Selectively deposited Ru top electrode on Pb(Zr0.3Ti0.7)O3 and Ru step coverage on TiN by digital chemical vapor deposition

A digital chemical vapor deposition (DCVD) process was used to selectively deposit ruthenium on hydroxyl-terminated Pb(Zr0.3Ti0.7)O3 (PZT) surface patterned with a photoresist; the PZT was on Ru/sapphire substrate. The DCVD of Ru was carried out at 280–320°C using an alternate delivery of Bis (2,2,6,6-tetramethyl-3,5-heptanedionato) (1,5-cyclooctadiene)Ru (dissolved in tetrahydrofuran) and oxygen. The ferroelectric hysteresis of Pb(Zr,Ti)O3 on Ru/sapphire with selectively deposited top Ru electrode by digital CVD was measured, which yielded a symmetric hysteresis loop with high remnant polarization of 40μC∕cm2. Additionally, Ru films, deposited by DCVD on high aspect ratio vias of TiN on Si, exhibited nearly 100% step coverage. This DCVD process shows promise for attaining three-dimensional metal/PZT/metal stacks for high density ferroelectric random access memories.