Kla Instruments Corporation

Russell M Singleton

Paul Sandland

Curt H Chadwick

Kenneth Levy

Howard I Dwyer

Michael L Hodgson

Gerald R Cutler

A system for automatic micro and macro inspection of patterned wafers, including a X-Y stage for supporting and positioning a wafer at a macro inspection station and a micro inspection station, a plurality of cassettes for storing a plurality of patterned wafers before and after inspection, a transfer arm and apparatus for transferring a wafer from the cassettes to a predetermined location on the X-Y stage, apparatus for centering the wafer on the macro inspection station, apparatus for aligning the wafer to obtain a preselected orientation for macro inspection, an optical system for effecting macro inspection of the wafer and storing a unique image thereof, apparatus for moving the wafer from the macro inspection station to the micro inspection station so that the area of the wafer corresponding to the stored unique image is in a micro optical path, autofocus apparatus for automatically focusing the lowest magnification objective lens on the area of the wafer to derive a real time image, a comparitor for comparing the stored unique image to the real time image, apparatus responsive to the comparison of the stored unique image and the real time image and operative to more precisely position the wafer in the micro optical path, apparatus for using areas of the wafer displaced one from the other to obtain more precise alignment of the wafer, apparatus for performing a pre-established micro inspection of selected areas of the wafer and apparatus for returning the wafer to a storage cassette.

Electronic control of an automatic wafer inspection system

An automatic semiconductor wafer inspection system including a wafer inspector, a system computer that performs movement and function control and data storage functions and a high speed image computer. Patterned wafers selected for inspection are automatically transported from cassette storage to a vacuum chuck located on the X-Y stage and positioned in a macro inspection station. The wafer is aligned and the surface illumination is changed to test for macro defects under different lighting conditions and levels of magnification. The reflected light is applied to a camera where the optical image is converted to an electrical representation thereof, stored, and then processed by the high speed image computer. After a wafer has been positioned and inspected in the macro inspection station at low magnification, it is moved by a macro-micro transport arm to the micro inspection station and a unique image previously found in the low power image is found again and used for initial alignment. An autofocus arrangment automatically focusses the objective lens to accomplish the micro inspection tests. Tests are typically carried out at a number of sites, each of which is positioned automatically by the machine.

Method and apparatus for automatic wafer inspection

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Sunnyvale, CA, United States of America

Russell M Singleton