Kla Instruments Corporation

Computervision Corporation

Kla Instrument Corporation

Kenneth Levy

Paul Sandland

Mark Joseph Wihl

Gilbert G Fryklund

David Friedman

Steve Buchholz

William H Broadbent, Jr

Russell M Singleton

Gerd Schliemann

Vance Parker

Michael L Hodgson

Alan J Fleming

David Corbin

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

Apparatus 20 for inspecting photomasks 26 and the like by comparison of duplicate die patterns, including improved defect detection. Two-dimensional pixel representations of two die patterns are formed, with pixels having values or black or white or shades or grey, depending upon the features of the die patterns. Defects in the die patterns are found by a defect detector circuit 60 at points of non-agreement between the pixel representations. Two window matrices 130 and 134 of adjacent pixels are defined for corresponding areas of the two die patterns. The center matrix of each window matrix is defined as a comparison matrix 132 and 136. An error value is computed for subsets of the window matrix by summing the squares of the differences between each of the pixel values of each subset and the corresponding pixel values of the opposite comparison matrix. If there is no defect and any misalignment between the two representations minimal, at least one error value will be less than a threshold error value. If none of the error values are less than the threshold error value, a defect is assumed. The magnitude of the threshold error value is automatically varied according to the number and type of edges within the window matrices to compensate for edge quantization errors of less than one pixel.

Photomask inspection apparatus and method with improved defect detection

Optical inspection apparatus for detecting differences between two dies in a photomask and including a carriage for supporting the objects to be inspected and for simultaneously moving such objects along an inspection path, an illuminator for illuminating corresponding portions of the objects as they are moved along the inspection path, electro-optical detectors for individually inspecting the illuminated portions and for developing first and second electrical signals respectively corresponding thereto, electronic memories for storing the first and second electrical signals, a computer for scanning the memories and for electronically aligning a readout of the first signal relative to a readout of the second signal, and a comparator for comparing the electronically aligned signals and for indicating any differences therebetween.

Automatic photomask inspection system and apparatus

An automatic wafer loading and pre-alignment system for integrated circuit wafer-mask Aligners. A belt feed track system is employed to transport wafers from a 'send' wafer storage carrier to a wafer pre-alignment station. The wafer is machanically pre-aligned with respect to the wafer chuck of the Aligner by means of a roller arm and flat-finder system. After completion of the pre-alignment process, the Aligner turntable is rotated to carry the pre-aligned wafer and chuck to the home position of the turntable and at the same time position another chuck at the pre-alignment station. If the new chuck at the pre-alignment station contains a wafer, the wafer is transported from the chuck to a 'receive' wafer storage carrier by means of a belt return track system. The feed and return wafer belt track systems have a common portion between the pre-alignment station and the respective 'send' and 'receive' wafer storage carriers. Photosensors are used to detect the presence or absence of wafers at critical locations in the loading system and at the pre-alignment station.

Automatic wafer loading and pre-alignment system

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Saratoga, CA, United States of America

Kenneth Levy