Profiles of a high-aspect-ratio grating determined by spectroscopic scatterometry and atomic-force microscopy.

The new and fast scatterometry method called optical diffraction microscopy is compared with atomic-force microscopy by use of cross-section scanning-electron microscope images as references. The sample is a high-aspect-ratio grating with a period of approximately 1000 nm. To allow the atomic-force microscope to track all parts of the grating profile, the grating is investigated at different tilt angles. The measured quantities of the profile include sidewall angle gamma (approximately 90 degrees), groove height h (approximately 2000 nm), and degree of filling f (approximately 40%). The two methods, which respond to quite different material properties, give consistent results within standard uncertainties of u(gamma)</=0.8 degrees , u(h)</=15 nm, and u(f)</=1%.

[1]  H. Kumar Wickramasinghe,et al.  Method for imaging sidewalls by atomic force microscopy , 1994 .

[2]  Lifeng Li,et al.  New formulation of the Fourier modal method for crossed surface-relief gratings , 1997 .

[3]  E. Glytsis,et al.  Two-dimensionally-periodic diffractive optical elements: limitations of scalar analysis. , 2002, Journal of the Optical Society of America. A, Optics, image science, and vision.

[4]  N. Otsu.  A threshold selection method from gray level histograms , 1979 .

[5]  Liam Blunt,et al.  Calibration of step heights and roughness measurements with atomic force microscopes , 2003 .

[6]  Lifeng Li,et al.  Fourier modal method for crossed anisotropic gratings with arbitrary permittivity and permeability tensors , 2003 .

[7]  Thomas K. Gaylord,et al.  Stable implementation of the rigorous coupled-wave analysis for surface-relief gratings: enhanced transmittance matrix approach , 1995 .

[8]  Hsu-ting Huang,et al.  Spectroscopic ellipsometry and reflectometry from gratings (Scatterometry) for critical dimension measurement and in situ, real-time process monitoring , 2004 .

[9]  J. Villarrubia.  Algorithms for Scanned Probe Microscope Image Simulation, Surface Reconstruction, and Tip Estimation , 1997, Journal of research of the National Institute of Standards and Technology.

[10]  M. Moharam,et al.  Limits of scalar diffraction theory for diffractive phase elements , 1994 .

[11]  Joseph H. Abeles,et al.  Direct measurement of nanoscale sidewall roughness of optical waveguides using an atomic force microscope , 2003 .

[12]  J. Schwider,et al.  Interferometric resolution examined by means of electromagnetic theory , 1995 .