Tantalum Oxide Films Prepared by Oxygen Plasma Anodization and Reactive Sputtering

Anodic tantalum oxide thin‐film capacitors have proved quite satisfactory for circuit applications, although some minor limitations exist in the maximum usable dielectric thickness, current asymmetry, and allowable counterelectrode materials. For this reason, two processes of glow discharge anodization and dc diode reactive sputtering were investigated for the formation of tantalum oxide films. Dielectrics up to a maximum thickness of 3000 A could be prepared by these methods with equal or larger than anticipated capacitance per unit area and dielectric strengths of about one third of anodically formed tantalum oxide. The dc diode reactive sputtering process produces thickness variations over 50 cm 2 of 4 to 20% compared with 4 and 1%, respectively, for glow discharge anodization and aqueous anodization. At the present time, the all‐vacuum methods are limited in applicability because of lower dielectric strength and lower formation rates.