Alumina CMP polishing liquid for rough polishing of silicon carbide wafers and polishing method thereof

Abstract

The present invention relates to an alumina CMP polishing liquid for rough polishing of silicon carbide wafers and a polishing method thereof. The polishing liquid comprises the following components, by weight percentage: 2-10 wt.% nano-alumina abrasive; 0.2-2 wt.% dispersant; 0.001-0.01 wt.‰ pH adjuster; and an oxidant concentration of 1-5 wt.%. The present invention utilizes a composite oxidant, utilizing potassium permanganate to oxidize manganese dioxide, the reduction product of the silicon carbide wafer surface, to activate potassium persulfate, generating a large number of sulfate free radicals in the polishing liquid. These highly oxidizing sulfate free radicals promote a chain oxidation reaction in the polishing liquid, further oxidizing the silicon carbide wafer surface and forming a relatively low-hardness oxide layer on the silicon carbide surface. This layer is ultimately removed by the mechanical action of the alumina abrasive, resulting in an ultra-smooth, damage-free silicon carbide wafer surface. The optimal surface roughness of the silicon carbide wafer achieved by the present invention is 0.125 nm, and the material removal rate is 3.5 μm / h. Compared to existing alumina polishing liquids, this polishing liquid significantly improves the surface quality and polishing efficiency of silicon carbide wafers.

Description

Technical Field

[0001] The present invention relates to the technical field of ultra-precision processing of semiconductor materials, and in particular to an aluminum oxide CMP polishing liquid for rough polishing of silicon carbide wafers and a polishing method thereof. Background Art

[0002] Silicon carbide (SiC), the most representative third-generation semiconductor material, boasts excellent properties such as a wide bandgap, high breakdown electric field strength, high thermal conductivity, and a high saturated electron drift velocity. It is an ideal material for high-temperature, high-frequency, high-power, and high-voltage devices. Currently, SiC, as an ideal substrate material, has been widely used in power electronics applications such as photovoltaics, wind power, rail transit, new energy vehicles, and charging stations.

[0003] As a substrate material, the surface quality of silicon carbide wafers directly impacts device performance. Therefore, a high-quality machined surface is essential for the widespread application of silicon carbide materials. Currently, chemical mechanical polishing (CMP) is widely used to process silicon carbide substrates, achieving an ultra-smooth, damage-free silicon carbide wafer surface. Polishing slurry is a key factor influencing material removal rate and polished surface quality during the CMP process.

[0004] However, due to the high hardness and strong chemical inertness of silicon carbide wafer materials, existing polishing fluids used for silicon carbide CMP have problems such as low material removal rate, poor processing surface quality, short cycle life, poor polishing fluid dispersibility, and easy sedimentation. Summary of the Invention

[0005] In response to the technical problems raised above, an aluminum oxide CMP polishing liquid and a polishing method thereof are provided for rough polishing of silicon carbide wafers. The polishing liquid has good dispersion and suspension properties, a high material removal rate and a long cycle life, and can achieve efficient and high surface quality chemical mechanical polishing of silicon carbide wafers.

[0006] The technical means adopted in the present invention are as follows:

[0007] An aluminum oxide CMP polishing liquid for rough polishing of silicon carbide wafers comprises nano-aluminum oxide abrasives, a dispersant, a pH regulator, an oxidant and deionized water. Calculated by weight, the polishing liquid comprises the following components: 2 to 10 wt.% of nano-aluminum oxide abrasives; 0.2 to 2 wt.% of the dispersant; 0.001 to 0.01 wt‰ of the pH regulator; and 1 to 5 wt.% of the oxidant.

[0008] Furthermore, the particle size of the nano-alumina abrasive is 200 to 800 nanometers.

[0009] Furthermore, the dispersant is one or more of sodium hexametaphosphate, polyethylene glycol, hexadecylmethylammonium bromide, glycerol, bentonite, sodium polyacrylate and ammonium polyacrylate.

[0010] Furthermore, among the pH regulators, the alkaline regulator is one or more of sodium hydroxide, ethanolamine, ammonia water and potassium hydroxide, and the acid regulator is one or more of nitric acid, oxalic acid, acetic acid, phosphoric acid and citric acid, and the pH of the polishing liquid is adjusted to 7.5-11.0.

[0011] Furthermore, the oxidant is a compound oxidant, and the components of the compound oxidant are potassium permanganate and potassium persulfate.

[0012] Furthermore, the mass ratio of potassium permanganate to potassium persulfate in the composite oxidant is 1:0.5-2.

[0013] The present invention discloses a polishing method based on the above-mentioned polishing liquid, comprising the following steps:

[0014] The loading pressure of the silicon carbide wafer is 4 to 8 psi, the flow rate of the polishing liquid is 100 to 1000 mL / min, the polishing head speed is 25 to 60 r / min, the polishing disk speed is 25 to 60 r / min, the polishing time is 30 to 120 min, and the polishing liquid supply method is circulating supply.

[0015] Furthermore, the polishing pad used in the polishing method is made of polyurethane.

[0016] Furthermore, the surface of the polishing pad used in the polishing method is grooved before use.

[0017] Furthermore, in the polishing method, the polishing pad is dressed online, and the dressing time ratio is 30% to 100% of the polishing time.

[0018] Compared with the existing technology, the present invention has the following advantages: the present invention adopts a composite oxidant and utilizes potassium permanganate to oxidize the reduction product manganese dioxide on the surface of the silicon carbide wafer to activate potassium persulfate, so that a large number of sulfate free radicals are generated in the polishing liquid. The sulfate free radicals have extremely strong oxidizing properties and can promote the polishing liquid to produce a chain oxidation reaction, further oxidize the surface of the silicon carbide wafer, and form an oxide layer with lower hardness on the silicon carbide surface, which is finally removed under the mechanical action of aluminum oxide abrasives, thereby forming an ultra-smooth, damage-free silicon carbide wafer surface; compared with the existing aluminum oxide polishing liquid, based on the polishing liquid and polishing method proposed in the present invention, the surface roughness of the silicon carbide wafer obtained after polishing can reach 0.12nm~0.57nm, and the silicon carbide polishing material removal rate can reach 2μm / h~3.5μm / h, which significantly improves the surface quality and polishing efficiency of the silicon carbide wafer. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0020] Figure 1 This is a graph showing the surface roughness measurement results of the silicon carbide wafer after chemical mechanical polishing according to Example 1 of the present invention.

[0021] Figure 2 This is a graph showing the surface roughness measurement results of the silicon carbide wafer after chemical mechanical polishing according to Example 2 of the present invention.

[0022] Figure 3 This is a graph showing the surface roughness measurement results of the silicon carbide wafer after chemical mechanical polishing according to Example 3 of the present invention.

[0023] Figure 4 This is a graph showing the surface roughness measurement results of the silicon carbide wafer after chemical mechanical polishing according to Example 4 of the present invention.

[0024] Figure 5 This is a graph showing the surface roughness measurement results of the silicon carbide wafer after chemical mechanical polishing according to Example 5 of the present invention.

[0025] Figure 6 This is a graph showing the surface roughness measurement results of the silicon carbide wafer after chemical mechanical polishing according to Example 6 of the present invention.

[0026] Figure 7 This is a graph showing the surface roughness measurement results of the silicon carbide wafer after chemical mechanical polishing in Comparative Example 1 of the present invention.

[0027] Figure 8 This is a graph showing the surface roughness measurement results of the silicon carbide wafer after chemical mechanical polishing in Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0028] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0029] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0030] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0031] Unless otherwise specifically stated, the relative arrangement of the parts and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present invention. At the same time, it should be clear that, for ease of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship. The technology, methods and equipment known to those of ordinary skill in the relevant art may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be considered as part of the specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, not as a limitation. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that similar numbers and letters represent similar items in the following figures, and therefore, once an item is defined in one figure, it does not need to be further discussed in subsequent figures.

[0032] In the description of the present invention, it should be understood that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "horizontal, vertical, vertical, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention: the directional words "inside and outside" refer to the inside and outside relative to the outline of each component itself.

[0033] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used herein to describe the spatial positional relationship of a device or feature to other devices or features as shown in the figures. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figures. For example, if the device in the drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below their position devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0034] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0035] An embodiment of the present invention discloses an alumina CMP polishing liquid for rough polishing of silicon carbide wafers, comprising nano-alumina abrasive, a dispersant, a pH regulator, an oxidant and deionized water. The polishing liquid comprises the following components by weight: 2 to 10 wt.% of nano-alumina abrasive; 0.2 to 2 wt.% of dispersant; 0.001 to 0.01 wt‰ of pH regulator; and 1 to 5 wt.% of the oxidant.

[0036] Furthermore, the particle size of the nano-alumina abrasive is 200 to 800 nanometers.

[0037] Furthermore, the dispersant is one or more of sodium hexametaphosphate, polyethylene glycol, hexadecylmethylammonium bromide, glycerol, bentonite, sodium polyacrylate and ammonium polyacrylate.

[0038] Furthermore, the pH adjuster is one or more of nitric acid, oxalic acid, acetic acid, phosphoric acid, citric acid, sodium hydroxide, ethanolamine, ammonia water and potassium hydroxide, and the pH of the polishing liquid is adjusted to 7.5 to 11.0. More preferably, the pH of the polishing liquid is 8.5.

[0039] Furthermore, the oxidant is a compound oxidant, and the components of the compound oxidant are potassium permanganate and potassium persulfate.

[0040] Furthermore, the mass ratio of potassium permanganate to potassium persulfate in the composite oxidant is 1:0.5-2.

[0041] The present invention also discloses a method for preparing the polishing liquid, comprising the following steps:

[0042] Step 1: Mix the dispersant with deionized water, stir in a high-speed centrifuge for 40-60 minutes at room temperature (20°C) to obtain an activated dispersion;

[0043] Step 2: Add the nano-alumina abrasive to the dispersion prepared in step 1, and stir the mixture in an ultrasonic oscillation device at room temperature for 10-20 minutes to ensure that the nano-alumina abrasive is evenly suspended in the aqueous solution, thereby preparing a nano-alumina suspension with good dispersion.

[0044] Step 3, adding an oxidant to the nano-alumina suspension in step 2, and adding a pH regulator to adjust the pH of the solution to 8.5;

[0045] Step 4: Stir the solution in step 3 in a high-speed centrifuge for 10-30 minutes at room temperature to obtain a silicon carbide CMP polishing liquid.

[0046] The present invention discloses a polishing method based on the above-mentioned polishing liquid, comprising the following steps:

[0047] The loading pressure of the silicon carbide wafer is 4 to 8 psi, the flow rate of the polishing liquid is 100 to 1000 mL / min, the polishing head speed is 25 to 60 r / min, the polishing disk speed is 25 to 60 r / min, the polishing time is 30 to 120 min, and the polishing liquid supply method is circulating supply.

[0048] Furthermore, the polishing pad used in the polishing method is made of polyurethane.

[0049] Furthermore, the surface of the polishing pad used in the polishing method is grooved before use. The dimensions of the grooves on the polishing pad surface are: 20 mm×20 mm×2.5 mm (length×width×height).

[0050] Furthermore, in the polishing method, the polishing pad is dressed online, and the dressing time ratio is 30% to 100% of the polishing time.

[0051] The grooving of the polishing pad surface mentioned in this invention is primarily intended to improve the polishing efficiency and surface quality of silicon carbide wafers. In silicon carbide CMP, shallow grooving limits the transfer and storage of polishing slurry, reducing material removal rates and increasing the risk of wafer scratches. Increasing grooving depth can improve these issues, but excessive grooving depth can compromise the structural stability of the polishing pad and the flatness of the wafer surface. A small grooving spacing promotes even distribution of the polishing slurry, improving material removal rates and wafer surface quality. Excessive spacing leads to uneven distribution of the polishing slurry, reducing material removal rates, and making the wafer more susceptible to scratches and defects.

[0052] The online dressing method for the polishing pad adopted in the present invention mainly maintains the surface performance of the polishing pad, maintains its ability to transmit polishing liquid by removing worn and contaminated parts, stabilizes the material removal rate, and reduces defects such as wafer scratches and poor flatness caused by surface problems of the polishing pad, thereby improving the surface quality of the wafer; in addition, the dressing time also has an important influence on the polishing effect: although frequent dressing can ensure a stable material removal rate and good wafer surface quality, it will reduce production efficiency and shorten the life of the polishing pad, and although dressing once at a longer interval can improve production efficiency and extend the service life of the polishing pad, it is easy to cause the performance of the polishing pad to deteriorate, affecting the material removal rate and the surface quality of the wafer.

[0053] The workpiece used for polishing was the silicon side of a 4H silicon carbide wafer, with a wafer size of 4 inches. The silicon carbide wafer was clamped to the polishing head by vacuum suction. The polishing machine used was a CP-610 precision single-sided chemical mechanical polisher. The polishing disk speed was 30-60 rpm, the polishing head speed was 30-40 rpm, the polishing pressure was 5-7 psi, the polishing pad diameter was 610 mm, the polishing fluid flow rate was 300-800 ml / min, and the polishing time was 60 minutes. The polishing test was conducted at room temperature.

[0054] The surface roughness of silicon carbide wafers was measured using a ZYGO white light interferometer before and after polishing.

[0055] Example 1

[0056] Polishing liquid: The concentration of nano-alumina abrasive is 5wt%, the abrasive particle size is 200nm, the concentration of dispersant sodium hexametaphosphate is 0.2wt%, the concentration of compound oxidant is 1.5wt%, the mass ratio of potassium permanganate and potassium persulfate is 1:0.5, and potassium hydroxide, a pH regulator, is added to adjust the pH of the polishing liquid to 8.5.

[0057] Polishing method: Set the silicon carbide wafer loading pressure to 5 psi, the polishing disc speed to 30 r / min, the polishing head speed to 30 r / min, the polishing liquid flow rate to 300 mL / min, the polishing time to 60 min, the polishing pad online dressing time to 20 min, and the polishing liquid supply method to circulating liquid supply.

[0058] like Figure 1 As shown, the surface roughness of the silicon carbide wafer after polishing is 0.439 nm, and the polishing material removal rate of the silicon carbide wafer is 2.1 μm / h.

[0059] Example 2

[0060] Polishing liquid: The concentration of nano-alumina abrasive is 7.5wt%, the abrasive particle size is 500nm, the concentration of dispersant polyethylene glycol is 0.5wt%, the concentration of compound oxidant is 2wt%, the mass ratio of potassium permanganate and potassium persulfate is 1:1, and potassium hydroxide, a pH adjuster, is added to adjust the pH of the polishing liquid to 8.5.

[0061] Polishing method: Set the silicon carbide wafer loading pressure to 6 psi, the polishing disc speed to 45 r / min, the polishing head speed to 35 r / min, the polishing liquid flow rate to 500 mL / min, the polishing time to 60 min, the polishing pad online dressing time to 30 min, and the polishing liquid supply method to circulating liquid supply.

[0062] like Figure 2 As shown, the surface roughness of the silicon carbide wafer after polishing is 0.328 nm, and the polishing material removal rate of the silicon carbide wafer is 2.6 μm / h.

[0063] Example 3

[0064] Polishing liquid: The concentration of nano-alumina abrasive is 2wt%, the abrasive particle size is 300nm, the concentration of dispersant ammonium polyacrylate is 2wt%, the concentration of compound oxidant is 3wt%, the mass ratio of potassium permanganate and potassium persulfate is 1:2, and sodium hydroxide, a pH adjuster, is added to adjust the pH of the polishing liquid to 8.5.

[0065] Polishing method: Set the silicon carbide wafer loading pressure to 4 psi, the polishing disc speed to 25 r / min, the polishing head speed to 30 r / min, the polishing liquid flow rate to 100 mL / min, the polishing time to 45 min, the polishing pad online dressing time to 25 min, and the polishing liquid supply method to circulating liquid supply.

[0066] like Figure 3 As shown, the surface roughness of the silicon carbide wafer after polishing is 0.509 nm, and the polishing material removal rate of the silicon carbide wafer is 2 μm / h.

[0067] Example 4

[0068] Polishing liquid: The concentration of nano-alumina abrasive is 8wt%, the abrasive particle size is 600nm, the concentration of dispersant hexadecylmethylammonium bromide is 1.5wt%, the concentration of compound oxidant is 4wt%, the mass ratio of potassium permanganate and potassium persulfate is 1:1.5, and ammonia water as pH regulator is added to adjust the pH of the polishing liquid to 8.5.

[0069] Polishing method: Set the silicon carbide wafer loading pressure to 6.5 psi, the polishing disc speed to 54 r / min, the polishing head speed to 42 r / min, the polishing liquid flow rate to 850 mL / min, the polishing time to 90 min, the polishing pad online dressing time to 45 min, and the polishing liquid supply method to circulating liquid supply.

[0070] like Figure 4 As shown, the surface roughness of the silicon carbide wafer after polishing is 0.135 nm, and the polishing material removal rate of the silicon carbide wafer is 3.1 μm / h.

[0071] Example 5

[0072] Polishing liquid: The concentration of nano-alumina abrasive is 6wt%, the abrasive particle size is 400nm, the concentration of dispersant bentonite is 0.6wt%, the concentration of compound oxidant is 1.8wt%, the mass ratio of potassium permanganate and potassium persulfate is 1:1.1, and potassium hydroxide, a pH regulator, is added to adjust the pH of the polishing liquid to 8.5.

[0073] Polishing method: Set the silicon carbide wafer loading pressure to 5.5 psi, the polishing disc speed to 40 r / min, the polishing head speed to 40 r / min, the polishing liquid flow rate to 450 mL / min, the polishing time to 60 min, the polishing pad online dressing time to 25 min, and the polishing liquid supply method to circulating liquid supply.

[0074] like Figure 5 As shown, the surface roughness of the silicon carbide wafer after polishing is 0.371 nm, and the polishing material removal rate of the silicon carbide wafer is 2.4 μm / h.

[0075] Example 6

[0076] Polishing liquid: The concentration of nano-alumina abrasive is 10wt%, the abrasive particle size is 800nm, the concentration of the dispersant is 1wt%, the dispersant is composed of a mixed dispersion of bentonite and sodium polyacrylate, wherein the mass ratio of bentonite and sodium polyacrylate is 1:1, the concentration of the compound oxidant is 4.5wt%, wherein the mass ratio of potassium permanganate and potassium persulfate is 1:1.25, and potassium hydroxide, a pH adjuster, is added to adjust the pH of the polishing liquid to 8.5.

[0077] Polishing method: Set the silicon carbide wafer loading pressure to 7 psi, the polishing disc speed to 60 r / min, the polishing head speed to 40 r / min, the polishing liquid flow rate to 1000 mL / min, the polishing time to 60 min, the polishing pad online dressing time to 40 min, and the polishing liquid supply method to circulating liquid supply.

[0078] like Figure 6As shown, the surface roughness of the silicon carbide wafer after polishing is 0.125 nm, and the polishing material removal rate of the silicon carbide wafer is 3.5 μm / h.

[0079] The interaction between the layered structure of bentonite and the nanoalumina particles in the mixed dispersion gradually forms a network structure, improving dispersion stability. Furthermore, sodium polyacrylate ionizes, generating a large amount of negative charge that adsorbs onto the surface of the nanoalumina, generating electrostatic repulsion between the particles. Simultaneously, the molecular chains of sodium polyacrylate stretch in the solution and, upon adsorption onto the particle surface, form a steric barrier around the particles, keeping them apart.

[0080] Through the multiple dispersion effects of the mixed dispersion, the nano-alumina abrasive has the advantages of good dispersibility, stable solution system, and short time and energy consumption. The surface roughness and removal rate of the polished silicon carbide wafer are better in each embodiment.

[0081] Based on this embodiment, as another scalable implementation method, the bentonite may also be an organically modified sheet silicate. The organic modified material may be one or more of γ-aminopropyltriethoxysilane, epoxy resin, polyurethane, polymethyl methacrylate, hexadecyltrimethylammonium bromide, sodium lauryl sulfate, and polyethylene glycol.

[0082] Comparative Example 1

[0083] The polishing method used is the same as that of Example 1. The difference from Example 1 is that the oxidant in the polishing liquid formula is only potassium permanganate, wherein the concentration of potassium permanganate is the same as that of the compound oxidant in Example 1, which is still 1.5 wt%.

[0084] like Figure 7 As shown, the surface roughness of the silicon carbide wafer after polishing is 1.075 nm, and the polishing material removal rate of the silicon carbide wafer is 1.1 μm / h.

[0085] Comparative Example 2

[0086] The polishing method used is the same as that of Example 1. The difference from Example 1 is that the oxidant in the polishing liquid formula is only potassium persulfate, wherein the concentration of potassium persulfate is the same as that of the compound oxidant in Example 1, which is still 1.5 wt %.

[0087] like Figure 8 As shown in FIG. 2 , the surface roughness of the silicon carbide wafer after polishing is 14.635 nm, and the polishing material removal rate of the silicon carbide wafer is only 0.5 μm / h.

[0088] It can be seen from the results of the above embodiments and comparative examples that the polishing liquid using a compound oxidant proposed in the present invention has a significantly improved material removal rate compared to the polishing liquid using a single oxidant. At the same time, based on the polishing liquid and polishing method of the present invention, the surface quality of the silicon carbide wafer obtained after polishing is good, without obvious damage, and the surface roughness is small, and it can be widely used in the processing of silicon carbide substrates and the manufacturing process of related devices.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An aluminum oxide CMP polishing liquid for rough polishing of silicon carbide wafers, characterized in that: It is composed of nano-alumina abrasive, dispersant, pH regulator, oxidant and deionized water; The dispersant is composed of a mixed dispersion of bentonite and sodium polyacrylate, wherein the mass ratio of bentonite to sodium polyacrylate is 1:1; The oxidant is a composite oxidant, the components of which are potassium permanganate and potassium persulfate, and the mass ratio of potassium permanganate to potassium persulfate is 1:1.25; The weight percentage of each component is as follows: nano-alumina abrasive 10 wt.%, abrasive particle size 800 nm; dispersant 1 wt.%; oxidant concentration 4.5 wt.%; The pH regulator is potassium hydroxide, which adjusts the pH of the polishing liquid to 8.5; and the balance deionized water; The specific polishing method is as follows: Set the silicon carbide wafer loading pressure to 7 psi, the polishing disk speed to 60 r / min, the polishing head speed to 40 r / min, the polishing liquid flow rate to 1000 mL / min, the polishing time to 60 min, the polishing pad online dressing time to 40 min, and the polishing liquid supply mode to circulating liquid supply.

2. The aluminum oxide CMP polishing liquid according to claim 1, characterized in that The polishing pad used is made of polyurethane.

3. The aluminum oxide CMP polishing liquid according to claim 2, characterized in that The surface of the polishing pad used in the polishing method is grooved before use.

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