Automated micro-assembly of optical MEMS structure by centrifugal force

A very fast, low-cost, and reliable method to assemble micro structures suitable for MOEMS (micro-opto-electro-mechanical systems) applications is reported in this paper. In general, due to the minute scale of MEMS devices, inertia force is often neglected when dealing with MEMS components. However, we have demonstrated that inertia force can be significant even if the mass of micro structure is <1μg (a 250μm × 100 μm mass with 3.5 μm thick polysilicon and 0.5 μm thick Au layers). At this scale, we have shown that, mass inertia force can overcome some surface forces and thus be used for non-contact self-assembly of MEMS structures. Centrifugal force was applied to several hinged MUMPs (multi-user-MEMS-processes) chips by attaching the chips to a rotating disc. The micro hinged structures on the chips were shown to self-assemble by rotating themselves 90° out of substrate plane in most cases, and automatically lock themselves to designed latches. The assembly is also applicable on complex dynamic micro mirror. Our experimental setup and systematic approach to acquire force data during the centrifugal assembly process is described in this paper.