High Temperature Mechanical Properties of Nano-twinned Copper

We report high temperature mechanical properties of nanotwinned (NT) Cu, a key material for interconnects in advanced packaging. Our results showed softening of NT-Cu from $25^{\circ} \mathrm{C}$ to $220^{\circ} \mathrm{C}$. Tensile strength and modulus decreased by $\sim 90 \%$ and $\sim 80 \%$ respectively, while the ductility increased by more than 3X. The results are critical in the process development for direct $\mathrm{Cu}-\mathrm{Cu}$ bonding as well as modeling of the thermomechanical behavior of interconnect joints.