Spherical nano aluminum oxide polishing solution for polishing silicon carbide wafer

Abstract

The invention discloses a spherical nano aluminum oxide polishing solution for silicon carbide wafer polishing, and relates to the technical field of preparation of semiconductor silicon carbide wafer polishing materials, and the spherical nano aluminum oxide polishing solution comprises the following raw materials by weight: 0.5-55% of aluminum oxide, 0.05-25% of an oxidant, 0.1-10% of an inhibitor, 0.01-12% of a surfactant, 0.01-15% of a dispersant, 0.1-10% of a pH regulator, and the balance of high purity water. The preparation process comprises the following steps: (1) preparing materials; (2) grinding material pretreatment; (3) mixing; (4) adjusting the pH value; and (5) high-pressure homogenization. The CMP polishing solution has the characteristics of high removal rate, good suspension dispersion performance, no damage to the surface of the silicon carbide wafer, extremely low surface roughness value, long cycle service life, easiness in cleaning, good universality and the like, and is suitable for CMP polishing of semiconductor silicon carbide wafers.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor silicon carbide wafer polishing material preparation, in particular to a spherical nano-aluminum oxide polishing liquid for silicon carbide wafer polishing and a preparation method thereof. Background Art

[0002] With the rapid development of semiconductor material technology and processing technology, the size of silicon carbide electronic devices has gradually decreased, and the requirements for wafer surface flatness have become increasingly higher, usually requiring the wafer surface flatness to reach the nanometer level. However, traditional planarization technology can only achieve local planarization, and the surface of the silicon carbide wafer is severely damaged, resulting in the surface quality of the product failing to meet the stringent requirements of electronic device production for surface quality. Chemical mechanical polishing (CMP) technology can not only achieve global planarization, but also outperform traditional planarization technology in processing performance and speed. Chemical mechanical polishing technology is to use chemical corrosion and mechanical force to smooth the surface of silicon carbide wafers or other substrate materials during processing; during the chemical corrosion process, the chemical substances in the polishing liquid react with the surface of the silicon carbide wafer to produce substances that are easier to remove, and further remove the substances generated in the chemical reaction process through mechanical force. At present, chemical mechanical polishing technology uses polishing liquids with oxides as active ingredients. Most of these silicon carbide polishing liquids using strong oxidants have poor stability, which in turn causes low efficiency in polishing silicon carbide wafers, and scratches are prone to appear on the polished surface.

[0003] The Chinese patent (patent application number is 201911356679.7) "Polishing powder for polishing silicon carbide wafers and its preparation method and polishing liquid", the preparation method of polishing powder for polishing silicon carbide wafers, comprises the following steps: S1, respectively configure liquid A, micron α-alumina dispersion, and liquid B, potassium hydroxide aqueous solution containing sodium metaaluminate; S2, at a certain reaction temperature, add liquid B and hydrochloric acid to liquid A, continue stirring for a period of time after adding liquid B and hydrochloric acid, obtain aluminum hydroxide coated micron α-alumina slurry, and then age it; S3, add nano α-alumina powder to the aged slurry while stirring, continue stirring for a period of time after adding nano α-alumina powder, obtain nano α-alumina coated aluminum hydroxide coated micron α-alumina slurry; S4, separate the above slurry and dry it, then calcine it at high temperature, and then obtain polishing powder after post-treatment. This invention can improve the polishing efficiency and surface yield of silicon carbide wafers.

[0004] Another Chinese patent (patent application number 202310608081.2) is "A silicon carbide wafer polishing liquid". The polishing liquid used is a neutral reagent with high storage stability. It does not contain any oxidants and is green, pollution-free and cost-effective.

[0005] There is also a Chinese patent (patent application number 202410470055.2) for "a silicon carbide wafer polishing liquid for double-sided synchronous polishing, a preparation method and an application". The components of the polishing liquid include: 20-30wt.% silica sol, 0.005-0.05wt.% surfactant, 8-17wt.% Ti0, coated SiO2 core-shell photocatalytic abrasive, 3-9wt.% hydrogen peroxide, and deionized water; wherein the TiO2 content accounts for 20-35wt.% of the core-shell photocatalytic abrasive; the contact angle of the polishing liquid with the carbon surface: the contact angle of the polishing liquid with the silicon surface is 2-3.5:1, and the pH value of the polishing liquid is 8-10; while increasing the material removal rate of the silicon surface, the excessively high material removal rate of the carbon surface is suppressed, and the material removal rate ratio of the carbon surface to the silicon surface is significantly reduced to 1.2-2, and at the same time, the material removal rate of the silicon surface can be increased to more than 150nm / h.

[0006] There is also a Chinese patent (patent application number 202410509104.9) for "a polishing liquid for polishing silicon carbide wafers, its preparation method and polishing method", the polishing liquid includes the following components: an oxidant, a dispersant, a first abrasive, a second abrasive, a pH adjuster and a solvent; the first abrasive is artemisinin crystals; the second abrasive includes any one of cerium dioxide, titanium dioxide or silicon dioxide or a combination of at least two. The combination of the first abrasive and the second abrasive takes into account the polishing efficiency and polishing effect of the polishing liquid on SiC wafers. The use of ultraviolet light catalysis-assisted chemical mechanical polishing simplifies the rough polishing + fine polishing mode of the traditional polishing process, shortens the polishing process steps, and improves the polishing efficiency.

[0007] There is also a Chinese patent (patent application number 202410644360.9) for "a high-quality silicon carbide polishing liquid and silicon carbide wafer", which effectively improves the surface removal rate of silicon carbide through electrochemical mechanical polishing treatment to obtain high-quality, low-roughness silicon carbide wafers.

[0008] There is also a Chinese patent (patent application number 202410961673.7) "A method for synchronous double-sided polishing of silicon carbide wafers", which uses the method for synchronous double-sided polishing of silicon carbide wafers of the present invention to synchronously polish the double-sided silicon carbide wafers, by simultaneously changing the hydrophilicity of the carbon surface and the silicon surface of the silicon carbide wafer, and simultaneously changing the contact angle between the subsequent polishing liquid and the carbon surface and the contact angle between the polishing liquid and the silicon surface, so that the removal rate ratio of the carbon surface and the silicon surface of the silicon carbide wafer during double-sided synchronous polishing is reduced. Although the removal rate of the Si surface is reduced, the C / Si surface removal rate ratio is reduced, the processing loss of the silicon carbide wafer is reduced, and the use requirements of device manufacturing are met while reducing the processing loss and processing cost. Summary of the invention

[0009] The technical problem to be solved by the present invention is to provide a silicon carbide wafer polishing liquid with high removal rate, good suspension and dispersion performance, no damage to the surface of the silicon carbide wafer, extremely low surface roughness value, long cycle life, easy cleaning and good versatility, and provide a preparation method thereof.

[0010] In order to solve the above technical problems, the technical solution adopted by the present invention is to invent a spherical nano-alumina polishing liquid for polishing silicon carbide wafers, wherein the raw materials used include alumina, an oxidant, an inhibitor, a surfactant, a dispersant, a pH regulator and high-purity water. Based on the total weight of the polishing liquid, the weight percentages of the raw materials are respectively:

[0011] Alumina 0.5-55 Oxidant 0.05-25

[0012] Inhibitor 0.1-10 Surfactant 0.01-12

[0013] Dispersant 0.01-15 pH adjuster 0.1-10

[0014] The balance is high-purity water;

[0015] The aluminum oxide is spherical nano aluminum oxide with a particle size of 20-100 nm.

[0016] The oxidant is one or more of peracetic acid, hydrogen peroxide, sodium perchlorate, potassium permanganate, ammonium persulfate, and sodium perborate, preferably peracetic acid. When there are two or more oxidants, the proportion of each component is equal by weight.

[0017] The inhibitor is one or more of sodium sulfide, sodium lignin, salicylic acid, sodium pyrophosphate, and octahydroxyquinoline, preferably sodium lignin. When there are two or more inhibitors, the proportion of each component is equal by weight.

[0018] The surfactant is one or more of silane coupling agent, hexadecyltrimethyl sodium bromide, fatty alcohol polyoxyethylene ether, and trisodium N-hydroxyethylethylenediaminetriacetate, preferably trisodium N-hydroxyethylethylenediaminetriacetate. When there are two or more, the proportion of each component is equal by weight.

[0019] The dispersant is one or more of quaternary ammonium salt, phosphate salt, acrylate, polyacrylate, preferably sodium phosphate. When there are two or more dispersants, the proportion of each component is equal by weight.

[0020] The pH regulator is one or more of ethanolamine, potassium hydroxide, piperazine, aluminum nitrate, aluminum chloride, and acetic acid, preferably piperazine. When there are two or more, the proportion of each component is equal by weight.

[0021] At the same time, a method for preparing a spherical nano-alumina polishing liquid for polishing silicon carbide wafers is also invented, which comprises the following steps:

[0022] ①. Prepare materials: according to the raw material ratio, weigh appropriate amounts of spherical nano-alumina, oxidant, inhibitor, surfactant, dispersant, pH adjuster and high-purity water respectively and set aside;

[0023] ②. Abrasive pretreatment: Add spherical nano-alumina into high-purity water at a weight ratio of 1:0.5-1.5, and disperse by ultrasonic for 10-20 minutes to obtain a spherical nano-alumina turbid liquid for later use;

[0024] ③. Mixing: Add the oxidant, inhibitor, surfactant and dispersant to the reserved spherical nano-alumina turbid liquid, stir evenly, filter out the insoluble impurities with a 0.3-5μm filter element to obtain a mixed liquid for use;

[0025] ④. pH adjustment: Add the pH adjuster to the reserved mixed solution and stir evenly.

[0026] Adjust the pH value to 1.5-12 to obtain a pH adjustment mixed solution for later use;

[0027] ⑤. High-pressure homogenization: Add the reserved pH-adjusted mixed solution into a high-pressure homogenizer, homogenize for 20-40 minutes, then add high-purity water to the total weight of the polishing solution, stir evenly, and you will get the spherical nano-alumina polishing solution for polishing silicon carbide wafers.

[0028] Optimally, the ultrasonic dispersion time is 15 min.

[0029] Optimally, the pH value of the polishing liquid ranges from 5 to 9.

[0030] Optimally, the homogenization time is 30 minutes.

[0031] Compared with similar products on the existing domestic and foreign markets, the spherical nano-alumina polishing liquid for polishing silicon carbide wafers of the present invention has the following advantages:

[0032] First, it does not damage the surface of the silicon carbide wafer and has an extremely low surface roughness value. The abrasives used in similar products on the domestic and foreign markets are mostly mallet-shaped, cluster-shaped, and flaky, and their particle size is generally greater than 1000nm. Therefore, they will cause greater damage to the surface of the silicon carbide wafer, resulting in a higher surface roughness value. The spherical nano-alumina polishing liquid for polishing silicon carbide wafers of the present invention uses spherical nano-alumina as an abrasive, and its particle size is less than 100nm. Therefore, it has almost no damage to the surface of the silicon carbide wafer, and the surface roughness value is extremely low, and its roughness Ra value can reach a level of less than 0.2nm.

[0033] Second, the removal rate is high. Similar products on the domestic market (i.e., alumina polishing liquid for silicon carbide wafer polishing) currently have poor stability and low efficiency, and the removal rate is generally lower than 1μm / hr; similar products on the foreign market (i.e., alumina polishing liquid for silicon carbide wafer polishing) have a removal rate as high as 2μm / hr. The spherical nano-alumina polishing liquid for silicon carbide wafer polishing of the present invention can maintain an efficient polishing value for a long time under the catalytic action of chemical additives, and its removal rate can reach 2.5μm / hr, so its removal rate is high.

[0034] The spherical nano-alumina polishing liquid for polishing silicon carbide wafers of the present invention can effectively inhibit the decomposition of the oxidant during the polishing process because it contains an inhibitor, thereby stabilizing the performance of the polishing liquid for a long time, thereby achieving the purpose of long service life.

[0035] Fourth, the spherical nano-alumina polishing liquid for polishing silicon carbide wafers of the present invention can fully suspend and disperse the spherical nano-alumina due to the addition of a hydrophilic dispersant, thereby ensuring the uniformity of the dispersion of the spherical nano-alumina in the polishing liquid.

[0036] Fifth, it is easy to clean. The spherical nano-alumina polishing liquid for polishing silicon carbide wafers of the present invention has a surfactant added therein, so that there are very few impurity particles on the surface of the polished silicon carbide wafers. Therefore, it is easy to clean. For 6- and 8-inch silicon carbide wafers, the number ratio of impurity elements is less than 10. -7 .

[0037] Sixth, it has good versatility. The spherical nano-alumina polishing liquid for polishing silicon carbide wafers of the present invention has an applicable pH value range of 1.5-12, and can be used to prepare strong acid polishing liquids, strong alkaline polishing liquids, weak acid polishing liquids or weak alkaline polishing liquids, and has wide applicability, and thus has good versatility. DETAILED DESCRIPTION

[0038] The present invention is further described below in conjunction with the embodiments. The following description is by way of example, but the protection scope of the present invention should not be limited thereto.

[0039] Embodiment 1:

[0040] The spherical nano-alumina polishing liquid for polishing silicon carbide wafers in this embodiment is prepared as follows:

[0041] ①, material preparation: according to the amount of spherical nano-alumina polishing liquid for preparing 10kg of silicon carbide wafer polishing, take 5kg of spherical nano-alumina (particle size is 20-100nm), 300g of peracetic acid (oxidant), 100g of sodium lignin (inhibitor), 50g of trisodium N-hydroxyethylethylenediaminetriacetate (surfactant), 100g of sodium phosphate (dispersant), 50g of piperazine (pH regulator), and appropriate amount of high-purity water, and set aside;

[0042] ②. Abrasive pretreatment: Add spherical nano-alumina (abrasive) into 4 kg of high-purity water, and disperse by ultrasonic for 15 minutes to obtain a spherical nano-alumina turbid liquid for standby use;

[0043] ③. Mixing: Add peracetic acid (oxidant), sodium lignin (inhibitor), trisodium N-hydroxyethylethylenediaminetriacetate (surfactant) and sodium phosphate (dispersant) to the reserved spherical nano-alumina turbid liquid, stir evenly, filter out insoluble impurities with a 0.3-5 μm filter element to obtain a mixed liquid for standby use;

[0044] ④. Adjusting pH: Add piperazine (pH adjuster) to the mixed solution, stir evenly, adjust the pH value to 9.0, and obtain a pH-adjusted mixed solution for standby use;

[0045] ⑤. High-pressure homogenization: Add the reserved pH-adjusted mixed solution into a high-pressure homogenizer of model KS-30, homogenize for 30 minutes, then add high-purity water to the total weight of the polishing solution, stir evenly, and you will get 10kg of spherical nano-alumina polishing solution for polishing silicon carbide wafers.

[0046] When used, the prepared spherical nano-alumina polishing liquid for silicon carbide wafer polishing is added to a TSP-910A single-sided polishing machine, and a silicon carbide wafer is put in, and the polishing pressure is set to 120 g / cm 2 The lower plate speed is 55 rpm, the upper plate speed is 45 rpm, the same direction, and the polishing time is 90 min. The test results after cleaning show that the removal rate of silicon carbide wafer is 2.59 μm / hr, the surface roughness (Ra) is 0.12 nm, and the number ratio of impurity elements is 1.2×10 -8 .

[0047] Embodiment 2:

[0048] The spherical nano-alumina polishing liquid for polishing silicon carbide wafers in this embodiment is prepared as follows:

[0049] ①, material preparation: according to the amount of spherical nano-alumina polishing liquid for preparing 10kg of silicon carbide wafer polishing, take 4kg of spherical nano-alumina (particle size is 20-100nm), 200g of peracetic acid and 200g of sodium perborate (oxidant), 80g of sodium lignin and 80g of octahydroxyquinoline (inhibitor), 30g of trisodium N-hydroxyethylethylenediaminetriacetate and 30g of silane coupling agent (surfactant), 50g of sodium phosphate and 50g of acrylate (dispersant), 20g of piperazine and 20g of ethanol (pH adjuster), and appropriate amount of high-purity water, and set aside;

[0050] ②. Abrasive pretreatment: Add spherical nano-alumina (abrasive) into 4 kg of high-purity water, and disperse by ultrasonic for 15 minutes to obtain a spherical nano-alumina turbid liquid for standby use;

[0051] ③. Mixing: add peracetic acid and sodium perborate (oxidant), sodium lignin and octahydroxyquinoline (inhibitor), trisodium N-hydroxyethylethylenediaminetriacetate and silane coupling agent (surfactant), sodium phosphate and acrylate (dispersant) to the reserved spherical nano-alumina turbid liquid, stir evenly, filter out insoluble impurities with a 0.3-5 μm filter element, and obtain a mixed liquid for standby use;

[0052] ④. Adjust pH: add piperazine and ethanol (pH adjuster) to the mixed solution, stir evenly, adjust the pH value to 8.0, and obtain a pH-adjusted mixed solution for standby use;

[0053] ⑤. High-pressure homogenization: Add the reserved pH-adjusted mixed solution into a high-pressure homogenizer of model KS-30, homogenize for 30 minutes, then add high-purity water to the total weight of the polishing solution, stir evenly, and you will get 10kg of spherical nano-alumina polishing solution for polishing silicon carbide wafers.

[0054] When used, the prepared spherical nano-alumina polishing liquid for silicon carbide wafer polishing is added to a TSP-910A single-sided polishing machine, and a silicon carbide wafer is put in, and the polishing pressure is set to 120 g / cm 2 The lower plate speed is 55 rpm, the upper plate speed is 45 rpm, the same direction, and the polishing time is 90 min. The test results after cleaning show that the removal rate of silicon carbide wafer is 2.51 μm / hr, the surface roughness (Ra) is 0.15 nm, and the number ratio of impurity elements is 1.3×10 -8 .

[0055] Embodiment 3:

[0056] The spherical nano-alumina polishing liquid for polishing silicon carbide wafers in this embodiment is prepared as follows:

[0057] ①, material preparation: according to the amount of spherical nano-alumina polishing liquid for preparing 10kg of silicon carbide wafer polishing, take 3kg of spherical nano-alumina (particle size is 20-100nm), 150g of peracetic acid and 150g of hydrogen peroxide (oxidant), 60g of sodium lignin and 60g of sodium pyrophosphate (inhibitor), 20g of trisodium N-hydroxyethylethylenediaminetriacetate and 20g of hexadecyltrimethyl sodium bromide (surfactant), 40g of sodium phosphate and 40g of quaternary ammonium salt (dispersant), 5g of piperazine and 5g of potassium hydroxide (pH adjuster), and appropriate amount of high-purity water, and set aside;

[0058] ②. Abrasive pretreatment: Add spherical nano-alumina (abrasive) into 4 kg of high-purity water, and disperse by ultrasonic for 15 minutes to obtain a spherical nano-alumina turbid liquid for standby use;

[0059] ③. Mixing: add peracetic acid and hydrogen peroxide (oxidant), sodium lignin and sodium pyrophosphate (inhibitor), trisodium N-hydroxyethylethylenediaminetriacetate and sodium cetyltrimethylbromide (surfactant), sodium phosphate and quaternary ammonium salt (dispersant) to the reserved spherical nano-alumina turbid liquid, stir evenly, filter out insoluble impurities with a 0.3-5 μm filter element, and obtain a mixed liquid for standby use;

[0060] ④. Adjust pH: Add piperazine and potassium hydroxide (pH adjuster) to the mixed solution, stir evenly, adjust the pH value to 7.0, and obtain a pH-adjusted mixed solution for standby use;

[0061] ⑤. High-pressure homogenization: Add the reserved pH-adjusted mixed solution into a high-pressure homogenizer of model KS-30, homogenize for 30 minutes, then add high-purity water to the total weight of the polishing solution, stir evenly, and you will get 10kg of spherical nano-alumina polishing solution for polishing silicon carbide wafers.

[0062] When used, the prepared spherical nano-alumina polishing liquid for silicon carbide wafer polishing is added to a TSP-910A single-sided polishing machine, and a silicon carbide wafer is put in, and the polishing pressure is set to 120 g / cm 2 The lower plate speed is 55 rpm, the upper plate speed is 45 rpm, the same direction, and the polishing time is 90 min. The test results after cleaning show that the removal rate of silicon carbide wafer is 2.50 μm / hr, the surface roughness (Ra) is 0.13 nm, and the number ratio of impurity elements is 1.5×10 -8 .

[0063] Embodiment 4:

[0064] The spherical nano-alumina polishing liquid for polishing silicon carbide wafers in this embodiment is prepared as follows:

[0065] ①, material preparation: according to the amount of spherical nano-alumina polishing liquid for preparing 10kg of silicon carbide wafer polishing, take 2kg of spherical nano-alumina (particle size is 20-100nm), 100g of peracetic acid and 100g of sodium perchlorate (oxidant), 50g of sodium lignin and 50g of salicylic acid (inhibitor), 10g of trisodium N-hydroxyethylethylenediaminetriacetate and 10g of fatty alcohol polyoxyethylene ether (surfactant), 30g of sodium phosphate and 30g of polyacrylate (dispersant), 15g of piperazine and 15g of aluminum nitrate (pH adjuster), and appropriate amount of high-purity water, and set aside;

[0066] ②. Abrasive pretreatment: Add spherical nano-alumina (abrasive) into 4 kg of high-purity water, and disperse by ultrasonic for 15 minutes to obtain a spherical nano-alumina turbid liquid for standby use;

[0067] ③. Mixing: add peracetic acid and sodium perchlorate (oxidant), sodium lignin and salicylic acid (inhibitor), trisodium N-hydroxyethylethylenediaminetriacetate and fatty alcohol polyoxyethylene ether (surfactant), sodium phosphate and polyacrylate (dispersant) to the reserved spherical nano-alumina turbid liquid, stir evenly, filter out insoluble impurities with a 0.3-5 μm filter element, and obtain a mixed liquid for standby use;

[0068] ④. Adjusting pH: Add piperazine and aluminum nitrate (pH adjuster) to the mixed solution, stir evenly, adjust the pH value to 6.0, and obtain a pH-adjusted mixed solution for standby use;

[0069] ⑤. High-pressure homogenization: Add the reserved pH-adjusted mixed solution into a high-pressure homogenizer of model KS-30, homogenize for 30 minutes, then add high-purity water to the total weight of the polishing solution, stir evenly, and you will get 10kg of spherical nano-alumina polishing solution for polishing silicon carbide wafers.

[0070] When used, the prepared spherical nano-alumina polishing liquid for silicon carbide wafer polishing is added to a TSP-910A single-sided polishing machine, and a silicon carbide wafer is put in, and the polishing pressure is set to 120 g / cm 2 The lower plate speed is 55 rpm, the upper plate speed is 45 rpm, the same direction, and the polishing time is 90 min. The test results after cleaning show that the removal rate of silicon carbide wafer is 2.52 μm / hr, the surface roughness (Ra) is 0.16 nm, and the number ratio of impurity elements is 1.7×10 -8 .

[0071] Embodiment 5:

[0072] The spherical nano-alumina polishing liquid for polishing silicon carbide wafers in this embodiment is prepared as follows:

[0073] ①, material preparation: according to the amount of spherical nano-alumina polishing liquid for preparing 10kg of silicon carbide wafer polishing, take 1kg of spherical nano-alumina (particle size is 20-100nm), 50g of peracetic acid and 50g of ammonium persulfate (oxidant), 40g of sodium lignin and 40g of sodium sulfide (inhibitor), 5g of trisodium N-hydroxyethylethylenediaminetriacetate (surfactant), 20g of sodium phosphate (dispersant), 25g of piperazine and 25g of aluminum chloride (pH adjuster), and appropriate amount of high-purity water, and set aside;

[0074] ②. Abrasive pretreatment: Add spherical nano-alumina (abrasive) into 4 kg of high-purity water, and disperse by ultrasonic for 15 minutes to obtain a spherical nano-alumina turbid liquid for standby use;

[0075] ③. Mixing: Add peracetic acid and ammonium persulfate (oxidant), sodium lignin and sodium sulfide (inhibitor), trisodium N-hydroxyethylethylenediaminetriacetate (surfactant), and sodium phosphate (dispersant) to the reserved spherical nano-alumina turbid liquid, stir evenly, and filter out insoluble impurities with a 0.3-5μm filter element to obtain a mixed liquid for standby use;

[0076] ④. Adjust pH: Add piperazine and aluminum chloride (pH adjuster) to the mixed solution, stir evenly, adjust the pH value to 5.0, and obtain a pH-adjusted mixed solution for standby use;

[0077] ⑤. High-pressure homogenization: Add the reserved pH-adjusted mixed solution into a high-pressure homogenizer of model KS-30, homogenize for 30 minutes, then add high-purity water to the total weight of the polishing solution, stir evenly, and you will get 10kg of spherical nano-alumina polishing solution for polishing silicon carbide wafers.

[0078] When used, the prepared spherical nano-alumina polishing liquid for silicon carbide wafer polishing is added to a TSP-910A single-sided polishing machine, and a silicon carbide wafer is put in, and the polishing pressure is set to 120 g / cm 2 The lower plate speed is 55 rpm, the upper plate speed is 45 rpm, the same direction, and the polishing time is 90 min. The test results after cleaning show that the removal rate of silicon carbide wafer is 2.55 μm / hr, the surface roughness (Ra) is 0.14 nm, and the number ratio of impurity elements is 1.8×10 -8 .

[0079] Embodiment 6:

[0080] The spherical nano-alumina polishing liquid for polishing silicon carbide wafers in this embodiment is prepared as follows:

[0081] ①, material preparation: according to the amount of spherical nano-alumina polishing liquid for preparing 10kg of silicon carbide wafer polishing, take 5.5kg of spherical nano-alumina (particle size is 20-100nm), 5g of peracetic acid (oxidant), 10g of sodium lignin (inhibitor), 1g of trisodium N-hydroxyethylethylenediaminetriacetate (surfactant), 1g of sodium phosphate (dispersant), 5g of aluminum nitrate and 5g of aluminum chloride (pH adjuster), and appropriate amount of high-purity water, and set aside;

[0082] ②. Abrasive pretreatment: Add spherical nano-alumina (abrasive) into 4 kg of high-purity water, and disperse by ultrasonic for 15 minutes to obtain a spherical nano-alumina turbid liquid for standby use;

[0083] ③. Mixing: Add peracetic acid (oxidant), sodium lignin (inhibitor), trisodium N-hydroxyethylethylenediaminetriacetate (surfactant), and sodium phosphate (dispersant) to the reserved spherical nano-alumina turbid liquid, stir evenly, and filter out insoluble impurities with a 0.3-5 μm filter element to obtain a mixed liquid for standby use;

[0084] ④. Adjust pH: Add aluminum nitrate and aluminum chloride (pH adjuster) to the mixed solution, stir evenly, adjust the pH value to 1.5, and obtain a pH-adjusted mixed solution for standby use;

[0085] ⑤. High-pressure homogenization: Add the reserved pH-adjusted mixed solution into a high-pressure homogenizer of model KS-30, homogenize for 30 minutes, then add high-purity water to the total weight of the polishing solution, stir evenly, and you will get 10kg of spherical nano-alumina polishing solution for polishing silicon carbide wafers.

[0086] When used, the prepared spherical nano-alumina polishing liquid for silicon carbide wafer polishing is added to a TSP-910A single-sided polishing machine, and a silicon carbide wafer is put in, and the polishing pressure is set to 120 g / cm 2 The lower plate speed is 55 rpm, the upper plate speed is 45 rpm, the same direction, and the polishing time is 90 min. The test results after cleaning show that the removal rate of silicon carbide wafer is 2.63 μm / hr, the surface roughness (Ra) is 0.19 nm, and the number ratio of impurity elements is 1.9×10 -8 .

[0087] Embodiment 7:

[0088] The spherical nano-alumina polishing liquid for polishing silicon carbide wafers in this embodiment is prepared as follows:

[0089] ①, material preparation: according to the amount of spherical nano-alumina polishing liquid for preparing 10kg of silicon carbide wafer polishing, take 50g of spherical nano-alumina (particle size is 20-100nm), 2.5kg of ammonium persulfate (oxidant), 1kg of sodium sulfide (inhibitor), 1.2kg of trisodium N-hydroxyethylethylenediaminetriacetate (surfactant), 1.5kg of sodium phosphate (dispersant), 1kg of potassium hydroxide (pH adjuster), and appropriate amount of high-purity water, and set aside;

[0090] ②. Abrasive pretreatment: Add spherical nano-alumina (abrasive) into 4 kg of high-purity water, and disperse by ultrasonic for 15 minutes to obtain a spherical nano-alumina turbid liquid for standby use;

[0091] ③. Mixing: Add ammonium persulfate (oxidant), sodium sulfide (inhibitor), trisodium N-hydroxyethylethylenediaminetriacetate (surfactant), and sodium phosphate (dispersant) to the reserved spherical nano-alumina turbid liquid, stir evenly, and filter out insoluble impurities with a 0.3-5μm filter element to obtain a mixed liquid for standby use;

[0092] ④. Adjust pH: Add potassium hydroxide (pH adjuster) to the mixed solution, stir evenly, adjust the pH value to 12, and obtain a pH-adjusted mixed solution for standby use;

[0093] ⑤. High-pressure homogenization: Add the reserved pH-adjusted mixed solution into a high-pressure homogenizer of model KS-30, homogenize for 30 minutes, then add high-purity water to the total weight of the polishing solution, stir evenly, and you will get 10kg of spherical nano-alumina polishing solution for polishing silicon carbide wafers.

[0094] When used, the prepared spherical nano-alumina polishing liquid for silicon carbide wafer polishing is added to a TSP-910A single-sided polishing machine, and a silicon carbide wafer is put in, and the polishing pressure is set to 120 g / cm 2 The lower plate speed is 55 rpm, the upper plate speed is 45 rpm, the same direction, and the polishing time is 90 min. The test results after cleaning show that the removal rate of silicon carbide wafer is 2.65 μm / hr, the surface roughness (Ra) is 0.19 nm, and the number ratio of impurity elements is 2.0×10 -8 .

[0095] After polishing the silicon carbide wafers using the spherical nano-alumina polishing liquids prepared in the five embodiments above, sampling tests were performed, and the test data are summarized as follows:

[0096]

[0097] Conclusion: The surface roughness Ra of the silicon carbide wafers in the above examples 1-7 is less than 0.2nm, the removal rate can reach 2.5μm / hr, and the number ratio of impurity elements is less than 10 -7 .

[0098] The above is a description of the implementation case of the present invention. Professionals and technicians in this field should understand that the principles and methods of the present invention can be improved and optimized without departing from the spirit or scope of the present invention. Therefore, some improvements and optimizations implemented without violating the spirit or scope of the present invention belong to the scope of protection claimed in the present invention.

[0099] The spherical nano-alumina polishing liquid for polishing silicon carbide wafers of the present invention is suitable for CMP polishing of semiconductor silicon carbide wafers.

Claims

1. A spherical nano-alumina polishing liquid for polishing silicon carbide wafers, characterized in that: The raw materials used include aluminum oxide, an oxidant, an inhibitor, a surfactant, a dispersant, a pH regulator and high-purity water. Based on the total weight of the polishing liquid, the weight percentages of the raw materials are as follows: Alumina 0.5-55 Oxidant 0.05-25 Inhibitor 0.1-10 Surfactant 0.01-12 Dispersant 0.01-15 pH adjuster 0.1-10 The balance is high-purity water; The aluminum oxide is spherical nano aluminum oxide with a particle size of 20-100 nm.

2. The spherical nano-alumina polishing liquid for polishing silicon carbide wafers according to claim 1, characterized in that: The oxidant is one or more of peracetic acid, hydrogen peroxide, sodium perchlorate, potassium permanganate, ammonium persulfate, and sodium perborate, preferably peracetic acid. When there are two or more oxidants, the proportion of each component is equal by weight.

3. The spherical nano-alumina polishing liquid for polishing silicon carbide wafers according to claim 1, characterized in that: The inhibitor is one or more of sodium sulfide, sodium lignin, salicylic acid, sodium pyrophosphate, and octahydroxyquinoline, preferably sodium lignin. When there are two or more inhibitors, the proportion of each component is equal by weight.

4. The spherical nano-alumina polishing liquid for polishing silicon carbide wafers according to claim 1, characterized in that: The surfactant is one or more of silane coupling agent, hexadecyltrimethyl sodium bromide, fatty alcohol polyoxyethylene ether, and trisodium N-hydroxyethylethylenediaminetriacetate, preferably trisodium N-hydroxyethylethylenediaminetriacetate. When there are two or more, the proportion of each component is equal by weight.

5. The spherical nano-alumina polishing liquid for polishing silicon carbide wafers according to claim 1, characterized in that: The dispersant is one or more of quaternary ammonium salt, phosphate salt, acrylate, polyacrylate, preferably sodium phosphate. When there are two or more dispersants, the proportion of each component is equal by weight.

6. The spherical nano-alumina polishing liquid for polishing silicon carbide wafers according to claim 1, characterized in that: The pH regulator is one or more of ethanolamine, potassium hydroxide, piperazine, aluminum nitrate, aluminum chloride, and acetic acid, preferably piperazine. When there are two or more, the proportion of each component is equal by weight.

7. A method for preparing a spherical nano-alumina polishing liquid for polishing a silicon carbide wafer as claimed in any one of claims 1 to 6, characterized in that: The following steps are involved: ①. Prepare materials: according to the raw material ratio, weigh appropriate amounts of spherical nano-alumina, oxidant, inhibitor, surfactant, dispersant, pH adjuster and high-purity water respectively and set aside; ②. Abrasive pretreatment: Add spherical nano-alumina into high-purity water at a weight ratio of 1:0.5-1.5, and disperse by ultrasonic for 10-20 minutes to obtain a spherical nano-alumina turbid liquid for later use; ③. Mixing: Add the oxidant, inhibitor, surfactant and dispersant to the reserved spherical nano-alumina turbid liquid, stir evenly, filter out the insoluble impurities with a 0.3-5μm filter element to obtain a mixed liquid for use; ④. pH adjustment: Add the pH adjuster to the reserved mixed solution, stir evenly, adjust the pH value to 1.5-12, and obtain the pH adjusted mixed solution for use; ⑤. High-pressure homogenization: Add the reserved pH-adjusted mixed solution into a high-pressure homogenizer, homogenize for 20-40 minutes, then add high-purity water to the total weight of the polishing solution, stir evenly, and you will get the spherical nano-alumina polishing solution for polishing silicon carbide wafers.

8. The method for preparing the spherical nano-alumina polishing liquid for polishing silicon carbide wafers according to claim 7, characterized in that: The ultrasonic dispersion time is 15 min.

9. The method for preparing the spherical nano-alumina polishing liquid for polishing silicon carbide wafers according to claim 7, characterized in that: The pH value of the polishing liquid ranges from 5 to 9.

10. The method for preparing the spherical nano-alumina polishing liquid for polishing silicon carbide wafers according to claim 7, characterized in that: The homogenization time is 30 min.

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