Structural and electrical properties of thin rf sputtered Ta2 O5

Elemental composition, chemical bonding and some electrical properties of rf sputtered tantalum oxide with thickness 10-70 nm, depending on process parameters, are investigated. The results indicate that tantalum oxide can be obtained by rf sputtering even in gas mixtures with N_c=2.5%, but 10% oxygen content is beneficial for obtaining stoichiometric and homogeneous Ta₂O₅ with an abrupt interface transition region. AES and XPS experiments show that the stoichiometry does not depend on thickness or the substrate temperature in the investigated ranges. Additionally the electrical measurements strongly suggest that Ta₂O₅ layers suitable for submicron application (with high dielectric constant and low fixed oxide charge) can be obtained only at T_s=493 K