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

Abstract

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 (~10−5A/cm2 at −2V). On the other hand, Sr–Ta–O showed the lowest leakage current densities (~10−9A/cm2 at −2V) as well as the smallest capacitance–voltage nonlinearity coefficients (40ppm/V2), but the dielectric constant was the smallest (20). The highest nonlinearity coefficients (290ppm/V2) were observed for Nb–Ta–O based MIM capacitors, although relatively high dielectric constant (40) and low leakage currents (~10−7A/cm2 at −2V) 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.