Electrothermal micro-motion platform integrated with flexoelectric position detection, detection method and preparation method of electro-thermal micro-motion platform

Abstract

The invention discloses an electric heating micro-motion platform integrated with flexoelectric position detection, a detection method and a preparation method thereof, and belongs to the technical field of micro electro mechanical systems, and the platform comprises a peripheral supporting structure, an electric heating driving structure, a micro-platform, and a flexoelectric position detection structure used for detecting the position and the motion state of the micro-platform. According to the invention, the flexoelectric position detection structure and the electrothermal micro-motion platform are integrated, so that the attitude information of the deflection angle and the deflection direction of the micro-motion structure can be stably obtained in real time and with high precision under the condition that the motion of the micro-motion structure is not influenced; and the complexity of a closed-loop control attitude feedback circuit of the device and a system thereof can be remarkably reduced, the structure and the size of related application products are optimized, and miniaturization and light weight of the device are realized.

Description

Technical Field

[0001] The present invention relates to the field of micro-electromechanical technology, and in particular to an electrothermal micro-motion platform with integrated flexoelectric position detection, a detection method and a preparation method thereof. Background Art

[0002] Electrothermal-driven MEMS (Micro-Electro-Mechanical System) micro-motion platforms are often used in MEMS devices such as micromirrors, micro-tweezers, and micro-switches because they can achieve large driving force and displacement with only a relatively low input voltage. They have received widespread attention and in-depth research in the fields of spectral analysis, bioengineering, and optical communications.

[0003] The stability of the electrothermal-driven MEMS micro-motion platform is an important indicator to ensure the performance of itself and the corresponding products. In this regard, there are currently two main methods: one is the material optimization of the electrothermal-driven structure, that is, by optimizing the material of the electrothermal-driven structure to obtain better mechanical strength and oxidation resistance, thereby improving the long-term stability of the device; the other is the position feedback of the electrothermal-driven MEMS micro-motion platform, that is, by introducing position information feedback in the device or system to form a closed-loop control, thereby improving the response speed, control accuracy and even stability of the device. In comparison, the second method focuses more on the control and application of the device, so it is more studied in engineering applications. However, the existing detection methods based on optical reflection and interference, detection methods based on electromagnetic coupling, position detection methods based on capacitance, and position detection methods based on piezoresistive resistance have deficiencies in system integration, detection circuits, or material compatibility. How to more effectively detect the position of the electrothermal-driven MEMS micro-motion platform is a difficult problem that needs to be solved urgently.

[0004] Different from the piezoelectric effect, the flexoelectric effect is a kind of electromechanical coupling property widely present in all dielectric materials. It is a phenomenon that the inversion symmetry is locally destroyed due to the strain gradient or non-uniform strain field, which leads to the polarization of crystals or even centrosymmetric crystals. The definition of the flexoelectric effect is: Where P l is the induced electric polarization, μ ijkl is the fourth-order flexoelectric coefficient tensor, ε ij is the elastic strain of the material, x k is the direction of the gradient. Therefore, the flexoelectric effect can be used to design sensors such as pressure, micro-mass, and micro-displacement. Compared with sensors based on the piezoelectric effect, flexoelectric sensors have more materials to choose from, and as the size of the structure decreases, the flexoelectric effect increases. Therefore, it is very suitable for application scenarios where small deformation and large strain gradient exist. Summary of the invention

[0005] The purpose of the present invention is to overcome the technical problems existing in the position detection method of the existing electrothermal MEMS micro-motion platform, and to provide an electrothermal micro-motion platform with integrated flexure electric position detection, a detection method and a preparation method thereof.

[0006] The present invention is achieved through the following technical solutions:

[0007] In a first aspect, an electrothermal MEMS micro-motion platform with integrated flexural electric position detection is provided, comprising a peripheral support structure, an electrothermal drive structure, a micro-platform, and a flexural electric position detection structure for detecting the position and motion state of the micro-platform.

[0008] In some embodiments, the flexoelectric position sensing structure is composed of a conductive material and a flexoelectric dielectric material.

[0009] Preferably, the flexoelectric position detection structure is formed by sequentially stacking a conductive material, a flexoelectric dielectric material, and a conductive material to form a sandwich detection structure.

[0010] Preferably, the flexoelectric position detection structure is a composite layered detection structure formed by multiple alternating laminations of conductive material and flexoelectric dielectric material.

[0011] Preferably, the flexural dielectric material is a dielectric material that only has flexural electric properties (graphene, hexagonal boron nitride, PDMS, Al2O3) or a composite material composed of one or more dielectric materials that have both flexural electric properties and piezoelectric properties (LiNbO3, LiTaO3, PVDF, PZT, BaTiO3, SrTiO3, BST).

[0012] Preferably, the conductive material is a metal conductive material (including single-layer metal, composite metal, alloy), a composite polymer conductive material (including conductive plastic, conductive coating, conductive adhesive) or a structural polymer conductive material (including π-conjugated polymer, metal chelate, charge transfer polymer complex).

[0013] In a second aspect, a position detection method of an electrothermal micro-motion platform with integrated flexure electric position detection is provided, comprising:

[0014] The flexoelectric position detection structure undergoes a strain gradient change due to the action of the electrothermal driving structure, and electric polarization is generated according to the flexoelectric principle. The amount of charge is positively correlated with the magnitude of the strain gradient, and the direction of the polarization electric field is related to the direction of the strain gradient. The generated charges are enriched on the electrodes of the flexoelectric position detection structure, and the charges are introduced into a charge amplifier to be converted into voltage or current signals. By establishing a relationship between the voltage or current and the stress on the flexoelectric position detection structure, and a relationship between the stress on the flexoelectric position detection structure and the deflection angle of the micro-platform, the position and motion state of the micro-platform can be determined by measuring the voltage or current.

[0015] In a third aspect, a method for preparing an electrothermal-driven MEMS micro-motion platform with integrated flexoelectric position detection is provided, comprising the following main steps:

[0016] S1: Prepare a wafer, which is a finished SOI wafer or a composite layer wafer prepared by other processes, including a device layer (such as single crystal silicon, epitaxial polysilicon), an isolation layer (such as thermal silicon oxide, PECVD silicon oxide, etc.) and a support layer (such as single crystal silicon);

[0017] S2: Patterning a layer of conductive material on the surface of the wafer using a stripping process or an etching process to form a lower electrode and a lead of a flexoelectric position detection structure, wherein the patterned material is a metal conductive material (including a single layer of metal, a composite metal, an alloy), a composite polymer conductive material (including conductive plastics, conductive coatings, conductive adhesives) or a structural polymer conductive material (including π-conjugated polymers, metal chelates, and charge transfer polymer complexes);

[0018] S3: growing a layer of flexoelectric dielectric material on the wafer, the material being a dielectric material having only flexoelectric properties (graphene, hexagonal boron nitride, PDMS, Al2O3) or a composite layer of one or more dielectric materials having both flexoelectric and piezoelectric properties (LiNbO3, LiTaO3, PVDF, PZT, BaTiO3, SrTiO3, BST);

[0019] S4: Patterning the flexural dielectric material using a lift-off process or an etching process to form contact holes on structures such as leads and pads;

[0020] S5: Patterning a layer of conductive material on the surface of the wafer using a stripping process or an etching process to form an upper electrode and a lead of a flexoelectric position detection structure, wherein the patterned material is a metal conductive material (including a single layer of metal, a composite metal, an alloy), a composite polymer conductive material (including conductive plastics, conductive coatings, conductive adhesives) or a structural polymer conductive material (including π-conjugated polymers, metal chelates, and charge transfer polymer complexes);

[0021] S6: growing an insulating dielectric layer on the surface of the wafer, the insulating dielectric layer being SiO2, Si3N4, Al2O3, AlN, SiC, HfO2, polysilicon, polyimide, or a composite layer thereof, and then patterning the insulating dielectric layer to form contact holes on the lead and pad structures;

[0022] S7: growing a low thermal expansion coefficient film on the surface of the wafer, and patterning it to form contact holes on the lead and pad structures;

[0023] S8: growing a layer of conductive material as a heating resistor layer on the surface of the wafer, and forming contact holes on the lead and pad structures through patterning;

[0024] S9: growing a high thermal expansion coefficient film on the surface of the wafer, and patterning it to form contact holes on the lead and pad structures;

[0025] S10: Patterning a layer of conductive material on the surface of the wafer to form pads and leads;

[0026] S11: growing a layer of low thermal expansion coefficient film on the surface of the wafer and patterning it to form a protective layer for the lead and ensure that the pad is in an open window state;

[0027] S12: Perform photolithography, deep silicon etching and other processes on the back of the wafer to release the micro-motion platform structure to form the final electrothermal driven MEMS micro-motion platform structure.

[0028] It should be further explained that the technical features corresponding to the above options can be combined or replaced with each other to form a new technical solution if there is no conflict.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The present invention integrates the flexural electric position detection structure with the electrothermal driven micro-motion platform in an integrated manner. It can not only obtain the micro-platform deflection angle, deflection direction and other posture information in real time, stably and with high precision without affecting the movement of the micro-platform, but also significantly reduce the complexity of the device and its closed-loop control feedback circuit. At the same time, it plays an important role in optimizing the structure and size of related application products, and realizing the miniaturization and lightweight of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A schematic diagram of the structure of an electrothermal driven MEMS micro-motion platform with integrated flexoelectric position detection according to an embodiment of the present invention;

[0032] Figure 2 It is a schematic diagram of the structure of an electrothermal driven MEMS micro-motion platform for position detection using a flexoelectric sandwich detection structure according to an embodiment of the present invention;

[0033] Figure 3 This is a schematic diagram of the flexoelectric effect according to an embodiment of the present invention;

[0034] Figure 4 A schematic diagram of the structure of an electrothermal driven MEMS micro-motion platform with an integrated array-type flexure electrical position detection structure according to an embodiment of the present invention;

[0035] Figure 5 — Fig.15The present invention is a schematic diagram of a manufacturing process of an electrothermal-driven MEMS micro-motion platform with integrated flexoelectric position detection according to an embodiment of the present invention.

[0036] In the figure: 1-peripheral supporting structure; 2-electrothermal driving structure; 3-flexural electric position detection structure; 4-micro-platform; 3a-conductive material; 3b-piezoelectric material. DETAILED DESCRIPTION

[0037] The technical solution of the present invention is clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present application generally described and shown in the accompanying drawings here can be arranged and designed in various different configurations. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0038] It should be noted that the defects existing in the solutions in the above-mentioned prior art are the results obtained by the inventor after practice and careful research. Therefore, the discovery process of the above-mentioned problems and the solutions proposed in the embodiments of the present application for the above-mentioned problems below should all be the contributions made by the inventor to the present application in the process of invention and creation, and should not be understood as technical contents known to technical personnel in this field.

[0039] In view of the technical problems pointed out in the background technology, the embodiments provided by the present invention are as follows:

[0040] Example 1

[0041] In an exemplary embodiment, referring to Figure 1 , an electrothermal driven MEMS micro-motion platform with integrated flexural electric position detection is provided, comprising a peripheral support structure 1, an electrothermal driving structure 2, and a micro-platform 4. The peripheral support structure 1 is also provided with a flexural electric position detection structure 3 for detecting the position and motion state of the micro-platform 4. The peripheral support structure 1 is used to provide mechanical support for the entire electrothermal micro-motion platform; the electrothermal driving structure 2 is applied with an electrical driving signal from the outside to convert electrical energy into thermal energy, and further converts it into mechanical energy to drive the micro-platform 4 to complete unidirectional movement, multi-directional tilting movement, and vertical lifting movement; the flexural electric position detection structure 3 has high strain sensitivity and high force-to-electric conversion efficiency, and can change the charge distribution inside the material through the strain gradient, generate polarization, and output electrical signals to the outside; under the action of the electrothermal driving structure 2, the micro-platform 4 has the ability to move in one direction, tilt in multiple directions, and move vertically.

[0042] Furthermore, in the electrothermal driven MEMS micro-motion platform designed by the present invention, the specific form of the micro-platform 4 can be a micro-mirror, micro-tweezers, micro-cage or micro-cantilever; for the structural forms of micro-mirror, micro-tweezers and micro-cantilever, the micro-platform 4 is mechanically connected to the peripheral supporting structure 1 through the electrothermal driving structure 2, and the movement state of the micro-platform 4 is driven by the electrothermal driving structure 2; for the structural form of a micro-cage, the micro-platform 4 is integrated with the electrothermal driving structure 2 to form a whole, and has both electrothermal driving and movement functions.

[0043] Furthermore, the flexoelectric position detection structure 3 is formed by stacking the conductive material 3a, the flexoelectric dielectric material 3b, and the conductive material 3a in sequence to form a sandwich detection structure (see Figure 2 ), or a composite layered detection structure is formed by multiple alternating stacking of conductive material 3a and flexible dielectric material 3b.

[0044] Furthermore, the sensing method of the flexoelectric position detection structure 3 is strictly speaking the positive flexoelectric effect, and its principle is as follows: Figure 3 shown.

[0045] Specifically, the detection principle of the flexoelectric position detection structure 3 is as follows:

[0046] When a single electrothermal drive structure 2 is driven by an external electrical signal, electrical energy will be converted into thermal energy, and further converted into mechanical energy to make the electrothermal drive structure 2 move, and drive the micro-platform 4 to deflect, and at the same time cause the strain gradient of the flexural electric position detection structure 3 to change. Due to the positive flexural electric effect, the strain gradient caused will cause polarization, and the charge will be enriched through the conductive material of the flexural electric position detection structure 3, and the amount of charge generated by the polarization is positively correlated with the magnitude of the strain gradient, and the electrical polarity of the conductive material is related to the direction of the strain gradient. By introducing the charge into the charge amplifier, a voltage or current signal can be obtained, and the relationship between the voltage or current amplitude (or phase, frequency) and the deflection angle of the micro-platform 4 can be further established. The deflection angle of the micro-platform 4 when the corresponding electrothermal drive structure 2 acts can be determined by measuring the corresponding induced voltage or current. Similarly, the various deflection angles of the micro-platform 4 when multiple electrothermal drive structures 2 act alone or simultaneously can also be obtained. Since the size of the micro-platform 4 is known, after obtaining the deflection angles in each direction, the position and state of the micro-platform 4 can be finally analyzed through spatial geometry.

[0047] Example 2

[0048] Based on the same concept as in Example 1, the flexural electrical position detection structure 3 in this example can be located on the electrothermal drive structure 2 to form an integrated structure, while having both electrothermal drive and position detection functions.

[0049] Example 3

[0050] Based on the same concept as Example 1 and Example 2, refer to Figure 4 In this example, the flexural electric position detection structure 3 can be arranged in an array form on the peripheral support structure 1 or on the electrothermal drive structure 2. Through distributed detection, more dynamic data about the structure can be obtained, and more accurate deflection angle, deflection direction and other posture information of the micro-platform can be obtained.

[0051] Example 4

[0052] Based on the same concept as in Example 1, this example provides a preparation process for an electrothermal-driven MEMS micro-motion platform with integrated flexure electrical position detection. The detailed preparation method and the formed device structure are as follows:

[0053] 1. As Figure 5 , prepare a wafer, which may be a finished SOI wafer or a composite layer wafer prepared by other processes, including a device layer (such as single crystal silicon, epitaxial polysilicon), an isolation layer (such as thermal silicon oxide, PECVD silicon oxide, etc.) and a support layer (such as single crystal silicon);

[0054] 2. If Figure 6 , using a stripping process or an etching process to pattern a layer of conductive material on the surface of the wafer to form a lower electrode and a lead of a flexure electric position detection structure, wherein the patterned material is a metal conductive material (including a single layer of metal, a composite metal, an alloy), a composite polymer conductive material (including conductive plastics, conductive coatings, conductive adhesives) or a structural polymer conductive material (including π-conjugated polymers, metal chelates, and charge transfer polymer complexes);

[0055] 3. Such as Figure 7 , growing a layer of flexoelectric dielectric material on the wafer, which material can be a dielectric material with only flexoelectric properties (graphene, hexagonal boron nitride, PDMS, Al2O3) or a composite layer of one or more dielectric materials with both flexoelectric and piezoelectric properties (LiNbO3, LiTaO3, PVDF, PZT, BaTiO3, SrTiO3, BST);

[0056] 4. Use a stripping process or an etching process to pattern the flexural dielectric material to form contact holes on structures such as leads and pads;

[0057] 5. Such as Figure 8, using a stripping process or an etching process to pattern a layer of conductive material on the surface of the wafer to form an upper electrode and a lead of a flexure electric position detection structure, wherein the patterned material is a metal conductive material (including a single layer of metal, a composite metal, an alloy), a composite polymer conductive material (including conductive plastics, conductive coatings, conductive adhesives) or a structural polymer conductive material (including π-conjugated polymers, metal chelates, and charge transfer polymer complexes);

[0058] 6. As Fig. 9 , growing an insulating dielectric layer on the surface of the wafer, the insulating dielectric layer may be SiO2, Si3N4, Al2O3, AlN, SiC, HfO2, polysilicon, polyimide, or a composite layer thereof, and then patterning the insulating dielectric layer to form contact holes on the lead and pad structures;

[0059] 7. Such as Fig.10 , growing a layer of low thermal expansion coefficient film on the surface of the wafer, and patterning it to form contact holes on the lead and pad structures;

[0060] 8. As Fig.11 , growing a layer of conductive material as a heating resistor layer on the surface of the wafer, and forming contact holes on the lead and pad structures through patterning;

[0061] 9. As Fig.12 , growing a high thermal expansion coefficient film on the surface of the wafer and patterning it to form contact holes on the lead and pad structures;

[0062] 10. As Fig.13 , patterning a layer of conductive material on the surface of the wafer to form pads and leads;

[0063] 11. As Fig.14 , a layer of low thermal expansion coefficient film is grown on the surface of the wafer and patterned to form a protective layer for the leads and ensure that the pads are in an open window state;

[0064] 12. If Fig.15 , photolithography, deep silicon etching and other processes are performed on the back of the wafer to release the micro-motion platform structure and form the final electrothermal driven MEMS micro-motion platform structure.

[0065] In the above preparation process, the process and structure can be changed. For example, the flexoelectric position detection structure can be obtained by sequentially growing a conductive material, a flexoelectric material, and a conductive material on a wafer and then etching each layer.

[0066] The above specific implementation methods are detailed descriptions of the present invention. It cannot be determined that the specific implementation methods of the present invention are limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions and substitutions can be made without departing from the concept of the present invention, which should be regarded as belonging to the protection scope of the present invention.

Claims

1. An electrothermal micro-motion platform with integrated flexure electric position detection, comprising a peripheral support structure, an electrothermal drive structure, and a micro-platform, characterized in that: The peripheral support structure is also provided with a flexoelectric position detection structure for detecting the position and motion state of the micro-platform.

2. The electrothermal micro-motion platform with integrated flexoelectric position detection according to claim 1, characterized in that: The flexoelectric position detection structure is composed of a conductive material and a flexoelectric material.

3. The electrothermal micro-motion platform with integrated flexoelectric position detection according to claim 2, characterized in that: The flexoelectric position detection structure is formed by stacking a conductive material, a flexoelectric material, and a conductive material in sequence.

4. The electrothermal micro-motion platform with integrated flexoelectric position detection according to claim 2, characterized in that: The flexoelectric material is a composite material composed of one or more dielectric materials (graphene, hexagonal boron nitride, PDMS, Al2O3) that only have flexoelectric properties or dielectric materials (LiNbO3, LiTaO3, PVDF, PZT, BaTiO3, SrTiO3, BST) that have both flexoelectric and piezoelectric properties.

5. The electrothermal micro-motion platform with integrated flexoelectric position detection according to claim 2, characterized in that: The flexoelectric position detection structure is a sandwich detection structure composed of conductive materials and flexoelectric materials or a composite layered detection structure formed by multiple alternating stacking.

6. A method for detecting a position of an electrothermal micro-motion platform with integrated flexure electric position detection as claimed in any one of claims 1 to 5, characterized in that: include: The flexoelectric position detection structure is affected by the electrothermal driving structure and produces a strain gradient change. Electric polarization is generated according to the flexoelectric principle. The amount of charge is positively correlated with the size of the strain gradient, and the direction of the polarization electric field is related to the direction of the strain gradient. The generated charges are enriched on the conductive material, and the charges are introduced into the charge amplifier to be converted into voltage or current signals. The relationship between the voltage or current and the stress on the flexoelectric position detection structure, and the relationship between the stress on the flexoelectric position detection structure and the deflection angle of the micro-platform are established, thereby determining the position and motion state of the micro-platform by measuring the voltage or current.

7. The method for preparing an electrothermal micro-motion platform with integrated flexoelectric position detection according to claim 1 comprises the following main steps: S1: Prepare a wafer, which is a finished SOI wafer or a composite layer wafer prepared by other processes, including a device layer, an isolation layer and a support layer; S2: Patterning a layer of conductive material on the surface of the wafer to form a lower electrode and a lead of the flexoelectric position detection structure, wherein the patterned material is a metal conductive material, a composite polymer conductive material or a structural polymer conductive material; S3: growing a layer of flexoelectric dielectric material on the wafer, wherein the flexoelectric dielectric material is a dielectric material having only flexoelectric properties or a composite layer of one or more dielectric materials having both flexoelectric properties and piezoelectric properties; S4: Patterning the flexural dielectric material to form contact holes on structures such as leads and pads; S5: patterning a layer of conductive material on the surface of the wafer to form an upper electrode and a lead of the flexoelectric position detection structure, wherein the patterned material is a metal conductive material, a composite polymer conductive material, or a structural polymer conductive material; S6: growing an insulating dielectric layer on the surface of the wafer, the insulating dielectric layer being one or more of SiO2, Si3N4, Al2O3, AlN, SiC, HfO2, polysilicon, and polyimide, and then patterning the insulating dielectric layer to form contact holes on the lead and pad structures; S7: growing a low thermal expansion coefficient film on the surface of the wafer, and patterning it to form contact holes on the lead and pad structures; S8: growing a layer of conductive material as a heating resistor layer on the surface of the wafer, and forming contact holes on the lead and pad structures through patterning; S9: growing a high thermal expansion coefficient film on the surface of the wafer, and patterning it to form contact holes on the lead and pad structures; S10: Patterning a layer of conductive material on the surface of the wafer to form pads and leads; S11: growing a layer of low thermal expansion coefficient film on the surface of the wafer and patterning it to form a protective layer for the lead and ensure that the pad is in an open window state; S12: releasing the micro-motion platform structure to form a final electrothermal driven MEMS micro-motion platform structure.

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