MONORAIL SEMICONDUCTOR WAFER CASSETTE TRANSPORT SYSTEM

摘要

This invention relates to semiconductor wafer processing systems and more particularly relates to a system for efficiently and automatically transporting semiconductor wafer cassettes throughout a processing plant. The system is comprised of a monorail (12) and a train (10) formed of a plurality of cars (14) riding on the monorail (12). The train (10) is driven by a plurality of stepper motors (20) equally spaced at distances along the monorail (12) sufficient to keep the train (10) moving. Each drive system is comprised of a stepper motor (20) and four Thrombil wheels that provide very low particle generation. The stepper motor (20) operates on a low duty cycle because it only operates when needed which is when a train (10) is passing over the stepper motor (20) and drive wheels. At other times, the motor is off lenghthening the life of the system.