Tetragonal Zirconia Stabilization by Metal Addition for Metal-Insulator-Metal Capacitor Applications

Abstract

Zirconium dioxide is a good candidate to reach the capacitance density of 40fF/μm² required for decoupling applications. Indeed zirconia has a promising dielectric constant of 47 in the tetragonal phase. However, pure tetragonal zirconia layers deposited by PEALD do not fulfill the reliability criteria. We thus stabilize zirconia by addition of different metals. Tantalum is alloyed with zirconia. Since Ta solubility in ZrO2 is low, an orthorhombic ternary compounds appears and reduce the global dielectric constant of the layer. We also alloy zirconium dioxide with germanium. At high Ge concentration ZrO2 layers remain amorphous even after post deposition annealing, with a reduced dielectric constant. However at lower germanium concentration zirconia layers crystallize in tetragonal phase with better electrical properties than pure ZrO2.