Cerium-based abrasive particle, preparation method thereof and polishing solution

Abstract

The invention belongs to the technical field of material synthesis and chemical mechanical polishing, and discloses a cerium-based abrasive particle, a preparation method thereof and a polishing solution. The method comprises the following steps: mixing a cerium salt aqueous solution and a zoledronic acid aqueous solution in proportion, standing and reacting at room temperature, centrifuging, and drying in vacuum to obtain the cerium-based abrasive particles. The method is simple in process and mild in condition, the cerium-based abrasive particles with regular rod-like morphology, uniform size, good dispersity and fluorescence characteristics are successfully prepared by utilizing the coordination effect of zoledronic acid and cerium ions, and the surfaces of the cerium-based abrasive particles are rich in trivalent cerium ions with high chemical activity. The invention also provides a chemical mechanical polishing solution containing the abrasive particles, the chemical mechanical polishing solution comprises the cerium-based abrasive particles, a dispersant and the balance of an aqueous medium based on the total weight of the polishing solution, and the pH value of the chemical mechanical polishing solution is 3-6. The polishing solution is suitable for polishing semiconductor wafers, optical glass and shallow trench isolation structures, and can effectively improve the material removal rate and obtain excellent surface quality.

Description

Technical Field

[0001] This invention belongs to the field of materials synthesis and chemical mechanical polishing technology, specifically relating to a cerium-based abrasive, its preparation method, and a polishing slurry. In particular, this invention provides a method for preparing cerium-based abrasives with fluorescent properties by coordinating zoledronic acid with cerium ions, and a high-performance chemical mechanical polishing slurry containing the abrasives. Background Technology

[0002] Chemical mechanical polishing (CMP) is a key process in semiconductor manufacturing and optical glass processing, achieving global planarization of the workpiece surface through the synergistic effect of chemical etching and mechanical grinding. During CMP, the abrasive particles in the polishing slurry are the core factor affecting polishing performance; their particle size, morphology, and chemical activity directly influence material removal rate and surface quality.

[0003] Cerium-based abrasives are widely used for polishing silicon-based materials due to their unique "chemical tooth" effect with silicon-based materials. Studies have shown that the concentration of trivalent cerium ions on the surface of cerium-based abrasives is a key factor affecting their polishing performance; a high trivalent cerium content can enhance the chemical activity of the abrasives and improve material removal rate. In addition, the morphology and size uniformity of the abrasives have an important impact on the polishing quality; spherical abrasives with uniform size can reduce surface scratches during the polishing process.

[0004] Currently, various methods exist for preparing cerium-based abrasives such as cerium oxide, including hydrothermal methods, molten salt methods, and precipitation-calcination methods. These methods typically adjust the physicochemical properties of the abrasives by doping them with other elements (such as aluminum, yttrium, ytterbium, or fluorine). However, existing methods still have some limitations: the preparation process is complex and often requires high-temperature treatment; the abrasives are prone to agglomeration and have a wide size distribution; the surface trivalent cerium concentration is insufficient; and the use of organic solvents may cause environmental pollution.

[0005] On the other hand, zoledronic acid is a bisphosphonate drug that has been mass-produced. Its molecule contains multiple coordinating atoms (O, N) that can form stable coordination compounds with metal ions. This characteristic makes it potentially valuable for metal ion chelation, but there are currently no reports of its use in the preparation of cerium-based abrasives. Therefore, developing a simple, mild method to prepare cerium-based abrasives with high trivalent cerium content and good dispersibility is of significant scientific research value and practical application importance. Summary of the Invention

[0006] The purpose of this invention is to provide a simple and mild method for preparing cerium-based abrasive particles. This method utilizes the coordination effect of zoledronic acid with cerium ions to prepare cerium-based abrasive particles with high trivalent cerium content and good dispersibility.

[0007] Another object of the present invention is to provide cerium-based abrasive grains prepared by the above method, which have regular morphology and fluorescence properties.

[0008] Another object of the present invention is to provide a chemical mechanical polishing slurry containing the above-mentioned cerium-based abrasive particles and its application.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing cerium-based abrasive grains includes the following steps: Step 1: Solution preparation: Accurately weigh cerium nitrate hexahydrate solid, dissolve it in deionized water to prepare a cerium salt aqueous solution; accurately weigh zoledronic acid solid, dissolve it in deionized water to prepare a zoledronic acid aqueous solution; Step 2: Synthesis reaction: Mix cerium salt aqueous solution and zoledronic acid aqueous solution in a 4:1 ratio at room temperature and stir until homogeneous. Allow to stand and react to obtain particles with fluorescent properties. Step 3: Post-processing: Centrifuge the reaction product from step 2, discard the supernatant, and collect the precipitate; vacuum dry the precipitate to remove water, and obtain cerium-based abrasive particles.

[0010] Furthermore, the concentration range of the cerium salt aqueous solution is 2.2~2.7 mM, and the concentration range of the zoledronic acid aqueous solution is 9.6~10.3 mM.

[0011] Furthermore, the settling reaction time is 20-40 minutes; the centrifugation speed is 8000-12000 rpm for 5-10 minutes; and the vacuum drying dehydration temperature is 40-60℃ for 4-8 hours.

[0012] Furthermore, the concentration of the cerium salt aqueous solution is 2.5 mM, and the concentration of the zoledronic acid aqueous solution is 10 mM.

[0013] The present invention also discloses a cerium-based abrasive obtained by the preparation method described above. The abrasive has a rod-shaped morphology and exhibits fluorescence under ultraviolet light irradiation. The surface of the abrasive is rich in trivalent cerium ions and has water dispersibility and chemical activity.

[0014] Furthermore, the cerium-based abrasive particles have a particle size distribution of 2 μm in length and 0.2 μm in radius.

[0015] The present invention also discloses a chemical mechanical polishing slurry containing the cerium-based abrasive particles, comprising 0.1-5 wt% cerium-based abrasive particles, 0.01-1 wt% dispersant and the balance being an aqueous medium, with a pH value of 3-6.

[0016] Furthermore, the dispersant is at least one of polyacrylic acid, sodium polyacrylate, and polyether dispersants.

[0017] Furthermore, it also includes one or more additives among oxidants, corrosion inhibitors, and surfactants.

[0018] Furthermore, the chemical mechanical polishing slurry is used in the chemical mechanical polishing of semiconductor wafers or optical glass.

[0019] The cerium-based abrasive grain, its preparation method, and the polishing fluid of the present invention have the following advantages compared with the prior art: 1. Simple preparation process and mild conditions: This method uses a static reaction at room temperature, without the need for high temperature, high pressure or complex equipment. It is easy to operate, has low energy consumption, is suitable for large-scale production, and avoids the use of organic solvents, making it environmentally friendly.

[0020] 2. The obtained abrasive particles have regular morphology, uniform size, and good dispersibility: Cerium-based nanoparticles with regular rod-shaped morphology were successfully prepared through the coordination of zoledronic acid and cerium ions. The particle size distribution is uniform and the particles have good monodispersity, which effectively avoids the problem of abrasive particle agglomeration and is conducive to uniform grinding during the polishing process.

[0021] 3. The abrasive surface is rich in highly active trivalent cerium ions: XPS analysis shows that the prepared cerium-based abrasive has a high content of trivalent cerium ions on its surface, which enhances the chemical activity of the abrasive and improves the material removal efficiency during the polishing process, making it particularly suitable for polishing silicon-based materials.

[0022] 4. Fluorescent properties facilitate process monitoring and characterization: The abrasive grains exhibit fluorescence under ultraviolet light irradiation, which not only facilitates real-time monitoring during the synthesis process but also provides the possibility for visual analysis of the distribution and behavior of abrasive grains in the polishing slurry.

[0023] 5. Excellent polishing slurry performance and wide applicability: The prepared polishing slurry can achieve efficient polishing with low abrasive content (0.1–5 wt%). It exhibits high material removal rate (up to 30 nm / min) and low surface roughness (Ra=0.18 nm) on semiconductor wafers, optical glass and shallow trench isolation structures, with excellent polishing quality.

[0024] 6. Strong controllability of components and good compatibility: Functional additives such as oxidants, corrosion inhibitors and surfactants can be flexibly added to the polishing fluid to meet the needs of different polishing scenarios. The pH value (3-6) is moderate and has low corrosiveness to equipment.

[0025] In summary, this invention not only provides a new, efficient, and environmentally friendly method for synthesizing cerium-based abrasive particles, but also develops a high-performance polishing slurry to complement it, which has significant application value and promising prospects in semiconductor manufacturing, optical processing, and other fields. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the cerium-based abrasive particle size distribution in Embodiment 1 of the present invention.

[0027] Figure 2This is a schematic diagram of the microstructure of cerium-based abrasive particles in Embodiment 1 of the present invention.

[0028] Figure 3 This is the fluorescence spectrum of cerium-based abrasive particles and hydrogen peroxide after mixing in Example 1 of the present invention (different pH, control group: cerium nitrate aqueous solution and hydrogen peroxide mixture).

[0029] Figure 4 This is a schematic diagram of the chemical mechanical polishing effect of the cerium-based abrasive polishing fluid of the present invention. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0031] This invention provides cerium-based abrasive grains with a particle size distribution of 2 μm in length and 0.2 μm in radius, exhibiting a regular rod-like morphology and fluorescence under ultraviolet light irradiation. The abrasive grain surface is rich in trivalent cerium ions, resulting in good water dispersibility and chemical activity.

[0032] The preparation method of the above-mentioned cerium-based abrasive grains includes the following steps: Step 1: Solution preparation: Accurately weigh cerium nitrate hexahydrate solid, dissolve it in deionized water, and prepare a cerium salt aqueous solution with a concentration of 2.2~2.7mM; accurately weigh zoledronic acid solid, dissolve it in deionized water, and prepare a zoledronic acid aqueous solution with a concentration of 9.6~10.3mM.

[0033] Step 2: Synthesis reaction: Mix cerium salt aqueous solution and zoledronic acid aqueous solution in a 4:1 ratio at room temperature and stir until homogeneous. Let the mixture stand for 10-30 minutes to obtain particles with fluorescent properties.

[0034] Step 3: Post-treatment: Centrifuge the reaction product at 8000-12000 rpm for 5-10 minutes, discard the supernatant, and collect the precipitate; vacuum dry the precipitate at 40-60℃ for 4-8 hours to remove water, obtaining cerium-based abrasive particles. This invention also provides a chemical mechanical polishing slurry containing the above-mentioned cerium-based abrasive particles, comprising, by weight, 0.1-5 wt% cerium-based abrasive particles, 0.01-1 wt% dispersant, and the balance being an aqueous medium, with a pH of 3-6. The dispersant is at least one selected from polyacrylic acid, sodium polyacrylate, and polyether dispersants. The polishing slurry may also contain one or more additives selected from oxidants, corrosion inhibitors, and surfactants.

[0035] The aforementioned chemical mechanical polishing slurry can be applied to the chemical mechanical polishing of semiconductor wafers, optical glass, or shallow trench isolation structures of integrated circuits.

[0036] Example 1: Method for preparing cerium-based abrasive particles: Step 1: Accurately weigh 32.57 g of cerium nitrate hexahydrate solid and dissolve it in 30 L of deionized water. Stir magnetically for 10 minutes until completely dissolved to obtain a 2.5 mM cerium salt aqueous solution. Accurately weigh 81.63 g of zoledronic acid solid and dissolve it in 3 L of deionized water. Stir magnetically for 15 minutes until completely dissolved to obtain a 10 mM zoledronic acid aqueous solution.

[0037] Step 2: Accurately measure 200 mL of the above cerium salt aqueous solution and 50 mL of the above zoledronic acid aqueous solution using a micropipette, place them in a 300 mL flask, stir magnetically to mix them thoroughly, and let them stand at room temperature for 10 minutes. Observe that the solution changes from colorless and transparent to slightly milky white. The fluorescence spectroscopy test shows that the preparation was successful.

[0038] Step 3: Centrifuge the reaction mixture at 10,000 rpm for 5 minutes, discard the supernatant, and collect the white precipitate. Dry the precipitate in a vacuum drying oven at 50°C for 6 hours to remove water, obtaining white powdery cerium-based abrasive particles.

[0039] like Figure 1-3 As shown, the abrasive grains exhibit a regular spherical morphology and good monodispersity. The surface of the abrasive grains has a high content of trivalent cerium ions, demonstrating a highly sensitive response to hydrogen peroxide catalysis (a common oxidant in polishing slurries).

[0040] Example 2: Preparation method of polishing slurry: The cerium-based abrasive particles prepared in Example 1 were dispersed in deionized water to prepare a suspension with a solid content of 1 wt%. 0.1 wt% sodium polyacrylate was added as a dispersant and 1% hydrogen peroxide was added as an oxidant (to react with surfaces such as silicon nitride to form a softer oxide layer, accelerating removal). The pH was adjusted to 6.0 with dilute nitric acid, and the mixture was ball-milled for 2 hours to obtain a chemical mechanical polishing slurry.

[0041] Polishing slurry performance testing: Chemical mechanical polishing (CMP) tests were conducted on 1cm × 1cm silicon nitride wafers using the aforementioned polishing slurry. The polishing pressure was 3.0 PSI, the polishing disc rotation speed was 90 RPM, the carrier rotation speed was 87 RPM, and the polishing slurry flow rate was 150 mL / min. The results showed that the polishing slurry achieved a material removal rate of 30 nm / min on the silicon wafer, with a surface roughness (Ra) of 0.18 nm, demonstrating excellent polishing performance. Figure 4 The image shown is a diagram illustrating the chemical mechanical polishing effect of a cerium-based abrasive polishing slurry.

[0042] Example 3: As shown in Table 1, this embodiment compares the effects of different process parameters on the performance of cerium-based abrasive particles: Table 1: Effects of different process parameters on the performance of cerium-based abrasive particles

[0043] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing cerium-based abrasive particles, characterized in that, Includes the following steps: Step 1: Solution preparation: Accurately weigh cerium nitrate hexahydrate solid, dissolve it in deionized water to prepare a cerium salt aqueous solution; accurately weigh zoledronic acid solid, dissolve it in deionized water to prepare a zoledronic acid aqueous solution; Step 2: Synthesis reaction: Mix cerium salt aqueous solution and zoledronic acid aqueous solution in a 4:1 ratio at room temperature and stir until homogeneous. Allow to stand and react to obtain particles with fluorescent properties. Step 3: Post-processing: Centrifuge the reaction product from step 2, discard the supernatant, and collect the precipitate; vacuum dry the precipitate to remove water, and obtain cerium-based abrasive particles.

2. The method for preparing cerium-based abrasive grains according to claim 1, characterized in that, The concentration range of the cerium salt aqueous solution is 2.2~2.7 mM, and the concentration range of the zoledronic acid aqueous solution is 9.6~10.3 mM.

3. The method for preparing cerium-based abrasive grains according to claim 1, characterized in that, The static reaction time is 20-40 minutes; the centrifugation speed is 8000-12000 rpm for 5-10 minutes; the vacuum drying dehydration temperature is 40-60℃ for 4-8 hours.

4. The method for preparing cerium-based abrasive grains according to claim 1, characterized in that, The concentration of the cerium salt aqueous solution is 2.5 mM, and the concentration of the zoledronic acid aqueous solution is 10 mM.

5. A cerium-based abrasive grain prepared by the preparation method according to any one of claims 1-4, characterized in that, The abrasive grains have a rod-shaped morphology and exhibit fluorescence under ultraviolet light irradiation. The surface of the abrasive grains is rich in trivalent cerium ions, and they have water dispersibility and chemical activity.

6. The cerium-based abrasive grains according to claim 5, characterized in that, The cerium-based abrasive particles have a particle size distribution of 2 μm in length and 0.2 μm in radius.

7. A chemical mechanical polishing slurry containing cerium-based abrasive particles as described in any one of claims 5-6, characterized in that, It includes 0.1-5 wt% cerium-based abrasive particles, 0.01-1 wt% dispersant, and the balance being an aqueous medium with a pH value of 3-6.

8. The chemical mechanical polishing slurry according to claim 6, characterized in that, The dispersant is at least one of polyacrylic acid, sodium polyacrylate, and polyether dispersants.

9. The chemical mechanical polishing slurry according to claim 6, characterized in that, It also contains one or more additives, including oxidants, corrosion inhibitors, and surfactants.

10. The chemical mechanical polishing slurry according to claim 6, characterized in that, The chemical mechanical polishing slurry is used in the chemical mechanical polishing of semiconductor wafers or optical glass.

Images