Enhanced dielectric properties of modified Ta2O5 thin films

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Abstract
Tantalum oxide (Ta2O5) 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 Ta2O5 samples were reported to enhance significantly through small substitutions of Al2O3. However, this improvement in the dielectric constant of (1-x)Ta2O5-xAl2O3 is not clearly understood. The present research attempts to explain the higher dielectric constant of (1-x)Ta2O5-xAl2O3 by fabricating thin films with enhanced dielectric properties. A higher dielectric constant of 42.8 was obtained for 0.9Ta2O5–0.1Al2O3 thin films compared to that reported for pure Ta2O5 (25–30). This increase was shown to be closely related to a-axis orientation. Pure Ta2O5 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 Al2O3 addition.