Preparation method of aluminum oxide polishing solution applied to gallium arsenide

Abstract

The invention provides a preparation method of an aluminum oxide polishing solution applied to gallium arsenide, and relates to the field of polishing materials.The preparation method comprises the steps that a protective layer is formed on the surface of an aluminum oxide raw material through a protective agent, then strong acid is added for ball milling, centrifugal separation is conducted after ball milling, washing is conducted to be neutral, neutral sediment is obtained, the neutral sediment is filtered after being dried, and the aluminum oxide polishing solution is obtained; the method comprises the following steps: firstly, pre-treating an alumina raw material, then removing gamma-phase alumina in the alumina raw material to obtain pre-treated alpha-phase alumina, then adding a copolymer dispersant to enable the dispersion stability of the alpha-phase alumina to be higher, and then adding a chelating agent and an oxidizing agent to form a polishing solution finished product. According to the preparation method, the purity of alpha-phase aluminum oxide is improved, the dispersity of the grinding material is further guaranteed by combining the steric hindrance effect of the copolymer dispersing agent, the alpha-phase aluminum oxide and the copolymer dispersing agent are in synergistic interaction, and the polishing rate and the polishing quality are improved.

Description

Technical Field

[0001] This invention relates to the field of polishing materials, and more specifically, to a method for preparing an alumina polishing slurry for gallium arsenide. Background Technology

[0002] Gallium arsenide (GaAs) is widely used in high-frequency communication devices, optoelectronic devices (such as LEDs, lasers, and solar cells), and integrated circuit substrates due to its excellent physicochemical properties, including high electron mobility, wide bandgap, and direct bandgap. With the continuous iteration of device technology, the surface quality requirements for gallium arsenide substrates are becoming increasingly stringent; chemical mechanical polishing (CMP) is currently the mainstream technology for achieving global wafer planarization. In the CMP process of gallium arsenide, the composition of the polishing slurry plays a decisive role in the polishing rate (MRR) and surface quality (roughness, scratches).

[0003] In the process of realizing this invention, the applicant discovered that: currently, increasing the polishing rate of gallium arsenide slurry usually involves α-phase alumina (α... Al2O3 was used as an abrasive; however, due to improper control of the calcination process and differences in raw material purity, the final α-abrasive obtained was... Al2O3 products often contain a certain amount of residual gamma. Al2O3, γ Al₂O₃ is a thermodynamically metastable crystal form, which is unstable and can affect the polishing rate and cause scratches during gallium arsenide polishing. Secondly, α-phase alumina is difficult to clean in terms of removing γ-phase impurities. When Al2O3 is used, the surface hydroxyl groups are usually destroyed, which damages the active groups of aluminum oxide and makes it difficult to disperse. As a result, gallium arsenide has a large surface roughness and causes scratches.

[0004] Therefore, how to develop a polishing slurry that can achieve both high gallium arsenide polishing rate and improved scratches and roughness is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art or related art, and provides a method for preparing an alumina polishing slurry for gallium arsenide. The polishing slurry prepared can achieve a high gallium arsenide polishing rate and improve scratches and roughness when used for polishing operations. Moreover, the abrasive dispersion is stable and it matches the surface potential of gallium arsenide well.

[0006] The first aspect of this invention discloses a method for preparing an alumina polishing slurry for gallium arsenide, comprising: alumina particle pretreatment: dispersing alumina particles in deionized water to obtain an abrasive dispersion system; adding 0.3% to 3% of a protective agent by mass fraction to the abrasive dispersion system and stirring to obtain an abrasive system with a protective layer; adding 2% to 10% of a strong acid to the abrasive system with the protective layer and stirring, followed by ball milling for 1 to 3 hours, centrifuging and washing until neutral to obtain a neutral precipitate, drying the neutral precipitate and filtering to obtain pretreated α-phase alumina; wherein the protective agent includes hydroxyphosphonic acid and / or hydroxyethylidene diphosphonic acid, and the strong acid includes one or more of nitric acid, hydrochloric acid, or sulfuric acid; and adding a copolymer for dispersion. Agent: The pretreated α-phase alumina is dispersed in deionized water, and an acidic pH adjuster is added to adjust the pH value to 2.5~4.5 to obtain an α-phase alumina dispersion system. Then, 0.5%~5% of PAA-b-PEG-b-PPA terpolymer and / or acrylic acid-acrylate-phosphonic acid-sulfonic acid quaternary copolymer are added by mass fraction and stirred. During stirring, an alkaline pH adjuster is added to adjust the pH value to 9~10 to obtain a dispersion-modified abrasive system. Chelating agent: 0.3%~2.5% of EDTA chelating agent is added by mass fraction to the dispersion-modified abrasive system to obtain an abrasive complex system. Oxidizing agent: 1%~2% of oxidizing agent is added by mass fraction to the abrasive complex system to obtain the polishing slurry product.

[0007] According to the method for preparing alumina polishing slurry for gallium arsenide provided by the present invention, preferably, in the step of pretreatment of alumina particles, alumina particles and deionized water are placed in a high-speed disperser and stirred and dispersed at a speed of 2500 r / min for 30 min to obtain an abrasive dispersion system; when adding a protective agent, stirring is carried out at a speed of 500 r / min; when adding a strong acid, the stirring speed is maintained at 500 r / min.

[0008] According to the method for preparing alumina polishing slurry for gallium arsenide provided by the present invention, preferably, the pretreatment step of alumina particles further includes: adding a strong acid and stirring, then transferring the solution to a planetary ball mill and ball milling at a speed of 1500 r / min for 1 h to 3 h; after ball milling, centrifuging at a speed of 8000 r / min for 10 min using a high-speed centrifuge, collecting the precipitate, and repeatedly washing the precipitate with deionized water until the pH of the washing solution is 7, thus obtaining a neutral precipitate.

[0009] According to the method for preparing alumina polishing slurry for gallium arsenide provided by the present invention, preferably, the step of pretreatment of alumina particles further includes: drying the neutral precipitate in a forced-air drying oven at 80°C for 4 hours, and filtering it through a 0.1μm microfiltration membrane after drying to obtain pretreated α-phase alumina.

[0010] According to the method for preparing alumina polishing slurry for gallium arsenide provided by the present invention, preferably, in the step of adding copolymer dispersant, pretreated α-phase alumina and deionized water are placed in a high-speed disperser and stirred and dispersed at a speed of 1000 r / min for 30 min. After adding PAA-b-PEG-b-PPA terpolymer and / or acrylic acid-acrylate-phosphonic acid-sulfonic acid quaternary copolymer, the mixture is stirred at a speed of 500 r / min for 1 h. Then, potassium hydroxide is added to adjust the pH value to 9-10.

[0011] According to the method for preparing alumina polishing slurry for gallium arsenide provided by the present invention, preferably, the protective agent is hydroxyphosphonic acid, and the amount used is 2% of the mass of the abrasive dispersion system; the strong acid is nitric acid, and the amount used is 9% of the mass of the abrasive dispersion system.

[0012] According to the method for preparing alumina polishing slurry for gallium arsenide provided by the present invention, preferably, the amount of PAA-b-PEG-b-PPA terpolymer and / or acrylic acid-acrylate-phosphonic acid-sulfonic acid quaternary copolymer is 3% of the mass of the α-phase alumina dispersion system.

[0013] According to the method for preparing alumina polishing slurry for gallium arsenide provided by the present invention, preferably, the amount of EDTA chelating agent is 1.5% of the mass of the dispersion-modified abrasive system.

[0014] According to the method for preparing the alumina polishing slurry for gallium arsenide provided by the present invention, preferably, the oxidant is sodium hypochlorite, and the mass of the oxidant accounts for 1.5% of the mass of the abrasive complex system.

[0015] The beneficial effects achieved by this invention include at least the following: (1) The alumina raw material is purified and protected by the alumina particle pretreatment process, which can significantly reduce the content of γ-phase Al2O3 while retaining the active hydroxyl groups on the surface of α-phase Al2O3. This reduces the possibility of scratches from the source and ensures the dispersion stability of the polishing liquid system. Specifically: α-phase Al2O3 (alumina) is chemically very stable and almost insoluble in common acids or bases, with a small amount of hydroxyl groups on its surface; γ-phase Al2O3 has a large specific surface area due to its lattice defects and porous structure, and has high chemical activity, so it can dissolve in strong acids or bases; based on this principle, this application adds a protective agent to form "Al-OP" groups with the hydroxyl groups on the surface of Al2O3, which serve as a protective layer for the hydroxyl groups. The protective agent contains hydroxyl groups and is easily dispersed in water; furthermore, the structure of γ-phase Al2O3 is destroyed by adding strong acid and ball milling, so that it can be removed by subsequent filtration; in this process, the H in the strong acid + This causes the hydroxyl groups of the protective agent to protonate and become positively charged, increasing the Zate potential of alumina. The alumina molecules are then more evenly dispersed due to repulsive forces. + It will adsorb into the pores of γ-Al2O3, corroding γ-Al2O3 and deteriorating its mechanical properties. In addition, mechanical ball milling reduces the particle size of γ-Al2O3 particles, while α-Al2O3 has high strength and is unaffected. By filtering or sieving, small particles of γ-Al2O3 are removed, while α-Al2O3 particles with hydroxyl groups and surface modification are retained, thereby achieving the purpose of impurity removal and improving dispersion stability. (2) The surface of purified and surface-modified α-Al2O3 particles was modified by adding copolymer dispersants, and the dispersibility of the polishing slurry system was further improved by utilizing the steric hindrance effect. Specifically, PAA-b-PEG-b-PPA terpolymer and / or acrylic acid-acrylate-phosphonic acid-sulfonic acid quaternary copolymer were selected. Because the copolymer has multiple carboxyl groups with negative charges, it can be adsorbed with the modified positively charged alumina, so that the alumina is modified with copolymer. Due to the steric hindrance effect, the stability of the alumina is higher; thus, the polishing rate of gallium arsenide is increased, and the roughness and scratches are improved. Attached Figure Description

[0016] Figure 1 A schematic flowchart of a method for preparing an alumina polishing slurry for gallium arsenide according to an embodiment of the present invention is shown. Detailed Implementation

[0017] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0018] like Figure 1As shown, according to an embodiment of the present invention, a method for preparing an alumina polishing slurry for gallium arsenide is disclosed, comprising: Step 1, Pretreatment of alumina particles: Alumina particles are stirred and dispersed in deionized water to obtain an abrasive dispersion system; 0.3%~3% of a protective agent is added to the abrasive dispersion system by mass fraction and stirred to obtain an abrasive system with a protective layer; 2%~10% of a strong acid is added to the abrasive system with the protective layer and stirred, followed by ball milling for 1h~3h, centrifugation after ball milling, and washing until neutral to obtain a neutral precipitate. The neutral precipitate is dried and filtered to obtain pretreated α-phase alumina; wherein, the protective agent includes hydroxyphosphonic acid and / or hydroxyethylidene diphosphonic acid, and the strong acid includes one or more of nitric acid, hydrochloric acid, or sulfuric acid; Step 2, Adding copolymer dispersant: Disperse the pretreated α-phase alumina in deionized water, and add an acidic pH adjuster to adjust the pH value to 2.5~4.5 to obtain an α-phase alumina dispersion system. Then, add 0.5%~5% of PAA-b-PEG-b-PPA terpolymer and / or acrylic acid-acrylate-phosphonic acid-sulfonic acid quaternary copolymer by mass fraction and stir. During stirring, add an alkaline pH adjuster to adjust the pH value to 9~10 to obtain a dispersion-modified abrasive system. Step 3, Add chelating agent: Add 0.3%~2.5% EDTA chelating agent to the dispersion-modified abrasive system by mass fraction to obtain the abrasive complex system; Step 4, Add oxidant: Add 1% to 2% oxidant to the abrasive complex system by mass fraction to obtain the finished polishing slurry.

[0019] In this embodiment, the α-phase alumina has a particle size of 50 nm to 1 μm and a morphology of spherical or flake-like. The oxidant is one or more of hydrogen peroxide and sodium hypochlorite. The particle dispersion stirring parameters are 1000 r / min to 3000 r / min. The ball milling parameters are 1500 r / min to 3000 r / min.

[0020] Example 1 According to yet another embodiment of the present invention, a specific implementation of the above-described method for preparing an alumina polishing slurry for gallium arsenide is also disclosed: Step 1, Pretreatment of alumina particles: Take 100g of Al2O3 powder and add it to 890g of deionized water. Place it in a high-speed disperser and disperse it at 2500r / min for 30min. Then add 20g of hydroxyphosphonic acid (protectant) and stir at 500r / min for 1h. Then slowly add 80g of nitric acid while stirring, adjusting the pH of the system to 2.5. After that, stir at 500r / min for 0.5h, adding 10g of nitric acid during stirring to maintain the pH of the system. The value was stabilized at 2.5±0.01. After stirring, the solution was transferred to a planetary ball mill and ball-milled at 1500 r / min for 3 h. After ball milling, the solution was centrifuged for 10 min using a high-speed centrifuge (8000 r / min), the precipitate was collected, and the precipitate was repeatedly washed with deionized water until the pH of the washing solution was 7. The washed precipitate was placed in an 80℃ forced-air drying oven and dried for 4 h. After drying, it was filtered through a 0.1 μm microfiltration membrane to remove ultrafine impurity particles and obtain pretreated α-phase alumina. Step 2, Add copolymer dispersant: Add 50g of pretreated α-phase alumina to 842g of deionized water and stir at 1000r / min for 30min; add 25g of hydrochloric acid to adjust the pH to 3, add 30g of PAA-b-PEG-b-PPA terpolymer, stir at 500r / min for 1h, and add 23g of KOH to adjust the pH to 9.5 to obtain the dispersion-modified abrasive system; Step 3, Add chelating agent: Add 15g of EDTA chelating agent to the dispersion-modified abrasive system to obtain an abrasive complex system; Step 4, Add oxidant: Add 15g of sodium hypochlorite to the abrasive complex system to obtain the polishing slurry product.

[0021] Example 2 The only difference between this embodiment and Example 1 is the amount of protective agent used in step 1. Specifically, in step 1, 5g of hydroxyphosphonic acid, the protective agent, is added. The remaining steps and parameters are the same as in Example 1, thus obtaining the polishing liquid product of this embodiment.

[0022] Example 3 The only difference between this embodiment and Example 1 is the amount of nitric acid used in step 1. Specifically, in step 1, a total of 30g of nitric acid was added to adjust the pH to 3.8. The remaining steps and parameters were the same as in Example 1, resulting in the polishing solution product of this embodiment.

[0023] Example 4 The only difference between this embodiment and Example 1 is the amount of polymer dispersant (PAA-b-PEG-b-PPA terpolymer) used in step 2. Specifically, in step 2, 10g of PAA-b-PEG-b-PPA terpolymer is added, while the remaining steps and parameters are the same as in Example 1, to obtain the polishing liquid product of this embodiment.

[0024] Example 5 The only difference between this embodiment and Example 1 is the type of protective agent used in step 1. Specifically, in step 1, the protective agent added is hydroxyethylidene diphosphonic acid, while the remaining steps, parameters, and dosages are completely consistent with those in Example 1, resulting in the polishing liquid product of this embodiment.

[0025] Example 6 The only difference between this embodiment and Example 1 is that nitric acid in step 1 is replaced with hydrochloric acid. The remaining steps, parameters and dosages are completely the same as in Example 1, and the polishing liquid product of this embodiment is obtained.

[0026] Example 7 The only difference between this embodiment and Example 1 is the type of copolymer dispersant used in step 2. Specifically, in step 2, an acrylic acid-acrylate-phosphonic acid-sulfonic acid quaternary copolymer is used as the copolymer dispersant, while the remaining steps, parameters, and dosages are completely consistent with those in Example 1, resulting in the polishing liquid product of this embodiment.

[0027] Comparative Example 1 Compared with Example 1, this embodiment differs in that a high-temperature calcination method is used instead of step 1 in Example 1 to obtain pretreated α-phase alumina. The remaining steps, parameters, and dosages are completely consistent with Example 1, resulting in the polishing slurry product of this embodiment. Specifically, the high-temperature calcination method involves heating the alumina raw material to 1200°C and holding it therefore for 3 hours.

[0028] Comparative Example 2 Compared with Example 1, this embodiment differs in that it uses a high-temperature calcination method instead of step 1 in Example 1 to obtain pretreated α-phase alumina, and directly skips step 2 to proceed to the steps of adding chelating agents and adding oxidants to obtain the polishing liquid product of this embodiment. Specifically, the high-temperature calcination method involves heating the alumina raw material to 1200°C and holding it therefore for 3 hours.

[0029] According to another embodiment of the present invention, polishing performance tests on the polishing slurry products obtained in Examples 1 to 7 and the polishing slurry products obtained in Comparative Examples 1 and 2 are also disclosed: Polishing test conditions: The same CMP polishing equipment was used, with an IC1000 polishing pad and a 4-inch gallium arsenide wafer as the substrate. The polishing pressure was 60 psi, the polishing head speed was 90 rpm, the polishing pad speed was 100 rpm, the polishing fluid flow rate was 60 mL / min, and the polishing time was 3 minutes. After polishing, the wafer was rinsed with deionized water and dried.

[0030] Test results: Polishing tests were conducted using the polishing slurry products of Examples 1-7 and Comparative Examples 1-2, respectively, and the material removal rate, surface roughness and number of scratches after polishing were evaluated. The results are summarized in Table 1 below.

[0031] Table 1 Polishing Test Results

[0032] As shown in the test results above, the polishing slurry products prepared using the technical solution of this invention in Examples 1-7 all exhibit significantly better polishing performance than the comparative examples. Example 1, in particular, achieved the highest material removal rate while obtaining the lowest surface roughness and scratches, demonstrating its excellent and efficient planarization ability. Examples 2 to 7, with adjustments to the protective agent, pH adjuster used in particle pretreatment, and the type and amount of copolymer, still showed performance far superior to the comparative examples, verifying the stability and adjustability of the technical solution of this invention. In contrast, Comparative Example 1, lacking the specific pretreatment of this invention, exhibited poor particle activity and dispersibility, resulting in a significant decrease in both removal rate and surface quality. Comparative Example 2, lacking both effective pretreatment and copolymer dispersant, showed severe agglomeration in its polishing slurry, exhibiting the worst performance. This indicates a synergistic effect between the alumina particle pretreatment process of this invention and the specific copolymer dispersion system, jointly constituting the key to the superior performance of the polishing slurry.

[0033] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing an alumina polishing slurry for gallium arsenide, characterized in that, include: Alumina particle pretreatment: Alumina particles are stirred and dispersed in deionized water to obtain an abrasive dispersion system; 0.3%~3% of a protective agent is added to the abrasive dispersion system by mass fraction and stirred to obtain an abrasive system with a protective layer; 2%~10% of a strong acid is added to the abrasive system with the protective layer and stirred, followed by ball milling for 1h~3h, centrifugation after ball milling, and washing until neutral to obtain a neutral precipitate; the neutral precipitate is dried and filtered to obtain pretreated α-phase alumina; wherein, the protective agent includes hydroxyphosphonic acid and / or hydroxyethylidene diphosphonic acid, and the strong acid includes one or more of nitric acid, hydrochloric acid, or sulfuric acid; Adding copolymer dispersant: The pretreated α-phase alumina is dispersed in deionized water, and an acidic pH adjuster is added to adjust the pH value to 2.5~4.5 to obtain an α-phase alumina dispersion system. Then, according to the mass fraction, 0.5%~5% of PAA-b-PEG-b-PPA terpolymer and / or acrylic acid-acrylate-phosphonic acid-sulfonic acid quaternary copolymer are added and stirred. During the stirring process, an alkaline pH adjuster is added to adjust the pH value to 9~10 to obtain a dispersion-modified abrasive system. Adding chelating agent: 0.3%~2.5% EDTA chelating agent was added to the dispersion-modified abrasive system by mass fraction to obtain an abrasive complex system; Adding oxidant: Add 1% to 2% oxidant to the abrasive complex system by mass fraction to obtain the finished polishing slurry.

2. The method for preparing the alumina polishing slurry for gallium arsenide according to claim 1, characterized in that, In the alumina particle pretreatment step, alumina particles and deionized water are placed in a high-speed disperser and stirred and dispersed at a speed of 2500 r / min for 30 min to obtain the abrasive dispersion system; when adding the protective agent, the stirring speed is 500 r / min; when adding the strong acid, the stirring speed is maintained at 500 r / min.

3. The method for preparing the alumina polishing slurry for gallium arsenide according to claim 2, characterized in that, Also includes: After adding strong acid and stirring, the solution is transferred to a planetary ball mill and milled at 1500 r / min for 1 h to 3 h. After milling, a high-speed centrifuge is used to centrifuge at 8000 r / min for 10 min. The precipitate is collected and repeatedly washed with deionized water until the pH of the washing solution is 7, resulting in a neutral precipitate.

4. The method for preparing the alumina polishing slurry for gallium arsenide according to claim 3, characterized in that, Also includes: The neutral precipitate was dried in an 80°C oven for 4 hours, and then filtered through a 0.1μm microfiltration membrane to obtain the pretreated α-phase alumina.

5. The method for preparing the alumina polishing slurry for gallium arsenide according to claim 1, characterized in that, In the step of adding copolymer dispersant, the pretreated α-phase alumina and deionized water are placed in a high-speed disperser and stirred and dispersed at 1000 r / min for 30 min. After adding PAA-b-PEG-b-PPA terpolymer and / or acrylic acid-acrylate-phosphonic acid-sulfonic acid quaternary copolymer, the mixture is stirred at 500 r / min for 1 h. Then, potassium hydroxide is added to adjust the pH value to 9-10.

6. The method for preparing the alumina polishing slurry for gallium arsenide according to any one of claims 1 to 5, characterized in that, The protective agent is hydroxyphosphonic acid, and the amount used is 2% of the mass of the abrasive dispersion system; the strong acid is nitric acid, and the amount used is 9% of the mass of the abrasive dispersion system.

7. The method for preparing the alumina polishing slurry for gallium arsenide according to any one of claims 1 to 5, characterized in that, The amount of the PAA-b-PEG-b-PPA terpolymer and / or acrylic acid-acrylate-phosphonic acid-sulfonic acid terpolymer is 3% of the mass of the α-phase alumina dispersion system.

8. The method for preparing the alumina polishing slurry for gallium arsenide according to claim 1, characterized in that, The amount of EDTA chelating agent used is 1.5% of the mass of the dispersion-modified abrasive system.

9. The method for preparing the alumina polishing slurry for gallium arsenide according to claim 1, characterized in that, The oxidant is sodium hypochlorite, and the mass of the oxidant accounts for 1.5% of the mass of the abrasive complex system.

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