Atomic-Layer-Deposition of Sn-Incorporated MoO ₂ Films as an Interface Control Layer for High-Performances TiO ₂ -Based DRAM Capacitors

As dynamic random-access memory (DRAM) technology continues to scale down to sub-10 nm nodes, achieving high memory density and enhanced operational performance poses increasing challenges. In particular, maintaining sufficient cell capacitance and minimizing the leakage current density have emerged as key issues. To address these issues, the development of novel electrode materials and carefully engineered interfaces between high-k dielectrics and electrodes is crucial. In this study, thermal atomic layer deposition (ALD) of Sn-incorporated MoO_<i>x</i> (TMO) films was performed using (N^tBu)₂(NMe)₂Mo and Sn(dmamp)₂ as the Mo and Sn precursors, respectively. The growth characteristics of the TMO films, particularly the interaction between the MoO_<i>x</i> and SnO_<i>x</i> subcycles, were systematically investigated. Controlled Sn incorporation into MoO_<i>x</i> successively stabilized the formation of the monoclinic MoO₂ phase, resulting in a smooth surface morphology and enhanced thermal and chemical stability. ALD TMO films were employed as an interface control layer (ICL) in a metal-insulator-metal capacitor to improve the interfacial properties between the (Al-doped) TiO₂ and TiN bottom electrodes. ALD TMO films promoted the in situ crystallization of rutile TiO₂ (with a dielectric constant of up to 156) and effectively suppressed the unwanted formation of a low-k TiO_<i>x</i>N_<i>y</i> layer, resulting in significant equivalent oxide thickness (EOT) scaling. Furthermore, the insertion of the TMO ICL significantly reduced the leakage current density of the (Al-doped) TiO₂ films, which was attributed to the higher work function of TMO (4.7-4.8 eV) compared to that of TiN (4.5 eV) and the minimal formation of defective TiO_<i>x</i>N_<i>y</i>. To evaluate the scalability of the ALD TMO ICL, its thickness was varied from 20 to 1 nm. Remarkably, even at the ultrathin thickness of 1-2 nm, TMO ICL maintained high capacitance and low leakage current density, achieving an EOT of 0.58 nm and leakage current density of 2.4 × 10^-7 A/cm². These results highlight the potential of ALD-grown TMO films as ICLs in next-generation DRAM capacitors.