FibDAC - Residual Stress Determination by Combination of Focused Ion Beam Technique and Digital Image Correlation

New challenges for design, manufacturing and packaging of MEMS/NEMS arise from the ongoing miniaturization process. Therefore there is a demand on detailed information on thermo-mechanical material properties of the applied materials. Because of size effects and the strong dependency of the thermo-mechanical behavior of active and passive components on process parameters often unsolved questions of residual stresses lead to system failure due to crack formation. With the fibDAC (Focused Ion Beam based Deformation Analysis by Correlation) method which is presented in this paper the classical hole drilling method for stress release measurement has been downscaled to the nanoscale. The ion beam of the FIB station is used as a milling tool which causes the stress release at silicon microstructures of MEMS devices. The analysis of the stress release is achieved by digital image correlation (DIC) applied to load state SEM images captured in a cross beam equipment (combination of SEM and FIB). The results of the DIC analysis are deformation fields which are transferred to stress solution by application of finite element analysis. In another step the resolution of the method has been improved by the application of trench milling instead of hole milling. Thereby deformation measurements in the nm range are established. The method is also a powerful tool for the analysis of sub-grain stresses of engineering materials.