MoS₂ Synthesized by Atomic Layer Deposition as Cu Diffusion Barrier

Abstract

Miniaturization in integrated circuits requires that the Cu diffusion barriers located in interconnects between the Cu metal line and the dielectric material should scale down. Replacing the conventional TaN with a 2D transition metal dichalcogenide barrier potentially offers the opportunity to scale to 1–2 nm thick barriers. In this article, it is demonstrated that MoS2 synthesized by atomic layer deposition (ALD) can be employed as a Cu diffusion barrier. ALD offers a controlled growth process at back‐end‐of‐line (BEOL) compatible temperatures. MoS2 films of different thicknesses (i.e., 2.2, 4.3, and 6.5 nm) are tested by time‐dependent dielectric breakdown (TDDB) measurements, demonstrating that ALD‐grown MoS2 can enhance dielectric lifetime by a factor up to 17 at an electric field of 7 MV cm−1. Extrapolation to lower E‐fields shows that the MoS2 barriers prepared by ALD have at least an order of magnitude higher median‐time‐to‐failure during device operation at 0.5 MV cm−1 compared with MoS2 barriers prepared by other methods. By scaling the thickness further down in future work, the ALD MoS2 films can be applied as ultrathin Cu diffusion barriers.

MoS2 as an Effective Cu Diffusion Barrier with a Back-End Compatible Process

“…The summary of different materials, lifetime improvement, and prediction at low field is listed in Table . Furthermore, compared to previous studies utilizing 2D materials as diffusion barriers, ,− we also demonstrate a significant improvement in the device reliability. This verifies that MW-PES can be considered an effective BEOL-compatible process.…”

Two-dimensional materials for future information technology: status and prospects

“…Therefore, current research focuses on using 2D materials as complementary technologies to Cu interconnects, aiming to improve performance and provide alternative pathways for further miniaturization of interconnect technology. Materials such as graphene [1037], MoS2 [1038,1039], TaS2 [1034,1040], and WS2 [1041] can serve as alternatives to traditional diffusion barriers of Cu interconnects, acting as barrier/liner structures to enhance reliability and ensure low resistance.…”