Abstract

We study the deformation behavior of a series of gold/polysilicon MEMS plate structures fabricated by the MUMPS surface micromachining process and subjected to uniform temperature changes from 100°C to room temperature. We measured, using an interferometric microscope, full-field deformed shapes of a series of square (L×L) gold (0.5 μm thick)/polysilicon (1.5 μm thick) plate structures of sizes ranging from L = 150 μm to L = 300 μm. In general, we observed three regimes of deformation as characterized by the average curvature as a function of temperature change: i) linear thermoelastic response independent of plate size, ii) geometrically nonlinear thermoelastic response that depends on plate size, and iii) bifurcations in the curvature-temperature response that also depend on plate size. We modeled the deformation response both analytically and with the finite element method. Good qualitative and quantitative agreement was obtained between predictions and measurements in all three deformation regimes. Good agreement was also obtained between measurements and predictions of the spatial nonuniformity of the curvature across the plate.

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