Evaluation of electrical characteristics through band alignment and defect analysis of ultrathin Pt/ZrO2–Al2O3–ZrO2/TiN DRAM metal–insulator–metal capacitors

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The continuous downscaling of dynamic random access memory (DRAM) demands advanced strategies to maintain sufficient charge storage and suppress leakage currents in high-aspect-ratio metal–insulator–metal (MIM) capacitors. As the dimensions of stacked dielectric and metal electrodes in MIM capacitors approach sub-10 nm scales, interfacial mixing significantly impacts device reliability due to the formation of defects and secondary interface oxides, which modify the physicochemical properties of the capacitor. The complexity of the dielectric–electrode interface poses substantial challenges in developing methodologies to effectively characterize ultrathin interfaces. This study investigates the ZrO2–Al2O3–ZrO2 (ZAZ) dielectric films used in DRAM MIM capacitors, with a focus on the inclusion of a thin TiO2 buffer layer. Advanced techniques such as angle-resolved x-ray photoelectron spectroscopy, spectroscopic ellipsometry, internal photoemission spectroscopy, and temperature-dependent I–V measurements are employed to analyze the physical and electrical characteristics of these films and their interfaces. Leakage current behavior is explained using Poole–Frenkel emission, trap-assisted tunneling, and direct tunneling models, revealing that leakage current mechanisms are governed by the trap-level energy depth of ZAZ dielectrics. The study also performs comparative analysis before and after annealing, examining changes in leakage current mechanisms, band alignment, and compositional variations. Based on these findings, this work proposes effective metrology approaches to characterize interfacial stabilization and highlights the critical role of ultrathin MIM capacitors and buffer layers in controlling leakage currents and enhancing device reliability.