Sunday, January 15, 2017

Claims to old Semiconductor Metrology and Defect Inspection Algorithms

Just for the record, Nanometrics bought Soluris, bought IVS where I developed the 'ripple' algorithm - for finding and measuring sub "peaks" in an optical signal. I also did the contact ("via") measurement algorithms. Tony Saporetti was one of three founders of IVS and did the initial metrology algorithms using WWII radar algorithms - based on the mean of a Gaussian to measure the location of a "peak" in a signal. He also was an original specifier of "frame grabber" electronics and the start of modern digital imaging - a real smart engineer. Insiders at Nanometrics will know that optical metrology depends on this use of the Gaussian mean. Tony also did the auto focus algorithm and for years the people at Cognex (every time I made the mistake of interviewing there) tried to pry the concept from me [guys: look up the "triangle inequality"]. But I figured out how to latch onto sub peaks in an optical signal and how to measure between inflection points and that is a key technology also.

Just for the record, KLA's bin defect pattern recognition uses the corpse of an algorithm I developed for a failed startup called "Applied Geometry Inc". The algorithm is the application of chi-squared to point scatters in a gridded field of view, where you count events in a grid cell and compare the distribution to what it would be if there was no spatial pattern to the events. A good basic algorithm for measuring goodness of fit between a pattern (usually an outline in 2D) and a scatter. I filed a patent but it got rejected for the strangest reason - the reviewer took issue with my using the word "dotted" to describe a line in a diagram. The patent application must be on file.

These algorithms still exist and are in use, although the companies got bought by larger and larger parents.

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