Inductively coupled plasma etching of tapered via in silicon for MEMS integration

An ICP plasma etching technique for fabrication of tapered vias on silicon substrates has been developed by means of single patterning and etching process. Experimentally, effects of parameters including ICP power, chamber pressure, gas ratio and RF bias power were investigated for their impact on etch rate, selectivity, profile and surface roughness. Monotonic profile angles in the range of 60-80 degrees have been achieved on 10-50 mu m wide vias through adjustment of the C4F8/SF6 ratio and optimization on other key parameters. We found that addition of O-2 controlled lateral etch rate only weakly, except when running the process at cryogenic temperature. Adjustment of the process powers was a significant factor in controlling sidewall roughness. (C) 2015 Elsevier B.V. All rights reserved.