MagScanner: A Magnetic Planar XY Stage for the Scanning Probe-Based Surface Profilometer

Abstract

Planar XY scanners are essential for scanning probe microscopes. To overcome limitations in current piezo-actuated scanners, a novel normal-stressed electromagnetic scanner named MagScanner is introduced to scan a chromatic confocal sensor probe and construct a non-contact scanning probe-based surface profilometer. The MagScanner has a monolithic armature to provide dual-axial decoupled driving forces and a set of dual-axial compliant bearings to guarantee the decoupled planar scans. To properly select the system parameters for satisfying the design target, analytical models and finite element simulations are combined for the electromagnetic and mechanical components of the MagScanner. The experiment test on the prototype shows a stroke of $ \pm 200~ \mu $ m and a natural frequency of around 220 Hz for each axis, and the mutual dynamic cross-talks are smaller than 36.34 dB. Furthermore, by adopting the internal model control principle, the prototype precisely follows the Lissajous scanning trajectory with a peak-to-valley tracking error of less than 0.37%. After calibrating the error motion-induced measurement errors, the single-shot sub-aperture measurement of a typical micro-structured surface is demonstrated to have a peak-to-valley form error within $ \pm ~60 $ nm, which is further verified by applying for the measurement of a large-area micro-structured surface. Note to Practitioners—This work was motivated by developing a probe-based surface profilometer for measuring micro-structured surfaces. Although a large scanning area with high frequency was essential to achieve efficient surface scanning, it was challenging for conventional piezoelectric scanners owing to the inherently limited strain rate of piezoelectric ceramics. Hence, we developed a novel planar XY scanner based on normal-stressed electromagnetic actuation, which is promising for implementing dual-axial direct-drive scanning in hundreds of micrometers with an outperforming natural frequency.