Study of the plasma and cleaning impact on a CoWPB material

Self-aligned barriers (SAB) are investigated for the 45 nm technology node and beyond to improve copper electromigration and stress-migration resistance. The impact of plasma and cleaning processes used in the integration were studied on CoWPB-SAB. Results extracted from complementary characterizations show that after fluorocarbon-based and/or oxidizing plasmas, CoWPB is slightly etched and a less dense zone is formed at the CoWPB surface. This zone is not protective during cleaning: CoWPB is alterated by diluted HF solution leading to pits at the surface and crystals for the samples treated by fluorocarbon-based plasma. Pitting corrosion can be caused by the dissolution of one of the two phases existing in the CoWPB: amorphous and crystalline. The solubility of these phases depends on their thermodynamic equilibrium in solution and their reaction kinetics with HF.