Properties of atomic-vapor and atomic-layer deposited Sr, Ti, and Nb doped Ta2O5 Metal-Insulator-Metal capacitors

Atomic Vapor Deposition and Atomic Layer Deposition techniques were applied for the depositions of Ta₂O₅, Ti-Ta-O, Sr-Ta-O and Nb-Ta-O oxide films for Metal-Insulator-Metal (MIM) capacitors used in back-end of line for Radio Frequency applications. Structural and electrical properties were studied. Films, deposited on the TiN bottom electrodes, in the temperature range of 225-400 °C, were amorphous, whereas the post deposition annealing at 600 °C resulted in the crystallization of Nb-Ta-O films. Electrical properties of MIM structures, investigated after sputtering Au top electrodes, revealed that the main characteristics were different for each oxide. On one hand, Ti-Ta-O based MIM capacitors possessed the highest dielectric constant (50), but the leakages currents were also the highest (~ 10^− 5 A/cm² at − 2 V). On the other hand, Sr-Ta-O showed the lowest leakage current densities (~ 10^− 9 A/cm² at − 2 V) as well as the smallest capacitance-voltage nonlinearity coefficients (40 ppm/V²), but the dielectric constant was the smallest (20). The highest nonlinearity coefficients (290 ppm/V²) were observed for Nb-Ta-O based MIM capacitors, although relatively high dielectric constant (40) and low leakage currents (~ 10^− 7 A/cm² at − 2 V) were measured. Temperature dependent leakage-voltage measurements revealed that only Sr-Ta-O showed no dependence of leakage current as a function of the measurement temperature.