A polishing fluid and its application

Abstract

This invention provides a polishing fluid and its application. The polishing fluid comprises an oxidant, a nitrate, cerium oxide particles, a dispersant, an anti-settling agent, a pH adjuster, and a surfactant. The cerium oxide particles are shaped as any one or a combination of at least two of the following: triangular prisms, spherical or quadrangular prisms. The average particle size of the cerium oxide particles is 20 nm–2000 nm. The anti-settling agent comprises flake-shaped particles. This invention, by optimizing the composition of the polishing fluid, significantly improves the surface quality of the workpiece after polishing, reduces scratches on the workpiece surface, and achieves high polishing efficiency.

Description

Technical Field

[0001] This invention relates to the field of semiconductor integrated circuit manufacturing, specifically to the field of semiconductor device polishing, and particularly to a polishing slurry and its application. Background Technology

[0002] With the development of emerging technologies such as electric vehicles and 5G communications, new substrates represented by gallium nitride and silicon carbide are receiving increasing attention. Third-generation semiconductors, represented by silicon carbide, have characteristics such as a large bandgap, high breakdown electric field, high saturated electron drift velocity, and high thermal conductivity, and have significant advantages, especially in high-voltage environments of 1200V.

[0003] SiC substrate processing technology is a crucial foundation for semiconductor device fabrication. The quality and precision of its surface processing directly affect the quality of epitaxial films and device performance. Typically, the wafer surface must be ultra-smooth, defect-free, and damage-free, with a surface roughness below the nanometer level. However, silicon carbide crystals possess characteristics such as high hardness, high brittleness, good wear resistance, and good chemical stability, which makes the processing of silicon carbide wafers extremely difficult.

[0004] CN118562392A discloses a polishing slurry for silicon carbide substrates, using alumina as the abrasive, ferrate as the oxidant, and trivalent soluble iron salt as a modifier, to improve polishing efficiency and surface quality. This slurry is free of strong acids, does not corrode processing equipment, does not pollute the environment, is low in cost, and can be stored stably for extended periods; however, its maximum polishing rate is only 0.71 μm / h.

[0005] CN111303772A discloses an ultrafast, low-loss polishing slurry for silicon carbide substrates and its preparation method, comprising additives and a polishing base liquid. The polishing base liquid includes nanodiamond powder, a strong oxidant, a stabilizer, etc. The additives include graphene, tungsten carbide, silica gel, and titanium dioxide in a certain weight ratio. The additives described in this invention balance the frictional force during polishing, preventing scratches or increased roughness on the silicon carbide substrate during high-speed polishing, but the surface roughness can only reach below 1.5 nm.

[0006] CN115975511A discloses a polishing slurry and polishing slurry coating for grinding silicon carbide substrates. The raw materials of the polishing slurry contain permanganate, abrasive particles, metal salt additives, and water. Specifically, it contains 0.1%-50% permanganate, 0.01%-30% abrasive particles, and 0.01%-10% metal salt additives by mass percentage. The pH value of the polishing slurry is adjusted to less than 7 using a pH adjuster. The abrasive particles include cerium oxide. However, the polishing slurry disclosed in this patent can only achieve a removal rate of 1.27 μm / h, resulting in an unsatisfactory improvement in the thinning rate of silicon carbide substrates.

[0007] The polishing slurries used in the prior art either use high-strength materials with hardness exceeding or approaching that of silicon carbide, such as alumina and nanodiamond. Although these materials can ensure high removal efficiency on the surface of silicon carbide substrates, they are prone to causing deep scratches on the surface of silicon carbide substrates, making it difficult to repair them in subsequent fine polishing processes. Alternatively, they use polishing particles with slightly lower hardness, such as silicon oxide and cerium oxide. Although these materials can improve the surface quality of silicon carbide substrates after polishing, the removal efficiency of silicon carbide substrates is difficult to meet.

[0008] Therefore, it is of great significance to provide a polishing slurry that can reduce scratches on silicon carbide surfaces, improve silicon carbide surface roughness, and also has a high silicon carbide substrate removal rate. Summary of the Invention

[0009] To address the shortcomings of existing technologies, the present invention aims to provide a polishing slurry and its application. This invention optimizes the components of the polishing slurry, selecting cerium oxide particles with a hardness lower than silicon carbide as abrasive particles. This reduces scratches on the silicon carbide surface after polishing, significantly improving the surface quality of the polished silicon carbide. Through the synergistic effect of dispersants and anti-precipitants, the dispersibility and stability of cerium oxide particles in the polishing slurry are ensured, fully utilizing the abrasive performance of the cerium oxide particles. Combined with the oxidizing effect of the oxidant, silicon carbide is oxidized to silicon oxide with lower hardness, greatly increasing the removal rate of the silicon carbide substrate.

[0010] To achieve this objective, the present invention adopts the following technical solution:

[0011] In a first aspect, the present invention provides a polishing liquid comprising an oxidant, a nitrate, cerium oxide particles, a dispersant, an anti-precipitant, a pH adjuster, and a surfactant;

[0012] The cerium oxide particles have the shape of any one or a combination of at least two of the following: triangular prism, spherical, or quadrangular prism; the average particle size of the cerium oxide particles is 20 nm to 2000 nm; the anti-precipitant includes flake particles; the average size of the flake particles in the length direction is 0.5 μm to 3 μm, and the average size in the width direction is 0.5 μm to 3 μm.

[0013] In this invention, cerium oxide particles with a hardness lower than silicon carbide are selected as grinding particles. The shape of the cerium oxide particles includes any one or a combination of at least two of the following: triangular prism, spherical, or quadrangular prism. Typical but non-limiting combinations include a combination of triangular prism and spherical, a combination of quadrangular prism and triangular prism, or a combination of spherical and quadrangular prism.

[0014] Since the surface of silicon carbide substrates is porous and stepped silicon oxide after oxidation, the shape of cerium oxide particles has a significant impact on polishing efficiency and quality. Triangular prism-shaped cerium oxide particles have more prominent tips, and due to their high edge removal efficiency, adding triangular prism-shaped cerium oxide particles to the polishing solution can significantly improve the polishing efficiency of the substrate. Spherical cerium oxide particles have no edges, and adding spherical cerium oxide particles to the polishing solution can significantly improve the surface quality of the substrate after polishing. Quadrangular prism-shaped cerium oxide particles have a good removal effect on stepped silicon oxide to a certain extent. At the same time, due to their flat surface, they can reduce the surface roughness of the silicon substrate after polishing. Using quadrangular prism-shaped cerium oxide particles in the polishing solution can improve substrate processing efficiency while improving substrate surface quality.

[0015] The average particle size of the cerium oxide particles is 20nm-2000nm, for example, it can be 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1000nm, 1200nm, 1400nm, 1600nm, 1800nm ​​or 2000nm, including but not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0016] In this invention, when the cerium oxide particles are triangular or quadrangular prisms, the average particle size refers to the average size of the longest side of the cerium oxide particles; when the cerium oxide particles are spherical, the average particle size refers to the average diameter of the cerium oxide particles.

[0017] Flake particles were selected as an anti-precipitant. On the one hand, the flake particles act between cerium oxide particles to maintain the dispersion of cerium oxide particles and their stability in the polishing solution, preventing the polishing solution from stratifying. On the other hand, the flake particles can also be adsorbed on the surface of cerium oxide particles and the surface of silicon carbide substrate, further improving the scratches on the substrate during the polishing process and reducing scratches.

[0018] The average size of the sheet-like particles along their length is 0.5μm-3μm, for example, it can be 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1μm, 1.2μm, 1.4μm, 1.6μm, 1.8μm, 2μm, 2.2μm, 2.4μm, 2.6μm, 2.8μm or 3μm, and the average size along their width is 0.5μm-3μm, for example, it can be 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1μm, 1.2μm, 1.4μm, 1.6μm, 1.8μm, 2μm, 2.2μm, 2.4μm, 2.6μm, 2.8μm or 3μm, including but not limited to the listed values, and other unlisted values ​​within the range are also applicable. The thickness of the sheet-like particles used in this invention is a single-digit molecular size, and is not specifically limited. For example, the thickness of the sheet-like particles can be 1nm-9nm, such as 1nm, 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm or 9nm, including but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0019] This invention optimizes the composition of the polishing slurry, selecting cerium oxide particles of specific shape and size as abrasive particles. Dispersants and anti-settling agents act on the surface and between the cerium oxide particles, respectively, preventing particle aggregation and maintaining the polishing slurry without stratification for a longer period. This ensures a high degree of dispersion of the cerium oxide particles in the slurry, facilitating their abrasive action. Combined with the oxidation effect of the oxidant on the silicon carbide substrate, this significantly improves the removal rate of the silicon carbide substrate and results in a marked improvement in the surface quality of the workpiece after polishing, reducing scratches. Furthermore, the flake-like particles can adsorb onto the cerium oxide particles and the silicon carbide substrate surface, further mitigating scratches during polishing and reducing overall damage.

[0020] Preferably, the flake particles comprise montmorillonite and / or bentonite.

[0021] Preferably, the cerium oxide particles include sintered cerium oxide particles and / or colloidal cerium oxide particles. Sintered cerium oxide particles are low in cost and have a larger particle size, resulting in a higher silicon carbide substrate thinning rate. Colloidal particles can have a smaller and more concentrated particle size, resulting in a higher substrate surface quality after polishing, but with a slower polishing rate.

[0022] Preferably, the average particle size of the cerium oxide particles is 30nm-1000nm, for example, it can be 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, or 1000nm, including but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0023] Preferably, the polishing liquid comprises, by weight:

[0024]

[0025]

[0026] This invention does not impose specific limits on the solid content of the polishing fluid, but can be adapted to meet polishing requirements.

[0027] The oxidant in the polishing liquid of the present invention has a weight ratio of 1 to 10 parts, for example, it can be 1 part, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts or 10 parts, including but not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0028] The cerium oxide particles in the polishing liquid of the present invention are 1.5 to 15 parts by weight, for example, 1.5, 3, 4.5, 6, 7.5, 9, 10.5, 12, 13.5 or 15 parts, including but not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0029] The weight of the dispersant in the polishing liquid of the present invention is 0.25-2.5 parts, for example, it can be 0.25 parts, 0.5 parts, 0.75 parts, 1 part, 1.25 parts, 1.5 parts, 1.75 parts, 2 parts, 2.25 parts or 2.5 parts, including but not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0030] The anti-settling agent in the polishing liquid of the present invention has a weight ratio of 0.25 parts to 2.5 parts, for example, it can be 0.25 parts, 0.5 parts, 0.75 parts, 1 part, 1.25 parts, 1.5 parts, 1.75 parts, 2 parts, 2.25 parts or 2.5 parts, including but not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0031] The surfactant in the polishing liquid of the present invention is 0.025-0.25 parts by weight, for example, 0.025 parts, 0.05 parts, 0.075 parts, 0.1 parts, 0.125 parts, 0.15 parts, 0.175 parts, 0.2 parts, 0.225 parts or 0.25 parts, including but not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0032] The water content in the polishing liquid of the present invention is 60-100 parts by weight, for example, it can be 60, 65, 70, 75, 80, 85, 90, 95 or 100 parts, including but not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0033] Preferably, the nitrate comprises any one or a combination of at least two of sodium nitrate, potassium nitrate, ammonium nitrate, calcium nitrate, magnesium nitrate, aluminum nitrate, ferric nitrate, cobalt nitrate, copper nitrate, zinc nitrate, or silver nitrate. Typical but non-limiting combinations include combinations of magnesium nitrate and aluminum nitrate, copper nitrate and magnesium nitrate, aluminum nitrate and copper nitrate, copper nitrate and sodium nitrate, copper nitrate and ammonium nitrate, copper nitrate and cobalt nitrate, or copper nitrate and zinc nitrate.

[0034] Preferably, the nitrate includes any one or a combination of at least two of magnesium nitrate, aluminum nitrate, or copper nitrate, with copper nitrate being the most preferred.

[0035] Preferably, the oxidant comprises any one or a combination of at least two of potassium permanganate, sodium permanganate, potassium perchlorate, potassium chlorate, potassium periodate, sodium periodate, hydrogen peroxide, or potassium persulfate. Typical but non-limiting combinations include combinations of potassium permanganate and sodium permanganate, combinations of potassium perchlorate and potassium chlorate, combinations of potassium periodate and sodium periodate, or combinations of hydrogen peroxide and potassium persulfate.

[0036] Preferably, the oxidant is potassium permanganate and / or sodium permanganate.

[0037] Preferably, the oxidant is potassium permanganate.

[0038] Adding a dispersant to the polishing slurry enables the cerium oxide particles to be evenly distributed in the slurry, ensuring consistent grinding efficiency throughout the polishing process.

[0039] Preferably, the dispersant comprises any one or a combination of at least two of sodium hexametaphosphate, sodium pyrophosphate, sodium tripolyphosphate, alkyl aryl phosphate, alkylbenzene sulfonate, dialkyl sulfosuccinate, trimethylstearamide chloride, or polyoxyethylene alkylphenol ether. Typical but non-limiting combinations include combinations of sodium hexametaphosphate and sodium pyrophosphate, combinations of sodium tripolyphosphate and alkyl aryl phosphate, combinations of alkylbenzene sulfonate and dialkyl sulfosuccinate, or combinations of trimethylstearamide chloride and polyoxyethylene alkylphenol ether.

[0040] Preferably, the surfactant comprises any one or a combination of at least two of hexadecyltrimethylammonium bromide, sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, sodium perfluorononenoxybenzenesulfonate, sodium polyacrylate, and 2-acrylamide-2-methylpropanesulfonic acid. Typical but non-limiting combinations include a combination of hexadecyltrimethylammonium bromide and sodium dodecylbenzenesulfonate, a combination of sodium dodecyl sulfate and sodium perfluorononenoxybenzenesulfonate, or a combination of sodium polyacrylate and 2-acrylamide-2-methylpropanesulfonic acid.

[0041] Preferably, the surfactant comprises sodium carboxymethyl cellulose and / or sodium perfluorononenoxybenzenesulfonate.

[0042] Preferably, the pH of the polishing solution is 3.5-6.5. For example, the pH of the polishing solution can be 3.5, 4, 4.5, 5, 5.5, 6 or 6.5, including but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0043] Preferably, the pH adjuster is an inorganic acid.

[0044] Preferably, the pH adjuster comprises any one or a combination of at least two of hydrochloric acid, nitric acid, sulfuric acid, or phosphoric acid. Typical but non-limiting combinations include combinations of hydrochloric acid and nitric acid, sulfuric acid and phosphoric acid, nitric acid and sulfuric acid, or phosphoric acid and hydrochloric acid, with nitric acid being the most preferred.

[0045] The polishing slurry provided by the present invention can be prepared by conventional methods in the art, without any particular limitation. For example, the polishing slurry can be prepared by mixing the components of the polishing slurry in the present application according to a specific mass ratio and then aging it.

[0046] Secondly, the present invention provides an application of the polishing slurry as described in the first aspect, wherein the polishing slurry is applied to the polishing of semiconductor devices, such as to the polishing of silicon carbide substrates.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] This invention optimizes the components in the polishing slurry and selects cerium oxide particles with a hardness lower than silicon carbide as abrasive particles, which reduces scratches on the silicon carbide surface after polishing and significantly improves the surface quality of silicon carbide after polishing. The synergistic effect of dispersant and anti-precipitant ensures the dispersibility and stability of cerium oxide particles in the polishing slurry. Combined with the oxidation effect of oxidant, it greatly improves the removal rate of silicon carbide substrate. Attached Figure Description

[0049] Figure 1 This is an SEM image of the cerium oxide particles used in the polishing solution in Example 1.

[0050] Figure 2 This is an SEM image of the cerium oxide particles used in the polishing solution in Example 2.

[0051] Figure 3 This is a SEM image of the cerium oxide particles used in the polishing solution in Example 3.

[0052] Figure 4 This is an SEM image of the cerium oxide particles used in the polishing solution in Example 4.

[0053] Figure 5 This is an SEM image of the cerium oxide particles used in the polishing solution in Example 5.

[0054] Figure 6 This is an SEM image of the cerium oxide particles used in the polishing solution in Example 6.

[0055] Figure 7 This is an AFM image of the silicon carbide surface after polishing with the polishing solution in Example 1.

[0056] Figure 8 This is an AFM image of the silicon carbide surface after polishing with the polishing solution in Example 2.

[0057] Figure 9 This is an AFM image of the silicon carbide surface after polishing with the polishing solution in Example 3.

[0058] Figure 10 This is an AFM image of the silicon carbide surface after polishing with the polishing solution in Example 4.

[0059] Figure 11 This is an AFM image of the silicon carbide surface after polishing with the polishing solution in Example 5.

[0060] Figure 12 This is an AFM image of the silicon carbide surface after polishing with the polishing solution in Example 6. Detailed Implementation

[0061] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0062] Example 1

[0063] This embodiment provides a polishing solution. The preparation method of the polishing solution includes mixing 2 parts by weight of potassium permanganate, 1 part by weight of copper nitrate, 3 parts by weight of cerium oxide particles, 0.5 parts by weight of sodium hexametaphosphate, 0.5 parts by weight of montmorillonite, 0.05 parts by weight of sodium dodecylbenzenesulfonate and 80 parts by weight of water, adjusting the pH of the mixed solution to 4 with nitric acid, and aging for 40 minutes to obtain the polishing solution.

[0064] In this embodiment, the cerium oxide particles have a diameter of 100 nm, a triangular prism shape, an average length dimension of 1 μm, an average width dimension of 1 μm, and a thickness of 6 nm.

[0065] The SEM image of the cerium oxide particles in this embodiment is as follows: Figure 1 As shown.

[0066] Example 2

[0067] This embodiment provides a polishing solution, which is prepared by mixing 1.5 parts by weight of sodium permanganate, 1 part by weight of aluminum nitrate, 1.55 parts by weight of cerium oxide particles, 0.25 parts by weight of sodium pyrophosphate, 0.8 parts by weight of bentonite, 0.025 parts by weight of sodium carboxymethyl cellulose and 100 parts by weight of water, adjusting the pH of the mixed solution to 3.5 with hydrochloric acid, and aging for 45 minutes to obtain the polishing solution.

[0068] In this embodiment, the cerium oxide particles have a diameter of 100 nm, a quadrangular prism shape, an average length dimension of 1 μm, an average width dimension of 1 μm, and a thickness of 4 nm.

[0069] The SEM image of the cerium oxide particles in this embodiment is as follows: Figure 2 As shown.

[0070] Example 3

[0071] This embodiment provides a polishing solution, which is prepared by mixing 5 parts by weight of potassium persulfate, 1 part by weight of magnesium nitrate, 7 parts by weight of cerium oxide particles, 1 part by weight of polyoxyethylene alkylphenol ether, 1.5 parts by weight of montmorillonite, 0.1 parts by weight of sodium perfluorononenoxybenzenesulfonate and 70 parts by weight of water, adjusting the pH of the mixed solution to 3.8 with phosphoric acid, and aging for 40 minutes to obtain the polishing solution.

[0072] In this embodiment, the cerium oxide particles have a diameter of 100 nm, are spherical in shape, and have an average length dimension of 1 μm, an average width dimension of 1 μm, and a thickness of 2 nm.

[0073] The SEM image of the cerium oxide particles in this embodiment is as follows: Figure 3 As shown.

[0074] Example 4

[0075] This embodiment provides a polishing solution. The preparation method of the polishing solution includes mixing 7 parts by weight of potassium permanganate, 1 part by weight of potassium nitrate, 8 parts by weight of cerium oxide particles, 1.5 parts by weight of sodium hexametaphosphate, 2 parts by weight of montmorillonite, 0.12 parts by weight of sodium dodecylbenzenesulfonate and 80 parts by weight of water, adjusting the pH of the mixed solution to 4.5 with nitric acid, and aging for 50 minutes to obtain the polishing solution.

[0076] In this embodiment, the cerium oxide particles have a diameter of 200 nm, a triangular prism shape, an average length dimension of 2 μm, an average width dimension of 2 μm, and a thickness of 9 nm.

[0077] The SEM image of the cerium oxide particles in this embodiment is as follows: Figure 4 As shown.

[0078] Example 5

[0079] This embodiment provides a polishing solution. The preparation method of the polishing solution includes mixing 8 parts by weight of potassium permanganate, 1 part by weight of copper nitrate, 12 parts by weight of cerium oxide particles, 2 parts by weight of sodium hexametaphosphate, 2.2 parts by weight of montmorillonite, 0.2 parts by weight of sodium dodecylbenzenesulfonate and 90 parts by weight of water, adjusting the pH of the mixed solution to 4 with nitric acid, and aging for 40 minutes to obtain the polishing solution.

[0080] In this embodiment, the cerium oxide particles have a diameter of 200 nm, a prismatic shape, an average length of 3 μm, an average width of 2 μm, and a thickness of 7 nm.

[0081] The SEM image of the cerium oxide particles in this embodiment is as follows: Figure 5 As shown.

[0082] Example 6

[0083] This embodiment provides a polishing solution. The preparation method of the polishing solution includes mixing 8 parts by weight of potassium permanganate, 1 part by weight of copper nitrate, 15 parts by weight of cerium oxide particles, 2.5 parts by weight of sodium hexametaphosphate, 2.5 parts by weight of montmorillonite, 0.25 parts by weight of sodium dodecylbenzenesulfonate and 60 parts by weight of water, adjusting the pH of the mixed solution to 4 with nitric acid, and aging for 40 minutes to obtain the polishing solution.

[0084] In this embodiment, the cerium oxide particles have a diameter of 200 nm, are spherical in shape, and have an average length dimension of 3 μm, an average width dimension of 3 μm, and a thickness of 6 nm.

[0085] The SEM image of the cerium oxide particles in this embodiment is as follows: Figure 6 As shown.

[0086] Example 7

[0087] This embodiment provides a polishing fluid, which is the same as that in Example 1 except that the particle size of the cerium oxide particles is 30 nm.

[0088] Example 8

[0089] This embodiment provides a polishing fluid, which is the same as that in Example 1 except that the particle size of the cerium oxide particles is 1000 nm.

[0090] Example 9

[0091] This embodiment provides a polishing liquid, which is the same as in Example 1 except that the mass fraction of cerium oxide particles is adjusted to 0.5 parts.

[0092] Example 10

[0093] This embodiment provides a polishing fluid, which is the same as in Example 1 except that the mass fraction of cerium oxide particles is adjusted to 20 parts.

[0094] Example 11

[0095] This embodiment provides a polishing fluid, which is the same as in Example 1 except that the mass fraction of montmorillonite is adjusted to 0.1 parts.

[0096] Example 12

[0097] This embodiment provides a polishing fluid, which is the same as in Example 1 except that the mass of montmorillonite is adjusted to 5 parts.

[0098] Example 13

[0099] This embodiment provides a polishing solution, which is the same as in Example 1 except that the mass fraction of sodium hexametaphosphate is adjusted to 0.1 parts.

[0100] Example 14

[0101] This embodiment provides a polishing solution, which is the same as in Example 1 except that the mass fraction of sodium hexametaphosphate is adjusted to 3.5 parts.

[0102] Comparative Example 1

[0103] This comparative example provides a polishing fluid that is identical to that of Example 1, except that the average dimension of the montmorillonite in the length direction is 0.5 μm and the average dimension in the width direction is 0.2 μm.

[0104] Comparative Example 2

[0105] This comparative example provides a polishing fluid that is identical to that of Example 1, except that the average dimension of the montmorillonite in the length direction is 5 μm and the average dimension in the width direction is 5 μm.

[0106] Comparative Example 3

[0107] This comparative example provides a polishing solution that is identical to that of Example 1, except that the cerium oxide particles have a particle size of 10 nm.

[0108] Comparative Example 4

[0109] This comparative example provides a polishing solution that is identical to that of Example 1, except that the cerium oxide particles have a particle size of 3000 nm.

[0110] Comparative Example 5

[0111] This comparative example provides a polishing solution that is identical to that in Example 1, except that montmorillonite is replaced with an equal part by weight of N-methylpyrrolidone solution of fumed silica-modified polyurea.

[0112] Comparative Example 6

[0113] This comparative example provides a polishing fluid that is identical to that of Example 1 except that montmorillonite is not added.

[0114] Comparative Example 7

[0115] This comparative example provides a polishing solution that is identical to that of Example 1 except that sodium hexametaphosphate is not added.

[0116] Performance testing:

[0117] Polishing experiments were conducted using a 16B polishing machine manufactured by Mingzheng Electronics Assembly Co., Ltd. The polishing substrate was a 6-inch 4H-SiC substrate, the polishing pad was SUBA800, the polishing pressure was 500 kg, the polishing speed was 35 rpm, the polishing slurry flow rate was 1200 ml, and the polishing time was 1 hour. The polishing experiment was conducted at room temperature. After polishing, the silicon carbide substrate was rinsed with water for 3 minutes and then dried with nitrogen gas. The thickness and surface roughness were measured. The test results are shown in Table 1. The AFM images of the silicon carbide surface after polishing with the polishing slurry in Examples 1-6 are shown below. Figures 7-12 As shown.

[0118] Table 1

[0119]

[0120]

[0121] Based on the test results of Examples 1-8, it can be determined that the present invention optimizes the components in the polishing slurry, selects cerium oxide particles with a hardness lower than silicon carbide as abrasive particles, and ensures the dispersibility and stability of cerium oxide particles in the polishing slurry under the combined action of dispersants and anti-precipitants. Combined with the oxidizing effect of oxidants, this significantly improves the removal rate of silicon carbide substrates and reduces scratches on the silicon carbide surface after polishing, resulting in a significant improvement in the surface quality of the polished silicon carbide. The polishing slurry provided by the present invention can achieve a removal rate of over 1.8 μm / h for silicon carbide substrates. In Example 8, when 1000 nm triangular prism-shaped cerium oxide particles were used, the removal rate of silicon carbide substrates could even reach 7.1 μm / h. In Example 5, when 200 nm quadrature prism-shaped cerium oxide particles were used, the removal rate of silicon carbide substrates could reach 3.7 μm / h, with only a few scratches and a roughness as low as 0.0847 nm. The polishing slurry provided by this invention only requires minor adjustments to the composition and selection of the shape of the cerium oxide particles to meet the needs of various application scenarios, such as those with high requirements for removal rate of silicon carbide substrates or high requirements for the quality of silicon carbide substrates after polishing.

[0122] Based on the test results of Examples 1 and 9-10, the mass fraction of cerium oxide particles affects the removal rate of silicon dioxide after oxidation of the silicon carbide substrate. This removal rate should match the oxidation rate. When the oxidation rate is constant, the removal rate of the silicon carbide substrate reaches saturation. Even if the mass fraction of cerium oxide particles is increased, the removal efficiency of the silicon carbide substrate cannot be further improved. If the mass fraction of cerium oxide particles is too small, the removal rate of silicon dioxide, the oxidation product on the silicon carbide surface, is not as fast as the oxidation rate of the silicon carbide substrate, resulting in the inability to remove silicon dioxide in time and leaving scratches.

[0123] Based on the test results of Examples 1 and 11-12, the mass fraction of montmorillonite affects the uniform distribution of cerium oxide particles in the polishing slurry and the viscosity of the polishing slurry. If the mass fraction of whole montmorillonite is too large, it will lead to excessively high viscosity of the polishing slurry and slow flow rate, which will greatly hinder the polishing rate. If the mass fraction of whole montmorillonite is too small, it will cause cerium oxide particles in the polishing slurry to settle too quickly, resulting in unstable polishing efficiency and scratches on the substrate surface after processing.

[0124] Based on the test results of Examples 1 and 13-14, the mass fraction of the dispersant affects the polishing effect. If the mass fraction of the dispersant is too large, the excessive dispersant will also compress the double electric layer of cerium oxide particles, causing cerium oxide particles to agglomerate, destroying the stability of the polishing fluid system, and greatly inhibiting the polishing rate. If the mass fraction of the dispersant is too small, the dispersive repulsion applied between cerium oxide particles will be too small, which will also lead to cerium oxide particle agglomeration. Both excessive and insufficient mass fraction of the dispersant will worsen the polishing effect.

[0125] According to the test results of Example 1 and Comparative Examples 1-2, the average size of the anti-precipitant flake particles affects the polishing effect. If the average size of the flake particles in the length and width directions is too large, that is, the surface area of ​​the flake particles is too large, they will adhere to the substrate surface, hindering the oxidation efficiency and the removal efficiency of silicon dioxide after oxidation of the silicon carbide substrate. If the surface area of ​​the flake particles is too large or too small, it cannot provide sufficient protection for the substrate surface, resulting in scratches on the substrate surface after processing.

[0126] Based on the test results of Example 1 and Comparative Examples 3 and 4, the particle size of cerium oxide particles affects the polishing rate and coarseness. If the particle size of cerium oxide particles is too small, the polishing rate is too slow; if the particle size of cerium oxide particles is too large, the substrate surface quality deteriorates.

[0127] According to the test results of Example 1 and Comparative Example 5, if the anti-precipitant is replaced with the N-methylpyrrolidone solution of fumed silica-modified polyurea used in the prior art, the stability of the polishing slurry deteriorates, and it cannot improve the scratches on the substrate during the polishing process, resulting in an increase in scratches on the substrate surface.

[0128] According to the test results of Example 1 and Comparative Example 6, if no anti-settling agent is added, the stability of the polishing slurry deteriorates and cannot improve the scratches on the substrate during the polishing process, resulting in an increase in scratches on the substrate surface.

[0129] According to the test results of Example 1 and Comparative Example 7, if no dispersant is added, the cerium oxide particles cannot be evenly distributed in the polishing liquid, the polishing liquid appears sandy, and polishing tests cannot be performed.

[0130] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A polishing liquid, characterized in that, The polishing solution, by weight, comprises 1 part nitrate, 1-10 parts oxidant, 1.5-15 parts cerium oxide particles, 0.25-2.5 parts dispersant, 0.25-0.5 parts anti-precipitant, 0.025-0.25 parts surfactant, 60-100 parts water, and pH adjuster. The cerium oxide particles have a shape including triangular prisms and / or quadrangular prisms; the average particle size of the cerium oxide particles is 100nm-200nm. The anti-settling agent comprises flake particles, and the flake particles comprise montmorillonite; The average size of the sheet-like particles along the length direction is 1μm-3μm, the average size along the width direction is 1μm-3μm, and the thickness of the sheet-like particles is 2nm-9nm; The surfactant comprises any one or a combination of at least two of the following: hexadecyltrimethylammonium bromide, sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, sodium perfluorononenoxybenzenesulfonate, sodium polyacrylate, sodium carboxymethyl cellulose, and 2-acrylamide-2-methylpropanesulfonic acid; The oxidant includes any one or a combination of at least two of potassium permanganate, sodium permanganate, potassium perchlorate, potassium chlorate, potassium periodate, sodium periodate, hydrogen peroxide, or potassium persulfate. The dispersant comprises any one or a combination of at least two of the following: sodium hexametaphosphate, sodium pyrophosphate, sodium tripolyphosphate, alkylaryl phosphate, alkylbenzene sulfonate, dialkyl sulfosuccinate, trimethylstearamide chloride, or polyoxyethylene alkylphenol ether. The pH of the polishing solution is 3.5-6.

5.

2. The polishing slurry as described in claim 1, characterized in that, The cerium oxide particles include sintered cerium oxide particles and / or colloidal cerium oxide particles.

3. The polishing slurry as described in claim 1, characterized in that, The nitrates include any one or a combination of at least two of sodium nitrate, potassium nitrate, ammonium nitrate, calcium nitrate, magnesium nitrate, aluminum nitrate, ferric nitrate, cobalt nitrate, copper nitrate, zinc nitrate, or silver nitrate.

4. The polishing slurry as described in claim 1, characterized in that, The pH adjuster includes any one or a combination of at least two of hydrochloric acid, nitric acid, sulfuric acid, or phosphoric acid.

5. An application of the polishing liquid as described in any one of claims 1-4, characterized in that, The polishing slurry is used for polishing semiconductor devices.

Images