Interfacial stabilization of ZrO2/Mo2N capacitors via ultrathin Nb2O5 insertion for scaled DRAM applications

초록

Achieving both high capacitance and low leakage current has become increasingly challenging in scaled DRAM cell capacitors. ZrO2-based dielectrics combined with nitride electrodes remain a technologically relevant platform due to their compatibility with DRAM integration. Among candidate electrode materials, MoNx is particularly attractive owing to its high work function, competitive resistivity, and favorable mechanical properties. However, its limited oxidation resistance can induce interfacial degradation during dielectric deposition and subsequent annealing, thereby deteriorating capacitor performance. In this study, we introduce a sub-nanometer Nb2O5 buffer layer between atomic-layer-deposited ZrO2 and a Mo2N bottom electrode and systematically investigate its effects on the structural, chemical, and electrical properties of metal–insulator–metal capacitors. Compared with buffer-free structures, Nb2O5 insertion improves surface morphology after annealing and suppresses the formation of interfacial reaction layers and oxygen-deficient species at the ZrO2/Mo2N interface. These interfacial improvements lead to reduced leakage current, improved capacitance–voltage characteristics, and enhanced capacitance density. Importantly, the interfacial stabilization enables effective EOT scaling without requiring excessively high bulk permittivity. These results indicate that the performance of Mo2N-based capacitors is governed not only by the intrinsic properties of the electrode but also by the stability of the dielectric/electrode interface during processing. Accordingly, this work demonstrates that ultrathin Nb2O5 insertion is an effective interfacial engineering strategy for stabilizing the ZrO2/Mo2N interface, providing a promising approach for future DRAM capacitor applications.

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