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WMSR (wafer map similarity ranking) can be used to retrieve wafer maps that are similar to a given queried wafer map. Because wafer maps with similar failure patterns tend to have identical failure causes, WMSR can assists engineers for identifying the root cause of similar failure patterns. In the similarity analysis, the WMSR can be done with the procedure below:
         i) Normalize the size of both the queried wafer map and all wafer maps in the dataset. The reason of this step is that the wafer maps vary in size.
         ii) Search the top-n similar wafer maps based on the Euclidean distance (see page4702) of the extracted features.
         iii) Rank the top-n candidates based on the 2D normalized correlation coefficient, e.g. template matching [1] in the field of image processing.

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[1] R. C. Gonzalez and R. E. Woods, Digital Image Processing, 3rd ed. Harlow, U.K.:Prentice-Hall, 2008.