F. H. Köklü

Widefield subsurface microscopy of integrated circuits

We apply the numerical aperture increasing lens technique to widefield subsurface imaging of silicon integrated circuits. We demonstrate lateral and longitudinal resolutions well beyond the limits of conventional backside imaging. With a simple infrared widefield microscope (lambda(0) = 1.2 microm), we demonstrate a lateral spatial resolution of 0.26 microm (0.22 lambda(0)) and a longitudinal resolution of 1.24 microm (1.03 lambda(0)) for backside imaging through the silicon substrate of an integrated circuit. We present a spatial resolution comparison between widefield and confocal microscopy, which are essential in integrated circuit analysis for emission and excitation microscopy, respectively.

Subsurface microscopy of integrated circuits with angular spectrum and polarization control.

We investigate the effect of an annular pupil-plane aperture in confocal imaging while using an NA increasing lens. We show that focal spot shape is highly sensitive to both polarization and angular spectrum of the incoming light. We demonstrate a lateral spatial resolution of 145 nm (lambda(0)/9) in the direction perpendicular to the polarization direction.

Chromatic and spherical aberration correction for silicon aplanatic solid immersion lens for fault isolation and photon emission microscopy of integrated circuits

Current state-of-the-art in backside fault isolation and logic analysis utilizes solid immersion lens (SIL) imaging in the central configuration. An attractive advancement is the development and integration of an aplanatic SIL, which allows significant improvement in resolution, signal acquisition and isolation capabilities, especially for the 22 nm node and beyond. However, aplanatic SIL configurations introduce both chromatic and spherical aberrations. We have developed backing objective designs capable of correcting for chromatic aberrations allowing application in photon emission microscopy, as well as deformable mirror designs and experiments that eliminate spherical aberrations of aplanatic SILs to account for variations in substrate thickness and off-axis imaging.

Spherical aberration correction in aplanatic solid immersion lens imaging using a MEMS deformable mirror

Aplanatic solid immersion lens (SIL) microscopy is required to achieve the highest possible resolution for next generation silicon IC backside inspection and failure analysis. However, aplanatic SILs are very susceptible to spherical aberrations introduced by substrate thickness mismatch. We correct this aberration using a MEMS deformable mirror. Good agreement between theory and experiment is achieved and spot intensity increases by a factor of two to three are demonstrated.

Coherent light scattering from a buried dipole in a high-aperture optical system

We develop a theoretical formulation to calculate the absolute and differential transmission of a focused laser beam through a high-aperture optical system. The focused field interacts with a point dipole that is buried in a high-index material, and is situated at the Gaussian focus of the focusing and collection two-lens system. The derived expressions account for the vectorial nature of the focused electromagnetic field and the inhomogeneous focal region environment. The results obtained are in agreement with recent resonant light-scattering experiments where the buried emitter is an indium arsenide semiconductor quantum dot in gallium arsenide.

Subsurface Imaging of Integrated Circuits with Widefield and Confocal Microscopy Using Numerical Aperture Increasing Lens

We report a lateral spatial resolution of 0.37 mum with a custom infrared widefield microscope while imaging subsurface features in silicon integrated circuits from backside. In addition, 2.65 mum apart polysilicon and metal layers can be differentiated.

Subsurface Imaging with Widefield and Confocal Numerical Aperture Increasing Lens Microscopes

We obtain lateral spatial resolutions of 0.88 mum and 0.29 mum with custom infrared widefield and confocal numerical aperture increasing lens microscopes, respectively, when imaging subsurface structures. We discuss the relative advantages of each microscope

Tailoring the local environment of quantum dots for enhanced collection efficiency

We theoretically demonstrate that location of a dipole emitter with respect to the interface significantly affects the collected signal intensity. Optimally engineered samples can provide 4 fold enhancement in collection.

Subsurface microscopy of integrated circuits with apodization and polarization control

We demonstrate a lateral spatial resolution of 160 nm (lambda0/8) using apodization in subsurface backside microscopy of silicon integrated circuits - a record resolution for one-photon excitation schemes.

Widefield Subsurface Microscopy of Integrated Circuits

Microscopy: We continue to find new performance enhancements even for mature technologies like optical microscopy.