Micro-nano device of semi-flexible sealing composite beam membrane island structure type and processing method thereof

Abstract

This invention discloses a semi-flexible sealed composite material beam-membrane-island structure for micro / nano devices and its fabrication method. The invention employs both rigid and flexible materials to construct the beam-membrane-island structure of the micro / nano device. The beam and island structures are made of rigid materials that can be fabricated in micro / nano dimensions, while flexible materials fill the periphery of the beam and island structures. The flexible filling layer acts as a "displacement coordination layer," ensuring a clear mechanical response while maintaining the high modulus of the silicon beam. Simultaneously, the local deformation of the flexible layer absorbs lateral coupling stress, allowing strain fields in different directions to be separated and amplified in the beam / island region. The flexible material forms a stress transition zone between the beam and island, preventing strong stress concentration in the pure silicon beam-island structure under concentrated loads. This invention still uses materials compatible with micro / nano fabrication processes as the main structural material, enabling integration with standard photolithography, reactive ion etching, deep silicon reactive ion etching, anodic bonding processes, through-silicon vias (TSVs), and glass vias, among other micro / nano processes.

Description

Technical Field

[0001] This invention relates to micro / nano devices with a semi-flexible sealed composite beam-membrane island structure and their fabrication methods, applicable to fields such as MEMS sensors and actuators, and belongs to the technical field of beam-membrane island micro / nano devices. Background Technology

[0002] Beam-membrane island micro / nano devices typically consist of a substrate, functional membranes, functional beams, and microstructure islands. The functional membranes, beams, and islands are integrated onto the substrate using chemical methods or micro / nano fabrication processes to achieve electrical, mechanical, or other sensing functions. In micro / nano devices, membrane structures and beam structures are the two most common and fundamental types of micromechanical structural units, widely used in MEMS (Micro-Electro-Mechanical Systems) sensors and actuators, undertaking key functions such as force transmission, signal conversion, and structural support.

[0003] Membrane structures typically refer to thin films formed on materials such as silicon, silicon nitride, silicon oxide, or polycrystalline silicon, with thicknesses generally ranging from hundreds of nanometers to tens or hundreds of micrometers. Membrane structures utilize in-plane tension or intra-membrane bending deformation as the primary form of stress, enabling them to produce measurable deformation under external pressure, stress, or temperature. Typical applications include: pressure sensors: achieving piezoresistive, capacitive, or optical signal output through diaphragm flexure; micromicrophones and acoustic sensors: converting sound pressure vibrations into electrical signals; infrared radiation detectors and thermal sensors: using membrane structures for thermal insulation and supporting thermistor elements to achieve highly sensitive thermal responses. The advantages of membrane structures lie in their high responsiveness, large area, and good fabrication compatibility; however, stress concentration and boundary fixation conditions often become critical factors in reliability design.

[0004] Beam structures, taking the form of long, narrow cantilever beams, double-ended fixed beams, folded beams, or forked beams, are the core units for strain detection, inertial measurement, and resonant frequency control. Under external forces or inertial loads, beam structures generate bending or tensile / compressive strain, which can be read out using piezoresistive, capacitive, or optical methods. Typical applications include: accelerometers and gyroscopes: using cantilever or folded beams to support mass blocks for inertial detection; force / strain sensors: integrating piezoresistive elements or optical waveguides on the beam for strain sensing; resonators and filters: utilizing the beam's natural frequency to achieve high-Q vibration detection and frequency control.

[0005] In addition, micro- and nano-devices also utilize flexible materials with low elastic modulus, such as silicone, polydimethylsiloxane, and polyimide, to fabricate membrane structures. The application of flexible materials in sensors has become an important development direction for intelligent electronics and human-computer interaction technologies. Compared to traditional rigid silicon-based materials, flexible materials are bendable, stretchable, lightweight, and biocompatible, enabling them to adapt to complex curved surfaces and dynamic environments. They are widely used in wearable devices, electronic skin, soft robots, and biomedical detection.

[0006] Currently commonly used flexible materials include polymeric elastomers (such as PDMS, Ecoflex, and PU), conductive composite materials (such as elastomers filled with silver nanowires / carbon nanotubes / graphene), and flexible metal thin films and organic conductors. These materials can detect force, pressure, strain, temperature, and physiological signals through mechanisms such as strain, capacitance, piezoresistive, piezoelectric, and thermoelectric. For example, PDMS-based piezoresistive sensors can achieve skin tactile monitoring; carbon nanotube or MXene composite elastomer sensors can achieve wide-range strain detection; and flexible piezoelectric thin films (such as PVDF or PZT composite films) show potential in self-powered sensors. In the field of flexible sensing, the key to flexible material design lies in balancing high sensitivity and mechanical stability. Through microstructured design (folds, microcone arrays, corrugated structures) and composite multi-scale conductive networks, signal response and fatigue resistance can be significantly improved. At the same time, low modulus and low interfacial stress help ensure stable output of devices under long-term deformation. However, the low modulus and low mechanical strength of flexible film materials make them prone to deformation, warping, or fatigue failure, leading to zero-point drift and reduced repeatability during long-term device operation. When flexible film materials are applied to high-precision micro-nano devices based on semiconductor materials and micro-nano fabrication, they suffer from drawbacks such as poor structural stability, insufficient reliability, high temperature sensitivity, and difficulty in process integration.

[0007] The semi-flexible sealed composite beam-membrane island structure proposed in this patent avoids the above-mentioned shortcomings of flexible membrane structures while taking into account the advantages of good sealing performance of membrane structures and a large adjustable range of horizontal equivalent stiffness of beam structures. Summary of the Invention

[0008] To overcome the technical challenges of stress concentration, poor adjustability of equivalent stiffness in various dimensions, and difficulty in achieving both good sealing performance in existing beam-membrane island-type micro-nano devices, this invention provides a semi-flexible sealed composite material beam-membrane island structure micro-nano device and its fabrication method, thereby improving the device's stress range, stiffness balance, and stability.

[0009] In a first aspect, the present invention provides a semi-flexible sealed composite material beam-membrane island structure micro / nano device, comprising:

[0010] A rigid structure comprising a beam structure and an island structure, wherein one end of the beam structure is connected to a fixed part and the other end is connected to the island structure to support the island structure and transmit external physical quantities;

[0011] A flexible sealant is filled in the gaps around the beam structure and / or island structure and cured to form a semi-flexible sealant structure, while also serving as a stress transition zone. The elastic modulus of the flexible sealant is lower than that of the rigid structure.

[0012] The rigid structure and the flexible seal together constitute a semi-flexible sealed composite beam-membrane island structure, which allows the equivalent stiffness of the device in at least two dimensions to be controlled by adjusting the contour and / or size of the beam structure, and the flexible seal isolates the sensitive area below the rigid structure from the external environment.

[0013] Secondly, the present invention provides a method for fabricating a semi-flexible sealed composite material beam-membrane island structure micro / nano device, comprising:

[0014] Patterned metal electrodes are formed on the device layer of the SOI wafer;

[0015] The sensitive structure contour is etched out in the device layer;

[0016] Through-holes are fabricated on a glass wafer and filled with conductive metal, with electrodes formed at both ends of the through-holes;

[0017] The SOI wafer is anode-bonded to the glass wafer, so that the patterned metal electrode is electrically connected to the glass wafer electrode.

[0018] Etching and releasing beam and island structures from the SOI wafer substrate layer, so that the island structure and the movable part of the device layer move synchronously.

[0019] A semi-flexible sealed structure is formed by filling the gaps around the beam structure and / or island structure with a flexible material whose elastic modulus is lower than that of the beam or island structure and then curing it. This allows for the adjustment of the beam structure's profile and / or dimensions to control the equivalent stiffness of at least two dimensions and isolate the sensitive area below from the external environment.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] This invention employs both rigid and flexible materials to construct a beam-membrane island structure for micro / nano devices. The beam and island structures are made of rigid materials that can be fabricated at the micro / nano scale, while flexible materials are used to fill the periphery of the beam and island structures. This semi-flexible, sealed composite silicon beam-membrane island structure offers the following advantages:

[0022] (1) The mechanical transmission and sensitivity are balanced. Pure silicon structures have high stiffness and extremely high force-strain transmission efficiency, but their response is too rigid under multidimensional stress, with significant lateral coupling, making it difficult to distinguish force components in different directions. Pure flexible membrane structures have high flexibility and can achieve multidimensional response, but stress concentration is not obvious, effective strain is small, signal amplitude is weak and easily affected by external disturbances. In the semi-flexible sealed composite beam-membrane island structure proposed in this application, the flexible filling layer plays the role of "displacement coordination layer". While ensuring that the high modulus of the silicon beam provides a clear mechanical response, the flexible layer absorbs lateral coupling stress through local deformation, so that the strain field in different directions is separated and amplified in the beam / island area.

[0023] (2) Stress distribution and decoupling characteristics optimization. The flexible material forms a stress transition zone between the beam and the island, avoiding strong stress concentration in the pure silicon beam-island structure under concentrated load. This makes the principal stress direction of the island region more stable and the distribution more predictable when subjected to forces along the x, y, and z axes, thereby improving the accuracy of independent measurement of multidimensional force components.

[0024] (3) Improved temperature and interface effects. Hard materials such as silicon, germanium, and quartz have small differences in thermal expansion, but high interface rigidity, and thermal stress tends to concentrate at the bonding edges. In contrast, purely flexible film structures exhibit significant thermal drift. In composite structures, flexible materials (such as polydimethylsiloxane (PDMS), polyimide (PI), and silicone rubber) absorb some of the thermal strain differences, reducing the risk of mechanical drift and cracking under thermal cycling.

[0025] (4) Dynamic response and damping control. The flexible filling layer can introduce controllable damping and energy dissipation characteristics, suppress high Q resonance or low frequency oscillation of the beam island system, improve the stability of the measurement system under dynamic load, and realize smooth response of multi-mode signals.

[0026] (5) Packaging and Manufacturing Compatibility. This invention still uses materials compatible with micro-nano fabrication processes as the main structural material, which can be integrated with standard photolithography, reactive ion etching, deep silicon reactive ion etching and anodic bonding processes, through-silicon vias, glass vias and other micro-nano processes; the flexible filling material can be achieved in the later process by spin coating or local filling, and the requirements for photolithography and alignment accuracy are relatively low. Compared with a fully flexible structure, it is easier to achieve wafer-level batch consistency, and the micro-nano devices can be sealed, which is expected to achieve sealing in specific atmospheric pressure environments and vacuum pressure environments, making the micro-nano devices more resistant to harsh environments and more stable and reliable. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a flowchart illustrating the fabrication process of the micro / nano device with a semi-flexible sealed composite beam-membrane island structure and its fabrication method according to Example 1 of the present invention.

[0029] Figure 2 The flowchart (1) shows the micro / nano device and its fabrication method based on the semi-flexible sealed composite beam-membrane island structure of the present invention.

[0030] Figure 3 The flowchart (2) shows the embodiment 1 of the micro / nano device and its fabrication method of the semi-flexible sealed composite beam-membrane island structure of the present invention.

[0031] Figure 4 The flowchart (3) shows the embodiment 1 of the micro / nano device and its fabrication method of the semi-flexible sealed composite beam-membrane island structure of the present invention.

[0032] Figure 5 The flowchart (4) shows the embodiment 1 of the micro / nano device and its fabrication method of the semi-flexible sealed composite beam-membrane island structure of the present invention.

[0033] Figure 6 The flowchart (5) shows the embodiment 1 of the micro / nano device and its fabrication method of the semi-flexible sealed composite beam-membrane island structure of the present invention.

[0034] Figure 7 The flowchart (6) shows the embodiment 1 of the micro / nano device and its fabrication method of the semi-flexible sealed composite beam-membrane island structure of the present invention.

[0035] Figure 8 The flowchart (7) shows the embodiment 1 of the micro / nano device and its fabrication method of the semi-flexible sealed composite beam-membrane island structure of the present invention.

[0036] Figure 9 The flowchart (8) shows the embodiment 1 of the micro / nano device and its fabrication method of the semi-flexible sealed composite beam-membrane island structure of the present invention.

[0037] Figure 10 The flowchart (9) shows an embodiment 1 of the micro / nano device and its fabrication method based on the semi-flexible sealed composite beam-membrane island structure of the present invention.

[0038] Figure 11 The flowchart (10) shows an embodiment 1 of the micro / nano device and its fabrication method based on the semi-flexible sealed composite beam-membrane island structure of the present invention.

[0039] Figure 12 This is a flowchart illustrating the fabrication process of the micro / nano device and its fabrication method based on the semi-flexible sealed composite beam-membrane island structure of the present invention, as described in Example 2.

[0040] Figure 13 The flowchart (1) is for Example 2 of the micro / nano device and its fabrication method based on the semi-flexible sealed composite beam-membrane island structure of the present invention.

[0041] Figure 14 The flowchart (2) shows the embodiment 2 of the micro / nano device and its fabrication method based on the semi-flexible sealed composite beam-membrane island structure of the present invention.

[0042] Figure 15The flowchart (3) is for Example 2 of the micro / nano device and its fabrication method based on the semi-flexible sealed composite beam-membrane island structure of the present invention.

[0043] Figure 16 The flowchart (4) is for Example 2 of the micro / nano device and its fabrication method of the semi-flexible sealed composite beam-membrane island structure of the present invention.

[0044] Figure 17 The flowchart (5) shows the embodiment 2 of the micro / nano device and its fabrication method of the semi-flexible sealed composite beam-membrane island structure of the present invention.

[0045] Figure 18 The flowchart (6) shows the embodiment 2 of the micro / nano device and its fabrication method of the semi-flexible sealed composite beam-membrane island structure of the present invention.

[0046] Figure 19 The flowchart (7) is for Example 2 of the micro / nano device and its fabrication method of the semi-flexible sealed composite beam-membrane island structure of the present invention.

[0047] Figure 20 The flowchart (8) shows the embodiment 2 of the micro / nano device and its fabrication method of the semi-flexible sealed composite beam-membrane island structure of the present invention.

[0048] Figure 21 The flowchart (9) shows Example 2 of the micro / nano device and its fabrication method based on the semi-flexible sealed composite beam-membrane island structure of the present invention.

[0049] Figure 22 The flowchart (10) shows the embodiment 2 of the micro / nano device and its fabrication method of the semi-flexible sealed composite beam-membrane island structure of the present invention.

[0050] Figure 23 The flowchart (11) shows the micro / nano device and its fabrication method of the semi-flexible sealed composite beam-membrane island structure of the present invention in Example 2.

[0051] Figure 24 The flowchart (12) shows the embodiment 2 of the micro / nano device and its fabrication method of the semi-flexible sealed composite beam-membrane island structure of the present invention.

[0052] Figure 25 Example 2 and Example 2 of the beam island structure of the semi-flexible sealed composite material beam membrane island structure of the present invention are illustrated in Figure (1).

[0053] Figure 26 This is a demonstration diagram (2) of the beam island structure of the micro / nano device and its fabrication method of the semi-flexible sealed composite material beam membrane island structure of the present invention, in Example 2 and Example 2.

[0054] Figure 27The first principal stress distribution diagram of a beam-membrane island structure with silicon membrane sealing when displaced by 1 micrometer in the x-direction.

[0055] Figure 28 The first principal stress distribution diagram of a beam-membrane island structure with silicon membrane sealing when displaced by 1 micrometer in the z-direction.

[0056] Figure 29 The first principal stress distribution diagram of a beam-membrane island structure sealed with a flexible material with an elastic modulus of 1 MPa when displaced by 1 micrometer in the x-direction.

[0057] Figure 30 The diagram shows the distribution of the first principal stress of a beam-membrane island structure sealed with a flexible material having an elastic modulus of 1 MPa when the material is displaced by 1 micrometer in the x-direction.

[0058] Figure 31 The first principal stress distribution diagram of a beam-membrane island structure sealed with a flexible material with an elastic modulus of 1 MPa when displaced by 1 micrometer in the z-direction.

[0059] Figure 32 The distribution of the first principal stress of a beam-membrane island structure sealed with a flexible material having an elastic modulus of 1 MPa is shown in the diagram when the flexible material is displaced by 1 micrometer in the z-direction.

[0060] Figure 33 The first principal stress distribution diagram of another beam-membrane island structure for silicon membrane sealing at a displacement of 1 micrometer in the x direction.

[0061] Figure 34 The first principal stress distribution diagram of another beam-membrane island structure for silicon membrane sealing at a displacement of 1 micrometer in the z-direction.

[0062] Figure 35 The first principal stress distribution diagram of another beam-membrane island structure sealed with a flexible material with an elastic modulus of 1 MPa at a displacement of 1 micrometer in the x-direction.

[0063] Figure 36 The distribution of the first principal stress of another beam-membrane island structure sealed with a flexible material having an elastic modulus of 1 MPa is shown in the x-direction displacement of 1 micrometer.

[0064] Figure 37 The first principal stress distribution diagram of another beam-membrane island structure sealed with a flexible material with an elastic modulus of 1 MPa at a displacement of 1 micrometer in the z-direction.

[0065] Figure 38 The first principal stress distribution of the flexible material in another beam-membrane island structure sealed with a flexible material having an elastic modulus of 1 MPa is shown in the z-direction displacement of 1 micrometer. Detailed Implementation

[0066] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms “first,” “second,” “third,” and similar terms used in this patent application specification and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the terms “an” or “a” and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms “comprising” or “including” and similar terms mean that the element or object preceding “comprising” or “including” encompasses the element or object listed following “comprising” or “including” and its equivalents, and do not exclude other elements or objects. The terms “connected” or “linked” and similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. “Up,” “down,” “left,” “right,” etc., are used only to indicate relative positional relationships, which may change accordingly when the absolute position of the described object changes. A and / or B indicates the presence of three cases: A, B, and A and B.

[0067] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0068] This application provides a method for fabricating a semi-flexible sealed composite material beam-membrane island structure for micro / nano devices, comprising the following steps:

[0069] Step 1: Prepare an SOI wafer, which includes an insulating substrate layer, a buried oxide layer and a device layer. Deposit and photolithographically etch patterned metal electrodes, including a first electrode and a second electrode, on the device layer.

[0070] Step 2: The trenches are patterned by photolithography on the device layer, and DRIE etching is performed down to the buried oxide layer to form the sensitive structure contour;

[0071] Step 3: Prepare a BF33 glass slide, wet-etch shallow grooves on the glass slide, prepare glass through holes in the shallow groove and non-shallow groove areas of the glass slide, and fill the through holes with conductive metal;

[0072] Step 4: Electrodes, including the fourth electrode, the fifth electrode, and the sixth electrode, are fabricated on the glass through-holes on both sides of the glass sheet using a lift-off process;

[0073] Step 5: Anodicly bond the SOI wafer from Step 2 to the BF33 glass sheet from Step 4 face to face, wherein the first electrode is connected to the fifth electrode, and the second electrode is connected to the sixth electrode. The edges of the first electrode and the fifth electrode, and the second electrode and the sixth electrode form a silicon glass bonding cross section with a gradually changing thickness.

[0074] Step 6: Photoresist is coated on the silicon dioxide substrate of the SOI wafer to perform photolithography, outlining the beam and island structures. Using the photoresist as a mask, the gap windows of the beam and island structures are etched on the substrate layer through reactive ion etching, and then the photoresist is removed.

[0075] Step 7: Using a patterned oxide layer as a mask, etch beam and island structures onto the substrate using deep reactive ion etching (DRIE).

[0076] Step 8: Expose the exposed silicon dioxide using fumed hydrofluoric acid to release the beam structure, the island structure, and the substrate layer structure, thereby connecting the island structure to the device layer structure and enabling synchronous movement;

[0077] Step 9: Apply a flexible material to the gaps around the beam structure using a precision coating process, and cure the flexible material according to the curing requirements to form a semi-flexible sealed structure.

[0078] Preferably, the flexible material is coated into the gaps around the beam structure and island structure using a precision printing method. Before curing, the flexible material has a certain viscosity and flowability, but the flow depth in the gap does not exceed 3 / 4 of the gap height. After coating, the flexible material is cured according to the material properties and curing requirements. The cured flexible material and the beam structure and island structure form a semi-flexible composite material film with good sealing performance.

[0079] Preferably, the precision coating process in step eight includes precision printing, direct coating, or stencil coating; the viscosity of the flexible material before curing satisfies that the flow depth does not exceed 3 / 4 of the gap height.

[0080] Preferably, the flexible material coating and curing process is carried out in a certain atmospheric pressure environment, with an atmospheric pressure value of 0.01 kPa to 200 kPa.

[0081] Preferably, the contour pattern formed by the photolithography process in step three includes an arc-shaped chamfer structure and an arc-shaped transition structure; the slit width formed by etching in step four is 1~100μm, and a limiting cavity is formed around the slit.

[0082] This application also provides a method for fabricating a semi-flexible sealed composite material beam-membrane-island structure micro / nano device. The fabricated micro / nano device includes a beam structure, an island structure, a flexible material, and a fixed structure.

[0083] One end of the beam structure is connected to a fixed structure, and the other end is connected to the island structure through a flexible material, which is used to support the island structure and transmit external physical quantities. There are gaps around the beam structure and the island structure. The flexible material is filled in the gaps and cured, forming a semi-flexible sealed structure together with the beam structure and the island structure. The beam structure and the island structure are made of hard materials with an elastic modulus higher than 50 GPa, and the elastic modulus of the flexible material is 0.1 kPa to 10 GPa.

[0084] Preferably, the projections of the beam structure onto the horizontal plane on both the x-axis and y-axis exceed its axial dimension;

[0085] Preferably, the connection between the beam structure and the island structure and the fixed structure is provided with an arc-shaped chamfer with a radius of 1~1000μm to distribute stress evenly and avoid stress concentration at the root. An arc-shaped transition structure is provided in the beam structure to avoid stress concentration and local fracture. An arc-shaped transition structure is provided at the corner of the beam structure.

[0086] Preferably, the outline of the beam structure is continuous and first-order differentiable, which improves the stress range, stiffness balance and stability of the device.

[0087] Preferably, the width of the gap is 1~100μm, and a limiting cavity is provided around the gap to prevent the flexible material from overflowing.

[0088] The micro-nano devices of this application are used to sense or transmit external physical quantities, such as mechanical force, air pressure, sound waves, light waves, heat energy, and electromagnetic waves. The beam structure supports the island structure and is connected to the fixed structure. At the same time, the beam structure also plays a role in improving the response sensitivity to external physical quantities, increasing the response range, reducing stress concentration, and improving linearity. Flexible materials are filled in the gaps of the beam structure. The flexible materials can play a sealing role, isolating the beam structure from other sensitive structures below the island structure from external environmental influences. The rigid and flexible materials of the island structure and the beam structure together constitute a semi-flexible beam-membrane island structure.

[0089] After the flexible material is cured, it forms a sealing layer that isolates the sensitive structures beneath the beam structure and the island structure from the external environment.

[0090] The semi-flexible sealed composite material beam-membrane island structure micro-nano devices proposed in this application can achieve multi-dimensional movement, and the equivalent stiffness in each dimension can be adjusted within a certain range. The equivalent stiffness in the horizontal direction and the stiffness in the vertical direction can be adjusted by adjusting the contour and size of the beam structure.

[0091] Example 1:

[0092] Reference Figure 1-11In this embodiment, the semi-flexible sealed composite material beam-membrane island structure micro-nano device and its processing method use single-crystal silicon (elastic modulus of about 169 GPa) as the hard material, polydimethylsiloxane (PDMS, elastic modulus of about 10 kPa) as the flexible material, and the insulating substrate as the insulating layer of SOI wafer.

[0093] Based on this, the present disclosure provides a method for fabricating a semi-flexible sealed composite material beam-membrane island structure for micro / nano devices, such as... Figure 1 As shown, it includes:

[0094] In step S101, the sensitive structure and electrodes of the micro / nano device are fabricated on the SOI wafer device layer.

[0095] In step S102, shallow trenches, TGV, and electrodes are fabricated on the glass wafer.

[0096] Electrodes are arranged in shallow grooves within the glass wafer.

[0097] In step S103, the SOI wafer is bonded to the glass wafer.

[0098] The device layer of the SOI wafer is bonded to the shallow trench surface of the glass wafer, and the electrodes on the SOI wafer are guided to the other side of the glass wafer through the electrodes of the glass wafer and TGV.

[0099] In step S104, movable beams and island structures are etched out.

[0100] Movable beam and island structures are etched at the substrate layer of SOI wafers, and the movable structures are released through a gas-phase hydrofluoric acid etching process.

[0101] In step S105, a flexible material is applied and cured.

[0102] Flexible material is coated into the gaps between the movable beams, island structures, and fixed structures of the substrate layer of the SOI wafer and then cured.

[0103] The detailed processing steps are as follows:

[0104] Step 1: Select a 6-inch diameter SOI wafer. The SOI wafer 1 includes a substrate layer 11, a buried oxide layer 12, and a device layer 13. Cr 100 nm and Au 100 nm are deposited on the device layer. Patterned metal electrodes are etched using photolithography. The photoresist is removed. The device layer includes a first electrode 21, a second electrode 22, and a third electrode 23. The resistivity of both the device layer 13 and the substrate layer 11 is less than 0.003 ohm·cm. Figure 2 As shown;

[0105] Step 2: Trenches are patterned by photolithography on the device layer, and DRIE etching is performed down to the buried oxide layer to form the sensitive structure contour, such as... Figure 3As shown;

[0106] Step 3: Prepare a BF33 glass slide 2. Use (Cr 100nm / Au 100nm) as a mask on the glass slide and wet-etch shallow grooves 3. Prepare glass vias 24 in the shallow grooves 3 and non-shallow groove areas of the glass slide. Fill the vias with conductive metal, such as... Figure 4 , 5 As shown;

[0107] Step 4: Electrodes are fabricated on the glass vias on both sides of the glass sheet using a lift-off process, including the fourth electrode 25, the fifth electrode 26, and the sixth electrode 27; specifically: (1) the electrode areas are photolithographically patterned; (2) a 100 nm Cr and 100 nm Au metal electrode layer is evaporated; (3) the photoresist is removed, and the photoresist in the non-metallic areas is stripped off; (4) the metal electrode on one side of the shallow trench is transferred to the other side of the glass sheet via TGV, such as... Figure 6 As shown.

[0108] Step 5: The SOI wafer 1 from Step 2 and the BF33 glass wafer 2 from Step 4 are anoly bonded face-to-face at 1200V and 330℃. The first electrode 21 is connected to the fifth electrode 26, the second electrode 22 to the sixth electrode 27, and the third electrode 23 and the fourth electrode 25 are spaced approximately 5μm apart. Due to height differences and factors such as the high-temperature softening of the BF33 glass and electrostatic adsorption after high-voltage bias, a gradually varying silicon glass bonding cross-section is formed at the edges of the first electrode 21 and the fifth electrode 26, and the second electrode 22 and the sixth electrode 27. Figure 7 As shown;

[0109] Step Six: Photoresist is coated onto the silicon dioxide substrate of the SOI wafer for photolithography to outline the beam and island structures. Using the photoresist as a mask, reactive ion etching is used to etch the gap windows of the beam and island structures onto the substrate. The photoresist is then removed. Figure 8 As shown;

[0110] For example, the contour pattern formed by the photolithography process includes an arc-shaped chamfer structure and an arc-shaped transition structure.

[0111] Step 7: Using a patterned oxide layer as a mask, etch the beam structure 31 and island structure 32 onto the substrate using deep reactive ion etching (DRIE). Figure 9 As shown;

[0112] For example, the projections of the beam structure onto the horizontal plane on both the x-axis and y-axis exceed its axial dimensions; the connection between the beam structure and the island structure and the fixed structure is provided with an arc-shaped chamfer with a radius of 1~1000μm to distribute stress evenly and avoid stress concentration at the root; an arc-shaped transition structure is provided in the beam structure to avoid stress concentration and local fracture; an arc-shaped transition structure is provided at the corner of the beam structure; the outline of the beam structure is continuous and first-order differentiable, which improves the stress range, stiffness balance and coordination and stability of the device.

[0113] For example, the width of the slit formed by etching in step four is 1~100μm, and a limiting cavity is formed around the slit.

[0114] Step 8: Expose the exposed silicon dioxide using fumed hydrofluoric acid to release the movable parts of the beam structure 31, the island structure 32, and the device layer 13, allowing the island structure 32 to connect with the movable structure of the device layer 13 and move synchronously. Figure 10 As shown;

[0115] Step Nine: Apply a flexible material to the gaps around the beam structure using a precision coating process, and cure the flexible material according to its curing requirements to form a semi-flexible sealing film structure 33. Figure 11 As shown.

[0116] For example, the flexible material is coated into the gaps around the beam structure and island structure by precision printing. The flexible material has a certain viscosity and flowability before curing, but the flow depth in the gap does not exceed 3 / 4 of the gap height. After coating, the flexible material is cured according to the material properties and curing requirements. The cured flexible material and the beam structure and island structure form a semi-flexible composite material film with good sealing performance.

[0117] Optionally, the precision coating process includes precision printing, direct coating, or stencil coating; the viscosity of the flexible material before curing satisfies that the flow depth does not exceed 3 / 4 of the gap height.

[0118] For example, the fabrication method of the semi-flexible sealed composite material beam-membrane-island structure micro / nano device fabricated includes a beam structure, an island structure, a flexible material, and a fixed structure. One end of the beam structure is connected to the fixed structure, and the other end is connected to the island structure through the flexible material, which is used to support the island structure and transmit external physical quantities. The beam structure and the island structure have gaps around their peripheries, and the flexible material is filled in the gaps and cured, forming a semi-flexible sealed structure together with the beam structure and the island structure. The beam structure and the island structure are made of hard materials with an elastic modulus higher than 50 GPa, and the elastic modulus of the flexible material is 0.1 kPa to 10 GPa.

[0119] For example, the hard material includes silicon, germanium, quartz, or diamond; the flexible material includes polydimethylsiloxane, polyimide, or silicone rubber.

[0120] Through the above steps, the fabrication of semi-flexible sealed composite material beam-membrane island structure micro-nano devices is completed.

[0121] Specifically, the embodiments of this application are used to sense or transmit external physical quantities, such as mechanical force, air pressure, sound waves, light waves, heat energy, and electromagnetic waves. The beam structure supports the island structure and is connected to the fixed structure. At the same time, the beam structure also plays a role in improving the response sensitivity to external physical quantities, increasing the response range, reducing stress concentration, and improving linearity. Flexible materials are filled in the gaps of the beam structure. The flexible materials can play a sealing role, isolating the beam structure from other sensitive structures below the island structure from external environmental influences. The rigid and flexible materials of the island structure and the beam structure together constitute a semi-flexible beam-membrane island structure.

[0122] For example, the external physical quantities include mechanical force, air pressure, sound waves, light waves, heat energy, and electromagnetic waves; after the flexible material is cured, it forms a sealing layer that isolates the sensitive structure below the beam structure and the island structure from the external environment.

[0123] Example 2:

[0124] Reference Figure 12-24 In the embodiments of this application, the semi-flexible sealed composite material beam-membrane island structure micro-nano device and its processing method are selected as follows: the hard material is single crystal silicon (elastic modulus of about 169 GPa), the flexible material is polydimethylsiloxane (PDMS, elastic modulus of about 1 MPa), and the insulating substrate is the insulating layer of SOI wafer.

[0125] This disclosure provides a fabrication flowchart for a flexible sealing composite material beam-membrane island structure micro / nano device, as shown in the embodiments below. Figure 12 As shown, the preparation method includes:

[0126] In step S201, shallow trenches, sensitive structures, and electrodes of micro / nano devices are fabricated on the SOI wafer device layer.

[0127] In step S202, TGV and electrodes are fabricated on a glass wafer.

[0128] In step S203, the SOI wafer is bonded to the glass wafer.

[0129] The device layer of the SOI wafer is bonded to the glass wafer, and the electrodes on the SOI wafer are guided to the other side of the glass wafer through the electrodes of the glass wafer and TGV.

[0130] In step S204, movable beams and island structures are etched out.

[0131] Movable beam and island structures are etched at the substrate layer of the SOI wafer, and the movable structures are released through a gas-phase hydrofluoric acid etching process.

[0132] In step S205, a flexible material is applied and cured.

[0133] Flexible material is coated into the gaps between the movable beams, island structures, and fixed structures of the substrate layer of the SOI wafer and then cured.

[0134] The detailed processing steps are as follows:

[0135] Step 1: Select a 6-inch diameter SOI wafer 1. The SOI wafer 1 includes an insulating substrate layer 11, a buried oxide layer 12, and a device layer 13. Perform standard cleaning on the SOI silicon wafer. Deposit Cr 100 nm and Au 100 nm on the device layer. Patterned metal electrodes are etched using photolithography. Remove the photoresist. This includes a first electrode 21 and a third electrode 23. The resistivity of both the device layer 13 and the substrate layer 11 is less than 0.003 ohm·cm. Figure 13 As shown;

[0136] Step 2: On the device layer 13 of SOI wafer 1, a 200nm SiO2 layer is deposited using plasma-enhanced chemical vapor deposition (PECVD). The layer is then patterned using photolithography to form a SiO2 protective layer on the CrAu electrode surface. Figure 14 As shown;

[0137] Step 3: Trenches are patterned by photolithography on the device layer. Using photoresist as a mask, DRIE etching is performed down to the buried oxide layer to form the sensitive structure contour, such as... Figure 15 As shown;

[0138] Step 4: Using PECVD SiO2 as a mask, etch a 5μm shallow trench using the DRIE process, such as... Figure 16 As shown; PECVD SiO2 is removed by a hydrofluoric acid dry etching process, such as... Figure 17 As shown;

[0139] Step 5: Prepare BF33 glass slide 2, and fabricate glass through-holes 24 on glass slide 2. Fill the through-holes with conductive metal, such as... Figure 18 ;

[0140] Step 6: Electrodes are fabricated on the glass vias on both sides of the glass sheet using a lift-off process, including the fourth electrode 25, the fifth electrode 26, and the sixth electrode 27; specifically (1) a 100 nm Cr and 100 nm Au metal electrode layer is sputtered on both sides of the glass sheet; (2) the electrode patterns on both sides are photolithographically etched; (3) the CrAu electrodes in the non-electrode areas are removed by wet etching; (4) the photoresist is removed; (4) the metal electrodes on both sides of the glass sheet are electrically connected by TGV, such as Figure 19 ;

[0141] Step 7: The SOI wafer 1 from Step 2 and the BF33 glass wafer 2 from Step 4 are anoly bonded face-to-face at 1200V and 330℃. The first electrode 21 is connected to the fifth electrode 26, and the third electrode 23 and the sixth electrode 27 are connected. The bottom of the shallow trench of SOI wafer 1 is approximately 5μm away from the fourth electrode 25. Due to height differences and factors such as the high-temperature softening of BF33 glass and electrostatic adsorption after high-voltage bias, the edges of the first electrode 21 and the fifth electrode 26, and the third electrode 24 and the sixth electrode 27 form a silicon glass bonding cross-section with gradually varying thickness. Figure 20 As shown;

[0142] Step 8: Photoresist is coated onto the silicon dioxide substrate of SOI wafer 1 for photolithography to outline the beam and island structures. Using the photoresist as a mask, reactive ion etching is used to etch the gap windows of the beam and island structures onto the substrate. The photoresist is then removed. Figure 21 As shown;

[0143] Step Nine: Using a patterned oxide layer as a mask, etch the beam structure 31 and island structure 32 onto the substrate using deep reactive ion etching (DRIE). Figure 22 As shown;

[0144] Step 10: Expose the exposed silicon dioxide using fumed hydrofluoric acid etching to release the movable structures in the beam structure 31, the island structure 32, and the device layer 13 of the SOI wafer 1, allowing the island structure to connect with the device layer structure and move synchronously. Figure 23 As shown;

[0145] Step 11: In a vacuum environment, a flexible material is coated into the gaps around the beam structure using a precision coating process. The flexible material is then cured according to its curing requirements to form a sealed membrane structure 33. Figure 24 As shown.

[0146] Through the above steps, the fabrication of semi-flexible sealed composite material beam-membrane island structure micro-nano devices is completed.

[0147] In the above embodiments 1 and 2, the beam structure of the device projects beyond the axial dimension on both the x and y axes. The arc-shaped structure design makes the stress distribution uniform, and the flexible material sealing membrane structure effectively isolates the external environment. The equivalent stiffness in each dimension can be flexibly adjusted by adjusting the beam structure outline and size, making it suitable for high-precision force sensors, air pressure sensors, and other fields.

[0148] For example, one and another beam-membrane island structure, such as Figure 25 , 26 As shown, the movable island structure 32 is connected to the fixed structure 34 through the beam structure 31.

[0149] It should be noted that, Figure 25 , Figure 26 The number of central beam structures 32 is only an example and does not represent a limitation on its number.

[0150] Exemplary, the spacing between the movable island structure 32, the beam structure 31, and the fixed structure 32 is 1 to 100 μm;

[0151] A demonstrative comparison illustrates that Figure 25 If the membrane structure in the beam-membrane island structure shown is made of the same monocrystalline silicon material as the beam-island structure, the monocrystalline silicon membrane structure is formed synchronously when the movable island structure 32 is etched through the beam structure 31 and the fixed structure 34. When the island structure 32 is subjected to 1μm in the x-direction and z-direction respectively, the maximum first principal stress generated by the structure will be 820.34MPa and 2057.44MPa, respectively, as shown in Table 1. The finite element simulation results are as follows. Figure 27 , Figure 28 When the default fracture strength of monocrystalline silicon material is 700 MPa, due to symmetry, at this time... Figure 25 The maximum displacements of the beam-membrane island structure shown are 0.85 μm, 0.85 μm, and 0.34 μm in the x, y, and z directions, respectively. When a flexible material with an elastic modulus of 1 MPa is used to fill the gaps between the movable island structure 32, the beam structure 31, and the fixed structure 32, a flexible sealed membrane structure 33 is formed. When the island structure 32 is subjected to 1 μm in the x and z directions, the maximum first principal stresses generated by this structure are 157 MPa and 96 MPa, respectively. The maximum first principal stresses of the flexible material are 1.01 MPa and 1.05 MPa, respectively. The finite element simulation results are as follows: Figures 29 to 32 When the flexible material also adopts the default fracture strength of 2MPa, due to symmetry, at this time... Figure 25 The maximum displacements of the beam-membrane island structure shown are 1.98 μm, 1.98 μm, and 1.9 μm in the x, y, and z directions, respectively.

[0152] Table 1. Comparison of simulation performance of sealed membrane structures constructed from monocrystalline silicon and flexible materials for one and another beam-membrane island structure.

[0153]

[0154] By way of example, the movable island structure 32, the beam structure 31, and the fixed structure 34 are connected by a flexible material. When this beam membrane island structure is applied to 3D and above multi-dimensional sensing and detection, it can effectively improve the detection range, reduce stress concentration, and adjust the equivalent stiffness of each dimension.

[0155] A demonstrative comparison illustrates that, in Figures 33 to 38 In this embodiment, the micro-nano device and its fabrication method based on another semi-flexible sealed composite material beam-membrane island structure can also effectively improve the detection range, reduce stress concentration, and adjust the equivalent stiffness of each dimension in other contour structures.

[0156] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A semi-flexible sealed composite material beam-membrane island structure micro / nano device, characterized in that, include: A rigid structure comprising a beam structure and an island structure, wherein one end of the beam structure is connected to a fixed part and the other end is connected to the island structure to support the island structure and transmit external physical quantities; A flexible sealant is filled in the gaps around the beam structure and / or island structure and cured to form a semi-flexible sealant structure, while also serving as a stress transition zone. The elastic modulus of the flexible sealant is lower than that of the rigid structure. The rigid structure and the flexible seal together constitute a semi-flexible sealed composite beam-membrane island structure, which allows the equivalent stiffness of the device in at least two dimensions to be controlled by adjusting the contour and / or size of the beam structure, and the flexible seal isolates the sensitive area below the rigid structure from the external environment.

2. The micro / nano device according to claim 1, characterized in that, The rigid structure is made of a hard material with an elastic modulus ≥ 50 GPa, and the flexible seal is made of a flexible material with an elastic modulus of 0.1 kPa to 10 GPa.

3. The micro / nano device according to claim 1 or 2, characterized in that, The projected lengths of the beam structure on the x and y axes in the horizontal plane are both greater than its own axial width, and the outline of the beam is continuous and first-order differentiable.

4. The micro / nano device according to claim 1 or 2, characterized in that, The connection between the beam structure and the island structure and the fixing part is provided with an arc-shaped chamfer with a radius of 1 to 1000 μm, and / or the beam corner is provided with an arc-shaped transition structure to reduce stress concentration.

5. A method for fabricating semi-flexible sealed composite material beam-membrane island structure micro / nano devices, characterized in that, include: Patterned metal electrodes are formed on the device layer of the SOI wafer; The sensitive structure contour is etched out in the device layer; Through-holes are fabricated on a glass wafer and filled with conductive metal, with electrodes formed at both ends of the through-holes; The SOI wafer is anode-bonded to the glass wafer, so that the patterned metal electrode is electrically connected to the glass wafer electrode. Etching and releasing beam and island structures from the SOI wafer substrate layer, so that the island structure and the movable part of the device layer move synchronously. A semi-flexible sealed structure is formed by filling the gaps around the beam structure and / or island structure with a flexible material whose elastic modulus is lower than that of the beam or island structure and then curing it. This allows for the adjustment of the beam structure's profile and / or dimensions to control the equivalent stiffness of at least two dimensions and isolate the sensitive area below from the external environment.

6. The method according to claim 5, characterized in that, The flexible material is filled in a gap with a width of 1 to 100 μm, and the flow depth before curing does not exceed 3 / 4 of the gap height; the flexible material is filled by precision printing, direct coating or stencil coating, and cured in a controlled air pressure environment of 0.01 kPa to 200 kPa.

7. The method according to claim 6, characterized in that, The anodic bonding is performed at 1200 V and 330 °C, which creates a bonding cross section with a gradually varying thickness at the silicon-glass interface and enables electrical interconnection.

8. The method according to claim 5, characterized in that, The release process uses gas-phase hydrofluoric acid to etch exposed silicon dioxide to completely release the movable parts of the beam structure, island structure, and device layer.

9. The method according to claim 5, characterized in that, The glass wafer is pre-etched with shallow trenches using wet etching, and the vias are glass vias filled with Cr / Au or Cu metal. The SOI wafer substrate layer is etched using deep reactive ion etching with a patterned oxide layer as a hard mask.

10. The method according to any one of claims 5-9, characterized in that, The flexible material is selected from polydimethylsiloxane, polyimide or silicone rubber, and its elastic modulus is 0.1 kPa to 10 GPa.

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