Open AccessThrough-focus technique for nano-scale grating pitch and linewidth analysis
Author(s) -
Yi-Sha Ku,
An-Shun Liu,
Nigel Smith
Publication year - 2005
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/opex.13.006699
Subject(s) - optics , focus (optics) , grating , laser linewidth , wavelength , feature (linguistics) , depth of focus (tectonics) , autofocus , materials science , diffraction grating , computer science , physics , laser , paleontology , philosophy , linguistics , subduction , biology , tectonics
We report results of experimental investigations into a through-focus method relevant to sub-wavelength feature dimension measurement. The method linearizes the partial derivative values of a focus indicator with respect to minimum intensity order, and hence permits determination of pitch using a classical linear method. By evaluating the variations in focus indicator of the different captured images obtained at various focal positions, the through-focus curves show a response to sub-resolution changes in the grating structure. The results suggest that sub-wavelength feature dimensions can be evaluated using regular optical microscopes by implementing the through focus method.