Initial growth step and annealing effect of Ta2O5 formed by anodization of Ta foil in an ammonium tartrate electrolyte

The initial growth step during the anodization of a Ta foil and structural changes in the Ta2O5 film with anodizing time and annealing temperature were investigated using cyclic voltammetry, chronoamperometry, ac impedance spectroscopy, atomic force microscopy, x-ray diffraction, and x-ray photoelectron spectroscopy. Under the conditions used here, the Ta2O5 film was anodized by the island growth mechanism and the initial growth step of Ta2O5 formation is via the tunneling mode. which is thickness dependent. that is, changing from direct tunneling to defect-enhanced tunneling as the thickness is increased up to a considerable thickness (about 200 Angstrom). The anodized Ta2O5/Ta samples were annealed by rapid thermal annealing (RTA) and Pt metals were then sputtered to produce the Pt/Ta2O5/Ta structure. Based on the leakage current versus voltage data for Pt/Ta2O5/Ta. we conclude that an anodized Ta2O5 film call be used as an insulating material for storage capacitors in combination with all optimum RTA treatment. (C) 2001 American Vacuum Society.