Measuring and modeling optical diffraction from subwavelength features

Abstract

We describe a technique for studying scattering from subwavelength features. A simple scatterometer was developed to measure the scattering from the single-submicrometer, subwavelength features generated with a focused ion beam system. A model that can describe diffraction from subwavelength features with arbitrary profiles is also presented and shown to agree quite well with the experimental measurements. The model is used to demonstrate ways in which the aspect ratios of subwavelength ridges and trenches can be obtained from scattering data and how ridges can be distinguished from trenches over a wide range of aspect ratios. We show that some earlier results of studies on distinguishing pits from particles do not extend to low-aspectratio features.

Analysis of optical interferometric displacement detection in nanoelectromechanical systems

“…In this respect, our work is complementary to a recent work where the interaction of light with subwavelength structures has been studied. Such studies are becoming increasingly important 27,28 as in many emerging technologies, devices are being miniaturized. 29 Numerical analysis of such problems has been performed using a variety of methods, such as finite difference time domain ͑FDTD͒, finite difference frequency domain 29 ͑FDFD͒, and integral formulation.…”

Optical storage of high-density information beyond the diffraction limit: A quantum study

“…In order to compute the reflected field, we simply assume that bumps and holes are generated in such a way that they induce a π phase shift between them at reflection on the field profile. Note that the holes depth is usually λ/4, but precise calculations would be required to give the exact shape of the pits, as they are supposed to be burnt below the wavelength size, and as the field penetration in those holes is not trivial [4,5,6]. As we have shown that only one vectorial component of the field was relevant in the focal plane, we can directly apply this phase shift to the amplitude profile of this component.…”

“…The reconstruction of an object from its image beyond the diffraction limit, typically of the order of the wavelength, is a hot field of research, though a very old one, as Bethe already dealt with the theory of diffraction by subwavelength holes in 1944 [1]. More recently, theory has been developed to be applied to the optical storage problem, in order to study the influence of very small variations of pit width or depth relative to the wavelength [1,2,3,4,5,6]. To date, only a few super-resolution techniques [7] include a quantum treatment of the noise in the measurement, but to our knowledge, none has been applied to the optical data storage problem.…”

<title>Imaging ellipsometry for high-spatial-resolution metrology</title>

“…Numerical simulation and experimental results have shown that the polarization effect depends on the shape of the structure, e.g. side-wall shape 9 . It is possible to apply spatially resolved ellipsometry to extract this ellipsometric information from the corresponding sub-wavelength structure and measure the side-wall shape, such as undercutting and side-wall slope.…”