REACTIVE ION ETCHING OF COPPER IN SICL4-BASED PLASMAS

Copper may become an alternative to aluminum as an interconnect material in ultralarge scale integration multilevel metallization schemes if it is possible to pattern Cu by dry etching in a manufacturable process. Here we report results on the reactive ion etching of Cu in SiCl4/Ar and SiCl4/N2 Plasmas. Etching has been investigated as a function of gas composition, pressure, and substrate temperature. We have obtained etch rates as high as 850 angstrom/min using SiCl4/N2 and a substrate temperature of approximately 220-degrees-C, with excellent etch selectivity of Cu relative to polyimide and SiO2. We demonstrate that it is feasible to pattern Cu anisotropically using polyimide as a high-temperature etch mask.