Measurement of stresses in MEMS structures by stress release

摘要

The paper presents a recently developed method of measuring frozen elastic stresses in micro components and devices. The approach bases on stress release at the component surface by focused ion beam (FIB) milling. Stresses are deduced from the experimentally determined deformation field around the FIB milling pattern, applying reasonable stress hypotheses and appropriate modeling of the stress release field. Because of the local nature of ion milling and the limited material volume affected by deformation, the method suites to very local stress measurement. Commonly, spatial resolution is achieved in a range from submicron to some tens of microns. Residual stresses in membrane type MEMS stmctures have been measured and results are reported. A broader group of potential applications is expected for non-membrane structures in micro-/nanosystems or their packaging. Possible approaches for those cases are discussed, considering comparison of measured deformation fields with either analytical solutions of the mechanical problem or with finite element simulations.