Ru ALD With Bulk-Like Resistivity for Interconnects

Ruthenium is viewed as a promising alternative to Cu and Co interconnect metals at M0/M1 interconnect layers due to its lower effective resistivity in highly-confined layers and vias, as well as its resistance to diffusion into porous low-k dielectrics and to electromigration. Atomic layer deposition of Ru has been reported with a variety of precursors, but the search for a Ru ALD process with a close-to-bulk (~7 μΩ·cm) resistivity is ongoing, with special interest in a process that can selectively-deposit low-resistance Ru films without passivants. In this work, Ru films with close-to-bulk resistivity deposited using Ru(CpEt)2 were investigated using four-point-probe resistivity measurements, Xray photoelectron spectroscopy (XPS) for chemical analysis, X-ray diffraction/reflectometry (XRD/XRR) for grain size and thicknesses, and scanning electron microscopy (SEM) and atomic force microscopy (AFM) for film morphology.