A method of making an aluminum oxide composite abrasive particle

Abstract

The application discloses a preparation method of an alumina composite abrasive particle. The alumina composite abrasive particle is a nano-sized alumina-metal organic framework material composite particle with irregular morphology, and the preparation method comprises the following steps: modifying alumina by using 1,2,4-benzoic anhydride and 2-amino-3-methylbutyric acid, then growing a layer of MIL-100 (MIL-100) on the carboxyl-modified alumina core by using ferrous chloride tetrahydrate and 1,3,5-benzoic acid through a water bath method, and obtaining the alumina composite abrasive particle with catalytic characteristics. Compared with conventional alumina abrasive particles, the alumina composite abrasive particle can increase the SiC material removal rate by 178% at most, and can effectively reduce the surface roughness after polishing.

Description

Technical Field

[0001] This invention relates to irregularly shaped nanoscale abrasive particles and their preparation method. Specifically, it relates to a method for preparing alumina composite abrasive particles, used in the polishing process of silicon carbide wafers, belonging to the field of surface polishing technology. Background Technology

[0002] Compared to traditional Si and GaAs, single-crystal silicon carbide (SiC) is one of the most promising next-generation semiconductor power device materials due to its superior chemical and mechanical properties, such as a wide bandgap, high thermal conductivity, low coefficient of thermal expansion, high breakdown voltage, and better lattice alignment with epitaxial GaN crystals. Therefore, it is widely used as a novel substrate material for light-emitting diodes in liquid crystal display light sources and in high-frequency, high-power, and high-temperature electronic devices. An atomically smooth and damage-free SiC substrate surface is essential, as surface quality affects the quality of the epitaxial layer and device performance.

[0003] Currently, chemical mechanical polishing (CMP) is a general processing technique used to assist in the grinding of single-crystal silicon carbide to achieve global planarization. Polishing slurry is the most important consumable in CMP, and abrasive grains are a crucial component of the slurry. Nano-alumina, due to its low cost and moderate hardness, has become the most widely used abrasive grain in silicon carbide polishing. However, due to the chemical component failure issues in traditional polishing slurries, sulfate-based advanced oxidation process (SRAOP) is a promising and environmentally friendly candidate process for SiC materials. Addressing the low material removal rate and the need to improve surface quality during silicon carbide polishing, we aim to develop alumina abrasive grains with higher material removal rates to meet the growing industrial demands. Summary of the Invention

[0004] The purpose of this invention is to solve the problems of poor dispersion stability and easy scratching of existing commercially available alumina abrasives, and to improve the material removal rate. It provides a simple and easy-to-implement water bath method for preparing Lavoisier skeleton material-alumina composite abrasives, and obtains an alumina composite abrasive through this method, as well as the application of the alumina composite abrasive in polishing fluid.

[0005] One objective of this invention is to provide a method for preparing alumina composite abrasive particles, employing the following technical solution:

[0006] A method for preparing alumina composite abrasive particles includes the following steps:

[0007] S1. Prepare a solution of carboxylated alumina and sodium benzoate;

[0008] S2. Preparation of alumina composite abrasive particles.

[0009] The process of preparing the carboxylated alumina in step S1 is as follows:

[0010] S01: Add 2-amino-3-methylbutyric acid to acetic acid, stir and mix well, then add 1,2,4-benzoic anhydride, stir at 120°C to obtain a clear solution, cool to room temperature, and rotary evaporate the solution to obtain carboxylated imide;

[0011] S02: Alumina with an average particle size of 300 nanometers and the carboxylated imide are added to methanol, stirred evenly at room temperature, and then centrifuged and dried to obtain the carboxylated modified alumina.

[0012] The process of preparing the sodium benzoate solution in step S1 is as follows: an appropriate amount of 1,3,5-benzoic acid is added to an aqueous NaOH solution to prepare the solution.

[0013] The process of preparing alumina composite abrasive particles in step S2 is as follows: the carboxyl-modified alumina and ferrous chloride tetrahydrate are added to deionized water and stirred at room temperature to obtain a mixed solution. Then, sodium benzoate solution is added dropwise to the mixed solution. After the addition is complete, the mixture is stirred evenly at room temperature. Then, solid-liquid separation is carried out by centrifugation. The obtained solid material is washed alternately with water and ethanol and finally dried to obtain the alumina composite abrasive particles.

[0014] Furthermore, in step S01, the mass ratio of 2-amino-3-methylbutyric acid, acetic acid, and 1,2,4-benzoic anhydride is 1.17:150:2.

[0015] Furthermore, in step S02, the mass ratio of alumina, methanol, and the carboxylated imide is 20:120:3.

[0016] Furthermore, in the preparation of the sodium benzoate solution, the mass ratio of the NaOH aqueous solution to 1,3,5-benzoic acid is 8.6:0.6, and the molar concentration of the NaOH aqueous solution is 1M.

[0017] Furthermore, in the process of preparing the alumina composite abrasive, the mass ratio of ferrous chloride tetrahydrate, water, the carboxyl-modified alumina, and the sodium benzoate solution is (0.86-3.44):120:20:(9.2-36.8).

[0018] The second objective of this invention is to provide an alumina composite abrasive, which is prepared by the above-mentioned method for preparing alumina composite abrasive, with nano-alumina particles inside and an organic framework coated with iron ions on the outside.

[0019] Preferably, the mass fraction of the organic framework of the iron ions is 5.5% to 22%.

[0020] More preferably, the mass fraction of the organic framework of the iron ions is 22%.

[0021] The third objective of this invention is to provide a method for preparing an alumina composite abrasive polishing slurry. This method utilizes the alumina composite abrasive prepared by the aforementioned method and applies it to the polishing slurry. The technical solution is as follows:

[0022] A polishing solution was prepared by sequentially adding alumina composite abrasive particles and ammonium persulfate to deionized water, wherein the mass fraction of the alumina composite abrasive particles was 2 wt.% and the mass fraction of the ammonium persulfate was 3 wt.%.

[0023] The present invention has the following beneficial effects:

[0024] This invention prepares alumina composite abrasive particles using a water bath method under mild conditions, where positively charged Fe in the aqueous solution... 2+ Alumina composite abrasive particles are prepared by adsorbing onto negatively charged Al2O3-COOH and then forming coordinate bonds with carbonyl oxygen in benzoic acid to grow a MIL-100 shell around the Al2O3-COOH core. This novel abrasive preparation method is simple and can be scaled up for industrial production.

[0025] The alumina composite abrasive prepared by this invention has rounded edges compared with conventional commercially available alumina abrasive, which helps to reduce hard damage such as scratches. Furthermore, it utilizes the highly efficient catalytic effect of MIL-100 on electron transfer to achieve efficient processing.

[0026] The alumina composite abrasive polishing slurry prepared in this invention, when applied to the chemical mechanical polishing of single-crystal silicon carbide, can effectively reduce the surface roughness of single-crystal silicon carbide. Compared with conventional commercially available alumina abrasives, the polishing rate of the alumina composite abrasive can be increased by up to 178%. Attached Figure Description

[0027] Figure 1 This is a field emission scanning electron microscope image of the alumina composite abrasive particles in Example 3 of the present invention.

[0028] Figure 2 This is a field emission scanning electron microscope image of commercially available unmodified alumina abrasive particles in Comparative Example 1 of this invention.

[0029] Figure 3 The image shows a comparison of the UV-Vis diffuse reflectance spectra of the composite abrasive particles in Example 3 and Comparative Example 1.

[0030] Figure 4 The image shows a comparison of the X-ray photoelectron spectroscopy (XPS) results of the alumina composite abrasive particles in Example 3 and Comparative Example 1. Image A shows the XPS results before polishing, and image B shows the XPS results after polishing.

[0031] Figure 5 The figure shows the effect of adding different inhibitors to the alumina composite abrasive polishing slurry on the material removal rate. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the present invention clearer, the specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0033] To facilitate understanding, the nouns or abbreviations mentioned below will be explained first:

[0034] APS: Ammonium persulfate.

[0035] MIL-100 is an organic framework containing iron ions, which is coated on the outside of alumina nanoparticles.

[0036] Example 1

[0037] This embodiment provides a method for preparing alumina composite abrasive particles, the steps of which are as follows:

[0038] S1. Preparation of carboxyl-modified alumina and sodium benzoate solution;

[0039] S2. Preparation of alumina composite abrasive particles.

[0040] In step S1, the preparation process of the carboxyl-modified alumina is as follows:

[0041] S01: Add 1.17g of 2-amino-3-methylbutyric acid to 150g of acetic acid, stir and mix well, then add 2g of 1,2,4-benzoic anhydride, stir at 120℃ for 5h to obtain a clear solution, cool to room temperature, and then perform rotary evaporation on the clear solution to obtain carboxylated imide.

[0042] S02: 20g of alumina with an average particle size of 300 nm and 3g of carboxylated imide were added to 120g of methanol, stirred at room temperature for 24h, and then dried by centrifugation at 5000 rpm to obtain carboxyl-modified alumina (Al2O3-COOH).

[0043] In step S1, the step of preparing the sodium benzoate solution is as follows:

[0044] Add 0.6 g of 1,3,5-benzoic acid to 8.6 g of 1 M NaOH aqueous solution.

[0045] In step S2, the alumina composite abrasive particles are prepared, and the specific steps are as follows:

[0046] 20g of carboxyl-modified alumina and 0.86g of ferrous chloride tetrahydrate were added to 120g of deionized water and stirred at room temperature for 2h to obtain a mixed solution. 9.2g of sodium benzoate solution was added dropwise to the mixed solution. After the addition was complete, the mixture was stirred at room temperature for 24h. Finally, the solid and liquid were separated by centrifugation at 5000rpm for 5min. The obtained solid was washed twice with water and twice with ethanol, and dried at 60℃ for 24h to obtain alumina composite abrasive particles with a MIL-100 content of 5.5wt.% (labeled as Al2O3-0.055Fe).

[0047] Example 2

[0048] This embodiment provides a method for preparing alumina composite abrasive particles, the steps of which are as follows:

[0049] S1. Preparation of carboxyl-modified alumina and sodium benzoate solution;

[0050] S2. Preparation of alumina composite abrasive particles.

[0051] In step S1, the preparation process of the carboxyl-modified alumina is as follows:

[0052] S01: Add 1.17g of 2-amino-3-methylbutyric acid to 150g of acetic acid, stir and mix well, then add 2g of 1,2,4-benzoic anhydride, stir at 120℃ for 5h to obtain a clear solution, cool, and then perform rotary evaporation on the clear solution to obtain carboxylated imide;

[0053] S02: 20g of alumina with an average particle size of 300 nm and 3g of carboxylated imide were added to 120g of methanol and stirred at room temperature for 24h. After centrifugation and drying at 5000 rpm at room temperature, carboxyl-modified alumina (Al2O3-COOH) was obtained.

[0054] In step S1, the step of preparing the sodium benzoate solution is as follows:

[0055] Add 1.2 g of 1,3,5-benzoic acid to 17.2 g of 1 M NaOH aqueous solution.

[0056] In step S2, the alumina composite abrasive particles are prepared, and the specific steps are as follows:

[0057] 20g of carboxyl-modified alumina and 1.72g of ferrous chloride tetrahydrate were added to 120g of deionized water and stirred at room temperature for 2h. 18.4g of sodium benzoate solution was added dropwise to the mixed solution of carboxyl-modified alumina and ferrous chloride tetrahydrate. After the addition was complete, the mixture was stirred at room temperature for 24h. Finally, the mixture was centrifuged at 5000rpm for 5min, and the precipitate was washed twice with water and twice with ethanol. The precipitate was then dried at 60℃ for 24h to obtain alumina composite abrasive particles with a MIL-100 content of 11wt.% (labeled as Al2O3-0.11Fe).

[0058] Example 3

[0059] This embodiment provides a method for preparing alumina composite abrasive particles, the steps of which are as follows:

[0060] S1. Preparation of carboxyl-modified alumina and sodium benzoate solution;

[0061] S2. Preparation of alumina composite abrasive particles.

[0062] In step S1, the preparation process of the carboxyl-modified alumina is as follows:

[0063] S01: Add 1.17g of 2-amino-3-methylbutyric acid to 150g of acetic acid, stir and mix well, then add 2g of 1,2,4-benzoic anhydride, stir at 120℃ for 5h to obtain a clear solution, cool, and then perform rotary evaporation on the clear solution to obtain carboxylated imide;

[0064] S02: 20g of alumina with an average particle size of 300 nm and 3g of carboxylated imide were added to 120g of methanol and stirred at room temperature for 24h. After centrifugation and drying at 5000 rpm at room temperature, carboxyl-modified alumina (Al2O3-COOH) was obtained.

[0065] In step S1, the step of preparing the sodium benzoate solution is as follows:

[0066] Add 2.4 g of 1,3,5-benzoic acid to 34.4 g of 1 M NaOH aqueous solution.

[0067] In step S2, the alumina composite abrasive particles are prepared, and the specific steps are as follows:

[0068] 20g of carboxyl-modified alumina and 3.44g of ferrous chloride tetrahydrate were added to 120g of deionized water and stirred at room temperature for 2h. 36.8g of sodium benzoate solution was added dropwise to the mixed solution of carboxyl-modified alumina and ferrous chloride tetrahydrate. After the addition was complete, the mixture was stirred at room temperature for 24h. Finally, the mixture was centrifuged at 5000rpm for 5min, and the precipitate was washed twice with water and twice with ethanol. The precipitate was then dried at 60℃ for 24h to obtain alumina composite abrasive particles with a MIL-100 content of 22wt.% (labeled as Al2O3-0.22Fe).

[0069] Comparative Example 1

[0070] Commercially available alumina powder with an average particle size of 300 nanometers was directly used as unmodified alumina abrasive particles (Al2O3).

[0071] The following describes the process of preparing polishing fluid using the alumina composite abrasives prepared in Examples 1 to 3 and the unmodified alumina abrasives in Comparative Example 1 as polishing abrasives. The specific steps are as follows:

[0072] The four polishing abrasives obtained above were added to deionized water in sequence with ammonium persulfate to prepare alumina abrasive polishing solutions with a composite abrasive mass fraction of 2 wt.% and an ammonium persulfate concentration of 3 wt.%. Four different polishing solutions were obtained and labeled as: 2 wt% Al2O3-0.055Fe / 3%APS, 2 wt% Al2O3-0.11Fe / 3%APS, 2 wt% Al2O3-0.22Fe / 3%APS, and 2 wt% Al2O3 / 3%APS.

[0073] The following tests were conducted on the aforementioned composite alumina abrasive grains and the related polishing slurry:

[0074] I. Scanning Electron Microscopy Testing

[0075] Figure 1 This is a scanning electron microscope (SEM) image of Al2O3-0.22Fe.

[0076] Figure 2 This is a scanning electron microscope image of Al2O3.

[0077] It can be seen that the surface of the Al2O3-0.22Fe alumina composite abrasive particles is rougher and the edges are blunted.

[0078] II. Comparative Experiment on the Polishing Effect of Polishing Slurry on Silicon Carbide

[0079] The experimental steps are as follows:

[0080] Polishing experiments were conducted on single-crystal silicon carbide using the four polishing slurries described above under specific polishing conditions.

[0081] The polishing conditions for the polishing test are as follows:

[0082] Polishing machine: UNIPOL-1502 automatic pressure grinding and polishing machine;

[0083] Workpiece: A single-crystal silicon carbide wafer with a diameter of 50mm (Si surface);

[0084] Polishing pad: Polyurethane polishing pad;

[0085] Polishing pressure: 6 kg;

[0086] Upper plate speed: 30 rpm;

[0087] Lower plate speed: 60 rpm;

[0088] Polishing time: 2 hours;

[0089] After polishing, the single-crystal silicon carbide wafers were washed and dried in the order of cleaning solution, deionized water, and ethanol. The mass of the single-crystal silicon carbide wafers before and after polishing was weighed using a precision analytical balance, and the material removal rate (MRR) was calculated. Additionally, the surface roughness Ra of the single-crystal silicon carbide wafers before and after polishing was measured using a 3D surface profilometer, with a step accuracy of 0.5%, step repeatability of 0.1%, vertical resolution of 0.1 nm, maximum lateral resolution of 0.14 nm, and a Z-direction scanning range of 0.1 nm–34 mm.

[0090] The polishing effects of the polishing slurries used in each embodiment and Comparative Example 1 on silicon carbide are shown in Table 1.

[0091] As shown in Table 1, under the same solid content, compared with 2wt% Al2O3 / 3% APS, the material removal rate of each modified alumina composite abrasive polishing slurry was significantly increased, and the surface roughness was significantly reduced. In Example 3, the alumina composite abrasive improved the removal rate by 178% compared with the unmodified alumina abrasive material used in polishing.

[0092] Table 1 Polishing effect of four polishing slurries on silicon carbide

[0093]

[0094] Note: MIL-100 content refers to the ratio of the mass of MIL-100 to the total mass of the polishing abrasive grains.

[0095] III. Ultraviolet-Visible Diffuse Reflectance Spectroscopy Test

[0096] The alumina composite abrasive particles Al2O3-0.22Fe prepared in Example 3 and the unmodified alumina abrasive particles of Comparative Example 1 were subjected to ultraviolet-visible diffuse reflectance spectroscopy tests. The test results are as follows: Figure 3 As shown:

[0097] according to Figure 3 The mid-ultraviolet-visible diffuse reflectance spectrum indicates that the alumina and MIL-100 composite can produce a light absorption effect in the 200-400 nm range, indicating that the composite material can be excited by both ultraviolet and visible light to generate electron-hole pairs.

[0098] IV. Comparison of X-ray photoelectron spectroscopy before and after polishing

[0099] The alumina composite abrasive particles Al2O3-0.22Fe prepared in Example 3, and the polished composite alumina abrasive particles extracted after the above polishing experiment, were subjected to X-ray photoelectron spectroscopy (XPS) analysis. The results are as follows: Figure 4 As shown:

[0100] Before polishing, the Fe valence state in the composite abrasive grains was +3. After polishing, compared with before polishing, a shoulder peak appeared to the right of both the vibration peak and the P3 / 2 peak in the composite abrasive grains, indicating that Fe... 2+ The presence of this, i.e., the in-situ Fe generation of composite abrasive grains under ultraviolet light irradiation during polishing, indicates that... 3+ Photoreduction to Fe 2+ This Fe 3+ Fe 2+ Electron transfer in the process can activate persulfate and promote the generation of sulfate free radicals.

[0101] V. Photocatalytic Reaction Test

[0102] The polishing experiments described above revealed that:

[0103] When the abrasive grains are pure alumina, the optimal composition of the polishing slurry is: 2% Al2O3 and 3% APS, i.e., 2wt% Al2O3 / 3% APS.

[0104] When the abrasive particles are composite particles, the optimal composition of the polishing fluid is: 2% Al2O3-0.22Fe, 3% APS, i.e., 2wt% Al2O3-0.22Fe / 3% APS;

[0105] An inhibitor was added to each of the two polishing solutions at a volume ratio of 2% to test the effect of SO4· radicals on SiC polishing. The polishing disc was irradiated with a mercury UV lamp during polishing. The inhibitor was either methanol or tert-butanol.

[0106] Experimental results are as follows Figure 5As shown, in the persulfate oxidation system, the free radicals SO4· or ·OH can exist alone or simultaneously. At pH < 7, SO4· is likely the dominant free radical. Compared to the blank experiment, the removal rate significantly decreased after adding tert-butanol or methanol under both light-free and light-illuminated conditions, indicating that the free radicals consumed by tert-butanol and methanol play an important role in activating the persulfate system. Due to methanol's quenching ability for both free radicals, the decrease in removal rate was more pronounced, suggesting that SO4· and ·OH likely coexist in the reaction. Furthermore, with the same dosage of inhibitor, the reduction in removal rate under photocatalytic conditions was significantly greater than that without photocatalytic conditions, indicating that photocatalysis can further activate persulfate to generate free radicals.

[0107] In summary, compared with conventional commercially available alumina abrasives, the alumina composite abrasives of this invention have a rougher surface and blunted edges. When used for polishing single-crystal silicon carbide, the composite abrasives, due to their porous surface structure and large specific surface area, can promote chemical reactions during the chemical mechanical polishing process, significantly improving material removal rate and effectively enhancing the surface finish after polishing.

[0108] The above description is merely a preferred embodiment of the present invention. The embodiments are not intended to limit the scope of patent protection of the present invention. Therefore, any equivalent structural changes made based on the description and drawings of the present invention should also be included within the scope of protection of the appended claims.

Claims

1. A method for preparing alumina composite abrasive particles, characterized in that, Includes the following steps: S1. Prepare a solution of carboxylated alumina and sodium benzoate, wherein... The method for preparing the carboxylated alumina is as follows: S01: Add 2-amino-3-methylbutyric acid to acetic acid, stir and mix well, then add 1,2,4-benzoic anhydride, stir at 120°C to obtain a clear solution, cool to room temperature, and rotary evaporate the solution to obtain carboxylated imide; S02: Alumina with an average particle size of 300 nanometers and the carboxylated imide are added to methanol, stirred evenly at room temperature, and then centrifuged and dried to obtain the carboxylated alumina; The sodium benzoate solution is prepared by adding an appropriate amount of 1,3,5-benzoic acid to an aqueous NaOH solution. S2. The carboxylated alumina and ferrous chloride tetrahydrate are added to deionized water and stirred at room temperature to obtain a mixed solution. Then, sodium benzoate solution is added dropwise to the mixed solution. After the addition is complete, the mixture is stirred evenly at room temperature. Then, solid-liquid separation is performed by centrifugation. The obtained solid material is washed alternately with water and ethanol and finally dried to obtain the alumina composite abrasive particles.

2. The method for preparing alumina composite abrasive particles as described in claim 1, characterized in that, In step S01, the mass ratio of 2-amino-3-methylbutyric acid, acetic acid, and 1,2,4-benzoic anhydride is 1.17:150:2; in step S02, the mass ratio of alumina, methanol, and the carboxylated imide is 20:120:

3.

3. The method for preparing alumina composite abrasive particles as described in claim 1, characterized in that, In step S1, during the preparation of the sodium benzoate solution, the mass ratio of the NaOH aqueous solution to 1,3,5-benzoic acid is 8.6:0.6, and the molar concentration of the NaOH aqueous solution is 1M.

4. The method for preparing alumina composite abrasive particles as described in claim 1, characterized in that, In the process of preparing the alumina composite abrasive, the mass ratio of ferrous chloride tetrahydrate, water, the carboxylated alumina, and the sodium benzoate solution is (0.86~3.44):120:20:(9.2~36.8).

5. An alumina composite abrasive prepared by the method for preparing alumina composite abrasives according to any one of claims 1-4, characterized in that, Its interior consists of nano-alumina particles, and its exterior is coated with an organic framework of iron ions, wherein the mass fraction of the organic framework of iron ions is 5.5% to 22%.

6. A method for preparing a polishing slurry using the alumina composite abrasive particles as described in claim 5, characterized in that, A polishing solution was prepared by sequentially adding alumina composite abrasive particles and ammonium persulfate to deionized water, wherein the mass fraction of the alumina composite abrasive particles was 2 wt.% and the mass fraction of the ammonium persulfate was 3 wt.%.

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