5 June 2001 High-resolution IC inspection technique
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Proceedings Volume 4275, Metrology-based Control for Micro-Manufacturing; (2001) https://doi.org/10.1117/12.429355
Event: Photonics West 2001 - LASE, 2001, San Jose, CA, United States
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.
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Stephen Bradley Ippolito, Stephen Bradley Ippolito, Anna K. Swan, Anna K. Swan, Bennett B. Goldberg, Bennett B. Goldberg, M. Selim Unlu, M. Selim Unlu, } "High-resolution IC inspection technique", Proc. SPIE 4275, Metrology-based Control for Micro-Manufacturing, (5 June 2001); doi: 10.1117/12.429355; https://doi.org/10.1117/12.429355
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