Pulsed deposition of metal–oxide thin films using dual metal precursors

A technique for depositing high-dielectric-constant metal–oxide thin films is demonstrated that consists of alternating pulses of metal–chloride precursors and $Hf(NO3)4$ in which $Hf(NO3)4$ is used as an oxidizing agent as well as a metal source. The use of $Hf(NO3)4,$ rather than a separate oxidizing agent such as $H2O,$ minimizes the potential for oxidation of the Si interface. Unlike $HfCl4,$ a widely used precursor, the high reactivity of $Hf(NO3)4$ initiates uniform deposition on H-terminated Si beginning with the first pulse. Effective dielectric constants obtained for $HfO2$ films produced by this method were comparable to $HfO2$ films deposited using other methods and the leakage current densities were three orders of magnitude less than $SiO2$ of the same equivalent thickness. Deposition of $HfAlOx$ and $HfZrOx$ ternary oxide films was also examined. The deposition rate for films produced using this method is greater than one monolayer per cycle, indicating a mechanism that is different from standard atomic-layer deposition.