Stress Relaxation and Grain Growth Behaviors of (111)-Preferred Nanotwinned Copper during Annealing

Abstract

Highly (111)-oriented nanotwinned Cu (nt-Cu) films were fabricated on silicon wafers for thermal-stress characterization. We tailored the microstructural features (grain scale and orientation) of the films by tuning the electroplating parameters. The films were heat-treated and the relaxation behaviors of thermal stresses in the films were explored using a bending beam system. Focused ion beam (FIB) and electron back-scattered diffraction (EBSD) were then employed to characterize the transformations of the microstructure, grain size, and orientation degree of the films. The results indicated that the degree of (111)-preferred orientation and grain size significantly decrease with increasing the current density. The nt-Cu films with a higher degree of (111)-preferred orientation and larger grains exhibit the slower rates of stress relaxation. The film with larger grains possesses a smaller grain boundary area; thus, the grain boundary diffusion for the thermal-stress release is suppressed. In addition, the induced tensile stress in the films with larger grains is smaller leading to the difference in microstructural changes under annealing.

Development and Research of New Hybrid Composites in Order to Increase Reliability and Durability of Structural Elements

“…To improve the characteristics of the layered composite materials, we carried out annealing. This procedure causes relaxation of internal stresses in the layers of hybrid composites [2,46,47]. Adhesive strength also increases during thermomechanical treatment due to the intensified diffusion processes at the boundary "Hastelloy X (NiCrFeMo)-AlCoCrCuFeNi alloy layer".…”