Characteristics of sputtered Ti1−xAlxN films for storage node electrode barriers

Abstract

We report on the characteristics of sputter-deposited Ti1−xAlxN (TiAlN) thin films for storage node electrode barriers of Pt/(BaSr)TiO3(BST)/Pt metal–insulator–metal (MIM) capacitors with a comparative study of TiN films. The substrate temperature (Ts) was found to be one of the key factors affecting the properties of TiAlN thin films, i.e., the resistivity of TiAlN is ∼350 μΩ cm for high Ts deposition (∼450 °C) and ∼1100 μΩ cm for low Ts (∼100 °C). The lower resistivity of TiAlN films deposited at high Ts (450 °C) is attributed to the (200) texture with larger grain size and smaller oxygen concentration compared to those prepared at low Ts. The electrical characteristics of Pt/BST/Pt MIM capacitors on TiAlN were superior to those on the TiN barrier in terms of smaller equivalent oxide thickness (tox), lower tangent δ, and lower leakage current. Better oxidation resistance of TiAlN over TiN appears to be responsible for the better electrical results, especially with the (111) or (200) texture. We also discuss a BST bulge and local thinning due to the Pt deformation on TiAlN over an anneal of 600 °C in O2, resulting in leakage current degradation of the BST MIM capacitor.