Patterning of Ru metal lines at 18nm pitch

In this work, we present two different approaches to pattern Ru metal lines at a metal pitch of 18 nm, by making use of self- aligned double patterning (SADP) in combination with EUV lithography. The first and more conventional patterning approach is to define the 18 nm pitch gratings into a hard mask by means of SADP, which is consequently transferred into the Ru layer by means of direct metal etch. The second and more innovative approach consists of a combination of direct metal etch and damascene filling of Ru. This so-called mixed flow is a patterning- friendly approach which enables the integration of self-aligned cuts and vias. We will share the schematics as well as the results for 18 nm pitch Ru gratings on 300 mm Si wafers for both approaches. Finally, we will discuss and demonstrate the enablement of selfaligned cuts and vias for the mixed flow, which makes this patterning flow a promising alternative to standard damascene patterning for future interconnects at sub- 20 nm metal pitches.