Conducting and topographic AFM analysis of Hf-doped and Al-doped Ta2O5 films

• Published in: Thin solid films 2011-09, Vol.519 (22), p.8182-8190
• Main Authors: ATANASSOVA, E, LYTVYN, P, KONAKOVA, R. V, MITIN, V. F, SPASSOV, D
• Format: Article
• Language: English
• Subjects: Aluminum; Atomic force microscopy; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Conductivity; Cross-disciplinary physics: materials science; rheology; Electric potential; Electrical properties of specific thin films; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Exact sciences and technology; Hafnium; Materials science; Mechanical and acoustical properties; Nanoscale materials and structures: fabrication and characterization; Nanostructure; Other topics in nanoscale materials and structures; Physical properties of thin films, nonelectronic; Physics; Resistivity; Structure and morphology; thickness; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Tantalum oxides; Thin film structure and morphology
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2011.06.055

A conductive atomic force microscopy (C-AFM) has been used to study conductivity and electrical degradation of ultrathin (4nm) Hf- and Al-doped Ta2O5 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 Ta2O5, provokes modification of the leakage current mechanism, and is effective in extending the potential of pure Ta2O5 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 Ta2O5 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.