Determination of the hardness and elastic modulus of low- k thin films and their barrier layer for microelectronic applications

Abstract

This paper presents the experimental results and analysis of the elastic modulus and hardness for several thicknesses of dielectric films, namely low- k films and their barrier layer, using the nano-indentation technique. The elastic modulus and hardness of the films were determined by “normal” nano-indentation analysis. The data were then analyzed by re-arranging the load–displacement data ( P– h) obtained by nano-indentation in such a way that the applied load divided by the corresponding displacement ( P/ h) versus the displacement ( h) was obtained, which effectively differentiates the film-only mechanical properties from those of the substrate. The low- k film, carbon-doped silicon oxide (SiOC), was prepared using a parallel plate PECVD system. The dielectric constant of the low- k film was measured to be 3.09, which is much lower than that of commonly used dielectric materials such as SiO 2 ( k∼3.9). The hardness and elastic modulus of the film were measured to be approximately 2.23 and 13.98 GPa, respectively. To enhance the mechanical properties of the low- k thin film, a low- k barrier layer (SiCN:H) with better mechanical properties was deposited between the low- k film and the substrate or on top of the low- k film. It was found that the barrier layer improved the mechanical properties of the low- k film and the barrier layer stacked in certain circumstances. The effects of the arrangement of the barrier layer and the low- k film on the mechanical behavior of the bi-layer system were studied in detail.