Growth and characterization of ultrathin metal films for ULSI interconnects

Abstract

Chemical and physical methods are used to deposit ruthenium films on dielectric and tantalum substrates with the goal of realizing ultrathin (3-5 nm), continuous films that can be used as copper diffusion barriers in dual damascene metallization processing. Chemical vapor deposition (CVD) is employed at temperatures ranging from 425 to 525 K. A Ru 3(CO) 12 precursor is employed and films grown near 425 K are characterized as polycrystalline with a columnar structure. Rf sputtering of metal targets is used for physical vapor deposition (PVD) onto substrates near 300 K. Films are characterized in situ using X-ray photoelectron spectroscopy (XPS), low energy ion scattering spectroscopy (LEISS) and ex situ using scanning and transmission electron microscopy, atomic force microscopy (AFM) and energy dispersive spectroscopy (EDS). AFM reveals the CVD films to have an RMS roughness of 1.43 nm and the PVD films to have a roughness of 0.105 nm. Establishing film thickness and film continuity in situ with XPS and LEISS are complicated by the three dimensional CVD growth mode. This paper explores the impact of film roughness and microstructure on how effective the various in situ techniques are in establishing film thickness. © 2005 American Institute of Physics.