Measurement of mechanical properties of thin solid films -hardness, elasticity, stress-

This article gives an overview of current techniques to determine hardness, Young's modulus and stress state of a thin solid film on a substrate. The former two are measured with an instrument sometimes referred to as a nanometer indenter. It is capable of detecting continuously the indentation depth of a diamond tip in dependence of load on the indenter with nanometer precision. From loading-unloading cycles the mechanical parameters hardness and Youngs's modulus are calculated. The stress state of thin films can be obtained by measuring the curvature of a bent substrate with the stressed film fixed to it or by x-ray techniques to determine the spacing between strained crystal planes. The mathematical theory, assumptions and limitations of these techniques are discussed and two examples of the information obtained from these measurements are presented.