Atomic Force Acoustic Microscopy (AFAM) is a powerful near field technique combining the high spatial resolution of Atomic Force Microscope (AFM) with ultrasonic stresses to access mechanical properties of material shallow surfaces (essentially local stiffness magnitudes like Young modulus). In this article, we discuss different experimental set-up and modelling approaches to determine quantitatively the Young modulus of thin films. Static experiments carried-out on dense and nanoporous silica have shown a good agreement with nanoindentation experiments. Stiffness mapping have also been performed on macroporous silica and copper interconnect structures, showing the ability of our set-up to sense different mechanical answers at sub-micrometer scale