Alumina CMP (Chemical Mechanical Polishing) solution for roughly polishing silicon carbide wafer and polishing method thereof

Abstract

The invention relates to an aluminum oxide CMP polishing solution for rough polishing of silicon carbide wafers and a polishing method of the aluminum oxide CMP polishing solution, and the aluminum oxide CMP polishing solution comprises the following components in percentage by weight: 2-10wt% of nano aluminum oxide abrasive; 0.2 to 2 wt.% of a dispersant; 0.001 to 0.01 wt% of a pH regulator; the concentration of the oxidizing agent is 1-5wt.%. By adopting the compound oxidant, potassium permanganate is utilized to oxidize a reduction product manganese dioxide on the surface of the silicon carbide wafer to activate potassium persulfate, so that a large amount of sulfate free radicals are generated in the polishing solution, the oxidability of the sulfate free radicals is extremely high, the polishing solution can be promoted to generate chain oxidation reaction, and the surface of the silicon carbide wafer is further oxidized; and an oxide layer with low hardness is formed on the surface of the silicon carbide and is finally removed under the mechanical action of the aluminum oxide abrasive, so that the ultra-smooth and damage-free surface of the silicon carbide wafer is formed. The surface roughness of the obtained optimal silicon carbide wafer is 0.125 nm, and the material removal rate is 3.5 [mu] m / h. Compared with an existing aluminum oxide polishing solution, the polishing solution has the advantage that the surface quality and the polishing efficiency of the silicon carbide wafer are remarkably improved.

Description

Technical Field

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

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

[0003] As a substrate material, the surface quality of silicon carbide wafers will directly affect the device performance. Therefore, a high-quality processed surface is a prerequisite for the wide application of silicon carbide materials. At present, in order to obtain a super-smooth and damage-free surface of silicon carbide wafers, chemical mechanical polishing (CMP) processes are generally used at home and abroad to process silicon carbide substrates. The polishing liquid is a key factor affecting the material removal rate and the polishing surface quality in the CMP process.

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

[0005] In view of the above-mentioned technical problems, an alumina CMP polishing liquid for rough polishing of silicon carbide wafers and a polishing method thereof are provided. The polishing liquid has good dispersion and suspension performance, a high material removal rate, and a long cycle service life, and can achieve high-efficiency and high-surface-quality chemical mechanical polishing of silicon carbide wafers.

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

[0007] An alumina CMP polishing liquid for rough polishing of silicon carbide wafers, comprising nano-alumina abrasive, dispersant, pH regulator, oxidant, and deionized water. By weight percentage, it comprises the following components: nano-alumina abrasive 2-10 wt.%; dispersant 0.2-2 wt.%; pH regulator 0.001-0.01 wt‰; the concentration of the oxidant is 1-5 wt.%.

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

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

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

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

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

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

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

[0015] Further, the material of the polishing pad used in the polishing method is polyurethane.

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

[0017] Further, the trimming method of the polishing pad in the polishing method is on-line trimming, and the trimming time ratio is 30% - 100% of the polishing time.

[0018] Compared with the prior art, the present invention has the following advantages: By adopting a compound oxidant, the present invention uses 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 radicals are generated in the polishing liquid. The sulfate radicals have extremely strong oxidizing properties and can promote the chain oxidation reaction of the polishing liquid, further oxidize the surface of the silicon carbide wafer, form an oxide layer with lower hardness on the silicon carbide surface, and finally be removed under the mechanical action of alumina abrasive, thereby forming a super-smooth and non-damaged surface of the silicon carbide wafer; Compared with the existing alumina polishing liquid, based on the polishing liquid and polishing method proposed by the present invention, the surface roughness of the silicon carbide wafer obtained after polishing can reach 0.12 nm - 0.57 nm, and the removal rate of the silicon carbide polishing material can reach 2 μm / h - 3.5 μm / h, significantly improving the surface quality and polishing efficiency of the silicon carbide wafer. Description of the Drawings

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0020] Figure 1 It is a diagram of the measurement result of the surface roughness of the silicon carbide wafer after chemical mechanical polishing in Embodiment 1 of the present invention.

[0021] Figure 2 It is a diagram of the measurement result of the surface roughness of the silicon carbide wafer after chemical mechanical polishing in Embodiment 2 of the present invention.

[0022] Figure 3 It is a diagram of the measurement result of the surface roughness of the silicon carbide wafer after chemical mechanical polishing in Embodiment 3 of the present invention.

[0023] Figure 4 It is a diagram of the measurement result of the surface roughness of the silicon carbide wafer after chemical mechanical polishing in Embodiment 4 of the present invention.

[0024] Figure 5 It is a diagram of the measurement result of the surface roughness of the silicon carbide wafer after chemical mechanical polishing in Embodiment 5 of the present invention.

[0025] Figure 6 It is a diagram of the measurement result of the surface roughness of the silicon carbide wafer after chemical mechanical polishing in Embodiment 6 of the present invention.

[0026] Figure 7 It is a diagram of the measurement result of the surface roughness of the silicon carbide wafer after chemical mechanical polishing in Comparative Example 1 of the present invention.

[0027] Figure 8 It is a diagram of the measurement result of the surface roughness of the silicon carbide wafer after chemical mechanical polishing in Comparative Example 2 of the present invention. Detailed Embodiments

[0028] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other. The following will detail the present invention with reference to the drawings and in combination with the embodiments.

[0029] To make the objectives, 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 with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are only a part rather than all of the embodiments of the present invention. The description of at least one exemplary embodiment is actually only illustrative and in no way restrictive of the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention.

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

[0031] Unless otherwise specifically stated, the relative arrangements of the components and steps, numerical expressions and 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 the sake of description, the dimensions of the various parts shown in the drawings are not drawn in actual proportional relationships. Technologies, methods and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, the said technologies, methods and devices should be regarded as part of the specification. In all the examples shown and discussed herein, any specific values should be construed as merely exemplary and not as a limitation. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that like reference numerals and letters denote like items in the following drawings, and thus, once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0032] In the description of the present invention, it should be understood that the orientation terms such as "front, rear, upper, lower, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom", etc. generally indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description. Without contrary description, these orientation terms do not indicate and imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and thus cannot be construed as limiting the scope of protection of the present invention. The orientation terms "inner, outer" refer to the inside and outside relative to the contour of each component itself.

[0033] For ease of description, spatial relative terms such as "above", "over", "on the upper surface", "upper" etc. can be used here to describe the spatial positional relationship of a device or feature shown in the figure with other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation in addition to the orientation depicted in the figure for the device. For example, if the device in the figure is inverted, a device described as "above" or "over" other devices or structures will then be positioned "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both the orientations of "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and corresponding interpretations are made for the spatial relative descriptions used here.

[0034] In addition, it should be noted that using terms such as "first", "second" etc. to limit components is only for the convenience of differentiating the corresponding components. Without additional statements, the above terms have no special meanings, and thus cannot be construed as limiting the protection scope of the present invention.

[0035] An embodiment of the present invention discloses an alumina CMP polishing liquid for rough polishing of silicon carbide wafers, which includes nano-alumina abrasive, dispersant, pH regulator, oxidant and deionized water. By weight percentage, it includes the following components: nano-alumina abrasive 2 - 10 wt.%; dispersant 0.2 - 2 wt.%; pH regulator 0.001 - 0.01 wt‰; the concentration of the oxidant is 1 - 5 wt.%.

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

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

[0038] Further, the pH regulator is one or several 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 - 11.0. More preferably, the pH of the polishing liquid is 8.5.

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

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

[0041] The present invention also discloses a preparation method of the polishing liquid, which comprises the following steps:

[0042] Step 1: Mix a dispersant with deionized water, and stir with a high-speed centrifuge at room temperature of 20 °C for 40 - 60 min to obtain an activated dispersion liquid;

[0043] Step 2: Add nano-aluminum oxide abrasive to the dispersion liquid obtained in Step 1, and oscillate and stir in an ultrasonic oscillation device at room temperature for 10 - 20 min to ensure that the nano-aluminum oxide abrasive is evenly suspended in the aqueous solution, and prepare a nano-aluminum oxide suspension with good dispersibility;

[0044] Step 3: Add an oxidant to the nano-aluminum oxide suspension obtained in Step 2, and add a pH regulator to adjust the pH of the solution to 8.5;

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

[0046] The present invention discloses a polishing method based on the above polishing liquid, which comprises the following steps:

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

[0048] Further, the polishing pad material used in the polishing method is polyurethane.

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

[0050] Further, the trimming method of the polishing pad in the polishing method is on-line trimming, and the trimming time ratio is 30% - 100% of the polishing time.

[0051] The grooving treatment of the polishing pad surface mentioned in the present invention is mainly to improve the polishing efficiency and surface quality of the silicon carbide wafer. In silicon carbide CMP, a shallower grooving depth will limit the transmission and storage of the polishing liquid, reduce the material removal rate and increase the risk of wafer scratches. Increasing the grooving depth can improve the above situation, but if it is too deep, it will affect the structural stability of the polishing pad and the flatness of the wafer surface; a small grooving spacing is beneficial to the uniform distribution of the polishing liquid, improving the material removal rate and the wafer surface quality. If the spacing is too large, it will lead to uneven distribution of the polishing liquid, reduced material removal rate and the wafer is prone to scratches and defects.

[0052] The in-situ dressing method of the polishing pad adopted in the present invention mainly functions to maintain the surface performance of the polishing pad. By removing the worn and contaminated parts, it can maintain its ability to transport the polishing liquid, stabilize the material removal rate, and at the same time reduce defects such as wafer scratches and poor flatness caused by the surface problems of the polishing pad, thus improving the surface quality of the wafer. In addition, the dressing time also has an important impact on the polishing effect: frequent dressing can ensure a stable material removal rate and good wafer surface quality, but it will reduce production efficiency and shorten the service life of the polishing pad. While dressing once for a longer time can improve production efficiency and extend the service life of the polishing pad, it is likely to cause deterioration of the polishing pad performance, affecting the material removal rate and wafer surface quality.

[0053] The workpiece for polishing is the silicon surface of a 4H silicon carbide wafer, and the wafer size is 4 inches. The silicon carbide wafer is clamped on the polishing head by vacuum adsorption. The polishing machine used for polishing is a CP-610 precision single-sided chemical mechanical polishing machine, with the polishing platen rotation speed of 30 - 60 r / min, the polishing head rotation speed of 30 - 40 r / min, the polishing load pressure of 5 - 7 psi, the polishing pad diameter of 610 mm, the polishing liquid flow rate of 300 - 800 ml / min, the polishing time of 60 min, and the polishing test is carried out at room temperature.

[0054] Before and after polishing, the surface roughness of the silicon carbide wafer is measured by a ZYGO white light interferometer.

[0055] Example 1

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

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

[0058] As Figure 1 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-aluminum oxide abrasive is 7.5 wt%, the abrasive particle size is 500 nm, the concentration of dispersant polyethylene glycol is 0.5 wt%, the concentration of compound oxidant is 2 wt%, where the mass ratio of potassium permanganate to potassium persulfate is 1:1, and pH regulator potassium hydroxide is added to adjust the pH of the polishing liquid to 8.5.

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

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

[0063] Example 3

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

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

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

[0067] Example 4

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

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

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

[0071] Example 5

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

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

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

[0075] Example 6

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

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

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

[0079] Through the interaction between the layered structure of bentonite and nano-aluminum oxide particles in the mixed dispersion, a network structure relationship is gradually formed to improve the dispersion stability; on the other hand, a large number of negative charges are generated by the ionization of sodium polyacrylate, which adsorbs on the surface of nano-aluminum oxide, and an electrostatic repulsive force is generated between the particles. At the same time, the molecular chains of sodium polyacrylate stretch in the solution and form a steric hindrance layer around the particles after adsorbing on the particle surface, keeping the particles away from each other.

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

[0081] On the basis of this embodiment, as other expandable embodiments, the bentonite can also be organically modified flaky silicate. The organic modification materials can be one or several of γ-aminopropyltriethoxysilane, epoxy resin, polyurethane, polymethyl methacrylate, cetyltrimethylammonium bromide, sodium dodecyl sulfate, and polyethylene glycol.

[0082] Comparative Example 1

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

[0084] As Figure 7 shown, the surface roughness of the polished silicon carbide wafer 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 in Example 1. The difference from Example 1 is that only potassium persulfate is used as the oxidant in the polishing liquid formula, and the concentration of potassium persulfate is the same as that of the compound oxidant in Example 1, still 1.5 wt%.

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

[0088] As can be seen from the results of the above embodiments and comparative examples, the polishing liquid using the compound oxidant proposed by the present invention has a significantly higher material removal rate compared with 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 manufacturing process of silicon carbide substrates and 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 them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions 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: The invention comprises nano aluminum oxide abrasive, dispersant, pH regulator, oxidant and deionized water, and comprises the following components by weight percentage: 2-10 wt.% of nano aluminum oxide abrasive; 0.2-2 wt.% of dispersant; 0.001-0.01 wt‰ of pH regulator; and the concentration of oxidant is 1-5 wt.%.

2. The aluminum oxide CMP polishing liquid for rough polishing of silicon carbide wafers according to claim 1, characterized in that: The particle size of the nano aluminum oxide abrasive is 200 to 800 nanometers.

3. The aluminum oxide CMP polishing liquid for rough polishing of silicon carbide wafers according to claim 1, characterized in that: The dispersant is one or more of sodium hexametaphosphate, polyethylene glycol, hexadecylmethylammonium bromide, glycerol, bentonite, sodium polyacrylate and ammonium polyacrylate.

4. The aluminum oxide CMP polishing liquid for rough polishing of silicon carbide wafers according to claim 1, characterized in that: 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.

5. The aluminum oxide CMP polishing liquid for rough polishing of silicon carbide wafers according to claim 1, characterized in that: The oxidant is a compound oxidant, and the components of the compound oxidant are potassium permanganate and potassium persulfate.

6. The aluminum oxide CMP polishing liquid for rough polishing of silicon carbide wafers according to claim 1, characterized in that: The mass ratio of potassium permanganate to potassium persulfate in the composite oxidant is 1:0.5-2.

7. A polishing method based on the polishing liquid according to any one of claims 1 to 6, characterized in that: The steps include: The loading pressure of the silicon carbide wafer is 4-8 psi, the flow rate of the polishing liquid is 100-1000 mL / min, the polishing head speed is 25-60 r / min, the polishing disc speed is 25-60 r / min, the polishing time is 30-120 min, and the polishing liquid supply method is circulating supply.

8. The polishing method according to claim 7, characterized in that: The polishing pad used is made of polyurethane.

9. The polishing method according to claim 8, characterized in that: The surface of the polishing pad used in the polishing method is grooved before use.

10. The polishing method according to claim 7, characterized in that: The dressing method of the polishing pad is online dressing, and the dressing time ratio is 30% to 100% of the polishing time.

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