Enhanced dielectric properties of modified Ta2O5 thin films

Tantalum oxide (Ta 2 O 5 ) is a promising high dielectric constant material for the DRAM applications because of its ease of integration compared to other complex oxide dielectrics. The dielectric constant and thermal stability characteristics of bulk Ta 2 O 5 samples were reported to enhance significantly through small substitutions of Al 2 O 3 . However, this improvement in the dielectric constant of (1-x)Ta 2 O 5 -xAl 2 O 3 is not clearly understood. The present research attempts to explain the higher dielectric constant of (1-x)Ta 2 O 5 -xAl 2 O 3 by fabricating thin films with enhanced dielectric properties. A higher dielectric constant of 42.8 was obtained for 0.9Ta 2 O 5 -0.1Al 2 O 3 thin films compared to that reported for pure Ta 2 O 5 (25-30). This increase was shown to be closely related to a-axis orientation. Pure Ta 2 O 5 thin films with similar a-axis orientation also exhibited a high dielectric constant of 51.7, thus confirming the orientation effect. The leakage current properties and the reliability characteristics were also found to be improved with Al 2 O 3 addition.