Preparation method of cerium oxide nanorod, cerium oxide nanorod and application of cerium oxide nanorod

Abstract

The invention discloses a preparation method of a cerium oxide nanorod, the cerium oxide nanorod and application of the cerium oxide nanorod, and cerium oxide nanorod particles are prepared through cerium carbonate high-pressure homogenization, wet ball milling, high-temperature calcination and secondary seed crystal growth. According to the preparation method disclosed by the invention, the surface smoothness of cerium oxide particles is improved through secondary seed crystal growth, and the number of polishing damage of the wafer is remarkably reduced. According to the method, the problems of the polishing rate of the cerium oxide abrasive in STI polishing and the wafer polishing surface quality are solved, and the STI polishing selection ratio is increased.

Description

Technical Field

[0001] The invention belongs to the technical field of nano material preparation and semiconductor polishing, and specifically relates to a preparation method of cerium oxide nanorods, the cerium oxide nanorods and the application of the cerium oxide nanorods in the field of STI polishing. Background Art

[0002] Chemical-mechanical polishing (CMP) is a process of overall flattening of non-planar surfaces produced during film deposition under the synergistic effect of mechanical and chemical effects. It is currently the only method that can achieve global flattening and has been widely used in many processes of integrated circuit (IC) manufacturing, such as polishing interlayer dielectrics (ILD) to form interconnections between devices and polishing shallow trench isolation (STI) structures to achieve device isolation. STI CMP involves the removal of both silicon oxide (SiO2) and silicon nitride (Si3N4), where the silicon nitride layer is located below the silicon oxide layer. After polishing silicon oxide, it is necessary to stop precisely on silicon nitride, that is, a higher silicon oxide polishing rate and a lower silicon nitride polishing rate are required. Currently, only cerium oxide can meet this requirement. The higher polishing rate and STI polishing selectivity of cerium oxide are attributed to its stronger redox properties, which makes it have a stronger chemical polishing effect during the polishing process, that is, it is easy to form Ce-O-Si bonds with the polishing layer silicon oxide, increasing the removal rate, and is chemically inert to silicon nitride, so the polishing selectivity is relatively high.

[0003] Density functional theory calculations show that the stability of the three low-index crystal planes of cerium oxide is {111}>{110}>{100}, and the activity order is the opposite [Chemistry of Materials 2012, 24, 1811-1821]. The oxygen vacancy formation energy of cerium oxide is {111}>{100}>{110}, and the surface stability and activity are {100}>{110}>{111}[The Journal of Physical Chemistry C, 2008, 112, 8643-8648], and the order of the number of oxygen vacancies is the opposite. Generally, cerium oxides of different morphologies expose different crystal planes. Nanoparticles and nanospheres mainly expose the most stable {111} crystal plane to reduce surface energy. Cerium oxide nanorods mainly expose {110} and {100} crystal planes. The structural diagram is shown in the figure below. Figure 6 As shown, it can be seen that the increase in the aspect ratio of cerium oxide can increase the proportion of highly active {100} crystal planes. Nanocubes expose {100} crystal planes [Angewandte Chemie International Edition, 2008, 47, 2884-2887], and nanorods and nanocubes have more oxygen vacancies.

[0004] The particle size, dispersibility, morphology and surface properties of cerium oxide have an important influence on the polishing selectivity in the STI process. At present, the improvement of STI polishing selectivity and wafer polishing surface quality is still a key issue. In the existing technology, the morphology of cerium oxide in cerium oxide polishing liquid is mainly spherical, and there are few reports on cerium oxide nanorod polishing liquid.

[0005] CN113120942A prepares nano-scale spindle-shaped cerium carbonate by a hydrothermal method, and then calcines it at high temperature to obtain spindle-shaped cerium oxide. The obtained cerium oxide can be used for CMP polishing after dispersion treatment, and shows good CMP polishing characteristics. CN115028185A prepares nano-scale rod-shaped cerium oxide by a hydrothermal method, and prepares it into a polishing liquid, which can improve the polishing removal rate and surface quality. JP2010526433A prepares cerium carbonate with different crystal structures by a coprecipitation method, and calcines it at high temperature to prepare cerium oxide with different morphologies. The obtained micron-sized rod-shaped cerium oxide shows a higher polishing rate and polishing selectivity. KR101101833B1 prepares micron-sized rod-shaped cerium carbonate by a coprecipitation method, and obtains spherical cerium oxide particles after high-temperature calcination and wet crushing. After wet grinding, cerium oxide generally obtains spherical particles. The rod-shaped cerium oxide directly obtained by calcining cerium carbonate is micrometer-sized. The main preparation method of nanometer-sized rod-shaped cerium oxide is the hydrothermal method, which has the disadvantages of high industrial cost and high reaction energy consumption.

[0006] Therefore, there is still a need for a new method for preparing cerium oxide nanorods, which can produce cerium oxide nanorods with low energy consumption and low cost. Summary of the invention

[0007] In view of the above problems, the present invention innovatively proposes a method for preparing cerium oxide nanorods, which adopts wet grinding of cerium carbonate to prepare nanoscale short rod-shaped cerium oxide, and improves the aspect ratio of cerium oxide nanorods through secondary seed growth. The cerium oxide prepared by the method is used as a polishing abrasive, which can improve the STI polishing selectivity of the cerium oxide abrasive and the surface quality of the wafer polishing.

[0008] Another object of the present invention is to provide cerium oxide nanorods prepared by the preparation method.

[0009] Another object of the present invention is to provide application of cerium oxide nanorods prepared by the preparation method in the field of STI polishing.

[0010] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solution:

[0011] A method for preparing cerium oxide nanorods comprises the following steps:

[0012] 1) Dispersion: adding cerium carbonate to an aqueous solution containing an anionic surfactant, adjusting the pH of the solution to alkaline with a pH adjuster, and stirring and dispersing to form a cerium carbonate dispersion;

[0013] 2) High-pressure homogenization: The cerium carbonate dispersion in step 1) is subjected to high-pressure homogenization and refinement using a high-pressure homogenizer to obtain micron-sized cerium carbonate composed of a rod-like structure with a length of 1-10 μm and a width of 0.5-1 μm;

[0014] 3) Wet grinding: using a ball mill to wet grind the cerium carbonate dispersion in step 2) to obtain a nanoscale short rod-shaped cerium carbonate slurry of 70-400 nm;

[0015] 4) high-temperature calcination: washing and drying the nanometer-scale short rod-shaped cerium carbonate slurry in step 3), and calcining at high temperature to obtain nanometer-scale short rod-shaped cerium oxide;

[0016] 5) Secondary growth: The nanoscale short rod-shaped cerium oxide in step 4) is dispersed in water as a seed crystal, and cerium salt and alkali are added, mixed and stirred to obtain a purple slurry, and then the purple slurry is transferred to a reactor for secondary growth to obtain cerium oxide nanorods.

[0017] In a specific embodiment, the particle size of the cerium carbonate in step 1) is 0.1-10 μm; and / or

[0018] The solid content of cerium carbonate in the cerium carbonate dispersion is 10-50wt%; and / or

[0019] The pH regulator is selected from at least one of KOH, NaOH, K2CO3, (NH4)2CO3, NH4HCO3, ammonia water or tetramethylammonium hydroxide;

[0020] Preferably, the pH is adjusted to 8-11, preferably 8-9;

[0021] Preferably, the anionic surfactant is selected from at least any one of triethanolamine dodecyl sulfate, ammonium dodecyl sulfate, triethanolamine polyoxyethylene alkyl ether sulfate, and polycarboxylic acid type polymer dispersants; More preferably, the polycarboxylic acid type polymer dispersant is a copolymer of a carboxylic acid monomer having an unsaturated double bond, a copolymer of a carboxylic acid monomer having an unsaturated double bond and a monomer having other unsaturated double bonds, and at least any one of their ammonium salts or amine salts; Further preferably, the carboxylic acid monomer having an unsaturated double bond is selected from at least any one of polyacrylic acid, ammonium polyacrylate, polymethacrylic acid, ammonium polymethacrylate, polymaleic acid, polyfumaric acid, and polyitaconic acid; and / or

[0022] The anionic surfactant is selected from at least one of polyacrylic acid, ammonium polyacrylate, polymethacrylic acid or ammonium polymethacrylate; and / or

[0023] The molecular weight of the anionic surfactant is 2000-10000, preferably 2000-3000; and / or

[0024] The added amount of the anionic surfactant is 3 / 100-6 / 100 of the mass of cerium carbonate.

[0025] In a specific embodiment, the pressure of the high-pressure homogenizer in step 2) is 300-500 bar, and the homogenization time is 10-20 min.

[0026] In a specific embodiment, the rotation speed of the ball mill in step 3) is 1000-3000 rpm, preferably 1500-2200 rpm; the size of the zirconium beads is 0.3-0.6 mm; and the grinding time is 10-20 min.

[0027] In a specific embodiment, the nanoscale short rod-shaped cerium carbonate slurry in step 4) is washed with water, the drying temperature is 50-100° C., and the drying time is 8-12 h; and / or

[0028] The high temperature calcination has a calcination temperature of 600-1000°C, preferably 700-800°C, and a calcination time of 2-8h, preferably 4-6h;

[0029] Preferably, the aspect ratio of the nanoscale short rod-shaped cerium oxide is 2: 1 to 4: 1. The morphology and size of the obtained cerium oxide are not significantly changed compared with those before calcination.

[0030] In a specific embodiment, in step 5), the seed crystals are dispersed in water, and the mass ratio of the added amount of the seed crystals to the added amount of the cerium salt is 1:2 to 1:5; and / or

[0031] The cerium salt is selected from any one of cerium nitrate, cerium chloride and cerium oxalate, preferably Ce(NO3)3·6H2O; the concentration of the cerium salt solution is 35-45wt%, preferably 35-40wt%; and / or

[0032] The alkali is any one of KOH, NaOH and ammonia water, preferably KOH, and the concentration of KOH solution is 30-40wt%, preferably 33-37wt%;

[0033] Preferably, the reaction temperature of the secondary growth is 100-180° C., preferably 130-160° C.; the reaction time of the secondary growth is 5-15 h, preferably 9-13 h;

[0034] More preferably, the aspect ratio of the cerium oxide nanorods is 4.3:1 to 9:1.

[0035] On the other hand, the cerium oxide nanorods prepared by the aforementioned preparation method have an aspect ratio of 4.3:1 to 9:1;

[0036] Preferably, the surface Ce of the cerium oxide nanorods 3+ The content is 20-40%; more preferably, the STI polishing selectivity of the cerium oxide nanorods is not less than 30.

[0037] On the other hand, the cerium oxide nanorods prepared by the aforementioned preparation method are used in the field of STI polishing. Preferably, the prepared cerium oxide nanorods are added to an aqueous solution containing an anionic surfactant, and the pH of the cerium oxide dispersion is adjusted to alkaline using a pH regulator to form a cerium oxide slurry. When in use, the cerium oxide slurry is diluted with deionized water and polishing can be performed.

[0038] In a specific embodiment, the anionic surfactant is selected from any one of triethanolamine dodecyl sulfate, ammonium dodecyl sulfate, triethanolamine polyoxyethylene alkyl ether sulfate, and polycarboxylic acid type polymer dispersant;

[0039] Preferably, the polycarboxylic acid type polymer dispersant is selected from any one of a copolymer of a carboxylic acid monomer having an unsaturated double bond, a copolymer of a carboxylic acid monomer having an unsaturated double bond and a monomer having other unsaturated double bonds, and an ammonium salt or an amine salt thereof; and / or

[0040] The carboxylic acid monomer having an unsaturated double bond is selected from any one of polyacrylic acid, ammonium polyacrylate, polymethacrylic acid, ammonium polymethacrylate, polymaleic acid, polyfumaric acid, and polyitaconic acid;

[0041] More preferably, the molecular weight of the anionic surfactant is 2000-10000, preferably 2000-3000; and / or

[0042] The mass content of the anionic surfactant in the cerium oxide slurry before dilution is 0.1-1 wt % of the total mass of the cerium oxide slurry used as the polishing liquid, preferably 0.3-0.6 wt %.

[0043] In a specific embodiment, the pH adjuster is selected from at least any one of KOH, NaOH, K2CO3, (NH4)2CO3, NH4HCO3, ammonia water and tetramethylammonium hydroxide;

[0044] Preferably, the pH is adjusted to 8-11, preferably 8-9;

[0045] Preferably, during polishing, the solid content of cerium oxide in the cerium oxide slurry is diluted to 0.1-1.0 wt %, preferably 0.1-0.5 wt %.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] The preparation method of the present invention comprises the following steps: wet ball milling cerium carbonate to a certain aspect ratio, calcining at high temperature to form cerium oxide nanorods, and then secondary seed growth to obtain cerium oxide nanorod particles with a larger aspect ratio, thereby promoting the rolling friction movement of cerium oxide during the polishing process and improving the Ce 3+ content and redox properties, thereby improving the P-TEOS polishing selectivity and polishing quality.

[0048] Compared with round-shaped ceria, ceria nanorods expose more active {100} and {110} crystal planes, which promotes the surface Ce 3+ The increase in the content of nanorods not only promotes the increase of active {100} surfaces, but also promotes the rolling friction movement of cerium oxide during polishing, increases the contact area between cerium oxide and polishing medium silicon oxide, and thus improves the P-TEOS polishing rate and STI polishing selectivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 The SEM image and XRD spectrum of cerium carbonate after high-pressure homogenization in Example 1 of the present invention.

[0050] Figure 2 This is a TEM image of cerium carbonate after wet grinding and before calcination in Example 1 of the present invention.

[0051] Figure 3 TEM image and XRD spectrum of cerium oxide obtained by calcining cerium carbonate in Example 1 of the present invention.

[0052] Figure 4 This is a TEM image of cerium oxide obtained after secondary growth in Example 1 of the present invention.

[0053] Figure 5 TEM image of cerium oxide obtained after calcination (a), washing and drying (b), and secondary growth (c) of cerium carbonate in Comparative Example 1 of the present invention.

[0054] Figure 6 This is a schematic diagram of the structure of cerium oxide nanorods. DETAILED DESCRIPTION

[0055] In order to better understand the technical solution of the present invention, the following examples will further illustrate the method provided by the present invention, but the present invention is not limited to the listed examples, and should also include any other known changes within the scope of the claims of the present invention.

[0056] A method for preparing cerium oxide nanorods comprises the following steps:

[0057] 1) Dispersion of cerium carbonate: Add cerium carbonate to a certain aqueous solution containing anionic surfactant, adjust the pH of the cerium carbonate dispersion to alkaline, and stir for a certain period of time;

[0058] 2) High-pressure homogenization and refinement of cerium carbonate: A high-pressure homogenizer is used to refine the cerium carbonate dispersion, and by adjusting the pressure and time, micron-sized cerium carbonate consisting of a rod-like structure with a length of 1-10 μm and a width of 0.5-1 μm is obtained.

[0059] 3) Wet grinding of cerium carbonate: using a ball mill to wet grind the cerium carbonate dispersion, by adjusting the rotation speed, zirconium beads and grinding time, a nano-scale cerium carbonate slurry is obtained, and the obtained cerium carbonate slurry is passed through a membrane filter with a pore size of 1 μm to remove coarse particles in the slurry;

[0060] 4) High-temperature calcination of cerium carbonate: washing and drying the cerium carbonate slurry, placing it in a crucible for high-temperature calcination to obtain cerium oxide;

[0061] 5) Secondary growth of cerium oxide: The nano-scale cerium oxide slurry is washed and dried, the obtained seed crystals are dispersed in water, stirred, and a certain concentration of Ce(NO3)3·6H2O aqueous solution and a certain concentration of KOH aqueous solution are added, mixed and stirred; then the purple slurry is transferred to a flask and reacted at a certain temperature for a certain time for secondary growth to obtain cerium oxide nanorods.

[0062] Wherein, the particle size of the cerium carbonate in step 1) is 0.1-10 μm, for example, 0.1 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, etc.

[0063] In step 1), the cerium carbonate is added to an aqueous solution containing an anionic surfactant, the solid content of the cerium carbonate is 10-50wt%, for example, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, etc., the anionic surfactant is triethanolamine dodecyl sulfate, ammonium dodecyl sulfate, triethanolamine polyoxyethylene alkyl ether sulfate, polycarboxylic acid type polymer dispersant; the polycarboxylic acid type polymer dispersant includes copolymers of carboxylic acid monomers having unsaturated double bonds such as polyacrylic acid, ammonium polyacrylate, polymethacrylic acid, ammonium polymethacrylate, polymaleic acid, polyfumaric acid, polyitaconic acid, etc. A copolymer of a carboxylic acid monomer having an unsaturated double bond and a monomer having other unsaturated double bonds, and their ammonium salts or amine salts; preferably, the anionic surfactant is at least any one of polyacrylic acid, ammonium polyacrylate, polymethacrylic acid or ammonium polymethacrylate; the molecular weight of the anionic surfactant is 2000-10000, for example, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000, preferably 2000-3000; the content of the anionic surfactant is 3 / 100-6 / 100 of the mass of cerium carbonate, for example, 3 / 100, 4 / 100, 5 / 100, 6 / 100, etc.

[0064] In step 1), the pH adjusting agent is at least any one of KOH, NaOH, K2CO3, (NH4)2CO3, NH4HCO3, ammonia water and tetramethylammonium hydroxide; the pH is adjusted to 8-11, such as 8.5, 9, 9.5, 10, 10.5, 11, etc., preferably 8-9.

[0065] In step 2), a high-pressure homogenizer is used to refine cerium carbonate, and the pressure is 300-500 bar, such as 300 bar, 350 bar, 400 bar, 450 bar, 500 bar, etc., and the homogenization time is 10-20 min, such as 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, 18 min, 19 min, 20 min, etc. Under the high-pressure homogenization conditions, micron-sized cerium carbonate with a rod-like structure of 1-10 μm in length and 0.5-1 μm in width can be obtained. The temperature of high-pressure homogenization is not particularly limited, for example, 20-40 ° C, such as 20 ° C, 30 ° C, 40 ° C.

[0066] In step 3), wet ball milling is used for wet pulverization, the ball mill speed is 1000-3000rpm, such as 1000rpm, 1500rpm, 2000rpm, 2500rpm, 3000rpm, etc., preferably 1500-2200rpm; the zirconium bead size is 0.3-0.6mm, such as 0.3mm, 0.4mm, 0.5mm, 0.6mm, etc.; the ball milling time is 10-20min, such as 10min, 15min, 20min, etc. Nano-scale cerium carbonate slurry is obtained by wet ball milling, for example, ball milling to 70-400nm, such as 80nm, 90nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, etc., preferably 100-300nm. The temperature of wet ball milling is not particularly limited, and is, for example, 20-40°C, such as 20°C, 30°C, 40°C, etc.

[0067] In step 4), the nanoscale short rod-shaped cerium carbonate slurry is washed with water, and the number of washing times is not particularly limited, for example, it is washed 1 to 3 times, and then dried, the drying temperature is 50-100°C, for example, 50°C, 60°C, 70°C, 80°C, 90°C, 1000°C, etc., and the drying time is 8-12h, for example, 8h, 9h, 10h, 11h, 12h; the high temperature calcination temperature is 600-1000°C, for example, 600°C, 700°C, 800°C, 850°C, 900°C, 1000°C, etc., preferably 700-800°C, and the calcination time is 2-8h, for example, 2h, 3h, 4h, 5h, 6h, 7h, 8h, etc., preferably 4-6h. The morphology and size of the obtained cerium oxide have no obvious change compared with before calcination. The aspect ratio of the nanoscale short rod-shaped cerium oxide is 2:1 to 4:1, for example, 2.0:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 3:1, 3.5:1, 4:1, etc.

[0068] In step 5), the seed crystals are dispersed in water, and the mass ratio of the added amount of the seed crystals to the added amount of the cerium salt is 1:2 to 1:5, for example, 1:2, 1:2.3, 1:2.5, 1:2.8, 1:3, 1:3.5, 1:4, 1:4.3, 1:4.5, 1:5, etc.; the cerium salt is selected from any one of cerium nitrate, cerium chloride, and cerium oxalate, preferably Ce(NO3)3·6H2O; specifically, the concentration of Ce(NO3)3·6H2O is 35-45wt%, for example, 35%, 40%, 45%, etc., preferably 35-40wt%; the base is any one of KOH, NaOH, and ammonia water, preferably KOH, and the concentration of KOH solution is 30- 40wt%, for example, 30%, 35%, 40%, etc., preferably 33-37wt%; the molar ratio of the two is 1:10-1:15, for example, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, etc.; the reaction temperature of the secondary growth is 100-180℃, for example, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, etc., preferably 130-160℃; the reaction time of the secondary growth is 5-15h, for example, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, etc., preferably 9-13h. The aspect ratio of the cerium oxide nanorods obtained by the secondary growth increases to 4.3:1 to 9:1, for example, 4.3:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.3:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1, 9:1, etc.

[0069] The cerium oxide nanorods prepared by the present invention are added to a certain aqueous solution containing anionic surfactant after the reactants are cooled to room temperature, and the pH of the cerium oxide dispersion is adjusted to alkaline with a pH regulator to obtain a polishing liquid slurry with cerium oxide as an abrasive; the obtained cerium oxide slurry is diluted with deionized water before use and polishing can be performed.

[0070] Wherein, the anionic surfactant is triethanolamine dodecyl sulfate, ammonium dodecyl sulfate, triethanolamine polyoxyethylene alkyl ether sulfate, and polycarboxylic acid type polymer dispersant; the polycarboxylic acid type polymer dispersant includes copolymers of carboxylic acid monomers with unsaturated double bonds such as polyacrylic acid, ammonium polyacrylate, polymethacrylic acid, ammonium polymethacrylate, polymaleic acid, polyfumaric acid, and polyitaconic acid, copolymers of carboxylic acid monomers with unsaturated double bonds and monomers with other unsaturated double bonds, and their ammonium salts or amine salts; preferably, the anionic surfactant is at least any one of polyacrylic acid, ammonium polyacrylate, polymethacrylic acid, or ammonium polymethacrylate; the molecular weight of the anionic surfactant is 2000-10000, for example, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000, preferably 2000-3000; the anionic surfactant may be the same or different from that in step 1), preferably the same as that in step 1). The content of anionic surfactant is 0.1-1wt% of the total mass of cerium oxide slurry as polishing liquid, for example, 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1wt%, etc., preferably 0.3-0.6wt%.

[0071] The pH regulator is at least one of KOH, NaOH, K2CO3, (NH4)2CO3, NH4HCO3, ammonia and tetramethylammonium hydroxide; the pH is adjusted to 8-11, such as 8, 8.5, 9, 9.5, 10, 10.5, 11, etc., preferably 8-9. The solid content of cerium oxide in the cerium oxide slurry as the polishing liquid is 0.1-1.0wt%, such as 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1wt%, etc., preferably 0.1-0.5wt%.

[0072] The aspect ratio of the cerium oxide nanorods of the present invention is 4.3:1 to 9:1, and the surface Ce 3+ The content is 20-40% of the total Ce content, for example 20%, 25%, 30%, 35%, 40%, etc.; more preferably, the STI polishing selectivity of the cerium oxide nanorods is not less than 30, for example 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 42, 45, 47, 50, etc.

[0073] The preparation method of the present invention is further explained below by more specific examples, but does not constitute any limitation.

[0074] The main raw materials used in the following examples and comparative examples are as follows:

[0075] raw material factory Specification Ultrapure water From mili-q direct pure water machine water 18.2MΩ.cm Ammonium polyacrylate Aladdin Premium Pure Potassium hydroxide Aladdin Premium Pure Cerous nitrate Aladdin Premium Pure Cerium carbonate Yiyang Hongyuan Rare Earth Co., Ltd. High purity

[0076] Detection method:

[0077] The particle size was measured using a laser diffraction particle size analyzer, with the light shielding ratio set to 2.2 and the light absorbance set to 1.3, and the particle size was measured after ultrasound. The results are shown in Table 1, and no agglomeration was observed.

[0078] XRD (X-ray diffraction) was used to detect the sample phase; SEM (transmission electron microscopy) was used to detect the morphology and particle size of micron-scale cerium carbonate and cerium oxide, and the aspect ratio was calculated; TEM (transmission electron microscopy) was used to detect the morphology and particle size of nano-scale cerium carbonate / cerium oxide. XPS (X-ray photoelectron spectroscopy) was used to detect the Ce on the surface of cerium oxide. 3+ content.

[0079] P-TEOS polishing rate evaluation:

[0080] A P-TEOS wafer with a diameter of 2 inches and a film thickness of 2 μm was used for insulating film CMP evaluation. The wafer was placed on the holder of the adsorption pad for mounting the substrate in the polishing device (Shenyang Kejing UNIPOL-1000S), and a porous polyurethane resin polishing pad (k-groove groove, manufactured by Rodel, model-IC1000) was attached to the polishing disc with a diameter of 300 mm. The holder was placed on the polishing pad so that the insulating film of the wafer faced down, and the wafer pressure was set to 3 psi. At the same time, cerium oxide polishing liquid was dripped on the polishing disc at a flow rate of 100 mL / min, and the polishing disc and wafer were rotated at 60 rpm and 70 rpm, respectively, to polish the above P-TEOS film for 1 minute. The polished wafer was thoroughly cleaned with pure water and dried, and then the residual film thickness of the SiO2 film at 10 points on the wafer surface was measured using an optical interference film thickness device. The polishing rate was calculated based on the reduction in film thickness compared to before polishing. The results are shown in Table 1.

[0081] Evaluation of polishing damage:

[0082] The polished P-TEOS wafer was immersed in a 0.5% hydrofluoric acid solution for 1 minute to remove the residual cerium oxide particles, and then thoroughly rinsed with pure water. Then, the P-TEOS surface was inspected for the number of defects using a defect inspection device (KLAT Teco, USA). The results are shown in Table 1.

[0083] Evaluation of polishing selectivity:

[0084] The silicon nitride wafer obtained by LPCVD (low pressure chemical vapor deposition) was polished in the same polishing manner as the above-mentioned P-TEOS wafer, and the thickness change before and after polishing was measured using the same system. The results are shown in Table 1. The ratio of the P-TEOS polishing rate to the silicon nitride polishing rate is the polishing selectivity.

[0085] The main process conditions of each embodiment and comparative example are as follows:

[0086] Example 1

[0087] 800g of cerium carbonate was added to an aqueous solution of ammonium polyacrylate, wherein the solid content of cerium carbonate was 20wt%, and the content of ammonium polyacrylate was 5 / 100 of the mass of cerium carbonate. The pH of the slurry was adjusted to 9 using KOH and stirred for 5h. The cerium carbonate material was refined using a high-pressure homogenizer at a pressure of 400bar for 20min. The obtained cerium carbonate structure contained a rod-like structure with a length of 1-10μm and a width of 0.5-1μm and a flake-like structure with a length of 1-60μm and a width of 0.5-1μm. Figure 1 a), SEM at a higher magnification shows that the sheet-like structure is composed of micrometer-scale rod-like structures ( Figure 1 b). XRD shows that its crystal structure is orthorhombic octahydrate cerium carbonate (Ce2(CO3)3·8H2O), such as Figure 1 c. The cerium carbonate slurry was wet-milled using a ball mill, wherein the rotation speed was 2000 rpm, the zirconium bead size was 0.5 mm, and the grinding time was 15 min. The obtained cerium carbonate slurry was passed through a membrane filter with a pore size of 1 μm to remove the coarse particles in the slurry, and cerium carbonate particles with a particle size distribution of 86-374 nm and an average particle size of 154 nm were obtained. The filtered cerium carbonate slurry was further centrifuged and washed, and dried at 70° C. for 12 h to obtain cerium carbonate powder, such as Figure 2 TEM showed that the obtained cerium carbonate was a short rod-like structure, indicating that the sheet-like cerium carbonate assembled from rod-like cerium carbonate and rod-like structures can be ground into nanoscale short rod-like structures after wet grinding. The cerium carbonate powder was calcined at 800℃ for 5h in a muffle furnace to obtain a yellow-white powder. XRD showed that its phase was cubic fluorite phase cerium oxide, such as Figure 3 b; TEM shows that its morphology is short rod-shaped, that is, the morphology does not change after calcination. The average length of the rod is about 40nm, the average width is about 16nm, and the average aspect ratio is 3:1. Figure 3 a; BET measured its specific surface area is 27.1m 2 / g. Weigh 100g of cerium oxide as seed crystals and disperse it in 300g of water, stir for 30min, add 1000g Ce(NO3)3·6H2O aqueous solution (38wt%) and 1000g KOH aqueous solution (35wt%), mix and stir for 30min. Then transfer the purple slurry to a 5L flask and react at 150℃ for 10h for secondary growth. After the reactant is cooled to room temperature, add 100g of ammonium polyacrylate aqueous solution (12.5wt%), use KOH to adjust the pH of the slurry to 9, and obtain a cerium oxide slurry with a particle size distribution of about 132-326nm and an average particle size of 195nm. The specific surface area measured by BET is 9.5m 2 / g, corresponding to a primary particle size of 89nm, and an average aspect ratio of 6:1. TEM showed that the obtained cerium oxide was a rod-like structure, with a length increasing to 62-238nm, an average length of about 138nm; a width increasing to 19-81nm, an average width of 50nm, such as Figure 4 , the average aspect ratio increased to 3.5:1.

[0088] The obtained cerium oxide slurry was diluted to 0.25wt% for polishing test, as shown in Table 1, Ce 3+ The content is 31%, and the P-TEOS polishing rate is The number of polishing damages on a single wafer is 0, and the polishing rate of silicon nitride is

[0089] Example 2

[0090] The cerium carbonate obtained by high pressure homogenization, wet grinding, filtration and drying was prepared in the same manner as in Example 1. The cerium carbonate powder was calcined at 700°C for 5 h in a muffle furnace to obtain a yellow-white powder. The specific surface area of ​​the powder was 32.3 m 2 / g, and the average aspect ratio is 2.6:1. Weigh 100g of cerium oxide as seed crystals and disperse it in 300g of water, stir for 30min, add 1000g of Ce(NO3)3·6H2O aqueous solution (38wt%) and 1000g of KOH aqueous solution (35wt%), mix and stir for 30min. Then transfer the purple slurry to a 5L flask and react at 150°C for 10h for secondary growth. After the reactant is cooled to room temperature, add 100g of ammonium polyacrylate aqueous solution (12.5wt%), use KOH to adjust the pH of the slurry to 9, and obtain a cerium oxide slurry with a particle size distribution of about 98-306nm and an average particle size of 189nm. The specific surface area measured by BET is 11.5m 2 / g, corresponding to a primary particle size of 73nm and an average aspect ratio of 5:1.

[0091] The obtained cerium oxide slurry was diluted to 0.25wt% for polishing test, as shown in Table 1, Ce 3+The content is 34%, and the P-TEOS polishing rate is The number of polishing damages on a single wafer is 2, and the polishing rate of silicon nitride is

[0092] Example 3

[0093] The cerium carbonate obtained by high pressure homogenization, wet grinding, filtration and drying was prepared in the same manner as in Example 1. The cerium carbonate powder was calcined at 900° C. for 5 h in a muffle furnace to obtain a yellow-white powder. The specific surface area of ​​the powder was 20.0 m 2 / g, and the average aspect ratio is 2.1:1. Weigh 100g of cerium oxide as seed crystals and disperse it in 300g of water, stir for 30min, add 1000g Ce(NO3)3·6H2O aqueous solution (38wt%) and 1000g KOH aqueous solution (35wt%), mix and stir for 30min. Then transfer the purple slurry to a 5L flask and react at 150°C for 10h for secondary growth. After the reactant is cooled to room temperature, add 100g of ammonium polyacrylate aqueous solution (12.5wt%), use KOH to adjust the pH of the slurry to 9, and obtain a cerium oxide slurry with a particle size distribution of about 134-362nm and an average particle size of 210nm. The specific surface area measured by BET is 8.2m 2 / g, corresponding to a primary particle size of 103nm and an average aspect ratio of 4.8:1.

[0094] The obtained cerium oxide slurry was diluted to 0.25wt% for polishing test, as shown in Table 1, Ce 3+ The content is 26%, and the P-TEOS polishing rate is The number of polishing damages on a single wafer is 4, and the polishing rate of silicon nitride is

[0095] Example 4

[0096] The cerium carbonate obtained by high pressure homogenization, wet crushing, filtering and drying was prepared in the same manner as in Example 1, wherein the size of the wet crushed zirconium beads was reduced to 0.3 mm, the particle size distribution of the obtained cerium carbonate particles was reduced to 78-287 nm, and the average particle size was reduced to 146 nm; the specific surface area of ​​the cerium oxide after calcination was 35.0 m 2 / g, and the average aspect ratio is 2.1:1. Weigh 100g of cerium oxide as seed crystals and disperse it in 300g of water, stir for 30min, add 1000g Ce(NO3)3·6H2O aqueous solution (38wt%) and 1000g KOH aqueous solution (35wt%), mix and stir for 30min. Then transfer the purple slurry to a 5L flask and react at 150°C for 10h for secondary growth. After the reactant is cooled to room temperature, add 100g of ammonium polyacrylate aqueous solution (12.5wt%), use KOH to adjust the pH of the slurry to 9, and obtain a cerium oxide slurry with a particle size distribution of about 104-312nm and an average particle size of 191nm. The specific surface area measured by BET is 10.6m 2 / g, corresponding to a primary particle size of 79nm and an average aspect ratio of 4.5:1.

[0097] The obtained cerium oxide slurry was diluted to 0.25wt% for polishing test, as shown in Table 1, Ce 3+ The content is 32%, and the P-TEOS polishing rate is The number of polishing damages on a single wafer is 2, and the polishing rate of silicon nitride is

[0098] Example 5

[0099] Cerium oxide obtained by high-pressure homogenization, wet grinding, filtration, drying and calcination was prepared in the same manner as described in Example 1. Weigh 100 g of cerium oxide as seed crystals and disperse it in 300 g of water, stir for 30 min, add 1000 g of Ce(NO3)3·6H2O aqueous solution (38 wt%) and 1000 g of KOH aqueous solution (40 wt%), mix and stir for 30 min. Then transfer the purple slurry to a 5L flask and react at 150°C for 10 h for secondary growth. After the reactant is cooled to room temperature, 100 g of ammonium polyacrylate aqueous solution (12.5 wt%) is added, and the pH of the slurry is adjusted to 9 using KOH to obtain a cerium oxide slurry with a particle size distribution of about 93-297 nm and an average particle size of 178 nm. The specific surface area measured by BET is 15.6 m 2 / g, corresponding to a primary particle size of 54nm and an average aspect ratio of 4.4:1.

[0100] The obtained cerium oxide slurry was diluted to 0.25wt% for polishing test, as shown in Table 1, Ce 3+ The content is 30%, and the P-TEOS polishing rate is The number of polishing damages on a single wafer is 5, and the polishing rate of silicon nitride is

[0101] Comparative Example 1

[0102] 800 g of cerium carbonate was placed in a muffle furnace and calcined at 800 °C for 5 h to obtain a yellow-white cerium oxide powder. The BET measured specific surface area of ​​the powder was 2.9 m 2 / g, SEM shows that the size of the cerium oxide obtained after calcination is reduced to 1-50μm, such as Figure 5 a. Add cerium oxide to an aqueous solution of ammonium polyacrylate, wherein the solid content of cerium oxide is 10wt%, and the content of ammonium polyacrylate is 5 / 100 of the mass of cerium oxide. Use KOH to adjust the pH of the slurry to 9 and stir for 9 hours. Use a high-pressure homogenizer to refine the cerium carbonate material at a pressure of 400 bar for 20 minutes. Then use a ball mill to wet-crush the cerium carbonate slurry at a speed of 2000rpm, a zirconium bead size of 0.5mm, and a grinding time of 15 minutes. Pass the obtained cerium oxide slurry through a membrane filter with a pore size of 1μm to remove the coarse particles in the slurry to obtain cerium oxide particles with a particle size distribution of 110-312nm and an average particle size of 181nm. Further, the filtered cerium oxide slurry is centrifuged and washed, and dried at 70°C for 12 hours to obtain cerium oxide powder, whose specific surface area measured by BET is 10.6m 2 / g, TEM shows that its morphology is irregular, the average particle size is about 79nm, and the particle size distribution range is 22-111nm. Figure 5 b. Weigh 100g of cerium oxide as seed crystals and disperse them in 300g of water. Stir for 30min and add 1000g of Ce(NO3)3·6H 25 O aqueous solution (38wt%) and 1000g KOH aqueous solution (35wt%) were mixed and stirred for 30min. The purple slurry was then transferred to a 5L flask and reacted at 150°C for 10h for secondary growth. After the reactant was cooled to room temperature, 100g ammonium polyacrylate aqueous solution (12.5wt%) was added, and the pH of the slurry was adjusted to 9 using KOH to obtain a cerium oxide slurry with a particle size distribution of about 140-382nm and an average particle size of 212nm. The specific surface area measured by BET was 7.4m 2 / g, corresponding to a primary particle size of 114nm. TEM shows that the obtained cerium oxide is a quasi-circular structure with an average particle size of about 114nm and a particle size distribution of 39-153nm. Figure 5 c.

[0103] The obtained cerium oxide slurry was diluted to 0.25wt% for polishing test, as shown in Table 1, Ce 3+ The content is 24%, and the P-TEOS polishing rate is The number of polishing damages on a single wafer is 8, and the polishing rate of silicon nitride is Compared with Example 1, the polishing rate and the quality of the polished surface of the wafer in this comparative example are significantly reduced. This is because the irregular circular cerium oxide particles prepared in this comparative example are not the cerium oxide nanorods of the present invention, which mainly expose the inert {111} crystal plane. 3+ The content is low.

[0104] Comparative Example 2

[0105] 800 g of cerium carbonate was placed in a muffle furnace and calcined at 800 °C for 5 h to obtain a yellow-white cerium oxide powder. The BET specific surface area was 3.0 m 2 / g. Cerium oxide was added to an aqueous solution of ammonium polyacrylate, with a solid content of 10wt% cerium oxide and an ammonium polyacrylate content of 5 / 100 of the mass of cerium oxide. The pH of the slurry was adjusted to 9 using KOH and stirred for 9 hours. The cerium carbonate material was refined using a high-pressure homogenizer at a pressure of 400 bar for 20 minutes. The obtained cerium oxide slurry was passed through a membrane filter with a pore size of 1μm to remove coarse particles in the slurry to obtain cerium oxide particles with a particle size distribution of 200-700nm and an average particle size of 418nm. The filtered cerium oxide slurry was further centrifuged and washed, and dried at 60°C for 14h to obtain cerium oxide powder, whose specific surface area measured by BET was 7.3m 2 / g. Weigh 100g of cerium oxide as seed crystals and disperse it in 300g of water, stir for 30min, add 1000g of Ce(NO3)3·6H2O aqueous solution (38wt%) and 1000g of KOH aqueous solution (35wt%), mix and stir for 30min. Then transfer the purple slurry to a 5L flask and react at 150℃ for 10h for secondary growth. After the reactant is cooled to room temperature, add 100g of ammonium polyacrylate aqueous solution (12.5wt%), use KOH to adjust the pH of the slurry to 9, and obtain a cerium oxide slurry with a particle size distribution of about 240-834nm and an average particle size of 360nm. The specific surface area measured by BET is 5.6m 2 / g, corresponding to a primary particle size of 150nm.

[0106] The obtained cerium oxide slurry was diluted to 0.25wt% for polishing test, as shown in Table 1, Ce 3+ The content is 19%, and the P-TEOS polishing rate is The number of polishing damages on a single wafer is 21, and the polishing rate of silicon nitride is

[0107] Comparative Example 3

[0108] The nanoscale short rod-shaped cerium oxide was prepared by high-pressure homogenization, wet crushing, filtering, drying and calcining in the same manner and under the same conditions as described in Example 1, except that the nanoscale short rod-shaped cerium oxide was directly prepared into a polishing liquid without undergoing secondary growth.

[0109] 100 g of cerium oxide was weighed and added to 100 g of ammonium polyacrylate aqueous solution (12.5 wt%). The pH of the slurry was adjusted to 9 using KOH to obtain a cerium oxide slurry with a particle size distribution of about 94-374 nm and an average particle size of 136 nm. The specific surface area measured by BET was 24.0 m 2 / g, corresponding to a primary particle size of 35nm.

[0110] The obtained cerium oxide slurry was diluted to 0.25wt% for polishing test, as shown in Table 1, Ce 3+ The content is 23%, and the P-TEOS polishing rate is The number of polishing damages on a single wafer is 16, and the polishing rate of silicon nitride is

[0111] Table 1 Product performance parameters in each embodiment and comparative example

[0112]

[0113] As can be seen from the table above, the embodiment of the present invention performs secondary seed growth on the cerium oxide obtained by high-pressure homogenization, wet ball milling and calcination of cerium carbonate, and the cerium oxide particles are in the shape of nanometer rods, and the surface smoothness is improved, so that the number of wafer polishing damage is significantly reduced. Compared with the round cerium oxide, the rod-shaped cerium oxide exposes more active {100} and {110} crystal planes, which promotes the surface Ce of cerium oxide. 3+ The content of cerium oxide increases, thereby improving the oxygen vacancy and redox performance of cerium oxide. In addition, the polishing rate, selectivity and surface quality of polished wafers are significantly improved after the secondary seed growth of cerium oxide. The reasons can be attributed to two points. First, after the secondary seed growth, the increase in the length and width of cerium oxide improves its rolling friction during the polishing process and increases the contact area between cerium oxide and polishing medium silicon oxide; second, the increase in aspect ratio promotes the increase of active {100} crystal planes. 3+ These structural features also promote the improvement of polishing rate, selectivity and polished wafer surface quality.

[0114] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as limiting the present invention. Those skilled in the art will appreciate that, under the guidance of this specification, some modifications or adjustments may be made to the present invention. These modifications or adjustments should also be within the scope defined by the claims of the present invention.

Claims

1. A method for preparing cerium oxide nanorods, characterized in that: The following steps are included: 1) Dispersion: adding cerium carbonate to an aqueous solution containing an anionic surfactant, adjusting the pH of the solution to alkaline with a pH adjuster, and stirring and dispersing to form a cerium carbonate dispersion; 2) High-pressure homogenization: The cerium carbonate dispersion in step 1) is subjected to high-pressure homogenization and refinement using a high-pressure homogenizer to obtain micron-sized cerium carbonate having a rod-like structure with a length of 1-10 μm and a width of 0.5-1 μm; 3) Wet grinding: using a ball mill to wet grind the cerium carbonate dispersion in step 2) to obtain a nanoscale short rod-shaped cerium carbonate slurry of 70-400 nm; 4) high-temperature calcination: washing and drying the nanometer-scale short rod-shaped cerium carbonate slurry in step 3), and calcining at high temperature to obtain nanometer-scale short rod-shaped cerium oxide; 5) Secondary growth: The nanoscale short rod-shaped cerium oxide in step 4) is dispersed in water as a seed crystal, and cerium salt and alkali are added, mixed and stirred to obtain a purple slurry, and then the purple slurry is transferred to a reactor for secondary growth to obtain cerium oxide nanorods.

2. The preparation method according to claim 1, characterized in that: The particle size of the cerium carbonate in step 1) is 0.1-10 μm; and / or The solid content of cerium carbonate in the cerium carbonate dispersion is 10-50wt%; and / or The pH regulator is selected from at least one of KOH, NaOH, K2CO3, (NH4)2CO3, NH4HCO3, ammonia water or tetramethylammonium hydroxide; Preferably, the pH is adjusted to 8-11, preferably 8-9; Preferably, the anionic surfactant is selected from at least any one of triethanolamine dodecyl sulfate, ammonium dodecyl sulfate, triethanolamine polyoxyethylene alkyl ether sulfate, and polycarboxylic acid type polymer dispersants; More preferably, the polycarboxylic acid type polymer dispersant is a copolymer of a carboxylic acid monomer having an unsaturated double bond, a copolymer of a carboxylic acid monomer having an unsaturated double bond and a monomer having other unsaturated double bonds, and at least any one of their ammonium salts or amine salts; Further preferably, the carboxylic acid monomer having an unsaturated double bond is selected from at least any one of polyacrylic acid, ammonium polyacrylate, polymethacrylic acid, ammonium polymethacrylate, polymaleic acid, polyfumaric acid, and polyitaconic acid; and / or The anionic surfactant is selected from at least one of polyacrylic acid, ammonium polyacrylate, polymethacrylic acid or ammonium polymethacrylate; and / or The molecular weight of the anionic surfactant is 2000-10000, preferably 2000-3000; and / or The added amount of the anionic surfactant is 3 / 100-6 / 100 of the mass of cerium carbonate.

3. The preparation method according to claim 1, characterized in that: The pressure of the high-pressure homogenizer in step 2) is 300-500 bar, and the homogenization time is 10-20 min.

4. The preparation method according to claim 1, characterized in that: In step 3), the ball mill has a rotation speed of 1000-3000 rpm, preferably 1500-2200 rpm; the zirconium bead size is 0.3-0.6 mm; and the grinding time is 10-20 min.

5. The preparation method according to claim 1, characterized in that: The nanoscale short rod-shaped cerium carbonate slurry in step 4) is washed with water at a drying temperature of 50-100° C. for a drying time of 8-12 h; and / or The high temperature calcination has a calcination temperature of 600-1000°C, preferably 700-800°C, and a calcination time of 2-8h, preferably 4-6h; Preferably, the aspect ratio of the nanoscale short rod-shaped cerium oxide is 2:1 to 4:

1.

6. The preparation method according to claim 1, characterized in that: In step 5), the seed crystals are dispersed in water, and the mass ratio of the added amount of the seed crystals to the added amount of the cerium salt is 1:2 to 1:5; and / or The cerium salt is selected from any one of cerium nitrate, cerium chloride and cerium oxalate, preferably Ce(NO3)3·6H2O; the concentration of the cerium salt solution is 35-45wt%, preferably 35-40wt%; and / or The alkali is any one of KOH, NaOH and ammonia water, preferably KOH, and the concentration of KOH solution is 30-40wt%, preferably 33-37wt%; Preferably, the reaction temperature of the secondary growth is 100-180° C., preferably 130-160° C.; the reaction time of the secondary growth is 5-15 h, preferably 9-13 h; More preferably, the aspect ratio of the cerium oxide nanorods is 4.3:1 to 9:

1.

7. The cerium oxide nanorods prepared by the preparation method according to any one of claims 1 to 6, characterized in that: The aspect ratio of the cerium oxide nanorods is 4.3:1 to 9:1; Preferably, the surface Ce of the cerium oxide nanorods 3+ The content is 20-40%; more preferably, the STI polishing selectivity of the cerium oxide nanorods is not less than 30.

8. Application of the cerium oxide nanorods prepared by the preparation method according to any one of claims 1 to 6 or the cerium oxide nanorods according to claim 7 in the field of STI polishing. Preferably, the prepared cerium oxide nanorods are added to an aqueous solution containing an anionic surfactant, and the pH of the cerium oxide dispersion is adjusted to alkaline with a pH regulator to form a cerium oxide slurry. When in use, the cerium oxide slurry is diluted with deionized water and polishing can be performed.

9. The use of the cerium oxide nanorods according to claim 8 in the field of STI polishing, characterized in that: The anionic surfactant is selected from any one of triethanolamine dodecyl sulfate, ammonium dodecyl sulfate, triethanolamine polyoxyethylene alkyl ether sulfate, and polycarboxylic acid type polymer dispersant; Preferably, the polycarboxylic acid type polymer dispersant is selected from any one of a copolymer of a carboxylic acid monomer having an unsaturated double bond, a copolymer of a carboxylic acid monomer having an unsaturated double bond and a monomer having other unsaturated double bonds, and an ammonium salt or an amine salt thereof; and / or The carboxylic acid monomer having an unsaturated double bond is selected from any one of polyacrylic acid, ammonium polyacrylate, polymethacrylic acid, ammonium polymethacrylate, polymaleic acid, polyfumaric acid, and polyitaconic acid; More preferably, the molecular weight of the anionic surfactant is 2000-10000, preferably 2000-3000; and / or The mass content of the anionic surfactant in the cerium oxide slurry before dilution is 0.1-1wt% of the total mass of the cerium oxide slurry used as the polishing liquid, preferably 0.3-0.6wt%.

10. The use of the cerium oxide nanorods according to claim 8 in the field of STI polishing, characterized in that: The pH regulator is selected from at least one of KOH, NaOH, K2CO3, (NH4)2CO3, NH4HCO3, ammonia water and tetramethylammonium hydroxide; Preferably, the pH is adjusted to 8-11, preferably 8-9; Preferably, during polishing, the solid content of cerium oxide in the cerium oxide slurry is diluted to 0.1-1.0 wt %, preferably 0.1-0.5 wt %.

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