A polishing liquid for silicon carbide wafer and its preparation method and application

Abstract

This invention relates to the field of silicon carbide wafer manufacturing, and discloses a silicon carbide wafer polishing slurry, its preparation method, and its application. The polishing slurry contains the following components, stored independently or in combination: functional components and water. The functional components include abrasives, sodium hexametaphosphate, triethylene glycol, hydroxyethyl cellulose, a wetting agent, and a pH adjuster. This polishing slurry exhibits a stable polishing removal rate, good surface finish, and is suitable for polishing pads of various materials.

Description

Technical Field

[0001] This invention relates to the field of silicon carbide wafer manufacturing, specifically to a silicon carbide wafer polishing slurry, its preparation method, and its application. Background Technology

[0002] As a new generation of power semiconductor material, silicon carbide (SiC) possesses excellent properties such as good thermal conductivity, high breakdown field strength, high saturated electron drift velocity, and high bonding energy. Therefore, electronic devices made of SiC can operate in extreme environments such as high temperature and high radiation, fully realizing the goals of miniaturization, high efficiency, and energy saving in electronic devices. It has enormous application potential and market prospects in the construction of a low-carbon and environmentally friendly society in the future.

[0003] However, due to the high hardness and highly stable chemical and physical properties of SiC, the Distortion Polishing (DMP) method used in the ultra-precision machining of SiC is difficult to quickly and effectively improve surface finish. Currently, in the processing of silicon carbide, the polishing removal rate of silicon carbide wafers is unstable and the surface finish deviates due to factors such as polishing particle loss, reduced polishing pad compression ratio, and plastic deformation.

[0004] CN107043600A discloses a diamond polishing slurry that can be used for polishing metal or sapphire sheets. However, this diamond polishing slurry has problems such as low uniformity of polishing particles, low solid content, and low removal rate when polishing metal, and it can only be applied to polishing metal or sapphire sheets.

[0005] CN115521714A discloses an oil-based diamond polishing slurry and its preparation method. However, this polishing slurry is for use on sapphire wafers and is an oil-based slurry. When applied to the polishing of SiC materials, it will have problems such as low removal rate and difficulty in surface cleaning.

[0006] In addition, different polishing pads are often required in the polishing process of silicon carbide, such as artificial fiber pads, polyurethane pads, and fiber and polyurethane hybrid pads. However, most polishing slurries on the market are not suitable for multiple polishing pads at the same time.

[0007] Therefore, it is of great significance to provide a polishing fluid for SiC materials that has a high and stable polishing removal rate, good surface finish, and is applicable to polishing pads of different materials. Summary of the Invention

[0008] The purpose of this invention is to overcome the problems of low and unstable polishing removal rate of SiC material polishing slurries, poor surface processing quality, and inapplicability to polishing pads of different materials in the existing technology.

[0009] To achieve the above objectives, a first aspect of the present invention provides a silicon carbide wafer polishing slurry, which contains the following components, either individually or in combination:

[0010] The functional components and water, wherein the functional components are abrasive, sodium hexametaphosphate, triethylene glycol, hydroxyethyl cellulose, humectant, and pH adjuster;

[0011] The abrasive is a mixture of single-crystal diamond with a volume average particle size of 0.5-3 μm and polycrystalline diamond with a volume average particle size of 0.5-2 μm, wherein the weight ratio of the single-crystal diamond to the polycrystalline diamond in the mixture is 1:0.01-1.

[0012] The viscosity of the hydroxyethyl cellulose in a 2 wt% aqueous solution at 35°C is 1000-14000 mPa·s;

[0013] On a dry basis, and based on the total weight of the functional components, the abrasive content is 8-25 wt%, the sodium hexametaphosphate content is 0.5-20 wt%, the triethylene glycol content is 0.2-15 wt%, the hydroxyethyl cellulose content is 30-50 wt%, the wetting agent content is 10-20 wt%, and the pH adjuster content is 0.2-9.0 wt%.

[0014] Preferably, the single-crystal diamond has a volume average particle size that is 0.1-10% larger than that of the polycrystalline diamond.

[0015] In a preferred embodiment, the weight ratio of the functional component to the water is 1:2-20.

[0016] Preferably, the wetting agent is selected from at least one of polyethylene glycol, polypropylene glycol, diethylene glycol, and polyacrylic acid.

[0017] In a preferred embodiment, the pH adjuster is selected from at least one of ethanolamine, triethanolamine, isopropanolamine, N-(2-hydroxyethyl)ethylenediamine, sodium hydroxide, and potassium hydroxide.

[0018] A second aspect of the present invention provides a method for preparing the silicon carbide wafer polishing slurry described in the first aspect, the method comprising:

[0019] (1) Sodium hexametaphosphate and abrasive were contact-mixed in the presence of water I to obtain mixture I;

[0020] (2) In the presence of water II, hydroxyethyl cellulose, triethylene glycol, wetting agent, pH adjuster and the mixture I are contact mixed II to obtain silicon carbide wafer polishing solution;

[0021] The weight ratio of water I to water II is 1:0.5-1, and the sum of the weights of water I and water II is the total weight of water in the polishing liquid.

[0022] In a preferred embodiment, in step (1), the contact mixing I operation includes: first mixing the water I with the sodium hexametaphosphate I to obtain a sodium hexametaphosphate solution, and then mixing the sodium hexametaphosphate solution with the abrasive II to obtain the mixture I.

[0023] In a preferred embodiment, in step (2), the operation of contact mixing II includes:

[0024] S1. First, mix the water (II) with the hydroxyethyl cellulose, the triethylene glycol, and the wetting agent (III) to obtain a premixed solution;

[0025] S2. Mix the premixed liquid with mixture I in IV to obtain mixture II;

[0026] S3. Mix the pH adjuster with the mixture II to obtain the silicon carbide wafer polishing solution with a pH value of 6-8.

[0027] In a preferred embodiment, the mixing I is performed under ultrasonic conditions, and at least the following conditions are met: frequency of 40-60 Hz, temperature of 20-30 °C, and time of 5-20 min.

[0028] In a preferred embodiment, the mixing II is performed under ultrasonic conditions and at least meets the following requirements: frequency of 90-110 Hz, temperature of 20-30°C, and time of 5-20 min.

[0029] Preferably, the mixing III is carried out under stirring conditions, and at least meets the following requirements: rotation speed of 10-20 rpm, temperature of 25-35℃, and time of 2-4 h.

[0030] Preferably, the contact mixing IV is carried out under stirring conditions, and at least meets the following requirements: rotation speed of 10-30 rpm, temperature of 30-35℃, and time of 2-4 h.

[0031] Preferably, the contact mixing V is carried out under stirring conditions, and at least meets the following requirements: rotation speed of 10-20 rpm, temperature of 20-25℃, and time of 2-4 h.

[0032] The third aspect of this invention provides the application of the silicon carbide wafer polishing slurry described in the first aspect in the field of silicon carbide wafer manufacturing.

[0033] The silicon carbide wafer polishing slurry provided by this invention utilizes a blend of single-crystal and polycrystalline diamonds of different particle sizes, along with the synergistic effect of hydroxyethyl cellulose of specific viscosity and other substances. This results in a stable polishing removal rate, good surface finish, and applicability to polishing pads of different materials. Detailed Implementation

[0034] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0035] As described above, the first aspect of the present invention provides a silicon carbide wafer polishing slurry, which contains the following components, which may be stored independently or in combination:

[0036] The functional components and water, wherein the functional components are abrasive, sodium hexametaphosphate, triethylene glycol, hydroxyethyl cellulose, humectant, and pH adjuster;

[0037] The abrasive is a mixture of single-crystal diamond with a volume average particle size of 0.5-3 μm and polycrystalline diamond with a volume average particle size of 0.5-2 μm, wherein the weight ratio of the single-crystal diamond to the polycrystalline diamond in the mixture is 1:0.01-1.

[0038] The viscosity of the hydroxyethyl cellulose in a 2 wt% aqueous solution at 35°C is 1000-14000 mPa·s;

[0039] On a dry basis, and based on the total weight of the functional components, the abrasive content is 8-25 wt%, the sodium hexametaphosphate content is 0.5-20 wt%, the triethylene glycol content is 0.2-15 wt%, the hydroxyethyl cellulose content is 30-50 wt%, the wetting agent content is 10-20 wt%, and the pH adjuster content is 0.2-9.0 wt%.

[0040] It should be noted that, in this invention, the single-crystal diamond is diamond micro powder with a regular and complete six-octahedral crystal shape, and the polycrystalline diamond is diamond micro powder formed by the polymerization of microcrystalline diamond through unsaturated bonds.

[0041] More preferably, in the mixture, the weight ratio of the single-crystal diamond to the polycrystalline diamond is 1:0.5-1.

[0042] Preferably, the volume average particle size of the single-crystal diamond is 0.1-12% larger than that of the polycrystalline diamond. The inventors have found that the silicon carbide wafer polishing slurry under this preferred condition has better stability and a higher removal rate.

[0043] More preferably, the volume average particle size of the single-crystal diamond is 0.5-1% larger than that of the polycrystalline diamond.

[0044] It should be noted that in this invention, "the volume average particle size of the single-crystal diamond is 0.1-12% larger than the volume average particle size of the polycrystalline diamond" refers to the formula: ((volume average particle size of single-crystal diamond - volume average particle size of polycrystalline diamond) / volume average particle size of polycrystalline diamond) * 100%, where the result is 0.1-12%. "The volume average particle size of the single-crystal diamond is 0.5-1% larger than the volume average particle size of the polycrystalline diamond" has a similar definition, only the numerical range is different.

[0045] In a preferred embodiment, the weight ratio of the functional component to the water is 1:2-20.

[0046] Preferably, the wetting agent is selected from at least one of polyethylene glycol, polypropylene glycol, diethylene glycol, and polyacrylic acid.

[0047] More preferably, the wetting agent is polyethylene glycol and / or polypropylene glycol, and the weight average molecular weight is 1000-5000.

[0048] In a preferred embodiment, the pH adjuster is selected from at least one of ethanolamine, triethanolamine, isopropanolamine, N-(2-hydroxyethyl)ethylenediamine, sodium hydroxide, and potassium hydroxide.

[0049] More preferably, the water is deionized water.

[0050] As described above, a second aspect of the present invention provides a method for preparing the silicon carbide wafer polishing slurry described in the first aspect, the method comprising:

[0051] (1) Sodium hexametaphosphate and abrasive were contact-mixed in the presence of water I to obtain mixture I;

[0052] (2) In the presence of water II, hydroxyethyl cellulose, triethylene glycol, wetting agent, pH adjuster and the mixture I are contact mixed II to obtain silicon carbide wafer polishing solution;

[0053] The weight ratio of water I to water II is 1:0.5-1, and the sum of the weights of water I and water II is the total weight of water in the polishing liquid.

[0054] In a preferred embodiment, in step (1), the contact mixing I operation includes: first mixing the water I with the sodium hexametaphosphate I to obtain a sodium hexametaphosphate solution, and then mixing the sodium hexametaphosphate solution with the abrasive II to obtain the mixture I.

[0055] In a preferred embodiment, in step (2), the operation of contact mixing II includes:

[0056] S1. First, mix the water (II) with the hydroxyethyl cellulose, the triethylene glycol, and the wetting agent (III) to obtain a premixed solution;

[0057] S2. Mix the premixed liquid with mixture I in IV to obtain mixture II;

[0058] S3. The pH adjuster is mixed with mixture II to obtain the silicon carbide wafer polishing slurry with a pH value of 6-8. The inventors have found that the silicon carbide wafer polishing slurry prepared under this preferred condition has a higher removal rate.

[0059] Preferably, the pH adjuster is sodium hydroxide and / or potassium hydroxide.

[0060] In a preferred embodiment, the mixing I is performed under ultrasonic conditions, and at least the following conditions are met: frequency of 40-60 Hz, temperature of 20-30 °C, and time of 5-20 min.

[0061] In a preferred embodiment, the mixing II is performed under ultrasonic conditions and at least meets the following requirements: frequency of 90-110 Hz, temperature of 20-30°C, and time of 5-20 min.

[0062] Preferably, the mixing III is carried out under stirring conditions, and at least meets the following requirements: rotation speed of 10-20 rpm, temperature of 25-35℃, and time of 2-4 h.

[0063] Preferably, the contact mixing IV is carried out under stirring conditions, and at least meets the following requirements: rotation speed of 10-30 rpm, temperature of 30-35℃, and time of 2-4 h.

[0064] Preferably, the contact mixing V is carried out under stirring conditions, and at least meets the following requirements: rotation speed of 10-20 rpm, temperature of 20-25℃, and time of 2-4 h.

[0065] As previously stated, the third aspect of this invention provides the application of the silicon carbide wafer polishing slurry described in the first aspect in the field of silicon carbide wafer manufacturing.

[0066] It should be noted that, in all aspects of the present invention, the same components or terms in each aspect are described only once in one aspect and not repeatedly, and those skilled in the art should not understand this as a limitation of the present invention.

[0067] The present invention will be described in detail below through examples. Unless otherwise specified, the raw materials used are all commercially available products and are of analytical grade.

[0068] Abrasive:

[0069] Abrasive I: is a mixture of single-crystal diamond with a volume average particle size of 1 μm and polycrystalline diamond with a volume average particle size of 0.9 μm;

[0070] Abrasive II: A mixture of single-crystal diamond with a volume average particle size of 1 μm and polycrystalline diamond with a volume average particle size of 2 μm;

[0071] Abrasive III: A mixture of single-crystal diamond with a volume average particle size of 4 μm and polycrystalline diamond with a volume average particle size of 4 μm;

[0072] Abrasive IV: Single-crystal diamond with a volume average particle size of 2 μm;

[0073] Abrasive V: Polycrystalline diamond with a volume average particle size of 2μm;

[0074] Abrasive VI: A mixture of single-crystal diamond with a volume average particle size of 2 μm and polycrystalline diamond with a volume average particle size of 2 μm;

[0075] Hydroxyethyl cellulose I: The viscosity of a 2 wt% aqueous solution at 35°C is 10000 mPa·s. It was purchased from Shanghai Chenqi Chemical Technology Co., Ltd. and is of industrial grade.

[0076] Hydroxyethyl cellulose II: The viscosity of a 2 wt% aqueous solution at 35°C is 100 mPa·s. It was purchased from Shanghai Chenqi Chemical Technology Co., Ltd. and is of industrial grade.

[0077] Wetting agent: polyethylene glycol, with a weight-average molecular weight of 2000;

[0078] pH adjuster: Sodium hydroxide.

[0079] Preparation Example 1

[0080] This preparation example illustrates that the silicon carbide wafer polishing slurry provided by the present invention is prepared according to the following method, and the dosages are shown in Table 1. The specific operation steps include:

[0081] Under ultrasonic conditions at a temperature of 25°C and a power of 50Hz, the water I and the sodium hexametaphosphate were first mixed for 20 minutes to obtain a sodium hexametaphosphate solution. Then, under ultrasonic conditions at a power of 100Hz, the sodium hexametaphosphate solution was mixed with the abrasive I for 20 minutes to obtain the mixture I.

[0082] S1. At 30°C and 20 rpm, the water II, hydroxyethyl cellulose I, triethylene glycol, and wetting agent are mixed for 2.5 h to obtain a premixed solution.

[0083] S2. At 30°C and 30 rpm, the premixed liquid and mixture I are mixed for 2 hours to obtain mixture II.

[0084] S3. At 25°C and 20 rpm, the pH adjuster () and the mixture II are mixed for 15 min to obtain the silicon carbide wafer polishing solution with a pH value of 7, named P1.

[0085] Preparation Example 2

[0086] This preparation example illustrates that the silicon carbide wafer polishing slurry provided by the present invention is prepared according to the following method, and the dosages are shown in Table 1. The specific operation steps include:

[0087] Under ultrasonic conditions at a temperature of 27°C and a power of 50Hz, the water I and the sodium hexametaphosphate were first mixed for 15 minutes to obtain a sodium hexametaphosphate solution. Then, under ultrasonic conditions at a power of 100Hz, the sodium hexametaphosphate solution was mixed with the abrasive I for 15 minutes to obtain the mixture I.

[0088] S1. At 32°C and 20 rpm, the water II, hydroxyethyl cellulose I, triethylene glycol, and wetting agent are mixed for 2 hours to obtain a premixed solution.

[0089] S2. At 30°C and 30 rpm, the premixed liquid and mixture I are mixed for 2 hours to obtain mixture II.

[0090] S3. At 25°C and 15 rpm, the pH adjuster and the mixture II are mixed for 15 min to obtain the silicon carbide wafer polishing solution with a pH value of 7, named P2.

[0091] Preparation Example 3

[0092] This preparation example was carried out using the same method as Preparation Example 1. The difference was that an equal mass of abrasive II was used instead of abrasive I for mixing II to obtain a silicon carbide wafer polishing slurry, named P3. All other parameters were the same as in Preparation Example 1.

[0093] Preparation Example 4

[0094] This preparation example was carried out using the same method as Preparation Example 1. The difference was that an equal mass of abrasive VI was used instead of abrasive I for mixing II to obtain a silicon carbide wafer polishing slurry, named P4. All other parameters were the same as in Preparation Example 1.

[0095] Comparative Example 1

[0096] This comparative example was prepared using the same method as in Preparation Example 1. The difference was that an equal mass of abrasive III was used instead of abrasive I for mixing II to obtain a silicon carbide wafer polishing slurry, named DP1. All other parameters were the same as in Preparation Example 1.

[0097] Comparative Example 2

[0098] This comparative example was prepared using the same method as in Preparation Example 1. The difference was that an equal mass of abrasive IV was used instead of abrasive I for mixing II to obtain a silicon carbide wafer polishing slurry, named DP2. All other parameters were the same as in Preparation Example 1.

[0099] Comparative Example 3

[0100] This comparative example was prepared using the same method as in Preparation Example 1. The difference was that an equal mass of abrasive V was used instead of abrasive I for mixing II to obtain a silicon carbide wafer polishing slurry, named DP3. All other parameters were the same as in Preparation Example 1.

[0101] Comparative Example 4

[0102] This comparative example was prepared using the same method as in Preparation Example 1. The difference was that in step S1, an equal mass of hydroxyethyl cellulose II was used instead of hydroxyethyl cellulose I for mixing III to obtain a silicon carbide wafer polishing solution, named DP4. All other parameters were the same as in Preparation Example 1.

[0103] Test Example 1

[0104] The polishing slurry prepared in the above examples was applied to the polishing of silicon carbide wafers: at a rotation speed of 45 rpm and a pressure of 300 g / cm. 2 Under the specified conditions, fiber polishing pads, polyurethane polishing pads, and fiber-polyurethane hybrid polishing pads were used respectively. The silicon carbide wafers (6-inch conductive silicon carbide) were polished using a Logitech high-precision surface treatment system and a double-sided polishing machine (model 16B double-sided polishing machine). The surface roughness and surface thickness removal rates of the polished silicon carbide wafers were obtained, and the results are shown in Table 2.

[0105] Table 1

[0106] Components Preparation Example 1 Preparation Example 2 Abrasive I Dosage / g 10 15 Sodium hexametaphosphate Dosage / g 10 11 Water I Dosage / g 100 300 Water II Dosage / g 800 600 Hydroxyethyl cellulose I Dosage / g 50 45 Triethylene glycol Dosage / g 10 12 wetting agent Dosage / g 19 15 pH adjuster Dosage / g 1 2

[0107] Table 2

[0108]

[0109] Table 2 (continued)

[0110]

[0111] The results above show that the silicon carbide wafer polishing slurry provided by the present invention, through the use of single crystal and polycrystalline diamond with different particle sizes and the synergistic effect of hydroxyethyl cellulose with specific viscosity and other substances, achieves a high and stable polishing removal rate, good surface processing quality, and is also suitable for polishing pads of different materials.

[0112] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A silicon carbide wafer polishing slurry, characterized in that, The polishing slurry contains the following components, either individually or in combination: The functional components and water, wherein the functional components are abrasive, sodium hexametaphosphate, triethylene glycol, hydroxyethyl cellulose, humectant, and pH adjuster; The abrasive is a mixture of single-crystal diamond with a volume average particle size of 0.5-3 μm and polycrystalline diamond with an average particle size of 0.5-2 μm, wherein the weight ratio of the single-crystal diamond to the polycrystalline diamond in the mixture is 1:0.01-1. The viscosity of the hydroxyethyl cellulose in a 2wt% aqueous solution at 35°C is 1000-14000 mPa·s; On a dry basis, and based on the total weight of the functional components, the abrasive content is 8-25 wt%, the sodium hexametaphosphate content is 0.5-20 wt%, the triethylene glycol content is 0.2-15 wt%, the hydroxyethyl cellulose content is 30-50 wt%, the wetting agent content is 10-20 wt%, and the pH adjuster content is 0.2-9.0 wt%. The weight ratio of the functional component to the water is 1:2-20.

2. The polishing slurry according to claim 1, characterized in that, The volume average particle size of the single-crystal diamond is 0.1-12% larger than that of the polycrystalline diamond.

3. The polishing slurry according to claim 1, characterized in that, The wetting agent is selected from at least one of polyethylene glycol, polypropylene glycol, diethylene glycol, and polyacrylic acid; and / or The pH adjuster is selected from at least one of ethanolamine, triethanolamine, isopropanolamine, N-(2-hydroxyethyl)ethylenediamine, sodium hydroxide, and potassium hydroxide.

4. A method for preparing the silicon carbide wafer polishing slurry according to any one of 1-3, characterized in that, The method includes: (1) Sodium hexametaphosphate and abrasive were contact-mixed in the presence of water I to obtain mixture I; (2) In the presence of water II, hydroxyethyl cellulose, triethylene glycol, wetting agent, pH adjuster and the mixture I are contact mixed II to obtain silicon carbide wafer polishing solution; The weight ratio of water I to water II is 1:0.5-1, and the sum of the weights of water I and water II is the total weight of water in the polishing liquid.

5. The method according to claim 4, characterized in that, In step (1), the contact mixing I operation includes: first mixing the water I with the sodium hexametaphosphate I to obtain a sodium hexametaphosphate solution, and then mixing the sodium hexametaphosphate solution with the abrasive II to obtain the mixture I.

6. The method according to claim 4, characterized in that, In step (2), the operation of contact mixing II includes: S1. First, mix the water (II) with the hydroxyethyl cellulose, the triethylene glycol, and the wetting agent (III) to obtain a premixed solution; S2. Mix the premixed liquid with mixture I in IV to obtain mixture II; S3. Mix the pH adjuster with the mixture II to obtain the silicon carbide wafer polishing solution with a pH value of 6-8.

7. The method according to claim 5, characterized in that, The mixing process I is performed under ultrasonic conditions and must at least meet the following requirements: frequency 40-60 Hz, temperature 20-30 °C, and time 5-20 min; and / or The mixing II is performed under ultrasonic conditions and must at least meet the following requirements: frequency of 90-110 Hz, temperature of 20-30 ℃, and time of 5-20 min.

8. The method according to claim 6, characterized in that, Mixing III is carried out under stirring conditions, and at least meets the following requirements: rotation speed of 10-20 rpm, temperature of 25-35℃, and time of 2-4 h; and / or The contact mixing IV is carried out under stirring conditions, and at least meets the following requirements: rotation speed of 10-30 rpm, temperature of 30-35℃, and time of 2-4 h; and / or The contact mixing V is carried out under stirring conditions, and at least meets the following requirements: rotation speed of 10-20 rpm, temperature of 20-25℃, and time of 2-4 h.

9. The application of the silicon carbide wafer polishing slurry according to any one of claims 1-3 in the field of silicon carbide wafer manufacturing.

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