Doping Ferroelectric Hafnium Oxide by in-Situ Precursor Mixing

Abstract

We employ a modified atomic layer deposition process utilizing in-situ mixing of precursors to obtain doped hafnium oxide thin films with improved ferroelectric properties. The method is demonstrated with aluminum, silicon, and lanthanum doping, where film composition and crystal structure are analyzed. With the modified process, low dopant concentrations are shown to be accessible, and improved wafer-level uniformity of dopant concentration is demonstrated for Si and La doping. Characterization of the ferroelectric hysteresis confirms increased remanent polarization values with the modified process variant for all examined dopants. The switching density of the 10 nm thick films is analyzed by using first-order reversal curve measurements, where confined peaks are observed, which are an indication of low defect density and reduced internal bias fields. Emerging applications of doped hafnium oxide thin films such as nonvolatile memory, infrared sensors, or neuromorphic devices may benefit from the enhanced stoichiometry control and film properties by using the proposed deposition method.