Experimental investigations through modeling and optimization for fabrication of fused silica in medium-pressure plasma process

Abstract

Due to its deterministic high material removal rate (MRR) and exceptional surface finish, the medium-pressure plasma process, which is based solely on chemical etching, has been developed as a promising fabrication method for fused silica. In the present investigation, the input parameters, such as radio-frequency power, total pressure, and processing time, are investigated and optimized for MRR and % change in surface roughness (%ΔRa) using response surface methodology. The process parameters, i.e., pressure ratio (SF6/O2) of 1:1 and gas composition (He: (SF6+O2)) of 90:10, have been kept constant during all experiments. The optimized value achieved for MRR and %ΔRa is 0.29 mm3/min and 3.4%, at RF power of 80 W, total pressure of 11.6 mbar, and processing time of 60 min. The result depicts that surface roughness marginally changes from 2.79 to 2.82 μm after plasma processing at optimum parametric conditions. Moreover, FESEM result shows that the cracks and irregularity have been reduced. EDX results reveal that elements silicon, oxygen, fluorine, and carbon appear on the plasma processed surface, showing the reaction occurring during plasma processing. Moreover, XPS results show the peaks of silicon (Si2p, Si2s), carbon (C1s), oxygen (O1s), and fluorine (F2p, F2s, F1s) on the processed surface of fused silica.