Figure 5
From: Copper-to-copper direct bonding on highly (111)-oriented nanotwinned copper in no-vacuum ambient
Reversed thermal bonding experiments by reversing the temperature gradient to 100 °C at the top die and 400 °C at the bottom die for bonding times of (a) 5 min; the nt-Cu in the bump has transformed to randomly oriented large grains, (b) 10 min; grain growth has occurred as some of the large grains grow into the nt-Cu thin film, and (c) 15 min; grain growth with annealing twins has occurred. The areas corresponding to the dashed rectangular boxes in (a) to (c) are enlarged in the right-hand side images.
