Hydrogen Permeation and Its Impacts on the Electrical Performance of Stacked ZrO2/Al2O3/ZrO2 Films

In this study, the effects of hydrogenation on the dielectric capacitance and leakage current of ZrO2/Al2O3/ZrO2 (ZAZ) films for dynamic-random-access memory (DRAM) capacitors were examined. Hydrogen permeation into ZAZ films reduced the dielectric capacitance and increased the leakage current with continued exposure to hydrogen during the forming gas annealing process. More specifically, the hydrogen ions distributed in the grain boundaries and at the Z/A interfaces appeared to disrupt the dipole motion and diminish the dielectric constant of the film, resulting in a decreased dielectric capacitance. Furthermore, the reaction of hydrogen atoms with the pre-existing oxygen of the ZrO2 films resulted in an oxygen vacancy with two captured electrons. Conduction electrons freed via ionization of the oxygen vacancy increased the conductivity of the ZAZ films, thereby increasing the leakage current throughout the ZAZ films.