Chemical and Elecrtrical Charaterization of ALD Cobalt Nitride (CoN) as an Alternative Barrier for Advanced Cu Interconnects

Abstract

As semiconductor device scaling progresses, the limitations of conventional Ta/TaN for Cu diffusion barrier layers have become increasingly evident. High electrical resistance, reduced Cu channel width due to thick barrier layers, and poor adhesion with Cu necessitate the exploration of alternative diffusion barrier materials. Cobalt Nitride (CoN) has emerged as a promising candidate to address these challenges. Compared to Ta/TaN, CoN provides excellent Cu diffusion barrier properties even at reduced thicknesses, contributing to lower electrical resistance, reduced signal delay, and decreased power consumption. Furthermore, its strong chemical affinity with Cu allows for direct integration without the need for an additional seed layer, simplifying its fabrication process. CoN also demonstrates structural stability at post-processing temperatures exceeding 500°C and exhibits high compatibility with CMP processes. In this study, we analyzed the potential of CoN as a barrier material and achieved lower resistivity compared to conventional Ta/TaN. Additionally, we successfully deposited CoN thin films via plasma-enhanced atomic layer deposition using a cobalt precursor and N/H reactants, achieving a composition close to a 1:1 ratio, as confirmed through RBS analysis. These findings suggest that CoN is a promising barrier material for next-generation Cu interconnect technology. As semiconductor scaling continues, CoN has the potential to replace conventional Ta/TaN barriers, enhancing the reliability and performance of advanced Cu interconnects.