THE ROLE OF N-2 IN ASPECT-RATIO-DEPENDENT ETCHING OF SIO2

We report mechanistic study of the role of nitrogen in reducing aspect -ratio-dependent etching when added to a mixture of hydrocarbon and fl uorocarbon gases in a magnetically enhanced reactive ion etcher. Throu gh examination of ion and neutral transport phenomenon, reactant trans port issues, and surface charging, the source of aspect-ratio-dependen t etching was identified for the CHF3/CF4/Ar etch chemistry processes investigated. The total flow of CHF3 + CF4 was held constant at 30 scc m. Polymerization was found to be the primary source of aspect-ratio-d ependent etching. The addition of nitrogen is investigated with respec t to its impact on etch and deposition rates.