On the morning of my professional career, as research and development engineer, I had the chance to work at the Institute of Micro Electronic Center (IMEC). This book presents the work I have done from February till September 2007 and its focuses on the investigation of mechanical properties of low-k materials using opto-acoustic technique. Before approaching the opto-acoustic method itself, I practiced the techniques of thin films deposition, plasma treatment and spectro-ellipsometric characterization of materials. Unlike spectro-ellipsometric thin films study, the opto-acoustic characterization requires working with samples which include a transducer material. So, at first, we have designed some samples geometries to be analyzed. The goal of this comparative study (mechanic and acoustic) is not only to establish a correlation between nanoindentation and acoustic wave techniques, but also to determine the factors which best describe mechanical properties of low-k materials. The work has been done in collaboration with the Laboratory of Condensed Matter Physics (LPEC), located in Le Mans (France).