The tribochemical mechanism of active abrasives on sapphire was investigated by comparing the scratching behavior of Si and SiO₂ probes through atomic force microscopy (AFM) and ReaxFF molecular dynamics (MD). Experiments revealed that the SiO₂ probe, due to its higher chemical activity, was more sensitive to changes in load and sliding cycles. It exhibited significantly greater increases in wear depth and volume compared to the Si probe. Simulations demonstrated that more Si-O-Al bonds appeared on the contact region of SiO₂ and sapphire, enhancing tribochemical reactions and mechanical force transfer. This revealed the atomic-removal pathway: hydration layer softening, solid-phase chemical reaction, and mechanical stripping. This study provides important insights serving as a valuable guidance to deeply understand the chemical mechanical polishing of sapphire by silica abrasives.

With the continuous miniaturization of integrated circuit (IC) devices, Co is recognized as the most promising alternative to Cu as an interconnecting metal. During IC processing, Co surfaces need to be flattened. This work describes dynamic polishing experiments and static corrosion experiments on the electrical, chemical, and mechanical factors involved in cobalt electrochemical mechanical polishing (ECMP). Then, the impact and proportion of individual and combined factors on the Co-ECMP are quantitatively analyzed. The experimental results show that mechanical action, rather than individual chemical or electrical action, plays a primary role in Co-ECMP. The ratios of individual mechanical, chemical, and electrical action proportions are 50.46%, 11.17%, and 6.20%, respectively. However, chemical and electrical assistance with mechanical action can achieve twofold efficiency and high-quality polishing of Co. For example, the ratios of mechanical–chemical or electrical–chemical–mechanical cooperation are 72.05% or 100%, respectively. In addition, polarization curves, energy dispersive spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS) were used to analyze the Co-ECMP process and products. Atomic-level mechanism analysis is performed for each factor. The results indicate that in Co-ECMP, the oxides formed on the Co surface are mainly CoO, Co(OH)₂, and Co₃O₄. The oxides react with the complexing agents to form loose and porous Co-benzotriazole (Co-BTA) complexes. Mechanical, chemical, and electrical factors collaborate to form and remove Co-BTA constantly, achieving rapid material removal and obtaining smooth atomic-level surfaces.

In response to the teaching needs of undergraduate students majoring in mechanical engineering, a teaching case of “ultrasonic chemical mechanical polishing (UVCMP) experiment” for mechanical non-traditional machining was designed. It was guided by a scientific research project. Through this case, students fully participated in the design and implementation of sapphire UVCMP orthogonal experiments. They learned and used atomic force microscopy, scanning electron microscope, transmission electron microscopy and other instruments to characterize sample properties. The mechanism of sapphire UVCMP was deeply explored. This experiment is beneficial for students to stimulate research interest, cultivate scientific literacy, and inspire innovative thinking.

Ultrasonic-assisted chemical mechanical polishing (UA-CMP) can greatly improve the sapphire material removal and surface quality, but its polishing mechanism is still unclear. This paper proposed a novel model of material removal rate (MRR) to explore the mechanism of sapphire UA-CMP. It contains two modes, namely two-body wear and abrasive-impact. Furthermore, the atomic force microscopy (AFM) in-situ study, computational fluid dynamics (CFD) simulation, and polishing experiments were conducted to verify the model and reveal the polishing mechanism. In the AFM in-situ studies, the tip scratched the reaction layer on the sapphire surface. The pit with a 0.22 nm depth is the evidence of two-body wear. The CFD simulation showed that abrasives could be driven by the ultrasonic vibration to impact the sapphire surface at high frequencies. The maximum total velocity and the air volume fraction (AVF) in the central area increased from 0.26 to 0.55 m/s and 20% to 49%, respectively, with the rising amplitudes of 1–3 μm. However, the maximum total velocity rose slightly from 0.33 to 0.42 m/s, and the AVF was nearly unchanged under 40–80 r/min. It indicated that the ultrasonic energy has great effects on the abrasive-impact mode. The UA-CMP experimental results exhibited that there was 63.7% improvement in MRR when the polishing velocities rose from 40 to 80 r/min. The roughness of the polished sapphire surface was R_a = 0.07 nm. It identified that the higher speed achieved greater MRR mainly through the two-body wear mode. This study is beneficial to further understanding the UA-CMP mechanism and promoting the development of UA-CMP technology.