Nanoscale Positioning of Air Bearing Guided Fine Motion Stage Driven by Pneumatic Bellows

Demand for ultra-precise positioning with nano-order is increasing, especially in the semiconductor industry, and fine movement stages driving piezoelectric elements are widely used. The authors proposed using pneumatic bellows instead of piezoelectric elements as actuators for this positioning and fabricated the elastic hinge-guided fine movement stage. The stage stroke was 200μm, several times longer than a general piezoelectric stage. The position resolution of less than 10nm was achieved by improving a control method, which is as precise as that of the stage driving piezoelectric elements. However, the stage oscillated continuously due to measurement noise of the stage position contained in the laser interferometer and fluid noise generated by the servo valve, resulting in significant variations in positioning. Also, the maximum stroke of the stage was determined by the elastic limit of the elastic hinge. In this study, an air bearing guided fine motion stage driven by pneumatic bellows was newly constructed and operated by a low flow noise servo valve that reduces flow noise using a slit type restrictor. Combined with the laser encoder being able to measure stage position with low noise, the positioning accuracy near the center of the stage was e±3σ=0.01±0.9nm, and positioning resolution was less than 1nm. The positioning accuracy of error, variation, and resolution was approximately ten times better than the positioning accuracy of the elastic hinge guide stage shown in the previous study. And the maximum stroke of the stage was ±1,250mm, close to the elastic limit of the bellows.