%0 Journal Article
%T Super-Resolution Raman Spectroscopy by Digital Image Processing
%A Motohiro Tomita
%A Hiroki Hashiguchi
%A Takuya Yamaguchi
%A Munehisa Takei
%A Daisuke Kosemura
%A Atsushi Ogura
%J Journal of Spectroscopy
%D 2013
%R 10.1155/2013/459032
%X We demonstrate the results of a strain (stress) evaluation obtained from Raman spectroscopy measurements with the super-resolution method (the so-called super-resolution Raman spectroscopy) for a Si substrate with a patterned SiN film (serving as a strained Si sample). To improve the spatial resolution of Raman spectroscopy, we used the super-resolution method and a high-numerical-aperture immersion lens. Additionally, we estimated the spatial resolution by an edge force model (EFM) calculation. One- and two-dimensional stress distributions in the Si substrate with the patterned SiN film were obtained by super-resolution Raman spectroscopy. The results from both super-resolution Raman spectroscopy and the EFM calculation were compared and were found to correlate well. The best spatial resolution, 70£¿nm, was achieved by super-resolution Raman measurements with an oil immersion lens. We conclude that super-resolution Raman spectroscopy is a useful method for evaluating stress in miniaturized state-of-the-art transistors, and we believe that the super-resolution method will soon be a requisite technique. 1. Introduction Raman spectroscopy is used as a stress evaluation method for strained Si, which is a technique for improving device performance. State-of-the-art metal-oxide-semiconductor field-effect transistors (MOSFETs) with strained Si have been scaled down and have become complicated. There is a significant demand to measure the strain induced in such Si nanodevices, because the electrical properties of transistors considerably depend on the strain. Various methods of nanoscale strain (stress) evaluation have been demonstrated, including convergent-beam electron diffraction (CBED), micro-Raman spectroscopy, and micro-X-ray diffraction (XRD) [1¨C5]. The Raman spectroscopy is advantageous because it permits the nondestructive and precise measurement of stress in Si with relatively high spatial resolution. In the previous study, the spatial resolution of Raman spectroscopy was improved by the use of a high-numerical-aperture (NA) immersion lens [6, 7]. However, the spatial resolution of current Raman measurements is insufficient to evaluate state-of-the-art MOSFETs, because the spatial resolution of an optical measurement cannot far exceed its wavelength due to the diffraction limit. The data diffusion is attributed to a variation in the probe shape, which is determined by mirrors, filters, and lenses on light path; the probe diameter especially was varied by NA of an objective lens. Generally, that is inevitable in optical evaluation techniques.
%U http://www.hindawi.com/journals/jspec/2013/459032/