The long-range scanning stage: a novel platform for scanned-probe microscopy

This paper describes a magnetically suspended six degree-of-freedom precision motion control stage with a horizontal positioning noise of less than 0.6 nm three sigma. The vertical positioning noise is less than 2.2 nm three sigma. The stage utilizes four levitation linear motors to suspend and servo the moving element (platen) throughout its 25 mm × 25 mm × 0.1 mm range of travel. Position feedback is provided by three plane mirror interferometers and three capacitance probes. The suspended platen (12 kg mass) is floated in oil to enhance the stage’s disturbance rejection and to reduce power dissipation in the actuators. The stage has been designed to achieve a positioning accuracy of 10 nm and is used to position samples beneath a scanned probe microscope. The ultimate purpose of this measuring machine is to provide a means of measuring submicron-scale features with nanometer-scale accuracy. The technology can easily be scaled to larger travels, with accuracy limited primarily by the wavelength instability of the HeNe light source. This article gives an overview of the LORS project, emphasizing the system error terms, tolerancing, and experimental results.