The effects of microstructure and surface terminal bonds of SiO2 aerogel films on dry etching were investigated using Ar, SF6, and C2F6 plasma gases. With Ar plasma etching, physical effect of ion bombardment on porous film was found. In residue-free SF6 plasma etching, reactive etchant transport and high-mass ion bombardment were observed. With C2F6 plasma etching, fluorocarbon residue layer was revealed to maintain surface morphology as acting a barrier to radical transport and ion bombardment. An etching of 450 degreesC-annealed SiO2 aerogel showed that a dense surface induced the decrease in reaction area, inhibition of etchant transport, and then uniform etching.