Design of XY Air Bearing Stage for Ultra-Precision

Precision motion system is used in many industries including electronics, optics, and automotive. In silicon wafer lithography process, the resolution has gone up as high as 10 nm and still going higher. Hence, ultra-precision machines have emerged with nano-level accuracy to cater to this requirement. This paper proposes a novel ultra-precision motion stage design with long range motion. The proposed machine has H-type configuration, supported on air bearings. Ironless direct drive motor is applied for actuation with motion feedback by optical linear encoders. The workspace is 300 mm(2) with maximum velocity of 1 m/s and maximum acceleration of 10 m/s(2). Designed static stiffness of the machine is 398 N/mu m and 156 N/mu m in X and Y-axis, respectively. Dominant vibration mode is predicted at 46 Hz in vertical mode of the gantry. A PID control is implemented, allowing higher positioning performance. The maximum tracking error predicted in plane for low speed is 2 mu m.