MEMS three-axis thermal convection acceleration sensor based on TGV structure

Abstract

The invention discloses an MEMS three-axis thermal convection acceleration sensor based on a TGV structure. The sensor adopts a three-layer stacked structure and comprises a first chip, a second chip and a middle layer which are provided with upper and lower glass substrates, and a closed fluid cavity is defined by the first chip, the second chip and the middle layer. TGV conductive through columns are arranged in the first chip and the second chip, and heaters, z-axis temperature detectors close to the heaters and peripheral plane temperature detectors are symmetrically arranged on the surfaces, close to the fluid cavity, of the first chip and the second chip. The low thermal conductivity characteristic of the glass substrate is utilized, high sensitivity can be achieved without deep silicon etching, and the mechanical reliability and impact resistance of the device are remarkably improved; meanwhile, the measurement of the x-axis acceleration, the y-axis acceleration and the z-axis acceleration is successfully realized through the unique layout of the up-down symmetrical temperature detectors and the corresponding differential measurement principle. In addition, the vertical interconnection realized by using the TGV technology is beneficial to miniaturization and high-density integration of the device.

Description

Technical Field

[0001] This invention belongs to the field of thermal convection acceleration sensor design, and particularly relates to a MEMS triaxial thermal convection acceleration sensor based on a TGV structure. Background Technology

[0002] There are various accelerometers on the market based on different sensing principles, mainly capacitive, piezoresistive, piezoelectric, and thermal convection types. Accelerometers based on the principle of thermal convection differ from traditional mechanical mass structures. They sense input acceleration by sensing the fluid motion generated by convection, which alters the temperature field distribution within the system. The biggest advantage of this type of accelerometer is the absence of a moving mass, allowing it to withstand significant impacts without damage. Its reliability, measurement range, and cost control are superior to traditional moving mass structures.

[0003] Microelectromechanical systems (MEMS) are a driving force behind the miniaturization and multifunctional integration of electronic devices, originating from integrated circuit (IC) technology. Compared to macroscopic electromechanical sensors, sensors fabricated using MEMS technology have the advantage of high sensitivity, and MEMS technology allows for mass production, effectively reducing device costs. Thermal convection accelerometers fabricated using MEMS technology combine the advantages of the aforementioned devices with the advantages of the manufacturing technology. However, most current research on thermal convection accelerometers focuses on improving sensitivity. Deep silicon etching processes are used to remove excess bulk silicon material from the silicon substrate to reduce lateral solid-state conduction, allowing more heat to be transferred through convection. The ultimate effect is improved device sensitivity, but this approach reduces device reliability to some extent. Through-glass via (TGV) technology is a next-generation advanced packaging and integration technology, expected to replace through-silicon via (TSV) technology as the mainstream technology for three-dimensional interconnect packaging and integration. MEMS sensors fabricated on TGV substrates can achieve vertically interconnected conductive channels, shortening the signal transmission path and enabling high-density wiring. In particular, for thermal convection accelerometers, the thermal conductivity of TGV substrates is two orders of magnitude lower than that of traditional silicon substrates, so high sensitivity can be obtained without additional etching. This further highlights the advantages of thermal convection accelerometers in terms of high reliability and shock resistance.

[0004] Accelerometers employing the principle of thermal convection place a heater in the center of the chip to provide a thermal field, and temperature sensors are placed at equal intervals around the heater to measure the temperature difference. Input acceleration in any direction on the xy-plane can be decomposed into the temperature difference output by the x-axis and y-axis temperature sensors, achieving acceleration measurement along two axes. However, measuring acceleration along the vertical z-axis is beyond the capabilities of conventional structures, limiting the application of thermal convection accelerometers in three-dimensional spatial measurement scenarios.

[0005] Acceleration measurement has wide applications in consumer electronics, automotive and transportation, industrial monitoring and manufacturing, aerospace, and healthcare. Thermal convection accelerometers, which do not require mass blocks, offer advantages in reliability and long-term stability, leading to a larger market share. Currently, mainstream thermal convection accelerometers are still based on traditional silicon substrates. To improve sensitivity, methods such as deep silicon etching are used to remove some bulk silicon to reduce lateral solid-state heat conduction. Furthermore, the connection to external circuits typically uses the mature wire bonding method. While this method is mature and stable, it is not suitable for the increasingly integrated development of sensor chips, and there are few commercially available thermal convection triaxial accelerometers both domestically and internationally. Existing thermal convection accelerometers often require deep silicon etching to improve sensitivity, thus reducing the device's mechanical reliability and shock resistance. In addition, traditional planar structures make it difficult to measure acceleration in the vertical z-axis direction. Moreover, traditional wire bonding connections are not conducive to further miniaturization and high-density integration of sensors. Summary of the Invention

[0006] The purpose of this invention is to provide a MEMS triaxial thermal convection acceleration sensor based on a TGV structure to solve the technical problems mentioned in the background art.

[0007] To solve the above-mentioned technical problems, the specific technical solution of the present invention is as follows: A triaxial thermal convection accelerometer based on a TGV structure MEMS employs a three-layer stacked structure, including a first chip, a second chip, and an intermediate layer between them. The intermediate layer has a through-hole etched cavity. The first chip and the second chip are hermetically bonded to the two sides of the intermediate layer, thereby jointly enclosing a sealed fluid cavity. The fluid cavity is filled with liquid or gas as the sensing medium. The substrate material of the first chip, the second chip, and the intermediate layer is all glass. Both the first chip and the second chip contain TGV conductive pillars penetrating their respective substrates. The surface of the first chip near the fluid cavity is provided with a first heater group consisting of several heating units, a first z-axis temperature sensor group near the first heater group, and a first planar temperature sensor group on the periphery. The second chip has a second heater group consisting of several heating units on its surface near the fluid cavity, as well as a second z-axis temperature sensor group near the second heater group and a second planar temperature sensor group on the periphery.

[0008] Furthermore, the first planar temperature sensor group on the first chip has a temperature measuring unit arranged in the positive x-axis direction, negative x-axis direction, positive y-axis direction, and negative y-axis direction, centered on the first heater group, for a total of four temperature measuring units distributed in the four directions, forming the overall structure of the first planar temperature sensor group; the second planar temperature sensor group on the second chip has a temperature measuring unit arranged in the positive x-axis direction, negative x-axis direction, positive y-axis direction, and negative y-axis direction, centered on the second heater group, for a total of four temperature measuring units distributed in the four directions, forming the overall structure of the second planar temperature sensor group; The overall structure of the first planar temperature sensor group on the first chip and the second planar temperature sensor group on the second chip is symmetrical about the x-axis and y-axis in the plane formed by the x-axis and y-axis.

[0009] Furthermore, the first z-axis temperature sensor group on the first chip has a temperature measuring unit arranged in the positive x-axis direction, negative x-axis direction, positive y-axis direction, and negative y-axis direction, centered on the first heater group, for a total of four temperature measuring units distributed in the four directions, forming the overall structure of the first z-axis temperature sensor group; the second z-axis temperature sensor group on the second chip has a temperature measuring unit arranged in the positive x-axis direction, negative x-axis direction, positive y-axis direction, and negative y-axis direction, centered on the second heater group, for a total of four temperature measuring units distributed in the four directions, forming the overall structure of the second z-axis temperature sensor group; The overall structure of the first z-axis temperature sensor group on the first chip and the second z-axis temperature sensor group on the second chip is symmetrical about the x-axis and y-axis in the plane formed by the x-axis and y-axis.

[0010] Furthermore, the projections of the patterns of the first heater group of the first chip and the second heater group of the second chip onto the plane formed by the x-axis and y-axis coincide; the projections of the patterns of the first z-axis thermometer group of the first chip and the second z-axis thermometer group of the second chip onto the plane formed by the x-axis and y-axis also coincide. The projections of the patterns of the first planar thermometer group of the first chip and the second planar thermometer group of the second chip onto the plane formed by the x-axis and y-axis coincide.

[0011] Furthermore, the fluid filling the fluid cavity is either a liquid or a gas.

[0012] Furthermore, one end of the TGV conductive post is connected to all the heater and temperature sensor groups, while the other end extends to a port away from the fluid cavity as a contact pad for connecting external circuitry.

[0013] The present invention discloses a MEMS triaxial thermal convection accelerometer based on a TGV structure, which has the following gain effects: 1. Combining high sensitivity and high reliability. Using glass as the substrate material, its natural low thermal conductivity allows for excellent thermal isolation without the need for destructive deep silicon etching as with traditional silicon substrates. This ensures high sensitivity while greatly improving the mechanical strength and shock resistance of the sensor structure. 2. Achieve triaxial acceleration measurement. Through a unique three-layer stacked structure and a symmetrical temperature sensor layout, combined with an innovative z-axis differential measurement principle, triaxial acceleration detection is achieved on a single acceleration sensor chip; 3. Excellent electrical performance and integration. Utilizing TGV technology to achieve vertical electrical signal transmission replaces traditional wire bonding, shortening the signal path, reducing parasitic parameters, improving electrical performance, and facilitating smaller wafer-level packaging and high-density integration. Attached Figure Description

[0014] Figure 1 This is a side view of a TGV-based MEMS triaxial thermal convection accelerometer disclosed in an embodiment of the present invention. Figure 2 This is a three-dimensional schematic diagram of a MEMS triaxial thermal convection acceleration sensor based on a TGV structure disclosed in an embodiment of the present invention; Figure 3 This is a schematic diagram of the first chip planar structure of an embodiment of a MEMS triaxial thermal convection accelerometer based on a TGV structure disclosed in this invention. Figure 4 This is a schematic diagram of the second chip planar structure of an embodiment of a MEMS triaxial thermal convection accelerometer based on a TGV structure disclosed in this invention. Figure 5 This is a schematic diagram of the fluid flow field of a MEMS triaxial thermal convection accelerometer based on a TGV structure disclosed in an embodiment of the present invention. The markings in the diagram are as follows: 1. First chip; 2. Second chip; 3. Intermediate layer; 4. Fluid cavity; 5. TGV conductive post; 6. Contact pad; 11. First heater group; 12. First z-axis temperature sensor group; 13. First planar temperature sensor group; 21. Second heater group; 22. Second z-axis temperature sensor group; 23. Second planar temperature sensor group. Detailed Implementation

[0015] To better understand the purpose, structure, and function of this invention, the following detailed description of a MEMS triaxial thermal convection acceleration sensor based on a TGV structure is provided in conjunction with the accompanying drawings.

[0016] A triaxial thermal convection accelerometer based on a TGV structure MEMS employs a three-layer stacked structure, including a first chip 1, a second chip 2, and an intermediate layer 3 located between them. The intermediate layer 3 has a through-hole etched cavity. The first chip 1 and the second chip 2 are hermetically bonded to the two sides of the intermediate layer 3, thereby jointly enclosing a sealed fluid cavity 4. The fluid cavity 4 is filled with liquid or gas as the sensing medium. The substrate material of the first chip 1, the second chip 2, and the intermediate layer 3 is glass. Both the first chip 1 and the second chip 2 contain TGV conductive pillars 5 penetrating their respective substrates. On the inner surfaces of the first chip 1 and the second chip 2 near the fluid cavity 4, there are heater and thermometer arrays with overlapping pattern projections and symmetrical about the x-axis and y-axis, respectively. Specifically, a heater group is located at the center of each chip, and the heater group consists of four heating units distributed in four directions on the xy-plane. Around each heater group, four z-axis temperature sensing units are respectively arranged along the positive x-axis, negative x-axis, positive y-axis, and negative y-axis. These four units together form a z-axis temperature sensing group adjacent to the heater group. Around the z-axis temperature sensing group, four planar temperature sensing units are also arranged along the positive x-axis, negative x-axis, positive y-axis, and negative y-axis. These four units together form a planar temperature sensing group. One end of the TGV conductive post 5 connects to these heaters and temperature sensors, and the other end extends to the chip surface away from the fluid cavity 4 and is equipped with a contact pad 6 for connecting to external circuitry.

[0017] Because of the unique dual-chip layer and the overlapping and symmetrical design of the heater and temperature sensor arrays, when calculating the temperature difference caused by acceleration input in the x-axis or y-axis direction, for the first chip layer, if there is acceleration input in the x-axis direction, the temperature difference on the x-axis is the difference between the temperatures of the planar temperature sensing units in the positive x-axis direction and the negative x-axis direction. Similarly, for the second chip layer, the temperature difference on the x-axis is also the difference between the temperatures of the planar temperature sensing units in the positive x-axis direction and the negative x-axis direction. The total temperature difference caused by acceleration in the x-axis direction is the sum of these two temperature differences. This calculation method also applies to input acceleration in the y-axis direction. When calculating the temperature difference caused by input acceleration in the vertical z-axis direction, the vertical acceleration alters the temperature difference distribution in the vertical direction. The total z-axis temperature difference is the difference between the sum of the temperatures of each z-axis temperature sensing unit in the first z-axis temperature sensor group of the first chip layer and the sum of the temperatures of each z-axis temperature sensing unit in the second z-axis temperature sensor group of the second chip layer. The structure and temperature difference calculation method proposed in this invention enable the measurement of triaxial acceleration, and also achieve better reliability and long-term stability. Example

[0018] A triaxial thermal convection accelerometer based on a TGV structure MEMS is described below for ease of understanding. Figure 3 This is a schematic diagram of the first chip planar structure in an embodiment. The second heating unit represents a heating unit in the negative x-axis direction, the fourth heating unit represents a heating unit in the positive x-axis direction, the first heating unit represents a heating unit in the positive y-axis direction, and the third heating unit represents a heating unit in the negative y-axis direction. The second z-axis temperature measuring unit represents a z-axis temperature measuring unit placed in the negative x-axis direction, the fourth z-axis temperature measuring unit represents a z-axis temperature measuring unit placed in the positive x-axis direction, the first z-axis temperature measuring unit represents a z-axis temperature measuring unit placed in the positive y-axis direction, and the third z-axis temperature measuring unit represents a z-axis temperature measuring unit placed in the negative y-axis direction. The second planar temperature measuring unit represents a planar temperature measuring unit in the negative x-axis direction, the fourth planar temperature measuring unit represents a planar temperature measuring unit in the positive x-axis direction, the first planar temperature measuring unit represents a planar temperature measuring unit in the positive y-axis direction, and the third planar temperature measuring unit represents a planar temperature measuring unit in the negative y-axis direction. Similarly, Figure 4 This is a schematic diagram of the second chip planar structure in the embodiment. The sixth heating unit represents the heating unit in the negative x-axis direction, the eighth heating unit represents the heating unit in the positive x-axis direction, the fifth heating unit represents the heating unit in the positive y-axis direction, and the seventh heating unit represents the heating unit in the negative y-axis direction. The sixth z-axis temperature measuring unit represents the z-axis temperature measuring unit placed in the negative x-axis direction, the eighth z-axis temperature measuring unit represents the z-axis temperature measuring unit placed in the positive x-axis direction, the fifth z-axis temperature measuring unit represents the z-axis temperature measuring unit placed in the positive y-axis direction, and the seventh z-axis temperature measuring unit represents the z-axis temperature measuring unit placed in the negative y-axis direction. The sixth planar temperature measuring unit represents the planar temperature measuring unit in the negative x-axis direction, the eighth planar temperature measuring unit represents the planar temperature measuring unit in the positive x-axis direction, the fifth planar temperature measuring unit represents the planar temperature measuring unit in the positive y-axis direction, and the seventh planar temperature measuring unit represents the planar temperature measuring unit in the negative y-axis direction. With the above definitions, the acceleration in the x-axis, y-axis, and z-axis directions can be described by the temperature measured by each temperature measuring unit.

[0019] Acceleration in the x-axis direction: (Fourth Plane Temperature Measurement Unit - Second Plane Temperature Measurement Unit) + (Eighth Plane Temperature Measurement Unit - Sixth Plane Temperature Measurement Unit); Acceleration in the y-axis direction: (First plane temperature measurement unit - Third plane temperature measurement unit) + (Fifth plane temperature measurement unit - Seventh plane temperature measurement unit); Acceleration in the z-axis direction: (First z-axis temperature measurement unit + Second z-axis temperature measurement unit + Third z-axis temperature measurement unit + Fourth z-axis temperature measurement unit) - (Fifth z-axis temperature measurement unit + Sixth z-axis temperature measurement unit + Seventh z-axis temperature measurement unit + Eighth z-axis temperature measurement unit); The purpose of this calculation method is that when there is input acceleration in the x or y direction, the planar temperature sensor will measure the temperature difference related to the magnitude of the acceleration. The acceleration in the z-axis direction is calculated by subtracting the sum of the temperatures measured by all z-axis temperature sensing units on the second chip from the sum of the temperatures measured by all z-axis temperature sensing units on the first chip. The symmetrical and overlapping projection structure eliminates the temperature difference caused by input acceleration in the x or y direction, so the temperature difference signal of the acceleration in the z-axis direction is not affected by the x or y direction. When external acceleration is input in the z-axis direction, the formula for calculating the acceleration in the z-axis direction will calculate the temperature difference caused by the acceleration and thus deduce the magnitude of the acceleration. For example... Figure 5 As shown, when the fluid flows vertically in the closed fluid cavity due to vertical acceleration, it will spread to the left and right after touching the upper wall. However, since the structure of the planar thermometer group on the x and y planes is symmetrically distributed, the fluid flow caused by the z-axis acceleration will not be reflected in the temperature difference measured by the planar thermometer group, thus realizing the measurement of the acceleration signal in the z-axis direction.

[0020] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of the present invention.

Claims

1. A MEMS tri-axial thermal convection acceleration sensor based on TGV structure, characterized in that ,Adopt three layers of stacking structure, first chip (1) and second chip (2) and middle layer (3) form fluid cavity (4); The substrate material of first chip (1), second chip (2) and middle layer (3) is glass, wherein first chip (1), second chip (2) further comprise TGV conductive pillar (5) through them; The surface of first chip (1) close to fluid cavity (4) is provided with first heater group (11) composed of several heating units, and first z-axis temperature detector group (12) close to first heater group (11) and peripheral first plane temperature detector group (13); The surface of second chip (2) close to fluid cavity (4) is provided with second heater group (21) composed of several heating units, and second z-axis temperature detector group (22) close to second heater group (21) and peripheral second plane temperature detector group (23).

2. The MEMS three-axis thermal convection acceleration sensor based on TGV structure according to claim 1, wherein, The first plane temperature detector group (13) on the first chip (1) is provided with one temperature measuring unit in the positive direction of x-axis, the negative direction of x-axis, the positive direction of y-axis and the negative direction of y-axis with the first heater group (11) as the center, and four temperature measuring units are distributed in the four directions, forming the overall structure of the first plane temperature detector group (13); The second plane temperature detector group (23) on the second chip (2) is provided with one temperature measuring unit in the positive direction of x-axis, the negative direction of x-axis, the positive direction of y-axis and the negative direction of y-axis with the second heater group (21) as the center, and four temperature measuring units are distributed in the four directions, forming the overall structure of the second plane temperature detector group (23). The overall structure of the first plane temperature detector group (13) on the first chip (1) and the second plane temperature detector group (23) on the second chip (2) is symmetrical about the x-axis and the y-axis in the plane formed by the x-axis and the y-axis.

3. The MEMS three-axis thermal convection acceleration sensor based on TGV structure according to claim 1, wherein, The first z-axis temperature detector group (12) on the first chip (1) is provided with one temperature measuring unit in the positive direction of x-axis, the negative direction of x-axis, the positive direction of y-axis and the negative direction of y-axis with the first heater group (11) as the center, and four temperature measuring units are distributed in the four directions, forming the overall structure of the first z-axis temperature detector group (12); The second z-axis temperature detector group (22) on the second chip (2) is provided with one temperature measuring unit in the positive direction of x-axis, the negative direction of x-axis, the positive direction of y-axis and the negative direction of y-axis with the second heater group (21) as the center, and four temperature measuring units are distributed in the four directions, forming the overall structure of the second z-axis temperature detector group (22). The overall structure of the first z-axis temperature detector group (12) on the first chip (1) and the second z-axis temperature detector group (22) on the second chip (2) is symmetrical about the x-axis and the y-axis in the plane formed by the x-axis and the y-axis.

4. A MEMS three-axis thermal convection acceleration sensor based on TGV structure as claimed in claim 1, wherein, The projection of the first heater group (11) of the first chip (1) and the second heater group (21) of the second chip (2) on the plane formed by the x-axis and the y-axis is coincident; The projection of the first z-axis temperature detector group (12) of the first chip (1) and the second z-axis temperature detector group (22) of the second chip (2) on the plane formed by the x-axis and the y-axis is coincident; The projection of the first planar temperature sensor group (13) of the first chip (1) and the second planar temperature sensor group (23) of the second chip (2) on the plane formed by the x-axis and the y-axis is coincident.

5. A MEMS three-axis thermal convection acceleration sensor based on TGV structure according to claim 1, wherein, The fluid filled in the fluid cavity (4) is liquid or gas.

6. A MEMS three-axis thermal convection acceleration sensor based on TGV structure according to claim 1, wherein, One end of the TGV conductive post (5) is connected with all the heater groups and temperature sensor groups, and the other end extends to the port away from the fluid cavity (4) as a contact pad (6) for connecting external circuits.

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