Perspective on high-entropy alloys and high-entropy nitrides as diffusion barriers for copper metallization

Published

September 1, 2025

Author(s)

Gheorghe Stan, Cristian Victor Ciobanu

Abstract

The adoption of copper as the material of choice for electrical contacts in semiconductor industry over three decades ago has been a key enabling factor for continuing the miniaturization trend that has led to faster and more efficient chips with specific functionalities. From the advanced packaging level where hybrid bonded structures are integrated in 3D with features sub-10 m, to the front end of the line with dimensions sub-10 nm, the use of copper for signal and power transmission poses the risk of electromigration into the nearby materials, i.e. dielectric or silicon. This risk is currently mitigated by using diffusion barriers, i.e., materials that prevent the migration of copper atoms at operating temperatures, thereby enabling significant improvements in reliability and lifetime of the contacts. Currently, the industry uses as diffusion barrier a layer of tantalum nitride (TaN) that is at least 3 nm thick. However, TaN is not a substrate that naturally allows for the conformal growth of copper, so surfactants (also called liner materials) need to be added so that metallic copper can be deposited/electroplated into vias. As such, metallization can become a significant difficulty for the miniaturization of purpose-built chiplets than can be assembled into complex architectures. While the dimension and performance of the diffusion barrier is more critical for the front of the line (FEOL) metallization technologies, materials advances can be leveraged to mitigate fabrication and alignment constraints faced at the advanced packaging level. The present paper gives an account of the possible alternatives for the copper diffusion barrier, highlighting two types of materials, amorphous high-entropy alloys (aHEA) and high-entropy nitrides (HEN). The promise of these materials as efficient barriers relies either on the absence of grain boundaries (aHEA) that would act as fast diffusion avenues for copper, or on the small interstitial spaces and high vacancy formation energies (HEN) that hamper diffusion.

Citation

Materials Letters

Pub Type

Journals

Download Paper

https://doi.org/10.1016/j.matlet.2025.138578

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Keywords

semiconductors, chips, diffusion barrier, high-entropy alloys, high-entropy nitrides

Citation

Stan, G. and Ciobanu, C. (2025), Perspective on high-entropy alloys and high-entropy nitrides as diffusion barriers for copper metallization, Materials Letters, [online], https://doi.org/10.1016/j.matlet.2025.138578, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=959607 (Accessed October 9, 2026)

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