Preparation method of high-purity cerium compound

Abstract

The invention provides a preparation method of a high-purity cerium compound, and relates to the technical field of rare earth recovery. The preparation method provided by the invention comprises the following steps: dropwise adding a mixed solution of hydrogen peroxide and ammonia water into cerium feed liquid at 45-55 DEG C; and after dropwise adding is finished, carrying out heat preservation reaction at 80-100 DEG C for 0.5-5 hours, carrying out solid-liquid separation, and washing to obtain the nano cerium hydroxide. The purity of the cerium compound can be effectively improved based on peroxidation precipitation and heated aggregation separation of cerium.

Description

Technical Field

[0001] The invention relates to the technical field of rare earth recovery, and in particular to a method for preparing a high-purity cerium compound. Background Art

[0002] Chemical mechanical polishing is one of the key processes in semiconductor manufacturing, which is used to achieve local and global uniformity on the surfaces of various substrates (such as silicon dioxide, tungsten, copper, etc.), and to improve the packaging density and stacking efficiency of integrated circuits by enhancing the surface conditions of these substrates. In recent years, with the rapid development of emerging technologies such as autonomous driving, artificial intelligence (AI), 5G communications, the Internet of Things, and large-scale data processing, higher requirements have been placed on integrated circuit chip manufacturing technology. The cerium oxide polishing material used in the manufacture of integrated circuit chips needs to have a relative purity of rare earths of more than 99.99%, and there are also strict requirements on the content of alkali metals, alkaline earth metals, and non-metallic elements therein. At present, rare earth smelting, extraction and separation can obtain a cerium liquid with a purity of 95 to 99.95%. Further use of extraction and separation technology or chromatography to reduce the content of rare earth impurities such as lanthanum and increase the relative purity of cerium is costly and consuming. Therefore, it is urgent to provide a solution to improve the above problems. Summary of the invention

[0003] The object of the present invention is to provide a method for preparing a high-purity cerium compound, which can effectively improve the purity of cerium based on the peroxidation precipitation and thermal aggregation separation of cerium.

[0004] The invention provides a method for preparing a high-purity cerium compound, comprising: adding a mixed solution of hydrogen peroxide and ammonia water dropwise to a cerium liquid at 45-55°C; after the addition is completed, reacting at 80-100°C for 0.5-5h, and washing to obtain nano cerium hydroxide after solid-liquid separation.

[0005] Optionally, the cerium solution is a rare earth chloride solution or a nitrate solution with a concentration of 0.5 mol / L-5 mol / L, and the relative purity of cerium in the cerium solution is 95%-99.95%.

[0006] Optionally, the molar ratio of the rare earth element in the cerium solution to the hydrogen peroxide in the mixed solution is 1:(0.5-2.5).

[0007] Optionally, the molar ratio of the rare earth element in the cerium solution to the ammonia water in the mixed solution is 1:(1-3.4).

[0008] Optionally, the cerium solution further comprises an additive, and the additive is ammonium tartrate and / or ammonium citrate.

[0009] Optionally, the mass ratio of the additive to the rare earth element in the cerium solution is (0.2-1):100.

[0010] Optionally, the nano-cerium hydroxide is dried and then calcined at 500° C.-900° C. to obtain nano-cerium oxide.

[0011] Optionally, the nano-cerium oxide is ultrasonically dispersed in deionized water and ammonia water is added to adjust the pH to 8 to prepare a polishing slurry.

[0012] Optionally, the nano-cerium hydroxide is ultrasonically dispersed in deionized water and ammonia water is added to adjust the pH to 8 to prepare a polishing slurry. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is an analysis diagram of the effect of different initial pH values ​​of the cerium solution on the lanthanum and cerium content in cerium hydroxide in Example 1 of the present invention;

[0014] Figure 2 This is an analysis diagram of the effect of different initial pH values ​​of the cerium solution on the cerium yield in Example 2 of the present invention;

[0015] Figure 3 This is an analysis diagram of the influence of different ratios of rare earth and ammonia water in the cerium feed solution on the lanthanum and cerium content in cerium hydroxide in Example 2 of the present invention;

[0016] Figure 4 This is an analysis diagram of the influence of different ratios of rare earth and ammonia water in the cerium feed solution on the cerium yield in Example 2 of the present invention;

[0017] Figure 5 This is an analysis diagram of the influence of different ratios of rare earth and hydrogen peroxide in the cerium feed solution on the lanthanum and cerium content in cerium hydroxide in Example 3 of the present invention;

[0018] Figure 6 This is an analysis diagram of the influence of different ratios of rare earth and hydrogen peroxide in the cerium solution on the cerium yield in Example 3 of the present invention;

[0019] Figure 7 This is an analysis diagram of the influence of different ratios of rare earth and ammonium citrate in the cerium feed solution on the lanthanum and cerium content in cerium hydroxide in Example 4 of the present invention;

[0020] Figure 8 This is an analysis diagram of the influence of different proportions of rare earth, ammonium citrate and ammonium tartrate in the cerium feed solution on the lanthanum and cerium content in cerium hydroxide in Example 5 of the present invention;

[0021] Fig. 9 This is an analysis diagram of the influence of different ratios of rare earth and ammonium tartrate in the cerium feed solution on the lanthanum and cerium content in cerium hydroxide in Example 6 of the present invention;

[0022] Fig.10 This is an analysis chart showing the influence of different proportions of rare earth, ammonium citrate and ammonium tartrate in the cerium feed solution on the lanthanum and cerium content in cerium hydroxide in Example 7 of the present invention;

[0023] Fig.11 This is a TEM image of the cerium hydroxide product synthesized in Example 9 of the present invention;

[0024] Fig.12 The following are the SEM images and particle size distribution diagrams of the cerium oxide product synthesized in Example 9 of the present invention. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Unless otherwise defined, the technical terms or scientific terms used herein should be the common meanings understood by people with general skills in the field to which the present invention belongs.

[0026] The present invention provides a method for preparing a high-purity cerium compound, comprising: dripping a mixed solution of hydrogen peroxide and ammonia water into a cerium liquid at 45°C-55°C; after the dripping is completed, keeping the temperature at 80°C-100°C for a reaction for 0.5h-5h, and washing to obtain nano cerium hydroxide after solid-liquid separation. In fact, by peroxidizing the cerium liquid and heating and aggregating and separating it, high-purity nano cerium hydroxide can be obtained.

[0027] In fact, the cerium feed solution is a rare earth chloride solution with a concentration of 0.5mol / L-5mol / L, and the relative purity of cerium in the cerium feed solution is 95%-99.95%. In fact, by peroxidation precipitation of rare earth chloride solution or nitrate solution and thermal aggregation separation, the relative purity of cerium can be increased from 1N to 2N, 2N to 3N, and 3N to 4N.

[0028] In fact, when the mixed solution is added dropwise to the cerium solution, the pH of the cerium solution is adjusted to 5.5-6.5, preferably 6, using ammonia water in advance. In addition, in addition to the cerium element, the cerium solution may also include a residual amount of lanthanum element, for example, the relative purity of cerium in the cerium solution is 95%-99.95%, and the relative purity of lanthanum is 0.05%-5%.

[0029] In some embodiments, when the mixed solution is added dropwise to the cerium solution and the mixed solution is completely added dropwise, the molar ratio of the rare earth element in the cerium solution to the hydrogen peroxide in the mixed solution is 1:(0.5-2.5), and the molar ratio of the rare earth element in the cerium solution to the ammonia in the mixed solution is 1:(1-3.4).

[0030] In addition, additives may be added to the cerium solution in advance, and the additives are ammonium tartrate and / or ammonium citrate, and the mass ratio of the additives to the rare earth elements in the cerium solution is (0.2-1):100.

[0031] In some embodiments, the nano-cerium hydroxide may be dried and then calcined at 500° C.-900° C. to obtain nano-cerium oxide. In addition, the nano-cerium hydroxide or nano-cerium oxide may be ultrasonically dispersed in deionized water, and ammonia water may be added to adjust the pH to 8 to obtain a polishing slurry.

[0032] Example 1: Four 100 mL portions of cerium chloride solution (cerium relative purity 95%, lanthanum 5%) with a rare earth concentration of 1 mol / L were placed in four beakers, and 0.8 mol / L ammonia water was added dropwise under room temperature stirring to adjust the pH of the cerium solution to 2, 4, 6, and 8, respectively. The solution was then transferred to a 50°C water bath and a mixed solution (500 mL of 0.4 mol / L hydrogen peroxide and 125 mL of 0.8 mol / L ammonia water, RE 3+ : H2O2: NH3·H2O molar ratio = 1:2:1); after the addition is completed, it turns into a reddish brown suspension, and after being kept in a 90°C water bath environment for 1 hour, it turns into a milky white suspension; the milky white suspension is subjected to solid-liquid separation, and the precipitate is washed with 70°C ultrapure water to obtain a cerium hydroxide product.

[0033] ICP-Mass was used to analyze the ratio of lanthanum and cerium in cerium hydroxide products. The results are as follows: Figure 1 As shown; the supernatant of the milky white suspension was titrated with EDTA to measure the rare earth element content, and the cerium yield of the peroxidation reaction was calculated as follows: Figure 2 shown.

[0034] Example 2: Six portions of 100 mL of cerium nitrate solution (cerium relative purity 95%, lanthanum 5%) with a rare earth concentration of 1 mol / L were placed in six beakers, and 0.8 mol / L ammonia water was added dropwise under room temperature stirring to adjust the pH of the cerium solution to 6, and then the solution was transferred to a 50°C water bath and mixed solution 1 (175 mL of 0.4 mol / L hydrogen peroxide and 125 mL of 0.8 mol / L ammonia water, RE 3+ :H2O2:NH3·H2O molar ratio=1:0.7:1), mixed solution 2 (175mL of 0.4mol / L hydrogen peroxide and 187.5mL of 0.8mol / L ammonia water, RE 3+ :H2O2:NH3·H2O molar ratio=1:0.7:1.5), mixed solution 3 (175mL of 0.4mol / L hydrogen peroxide and 250mL of 0.8mol / L ammonia water, RE 3+:H2O2:NH3·H2O molar ratio=1:0.7:2), mixed solution 4 (175mL of 0.4mol / L hydrogen peroxide and 312.5mL of 0.8mol / L ammonia water, RE 3+ :H2O2:NH3·H2O molar ratio=1:0.7:2.5), mixed solution 5 (175mL of 0.4mol / L hydrogen peroxide and 375mL of 0.8mol / L ammonia water, RE 3+ :H2O2:NH3·H2O molar ratio=1:0.7:3), mixed solution 6 (175mL of 0.4mol / L hydrogen peroxide and 425mL of 0.8mol / L ammonia water, RE 3+ :H2O2:NH3·H2O molar ratio=1:0.7:3.4); after the addition is completed, it turns into a reddish brown suspension, and after being kept in an 80°C water bath environment for 5 hours, it turns into a milky white suspension; after the milky white suspension is separated from the solid and liquid, the precipitate is washed with 70°C ultrapure water to obtain a cerium hydroxide product.

[0035] ICP-Mass was used to analyze the ratio of lanthanum and cerium in cerium hydroxide products. The results are as follows: Figure 3 As shown; the supernatant of the milky white suspension was titrated with EDTA to measure the rare earth element content, and the cerium yield of the peroxidation reaction was calculated as follows: Figure 4 shown.

[0036] Example 3: Five portions of 100 mL of cerium chloride solution (cerium relative purity 95%, lanthanum 5%) with a rare earth concentration of 2 mol / L were placed in five beakers, and 0.8 mol / L ammonia water was added dropwise under room temperature stirring to adjust the pH of the cerium solution to 6, and then the solution was transferred to a 50°C water bath and mixed solution 1 (125 mL of 0.8 mol / L hydrogen peroxide and 125 mL of 1.6 mol / L ammonia water, RE 3+ :H2O2:NH3·H2O molar ratio=1:0.5:1), mixed solution 2 (250mL of 0.8mol / L hydrogen peroxide and 125mL of 1.6mol / L ammonia water, RE 3+ :H2O2:NH3·H2O molar ratio=1:1:1)、mixed solution 3 (375mL of 0.8mol / L hydrogen peroxide and 125mL of 1.6mol / L ammonia water, RE 3+ :H2O2:NH3·H2O molar ratio=1:1.5:1), mixed solution 4 (500mL of 0.8mol / L hydrogen peroxide and 125mL of 1.6mol / L ammonia water, RE 3+:H2O2:NH3·H2O molar ratio=1:2:1), ​​mixed solution 5 (625mL of 0.8mol / L hydrogen peroxide and 125mL of 1.6mol / L ammonia water, RE 3+ : H2O2: NH3·H2O molar ratio = 1:2.5:1); after the addition is completed, it turns into a reddish brown suspension, and after being kept in an 80°C water bath environment for 5 hours, it turns into a milky white suspension; the milky white suspension is subjected to solid-liquid separation and the precipitate is washed with 70°C ultrapure water to obtain a cerium hydroxide product.

[0037] ICP-Mass was used to analyze the ratio of lanthanum and cerium in cerium hydroxide products. The results are as follows: Figure 5 As shown; the supernatant of the milky white suspension was titrated with EDTA to measure the rare earth element content, and the cerium yield of the peroxidation reaction was calculated as follows: Figure 6 shown.

[0038] Example 4: Five 100 mL portions of cerium nitrate solution (cerium relative purity 95%, lanthanum 5%) with a rare earth concentration of 1 mol / L were placed in five beakers, and 0.028 g (ammonium citrate to rare earth mass ratio of 0.2:100), 0.056 g (ammonium citrate to rare earth mass ratio of 0.4:100), 0.084 g (ammonium citrate to rare earth mass ratio of 0.6:100), 0.112 g (ammonium citrate to rare earth mass ratio of 0.7:100) and 0.12 g (ammonium citrate to rare earth mass ratio of 0.6:100) were added respectively. After mixing, 0.8 mol / L ammonia water was added dropwise under room temperature stirring to adjust the pH of the cerium solution to 6, and then the solution was transferred to a 50°C water bath and the mixed solution (500 mL of 0.4 mol / L hydrogen peroxide and 125 mL of 0.8 mol / L ammonia water, RE) was added dropwise under stirring. 3+ : H2O2: NH3·H2O molar ratio = 1:2:1); after the addition is completed, it turns into a reddish brown suspension, and after being kept in a 90°C water bath environment for 1 hour, it turns into a milky white suspension; the milky white suspension is subjected to solid-liquid separation, and the precipitate is washed with 70°C ultrapure water to obtain a cerium hydroxide product.

[0039] ICP-Mass was used to analyze the ratio of lanthanum and cerium in cerium hydroxide products. The results are as follows: Figure 7 As shown; the supernatant of the milky white suspension was titrated with EDTA to measure the rare earth element content therein, and the cerium yield of the peroxidation reaction was calculated to be 54%-55%.

[0040] Example 5: Four 100 mL portions of cerium chloride solution (cerium relative purity 95%, lanthanum 5%) with a rare earth concentration of 0.5 mol / L were placed in four beakers, 0.042 g of ammonium citrate was added and stirred to dissolve, and then 0.014 g (ammonium tartrate, ammonium citrate, rare earth mass ratio of 0.2:0.6:100), 0.028 g (ammonium tartrate, ammonium citrate, rare earth mass ratio of 0.4:0.6:100), 0.042 g (ammonium tartrate, ammonium citrate, rare earth mass ratio of 0.03:0.6:100) were added respectively. After mixing, 0.56 g (ammonium tartrate, ammonium citrate, rare earth mass ratio is 0.8:0.6:100) ammonium tartrate was added dropwise with 0.8 mol / L ammonia water under room temperature stirring environment to adjust the pH of the cerium solution to 6, and then transferred to a 50°C water bath environment and the mixed solution (500 mL of 0.2 mol / L hydrogen peroxide and 125 mL of 0.4 mol / L ammonia water, RE 3+ : H2O2: NH3·H2O molar ratio = 1:2:1); after the addition is completed, it turns into a reddish brown suspension, and after being kept in a 90°C water bath environment for 1 hour, it turns into a milky white suspension; the milky white suspension is subjected to solid-liquid separation, and the precipitate is washed with 70°C ultrapure water to obtain a cerium hydroxide product.

[0041] ICP-Mass was used to analyze the ratio of lanthanum and cerium in cerium hydroxide products. The results are as follows: Figure 8 As shown; the supernatant of the milky white suspension was titrated with EDTA to measure the rare earth element content therein, and the cerium yield of the peroxidation reaction was calculated to be 54%-55%.

[0042] Example 6: Five 100 mL portions of cerium nitrate solution (cerium relative purity 99.5%, lanthanum 0.5%) with a rare earth concentration of 1 mol / L were placed in five beakers, and 0.028 g (ammonium tartrate to rare earth mass ratio 0.2:100), 0.056 g (ammonium tartrate to rare earth mass ratio 0.4:100), 0.084 g (ammonium tartrate to rare earth mass ratio 0.6:100), 0.112 g (ammonium tartrate to rare earth mass ratio 0.6:100) and 0.12 g (ammonium tartrate to rare earth mass ratio 0.6:100) were added respectively. After mixing, 0.8 mol / L ammonia water was added dropwise under room temperature stirring to adjust the pH of the cerium solution to 6, and then the solution was transferred to a 50°C water bath and the mixed solution (400 mL of 0.4 mol / L hydrogen peroxide and 187.5 mL of 0.8 mol / L ammonia water, RE) was added dropwise under stirring. 3+:H2O2:NH3·H2O molar ratio=1:1.6:1.5); after the addition is completed, it turns into a reddish brown suspension, and after being kept in a 95℃ water bath environment for 1h, it turns into a milky white suspension; after the milky white suspension is separated from the solid and liquid, the precipitate is washed with 70℃ ultrapure water to obtain a cerium hydroxide product.

[0043] ICP-Mass was used to analyze the ratio of lanthanum and cerium in cerium hydroxide products. The results are as follows: Fig. 9 As shown; the supernatant of the milky white suspension was titrated with EDTA to measure the rare earth element content therein, and the cerium yield of the peroxidation reaction was calculated to be 71%-72%.

[0044] Example 7: Four 100 mL portions of cerium chloride solution (cerium relative purity 99.5%, lanthanum 0.5%) with a rare earth concentration of 1.5 mol / L were placed in four beakers, 0.126 g of ammonium tartrate was added and stirred to dissolve, and then 0.042 g (ammonium tartrate, ammonium citrate, rare earth mass ratio of 0.6:0.2:100), 0.084 g (ammonium tartrate, ammonium citrate, rare earth mass ratio of 0.6:0.4:100), 0.126 g (ammonium tartrate, ammonium citrate, rare earth mass ratio of 0.6:0.4:100) were added respectively. After the cerium solution was dissolved by stirring, 0.8 mol / L ammonia water was added dropwise under room temperature stirring to adjust the pH of the cerium solution to 6, and then the solution was transferred to a 50°C water bath and a mixed solution (500 mL of 0.6 mol / L hydrogen peroxide and 125 mL of 1.2 mol / L ammonia water) was added dropwise under stirring. 3+ : H2O2: NH3·H2O molar ratio = 1:2:1); after the addition is completed, it turns into a reddish brown suspension, and after being kept in a 90°C water bath environment for 3 hours, it turns into a milky white suspension; the milky white suspension is subjected to solid-liquid separation, and the precipitate is washed with 70°C ultrapure water to obtain a cerium hydroxide product.

[0045] ICP-Mass was used to analyze the ratio of lanthanum and cerium in cerium hydroxide products. The results are as follows: Fig.10 As shown; the supernatant of the milky white suspension was titrated with EDTA to measure the rare earth element content therein, and the cerium yield of the peroxidation reaction was calculated to be 54%-55%.

[0046] Example 8: 300 mL of cerium nitrate solution with a rare earth concentration of 1 mol / L (cerium relative purity 99.95%, lanthanum 0.05%) was placed in a double-layer glass reactor, 0.252 g of ammonium tartrate (the mass ratio of ammonium tartrate to rare earth was 0.6:100) was added and stirred, and then 0.8 mol / L ammonia water was added dropwise under room temperature stirring to adjust the pH of the cerium solution to 6, and the circulating water temperature of the reactor was raised to 50°C, and the mixed solution (1650 mL of 0.4 mol hydrogen peroxide and 375 mL of 0.8 mol / L ammonia water, RE 3+ :H2O2:NH3·H2O molar ratio=1:2.2:1); after the addition is completed, it turns into a reddish brown suspension, and the circulating water temperature of the reactor is adjusted to 90℃ and kept warm for 3h before turning into a milky white suspension; after the milky white suspension is separated into solid and liquid, it is washed with 70℃ ultrapure water to obtain a cerium hydroxide product, which is dried at 70℃ and calcined at 700℃ to obtain cerium oxide. The content of rare earth impurities, sodium, potassium, magnesium, iron, aluminum and other impurities in cerium oxide is tested, and the results are shown in Table 1 below. It can be seen from Table 1 that the purity of the product CeO2 is greater than 99.995%, and the yield of cerium is 53.55%.

[0047] Table 1 Composition analysis of cerium oxide product in Example 8 (unit %)

[0048]

[0049]

[0050] Example 9: 300 mL of cerium chloride solution with a rare earth concentration of 1 mol / L (cerium relative purity 99.95%, lanthanum 0.05%) was placed in a double-layer glass reactor, 0.252 g of ammonium tartrate and 0.252 g of ammonium citrate (the mass ratio of ammonium tartrate, ammonium citrate to rare earth was 0.6:0.6:100) were added and stirred, and then 0.8 mol / L ammonia water was added dropwise under room temperature stirring to adjust the pH of the cerium solution to 6, and the circulating water temperature of the reactor was raised to 50°C, and the mixed solution (1650 mL of 0.4 mol hydrogen peroxide and 375 mL of 0.8 mol / L ammonia water, RE 3+: H2O2: NH3·H2O molar ratio = 1:2.2:1); after the addition is completed, it turns into a reddish brown suspension. The circulating water temperature of the reactor is adjusted to 85°C and kept warm for 5 hours before turning into a milky white suspension; the milky white suspension is subjected to solid-liquid separation and then washed with 70°C ultrapure water to obtain a cerium hydroxide product, which is dried at 80°C and calcined at 900°C to obtain cerium oxide. The content of rare earth impurities, sodium, potassium, magnesium, iron, aluminum and other impurities in cerium oxide is detected, and the results are shown in Table 2 below. It can be seen from Table 2 that the purity of the product CeO2 is greater than 99.996%, and the yield of cerium is 53.67%. The cerium hydroxide product obtained in Example 9 was characterized by TEM as shown in the following table. Fig.11 As shown, the cerium oxide product was characterized by SEM. Fig.12 shown.

[0051] Table 2 Composition analysis of cerium oxide product in Example 9 (unit %)

[0052] <![CDATA[La2O3 / TREO]]> <![CDATA[CeO2 / TREO]]> <![CDATA[Pr6O 11 / HANGING]]> <![CDATA[Nd2O3 / TREO]]> <![CDATA[Sm2O3 / TREO]]> 0.0031 >99.996 <0.00005 <0.00002 <0.00002 <![CDATA[Eu2O3 / TREO]]> <![CDATA[Gd2O3 / TREO]]> <![CDATA[Tb4O7 / TREO]]> <![CDATA[Dy2O3 / TREO]]> <![CDATA[Ho2O3 / TREO]]> <0.00002 <0.00005 <0.00005 <0.00002 <0.00002 <![CDATA[Er2O3 / TREO]]> <![CDATA[Tm2O3 / TREO]]> <![CDATA[Yb2O3 / TREO]]> <![CDATA[Lu2O3 / TREO]]> <![CDATA[Y2O3 / TREO]]> <0.00002 <0.00002 <0.00002 <0.00002 <0.00002 sodium Potassium magnesium iron aluminum <0.0005 <0.0005 <0.0001 <0.0004 <0.0003

[0053] Example 10: The cerium hydroxide product and cerium oxide product prepared in Example 9 were respectively prepared with deionized water into polishing slurries with different contents, and K9 glass was polished on an Engis EJW-400In polishing machine. Test conditions: room temperature, LP66-1.5 polishing pad, carrier speed 150rpm, pressure 3psi, slurry flow rate 26mL / min, polishing time 30min. The polished surface quality was observed with an optical microscope, and the surface roughness was measured with a surface profiler. The surface roughness of the K9 workpiece before polishing was 1.106nm, and the results are shown in Table 3 below.

[0054] The material removal rate (MRR) is calculated according to the following formula: MRR (nm / min) = (m0-m) / (ρts); where m0 is the mass of the workpiece material before polishing (g), m is the mass of the workpiece material after polishing (g), ρ is the density of K9 material, t is the polishing time (min), and s is the contact area between the workpiece material and the polishing pad (cm 2 ).

[0055] Table 3 Polishing slurry polishing effect

[0056]

[0057] Although the embodiments of the present invention are described in detail above, it is obvious to those skilled in the art that various modifications and variations can be made to these embodiments. However, it should be understood that such modifications and variations are within the scope and spirit of the present invention as described in the claims. Moreover, the present invention described herein may have other embodiments and may be implemented or realized in a variety of ways.

Claims

1. A method for preparing a high-purity cerium compound, characterized in that: include: A mixed solution of hydrogen peroxide and ammonia water is added dropwise to the cerium liquid at 45°C-55°C; after the addition is completed, the mixture is kept at 80°C-100°C for 0.5h-5h, and the nano-cerium hydroxide is obtained by washing after solid-liquid separation.

2. The preparation method according to claim 1, characterized in that: The cerium solution is a rare earth chloride solution or a nitrate solution with a concentration of 0.5 mol / L-5 mol / L, and the relative purity of cerium in the cerium solution is 95%-99.95%.

3. The preparation method according to claim 2, characterized in that: The molar ratio of the rare earth element in the cerium solution to the hydrogen peroxide in the mixed solution is 1:(0.5-2.5); and / or the molar ratio of the rare earth element in the cerium solution to the ammonia in the mixed solution is 1:(1-3.4).

4. The preparation method according to claim 2, characterized in that: The cerium solution also includes an additive, which is ammonium tartrate and / or ammonium citrate.

5. The preparation method according to claim 4, characterized in that: The mass ratio of the additive to the rare earth element in the cerium solution is (0.2-1):

100.

6. The preparation method according to claim 1, characterized in that: The nano cerium hydroxide is dried and then calcined at 500° C.-900° C. to obtain nano cerium oxide.

7. The preparation method according to claim 6, characterized in that: The nano-cerium oxide is ultrasonically dispersed in deionized water and ammonia water is added to adjust the pH to 8 to prepare a polishing slurry.

8. The preparation method according to any one of claims 1 to 5, characterized in that: The nano-cerium hydroxide is ultrasonically dispersed in deionized water and ammonia water is added to adjust the pH to 8 to prepare a polishing slurry.

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