Acidic lithium tantalate polishing solution and polishing method

Abstract

The invention relates to the technical field of polishing solutions, in particular to an acidic lithium tantalate polishing solution and a polishing method. The polishing solution comprises the following components: silica sol, a complexing agent, a water-soluble high-molecular compound, an optional pH regulator and water, wherein the pH value of the acidic lithium tantalate polishing solution is less than 7. The acid chemical mechanical polishing solution provided by the invention can remarkably improve the removal rate of the surface of a lithium tantalate wafer, the polished surface still has good roughness, and meanwhile, a modified acid system still can be kept stable under the condition of high concentration.

Description

Technical Field

[0001] The present invention relates to the technical field of polishing liquids, and particularly relates to an acidic lithium tantalate polishing liquid and a polishing method. Background Art

[0002] Lithium tantalate (abbreviated as LT, LiTaO3) is an excellent multifunctional crystal material, which has excellent piezoelectric, electro-optic and pyroelectric properties such as a large electromechanical coupling coefficient, low loss, high temperature stability and good high-frequency performance. With the rapid development of mobile communication and the information industry, lithium tantalate wafers are increasingly widely used in the manufacture of high-frequency, medium-frequency bandwidth, low insertion loss, high-frequency stability and miniaturized surface acoustic wave and bulk wave devices such as surface acoustic wave filters, resonators, etc.

[0003] Lithium tantalate is a hard and brittle material, and generally takes a long time in the polishing process. The traditional polishing method is to polish by circulating the liquid supply through a liquid supply system with an alkaline silica sol system and substances such as chelating agents, and there is still great room for improvement in its polishing efficiency. Summary of the Invention

[0004] The purpose of the present invention is to provide an acidic lithium tantalate polishing liquid with higher polishing efficiency.

[0005] In order to achieve the above purpose, the first aspect of the present invention provides an acidic lithium tantalate polishing liquid, which comprises the following components: silica sol, complexing agent, water-soluble polymer compound, optionally pH regulator and water; wherein, the pH value of the acidic lithium tantalate polishing liquid is less than 7.

[0006] The acidic lithium tantalate polishing liquid in the present invention has more excellent polishing performance, and it can also improve the problem of surface scratches after polishing, so that the surface roughness Ra after polishing is lower than 0.2 nm.

[0007] As a preferred technical solution of the present invention, the pH value of the acidic lithium tantalate polishing liquid is 1-5, such as 1, 2, 3, 4 or 5, preferably 2-3.

[0008] In the present invention, by controlling the acidic lithium tantalate polishing liquid within the above preferred range, the polishing effect can be better achieved.

[0009] In the present invention, the optionally pH regulator means that the pH regulator can be used or not used according to needs. Preferably, the pH regulator is used in the system of the present invention. As a preferred technical solution of the present invention, the dosage of the pH regulator makes the pH value of the acidic lithium tantalate polishing liquid 1-5, preferably 2-3.

[0010] In the present invention, the pH regulator can be of conventional types in the art. Preferably, the pH regulator is selected from sodium hydroxide, potassium hydroxide, hydrochloric acid, nitric acid, acetic acid, etc., preferably potassium hydroxide and / or nitric acid.

[0011] In the present invention, nitric acid generally exists in the form of an aqueous solution of HNO 3 with a concentration generally of 40 - 70 wt%.

[0012] As a preferred technical solution of the present invention, the mass ratio of the silica sol to water is (0.1 - 1):1, for example, 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, and preferably (0.3 - 0.6):1.

[0013] As a preferred technical solution of the present invention, the mass ratio of the complexing agent to water is (0.002 - 0.02):1, for example, 0.002:1, 0.004:1, 0.006:1, 0.007:1, 0.008:1, 0.009:1, 0.01:1, 0.012:1, 0.015:1, 0.017:1, 0.02:1, and preferably (0.006 - 0.009):1.

[0014] As a preferred technical solution of the present invention, the mass ratio of the water-soluble polymer compound to water is (0.001 - 0.01):1, for example, 0.001:1, 0.002:1, 0.003:1, 0.004:1, 0.005:1, 0.006:1, 0.007:1, 0.008:1, 0.009:1, 0.01:1, and preferably (0.002 - 0.005):1.

[0015] As a preferred technical solution of the present invention, the average particle size of the silica sol is 6 - 1000 nm, for example, 6 nm, 10 nm, 20 nm, 30 nm, 50 nm, 80 nm, 110 nm, 150 nm, 200 nm, 400 nm, 600 nm, 800 nm or 1000 nm, preferably 50 - 200 nm, and more preferably 80 - 110 nm.

[0016] As a preferred technical solution of the present invention, in the silica sol, the content of silicon oxide is 30 - 50 wt%.

[0017] As a preferred technical solution of the present invention, the aluminum-modified acidic silica sol is an aluminum-modified acidic silica sol, and the preparation method of the aluminum-modified acidic silica sol includes:

[0018] (1) Contacting the alkaline silica sol with a cation exchange resin to obtain an acidic silica sol with a pH less than 3;

[0019] (2) Reacting the acidic silica sol with an aqueous solution of aluminum salt to obtain an aluminum-modified silica sol;

[0020] (3) Contact the aluminum-modified silica sol with an organic acid to adjust the pH value of the aluminum-modified silica sol to 1-5, obtaining an aluminum-modified acidic silica sol.

[0021] As a preferred technical solution of the present invention, in step (1), the mass ratio of the alkaline silica sol to the cation exchange resin is 0.5-5:1, such as 0.5:1, 1:1, 2:1, 3:1, 4:1 or 5:1.

[0022] As a preferred technical solution of the present invention, the cation exchange resin is selected from strongly acidic cation resins, such as 001×7 type (strongly acidic styrene-based cation exchange resin), PC003 type (strong acid polystyrene cation exchange resin), Lewatit-100 type (strongly acidic styrene-based cation exchange resin).

[0023] As a preferred technical solution of the present invention, the average particle size of the alkaline silica sol is 6-1000 nm, such as 6 nm, 10 nm, 20 nm, 30 nm, 50 nm, 80 nm, 110 nm, 150 nm, 200 nm, 400 nm, 600 nm, 800 nm or 1000 nm, preferably 50-200 nm, more preferably 80-110 nm.

[0024] As a preferred technical solution of the present invention, in the alkaline silica sol, the content of silicon oxide is 1-50 wt%, such as 1 wt%, 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%.

[0025] In step (1) of the present invention, the contact conditions are not particularly limited as long as the pH of the system can be made less than 3, such as pH being 1, 2 or 3.

[0026] As a preferred technical solution of the present invention, in step (2), the reaction conditions include: temperature is 100-110 °C, stirring speed is 100-150 rpm / min, and time is 3-24 h.

[0027] As a preferred technical solution of the present invention, in the aqueous aluminate solution, the aluminate is selected from at least one of sodium metaaluminate, sodium tetrahydroxyaluminate and potassium metaaluminate.

[0028] As a preferred technical solution of the present invention, the concentration of the aqueous aluminate solution is 0.1-10 wt%, such as 0.1 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt% or 10 wt%.

[0029] As a preferred technical solution of the present invention, the dosage of the aqueous aluminate solution is 0.005-0.5 wt% of the mass of the acidic silica sol, for example, 0.05 wt%, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt% or 0.5 wt%.

[0030] As a preferred technical solution of the present invention in step (2), the aqueous aluminate solution is added dropwise to the acidic silica sol at a flow rate of 0.1-20 L / h (for example, 0.1 L / h, 1 L / h, 3 L / h, 5 L / h, 8 L / h, 10 L / h, 12 L / h, 15 L / h, 18 L / h or 20 L / h), and then reacted for 3-24 h to obtain the aluminum-modified silica sol.

[0031] As a preferred technical solution of the present invention, the number-average molecular weight of the water-soluble polymer compound is 4000-10000, for example, 4000, 5000, 6000, 7000, 8000, 9000, 1000.

[0032] As a preferred technical solution of the present invention, the water-soluble polymer includes at least one of polyacrylic acid, polyvinylpyrrolidone, chitosan and hydroxyethyl cellulose, and preferably includes polyacrylic acid.

[0033] As a preferred technical solution of the present invention, the water-soluble polymer further includes a polyquaternary ammonium salt, such as polydimethyldiallylammonium chloride.

[0034] As a more preferred technical solution of the present invention, the water-soluble polymer is polyacrylic acid and polydimethyldiallylammonium chloride, and preferably the mass ratio of polyacrylic acid to polydimethyldiallylammonium chloride is 1:1.

[0035] As a more preferred technical solution of the present invention, the complexing agent is selected from complexing agent A and / or complexing agent B; complexing agent A is selected from one or more of malonic acid, ethylenediaminetetraacetic acid, phthalic acid, oxalic acid, succinic acid, adipic acid, citric acid, maleic acid or their corresponding ammonium salts, sodium salts or potassium salts; complexing agent B is selected from amino polyol substances, preferably selected from amino-polyethylene glycol-acetic acid, amino-polyethylene glycol-amino, etc., and preferably amino-undecapolyethylene glycol-acetic acid.

[0036] As a more preferred technical solution of the present invention, complexing agent A is selected from malonic acid and / or citric acid, and preferably citric acid.

[0037] As a preferred technical solution of the present invention, the complexing agent is complexing agent A and complexing agent B, and preferably the mass ratio of complexing agent A to complexing agent B is (0.5-2):1, for example, 0.5:1, 1:1, 1.5:1 or 2:1.

[0038] The preparation method of the acidic lithium tantalate polishing liquid in the present invention is not particularly limited, and each component in the acidic lithium tantalate polishing liquid can be mixed evenly.

[0039] The second aspect of the present invention provides a polishing method for lithium tantalate, which includes:

[0040] Polishing lithium tantalate with a polishing pad and an acidic lithium tantalate polishing liquid;

[0041] Among them, the conditions for the polishing include: the polishing pressure is 200 - 400 g / cm 2 , the polishing rotation speed of the head / disk is (15 - 25) / (30 - 40) rpm, the temperature of the polishing disk surface is 20 - 25 °C, the flow rate of the lithium tantalate polishing liquid is 80 - 120 g / min, and the polishing time is 20 - 40 min.

[0042] The polishing pad in the present invention can be a conventional polishing pad in the art, such as a commonly used polyurethane polishing pad. In the present invention, the polishing pad of Shanghai Yingzhi Abrasive Materials Co., Ltd., model PU - 80 is used as an exemplary illustration.

[0043] The present invention has at least the following beneficial effects:

[0044] 1. The acidic chemical mechanical polishing liquid provided by the present invention can significantly improve the removal rate of the surface of the lithium tantalate wafer, and the surface after polishing still has good roughness. At the same time, the modified acidic system can still remain stable under high - concentration conditions.

[0045] 2. In the present invention, an acidic polishing liquid system is established based on modified silica sol, and is paired with a variety of preferably selected chelating agents, water - soluble polymer compounds, etc., which can achieve a substantial improvement in polishing performance, and at the same time has good storage stability and circulation stability.

[0046] 3. The use of water - soluble polymer compounds in the present invention can better improve the problem of surface scratches after polishing, making the surface roughness Ra after polishing lower than 0.2 nm.

[0047] 4. The use of a specific complexing agent in the present invention has a higher removal rate compared to using it alone. Specific Embodiments

[0048] The present invention will be described in detail below through examples. The following examples are only illustrative descriptions of the specific technical solutions of the present invention, and do not limit the scope of the present invention. That is, it should be understood that non - essential simple corrections, adjustments, and combinations made by those skilled in the art based on the inventive concept of the present invention are all within the scope of protection required by the present invention.

[0049] In the following examples:

[0050] The pH value of silica sol A is 9.5, the solid content is 30 wt%, and the average particle size is 80 nm;

[0051] The pH value of silica sol B is 9.5, the solid content is 30 wt%, and the average particle size is 110 nm;

[0052] The preparation method of aluminum-modified acidic silica sol A is as follows:

[0053] Take 50 kg of silica sol A, react it with a cation exchange resin (Lewatit-100 type) to obtain an acidic silica sol (the mass of the cation exchange resin is 70 wt% of the mass of silica sol A), with a pH of 2. Heat it to 105 °C under stirring, keep stirring, with a stirring speed of 100 rpm / min. Dropwise add an aqueous solution of sodium metaaluminate with a concentration of 0.1 mg / L at a flow rate of 3 L / h, with an addition amount of 0.16 wt%, and react for 6 h to obtain an aluminum-modified silica sol. Then use acetic acid to adjust the pH of the system to 3 to obtain aluminum-modified acidic silica sol A.

[0054] The preparation method of aluminum-modified acidic silica sol B is as follows: Take 50 kg of silica sol B, react it with a cation exchange resin (Lewatit-100 type) to obtain an acidic silica sol (the mass of the cation exchange resin is 70 wt% of the mass of silica sol A), with a pH of 2. Heat it to 105 °C under stirring, keep stirring, with a stirring speed of 100 rpm / min. Dropwise add an aqueous solution of sodium metaaluminate with a concentration of 0.1 mg / L at a flow rate of 3 L / h, with an addition amount of 0.16 wt%, and react for 6 h to obtain an aluminum-modified silica sol. Then use acetic acid to adjust the pH of the system to 3 to obtain aluminum-modified acidic silica sol A.

[0055] Comparative Example 1

[0056] Take 30 wt% of silica sol A, 0.5 wt% of citric acid, and make up the water to 100 w% and mix evenly. Then use nitric acid with a concentration of 50 wt% to adjust the pH value of the system to 2.

[0057] Comparative Example 2

[0058] Take 30 wt% of silica sol A, 0.5 wt% of amino-undecaethylene glycol-acetic acid, and make up the water to 100 w% and mix evenly. Then use nitric acid with a concentration of 50 wt% to adjust the pH value of the system to 2.

[0059] Comparative Example 3

[0060] Take 30 wt% of silica sol A, 0.3 wt% of citric acid, 0.2 wt% of amino-undecaethylene glycol-acetic acid, and make up the water to 100 w% and mix evenly. Then use nitric acid with a concentration of 50 wt% to adjust the pH value of the system to 2.

[0061] Comparative Example 4

[0062] Take 30 wt% of silica sol B, 0.2 wt% of polyacrylic acid with a number-average molecular weight of 6000, 0.3 wt% of malonic acid, 0.2 wt% of amino-undecaethylene glycol-acetic acid, and make up 100 w% with water, mix evenly, and then use potassium hydroxide to adjust the pH value of the system to 10.

[0063] Example 1

[0064] Take 30 wt% of silica sol A, 0.2 wt% of polyacrylic acid with a number-average molecular weight of 6000, 0.3 wt% of citric acid, 0.2 wt% of amino-undecaethylene glycol-acetic acid, and make up 100 w% with water, mix evenly, and then use 50 wt% nitric acid to adjust the pH value of the system to 2.

[0065] Example 2

[0066] Take 30 wt% of silica sol A, 0.2 wt% of polyacrylic acid with a number-average molecular weight of 6000, 0.5 wt% of malonic acid, and make up 100 w% with water, mix evenly, and then use 50 wt% nitric acid to adjust the pH value of the system to 2.

[0067] Example 3

[0068] Take 30 wt% of silica sol A, 0.2 wt% of polyacrylic acid with a number-average molecular weight of 6000, 0.5 wt% of amino-undecaethylene glycol-acetic acid, and make up 100 w% with water, mix evenly, and then use 50 wt% nitric acid to adjust the pH value of the system to 2.

[0069] Example 4

[0070] Take 30 wt% of silica sol A, 0.2 wt% of polyacrylic acid with a number-average molecular weight of 6000, 0.3 wt% of malonic acid, 0.2 wt% of amino-undecaethylene glycol-acetic acid, and make up 100 w% with water, mix evenly, and then use 50 wt% nitric acid to adjust the pH value of the system to 2.

[0071] Example 5

[0072] Take 30 wt% of silica sol A, 0.2 wt% of polyacrylic acid with a number-average molecular weight of 6000, 0.3 wt% of malonic acid, 0.2 wt% of amino-undecaethylene glycol-acetic acid, and make up 100 w% with water, mix evenly, and then use 50 wt% nitric acid to adjust the pH value of the system to 3.

[0073] Example 6

[0074] Take 30 wt% of silica sol B, 0.2 wt% of polyacrylic acid with a number-average molecular weight of 6000, 0.3 wt% of malonic acid, 0.2 wt% of amino-undecaethylene glycol acetic acid, and supplement water by 100 w% and mix evenly. Then, use 50 wt% nitric acid to adjust the pH value of the system to 3.

[0075] Example 7

[0076] Take 30 wt% of aluminum-modified acidic silica sol A, 0.2 wt% of polyacrylic acid with a number-average molecular weight of 6000, 0.3 wt% of malonic acid, 0.2 wt% of amino-undecaethylene glycol acetic acid, and supplement water by 100 w% and mix evenly. Then, use 50 wt% nitric acid to adjust the pH value of the system to 2.

[0077] Example 8

[0078] Take 30 wt% of aluminum-modified acidic silica sol B, 0.2 wt% of polyacrylic acid with a number-average molecular weight of 6000, 0.3 wt% of malonic acid, 0.2 wt% of amino-undecaethylene glycol acetic acid, and supplement water by 100 w% and mix evenly. Then, use 50 wt% nitric acid to adjust the pH value of the system to 2.

[0079] Example 9

[0080] Take 30 wt% of aluminum-modified acidic silica sol A, 0.2 wt% of polyacrylic acid with a number-average molecular weight of 6000, 0.3 wt% of malonic acid, 0.2 wt% of amino-undecaethylene glycol acetic acid, and supplement water by 100 w% and mix evenly. Then, use 50 wt% nitric acid to adjust the pH value of the system to 3.

[0081] Example 10

[0082] Take 30 wt% of aluminum-modified acidic silica sol B, 0.2 wt% of polyacrylic acid with a number-average molecular weight of 6000, 0.3 wt% of malonic acid, 0.2 wt% of amino-undecaethylene glycol acetic acid, and supplement water by 100 w% and mix evenly. Then, use 50 wt% nitric acid to adjust the pH value of the system to 3.

[0083] Example 11

[0084] Take 30 wt% of aluminum-modified acidic silica sol B, 0.15 wt% of polyacrylic acid with a number-average molecular weight of 6000, 0.15 wt% of polydimethyldiallylammonium chloride with a number-average molecular weight of 4500, 0.3 wt% of malonic acid, 0.2 wt% of amino-undecaethylene glycol acetic acid, and supplement water by 100 w% and mix evenly. Then, use 50 wt% nitric acid to adjust the pH value of the system to 2.

[0085] Example 12

[0086] Take 30 wt% of aluminum-modified acidic silica sol B, 0.15 wt% of polyacrylic acid with a number-average molecular weight of 6000, 0.15 wt% of polydimethyldiallylammonium chloride with a number-average molecular weight of 4500, 0.3 wt% of malonic acid, 0.2 wt% of amino-undecaethylene glycol-acetic acid, and make up the balance with water to 100 wt% and mix evenly. Then adjust the pH value of the system to 3 using 50 wt% nitric acid.

[0087] Test Example

[0088] Polishing process:

[0089] The polishing machine is Kizi KD24QX, equipped with a self-produced NWD-80 polishing pad (purchased from Shanghai Yingzhi Abrasive Materials Co., Ltd., model PU-80). The lithium tantalate is a 4-inch wafer, the polishing pressure is 300 g / cm 2 , the polishing speed is 20 / 35 rpm for the head / platen, the temperature of the polishing platen surface is 25 ± 5 °C, the flow rate is 100 g / min, and the polishing time is 30 min.

[0090] Test method:

[0091] 1. Calculate the removal rate by weight conversion before and after polishing.

[0092] 2. Observe whether there are obvious scratches on the polished surface after ultrasonic cleaning with deionized water under a strong light.

[0093] 3. Atomic force microscope roughness test: The machine model is DIMENSION EDGE System, the test size is 5 um * 5 um at the center point, and whether the surface roughness is < 0.2 nm.

[0094] 4. Observe the residual amount of abrasive particles on the surface of the 4-inch wafer under a microscope.

[0095] The test results are shown in Table 1.

[0096] Table 1

[0097]

[0098]

[0099] From the results in Table 1, it can be obtained that: From Comparative Examples 1-3 and Examples 1-3, it can be seen that the addition of the water-soluble polymer in the present invention can, although it causes a decrease in the polishing rate, improve the problem of surface scratches after polishing, making the surface roughness Ra after polishing lower than 0.2 nm; From Comparative Example 3 and Example 1, it can be seen that the addition of the water-soluble polymer in the present invention can, although it causes a decrease in the polishing rate, improve the problem of surface scratches after polishing, making the surface roughness Ra after polishing lower than 0.2 nm; From Examples 1-4, it can be seen that in an acidic system, when organic acids and amino polyols are used simultaneously as complexing agents in the polishing liquid of the present invention, especially when malonic acid is combined with amino-undecaethylene glycol acetic acid, it has a higher removal rate compared with a single organic acid or amino polyol; From Examples 4-6 and Comparative Example 4, it can be seen that silica sol with a particle size of 110 nm and a lower pH can further improve the polishing rate; From Examples 4-6 and Examples 7-10, it can be seen that the silica sol modified by acid can improve the polishing rate on the basis of ordinary silica sol, and still maintain an excellent surface after polishing. Moreover, when the polishing liquid prepared with ordinary silica sol is under acidic conditions, the particle size increases, which will cause the polishing liquid to agglomerate and deteriorate, while the acid-modified polishing liquid can still maintain the original particle size after aging at 50 degrees; From Examples 8, 10, 11-12, it can be seen that adding polyquaternary ammonium salts, such as polydimethyldiallylammonium chloride, in the present invention can further optimize the performance of the polishing liquid.

Claims

1. An acidic lithium tantalate polishing liquid, characterized in that: The invention comprises the following components: silica sol, a complexing agent, a water-soluble polymer compound, an optional pH adjusting agent and water; Wherein, the pH value of the acidic lithium tantalate polishing liquid is less than 7.

2. The acidic lithium tantalate polishing liquid according to claim 1, characterized in that: The pH value of the acidic lithium tantalate polishing liquid is 1-5; The pH regulator is used in an amount such that the pH value of the acidic lithium tantalate polishing liquid is 1-5; The pH adjuster is selected from at least one of sodium hydroxide, potassium hydroxide, hydrochloric acid, nitric acid and acetic acid.

3. The acidic lithium tantalate polishing liquid according to claim 1, characterized in that: The mass ratio of the silica sol to water is (0.1-1):1; The mass ratio of the complexing agent to water is (0.002-0.02):1; The mass ratio of the water-soluble polymer compound to water is (0.001-0.01):

1.

4. The acidic lithium tantalate polishing liquid according to claim 1, characterized in that: The average particle size of the silica sol is 6-1000nm; In the silica sol, the content of silicon oxide is 30-50wt%.

5. The acidic lithium tantalate polishing liquid according to any one of claims 1 to 4, characterized in that: The aluminum-modified acidic silica sol is an aluminum-modified acidic silica sol; The preparation method of the aluminum-modified acidic silica sol comprises: (1) contacting alkaline silica sol with a cation exchange resin to obtain an acidic silica sol having a pH value less than 3; (2) reacting the acidic silica sol with an aqueous aluminate solution to obtain an aluminum-modified silica sol; (3) The aluminum-modified silica sol is contacted with an organic acid to make the pH value of the aluminum-modified silica sol be 1-5, thereby obtaining an aluminum-modified acidic silica sol.

6. The acidic lithium tantalate polishing liquid according to claim 5, characterized in that: In step (1), the mass ratio of alkaline silica sol to cation exchange resin is 0.5-5:1; the cation exchange resin is selected from a strongly acidic cation resin; The average particle size of the alkaline silica sol is 6-1000nm; In the alkaline silica sol, the content of silicon oxide is 1-50wt%.

7. The acidic lithium tantalate polishing liquid according to claim 5, characterized in that: In step (2), the reaction conditions include: temperature of 100-110° C., stirring speed of 100-150 rpm / min, and reaction time of 3-24 h; In the aluminate aqueous solution, the aluminate is selected from at least one of sodium metaaluminate, sodium tetrahydroxyaluminate and potassium metaaluminate; The concentration of the aluminate aqueous solution is 0.1-10wt%; The amount of the aluminate aqueous solution is 0.005-0.5wt% of the mass of the acidic silica sol; In step (2), an aqueous aluminate solution is added dropwise to the acidic silica sol at a flow rate of 0.1-20 L / h, followed by reaction for 3-24 hours to obtain an aluminum-modified silica sol.

8. The acidic lithium tantalate polishing liquid according to claim 1, characterized in that: The number average molecular weight of the water-soluble polymer compound is 4000-10000; The water-soluble polymer includes at least one of polyacrylic acid, polyvinyl pyrrolidone, chitosan and hydroxyethyl cellulose.

9. The acidic lithium tantalate polishing liquid according to claim 1, characterized in that: The complexing agent is selected from complexing agent A and / or complexing agent B; the complexing agent A is selected from one or more of malonic acid, ethylenediaminetetraacetic acid, phthalic acid, oxalic acid, succinic acid, adipic acid, citric acid, maleic acid or their corresponding ammonium salts, sodium salts or potassium salts; the complexing agent B is selected from amino polyol substances.

10. A method for polishing lithium tantalate, characterized in that: The method includes: Polishing lithium tantalate using a polishing pad and an acidic lithium tantalate polishing solution; The polishing conditions include: polishing pressure of 200-400g / cm 2 The polishing speed is head / disk (15-25) / (30-40) rpm, the polishing disk surface temperature is 20-25°C, the flow rate of lithium tantalate polishing liquid is 80-120g / min, and the polishing time is 20-40min.

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