Application of surface analysis in study on removal mechanism and abrasive selection during fused silica chemical mechanical polishing

Abstract

In this work, surface analysis technology is employed to investigate the removal mechanism and the selection of abrasive during fused silica chemical mechanical polishing (CMP). Morphology of abrasives is inspected by scanning electron microscope (SEM). The atomic force microscope (AFM) is used to determine the surface roughness (Rq) and undulating (PV) of the polished fused silica surface. The resultsshow that abrasive morphology has a tremendous influence on removal rate (MRR) and PV but has little effect on the Rq. The AFM and infrared spectroscopy (IR) analysis show that a soft layer, called "silica gel membrane (SGM)," existed on the polished surface is the critical reason for the differences of MRR, Rq, and PV during CMP. For three kinds of micro-ceria abrasives, the abrasive with a rougher surface gets more opportunities to contact the surface of fused silica, yielding higher MRR. Regarding different kinds of nano-abrasives, there are more SGM induced by nano-ceria abrasive resulting from higher chemical reaction rate. The element contaminations on the polished fused silica have been assessed using X-ray photoelectron spectroscopy (XPS), and the results suggest that there are depths of 3.6 and 5.4-nm element contaminations on the polished surface of fused silica with nano-ceria and nanoalumina abrasives, respectively. While the surface polished by nano-silica is free of heterogeneous element contaminations. Based on study results, a novel polishing slurry is designed by modifying the chemical composition of nano-silica. Comparing with ceria-based slurry, the silica-based slurry has better removal efficiency, and surface quality in fused silica precision machining.

Recent Advances on Porous Siliceous Materials Derived from Waste

“…Several studies reported and described how it is possible to obtain SiO 2 nanoparticles (NPs) with different aspect ratios and textural properties, involving different types of porosities and high active surface areas [ 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 ]. Furthermore, its chemical inertness and insulating features favor the exploitation of SiO 2 in a plethora of technological applications [ 28 , 29 , 30 , 31 , 32 , 33 ]. Among these, SiO 2 is widely applied in nanocomposite formulations (as filler) [ 34 , 35 , 36 ], industrial catalysis (as substrate) [ 37 , 38 , 39 ], wastewater remediation processes (as adsorbent) [ 40 , 41 ], as a building material component [ 42 , 43 ], and in different advanced biomedical applications (e.g., as a drug-carrier system) [ 44 , 45 , 46 ].…”

Effects of functional alkali in magnetorheological finishing fluid

“…Correspondingly, the chemical effects during the interaction between MR fluid and workpiece were considered. Jacobs reported that the aqueous based MR fluid showed significant higher MRR (two-magnitude enhancement) when compared with the non-aqueous MR fluid in MRF while finishing the fused silica (FS) [11], such phenomenon indicated the water can significantly enhance the MRR in FS finishing. The origin of the enhanced MRR can be summarized into two perspectives: (a) dissolution of the FS, then its hardness can be reduced to facilitate the material removal [12]; (b) water based chemical reaction between the FS and the polishing grains, the classical chemical 'bond bridge' effects proposed by Cook is well-acknowledged to explain the MRR enhancement [13].…”

A Novel Strategy Achieving GaN Ultra-Smooth Surface via a Square, Flat Top Beam Shaped Femtosecond Laser Processing Combined with Chemical Mechanical Polishing

“…5 Chemical mechanical polishing is considered as the most effective global flattening technology. 6,7 However, it takes a lot of time to obtain ultra-smooth surface using a single method, 8 due to the high hardness and good chemical stability of GaN. To date, great efforts have been made to fabricate GaN with low Ra and high material removal rate.…”