Electrical properties in low temperature range (5 K-300 K) of tantalum oxide dielectric MIM capacitors

Tantalum oxide (Ta2O5) is widely used for MINI (Metal-Insulator-Metal) capacitor owing of its high dielectric constant. This work examines current-voltage and capacitance-voltage characteristics in the 5 K-300 K temperature range. Working at low temperature was chosen in order to freeze trapping mechanisms of the MIM capacitor. The curvature of C-V characteristics radically changes from 5 K to 300 K. The capacitance variation under voltage at 50 K and below can be investigated using the Langevin theory. From this model the permanent dipole moment and the number of dipoles have been extracted. From Poole-Frenkel identification curves, activation energy around 0.20 eV and a dielectric constant of 26 were found for positive polarisation. However, conduction mechanisms cannot be reduced to strick Poole-Frenkel modelling. (c) 2004 Elsevier Ltd. All rights reserved.