Following the course of Moore’s law, the semiconductor industry has transitioned from microelectronics to nanoelectronics, to the present days when we are entering the atomic-scale era. Developing advanced technology at sub-10 nm scale comes with unprecedented challenges for semiconductor fabrication. Atomic Layer Etching (ALE) is a technique that is becoming increasingly important in semiconductor fabrication, however, it has yet to be widely adopted. Many examples of ALE use harsh chemistry such as halogenated compounds or plasma, which result in damaged and non-conformal structures. Copper is an important interconnect material, so scalable copper ALE is of high importance and further research of both metallic Cu activation and etch are required. Oxidation of metallic Cu surfaces with unselective oxidants (H2O2, O3, oxygen plasma etc.) tend to produce multiple oxidation states of Cu (+1 and +2) as well as Cu mobility at elevated temperatures. We have studied the use of milder, more selective oxidizing agents, which will result in a more controlled oxidation of Cu surfaces. In this talk we will discuss our study of surface Cu oxidation benchmarked with more traditional oxidants. X-ray absorption spectroscopy (XAS) and other characterization techniques such as XPS have been used to determine oxidation depth and Cu oxidation state. These measurements provide a better understanding of the relationship between oxidant strength versus depth as a function of various oxidants. These results give insight into the etch-per-cycle as well, Cu surface roughening, and other metrics for the final films. We also have designed and synthesized ligands that are halogen-free and oxidation resistant towards CuOx species and yield a volatile Cu complex. Mechanistic studies have also been performed in solution and the results of these studies will be reported as time permits.

New oxidants and etch ligands for ALE of copper

ACS Spring 2022

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