Scaling of Metal Interconnects: Challenges to Functionality and Reliability

Copper‐based nano interconnects featuring CDs well beyond today’s chip generations and air gap structures were fabricated and subjected to electrical characterization and tests to get already today insight on functionality and reliability aspects of metallization schemes in future semiconductor products. Size effects observed already in today’s advanced products will definitely limit the resistivity in future interconnects. Copper diffusion barrier layers were scaled down to the 1nm regime of thicknesses without observable degradation effects regarding adhesion properties and functionality. Interconnect reliability was found to decrease with decreasing barrier thickness. Worst results regarding adhesion properties and interconnect reliability were obtained for vanishing barrier thickness which promotes unrestricted mass flow of copper along the interconnect line. Air gaps were developed and characterized as an alternative approach to porous ultra low‐k materials. They allowed the realization of effective ...