A double differential MEMS accelerometer structure

Abstract

The application provides a double-differential MEMS accelerometer structure, which comprises a substrate, a sensitive structure layer suspended on the substrate, and an anchor point layer between the substrate and the sensitive structure layer and providing support for the suspension of the sensitive structure layer on the substrate. The sensitive structure layer comprises two symmetric sensitive structure units, each of which comprises a sensitive mass, a pair of support beams symmetrically arranged on two sides of the sensitive mass, and a plurality of groups of comb electrode symmetrically arranged between the sensitive mass and the support beams. The application can realize double-carrier acceleration detection of the MEMS accelerometer, and balance the performance of the acceleration detection of the MEMS accelerometer structure among sensitivity, stability and frequency characteristics.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of micro-electro-mechanical system (MEMS) devices, and in particular to a double-differential MEMS accelerometer structure. BACKGROUND

[0002] As a core technology in the field of inertial sensing, Micro-Electro-Mechanical Systems (MEMS) accelerometers have developed from the laboratory to commercialization since the 1980s. The core principle is to convert acceleration into an electrical signal output through the synergistic effect of a micron-level mechanical structure and an integrated circuit, and it is widely used in smart phone posture sensing, automobile airbag triggering, industrial equipment vibration monitoring, high-precision inertial navigation and other fields. As the application scenarios extend from consumer level to industrial level and military level, the market demands for the performance of accelerometers are increasingly stringent, especially in terms of zero bias stability in extreme temperature environments, process deviation resistance, and compatibility of miniaturization and high sensitivity.

[0003] The sensitive structure of a MEMS accelerometer usually needs to be connected to the substrate through anchors. These anchors are the only connection points between the sensitive structure of the acceleration sensor chip and the substrate. Residual stress and thermal stress introduced by manufacturing processes, packaging patches, and thermal stress generated by changes in external environmental temperature will be transmitted to the sensitive structure through the anchors, causing the sensitive structure to deform and change the detection capacitance, thereby affecting the output stability of the accelerometer. The existing technology has several solutions to improve the output stability of the MEMS accelerometer, but they will all cause a decrease in the sensitivity and / or resonance frequency of the MEMS accelerometer to a certain extent.

[0004] Therefore, how to need a new double-differential MEMS accelerometer structure scheme to further improve the thermal stability of a capacitive MEMS accelerometer and achieve a balance between sensitivity, stability and frequency characteristics of the MEMS accelerometer is one of the technical problems that people in the field urgently need to solve. SUMMARY

[0005] The present application aims to at least solve one of the technical problems in the related art to some extent.

[0006] To achieve the above-mentioned purpose, the first aspect of the present application proposes a double-differential MEMS accelerometer structure, which comprises a substrate, a sensitive structure layer suspended on the substrate, and an anchor layer between the substrate and the sensitive structure layer, the sensitive structure layer comprising a pair of sensitive structure units symmetrical to each other along a first direction, the anchor layer comprising a pair of anchor units symmetrical to each other along the first direction, and the sensitive structure units and the anchor units corresponding to each other one by one.

[0007] Each of the sensitive structure units comprises 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 a plurality of groups of comb electrodes symmetrically arranged between the sensitive mass block and the support beams, each group of the comb electrodes comprising first combs and second combs arranged alternately and at intervals.

[0008] Each of the anchor point units comprises a pair of first anchor points, a pair of second anchor points, and a pair of third anchor points arranged alternately and at intervals on the central axis of the sensitive mass block along the first direction; the first anchor points are connected to the support beams, and the first combs of each group of the comb electrodes are connected to the sensitive mass block one by one, so that the sensitive mass block and the first combs can be suspended on the substrate through the first anchor points; the second combs of each group of the comb electrodes are connected to the second anchor points or the third anchor points one by one, so that the second combs can be suspended on the substrate through the second anchor points or the third anchor points.

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

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

[0011] Optionally, each of the sensitive structure units further comprises a plurality of elastic beams, and the plurality of elastic beams are symmetric with respect to each other along the first direction and / or the second direction.

[0012] Optionally, each of the sensitive structure units further comprises a pair of elastic beams; and in the first direction, each of the elastic beams is symmetric with respect to the central axis of the sensitive mass block along the second direction; in the second direction, the pair of elastic beams are symmetric with respect to the central axis of the sensitive mass block along the first direction.

[0013] Optionally, the elastic beams are serpentine folded beam structures composed of a plurality of 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 along the second direction in a serpentine shape and is connected to one end of the support beam along the second direction.

[0014] Optionally, the second comb teeth are connected one-to-one with the second anchor points and the third anchor points, and the number of connections of the second comb teeth with the second anchor points and the third anchor points is equal respectively.

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

[0016] Optionally, a plurality of groups of the comb electrode 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 arrays and the second capacitor arrays are mutually symmetrical along the second direction.

[0017] Optionally, the static capacitance and the 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 capacitor are opposite.

[0018] The double-differential MEMS accelerometer structure provided in the application has at least the following beneficial effects:

[0019] The application provides a double-differential MEMS accelerometer structure, which comprises a substrate, a sensitive structure layer suspended on the substrate, and an anchor point layer located between the substrate and the sensitive structure layer and providing support for the suspension of the sensitive structure layer on the substrate. The sensitive structure layer comprises two mutually symmetrical sensitive structure units, each of which comprises a sensitive mass block, a pair of support beams symmetrically arranged on both sides of the sensitive mass block, and a plurality of groups of comb electrodes symmetrically arranged between the sensitive mass block and the support beams. The application can realize double-carrier acceleration detection of the MEMS accelerometer, and balance the performance of the acceleration detection of the MEMS accelerometer structure in sensitivity, stability and frequency characteristics.

[0020] Additional aspects and advantages of the application will be in part apparent and in part pointed out hereinafter. BRIEF DESCRIPTION OF DRAWINGS

[0021] The above and / or additional aspects and advantages of the application will become apparent and be readily appreciated from the following description, including the accompanying drawings, in which:

[0022] Figure 1 It is a longitudinal sectional structure schematic diagram of a MEMS accelerometer structure according to an embodiment of the application.

[0023] Figure 2 It is a transverse sectional structure schematic diagram of a first MEMS accelerometer structure according to an embodiment of the application.

[0024] Figure 3 FIG. 2 is a schematic diagram of a cross-sectional structure of a second MEMS accelerometer structure according to an embodiment of the present application.

[0025] Figure 4 FIG. 3 is a schematic diagram of an electrical connection structure of a MEMS accelerometer structure according to an embodiment of the present application.

[0026] 100 substrate; 200 anchor layer; 201 first anchor; 202 second anchor; 203 third anchor; 300 sensitive structure layer; 301 first sensitive structure unit; 302 second sensitive structure unit; 310 sensitive mass; 320 support beam; 330 comb electrode; 331 first comb; 332 second comb; 3301 first capacitor array; 3302 second capacitor array; 340 elastic beam; 350 first connecting part; 360 second connecting part; 370 third connecting part. DETAILED DESCRIPTION

[0027] Embodiments of the present application are described in detail below with reference to examples illustrated in the accompanying drawings, in which the same or similar reference numerals represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by reference to the accompanying drawings are exemplary and are intended to explain the present application, and cannot be understood as limiting the present application.

[0028] Micro-electro-mechanical system (MEMS) accelerometers, as a core technology in the field of inertial sensing, have gone from the laboratory to large-scale commercial use since the 1980s. Early MEMS accelerometers mostly used single-axis cantilever beam design, and acceleration detection was achieved through the change in capacitance caused by the displacement of the sensitive mass. Later, the academic community proposed monolithic integrated multi-axis detection structures, such as using a central mass and symmetrically distributed detection beams to achieve dual-axis synchronous measurement. However, the existing multi-axis detection structures often cause key size deviations (e.g., deviations exceeding 8%) due to the asymmetry of the structure in deep reactive ion etching (DRIE) process, or stress concentration of the support beams caused by the difference in thermal expansion coefficient, so that the zero bias temperature coefficient (TCoB) of the existing accelerometer structure fluctuates by ±2 mg / °C in the range of -40-85°C, which is difficult to meet the needs of high-precision scenarios such as aerospace.

[0029] Further, the existing MEMS accelerometer usually adopts silicon-based material for the support anchor point and the sensitive mass block, and the connection part can introduce a metal layer or a silicon oxide insulating layer, and the difference in the thermal expansion coefficient of different materials can 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, thereby causing the change in the distance between the capacitor plates to exceed 15% of the design value, resulting in zero point drift. In addition, the process deviation has a more significant impact on the performance of the MEMS accelerometer. For example, a slight deviation (such as ± 5% of the etching non-uniformity) in the etching depth or the sidewall angle of the comb electrode can cause the differential capacitance to be unbalanced, and the sensitivity can be reduced by more than 30%.

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

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

[0032] According to one aspect of the present application, as shown in Figures 1-3 A double-differential MEMS accelerometer structure is provided, which includes a substrate 100, a sensitive structure layer 300 suspended on the substrate 100, and an anchor point layer 200 located between the substrate 100 and the sensitive structure layer 300 and providing support for the suspension of the sensitive structure layer 300 on the substrate 100. The sensitive structure layer 300 includes at least two sensitive structure units symmetric to each other along a first direction, the anchor point layer 200 includes at least two anchor point units symmetric to each other along the first direction, and the sensitive structure units and the anchor point 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 point 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 a plurality of groups of comb electrodes 330 symmetrically arranged between the sensitive mass block 310 and the support beams 320; the two ends of the second direction are respectively elastically connected to the two ends of the sensitive mass block 310 along the second direction, and the plurality of groups of comb electrodes 330 are surrounded, and each group of comb electrodes 330 includes at least a pair of first comb teeth 331 and second comb teeth 332 arranged alternately 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 staggered and spaced on the central axis of the sensitive mass 310 along the first direction, wherein the first anchors 201 are connected with the support beams 320, and the first comb teeth 331 of each group of comb electrodes 330 are configured to be connected with the sensitive mass 310 one-to-one, so that the sensitive mass 310 and the first comb teeth 331 can be suspended on the substrate 100 through the first anchors 201; and the second comb teeth 332 of each group of comb electrodes 330 are configured to be connected with the second anchors 202 or the third anchors 203 one-to-one, so that the second comb teeth 332 can be suspended on the substrate 100 through the second anchors 202 or the third anchors 203.

[0035] For ease 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 the 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 symmetrical to each other along the first direction are symmetrical to each other about the symmetry axis Z0; the plurality of groups of comb electrodes 330 symmetrical to each other along the first direction are symmetrical to each other about the symmetry axis Z1, and the symmetry axis Z0 is also the central axis of the sensitive mass 310 along the second direction; the plurality of groups of comb electrodes 330 symmetrical to each other along the second direction are symmetrical to each other about the symmetry axis Z2, and the symmetry axis Z2 is also the central axis of the sensitive mass 310 along the first direction. In the subsequent content, unless otherwise specified, the symmetry relationship along the first direction and the second direction in each sensitive structure unit represents the symmetry about Z1 or Z2 as the axis.

[0036] It can be understood that the substrate 100 can be any suitable substrate material known in the art, including but not limited to a semiconductor material of silicon or any other semiconductor material, a non-semiconductor material, etc., and the non-semiconductor material includes but is not limited to glass, plastic, metal or ceramic, etc. If necessary, the substrate 100 can also be an integrated circuit manufactured on the above-mentioned material. The sensitive structure layer 300 can be any material known in the art, including but not limited to a semiconductor material of polysilicon or any other semiconductor material.

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

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

[0039] Since the multiple sets of comb tooth electrodes 330 are symmetrically arranged between the sensitive mass 310 and the support beam 320, when the second comb teeth 332 are connected with the second anchor point 202 and the third anchor point 203 one by one, and the number of connections of the second comb teeth 332 with the second anchor point 202 and the third anchor point 203 are equal, the multiple sets of comb tooth electrodes 330 in each sensitive structure unit can at least form a pair of the first capacitor array 3301 and a pair of the second capacitor array 3302 symmetrically arranged along the first direction, and the first capacitor array 3301 and the second capacitor array 3302 are symmetrically arranged along the second direction.

[0040] Since the pair of the first capacitor array 3301 and the pair of the second capacitor array 3302 in each sensitive structure unit are symmetrically arranged along the second direction, the first capacitor array 3301 and the second capacitor array 3302 together form a differential capacitor structure symmetrically arranged along the first direction and the second direction.

[0041] Therefore, when the sensitive mass 310 generates displacement along the second direction under the action of the 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, and based on the actual change amount of the capacitances and the actual displacement amount of the sensitive mass 310, and in combination 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 calculated.

[0042] Meanwhile, since the first capacitor array 3301 and the second capacitor array 3302 together form a differential capacitor structure symmetrically arranged along the first direction and the second direction, even if the sensitive structure unit is subjected to lateral interference along the first direction during the acceleration detection process along the second 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 stability of the accelerometer.

[0043] In addition, since the first capacitor array 3301 and the second capacitor array 3302 jointly constitute a differential capacitor structure symmetrical to each other in the first direction and the second direction, the MEMS accelerometer structure can be free from interference of changes in external ambient temperature and / or power supply fluctuations during acceleration detection. That is, even if the first capacitor array 3301 and the second capacitor array 3302 produce slight displacement of the comb electrodes 330 due to temperature changes, the first capacitor and the second capacitor will exhibit the same amount of capacitance change due to the symmetrical structure of the first capacitor and the second capacitor, and the capacitance change will be eliminated in the differential working mode, thereby playing a common-mode rejection role 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 jointly constitute a differential capacitor structure symmetrical to each other in the first direction and / or the second direction, the sensitive mass unit will form a symmetrical heat conduction path during the etching process of the process, and the symmetry of the heat dissipation channel can improve the consistency of the structure of the sensitive structure layer 300 in the preparation process, further ensuring the measurement accuracy and measurement stability of the accelerometer.

[0045] Since the first anchor point 201, the second anchor point 202, and the third anchor point 203 are staggered and spaced apart on the central axis of the sensitive mass block 310 in the first direction, the internal stress gradient or deformation mismatch caused by the difference in the thermal expansion coefficient of different materials between the sensitive structure layer 300, the anchor point layer 200, and the substrate 100 when the temperature changes can be mutually offset, thereby reducing the temperature stress sensitivity and patch stress sensitivity of the accelerometer structure.

[0046] Each first anchor point 201, second anchor point 202, and third anchor point 203 is arranged on the two sides of the sensitive mass block 310 in the first direction, and the center of the first anchor point 201, the second anchor point 202, and the third anchor point 203 is collinear with the central axis of the sensitive mass block 310 in the first direction.

[0047] Further, in the first direction, a pair of first anchor points 201 are symmetrically arranged on the two sides of the sensitive mass block 310, a pair of second anchor points 202 and a pair of third anchor points 203 are asymmetrically arranged on the two sides of the sensitive mass block 310, and the distance between the pair of second anchor points 202 is equal to the distance between the pair of third anchor points 203, and the sum of the distances of the second anchor points 202 and the third anchor points 203 on the two sides from the central axis of the sensitive mass block 310 in the second direction is equal.

[0048] Furthermore, since the sensitive structure layer 300 provided in this application includes at least two mutually symmetrical sensitive structure units, and the electrical signals received by the two mutually symmetrical sensitive structure units can form a dual differential capacitor structure, the dual differential capacitor structure can further reduce or even eliminate residual interference in the differential mode signal (such as nonlinear terms and second-order common-mode errors in the differential mode) based on the single differential capacitor structure. It can achieve differential elimination of various errors at different positions, or higher-order error cancellation, without affecting the resonant frequency, further optimizing the measurement accuracy, measurement sensitivity, and anti-interference capability of the accelerometer structure, and achieving a performance balance between sensitivity, stability, and frequency characteristics of the MEMS accelerometer. At the same time, the arrangement of the dual differential capacitor structure can ensure the sensitivity of the capacitor within a limited size, thereby avoiding the impact on dimensional accuracy caused by the thermal expansion and deformation of the distal end of the large-size comb electrode 330, and solving the contradiction between high precision and miniaturization of the MEMS accelerometer.

[0049] Specifically, the basic working principle of the capacitors in the first capacitor array 3301 and the second capacitor array 3302 in each sensitive structural unit can be explained using a parallel plate capacitor. Ignoring edge effects, 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 capacitor plates, A is the area between the capacitor plates facing each other, and d is the distance between the capacitor plates.

[0052] Therefore, when the displacement direction of the sensitive mass block 310 is parallel to the direction directly opposite the electrode plate, such as Figure 2 As shown, the first comb tooth 331 will also be displaced by x along the second direction under the action of inertial force along with the sensitive mass block 310, thereby changing the electrode spacing d between the plates. Since the first capacitor array 3301 and the second capacitor array 3302 are symmetrical, it can be assumed here that the initial spacing between the plates in the first capacitor array 3301 and the second capacitor array 3302 is the same, that is, the electrode spacing between the first comb tooth 331 and the second comb tooth 332 in the first capacitor array 3301 changes from the initial spacing d0 to d0+x; the electrode spacing between the first comb tooth 331 and the second comb tooth 332 in the second capacitor array 3302 will change from the initial spacing d0 to d0-x, thereby causing a change in the capacitance of the differential capacitor structure.

[0053] Similarly, when the displacement direction of the sensitive mass block 310 is perpendicular to the direction directly opposite the electrode plate, such as Figure 3As shown, the first comb teeth 331 will also produce displacement x in the second direction under the action of the inertial force, so as to change 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 assumed that the initial facing area between the plates in the first capacitor array 3301 and the second capacitor array 3302 is the same, that is, the facing area between the plates of the first comb teeth 331 and the second comb teeth 332 in the first capacitor array 3301 changes from the initial facing area A0 to A0+ΔA; the facing area between the plates of the first comb teeth 331 and the second comb teeth 332 in the second capacitor array 3302 changes from the initial facing area A0 to A0-ΔA, thereby causing the capacitance of the differential capacitor structure to change. ΔA is the change of the facing area between the plates, and ΔA satisfies ΔA=Lx, L is the edge length of the plate perpendicular to the displacement direction.

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

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

[0056]

[0057] Wherein, 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 ΔC total and the moving displacement x of the mass sensitive block under the action of the inertial force, and the equivalent relationship between the acceleration a and the moving displacement x of the sensitive mass block 310 under the action of the inertial force, the equivalent relationship between the acceleration a and the total capacitance change ΔC total of the double-differential capacitor structure can be obtained.

[0059] For ease of description, as shown in Figure 4 , and in combination withFigure 2 and Figure 3 The pair of 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, and the third anchor point 203 is connected to the negative carrier, 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 negative carrier, and the third anchor point 203 is connected to the positive carrier, and the parameters of the positive polarity carrier and the negative polarity carrier are equal in size and opposite in polarity. Thus, the first sensitive structure unit 301 and the second sensitive structure unit 302 each contain a pair of first capacitor arrays 3301 and a pair of second capacitor arrays 3302 with opposite positive and negative polarities, 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 the dual-carrier detection of the MEMS accelerometer with two identical and independent sensitive structure units.

[0060] In some embodiments, the sensitive structure layer 300 can further include a plurality of first connecting portions 350, second connecting portions 360, and third connecting portions 370. Each first connecting portion 350 extends from the middle of the support beam 320 in the first direction and covers the first anchor point 201, and each first connecting 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 electrical connection channels for the support beam 320 suspended above the substrate 100 through the first connecting portion 350. Each second connecting portion 360 extends from the side of the second comb tooth 332 in the second capacitor array 3301 close to the second anchor point 202 in the second direction and covers the second anchor point 202, and each second connecting 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 electrical connection channels for the second comb tooth 332 in the first capacitor array 3301 suspended above the substrate 100 through the second connecting portion 360. Each third connecting portion 370 extends from the side of the second comb tooth 332 in the second capacitor array 3302 close to the third anchor point 203 in the second direction and covers the third anchor point 203, and each third connecting 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 electrical connection channels for the second comb tooth 332 in the second capacitor array 3302 suspended above the substrate 100 through the third connecting portion 370.

[0061] In some embodiments, each sensitive structure unit further comprises a plurality of elastic beams 340, and the plurality of elastic beams 340 are symmetric to each other in the first direction and / or the second direction, and the two ends of the sensitive mass 310 in the second direction are connected to the two ends of the support beam 320 in the second direction which are arranged on the two sides of the sensitive mass 310.

[0062] As an example, each sensitive structure unit comprises a pair of elastic beams 340, and in the first direction, each elastic beam 340 is symmetric about the central axis of the sensitive mass 310 in the second direction; in the second direction, the pair of elastic beams 340 are symmetric about the central axis of the sensitive mass 310 in the first direction, thereby also achieving the effect of further reducing the non-linear error of the MEMS accelerometer.

[0063] The elastic beam 340 can specifically be a serpentine folded structure composed of a plurality of folded beams, and 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 in a serpentine shape in the second direction and is connected to one end of the support beam 320 in the second direction, thereby also enabling the sensitive mass 310 to be elastically connected with the support beam 320 and enabling the sensitive mass 310 to be suspended above the substrate 100 without being in direct contact with the substrate 100, so as to enable the sensitive mass 310 to be displaced relative to the substrate 100 in the second direction.

[0064] In summary, the present application provides a double-differential MEMS accelerometer structure, which comprises a substrate 100, a sensitive structure layer 300 suspended on the substrate 100, and an anchor layer 200 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 comprises two symmetric sensitive structure units, each of which comprises a sensitive mass 310, a pair of support beams 320 symmetrically arranged on the two sides of the sensitive mass 310, and a plurality of groups of comb electrodes 330 symmetrically arranged between the sensitive mass 310 and the support beam 320. The present application can realize double-carrier acceleration detection of the MEMS accelerometer, and enable the acceleration detection of the MEMS accelerometer structure to achieve a performance balance between sensitivity, stability and frequency characteristics.

[0065] In the foregoing detailed description, reference is made to the terms "one embodiment", "some embodiments", "an example", "a specific example" or "some examples" etc. which describe a particular feature, structure, material, or characteristic included in at least one embodiment or example of the application. The illustrative discussion of these terms are not intended to teach that there are any, notwithstanding the fact that the terms so refer to a particular embodiment or example. Moreover, these terms can be used interchangeably to signify that a particular feature, structure, material, or characteristic is included in at least one embodiment or example. Additionally, the description can use perspective-based adjectives such as "first", "second", "third", etc. to describe a particular name, characteristic, property, or the like, but these adjectives are used merely for description and do not imply or suggest any relative importance or an implied reference to the number of the indicated technical features. Thus, a feature defined with "first", "second" can explicitly or implicitly include at least one of the features. In the description of the application, the meaning of "a plurality" is at least two, for example, two, three, etc., unless otherwise specifically limited.

[0066] Furthermore, the terms "first", "second", etc. are used herein only to describe various features, and do not imply or suggest relative importance or an implied reference to the number of the indicated technical features. Thus, a feature defined with "first", "second" can explicitly or implicitly include at least one of the features. In the description of the application, the meaning of "a plurality" is at least two, for example, two, three, etc., unless otherwise specifically limited.

Claims

1. A dual-differential MEMS accelerometer structure, characterized in that, The device 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 mutually symmetrical sensitive structure units along a first direction, and the anchor layer includes a pair of mutually symmetrical anchor units along the first direction. The sensitive structure units and the anchor units correspond one-to-one. Each of the sensitive structural units includes at least a sensitive mass block, symmetrically arranged on both sides of the sensitive mass block along the first direction, and a pair of support beams elastically connected to the two ends of the sensitive mass block along the second direction, as well as multiple sets of comb-tooth electrodes symmetrically arranged between the sensitive mass block and the support beams, each set of comb-tooth electrodes including staggered and spaced first comb teeth and second comb teeth. Each anchor point unit includes a pair of first anchor points, a pair of second anchor points, and a pair of third anchor points that are staggered and spaced apart on the central axis of the sensitive mass block along the first direction; the first anchor points are connected to the support beam, and the first comb teeth of each group of comb electrodes are connected one-to-one with the sensitive mass block so that the sensitive mass block and the first comb teeth can be suspended on the substrate through the first anchor points; the second comb teeth of each group of comb electrodes are connected one-to-one with the second anchor points or the third anchor points so that the second comb teeth can be suspended on the substrate through the second anchor points or the third anchor points.

2. The dual-differential MEMS accelerometer structure according to claim 1, characterized in that, Each of the first anchor point, the second anchor point, and the third anchor point is located on both sides of the sensitive mass block along the first direction, and the centers of the first anchor point, the second anchor point, and the third anchor point 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 first anchor points are symmetrically distributed on both sides of the sensitive mass block, a pair of second anchor points and a pair of third anchor points are asymmetrically distributed on both sides of the sensitive mass block, and the distance between the pair of second anchor points is equal to the distance between the pair of third anchor points.

4. The dual-differential MEMS accelerometer structure according to claim 1, characterized in that, Each of the sensitive structural units further includes a plurality of elastic beams, which are symmetrical to each other in the first direction and / or the second direction.

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

6. The dual-differential MEMS accelerometer structure according to claim 5, characterized in that, The elastic beam is a serpentine folded beam structure composed of multiple folded beams, and one end of each elastic beam is connected to one end of the sensitive mass block along the second direction, and the other end of each elastic beam 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 tooth is connected to the second anchor point and the third anchor point in a one-to-one correspondence, and the number of connections between the second anchor point and the third anchor point and the second comb tooth is equal.

8. The dual-differential MEMS accelerometer structure according to claim 7, characterized in that, The second comb tooth connected to the second anchor point and the first comb tooth on the opposite side combine to form a first capacitor array; the second comb tooth connected to the third anchor point and the first comb tooth on the opposite side combine to form a second capacitor array.

9. The dual-differential MEMS accelerometer structure according to claim 8, characterized in that, The multiple sets of comb electrodes form at least a pair of first capacitor arrays and a pair of second capacitor arrays symmetrically arranged along the first direction, and the first capacitor array and the second capacitor array are symmetrical to each other along the second direction.

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

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