3-D self-assembling and actuation of electrostatic microstructures

An advanced three-dimensional (3-D) self-assembling technique of surface micro-machined polysilicon structures is presented here for the realization of dedicated actuators for optical applications such as micro-mirror arrays with large deflection angles. Three-dimensional polysilicon microparts are self-assembled by beam buckling induced by integrated scratch drive actuators (SDAs). With this technique, 380×250 μm² microplates were lifted 30 μm above the substrate plane. Once the assembling is performed, the 3-D shapes were held permanently by an integrated mechanical lock. Subsequent to the 3-D assembling, micro-mirrors were successfully actuated by biasing buried electrodes. Controlled motion up to ±15° rotation was measured and analyzed by means of analytical models. Long-term actuations were carried out without any observable change, even for 0.5-μm thin polysilicon structures. This self-assembling technique of 3-D devices from surface micro-machining opens new integration capabilities and new applications for micro-opto-electro-mechanical systems (MOEMS)