Vacuum Compatible Two d.o.f. Wafer Handling Robot by Electro-magnetic Suspension System.

Abstract

From the viewpoint of freedom from contamination, wafer handling systems with contactless mechanisms are required in the production of VLSI. Authors have developed a clean and vacuum-compatible wafer handling robot using an electro-magnetic suspension system. This two d. o. f. (degree of freedom) wafer handring robot can be applied to a wafer-hoist, a turn-table and a swing-arm in an ultra-high vacuum. The robot controller is fully digitalized by multi-DSP system. And the following advanced control methods are implemennted: 1) Electro-magnetic suspension control by decoupling control scheme. 2) Precise positioning by sliding mode control. The decoupling control enables to hold the position of the rotational axis precisely, regardless influence of the arm position. The sliding mode control using the coarse signal (72 pulse/rev. ) of position sensor significantly improves the overshoot at the rotational positioning. These control schemes are introduced and experimental results are shown in this paper.