In the packaging of integrated circuits, semiconductor dies may be stacked through bonding, and may be bonded to other package components such as interposers and package substrates. The resulting packages are known as Three-Dimensional Integrated Circuits (3DICs). The heat dissipation is a challenge in the 3DICs. There exists a bottleneck in efficiently dissipating the heat generated in the inner dies of the 3DICs. The heat generated in the inner dies has to be dissipated to outer components such as outer dies before the heat can be conducted to any heat spreader. Between the stacked dies, however, there exist other materials such as underfill, molding compound, etc, which are not effective in conducting heat. Furthermore, the stacked dies may also be molded in a molding compound, which prevents the efficient heat dissipation.