Indirect heating type reconfigurable intelligent metasurface based on phase change material and preparation method thereof

Abstract

The invention provides an indirect heating type reconfigurable intelligent metasurface based on a phase change material and a preparation method of the metasurface. The metasurface is composed of a plurality of metasurface units arranged in an array mode. Each metasurface unit comprises a substrate, a first dielectric layer, a middle metal layer, a second dielectric layer, an electrical isolation layer, a phase change material layer and a metal patch radiation structure which are sequentially arranged from bottom to top; a contact electrode is arranged in the substrate, a micro heater is arranged in the electrical isolation layer, the micro heater is provided with a first port and a second port, the first port is electrically connected to the upper surface of the middle metal layer through a first vertical through hole, and the second port is electrically connected to the contact electrode through a second vertical through hole; the first dielectric layer, the second dielectric layer and the electrical isolation layer are insulating layers; heat generated by the micro heater drives the phase change material to generate crystalline / amorphous transition in an indirect heating mode, and an equivalent conductive path, electromagnetic coupling strength or local impedance between the metal patch radiation structures is changed in different phase states.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic metamaterials technology, specifically relating to an indirect heating type reconfigurable smart metasurface based on phase change materials and its preparation method. Background Technology

[0002] Reconfigurable smart metasurfaces enable programmable control of the amplitude, phase, and polarization of unit cells, achieving beamforming, environmental reconfiguration, and multifunctional electromagnetic control, making them a key technology for 6G. Their core lies in the performance and programmability of the tunable unit structure. Current mainstream implementation schemes include PIN diodes, varactor diodes, and MEMS switches, but all have varying degrees of limitations: PIN diodes are mostly two-state switches with low phase resolution, and combined schemes increase unit size and losses; varactor diodes require continuous bias to maintain their state, resulting in static power consumption and limited tuning linearity; MEMS switches have slow switching speeds, are susceptible to mechanical fatigue, and struggle to achieve reliable high-density arrays.

[0003] Phase change materials (PCMs) have become important candidate materials for achieving low-power, multi-bit phase control due to their reversible switching between crystalline and amorphous states, non-volatility, and significant difference in dielectric constant. However, existing PCM-based metasurface structures still have shortcomings: one approach relies on external laser heating excitation, resulting in complex systems that are difficult to integrate into arrays; another approach uses direct current flowing through the PCM for heating, which is prone to problems such as local breakdown, material thermal failure, and unstable conductive paths, making it difficult to meet the requirements of high-reliability array applications.

[0004] Therefore, there is an urgent need for a reconfigurable metasurface unit structure that can utilize non-volatile phase change materials to achieve stable phase state control through indirect thermal excitation, and possesses low power consumption, high reliability, and good array compatibility. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide an indirect heating type reconfigurable smart metasurface based on phase change materials and its preparation method.

[0006] This invention provides the following technical solution:

[0007] This invention provides an indirect heating reconfigurable smart metasurface based on phase change material. The metasurface is composed of multiple metasurface units arranged in an array. Each metasurface unit includes, from bottom to top, a substrate, a first dielectric layer, an intermediate metal layer, a second dielectric layer, an electrically insulating layer, a phase change material layer, and a metal patch radiating structure. The phase change material layer is disposed in the middle of the metal patch radiating structure to connect the patches on both sides of the metal patch radiating structure.

[0008] The substrate is provided with a contact electrode electrically connected to the feed network, and the electrical isolation layer is provided with a micro heater. The micro heater is provided with a first port and a second port. The first port is electrically connected to the upper surface of the intermediate metal layer through a first vertical via, and the second port is electrically connected to the contact electrode through a second vertical via.

[0009] The first dielectric layer, the second dielectric layer, and the electrical isolation layer are insulating layers; the heat generated by the micro heater drives the phase change material to undergo a crystalline / amorphous state transition in an indirect heating manner, changing the equivalent conductive path, electromagnetic coupling strength, or local impedance between the metal patch radiation structures under different phase states.

[0010] This invention introduces a microheater structure beneath the phase change material (PCM) layer and effectively isolates the microheater from the PCM through an electrical isolation layer. Simultaneously, it utilizes vias for reliable interconnection with the underlying power supply network, achieving a controllable, uniform, and indirect heating method that does not rely on the PCM body being energized. This invention drives the PCM to reversibly switch between crystalline and amorphous states through the localized thermal field generated by the microheater, forming controllable conductive or electromagnetic coupling paths between the metal patch structures, thereby enabling multi-bit phase programmable control of the metasurface unit.

[0011] To ensure that the localized thermal field generated by the microheater can effectively transfer heat to the phase change material layer, the vertical distance between the microheater and the phase change material layer is set to 60-300 nm.

[0012] Furthermore, the phase change material is a chalcogenide compound or a chalcogenide compound doped with one or more of the elements Se, Bi, Sn, N, In, Hf, Y, Sc, Ga, and Ti, and the chalcogenide compound includes germanium telluride, antimony telluride, and germanium-antimony-telluride.

[0013] Furthermore, the microheater is composed of one or more of tungsten, chromium, nickel, titanium nitride, titanium tungsten, and ITO.

[0014] Furthermore, the first vertical through-hole penetrates the second dielectric layer, and the second vertical through-hole penetrates the second dielectric layer, the intermediate metal layer, and the first dielectric layer. The intermediate metal layer is provided with an insulating clearance area, and the second vertical through-hole passes through the insulating clearance area.

[0015] Furthermore, the metal patch radiation structure is one of a bow-shaped patch, a double patch structure, or a multi-region patch topology.

[0016] Furthermore, both the first vertical through hole and the second vertical through hole are filled with one or more of copper and tungsten.

[0017] Furthermore, the dielectric of the first dielectric layer includes one of silicon dioxide, silicon nitride, aluminum nitride, and aluminum oxide; the dielectric of the second dielectric layer includes one of silicon dioxide, silicon nitride, aluminum nitride, and aluminum oxide; and the dielectric component of the electrical isolation layer includes one or more of silicon dioxide, silicon nitride, aluminum nitride, and aluminum oxide.

[0018] Furthermore, the substrate comprises one or more of the following: high-resistivity silicon, diamond, sapphire, silicon carbide, indium phosphide, gallium arsenide, gallium nitride, quartz, and glass.

[0019] Furthermore, the intermediate metal layer comprises one or more of gold, copper, silver, aluminum, or platinum; the contact electrode comprises one or more of gold, copper, silver, aluminum, and platinum; and the metal patch comprises one or more of gold, copper, silver, aluminum, and platinum.

[0020] This invention also provides a method for preparing the above-mentioned indirect heating reconfigurable smart metasurface based on phase change materials, comprising the following steps:

[0021] S1. Fabricate contact electrodes in the substrate;

[0022] S2. Deposit a first dielectric layer over the substrate, deposit an intermediate metal layer over the first dielectric layer, and deposit a second dielectric layer over the intermediate metal layer.

[0023] S3. Prepare a first vertical through-hole and a second vertical through-hole in the first dielectric layer, the intermediate metal layer and the second dielectric layer;

[0024] S4. Prepare a microheater and deposit an electrically insulating layer on top of the second medium;

[0025] S5. Deposit a phase change material layer on the electrically insulating layer;

[0026] S6. Deposit a metal patch radiating structure on a phase change material.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. This invention drives the phase change material to undergo a crystalline / amorphous state transition by indirectly heating it with heat generated by a micro-heater. By adjusting the phase state of the phase change material, the coupling state, current distribution, or local impedance between the patches can be changed, thereby achieving multi-bit phase modulation of the unit and improving beamforming accuracy. The phase change material can maintain the set crystalline / amorphous state without the need for continuous bias to maintain the state, which significantly reduces the static power consumption of the metasurface array.

[0029] 2. The metasurface unit structure of the present invention can be integrated into a large-scale array using standard micro-nano processes, and is suitable for reflective, transmissive and hybrid reflective-transmissive tunable metasurfaces;

[0030] 3. The present invention provides a reconfigurable smart metasurface structure based on phase change materials, which realizes low power consumption, high reliability and high precision multi-bit phase modulation, and provides a highly engineering feasible technical solution for millimeter wave / terahertz antennas, intelligent electromagnetic environment construction and future 6G communication. Attached Figure Description

[0031] 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.

[0032] Figure 1 A three-dimensional structural schematic diagram of a reconfigurable smart metasurface unit based on phase change materials provided in an embodiment of the present invention;

[0033] Figure 2 A front cross-sectional view of the reconfigurable smart metasurface unit based on phase change materials provided in an embodiment of the present invention;

[0034] Figure 3 A side cross-sectional view of a reconfigurable smart metasurface unit based on phase change materials provided in an embodiment of the present invention;

[0035] Figure 4 This is a top view of the top-level radiative patch structure and phase change layer of a reconfigurable smart metasurface unit based on phase change materials, provided in an embodiment of the present invention.

[0036] Figure 5 These are simulation diagrams of the phase response of the metasurface unit under two different states in an embodiment of the present invention;

[0037] Figure 6 These are simulation diagrams of the amplitude response of the metasurface unit under two different states in an embodiment of the present invention;

[0038] Figure 7 This is a schematic diagram of the atomic structure of a phase change material with polymorphic properties in an embodiment of the present invention;

[0039] Figure 8 This is the amplitude response diagram of multi-bit phase modulation achieved by the metasurface unit in an embodiment of the present invention.

[0040] In the figure: 1-substrate; 101-contact electrode; 2-first dielectric layer; 3-intermediate metal layer; 4-second dielectric layer; 5-electrical isolation layer; 6-phase change material layer; 71-first metal patch; 72-second metal patch; 81-first vertical via; 82-second vertical via. Detailed Implementation

[0041] 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.

[0042] Example 1:

[0043] like Figure 1-4 As shown, the metasurface unit of this embodiment includes, from bottom to top, a substrate 1, a first dielectric layer 2, an intermediate metal layer 3, a second dielectric layer 4, an electrical isolation layer 5, a phase change material layer 6, and a first metal patch 71 and a second metal patch 72 of a metal patch radiating structure. The electrical isolation layer 5 is in contact with the phase change material layer 6, and gaps are provided between the first metal patch 71 and the second metal patch 72 and the electrical isolation layer 5. Figure 4 As shown, a phase change material layer 6 is disposed between the first metal patch 71 and the second metal patch 72; multiple metasurface units can be arranged in an array to form a metasurface structure.

[0044] The substrate 1 contains a contact electrode 101 for transmitting control signals; a micro heater 501 is embedded in the electrical isolation layer 5, which has two ports (a first port and a second port); a first vertical through-hole 81 and a second vertical through-hole 82 are provided in the first dielectric layer 2, the intermediate metal layer 3, and the second dielectric layer 4.

[0045] In this embodiment, the first vertical through-hole 81 penetrates the second dielectric layer 4, with its top end connected to the first port of the micro heater 501 and its bottom end connected to the intermediate metal layer 3; the second vertical through-hole 82 penetrates the second dielectric layer 4, the intermediate metal layer 3, and the first dielectric layer 2, with its top end connected to the second port of the micro heater 501 and its bottom end connected to the contact electrode 101; in addition, there is an insulating clearance area 301 in the intermediate metal layer 3 through which the second vertical through-hole 82 passes. This area is larger than the area of ​​the second vertical through-hole 82 in the horizontal direction, and the second vertical through-hole 82 is contained within this area. This area is used to prevent the vertical through-hole 82 from short-circuiting with the intermediate metal layer 3; in this embodiment, the insulating clearance area 301 is ring-shaped and is made of an insulating material (such as alumina, aluminum nitride, silicon dioxide, etc.); in other embodiments, the shape of the insulating clearance area 301 is sufficient to surround the second vertical through-hole for insulation, and its shape is not specially designed.

[0046] The phase change material layer 6 is located directly above the microheater 501. By applying an electrical signal to the microheater 501, heat is generated and transferred to the phase change layer 6 through the electrical isolation layer 5, controlling the crystallization or amorphization of the phase change material. In this embodiment, the vertical distance between the microheater 501 and the phase change material layer 6 is set to 60 nm. In other embodiments, the distance can be set to any value between 60 and 300 nm, all of which can ensure heat transfer.

[0047] The first metal patch 71 and the second metal patch 72 are respectively disposed at both ends of the phase change material layer 6 and above the phase change material layer 6. An opening structure is included between the first metal patch 71 and the second metal patch 72, and the two do not contact each other. When the phase change material layer 6 is in a crystalline state, it has a low resistance, and an effective conductive path can be formed between the first metal patch 71 and the second metal patch 72. When the phase change material layer 6 is in an amorphous state, it has a high resistance, and the equivalent coupling between the first metal patch 71 and the second metal patch 72 is weakened or broken. By utilizing the difference in conductivity of the phase change material layer 6 in different states, a stable state with two obvious phase differences can be formed.

[0048] In this embodiment, the selection of materials for each structural layer follows the following principles:

[0049] Phase change materials need to possess significant reversible phase change characteristics, a large conductivity change ratio, good cycle stability, and compatibility with micro / nano fabrication processes; the microheater 501 material needs to have low resistivity, good thermal stability, and controllable heating characteristics to achieve localized heating at low drive power; the dielectric layer material needs to have good electrical isolation performance, high dielectric strength, and thermal stability to achieve effective isolation between the heating circuit and the radio frequency circuit; the intermediate metal layer 3 and the metal patch need to have high conductivity to reduce losses; the substrate 1 material needs to have low dielectric loss, high thermal conductivity, or good process compatibility to meet the application requirements of millimeter-wave / terahertz bands.

[0050] Therefore, in this embodiment, the phase change material is selected as germanium-antimony-tellurium (Ge2Sb2Te5, GST), which has a significant difference in electrical conductivity between the amorphous and crystalline states, enabling effective control of the reflection phase and amplitude of the metasurface unit. The microheater 501 adopts a tungsten thin-film resistance heating structure, which combines good thermal stability and integrability, facilitating on-chip localized controllable heating. The first dielectric layer 2 and the second dielectric layer 4 are selected as alumina (Al2O3) to achieve electrical isolation between the contact electrode 101 and the microheater 501. The electrical isolation layer 5 is selected as nitride. Aluminum (AlN) has both good electrical insulation and thermal conductivity, which is beneficial for efficiently transferring heat to the phase change material layer 6; the intermediate metal layer 3 is made of copper (Cu) to reduce ohmic losses in the interconnection path between the feed network and the micro heater 501; the contact electrode 101 is made of gold (Au) to improve the ohmic contact performance with the phase change material and the micro heater 501; the substrate 1 is made of a high-resistivity silicon substrate to balance process maturity and RF performance; the metal radiating patch layer is made of copper or gold to form the radiating structure of the metasurface unit and realize electromagnetic wave phase modulation.

[0051] In other optional embodiments, the substrate 1 includes, but is not limited to, one or more of high-resistivity silicon, diamond, silicon carbide, indium phosphide, gallium arsenide, gallium nitride, quartz, and glass; the contact electrode 101 includes, but is not limited to, one or more of high-conductivity metal materials such as gold, copper, silver, aluminum, and platinum; the first dielectric layer 2 includes, but is not limited to, one or more of silicon dioxide, silicon nitride, and aluminum nitride; the intermediate metal layer 3 includes, but is not limited to, one or more of high-conductivity metal materials such as gold, copper, silver, aluminum, and platinum; the second dielectric layer 4 includes, but is not limited to, one or more of silicon dioxide, silicon nitride, and aluminum nitride; the first vertical via 81 and the second The vertical through-hole 82 is filled with materials including but not limited to one or more of copper and tungsten; the micro heater 501 includes but is not limited to one or more of tungsten, chromium, nickel, titanium nitride, titanium tungsten, and ITO; the electrical isolation layer 5 includes but is not limited to one or more of silicon dioxide, silicon nitride, aluminum nitride, and aluminum oxide; the phase change material is a chalcogenide compound, or a chalcogenide compound doped with one or more of elements such as indium, hafnium, yttrium, scandium, gallium, and titanium, wherein the chalcogenide compound includes germanium telluride, antimony telluride, and germanium antimony telluride; the first metal patch 71 and the second metal patch 72 include but are not limited to one or more of metal materials with high electrical conductivity such as gold, copper, silver, aluminum, and platinum.

[0052] It should be noted that the metal patch radiation structure in the present invention can not only adopt the bow-shaped patch structure used in Example 1, but also adopt a double patch structure or a multi-region patch topology structure, as long as the two sides of the metal patch radiation structure are connected by a phase change material layer.

[0053] Example 2:

[0054] In this embodiment, a method for preparing the reconfigurable smart metasurface based on phase change materials as described in Example 1 is provided, and the specific steps are as follows:

[0055] S1: A bottom contact electrode is fabricated on substrate 1. High-resistivity silicon is selected as substrate 1. After cleaning substrate 1, the bottom electrode window is defined at a predetermined position on the substrate surface using photolithography and etching processes. A metal layer Cr / Au is deposited using photolithography and electron beam evaporation deposition processes (Cr is used as an adhesion layer in conventional deposition processes to ensure the reliability of material deposition), and then peeled off to form contact electrode 101. The materials selected above are only one specific embodiment. Substrate 1 can also be one or more of high-resistivity silicon, diamond, silicon carbide, indium phosphide, gallium arsenide, gallium nitride, quartz, and glass. Contact electrode 101 can also be a multilayer structure composed of one or more of gold, copper, silver, aluminum, platinum, and other metal materials with high electrical conductivity.

[0056] S2: Prepare a first dielectric layer 2 on substrate 1. Specifically, use plasma enhanced chemical vapor deposition (PECVD) to deposit the first dielectric layer 2 aluminum oxide on substrate 1. The first dielectric layer 2 can also be one of silicon dioxide, silicon nitride, and aluminum nitride.

[0057] S3: An intermediate metal layer 3 is deposited above the first dielectric layer 2. Specifically, copper is deposited using an electron beam evaporation deposition process, and patterned using photolithography and etching processes to define the avoidance area 301 of the via, forming an intermediate bias / ground signal layer. The intermediate metal layer 3 can also be one or more of the following metal materials with high electrical conductivity: gold, copper, silver, aluminum, platinum, etc.

[0058] S4: A second dielectric layer 4 is deposited above the intermediate metal layer 3. Specifically, aluminum oxide is deposited by PECVD as an insulating layer and chemical mechanical polishing (CMP) is performed to achieve surface planarization. The second dielectric layer 4 can also be one of silicon dioxide, silicon nitride, or aluminum nitride.

[0059] S5: In the above structure, a first vertical via 81 and a second vertical via 82 are fabricated. Specifically, the vertical vias are fabricated using photolithography and deep reactive ion etching (DRIE) processes. Through step-by-step etching or by using etch stop layers of different depths, the first etching depth reaches the surface of the intermediate metal layer 3 to obtain the first vertical via 81. The second etching depth penetrates the intermediate metal layer 3 and the first dielectric layer 2, reaching the bottom contact electrode 101 to obtain the second vertical via 82. The vias are filled with copper using an electroplating process, and then CMP polishing is performed to remove excess metal from the surface, completing the fabrication of the first vertical via 81 and the second vertical via 82. The first vertical via 81 and the second vertical via 82 will serve as the vertical interconnection of the heating current path for the phase change unit. The filling material for the first vertical via 81 and the second vertical via 82 can also be one or more of copper and tungsten.

[0060] S6: An electrical isolation layer 5 and a microheater 501 are fabricated above the second dielectric layer 4. Specifically, tungsten is prepared by chemical vapor deposition (CVD), and the microheater is patterned using photolithography and etching processes to obtain the microheater 501. Aluminum nitride is deposited by CVD, and the surface is planarized using CMP to complete the fabrication of the electrical isolation layer 5. The dielectric in the electrical isolation layer can also be one or more of silicon dioxide, silicon nitride, and aluminum oxide.

[0061] S7: Deposit a phase change material layer 6 on the electrically isolated layer 5. Specifically, in an optional embodiment, a phase change material Ge2Sb2Te5 is deposited on the electrically isolated layer 5 as the phase change material layer 6 using magnetron sputtering. The phase change material is patterned using photolithography, and the phase change material outside the patterned area is etched away using etching. After removing the resist, the preparation of the phase change material layer 6 is completed. The phase change material is a chalcogenide compound, or a chalcogenide compound doped with one or more elements such as indium, hafnium, yttrium, scandium, gallium, and titanium. The chalcogenide compounds include germanium telluride, antimony telluride, and germanium-antimony-telluride.

[0062] S8: Deposit a first metal patch 71 and a second metal patch 72 on the phase change layer 6. Specifically, the metal patch structure is patterned on the wafer using photolithography. Chromium and gold films are deposited sequentially on the wafer using electron beam evaporation deposition. The photoresist and metal materials outside the patterned area are removed using a wet stripping process. The wet stripping process specifically involves cleaning with acetone, stripping solution, isopropanol, and ultrapure water in sequence to complete the preparation of the first metal patch 71 and the second metal patch 72. The materials selected for the first metal patch 71 and the second metal patch 72 include, but are not limited to, one or more of the following metal materials with high electrical conductivity: gold, copper, silver, aluminum, platinum, etc.

[0063] In this invention, single-bit phase switching is achieved by completely switching the phase change material between a crystalline and amorphous states. When the phase change material transforms from an amorphous to a crystalline state, a wide-pulse, high-voltage, or high-power excitation is applied through a feeding network, causing the entire phase change material to heat up to its crystallization temperature range and maintain this temperature for a sufficient time. This transforms the disordered atomic structure within the material into an ordered lattice structure, thereby forming a continuous crystallization region in the phase change material area. At this point, the phase change material exhibits high conductivity, a stable conductive path is formed between the regions on both sides of the metal patch, the equivalent impedance of the metasurface unit changes, and the reflection or transmission phase jumps to the first state. The crystalline state is a non-volatile state and can be maintained for a long time without external bias.

[0064] When a phase change material (PCM) reverts from a crystalline to an amorphous state, a narrow-pulse, high-voltage excitation is applied, causing the material to locally and instantaneously heat up to its melting temperature. Following rapid quenching after the excitation, a disordered structure is formed. This process causes the PCM to re-enter the amorphous state, exhibiting high impedance characteristics. The conductive paths between the patch structures are interrupted or significantly weakened, and the reflection phase of the unit cells jumps to a second state. Combined with... Figure 5 It can be seen that the reflection phase curve corresponding to the amorphous state is generally located in the high phase range, maintaining a clear and stable phase interval with the crystalline state curve within the target operating frequency band. This indicates that the unit can form a distinguishable discrete phase response in both states. The phase difference between the crystalline and amorphous states depends on the unit structure design and the phase change material parameters, which can be illustrated by the simulation results of the phase difference and return loss in the attached figures. Both states can remain stable after the external excitation is removed, exhibiting non-volatility and repeatability.

[0065] Furthermore, such as Figure 6 As shown, within the same frequency band, the metasurface unit maintains a low amplitude loss level in both crystalline and amorphous states. The reflection amplitude changes smoothly with frequency without drastic fluctuations, indicating that the phase change material state switching does not introduce significant additional losses. Compared to the amorphous state, the reflection amplitude changes slightly in the crystalline state due to the formation of the conduction path, but it remains within an acceptable range overall, which is beneficial for maintaining amplitude-phase consistency in array-level applications.

[0066] Taking a reflective tunable metasurface as an example, when the phase change material is in a crystalline state, its high conductivity allows the bow-shaped metal patch to form a continuously conducting current path, and the unit exhibits an equivalent radiation structure with a large electrical size, corresponding to the first reflection phase state (e.g., 0°). When the phase change material transforms into an amorphous state, its conductivity significantly decreases, the current path in the central region of the patch is effectively broken, the current distribution path within the unit changes, the equivalent electrical size of the unit decreases, and its resonant characteristics change accordingly, thus corresponding to the second reflection phase state (e.g., 180°) at the same operating frequency. In the parameter design of this embodiment, by synergistically optimizing the geometric dimensions of the metal patch and the size of the phase change region, the reflection phase difference between the two states near the approximately 90 GHz operating frequency band is made close to 180°, thereby realizing 1-bit digital phase encoding for programmable control of the reflected electromagnetic wavefront.

[0067] In a transmissive tunable metasurface structure, a phase change material is placed between upper and lower metal patches or a slot coupling structure. Its phase change is used to adjust the electromagnetic coupling strength and equivalent impedance characteristics inside the unit.

[0068] When the phase change material is in a crystalline state, the unit cell forms a strong coupling channel for the incident electromagnetic wave, enabling the transmitted wave to acquire a first transmission phase state. When the phase change material is in an amorphous state, the coupling within the unit cell weakens or is effectively shut off, and the transmitted wave acquires a second transmission phase state different from the aforementioned first transmission phase state. By designing the unit cell structural parameters, discrete transmission phase switching can be achieved within the target frequency band, which can be used to construct a programmable transmission array.

[0069] Figure 4 This is a top view of the top-layer radiating patch structure and phase change layer of a reconfigurable smart metasurface based on phase change materials provided in an embodiment of the present invention. In an optional embodiment, the patch antenna is as follows: Figure 4 The bow shape shown has patches 71 and 72 that are axially symmetrical, with key dimensions L1, L2, and L3 respectively. The phase change layer 6 is located between the two patches, with a width of W1 and a length of W2.

[0070] Furthermore, to verify the phase response capability of the reconfigurable smart metasurface unit to electromagnetic signals in the embodiments of the present invention, a model of the reconfigurable smart metasurface unit based on phase change material was established using HFSS software, and the phase response characteristics of the reconfigurable smart metasurface unit with the phase change material in different states were simulated. In an optional embodiment, the patch dimensions are L1=200um, L2=300um, and L3=100um, and the width of the phase change layer is W1=15um and the length is W2=15um.

[0071] Furthermore, multi-value switching can be achieved by controlling the phase change material. By applying electrical signals with different pulse widths and amplitudes to the phase change material, the resistance value of the phase change material is changed, so that the equivalent conductance path between the patches has multi-level adjustable characteristics, thereby obtaining more than two stable phase states and realizing multi-bit phase control. Figure 7 The atomic structure diagram of a phase change material with multiple crystalline states is shown. In one optional embodiment, the GeSbTe material has a cubic phase crystalline state and a hexagonal phase crystalline state. The transformation from the amorphous state to the cubic phase and from the cubic phase to the hexagonal phase can be achieved by different thermal excitation conditions, and each crystalline state corresponds to different electrical parameter characteristics.

[0072] like Figure 8 As shown, due to the different resistivities of the phase change materials, their equivalent conductivity, local impedance between patch regions, and coupling strength all exhibit continuous variations. Therefore, the corresponding reflection or transmission phase also presents multiple discrete, rewritable stable states. This invention utilizes the resistance of the different states of the aforementioned phase change materials to achieve multi-bit phase encoding. For example, the amorphous state corresponds to the first phase state, the cubic phase to the second phase state, and the hexagonal phase to the third phase state. Each state can be reliably written by applying a preset pulse excitation condition.

[0073] In array applications, the unit structure of this invention can be arranged in a two-dimensional array. By writing different phase response information to different units, multi-level control of the reflected or transmitted wavefront can be achieved, which can be used for applications such as beamforming, wide-angle scanning, sidelobe suppression, or multi-functional electromagnetic field control. Since all states of the phase change material are non-volatile, the array can still maintain the set wavefront distribution after the external excitation is removed, thereby significantly reducing system power consumption and improving the reliability and environmental adaptability of array operation.

[0074] In summary, the reconfigurable smart metasurface structure based on phase change materials disclosed in this invention solves the problem of heat loss to the substrate and isolation layer during microheater heating, reduces heat transfer loss and power consumption, and drives the phase change material to undergo a crystalline / amorphous transition. By adjusting the phase state of the phase change material, the coupling state, current distribution or local impedance between the patches can be changed.

[0075] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A reconfigurable smart metasurface based on indirect heating of phase change materials, characterized in that, The metasurface is composed of multiple metasurface units arranged in an array. Each metasurface unit includes, from bottom to top, a substrate, a first dielectric layer, an intermediate metal layer, a second dielectric layer, an electrical isolation layer, a phase change material layer, and a metal patch radiating structure. The phase change material layer is located in the middle of the metal patch radiating structure to connect the patches on both sides of the metal patch radiating structure. The substrate is provided with a contact electrode electrically connected to the feed network, and the electrical isolation layer is provided with a micro heater. The micro heater is provided with a first port and a second port. The first port is electrically connected to the upper surface of the intermediate metal layer through a first vertical via, and the second port is electrically connected to the contact electrode through a second vertical via. The first dielectric layer, the second dielectric layer, and the electrical isolation layer are insulating layers; the heat generated by the micro heater drives the phase change material to undergo a crystalline / amorphous state transition in an indirect heating manner, changing the equivalent conductive path, electromagnetic coupling strength, or local impedance between the metal patch radiation structures under different phase states.

2. The indirect heating reconfigurable smart metasurface based on phase change materials as described in claim 1, characterized in that: The phase change material is a chalcogenide compound or a chalcogenide compound doped with one or more of the elements Se, Bi, Sn, N, In, Hf, Y, Sc, Ga, and Ti. The chalcogenide compound includes germanium telluride, antimony telluride, and germanium-antimony-telluride.

3. The reconfigurable smart metasurface based on indirect heating of phase change materials as described in claim 1, characterized in that: The components of the micro heater include one or more of tungsten, chromium, nickel, titanium nitride, titanium tungsten, and ITO.

4. The indirect heating reconfigurable smart metasurface based on phase change materials as described in claim 1, characterized in that: The first vertical through-hole penetrates the second dielectric layer, and the second vertical through-hole penetrates the second dielectric layer, the intermediate metal layer, and the first dielectric layer. The intermediate metal layer has an insulating clearance area, and the second vertical through-hole passes through the insulating clearance area.

5. The indirect heating reconfigurable smart metasurface based on phase change materials as described in claim 1, characterized in that: The metal patch radiation structure is one of the following: a bow-shaped patch, a double patch structure, or a multi-region patch topology.

6. The indirect heating reconfigurable smart metasurface based on phase change materials as described in claim 4, characterized in that: Both the first vertical through hole and the second vertical through hole are filled with one or more of copper and tungsten.

7. The indirect heating reconfigurable smart metasurface based on phase change materials as described in claim 1, characterized in that: The dielectric of the first dielectric layer is one of silicon dioxide, silicon nitride, aluminum nitride, and aluminum oxide; the dielectric of the second dielectric layer is one of silicon dioxide, silicon nitride, aluminum nitride, and aluminum oxide; the dielectric component of the electrical isolation layer is one or more of silicon dioxide, silicon nitride, aluminum nitride, and aluminum oxide.

8. The reconfigurable smart metasurface based on indirect heating of phase change materials as described in claim 1, characterized in that: The substrate includes one or more of the following: high-resistivity silicon, diamond, sapphire, silicon carbide, indium phosphide, gallium arsenide, gallium nitride, quartz, and glass.

9. The reconfigurable smart metasurface based on indirect heating of phase change materials as described in claim 1, characterized in that: The intermediate metal layer is composed of one or more of gold, copper, silver, aluminum, or platinum; the contact electrode is composed of one or more of gold, copper, silver, aluminum, or platinum; and the metal patch is composed of one or more of gold, copper, silver, aluminum, or platinum.

10. The method for preparing an indirect heating reconfigurable smart metasurface based on phase change materials according to any one of claims 1 to 9, characterized in that: Includes the following steps: S1. Fabricate contact electrodes in the substrate; S2. Deposit a first dielectric layer over the substrate, deposit an intermediate metal layer over the first dielectric layer, and deposit a second dielectric layer over the intermediate metal layer. S3. Prepare a first vertical through-hole and a second vertical through-hole in the first dielectric layer, the intermediate metal layer and the second dielectric layer; S4. Prepare a microheater and deposit an electrically insulating layer on top of the second medium; S5. Deposit a phase change material layer on the electrically insulating layer; S6. Deposit a metal patch radiating structure on a phase change material.

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