Self-Activating atomic layer deposition: A kinetic strategy for growth of metastable, high work function MoO2 thin films

초록

Molybdenum dioxide (MoO2) is a promising electrode material for next-generation DRAM capacitors due to its high work function and ability to suppress oxygen scavenging. Although H2O is often preferred over ozone as a reactant for achieving superior conformality in complex device structures, H2O-based atomic layer deposition (ALD) of MoO2 is severely hindered by kinetic limitations, resulting in negligible growth. In this study, we investigated this kinetic anomaly and observed that the growth rate increased linearly with the purge duration following rapid precursor adsorption. Comprehensive kinetic analysis reveals an activation energy of similar to 1.0 eV, indicating that retained surface ligands create a dense "amplified steric shield" that strongly blocks H2O access, requiring thermal energy to resolve. To overcome this barrier, we developed a Self-Activating ALD (SA-ALD) process that strategically utilizes the purge period for thermal activation to decompose these ligands, coordinated with an early H2O injection to successfully capture transient active centers. This kinetic strategy yielded metastable, conductive MoO2 films exhibiting a high work function (5.15 eV) and near-perfect step coverage in high-aspect-ratio structures. Consequently, SA-ALD effectively converts the kinetic bottleneck of steric hindrance into latent reactivity, resolving the critical trade-off between reactivity and conformality in conductive oxide deposition.

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