Extended Range Six-DOF High-Precision Positioner for Wafer Processing
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A high-precision positioner using a novel superimposed concentrated field permanent magnet matrix is presented in this paper. It can generate all six-degrees-of-freedom (DOF) motions with only a single moving part. This extended range multi axis positioner is actuated by three planar levitation motors, which are attached on the bottom of the moving part. Three aerostatic bearings are currently used to provide the suspension force for the system against gravity. We designed and implemented digital head-lag controllers running on a digital signal processor (DSP). To improve the closed-loop dynamic performance in the vertical directions, we implemented a controller in the minor feedback loop as well. The positioner demonstrates a position resolution of 20 nm and a position noise of 10-nm root mean square (rms) in x and y and 15-nm rms in z. The angular resolution around the x-, y-, and z-axes is of submicroradian order. The planar travel range is 160 mm × 160 mm, and the maximum velocity achieved is 0.5 m/s at the 5- m/s2 acceleration, which can enhance the throughput in wafer processing. Several two-dimensional motion profiles are presented to demonstrate the positioner's capability of accurately tracking any extended range planar trajectories. The experimental results verified the utility of this extended range six-DOF high-precision positioner in semiconductor manufacturing and factory automation. © 2006 IEEE.
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