A 3 nm Self-Forming InOx Diffusion Barrier for Advanced Cu/Porous Low-k Interconnects

Abstract

The copper diffusion barrier properties of a 3 nm self-forming InOx layer on a porous ultralow-k (p-ULK) film have been investigated. A 5 at. % In doped Cu film was directly deposited onto porous low-k films by co-sputtering, followed by annealing at various temperatures. Transmission electron microscopy (TEM) images showed that a 3 nm layer was self-formed at the interface between Cu–In and p-ULK films after annealing at 400 °C for 1 h. An EDS line scan on the region near this interface showed obvious accumulation of In at the interface. X-ray photoelectron spectroscopy (XPS) analyses indicated that the self-formed interfacial layer was InOx. The self-forming InOx layer prevented Cu agglomeration on the p-ULK film surface. The XPS atomic depth profiles showed that the self-formed InOx barrier was thermally stable against Cu diffusion to at least 500 °C for 5 h. The sheet resistance of the post 500 °C annealed Cu–In film was comparable to that of a pure Cu film. The Cu–In self-forming barrier approach may be a viable candidate for Cu/p-ULK interconnects.