Comparison of numerical aperture increasing lens and standard subsurface microscopy

Subsurface inspection of a Si integrated circuit (IC) by a Numerical Aperture Increasing Lens (NAIL) microscope has yielded a lateral spatial resolution of better than 0.23 /spl mu/m. We compare NAIL microscopy to standard subsurface microscopy using the Hamamatsu /spl mu/AMOS-200, IC Failure Analysis System. The NAIL improves the microscope's lateral spatial resolution from /spl sim/1.7 /spl mu/m to /spl sim/0.3 /spl mu/m. It is difficult to obtain the longitudinal spatial resolution because the sample has multiple longitudinal dielectric interfaces.