Low-temperature atomic layer deposition of metastable MnTe films for phase change memory devices

Abstract

This work demonstrates an atomic layer deposition (ALD) process for achieving the MnTe film with metastable β phase at a growth temperature of 100 °C. By employing a nitrogen-coordinated Mn precursor (bis[bis(trimethylsilyl)amido]manganese(II)) and co-injecting NH₃ with the Te precursor (bis(trimethylsilyl)telluride(II)), stoichiometric and high-purity β-MnTe films were deposited with self-limiting behavior on SiO₂ substrate at a growth temperature of 100 °C. The metastable β phase was stabilized without needing non-equilibrium synthesis methods, offering smooth (root-mean-squared roughness ∼0.55 nm) nanocrystalline films with excellent uniformity and conformality on both planar and high-aspect-ratio structures. Substrate- and temperature-dependent growth behaviors revealed that the formation of β-MnTe is governed by the chemical bonding environment, with the phase transitioning to the stable α phase on conductive substrates or at higher growth temperatures. Annealing studies demonstrated the β to α phase transition via a displacive transformation, highlighting the feasibility of the ALD MnTe films for future phase change memory devices. This work offers insights into the ALD of metastable-phase chalcogenides, enabling their integration into advanced electronic devices.