Mechanism of Cu diffusion in porous low-k dielectrics -: art. no. 024108

This work is aimed at understanding the nature of the interactions between metal interconnects and nanoporous dielectrics in integrated circuits. Electrical testing of metal-insulator-semiconductor capacitors is used to assess Cu diffusion and charge injection in the dielectric in the presence of an electric field. We show that the effect of surface chemistry in Cu diffusion is stronger than the effect of porosity. The surface chemistry or the amount of organic content in a porous dielectric depends on the pore morphology and it is limited by steric hindrance during dielectric fabrication. Furthermore, we show that the reinclusion of organic groups in a damaged dielectric results in an increasing resistance to Cu diffusion. We propose that a combination of moisture-related species in the dielectric and interfacial oxygen oxidizes Cu. The copper oxide acts as a source for Cu ions available for diffusion. A quantitative analysis of Cu drift in nanoporous dielectrics that shows the importance of surface chemistry and porosity is presented and the mechanism of metal diffusion and charge injection in nanoporous dielectrics is discussed. (c) 2005 American Institute of Physics.