STUDY OF ALUMINUM-OXIDE FILMS FORMED BY PLASMA ANODIZATION

Anodic oxidation plays an important role in microelectronics as well as in thin film devices. Oxide films obtained on metals such as aluminium and tantalum by anodization using a gaseous electrolyte are found to be superior to those formed by using aqueous solution. Earlier researchers have shown that anodization can be carried out more efficiently at an optimum pressure of 6.7 Pa (50 mTorr) and an optimum bias voltage of 5V. It is also reported that the optimum pressure depends on the system geometry. This work was carried out to determine the effect of cylindrical geometry. It is observed that the optimum pressure for the cylindrical geometry is 26.8 Pa (200 mTorr) while the optimum bias voltage is found to be 5V. Formation of Al2O3 is confirmed by using electron spectroscopy for chemical analysis. Small-angle X-ray diffraction results indicate the formation of the gamma-Al2O3 phase at low bias voltages whereas the beta-Al2O3 phase is more dominant at higher bias voltages