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System for microscopic inspection of articles    

System for detecting defects in a VLSI reticle by comparison to a reference.

Overview

A defect detection system for inspecting objects such as reticles, photomasks, semiconductor wafers, flat panel displays and other patterned objects has two or more stages, whereby the object is examined separately for fine defects, by inspecting a binary level representation of the object, and for ultra fine defects, by inspecting a gray level representation of the object. The system also includes re-inspection apparatus for re-inspection of detected defects, thereby to reduce the false alarm rate, and for classifying the remaining defects by size, area and type.

Summary of Technology

The technology seeks to provide an improved system for inspection of and detection of defects in objects such as reticles, photomasks, semiconductor wafers, flat panel displays and other patterned objects. Preferably, the system has two or more stages, whereby the object is examined separately for fine defects, preferably by inspecting a binary level representation of the object, and for ultra fine defects, preferably by inspecting a gray level representation of the object.

The two-stage inspection system has the advantage of allowing different algorithms to be used for fine defect detection and for ultra fine defect detection, each algorithm being generally optimal for defects of the size it is intended for but not necessarily for defects of other sizes. The system may make die to database comparisons or die to die comparisons.

The system also preferably includes reinspection apparatus for reinspection of detected defects, thereby to reduce the false alarm rate, and for classifying the remaining defects by size, area and type. Preferably the system also includes diagnostic apparatus for performing diagnostic functions such as inspecting the flow of information through the system and diagnosing which component of the system may be misoperating.

Patent Summary

U.S. Patent Classes & Classifications Covered in this listing:

Class 382: Image Analysis

This is the generic class for apparatus and corresponding methods for the automated analysis of an image or recognition of a pattern. Included herein are systems that transform an image for the purpose of (a) enhancing its visual quality prior to recognition, (b) locating and registering the image relative to a sensor or stored prototype, or reducing the amount of image data by discarding irrelevant data, and (c) measuring significant characteristics of the image.

Subclass 148: At plural magnifications or resolutions
Subclass 149: Fault or defect detection
Subclass 151: Alignment, registration, or position determination

Class 250: Radiant Energy

This class provides for all methods and apparatus for using, generating, controlling or detecting radiant energy, combinations including such methods or apparatus, subcombinations of same and accessories therefore not classifiable elsewhere.

Subclass 559.39: With comparison to reference or standard
Subclass 559.45: With defect discrimination circuitry