Automated wafer inspection system

摘要

A high precision automated wafer inspection station provides a base table area on which an X-Y stage is movable in mutually orthogonal directions relative to an inspection axis in alignment with a microscope or measuring instrument which is mounted on a bridge support above the table. The stage mechanism includes a wafer-supporting vacuum chuck having a top engagement surface for receiving and retaining the wafer, the chuck being rotatable about a central axis to provide angular positioning of the wafer, and focusable along the inspection axis. The wafer is moved on a dual probe mechanism in a horizontal plane from a first cassette controlled by an elevator at one side back to the first cassette, or to a second cassette controlled by an elevator at the opposite side of the table area. The probe is driven from side to side on a trolley coupled on a piston within a cylinder having a movable seal, and the cylinder itself is movable along an orthogonal axis for entry into and withdrawal from the various mechanisms. Small delta motions of the cassettes and of the vacuum chuck on the movable stage are used for secure but dust free movement of the wafer, and transfer between the different operative positions. The X-Y stage may be moved in extremely small increments of movement to position selected microareas within predetermined dies on a wafer at the inspection axis.