Double-differential MEMS accelerometer structure

Abstract

The invention provides a double-differential MEMS accelerometer structure which comprises a substrate, a sensitive structure layer suspended on the substrate, and an anchor point layer which is located between the substrate and the sensitive structure layer and provides support for suspending the sensitive structure layer on the substrate. The sensitive structure layer comprises two symmetrical sensitive structure units, and each sensitive structure unit comprises a sensitive mass block, a pair of supporting beams symmetrically arranged on the two sides of the sensitive mass block, and a plurality of groups of comb teeth electrodes symmetrically arranged between the sensitive mass block and the supporting beams. According to the invention, the dual-carrier acceleration detection of the MEMS accelerometer can be realized, and the acceleration detection of the MEMS accelerometer structure achieves performance balance among sensitivity, stability and frequency characteristics.

Description

Technical Field

[0001] This application relates to the technical field of microelectromechanical system devices, and particularly to a dual-differential MEMS accelerometer structure. Background Art

[0002] As a core technology in the field of inertial sensing, microelectromechanical systems (MEMS) accelerometers have developed from laboratories to large-scale commercial applications since the 1980s. Its core principle is to convert acceleration into an electrical signal output through the collaborative action of micron-scale mechanical structures and integrated circuits, and is widely used in fields such as smartphone attitude sensing, automotive airbag triggering, industrial equipment vibration monitoring, and high-precision inertial navigation. As the application scenarios extend from consumer-grade to industrial-grade and military-grade, the market's performance requirements for accelerometers are becoming increasingly stringent, especially in terms of zero-bias stability in extreme temperature environments, resistance to process variations, and the compatibility between miniaturization and high sensitivity.

[0003] The sensitive structure of a MEMS accelerometer usually needs to be connected to the substrate through anchor points, which are the only connection points between the sensitive structure of the accelerometer sensor chip and the substrate. Residual stress and thermal stress introduced during manufacturing processes, packaging and chip mounting, as well as thermal stress generated by external environmental temperature changes, will be transmitted to the sensitive structure through the anchor points, resulting in deformation of the sensitive structure and changes in the detection capacitance, thereby affecting the output stability of the accelerometer. There have been several existing technologies to improve the output stability of MEMS accelerometers, but they will all cause a certain degree of reduction in the sensitivity and / or resonant frequency of MEMS accelerometers. It is difficult.

[0004] Therefore, there is a need for a new dual-differential MEMS accelerometer structure solution to further improve the thermal stability of capacitive MEMS accelerometers and achieve a balance between the sensitivity, stability, and frequency characteristics of MEMS accelerometers, which has become one of the technical problems that need to be urgently solved by those skilled in the art. Summary of the Invention

[0005] This application aims to solve at least one of the technical problems in the related technologies to some extent.

[0006] To achieve the above object, an embodiment of the first aspect of this application proposes a dual-differential MEMS accelerometer structure, including a substrate, a sensitive structure layer suspended on the substrate, and an anchor point layer located between the substrate and the sensitive structure layer. The sensitive structure layer includes a pair of sensitive structure units symmetric to each other along a first direction, the anchor point layer includes a pair of anchor point units symmetric to each other along the first direction, and there is a one-to-one correspondence between the sensitive structure units and the anchor point units;

[0007] Each of the sensitive structural units includes at least a sensitive mass block, a pair of support beams symmetrically arranged on both sides of the sensitive mass block along the first direction and elastically connected to both ends of the sensitive mass block along the second direction, and multiple sets of comb electrodes symmetrically arranged between the sensitive mass block and the support beams. Each set of the comb electrodes includes first comb teeth and second comb teeth that are staggered and spaced apart;

[0008] Each of the anchor units includes a pair of first anchors, a pair of second anchors, and a pair of third anchors that are staggered and spaced apart on the central axis of the sensitive mass block along the first direction; the first anchors are connected to the support beams, and the first comb teeth of each set of the comb electrodes are connected to the sensitive mass block one by one, so that the sensitive mass block and the first comb teeth can be suspended on the substrate through the first anchors; the second comb teeth of each set of the comb electrodes are connected to the second anchors or the third anchors one by one, so that the second comb teeth can be suspended on the substrate through the second anchors or the third anchors.

[0009] Optionally, each of the first anchors, the second anchors, and the third anchors are respectively arranged on both sides of the sensitive mass block along the first direction, and the centers of the first anchors, the second anchors, and the third anchors are collinear with the central axis of the sensitive mass block along the first direction.

[0010] Optionally, in the first direction, a pair of the first anchors are symmetrically arranged on both sides of the sensitive mass block, a pair of the second anchors and a pair of the third anchors are asymmetrically arranged on both sides of the sensitive mass block, and the distance between the pair of the second anchors is equal to the distance between the pair of the third anchors.

[0011] Optionally, each of the sensitive structural units further includes multiple elastic beams, and the multiple elastic beams are symmetric with each other in the first direction and / or the second direction.

[0012] Optionally, each of the sensitive structural units further includes a pair of elastic beams; and in the first direction, each of the elastic beams is symmetric about the central axis of the sensitive mass block along the second direction; in the second direction, the pair of the elastic beams are symmetric about the central axis of the sensitive mass block along the first direction.

[0013] Optionally, the elastic beam is a serpentine folded beam structure composed of multiple folded beams, and one end of each of the elastic beams is connected to one end of the sensitive mass block along the second direction, and the other end of each of the elastic beams extends serpentinely along the second direction and is connected to one end of the support beam along the second direction.

[0014] Optionally, the second comb teeth are connected to the second anchor point and the third anchor point in a one-to-one correspondence, and the connection numbers of the second anchor point and the third anchor point to the second comb teeth are equal respectively.

[0015] Optionally, the second comb teeth connected to the second anchor point and the first comb teeth opposite thereto form a first capacitor array; the second comb teeth connected to the third anchor point and the first comb teeth opposite thereto form a second capacitor array.

[0016] Optionally, multiple groups of the comb teeth electrodes form at least a pair of the first capacitor arrays and a pair of the second capacitor arrays symmetrically arranged along the first direction, and the first capacitor array and the second capacitor array are symmetric to each other along the second direction.

[0017] Optionally, the static capacitances and sensitivities of each capacitor in the first capacitor array and the second capacitor array are the same, and the positive and negative polarities of the capacitors are opposite.

[0018] The dual-differential MEMS accelerometer structure provided by the present application has at least the following beneficial effects:

[0019] The present application provides a dual-differential MEMS accelerometer structure, including a substrate, a sensitive structure layer suspended on the substrate, and an anchor layer located between the substrate and the sensitive structure layer and providing support for the sensitive structure layer to be suspended on the substrate. The sensitive structure layer includes two symmetrically arranged sensitive structure units, and each sensitive structure unit includes a sensitive mass block, a pair of support beams symmetrically arranged on both sides of the sensitive mass block, and multiple groups of comb teeth electrodes symmetrically arranged between the sensitive mass block and the support beams. The present application can achieve dual-carrier acceleration detection of the MEMS accelerometer and balance the performance of the MEMS accelerometer structure in terms of sensitivity, stability, and frequency characteristics.

[0020] The additional aspects and advantages of the present application will be partially given in the following description, partially become obvious from the following description, or be understood through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The above and / or additional aspects and advantages of the present application will become obvious and easy to understand from the following description of the embodiments in conjunction with the drawings, where:

[0022] Figure 1 FIG. is a longitudinal cross-sectional structure schematic diagram of the MEMS accelerometer structure shown according to an embodiment of the present application.

[0023] Figure 2 FIG. is a cross-sectional structure schematic diagram of the first MEMS accelerometer structure shown according to an embodiment of the present application.

[0024] Figure 3 It is a schematic cross-sectional structure diagram of the second MEMS accelerometer structure shown according to an embodiment of the present application.

[0025] Figure 4 It is a schematic diagram of the electrical connection structure of the MEMS accelerometer structure shown according to an embodiment of the present application.

[0026] 100 Substrate; 200 Anchor layer; 201 First anchor; 202 Second anchor; 203 Third anchor; 300 Sensing structure layer; 301 First sensing structure unit; 302 Second sensing structure unit; 310 Sensing mass; 320 Support beam; 330 Comb electrode; 331 First comb tooth; 332 Second comb tooth; 3301 First capacitor array; 3302 Second capacitor array; 340 Elastic beam; 350 First connection part; 360 Second connection part; 370 Third connection part. Detailed implementation manners

[0027] The embodiments of the present application will be described in detail below. Examples of the embodiments are shown in the drawings, where the same or similar reference numerals denote the same or similar elements or elements with the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary and are intended to explain the present application, and should not be construed as limiting the present application.

[0028] As a core technology in the field of inertial sensing, microelectromechanical system (MEMS) accelerometers have developed from the laboratory to large-scale commercial use since the 1980s. In the early days, most MEMS accelerometers adopted a single-axis cantilever beam design, and realized acceleration detection through the capacitance change caused by the displacement of the sensing mass. Later, the academic community proposed a monolithic integrated multi-axis detection structure, such as using a central mass and symmetrically distributed detection beams to achieve biaxial synchronous measurement. However, existing multi-axis detection structures often suffer from critical dimension deviations (such as deviations exceeding 8%) due to structural asymmetry in the deep reactive ion etching (DRIE) process, or stress concentration of the support beam due to differences in the coefficient of thermal expansion, resulting in the zero-bias temperature coefficient (TCoB) of the existing accelerometer structure fluctuating up to ±2mg / °C in the range of -40 to 85°C, making it difficult to meet the requirements of high-precision scenarios such as aerospace.

[0029] Furthermore, in existing MEMS accelerometers, since the support anchor points and the sensitive mass blocks usually use silicon-based materials, and the connection parts may introduce a metallization layer or a silicon oxide insulating layer, the difference in the thermal expansion coefficients of different materials will generate an internal stress gradient when the temperature changes. For example, when the ambient temperature rises from 25°C to 85°C, the maximum deformation of the existing four-beam support structure can reach 0.2 μm, resulting in a change in the capacitance plate spacing exceeding 15% of the design value, leading to zero-point drift. In addition, the influence of the preparation process deviation on the performance of the MEMS accelerometer is more significant. For example, a slight deviation in the etching depth or sidewall angle of the comb electrodes (such as ±5% etching non-uniformity) will cause the differential capacitance to be unbalanced, resulting in a sensitivity decrease of more than 30%.

[0030] Currently, the industry generally uses a single differential capacitance layout to suppress common-mode interference. However, under the arrangement of high-density comb electrodes, the structural warping caused by the etching residual stress will still amplify the thermal deformation error, forming a coupling effect of temperature and process deviation. For example, the existing dual-mass block coupling structure can achieve error mutual compensation through two independent detection units, but its complex mechanical linkage structure will also cause the resonance frequency to decrease by 40%, sacrificing the dynamic response ability.

[0031] Based on the above problems, the present application provides a dual-differential MEMS accelerometer, which can achieve a balance among the sensitivity, stability, and frequency characteristics of the accelerometer.

[0032] According to one aspect of the present application, as Figures 1 to 3 shown, a dual-differential MEMS accelerometer structure is provided. The structure includes a substrate 100, a sensitive structure layer 300 suspended on the substrate 100, and an anchor layer 200 located between the substrate 100 and the sensitive structure layer 300 and providing support for the sensitive structure layer 300 to be suspended on the substrate 100. The sensitive structure layer 300 includes at least two sensitive structure units symmetric to each other along a first direction, and the anchor layer 200 includes at least two anchor units symmetric to each other along the first direction, and the sensitive structure units and the anchor units correspond to each other one by one, so that each sensitive structure unit can be suspended on the substrate 100 through the corresponding anchor unit.

[0033] Each sensitive structure unit includes at least a sensitive mass block 310, a pair of support beams 320 symmetrically arranged on both sides of the sensitive mass block 310 along the first direction, and multiple groups of comb electrodes 330 symmetrically arranged between the sensitive mass block 310 and the support beams 320; both ends in a second direction are elastically connected to both ends of the sensitive mass block 310 along the second direction and surround the multiple groups of comb electrodes 330, and each group of comb electrodes 330 includes at least a pair of first comb teeth 331 and second comb teeth 332 that are staggered and spaced apart.

[0034] Each anchor unit includes a pair of first anchors 201, a pair of second anchors 202, and a pair of third anchors 203 that are staggered and spaced along the central axis of the sensitive mass 310 in the first direction. Among them, the first anchor 201 is connected to the support beam 320, and the first comb teeth 331 of each group of comb electrodes 330 are configured to be connected to the sensitive mass 310 one by one, so that the sensitive mass 310 and the first comb teeth 331 can be suspended on the substrate 100 through the first anchor 201; the second comb teeth 332 of each group of comb electrodes 330 are configured to be connected to the second anchor 202 or the third anchor 203 one by one, so that the second comb teeth 332 can be suspended on the substrate 100 through the second anchor 202 or the third anchor 203.

[0035] For the convenience of description, the X direction in the figure can be set as the first direction, that is, the displacement direction of the sensitive mass 310 under the action of inertial force, and the Y direction in the figure can be set as the second direction, and the first direction and the second direction are orthogonal. Among them, two sensitive structure units that are symmetric with each other along the first direction are symmetric with respect to the symmetry axis Z0; multiple groups of comb electrodes 330 that are symmetric along the first direction are symmetric with respect to the symmetry axis Z1, and the symmetry axis Z0 is also the central axis of the sensitive mass 310 along the second direction; multiple groups of comb electrodes 330 that are symmetric along the second direction are symmetric with respect to the symmetry axis Z2, and the symmetry axis Z2 is also the central axis of the sensitive mass 310 along the first direction. Unless otherwise specified in the following content, for the symmetry relationship along the first direction and the second direction within each sensitive structure unit, it means symmetry with respect to the symmetry axis Z1 or Z2.

[0036] It can be understood that the substrate 100 can be any suitable substrate material known in the art, including but not limited to semiconductor materials such as silicon or any other semiconductor materials, non-semiconductor materials, etc. Non-semiconductor materials include but not limited to glass, plastic, metal, or ceramic, etc. If necessary, the substrate 100 can also be an integrated circuit fabricated on the above materials. The sensitive structure layer 300 can be any material known in the art, including but not limited to semiconductor materials such as polysilicon or any other semiconductor materials.

[0037] Since each anchor unit includes a sensitive mass 310, a support beam 320, and multiple groups of comb electrodes 330, the dual-differential MEMS accelerometer structure provided by the present application is a capacitive MEMS accelerometer structure. Its working principle is usually based on the fact that the change in the displacement of the sensitive mass 310 under the action of inertial force will cause the change of the electrical signal parameters in the capacitor composed of the comb electrodes 330, thereby realizing the conversion between electrical quantities and mechanical physical quantities.

[0038] Since the sensitive mass 310 and the first comb teeth 331 are suspended on the substrate 100 through the first anchor 201, while the second comb teeth 332 are suspended on the substrate 100 through the second anchor 202 or the third anchor 203, thus, the capacitor formed by combining the second comb teeth 332 connected to the second anchor 202 and the opposite first comb teeth 331 can be called the first capacitor array 3301; the capacitor formed by combining the second comb teeth 332 connected to the third anchor 203 and the opposite first comb teeth 331 can be called the second capacitor array 3302.

[0039] Since multiple groups of comb electrodes 330 are symmetrically arranged between the sensitive mass 310 and the support beam 320, thus, when the second comb teeth 332 are respectively connected to the second anchor 202 and the third anchor 203 in a one-to-one correspondence, and the connection numbers of the second anchor 202 and the third anchor 203 to the second comb teeth 332 are equal, at least a pair of the first capacitor arrays 3301 and a pair of the second capacitor arrays 3302 that are symmetrically arranged along the first direction can be formed by multiple groups of comb electrodes 330 in each sensitive structure unit, and the first capacitor array 3301 and the second capacitor array 3302 are symmetric to each other along the second direction.

[0040] Since a pair of the first capacitor arrays 3301 and a pair of the second capacitor arrays 3302 in each sensitive structure unit are symmetric to each other along the second direction, the first capacitor array 3301 and the second capacitor array 3302 together constitute a differential capacitance structure that is symmetric in both the first direction and the second direction.

[0041] Thus, when the sensitive mass 310 generates a displacement along the second direction under the action of an inertial force, the change in the displacement amount will cause the capacitances of the first capacitor array 3301 and the second capacitor array 3302 to change. Based on the actual change amount of the capacitance and the actual displacement amount of the sensitive mass 310, and combined with the inherent physical parameters of the sensitive mass 310, the acceleration of the sensitive mass 310 under the action of the inertial force can be measured.

[0042] At the same time, since the first capacitor array 3301 and the second capacitor array 3302 together constitute a differential capacitance structure that is symmetric in both the first direction and the second direction, during the acceleration detection process of the MEMS accelerometer structure in the second direction, even if the sensitive structure unit is under the influence of a lateral interference along the first direction, the change amounts of the capacitances in the first capacitor array 3301 and the second capacitor array 3302 will be basically the same, thereby ensuring the measurement accuracy and measurement stability of the accelerometer.

[0043] In addition, since the first capacitor array 3301 and the second capacitor array 3302 together form a differential capacitor structure that is symmetric in the first and second directions, during the acceleration detection process of the MEMS accelerometer structure, it can be free from the interference of changes in the external environmental temperature and / or power supply fluctuations. That is to say, even if the first capacitor array 3301 and the second capacitor array 3302 produce slight displacements of the comb electrodes 330 due to temperature changes, due to the symmetric structure of the first capacitor and the second capacitor, the first capacitor and the second capacitor will exhibit the same amount of capacitance change, and this capacitance change will be eliminated in the differential working mode, thereby playing a role in common-mode rejection and improving the measurement accuracy and measurement sensitivity of the accelerometer structure.

[0044] Similarly, since the first capacitor array 3301 and the second capacitor array 3302 together form a differential capacitor structure that is symmetric in the first direction and / or the second direction, it will also cause the sensitive mass unit to form a symmetric heat conduction path during the etching process of the manufacturing process, and the symmetry of the heat dissipation channels can improve the structural consistency of the sensitive structure layer 300 in the manufacturing process, further ensuring the measurement accuracy and measurement stability of the accelerometer.

[0045] Since the first anchor 201, the second anchor 202, and the third anchor 203 are staggered and spaced on the central axis of the sensitive mass block 310 along the first direction, the detection capacitance mismatch caused by the internal stress gradient or deformation mismatch generated due to the difference in the thermal expansion coefficients of different materials between the sensitive structure layer 300, the anchor layer 200, and the substrate 100 during temperature changes can also be offset from each other, thereby reducing the temperature stress sensitivity and the patch stress sensitivity of the accelerometer structure.

[0046] Among them, each of the first anchor 201, the second anchor 202, and the third anchor 203 is disposed on both sides of the sensitive mass block 310 along the first direction, and the centers of the first anchor 201, the second anchor 202, and the third anchor 203 are collinear with the central axis of the sensitive mass block 310 along the first direction.

[0047] Furthermore, in the first direction, a pair of first anchors 201 are symmetrically disposed on both sides of the sensitive mass block 310, a pair of second anchors 202 and a pair of third anchors 203 are asymmetrically disposed on both sides of the sensitive mass block 310, and the distance between the pair of second anchors 202 is equal to the distance between the pair of third anchors 203, and the sum of the distances between the second anchors 202 and the third anchors 203 on both sides and the central axis of the sensitive mass block 310 along the second direction is equal.

[0048] Furthermore, since the sensitive structure layer 300 provided in this application includes at least two mutually symmetric sensitive structure units, the electrical signals received by the two mutually symmetric sensitive structure units can form a double-differential capacitance structure. Based on the above single-differential capacitance structure, the double-differential capacitance structure can further reduce or even eliminate the residual interference in the differential mode signals (such as the non-linear terms and second-order common-mode errors in the differential mode), and can achieve the differential elimination of various errors at different positions or higher-order error cancellation without affecting the resonance frequency, further optimizing the measurement accuracy, measurement sensitivity, and anti-interference ability of the accelerometer structure, and achieving the performance balance among sensitivity, stability, and frequency characteristics of the MEMS accelerometer. At the same time, the arrangement of the double-differential capacitance structure can ensure the capacitance sensitivity under limited dimensions, thus avoiding the influence of the dimensional accuracy caused by the thermal expansion and deformation of the distal end of the large-size structure comb electrodes 330, and solving the contradiction between the high precision and miniaturization of the MEMS accelerometer.

[0049] Specifically, the basic working principle of the capacitors in the first capacitance array 3301 and the second capacitance array 3302 in each sensitive structure unit can be illustrated by a parallel-plate capacitor. Ignoring the edge effect, the capacitance of the capacitor can be expressed as:

[0050]

[0051] where C is the capacitance, ε is the dielectric constant of the medium between the plates of the capacitor, A is the area of the plates of the capacitor facing each other, and d is the distance between the plates of the capacitor.

[0052] Thus, when the displacement direction of the sensitive mass block 310 is parallel to the facing direction of the plates, as Figure 2 shown, the first comb 331 will also generate a displacement x along the second direction under the action of inertial force following the sensitive mass block 310, thereby changing the distance d between the plates. Since the first capacitance array 3301 and the second capacitance array 3302 are mutually symmetric, it can be defaulted here that the initial distances between the plates in the first capacitance array 3301 and the second capacitance array 3302 are the same, that is, the distance between the first comb 331 and the second comb 332 in the first capacitance array 3301 changes from the initial distance d0 to d0 + x; the distance between the first comb 331 and the second comb 332 in the second capacitance array 3302 will change from the initial distance d0 to d0 - x, resulting in a change in the capacitance of the differential capacitance structure.

[0053] Similarly, when the displacement direction of the sensitive mass block 310 is perpendicular to the facing direction of the plates, as Figure 3As shown, the first comb tooth 331 will also generate a displacement x in the second direction along with the sensitive mass block 310 under the action of inertial force, thereby changing the facing area A between the plates. Since the first capacitor array 3301 and the second capacitor array 3302 are symmetrical to each other, it can be defaulted here that the initial facing areas between the plates in the first capacitor array 3301 and the second capacitor array 3302 are the same, that is, the facing area between the first comb tooth 331 and the second comb tooth 332 in the first capacitor array 3301 changes from the initial facing area A0 to A0 + ΔA; the facing area between the first comb tooth 331 and the second comb tooth 332 in the second capacitor array 3302 changes from the initial facing area A0 to A0 - ΔA, resulting in a change in the capacitance of the differential capacitance structure. ΔA is the change amount of the facing area between the plates, and ΔA satisfies ΔA = Lx, where L is the side length of the plate perpendicular to the displacement direction.

[0054] Therefore, when the permittivity ε remains unchanged, the change in the facing area A between the plates and / or the scaling of the plate spacing d will both cause a change in the capacitance C of the differential capacitance structure, and form an exact functional relationship with the capacitance change amount ΔC. Then, the capacitance change amounts ΔC of the first capacitor array 3301 and the second capacitor array 3302 of the two sensitive structure units are respectively subjected to the first difference, and the first difference results of the two sensitive structure units are subjected to the second difference to obtain the total capacitance change amount ΔC total . Finally, based on the total capacitance change amount ΔC of the double-differential capacitance structure total and the functional relationship between the moving displacement x and the acceleration a of the mass-sensitive block under the action of inertial force, the actual acceleration a of the sensitive mass unit under the action of inertial force is obtained.

[0055] According to Hooke's law, when the sensitive mass block 310 generates a displacement in the second direction under the action of inertial force, the relationship between the displacement x and the acceleration a of the sensitive mass block 310 satisfies:

[0056]

[0057] where F is the inertial force, n is the mass of the sensitive mass block 310, and k is the elastic coefficient of the sensitive mass block 310.

[0058] Therefore, based on the equivalent relationship between the total capacitance change amount ΔC total and the moving displacement x of the mass-sensitive block under the action of inertial force, as well as the equivalent relationship between the acceleration a and the moving displacement x of the sensitive mass block 310 under the action of inertial force, the equivalent relationship between the acceleration a and the total capacitance change amount ΔC of the double-differential capacitance structure total can be obtained.

[0059] For the sake of convenience of expression, as Figure 4 shown, and combined withFigure 2 and Figure 3 A pair of mutually symmetric sensitive structure units in the sensitive structure layer 300 can be set as the first sensitive structure unit 301 and the second sensitive structure unit 302. The first anchor point 201 in the first sensitive structure unit 301 is connected to the positive electrode of the operational amplifier, the second anchor point 202 is connected to the positive carrier wave, the third anchor point 203 is connected to the load wave, and the first anchor point 201 in the second sensitive structure unit 302 is connected to the negative electrode of the operational amplifier, the second anchor point 202 is connected to the load wave, and the third anchor point 203 is connected to the positive carrier wave. Moreover, the parameter magnitudes of the positive-polarity carrier wave and the negative-polarity carrier wave are equal and the polarities are opposite. Thus, a pair of first capacitor arrays 3301 and a pair of second capacitor arrays 3302 with opposite positive and negative polarities are simultaneously included in the first sensitive structure unit 301 and the second sensitive structure unit 302, and the static capacitance and sensitivity of each capacitor in the first capacitor array 3301 and the second capacitor array 3302 are the same, thereby realizing dual-carrier detection of the MEMS accelerometer with two completely identical and mutually independent sensitive structure units.

[0060] In some embodiments, the sensitive structure layer 300 may further include a plurality of mutually spaced first connection portions 350, second connection portions 360, and third connection portions 370. Among them, each first connection portion 350 extends from the middle of the support beam 320 along the first direction and covers the first anchor point 201, and each first connection portion 350 is connected to each first anchor point 201 in a one-to-one correspondence, so that the first anchor point 201 can provide bottom support and an electrical connection channel for the support beam 320 to be suspended above the substrate 100 through the first connection portion 350. Each second connection portion 360 extends from the side of the second comb teeth 332 close to the second anchor point 202 in each first capacitor array 3301 along the second direction and covers the second anchor point 202, and each second connection portion 360 is connected to each second anchor point 202 in a one-to-one correspondence, so that the second anchor point 202 can provide bottom support and an electrical connection channel for the second comb teeth 332 in the first capacitor array 3301 to be suspended above the substrate 100 through the second connection portion 360. Each third connection portion 370 extends from the side of the second comb teeth 332 close to the third anchor point 203 in each second capacitor array 3302 along the second direction and covers the third anchor point 203, and each third connection portion 370 is connected to each third anchor point 203 in a one-to-one correspondence, so that the third anchor point 203 can provide bottom support and an electrical connection channel for the second comb teeth 332 in the second capacitor array 3302 to be suspended above the substrate 100 through the third connection portion 370.

[0061] In some embodiments, each sensitive structural unit further includes a plurality of elastic beams 340, and the plurality of elastic beams 340 are symmetric with each other in the first direction and / or the second direction. The two ends of the sensitive mass 310 in the second direction are respectively and correspondingly connected to the two ends of the support beams 320 arranged on both sides of the sensitive mass 310 in the second direction.

[0062] As an example, each sensitive structural unit includes a pair of elastic beams 340. In the first direction, each elastic beam 340 is axisymmetric about the center axis of the sensitive mass 310 in the second direction; in the second direction, the pair of elastic beams 340 are axisymmetric about the center axis of the sensitive mass 310 in the first direction. Thus, the effect of further reducing the non-linear error of the MEMS accelerometer can also be achieved.

[0063] Specifically, the elastic beam 340 can be a serpentine folding structure composed of multiple folded beams. One end of each elastic beam 340 is connected to one end of the sensitive mass 310 in the second direction, and the other end extends serpentinely in the second direction and is connected to one end of the support beam 320 in the second direction. Thus, it also enables the sensitive mass 310 to maintain an elastic connection with the support beam 320, and enables the sensitive mass 310 to be suspended above the substrate 100 without directly contacting the substrate 100, thereby realizing that the sensitive mass 310 can be displaced relative to the substrate 100 in the second direction.

[0064] In summary, the present application provides a dual-differential MEMS accelerometer structure, including a substrate 100, a sensitive structure layer 300 suspended on the substrate 100, and an anchor layer 200 located between the substrate 100 and the sensitive structure layer 300 and providing support for the sensitive structure layer 300 to be suspended on the substrate 100. The sensitive structure layer 300 includes two mutually symmetric sensitive structural units. Each sensitive structural unit includes a sensitive mass 310, a pair of support beams 320 symmetrically arranged on both sides of the sensitive mass 310, and multiple groups of comb electrodes 330 symmetrically arranged between the sensitive mass 310 and the support beams 320. The present application can realize the dual-carrier acceleration detection of the MEMS accelerometer, and achieve a performance balance among the sensitivity, stability and frequency characteristics of the acceleration detection of the MEMS accelerometer structure.

[0065] In the descriptions of the foregoing embodiments, the descriptions with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, without contradiction, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0066] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present application, "a plurality of" means at least two, such as two, three, etc., unless otherwise specifically defined.

Claims

1. A dual-differential MEMS accelerometer structure, characterized in that, It includes a substrate, a sensitive structure layer suspended on the substrate, and an anchor layer located between the substrate and the sensitive structure layer. The sensitive structure layer includes a pair of sensitive structure units symmetric with each other along a first direction. The anchor layer includes a pair of anchor units symmetric with each other along the first direction. The sensitive structure units and the anchor units are in one-to-one correspondence; Each of the sensitive structure units at least includes a sensitive mass block, a pair of support beams symmetrically arranged on both sides of the sensitive mass block along the first direction and elastically connected to both ends of the sensitive mass block along a second direction, and multiple groups of comb electrodes symmetrically arranged between the sensitive mass block and the support beams. Each group of the comb electrodes includes first comb teeth and second comb teeth arranged alternately and at intervals; Each of the anchor units includes a pair of first anchors, a pair of second anchors, and a pair of third anchors arranged alternately and at intervals on the central axis of the sensitive mass block along the first direction. The first anchors are connected to the support beams. The first comb teeth of each group of the comb electrodes are connected to the sensitive mass block in one-to-one correspondence, so that the sensitive mass block and the first comb teeth can be suspended on the substrate through the first anchors; the second comb teeth of each group of the comb electrodes are connected to the second anchors or the third anchors in one-to-one correspondence, so that the second comb teeth can be suspended on the substrate through the second anchors or the third anchors.

2. The dual-differential MEMS accelerometer structure according to claim 1, characterized in that, Each of the first anchors, the second anchors, and the third anchors are respectively arranged on both sides of the sensitive mass block along the first direction, and the centers of the first anchors, the second anchors, and the third anchors are collinear with the central axis of the sensitive mass block along the first direction.

3. The dual-differential MEMS accelerometer structure according to claim 2, characterized in that, In the first direction, a pair of the first anchors are symmetrically arranged on both sides of the sensitive mass block, a pair of the second anchors and a pair of the third anchors are asymmetrically arranged on both sides of the sensitive mass block, and the distance between the pair of the second anchors is equal to the distance between the pair of the third anchors.

4. The double-differential MEMS accelerometer structure according to claim 1, wherein Each of the sensitive structure units further includes multiple elastic beams, and the multiple elastic beams are symmetric with each other in the first direction and / or the second direction.

5. The double-differential MEMS accelerometer structure according to claim 1, characterized in that, Each of the sensitive structure units further includes a pair of elastic beams; and in the first direction, each of the elastic beams is symmetric about the central axis of the sensitive mass block along the second direction; in the second direction, the pair of elastic beams are symmetric about the central axis of the sensitive mass block along the first direction.

6. The dual-differential MEMS accelerometer structure according to claim 5, wherein, The elastic beam is a serpentine folded beam structure composed of multiple folded beams, and one end of each of the elastic beams is connected to one end of the sensitive mass block along the second direction, and the other end of each of the elastic beams extends serpentinely along the second direction and is connected to one end of the support beam along the second direction.

7. The dual-differential MEMS accelerometer structure according to claim 1, characterized in that, The second comb teeth are connected to the second anchors and the third anchors in one-to-one correspondence, and the connection numbers of the second anchors and the third anchors with the second comb teeth are equal respectively.

8. The double-differential MEMS accelerometer structure according to claim 7, characterized in that, The second comb teeth connected to the second anchor point and the first comb teeth opposite thereto are combined to form a first capacitor array; the second comb teeth connected to the third anchor point and the first comb teeth opposite thereto are combined to form a second capacitor array.

9. The dual-differential MEMS accelerometer structure according to claim 8, wherein Multiple sets of the comb teeth electrodes at least form a pair of the first capacitor arrays and a pair of the second capacitor arrays symmetrically arranged along the first direction, and the first capacitor array and the second capacitor array are symmetric with each other along the second direction.

10. The dual-differential MEMS accelerometer structure according to claim 8, characterized in that, The static capacitance and sensitivity of each capacitor in the first capacitor array and the second capacitor array are the same, and the positive and negative polarities of the capacitors are opposite.

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