A multi-layer core-shell structure polishing abrasive, polishing liquid, preparation method and application

Abstract

The present invention relates to a multi-layer core-shell structure polishing abrasive, polishing liquid, preparation method and application. The polishing liquid, in parts by weight, comprises the following components: 1-30 parts of multi-layer core-shell structure polishing abrasive; 1-20 parts of pH regulator; 0.1-10 parts of dispersant; 0.1-10 parts of dispersing aid; 20-70 parts of deionized water. The present invention adopts the method of impregnation, oxygen atmosphere calcination and concentrated sulfuric acid activation to prepare the multi-layer core-shell structure polishing abrasive, and the impregnation allows the metal salt to be combined with the polishing abrasive through the chelation of the chelating agent; the oxygen atmosphere can oxidize the abrasive to improve the dispersibility of the abrasive; the chelating agent can be removed during the high-temperature calcination process, thereby increasing the loading amount of the metal salt; the core-shell structure after the concentrated sulfuric acid activation will be loosened accordingly, exposing more catalytic sites, and the multi-layer core-shell structure is obtained through repeated multiple wrapping.

Description

Technical Field

[0001] The invention belongs to the polishing liquid technology, and in particular relates to a multi-layer core-shell structure polishing abrasive, a polishing liquid, a preparation method and an application. Background Art

[0002] As a third-generation semiconductor material, silicon carbide (SiC) has two significant characteristics: high hardness and chemical inertness. Due to the high hardness of SiC materials, the Mohs hardness of silicon carbide is 9.2, and it is difficult to finely process it with ordinary abrasives. At present, the mechanical polishing of silicon carbide uses a polishing liquid containing diamond powder. Diamond powder has a sharp and irregular morphology, and a Mohs hardness of 10, which is the hardest substance in nature.

[0003] Selecting diamond micro-powder polishing liquid has a faster polishing efficiency, but due to the irregular morphology and high hardness of diamond abrasives, after mechanical polishing, several scratches of varying depths can be seen on the surface of the silicon carbide wafer under a microscope. This indicates that the surface damage layer is deep, which will make it difficult to completely remove the damage layer caused by mechanical polishing by subsequent chemical mechanical polishing.

[0004] However, when using acidic (pH < 7, especially pH < 4) silicon carbide chemical mechanical polishing liquid with α-Al2O3 abrasive, which is second only to silicon carbide in hardness, the edges and corners of the α-Al2O3 abrasive are easily passivated by the hard SiC, causing the polishing efficiency to decay rapidly over time and the SiC removal rate to be low. Summary of the invention

[0005] The technical problem solved by the present invention is that the existing polishing liquid has the problems of low SiC removal rate and severe scratches to varying degrees. A multi-layer core-shell structure polishing abrasive, polishing liquid, preparation method and application are proposed. The polishing abrasive has a special core-shell structure. The polishing liquid using the polishing abrasive is used to polish silicon carbide, which has the advantages of high removal rate and low scratches. The polishing liquid is also applicable to semiconductor materials such as gallium nitride and sapphire.

[0006] In view of the technical problems existing in the prior art, the present invention designs a multi-layer core-shell structure polishing abrasive, a polishing liquid, a preparation method and an application.

[0007] It should be noted that, in the present invention, unless otherwise specified, the specific meaning of "including" in relation to composition limitations and descriptions includes both open-ended "including", "comprising" and similar meanings, and closed-ended "consisting of..." and similar meanings.

[0008] In order to solve the above-mentioned technical problems, the present invention adopts the following solutions:

[0009] [The first technical solution]

[0010] The invention provides a method for preparing a multi-layer core-shell structure polishing abrasive, comprising the following steps:

[0011] Step 1: preparing a metal-abrasive single-layer core-shell structure abrasive;

[0012] Step 1.1: impregnating the polishing abrasive in a mixed solution of a metal salt solution, a chelating agent and a background solvent, and filtering after the impregnation to obtain an abrasive precursor having a metal-abrasive single-layer core-shell structure;

[0013] Step 1.2: The precursor obtained in step 1.1 is calcined at high temperature in an oxygen atmosphere to obtain a core-shell structure abrasive with catalytic properties;

[0014] Step 1.3: placing the abrasive obtained in step 1.2 in concentrated sulfuric acid, activating the metal-abrasive single-layer core-shell structure abrasive with catalytic properties under water bath heating, and washing after activation to obtain the metal-abrasive single-layer core-shell structure abrasive;

[0015] Step 2: preparing abrasives with a metal-abrasive multilayer core-shell structure;

[0016] The metal-abrasive single-layer core-shell structure abrasive prepared in step 1 is used as a polishing abrasive, and is immersed in a mixed solution of a metal salt solution, a chelating agent and a background solvent. After the immersion is completed, it is filtered, calcined at high temperature under an oxygen atmosphere, and activated with concentrated sulfuric acid to obtain a metal-abrasive double-layer core-shell structure abrasive;

[0017] Repeat the operation of step 1 again to obtain the abrasive with a metal-abrasive double-layer core-shell structure, so as to obtain the abrasive with a metal-abrasive multi-layer core-shell structure.

[0018] Furthermore, the mass ratio of the polishing abrasive, the metal salt solution, the chelating agent and the background solvent is 2.5-10: 0.5-2: 20-30: 20-70;

[0019] Preferably, the mass ratio of the polishing abrasive to the metal salt solution is 4:1-6:1.

[0020] Furthermore, the polishing abrasive is one or more of aluminum oxide, silicon oxide, and cerium oxide;

[0021] The metal element in the metal salt solution is one or more of nickel, cobalt, iron, palladium, copper and zinc, and the salt in the metal salt solution is one or more of nitrate, hydrochloride and sulfate;

[0022] The chelating agent is one or more of valine, methionine, phenylalanine, threonine and glutamic acid;

[0023] The background solvent is one or more of ethanol, methanol, acetone, dimethylformamide and dimethylacetamide.

[0024] Furthermore, in the step 1.1, the immersion time is 2-24 hours;

[0025] In the step 1.2, the flow rate of oxygen is 0.1-1 L / min;

[0026] In the step 1.2, the high temperature calcination temperature is 350-1000°C, and the calcination time is 5-20h;

[0027] In the step 1.3, the water bath heating temperature is 40-85° C. and the heating time is 1-4 h.

[0028] Furthermore, the particle size of the metal-abrasive single-layer core-shell structure abrasive described in step 1 is in the range of 10-150 nm.

[0029] The particle size range of the metal-abrasive multilayer core-shell structure abrasive described in step 2 is 20-160nm.

[0030] In the present invention, the mass ratio of the metal salt solution, the chelating agent and the background solvent may preferably be 1:25:65; the mass ratio of the polishing abrasive and the metal salt solution may preferably be 5:1.

[0031] In the present invention, the polishing abrasive is preferably aluminum oxide;

[0032] The metal element in the metal salt solution is preferably palladium, and the salt solution in the metal salt solution is preferably nitrate;

[0033] The chelating agent is preferably glutamic acid;

[0034] The background solvent is preferably ethanol.

[0035] The metal salt solution is a mixture of metal salt and deionized water, and the mass ratio of the metal salt to deionized water is 10-20:80-100; preferably 15-18:80-90.

[0036] In the present invention, the particle size range of the metal-abrasive single-layer core-shell structure abrasive in step 1 is preferably 55-75 nm.

[0037] The particle size of the metal-abrasive multilayer core-shell structure abrasive described in step 2 is preferably in the range of 60-80 nm, and the particle size of the multilayer core-shell structure abrasive is larger than that of the single-layer core-shell structure abrasive.

[0038] In the present invention, the immersion time in step 1.1 is preferably 12 hours.

[0039] In step 1.2, the flow rate of oxygen is preferably 0.6 L / min.

[0040] In step 1.2, the high temperature calcination temperature is preferably 600-1000° C., more preferably 800° C., and the calcination time is preferably 8-14 h, more preferably 12 h.

[0041] In step 1.3, the water bath heating temperature is preferably 60° C., and the heating time is preferably 2 h.

[0042] Furthermore, the single-layer core-shell structure abrasive obtained in step 1 is washed and filtered with deionized water, and then dried at a temperature of 50-70° C., preferably 60° C., and a drying time of 5-8 h, preferably 7 h.

[0043] It should be noted that after each activation treatment, cleaning, filtration and drying are required.

[0044] The preparation method of the multi-layer core-shell structure polishing abrasive of the present invention has unique advantages:

[0045] First, the oxygen atmosphere can oxidize the abrasive, generating oxygen-containing groups on its surface, which is beneficial for the polishing abrasive to work synergistically with the dispersant in the polishing liquid and improve the dispersibility of the abrasive;

[0046] Secondly, the chelating agent can be removed during the high-temperature calcination process, thereby encapsulating the metal salt in the abrasive, and taking advantage of the large specific surface area of ​​the polishing abrasive, the loading capacity of the metal salt is increased;

[0047] Thirdly, the core-shell structure after activation with concentrated sulfuric acid will become loose, which not only allows its surface to have more hydroxyl groups, but also exposes more catalytic sites. It can also improve the dispersibility of the abrasive in the polishing process. Through repeated wrapping, a multi-layer core-shell structure polishing abrasive with alternating metal salt-polishing abrasive-metal salt-polishing abrasive is obtained.

[0048] In general, the present invention adopts the methods of impregnation, oxygen atmosphere calcination and concentrated sulfuric acid activation to prepare the multilayer core-shell structure polishing abrasive. The impregnation allows the metal salt to be combined with the polishing abrasive through the chelation of the chelating agent.

[0049] The activation step of the present invention is of special significance:

[0050] In the present invention, the metal salt serves as the "core" in the core-shell structure and has a catalytic effect.

[0051] The activation step is a special treatment step for the core of the core-shell structure under a polishing system, which is not involved in general catalyst preparation. The main reason is that in general catalytic systems, issues such as the reuse of catalysts need to be involved, so the structural stability of the catalyst needs to be considered and valued, and the core-shell structure after activation will be relatively loose, which does not meet the actual application requirements of existing catalysts.

[0052] In the polishing system of the present invention, the catalytic performance of the core of the core-shell structure and the loose structure after activation are utilized, which can not only expose more catalytic sites but also improve the dispersibility of the abrasive in the polishing process.

[0053] [Second technical solution]

[0054] The invention provides a multi-layer core-shell structure polishing abrasive prepared by the preparation method.

[0055] The present invention adopts a specific multi-layer core-shell structure with unique advantages:

[0056] In the polishing process, the metal salt as the "core" in the core-shell structure will disperse along with the dispersion of the polishing abrasive. During the polishing process, the polishing abrasive (shell) breaks and exposes the core-shell abrasive inside. The present invention is a multi-layer core-shell structure, which can expose more active sites, enhance its catalytic effect, effectively prevent the problem of embedding the active sites of the core, and effectively reduce scratches during the polishing process.

[0057]

Third technical solution

[0058] The invention provides a polishing liquid, comprising the above-mentioned multi-layer core-shell structure polishing abrasive, wherein the polishing liquid comprises the following components in parts by weight:

[0059] 1-30 parts of multi-layer core-shell structure polishing abrasive;

[0060] 1-20 parts of pH regulator;

[0061] Dispersant 0.1-10 parts;

[0062] Dispersing aid 0.1-10 parts;

[0063] 20-70 parts of deionized water.

[0064] Furthermore, the pH regulator is an alkaline regulator; the alkaline regulator is an organic base, and the organic base is one or more of diethanolamine, triisopropanolamine, and triethanolamine;

[0065] The dispersant is an aqueous dispersant; the aqueous dispersant is one or more of sodium polyacrylate, sodium dodecylbenzene sulfonate and sodium dodecyl sulfonate;

[0066] The dispersing aid is one or more of aminopropylamine dioleate, octadecenylamine sodium acetate, metoclopramide N4-sulfonate, and 2-hydroxyethylsulfonic acid dimethylamine.

[0067] In the present invention, in order to further optimize the performance of the polishing liquid, its components can be optimized: multilayer core-shell structure polishing abrasive is 10-25 parts; pH adjuster is 3-10 parts; dispersant is 1-5 parts; dispersant auxiliary is 5-10 parts; deionized water is 30-50 parts.

[0068] In the present invention, the pH adjuster is preferably triethanolamine;

[0069] The dispersant is preferably sodium dodecyl sulfate;

[0070] The dispersing aid is preferably metoclopramide N4-sulfonate.

[0071] In the present invention, the pH of the prepared polishing liquid is 7-9, and the pH may be further preferably 8-9.

[0072]

The fourth technical solution

[0073] A method for preparing the polishing liquid is provided, comprising the following steps:

[0074] Firstly, each component is weighed according to a proportion, and then all components except the multi-layer core-shell structure polishing abrasive are fully mixed and stirred to obtain a mixed solution; finally, the multi-layer core-shell structure polishing abrasive is added to the mixed solution and stirred evenly to prepare the polishing liquid.

[0075] Further, before adding the multilayer core-shell structure polishing abrasive, stirring at 30-100 r / min for 30-90 min;

[0076] Before adding the multi-layer core-shell structure polishing abrasive, it can be preferably stirred at 45-80 r / min for 45-80 min.

[0077] Further, after adding the multilayer core-shell structure polishing abrasive, stirring at 30-100 r / min for 10-50 min;

[0078] After adding the multi-layer core-shell structure polishing abrasive, stirring may be preferably performed at 45-80 r / min for 15-45 min.

[0079]

Fifth technical solution

[0080] The invention provides a polishing process of the polishing liquid, comprising the following steps:

[0081] Step 1: Dilute the polishing liquid 2-5 times;

[0082] Step 2: setting ultraviolet light to irradiate the substrate surface, with a wavelength of 100-400nm;

[0083] Step 3: Set the polishing machine speed to 50-100r / min, the pressure to 15-30kg, and drip the polishing liquid on the substrate surface at 5-200mL / min for polishing for 10-800min;

[0084] In the polishing process of the present invention, the substrate is sapphire, silicon carbide or gallium nitride.

[0085] In the polishing process of the present invention, the amount of polishing liquid used per unit area of ​​the sapphire, silicon carbide or gallium nitride surface is 3 to 5 mL.

[0086] [Sixth technical solution]

[0087] The invention aims to provide a polishing liquid of the multi-layer core-shell structure polishing abrasive for use in the polishing field of silicon carbide, sapphire and gallium nitride.

[0088] The present invention provides a multi-layer core-shell structure polishing abrasive, a polishing liquid, a preparation method and an application thereof, which have the following beneficial effects:

[0089] 1. The present invention adopts the methods of impregnation, oxygen atmosphere calcination and concentrated sulfuric acid activation to prepare a multi-layer core-shell structure polishing abrasive. The impregnation allows the metal salt to be combined with the polishing abrasive through the chelation of a chelating agent; the oxygen atmosphere can oxidize the abrasive to improve the dispersibility of the abrasive; the chelating agent can be removed during the high-temperature calcination process to increase the loading amount of the metal salt; the core-shell structure after activation with concentrated sulfuric acid will be loosened accordingly, which can not only make the surface of the core-shell structure have more hydroxyl groups, but also expose more catalytic sites, and can also improve the dispersibility of the abrasive in the polishing process. By repeatedly wrapping, a multi-layer core-shell structure polishing abrasive is obtained.

[0090] 2. In the preparation method of the present invention, in step 1, a polishing abrasive is used as a shell to wrap a metal salt as a core to obtain a metal-abrasive assembled ball; then, the metal-abrasive assembled ball is used as a shell to form a shell layer outside the metal salt added in step 2 (the shell layer is formed by assembling a plurality of the above-mentioned metal-abrasive assembled balls); finally, an abrasive with a multi-layer core-shell structure is formed; the present invention uses an abrasive with a multi-layer core-shell structure with a specific structure. During the polishing process, the outer shell layer will be broken to produce a plurality of metal-abrasive assembled balls, and dispersed with the dispersion of the polishing abrasive. Since each metal-abrasive assembled ball can absorb energy under ultraviolet irradiation, the electrons on the valence band transition to the conduction band, leaving a positively charged hole on the original valence band, thereby exposing more active sites and enhancing its catalytic effect; at the same time, the hole can react with OH- on the surface of other abrasives to generate highly oxidizing ·OH radicals, oxidize the silicon carbide surface, reduce its hardness, effectively reduce scratches, thereby achieving a polishing effect and effectively preventing the problem of active site embedding of the core.

[0091] 3. The present invention improves the dispersibility of the abrasive by adding a dispersant aid and a combination of the dispersant aid and the dispersant, so that the surface quality of the substrate after polishing is better; at the same time, the pH stability can be well maintained, so that the pH during the polishing process is maintained within the alkaline range, so that the polishing liquid can remain stable and the polishing rate is stable.

[0092] 4. The activation step of the present invention is advantageous in the polishing system, as it can expose more catalytic sites and improve the dispersibility of the abrasive during the polishing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0093] Figure 1 : is a photo of the silicon carbide surface after polishing with the polishing solution of Example 1 of the present invention;

[0094] Figure 2 : A photo of the silicon carbide surface after polishing with the polishing liquid of Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0095] The present invention will be further described below in conjunction with specific embodiments and accompanying drawings:

[0096] The method for preparing multiple groups of multi-layer core-shell structure polishing abrasives involved in the present invention comprises the following steps:

[0097] Step 1: Preparation of metal-abrasive single-layer core-shell structure abrasive

[0098] Step 1.1: The polishing abrasive is immersed in a mixed solution of a metal salt solution, a chelating agent and a background solvent for 12 hours, washed and filtered with deionized water, and dried in an oven at a temperature of 60° C. for 7 hours to obtain an abrasive precursor having a metal-abrasive single-layer core-shell structure;

[0099] Step 1.2: calcining the precursor obtained in step 1.1 at 800° C. in an oxygen atmosphere with an oxygen flow rate of 0.6 L / min for 12 h to obtain a core-shell structure abrasive with catalytic properties;

[0100] Step 1.3: placing the abrasive obtained in step 1.2 in concentrated sulfuric acid, heating in a water bath at 60°C for 2h, washing and filtering with deionized water, and drying in an oven at a temperature of 60°C for 7h to obtain a metal-abrasive single-layer core-shell structure abrasive with catalytic properties;

[0101] Step 2: Preparation of abrasives with metal-abrasive multilayer core-shell structure

[0102] The single-layer core abrasive prepared in step 1 is immersed in a mixed solution of a metal salt solution, a chelating agent and a background solvent for 12 hours, washed and filtered with deionized water, and dried in an oven at a temperature of 60° C. for 7 hours to obtain an abrasive precursor having a metal-abrasive double-layer core-shell structure;

[0103] Subsequently, the precursor was calcined at 800° C. in an oxygen atmosphere with an oxygen flow rate of 0.6 L / min. After calcination for 12 h, a core-shell structure abrasive with catalytic properties was obtained.

[0104] The core-shell structure abrasive with catalytic properties is placed in concentrated sulfuric acid, heated in a water bath at 60°C, heated for 2 hours, washed and filtered with deionized water, and dried in an oven at 60°C for 7 hours to obtain a metal-abrasive double-layer core-shell structure abrasive with catalytic properties;

[0105] Step 3: Repeat the above step 1 with the abrasive having a metal-abrasive double-layer core-shell structure to obtain an abrasive having a metal-abrasive triple-layer core-shell structure.

[0106] The preparation method of the metal salt solution in the above steps 1-3 is: dissolving 18 parts of metal salt in 82 parts of deionized water to obtain the metal salt solution.

[0107] Table 1 Multilayer core-shell structure polishing abrasive 1-abrasive 5

[0108]

[0109] Abrasive 6: A method for preparing a single-layer core-shell structure polishing abrasive is provided:

[0110] Step 1: Preparation of metal-abrasive single-layer core-shell structure abrasive

[0111] Same as abrasive 1.

[0112] Abrasive 7: The difference from abrasive 1 is that concentrated sulfuric acid is not used for activation.

[0113] The method for preparing the polishing liquid involved in the present invention comprises the following steps:

[0114] Weigh each component according to the proportion, stir all components except the multi-layer core-shell structure polishing abrasive at 60 r / min for 60 min, then add the multi-layer core-shell structure polishing abrasive to the above solution, and continue stirring at 60 r / min for 35 min to obtain a polishing liquid containing polishing abrasive.

[0115] Table 2 Examples 1 to 5 of polishing liquid

[0116]

[0117] Table 3 Comparative Examples 1 to 4 of Polishing Liquids

[0118]

[0119] Performance 1 Material Removal Rate (MRR)

[0120] The test method is: the mass of the substrate before and after polishing is measured, and the thickness of the removed silicon carbide layer is indirectly calculated based on the density and substrate area. The biggest feature of this method is that the measurement is simple and the removal rate can be quickly obtained. The evaluation of the material removal rate in the examples and comparative examples of this application is as follows:

[0121] MRR=△m / (ρSt)

[0122] Where: Δm is the mass change of SiC before and after polishing, ρ is the density of SiC, S is the area of ​​SiC wafer, and t is the polishing time.

[0123] Performance 2 Surface roughness (Ra)

[0124] The test method is: use a surface roughness measuring instrument to measure the surface roughness of the polished silicon carbide wafer and observe the degree of surface scratches. The test results are shown in Figure 1-2 .

[0125] Table 4 Test data

[0126]

[0127] Based on Table 4, it can be seen that in the embodiment of the present invention: the material removal rate (MRR) ranges from 5.0 to 6.1 µm / h, and the surface roughness (Ra) ranges from 0.13 to 0.25 nm.

[0128] Comparative example: Material removal rate (MRR) ranges from 4.6-5.4µm / h, and surface roughness (Ra) ranges from 0.26-0.51nm.

[0129] Compared with the comparative example, the embodiment of the present invention improves the material removal rate and reduces the surface roughness. The roughness can also prove the severity of the scratches on the silicon carbide surface. The greater the roughness, the rougher and more uneven the surface is, which further proves that the polishing liquid of the embodiment of the present invention has a low scratch effect.

[0130] In Comparative Example 1, aluminum oxide abrasive is used, which is very easy to agglomerate in the solution, resulting in insufficient dispersion of the abrasive in the solution. Therefore, the polishing effect on the substrate is poor, the material removal rate is low, and corresponding scratches are generated.

[0131] In Comparative Example 2, a single-layer core-shell abrasive 6 was used, resulting in fewer exposed active sites during the polishing process, weakened catalytic effect, and failure to solve the problem of embedding the active sites of the core of the core-shell structure, resulting in a high surface roughness.

[0132] In Comparative Example 3, the abrasive 7 that was not activated with concentrated sulfuric acid was used. The unactivated abrasive had no active groups, the chemical inertness of the shell was enhanced, and it could not be further modified, and it was not easy to form a multilayer structure, resulting in a low removal rate and high surface roughness.

[0133] In Comparative Example 4, no dispersing aid was added, resulting in insufficient dispersibility. In addition, during the polishing process, the pH of the solution could not be stabilized well, and the polishing rate fluctuated, that is, the polishing rate was faster in the early stage, but became lower after a period of use.

[0134] The polishing effect of the present invention is further described with reference to the accompanying drawings:

[0135] Figure 1 This is a photo of the silicon carbide surface after polishing with the polishing solution of Example 1 of the present invention; Figure 2 This is a photo of the silicon carbide surface after polishing with the polishing liquid of Comparative Example 1 of the present invention.

[0136] Combination Figure 1 and Figure 2 , it can be seen that Figure 2 There are many scratches on the surface, which proves that the silicon carbide treated with the polishing liquid in Comparative Example 1 has scratches. Figure 1 No obvious scratches were observed, which proves that the polishing liquid of Example 1 of the present invention has low scratch performance.

[0137] The invention adopts the methods of impregnation, oxygen atmosphere calcination and concentrated sulfuric acid activation to prepare a multi-layer core-shell structure polishing abrasive. The impregnation allows the metal salt to be combined with the polishing abrasive through the chelation of a chelating agent. The oxygen atmosphere can oxidize the abrasive to improve the dispersibility of the abrasive. The chelating agent can be removed during the high-temperature calcination process to increase the loading amount of the metal salt. The core-shell structure after activation with concentrated sulfuric acid will be loosened accordingly, which can not only make the surface of the core-shell structure have more hydroxyl groups, but also expose more catalytic sites, and can also improve the dispersibility of the abrasive in the polishing process. The multi-layer core-shell structure can be obtained by repeated encapsulation.

[0138] The present invention is described exemplarily above in conjunction with the embodiments and drawings. It is obvious that the implementation of the present invention is not limited to the above-mentioned methods. As long as various improvements are made using the method concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A polishing liquid, characterized in that: The polishing liquid comprises the following components in parts by weight: 1-30 parts of multi-layer core-shell structure polishing abrasive; 1-20 parts of pH regulator; Dispersant 0.1-10 parts; Dispersing aid 0.1-10 parts; 20-70 parts of deionized water; The method for preparing the multi-layer core-shell structure polishing abrasive comprises the following steps: Step 1: preparing a metal-abrasive single-layer core-shell structure abrasive; Step 1.1: impregnating the polishing abrasive in a mixed solution of a metal salt solution, a chelating agent and a background solvent, and filtering after the impregnation to obtain an abrasive precursor having a metal-abrasive single-layer core-shell structure; Step 1.2: The precursor obtained in step 1.1 is calcined at high temperature in an oxygen atmosphere to obtain a core-shell structure abrasive with catalytic properties; Step 1.3: placing the abrasive obtained in step 1.2 in concentrated sulfuric acid, activating the metal-abrasive single-layer core-shell structure abrasive with catalytic properties under water bath heating, and washing after activation to obtain the metal-abrasive single-layer core-shell structure abrasive; Step 2: preparing abrasives with a metal-abrasive multilayer core-shell structure; The metal-abrasive single-layer core-shell structure abrasive prepared in step 1 is used as a polishing abrasive, and the operation of step 1 is repeated at least twice to obtain a multi-layer metal-abrasive core-shell structure abrasive.

2. The polishing liquid according to claim 1, characterized in that: The specific operation of preparing the abrasive of the metal-abrasive multilayer core-shell structure in step 2 is as follows: The metal-abrasive single-layer core-shell structure abrasive prepared in step 1 is used as a polishing abrasive, and is immersed in a mixed solution of a metal salt solution, a chelating agent and a background solvent. After the immersion is completed, it is filtered, calcined at high temperature under an oxygen atmosphere, and activated with concentrated sulfuric acid to obtain a metal-abrasive double-layer core-shell structure abrasive; Repeat the operation of step 1 again to obtain the abrasive with a metal-abrasive double-layer core-shell structure, so as to obtain the abrasive with a metal-abrasive multi-layer core-shell structure.

3. The polishing liquid according to claim 2, characterized in that: The mass ratio of the metal salt solution, the chelating agent and the background solvent is 0.5-2:20-30:20-70; The mass ratio of the polishing abrasive to the metal salt solution is 4:1-6:

1.

4. The polishing liquid according to claim 2, characterized in that: The metal elements in the metal salt solution are one or more of nickel, cobalt, iron, palladium, copper and zinc, and the salts in the metal salt solution are one or more of nitrates, hydrochlorides and sulfates.

5. The polishing liquid according to claim 1, characterized in that: The pH regulator is an alkaline regulator; The alkaline regulator is an organic base, and the organic base is one or more of diethanolamine, triisopropanolamine, and triethanolamine; The dispersant is an aqueous dispersant; the aqueous dispersant is one or more of sodium polyacrylate, sodium dodecylbenzene sulfonate and sodium dodecyl sulfonate; The dispersing aid is one or more of aminopropylamine dioleate, octadecenylamine sodium acetate, metoclopramide N4-sulfonate, and 2-hydroxyethylsulfonic acid dimethylamine.

6. A method for preparing the polishing liquid according to any one of claims 1 to 5, characterized in that The following steps are involved: Firstly, each component is weighed according to a proportion, and then all components except the multi-layer core-shell structure polishing abrasive are fully mixed and stirred to obtain a mixed solution; finally, the multi-layer core-shell structure polishing abrasive is added to the mixed solution and stirred evenly to prepare the polishing liquid.

7. A polishing process using the polishing liquid according to any one of claims 1 to 5, characterized in that The following steps are involved: Step 1: Dilute the polishing liquid 2-5 times; Step 2: setting ultraviolet light to irradiate the substrate surface, with a wavelength of 100-400nm; Step 3: Set the polishing machine speed to 50-100r / min and the pressure to 15-30kg, drip the polishing liquid onto the substrate surface at 5-200mL / min, and polish for 10-800min.

8. Use of the polishing liquid according to any one of claims 1 to 5 in the polishing field of silicon carbide, sapphire and gallium nitride.

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