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STRUCTURE AND METHOD FOR DETERMINING AN OVERLAY ACCURACY

  • US 20090087756A1
  • Filed: 04/11/2008
  • Published: 04/02/2009
  • Est. Priority Date: 09/29/2007
  • Status: Active Grant
First Claim
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1. An overlay target assembly adapted for use in determining an alignment accuracy of a first layer and a second layer of a multi-layered device, said assembly comprising:

  • at least two targets, each target having a first sub-structure of said first layer and a second sub-structure of said second layer;

    wherein, when said first layer and said second layer are correctly aligned;

    said first sub-structure and said second sub-structure of at least one of said targets are offset with respect to each other by a programmed offset; and

    said overlay target assembly is invariant to at least one transformation selected from rotation about a predetermined angle and reflection.

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