# A Short Review of Through-Silicon via (TSV) Interconnects: Metrology and Analysis
## 3 TSV Reliability
### Thermal Management
This mismatch in CTE can trigger various problems, such as copper plastic expansion outwards, interface cracking, silicon substrate rupture, and more. If these problems are not adequately addressed, they can eventually lead to a significant impact on the service life and reliability of the 3D integrated system. The thermal expansion mismatch between SiO\({}_{2}\) and copper is a critical issue that needs to be resolved to ensure the long-term reliability of TSV technology. When subjected to temperature changes, the difference in the CTE of SiO\({}_{2}\) and copper can result in mechanical stresses that can cause the copper to deform or even crack, leading to a failure of the TSV structure. Furthermore, the thermal expansion mismatch can also cause the SiO\({}_{2}\) to crack or delaminate from the copper, leading to additional reliability issues. To overcome these challenges, several alternative materials are being investigated to replace SiO\({}_{2}\) as the insulating dielectric layer material. One promising option are low-CTE materials, such as silicon nitride (Si\({}_{3}\)N\({}_{4}\)), which can provide a closer match to the CTE of copper and reduce the mechanical stresses on the TSV structure during thermal cycling. Other materials, such as organic polymers and spin-on glasses, are also being investigated as potential candidates for insulating dielectric layers in TSVs. In conclusion, the mismatch in the thermal expansion coefficient between SiO\({}_{2}\) and copper presents a notable challenge in TSV technology. This challenge has the potential to adversely affect the reliability and long-term performance of 3D integrated systems. To overcome this issue and enhance the reliability of TSV structures, researchers are exploring the use of alternative materials with lower coefficients of thermal expansion (CTE). Additionally, the implementation of microfluidic cooling has emerged as a promising solution for 3D ICs with high power density. Since 2012, the US Defense Advanced Research Projects Agency (DARPA) has been actively involved in the development of the Intra-Chip/Inter-Chip Enhanced Cooling (ICECool) thermal packaging program. This program aims to address cooling limitations and overcome significant barriers to further progress in Moore's  
Figure 9: **(a)** TSV sample; **(b)** TSV sample after 550 \({}^{\circ}\)C annealing; **(c)** TSV sample after 550 \({}^{\circ}\)C annealing and aging 35 days at room temperature; **(d)** SEM micrographs showing the top view of an array of CF\(-\)TSV after annealing at 450 \({}^{\circ}\)C after 70 days of natural ageing; **(e)** SEM micrograph showing the procedure used for measuring the crack length. **(f)** Variation in crack length of different surface cracks with the duration of natural ageing (adapted from [7]). Law for electronic components and systems. Microfluidic cooling is employed as an active thermal management technique, enabling direct cooling of heat-generating sites within the chip, substrate, and/or package. By controlling the flow rate in liquid cooling, thermal hot spots can be mitigated while optimizing the overall energy consumption of the cooling system. Minimizing the pressure drop in integrated microchannel cooling networks is a key challenge that needs to be addressed in order to achieve efficient cooling [45; 50]. Microfluidic cooling stands out as a highly promising thermal management technology for 3D ICs. However, there are several significant technical challenges that need to be addressed to ensure the widespread adoption of this technology. From a scientific standpoint, it is crucial to gain a comprehensive understanding of the physical properties of liquid-gas phase change processes, with a particular focus on optimizing heat dissipation. This includes exploring scenarios, like thin film evaporation, to maximize the efficiency of heat transfer.