Abstract
Thin film materials are normally under residual stresses as a result of fabrication processes. Unlike microelectronics devices, a micro-mechanical structure is no longer constrained by its underlying silicon substrate after anisotropic etch undercutting; therefore, residual stresses may result in bending and buckling of a micromechanical structure. The buckling behavior has been exploited to measure residual stresses of thin films. This characteristic can also be applied to fabricate out-of-plane three-dimensional micromechanical structures if their deflections are controllable. The buckling of a microbridge is difficult to be predicted since it is strongly dominated by its fabrication processes and boundary conditions. The information regarding the buckling of micromachined structures recently is still not complete. The application of the buckling behavior therefore is limited. In this research, the effects of boundary conditions and gradient residual stresses on the buckling behavior of microbridges were studied through analytical and experimental approach. The variations of the buckling amplitude orientations with the thickness and length of the microbridges were obtained; therefore, the buckling behavior can be predicted and then exploited to fabricate useful micromechanical structures. The potential application of this research lies in preventing leakage of the microvalves.