Determination of Young's modulus of thin films used in embedded passive devices

An experimental study to determine the Young's modulus of thin films has been performed using both a standard tensile test and a Vickers microindentation test. Currently, the mechanical properties of thin films such as Young's modulus have not been determined by a standard tensile test because of the problem associated with separating the thin films from the silicon wafers without deforming them. To avoid these difficulties, we have implemented a simple technique based on a tensile test of thin film assemblies. In our work, a flexible polyimide film is utilized as the substrate onto which a thin film is deposited. The testing procedure and specimen used were according to ASTM-D882 standards for thin plastic sheeting. Within the ASTM standard conditions and the specified specimen's dimensions, the proposed method is suitable for determining the Young's modulus of aluminum thin films (within 20% uncertainty) providing that the thickness ratio of the tested assembly is greater than 0.72. The results from the tensile test procedure are compared to results obtained using the microindentation technique. The Vickers microindentation method was used to determine the Young's modulus of the polyimide film by analyzing the unloading microindentation curve. The major disadvantage of this technique is that a relatively thick film (>20 /spl mu/m) is required.