Chemical mechanical polishing composition for polishing silicon carbide substrate and polishing method thereof

Abstract

The invention provides a chemical mechanical polishing composition for polishing a silicon carbide substrate and a polishing method thereof. The chemical mechanical polishing composition comprises cerium oxide abrasive particles, an oxidizing agent and an oxidizing agent regenerant. Wherein the oxidant comprises permanganate, and the permanganate is reduced into Mn < 2 + > ions in the oxidation reaction process; and an oxidant regenerant comprising bismuthate that oxidizes the Mn < 2 + > ions to permanganate, thereby maintaining the concentration of the permanganate in the composition.

Description

Technical Field

[0001] This application relates to the field of chemical mechanical polishing technology, and more particularly to a chemical mechanical polishing composition for polishing silicon carbide substrates and a polishing method thereof. Background Technology

[0002] Chemical mechanical polishing (CMP) is a surface planarization technique that combines chemical reactions with mechanical abrasion, and is widely used in precision machining fields such as semiconductor manufacturing. Depending on the process flow, CMP can be divided into single-pass polishing and multi-pass polishing. Single-pass polishing uses only one polishing composition throughout the entire process to achieve material removal and planarization. Multi-pass polishing, on the other hand, employs a staged approach. Typically, a high-removal-rate coarse polishing composition is used for rapid material removal first, followed by a fine-particle or particle-free fine polishing composition for surface finishing, resulting in an ultra-smooth surface with lower surface roughness and fewer defects.

[0003] Therefore, in single-pass polishing, to achieve a planarization effect comparable to multiple-pass polishing while simplifying the process, higher overall performance requirements are placed on the polishing composition used. This composition not only needs a high material removal rate for rapid finishing and planarization, but also needs to effectively control surface defects and obtain good surface smoothness and uniformity without requiring secondary fine polishing.

[0004] However, how to balance chemical reactivity and surface quality control in a chemical mechanical polishing composition remains a key problem that needs to be solved in current CMP technology. Summary of the Invention

[0005] This application provides a chemical mechanical polishing composition and method for polishing silicon carbide substrates, wherein chamfered octahedral cerium oxide abrasive particles and an oxidant regenerator are added to the composition, thereby improving the removal rate while reducing scratches.

[0006] To achieve the above objectives, the embodiments of this application adopt the following technical solutions:

[0007] In a first aspect, embodiments of this application provide a chemical mechanical polishing composition for polishing silicon carbide substrates, comprising: cerium oxide abrasive particles; and an oxidant, including permanganate, wherein the permanganate is reduced to Mn during the oxidation reaction. 2 + ions; and oxidizing regenerators, including bismuthates, for the Mn 2 + Ion oxidation generates permanganate, thereby maintaining the concentration of the permanganate in the composition.

[0008] According to some embodiments of this application, the bismuthate includes sodium bismuthate.

[0009] According to some embodiments of this application, the bismuthate comprises 0.01-5 wt.% of the composition by mass.

[0010] According to some embodiments of this application, the pH value of the composition is less than 7.

[0011] According to some embodiments of this application, the composition further includes a catalyst comprising a nitrate, wherein the catalyst does not include bismuthates.

[0012] According to some embodiments of this application, the cerium oxide abrasive grains include chamfered octahedral cerium oxide abrasive grains.

[0013] According to some embodiments of this application, the ratio of the cumulative volume of abrasive grains having an average particle size more than twice that measured by scanning electron microscopy to the cumulative volume of abrasive grains having a particle size less than that measured by scanning electron microscopy in the chamfered octahedral cerium oxide abrasive grains is at least 0.1.

[0014] According to some embodiments of this application, the coefficient of variation of the average particle size of the chamfered octahedral cerium oxide abrasive grains, as measured by scanning electron microscopy, is greater than 30%.

[0015] According to some embodiments of this application, the polydispersity index of the chamfered octahedral cerium oxide abrasive grains, as measured by scanning electron microscopy, is at least 0.1.

[0016] In a second aspect, this application provides a polishing method for a silicon carbide substrate, the method utilizing a chemical mechanical polishing composition as described in any one of the first aspects above to polish the silicon carbide substrate. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this specification, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this specification. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A scanning electron microscope image of chamfered octahedral cerium oxide provided according to an embodiment of this specification is shown. Detailed Implementation

[0019] The following description provides specific application scenarios and requirements for this specification, intended to enable those skilled in the art to make and use the contents of this specification. Various partial modifications to the disclosed embodiments will be apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments and applications without departing from the spirit and scope of this specification. Therefore, this specification is not limited to the embodiments shown, but rather to the widest scope consistent with the claims.

[0020] The terminology used herein is for the purpose of describing particular exemplary embodiments only and is not restrictive. For example, unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “the” used herein may also include the plural forms. When used in this specification, the terms “comprising,” “including,” and / or “containing” mean that the associated integers, steps, operations, elements, and / or components are present, but do not exclude the presence of one or more other features, integers, steps, operations, elements, components, and / or groups, or that other features, integers, steps, operations, elements, components, and / or groups may be added to the system / method.

[0021] In this application, "X includes at least one of A, B, or C" means that X includes at least A, or X includes at least B, or X includes at least C. That is, X can include any combination of A, B, and C, or any combination of A, B, and C, as well as other possible content / elements. The arbitrary combination of A, B, and C can be A, B, C, AB, AC, BC, or ABC.

[0022] Considering the following description, these and other features of this specification, as well as the operation and function of related structural elements, and the economy of assembly and manufacture of components, can be significantly improved. This description also includes all figures and text in the accompanying drawings, all of which form part of this specification. However, it should be clearly understood that the drawings are for illustrative and descriptive purposes only and are not intended to limit the scope of this specification. It should also be understood that the drawings are not drawn to scale.

[0023] In the CMP process on silicon carbide substrates, the chemical mechanical polishing (CMP) composition is typically recycled. To maintain the oxidizing capacity of the CMP composition, oxidants such as permanganate are usually added. These oxidants react with the substrate surface to form an easily removable oxide layer, thereby improving material removal rate and surface smoothness. However, with the recycling of the polishing slurry, the oxidant is continuously consumed in the reaction, leading to a gradual decrease in its concentration. This, in turn, affects the polishing effect, resulting in reduced removal rate, increased surface roughness, and increased defect density.

[0024] Therefore, this application provides a chemical mechanical polishing (CMP) composition and a polishing method for polishing silicon carbide substrates. An oxidant regenerator is added to the CMP composition. This oxidant regenerator can catalyze the conversion of oxidant products consumed during the polishing process back into active oxidants, thereby effectively maintaining a stable oxidant concentration in the CMP composition. This regeneration mechanism not only extends the service life of the CMP composition but also improves surface smoothness and gloss while increasing material removal rate, reducing scratches and micro-defects, thus improving overall polishing quality and process stability. It is particularly suitable for planarization of silicon carbide materials with stringent surface performance requirements in high-precision semiconductor manufacturing.

[0025] Before describing the specific embodiments in this specification, the application scenarios of this specification will be introduced as follows, wherein the chemical mechanical polishing composition is referred to as the composition.

[0026] The compositions provided in this specification can be used in chemical mechanical polishing (CMP) processes for hard or brittle materials where high surface quality standards need to be achieved while maintaining high removal efficiency. Specifically, the compositions provided in this specification can be used for CMP polishing of substrates such as silicon carbide, alumina (sapphire), carbon (diamond), and gallium nitride. The following description uses the composition for polishing silicon carbide substrates as an example.

[0027] The composition of this invention is particularly suitable for efficient and high-quality chemical mechanical polishing of silicon carbide substrates, exhibiting excellent performance especially in single-pass polishing processes. Due to the characteristics of its crystal structure, silicon carbide wafers are not mirror-symmetrical and are typically divided into silicon-face and carbon-face surfaces with different properties. This composition shows good adaptability to both silicon and carbon surfaces, exhibiting superior polishing effects on the silicon surface, characterized by higher removal rates and lower surface defect density. This composition can achieve fine finishing of the silicon carbide wafer surface without relying on multi-step polishing processes, meeting the requirements for high flatness and low roughness. The silicon carbide substrate can be undoped or doped (e.g., nitrogen-doped, aluminum-doped), and in specific applications, it may also contain impurities such as aluminum oxide (Al₂O₃), iron oxide (Fe₂O₃), or calcium oxide (CaO).

[0028] The composition includes cerium oxide abrasive grains. These abrasive grains provide both mechanical abrasive action, removing softened silicon carbide substrate through physical friction, and chemical abrasive action, removing abrasive debris by forming silicon-oxygen-cerium bonds with oxidized silicon atoms. Among various cerium oxide abrasive grains, the cerium oxide abrasive grains of this embodiment include chamfered octahedral cerium oxide abrasive grains. The term "chamfered octahedron" as used in this application refers to a polyhedron, specifically a polyhedron with eight hexagonal faces and six square faces. Within the scope of this application, "chamfered octahedral cerium oxide" is not limited to an ideal truncated octahedral shape, but also includes octahedrons whose shape changes due to manufacturing processes or other factors. For example, chamfered octahedral cerium oxide abrasive grains may have more or fewer than eight hexagonal faces, and / or more or fewer than six square faces. The hexagonal or square faces may exhibit shape deviations (such as imperfect symmetry, irregular side lengths, or slight curvature). In some embodiments, the surface of the chamfered octahedral cerium oxide abrasive grains may exhibit a certain degree of unevenness or deformation. Studies have found that the chamfered octahedral morphology can improve the surface morphology of silicon carbide substrates while still exhibiting a high removal rate.

[0029] In some embodiments, the chamfered octahedral cerium oxide abrasive grains are doped cerium oxide abrasive grains. Suitable dopants are, for example, metal ions (such as Ca, Mg, Zn, Zr, Sc, Y) or lanthanides (such as lanthanum, praseodymium, neodymium, promethium, or samarium). However, it has been found that the chamfered octahedral cerium oxide abrasive grains of the present invention can exhibit high removal rates even without dopants. Therefore, the chamfered octahedral cerium oxide abrasive grains are substantially dopant-free. Dopants may exist as impurities in the abrasive grains, and these impurities may originate from the raw materials or starting materials used to prepare the abrasive grains.

[0030] It should be noted that the chamfered octahedral cerium oxide abrasive grains may contain impurities. These impurities originate from the raw materials or processes used to prepare the abrasive grains and can be considered as not being part of the abrasive grain mixture; that is, these impurities are not added to the composition as a single component. This means that the impurities are not added in actual mass. The actual mass of the present invention is less than 30 ppm, further less than 20 ppm, further less than 10 ppm, and further less than 1 ppm. Here, ppm refers to weight ppm. It should be noted that the chamfered octahedral cerium oxide abrasive grains in this composition are preferably chamfered octahedral cerium oxide abrasive grains without impurities. For ease of illustration, the following description will use 100 wt% chamfered octahedral cerium oxide abrasive grains without impurities.

[0031] Chamfered octahedral cerium oxide abrasive grains can be sol-gel cerium oxide abrasive grains, that is, cerium oxide abrasive grains prepared by hydrolysis or sol-gel methods. Among them, sol-gel cerium oxide abrasive grains can be obtained by wet processes, such as precipitation (e.g., precipitation synthesis of cerium oxide), hydrolysis-condensation reaction, or hydrothermal methods.

[0032] The average particle size of the chamfered octahedral cerium oxide abrasive particles, as measured by scanning electron microscopy, is 10 nm–200 nm. In some embodiments, the average particle size of the chamfered octahedral cerium oxide abrasive particles, as measured by scanning electron microscopy, is 20 nm–100 nm. Furthermore, the average particle size of the chamfered octahedral cerium oxide abrasive particles, measured by scanning electron microscopy, is 10nm-20nm, 20nm-30nm, 30nm-40nm, 40nm-50nm, 50nm-60nm, 60nm-70nm, 70nm-80nm, 80nm-90nm, 80nm-90nm, 90nm-100nm, 100nm-110nm, 110nm-120nm, 120nm-130nm, 130nm-140nm, 140nm-150nm, 150nm-160nm, 160nm-170nm, 170nm-180nm, 180nm-190nm, and 190nm-200nm. The average particle size refers to the arithmetic mean of the maximum distance between two points on the particle boundary.

[0033] The particle size distribution of the chamfered octahedral cerium oxide abrasive grains can be described using the coefficient of variation (CV) of the average particle size measured by scanning electron microscopy. Further, the coefficient of variation of the average particle size CV = (σ / μ) × 100%, where σ is the standard deviation of the average particle size and μ is the average particle size measured by scanning electron microscopy. In this embodiment, the coefficient of variation of the average particle size of the chamfered octahedral cerium oxide abrasive grains measured by scanning electron microscopy is greater than 30%. Further, the coefficient of variation of the average particle size of the chamfered octahedral cerium oxide abrasive grains measured by scanning electron microscopy is greater than 31%, 32%, 33%, 34%, or 35%. It should be noted that the standard deviation and coefficient of variation of the average particle size are determined by SEM. Studies show that the coefficient of variation of the average particle size of the present invention can improve the removal rate of silicon carbide substrates.

[0034] The particle size distribution of chamfered octahedral cerium oxide abrasive grains can be described using the polydispersity index (PDI) measured by scanning electron microscopy. Chamfered octahedral cerium oxide abrasive grains exhibit a non-monodispersive particle size distribution. Further, the polydispersity index PDI = σ 2 / μ 2 Where σ is the standard deviation of the average particle size, and μ is the average particle size measured by scanning electron microscopy (SEM). It should be noted that the PDI measured by SEM differs fundamentally from that measured by dynamic light scattering (DLS) or laser diffraction. In this embodiment, the polydispersity index (PDI) of the chamfered octahedral cerium oxide abrasive particles, measured by SEM, is at least 0.1. Further, the PDI of the chamfered octahedral cerium oxide abrasive particles, measured by SEM, is at least 0.105, 0.110, 0.115, or 0.120. It should be noted that the standard deviation of the average particle size and the PDI are determined by SEM. Studies have shown that the PDI of this invention can improve the removal rate of silicon carbide substrates.

[0035] During the polishing process, the particle size of the chamfered octahedral cerium oxide abrasive grains affects the material removal rate of the substrate. Larger-diameter chamfered octahedral cerium oxide abrasive grains can enhance the material removal rate, while smaller-diameter grains can fill the gaps between the larger grains, thus preventing surface defects in the substrate material caused by the large-diameter grains. In this embodiment, at least 0.5% of the chamfered octahedral cerium oxide abrasive grains have a particle size greater than twice the average particle size as measured by scanning electron microscopy. Further, at least 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, or 1.7% of the chamfered octahedral cerium oxide abrasive grains have a particle size greater than twice the average particle size as measured by scanning electron microscopy.

[0036] In this scheme, the ratio of the cumulative volume of abrasive grains having an average particle size more than twice that measured by scanning electron microscopy to the cumulative volume of abrasive grains with a particle size less than that measured by scanning electron microscopy in the chamfered octahedral cerium oxide abrasive is at least 0.1. Further, the ratio of the cumulative volume of abrasive grains having an average particle size more than twice that measured by scanning electron microscopy to the cumulative volume of abrasive grains with a particle size less than that measured by scanning electron microscopy in the chamfered octahedral cerium oxide abrasive is at least 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.46, or 0.50. Studies have found that the aforementioned ratios can improve the removal rate of silicon carbide substrates.

[0037] In some embodiments, the chamfered octahedral cerium oxide abrasive grains are positively charged in the composition. The charge refers to the zeta potential, which can be measured, for example, by a Mastersizer S (Malvern Instruments). As known to those skilled in the art, the zeta potential is the potential at the interface between the moving fluid within the composition and the fluid-stabilized layer attached to the abrasive grains dispersed in the composition. A higher absolute value of the zeta potential results in stronger electrostatic repulsion between particles, thereby increasing the stability of the particle dispersion in the composition. The chamfered octahedral cerium oxide abrasive grains in the composition have a zeta potential of 5 mV to 40 mV at pH 2 to 4. For example, the chamfered octahedral cerium oxide abrasive grains in the composition have zeta potentials of 5 mV to 10 mV, 10 mV to 15 mV, 15 mV to 20 mV, 20 mV to 25 mV, 25 mV to 30 mV, and 35 mV to 40 mV at pH 2 to 4. It is understood that the range of zeta potentials mentioned above can be arbitrarily combined; for example, chamfered octahedral cerium oxide abrasive grains in the composition have a zeta potential of 15 mV to 30 mV at pH 2 to 4.

[0038] The composition includes abrasive grains. The abrasive grains provide a mechanical abrasive action, removing minute bumps and uneven portions from the surface of the silicon oxide substrate through physical friction, thereby planarizing the silicon oxide substrate. The weight percentage of abrasive grains in the composition is between 0.01 and 8 wt%. In some embodiments, the weight percentage of abrasive grains in the composition is between 0.1 and 5 wt%. In some embodiments, the weight percentage of abrasive grains in the composition is between 0.5 and 3 wt%. Furthermore, the weight ratio of abrasive particles in the composition can be selected from 0.01wt%-0.05wt%, 0.05wt%-0.1wt%, 0.1wt%-0.5wt%, 0.5wt%-1wt%, 1wt%-1.5wt%, 1.5wt%-2wt%, 2wt%-2.5wt%, 2.5wt%-3wt%, 3wt%-3.5wt%, 3.5wt%-4wt%, 4wt%-4.5wt%, 4.5wt%-5wt%, 5wt%-5.5wt%, 5.5wt%-6wt%, 6wt%-6.5wt%, 6.5wt%-7wt%, 7wt%-7.5wt%, and 7.5wt%-8wt%. It is understood that the above ranges of abrasive particle weight ratios can be arbitrarily combined; for example, the weight ratio of abrasive particles in the composition can range from 1.5wt% to 3.5wt%.

[0039] The composition also includes one or more chemical additives. These chemical additives can interact with abrasive particles and / or with the substrate and / or with the polishing pad during the CMP process. This interaction can be based on, for example, hydrogen bonds, van der Waals forces, electrostatic forces, etc. The chemical additives can be any component suitable for use as, for example, a removal rate promoter, a polishing rate inhibitor, a surfactant, a thickener, a regulator, a complexing agent, a chelating agent, a biocide, a dispersant, an oxidizing agent, a film-forming agent, an etching inhibitor, a catalyst, a terminating compound, a dissolution inhibitor, or a combination thereof.

[0040] The composition includes a liquid carrier. The liquid carrier can contain other components of the composition besides the liquid carrier itself, suspending these components in the liquid carrier and allowing them to contact the substrate for polishing. The liquid carrier can be an aqueous carrier, or any component suitable for suspending silica abrasive particles and chemical additives. The liquid carrier can be one of water, ethers (such as dioxane and tetrahydrofuran), and alcohols (such as methanol and ethanol), or a combination of water, ethers (such as dioxane and tetrahydrofuran), and alcohols (such as methanol and ethanol). When the liquid carrier is a combination of multiple components, the liquid carrier contains at least 50 wt% water, for example, the aqueous carrier contains 50 wt%, 70 wt%, 90 wt%, 95 wt%, or 99 wt% water. The liquid carrier is water. Further, the water is deionized water.

[0041] The composition includes an oxidizing agent. This oxidizing agent reacts with the surface of a silicon carbide substrate and promotes material removal during the polishing process. Specifically, the oxidizing agent chemically reacts with the surface of the silicon carbide substrate to generate a softer, easily removable oxide layer (such as silicon dioxide and carbon oxide). This oxide layer has lower hardness and higher reactivity than the original silicon carbide, which is beneficial for subsequent mechanical polishing, thereby improving material removal rate and surface smoothness.

[0042] The oxidizing agent may include organic oxidizing agents and / or inorganic oxidizing agents. Organic oxidizing agents may include, but are not limited to, benzoyl peroxide, peracetic acid, and di-tert-butyl peroxide. Inorganic oxidizing agents may include, but are not limited to, hydrogen peroxide, sodium peroxide, urea peroxide, percarbonate, chlorate, chlorite, bromate, iodic acid, iodate, nitrate, nitrite, chromate, permanganate, ferrate, perrhenate, perruthenate, monopersulfate, dipersulfate, persulfate, perboric acid and its salts, perchloric acid and its salts, perbromic acid and its salts, periodic acid and its salts, or combinations thereof. Among the numerous oxidizing agents mentioned above, permanganate, persulfate, iodate, periodate, hydrogen peroxide, chlorite, or combinations thereof are preferred as the oxidizing agent in this application. Further, permanganate is most preferred. Permanganate is an important class of inorganic oxidizing agents, including but not limited to potassium permanganate (KMnO4), sodium permanganate (NaMnO4), or combinations thereof.

[0043] When used, the composition comprises 2-20 wt% of an oxidizing agent. In some embodiments, the composition comprises 4-13 wt% of an oxidizing agent. In some embodiments, the composition comprises 5-10 wt% of an oxidizing agent. Further, the composition comprises 2 wt%-5 wt%, 5 wt%-8 wt%, 8 wt%-10 wt%, 10 wt%-13 wt%, 13 wt%-15 wt%, 15 wt%-18 wt%, or 18 wt%-20 wt% of an oxidizing agent. It is understood that the above ranges of oxidizing agents can be arbitrarily combined; for example, the composition may comprise 2-13 wt% of an oxidizing agent.

[0044] The composition also includes an oxidant regenerator. As mentioned above, the oxidant includes permanganates, such as potassium permanganate or sodium permanganate, which act as strong oxidants in applications such as silicon carbide polishing. However, during the reaction, the permanganate may be reduced to a lower valence state of Mn. 2 The presence of + ions reduces its oxidizing power. To maintain an effective concentration of permanganate in the composition, an oxidant regenerator is introduced into the system. This oxidant regenerator catalyzes the reaction to remove Mn+ ions. 2 The ions are re-oxidized to form permanganate, thus achieving the recycling and regeneration of the oxidant and maintaining the concentration of permanganate in the composition. This regeneration mechanism not only improves the utilization efficiency of the oxidant but also helps maintain the stability of the oxidizing power during polishing, thereby improving the material removal rate and surface finish.

[0045] In this application, the oxidant regenerator includes, but is not limited to, persulfates or bismuthates. Persulfates include at least one of ammonium persulfate ((NH4)2S2O8), potassium persulfate (K2S2O8), or sodium persulfate (Na2S2O8). Bismuthates include at least one of sodium bismuthate (NaBio3), potassium bismuthate (KBiO3), lithium bismuthate (LiBiO3), rubidium bismuthate (RbBiO3), cesium bismuthate (CsBiO3), ammonium bismuthate ((NH4)BiO3), or tetramethylammonium bismuthate. Among the numerous oxidant regenerators mentioned above, bismuthates are preferred as the oxidant regenerator in this application. Furthermore, sodium bismuthate is most preferred.

[0046] When used, the composition includes 0.01-5 wt% of an oxidant regenerator. In some embodiments, the composition includes 0.1-4 wt% of an oxidant regenerator. In some embodiments, the composition includes 0.1-1.5 wt% of an oxidant regenerator. Further, the composition includes an oxidant regenerator in amounts between 0.01 wt%-0.05 wt%, 0.05 wt%-0.1 wt%, 0.1 wt%-0.5 wt%, 0.5 wt%-1 wt%, 1 wt%-1.5 wt%, 1.5 wt%-2 wt%, 2 wt%-2.5 wt%, 2.5 wt%-3 wt%, 3 wt%-3.5 wt%, 3.5 wt%-4 wt%, 4 wt%-4.5 wt%, and 4.5 wt%-5 wt%. It is understood that the above ranges of oxidant regenerators can be arbitrarily combined; for example, the composition may include 0.1-2.5 wt% of an oxidant regenerator.

[0047] The composition includes a catalyst. The catalyst can synergistically work with the oxidant to improve the material removal rate of polished silicon carbide substrates. Specifically, during the polishing process of silicon carbide substrates, the catalyst and oxidant work synergistically to significantly improve the material removal rate by lowering the reaction activation energy, promoting the decomposition of the oxidant to generate highly reactive species (such as hydroxyl radicals), and enhancing the surface oxidation reaction rate. Simultaneously, the catalyst can also regulate the local chemical environment, enhancing the reaction efficiency of the oxidant and achieving more efficient and uniform surface removal, thereby improving the polishing effect and surface quality.

[0048] The catalyst includes at least one of the following: iron-containing compounds, copper-containing compounds, cobalt-containing compounds, manganese-containing compounds, cerium-containing compounds, aluminum-containing compounds, or nickel-containing compounds. Among them, iron-containing compounds include, but are not limited to, ferric sulfate, ferric chloride, ferric nitrate, ferric cyanide, ferric sulfate, ferric fluoride, ferric chloride, ferric bromide, ferric iodide, ferric perchlorate, ferric perbromate, ferric periodate, ferric ammonium sulfate, ferric acetate, ferric acetylacetone, ferric citrate, ferric gluconate, ferric malonate, ferric oxalate, ferric phthalate, ferric succinate, or combinations thereof. Copper-containing compounds include, but are not limited to, copper nitrate, copper sulfate, or combinations thereof. Cobalt-containing compounds include, but are not limited to, cobalt nitrate, cobalt sulfate, cobalt chloride, cobalt phosphonate, or combinations thereof. Manganese-containing compounds include, but are not limited to, manganese nitrate, manganese chloride, manganese phosphate, or combinations thereof. Cerium-containing compounds include, but are not limited to, cerium nitrate, cerium sulfate, cerium chloride, or combinations thereof. Aluminum-containing compounds include, but are not limited to, aluminum nitrate, aluminum chloride, aluminum isopropoxide, or combinations thereof. Nickel-containing compounds include, but are not limited to, nickel chloride, or combinations thereof. Among the numerous catalysts mentioned above, cerium nitrate, aluminum nitrate, ferric nitrate, cobalt nitrate, cobalt chloride, cobalt phosphate, copper nitrate, cerium chloride, manganese chloride, manganese phosphate, or combinations thereof are preferred as the catalysts of this application. Further, aluminum nitrate, cerium nitrate, manganese nitrate, or combinations thereof are most preferred.

[0049] It should be noted that in this composition, the catalyst and the oxidant regenerator are two functional components with significant differences in their mechanisms of action and chemical composition. The catalyst is used to accelerate the reaction process without participating in the final chemical change and does not contain bismuthates. The oxidant regenerator, on the other hand, is used to restore the activity of the oxidant, and its composition includes bismuthates as a key component.

[0050] The composition also includes a pH adjuster. This pH adjuster helps the composition achieve a suitable pH. The pH adjuster can be an acid or a salt thereof. The acid or its salt can be an organic acid, an inorganic acid, or a combination thereof. Organic acids include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, methylbutyric acid, hexanoic acid, dimethylbutyric acid, ethylbutyric acid, methylvaleric acid, heptanoic acid, methylhexanoic acid, octanoic acid, ethylhexanoic acid, benzoic acid, glycolic acid, salicylic acid, glyceric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, maleic acid, malic acid, phthalic acid, tartaric acid, citric acid, lactic acid, diethylene glycol, furanyl carboxylic acid, tetrahydrofuranic acid, methoxyacetic acid, methoxyphenylacetic acid, phenoxyacetic acid, methanesulfonic acid, ethanesulfonic acid, sulfosuccinic acid, benzenesulfonic acid, toluenesulfonic acid, phenylphosphonic acid, hydroxyethyl diphosphonic acid, and combinations thereof. Inorganic acids include hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, boric acid, carbonic acid, hypophosphorous acid, phosphorous acid, phosphoric acid, and combinations thereof.

[0051] In some embodiments, the preferred pH adjuster is an inorganic acid. In a particularly preferred embodiment, the inorganic acid is nitric acid.

[0052] It should be noted that when the catalyst is cerium nitrate, cerium nitrate can act as both a catalyst and a pH adjuster, so no additional pH adjuster needs to be added to the composition.

[0053] In some embodiments, the composition optionally further comprises a pH buffer. The pH buffer helps maintain a suitable pH in the composition. The pH buffer can be any suitable buffer. For example, the pH buffer can be a phosphate, sulfate, acetate, borate, ammonium salt, or a combination thereof.

[0054] The pH value of the composition affects the removal rate of silicon carbide substrate during CMP treatment. In some embodiments, the composition has a pH value below 7 when used. In some embodiments, the composition has a pH value of 2 to 4 when used. In some embodiments, the composition has a pH value of 2 to 3 when used. Further, the composition has a pH value between 2 and 3, 3 and 4, 4 and 5, 5 and 6, and 6 and 7 when used. It is understood that the above pH ranges can be arbitrarily combined; for example, the composition has a pH value of 2-5 when used.

[0055] Secondly, this application also provides a polishing method for a silicon carbide substrate. The method includes the following steps: (a) providing the above-described chemical mechanical polishing composition; (b) contacting the silicon carbide substrate with the chemical mechanical polishing composition and a polishing pad; (c) moving the polishing pad relative to the silicon carbide substrate, with the chemical mechanical polishing composition positioned therebetween; and (d) removing at least a portion of the silicon carbide substrate. The method may optionally include other steps.

[0056] The composition can be prepared using suitable techniques known to those skilled in the art. The chamfered octahedral cerium oxide abrasive particles as described above and other components besides the chamfered octahedral cerium oxide abrasive particles can be added to the liquid carrier in any order and in suitable amounts to achieve the desired concentration. The chamfered octahedral cerium oxide abrasive particles and other components can be mixed and stirred in the liquid carrier. The pH value can be adjusted using the pH adjuster and pH buffer described above to obtain and maintain the desired pH. The chamfered octahedral cerium oxide abrasive particles and other components can be added at any time before use or during CMP treatment.

[0057] The composition can be provided as a single-part system, a two-part system, or a multi-part system. For example, as a two-part system, the first part may include chamfered octahedral cerium oxide abrasive grains, and the second part may include one or more other components. The first and second parts can be mixed at any time before or during the CMP treatment.

[0058] The following are specific embodiments of the compositions designed according to the above disclosure. It should be understood that the following embodiments are merely illustrative of the compositions and polishing methods disclosed above, and the specific implementation methods and parameters used are only one or more of the numerous parameters and methods described above. Those skilled in the art can use other parameters to perform chemical mechanical polishing according to the above methods without departing from the core spirit of the disclosure.

[0059] [Data Measurement]

[0060] Sample: A silicon carbide wafer with a diameter of 15cm (approximately 6 inches) and a thickness of 350μm;

[0061] Experimental conditions: Silicon carbide wafers were polished for 15 minutes using Kizi polishing tools (Dongguan Jinyan Precision Grinding Machinery Manufacturing Co., Ltd.) at a platen speed of 90 rpm, a downward pressure of 5 psi, and a slurry flow rate of 50 ml / min.

[0062] Scratch count: The silicon surface of the polished silicon carbide wafer was inspected for surface defects to determine the number of scratches. A Candela 8520 (KLA) was used to inspect the silicon surface of the polished 6-inch silicon carbide wafer for surface defects and count the scratches.

[0063] Material Removal Rate (RR): Measured using an electronic balance, the material removal rate of the silicon surface of the silicon carbide wafer is calculated based on the weight difference before and after polishing. The material removal rate is listed in Table 1 as the number of micrometers removed per hour [μm / h].

[0064] Surface roughness (Ra): 10 μm at the center of the silicon wafer using Park AFM instruments. 2 The surface roughness (Ra) of a polished and cleaned silicon carbide wafer was measured at two randomly selected measurement points, one 1 cm from the edge of the wafer, in a designated area. Surface roughness (Ra) is the arithmetic mean of the absolute values ​​by which the profile height deviates from the average height. In the following examples, surface roughness (Ra) is listed in nm as the average of two measurement points near the center and edge.

[0065] [Abrasive Grain Preparation]

[0066] Calcined alumina: purchased from Baikowski, D50 of 125 nm, the D50 was measured by laser diffraction using a Horiba LA960;

[0067] Colloidal alumina: purchased from Xuancheng Jingrui New Materials Co., Ltd., with a D50 of 90 nm. The D50 was measured by laser diffraction using a Horiba LA960.

[0068] Colloidal zirconia: purchased from Xuancheng Jingrui New Materials Co., Ltd., with a D50 of 90 nm. The D50 was measured by laser diffraction using a Horiba LA960.

[0069] Cubic cerium oxide: D50 is 80.37 nm, which was measured using a Horiba LA960 laser particle size analyzer. The synthesis method of cubic cerium oxide is as follows: 0.03 mol of cerium(III) nitrate hexahydrate (Ce(NO3)3·6H2O) was dissolved in 100 mL of deionized water and stirred at room temperature until the solid dissolved; this is denoted as liquid A. 3.6 mol of sodium hydroxide (NaOH) was dissolved in 500 mL of deionized water and stirred until the solid dissolved; this was then cooled to room temperature; this is denoted as liquid B. Liquid A was slowly added to liquid B while stirring at room temperature for 30 minutes. The mixture was transferred to a stainless steel hydrothermal reactor with a Teflon liner, and the synthesis temperature was 120℃ for 24 hours, followed by natural cooling to room temperature. Centrifugation of the cooled mixture yielded a white solid. The centrifuged white solid was washed three times with water and three times with ethanol until the conductivity of the supernatant was less than 1 mS·cm. Drying the solid obtained from the final cleaning at 120°C yields cubic cerium oxide abrasive grains with preferred properties.

[0070] Chamfered octahedral cerium oxide: 200g of cerium(III) nitrate hexahydrate (Ce(NO3)3·6H2O) was dissolved in 500mL of deionized water and stirred at room temperature until the solid dissolved; this solution is denoted as solution A. 100mL of ammonia water was dissolved in 400mL of deionized water and stirred until the solid dissolved; this solution is denoted as solution B. Solution B was slowly added to solution A while stirring at room temperature for 30 minutes. The mixture was placed in a water bath at 85℃ for 4 hours. The cooled mixture was centrifuged to obtain a white solid, which was then acidified with water and acetic acid to obtain a suspension of chopped octahedral cerium oxide. The resulting chopped octahedral cerium oxide abrasive particles were obtained.

[0071] The average particle size of the chamfered octahedral cerium oxide abrasive grains is 42.25 nm. The average particle size was measured using a NovaNano 450 scanning electron microscope. The average particle size was obtained by the arithmetic mean of the maximum distances between two points on the particle boundary measured from 1000 particles. As mentioned above, the coefficient of variation (CV) of the average particle size was calculated to be 36.30 using the formula CV = (σ / μ) × 100% (where σ is the standard deviation of the average particle size and μ is the average particle size). As mentioned above, the polydispersity index (PDI) was calculated using the formula PDI = σ 2 / μ 2The calculated value is 0.13. The percentage of particles exceeding twice the average particle size is 2.0. The ratio of (cumulative volume of particles exceeding twice the average particle size) to (cumulative volume of particles with the largest average particle size) is 0.86. As mentioned above, the ratio of (cumulative volume of particles exceeding twice the average particle size) to (cumulative volume of particles with the largest average particle size) can be used to calculate the volume of the chamfered octahedral cerium oxide abrasive grains using the general mathematical formula for square particles and spheres (assuming spherical particles).

[0072] Example 1

[0073] The abrasive grains in A1-A3 and E1-E2 are prepared by the above method.

[0074] Composition: 4.5 wt% potassium permanganate, 1 wt% aluminum nitrate. The pH was adjusted to 2.5 with nitric acid. Abrasive particles were added to A1-A3 and E1-E2, and the specific types and contents of abrasive particles are shown in Table 1.

[0075] Table 1

[0076]

[0077]

[0078] in conclusion:

[0079] (1) Compared with A1, chemical mechanical polishing (CMP) using chamfered octahedral cerium oxide abrasives results in lower surface roughness and fewer scratches on the polished silicon carbide wafers, indicating better surface quality. Furthermore, a comparison between E1 and A1 reveals that CMP using chamfered octahedral cerium oxide abrasives achieves a higher material removal rate.

[0080] (2) Compared with A2, E1 has a higher material removal rate when chemical mechanical polishing with diced cerium oxide abrasives, but also more scratches.

[0081] (3) Compared with A3, although the material removal rate of chemical mechanical polishing using chamfered octahedral cerium oxide abrasive and using 50% colloidal alumina + 50% colloidal zirconium oxide abrasive is the same, the surface roughness of chemical mechanical polishing using chamfered octahedral cerium oxide abrasive is lower. That is, chemical mechanical polishing using chamfered octahedral cerium oxide abrasive can make the surface quality of the polished silicon carbide wafer better.

[0082] (4) Compared with E2, adding more chamfered octahedral cerium oxide abrasive particles to E1 can improve the material removal rate without increasing surface roughness and scratches.

[0083] Example 2

[0084] Composition: A4, A5, E3, and E4 all contain 0.5 wt% chopped octahedral cerium oxide abrasive grains, 1 wt% cerium nitrate, and a pH of 2.5. Additionally, different oxidants and oxidant regenerators are added to A4, A5, E3, and E4; the specific types and contents are shown in Table 2.

[0085] Table 2

[0086]

[0087]

[0088] in conclusion:

[0089] (1) Compared with A4, adding more potassium permanganate to the composition of A5 can improve the material removal rate, but it will lead to more scratches, thereby reducing the surface quality of the polished silicon carbide wafer.

[0090] (2) Compared with A4, E3 can improve the material removal rate by adding sodium bismuthate to the same amount of potassium permanganate in the composition, without causing scratches.

[0091] (3) Compared with E3, E4 adds more sodium bismuthate to the same amount of potassium permanganate in the composition, which can improve the material removal rate without causing or increasing scratches.

[0092] The foregoing has described specific embodiments of this specification. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recited in the claims may be performed in a different order than that shown in the embodiments and may still achieve the desired result. Furthermore, the processes depicted in the drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing are possible or may be advantageous.

[0093] In summary, after reading this detailed disclosure, those skilled in the art will understand that the foregoing detailed disclosure may be presented by way of example only and may not be restrictive. Although not explicitly stated herein, those skilled in the art will understand that this specification requires various reasonable changes, improvements, and modifications to the embodiments. These changes, improvements, and modifications are intended to be made by this specification and are within the spirit and scope of the exemplary embodiments described herein.

[0094] Furthermore, certain terms in this specification have been used to describe embodiments of this specification. For example, "an embodiment," "an embodiment," and / or "some embodiments" mean that a particular feature, structure, or characteristic described in connection with that embodiment may be included in at least one embodiment of this specification. Therefore, it is to be emphasized and understood that two or more references to "an embodiment" or "an embodiment" or "alternative embodiment" in various parts of this specification do not necessarily refer to the same embodiment. Moreover, specific features, structures, or characteristics may be suitably combined in one or more embodiments of this specification.

[0095] It should be understood that in the foregoing description of the embodiments in this specification, various features are combined in a single embodiment, drawing, or description for the purpose of simplifying the description and to aid in understanding a feature. However, this does not mean that the combination of these features is necessary, and those skilled in the art may extract some features as individual embodiments when reading this specification. That is, the embodiments in this specification can also be understood as an integration of multiple sub-embodiments. It is also valid when each sub-embodiment contains fewer than all the features of a single foregoing disclosed embodiment.

[0096] Every patent, patent application, publication of a patent application, and other material, such as articles, books, specifications, publications, documents, and literature (excluding any related historical examination documents), cited in this disclosure is incorporated herein for all purposes, including, for example, in the specification and claims of this disclosure. However, in the event of any inconsistency or conflict between the descriptions, definitions, and / or terms used in the foregoing and those used in this disclosure, the descriptions, definitions, and / or terms used in this disclosure shall prevail.

[0097] Finally, it should be understood that the embodiments disclosed herein are illustrative of the principles of the embodiments described in this specification. Other modified embodiments are also within the scope of this specification. Therefore, the embodiments disclosed in this specification are merely examples and not limitations. Those skilled in the art can implement the applications described in this specification using alternative configurations based on the embodiments in this specification. Therefore, the embodiments in this specification are not limited to the embodiments precisely described in the applications.

Claims

1. A chemical mechanical polishing composition for polishing a silicon carbide substrate, characterized by, Compositions include: ceria abrasive particles; Oxidizing agents, including permanganates, which are reduced to Mn 2 + ions; and Oxidant regenerant, including bismuthate, will oxidize the Mn 2 + ions to permanganate, thereby maintaining the concentration of permanganate in the composition.

2. The composition of claim 1, wherein, the bismuthate comprises sodium bismuthate.

3. The composition according to any one of claims 1 or 2, characterized in that, the bismuthate comprises 0.01-5 wt.% of the composition.

4. The composition of claim 1, wherein, the composition has a pH of less than 7.

5. The composition of claim 1, wherein, the composition further comprises a catalyst comprising a nitrate, wherein the catalyst does not comprise the bismuthate.

6. The composition of claim 1, wherein, the ceria abrasive particles comprise truncated octahedral ceria abrasive particles.

7. The composition of claim 6, wherein, the ratio of the cumulative volume of the truncated octahedral ceria abrasive particles having an average particle size of more than twice the average particle size of the truncated octahedral ceria abrasive particles to the cumulative volume of the truncated octahedral ceria abrasive particles having an average particle size of less than or equal to the average particle size of the truncated octahedral ceria abrasive particles is at least 0.

1.

8. The composition of claim 6, wherein, the coefficient of variation of the average particle size of the truncated octahedral ceria abrasive particles is greater than 30% as measured by scanning electron microscopy.

9. The composition of claim 6, wherein, the polydispersity index of the truncated octahedral ceria abrasive particles is at least 0.1 as measured by scanning electron microscopy.

10. A polishing method for a silicon carbide substrate, characterized by, the method utilizes a chemical mechanical polishing composition as claimed in any one of claims 1-9 to achieve polishing of the silicon carbide substrate.

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