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Automated wafer defect inspection system and a process of performing such inspection

  • US 6,324,298 B1
  • Filed: 07/13/1999
  • Issued: 11/27/2001
  • Est. Priority Date: 07/15/1998
  • Status: Expired due to Term
First Claim
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1. An automated method of inspecting a semiconductor wafer in any form including whole patterned wafers, sawn wafers, broken wafers, and wafers of any kind on film frames, dies, die in gel paks, die in waffle paks, multi-chip modules often called MCMs, JEDEC trays, Auer boats, and other wafer and die package configurations for defects, the method comprising:

  • training a model as to parameters of a good wafer via optical viewing of multiple known good wafers, the training including aligning and viewing the multiple known good wafers, taking a gray scale measurement of each pixel in a grid of pixels on each of the multiple known good wafers, calculating the mean and standard deviation of all of the gray scale measurements for each pixel location on the multiple known good wafers, and then determining an upper and lower limit for each pixel location in between which a gray scale measurement on an equivalent pixel on an unknown quality wafer is deemed good while a gray scale measurement on an equivalent pixel on an unknown quality wafer outside of the upper and lower limits is deemed of at least questionable integrity and so noted, the upper limit being calculated as the maximum of one of the mean plus the product of the standard deviation multiplied by a first sensitivity, or the mean plus a first minimum contrast, and the lower limit being calculated as the minimum of one of the mean minus the product of the standard deviation multiplied by a second sensitivity, or the mean plus a second minimum contrast; and

    inspecting unknown quality wafers using the model, where such inspecting involves calculating the gray scale measurement for each pixel on the unknown quality wafer and comparing the gray scale measurement of each pixel with the upper and lower limit for that given pixel location to determine if the gray scale measurement for that pixel is between the upper and lower limits and thus deemed good or is outside of a range between the upper and lower limits and thus deemed of at least questionable integrity.

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