Preparation method of monodisperse spherical nano-alumina and application thereof
Monodisperse spherical nano-alumina was prepared by a controlled hydrolysis-hydrothermal/solventothermal morphology-guided high-temperature crystallization process. Combined with polishing slurry composition optimization, the morphology and dispersibility problems of traditional nano-alumina during the polishing process were solved, achieving high-efficiency polishing performance and reduced surface defects, which is suitable for integrated circuit manufacturing.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- XINGHUA TSINGKE (TIANJIN) ELECTRONIC MATERIALS CO LTD
- Filing Date
- 2026-03-30
- Publication Date
- 2026-06-19
AI Technical Summary
Traditional nano-alumina particles have uneven morphology and size, poor dispersion stability, and difficult-to-control surface chemical properties, resulting in surface defects such as scratches and particle residues during chemical mechanical polishing, which makes it difficult to meet the high requirements of advanced integrated circuit manufacturing.
Monodisperse spherical nano-alumina was prepared by a synergistic process of controlled hydrolysis-hydrothermal/solventothermal morphology guidance-high temperature crystallization. Combined with dispersants and corrosion inhibitors in the polishing slurry, a highly stable dispersion system was formed, thus optimizing the polishing performance.
It achieves controllable morphology and size of nano-alumina, improves dispersion stability and polishing performance, significantly reduces surface defects, meets the high flatness and high selectivity requirements of integrated circuit manufacturing, and is suitable for mass production.
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Figure CN122233411A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a method for preparing nano-alumina and its applications, and more particularly to a method for preparing monodisperse spherical nano-alumina and its applications. Background Technology
[0002] As integrated circuit manufacturing technology advances to advanced processes (such as 14nm, 7nm, 5nm and below), unprecedented demands are placed on chemical mechanical polishing (CMP) processes. CMP requires global high planarization while demanding extremely low surface defects (such as scratches, particle residue, pits, etc.), high material removal selectivity, and perfect surface roughness control. Nano-alumina (α-Al2O3), due to its extremely high hardness (Mohs hardness 9), excellent chemical stability, and thermal stability, is often used as abrasive particles in CMP polishing slurries, especially suitable for polishing dielectric layers and metal layers with high hardness or requiring high polishing rates. However, traditional nano-alumina particles have the following prominent problems: (1) Uneven shape and size: The particles are mostly irregular in shape and have a wide size distribution (mostly dispersed). During the polishing process, uneven force can easily cause scratches on the wafer surface, resulting in fatal defects.
[0003] (2) Poor dispersion stability: Particles are prone to agglomeration to form large secondary particles, and these agglomerates are the main source of scratches and residual pollution.
[0004] (3) Surface chemical properties are difficult to control: the surface charge and hydroxyl density of particles affect their dispersibility in polishing liquid and their interaction with polishing additives (such as corrosion inhibitors and oxidants), which in turn affect polishing selectivity and rate.
[0005] Therefore, developing a method to prepare high-purity, monodisperse (narrow size distribution), spherical nano-alumina with controllable surface properties and applying it to high-performance polishing slurries is crucial to meeting the stringent requirements of advanced integrated circuit manufacturing processes. Summary of the Invention
[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing monodisperse spherical nano-alumina with controllable process and good repeatability.
[0007] Another object of the present invention is to provide a polishing fluid with nano-alumina as the main abrasive particles obtained by the above method.
[0008] Another object of the present invention is to provide the application of the polishing slurry in chemical mechanical polishing of advanced integrated circuit manufacturing processes.
[0009] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing monodisperse spherical nano-alumina, characterized by comprising the following steps: Step S1: Preparation of precursor solution An aluminum source is dissolved in a polar organic solvent to form a clear and transparent aluminum precursor solution; the aluminum source is selected from at least one of aluminum isopropoxide, aluminum sec-butoxide, and aluminum nitrate; the polar organic solvent is selected from at least one of ethanol, isopropanol, and ethylene glycol; the concentration of the aluminum source is 0.05~0.5 mol / L.
[0010] Step S2: Hydrolysis and Aging Under continuous stirring, deionized water or a dilute solution containing a hydrolysis catalyst (such as nitric acid or hydrochloric acid) is slowly added dropwise to the precursor solution obtained in step S1, and the dropping rate is controlled to keep the system temperature stable. After the addition is completed, the mixture is stirred and aged at 40~80°C for 2~24 hours to obtain a white sol. The molar ratio of water to aluminum source is (50~200):1.
[0011] Step S3: Formation and growth of spherical particles The sol obtained in step S2 was transferred to a high-pressure reactor. A mixed gas containing 1-5% CO2 by volume was first introduced into the reactor space, and a hydrothermal or solvothermal reaction was carried out at 120-180°C for 6-48 hours. During this process, the amorphous aluminum hydroxide or boehmite precursor dissolved and recrystallized, leading to the formation of a spherical morphology. CO2 can react with the system under high temperature and pressure, forming weak coordination on the particle surface [z1] [2], further guiding the spherical morphology and reducing hard agglomeration.
[0012] Step S4: Washing and Drying After the reaction was completed, the mixture was allowed to cool naturally to room temperature. The precipitate was collected by centrifugation and washed repeatedly with ethanol and deionized water until the supernatant was neutral. The washed product was then dried under vacuum at 60-100°C to obtain a white powder.
[0013] Step S5: High-temperature crystallization The dried precursor powder obtained in step S4 was placed in a high-temperature furnace and heated to 800-1200°C at a rate of 1-5°C / min under air atmosphere. The temperature was held for 1-4 hours for high-temperature calcination, completely transforming the precursor into highly crystalline α-phase alumina (α-Al₂O₃) while maintaining its spherical morphology. After calcination, it was naturally cooled to obtain the final monodisperse spherical nano-alumina powder.
[0014] Preferably, in step S1 or S2, a surface modifier, such as polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), or citric acid, accounting for 0.1% to 5% of the molar amount of aluminum source, may be added to control the particle size and improve dispersibility during the particle growth stage.
[0015] In a second aspect, the present invention provides a nano-alumina polishing slurry, characterized in that monodisperse spherical nano-alumina prepared according to the method described in the first aspect above is used as abrasive particles.
[0016] The polishing slurry comprises the following components by mass percentage: Monodisperse spherical nano-alumina particles: 0.5%~10%; Composite dispersant-corrosion inhibitor 0.1~5%: composed of polyaspartic acid (PASP) and sodium tungstate (Na2WO4) in a certain proportion (e.g., 1:0.2~1:1 molar ratio); Dispersant: 0.1%~3%, selected from at least one of polyacrylic acid, polymaleic acid, aminotrimethylphosphonic acid (ATMP) or its salts; pH adjuster: Appropriate amount, used to adjust the pH value of the polishing solution to the required range of 2~11; Oxidizing agent: 0~5%, depending on the material being polished, such as hydrogen peroxide, ferric nitrate, potassium iodate, etc.; Corrosion inhibitors: 0~2%, such as benzotriazole (BTA), 1,2,4-triazole, etc. (used for metal polishing). Surfactant: 0~0.5%, such as nonionic surfactants; Deionized water: Balance.
[0017] The monodisperse spherical nano-alumina particles have an average particle size of 20~200 nm, a particle size distribution standard deviation (D90-D10) / D50 < 0.5, and a purity > 99.99%.
[0018] Thirdly, the present invention provides the application of the nano-alumina polishing slurry in chemical mechanical polishing of advanced integrated circuit manufacturing processes. The polishing slurry is used to perform chemical mechanical polishing on at least one of silicon substrates, dielectric layers (such as silicon dioxide, silicon nitride), metal layers (such as copper, tungsten, cobalt), or barrier layers (such as tantalum, tantalum nitride) in integrated circuit manufacturing, and is particularly suitable for manufacturing processes of 14 nanometer and below technology nodes.
[0019] The present invention has the following beneficial effects: (1) Controllable morphology and size: Through the synergistic process of “controllable hydrolysis-hydrothermal / solventothermal morphology guidance-high temperature crystallization”, the spherical morphology, monodispersity and final size of nano alumina are precisely controlled, effectively avoiding the generation of irregular sharp particles.
[0020] (2) High dispersion stability: The surface of the prepared spherical nano alumina is smooth. Combined with the effect of the dispersant in the subsequent polishing liquid, it can form a highly stable and anti-agglomeration dispersion system in the slurry, which greatly reduces the risk of scratches caused by particle agglomeration.
[0021] (3) Excellent polishing performance: During the polishing process, the spherical particles have “surface contact” with the wafer surface, which is more uniform in stress distribution compared with the “point contact” of irregular particles. This can significantly reduce surface defects such as scratches and pits, and obtain a lower surface roughness (Ra). At the same time, its high hardness and chemical stability ensure a high material removal rate.
[0022] (4) Good process compatibility: The prepared polishing slurry can be flexibly adjusted in pH value and additive composition according to the polished material (medium, metal, etc.) to achieve high selectivity and high planarization efficiency, meeting the stringent requirements of advanced processes for CPM process.
[0023] (5) The preparation method has good repeatability and is suitable for large-scale production: the raw materials are readily available, the process conditions are mild and controllable, and it is easy to achieve batch preparation. Attached Figure Description
[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0025] Figure 1 This is a schematic flowchart illustrating a method for preparing monodisperse spherical nano-alumina according to an embodiment of the present invention. Detailed Implementation
[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.
[0027] Reference manual attached Figure 1 The diagram shows a flow chart of a method for preparing monodisperse spherical nano-alumina provided by an embodiment of the present invention.
[0028] Example 1: Preparation of monodisperse spherical nano-alumina Dissolve 0.1 mol aluminum isopropoxide in 500 mL of anhydrous ethanol and stir magnetically until completely dissolved. Then add 10 mL of 0.1 mol / L PVP ethanol solution to obtain a clear solution.
[0029] Under vigorous stirring, 10 mL of deionized water containing 0.1 mL of concentrated nitric acid was slowly added dropwise to the above solution, with the addition time controlled at approximately 30 minutes. The mixture was then placed in a 70°C water bath and aged under constant temperature and stirring for 12 hours to obtain a translucent sol.
[0030] The sol was transferred into a 1L polytetrafluoroethylene-lined high-pressure reactor, and a mixed gas containing 2% CO2 by volume was introduced into the reaction system. The reaction was carried out at 160°C for 24 hours.
[0031] After the reaction was complete, the white precipitate was collected by centrifugation and washed three times each with ethanol and deionized water. The product was then vacuum dried overnight at 80°C.
[0032] The dried powder was placed in an alumina crucible and heated to 1000°C in a muffle furnace at a rate of 2°C / min. The temperature was maintained for 2 hours, and the powder was cooled with the furnace to obtain a white powder product.
[0033] Example 2: Preparation of monodisperse spherical nano-alumina Add 20 ml of 0.1 mol / L PVP ethanol solution, and follow the same steps as in Example 1.
[0034] Example 3 Without adding 0.1 mol / L PVP ethanol solution, the remaining steps are the same as in Example 1.
[0035] Example 4 The difference from Example 1 is that controlled hydrolysis is omitted: the aluminum source and water are rapidly mixed (added within 1 minute), and the mixture is directly transferred to hydrothermal treatment without aging. (This verifies the necessity of "controlled hydrolysis") Example 5 The hydrothermal step was omitted: the hydrolyzed and aged sol was directly dried and then subjected to high-temperature crystallization. (This verifies the necessity of the "hydrothermal morphology-guided" approach.) Example 6 Omitted CO2 atmosphere: The hydrothermal reaction was carried out in an air atmosphere without CO2 (to verify the necessity of "CO2 guidance").
[0036] The particle size test results are shown in Table 1. Table 1
[0037] As can be seen, the particle size of Example 1 is about 80 nm, the distribution width is 0.49, and the monodispersity is good; the particle size of Example 2 increases to about 144 nm, and the distribution is narrower (0.33), indicating that the increase of PVP concentration is beneficial to the uniform growth of particle size, but the particle size itself is controlled by the concentration; the particle size of Example 3 is about 113 nm, and the distribution width is 0.65, indicating that the surface modifier plays an important role in controlling the uniformity of particle size and inhibiting agglomeration.
[0038] Example 4 showed a significantly increased particle size, wider distribution, and irregular morphology. This indicates that an excessively rapid hydrolysis rate leads to uneven nucleation, preventing the formation of uniform spherical precursors, thus demonstrating the importance of controllable hydrolysis.
[0039] The product of Example 5 was blocky with extremely large particle size and no spherical morphology. This demonstrates that the hydrothermal / solvothermal process is a key step in the formation of spherical morphology, and morphology guidance cannot be achieved without this step.
[0040] Although the product in Example 6 was nearly spherical, it showed significant agglomeration and a wide distribution. This indicates that the carbonate / bicarbonate adsorption layer formed by CO2 under high temperature and pressure effectively inhibited hard agglomeration and ensured monodispersity.
[0041] The aforementioned differences directly demonstrate the role of CO2. In the absence of CO2, the hydroxyl groups (-OH) on the particle surface readily undergo dehydration condensation in a hydrothermal environment, leading to the formation of strong chemical bonds between particles (i.e., hard agglomeration). However, when CO2 is introduced, it dissolves in water to form carbonate / bicarbonate ions. These groups, under high temperature and pressure, form a weakly coordinated adsorption layer with aluminum sites on the particle surface. This adsorption layer acts as a steric hindrance, guiding isotropic spherical growth on one hand, and effectively shielding the direct contact of hydroxyl groups on the particle surface on the other, thus significantly inhibiting hard agglomeration and ensuring the monodispersity of the final product.
[0042] The results of impurity detection are shown in Table 2. Table 2
[0043] As can be seen from Table 2, the impurity content in all examples is at an extremely low level, and the purity is greater than 99.99%.
[0044] Although Examples 3-6 differ in the morphology control steps, none of these steps introduce additional metal impurities, thus maintaining consistent product purity. This data demonstrates that the preparation process of this invention can maintain consistent high product purity while achieving morphology and dispersibility control, meeting the stringent requirements for material purity in integrated circuit manufacturing.
[0045] Example 7: Preparation of polishing slurry for polishing copper interconnects Prepare the polishing solution according to the following mass percentages: Nano-alumina (average particle size 50 nm) prepared using the method in Example 1: 2% Composite dispersant-corrosion inhibitor 0.5%: composed of polyaspartic acid (PASP) and sodium tungstate (Na2WO4) in a molar ratio of 1:0.5; Pentasodium aminotrimethylphosphonate (dispersant and corrosion inhibitor): 1.5% Hydrogen peroxide (oxidant): 1% Benzotriazole (BTA, corrosion inhibitor): 0.3% Nitric acid (pH adjuster): Adjusts the pH to 4.0. Deionized water: Balance Preparation method: After mixing the components, disperse them for 30 minutes using a high-speed shear disperser, and then filter them through a 0.1 μm filter to obtain a polishing liquid with good stability and no obvious precipitation.
[0046] Example 8 The difference from Example 7 is that it contains only 0.5% PASP and does not contain sodium tungstate.
[0047] Example 9 The difference from Example 7 is that it contains only 0.5% sodium tungstate and no PASP.
[0048] Example 10 The difference from Example 7 is that it is a strongly acidic system with a pH of 2.
[0049] Example 11 The difference from Example 7 is that it is a neutral system with a pH of 7.
[0050] Example 12 The difference from Example 7 is that it is an alkaline system with a pH of 10.
[0051] Comparative Example 1 The traditional precipitation method is used: aluminum nitrate solution is rapidly mixed with excess ammonia water to generate aluminum hydroxide precipitate, which is then washed, dried, and calcined at 1000°C to obtain aluminum oxide.
[0052] Application test case: The polishing slurries prepared in Examples 7-12 were used to polish wafers coated with copper film and compared with commercial copper polishing slurries. The test results are shown in Table 3.
[0053] Table 3
[0054] The results showed that Example 7 was superior to the single component in terms of particle size distribution, dispersibility, surface roughness, removal rate, and selectivity. This indicates that the combination of the two components has a synergistic effect; PASP provides dispersion and chelation, while Na2WO4 enhances corrosion inhibition and surface passivation, jointly improving the overall polishing performance.
[0055] A comparison of Examples 7 and 10-12 shows that pH=4 (Example 7) exhibits the best dispersibility, lowest surface roughness (0.32 nm), and highest selectivity (12.5:1). Although pH=2 (Example 10) has the highest removal rate (340 nm / min), it also shows poor dispersibility, increased roughness, and decreased selectivity, indicating reduced particle stability under strong acid conditions. Both pH=7 (Example 11) and pH=10 (Example 12) show poor dispersibility, significantly increased surface roughness, and decreased selectivity. The optimal polishing range is pH=4-5, which achieves the best balance between dispersibility, planarization effect, and selectivity.
[0056] Comparative Example 1 (traditional precipitation method) produced products with large particle size, extremely wide distribution (1.85 nm), and severe agglomeration, resulting in high surface roughness (1.20 nm), low removal rate (180 nm / min), and poor selectivity (6.5:1) after polishing. The polishing solution of this invention is significantly superior to the traditional method in all indicators, demonstrating the significant advantages of monodisperse spherical nano-alumina in CMP applications.
[0057] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.
Claims
1. A method for preparing monodisperse spherical nano-alumina, characterized in that, Includes the following steps: S1: Dissolve the aluminum source in a polar organic solvent to form a clear aluminum precursor solution; S2: Under stirring, water or an acidic aqueous solution is added dropwise to the precursor solution for hydrolysis, followed by aging at 40~80°C to obtain a sol; S3: The sol is subjected to a hydrothermal or solvothermal reaction. Before the hydrothermal or solvothermal reaction, a mixed gas containing 1-5% by volume CO2 is introduced into the reaction system. The reaction temperature is 120-180°C, and the reaction time is 6-48 hours. S4: Centrifuge, wash and dry the product after hydrothermal or solvothermal reaction to obtain precursor powder; S5: Calcine the precursor powder at 800~1200°C for 1~4 hours to obtain monodisperse spherical nano-α-alumina powder.
2. The preparation method according to claim 1, characterized in that, In step S1, the aluminum source is selected from at least one of aluminum isopropoxide, aluminum sec-butoxide, and aluminum nitrate; the polar organic solvent is selected from at least one of ethanol, isopropanol, and ethylene glycol; and the concentration of the aluminum source is 0.05~0.5 mol / L.
3. The preparation method according to claim 1, characterized in that, In step S2, the amount of water or acidic aqueous solution added is such that the molar ratio of water to aluminum source is (50~200):1; the aging time is 2~24 hours.
4. The preparation method according to claim 1, characterized in that, In step S1 or S2, a surface modifier is added at a molar weight of 0.1% to 5% of the aluminum source, wherein the surface modifier is selected from polyethylene glycol, polyvinylpyrrolidone, or citric acid.
5. A nano-alumina polishing slurry, characterized in that, It contains monodisperse spherical nano-alumina prepared by the method according to any one of claims 1-4 as grinding particles.
6. The nano-alumina polishing slurry according to claim 5, characterized in that, By mass percentage, it includes the following components: Monodisperse spherical nano-alumina particles: 0.5%~10%; Composite dispersant-corrosion inhibitor 0.1~5%: composed of polyaspartic acid (PASP) and sodium tungstate (Na2WO4) in a certain proportion (e.g., 1:0.2~1:1 molar ratio); Dispersant: 0.1%~3%, wherein the dispersant is selected from at least one of polyacrylic acid, polymaleic acid, aminotrimethylphosphonic acid or its salts; pH adjuster: Used to adjust the pH value of the polishing solution to 2~11; Deionized water: Balance.
7. The nano-alumina polishing slurry according to claim 6, characterized in that, It also contains at least one of the following components: Oxidizing agent: 0~5%; Corrosion inhibitor: 0~2%; Surfactant: 0~0.5%.
8. The nano-alumina polishing slurry according to claim 5, characterized in that, The monodisperse spherical nano-alumina particles have an average particle size of 20~200 nm, a particle size distribution that satisfies (D90-D10) / D50 < 0.5, and a purity greater than 99.99%.
9. The application of the nano-alumina polishing slurry according to any one of claims 5-8 in the chemical mechanical polishing process of integrated circuit manufacturing.
10. The application according to claim 9, characterized in that, The polishing slurry is used to polish at least one material selected from silicon substrate, dielectric layer, metal layer or barrier layer, and the integrated circuit manufacturing process is an advanced process with a technology node of 14 nanometers or below.