Controllable Etching of Ta Nanofilms by ICP-RIE: Parameter Optimization and Morphological Evolution

Ta nanofilms play an important role in magnetic random-access memory (MRAM) devices. In particular, Ta can function as a seed layer that influences crystallographic texture and as a hard mask during magnetic tunnel junction (MTJ) patterning. In this article, the etching behavior of 40 nm Ta nanofilms was systematically examined using an inductively coupled plasma reactive ion etching (ICP-RIE) system with SF₆/Ar gas mixtures. The study focuses on the interplay between plasma chemistry and ion-driven effects under controlled variations in gas composition, chamber pressure, coil power, bias power, and etching duration. Etch rate, sidewall profile, and nanocolumn diameter were quantitatively evaluated to reveal morphology–parameter correlations. The results show that enhanced ion density and energy—achieved through increased coil and bias power—accelerate Ta removal, whereas reduced chamber pressure promotes more directional etching and improved sidewall definition. Adjusting the SF₆ fraction alters the balance between chemical fluorination and physical sputtering, enabling tunable control over nanocolumn geometry. Finally, a mechanistic framework describing the coupled chemical–physical etching pathways of Ta in SF₆/Ar plasma is proposed. These findings provide practical guidance for optimizing dry etching strategies in MTJ fabrication and support further scaling of MRAM technologies toward high-density integration.