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

The TiO x N y interfacial layer formed by an O 3 reactant during the atomic layer deposition (ALD) of ZrO 2 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 TiO x N y interfacial layer during the O 3 -based ALD of ZrO 2 . The MgO thin film inserted at the ZrO 2 /TiN interface effectively prevented oxygen diffusion into the TiN bottom electrode (BE) via O 3 during ALD of ZrO 2 . Therefore, the formation of the TiO x N y interfacial layer due to oxidation of the TiN BE was suppressed during ZrO 2 ALD, and tetragonal ZrO 2 was grown without deteriorating the crystallinity owing to the low lattice constant mismatch between MgO and tetragonal ZrO 2 . 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 ZrO 2 . 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/cm 2 at an applied voltage of +0.8 V).