Characterization of thin film tantalum oxide capacitors on polyimide substrates

Thin film tantalum oxide capacitors were fabricated on flexible polyimide substrates and characterized. The capacitance and dielectric constant were found to be independent of frequency from 100 MHz-1 GHz. The leakage current-voltage (I-V) characteristics of the virgin tantalum oxide capacitors were erratic. Both current-induced and temperature-induced annealing effects on virgin capacitors were observed. It was found that the defects of the capacitors depend, not only on the tantalum oxide dielectric, but also on the underlying electrode. Copper particulates embedded in the bottom electrode were the primary cause of electrical shorts. The conduction mechanism was found to be ionic. The ionic conduction activation energies are linearly dependent on the applied electric field, ranging from 0.47 eV for an electric field of 0.13 MV/cm to 0.38 eV for 0.73 MV/cm.