CN213843299U - Micro-electro-mechanical system triaxial acceleration sensor chip - Google Patents

Abstract

The application provides a micro-electromechanical system triaxial acceleration sensor chip includes: a first axis acceleration sensor unit for sensing acceleration in a first axis direction; a second shaft acceleration sensor unit senses acceleration in a second shaft direction; and a third axis acceleration sensor unit for sensing acceleration in a third axis direction; the first shaft acceleration sensor unit and the second shaft acceleration sensor unit are arranged in a stacked manner; the third shaft acceleration sensor unit comprises a fourth acceleration sensor subunit and a fifth acceleration sensor subunit, the fourth acceleration sensor subunit is arranged on one side of the first shaft acceleration sensor unit, the fifth acceleration sensor subunit is arranged on one side of the second shaft acceleration sensor unit, and the fourth acceleration sensor subunit and the fifth acceleration sensor subunit are in an asymmetric structure. The first, second and third axis acceleration sensor units are sealed in the same sealed cavity.

Description

Micro-electro-mechanical system triaxial acceleration sensor chip

Technical Field

The application relates to the field of semiconductor chips, in particular to a micro-electromechanical system triaxial acceleration sensor chip.

Background

A Micro-electro mechanical System (MEMS), hereinafter referred to as MEMS, refers to a sensor device with a size of several millimeters or less, and its internal structure is generally in the micrometer or nanometer scale, and is an independent intelligent System. The current MEMS acceleration sensor has a plurality of implementation modes, which can be mainly classified into a piezoelectric type, a capacitive type and a thermal induction type. Taking the technical principle of the capacitive triaxial accelerometer as an example, the capacitive accelerometer can sense motion conditions such as acceleration or vibration in different directions. The movable mechanical structure is designed by mainly utilizing the good mechanical characteristics of silicon, the distance between two electrodes is changed due to the acceleration through the mechanical cantilever, so that the parameter of capacitance between the two electrodes is changed, and the change of the parameter of the capacitance is measured through the integrated switched capacitor amplification circuit, so that the voltage output in direct proportion to the acceleration is obtained. The triaxial acceleration sensor designs corresponding mechanical structures in three different axial directions (X, Y, Z), and can measure acceleration in different axial directions.

In the prior art, most of acceleration sensors for measuring an X axis, a Y axis and a Z axis of an MEMS triaxial acceleration sensor chip are arranged in parallel, so that the size of the chip is large, and the sensitivity is influenced; in addition, the lower electrode of the Z-axis accelerometer is usually directly connected to the bottom plate of the chip, and is easily affected by package stress, so that the performance of the Z-axis among three axes is the worst.

The MEMS triaxial accelerometer in the first prior art (patent CN 102798734) respectively realizes X, Y, Z-axis acceleration signal detection through three independent sensing masses, as shown in fig. 1, the three masses are on one plane, and the Z axis employs a comb-tooth manner to detect capacitance signals, which is smaller in capacitance variation value, smaller in product range and lower in sensitivity compared to a flat-plate capacitance sensing manner.

In a second prior art (patent US7430909B2), a MEMS triaxial accelerometer is composed of two masses, as shown in fig. 2, a first mass measuring accelerations in the X-axis and Z-axis directions, and a second mass measuring accelerations in the Y-axis and Z-axis directions. The acceleration sensor structures of the X axis and the Y axis adopt a spring and comb tooth sensing structure; the Z-axis acceleration sensor structure adopts a cantilever beam structure as a measuring mode. The two Z-axes may be tested independently or for differential signaling. X, Y, Z triaxial accelerometers of the triaxial accelerometer are on the same plane, and the occupied chip area is large; and the capacitance is measured by the Z axis in a comb tooth mode, and compared with a flat capacitance sensing mode, the capacitance change value is small, the measuring range of the product is small, and the sensitivity is not high.

In the third prior art (patent US20070059857a1), the accelerometers of the X-axis and the Y-axis of the MEMS triaxial accelerometer adopt a spring and comb structure, and the accelerometer of the Z-axis adopts a seesaw plate capacitor structure, as shown in fig. 3, the accelerometers of the X-axis, the Y-axis and the Z-axis are in the same plane, and this design requires a large chip area and high cost.

Disclosure of Invention

The application provides a micro-electromechanical system triaxial acceleration sensor chip, this chip has less volume, higher sensitivity, and X, Y, Z three axial acceleration performance unanimity.

In order to achieve the above object, the present application provides a three-axis acceleration sensor chip of a micro electro mechanical system, the chip includes: a first axis acceleration sensor unit for sensing acceleration in a first axis direction; a second axis acceleration sensor unit for sensing acceleration in a second axis direction, the first axis direction and the second axis direction being perpendicular to each other; and a third axis acceleration sensor unit for sensing acceleration in a third axis direction; the third axis direction is perpendicular to the first axis direction and the second axis direction; wherein the first and second axis acceleration sensor units are arranged in a stack; the third shaft acceleration sensor unit comprises a fourth acceleration sensor subunit and a fifth acceleration sensor subunit which are arranged in a stacked mode, the fourth acceleration sensor subunit is arranged on one side of the first shaft acceleration sensor unit, the fifth acceleration sensor subunit is arranged on one side of the second shaft acceleration sensor unit, and the fourth acceleration sensor subunit and the fifth acceleration sensor subunit are in an asymmetric structure; the first shaft acceleration sensor unit, the second shaft acceleration sensor unit and the third shaft acceleration sensor unit are sealed in the same sealing cavity.

In one possible embodiment, the asymmetric structure of the fourth acceleration sensor subunit and the fifth acceleration sensor subunit is: the fourth acceleration sensor subunit comprises a third mass block, a fourth mass block, a fifth mass block and a torsion beam; the third mass block is connected with the fourth mass block; a hollow structure is formed between the third mass block and the fourth mass block, and the torsion beam is arranged between the hollow structures; the fourth mass block is connected with the middle of the fifth mass block; the fifth speed sensor subunit comprises a sixth mass, a fifth electrode and a sixth electrode; the sixth mass block is isolated from the fifth electrode, and the fifth electrode is isolated from the sixth electrode; the fifth electrode corresponds to the third mass block up and down, and a gap is formed between the fifth electrode and the third mass block for isolation; the sixth electrode corresponds to the fourth mass block up and down, and a gap is formed between the sixth electrode and the fourth mass block for isolation; the fifth mass block corresponds to the sixth mass block up and down and is connected through an oxide layer; the fifth electrode and the sixth electrode are fixed on the bottom plate through anchor points, and a gap is formed between the fifth electrode and the bottom plate.

In one possible embodiment, the first axial acceleration sensor unit includes a first axial mass, a first movable electrode, a second movable electrode, a first fixed electrode, and a second fixed electrode; the first axial mass block is of a frame structure, a first movable electrode is arranged in the frame structure, the first movable electrode corresponds to the first fixed electrode, and a gap exists between the first movable electrode and the first fixed electrode; a second movable electrode is arranged inside the first axial mass block; the second movable electrode corresponds to the second fixed electrode, and a gap is formed between the second movable electrode and the second fixed electrode; when the first shaft mass block drives the first movable electrode and the second movable electrode to move along the first shaft direction, the first fixed electrode and the second fixed electrode are fixed.

In one possible embodiment, the first axial acceleration unit comprises a first axial mass, the first axial mass is a frame structure, a first spring and a second spring are symmetrically arranged in the middle of the frame structure, and the first axial mass is balanced under the acting force of the first spring and the second spring; when acceleration in a first axis direction is applied to the three-axis acceleration sensor chip, the first axial mass moves in the first axis direction.

In one possible embodiment, the second shaft acceleration unit includes a second shaft mass block, the second shaft mass block is a frame structure, a third movable electrode is arranged inside the frame structure, the third movable electrode corresponds to the third fixed electrode, and a gap exists between the third movable electrode and the third fixed electrode; a fourth movable electrode is arranged inside the second shaft mass block; the fourth movable electrode corresponds to the fourth fixed electrode, and a gap is formed between the fourth movable electrode and the fourth fixed electrode; when the second shaft mass block drives the third movable electrode and the fourth movable electrode to move along the second shaft direction, the third fixed electrode and the fourth fixed electrode are fixed.

In one possible embodiment, the second shaft acceleration unit comprises a second shaft mass block, the second shaft mass block is a frame structure, a third spring and a fourth spring are symmetrically arranged in the middle of the frame structure, and the second shaft mass block keeps balance under the acting force of the third spring and the fourth spring; when acceleration in a second axial direction is applied to the triaxial acceleration sensor chip, the second axial mass moves in the second axial direction.

In one possible embodiment, the chip further comprises a second electrode layer, a first electrode layer and at least one metal conductive plug; the first axis acceleration unit and the fourth acceleration subunit are arranged on the second electrode layer; the second shaft acceleration unit and the fifth acceleration subunit are arranged on the first electrode layer; the second electrode layer is provided with at least one first electrode anchor point; the first electrode layer is provided with at least one second electrode anchor point; the at least one metal conductive plug connects the at least one first electrode anchor with the corresponding at least one second electrode anchor.

In one possible embodiment, a distance between the first axis acceleration sensor unit and the second axis acceleration sensor unit in the third axis direction is significantly larger than a distance between the fourth acceleration sensor unit and the fifth acceleration sensor unit.

The embodiment of the application provides a sensor inside triaxial acceleration sensor chip adopts range upon range of mode to arrange, and this kind of range upon range of mode is arranged and is compared with the design of arranging in a parallel and has reduced the chip area, very big reduction in cost, and the bottom electrode and the chip bottom plate of third axis acceleration sensor unit (being equivalent to Z axle accelerometer) do not have the direct connection in addition, have reduced by the leading-in mechanical stress of encapsulation, have improved Z axle accelerometer's performance.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments disclosed in the present specification, the drawings needed to be used in the description of the embodiments will be briefly introduced below, it is obvious that the drawings in the following description are only embodiments disclosed in the present specification, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.

FIG. 1 is a schematic diagram of a first prior art MEMS triaxial accelerometer;

FIG. 2 is a schematic diagram of a second prior art MEMS triaxial accelerometer composed of two masses;

FIG. 3 is a schematic structural diagram of a third prior art MEMS triaxial accelerometer with springs and comb structures in the X-axis and the Y-axis;

fig. 4 is a schematic structural diagram of a three-axis acceleration sensor chip according to an embodiment of the present disclosure;

FIG. 5 is a top view of the Y-axis acceleration sensor structure 22 of FIG. 1;

FIG. 6 is a top view of the x-axis acceleration sensor structure 24 of FIG. 1;

FIG. 7a is a schematic plan view of the Z-axis electrode structure 261 of FIG. 1;

FIG. 7b is a schematic plan view of the Z-axis electrode structure 262 of FIG. 1;

FIG. 8 is a schematic plan view of the electrode layer 15 of FIG. 1;

fig. 9 is a schematic plan view of the electrode layer 19 in fig. 1.

FIG. 10 is a schematic plan view of the bonded electrode layer 15 shown in FIG. 8 and the electrode layer 19 shown in FIG. 9;

FIG. 11a is a cross-sectional view of the tri-axial acceleration sensor chip of FIG. 10 along the dashed line A-B;

FIG. 11b is a cross-sectional view of the tri-axial acceleration sensor chip of FIG. 10 along the dashed line C-D;

fig. 12 is a schematic cross-sectional view illustrating a bottom plate wafer after an oxide layer pattern is formed in the method for manufacturing a three-axis acceleration sensor chip according to the embodiment of the present disclosure;

FIG. 13 is a cross-sectional view of a wafer of a substrate after bonding a first electrode layer;

FIG. 14 is a cross-sectional view of a wafer of a substrate after etching a first electrode layer and growing an oxide layer;

FIG. 15 is a schematic cross-sectional view of a second electrode layer wafer after an oxide layer pattern is formed;

FIG. 16 is a cross-sectional view of the second electrode layer wafer after forming the cavity pattern;

FIG. 17 is a schematic cross-sectional view of a secondary bonded wafer after bonding a base plate wafer and a second electrode layer wafer;

FIG. 18 is a schematic cross-sectional view of a secondary bonded wafer after formation of a deep hole;

FIG. 19 is a schematic cross-sectional view of a secondary bonded wafer after formation of a metal plug;

FIG. 20a is a schematic cross-sectional view of a secondary bonding wafer after patterning a second electrode layer wafer;

FIG. 20b is a schematic cross-sectional view of the secondary bonded wafer after removal of the oxide layer;

FIG. 21 is a schematic cross-sectional view of a TSV wafer;

FIG. 22 is a schematic cross-sectional view of a three-axis acceleration sensor wafer after a TSV wafer is bonded with a secondary bonding wafer;

fig. 23 is a schematic cross-sectional view of a triaxial acceleration sensor wafer after metal wiring.

The reference numerals in the above figures 1-23 are in order:

1-base plate wafer; 3-bonding a wafer for the first time; 5-a second electrode layer wafer; 7-secondary bonding of the wafer; 9-TSV wafer; bonding the wafer for 10-three times; 11-a base plate; 13-a first oxide layer; 15-a first electrode layer; 15 a-Z-electrode; 15 b-lower electrode anchor; 15c-Z + electrodes; 15 d-additional mass; 15 e-lower electrode sealing zone; 15f-Y axis structure; 16-a first gap; 17-a second oxide layer; 18-a second gap; 19-a second electrode layer; 19 a-Z-mass; 19 b-upper electrode anchor; 19c-Z + mass block; 19 d-an elongated mass; 19 e-upper electrode sealing zone; 19f-X axis structural layer; 19 g-second electrode layer cavity; 20-a third gap; 23-a conductive solder layer; a 22-Y axis acceleration sensor configuration; a 24-X axis acceleration sensor configuration; 26-Z axis acceleration sensor configuration; 31-a TSV substrate layer; 31 a-a TSV bond post; 31 b-a TSV layer sealing region; 33-a cavity; 35-TSV isolation trench/isolation trench insulation layer; 37-TSV sealing holes; 39-a third oxide layer; 41-sealing the cavity; 43-conductive plugs; 45-contact holes; 49-a metal layer; 51-a passivation layer; 53-pad window; 59-Z axis additional mass; a 61-Z + anchor point; anchoring points under the 62-Z axis quality blocks; 63-Z-anchor; 69-Y axis mass blocks; 70-a first Y-axis spring; 70' -second Y-axis spring 71-Y + fixed electrode; 72-Y + movable electrode; 73-Y-fixed electrode; 74-Y-movable electrode; 75-Y-anchor point; 76-X + anchor point; 77-Y + anchor; 78-X-down anchor point; 79-Y mass anchor point; an anchor point on 81-Z +; 82-Z axis mass block anchor points; 83-Z-upper anchor point; an 85-Z axis twist beam; 87-a release orifice; 89-X axis mass blocks; 90-a first X-axis spring; 90' -a second X-axis spring; 91-X + fixed electrode; 92-X + movable electrode; 93-X-fixed electrode; 94-X-movable electrode; 95-Y-anchor point; 96-X + anchor point; 97-Y + anchor point; 98-X-anchor point; a 99-X mass anchor point; 261-a first Z-axis electrode structure; 262-a second Z-axis electrode structure; 101-a fourth oxide layer; 103-a second electrode layer wafer substrate; 105-a fifth oxide layer; 107-deep holes; A/B-dotted line, cross section; C/D-dotted line, cross section.

Detailed Description

The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.

The embodiment of the application provides an MEMS triaxial acceleration sensor chip, which takes an X axis as a first axis, a Y axis perpendicular to the X axis as a second axis, and a Z axis perpendicular to an X-Y plane as a third axis. The triaxial acceleration sensor chip is composed of three independent units of an X-axis acceleration sensor structure, a Y-axis acceleration sensor structure and a Z-axis acceleration sensor structure. The X-axis acceleration sensor structure senses the acceleration in the X-axis direction; the Y-axis acceleration sensor structure senses acceleration in the Y-axis direction, and the Z-axis acceleration sensor structure senses acceleration in the Z-axis direction; wherein the X-axis acceleration sensor structure and the Y-axis acceleration sensor structure are arranged in a stacked manner; the Z-axis acceleration sensor structure comprises two different electrode structures which are arranged in a stacked mode, one electrode structure is arranged on one side of the X-axis acceleration sensor structure, the second electrode structure is arranged on one side of the Y-axis acceleration sensor structure, and the two electrode structures are asymmetric structures; the X-axis acceleration sensor structure, the Y-axis acceleration sensor structure and the Z-axis acceleration sensor structure are sealed in the sealing cavity. The chip has compact structural layout, saves space and greatly reduces the volume of the chip.

Fig. 4 is a schematic structural diagram of a three-axis acceleration sensor chip according to an embodiment of the present application. As shown in fig. 4, the direction indicated by the arrow of the Z axis is upward, the chip includes an electrode layer 15 and an electrode layer 19, and the electrode layer 15 and the electrode layer 19 are stacked. The electrode layer 15 may be referred to as a first electrode layer, and the electrode layer 19 may be referred to as a second electrode layer.

The electrode layer 19 includes the X-axis acceleration sensor structure 24 and the Z-axis electrode structure 261 of the Z-axis acceleration sensor structure 26. The Z-axis electrode structure 261 is located on one side of the X-axis acceleration sensor structure 24.

The electrode layer 15 includes the Y-axis acceleration sensor structure 22 and the Z-axis electrode structure 262 of the Z-axis acceleration sensor structure 26. The Z-axis electrode structure 262 is located on one side of the Y-axis acceleration sensor structure 22. The Z-axis electrode structure 261 and the Z-axis electrode structure 262 are stacked up and down.

Fig. 5 is a plan view of the Y-axis acceleration sensor structure 22. As shown in fig. 5, the projection of the Y-axis acceleration sensor structure 22 on the X-Y plane, with the Y-axis arrow pointing upwards; the X-axis arrow indicates the direction to the right.

The Y-axis acceleration sensor structure 22 includes a Y-axis mass 69, the Y-axis mass 69 being a frame structure; in some embodiments, the frame structure may be any symmetrical frame structure, in this embodiment a rectangular frame structure.

The frame structure includes a spring 70 and a spring 70 'symmetrically arranged in the middle, and the spring 70 may be referred to as a first spring and the spring 70' may be referred to as a second spring. One end of the spring 70 is connected to the first frame of the inner wall of the mass 69, and the other end of the spring 70 is connected to the spring 70 'through a fixed beam, and the other end of the spring 70' is connected to the third frame of the inner wall of the mass 69. A Y-axis mass anchor point 79 is provided on the fixed beam between the spring 70 and the spring 70', and the Y-axis mass anchor point 79 fixes and supports the Y-axis mass. The symmetrically arranged springs 70 and 70' can keep the Y-axis acceleration sensor structure 22 balanced in the X-Y plane when the mass 69 moves, thereby reducing interference from Z-axis directional acceleration. The springs 70 and 70' are symmetrically arranged along the Y-axis direction through the fixing beams, so that when the mass block 69 moves along the Y-axis direction, the balance weight and inertia in the Y-axis direction can be increased, the sensitivity of sensing acceleration in the Y-axis direction is improved, and the interference from acceleration in the X-axis direction is reduced.

At least one Y + movable electrode 72 is arranged on the left inner wall of the frame structure at intervals, at least one Y + fixed electrode 71 is arranged corresponding to the Y + movable electrode 72, and a certain gap is formed between the Y + movable electrode 72 and the Y + fixed electrode 71.

At least one Y-movable electrode 74 is arranged on the right inner wall of the frame structure at intervals; disposed corresponding to the Y-movable electrode 74 is at least one Y-fixed electrode 73, with a certain gap between the Y-movable electrode 74 and the Y-fixed electrode 73.

The Y + movable electrode 72 is denoted as a first movable electrode, the Y-movable electrode 74 is denoted as a second movable electrode, the Y + fixed electrode 71 is denoted as a first fixed electrode, the Y-fixed electrode 73 is denoted as a second fixed electrode, and the Y-axis mass 69 is denoted as a first axial mass.

When the Y + movable electrode 72 and the Y-movable electrode 74 move in the Y-axis direction with the mass block 69, the Y + fixed electrode 71 and the Y-fixed electrode 73 remain stationary at fixed positions. The change in the distance between the electrodes changes the capacitance between the two electrodes.

The distance between the Y + movable electrode 72 and the Y + fixed electrode 71 changes in a direction opposite to the direction of the change in the distance between the Y-movable electrode 74 and the Y-fixed electrode 73, so that when the Y-axis mass block 69 drives the Y + movable electrode 72 and the Y-movable electrode 74 to move in the Y-axis direction, the Y + fixed electrode 71 outputs a Y + electrical signal, and the Y-fixed electrode 73 outputs a Y-electrical signal.

The connecting bridge of the Y + fixed electrode 71 is provided with a Y + anchor point 77, and the Y + anchor point 77 is used for leading out a Y + electric signal. The Y-anchor 75 is provided on the connecting bridge of the Y-fixed electrode 73 and derives the Y-electric signal.

Fig. 6 is a top view of the x-axis acceleration sensor structure 24. As shown in fig. 6, the projection of the X-axis acceleration sensor structure 24 onto the X-Y plane, with the Y-axis arrow pointing upwards; the X-axis arrow indicates the direction to the right.

The X-axis acceleration sensor structure 24 comprises an X-axis mass block 89, and the X-axis mass block 89 is a rectangular frame structure; in some embodiments, the frame structure may be any symmetrical frame structure, in this embodiment a rectangular frame structure.

The frame structure includes a spring 90 and a spring 90 'symmetrically arranged in the middle, and the spring 90 may be referred to as a third spring and the spring 90' as a fourth spring. One end of the spring 90 is connected with the inner wall of the left side frame of the X-axis mass block 89, the other end is connected with the spring 90 'through the fixed beam, and the other end of the spring 90' is connected with the inner wall of the right side frame of the X-axis mass block 89. An X-axis mass block anchor point 99 is arranged on the fixed beam between the spring 90 and the spring 90' and can fix and support the X-axis mass block 89.

The symmetrically disposed springs 90 and 90' may maintain the X-axis acceleration sensor structure 24 balanced in the X-Y plane as the X-axis proof mass 89 moves, thereby reducing interference from Z-axis directional acceleration. The springs 90 and 90' are symmetrically arranged along the X-axis direction through the fixed beam, so that the balance weight and inertia in the X-axis direction can be increased when the mass block 89 moves along the X-axis direction, the sensitivity of sensing the acceleration in the X-axis direction is improved, and the interference from the acceleration in the Y-axis direction is reduced.

At least one X + movable electrode 92 is arranged on the inner wall of the upper side frame of the frame structure; provided corresponding to the X + movable electrode 92 is at least one X + fixed electrode 91, and a certain gap exists between the X + movable electrode 92 and the X + fixed electrode 91, and the gap increases or decreases as the position of the X + electrode changes.

At least one X-movable electrode 94 is disposed on the lower interior wall of the frame structure; disposed corresponding to the X-movable electrode 94 is the X-fixed electrode 93, and a certain gap exists between the X-movable electrode 94 and the X-fixed electrode 93, the gap increasing or decreasing with a change in the position of the X-movable electrode 94.

While the X + movable electrode 92 and the X-movable electrode 94 can move in the X-axis direction along with the mass block 89, the X + fixed electrode 91 and the X-fixed electrode 93 remain stationary at fixed positions. The change in the gap distance between the electrodes changes the capacitance between the two electrodes.

The distance between the X + movable electrode 92 and the X + fixed electrode 91 changes in a direction opposite to the direction of the change in the distance between the X-movable electrode 94 and the X-fixed electrode 93, so that when the X-axis mass block 89 drives the X + movable electrode 92 and the X-movable electrode 94 to move along the X-axis direction, the X + electrode 91 outputs an X + electrical signal, and the X-fixed electrode 93 outputs an X-electrical signal.

The connecting bridge of the X + fixed electrode 91 is provided with an X + anchor point 96 which can fix and support the X + electrode and lead out an X + electric signal. The connecting bridge of the X-fixed electrode 93 is provided with an X-anchor point 98 which can fix and support the X-electrode and lead out an X-electric signal.

The X + movable electrode 92, the X-movable electrode 94, the X + fixed electrode 91, the X + fixed electrode 93, and the X-axis mass block 89 may be referred to as a third movable electrode, a fourth movable electrode, a third fixed electrode, and a fourth fixed electrode, respectively.

The Z-axis acceleration sensor structure is an asymmetric structure and comprises a Z-axis electrode structure 261 positioned on the electrode layer 19 and a Z-axis electrode structure 262 positioned on the electrode layer 15. The Z-axis electrode structure 261 includes a Z + proof mass, a Z-proof mass, and an attachment proof mass; the Z-axis electrode structure 262 includes an elongated mass, Z + electrodes 15c and Z-electrodes 15 a. The Z-axis electrode structure 261 is denoted as the fourth acceleration subunit, and the Z-axis electrode structure 262 is denoted as the fifth acceleration subunit.

Fig. 7a is a top view of the Z-axis electrode structure 262. As shown in FIG. 7a, the projection of the Z-axis electrode structure 262 onto the X-Y plane, with the Y-axis arrow pointing in the upward direction; the X-axis arrow indicates the direction to the right.

The Z-axis electrode structure 262 includes: an additional mass 15d, a Z + electrode 15c and a Z-electrode 15 a. The additional mass block 15d is adjacent to the Z + electrode 15c, and a certain gap is formed between the additional mass block and the Z + electrode; the Z-electrode 15a is arranged on the other side of the Z + electrode 15c, and a certain gap is formed between the Z + electrode 15c and the Z-electrode 15 a. The additional mass 15d, the Z + electrode 15c, and the Z-electrode 15a are denoted as sixth masses, fifth electrodes, and sixth electrodes, respectively.

The Z-axis mass block lower anchor point 62 is arranged between the Z + electrode 15c and the Z-electrode 15 in an isolated manner; the Z + electrode 15c is connected with the Z + anchor point 61; the Z-electrode 15a is connected with a Z-anchor point 63; the Z + anchor 61 and the Z-anchor 63 are fixed to the substrate such that there is a gap between the Z + electrode 15c and the Z-electrode 15a and the substrate.

Fig. 7b is a top view of the Z-axis electrode structure 261. As shown in fig. 7b, the projection of the Z-axis electrode structure 261 onto the X-Y plane, with the Y-axis arrow pointing in the upward direction; the X-axis arrow indicates the direction to the right.

Z-axis electrode structure 261 includes: a Z-mass 19a, a Z + mass 19c, and an extended mass 19 d. Two connecting lines extend out of the middle of one side of the extended mass block 19d and are connected with the Z + mass block 19c, two sides of the Z + mass block 19c are connected with corresponding sides of the Z-mass block 19a, and a hollow structure is formed between the two extending sides of the Z-mass block 19a and the Z + mass block 19 c. The middle of the hollow structure is provided with a Z-axis torsion beam 85. The Z-mass 19a is denoted as a third mass and the Z + mass 19c is denoted as a fourth mass. The extension mass 19d is denoted as a fifth mass and the Z-axis torsion beam 85 is denoted as a torsion beam.

The Z-axis electrode structure 261 and the Z-axis electrode structure 262 are asymmetric structures and are located on the electrode layer 19 and the electrode layer 15, respectively. Wherein the additional mass 15d and the extension mass 19d are stacked and connected together through an oxide layer, and the combination is denoted as a Z-axis additional mass 59 (see fig. 11 b); a certain gap exists between the Z + mass block 19c and the Z + electrode 15c, and a certain gap exists between the Z-mass block 19a and the Z-electrode 15 a.

The asymmetrical structure of the Z-axis acceleration sensor structure increases the counter weight and greatly improves the sensitivity of Z-axis acceleration.

Specifically, when the Z-axis direction movement occurs, the Z-axis acceleration sensor structure increases the local inertia due to the weight of the Z-axis additional block 59, and under the pulling of the Z-axis additional block 59, the Z + mass 19c and the Z-mass 19a move toward the Z-axis direction at different speeds, respectively, so that the Z-axis electrode structure 261 is distorted and deformed along the axial direction of the distortion beam 85, the distance between the Z + mass 19c and the Z + electrode 15c is changed, and the distance between the Z-mass 19a and the Z-electrode 15a is also changed. The distance between the mass and the electrode changes, which changes the capacitance between the mass and the electrode.

Since the Z + mass 19c is connected to the Z-mass 19a, when the Z + mass 19c is twisted in the axial direction of the twist beam 85, the direction of change in the distance between the Z + mass 19c and the Z + electrode 15c is opposite to the direction of change in the distance between the Z-mass 19a and the Z-electrode 15a, and thus a Z + electric signal is output to the Z + electrode 15c and a Z-electric signal is output to the Z-electrode 15 a.

The Z-mass 19a and Z + mass 19c are provided with a plurality of release holes 87, the release holes 87 being used for introducing gaseous phase Hydrogen Fluoride (HF) during the manufacturing process to remove the oxidized layer.

A Z-axis mass block anchor point 82 is arranged on the Z-axis torsion beam 85, and a Z + upper anchor point 81 and a Z-upper anchor point 83 are arranged in the hollow structure in an isolated mode.

The asymmetrical structure of the Z-axis acceleration sensor structure increases the counter weight and greatly improves the sensitivity of Z-axis acceleration.

Fig. 8 is a top view of the electrode layer 15 of fig. 4. As shown in fig. 8, the electrode layer 15 of the triaxial acceleration sensor structure includes the Y-axis acceleration sensor structure 22 shown in fig. 5 and the Z-axis electrode structure 262 shown in fig. 7 a.

A lower electrode sealing region 15e in a closed loop state is provided around the Y-axis acceleration sensor structure 22 and the Z-axis electrode structure 262. A certain gap exists between the lower electrode sealing area 15e and the Y-axis acceleration sensor structure 22 and the Z-axis electrode structure 262, and a certain gap exists between the Y-axis acceleration sensor structure 22 and the Z-axis electrode structure 262.

The electrode layer 15 further includes: a Y mass anchor point 79, a Y + anchor point 77, a Y-anchor point 75, an X + anchor point 76, an X-anchor point 78, a Z-mass anchor point 62, a Z + anchor point 61, and a Z-anchor point 63. The anchors may be collectively referred to as lower electrode anchors 15 b.

Fig. 9 is a top view of the electrode layer 19 of fig. 4. As shown in fig. 9, the electrode layer 19 includes the X-axis acceleration sensor structure 24 shown in fig. 6 and the Z-axis electrode structure 261 shown in fig. 4.

An upper electrode sealing region 19e in a closed ring state is provided around the X-axis acceleration sensor structure 24 and the Z-axis electrode structure 261. A certain gap exists between the upper electrode sealing region 19e and the X-axis acceleration sensor structure 24 and the Z-axis electrode structure 261, and a certain gap exists between the X-axis acceleration sensor structure 24 and the Z-axis electrode structure 261.

The electrode layer 19 further includes: an X-axis mass block anchor 99, an X + anchor 96, an X-anchor 98, a Y + upper anchor 97, a Y-upper anchor 95, a Z-axis mass block upper anchor 82, a Z + upper anchor 81, and a Z-upper anchor 83. The anchors may be collectively referred to as upper electrode anchors 19 b.

Fig. 10 is a schematic top view of the bonded electrode layer 15 shown in fig. 8 and the electrode layer 19 shown in fig. 9. As shown in fig. 10, the electrode layer 19 is located above the electrode layer 15, and each electrical signal of the electrode layer 15 can be conducted to a corresponding anchor point of the electrode layer 19 through each anchor point.

The Y + upper anchor point 97 is connected with the Y + anchor point 77, supports and fixes the Y + fixed electrode 71, and outputs a Y + electric signal; the Y-up anchor 95 is connected to the Y-anchor 75, supports and fixes the Y-fixed electrode 73, and outputs a Y-electric signal.

The X + anchor 96 is connected to the X + lower anchor 76, supports and fixes the X + electrode, and outputs an X + electrical signal. The X-anchor 98 is connected to the X-down anchor 78, supports and secures the X-electrode, and outputs an X-electrical signal.

The Z + upper anchor point 81 is connected with the Z + anchor point 61, supports and fixes the Z + electrode 15c and outputs a Z + electric signal; the Z-axis mass block anchor point 82 is connected with the lower Z-axis mass block anchor point 62 and supports and fixes the Z-axis mass block; the Z-upper anchor 83 is connected to the Z-anchor 63, supports and fixes the Z-electrode 15a, and outputs a Z-electric signal.

Fig. 11a is a cross-sectional view of the tri-axial acceleration sensor chip of fig. 10 along the dotted line a-B. The cross-sectional view provides the structural layout of the various components of the three-axis acceleration sensor chip. As shown in fig. 11a, the triaxial acceleration sensor chip includes a first electrode layer wafer and a second electrode layer wafer.

Specifically, the first electrode layer wafer 1 includes a base plate 11, an oxide layer 13, a Y-axis structure 15f, a Z + electrode 15c, a lower electrode sealing region 15e, and an oxide layer 17. The Y-axis structure 15f is a cross section of the Y-axis acceleration sensor structure 22.

The Y-axis structure 15f and the Z + electrode 15c are located on the oxide layer 13, and a lower electrode sealing area 15e is provided on the oxide layer 13 around the first electrode layer wafer. Below the oxide layer 13 is a bottom plate 11. The oxide layer 13 is referred to as a first oxide layer.

A gap 16 exists between the Y-axis structure 15f and the Z + electrode 15c and the base plate 11. The gap 16 is denoted as a first gap.

Overlying the Y-axis structure 15f and the Z + electrode 15c is an oxide layer 17. The oxide layer 17 is referred to as a second oxide layer.

The second electrode layer wafer comprises a TSV substrate layer 31, a conductive solder layer 23, an X-axis structure layer 19f, a Z + proof mass 19c, an upper electrode sealing area 19e and an oxide layer 17. The X-axis structural layer 19f is a cross section of the X-axis acceleration sensor structure 24.

Beneath the TSV substrate layer 31 is a conductive solder layer 23.

An X-axis structural layer 19f, a Z + proof mass 19c is disposed under the conductive solder layer 23. The structural layer 19f and the Z + proof mass 19c are upper electrode sealing regions 19e around the X axis. A cavity 33 is formed between the X-axis structural layer 19f and the Z + mass 19c, the TSV substrate layer 31 and the conductive solder 23.

Beneath the X-axis structural layer 19f and the Z + proof mass 19c is an oxide layer 17'.

And bonding the oxide layer 17 with the oxide layer 17 of the second electrode layer, and forming a sealed cavity by the first electrode layer wafer and the second electrode layer wafer. After bonding, a gap 18 exists between the Z + mass block 19c and the Z + electrode 15c, and a gap 20 exists between the X-axis structure layer 19f and the Y-axis structure layer 15 f; the gap 18 is referred to as a second gap, and the gap 20 is referred to as a third gap.

The cavity 33, gap 16, gap 18 and gap 20 isolate the electrodes of the triaxial sensor from each other. The cavity 33, the gap 16, the gap 18 and the gap 20 have different spacing values, so that the isolation effect between the electrodes is better, and the noise interference of electric signals is reduced.

The three-axis acceleration sensor chip shown in fig. 11a further includes a plurality of metal plugs 43, and the upper electrode anchor point 19b and the lower electrode anchor point 15b may be connected by one metal plug 43, so that the X-axis structure layer 19f and the Y-axis structure layer 15f form an equipotential and fix relative positions. Note that an oxide layer 17 exists between the upper electrode anchor 19b and the lower electrode anchor 15 b.

The metal plugs 43 are plural in number, insulated from each other, and connected to the respective anchor points of the electrode layers 19 and 15, respectively. The X + electrical signal, the X-electrical signal, the Y + electrical signal, and the Y-electrical signal are connected to the conductive solder layer 23 through different metal plugs 43, respectively. The conductive solder layer 23 is provided with a conductive line in accordance with a set circuit.

Above the conductive solder layer 23, an insulating layer 35 is provided within the TSV substrate layer 31 in the cross-sectional projection direction of the metal plug 43, and the insulating layer 35 isolates the TSV sealing hole 37 from the TSV substrate layer 31.

An oxide layer 39 is tiled on the outer surface of the TSV substrate layer 31; the oxide layer 39 is referred to as a third oxide layer. A contact hole 45 with a cross-sectional area smaller than the projected area of the TSV sealing hole 37 is formed in the region of the oxide layer 39 corresponding to the TSV sealing hole 37. The respective electrical signals connected to the conductive solder layer 23 can be measured through the contact holes 45.

A metal layer 49 is arranged at a set position on the oxide layer 39; the metal layer 49 is provided with a wiring according to a predetermined circuit pattern. A passivation layer 51 is laid on the metal layer 49 and the oxide layer 39, and a pad window 53 is provided at a predetermined position on the passivation layer 51 to be connected to a certain point of the metal layer 49.

Fig. 11b is a cross-sectional view of the tri-axial acceleration sensor chip of fig. 10 along the dotted line C-D. This cross-sectional view provides the structure of the various components within the Z-axis acceleration sensor structure 24, as shown in fig. 11b, with the Z + proof mass 19c, Z-proof mass 19a and extended proof mass 19d disposed on the electrode layer 19, and the Z + electrode 15c, Z-electrode 15a and additional proof mass 15d disposed on the electrode layer 15. The Z + mass 19c is located above the Z + electrode 15c, the Z-mass 19a is located above the Z-electrode 15a, and the extended mass 19d is located between the additional mass 15d with the oxide layer 17.

The metal plug 43 connects the upper electrode anchor 19b and the lower electrode anchor 15b with the oxide layer 17 between the upper electrode anchor 19b and the lower electrode anchor 15 b. The thickness of the oxide layer 17 determines the thickness of the gap 18.

The upper electrode anchor point 19b includes a Z-axis mass block upper anchor point 82, a Z + upper anchor point 81 and a Z-upper anchor point 83, and the lower electrode anchor point 15b includes a Z-axis mass block lower anchor point 62, a Z + lower anchor point 61 and a Z-lower anchor point 63. Not visible in fig. 11b is that one metal plug 43 connects the Z-axis mass block upper anchor 82 and the Z-axis mass block lower anchor 62, and the second metal plug 43 connects the Z + upper anchor 81 and the Z + lower anchor 61; a third metal plug 43 connects the Z-up anchor 83 and the Z-down anchor 63. And the metal plugs are insulated from each other.

The Z + electrical signal and the Z + electrical signal are connected to the conductive solder layer 23 through different metal plugs 43, respectively. The conductive solder layer 23 is provided in accordance with a set circuit.

The arrangement of the layers above the conductive solder layer 23 and in the projection direction of the cross section of the metal plug 43 is the same as that in fig. 8, and will not be described herein.

The specific manufacturing process of the manufacturing method of the micro-electromechanical system triaxial acceleration sensor chip provided by the embodiment of the application is shown in fig. 12-22.

Fig. 12 is a schematic cross-sectional view of a bottom plate wafer 1 after an oxide layer pattern is formed in the method for manufacturing a three-axis acceleration sensor chip of a mems according to an embodiment of the present disclosure. As shown in fig. 12, a first oxide layer (SiO2)13 is formed on the Si wafer base plate 11, typically 0.5 to 2 μm thick; and photoetching and etching the first oxidation layer 13 according to a designed pattern to form an oxidation layer pattern 13a with shallow grooves, wherein the thickness of the oxidation layer pattern is usually 0.2-1.5 micrometers, and the manufacture of the bottom plate wafer 1 is completed.

Fig. 13 is a cross-sectional view of a wafer of a substrate after bonding of a first electrode layer. As shown in fig. 13, bonding the first oxide layer (SiO2)13 pattern of the base plate wafer 1 with the electrode layer 15, wherein the electrode layer 15 can be a common double-side polished Si wafer or an SOI wafer; if the wafer is an SOI wafer, the supporting layer and the interlayer oxide layer need to be removed after bonding; if the electrode layer 15 is a double-side polished Si wafer, it needs to be thinned and polished to a desired thickness to form the primary bond wafer 3.

FIG. 14 is a cross-sectional view of a wafer of substrate after etching of the first electrode layer and growth of an oxide layer. As shown in fig. 14, the first electrode layer 15 is etched to form a Y-axis acceleration sensor structure 22 and a lower electrode portion of a Z-axis acceleration sensor structure by photolithography and etching processes; the method specifically comprises the following steps: a lower electrode anchor point 15b, a Z + electrode 15c, an additional mass 15d, a lower electrode seal 15e, and a Y-axis structure 15 f. And oxidizing the electrode layer 15 to form a fourth oxide layer 101, wherein the fourth oxide layer 101 is a protective layer of a lower electrode structure, and the thickness is generally between 0.1 micron and 1 micron, thereby completing the manufacture of the bonding wafer 3.

FIG. 15 is a cross-sectional view of a wafer of the second electrode layer after patterning the oxide layer. As shown in fig. 15, the SOI wafer is composed of a substrate 103, a fifth oxide layer 105, a second electrode layer 19, and a second oxide layer 17, and the second electrode layer 5 is formed by etching the surface of the second electrode layer 19 by photolithography and etching processes to form a pattern of the second oxide layer 17.

FIG. 16 is a cross-sectional view of a wafer of the second electrode layer after formation of a recess pattern. As shown in fig. 16, the second electrode layer 19 is etched by photolithography and etching processes to form an X-axis structure layer 19f and a second electrode layer cavity 19g, thereby completing the fabrication of the second electrode layer wafer 5.

Fig. 17 is a schematic cross-sectional view of a secondary bonded wafer after bonding a base wafer and a second electrode layer wafer. As shown in fig. 17, the second electrode layer wafer 5 and the primary bonding wafer 3 are aligned and bonded, and the substrate layer 103 of the SOI wafer is removed to form a secondary bonding wafer 7.

FIG. 18 is a schematic cross-sectional view of a secondary bonded wafer after formation of a recess. As shown in fig. 18, a deep hole 107 is formed in the wafer 7 after the secondary bonding by photolithography and etching processes, and the deep hole 107 penetrates through the fifth oxide layer 105, the electrode layer 19, the second oxide layer 17, and the fourth oxide layer 101 to reach the electrode layer 15.

Fig. 19 is a cross-sectional view of a secondary bonded wafer after formation of a metal plug. As shown in fig. 19, heavily doped polysilicon or metal is deposited as the electrical material 43 on the second bonded wafer 7 after the step shown in fig. 18, the deep hole 107 is filled with the conductive plug 43, the conductive material 43 in the non-deep space 107 region is removed by back etching or CMP (mechanical polishing), and the fifth oxide layer 105 is removed.

FIG. 20a is a cross-sectional view of a secondary bonded wafer after patterning a second electrode layer. As shown in fig. 20a, the second electrode layer 19 is etched by photolithography and etching processes to form the X-axis acceleration sensor structure 24 and the upper electrode portion of the Z-axis acceleration sensor structure 26; the method specifically comprises the following steps: an upper electrode sealing area 19e, an X-axis structural layer 19f, an extended mass 19b, an X-axis mechanism layer 19f, a Z + mass 19c, an X-axis mass anchor point 99, and an extended mass 19 d. The electrode layer 15 is protected by the fourth oxide layer 101 and is not etched.

FIG. 20b is a cross-sectional view of the secondary bonded wafer after patterning the first electrode layer. As shown in fig. 20b, the fourth oxide layer 101 of the protective layer of the lower electrode structure and the first oxide layer 13 between the electrode layer 15 and the bottom plate are removed by gas phase HF to release the lower electrode structure, forming a gap 16, a gap 18 and a gap 20; the secondary bonded wafer 7 is completed.

Fig. 21 is a schematic cross-sectional view of a TSV wafer. As shown in fig. 21, a heavily doped single crystal Si wafer is used as a material of the TSV substrate layer 31, a TSV isolation groove is formed by etching, the TSV isolation groove is oxidized, an isolation groove insulating layer 35 is formed, the depth of the isolation groove insulating layer is 50-500 micrometers, a conductive solder layer 23 is deposited, a conductive solder pattern 23 is formed by a photoetching and etching process, and a cavity 33, a TSV bonding column 31a and a TSV layer sealing area 31b are formed by the photoetching and etching process; and finishing the TSV wafer manufacturing.

FIG. 22 is a schematic cross-sectional view of a three-axis acceleration sensor wafer after bonding of a TSV wafer and a secondary bonding wafer; as shown in fig. 22, the secondary bonding wafer 7 shown in fig. 20b is aligned and bonded with the TSV wafer 9 to form a sealed cavity 41, the TSV substrate layer 31 is polished to expose the TSV isolation trench insulating layer 35, and the fabrication of the tertiary bonding wafer 10 is completed.

Fig. 23 is a schematic cross-sectional view of a triaxial acceleration sensor wafer after metal wiring. As shown in fig. 23, depositing a third oxide layer 39 on the surface of the TSV layer 31 of the three-time bonded wafer 10, forming a contact hole 45 on the third oxide layer 39 through photolithography and etching processes, depositing a metal layer 49, and etching the metal layer 49 to form a wire pattern; and depositing a passivation layer 51, and etching the passivation layer to form a bonding window 53, thereby completing the manufacture of the triaxial accelerometer wafer.

It will be further appreciated by those of ordinary skill in the art that the elements and algorithm steps of the examples described in connection with the embodiments disclosed herein may be embodied in electronic hardware, computer software, or combinations of both, and that the components and steps of the examples have been described in a functional general in the foregoing description for the purpose of illustrating clearly the interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present application.

The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are merely exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (8)

1. A mems three-axis acceleration sensor chip, the chip comprising:

a first axis acceleration sensor unit for sensing acceleration in a first axis direction;

a second axis acceleration sensor unit for sensing acceleration in a second axis direction; the first axis direction and the second axis direction are perpendicular to each other; and

the third shaft acceleration sensor unit is used for sensing the acceleration in the third shaft direction; the third axis direction is perpendicular to the first axis direction and the second axis direction;

wherein the first and second axis acceleration sensor units are arranged in a stack; the third shaft acceleration sensor unit comprises a fourth acceleration sensor subunit and a fifth acceleration sensor subunit which are arranged in a stacked mode, the fourth acceleration sensor subunit is arranged on one side of the first shaft acceleration sensor unit, the fifth acceleration sensor subunit is arranged on one side of the second shaft acceleration sensor unit, and the fourth acceleration sensor subunit and the fifth acceleration sensor subunit are in an asymmetric structure;

the first shaft acceleration sensor unit, the second shaft acceleration sensor unit and the third shaft acceleration sensor unit are sealed in the same sealing cavity.

2. The mems triaxial acceleration sensor chip of claim 1, wherein the asymmetric structure of the fourth acceleration sensor subunit and the fifth acceleration sensor subunit is: the fourth acceleration sensor subunit comprises a third mass block, a fourth mass block, a fifth mass block and a torsion beam;

the third mass block is connected with the fourth mass block;

a hollow structure is formed between the third mass block and the fourth mass block, and the torsion beam is arranged between the hollow structures;

the fourth mass block is connected with the middle of the fifth mass block;

the fifth speed sensor subunit comprises a sixth mass, a fifth electrode and a sixth electrode;

the sixth mass block is isolated from the fifth electrode, and the fifth electrode is isolated from the sixth electrode;

the fifth electrode corresponds to the third mass block up and down, and a gap is formed between the fifth electrode and the third mass block for isolation;

the sixth electrode corresponds to the fourth mass block up and down, and a gap is formed between the sixth electrode and the fourth mass block for isolation;

the fifth mass block corresponds to the sixth mass block up and down and is connected through an oxide layer;

the fifth electrode and the sixth electrode are fixed on the bottom plate through anchor points, and a gap is formed between the fifth electrode and the bottom plate.

3. The mems triaxial acceleration sensor chip of claim 1, wherein the first axis acceleration sensor unit includes a first axial mass, a first movable electrode, a second movable electrode, a first fixed electrode, and a second fixed electrode;

the first axial mass block is of a frame structure, a first movable electrode is arranged in the frame structure, the first movable electrode corresponds to the first fixed electrode, and a gap exists between the first movable electrode and the first fixed electrode;

a second movable electrode is arranged inside the first axial mass block; the second movable electrode corresponds to the second fixed electrode, and a gap is formed between the second movable electrode and the second fixed electrode;

when the first shaft mass block drives the first movable electrode and the second movable electrode to move along the first shaft direction, the first fixed electrode and the second fixed electrode are fixed.

4. The mems triaxial acceleration sensor chip of claim 1, wherein the first axial acceleration unit comprises a first axial mass, the first axial mass is a frame structure, a first spring and a second spring are symmetrically disposed in the middle of the frame structure, and the first axial mass is balanced by the acting force of the first spring and the second spring; when acceleration in a first axis direction is applied to the triaxial acceleration sensor chip, the first axial mass moves in the first axis direction.

5. The mems triaxial acceleration sensor chip of claim 1, wherein the second axis acceleration unit comprises a second axis mass, the second axis mass is a frame structure, a third movable electrode and a third fixed electrode are disposed inside the frame structure, the third movable electrode corresponds to the third fixed electrode, and a gap exists between the third movable electrode and the third fixed electrode;

a fourth movable electrode and a fourth fixed electrode are arranged in the second shaft mass block; the fourth movable electrode corresponds to the fourth fixed electrode, and a gap is formed between the fourth movable electrode and the fourth fixed electrode;

when the second shaft mass block drives the third movable electrode and the fourth movable electrode to move along the second shaft direction, the third fixed electrode and the fourth fixed electrode are fixed.

6. The mems triaxial acceleration sensor chip of claim 1, wherein the second axial acceleration unit comprises a second axial mass, the second axial mass is a frame structure, a third spring and a fourth spring are symmetrically disposed in the middle of the frame structure, and the second axial mass is balanced by the acting force of the third spring and the fourth spring; when acceleration in a second axial direction is applied to the triaxial acceleration sensor chip, the second axial mass moves in the second axial direction.

7. The mems triaxial acceleration sensor chip of claim 1, wherein the chip further comprises a second electrode layer, a first electrode layer and at least one metal conductive plug;

the first axis acceleration unit and the fourth acceleration subunit are arranged on the second electrode layer;

the second shaft acceleration unit and the fifth acceleration subunit are arranged on the first electrode layer;

the second electrode layer is provided with at least one first electrode anchor point;

the first electrode layer is provided with at least one second electrode anchor point;

the at least one metal conductive plug connects the at least one first electrode anchor with the corresponding at least one second electrode anchor.

8. The mems triaxial acceleration sensor chip of claim 1, wherein a distance between the first and second axial acceleration sensor units along the third axial direction is greater than a distance between the fourth and fifth acceleration sensor units.

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