive microelectromechanical accelerometer according to claim 4, characterized in that, The first positive fixed electrode (240), the second positive fixed electrode (241), the first negative fixed electrode (250) and the second negative fixed electrode (251) are all plate-shaped fixed electrodes, and have inclined edge portions and / or convergent edge portions formed on the side facing the first movable mass block (210).

6. The triaxial capacitive microelectromechanical accelerometer according to claim 1, characterized in that, The first mass region (411) is a mass region with a large solid retention area, and the second mass region (412) is provided with at least one weight reduction area so that the mass of the first mass region (411) is greater than the mass of the second mass region (412), and / or the distance from the center of mass of the first mass region (411) to the torsion axis (460) is greater than the distance from the center of mass of the second mass region (412) to the torsion axis (460).

7. The triaxial capacitive microelectromechanical accelerometer according to claim 6, characterized in that, The first bottom electrode (440) and the second bottom electrode (441) are arranged below the mass block (410) with the central anchor point (420) as the center of symmetry. When there is no acceleration in the Z-axis direction, the initial distance between the first bottom electrode (440) and the mass block (410) is equal to or substantially equal to the initial distance between the second bottom electrode (441) and the mass block (410), so that the corresponding initial detection capacitances are equal to or substantially equal.

8. The triaxial capacitive microelectromechanical accelerometer according to claim 3, characterized in that, The in-plane detection unit (200) and the Y-axis detection unit (300) are respectively arranged along two mutually perpendicular in-plane directions, and are arranged side by side with the Z-axis detection unit (400) on the substrate (110); wherein, the Z-axis detection unit (400) is arranged in the remaining layout area formed by the arrangement of the in-plane detection unit (200) and the Y-axis detection unit (300).

9. The triaxial capacitive microelectromechanical accelerometer according to claim 6, characterized in that, The first mass region (411) is provided with a reserved area (450), and at least a part of the structure of the in-plane detection unit (200) is disposed in the reserved area (450); the reserved area (450) is a local layout accommodating area disposed in the first mass region (411), the boundary of which is enclosed by the solid part of the first mass region (411) and does not penetrate the entire mass block (410).

10. The triaxial capacitive microelectromechanical accelerometer according to claim 9, characterized in that, The reserved area (450) is located on the side away from the central anchor point (420), and the in-plane detection unit (200) is embedded in the reserved area (450), while the Y-axis detection unit (300) is disposed outside the Z-axis detection unit (400) so that the effective arm of the first mass area (411) relative to the torsion axis (460) is increased.

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