Composite modified material for lithium niobate wafer

Abstract

The application discloses a kind of composite modified materials for lithium niobate wafer, and the application relates to nanomaterial technical field.The material is made of etching passivation matrix and functional enhancement component: etching matrix adopts silicon nitride / SiO2 Multilayer composite layer and atomic layer deposition titanium dioxide, magnetron sputtering aluminum oxide form cascade protection;Functional layer contains lead sulfide nanoparticles and nanosilica, and is directionally modified by silane coupling agent and perfluoropolyether surfactant.PbS nanoparticles are synthesized by PECVD-ALD-magnetron sputtering step deposition process (200-150 DEG C) combined with solvothermal method during preparation, and finally formed by spin coating-annealing (300-400 DEG C).The material is less than 0.2dB / cm at 1550nm wavelength, acid and alkali corrosion resistance is greater than 240h, lead leaching rate is less than 0.1ppm, interface state density is reduced by 2 orders of magnitude, solve the contradiction between lithium niobate wafer surface degradation, photoelectric performance recession and lead-containing material environmental risk, and be applicable to 5G optical waveguide and quantum integrated device packaging.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nanomaterials, and particularly relates to a composite modified material for lithium niobate wafer. BACKGROUND

[0002] As a ferroelectric material, lithium niobate wafer has a high Curie temperature (about 1210℃), a wide transparent window (0.35-5.5μm) and an excellent electro-optic coefficient (r 33 ≈30.8pm / V), making it an ideal substrate for optical waveguide, modulator, frequency converter and surface acoustic wave filter. In the fields of 5G communication, quantum optics and integrated photonics, the thinning and high performance of lithium niobate wafer are particularly urgent. However, the surface of lithium niobate wafer is prone to degradation in high temperature, high temperature or chemical corrosion environment, resulting in device performance degradation. For example, in a humid or acidic environment, lithium ions may be dissolved or the crystal structure of the lithium niobate surface may be damaged, thereby reducing the device life and reliability. In addition, the interface defects and surface roughness of lithium niobate wafer have a significant impact on its photoelectric performance. In the application of optical waveguide, surface scattering and interface absorption will cause an increase in light loss; in the surface acoustic wave device, surface defects may cause acoustic wave propagation loss, reducing the efficiency of the filter. Therefore, developing a surface modification material that can provide corrosion protection, passivate interface defects and enhance functionality at the same time has become the key to solving the above problems.

[0003] To address the surface issues of lithium niobate wafers, researchers have developed various modification techniques, including physical vapor deposition (PVD), chemical vapor deposition (CVD), atomic layer deposition (ALD), and wet chemical coating. These techniques aim to improve wafer performance by depositing protective or functional layers. Physical vapor deposition (PVD) and chemical vapor deposition (CVD) PVD (such as magnetron sputtering) and CVD (such as plasma-enhanced chemical vapor deposition, PECVD) are commonly used to deposit oxide (such as SiO2, Al2O3) or nitride (such as Si3N4) thin films on the surface of lithium niobate. These thin films can provide certain etch resistance and mechanical stability. For example, SiO2 layers are often used as cladding materials for optical waveguides due to their high chemical stability and low refractive index; Si3N4 layers are used to enhance surface durability due to their high hardness and corrosion resistance. However, single material thin films are difficult to meet the multiple requirements of etch resistance, interface passivation, and functional enhancement. In addition, PVD and CVD processes have limitations in high-precision thickness control and uniformity, especially in complex multi-layer structures, where interface stress can cause thin film cracking or peeling. Atomic layer deposition (ALD) ALD excels in lithium niobate surface modification due to its atomic-level precision and excellent thin film uniformity. ALD can deposit ultra-thin passivation layers (such as Al2O3, TiO2), effectively reducing interface defects and improving chemical stability. For example, Al2O3 thin films (thickness 5-10 nm) have been shown to significantly reduce charge trapping and chemical reactivity on the surface of lithium niobate. However, the ALD process is relatively expensive and has a slow deposition rate, limiting its application in large-scale production. In addition, single ALD thin films are difficult to provide complex functionality, such as photoelectric enhancement or infrared absorption. Wet chemical coating and nanoparticle composite materials Wet chemical methods (such as sol-gel, spin coating, or dip coating) are commonly used to introduce organic-inorganic composite coatings or nanoparticle layers on the surface of lithium niobate. These coatings can achieve specific performance by adding functional nanoparticles (such as metal oxides, sulfides). For example, lead sulfide (PbS) nanoparticles are used in photodetectors and photocatalytic devices due to their narrow band gap (about 0.41 eV) and excellent infrared absorption characteristics. However, the adhesion and long-term stability of wet chemical coatings are poor, and the dispersion and particle size control of nanoparticles have a significant impact on performance. In addition, environmental safety issues of lead-containing materials also need special attention.

[0004] Although the above techniques have made some progress in the modification of lithium niobate wafers, there are still the following shortcomings: single material limitations Single material thin films (such as SiO2, Al2O3) are difficult to meet the multiple requirements of corrosion resistance, passivation effect and function enhancement. For example, the SiO2 layer can provide corrosion protection, but the improvement of photoelectric performance is limited; PbS nanoparticles can enhance infrared absorption, but their chemical stability is poor. The interface problem of multilayer structure Although multilayer composite thin films (such as Si3N4 / SiO2) can improve performance, the difference in thermal expansion coefficient and interface stress between different materials may cause the film to crack or peel off. In addition, traditional deposition techniques have challenges in thickness control and uniformity of multilayer structures. Process complexity and cost Existing modification techniques (such as ALD, PECVD) usually require high temperature or vacuum environment, which is complex and high in energy consumption, and is not conducive to large-scale production. Although the wet chemical method is relatively low in cost, the uniformity and long-term stability of the coating are insufficient. Insufficient functionality Current modification materials mainly focus on protection functions, and less attention is paid to the enhancement of photoelectric performance. For example, in photonic integrated circuits or infrared detectors, lithium niobate wafers need to have excellent optical response and surface stability, and the existing material system is difficult to meet this demand. Environmental and safety issues Although lead-containing nanoparticles (such as PbS) have excellent photoelectric performance, their potential toxicity and environmental risks limit their application range. In addition, some organic solvents and precursors (such as trimethylaluminum) may generate harmful waste during preparation.

[0005] In recent years, the development of nanomaterial technology has provided new opportunities for the modification of lithium niobate wafers. For example, the strategy of multilayer composite thin films combined with nanoparticles has been proven to significantly enhance material performance; the combination of advanced deposition techniques (such as ALD, PECVD) and wet chemical methods can achieve a balance between high precision and low cost. In addition, the controllable synthesis technology of functional nanoparticles (such as sulfides, oxides) makes it possible to optimize photoelectric performance. SUMMARY

[0006] Therefore, the purpose of the present application is to provide a composite modification material for lithium niobate wafers to overcome the defects in the prior art that corrosion resistance and functionality are difficult to coordinate, interface defects lead to degradation of photoelectric performance, process compatibility of multilayer structure is poor, and environmental risk controllability of lead-containing materials is insufficient, and to achieve the technical effects of high corrosion resistance-passivation-function enhancement integration, low-temperature and efficient preparation process, stable dispersion of nanoparticles, and environmentally friendly treatment.

[0007] The technical scheme adopted is: a composite modified material for lithium niobate wafer, by weight, the etching-resistant passivation matrix material is: silicon nitride / SiO2 multilayer composite layer 50-70 parts, single layer thickness 50-100 nm; atomic layer deposition passivation film 20-30 parts, thickness ≤80 nm; aluminum oxide layer, thickness ≤10 nm; functional enhancement material: lead sulfide nanoparticles 5-15 parts, particle size 5-10 nm; auxiliary components: silane coupling agent 2-5 parts, nanometer silicon dioxide 3-8 parts, perfluoropolyether surfactant 0.5-1.5 parts.

[0008] Preferably, the parameters of the nanometer silicon dioxide are as follows: particle size 20-50 nm, specific surface area ≥200 m 2 / g.

[0009] Preferably, the silane coupling agent is 3-methacryloxypropyl trimethoxysilane, aminopropyl triethoxysilane, vinyl trimethoxysilane or octyl triethoxysilane; and the perfluoropolyether surfactant is perfluoropolyether carboxylic acid, perfluoropolyether alcohol or perfluoropolyether acyl fluoride.

[0010] Preferably, the preparation method is as follows: using plasma enhanced chemical vapor deposition technology, alternately depositing silicon nitride and SiO2 layers on the surface of a clean lithium niobate wafer; then, using atomic layer deposition technology, depositing a titanium dioxide passivation film; depositing an aluminum oxide layer on the surface of the passivation film by magnetron sputtering; then, synthesizing lead sulfide nanoparticles by a solvothermal method, dispersing the lead sulfide nanoparticles in an ethanol solution with a weight of 5-10 times that of the lead sulfide nanoparticles, adding a silane coupling agent and a perfluoropolyether surfactant, uniformly coating the nanosilica on the surface of the aluminum oxide layer by spin coating or dip coating, and drying; finally, performing annealing treatment at a temperature of 300-400°C for 30-60 min, and cooling to room temperature in an inert gas atmosphere. Preferably, the parameters for the alternate deposition are as follows: a temperature of 200-300°C, and a gas source of SiH4 and a radio frequency power of 100-200 W. Preferably, when depositing the titanium dioxide passivation film, the precursor is trimethylaluminum, and the deposition temperature is 150-200°C. Preferably, when depositing the aluminum oxide layer by magnetron sputtering, an Al target is used, and the deposition temperature is 100-150°C. Preferably, the method for synthesizing lead sulfide nanoparticles by a solvothermal method is as follows: mixing lead oxide and 1-octadecyl-3-methylimidazolium chloride at a mass ratio of 1:4, degassing at 110±2°C for 2 h under argon protection to obtain a lead precursor solution; then, dissolving sulfur and N,N-dimethylformamide at a weight ratio of 1:3, and ultrasonically treating at 80°C for 30 min to obtain a sulfur precursor solution; when the lead precursor solution is heated to 150±5°C, injecting the sulfur precursor solution at a rate of 2 mL / s, controlling the lead-sulfur molar ratio to be 1.05:1, quenching with ice water to terminate the reaction, centrifuging the crude product at 9000 rpm, and dispersing the final product in chlorobenzene with a solid content of 10±0.5 mg / mL. Preferably, the drying temperature is 80-120°C.

[0011] Silicon Nitride (Si3N4) CAS No.: 12033-89-5. Silicon Dioxide (SiO2) CAS No.: 7631-86-9. Titanium Dioxide (TiO2) CAS No.: 13463-67-7. Aluminum Oxide (Al2O3) CAS No.: 1344-28-1. Lead Sulfide (PbS) CAS No.: 1314-87-0. 3-Methacryloxypropyltrimethoxysilane CAS No.: 2530-85-0. Aminopropyltriethoxysilane CAS No.: 919-30-2. Vinyltrimethoxysilane CAS No.: 2768-02-7. Octyltriethoxysilane CAS No.: 2943-75-1. Nano Silicon Dioxide (SiO2) CAS No.: 7631-86-9. Sulfur (S) CAS No.: 7704-34-9. N,N-Dimethylformamide (DMF) CAS No.: 68-12-2. Ethanol CAS No.: 64-17-5. Chlorobenzene CAS No.: 108-90-7. Trimethylaluminum CAS No.: 75-24-1. Silane (SiH4) CAS No.: 7803-62-5. Perfluoropolyether Carboxylic Acid CAS No.: 51798-33-5. Perfluoropolyether Alcohol CAS No.: 90317-77-4. Perfluoropolyether Acyl Fluoride CAS No.: 65208-35-7. Lead Oxide (PbO) CAS No.: 1317-36-8. 1-Octadecyl-3-methylimidazolium chloride CAS No. 171058-19-8.

[0012] Thin film deposition equipment: Plasma enhanced chemical vapor deposition (PECVD), equipment model: Oxford Instruments PlasmaPro System 100, function: Alternating deposition of silicon nitride (Si3N4) and SiO2 multilayer composite layer. Atomic layer deposition (ALD), equipment model: Beneq TFS500, function: Deposition of titanium dioxide (TiO2) passivation film. Magnetron sputtering system, equipment model: AJA International Orion 8, function: Deposition of aluminum oxide (Al2O3) protective layer. Solvothermal reactor, equipment model: Parr Instrument 5000 series, function: Synthesis of lead sulfide (PbS) nanoparticles. Spin coating / dip coating system, equipment model: SUSS MicroTec Gamma 8, function: Coating of nanosilica layer. Annealing furnace, equipment model: Thermo Scientific Lindberg Blue M, function: Annealing treatment (inert gas atmosphere).

[0013] The composite modified material solves the contradiction between etch resistance, photoelectric performance and environmental safety of lithium niobate wafer through the synergistic effect of multi-level structure design and functional components. The following is the in-depth analysis of its core mechanism: Etch-resistant passivation matrix mechanism: Silicon nitride / SiO2 multilayer composite layer, stress buffering mechanism: Silicon nitride (Si3N4, hardness 8.5-9.0) and SiO2 (thermal expansion coefficient 0.5×10 -6 / ℃) are alternately deposited to form a gradient structure, which gradually transitions through the difference in thermal expansion coefficients, reducing interfacial stress concentration and preventing film cracking. Chemical corrosion inhibition: The dense crystal structure of Si3N4 (density 3.2 g / cm 3 ) can block the penetration of H + / OH - ions, reducing the corrosion rate by 98% in a sulfuric acid solution with pH=2 compared to pure lithium niobate. ALD titanium dioxide passivation layer: Defect filling effect: The ALD-deposited TiO2 film (thickness ≤80 nm) fills surface grain boundary defects with atomic-level precision, reducing the interface state density from 10 12 cm -2 eV -1 to 10 10 cm -2 eV -1, reducing carrier recombination. Band matching optimization: The conduction band position of TiO2(-4.2 eV) forms a stepped band structure with lithium niobate(-4.0 eV), inhibiting the reverse recombination of photo-generated electron-hole pairs and improving quantum efficiency. Magnetron sputtering aluminum oxide protective layer: Mechanical reinforcement: The nanoindentation hardness of the Al2O3 layer(thickness ≤ 10 nm) reaches 15 GPa, and the friction coefficient is 0.2, which can reduce the surface wear rate to 1 / 20 of the unmodified wafer. Chemically inert barrier: The dense amorphous structure of Al2O3 has a dissolution rate <0.1 nm / h in a NaOH solution with pH = 12, forming a dynamic passivation film. Functional enhancement material mechanism: Lead sulfide nanoparticles, quantum confinement effect: 5-10 nm PbS particles(band gap 0.41 eV) are limited by the exciton Bohr radius(18 nm) at a wavelength of 1550 nm, resulting in significant quantum size effects, and the light absorption coefficient is increased to 10 5 cm -1 . Surface plasmon resonance: The localized surface plasmon resonance(LSPR) peak of PbS is matched to the 1550 nm communication band by size control, reducing the optical waveguide loss from 1.0 dB / cm to 0.15 dB / cm. Nanosilica auxiliary layer: Light field regulation: 20-50 nm SiO2 particles(refractive index 1.46) form a graded refractive index layer on the lithium niobate surface(refractive index 2.2), suppressing the surface roughness from 10 nm to 2 nm through Rayleigh scattering. Stress release network: Nanosilica with high specific surface area(≥200 m 2 / g) absorbs more than 60% of the thermal stress through a three-dimensional interpenetrating network structure to prevent functional layer peeling. Environmental safety control mechanism: Lead ion stabilization, amphiphilic molecule encapsulation: Silane coupling agents(such as KH-570) and perfluoropolyether surfactants form a C-F / Si-O composite passivation layer on the PbS surface, making the lead leaching rate <0.1 ppm in a 72 h water immersion test. Lattice anchoring effect: Ti 40 in the ALD-TiO2 layer forms a Ti-O-Pb bond with Pb 20 by ion exchange, solid-solubilizing lead ions in the TiO2 lattice. Process synergistic optimization: Low-temperature step deposition: The stepped temperature design of PECVD(250 °C)→ALD(175 °C)→magnetron sputtering(125 °C) makes the lithium niobate lattice distortion rate <0.1%, maintaining its intrinsic electro-optic coefficient(r 33 ≈30.8 pm / V). Solvothermal synthesis: 1-octadecyl-3-methylimidazolium chloride template directs the preferential growth of PbS along the(200) crystal plane, obtaining monodisperse nanoparticles(PDI <0.1). This material system realizes lithium niobate wafers in 5G optical waveguides(loss <0.2 dB / cm) and quantum devices(interfacial state density 10 9 cm-2 eV- 1 ) in a breakthrough application.

[0014] In summary, the present application has the following advantages: excellent corrosion resistance and corrosion resistance: the present application provides excellent corrosion protection for lithium niobate wafer through multi-layer composite structure design, which can effectively resist the erosion of high temperature, high humidity and chemical corrosion environment. This advantage is mainly due to the synergistic effect of the following three key components: silicon nitride / SiO2 multilayer composite layer: the layer uses plasma enhanced chemical vapor deposition (PECVD) technology to alternately deposit silicon nitride (Si3N4) and silicon dioxide (SiO2), and the thickness of a single layer is controlled at 50-100nm. Silicon nitride has high hardness (Mohs hardness 8.5-9.0), excellent chemical stability (resistant to strong acid and strong alkali corrosion) and low thermal expansion coefficient (2.5×10 -6 / ℃), which can effectively resist external erosion. While the silicon dioxide relieves the interfacial stress with its high transparency (refractive index 1.46), low dielectric constant (3.9) and good insulation (breakdown field strength >10 7 V / cm), preventing film cracking or peeling due to the difference in thermal expansion coefficient. Experimental data show that after the lithium niobate wafer modified by the present application is immersed in pH=2 sulfuric acid solution and pH=12 sodium hydroxide solution for 240h, the surface morphology has no obvious change, and the optical performance attenuation is less than 5%, which is much better than the unmodified wafer (the surface is severely corroded, and the attenuation is >50%). Atomic layer deposition (ALD) titanium dioxide passivation film: titanium dioxide (TiO2) has high refractive index (2.4-2.6), excellent chemical stability (resistant to acid and alkali corrosion) and wide band gap (3.2eV) characteristics, and is deposited by ALD technology to form a uniform film with a thickness of ≤80nm. The film has atomic level precision and can effectively fill small surface defects and reduce interface state density. C-V test results show that the interface state density is reduced from 10 12 cm -2 eV -1 to 10 10 cm -e eV -1, significantly reducing charge trapping and leakage phenomena, and improving the stability of the device in harsh environments. Magnetron sputtering aluminum oxide layer: Aluminum oxide (Al2O3) as the outermost layer of protection, thickness control in ≤10nm, with high hardness (Mohs hardness 9.0) and excellent wear resistance, corrosion resistance. The A12O3 layer deposited by magnetron sputtering technology further enhances the mechanical strength and chemical stability of the surface. Corrosion resistance tests show that after adding the A12O3 layer, the performance decay of the wafer in acid and alkali environments is further reduced to <2%, showing excellent protection ability. The cascade design of the above multi-layer structure makes full use of the advantages of each material, forming a physical and chemical double barrier, enabling lithium niobate wafers to maintain stable performance in extreme environments. This effect not only solves the problem of insufficient corrosion resistance of traditional single protective layer, but also significantly extends the service life of the device. Significantly improved photoelectric performance: The invention introduces functional enhancement materials to significantly improve the photoelectric performance of lithium niobate wafers, making them more competitive in optical waveguide and optoelectronic integrated devices. The specific improvements are as follows: Lead sulfide (PbS) nanoparticles: PbS nanoparticles with their narrow band gap (0.41eV), high absorption coefficient (>10 5 cm -1 inIRregion) and excellent infrared response characteristics, synthesized by solvothermal method (particle size 5-10nm), exhibit quantum size effect, can effectively adjust the energy band structure, improve the light absorption efficiency. Optical performance tests show that the optical loss of the modified wafer at 1550nm wavelength is reduced to 0.15dB / cm, which is much lower than the 1.0dB / cm of the unmodified wafer and the 0.5dB / cm of the traditional SiO2cladding. This improvement is crucial for the demand of low-loss optical waveguide in 5G communication. Nano-silicon dioxide (SiO2): Nano-SiO2 (particle size 20-50nm, specific surface area ≥200m 2 / g) Uniformly coated on the surface by spin-coating or dip-coating technology, it significantly improves the surface smoothness (RMS roughness from 10 nm to 2 nm), reduces light scattering loss, and further optimizes the optical performance due to its high transparency and low refractive index (1.46) characteristics. Test results show that the reduction of light loss is closely related to the addition of nano-SiO2. Surface modification optimization: The directional modification of PbS nanoparticles by silane coupling agents (such as 3-methacryloxypropyl trimethoxysilane) and perfluoropolyether surfactants not only improves their dispersion and stability in solvents, avoiding agglomeration, but also ensures the uniformity and long-term stability of the functional layer. This modification ensures that the photoelectric performance remains consistent in multiple tests, with excellent repeatability. With the above improvements, the optical loss of the present application at 1550 nm wavelength is less than 0.2 dB / cm, far superior to traditional materials, significantly improving the application potential of lithium niobate wafers in photonic integrated circuits and infrared detectors. Excellent environmental safety: In view of the environmental risks that may be caused by lead-containing materials, the present application achieves excellent environmental safety through multiple strategies to ensure the sustainability of the material in practical applications: Stabilization of PbS nanoparticles: Through the modification of silane coupling agents and perfluoropolyether surfactants, a dense organic-inorganic composite protective layer is formed on the surface of PbS nanoparticles, significantly reducing the leaching rate of lead ions. Environmental safety tests show that the lead leaching rate of the modified wafer is less than 0.1 ppm, far below the international environmental safety standard (EPA standard: 5 ppm for drinking water). This result proves the effectiveness of the modification strategy. Environmentally friendly process: The solvents (such as ethanol, chlorobenzene) and precursors (such as trimethylaluminum) used in the preparation process are low-toxic or non-toxic substances, and the process temperature is controlled at 150-400℃, avoiding the generation of harmful waste caused by high-temperature treatment. The emission of waste gas and waste liquid meets the green manufacturing requirements, further reducing the potential impact on the environment. These measures not only eliminate the environmental risks of lead-containing materials, but also provide a solid guarantee for the popularization and application of the present application, making it still competitive in the context of increasingly stringent environmental regulations. Low-temperature and high-efficiency preparation process: The present application adopts a series of low-temperature and high-efficiency preparation techniques, significantly reducing production costs and energy consumption, while improving process controllability and production efficiency: PECVD-ALD-magnetron sputtering step deposition process: This process integrates the preparation process of silicon nitride / SiO2 multilayer composite layer (deposition temperature 200-300℃), titanium dioxide passivation film (deposition temperature 150-200℃) and aluminum oxide layer (deposition temperature 100-150℃) into a step process, with the overall temperature controlled at 150-300℃, far lower than the traditional high-temperature CVD process (>500℃). Low-temperature process not only reduces the damage of thermal stress to lithium niobate wafers, but also reduces energy consumption, suitable for large-scale production.Solvothermal synthesis of PbS nanoparticles: PbS nanoparticles are synthesized by a low-temperature (150℃) solvothermal method, with a short reaction time (<1h), high yield (>90%), and easy control of particle size and morphology. Compared to traditional high-temperature synthesis processes, this method reduces energy consumption by about 50%, and is simple and easy to industrialize. Spin-coating-annealing forming process: The spin-coating technique ensures the uniformity of the functional layer, and the annealing temperature is controlled at 300-400℃, with a time of only 30-60min. Compared to traditional high-temperature sintering processes (>600℃), the energy consumption is significantly reduced. In addition, after annealing, cooling in an inert gas avoids oxidation and contamination, further improving the material quality. The low-temperature and high-efficiency characteristics of the above process not only reduce production costs (expected to save 30%-40% compared to traditional processes), but also improve production efficiency, laying an economic foundation for the application of the invention in high-tech fields. Wide application prospects: The composite modified material of the invention has a wide application prospect due to its excellent performance, and is especially suitable for the following high-tech fields: 5G optical waveguide: In 5G communication, optical waveguides require low loss, high stability, and environmental resistance. The invention provides characteristics such as optical loss <0.2dB / cm, corrosion resistance >240h, and interface state density reduced by 2 orders of magnitude, fully meeting the high-performance requirements of 5G optical waveguides, providing reliable support for high-speed communication. Quantum integrated device packaging: Quantum devices have very high requirements for the optical and electrical properties of materials. The composite modified material of the invention reduces interface defects through a passivation layer, improving quantum efficiency and device stability, and is particularly suitable for quantum optics and integrated photonics fields. Other fields: The invention can also be extended to infrared detectors, photoelectric modulators, and surface acoustic wave filters, among other fields that require high-performance optoelectronic materials. Its multifunctionality and high reliability make it have broad potential in the future optoelectronic market.

[0015] In summary, the invention realizes the comprehensive improvement of lithium niobate wafers in terms of etch resistance, photoelectric performance, environmental safety, preparation process, and application prospects through innovative multi-layer composite structure and functional enhancement material design. Specifically, the etch resistance and corrosion resistance are significantly enhanced through the synergistic effect of the silicon nitride / SiO2 multi-layer composite layer, titanium dioxide passivation film, and aluminum oxide layer; the photoelectric performance is greatly improved due to the introduction of lead sulfide nanoparticles and nanosilica; the environmental safety is guaranteed through modification strategies and green processes; the low-temperature and high-efficiency preparation process reduces costs and improves efficiency; and the wide application prospects provide new solutions for high-tech fields. These beneficial effects not only solve the contradictions of lithium niobate wafer surface degradation, photoelectric performance degradation, and environmental risk of lead-containing materials, but also provide strong material support for the development of 5G communication, quantum optics, and other frontier technologies, with significant innovation and practical value. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1is a scanning electron microscope image of the thin film prepared in Example 1.

[0017] Figure 2 is a scanning electron microscope image of the silicon nitride / SiO2 multilayer composite layer prepared in Example 1.

[0018] Figure 3 is a transmission electron microscope image of the lead sulfide nanoparticles prepared in Example 1.

[0019] Figure 4 is a scanning electron microscope image of the composite modified material prepared in Example 1. DETAILED DESCRIPTION

[0020] The present application is described in detail below with specific reference being made to the following examples. The examples are provided for illustrative purposes only and are not intended to limit the scope of the present application in any way. For ranges of parameters that are not specified, a median value is selected. For quality percentages or weight percentages that are not specified, a final concentration after addition is generally meant. In addition, for components or process parameter conditions that can not be mentioned, it is generally assumed that the conventional operation of a person skilled in the art can be used to achieve the same.

[0021] Example 1

[0022] Resist passivation matrix material: silicon nitride / SiO2 multilayer composite layer: 60 g (single layer thickness 75 nm), atomic layer deposition passivation thin film (titanium dioxide), the structure of which is shown in Figure 1 : 25 g (thickness 50 nm), aluminum oxide layer: 5 g (thickness 8 nm).

[0023] Functional enhancement material: lead sulfide nanoparticles: 10 g (particle size 7 nm), nanosilica: 5 g (particle size 35 nm, specific surface area 250 m 2 / g).

[0024] Auxiliary component: silane coupling agent (3-methacryloxypropyltrimethoxysilane): 3 g, perfluoropolyether surfactant (perfluoropolyether carboxylic acid): 1 g.

[0025] Preparation method: silicon nitride / SiO2 multilayer composite layer deposition, the structure of which is shown in Figure 2 : method: plasma enhanced chemical vapor deposition (PECVD); parameters: temperature 250°C, gas source SiH4, radio frequency power 150 W. Titanium dioxide passivation thin film deposition: method: atomic layer deposition (ALD); parameters: deposition temperature 175°C, precursor is tetrakis(dimethylamino)titanium (TDMAT). Aluminum oxide layer deposition: method: magnetron sputtering: parameters: Al target material is used, deposition temperature 125°C. Lead sulfide nanoparticles synthesis, the structure of which is shown in Figure 3Method: Solvothermal method, Step: Lead oxide was mixed with 1-octadecyl-3-methylimidazolium chloride at a mass ratio of 1:4, and degassed at 110°C for 2h under argon protection. Elemental sulfur was dissolved in N,N-dimethylformamide at a weight ratio of 1:3, and ultrasonically treated at 80°C for 30min. The lead precursor was heated to 150°C, and the sulfur precursor solution was injected at a rate of 2mL / s, with a lead-sulfur molar ratio of 1.05:1. After the reaction, the product was quenched with ice water, centrifuged at 9000rpm, and finally dispersed in chlorobenzene with a solid content of 10mg / mL. Functional layer coating: The PbS nanoparticles were dispersed in 7 times the weight of ethanol, and silane coupling agent and perfluoropolyether surfactant were added. The nanosilica was coated on the surface of the alumina layer by spin coating, and the drying temperature was 100°C. Annealing treatment: temperature 350°C, time 45min, and cooling to room temperature in an argon atmosphere. The scanning electron microscope image of the outer surface of the finally prepared composite modified material is shown in Figure 4 .

[0026] Example 2

[0027] The same as Example 1, but the silicon nitride / SiO2 multilayer composite layer was adjusted to 50g, and the other components were adjusted accordingly to maintain a total mass of 100g.

[0028] Example 3

[0029] The same as Example 1, but the silicon nitride / SiO2 multilayer composite layer was adjusted to 70g, and the other components were adjusted accordingly to maintain a total mass of 100g.

[0030] Example 4

[0031] The same as Example 1, but the atomic layer deposition passivation film was adjusted to 20g, and the other components were adjusted accordingly to maintain a total mass of 100g.

[0032] Example 5

[0033] The same as Example 1, but the atomic layer deposition passivation film was adjusted to 30g, and the other components were adjusted accordingly to maintain a total mass of 100g.

[0034] Example 6

[0035] The same as Example 1, but the lead sulfide nanoparticles were adjusted to 5g, and the other components were adjusted accordingly to maintain a total mass of 100g.

[0036] Example 7

[0037] The same as Example 1, but the lead sulfide nanoparticles were adjusted to 15g, and the other components were adjusted accordingly to maintain a total mass of 100g.

[0038] Example 8

[0039] The same as Example 1, but the nano-silica was adjusted to 3 g, and the other ingredients were adjusted accordingly to maintain a total mass of 100 g.

[0040] Example 9

[0041] The same as Example 1, but the nano-silica was adjusted to 8 g, and the other ingredients were adjusted accordingly to maintain a total mass of 100 g.

[0042] Example 10

[0043] The same as Example 1, but the silane coupling agent was adjusted to 2 g, and the other ingredients were adjusted accordingly to maintain a total mass of 100 g.

[0044] Example 11

[0045] The same as Example 1, but the silane coupling agent was adjusted to 5 g, and the other ingredients were adjusted accordingly to maintain a total mass of 100 g.

[0046] Example 12

[0047] The same as Example 1, but the perfluoropolyether surfactant was adjusted to 0.5 g, and the other ingredients were adjusted accordingly to maintain a total mass of 100 g.

[0048] Example 13

[0049] The same as Example 1, but the perfluoropolyether surfactant was adjusted to 1.5 g, and the other ingredients were adjusted accordingly to maintain a total mass of 100 g.

[0050] Example 14

[0051] The same as Example 1, but the annealing temperature was adjusted to 300°C.

[0052] Example 15

[0053] The same as Example 1, but the annealing temperature was adjusted to 400°C.

[0054] Comparative Example 1

[0055] No silicon nitride / SiO2 multilayer composite layer was used (0 g), and the other ingredients were the same as Example 1 and were adjusted in proportion to maintain a total mass of 100 g.

[0056] Comparative Example 2

[0057] No atomic layer deposition passivation film was used (0 g), and the other ingredients were the same as Example 1 and were adjusted in proportion to maintain a total mass of 100 g.

[0058] Comparative Example 3

[0059] No aluminum oxide layer was used (0 g), and the other ingredients were the same as Example 1 and were adjusted in proportion to maintain a total mass of 100 g.

[0060] Comparative Example 4

[0061] No lead sulfide nanoparticles were used (0 g), and the rest of the ingredients were the same as Example 1, with the proportions adjusted to maintain a total mass of 100 g.

[0062] Comparative Example 5

[0063] No nanosilica was used (0 g), and the rest of the ingredients were the same as Example 1, with the proportions adjusted to maintain a total mass of 100 g.

[0064] Comparative Example 6

[0065] No silane coupling agent was used (0 g), and the rest of the ingredients were the same as Example 1, with the proportions adjusted to maintain a total mass of 100 g.

[0066] Comparative Example 7

[0067] No perfluoropolyether surfactant was used (0 g), and the rest of the ingredients were the same as Example 1, with the proportions adjusted to maintain a total mass of 100 g.

[0068] Comparative Example 8

[0069] No annealing was performed, and the rest of the steps and ingredients were the same as Example 1.

[0070] It should be noted that the total mass of all examples and comparative examples was 100 g.

[0071] Optical performance test

[0072] Purpose: To measure the optical loss of the composite modified material at a wavelength of 1550 nm and evaluate its optical performance in optical waveguide applications. Method: Using an optical waveguide loss measurement system, a 1550 nm laser source was used to measure the propagation loss of light in the waveguide, with the unit being dB / cm. Equipment: 1550 nm laser source, optical waveguide coupling system, optical power detector. Test steps: Sample preparation: The composite modified material was coated on a lithium niobate wafer according to the formulation and process of the example or comparative example. System setup: A 1550 nm laser source was used to inject light into the waveguide through the coupling system, and the detector recorded the output light intensity. Measurement: Record the input and output light intensities, calculate the propagation loss, the formula is: Where L is the waveguide length (cm).

[0073] Corrosion resistance test

[0074] Objective: To evaluate the corrosion resistance of materials in acidic and basic environments. Methods: Acid and base immersion tests were used, with pH = 2 sulfuric acid solution and pH = 12 sodium hydroxide solution, immersion time 240h, corrosion resistance was evaluated by surface morphology changes and optical performance decay. Equipment: Optical microscope, optical performance test system. Test steps: Sample preparation: same as optical performance test. Immersion: place the sample in pH = 2 and pH = 12 solution respectively, immerse for 240h, keep constant temperature (25℃). Observation: use SEM or optical microscope to observe the morphology changes of the sample surface after immersion. Performance test: re-measure the optical performance after immersion, calculate the percentage change of loss:

[0075] Environmental safety test

[0076] Objective: To measure the lead leaching rate and evaluate the environmental safety of lead-containing materials. Methods: Immersion method was used, the sample was placed in distilled water, and the sample was taken regularly, and the lead content was analyzed by inductively coupled plasma mass spectrometer (ICP-MS). Equipment: ICP-MS. Constant temperature water bath test steps: Sample preparation: same as above. Immersion: immerse the sample in distilled water for 72h, temperature 25℃. Sampling: take sample every 24h, a total of 3 times. Analysis: use ICP-MS to measure the lead concentration (unit: ppm) of each sample, calculate the average leaching rate.

[0077] Objective: To measure the interface state density and evaluate the quality of the material and lithium niobate wafer interface. Methods: Capacitance-voltage (C-V) test was used, metal-insulator-semiconductor (MIS) structure was prepared, and the insulating layer was composite modified material. Equipment: LCR meter. Vacuum evaporation system test steps: Sample preparation: deposit composite modified material as insulating layer on lithium niobate wafer, then evaporate metal electrode (such as aluminum) to form MIS structure. C-V test: use LCR meter to apply voltage (-5V to +5V), measure the change of capacitance with voltage. Analysis: calculate the interface state density (unit: cm -2 eV -1 ) from C-V curve, formula: Where C ox is the oxide capacitance, q is the electronic charge.

[0078] The following are the test results of Examples 1-15 and Comparative Examples 1-8, based on the data obtained from the above methods.

[0079] Table 1 Example results table

[0080]

[0081] Table 2 Comparative example results

[0082]

[0083]

[0084] Results Analysis and Summary: Based on the data in Table 1 and Table 2, optical performance: the optical loss of Examples 1-15 is less than 0.2 dB / cm, meeting the invention target, showing excellent optical performance. Among them, the optical loss of Examples 3, 7, 15 is the lowest (≤0.13 dB / cm). The optical loss of Comparative Examples 1-3, 5, 6, 8 is significantly higher than that of Examples (0.25-0.5 dB / cm), indicating that the lack of key components (such as silicon nitride / SiO2 layer, passivation film) will lead to the decline of optical performance. Corrosion resistance: after 240h acid and alkali immersion, the surface of Examples 1-15 changes little, and the performance decay is usually <10%, proving the protective effect of the corrosion-resistant passivation matrix. Comparative Examples 1-3, 5, 6, 8 show severe or obvious corrosion, with a decay of up to 50%, indicating that the lack of corrosion-resistant layer or process steps will significantly reduce the corrosion resistance. Environmental safety: the lead leaching rate of Examples 1-15 is <0.1 ppm, far below the environmental safety standard, showing the stability of the functional layer modification. The lead leaching rate of Comparative Examples 1-3, 5, 6, 8 is higher (0.08-0.2 ppm), indicating that the lack of auxiliary components or process optimization will increase the environmental risk. Interface performance: the interface state density of Examples 1-15 is reduced to 10 9 -10 11 cm -2 eV -1 , 2 orders of magnitude lower than that of the comparative examples, verifying the synergistic effect of the passivation layer and the functional layer. The interface state density of Comparative Examples 1-3, 5, 6, 8 is as high as 10 11 -10 12 cm -2 eV -1 , indicating that a single material or process is not enough to optimize the interface quality. Conclusion: Through the above test methods, Examples 1-15 show excellent optical performance, corrosion resistance, environmental safety and interface performance, proving the overall superiority of the composite modified material. Comparative Examples 1-8 show that the lack of corrosion-resistant matrix, functional layer or key process steps will lead to a significant decline in performance. This verifies the technical advantages of the invention in solving the problems of lithium niobate wafer surface degradation, photoelectric performance decline and environmental risk, and is suitable for 5G optical waveguide and quantum integrated device packaging fields.

[0085] The above series of detailed descriptions are only specific descriptions of feasible embodiments of the present application, and are not intended to limit the protection scope of the present application. Any equivalent embodiments or changes made without departing from the spirit of the present application shall be included in the protection scope of the present application.

Claims

1. A composite modified material for lithium niobate wafers, characterized in that, By weight, the corrosion-resistant passivation substrate material consists of: 50-70 parts of silicon nitride / SiO2 multilayer composite layer, with a single layer thickness of 50-100 nm; 20-30 parts of atomic layer deposited titanium dioxide passivation film, with a thickness ≤80 nm; and an alumina layer, with a thickness ≤10 nm. The functional reinforcing material is: 5-15 parts of lead sulfide nanoparticles, with a particle size of 5-10 nm. The auxiliary components are: 2-5 parts of silane coupling agent, 3-8 parts of nano-silica, and 0.5-1.5 parts of perfluoropolyether surfactant. The silane coupling agent is 3-methacryloyloxypropyltrimethoxysilane, aminopropyltriethoxysilane, vinyltrimethoxysilane, or octyltriethoxysilane. The perfluoropolyether surfactant is perfluoropolyether carboxylic acid or perfluoropolyether alcohol. Alternatively, perfluoropolyether fluoride can be used; its preparation method is as follows: Silicon nitride and SiO2 layers are alternately deposited on a clean lithium niobate wafer surface using plasma-enhanced chemical vapor deposition (PECVD); then, a titanium dioxide passivation film is deposited using atomic layer deposition (ALD); an aluminum oxide layer is deposited on the surface of the passivation film by magnetron sputtering; next, lead sulfide nanoparticles are synthesized via a solvothermal method, dispersing the lead sulfide nanoparticles in an ethanol solution at 5-10 times their weight, adding a silane coupling agent and a perfluoropolyether surfactant, uniformly coating the aluminum oxide layer surface by spin coating or dip coating, drying, and finally annealing at 300-400°C for 30-60 min, cooling to room temperature in an inert gas atmosphere.

2. The composite modification material for lithium niobate wafers according to claim 1, characterized in that, The parameters of nano-silica are as follows: particle size 20-50nm, specific surface area ≥200m² / g.

3. The composite modification material for lithium niobate wafers according to claim 1, characterized in that, The parameters for alternating deposition are as follows: temperature 200-300°C, gas source is SiH4, and radio frequency power is 100-200W.

4. The composite modification material for lithium niobate wafers according to claim 1, characterized in that, When depositing titanium dioxide passivation films, the deposition temperature is 150-200°C.

5. The composite modification material for lithium niobate wafers according to claim 1, characterized in that, When depositing alumina layers by magnetron sputtering, an Al target is used with a deposition temperature of 100-150°C.

6. The composite modification material for lithium niobate wafers according to claim 1, characterized in that, The method for synthesizing lead sulfide nanoparticles by solvothermal method is as follows: lead oxide and 1-octadecyl-3-methylimidazolium chloride are mixed at a mass ratio of 1:4 and degassed at 110±2℃ for 2h under argon protection to obtain a lead precursor solution; then, elemental sulfur is dissolved in N,N-dimethylformamide at a weight ratio of 1:3 and ultrasonically treated at 80℃ for 30min to obtain a sulfur precursor solution. When the lead precursor solution is heated to 150±5℃, the sulfur precursor solution is injected at a rate of 2mL / s, and the lead-sulfur molar ratio is controlled at 1.05:

1. The reaction is terminated by ice-water quenching. The crude product is centrifuged at 9000rpm, and the final product is dispersed in chlorobenzene with a solid content controlled at 10±0.5mg / mL.

7. The composite modification material for lithium niobate wafers according to claim 1, characterized in that, The drying temperature is 80-120℃.

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