Abrasive mechanisms and interfacial mechanics of amorphous silicon carbide thin films in chemical-mechanical planarization
VT Nguyen and TH Fang, JOURNAL OF ALLOYS AND COMPOUNDS, 845, 156100 (2020).
In this paper, the polishing process of a silicon carbide (SiC) substrate covered with a thin amorphous SiC (a-SiC) film is investigated by molecular dynamics simulation method. A diamond abrasive particle slides or rolls over the SiC workpiece surface with different depths and speeds. The results indicated that in the sliding motion, increasing the sliding depth leads to a higher force, stress, temperature, and a higher number of atoms removed. The best surface quality gains by sliding at 10 angstrom depth or at the depth that equal to the a-SiC layer thickness. At this polishing depth, the a-SiC plays a role as a padding layer that prevents the SiC substrate from subsurface damage. At a deeper depth, the crystalline SiC atoms at the interfacial area are transformed into the amorphous state. In sliding motion, the ploughing and cutting regimes dominate the atomic removal mechanism. Similar to the sliding motion, improving the rolling depth results in a higher force, stress, temperature, and the number of atoms removed. However, the rolling movement generates higher stress, deeper subsurface damage (SSD) zone, rougher surface and lower number of atoms removed. In rolling motion, the removal mechanism is mainly adhering to which the workpiece atoms are adhered by the abrasive surface. This report also investigates the effect of the abrasive size and the a-SiC thickness to the removal process. The bigger abrasive the higher force, stress, and the number of atoms removed. While increasing the a-SiC film thickness leads to a lower force and shallower SSD zone. Despite the differences in the abrasive size and the thickness, the sliding motion always performs a dramatically better ability to remove the workpiece atoms than the rolling one. A SiC model with the ripple structure is also constructed and analyzed. The bigger ripple mostly generates a higher force, temperature, strain, and a higher number of atoms removed. The high- temperature and high-value atomic strain areas mainly exist in the a-SiC film, at the upper side of the interface. The sliding motion again wipes out more atoms and creates a smoother groove than the rolling motion. Additionally, in the rolling motion, the large ripple can be lengthened and stuck to the substrate. (C) 2020 Elsevier B.V. All rights reserved.
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