Iron-doped CeO2 abrasive and SiC material chemical mechanical polishing method

Abstract

The application provides a kind of iron-doped CeO2 abrasive and SiC material chemical mechanical polishing method;Fe-doped ceria is used as core abrasive and catalyst, which breaks through the kinetic barrier of Fenton-like reaction in alkaline environment. Through the substitutional doping engineering of Fe element, high concentration of oxygen vacancies and Ce 3+ Defects are induced in the CeO2 lattice, significantly narrowing the material band gap and achieving wide spectral response. At the same time, the high-energy photo-generated electrons generated by 365 nm ultraviolet light excitation accelerate the Fe(III) / Fe(II) redox cycle at the alkaline solid-liquid interface, thereby constructing an alkaline Fenton-like reaction pool driven by photoelectric coupling. The modified CeO2 abrasive acts as a photocatalyst and Fenton reagent, continuously releasing high concentrations of hydroxyl radicals and superoxide radicals in situ on the surface of silicon carbide wafers, breaking down the rigid network of Si-C bonds and generating a softer modified oxide layer. Subsequently, with the help of flexible mechanical shearing of dispersed abrasive, high material removal rate and lower surface roughness are achieved.

Description

Technical Field

[0001] This invention relates to the field of wafer processing technology, and in particular to a method for developing a silicon carbide polishing slurry with better performance, specifically a chemical mechanical polishing method for iron-doped CeO2 abrasive and SiC materials. Background Technology

[0002] Single-crystal silicon carbide, with its extremely wide bandgap, extremely high thermal conductivity, and huge breakdown electric field strength, has become an indispensable core material in aerospace, new energy vehicles, and high-power high-frequency electronic devices. However, these excellent physicochemical properties endow silicon carbide with extremely high chemical inertness and mechanical hardness, leading to significant technical bottlenecks in its surface planarization process. Chemical mechanical polishing (CMP) is currently the mainstream, and even the only effective, technical approach for achieving global planarization of silicon carbide wafers. Its core mechanism lies in the interfacial reaction between the chemically active substances in the polishing slurry and the silicon carbide wafer surface, generating a relatively soft chemically modified layer, which is then removed by the mechanical shearing action of the polishing pad and abrasive. In this complex solid-liquid interfacial reaction kinetics, balancing the chemical reaction rate and the mechanical removal rate is the key factor determining the wafer surface processing quality and material removal efficiency.

[0003] Against this backdrop, developing ultra-small monodisperse cerium oxide (CeO2) nanoparticles with sizes below 30 nm, uniform morphology, and excellent colloidal dispersibility, surpassing traditional large-particle abrasives, has become a key material platform for overcoming the bottleneck of atomic-level planarization. Although ultra-small cerium oxide abrasives have shown great potential in reducing surface roughness, their inherently low chemical reactivity often results in material removal rates that cannot meet the demands of industrial mass production. To simultaneously achieve both low surface roughness and high material removal rates, photocatalytic-assisted and Fenton reaction-assisted chemical mechanical polishing technologies have emerged. These technologies utilize photocatalysts or Fe... 2+ Introducing ions into polishing slurries triggers photocatalytic or Fenton reactions, generating highly reactive oxygen species with strong oxidizing capabilities, which can significantly accelerate the chemical oxidation process on silicon carbide surfaces. However, traditional Fenton reactions heavily rely on a strictly acidic environment, which contradicts the alkaline slurry environment typically used in industrial silicon carbide chemical mechanical polishing. Under alkaline conditions, conventional transition metals readily undergo hydrolysis and precipitation, leading to a sharp loss of catalytic activity. This constitutes the biggest theoretical and engineering obstacle to applying iron-based and copper-based Fenton systems to alkaline polishing slurries. Summary of the Invention

[0004] The purpose of this invention is to address the problems existing in the background art by proposing a chemical mechanical polishing (CMP) method for iron-doped CeO2 abrasives and SiC materials. This method significantly improves the polishing performance of silicon carbide wafers through Fenton-like reaction-assisted photocatalytic CMP. The CeO2 abrasive particles provided by this invention are characterized by a grain size of 200-250 nm, which generates a high concentration of oxygen vacancies and narrows the band gap, achieving deep coupling between the Fenton-like reaction and photocatalytic CMP under alkaline conditions.

[0005] The technical solution of this invention to solve the aforementioned technical problem is: designing an iron-doped CeO2 abrasive, characterized in that the preparation method of the abrasive includes the following steps: Step 1: Add 5g of CeO2 powder to 100ml of deionized water and stir continuously for 30-60 minutes to form a CeO2 mixture; Step 2: Add Fe(NO3)3·9H2O crystals containing 0.025-0.15g of Fe element to a CeO2 mixture, stir for 30 minutes, and then dry in an oven at 110℃ for 12 hours to obtain a solid; Step 3: Grind the solid from Step 2 into powder and calcine it in air at 500℃-550℃ for 2-4 hours, with a heating rate of 5-10℃ / min, to obtain the final CeO2 abrasive.

[0006] Furthermore, this invention provides a chemical mechanical polishing method for SiC materials, characterized in that the method uses CeO2 abrasive as described above. The specific process of the method is as follows: the above-mentioned CeO2 abrasive is added to deionized water and stirred to prepare a 1wt% CeO2 abrasive solution. 5 vol% H2O2 is added to the above solution, and after magnetic stirring, the pH value is adjusted to 9 using saturated KOH solution to obtain a polishing solution. Then, the SiC material is chemically mechanically polished under 365 nm ultraviolet light irradiation using the above polishing solution to obtain polished SiC material.

[0007] Compared with existing technologies, the advantages of this invention are as follows: This invention uses Fe-doped cerium oxide as the core abrasive and catalyst, breaking through the kinetic barrier of Fenton-like reactions under alkaline conditions. Through Fe substitutional doping engineering, a high concentration of oxygen vacancies and CeO2 atoms are induced within the CeO2 lattice. 3+The defects are significantly narrowed, resulting in a broad spectral response. Simultaneously, high-energy photogenerated electrons generated by 365 nm ultraviolet light excitation accelerate the Fe(III) / Fe(II) redox cycle at the alkaline solid-liquid interface, thus constructing a photoelectrically coupled alkaline Fenton-like reaction cell. Modified CeO2 abrasive acts as a photocatalyst and Fenton reactant, continuously releasing high concentrations of hydroxyl and superoxide radicals in situ on the silicon carbide wafer surface, breaking down the rigid Si-C bond network and generating a softer oxide-modified layer. Subsequently, the flexible mechanical shearing of the dispersed abrasive achieves a high material removal rate and lower surface roughness. Attached Figure Description

[0008] To more clearly illustrate the technical solutions of the embodiments of the present invention, 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 the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0009] Figure 1 The figure illustrates the removal rates of SiC materials by different proportions of Fe-doped CeO2 abrasives according to this invention. (In the figure, CMP stands for Chemical Mechanical Polishing, a common wafer fabrication technique. PCMP stands for Photocatalytic Chemical Mechanical Polishing, which introduces ultraviolet light irradiation on top of CMP. The core of PCMP is to excite the photocatalyst (such as CeO2) in the polishing solution with ultraviolet light to generate highly oxidizing hydroxyl radicals, thereby enhancing the oxidation performance of the material and making it easier to remove.) Figure 2 This invention relates to the surface quality of SiC material after CMP treatment using CeO2 abrasives with different proportions of Fe doping. Figure 2 In this context, 'a' represents an atomic force microscope image of SiC after CMP treatment with CeO2 abrasive doped with 0.5 wt% Fe. Figure 2 In this image, b represents an atomic force microscope image of SiC after CMP treatment with CeO2 abrasive doped with 1 wt% Fe. Figure 2 In this image, 'c' represents an atomic force microscope image of SiC after CMP treatment with CeO2 abrasive doped with 1.5 wt% Fe. Figure 2 In this context, d represents an atomic force microscope image of SiC after CMP treatment with CeO2 abrasive doped with 2wt% Fe. Figure 2 In this image, 'e' represents an atomic force microscope image of SiC after CMP treatment with CeO2 abrasive doped with 2.5 wt% Fe. Figure 2 In this context, f represents an atomic force microscope image of SiC after CMP treatment with CeO2 doped with 3wt% Fe.

[0010] Figure 3 The X-ray diffraction patterns of CeO2 abrasive, CeO2 powder, and Fe3O2 powder obtained in Example 2 of this invention are shown.

[0011] Figure 4 for Figure 3 A magnified view of a portion of the diffraction peaks.

[0012] Figure 5 These are Raman images of the CeO2 abrasive and CeO2 powder obtained in Example 2 of the present invention. Detailed Implementation

[0013] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0014] Many specific details are set forth in the following description to provide a thorough understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below. Furthermore, the term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it an embodiment that is mutually exclusive, either alone or selectively, with other embodiments.

[0015] This invention provides an iron-doped CeO2 abrasive, the preparation method of which includes the following steps: Step 1: Add 5g of CeO2 powder to 100ml of deionized water and stir continuously for 30-60 minutes to form a CeO2 mixture; Step 2: Add Fe(NO3)3·9H2O crystals containing 0.025-0.15g of Fe element to a CeO2 mixture, stir for 30 minutes, and then dry in an oven at 110℃ for 12 hours to obtain a solid; Step 3: Grind the solid from Step 2 into powder and calcine it in air at 500℃-550℃ for 2-4 hours, with a heating rate of 5-10℃ / min, to obtain the final CeO2 abrasive.

[0016] Furthermore, this invention provides a chemical mechanical polishing method for SiC materials, characterized in that the method uses CeO2 abrasive as described above. The specific process of the method is as follows: the above-mentioned CeO2 abrasive is added to deionized water and stirred to prepare a 1wt% CeO2 abrasive solution. 5 vol% H2O2 is added to the above solution, and after magnetic stirring, the pH value is adjusted to 9 using saturated KOH solution to obtain a polishing solution. Then, the SiC material is chemically mechanically polished under 365 nm ultraviolet light irradiation using the above polishing solution to obtain polished SiC material.

[0017] Example 1 This embodiment provides a chemical mechanical polishing method for iron-doped CeO2 abrasive and SiC materials. The preparation method of the iron-doped CeO2 abrasive is as follows: Step 1: Add 5g of CeO2 powder to 100ml of deionized water and stir continuously for 30-60 minutes to form a CeO2 mixture; Step 2: Add Fe(NO3)3·9H2O crystals containing 0.025g of Fe element to a CeO2 mixture, stir for 30 minutes, and then dry in an oven at 110℃ for 12 hours to obtain a solid; Step 3: Grind the solid from Step 2 into powder and calcine it in air at 500℃-550℃ for 2-4 hours, with a heating rate of 5-10℃ / min, to obtain the final CeO2 abrasive.

[0018] Furthermore, the present invention provides a chemical mechanical polishing method for SiC materials, characterized in that the method uses CeO2 abrasive as described above, and the specific process is as follows: The above-mentioned CeO2 abrasive is added to deionized water and stirred to prepare a 1wt% CeO2 abrasive solution. 5 vol% H2O2 is added to the above solution, and after magnetic stirring, the pH value is adjusted to 9 using saturated KOH solution to obtain a polishing solution. Then, the SiC material is chemically mechanically polished under 365 nm ultraviolet light irradiation to obtain polished SiC material.

[0019] In this embodiment, a material removal rate of 370 nm / h and a surface roughness of 0.258 nm were ultimately achieved.

[0020] Example 2 This embodiment provides a chemical mechanical polishing method for iron-doped CeO2 abrasive and SiC materials. The preparation method of the iron-doped CeO2 abrasive is as follows: Step 1: Add 5g of CeO2 powder to 100ml of deionized water and stir continuously for 30-60 minutes to form a CeO2 mixture; Step 2: Add Fe(NO3)3·9H2O crystals containing 0.05g of Fe element to a CeO2 mixture, stir for 30 minutes, and then dry in an oven at 110℃ for 12 hours to obtain a solid; Step 3: Grind the solid from Step 2 into powder and calcine it in air at 500℃-550℃ for 2-4 hours, with a heating rate of 5-10℃ / min, to obtain the final CeO2 abrasive.

[0021] Furthermore, this invention provides a chemical mechanical polishing method for SiC materials, characterized in that the method uses CeO2 abrasive as described above. The specific process of the method is as follows: the above-mentioned CeO2 abrasive is added to deionized water and stirred to prepare a 1wt% CeO2 abrasive solution. 5 vol% H2O2 is added to the above solution, and after magnetic stirring, the pH value is adjusted to 9 using saturated KOH solution to obtain a polishing solution. Then, the SiC material is chemically mechanically polished under 365 nm ultraviolet light irradiation using the above polishing solution to obtain polished SiC material.

[0022] In this embodiment, a material removal rate of 529 nm / h and a surface roughness of 0.184 nm were ultimately achieved.

[0023] Example 3 This embodiment provides a chemical mechanical polishing method for iron-doped CeO2 abrasive and SiC materials. The preparation method of the iron-doped CeO2 abrasive is as follows: Step 1: Add 5g of CeO2 powder to 100ml of deionized water and stir continuously for 30-60 minutes to form a CeO2 mixture; Step 2: Add Fe(NO3)3·9H2O crystals containing 0.75g of Fe element to a CeO2 mixture, stir for 30 minutes, and then dry in an oven at 110℃ for 12 hours to obtain a solid; Step 3: Grind the solid from Step 2 into powder and calcine it in air at 500℃-550℃ for 2-4 hours, with a heating rate of 5-10℃ / min, to obtain the final CeO2 abrasive.

[0024] Furthermore, the present invention provides a chemical mechanical polishing method for SiC materials, characterized in that the method uses CeO2 abrasive as described above, and the specific process is as follows: The above-mentioned CeO2 abrasive is added to deionized water and stirred to prepare a 1wt% CeO2 abrasive solution. 5 vol% H2O2 is added to the above solution, and after magnetic stirring, the pH value is adjusted to 9 using saturated KOH solution to obtain a polishing solution. Then, the SiC material is chemically mechanically polished under 365 nm ultraviolet light irradiation to obtain polished SiC material.

[0025] In this embodiment, a material removal rate of 504 nm / h and a surface roughness of 0.193 nm were ultimately achieved.

[0026] Example 4 This embodiment provides a chemical mechanical polishing method for iron-doped CeO2 abrasive and SiC materials. The preparation method of the iron-doped CeO2 abrasive is as follows: Step 1: Add 5g of CeO2 powder to 100ml of deionized water and stir continuously for 30-60 minutes to form a CeO2 mixture; Step 2: Add Fe(NO3)3·9H2O crystals containing 0.1g of Fe element to CeO2 mixture, stir for 30 minutes, and then dry in an oven at 110℃ for 12 hours to obtain solid; Step 3: Grind the solid from Step 2 into powder and calcine it in air at 500℃-550℃ for 2-4 hours, with a heating rate of 5-10℃ / min, to obtain the final CeO2 abrasive.

[0027] Furthermore, this invention provides a chemical mechanical polishing method for SiC materials, characterized in that the method uses CeO2 abrasive as described above. The specific process of the method is as follows: the above-mentioned CeO2 abrasive is added to deionized water and stirred to prepare a 1wt% CeO2 abrasive solution. 5 vol% H2O2 is added to the above solution, and after magnetic stirring, the pH value is adjusted to 9 using saturated KOH solution to obtain a polishing solution. Then, the SiC material is chemically mechanically polished under 365 nm ultraviolet light irradiation using the above polishing solution to obtain polished SiC material.

[0028] In this embodiment, a material removal rate of 384 nm / h and a surface roughness of 0.3 nm were ultimately achieved.

[0029] Example 5 This embodiment provides a chemical mechanical polishing method for iron-doped CeO2 abrasive and SiC materials. The preparation method of the iron-doped CeO2 abrasive is as follows: Step 1: Add 5g of CeO2 powder to 100ml of deionized water and stir continuously for 30-60 minutes to form a CeO2 mixture; Step 2: Add Fe(NO3)3·9H2O crystals containing 0.125 Fe elements to a CeO2 mixture, stir for 30 minutes, and then dry in an oven at 110℃ for 12 hours to obtain a solid. Step 3: Grind the solid from Step 2 into powder and calcine it in air at 500℃-550℃ for 2-4 hours, with a heating rate of 5-10℃ / min, to obtain the final CeO2 abrasive.

[0030] Furthermore, this invention provides a chemical mechanical polishing method for SiC materials, characterized in that the method uses CeO2 abrasive as described above. The specific process of the method is as follows: the above-mentioned CeO2 abrasive is added to deionized water and stirred to prepare a 1wt% CeO2 abrasive solution. 5 vol% H2O2 is added to the above solution, and after magnetic stirring, the pH value is adjusted to 9 using saturated KOH solution to obtain a polishing solution. Then, the SiC material is chemically mechanically polished under 365 nm ultraviolet light irradiation using the above polishing solution to obtain polished SiC material.

[0031] In this embodiment, a material removal rate of 185 nm / h and a surface roughness of 0.292 nm were ultimately achieved.

[0032] Example 6 This embodiment provides a chemical mechanical polishing method for iron-doped CeO2 abrasive and SiC materials. The preparation method of the iron-doped CeO2 abrasive is as follows: Step 1: Add 5g of CeO2 powder to 100ml of deionized water and stir continuously for 30-60 minutes to form a CeO2 mixture; Step 2: Add Fe(NO3)3·9H2O crystals containing 0.125 Fe elements to a CeO2 mixture, stir for 30 minutes, and then dry in an oven at 110℃ for 12 hours to obtain a solid. Step 3: Grind the solid from Step 2 into powder and calcine it in air at 500℃-550℃ for 2-4 hours, with a heating rate of 5-10℃ / min, to obtain the final CeO2 abrasive.

[0033] Furthermore, this invention provides a chemical mechanical polishing method for SiC materials, characterized in that the method uses CeO2 abrasive as described above. The specific process of the method is as follows: the above-mentioned CeO2 abrasive is added to deionized water and stirred to prepare a 1wt% CeO2 abrasive solution. 5 vol% H2O2 is added to the above solution, and after magnetic stirring, the pH value is adjusted to 9 using saturated KOH solution to obtain a polishing solution. Then, the SiC material is chemically mechanically polished under 365 nm ultraviolet light irradiation using the above polishing solution to obtain polished SiC material.

[0034] In this embodiment, a material removal rate of 162 nm / h and a surface roughness of 0.245 nm were ultimately achieved.

[0035] Comparative Example 1 This comparative example provides a chemical mechanical polishing method for SiC materials, characterized by using commercially available CeO2 as the abrasive. The specific process is as follows: The CeO2 abrasive is added to deionized water and stirred to prepare a 1 wt% CeO2 solution. Then, 5 vol% H2O2 is added to the solution, and after magnetic stirring, the pH is adjusted to 9 using a saturated KOH solution to obtain the polishing solution. Finally, the SiC material is chemically mechanically polished under 365 nm ultraviolet light irradiation using the polishing solution to obtain the polished SiC material.

[0036] In this comparative example, a material removal rate of 101 nm / h was ultimately achieved.

[0037] Comparative Example 2 This comparative example provides a chemical mechanical polishing method for SiC materials, characterized by using Fe2O3 as the abrasive for polishing the SiC material. The specific process is as follows: the abrasive is added to deionized water and stirred to prepare a 1 wt% CeO2 solution. 5 vol% H2O2 is added to the solution, and after magnetic stirring, the pH is adjusted to 9 using a saturated KOH solution to obtain the polishing solution. Then, the SiC material is chemically mechanically polished using the polishing solution under 365 nm ultraviolet light irradiation to obtain the polished SiC material.

[0038] The above-mentioned abrasive is obtained by calcining Fe(NO3)3·9H2O crystals in air at 500-550℃ for 2-4 h, with a heating rate of 5-10℃ / min.

[0039] In this comparative example, a material removal rate of 48 nm / h was ultimately achieved.

[0040] The test results of the polished SiC materials obtained in Examples 1 to 6 and Comparative Examples 1 and 2 show that the optimal ratio of Fe-doped CeO2 is 1 wt%, achieving a material removal rate of 504 nm / h and a surface roughness of 0.184 nm.

[0041] CeO2 doped with 0.5 wt%, 1.0 wt%, 1.5 wt%, 2.0 wt%, 2.5 wt%, and 3.0 wt% Fe (see...) Figure 1 After CMP (conventional chemical mechanical polishing) and PCMP (chemical mechanical polishing followed by cleaning) treatments, the surface roughness was lowest with the 1.0 wt% Fe / CeO2 PCMP treatment, which reduced the roughness to 0.184 nm (see [link to product description]). Figure 2 ).

[0042] XRD characterization tests were performed on undoped CeO2 abrasive and CeO2 with different iron doping ratios, as shown below. Figure 3 As shown, no obvious impurity peaks were observed, indicating that iron doping did not change the main crystal structure and no lattice collapse or amorphization occurred.

[0043] Figure 4 yes Figure 3 The magnified view of the (111) peak shows that the intensity of the (111) peak of Fe / CeO2 is much lower than that of pure CeO2 and there is a peak shift of 0.08 degrees, which proves that Fe ions have been successfully incorporated into the CeO2 lattice.

[0044] Raman spectroscopy ( Figure 5 Lattice defects were detected. In CeO2 doped with 1 wt% Fe, the peak shifted to 462.4 cm⁻¹. -1 Furthermore, the strength is weakened, mainly due to Fe 3+ (Ionic radius approximately 0.645 Å, octet) Ce-substituted 4+ (Ionic radius approximately 0.97 Å, octet coordination) Lattice distortion produces more defects, leading to changes in Ce-O bond length and bond force constant, which in turn causes the main peak shift.

[0045] Any aspects not covered in this invention are applicable to existing technologies.

Claims

1. An iron-doped CeO2 abrasive, characterized in that, The preparation method of this abrasive includes the following steps: Step 1: Add 5g of CeO2 powder to 100ml of deionized water and stir continuously for 30-60 minutes to form a CeO2 mixture; Step 2: Add Fe(NO3)3·9H2O crystals containing 0.025-0.15g of Fe element to a CeO2 mixture, stir for 30 minutes, and then dry in an oven at 110℃ for 12 hours to obtain a solid; Step 3: Grind the solid from Step 2 into powder and calcine it in air at 500℃-550℃ for 2-4 hours, with a heating rate of 5-10℃ / min, to obtain the final CeO2 abrasive.

2. The iron-doped CeO2 abrasive according to claim 1, characterized in that, In step two, Fe(NO3)3·9H2O crystals containing 0.1g of Fe element are added to the CeO2 mixture.

3. The iron-doped CeO2 abrasive according to claim 1, characterized in that, In step three, the roasting time is 3 hours.

4. A chemical mechanical polishing method for SiC materials, characterized in that, The method uses CeO2 abrasive as described in claim 1. The specific process is as follows: CeO2 abrasive is added to deionized water and stirred to prepare a 1wt% CeO2 abrasive solution. 5 vol% H2O2 is added to the solution and stirred magnetically. The pH value is then adjusted to 9 using saturated KOH solution to obtain a polishing solution. Then, the SiC material is chemically and mechanically polished using the polishing solution under 365 nm ultraviolet light irradiation to obtain the polished SiC material.

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