Self-buckling of micromachined beams under resistive heating

Self-buckling behavior of micromachined beams under resistive heating is described by an electromechanical model with experimental verifications. This model consists of both electro-thermal and thermo-elastic analyses for beam-shape polysilicon microstructures that are fabricated by a standard surface micromachining process. When an input electrical current is applied, joule-heating effects trigger the thermal expansion of beam structures and cause mechanical buckling. The standard testing devices are clamped-clamped bridges, 2-mu m wide, 2-mu m thick, and 100-mu m long. It is found that a minimum current of 3.5 mA is required to cause beam buckling. Under an input current of 4.8 mA, a lateral deflection of 2.9+/-0.2 mu m at the center of the bridge is measured with a computer image processing scheme. The experimental measurements are found to be consistent with analytical predictions. A discussion of modeling considerations and process variations is presented. [412].