High-speed polishing solution for polishing silicon carbide wafer and preparation method of high-speed polishing solution

Abstract

The invention discloses a high-speed polishing solution for polishing a silicon carbide wafer and a preparation method of the high-speed polishing solution, and relates to the field of polishing solutions. The polishing solution comprises aluminum oxide powder, a thixotropic agent, a polishing accelerator and water; the particle size of the alumina powder is 0.5-1.5 [mu] m, and the thixotropic agent is at least one of agar, hydrogenated castor oil, propylene glycol alginate, flaxseed gum and ammonium chloride. The thixotropic agent in the polishing solution can well suspend aluminum oxide powder, aluminum oxide particles are prevented from being agglomerated, the polishing rate of the polishing solution is increased, scratches are not likely to be caused during polishing, the polishing accelerator is a surfactant with a complexing function, the infiltration effect of the polishing solution can be improved, and the polishing effect of the polishing solution is improved. And surface wrapping can be formed on the surface of the aluminum oxide powder through complexing, large scratches are not likely to be caused, and the excellent surface polishing effect and polishing efficiency are guaranteed.

Description

Technical Field

[0001] The present invention relates to the field of polishing fluids, and particularly to a high-rate polishing fluid for silicon carbide wafer polishing and a preparation method thereof. Background Art

[0002] Silicon carbide (SiC) is one of the main representatives of the third-generation semiconductors. Due to its high thermal conductivity, high breakdown field strength, large bandgap width, and high electron saturation drift rate, it has become an ideal semiconductor material for manufacturing high-temperature, high-frequency, and high-power power electronic devices, such as in the fields of new energy vehicles, charging piles, and photovoltaic power generation. With the rapid development of the semiconductor industry, the size of electronic devices has been reduced, and at the same time, the surface flatness of wafers is required to reach the nanometer level. Since silicon carbide has extremely high hardness and strong surface tension, with a Mohs hardness of 9.2, traditional planarization techniques can only achieve local planarization, and the mechanical processing technology threshold is quite high. The chemical mechanical polishing technology (CMP) can not only achieve global planarization but also is superior to traditional planarization techniques in terms of processing performance and speed.

[0003] The alumina polishing fluid commonly used in chemical mechanical polishing technology is a liquid for polishing and processing metal surfaces. It is usually used to improve the surface finish and brightness of metal products, and at the same time, it can remove surface defects, oxide layers, and other dirt, making the metal surface look smoother and more shiny. However, in the current technology, the alumina polishing fluid for 8-inch silicon carbide wafers generally has problems such as insufficient dispersion, low polishing efficiency, and scratches on the polished surface. Summary of the Invention

[0004] The present invention provides a high-rate polishing fluid for silicon carbide wafer polishing and a preparation method thereof to solve the problems of low polishing efficiency caused by uneven powder dispersion in the alumina polishing fluid and high surface roughness and scratches after polishing.

[0005] To solve the above technical problems, one of the objectives of the present invention is to provide a high-rate polishing fluid for silicon carbide wafer polishing, which includes the following components by mass fraction:

[0006] Alumina powder: 5wt%-10wt%;

[0007] Thixotropic agent: 10wt%-20wt%;

[0008] Polishing accelerator: 10wt%-20wt%;

[0009] Water: the balance;

[0010] The particle size of the alumina powder is 0.5-1.5μm, and the thixotropic agent is at least one of agar, hydrogenated castor oil, propylene glycol alginate, linseed gum, and ammonium chloride, preferably agar and / or hydrogenated castor oil.

[0011] The thixotropic agent in the polishing liquid of the present invention can suspend the alumina powder well. The thixotropic agent utilizes a spatial network structure to form layers of grids between the alumina powders, preventing the mutual aggregation and linking of alumina particles, enabling the alumina powder particles in the polishing liquid to be evenly distributed, not agglomerated, not caked, and not easily precipitated, ensuring the good suspension of the polishing liquid. Furthermore, the mechanical action of the alumina powder in the polishing liquid is maximally exerted, improving the polishing rate of the polishing liquid. Moreover, the evenly dispersed alumina particles are round and have no sharp edges, will not cause scratches, and are not likely to cause scratches on the surface of the silicon carbide wafer during polishing. The surface roughness Ra can reach below 0.2 nm, ensuring a high-quality surface effect and excellent polishing efficiency at the same time.

[0012] As a preferred solution, the polishing accelerator is at least one of cetyl alcohol, methanol, stearyl alcohol, diethylene glycol, diethylene glycol butyl ether, propylene glycol methyl ether, methyl ether, 1,4-butanediol, preferably diethylene glycol butyl ether and / or propylene glycol methyl ether.

[0013] The polishing accelerator selected in this application is a surfactant with a complexing function. Compared with ordinary surfactants, it can not only improve the wetting effect of the polishing liquid on the surface of the silicon carbide wafer and accelerate the polishing rate, enabling the polishing efficiency to reach more than 4.5 μm / h; at the same time, it can also form a complexing coating interface on the surface of the alumina powder, not easily causing large scratches on the silicon carbide wafer, and modifying the surface to obtain a smooth and scratch-free surface effect.

[0014] As a preferred solution, the polishing liquid further includes a brightening agent with a mass fraction of 5wt%-10wt%.

[0015] As a preferred solution, the brightening agent is at least one of sodium perchlorate, sodium hypochlorite, and sodium peroxide.

[0016] As a preferred solution, the polishing liquid further includes a pH regulator, and the pH of the polishing liquid is 8-11.

[0017] As a preferred solution, the pH of the polishing agent is any one or the range value of any two of 8, 9, 10, and 11.

[0018] As a preferred solution, the pH regulator is at least one of sodium hydroxide, ethanolamine, diethanolamine, and potassium hydroxide.

[0019] As a preferred solution, the crystal form of the alumina powder is the α phase.

[0020] As a preferred solution, the particle size of the alumina powder is 0.5 μm, 0.8 μm, 1.0 μm, 1.2 μm,

[0021] The range value of any one or any two of 1.5 μm. Preferably, the particle size of the alumina powder is 0.5 - 1 μm.

[0022] As a preferred embodiment, the polishing liquid comprises the following components by mass fraction: alumina powder: 5wt% - 7wt%; thixotropic agent: 15wt% - 20wt%; polishing accelerator: 10wt% - 15wt%; brightening agent: 5wt% - 7wt%; water: the balance.

[0023] To solve the above technical problems, the second object of the present invention is to provide a preparation method of a high - rate polishing liquid for silicon carbide wafer polishing, comprising the following steps:

[0024] (1) Disperse the alumina powder in water, and sequentially add the thixotropic agent, polishing accelerator and brightening agent under stirring conditions, and stir evenly to obtain a premixed liquid;

[0025] (2) Add a pH regulator to the premixed liquid to adjust the pH to 8 - 11, and thus obtain the alumina polishing liquid.

[0026] As a preferred embodiment, in step (1), the stirring rate is 2000 - 5000 r / min, preferably 3000 - 4000 r / min.

[0027] The preparation method of the low - content high - rate polishing liquid for silicon carbide wafer polishing of the present invention, based on the characteristics of the components of the alumina polishing liquid, mixes the components by a specific process to obtain an alumina polishing liquid with good dispersion uniformity and good stability, low cost and simple operation, which is conducive to large - scale production.

[0028] As a preferred embodiment, in step (1), the mass fraction of the brightening agent is 5wt% - 10wt%.

[0029] As a preferred embodiment, the brightening agent is at least one of sodium perchlorate, sodium hypochlorite and sodium peroxide.

[0030] As a preferred embodiment, in step (2), the pH regulator is at least one of sodium hydroxide, ethanolamine, diethanolamine and potassium hydroxide.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. The thixotropic agent in the polishing liquid of the present invention utilizes a spatial network structure to form layers of grids between alumina powder particles, preventing the mutual aggregation and connection of alumina particles, enabling the alumina powder particles in the polishing liquid to be evenly distributed. As a result, the mechanical action of the alumina powder in the polishing liquid is maximally exerted, improving the polishing rate of the polishing liquid. Moreover, when used for polishing, it is not easy to cause scratches on the surface of the silicon carbide substrate wafer, and the surface roughness Ra can reach below 0.2 nm, ensuring a high-quality surface effect.

[0033] 2. The polishing accelerator selected in this application is a surfactant with a complexing function. Compared with ordinary surfactants, it can not only improve the wetting effect of the polishing liquid on the surface of the silicon carbide wafer and accelerate the polishing rate, enabling the polishing efficiency to reach more than 4.5 μm / h; at the same time, it can also form a coating layer by complexing on the surface of the alumina powder, preventing the alumina powder from causing large scratches on the silicon carbide, making the modified surface of the silicon carbide wafer smooth and scratch-free, and improving the polishing quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 : It is the particle size morphology diagram of the alumina powder used in the embodiment and comparative example of the present invention;

[0035] Figure 2 : It is the atomic force microscope image of the silicon carbide wafer treated with the polishing liquid of Embodiment 2 of the present invention detected by AFM;

[0036] Figure 3 : It is the atomic force microscope image of the silicon carbide wafer treated with the polishing liquid of Proportion 4 of the present invention detected by AFM. DETAILED DESCRIPTION OF THE INVENTION

[0037] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts belong to the scope of protection of the present invention.

[0038] It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention. In addition, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded within the range.

[0039] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Although this invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of this invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the said documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0040] To further illustrate the present invention, the present invention will be described in detail below in conjunction with embodiments, but they should not be construed as limiting the scope of protection of the present invention. The raw materials used in the following embodiments and comparative examples of this application can be obtained commercially unless otherwise specified, and the same raw materials are used in parallel experiments.

[0041] Example 1

[0042] A high-rate polishing liquid for polishing silicon carbide wafers, comprising the following components by mass fraction: 5 wt% alumina powder, 10 wt% agar, 5 wt% sodium perchlorate, 10 wt% propylene glycol methyl ether, potassium hydroxide and the balance deionized water. Among them, the particle size of the alumina powder is 0.5 μm, and the crystal form is α-phase. The preparation method of the polishing liquid comprises the following steps:

[0043] (1) Disperse the alumina powder in deionized water to form an alumina powder solution. Under the stirring condition of 3000 r / min, add agar, sodium perchlorate, and propylene glycol methyl ether to the alumina powder solution in sequence, and stir and dissolve evenly to obtain a premixed solution;

[0044] (2) Add potassium hydroxide to the premixed solution, continue stirring for 10 minutes until evenly mixed, and adjust the pH value to 11 with potassium hydroxide to obtain the alumina polishing liquid.

[0045] Example 2

[0046] A high-rate polishing liquid for polishing silicon carbide wafers, comprising the following components by mass fraction: 5 wt% alumina powder, 20 wt% agar, 5 wt% sodium perchlorate, 10 wt% propylene glycol methyl ether, potassium hydroxide and the balance deionized water. Among them, the particle size of the alumina powder is 0.5 μm, and the crystal form is α-phase. The preparation method of the polishing liquid comprises the following steps:

[0047] (1) Disperse the alumina powder in deionized water to form an alumina powder solution. Under the stirring condition of 3000 r / min, add agar, sodium perchlorate, and propylene glycol methyl ether to the alumina powder solution in sequence, and stir and dissolve evenly to obtain a premixed solution;

[0048] (2) Add potassium hydroxide to the premixed solution, and continue stirring for 10 minutes until evenly mixed. Adjust the pH value to 11 with potassium hydroxide to obtain the alumina polishing solution.

[0049] Example 3

[0050] A high-rate polishing solution for silicon carbide wafer polishing, comprising the following components by mass fraction: 5 wt% alumina powder, 10 wt% linseed gum, 10 wt% sodium perchlorate, 20 wt% propylene glycol methyl ether, potassium hydroxide, and the balance deionized water. Among them, the particle size of the alumina powder is 0.5 μm, and the crystal form is α-phase. The preparation method of the polishing solution comprises the following steps:

[0051] (1) Disperse the alumina powder in deionized water to form an alumina powder solution. Under the stirring condition of 3000 r / min, add linseed gum, sodium perchlorate, and propylene glycol methyl ether to the alumina powder solution in sequence, and stir to dissolve evenly to obtain a premixed solution;

[0052] (2) Add potassium hydroxide to the premixed solution, and continue stirring for 10 minutes until evenly mixed. Adjust the pH value to 10 with potassium hydroxide to obtain the alumina polishing solution.

[0053] Example 4

[0054] A high-rate polishing solution for silicon carbide wafer polishing, comprising the following components by mass fraction: 7 wt% alumina powder, 10 wt% hydrogenated castor oil, 5 wt% sodium perchlorate, 10 wt% 1,4-butanediol, potassium hydroxide, and the balance deionized water. Among them, the particle size of the alumina powder is 0.8 μm, and the crystal form is α-phase. The preparation method of the polishing solution comprises the following steps:

[0055] (1) Disperse the alumina powder in deionized water to form an alumina powder solution. Under the stirring condition of 3000 r / min, add hydrogenated castor oil, sodium perchlorate, and 1,4-butanediol to the alumina powder solution in sequence, and stir to dissolve evenly to obtain a premixed solution;

[0056] (2) Add potassium hydroxide to the premixed solution, and continue stirring for 10 minutes until evenly mixed. Adjust the pH value to 10 with potassium hydroxide to obtain the alumina polishing solution.

[0057] Example 5

[0058] A high-rate polishing solution for silicon carbide wafer polishing, comprising the following components by mass fraction: 5 wt% alumina powder, 20 wt% hydrogenated castor oil, 5 wt% sodium hypochlorite, 10 wt% diethylene glycol butyl ether, potassium hydroxide, and the balance deionized water. Among them, the particle size of the alumina powder is 0.8 μm, and the crystal form is α-phase. The preparation method of the polishing solution comprises the following steps:

[0059] (1) Disperse the alumina powder in deionized water to form an alumina powder solution. Under the stirring condition of 3000 r / min, add hydrogenated castor oil, sodium hypochlorite, and diethylene glycol butyl ether to the alumina powder solution in sequence, and stir until dissolved and evenly mixed to obtain a premixed solution;

[0060] (2) Add potassium hydroxide to the premixed solution, continue stirring for 10 minutes until evenly mixed, and adjust the pH value to 9.5 with potassium hydroxide to obtain the alumina polishing solution.

[0061] Example 6

[0062] A high-rate polishing solution for silicon carbide wafer polishing, comprising the following components by mass fraction: 7 wt% alumina powder, 10 wt% propylene glycol alginate, 10 wt% sodium hypochlorite, 20 wt% diethylene glycol butyl ether, potassium hydroxide, and the balance deionized water. Among them, the particle size of the alumina powder is 0.8 μm, and the crystal form is α-phase. The preparation method of the polishing solution includes the following steps:

[0063] (1) Disperse the alumina powder in deionized water to form an alumina powder solution. Under the stirring condition of 3000 r / min, add propylene glycol alginate, sodium hypochlorite, and diethylene glycol butyl ether to the alumina powder solution in sequence, and stir until dissolved and evenly mixed to obtain a premixed solution;

[0064] (2) Add potassium hydroxide to the premixed solution, continue stirring for 10 minutes until evenly mixed, and adjust the pH value to 9.5 with potassium hydroxide to obtain the alumina polishing solution.

[0065] Example 7

[0066] A high-rate polishing solution for silicon carbide wafer polishing, comprising the following components by mass fraction: 10 wt% alumina powder, 20 wt% propylene glycol alginate, 10 wt% sodium peroxide, 10 wt% diethylene glycol, potassium hydroxide, and the balance deionized water. Among them, the particle size of the alumina powder is 1.0 μm, and the crystal form is α-phase. The preparation method of the polishing solution includes the following steps:

[0067] (1) Disperse the alumina powder in deionized water to form an alumina powder solution. Under the stirring condition of 3000 r / min, add propylene glycol alginate, sodium peroxide, and diethylene glycol to the alumina powder solution in sequence, and stir until dissolved and evenly mixed to obtain a premixed solution;

[0068] (2) Add potassium hydroxide to the premixed solution, continue stirring for 10 minutes until evenly mixed, and adjust the pH value to 9 with potassium hydroxide to obtain the alumina polishing solution.

[0069] Example 8

[0070] A high-rate polishing liquid for silicon carbide wafer polishing, comprising the following components by mass fraction: 10 wt% alumina powder, 10 wt% ammonium chloride, 10 wt% sodium peroxide, 10 wt% methanol, potassium hydroxide, and the balance deionized water. Among them, the particle size of the alumina powder is 1.0 μm, and the crystal form is α-phase. The preparation method of the polishing liquid comprises the following steps:

[0071] (1) Disperse the alumina powder in deionized water to form an alumina powder solution. Under the stirring condition of 3000 r / min, add ammonium chloride, sodium peroxide, and methanol to the alumina powder solution in sequence, and stir and dissolve evenly to obtain a premixed liquid;

[0072] (2) Add potassium hydroxide to the premixed liquid, continue to stir for 10 minutes until evenly mixed, and adjust the pH value to 8 with potassium hydroxide to obtain the alumina polishing liquid.

[0073] Example 9

[0074] A high-rate polishing liquid for silicon carbide wafer polishing, comprising the following components by mass fraction: 10 wt% alumina powder, 20 wt% ammonium chloride, 5 wt% sodium peroxide, 20 wt% methanol, potassium hydroxide, and the balance deionized water. Among them, the particle size of the alumina powder is 1.0 μm, and the crystal form is α-phase. The preparation method of the polishing liquid comprises the following steps:

[0075] (1) Disperse the alumina powder in deionized water to form an alumina powder solution. Under the stirring condition of 3000 r / min, add ammonium chloride, sodium peroxide, and methanol to the alumina powder solution in sequence, and stir and dissolve evenly to obtain a premixed liquid;

[0076] (2) Add potassium hydroxide to the premixed liquid, continue to stir for 10 minutes until evenly mixed, and adjust the pH value to 8 with potassium hydroxide to obtain the alumina polishing liquid.

[0077] Example 10

[0078] A high-rate polishing liquid for silicon carbide wafer polishing, comprising the following components by mass fraction: 5 wt% alumina powder, 20 wt% agar, 5 wt% sodium perchlorate, 10 wt% propylene glycol methyl ether, potassium hydroxide, and the balance deionized water. The particle size of the alumina powder is 1.0 μm, and the crystal form is α-phase. The preparation method of the polishing liquid comprises the following steps:

[0079] (1) Disperse the alumina powder in deionized water to form an alumina powder solution. Under the stirring condition of 3000 r / min, add agar, sodium perchlorate, and propylene glycol methyl ether to the alumina powder solution in sequence, and stir and dissolve evenly to obtain a premixed liquid;

[0080] (2) Add potassium hydroxide to the premixed solution and continue stirring for 10 minutes until evenly mixed. Adjust the pH value to 11 using potassium hydroxide to obtain the polishing solution.

[0081] Example 11

[0082] A high-rate polishing solution for silicon carbide wafer polishing, comprising the following components by mass fraction: 5 wt% alumina powder, 20 wt% agar, 5 wt% sodium perchlorate, 10 wt% propylene glycol methyl ether, potassium hydroxide, and the balance deionized water. The particle size of the alumina powder is 1.5 μm, and the crystal form is the a-phase. The preparation method of the polishing solution comprises the following steps:

[0083] (1) Disperse the alumina powder in deionized water to form an alumina powder solution. Under the stirring condition of 3000 r / min, add agar, sodium perchlorate, and propylene glycol methyl ether to the alumina powder solution in sequence, and stir and dissolve evenly to obtain a premixed solution;

[0084] (2) Add potassium hydroxide to the premixed solution and continue stirring for 10 minutes until evenly mixed. Adjust the pH value to 11 using potassium hydroxide to obtain the polishing solution.

[0085] Example 12

[0086] A high-rate polishing solution for silicon carbide wafer polishing, the steps of its preparation method and the reagents, equipment, and process parameters used in each step are the same as those in Example 2. The difference is that the agar is replaced with an equal amount of linseed gum.

[0087] Example 13

[0088] A high-rate polishing solution for silicon carbide wafer polishing, the steps of its preparation method and the reagents, equipment, and process parameters used in each step are the same as those in Example 2. The difference is that the agar is replaced with an equal amount of hydrogenated castor oil.

[0089] Example 14

[0090] A high-rate polishing solution for silicon carbide wafer polishing, the steps of its preparation method and the reagents, equipment, and process parameters used in each step are the same as those in Example 2. The difference is that the agar is replaced with an equal amount of propylene glycol alginate.

[0091] Example 15

[0092] A high-rate polishing solution for silicon carbide wafer polishing, the steps of its preparation method and the reagents, equipment, and process parameters used in each step are the same as those in Example 2. The difference is that the agar is replaced with an equal amount of ammonium chloride.

[0093] Comparative Example 1

[0094] A polishing liquid for silicon carbide wafer polishing, comprising the following components by mass fraction: 5wt% silica sol, 20wt% agar, 5wt% sodium perchlorate, 10wt% propylene glycol methyl ether, potassium hydroxide, and the balance deionized water. The particle size of the silica sol is 120nm. The preparation method of the polishing liquid comprises the following steps:

[0095] (1) Disperse the silica sol in deionized water to form a silica sol solution. Under the stirring condition of 3000r / min, add agar, sodium perchlorate, and propylene glycol methyl ether to the silica sol solution in sequence, stir and dissolve evenly to obtain a premixed liquid;

[0096] (2) Add potassium hydroxide to the premixed liquid, continue stirring for 10 minutes until evenly mixed, and adjust the pH value to 11 with potassium hydroxide to obtain the polishing liquid.

[0097] Comparative Example 2

[0098] A polishing liquid for silicon carbide wafer polishing, comprising the following components by mass fraction: 5wt% diamond powder, 20wt% agar, 5wt% sodium perchlorate, 10wt% propylene glycol methyl ether, potassium hydroxide, and the balance deionized water. The particle size of the diamond powder is 0.5μm. The preparation method of the polishing liquid comprises the following steps:

[0099] (1) Disperse the diamond powder in deionized water to form a diamond powder solution. Under the stirring condition of 3000r / min, add agar, sodium perchlorate, and propylene glycol methyl ether to the diamond powder solution in sequence, stir and dissolve evenly to obtain a premixed liquid;

[0100] (2) Add potassium hydroxide to the premixed liquid, continue stirring for 10 minutes until evenly mixed, and adjust the pH value to 11 with potassium hydroxide to obtain the polishing liquid.

[0101] Comparative Example 3

[0102] A polishing liquid for silicon carbide wafer polishing, comprising the following components by mass fraction: 5wt% alumina powder, 20wt% agar, 5wt% sodium perchlorate, 10wt% propylene glycol methyl ether, potassium hydroxide, and the balance deionized water. The particle size of the alumina powder is 2μm, and the crystal form is α-phase. The preparation method of the polishing liquid comprises the following steps:

[0103] (1) Disperse the alumina powder in deionized water to form an alumina powder solution. Under the stirring condition of 3000r / min, add agar, sodium perchlorate, and propylene glycol methyl ether to the alumina powder solution in sequence, stir and dissolve evenly to obtain a premixed liquid;

[0104] (2) Add potassium hydroxide to the premixed liquid, continue stirring for 10 minutes until evenly mixed, and adjust the pH value to 11 with potassium hydroxide to obtain the polishing liquid.

[0105] Comparative Example 4

[0106] A polishing liquid for polishing silicon carbide wafers, comprising the following components by mass fraction: 5 wt% alumina powder, 5 wt% sodium perchlorate, 10 wt% propylene glycol methyl ether, potassium hydroxide, and the balance deionized water. The particle size of the alumina powder is 0.5 μm, and the crystal form is the a-phase. The preparation method of the polishing liquid comprises the following steps:

[0107] (1) Disperse the alumina powder in deionized water to form an alumina powder solution. Under the stirring condition of 3000 r / min, sequentially add sodium perchlorate and propylene glycol methyl ether to the alumina powder solution, and stir and dissolve evenly to obtain a premixed solution;

[0108] (2) Add potassium hydroxide to the premixed solution, continue to stir for 10 minutes until evenly mixed, and adjust the pH value to 11 with potassium hydroxide to obtain the polishing liquid.

[0109] Comparative Example 5

[0110] A polishing liquid for polishing silicon carbide wafers, comprising the following components by mass fraction: 5 wt% alumina powder, 20 wt% silica, 5 wt% sodium perchlorate, 10 wt% propylene glycol methyl ether, potassium hydroxide, and the balance deionized water. The particle sizes of the silica and the alumina powder are 0.5 μm, and the crystal form is the a-phase. The preparation method of the polishing liquid comprises the following steps:

[0111] (1) Disperse the alumina powder in deionized water to form an alumina powder solution. Under the stirring condition of 3000 r / min, sequentially add silica, sodium perchlorate, and propylene glycol methyl ether to the alumina powder solution, and stir and dissolve evenly to obtain a premixed solution;

[0112] (2) Add potassium hydroxide to the premixed solution, continue to stir for 10 minutes until evenly mixed, and adjust the pH value to 11 with potassium hydroxide to obtain the polishing liquid.

[0113] Comparative Example 6

[0114] A polishing liquid for polishing silicon carbide wafers, comprising the following components by mass fraction: 5 wt% alumina powder, 20 wt% wheat starch, 5 wt% sodium perchlorate, 10 wt% propylene glycol methyl ether, potassium hydroxide, and the balance deionized water. The particle size of the alumina powder is 0.5 μm, and the crystal form is the a-phase. The preparation method of the polishing liquid comprises the following steps:

[0115] (1) Disperse the alumina powder in deionized water to form an alumina powder solution. Under the stirring condition of 3000 r / min, sequentially add silica, sodium perchlorate, and propylene glycol methyl ether to the alumina powder solution, and stir and dissolve evenly to obtain a premixed solution;

[0116] (2) Add potassium hydroxide to the premixed solution, continue stirring for 10 minutes until evenly mixed, and adjust the pH value to 11 with potassium hydroxide to obtain the polishing solution.

[0117] Comparative Example 7

[0118] A polishing solution for polishing silicon carbide wafers, comprising the following components by mass fraction: 5 wt% alumina powder, 20 wt% agar, 5 wt% sodium perchlorate, potassium hydroxide, and the balance deionized water. The particle size of the alumina powder is 0.5 μm, and the crystal form is α-phase. The preparation method of the polishing solution comprises the following steps:

[0119] (1) Disperse the alumina powder in deionized water to form an alumina powder solution. Under the stirring condition of 3000 r / min, add agar and sodium perchlorate to the alumina powder solution in sequence, and stir and dissolve evenly to obtain a premixed solution;

[0120] (2) Add potassium hydroxide to the premixed solution, continue stirring for 10 minutes until evenly mixed, and adjust the pH value to 11 with potassium hydroxide to obtain the polishing solution.

[0121] Comparative Example 8

[0122] A polishing solution for polishing silicon carbide wafers, comprising the following components by mass fraction: 5 wt% alumina powder, 20 wt% agar, 5 wt% sodium perchlorate, 10 wt% sodium dodecylsulfonate, potassium hydroxide, and the balance deionized water. Among them, the particle size of the alumina powder is 0.5 μm, and the crystal form is α-phase. The preparation method of the polishing solution comprises the following steps:

[0123] (1) Disperse the alumina powder in deionized water to form an alumina powder solution. Under the stirring condition of 3000 r / min, add agar, sodium perchlorate, and propylene glycol methyl ether to the alumina powder solution in sequence, and stir and dissolve evenly to obtain a premixed solution;

[0124] (2) Add potassium hydroxide to the premixed solution, continue stirring for 10 minutes until evenly mixed, and adjust the pH value to 11 with potassium hydroxide to obtain the alumina polishing solution.

[0125] Performance detection test

[0126] 1. Polishing test: Test machine: 610# single-sided polishing machine; Test wafer: 8-inch silicon carbide polishing wafer; Polishing pad: SUB800; Time: 1h; Detection method: The removal rate is tested by an analytical balance to determine the quality difference before and after polishing, MRR = ΔM / Pπr2t, where MRR is the removal rate, ΔM is the quality difference before and after, p is the density of the silicon carbide wafer, t is the polishing time, πr2 is the area of ​​the silicon carbide wafer, AFM is used to detect the roughness Ra after polishing, and the surface scratches are observed. The test results are as follows Figure 2 And as shown in Table 1.

[0127] 2. The alumina powder used in the examples and comparative examples was subjected to SEM testing. The particle size and morphology test results are as follows: Figure 1 shown.

[0128] Table 1 - Polishing test results of the polishing liquids of the present application examples and comparative examples

[0129]

[0130]

[0131] As shown in Table 1, the polishing liquid in Example 2 uses aluminum oxide powder as a polishing abrasive. The aluminum oxide particles are round, have no edges and corners, and have moderate hardness. The polishing effect on the surface of the silicon carbide wafer is good and the surface roughness is low. Comparative Examples 1 and 2 use silica sol and diamond powder as polishing abrasives, respectively. The silica sol polishing liquid in Comparative Example 1 has a low removal rate and scratches on the surface. This is because the silica sol is relatively soft and cannot polish the surface of silicon carbide, resulting in the film on the surface of silicon carbide cannot be completely removed. The scratches left by the previous fine grinding process, while the diamond abrasive in the diamond polishing liquid in Comparative Example 2 has a relatively high hardness and is easy to remove the rough surface of the silicon carbide surface. However, the hardness is too high and the diamond powder is relatively rough, resulting in more scratches on the surface. The surface roughness Ra of the silicon carbide wafer after polishing is too large and cannot meet the requirements.

[0132] As shown in Table 1, agar, flaxseed gum, hydrogenated castor oil, propylene glycol alginate, and ammonium chloride were added as thixotropic agents in Examples 2 and 12 - 15 respectively. The thixotropic agent molecules arrange the alumina powder in an orderly manner through steric hindrance, which can better suspend the alumina powder, prevent the mutual aggregation and connection of alumina particles, improve the dispersion performance of the powder in the polishing liquid, making it not easy to agglomerate and precipitate. Each particle can effectively contact the polishing pad and the silicon carbide wafer during the grinding and polishing process to play the best role, increasing the polishing rate. Moreover, the uniformly dispersed alumina particles are round and have no sharp edges, so they will not scratch the silicon carbide wafer during the polishing process, thus obtaining a lower surface roughness. In Comparative Example 4, no thixotropic agent was added, and the alumina powder in the polishing liquid was prone to agglomeration and caking, with larger particles having distinct edges and corners. During polishing, it was easy to cause serious scratches on the silicon carbide wafer. Although the removal rate increased, the surface roughness increased, which had an impact on subsequent fine polishing. In Comparative Examples 5 and 6, silica and wheat starch were used as thixotropic agents respectively, which were prone to combine with the alumina powder to form agglomerates, affecting the dispersibility of the alumina powder, resulting in an increase in the surface roughness of the silicon carbide wafer after polishing and a decrease in the polishing rate.

[0133] As shown in Table 1, propylene glycol methyl ether was added as a polishing accelerator in the polishing liquid of Example 2. It reduces the surface tension of the liquid through wetting, and at the same time enhances the dispersion performance of the thixotropic agent on the alumina powder, increasing the polishing rate of the liquid. On the other hand, propylene glycol methyl ether can form a surface coating by complexing on the surface of the alumina powder, which can prevent the alumina powder from causing large scratches on the silicon carbide, making the modified surface of the silicon carbide wafer smooth and scratch - free, improving the polishing quality. Moreover, propylene glycol methyl ether has the function of a surfactant, which can remove the dirt on the product surface, making the surface cleaner and achieving a brightening effect. In Comparative Example 7, since no propylene glycol methyl ether or other polishing accelerator was added, the polishing efficiency of the product was significantly reduced, and the surface roughness of the silicon carbide wafer after polishing increased, and the surface quality deteriorated. In Comparative Example 8, the sodium dodecyl sulfate added did not have a complexing effect, and the alumina powder was prone to scratch the silicon carbide wafer during the polishing process, increasing the surface roughness of the product.

[0134] As shown in Table 1, the particle size of the alumina powder in Examples 2 and 10 - 11 was 0.5 - 1.5 μm. It can be found that as the alumina particle size increases, the removal rate and surface roughness gradually increase. In Comparative Example 3, the particle size of the alumina powder was 2 μm. This is because large - particle - size alumina powder is not easy to disperse. When the alumina powder particle size is too large, it is prone to agglomeration and scratching. The mechanical friction of the powder acting on the silicon carbide surface is relatively large, resulting in an increase in the surface roughness of the silicon carbide and poor polishing quality.

[0135] The specific embodiments described above further elaborate on the objectives, technical solutions, and beneficial effects of the present invention. It should be understood that the above description is only for the specific embodiments of the present invention and is not intended to limit the protection scope of the present invention. In particular, it is pointed out that for those skilled in the art, any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A high-speed polishing liquid for silicon carbide wafer polishing, characterized in that, Comprising the following components by mass fraction: Aluminum oxide powder: 5wt% - 10wt%; Thixotropic agent: 10wt% - 20wt%; Polishing accelerator: 10wt% - 20wt%; Water: the balance; The particle size of the aluminum oxide powder is 0.5 - 1.5μm, and the thixotropic agent is at least one of agar, hydrogenated castor oil, propylene glycol alginate, linseed gum, and ammonium chloride.

2. The high-rate polishing liquid for silicon carbide wafer polishing according to claim 1, wherein, The polishing accelerator is at least one of cetyl alcohol, methanol, stearyl alcohol, diethylene glycol, diethylene glycol monobutyl ether, propylene glycol methyl ether, methyl ether, and 1,4 - butanediol.

3. The high-rate polishing liquid for silicon carbide wafer polishing according to claim 1, wherein The polishing liquid further comprises a brightening agent with a mass fraction of 5wt% - 10wt%.

4. The high-rate polishing liquid for silicon carbide wafer polishing according to claim 3, characterized in that, The brightening agent is at least one of sodium perchlorate, sodium hypochlorite, and sodium peroxide.

5. The high-rate polishing liquid for polishing silicon carbide wafers according to claim 1, wherein The polishing liquid further comprises a pH regulator, and the pH of the polishing liquid is 8 - 11.

6. The high-rate polishing liquid for polishing silicon carbide wafers according to claim 5, wherein, The pH regulator is at least one of sodium hydroxide, ethanolamine, diethanolamine, and potassium hydroxide.

7. The high-rate polishing liquid for silicon carbide wafer polishing according to claim 1, wherein The crystal form of the aluminum oxide powder is the α phase.

8. The high-rate polishing liquid for polishing silicon carbide wafers according to claim 1, wherein The particle size of the aluminum oxide powder is 0.5 - 1μm.

9. A method for preparing a high-rate polishing liquid for silicon carbide wafer polishing according to any one of claims 1-8, characterized in that, Comprising the following steps: (1) Disperse the aluminum oxide powder in water, and sequentially add the thixotropic agent, the polishing accelerator, and the brightening agent under stirring conditions, and stir evenly to obtain a premixed liquid; (2) Add the pH regulator to the premixed liquid, and adjust the pH to 8 - 11 to obtain the aluminum oxide polishing liquid.

10. The preparation method of the high-rate polishing liquid for silicon carbide wafer polishing according to claim 9, characterized in that, In step (1), the stirring rate is 2000 - 5000r / min; and / or, in step (1), the mass fraction of the brightening agent is 5wt% - 10wt%; and / or, the brightening agent is at least one of sodium perchlorate, sodium hypochlorite, and sodium peroxide; and / or, in step (2), the pH regulator is at least one of sodium hydroxide, ethanolamine, diethanolamine, and potassium hydroxide.

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