In situ transmission electron microscopy observations of 1.8 μm and 180 nm Cu interconnects under thermal stresses

In situ heating transmission electron microscopy was used to observe the stress relaxation behavior in 1.8 mu m and 180 nm wide Cu interconnects in real time. 1.8 mu m lines exhibit dislocation nucleation at the grain boundaries, while void nucleation/growth was observed in the 180 nm lines. The difference in the stress relaxation mechanism is due to distinct stress states among the two lines, namely, biaxial for the 1.8 mu m lines and quasihydrostatic stress for the 180 nm lines. Quasihydrostatic stresses in the 180 nm lines are likely to lead to an absence of dislocation motion. (c) 2006 American Institute of Physics.