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Apparatus and methods for detecting overlay errors using scatterometry

  • US 20040233439A1
  • Filed: 02/23/2004
  • Published: 11/25/2004
  • Est. Priority Date: 02/22/2003
  • Status: Active Grant
First Claim
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1. A method of determining an overlay error between two layers of a multiple layer sample, the method comprising:

  • for each of a plurality of periodic targets target that each have a first structure formed from a first layer and a second structure formed from a second layer of the sample, measuring a plurality of optical signals at a plurality of incident angles, wherein there are predefined offsets between the first and second structures; and

    determining an overlay error between the first and second structures by analyzing the measured optical signals at the plurality of incident angles from the periodic targets using a scatterometry overlay technique based on the predefined offsets without using a calibration operation.

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