Preparation method and application of EDTA-modified alumina composite abrasive grains

Abstract

A preparation method of EDTA-modified alumina composite abrasive grains, characterized by comprising the following steps: adding α-alumina particles, NaOH, and 30 wt% hydrogen peroxide into deionized water, adding ethylenediaminetetraacetic acid into thionyl chloride, reacting at a constant temperature of 70 °C for 3 h until no gas is released in the reaction system, adding the hydroxylated alumina particles into N,N-dimethylformamide solvent, and ultrasonicating with an ultrasonic device for 30 min until the suspension is uniformly dispersed, and drying the obtained product in an oven at 50 °C for 20 h to obtain alumina-ethylenediaminetetraacetic acid abrasive grains. The preparation method and application of the EDTA-modified alumina composite abrasive grains of the present invention have the advantages of improving the material removal rate, effectively reducing the surface roughness of sapphire. Compared with conventional commercial alumina abrasive grains, the material removal rate of the alumina-ethylenediaminetetraacetic acid abrasive grains is increased by 101%, and the surface roughness is reduced by less than 65%.

Description

Technical Field

[0001] The present invention relates to a micron-sized alumina composite abrasive with an irregular morphology and a preparation method thereof. In particular, an alumina-EDTA composite abrasive is used in the polishing process of a sapphire substrate, belonging to the technical field of surface polishing. Background Art

[0002] Sapphire, also known as corundum, is composed of single-crystal α-aluminum oxide (α-Al2O3) and has many excellent properties, such as high hardness (Mohs hardness of 9), high strength, good wear resistance, thermal stability, light transmission performance, and chemical stability, which makes it one of the most widely used wafers in aerospace, light-emitting diodes (LEDs), fine ceramics, semiconductor devices, and other precision optical devices. The surface quality of the substrate material significantly affects the performance and service life of these workpieces. Therefore, with the rapid development of optoelectronic technology, higher requirements are put forward for the processing efficiency and surface quality of sapphire substrates. However, due to its high hardness, brittleness, and corrosion resistance, it is difficult to achieve an ideal flatness of the sapphire substrate through traditional polishing methods.

[0003] Chemical mechanical polishing is one of the current global planarization technologies that can obtain a globally atomically smooth surface. The polishing fluid is the main consumable in chemical mechanical polishing, and inorganic nano-abrasives are an important part of the polishing fluid. With the wide application of sapphire in industry, large-scale production and cost control have attracted attention to alumina abrasives with high polishing rates. Conventional alumina abrasives are prone to agglomeration, precipitation, and even scratching the surface of the substrate, and the surface of the polished substrate cannot meet the quality requirements. Summary of the Invention

[0004] The purpose of the present invention is to solve the problem of poor surface quality of the sapphire substrate after polishing without reducing the polishing rate of alumina abrasives, and to provide a preparation method for EDTA-modified alumina composite abrasives.

[0005] Another purpose of the present invention is to propose the application of EDTA-modified alumina composite abrasives in the polishing process of sapphire substrates.

[0006] In order to achieve the above purpose, the present invention adopts the following technical solution. A preparation method for EDTA-modified alumina composite abrasives is characterized by including the following steps:

[0007] S01: Add α-aluminum oxide particles, NaOH, and 30wt% hydrogen peroxide to deionized water, and ball-mill in a ball-mill tank at a rotation speed of 260 rpm for 2 h. After the ball-milling is completed, wash the obtained particles with deionized water until neutral, and dry them in an oven at 50 °C for 24 h to obtain ball-milled hydroxylated alumina particles;

[0008] S02: Add ethylenediaminetetraacetic acid to thionyl chloride, react at a constant temperature of 70 °C for 3 h until no gas is released from the reaction system, and absorb the reaction tail gas with a saturated NaOH solution; after the reaction, use a suction filtration device to separate the solid and liquid of the obtained product, and volatilize the obtained acyl chloride ethylenediaminetetraacetic acid in a fume hood for 15 h until there is no thionyl chloride on the surface;

[0009] S03: Add hydroxylated alumina particles to N,N-dimethylformamide solvent, use an ultrasonic device to ultrasonicate for 30 min until the suspension is evenly dispersed, place it in a water bath and stir magnetically. When the reaction temperature reaches 40 °C, add acyl chloride ethylenediaminetetraacetic acid, react the obtained product at 40 °C for 8 h, then add it to deionized water for hydrolysis for 30 min, and then wash it with deionized water until neutral, and dry the obtained product in an oven at 50 °C for 20 h to obtain alumina-ethylenediaminetetraacetic acid abrasive grains.

[0010] The preparation method of the alumina-EDTA abrasive grains of the present invention can also be further realized by adopting the following technical measures.

[0011] The aforementioned method, wherein in the step S01, the mass ratio of α-alumina particles, NaOH, 30 wt% hydrogen peroxide, and deionized water is 20:0.5:5:100.

[0012] The aforementioned method, wherein in the step S02, the mass ratio of ethylenediaminetetraacetic acid to thionyl chloride is 30:262.

[0013] The aforementioned method, wherein in the step S03, the mass ratio of hydroxylated alumina, N,N-dimethylformamide, acyl chloride ethylenediaminetetraacetic acid, and deionized water is 30:95:0.5 - 3:200.

[0014] An application of an EDTA-modified alumina composite abrasive grain in the polishing process of a sapphire substrate.

[0015] After adopting the above technical solutions, the preparation method and application of the EDTA-modified alumina composite abrasive grains of the present invention have the following advantages:

[0016] (1) By using the method of acyl chloride EDTA-modifying hydroxylated alumina abrasive grains, the carboxyl functional group is successfully grafted onto the surface of alumina particles to prepare alumina-EDTA abrasive grains; this abrasive grain preparation method is simple and effective and can be scaled up for industrial production.

[0017] (2) The alumina-ethylenediaminetetraacetic acid abrasive grain polishing liquid of the present invention is applied to the chemical mechanical polishing of a sapphire substrate, which not only improves the material removal rate but also can effectively reduce the surface roughness of the sapphire. Compared with conventional commercial alumina abrasive grains, the material removal rate of the alumina-ethylenediaminetetraacetic acid abrasive grains is increased by 101%, and the surface roughness is reduced by 65%.

[0018] (3) The alumina-ethylenediaminetetraacetic acid abrasive grains of the present invention have improved dispersibility compared with conventional industrial alumina abrasive grains. The number of effective particles participating in polishing increases, and the ethylenediaminetetraacetic acid on the surface of the abrasive grains also increases the chemical action during the polishing process. The optimization of the synergistic effect of mechanical grinding and chemical etching is a prerequisite for improving the removal rate and the surface quality of the substrate. Detailed implementation manners

[0019] To make the objectives, technical solutions and advantages of the present invention clearer, the following further elaborates on the detailed implementation manners of the present invention.

[0020] A preparation method of alumina-EDTA abrasive grains provided by the present invention includes the following steps:

[0021] S01: Add α-alumina abrasive grains, flaky solid NaOH, and hydrogen peroxide (30 wt%) to deionized water, and ball mill for 2 h at a rotation speed of 260 rpm. After the ball milling is completed, wash the abrasive grains until they are nearly neutral, that is, the pH is between 7 and 8, and dry them in an oven at 50 °C for 24 h to obtain ball-milled hydroxylated alumina particles; among them, the mass ratio of α-alumina particles, NaOH, hydrogen peroxide (30 wt%), and deionized water is 20:0.5:5:100.

[0022] S02: Put thionyl chloride into a dry three-necked flask, then place the three-necked flask in a water bath, heat it to 70 °C, add EDTA and keep stirring. React for 3 h until no gas is released from the system, and absorb the experimental tail gas with a saturated NaOH solution; after the reaction is completed, use a suction filtration device to separate the solid and liquid, and let the obtained acylated ethylenediaminetetraacetic acid volatilize in a fume hood for 15 h until there is no thionyl chloride on the surface; among them, the mass ratio of EDTA to thionyl chloride is 30:262.

[0023] S03: Add the hydroxylated alumina particles to an N,N-dimethylformamide (DMF) solvent, ultrasonicate for 30 min until the suspension is evenly dispersed, place it in a water bath and stir magnetically. When the reaction temperature reaches 40 °C, add acylated EDTA. After reacting at 40 °C for 8 h, add it to deionized water for hydrolysis for 30 min to obtain alumina-EDTA abrasive grains. The mass ratio of hydroxylated alumina, N,N-dimethylformamide, acylated EDTA, and deionized water is 30:95:0.5-3:200. By using different dosages of EDTA, alumina-EDTA composite abrasive grains with different grafting amounts can be obtained.

[0024] An application of the alumina abrasive grains of the present invention. Using the above alumina-EDTA abrasive grains to prepare a polishing liquid and applying it to the polishing of a sapphire substrate can significantly improve the polishing rate and the polishing precision of the alumina abrasive grains, achieving a polishing effect of "high efficiency, high precision".

[0025] The preparation method of the present invention will be further described below with reference to examples:

[0026] Example 1:

[0027] This example provides a preparation method of alumina-EDTA abrasive grains. The alumina-EDTA abrasive grains are prepared by the acyl chlorination method. The preparation method is as follows:

[0028] (1) 200 g of α-alumina particles, 5 g of NaOH, 50 g of 30% hydrogen peroxide and 1000 ml of deionized water are evenly added to two ball milling jars, and ball milled at a speed of 260 rpm for 2 h. After the ball milling is completed, the particles are washed three times with deionized water, and 1.5 L of deionized water is added each time, until the pH of the upper layer liquid after centrifugation of the particles is between 7 and 8. Then, it is dried in an oven at 50 °C for 24 h to obtain hydroxylated alumina particles.

[0029] (2) 262 g of thionyl chloride is placed in a dry three-necked flask, and then the three-necked flask is placed in a water bath and heated to 70 °C. 30 g of EDTA is added and stirred continuously. React for 3 h until no gas is released from the system, and the experimental tail gas is absorbed by a saturated NaOH solution; after the reaction is completed, a suction filtration device is used to separate the solid and liquid, and the obtained acyl chlorinated ethylenediaminetetraacetic acid is volatilized in a fume hood for 15 h until there is no thionyl chloride on the surface.

[0030] (3) 30 g of hydroxylated alumina particles are added to 95 g of N,N-dimethylformamide (DMF) solvent, and ultrasonicated for 30 min until the suspension is evenly dispersed. Then, it is placed in a water bath and stirred magnetically. When the reaction temperature reaches 40 °C, 0.5 g of acyl chlorinated EDTA is added. After reacting at 40 °C for 8 h, it is added to deionized water for hydrolysis for 30 min, and then washed three times with deionized water, and 1 L of deionized water is added each time, until the pH of the upper layer liquid after centrifugation of the particles is between 6 and 7. Then, it is dried in an oven at 50 °C for 24 h to obtain alumina-EDTA composite particles with an EDTA mass content of 1.6 wt.%.

[0031] 2 g of the above-obtained alumina-EDTA composite abrasive grains, 100 g of deionized water and 0.5 g of sodium hydroxide are added, and the mixture is ultrasonicated and dispersed for 30 min to prepare an alumina-EDTA abrasive polishing liquid with a solid mass fraction of 2.5 wt.%, that is, the polishing liquid of Example 1 is obtained.

[0032] The polishing effect of the polishing liquid of this example on the sapphire substrate is shown in Table 1.

[0033] Example 2

[0034] This embodiment provides a method for preparing alumina-EDTA abrasive grains. The alumina-EDTA abrasive grains are prepared by the acyl chlorination method. The preparation method is the same as that of Example 1, except that in step (3), the amount of acyl chlorinated EDTA used is 2 g. Alumina-EDTA composite particles with an EDTA mass content of 6.25 wt.% are obtained.

[0035] Take 2 g of the above-obtained alumina-EDTA composite abrasive grains, add 100 g of deionized water and 0.5 g of sodium hydroxide, and ultrasonically disperse the mixture for 30 minutes to prepare an alumina-EDTA abrasive grain polishing solution with a solid mass fraction of 2.5 wt.%, that is, the polishing solution of Example 2 is obtained.

[0036] The polishing effect of the sapphire substrate using the polishing solution of this embodiment is shown in Table 1.

[0037] Example 3

[0038] This embodiment provides a method for preparing alumina-EDTA abrasive grains. The alumina-EDTA abrasive grains are prepared by the acyl chlorination method. The preparation method is the same as that of Example 1, except that in step (3), the amount of acyl chlorinated EDTA used is 3 g. Alumina-EDTA composite particles with an EDTA mass content of 9.09 wt.% are obtained.

[0039] Take 2 g of the above-obtained alumina-EDTA composite abrasive grains, add 100 g of deionized water and 0.5 g of sodium hydroxide, and ultrasonically disperse the mixture for 30 minutes to prepare an alumina-2EDTA abrasive grain polishing solution with a solid mass fraction of 2.5 wt.%, that is, the polishing solution of Example 2 is obtained.

[0040] The polishing effect of the sapphire substrate using the polishing solution of this embodiment is shown in Table 1.

[0041] Comparative Example 1

[0042] In the comparative example, the polished liquid is directly prepared using the commercial alumina particles before modification for comparison. Take 2 g of industrial alumina abrasive grains, add 100 g of deionized water and 0.5 g of sodium hydroxide, and prepare an alumina abrasive grain polishing solution with a solid mass fraction of 2.5 wt.%, that is, the polishing solution of Comparative Example 1 is obtained.

[0043] The polishing effect of the sapphire wafer using the polishing solution of this comparative example is shown in Table 1.

[0044] Use the polishing solutions of the above Examples 1-3 and Comparative Example 1 to conduct a polishing test on the sapphire wafer under certain polishing conditions.

[0045] The polishing conditions of the polishing test are as follows:

[0046] Polishing machine: UNIPOL-1000S automatic pressure grinding and polishing machine;

[0047] Workpiece: Sapphire (0001) plane with a diameter of 50.8 mm;

[0048] Polishing pad: Polyurethane polishing pad;

[0049] Polishing pressure: 6 kg;

[0050] Upper platen rotation speed: 30 rpm;

[0051] Lower platen rotation speed: 70 rpm;

[0052] Polishing time: 1 h;

[0053] After polishing, the sapphire wafer is washed and dried in the order of cleaning solution, deionized water, and ethanol, and the mass of the sapphire wafer before and after polishing is weighed with a precision analytical balance to calculate the material removal rate MRR. In addition, the surface roughness Ra of the sapphire before and after polishing is measured by an Ambios Xi-100 surface profiler, with a resolution of The depth of focus is 3.0 μm, the working distance is 7.4 mm, and the measurement area is 500 μm × 500 μm.

[0054] The polishing effects of the polishing fluids in each example on the sapphire wafer are shown in Table 1 respectively. It can be seen from Table 1 that compared with the industrial commercial alumina abrasive polishing fluid with the same solid content in the comparative example, the material removal rates of the alumina composite abrasive polishing fluids modified with different contents of EDTA in Examples 1-3 are all significantly increased, and the surface roughness after polishing is improved. Among them, the material removal rate of the alumina-EDTA composite abrasive with an EDTA grafting amount of 9.09 wt.% in Example 3 is increased by 101% compared with the industrial alumina abrasive, and the surface roughness is decreased by 65%.

[0055] Table 1. Polishing effects of alumina abrasives in each example and comparative example of the present invention on the sapphire substrate

[0056]

[0057] In summary, compared with the conventional industrial alumina abrasive, the alumina-EDTA abrasive of the present invention can significantly improve the material removal rate and reduce the surface roughness of the sapphire substrate when used for polishing the sapphire substrate. The alumina-EDTA abrasive of the present invention improves the dispersibility compared with the conventional industrial alumina abrasive, increases the chemical action during the polishing process, promotes the synergistic effect of chemical etching and mechanical removal, so as to achieve a higher removal rate and better surface accuracy.

[0058] The above are only the preferred embodiments of the present invention, and the embodiments are not used to limit the patent protection scope of the present invention. Therefore, any equivalent structural changes made by using the content of the specification of the present invention should, by the same token, be included in the protection scope of the appended claims of the present invention.

Claims

1. A preparation method of EDTA-modified alumina composite abrasive grains, characterized in that, It includes the following steps: S01: Add α-aluminum oxide particles, NaOH, and 30 wt% hydrogen peroxide into deionized water, and ball-mill them in a ball-milling tank at a rotation speed of 260 rpm for 2 h. After the ball-milling is completed, wash the obtained particles with deionized water until neutral, and dry them in an oven at 50 °C for 24 h to obtain ball-milled hydroxylated aluminum oxide particles; S02: Add ethylenediaminetetraacetic acid into thionyl chloride, react at a constant temperature of 70 °C for 3 h until no gas is released in the reaction system, and absorb the reaction tail gas with a saturated NaOH solution; after the reaction is completed, use a suction filtration device to separate the solid and liquid of the obtained product, and let the obtained acylated ethylenediaminetetraacetic acid volatilize in a fume hood for 15 h until there is no thionyl chloride on the surface; S03: Add the hydroxylated aluminum oxide particles into an N,N-dimethylformamide solvent, and ultrasonically treat them with an ultrasonic device for 30 min until the suspension is evenly dispersed. Place it in a water bath and stir magnetically. When the reaction temperature reaches 40 °C, add acylated ethylenediaminetetraacetic acid, let the obtained product react at 40 °C for 8 h, then add it into deionized water for hydrolysis for 30 min, and then wash it with deionized water until neutral. Let the obtained product dry in an oven at 50 °C for 20 h to obtain aluminum oxide-ethylenediaminetetraacetic acid abrasive grains.

2. The preparation method of the EDTA-modified alumina composite abrasive grains according to claim 1, wherein, In the step S01, the mass ratio of the α-aluminum oxide particles, NaOH, 30 wt% hydrogen peroxide, and deionized water is 20:0.5:5:

100.

3. The preparation method of the EDTA-modified alumina composite abrasive grains according to claim 1, characterized in that, In the step S02, the mass ratio of the ethylenediaminetetraacetic acid and thionyl chloride is 30:

262.

4. The preparation method of the EDTA-modified alumina composite abrasive grains according to claim 1, wherein, In the step S03, the mass ratio of the hydroxylated aluminum oxide, N,N-dimethylformamide, acylated ethylenediaminetetraacetic acid, and deionized water is 30:95:0.5 - 3:200.

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