  The interconnect half-pitch size will reach ~20 nm in the coming sub-5 nm
technology node. Meanwhile, the TaN/Ta (barrier/liner) bilayer stack has to be
> 4 nm to ensure acceptable liner and diffusion barrier properties. Since
TaN/Ta occupy a significant portion of the interconnect cross-section and they
are much more resistive than Cu, the effective conductance of an ultra-scaled
interconnect will be compromised by the thick bilayer. Therefore, two
dimensional (2D) layered materials have been explored as diffusion barrier
alternatives. However, many of the proposed 2D barriers are prepared at too
high temperatures to be compatible with the back-end-of-line (BEOL) technology.
In addition, as important as the diffusion barrier properties, the liner
properties of 2D materials must be evaluated, which has not yet been pursued.
Here, a 2D layered tantalum sulfide (TaSx) with ~1.5 nm thickness is developed
to replace the conventional TaN/Ta bilayer. The TaSx ultra-thin film is
industry-friendly, BEOL-compatible, and can be directly prepared on
dielectrics. Our results show superior barrier/liner properties of TaSx
compared to the TaN/Ta bilayer. This single-stack material, serving as both a
liner and a barrier, will enable continued scaling of interconnects beyond 5 nm
node.
