Use of anodic tantalum pentoxide for high-density capacitor fabrication

Abstract

In this work we report on very thin (10 to 100 nm) tantalum oxide fabricated by anodic oxidation of tantalum nitride and tantalum silicide to be used as the dielectric of high density MIM and MIS capacitors. These films exhibit greatly improved leakage currents, breakdown voltage and very low defect density, thus allowing the fabrication of large area capacitors. Several counter and bottom electrodes have been used and compared. The effects of the different processing conditions (top-electrode metals, annealing conditions, bottom electrode stoichiometry) on the capacitor performances are extensively discussed throughout this work. The nitrogen content of tantalum nitride films seems to have an important influence on the insulator quality. Leakage currents in the insulator have been carefully studied in order to determine the nature and physical origin of the dominant conduction mechanisms in the insulator. The electrical behaviour of the resulting high-density MIM capacitors has been extensively characterized. Finally, we describe a new method to fabricate MIS diodes with anodic tantalum oxide as insulator.