Kla Corporation

Chaohong Wu

Yong Zhang

Songyang Yu

Premchandra M Shankar

Methods and systems for image alignment are provided. One method includes selecting three or more salient feature points for use in test image to reference image alignment by applying a selected salient feature point detection method to at least a reference image generated for the specimen. The method also includes detecting the three or more salient feature points in the test image and the reference image and aligning the detected three or more salient feature points in the test image to the detected three or more salient feature points in the reference image. The method further includes aligning remaining portions of the test image to remaining portions of the reference image based on results of the previous aligning step.

Salient feature point based image alignment

An inspection system is disclosed. The system includes a controller communicatively couplable with an inspection sub-system configured to receive illumination from a sample and generate image data. The controller includes one or more processors configured to execute program instructions causing the one or more processors to receive the image data, wherein the image data comprises at least one image, downsample the at least one image using bicubic interpolation or bilinear interpolation, transform the at least one image from a spatial domain to a frequency domain using a Fourier transform, filter frequencies higher than a threshold frequency from the at least one image, transform the at least one image from the frequency domain to the spatial domain using an inverse Fourier transform, and detect one or more flat-pattern defects in the at least one image.

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Fremont, CA, United States of America

Chaohong Wu