Copper interconnection integration and reliability

A processing sequence to produce a multilevel Cu/polyimide structure which is stable in a corrosive environment is described. Using a combination of dry etching and chemical-mechanical polishing, a fully planarized Cu/polyimide wiring structure was obtained. This technology has been successfully applied to the fabrication of 64 kb complementary metal-oxide-semiconductor static random access memory (CMOS SRAM) chips. Chip functionality was not affected by 12 thermal cycles from 20 to 400 °C. The electromigration activation energy for evaporated Cu, Cu(Mg), Cu(Zr), Cu(Sn) and chemical vapour deposition (CVD) pure Cu was evaluated using a drift velocity technique. The mass transport rates of CVD Cu and evaporated Cu were found to be essentially the same, with an electromigration activation energy of 0.70 ± 0.05 eV. An Mg impurity in Cu enhances the electromigration damage rate in Cu, while Sn and Zr drastically increase the Cu electromigration failure lifetime. © 1995.