A CMOS Compatible Carbon Nanotube Growth Approach

ABSTRACTIn future technology nodes, 22nm and below, carbon nanotubes (CNTs) may provide a viable alternative to Cu as an interconnect material. CNTs exhibit a current carrying capacity (up to 109 A/cm2), whilst also providing a significantly higher thermal conductivity (SWCNT ~ 5000 WmK) over Copper (106 A/cm2 and ~400WmK). However, exploiting such properties of CNTs in small vias is a challenging endeavor. In reality, to outperform Cu in terms of a reduction in via resistance alone, densities in the order of 1013 CNTs/cm2 are required. At present, conventional thermal CVD of carbon nanotubes is carried out at temperatures far in excess of CMOS temperature limits (400 C). Furthermore, high density CNT bundles are most commonly grown on insulating supports such as Al2O3 and SiO2 as they can effectively stabilize metallic nanoparticles at elevated temperatures but this limits their application in electronic devices. To circumvent these obstacles we employ a remote microwave plasma to grow high density CNTs at a temperature of 400 C on conductive underlayers such as TiN. We identify some critical factors important for high-quality CNTs at low temperatures such as control over the catalyst to underlayer interaction and plasma growth environment while presenting a fully CMOS compatible carbon nanotube synthesis approach