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 degreesC-500 degreesC 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.