NSF Award
9100075
Optical instruments for performing linewidth measurement or for finding the geometry of small features are limited by the resolution associated with the wavelength of light. Basic optical theory states that features smaller than one-half of the illumination wavelength are unresolvable. However, information is present in the image about higher spatial frequencies than given by the optical resolution. By measuring phase rather than intensity, 0.3 to 0.5 um features can be measured with an interferometric optical microscope. Information about higher spatial frequencies may be extracted by applying image processing techniques such as simulated annealing, linear and nonlinear least-squares estimation, and the Gerchberg algorithm. The aim of this research is to apply these techniques in an interferometric optical profiler to extend the range of submicron linewidth measurements down to 0.1 um. An applicable technique would be useful in a commercial product. Possible applications include the measurement of integrated circuit or integrated optical device geometries as well as measurement of pits in compact disk masters, and magnetic recording head geometry.
