Low-resistivity epitaxial Ru films on AlN (0001)/Si (111) for interconnect applications

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Abstract
Ru is a promising candidate for future post-Cu interconnect metallization because of its short electron mean free path and barrier-free reliability. Here, we demonstrate epitaxial Ru thin films on CMOS-compatible AlN (0001)/Si (111) grown by physical vapor deposition. X-ray diffraction, Rutherford backscattering ion channeling, and transmission electron microscopy confirm the single-crystal nature of the Ru films with a honeycomb epitaxial relationship. The films exhibit low resistivity of 7.8 μΩ cm at 30 nm thickness and a high residual resistivity ratio of 11, approaching bulk Ru values and outperforming polycrystalline Ru and Cu in the ultrathin film regime. Additional epitaxial growth on 300 mm wafers establishes epitaxial Ru on AlN (0001)/Si (111) as a scalable, CMOS-compatible platform for low-resistivity interconnect metallization.

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