Optics: measuring and testing – By alignment in lateral direction – With registration indicia
Reexamination Certificate
2011-08-23
2011-08-23
Pham, Hoa Q (Department: 2886)
Optics: measuring and testing
By alignment in lateral direction
With registration indicia
Reexamination Certificate
active
08004679
ABSTRACT:
Disclosed are methods and apparatus for determining overlay error. Radiation that is scattered from each of a plurality of cells of a target is measured. Each cell includes at least a first grating structure formed by a first process and a second grating structure formed by a second process and wherein each cell has a predefined offset between such each cell's first and second grating structures. The first and second grating structures of the different cells have different predefined offsets, and each predefined offset of each cell is selected to cause one or more terms to be cancelled from a periodic function that represents radiation scattered and measured from each cell. The scattered radiation of each cell is represented with a periodic function having a plurality of unknowns parameters, including an unknown overlay error, and the unknown overlay error is determined based on the plurality of periodic functions for the plurality of cells.
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Kandel Daniel
Levinski Vladimir
Kla-Tencor Corporation
Pham Hoa Q
Weaver Austin Villeneuve & Sampson LLP
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