Controllable and Nanoscale Linear Etching of Atomic Layer Deposited Molybdenum Using Cyclic Stepwise CHF₃/O₂ Plasma

Precise nanoscale control of molybdenum (Mo) etching is critical for state-of-the-art interconnects, 3D NAND, and other key applications like back-side power delivery network. Herein, we demonstrate a controllable, nanoscale etching process for Mo films using a cyclic stepwise CHF₃/O₂ plasma approach. Compared to continuous etching, cyclic stepwise etching achieves exceptional etching linearity (R² = 0.999) with a precisely tunable etch depth per cycle ranging from 0.74 nm/cycle at 45 W to 1.71 nm/cycle at 90 W. Furthermore, the cyclic process significantly improves surface quality, reducing root-mean-square roughness by 8.8% and peak-to-valley roughness by 24.3% compared to the as-deposited film. Surface analysis and density functional theory calculations reveal that the process is enabled by a dynamic synergy between surface oxidation and polymer-regulated fluorination. Comprehensive characterization results suggest that the cyclic etching process preserves the crystalline structure and chemical purity of the remaining Mo film. This work provides a promising pathway toward precise and tunable Mo etching processes for the next-generation Mo-based interconnect architectures.