Leveraging Plasma Enhanced Atomic Layer Etching for Sustainable Catalytic Processing

ALE was developed in recent years to address critical needs in micro- and nano-electronics fabrication where precision in nano-scale patterning is required to integrate novel metal and metal alloys in nano-electronics, nano-photonics, spintronics, and sensors. Many of these materials are inert or less reactive, making it a challenge to turn a non-etchable material into an etchable one. Our previous work demonstrated that a viable ALE process utilizes chemically reactive and low energy directional oxygen ions to tailor the surface modification/conversion process and form a metal oxide layer while suppressing any deleterious sputtering. The surface reaction kinetics dictate the controlled and directional change in the materials’ composition and properties, thereby enabling the chemical contrast needed to selectively remove the materials. Such an effective ALE process can potentially be used to de-poison catalysts, by removing just one atomic layer of material at a time (the poisoned layer). The site specificity in these ALE reactions can also help regenerate the preferred sites for catalytic reactions.<br/> <br/>The feasibility of utilizing ALE to de-poison catalysts is based on strong and selective chemical reactions on the surfaces of metals. Interestingly, many of the materials requiring nano-scale patterning have been used as catalysts. While a chemical reaction leading to the formation of a strongly chemisorbed species is considered poisoning in catalysis, it is actually a necessary step in initiating atomic layer etching of metals. By identify a chemical reaction that can form strong chemical bonds, thereby modifying an atomically thin surface layer to form a new compound, a distinct chemical contrast can be created to allow one atomic layer of the modified surface to be selectively removed, leaving behind the unmodified material. This presentation will focus on the intersection of two interdisciplinary research areas for microelectronics and catalysis, leveraging what was achieved in ALE of metals to help de-poison/regenerate the catalysts. The specific examples include Ni and Cu (both are common and useful catalysts) because these two suffer sulfur and carbon poisoning (coking) as two major deactivation processes. The discuss will demonstrate the feasibility of utilizing ALE to remedy catalyst poisoning and make the catalytic processing more sustainable.