Method and apparatus for embedded encoding of overlay data ordering in an in-situ interferometer
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.
1. A method of embedded encoding of overlay data ordering, the method comprising:
exposing a reticle pattern in a first position onto a substrate with a recording media, the reticle comprising a plurality of separate and distinguishable alignment attributes, wherein a desired number of the alignment attributes at desired locations are shifted with non-coupling offsets;
measuring the exposed reticle pattern;
determining non-coupled portion of the overlay data and reticle error; and
correlating known overlay data with known non-coupling offsets to determine a statistical integrity.
2. A method as defined in claim 1 , further comprising determining if the statistical integrity is above a threshold.
3. A method as defined in claim 1 , wherein the non-coupled offsets are derived from shifts representing pupil decentering.
4. A method as defined in claim 1 , wherein the non-coupled offsets are derived from shifts representing telecentricity.
5. A method as defined in claim 1 , wherein the non-coupled offsets comprise one or more vortices.
6. A method as defined in claim 1 , further comprising reconstructing a wavefront.
7. A method as defined in claim 1 , further comprising reconstruction of a wafer-side telecentricity.