Method and apparatus for embedded encoding of overlay data ordering in an in-situ interferometer

Abstract

A method and apparatus for embedded encoding of overlay data ordering in an in-situ interferometer is described. An in-situ interferometer is encoded, or augmented, with special or missing alignment attributes at desired positions. Exposing a sequence of the encoded in-situ interferometer onto a silicon wafer coated with a suitable recording media. Then measuring the alignment attributes. The encoded overlay data is processed to verify the proper order and physical location of each overlay measurement. The data is collected without increasing the overall number of required overlay measurements required. Collection of overlay data allows for the proper reconstruction of the aberrated wavefront. Non-coupling alignment attribute offsets can also be used to perform similar operations using singular value decomposition and null space operations.

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