Effect of Al inclusion in HfO₂ on the physical and electrical properties of the dielectrics

This letter presents the effect of Al inclusion in HfO₂ on the crystallization temperature, leakage current, band gap, dielectric constant, and border traps. It has been found that the crystallization temperature is significantly increased by adding Al into the HfO₂ film. With an addition of 31.7% Al, the crystallization temperature is about 400 ° C-500 °C higher than that without Al. This additional Al also results an increase of the band gap of the dielectric from 5.8 eV for HfO₂ without Al to 6.5 eV for HfAlO with 45.5% Al and a reduced dielectric constant from 19.6 for HfO₂ without Al to 7.4 for Al₂O₃ without Hf. Considering the tradeoff among the crystallization temperature, band gap, and dielectric constant, we have concluded that the optimum Al concentration is about 30% for conventional self-aligned CMOS gate processing technology.