Extendibility of Ta₂O₅ Metal-Insulator-Metal Capacitor Using Ru Electrode

Abstract

The electrical properties of the Ru/Ta 2 O 5 /Ru planar capacitor structure were investigated. It was determined that the leakage current and temperature dependence were improved using a bottom electrode annealed in Ar/H 2 mixture ambient. A step-and-terrace structure was obtained on the Ru surface when annealed in Ar/H 2 mixture ambient, unlike that obtained from the conventional inert ambient anneal. Since a physical analysis of the two Ru bottom electrodes did not show any other difference, we considered the difference in surface morphology to be one of the major reasons for the improvement in temperature dependence of the leakage current. In addition, a cylindrical bottom Ru electrode of 20 nm thickness and 0.3 µm height was demonstrated, as the thin Ru film had sufficient physical strength to fabricate this cylindrical structure. Using the obtained parameters, the Ru thickness, the dielectric leakage and other characteristics, from the experimental results, we discussed the extendibility of the Ta 2 O 5 -MIM capacitor structure. By assuming the effective thickness of Ta 2 O 5 to be 0.9 nm and capacitance to be 25 fF/cell, an electrode height of 0.7 µm was expected with a leakage current of less than 1 fA/cell at the 0.1-µm-node cylindrical structure.