Alignment target with designed in offset

  • US 7,230,705 B1
  • Filed: 03/07/2005
  • Issued: 06/12/2007
  • Est. Priority Date: 04/04/2002
  • Status: Expired due to Fees
First Claim
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1. An alignment target for determining the alignment between a first element and a second element, said alignment target comprising:

  • a first location comprising;

    a first periodic pattern on said first element;

    a second periodic pattern on said second element;

    wherein said first periodic pattern and said second periodic pattern have the same pitch and said second periodic pattern has a designed in offset of a first magnitude in a first direction with said first periodic pattern such that when said first element and said second element are properly aligned said first periodic pattern and said second periodic pattern overlap and will be offset by said first magnitude in said first direction;

    a second location comprising;

    a third periodic pattern on said first element;

    a fourth periodic pattern on said second element;

    wherein said third periodic pattern and said fourth periodic pattern have the same pitch and said fourth periodic pattern has a designed in offset of a second magnitude in a second direction with said third periodic pattern such that when said third element and said fourth element are properly aligned said third periodic pattern and said fourth periodic pattern overlap and will be offset by said second magnitude in said second direction; and

    a third location comprising;

    a fifth periodic pattern on said first element; and

    a sixth periodic pattern on said second element;

    wherein said fifth periodic pattern and said sixth periodic pattern have the same pitch and said sixth periodic pattern has a designed in offset with a third magnitude in a third direction with said fifth periodic pattern such that when said first element and said second element are properly aligned said fifth periodic pattern and said sixth periodic pattern overlap and will be offset by said third magnitude in a third direction;

    wherein said first periodic pattern and said third periodic pattern have a pitch and said first magnitude and said second magnitude are approximately 25% of said pitch; and

    wherein said third magnitude is equal to said first magnitude plus the magnitude of a reference offset, wherein said magnitude of said reference offset is between approximately 1% to 10% of the pitch of said fifth periodic pattern, and wherein said third direction is equal to said first direction.

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