Development of Fine Motion Stages for Six Degree-of-Freedom Submicron Positioning

Abstract

Submicron positioning stages are an invaluable tool in a variety of high precision applications including microscopy, optics, micromachining, and photolithography. This thesis covers the development and testing of a mechanical fine motion stage that uses a novel configuration of precision ballscrews and flexures to produce controlled motion in 6 degrees of freedom. The stage is designed to be capable of submicron repeatability within a range of motion that spans ±0.1 mm in 𝑥 and 𝑦, ±1.5 mm in 𝑧, ±1 mrad in 𝜃ₓ and 𝜃ᵧ, and ±52 mrad in 𝜃 subscript 𝑧.

A full system architecture for controlling the stage and evaluating its performance is developed in this work. This includes the design of a metrology system using low cost position sensors for monitoring the position and orientation of the stage.

Tests show the repeatability of the stage to be on the order of 0.4 µm in 𝑥 and 𝑦, 25 nm in 𝑧 and on the microradian level for the rotational degrees of freedom, with room for improvement in all degrees of freedom through the use of endpoint feedback and higher resolution sensors. Frequency response measurements show that the dynamics of the stage with a 3 kg payload are well behaved to at least 170 Hz, which indicates that closed loop bandwidths up this frequency are readily achievable.

In addition, this thesis presents practical considerations for the structural design and actuator integration of an electromagnetically levitated fine motion stage.