Interconnects beyond Cu: Investigation of single crystal metal interconnects
The scaling of integrated circuit (IC) chips with each new technology node has resulted in performance and reliability issues that are associated with the use of polycrystalline copper interconnects. In addition to increased interconnect resistance with aggressive dimensional scaling, Cu resistivity rises as the critical dimension of interconnects approaches the electron mean free path of Cu (39 nm at room temperature). This so-called resistivity-size effect is largely the result of electron scattering at grain boundaries and is estimated to increase the resistivity of a 10 nm-wide polycrystalline Cu interconnect line an order of magnitude above its bulk resistivity. Co and Ru are both candidate metals of interest to replace Cu despite their larger bulk resistivities due to their much lower mean free paths. This project investigates the fabrication of single crystal Co, Ru, and Cu interconnects using electrodeposition to replace polycrystalline copper as the interconnect material on integrated circuit (IC) chips.