A liquid atomic layer deposition method

Abstract

This application provides a liquid atomic-level deposition method, relating to the field of deposition technology. Surface treatment of the substrate ensures uniform adsorption and reactivity of precursor molecules. Subsequently, the diluted liquid precursor is coated to form a uniform monolayer, and the precursor molecules are cleaved at room temperature using a 172nm excimer ultraviolet light source to generate a first active species. Depending on the type of target thin film, a reactive gas is selectively introduced. Under irradiation with the 172nm excimer ultraviolet light source, the reactive gas undergoes a cleavage reaction to generate a second active species. The second active species reacts chemically with the first active species to form the target thin film material. Through repeated cycles, layer-by-layer growth and precise atomic-level thickness control of the thin film are achieved. This self-constrained "physical-chemical" liquid-phase deposition mechanism enables atomically uniform deposition of thin films, overcoming the limitations of traditional gas-phase ALD in terms of precursor selection, equipment complexity, and process temperature.

Description

Technical Field

[0001] This application relates to the field of coating technology, and more specifically, to a liquid atomic-level coating method. Background Technology

[0002] Atomic-level manufacturing, particularly atomic layer deposition (ALD), is one of the core processes in modern nanotechnology and the semiconductor industry. Traditional ALD technology involves alternating pulses of gaseous precursors into a reaction chamber, causing them to undergo self-limiting chemical adsorption and reaction on the substrate surface, thereby depositing thin films layer by layer. This method offers excellent uniformity, conformality, and thickness control precision, and is widely used in the fabrication of three-dimensional chips with high aspect ratios.

[0003] However, vapor-phase ALD technology has some inherent limitations. First, the choice of precursors is limited; suitable gaseous precursors for many materials with ideal film-forming properties are often difficult to obtain, as these precursors may have low vapor pressure, poor stability, low activity, or be expensive. Second, the equipment is complex and costly, requiring precise control of the gas path, temperature control, and pulse sequence, resulting in high equipment costs and maintenance requirements. Furthermore, traditional thermally driven ALD processes typically still require relatively high temperatures of 300-400°C to activate the chemical reaction between precursor molecules and the substrate surface. This limits the application of temperature-sensitive substrates, such as most flexible polymers, pre-patterned photoresists, and biomaterials, in emerging fields such as flexible electronics and biosensing.

[0004] Therefore, existing atomic-level manufacturing technologies, especially the dominant gas-phase ALD, face a core contradiction: how to significantly improve process efficiency, reduce costs and complexity, and broaden the range of processable materials and substrates without sacrificing their atomic-level precision, excellent uniformity and shape preservation, so as to meet the requirements of low-temperature, low-damage film formation and get rid of dependence on high vapor pressure gaseous precursors.

[0005] There is currently no effective technical solution to the above problems. Summary of the Invention

[0006] The purpose of this application is to provide a liquid atomic-level coating method, which aims to overcome the limitations of existing atomic-level manufacturing technologies in improving process efficiency, reducing costs and complexity, broadening the range of processable materials and substrates, and adapting to the requirements of low-temperature and low-damage film formation, and to eliminate the dependence on high vapor pressure gaseous precursors.

[0007] In a first aspect, this application provides a liquid atomic-level coating method, comprising the following steps:

[0008] S1. Perform surface treatment on the substrate to remove surface contaminants and activate the substrate surface;

[0009] S2. Obtain the liquid precursor and dilute it to a preset concentration;

[0010] S3. Coat the diluted liquid precursor onto the substrate surface, so that the liquid precursor spreads on the substrate surface and forms a uniform precursor monolayer.

[0011] S4. At room temperature, a precursor monolayer formed on the substrate surface is irradiated by a 172nm excimer ultraviolet light source to cause the precursor molecules to undergo a cleavage reaction to produce the first active species.

[0012] S5. If the target thin film is a metal or non-metal elemental film, proceed to step S6; otherwise, according to the type of the target thin film, the corresponding reaction gas is introduced. The reaction gas undergoes a decomposition reaction under 172nm excimer ultraviolet light source irradiation to generate a second active species. The second active species reacts chemically with the first active species to generate a single-layer thin film material on the substrate surface, and step S6 is executed.

[0013] S6. Purge the substrate surface to remove unreacted byproducts and residual solvents;

[0014] S7. Repeat steps S3 to S6 until the preset film thickness is reached.

[0015] This technical solution achieves a "physical-chemical" self-limiting growth effect similar to traditional ALD in the liquid phase. Utilizing the high-energy characteristics of 172nm light, it enables precise breaking and cross-linking of chemical bonds, thereby achieving atomically uniform deposition and precise thickness control of the thin film. The entire process can be completed under normal pressure or a controlled atmosphere, without requiring high temperature, high pressure, or vacuum environments. This greatly satisfies the deposition process requirements of polymer substrates with poor heat resistance, making it suitable for scenarios requiring low-temperature, low-damage film formation, and expanding the material library for atomic-level manufacturing technologies.

[0016] Optionally, step S1 includes:

[0017] The substrate is initially cleaned to remove oil, organic contaminants, particulate impurities, and the natural oxide layer from its surface.

[0018] After initial cleaning, the substrate is subjected to plasma treatment, oxidation treatment, reduction treatment, or deposition of a nanoscale seed layer to increase the reactivity of the substrate surface.

[0019] The substrate with increased reactivity was dried and then sealed for storage.

[0020] This technical solution not only thoroughly removes surface contaminants, but also significantly enhances the reactivity of the substrate surface through plasma treatment, oxidation treatment, reduction treatment, or deposition of nanoscale seed layers. This provides an ideal interface for the uniform spreading and reaction of subsequent precursor molecules, thereby ensuring the quality and uniformity of thin film deposition.

[0021] Optionally, step S2 includes:

[0022] Obtain a liquid precursor, dissolve the liquid precursor in an inert solvent, and dilute it to a preset critical concentration to form a precursor solution;

[0023] The precursor solution is dispersed to ensure that the precursor molecules are fully dispersed.

[0024] This technical solution effectively avoids the aggregation of precursor molecules by dissolving the liquid precursor in an inert solvent and diluting it to a critical concentration for dispersion treatment, ensuring the uniform dispersion of the precursor in the solution and laying the foundation for the subsequent formation of a uniform monolayer on the substrate surface.

[0025] Optionally, the step of dispersing the precursor solution to ensure uniform dispersion of the precursor molecules includes:

[0026] The precursor molecules are dispersed using ultrasonic waves at a frequency of 40kHz-50kHz for 20-30 minutes to ensure uniform dispersion.

[0027] This technical solution employs ultrasonic dispersion, which efficiently and uniformly disperses precursor molecules, preventing molecular aggregation and ensuring the high uniformity of the precursor solution. This provides a guarantee for the subsequent formation of high-quality monolayer films.

[0028] Optionally, the liquid precursor is a compound solution that can be activated by 172 nm ultraviolet light.

[0029] This technical solution clarifies the liquid precursors that can be used in this method, greatly expanding the material library for atomic-level manufacturing technology and making it possible to prepare novel metal oxides, nitrides, etc., which are difficult to prepare using traditional gas-phase ALD.

[0030] Optionally, step S3 includes:

[0031] The diluted liquid precursor is sprayed onto the substrate surface;

[0032] The liquid precursor is spread using a first preset rotation speed so that the liquid precursor is spread evenly on the substrate surface under the action of centrifugal force to form an initial precursor film, avoiding local accumulation or missed coating.

[0033] The precursor film is homogenized using a second preset rotation to remove excess solvent from the precursor film and to promote the spontaneous formation of a uniform precursor monolayer by liquid precursor molecules.

[0034] Optionally, the first preset speed is 500rpm-600rpm, and the second preset speed is 2000rpm-2500rpm.

[0035] Optionally, step S5 includes:

[0036] If the target thin film is a metal or non-metal elemental film, proceed to step S6.

[0037] Otherwise, if the target thin film is a metal oxide type, oxygen is introduced. The oxygen is decomposed under 172nm excimer ultraviolet light source to produce oxygen atoms. The oxygen atoms act as the second active species and react chemically with the first active species to generate a single-layer thin film material on the substrate surface.

[0038] If the target thin film is a nitride type, nitrogen or ammonia gas is introduced. Nitrogen or ammonia gas undergoes a decomposition reaction under 172nm excimer ultraviolet light source irradiation to produce nitrogen atoms. Nitrogen atoms act as the second active species and react chemically with the first active species to generate a monolayer thin film material on the substrate surface.

[0039] Optionally, the power density of the 172nm excimer ultraviolet light source is 20-50 mW / cm².

[0040] Optionally, step S6 includes:

[0041] Nitrogen gas of preset purity was used to purge the substrate surface at a flow rate of 10-20 L / min and a purging time of 10-15 s to remove unreacted byproducts and residual solvents.

[0042] As can be seen from the above, the liquid atomic-level film deposition method provided in this application overcomes the limitations of existing atomic-level manufacturing technologies in terms of efficiency, cost, material and substrate range, and low-temperature, low-damage film deposition in the following ways:

[0043] First, this application eliminates the dependence on gaseous precursors. Theoretically, any compound soluble in a suitable solvent and capable of being activated by 172nm light can potentially serve as a precursor. This greatly expands the material library for atomic-level manufacturing technologies, making it possible to deposit novel metal oxides, nitrides, and other composite materials that are difficult to prepare using traditional gas-phase ALD, thus overcoming the limitation in precursor selection in traditional ALD.

[0044] Secondly, this method utilizes the high-energy characteristics of a 172nm excimer ultraviolet light source (photon energy up to 697 kJ / mol, higher than the bond energies of many compounds) to "in-situ" cleave monolayer spread liquid precursor molecules into active intermediates at room temperature. This achieves precise chemical bond breaking and cross-linking, enabling atomically uniform deposition of thin films and precise control of film thickness, maintaining the excellent uniformity, conformality, and thickness control accuracy of ALD technology. This light-driven cleavage reaction avoids the high-temperature environment (typically 300-400°C) required by traditional thermally driven ALD, greatly satisfying the needs of low-temperature, low-damage film deposition for temperature-sensitive polymer substrates, flexible electronics, and optical devices.

[0045] Furthermore, the entire process can be completed under one atmosphere or a controlled atmosphere, without the need for high temperature, high pressure or vacuum environments (except for special high purity requirements), which significantly reduces equipment complexity and operating costs, making atomic-level manufacturing technology easier to scale up.

[0046] In summary, this application effectively solves the problems of limited selection of precursors, complex and costly equipment, and high-temperature film formation limitations in traditional gas-phase ALD by using innovative technical solutions such as liquid-phase self-limiting growth, 172nm ultraviolet light low-temperature pyrolysis, and atmospheric pressure operation. It achieves atomic-level uniform deposition and precise thickness control of thin films, greatly expanding the material library and application scope of atomic-level manufacturing technology, and has significant technological progress and economic benefits.

[0047] Other features and advantages of this application will be set forth in the following description and will be apparent in part from the description or may be learned by practicing embodiments of this application. The objectives and other advantages of this application may be realized and obtained by means of the structures particularly pointed out in the written description and the accompanying drawings. Attached Figure Description

[0048] Figure 1 This is a flowchart of a liquid atomic-level coating method provided in an embodiment of this application.

[0049] Figure 2 This is a schematic diagram of the liquid atomic-level coating equipment provided in the embodiments of this application.

[0050] Labeling: 101, housing; 102, vacuum chamber; 103, rotating stage; 104, substrate; 105, transparent window; 106, liquid nozzle; 107, gas inlet; 108, exhaust port; 109, humidifier; 200, gas equipment; 201, vacuum pump system; 202, 172nm excimer ultraviolet light source. Detailed Implementation

[0051] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0052] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this application, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0053] Firstly, referring to Figure 1 This application provides a liquid atomic-level coating method, including the following steps:

[0054] S1. Perform surface treatment on the substrate to remove surface contaminants and activate the substrate surface;

[0055] S2. Obtain the liquid precursor and dilute it to a preset concentration;

[0056] S3. Coat the diluted liquid precursor onto the substrate surface, so that the liquid precursor spreads on the substrate surface and forms a uniform precursor monolayer.

[0057] S4. At room temperature, a precursor monolayer formed on the substrate surface is irradiated by a 172nm excimer ultraviolet light source to cause the precursor molecules to undergo a cleavage reaction to produce the first active species.

[0058] S5. If the target thin film is a metal or non-metal elemental film, proceed to step S6; otherwise, according to the type of the target thin film, the corresponding reaction gas is introduced. The reaction gas undergoes a decomposition reaction under 172nm excimer ultraviolet light source irradiation to generate a second active species. The second active species reacts chemically with the first active species to generate a single-layer thin film material on the substrate surface, and step S6 is executed.

[0059] S6. Purge the substrate surface to remove unreacted byproducts and residual solvents;

[0060] S7. Repeat steps S3 to S6 until the preset film thickness is reached.

[0061] This application achieves a "physical-chemical" self-limiting effect in the liquid phase and relies on the high energy characteristics of 172nm light to achieve precise breaking and cross-linking of chemical bonds, thereby realizing atomic-level uniform deposition and precise thickness control of thin films, effectively solving the limitations of traditional gas-phase ALD.

[0062] The liquid atomic-level deposition method proposed in this application aims to achieve precise deposition of atomic-level thin films via a liquid-phase approach. Here, "substrate" refers to the base material used to support the thin film, which can be various materials such as silicon wafers, glass, and polymers. "Liquid precursor" refers to a liquid compound containing the target thin film material components, which can decompose or react under specific conditions to form a thin film. "Precursor monolayer" refers to a uniform thin film, only one molecule thick, formed on the substrate surface by liquid precursor molecules; this is crucial for achieving atomic-level deposition. "172nm excimer ultraviolet light source" is a high-energy ultraviolet light source whose emitted photons have sufficient energy to break the chemical bonds of precursor molecules, generating reactive species. "First reactive species" and "second reactive species" refer to highly reactive intermediate products generated by the decomposition of precursor molecules and reactant gases under ultraviolet light irradiation; these react chemically to form a thin film.

[0063] The liquid atomic-level deposition method of this application achieves atomic-level deposition of thin films in a liquid environment through a series of precisely controlled steps.

[0064] In step S1, surface treatment of the substrate is fundamental to ensuring the quality of subsequent thin film deposition. Specifically, methods such as wet chemical cleaning, plasma treatment, or ultraviolet ozone treatment can be used to remove organic contaminants, particulate impurities, and native oxide layers from the substrate surface. For example, surface contaminants can be effectively removed by immersing the substrate in an acidic or alkaline cleaning solution combined with ultrasonic cleaning. Furthermore, plasma treatment or the deposition of nanoscale seed layers can increase the reactivity of the substrate surface, thereby promoting the uniform adsorption and reaction of precursor molecules.

[0065] In step S2, obtaining the liquid precursor and diluting it to a preset concentration is crucial for forming a uniform precursor monolayer. The liquid precursor can be various compounds containing elements of the target thin film material, such as methyl silicone oil, aluminum triisopropoxide, or tridimethylaminoaluminum. Dissolving the liquid precursor in an inert solvent and diluting it to a preset critical concentration of approximately 0.01-0.1 wt% can effectively prevent precursor molecules from agglomerating or stacking on the substrate surface. To ensure uniform dispersion of precursor molecules in the solution, ultrasonic dispersion can be used, for example, dispersion at an ultrasonic frequency of 40 kHz-50 kHz for 20-30 minutes.

[0066] In step S3, the diluted liquid precursor is coated onto the substrate surface to form a uniform precursor monolayer. The coating method can be spin coating, dip coating, or spray coating. For example, by spin coating, the liquid precursor molecules are first spread at a low rotation speed (e.g., 500-600 rpm), utilizing the intermolecular forces between the liquid precursor molecules and the substrate surface to promote uniform spread of the liquid precursor molecules on the substrate surface. Subsequently, a higher rotation speed (e.g., 2000-2500 rpm) is used for homogenization to remove excess solvent from the precursor film and promote the spontaneous formation of a uniform precursor monolayer. This spontaneous spreading and monolayer formation mechanism is achieved using intermolecular forces (such as van der Waals forces) and surface tension, ensuring that the precursor layer is free from aggregation and stacking.

[0067] In step S4, the precursor monolayer formed on the substrate surface is irradiated with a 172nm excimer ultraviolet light source, causing the precursor molecules to undergo a cleavage reaction to generate the first active species. The 172nm excimer ultraviolet light source has high-energy photons, which can precisely break the chemical bonds of the precursor molecules, thereby generating the first active species with high reactivity. For example, when methyl silicone oil is used as a precursor, under 172nm ultraviolet light irradiation, the C-Si, CH, and other bonds in its molecules will break, generating silicon-based active species. This photo-cleavage method avoids the high-temperature environment required by traditional thermally driven ALDs and is suitable for temperature-sensitive substrate materials.

[0068] In step S5, if the target thin film is a metal or non-metal elemental film, proceed to step S6; otherwise, depending on the type of target thin film, a corresponding reactive gas is introduced. Under irradiation with a 172nm excimer ultraviolet light source, the reactive gas undergoes a decomposition reaction to generate a second active species. This second active species reacts chemically with the first active species to form a monolayer thin film material on the substrate surface, and step S6 is then executed. For example, if the target thin film is a metal oxide, oxygen can be introduced as the reactive gas. Under irradiation with 172nm ultraviolet light, the oxygen gas decomposes to generate oxygen atoms, which then react with the first active species as the second active species to form a metal oxide thin film. If the target thin film is a nitride, nitrogen or ammonia can be introduced as the reactive gas. Under ultraviolet light irradiation, these gases decompose to generate nitrogen atoms, which then react with the first active species as the second active species to form a nitride thin film. This selective introduction of reactive gases allows this method to prepare various types of thin films, such as metal oxide thin films, nitride thin films, and metal and non-metal elemental films.

[0069] In step S6, the substrate surface is purged to remove unreacted byproducts and residual solvent. Purging can be performed using a high-purity inert gas, such as nitrogen of a predetermined purity. The purging flow rate can be controlled between 10 L / min and 20 L / min, and the purging time is 10 s to 15 s. This step ensures the purity of the film and avoids the influence of impurities on the film's performance.

[0070] In step S7, steps S3 to S6 are repeated until the preset film thickness is reached. By repeatedly cycling the "coating-photo-reaction-purge" process, layer-by-layer film growth can be achieved, and the final film thickness can be precisely controlled.

[0071] The liquid atomic-level deposition method of this application achieves precise deposition of atomic-level thin films in a liquid phase through the synergistic effect of the above steps. First, the surface treatment of the substrate ensures uniform adsorption and reactivity of precursor molecules. Subsequently, the diluted liquid precursor is precisely coated to form a uniform monolayer, laying the foundation for subsequent photolysis. The high-energy photons of the 172nm excimer ultraviolet light source can efficiently and precisely cleave precursor molecules to generate active species without requiring a high-temperature environment. Next, depending on the type of target thin film, reactive gases are selectively introduced to react with the active species to form the target thin film material. Finally, by-products and residual solvents are removed by purging to ensure the purity of the thin film. The entire process is repeated in cycles, enabling layer-by-layer growth and precise thickness control of the thin film. This "physical-chemical" self-limiting liquid-phase deposition mechanism makes atomic-level uniform deposition of thin films possible, effectively solving the limitations of traditional gas-phase ALD in terms of precursor selection, equipment complexity, and process temperature.

[0072] The core innovation of this application lies in eliminating the dependence on gaseous precursors. Theoretically, any compound soluble in a suitable solvent and capable of being activated by 172nm light can potentially serve as a precursor, such as methyl silicone oil, aluminum triisopropoxide, and tridimethylaminoaluminum. This makes it possible to deposit novel metal oxides, nitrides, and even multi-component composite materials that are difficult to prepare using traditional gas-phase ALD, greatly expanding the material library for atomic-level manufacturing technologies. Compared to the complex equipment and high cost of traditional ALD, this application features a simpler process, simpler equipment, and lower cost, enabling large-scale production and demonstrating significant economic benefits and application prospects.

[0073] Furthermore, this application introduces a 172nm excimer ultraviolet light source for photolysis. The 172nm photon energy is as high as 697kJ / mol (approximately 7.2 eV), exceeding the bond energies of many compounds, enabling the "in-situ" cleavage of monolayer spread liquid precursor molecules into active intermediates, achieving precise chemical bond breaking and cross-linking. This photodriven mechanism allows the entire process to be carried out at room temperature, greatly satisfying the requirements of polymer substrate thin film deposition processes with poor heat resistance, and is suitable for applications such as flexible electronics and optical devices that require low-temperature, low-damage film deposition.

[0074] The liquid atomic-level deposition method of this application requires deposition equipment. For example, a rotating stage 103 is provided in a vacuum chamber 102, and a substrate 104 is placed above the rotating stage 103. The housing 101 of the vacuum chamber 102 is provided with a liquid nozzle 106, multiple gas inlets 107, an extraction port 108, and a transparent window 105. The liquid nozzle 106 is used to introduce a liquid precursor, the multiple gas inlets 107 are used to connect to an external gas device 200 to introduce different reactive gases, the extraction port 108 is used to connect to an external vacuum pump system 201, and the transparent window 105 is used to allow a 172nm excimer ultraviolet light source 202 to irradiate the entire rotating stage 103. Figure 2 As shown, when oxygen needs to be introduced, a humidifier 109 can be installed in the corresponding gas inlet 107 to promote oxygen decomposition.

[0075] In some implementations, step S1 includes:

[0076] The substrate is initially cleaned to remove oil, organic contaminants, particulate impurities, and the natural oxide layer from its surface.

[0077] After initial cleaning, the substrate is subjected to plasma treatment, oxidation treatment, reduction treatment, or deposition of a nanoscale seed layer to increase the reactivity of the substrate surface.

[0078] The substrate with increased reactivity was dried and then sealed for storage.

[0079] Preliminary cleaning refers to the effective removal of oil, organic contaminants, particulate impurities, and any existing natural oxide layer from the substrate surface using physical or chemical methods, such as solvent cleaning, ultrasonic cleaning, or immersion in acid or alkaline solutions. Its purpose is to provide a clean starting surface for subsequent surface activation treatments.

[0080] Furthermore, the pre-cleaned substrate is subjected to plasma treatment, oxidation treatment, reduction treatment, or deposition of a nanoscale seed layer to increase the reactivity of the substrate surface. Specifically, plasma treatment can remove residual organic matter and introduce active groups by bombarding the substrate surface with high-energy particles; oxidation or reduction treatment can change the chemical state of the substrate surface through chemical reactions to generate more active sites; and deposition of a nanoscale seed layer can form a thin film with high surface energy or specific chemical activity on the substrate surface, thereby significantly improving the substrate's adsorption capacity and reactivity for subsequent precursor molecules.

[0081] In addition, the substrate with increased reactivity is dried and sealed for storage. The purpose of this is to prevent the activated substrate surface from re-adsorbing water vapor, oxygen or other pollutants from the air, thereby reducing the density of surface active sites and ensuring that the substrate maintains high reactivity in subsequent coating steps.

[0082] This application's solution refines the substrate surface treatment step S1 into three stages: preliminary cleaning, activation treatment, and drying and sealing for preservation. This ensures that the substrate surface reaches its optimal state before liquid atomic-level deposition. The preliminary cleaning stage thoroughly removes various contaminants that may hinder precursor adsorption and reaction, laying the foundation for subsequent atomic-level deposition. The activation treatment stage uses various methods such as plasma, oxidation, reduction, or seed layer deposition to specifically create or expose a large number of active sites on the substrate surface. These active sites are crucial for the uniform adsorption and cleavage reaction of precursor molecules. Finally, drying and sealing for preservation effectively maintain the high activity state of the substrate surface, preventing it from being contaminated or passivated again before deposition, thereby ensuring the stability of the entire deposition process and the uniformity of the film quality.

[0083] In some preferred embodiments, a 10mm × 20mm × 0.8mm Si wafer is used as the substrate. First, an acidic hydrogen peroxide cleaning solution is prepared by mixing deionized water, 30 wt% H₂O₂, and 25 wt% concentrated hydrochloric acid in a volume ratio of 6:2:1. This acidic hydrogen peroxide cleaning solution is heated to 80°C, and the Si wafer is then immersed in the solution for ultrasonic cleaning to remove organic matter. It is then rinsed 3-5 times with deionized water. Next, an alkaline hydrogen peroxide cleaning solution is prepared by mixing deionized water, 30 wt% H₂O₂, and 25 wt% concentrated ammonia in a volume ratio of 5:2:1. This alkaline hydrogen peroxide cleaning solution is heated to 80°C, and the Si wafer is then immersed in the solution for ultrasonic cleaning to remove particles and metal contaminants from the Si wafer surface. It is then rinsed 3-5 times with deionized water. Next, the Si wafers were soaked in 10 wt% dilute hydrofluoric acid to dissolve the silicon oxides on the surface of the Si wafers, and then rinsed several times with deionized water. Finally, the washed Si wafers were ultrasonically cleaned in alcohol and then dried and sealed in N2 (purity 99.999%) to avoid exposure to air for more than 30 minutes, in order to prevent the surface from re-adsorbing moisture and reducing the density of active sites.

[0084] In some implementations, step S2 includes:

[0085] Obtain a liquid precursor, dissolve the liquid precursor in an inert solvent, and dilute it to a preset critical concentration to form a precursor solution;

[0086] The precursor solution is dispersed to ensure that the precursor molecules are fully dispersed.

[0087] Obtaining a liquid precursor involves selecting a suitable liquid compound as the precursor based on the type of the target thin film material. This liquid precursor must possess good solubility in an inert solvent and be able to undergo a pyrolysis reaction under 172nm excimer ultraviolet light irradiation to generate active species. Dissolving the liquid precursor in an inert solvent aims to provide a stable dispersion medium for the precursor molecules, preventing unnecessary reactions or aggregation in the undiluted state. Dilution to a preset critical concentration aims to precisely control the density of precursor molecules in the solution, ensuring the formation of a uniform monolayer when coated onto the substrate surface, avoiding excessive concentrations that could lead to multilayer stacking or aggregation. The preset critical concentration typically refers to the lowest effective concentration that allows for monolayer spreading without aggregation.

[0088] In practical applications, the precursor solution is dispersed to ensure that the liquid precursor molecules achieve a highly uniform dispersion in an inert solvent. This uniform dispersion is crucial for the subsequent formation of a non-agglomerated and non-stacking precursor monolayer during the precursor coating process.

[0089] The present application's solution effectively controls the initial state of precursor molecules by dissolving the liquid precursor in an inert solvent and diluting it to a preset critical concentration. The choice of inert solvent ensures that the precursor does not undergo unnecessary chemical reactions in the solution, while providing a stable dispersion environment. Dilution to the preset critical concentration ensures that the precursor molecules maintain appropriate spacing in the solution, reducing the tendency for aggregation caused by intermolecular interactions, thus providing favorable conditions for the subsequent formation of a uniform monolayer on the substrate surface. Furthermore, by dispersing the precursor solution, such as using physical dispersion methods like ultrasound, any potential micro-agglomerations are further broken up, ensuring a highly uniform distribution of precursor molecules throughout the solution. This uniform and moderately diluted precursor solution, when subsequently coated onto the substrate surface, can better utilize intermolecular forces (such as van der Waals forces) and surface tension to promote the spontaneous spreading of precursor molecules on the substrate surface, forming a uniform monolayer without aggregation or stacking, laying a solid foundation for subsequent atomic-level film deposition.

[0090] In some embodiments, the step of dispersing the precursor solution to ensure uniform dispersion of the precursor molecules includes:

[0091] The precursor molecules are dispersed using ultrasonic waves at a frequency of 40kHz-50kHz for 20-30 minutes to ensure uniform dispersion.

[0092] Specifically, ultrasonic dispersion refers to utilizing the cavitation effect, mechanical vibration, and acoustic flow generated when ultrasound propagates in a liquid to break up potentially agglomerated precursor molecule clusters in the solution, allowing them to distribute uniformly within the solvent. The method described in this application, by employing ultrasound at specific frequencies and durations for dispersion, effectively overcomes the potential agglomeration tendency of precursor molecules in solution. When ultrasound propagates in a liquid, it generates high-frequency vibrations and cavitation effects, forming tiny bubbles that rapidly expand and burst within a short time. The bursting of these cavitation bubbles generates localized high temperatures, high pressures, and high-speed microjets. These physical forces effectively break up weak interactions such as van der Waals forces or hydrogen bonds between precursor molecules, thereby decomposing agglomerates into individual molecules or even smaller dispersed units. By precisely controlling the ultrasonic frequency within the 40kHz-50kHz range, the intensity and efficiency of the cavitation effect can be optimized, ensuring effective dispersion. Meanwhile, setting the dispersion time to 20-30 minutes ensures that the precursor molecules have enough time to complete full depolymerization and uniform distribution, thus laying the foundation for the subsequent formation of a non-agglomerated and non-stacked precursor monolayer on the substrate surface.

[0093] In some embodiments, the liquid precursor is a solution of a compound that can be activated by 172 nm ultraviolet light.

[0094] The aforementioned liquid precursor refers to a compound whose molecules can undergo a cleavage reaction and produce a first active species under irradiation with a 172nm excimer ultraviolet light source. "Activated by 172nm ultraviolet light" means that the chemical bond energy of the compound is lower than or close to the energy carried by a 172nm photon. The energy of a 172nm photon is as high as 697 kJ / mol (approximately 7.2 eV), higher than the bond energies of many compounds, such as C-Si, N-Si, CH, and CC. Therefore, theoretically, any compound that is soluble in a suitable solvent and whose chemical bonds can be effectively broken by a 172nm photon can serve as the liquid precursor described in this application, greatly expanding the material library for atomic-level manufacturing technologies. For example, compound solutions that can be activated by 172nm ultraviolet light can be methyl silicone oil, aluminum triisopropoxide, or tridimethylaminoaluminum. These chemical melts can be precisely broken by high-energy photons from a 172nm excimer ultraviolet light source, breaking chemical bonds in the molecules, such as C-Si, N-Si, CH, and CC, thereby generating highly active intermediate species "in situ." These primary active species then react chemically with introduced reactive gases (such as oxygen, nitrogen, or ammonia) on the substrate surface, or directly form metallic or non-metallic elemental films under specific conditions. This method, based on liquid-phase precursors and high-energy ultraviolet light activation, eliminates the dependence on high vapor pressure gaseous precursors in traditional atomic layer deposition (ALD), making it theoretically possible for any compound soluble in a suitable solvent and activated by 172nm light to become a thin film precursor.

[0095] Methyl silicone oil is an organosilicon compound with silicon-oxygen-carbon bonds in its molecular structure. Under appropriate conditions, it can cleave and react with oxygen to form a silica film. Aluminum triisopropoxide is an organometallic compound with aluminum-oxygen-carbon bonds in its molecular structure. It can be used as an aluminum source to react with oxygen to form an alumina film. Tris(dimethylaminoaluminum) is also an organometallic compound with aluminum-nitrogen bonds in its molecular structure. It can be used as an aluminum source to react with nitrogen or ammonia to form an aluminum nitride film. These precursors are all soluble in inert solvents and can be uniformly dispersed through dispersion treatment, providing uniform reactants for subsequent atomic-level coating.

[0096] Through the above technical solutions, this application can greatly expand the material library of atomic-level manufacturing technologies. This makes it possible to deposit some novel materials, and even multi-component composite materials, that are difficult to prepare using traditional vapor-phase ALD, thereby significantly improving the flexibility and diversity of thin film material preparation.

[0097] In some implementations, step S3 includes:

[0098] The diluted liquid precursor is sprayed onto the substrate surface;

[0099] The liquid precursor is spread using a first preset rotation speed so that the liquid precursor is spread evenly on the substrate surface under the action of centrifugal force to form an initial precursor film, avoiding local accumulation or missed coating.

[0100] The precursor film is homogenized using a second preset rotation to remove excess solvent from the precursor film and to promote the spontaneous formation of a uniform precursor monolayer by liquid precursor molecules.

[0101] Spraying the diluted liquid precursor onto the substrate surface refers to applying the diluted liquid precursor to the substrate surface through spraying. Specifically, this can be achieved using a sprayer, nozzle, or similar spraying equipment, ensuring that the precursor solution can uniformly cover the substrate surface in the form of fine droplets, laying the foundation for subsequent spreading and film formation.

[0102] Furthermore, spreading the liquid precursor using a first preset rotation angle refers to rotating the substrate to allow the liquid precursor to diffuse towards the substrate edge under centrifugal force, thereby forming a uniform initial precursor film on the substrate surface. The purpose is to use centrifugal force to rapidly and uniformly spread the liquid precursor towards the substrate edge, thus avoiding localized liquid accumulation or missed areas due to uneven spreading on the substrate surface.

[0103] Furthermore, the second preset rotation speed refers to the rotational speed used for spin coating the precursor film after the first stage of spreading is completed. The spin coating process aims to accelerate the evaporation of solvent through continuous centrifugal force, thereby removing excess solvent from the precursor film and promoting the spontaneous alignment of liquid precursor molecules on the substrate surface, ultimately forming a highly uniform and dense precursor monolayer.

[0104] This application's solution effectively addresses the challenge of uniformly spreading and forming a monolayer of liquid precursors on a substrate surface by introducing a staged spin-coating method. The liquid precursor is sprayed onto the substrate surface and spread using a first preset rotation. Precisely controlled centrifugal force allows the liquid precursor to quickly and uniformly cover the entire substrate surface, forming an initial precursor film, thus avoiding localized accumulation or missed coating phenomena that may occur in traditional coating methods. Based on this, a second preset rotation is used for spin coating. This step not only accelerates the evaporation of the solvent in the precursor film, but more importantly, the surface tension changes and intermolecular forces caused by solvent evaporation induce spontaneous rearrangement and adsorption of liquid precursor molecules on the substrate surface, ultimately forming a highly uniform and dense precursor monolayer. This staged spin-coating strategy enables precursor molecules to achieve atomic-level planar spread on the substrate surface in a controlled manner, laying a solid foundation for subsequent atomic-level deposition reactions.

[0105] In some preferred embodiments, the specific process of liquid precursor coating is as follows:

[0106] Low-viscosity, high-purity methyl silicone oil (viscosity 5-10 cSt, purity ≥99.99%) was selected as the precursor, diluted to 0.05 wt% with anhydrous n-hexane, and ultrasonically dispersed for 30 min (frequency 40 kHz) to prevent silicone oil molecule aggregation and ensure solution homogeneity. Subsequently, the diluted silicone oil was spin-coated onto the substrate surface. The spin-coating parameters were specifically set as follows: first, a spin speed of 500 rpm for 10 seconds was used for initial spreading of the silicone oil film; then, a spin speed of 2000 rpm for 30 seconds was used for homogenization to remove excess solvent and promote the spontaneous formation of a uniform monolayer of silicone oil molecules. Through this process, a uniform silicone oil film was obtained on the substrate surface.

[0107] In some implementations, the first preset speed is 500rpm-600rpm, and the second preset speed is 2000rpm-2500rpm.

[0108] This application's solution achieves more precise control of centrifugal force during spin coating by accurately limiting the first preset rotation speed to 500-600 rpm and the second preset rotation speed to 2000-2500 rpm. In the first stage, the low-speed rotation of 500-600 rpm utilizes centrifugal force to smoothly and comprehensively cover the entire substrate with the precursor, avoiding local accumulation or missed coating. In the second stage, the higher rotation speed of 2000-2500 rpm effectively removes excess solvent from the film, prompting the precursor molecules to spontaneously rearrange on the substrate surface through intermolecular forces (such as van der Waals forces and surface tension), ultimately forming a highly uniform, non-agglomerated, and non-stacked precursor monolayer. This staged, precisely controlled rotation speed ensures the quality of the precursor monolayer, laying a solid foundation for subsequent atomic-level coating.

[0109] In some preferred embodiments, the specific implementation is as follows: When coating the liquid precursor, a spin coating method is used to coat the diluted liquid precursor onto the substrate surface. The spin coating parameters are set as follows: first, a spreading speed of 550 rpm is used for 10-15 seconds, followed by a homogenization speed of 2200 rpm for 20-30 seconds. This precisely controlled spin coating parameter ensures that a highly uniform and defect-free precursor monolayer is formed on the substrate surface, providing ideal starting conditions for the subsequent photolysis reaction.

[0110] In some implementations, step S5 includes:

[0111] If the target thin film is a metal or non-metal elemental film, proceed to step S6.

[0112] Otherwise, if the target thin film is a metal oxide type, oxygen is introduced. The oxygen is decomposed under 172nm excimer ultraviolet light source to produce oxygen atoms. The oxygen atoms act as the second active species and react chemically with the first active species to generate a single-layer thin film material on the substrate surface.

[0113] If the target thin film is a nitride type, nitrogen or ammonia gas is introduced. Nitrogen or ammonia gas undergoes a decomposition reaction under 172nm excimer ultraviolet light source irradiation to produce nitrogen atoms. Nitrogen atoms act as the second active species and react chemically with the first active species to generate a monolayer thin film material on the substrate surface.

[0114] Specifically, when the target thin film is determined to be a metallic or non-metallic elemental film, such as a silicon elemental film or a metallic aluminum film, no additional reactive gas is required. In this case, the active species generated by the cleavage of precursor molecules in step S4 can be directly deposited on the substrate surface without the participation of other reactive gases, thereby forming the desired elemental thin film material. In this case, the process flow will directly jump to step S6 for subsequent purging. However, if the target thin film is a metal oxide type, such as a silicon dioxide film or an aluminum oxide film, oxygen is required as the reactive gas. Under irradiation with a 172nm excimer ultraviolet light source, the molecular bonds of oxygen are broken by high-energy photons, generating highly reactive oxygen atoms. These oxygen atoms, acting as the second active species, can chemically react with the first active species generated by the cleavage of the precursor monolayer, thereby promoting the formation of a monolayer metal oxide thin film material on the substrate surface. In practical applications, if the target thin film is a nitride type, such as aluminum nitride or silicon nitride, nitrogen or ammonia gas is introduced. Under irradiation with a 172nm excimer ultraviolet light source, the molecular bonds of nitrogen or ammonia are broken, generating highly reactive nitrogen atoms. These nitrogen atoms, acting as secondary reactive species, react chemically with the primary reactive species to form a monolayer nitride thin film material on the substrate surface. The choice of nitrogen or ammonia gas can be adjusted based on the characteristics of the precursor, the required reactivity, and the purity requirements of the final thin film.

[0115] Through the above technical solution, this application achieves highly precise control over the type of deposited thin film material, greatly expanding the range of materials that can be prepared by liquid atomic-level deposition methods. Specifically, this method can not only efficiently prepare metal or non-metal elemental films, but also accurately synthesize metal oxide films and nitride films, avoiding the problems of film composition deviation or poor performance caused by improper selection of reactive gases. This targeted introduction of reactive gases enables atomic-level uniform deposition and precise thickness control of thin films in a wider range of material systems, thereby significantly improving the quality and functionality of the films and providing more high-performance thin film material options for fields such as flexible electronics and optical devices.

[0116] In some preferred embodiments, this application is implemented as follows:

[0117] In step S4, the precursor monolayer formed on the substrate surface is irradiated with a 172nm excimer ultraviolet light source, causing the precursor molecules to undergo a decomposition reaction to generate active species. If the target thin film is a metal or non-metal elemental film, such as a silicon elemental film, after the photo-irradiation reaction, the process jumps directly to step S6 for purging, without the need to introduce additional reaction gas. If the target thin film is a metal oxide type, such as a silicon dioxide film, high-purity oxygen (99.999%) is introduced during the photo-irradiation reaction, and its flow rate is controlled at 30-50 sccm. To promote oxygen decomposition and improve reaction efficiency, a humidifier 109 can be connected in series in the oxygen pipeline. By adjusting the ratio of the gas flow rate through the humidifier 109 to the gas flow rate of the reaction gas, the relative humidity is controlled at 30%-60%. Oxygen decomposition produces oxygen atoms as a second active species, which react with the first active species to form a uniform silicon dioxide monolayer thin film on the substrate surface. If the target thin film is a nitride type, such as aluminum nitride, high-purity nitrogen or ammonia gas is introduced during the photo-reaction process, and its flow rate is controlled. The nitrogen or ammonia reacts with the active species, thereby forming a uniform aluminum nitride monolayer film on the substrate surface. In this way, the reaction atmosphere can be flexibly selected and controlled according to the specific thin film material requirements, ensuring the acquisition of the target thin film material.

[0118] In some implementations, the power density of the 172nm excimer ultraviolet light source is 20-50 mW / cm².

[0119] Power density refers to the light energy output per unit area of ​​a 172nm excimer ultraviolet light source. Setting it within the range of 20-50 mW / cm² can provide a sufficiently high photon flux to efficiently induce the breaking of chemical bonds in precursor molecules, generating the desired active intermediates, while avoiding local overheating or uneven reactions that may be caused by excessively high power density.

[0120] Specifically, by limiting the power density of the 172nm excimer ultraviolet light source to the range of 20-50 mW / cm², the input of photon energy can be precisely controlled. It is precisely this power density range that allows the precursor monolayer formed on the substrate surface in step S4 to be effectively and gently activated, promoting a controllable cleavage reaction of the precursor molecules to generate the desired first active species. Simultaneously, in step S5, when the reactive gas is introduced, this power density also ensures that the reactive gas is efficiently cleaved under the 172nm excimer ultraviolet light source to generate a second active species, which then undergoes a precise chemical reaction with the first active species, ultimately forming a high-quality monolayer thin film material on the substrate surface. This precise energy control avoids the problems of energy excess or deficiency that may occur in traditional methods, ensuring the accuracy and repeatability of atomic-level deposition.

[0121] In some implementations, step S6 includes:

[0122] Nitrogen gas of preset purity was used to purge the substrate surface at a flow rate of 10-20 L / min and a purging time of 10-15 s to remove unreacted byproducts and residual solvents.

[0123] Specifically, nitrogen gas of a preset purity is used for purging. As an inert gas, nitrogen's high purity effectively prevents the introduction of new contaminants during purging, thus ensuring the purity of the film. In practical applications, the purity of nitrogen gas can reach 99.999% or higher. The purging flow rate is set within the range of 10 L / min to 20 L / min. This flow rate range provides sufficient kinetic energy to effectively strip and remove unreacted byproducts and residual solvents adhering to the substrate surface, while avoiding physical damage to the formed film or substrate surface due to excessive flow. Furthermore, the purging time is controlled within 10 s to 15 s. This optimized time period is sufficient to ensure adequate removal of byproducts and solvents while avoiding unnecessary prolonged purging, thereby improving overall process efficiency.

[0124] The above technical solutions can significantly improve the purity and quality of thin films, effectively avoiding defects such as pores, agglomeration, or inhomogeneity caused by byproducts or solvent residues. Furthermore, the precisely controlled purging process helps enhance the adhesion between the film and the substrate and ensures that the self-limiting properties of each deposition cycle are fully utilized, thereby achieving more precise film thickness control and superior film performance.

[0125] In some preferred embodiments, after the precursor photo-irradiation reaction is completed, the substrate surface is purged with high-purity nitrogen gas (99.999% purity). Specifically, the nitrogen purging flow rate is set in the range of 10 L / min to 20 L / min, and purging is continued for 10 to 15 seconds. This precisely controlled purging process effectively removes unreacted small molecule byproducts and excess solvent from the substrate surface, thereby providing a clean and active surface for subsequent thin film growth cycles.

[0126] In this document, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, without necessarily requiring or implying any such actual relationship or order between these entities or operations.

[0127] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for liquid atomic layer deposition, characterized by, The method comprises the steps of: S1, performing surface treatment on the substrate to remove surface contaminants and achieve surface activation of the substrate; S2, obtaining a liquid precursor and diluting it to a preset concentration; S3, coating the diluted liquid precursor onto the substrate surface, allowing the liquid precursor to spread on the substrate surface and form a uniform monolayer of the precursor; S4, at room temperature, irradiating the monolayer of the precursor formed on the substrate surface with a 172 nm excimer UV light source to cause the precursor molecules to undergo a cracking reaction to generate a first active species; S5, if the target thin film type is a metal or non-metal elemental film, jump to step S6; otherwise, according to the target thin film type, a corresponding reaction gas is introduced, which undergoes a cracking reaction under the irradiation of the 172 nm excimer UV light source to generate a second active species, and the second active species and the first active species undergo a chemical reaction to generate a monolayer of thin film material on the substrate surface, and step S6 is performed; S6, purging the substrate surface to remove unreacted byproducts and residual solvents; S7, repeating steps S3 to S6 until a preset film thickness is reached; Step S2 comprises: obtaining a liquid precursor, dissolving the liquid precursor in an inert solvent, and diluting it to a preset critical concentration to form a precursor solution; dispersing the precursor solution to ensure that the precursor molecules are fully dispersed; The liquid precursor is a compound solution that can be activated by 172 nm ultraviolet light; Step S3 comprises: spraying the diluted liquid precursor onto the substrate surface; spreading the liquid precursor at a first preset speed to uniformly spread the liquid precursor on the substrate surface under the action of centrifugal force, forming an initial precursor film; uniformly coating the uniformly spread precursor film at a second preset speed to remove excess solvent from the precursor film and promote the liquid precursor molecules to spontaneously form a uniform monolayer of the precursor.

2. The liquid atomic layer deposition method according to claim 1, wherein Step S1 comprises: performing preliminary cleaning on the substrate to remove oil, organic contaminants, particulate impurities, and native oxide layers on the substrate surface; performing plasma treatment, oxidation treatment, reduction treatment, or depositing a nanoscale seed layer on the preliminarily cleaned substrate to increase the reactivity of the substrate surface; drying the substrate with increased reactivity and sealing for storage.

3. The liquid atomic layer deposition method according to claim 1, wherein The step of dispersing the precursor solution to ensure uniform dispersion of the precursor molecules comprises: dispersing with ultrasonic waves at a frequency of 40 kHz-50 kHz for 20-30 minutes to ensure uniform dispersion of the precursor molecules.

4. The liquid atomic layer deposition method according to claim 1, wherein The first preset speed is 500-600 rpm, and the second preset speed is 2000-2500 rpm.

5. The liquid atomic layer deposition method according to claim 1, wherein Step S5 comprises: if the target thin film type is a metal or non-metal elemental film, jump to step S6; otherwise, if the target thin film is a metal oxide type, introduce oxygen, which undergoes a cracking reaction under the irradiation of the 172 nm excimer UV light source to generate oxygen atoms as a second active species, which undergoes a chemical reaction with the first active species to generate a monolayer of thin film material on the substrate surface; If the target thin film is a nitride type, nitrogen or ammonia is introduced, and nitrogen or ammonia is cracked by irradiation of the 172 nm excimer UV light source to generate nitrogen atoms, which act as a second active species to chemically react with the first active species to generate a monolayer of thin film material on the substrate surface.

6. The liquid atomic layer deposition method according to claim 1, wherein The power density of the 172 nm excimer UV light source is 20-50 mW / cm².

7. The liquid atomic layer deposition method according to claim 1, wherein Step S6 includes: The substrate surface is purged with nitrogen of a preset purity at a purging flow rate of 10-20 L / min and a purging time of 10-15 s to remove unreacted by-products and residual solvents.

Images