A cerium oxide composite abrasive particle with a core-shell structure, a preparation method and application thereof

Abstract

The application belongs to the field of polishing materials and relates to a cerium oxide composite abrasive particle with a core-shell structure, a preparation method and application thereof.The cerium oxide composite abrasive particle with the core-shell structure comprises an inner core composed of solid cerium oxide nanospheres and a coated shell layer composed of mesoporous cerium oxide nanomaterials.The inner core structure of the cerium oxide composite abrasive particle is compact, and the coated shell layer has abundant pore structures and a large specific surface area.The surface layer of the cerium oxide composite abrasive particle is mesoporous cerium oxide, which can reduce the roughness of the wafer surface.The internal support provided by the inner core can reduce the collapse of the mesoporous cerium oxide nanomaterials, so that the cerium oxide composite abrasive particle has good wear resistance.Compared with single cerium oxide particles, the chemical reaction activity and material removal rate of the cerium oxide composite abrasive particle of the application are significantly improved, which can significantly improve the material removal rate, polishing efficiency and surface quality in the polishing process of the super-precision surface, so as to meet the demand of the modern chip industry for high-precision manufacturing processes.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of polishing materials, and particularly relates to a cerium oxide composite abrasive particle with a core-shell structure, a preparation method and application thereof. BACKGROUND

[0002] Since the invention of integrated circuits (IC), the semiconductor industry has experienced several technological revolutions, constantly driving electronic products towards miniaturization, high performance and low power consumption. In the process of chip manufacturing, the requirement for planarization technology is also increasing, and the quality of planarization technology directly affects the performance and yield of chips.

[0003] Chemical mechanical polishing (CMP) is a planarization technology widely used in integrated circuit manufacturing. It combines chemical corrosion and mechanical grinding to use abrasive particles and chemical reagents in the abrasive suspension to jointly act on the material surface for planarization treatment.

[0004] Abrasive particles (abrasive particles) are the core component of the chemical mechanical polishing process, and their performance directly affects the polishing effect and surface quality. According to their materials and characteristics, polishing abrasives can be divided into various types, including alumina abrasives, silica abrasives and ceria abrasives. Among them, ceria abrasives are widely favored due to their high chemical reactivity and excellent mechanical properties. At present, there are many studies on ceria abrasives with different morphologies, such as solid ceria nanospheres, mesoporous ceria nanospheres and ceria nanoclusters. Among them, solid ceria nanospheres have a dense internal structure, good wear resistance and stability, but their low specific surface area limits their chemical reactivity, resulting in a low material removal rate during chemical mechanical polishing, and polishing the wafer with solid ceria nanospheres will result in a high roughness of the wafer surface. Mesoporous ceria particles have abundant pore structures and large specific surface areas, providing more chemical reaction sites, significantly improving chemical reactivity and material removal rate, but the porous structure makes it lack of hardness, resulting in poor wear resistance and easy structure collapse, which may cause rapid wear during long-term or high-intensity polishing.

[0005] Therefore, it is necessary to provide an abrasive with high wear resistance, good polishing effect and high material removal rate to make up for the defects of single abrasives and provide more efficient and stable polishing solutions. SUMMARY

[0006] (I) Technical problems to be solved

[0007] In order to solve the problems of poor wear resistance, high roughness of wafer surface and low material removal rate caused by single ceria abrasive in the prior art, the application provides a ceria composite abrasive with a core-shell structure, a preparation method and application thereof.

[0008] (II) Technical solutions

[0009] In order to achieve the above-mentioned purpose, the main technical solutions adopted by the application include:

[0010] In a first aspect, the application provides a ceria composite abrasive with a core-shell structure, comprising an inner core composed of solid ceria nanospheres and a coating shell layer composed of mesoporous ceria nanomaterials.

[0011] The ceria composite abrasive with a core-shell structure as described above is preferably prepared by surface modification treatment of the solid ceria nanospheres with polyethyleneimine.

[0012] The ceria composite abrasive with a core-shell structure as described above is preferably prepared by surface modification treatment of the solid ceria nanospheres with polyethyleneimine.

[0013] The ceria composite abrasive with a core-shell structure as described above is preferably prepared by surface modification treatment of the solid ceria nanospheres with polyethyleneimine.

[0014] In a second aspect, the application provides a preparation method of the ceria composite abrasive with a core-shell structure as described above, comprising the following steps:

[0015] S1: preparing solid ceria nanospheres by a hydrothermal method;

[0016] S2: performing surface modification treatment on the solid ceria nanospheres with polyethyleneimine;

[0017] S3: coating mesoporous ceria nanomaterials on the surface of the solid ceria nanospheres subjected to surface modification treatment by an in-situ chemical precipitation method to obtain the ceria composite abrasive.

[0018] The preparation method of the ceria composite abrasive with a core-shell structure as described above is preferably prepared by surface modification treatment of the solid ceria nanospheres with polyethyleneimine.

[0019] S11: performing hydrothermal reaction on a cerium source, a structure directing agent and a precipitating agent to obtain a ceria precursor;

[0020] S12: calcining the ceria precursor to obtain the solid ceria nanospheres;

[0021] In step S11, the cerium source is cerium nitrate hexahydrate, the structure-directing agent is polyethylene glycol, and the precipitant is urea; the molar ratio of urea to cerium nitrate hexahydrate is 25-150, the molecular weight of polyethylene glycol is 4000-20000 Da; the hydrothermal reaction temperature is 90-110℃, and the hydrothermal reaction time is 2.5-3.5h;

[0022] In step S12, the calcination is performed in an air atmosphere, the calcination temperature is 500-600℃, and the calcination time is 2-4h.

[0023] Preferably, step S2 of the preparation method of the ceria composite abrasive particle with a core-shell structure as described above comprises the following steps:

[0024] The solid ceria nanospheres are dispersed in water, and after the addition of polyethyleneimine, ultrasonic reaction is performed for 20-30min, and then post-treatment is performed to obtain the solid ceria nanospheres subjected to surface modification treatment;

[0025] The molecular weight of the polyethyleneimine is 10000-15000 Da.

[0026] Preferably, step S3 of the preparation method of the ceria composite abrasive particle with a core-shell structure as described above comprises the following steps:

[0027] S31: The solid ceria nanospheres subjected to surface modification treatment, citric acid, cetyltrimethylammonium bromide, sodium salicylate, hexamethylenetetramine, cerium chloride hexahydrate, and cyclohexane are added to deionized water, stirring is performed, and then the mixed system is allowed to react under the condition of heating and stirring to obtain the solid ceria nanospheres coated with mesoporous cerium hydroxide nanomaterials;

[0028] S32: The solid ceria nanospheres coated with mesoporous cerium hydroxide nanomaterials are calcined to obtain the ceria composite abrasive particle.

[0029] Preferably, step S3 of the preparation method of the ceria composite abrasive particle with a core-shell structure as described above comprises the following steps:

[0030] In step S31, the mass ratio of sodium salicylate to the solid ceria nanospheres is 4:1-6:1, after the addition of the components to deionized water, the concentration of citric acid is 0.05-0.15g / L, the concentration of cetyltrimethylammonium bromide is 1-3g / L, the concentration of sodium salicylate is 1-2g / L, the concentration of hexamethylenetetramine is 0.2-0.4g / L, the concentration of cerium chloride hexahydrate is 1.5-2g / L, and the volume ratio of cyclohexane to deionized water is (2-4):(9-11); the stirring time is 1-2h, the heating temperature is 60-80℃, and the reaction time is 7-8h.

[0031] In step S32, the solid ceria nanospheres coated with mesoporous ceria nanomaterials are subjected to a first-stage calcination treatment in a protective atmosphere, and then subjected to a second-stage calcination treatment in an air atmosphere;

[0032] The calcination temperature of the first-stage calcination treatment is 500-600 DEG C, and the calcination time is 4-6h;

[0033] The calcination temperature of the second-stage calcination treatment is 500-600 DEG C, and the calcination time is 2-4h.

[0034] In a third aspect, the application also provides an application of the above-mentioned ceria composite abrasive particle or the ceria composite abrasive particle prepared by the above-mentioned preparation method, wherein the ceria composite abrasive particle is used in a polishing liquid.

[0035] (III) Beneficial effects

[0036] The application provides a brand-new ceria composite abrasive particle with a core-shell structure, which comprises an inner core composed of solid ceria nanospheres and a coating shell layer composed of mesoporous ceria nanomaterials. The ceria composite abrasive particle with the core-shell structure is structurally stable, integrates the advantages of the solid ceria nanospheres and the mesoporous ceria nanomaterials, has a compact inner core structure, and has a coating shell layer with abundant pore structures and a large specific surface area.

[0037] The surface layer of the ceria composite abrasive particle is mesoporous ceria, which can reduce the roughness of a wafer surface after polishing. In the ceria composite abrasive particle, the solid ceria nanospheres of the inner core provide a firm internal support, can reduce the deformation and collapse of the mesoporous ceria nanomaterials, and enhance the overall strength and wear resistance of the coating shell layer, so that the ceria composite abrasive particle has good wear resistance and reduces wear. In addition, compared with the single solid ceria nanospheres and the mesoporous ceria nanomaterials, the ceria composite abrasive particle with the core-shell structure has significantly improved chemical reaction activity and material removal rate.

[0038] Therefore, the ceria composite abrasive particle with the core-shell structure in the application can significantly improve the material removal rate, polishing efficiency and surface quality in the polishing process of an ultra-precision surface, so as to meet the demand of the high-precision manufacturing process of the modern chip industry. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 a- Figure 1 Fig. f is a transmission electron microscope image of the solid ceria nanospheres prepared in Example 1-6;

[0040] Figure 2 a is a transmission electron microscope image of sCeO2-mCeO2 prepared in Example 7;

[0041] Figure 2 b is Figure 2 a is a partial enlarged view of;

[0042] Figure 3 The transmission electron micrograph of the product prepared for Comparative Example 1;

[0043] Figure 4 The XRD curve of sCeO2 prepared in Example 2 and sCeO2-mCeO2 prepared in Example 7;

[0044] Figure 5 The N2 adsorption-desorption isotherm graph of sCeO2-mCeO2 prepared in Example 7;

[0045] Figure 6 The pore size distribution graph of sCeO2-mCeO2 prepared in Example 7;

[0046] Figure 7a The XPS curve of sCeO2 prepared in Example 2;

[0047] Figure 7b The XPS curve of sCeO2-mCeO2 prepared in Example 7;

[0048] Figure 8a The two-dimensional AFM topography of the surface of the silicon oxide wafer after polishing by the polishing liquid prepared by using sCeO2-mCeO2 prepared in Example 7;

[0049] Figure 8b The three-dimensional AFM topography of the surface of the silicon oxide wafer after polishing by the polishing liquid prepared by using sCeO2-mCeO2 prepared in Example 7. DETAILED DESCRIPTION

[0050] In order to better explain the present application, the following detailed description will be given in combination with specific embodiments.

[0051] The present application provides a cerium oxide composite abrasive particle with a core-shell structure, which comprises an inner core composed of solid cerium oxide nanospheres and a coating shell layer composed of mesoporous cerium oxide nanomaterials.

[0052] The cerium oxide composite abrasive particle with the core-shell structure in the application integrates the advantages of the solid cerium oxide nanospheres and the mesoporous cerium oxide nanomaterials, the inner core structure is compact, the coating shell layer has abundant pore structure and high specific surface area. The strength of the cerium oxide composite abrasive particle is improved, the overall strength is between the solid cerium oxide nanospheres and the mesoporous cerium oxide nanomaterials, the surface layer is the mesoporous cerium oxide, and the polishing effect is close to the mesoporous cerium oxide nanomaterials, compared with the single cerium oxide nanosphere abrasive particle, the roughness of the wafer surface can be reduced.

[0053] In the cerium oxide composite abrasive particle of the application, the solid cerium oxide nanospheres of the inner core provide firm internal support, can effectively disperse and absorb stress, reduce the deformation and collapse of the mesoporous cerium oxide nanomaterials, and enhance the overall strength and wear resistance of the coating shell layer, so that the cerium oxide composite abrasive particle has good wear resistance and reduces the wear of the abrasive particle in the long-time or high-intensity polishing process.

[0054] In addition, compared with the single solid cerium oxide nanosphere and the single mesoporous cerium oxide nanomaterial, the content of trivalent cerium ions in the cerium oxide composite abrasive particle with the core-shell structure is increased, the chemical reaction activity and the material removal rate are significantly improved, the material removal rate is increased by about 40-50% (under the condition that the abrasive particle concentration in the polishing liquid is the same) compared with the single solid cerium oxide nanosphere, the content of trivalent cerium ions can be increased by 20-30% at most, and the material removal rate is increased by about 20-30% (under the condition that the abrasive particle concentration in the polishing liquid is the same) compared with the single mesoporous cerium oxide nanomaterial.

[0055] Therefore, the cerium oxide composite abrasive particle with the core-shell structure in the application can significantly improve the material removal rate, polishing efficiency and surface quality in the polishing process of the ultra-precision surface, so as to meet the demand of the high-precision manufacturing process of the modern chip industry.

[0056] Preferably, the inner core of the cerium oxide composite abrasive particle is prepared by surface modification treatment of the solid cerium oxide nanospheres with polyethyleneimine. The diameter of the inner core is preferably 100-200 nm, further preferably 100-160 nm, and more preferably 120 nm, 130 nm, 135 nm, 140 nm and 150 nm, etc. The thickness of the coating shell layer is preferably 10-50 nm, further preferably 10-25 nm, and more preferably 10 nm, 20 nm, 25 nm, 30 nm, 40 nm and 50 nm.

[0057] The surface modification treatment with polyethyleneimine is the key to successfully coating the coating shell layer on the surface of the solid cerium oxide nanospheres to form the core-shell structure. If the solid cerium oxide nanospheres in the application are not subjected to surface modification treatment with polyethyleneimine, the mesoporous cerium hydroxide / cerium oxide nanomaterial cannot be coated on the surface of the solid cerium oxide nanospheres, and the cerium oxide composite abrasive particle with the core-shell structure cannot be obtained.

[0058] In the present application, the diameter and thickness of the core and the coating layer directly determine the polishing effect of the ceria composite abrasive. If the diameter of the core is less than 100 nm and the thickness of the coating layer is less than 10 nm, the particle size of the ceria composite abrasive will be too small, which will reduce the material removal rate and the polishing efficiency. In addition, the ceria composite abrasive with too small particle size has high affinity with the wafer, which is easy to adhere to the wafer surface after polishing and difficult to clean and remove. If the diameter of the core is greater than 200 nm and the thickness of the coating layer is greater than 40 nm, the particle size of the ceria composite abrasive will be too large, which will increase the scratching of the wafer surface and the width of the scratches, resulting in high roughness of the wafer surface after polishing and affecting the subsequent process of the chip.

[0059] The present application also provides a preparation method of the ceria composite abrasive with core-shell structure as described above, comprising the following steps:

[0060] S1: preparing solid ceria nanospheres by a hydrothermal method.

[0061] S2: performing surface modification treatment on the solid ceria nanospheres by polyethyleneimine.

[0062] S3: coating mesoporous ceria nanomaterials on the surface of the solid ceria nanospheres subjected to the surface modification treatment by an in-situ chemical precipitation method to obtain ceria composite abrasive.

[0063] Both the hydrothermal method and the chemical precipitation method are common methods for synthesizing nanomaterials. The hydrothermal method refers to a powder preparation method in which a precursor in a certain form is placed in an aqueous solution in an autoclave, and a hydrothermal reaction is performed under high temperature and high pressure, followed by separation, washing, drying and other post-treatment. The chemical precipitation method refers to a method in which a precipitant is added to a salt solution to react, and the precipitate is heat-treated to obtain nanomaterials. In theory, there is no special limitation on the raw materials, equipment and steps used for the hydrothermal method and the chemical precipitation method. However, by special selection of raw materials and control of experimental conditions, the present application obtains core-shell structure nanomaterials with relatively better performance and better physicochemical morphology.

[0064] Preferably, the above step S1 specifically comprises the following steps:

[0065] S11: performing a hydrothermal reaction on cerium source, structure directing agent and precipitant to obtain ceria precursor.

[0066] S12: calcining the ceria precursor to obtain solid ceria nanospheres.

[0067] In step S11, the cerium source is preferably cerium nitrate hexahydrate, the structure-directing agent is preferably polyethylene glycol, and the precipitant is preferably urea. The molar ratio of urea to cerium nitrate hexahydrate is 25-150, the molecular weight of polyethylene glycol is 4000-20000 Da, the hydrothermal reaction temperature is 90-110°C, preferably 100°C, and the hydrothermal reaction time is 2.5-3.5h, preferably 3h.

[0068] In step S12, the calcination is performed in an air atmosphere, the calcination temperature is 500-600°C, and the calcination time is 2-4h.

[0069] Further, in step S11, the urea can be mixed with deionized water to prepare solution A, the cerium nitrate hexahydrate, polyethylene glycol and deionized water are mixed to prepare solution B, and then solution A and solution B are mixed uniformly and transferred to a hydrothermal reactor for heating reaction in a forced air drying oven. The concentration of urea in solution A is preferably 2-6mol / L, the concentration of cerium nitrate hexahydrate in solution B is preferably 0.01-0.04mol / L, and the amount of polyethylene glycol in solution B is 0.04-0.06g per ml of deionized water.

[0070] After the hydrothermal reaction is completed, the cerium oxide precursor solid particles are obtained after cooling, separation, washing and drying. The drying temperature is 60-70°C, and the drying time is 8-12h.

[0071] In the above hydrothermal reaction, different particle size distributions of solid cerium oxide nanosphere materials can be prepared by adjusting the amount or type of raw materials, such as the amount of cerium nitrate hexahydrate and urea, and the molecular weight of PEG.

[0072] Preferably, step S2 includes the following steps:

[0073] The solid cerium oxide nanospheres are dispersed in water, polyethyleneimine is added, and ultrasonic reaction is performed for 20-30min, followed by post-treatment to obtain solid cerium oxide nanospheres after surface modification.

[0074] The molecular weight of polyethyleneimine is preferably 10000-15000 Da, and more preferably 10000 Da.

[0075] Further, in step S2, the solid cerium oxide nanospheres prepared in step S1 are dispersed in deionized water, then mixed with polyethyleneimine to prepare solution C, and ultrasonic reaction is performed on solution C. After the ultrasonic reaction is completed, solution C is separated and washed, and the obtained solid is re-dispersed in deionized water to obtain solution D for standby use.

[0076] Further preferably, the concentration of the solid cerium oxide nanospheres in solution C is 0.1-0.2 g / L, more preferably 0.15 g / L, the concentration of the polyethyleneimine is 0.2-0.3 g / L, more preferably 0.25 g / L, and the mass ratio of the polyethyleneimine to the solid cerium oxide nanospheres is preferably 5:3.

[0077] Preferably, the above step S3 comprises the following steps:

[0078] S31: The solid cerium oxide nanospheres after surface modification treatment, citric acid, cetyltrimethylammonium bromide, sodium salicylate, hexamethylenetetramine, cerium chloride hexahydrate, and cyclohexane are added to deionized water, stirred, and then reacted under the condition of heating and stirring to obtain solid cerium oxide nanospheres coated with mesoporous cerium hydroxide nanomaterials. The cyclohexane is an oil phase, the deionized water is an aqueous phase, the cerium chloride hexahydrate is a cerium source, the cetyltrimethylammonium bromide is a structure directing agent, the hexamethylenetetramine is a precipitating agent, the citric acid is a chelating agent, and the sodium salicylate is a viscosity regulator. The water-oil two-phase system helps to form a dendritic mesoporous material. The sodium salicylate helps to form a spherical mesoporous nanomaterial on one hand and provides appropriate viscosity on the other hand, which is conducive to the adhesion of cerium hydroxide on the surface of the solid cerium oxide nanospheres and the formation of a compact core-shell structure.

[0079] S32: The solid cerium oxide nanospheres coated with mesoporous cerium hydroxide nanomaterials are calcined to obtain cerium oxide composite abrasive particles. The mesoporous cerium hydroxide nanomaterials prepared in step S31 are calcined in step S32 to obtain mesoporous cerium oxide nanomaterials.

[0080] In step S31, the citric acid, cetyltrimethylammonium bromide, sodium salicylate, hexamethylenetetramine, cerium chloride hexahydrate, and cyclohexane can be mixed with the above solution D containing the solid cerium oxide nanospheres after surface modification treatment, stirred vigorously to obtain solution E, and then continue to react under the condition of heating and stirring.

[0081] The mass ratio of sodium salicylate to solid cerium oxide nanospheres is 4:1-6:1, preferably 5:1, the concentration of citric acid in solution E is 0.05-0.15 g / L, the concentration of cetyltrimethylammonium bromide is 1-3 g / L, the concentration of sodium salicylate is 1-2 g / L, the concentration of hexamethylenetetramine is 0.2-0.4 g / L, the concentration of cerium chloride hexahydrate is 1.5-2 g / L, and the volume ratio of cyclohexane to deionized water is (2-4):(9-11); the stirring time is 1-2 h, the heating temperature is 60-80 DEG C, preferably 70 DEG C, and the reaction time is 7-8 h. Further, in solution E, the concentration of citric acid is preferably 0.1 g / L, the concentration of cetyltrimethylammonium bromide is preferably 2 g / L, the concentration of sodium salicylate is preferably 1.5 g / L, the concentration of hexamethylenetetramine is preferably 0.3 g / L, the concentration of cerium chloride hexahydrate is preferably 1.5-2 g / L, and the volume ratio of cyclohexane to deionized water is preferably 3:10.

[0082] In step S31, after the heating reaction of solution E is completed, it is cooled, separated, washed, and dried to obtain solid cerium oxide nanospheres coated with mesoporous cerium hydroxide nanomaterials, and the drying temperature is preferably 60-70 DEG C, and the drying time is preferably 8-12 h.

[0083] In step S32, the calcination is divided into two stages, first, the solid cerium oxide nanospheres coated with mesoporous cerium hydroxide nanomaterials are subjected to first-stage calcination treatment in a protective atmosphere, and then the solid cerium oxide nanospheres coated with mesoporous cerium hydroxide nanomaterials are subjected to second-stage calcination treatment in an air atmosphere. Further preferably, the calcination temperature of the first-stage calcination treatment is 500-600 DEG C, and the calcination time is 4-6 h, and the first-stage protective gas can be nitrogen, and the calcination temperature of the second-stage calcination treatment is 500-600 DEG C, and the calcination time is 2-4 h.

[0084] The polyethyleneimine in the present application is positively charged, and is used to modify the surface of the solid cerium oxide nanospheres, which can make the surface of the solid cerium oxide nanospheres positively charged, and is beneficial to improving the dispersibility of the solid cerium oxide nanospheres, so that in the subsequent synthesis of mesoporous cerium hydroxide nanomaterials, one of the raw materials, citric acid chelating agent, is negatively charged, so the solid cerium oxide nanospheres with a positive surface can be attracted by the negative citric acid, which is beneficial to in-situ precipitation of a mesoporous cerium hydroxide shell on the surface of the solid cerium oxide nanospheres, and the cerium oxide composite abrasive particles obtained have uniform particle size, which can ensure the stability and consistency in the polishing process. If the surface modification treatment by polyethyleneimine is not performed in step S2, the mesoporous cerium hydroxide nanomaterials cannot be coated on the surface of the solid cerium oxide nanospheres.

[0085] The application further provides an application of the cerium oxide composite abrasive particle or the cerium oxide composite abrasive particle prepared by the preparation method.

[0086] Preferably, the cerium oxide composite abrasive particle can be added into deionized water to obtain a polishing slurry with a mass concentration of 0.2-0.5 wt%, and an acid reagent such as acetic acid is used to adjust the pH value of the polishing slurry to about 4, so as to obtain a polishing liquid which can be used in chip preparation.

[0087] In addition, the cerium oxide composite abrasive particle has a hardness between that of the solid cerium oxide nanosphere and the mesoporous cerium oxide nanomaterial, has appropriate hardness, can effectively remove materials, is not easy to cause scratches and damage to the wafer surface, has good chemical stability, has stable chemical properties in the polishing liquid and is not easy to cause chemical reaction or decomposition, can ensure controllability of the polishing process, has high purity and can avoid the influence of impurities on the polishing effect and the wafer surface quality.

[0088] Therefore, the cerium oxide composite abrasive particle can effectively integrate the above-mentioned advantages and improve the overall performance of the polishing liquid.

[0089] In order to further clarify the application scheme and its technical progress, the following specific examples and technical effects are described.

[0090] Example 1

[0091] The embodiment provides a preparation method of the solid cerium oxide nanosphere, which comprises the following steps:

[0092] Urea is dissolved in deionized water to obtain solution A, and the solution A is stirred at room temperature for 30 min. Cerium nitrate hexahydrate and polyethylene glycol (PEG) are dissolved in deionized water to obtain solution B, and the solution B is stirred at room temperature for 30 min. The solution A and the solution B are mixed and stirred for 1 hour.

[0093] Subsequently, the mixed solution is transferred into a hydrothermal reactor and reacted at 100℃ for 3h. After the reaction is completed, the solid is obtained by cooling and centrifugal separation, and then the solid is washed with ethanol and deionized water, and then dried in a drying box at 60℃ overnight to obtain a cerium oxide precursor.

[0094] Finally, the dried cerium oxide precursor is calcined in a muffle furnace at 500℃ for 2h to obtain a solid cerium oxide nanosphere material.

[0095] In this embodiment, the molecular weight of PEG is 4000 Da, the molar ratio of urea to cerium nitrate hexahydrate is 25, the concentration of urea in solution A is 2 mol / L, the concentration of cerium nitrate hexahydrate in solution B is 0.0267 mol / L, and the amount of PEG in solution B is 1.6 g per 30 mL of deionized water.

[0096] Embodiments 2-6

[0097] Embodiments 2-6 provide a method for preparing solid ceria nanospheres, which is different from Embodiment 1 in that:

[0098] In Embodiment 2, the molecular weight of PEG is 20000 Da, the molar ratio of urea to cerium nitrate hexahydrate is 40:0.6, the concentration of urea in solution A is 4 mol / L, and the concentration of cerium nitrate hexahydrate in solution B is 0.02 mol / L.

[0099] In Embodiment 3, the molecular weight of PEG is 20000 Da, the molar ratio of urea to cerium nitrate hexahydrate is 100, the concentration of urea in solution A is 4 mol / L, and the concentration of cerium nitrate hexahydrate in solution B is 0.0133 mol / L.

[0100] In Embodiment 4, the molecular weight of PEG is 20000 Da, the molar ratio of urea to cerium nitrate hexahydrate is 50, the concentration of urea in solution A is 6 mol / L, and the concentration of cerium nitrate hexahydrate in solution B is 0.04 mol / L.

[0101] In Embodiment 5, the molecular weight of PEG is 20000 Da, the molar ratio of urea to cerium nitrate hexahydrate is 60, the concentration of urea in solution A is 6 mol / L, and the concentration of cerium nitrate hexahydrate in solution B is 0.0333 mol / L.

[0102] In Embodiment 6, the molecular weight of PEG is 20000 Da, the molar ratio of urea to cerium nitrate hexahydrate is 150, the concentration of urea in solution A is 6 mol / L, and the concentration of cerium nitrate hexahydrate in solution B is 0.0133 mol / L.

[0103] Figure 1 a- Figure 1 Figures f respectively show the transmission electron microscope (TEM) images of the solid ceria nanospheres prepared in Embodiments 1-6. The particle size of the solid ceria nanospheres prepared in Embodiments 1-6 is shown in Table 1. Figure 1It can be seen that the solid ceria nanospheres of Examples 1-6 all have a relatively uniform spherical structure, and the particle size (spherical diameter) is about 120-160 nm. Specifically, the average particle size of the solid ceria nanospheres prepared in Examples 1-6 is 135 nm, 130 nm, 140 nm, 160 nm, 160 nm and 150 nm, respectively. It can be seen that by appropriately adjusting the amount of the preparation raw material or the molecular weight of PEG, solid ceria nanosphere materials (sCeO2) with excellent morphology and adjustable size can be obtained.

[0104] Example 7

[0105] In this embodiment, the sCeO2 prepared in Example 2 is treated as follows:

[0106] First, the sCeO2 is surface-modified with polyethyleneimine (PEI) as follows: The sCeO2 is dissolved in deionized water, and then the mixture is added to deionized water containing PEI to obtain solution C. Solution C is ultrasonically dispersed for 20 min, centrifuged, washed with deionized water, and then the sCeO2 with PEI-modified surface is redispersed in deionized water to obtain solution D.

[0107] Second, the surface of the PEI-modified sCeO2 is coated with mesoporous cerium hydroxide (mCe(OH)3): citric acid, cetyltrimethylammonium bromide, sodium salicylate, hexamethylenetetramine, cerium chloride hexahydrate, and cyclohexane are added to solution D to obtain solution E. Solution E is stirred vigorously for 1 h, and then placed in a 70°C oil bath for 7 h. After cooling, centrifugal separation, and washing with deionized water and ethanol, a solid product is obtained. The solid product is further dried in a drying oven at 60°C overnight to obtain solid ceria nanospheres coated with mesoporous cerium hydroxide nanomaterials (sCeO2-mCe(OH)3).

[0108] Finally, ceria composite abrasive particles are obtained by high-temperature calcination: The sCeO2-mCe(OH)3 is calcined in a tubular furnace at a heating rate of 2°C / min under N2 atmosphere to 600°C, and kept at 600°C for 6 h. Then, further heating to 600°C at a rate of 3°C / min in air continues for 2 hours to remove residual carbon, to obtain mesoporous ceria-coated solid ceria nanospheres (sCeO2-mCeO2), i.e. ceria composite abrasive particles.

[0109] In this embodiment, the molecular weight of the polyethyleneimine is 10000 Da, the concentration of sCeO2 in solution C is 0.15 g / L, the concentration of polyethyleneimine is 0.25 g / L, and the mass ratio of polyethyleneimine to solid ceria nanospheres is 5:3.

[0110] The mass ratio of sodium salicylate to the solid cerium oxide nanospheres is 5:1, and the mass ratio of citric acid, cetyltrimethylammonium bromide, sodium salicylate, hexamethylenetetramine, and cerium chloride hexahydrate is 1:20:15:3:15. In the solution E, the concentration of citric acid is 0.1 g / L, the concentration of cetyltrimethylammonium bromide is 2 g / L, the concentration of sodium salicylate is 1.5 g / L, the concentration of hexamethylenetetramine is 0.3 g / L, and the concentration of cerium chloride hexahydrate is 1.5 g / L. The volume ratio of cyclohexane to deionized water is 3:10.

[0111] Figure 2 a- Figure 2 b is a transmission electron microscope (TEM) image of the cerium oxide composite abrasive sCeO2-mCeO2 prepared in the embodiment, and the image is obtained by Figure 2 It can be seen that the sCeO2-mCeO2 has a clear core-shell structure, and the mesoporous cerium oxide material with a low density is uniformly coated on the surface of the solid cerium oxide nanospheres with a high density, and the whole has a spherical structure with a diameter of about 170 nm, wherein the thickness of the mesoporous cerium oxide shell is about 20 nm.

[0112] Comparative Example 1

[0113] The difference between the present comparative example and Example 7 is that the sCeO2 is not subjected to surface modification treatment by polyethyleneimine (PEI).

[0114] Figure 3 b is a transmission electron microscope (TEM) image of the cerium oxide composite abrasive sCeO2-mCeO2 prepared in the embodiment, and the image is obtained by Figure 3 It can be seen that only part of the surface of the solid cerium oxide nanospheres is wrapped with the mesoporous cerium oxide material, and the coating is not uniform. It can be seen that the surface modification of the sCeO2 by PEI is the key to coating the mesoporous cerium hydroxide nanomaterial on the surface of the solid cerium oxide nanospheres, and is helpful to obtain the solid cerium oxide nanospheres (sCeO2-mCe(OH)3) with more uniform surface coating of the mesoporous cerium hydroxide nanomaterial.

[0115] Performance test:

[0116] The sCeO2 prepared in Example 2 and the sCeO2-mCeO2 prepared in Example 7 are subjected to physicochemical performance characterization, including X-ray diffraction analysis (XRD), N2 adsorption-desorption isotherm analysis, pore size distribution analysis, and X-ray photoelectron spectroscopy analysis (XPS):

[0117] Figure 4 b is an XRD curve of the sCeO2 and the sCeO2-mCeO2, and the curve is obtained by Figure 4It can be seen that the characteristic peak positions of the XRD curves of sCeO2 and sCeO2-mCeO2 are consistent with the standard card PDF #34-0394 of CeO2, and the characteristic diffraction peaks of sCeO2-mCeO2 are enhanced after the mesoporous ceria coating, indicating that sCeO2 and sCeO2-mCeO2 are both cubic fluorite structure CeO2.

[0118] Figure 5 The N2 adsorption-desorption isotherm graph of sCeO2-mCeO2 is as follows, Figure 6 The pore size distribution graph of sCeO2-mCeO2 is as follows, Figure 5 and Figure 6 It can be seen that sCeO2-mCeO2 shows IV type isotherm with H3 hysteresis loop, which is the characteristic of porous materials, and the specific surface area is 58.119 m 2 / g, the pore volume is 0.134 cm 3 / g, and the pore size is 12.303 nm.

[0119] The XPS curve of sCeO2 and sCeO2-mCeO2 is as follows, it can be seen from the XPS curve that the content of trivalent cerium ions in sCeO2-mCeO2 formed after the mesoporous ceria coating is increased from 18.36% to 19.2% compared with sCeO2, which indicates that the mesoporous structure of the coating shell has a higher content of trivalent cerium ions while having abundant pore structure and larger specific surface area, and has better chemical reaction activity.

[0120] Application example:

[0121] The sCeO2-mCeO2 composite abrasive particles prepared in Example 7 are taken, water is used as the solvent, and the sCeO2-mCeO2 composite abrasive particles are prepared into a polishing liquid with a mass fraction of 0.2%, and the pH value of the polishing liquid is adjusted to 4 with acetic acid, and after ultrasonic dispersion for 20 min, the polishing liquid is used for polishing of a silicon wafer.

[0122] Generally, when the Zeta potential value is greater than 30 mv, it can be considered that the solution has relatively good stability. The Zeta potential of the above polishing liquid is measured to be 40.07 mV, and it can be seen that the polishing liquid prepared by using the sCeO2-mCeO2 composite abrasive particles has relatively good stability.

[0123] The above prepared polishing liquid is used to polish a silicon wafer under the process conditions of a polishing pressure of 2.84 psi, a polishing disc rotation speed of 57 r / min, a polishing head rotation speed of 63 r / min, a polishing liquid flow rate of 400 mL / min, and a polishing time of 1 min, and the mass loss of the wafer after polishing is recorded to calculate the material removal rate of the wafer.

[0124] Figure 8 shows an AFM topography image of the polished silicon oxide wafer surface. Measurements show that the surface roughness Ra is 0.155 nm and Rq is 0.195 nm within a 5 μm x 5 μm area. The calculated material removal rate (MRR) is 127 nm / min. This demonstrates that polishing silicon oxide wafers with a polishing slurry formulated with sCeO₂-mCeO₂ composite abrasives achieves both a low roughness and a high polishing rate. Furthermore, testing has shown that the MRR doubles when the polishing slurry is at a concentration of 0.5%.

[0125] 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 cerium oxide composite abrasive with a core-shell structure, characterized in that: It comprises a core composed of solid cerium oxide nanospheres and a coating shell composed of mesoporous cerium oxide nanomaterials; the core is made of solid cerium oxide nanospheres subjected to surface modification treatment with polyethyleneimine; the diameter of the core is 100-200nm, and the thickness of the coating shell is 10-50nm.

2. The cerium oxide composite abrasive grain having a core-shell structure according to claim 1, wherein The diameter of the core is 100-160 nm, and the thickness of the coating shell is 10-25 nm.

3. A method for preparing the cerium oxide composite abrasive having a core-shell structure according to any one of claims 1 to 2, characterized in that: The steps include: S1: Preparation of solid cerium oxide nanospheres by hydrothermal method; S2: Surface modification of solid cerium oxide nanospheres by polyethyleneimine; S3: The mesoporous cerium oxide nanomaterial is coated on the surface of the solid cerium oxide nanospheres after surface modification by an in-situ chemical precipitation method to obtain cerium oxide composite abrasives.

4. The method for preparing the cerium oxide composite abrasive grains having a core-shell structure according to claim 3, wherein: Step S1 includes the following steps: S11: hydrothermally reacting a cerium source, a structure directing agent, and a precipitant to obtain a cerium oxide precursor; S12: calcining the cerium oxide precursor to obtain solid cerium oxide nanospheres; In step S11, the cerium source is cerium nitrate hexahydrate, the structure-directing agent is polyethylene glycol, and the precipitant is urea; the molar ratio of urea to cerium nitrate hexahydrate is 25-150, and the molecular weight of polyethylene glycol is 4000-20000 Da; the hydrothermal reaction temperature is 90-110° C., and the hydrothermal reaction time is 2.5-3.5 hours; In step S12, calcination is performed in an air atmosphere at a temperature of 500-600° C. and a calcination time of 2-4 hours.

5. The method for preparing the cerium oxide composite abrasive grains having a core-shell structure according to claim 3, wherein: Step S2 includes the following steps: Solid cerium oxide nanospheres are dispersed in water, polyethyleneimine is added, ultrasonic reaction is performed for 20-30 minutes, and then post-treatment is performed to obtain solid cerium oxide nanospheres that have been surface-modified; The molecular weight of polyethyleneimine is 10,000-15,000 Da.

6. The method for preparing the cerium oxide composite abrasive grains having a core-shell structure according to claim 3, wherein: Step S3 includes the following steps: S31: adding surface-modified solid cerium oxide nanospheres, citric acid, hexadecyltrimethylammonium bromide, sodium salicylate, hexamethylenetetramine, cerium chloride hexahydrate, and cyclohexane into deionized water, stirring the mixture, and then reacting the mixture under heating and stirring conditions to obtain solid cerium oxide nanospheres with a surface-coated mesoporous cerium hydroxide nanomaterial; S32: calcining the solid cerium oxide nanospheres whose surfaces are coated with mesoporous cerium hydroxide nanomaterials to obtain cerium oxide composite abrasive particles.

7. The method for preparing the cerium oxide composite abrasive grains having a core-shell structure according to claim 6, wherein: In step S31, the mass ratio of sodium salicylate to solid cerium oxide nanospheres is 4:1-6:

1. After the components are added to deionized water, the concentration of citric acid is 0.05-0.15 g / L, the concentration of hexadecyltrimethylammonium bromide is 1-3 g / L, the concentration of sodium salicylate is 1-2 g / L, the concentration of hexamethylenetetramine is 0.2-0.4 g / L, the concentration of cerium chloride hexahydrate is 1.5-2 g / L, and the volume ratio of cyclohexane to deionized water is (2-4):(9-11); the stirring time is 1-2 h, the heating temperature is 60-80 ° C, and the reaction time is 7-8 h; In step S32, the solid cerium oxide nanospheres with the surface coated with the mesoporous cerium hydroxide nanomaterial are first subjected to a first-stage calcination treatment under a protective atmosphere, and then the solid cerium oxide nanospheres with the surface coated with the mesoporous cerium hydroxide nanomaterial are subjected to a second-stage calcination treatment under an air atmosphere; The calcination temperature of the first stage calcination treatment is 500-600℃ and the calcination time is 4-6h; The calcination temperature of the second stage calcination treatment is 500-600°C and the calcination time is 2-4h.

8. Use of the cerium oxide composite abrasive according to any one of claims 1 to 2, characterized in that: The cerium oxide composite abrasive grains are used in polishing liquid.

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