Inventors:
Robert M. Spencer - San Juan Capistrano CA
Christopher O. Lada - Palo Alto CA
Assignee:
Lam Research - Fremont CA
International Classification:
G01B 731
Abstract:
A system for locating and positioning wafers includes a wafer shuttle, a spindle, and a position sensor. The wafer shuttle retrieves wafers from a storage location, typically a wafer cassette, and transports the wafers to the spindle. The wafers are then incrementally rotated on the spindle, and the distance between the center of rotation and the periphery of the wafer along a linear path is measured. By using three such measurements, the distance and angle with which the center of the wafer is offset from the center of rotation may be calculated. The wafer can then be centered on the spindle by rotation and translated a proper distance by the wafer shuttle. Usually, the wafers will be further rotationally oriented so that the crystal lattice lies in a desired direction.