Wojcik H.,Institute for Semiconductor and Microsystems Technology IHM |
Kaltofen R.,Leibniz Institute for Solid State and Materials Research |
Merkel U.,Institute for Semiconductor and Microsystems Technology IHM |
Krien C.,Leibniz Institute for Solid State and Materials Research |
And 11 more authors.
Microelectronic Engineering | Year: 2012
Co-sputtered Ru-Ta(N), Ru-W(N) and Ru-Mn composites are investigated in terms of their barrier properties against Cu diffusion. A wide range of stoichiometries is analyzed with regard to crystallization, barrier properties, resistivity, Cu adhesion and direct Cu plating behaviour. All films were annealed at 350°C and 600°C in forming gas for 1h and subsequently stressed at elevated temperatures and electrical fields (BTS, 250°C, 2 MV/cm, 30 min). The leakage current was monitored during BTS to observe increased leakage due to Cu diffusion. The Cu ions that eventually have passed the barrier and drifted into the dielectric of the MIS test structure were detected and quantified using the triangular voltage sweep method. The addition of 10% W or Ta into a Ru film already leads to a highly improved barrier performance against Cu diffusion, comparable to TaN, as long as the temperatures involved are kept below 350°C. Outstanding barriers were identified after 600°C annealing and subsequent BTS, among them Ru 50W 50, Ru 50Ta 50 and Ru 95Mn 5. However, only Ru 90Ta 10 and Ru 95Mn 5 offer an excellent Cu adhesion and the possibility of direct Cu plating. © 2011 Elsevier B.V. All rights reserved.