A blade-type Z-axis MEMS accelerometer

Abstract

The present invention discloses a blade-type Z-axis MEMS accelerometer, which is formed by connecting a silicon substrate and a silicon cap to form a cavity, and each of the silicon substrate and the silicon cap is provided with a detection electrode. In particular, the cavity is provided with an anchor point, a support frame, and two or more blade-type mass blocks with asymmetric mass. Each group of mass blocks is connected by an elastic beam located in the middle and is equidistantly distributed on the support frame around the anchor point, and is rotationally symmetrical around the anchor point. Under the input acceleration along the Z axis where the anchor point is axial, the mass block rotates outside the XY plane around the support arm of the support frame where the elastic beam is located, and the detection electrode and the mass block form two or more differential capacitors for detecting acceleration. By applying the MEMS accelerometer of the present invention, by designing the mass block into a blade-type structure that is rotationally symmetrical relative to the anchor point, the packaging stress error can be differentially offset to the maximum extent, which can greatly improve the temperature characteristics of the Z-axis MEMS accelerometer, and has higher error interference resistance and universality with other MEMS-related devices.

Description

Technical Field

[0001] The present invention relates to a chip-level sensor design, in particular to an innovative structure of a blade-type Z-axis MEMS accelerometer, belonging to the field of micro-electromechanical technology. Background Art

[0002] MEMS (Micro-electromechanical Systems) is a cutting-edge, multidisciplinary research field developed on the basis of microelectronics technology. It involves a wide range of disciplines and technologies, including electronics, mechanics, materials, physics, chemistry, biology, and medicine, and has broad application prospects. MEMS pressure sensors, accelerometers, and gyroscopes are typical force-sensitive devices. They are widely used for high-precision measurement of physical quantities such as pressure, acceleration, and angular velocity. They are characterized by their small size, low power consumption, compatibility with integrated circuit processes, and ease of mass production.

[0003] MEMS accelerometers are miniature sensors that use a micro proof mass to measure acceleration. Based on their detection principle, they can be categorized as piezoresistive, piezoelectric, capacitive, and thermal flow. Currently, most high-precision, commercial MEMS accelerometers are capacitive. However, regardless of the detection principle, MEMS accelerometers inevitably introduce additional stress during the packaging process.

[0004] The MEMS chip of the MEMS accelerometer is usually packaged in a ceramic, metal or plastic shell. The MEMS chip is usually fixed in the package shell cavity with adhesive. Because the MEMS chip, adhesive and package shell are made of different materials, their coefficient of thermal expansion (CTE) is inconsistent. When the ambient temperature changes, there is a thermal stress mismatch between the MEMS chip, adhesive and package shell, which in turn generates package thermal stress (such as Figure 3 (as shown). Under thermal stress, the fixed electrode attached to the silicon substrate or cap deforms, causing a change in the plate capacitance formed by the fixed electrode and the movable electrode of the proof mass. This change is not caused by the input acceleration and is therefore an error signal.

[0005] The sensitive structure of the traditional Z-axis MEMS accelerometer is a seesaw structure (such as Figure 1 as shown) or in sandwich form (as Figure 2(As shown in the figure). Z-axis accelerometers typically use a plate capacitor detection method. Therefore, the fixed electrodes of the detection capacitors are typically attached to the silicon substrate or silicon cap to detect the motion displacement of the micromass along the Z-axis. When there is a Z-axis input acceleration, the micromass moves along the Z-axis, generating a displacement proportional to the input acceleration. The fixed electrodes arranged on the silicon substrate and / or silicon cap and the movable electrodes of the micromass form one or more pairs of plate capacitors. As the micromass deflects in response to the input acceleration, the capacitance of the plate capacitors changes. By detecting this change in capacitance, the magnitude of the input acceleration can be calculated.

[0006] How to reduce packaging stress is an important technical bottleneck that needs to be solved to further improve the performance of MEMS accelerometers. Researchers at home and abroad have proposed a variety of solutions:

[0007] Analog Devices proposed a "MEMS accelerometer with Z-axis anchor tracking" approach, designing a tracking anchor structure that couples force application to a torsional spring of mass to offset the effect of strain on the output acceleration.

[0008] EP1571454B1 discloses a Z-axis silicon micro-accelerometer with a sandwich structure and chip-level stress isolation, in which stress release beams are arranged around the intermediate layer mass block to reduce the stress transmitted to the sandwich sensitive structure through stress release.

[0009] US7140250 and CN201911125779.9 disclose two seesaw Z-axis accelerometers based on comb-tooth capacitance detection. Comb-tooth capacitors of unequal height are used instead of flat plate capacitors, which to a certain extent reduces the sensitivity of sensitive capacitors to stress and temperature. The disadvantage is that the gain from mechanical displacement to capacitance change is relatively low.

[0010] Another company (referred to as "Northern Core Dynamic Link") has proposed a MEMS component with a structure that reduces package stress (patent application number: 201320205008.2). This component features at least one die-stud mounted on the backside layer, surrounded by a die-bonding adhesive on the bottom plate of the package. The die-bonding adhesive on the backside layer of the MEMS chip and the die-bonding adhesive on the bottom plate secure the MEMS chip to the package base. However, uniformity and symmetry are difficult to control, and the reduced total bonding area between the chip and the package results in insufficient resistance to mechanical shock.

[0011] The structure of the sandwich Z-axis MEMS accelerometer can be simplified as follows: Figure 2As shown, it consists of a mass block 201 that moves along the Z axis, detection electrodes distributed above and below the mass block, a silicon cap 204, and a silicon substrate 205. The mass block 201 and the upper detection electrode 202a form a pair of parallel plate capacitors 203a, and the mass block 201 and the lower detection electrode 202b form another pair of parallel plate capacitors 203b.

[0012] The structure of the seesaw Z-axis MEMS accelerometer can be simplified as follows: Figure 1 As shown, it consists of a mass block 101 moving along the Z axis, detection electrodes distributed on both sides (above and below) of the mass block, and a silicon cap 104 and a silicon substrate 105. The mass block 101 and the upper left detection electrode 102a form a pair of capacitances C a The parallel plate capacitor 103a, the mass block 101 and the lower left detection electrode 102b form a pair of capacitance values The parallel plate capacitor 103b, the mass block 101 and the upper right detection electrode 102c form a pair of capacitance values The parallel plate capacitor 103c, the mass block 101 and the lower right detection electrode 102d form a pair of capacitance values When there is no external Z-axis input acceleration, the mass block 101 is located between the upper detection electrodes 102a, 102c and the lower detection electrodes 102b, 102d. The distance between the mass block 101 and the upper detection electrodes 102a, 102c is equal to the distance between the mass block 101 and the lower detection electrodes 102b, 102d. Therefore, the capacitance of the parallel plate capacitor 103a is equal to that of the parallel plate capacitor 103b, and the capacitance of the parallel plate capacitor 103c is equal to that of the parallel plate capacitor 103d. The parallel plate capacitor 103a and the parallel plate capacitor 103b form a pair of differential capacitors, and the parallel plate capacitor 103c and the parallel plate capacitor 103d form another pair of differential capacitors. When there is external Z-axis input acceleration, the mass block moves outside the XY plane around the elastic beam under the action of the acceleration, causing the distance between the mass block and the detection electrode on one side to decrease, while the distance between the mass block and the detection electrode on the other side to increase, thereby causing one of the two parallel plate capacitors to increase and the other to decrease. By detecting the differential change of differential capacitance △C out =(C a - )-( - ), the magnitude and direction of the Z-axis acceleration can be calculated.

[0013] Figure 3The figure shows a simplified isometric view of the seesaw Z-axis MEMS accelerometer structure without the silicon cap and front sidewall. Given the aforementioned explanation of the principle of thermal stress deformation of multilayer materials, MEMS chips are typically bonded using a surface bonding method where the entire bottom surface of the chip is coated with adhesive, or a point bonding method where a circular adhesive is applied to the center area of the bottom surface of the chip. In both conventional bonding methods, the adhesive is applied in a completely symmetrical manner about the central axis of the chip. Accordingly, the deformation of the chip caused by the packaging stress generated is also completely symmetrical about the central axis of the chip, as shown in FIG. Figure 4 and Figure 5 shown.

[0014] The MEMS structure chip will deform under the action of thermal stress. Figure 1 In the embodiment shown, the detection electrodes 102b, 102d attached to the silicon substrate and the detection electrodes 102a, 102c attached to the silicon cap will deform accordingly. One deformation mode is as follows: Figure 6 As shown in the figure, since the mass block is suspended within the MEMS chip by a beam structure, the beam structure provides stress relief, preventing significant deformation of the mass block. However, the deformation caused by thermal stress can cause the capacitances of parallel plate capacitors 103a and 103b to be unequal, and the capacitances of parallel plate capacitors 103c and 104d to be unequal. This unequal capacitance is caused by stress, not input acceleration.

[0015] Therefore, when stress is generated and the MEMS structure is deformed, the MEMS chip will detect the capacitance change, regardless of whether there is input acceleration, that is, the parallel plate capacitance 103a changes. , the parallel plate capacitance 103b changes , the parallel plate capacitance 103c changes , the parallel plate capacitance 103d changes .because ≠ and ≠ ,

[0016] △C out =(C a - )-( - )=( - )-( - )≠0. At this time, the device will output a non-zero error signal, which is a major cause of the measurement error of the MEMS accelerometer. In other words, in actual situations, the change in differential capacitance is a function of the input acceleration a and a function of stress σ Composed of, that is, △C out = + .

[0017] In addition, if Figure 7 As shown in FIG. 7 , the contour line 701 of the deformation caused by the packaging stress on the chip silicon substrate is annular. Ideally, the capacitance change caused by the stress on the capacitors formed by each electrode is = , = However, in reality, various processing errors, such as uneven glue coating thickness and deviation in glue coating position, will lead to differences in the stress on the electrodes distributed on both sides. The projection shape of the detection mass block and detection electrode of the traditional sandwich structure and seesaw structure accelerometer in the XY plane does not completely match the projection shape of this stress deformation shape in the XY plane. Therefore, this difference cannot be eliminated by the differential capacitance detection method of the traditional sandwich structure and seesaw structure. Summary of the Invention

[0018] The purpose of the present invention is to provide a blade-type Z-axis MEMS accelerometer to solve the problem of acceleration measurement error caused by stress introduced by packaging.

[0019] The technical solution of the present invention to achieve the above-mentioned purpose is a blade-type Z-axis MEMS accelerometer, which is composed of a silicon substrate and a silicon cap connected to form a cavity, and a detection electrode is provided on each of the silicon substrate and the silicon cap. The characteristic is that: an anchor point, a support frame and two or more groups of blade-type mass blocks with asymmetric mass are provided in the cavity, and each group of mass blocks is connected by an elastic beam located in the middle and is equidistantly distributed on the support frame around the anchor point, and is rotationally symmetrical around the anchor point; under the input acceleration along the Z axis where the anchor point is axial, the mass block rotates out of the XY plane around the support arm of the support frame where the elastic beam is located, and the detection electrode and the mass block constitute two or more groups of differential capacitors for detecting acceleration.

[0020] In the above-mentioned blade-type Z-axis MEMS accelerometer, further, the mass block is symmetrical along the support arm in shape but asymmetrical in mass.

[0021] In the above-mentioned blade-type Z-axis MEMS accelerometer, further, the mass block is configured to conform to and be distributed corresponding to the strain shape generated by stress on the silicon substrate.

[0022] The above-mentioned blade-type Z-axis MEMS accelerometer further has the detection electrode and the projection of the mass block on the XY plane coincide with each other.

[0023] The above-mentioned blade-type Z-axis MEMS accelerometer can further have projections of the detection electrode and the mass block on the XY plane that are proportionally enlarged or proportionally reduced.

[0024] The above-mentioned blade-type Z-axis MEMS accelerometer, further, the mass block is four groups of fan-shaped blades that evenly divide the disk, each group of fan-shaped blades is centrally separated and connected as a whole by elastic beams, the elastic beams are positioned and inserted into the slots of the support frame, and adjacent groups of fan-shaped blades are separated by the support frame.

[0025] The above-mentioned blade-type Z-axis MEMS accelerometer, further, the mass block is in the form of a nested inner and outer ring within the radial range of the anchor point, wherein the inner ring is set as two or more groups of fan-shaped blades that evenly divide the circular disk, each group of fan-shaped blades are separated in the center and connected as a whole by elastic beams, and adjacent groups of fan-shaped blades are separated by a supporting frame; the outer ring is set as two or more groups of fan-ring blades that evenly divide the circular ring, each group of fan-ring blades are separated in the center and connected as a whole by elastic beams, and adjacent groups of fan-ring blades are separated by a supporting frame, and the elastic beams are positioned and inserted into the slots of the support frame.

[0026] The blade-type Z-axis MEMS accelerometer further has the support arms of the support frame corresponding to the slots compatible with the elastic beams of the inner ring and the outer ring being collinear or mutually staggered.

[0027] The above-mentioned blade-type Z-axis MEMS accelerometer further has the blade of the mass block having an outer shape of at least a rectangle, a trapezoid, or a circular ring.

[0028] The blade-shaped Z-axis MEMS accelerometer employing this invention offers significant advancements: by designing the mass into a blade-shaped structure that is rotationally symmetrical about the anchor point, this accelerometer maximizes differential cancellation of package stress errors, significantly improving the Z-axis MEMS accelerometer's temperature characteristics and enhancing its error-tolerance capability. It is also applicable to MEMS accelerometers with other sensitive axes or other stress-sensitive MEMS devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the front-view cross-section structure of a seesaw-type Z-axis MEMS accelerometer.

[0030] Figure 2 Schematic diagram of the front-view cross-section structure of a sandwich-type Z-axis MEMS accelerometer.

[0031] Figure 3 Isometric diagram of a seesaw Z-axis MEMS accelerometer without the silicon cap and front sidewall.

[0032] Figure 4 A side view schematic diagram of the chip deformation affected by temperature.

[0033] Figure 5 An isometric diagram showing the deformation of a chip's silicon substrate due to temperature.

[0034] Figure 6 This is a front view schematic diagram of the seesaw Z-axis MEMS accelerometer after stress deformation.

[0035] Figure 7 Schematic diagram of stress and deformation of the silicon substrate after stress deformation under ideal conditions.

[0036] Figure 8 Schematic diagram of the front view of the blade-type Z-axis MEMS accelerometer.

[0037] Figure 9 Isometric diagram of a blade-type Z-axis MEMS accelerometer (silicon cap and sidewalls not shown).

[0038] Figure 10 This is an isometric diagram of the silicon cap and the electrodes fixed on the silicon cap of a blade-type Z-axis MEMS accelerometer.

[0039] Figure 11 This is an isometric diagram of the silicon substrate and the fixed electrodes on the silicon substrate of a blade-type Z-axis MEMS accelerometer.

[0040] Figure 12 Schematic diagram of a blade structure of a blade-type Z-axis MEMS accelerometer.

[0041] Figure 13 Schematic diagram of the multi-layer nested blade-type Z-axis MEMS accelerometer structure. DETAILED DESCRIPTION

[0042] The specific implementation methods of the present invention will be further described below in conjunction with the accompanying drawings to make the technical solutions of the present invention easier to understand and grasp, thereby making a clearer definition of the protection scope of the present invention.

[0043] In response to the defects of existing Z-axis MEMS accelerometer structures, such as high sensitivity to stress deformation introduced by the package and insufficient coping ability, which makes it difficult to offset acceleration measurement errors through differential compensation, the designers of this invention, relying on long-term production line experience, innovatively proposed a blade-type Z-axis MEMS accelerometer to reduce the interference of stress deformation on measured acceleration.

[0044] From the technical overview, the preferred implementation of the blade-type Z-axis MEMS accelerometer is as follows: Figure 8 and Figure 9As shown, the cavity is formed by the connection of a silicon substrate 808 and a silicon cap 807. Detection electrodes 805 are provided on the silicon substrate 808, and detection electrodes 804 are provided on the silicon cap 807. As a core design for structural optimization, the cavity is equipped with an anchor point 803 (central axis cylinder), a support frame 809, and four sets of blade-like masses 801a-801d with asymmetric masses. Each set of masses is connected by elastic beams 802a-802d located in the center and is evenly spaced on the support frame around anchor point 803, with rotational symmetry around that point. In the smallest feasible implementation, two sets of blade-like masses with asymmetric masses can meet measurement requirements. However, for ease of understanding and optimal implementation, four sets are selected in the illustrated embodiment. When an acceleration a is applied along the Z-axis, centered on anchor point 803, each mass group undergoes rotational motion outside the XY plane around arm 8091 of support frame 809, where the elastic beam is located. The detection electrodes and the masses form four differential capacitors that detect acceleration. Each mass group is symmetrical along the arm's shape but asymmetric in mass; the detection electrodes are designed to conform to the corresponding mass group.

[0045] The above overview illustrates the novel blade-shaped Z-axis MEMS accelerometer structure proposed in this invention. Unlike traditional sandwich or seesaw structures, this design features blades distributed around a central axis, forming a multi-group differential structure. This multi-group differential structure minimizes common-mode errors caused by substrate stress and deformation, as well as coupling errors resulting from input acceleration in the XY plane.

[0046] In detail, the anchor point is located at the center of the structure, supporting the entire structure along the Z-axis within the cavity formed by the silicon substrate and silicon cap. A support frame extends radially outward from the anchor point, providing suspended support for the mass. The design connects several blade-like masses via elastic beams and distributes them equidistantly around the central anchor point on the support frame. This ensures rotational symmetry of the blade-like masses about the central axis of the structure; the elastic beams facilitate out-of-plane torsion of the blade-like masses.

[0047] The mass of the designed blade-type mass block is asymmetric about the arm where the elastic beam is connected to it. The asymmetry of the mass can be achieved by thinning the upper surface of the mass block on one side of the elastic beam by micro-machining, or by machining multiple sets of hole structures in the mass block on one side of the elastic beam to reduce the mass on one side. When there is a Z-axis input acceleration, the asymmetric mass generates a non-zero torque around the arm where the elastic beam is located under the action of the acceleration, causing the mass block to rotate around the elastic beam outside the XY plane. With the help of detection electrodes arranged on the silicon substrate and / or the silicon cap, the torsional displacement or angle of the blade-type mass block can be detected, and then the magnitude and direction of the input acceleration can be calculated. By designing the accelerometer structure into a blade that is rotationally symmetric about the central axis, the differential cancellation of the packaging stress error can be maximized.

[0048] From the perspective of further optional optimization features, in order to reduce the interference of stress on the detected acceleration, the above structural optimization has two advantages: The proof-mass structure is designed to conform to the strain shape induced by stress on the silicon substrate. The corresponding fixed detection electrodes are also designed to conform to the strain shape and distribution induced by stress on the silicon substrate. This ensures that the deformation induced by stress on all detection electrodes is the same, and therefore the capacitance change induced by stress on all fixed electrodes is also the same. In traditional seesaw accelerometers, the sensing electrodes are located on either side of the mass, relatively far apart. Generally, the greater the distance, the more likely the stresses are to vary. However, within a smaller region, stress rarely changes suddenly, resulting in similar stresses and, consequently, similar deformations.

[0049] like Figures 8 to 11 The schematic structural diagrams of the preferred embodiment shown in different perspectives and with varying degrees of complexity show that the four groups of blade-type masses 801a, 801b, 801c, and 801d are four sets of fan-shaped blades that evenly divide a circular disk. Each set of fan-shaped blades is centrally separated and connected to form a whole by elastic beams 802a, 802b, 802c, and 802d. The elastic beams are positioned and inserted into slots in the support frame, and adjacent sets of fan-shaped blades are separated by the support frame. The masses are evenly spaced around the central axis of the anchor point, and each mass is connected to the support frame and anchor point 803 via elastic beams. The masses are arranged to have an asymmetric mass distribution about the elastic beams. When an acceleration a is input on the Z axis, the mass blocks twist around the arms on which the elastic beams are located, causing the detection electrodes distributed on the silicon cap and silicon substrate to measure the corresponding change in capacitance. As can be seen from the figure, the detection electrodes 804a, 804b, 804c, 804d, 804e, 804f, 804g, and 804h distributed on the silicon cap 807 and the detection electrodes 805a, 805b, 805c, 805d, 805e, 805f, 805g, and 805h on the silicon substrate 808 are all conformal to the blade shape of the mass block; and the projections of the detection electrodes and the mass block in the XY plane coincide with each other and can be proportionally enlarged or reduced.

[0050] More specifically, if Figure 12As shown, the detection electrodes 804a, 804b on the silicon cap and the detection electrodes 805a, 805b on the silicon substrate and the mass block 801a constitute a group of differential capacitors 806a; the detection electrodes 804c, 804d on the silicon cap and the detection electrodes 805c, 805d on the silicon substrate and the mass block 801b constitute a group of differential capacitors 806b; the detection electrodes 804e, 804f on the silicon cap and the detection electrodes 805e, 805f on the silicon substrate and the mass block 801c constitute a group of differential capacitors 806c; the detection electrodes 804g, 804h on the silicon cap and the detection electrodes 805g, 805h on the silicon substrate and the mass block 801d constitute a group of differential capacitors 806d.

[0051] The capacitance 811a formed by the mass block 801a and the detection electrode 804a changes ΔC 811a , the capacitance 811b formed by the mass block 801a and the detection electrode 804b changes △C 811b , the capacitance 812a formed by the mass block 801a and the detection electrode 805a changes , the capacitance 812b formed by the mass block 801a and the detection electrode 805b changes The same applies to the other groups of mass blocks 801b, 801c, and 801d. When there is Z-axis acceleration input, the capacitance change is and Increase (or decrease), capacitance change and Therefore, the output capacitance change of the differential capacitor (806a) is △C' a =(△C 811a -△C 812a )+(△C 812b -△C 811b ). Similarly, the differential capacitance of other blade structures (801b, 801c, 801d) is calculated using the same method. Calculate the output capacitance change of differential capacitance 806b , the output capacitance change of differential capacitor 806c , the output capacitance change of differential capacitor 806d The final change in the accelerometer's detection capacitor output capacitance is △C' out =△C' a + + + .

[0052] When packaging stress causes the detection electrodes to deform, the blade-type mass and its corresponding detection electrodes are designed to conform to the strain contours, so the strain has almost the same effect on all detection electrodes. At the same time, since the spacing between a group of detection electrodes corresponding to each mass is several times smaller than the spacing between electrodes in a traditional structure, the detection electrodes corresponding to each mass are almost the same in terms of strain. Take mass 801a as an example. When packaging stress exists, the capacitance change is and Same, capacitance change and Therefore, the output capacitance change of the differential capacitor 806a caused by stress is = 0. The strain-conformal differential capacitor design can significantly reduce the detection error caused by stress compared to the traditional seesaw structure.

[0053] In addition to the above preferred embodiments, Figure 13 Another preferred embodiment, as shown in the diagram, features a mass block with nested inner and outer rings within the radial range of the anchor point. The inner ring consists of four groups of fan-shaped blades 901a, 901b, 901c, and 901d, evenly dividing the disk. Each group of fan-shaped blades is centered and separated, connected by elastic beams, and separated by a support frame. Adjacent groups of fan-shaped blades are separated by a support frame. The outer ring consists of four groups of fan-shaped blades 901e, 901f, 901g, and 901h, evenly dividing the ring. Each group of fan-shaped blades is centered and separated, connected by elastic beams, and separated by a support frame 902. The elastic beams are positioned and inserted into slots in the support frame. The support arms 904 corresponding to the slots in the inner and outer rings, where the elastic beams are compatible, are collinear or offset by 45° (as shown in the illustrated embodiment). From another perspective, if the number of fan-shaped blade groups changes during the nesting of the inner and outer rings, their arms can be collinear or offset by any angle.

[0054] In addition, the blade shape of the above-mentioned mass block is not limited to the illustrated embodiment, and can also be rectangular, trapezoidal, circular, etc.; and the number of mass blocks distributed can also be 3, 5, 6 or more.

[0055] From the above introduction to the blade-shaped Z-axis MEMS accelerometer and detailed description of its embodiments, it is clear that this solution possesses outstanding substantive features and significant advancements: By designing the mass into a blade-shaped structure that is rotationally symmetric relative to the anchor point, this accelerometer maximizes differential cancellation of package stress errors, significantly improving the temperature characteristics of the Z-axis MEMS accelerometer and enhancing its error-tolerance capability. It is also applicable to MEMS accelerometers with other sensitive axes or other stress-sensitive MEMS devices.

[0056] In addition to the above embodiments, the present invention may also have other implementation methods. Any technical solutions formed by equivalent replacement or equivalent transformation fall within the scope of protection required by the present invention.

Claims

1. A blade-type Z-axis MEMS accelerometer, comprising a silicon substrate and a silicon cap connected to form a cavity, with detection electrodes provided on each of the silicon substrate and the silicon cap, characterized in that: An anchor point, a support frame, and two or more blade-type mass blocks with asymmetric mass are provided in the cavity. Each group of mass blocks is connected by an elastic beam located in the middle and is equidistantly distributed on the support frame around the anchor point. The mass blocks are rotationally symmetrical around the anchor point. The mass blocks are configured to conform to and correspond to the strain shape generated by stress on the silicon substrate. When an acceleration is input along the Z axis where the anchor point is axial, the mass blocks rotate out of the XY plane around the arms of the support frame where the elastic beams are located. The detection electrodes and the mass blocks constitute two or more differential capacitors for detecting acceleration.

2. The blade-type Z-axis MEMS accelerometer according to claim 1, characterized in that: The mass block is symmetrical along the support arm in shape but asymmetrical in mass.

3. The blade-type Z-axis MEMS accelerometer according to claim 1, characterized in that: The detection electrode and the projection of the mass block on the XY plane coincide with each other.

4. The blade-type Z-axis MEMS accelerometer according to claim 1, characterized in that: The projections of the detection electrode and the mass block on the XY plane are proportionally enlarged or reduced.

5. The blade-type Z-axis MEMS accelerometer according to claim 1, characterized in that: The mass block is four groups of fan-shaped blades that evenly divide the disk. Each group of fan-shaped blades is centrally separated and connected as a whole by elastic beams. The elastic beams are positioned and inserted into the slots of the support frame. Adjacent groups of fan-shaped blades are separated by the support frame.

6. The blade-type Z-axis MEMS accelerometer according to claim 1, characterized in that: The mass block is in the form of nested inner and outer rings within the radial range of the anchor point, wherein the inner ring is configured as two or more groups of fan-shaped blades that evenly divide the circular disk, each group of fan-shaped blades is separated in the center and connected as a whole by elastic beams, and adjacent groups of fan-shaped blades are separated by a support frame; the outer ring is configured as two or more groups of fan-ring blades that evenly divide the circular ring, each group of fan-ring blades is separated in the center and connected as a whole by elastic beams, and adjacent groups of fan-ring blades are separated by a support frame, and the elastic beams are positioned and inserted into the slots of the support frame.

7. The blade-type Z-axis MEMS accelerometer according to claim 6, characterized in that: The supporting arms of the inner ring and the outer ring of the support frame, where the slots are compatible with the elastic beams, are collinear or mutually staggered.

8. The blade-type Z-axis MEMS accelerometer according to claim 1, characterized in that: The blade shape of the mass block is at least rectangular, trapezoidal, or circular.

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