Heat dissipation is one of the factors limiting the continuous miniaturization of electronics. In the study presented in this paper, we designed an ultra-thin heat sink using carbon nanotubes (CNTs) as micro cooling fins attached directly onto a chip. A metal-enhanced CNT transfer technique was utilized to improve the interface between the CNTs and the chip surface by minimizing the thermal contact resistance and promoting the mechanical strength of the microfins. In order to optimize the geometrical design of the CNT microfin structure, multi-scale modeling was performed. A molecular dynamics simulation (MDS) was carried out to investigate the interaction between water and CNTs at the nanoscale and a finite element method (FEM) modeling was executed to analyze the fluid field and temperature distribution at the macroscale. Experimental results show that water is much more efficient than air as a cooling medium due to its three orders-of-magnitude higher heat capacity. For a hotspot with a high power density of 5000 W cm(-2), the CNT microfins can cool down its temperature by more than 40 °C. The large heat dissipation capacity could make this cooling solution meet the thermal management requirement of the hottest electronic systems up to date.

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Cu pumping of through silicon vias (TSV) may result in deformations of the Cu/low-k interconnect wiring above the TSVs and affect the back-end-of-line (BEOL) metal and dielectric reliability. We investigate the impact of Cu TSVs on the BEOL reliability, including stress induced voiding (SIV) of Cu vias on top of the TSV and the dielectric reliability of both interand intralevel low-k materials in Cu damascene interconnects.Possible solutions to mitigate the reliability risks are also discussed. Keywords-BEOL reliability; through silicon vias (TSV); stress induced voiding (SIV); time dependent dielectric breakdown (TDDB)

Using Finite element methods, a model to predict the Cu pumping in Through Silicon Vias (TSV) is built. The processes which a TS V undergoes after Cu electroplating are considered and the model is built in such a way that after each process sequence, the stress and strain data are transferred into the following sequence and used as input conditions. The stress and Cu pumping at the end of the simulations are extracted and compared with experimental results. This allows virtual studies and predictions of Cu pumping for different TSV geometries and the possible effects of Back-end of line (BEOL) layers.