Micro-opto-electro-mechanical systems alignment stages with Vernier latch mechanisms

Latching alignment stages for micro-opto-mechanical systems are constructed by deep reactive-ion etching of bonded silicon on insulator. Linear, rotary and tilt stages are demonstrated. Linear stages are driven using buckling electrothermal actuators, and latching is performed by a rack-and-tooth mechanism driven by shape bimorph actuators. In-plane rotation is obtained by using a linear actuator to drive a passive rotary table, and tilt motion is achieved using an inserted mirror. Finite element modelling is used to estimate limitations in performance and propose design improvements. A rack period of 10 mu m is achieved with a structural depth of 85 mu m. A Vernier mechanism based on multiple rack-and-tooth latches is used to increase precision beyond the value set by pattern transfer. Two- and four-section Vernier latches are demonstrated, and difficulties with multi-section latches are identified.