Mixed carbon nanotube bundle: Capacitance analysis and comparison with copper interconnect

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With technology scaling, copper (Cu) interconnect dimensions begin to come into the range of mean free path of electron typically 40nm. This results in surface and grain boundary scattering. Owing to these scattering phenomena resistivity of Cu begins to increase. This drives us to look for new materials for future very large scale integration (VLSI) interconnects. Mixed carbon nanotube (CNT) bundle has superior properties like current carrying capacity and conductivity compared to Cu interconnect. It is the mixture of single wall carbon nanotubes (SWCNTs) and multi-wall carbon nanotubes (MWCNTs). This is due to the nature of the bottom-up fabrication process. This paper presents capacitive analysis for mixed CNT bundle with respect to various process parameters viz. average diameter, inner to outer diameter ratio and probability of metallic tubes of bundle at 32nm technology node. The optimum values of these parameters provide minimum bundle capacitance. Results show that capacitance of the bundle is smaller compared to that of Cu for intermediate and global interconnect levels. It is also found that with technology scaling from 45nm to 22nm, bundle capacitance increases which is unlike the case of Cu interconnect. Furthermore, the bundle capacitance remains smaller than copper counterpart at these Nano-regime technologies.