Preparation method and application of polishing abrasive material of cerium cluster coated substrate material

Abstract

The invention provides a preparation method and application of a polishing abrasive with a cerium cluster coated substrate material, and the preparation method comprises the following steps: uniformly dispersing ceric ammonium nitrate in pyridine, then dropwise adding a pyridine pivalate solution, stirring for reaction, and centrifuging to obtain a supernatant liquid; dropwise adding acetonitrile into the supernatant, standing, and drying to obtain cerium clusters; then taking a substrate material, and ultrasonically dispersing the substrate material in ethanol to obtain a reaction solution; performing ultrasonic dispersion on the cerium cluster in dichloromethane to obtain a mixed solution, then uniformly dropwise adding the mixed solution into the reaction solution, stirring for 5-15 hours, then performing centrifugal drying, and calcining to obtain the cerium-based catalyst. The surface of the substrate material is firmly coated with a layer of cerium clusters through the electrostatic interaction to obtain the polishing abrasive material, the polishing abrasive material is prepared into the polishing solution for mechanical polishing, the polishing efficiency of the substrate material can be remarkably improved, the surface flatness of the substrate material is reserved, the synthesis process is simple, and the cost is low.

Description

Technical Field

[0001] The present invention relates to the technical field of polishing, in particular to a preparation method and application of a polishing abrasive of a cerium cluster-coated base material. Background Art

[0002] Chemical mechanical polishing (CMP) is a key process in semiconductor manufacturing, optical glass processing, and integrated circuit fabrication. Its primary purpose is to achieve global surface planarization. CMP removes material and achieves high-precision surface quality through a combination of mechanical action and chemical reaction. However, with technological advancements, the silica (SiO2) abrasives and coatings used in traditional CMP processes have several shortcomings, requiring urgent improvement.

[0003] Although traditional polishing abrasives have high hardness and stability, their polishing rate is low and they are prone to scratches and ripples. In addition, the base materials of most polishing abrasives are chemically stable and oxidize slowly. Even in an alkaline environment, the surface coating of the silicon wafer can only be gradually removed through surface alkali dissolution and hydration. This process is very slow and limits the rate of chemical mechanical polishing (CMP). Today, polishing abrasive modification technology has significant advantages in improving polishing efficiency and quality, but it also has some limitations. Through doping or organic coating, it can increase the number of surface active sites and reduce the friction coefficient, thereby improving polishing efficiency. However, high-end modified materials are often highly technology-dependent and complex to prepare. In addition, different materials have different adaptability to abrasives, and it is difficult to unify the grinding rate and flatness.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The first purpose of the present invention is to provide a method for preparing a polishing abrasive of a cerium cluster-coated base material. The method adopts a direct solvent method to synthesize and calcine the base material mixed with cerium clusters to coat the surface of the base material, so that the surface of the base material is firmly coated with a layer of cerium clusters through electrostatic action to obtain a polishing abrasive. The polishing efficiency of the base material can be significantly improved by configuring it into a polishing liquid for mechanical polishing, while retaining the advantage of the surface flatness of the base material. The synthesis process is simple and the cost is low.

[0006] The second object of the present invention is to provide the use of the polishing abrasive of the cerium cluster-coated base material in polishing liquid.

[0007] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted: A method for preparing a polishing abrasive of a cerium cluster-coated base material comprises the following steps: Disperse ammonium cerium nitrate evenly in pyridine, then dropwise add pivalic acid pyridine solution, stir for reaction and centrifuge to obtain the supernatant; Then, acetonitrile was added dropwise to the supernatant solution and allowed to stand and then dried to obtain cerium clusters; Then, a base material is taken and ultrasonically dispersed in ethanol to obtain a reaction solution; The cerium clusters are ultrasonically dispersed in dichloromethane to obtain a mixed solution, which is then uniformly added dropwise to the reaction solution, stirred for 5-15 hours, centrifugally dried, and calcined to obtain the product.

[0008] In the preparation method of the present invention, pyridine is used to dissolve ammonium cerium nitrate, and then pivalic acid and pyridine are prepared to form a pivalic acid pyridine solution and added dropwise thereto. At this time, when pyridine is used to dissolve ammonium cerium nitrate, no significant chemical reaction occurs between ammonium cerium nitrate and pyridine. This is because ammonium cerium nitrate is a strong oxidant, which mainly provides Ce in the reaction. 4+ ions, and Ce 4+ It has strong oxidizing properties, but the chemical properties of pyridine are relatively stable and it is not easily oxidized under mild conditions. Therefore, pyridine is used to dissolve ammonium cerium nitrate, which can achieve a good dissolution effect and stabilize its ions through solvation. After the ammonium cerium nitrate is completely dissolved, the pivalic acid pyridine solution is added thereto. At this time, the ammonium cerium nitrate reacts with pyridine and pivalic acid. This is because the addition of pivalic acid changes the chemical environment of the system, and pivalic acid, as a carboxylic acid, has a certain reducing property, which enables it to be oxidized by Ce after addition. 4+ Ion oxidation, when pivalic acid is added Ce 4+ Ions will preferentially oxidize pivalic acid, and after the chemical environment changes, pyridine can provide ligands for ammonium cerium nitrate, thereby connecting the pyridine molecule to the cerium molecular structure. Therefore, it can be known that the introduction of pivalic acid is the key to the formation of cerium clusters, because the introduction of pivalic acid provides a substrate that is easily oxidized, making Ce 4+ The oxidizing property of the ion is brought into play, and before the addition of pivalic acid, pyridine itself does not participate in the redox reaction, but after the introduction of pivalic acid, the reaction is indirectly promoted through the coordination effect, so that pivalic acid and pyridine are Ce at the same time in the whole process. 4+ A ligand is provided to generate cerium clusters, and then acetonitrile is slowly added to the obtained solution to uniformly disperse it to form two layers, and then the cerium clusters are obtained by centrifugation; then, a reaction solution and a mixed solution are obtained by ultrasonically dispersing the base material and the cerium clusters in different organic solvents, and the mixed solution is uniformly added to the reaction solution for reaction. At this time, the cerium clusters will be coated on the surface of the base material due to electrostatic action, thereby modifying the surface of the base material, thereby significantly improving the polishing performance of the base material.

[0009] Preferably, as a further specific embodiment, the substrate material comprises one or more of mesoporous solid ceria nanospheres, mesoporous hollow ceria nanospheres, mesoporous silica nanospheres, silica nanospheres, non-spherical ceria or silica powder; Preferably, the substrate material is mesoporous solid cerium dioxide nanospheres and silicon dioxide nanospheres.

[0010] In the present invention, the selection of the base material is subject to certain limitations. When the base material is selected as one or more of mesoporous solid cerium dioxide nanospheres, mesoporous hollow cerium dioxide balls, mesoporous silica nanospheres, silica nanospheres, non-spherical cerium dioxide or silica powder; preferably, when the base material is mesoporous solid cerium dioxide nanospheres and silica nanospheres, the polishing liquid formed by the polishing abrasive configuration prepared therefrom has excellent effect. This is because the above-mentioned base material has good dispersibility and uniform particle size distribution, and reduces surface scratches and defects, and can further achieve global flattening of the wafer surface, thereby improving the polishing efficiency while ensuring high repeatability and consistency of the wafer surface, and the base material is selected as nanoparticles with small size, large specific surface area and high surface energy, so that it can be more easily dispersed in the solvent, thereby improving the product yield.

[0011] Preferably, as a further specific embodiment, the mass ratio of the base material to the ethanol is (10:1000)-(13.3:1000); Preferably, the mass ratio of the base material to the ethanol is (11.4:1000)-(12.4:1000).

[0012] In the present invention, the ratio between the base material and ethanol when ultrasonically dispersing the base material in ethanol has an important influence on the dispersion effect and the stability of the dispersion system. This is because the base material usually contains some groups, which form chemical bonds with ethanol molecules to enhance the interaction between the base material and ethanol, thereby promoting the dispersion of the base material. In addition, when in an ethanol solution, the surface of the base material itself may have a certain charge, and the repulsive effect between the charges can prevent the agglomeration of particles and thus promote the uniform dispersion of the base material. Based on this, it can be seen that the mass ratio between the base material and ethanol has an important influence on the dispersion effect of the base material. For the present invention, when the mass ratio of the base material to the ethanol is (6:1000)-(12:1000), preferably, the mass ratio of the base material to the ethanol is (11.4:1000)-( 12.4:1000), the effect it can achieve is excellent. If the mass ratio is relatively low, that is, a small amount of base particles and a large amount of ethanol, the particle concentration in ethanol is low, the interaction between particles is weak, and ultrasonic dispersion is easier to achieve. However, since the particle concentration is too low, the dispersibility of the cerium cluster ions will be affected to a certain extent. The particle concentration is too low, resulting in a large proportion of cerium cluster particles in the solution and a small proportion of base material particles. As a result, the coating material will agglomerate during the subsequent coating process of the cerium cluster-coated base material particles, thereby affecting the uniformity of the coating; and if the mass ratio is too high, that is, a large amount of particles and a small amount of ethanol, the particle concentration in the ethanol solution is high, and the interaction between particles is enhanced. Therefore, the base material cannot be evenly dispersed in the ethanol, and is prone to agglomeration, resulting in a more viscous dispersion system with poor stability, and ultrasonic dispersion requires higher energy and time to achieve uniform dispersion.

[0013] Preferably, as a further specific embodiment, the mass ratio of the cerium clusters to dichloromethane is (0.4:1000)-(2.4:1000); Preferably, the mass ratio of the cerium clusters to dichloromethane is (1.8:100)-(2.4-1000).

[0014] In the present invention, the mass ratio between the cerium clusters and dichloromethane is limited to a certain extent. This is because when the cerium clusters are ultrasonically dispersed in dichloromethane, the surface of the cerium clusters is modified by ligands, and the hydrophobic part of the ligand is compatible with dichloromethane, thereby achieving stable dispersion of the cerium clusters. The dichloromethane molecules interact with the organic ligands on the surface of the cerium clusters through van der Waals forces to form a solvation layer, which further helps the cerium clusters to be dispersed in the solution. Therefore, a certain mass ratio is required between the two to control the dispersion of the cerium clusters in dichloromethane. When the mass ratio of the cerium clusters to dichloromethane is (0.4:1000)-(2.4:1000), preferably, when the mass ratio of the cerium clusters to dichloromethane is (1.8:100)-(2.4-1000), the effect that can be achieved is excellent. This is because when the mass ratio between the two is in an appropriate range, the cerium clusters can be uniformly and stably dispersed in In dichloromethane, no aggregation occurs, so as to avoid affecting the subsequent coating effect. If the mass ratio between the two is too low, that is, a small amount of cerium clusters and a large amount of dichloromethane, the concentration of cerium clusters in the solution is low, the dispersion is more even and not easy to aggregate, but due to the low concentration of cerium clusters in the solution, the coating layer on the surface of the substrate material is thinner during the subsequent coating process, and a single layer or sub-monolayer coating may be formed on the surface of the substrate material, thereby affecting the polishing performance; and if the mass ratio is too high, that is, a large amount of cerium clusters and a small amount of dichloromethane, the concentration of cerium clusters in the solution is high, and the cerium clusters in the solution are easy to agglomerate, resulting in uneven dispersion and poor dispersion state, resulting in uneven coating in the subsequent coating process. Excessive coating on the surface of the substrate material affects the surface properties of the substrate material, and the cerium cluster aggregates coating the surface of the substrate material may cover the active sites of the substrate material, thereby reducing its functionality and affecting the polishing effect.

[0015] Preferably, as a further specific embodiment, when the substrate material is silicon dioxide, the mass ratio of the silicon dioxide to the cerium clusters is (2:1)-(10:1); Preferably, the mass ratio of the silicon dioxide to the cerium clusters is 2:1-10:3.

[0016] Preferably, as a further specific embodiment, when the substrate material is ceria, the mass ratio of ceria to the cerium clusters is (5:1)-(10:1); Preferably, the mass ratio of the cerium dioxide to the cerium clusters is 5:1-7:1.

[0017] In the present invention, when silicon dioxide is used as the base material, the mass ratio of the silicon dioxide to the cerium cluster is limited. This is because when the silicon dioxide is coated with the cerium cluster, the mass ratio between the two is the key to the coating effect. When the mass ratio of silicon dioxide to the cerium cluster is (2:1)-(10:1), preferably, when the mass ratio of silicon dioxide to the cerium cluster is 2:1-10:3, the effect that can be achieved is excellent. This is because if the mass ratio is too low, that is, a small amount of cerium clusters and a large amount of silicon dioxide, at this time due to the cerium clusters If the amount of cerium used is small, it can only form a monolayer or sub-monolayer coating on the surface of the silicon dioxide. The coating is thin, which affects the polishing performance. If the mass ratio is too high, that is, a large number of cerium clusters and a small amount of silicon dioxide, the excessive amount of cerium clusters will cause a thick layer of coating to form on the surface of the silicon dioxide, or even cluster accumulation. The accumulation of cerium clusters can easily lead to uneven coating, with some areas being over-coated and others under-coated. The thick coating may mask the surface properties of the silicon dioxide, thereby reducing its specific surface area and active sites and affecting its polishing effect. When ceria is used as the base material, due to the different relative molecular masses between silicon dioxide and ceria, the mass ratios of the two to the cerium clusters are different.

[0018] Preferably, as a further specific embodiment, the pivalic acid pyridine solution is prepared by mixing pivalic acid and pyridine in a mass ratio of (20:1000) to (25:1000); Preferably, the pivalic acid pyridine solution is prepared by mixing pivalic acid and pyridine in a mass ratio of (22.5:1000) to (23.5:1000).

[0019] Preferably, as a further specific embodiment, the mass ratio of the ceric ammonium nitrate to the pyridine is (55:100)-(60:100); Preferably, the mass ratio of the ceric ammonium nitrate to the pyridine is (55:100)-(57:100).

[0020] In the present invention, pivalic acid and pyridine are prepared in a certain mass ratio to obtain a pivalic acid-pyridine solution, which is then dripped into a pyridine solution containing ammonium cerium nitrate. At this time, since ammonium cerium nitrate does not react with pyridine itself, the addition of pivalic acid changes the chemical environment of the solution after the addition of the pivalic acid-pyridine solution, causing the ammonium cerium nitrate to react with both pyridine and pivalic acid. Therefore, it can be seen that the ratio between the two in the pivalic acid-pyridine solution has an important influence on the reaction process and product properties. When the mass ratio of pivalic acid to pyridine is (20:1000)-(25:1000), preferably, the pivalic acid-pyridine solution is prepared by pivalic acid and pyridine in a mass ratio of (22.5:1000)-(23.5:1000) to form the pivalic acid-pyridine solution, the effect achieved is excellent. This is because during the reaction of ammonium cerium nitrate with the pivalic acid-pyridine solution, pivalic acid, as one of the reactants, can provide a ligand C(CH3)3COO- to react with the cerium ion (Ce) in the ammonium cerium nitrate. 4+ ) to coordinate, and pyridine as a nitrogen-containing heterocyclic compound can also act as a ligand to coordinate with cerium ions to form cerium clusters, and pyridine can also be used as an acidic by-product generated in the alkali neutralization reaction. Therefore, if the mass ratio is too low, that is, a small amount of pivalic acid and a large amount of pyridine, at this time, due to the strong alkalinity in the reaction system caused by excessive pyridine, the small amount of pivalic acid will limit its reaction with cerium ions, resulting in incomplete reaction, thereby affecting the formation of cerium clusters, and a small amount of pivalic acid may cause pyridine to preferentially ligand with cerium ions, thereby affecting the interaction between pivalic acid and cerium ions. If the mass ratio is too high, that is, a large amount of pivalic acid and a small amount of pyridine, there is excess pivalic acid in the solution, the acidity in the reaction system is strong, and the small amount of pyridine may not be able to completely neutralize the acidic by-products generated in the reaction, thereby causing an unstable reaction environment, and excessive pivalic acid will lead to the generation of side reactions and product agglomeration, affecting the formation of cerium clusters.

[0021] Preferably, as a further specific embodiment, the calcination time is 2-4 hours.

[0022] The present invention also provides a method for preparing a polishing abrasive of a cerium cluster-coated base material, and application of the polishing abrasive prepared by the method in a polishing liquid.

[0023] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention provides a method for preparing a polishing abrasive of a base material coated with cerium clusters. The method comprises the following steps: mixing the base material with cerium clusters and synthesizing and calcining the base material by direct solvent method, thereby coating the surface of the base material. The surface of the base material is firmly coated with a layer of cerium clusters through electrostatic action, thereby obtaining a polishing abrasive. The polishing efficiency of the base material can be significantly improved by configuring the base material into a polishing liquid for mechanical polishing, while retaining the surface flatness of the base material. The synthesis process is simple and the cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be construed as limiting the present invention. The same reference numerals are used throughout the accompanying drawings to denote the same components.

[0025] Figure 1 This is an AFM test image of the silicon wafer polished with the cerium cluster-coated silica polishing solution in Experimental Example 1; Figure 2 This is an electron microscope image of the cerium cluster-coated silica polishing abrasive prepared in Experimental Example 2 when the mass ratio of silica to cerium clusters is 1:1; Figure 3 This is an electron microscope image of the cerium cluster-coated silica polishing abrasive prepared in Experimental Example 2 when the mass ratio of silica to cerium clusters is 1:2; Figure 4 This is an electron microscope image of the cerium cluster-coated silica polishing abrasive prepared in Experimental Example 2 when the mass ratio of silica to cerium clusters is 10:1; Figure 5 This is an electron microscope image of the cerium cluster-coated silica polishing abrasive prepared in Experimental Example 2 when the mass ratio of silica to cerium clusters is 10:3; Figure 6 This is an electron microscope image of the cerium cluster-coated silica polishing abrasive prepared in Experimental Example 2 when the mass ratio of silica to cerium clusters is 5:1; Figure 7 This is an electron microscope image of the cerium cluster-coated silica polishing abrasive prepared in Experimental Example 2 when the mass ratio of silica to cerium clusters is 5:2; Figure 8 This is an electron microscope image of the cerium cluster-coated silica polishing abrasive prepared in Experimental Example 2 when the mass ratio of silica to cerium clusters is 2:1; Figure 9 This is an electron microscope image of the cerium cluster-coated silica polishing abrasive prepared in Experimental Example 2 when the mass ratio of silica to cerium clusters is 50:1; Figure 10 This is an AFM image of the cerium cluster-coated silica polishing solution prepared when the amount of cerium clusters used in Experimental Example 3 is 250 mg, after polishing a silicon wafer; Figure 11 This is an AFM image obtained after polishing a silicon wafer using the cerium cluster-coated silica polishing solution prepared when the amount of cerium clusters used in Experimental Example 3 is 500 mg; Figure 12This is an electron microscope image of the cerium cluster-coated cerium dioxide polishing abrasive prepared in Experimental Example 5 when the mass ratio of cerium dioxide to cerium clusters is 10:1; Figure 13 This is an electron microscope image of the cerium cluster-coated cerium dioxide polishing abrasive prepared when the mass ratio of cerium dioxide to cerium clusters is 5:1 in Experimental Example 5; Figure 14 This is an electron microscope image of the cerium cluster-coated cerium dioxide polishing abrasive prepared in Experimental Example 5 when the mass ratio of cerium dioxide to cerium clusters is 10:3; Figure 15 This is an electron microscope image of the cerium cluster-coated cerium dioxide polishing abrasive prepared when the mass ratio of cerium dioxide to cerium clusters is 5:2 in Experimental Example 5; Figure 16 This is an electron microscope image of the cerium cluster-coated cerium dioxide polishing abrasive prepared in Experimental Example 5 when the mass ratio of cerium dioxide to cerium clusters is 2:1; Figure 17 This is an operation diagram of the cerium cluster-coated cerium dioxide polishing abrasive prepared in Experimental Example 5 with a mass ratio of cerium dioxide to cerium clusters of 5:2 when configured into a polishing liquid; Figure 18 The Ce, Si, O, and C scanning electron microscope (EDS) images of the cerium cluster-coated silica polishing abrasive prepared when the mass ratio of cerium dioxide to cerium clusters was 2:1 in Experimental Example 5 are shown; Figure 19 This is a scanning electron microscope (EDS) image of Ce, O, and C of the cerium cluster-coated cerium dioxide polishing abrasive prepared when the mass ratio of cerium dioxide to cerium clusters is 5:2 in Experimental Example 5. DETAILED DESCRIPTION

[0026] The technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. However, those skilled in the art will understand that the embodiments described below are part of the embodiments of the present invention, not all of them, and are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0027] In order to more clearly illustrate the technical solutions of the present invention, specific embodiments are provided below for illustration.

[0028] Example 1 The preparation process of cerium cluster-coated silica nanosphere polishing abrasive is as follows: 550 mg of cerium ammonium nitrate was evenly dispersed in 1 ml of pyridine, and then a pivalic acid pyridine solution was evenly added dropwise, wherein the pivalic acid pyridine solution was prepared according to a mass ratio of pivalic acid: pyridine = 20:1000. After continuous stirring for 0.5 h, the reaction solution was transferred to a centrifuge tube and centrifuged at 10,000 rpm for 2 min to obtain a supernatant. The supernatant was transferred to a 25 ml colorimetric tube, acetonitrile was slowly added dropwise to separate the layers, and the mixture was allowed to diffuse for a week before the crystals were separated and vacuum dried to obtain a cerium cluster (Ce16) sample, which was then weighed. Then, the amount of silica nanospheres was weighed according to the weight of the obtained cerium cluster sample and the mass ratio of silica to cerium cluster was 2:1; Then, the silica nanospheres were ultrasonically dispersed in ethanol at a mass ratio of 10:1000 to obtain a reaction solution; Subsequently, the cerium clusters were ultrasonically dispersed in dichloromethane at a mass ratio of 0.4:1000 to obtain a mixed solution, and the mixture was then evenly added dropwise to the reaction solution, magnetically stirred with a film in a 500ml beaker for 5 hours, and then centrifuged. After washing, centrifugal separation was performed and dried in an oven at 50°C for 12 hours to obtain a preliminary sample of cerium cluster-coated silica nanospheres. The sample was then calcined at 550°C in a muffle furnace for 2 hours to obtain a cerium cluster-coated silica nanosphere polishing abrasive.

[0029] Example 2 600 mg of cerium ammonium nitrate was evenly dispersed in 1 ml of pyridine, and then a pivalic acid pyridine solution was evenly added dropwise, wherein the pivalic acid pyridine solution was prepared according to a mass ratio of pivalic acid: pyridine = 25:1000. After continuous stirring for 0.5 h, the reaction solution was transferred to a centrifuge tube and centrifuged at 10,000 rpm for 2 min to obtain a supernatant. The supernatant was transferred to a 25 ml colorimetric tube, acetonitrile was slowly added dropwise to separate the layers, and the mixture was allowed to diffuse for a week before the crystals were separated and vacuum dried to obtain a cerium cluster (Ce16) sample, which was then weighed. Then, the amount of silica nanospheres was weighed according to the weight of the obtained cerium cluster sample, with a mass ratio of silica to cerium cluster of 10:1; Then, the silica nanospheres were ultrasonically dispersed in ethanol at a mass ratio of 13.3:1000 to obtain a reaction solution; Subsequently, the cerium clusters were ultrasonically dispersed in dichloromethane according to the mass ratio of cerium clusters to dichloromethane of 2.4:1000 to obtain a mixed solution, and then the mixture was evenly added dropwise to the reaction solution, magnetically stirred with a film in a 500ml beaker for 15 hours, and then centrifuged. After washing, centrifugal separation was carried out, and the sample was dried in an oven at 50°C for 12 hours to obtain a preliminary sample of cerium cluster-coated silica nanospheres. The sample was then calcined at 550°C in a muffle furnace for 4 hours to obtain a cerium cluster-coated silica nanosphere polishing abrasive.

[0030] Example 3 The preparation process of cerium cluster-coated cerium dioxide nanosphere polishing abrasive is as follows: 550 mg of cerium ammonium nitrate was evenly dispersed in 1 ml of pyridine, and then a pivalic acid pyridine solution was evenly added dropwise, wherein the pivalic acid pyridine solution was prepared according to a mass ratio of pivalic acid: pyridine = 22:1000. After continuous stirring for 0.5 h, the reaction solution was transferred to a centrifuge tube and centrifuged at 10,000 rpm for 2 min to obtain a supernatant. The supernatant was transferred to a 25 ml colorimetric tube, acetonitrile was slowly added dropwise to separate the layers, and the mixture was allowed to diffuse for a week before the crystals were separated and vacuum dried to obtain a cerium cluster (Ce16) sample, which was then weighed. Then, the amount of cerium dioxide nanospheres was weighed according to the weight of the obtained cerium cluster sample at a mass ratio of cerium dioxide to cerium clusters of 5:1; Then, the cerium dioxide nanospheres were ultrasonically dispersed in ethanol at a mass ratio of 12:1000 to obtain a reaction solution; Subsequently, the cerium clusters were ultrasonically dispersed in dichloromethane at a mass ratio of 1:1000 to obtain a mixed solution, and the mixture was then evenly added dropwise to the reaction solution, magnetically stirred with a film in a 500ml beaker for 15 hours, and then centrifuged. After washing, centrifugal separation was performed and the mixture was dried in an oven at 50°C for 12 hours to obtain a preliminary sample of cerium cluster-coated cerium dioxide nanospheres. The sample was then calcined at 550°C in a muffle furnace for 4 hours to obtain a cerium cluster-coated cerium dioxide nanosphere polishing abrasive.

[0031] Example 4 The preparation process of cerium cluster-coated cerium dioxide nanosphere polishing abrasive is as follows: 550 mg of cerium ammonium nitrate was evenly dispersed in 1 ml of pyridine, and then a pivalic acid pyridine solution was evenly added dropwise, wherein the pivalic acid pyridine solution was prepared according to a mass ratio of pivalic acid: pyridine = 22:1000. After continuous stirring for 0.5 h, the reaction solution was transferred to a centrifuge tube and centrifuged at 10,000 rpm for 2 min to obtain a supernatant. The supernatant was transferred to a 25 ml colorimetric tube, acetonitrile was slowly added dropwise to separate the layers, and the mixture was allowed to diffuse for a week before the crystals were separated and vacuum dried to obtain a cerium cluster (Ce16) sample, which was then weighed. Then, the amount of cerium dioxide nanospheres was weighed according to the weight of the obtained cerium cluster sample at a mass ratio of cerium dioxide to cerium clusters of 10:1; Then, the cerium dioxide nanospheres were ultrasonically dispersed in ethanol at a mass ratio of 12:1000 to obtain a reaction solution; Subsequently, the cerium clusters were ultrasonically dispersed in dichloromethane at a mass ratio of 1:1000 to obtain a mixed solution, and the mixture was then evenly added dropwise to the reaction solution, magnetically stirred with a film in a 500ml beaker for 15 hours, and then centrifuged. After washing, centrifugal separation was performed and the mixture was dried in an oven at 50°C for 12 hours to obtain a preliminary sample of cerium cluster-coated cerium dioxide nanospheres. The sample was then calcined at 550°C in a muffle furnace for 4 hours to obtain a cerium cluster-coated cerium dioxide nanosphere polishing abrasive.

[0032] Experimental Example 1 0.6 g of the cerium cluster-coated silica polishing abrasive powder obtained in Example 1 was uniformly dispersed in 400 ml of deionized water. After 30 minutes of ultrasonication, it was prepared into a 0.15 wt% polishing solution. A 1 mm thick silica wafer was polished and the removal rate was 25.784 nm / min. At the same time, the polished silica wafer was tested by AFM to measure its surface roughness. The results are as follows: Figure 1 shown.

[0033] Experimental Example 2: Exploring the mass ratio of silica to cerium clusters The specific implementation steps are consistent with those in Example 1, except that the ratio of silica nanospheres to cerium clusters is changed when preparing the preliminary sample of cerium cluster-coated silica in Example 1. The mass ratio of SiO2 to ethanol is 2:1-10:1 for silica:cerium clusters. The specific data are shown in the following table. The electron microscopy results are shown in Figure 2-9 shown.

[0034] Table 1

[0035] Therefore, the data in the table and the instructions are Figure 2-9 It can be seen that when the mass ratio of the base material silica to the cerium clusters is between 2:1 and 10:1, the cerium clusters coated silica preliminary sample prepared by the electron microscope can be seen that the cerium clusters successfully form a coating layer of appropriate thickness and uniformity on the surface of the silica. However, when the mass ratio of the cerium clusters to the silica is not within the range provided by the present invention, the cerium clusters coated silica preliminary sample prepared by the electron microscope does not perform well, as shown in FIG. Figure 2As shown in Figure 2, when the mass ratio is 1:1, the cerium clusters form a thicker coating layer on the surface of the silicon dioxide, and there are some protrusions of different shapes on the surface of the silicon dioxide. Therefore, it can be seen that when the mass ratio of the two is 1:1, the cerium cluster coating layer is unevenly distributed on the surface of the silicon dioxide; Figure 3 As shown in , when the mass ratio of the two is 1:2, the coating effect is extremely poor, the cerium clusters are not successfully coated on the surface of silica and agglomerate; Figure 9 As shown in the figure, when the mass ratio of the two is 50:1, the coating layer formed by the cerium clusters on the surface of the silicon dioxide is extremely thin and multiple silicon spheres are easily connected around one cerium cluster. Therefore, for the present invention, when the base material is silica, the mass ratio of the silica to the cerium clusters is subject to certain limitations. This is because when cerium clusters are used to coat silica, the mass ratio between the two is the key to affecting the coating effect. When the mass ratio of silica to the cerium clusters is (2:1)-(10:1), the effect that can be achieved is excellent. This is because if the mass ratio is too low, that is, a small amount of cerium clusters and a large amount of silica, at this time, due to the small amount of cerium clusters, they can only form a monolayer or sub-monolayer coating on the surface of silica, so that the coating layer is thin and affects the polishing performance; and if the mass ratio is too high, that is, a large amount of cerium clusters and a small amount of silica, at this time, due to the excessive amount of cerium clusters, a thick layer of coating is formed on the surface of silica or even cluster accumulation occurs. The accumulation of cerium clusters easily leads to uneven coating, some areas may be over-coated and other areas may be under-coated, and the thick coating layer may mask the surface properties of silica, thereby reducing its specific surface area and active sites and affecting its polishing effect.

[0036] Experimental Example 3 Effect of Cerium Cluster Concentration in Mixed Solution on the Thickness of Coating Layer The specific implementation steps are consistent with those in Example 1, except that the amount of cerium clusters in the mixed solution is changed to 250 mg and 500 mg, and then a cerium cluster-coated cerium dioxide polishing abrasive is prepared. The polishing abrasive is made into a polishing solution and a silica nanosphere polishing solution not coated with cerium clusters is prepared. The removal efficiency is shown in Table 2, where the AFM images of the polishing solutions prepared with different amounts of cerium cluster-coated silica after polishing the silicon wafer are shown in Table 2. Figure 10-11 shown.

[0037] Table 2

[0038] Among them Figure 10-11It can be seen that by adjusting the amount of cerium clusters in the mixed liquid, the cerium cluster coating on the surface of the silica can be controlled, and as the thickness of the coating formed by the cerium clusters on the surface of the silica increases, the removal rate of the polishing liquid prepared thereby increases significantly during polishing, and no obvious change is found in its surface roughness and flatness. However, as the thickness of the coating gradually increases and reaches a peak, the polishing performance of the polishing liquid prepared thereby decreases.

[0039] Experimental Example 4 Effect of Calcination Time on the Performance of Polishing Abrasives The specific implementation steps were consistent with those in Example 1, except that the calcination time of the preliminary sample of cerium cluster-coated silica in the muffle furnace was adjusted to 0 h, 2 h, and 4 h, respectively. The resulting polishing abrasives were then prepared into polishing slurries for testing, and the resulting removal rates are shown in Table 3. It was found that the polishing performance of the abrasive increased with increasing calcination time.

[0040] Table 3

[0041] Experimental Example 5: Exploring the Mass Ratio of Cerium Dioxide to Cerium Clusters The specific implementation steps are consistent with those in Example 3, except that the mass ratio between cerium dioxide and cerium clusters is changed to explore the performance of the coated polishing abrasive in the process of changing the mass ratio from 2:1 to 10:1. The data are shown in Table 4 below, and the corresponding electron microscope images of the polishing abrasive prepared are shown in Table 4 below. Figure 12-16 shown.

[0042] Table 4

[0043] It can be seen from the electron microscope that when the mass ratio of ceria to cerium clusters is appropriate, the cerium cluster-coated ceria polishing abrasive prepared therefrom performs excellently under the electron microscope. However, when the mass ratio is 10:3, 5:2 and 2:1, the cerium cluster-coated ceria polishing abrasive prepared therefrom shows that its coating layer is too thick or aggregated under the electron microscope, as shown in FIG. Figure 17 As shown, when the polishing liquid is subsequently prepared, the cerium cluster-coated cerium dioxide polishing abrasive cannot be dissolved regardless of the stirring speed and the ultrasonic rate, and floats on the water.

[0044] In summary, the preparation method of the present invention is mainly to dissolve ammonium cerium nitrate by using pyridine, and then configure pivalic acid and pyridine to form a pivalic acid pyridine solution and add it dropwise thereto. At this time, when pyridine was previously used to dissolve ammonium cerium nitrate, no significant chemical reaction occurred between ammonium cerium nitrate and pyridine. This is because ammonium cerium nitrate is a strong oxidant, which mainly provides Ce4+ ions in the reaction, and Ce4+ has strong oxidizing properties, but the chemical properties of pyridine are relatively stable and are not easily oxidized under mild conditions. Therefore, pyridine is used to dissolve ammonium cerium nitrate, which can achieve a good dissolution effect while stabilizing its ions through solvation. Subsequently, after the ammonium cerium nitrate is completely dissolved, when the pivalic acid pyridine solution is added thereto, a reaction occurs between ammonium cerium nitrate, pyridine and pivalic acid. This is because the addition of pivalic acid changes the chemical environment of the system, and pivalic acid, as a carboxylic acid, has a certain reducing property, so that it can be oxidized by Ce4+ ions after addition. When pivalic acid is added, Ce4+ ions will preferentially oxidize pivalic acid. Acid, and after the chemical environment changes, pyridine can provide ligands for ammonium cerium nitrate, thereby connecting the entire pyridine molecule to the cerium molecular structure. Therefore, it can be known that the introduction of pivalic acid is key in the process of generating cerium clusters, because the introduction of pivalic acid provides an easily oxidized substrate, so that the oxidizing property of Ce4+ ions can be exerted, and before the addition of pivalic acid, pyridine itself does not participate in the redox reaction, but after the introduction of pivalic acid, it indirectly promotes the reaction through the coordination effect, so that pivalic acid and pyridine simultaneously provide ligands for Ce4+ in the whole process, thereby generating cerium clusters, and then acetonitrile is slowly added to the obtained solution so that it can be evenly dispersed to form two layers, and then centrifuged to obtain cerium clusters; then the base material and the cerium clusters are respectively dispersed in different organic solvents by ultrasonic means to obtain a reaction solution and a mixed solution, and then the mixed solution is evenly added to the reaction solution for reaction. At this time, the cerium clusters will be coated on the surface of the base material due to electrostatic action, thereby modifying the surface of the base material, thereby significantly improving the polishing performance of the base material.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a polishing abrasive of a cerium cluster-coated base material, characterized in that: The following steps are involved: Disperse ammonium cerium nitrate evenly in pyridine, then dropwise add pivalic acid pyridine solution, stir for reaction and centrifuge to obtain the supernatant; Then, acetonitrile was added dropwise to the supernatant solution and allowed to stand and then dried to obtain cerium clusters; Then, a base material is taken and ultrasonically dispersed in ethanol to obtain a reaction solution; The cerium clusters are ultrasonically dispersed in dichloromethane to obtain a mixed solution, which is then uniformly added dropwise to the reaction solution, stirred for 5-15 hours, centrifugally dried, and calcined to obtain the product.

2. The method for preparing the polishing abrasive of the cerium cluster-coated base material according to claim 1, characterized in that: The substrate material comprises one or more of mesoporous solid ceria nanospheres, mesoporous hollow ceria nanospheres, mesoporous silica nanospheres, silica nanospheres, non-spherical ceria or silica powder; Preferably, the substrate material is mesoporous solid cerium dioxide nanospheres and silicon dioxide nanospheres.

3. The method for preparing the polishing abrasive of the cerium cluster-coated base material according to claim 1, characterized in that: The mass ratio of the base material to the ethanol is (10:1000)-(13.3:1000); Preferably, the mass ratio of the base material to the ethanol is (11.4:1000)-(12.4:1000).

4. The method for preparing the polishing abrasive of the cerium cluster-coated base material according to claim 1, characterized in that: The mass ratio of the cerium cluster to dichloromethane is (0.4:1000)-(2.4:1000); Preferably, the mass ratio of the cerium clusters to dichloromethane is (1.8:100)-(2.4-1000).

5. The method for preparing the polishing abrasive of the cerium cluster-coated base material according to claim 2, characterized in that: When the substrate material is silicon dioxide, the mass ratio of silicon dioxide to the cerium clusters is (2:1)-(10:1); Preferably, the mass ratio of the silicon dioxide to the cerium clusters is 2:1-10:

3.

6. The method for preparing the polishing abrasive of the cerium cluster-coated base material according to claim 2, characterized in that: When the substrate material is ceria, the mass ratio of ceria to the cerium clusters is (5:1)-(10:1); Preferably, the mass ratio of the cerium dioxide to the cerium clusters is 5:1-7:

1.

7. The method for preparing a polishing abrasive of a cerium cluster-coated substrate material according to claim 1, characterized in that: The pivalic acid pyridine solution is prepared by mixing pivalic acid and pyridine in a mass ratio of (20:1000) to (25:1000); Preferably, the pivalic acid pyridine solution is prepared by mixing pivalic acid and pyridine in a mass ratio of (22.5:1000) to (23.5:1000).

8. The method for preparing a polishing abrasive of a cerium cluster-coated substrate material according to claim 1, characterized in that: The mass ratio of the cerium ammonium nitrate to the pyridine is (55:100)-(60:100); Preferably, the mass ratio of the ceric ammonium nitrate to the pyridine is (55:100)-(57:100).

9. The method for preparing a polishing abrasive of a cerium cluster-coated substrate material according to claim 1, characterized in that: The calcination time is 2-4 hours.

10. Use of the polishing abrasive prepared by the method for preparing a polishing abrasive of a cerium cluster-coated substrate material according to any one of claims 1 to 9 in a polishing liquid.

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