Charge Transport in Anodized Ta sub 2 O sub 5, HfO sub 2, and ZrO sub 2 Thin Films

The electrical leakage characteristics of anodic Ta sub 2 O sub 5 thin films (epsilon = 23 +- 2) have been studied in detail and are compared to anodic films of ZrO sub 2 (epsilon = 19 +- 2) and HfO sub 2 (epsilon = 16 +- 2). Both transient and steady state leakage mechanisms have been observed in metal-oxide-metal capacitor structures. The transient currents decay as a power-law in time and, for a given dielectric thickness and applied field, are similar in magnitude for each material. Annealing experiments on anodic Ta sub 2 O sub 5 suggest that the steady state currents are due to defects. Steady state currents were eliminated when either the defects did not span the width of the film or when an inert, high work function metal electrode was used that creates a barrier to defect band conduction. Similar steady state leakage characteristics were observed with anodized HfO sub 2 and ZrO sub 2 films.