Conducting and topographic AFM analysis of Hf-doped and Al-doped Ta 2O 5 films

Abstract

A conductive atomic force microscopy (C-AFM) has been used to study conductivity and electrical degradation of ultrathin (4 nm) Hf- and Al-doped Ta 2O 5 at the nanometer scale. The hardness testing has been also performed using the force measuring ability of the AFM. Since the size of the analyzed area is very small, features which are not visible by macroscopic tests are observed: extremely low leakage current (~ pA) up to significantly higher than the fields during standard current–voltage measurements; charge trapping/detrapping processes manifesting as current peaks at pre-breakdown voltages. Hf and Al addition improves the local conductivity of Ta 2O 5, provokes modification of the leakage current mechanism, and is effective in extending the potential of pure Ta 2O 5 as a high- k material at the nanoscale. The results point to a decisive role of the type of the dopant on the electrical and mechanical properties of the films and their local response to short term microwave irradiation. Hf-doped Ta 2O 5 exhibits excellent electrical stability and high hardness. Al doping provides more plastic films with large electrical inhomogeneities; the microwave treatment at room temperature is a way to improve these parameters to a level comparable to those of Hf-doped films.