Study on residual stresses in MEMS thin films

Residual stresses of thin films have large effects on MEMS structures. It is introduced in this paper how they are generated, measured and controlled in MEMS designing and manufacturing. Particularly, thermal stresses in multi-layer MEMS structures are modeled with FEM and analyzed. To measure residual stresses, a new microstructure (micro-rotating-structure) is simulated and the results reveal simple relation of linearity between offset of the rotating beam tip and residual strain in MEMS thin films. Due to its many advantages, micro-rotating-structure is proved to be efficient for measuring residual stresses. In the end, three methods to control residual stresses in MEMS thin films are briefly introduced: film deposition processing, strain counteraction and rapid thermal annealing.