Dark-field optical scatterometry for line-width-roughness metrology

G. Vera Zhuang; Steven Spielman; John Fielden; Daniel C Wack; Leonid Poslavsky; Benjamin D. Bunday

doi:10.1117/12.813007

23 March 2009 Dark-field optical scatterometry for line-width-roughness metrology

G. Vera Zhuang, Steven Spielman, John Fielden, Daniel C Wack, Leonid Poslavsky, Benjamin D. Bunday

Proceedings Volume 7272, Metrology, Inspection, and Process Control for Microlithography XXIII; 72720L (2009) https://doi.org/10.1117/12.813007
Event: SPIE Advanced Lithography, 2009, San Jose, California, United States

Abstract

As CMOS transistor critical dimensions (CDs) shrink to 35 nm and below, monitoring and control of line width roughness (LWR) and line edge roughness (LER) will become increasingly important. We used dark-field twodimensional beam profile reflectometry at 405 nm wavelength with a 0.9 numerical aperture (NA) objective to measure the low levels of diffuse scattered light from the roughness on the surfaces of lines in test structures on a wafer created by ISMI. This wafer contains a variety of amorphous etched gate test structures with a range of CDs from approximately 20 nm to 50 nm. Selected structures were thoroughly characterized for CD, LER and LWR by a critical-dimension scanning electron microscope (CD-SEM). The integrated diffuse scattered intensities obtained from structures with different CD and LWR values were compared to LWR as measured by the CD-SEM. The diffuse scattered optical signal intensity showed, at best, a weak correlation to the CD-SEM measured LWR. However a plot of the diffuse scattered intensity versus CD-SEM measured CD showed a strong, but nonlinear, correlation. This indicates that the scattering depends not only on the surface roughness but also on the CD of the line (and presumably other details of the profile).

Citation Download Citation

G. Vera Zhuang, Steven Spielman, John Fielden, Daniel C Wack, Leonid Poslavsky, and Benjamin D. Bunday "Dark-field optical scatterometry for line-width-roughness metrology", Proc. SPIE 7272, Metrology, Inspection, and Process Control for Microlithography XXIII, 72720L (23 March 2009); https://doi.org/10.1117/12.813007

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