In the search of new etchant gas combinations which address the earth's environmental concerns, a new C3F6-based plasma etch chemistry is investigated and evaluated for patterning fine SiO2 structures. Trimethylsilane and O-2 are added first separately to C3F6 to investigate their respective influence. It is shown that both trimethylsilane and O-2 additive gases have beneficial effects on the hole etching process but also result in undesired effects such as enhancement of the microloading effect upon trimethylsilane addition, and poor BPSG/resist selectivity upon O-2 addition. When trimethylsilane and O-2 are combined and mixed with C3F6, the opening of fine deep holes are achieved. For example, 0.15 mu m holes with an aspect ratio of 15 are fabricated using C3F6/8% trimethylsilane/20% O-2. The plasma conditions employed are a pressure of 10 mTorr, an rf source power of 500 W, a total flow rate of 30 seem, and a bias power of 150 W. These plasma conditions allow good control of the hole size, practical resist selectivity for deep hole processing, and microloading-free etching of holes down to 0.15 mu m. The C3F6-based plasma etch performance is further evaluated for nanometer-scale patterns using the simpler C3F6/O-2 gas system. Line and space and mesh hole patterns delineated by electron lithography are fabricated with dimensions as small as 20 and 70 nm, respectively.