High-Aspect-Ratio Ruthenium Lines for Buried Power Rail

Abstract

High-aspect-ratio (HAR) Ru power rails, buried in front-end-of-line (FEOL) oxide, can potentially replace conventional middle-end-of-line (MOL) Cu power rails. The HAR feature can boost performance by reducing resistance and voltage drop along the power line. The buried nature, helps to minimize standard cell height by freeing up routing resources at MOL, enabling overall area scaling. This paper demonstrates, Ru lines of aspect ratio up to 7, at a CD of 18 nm. Line resistance at these dimensions, measures at 60 Ω/µm, with the minimum electrical resistivity of 8.8 µΩcm, as extracted from the temperature-controlled-resistance (TCR) measurements. HAR Ru lines are also found to withstand very high FEOL thermal budgets, such as 1000 °C activation anneal for 1.5 s. The combination of all these factors, make HAR Ru buried power rail, a promising scaling booster for next generation technology nodes.