The influence of dc bias an dielectric properties of thin sputtered tantalum oxide films

The influence of dc bias on the dielectric properties of thin rf-sputtered tantalum oxide films. The oxide layer thickness of the standard samples sandwiched between aluminum electrodes is in the range of 40-460 nm. The dielectric constant and dielectric loss tangent (tan /spl delta/) in the high frequency range above 1 kHz show similar values to those published in articles, however their values are larger by two or three times in the low frequency and high temperature ranges. Besides, the dc bias gives a slight increase in the dielectric constant and also dielectric loss tangent. The response of this increase for the dc bias imposed to the signal is in the order of 10-100 sec which is relatively fast compared to the ionic hetero space charge behaviors. This phenomena is tentatively interpreted in terms of two site hopping polarization of space charges modified by injected charges from the electrodes.