Measuring overlay and profile asymmetry using symmetric and...

Optics: measuring and testing – By polarized light examination – Of surface reflection

Reexamination Certificate

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C250S559090

Reexamination Certificate

active

11325872

ABSTRACT:
Systems and methods are disclosed for using ellipsometer configurations to measure the partial Mueller matrix and the complete Jones matrix of a system that may be isotropic or anisotropic. In one embodiment two or more signals, which do not necessarily satisfy any symmetry assumptions individually, are combined into a composite signal which satisfies a symmetry assumption. The individual signals are collected at two or more analyzer angles. Symmetry properties of the composite signals allow easy extraction of overlay information for any relative orientation of the incident light beam with respect to a 1D grating target, as well as for targets comprising general 2D gratings. Signals of a certain symmetry property also allow measurement of profile asymmetry in a very efficient manner. In another embodiment a measurement methodology is defined to measure only signals which satisfy a symmetry assumption. An optional embodiment comprises a single polarization element serving as polarizer and analyzer. Another optional embodiment uses an analyzing prism to simultaneously collect two polarization components of reflected light.

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TDB, “Mask Overlay Determination” IBM Technical Disclosure Bulletin, Dec. 1978, pp. 272-2773. www.delphion.com.
TDB, “Phase-Sensitive Overlay Analysis Spectrometry,” IBM Technical Disclosure Bulletin, Mar. 1990. pp. 170-174 www.delphion.com.
TDB, Interferometric Method of Checking the Overlay Accuracy in Photolitho Graphic Exposure Processes.

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