In high numerical aperture (NA) subsurface imaging, we can obtain higher resolution in selected directions at the expense of resolutions in other directions, utilizing the vectorial properties of polarized light. In this work, we propose an image fusion framework that produces a single image with higher resolution and image quality in all directions by processing multiple images acquired by varying the polarization direction of the linearly polarized input laser light.

Sparse image reconstruction techniques have been used to recover high frequency information lost during the acquisition process in different imaging domains, such as ultrasound, synthetic aperture radar, optical microscopy, and astronomical and microscopic imaging. In this work, a signal processing framework is proposed to estimate the Point Spread Function (PSF) of the dark-field subsurface microscopy system from observation data. This PSF is incorporated into an image reconstruction framework, which can be formulated with two different image reconstruction techniques, regularized image reconstruction and dictionary-based image reconstruction. It is observed that both techniques provide at least 12% resolution improvement; lines with 224 nm spacing were localized after resolution improvement while lines with 252 nm spacing are at the limit of localization in experimental data. However, dictionary-based image reconstruction provides higher edge resolution and maintains the homogeneity of the intensity within the structures.

The demand for high resolution has raised interest for the use of aplanatic solid immersion lenses (aSIL) for backside optical inspection and failure analysis of integrated circuits due to its high numerical aperture capability. This work investigates the performance of aSIL microscopy in imaging of fully depleted silicon on insulator (SOI) chips and explores the effect of the buried oxide (BOx) thickness on the spatial resolution and photon collection efficiency. Three different cases, namely, bulk silicon, SOI with an ultrathin BOx of 10 nm, and SOI with a standard BOx thickness of 145 nm, are studied. It is observed that there is a 15% drop in the collection efficiency for ultra-thin BOx compared to bulk silicon and up to 80% decrease in the collection efficiency and 30% increase in the spot-size for standard Box.

As feature sizes in integrated circuits (ICs) become smaller, higher-resolution defect detection and failure analysis techniques are required. The introduction of solid immersion lenses (SIL) has been an enabling technology for highresolution backside IC imaging. High Numerical Aperture (NA) SIL imaging introduces properties of focused light which cannot be predicted by scalar beam optics. For example, spatial resolution can be manipulated in selected directions by modification of the polarization direction in linearly polarized light. In this work, we propose a unified framework combining multiple SIL microscopy images collected using polarizations at different directions in order to improve image reconstruction performance and ultimately resolution and defect localization. We show improvement in reconstruction quality by combining data taken using light with multiple polarizations. We demonstrate the effectiveness of our framework on experimental data.