Modified cerium oxide and preparation method thereof
By modifying cerium oxide with polyvinylpyrrolidone, a uniformly dispersed polishing liquid is prepared, which solves the problem of wafer surface scratches caused by uneven distribution of suspended cerium oxide, and achieves efficient polishing effect and high-quality integrated circuit production.
Patent Information
- Application Number
- CN202311831826.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-28
- Publication Date
- 2025-07-01
AI Technical Summary
In the existing CMP process, the uneven distribution of cerium oxide suspended particles in the polishing liquid leads to scratch defects on the wafer surface and the surface quality of the polished workpieces, which cannot meet the needs of large-scale high-quality integrated circuit production.
The surface modification of cerium oxide is used to prepare modified cerium oxide to form a uniformly dispersed polishing liquid to reduce the generation of large particles.
The modified cerium oxide polishing liquid effectively reduces wafer surface scratches, improves polishing effect, and meets the needs of large-scale high-quality integrated circuit production.
Smart Images
Figure BDA0004636550790000071 
Figure BDA0004636550790000081
Abstract
Description
Technical Field
[0001] The present invention relates to a modified cerium oxide and a preparation method thereof. Background Art
[0002] Chemical Mechanical Planarization (CMP) technology is the core technology for achieving global planarization of multi-layer copper wiring in Very Large Scale Integration (VLSI), and it is currently the only technology that can achieve local and global planarization of the wafer surface. The purpose of this process is to obtain a high flatness on the wafer surface, reduce wafer surface scratches, and reduce metal ion contamination. In the CMP process, the rotating wafer is pressed against the rotating polishing pad, and at the same time, a polishing liquid containing some chemical reagents and abrasive particles is fed into the wafer-polishing pad interaction area. The material to be processed undergoes mechanical friction with the polishing pad under a certain pressure, and at the same time, a chemical reaction occurs with the polishing liquid in the grooves. Under the synergistic action of chemical reaction and mechanical grinding, and under the chemical and mechanical interaction, the substances on the wafer surface are removed to form a flat surface. The polishing liquid is a suspension formed by mixing cerium oxide suspension particles, chemical additives, and deionized water in a certain proportion. The abrasive particles contained in the polishing liquid are unevenly distributed, and the Large Particle Count (LPC) has a direct relationship with wafer surface scratches. The large particles generated by aggregation will cause problems such as wafer surface scratch defects, poor flatness parameters, and degradation of the surface quality of the polished workpiece, and cannot meet the requirements of large-scale high-quality integrated circuit production. Summary of the Invention
[0003] Aiming at the above problems in the prior art, the present invention provides a polishing liquid composed of polyvinylpyrrolidone-modified cerium oxide, a preparation method thereof, and an application thereof. The polishing liquid has a good polishing effect, effectively reduces wafer surface scratches, and can meet the requirements of large-scale high-quality integrated circuit production.
[0004] In the first aspect of the present invention, a modified cerium oxide is provided, which includes the following steps: using polyvinylpyrrolidone to modify the surface of cerium oxide to obtain modified cerium oxide.
[0005] In some embodiments, the D90 particle size of the cerium oxide is 20-50 nm.
[0006] In some embodiments, the mass ratio of polyvinylpyrrolidone to cerium oxide in the modified cerium oxide is 1:(1-20), preferably 1:(2-10); for example, 1:2, 1:10, 1:2.5, or 1:5.
[0007] In some embodiments, the method for preparing the modified cerium oxide comprises the following steps: in the presence of a dispersant, in a solvent, polyvinylpyrrolidone is used to modify the surface of cerium oxide to obtain modified cerium oxide.
[0008] Wherein, the dispersant is a dispersant used in the art, preferably one or more of polyethylene glycol, sodium dodecyl sulfonate, sodium dodecyl sulfate, polyethylene glycol, polyacrylic acid and polyacrylate salts, ethylenediaminetetraacetic acid or disodium ethylenediaminetetraacetate, such as sodium dodecyl sulfate.
[0009] Wherein, the mass ratio of the dispersant to the cerium oxide is a mass ratio used in the art, preferably (0.9 - 1.1):1, such as 1:1.
[0010] Wherein the mass percentage of the dispersant is a mass percentage used in the art, preferably 2% - 10% (the percentage of the dispersant in the total mass of all raw materials in the modification process), such as 2%, 10% or 5%.
[0011] Wherein, the solvent is a conventional solvent in the art, preferably water, and further preferably one or more of deionized water, distilled water and ultrapure water, such as deionized water.
[0012] Wherein the mass percentage of the cerium oxide is a mass percentage used in the art, preferably 2% - 10% (the percentage of the cerium oxide in the total mass of all raw materials in the modification process), such as 2%, 10% or 5%.
[0013] Wherein the mass percentage of the polyvinylpyrrolidone is a mass percentage used in the art, preferably 0.2% - 5%, for example, 0.2%, 0.4%, 0.5%, 0.8%, 1%, 2%, 2.5%, 4% or 5%.
[0014] Preferably, the method for preparing the modified cerium oxide comprises the following steps:
[0015] Step 1: Mix the dispersant, the cerium oxide and the solvent to obtain a cerium oxide dispersion;
[0016] Step 2: Adjust the pH value of the cerium oxide dispersion to 6 - 7 to obtain a mixed solution;
[0017] Step 3: Mix polyvinylpyrrolidone and the mixed solution to obtain modified cerium oxide.
[0018] In some embodiments, in Step 1, the temperature of the mixing is room temperature.
[0019] In some embodiments, in Step 1, the mixing is carried out by mechanical stirring.
[0020] In some embodiments, in step 1, the mixing time is 10 - 50 min, for example 20 min.
[0021] In some embodiments, in step 2, the pH value of the cerium oxide dispersion is adjusted to pH 6.5.
[0022] In some embodiments, in step 2, a pH regulator is used to adjust the pH value of the cerium oxide dispersion to 6 - 7. The pH regulator is one or more of acetic acid, hydrochloric acid, nitric acid or phosphoric acid, preferably acetic acid; more preferably an acetic acid aqueous solution with a mass percentage of 10%.
[0023] In some embodiments, in step 3, the mixing temperature is 50 - 70 °C; for example 60 °C.
[0024] In some embodiments, in step 3, the mixing time is 5 - 12 h, for example 6 h.
[0025] In some embodiments, after the reaction is completed, the post-treatment steps include centrifugal separation and drying.
[0026] In some embodiments, the D90 particle size of the cerium oxide is 20 - 50 nm; the mass ratio of polyvinylpyrrolidone to cerium oxide in the modified cerium oxide is 1:(2 - 10).
[0027] In some embodiments, the D90 particle size of the cerium oxide is 20 - 50 nm; the mass ratio of polyvinylpyrrolidone to cerium oxide in the modified cerium oxide is 1:(2 - 10); the dispersant is sodium dodecyl sulfonate; the mass ratio of the dispersant to cerium oxide is 1:1; the mass percentage of the dispersant is 2% - 10%; the solvent is deionized water, the mass percentage of the cerium oxide is 2% - 10%; the mass percentage of polyvinylpyrrolidone is 0.2% - 5%; the reaction temperature is 60 °C; the modification reaction time is 6 h; the reaction pH is 6.5; the pH regulator is a dilute acetic acid aqueous solution (10% mass percentage).
[0028] In some embodiments, the D90 particle size of the cerium oxide is 20 - 50 nm; the mass percentage of the cerium oxide is 2%; the mass ratio of polyvinylpyrrolidone to the cerium oxide is 1:2; the reaction temperature is 60 °C; the modification reaction time is 6 h; the reaction pH is 6.5; the mass ratio of the dispersant to cerium oxide is 1:1; the pH regulator is a dilute acetic acid aqueous solution (10% mass percentage).
[0029] In some embodiments, the D90 particle size of the cerium oxide is 20 - 50 nm; the mass percentage of the cerium oxide is 2%; the mass ratio of polyvinylpyrrolidone to the cerium oxide is 1:5; the temperature of the reaction is 60 °C; the reaction time for modification is 6 h; the pH of the reaction is 6.5; the mass ratio of the dispersant to the cerium oxide is 1:1; the pH regulator is a dilute acetic acid aqueous solution (10% mass percentage).
[0030] In some embodiments, the D90 particle size of the cerium oxide is 20 - 50 nm; the mass percentage of the cerium oxide is 2%; the mass ratio of polyvinylpyrrolidone to the cerium oxide is 1:2.5; the temperature of the reaction is 60 °C; the reaction time for modification is 6 h; the pH of the reaction is 6.5; the mass ratio of the dispersant to the cerium oxide is 1:1; the pH regulator is a dilute acetic acid aqueous solution (10% mass percentage).
[0031] In some embodiments, the D90 particle size of the cerium oxide is 20 - 50 nm; the mass percentage of the cerium oxide is 2%; the mass ratio of polyvinylpyrrolidone to the cerium oxide is 1:10; the temperature of the reaction is 60 °C; the reaction time for modification is 6 h; the pH of the reaction is 6.5; the mass ratio of the dispersant to the cerium oxide is 1:1; the pH regulator is a dilute acetic acid aqueous solution (10% mass percentage).
[0032] In some embodiments, the D90 particle size of the cerium oxide is 20 - 50 nm; the mass percentage of the cerium oxide is 5%; the mass ratio of polyvinylpyrrolidone to the cerium oxide is 1:2; the temperature of the reaction is 60 °C; the reaction time for modification is 6 h; the pH of the reaction is 6.5; the mass ratio of the dispersant to the cerium oxide is 1:1; the pH regulator is a dilute acetic acid aqueous solution (10% mass percentage).
[0033] In some embodiments, the D90 particle size of the cerium oxide is 20 - 50 nm; the mass percentage of the cerium oxide is 5%; the mass ratio of polyvinylpyrrolidone to the cerium oxide is 1:5; the temperature of the reaction is 60 °C; the reaction time for modification is 6 h; the pH of the reaction is 6.5; the mass ratio of the dispersant to the cerium oxide is 1:1; the pH regulator is a dilute acetic acid aqueous solution (10% mass percentage).
[0034] In some embodiments, the D90 particle size of the cerium oxide is 20 - 50 nm; the mass percentage of the cerium oxide is 5%; the mass ratio of polyvinylpyrrolidone to the cerium oxide is 1:2.5; the temperature of the reaction is 60 °C; the reaction time for modification is 6 h; the pH of the reaction is 6.5; the mass ratio of the dispersant to the cerium oxide is 1:1; the pH regulator is a dilute acetic acid aqueous solution (10% mass percentage).
[0035] In some embodiments, the D90 particle size of the cerium oxide is 20 - 50 nm; the mass percentage of the cerium oxide is 5%; the mass ratio of polyvinylpyrrolidone to the cerium oxide is 1:10; the temperature of the reaction is 60 °C; the reaction time for modification is 6 h; the pH of the reaction is 6.5; the mass ratio of the dispersant to the cerium oxide is 1:1; the pH regulator is a dilute acetic acid aqueous solution (10% mass percentage).
[0036] In some embodiments, the D90 particle size of the cerium oxide is 20 - 50 nm; the mass percentage of the cerium oxide is 10%; the mass ratio of polyvinylpyrrolidone to the cerium oxide is 1:2; the temperature of the reaction is 60 °C; the reaction time for modification is 6 h; the pH of the reaction is 6.5; the mass ratio of the dispersant to the cerium oxide is 1:1; the pH regulator is a dilute acetic acid aqueous solution (10% mass percentage).
[0037] In some embodiments, the D90 particle size of the cerium oxide is 20 - 50 nm; the mass percentage of the cerium oxide is 10%; the mass ratio of polyvinylpyrrolidone to the cerium oxide is 1:10; the temperature of the reaction is 60 °C; the reaction time for modification is 6 h; the pH of the reaction is 6.5; the mass ratio of the dispersant to the cerium oxide is 1:1; the pH regulator is a dilute acetic acid aqueous solution (10% mass percentage).
[0038] In some embodiments, the D90 particle size of the cerium oxide is 20 - 50 nm; the mass percentage of the cerium oxide is 10%; the mass ratio of polyvinylpyrrolidone to the cerium oxide is 1:5; the temperature of the reaction is 60 °C; the reaction time for modification is 6 h; the pH of the reaction is 6.5; the mass ratio of the dispersant to the cerium oxide is 1:1; the pH regulator is a dilute acetic acid aqueous solution (10% mass percentage).
[0039] In some embodiments, the D90 particle size of the cerium oxide is 20 - 50 nm; the mass percentage of the cerium oxide is 10%; the mass ratio of the polyvinylpyrrolidone to the cerium oxide is 1:2.5; the temperature of the reaction is 60 °C; the reaction time for modification is 6 h; the pH of the reaction is 6.5; the mass ratio of the dispersant to the cerium oxide is 1:1; the pH regulator is a dilute acetic acid aqueous solution (10% mass percentage).
[0040] The second aspect of the present invention provides a method for preparing the above-mentioned modified cerium oxide, which includes the following steps: using polyvinylpyrrolidone to modify the surface of cerium oxide to obtain modified cerium oxide.
[0041] Among them, the operations and conditions of the preparation method are as described in the first aspect.
[0042] The third aspect of the present invention provides a use of the above-mentioned modified cerium oxide as a CMP abrasive.
[0043] The fourth aspect of the present invention further provides a polishing liquid, which comprises the following components: the above-mentioned modified cerium oxide and water.
[0044] In some embodiments, the mass percentage of the modified cerium oxide in the polishing liquid is 0.1% - 10%, preferably 0.5%.
[0045] In some embodiments, the polishing liquid further comprises one or more of 0.1 - 5% inhibitor, 50 - 500 ppm anionic surfactant, 0.01 - 2 wt% pH regulator or dispersant.
[0046] In some embodiments, the inhibitor is an amino acid, preferably one or more of glycine, alanine, valine, leucine, isoleucine, methionine, proline, tryptophan, serine, tyrosine, cysteine, phenylalanine, asparagine, glutamine, threonine, aspartic acid, glutamic acid, lysine, arginine or histidine.
[0047] In some embodiments, the anionic surfactant is a carboxylate or sulfonate, preferably one or more of carboxylate, carboxylic acid ester and its salts, fatty alcohol polyether - n carboxylate salts, alkyl sulfonates, alkyl benzene sulfonates, alkyl naphthalene sulfonates or sulfosuccinate esters.
[0048] In some embodiments, the dispersant is one or more of polyethylene glycol, sodium dodecyl sulfonate, sodium dodecyl sulfate, polyethylene glycol, polyacrylic acid and its salts, ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetate.
[0049] In some embodiments, the water is one or more of deionized water, distilled water, and ultrapure water, such as deionized water.
[0050] In some embodiments, the polishing liquid is composed of the following components by mass fraction: 0.1%-10% of the above-mentioned modified cerium oxide and the balance of water.
[0051] Preferably, the polishing liquid is composed of the following components by mass fraction: 0.5% of the above-mentioned modified cerium oxide and the balance of deionized water.
[0052] The fifth aspect of the present invention also provides a preparation method of the polishing liquid as described above. The above-mentioned components are mixed to obtain the polishing liquid.
[0053] The sixth aspect of the present invention also provides an application of the polishing liquid as described above in the polishing of the silicon dioxide dielectric layer of an integrated circuit.
[0054] The reagents and raw materials used in the present invention are all commercially available. Among them, cerium oxide is purchased from Leshan Dongcheng New Materials Co., Ltd.
[0055] In the present invention, where the specific operating temperature is not limited, it is all carried out under the condition of room temperature (20-35°C).
[0056] The positive and progressive effects of the present invention are as follows: The polishing liquid of the present invention can be used for the polishing of the silicon dioxide dielectric layer of an integrated circuit. The polishing liquid has a relatively high polishing selectivity between silicon oxide and silicon nitride, with good polishing effect, reducing scratches on the wafer surface, and good flatness parameters and surface quality of the polished workpiece. Specific Embodiments
[0057] I. Preparation of Surface-Modified Cerium Oxide Particles
[0058] Cerium oxide particles with a diameter of 20-50 nm (D90), sodium dodecyl sulfate, and deionized water are mixed and mechanically stirred and dispersed for 20 min; then the pH value is adjusted with a dilute acetic acid aqueous solution (10% mass percentage), and stirred evenly to obtain a cerium oxide dispersion. Polyvinylpyrrolidone as a modifier is added to the above dispersion, and the reaction is carried out at 60°C for 6 h under heating conditions. After the reaction is completed, centrifugal separation and drying are carried out to finally obtain surface-modified cerium oxide particles after modification.
[0059] In the following examples, where the specific operating temperature is not limited, it is all carried out under the condition of room temperature (20-35°C).
[0060] The content (mass percentage) of each raw material component in the examples and the reaction conditions for preparing the surface-modified cerium oxide abrasive are shown in the following table.
[0061]
[0062]
[0063] II. Preparation of polishing liquid:
[0064] The modified cerium oxide abrasives prepared in Examples 1-12 and deionized water were respectively used to prepare a polishing liquid with a mass percentage of 0.5%. The above polishing liquids were respectively used for polishing under the following polishing conditions:
[0065] 1. Polishing device: AP-300 (CTS)
[0066] 2. Pad: IC1000
[0067] 3. Polishing time: 60 s
[0068] 4. Platen speed: 110 rpm
[0069] 5. Spindle speed: 108 rpm
[0070] 6. Wafer pressure: 3.5 psi
[0071] 7. Flow rate of slurry: 200 mL / min
[0072] 8. Wafers: PE-TEOS (thickness 6KA); silicon nitride wafer (thickness 6KA); patterned wafer (15KA)
[0073] 9. Observe the scratches on the wafer surface through scanning electron microscope (SEM)
[0074] 10. Polishing effect: as shown in the following table.
[0075] Example Scratch on the wafer surface Examples 1 - 12 No scratch Comparative Example 1 Slight scratch
[0076] III. Detection of total particle count (LPC)
[0077] 1. Equipment for detecting total particle count (LPC): PSS780
[0078] 2. After taking the prepared polishing liquid and diluting it 1000 times with deionized water, the large particles > 1.01 um in the liquid were detected at room temperature. In the comparative example, the number of large particles > 10 3 ~10 4 pieces / mL, and in Examples 1-12 < 10 3 ~10 4 pieces / mL.
Claims
1. A modified cerium oxide, characterized in that, It is prepared by the following preparation method, and the preparation method includes the following steps: modifying the surface of cerium oxide with polyvinylpyrrolidone to obtain modified cerium oxide.
2. The modified cerium oxide according to claim 1, wherein The D90 particle size of the cerium oxide is 20 - 50 nm.
3. The modified cerium oxide according to claim 1, wherein In the modified cerium oxide, the mass ratio of polyvinylpyrrolidone to cerium oxide is 1:(1 - 20), preferably 1:(2 - 10); for example, 1:2, 1:10, 1:2.5 or 1:
5.
4. The modified cerium oxide according to claims 1-3, characterized in that, The preparation method of the modified cerium oxide includes the following steps: in the presence of a dispersant, in a solvent, modifying the surface of cerium oxide with polyvinylpyrrolidone to obtain modified cerium oxide.
5. The modified cerium oxide according to claim 4, wherein The preparation method meets one or more of the following conditions: (1) The dispersant is one or more of polyethylene glycol, sodium dodecyl sulfonate, sodium dodecyl sulfate, polyethylene glycol, polyacrylic acid and polyacrylates, ethylenediaminetetraacetic acid or disodium ethylenediaminetetraacetate, for example, sodium dodecyl sulfate; (2) The mass ratio of the dispersant to the cerium oxide is (0.9 - 1.1):1, for example, 1:1; (3) The mass percentage of the dispersant is 2% - 10%, such as 2%, 10% or 5%; (4) The solvent is water; the water is preferably one or more of deionized water, distilled water and ultrapure water, for example, deionized water; (5) The mass percentage of the cerium oxide is 2% - 10%, such as 2%, 10% or 5%; (6) The mass percentage of polyvinylpyrrolidone is 0.2% - 5%, for example, 0.2%, 0.4%, 0.5%, 0.8%, 1%, 2%, 2.5%, 4% or 5%.
6. The modified cerium oxide according to claim 5, characterized in that, The preparation method includes the following steps: Step 1: Mix the dispersant, the cerium oxide and the solvent to obtain a cerium oxide dispersion; Step 2: Adjust the pH value of the cerium oxide dispersion to 6 - 7 to obtain a mixed solution; Step 3: Mix polyvinylpyrrolidone and the mixed solution to obtain modified cerium oxide.
7. The modified cerium oxide according to claim 6, wherein, Meet one or more of the following conditions: (1) In Step 1, the temperature of the mixing is room temperature; (2) In Step 1, the mixing is carried out by mechanical stirring; (3) In Step 1, the mixing time is 10 - 50 min, for example, 20 min; (4) In Step 2, adjust the pH value of the cerium oxide dispersion to pH 6.5; (5) In Step 2, use a pH regulator to adjust the pH value of the cerium oxide dispersion to 6 - 7, and the pH regulator is one or more of acetic acid, hydrochloric acid, nitric acid or phosphoric acid, preferably acetic acid; more preferably, an acetic acid aqueous solution with a mass percentage of 10%; (6) In Step 3, the temperature of the mixing is 50 - 70 °C; for example, 60 °C; (7) In Step 3, the mixing time is 5 - 12 h, for example, 6 h; (8) After the reaction ends, the post-treatment steps include centrifugal separation and drying.
8. The modified cerium oxide according to claim 7, wherein, The D90 particle size of the cerium oxide is 20 - 50 nm; in the modified cerium oxide, the mass ratio of polyvinylpyrrolidone to cerium oxide is 1:(2 - 10); Preferably, the D90 particle size of the cerium oxide is 20 - 50 nm; the mass ratio of the polyvinylpyrrolidone to the cerium oxide in the modified cerium oxide is 1:(2 - 10); the dispersant is sodium dodecyl sulfonate; the mass ratio of the dispersant to the cerium oxide is 1:1; the mass percentage of the dispersant is 2% - 10%; the solvent is deionized water, the mass percentage of the cerium oxide is 2% - 10%; the mass percentage of the polyvinylpyrrolidone is 0.2% - 5%; the temperature of the reaction is 60 °C; the reaction time for modification is 6 h; the pH of the reaction is 6.5; the pH regulator is a dilute acetic acid aqueous solution (10% mass percentage); More preferably, it is any one of the following: (1) The D90 particle size of the cerium oxide is 20 - 50 nm; the mass percentage of the cerium oxide is 2%; the mass ratio of the polyvinylpyrrolidone to the cerium oxide is 1:2; the temperature of the reaction is 60 °C; the reaction time for modification is 6 h; the pH of the reaction is 6.5; the mass ratio of the dispersant to the cerium oxide is 1:1; the pH regulator is a dilute acetic acid aqueous solution; (2) The D90 particle size of the cerium oxide is 20 - 50 nm; the mass percentage of the cerium oxide is 2%; the mass ratio of the polyvinylpyrrolidone to the cerium oxide is 1:5; the temperature of the reaction is 60 °C; the reaction time for modification is 6 h; the pH of the reaction is 6.5; the mass ratio of the dispersant to the cerium oxide is 1:1; the pH regulator is a dilute acetic acid aqueous solution; (3) The D90 particle size of the cerium oxide is 20 - 50 nm; the mass percentage of the cerium oxide is 2%; the mass ratio of the polyvinylpyrrolidone to the cerium oxide is 1:2.5; the temperature of the reaction is 60 °C; the reaction time for modification is 6 h; the pH of the reaction is 6.5; the mass ratio of the dispersant to the cerium oxide is 1:1; the pH regulator is a dilute acetic acid aqueous solution; (4) The D90 particle size of the cerium oxide is 20 - 50 nm; the mass percentage of the cerium oxide is 2%; the mass ratio of the polyvinylpyrrolidone to the cerium oxide is 1:10; the temperature of the reaction is 60 °C; the reaction time for modification is 6 h; the pH of the reaction is 6.5; the mass ratio of the dispersant to the cerium oxide is 1:1; the pH regulator is a dilute acetic acid aqueous solution; (5) The D90 particle size of the cerium oxide is 20 - 50 nm; the mass percentage of the cerium oxide is 5%; the mass ratio of the polyvinylpyrrolidone to the cerium oxide is 1:2; the temperature of the reaction is 60 °C; the reaction time for modification is 6 h; the pH of the reaction is 6.5; the mass ratio of the dispersant to the cerium oxide is 1:1; the pH regulator is a dilute acetic acid aqueous solution; (6) The D90 particle size of the cerium oxide is 20 - 50 nm; the mass percentage of the cerium oxide is 5%; the mass ratio of the polyvinylpyrrolidone to the cerium oxide is 1:5; the reaction temperature is 60 °C; the reaction time for modification is 6 h; the pH of the reaction is 6.5; the mass ratio of the dispersant to the cerium oxide is 1:1; the pH regulator is a dilute acetic acid aqueous solution; (7) The D90 particle size of the cerium oxide is 20 - 50 nm; the mass percentage of the cerium oxide is 5%; the mass ratio of the polyvinylpyrrolidone to the cerium oxide is 1:2.5; the reaction temperature is 60 °C; the reaction time for modification is 6 h; the pH of the reaction is 6.5; the mass ratio of the dispersant to the cerium oxide is 1:1; the pH regulator is a dilute acetic acid aqueous solution; (8) The D90 particle size of the cerium oxide is 20 - 50 nm; the mass percentage of the cerium oxide is 5%; the mass ratio of the polyvinylpyrrolidone to the cerium oxide is 1:10; the reaction temperature is 60 °C; the reaction time for modification is 6 h; the pH of the reaction is 6.5; the mass ratio of the dispersant to the cerium oxide is 1:1; the pH regulator is a dilute acetic acid aqueous solution (10% mass percentage); (9) The D90 particle size of the cerium oxide is 20 - 50 nm; the mass percentage of the cerium oxide is 10%; the mass ratio of the polyvinylpyrrolidone to the cerium oxide is 1:2; the reaction temperature is 60 °C; the reaction time for modification is 6 h; the pH of the reaction is 6.5; the mass ratio of the dispersant to the cerium oxide is 1:1; the pH regulator is a dilute acetic acid aqueous solution; (10) The D90 particle size of the cerium oxide is 20 - 50 nm; the mass percentage of the cerium oxide is 10%; the mass ratio of the polyvinylpyrrolidone to the cerium oxide is 1:10; the reaction temperature is 60 °C; the reaction time for modification is 6 h; the pH of the reaction is 6.5; the mass ratio of the dispersant to the cerium oxide is 1:1; the pH regulator is a dilute acetic acid aqueous solution; (11) The D90 particle size of the cerium oxide is 20 - 50 nm; the mass percentage of the cerium oxide is 10%; the mass ratio of the polyvinylpyrrolidone to the cerium oxide is 1:5; the reaction temperature is 60 °C; the reaction time for modification is 6 h; the pH of the reaction is 6.5; the mass ratio of the dispersant to the cerium oxide is 1:1; the pH regulator is a dilute acetic acid aqueous solution; (12) The D90 particle size of the cerium oxide is 20 - 50 nm; the mass percentage of the cerium oxide is 10%; the mass ratio of the polyvinylpyrrolidone to the cerium oxide is 1:2.5; the reaction temperature is 60 °C; the reaction time for modification is 6 h; the pH of the reaction is 6.5; the mass ratio of the dispersant to the cerium oxide is 1:1; the pH regulator is a dilute acetic acid aqueous solution.
9. A method for preparing a modified cerium oxide as described in any one of claims 1-8, characterized in that, It includes the following steps: using polyvinylpyrrolidone to modify the surface of cerium oxide to obtain modified cerium oxide.
10. The method for preparing the modified cerium oxide according to claim 9, wherein, The operations and conditions of the preparation method are as described in any one of claims 2-8.