Patent ID: 6091846
Filing Date: 2000-07-18
Classification: G01N,G06T,H01L

Abstract:
A system for detecting anomalies on a semiconductor wafer, the system comprising:a moveable stage for holding and positioning the semiconductor wafer;a camera for capturing an image of the semiconductor wafer;a digitizer coupled to the camera for producing a digital-pixel-based representation of the image;a computer having a processor and memory, the computer coupled to the digitizer for receiving the digital-pixel-based representation from the digitizer and coupled to the stage for selectively moving the stage to align the wafer; andthe computer is programmed to be operable to:symbolically decompose the digital-pixel-based representation of an image to create a primitive-based representation of the image,the computer further operable to develop a histogram of angles and lengths of geometric objects within the image and compare the histogram to a reference histogram of a reference image to determine rotational shift of the image.