A method for synthesizing cerium oxide nanoparticles and a chemical mechanical polishing liquid
By synthesizing cerium oxide nanoparticles through doping with metal ions, the problem of insufficient polishing activity in cerium oxide polishing slurry was solved, achieving a high polishing rate and uniform particle size distribution, and avoiding particle agglomeration caused by high-temperature calcination.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ANJI MICROELECTRONICS TECH (SHANGHAI) CO LTD
- Filing Date
- 2024-12-26
- Publication Date
- 2026-06-26
AI Technical Summary
Existing technologies are insufficient to meet the stringent requirements of STI-CMP in advanced semiconductor manufacturing processes. The polishing activity of cerium oxide polishing slurry is insufficient, and the high-temperature calcination process leads to severe particle agglomeration.
Cerium oxide nanoparticles were synthesized by doping with at least two metal ions. The crystallization reaction was carried out by mixing a cerium salt aqueous solution with a multivalent metal salt solution and then purifying the nanoparticles at low temperature and normal pressure, avoiding high-temperature calcination.
It increases the number of oxygen vacancies on the surface of cerium oxide particles, improves their reactivity with silicon oxide substrate, reduces particle agglomeration, increases polishing rate, and improves particle size distribution uniformity.
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Figure BDA0005210272470000051 
Figure BDA0005210272470000052
Abstract
Description
Technical Field
[0001] This invention relates to the field of chemical mechanical polishing, and more particularly to a method for synthesizing cerium oxide nanoparticles and a chemical mechanical polishing fluid. Background Technology
[0002] Chemical mechanical polishing (CMP) is a crucial technological step in integrated circuit manufacturing. Cerium oxide, a common nano-abrasive particle, possesses abundant crystal defects on its surface, effectively enhancing its reactivity with silicon oxide substrates. Therefore, cerium oxide polishing slurries are widely used in polishing processes such as STI and ILD.
[0003] To meet the stringent requirements of STI-CMP technology in advanced semiconductor manufacturing processes, there is an urgent need for a cerium oxide synthesis method with high polishing activity. Summary of the Invention
[0004] The purpose of this invention is to provide a method for synthesizing cerium oxide nanoparticles, comprising the following steps: S1: preparing an aqueous solution of cerium salt, adding two polyvalent metal salt solutions to it and mixing them evenly to obtain solution A; S2: preparing precipitant B in a closed reaction vessel, then rapidly adding solution A to B and stirring vigorously; S3: heating to T1 to carry out a crystallization reaction, with a reaction time of t1; S4: after cooling, performing purification and dispersion treatments to obtain cerium oxide nanoparticles.
[0005] Furthermore, in S1, the cerium salt aqueous solution is cerium nitrate, cerium chloride, and cerium sulfate.
[0006] Furthermore, in S1, one of the polyvalent metal salts includes a rare earth metal element, and the other includes a non-rare earth metal element.
[0007] Furthermore, the rare earth metal element is selected from one or more of praseodymium, neodymium, and samarium.
[0008] Furthermore, the non-rare earth metal element is selected from one or more of yttrium, manganese, aluminum, nickel, zirconium, strontium, and bismuth.
[0009] Furthermore, in S1, the molar ratio of any polyvalent metal ion to cerium ion is 0.1 / 100-1 / 100.
[0010] Furthermore, the molar ratio of A to B is (1 / 3.5) - (1 / 8).
[0011] Furthermore, the concentration of A is 0.2 mol / L-1.0 mol / L; the concentration of B is 1.0-5.0 mol / L.
[0012] Furthermore, T1 is 50℃-95℃.
[0013] Furthermore, t1 is 5h-24h.
[0014] Furthermore, the purification process is a desalting process, which involves washing the system three times with deionized water to reduce the concentration of soluble impurity ions. The system is then dispersed to obtain a nano-cerium oxide dispersion.
[0015] The present invention also discloses a chemical mechanical polishing fluid comprising cerium oxide nanoparticles prepared by any of the methods described above.
[0016] Compared with existing technologies, the above technical solution has the following advantages:
[0017] 1. This invention effectively increases the number of oxygen vacancies on the surface of cerium oxide particles by doping with at least two metal ions, thereby enhancing their reactivity with silicon oxide substrate and significantly improving the polishing rate.
[0018] 2. The synthesis reaction of the present invention is carried out at low temperature and normal pressure, and there is no calcination process, so the degree of particle agglomeration is greatly reduced and the size is more uniform. Detailed Implementation
[0019] The advantages of the present invention will be further illustrated below with reference to specific embodiments.
[0020] Based on the reactants and their concentrations shown in Table 1, cerium oxide was synthesized in Examples 1-8 and Comparative Examples 1-2. These examples are intended to illustrate specific embodiments of the invention, but the scope of protection of the invention is not limited to the following examples. Specific synthesis conditions are exemplified below:
[0021] Example 1
[0022] Weigh 90.61g of ammonia water (commercially available ammonia water with a concentration of about 30%), and dilute it with deionized water to 533g for later use; weigh 171.1g of cerium nitrate hexahydrate, 1.53g of yttrium nitrate hexahydrate, and 0.25g of manganese chloride, and dissolve them in 1000g of deionized water under stirring for later use.
[0023] Cerium salt solution was rapidly added to ammonia water under stirring at room temperature. The reaction system temperature was then raised to 70°C, and the reaction was carried out for a total of 10 hours with stirring throughout. After 10 hours, the heating was turned off, and the mixture was allowed to cool naturally to room temperature. The resulting precipitate was washed three times with deionized water, and then dispersed to obtain cerium oxide nanoparticles.
[0024] Example 2
[0025] Weigh 226.4g of ammonia water (commercially available ammonia water concentration of about 30%), dilute it with deionized water to 800g and set aside; weigh 195.8g of cerium chloride, 0.11g of aluminum chloride, and 2.09g of praseodymium nitrate hexahydrate, dissolve them in 1000g of deionized water under stirring and set aside.
[0026] Cerium salt solution was rapidly added to ammonia water under stirring at room temperature. The reaction system temperature was then raised to 90°C, and the reaction was carried out for a total of 6 hours with stirring throughout. After 6 hours, the heating was turned off, and the mixture was allowed to cool naturally to room temperature. The resulting precipitate was washed three times with deionized water, and then dispersed to obtain cerium oxide nanoparticles.
[0027] Example 3
[0028] Weigh 39.2g of potassium hydroxide solid and dissolve it in 700g of deionized water under stirring. Weigh 111.9g of cerium sulfate, 0.61g of yttrium sulfate octahydrate, and 0.30g of manganese sulfate and dissolve them in 1000g of deionized water under stirring.
[0029] Cerium salt solution was rapidly added to potassium hydroxide solution under stirring at room temperature. The reaction system temperature was then raised to 95°C, and the reaction was carried out for a total of 8 hours with stirring throughout. After 8 hours, the heating was turned off, and the mixture was allowed to cool naturally to room temperature. The resulting precipitate was washed three times with deionized water, and then dispersed to obtain cerium oxide nanoparticles.
[0030] Example 4
[0031] Weigh 170g of ammonia water (commercially available ammonia water with a concentration of about 30%) and dilute it with deionized water to 2000g for later use; weigh 213.2g of cerium nitrate hexahydrate, 1.45g of nickel nitrate hexahydrate, and 1.75g of neodymium nitrate hexahydrate, and dissolve them in 1000g of deionized water under stirring for later use.
[0032] Cerium salt solution was rapidly added to ammonia water under stirring at room temperature. The reaction system temperature was then raised to 65°C, and the reaction was carried out for a total of 12 hours with stirring throughout. After 12 hours, the heating was turned off, and the mixture was allowed to cool naturally to room temperature. The resulting precipitate was washed three times with deionized water, and then dispersed to obtain cerium oxide nanoparticles.
[0033] Example 5
[0034] Weigh 448g of potassium hydroxide solid and dissolve it in 1600g of deionized water under stirring. Weigh 241.53g of cerium chloride, 2.33g of zirconium chloride, and 3.15g of bismuth chloride and dissolve them in 1000g of deionized water under stirring.
[0035] Cerium salt solution was rapidly added to potassium hydroxide solution under stirring at room temperature. The reaction system temperature was then raised to 60°C, and the reaction was carried out for a total of 5 hours with stirring throughout. After 5 hours, the heating was turned off, and the mixture was allowed to cool naturally to room temperature. The resulting precipitate was washed three times with deionized water, and then dispersed to obtain cerium oxide nanoparticles.
[0036] Example 6
[0037] Weigh 198.33g of ammonia water (commercially available ammonia water concentration of about 30%) and dilute it with deionized water to 1166g for later use; weigh 561.6g of cerium sulfate, 2.67g of samarium nitrate hexahydrate, and 1.84g of strontium sulfate and dissolve them in 1000g of deionized water under stirring for later use.
[0038] Cerium salt solution was rapidly added to ammonia water under stirring at room temperature. The reaction system temperature was then raised to 50°C, and the reaction was carried out for a total of 24 hours with stirring throughout. After 24 hours, the heating was turned off, and the mixture was allowed to cool naturally to room temperature. The resulting precipitate was washed three times with deionized water, and then dispersed to obtain cerium oxide nanoparticles.
[0039] Example 7
[0040] Weigh 117.6g of potassium hydroxide solid and dissolve it in 420g of deionized water under stirring. Weigh 254.15g of cerium nitrate hexahydrate, 4.39g of yttrium sulfate octahydrate, and 3.13g of praseodymium nitrate hexahydrate and dissolve them in 1000g of deionized water under stirring.
[0041] Cerium salt solution was rapidly added to ammonia water under stirring at room temperature. The reaction system temperature was then raised to 85°C, and the reaction was carried out for a total of 6 hours with stirring throughout. After 6 hours, the heating was turned off, and the mixture was allowed to cool naturally to room temperature. The resulting precipitate was washed three times with deionized water, and then dispersed to obtain cerium oxide nanoparticles.
[0042] Example 8
[0043] Weigh 272.16g of ammonia water (commercially available ammonia water with a concentration of about 30%) and dilute it with deionized water to 9600g for later use; weigh 515.83g of cerium nitrate hexahydrate, 0.23g of yttrium nitrate hexahydrate, and 0.76g of manganese chloride and dissolve them in 1000g of deionized water under stirring for later use.
[0044] Cerium salt solution was rapidly added to ammonia water under stirring at room temperature. The reaction system temperature was then raised to 70°C, and the reaction time was 15 hours, with stirring maintained throughout. After 24 hours, heating was turned off, and the mixture was allowed to cool naturally to room temperature. The resulting precipitate was washed three times with deionized water, followed by dispersion treatment to obtain cerium oxide nanoparticles.
[0045] Comparative Example 1
[0046] Weigh 90.6g of ammonia water (commercially available ammonia water with a concentration of about 30%) and dilute it with deionized water to 533g for later use; weigh 171.95g of cerium nitrate hexahydrate and 1.53g of yttrium nitrate hexahydrate and dissolve them in 1000g of deionized water under stirring for later use.
[0047] Cerium salt solution was rapidly added to ammonia water under stirring at room temperature. The reaction system temperature was then raised to 70°C, and the reaction was carried out for a total of 12 hours with stirring throughout. After 12 hours, the heating was turned off, and the mixture was allowed to cool naturally to room temperature. The resulting precipitate was washed three times with deionized water, and then dispersed to obtain cerium oxide nanoparticles.
[0048] Comparative Example 2
[0049] Weigh 272.04g of ammonia water (commercially available ammonia water with a concentration of about 30%) and dilute it with deionized water to 1200g for later use; weigh 197.18g of cerium chloride and dissolve it in 1000g of deionized water under stirring for later use.
[0050] Cerium salt solution was rapidly added to ammonia water under stirring at room temperature. The reaction system temperature was then raised to 60°C, and the reaction was carried out for a total of 10 hours with stirring throughout. After 10 hours, the heating was turned off, and the mixture was allowed to cool naturally to room temperature. The resulting precipitate was washed three times with deionized water, and then dispersed to obtain cerium oxide nanoparticles.
[0051] Table 1. Components and proportions of the embodiments and comparative examples of the present invention.
[0052]
[0053] The examples and comparative examples in Table 1 were prepared as cerium oxide polishing slurries with a solid content of 1 wt%. The pH of the system was adjusted to 4.5 ± 0.1, and the polishing rate of TEOS blank wafers was tested under different pressure conditions. Specific polishing conditions were set as follows:
[0054] 1. Polishing machine: Mirra
[0055] 2. Polishing pad: IC1000
[0056] 3. Plattern speed: 93 rpm; Carrier speed: 87 rpm
[0057] 4. Polishing pressure: 3.0 psi
[0058] 5. Polishing slurry flow rate: 150 ml / min
[0059] 6. Polishing time: 60s
[0060] Table 2. Polishing results of cerium oxide dispersions in Examples 1-6 and Comparative Examples 1-2.
[0061]
[0062] As can be seen from the data in Table 2, compared with Comparative Example 1 (single element doping) and Comparative Example 2 (no doping), Examples 1-6 containing two element dopings have better polishing activity.
[0063] As can be seen from Example 7, when the ratio of any doped metal ion concentration to cerium ion concentration is 1.2 / 100, which is outside the preferred molar ratio range of this application, the polishing rate decreases.
[0064] As can be seen from Example 8, the polishing rate also decreases when the concentrations of solution A and B are outside the preferred range of this application.
[0065] The co-doped cerium oxide particles synthesized by this invention can effectively improve polishing activity. The synthesis reaction can be carried out at low temperature and normal pressure, which makes the process safer. There is no high-temperature calcination process for powder, which effectively improves the uniformity of particle size distribution.
[0066] It should be noted that the embodiments of the present invention have better implementability and are not intended to limit the present invention in any way. Any person skilled in the art may use the above-disclosed technical content to change or modify it into equivalent effective embodiments. However, any modifications or equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of the technical solution of the present invention.
Claims
1. A method for synthesizing cerium oxide nanoparticles, characterized in that, Includes the following steps: S1: Prepare an aqueous solution of cerium salt, add two polyvalent metal salt solutions to it and mix them evenly to obtain solution A; S2: Prepare precipitant B in a closed reaction vessel, then quickly add solution A to B and stir vigorously; S3: Heat to T1 to carry out the crystallization reaction, and the reaction time is t1; S4: After cooling, purification and dispersion processes are performed to obtain cerium oxide nanoparticles.
2. The method as described in claim 1, characterized in that, In S1, the cerium salt aqueous solution is cerium nitrate, cerium chloride, and cerium sulfate.
3. The method as described in claim 1, characterized in that, In S1, one of the polyvalent metal salts includes a rare earth metal element, and the other includes a non-rare earth metal element.
4. The method as described in claim 3, characterized in that, The rare earth metal element is selected from one or more of praseodymium, neodymium, and samarium.
5. The method as described in claim 1, characterized in that, The non-rare earth metal element is selected from one or more of yttrium, manganese, aluminum, nickel, zirconium, strontium, and bismuth.
6. The method as described in claim 1, characterized in that, In S1, the molar ratio of any polyvalent metal ion to cerium ions is 0.1 / 100-1 / 100.
7. The method as described in claim 1, characterized in that, The molar ratio of A to B is (1 / 3.5) - (1 / 8).
8. The method as described in claim 7, characterized in that, The concentration of A is 0.2 mol / L-1.0 mol / L; the concentration of B is 1.0 mol / L-5.0 mol / L.
9. The method as described in claim 1, characterized in that, T1 is 50℃-95℃.
10. The method as described in claim 1, characterized in that, t1 is 5h-24h.
11. The method as described in claim 1, characterized in that, The purification process is a desalting process.
12. A chemical mechanical polishing slurry, characterized in that, Including cerium oxide nanoparticles prepared by the method of any one of claims 1-11.