Suppressing Interfacial Layer Formation in ZrO₂-Based Capacitors with TiN Electrodes via a MgO Thin-Film Oxygen Diffusion Barrier

The TiOxNy interfacial layer formed by an O3 reactant during the atomic layer deposition (ALD) of ZrO2 on a TiN electrode is a challenge to further scaling dynamic random-access memory (DRAM). This interfacial layer degrades the electrical properties and reliability of metal–insulator–metal (MIM) capacitors because of its high defect density. In this paper, we reveal the results of introducing a MgO oxygen diffusion barrier to suppress the formation of a TiOxNy interfacial layer during the O3-based ALD of ZrO2. The MgO thin film inserted at the ZrO2/TiN interface effectively prevented oxygen diffusion into the TiN bottom electrode (BE) via O3 during ALD of ZrO2. Therefore, the formation of the TiOxNy interfacial layer due to oxidation of the TiN BE was suppressed during ZrO2 ALD, and tetragonal ZrO2 was grown without deteriorating the crystallinity owing to the low lattice constant mismatch between MgO and tetragonal ZrO2. Thus, the degradation of the electrical properties due to the trap sites in the dielectric was mitigated without notable deterioration in the dielectric properties of ZrO2. In particular, the leakage current characteristics were significantly improved when MgO was inserted, and a minimum equivalent oxide thickness of 0.79 nm was achieved while satisfying the specification of the DRAM leakage current density (<10–7 A/cm2 at an applied voltage of +0.8 V).