Preparation of SiO2@MnO2 composite abrasives and their performance in chemical-mechanical polishing of SiC substrates

Enhancing chemical mechanical polishing (CMP) performance is the key to improving the surface quality and processing cost of silicon carbide (SiC). However, traditional SiO2 abrasive fails to meet the material removal rate (MRR) requirement for SiC processing. In order to solve this problem, we use chemical deposition method to coat MnO2 on the surface of SiO2 to enhance CMP performance. A series of SiO2@MnO2 composite abrasives (the coating mass fraction of MnO2 on the surface of SiO2 is 0, 0.03 wt%, 0.05 wt%, 0.07 wt%, 0.10 wt%, respectively) are synthesized and characterized. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and the size distribution analyses confirm that the composite abrasive possesses a core-shell structure, wherein the core is composed of SiO2 while the shell consists of MnO2. The results of CMP experiments demonstrate that the MRR of SiO2@MnO2 (0.05 wt%) can reach 403 nm/h, which is 220% higher than that traditional SiO2 abrasive, effectively resolving the limitation of MRR in previous literature. Additionally, the surface roughness (Sa) is reduced to 0.62 nm (measuring area: 500 mu m x 500 mu m). X-ray photoelectron spectroscopy analysis, contact angle test and dynamic friction test are used to further explore the removal mechanism of composite abrasives in SiC CMP. As a result, Mn-O-Si bond is formed by chemical interaction between the slurry including SiO2@MnO2 composite abrasive and SiC substrate, which weakens Si-C bond of SiC surface. The dynamic friction coefficient of the composite abrasive on SiC substrate is enhanced, implying that the coating of MnO2 also increases the contact sites and mechanical effect between the abrasive and SiC. Under the synergistic action of chemical and mechanical effects, the MRR of SiC is improved, and a better flatness is obtained.