Measurement of discontinuous surfaces using multiple-wavelength interferometry

Paul Kumar Upputuri; Nandigana Krishna Mohan Sr.; Mahendra Prasad Kothiyal Sr.

doi:10.1117/1.3159867

1 July 2009 Measurement of discontinuous surfaces using multiple-wavelength interferometry

Paul Kumar Upputuri, Nandigana Krishna Mohan Sr., Mahendra Prasad Kothiyal Sr.

Author Affiliations +

Optical Engineering, Vol. 48, Issue 7, 073603 (July 2009). https://doi.org/10.1117/1.3159867

Abstract

Interferometric surface profilers using a single wavelength offer excellent vertical resolution, but have an ambiguity-free range of less than half a wavelength. Multiple-wavelength or white light interference techniques are used to overcome the problem. We discuss a three-wavelength interferometric technique used with a phase-shifting phase evaluation procedure. The phase evaluation at the three wavelengths gives wrapped phase at any pixel corresponding to these wavelengths. We use the fact that the variation of phase with wavenumber for a given profile height is linear to determine the absolute value of the profile height. The height is then used to ascertain the fringe order. The fringe order, along with the wrapped phase, gives the profile height with a resolution given by the phase-shifting technique. Experimental results for large step height measurement on etched silicon samples are presented.

©(2009) Society of Photo-Optical Instrumentation Engineers (SPIE)

Citation Download Citation

Paul Kumar Upputuri, Nandigana Krishna Mohan Sr., and Mahendra Prasad Kothiyal Sr. "Measurement of discontinuous surfaces using multiple-wavelength interferometry," Optical Engineering 48(7), 073603 (1 July 2009). https://doi.org/10.1117/1.3159867

Published: 1 July 2009

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