Method for preparing cerium hydroxide dispersion liquid and cerium hydroxide particle dispersion liquid

Abstract

According to the preparation method, cerium hydroxide with positive charges and without charge treatment on the surface is subjected to ultrasonic oscillation, so that a polymer or monomer containing negative charges and cerium hydroxide particles form coordinate bonds, first layer coating on the surface is realized, and surface charges are reversed into negative charges. Coating for the second time, adding a polymer with weak positive charges, polymerizing ion pairs through charge attraction, realizing secondary charge reversal and changing into positive charges. The invention discloses a method for repeatedly coating the surface of a cerium hydroxide particle, the electrical property of the coated cerium hydroxide particle is not changed, and the defect, namely particle adhesion, generated by mechanical force in the polishing process can be greatly reduced, so that the yield of a product is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to a preparation method of a cerium hydroxide dispersion liquid and a chemical mechanical polishing liquid comprising the cerium hydroxide particle dispersion liquid. BACKGROUND

[0002] The cerium hydroxide abrasive particles are prepared by a sol method, and the surface thereof is generally not subjected to charge treatment and is positively charged. In polishing, the wafer surface generally adsorbs a large number of particles. If, like the sol-type cerium oxide particles, the thickness of the coating layer on the surface of the cerium hydroxide particles is increased by using two different polymer molecules to achieve a polyion pair through charge attraction without changing the electrical property of the particles, the coating layer on the surface of the particles becomes a multilayer of molecules containing different components (inorganic-organic composite material). Theoretically, increasing the thickness of the coating layer on the surface of the cerium hydroxide particles (hard shell and soft core) reduces the mechanical collision force of the particles on the wafer surface, like putting a multilayer thick clothes on the surface of a metal ball to reduce the defects due to mechanical force, i.e., particle adhesion. However, the particle size of the sol-type cerium hydroxide particles is only 15-20 nm, and the surface modification is relatively difficult due to the small particle size. There is no report on the multiple coating of the surface of the cerium hydroxide particles. SUMMARY

[0003] In view of the above technical problems, the present application discloses a method for multiple coating of the surface of cerium hydroxide particles. The coated cerium hydroxide particles do not change the electrical property of the particles, and can greatly reduce the defects due to mechanical force in the polishing process, i.e., particle adhesion, thereby improving the yield of the product. Specifically, the present application provides a preparation method for secondary reverse of the surface charge of cerium hydroxide particles and its polishing application.

[0004] One aspect of the present application discloses a preparation method of a cerium hydroxide particle dispersion liquid, comprising:

[0005] S1: preparing a negative charge cerium hydroxide particle dispersion liquid: preparing a solution containing a multivalent phosphoric acid or carboxylate-based negative charge polymer or monomer, adding an alkaline pH adjuster to adjust the pH, adding the cerium hydroxide particle dispersion liquid under stirring, stirring for at least T1, transferring the solution to an ultrasonic tank, and ultrasonicating until the particles are dispersed; obtaining a negative charge cerium hydroxide particle dispersion liquid R1;

[0006] S2: preparing a positive charge cerium hydroxide particle dispersion liquid: preparing a solution of a positive charge polymer, adding R1 under stirring, stirring for at least T2, transferring the solution to an ultrasonic tank, adding an acidic pH adjuster to adjust the pH after the solution is clear, and continuously ultrasonicating until the clear liquid is maintained; obtaining a positive charge cerium hydroxide particle dispersion liquid R2.

[0007] Further, the negatively charged polymer or monomer containing polyphosphoric acid or carboxylate is polyphosphoric acid, phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, hydroxyethylidene diphosphonic acid, citric acid, diammonium hydrogen citrate, ammonium citrate.

[0008] Further, the positively charged polymer is a weakly positively charged polymer of primary or secondary amine-HCl.

[0009] Further, the positively charged polymer is PEI-HCl (Mw=10000), PAA-HCl-03 (Mw=3000), PAA-HCl-3L (Mw=15000), PAA-D19-HCl (Mw=40000), PAA-D11-HCl (Mw=100000).

[0010] Further, the concentration of the negatively charged polymer containing polyphosphoric acid or carboxylate in R1 is 0.05%-0.5%.

[0011] Further, the concentration of the positively charged polymer in R2 is 0.1-1.0%.

[0012] Further, the concentration of cerium hydroxide particles in R2 is 0.5-1.0%.

[0013] Further, in S1, the pH is adjusted to 7-9; in S2, the pH is adjusted to 2-6.

[0014] Further, in S1, T1=30-60 minutes; in S2, T2=30-60 minutes.

[0015] Further, in S1, the basic pH adjuster is selected from KOH, ammonia, imidazole.

[0016] Further, in S2, the acidic pH adjuster is selected from HNO3, acetic acid, picolinic acid.

[0017] Another aspect of the present application also discloses a cerium hydroxide polishing solution obtained by any of the above methods, characterized in that the solid content of cerium hydroxide in R2 is less than 2wt%.

[0018] The present application also discloses a method for using the cerium hydroxide particle dispersion liquid, and the application method of the above any cerium hydroxide particle dispersion liquid for polishing silicon oxide.

[0019] Sol-type cerium hydroxide abrasive particles typically have an untreated surface and carry a positive charge. To reduce the mechanical impact force between the abrasive particles and the polished surface without altering the particle's intrinsic electrical properties, cerium hydroxide can be coated with two different molecules. This coating is achieved through a second charge reversal. This invention uses ultrasonic vibration to allow negatively charged polymers or monomers to form coordination bonds with the cerium hydroxide particles, achieving the first layer of surface coating and reversing the surface charge to negative. The second coating involves adding a weakly positively charged polymer; through charge attraction, polymeric ion pairs are formed, achieving a second charge reversal and converting the particles to a positive charge.

[0020] Compared with existing technologies, the above technical solution has the following advantages: when surface-treated cerium hydroxide is used for polishing, it greatly reduces defects caused by mechanical force during the polishing process, such as particle adhesion, thereby improving the product yield. Detailed Implementation

[0021] The advantages of the present invention will be further illustrated below with reference to specific embodiments.

[0022] Comparative sample A: 2% cerium hydroxide (particle size measured by light scattering was 20 nm) was diluted with deionized water to form a 1% dispersion, pH 4.5.

[0023] Comparative Sample B1: 1.0 g of 50% polyphosphoric acid was added to 499.0 g of deionized water. The pH was adjusted using KOH. Then, 500 g of 2% cerium hydroxide (particle size measured by light scattering was 20 nm) was added with stirring. The mixture was stirred for at least 30 minutes. The solution was then transferred to a 20 kHz ultrasonic bath and sonicated until the particles were dispersed. The final solution contained 1% cerium hydroxide, 0.05% polyphosphoric acid, and had a pH of 8.5.

[0024] Comparative Sample B2: 3.0 g of 50% polyphosphoric acid was added to 497.0 g of deionized water, adjusted with KOH, and then 500 g of 2% cerium hydroxide (particle size measured by light scattering, 20 nm) was added with stirring. The mixture was stirred for at least 30 minutes, then transferred to a 20 kHz ultrasonic bath and sonicated until the particles were dispersed. The final solution contained 1% cerium hydroxide, 0.15% polyphosphoric acid, and pH 8.6.

[0025] Comparative Sample B3: 10.0 g of 50% polyphosphoric acid was added to 490.0 g of deionized water, adjusted with KOH, and then 500 g of 2% cerium hydroxide (particle size measured by light scattering, 20 nm) was added with stirring. The mixture was stirred for at least 30 minutes, then transferred to a 20 kHz ultrasonic bath and sonicated until the particles were dispersed. The final solution contained 1% cerium hydroxide, 0.5% polyphosphoric acid, and pH 9.0.

[0026] Comparative samples C1a-C1c: 0.5 g of 99% phosphoric acid / ammonium dihydrogen phosphate / diammonium hydrogen phosphate was added to 499.5 g of deionized water. The pH was adjusted using imidazole. Then, 500 g of 2% cerium hydroxide (particle size measured by light scattering, 20 nm) was added with stirring. The mixture was stirred for at least 30 minutes. The solution was then transferred to a 20 kHz ultrasonic bath and sonicated until the particles were dispersed. The final solution contained 1% cerium hydroxide, 0.05% phosphoric acid / ammonium dihydrogen phosphate / diammonium hydrogen phosphate, and pH 7.4.

[0027] Comparative samples C2a-C2c: 1.5 g of 99% phosphoric acid / ammonium dihydrogen phosphate / diammonium hydrogen phosphate was added to 498.5 g of deionized water. The pH was adjusted using imidazole. Then, 500 g of 2% cerium hydroxide (particle size measured by light scattering, 20 nm) was added with stirring. The mixture was stirred for at least 30 minutes, and the solution was transferred to a 20 kHz ultrasonic bath and sonicated until the particles were dispersed. The final solution contained 1% cerium hydroxide, 0.15% phosphoric acid / ammonium dihydrogen phosphate / diammonium hydrogen phosphate, and pH 7.5.

[0028] Comparative samples C3a-C3c: 5.0 g of 99% phosphoric acid / ammonium dihydrogen phosphate / diammonium hydrogen phosphate was added to 495.0 g of deionized water. The pH was adjusted using imidazole. Then, 500 g of 2% cerium hydroxide (particle size measured by light scattering, 20 nm) was added with stirring. The mixture was stirred for at least 30 minutes. The solution was then transferred to a 20 kHz ultrasonic bath and sonicated until the particles were dispersed. The final solution contained 1% cerium hydroxide, 0.5% phosphoric acid / ammonium dihydrogen phosphate / diammonium hydrogen phosphate, and pH 8.0.

[0029] Comparative sample D1: 0.5 g of 98% hydroxyethylidene diphosphonic acid was added to 499.5 g of deionized water. The pH was adjusted using imidazole, and then 500 g of 2% cerium hydroxide (particle size measured by light scattering, 20 nm) was added with stirring. The mixture was stirred for at least 30 minutes, and then transferred to a 20 kHz ultrasonic bath and sonicated until the particles were dispersed. The final solution contained 1% cerium hydroxide, 0.05% hydroxyethylidene diphosphonic acid, and had a pH of 8.1.

[0030] Comparative sample D2: 3.0 g of 98% hydroxyethylidene diphosphonic acid was added to 497.0 g of deionized water. The pH was adjusted using imidazole. Then, 500 g of 2% cerium hydroxide (particle size measured by light scattering was 20 nm) was added with stirring. The mixture was stirred for at least 30 minutes, and the solution was transferred to a 20 kHz ultrasonic bath and sonicated until the particles were dispersed. The final solution contained 1% cerium hydroxide, 0.3% hydroxyethylidene diphosphonic acid, and pH 8.4.

[0031] Comparative sample D3: 5.0 g of 98% hydroxyethylidene diphosphonic acid was added to 495.0 g of deionized water. The pH was adjusted using imidazole. Then, 500 g of 2% cerium hydroxide (particle size measured by light scattering was 20 nm) was added with stirring. The mixture was stirred for at least 30 minutes, then transferred to a 20 kHz ultrasonic bath and sonicated until the particles were dispersed. The final solution contained 1% cerium hydroxide, 0.5% hydroxyethylidene diphosphonic acid, and had a pH of 8.6.

[0032] Comparative samples E1a-E1c: 0.5 g of 99% citric acid / diammonium hydrogen citrate / ammonium citrate was added to 499.5 g of deionized water. The pH was adjusted using ammonia. Then, 500 g of 2% cerium hydroxide (particle size measured by light scattering was 20 nm) was added with stirring. The mixture was stirred for at least 30 minutes. The solution was then transferred to a 20 kHz ultrasonic bath and sonicated until the particles were dispersed. The final solution contained 1% cerium hydroxide, 0.05% citric acid / diammonium hydrogen citrate / ammonium citrate, and had a pH of 7.0.

[0033] Comparative samples E2a-E2c: 2.0 g of 99% citric acid / diammonium hydrogen citrate / ammonium citrate was added to 498.0 g of deionized water. The pH was adjusted using ammonia. Then, 500 g of 2% cerium hydroxide (particle size measured by light scattering was 20 nm) was added with stirring. The mixture was stirred for at least 30 minutes. The solution was then transferred to a 20 kHz ultrasonic bath and sonicated until the particles were dispersed. The final solution contained 1% cerium hydroxide, 0.2% citric acid / diammonium hydrogen citrate / ammonium citrate, and had a pH of 7.3.

[0034] Comparative samples E3a-E3c: 5.0 g of 99% citric acid / diammonium hydrogen citrate / ammonium citrate was added to 495.0 g of deionized water. The pH was adjusted using ammonia. Then, 500 g of 2% cerium hydroxide (particle size measured by light scattering, 20 nm) was added with stirring. The mixture was stirred for at least 30 minutes. The solution was then transferred to a 20 kHz ultrasonic bath and sonicated until the particles were dispersed. The final solution contained 1% cerium hydroxide, 0.5% citric acid / diammonium hydrogen citrate / ammonium citrate, and had a pH of 7.9.

[0035] The zeta potential and particle size of cerium hydroxide particles before and after surface treatment are listed in Table 1.

[0036] Comparative sample A shows the surface charge (zeta = +45 mV) and particle size (size = 20 nm) of cerium hydroxide particles before surface treatment, when they are stable. When polyphosphoric acid (a polyphosphate polymer, comparative sample B) is added, the zeta potential becomes less than -30 mV, and the particles do not show significant growth after three weeks. Similarly, when phosphoric acid / ammonium dihydrogen phosphate / diammonium hydrogen phosphate / hydroxyethylidene diphosphonic acid (polyphosphate monomers, comparative samples C and D) are added, both the zeta potential and particle size remain stable. When citric acid / diammonium hydrogen citrate / ammonium citrate (polycarboxylic acid monomers, comparative sample E) is added, the zeta potential is less than -30 mV, and the particles do not show significant growth after three weeks.

[0037] Polyphosphoric acid, phosphoric acid / diammonium dihydrogen phosphate / diammonium hydrogen phosphate, hydroxyethylidene diphosphonic acid, and citric acid / diammonium hydrogen citrate / ammonium citrate can all induce the first charge reversal on the surface of cerium hydroxide particles while maintaining sol stability. We preferred the control samples E2b (containing polycarboxylate groups) and B2 (containing polyphosphate groups) to induce the second charge reversal, respectively.

[0038] Invention sample A1: 1.0 g of 99% PEI-HCl was added to 499.0 g of deionized water, followed by the addition of 500.0 g of control sample E2b under stirring. The mixture was stirred for at least 30 minutes, then transferred to a 20 kHz ultrasonic bath. After the colloid clarified, the pH was adjusted with acetic acid, and ultrasonic dispersion was continued until the clarified solution remained. Ultimately, the sample contained 0.5% cerium hydroxide, 0.1% diammonium hydrogen citrate, and 0.1% PEI-HCl, at pH 2.0. The particles remained stable with a zeta potential of +40 Mv.

[0039] Inventive sample A2: 2.0 g of 99% PEI-HCl was added to 498.0 g of deionized water, followed by 500.0 g of control sample E2b under stirring. The mixture was stirred for at least 30 minutes, then transferred to a 20 kHz ultrasonic bath. After the colloid clarified, the pH was adjusted with acetic acid, and ultrasonic dispersion was continued until the clear solution remained. Ultimately, the sample contained 0.5% cerium hydroxide, 0.1% diammonium hydrogen citrate, and 0.2% PEI-HCl, with a pH of 3.4. The particles remained stable with a zeta potential of +42 Mv.

[0040] Invention sample A3: 10.0 g of 99% PEI-HCl was added to 490.0 g of deionized water, followed by 500.0 g of control sample E2b under stirring. The mixture was stirred for at least 30 minutes, then transferred to a 20 kHz ultrasonic bath. After the colloid clarified, the pH was adjusted with acetic acid, and ultrasonic dispersion was continued until the clear solution remained. Ultimately, the sample contained 0.5% cerium hydroxide, 0.1% diammonium hydrogen citrate, and 1.0% PEI-HCl, at pH 4.0. The particles remained stable with a zeta potential of +43 Mv.

[0041] Invention sample B1a: 2.5 g of 40% PAA-HCl-O3 was added to 497.5 g of deionized water, followed by the addition of 500.0 g of control sample E2b under stirring. The mixture was stirred for at least 30 minutes, then transferred to a 20 kHz ultrasonic bath. After the colloid clarified, the pH was adjusted with HNO3, and ultrasonic dispersion was continued until the clarified solution remained. Ultimately, the sample contained 0.5% cerium hydroxide, 0.1% diammonium hydrogen citrate, and 0.1% PAA-HCl-O3, at pH 3.0. The particles remained stable with a zeta potential of +42 Mv.

[0042] Invention sample B1b: 5.0 g of 40% PAA-HCl-O3 was added to 495.0 g of deionized water, followed by 500.0 g of control sample E2b under stirring. The mixture was stirred for at least 30 minutes, then transferred to a 20 kHz ultrasonic bath. After the colloid clarified, the pH was adjusted with HNO3, and ultrasonic dispersion was continued until a clear solution was maintained. Ultimately, the sample contained 0.5% cerium hydroxide, 0.1% diammonium hydrogen citrate, and 0.2% PAA-HCl-O3, with a pH of 4.2. The particles remained stable with a zeta potential of +38 Mv.

[0043] 25.0 g of 40% PAA-HCl-O3 (inventory sample B1c) was added to 475.0 g of deionized water, followed by 500.0 g of control sample E2b under stirring. The mixture was stirred for at least 30 minutes, then transferred to a 20 kHz ultrasonic bath. After the colloid clarified, the pH was adjusted with HNO3, and ultrasonic dispersion was continued until a clear solution was maintained. Ultimately, the sample contained 0.5% cerium hydroxide, 0.1% diammonium hydrogen citrate, and 1.0% PAA-HCl-O3, at pH 5.0. The particles remained stable with a zeta potential of +35 mV.

[0044] Invention sample B2a: 2.0 g of 50% PAA-HCl-3 L was added to 498.0 g of deionized water, followed by 500.0 g of control sample E2b under stirring. The mixture was stirred for at least 30 minutes, then transferred to a 20 kHz ultrasonic bath. After the colloid clarified, the pH was adjusted with HNO3, and ultrasonic dispersion was continued until a clear solution was maintained. Ultimately, the sample contained 0.5% cerium hydroxide, 0.1% diammonium hydrogen citrate, and 0.1% PAA-HCl-3 L, at pH 3.0. The particles remained stable, and the zeta potential became +45 mV.

[0045] Invention sample B2b: 4.0 g of 50% PAA-HCl-3 L was added to 496.0 g of deionized water, followed by 500.0 g of control sample E2b under stirring. The mixture was stirred for at least 30 minutes, then transferred to a 20 kHz ultrasonic bath. After the colloid clarified, the pH was adjusted with HNO3, and ultrasonic dispersion was continued until a clear solution was maintained. Ultimately, the sample contained 0.5% cerium hydroxide, 0.1% diammonium hydrogen citrate, and 0.2% PAA-HCl-3 L, at pH 4.2. The particles remained stable, and the zeta potential became +48 mV.

[0046] Invention sample B2c: 20.0 g of 50% PAA-HCl-3 L was added to 480.0 g of deionized water, followed by 500.0 g of control sample E2b under stirring. The mixture was stirred for at least 30 minutes, then transferred to a 20 kHz ultrasonic bath. After the colloid clarified, the pH was adjusted with HNO3, and ultrasonic dispersion was continued until a clear solution was maintained. Ultimately, the sample contained 0.5% cerium hydroxide, 0.1% diammonium hydrogen citrate, and 1.0% PAA-HCl-3 L, at pH 5.0. The particles remained stable, and the zeta potential became +48 mV.

[0047] Invention sample C1a: 5.0 g of 21% PAA-D19-HCl was added to 495.0 g of deionized water, followed by 500.0 g of control sample E2b under stirring. The mixture was stirred for at least 30 minutes, then transferred to a 20 kHz ultrasonic bath. After the colloid clarified, the pH was adjusted with HNO3, and ultrasonic dispersion was continued until the clear solution remained. Ultimately, the sample contained 0.5% cerium hydroxide, 0.1% diammonium hydrogen citrate, and 0.1% PAA-D19-HCl, at pH 4.0. The particles remained stable, and the zeta potential became +40 mV.

[0048] Invention sample C1b: 9.5 g of 21% PAA-D19-HCl was added to 490.5 g of deionized water, followed by the addition of 500.0 g of control sample E2b under stirring. The mixture was stirred for at least 30 minutes, then transferred to a 20 kHz ultrasonic bath. After the colloid clarified, the pH was adjusted with HNO3, and ultrasonic dispersion was continued until a clear solution was maintained. Ultimately, the sample contained 0.5% cerium hydroxide, 0.1% diammonium hydrogen citrate, and 0.2% PAA-D19-HCl, at pH 5.3. The particles remained stable, and the zeta potential became +48 mV.

[0049] Invention sample C1c: 50.0 g of 21% PAA-D19-HCl was added to 450.0 g of deionized water, followed by 500.0 g of control sample E2b under stirring. The mixture was stirred for at least 30 minutes, then transferred to a 20 kHz ultrasonic bath. After the colloid clarified, the pH was adjusted with HNO3, and ultrasonic dispersion was continued until a clear solution was maintained. Ultimately, the sample contained 0.5% cerium hydroxide, 0.1% diammonium hydrogen citrate, and 1.0% PAA-D19-HCl, at pH 6.0. The particles remained stable, and the zeta potential became +44 mV.

[0050] Invention sample C2a: 2.5 g of 40% PAA-D11-HCl was added to 497.5 g of deionized water, followed by 500.0 g of control sample E2b under stirring. The mixture was stirred for at least 30 minutes, then transferred to a 20 kHz ultrasonic bath. After the colloid clarified, the pH was adjusted with HNO3, and ultrasonic dispersion was continued until the clear solution remained. Ultimately, the sample contained 0.5% cerium hydroxide, 0.1% diammonium hydrogen citrate, and 0.1% PAA-D11-HCl, at pH 4.0. The particles remained stable, and the zeta potential became +48 mV.

[0051] Invention sample C2b: 5.0 g of 40% PAA-D11-HCl was added to 495.0 g of deionized water, followed by 500.0 g of control sample E2b under stirring. The mixture was stirred for at least 30 minutes, then transferred to a 20 kHz ultrasonic bath. After the colloid clarified, the pH was adjusted with HNO3, and ultrasonic dispersion was continued until a clear solution was maintained. Ultimately, the sample contained 0.5% cerium hydroxide, 0.1% diammonium hydrogen citrate, and 0.2% PAA-D11-HCl, at pH 5.3. The particles remained stable, and the zeta potential became +50 mV.

[0052] Invention sample C2c: 25.0 g of 40% PAA-D11-HCl was added to 475.0 g of deionized water, followed by the addition of 500.0 g of control sample E2b under stirring. The mixture was stirred for at least 30 minutes, then transferred to a 20 kHz ultrasonic bath. After the colloid clarified, the pH was adjusted using HNO3, and ultrasonic dispersion was continued until a clear solution was maintained. Ultimately, the sample contained 0.5% cerium hydroxide, 0.1% diammonium hydrogen citrate, and 1.0% PAA-D11-HCl, at pH 6.0. The particles remained stable, and the zeta potential became +45 mV.

[0053] Invention sample D1: 2.5 g of 40% PAA-HCl-O3 was added to 497.5 g of deionized water, followed by the addition of 500.0 g of control sample B2 under stirring. The mixture was stirred for at least 30 minutes, then transferred to a 20 kHz ultrasonic bath. After the colloid clarified, the pH was adjusted using pyridine carboxylic acid, and ultrasonic dispersion was continued until the clear solution remained. Ultimately, the sample contained 0.5% cerium hydroxide, 0.1% polyphosphoric acid, and 0.1% PAA-HCl-O3, with a pH of 4.0. The particles remained stable, and the zeta potential became +40 Mv.

[0054] Invention sample D2: 5.0 g of 40% PAA-HCl-O3 was added to 495.0 g of deionized water, followed by 500.0 g of control sample B2 under stirring. The mixture was stirred for at least 30 minutes, then transferred to a 20 kHz ultrasonic bath. After the colloid clarified, the pH was adjusted using pyridine carboxylic acid, and ultrasonic dispersion was continued until the clear solution remained. Ultimately, the sample contained 0.5% cerium hydroxide, 0.1% polyphosphoric acid, and 0.2% PAA-HCl-O3, with a pH of 5.1. The particles remained stable, and the zeta potential became +44 mV.

[0055] Invention sample D3: 25.0 g of 40% PAA-HCl-O3 was added to 475.0 g of deionized water, followed by the addition of 500.0 g of control sample B2 under stirring. The mixture was stirred for at least 30 minutes, then transferred to a 20 kHz ultrasonic bath. After the colloid clarified, the pH was adjusted using pyridine carboxylic acid, and ultrasonic dispersion was continued until the clear solution remained. Ultimately, the sample contained 0.5% cerium hydroxide, 0.1% polyphosphoric acid, and 1.0% PAA-HCl-O3, with a pH of 6.0. The particles remained stable, and the zeta potential became +47 mV.

[0056] The zeta potential and particle size of cerium hydroxide particles before and after surface treatment are listed in Table 1.

[0057] Table 1 Zeta potential and particle size

[0058]

[0059]

[0060]

[0061] All percentages in this invention are mass percentages.

[0062] From the examples above, we can see that the first coating of cerium hydroxide particles can be achieved using polymers or monomers containing negatively charged polyphosphates or carboxylates, such as polyphosphoric acid, phosphoric acid / ammonium dihydrogen phosphate / diammonium hydrogen phosphate, hydroxyethylidene diphosphonic acid, and citric acid / diammonium hydrogen citrate / ammonium citrate, etc., to achieve a charge reversal to a negative charge. The second coating uses polymers containing weakly positively charged primary or secondary amine-HCl, such as PEI-HCl, PAA-HCl-03, PAA-HCl-3L, PAA-D19-HCl, and PAA-D11-HCl, etc., to achieve a second charge reversal to a positive charge.

[0063] Polishing target: TEOS blank wafer

[0064] Polishing instruments: Mirra polishing machine; IC1000 polishing pad; NanoSpec film thickness measurement system (NanoSpec6100-300, Shanghai Nanospec Technology Corporation); white light interferometer.

[0065] Polishing conditions: Platten and Carrier speeds were 93 rpm and 87 rpm, respectively; polishing pressure was 4.0 psi; and polishing fluid flow rate was 150 mL / min.

[0066] Polishing steps: The TEOS blank wafers were polished using the polishing slurry prepared above, and the polishing instruments and conditions described above were used for polishing. After polishing, the adhesion on the surface of the TEOS blank wafers was detected using a white light interferometer, and the results are shown in Table 2.

[0067] Table 2. Surface adhesion of TEOS blank wafers before and after polishing

[0068]

[0069]

[0070] As shown in Table 2, polishing TEOS blank wafers using bare cerium hydroxide particles (Comparative Sample A) results in severe particle adhesion on the surface. However, once the cerium hydroxide surface is coated (Invention Samples A, B, C, and D), particle adhesion on the TEOS blank wafer surface is greatly reduced without altering its electrical properties. This is because the double coating increases the thickness of the cerium hydroxide particle surface, much like dressing a metal sphere with multiple layers of thick clothing. This prevents the coated cerium hydroxide particles from directly contacting each other. Simultaneously, the polymer-coated cerium hydroxide particles become polymer macromolecules, weakening the attraction between them and effectively reducing particle adhesion.

[0071] In summary, by using the negatively charged polymer or monomer and the weakly positively charged polymer as defined in this application, the secondary inversion of cerium hydroxide particles can be effectively achieved. The coated cerium hydroxide particles do not change their own electrical properties. Furthermore, by increasing the thickness of the coating layer on the surface of the cerium hydroxide particles (from hard shell to soft core), defects caused by mechanical forces on the wafer surface during polishing—particle adhesion—can be reduced, thereby greatly improving the product yield.

[0072] 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 preparing a cerium hydroxide particle dispersion, characterized in that, include: S1: Preparation of negatively charged cerium hydroxide particle dispersion: Prepare a solution containing a negatively charged polymer or monomer of polyphosphate or carboxylate groups, add an alkaline pH adjuster to adjust the pH, add the cerium hydroxide particle dispersion while stirring, stir for at least T1, transfer the solution to an ultrasonic tank, and sonicate until the particles are dispersed; obtain negatively charged cerium hydroxide particle dispersion R1. S2: Preparation of positively charged cerium hydroxide particle dispersion: Prepare a solution of positively charged polymer, add R1 while stirring, stir for at least T2, transfer the solution to an ultrasonic tank, add an acidic pH adjuster to adjust the pH after the solution becomes clear, continue ultrasonic dispersion until the clear solution is maintained, and obtain positively charged cerium hydroxide particle dispersion R2.

2. The cerium hydroxide particle dispersion as described in claim 1, characterized in that, The polymers or monomers containing negatively charged polyphosphates or carboxyl groups are polyphosphoric acid, phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, hydroxyethylidene diphosphonic acid, citric acid, diammonium hydrogen citrate, and ammonium citrate.

3. The cerium hydroxide particle dispersion as described in claim 1, characterized in that, The positively charged polymer is a weakly positively charged polymer of primary or secondary amine-HCl type.

4. The cerium hydroxide particle dispersion as described in claim 3, characterized in that, The positively charged polymers are PEI-HCl, PAA-HCl-03, PAA-HCl-3L, PAA-D19-HCl, and PAA-D11-HCl.

5. The cerium hydroxide particle dispersion as described in claim 1, characterized in that, The mass percentage concentration of the polymer containing negatively charged polyphosphates or carboxylates in R1 is 0.05% to 0.5%.

6. The cerium hydroxide particle dispersion as described in claim 1, characterized in that, The mass percentage concentration of the positively charged polymer in R2 is 0.1% to 1.0%.

7. The cerium hydroxide particle dispersion as described in claim 1, characterized in that, The concentration of cerium hydroxide particles in R2 is 0.5-1.0%.

8. The cerium hydroxide particle dispersion as described in claim 1, characterized in that, In S1, adjust the pH to 7-9.

9. The cerium hydroxide particle dispersion as described in claim 1, characterized in that, In S2, adjust the pH to 2-6.

10. The cerium hydroxide particle dispersion as described in claim 1, characterized in that, In S1, T1 = 30-60 minutes; in S2, T2 = 30-60 minutes.

11. The cerium hydroxide particle dispersion as described in claim 1, characterized in that, In S1, the alkaline pH adjuster is selected from KOH, ammonia, and imidazole.

12. The cerium hydroxide particle dispersion as described in claim 1, characterized in that, In S2, the acidic pH adjuster is selected from HNO3, acetic acid, and pyridinecarboxylic acid.

13. The cerium hydroxide particle dispersion as described in claim 1, characterized in that, The cerium hydroxide particles in R1 have a particle size of 20-60 nm.

14. The cerium hydroxide particle dispersion as described in claim 1, characterized in that, The cerium hydroxide particles in R2 have a particle size of 50-130 nm.

15. A cerium hydroxide polishing solution obtained by the method of any one of the preceding claims, characterized in that, The solid content of cerium hydroxide in R2 is less than 2 wt%.

16. A method of using a cerium hydroxide particle dispersion, comprising the application of the cerium hydroxide particle dispersion as described in any one of claims 1-15 for polishing silicon oxide.

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