Recovering dielectric integrity in atomic layer etched ZrO2 MIM capacitors via post-etch annealing

초록

Atomic layer etching (ALE) enables Ångström-level thickness control of high-k dielectrics but inevitably introduces residual halide species when halogen-based chemistries, which are indispensable for high-k ALE, are employed. In ZrO2 thin films, these residual fluorine and chlorine species accumulate within the film and act as electrically active defects, leading to degradation of dielectric properties in metal–insulator–metal (MIM) capacitors. In this study, post-etch treatment strategies are investigated to mitigate halide-induced degradation in ALE-processed ZrO2 thin films. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) reveals significant incorporation of halide species throughout the film following ALE using HF and TiCl4, which correlates with reduced dielectric constant, increased leakage current density, and degraded breakdown characteristics. Among the examined treatments, post-etch annealing (PEA) at 500 °C in N2 is identified as the most effective approach for restoring dielectric performance. The recovery is attributed to thermally activated bulk diffusion of halide species toward the surface, followed by their volatilization and desorption. As a result, the electrical properties of ALE-processed ZrO2 MIM capacitors are recovered, approaching those of as-deposited ALD reference films. These results demonstrate that integrating a PEA step into the ALE process enables precise thickness control and reliable dielectric performance in ZrO2-based capacitor applications. © 2026

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