Optics: measuring and testing – Dimension – Thickness
Reexamination Certificate
2006-06-19
2008-10-07
Chowdhury, Tarifur R (Department: 2886)
Optics: measuring and testing
Dimension
Thickness
Reexamination Certificate
active
07433060
ABSTRACT:
A method for correlating a structural parameter of a plurality of gratings acquires images from a plurality of gratings, which have different structural parameters. A focus metrics algorithm is then performed to find the off-focus offset of the orders of each grating from the intensity variation of these images, and the variation ratio of the off-focus offset to the order for each grating is calculated later. Consequently, the structural parameters of these gratings can be correlated based on the variation ratio of the off-focus offset to the order. The present method acquires images from an unknown grating at different off-focus offsets, and performs a focus metrics algorithm to find the off-focus offset of the orders of the unknown grating. The variation ratio is calculated and the structural parameter of the unknown grating is determined based on the variation ratio.
REFERENCES:
Ravikiran Attota, Application of through-focus focus-metric analysis in high resolution optical metrology, Jun. 21, 2005, SPIE, vol. 5752, pp. 1441-1449.
Ku Yi Sha
Liu An Shun
Accent Optical Technologies, Inc.
Chowdhury Tarifur R
Industrial Technology Research Institute
Lapage Michael
Volentine & Whitt PLLC
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