Reduced target dimensions requiring improved resolution and sensitivity have driven the need to use and analyze the phase and scattered frequency information available when using image-based scatterometry systems. One such system is scatterfield microscopy, which provides high magnification imaging, spatial selectivity, and a capability to capture all phase and frequency information within the collection numerical aperture. It has been shown that sensitivity to nanometer scale changes can be observed when measuring critical dimensions of sub-wavelength dense arrays that scatter only the 0th-order specular diffraction component by engineering the microscope illumination to yield angle-resolved measurements . Acceptable quantitative statistical analysis with rigorous agreement between experiment and theory has represented an important advance in image-based optical metrology to realize sub-nanometer scale uncertainty measurement for these 0th-order targets . However, many interesting features are either non-repetitive, irregular, or have pitches greater than the wavelength of light leading to scattering of multiple (or even a continuum of) frequency components. Of particular interest are the edges of a finite scatterometry target, whose optical response is a combination of its nearby substrate and the dense specular or high-order optical response from the linearly arrayed region. Here we present our new approach that enables rigorous analysis of 3-D through-focus and angle-resolved optical images that samples the three-dimensional electromagnetic field above and into finite targets of interest that scatter a continuum of scattered frequency contents. This technique involves parametric fitting of the three-dimensional scattered field with rigorous electromagnetic simulation, experimental Fourier domain normalization procedures, and statistical methods to evaluate sensitivities and uncertainties.
Conference Dates: March 25-28, 2013
Conference Location: Gaithersburg, MD
Conference Title: 2013 International Conference on Frontiers of Characterization and Metrology for Nanoelectronics
Pub Type: Conferences
OCD metrology, phase sensitive measurement, transmission tool function, Fourier domain normalization, parametric fitting and uncertainty analysis