A method for producing ceria abrasive particles

Abstract

This invention provides a method for preparing cerium oxide abrasive particles, comprising: preparing a cerium carbonate dispersion; continuously stirring the cerium carbonate dispersion, slowly adding fatty acids to the dispersion, dispersing evenly, and removing water; after water removal, removing excess oil from the cerium carbonate dispersion; and calcining the oil-removed cerium carbonate dispersion to obtain cerium oxide abrasive particles. Introducing fatty acids to organically modify and coat the surface of the cerium oxide abrasive particle precursor effectively reduces particle agglomeration during the high-temperature calcination synthesis of abrasive cerium oxide, achieving uniform and easily dispersed particles, and significantly reducing polishing scratches.

Description

Technical Field

[0001] This invention relates to the field of polishing slurries for semiconductor devices, and more particularly to a method for preparing cerium oxide abrasive particles. Background Technology

[0002] CMP abrasives require nanoscale particle sizes, but previous abrasive synthesis methods mainly involve high-temperature calcination of cerium carbonate to prepare abrasive particles, such as cerium oxide abrasive particles. High-temperature treatment inevitably leads to particle sintering and agglomeration, resulting in scratches during application and limiting its use in advanced process semiconductor chip CMP polishing.

[0003] Therefore, developing a cerium oxide particle preparation process that can effectively reduce particle agglomeration, achieve uniform and easily dispersed particles, and significantly reduce polishing scratches has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0004] To overcome the aforementioned technical deficiencies, the present invention aims to provide a method for preparing cerium oxide abrasive particles. By introducing fatty acids to organically modify and coat the surface of the cerium oxide abrasive particle precursor, particle agglomeration can be effectively reduced during the high-temperature calcination synthesis of abrasive cerium oxide, resulting in uniform and easily dispersed particles, and significantly reducing polishing scratches.

[0005] This invention discloses a method for preparing cerium oxide abrasive particles, comprising:

[0006] Preparation of cerium carbonate dispersion;

[0007] While stirring the cerium carbonate dispersion, slowly add water to the dispersion until it is evenly dispersed and removed.

[0008] After removing water, excess oil is removed from the cerium carbonate dispersion;

[0009] The cerium carbonate dispersion after oil removal was calcined to obtain cerium oxide abrasive particles.

[0010] Optionally, the amount of fatty acid added is 50%-100% of the mass of cerium carbonate. Optionally, the fatty acid is divided into 10 equal parts, the cerium carbonate dispersion is kept stirred, 2 equal parts of fatty acid are slowly added to the dispersion, and the emulsion is prepared by high-speed shear dispersion. The water in the emulsion is removed to obtain the first stage cerium carbonate dispersion.

[0011] The remaining equal amount of fatty acids was added to the first-stage cerium carbonate dispersion and dispersed evenly. The water was then removed to obtain the second-stage cerium carbonate dispersion.

[0012] Optionally, the fatty acid includes at least one of oleic acid or stearic acid.

[0013] Optionally, after obtaining the emulsion, the method further includes: adding a pH adjuster to the emulsion to adjust the pH value of the emulsion to 9-10.0.

[0014] Optionally, the pH adjuster is ammonia.

[0015] Optionally, the water in the emulsion can be removed by drying, centrifugation, or plate and frame filtration.

[0016] Optionally, after adding the remaining 8 equal parts of fatty acids to the first-stage cerium carbonate dispersion, the mixture is dispersed evenly by a colloid mill, and after removing water, the second-stage cerium carbonate dispersion is obtained.

[0017] Optionally, the second-stage cerium carbonate dispersion can be subjected to plate and frame filtration to remove excess oil.

[0018] Optionally, the specific roasting process includes:

[0019] The second-stage cerium carbonate dispersion after oil removal is kept at 200-300 degrees Celsius for 5-10 hours, and nitrogen is introduced as a protective gas to form a carbonized layer on the surface of cerium oxide particles.

[0020] Then raise the ambient temperature to 600-800 degrees Celsius and keep it warm for 2-6 hours;

[0021] Then, the temperature is lowered to 250-400 degrees Celsius, and the nitrogen atmosphere is changed to air or oxygen. The mixture is then kept at this temperature for 2-6 hours to remove the carbonized layer on the surface of the particles, thus obtaining cerium oxide abrasive particles.

[0022] Compared with existing technologies, the above technical solution has the following advantages:

[0023] 1. By introducing fatty acids to organically modify and coat the surface of cerium oxide abrasive particle precursors, the agglomeration between particles can be effectively reduced during the high-temperature calcination synthesis of cerium oxide abrasive, resulting in uniform and easily dispersed particles, which can significantly reduce polishing scratch defects. Attached Figure Description

[0024] Figure 1 A schematic flowchart of a method for preparing cerium oxide abrasive particles according to an embodiment of the present invention is shown;

[0025] Figure 2 The particle size distribution curves of cerium oxide particles conforming to Examples 1-3 and Comparative Example 1 of the present invention are shown. Detailed Implementation

[0026] The advantages of the present invention are further illustrated below through specific embodiments, but the scope of protection of the present invention is not limited to the following embodiments.

[0027] The preparation of the cerium carbonate dispersion uses commercially available cerium carbonate as raw material. 100 grams of cerium carbonate is weighed and prepared into a 40% solids content aqueous solution. After high-speed shear dispersion, it is further dispersed by ball milling. Ball milling is stopped when the particle size reaches within 250 nanometers. Other formulations can also be used, and the particle size is not limited to the dimensions provided in the embodiments of this invention. This invention applies to any cerium carbonate dispersion.

[0028] The weight of the cerium carbonate dispersion selected for the experiment can be weighed as needed. In this invention, 100g was selected for the experiment, and the concentration of fatty acids was 100%. The method for dehydrating the emulsion was drying, specifically setting the drying temperature to 120℃ and drying time to 12 hours. Other dehydration methods are also within the scope of protection of this invention, but this invention is not limited thereto.

[0029] Figure 1 A schematic flow chart of a method for preparing cerium oxide abrasive particles is shown. Based on... Figure 1 The preparation process, as described in Examples 1-3, is as follows:

[0030] Example 1:

[0031] Using commercially available cerium carbonate as raw material, 100 grams of cerium carbonate were weighed and prepared into an aqueous solution with a solid content of 40%. After high-speed shear dispersion, it was further dispersed by ball milling. When the particle size reached within 300 nanometers, the ball milling was stopped.

[0032] Weigh 20 grams of oleic acid, keep the material stirring, and slowly add 20 grams of oleic acid to the dispersion. Prepare an oleic acid emulsion by high-speed shear dispersion. Then add ammonia water to the oleic acid emulsion to adjust the pH of the emulsion to between 9.0 and 10.0.

[0033] The above emulsion was dried and dehydrated at a temperature of 120°C for 12 hours.

[0034] Weigh out 20 grams of oleic acid, add 80 grams of oleic acid to the material, and disperse it evenly through a colloid mill;

[0035] The mixed sample is then subjected to plate and frame filtration to remove excess oil.

[0036] Finally, the mixture is calcined in a muffle furnace at 300°C for 5 hours under nitrogen atmosphere. Then, the temperature is raised to 800°C and held for 2 hours. After that, the temperature is lowered to 250°C, and the atmosphere in the muffle furnace is changed to air. The mixture is then calcined at 250°C for 6 hours. After cooling, the target cerium oxide powder product is obtained. The powder material is loose, with weak particle agglomeration, and is easy to further disperse to obtain a cerium oxide dispersion with a particle size of 85 nanometers.

[0037] Example 2:(Oleic acid in Example 1 was replaced with stearic acid; the pH value of the emulsion was adjusted from 9.0-10.0 to between 9.5-10.0; and the time and temperature parameters of the particle calcination program were also adjusted.)

[0038] Using commercially available cerium carbonate as raw material, 100 grams of cerium carbonate were weighed and prepared into an aqueous solution with a solid content of 40%. After high-speed shear dispersion, it was further dispersed by ball milling. When the particle size reached within 250 nanometers, the ball milling was stopped.

[0039] Weigh 50 grams of oleic acid, keep the material stirred, and slowly add 10 grams of stearic acid to the dispersion. Prepare an emulsion by high-speed shear dispersion.

[0040] Add ammonia to the emulsion to adjust its pH to between 9.5 and 10.0;

[0041] The above emulsion was subjected to drying and dehydration treatment at 120℃ for 12 hours.

[0042] After dehydration, 40 grams of stearic acid were added to the material and dispersed evenly using a colloid mill.

[0043] The mixed sample is then subjected to plate and frame filtration to remove excess oil.

[0044] Finally, the mixture is calcined in a muffle furnace at 200°C for 10 hours under nitrogen atmosphere. Then, the temperature is raised to 600°C and held for 6 hours. After that, the temperature is lowered to 400°C, and the atmosphere in the muffle furnace is changed to air. The mixture is then calcined at 400°C for 2 hours. After cooling, the target cerium oxide powder product is obtained. The powder material is loose, with weak particle agglomeration, and is easy to further disperse to obtain a cerium oxide dispersion with a particle size of 94 nanometers.

[0045] Example 3: (Example 3 is based on Example 2, but with adjustments to the time and temperature parameters of the particle roasting process.) )

[0046] Using commercially available cerium carbonate as raw material, 100 grams of cerium carbonate were weighed and prepared into an aqueous solution with a solid content of 40%. After high-speed shear dispersion, it was further dispersed by ball milling. When the particle size reached within 250 nanometers, the ball milling was stopped.

[0047] Weigh 75 grams of oleic acid, keep the material stirred, and slowly add 15 grams of stearic acid to the dispersion. Prepare an emulsion by high-speed shear dispersion.

[0048] Then add ammonia water to the emulsion to adjust the pH of the emulsion to between 9.5 and 10.0; dry the above emulsion to remove water at a temperature of 120°C, add 60 grams of stearic acid to the material after water removal, and disperse it evenly through a colloid mill.

[0049] The mixed sample is then subjected to plate and frame filtration to remove excess oil.

[0050] Finally, the mixture is calcined in a muffle furnace at 250°C for 8 hours under nitrogen atmosphere. Then, the temperature is raised to 700°C and held for 4 hours. After that, the temperature is lowered to 350°C, and the atmosphere in the muffle furnace is changed to air. The mixture is then calcined at 350°C for 3 hours. After cooling, the target cerium oxide powder product is obtained. The powder material is loose, with weak particle agglomeration, and is easy to further disperse to obtain a cerium oxide dispersion with a particle size of 81 nanometers.

[0051] This invention introduces excess oleic acid and stearic acid as surface coating agents to modify the surface of ball-milled cerium carbonate particles. The modified cerium carbonate is then dried. Since oleic acid and fatty acids have higher boiling points than water, moisture can be fully removed during the 100°C drying process, preventing particle agglomeration. Further, excess oleic acid in the dehydrated cerium carbonate is squeezed out and recovered through plate and frame filtration. The filtered cerium carbonate is then calcined at high temperature. The resulting cerium oxide is pulverized and dispersed to obtain a cerium oxide dispersion with particle sizes of 80-100 nm and good dispersibility.

[0052] When calcining cerium carbonate after pressure filtration at high temperature, this invention incorporates nitrogen protection during the calcination process and sets a specific calcination temperature program: first, the temperature is raised to 200-300 degrees Celsius and held for 5-10 hours to form a carbonized layer on the particle surface; then, the temperature is raised to 600-800 degrees Celsius and held for 2-6 hours; finally, the temperature is lowered to 250-400 degrees Celsius, and the nitrogen atmosphere is changed to air or oxygen, with continued calcination for 2-6 hours to remove the carbonized layer from the particle surface. By controlling the high-temperature calcination atmosphere, a carbonized layer forms on the surface of the cerium oxide particles during calcination, preventing sintering and agglomeration between particles. Furthermore, a reducing atmosphere is formed during the oxygen-based decarburization process, thereby controlling the oxygen vacancies on the surface of the cerium oxide particles and ultimately regulating their polishing activity.

[0053] The cerium oxide dispersion obtained by this invention exhibits good particle size distribution characteristics, good CMP polishing activity, and low polishing scratch defects.

[0054] Comparative Example 1: (No fatty acids were selected; the mixture was directly roasted after ball milling, and the roasting procedure was exactly the same as in Example 3.)

[0055] Using commercially available cerium carbonate as raw material, 100 grams of cerium carbonate were weighed and prepared into an aqueous solution with a solid content of 40%. After high-speed shear dispersion, it was further dispersed by ball milling. When the particle size reached within 250 nanometers, the ball milling was stopped.

[0056] The above dispersion was dried to remove water at a temperature of 120°C.

[0057] After dehydration, the material is calcined in a muffle furnace at 200°C for 10 hours under nitrogen atmosphere. Then, the temperature is raised to 600°C and held for 6 hours. After that, the temperature is lowered to 400°C, and the atmosphere in the muffle furnace is changed to air. The material is then calcined at 400°C for 2 hours. After cooling, cerium oxide powder is obtained. The powder material shows obvious particle agglomeration and is easy to further disperse to obtain a cerium oxide dispersion with a particle size of 504 nanometers. When applied to CMP polishing, it will show obvious polishing defects.

[0058] Figure 2 The particle size distributions of the synthesized particles in the three examples and comparative examples are compared.

[0059] Comparing Examples 1-3 with Comparative Example 1, it can be clearly seen that the cerium oxide synthesized in Examples 1-3 has a significantly smaller particle size and exhibits superior polishing characteristics in advanced process chip CMP polishing.

[0060] 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 the production of ceria abrasive particles, characterized in that, include: Preparation of cerium carbonate dispersion; While stirring the cerium carbonate dispersion, fatty acids are slowly added to the dispersion until it is evenly dispersed, and then the water is removed. After removing water, excess oil is removed from the cerium carbonate dispersion; The cerium carbonate dispersion after oil removal is calcined to obtain cerium oxide abrasive particles.

2. The method of claim 1, wherein the ceria abrasive particles have a size distribution such that at least 90% of the ceria abrasive particles have a size of less than 5 microns. The amount of fatty acid added is 50%-100% of the mass of cerium carbonate.

3. The method of claim 2, wherein the ceria abrasive particles have a size distribution such that at least 90% of the particles have a size of less than 1.5 μm. The steps of maintaining the cerium carbonate dispersion with stirring, slowly adding fatty acids to the dispersion, dispersing evenly, and removing water specifically include: The fatty acids were divided into 10 equal parts. The cerium carbonate dispersion was kept stirred and 2 equal parts of fatty acids were slowly added to the dispersion. The mixture was then dispersed by high-speed shearing to prepare an emulsion. The water in the emulsion was removed to obtain the first stage cerium carbonate dispersion. The remaining 8 equal parts of fatty acids were added to the first-stage cerium carbonate dispersion and dispersed evenly. The water was then removed to obtain the second-stage cerium carbonate dispersion.

4. The method of claim 1, wherein the ceria abrasive particles have a size distribution such that at least 90% of the particles have a size of 0.5 to 2.0 μm. The fatty acid includes at least one of oleic acid or stearic acid.

5. The method of claim 1, wherein the ceria abrasive particles have a size distribution such that at least 90% of the particles have a size of 0.5 to 2.0 μm. After obtaining the emulsion, the process further includes: adding a pH adjuster to the emulsion to adjust the pH value of the emulsion to 9-10.

0.

6. The method of claim 5, wherein the ceria abrasive particles have a size distribution such that at least 90% of the particles have a size of less than 1.5 μm. The pH adjuster is ammonia.

7. The method for preparing cerium oxide abrasive particles as described in claim 1, characterized in that, The water in the emulsion can be removed by drying, centrifugation or plate and frame filtration.

8. The method for preparing cerium oxide abrasive particles as described in claim 1, characterized in that, After adding the remaining 8 equal parts of fatty acids to the first-stage cerium carbonate dispersion, the mixture is dispersed evenly by a colloid mill, and the water is removed to obtain the second-stage cerium carbonate dispersion.

9. The method of claim 1, wherein the ceria abrasive particles have a size distribution such that at least 90% of the particles have a size of less than 1.0 μm. The second-stage cerium carbonate dispersion was subjected to plate and frame filtration to remove excess oil.

10. The method of claim 1, wherein the ceria abrasive particles have a size distribution such that at least 90% of the particles have a size of less than 1.5 microns. The specific roasting process includes: The second-stage cerium carbonate dispersion after oil removal is kept at 200-300 degrees Celsius for 5-10 hours, and nitrogen is introduced as a protective gas to form a carbonized layer on the surface of cerium oxide particles. Then raise the ambient temperature to 600-800 degrees Celsius and keep it warm for 2-6 hours; Then, the temperature is lowered to 250-400 degrees Celsius, and the nitrogen atmosphere is changed to air or oxygen. The mixture is then kept at this temperature for 2-6 hours to remove the carbonized layer on the surface of the particles, thus obtaining cerium oxide abrasive particles.

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