Atomic layer etching of ZrO2 thin films for DRAM capacitors using NF3 plasma and TiCl4

초록

The continuous scaling of dynamic random-access memory (DRAM) devices is imperative for advancing memory technology and meeting the increasing demands of next-generation electronic applications. As the aspect ratio of device structures increases, the need for atomic-level precision in thin-film deposition and etching processes has become essential to ensure thickness uniformity and achieve conformal step coverage. As DRAM capacitors continue to scale down, reductions in dielectric constant and increases in leakage current within ultra-thin dielectric layers present significant challenges. To address these issues, an atomic layer etching (ALE) process of ZrO2 thin films was developed using NF3 plasma and TiCl4. At 250 °C, ZrO2 films were fluorinated to ZrF4 via NF3 plasma, followed by etching through ligand-exchange reactions involving TiCl4. Additionally, an Al2O3 etch stopper layer was applied to mitigate TiN substrate etching, ensuring etch selectivity. Consequently, the Au/annealed ZrO2/Al2O3/TiN capacitor exhibited a bulk dielectric constant of 44.4 and an equivalent oxide thickness of 3.7 nm with no film property degradation by ALE process. © 2025 Elsevier Ltd and Techna Group S.r.l.

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