Linear Drive Systems and their Related Technologies. Development of Magnetically Suspended Linear Pulse Motor for Contactless Direct Drive in Vacuum Chamber Robot.

Abstract

In the semiconductor manufacturing industries, the demand for semiconductor wafer processes in an ultra-high vacuum chamber is increasing in connection with development of more highly integrated circuits. This may impose severer restrictions on wafer transfer robot with regard to contamination of the vacuum environment. In the severest case, a robot mechanism without use of lubricant, generation of dust particle and release of gases will be necessary. One of advantage methods for realizing such mechanism is to drive robot arm directly without mechanical contact by means of magnetic suspention techniques. For example, it is considered to employ a linear motor and magnetic bearings which are hermetically enclosed in a box-like casing.In this paper, a magnetically suspended linear pulse motor (LPM) is proposed as contactless direct drive mechanism of vacuum chamber robot. Here the major problem is a marked lowering of thrust caused by a broad air gap which must be arranged between stator teeth and mover ones in consideration of the wall thickness of the motor casing. So the LPM is designed to be composed of a pair of flat-type stators and a ladder-like robot arm corresponding to the floating mover so that it can be compensated for the resultant decrease of the ratio of thrust to mover mass. The validity of this approach is examined by the static thrust measurements for a tested LPM, and confirmed through the experiments on the robot arm transfer with a magnetic suspention system.