Atomic Layer Deposition of Metallic Molybdenum Dioxide Thin Films Enabling High‐ k Rutile Capacitors

Molybdenum dioxide (MoO 2 ) thin films have attracted considerable attention as electrode materials for high‐ k capacitors, such as those used in dynamic random‐access memory (DRAM) devices. Properties that make MoO 2 highly attractive include high conductivity, high work function (> 5 eV), distorted rutile crystal structure, and chemical stability. However, currently, atomic layer deposition (ALD) of crystalline MoO 2 is not possible without additional (post‐)deposition steps. In this work, the first direct ALD process for MoO 2 thin films is presented using molybdenum(II) acetate dimer (Mo 2 (OAc) 4 ) and oxygen (O 2 ) as precursors. Controlled growth was observed at 235°C–275°C, yielding crystalline MoO 2 films with a distorted rutile (tugarinovite) crystal structure. The films were stoichiometric, exceptionally pure with ∼1 at.% total impurities, and highly conductive with a resistivity of 400 µΩ∙cm. Application potential of the process was demonstrated by depositing low temperature (150°C–275°C) high‐ k rutile titanium dioxide (TiO 2 ) dielectric thin films and subsequently capacitor devices based on MoO 2 electrodes. This work expands the selection of thin film materials deposited by ALD with MoO 2 , enabling deposition of a full range of molybdenum oxides from MoO 2 to MoO x<3 to MoO 3 .