Mechanisms for microstructure evolution in electroplated copper thin films

Abstract

We present a model which accounts for the dramatic evolution in the microstructure of electroplated copper thin films near room temperature. Microstructure evolution occurs during a transient period of hours following deposition, and includes an increase in grain size, changes in preferred crystallographic texture, and decreases in resistivity, hardness and compressive stress. As the grain size increases from the as-deposited value of 0.05-0.1 μm up to several μm, the decreasing grain boundary contribution to electron scattering lowers the resistivity by tens of percent to near-bulk values. Concurrently, as the volume of grain boundaries decreases, the stress is shown to change in the tensile direction by tens of MPa. The as-deposited grain size is also shown to be consistent with grain boundary pinning.