Automated optical surface profile measurement system

Abstract

A fully automated surface profiling system having a loading chamber and an adjacent measurement chamber containing a phase differential laser optical scanning system and a five-axis positioner having a vacuum chuck for holding and orienting a wafer for surface profile measurement. The positioner can displace a mounted wafer lengthwise and crosswise of the chamber, can rotate the wafer about vertical and horizontal axes through the positioner, and can rotate the wafer about its own axis. Each motion is motor-driven and can be carried out independently of all the others or in compound motion as needed. The positioner can accommodate a series of replaceable chucks for holding wafers of different diameters. The loading chamber has a cassette dock for receiving a cassette containing wafers to be tested, a robotic server, and a prealigner. All operations within the profilometer are controlled by a programmable CPU at a control station. Test results and analysis can be displayed on an onboard monitor or printed out or stored or transmitted. In operation, the robotic server selects a wafer from the cassette, presents the wafer to the prealigner for centering and orientation, and transfers the wafer through a slot into the measurement chamber and installs the wafer on the positioner for measurement. The positioner orients the wafer responsive to program commands from the CPU, and the desired surface profile measurements are made. When all measurements have been completed on a wafer, the robotic server removes the wafer from the positioner, returns it to the cassette, and selects another wafer for testing.