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Proceedings Paper

High-resolution IC inspection technique
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Paper Abstract

We demonstrate a through the substrate, numerical aperture increasing lens (NAIL) technique for high-resolution inspection of silicon devices. We experimentally demonstrate a resolution of 0.2 micrometers , with the ultimate diffraction limit of 0.14 micrometers . Absorption limits inspection in silicon to wavelengths greater than 1 micrometers , placing an ultimate limit of 0.5 micrometers resolution on standard subsurface microscopy techniques. Our numerical aperture increasing lens reduces this limit to 0.14 micrometers , a significant improvement for device visual inspection (patent pending). The NAIL technique yields a resolution improvement over standard optical microscopy of at least a factor of n, the refractive index of the substrate material, and up to a factor of n 2. In silicon, this constitutes a resolution improvement between 3.6 and 13. This is accomplished by increasing the numerical aperture of the imaging system, without introducing any spherical aberration to the collected light. A specialized lens made of the same material as the substrate is placed on the back surface of the substrate. The convex surface of this lens is spherical with a radius of curvature, R. The vertical thickness of the lens, D, should be selected according to D equals $ (1 + 1/n)-X and the substrate thickness X.

Paper Details

Date Published: 5 June 2001
PDF: 12 pages
Proc. SPIE 4275, Metrology-based Control for Micro-Manufacturing, (5 June 2001); doi: 10.1117/12.429355
Show Author Affiliations
Stephen Bradley Ippolito, Boston Univ. (United States)
Anna K. Swan, Boston Univ. (United States)
Bennett B. Goldberg, Boston Univ. (United States)
M. Selim Unlu, Boston Univ. (United States)

Published in SPIE Proceedings Vol. 4275:
Metrology-based Control for Micro-Manufacturing
Kenneth W. Tobin Jr.; Fred Lakhani, Editor(s)

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