The residual stress of thin films during the deposition process can cause the components to have unpredictable deformation and damage, which could affect the service life and reliability of the microsystems. Developing an accurate and reliable method for measuring the residual stress of thin films at the micrometer and nanometer scale is a great challenge. To analyze the residual stress regarding factors such as the mechanical anisotropy and preferred orientation of the materials, information related to the in-depth lattice strain function is required when calculating the depth profiles of the residual strain. For depth-resolved measurements of residual stress, it is strategically advantageous to develop a measurement procedure that is microstructurally independent. Here, by performing an incremental focused ion beam (FIB) ring-core drilling experiment with various depth steps, the digital image correlation (DIC) of the specimen images was obtained. The feasibility of DIC to FIB images was evaluated after the translation test, and an appropriate procedure for reliable results was established. Furthermore, the condition of the film in the function of residual stress was assessed and compared to elucidate the applicability of this technology.

In this study, the effects of electromigration on a solder/copper substrate due to temperature and current density stress were investigated. The copper–tin (Cu–Sn) film samples were subjected under a fixed current and various heating conditions (130 °C and 180 °C) and current densities (different cross-sectional areas). The micro-structural changes and intermetallic compound (IMC) formation were observed, and failure phenomena (brittle cracks, voids, bumps, etc.) on the structures of samples were discussed. The results showed that the IMC thickness increased as the temperature and current density increased. Moreover, it was found that the higher the temperature and current density was, the greater the defects that were observed. By adjusting the designs of sample structures, the stress from the current density can be decreased, resulting in reduced failure phenomena, such as signal delay, distortion, and short circuiting after long-term use of the material components. A detailed IMC growth mechanism and defect formation were also closely studied and discussed.

In this work, an electrostatic comb-drive micro-mirror with the Pd-based metallic glass torsion bar and the self-aligned structures was proposed and developed. The self-aligned structure of the comb-drive micro-mirror is achieved avoiding the comb structure alignment process. The fixed combs of the top mirror wafer were lifted by the bottom activation post for making the comb height difference. The height difference between the fixed combs and moving combs could effectively increase the torque to the mirror structure. The static tilting angle of 16° was achieved when the input voltage is 45.6 V. In the resonant mode, the scanning angle of 40.5° was achieved when the input voltage is 30 Vpp at 95 Hz. According to the measurement results and comparing with other silicon torsion bar micro-mirrors, the driving voltage could be decreased 50% and the tilting angle could be increased around four times for the proposed micro-mirror.