Foundations of atomic-level plasma processing in nanoelectronics

This article discusses key elementary surface-reaction processes in state-of-the-art plasma
etching and deposition relevant to nanoelectronic device fabrication and presents a concise
guide to the forefront of research on plasma-enhanced atomic layer etching (PE-ALE) and
plasma-enhanced atomic layer deposition (PE-ALD). As the critical dimensions of
semiconductor devices approach the atomic scale, atomic-level precision is required in plasma
processing. The development of advanced plasma processes with such accuracy necessitates
an in-depth understanding of the surface reaction mechanisms. With this in mind, we first
review the basics of reactive ion etching (RIE) and high-aspect-ratio (HAR) etching and we
elaborate on the methods of PE-ALE and PE-ALD as surface-controlled processing, as
opposed to the conventional flux-controlled processing such as RIE and chemical vapor
deposition (CVD). Second, we discuss the surface reaction mechanisms of PE-ALE and
PE-ALD and the roles played by incident ions and radicals in their reactions. More
specifically, we discuss the role of transport of ions and radicals, including their surface
reaction probabilities and ion-energy-dependent threshold effects in processing over HAR
features such as deep holes and trenches.