Fabricating MoO2 films for DRAM applications through Atomic Layer Deposition with a Mo(IV) precursor and oxygen reactant

Abstract

Molybdenum dioxide (MoO2) is a conductive metal oxide that has gained significant attention as a promising electrode material for next-generation Dynamic Random Access Memory(DRAM) due to its high crystallinity and high work function. In this study, we developed an atomic layer deposition (ALD) process for MoO2 thin films that exhibits high crystallinity and a very high work function of over 4.8 eV. We used (NMe2)4Mo as a highly reactive 4+ precursor and oxygen reactants (oxygen gas and ozone) for the deposition of MoOx. We observed a significant difference in growth rates, with oxygen gas and ozone deposited MoOx showing growth rates of approximately 0.23 Å/cycle and 1.36 Å/cycle, respectively. This reactivity-driven difference also influenced the O/Mo ratio, which was 2.69 for oxygen gas based MoOx and 2.96 for ozone based MoOx. Both oxygen gas based MoOx and ozone based MoOx exhibited high work functions of 4.81 and 5.12 eV, respectively. Subsequently, through a thermal annealing process, we successfully induced the monoclinic MoO2 structure. This structure was exclusively observed in the case of oxygen gas based MoOx films subjected to reduction annealing. In contrast, regardless of the annealing condition, only orthorhombic MoO3 was observed in the case of ozone based MoOx films. These results confirm the formation of monoclinic MoO2, which was deposited using a highly reactive 4+ precursor and oxygen gas during the reduction annealing process