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Apparatus for determining an overlay error and critical dimensions in a semiconductor structure by means of scatterometry

  • US 6,816,252 B2
  • Filed: 04/29/2002
  • Issued: 11/09/2004
  • Est. Priority Date: 08/30/2001
  • Status: Expired due to Fees
First Claim
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1. An apparatus for obtaining information on critical dimensions and overlay accuracy of features formed in a semiconductor structure, wherein the semiconductor structure includes a first diffracting pattern oriented with respect to a first direction and a second diffracting pattern oriented with respect to a second direction, the apparatus comprising:

  • a light source for emitting at least one light beam;

    a first plurality of deflecting elements defining a first optical path in a first plane of incidence corresponding to the first direction, and a second plurality of deflecting elements defining a second optical path in a second plane of incidence corresponding to the second direction;

    a detector optically connectable to the first and second optical paths to receive a light beam diffracted by the first and the second diffracting patterns, respectively; and

    a first partially reflecting mirror directing a first portion of an incident light beam into the first optical path and directing a second portion of the incident light beam into the second optical path, wherein a common transmittance of the first partially reflecting mirror and of a transmissive element arranged in the second optical path is substantially equal to a reflectivity of the first partially reflecting mirror.

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