<title>Strain measurement in micrometrology</title>

Abstract

New generations of microelectronics and microsystem devices call for the utilization of a variety of new materials and the combination of materials with a widespread of their mechanical and thermal characteristics. Related thermo- mechanical reliability issues as well as functional aims bear a big challenge to understand and to design mechanical behavior of devices and components. Finite elements analysis of components and devices is widely utilized in the R and D process as a tool of predictive engineering. Unfortunately, uprising miniaturization, higher system complexity and advanced material application more often question mechanical modeling for simulation. So, a strong need exists to measure simultaneously stresses and strains on real components. At the IZM Berlin different classical kinds of laser methods have been used to determine deformation behavior of components due to thermo-mechanical load and functional performance of systems. The principal restriction of those methods with regard to spatial and measurement resolution had forced the development of new methods. In particular, microDAC a displacement and strain measurement method has been established. It bases on image processing algorithms permitting to extract strains form load state micrographs, which are picked up by SEM, optical microscopy and other high resolution imaging devices. Besides a brief review, corresponding interferometry and MicroMoire applications of the authors to micro deformation analysis, this paper mainly focuses on the microDAC technique. The basics of the microDAC concept, its main features like measurement resolution, data presentation and coupling to finite element analysis as well as applications are presented. Different kinds of measurements on modern electronics structures, like, e.g., used in flip chip technology, chip scale packaging and optoelectronics, illustrate its capability. Finally, a discussion of possible future developments is added, which can be directed to the adoption of higher resolution imaging equipment, namely scanning force microscopy.