Sandwich type triaxial acceleration chip and processing method thereof

Abstract

This invention relates to the field of accelerometer chip technology, and discloses a sandwich-type triaxial accelerometer chip and its fabrication method. The fabrication method includes: forming a top electrode plate on a top glass substrate; fixing the top electrode plate to a first SOI substrate; thinning a first bottom silicon layer; forming a first accelerometer sub-assembly and a first Z-axis capacitor; forming a bottom electrode plate on a bottom glass substrate; fixing a second SOI substrate to the bottom electrode plate; thinning a second bottom silicon layer; forming a second accelerometer sub-assembly and a second Z-axis capacitor, which together with the first Z-axis capacitor forms a third differential capacitor; the movable mass blocks of the two accelerometer components along a first direction and the intermediate electrode block form the first differential capacitor; and the movable mass blocks of the two accelerometer components along a second direction and the intermediate electrode block form the second differential capacitor. The chip fabricated by the method disclosed in this invention has good integration, large capacitance, high sensitivity, and good linearity.

Description

Technical Field

[0001] This invention relates to the field of triaxial accelerometer chip technology, and in particular to a sandwich-type triaxial accelerometer chip and its fabrication method. Background Technology

[0002] MEMS accelerometers are classified into piezoresistive, capacitive, piezoelectric, and tunneling types based on their operating principles. In the high-precision field, capacitive accelerometers are currently the mainstream type, attracting widespread attention from various industries both domestically and internationally due to their advantages such as low temperature drift, high precision, good consistency, low power consumption, and high reliability. Currently, monolithic triaxial integrated accelerometer chips generally have a comb-tooth structure, where the on-chip X, Y, and Z axis sensing structures are typically independent, integrated monolithically using MEMS technology. These structures lack motion and electrical connections with each other, and therefore, due to chip area limitations, the capacitance value for each axis is relatively small, significantly restricting the sensor's sensitivity. Summary of the Invention

[0003] Based on the above, the purpose of this invention is to provide a sandwich-type triaxial accelerometer chip and its processing method, which can integrate the X, Y, and Z axis sensing structures together, and solve the problems of small capacitance and low sensitivity of existing triaxial accelerometer chips.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A method for fabricating a sandwich-type triaxial accelerometer chip includes:

[0006] A top glass substrate is provided, and a top electrode plate is formed on the top glass substrate, the top glass substrate and the top electrode plate forming a top encapsulation assembly;

[0007] A first SOI substrate is provided, and the top electrode plate is fixedly connected to the first SOI substrate. The first top silicon layer and the first bottom silicon layer of the first SOI substrate are electrically connected. The first top silicon layer can be electrically connected to an external power source through the top packaging assembly.

[0008] Thin the first bottom silicon layer of the first SOI substrate;

[0009] The first SOI substrate is etched to form four spaced-out first acceleration sub-assemblies on the first SOI substrate. Each first acceleration sub-assembly includes a first movable sub-mass block, a first intermediate sub-electrode assembly, a first support sub-elastic element, a first support sub-beam and a first support sub-mass block. The first movable sub-mass block and the top electrode plate form a first Z-axis capacitor. The top encapsulation assembly and the first SOI substrate form a first acceleration structure.

[0010] A bottom electrode plate is formed on the bottom glass substrate to form a bottom encapsulation component;

[0011] A second SOI substrate is provided, and the second SOI substrate is fixedly connected to the bottom electrode plate at a third position, and the second top silicon layer of the second SOI substrate is electrically connected to the second bottom silicon layer.

[0012] Thin the second bottom silicon layer of the second SOI substrate;

[0013] The second SOI substrate is etched to form four spaced-apart second acceleration sub-assemblies. Each second acceleration sub-assembly corresponds to one of the first acceleration sub-assemblies, and the two together form an acceleration assembly. Each second acceleration sub-assembly includes a second movable sub-mass block, a second intermediate sub-electrode assembly, a second support sub-elastic element, a second support sub-beam, and a second support sub-mass block. The second movable sub-mass block and the bottom electrode plate form a second Z-axis capacitor. The first Z-axis capacitor and the second Z-axis capacitor form a third differential capacitor. The third differential capacitor is used to detect acceleration along a third direction. The bottom packaging assembly and the second SOI substrate form a second acceleration structure.

[0014] The first bottom silicon layer of the first acceleration structure is fixed and electrically connected to the second bottom silicon layer of the second acceleration structure. The first acceleration structure excluding the top encapsulation component and the second acceleration structure excluding the bottom encapsulation component form an intermediate electrode assembly. Each first movable sub-mass block of each acceleration assembly is positioned opposite a second movable sub-mass block, and the two together form a movable mass block. The movable mass block is capable of movement along a first direction, a second direction, and a third direction. Each first support sub-elastic element of each acceleration assembly is positioned opposite a second support elastic element, and the two together form a support elastic element. Each of the first support sub-mass blocks of the acceleration components is positioned opposite a second support sub-mass block, and the two together form a support mass block. Each of the first intermediate sub-electrode components of the acceleration components is positioned opposite a second intermediate sub-electrode component, and the two together form an intermediate electrode block. The movable mass blocks of the two acceleration components positioned opposite each other along a first direction and the intermediate electrode block form a first differential capacitor, which can detect acceleration along the first direction. The movable mass blocks of the two acceleration components positioned opposite each other along a second direction and the intermediate electrode block form a second differential capacitor, which can detect acceleration along the second direction.

[0015] In a preferred embodiment of a fabrication method for a sandwich-type triaxial accelerometer chip, the fabrication steps of the top packaging component include:

[0016] A top glass substrate is provided, on which the top electrode plate is formed;

[0017] A first conductive hole, a second conductive hole, and a third conductive hole are formed through the top electrode plate and the top glass substrate;

[0018] Sputtering metal material, wherein a first electrical connector is formed in the first conductive hole, a second electrical connector is formed in the second conductive hole, and a third electrical connector is formed in the third conductive hole;

[0019] The top electrode plate is etched to form a first insulating annular hole that penetrates the top electrode plate and surrounds the first electrical connector, and a second insulating annular hole that penetrates the top electrode plate and surrounds the second electrical connector.

[0020] A first insulating layer is formed in the first insulating annular hole, and a second insulating layer is formed in the second insulating annular hole. The first insulating layer wraps around the outer wall of the first electrical connector, and the second insulating layer wraps around the outer wall of the second electrical connector.

[0021] As a preferred embodiment of a fabrication method for a sandwich-type triaxial accelerometer chip, the fabrication steps of the bottom packaging component include:

[0022] A bottom glass substrate is provided, and the bottom electrode plate is formed on the bottom glass substrate;

[0023] The bottom electrode plate and the bottom glass substrate are etched to form a fourth conductive hole penetrating the bottom electrode plate and the bottom glass substrate;

[0024] A conductive pillar is formed in the fourth conductive hole, and a conductive layer is formed on the side of the bottom electrode plate opposite to the bottom glass substrate. The conductive pillar and the conductive layer are electrically connected and together form a fourth electrical connector.

[0025] A sandwich-type triaxial accelerometer chip is fabricated using the sandwich-type triaxial accelerometer chip fabrication method described in any of the above-mentioned schemes, defining a first direction, a second direction, and a third direction that are perpendicular to each other. The sandwich-type triaxial accelerometer chip includes a top packaging assembly, a middle electrode assembly, and a bottom packaging assembly stacked sequentially. The top packaging assembly includes a top glass substrate and a top electrode plate fixed on the top glass substrate. The middle electrode assembly includes four spaced-apart accelerometer components orthogonally and symmetrically distributed. Each accelerometer component includes a movable mass block, a supporting mass block, a middle electrode block, a supporting elastic element, and a supporting beam. The movable mass block is spaced apart from the top electrode plate and can move along the first direction, the second direction, and the third direction. In the motion, the movable mass block is fixed to the supporting mass block in sequence by the supporting beam and the supporting elastic element. The movable mass block and the intermediate electrode block form a capacitor. Two of the acceleration components are distributed along a first direction and form a first differential capacitor, which is used to detect acceleration along the first direction. The other two acceleration components are distributed along a second direction and form a second differential capacitor, which is used to detect acceleration along the second direction. The bottom encapsulation assembly includes a bottom glass substrate and a bottom electrode plate fixed on the bottom glass substrate. The bottom electrode plate is fixed to the supporting mass block and is spaced apart from the movable mass block. The movable mass block, the top electrode plate, and the bottom electrode plate form a third differential capacitor.

[0026] As a preferred embodiment of a sandwich-type triaxial accelerometer chip, the intermediate electrode assembly includes two electrically connected SOI substrates. The movable mass block, the supporting mass block, the intermediate electrode block, the supporting elastic element, and the supporting beam are all formed on the two SOI substrates. The supporting mass block is provided with a first conductive bump that electrically connects the top silicon layer and the bottom silicon layer of the SOI substrate. The intermediate electrode block is provided with a second conductive bump that electrically connects the top silicon layer and the bottom silicon layer. The movable mass block is provided with a third conductive bump that electrically connects the top silicon layer and the bottom silicon layer.

[0027] As a preferred embodiment of a sandwich-type triaxial accelerometer chip, the two SOI substrates are a first SOI substrate and a second SOI substrate. Four first accelerometer sub-assemblies are formed on the first SOI substrate in an orthogonal symmetrical arrangement, and four second accelerometer sub-assemblies are formed on the second SOI substrate in an orthogonal symmetrical arrangement. The four first accelerometer sub-assemblies and the four second accelerometer sub-assemblies are arranged in a one-to-one correspondence, and each first accelerometer sub-assembly and its corresponding second accelerometer sub-assembly form an accelerometer assembly. Each first accelerometer sub-assembly includes a first movable sub-mass block, a first intermediate sub-electrode assembly, a first support sub-elastic element, a first support sub-beam, and a first support. Each of the second acceleration sub-assemblies includes a second movable sub-mass block, a second intermediate sub-electrode assembly, a second support sub-elastic member, a second support sub-beam, and a second support sub-mass block. The first movable sub-mass block is positioned opposite the second movable sub-mass block, and the two together constitute the movable mass block. The first intermediate sub-electrode assembly is positioned opposite the second intermediate sub-electrode assembly, and the two together constitute the intermediate electrode block. The first support sub-elastic member is positioned opposite the second support sub-elastic member, and the two together constitute the support elastic member. The first support sub-beam is positioned opposite the second support sub-beam, and the two together constitute the support beam. The first support sub-mass block is positioned opposite the second support sub-mass block, and the two together constitute the support mass block.

[0028] As a preferred embodiment of a sandwich-type triaxial accelerometer chip, a first slot is formed on the first bottom silicon layer of the first SOI substrate facing the first support sub-elastic member and the first support sub-beam, and a second slot is formed on the second bottom silicon layer of the second SOI substrate facing the second support sub-elastic member and the second support sub-beam. The first slot and the second slot together form a cavity.

[0029] As a preferred embodiment of a sandwich-type triaxial accelerometer chip, the sandwich-type triaxial accelerometer chip further includes a first electrical connector, a second electrical connector, a third electrical connector, and a fourth electrical connector. The first electrical connector penetrates the top glass substrate and the top electrode plate and is electrically connected to the supporting mass block. A first insulating layer is provided between the first electrical connector and the top electrode plate. The second electrical connector penetrates the top glass substrate and the top electrode plate and is electrically connected to the middle electrode block. A second insulating layer is provided between the second electrical connector and the top electrode plate. The third electrical connector penetrates the top glass substrate and is electrically connected to the top electrode plate. The fourth electrical connector penetrates the bottom glass substrate and is electrically connected to the bottom electrode plate. The first, second, third, and fourth electrical connectors can all be electrically connected to an external power source.

[0030] As a preferred embodiment of a sandwich-type triaxial accelerometer chip, the fourth electrical connector includes an electrically connected conductive layer and a conductive post. The conductive layer is formed on the side of the bottom glass substrate opposite to the bottom electrode plate, and the conductive post penetrates the bottom glass substrate and is electrically connected to the bottom electrode plate.

[0031] As a preferred embodiment of a sandwich-type triaxial accelerometer chip, each of the accelerometer components includes a movable mass block, a supporting mass block, an intermediate electrode block, two supporting elastic elements, and two supporting beams. The two supporting elastic elements are respectively connected to both ends of the supporting mass block, and the two supporting beams are respectively connected to both ends of the movable mass block. Each supporting elastic element is connected to one of the supporting beams.

[0032] The beneficial effects of the present invention are as follows: The processing method of the sandwich-type triaxial accelerometer chip disclosed in the present invention has a simple processing technology, is easy to control and implement, and produces an accelerometer chip with a small area, which reduces the manufacturing cost of the chip. The sandwich-type triaxial accelerometer chip also has the characteristics of good integration, large capacitance, high sensitivity and good linearity.

[0033] The sandwich-type triaxial accelerometer chip disclosed in this invention has the characteristics of good integration, large capacitance, high sensitivity and good linearity. The first differential capacitor formed by the middle electrode block of the two accelerometer components distributed along the first direction and the movable mass block can detect the acceleration along the first direction. The second differential capacitor formed by the middle electrode block of the two accelerometer components distributed along the second direction and the movable mass block can detect the acceleration along the second direction. The third differential capacitor formed by the movable mass block along the third direction and the top electrode plate and the bottom electrode plate can detect the acceleration along the third direction. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the content of the embodiments of the present invention and these drawings without creative effort.

[0035] Figure 1 This is a cross-sectional view of the sandwich-type triaxial accelerometer chip provided in a specific embodiment of the present invention;

[0036] Figure 2 This is a top view of the acceleration component of the sandwich-type triaxial accelerometer chip provided in a specific embodiment of the present invention;

[0037] Figure 3This is a schematic diagram of the supporting elastic element of the sandwich-type triaxial accelerometer chip provided in a specific embodiment of the present invention;

[0038] Figure 4 This is a flowchart of the fabrication method of the sandwich-type triaxial accelerometer chip provided in a specific embodiment of the present invention;

[0039] Figures 5 to 28 This is a schematic diagram of the manufacturing process of the sandwich-type triaxial accelerometer chip provided in a specific embodiment of the present invention.

[0040] In the picture:

[0041] 101. First conductive hole; 102. Second conductive hole; 103. Third conductive hole; 11. Top glass substrate; 12. Top electrode plate; 120. First gap;

[0042] 2. Acceleration component; 20. Chamber; 201. First SOI substrate; 2010. First empty space; 2011. First top silicon layer; 2012. First buried oxide layer; 2013. First bottom silicon layer; 202. Second SOI substrate; 2020. Second empty space; 2021. Second top silicon layer; 2022. Second buried oxide layer; 2023. Second bottom silicon layer; 21. Movable mass block; 211. First movable submass block; 212. Second movable submass block Gauge blocks; 2101, First mass block; 2102, Second mass block; 2103, Third mass block; 2104, Fourth mass block; 22, Support mass block; 221, First support sub-mass block; 222, Second support sub-mass block; 23, Intermediate electrode block; 231, First intermediate sub-electrode assembly; 232, Second intermediate sub-electrode assembly; 24, Support elastic element; 241, First support sub-elastic element; 242, Second support sub-elastic element; 25, Support beam;

[0043] 30. Fourth conductive hole; 31. Bottom glass substrate; 32. Bottom electrode plate; 320. Second gap;

[0044] 41. First conductive bump; 42. Second conductive bump; 43. Third conductive bump;

[0045] 51. First electrical connector; 52. Second electrical connector; 53. Third electrical connector; 54. Fourth electrical connector; 541. Conductive layer; 542. Conductive post;

[0046] 61. First insulating layer; 62. Second insulating layer;

[0047] 71. First bond block; 72. Second bond block; 73. Third bond block; 74. Fourth bond block; 75. First connecting block; 76. Second connecting block;

[0048] 81. First metal connecting plate; 82. Second metal connecting plate; 83. Third metal connecting plate;

[0049] 91. First electrical connection hole; 92. Second electrical connection hole; 93. Third electrical connection hole; 94. Fourth electrical connection hole; 95. Fifth electrical connection hole; 96. Sixth electrical connection hole; 97. First isolation hole; 98. Second isolation hole;

[0050] 100, First photoresist layer; 200, Fifth photoresist layer. Detailed Implementation

[0051] To make the technical problems solved by the present invention, the technical solutions adopted, and the technical effects achieved clearer, the technical solutions of the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0052] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The terms "first position" and "second position" refer to two different positions.

[0053] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections or detachable connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0054] This embodiment provides a sandwich-type triaxial accelerometer chip, such as Figures 1 to 3As shown, the chip includes a top packaging assembly, a middle electrode assembly, and a bottom packaging assembly stacked sequentially. The top packaging assembly includes a top glass substrate 11 and a top electrode plate 12 fixed on the top glass substrate 11. The middle electrode assembly includes four orthogonally symmetrically distributed acceleration components 2, which are spaced apart. Each acceleration component 2 includes a movable mass block 21, a supporting mass block 22, a middle electrode block 23, a supporting elastic element 24, and a supporting beam 25. The supporting mass block 22 and the middle electrode block 23 are fixedly connected to the top electrode plate 12. The movable mass block 21 is spaced apart from the top electrode plate 12 and can move along a first direction, a second direction, and a third direction. The movable mass block 21 is sequentially supported by the supporting beam 25 and the supporting elastic element 25. The movable mass block 21 and the intermediate electrode block 23 form a capacitor. Two acceleration components 2 are distributed along a first direction and form a first differential capacitor, which is used to detect acceleration along the first direction. The other two acceleration components 2 are distributed along a second direction and form a second differential capacitor, which is used to detect acceleration along the second direction. The bottom encapsulation component includes a bottom glass substrate 31 and a bottom electrode plate 32 fixed on the bottom glass substrate 31. The bottom electrode plate 32 is fixed on the support mass block 22 and the intermediate electrode block 23. The bottom electrode plate 32 and the movable mass block 21 are spaced apart. The movable mass block 21, the top electrode plate 12 and the bottom electrode plate 32 form a third differential capacitor.

[0055] It should be noted that the first direction, second direction, and third direction mentioned in this embodiment are the X-axis direction, Y-axis direction, and Z-axis direction, respectively. The X-axis, Y-axis, and Z-axis are specifically as follows: Figure 1 and Figure 2 As shown, the structure supporting the elastic element 24 is as follows: Figure 3 As shown, the supporting elastic element 24 with this structure is easy to manufacture and has high measurement accuracy. Specifically, when measuring acceleration in the first or second direction, the movable mass block 21 can move along the first or second direction, changing the distance between the movable mass block 21 and the intermediate electrode block 23, and the first or second differential capacitor changes accordingly, ultimately measuring the acceleration in the first or second direction. When measuring acceleration in a third direction, the movable mass block 21 can move along the third direction, changing the distance between the movable mass block 21 and the top electrode plate 12 and the bottom electrode plate 32, and the third differential capacitor changes accordingly, ultimately measuring the acceleration in the third direction. In other embodiments of the present invention, the structure of the supporting elastic element 24 is not limited to this embodiment, and can also be formed by connecting multiple Z-shaped elastic units end to end or by other structures, depending on actual needs.

[0056] The sandwich-type triaxial accelerometer chip provided in this embodiment has the characteristics of good integration, large capacitance, high sensitivity and good linearity. The first differential capacitor formed by the middle electrode block 23 of the two accelerometer components 2 distributed along the first direction and the movable mass block 21 can detect the acceleration along the first direction. The second differential capacitor formed by the middle electrode block 23 of the two accelerometer components 2 distributed along the second direction and the movable mass block 21 can detect the acceleration along the second direction. The third differential capacitor formed by the movable mass block 21 along the third direction with the top electrode plate 12 and the bottom electrode plate 32 can detect the acceleration along the third direction.

[0057] like Figure 2 As shown, each acceleration component 2 includes a movable mass block 21, a supporting mass block 22, an intermediate electrode block 23, two supporting elastic elements 24, and two supporting beams 25. The two supporting elastic elements 24 are respectively connected to both ends of the supporting mass block 22, and the two supporting beams 25 are respectively connected to both ends of the movable mass block 21. Each supporting elastic element 24 is connected to one supporting beam 25. Figure 2 As shown, the movable mass block 21 in this embodiment is an isosceles right triangle. All four movable mass blocks 21 are the same size, and each base corner of the movable mass block 21 is connected to the supporting mass block 22 via a supporting beam 25 and a supporting elastic element 24. For sandwich-type triaxial accelerometer chips with the same range, the isosceles right triangle design of the movable mass block 21 minimizes the chip's volume and maximizes the mass of the movable mass block 21, improving the chip's space utilization and facilitating miniaturization. In other embodiments of the invention, the shape of the movable mass block 21 is not limited to this embodiment; it can also be a rectangle, square, trapezoid, or other shape. The number of movable mass blocks 21 is also not limited to four in this embodiment; it can also be eight or other numbers, selected according to actual needs.

[0058] Each acceleration component 2 has a supporting elastic element 24 located between the supporting mass block 22 and the intermediate electrode block 23, and between the top electrode plate 12 and the bottom electrode plate 32. When the DC voltage applied to any electrode on the intermediate electrode block 23, the top electrode plate 12 and the bottom electrode plate 32 changes, the elastic coefficient of the supporting elastic element 24 changes accordingly.

[0059] Specifically, when the DC voltage applied to the intermediate electrode block 23 of the two acceleration components 2 distributed along the first direction changes, the electrostatic force between the intermediate electrode block 23 and the movable mass block 21 changes. Since the supporting elastic element 24 is connected to the movable mass block 21 through the supporting beam 25, the length of the supporting elastic element 24 changes, that is, the elastic coefficient of the supporting elastic element 24 in the first direction changes. When used to detect acceleration in the first direction, because the elastic coefficient of the supporting elastic element 24 in the first direction changes, the movement amplitude of the movable mass block 21 in the first direction changes, ultimately changing the range of the sandwich-type triaxial accelerometer chip in the first direction. This changes the sensitivity, overload capacity, and linearity of the sandwich-type triaxial accelerometer chip in the first direction, realizing online adjustment of the range of the sandwich-type triaxial accelerometer chip. When the DC voltage applied to the intermediate electrode block 23 of the two acceleration components 2 distributed along the second direction changes, the elastic coefficient of the supporting elastic element 24 in the second direction changes, thereby making the range of the sandwich-type triaxial accelerometer chip in the second direction adjustable.

[0060] When the DC voltage applied to at least one of the top electrode plate 12 and the bottom electrode plate 32 changes, the electrostatic force between the movable mass block 21 and the top electrode plate 12 and the bottom electrode plate 32 changes. Since the supporting elastic element 24 is connected to the movable mass block 21 through the supporting beam 25, the elastic coefficient of the supporting elastic element 24 along the third direction changes. When used to detect acceleration in the third direction, the change in the elastic coefficient of the supporting elastic element 24 along the third direction changes the motion amplitude of the movable mass block 21 in the third direction, ultimately changing the range of the sandwich-type triaxial accelerometer chip in the third direction. This changes the sensitivity, overload capacity, and linearity of the sandwich-type triaxial accelerometer chip in the third direction, realizing the online adjustable range of the sandwich-type triaxial accelerometer chip.

[0061] like Figure 1 As shown, in this embodiment, a first gap 120 is formed between the movable mass block 21 and the top electrode plate 12, so that the two form a first Z-axis capacitor in the third direction. A second gap 320 is formed between the bottom electrode plate 32 and the movable mass block 21, so that the two form a second Z-axis capacitor in the third direction. The second Z-axis capacitor and the first Z-axis capacitor form a third differential capacitor. Under the excitation of acceleration in the third direction, the first Z-axis capacitance of the first Z-axis capacitor and the second Z-axis capacitance of the second Z-axis capacitor change in opposite directions.

[0062] When the capacitive triaxial accelerometer chip of this embodiment detects acceleration along a third direction, the four movable mass blocks 21 and the eight support beams 25 can move synchronously and with the same amplitude along the third direction, causing the distance between the movable mass blocks 21 and the top electrode plate 12 to change, the capacitance of the first Z-axis capacitor to change, and at the same time, the distance between the movable mass blocks 21 and the bottom electrode plate 32 to change, the capacitance of the second Z-axis capacitor to change accordingly. Based on the changes in the capacitance of the first Z-axis capacitor and the second Z-axis capacitor, the magnitude of the acceleration along the third direction can be detected.

[0063] For this sandwich-type triaxial accelerometer chip, two accelerometer components 2 are distributed along a first direction, and the other two accelerometer components 2 are distributed along a second direction. The supporting elastic element 24 of the two accelerometer components 2 distributed along the first direction can deform along the first direction. The movable mass block 21 and the intermediate electrode block 23 of each accelerometer component 2 form a first-direction capacitor. The two first-direction capacitors form a first differential capacitor. Under the excitation of acceleration in the first direction, the first-direction capacitance of the two first-direction capacitors of the first differential capacitor changes in opposite directions. Similarly, the supporting elastic element 24 of the two accelerometer components 2 distributed along the second direction can deform along the second direction. The movable mass block 21 and the intermediate electrode block 23 of each accelerometer component 2 form a second-direction capacitor. The two second-direction capacitors form a second differential capacitor. Under the excitation of acceleration in the second direction, the second-direction capacitance of the two second-direction capacitors of the second differential capacitor changes in opposite directions.

[0064] definition Figure 2 The four movable mass blocks 21 are respectively the first mass block 2101, the second mass block 2102, the third mass block 2103, and the fourth mass block 2104. When the detection is along such... Figure 2 When the acceleration is in direction a, as shown, the distance between the first mass block 2101 and the intermediate electrode block 23 increases, the capacitance of the second-direction capacitor of the acceleration component 2 containing the first mass block 2101 decreases, the distance between the third mass block 2103 and the intermediate electrode block 23 decreases, and the capacitance of the second-direction capacitor of the acceleration component 2 containing the third mass block 2103 increases, thereby causing the two second-direction capacitances of the second differential capacitor to change in opposite directions; when the detection is along the direction shown, as shown, the capacitance of the second-direction capacitor increases, and the capacitance of the second-direction capacitor of the acceleration component 2 containing the third mass block 2103 increases, thus causing the two second-direction capacitances of the second differential capacitor to change in opposite directions. Figure 2 When the acceleration is in the opposite direction to direction a, as shown, the distance between the first mass block 2101 and the intermediate electrode block 23 decreases, the capacitance of the second-direction capacitor of the acceleration component 2 containing the first mass block 2101 increases, and the distance between the third mass block 2103 and the intermediate electrode block 23 increases, the capacitance of the second-direction capacitor of the acceleration component 2 containing the third mass block 2103 decreases, thus causing the two second-direction capacitances of the second differential capacitor to change in opposite directions. When the detection is along the direction shown... Figure 2When the acceleration is in the direction b, as shown, the distance between the second mass block 2102 and the intermediate electrode block 23 decreases, the capacitance of the first-direction capacitor of the acceleration component 2 containing the second mass block 2102 increases, the distance between the fourth mass block 2104 and the intermediate electrode block 23 increases, and the capacitance of the first-direction capacitor of the acceleration component 2 containing the fourth mass block 2104 decreases, thereby causing the two first-direction capacitances of the first differential capacitor to change in opposite directions; when the detection is along the direction b, as shown, the distance between the second mass block 2102 and the intermediate electrode block 23 decreases, the capacitance of the first-direction capacitor of the acceleration component 2 containing the fourth mass block 2104 decreases, thereby causing the two first-direction capacitances of the first differential capacitor to change in opposite directions. Figure 2 When the acceleration is in the opposite direction of direction b, the distance between the second mass block 2102 and the intermediate electrode block 23 increases, the capacitance of the first direction capacitor of the acceleration component 2 containing the second mass block 2102 decreases, the distance between the fourth mass block 2104 and the intermediate electrode block 23 decreases, and the capacitance of the first direction capacitor of the acceleration component 2 containing the fourth mass block 2104 increases, thereby making the changes in the two first direction capacitances of the first differential capacitor in opposite directions.

[0065] The intermediate electrode assembly in this embodiment includes two electrically connected SOI substrates. A movable mass block 21, a supporting mass block 22, an intermediate electrode block 23, a supporting elastic element 24, and a supporting beam 25 are all formed on the two SOI substrates. Figure 1 As shown, the supporting mass block 22 is provided with a first conductive bump 41 that electrically connects the top silicon layer and the bottom silicon layer of the SOI substrate, the intermediate electrode block 23 is provided with a second conductive bump 42 that electrically connects the top silicon layer and the bottom silicon layer, and the movable mass block 21 is provided with a third conductive bump 43 that electrically connects the top silicon layer and the bottom silicon layer.

[0066] like Figure 1 As shown, the two SOI substrates in this embodiment are a first SOI substrate 201 and a second SOI substrate 202. Four first accelerometer sub-components are formed on the first SOI substrate 201 in an orthogonal symmetrical arrangement, and four second accelerometer sub-components are formed on the second SOI substrate 202 in an orthogonal symmetrical arrangement. The four first accelerometer sub-components and four second accelerometer sub-components are arranged in a one-to-one correspondence, and each first accelerometer sub-component and its directly opposite second accelerometer sub-component form an accelerometer component 2. Figure 27 As shown, each first acceleration sub-assembly includes a first movable sub-mass block 211, a first intermediate sub-electrode assembly 231, a first support sub-elastic element 241, a first support sub-beam, and a first support sub-mass block 221, as follows. Figure 28As shown, each second acceleration sub-assembly includes a second movable sub-mass block 212, a second intermediate sub-electrode assembly 232, a second support sub-elastic member 242, a second support sub-beam, and a second support sub-mass block 222. The first movable sub-mass block 211 is positioned opposite the second movable sub-mass block 212, and the two together form a movable mass block 21. The first intermediate sub-electrode assembly 231 is positioned opposite the second intermediate sub-electrode assembly 232, and the two together form an intermediate electrode block 23. The first support sub-elastic member 241 is positioned opposite the second support sub-elastic member 242, and the two together form a support elastic member 24. The first support sub-beam is positioned opposite the second support sub-beam, and the two together form a support beam 25. The first support sub-mass block 221 is positioned opposite the second support sub-mass block 222, and the two together form a support mass block 22.

[0067] like Figure 1 As shown, in this embodiment, a first slot 2010 is formed on the first bottom silicon layer 2013 of the first SOI substrate 201 facing the first support sub-elastic member 241 and the first support sub-beam. A second slot 2020 is formed on the second bottom silicon layer 2023 of the second SOI substrate 202 facing the second support sub-elastic member 242 and the second support sub-beam. The first slot 2010 and the second slot 2020 form a chamber 20. When processing the first slot 2010, the first bottom silicon layer 2013 corresponding to the first support sub-elastic member 241 and the first support sub-beam is etched, that is, the first slot 2010 is formed on the first SOI substrate 201. When processing the second slot 2020, the second bottom silicon layer 2023 corresponding to the second support sub-elastic member 242 and the second support sub-beam is etched, that is, the second slot 2020 is formed on the second SOI substrate 202. After the first SOI substrate 201 and the second SOI substrate 202 are fixed together, the first empty slot 2010 and the second empty slot 2020 form the aforementioned chamber 20.

[0068] like Figure 1 As shown, in this embodiment, a first bonding block 71 is provided on the first bottom silicon layer 2013 of the first SOI substrate 201, and a second bonding block 72 is provided on the second bottom silicon layer 2023 of the second SOI substrate 202. The first bonding block 71 can be bonded to the second bonding block 72, so that the first SOI substrate 201 and the second SOI substrate 202 are fixed and electrically connected.

[0069] Specifically, in forming the first bonding block 71 and the second bonding block 72 of this embodiment, a chromium layer is first sputtered, then a gold layer is sputtered onto the chromium layer, and finally, excess chromium and gold layers are removed. The sputtered chromium layer prevents gold from penetrating into the silicon, ensuring that the sputtered gold forms a gold layer. The first bonding block 71 and the second bonding block 72 are fixedly connected together using a gold-to-gold bonding process. In other embodiments of the present invention, the first bonding block 71 and the second bonding block 72 may also be made using other processing techniques or conductive materials, depending on actual needs.

[0070] For the first acceleration sub-component and the second acceleration sub-component that are positioned opposite each other, two first support sub-elastic elements 241 and two second support sub-elastic elements 242 are configured in a one-to-one correspondence. Each first support sub-elastic element 241 and one second support sub-elastic element 242 form a support elastic element 24. Each acceleration component 2 includes two support elastic elements 24.

[0071] like Figure 1 As shown, in this embodiment, the bottom electrode plate 32 is provided with a first connecting block 75 on the side near the second SOI substrate 202, and the supporting mass block 22 and the intermediate electrode block 23 of the second SOI substrate 202 are both provided with second connecting blocks 76. The first connecting block 75 can be fixedly connected to the second connecting block 76, so that the bottom packaging assembly and the intermediate electrode assembly are fixedly connected, and the bottom packaging assembly and the intermediate electrode assembly are not electrically connected.

[0072] Specifically, in this embodiment, both the first connecting block 75 and the second connecting block 76 are glass solder blocks formed by screen printing glass solder, and the first connecting block 75 and the second connecting block 76 are fixedly connected by a bonding process. In other embodiments of the present invention, the first connecting block 75 and the second connecting block 76 may also be made of other non-conductive materials or by other processing techniques, depending on actual needs.

[0073] like Figure 1 As shown, the sandwich-type triaxial accelerometer chip of this embodiment also includes a first electrical connector 51, a second electrical connector 52, a third electrical connector 53, and a fourth electrical connector 54. The first electrical connector 51 penetrates the top glass substrate 11 and the top electrode plate 12 and is electrically connected to the supporting mass block 22. A first insulating layer 61 is provided between the first electrical connector 51 and the top electrode plate 12. The second electrical connector 52 penetrates the top glass substrate 11 and the top electrode plate 12 and is electrically connected to the middle electrode block 23. A second insulating layer 62 is provided between the second electrical connector 52 and the top electrode plate 12. The third electrical connector 53 penetrates the top glass substrate 11 and is electrically connected to the top electrode plate 12. The fourth electrical connector 54 penetrates the bottom glass substrate 31 and is electrically connected to the bottom electrode plate 32. The first electrical connector 51, the second electrical connector 52, the third electrical connector 53, and the fourth electrical connector 54 can all be electrically connected to an external power source.

[0074] like Figure 1As shown, the fourth electrical connector 54 in this embodiment includes an electrically connected conductive layer 541 and a conductive post 542. The conductive layer 541 is formed on the side of the bottom glass substrate 31 facing away from the bottom electrode plate 32, and the conductive post 542 penetrates the bottom glass substrate 31 and is electrically connected to the bottom electrode plate 32. Specifically, both the conductive layer 541 and the conductive post 542 are made of conductive material. In use, the sandwich-type triaxial accelerometer chip is mounted on a housing with a metal sheet. The metal sheet is electrically connected to the pins. During installation, the conductive layer 541 is soldered onto the metal sheet, so that the bottom electrode plate 32 is electrically connected to the pins through the conductive layer 541 and the metal sheet.

[0075] like Figure 1 As shown, in this embodiment, a third bonding block 73 is provided on the first top silicon layer 2011 of the first SOI substrate 201, and the third bonding block 73 is electrically connected to the first conductive bump 41 and the second conductive bump 42 respectively; a fourth bonding block 74 is formed on the top electrode plate 12, and the fourth bonding block 74 is electrically connected to the first electrical connector 51 and the second electrical connector 52 respectively.

[0076] It should be noted that the first Z-axis capacitance of the first Z-axis capacitor in this embodiment is determined by the upper surface area of ​​the movable mass block 21 and the height of the first gap 120 along the third direction, wherein the height of the first gap 120 along the third direction is determined by the height of the third bonding block 73 and the fourth bonding block 74; the second Z-axis capacitance of the second Z-axis capacitor is determined by the lower surface area of ​​the movable mass block 21 and the height of the second gap 320 along the third direction, wherein the height of the second gap 320 along the third direction is determined by the height of the first connecting block 75 and the second connecting block 76.

[0077] Specifically, in this embodiment, both the top electrode plate 12 and the bottom electrode plate 32 are silicon electrode plates. When forming the third bonding block 73 and the fourth bonding block 74, a chromium layer is first sputtered, then a gold layer is sputtered onto the chromium layer, and finally, excess chromium and gold layers are removed. The sputtered chromium layer prevents gold from penetrating into the silicon, ensuring that the sputtered gold forms a gold layer. The third bonding block 73 and the fourth bonding block 74 are fixed and electrically connected together using a gold-to-gold bonding process. In other embodiments of the present invention, the third bonding block 73 and the fourth bonding block 74 can also be made using other processing techniques or conductive materials, selected according to actual needs.

[0078] The sandwich-style triaxial accelerometer chip in this embodiment features a sandwich structure design, enabling high-sensitivity acceleration signal pickup in the third direction. The design of the supporting elastic element 24 liberates the movable mass block 21 from the degrees of freedom in the first and second directions. Therefore, while simultaneously pickuping acceleration signals in the third direction, it can also pick up acceleration signals in the first and second directions. This achieves integrated triaxial acceleration signal pickup capability on a single chip while ensuring high-sensitivity capacitive signal pickup. Compared to traditional single-chip triaxial accelerometer chip structures, this is a truly high-sensitivity, triaxial integrated structure. Since different DC voltages can be applied between the bottom electrode plate 32, the middle electrode block 23, and the movable mass block 21, the magnitude of the electrostatic force between these electrodes and the movable mass block 21 can be freely controlled in the three axes. This allows for online range adjustment through the spring softening effect, while simultaneously improving the chip's overload resistance. When the capacitive triaxial accelerometer chip is working, under the excitation of an external acceleration signal, the motion amplitude of the movable mass block 21 in the first, second, and third directions is maintained at the micrometer level, all within the elastic deformation range, which can greatly ensure the linearity index of the chip output signal.

[0079] This embodiment also provides a method for fabricating a sandwich-type triaxial accelerometer chip, such as... Figures 5 to 28 As shown, the process for fabricating the sandwich-type triaxial accelerometer chip described in the above technical solution specifically includes the following steps, such as... Figure 4 As shown.

[0080] S1. A top glass substrate 11 is provided, and a top electrode plate 12 is formed on the top glass substrate 11. The top glass substrate 11 and the top electrode plate 12 form a top encapsulation assembly, specifically including the following steps:

[0081] S11, Provide a top glass substrate 11, and form a top electrode plate 12 on the top glass substrate 11, such as Figure 5 As shown;

[0082] S12. A first photoresist layer 100 is formed on the top electrode plate 12;

[0083] S13. Pattern the first photoresist layer 100 to form a first preset opening region, a second preset opening region, and a third preset opening region. Etch the top electrode plate 12 and the top glass substrate 11 opposite to the first preset opening region, the second preset opening region, and the third preset opening region. Form through-holes 101, 102, and 103 on the top electrode plate 12 and the top glass substrate 11. Figure 6 As shown;

[0084] S14. Sputter metal material to form a first electrical connector 51 in the first conductive hole 101, a second electrical connector 52 in the second conductive hole 102, and a third electrical connector 53 in the third conductive hole 103. Finally, remove the patterned first photoresist layer 100. Figure 7 As shown;

[0085] S15. A second photoresist layer is formed on the top electrode plate 12;

[0086] S16. Pattern the second photoresist layer to form a fourth preset opening region and a fifth preset opening region. Etch the top electrode plate 12 facing the fourth preset opening region and the fifth preset opening region to form a first insulating annular hole that penetrates the top electrode plate 12 and surrounds the first electrical connector 51, and a second insulating annular hole that penetrates the top electrode plate 12 and surrounds the second electrical connector 52.

[0087] S17. A first insulating layer 61 is formed in the first insulating annular hole, and a second insulating layer 62 is formed in the second insulating annular hole. The first insulating layer 61 wraps around the outer wall of the first electrical connector 51, and the second insulating layer 62 wraps around the outer wall of the second electrical connector 52. Finally, the patterned second photoresist layer is removed. Figure 8 As shown;

[0088] S18. A third photoresist layer is formed on the top glass substrate 11;

[0089] S19. Pattern the third photoresist layer, forming a sixth, seventh, and eighth preset opening regions on the third photoresist layer. Sputter metal material onto the sixth, seventh, and eighth preset opening regions and the third photoresist layer. Form a first metal connection disk 81 in the sixth preset opening region, electrically connected to the first electrical connector 51. Form a second metal connection disk 82 in the seventh preset opening region, electrically connected to the second electrical connector 52. Form a third metal connection disk 83 in the eighth preset opening region, electrically connected to the third electrical connector 53. Finally, remove the patterned third photoresist layer. Figure 9 As shown;

[0090] S110. A fourth photoresist layer is formed on the top electrode plate 12;

[0091] S111. Pattern the fourth photoresist layer to form the ninth preset opening region. Sputter metal material to form the fourth bonding block 74 within the ninth preset opening region. The fourth bonding block 74 is electrically connected to the first electrical connector 51 and the second electrical connector 52, respectively. Finally, remove the patterned fourth photoresist layer. Figure 10 As shown.

[0092] In this embodiment, the top glass substrate 11 is not conductive, and the top electrode plate 12 is a silicon electrode plate. The top electrode plate 12 can be directly formed on the top glass substrate 11, or the silicon electrode plate and the top glass substrate 11 can be fixed together by a bonding process, depending on the actual needs.

[0093] In this embodiment, both the first insulating layer 61 and the second insulating layer 62 are silicon dioxide layers, and both are directly formed on the silicon electrode plate. In other embodiments, the first insulating layer 61 and the second insulating layer 62 may also be a single-layer structure formed of insulating materials such as silicon nitride or aluminum oxide, or a structure of at least two layers formed of insulating materials such as silicon dioxide, silicon nitride, or aluminum oxide, depending on the actual needs.

[0094] S2, providing such as Figure 11 The first SOI substrate 201 shown is fixedly connected to the top electrode plate 12. The first top silicon layer 2011 and the first bottom silicon layer 2013 of the first SOI substrate 201 are electrically connected. The first top silicon layer 2011 can be electrically connected to an external power supply through the top packaging assembly. The specific steps include:

[0095] S21. A fifth photoresist layer 200 is formed on the first top silicon layer 2011 of the first SOI substrate 201.

[0096] S22. Pattern the fifth photoresist layer 200 to form the tenth, eleventh, and twelfth preset opening regions. Use the DRIE process to etch the first top silicon layer 2011 and the first buried oxide layer 2012 opposite to the tenth, eleventh, and twelfth preset opening regions, forming a first electrical connection hole 91 opposite to the tenth preset opening region, a second electrical connection hole 92 opposite to the eleventh preset opening region, and a third electrical connection hole opposite to the twelfth preset opening region. Figure 12 As shown;

[0097] S23. Sputter metal material to form a first conductive bump 41 in the first electrical connection hole 91, a second conductive bump 42 in the second electrical connection hole 92, and a third conductive bump 43 in the third electrical connection hole 93. The first conductive bump 41, the second conductive bump 42, and the third conductive bump 43 all electrically connect the first bottom silicon layer 2013 and the first top silicon layer 2011 of the first SOI substrate 201. Finally, the patterned fifth photoresist layer 200 is removed.

[0098] S24. A sixth photoresist layer is formed on the first top silicon layer 2011, the first conductive bump 41, the second conductive bump 42 and the third conductive bump 43 of the first SOI substrate 201.

[0099] S25. Pattern the sixth photoresist layer to form the thirteenth preset opening region. Use the DRIE process to etch the first top silicon layer 2011 and the first buried oxide layer 2012 facing the thirteenth preset opening region to form the first isolation hole 97. Finally, remove the patterned sixth photoresist layer.

[0100] S26. A seventh photoresist layer is formed in the first top silicon layer 2011, the first conductive bump 41, the second conductive bump 42, the third conductive bump 43 and the first isolation hole 97 of the first SOI substrate 201.

[0101] S26. Pattern the seventh photoresist layer to form the fourteenth preset opening region. Sputter metal material to form a third bonding block 73 within the fourteenth preset opening region. The third bonding block 73 is electrically connected to the first conductive bump 41 and the second conductive bump 42, respectively. Finally, remove the patterned seventh photoresist layer. Figure 13 As shown;

[0102] S27. The fourth bonding block 74 and the third bonding block 73 are bonded together, so that the first SOI substrate 201 is fixed and electrically connected to the top electrode plate 12, and a first gap 120 is formed between the first SOI substrate 201 and the top electrode plate 12.

[0103] It should be noted that, in forming the third bonding block 73 and the fourth bonding block 74 of this embodiment, a chromium layer is first sputtered, then a gold layer is sputtered on the chromium layer, and finally the excess chromium and gold layers are removed. The sputtered chromium layer can prevent gold from penetrating into the silicon, ensuring that the sputtered gold forms a gold layer. The third bonding block 73 and the fourth bonding block 74 are fixed and electrically connected together using a gold-to-gold bonding process. In other embodiments of the present invention, the third bonding block 73 and the fourth bonding block 74 can also be made using other processing techniques or conductive materials, depending on actual needs.

[0104] S3. Thin the first bottom silicon layer 2013 of the first SOI substrate 201 to 100 μm, as shown. Figure 14 As shown.

[0105] In other embodiments, the thickness of the first bottom silicon layer 2013 of the thinned first SOI substrate 201 is not limited to the limitation of this embodiment, and can be other values, specifically set according to actual needs.

[0106] S4. Etch the first SOI substrate 201 to form four spaced-apart first accelerometer sub-assemblies on the first SOI substrate 201. Each first accelerometer sub-assembly includes a first movable sub-mass block 211, a first intermediate sub-electrode assembly 231, a first support sub-elastic member 241, a first support sub-beam, and a first support sub-mass block 221. The first movable mass block 211 and the top electrode plate 12 form a first Z-axis capacitor. The top encapsulation assembly and the first SOI substrate 201 form a first accelerometer structure. Specifically, this includes the following steps:

[0107] S41. An eighth photoresist layer is formed on the first bottom silicon layer 2013;

[0108] S42. Pattern the eighth photoresist layer to form the fifteenth preset opening region and the sixteenth preset opening region, wherein the fifteenth preset opening region is set opposite to the first isolation hole 97;

[0109] S43. The first bottom silicon layer 2013 of the first SOI substrate 201, facing the fifteenth and sixteenth preset opening regions, is etched using the DRIE process. A first movable submass block 211 and a first empty slot 2010 are formed on the first SOI substrate 201. Finally, the patterned eighth photoresist layer is removed. Figure 15 As shown;

[0110] S44. A ninth photoresist layer is formed in the first bottom silicon layer 2013 and the first trench 2010;

[0111] S45. Pattern the ninth photoresist layer to form the seventeenth preset opening region facing the first empty slot 2010;

[0112] S46. The first buried oxide layer 2012 and the first top silicon layer 2011 facing the seventeenth preset opening area are etched using RIE process to form the first support sub-mass block 221, the first support sub-elastic element 241, the first support sub-beam and the first intermediate sub-electrode assembly 231, and finally the patterned ninth photoresist layer is removed.

[0113] S47. A tenth photoresist layer is formed on the first bottom silicon layer 2013;

[0114] S48. Pattern the tenth photoresist layer to form the eighteenth preset opening region;

[0115] S49. Chromium and gold are sequentially sputtered onto the tenth photoresist layer and the eighteenth preset opening area. Finally, the patterned tenth photoresist layer is removed, and the remaining chromium and gold form the first bonding block 71. The thickness of the first bonding block 71 on the first support sub-mass block 221 and the first intermediate sub-electrode assembly 231 is 1 μm, and the thickness of the first bonding block 71 on the first movable sub-mass block 211 is less than 1 μm, forming the first acceleration structure, such as... Figure 16 As shown.

[0116] Specifically, in this embodiment, four spaced-apart first acceleration sub-assemblies are formed on the first SOI substrate 201. Two of the first acceleration sub-assemblies are symmetrically distributed along a first direction, and the other two are symmetrically distributed along a second direction. Each first acceleration sub-assembly includes a first movable sub-mass block 211, a first support sub-mass block 221, a first intermediate sub-electrode assembly 231, two first support sub-beams, and two first support sub-elastic members 241. The four first movable sub-mass blocks 211 are all isosceles right triangles, with the hypotenuses of the isosceles right triangles extending along the edge of the first SOI substrate 201. The first end of the first support sub-mass block 221 is connected to the second end of the first movable sub-mass block 211 through a first support sub-elastic member 241 and a first support sub-beam. The third end of the first support sub-mass block 221 is connected to the fourth end of the first movable sub-mass block 211 through another first support sub-elastic member 241 and another first support sub-beam.

[0117] In other embodiments, the material of the first bonding block 71 may also be a conductive material such as indium or tin, depending on the actual needs.

[0118] Specifically, each first support subelastic element 241 in this embodiment consists of 5 folded springs, and the width of each folded spring is between 2μm and 3μm, and the length is less than half of the top electrode plate 12. The two first support subelastic elements 241 of each first acceleration sub-assembly are symmetrically distributed.

[0119] S5. A bottom electrode plate 32 is formed on the bottom glass substrate 31 to form a bottom encapsulation assembly. The specific processing steps are as follows:

[0120] S51, a bottom glass substrate 31 is provided, and a bottom electrode plate 32 is formed on the bottom glass substrate 31, such as... Figure 17 As shown;

[0121] S52, An eleventh photoresist layer is formed on the bottom electrode plate 32;

[0122] S53. Pattern the eleventh photoresist layer to form the nineteenth predetermined opening region. Etch the bottom electrode plate 32 and the bottom glass substrate 31 opposite the nineteenth predetermined opening region to form the fourth conductive hole 30 penetrating the bottom electrode plate 32 and the bottom glass substrate 31. Remove the patterned eleventh photoresist layer. Figure 18 As shown;

[0123] S53. Sputter metal material onto the side of the bottom glass substrate 31 away from the bottom electrode plate 32 and into the fourth conductive hole 30 to thin and flatten the metal layer on the bottom glass substrate 31. Form a conductive pillar 542 in the fourth conductive hole 30. Form a conductive layer 541 on the side of the bottom electrode plate 32 away from the bottom glass substrate 31. The conductive pillar 542 and the conductive layer 541 are electrically connected, and the two form a fourth electrical connector 54. Figure 19 As shown;

[0124] S54. A twelfth photoresist layer is formed on the bottom electrode plate 32 and the conductive pillar 542.

[0125] S55. Pattern the twelfth photoresist layer to form the twentieth preset opening region. Sputter metal material to form the first connecting block 75 within the twentieth preset opening region. Finally, remove the patterned twelfth photoresist layer. Figure 20 As shown.

[0126] In this embodiment, the bottom glass substrate 31 is non-conductive, and the bottom electrode plate 32 is a silicon electrode plate. The bottom electrode plate 32 can be directly formed on the bottom glass substrate 31, or the silicon electrode plate and the bottom glass substrate 31 can be fixed together by a bonding process, depending on the actual needs.

[0127] S6, providing such as Figure 21 The second SOI substrate 202 shown is fixedly connected to the bottom electrode plate 32 at a third position, and the second top silicon layer 2021 and the second bottom silicon layer 2023 of the second SOI substrate 202 are electrically connected. Specifically, the following steps are included:

[0128] S61. A thirteenth photoresist layer is formed on the second SOI substrate 202;

[0129] S62. Pattern the thirteenth photoresist layer to form the twenty-first, twenty-second, and twenty-third preset opening regions. Use the DRIE process to etch the second top silicon layer 2021 and the second buried oxide layer 2022 opposite to the twenty-first, twenty-second, and twenty-third preset opening regions, forming the fourth electrical connection hole 94 opposite to the twenty-first preset opening region, the fifth electrical connection hole 95 opposite to the twenty-second preset opening region, and the sixth electrical connection hole 96 opposite to the twenty-third preset opening region. Figure 22 As shown;

[0130] S63. Sputter metal material to form a first conductive bump 41 in the fourth electrical connection hole 94, a second conductive bump 42 in the fifth electrical connection hole 95, and a third conductive bump 43 in the sixth electrical connection hole 96. The first conductive bump 41, the second conductive bump 42, and the third conductive bump 43 electrically connect the second bottom silicon layer 2023 and the second top silicon layer 2021 of the second SOI substrate 202. Finally, the patterned thirteenth photoresist layer is removed.

[0131] S64. A fourteenth photoresist layer is formed on the second top silicon layer 2021, the first conductive bump 41, the second conductive bump 42 and the third conductive bump 43 of the second SOI substrate 202.

[0132] S65. Pattern the fourteenth photoresist layer to form the twenty-fourth preset opening region. Use the DRIE process to etch the second top silicon layer 2021 and the second buried oxide layer 2022 opposite to the twenty-fourth preset opening region to form the second isolation via 98. Finally, remove the patterned fourteenth photoresist layer. Figure 23 As shown;

[0133] S66. A fifteenth photoresist layer is formed in the second top silicon layer 2021, the first conductive bump 41, the second conductive bump 42, the third conductive bump 43 and the second isolation hole 98 of the second SOI substrate 202.

[0134] S67. Pattern the fifteenth photoresist layer to form the twenty-fifth preset opening region. Sputter metal material to form a second connecting block 76 within the twenty-fifth preset opening region. The second connecting block 76 is electrically connected to the first conductive bump 41 and the second conductive bump 42, respectively. Finally, remove the patterned fifteenth photoresist layer. Figure 24 As shown;

[0135] S67. The second connecting block 76 is bonded to the first connecting block 75, so that the second SOI substrate 202 is fixed and electrically connected to the bottom electrode plate 32, and the second SOI substrate 202 and the bottom electrode plate 32 form a second gap 320.

[0136] It should be noted that the first connecting block 75 and the second connecting block 76 are formed by curing non-conductive glass material. In other embodiments of the present invention, the first connecting block 75 and the second connecting block 76 may also be made using other processing techniques or conductive materials, depending on actual needs.

[0137] S7. Thin the second bottom silicon layer 2023 of the second SOI substrate 202 to 100 μm, as shown. Figure 25 As shown.

[0138] In other embodiments, the thickness of the second bottom silicon layer 2023 of the thinned second SOI substrate 202 is not limited to the limitation of this embodiment, and can be other values, specifically set according to actual needs.

[0139] S8. Etch the second SOI substrate 202 to form four spaced-apart second accelerometer sub-assemblies on the second SOI substrate 202. Each second accelerometer sub-assembly corresponds to a first accelerometer sub-assembly, and the two together form an accelerometer assembly 2. Each second accelerometer sub-assembly includes a second movable sub-mass block 212, a second intermediate sub-electrode assembly 232, a second support sub-elastic member 242, a second support sub-beam, and a second support sub-mass block 222. The second movable sub-mass block 212 and the bottom electrode plate 32 form a second Z-axis capacitor. The first Z-axis capacitor and the second Z-axis capacitor form a third differential capacitor. The third differential capacitor is used to detect acceleration along a third direction. The bottom packaging assembly and the second SOI substrate 202 form a second acceleration structure. Specifically, the following steps are included:

[0140] S81, A sixteenth photoresist layer is formed on the second bottom silicon layer 2023;

[0141] S82. Pattern the sixteenth photoresist layer to form the twenty-sixth preset opening region and the twenty-seventh preset opening region, wherein the twenty-sixth preset opening region is positioned opposite the second isolation hole 98;

[0142] S83. The second bottom silicon layer 2023 of the second SOI substrate 202, which faces the twenty-sixth and twenty-seventh preset opening regions, is etched using the DRIE process. A second movable submass block 212 and a second empty slot 2020 are formed on the second SOI substrate 202. Finally, the patterned sixteenth photoresist layer is removed. Figure 26 As shown;

[0143] S84. A seventeenth photoresist layer is formed in the second bottom silicon layer 2023 and the second trench 2020.

[0144] S85. Pattern the seventeenth photoresist layer to form the twenty-eighth preset opening area facing the second empty slot 2020;

[0145] S86. The second buried oxide layer 2022 and the second top silicon layer 2021 facing the twenty-eighth preset opening area are etched using RIE process to form the second support sub-mass block 222, the second support sub-elastic element 242, the second support sub-beam and the second intermediate sub-electrode assembly 232, and finally the patterned seventeenth photoresist layer is removed.

[0146] S87. An eighteenth photoresist layer is formed on the second bottom silicon layer 2023;

[0147] S88. Pattern the eighteenth photoresist layer to form the twenty-ninth preset opening region;

[0148] S89. Chromium and gold are sequentially sputtered onto the eighteenth photoresist layer and the twenty-ninth preset opening area. Finally, the patterned eighteenth photoresist layer is removed, and the remaining chromium and gold form the second bonding block 72. The thickness of the second bonding block 72 on the second support sub-mass block 222 and the second intermediate sub-electrode assembly 232 is 1 μm, and the thickness of the second bonding block 72 on the second movable sub-mass block 212 is less than 1 μm, forming the second acceleration structure, as shown. Figure 27 As shown.

[0149] Specifically, in this embodiment, four spaced-apart second accelerometer sub-assemblies are formed on the second SOI substrate 202. Two of the second accelerometer sub-assemblies are symmetrically distributed along a first direction, and the other two are symmetrically distributed along a second direction. Each second accelerometer sub-assembly includes a second movable sub-mass block 212, a second support sub-mass block 222, a second intermediate sub-electrode assembly 232, two second support sub-beams, and two second support sub-elastic members 242. The four second movable sub-mass blocks 212 are all isosceles right triangles, with the hypotenuses of the isosceles right triangles extending along the edge of the second SOI substrate 202. The fifth end of the second support sub-mass block 222 is connected to the sixth end of the second movable sub-mass block 212 through a second support sub-elastic member 242 and a second support sub-beam. The seventh end of the second support sub-mass block 222 is connected to the eighth end of the second movable sub-mass block 212 through another second support sub-elastic member 242 and another second support sub-beam.

[0150] In other embodiments, the material of the second bonding block 72 may also be a conductive material such as indium or tin, depending on the actual needs.

[0151] Specifically, each second support sub-elastic element 242 in this embodiment consists of 5 folded springs, and the width of each folded spring is between 2μm and 3μm, and the length is less than half of the top electrode plate 12. The two second support sub-elastic elements 242 of each second acceleration sub-assembly are symmetrically distributed.

[0152] S9. Fix the first bonding block 71 of the first acceleration structure and electrically connect it to the second bonding block 72 of the second acceleration structure, as follows: Figure 28As shown, the first bonding block 71 and the second bonding block 72 are fixedly connected by a gold-to-gold bonding process. The first part of the first acceleration structure excluding the top encapsulation component and the second part of the second acceleration structure excluding the bottom encapsulation component form an intermediate electrode assembly. Each acceleration assembly 2 has a first movable sub-mass block 211 facing a second movable sub-mass block 212, and the two together form a movable mass block 21. The movable mass block 21 can move along the first direction, the second direction, and the third direction. Each acceleration assembly 2 has a first support sub-elastic element 241 facing a second support sub-elastic element 242, and the two together form a support elastic element 24. Each first support sub-mass block 221 is positioned opposite a second support sub-mass block 222, and the two together form a support mass block 22. Each first intermediate sub-electrode assembly 231 of each acceleration component 2 is positioned opposite a second intermediate sub-electrode assembly 232, and the two together form an intermediate electrode block 23. The movable mass blocks 21 of the two acceleration components 2 positioned opposite each other along the first direction and the intermediate electrode block 23 form a first differential capacitor, which can detect acceleration along the first direction. The movable mass blocks 21 of the two acceleration components 2 positioned opposite each other along the second direction and the intermediate electrode block 23 form a second differential capacitor, which can detect acceleration along the second direction.

[0153] The sandwich-type triaxial accelerometer chip processing method provided in this embodiment is simple, easy to control and implement, and produces a small-area accelerometer chip, reducing the chip manufacturing cost. The sandwich-type triaxial accelerometer chip also features good integration, large capacitance, high sensitivity and good linearity, and can be widely used in the measurement of acceleration signals in many fields such as industrial control, earthquake monitoring, inertial navigation, aerospace and defense.

[0154] The sandwich-type triaxial accelerometer chip fabricated using this method can have its gaps between the top electrode plate 12, bottom electrode plate 32, and middle electrode block 23 and the movable mass block 21 precisely controlled using dry etching, sputtering, and bonding processes. This maximizes the capacitance of the fabricated chip and allows it to be used to detect speeds up to 19.6 m / s². 2 Up to 1960m / s 2 The acceleration between them.

[0155] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A method of processing a sandwich triaxial acceleration chip, characterized by, include: A top glass substrate is provided, and a top electrode plate is formed on the top glass substrate, the top glass substrate and the top electrode plate forming a top encapsulation assembly; A first SOI substrate is provided, and the top electrode plate is fixedly connected to the first SOI substrate. The first top silicon layer and the first bottom silicon layer of the first SOI substrate are electrically connected. The first top silicon layer can be electrically connected to an external power source through the top packaging assembly. Thin the first bottom silicon layer of the first SOI substrate; The first SOI substrate is etched to form four spaced-out first acceleration sub-assemblies on the first SOI substrate. Each first acceleration sub-assembly includes a first movable sub-mass block, a first intermediate sub-electrode assembly, a first support sub-elastic element, a first support sub-beam and a first support sub-mass block. The first movable sub-mass block and the top electrode plate form a first Z-axis capacitor. The top encapsulation assembly and the first SOI substrate form a first acceleration structure. A bottom electrode plate is formed on the bottom glass substrate to form a bottom encapsulation component; A second SOI substrate is provided, and the second SOI substrate is fixedly connected to the bottom electrode plate at a third position, and the second top silicon layer of the second SOI substrate is electrically connected to the second bottom silicon layer. Thin the second bottom silicon layer of the second SOI substrate; The second SOI substrate is etched to form four spaced-apart second acceleration sub-assemblies. Each second acceleration sub-assembly corresponds to one of the first acceleration sub-assemblies, and the two together form an acceleration assembly. Each second acceleration sub-assembly includes a second movable sub-mass block, a second intermediate sub-electrode assembly, a second support sub-elastic element, a second support sub-beam, and a second support sub-mass block. The second movable sub-mass block and the bottom electrode plate form a second Z-axis capacitor. The first Z-axis capacitor and the second Z-axis capacitor form a third differential capacitor. The third differential capacitor is used to detect acceleration along a third direction. The bottom packaging assembly and the second SOI substrate form a second acceleration structure. The first bottom silicon layer of the first acceleration structure is fixed and electrically connected to the second bottom silicon layer of the second acceleration structure. The first acceleration structure excluding the top encapsulation component and the second acceleration structure excluding the bottom encapsulation component form an intermediate electrode assembly. Each first movable sub-mass block of each acceleration assembly is positioned opposite a second movable sub-mass block, and the two together form a movable mass block. The movable mass block is capable of movement along a first direction, a second direction, and a third direction. Each first support sub-elastic element of each acceleration assembly is positioned opposite a second support elastic element, and the two together form a support elastic element. Each of the first support sub-mass blocks of the acceleration components is positioned opposite a second support sub-mass block, and the two together form a support mass block. Each of the first intermediate sub-electrode components of the acceleration components is positioned opposite a second intermediate sub-electrode component, and the two together form an intermediate electrode block. The movable mass blocks of the two acceleration components positioned opposite each other along a first direction and the intermediate electrode block form a first differential capacitor, which can detect acceleration along the first direction. The movable mass blocks of the two acceleration components positioned opposite each other along a second direction and the intermediate electrode block form a second differential capacitor, which can detect acceleration along the second direction.

2. The method of claim 1, wherein the three-axis acceleration chip is a sandwich type three-axis acceleration chip. The processing steps of the top encapsulation component include: A top glass substrate is provided, on which the top electrode plate is formed; A first conductive hole, a second conductive hole, and a third conductive hole are formed through the top electrode plate and the top glass substrate; Sputtering metal material, wherein a first electrical connector is formed in the first conductive hole, a second electrical connector is formed in the second conductive hole, and a third electrical connector is formed in the third conductive hole; The top electrode plate is etched to form a first insulating annular hole that penetrates the top electrode plate and surrounds the first electrical connector, and a second insulating annular hole that penetrates the top electrode plate and surrounds the second electrical connector. A first insulating layer is formed in the first insulating annular hole, and a second insulating layer is formed in the second insulating annular hole. The first insulating layer wraps around the outer wall of the first electrical connector, and the second insulating layer wraps around the outer wall of the second electrical connector.

3. The method of claim 1, wherein the three-axis acceleration chip is a sandwich type three-axis acceleration chip. The processing steps of the bottom encapsulation component include: A bottom glass substrate is provided, and the bottom electrode plate is formed on the bottom glass substrate; The bottom electrode plate and the bottom glass substrate are etched to form a fourth conductive hole penetrating the bottom electrode plate and the bottom glass substrate; A conductive pillar is formed in the fourth conductive hole, and a conductive layer is formed on the side of the bottom electrode plate opposite to the bottom glass substrate. The conductive pillar and the conductive layer are electrically connected and together form a fourth electrical connector.

4. A sandwich triaxial acceleration chip, characterized by The chip is manufactured using the processing method of any one of claims 1 to 3, defining a first direction, a second direction, and a third direction that are perpendicular to each other. The sandwich-type triaxial accelerometer chip includes a top packaging assembly, a middle electrode assembly, and a bottom packaging assembly stacked sequentially. The top packaging assembly includes a top glass substrate and a top electrode plate fixed on the top glass substrate. The middle electrode assembly includes four spaced-apart accelerometer components, orthogonally and symmetrically distributed. Each accelerometer component includes a movable mass block, a supporting mass block, a middle electrode block, a supporting elastic element, and a supporting beam. The movable mass block is spaced apart from the top electrode plate and is capable of moving along the first direction, the second direction, and the third direction. The movable mass block is fixed to the supporting mass block in sequence by the supporting beam and the supporting elastic element. The movable mass block and the intermediate electrode block form a capacitor. Two of the acceleration components are distributed along a first direction and form a first differential capacitor, which is used to detect acceleration along the first direction. The other two acceleration components are distributed along a second direction and form a second differential capacitor, which is used to detect acceleration along the second direction. The bottom encapsulation assembly includes a bottom glass substrate and a bottom electrode plate fixed on the bottom glass substrate. The bottom electrode plate is fixed to the supporting mass block and is spaced apart from the movable mass block. The movable mass block, the top electrode plate, and the bottom electrode plate form a third differential capacitor.

5. The sandwich triaxial acceleration chip according to claim 4, wherein The intermediate electrode assembly includes two electrically connected SOI substrates. The movable mass block, the supporting mass block, the intermediate electrode block, the supporting elastic element, and the supporting beam are all formed on the two SOI substrates. The supporting mass block is provided with a first conductive bump that electrically connects the top silicon layer and the bottom silicon layer of the SOI substrate. The intermediate electrode block is provided with a second conductive bump that electrically connects the top silicon layer and the bottom silicon layer. The movable mass block is provided with a third conductive bump that electrically connects the top silicon layer and the bottom silicon layer.

6. The sandwich triaxial acceleration chip according to claim 5, wherein The two SOI substrates are a first SOI substrate and a second SOI substrate, respectively. Four first accelerometer sub-assemblies are formed on the first SOI substrate in an orthogonal symmetrical arrangement, and four second accelerometer sub-assemblies are formed on the second SOI substrate in an orthogonal symmetrical arrangement. The four first accelerometer sub-assemblies and four second accelerometer sub-assemblies are arranged in a one-to-one correspondence, and each first accelerometer sub-assembly and its directly opposite second accelerometer sub-assembly form an accelerometer assembly. Each first accelerometer sub-assembly includes a first movable sub-mass block, a first intermediate sub-electrode assembly, a first support sub-elastic element, a first support sub-beam, and a first support sub-mass block. Each of the second acceleration sub-assemblies includes a second movable sub-mass block, a second intermediate sub-electrode assembly, a second support sub-elastic member, a second support sub-beam, and a second support sub-mass block. The first movable sub-mass block is positioned opposite the second movable sub-mass block, and the two together constitute the movable mass block. The first intermediate sub-electrode assembly is positioned opposite the second intermediate sub-electrode assembly, and the two together constitute the intermediate electrode block. The first support sub-elastic member is positioned opposite the second support sub-elastic member, and the two together constitute the support elastic member. The first support sub-beam is positioned opposite the second support sub-beam, and the two together constitute the support beam. The first support sub-mass block is positioned opposite the second support sub-mass block, and the two together constitute the support mass block.

7. The sandwich triaxial acceleration chip according to claim 6, wherein A first slot is formed on the first bottom silicon layer of the first SOI substrate facing the first support sub-elastic member and the first support sub-beam, and a second slot is formed on the second bottom silicon layer of the second SOI substrate facing the second support sub-elastic member and the second support sub-beam. The first slot and the second slot form a cavity.

8. The sandwich triaxial acceleration chip according to claim 4, wherein The sandwich-type triaxial accelerometer chip further includes a first electrical connector, a second electrical connector, a third electrical connector, and a fourth electrical connector. The first electrical connector penetrates the top glass substrate and the top electrode plate and is electrically connected to the supporting mass block. A first insulating layer is provided between the first electrical connector and the top electrode plate. The second electrical connector penetrates the top glass substrate and the top electrode plate and is electrically connected to the middle electrode block. A second insulating layer is provided between the second electrical connector and the top electrode plate. The third electrical connector penetrates the top glass substrate and is electrically connected to the top electrode plate. The fourth electrical connector penetrates the bottom glass substrate and is electrically connected to the bottom electrode plate. The first, second, third, and fourth electrical connectors can all be electrically connected to an external power source.

9. The sandwich-type triaxial accelerometer chip according to claim 8, characterized in that, The fourth electrical connector includes an electrically connected conductive layer and a conductive post. The conductive layer is formed on the side of the bottom glass substrate opposite to the bottom electrode plate, and the conductive post penetrates the bottom glass substrate and is electrically connected to the bottom electrode plate.

10. The sandwich triaxial acceleration chip according to claim 4, wherein Each of the acceleration components includes a movable mass block, a supporting mass block, an intermediate electrode block, two supporting elastic elements, and two supporting beams. The two supporting elastic elements are respectively connected to both ends of the supporting mass block, and the two supporting beams are respectively connected to both ends of the movable mass block. Each supporting elastic element is connected to one of the supporting beams.

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