Enhanced\nOxidation Resistance and Interface Stability\nof Atomic-Layer-Deposited MoN<sub><i>x</i></sub> Electrodes\nvia TiN Passivation for DRAM Cell Capacitor Applications

The\ncontinuous miniaturization of dynamic random-access memory\n(DRAM) capacitors has amplified the demand for electrode materials\nfeaturing specific characteristics, such as low resistivity, high\nwork function, chemical stability, excellent interface quality with\nhigh-k dielectrics, and superior mechanical properties. In this study,\nmolybdenum nitride (MoN<sub><i>x</i></sub>) films were deposited\nusing a plasma-enhanced atomic layer deposition (PEALD) employing\nbis(isopropylcyclopentadienyl)molybdenum(IV) dihydride and NH<sub>3</sub> plasma for DRAM capacitor electrode applications. Depending\non the deposition temperatures of the PEALD MoN<sub><i>x</i></sub> films ranging from 200 to 400 °C, the Mo/N ratio and\ncrystal structure varied, transitioning from the cubic NaCl-B1-type\nMoN phase with Mo/N ratio of 1.4 to the cubic γ-Mo<sub>2</sub>N phase with Mo/N ratio of 1.9. Notably, MoN<sub><i>x</i></sub> films grown at 400 °C exhibited low resistivity (435\nμΩ·cm), a high work function (5.28 eV), and superior\nmechanical hardness (11.3 GPa) compared to ALD TiN films. Despite\nthese excellent properties, the PEALD MoN<sub><i>x</i></sub> electrode demonstrated insufficient chemical stability, particularly\nin terms of oxidation resistance and interface quality with ALD Hf<sub><i>x</i></sub>Zr<sub>1–<i>x</i></sub>O<sub>2</sub> (HZO) films. This resulted in poor morphology and the formation\nof significant oxygen-deficient HZO layers (such as HfO<sub>2–<i>x</i></sub>), leading to considerable degradation in the electrical\nperformance of metal–insulator–metal (MIM) capacitors.\nTo mitigate this issue, a thin (2.5–14 nm) ALD TiN layer was\nintroduced as a passivation layer between the MoN<sub><i>x</i></sub> bottom electrode and HZO dielectric. The TiN-passivated MoN<sub><i>x</i></sub> (TiN/MoN<sub><i>x</i></sub>) electrode\nshowed substantially enhanced oxidation resistance and reduced interfacial\nreactions with the HZO dielectric. Consequently, MIM capacitors with\nTiN/MoN<sub><i>x</i></sub> bottom electrodes demonstrated\noutstanding electrical performance, including excellent dielectric\nproperties, low leakage current density, and high mechanical strength.\nHence, this study proposes a promising candidates for storage nodes\nin the next-generation DRAM capacitors.