Enhancing Interconnect Reliability and Performance by Converting Tantalum to 2D Layered Tantalum Sulfide at Low Temperature

TL;DR

This paper introduces a low-temperature, industry-compatible 2D tantalum sulfide film that replaces traditional bilayer barriers in interconnects, enhancing reliability and performance for future ultra-scaled semiconductor nodes.

Contribution

Development of a 2D layered tantalum sulfide (TaSx) film as a dual-function barrier and liner, compatible with BEOL processes, outperforming conventional TaN/Ta bilayers.

Findings

TaSx exhibits superior barrier properties.

TaSx is ultra-thin (~1.5 nm) and industry-friendly.

Enables continued scaling of interconnects beyond 5 nm.

Abstract

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.