Magnetically-Suspended Stage for Accurate Positioning of Large Samples in Scanned Probe Microscopy

This paper describes a magnetically-suspended six-degree-of-freedom precision motion control stage which was built in the Precision Engineering Laboratory at the University of North Carolina at Charlotte (Holmes, 1998). This Long-Range Scanning (LORS) stage has travel in the horizontal plane of 25 mm by 25 mm with 100 //m of vertical travel. Vertical position feedback is provided by three capacitance probe sensors while heterodyne laser interferometry is used for lateral position feedback. The forces to suspend and servo the moving element are provided by four six-phase linear motors. The stage was designed to have a positioning resolution of 0.1 nm, positioning repeatability of 1 nm, and a positioning accuracy of 10 nm. These performance objectives were chosen to match the measurement requirements associated with present and future production needs for devices such as integrated circuits, photo-masks, and micromechanical actuators. The LORS stage is used to position samples beneath a scanning-tunneling microscope (STM). The STM will ultimately be used to characterize the performance of the LORS stage. This paper presents a summary of the final design along with some initial performance characterization data.