Mechanical Characterization of Thin Films by Use of Atomic Force Acoustic Microscopy



The atomic force acoustic microscopy (AFAM) technique has been used to determine elastic properties of films with thicknesses decreasing from several hundreds of nanometers to several nanometers. It has been shown that metal films as thin as 50 nm can be characterized directly without the need to consider the influence of the substrate. For films with thicknesses ranging from about 30 to 50 nm, measurement parameters can be chosen such as to allow characterization of the elastic properties of either the film or the film–substrate interface. This attribute has been combined with the ability of the method to obtain qualitative stiffness images to show variations in the film–substrate adhesion. The AFAM technique has been also used to determine the indentation modulus of thin films of silicon oxide with thicknesses ranging from 7 to 28 nm. In this case, elastic properties of the substrate had to be considered. The examples of the applications of the AFAM method reported here for characterization of elastic properties of very thin films have shown that this technique has the lateral and depth resolution required to characterize the very thin films used nowadays in microelectronics industry.