Theoretical study and computer simulations of submicron linewidth measurement using optical phase-shifting interferometry

Yiping Xu

doi:10.1117/12.149009

4 August 1993 Theoretical study and computer simulations of submicron linewidth measurement using optical phase-shifting interferometry

Yiping Xu

Author Affiliations +

Proceedings Volume 1926, Integrated Circuit Metrology, Inspection, and Process Control VII; (1993) https://doi.org/10.1117/12.149009
Event: SPIE'S 1993 Symposium on Microlithography, 1993, San Jose, CA, United States

Abstract

A new approach to measuring submicron linewidths using optical phase-shifting interferometry is proposed. The technique has two main features. First, the surface topography is measured directly by determining phase information from the wavefront reflected from the surface of the object. Theoretical analysis indicates that the phase image of a line feature gives better lateral resolution than that of the intensity image of the same optical system. By comparing the intensity images and phase images from the computer simulations, it will be shown that the phase image (1) is affected less by the diffraction limitation; (2) has sharper edge definition; and (3) is insensitive to the variations of material composition and step height of the object. Second, the surface reflectivity can also be measured using phase-shifting interferometry. Unlike the intensity image measured by conventional methods, the measured reflectivity is not affected by any variations associated with the light source across the entire illumination field. The relative reflectivity between the line feature and the substrate is then determined. These advantages will result in better resolution and accuracy in measuring submicron linewidths. Theory and simulations predict that accurate measurements of 0.2 micrometers linewidths should be possible.

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Yiping Xu "Theoretical study and computer simulations of submicron linewidth measurement using optical phase-shifting interferometry", Proc. SPIE 1926, Integrated Circuit Metrology, Inspection, and Process Control VII, (4 August 1993); https://doi.org/10.1117/12.149009

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KEYWORDS

Reflectivity

Phase interferometry

Wavefronts

Phase shifts

Diffraction

Phase measurement

Computer simulations

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