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

Abstract 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 cm2/V-s and 450 cm2/V-s respectively, where as in c-Germanium, the respective values are 3900 cm2/V-s and 1900 cm2/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 (SiO2). 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/SiO2, 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.