Design and control of a magnetically levitated six degrees-of-freedom planar motor using t-shape halbach magnet array

Abstract

The smaller, the faster, the cheaper. These are the fundamental goals of the next-generation semiconductor industry. Magnetically levitated planar motors are the only solution to meet these requirements. It can move in six-degrees-of freedom over long range with nano positioning accuracy in vacuum environment. To achieve these goals, we propose, design and control a new type of magnetically levitated planar motor. The proposed planar motor consists of moving magnet array(mover) and multiple coil arrays(stator). The key feature of the the planar motor is to use newly developed T-shape Halbach magnet array. The T-shape Halbach magnet array has several advantages such as higher force, lower force ripple and cost effectiveness compared with previously developed planar motors. These characteristics are very important features to meet the fundamental goals for the next-generation lighography system. High force capability enables fast movement with high control bandwidth, and therefore improves positionig accuracy and product throughput. Low force ripple reduces disturbances, and therefore improves sanning performance. Cost effectiveness, caused by easy-assembly, enables modular manufacturing process of the planar motor. These key featues enable applying the proposed planar motor to the wafer stage of the next-generation lithography system. We present design optimization frameworks in order to maximze force density and minimize force ripple. At first, analytic modeling method based on the Maxwell equation is presented in order to calculate magnetic flux distribution and generated forces. This method predicts six degrees-of-freedom motion of the planar motor at arbitrary position. Secondly, parametric analysis is performed in order to investigate the effect of the design variables on the performances. We can know the correlations between design variables and the performance of the planar motor. Finally, we perform design optimization process in order to find optima...