Silicon carbide polishing liquid and method for preparing the same

Abstract

The application discloses a silicon carbide polishing liquid and a preparation method thereof. The application relates to the field of semiconductor polishing. The silicon carbide polishing liquid comprises the following components: abrasive, wherein the abrasive is composed of abrasive with a first morphology and abrasive with a second morphology; an oxidizing agent; a dispersing agent, wherein the dispersing agent comprises at least one nonionic surfactant and at least one phosphate chelating agent; and water; wherein the pH value of the polishing liquid composition is 3-6; the first morphology is a polyhedral morphology with an acute angle or an angular structure, and preferably a triangular shape, a cubic shape or an irregular polyhedral shape; and the second morphology is a spherical or spherical-like morphology. The polishing liquid can realize the unification of high material removal rate and ultra-low surface roughness in the silicon carbide wafer polishing process by introducing the abrasive with the first morphology and the abrasive with the second morphology and cooperating with the dispersing agent system comprising the nonionic surfactant and the phosphate chelating agent under the condition that the pH value is 3-6.

Description

Technical Field

[0001] This invention relates to the field of semiconductor polishing technology, and in particular to a silicon carbide polishing slurry and its preparation method. Background Technology

[0002] Silicon carbide (SiC), as a typical representative material of third-generation semiconductors, has become an ideal choice for manufacturing power devices under extreme conditions such as high voltage, high frequency, and high temperature due to its significant characteristics such as wide bandgap, high breakdown voltage, excellent thermal conductivity, and high electron mobility. It shows broad application prospects in key areas such as high-power electronic devices, aerospace applications, space optical systems, and fifth-generation mobile communication technology (5G). However, the true performance advantages and application value of silicon carbide materials are highly dependent on the atomically smooth and flat state of its substrate surface. Surface roughness is a core indicator for measuring the quality of silicon carbide substrates, directly restricting the quality of subsequent epitaxial growth and the performance of the final device. Specifically, reducing surface roughness can effectively improve the electrical breakdown field strength and charge breakdown capability of silicon carbide substrates, and significantly improve the transconductance characteristics of devices such as metal-oxide-semiconductor field-effect transistors. If surface roughness is not properly controlled and exceeds a certain threshold, it can easily lead to cascading physical failures in devices, directly causing a significant drop in production yield and seriously hindering the large-scale development of the silicon carbide semiconductor industry.

[0003] The fabrication of silicon carbide wafers involves a series of processing steps, including sawing, grinding, and preliminary mechanical polishing. These processes inevitably introduce various types of damage layers, such as scratches, cracks, and dislocations, into the substrate surface and subsurface. More importantly, silicon carbide itself possesses extremely high hardness and significant chemical inertness, making it resistant to reaction with common acid and alkali solutions at room temperature and pressure. This characteristic poses a significant challenge to traditional, single-method mechanical polishing: not only is it difficult to effectively reduce surface roughness, but the mechanical force applied during polishing may also introduce new micro-scratches or deepen existing subsurface damage, further deteriorating surface quality and making the goal of achieving an atomically smooth surface seem unattainable. Therefore, to achieve reliable applications of silicon carbide materials in high-end power devices, more advanced surface finishing technologies are necessary to completely eliminate the damage left by previous processes and obtain an ultra-smooth, damage-free surface. Chemical mechanical polishing (CMP) technology is the core process that meets this requirement. This technology, through the synergistic combination of chemical and mechanical actions, can achieve nanoscale or even atomic-level removal of materials on a global scale, thereby obtaining a perfect surface with extremely low roughness and no defects. It is an indispensable key step in improving the performance of silicon carbide materials and promoting their industrial application.

[0004] In the chemical mechanical polishing (CMP) process for silicon carbide, the polishing slurry plays a crucial role. Its working principle typically involves a dynamic "oxidation-removal" cycle: the oxidant component in the slurry first reacts chemically with the silicon carbide wafer surface, oxidizing the surface layer to form a soft silicon-carbon-oxygen transition layer with a lower hardness than the original silicon carbide. Subsequently, abrasive particles suspended in the slurry, under the pressure and relative motion of the polishing pad, remove this soft layer through mechanical friction, exposing a new silicon carbide surface for the next round of oxidation. This cycle repeats, gradually achieving global surface planarization. To address the extremely high hardness of silicon carbide, current technologies generally favor adding high-hardness abrasive particles to the polishing slurry, such as diamond, boron carbide, alumina, silicon carbide powder itself, or silica. Using these high-hardness abrasives can indeed significantly improve the material removal rate, meeting certain production efficiency requirements.

[0005] However, this existing technology, which uses high-hardness abrasives as its core, has significant drawbacks and limitations. The primary problem is that while the high-hardness abrasive particles mechanically remove the soft oxide layer, they easily scratch the relatively "soft" oxide layer beneath, or the unoxidized original silicon carbide substrate. These newly introduced scratches, microcracks, and other mechanical damage directly disrupt the surface integrity, making it difficult to achieve atomic-level smoothness after polishing, and potentially even worse than before polishing. Secondly, many high-hardness abrasives (such as diamond and boron carbide) have high density or poor dispersion stability in polishing slurries, making them prone to sedimentation or agglomeration. The larger particles formed by agglomeration become sharp, "destructive large-size agglomerates" during polishing, causing severe, random deep scratches, significantly affecting the consistency of the polished surface and the yield rate. Furthermore, the chemical oxidation efficiency of existing polishing slurries is often mismatched with the mechanical removal efficiency. If the chemical oxidation is too weak, the soft layer formed on the surface will be too thin or discontinuous, and the high-hardness abrasive will mainly come into direct contact with the hard silicon carbide matrix, exacerbating mechanical damage. On the other hand, if strong oxidants or high-concentration oxidants are used to improve oxidation efficiency, they may cause corrosion to polishing equipment components or lead to environmental problems such as wastewater treatment. In addition, although some technical solutions attempt to use softer abrasives (such as silica gel), they often suffer from insufficient design of the chemical oxidation process, resulting in an excessively low material removal rate for silicon carbide, which cannot meet the efficiency requirements of actual production and thus limits their practicality.

[0006] In summary, existing silicon carbide polishing slurry technologies, especially those relying on high-hardness abrasives, present an irreconcilable contradiction between polishing efficiency and surface quality. The silicon carbide wafers prepared using these slurries are prone to residual mechanical damage such as scratches, and the overall roughness control level is insufficient to meet the stringent requirements of next-generation high-performance semiconductor devices for atomically smooth substrate surfaces.

[0007] Therefore, developing a novel silicon carbide polishing slurry and its preparation method, which can effectively avoid or reduce mechanical damage to the wafer surface during polishing while maintaining a high material removal rate, has become an urgent need to promote the technological progress and large-scale development of the silicon carbide semiconductor industry. Summary of the Invention

[0008] The purpose of this invention is to develop a novel silicon carbide polishing slurry and its preparation method, which can effectively avoid or reduce mechanical damage to the wafer surface during polishing while maintaining a high material removal rate.

[0009] A silicon carbide polishing slurry, comprising the following components:

[0010] The abrasive is composed of abrasive with a first morphology and abrasive with a second morphology; Oxidizing agent; A dispersant comprising at least one nonionic surfactant and at least one phosphate chelating agent; water; The pH value of the polishing fluid composition is 3-6; The first morphology is a polyhedral morphology with acute angles or angular structures, preferably a triangle, a cube, or an irregular polyhedron; the second morphology is a spherical or near-spherical morphology.

[0011] According to embodiments of the present invention, one of the technical solutions has at least one of the following advantages or beneficial effects: The polishing slurry of this invention combines a first-morphology abrasive with an acute or angular structure with a second-morphology abrasive with a spherical or near-spherical shape, and is combined with a dispersant system containing a nonionic surfactant and a phosphate chelating agent. Under pH conditions of 3 to 6, it can synergistically achieve a high material removal rate and ultra-low surface roughness during the polishing process of silicon carbide wafers.

[0012] Specifically, the sharp edges of the first-morphology abrasive generate extremely high local pressure under polishing pressure, which can efficiently cut the SiC surface layer softened by the oxidant like a "micro-tool", thus dominating the improvement of the polishing rate; the rounded surface of the second-morphology abrasive makes the contact stress distribution uniform, gently removing the material and smoothing the micro-undulations in a "rolling and grinding" manner, thus dominating the reduction of surface roughness and scratch risk.

[0013] Nonionic surfactants prevent particle agglomeration by forming a steric hindrance layer on the surface of abrasives through adsorption; phosphate chelating agents inhibit the ineffective decomposition of oxidants and the resulting chemical agglomeration by complexing metal ions.

[0014] In a weakly acidic environment with a pH of 3 to 6, the functions of the above components are optimally performed and balanced, thereby obtaining an atomically smooth surface while performing high-speed polishing.

[0015] According to one embodiment of the present invention, the silicon carbide polishing slurry comprises the following components by weight percentage: Abrasive: 1 wt.% ~ 5 wt.%; Oxidizing agent: 0.5 wt.% ~ 5 wt.%; Dispersant: 0.1 wt.% ~ 3 wt.%.

[0016] According to one embodiment of the present invention, the abrasive in the silicon carbide polishing slurry accounts for 1 wt.% to 3 wt.% of the total weight of the silicon carbide polishing slurry.

[0017] According to one embodiment of the present invention, the abrasive in the silicon carbide polishing slurry accounts for 1.5 wt.% to 3 wt.% of the total weight of the silicon carbide polishing slurry.

[0018] According to one embodiment of the present invention, the silicon carbide polishing slurry further comprises 0.1 wt.% to 2 wt.% of a pH adjuster.

[0019] According to one embodiment of the present invention, the pH adjuster is an acid and / or a base, wherein the acid is selected from at least one of nitric acid, hydrochloric acid, phosphoric acid, and acetic acid, and the base is selected from at least one of potassium hydroxide, sodium hydroxide, and ammonia water; preferably nitric acid and / or potassium hydroxide.

[0020] According to one embodiment of the present invention, the silicon carbide polishing slurry further comprises a pH stabilizer accounting for 0.1 wt.% to 2 wt.% of the total weight of the silicon carbide polishing slurry, wherein the pH stabilizer is selected from at least one of phosphate buffer pairs, acetate buffer pairs, and citrate buffer pairs. Adding a pH stabilizer can enhance the polishing slurry's resistance to external disturbances.

[0021] According to one embodiment of the present invention, the abrasive with the first morphology and the abrasive with the second morphology are each independently selected from cerium oxide abrasive or silicon oxide abrasive.

[0022] According to one embodiment of the present invention, both the first and second morphologies of the abrasive are cerium oxide abrasives. Cerium oxide abrasives not only possess moderate hardness, but also have a Ce-rich surface. 3+ / Ce 4+The variable valence state can also undergo tribochemical reactions with the SiC surface during polishing to form strong Si-O-Ce chemisorption bonds. This enhances the effective friction between the polishing pad, abrasive, and wafer, thereby further improving material removal efficiency and helping to obtain a better chemically smooth surface without significantly increasing the risk of mechanical damage.

[0023] According to one embodiment of the present invention, the quasi-spherical shape is a particle with an aspect ratio in the range of 1:1 to 1:1.5.

[0024] According to one embodiment of the present invention, the average particle size (D50) of the abrasive with the first morphology is 50 nm to 200 nm; and / or, the average particle size (D50) of the abrasive with the second morphology is 50 nm to 150 nm. A suitable particle size range enables the abrasive to possess sufficient force and number density to effectively remove material, while avoiding problems such as deep scratches that may result from excessively large particle sizes or low polishing efficiency and difficulties in slurry filtration that may result from excessively small particle sizes. This is a necessary condition for achieving efficient and fine polishing.

[0025] According to one embodiment of the present invention, the average particle size (D50) of the abrasive with the first morphology is 90 nm to 115 nm.

[0026] According to one embodiment of the present invention, the average particle size (D50) of the abrasive with the second morphology is 90 nm to 150 nm.

[0027] According to one embodiment of the present invention, the first morphology is triangular; the second morphology is spherical.

[0028] According to one embodiment of the present invention, the nonionic surfactant is selected from at least one of fatty alcohol polyoxyethylene ether, alkyl glycoside, and polyvinylpyrrolidone; preferably fatty alcohol polyoxyethylene ether and / or alkyl glycoside. Fatty alcohol polyoxyethylene ether (such as AEO-9), alkyl glycoside (such as APG-1214), and polyvinylpyrrolidone (PVP) nonionic surfactants have polar groups such as ether bonds, hydroxyl groups, or amide groups in their molecules that can be firmly adsorbed onto the surface of abrasive particles, while their long-chain lipophilic groups or polymer chains extend in water, forming a steric hindrance layer. This protective layer can effectively resist the effects of weakly acidic and oxidizing environments, preventing abrasive particles from approaching each other, flocculating, or settling due to van der Waals forces, and is the basis for maintaining the stable dispersion of the polishing fluid and obtaining a scratch-free surface.

[0029] According to one embodiment of the present invention, the nonionic surfactant is a mixture of fatty alcohol polyoxyethylene ether and alkyl glycoside. AEO-9 (fatty alcohol polyoxyethylene ether) and APG-1214 (alkyl glycoside) have different molecular structures and adsorption properties. The combined use of the two can form a denser and more complete mixed adsorption layer on the abrasive surface, providing a stronger steric hindrance effect, thereby providing more comprehensive and effective protection for abrasive particles in harsh polishing environments, further improving the storage stability and dispersion stability of the polishing slurry during use.

[0030] According to one embodiment of the present invention, the phosphate chelating agent is selected from at least one of sodium pyrophosphate, sodium tripolyphosphate, and sodium hexametaphosphate.

[0031] According to one embodiment of the present invention, the phosphate chelating agent is sodium pyrophosphate. Sodium pyrophosphate has an extremely strong chelating ability for trivalent manganese ions and can rapidly capture Mn generated during the reduction of potassium permanganate during polishing. 3+ The intermediate forms a stable, soluble complex. This fundamentally inhibits the formation of Mn. 3+ Further disproportionation to generate manganese dioxide precipitate and the side reaction chain that catalyzes the decomposition of potassium permanganate are effective measures to maintain the long-lasting activity of potassium permanganate oxidant and prevent discoloration, agglomeration and scratches of slurry caused by MnO2 formation.

[0032] According to one embodiment of the present invention, the oxidant is selected from potassium permanganate or sodium permanganate; preferably, potassium permanganate is the oxidant. Under acidic to weakly acidic conditions with a pH of 3-6, potassium permanganate can effectively oxidize the SiC surface to form a silicon-oxygen-carbon (Si-CO) transition layer with low hardness, which is easily removed by subsequent mechanical action. The strong oxidizing property of potassium permanganate is the key chemical component contributing to the high polishing rate. When combined with a phosphate chelating agent (such as sodium pyrophosphate), it can significantly inhibit the decomposition of potassium permanganate into manganese dioxide, maintaining a stable oxidation process.

[0033] According to one embodiment of the present invention, the mass ratio of the abrasive with the first morphology to the abrasive with the second morphology is 0.5-5:1-5. Adjusting the ratio of the first morphology (high-efficiency cutting type) to the second morphology (low-damage type) abrasive can directly change the ratio of the "aggressive" to the "mild" mechanical action during polishing. This achieves an optimal balance between material removal rate and surface roughness, meeting the extremely high requirements of both in fine polishing applications.

[0034] According to one embodiment of the present invention, the mass ratio of the abrasive with the first morphology to the abrasive with the second morphology is 0.5-2:1-2.

[0035] According to one embodiment of the present invention, the mass ratio of the abrasive with the first morphology to the abrasive with the second morphology includes, but is not limited to, one of: 0.5:1, 1:1, 2:1, 3:1, 4:1, 1:2, 1:3, 1:4, 1:5.

[0036] Specifically, the technical solution adopted according to the second aspect of the present invention is as follows: A method for preparing the silicon carbide polishing slurry includes the following steps: S1: Mix the abrasive with the first morphology and the abrasive with the second morphology in water, stir, and form an abrasive dispersion; S2: Add dispersant and oxidant to the abrasive dispersion, adjust the pH value to 3-6, stir, and obtain the silicon carbide polishing slurry.

[0037] According to embodiments of the present invention, one of the technical solutions has at least one of the following advantages or beneficial effects: Step S1 first disperses the abrasive in deionized water; Step S2 then adds a dispersant, allowing it ample opportunity to adsorb onto the abrasive surface and form a stable protective layer. This is a crucial pretreatment to prevent particle agglomeration in subsequent steps. The addition of an oxidant prevents premature reaction or decomposition in the unprotected abrasive system. This sequence is scientifically sound and maximizes the protection of the activity and stability of each component.

[0038] According to one embodiment of the present invention, in step S1, the stirring time is 10 to 30 minutes.

[0039] According to one embodiment of the present invention, in step S2, the stirring time after pH adjustment is 10-60 minutes.

[0040] Another aspect of the present invention relates to a polishing method for silicon carbide wafers, comprising performing chemical mechanical polishing on the silicon carbide wafers using the aforementioned silicon carbide polishing slurry.

[0041] According to one embodiment of the present invention, the polishing pressure is 3 to 6 psi.

[0042] According to one embodiment of the present invention, the polishing disc rotates at a speed of 15 to 80 rpm.

[0043] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0044] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 The images show SEM images of the spherical cerium oxide abrasives used in Examples 1-6.

[0045] Figure 2 The image shows the SEM images of the triangular cerium oxide abrasives used in Examples 1-6.

[0046] Figure 3 The image shows the AFM image of a silicon carbide wafer polished with the silicon carbide polishing slurry of Example 1.

[0047] Figure 4 The image shows the AFM image of a silicon carbide wafer polished with the silicon carbide polishing slurry of Example 2.

[0048] Figure 5 The image shows the AFM image of a silicon carbide wafer polished with the silicon carbide polishing slurry of Example 3.

[0049] Figure 6 The image shows the AFM image of the silicon carbide wafer after polishing with the silicon carbide polishing slurry of Example 4.

[0050] Figure 7 The image shows the AFM image of a silicon carbide wafer polished with the silicon carbide polishing slurry of Example 5.

[0051] Figure 8 The image shows the AFM image of a silicon carbide wafer polished with the silicon carbide polishing slurry of Example 6.

[0052] Figure 9 The image shows the AFM image of a silicon carbide wafer polished with the silicon carbide polishing slurry of Comparative Example 1.

[0053] Figure 10 The image shows the AFM image of the silicon carbide wafer after polishing with the silicon carbide polishing slurry of Comparative Example 2.

[0054] Figure 11 The image shows the AFM image of the silicon carbide wafer after polishing with the silicon carbide polishing slurry of Comparative Example 3. Detailed Implementation

[0055] The terms "preferred," "more preferred," etc., used in this invention refer to embodiments of the invention that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this invention.

[0056] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0057] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of the present invention.

[0058] In the examples and comparative examples, the particle size parameters of the abrasive particles were obtained by measuring the average particle size of the abrasive using a HORIBA particle size distribution tool (particle size analyzer).

[0059] In the examples and comparative examples, the triangular cerium oxide abrasive was prepared with reference to the patent publication number CN119911956A.

[0060] In the examples and comparative examples, the spherical cerium oxide abrasive was prepared with reference to the patent publication number CN119873872A.

[0061] Unless otherwise specified, the reagents, methods and equipment used in this invention are all conventional reagents, methods and equipment in this technical field.

[0062] Example 1 A silicon carbide polishing slurry, comprising the following components by weight percentage: Triangular cerium oxide abrasive: 1 wt.%; Spherical cerium oxide abrasive: 1 wt.%; Oxidizing agent: potassium permanganate: 1 wt.% Dispersant AEO-9: 1 wt.%; Dispersant APG-1214: 1 wt.%; Sodium pyrophosphate dispersant: 1 wt.% Water, remaining amount.

[0063] A method for preparing the above-mentioned silicon carbide polishing slurry includes the following steps: S1: Mix triangular cerium oxide with a D50 of 115 nm in water and stir for 10 min. Then add spherical cerium oxide with a D50 of 90 nm and stir for 10 min to form an abrasive dispersion. S2: Add dispersant AEO-9, dispersant APG-1214, and dispersant sodium pyrophosphate to the above abrasive dispersion, stir for 10 min, add oxidant potassium permanganate, stir for 10 min, adjust the pH value to 6, stir at room temperature for 30 min, and obtain the above silicon carbide polishing slurry.

[0064] Example 2 The difference between Example 2 and Example 1 lies in the D50 particle size of the triangular cerium oxide abrasive. Specifically, the D50 particle size of the triangular cerium oxide abrasive in Example 1 is 115 nm, while that in Example 2 is 90 nm.

[0065] Specifically: A silicon carbide polishing slurry, comprising the following components by weight percentage: Triangular cerium oxide abrasive: 1 wt.%; Spherical cerium oxide abrasive: 1 wt.%; Oxidizing agent: potassium permanganate: 1 wt.% Dispersant AEO-9: 1 wt.%; Dispersant APG-1214: 1 wt.%; Sodium pyrophosphate dispersant: 1 wt.% Water, remaining amount.

[0066] A method for preparing the above-mentioned silicon carbide polishing slurry includes the following steps: S1: Mix triangular cerium oxide with a D50 of 90 nm in water and stir for 10 min. Then add spherical cerium oxide with a D50 of 90 nm and stir for 10 min to form an abrasive dispersion. S2: Add dispersant AEO-9, dispersant APG-1214, and dispersant sodium pyrophosphate to the above abrasive dispersion, stir for 10 min, add oxidant potassium permanganate, stir for 10 min, adjust the pH value to 6, stir at room temperature for 30 min, and obtain the above silicon carbide polishing slurry.

[0067] Example 3 The difference between Example 3 and Example 1 is that spherical silicon oxide is used instead of spherical cerium oxide.

[0068] Specifically: A silicon carbide polishing slurry, comprising the following components by weight percentage: Triangular cerium oxide abrasive: 1 wt.%; Spherical silica abrasive: 1 wt.%; Oxidizing agent: potassium permanganate: 1 wt.% Dispersant AEO-9: 1 wt.%; Dispersant APG-1214: 1 wt.%; Sodium pyrophosphate dispersant: 1 wt.% Water, remaining amount.

[0069] A method for preparing the above-mentioned silicon carbide polishing slurry includes the following steps: S1: Mix triangular cerium oxide with a D50 of 115 nm in water and stir for 10 min. Then add spherical silicon oxide with a D50 of 90 nm and stir for 10 min to form an abrasive dispersion. S2: Add dispersant AEO-9, dispersant APG-1214, and dispersant sodium pyrophosphate to the above abrasive dispersion, stir for 10 min, add oxidant potassium permanganate, stir for 10 min, adjust the pH value to 6, stir at room temperature for 30 min, and obtain the above silicon carbide polishing slurry.

[0070] Example 4 The difference between Example 4 and Example 1 lies in the amount of triangular cerium oxide abrasive used. Specifically, Example 1 used 1 wt.% of the triangular cerium oxide abrasive, while Example 4 used 0.5 wt.%.

[0071] Specifically: A silicon carbide polishing slurry, comprising the following components by weight percentage: Triangular cerium oxide abrasive: 0.5 wt.%; Spherical cerium oxide abrasive: 1 wt.%; Oxidizing agent: potassium permanganate: 1 wt.% Dispersant AEO-9: 1 wt.%; Dispersant APG-1214: 1 wt.%; Sodium pyrophosphate dispersant: 1 wt.% Water, remaining amount.

[0072] A method for preparing the above-mentioned silicon carbide polishing slurry includes the following steps: S1: Mix triangular cerium oxide with a D50 of 115 nm in water and stir for 10 min. Then add spherical cerium oxide with a D50 of 90 nm and stir for 10 min to form an abrasive dispersion. S2: Add dispersant AEO-9, dispersant APG-1214, and dispersant sodium pyrophosphate to the above abrasive dispersion, stir for 10 min, add oxidant potassium permanganate, stir for 10 min, adjust the pH value to 6, stir at room temperature for 30 min, and obtain the above silicon carbide polishing slurry.

[0073] Example 5 The difference between Example 5 and Example 1 lies in the amount of triangular cerium oxide abrasive used. Specifically, Example 1 used 1 wt.% of the triangular cerium oxide abrasive, while Example 5 used 2 wt.%.

[0074] Specifically: A silicon carbide polishing slurry, comprising the following components by weight percentage: Triangular cerium oxide abrasive: 2 wt.% Spherical cerium oxide abrasive: 1 wt.%; Oxidizing agent: potassium permanganate: 1 wt.% Dispersant AEO-9: 1 wt.%; Dispersant APG-1214: 1 wt.%; Sodium pyrophosphate dispersant: 1 wt.% Water, remaining amount.

[0075] A method for preparing the above-mentioned silicon carbide polishing slurry includes the following steps: S1: Mix triangular cerium oxide with a D50 of 115 nm in water and stir for 10 min. Then add spherical cerium oxide with a D50 of 90 nm and stir for 10 min to form an abrasive dispersion. S2: Add dispersant AEO-9, dispersant APG-1214, and dispersant sodium pyrophosphate to the above abrasive dispersion, stir for 10 min, add oxidant potassium permanganate, stir for 10 min, adjust the pH value to 6, stir at room temperature for 30 min, and obtain the above silicon carbide polishing slurry.

[0076] Example 6 The difference between Example 6 and Example 3 lies in the D50 particle size of the triangular cerium oxide abrasive. Specifically, the D50 particle size of the triangular cerium oxide abrasive in Example 3 is 115 nm, while that in Example 6 is 90 nm.

[0077] Specifically: A silicon carbide polishing slurry, comprising the following components by weight percentage: Triangular cerium oxide abrasive: 1 wt.%; Spherical silica abrasive: 1 wt.%; Oxidizing agent: potassium permanganate: 1 wt.% Dispersant AEO-9: 1 wt.%; Dispersant APG-1214: 1 wt.%; Sodium pyrophosphate dispersant: 1 wt.% Water, remaining amount.

[0078] A method for preparing the above-mentioned silicon carbide polishing slurry includes the following steps: S1: Mix triangular cerium oxide with a D50 of 90 nm in water and stir for 10 min. Then add spherical silica with a D50 of 90 nm and stir for 10 min to form an abrasive dispersion. S2: Add dispersant AEO-9, dispersant APG-1214, and dispersant sodium pyrophosphate to the above abrasive dispersion, stir for 10 min, add oxidant potassium permanganate, stir for 10 min, adjust the pH value to 6, stir at room temperature for 30 min, and obtain the above silicon carbide polishing slurry.

[0079] Example 7 The difference between Example 7 and Example 1 is that the D50 particle size of the triangular cerium oxide abrasive is different. Specifically, the D50 particle size of the triangular cerium oxide abrasive in Example 1 is 115 nm, while that in Example 7 is 150 nm.

[0080] Specifically: A silicon carbide polishing slurry, comprising the following components by weight percentage: Triangular cerium oxide abrasive: 1 wt.%; Spherical cerium oxide abrasive: 1 wt.%; Oxidizing agent: potassium permanganate: 1 wt.% Dispersant AEO-9: 1 wt.%; Dispersant APG-1214: 1 wt.%; Sodium pyrophosphate dispersant: 1 wt.% Water, remaining amount.

[0081] A method for preparing the above-mentioned silicon carbide polishing slurry includes the following steps: S1: Mix triangular cerium oxide with a D50 of 150 nm in water and stir for 10 min. Then add spherical cerium oxide with a D50 of 90 nm and stir for 10 min to form an abrasive dispersion. S2: Add dispersant AEO-9, dispersant APG-1214, and dispersant sodium pyrophosphate to the above abrasive dispersion, stir for 10 min, add oxidant potassium permanganate, stir for 10 min, adjust the pH value to 6, stir at room temperature for 30 min, and obtain the above silicon carbide polishing slurry.

[0082] Comparative Example 1 The difference between Comparative Example 1 and Example 5 is that the silicon carbide polishing slurry in Comparative Example 1 contains only 2 wt.% triangular cerium oxide abrasives and no spherical cerium oxide abrasives.

[0083] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the triangular cerium oxide abrasive with a D50 particle size of 115 nm in the silicon carbide polishing slurry of Comparative Example 2 was replaced with rod-shaped cerium oxide abrasive with a D50 particle size of 200 nm.

[0084] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that the dispersant in the silicon carbide polishing slurry of Comparative Example 3 is only 1 wt.% sodium pyrophosphate.

[0085] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that the silicon carbide polishing slurry of Comparative Example 4 does not contain dispersant AEO-9, dispersant APG-1214 and dispersant sodium pyrophosphate.

[0086] Comparative Example 5 The difference between Comparative Example 5 and Example 1 is that the pH of the silicon carbide polishing slurry in Comparative Example 5 is 2.

[0087] Comparative Example 6 The difference between Comparative Example 6 and Example 1 is that the pH of the silicon carbide polishing slurry in Comparative Example 6 is 9.

[0088] Performance testing: The polishing performance of the silicon carbide polishing slurries prepared in Examples 1-7 and Comparative Examples 1-6 was tested, and the test results are shown in Table 1.

[0089] The polishing performance test used a HAMAI16B double-sided polishing equipment with a DuPont polyurethane polishing pad. A 6-inch silicon carbide wafer was used as the substrate. The test parameters were set as follows: polishing pad diameter 610 mm, polishing pressure 3–6 psi, polishing pad rotation speed 15–80 rpm, polishing fluid flow rate 150 mL / min, and polishing time 2 hours. The entire experiment was conducted at room temperature. After polishing, the silicon carbide wafer substrate was first cleaned with an ultrasonic cleaner and then dried with dry air. The weights before and after polishing were then measured using an electronic balance to calculate the substrate removal rate (unit: nm / h).

[0090] The wafer cleaning and performance evaluation process for polishing performance testing is as follows: I. Wafer Cleaning Process Pre-treatment wiping: Use an organic acid solution and a PVA brush with added surfactant to physically wipe and clean the wafer surface; Wet chemical cleaning: Deep chemical cleaning of the wafer substrate is performed using a mixture of sulfuric acid and hydrogen peroxide (SPM). II. Polishing Performance Evaluation Methods Surface roughness inspection: The Ra value (arithmetic mean roughness) of the wafer surface is measured using an atomic force microscope (AFM), with the measurement area set to a square range of 10 micrometers × 10 micrometers.

[0091] Table 1 name Removal rate (nm / h) Roughness (nm) Surface quality Example 1 980 0.06 No obvious scratches Example 2 830 0.06 No obvious scratches Example 3 790 0.06 No obvious scratches Example 4 770 0.07 No obvious scratches Example 5 1050 0.2 No obvious scratches Example 6 920 0.07 No obvious scratches Example 7 1110 0.2 No obvious scratches Comparative Example 1 1080 0.3 There are obvious scratches Comparative Example 2 750 2 There are obvious scratches Comparative Example 3 970 >1 There are obvious scratches Comparative Example 4 - - - Comparative Example 5 1100 >10 There are obvious scratches Comparative Example 6 750 >10 There are obvious scratches As shown in Table 1, in Example 2 compared to Example 1, the triangular cerium oxide particle size was reduced from 115 nm to 90 nm, which caused the removal rate (RR) to decrease from 980 nm / h to 830 nm / h. The reduction in particle size resulted in a decrease in the cutting edge size and mass of a single abrasive grain, which reduced its local indentation depth and cutting ability under the same pressure. Therefore, the mechanical removal efficiency was reduced, leading to a decrease in RR.

[0092] The difference between Example 3 and Example 1 is that Example 3 uses spherical silicon oxide instead of spherical cerium oxide, which leads to a decrease in the removal rate of Example 3, indicating that cerium oxide abrasive is preferred.

[0093] In Example 4, compared to Example 1, the amount of triangular cerium oxide was halved, resulting in a decrease in the removal rate (RR) from 980 nm / h to 770 nm / h, and a slight increase in roughness (Ra) from 0.06 nm to 0.07 nm. The halving of the amount of triangular cerium oxide, the primary cutting force, directly led to a decrease in material removal capacity and a lower RR. Simultaneously, due to the relatively increased proportion of spherical cerium oxide, the polishing process leaned more towards a "gentle grinding" mode, which is beneficial for surface protection. Therefore, the roughness only increased slightly (0.07 nm), remaining within the ultra-smooth range, demonstrating the robustness of the composite abrasive system's performance under varying proportions.

[0094] In Example 5, compared to Example 1, the amount of triangular cerium oxide was doubled, resulting in an increase in removal rate (RR) from 980 nm / h to 1050 nm / h and a significant increase in roughness (Ra) from 0.06 nm to 0.2 nm. The substantial increase in the concentration of cutting abrasive significantly enhanced the overall mechanical removal capability, thus leading to a significant increase in RR. However, the excessive number of sharp-angled particles also increased the probability of severe cutting and collision with the wafer surface during polishing, introducing scratches or deep trenches. Even with the buffering effect of spherical abrasive, it was difficult to completely offset the negative impact, leading to a deterioration in surface roughness.

[0095] In Example 7, the triangular cerium oxide particle size was increased to 150 nm compared to Example 1, resulting in an increase in removal rate (RR) from 980 nm / h to 1110 nm / h and a significant increase in surface roughness (Ra) from 0.06 nm to 0.2 nm. The increased triangular cerium oxide particle size of 150 nm implies greater mass and a higher likelihood of macroscopically sharp edges, leading to stronger mechanical cutting ability and thus the highest RR (1110 nm / h). However, the larger, sharp-angled particles also exert a more significant impact and ploughing effect on the surface, resulting in deeper microscopic damage. Despite the buffering effect of spherical abrasives, this still leads to a significant deterioration in surface roughness.

[0096] Compared to Example 5, which contained only 2 wt.% triangular cerium oxide (without spherical cerium oxide), Comparative Example 1 showed a significant deterioration in roughness (Ra) from 0.06 nm to 0.3 nm, with noticeable scratches. The abrasive system in Comparative Example 1 consisted of a single triangular cerium oxide. The stress buffering and surface finishing functions of spherical abrasives were lacking. The polishing process was entirely dominated by sharp particles, which easily plowed grooves and scratches into the oxidized soft SiC surface, resulting in a significant increase in surface roughness and macroscopic scratches. This validates the necessity of spherical abrasives for obtaining low-damage surfaces.

[0097] Compared to Example 1, Comparative Example 2 replaced triangular cerium oxide with rod-shaped cerium oxide with a large aspect ratio, resulting in a significant decrease in removal rate (RR) from 980 nm / h to 750 nm / h, and a sharp deterioration in roughness (Ra) from 0.06 nm to 2 nm, with obvious scratches. In Comparative Example 2, the rod-shaped particles tend to roll rather than cut steadily during polishing, leading to low mechanical removal efficiency and a significant decrease in RR. Simultaneously, their non-uniform shape and large size (200 nm) result in uncontrollable contact with the substrate, easily causing severe scratches and deep scratches, leading to complete destruction of surface quality (Ra = 2 nm), demonstrating the importance of specific sharp-angle morphology for efficient and controllable cutting.

[0098] Compared to Example 1, Comparative Example 3 retained only the chelating agent (sodium pyrophosphate) in its dispersant system, removing the nonionic surfactants (AEO-9, APG-1214). While sodium pyrophosphate can chelate ions to stabilize the chemical environment, it lacks the ability to create steric hindrance on the abrasive surface. Abrasive particles (especially triangular cerium oxide) readily agglomerate due to van der Waals forces, forming large agglomerates. These agglomerates, acting as hard, large particles during polishing, cause severe surface scratches, leading to a sharp increase in roughness. This demonstrates the crucial role of nonionic surfactants in maintaining abrasive dispersion stability and preventing physical scratches.

[0099] Comparative Example 4 contained no dispersant and completely lacked a dispersion stabilization mechanism. In the complex system containing high concentrations of abrasive and oxidant, the abrasive particles rapidly agglomerated and settled, causing the polishing slurry to lose its uniformity and stability. It was unable to form an effective and stable working film on the polishing pad, resulting in the complete failure of the polishing process.

[0100] Comparative Example 5, with its pH value reduced to a strongly acidic level compared to Example 1, experienced a dramatic increase in roughness (Ra) from 0.06 nm to >10 nm, resulting in noticeable scratches. The strongly acidic environment can destabilize or deactivate the nonionic surfactants (AEO-9, APG-1214), while simultaneously exacerbating abrasive surface dissolution or charge alteration, leading to severe abrasive agglomeration and the formation of oversized particles. These oversized particles caused catastrophic surface scratches, resulting in completely out-of-control roughness (>10 nm), demonstrating the critical importance of maintaining the pH at 3-6 for balancing oxidation rate and dispersion stability.

[0101] Compared to Example 1, Comparative Example 6, with its alkaline pH, experienced a decrease in removal rate (RR) to 750 nm / h and a dramatic increase in roughness (Ra) from 0.06 nm to >10 nm, resulting in noticeable scratches. Under alkaline conditions, the potassium permanganate oxidant is unstable and prone to decomposition and failure, leading to a weakened chemical softening effect and a decrease in RR. Simultaneously, the alkaline environment alters the zeta potential of the abrasive particle surface, potentially causing charge neutralization and agglomeration, or even hydrolysis of certain components. The severe agglomeration of the abrasive again produced destructive large particles, resulting in severe surface scratches and extremely high roughness (>10 nm), further confirming that pH 3-6 is the optimal window for ensuring synergistic effects of the components.

[0102] The spherical cerium oxide abrasive used in the examples was characterized by SEM, and the results are as follows: Figure 1 ,from Figure 1 It can be seen that the morphology of spherical cerium oxide abrasive is spherical or near-spherical.

[0103] The triangular cerium oxide abrasive used in the examples was characterized by SEM, and the results are as follows: Figure 2 ,from Figure 2 It can be seen that the morphology of triangular cerium oxide abrasive is triangular or triangular-like.

[0104] The AFM image of the silicon carbide wafer polished with the silicon carbide polishing slurry of Example 1 is shown below. Figure 3 As shown in the figure, the height sensor is the height sensor; The AFM image of the silicon carbide wafer polished with the silicon carbide polishing slurry of Example 2 is shown below. Figure 4 As shown; The AFM image of the silicon carbide wafer polished with the silicon carbide polishing slurry of Example 3 is shown below. Figure 5 As shown; The AFM image of the silicon carbide wafer polished with the silicon carbide polishing slurry of Example 4 is shown below. Figure 6 As shown; The AFM image of the silicon carbide wafer polished with the silicon carbide polishing slurry of Example 5 is shown below. Figure 7 As shown; The AFM image of the silicon carbide wafer polished with the silicon carbide polishing slurry of Example 6 is shown below. Figure 8 As shown; The AFM image of the silicon carbide wafer polished with the silicon carbide polishing slurry of Comparative Example 1 is shown below. Figure 9 As shown; The AFM image of the silicon carbide wafer polished with the silicon carbide polishing slurry of Comparative Example 2 is shown below. Figure 10 As shown; The AFM image of the silicon carbide wafer polished with the silicon carbide polishing slurry of Comparative Example 3 is shown below. Figure 11 As shown.

[0105] Comparative analysis shows that the corresponding examples 1-6 Figures 3-8 The wafer surface is smoother and flatter, with a significant reduction in roughness; while the corresponding surfaces in Comparative Examples 1-3 are... Figures 9-11 The surface exhibits obvious unevenness and high roughness, indicating that the silicon carbide polishing slurry in the embodiment performs better in improving the flatness of the wafer surface.

[0106] The above are merely embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent modifications made based on the content of the present invention specification, or direct or indirect applications in related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A silicon carbide polishing slurry, characterized in that: Includes the following components: The abrasive is composed of abrasive with a first morphology and abrasive with a second morphology; Oxidizing agent; A dispersant comprising at least one nonionic surfactant and at least one phosphate chelating agent; water; The pH value of the polishing fluid composition is 3-6; The first morphology is a polyhedral morphology with acute angles or angular structures, preferably a triangle, a cube, or an irregular polyhedron; the second morphology is a spherical or near-spherical morphology.

2. The silicon carbide polishing slurry according to claim 1, characterized in that: The silicon carbide polishing slurry comprises the following components by weight percentage: Abrasive: 1 wt.% ~ 5 wt.%; Oxidizing agent: 0.5 wt.% ~ 5 wt.%; Dispersant: 0.1 wt.% ~ 3 wt.%.

3. The silicon carbide polishing slurry according to claim 1, characterized in that: The abrasive with the first morphology and the abrasive with the second morphology are each independently selected from cerium oxide abrasive or silicon oxide abrasive.

4. The silicon carbide polishing slurry according to claim 1, characterized in that: The first morphology of the abrasive has a D50 particle size of 50 nm to 200 nm; and / or, the second morphology of the abrasive has a D50 particle size of 50 nm to 150 nm.

5. The silicon carbide polishing slurry according to claim 1, characterized in that: The first morphology is triangular; the second morphology is spherical.

6. The silicon carbide polishing slurry according to claim 1, characterized in that: The nonionic surfactant is selected from at least one of fatty alcohol polyoxyethylene ether, alkyl glycoside, and polyvinylpyrrolidone; preferably fatty alcohol polyoxyethylene ether and / or alkyl glycoside.

7. The silicon carbide polishing slurry according to claim 1, characterized in that: The phosphate chelating agent is selected from at least one of sodium pyrophosphate, sodium tripolyphosphate, and sodium hexametaphosphate.

8. The silicon carbide polishing slurry according to claim 1, characterized in that: The mass ratio of the abrasive with the first morphology to the abrasive with the second morphology is 0.5-5:1-5.

9. A method for preparing the silicon carbide polishing slurry as described in any one of claims 1 to 8, characterized in that: Includes the following steps: S1: Mix the abrasive with the first morphology and the abrasive with the second morphology in water, stir, and form an abrasive dispersion; S2: Add dispersant and oxidant to the abrasive dispersion, adjust the pH value to 3-6, stir, and obtain the silicon carbide polishing slurry.

10. A polishing method for silicon carbide wafers, characterized in that: This includes performing chemical mechanical polishing on silicon carbide wafers using the silicon carbide polishing slurry according to any one of claims 1 to 8.

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