Publications Details

Effects of mechanical stress on thermal microactuator performance

Phinney, Leslie M.; Spletzer, Matthew A.; Baker, Michael S.; Serrano, Justin R.

Mechanical stresses on microsystems die induced by packaging processes and varying environmental conditions can affect the performance and reliability of microsystems devices. Thermal microactuators and stress gauges were fabricated using the Sandia five-layer SUMMiT surface micromachining process and diced to fit in a four-point bending stage. The sample dies were tested under tension and compression at stresses varying from ?250 MPa, compressive, to 200 MPa, tensile. Stress values were validated by both on-die stress gauges and micro-Raman spectroscopy measurements. Thermal microactuator displacement is measured for applied currents up to 35 mA as the mechanical stress is systematically varied. Increasing tensile stress decreases the initial actuator displacement. In most cases, the incremental thermal microactuator displacement from the zero current value for a given applied current decreases when the die is stressed. Numerical model predictions of thermal microactuator displacement versus current agree with the experimental results. Quantitative information on the reduction in thermal microactuator displacement as a function of stress provides validation data for MEMS models and can guide future designs to be more robust to mechanical stresses. © 2010 IOP Publishing Ltd.