Method and apparatus for aligning the loading/unloading of a wafer cassette to/from a loadport by an overhead hoist transport system

摘要

An apparatus and a method for aligning the loading/unloading of a wafer cassette to/from a loadport by an overhead hoist transport system are described. The apparatus utilizes a loadport that is equipped with at least two spaced-apart laser beam projectors mounted on a top surface of the loadport for projecting laser beams into a CCD array mounted on the bottom surface of the OHT rail facing the loadport. The actual position of the loadport can thus be continuously monitored and determined, and any necessary adjustment in positions of the OHT delivery arm for the wafer cassette can be made. A process controller is further provided for receiving the signal from the CCD array, or any other energy receiving means and for comparing to pre-stored data for sending a control signal to the OHT delivery arm.