High Resolution Backside Imaging and Thermography using a Numerical Aperature Increasing Lens
M.S. Ünlü, S.B. Ippolito, M.G. Eraslan, S.A. Thorne, A. Vamivakas, B.B. Goldberg and Y. Leblebici
Boston University, US
Keywords: thermal imaging, high-resolution, failure analysis, solid immersion lens
Nanoscale imaging of defects in ICs is a great current technological challenge as IC feature sizes continue to shrink. We have developed novel techniques based on a Numerical Aperture Increasing Lens (NAIL) to study semiconductors at very high spatial resolution. The NAIL is placed on the surface of a sample and its convex surface effectively transforms the NAIL and the planar sample into an integrated solid immersion lens. Addition of the NAIL to a standard microscope increases the NA by a factor of square of the index n, to a maximum of NA = n. In silicon, the NA is increased by a factor of 13, to NA = 3.6. The spatial resolution improvement laterally is about a factor of 4 while longitudinally it is a factor of 12.5 corresponding to an overall reduction of the volume of interrogation by a factor of 50. Subsurface solid immersion microscopy can be applied to thermal imaging of blackbody radiation at IR wavelengths. We have designed, built, and demonstrated the use of a subsurface solid immersion microscope with capability for confocal imaging in 3-5µm wavelength range and demonstrated a resolution of 1.4µm, representing the highest resolution subsurface thermography to date.
Nanotech 2004 Conference Technical Program Abstract