Patent for License:Adaptive mask technique for defect inspection
A two-dimensional scatter plot is created by plotting the gray levels of pixels from a test image against the gray levels of corresponding pixels from a reference image. A noise reduction filter is applied on the scatter plot to define a mask shape which can be extracted and filled-in to generate a mask. Defect pixels on the test image are identified by comparing corresponding pixel gray values against the mask. A typical application is detecting defects in a semiconductor wafer during device fabrication.
U.S. Patent Classes & Classifications Covered in this Patent:
Class 382: Image AnalysisThis 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 144: Mask inspection (e.g., semiconductor photomask)
Subclass 149: Fault or defect detection
Subclass 151: Alignment, registration, or position determination
Subclass 168: HISTOGRAM PROCESSING
Subclass 203: Shape and form analysis
Subclass 260: Image filter
Class 257: Active Solid-State Devices (E.G., Transistors, Solid-State Diodes)This class provides for active solid-state electronic devices, that is, electronic devices or components that are made up primarily of solid materials, usually semiconductors, which operate by the movement of charge carriers - electrons or holes - which undergo energy level changes within the material and can modify an input voltage to achieve rectification, amplification, or switching action, and are not classified elsewhere.
Subclass E21.53: For structural parameters, e.g., thickness, line width, refractive index, temperature, warp, bond strength, defects, optical inspection, electrical measurement of structural dimensions, metallurgic measurement of diffusions (EPO)