MEMS Test Structures for Residual Stress Measurements
A set of microstructures for in situ stress measurement is presented, based on a lancet principle having dedicated designs for the amplification of dimensional variation induced by internal stress of the materials. The presented technique has an advantage over the traditional rotating structures and wafer curvature measurements in terms of the simplified readout mechanism. The test structures are realized by surface micromachining techniques, adopting photo-resist as a sacrificial layer and electroplated gold as a structural layer. COMSOL Multiphysics simulations are adopted to analyze the behavior of gold structures under the influence of thermal variation using “thermal structural interaction” in the MEMS module. The residual stress is obtained in the range of 200±30MPa.