Dimensional metrology of stage motions for precision nanomanufacturing: Multi-axis grating encoders

摘要

This paper describes multi-axis grating encoders used in dimensional metrology of stage motions for precision nanomanufacturing. Instead of plane mirrors in the conventional Michelson laser interferometer for measurement of the Z-directional displacement, grating mirrors are employed in the proposed multi-axis surface encoders. One of the grating mirrors is utilized as the scale of the surface encoder. The other grating mirror is included in the sensor head. The ±1 order diffracted beams from the two grating mirrors are superimposed to generate interference signals, which have information about the not only Z-directional out-of-plane displacement but also X or Y-directional in-plane displacement. The multi-axis displacements can be calculated from the outputs of the interference signals simultaneously. A two-axis linear encoder for X-and Z-directional measurement and a three-axis surface encoder for X-, Y-and Z-directional measurement are presented.