A polishing liquid for polishing a silicon carbide wafer and a method for preparing the same

Abstract

The application belongs to the technical field of silicon carbide wafer post-processing, and particularly relates to a polishing liquid for polishing silicon carbide wafers and a preparation method thereof. The polishing liquid for polishing silicon carbide wafers comprises the following components in percentage by mass: abrasive 5-30%, oxidizing agent 3-8%, slow-release ionic liquid 1-5%, dispersing agent 0.05-1%, pH regulator 0.05-1%, and deionized water to make up the balance to 100%. The slow-release ionic liquid is an ester-based ionic liquid grafted on amino polystyrene microspheres. The application creatively uses the slow-release ionic liquid to avoid damage of the abrasive to the silicon carbide wafer, while reducing roughness and improving polishing rate.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of silicon carbide wafer post-processing, and particularly relates to a polishing liquid for polishing silicon carbide wafers and a preparation method thereof. BACKGROUND

[0002] Monocrystalline silicon carbide has the advantages of large band gap, high thermal conductivity and high hardness, and can meet the requirements of modern electronic components for high frequency, high power and high temperature applications, so it becomes a typical representative of the third generation of semiconductor materials and has a wide application prospect in the fields of electric vehicles, 5G communication, smart grids and aerospace.

[0003] As a substrate material, the quality and precision of the surface processing of monocrystalline silicon carbide directly affect the working effect and performance of the electronic components, and the processing procedures of the silicon carbide wafer mainly include slicing, grinding and polishing processes, in which the polishing process is crucial to ensuring the product quality of the silicon carbide substrate.

[0004] Chemical mechanical polishing (CMP) is the most commonly used polishing technology in the field of polishing processing of silicon carbide wafers, and the polishing liquid is crucial to the polishing effect and the surface quality of the silicon carbide substrate in the CMP process. However, the hardness of silicon carbide is extremely high, and it is brittle and easy to produce cracks and scratches during polishing, which affects the surface quality. Therefore, it is of great significance to provide a polishing liquid for polishing silicon carbide wafers that can achieve high polishing efficiency while avoiding damage.

[0005] A spherical nano-alumina polishing liquid for polishing silicon carbide wafers is disclosed in Chinese Patent No. CN119410272A in the technical field of semiconductor silicon carbide wafer polishing material preparation, and the weight percentages of the raw materials used are as follows: alumina 0.5-55, oxidizing agent 0.05-25, inhibitor 0.1-10, surfactant 0.01-12, dispersant 0.01-15, pH adjuster 0.1-10, and the balance is high-purity water; the preparation process is as follows: ①, preparing materials; ②, abrasive pretreatment; ③, mixing; ④, pH adjustment; ⑤, high-pressure homogenization. It has the characteristics of high removal rate, good suspension and dispersion performance, no damage to the surface of the silicon carbide wafer, extremely low surface roughness value, long service life, easy cleaning, good versatility, etc., and is suitable for CMP polishing of semiconductor silicon carbide wafers. However, the surface roughness of the silicon carbide wafer of this technical solution is relatively large.

[0006] A Chinese patent with the publication number CN118085731B discloses a polishing liquid for polishing silicon carbide wafers, as well as a preparation method and a polishing method thereof. The polishing liquid comprises the following components: an oxidizing agent, a dispersing agent, a first abrasive, a second abrasive, a pH adjuster, and a solvent. The first abrasive is artemisinin crystals. The second abrasive comprises any one or a combination of at least two of cerium dioxide, titanium dioxide, or silicon dioxide. This technical solution combines the first abrasive with the second abrasive to balance the polishing efficiency and effect of the polishing liquid on SiC wafers. The chemical mechanical polishing assisted by ultraviolet light catalysis simplifies the traditional polishing process of rough polishing + fine polishing, shortens the polishing process steps, and improves the polishing efficiency. However, artemisinin is a drug component, and its extraction and purification cost may be high, which may increase the production cost of the polishing liquid. In addition, the technical solution requires additional ultraviolet light irradiation. SUMMARY

[0007] The present application aims to at least solve one of the above-mentioned technical problems in the prior art. To this end, the present application aims to provide a polishing liquid for polishing silicon carbide wafers, which creatively uses a slow-release ionic liquid to avoid damage to the silicon carbide wafer while reducing roughness and improving polishing rate.

[0008] The second aspect of the present application provides a preparation method of a polishing liquid for polishing silicon carbide wafers.

[0009] To achieve the above-mentioned purpose, the technical solution adopted by the present application is as follows:

[0010] The first aspect of the present application provides a polishing liquid for polishing silicon carbide wafers, which comprises the following components in terms of mass percentage: abrasive 5-30%, oxidizing agent 3-8%, slow-release ionic liquid 1-5%, dispersing agent 0.05-1%, pH adjuster 0.05-1%, and deionized water to make up the balance to 100%. The slow-release ionic liquid is an ester-based ionic liquid grafted with amino polystyrene microspheres.

[0011] The mass percentage of the above-mentioned abrasive can be 5%, 10%, 15%, 20%, 25%, or 30%, etc., but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0012] As a preferred technical solution of the present application, the abrasive is a mixture of nano-sized alpha phase aluminum oxide and nano-sized cerium oxide.

[0013] Preferably, the mass ratio of the nano-sized alpha phase aluminum oxide and the nano-sized cerium oxide is 3-6:1.

[0014] Preferably, the particle size of the nano-sized alpha phase aluminum oxide is 50-200 nm.

[0015] In a preferred embodiment, the nano-sized alpha phase alumina has a particle size of 200 nm.

[0016] Preferably, the nano-sized cerium oxide has a particle size of 500 nm.

[0017] The mass percentage of the oxidizing agent can be 3%, 4%, 5%, 6%, 7%, or 8%, etc., but is not limited to the listed values, and other values not listed within the value range are also applicable.

[0018] As a preferred technical solution of the present application, the oxidizing agent is selected from at least one of hydrogen peroxide, potassium permanganate, sodium perchlorate, and potassium manganate.

[0019] In a preferred embodiment, the oxidizing agent is potassium permanganate.

[0020] The mass percentage of the slow-release ionic liquid can be 1%, 2%, 3%, 4%, or 5%, etc., but is not limited to the listed values, and other values not listed within the value range are also applicable.

[0021] As a preferred technical solution of the present application, the preparation method of the slow-release ionic liquid comprises the following steps: uniformly mixing amino polystyrene microspheres, ester-based ionic liquid, and methanol, stirring at 78-82°C for 1-3h, filtering, washing, and drying to obtain the slow-release ionic liquid.

[0022] Preferably, the washing is methanol washing.

[0023] Preferably, the mass ratio of the amino polystyrene microspheres, ester-based ionic liquid, and methanol is 1:3-6:30-50.

[0024] In a preferred embodiment, the mass ratio of the amino polystyrene microspheres, ester-based ionic liquid, and methanol is 1:5:50.

[0025] Preferably, the particle size of the amino polystyrene microspheres is 100-200 nm.

[0026] In a preferred embodiment, the particle size of the amino polystyrene microspheres is 150 nm, and the amino polystyrene microspheres are purchased from Nanjing Jikeway Biotech Co., Ltd., with the product number: JK-05-006-150.

[0027] Preferably, the ester-based ionic liquid is selected from at least one of 1-methyl acetate-3-methyl imidazole hexafluorophosphate and 1-ethyl acetate-3-methyl imidazole hexafluorophosphate.

[0028] In a preferred embodiment, the ester-based ionic liquid is 1-methyl acetate-3-methyl imidazole hexafluorophosphate.

[0029] The mass percentage of the dispersant can be 0.05%, 0.06%, 0.07%, 0.08%, 0.09% or 1%, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0030] As a preferred technical solution of the present application, the dispersant is a mixture of polybutyl acrylate-styrene-acrylic acid block polymer and succinate block copolymer.

[0031] Preferably, the mass ratio of the polybutyl acrylate-styrene-acrylic acid block polymer and the succinate block copolymer is 1-2:1-2.

[0032] In a preferred embodiment, the mass ratio of the polybutyl acrylate-styrene-acrylic acid block polymer and the succinate block copolymer is 1:1.

[0033] The mass percentage of the pH adjuster can be 0.05%, 0.06%, 0.07%, 0.08%, 0.09% or 1%, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0034] As a preferred technical solution of the present application, the pH adjuster is selected from at least one of citric acid, malic acid, tartaric acid, oxalic acid and acetic acid.

[0035] In a preferred embodiment, the pH adjuster is acetic acid.

[0036] The second aspect of the present application provides a preparation method of a polishing liquid for polishing a silicon carbide wafer, comprising the following steps: first, uniformly mixing abrasive and deionized water, then uniformly mixing an oxidizing agent, a slow-release ionic liquid and a dispersant, and finally adding a pH adjuster to adjust the pH to 5 to obtain the polishing liquid.

[0037] Compared with the prior art, the present application has the following beneficial effects:

[0038] One, in order to avoid the damage of the abrasive to the silicon carbide wafer in the polishing process, the abrasive is often modified in the prior art, and the slow-release ionic liquid is prepared creatively to solve the technical problem; the nano alpha phase alumina and the nano cerium oxide are used as the abrasive, the different particle sizes are controlled, the advantages of the small scratch and the low surface roughness of the cerium oxide and the fast removal rate of the nano alpha phase alumina are utilized, the two are used in combination, the polishing quality is optimized to a certain extent, on this basis, the amino polystyrene microspheres are used as the carrier, the ester group ionic liquid is grafted on the surface of the amino polystyrene microspheres by utilizing the interaction between the amino group and the imidazole ring, in the polishing process of the silicon carbide wafer, the amino polystyrene microspheres can act together with the nano alpha phase alumina and the nano cerium oxide to remove the oxide on the surface of the silicon carbide wafer by friction, meanwhile, the binding force between the ester group ionic liquid and the polystyrene microspheres is weakened, and then the slow release is realized, the lubricity and the acidity of the ionic liquid are utilized, the damage of the abrasive to the silicon carbide wafer is effectively avoided, the roughness is reduced, and the polishing rate is improved.

[0039] Secondly, the dispersant in the polishing liquid can not only effectively disperse the abrasive and avoid the agglomeration of the abrasive, but also affect the polishing quality of the polishing liquid, the mixture of the polybutyl acrylate-styrene-acrylic acid block polymer and the succinate block copolymer is used as the dispersant, the agglomeration of the abrasive is inhibited, the contact between the polishing liquid and the silicon carbide wafer is improved, the friction of the abrasive is optimized, the polishing efficiency is improved, the roughness of the silicon carbide wafer is reduced, and the damage of the abrasive to the silicon carbide wafer can be avoided to a certain extent. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 The SEM diagram of the polishing liquid for polishing the silicon carbide wafer provided in the embodiment 4 of the present application.

[0041] Figure 2 The AFM diagram of the silicon carbide wafer treated by the polishing liquid for polishing the silicon carbide wafer provided in the embodiment 4 of the present application;

[0042] Figure 3 The AFM diagram of the silicon carbide wafer treated by the polishing liquid for polishing the silicon carbide wafer provided in the comparative example 1 of the present application. DETAILED DESCRIPTION

[0043] In order to have a clearer understanding of the technical features, objects and effects of the present application, the specific implementation schemes are described in detail.

[0044] The application will be further described in connection with the following examples, but the application is not limited to the following examples. The implementation conditions used in the examples can be further adjusted according to different requirements of specific use, and the implementation conditions not specified are conventional conditions in the industry. The technical features involved in each embodiment of the application can be combined with each other as long as they do not conflict with each other.

[0045] In the following examples and comparative examples, the raw materials used are commercially available or prepared by conventional methods in the art, unless otherwise specified.

[0046] Example 1

[0047] (1) The polishing liquid for polishing silicon carbide wafers, by mass percentage, consists of: abrasive 5%, oxidizing agent 3%, slow-release ionic liquid 1%, dispersant 0.05%, pH adjuster 0.05%, and deionized water to make up the balance to 100%.

[0048] The abrasive is a mixture of nanoscale alpha alumina and nanoscale cerium oxide in a mass ratio of 5:1.

[0049] The nanoscale alpha alumina has a particle size of 200 nm and is purchased from Hangzhou Hengna New Material Co., Ltd., model number HN-L30F.

[0050] The nanoscale cerium oxide has a particle size of 500 nm and is purchased from Hangzhou Hengna New Material Co., Ltd., model number HN-Ce05.

[0051] The oxidizing agent is potassium permanganate.

[0052] The preparation method of the slow-release ionic liquid is as follows: mix amino polystyrene microspheres, ester-based ionic liquid, and methanol uniformly, stir at 80°C for 2h, filter, wash with methanol, and dry to obtain.

[0053] The mass ratio of the amino polystyrene microspheres, ester-based ionic liquid, and methanol is 1:5:50.

[0054] The amino polystyrene microspheres have a particle size of 150 nm and are purchased from Nanjing Jikuo Biological Technology Co., Ltd., item number JK-05-006-150.

[0055] The ester-based ionic liquid is 1-methyl acetate-3-methyl imidazole hexafluorophosphate (CAS number: 503439-48-3) and is purchased from Qingdao Aolike New Material Technology Co., Ltd.

[0056] The dispersant is a mixture of polybutyl acrylate-styrene-acrylic acid block polymer and succinate block copolymer in a mass ratio of 1:1.

[0057] The polybutyl acrylate-styrene-acrylic acid block polymer is purchased from Guangzhou Houxie Chemical Auxiliary Co., Ltd., model number: 2011X.

[0058] The succinate block copolymer is purchased from Shandong Aishengte New Material Co., Ltd., model number: PE100.

[0059] The pH regulator is acetic acid.

[0060] (2) The preparation method of the polishing liquid for polishing silicon carbide wafers is as follows: first, mix the abrasive and deionized water uniformly, then mix the oxidizing agent, the slow-release ionic liquid and the dispersant uniformly, and finally add the pH regulator to adjust the pH to 5.

[0061] Example 2

[0062] (1) The polishing liquid for polishing silicon carbide wafers, in terms of mass percentage, comprises the following components: abrasive 10%, oxidizing agent 4%, slow-release ionic liquid 2%, dispersant 0.07%, pH regulator 0.06%, and deionized water to make up the balance to 100%.

[0063] The abrasive is a mixture of nanoscale alpha phase alumina and nanoscale cerium oxide in a mass ratio of 5:1.

[0064] The nanoscale alpha phase alumina has a particle size of 200 nm and is purchased from Hangzhou Hengna New Material Co., Ltd., model number: HN-L30F.

[0065] The nanoscale cerium oxide has a particle size of 500 nm and is purchased from Hangzhou Hengna New Material Co., Ltd., model number: HN-Ce05.

[0066] The oxidizing agent is potassium permanganate.

[0067] The preparation method of the slow-release ionic liquid is as follows: mix amino polystyrene microspheres, ester-based ionic liquid and methanol uniformly, stir at 80°C for 2 h, filter, wash with methanol, and dry to obtain the slow-release ionic liquid.

[0068] The mass ratio of the amino polystyrene microspheres, the ester-based ionic liquid and the methanol is 1:5:50.

[0069] The amino polystyrene microspheres have a particle size of 150 nm and are purchased from Nanjing Jikuo Biological Technology Co., Ltd., item number: JK-05-006-150.

[0070] The ester-based ionic liquid is 1-methylcarboxylate-3-methylimidazole hexafluorophosphate (CAS number: 503439-48-3) and is purchased from Qingdao Aolike New Material Technology Co., Ltd.

[0071] The polybutyl acrylate-styrene-acrylic acid block polymer is purchased from Guangzhou Houxie Chemical Auxiliary Co., Ltd., model number: 2011X.

[0072] The succinate block copolymer is purchased from Shandong Aishengte New Material Co., Ltd., model number: PE100.

[0073] The dispersant is a mixture of the polybutyl acrylate-styrene-acrylic acid block polymer and the succinate block copolymer in a mass ratio of 1:1.

[0074] The pH regulator is acetic acid.

[0075] The preparation method of the polishing liquid for polishing the silicon carbide wafer is as follows: first, the abrasive and deionized water are uniformly mixed, then the oxidizing agent, the slow-release ionic liquid, and the dispersant are uniformly mixed, and finally the pH regulator is added to adjust the pH to 5.

[0076] Example 3

[0077] (1) The polishing liquid for polishing the silicon carbide wafer, in terms of mass percentage, comprises the following components: abrasive 20%, oxidizing agent 5%, slow-release ionic liquid 3%, dispersant 0.08%, pH regulator 0.08%, and deionized water to make up the balance to 100%.

[0078] The abrasive is a mixture of nanoscale alpha alumina and nanoscale cerium oxide in a mass ratio of 5:1.

[0079] The nanoscale alpha alumina has a particle size of 200 nm and is purchased from Hangzhou Hengna New Material Co., Ltd., model number: HN-L30F.

[0080] The nanoscale cerium oxide has a particle size of 500 nm and is purchased from Hangzhou Hengna New Material Co., Ltd., model number: HN-Ce05.

[0081] The oxidizing agent is potassium permanganate.

[0082] The preparation method of the slow-release ionic liquid is as follows: the amino polystyrene microspheres, the ester-based ionic liquid, and the methanol are uniformly mixed, stirred at 80°C for 2 h, filtered, washed with methanol, and dried to obtain the slow-release ionic liquid.

[0083] The mass ratio of the amino polystyrene microspheres, the ester-based ionic liquid, and the methanol is 1:5:50.

[0084] The amino polystyrene microspheres have a particle size of 150 nm and are purchased from Nanjing Jikuo Biological Technology Co., Ltd., item number: JK-05-006-150.

[0085] The ester-based ionic liquid is 1-methyl acetate-3-methyl imidazole hexafluorophosphate (CAS No. 503439-48-3) purchased from Qingdao Oliko New Material Technology Co., Ltd.

[0086] The dispersant is a mixture of polybutyl acrylate-styrene-acrylic acid block polymer and succinate block copolymer with a mass ratio of 1:1.

[0087] The polybutyl acrylate-styrene-acrylic acid block polymer is purchased from Guangzhou Houxie Chemical Auxiliary Co., Ltd., model number: 2011X.

[0088] The succinate block copolymer is purchased from Shandong Aishengte New Material Co., Ltd., model number: PE100.

[0089] The pH regulator is acetic acid.

[0090] (2) The preparation method of the polishing liquid for polishing silicon carbide wafers is as follows: first, mix the abrasive and deionized water uniformly, then add the oxidizing agent, slow-release ionic liquid, and dispersant uniformly, and finally add the pH regulator to adjust the pH to 5.

[0091] Example 4

[0092] (1) The polishing liquid for polishing silicon carbide wafers, by mass percentage, comprises the following components: abrasive 30%, oxidizing agent 8%, slow-release ionic liquid 3%, dispersant 0.08%, pH regulator 0.08%, and deionized water to make up the balance to 100%.

[0093] The abrasive is a mixture of nano-sized alpha phase alumina and nano-sized cerium oxide with a mass ratio of 5:1.

[0094] The nano-sized alpha phase alumina has a particle size of 200 nm and is purchased from Hangzhou Hengna New Material Co., Ltd., model number: HN-L30F.

[0095] The nano-sized cerium oxide has a particle size of 500 nm and is purchased from Hangzhou Hengna New Material Co., Ltd., model number: HN-Ce05.

[0096] The oxidizing agent is potassium permanganate.

[0097] The preparation method of the slow-release ionic liquid is as follows: mix amino polystyrene microspheres, ester-based ionic liquid, and methanol uniformly, stir at 80°C for 2h, filter, wash with methanol, and dry to obtain the slow-release ionic liquid.

[0098] The mass ratio of the amino polystyrene microspheres, ester-based ionic liquid, and methanol is 1:5:50.

[0099] The particle size of the amino polystyrene microspheres is 150 nm, which is purchased from Nanjing Jikuo Biotechnology Co., Ltd., and the item number is JK-05-006-150.

[0100] The ester-based ionic liquid is 1-methylcarboxylate-3-methyl imidazole hexafluorophosphate (CAS number: 503439-48-3), which is purchased from Qingdao Oliko New Material Technology Co., Ltd.

[0101] The dispersant is a mixture of polybutyl acrylate-styrene-acrylic block polymer and succinate block copolymer with a mass ratio of 1:1.

[0102] The polybutyl acrylate-styrene-acrylic block polymer is purchased from Guangzhou Houxie Chemical Auxiliary Co., Ltd., and the model number is: 2011X.

[0103] The succinate block copolymer is purchased from Shandong Aishengte New Material Co., Ltd., and the model number is PE100.

[0104] The pH regulator is acetic acid.

[0105] (2) The preparation method of the polishing liquid for polishing silicon carbide wafers is: first, mix the abrasive and deionized water uniformly, then add the oxidizing agent, the slow-release ionic liquid, the dispersant, and mix uniformly, and finally add the pH regulator to adjust the pH to 5.

[0106] The SEM image of the polishing liquid for polishing silicon carbide wafers provided by the embodiment is shown in Figure 1 .

[0107] Comparative Example 1

[0108] This comparative example provides a polishing liquid for polishing silicon carbide wafers and a preparation method thereof, except that there is no slow-release ionic liquid, i.e. the mass percentage of the slow-release ionic liquid is 0%, and other conditions are the same as those of Example 4.

[0109] Comparative Example 2

[0110] This comparative example provides a polishing liquid for polishing silicon carbide wafers and a preparation method thereof, except that the slow-release ionic liquid is replaced by a mixture of 1-methylcarboxylate-3-methyl imidazole hexafluorophosphate and amino polystyrene microspheres with a mass ratio of 1:5, and other conditions are the same as those of Example 4.

[0111] Comparative Example 3

[0112] The comparative example provides a polishing liquid for polishing silicon carbide wafers and a preparation method thereof, except that 1-methoxyacetic acid-3-methyl imidazole hexafluorophosphate is replaced by 1-ethyl-3-methyl imidazole hexafluorophosphate, and 1-ethyl-3-methyl imidazole hexafluorophosphate (CAS number: 155371-19-0) is also purchased from Qingdao Oliko New Material Technology Co., Ltd.; other conditions are the same as in Example 4.

[0113] Comparative Example 4

[0114] The comparative example provides a polishing liquid for polishing silicon carbide wafers and a preparation method thereof, except that 1-methoxyacetic acid-3-methyl imidazole hexafluorophosphate is replaced by 1-ethyl-3-methyl imidazole hexafluorophosphate, and 1-ethyl-3-methyl imidazole hexafluorophosphate (CAS number: 155371-19-0) is also purchased from Qingdao Oliko New Material Technology Co., Ltd.; other conditions are the same as in Example 4.

[0115] Comparative Example 5

[0116] The comparative example provides a polishing liquid for polishing silicon carbide wafers and a preparation method thereof, except that succinate block copolymer is replaced by polybutyl acrylate-styrene-acrylic acid block polymer; other conditions are the same as in Example 4.

[0117] Comparative Example 6

[0118] The comparative example provides a polishing liquid for polishing silicon carbide wafers and a preparation method thereof, except that polybutyl acrylate-styrene-acrylic acid block polymer is replaced by polycarboxylic acid sodium salt, and polycarboxylic acid sodium salt is purchased from Shandong Aishengte New Material Co., Ltd.; other conditions are the same as in Example 4.

[0119] Application Example

[0120] The polishing liquid of Example 1-4 and Comparative Example 1-6 is used for single-sided polishing treatment of a 6-inch silicon carbide wafer, and the parameters are as follows: polishing pad (polyurethane polishing pad, purchased from Shanghai Yanya Optoelectronic Technology Co., Ltd., model: IC1010), polishing liquid flow rate is 100 mL / min, polishing head rotation speed is 70 rpm, polishing pressure is 150 g / cm 2 , polishing disc rotation speed is 50 rpm, and polishing time is 1 h.

[0121] The polished silicon carbide wafer is detected as follows:

[0122] The surface roughness of the polished silicon carbide wafer is detected by using an AFM atomic force microscope; the mass difference of the silicon carbide wafer before and after polishing is weighed by using an analytical balance, and the polishing rate is calculated according to the formula (polishing rate = mass difference of the silicon carbide wafer before and after polishing / [density of the silicon carbide wafer x area of the silicon carbide wafer x polishing time]); whether there are scratches on the surface of the silicon carbide wafer is observed: no obvious scratches are recorded as level 1, the number of scratches is less than 5 is recorded as level 2, the number of scratches is greater than 5 but less than 10 is recorded as level 3, and the number of scratches is greater than 10 is recorded as level 4, and the detection results are shown in Table 1, and the AFM graph of the silicon carbide wafer treated by using the polishing liquid for polishing the silicon carbide wafer provided in Example 4 is shown in Figure 2 Table 1. Figure 3

[0123] Table 1. Detection results of the polished silicon carbide wafer

[0124] Sample Roughness Ra (nm) Polishing rate (pm / h) Scratch grade Example 1 0.08 3.22 1 Example 2 0.06 3.85 1 Example 3 0.05 4.51 1 Example 4 0.03 5.10 1 Comparative Example 1 0.35 2.25 4 Comparative Example 2 0.28 2.83 3 Comparative Example 3 0.15 3.05 2 Comparative Example 4 0.20 3.31 3 Comparative Example 5 0.18 2.77 3 Comparative Example 6 0.21 2.52 3

[0125] As can be seen from Table 1, the silicon carbide wafer obtained by using the polishing liquid provided in the application not only has a lower roughness and a higher polishing rate, but also can avoid damage to the surface of the silicon carbide wafer.

[0126] In combination with Example 4 and Comparative Examples 1-2, it can be seen that the self-made slow-release ionic liquid in the application not only avoids damage to the surface of the silicon carbide wafer, but also can reduce the roughness of the silicon carbide wafer and increase the polishing rate.

[0127] In combination with Example 4 and Comparative Examples 2-3, it can be seen that the type of ionic liquid in the slow-release ionic liquid also has a significant effect on the roughness, polishing rate and surface damage of the silicon carbide wafer.

[0128] In combination with Example 4 and Comparative Examples 5-6, it can be seen that the dispersant in the application can effectively reduce the roughness of the silicon carbide wafer, improve the polishing rate and reduce the surface damage.

[0129] Finally, it should be noted that the above content is only used to illustrate the technical solutions of the application, and is not a limitation on the protection scope of the application. Simple modifications or equivalent replacements of the technical solutions of the application made by those skilled in the art do not deviate from the essence and scope of the technical solutions of the application.​

Claims

1. A polishing liquid for polishing a silicon carbide wafer, characterized by comprising: a silicate compound; and a surfactant. By mass percentage, it comprises the following components: abrasive 5-30%, oxidant 3-8%, slow-release ionic liquid 1-5%, dispersant 0.05-1%, pH regulator 0.05-1%, and deionized water makes up the balance to 100%; the slow-release ionic liquid is ester-based ionic liquid grafted on aminopolystyrene microspheres; The ester-based ionic liquid is at least one selected from 1-methyl acetate-3-methyl imidazole hexafluorophosphate and 1-ethyl acetate-3-methyl imidazole hexafluorophosphate; The preparation method of the slow-release ionic liquid comprises the following steps: uniformly mixing aminopolystyrene microspheres, ester-based ionic liquid and methanol, stirring at 78-82℃ for 1-3h, filtering, washing, and drying to obtain the slow-release ionic liquid. The dispersant is a mixture of polybutyl acrylate-styrene-acrylic acid block polymer and succinate block copolymer.

2. The polishing liquid for polishing a silicon carbide wafer according to claim 1, wherein The abrasive is a mixture of nanoscale alpha phase alumina and nanoscale cerium oxide.

3. The polishing liquid for polishing a silicon carbide wafer according to claim 2, wherein The particle size of the nanoscale alpha phase alumina is 50-200nm; the particle size of the nanoscale cerium oxide is 500nm.

4. The polishing liquid for polishing a silicon carbide wafer according to claim 1, wherein The oxidant is at least one selected from hydrogen peroxide, potassium permanganate, sodium perchlorate and potassium manganate.

5. The polishing liquid for polishing a silicon carbide wafer according to claim 1, wherein The mass ratio of the aminopolystyrene microspheres, ester-based ionic liquid and methanol is 1:3-6:30-50.

6. The polishing liquid for polishing a silicon carbide wafer according to claim 5, wherein The particle size of the aminopolystyrene microspheres is 100-200nm.

7. The method of producing a polishing liquid for polishing a silicon carbide wafer according to any one of claims 1 to 6, characterized by, It comprises the following steps: first, uniformly mixing the abrasive and deionized water, then adding the oxidant, slow-release ionic liquid and dispersant, and finally adding the pH regulator to adjust the pH to 5.

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