A polishing liquid for chemical mechanical polishing of silicon carbide substrates, and a method of preparing and use thereof

Abstract

The application discloses a polishing liquid for chemical mechanical polishing of a silicon carbide lining pipe, a preparation method and application thereof, and the polishing liquid comprises the following raw material components in mass percentage: 0.1-3% of silicon oxide; 1-5% of cerium oxide; 0.5-5% of an oxidizing agent; 0.2-2% of a surface modifier; 0.0001-0.01% of a surfactant; 0.2-2% of a pH buffer; and the balance of water. By adding silicon oxide particles and a surface modifier into the cerium oxide polishing liquid in an alkaline system, and by using a pH buffer to control the pH value in the polishing process, irreversible agglomeration of abrasives is avoided, so that the polishing liquid has a good polishing rate and a good polishing effect, and the whole polishing liquid system is stable and is not prone to aggregation and sedimentation.

Description

Technical Field

[0001] This invention relates to the field of silicon carbide polishing slurry technology, and in particular to a polishing slurry for chemical mechanical polishing of silicon carbide substrates, its preparation method, and its uses. Background Technology

[0002] Due to the high Mohs hardness and strong chemical inertness of silicon carbide crystals, post-processing of crystal materials, including cutting, grinding, and CMP polishing, suffers from long processing times and relatively low efficiency. Currently, the chemical mechanical polishing slurry systems widely used in silicon carbide CMP polishing processes are mainly divided into two systems: silicon oxide-hydrogen peroxide CMP polishing slurry and α-Al₂O₃-potassium permanganate CMP polishing slurry, which has a Mohs hardness second only to silicon carbide. The former, the silica sol system, has a very low polishing speed, mainly because of the low hardness of silicon oxide (6-7) and the weak chemical effect of the oxidant. The latter, the alumina system, suffers from difficulty in controlling the surface polishing effect, primarily due to the high particle hardness and the potential for particle instability during slurry circulation, leading to agglomeration and surface scratches, thus affecting polishing quality.

[0003] Therefore, improving the removal rate of the polishing slurry and ensuring its polishing quality during use are the key technical challenges that silicon carbide CMP polishing slurries need to address. Summary of the Invention

[0004] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a polishing slurry for chemical mechanical polishing of silicon carbide substrates, its preparation method and uses, in order to solve the problems in the prior art.

[0005] To achieve the above and other related objectives, the present invention is obtained through the following technical solution.

[0006] This invention provides a polishing slurry for chemical mechanical polishing of silicon carbide substrates, comprising the following raw material components by weight percentage:

[0007]

[0008] For example, the amount of silicon dioxide used can be 0.1-0.5%, 0.5-1%, 1-1.5%, 1.5-2%, 2-2.5%, or 2.5-3%.

[0009] For example, the mass ratio of cerium oxide can be 1-2%, 2-3%, 3-4%, or 4-5%.

[0010] The amount of oxidant can be 0.5-1%, 1-2%, 2-3%, 3-4%, or 4-5%, preferably 2-4%.

[0011] For example, the amount of surface modifier can be 0.2-0.5%, 0.5-1%, 1-1.5%, or 1.5-2%.

[0012] For example, the amount of surfactant used can be 0.0001–0.001%, 0.001–0.005%, or 0.005–0.01%.

[0013] For example, the dosage of pH buffer can be 0.2–0.3%, 0.3–0.4%, 0.4–0.5%, 0.5–0.6%, 0.6–1.0%, 1–1.5%, or 1.5–2%.

[0014] Preferably, the particle size of the silicon oxide is 0.05-0.5 μm, more preferably 0.05-0.2 μm.

[0015] Preferably, the silicon dioxide particles have one or more of the following morphologies: spherical, near-spherical, and peanut-shaped.

[0016] Preferably, the silicon dioxide is colloidal silicon dioxide.

[0017] Preferably, the cerium oxide particles have a particle size of 0.05–1 μm, more preferably 0.05–0.3 μm.

[0018] Preferably, the morphology of the cerium oxide particles is selected from one or more of spherical, near-spherical, plate-like, and amorphous shapes.

[0019] Preferably, the specific surface area of ​​the cerium oxide is 35–55 m². 2 / g.

[0020] Preferably, the oxidant is potassium permanganate.

[0021] Preferably, the surface modifier is one or more selected from sodium polyacrylate, polyacrylamide, sodium hydroxymethyl cellulose and polyacrylamide-2-methylpropanesulfonic acid.

[0022] Preferably, the surfactant is selected from one or more of glycerol, polyglycerol, sodium lauryl sulfate, sodium oleate, polymethacrylic acid, polyvinylpyrrolidone, triethanolamine oleic acid soap, polysorbate-20, fatty alcohol polyoxyethylene ether, sodium fatty acid methyl ester sulfonate, sodium perfluorononenoxybenzenesulfonate, and nonylphenol polyoxyethylene ether.

[0023] Preferably, the pH buffer is selected from one or more of sodium carbonate-sodium bicarbonate, potassium carbonate-potassium bicarbonate, acetic acid-sodium acetate, disodium hydrogen phosphate-sodium dihydrogen phosphate, and potassium hydroxide-potassium carbonate.

[0024] Preferably, the pH of the pH buffer is 9 to 11.

[0025] Preferably, the raw material components further include a pH adjuster, wherein the pH adjuster is a strong base.

[0026] More preferably, the pH adjuster is one or more selected from sodium hydroxide, potassium hydroxide, calcium hydroxide and barium hydroxide.

[0027] Preferably, the pH of the polishing solution is 7 to 9.

[0028] The present invention also discloses a method for preparing the polishing slurry as described above, comprising the following steps:

[0029] The cerium oxide, the surface modifier, and water are mixed to form a concentrated solution;

[0030] The surfactant, the oxidant, the pH buffer and water are mixed, and then a pH adjuster is added to adjust the pH to 7-9 to obtain a mixture.

[0031] The polishing solution is obtained by mixing the concentrate, the mixture and the silica.

[0032] Preferably, the cerium oxide content in the concentrate is 10-20 wt%.

[0033] The present invention also discloses the use of the polishing slurry as described above in the chemical mechanical polishing of silicon carbide substrates.

[0034] This invention discloses a polishing slurry for chemical mechanical polishing of silicon carbide substrates, its preparation method and application. By adding silicon oxide particles and surface modifiers to an alkaline cerium oxide polishing slurry and using a pH buffer to control the pH value during the polishing process, irreversible agglomeration of abrasives is avoided. This ensures that the polishing slurry has a good polishing rate and a good polishing effect during the polishing process, and the entire polishing slurry system is stable and does not easily aggregate or settle. Detailed Implementation

[0035] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0036] Before further describing specific embodiments of the present invention, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments described below; it should also be understood that the terminology used in the embodiments of the present invention is for describing specific embodiments and not for limiting the scope of protection of the present invention. Test methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or as recommended by the respective manufacturers.

[0037] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. In addition to the specific methods, apparatus, and materials used in the embodiments, based on the knowledge of the prior art possessed by one of ordinary skill in the art and the description of this invention, any prior art methods, apparatus, and materials similar to or equivalent to those described, apparatus, and materials in the embodiments of this invention may be used to implement the present invention.

[0038] The raw materials used in the following embodiments and comparative examples of the present invention are as follows:

[0039] Cerium oxide: spherical, with a particle size of 100-200 nm and a specific surface area of ​​40 m². 2 / g.

[0040] Colloidal silica: spherical, with a particle size of 60-180 nm.

[0041] Particle size was measured using a Baxter 2600 particle size analyzer, and specific surface area was measured using a specific surface area and pore size analyzer.

[0042] Examples 1-7

[0043] Examples 1-7 provide a specific polishing liquid, prepared by the following method:

[0044] (1) Cerium oxide, surface modifier and water are mixed to form a concentrated solution; the content of cerium oxide in the concentrated solution is 20 wt%;

[0045] (2) After mixing the surfactant, potassium permanganate, pH buffer and water, add sodium hydroxide solution to adjust the pH to 9 to obtain a mixture;

[0046] (3) The concentrate, the mixture and the silica are mixed to obtain the polishing solution.

[0047] The amounts of silicon oxide, cerium oxide, surface modifier, surfactant, potassium permanganate, and pH buffer in the polishing slurry are shown in Table 1, with the remainder being water.

[0048] Comparative Examples 1-7

[0049] Comparative Examples 1 to 7 are comparative examples of the embodiments. The preparation methods are basically the same as those of the embodiments, except that the raw material components and amounts are different, as shown in Table 1.

[0050] Table 1 0.1-0.3

[0051]

[0052]

[0053] The polishing solutions prepared in Examples 1-7 and Comparative Examples 1-7 were subjected to the following performance tests: polishing rate, number of scratches, surface roughness, pH value of polishing solution after 8 hours of polishing, softness of the bottom sediment layer after 15 days of standing, and particle size. The test results are shown in Tables 2-3.

[0054] The testing method is as follows:

[0055] 1. Polishing Rate: A 6-inch silicon carbide substrate was polished using a Zhejiang Mingzheng 36B single-sided polishing machine. The quality difference of the silicon carbide substrate before and after polishing was recorded, and then the polishing rate was calculated. Polishing machine stage: 915mm; polishing slurry prepared according to the example; polishing slurry flow rate: 400ml / min; polishing pressure: 238g / cm. 3 The lower chassis speed is 40 rpm.

[0056] Polishing time is 1 hour.

[0057] Polishing rate = thickness removed (µm) / polishing time (h) = mass removed (mg) / 56.52 (g / cm) / polishing time (h).

[0058] 2. Number of scratches: Scratch detection was performed on the silicon carbide substrate used for polishing rate testing. The scratches were observed with the naked eye under a strong light (Yamada Optical YP250). Bright lines with a length of more than 2cm were identified as scratches, and the number of scratches was recorded.

[0059] 3. Surface roughness: Tested using a VEECO atomic force microscope. The test area at each location is 5μm*5μm, and the average roughness of 3 locations is calculated.

[0060] 3. The softness of the bottom sediment layer after 15 days: Observe the settling state of the particles in the transparent container with the naked eye after shaking; if it immediately becomes a uniform turbid suspension after shaking and does not separate into layers within 2 hours, the dispersion is easily dispersible; if it is difficult to become a uniform suspension again after shaking and separates into layers quickly within 30 minutes, the dispersion is gel-like; if it cannot be shaken, or separates into layers immediately after shaking, the dispersion is hardened.

[0061] 4. Particle size: After the polishing slurry has been left to stand for 1 week, 2 weeks, 3 weeks and 4 weeks, the particle size of the polishing slurry is tested using a Baxter 2600 particle size analyzer.

[0062] Table 2

[0063]

[0064] Table 3 Stability evaluation of particulate matter

[0065]

[0066]

[0067] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A polishing slurry for chemical mechanical polishing of silicon carbide substrates, characterized in that, The raw material components include the following percentages by weight: Silicon oxide 0.1~3%; 1-5% cerium oxide; Oxidizing agent 0.5~5%; Surface modifier 0.2-2%; Surfactant 0.0001-0.01%; pH buffer 0.2-2%; The remainder is water; The surface modifier is one or more selected from sodium polyacrylate, polyacrylamide, sodium carboxymethyl cellulose, and polyacrylamide-2-methylpropanesulfonic acid; The pH buffer is selected from one or more of sodium carbonate-sodium bicarbonate, potassium carbonate-potassium bicarbonate, acetate-sodium acetate, disodium hydrogen phosphate-sodium dihydrogen phosphate, and potassium hydroxide-potassium carbonate. The pH of the pH buffer is 9-11; The particle size of the silicon oxide is 0.05~0.5μm; The cerium oxide particles have a particle size of 0.05~1μm; the raw material components also include a pH adjuster, and the polishing solution has a pH of 7~9; The oxidant is potassium permanganate; The surfactant is selected from one or more of glycerol, polyglycerol, sodium lauryl sulfate, sodium oleate, polymethacrylic acid, polyvinylpyrrolidone, triethanolamine oleic acid soap, polysorbate-20, fatty alcohol polyoxyethylene ether, sodium fatty acid methyl ester sulfonate, sodium perfluorononenoxybenzenesulfonate, and nonylphenol polyoxyethylene ether.

2. The polishing slurry according to claim 1, characterized in that, Includes one or more of the following features: The silicon dioxide particles have one or more of the following morphologies: spherical, near-spherical, and peanut-shaped. The silicon dioxide is colloidal silicon dioxide; The morphology of the cerium oxide particles is selected from one or more of the following: spherical, near-spherical, plate-like, and amorphous. The specific surface area of ​​the cerium oxide is 35~55m². 2 / g.

3. The polishing slurry according to claim 1, characterized in that, The pH adjuster is a strong base.

4. The polishing slurry according to claim 3, characterized in that, The pH adjuster is selected from one or more of sodium hydroxide, potassium hydroxide, calcium hydroxide, and barium hydroxide.

5. A method for preparing a polishing slurry as described in any one of claims 1 to 4, characterized in that, Includes the following steps: The cerium oxide, the surface modifier, and water are mixed to form a concentrated solution; The surfactant, the oxidant, the pH buffer and water are mixed, and then a pH adjuster is added to adjust the pH to 7-9 to obtain a mixture. The polishing solution is obtained by mixing the concentrate, the mixture and the silica.

6. The preparation method according to claim 5, characterized in that, In the concentrated solution, the content of cerium oxide is 10~20wt%.

7. The use of the polishing slurry as described in any one of claims 1 to 4 in chemical mechanical polishing of silicon carbide substrates.

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