A New Methodology For In-Situ Residual Stress Measurement In MEMS Structures

In this paper, a new approach is presented for local residual stress measurement in MEMS structures. The newly proposed approach involves incremental focused ion beam (FIB) milling of annular trenches at material surface, combined with high resolution SEM imaging and Digital Image Correlation (DIC) analysis for the measurement of the strain relief over the surface of the remaining central pillar. The proposed technique allows investigating the average residual stress on suspended micro-structures, with a spatial resolution lower than 1 μm. Results are presented for residual stress measurement on double clamped micro-beams, whose layers are obtained by DC-sputtering (PVD) deposition. Residual stresses were also independently measured by the conventional curvature method (Stoney's equation) on a similar homogeneous coating obtained by the same deposition parameters and a comparison and discussion of obtained results is performed.