A sapphire etching solution, a preparation method and application thereof
By preparing a sapphire etching solution containing alkali metal ions, NO3-, OH- and transition metal ions, the problems of uneven etching and short etching solution life caused by aluminate adhesion were solved, achieving efficient and stable sapphire etching effect and reducing costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- LENS TECHNOLOGY CO LTD
- Filing Date
- 2026-02-03
- Publication Date
- 2026-06-09
AI Technical Summary
Existing alkaline etching processes for sapphire suffer from uneven etching, low efficiency, and short etching solution life due to the adhesion and accumulation of aluminates, and traditional adsorbents are prone to introducing secondary impurities.
An etching solution containing alkali metal ions, NO3-, OH-, and transition metal ions (with a valence of 3 or higher) was prepared by melt mixing. The molar concentration of transition metal ions in the etching solution was 0.02-0.08 mol/kg. The composition ratio and process conditions of the etching solution were optimized to ensure etching uniformity and stability.
It achieves efficient removal of aluminates, improves etching uniformity and etching solution stability, avoids the introduction of impurities, reduces costs, and improves etching depth and surface quality.
Smart Images
Figure CN122168285A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of sapphire processing technology, specifically to a sapphire etching solution, its preparation method, and its application. Background Technology
[0002] Chemical etching of sapphire (primarily composed of aluminum oxide) is a processing method that uses chemical reagents to selectively react with the material surface to remove excess material and obtain the desired microstructure and morphology. This method can be broadly classified into acidic etching and alkaline etching. Alkaline etching typically uses monovalent cationic hydroxides such as potassium hydroxide, sodium hydroxide, and lithium hydroxide, mixed with corresponding nitrates such as potassium nitrate, sodium nitrate, and lithium nitrate in a specific ratio. These are then reacted with the sapphire surface in a high-temperature molten state to generate soluble aluminates, thereby achieving material removal.
[0003] However, this technology faces significant challenges in industrial applications: the large amount of aluminate generated after the reaction of strongly alkaline molten salt with sapphire is partly suspended in the molten salt system in colloidal form, and partly adheres to the sapphire surface, hindering further reaction. This directly leads to bottleneck problems such as uneven etching process, reduced effective etching amount, and shortened molten salt life.
[0004] Currently, common silicon-based or carbon-based adsorbents struggle to achieve efficient and selective removal of aluminates in molten salt environments characterized by high temperature, strong corrosion, and strong oxidation. Furthermore, the inherent high temperature, strong corrosiveness, and strong oxidizing properties of mixed molten salts can even lead to the corrosion or oxidation of these types of adsorbents, introducing other impurities into the molten salt.
[0005] Therefore, developing a technology that can solve the problem of aluminates in molten salts and improve etching uniformity and efficiency is the key to achieving an industrial breakthrough in sapphire processing. Summary of the Invention
[0006] The purpose of this invention is to solve the problems of uneven etching, low efficiency, and short etching solution life caused by the adhesion and accumulation of aluminates in the existing alkaline etching process for sapphire, as well as the easy introduction of secondary impurities by existing purification methods.
[0007] To achieve the above objectives, a first aspect of the present invention provides a sapphire etching solution containing alkali metal ions and NO3. - OH - Transition metal ions; the transition metal ions are provided by inorganic salts containing transition metal elements, and the ionic valence state of the transition metal elements is 3 or higher; The molar concentration of transition metal ions in the etching solution is 0.02-0.08 mol / kg.
[0008] A second aspect of the present invention provides a method for preparing the sapphire etching solution described in the first aspect, the method comprising: The sapphire etching solution is obtained by melting and mixing a nitrate compound containing a transition metal element, a nitrate compound containing an alkali metal element, and a hydroxide containing an alkali metal element; the ionic valence state of the transition metal element is 3 or higher.
[0009] A third aspect of the present invention provides an application of the sapphire etching solution described in the first aspect in etching sapphire.
[0010] Compared with the prior art, the technical solution provided by the present invention has at least the following beneficial effects: (1) Efficient removal of aluminates, ensuring etching amount and improving uniformity. The sapphire etching solution provided by the present invention can efficiently remove aluminates generated and suspended in alkaline molten salt reaction, effectively solving the core problem of aluminate colloids adhering to the sapphire surface and hindering the reaction process; this not only ensures that the process can achieve the expected etching depth (etching amount), but also significantly improves the overall uniformity and consistency of the etched surface, and can achieve high-quality micromorphological control.
[0011] (2) Strong compatibility and no secondary pollution. The sapphire etching solution provided by this invention has excellent high temperature resistance, strong alkali resistance and oxidation resistance. It can work stably for a long time in harsh molten salt environment, avoiding the problem of introducing new impurities into the system due to self-consumption or decomposition in traditional adsorbent solutions, and ensuring the purity and long-term stability of the etching process.
[0012] (3) The process has significant economic advantages, and the overall cost is lower than that of traditional adsorbent solutions. Compared with traditional purification methods that rely on the continuous addition and replacement of adsorbents, the technical solution provided by this invention reduces material consumption through process optimization, reduces the frequency of waste liquid treatment by extending the service life of molten salt, or saves maintenance costs by simplifying the operation process, thereby achieving better economic benefits overall. Attached Figure Description
[0013] Figure 1 This is an electron microscope image of the sapphire surface after etching with the sapphire etching solution provided in Example 1, provided by the present invention. Figure 2 This is an electron microscope image of the sapphire surface after etching with the sapphire etching solution provided in Example 2, provided by the present invention. Figure 3 This is an electron microscope image of the sapphire surface after etching with the sapphire etching solution provided in Example 3, provided by the present invention. Figure 4This is an electron microscope image of the sapphire surface after etching with the sapphire etching solution provided in Comparative Example 1, provided by an exemplary embodiment of the present invention. Figure 5 This is an electron microscope image of an unetched sapphire surface provided by an example of the present invention. Detailed Implementation
[0014] The endpoints and any values of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.
[0015] As previously described, a first aspect of the present invention provides a sapphire etching solution containing alkali metal ions and NO3. - OH - Transition metal ions; the transition metal ions are provided by inorganic salts containing transition metal elements, and the ionic valence state of the transition metal elements is 3 or higher; The molar concentration of transition metal ions in the etching solution is 0.02-0.08 mol / kg.
[0016] It should be noted that, in this invention, molality refers to the amount of a specified ion contained in each kilogram of etching solution. For example, a molality of transition metal ions in the etching solution of 0.02-0.08 mol / kg means that the content of transition metal ions in each kilogram of etching solution is 0.02-0.08 mol.
[0017] The transition metal in the etching solution includes rare earth elements.
[0018] This invention, through inventive research, discovers that hydroxide and nitrate ions in the etching solution, under the synergistic effect of alkali metal ions, exert a strong alkaline corrosion and oxidizing effect on the molten salt medium in a high-temperature environment, achieving highly efficient etching of sapphire. Simultaneously, the introduction of appropriate amounts of transition metal ions into the alkaline molten salt, while avoiding excessively high transition metal ion concentrations that react with hydroxide ions to produce turbidity and precipitation, also allows for effective control of the influence of aluminates. This significantly improves etching uniformity and surface morphology consistency while ensuring etching depth. The etching system formed by this method possesses excellent high-temperature resistance, strong alkali resistance, and oxidation resistance, enabling long-term stable operation under harsh process conditions. It not only avoids the problem of impurities introduced by traditional adsorbents due to corrosion or decomposition but also comprehensively improves the purity, stability, and controllability of the etching process.
[0019] Preferably, the alkali metal ion concentration in the etching solution is 12-34 mol / kg, and NO3- - The molality of OH is 3-10 mol / kg. - The molality of the etching solution is 5-30 mol / kg. In this preferred embodiment, the present invention can precisely control the alkalinity and high-temperature molten salt characteristics of the etching solution, achieving a stable and controllable etching rate. This ensures the achievement of the expected etching depth and surface quality while effectively avoiding localized over-etching and uneven morphology caused by excessively rapid reactions. Simultaneously, this system helps promote uniform heat transfer in the reaction system, enhances the contact and diffusion efficiency of reactants, and allows the etchant to react more fully and uniformly with the sapphire surface, thus improving etching uniformity and optimizing the microstructure.
[0020] More preferably, the alkali metal ion concentration in the etching solution is 12-18 mol / kg, and NO3- - The molality of OH is 3.5-7 mol / kg. - The molar concentration of the ions is 5-15 mol / kg, and the molar concentration of the transition metal ions is 0.02-0.08 mol / kg. In this preferred configuration, the specific concentration combination of each component ensures that the transition metal ions exist in a highly active, soluble, and non-agglomerated form. After efficient removal of aluminates, they can be completely discharged with the molten salt, avoiding the formation of metal residues or lattice damage on the sapphire surface, thereby improving the etching depth.
[0021] More preferably, the OH in the etching solution - The mass molar concentration is 5-10 mol / kg; the mass molar concentration of transition metal ions is 0.03-0.07 mol / kg; the hydroxide ion concentration is the key to determining the chemical stability of transition metal ions in high-temperature alkaline molten salt. Under this preferred condition, it is ensured that the transition metal ions remain in the optimal soluble active valence state throughout the etching process, so that the etching depth can be further significantly improved.
[0022] Preferably, the NO3 in the etching solution - and OH - The molar concentration ratio is 0.15-1.3:1. NO3 control - and OH - The mass molar concentration ratio can achieve synergistic optimization of sapphire etching rate and uniformity.
[0023] More preferably, the NO3 in the etching solution - and OH -The molar concentration ratio is 0.5-0.6:1. This invention, through inventive research, discovered that NO3... - and OH - The molar concentration ratio of NO3 is controlled within this preferred range. - This reduces melt viscosity, significantly improving mass transfer and thermal uniformity; simultaneously, it provides a mild oxidizing environment, promoting the reaction between high-valence transition metal ions and aluminates in the etching solution, allowing them to react with OH groups. - The strong corrosive effect works synergistically to achieve a faster, more uniform, and controllable sapphire etching effect.
[0024] Preferably, the transition metal ions are provided by a nitrate compound containing a transition metal element. Nitrate compounds containing transition metal elements can provide a more stable cationic environment in the molten salt system, maintain chemical inertness under high-temperature and strongly alkaline conditions, avoid introducing interfering impurity ions into the etching system, and ensure process purity; simultaneously, they can also provide NO3. - It also helps maintain the NO3 content in the etching solution. - The dynamic balance of concentration ensures the long-term stability of the etching reaction kinetics and the controllability of the process.
[0025] More preferably, the transition metal element is selected from at least one of lanthanum, cerium, yttrium, iron, chromium, zirconium, and thorium. In this preferred embodiment, aluminate ions in alkaline molten salts can be removed more effectively, while simultaneously reducing raw material procurement and process operating costs without affecting etching performance, thus providing an economically feasible technical basis for large-scale industrial applications.
[0026] More preferably, the nitrate compound containing the transition metal element is selected from at least one of lanthanum nitrate hexahydrate, cerium nitrate hexahydrate, yttrium nitrate hexahydrate, ferric nitrate nonahydrate, chromium nitrate nonahydrate, zirconium nitrate pentahydrate, and thorium nitrate tetrahydrate. In this preferred embodiment, the cations and water molecules have a strong coordination effect, and during the crystallization process, water molecules will stably bind around the cations to form a stable hydrated crystal structure, ensuring the uniformity of the transition metal source used during long-term storage; in the process, the presence of water of crystallization alleviates thermal shock, allowing the transition metal ions to be released smoothly and controllably and integrated into the etching system.
[0027] Preferably, the alkali metal ions are provided by a hydroxide containing an alkali metal element. The alkali metal hydroxide, as an etchant, is strongly alkaline and can react with alumina to form aluminates, thus achieving chemical etching.
[0028] More preferably, the hydroxide containing an alkali metal element is selected from at least one of potassium hydroxide, sodium hydroxide, and lithium hydroxide.
[0029] More preferably, the hydroxide of the alkali metal element is potassium hydroxide. In this preferred embodiment, OH in the molten state... - It has greater freedom and activity, and a stronger ability to etch sapphire.
[0030] Preferably, the alkali metal ions are further provided by a nitrate compound containing an alkali metal element. In this preferred embodiment, it also provides NO3 as a reaction medium and flux. - It helps to achieve uniform heat transfer, improve the contact and diffusion efficiency between reactants, and enable alkali metal hydroxides to more effectively contact and react with the sapphire surface. It also has the auxiliary role of improving etching uniformity and controlling etching morphology.
[0031] More preferably, the nitrate compound containing an alkali metal element is selected from at least one of potassium nitrate, sodium nitrate, and lithium nitrate. Under this preferred embodiment, no foreign impurities are introduced into the etching system, which helps maintain the purity of the etching system and the repeatability of the process.
[0032] As previously described, a second aspect of the present invention provides a method for preparing the sapphire etching solution described in the first aspect, the method comprising: The sapphire etching solution is obtained by melting and mixing a nitrate compound containing a transition metal element, a nitrate compound containing an alkali metal element, and a hydroxide containing an alkali metal element; the ionic valence state of the transition metal element is 3 or higher.
[0033] Preferably, the conditions for the melt mixing include a temperature of 250-450°C.
[0034] More preferably, the melting and mixing conditions further include a time of not less than 12 hours. Under this preferred condition, it is possible to ensure that all components melt uniformly, and that the etching solution is ready to use, stable, and repeatable.
[0035] As previously stated, the third aspect of the present invention provides the application of the sapphire etching solution described in the first aspect in etching sapphire.
[0036] Preferably, the application is performed using a method comprising the following steps: The sapphire is immersed in the sapphire etching solution to obtain a sapphire with surface etching.
[0037] Preferably, the sapphire undergoes a pretreatment before impregnation, and the pretreatment steps include: SI. Wash the sapphire sequentially with acetone, ethanol and water, and then dry it. SII. Preheat the dried sapphire.
[0038] Preferably, the drying conditions include a temperature of 80-120°C and a time of 12-24 hours.
[0039] In a preferred embodiment, the preheating conditions include: a temperature of 200-400℃ and a time of ≥1h.
[0040] Preferably, the impregnation conditions include: a temperature of 250-450°C and a time of 3-7 hours.
[0041] In a preferred embodiment, the method further includes: sequentially washing and drying the impregnated sapphire with water.
[0042] It should be noted that the present invention does not limit the specific operation method and conditions of water washing. Those skilled in the art can choose to perform it in a conventional manner. For example, water washing is performed under ultrasonic conditions, and the temperature of the water washing is 60-100℃.
[0043] The invention will now be described in detail through implementation. Unless otherwise specified, all instruments and reagents used in the following examples are commercially available.
[0044] This embodiment is used to illustrate that the sapphire etching solution provided by the present invention is melt-mixed according to the formula in Table 1 (temperature is 350°C, time is 12h). Unless otherwise specified, the remaining embodiments and comparative examples follow a similar process to that of Example 1. The difference is that the formulations used in each example are different, as detailed in Table 1 (Note: Parameters not listed in Table 1 are the same as those in Example 1); in Table 1, each wt% represents 1g.
[0045] In Table 1, taking Example 1 as an example, the calculation formulas for each ion concentration are as follows:
[0046] Table 1
[0047] Table 1 (continued)
[0048] Test case After etching sapphire using the etching solutions obtained in the aforementioned embodiments and comparative examples, the morphology of the sapphire wafer surface after etching was observed, and the Al element content in the etching solution was detected; the specific operations are as follows: 1. After the CNC-machined sapphire sheet (50mm×40mm×1mm) is cleaned in an ultrasonic cleaner (power 1400W) with acetone, ethanol and deionized water in sequence, it is then placed in a 105℃ drying oven for 12 hours. 2. Place the cleaned and dried sapphire wafers into a muffle furnace at 300℃ and preheat for at least 1 hour; 3. Immerse the preheated sapphire sheet in the etching solution prepared in the previous example, etch for 5 hours, then remove it and wash it with deionized water at 80°C in an ultrasonic cleaner for more than 3 times, 30 minutes each time. Place the cleaned sapphire sheet in a drying oven at 105°C to dry it, and observe the morphology of the sapphire sheet surface after etching using SEM (scanning electron microscope).
[0049] 4. Use ICP (Inductively Coupled Plasma Emission Spectrometry) to detect the Al content in the molten salt.
[0050] The results are shown in Table 2.
[0051] Table 2
[0052] As can be seen from the results in Table 2, the sapphire etching solution provided by the present invention significantly improves the etching depth of sapphire and significantly reduces the aluminum content of the molten salt in the etching solution; while the silicon-based and carbon-based adsorbents in the comparative example do not have obvious adsorption capacity in the above molten salt of the etching solution, and the etching depth of sapphire does not change significantly.
[0053] The present invention also provides, by way of example, an electron microscope image of the sapphire surface after etching with the sapphire etching solution provided in Example 1 ( Figure 1 Electron microscope image of the sapphire surface after etching with the sapphire etching solution provided in Example 2 ( Figure 2 Electron microscope image of the sapphire surface after etching with the sapphire etching solution provided in Example 3 ( Figure 3 Electron microscope image of the sapphire surface after etching with the sapphire etching solution provided in Comparative Example 1 ( Figure 4 Electron micrograph of unetched sapphire surface ( Figure 5 );from Figures 1 to 5 It is evident that the unetched sapphire surface exhibits irregular protrusions or depressions resembling small grains, with a relatively uniform overall distribution. The etched sapphire surfaces in Examples 1, 2, and 3 show high overall smoothness, with Example 1 demonstrating the best results. In Comparative Example 1, the etched sapphire surface exhibits high roughness, with deep and unevenly distributed depressions. These results demonstrate that the sapphire etching solution provided by this invention can significantly improve the etching amount and uniformity of sapphire etching.
[0054] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.
Claims
1. A sapphire etching solution, characterized in that, The etching solution contains alkali metal ions and NO3. - OH - Transition metal ions; the transition metal ions are provided by inorganic salts containing transition metal elements, and the ionic valence state of the transition metal elements is 3 or higher; The molar concentration of transition metal ions in the etching solution is 0.02-0.08 mol / kg.
2. The sapphire etching solution according to claim 1, characterized in that, The etching solution contains alkali metal ions with a molar concentration of 12-34 mol / kg and NO3-. - The molality of OH is 3-10 mol / kg. - The molality is 5-30 mol / kg.
3. The sapphire etching solution according to claim 2, characterized in that, The etching solution contains 12-18 mol / kg of alkali metal ions and NO3. - The molality of OH is 3-7 mol / kg. - The molar concentration of the metal ions is 5-15 mol / kg, and the molar concentration of the transition metal ions is 0.02-0.08 mol / kg.
4. The sapphire etching solution according to claim 3, characterized in that, OH in the etching solution - The molality of the transition metal ions is 5-10 mol / kg; the molality of the transition metal ions is 0.03-0.07 mol / kg. And / or, NO3 in the etching solution - and OH - The molar concentration ratio is 0.25-1.4:1; preferably 0.5-0.6:
1.
5. The sapphire etching solution according to any one of claims 1-4, characterized in that, The transition metal ions are provided by nitrate compounds containing transition metal elements; And / or, the transition metal element is selected from at least one of lanthanum, cerium, yttrium, iron, chromium, zirconium, and thorium.
6. The sapphire etching solution according to any one of claims 1-4, characterized in that, The alkali metal ions are provided by hydroxides containing alkali metal elements; And / or, the hydroxide containing an alkali metal element is selected from at least one of potassium hydroxide, sodium hydroxide, and lithium hydroxide.
7. The sapphire etching solution according to claim 6, characterized in that, The alkali metal ions are also provided by nitrate compounds containing alkali metal elements; And / or, the nitrate compound containing an alkali metal element is selected from at least one of potassium nitrate, sodium nitrate, and lithium nitrate.
8. A method for preparing the sapphire etching solution according to any one of claims 1-7, characterized in that, The method includes: The sapphire etching solution is obtained by melting and mixing a nitrate compound containing a transition metal element, a nitrate compound containing an alkali metal element, and a hydroxide containing an alkali metal element; the ionic valence state of the transition metal element is 3 or higher. And / or, the conditions for the melt mixing include a temperature of 250-450°C.
9. The application of the sapphire etching solution according to any one of claims 1-7 in etching sapphire.
10. The application according to claim 9, characterized in that, The application is performed using a method that includes the following steps: The sapphire is immersed in the sapphire etching solution to obtain a sapphire with surface etching. And / or, the impregnation conditions include: a temperature of 250-450°C and a time of 3-7 hours.