Characterization of the thermal impact of Cu-Cu bonds achieved using TSVs on hot spot dissipation in 3D stacked ICs

3D-IC stacking is a promising technique for miniaturization and performance enhancement of electronic systems. The complexity of the interconnect structures, combined with the reduced thermal spreading in the thinned dies used for the stacking and the poorly thermally conductive adhesives adopted for bonding the dies in the stack complicate the modeling of the thermal behavior of 3D ICs. The same amount of energy dissipation will lead to higher temperatures and a more pronounced temperature peak in a stacked die with respect to a single die. Therefore, the thermal behavior in a 3D-IC needs to be studied thoroughly. In this paper, the impact of TSVs and the Cu-Cu bonding on the temperature profile of the top and bottom die of a 3D stack is characterized by using dedicated test chips with integrated thermal heaters and temperature sensors. A specific experimental set-up is conceived and used to evaluate and improve the thermal models for the 3D stacks.