Preparation method of spherical cerium oxide

Abstract

In order to overcome the problem of low sphericity yield in the existing cerium oxide preparation method, the invention provides a preparation method of spherical cerium oxide, which comprises the following operation steps: a dropwise adding process: dropwise adding a precipitant solution into a cerium source solution to obtain a reaction solution; a reaction process: heating the reaction liquid, and reacting to obtain a precursor precipitate; the dropwise adding process and the reaction process meet the following conditions: pH < = 9.5, 0.3 < = c1 < = 0.8, and 80 < = t < = 200; wherein A is a constant, and is defined as 1900.24; the pH is the pH value of the cerium source solution in the dropwise adding process; c1 is the molar concentration of the cerium element in the cerium source solution, and the unit is mol / L; t is the temperature of the reaction liquid, and the unit is DEG C; and roasting the precursor precipitate to obtain the spherical cerium oxide. The preparation method of the spherical cerium oxide, provided by the invention, is beneficial to improving the sphericity of the prepared spherical cerium oxide through multi-condition synergy.

Description

Technical Field

[0001] This invention belongs to the field of cerium oxide preparation technology, and specifically relates to a method for preparing spherical cerium oxide. Background Technology

[0002] With the diversification and high integration of semiconductor devices, their surface structures are becoming increasingly complex. The planarity between layers in each process is a crucial factor in improving photolithography accuracy. In semiconductor device manufacturing, chemical mechanical polishing (CMP) is used for global planarization. For example, it's used to planarize ILD (interlayer barrier) as the material filling the space between silicon and the first metal interconnect, and to planarize STI (shallow trench isolation) for chip-to-chip insulation. Compared to traditional polishing slurries, CeO2 abrasive polishing slurries offer advantages such as high polishing efficiency, good surface finish, and long lifespan, making them an indispensable material for advanced process film polishing. In CMP (Chemical Metallurgy) processes, polishing quality, surface roughness (Ra), and the absence of scratches after polishing are key application indicators. The abrasive grain properties in the cerium oxide polishing slurry are crucial factors affecting performance, with the morphology of cerium oxide abrasive grains having a significant impact. Spherical morphologies result in better polishing quality, lower roughness, and fewer scratches. Conversely, angular morphologies (such as blocky, rod-shaped, or needle-shaped grains) are less effective than spherical grains, leading to increased roughness and scratches. For advanced semiconductor CMP processes, high polishing quality, low roughness, and no scratches are required; therefore, spherical morphology is the optimal choice. However, the cerium oxide synthesis process involves multiple steps, and various parameters influence the final cerium oxide morphology, leading to significant uncertainties and a low sphericity yield. Therefore, precisely controlling the morphology of cerium oxide abrasive grains to achieve spherical shapes is a critical problem that needs to be solved. Summary of the Invention

[0003] To address the issue of poor sphericity in existing cerium oxide preparation methods, this invention provides a method for preparing spherical cerium oxide.

[0004] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: This invention provides a method for preparing spherical cerium oxide, comprising the following steps: Droplet addition process: A precipitant solution is added dropwise to the cerium source solution to obtain a reaction solution; Reaction process: The reaction solution is heated, and the reaction yields a precursor precipitate; The dropwise addition process and the reaction process must satisfy the following conditions: And pH≤9.5, 0.3≤c1≤0.8, 80≤t≤200; Where A is a constant, defined as 190024; pH refers to the pH value of the cerium source solution during the dropwise addition process; c1 is the molar concentration of cerium in the cerium source solution, in mol / L; t is the temperature of the reaction solution, in °C; The precursor precipitate was calcined to obtain spherical cerium oxide.

[0005] Optionally, the dropping process and the reaction process must satisfy the following conditions: .

[0006] Optionally, the pH of the cerium source solution during the dropwise addition process is 4.6 to 9.5.

[0007] Optionally, the molar concentration c1 of cerium in the cerium source solution is 0.4~0.6 mol / L.

[0008] Optionally, the temperature t of the reaction solution is 110℃~150℃.

[0009] Optionally, the duration of the dropping process is 0.01~1h, the molar concentration of the precipitant in the precipitant solution is 0.1~1mol / L, the molar ratio of the precipitant to the cerium source in the cerium source solution is (0.4~0.6):(0.4~1), and the molar concentration of the precipitant in the precipitant solution is greater than or equal to the molar concentration of the cerium source in the cerium source solution.

[0010] Optionally, the precipitant solution includes one or more of the following: urea solution, ammonia water, ammonium carbonate solution, ammonium bicarbonate solution, carbonic acid solution, and organic amine solution.

[0011] Optionally, the cerium source includes one or more of cerium chloride, cerium nitrate, cerium carbonate, cerium sulfate, and cerium ammonium nitrate.

[0012] Optionally, the reaction duration is 1 to 24 hours.

[0013] Optionally, after the precursor precipitate is obtained from the reaction, it is subjected to solid-liquid separation treatment, and then dried to obtain the precursor precipitate.

[0014] According to the method for preparing spherical cerium oxide provided by the present invention, a precursor precipitate is formed by dropwise addition of a precipitant solution to a cerium source solution, followed by calcination to obtain spherical cerium oxide. To ensure the sphericity of the prepared spherical cerium oxide, the inventors conducted extensive experiments on several key control parameters during the preparation process and discovered that the pH value of the cerium source solution, the temperature t of the reaction solution, and the molar concentration c1 of cerium in the cerium source solution have interrelated effects on the morphology of cerium oxide. Specifically, by controlling the pH value of the cerium source solution, the temperature t of the reaction solution, and the molar concentration c1 of cerium in the cerium source solution to meet certain conditions... Furthermore, pH≤9.5, 0.3≤c1≤0.8, and 80≤t≤200 can effectively improve the sphericity of the prepared spherical cerium oxide. It is speculated that under these conditions, spherical crystal nuclei can be formed during the nucleation of the precursor precipitate, while maintaining its initial morphology as much as possible during the growth period, ultimately controlling the morphology of the precursor precipitate to be spherical. Attached Figure Description

[0015] Figure 1 This is a SEM image of cerium oxide synthesized in Example 1 of the present invention; Figure 2 This is a SEM image of cerium oxide synthesized in Example 5 of the present invention; Figure 3 This is a SEM image of cerium oxide synthesized in Example 6 of the present invention; Figure 4 This is a SEM image of the cerium oxide synthesized in Comparative Example 1 provided by the present invention. Detailed Implementation

[0016] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0017] This invention provides a method for preparing spherical cerium oxide, comprising the following steps: Droplet addition process: A precipitant solution is added dropwise to the cerium source solution to obtain a reaction solution; Reaction process: The reaction solution is heated, and the reaction yields a precursor precipitate; The dropwise addition process and the reaction process must satisfy the following conditions: And pH≤9.5, 0.3≤c1≤0.8, 80≤t≤200; Where A is a constant, defined as 190024; pH refers to the pH value of the cerium source solution during the dropwise addition process; c1 is the molar concentration of cerium in the cerium source solution, in mol / L; t is the temperature of the reaction solution, in °C; The precursor precipitate was calcined to obtain spherical cerium oxide.

[0018] The cerium oxide and the precursor precipitate maintain good consistency in morphology before and after calcination. Therefore, the sphericity of the precursor precipitate itself is directly related to the sphericity of the final cerium oxide. The preparation process of the precursor precipitate is divided into two stages. The first stage is the dropwise addition process, which is mainly used to form the crystal nuclei of the precursor precipitate. The second stage is the reaction process, which is used for the growth of the precursor precipitate. Theoretically, when the precursor precipitate is generated, the growth will tend to grow along the {111} and {100} planes with the lowest energy. The resulting product should be a polyhedral structure with sharp edges. However, according to the principle of spontaneous homogenization of grains and the principle of minimum energy, the nascent grains will tend to shrink their surface as much as possible to reduce their surface energy, that is, to move towards the formation of spherical particles. The conditions provided for the formation of spherical precursor precipitates can be achieved by adjusting environmental factors to make the precursor precipitate form a spherical structure.

[0019] To ensure the sphericity of the prepared spherical cerium oxide, the inventors conducted extensive experiments on several key control parameters during the preparation process. They discovered a correlation between the pH value of the cerium source solution, the temperature t of the reaction solution, and the molar concentration c1 of cerium in the cerium source solution during the dropwise addition process, all of which have an impact on the morphology of the cerium oxide. Specifically, by controlling the pH value of the cerium source solution, the temperature t of the reaction solution, and the molar concentration c1 of cerium in the cerium source solution to meet certain conditions... Furthermore, pH≤9.5, 0.3≤c1≤0.8, and 80≤t≤200 can effectively improve the sphericity of the prepared spherical cerium oxide. It is speculated that under these conditions, spherical crystal nuclei can be formed during the nucleation of the precursor precipitate, while maintaining its initial morphology as much as possible during the growth period, ultimately controlling the morphology of the precursor precipitate to be spherical.

[0020] In a preferred embodiment, the dropping process and the reaction process satisfy the following conditions: .

[0021] When the pH value of the cerium source solution, the temperature t of the reaction solution, and the molar concentration c1 of cerium in the cerium source solution further satisfy the above conditions during the dropwise addition, it is beneficial to further ensure the sphericity of the prepared cerium oxide. Specifically, when The closer the value is to 0, the higher the sphericity of the cerium oxide obtained.

[0022] In a specific embodiment, the pH value of the cerium source solution during the dropwise addition process can be 4, 4.3, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 7.8, 8, 8.5, 9, or 9.5.

[0023] In some preferred embodiments, the pH of the cerium source solution is 4.6 to 9.5 during the dropwise addition process.

[0024] Since the precipitant solution added during the dropping process usually has a different pH value than the cerium source solution, the pH value of the cerium source solution needs to be continuously monitored during the dropping process. The pH value of the cerium source solution is then adjusted by controlling the dropping rate of the precipitant solution and the formation rate of precursor precipitate nuclei to maintain the stability of the precursor precipitate nucleus formation environment. This helps to control the supersaturation stability of the precursor precipitate during the formation of precursor precipitate nuclei and form spherical nuclei.

[0025] In a specific embodiment, the molar concentration c1 of cerium in the cerium source solution can be 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, or 0.8 mol / L.

[0026] In some preferred embodiments, the molar concentration c1 of cerium in the cerium source solution is 0.4~0.6 mol / L.

[0027] The molar concentration c1 of cerium in the cerium source solution affects the supersaturation of the precursor precipitate, which in turn has a significant impact on the formation rate of crystal nuclei during the dropping process and the growth rate of crystals during the reaction. By adapting the molar concentration c1 of cerium in the cerium source solution to the pH value of the cerium source solution during the dropping process, the formation rate and morphology of crystal nuclei can be controlled significantly. When the molar concentration c1 of cerium in the cerium source solution is within the above-mentioned range, it is beneficial to improve the sphericity of the crystal nuclei morphology during the dropping process and the crystal growth morphology during the reaction.

[0028] In a specific embodiment, the temperature t of the reaction solution can be 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃ or 200℃.

[0029] In some preferred embodiments, the temperature t of the reaction solution is 110°C to 150°C.

[0030] During the reaction, the temperature t of the reaction solution has a significant impact on the growth rate of the precursor precipitate. When the temperature t of the reaction solution is within the above-mentioned range, it is beneficial to increase the growth rate of the precursor precipitate while avoiding the problem of crystal deformation caused by excessively rapid growth.

[0031] In some embodiments, the solvents for both the cerium source solution and the precipitant solution are selected from water.

[0032] In some embodiments, the duration of the dropping process is 0.01-1 h, the molar concentration of the precipitant in the precipitant solution is 0.1-1 mol / L, the molar ratio of the precipitant to the cerium source in the cerium source solution is (0.4-0.6):(0.4-1), and the molar concentration of the precipitant in the precipitant solution is greater than or equal to the molar concentration of the cerium source in the cerium source solution.

[0033] In some embodiments, the precipitant solution includes one or more of urea solution, ammonia water, ammonium carbonate solution, ammonium bicarbonate solution, carbonic acid solution, and organic amine solution.

[0034] In some embodiments, the cerium source includes one or more of cerium chloride, cerium nitrate, cerium carbonate, cerium sulfate, and cerium ammonium nitrate.

[0035] In some embodiments, the reaction duration is 1 to 24 hours.

[0036] If the reaction duration is too short, the raw materials cannot be fully utilized, resulting in material waste, and the resulting cerium oxide particles are too small to meet the requirements for use as polishing slurry particles. If the reaction duration is too long, on the one hand, it leads to a decrease in production efficiency, and on the other hand, it can easily affect the sphericity of the precursor precipitate, resulting in problems such as excessively large particle size.

[0037] In some embodiments, after the precursor precipitate is obtained from the reaction, it is subjected to solid-liquid separation treatment, and then dried to obtain the precursor precipitate.

[0038] In some embodiments, the solid-liquid separation process includes one or more of filtration, centrifugation, and distillation.

[0039] The drying operation employs hot air drying, with the temperature of the hot air being 100℃~200℃. Preferably, the temperature of the hot air is 110℃~150℃.

[0040] In some embodiments, the calcination temperature of the precursor precipitate is 400°C to 1000°C.

[0041] Another embodiment of the present invention provides spherical cerium oxide prepared by the preparation method described above.

[0042] Another embodiment of the present invention provides a polishing fluid comprising a solvent and spherical cerium oxide prepared by the preparation method described above.

[0043] The present invention will be further illustrated by the following examples.

[0044] Table 1 Example 1 This embodiment illustrates the preparation method of spherical cerium oxide disclosed in this invention, including the following steps: Step 1, Dropping process: Dissolve the cerium source in water to prepare a cerium source solution; dissolve the precipitant in water to prepare a precipitant solution with a molar concentration of 0.6 mol / L; drop the precipitant solution into the cerium source solution, continuously monitoring the pH of the cerium source solution during the addition process and controlling the dropping rate to stabilize the pH of the cerium source solution. The molar ratio of the precipitant to the cerium source in the cerium source solution is 2:3. After the dropping is completed, a reaction solution is obtained. The selection of the cerium source and precipitant, the molar concentration of the cerium source solution, and the pH value of the cerium source solution are shown in Table 1.

[0045] Step 2, Reaction process: The reaction solution is heated in a hydrothermal reactor at the temperature shown in Table 1. The reaction duration is 12 hours. The precursor precipitate is obtained by the reaction. The precursor precipitate is filtered, washed with water and dried. Step 3: Place the precursor precipitate in a muffle furnace and calcine it at a temperature of 800℃ to obtain spherical cerium oxide.

[0046] Examples 2-18 Examples 2-18 illustrate the method for preparing spherical cerium oxide disclosed in this invention, including most of the operational steps in Example 1, with the following differences: The selection of cerium source and precipitant during the dropwise addition process, the molar concentration of the precipitant, the molar concentration of the cerium source solution, the pH value of the cerium source solution, the reaction time, and the reaction temperature during the reaction process are shown in Examples 2-18 of Table 1.

[0047] Comparative Examples 1-9 Comparative Examples 1-9 are used to illustrate the preparation method of cerium oxide disclosed in this invention, including most of the operational steps in Example 1, with the following differences: The selection of cerium source and precipitant, the molar concentration of the precipitant, the molar concentration of the cerium source solution, the pH value of the cerium source solution, the reaction time, and the reaction temperature during the reaction process are shown in Comparative Examples 1 to 9 in Table 1.

[0048] Performance testing The cerium oxide prepared above was subjected to the following tests: 1. Electron microscopy was performed on the cerium oxide synthesized in Examples 1, 5, 6 and Comparative Example 1. The observation results are as follows: Figures 1-4 As shown, the cerium oxide prepared by the preparation method provided by the present invention has a relatively regular spherical structure, while the cerium oxide prepared by Comparative Example 1 has an inconsistent morphology and tends to form angular particles.

[0049] 2. The sphericity of the cerium oxide prepared in Examples 1-18 and Comparative Examples 1-9 was tested.

[0050] The sphericity test and calculation method is as follows: Divide the SEM image into 4 regions according to the center point, and randomly select one particle in each region to measure its diameter 4 times (test along the four lines X=0, Y=0, Y=X, Y=-X). Calculate the relative standard deviation (RSD) of the test results of a single particle, and then calculate the average value of the RSD of each particle test. According to the test results, if the average RSD is ≤2%, it is spherical.

[0051] (1) The test results obtained from Examples 1-13 and Comparative Examples 1-9 are filled in Table 2.

[0052] Table 2 The test results from Examples 1-13 and Comparative Examples 1-9 show that the pH value of the cerium source solution, the temperature t of the reaction solution, and the molar concentration c1 of cerium in the cerium source solution have a significant correlation in affecting the morphology of cerium oxide during the dropwise addition process. The relationship between these factors is as follows: Furthermore, when pH ≤ 9.5, 0.3 ≤ c1 ≤ 0.8, and 80 ≤ t ≤ 200, the obtained cerium oxide exhibits superior sphericity. It is speculated that under these conditions, spherical nuclei can be formed during the nucleation of the precursor precipitate, and the initial morphology can be maintained as much as possible during the growth period by controlling these conditions, ultimately resulting in a spherical morphology of the precursor precipitate.

[0053] The test results from Examples 1-13 show that when the pH value of the cerium source solution, the temperature t of the reaction solution, and the molar concentration c1 of cerium in the cerium source solution further meet the conditions... The cerium oxide obtained has the best sphericity when 4.6≤pH≤9.5, 0.4≤c1≤0.6, and 110≤t≤150.

[0054] The test results from Comparative Examples 1 to 9 show that when pH, t, and c1 values ​​do not meet the requirements... When the pH value of the cerium source solution, the temperature t of the reaction solution, and the molar concentration c1 of cerium in the cerium source solution are all limited, the morphology of cerium oxide will be deteriorated. This indicates that there is an interaction between the pH value of the cerium source solution, the temperature t of the reaction solution, and the molar concentration c1 of cerium in the cerium source solution. Only when the three reach a good equilibrium can the morphology of cerium oxide be significantly improved.

[0055] (2) The test results obtained from Examples 1, 14-18 and Comparative Examples 1, 6-9 are filled in Table 2.

[0056] Table 2 The test results of Examples 1, 14-18 and Comparative Examples 1, 6-9 show that in the operating system provided by this invention, different cerium sources and different precipitants are used, and the pH value of the cerium source solution, the temperature t of the reaction solution, and the molar concentration c1 of cerium in the cerium source solution meet the following conditions: Furthermore, when pH≤9.5, 0.3≤c1≤0.8, and 80≤t≤200, the obtained cerium oxide all exhibit good sphericity, indicating that the preparation method provided by this invention is universally applicable to different cerium sources and precipitants.

[0057] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for producing a spherical cerium oxide, characterized by, The method comprises the following steps: The dropwise adding process: dropwise adding a precipitant solution into a cerium source solution to obtain a reaction liquid; The reaction process: heating the reaction liquid to obtain a precursor precipitate; The dropwise adding process and the reaction process meet the following conditions: and pH < 9.5, 0.3 < c1 < 0.8, 80 < t < 200; Wherein, A is a constant, defined as 1900.24; pH is the pH value of the cerium source solution in the dropwise adding process; c1 is the molar concentration of cerium in the cerium source solution, in mol / L; t is the temperature of the reaction liquid, in ℃; The precursor precipitate is calcined to obtain spherical cerium oxide.

2. The method for producing spherical cerium oxide according to claim 1, characterized by, The dropwise adding process and the reaction process meet the following conditions: 。 3. The method of claim 1, wherein the ceria particles have a D50 of 0.1 to 10 μm. The pH value of the cerium source solution in the dropwise adding process is 4.6-9.

5.

4. The method of claim 1, wherein the ceria particles have a D50 of 0.1 to 10 μm. The molar concentration c1 of cerium in the cerium source solution is 0.4-0.6 mol / L.

5. The method of claim 1, wherein the ceria particles have a D50 of 0.5 to 5 μm. The temperature t of the reaction liquid is 110-150 ℃.

6. The method of claim 1, wherein the ceria particles have a D50 of 0.5 to 5 μm. The duration of the dropwise adding process is 0.01-1 h, the molar concentration of the precipitant in the precipitant solution is 0.3-1 mol / L, the molar ratio of the precipitant to the cerium source in the cerium source solution is (0.4-0.6):(0.4-1), and the molar concentration of the precipitant in the precipitant solution is greater than or equal to the molar concentration of the cerium source in the cerium source solution.

7. The method of claim 1, wherein the ceria particles have a D50 of 0.5 to 5 μm. The precipitant solution comprises one or more of urea solution, ammonia water, ammonium carbonate solution, ammonium bicarbonate solution, carbonic acid solution and organic amine solution.

8. The method of claim 1, wherein the ceria particles have a D50 of 0.5 to 5 μm. The cerium source comprises one or more of cerium chloride, cerium nitrate, cerium carbonate, cerium sulfate and cerium ammonium nitrate.

9. The method of claim 1, wherein the ceria particles have a D50 of 0.5 to 5 μm. In the reaction process, the reaction duration is 1-24 h.

10. The method of claim 1, wherein the ceria particles have a D50 of 0.5 to 5 μm. After the reaction obtains the precursor precipitate, solid-liquid separation treatment is performed, and after the solid-liquid separation, drying is performed to obtain the precursor precipitate.

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