Engineering the grain boundary network of thin films via ion-irradiation: Towards improved electromigration resistance

Abstract

Controlling the grain boundary network of small-scale materials-such as coatings and thin films-is an ambitious goal that would ultimately enable the production of components with tailored properties and improved reliability. In this work we present a new techniquewhich we term ion-induced grain boundary engineering (iGBE)-to engineer the character distribution and connectivity of grain boundaries in gold films in situ, as they are being deposited. iGBE consists of a repeated sequence of ion-induced material removal and material deposition which results in the selection and growth of crystal grains in twinned relationship. This phenomenon yields a substantial increase in the density and connectivity of Σ3 twin boundaries, which have renowned beneficial effect on the material's resistance to intergranular degradation. We confirm the improved reliability of iGBE microstructures by assessing their resistance to electromigration-one of the most common causes of failure in integrated circuit interconnects. We find that, through iGBE, interconnect lifetime increases by three orders of magnitude at standard operating conditions. Since iGBE is materialinsensitive and compatible with standard microfabrication technology, we expect it to have significant impact on microelectronics industry.

Pronounced grain boundary network evolution in nanocrystalline Cu subjected to large cyclic strains

“…This parallels conventional grain boundary engineering (i.e., grain boundary manipulation in coarse-grained materials), where improvements in properties have also come from an increase in the twin fraction [6,7]. Other nanocrystalline grain boundary engineering techniques have used either in situ deposition treatments or post-deposition annealing to increase the Σ3 fraction [8,9]. Improvements in ductility [5], fatigue life [10], corrosion resistance [11], and conductivity [5] have been reported.…”

Local Crystallographic Orientation Correlation Measurements Connecting the Processing and Properties of Face-Centered Cubic Metals

“…This parallels conventional grain boundary engineering, where improvements in properties have also come from techniques that increase the twin fraction [95,179]. Other nanocrystalline GB engineering techniques have used either in situ deposition treatments or post-deposition annealing to increase the Σ3 fraction [291,292]. The results have included improvements in ductility [119], fatigue life [293], corrosion resistance [162] and conductivity [119].…”