A MEMS XY-stage with sub-nanometer positioning resolution

This paper reports a micro-electro-mechanical systems (MEMS) based XY-stage integrating compliant motion amplification mechanisms for nanopositioning at sub nanometer resolution. The MEMS stage is driven by bidirectional Z-beam electrothermal actuators that generate large output forces to activate the amplification mechanisms. The amplification mechanisms are used in their inverse (motion reduction) mode to convert micrometer input displacements (from the Z-beam actuators) into nanometer output displacements at a constant motion reduction ratio with good linearity. This unique design significantly enhances the positioning resolution of the XY-stage. An analytical model is developed to predict output displacements of the XY-stage as a function of the input voltages applied to the Z-beam actuators, and the predicted results agree with the experimental results. Capacitive position sensors are arranged along both X- and Y-axes for measuring the input displacements of the amplification mechanisms, enabling closed-loop nanopositioning control of the XY-stage. The device calibration results show that, within an actuation voltage of ±15 V, the MEMS stage offers a motion range of ±1 μm and a displacement resolution better than 0.3 nm.