Fluid wall shear pressure stress composite sensor chip and manufacturing method thereof

Abstract

The invention relates to a fluid wall shear pressure stress composite sensor chip and a manufacturing method thereof, and belongs to the technical field of MEMS sensors. Comprising a bottom electrode layer, a conductive substrate layer, an insulating supporting layer, a pressure sensitive layer, a metal bonding layer and a shear stress sensitive layer which are sequentially integrated in the lamination direction. The bottom electrode layer is provided with an independent pressure measuring electrode and an independent shear stress measuring electrode; the conductive substrate layer is divided into a plurality of conductive areas through the isolation grooves; the insulating support layer is provided with a vertically through electrode through hole and a double-cavity structure, and double cavities comprise a top cavity and a bottom cavity which are arranged in a through manner; the pressure sensitive layer is positioned between the top concave cavity and the bottom concave cavity; the metal bonding layer is divided into a plurality of bonding areas through the isolation grooves; the shear stress sensitive layer is connected with the insulating supporting layer through the metal bonding layer. According to the invention, in-situ synchronous measurement of fluid wall shear stress and pressure is realized, and the spatial resolution of the sensor is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of MEMS sensors, and in particular relates to a fluid wall shear and compression stress composite sensor chip and a manufacturing method thereof. Background Art

[0002] In the fields of fluid mechanics and engineering testing, accurate measurement of fluid wall shear and compressive stresses is crucial for applications such as turbulence characterization, fluid dynamics analysis, and aerodynamic optimization. Wall shear stress is related to fluid friction, while compressive stress reflects the positive force acting on the fluid. Together, they influence the properties of the fluid boundary layer and its dynamic behavior. Therefore, simultaneous measurement of both wall shear and compressive stresses is crucial for comprehensive characterization of the flow field. The small magnitude, high dynamics, and small flow feature sizes of both wall shear and compressive stresses pose significant measurement challenges. Traditional measurement techniques have numerous drawbacks, including poor sensitivity, making it difficult to capture subtle changes in these minute quantities; large size, which is unsuitable for space-critical applications; and potential interference with the original fluid flow field. Furthermore, most current MEMS sensors can only measure a single type of wall stress, such as shear or compressive stress, making simultaneous measurement of both difficult and challenging, limiting their application in complex flow field analysis.

[0003] Related technologies typically use separate compressive stress sensors or two-dimensional shear stress sensors. To date, there is no composite sensor capable of integrating the two-dimensional shear stress and compressive stress of a fluid wall. While existing technologies have leveraged MEMS integrated processing technology to integrate compressive stress sensors and two-dimensional shear stress sensors on the same millimeter-scale chip, achieving a degree of structural compactness and simplified processing, array-based measurement cannot accurately measure the flow characteristics at key points within the flow field due to the complex temporal and spatial variations in the stress distribution within the flow field. Summary of the Invention

[0004] Technical issues to be solved: To overcome the shortcomings of existing technologies, the present invention provides a fluid wall shear and compressive stress composite sensor chip and its manufacturing method. This chip forms a capacitive floating shear stress and pressure measurement combination in three dimensions, enabling in-situ simultaneous measurement of fluid wall shear stress and pressure, thereby improving the sensor's spatial resolution. The bottom cavity and the conductive substrate form a capacitive absolute pressure cavity, while the top cavity provides floating space for the shear stress-sensitive layer, preventing signal crosstalk.

[0005] The technical solution of the present invention is: a fluid wall shear and compressive stress composite sensor chip, comprising a bottom electrode layer, a conductive base layer, an insulating support layer, a pressure sensitive layer, a metal bonding layer and a shear stress sensitive layer sequentially integrated along the stacking direction; The bottom electrode layer is provided with independent pressure measurement electrodes and shear stress measurement electrodes; The conductive base layer is divided into a plurality of conductive areas by isolation grooves, wherein the middle area constitutes the pressure measurement lower electrode plate; The insulating support layer is provided with a vertically penetrating electrode through-hole and a double-cavity structure, wherein the double-cavity includes a top cavity and a bottom cavity which are arranged through-through, and the depth of the top cavity is greater than that of the bottom cavity; The pressure sensitive layer is located between the top cavity and the bottom cavity, and forms a capacitive pressure measurement part with the conductive base layer; The metal bonding layer is divided into a plurality of bonding areas by isolation grooves; The shear stress sensitive layer is connected to the insulating support layer through a metal bonding layer, and includes a capacitive shear stress measuring part consisting of movable comb teeth and fixed comb teeth; Among them, the pressure-sensitive layer and the shear stress-sensitive layer are stacked and integrated in the vertical space to realize the in-situ synchronous measurement of the fluid wall shear stress and pressure.

[0006] A further technical solution of the present invention is: metal is filled in the electrode through-holes of the insulating support layer to transmit the electrical signals of the shear stress sensitive layer and the pressure sensitive layer to the bottom electrode layer, thereby realizing three-dimensional back leads for all signals.

[0007] A further technical solution of the present invention is that the electrode through-hole has a diameter of 50-100 μm and a depth-to-width ratio of ≥2.5:1, and is processed by a femtosecond laser process. A further technical solution of the present invention is: the top cavity depth of the insulating support layer is 100-150 μm, the bottom cavity depth is 50-100 μm, and the depth ratio is ≥1.5:1, ensuring that the floating space of the shear stress sensitive layer and the deformation range of the pressure sensitive layer do not interfere with each other.

[0008] A further technical solution of the present invention is: the pressure sensitive layer is a circular or rectangular low-resistance silicon film with a thickness of 1-10 μm, the edge of which is supported by a bottom cavity, and the bottom cavity is combined with a conductive base layer and an insulating support layer to form a sealed absolute pressure cavity. A further technical solution of the present invention is that the shear stress sensitive layer includes a fixed component and a movable component: The fixing assembly includes a fixing anchor point and evenly arranged fixing comb teeth, wherein the fixing anchor point is bonded to the metal bonding layer; The movable component includes a folding beam, a sensitive unit and movable comb teeth. The sensitive unit is connected to a fixed anchor point through the folding beam. The movable comb teeth are evenly arranged on the sensitive unit. The movable comb teeth and the fixed comb teeth form a differential capacitor structure.

[0009] A further technical solution of the present invention is that the folding beam is a symmetrical multi-fold structure, so that the sensitive unit produces in-plane displacement under the action of shear stress. A further technical solution of the present invention is that the metal bonding layer is a chromium / gold composite film with a thickness of 100-500nm, and the isolation groove width is 30-50um, isolating the electrical signal transmission paths of each bonding area. A further technical solution of the present invention is that the conductive base layer is low-resistance silicon with a thickness of 200-300 μm, and the isolation trench thereof penetrates the entire layer, and the conductive area formed by the separation includes a lower electrode plate and multiple shear stress electrode areas: The lower electrode plate is connected to the pressure measuring electrode; The shear stress electrode regions are respectively connected to the movable comb teeth and the fixed comb teeth of the shear stress sensitive layer.

[0010] A method for manufacturing a fluid wall shear and compressive stress composite sensor chip, the specific steps are as follows: The top cavity is etched on the front side of the BF33 wafer, a silicon film is deposited to form a pressure-sensitive layer, electrode through-holes are processed by femtosecond laser, and the bottom cavity is etched on the back side; After the conductive silicon wafer is anodically bonded to the BF33 wafer, chromium / gold is sputtered on the front side to form a metal bonding layer; Chromium / gold is sputtered on the front side of the SOI wafer to form a bonding layer, which is then aligned with the double-layer wafer and then bonded to gold; The bottom electrode layer is formed by sputtering chromium / gold on the back of the three-layer wafer; Etch away the SOI base layer and buried oxide layer, etch the isolation groove on the back to BF33 to form a conductive base layer, and etch the front to the metal bonding layer to form a shear stress sensitive layer; Among them, the gold-gold bonding temperature is 300-400℃ and the pressure is 1.2-1.5MPa to avoid thermal mismatch at the interface of heterogeneous materials.

[0011] Beneficial effects The beneficial effects of the present invention are: through the vertical stacking integration of the pressure-sensitive layer and the shear-stress-sensitive layer, the present invention realizes zero-delay synchronous measurement of shear stress and pressure, and completely solves the temporal and spatial misalignment problem of the split sensor. The specific effects are as follows: 1. In terms of structural design, the present invention adopts a double-cavity structure, with the pressure-sensitive layer located between the upper and lower cavities, which not only ensures the floating space of the shear stress sensitive unit, but also enhances the sensitivity and stability of the pressure measurement part. The vertical stacking design of the shear stress measurement part and the pressure measurement part has the effect of direct spatial coupling of the flow field, eliminating the spatiotemporal errors of traditional split sensors, and significantly improving the spatial resolution of the chip, enabling it to accurately sense the changes in fluid wall stress in a small-scale area, meeting the needs of high-precision measurement. The overall size of the sensor is less than 16mm. 2 , sensitive area <2mm 2, which can meet the needs of fine measurement, and its spatial resolution is better than 2mm 2 The fluid wall shear and compressive stress composite sensor chip in the example realizes in-situ synchronous measurement of shear stress and pressure through innovative structural design, effectively improving the temporal and spatial consistency of the measurement.

[0012] The bottom cavity forms a sealed absolute pressure chamber, isolating fluid disturbances; the top cavity provides floating space, isolating the pressure-sensitive layer from deformation disturbances. Further constraints were established, with the top cavity depth (100–150 μm) greater than the bottom cavity depth (50–100 μm), resulting in a shear stress floating space volume that is 1.5 times greater than the pressure deformation volume, achieving physical isolation and mechanical coupling.

[0013] 2. In terms of manufacturing process, the present invention adopts mature micro-electromechanical system manufacturing technologies such as inductively coupled plasma etching, chemical vapor deposition, magnetron sputtering and gold-gold bonding to achieve high-precision processing and ensure the consistency and reliability of the device. In addition, through the metal filling of the through-hole structure, the signal transmission path is optimized, the back lead of the measurement signal is realized, the parasitic effect is reduced, and the stability and anti-interference ability of the signal acquisition are improved. The chip adopts the capacitive measurement principle, so that the shear stress and pressure signals are output in the form of capacitance changes, avoiding crosstalk between different signals, improving the stability and accuracy of the measurement, and simplifying the back-end circuit design and reducing the complexity of signal processing.

[0014] 3. Through innovative structural optimization and high-precision manufacturing technology, the present invention has significant advantages in synchronous measurement, signal stability, spatial resolution, structural reliability and adaptability to batch manufacturing. It can be widely used in high-precision measurement fields such as fluid mechanics research, aerodynamic testing and industrial fluid monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A cross-sectional view of a fluid wall shear and compressive stress composite sensor chip in an exemplary embodiment of the present invention is schematically shown; Figure 2 Schematically shows a bottom view of a sensor chip in an exemplary embodiment of the present invention; Figure 3 Schematically shows a top view of a conductive substrate layer in an exemplary embodiment of the present invention; Figure 4 Schematically shows a cross-sectional view of an insulating support layer in an exemplary embodiment of the present invention; Figure 5 Schematically shows a cross-sectional view of a combination of an insulating support layer and a pressure-sensitive layer in an exemplary embodiment of the present invention; Figure 6 Schematically shows a top view of a metal bonding layer in an exemplary embodiment of the present invention; Figure 7 Schematically shows a top view of a shear stress sensitive layer in an exemplary embodiment of the present invention; Figure 8 Schematically showing the steps of a method for manufacturing a fluid wall shear and compressive stress composite sensor chip in an exemplary embodiment of the present invention; Figure 9 The process flow chart of the fluid wall shear and compressive stress composite sensor chip in an exemplary embodiment of the present invention is schematically shown; Figure 10 Schematically shows a graph of shear stress and displacement of a sensitive unit under the action of a fluid in an exemplary embodiment of the present invention; Figure 11 Schematically shows a graph of compressive stress and central displacement of a pressure-sensitive layer under the action of a fluid in an exemplary embodiment of the present invention; Figure 12 The figure schematically shows a graph showing the percentage of the non-sensitive direction and the sensitive direction and the displacement in the sensitive direction of the shear stress sensitive unit under the action of fluid in an exemplary embodiment of the present invention.

[0016] Explanation of the accompanying symbols: 1. Bottom electrode layer, 11. Pressure measurement part electrode, 12. Shear stress measurement part electrode; 2. Conductive base layer, 21. Isolation groove, 22. First shear stress electrode area, 23. Lower electrode plate, 24. Second shear stress electrode area, 25. Third shear stress electrode area, 26. Fourth shear stress electrode area; 3. Insulating support layer, 31. Top cavity, 32. Electrode through hole, 33. Bottom cavity; 4. Pressure sensitive layer; 5. Metal bonding layer, 51. Isolation groove, 52. Bonding area; 6. Shear stress sensitive layer, 61. Fixed anchor point, 62. Fixed comb teeth, 63. Folding beam, 64. Movable comb teeth, 65. Sensitive unit. DETAILED DESCRIPTION

[0017] The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present invention, but should not be construed as limiting the present invention.

[0018] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0019] Based on the problem that existing sensors can only measure a single physical quantity (shear stress or pressure) and cannot synchronously obtain multi-dimensional mechanical parameters of the fluid wall, the invention provides a fluid wall shear and compressive stress composite sensor chip, including a bottom electrode layer, a conductive base layer, an insulating support layer, a pressure sensitive layer, a metal bonding layer and a shear stress sensitive layer sequentially integrated along the stacking direction; the bottom electrode layer is provided with an independent pressure measurement electrode and a shear stress measurement electrode; the conductive base layer is divided into multiple conductive areas by an isolation groove, the middle area of ​​which constitutes a pressure measurement lower electrode plate; the insulating support layer is provided with a vertically penetrating electrode through hole and a double The double cavity structure includes a top cavity and a bottom cavity that are arranged through each other, and the depth of the top cavity is greater than that of the bottom cavity; the pressure-sensitive layer is located between the top cavity and the bottom cavity, and constitutes a capacitive pressure measurement part with the conductive base layer; the metal bonding layer is divided into multiple bonding areas by the isolation groove; the shear stress-sensitive layer is connected to the insulating support layer through the metal bonding layer, and includes a capacitive shear stress measurement part consisting of movable comb teeth and fixed comb teeth; wherein the pressure-sensitive layer and the shear stress-sensitive layer are stacked and integrated in the vertical space to realize in-situ synchronous measurement of fluid wall shear stress and pressure.

[0020] The fluid wall shear and pressure composite sensor chip proposed in this paper utilizes an innovative structural design to create a unique three-dimensional capacitive floating shear stress and pressure measurement combination, enabling more precise measurements and significantly improving the sensor's spatial resolution. Furthermore, the chip outputs both shear stress and pressure signals as capacitive signals, effectively avoiding crosstalk between the different signals and significantly simplifying the complexity of the back-end circuitry. This fully meets the demand for precise in-situ measurement of fluid wall shear stress and pressure, and is expected to achieve significant technological breakthroughs in fluid dynamics research and various related engineering applications.

[0021] The above technical solution is further described below with reference to the accompanying drawings and examples: In one embodiment, referring to Figure 1 As shown, this embodiment of a fluid wall shear and compressive stress composite sensor chip includes, from bottom to top, a bottom electrode layer, a conductive base layer, an insulating support layer, a pressure-sensitive layer, a metal bonding layer, and a shear stress-sensitive layer. The conductive base layer, the insulating support layer, and the pressure-sensitive layer constitute the pressure measurement section, which measures fluid wall pressure. The insulating support layer, the metal bonding layer, and the shear stress-sensitive layer constitute the shear stress measurement section, which measures fluid wall shear stress. The pressure measurement section is located at the bottom of the shear stress measurement section, and the two sections operate simultaneously to provide in-situ, precise measurement of fluid wall shear stress and pressure.

[0022] Specifically, the bottom electrode layer is provided with a plurality of electrode points for extracting the measured shear stress and pressure electrical signals from the back side.

[0023] Specifically, isolation grooves are provided on the conductive base layer to form a plurality of conductive parts. The conductive parts transmit electrical signals of different structures, and the middle part forms the lower electrode plate of the pressure measuring part.

[0024] Specifically, two cavities are provided in the middle of the insulating support layer, namely a top cavity and a bottom cavity. The pressure sensitive layer is located in the middle of the two cavities. The edge of the bottom cavity supports the pressure sensitive layer. The bottom cavity is used as the absolute pressure cavity of the pressure measuring part, and the top cavity provides a floating space for the shear stress sensitive layer. Specifically, a plurality of through holes are provided around the insulating support layer, and the through holes are filled with metal for transmitting three-dimensional structure electrical signals.

[0025] Specifically, the pressure sensitive layer is a circular or rectangular sensitive film, which is used to sense pressure and produce deformation. The metal bonding layer is provided with a plurality of isolation grooves, and the bonding area is used for transmitting electrical signals in different areas.

[0026] Specifically, the metal bonding layer is used to connect the insulating support layer and the shear stress sensitive layer.

[0027] Specifically, the shear stress sensitive layer includes a movable component and a fixed component, the fixed component includes a fixed anchor point and fixed comb teeth, the fixed anchor point is connected to the metal bonding layer, and the fixed comb teeth are evenly arranged on the fixed anchor point. The movable component includes a number of folding beams, sensitive units and movable comb teeth, the folding beams connect the sensitive units and the fixed anchor points, and the movable comb teeth are evenly arranged on the sensitive units and match the fixed comb teeth.

[0028] The innovative structural optimization and high-precision manufacturing process of the above-mentioned fluid wall shear and compressive stress composite sensor chip have significant advantages in synchronous measurement, signal stability, spatial resolution, structural reliability and adaptability to batch manufacturing. It can be widely used in high-precision measurement fields such as fluid mechanics research, aerodynamic testing and industrial fluid monitoring.

[0029] In one embodiment, referring to Figure 1 As shown, the conductive base layer 2, insulating support layer 3, and pressure-sensitive layer 4 constitute the pressure measurement section, which measures fluid wall pressure. The insulating support layer 3, metal bonding layer 5, and shear stress-sensitive layer 6 constitute the shear stress measurement section, which measures fluid wall shear stress. The pressure measurement section is located at the bottom of the shear stress measurement section, and the two sections operate simultaneously to provide precise in-situ measurement of fluid wall shear stress and pressure.

[0030] In one embodiment, referring to Figure 2As shown, the material of the bottom electrode layer 1 can be chromium-gold, with thicknesses of 20-50 nm and 80-450 nm respectively. The electrodes are divided into pressure measurement part electrodes 11 and shear stress measurement part electrodes 12. These electrodes are distributed in different isolation areas and are used to lead out the shear stress and pressure electrical signals measured from the back.

[0031] In one embodiment, referring to Figure 3 As shown, the material of the conductive base layer 2 can be low-resistance silicon of 200-300 um. An isolation groove 21 is provided on the conductive base layer to form a plurality of conductive parts 22-26. Each conductive part transmits electrical signals of different structures, and the middle part forms the lower electrode 23 of the pressure measuring part.

[0032] In one embodiment, referring to Figure 4 As shown, the material of the insulating support layer 3 can be Borofloat 33, with a thickness of 200-300 um. There are two cavities in the middle, namely the top cavity 31 and the bottom cavity 33. The top cavity 31 is 100-150 um deep, and the bottom cavity 33 is 50-100 um deep. The bottom cavity 33 is the absolute pressure cavity of the pressure measurement part, and the top cavity 31 provides a floating space for the shear stress sensitive layer. Four electrode through holes 32 are distributed around the cavity for transmitting electrical signals.

[0033] In one embodiment, referring to Figure 5 As shown, the material of the pressure-sensitive layer 4 can be 1-10 um low-resistance silicon, and its shape can be circular or rectangular. It is used to sense pressure and form a parallel capacitor with the conductive base layer 2. It deforms under the action of pressure. The pressure-sensitive layer 4 is located between the two cavities, and the edge of the bottom cavity supports the pressure-sensitive layer 4.

[0034] In one embodiment, referring to Figure 6 As shown, the material of the metal bonding layer 5 can be chromium-gold, with thicknesses of 20-50nm and 80-450nm respectively. The metal bonding layer 5 is provided with several isolation grooves 51 for transmitting electrical signals in different areas; the bonding area 52 is used to connect the insulating support layer 3 and the shear stress sensitive layer 6.

[0035] In one embodiment, referring to Figure 7 As shown, the shear stress sensitive layer 6 can be 30-50um low-resistance silicon, including a movable component and a fixed component. The fixed component includes a fixed anchor point 61 and a fixed comb tooth 62. The fixed anchor point 61 is connected to the metal bonding layer 5. The fixed comb teeth 62 are evenly arranged on the fixed anchor point 61. The movable component includes a number of folding beams 63, sensitive units 65 and movable comb teeth 64. The folding beam 63 connects the sensitive unit 65 and the fixed anchor point 61. The movable comb teeth 64 are evenly arranged on the sensitive unit and match the fixed comb teeth 62.

[0036] Furthermore, this exemplary embodiment also provides a method for manufacturing a fluid wall shear stress composite sensor chip. Figure 8 and Figure 9 As shown, the method for manufacturing the fluid wall shear stress sensor chip may include: steps S1 to S5.

[0037] Step S1: preparing structures such as a cavity, a pressure sensitive membrane, and an electrode hole on a BF33 wafer.

[0038] Sub-step S11: patterning a cavity structure on the front side of the cleaned BF33 wafer by photolithography, and etching a top cavity by using an inductively coupled plasma etching process.

[0039] Sub-step S12: patterning the cavity shape on the front side of the BF33 wafer by photolithography, depositing a silicon film in the top cavity by chemical vapor deposition, and forming a pressure-sensitive layer by a lift-off process.

[0040] Sub-step S13: using a femtosecond laser process to etch through holes on the front side of the BF33 wafer to form electrode holes; Sub-step S14: patterning a cavity structure on the back side of the BF33 wafer by photolithography, and etching a bottom cavity by using an inductively coupled plasma etching process.

[0041] Step S2: Anodic bonding process between conductive silicon wafer and BF33 wafer and preparation of metal bonding layer Sub-step S21: Place the cleaned conductive silicon wafer and the BF33 wafer in step S1 in a photolithography machine for alignment, and perform anodically bonding in a bonding machine to form a double-layer wafer.

[0042] Sub-step S22: Photolithographically patterning the bonding layer shape on the front side of the double-layer wafer.

[0043] Sub-step S23: sputtering metal chromium-gold on the front side of the double-layer wafer using a magnetron sputtering process, with thicknesses of 20 nm and 300 nm respectively.

[0044] Sub-step S24: placing the sputtered double-layer wafer in an acetone solution, and placing it in an ultrasonic instrument for stripping to remove the photoresist and form the bonding layer.

[0045] Step S3: Preparation of a metal bonding layer on the SOI wafer.

[0046] Sub-step S31: patterning the bonding layer shape on the device layer of the SOI wafer by photolithography.

[0047] Sub-step S32: using the magnetron sputtering process to sputter metal chromium-gold on the front surface of the SOI wafer, with thicknesses of 20 nm and 300 nm respectively.

[0048] Sub-step S33: placing the sputtered double-layer wafer in an acetone solution, and placing it in an ultrasonic instrument for stripping to remove the photoresist and form the bonding layer.

[0049] Step S4: gold-gold bonding between the SOI wafer and the double-layer wafer, and back electrode fabrication.

[0050] Sub-step S41: aligning the SOI wafer and the double-layer wafer and performing gold-gold bonding to form a three-layer wafer.

[0051] Sub-step S42: Photolithographically patterning the back side of the three-layer wafer to form electrode points.

[0052] Sub-step S43: using the magnetron sputtering process to sputter metal chromium-gold on the back side of the three-layer wafer, with thicknesses of 20 nm and 300 nm respectively.

[0053] Sub-step S44: removing the photoresist by using the stripping process to form the bottom electrode layer.

[0054] Step S5: preparing a shear stress sensitive structure and etching an isolation structure.

[0055] Sub-step S51: using the inductively coupled plasma etching process to remove the base layer and buried oxide layer of the three-layer wafer.

[0056] Sub-step S52: patterning an isolation trench structure on the back side of the three-layer wafer, etching to BF33 using the inductively coupled plasma etching process to form the conductive base layer.

[0057] Sub-step S53: patterning a sensitive structure on the front side of the three-layer wafer, and etching to the metal bonding layer using the inductively coupled plasma etching process to form the shear stress sensitive layer.

[0058] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and purpose of the present invention.

Claims

1. A fluid wall shear and compressive stress composite sensor chip, characterized by: It includes a bottom electrode layer, a conductive base layer, an insulating support layer, a pressure sensitive layer, a metal bonding layer and a shear stress sensitive layer which are sequentially integrated along the stacking direction; The bottom electrode layer is provided with independent pressure measurement electrodes and shear stress measurement electrodes; The conductive base layer is divided into a plurality of conductive areas by isolation grooves, wherein the middle area constitutes the pressure measurement lower electrode plate; The insulating support layer is provided with a vertically penetrating electrode through-hole and a double-cavity structure, wherein the double-cavity includes a top cavity and a bottom cavity which are arranged through-through, and the depth of the top cavity is greater than that of the bottom cavity; The pressure sensitive layer is located between the top cavity and the bottom cavity, and forms a capacitive pressure measurement part with the conductive base layer; The metal bonding layer is divided into a plurality of bonding areas by isolation grooves; The shear stress sensitive layer is connected to the insulating support layer through a metal bonding layer, and includes a capacitive shear stress measuring part consisting of movable comb teeth and fixed comb teeth; Among them, the pressure-sensitive layer and the shear stress-sensitive layer are stacked and integrated in the vertical space to realize the in-situ synchronous measurement of the fluid wall shear stress and pressure.

2. The fluid wall shear and compressive stress composite sensor chip according to claim 1, characterized in that: The electrode through holes of the insulating support layer are filled with metal to transmit the electrical signals of the shear stress sensitive layer and the pressure sensitive layer to the bottom electrode layer, thereby realizing the back three-dimensional leads of all signals.

3. The fluid wall shear and compressive stress composite sensor chip according to claim 2, characterized in that: The electrode through-hole has a diameter of 50-100 μm and a depth-to-width ratio of ≥2.5:1, and is processed by a femtosecond laser process.

4. The fluid wall shear and compressive stress composite sensor chip according to claim 1, characterized in that: The top cavity depth of the insulating support layer is 100-150 μm, the bottom cavity depth is 50-100 μm, and the depth ratio is ≥1.5:1, ensuring that the floating space of the shear stress sensitive layer and the deformation range of the pressure sensitive layer do not interfere with each other.

5. The fluid wall shear and compressive stress composite sensor chip according to claim 4, characterized in that: The pressure sensitive layer is a circular or rectangular low-resistance silicon film with a thickness of 1-10 μm. Its edge is supported by a bottom cavity, which is combined with a conductive base layer and an insulating support layer to form a sealed absolute pressure cavity.

6. The fluid wall shear and compressive stress composite sensor chip according to claim 1, characterized in that: The shear stress sensitive layer includes a fixed component and a movable component: The fixing assembly includes a fixing anchor point and evenly arranged fixing comb teeth, wherein the fixing anchor point is bonded to the metal bonding layer; The movable component includes a folding beam, a sensitive unit and movable comb teeth. The sensitive unit is connected to a fixed anchor point through the folding beam. The movable comb teeth are evenly arranged on the sensitive unit. The movable comb teeth and the fixed comb teeth form a differential capacitor structure.

7. The fluid wall shear and compressive stress composite sensor chip according to claim 6, characterized in that: The folding beam is a symmetrical multi-fold structure, which enables the sensitive unit to generate in-plane displacement under the action of shear stress.

8. The fluid wall shear and compressive stress composite sensor chip according to claim 1, characterized in that: The metal bonding layer is a chromium / gold composite film with a thickness of 100-500nm and an isolation groove width of 30-50um, which isolates the electrical signal transmission paths of each bonding area.

9. The fluid wall shear and compressive stress composite sensor chip according to claim 1, characterized in that: The conductive base layer is low-resistance silicon with a thickness of 200-300 μm. The isolation trench depth runs through the entire layer, and the conductive area formed by the separation includes a lower plate and multiple shear stress electrode areas: The lower electrode plate is connected to the pressure measuring electrode; The shear stress electrode regions are respectively connected to the movable comb teeth and the fixed comb teeth of the shear stress sensitive layer.

10. A method for manufacturing a fluid wall shear and compressive stress composite sensor chip according to any one of claims 1 to 9, characterized in that The specific steps are as follows: The top cavity is etched on the front side of the BF33 wafer, a silicon film is deposited to form a pressure-sensitive layer, electrode through-holes are processed by femtosecond laser, and the bottom cavity is etched on the back side; After the conductive silicon wafer is anodically bonded to the BF33 wafer, chromium / gold is sputtered on the front side to form a metal bonding layer; Chromium / gold is sputtered on the front side of the SOI wafer to form a bonding layer, which is then aligned with the double-layer wafer and then bonded to gold; The bottom electrode layer is formed by sputtering chromium / gold on the back of the three-layer wafer; Etch away the SOI base layer and buried oxide layer, etch the isolation groove on the back to BF33 to form a conductive base layer, and etch the front to the metal bonding layer to form a shear stress sensitive layer; The gold-gold bonding temperature is 300-400°C and the pressure is 1.2-1.5MPa to avoid thermal mismatch at the interface of heterogeneous materials.

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