Solid Immersion Lens Microscopy Research Articles

Feature-based filter design for resolution enhancement of known features in microscopy.

We present a new feature-based design concept for filter design in which a filter is designed specifically to image a known feature with dimensions lower than the optical resolution of the system. Unlike the conventional filter design based on focal spot engineering, we use the complete response of the microscope to form a resolution factor and consider minimizing the resolution factor as the design goal. We consider three design goals (i.e., resolution factors) based on the system response and show that a feature matching approach is more suitable in practice. It is shown that a three-bar pattern and grid of square dots of critical dimension, 0.08λ, can be resolved using a simple two-layer feature-based filter designed for radially polarized illumination in aplanatic solid immersion lens microscopy. An example that requires a more complex filter is also shown. Applicability of the concept of feature-based filter design in diverse microscopy scenarios is discussed as well.

Evanescent waves in high numerical aperture aplanatic solid immersion microscopy: Effects of forbidden light on subsurface imaging

The collection of light at very high numerical aperture allows detection of evanescent waves above the critical angle of total internal reflection in solid immersion lens microscopy. We investigate the effect of such evanescent modes, so-called forbidden light, on the far-field imaging properties of an aplanatic solid immersion microscope by developing a dyadic Green's function formalism in the context of subsurface semiconductor integrated circuit imaging. We demonstrate that the collection of forbidden light allows for sub-diffraction spatial resolution and substantial enhancement of photon collection efficiency albeit inducing wave-front discontinuities and aberrations.

Aberration compensation in aplanatic solid immersion lens microscopy

The imaging quality of an aplanatic SIL microscope is shown to be significantly degraded by aberrations, especially when the samples have thicknesses that are more than a few micrometers thicker or thinner than the design thickness. Aberration due to the sample thickness error is modeled and compared with measurements obtained in a high numerical aperture (NA ~3.5) microscope. A technique to recover near-ideal imaging quality by compensating aberrations using a MEMS deformable mirror is described and demonstrated.

Dielectric interface effects in subsurface microscopy of integrated circuits

We investigate the defocus and image quality affected by a dielectric interface on high numerical aperture focusing of linearly polarized illumination in aplanatic mode. Theoretical and experimental demonstration is performed on subsurface backside microscopy of silicon integrated circuits, showing that the high longitudinal magnification provided by solid immersion lens microscopy allows the observation of significant astigmatism. It is shown that a 50micron longitudinal displacement of the objective lens with respect to the sample is necessary to achieve maximum resolutions in two directions.

Imaging performance of widefield solid immersion lens microscopy

We investigate the performance of a widefield imaging system employing an aplanatic solid immersion lens. Off-axis imaging quality is examined theoretically at different radii and thicknesses of the aplanatic solid immersion lens. It is found that field curvature is the major aberration affecting the imaging quality. Aberrations are measured experimentally, and the results are in very good agreement with those obtained from simulations and demonstrate the situations where high quality images can be obtained with the aplanatic solid immersion lens.