Performance evaluation of noise coupling on Germanium based TSV filled material for future IC integration technique

Abstract

• Due to its CTE mismatch and Electromigration (EM) issues of Cu as TSV, Germanium can be used as an alternative material. • Quantum-well (QW) formed between Silicon substrate and Germanium core can be used as a high-speed TSV interconnect. • It opens up the window towards the future IC Integration (3D IC). 3D IC Integration shows the most emerging technology for future integration nodes which is now a most important trend for the semiconductor industries. Through-silicon-via (TSV) based integration is the prime technique to facilitate 3D IC integration without compromising the Moore’s law. It is likely to usher the IC industries a paradigm shift from planar integration as it provides major benefits like improvement of system performance, power and enables heterogeneous integration. In this paper, we report Germanium/poly-germanium as an substitute material for Silicon/poly-silicon due to its superior carrier mobility. Mobility of electrons and holes in c-Silicon is 1500 cm 2 /V-s and 450 cm 2 /V-s respectively, where as in c-Germanium, the respective values are 3900 cm 2 /V-s and 1900 cm 2 /V-s. Therefore, considering these carrier mobility values we can envisage that poly germanium will be one of the ideal candidate towards realizing a high speed TSV interconnect when compared with poly-silicon. Nevertheless, even though copper is used widely to fill TSVs, it is also bereft of proper thermal expansion match with Silicon/dielectric (SiO 2 ). The coefficient of thermal expansion (CTE) of Cu (∼17.5x 10 -6 /°C) is many times more than of silicon (∼2.5x 10 -6 /°C). Hence, there will be heavy mismatch between Cu filled TSV and Silicon/SiO 2 , and then it creates stress and strain between the interfaces. The CTE of germanium (5.8x 10–6/°C) is very close to Silicon, thus there CTE mismatch is very less, this fact is also an added advantage for Germanium to challenge copper as TSV material.