Electrical properties of carbon nanotube via interconnects for 30 nm linewidth and beyond

•Review current status of CNT via interconnect performance, reliability, and key factors limiting its electrical performance•Report using measured resistances for individual CNTs with diameter of 50 nm to obtain CNT resistivity and CNT-metal contact resistance•Review using measured resistances for CNT vias with widths ranging from 150 nm to 60 nm to project 30 nm via resistance•Report comparisons of projected 30 nm CNT via resistances from the two independent approaches and with their Cu and W counterparts•Assess measured current capacities of individual CNTs and CNT vias

The continuous downward scaling in integrated circuit (IC) technologies has led to rapid shrinking of transistor and interconnect feature sizes. While scaling benefits transistors by increasing the switching speed and reducing the power consumption, it has an adverse impact on interconnects by degrading its electrical performance and reliability. Scaling causes reduction in interconnect linewidth, which leads to surge in resistance due to increased contributions from grain boundary and surface scattering of electrons in the metal lines. Further, current density inside interconnects is also enhanced by the reduced linewidth and is approaching or exceeding the current-carrying capacity of the existing interconnect metals, copper (Cu) and tungsten (W). The resulting failure due to electromigration presents a critical challenge for end-of-roadmap IC technology nodes. Therefore, alternative materials such as nanocarbons and silicides are being investigated as potential replacements for Cu and W as they have superior electrical and mechanical properties in the nanoscale. In this review, the electrical properties of nanocarbons, in particular carbon nanotubes (CNTs), are examined and their performance and reliability in the sub-100 nm regime are assessed. Further, the measured properties are used to project 30 nm CNT via properties, which are compared with those of Cu and W.